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51.
We have investigated the phylogenetic relationships of monotremes and marsupials using nucleotide sequence data from the
neurotrophins; nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3). The study included
species representing monotremes, Australasian marsupials and placentals, as well as species representing birds, reptiles,
and fish. PCR was used to amplify fragments encoding parts of the neurotrophin genes from echidna, platypus, and eight marsupials
from four different orders. Phylogenetic trees were generated using parsimony analysis, and support for the different tree
structures was evaluated by bootstrapping. The analysis was performed with NGF, BDNF, or NT-3 sequence data used individually
as well as with the three neurotrophins in a combined matrix, thereby simultaneously considering phylogenetic information
from three separate genes. The results showed that the monotreme neurotrophin sequences associate to either therian or bird
neurotrophin sequences and suggests that the monotremes are not necessarily related closer to therians than to birds. Furthermore,
the results confirmed the present classification of four Australasian marsupial orders based on morphological characters,
and suggested a phylogenetic relationship where Dasyuromorphia is related closest to Peramelemorphia followed by Notoryctemorphia
and Diprotodontia. These studies show that sequence data from neurotrophins are well suited for phylogenetic analysis of mammals
and that neurotrophins can resolve basal relationships in the evolutionary tree.
Received: 27 January 1997 / Accepted: 20 March 1997 相似文献
52.
Abstract: In astrocytes, nerve growth factor (NGF) synthesis has been described to be stimulated by the cytokines interleukin-1β (IL-1β) and transforming growth factor-β1 (TGF-β1) and inhibited by corticosterone. As all three factors are present in the brain under certain conditions, we investigated the effect of their combined application on NGF secretion in the astroglial cell line RC7 and, in addition, studied the effect of calcitriol (1α,25-dihydroxyvitamin D3 ). Calcitriol stimulated NGF secretion, whereas corticosterone reduced basal levels of NGF secretion as well as inhibited the NGF secretion induced by IL-1β, calcitriol, and TGF-β1. Calcitriol had an additive effect when applied together with IL-1β and a synergistic effect when applied with TGF-β1. Moreover, calcitriol not only counteracted the inhibitory effect of corticosterone on NGF secretion stimulated by TGF-β1 but even augmented it to a level more than threefold higher than that reached with TGF-β1 alone. Due to the trophic effect of NGF on basal forebrain cholinergic neurons, these findings might be of therapeutic relevance under conditions where cholinergic function is impaired and the endogenous levels of corticosterone, IL-1β, or TGF-β1 are elevated. 相似文献
53.
Cholinergic Control of Nerve Growth Factor in Adult Rats: Evidence from Cortical Cholinergic Deafferentation and Chronic Drug Treatment 总被引:2,自引:0,他引:2
Steffen Roßner Gitta Wörtwein †Zezong Gu †Juan Yu Reinhard Schliebs Volker Bigl † J. Regino Perez-Polo 《Journal of neurochemistry》1997,69(3):947-953
Abstract: It is well documented that nerve growth factor (NGF) plays an important role in maintaining functions of cholinergic basal forebrain neurons. In the present study, we tested the hypothesis that cholinergic activity controls NGF levels in cholinoceptive neurons of the cerebral cortex and hippocampus. To address that question, we used both cholinergic deafferentation of cerebral cortex and hippocampus by cholinergic immunolesion with 192IgG-saporin and chronic pharmacological treatment of sham-treated and immunolesioned rats with the cholinergic agonist pilocarpine and the cholinergic antagonist scopolamine. We observed an increase in NGF protein levels in the cortex and hippocampus after cholinergic immunolesions and also after muscarinic receptor blockade by chronic intracerebroventricular scopolamine infusion in sham-treated rats after 2 weeks. There was no further increase in the accumulation of NGF after scopolamine treatment of immunolesioned rats. Chronic infusion of pilocarpine had no effect on cortical and hippocampal NGF protein levels in sham-treated rats. In rats with cholinergic immunolesions, however, pilocarpine did prevent the lesion-induced accumulation of NGF. There was no effect of cholinergic lesion and drug treatment on cortical or hippocampal NGF mRNA levels, consistent with the importance of NGF retrograde transport as opposed to its de novo synthesis. This study provides strong evidence for the hypothesis that there is cholinergic control of cortical and hippocampal NGF protein but not mRNA levels in adult rats. 相似文献
54.
BCL-2-Related Protein Expression in Apoptosis: Oxidative Stress Versus Serum Deprivation in PC12 Cells 总被引:5,自引:0,他引:5
Abstract: Expression of the BCL-2 protein family members, BAX, BAK, BAD, BCL-xL, BCL-xS, and BCL-2, was measured (by western blotting using specific antibodies) in PC12 cells before and during apoptosis induced by either H2 O2 treatment or by serum deprivation and during rescue from apoptosis by nerve growth factor (NGF). H2 O2 -induced apoptosis, as measured by DNA fragmentation, caused: (a) a dose-dependent increase in BAX, (b) a dose-independent increase in BAK, and (c) a dose-dependent inhibition of BAD expression. By comparison, apoptosis induced by serum deprivation resulted in a time-dependent decrease in both BAX and BAK, along with a dramatic and sudden decrease in BAD expression. However, when PC12 cells were incubated in an apoptosis-sparing medium (i.e., NGF-supplemented serum-free medium), both BAX and BAK were increased significantly, whereas BAD expression remained inhibited. BCL-xL expression was increased by H2 O2 but unaffected by serum deprivation or long-term NGF treatment. Neither BCL-2 nor BCL-xS expression could be detected in PC12 cells under the experimental conditions tested. Our results show that the expression of BAX, BAK, BAD, and BCL-xL is altered in a stimulus-dependent manner but cannot be used to define whether a cell will undergo or survive apoptosis. The similarity between changes in expression of BCL-2-related proteins induced by H2 O2 exposure and NGF rescue could reflect activation in part of a common antioxidant pathway. 相似文献
55.
神经生长因子家族及其受体研究进展 总被引:9,自引:0,他引:9
过去几年在神经营养因子、受体和神经元细胞程序性死亡的研究领域中取得了几项引人注目的进展:(1)神经生长因子(NGF)基因家族的其他一些成员包括脑源性神经营养因子(BDNF)、神经营养素-3(NT-3)、神经营养素-4(NT-4)、神经营养素-5(NT-5)的发现;(2)神经生长因子三维结构及功能和进化之关系的阐明;(3)定性了两种神经生长因子受体P75^NGFR和原癌基因p140^trkA以及相关 相似文献
56.
Neurotrophins, which are structurally related to nerve growth factor, have been shown to promote survival of various neurons.
Recently, we found a novel activity of a neurotrophin in the brain: Brain-derived neurotrophic factor (BDNF) enhances expression
of various neuropeptides. The neuropeptide differentiation activity was then compared among neurotrophins both in vivo and
in vitro. In cultured neocortical neurons, BDNF and neurotrophin-5 (NT-5) remarkably increased levels of neuropeptide Y and
somatostatin, and neurotrophin-3 (NT-3) also increased these peptides but required higher concentrations. At elevating substance
P, however, NT-3 was as potent as BDNF. In contrast, NGF had negligible or no effect. Neurotrophins administered into neonatal
brain exhibited slightly different potencies for increasing these neuropeptides: The most marked increase in neuropeptide
Y levels was obtained in the neocortex by NT-5, whereas in the striatum and hippocampus by BDNF, although all three neurotrophins
increased somatostatin similarly in all the brain regions examined. Overall spatial patterns of the neuropeptide induction
were similar among the neurotrophins. Neurons in adult rat brain can also react with the neurotrophins and alter neuropeptide
expression in a slightly different fashion. Excitatory neuronal activity and hormones are known to change expression of neurotrophins.
Therefore, neurotrophins, neuronal activity, and hormones influence each other and all regulate neurotransmitter/peptide expression
in developing and mature brain. Physiological implication of the neurotransmitter/peptide differentiation activities is also
discussed. 相似文献
57.
S V Rana S Mehta J S Chopra C K Nain U K Dhand J Mehta 《Journal of medical primatology》1984,13(4):205-217
An experimental model of protein calorie malnutrition (PCM) was created in young rhesus monkeys. Ulnar and tibial nerves from six monkeys with PCM, six rehabilitated and 12 control monkeys were studied for lipid composition and activity of myelin marker enzyme. Total lipids, myelin marker lipids and activity of myelin marker enzyme, 2', 3'-cyclic nucleotide 3' - phosphohydrolase were decreased, while esterified cholesterol and free fatty acids were increased in PCM as compared to controls. There was partial recovery in myelin marker lipids and complete restoration of other lipids on nutritional rehabilitation. 相似文献
58.
Dr. B. E. Brooker 《Cell and tissue research》1978,191(3):525-538
Summary Fibres growing from neurons of explanted dorsal root ganglia from 10 day chick embryos were transected and subsequently observed by light and electron microscopy after periods of a few to fifty minutes. Changes immediately proximal and distal to the cut together with alterations further away from the site of injury on both sides of the cut were recorded. Observations were also made on the growth cones of damaged axons and on changes in associated glial cells.Reactive and degenerative changes including the rotation, retraction and swelling of cut axons occurred rapidly. Electron microscopy revealed tracts of filamentous material close to the sealed-off ends of axons, swollen organelles such as mitochondria, and lamellar bodies of varying dimensions.Proximal to the injury and closer to the expiant, damaged and degenerating axons mingled with normal processes. Many contained only a fine granular material, others clumps of organelles, particularly mitochondria.Distal to the cut, microspikes were lost from some growth cones. The dense granular material filling microspikes and growth cones remained unchanged. Clumps of large clear vesicles, lamellar bodies and swollen degenerating mitochondria were present, not only within growth cones, but also in all parts of the axon distal to the cut.Glial cells associated with transected axons soon developed an electron dense cytoplasm containing swollen organelles. Large numbers of vesicles filled with a particulate substance were also found.The possible significance of the changes observed after transection are considered and discussed.The author wishes to thank Prof. D.W. James in whose laboratory at University College London these studies were initiated, Dr. A.R. Lieberman for his expert help and advice and the University of London Central Research Fund and Wellcome Trust for financial assistance 相似文献
59.
Eric Jakobsson 《Journal of mathematical biology》1978,6(3):235-248
Summary The axon membrane is simulated by standard Hodgkin-Huxley leakage and potassium channels plus a coupled transient excited
state kinetic scheme for the sodium channel. This scheme for the sodium channel is as proposed previously by the author. Simultations
are presented showing the form of the action potential, threshold behavior, accommodation, and repetitive firing. It is seen
that the form of the individual action potential, its all-or-none nature, and its refractory period are well simulated by
this model, as they are by the standard Hodgkin-Huxley model. However, the model differs markedly from the Hodgkin-Huxley
model with respect to repetitive firing and accommodation to stimulating currents of slowly rising intensity, in ways that
are anomn to be related to those features of the sodium inactivation which are anomalous to the H-H model. The tendency for
repetitive firing is highly dependent on that parameter which primarily determintes the existence of the inactivation shift
in voltage clamp experiments, in such a way that the more pronounced the inactivation shift, the less the tendency for repetitive
firing,. The tendency for accommodation is highly dependent on that parameter which primarily determines the “τc − τh” separation, in such a way that the greater the separation the greater the tendency for the membrane to accommodate without
firing action potentials to a slowly rising current. 相似文献
60.
Summary An ultrastructural analysis is presented of the cuticular and neural structures formed by the prothoracic leg and wing imaginal discs of maleDrosophila melanogaster larvae during culture in vitro with 0.2 g/ml of -ecdysone. A pupal cuticle, and subsequently an imaginal cuticle with a well-defined epicuticle and a laminated endocuticle is formed. The ultrastructure of the epidermis and of cuticular structures such as bristles, trichomes, apodemes, and tracheoles is very similar to that found in situ. Dendrites and nerve cell bodies are formed in vitro, and sensory axons form nerve bundles similar to those of normal appendages in situ, despite their isolation from the central nervous system. It is concluded that at the ultrastructural level, differentiation in vitro closely parallels the normal course of development. 相似文献