Major changes in the brain histamine system of the ground squirrel Citellus lateralis during hibernation.
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Hibernation in mammals such as the rodent hibernator Citellus lateralis is a physiological state in which CNS activity is endogenously maintained at a very low, but functionally responsive, level. The neurotransmitter histamine is involved in the regulation of diurnal rhythms and body temperature in nonhibernators and, therefore, could likely play an important role in maintaining the hibernating state. In this study, we show that histamine neuronal systems undergo major changes during hibernation that are consistent with such a role. Immunohistochemical mapping of histaminergic fibers in the brains of hibernating and nonhibernating golden-mantled ground squirrels (C. lateralis) showed a clear increase in fiber density during the hibernating state. The tissue levels of histamine and its first metabolite tele-methylhistamine were also elevated throughout the brain of hibernating animals, suggesting an increase in histamine turnover during hibernation, which occurs without an increase in histidine decarboxylase mRNA expression. This hibernation-related apparent augmentation of histaminergic neurotransmission was particularly evident in the hypothalamus and hippocampus, areas of importance to the control of the hibernating state, in which tele-methylhistamine levels were increased more than threefold. These changes in the histamine neuronal system differ from those reported for the metabolic pattern in other monoaminergic systems during hibernation, which generally indicate a decrease in turnover. Our results suggest that the influence of histamine neuronal systems may be important in controlling CNS activity during hibernation. (+info)
Vectors of Chikungunya virus in Senegal: current data and transmission cycles.
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Chikungunya fever is a viral disease transmitted to human beings by Aedes genus mosquitoes. From 1972 to 1986 in Kedougou, Senegal, 178 Chikungunya virus strains were isolated from gallery forest mosquitoes, with most of them isolated from Ae. furcifer-taylori (129 strains), Ae. luteocephalus (27 strains), and Ae. dalzieli (12 strains). The characteristics of the sylvatic transmission cycle are a circulation periodicity with silent intervals that last approximately three years. Few epidemics of this disease have been reported in Senegal. The most recent one occurred in 1996 in Kaffrine where two Chikungunya virus strains were isolated from Ae. aegypti. The retrospective analysis of viral isolates from mosquitoes, wild vertebrates, and humans allowed to us to characterize Chikungunya virus transmission cycles in Senegal and to compare them with those of yellow fever virus. (+info)
Blastomycosis acquired occupationally during prairie dog relocation--Colorado, 1998.
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On August 31, 1998, two suspected cases of fungal pneumonia were reported to the Boulder County (Colorado) Health Department (BCHD). Both patients were immunocompetent, otherwise healthy adults working for the City of Boulder Open Space (CBOS) program on a prairie dog relocation project. This report summarizes the epidemiologic investigation by BCHD, the Colorado Department of Public Health and Environment, and CDC; the findings indicate that these two persons acquired blastomycosis in Colorado, which is outside the area where the disease is endemic. (+info)
Light-induced uncoupling of multioscillatory circadian system in a diurnal rodent, Asian chipmunk.
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Responses of the circadian locomotor rhythm to a single light pulse were examined in a diurnal rodent, Asian chipmunk, by exposing it to a 1-h light pulse of 2,000 lx under constant conditions. A light pulse given at the beginning and end of the subjective night produced a phase delay and advance shifts, respectively. When pulsed around the midpoint of the subjective night, the circadian rhythm was shifted as much as 12 h in most animals or became arrhythmic in some. In the latter case, an additional light pulse restored the circadian rhythm. Some animals were unresponsive to light. The phase response curve is categorized as type 0. A large phase-shift was sometimes followed by splitting of an activity band into two components. These results are best explained by an assumption that the chipmunk circadian system is composed of two mutually coupled major oscillators, each of which is constituted by multiple oscillators. Our results suggest that light affects the oscillatory coupling not only of the major oscillators but also of constitutional oscillators. (+info)
Gene expression in the brain across the hibernation cycle.
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The purpose of this study was to characterize changes in gene expression in the brain of a seasonal hibernator, the golden-mantled ground squirrel, Spermophilus lateralis, during the hibernation season. Very little information is available on molecular changes that correlate with hibernation state, and what has been done focused mainly on seasonal changes in peripheral tissues. We produced over 4000 reverse transcription-PCR products from euthermic and hibernating brain and compared them using differential display. Twenty-nine of the most promising were examined by Northern analysis. Although some small differences were observed across hibernation states, none of the 29 had significant changes. However, a more direct approach, investigating expression of putative hibernation-responsive genes by Northern analysis, revealed an increase in expression of transcription factors c-fos, junB, and c-Jun, but not junD, commencing during late torpor and peaking during the arousal phase of individual hibernation bouts. In contrast, prostaglandin D2 synthase declined during late torpor and arousal but returned to a high level on return to euthermia. Other genes that have putative roles in mammalian sleep or specific brain functions, including somatostatin, enkephalin, growth-associated protein 43, glutamate acid decarboxylases 65/67, histidine decarboxylase, and a sleep-related transcript SD464 did not change significantly during individual hibernation bouts. We also observed no decline in total RNA or total mRNA during torpor; such a decline had been previously hypothesized. Therefore, it appears that the dramatic changes in body temperature and other physiological variables that accompany hibernation involve only modest reprogramming of gene expression or steady-state mRNA levels. (+info)
Adaptation in the vertebral column: a comparative study of patterns of metameric variation in seven species of small mammals.
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The pattern of variation of certain vertebral measurements along the vertebral column is known to differ in man and mouse. This paper investigates changes in this pattern in 7 species of small mammals and attempts to correlate them with locomotor adaptations and limb dimensions. (+info)
Endothelial nitric oxide synthase (eNOS) is localized to Muller cells in all vertebrate retinas.
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The distribution of endothelial nitric oxide synthase immunoreactivity (eNOS-IR) was investigated in the retinas of all phylogenetic vertebrate classes by using a monoclonal eNOS antibody. Confocal light microscopy showed immunoreactive labeling in Muller cells of fish, frog, salamander, turtle, chicken, rat, ground squirrel, and monkey retina. In vascularized retinas (rat, monkey), astrocytes and some blood vessels were also stained. Furthermore, eNOS-IR was localized to axon terminals of turtle and fish horizontal cells. These observations are the first to show the presence of eNOS-IR in Muller glia and horizontal cell structures of the vertebrate retina. (+info)
Effect of isoproterenol on the L-type Ca2+ current in cardiac cells from rats and hybernating ground squirrels.
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The perforated patch clamp method was used to study the effect of the agonist of beta-adrenoreceptors isoproterenol on L-type Ca2+ current in cardiocytes of rats and ground squirrels in two states: active and hibernating. It is shown that isoproterenol exerts a dual effect on Ca2+ currents of rats and ground squirrels in the active state: at Vh = -50 mV, the current increases, whereas at Vh = -30 mV, it decreases. In hibernating ground squirrels, the dual effect of isoproterenol is not observed: isoproterenol increases Ca2+ current at any Vh values. The hypothesis is put forward that, during the entrance of ground squirrels into hibernation, the phosphorylation of one of the sites (not cAMP-dependent) of L-type Ca2+ channels is blocked. (+info)