Journal articles: 'Egg apparatus'

1

Wilms, H. J. "Ultrastructure of the egg apparatus of Spinacia." Acta Societatis Botanicorum Poloniae 50, no. 1-2 (2014): 165–68. http://dx.doi.org/10.5586/asbp.1981.024.

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The egg apparatus of <em>Spinacia</em> was studied from the time the embryo sac reaches its maximal size to just before fertilization, i.e., until about 8-9 hours after pollination. At maturity each synergid has a large elongated nucleus and prominent chalazal vacuoles, Numerous mitochondria, plastids, dictyosomes, free ribosomes, rough endoplasmic reticulum (RER), and lipid bodies are present. The cell wall exists only around the micropylar half of the synergids and each cell has a distinct, striated filiform apparatus. In general, degeneration of one synergid starts after pollination. The egg cell has a spherical nucleus and nucleolus and a large micropylar vacuole. Numerous mitochondria, some plastids with starch grains, dictyosomes, free ribosomes, and HER are present. A continuous cell wall is absent around the chalazal end of the egg cell.

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2

Halada, Richard. "Rotational Collision Apparatus for Indoor Egg Drops." Physics Teacher 41, no. 5 (2003): 305. http://dx.doi.org/10.1119/1.1571269.

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Sumner, M. J., and L. Van Caeseele. "The ultrastructure and cytochemistry of the egg apparatus of Brassica campestris." Canadian Journal of Botany 67, no. 1 (1989): 177–90. http://dx.doi.org/10.1139/b89-026.

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The egg apparatus of Brassica campestris L. cv. Candle (canola-rapeseed) is composed of an egg and two synergids juxtaposed at the extreme micropylar end of the megagametophyte with the egg cell displaced in a chalazal direction. The cell walls of the synergids and egg are uniformly PAS and PA–TCH–SP-positive, but contained β-linked glucans only in the micropylar region. The number and development of the cytoplasmic organelles suggested that the egg cell is relatively inactive metabolically while the synergid cells are active. The synergids contain large numbers of dictyosomes with PA–TCH–SP-positive vesicles at the maturing face. These vesicles appear to fuse with the plasma membrane in the region of the filiform apparatus. The filiform apparatuses of the synergids are micropylar finger-like projections that extend into the cytoplasm of the synergid. These are PAS and PA–TCH–SP-positive, fluoresce in uv light when stained with Calcofluor, and show a positive response for acidic polysaccharides when stained with alcian blue. After treatment with cellulase, fluorescence was not observed. The incipient degenerate synergid was intensely stained by cationic dyes 24–36 h after anthesis.

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Sun, Yang, Xiu Wang, Lin Pan, et al. "Plant egg cell fate determination depends on its exact position in female gametophyte." Proceedings of the National Academy of Sciences 118, no. 8 (2021): e2017488118. http://dx.doi.org/10.1073/pnas.2017488118.

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Plant fertilization involves both an egg cell, which fuses with a sperm cell, and synergid cells, which guide pollen tubes for sperm cell delivery. Therefore, egg and synergid cell functional specifications are prerequisites for successful fertilization. However, how the egg and synergid cells, referred to as the “egg apparatus,” derived from one mother cell develop into distinct cell types remains an unanswered question. In this report, we show that the final position of the nuclei in female gametophyte determines the cell fate of the egg apparatus. We established a live imaging system to visualize the dynamics of nuclear positioning and cell identity establishment in the female gametophyte. We observed that free nuclei should migrate to a specific position before egg apparatus specialization. Artificial changing in the nuclear position on disturbance of the actin cytoskeleton, either in vitro or in vivo, could reset the cell fate of the egg apparatus. We also found that nuclei of the same origin moved to different positions and then showed different cell identities, whereas nuclei of different origins moved to the same position showed the same cell identity, indicating that the final positions of the nuclei, rather than specific nucleus lineage, play critical roles in the egg apparatus specification. Furthermore, the active auxin level was higher in the egg cell than in synergid cells. Auxin transport inhibitor could decrease the auxin level in egg cells and impair egg cell identity, suggesting that directional and accurate auxin distribution likely acts as a positional cue for egg apparatus specialization.

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5

Folsom, M. W., and D. D. Cass. "Embryo sac development in soybean: cellularization and egg apparatus expansion." Canadian Journal of Botany 68, no. 10 (1990): 2135–47. http://dx.doi.org/10.1139/b90-279.

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An ultrastructural study of soybean embryo sac development was performed. Prior to the final mitotic division and cellularization a nuclear rearrangement occurs that involves the chalazal movement of one of the two micropylar nuclei. During cellularization this nucleus divides to form the egg and micropylar polar nuclei and produces the wall that separates the central ceil from title space occupied by the egg apparatus. Within this space the other nucleus divides to form the two synergid nuclei and one of the two walls that separate the egg and synergid cells from one another. Egg apparatus cells are initially densely cytoplasmic, each is enclosed by thick, highly dissected walls, and they are all similar with respect to distribution of organelles except that synergid nuclei are micropylar to the egg nucleus. There is a progressive thinning and segmentation of egg apparatus walls during cellular expansion until they resemble the beaded chain structure seen in the mature egg and synergid cell walls. Taken as a whole these observations suggest that the chalazal movement of one of the two micropylar nuclei during the 4-nucleate stage is pivotal in determining future patterns of egg apparatus development.

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6

Flores-Tornero, María, Sebastian Proost, Marek Mutwil, Charles P. Scutt, Thomas Dresselhaus, and Stefanie Sprunck. "Transcriptomics of manually isolated Amborella trichopoda egg apparatus cells." Plant Reproduction 32, no. 1 (2019): 15–27. http://dx.doi.org/10.1007/s00497-019-00361-0.

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Cass, D. D., D. J. Peteya, and B. L. Robertson. "Megagametophyte development in Hordeum vulgare. 2. Later stages of wall development and morphological aspects of megagametophyte cell differentiation." Canadian Journal of Botany 64, no. 10 (1986): 2327–36. http://dx.doi.org/10.1139/b86-305.

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The micropylar quartet of nuclei in the barley megagametophyte is first partitioned by a vertical wall between the synergid nuclei and by an initially horizontal wall between the micropylar polar and egg nuclei. The latter wall continues to grow in an expanding horizontal plane forming much of the upper wall of all three egg apparatus cells and eventually fusing with the megagametophyte wall peripherally. A branch of the egg – polar nucleus wall grows in a micropylar direction and becomes attached to the megagametophyte wall. After partitioning, the egg apparatus is composed of three flat cells having a ceiling wall and two upright supporting walls, which are fused centrally. The micropylar polar nucleus lies just chalazal to the ceiling wall. Expansion of the egg apparatus results in rounding of all three cells followed by lengthening and thinning of their walls in contact with the central cell. Probable membrane contacts may facilitate sperm transmission after pollination. Partitioning of the chalazal quartet of nuclei exhibits many similarities to that of the egg apparatus but with a different cellular arrangement. Transfer cell wall ingrowths appear in cells at both poles of the megagametophyte. Such ingrowths appear in the two synergid cells, representing the filiform apparatus. They also develop in two of the original three antipodal cells where these cells are in contact with the megagametophyte wall. Either the micropylar or chalazal polar nucleus migrates to a position close to the other polar nucleus. Partial fusion of polar nuclei occurs later.

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8

MAEDA, Eizo, and Kazuko MAEDA. "Ultrastructure of egg apparatus of rice (Oryza sativa) after anthesis." Japanese journal of crop science 59, no. 1 (1990): 179–97. http://dx.doi.org/10.1626/jcs.59.179.

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9

Marton, M. L. "Micropylar Pollen Tube Guidance by Egg Apparatus 1 of Maize." Science 307, no. 5709 (2005): 573–76. http://dx.doi.org/10.1126/science.1104954.

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10

Schram, T. A., and P. A. Heuch. "The egg string attachment mechanism of selected pennellid copepods." Journal of the Marine Biological Association of the United Kingdom 81, no. 1 (2001): 23–32. http://dx.doi.org/10.1017/s0025315401003368.

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The anatomy of the hook apparatus that attaches egg strings to the fish parasites Haemobaphes cyclopterina, Lernaeocera branchialis, Lernaeocera lusci, Lernaeenicus sprattae, Sarcotretes scopeli and Pennella balaenoptera (Copepoda: Pennellida) is described and illustrated. The hook rises from a cupulate base, extending posteriorly and anteriorly in the body cavity. The suspension of the apparatus in the trunk of the different species differs, but the function is similar. The hook tip enters the genital antrum, nearly penetrates the proximal end of the egg string, and continues into a notch on the antrum wall. The apex of the egg string acquires a concave depression like the finger end of a glove. In this way the string is mechanically attached inside the female genital segment. The mobile ectoparasites Lepeophtheirus salmonis and Hatschekia hippoglossi have hooks which function similarly, but perforate the strings.

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11

Jane, Wann-Neng. "Ultrastructure of the Maturing Egg Apparatus in Arundo formosana Hack. (Poaceae)." International Journal of Plant Sciences 158, no. 6 (1997): 713–26. http://dx.doi.org/10.1086/297483.

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12

Yang, Wei, Richard A. Jefferson, Eric Huttner, James M. Moore, Wendy B. Gagliano, and Ueli Grossniklaus. "An Egg Apparatus-Specific Enhancer of Arabidopsis, Identified by Enhancer Detection." Plant Physiology 139, no. 3 (2005): 1421–32. http://dx.doi.org/10.1104/pp.105.068262.

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13

Flores-Tornero, María, Sebastian Proost, Marek Mutwil, Charles P. Scutt, Thomas Dresselhaus, and Stefanie Sprunck. "Correction to: Transcriptomics of manually isolated Amborella trichopoda egg apparatus cells." Plant Reproduction 32, no. 2 (2019): 229. http://dx.doi.org/10.1007/s00497-019-00367-8.

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14

Gao, Chao, Rui Yang, and Deyi Yuan. "Characteristics of Developmental Differences between Fertile and Aborted Ovules in Camellia oleifera." Journal of the American Society for Horticultural Science 142, no. 5 (2017): 330–36. http://dx.doi.org/10.21273/jashs04164-17.

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Camellia oleifera is an important woody edible oil plant in southern China. In this study, the developmental differences in ovules at different positions in the ovary of C. oleifera were observed. The developmental type and characteristics of aborted ovules, ratios of normal and aborted ovules, and their developmental differences after flowering were examined. Ovules near the stylar end and in the middle exhibit normal development and are able to form embryo sacs; lower ovules near the pedicel end are usually aborted. The proportion of abortion of four examined cultivars ranges from 10.2% to 33.3%. Aborted ovules can be divided into four categories: 1) nascent egg apparatus lacking distinguishable cells; 2) completely absent egg apparatus structure consisting of flocculent tissue; 3) lack of tissue, comprising only integument cells; and 4) the inner integument not constituting a micropyle channel, with incomplete egg apparatus development and generating abnormal ovules. At 120 days after pollination (DAP), significant distinguishable size differences were found between fertile and aborted ovules; aborted ovules ceased growth at 180 DAP. On fruit maturation, aborted seeds were still attached to the placenta.

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15

Watanabe, Akihiko, and Kazuo Onitake. "The Urodele Egg-Coat as the Apparatus Adapted for the Internal Fertilization." Zoological Science 19, no. 12 (2002): 1341–47. http://dx.doi.org/10.2108/zsj.19.1341.

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16

BANIEL, A., A. FAINS, and Y. POPINEAU. "Foaming Properties of Egg Albumen with a Bubbling Apparatus Compared with Whipping." Journal of Food Science 62, no. 2 (1997): 377–81. http://dx.doi.org/10.1111/j.1365-2621.1997.tb04005.x.

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17

Mansfield, S. G., L. G. Briarty, and S. Erni. "Early embryogenesis in Arabidopsis thaliana. I. The mature embryo sac." Canadian Journal of Botany 69, no. 3 (1991): 447–60. http://dx.doi.org/10.1139/b91-062.

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Arabidopsis thaliana has a seven-celled eight-nucleate megagametophyte of the Polygonum type; each cell type displays a different form of structural specialization. The egg apparatus cells are highly polarized; the egg has a large micropylar vacuole and chalazally sited nucleus, whereas the opposite is true for the synergids. At the chalazal region of the egg apparatus cells there are no cell wall boundaries, although their plasmalemmas are in intimate contact. The common wall between the two synergids is thin and irregular and contains plasmodesmatal connections. The synergid cytoplasm is rich in organelles; profiles of rough endoplasmic reticulum appear in masses of parallel stacked cisternae, and large accumulations of mitochondria occur adjacent to the filiform apparatus. The egg cell cytoplasm is quiescent; ribosome concentration and frequencies of dictyosomes and endoplasmic reticulum are noticeably lower and plastids are poorly differentiated. The central cell is long and vacuolate with a large diploid nucleus; fusion of the polar nuclei occurs prior to embryo sac maturity. The cytoplasm contains numerous starch-containing plastids accumulated in a shell around the nucleus. A high ribosome concentration and the absence of vacuoles and dictyosomes typifies the antipodal cell cytoplasm. All antipodal cells are interconnected by plasmodesmata as well as being connected to the nucellus and central cell. Key words: Arabidopsis, embryo sac, embryogenesis, cell specializations, stereology.

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18

Riparbelli, M. G., and G. Callaini. "Meiotic spindle organization in fertilized Drosophila oocyte: presence of centrosomal components in the meiotic apparatus." Journal of Cell Science 109, no. 5 (1996): 911–18. http://dx.doi.org/10.1242/jcs.109.5.911.

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We examined spindle reorganization during the completion of meiosis in fertilized and unfertilized oocytes of Drosophila using indirect immunofluorescence and laser scanning confocal microscopy. The results defined a complex pathway of spindle assembly during resumption of meiosis, and revealed a transient array of microtubules radiating from the equatorial region of the spindle towards discrete foci in the egg cortex. A monastral array of microtubules was observed between twin metaphase II spindles in fertilized and unfertilized eggs. The microtubules originated from disk-shaped material stained with Rb188 antibody specific for an antigen associated with the centrosome of Drosophila embryos. The Drosophila egg, therefore, contains a maternal pool of centrosomal components undetectable in mature inactivated oocytes. These components nucleate microtubules in a monastral array after activation, but are unable to organize bipolar spindles.

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19

Ishii, Ryuichi, and Takashi Shimizu. "Unequal first cleavage in the Tubifex egg: involvement of a monastral mitotic apparatus." Development, Growth and Differentiation 37, no. 6 (1995): 687–701. http://dx.doi.org/10.1046/j.1440-169x.1995.t01-5-00007.x.

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20

Hamaguchi, Y., M. Toriyama, H. Sakai, and Y. Hiramoto. "Distribution of fluorescently labeled tubulin injected into sand dollar eggs from fertilization through cleavage." Journal of Cell Biology 100, no. 4 (1985): 1262–72. http://dx.doi.org/10.1083/jcb.100.4.1262.

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Porcine brain tubulin labeled with fluorescein isothiocyanate (FITC) was able to polymerize by itself and co-polymerize with tubulin purified from starfish sperm flagella. When we injected the FITC-labeled tubulin into unfertilized eggs of the sand dollar, Clypeaster japonicus, and the eggs were then fertilized, the labeled tubulin was incorporated into the sperm aster. When injected into fertilized eggs at streak stage, the tubulin was quickly incorporated into each central region of growing asters. It was clearly visualized that the labeled tubulin, upon reaching metaphase, accumulated in the mitotic apparatus and later disappeared over the cytoplasm during interphase. The accumulation of the fluorescence in the mitotic apparatus was observed repeatedly at successive cleavage. After lysis of the fertilized eggs with a microtubule-stabilizing solution, fluorescent fibrous structures around the nucleus and those of the sperm aster and the mitotic apparatus were preserved and coincided with the fibrous structures observed by polarization and differential interference microscopy. We found the FITC-labeled tubulin to be incorporated into the entire mitotic apparatus within 20-30 s when injected into the eggs at metaphase or anaphase. This rapid incorporation of the labeled tubulin into the mitotic apparatus suggests that the equilibrium between mitotic microtubules and tubulin is attained very rapidly in the living eggs. Axonemal tubulin purified from starfish sperm flagella and labeled with FITC was also incorporated into microtubular structures in the same fashion as the FITC-labeled brain tubulin. These results suggest that even FITC-labeled heterogeneous tubulins undergo spatial and stage-specific regulation of assembly-disassembly in the same manner as does sand dollar egg tubulin.

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21

You, Ruilin, and William A. Jensen. "Ultrastructural observations of the mature megagametophyte and the fertilization in wheat (Triticum aestivum)." Canadian Journal of Botany 63, no. 2 (1985): 163–78. http://dx.doi.org/10.1139/b85-019.

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The mature embryo sac of wheat contains an egg apparatus composed of an egg cell and two synergids at the micropylar end, a central cell with two large polar nuclei in the middle, and a mass of 20 to 30 antipodals at the chalazal end. A comparison was made of the ultrastructural features of the various cells of the embryo sac. The features included the position of the nucleus and vacuoles, the number, structure, and distribution of organelles, and the extent of the cell walls surrounding each cell. The pollen tube enters one synergid through the filiform apparatus from the micropyle. The penetration and discharge of the pollen tube causes the further degeneration of that synergid, which had already undergone changes before pollination. The second synergid does not change further in appearance following the penetration of the first by the pollen-altered tube. Half an hour after pollination at 20–25 °C, two male nuclei are seen in the cytoplasm of the egg and the central cell. At about 1 h after pollination, one sperm has made contact with the egg nucleus, while the other sperm is fusing with one of the polar nuclei.

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22

Tanasichuk, R. W., C. Armstrong, and D. M. Ware. "An Improved Photo-Electric Fish Egg Counter." Canadian Journal of Fisheries and Aquatic Sciences 42, no. 7 (1985): 1255–58. http://dx.doi.org/10.1139/f85-156.

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We describe an improved design and operating procedure for a photo-electric fish egg counter. The design was simplified so that the apparatus can function as a flow-through system using tap water. The procedure for operating the counter was changed so that coincidence counting can be corrected for. Triplicate fecundity determinations, made gravimetrically for 10 randomly selected Pacific herring (Clupea harengus pallasi), were repeated using our method to compare the accuracy and precision of estimates made with both procedures. Mean fecundity estimates did not differ significantly between methods. The precision of estimates made using the counter was at least sixfold greater, and single determinations were accurate to within 5% of the true mean value with 95% probability. Our procedure is also less tedious and about 70% faster than the gravimetric method. The counter, unmodified, should be capable of counting eggs from 25 marine and 6 freshwater fish species. We believe that it can be easily adapted to count eggs that differ substantially in size from those of Pacific herring.

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23

Schram, Thomas A. "The egg string attachment mechanism in salmon lice Lepeophtheirus salmonis (Copepoda: Caligidae)." Contributions to Zoology 69, no. 1-2 (2000): 21–29. http://dx.doi.org/10.1163/18759866-0690102002.

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The anatomy of the genital complex and the hook apparatus that keeps the trailing egg strings in position, are illustrated and described. Based on light and scanning electron microscopy, it is shown how the sacs are mechanically secured by the penetration of a pair of hooks through the proximal ends of the strings. The muscle groups that move the hooks are described and a mechanism of operation is suggested.

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24

Davenport, Thomas L. "529 Pollen Tube Growth in Stage 2 Pollinated Avocado Flowers." HortScience 35, no. 3 (2000): 486C—486. http://dx.doi.org/10.21273/hortsci.35.3.486c.

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Individual avocado (Persea americana Mill.) flowers are perfect, opening two times to display two distinct reproductive stages on consecutive days. Stage 1 focuses on presentation of pistils and Stage 2 on presentation of pollen. The Stage 1 opening offers the greatest opportunity for outcrossing due to the absence of available pollen in that stage. Stage 2 flowers, however, are self-pollinated within flowers in direct proportion to the number of white stigmas present at the time of pollen dispersal. The potential success of these self-pollination events was examined in orchard trees of seven commercial Florida cultivars: Booth 7, Brooks Late, Choquette, Monroe, Simmonds, Tonnage, and Tower 2 and compared with hand-pollinations from complementary cultivars (cross pollination) and from flowers of the same cultivar (close pollination). The furthest advancement of pollen tubes down styles and into the ovaries on their way to the egg apparatus was noted in hundreds of individual flowers 24 and 48 h after pollen deposition on receptive white stigmas of the Stage 2 flowers. Virtually none of the seven cultivars exhibited pollen tubes reaching the egg apparatus by 24 h after deposition. By 48 h, however, pollen tubes had reached the egg apparatus in 25% to 85% of the pollinated flowers, depending upon cultivar. Pollen source was inconsequential. The results demonstrate the success of self-pollination in avocados. It is especially important for cultivars growing in humid climates, which display a high proportion of receptive white stigmas in Stage 2.

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25

van Rensburg, Josephina G. J., and P. J. Robbertse. "Seed development of Ornithogalum dubium, with special reference to fertilization and the egg apparatus." South African Journal of Botany 54, no. 3 (1988): 196–202. http://dx.doi.org/10.1016/s0254-6299(16)31319-9.

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26

Fu, Ying, Ming Yuan, B. Q. Huang, Hong-Yuan Yang, Sze-Yong Zee, and T. P. O'Brien. "Changes in actin organization in the living egg apparatus of Torenia fournieri during fertilization." Sexual Plant Reproduction 12, no. 6 (2000): 315–22. http://dx.doi.org/10.1007/s004970000026.

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27

Kane, R. E. "TAME stabilizes the cortex and mitotic apparatus of the sea urchin egg during isolation." Experimental Cell Research 162, no. 2 (1986): 495–506. http://dx.doi.org/10.1016/0014-4827(86)90353-8.

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28

Zimmerman, S., A. M. Zimmerman, G. D. Fullerton, R. F. Luduena, and I. L. Cameron. "Water ordering during the cell cycle: nuclear magnetic resonance studies of the sea-urchin egg." Journal of Cell Science 79, no. 1 (1985): 247–57. http://dx.doi.org/10.1242/jcs.79.1.247.

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Nuclear magnetic resonance was used to measure spin-lattice water proton relaxation times (T1) during the first cell cycle in sea-urchin zygotes of packed Strongylocentrotus purpuratus. Following insemination there was a 90% increase in the T1 value. The increase in T1 at fertilization could be accounted for by the accumulation of extracellular fluid between the egg surface and the fertilization envelope. The T1 value then remained without change during the first cell cycle, except at metaphase when there was a significant 13% decrease. The lowered T1 values measured at metaphase were not related to a change in the water content of the packed cells, which remained fairly constant throughout the cell cycle. High hydrostatic pressure, low temperature and colchicine (agents that depolymerize mitotic apparatus microtubules) did not affect the T1 values in fertilized eggs. Treatment in vitro of a microtubule protein preparation with low temperature and colchicine resulted in an increased T1, which accompanied the depolymerization of microtubule protein. Since depolymerization of the microtubules associated with the mitotic apparatus by high pressure, colchicine or low temperature does not alter the T1 of water protons in the cell, it is proposed that the increased state of ordered water molecules at metaphase is maintained by nonmicrotubular factor(s) of the metaphase egg.

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Whalley, T., I. Crossley, and M. Whitaker. "Phosphoprotein inhibition of calcium-stimulated exocytosis in sea urchin eggs." Journal of Cell Biology 113, no. 4 (1991): 769–78. http://dx.doi.org/10.1083/jcb.113.4.769.

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We have investigated the role of protein phosphorylation in the control of exocytosis in sea urchin eggs by treating eggs with a thio-analogue of ATP. ATP gamma S (adenosine 5'-O-3-thiotriphosphate) is a compound which can be used as a phosphoryl donor by protein kinases, leading to irreversible protein thiophosphorylation (Gratecos, D., and E.H. Fischer. 1974. Biochem. Biophys. Res. Commun. 58:960-967). Microinjection of ATP gamma S inhibits cortical granule exocytosis, but has no effect on the sperm-egg signal transduction mechanisms which normally cause exocytosis by generating an increase in [Ca2+]i. ATP gamma S requires cytosolic factors for its inhibition of cortical granule exocytosis: it does not affect exocytosis when applied directly to the isolated exocytotic apparatus. Our data suggest that ATP gamma S irreversibly inhibits exocytosis via thiophosphorylation of proteins associated with the egg cortex. We have identified two thiophosphorylated proteins (33 and 27 kD) that are associated with the isolated exocytotic apparatus. They may mediate the inhibition of exocytosis by ATP gamma S. In addition, we show that okadaic acid, an inhibitor of phosphoprotein phosphatases, prevents cortical granule exocytosis at fertilization without affecting calcium mobilization. Like ATP gamma S, okadaic acid has no effect on exocytosis in vitro. Our results suggest that an inhibitory phosphoprotein can obstruct calcium-stimulated exocytosis in sea urchin eggs; on the other hand, they do not readily support the idea that a protein phosphatase is an essential component of the mechanism controlling exocytosis.

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Brajkovic, M., Z. Nikolic, S. B. Curcic, Ivana Zivic, and D. Stojanovic. "Morphological changes of the ovipositor in species of Cheloninae (Hymenoptera: Braconidae) in the course of adaptation to egg-larval parasitism." Archives of Biological Sciences 62, no. 2 (2010): 469–77. http://dx.doi.org/10.2298/abs1002469b.

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Adaptation to the parasitic way of life in braconids has led to a number of consequences in the morphology of the ovipositor of females. As a derivative of the paired appendages of the eighth and ninth abdominal segments, the ovipositor is a complex morphological structure of gonapophysal origin whose muscular system makes possible highly complex movements during the act of egg-laying. In some groups of braconids, imaginal and egg-larval forms of parasitism have developed in the course of evolution. In adapting to these two forms of parasitism, the ovipositor underwent significant changes, while still remaining a successful structure for the paralyzation and laying of eggs in the host. This paper presents a survey of the ovipository apparatus structure in the species of the genera Ascogaster Wesmael, Leptodrepana Shaw, Chelonus Panzer, Microchelonus Szepligeti, and Phanerotoma Wesmael, and gives a review of the changes in structure of the ovipositor during adaptation to egg-larval parasitism.

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Deng, Wei, Yunling Xie, and Yilan Qiu. "Isolation of Sperm and Egg Cells from Pepper." Journal of the American Society for Horticultural Science 143, no. 4 (2018): 310–15. http://dx.doi.org/10.21273/jashs04433-18.

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Pepper (Capsicum annuum) pollen is bicellular and contains a vegetative cell and a generative cell, which divides in pollen tubes to form two sperm cells. Sperm cells of pepper were isolated using an in vivo–in vitro method. Hand-pollinated styles were first grown in vivo for several hours, then cut from their base and cultured in vitro until pollen tubes grew from the cut end. When the pollen tubes were transferred to a breaking solution, sperm cells were released from broken tubes. Viable embryo sac cells of pepper were isolated using enzymatic digestion and mechanical dissection. Isolated ovules were digested using cellulase and pectinase for 40 minutes and then transferred to an enzyme-free solution for mechanical dissection. Three cells of the egg apparatus and a central cell were released from a cut at the chalazal end of each ovule by pressing on the micropylar area of the ovule with a microneedle. Optimal isolation conditions included 11% mannitol, 0.04% CaCl2, 1% bovine serum albumin (BSA), 1% cellulase, 1% pectinase, and 0.3% pectolyase. Using this protocol, populations of pepper egg cells, synergids, and central cells were isolated.

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Sumner, M. J., and L. Van Caeseele. "Ovule development in Brassica campestris: a light microscope study." Canadian Journal of Botany 66, no. 12 (1988): 2459–69. http://dx.doi.org/10.1139/b88-334.

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A light microscope study was made of ovule development in Brassica catnpestris L. cv. Candle (canola, rapeseed), from the initiation of the ovule to the mature megagametophyte. The ovule is bitegmic and campylotropous and exhibits the Polygonum-type of megagametophyte development. The inner integument is dermal in origin from a series of wedge-shaped initials. The outer integument is derived from both dermal and subdermal initials that originate proximal to the inner integument. The megasporocyte arises from an archesporial or primary sporogenous cell. The products of meiosis are a triad or tetrad of megaspores. Expansion of the megagametophyte is micropylar and coincides with the formation of a large central vacuole. The mature binucleate central cell is devoid of the large central vacuole characteristic of the coenocytic and early cellular stages of megagametophyte development. The cell walls of the mature egg apparatus and antipodals are periodic acid – Schiff positive. The antipodals, unlike the cells of the egg apparatus, do not increase in size following their formation.

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Li, Dong Xiao, Hai Yan Hu, Zhen Gang Ru, and Hui Qiao Tian. "Wheat egg in vitro fusion with wheat and green bristlegrass sperm." Zygote 27, no. 3 (2019): 126–30. http://dx.doi.org/10.1017/s0967199418000461.

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SummaryIsolated gametes can be used to investigate fertilization mechanisms, and probe distant hybridization between different species. Pollen grains of wheat and Setaria viridis are tricellular, containing sperm cells at anthesis. Sperm from these plants were isolated by breaking open pollen grains in a osmotic solution. Wheat ovules were digested in an enzyme solution for 20 min, and then transferred to an isolation solution without enzymes to separate egg cells from ovules. The fusion of wheat egg cells with wheat and S. viridis sperm was conducted using an electro-fusion apparatus. Under suitable osmotic pressure (10% mannitol), calcium concentration of 0.001% (CaCl2·2H2O), and a 30–35 V alternating electric field for 15 s, egg cells and sperm adhered to each other and became arranged in a line. Electroporation of the plasma membrane of egg cells and sperm using a 300–500 V direct-current electric field (45 µs amplitude pulse) caused them to fuse.

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Paoli, Francesco, Marco Gottardo, Daniela Marchini, Romano Dallai, and Pio Federico Roversi. "Ultrastructure of the female reproductive apparatus of the egg parasitoid Gryon pennsylvanicum (Ashmead) (Hymenoptera, Platygastridae)." Micron 61 (June 2014): 28–39. http://dx.doi.org/10.1016/j.micron.2014.02.002.

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Vielle, J. Ph, B. L. Burson, E. C. Bashaw, and M. A. Hussey. "Early fertilization events in the sexual and aposporous egg apparatus of Pennisetum ciliare (L.) Link." Plant Journal 8, no. 2 (1995): 309–16. http://dx.doi.org/10.1046/j.1365-313x.1995.08020309.x.

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Wu, Bingbing, Hui Gao, Chao Liu, and Wei Li. "The coupling apparatus of the sperm head and tail†." Biology of Reproduction 102, no. 5 (2020): 988–98. http://dx.doi.org/10.1093/biolre/ioaa016.

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Abstract A strong sperm head–tail coupling apparatus (HTCA) is needed to ensure the integrity of spermatozoa during their fierce competition to fertilize the egg. A lot of HTCA-specific components have evolved to strengthen the attachment of the tail to the implantation fossa at the sperm head. Defects in HTCA formation lead to acephalic spermatozoa syndrome and pathologies of some male infertility. Recent studies have provided insights into the pathogenic molecular mechanisms of acephalic spermatozoa syndrome. Here, we summarize the proteins involved in sperm neck development and focus on their roles in the formation of HTCA. In addition, we discuss the fine structures of the sperm neck in different species from an evolutionary view, highlighting the potential conservative mechanism of HTCA formation.

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Huang, Li, and Wendy Hanna-Rose. "EGF signaling overcomes a uterine cell death associated with temporal mis-coordination of organogenesis within the C. elegans egg-laying apparatus." Developmental Biology 300, no. 2 (2006): 599–611. http://dx.doi.org/10.1016/j.ydbio.2006.08.024.

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Ross, Cynthia M., and Michael J. Sumner. "Development of the unfertilized embryo sac and pollen tubes in the dwarf mistletoe Arceuthobium americanum (Viscaceae)." Canadian Journal of Botany 82, no. 11 (2004): 1566–75. http://dx.doi.org/10.1139/b04-121.

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Megasporogenesis, embryo sac development, and pollen tubes in Arceuthobium americanum Nutt. ex Engelm. were investigated with light, fluorescence, and electron microscopy. The orthotropous ovular structure of A. americanum lacked integuments and possessed a nucellus that was largely continuous with and indistinguishable from the placenta; we coined this structure the placental–nucellar complex (PNC). Two megasporocytes became evident in the tenuinucellate PNC by mid-April, and had undergone bisporic megasporogenesis by mid-May. The upper cell from each dyad (distal to the base of the PNC) became a functional megaspore, although only one would develop into a seven-celled embryo sac. Like typical angiosperm embryo sacs, that of A. americanum possessed an egg cell having the ultrastructure reflective of a quiescent cell, and lacked cellulosic and (or) hemicellulosic wall material between the egg apparatus and central cell. However, the egg apparatus arose at the lower embryo sac pole, not at the upper as expected for an orthotropous ovule. A hypothetical model for the development of Arceuthobium ovules is the ancestral fusion and subsequent reduction of two anatropous ovules to form two embryo sacs within the PNC, of which only one completes development. The synergids have no role in pollen tube guidance, as tubes could be seen below each functional megaspore prior to megagametogenesis.Key words: Arceuthobium, embryo sac, megasporogenesis, mistletoe, pollen tubes, ultrastructure.

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Henson, J. H., D. A. Begg, S. M. Beaulieu, et al. "A calsequestrin-like protein in the endoplasmic reticulum of the sea urchin: localization and dynamics in the egg and first cell cycle embryo." Journal of Cell Biology 109, no. 1 (1989): 149–61. http://dx.doi.org/10.1083/jcb.109.1.149.

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Using an antiserum produced against a purified calsequestrin-like (CSL) protein from a microsomal fraction of sea urchin eggs, we performed light and electron microscopic immunocytochemical localizations on sea urchin eggs and embryos in the first cell cycle. The sea urchin CSL protein has been found to bind Ca++ similarly to calsequestrin, the well-characterized Ca++ storage protein in the sarcoplasmic reticulum of muscle cells. In semi-thin frozen sections of unfertilized eggs, immunofluorescent staining revealed a tubuloreticular network throughout the cytoplasm. Staining of isolated egg cortices with the CSL protein antiserum showed the presence of a submembranous polygonal, tubular network similar to ER network patterns seen in other cells and in egg cortices treated with the membrane staining dye DiIC16[3]. In frozen sections of embryos during interphase of the first cell cycle, a cytoplasmic network similar to that of the unfertilized egg was present. During mitosis, we observed a dramatic concentration of the antibody staining within the asters of the mitotic apparatus where ER is known to aggregate. Electron microscopic localization on unfertilized eggs using peroxidase-labeled secondary antibody demonstrated the presence of the CSL protein within the luminal compartment of ER-like tubules. Finally, in frozen sections of centrifugally stratified eggs, the immunofluorescent staining concentrated in the clear zone: a layer highly enriched in ER and thought to be the site of calcium release upon fertilization. This localization of a CSL protein within the ER of the egg provides evidence for the ability of this organelle to serve a Ca++ storage role in the regulation of intracellular Ca++ in nonmuscle cells in general, and in the regulation of fertilization and cell division in sea urchin eggs in particular.

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Zarani, Flora E., and Lukas H. Margaritis. "The eggshell of Drosophila melanogaster. V. Structure and morphogenesis of the micropylar apparatus." Canadian Journal of Zoology 64, no. 11 (1986): 2509–19. http://dx.doi.org/10.1139/z86-372.

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The micropylar apparatus in Drosophila melanogaster consists of two parts. The inner part is a protrusion of vitelline membrane, whereas the outer part is a chorionic protrusion containing a canal, through which the spermatozoon enters. In the formation of the micropylar apparatus two follicle cell subpopulations are involved: the border cells, i.e., a group of 9 follicle cells, and the peripheral cells (about 36 cells). The morphogenesis of the micropyle starts at stage 10B, when the border cells secrete the paracrystalline region of the vitelline membrane. The micropylar canal (length 7 μm, diameter 0.7 μm) and the pocket that penetrates within the paracrystalline structure are moulded by two border cell projections, full of microtubules. The formation of the micropyle terminates at stage 14B, when its chorionic part is completed and the border cell projections degenerate. The structure of the micropyle in fertilized and unfertilized laid eggs differs from the mature (stage 14B) egg in that the vitelline membrane is modified and appears homogeneous as in the rest of the eggshell. These transformations seem to be unrelated to sperm entry.

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Watanabe, Kenji, Miyako S. Hamaguchi, and Yukihisa Hamaguchi. "Effects of intracellular ph on the mitotic apparatus and mitotic stage in the sand dollar egg." Cell Motility and the Cytoskeleton 37, no. 3 (1997): 263–70. http://dx.doi.org/10.1002/(sici)1097-0169(1997)37:3<263::aid-cm8>3.0.co;2-7.

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Zarani, Flora E., and Lukas H. Margaritis. "A cell biological study of the micropylar apparatus in dipterans of economic importance." Proceedings, annual meeting, Electron Microscopy Society of America 48, no. 3 (1990): 484–85. http://dx.doi.org/10.1017/s0424820100159965.

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The micropylar apparatus is a specialized region of the eggshell, serving as a passage (micropylar canal) to the spermatozoon. The entire eggshell is secreted by the follicle cells during oogenesis, in successive layers, in the following order: vitelline membrane, wax layer, innermost chorionic layer, endochorion, exochorion. This study is an E.M. investigation of the structure and morphogenesis of the micropylar apparatus at the follicles of Dipterans of economic importance, such as Ceratitis capitata, Dacus oleae and Rhagoletis cerasi. These insects affect the fruits of orange, olive and cherry trees respectively.The micropylar apparatus of the Dipterans C. capitata, D. oleae and R. cerasi. forms a protrusion at the anterior part of the egg. This apparatus consists of the vitelline membrane (Vm), which is surrounded by the wax layer (wl); the innermost chorionic layer (icl); the endochorion (En); and the exochorionic “tuft”. The endochorion has many cavities which probably take part in the air storage, in order to facilitate the embryo’s respiratory needs (Figs. 1,3,5). The micropylar canal is covered by the characteristic tuft, resulting in the vitelline membrane, where it becomes thinner and forms the pocket.

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DUTE, R. R., C. M. PETERSON, and A. E. RUSHING. "Ultrastructural Changes of the Egg Apparatus Associated with Fertilization and Proembryo Development of Soybean, Glycine max (Fabaceae)." Annals of Botany 64, no. 2 (1989): 123–35. http://dx.doi.org/10.1093/oxfordjournals.aob.a087816.

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Giełwanowska, Irena, and Wioleta Kellmann−Sopyła. "Generative reproduction of Antarctic grasses, the native species Deschampsia antarctica Desv. and the alien species Poa annua L." Polish Polar Research 36, no. 3 (2015): 261–79. http://dx.doi.org/10.1515/popore-2015-0016.

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AbstractThe embryology of two species, Deschampsia antarctica, a native species, and Poa annua, an alien species in the Antarctic we studied. Flowering buds of plants growing in their natural habitats on King George Island and generative tissues of both plant species grown in a greenhouse were analyzed. Adaptations to autogamy and anemogamy were observed in the flower anatomy of both species. The microsporangia of the evaluated grasses produce a small number of three−celled pollen grains. Numerous pollen grains do not leave the microsporangium and germinate in the thecae. Deschampsia antarctica and P. annua plants harvested in Antarctica developed a particularly small number of microspores in pollen chambers. In D. antarctica, male gametophytes were produced at a faster rate: generative cells in pollen did not become detached from the wall of the pollen grain, they were not embedded in the cytoplasm of vegetative cells, and they divided into two sperm cells situated close to the wall. The monosporous Polygonum type of embryo sac development was observed in the studied species. The egg apparatus had typical polarization, and the filiform apparatus did not develop in synergids. Large antipodals with polyploidal nuclei were formed in the embryo sacs of D. antarctica and P. annua. Poa annua was characterized by numerous antipodal cells which formed antipodal tissue in the chalazal region of the embryo sac. Three distinct antipodals with atypical, lateral position in the vicinity of the egg apparatus were observed in D. antarctica. The diaspores of the investigated grass species were characterized by small size, low weight and species-specific primary and secondary sculpture of the testa and caryopsis coat.

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Song, Kee Nam, Soo Sung Kim, Soo Bum Lee, and Yong Wan Kim. "Development of a LASER Welding Apparatus and a Method for an Inner-Strap Welding of a Spacer Grid Assembly for a PWR Fuel Assembly." Materials Science Forum 580-582 (June 2008): 507–10. http://dx.doi.org/10.4028/www.scientific.net/msf.580-582.507.

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A spacer grid assembly, which is an interconnected array of slotted grid straps welded at the intersections to form an egg crate structure, is one of the core structural components for the nuclear fuel assemblies of a Pressurized light Water Reactor (PWR). The commercial spacer grid assembly is spot-welded at the crossing points of the intersections by a TIG welding, LASER beam welding or Electron beam welding method. In this study, a LASER beam welding apparatus and a method for an inner strap welding has been proposed to obtain a longer and finer weld line and a smaller weld bead size for a spacer grid assembly for a PWR fuel assembly. Also a rapid welding and excellent weld quality have been achieved by the proposed welding apparatus and method.

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Cass, David D. "Structural relationships among central cell and egg apparatus cells of barley as related to transmission of male gametes." Acta Societatis Botanicorum Poloniae 50, no. 1-2 (2014): 177–79. http://dx.doi.org/10.5586/asbp.1981.027.

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Barley embryo sacs were examined using light and electron microscopy before and during fertilization. One synergid degenerates after pollination with loss of nuclear and cytoplasmic organization and cell wall material between synergid and central cell. Some wall between egg and central cell is also lost. After pollen tube discharge into the degenerate synergid, the male gametes leave the synergid entering a pocket of central cell cytoplasm separated from the synergid only by membranes. This could provide for efficient gamete transmission and possible recognition through specific membrane contacts.

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Abdullah, Zulaikha, Sufizar Ahmad, Azzura Ismail, and Najeed Ahmed Khan. "Processing of Porous Stainless Steel by Compaction Method Using Egg Shell as Space Holder." Key Engineering Materials 791 (November 2018): 123–28. http://dx.doi.org/10.4028/www.scientific.net/kem.791.123.

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Development of lightweight materials becomes essential and has been applied for various structural and functional applications in industrial field since last decade. Porous metal can contribute to lightweight material with great mechanical, thermal and electrical properties. In this study, porous stainless steel was fabricated by using powder metallurgy technique and egg shell as a new potential space holder material. Stainless steel 316L was used as metal matrix powder, egg shells as space holder material, and polyethylene glycol (PEG) as binder to increase the green density of the preforms. The material was mixed using roller mill before the mixtures are ready to the next process of compaction by using uniaxial pressing machine. The samples were sintered to two-stage sintering at temperature 1000°C in a tube furnace. Physical properties of porous stainless steel were studies by performing density and porosity test. Scanning Electron Microscopy (SEM) apparatus was used to characterize morphology properties. The results show that, porous stainless steel with the composition of 30 wt. % of egg shells added into formulation yields the highest porosity compared to other compositions and the distribution of pores can be classify as micro-pores.

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Erdelská, Oľga. "Polyembryony in maize: histological analysis." Acta Societatis Botanicorum Poloniae 65, no. 1-2 (2014): 123–25. http://dx.doi.org/10.5586/asbp.1996.021.

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The histological analysis enabled to distinguish the main types of polyembryony in maize according to the origin of embryos connected with their localization in caryopses, differences in their structure (presence of common tissues) and type of germination. Twin embryos from multiple embryo sacs are usually localized on opposite sides (or distant places) of the caryopsis, they have no common tissues and the germination is separate. Twins or triplets from individual cells of the egg apparatus or multiple egg cells are closely adherent, but strictly separated by epidermal layers. Endosperm is common. Plumules and radicles are independent. Cleavage polyembryos arising <em>in vivo</em> spontaneously or after induction share a common suspensor, part of scutellum and surface layers of radicles. Therefore they germinate with one radicular complex and with separated plumules.

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Zhou, Wei, Xiaoming Wang, Jianhua Chen, Liangming Chen, Zhongquan Qiao, and Huijie Zeng. "Abortion Categories and Characteristics of Acarpous Crape Myrtle Floral Organs." Journal of the American Society for Horticultural Science 144, no. 6 (2019): 387–93. http://dx.doi.org/10.21273/jashs04757-19.

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Lagerstroemia indica (crape myrtle) is a popular Chinese landscape plant with a long flowering period that contributes to its gorgeous flowers and high ornamental value, which motivate L. indica breeding. We found a wild acarpous individual of L. indica that did not bear seeds after flowering and had a significantly longer flowering period than fructiferous L. indica. This study identified differences in floral organ morphology, and stamen and pistil structure between fructiferous and acarpous L. indica through observation, paraffin sectioning, and scanning electron microscopy (SEM). The flowering time of each acarpous L. indica inflorescence lasts as long as 18 to 25 days. When a single flower withers, it falls from the pedicel without any fruit. The abortion in the floral organ of acarpous L. indica is characterized by sterile and undehisced anthers, pollen abortion, and deformed and irregularly arranged filament cells. Acarpous L. indica features short and loosely arranged papilla cells in the stigma, a flat style and narrow stylar canal, loosely arranged epidermal cells, and no obvious nuclei. No embryo sac cavity is found in acarpous L. indica ovules. In some nucelli, the egg apparatus structure can be observed indistinctly but without cell contour. In others, the egg apparatus structure is completely absent, and only flocculent tissue is observed. This study may provide a theoretical foundation for future studies on the molecular mechanisms of the mutations in acarpous L. indica.

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Sumner, M. J., and L. van Caeseele. "The development of the central cell of Brassica campestris prior to fertilization." Canadian Journal of Botany 68, no. 12 (1990): 2553–63. http://dx.doi.org/10.1139/b90-322.

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The development of the central cell of Brassica campestris cv. Candle (canola-rapeseed) was examined using techniques of light and electron microscopy and cytochemistry. The mature central cell is devoid of the large central vacuole characteristic of the early cellular stage of megagametophyte development. Prior to anthesis, cell wall projections, of the transfer cell type, develop on the lateral wall of the central cell. These central cell wall projections extend from the midregion of the megagametophyte to the egg apparatus and are immediately adjacent to the starch-containing region of the inner and outer integuments. The cell wall projections are periodic acid – thiocarbohydrazide – silver proteinate positive as are the contents of dictyosome vesicles that appear to contribute to their formation. Mitochondria are associated with the wall projections as is a network of central cell endoplasmic reticulum that extends from the wall projections to the egg apparatus. Microtubules are associated with the migrating chalazal polar nucleus. The two polar nuclei partially fuse prior to double fertilization, united by nuclear bridges and endoplasmic reticulum interconnections. Proplastids are a characteristic feature of the immature cellular megagametophyte. By anthesis, the proplastids of the mature central cell develop into chloroplasts with stacked thylakoids and starch deposits. Microbodies are frequently found associated with lipid bodies, and polysomes with the endoplasmic reticulum of the mature central cell. Key words: Brassica, central cell, megagametophyte, ovule, transfer cell.

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Journal articles on the topic 'Egg apparatus'

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