Corticotropin releasing factor (CRF), synthesized in neurons of the hypothalamic paraventricular nucleus (PVN), is one of the main regulators of the pituitary-adrenal cortex endocrine axis. In order to elucidate the possible involvement of the central neuropeptide-Y (NPY)- and adrenocorticotroph hormone (ACTH)-immunoreactive (IR) systems in the innervation of hypophysiotrophic CRF-synthesizing neurons, immunocytochemical double labelling studies were conducted in the hypothalamus of the rat to localize CRF-synthesizing neurons, as well as neuronal fibers exhibiting NPY and ACTH-immunoreactivity, respectively. The parvocellular subnuclei of the PVN received an intense NPY- and ACTH-IR innervation. At the light microscopic level, these peptidergic axons were associated with the dendrites and perikarya of CRF-IR neurons. Ultrastructural analysis revealed that NPY- and ACTH-IR axons established synaptic specializations with parvocellular neurons expressing CRF-immunoreactivity. These findings indicate that both neuropeptide-Y and adrenocorticotroph hormone containing neuronal systems of the brain are capable of influencing adrenal function via synaptic interactions with hypophysiotrophic CRF-synthesizing neurons. The data also support the concept that NPY and ACTH might be utilized as neuromodulators within the PVN. 相似文献
Growth hormone (GH) production of the anterior pituitary gland is controlled by inhibiting and releasing hormones that are synthesized in the diencephalon. In order to elucidate the possible interrelationships between somatostatin and growth hormone-releasing factor (GRF) synthesizing neurons at the hypothalamic level, immunocytochemical double labelling studies were performed on sections containing the arcuate nucleus (ARC) of the rat. Somatostatin producing neurons were located in the dorsomedial part of the ARC, while somatostatin immunoreactive (IR) axons were found in the ventro-lateral part of the nucleus, an area containing GRF-synthesizing cells. The use of the dual antigen localization technique revealed the approach and juxtaposition of somatostatin containing axons to dendrites and cell bodies of GRF-synthesizing neurons. At the light microscopic level, several somatostatinergic axon varicosities were clustered around single GRF-synthesizing cells. Ultrastructural analysis of the ventro-lateral part of the ARC showed that (i), somatostatinergic axons established synaptic connections (ii), GRF-producing neurons received axons terminals on their somata and dendrites and (iii), somatostatin-IR axons formed asymmetric synaptic specializations with both dendrites and somata of GRF-synthesizing neurons. These morphological findings indicate that the hormone production and release of hypophysiotrophic GRF-IR neurons can be influenced by the central somatostatin system via direct synaptic mechanisms. The data support the concept, that the interaction of inhibiting and releasing hormones, which determines responses of the pituitary target cells, may take place also at the hypothalamic level. 相似文献
Summary Corticotropin releasing factor (CRF), synthesized in neurons of the hypothalamic paraventricular nucleus (PVN), is one of the main regulators of the pituitaryadrenal cortex endocrine axis. In order to elucidate the possible involvement of the central neuropeptide-Y (NPY)-and adrenocorticotroph hormone (ACTH)-immunoreactive (IR) systems in the innervation of hypophysiotrophic CRF-synthesizing neurons, immunocytochemical double labelling studies were conducted in the hypothalamus of the rat to localize CRF-synthesizing neurons, as well as neuronal fibers exhibiting NPY and ACTH-immunoreactivity, respectively.The parvocellular subnuclei of the PVN received an intense NPY-and ACTH-IR innervation. At the light microscopic level, these peptidergic axons were associated with the dendrites and perikarya of CRF-IR neurons. Ultrastructural analysis revealed that NPY- and ACTH-IR axons established synaptic specializations with parvocellular neurons expressing CRF-immunoreactivity. These findings indicate that both neuropeptide-Y and adrenocorticotroph hormone containing neuronal systems of the brain are capable of influencing adrenal function via synaptic interactions with hypophysiotrophic CRF-synthesizing neurons. The data also support the concept that NPY and ACTH might be ntilized as neuromodulators within the PVN.Dedicated to Professor Dr. T.H. Schiebler on the occasion of his 65th birthday 相似文献
Fruit of soursop, Annona muricata L., showed increased CO2 production 2 days after harvest, preceding the respiratory increase that coincided with autocatalytic ethylene evolution and other ripening phenomena. Experiments to alter gas exchange patterns of postharvest fruit parts and tissue cylinders had little success.
The respiratory quotient of tissue discs was near unity throughout development. 2,4-Dinitrophenol uncoupled respiration more effectively than carbonylcyanide m-chlorophenylhydrazone; 0.4 millimolar KCN stimulated, 4 millimolar salicylhydroxamic acid slightly inhibited, and their combination strongly inhibited respiration, as did 10 millimolar NaN3. Tricarboxylic acid cycle members and ascorbate were more effective substrates than sugars, but acetate and glutarate strongly inhibited.
Disc respiration showed the same early peak as whole fruit respiration; this peak is thus an inherent characteristic of postharvest development and cannot be ascribed to differences between ovaries of the aggregatetype fruit. The capacity of the respiratory apparatus did not change during this preclimacteric peak, but the contents of rate-limiting malate and citrate increased after harvest.
It is concluded that the preclimacteric rise in CO2 evolution reflects increased mitochondrial respiration because of enhanced supply of carboxylates as a substrate, probably induced by detachment from the tree. The second rise corresponds with the respiration during ripening of other climacteric fruits.
Physiological and genetic studies have been undertaken to further the understanding of genetic variation in response to high concentrations of B in the soil and so facilitate the breeding of tolerant varieties for cultivation in high B regions. Genetic variation in response to high concentrations of B has been identified for a number of crop and pasture species of southern Australia, including wheat, barley, oats, field peas and annual pasture medics. The wheat variety Halberd, which was the most widely grown variety in Australia during the 1970s and early 1980s, is the most tolerant of the current Australian wheat varieties. The mechanism of tolerance for all species studied is reduced accumulation of B by tolerant genotypes in both roots and shoots. Results from experiments of uptake kinetics indicate that control of B uptake is a non-metabolic process. The response of wheat to high B supply is under the control of several major additive genes, one of which has been located to chromosome 4A. 相似文献
The Mre11-Rad50 complex is highly conserved, yet the mechanisms by which Rad50 ATP-driven states regulate the sensing, processing and signaling of DNA double-strand breaks are largely unknown. Here we design structure-based mutations in Pyrococcus furiosus Rad50 to alter protein core plasticity and residues undergoing ATP-driven movements within the catalytic domains. With this strategy we identify Rad50 separation-of-function mutants that either promote or destabilize the ATP-bound state. Crystal structures, X-ray scattering, biochemical assays, and functional analyses of mutant PfRad50 complexes show that the ATP-induced ‘closed’ conformation promotes DNA end binding and end tethering, while hydrolysis-induced opening is essential for DNA resection. Reducing the stability of the ATP-bound state impairs DNA repair and Tel1 (ATM) checkpoint signaling in Schizosaccharomyces pombe, double-strand break resection in Saccharomyces cerevisiae, and ATM activation by human Mre11-Rad50-Nbs1 in vitro, supporting the generality of the P. furiosus Rad50 structure-based mutational analyses. These collective results suggest that ATP-dependent Rad50 conformations switch the Mre11-Rad50 complex between DNA tethering, ATM signaling, and 5′ strand resection, revealing molecular mechanisms regulating responses to DNA double-strand breaks. 相似文献
A population of neuronal cell bodies and their fiber pathways have been elucidated within the ovine hypothalamus. The immunoreactive neurons were located in the anterior and dorsal hypothalamus interspersed throughout the paraventricular nucleus. These perikarya were only observed when an antiserum that was generated against the C-terminal of CRF was employed. A dense fiber projection traversed the medial-basal hypothalamus and ended within the palisade-contact zone of the median eminence and neural stem. Fibers were revealed by antisera generated against both the N-terminal and the C-terminal of CRF. Antisera pre-absorbed with synthetic CRF failed to yield immunoreactivity. 相似文献
A sample of winter faba bean germplasm from China was compared with germplasm from outside China, using AFLP analyses. Both
sets of germplasm were obtained from the National Genebank of China, Institute of Crop Sciences (ICS), Chinese Academy of
Agricultural Sciences, Beijing, China. A sample of 39 winter type accessions from outside of China and 204 Chinese landraces
and varieties (201 winter types and 3 spring types) were characterized with 10 AFLP primers. These detected 266 polymorphic
bands. The Chinese germplasm was clearly separated from the rest of the world in principal component analysis and clustering
analysis, with the spring types from China showing the greatest separation. Yunnan germplasm, both landraces and commercial
varieties, showed the greatest separation among the germplasm of Chinese winter faba bean provinces. The landraces/varieties
from Anhui, Zhejiang, Sichuan, Jianxi, Guizhou and Fujian provinces clustered in a central group.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
Double-strand breaks in chromosomal DNA are repaired efficiently in eukaryotic cells through pathways that involve direct religation of broken ends, or through pathways that utilize an unbroken, homologous DNA molecule as a template for replication. Pathways of repair that require homology initiate with the resection of the 5' strand at the break site, to uncover the 3' single-stranded DNA that becomes a critical intermediate in single-strand annealing and in homologous strand exchange. Resection of the 5' strand is regulated to occur most efficiently in S and G(2) phases of the cell cycle when sister chromatids are present as recombination templates. The mechanisms governing resection in eukaryotes have been elusive for many years, but recent work has identified the major players in short-range processing of DNA ends as well as the extensive resection of breaks that has been observed in vivo. This review focuses on the Mre11/Rad50/Xrs2(Nbs1) complex and the Sae2(CtIP) protein and their roles in initiating both short-range and long-range resection, the effects of topoisomerase-DNA conjugates on resection in vivo, and the relationship between these factors and NHEJ proteins in regulating 5' strand resection in eukaryotic cells. 相似文献