Non-neural Tissues (non-neural + tissue)

Distribution by Scientific Domains

Selected Abstracts

Challenging the omnipotence of the suprachiasmatic timekeeper: are circadian oscillators present throughout the mammalian brain?

Clare Guilding
Abstract The suprachiasmatic nucleus of the hypothalamus (SCN) is the master circadian pacemaker or clock in the mammalian brain. Canonical theory holds that the output from this single, dominant clock is responsible for driving most daily rhythms in physiology and behaviour. However, important recent findings challenge this uniclock model and reveal clock-like activities in many neural and non-neural tissues. Thus, in addition to the SCN, a number of areas of the mammalian brain including the olfactory bulb, amygdala, lateral habenula and a variety of nuclei in the hypothalamus, express circadian rhythms in core clock gene expression, hormone output and electrical activity. This review examines the evidence for extra-SCN circadian oscillators in the mammalian brain and highlights some of the essential properties and key differences between brain oscillators. The demonstration of neural pacemakers outside the SCN has wide-ranging implications for models of the circadian system at a whole-organism level. [source]

Laboratory diagnosis of variant Creutzfeldt,Jakob disease

J W Ironside
The neuropathological and biochemical features of 33 cases of variant Creutzfeldt,Jakob disease (vCJD) diagnosed up to the end of 1998 are analysed in relation to the 646 cases of suspected CJD referred to the CJD Surveillance Unit laboratory from 1990 to 1998. Morphological studies of the central nervous system, lymphoid tissues and other organs were accompanied by immunocytochemistry; Western blot analysis of PrPRES was performed on frozen brain tissue. The findings were analysed in relation to clinical and genetic data. The pathology of vCJD showed morphological and immunocytochemical characteristics distinct from other cases of CJD. PrP accumulation was widespread in lymphoid tissues in vCJD, but was not identified in other non-neural tissues. PrPRES accumulation in vCJD brain tissue showed a uniform glycotype pattern distinct from sporadic CJD. All analysed cases of vCJD were methionine homozygotes at codon 129 of the PrP gene. No evidence currently exists to suggest that cases of CJD diagnosed in individuals who are MV or VV at codon 129 of the PrP gene represent ,human bovine spongiform encaphalopathy (BSE)'. Continued surveillance is required to further investigate this possibility, with the need to investigate autopsy tissues from suspected cases by histological and biochemical techniques. [source]

Neurocalcin-like immunoreactivity in embryonic stages of the gastropod molluscs Aplysia californica and Lymnaea stagnalis

Amanda J.G. Dickinson
Neurocalcin is a calcium-binding protein that has been localized in neural and non-neural tissues of vertebrates, the arthropod Drosophila melanogaster, and in juveniles and adults of the mollusc Aplysia californica. We examine the distribution of neurocalcin in pre-hatching stages of the molluscs A. californica and Lymnaea stagnalis to elucidate where this calcium-binding protein functions in early development, as well as to localize novel neuronal populations in early stages of ontogeny. Aplysia neurocalcin (ApNc)-like immunoreactivity was localized in shell-secreting cells in embryonic stages of both A. californica and L. stagnalis. In A. californica, central and anterior regions of the embryo were diffusely labeled, as were a few identifiable neurons in veliger stages, On the other hand, in L. stagnalis, ApNc-like immunoreactivity was clearly detected in cells and fibers in the same locations as neuronal elements that have been previously identified very early in development and throughout the embryonic period using techniques to localize specific transmitters and peptides. Furthermore, additional neurons are also identified with anti- ApNc in this species. Establishing the distribution of neurocalcin-like proteins in embryonic stages of these two molluscs provides the first step to understanding the role of such proteins during development. [source]

Daily oscillations in liver function: diurnal vs circadian rhythmicity

Alec J. Davidson
Abstract: The rodent suprachiasmatic nucleus (SCN), a site in the brain that contains a light-entrained biological (circadian) clock, has been thought of as the master oscillator, regulating processes as diverse as cell division, reproductive cycles, sleep, and feeding. However, a second circadian system exists that can be entrained by meal feeding and has an influence over metabolism and behavior. Recent advances in the molecular genetics of circadian clocks are revealing clock characteristics such as rhythmic clock gene expression in a variety of non-neural tissues such as liver. Although little is known regarding the function of these clock genes in the liver, there is a large literature that addresses the capabilities of this organ to keep time. This time-keeping capability may be an adaptive function allowing for the prediction of mealtime and therefore improved digestion and energy usage. Consequently, an understanding of these rhythms is of great importance. This review summarizes the results of studies on diurnal and circadian rhythmicity in the rodent liver. We hope to lend support to the hypothesis that there are functionally important circadian clocks outside of the brain that are not light- or SCN-dependent. Rather, these clocks are largely responsive to stimuli involved in nutrient intake. The interaction between these two systems may be very important for the ability of organisms to synchronize their internal physiology. [source]