Academic literature on the topic 'Parthogenesis'

In the field of comparative neuroanatomy, a meaningful interspecific comparison demands quantitative data referring to method-specific artifacts. For evaluating the potential of state-of-the-art imaging techniques in arthropod neuroanatomy, micro-computed X-ray microscopy (μCT) and two different approaches using confocal laser-scanning microscopy (cLSM) were applied to obtain volumetric data of the brain and selected neuropils inProcambarus fallaxformavirginalis(Crustacea, Malacostraca, Decapoda). The marbled crayfishP. fallaxcf.virginalisfeatures a parthogenetic reproduction generating genetically identical offspring from unfertilized eggs. Therefore, the studied organism provides ideal conditions for the comparative analysis of neuroanatomical imaging techniques and the effect of preceding sample preparations of nervous tissue. We found that wet scanning of whole animals conducted with μCT turned out to be the least disruptive method. However, in an additional experiment it was discovered that fixation in Bouin’s solution, required for μCT scans, resulted in an average tissue shrinkage of 24% compared to freshly dissected and unfixed brains. The complete sample preparation using fixation in half-strength Karnovsky’s solution of dissected brains led to an additional volume decrease of 12.5%, whereas the preparation using zinc-formaldehyde as fixative resulted in a shrinkage of 5% in comparison to the volumes obtained by μCT. By minimizing individual variability, at least for aquatic arthropods, this pioneer study aims for the inference of method-based conversion factors in the future, providing a valuable tool for reducing quantitative neuroanatomical data already published to a common denominator. However, volumetric deviations could be shown for all experimental protocols due to methodological noise and/or phenotypic plasticity among genetically identical individuals. MicroCT using undried tissue is an appropriate non-disruptive technique for allometry of arthropod brains since spatial organ relationships are conserved and tissue shrinkage is minimized. Collecting tissue-based shrinkage factors according to specific sample preparations might allow a better comparability of volumetric data from the literature, even if another technique was applied.

Syringomyelia is a disease in which fluid-filled cavities, called syrinxes, form in the spinal cord causing progressive loss of sensory and motor functions. Invasive monitoring of pressure waves in the spinal subarachnoid space implicates a hydrodynamic origin. Poor treatment outcomes have led to myriad hypotheses for its pathogenesis, which unfortunately are often based on small numbers of patients due to the relative rarity of the disease. However, only recently have models begun to appear based on the principles of mechanics. One such model is the mathematically rigorous work of Carpenter and colleagues. They suggest that a pressure wave due to a cough or sneeze could form a shock-like elastic jump, which when incident at a stenosis, such as a hindbrain tonsil, would generate a transient region of high pressure within the spinal cord and lead to fluid accumulation. The salient physiological parameters of this model are reviewed from the literature and the assumptions and predictions re-evaluated from a mechanical standpoint. It is found that, while the spinal geometry does allow for elastic jumps to occur, their effects are likely to be weak and subsumed by the small amounts of damping that have been measured in the subarachnoid space. The analysis presented here does not support the elastic-jump hypothesis for syrinx formation. Furthermore, the site of maximum transpial pressure dierential due to a cough-induced pulse is most likely to be at the site of pulse origin|not, as supposed, at a distant reflection site. This suggests that there must be some other localising factor more critical to providing the necessary conditions for syrinx formation. Two coaxial tube models are developed that incorporate Darcy's law separately in the pial membrane and the spinal cord tissue. It is shown that permeability plays opposing roles in the spinal cord and pia for wave attenuation; the propagation of a pressure wave is aided by a less-permeable pia but a more-permeable spinal cord. This may have implications in a syringomyelic cord. To understand the dynamic interaction of the fluid and solid components of the spinal cord tissue Biot's theory of poroelasticity is employed. It is concluded that physiological frequencies are probably too low for poroelastic dissipation to be of signicance in such a soft and weak material as the spinal cord. Accumulating evidence in the last decade from animal studies implicates arterial pulsations in syrinx formation. In particular, Bilston and colleagues suggested that a phase difference between the pressure pulse in the spinal subarachnoid space and the perivascular spaces, due to a pathologically disturbed blood supply, could result in a net in flux of cerebrospinal fluid into the spinal cord. A lumped-parameter model is developed of the cerebrospinal system to investigate this conjecture. It is found that although this phase-lag mechanism may operate, it requires the spinal cord to have an intrinsic storage capacity due to the collapsibility of the contained venous reservoir. If this storage requirement is met then the results presented here suggest that, on mechanical grounds, a syringo-subarachnoid shunt may be a better surgical treatment option than a subarachnoid bypass for post-traumatic syringomyelia.

La principale question à laquelle cette thèse tente de répondre, c’est la façon dont est abordée et révélée la question de la maternité et, plus largement, de la parentalité dans la mythologie grecque et comment, par le biais de cette approche, nous pouvons déceler et expliquer la situation sociale des femmes et leur statut maternel dans le système de valeurs que véhicule la mythologie. En utilisant la catégorie du genre dans le traitement de cette thématique, cette thèse s’efforce de proposer de nouvelles possibilités pour interpréter et expliquer l'abolition de la maternité et plus largement de la parentalité, l'infanticide, mais aussi la survivance du système pré-patriarcal dans le système religieux androcentré du panthéon grec. On examine les mythes en prenant en compte leur contexte social, culturel et historique afin d’en tirer des conclusions sur la position de chaque sexe dans la sphère publique et privée, sur le rôle respectif des hommes et des femmes dans leur vie privée, sur les relations de pouvoir et de subordination entre les sexes, ainsi que sur le système des valeurs et des perceptions qui dominent, mais – surtout – sur la représentation qui est donnée de ce système dans les mythes grecs. En sens, cette thèse se veut une contribution à la tentative plus large qui est universellement en cours pour réintégrer les femmes dans le contexte non seulement de l'histoire, mais aussi de la mythologie
The main question that this thesis tries to answer is how the subject of maternity and, in general, parenthood is discussed and revealed through the Greek mythology and how we can, through this approach, pinpoint and explain the social status of women and maternity in the mythological value system. By using the category of “sex” in this subject’s approach, analysis and conclusions, the purpose of this thesis is to offer new possibilities to interpret and explain, regarding the abolishment of maternity and, generally, parenthood, the act of infanticide, but also the survival of the prοpatriachal system in the male-dominated religious belief of the Greek pantheon. The myths are being examined by taking into consideration their social, cultural and historical context in order to come to conclusions about each sex’s position in the public and private sector, about the roles of men and women in their private lives, about the relationships of power and submission between them, as well as the dominant value and perception system and, above all, about the representation of this system in the Greek mythology. In this sense, this thesis aims to be a contribution to the ongoing wider global effort to reintegrate women not only in a historical context but also in mythology