RESUMO
We report on the changes the photosynthetic apparatus of Chlamydomonas reinhardtii undergoes upon acclimation to different light intensity. When grown in high light, cells had a faster growth rate and higher biomass production compared with low and control light conditions. However, cells acclimated to low light intensity are indeed able to produce more biomass per photon available as compared with high light-acclimated cells, which dissipate as heat a large part of light absorbed, thus reducing their photosynthetic efficiency. This dissipative state is strictly dependent on the accumulation of LhcSR3, a protein related to light-harvesting complexes, responsible for nonphotochemical quenching in microalgae. Other changes induced in the composition of the photosynthetic apparatus upon high light acclimation consist of an increase of carotenoid content on a chlorophyll basis, particularly zeaxanthin, and a major down-regulation of light absorption capacity by decreasing the chlorophyll content per cell. Surprisingly, the antenna size of both photosystem I and II is not modulated by acclimation; rather, the regulation affects the PSI/PSII ratio. Major effects of the acclimation to low light consist of increased activity of state 1 and 2 transitions and increased contributions of cyclic electron flow.
Assuntos
Adaptação Fisiológica/efeitos da radiação , Chlamydomonas reinhardtii/fisiologia , Chlamydomonas reinhardtii/efeitos da radiação , Luz , Fotossíntese/efeitos da radiação , Chlamydomonas reinhardtii/crescimento & desenvolvimento , Chlamydomonas reinhardtii/metabolismo , Escuridão , Relação Dose-Resposta à Radiação , Transporte de Elétrons/efeitos da radiação , Complexos de Proteínas Captadores de Luz/metabolismo , Complexo de Proteína do Fotossistema I/metabolismo , Complexo de Proteína do Fotossistema II/metabolismo , Pigmentos Biológicos/metabolismoRESUMO
Branched-chain aminotransferase (BCAT) catalyzes the transamination of essential branched-chain amino acids (BCAAs: leucine, isoleucine and valine) with alpha-ketoglutarate. Through this reaction, BCAAs provide nitrogen for the synthesis of glutamate, the predominant excitatory neurotransmitter. Two BCAT isoforms have been identified: one cytosolic (BCATc) and one mitochondrial (BCATm). In adult rodents, BCATc is expressed in a wide variety of structures of the central nervous system (CNS), in neurons. So far, no data were available about the expression of BCATc in the developing CNS. Here, we analyse the expression profile of BCATc mRNA in the mouse brain from embryonic day 12.5 to adult age. BCATc mRNA gradually appears in different brain regions starting from early stages of neural development, and is maintained until adulthood. BCATc mRNA is predominantly present in the cerebral cortex, hippocampus, thalamus, ventral midbrain, raphe, cerebellum and precerebellar system. This study represents the first detailed analysis of BCATc mRNA expression in the developing mouse brain.
Assuntos
Encéfalo/embriologia , Encéfalo/enzimologia , Expressão Gênica , Transaminases/genética , Animais , Citosol/enzimologia , Embrião de Mamíferos/enzimologia , Embrião de Mamíferos/metabolismo , Feminino , Masculino , Camundongos , Camundongos Endogâmicos C57BL , RNA MensageiroRESUMO
Branched chain aminotransferase (BCAT) catalyzes the transamination of the essential branched chain amino acids (leucine, isoleucine and valine) with alpha-ketoglutarate. BCAT exists in two isoforms: one cytosolic (BCATc), mainly expressed in the nervous system, and the other mitochondrial (BCATm), present in a greater number of tissues. We previously showed that BCATc mRNA and protein expression in the dorsal lateral geniculate nucleus of the thalamus is up-regulated by exogenous administration of brain-derived neurotrophic factor (BDNF) following lesion of the visual cortex in newborn rats. Here, we analyzed the expression of BCATc mRNA in the brain of transgenic mice overexpressing the rat BDNF cDNA under the control of the alpha-calcium/calmodulin-dependent kinase II (alphaCaMKII) promoter. In these animals, BDNF is overexpressed in the telencephalon starting from the second postnatal week. RT-PCR and in situ hybridization experiments showed that BCATc mRNA is overexpressed in restricted regions of the cerebral cortex (parietal area) and hippocampus (hilus and CA3 pyramidal cell layer) of adult BDNF transgenic mice respect to wild-type animals. These differences between wt and BDNF mice were not detected in animals of 1 week of age. These results demonstrate that the expression of the BCATc gene in the brain is specifically regulated by BDNF in a time- and region-dependent fashion.
Assuntos
Fator Neurotrófico Derivado do Encéfalo/genética , Encéfalo/crescimento & desenvolvimento , Encéfalo/metabolismo , Camundongos , RNA Mensageiro/metabolismo , Transaminases/genética , Regulação para Cima/fisiologia , Envelhecimento/genética , Animais , Animais Recém-Nascidos , Encéfalo/anatomia & histologia , Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina , Proteínas Quinases Dependentes de Cálcio-Calmodulina/genética , Córtex Cerebral/anatomia & histologia , Córtex Cerebral/crescimento & desenvolvimento , Córtex Cerebral/metabolismo , Regulação da Expressão Gênica no Desenvolvimento/genética , Hipocampo/anatomia & histologia , Hipocampo/crescimento & desenvolvimento , Hipocampo/metabolismo , Camundongos Transgênicos , Regiões Promotoras Genéticas/genética , Fatores de TempoRESUMO
Polycythemia vera (PV) is a hematologic malignancy characterized by excessive proliferation of erythroid, myeloid and megakaryocytic elements in the bone marrow. Patients suffering from PV may subsequently be affected by other neoplasms of the haematopoietic system, but lymphomas are very rare and no cases of oral lymphoma have yet been reported. We report the case of a patient with PV in whom a primary non-Hodgkin's lymphoma (high grade malignancy on the Kiel scale) of the oral cavity subsequently developed. The case is unusual for its extranodal onset, its location in the oral cavity and the clinical presentation.