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164 ABSTRACTS BIOCELL 30(1), 2006
BIOCELL 30(1), 2006 ABSTRACTS 165 Miguel Lillo Lecture L. 1. ROLE OF NEUROTRANSMITTERS IN THE CONTROL OF TESTICULAR FUNCTION. Ricardo S. Calandra Male infertility has been attributed to alterations in the hypothalamus-hypophyseal-gonadal axis (H-H-G) in a reduced number of cases (Bartlett et al., Int.J.Androl., 1989). Furthermore, physiological intratesticular or potential factors are involved in the regulation of the testicular function at paracrine level. GABA is a powerful neurotransmitter (N-T) of the Central Nervous System that takes part in neuron proliferation and in the modulation of neurosteroids production. GABA has been identified in rat testis (Ritta et al., Adv.Biochem.Psychopharm.,1986); Rs- GABA in rat Leydig cells (Ritta et al., J.Neurochem.,1991), Rs-GABA-A/B in testis Leydig cells from different species, including humans (Geigerseder et al., Neuroendo-crinology 2003), GABA-glutamate-decarboxylase enzyme (GAD65 and/or 67) and the expression of the vesicular inhibitory aminoacid transporter (VIAAT / VGAT). The presence of Rs-GABA-A- α1 subunit in rat Leydig cells has been confirmed by laser microdissection and RT-PCR. Our studies and other research groups have reported that human testis mastocytes are localized in the interstitial compartment and in the seminiferous tubules walls. Thus, testicular biopsies and immunohistochemical techniques revealed a significant increase of mastocyte population in samples from patients with Sertoli Cell and Germinal Arrest Syndrome (Meineke et al., Fert.Steril., 2000). Testicular mastocytes were also found to contain serine triptase protease (Frungieri et al., PNAS USA, 2002). On the other hand, triptase exerts a fiber-proliferative action involving the receptor activation by proteases 2 (PAR2), an increase in the expression of cyclooxigenase 2 (COX2, essential for prostaglandins –PGs- biosynthesis) enzyme, and the binding of 15-deoxi-Δ12,14-PGJ12 (15d-PGJ2) to its nuclear receptors PPARγ. Since PAR2-COX2-15d-PGJ2- PPARγ triptase system components are present in the human testis, an increase in mastocyte population could be involved in the peritubular fibrosis of pathologies described. Other authors (Izzo et al., J.Exp.Biol., 2004) suggest that Melatonin (Mel) regulates the number of testicular mastocytes. Our studies in hamsters revealed an increase in the number of testicular mastocytes and Mel levels when animals were exposed to short photoperiods (8h light/day) (Frungieri et al., Neuroendocrinology, 2002). Mel effect on the H-H axis of photosensitive species is already well-known. We have previously mentioned the interaction of the serotoninergic, catecholaminergic and CRF systems in hamster Leydig cells (Frungieri et al., Neuroendocrinology, 2002). Serotonin N-acetiltransferase expression, essential for Mel synthesis, has been recently described for these cells. We have recently described Rs-Mel 1a , inhibition of AMP c / androgen production post-hCG and also the StAR expression and related enzymes (Frungieri et al., Endocrinology, 2005). Briefly, the new findings on the testicular regulation of steroidogenesis suggest the importance of a “fine tunning” of local components which could be significant for the understanding of Idiopathic Syndromes at cell level. Opening Lecture L. 2. GEOLOGICAL TIME AND PALEONTOLOGY Carlos L. Azcuy Professor of Paleontology, Geological Science Department. University of Buenos Aires. CONICET Main Researcher. E-mail: azcuy@ciudad.com.ar Geological time is measured in millions of years and has been represented by means of tables in successive approximations, that have allowed the age of the planet and the beginning and later development of life in the world to be established. At first, the different degrees of evolution of the organic beings preserved on the terrestrial surface, which were called fossils, were used to segment the time represented by the enormous deposits of sedimentary rocks. That is how innumerable fossil remains were found among the strata, which were classified according to their morphological characteristics, recognizing in them most of the fila living at present, and their ancestors. This allowed for a frame of the evolution to be conformed, which served as a basis for the first tables in which geological time was divided. More recently the methodology of the absolute ages was developed, also measured in millions of years but on the basis of the radiation of certain elements present in the sedimentites or in the magmatic rocks, which transform into isotopes of the same element or into others. These measurements are based on the period of time that certain elements take to transform into others. A modern discipline based on research about magnetic paleopoles, and their displacement in the course of time, has also contributed to the knowledge of ages. This has allowed the position of poles in certain periods of time to be known, and, as a consequence, the paleolatitudes that the continents have had throughout time. That is how the paleogeographical reconstructions of the different continents began to be established, especially Eurasia and Gondwana, which confirmed that during the Carboniferous, Eurasia was very close to the Equator, while Gondwana remained close to the Southern Pole. The radiometric research practiced on rocks devoid of fossils allowed an age of 4600 MA for the planet, and 3200 MA for the first indication of life, occurred on the African continent, to be established: the discovery of a procariot fossil bacterium. However, the Fanerozoic Era in which the appearance of the major part of the living fila occurred, is placed in 550 MA in the Cambric Period. Several important processes take place quickly during evolution: the passage to eucariots, the conquest of the earth by vegetable plants, the apparition of multi-cellular organisms with the cellular specialization in the reproductive function and the later apparition of organs and tissues. An arguable datum was the concept of fossil, which is not given by its age, in other words a figure of thousands or millions of years since its demise, but by the time when it shows evidence of having been subjected to the processes of diagenesis suffered by the rock or stratum in which it is contained; that is to say since the recent sediment transforms into hard rock, or sedimentite. A first division of fossil organisms found on the terrestrial surface allows for the following disciplines or specializations to be recognized: Paleoinvertebrate, Paleovertebrate and Paleobotany. With the advent of the microscope another specialization began to be developed, micropaleontology, which included both vegetal and animal organisms and those of dubious system positioning. In the Paleozoic Era sexual reproduction and a varied number of paleoinvertebrate appear, such as the brachiopods; among the paleovertebrate the armoured fish appear, as well as the eucariot plants like algae and primitive vascular plants and ferns, and towards the end of the era, the first gymnosperms. During the Mesozoic plants were dominated by gymnosperms and ferns and only towards the end of the era angiosperms make their explosive apparition. Among the paleovertebrate dinosaurs prevailed, and halfway through this era birds appeared. The Cenozoic had as a characteristic the dominance of plants with flowers and among the paleovertebrate, mammals were dominant.
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XXII Annual Scientific Meeting, Tucuman Biology Society ...

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