Literatura académica sobre el tema "Morphology of stem"
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Artículos de revistas sobre el tema "Morphology of stem"
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Camilleri, Maris. "Island morphology : morphology's interactions in the study of stem patterns". Linguistica 51, n.º 1 (31 de diciembre de 2011): 65–85. http://dx.doi.org/10.4312/linguistica.51.1.65-85.
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The paper discusses the notion of morphological complexity, with a focus on stem patterns. Stem patterns, creating stem-based inflectional classes, are morphological constructs which come about as a result of observing the patterns rendered by the stem-form alternations (or stem splits (Baerman/Corbett forthcoming)), which one extracts after the formation of word-forms within paradigms. Stem-based inflectional class formation constitutes one aspect in the analysis of non-canonical paradigms, which also include affix-based inflectional classes, syncretism, defectiveness, and overabundance Corbett 2005, 2007, 2009; Baerman, Brown and Corbett 2005; Thornton 2010). While these non-canonical instances are in themselves interesting to observe, it is even more intriguing to be able to see what interactions can arise, which at times do not seem to be the result of something exterior to morphology proper. Through data taken from Maltese verbal paradigms the phenomenon of stem-based inflectional classes will be explored, which will exhibit how internal to the paradigm there exists a complex system in itself, which is based on the distinct organisation of different conflated morphosyntactic features which come about via syncretism. These patterns should illustrate a paradigm-internal morphological phenomenon that is irrelevant to the syntax, where while morphology borders with it, there need not be any interaction at this interface. At the same time, it will also be shown how at times, the border with phonology is blurred, where while the phonology may often try to build bridges that interface with the morphological island, the island's internal forces that drive its autonomy may deem to be more superior than the phonology's strive to impose its interacting requirements, which render some interesting morphophonological mismatches as a result.
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Comba, Luca Costanzo, Luca Gagliardi, Francesco Onorato y Fabrizio Rivera. "Periprosthetic Hip Fractures around the Stem: Can the Stem Design Affect Fracture Features?" Journal of Clinical Medicine 13, n.º 9 (29 de abril de 2024): 2627. http://dx.doi.org/10.3390/jcm13092627.
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Total hip arthroplasty is one of the most successful orthopedic surgeries; nevertheless, many of these surgeries are the causes of failure, and among them, periprosthetic fractures are one of the major causes of revision. Our study focuses on periprosthetic hip fractures with two different stem designs. The aim of the study was to analyze the obtained results, focusing on the features of periprosthetic stem fractures observed. Methods: We retrospectively reviewed periprosthetic fractures occurring between 2010 and 2023, involving Alloclassic® or CLS® uncemented femoral stems. We analyzed demographic data, proximal femur morphology, and the fracture type. Results: We identified 97 patients. Considering the proximal femur morphology, we found that there was statistically significant prevalence of Dorr A proximal femur morphology in the CLS® group and of Dorr C in the Alloclassic® group. Considering the distribution of the fracture pattern, we reported a non-statistically significant prevalence of the fracture pattern with stable stems in the CLS® group. Conclusions: The choice of the prosthetic design of the femoral stem is a crucial element when planning total hip arthroplasty. However, we found a non-statistically significant difference between the two stems considered, raising questions about the real role of stem design as a primary determinant of periprosthetic hip fractures.
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Gerber, Pascal. "Verb stem alternation in Gongduk". Language and Linguistics / 語言暨語言學 23, n.º 2 (29 de marzo de 2022): 240–73. http://dx.doi.org/10.1075/lali.00105.ger.
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Abstract This paper provides a first overview of verb stem alternation in Gongduk (eastern Bhutan, Trans-Himalayan). Verb stem alternation in Gongduk is conditioned both by morphophonology and by grammatical categories. This paper presents both the morphophonologically transparent as well as the phonologically opaque, paradigmatic stem alternation. The analysis provided in this paper identifies seven verb classes and a small number of irregular verbs. Additionally, this paper provides some diachronic observations on Gongduk verb stems and shows that different stem classes of Gongduk preserve derivational morphology (valence, direction) with cognates in other branches of the language family. Gongduk therefore provides important evidence for the historical investigation of derivational morphology and verb stem alternation in Trans-Himalayan.
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Tatevosov, Sergei G. "Event-structural morphology in Tundra Nenets". Rhema, n.º 3, 2018 (2018): 88–118. http://dx.doi.org/10.31862/2500-2953-2018-3-88-118.
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The paper explores semantic characteristics of verbal stems in Tundra Nenets that can take different stem-final vowels. I argue that the distribution of these vowels and interpretational effects they induce are best accounted for under an analysis that treats them as phonological signatures of different event structural configurations.
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Arjin, Chaiwat, Chanmany Souphannavong, Apinya Sartsook, Mintra Seel-audom, Supamit Mekchay y Korawan Sringarm. "Efficiency of Fresh and Fermented Banana Stem in Low Protein Diet on Nutrient Digestibility, Productive Performance and Intestinal Morphology of Crossbred Pig ((Thai native x Meishan) x Duroc)". Veterinary Integrative Sciences 19, n.º 1 (28 de agosto de 2020): 51–64. http://dx.doi.org/10.12982/vis.2021.005.
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Banana stem is a common feed component for raising pigs in mountainous Southeast Asia. However, its nutritive value and digestibility are low. This study was carried out to investigate the effects of unfermented and fermented banana stems on crossbred pigs concerning nutrient digestibility, productive performance, and intestinal morphology. Initially, an in vitro ileal digestibility test was performed for the following feedstuffs: fresh banana stem (BS), fermented banana stem (FBS), concentrate (C), fresh banana stem + concentrate (BSC), and fermented banana stem + concentrate (FBSC). For the 120-day experiment, 16 crossbred pigs were divided into two groups and fed with BSC and FBSC. They were placed in individual cages and subsequently moved to metabolic cages for seven days to determine apparent total tract digestibility (ATTD). Finally, all pigs were slaughtered and their small intestines were analyzed for intestinal morphology. The results show that pure fresh and fermented banana stems had low digestibility. However, their digestibility increased by 50% when mixed with concentrate. Crossbred pigs fed BSC and FBSC did not exhibit significant differences in their performance, but the intestinal morphology of the FBSC group had improved intestinal morphology, especially the villi height. In conclusion, both fresh and fermented banana stems can be recommended in a low protein diet as feed for crossbred pigs in an improved production system. This is relevant for raising pigs in mountainous areas, as it has the potential to reduce feed cost and maintain production performance.
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M. Arkadiev, Peter. "Stems in Lithuanian verbal inflection (with remarks on derivation)". Word Structure 5, n.º 1 (abril de 2012): 7–27. http://dx.doi.org/10.3366/word.2012.0017.
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This paper deals with the three stems traditionally postulated in the description of Lithuanian verbal inflection, viz. the Present stem, the Past stem and the Infinitive stem. These stems play a major role in the subgrouping of verbs into inflectional classes. The status of each of the stems as ‘morphomic’ or ‘inflectional’ is assessed in the light of data from both inflectional and derivational morphology. It is argued on the basis of intricate prosodic and morphophonological data that the Infinitive stem is indeed necessary for an adequate description of the Lithuanian verbal system, and also that a separate Past Passive Participle stem relevant for deverbal derivation can be postulated.
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Pakerys, Jurgis. "Verbal morphology in the Database of New Borrowings into Lithuanian". Taikomoji kalbotyra, n.º 3 (2 de marzo de 2015): 1–26. http://dx.doi.org/10.15388/tk.2014.17480.
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The Database of New Borrowings into Lithuanian lists 129 verbs which were either directly borrowed or derived from the borrowed nominal and adjectival stems. In terms of morphosyntactic adaptation, two suffixes, viz. uo ti and in ti, are used as indirect insertion strategy devices (Wohlgemuth 2009: 94 ff.). The suffix uo ti is the most productive verbalizer in modern Lithuanian and is predominantly used to integrate the so called internationalisms in the standard language, while in ti is the main factitive/causative affix and is employed in the non standard language domain to accommodate the verbal borrowings coming mostly from English. In very many cases, verbs, nouns and some adjectives sharing the same stem were borrowed and I argue that a synchronic derivational link between them can be recognized in Lithuanian, no matter what the derivational history of these words in the donor language was. If a borrowed verb has a suffix, but no corresponding noun or adjective is found in the current usage, the suffix can be interpreted as a device of morpho-syntactic adaptation only. Compared to uo ti and in ti, other suffixes are only rarely attested in the database, but they clearly reflect productive types of verb formation, namely, the denominal similatives in au ti and the deadjectival inchoatives in ė ti. The data on prefixal and reflexive derivatives is too scarce to note any definite trends. As far as inflectional productivity is concerned, in ti and uo ti definitely play a major role in enriching the classes characterized by the present stem affixes of the a-type and the past stems affixes of the o-type. The inflexion of verbs in uo ti is also affected by morpho-phonological alternation of the suffix to resolve hiatus, viz. the infinitive stem has /uo/ (no hiatus), the present stem is augmented by the palatal glide /j/ ( uoj ), while in the past stem, /uo/ is replaced by /av/ (i.e. uo ti, uoj a, av o).
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Marusch, Tina, Lena Ann Jäger, Frank Burchert y Lyndsey Nickels. "Verb morphology in speakers with agrammatic aphasia". Mental Lexicon 12, n.º 3 (31 de diciembre de 2017): 373–403. http://dx.doi.org/10.1075/ml.17006.mar.
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Abstract This paper reports an investigation of the production of verb morphology in English speakers with agrammatic aphasia. Our main goal was to test four accounts of the processing of (ir-)regularity by quantifying regularity using affix type and the presence or absence of stem changes. Production accuracy of regular, mixed and two types of irregular past participles (irregular 1, irregular 2) was tested in English using a sentence completion task with a group of five speakers with agrammatic aphasia. The results showed significant effects on production accuracy of whether the verb required a stem change and of time reference frame but no effect of affix type: past participles that required stem changes (mixed and irregular 2 past participles) were more difficult to produce than past participles that did not change their stem (regular and irregular 1 past participles). Moreover, the production of present continuous forms was more accurate compared to past participle forms. These results suggest that a categorical conception of regular versus irregular is over-simplified, as accuracy was best predicted by stem change rather than by regularity. This is a finding most consistent with the Stem-based Assembly model. The results of this study have implications for the design and selection of stimuli in future experiments: Experimental stimuli need to be controlled for stem changes and affix type rather than assuming that irregular verbs are homogeneous.
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Rightor, E. G., E. I. Garcia-Meitin y D. W. Liou. "Investigation of CPE/PVC morphology via STEM". Proceedings, annual meeting, Electron Microscopy Society of America 46 (1988): 932–33. http://dx.doi.org/10.1017/s0424820100106727.
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Microscopic characterization of the phase morphology of poly(vinyl chloride) (PVC) modified with chlorinated polyethylene (CPE) is vital to understanding the blend physical properties. A 2-3 week CPE selective staining technique, developed by Fleischner et al., has been the mainstay for recent TEM investigations of CPE/PVC. Several researchers employing this method have reported a network structure of CPE surrounding primary PVC particles.Rapid electron beam-induced dehydrochlorination of chlorinated polymers prohibits TEM examination of unstained sections. Chemical changes resulting from such dehydrochlorination of polymers was addressed recently by Vesely and Finch. In this study we investigated unstained thin sections, obtained at ambient temperature with a diamond knife, by scanning transmission electron microscopy (STEM) on a JEOL 2000 FX.As the STEM micrographs show (Figs. 1-3), sufficient contrast was available to distinguish CPE (light phase) from the PVC matrix (dark). Differences in initial chlorine concentration and rates of beam-induced mass loss most likely account for the contrast between phases.
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Weryszko-Chmielewska, Elżbieta. "Anatomical and morphological copper provision indexes in wheat (Triticum aestivum L.)". Acta Agrobotanica 46, n.º 1 (2013): 83–97. http://dx.doi.org/10.5586/aa.1993.008.
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The morphology and anatomy of wheat (<i>Triticum aestivum</i> L.) stems under conditions of copper deficiency were investigated. Copper was supplied at 0, 5 and 125 mg per Mitscherlich pot. The lignification of tissues in plants from field experiments (0; 5; 10; 20 mg Cu/ha) was also studied. Significant changes in stem and leaf morphology and anatomy were found along inhibition of inflorescence and flower development. The anthers produces sterile and deformed pollen grains. The diminished stability of stems was caused by the following anatomical changes: considerable reduction of steam diameter and culm wall thickness and decreased numbers and dimensions of sclerenchyma and parenchyma cells and layers. In addition, the size of vascular bundles and the diameter of xylem vessels were decreased and the sclerenchyma sheath around the vascular bundles was reduced. The epidermis and sclerenchyma cells had thinner walls. The absence of lignification of cells walls was observed most frequently in the peripheral tissues (epidermis, sclerenchyma and parenchyma). It was demonstrated that it was possible to histochemically determine the degree of stem lignification in the early phases of wheat development.
Tesis sobre el tema "Morphology of stem"
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O'Meara, John 1954. "Delaware stem morphology". Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=39236.
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The derivational morphology of Munsee Delaware, an Eastern Algonquian language spoken in southwestern Ontario, is analysed and described. Chapter I presents general information about Delaware, including a summary of grammatical information necessary for the understanding of word structure. The theoretical constructs assumed are summarized. A distinction is made between primary derivation, in which suffixes are attached to roots (and affixes) to form stems; and secondary derivation, in which suffixes are attached to stems to form new stems. Inflectional affixes are attached to stems which are formed in primary or secondary derivation. Chapter II discusses verb-forming suffixes ('finals') added to roots and certain suffixes to form verb stems. Chapter III discusses verb-forming suffixes which attach to existing noun and verb stems to form verb stems (secondary derivation). Chapter IV discusses 'medials', which prototypically occur between roots and 'final' suffixes. Chapter V discusses noun-forming suffixes which are attached to roots and medials. Chapter VI discusses noun-forming suffixes which attach to existing noun and verb stems to form noun stems (secondary derivation). Chapter VII discusses bound variants of noun stems, morphological elements which occur as members of morphologically complex noun stems.
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Partridge, Roland William. "Morphogenesis and morphology of intestinal villi". Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/28884.
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Paediatric intestinal failure following bowel resection causes significant morbidity and mortality. There is a pressing need for improved treatment modalities. Following loss of bowel, the remaining intestine undergoes a period of adaptation, characterised by an increase in height of the intestinal villi. Better understanding the factors that govern the formation and growth of villi may lead to therapeutic interventions that amplify the intrinsic adaptation response. This thesis aims to explore the processes by which intestinal villi form during embryological development, the contribution of intestinal stem cells to this, and candidate signalling pathways that may yield insights into new therapeutic interventions for patients with intestinal failure. Abstract: Aim I will examine the morphogenesis and morphology of intestinal villi by investigating three themes: 1) Villus morphogenesis: When and where do villi form along the gut tube? Can this process be quantified, both in vivo and in vitro? Is this initiated by a dominolike signaling-cascade along the bowel, or location-specific intrinsic triggers? 2) Stem cells: What is the spatiotemporal appearance of the Lgr5-expressing intestinal stem cells during development? How does this relate to the process of villus morphogenesis? 3) Signalling pathways: Can a genetic mutation mouse model help elucidate pathways by which post bowel resection adaptation might occur? Can this be used to help identify potential intestinotrophic agents? Abstract: Materials and Methods Three mice models were used as the foundation for this work. Embryonic tissue was analysed from wild-type CD1 and Lgr5-eGFP-IRES-CreERT2 mice, and adult intestinal tissue examined from tamoxifen-activated Villin-Cre-ERT2 Pten-/- Brafv600E mice. Culture of wild-type embryonic mouse intestine with and without segments removed and / or reversed was performed to investigate the question of what triggers the proximal-to-distal wave of villus morphogenesis. Immunohistochemical interrogation using anti-GFP antibodies was used in the Lgr5- GFP mice to identify the location of Lgr5-expressing cells during the development of villi. Bright-field microscopy, time-lapse in-incubator microscopy, and histological sections assessed villus morphology. The Villin-Cre-ERT2 Pten-/- Brafv600E mouse mutant was explored regarding the intestinal epithelial morphometric changes that occur following tamoxifen-induction. Abstract: Results The proximal-to-distal wave of villus morphogenesis was observed both in vivo and in vitro. Villus morphogenesis commences at embryonic day 14.5 in vivo and after three days in culture from e11.5 in vitro. The villus structures formed in vitro are significantly attenuated compared to in vivo development. An attempt was made to overcome this by providing intestinal explants with a blood supply to aid growth. Evidence is presented that suggest the proximal-to-distal wave of villus morphogenesis is driven by location specific factors intrinsic to each part of the bowel, rather than a domino-like signalling cascade travelling along the intestine. Lgr5-expressing intestinal stem cells were present in early development. Prior to villus morphogenesis they were uniformly distributed along the luminal surface of the intestinal epithelia. During the intense proliferation associated with villus morphogenesis they progressively congregated to the inter-villus spaces. Once villi are fully formed they were absent from the villi but identified in the inter-villus spaces. The Pten/Braf mouse mutant demonstrates villus morphological changes similar to those found following post-bowel resection adaptation. This suggests that there may be a role for Pten/Braf in the epithelial proliferation following extensive bowel resection. Signalling factors in these pathways may be candidate intestinotrophic agents for the treatment of short bowel syndrome. Abstract: Conclusions Before any processes that manipulate intestinal epithelia can be safely translated into therapies to aid adaptation in patients with intestinal failure, it is important to have a full and detailed understanding of the basic science principles that underpin the behaviour of the epithelial cells, both during development and in adulthood. I have explored and quantified the process of villus morphogenesis in the embryonic mouse, investigated the timing of appearance of Lgr5 intestinal stem cells, and interrogated a genetic mouse model with morphometric changes similar to those seen following small bowel resection. I propose two candidate intestinotrophic agents that may hold regenerative potential to augment post small bowel resection adaptation. The next stage of investigation would be to use a mouse model of small bowel resection with manipulation of cell signalling factors to assess impact on post resection adaptation. The ultimate goal would be to investigate epithelial activity in human neonatal intestine and explore methods of modulating this to improve the outcomes from post bowel resection intestinal failure.
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Roshan, Amit. "Stochasticity and order : studies of keratinocyte proliferation". Thesis, University of Cambridge, 2014. https://www.repository.cam.ac.uk/handle/1810/252966.
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A central tenet of stem cell biology has been that proliferating tissues are maintained through a cellular hierarchy comprising of self-renewing stem cells at the apex, multiple lineage-restricted short-lived progenitor cells, and post-mitotic differentiated cells. The wide range of colony sizes in cultured human keratinocytes has been taken to support this hypothesis. Contrary to this model, researchers using genetic lineage tracing in mouse epidermis have inferred a single progenitor population for homeostasis, and a quiescent stem cell population activated upon wounding or genetic mutation. To study the proliferative behaviour of human keratinocytes, I used live imaging in vitro at single cell resolution. This shows two modes of proliferation: Type 1 cell division is stochastic with equal odds of generating dividing or non-dividing progeny, while Type 2 cell division predominantly produces two dividing daughters. These two modes are sufficient to explain the entire range of colony sizes seen after 7-12 days of culture and does not require a spectrum of proliferative ability. This insight provides a simple way to study the effects of external factors on cell fate. To exemplify this, I observed the effects of epidermal growth factor (EGF) and the Wnt agonist R-spondin on proliferation. Here I find proliferation in type 2 colonies changes by changing the proportion of cells dividing. This has implications for the limited success of EGF therapies in clinical trials following burns. To examine clonal contributions to wound repair, I used the mouse oesophageal epithelium which is exclusively composed of, and maintained by, a single progenitor population. I developed a micro-endoscopic wounding technique that produced localised superficial wounds. Here, I found that these wounds healed by uniform contribution from surrounding keratinocytes, demonstrating that reserve stem cells are not obligatory for wound repair. In summary, my work shows that human keratinocytes in vitro have two, and only two, modes of proliferation: a stochastic mode that is insensitive to external EGF signalling, and a EGF-sensitive exponential mode. Additionally, proliferation during wound repair can occur with stochastically dividing progenitors, and does not obligate stem cell recruitment in vivo.
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Siddiqi, Daniel A. "Minimize Exponence: Economy Effects on a Model of the Morphosyntactic Component of the Grammar". Diss., The University of Arizona, 2006. http://hdl.handle.net/10150/194752.
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Working within the morphosyntactic framework of Distributed Morphology (DM, Halle and Marantz 1993, 1994) within the Minimalist Program (Chomsky 1995), this dissertation proposes a new economy constraint on the grammar, MINIMIZE EXPONENCE, which selects the derivation that realizes all its interpretable features with the fewest morphemes. The purpose of this proposal is to capture the conflicting needs of the grammar to be both maximally contrastive and maximally efficient.I show that the constraint MINIMIZE EXPONENCE has a number of effects on analyses of morphosyntactic phenomena. I propose that, in order to satisfy MINIMIZE EXPONENCE, the roots in a derivation fuse with the functional heads projected above them, resulting in a simplex head that contains both a root and interpretable features. Following the tenets of DM, this head is now a target for the process of Vocabulary insertion. Since the target node contains both content and functional information, so too can Vocabulary Items (VIs) be specified for both types of information. This allows VIs such as eat and ate to compete with each other. This competition of forms linked to the same root allows for a new model of root allomorphy within the framework of DM. In this model of root allomorphy, following proposals by Pfau (2000), VIs that realize roots participate in competition in the same was as do VIs that realize abstract morphemes. Since root VIs are participating in competition and are specified for both content and formal features, the need for licensing through secondary exponence as proposed by Harley and Noyer (2000) is removed from the framework. Further, since eat and ate in this model are different VIs with different specifications that compete with each other for insertion, this model of root allomorphy also eliminates the need for readjustment rules as proposed by Halle and Marantz (1993, 1994) and elaborated on by Marantz (1997). This new model of root allomorphy allows for an account of the blocking of regular inflection in English nominal compounds (e.g. *rats-catcher), which was problematic for theorists working with DM, given the tenets of the framework.I also show that the fusion of roots and functional elements driven by MINIMIZE EXPONENCE allows for a new account of subcategorization. The model of subcategorization presented here falls out of the following facts: 1) arguments are introduced by functional heads; 2) those heads fuse with the root they are projected above, resulting in the node containing both the root and the features of the functional heads; 3) since the root now contains both the root and the formal features, the corresponding VI can be specified for both; 4) VIs that realize roots can also be specified for compatibility or incompatibility of the features of the functional heads that license argument structure. The result here is an underspecification model of subcategorization that predicts a number of behaviors of verbs with respect to their argument structure that it is difficult for a full specification model to account for. Those include polysemy (I ran the ball to Mary) and structural coercion (I thought the book to Mary).
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Heintz, Ilana. "Arabic Language Modeling with Stem-Derived Morphemes for Automatic Speech Recognition". The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1275053334.
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Boone, Jason Nathaniel 1976. "Characterization of novel neural stem cell populations in the Drosophila central nervous system". Thesis, University of Oregon, 2008. http://hdl.handle.net/1794/8160.
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xi, 88 p. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.Neuroblasts are the neural stem cells of the Drosophlia central nervous system. They are large cells that divide asymmetrically to renew another neuroblast and generate a smaller ganglion mother cell (gmc) that will divide once to produce two neurons. Combining genetic lineage tracing experiments with cell fate markers I isolated two separate neural stem cell populations with distinct locations and cellular behaviors in the larval brain. In my first chapter I introduce the central nervous system of Drosophila and in the next two sections of chapter I, I introduce the development of the optic lobe and central brain, two separate structures of the central nervous system. In my second chapter I characterize the lineage relationship of cells within the developing larval optic lobe and use cell fate markers to determine the identity of these cells. Next I examine the effect of spindle orientation on cell fate within epithelial cells of the optic lobe. In my third chapter I characterize another novel neural stem cell lineage in the larval brain containing GMCs with greater proliferation potential than a "canonical" GMC, and I term these, transit amplifying gmcs (TA-GMCs). Further I show that the parent neuroblast of these novel TA-GMCs does not asymmetrically segregate the fate determinant Prospero (Pros) thereby producing a GMC with greater proliferation potential. Finally I show that TA-GMCs do asymmetrically segregate the fate determinant Pros, divide slowly and give rise to up to 10 neurons which normal gmcs never do. In my fourth chapter I show preliminary work on the characterization of a mutation that causes excessive production of neuroblasts specifically in novel TA-GMC lineages. These findings reveal novel neural stem cell lineages, patterns of asymmetric cell division and patterns of neurogenesis that could aid in our understanding of neural stem cell biology and tumorogenesis. This dissertation includes both my previously published and my co-authored materials.
Adviser: Chris Doe
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Lanci, Aliai <1987>. "Morphology and Microscopy of Equine Umbilical Cord and Characterization of Mesenchymal Stem Cells Isolated from Foetal Adnexa". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amsdottorato.unibo.it/7890/1/TESI%20DOTTORATO%20ALIAI%20LANCI.pdf.
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The purpose of this PhD thesis is to perform a dissertation about the equine umbilical cord (UC), with particular attention to its macroscopic characteristics moving into its microscopic features. Furthermore, equine UC was microscopically and immunohistochemically described. The coiling makes the UC a structure both flexible and strong, and provides resistance to external forces, which could compromise blood flow. Data obtained from the present study could be considered as a normal range of number of coils and UCI in the equine physiological pregnancies. The second and major component of this dissertation was focused on umbilical cord as a Mesenchymal Stem Cells (MSCs) niche. In particular, the ultrastructural characterization and immune profile of equine MSCs derived from foetal tissues (Wharton’s jelly and blood) were investigated; equine foetal MSCs were then compared to human foetal MSCs and equine adult MSCs. The third section included the clinical applications of MSCs derived from AF and WJ on cutaneous wounds of different ages’ foals. The employ of foetal MSCs on cutaneous wounds decreased their healing both in neonatal foals and six-month foals, in comparison with other traditional treatments. In conclusion, one of the most important feature of placenta’s evaluation is the observation of normal characteristic of the equine UC. Furthermore, since the UC is a discarded material after delivery, it represents an excellent non-invasive alternative source of MSCs with reliable migration and differentiation capacities, and it is a convenient cell source for autologous or allogeneic regenerative therapies. Finally, it is important a constant update about regenerative medicine and the development of research in this field considering that the horse serves as a perfect model for humans.
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Koch, Britta. "Scaffold dimensionality and confinement determine single cell morphology and migration". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-194717.
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This thesis describes a highly interdisciplinary approach to discern the differing impact of scaffold dimensionality and physical space restrictions on the behavior of single cells. Rolled-up nanotechnology is employed to fabricate three-dimensional (3D) SiO/SiO2 microtube geometries of varied diameter, that after a biofunctionalization step are shown to support the growth of U2OS and six different types of stem cells. Cell confinement quantifiable through the given microtube diameter is tolerated by U2OS cells through a remarkable elongation of the cell body and nucleus down to a certain threshold, while the integrity of the DNA is maintained.
This confinement for NSPCs also leads to the approaching of the in vivo morphology, underlining the space-restrictive property of live tissue. The dimensionality of the cell culture scaffold however is identified as the major determiner of NSPC migration characteristics and leads to a morphologically distinct mesenchymal to amoeboid migration mode transition. The 3D microtube migration is characterized by exclusively filopodia protrusion formation, a higher dependence on actin polymerization and adopts aspects of in vivo-reported saltatory movement. The reported findings contribute to the determination of biomaterial scaffold design principles and advance our current understanding of how physical properties of the extracellular environment affect cell migration characteristics.
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Yu, Leqian. "The Effect of Micro and Nano Mechanical Environment on Pluripotent Stem Cells". Kyoto University, 2017. http://hdl.handle.net/2433/227624.
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Demir, Özlem. "Functional Characterization of Microtubule Associated Proteins in ES Cell Division and Neuronal Differentiation". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-163103.
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Microtubules are tubular polymers that are involved in a variety of cellular processes such as cell movement, mitosis and intracellular transport. The dynamic behavior of microtubules makes this possible because all of these processes require quick responses. Embryonic stem (ES) cells were first isolated from mouse embryos and they have two unique characteristics; they can be kept undifferentiated for many passages with a stable karyotype and they can be differentiated into any type of cells under appropriate conditions. The pluripotency of ES cells, their ease of manipulation in culture, and their ability to contribute to the mouse germ-line provides us a model of differentiation both in vitro and in vivo. In my thesis I focused on the cell division and neuronal differentiation of ES cells and developed two methods to understand the effects of microtubule dynamics in spindle assembly and chromosome segregation and to reveal the roles of different Microtubule Associated Proteins (MAPs) in the neuronal morphology formation.
In the first part, we developed a live-cell imaging method for ES cells to visualize, track and analyze the single cell behavior in a cell population over a time period. So far many techniques have been adapted and combined for imaging of cell lines, mainly for the cancer or immortalized ones. However, because ES cells are very prone to apoptosis, tend to form spheres and hard to stably label, it is quite tricky to image them in culture conditions. In our system, we combined the BAC-based gene expression with wide-field deconvolution microscopy for ES cells that are plated onto the laminin-511 coated surface and kept in CO2 independent culture conditions. This combined technique does not interfere with the growth of cells and keeps them healthy up to 24 hours on the microscope stage.
In the second part, we analyzed the effects of MAPs chTOG, EB1, Kif18A and MCAK in the overall spindle morphology and mitotic progression in mES cells. For this purpose, we utilized our stable TUBB-GFP and H2A-GFP cell lines along with our live-cell imaging set-up to reveal the effects of the above-mentioned proteins and the interplay among each other. By using RNAi method we either single or co-depleted the genes by siRNAs and measured the spindle length and width in RNAi conditions. We further analyzed the mitotic progression in H2A-GFP cell line in terms of the metaphase timing and the percentage of chromosome segregation errors. Our results showed that, EB1 depletion did not cause any significant changes in the overall spindle morphology or in the metaphase timing. However, the co-depletion of EB1 with chTOG partially rescued the sichTOG specific mini-spindle phenotype. siKif18A produced longer spindles without any change in the spindle width. Surprisingly, the co-depletion of antagonistic chTOG and Kif18A proteins had additive effects on the spindle dynamics and on mitotic progression in a way that spindle assembly was severely disrupted by the absence of these two proteins and as a result of this, both metaphase timing and chromosome missegregation levels increased significantly. These results overall indicate that MAPs have important roles in the regulation of dynamic instability and these proteins have an interplay among each other to be able to control the morphology of the spindle as well as the correct segregation of chromosomes into daughter cells.
In the last part, I will introduce you a new ES cell based differentiation and morphology model, which brings the advantages of high resolution imaging capacity, control over development and easy genetic manipulation and culturing. We have generated Tet-induced shRNA cell lines against chTOG, Kif18A and MCAK, which are also stably expressing TUBB-GFP. These labeled cells were mixed with unlabeled wild-type mES cells before differentiation at 1:1000 ratio and then they were differentiated into mouse cortical cells and spinal motor neurons. Our results showed that, all of the three genes could be successfully knocked-down by shRNA after 48 hours of Tet induction. After mixing the labeled and unlabeled cells, single neurons could be imaged at high resolution and their skeletons could be generated afterwards. The RNAi studies in shchTOG cell line showed that, the knock-down of this gene in early differentiation interferes with the neuronal differentiation.
Libros sobre el tema "Morphology of stem"
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Rieppel, Olivier. Osteology of Simosaurus gaillardoti and the relationships of stem-group Sauropterygia. [Chicago, Ill.]: Field Museum of Natural History, 1994.
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Sliva, Monica Dawn. Developmental morphology of stem galls induced by Aulacidea hieracii (Hymenoptera: cynipidae) on Hawkweed and Diplolepis spinosa (Hymenoptera: cynipidae) on Rose: Y Monica Dawn Sliva. Sudbury, Ont: Laurentian University, School of Graduate Studies, 2005.
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L, Gartner Barbara, ed. Plant stems: Physiology and functional morphology. San Diego, CA: Academic Press, 1995.
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Rudes, Blair A. Tuscarora roots, stems, and particles: Towards a dictionary of Tuscarora. Winnipeg: Algonquian and Iroquoian Linguistics, 1987.
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Rudes, Blair A. Tuscarora roots, stems, and particles: Towards a dictionary of Tuscarora. Winnipeg: Algonquian and Iroquoian Linguistics, 1987.
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Morphology by itself: Stems and inflectional classes. Cambridge, Mass: MIT Press, 1994.
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Aronoff, Mark. Morphology by itself: Stems and inflectional classes. Cambridge, Mass: MIT Press, 1994.
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Stüber, Karin. The historical morphology of N-stems in Celtic. Maynooth: Department of Old Irish, National University of Ireland, Maynooth, 1998.
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Downs, Colleen T. y Lorinda A. Hart, eds. Invasive birds: global trends and impacts. Wallingford: CABI, 2020. http://dx.doi.org/10.1079/9781789242065.0000.
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Abstract This 381-paged book covers the biology, ecology, impact and management of 34 common alien invasive species, with reviews on the history and context of avian introductions and invasions in five major regions (Oceania, Africa, Europe (including the Middle East, Asia and South America)), as well as management challenges and the potential of citizen science for monitoring alien birds. The book pitches at the introductory level and is ideal for readers to gain a quick and comprehensive view of the current status of global avian invasions. It has brought the records and research of avian invasion one step ahead of other alien invasive animal taxa. Many chapters contain distribution maps and data tables on the diet and morphology of the species, providing a good reference for the species and its management issues. Each chapter also contains a rich list of references that could help readers dive further into the topic.
Capítulos de libros sobre el tema "Morphology of stem"
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Lapointe, Steven G. "Stem selection and OT". En Yearbook of Morphology 1999, 263–97. Dordrecht: Springer Netherlands, 2001. http://dx.doi.org/10.1007/978-94-017-3722-7_10.
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Hettwer, Caroline y Nanna Fuhrhop. "Chapter 6. Stem constancy under the microscope". En All Things Morphology, 99–116. Amsterdam: John Benjamins Publishing Company, 2021. http://dx.doi.org/10.1075/cilt.353.06het.
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Bonami, Olivier y Sacha Beniamine. "Chapter 5. Leaving the stem by itself". En All Things Morphology, 81–98. Amsterdam: John Benjamins Publishing Company, 2021. http://dx.doi.org/10.1075/cilt.353.05bon.
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Duvernoy, Henri M. "A Survey of the Brain Stem Morphology". En Human Brain Stem Vessels, 5–23. Berlin, Heidelberg: Springer Berlin Heidelberg, 1999. http://dx.doi.org/10.1007/978-3-662-07813-6_3.
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Leong, Wen Shing, Chor Yong Tay y Lay Poh Tan. "Engineering Stem Cell Niche: Regulation of Cellular Morphology and Function". En Stem Cells and Cancer Stem Cells,Volume 3, 345–55. Dordrecht: Springer Netherlands, 2011. http://dx.doi.org/10.1007/978-94-007-2415-0_35.
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Gębski, Wiktor. "3. Verbal morphology". En Semitic Languages and Cultures, 91–138. Cambridge, UK: Open Book Publishers, 2024. http://dx.doi.org/10.11647/obp.0394.03.
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This chapter aims to evaluate the similarities and differences between the verbal systems of the Jewish dialect of Gabes and other Maghrebi dialects. Notably, both Jewish Gabes and Jewish Djerba exhibit gender distinction in the 2FS forms marked by the /-i/ suffix, a feature absent in Jewish Tunis, where masculine forms are also used for the feminine. The study affirms the sedentary nature of Jewish Gabes, indicated by the /-āw/ suffix in verbs with a weak third radical in stem I, in contrast to the /u/ found in Bedouin dialects. Regarding the vowel distribution of stem I verbal forms, Jewish Gabes shares similarities with neighbouring Jewish dialects, particularly in the basic theme vowel being /ə/ or /a/ in proximity to gutturals. In contrast, Muslim dialects and Jewish Wad-Souf demonstrate a broader array of vowel qualities. Additionally, the analysis reveals that Jewish Gabes has developed an alternative method for expressing the passive voice, a bipartite construction involving an active verb with a personal object pronoun.
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Schweingruber, Fritz H. y Annett Börner. "Morphology of the plant body – Tried and tested for 400 million years". En The Plant Stem, 7–10. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-73524-5_3.
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Kaplan, Donald R. y Chelsea D. Specht. "The Effect of Stem Thickening Growth on Shoot Form". En Kaplan's Principles of Plant Morphology, 213–41. Boca Raton: CRC Press, 2022. http://dx.doi.org/10.1201/9781315118642-10.
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Kameda, Hiroyuki, Hiroaki Ishihata y Tomoyasu Sugiyama. "Deep Learning of Cancer Stem Cell Morphology". En Methods in Molecular Biology, 231–56. New York, NY: Springer US, 2024. http://dx.doi.org/10.1007/978-1-0716-3730-2_17.
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Brück, K. "Significance of Brain Stem Neuronal Connectivities for Thermoregulation and Thermal Adaptation". En Functional Morphology of Neuroendocrine Systems, 51–64. Berlin, Heidelberg: Springer Berlin Heidelberg, 1987. http://dx.doi.org/10.1007/978-3-642-72886-0_5.
Texto completoActas de conferencias sobre el tema "Morphology of stem"
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Ariffin, Shahrul Hisham Zainal, Thanaletchumi Manogaran, Intan Zarina Zainol Abidin, Sahidan Senafi y Rohaya Megat Abdul Wahab. "Isolation and morphology of Stem Cells from Deciduous Tooth (SHED) and Human Dental Pulp Stem Cells (hDPSC)". En THE 2016 UKM FST POSTGRADUATE COLLOQUIUM: Proceedings of the Universiti Kebangsaan Malaysia, Faculty of Science and Technology 2016 Postgraduate Colloquium. Author(s), 2016. http://dx.doi.org/10.1063/1.4966718.
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Arnold, Jordan William, J. K. Haschenburger y J. K. Haschenburger. "THE SIGNIFICANCE OF TRIBUTARY SEDIMENT INPUT IN CONTROLLING MAIN STEM RIVER MORPHOLOGY". En GSA 2020 Connects Online. Geological Society of America, 2020. http://dx.doi.org/10.1130/abs/2020am-359071.
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Chen, Weiqiang, Luis G. Villa-Diaz, Yubing Sun, Shinuo Weng, Jin Koo Kim, Paul H. Krebsbach y Jianping Fu. "Nanotopography Directs Fate of Human Embryonic Stem Cells". En ASME 2012 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/sbc2012-80222.
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Human embryonic stem cells (hESCs) have remarkable potentials for breakthroughs in future cell-based therapeutics owing to their self-renewal capability and pluripotency [1–2]. However, their intrinsic mechanosensitivity to biophysical signals from the local cellular microenvironment is not well characterized [3–4]. In this work, we introduced a simple, yet precise, microfabrication strategy for accurate control and patterning of local nanoroughness on glass surfaces using photolithography and reactive ion etching (RIE). Our results demonstrated that nanoscale topological features could provide a potent regulatory signal over a diverse array of hESC behaviors, including their morphology, adhesion, proliferation and clonal expansion, and differentiation.
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Wen, Shin-Min y Pen-Hsiu Grace Chao. "Temporal Cell Morphology Responses to Mechanical Stimulation". En ASME 2012 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/sbc2012-80939.
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Many cells respond to mechanical stimulation by changing their morphology, such as elongation and alignment [1–2]. Studies investigating cell responses to mechanical stimulation are often conducted immediately after unloading [1]. Most tissue engineering studies, however, apply mechanical stimulation with intermittent resting periods and monitor the long term cell reactions. In the current study, we examine the cell morphology change in response to mechanical loading with a 24 hour recovery time. Human mesenchymal stem cells (MSCs) were subjected to dynamic tensile or compressive loadings and their morphological changes were compared to those under static loads. A delayed response was found, in addition to changes in active RhoA signals.
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Fu, Jianping. "Micro-Engineered Sythetical Extrocellular Metrix for Stem Cell Differentiation Study". En ASME 2010 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2010. http://dx.doi.org/10.1115/sbc2010-19312.
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We report the use of micromolded elastomeric micropost arrays to modulate substrate rigidity independently of effects on adhesive and other material surface properties. We demonstrate that micropost rigidity impacts cell morphology, focal adhesions, cytoskeletal contractility, and stem cell differentiation. Furthermore, these micropost arrays reveal that changes in cytoskeletal contractility can precede stem cell differentiation and be utilized as a non-destructive predictor for fate decisions at the single cell level.
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Fu, Jianping. "Mechanical Regulation of Stem Cell Differentiation on Geometrically Modulated Elastomeric Substrates". En ASME 2010 First Global Congress on NanoEngineering for Medicine and Biology. ASMEDC, 2010. http://dx.doi.org/10.1115/nemb2010-13199.
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We report the use of micromolded elastomeric micropost arrays to modulate substrate rigidity independently of effects on adhesive and other material surface properties. We demonstrate that micropost rigidity impacts cell morphology, focal adhesions, cytoskeletal contractility, and stem cell differentiation. Furthermore, these micropost arrays reveal that changes in cytoskeletal contractility can precede stem cell differentiation and be utilized as a non-destructive predictor for fate decisions at the single cell level.
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Silverstein, Amy M. y Robert L. Mauck. "Mesenchymal Stem Cell Morphology in a Fibrous Microenvironment With Length Scales Matching the Native Meniscus". En ASME 2012 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/sbc2012-80729.
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The meniscus is a crescent shaped fibrocartilage in the knee comprised of a circumferentially aligned collagenous extracellular matrix (ECM) that functions to transmit load and enhance joint stability. The meniscus ECM varies as a function of region, where the inner meniscus is comprised of 70% collagen (60% type II vs. 40% type I), while the outer meniscus contains 80% collagen (99% type I) [1]. Similarly, cells within the inner meniscus are rounder and more ‘chondrocyte-like’, while those in the outer meniscus are elongated and ‘fibroblast-like’ [2]. Injury of the meniscus alters joint loading and hastens the onset of osteoarthritis. As meniscus healing is limited, there exists a need for functional meniscus replacements.
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Finan, John D. y Farshid Guilak. "Osmotic Stress Affects Nuclear Morphology and Genome Architecture". En ASME 2009 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2009. http://dx.doi.org/10.1115/sbc2009-205759.
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The spatial organization of the genome influences its function [1]. Therefore, physical signals that deform the nucleus and the genome within may directly affect gene transcription and translation. In articular chondrocytes, nuclear deformation in response to osmotic stress is not sensitive to actin organization [2]. However, articular chondrocytes differ from most mammalian cells in that they remain round with cortically organized actin in monolayer culture. Adherent cells such as adipose stem cells (ASCs) spread in monolayer culture, forming a more typical, highly bundled actin cytoskeleton. These actin bundles exert tensile stress on the nucleus so we hypothesized that the osmotic sensitivity of the cell nucleus would be modulated by actin organization in ASCs. The osmotic sensitivity of the nucleus was quantified by measuring changes in the size and shape of the nucleus and the spatial arrangement of the chromatin within using 3D confocal microscopy.
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Sumrall, Colin D. y Aidan Sweeney. "MORPHOLOGY AND FUNCTION OF THE SPIRALING PIVOT POINTS IN THE PROXIMAL STEM OF GLYPTOCYSTITOID RHOMBIFERAN ECHINODERMS". En 68th Annual GSA Southeastern Section Meeting - 2019. Geological Society of America, 2019. http://dx.doi.org/10.1130/abs/2019se-327060.
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Sweeney, Aidan y Colin D. Sumrall. "MODERN ECOLOGY AND ANCIENT STEMMED ECHINODERMS: REVIEWING RHOMBIFERAN STEM MORPHOLOGY THROUGH THE LENS OF ORGANISMAL ECOLOGY". En GSA Annual Meeting in Phoenix, Arizona, USA - 2019. Geological Society of America, 2019. http://dx.doi.org/10.1130/abs/2019am-333880.
Texto completoInformes sobre el tema "Morphology of stem"
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Wong, E. A. y Z. Uni. Modulating intestinal cellular maturation and differentiation in broilers by in ovo feeding. Israel: United States-Israel Binational Agricultural Research and Development Fund, 2018. http://dx.doi.org/10.32747/2018.8134161.bard.
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Mortality in a broiler flock will typically range from 4-5% of the population over the course of 6- 7 weeks in the U.S. and 7-8% of the population in Israel. Suboptimal intestinal maturation and functionality are one of the major factors that contribute to early age mortality and hinder flock body weight uniformity. The development of absorptive and secretory functions is orchestrated by differentiation of cells that arise from stem cells. Supplying compounds by in ovo feeding (IOF) during late embryogenesis provides nutrients that may change the dynamics of stem cell differentiation. We hypothesize that the introduction of specific nutrients or probiotics to the late embryonic chick via IOF will result in an acceleration of the maturation of the small intestine as measured by villus/crypt morphology and the number and distribution of absorptive and secretory cells. A chick that can absorb nutrients more efficiently by increasing the number of cells expressing nutrient transporters and resist enteric pathogens by increasing the number of cells expressing mucin and host defense peptides will be healthier at hatch. This chick may have less need for antibiotics and may show reduced early mortality. The objectives of this proposal are to: 1) develop a model for the development of putative stem cells and absorptive/secretory cells in the small intestine of the late embryonic and early post hatch broiler. 2) determine the ability of IOF of nutrients to modulate the population of differentiated cells in the intestine. 3) determine the ability of IOF of probiotics to modulate the population of differentiated cells in the intestine. 4) reduce early mortality and increase body weight uniformity by IOF of selected nutrients or probiotics. This proposal combines the IOF expertise of Zehava Uni (Hebrew University) with the RNAscope in situ hybridization technique of Eric Wong (Virginia Tech). Previous studies using quantitative PCR to examine expression of genes in the intestine were unable to identify specific cells expressing these genes. RNAscope allows the ability to identify putative stem, absorptive and secretory cells in the small intestine. Thus, we will be able to investigate the effect of IOF on the presence of intestinal absorptive and secretory cells at the cellular level. Understanding the mechanisms for intestinal development and function are key to maintaining peak growth and health of chickens and thus would be of great economic benefit to the poultry industry.
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Halevy, Orna, Sandra Velleman y Shlomo Yahav. Early post-hatch thermal stress effects on broiler muscle development and performance. United States Department of Agriculture, enero de 2013. http://dx.doi.org/10.32747/2013.7597933.bard.
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In broilers, the immediate post-hatch handling period exposes chicks to cold or hot thermal stress, with potentially harmful consequences to product quantity and quality that could threaten poultry meat marketability as a healthy, low-fat food. This lower performance includes adverse effects on muscle growth and damage to muscle structure (e.g., less protein and more fat deposition). A leading candidate for mediating the effects of thermal stress on muscle growth and development is a unique group of skeletal muscle cells known as adult myoblasts (satellite cells). Satellite cells are multipotential stem cells that can be stimulated to follow other developmental pathways, especially adipogenesis in lieu of muscle formation. They are most active during the first week of age in broilers and have been shown to be sensitive to environmental conditions and nutritional status. The hypothesis of the present study was that immediate post-hatch thermal stress would harm broiler growth and performance. In particular, growth characteristics and gene expression of muscle progenitor cells (i.e., satellite cells) will be affected, leading to increased fat deposition, resulting in long-term changes in muscle structure and a reduction in meat yield. The in vitro studies on cultured satellite cells derived from different muscle, have demonstrated that, anaerobic pectoralis major satellite cells are more predisposed to adipogenic conversion and more sensitive during myogenic proliferation and differentiation than aerobic biceps femoris cells when challenged to both hot and cold thermal stress. These results corroborated the in vivo studies, establishing that chronic heat exposure of broiler chicks at their first two week of life leads to impaired myogenicity of the satellite cells, and increased fat deposition in the muscle. Moreover, chronic exposure of chicks to inaccurate temperature, in particular to heat vs. cold, during their early posthatch periods has long-term effects of BW, absolute muscle growth and muscle morphology and meat quality. The latter is manifested by higher lipid and collagen deposition and may lead to the white striping occurrence. The results of this study emphasize the high sensitivity of muscle progenitor cells in the early posthatch period at a time when they are highly active and therefore the importance of rearing broiler chicks under accurate ambient temperatures. From an agricultural point of view, this research clearly demonstrates the immediate and long-term adverse effects on broiler muscling and fat formation due to chronic exposure to hot stress vs. cold temperatures at early age posthatch. These findings will aid in developing management strategies to improve broiler performance in Israel and the USA. BARD Report - Project4592 Page 2 of 29
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Yahav, Shlomo, John McMurtry y Isaac Plavnik. Thermotolerance Acquisition in Broiler Chickens by Temperature Conditioning Early in Life. United States Department of Agriculture, 1998. http://dx.doi.org/10.32747/1998.7580676.bard.
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The research on thermotolerance acquisition in broiler chickens by temperature conditioning early in life was focused on the following objectives: a. To determine the optimal timing and temperature for inducing the thermotolerance, conditioning processes and to define its duration during the first week of life in the broiler chick. b. To investigate the response of skeletal muscle tissue and the gastrointestinal tract to thermal conditioning. This objective was added during the research, to understand the mechanisms related to compensatory growth. c. To evaluate the effect of early thermo conditioning on thermoregulation (heat production and heat dissipation) during 3 phases: (1) conditioning, (2) compensatory growth, (3) heat challenge. d. To investigate how induction of improved thermotolerance impacts on metabolic fuel and the hormones regulating growth and metabolism. Recent decades have seen significant development in the genetic selection of the meat-type fowl (i.e., broiler chickens); leading to rapid growth and increased feed efficiency, providing the poultry industry with heavy chickens in relatively short growth periods. Such development necessitates parallel increases in the size of visceral systems such as the cardiovascular and the respiratory ones. However, inferior development of such major systems has led to a relatively low capability to balance energy expenditure under extreme conditions. Thus, acute exposure of chickens to extreme conditions (i.e., heat spells) has resulted in major economic losses. Birds are homeotherms, and as such, they are able to maintain their body temperature within a narrow range. To sustain thermal tolerance and avoid the deleterious consequences of thermal stresses, a direct response is elicited: the rapid thermal shock response - thermal conditioning. This technique of temperature conditioning takes advantage of the immaturity of the temperature regulation mechanism in young chicks during their first week of life. Development of this mechanism involves sympathetic neural activity, integration of thermal infom1ation in the hypothalamus, and buildup of the body-to-brain temperature difference, so that the potential for thermotolerance can be incorporated into the developing thermoregulation mechanisms. Thermal conditioning is a unique management tool, which most likely involves hypothalamic them1oregulatory threshold changes that enable chickens, within certain limits, to cope with acute exposure to unexpected hot spells. Short-tem1 exposure to heat stress during the first week of life (37.5+1°C; 70-80% rh; for 24 h at 3 days of age) resulted in growth retardation followed immediately by compensatory growth" which resulted in complete compensation for the loss of weight gain, so that the conditioned chickens achieved higher body weight than that of the controls at 42 days of age. The compensatory growth was partially explained by its dramatic positive effect on the proliferation of muscle satellite cells which are necessary for further muscle hypertrophy. By its significant effect of the morphology and functioning of the gastrointestinal tract during and after using thermal conditioning. The significant effect of thermal conditioning on the chicken thermoregulation was found to be associated with a reduction in heat production and evaporative heat loss, and with an increase in sensible heat loss. It was further accompanied by changes in hormones regulating growth and metabolism These physiological responses may result from possible alterations in PO/AH gene expression patterns (14-3-3e), suggesting a more efficient mechanism to cope with heat stress. Understanding the physiological mechanisms behind thermal conditioning step us forward to elucidate the molecular mechanism behind the PO/AH response, and response of other major organs. The thermal conditioning technique is used now in many countries including Israel, South Korea, Australia, France" Ecuador, China and some places in the USA. The improvement in growth perfom1ance (50-190 g/chicken) and thermotolerance as a result of postnatal thermal conditioning, may initiate a dramatic improvement in the economy of broiler's production.
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Fridman, Eyal y Eran Pichersky. Tomato Natural Insecticides: Elucidation of the Complex Pathway of Methylketone Biosynthesis. United States Department of Agriculture, diciembre de 2009. http://dx.doi.org/10.32747/2009.7696543.bard.
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Plant species synthesize a multitude of specialized compounds 10 help ward off pests. and these in turn may well serve as an alternative to synthetic pesticides to reduce environmental damage and health risks to humans. The general goal of this research was to perform a genetic and biochemical dissection of the natural-insecticides methylketone pathway that is specific to the glandular trichomes of the wild species of tomato, Solanumhabrochaites f. glabratum (accession PI126449). Previous study conducted by us have demonstrated that these compounds are synthesized de novo as a derivate pathway of the fatty acid biosynthesis, and that a key enzyme. designated MethylketoneSynthase 1 (MKS 1). catalyzes conversion of the intermediate B-ketoacyl- ACPs to the corresponding Cn-1 methylketones. The approach taken in this proposed project was to use an interspecific F2 population. derived from the cross between the cultivated lV182 and the wild species PIl26449. for three objectives: (i) Analyze the association between allelic status of candidate genes from the fatty acid biosynthesis pathway with the methylketone content in the leaves (ii) Perform bulk segregant analysis of genetic markers along the tomato genome for identifying genomic regions that harbor QTLs for 2TD content (iii) Apply differential gene expression analysis using the isolated glands of bulk segregant for identifying new genes that are involved in the pathway. The genetic mapping in the interspecific F2 population included app. 60 genetic markers, including the candidate genes from the FAS pathway and SSR markers spread evenly across the genome. This initial; screening identified 5 loci associated with MK content including the candidate genes MKS1, ACC and MaCoA:ACP trans. Interesting observation in this genetic analysis was the connection between shape and content of the glands, i.e. the globularity of the four cells, typical to the wild species. was associated with increased MK in the segregating population. In the next step of the research transcriptomic analysis of trichomes from high- and 10w-MK plants was conducted. This analysis identified a new gene, Methy1ketone synthase 2 (MKS2), whose protein product share sequence similarity to the thioesterase super family of hot-dog enzymes. Genetic analysis in the segregating population confirmed its association with MK content, as well as its overexpression in E. coli that led to formation of MK in the media. There are several conclusions drawn from this research project: (i) the genetic control of MK accumulation in the trichomes is composed of biochemical components in the FAS pathway and its vicinity (MKS 1 and MKS2). as well as genetic factors that mediate the morphology of these specialized cells. (ii) the biochemical pathway is now realized different from what was hypothesized before with MKS2 working upstream to I\1KS 1 and serves as the interface between primary (fatty acids) and secondary (MK) metabolism. We are currently testing the possible physical interactions between these two proteins in vitro after the genetic analysis showed clear epistatic interactions. (iii) the regulation of the pathway that lead to specialized metabolism in the wild species is largely mediated by transcription and one of the achievements of this project is that we were able to isolate and verify the specificity of the MKS1 promoter to the trichomes which allows manipulation of the pathways in these cells (currently in progress). The scientific implications of this research project is the advancement in our knowledge of hitherto unknown biochemical pathway in plants and new leads for studying a new family in plants (hot dog thioesterase). The agricultural and biotechnological implication are : (i) generation of new genetic markers that could assist in importing this pathway to cultivated tomato hence enhancing its natural resistance to insecticides, (ii) the discovery of MKS2 adds a new gene for genetic engineering of plants for making new fatty acid derived compounds. This could be assisted with the use of the isolated and verified MKS1 promoter. The results of this research were summarized to a manuscript that was published in Plant Physiology (cover paper). to a chapter in a proceeding book. and one patent was submitted in the US.