Efeito do cloreto de cádmio sobre as gônadas de girinos de rãs-touro (Lithobates catesbeianus)

A study about the effects of cadmium chloride (CdCl2) on tadpoles at Gosner stage 25 exposed for 4 and 16 days, to dosage environmentally accepted by National Council on the Environment (CONAMA) for the water classes 1 and 2, was performed. The results showed significant morphological and functional changes. On the ovaries of individuals exposed for 4 days, acceleration in the initial gametogenesis was observed, evidenced by the increased incidence of the number of oocytes in stages I, II and III and increased incidence of micronucleoli, which demonstrates high RNA synthesis. The histochemical and immunohistochemical techniques revealed no relevant changes caused by this trace metal. On the ovaries of individuals exposed for 16 days, acceleration in the initial gametogenesis was also observed, as reported by individuals exposed for 4 days. Immunohistochemistry showed overexpression of HSP70, indicating oxidative stress or physiological adaptive response to CdCl2. On the testicles of individuals exposed for 4 days, there were cases of anatomical changes, cell death, changes in somatic cell death and resorption of the germ cells, degeneration of gonadal tissue, adipogenesis and nonfunctional polygonadism. As noted on the ovaries for this period of exposure, the histochemical and immunohistochemical techniques revealed no relevant changes caused by this trace metal, showing basal expression. On the testes of individuals exposed during 16 days, the acceleration of testicular development was observed, with early primary spermatocytes organizing to form the primary seminiferous ducts, mixed polygonadism, as well as sex reversal. Immunohistochemistry showed no significant differences between the control and exposed groups regarding the expression of HSP70, however it is notable that this expression is below that observed in the group exposed for 4 days. For these reasons, the research shows that the parameters used by CONAMA as doses...Foi realizado um estudo sobre o efeito do Cloreto de cádmio (CdCl2) em girinos no estágio 25 de Gosner expostos durante 4 e 16 dias à dose ambientalmente aceita pelo Conselho Nacional do Meio Ambiente (CONAMA) para os corpos d´água de classes 1 e 2. Os resultados mostraram mudanças morfofuncionais significantes. Nos ovários dos indivíduos expostos durante 4 dias observou-se a aceleração na gametogênese inicial, evidenciado pelo aumento da incidência do número de ovócitos nos estágios I, II e III e aumento da incidência de micronucléolos, que demonstram alta síntese de RNA. As técnicas histoquímica e imuno-histoquimica não revelaram mudanças relevantes causadas por esse metal traço. Nos ovários dos indivíduos expostos durante 16 dias também observou-se aceleração na gametogênese inicial, como descrito para os indivíduos expostos durante 4 dias. A imuno-histoquimica demonstrou superexpressão da HSP70, indicando estresse oxidativo ou uma resposta adaptativa fisiológica ao CdCl2. Nos testículos dos indivíduos expostos durante 4 dias, observaram-se alterações anatômicas, morte celular, modificações nas células somáticas, morte e reabsorção das células germinativas, além da degeneração do tecido gonadal, adipogênese e poligonadismo não funcional. Como observado nos ovários, para esse período de exposição; as técnicas histoquímica e imuno-histoquimica não revelaram mudanças relevantes causadas por esse metal traço, demonstrando expressão basal. Nos testículos dos indivíduos expostos durante 16 dias observou-se aceleramento do desenvolvimento testicular já observando-se início dos espermatócitos primários organizando-se para formar os ductos seminíferos primordiais, poligonadismo misto, bem como, reversão sexual. A imuno-histoquimica não demonstrou diferenças significantes entre grupo controle e exposto quanto à expressão da HSP70, porém notou-se que esta está abaixo da observada no...Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Lead Concentrations Within The Condor Skeleton: Advancing Biomarkers Of Lead Exposure History And Poisoning

Lead (Pb) poisoning is a global problem among avian species, including the endangered California Condor (Gymnogyps californianus). Condors are highly monitored and frequently lead poisoned and may serve as a model species to investigate Pb exposure biomarkers. Bone Pb levels are a well-recognized biomarker of Pb exposure and related health effects in humans but have not been used widely in avian species. My overarching objective is to further establish biomarkers of lead exposure history and poisoning in avian species using bone Pb concentrations. In chapter 1, I investigated whether bone Pb differed between and within condor bones, depending on Pb exposure history between epiphyses, mostly composed of trabecular bone type, and diaphysis, mostly composed of compact bone type. In chapter 2, I determined if Pb levels in different bones can be used as biomarkers of recent and cumulative Pb exposure history and examined the effects of Pb exposure on bone mineral density and potential risk for bone fracture. In chapter 3, I used Pb stable isotopic composition to inform about Pb uptake into multiple bones and bone regions. My results showed that Pb concentrations were ~3-fold higher in epiphysis than diaphysis of tibiotarsus in condors that died of Pb toxicosis but less than 2-fold in condors that died of other causes. A discriminant analysis using bone Pb concentrations correctly classified 17 out of 18 birds as to whether they were Pb poisoned at the time of death, suggesting that bone Pb, particularly tibiotarsus epiphysis proximal, can be used as an additional piece of information to inform recent Pb exposure. Bone Pb levels, particularly in tibiotarsus diaphysis, were associated with time in the wild, consistent with prior studies in humans showing that bone Pb levels in long bones reflect long term cumulative Pb exposure. I also found a modest negative association between bone Pb and bone mineral contents in epiphyses of long bones, suggesting that bone Pb may be associated with a reduction in bone mineral. Finally, using stable lead isotopes, I found that there was ~10-fold difference in the rate of Pb incorporation between the tibiotarsus proximal epiphysis and diaphysis following a Pb exposure event. In conclusion, bone Pb levels in condors, and by extension other large avian species, appear to be a valuable biomarker of both recent acute and cumulative Pb exposure, and may help inform Pb poisoning status at the time of death

Cardiac Adaptations Of Bullfrog Tadpoles In Response To Chytrid Infection.

The chytrid fungus Batrachochytrium dendrobatidis (Bd) can result in heart failure in Bd-susceptible species. Since Bd infection generally does not cause mortality in North American bullfrogs, the aim of this work was to verify whether this species presents any cardiac adaptation that could improve the tolerance to the fungus. Thus, we analyzed tadpoles' activity level, relative ventricular mass, ventricle morphology, in loco heart frequency, and in vitro cardiac function. The results indicate that infected animals present an increase in both ventricular relative mass and in myofibrils' incidence, which accompanied the increase in myocytes' diameter. Such morphological alterations enabled an increase in the in vitro twitch force that, in vivo, would result in elevation of the cardiac stroke volume. This response requires much less energy expenditure than an elevation in heart frequency, but still enables the heart to pump a higher volume of blood per minute (i.e., an increase in cardiac output). As a consequence, the energy saved in the regulation of the cardiac function of Bd-infected tadpoles can be employed in other homeostatic adjustments to avoid the lethal effect of the fungus. Whether other species present this ability, and to what extent, remains uncertain, but such possible interspecific variability might explain different mortality rates among different species of Bd-infected amphibians.323487-49