Orientador: José Paulo Leite Guadanucci / Abstract: Spiders are generally solitary, aggressive, potential cannibal predators, and have poor visual acuity. These features may have favored a strong selection for long-distance communication, such as chemical and/or vibratory signaling. The pheromone usage is an example of signal used during intersexual communication and have been chemically identified in eleven araneomorph species. To the emission of the pheromones, females can use their cuticle or web, and for the perception of these substances, araneomorph males use chemosensory setae located in the dorsal side of the pedipalps. In mygalomorphs, it was reported the presence of a chemosensory setae in an Idiops pylorus male, identified by Scanning Electron Microscopy micrographies. Besides that, recently it was reported a tarsal setae exclusive of mygalomorph males, that have been considered a chemosensory setae because of it’s similarity with the one’s found in Idiops pylorus, and even with the ones found in araneomorphs, despite the contrast in disposition of the setae between the infraorders. They can be arranged densely on tarsus, similar to those setae found in the scopula (and in this case, named pseudoscopula), or be sparsely distributed on ventral tarsus among other setae types. These male setae also differ from other chemosensory ones that are widespread in both males and females of mygalomorph spiders In the present study, the pseudoscopula of a mygalomorph representative, Ischnothele annulata, was investigated through... (Complete abstract click electronic access below) / Resumo: As aranhas geralmente são criaturas solitárias, de pouca acuidade visual, agressivas e potenciais predadoras canibais, características que podem ter selecionado formas de comunicação à longa distância, como sinais químicos e/ou vibratórios. Os feromônios são um exemplo de sinal utilizado durante a comunicação intersexual, já tendo sido caracterizado quimicamente para onze espécies de araneomorfas. A emissão dessas substâncias é feita pelas fêmeas por meio da seda ou pela cutícula. Para sua recepção, machos de araneomorfas utilizam cerdas quimiossensoriais presentes no dorso dos palpos. Para migalomorfas, foi reportada a presença de cerdas quimiossensorias em um macho de Idiops pylorus a partir de análises de Microscopia Eletrônica de Transmissão. Além disso, recentemente foi reportada a presença de uma cerda tarsal exclusiva de machos de Mygalomorphae, que por sua similaridade com as encontradas em I. pylorus, e até mesmo com as cerdas quimiossensoriais encontradas em araneomorfas, também foi considerada quimiossensorial, apesar da diferença de disposição entre as duas infraordens. Elas podem estar arranjadas de forma densa (sendo chamadas pseudoescópula), ou estarem esparsamente distribuídas juntamente com outros tipos de cerda. Estas cerdas também diferem de outras sensoriais que são amplamente encontradas em machos e fêmeas de migalomorfas. No presente estudo, as cerdas da pseudoescópula de um representante de Mygalomorphae, Ischnothele annulata, foram investigadas por mei... (Resumo completo, clicar acesso eletrônico abaixo) / Mestre

At maturity, spermatozoids of the green alga Chara vulgaris are biflagellated, contain little cytoplasm, and coil for approximately 2 1/4 gyres within the mother cell wall. The anterior of the cell contains an ovoid headpiece anchoring two slightly staggered basal bodies that are positioned above and directly in front of approximately 30 linearly arranged mitochondria. An elongated stellate pattern occupies the transition zone between the BBs and axonemes. Flagella emerge from the cell just in front of the nucleus and encircle the full length of the spermatozoid. The spline comprises a maximum of 38 microtubules surrounding the anterior mitochondria and gradually decreases posteriorly to a minimum of 11. The dense nucleus is narrow, cylindrical, and occupies the central revolution of the cell. Six starch-laden plastids and associated mitochondria are linearly arranged at the cell posterior. Phylogenetic analyses of charalean taxa and archegoniates based on spermatogenesis strongly support the order Charales, with Nitella as the sister group to Chara. Diagnostic features of Chara spermatozoids include absence of a lamellar strip and axonemes embedded in the cell for almost the entire length of the anterior mitochondria. Potential relationships among Charales, Coleochaetales and archegoniates are evaluated in regards to the probable course of evolution of streamlined biflagellated gametes.

The vagal postganglionic control of cardiac rate is mediated by two intracardiac ganglia, i.e., the sinoatrial (SA) and posterior atrial (PA) ganglia. Nothing is known about the vagal preganglionic neurons (VPNs) that innervate the PA ganglion or about the neurochemical anatomy of central afferents that innervate these VPNs. These issues were examined using light microscopic retrograde labeling methods and dual-labeling electron microscopic histochemical and immunocytochemical methods. VPNs projecting to the PA ganglion are found in a narrow column exclusively in the ventrolateral nucleus ambiguus (NA-VL). These neurons are relatively large (37.6 ± 2.7 μm by 21.3 ± 3.4 μm) with abundant cytoplasm and intracellular organelles, rare somatic and dendritic spines, round uninvaginated nuclei, and myelinated axons. Previous physiological data indicated that microinjections of neuropeptide Y (NPY) into the NA-VL cause negative chronotropic effects. The present morphological data demonstrate that NPY-immunoreactive nerve terminals formed 18 ± 4% of the axodendritic or axosomatic synapses and close appositions on VPNs projecting to the PA ganglion. Three approximately equal populations of VPNs in the NA-VL were retrogradely labeled from the SA and PA ganglia. One population each projects to the SA ganglion, the PA ganglion, or to both the SA and PA ganglia. Therefore, there are both shared and independent pathways involved in the vagal preganglionic controls of cardiac rate. These data are consistent with the hypothesis that the central and peripheral parasympathetic controls of cardiac rate are coordinated by multiple potentially redundant and/or interacting pathways and mechanisms.

The tegmentum vasculosum of the avian cochlear duct mimics the stria vascularis of the mammalian cochlear duct in both location and structure, and previous studies indicate that it may be its functional counterpart with regard to endolymph synthesis. In the present study, we report on the enzymatic activity and ultrastructural localization of the Na+,K+-ATPase in the tegmentum vasculosum of the duckling. Na+,K+-ATPase activity was determined by measuring K+-dependent, ouabain-sensitive p-nitrophenyl phosphatase (p-NPPase) activity in homogenates of dissected regions of the cochlear duct. The ultrastructural localization of the Na+,K+-ATPase was identified using K+-dependent, ouabain-sensitive, p-NPPase cytochemistry. Specific enzyme activity was localized primarily in homogenates of the tegmentum vasculosum (2.27 μmol p-nitrophenyl phosphate/mg protein/min) when compared to homogenates of the entire cochlear duct (0.69 μmol p-nitrophenyl phosphate/mg protein/min). Reaction product for p-NPPase was localized primarily along the basolateral plasma membrane folds of the dark cells. The cytochemical deposits appeared to be located exclusively on the cytoplasmic side of the plasma membrane. The light cells were devoid of reaction product. Biochemical and cytochemical localization of p-NPPase activity on the basolateral plasma membrane folds of the dark cells of the tegmentum vasculosum in conjunction with the ultrastructural morphology of these cells is compatible with a Na+,K+-ATPase-dependent ion transport function related to endolymph synthesis.

The majority of ancient people worshipped the sun and viewed it as a health - bringing deity. During the eighteenth and nineteenth century therapeutic benefits of sunlight exposure were beginning to be understood and by the end of the nineteenth century the importance of ultraviolet radiation was being realized. Danish physician Niels Finsen, whom many regard as the father of ultraviolet phototherapy, also stressed that it was ultraviolet radiation in the solar spectrum which cause sunburn. We now recognize that the small portion of ultraviolet radiation which reaches the earth's surface is not necessarily therapeutic, but in fact could be harmful to humans. There are numerous accounts of the harmful effects of UV radiation to the skin and the eye as a whole. These effects may be caused by either acute or chronic exposure to UV radiation. For example, some acute effects of UV-B radiation include conjunctivitis and photokeratitis. "Snow blindness" and "arc welders eye" are further examples of acute ultraviolet damage specifically to the surface of the cornea. On the other hand, chronic exposure to ultraviolet radiation is thought to be responsible for pterygia, climatic droplet keratopathy Hill and Maske (1989), cancers of the external eye, cataracts and various types of retinal diseases. The present study is an extension of ongoing studies on ultraviolet radiation damage to the cornea in the Department of Ophthalmology, University of Cape Town and Groote Schuur Hospital. Their specific interest lies in the causes and treatment of climatic droplet keratopathy. The aims of the present study are: 1) Establish a possible role of ultraviolet B radiation in human corneal diseases such as climatic droplet keratopathy and pterygium using the rabbit as an animal model. 2) Determine by means of SEM the initial effects and subsequent recovery of the epithelium after a 3-hour dose of ultraviolet B radiation. We refer to this study as "acute" response to ultraviolet B radiation. 3) To try and confirm the effects observed by SEM with ultrastructural studies using TEM. 4) In addition, we are also looking at the possible effects after exposing rabbit cornea to a daily dose of low level ultraviolet B radiation, over a long period of time. We refer to this as chronic exposure to ultraviolet B radiation. It is hoped that by exposing rabbits to ultraviolet light, principally ultraviolet B radiation, diseases similar to those found in humans could be simulated and disease progression studied. People are generally exposed to substantial amounts of UV radiation for a very long time. Since people generally live longer they will be exposed to an ever-increasing amount of solar UV radiation and subsequently, there is an increasing risk of developing corneal diseases. The possible threat to the ozone is also a real possibility and could lead to increased levels of ultraviolet radiation reaching the earth's surface. This will require a greater understanding of the very nature of corneal damage due to acute and chronic exposure. This study focusses mainly on the acute response to UV-B radiation since most studies have investigated effects of prolonged exposure to UV light. Accordingly, much less is known about acute exposure. Many people suffering from acute UV B radiation effects probably never visit the ophthalmologist or wait for a couple of days. This could also contribute to the fact that effects of short-term damage is not well documented.

The photosynthesis of the aerial roots of epiphytic orchids has been the subject of numerous studies. However, the roots are always evaluated as a homogeneous structure, even though they actually consist of significantly different areas. This work deals for the first time with the possibility of the spatial distribution of photosynthesis between the root layers, specifically the cortex and the stele. A combination of various microscopic techniques, the histochemical characterization of the apoplastic barriers and the immunohistochemical localization of the photosynthetic enzyme phosphoenolpyruvate carboxylase has been used. The results show that well-developed chloroplasts in the stele probably occur in the subfamily Epidendroideae in all epiphytic representatives, while in the subfamily Vanilloideae they occur occasionally. The ultrastructure of chloroplasts from both areas is systematically different, so it is likely that their functions also differ. Apoplastic barriers are prominent in the roots and differentiate early during root development, which can effectively isolate chloroplasts in the stele from the cortex. Chloroplasts also occur in the sclerenchyma cells of the stele, where were identified hitherto unknown pits in cell walls that could provide gas exchange within the stele....

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<p> Previous work on the ultrastructure of leaf surfaces has been confined to commercial terrestrial plants. Until recently there was a conflicting overlap of definitions of surface structures. Lately, studies have concentrated on the role of the epicuticular wax layer in surface phenomena such as water permeability, transpiration, and herbicide susceptibility. The initiating factors in surface wax formation and the mode of extrusion still remain unresolved. </p> <p> An emergent hydrophyte, Zizania aquatica L., was selected to attempt to clarify the initiation and extrusion of epicuticular wax. The first appearance of epicuticular wax occurs while the whole plant is submerged. The wax platelet shape is probably controlled by an endogenous circadian rhythm with very little environmental control. The significance of water depth, temperature, continous light, physical and chemical abrasion are discussed in terms of the surface morphology of the three types of leaves. </p> / Thesis / Master of Science (MSc)

No description available.

<p>The chaplin proteins are functional amyloids that are produced by filamentous <em>Streptomyces</em> bacteria. The chaplins are essential for the morphological development of <em>S. coelicolor</em>, and are important for altering the surface ultrastructure of aerial hyphae and spores. Although it is well established that the chaplins play an important role in <em>S. coelicolor </em>aerial development, there is still much that remains unknown regarding their activity; in particular, how each of the chaplins contribute to promoting aerial development, and the importance that chaplin amyloidogenesis has in this process.</p> <p>Previous work has revealed that only three of the eight chaplins (ChpE, ChpC, and ChpH) are necessary for promoting aerial development, and that ChpH plays a significant role in this process. For this reason, ChpH was used as the ‘model chaplin’ to examine the primary sequence determinants governing chaplin amyloidogenesis, and to explore the relationship between ChpH amyloid fiber formation and ChpH-dependent aerial development. This analysis revealed that ChpH contains two amyloidogenic regions, at the N- and C-termini, both of which are necessary for promoting aerial development, while the N-terminal domain is dispensable for surface fiber assembly.</p> <p>A separate study focused on the role of the short chaplin ChpE. One of the surprising findings of this work is that, unlike the other chaplins, ChpE is essential for maintaining cell viability. The relationship between ChpE cell surface localization and the presence of the long chaplins was also examined. This work showed that the long chaplins are not required for the surface attachment of ChpE (nor the other short chaplins), but do function to enhance the activity of the short chaplins in promoting aerial development, in addition to being necessary for the organization and assembly of surface fibers.</p> / Doctor of Philosophy (PhD)