Effect of neutron-gamma radiation on dopamine and serotonin metabolism in the rat brain: a regional analysis

Impact of low-dose UV-A in Caenorhabditis elegans during candidate bacterial infections

Ultraviolet radiation is a non-ionizing radiation produced by longer wavelength energy sources with lower frequency and is categorized into UV-A, UV-B, and UV-C. Minimal exposure to this radiation has several health benefits, which include treating microbial contaminations and skin therapies. However, the antimicrobial action of low-dose UV-A during pathogenic bacterial infections is still unrevealed. In this study, the impact of low-dose UV-A as pre- or post-treatment using the model organism, Caenorhabditis elegans with candidate pathogens (Acinetobacter baumannii and Staphylococcus aureus) mediated infections was investigated. The results indicated enrichment of metabolites, reduced level of antioxidants, increased expression of dopamine biosynthesis and transportation, and decrease in serotonin biosynthesis when the organism was exposed to low-dose UV-A for 5 min. This, in turn, elevated the expression of candidate regulatory proteins involved in lifespan determination, innate immunity, and cAMP-response element binding protein (CREB), which appear to increase the lifespan and brood size of C. elegans during A. baumannii and S. aureus infections. The findings suggested that the low-dose UV-A treatment during A. baumannii and S. aureus infections prolonged the lifespan and increased the egg-laying capacity of C. elegans.

Radiation-induced hyposuppression of the hypothalamic-pituitary-adrenal axis is associated with alterations of hippocampal corticosteroid receptor expression

Therapeutic brain irradiation in children can cause a progressive decline in cognitive functions through a diminished capability to learn and memorize. Because of the known involvement of the hippocampus in memory consolidation, this study was aimed at examining the late effects of gamma radiation on hypothalamic-pituitary-adrenal (HPA) axis activity and hippocampal corticosteroid receptor expression in an animal model of cranial radiotherapy. In the late-response phase, the basal and stress-induced corticosterone levels were not affected by radiation, but the suppression of glucocorticoid negative feedback by dexamethasone was attenuated in irradiated rats. Western blot analyses showed that exposure to radiation led to a decrease of cytosolic glucocorticoid receptor (GR) levels and a concomitant elevation of mineralocorticoid receptor (MR). The results obtained were complemented by those of RT-PCR, since the ratio of GR/MR mRNA was also decreased after radiation exposure. Dexamethasone appeared to be much less effective in shifting GR to the nuclear compartment in irradiated rats than in sham-irradiated animals. However, the expression of chaperones that aid GR intracellular trafficking, Hsp90 and Hsp70, remained unaffected. In conclusion, our data suggest that the hallmark of the late response to gamma radiation is a hyposuppressive state of the HPA axis that is associated with a decrease in both the GR/MR ratio and the nuclear accumulation of dexamethasone-activated GR in the hippocampus.

Effect of U and 137Cs chronic contamination on dopamine and serotonin metabolism in the central nervous system of the rat

Following the Chernobyl accident, the most significant problem for the population of the former Soviet Union for the next 50-70 years will be chronic internal contamination by radionuclides. One of the few experiments carried out in this field reported that neurotransmitter metabolism in the central nervous system of the rat was disturbed after feeding with oats contaminated by 137Cs for 1 month. The present study assessed the effect of chronic contamination by depleted U or 137Cs on the metabolism of two neurotransmitters in cerebral areas of rats. Dopamine and serotonin were chosen because their metabolism has been shown to be disturbed after external irradiation, even at moderate doses. Dopamine, serotonin, and some of their catabolites were measured by high-pressure liquid chromatography coupled with an electrochemical detector in five cerebral structures of rats contaminated over a 1-month period by drinking water (40 mg U·L–1 or 6500 Bq 137Cs·L–1). In the striatum, hippocampus, cerebral cortex, thalamus, and cerebellum, the dopamine, serotonin, and catabolite levels were not significantly different between the control rats and rats contaminated by U or 137Cs. These results are not in accordance with those previously described.Key words: uranium, caesium, dopamine, serotonin, HPLC.

[The SILENE reactor: a tool adapted for applied study of moderate and large doses]

Designed in 1974 to study the phenomenology and consequences of a critical accident, the SILENE experimental reactor, an intense source of mixed neutron and gamma radiation, is also suited to radiobiological studies.

Efeitos da radiação ionizante sobre comportamentos mantidos por contingências operantes

Pesquisas de laboratório com animais são tentativas para suprimir lacunas deixadas pelas metodologias utilizadas nos estudos com humanos sobre os fenômenos comportamentais que acompanham uma exposição à radiação. Neste trabalho, tratamos de estudos sobre comportamentos mantidos por diferentes tipos de contingências operantes e de variáveis radiogênicas como a dosagem de radiação. Os efeitos observados com esquemas simples de reforçamento mostram redução nas taxas de resposta. Esses efeitos são dose-dependentes e interagem com outras variáveis tais como o tipo de linha de base, taxa de respostas na linha de base e tipo de estímulo reforçador. Além disso, em esquemas concorrentes os efeitos são seletivos, segundo os componentes do esquema. Dados obtidos em procedimentos de aquisição repetida indicam uma interação da radiação com o tipo de tarefa em execução. As implicações dos estudos com animais para a compreensão das manifestações comportamentais observadas em indivíduos expostos a eventos radioativos são discutidas.