Biomedical subjects

X F Zhou

Publications and source records attributed to X F Zhou.

At least 55 records · Page 3Linked to original sources

PubMed1997

Increased brain-derived neurotrophic factor immunoreactivity in rat dorsal root ganglia and spinal cord following peripheral inflammation.

Our recent study showed that peripheral inflammation induced an increased expression of brain-derived neurotrophic factor (BDNF) mRNA which was mediated by nerve growth factor (NGF) in the dorsal root ganglion (DRG). In the present study, we evaluated the change of BDNF immunoreactivity in the DRG and spinal cord following peripheral inflammation by means of immunohistochemistry. Significant increases in the percentage of BDNF-immunoreactive (IR) neuron profiles in the L5 DRG and marked elevation in the expression of BDNF-IR terminals in the spinal dorsal horn were observed following peripheral tissue inflammation produced by an intraplantar injection of Freund's adjuvant into the rat paws. These findings suggest that peripheral tissue inflammation induces an increased BDNF synthesis in the DRG and an elevated anterograde transport of BDNF to the spinal dorsal horn. The functional role of this increased BDNF was discussed briefly.

Animals↗

PubMed1997

Ultrastructural changes of sympathetic neurons following neurotrophin 3 antiserum treatment in young rat.

We have previously demonstrated that neurotrophin-3 antiserum administration to rats during the first 2 postnatal weeks results in a massive reduction of neurons in the superior cervical ganglion. In the present study, an ultrastructural analysis was undertaken to elucidate the mechanism by which neurotrophin-3 deprivation causes neuronal death. Newborn and 4-week-old rats were injected with either neurotrophin-3 antiserum or normal rabbit serum or used without injection. Superior cervical ganglia from each animal were examined by routine electron microscopy. Most neurons in the ganglia from untreated rats had a large and round nucleus with one or two nucleoli. Chromatin within the nucleus was evenly distributed. A double-layer nuclear membrane could be distinguished and the cytoplasm contained abundant organelles. Treatment with neurotrophin-3 antiserum for 24 h in neonates resulted in chromatin clumping in the nucleus of many neurons. The nuclear membrane became rough and occasionally folded. In the cytoplasm, the Golgi apparatus was disrupted. Three days after treatment, these changes became more obvious. The chromatin in the nucleus was often aggregated and marginalized. Vacuolation was present in many membranous organelles throughout the cytoplasm. Although neurotrophin-3 antiserum given to 4-week-old rats had little effect on overall neuronal numbers (Tafreshi, Zhou, and Rush, unpublished), a few neurons, undergoing either apoptotic or cytolytic cell death, were identified 7 days later. Most affected neurons were located near small blood vessels or capillaries and were associated with numerous nonneuronal cells. The debris of degenerating neurons were surrounded by the processes of glia cells. These findings support the view that loss of endogenous neurotrophin-3 following neutralization with specific antibody leads to activation of apoptotic pathways within the affected neurons. However, the presence of neurons dying as a result of cytolysis suggests that other mechanisms may also be involved.

Animals↗

PubMed1997

Neurotrophic factors are required by mature sympathetic neurons for survival, transmission and connectivity.

1. Two neuronal growth factors, nerve growth factor (NGF) and neurotrophin 3 (NT3), have been studied for their action on the developing and mature sympathetic nervous system. 2. Antibodies to each factor have proved useful as reagents for the detection and quantification of NGF and NT3. They have also proved valuable in uncovering the functional roles of each factor by their ability to neutralize the endogenous molecules. 3. Nerve growth factor acts on postnatal neurons to control neurotransmission, connectivity and survival. Like NGF, NT3 is synthesized by effector tissues and is retrogradely transported by post-ganglionic neurons to prevent cell death. However, the two factors have been shown to have quite distinct functions in mature neurons, indicating the existence of different signalling pathways. This differential action extends to secondary influences on satellite glia. 4. Pathological consequences result from excessive growth factor synthesis leading, in the hypertensive rat, to hyperinnervation and elevated blood pressure. Satellite glial cell synthesis of the factors and their receptors following peripheral nerve damage appears to be responsible for the establishment of inappropriate neuronal connections between sympathetic nerve terminals and sensory somata. 5. It is concluded that these potent factors control, by both coincident and independent mechanisms, sympathetic neuronal function throughout the life of the animal.

Animals↗

PubMed1997

Rat mature sympathetic neurones derive neurotrophin 3 from peripheral effector tissues.

In a previous study we have demonstrated that endogenous neurotrophin 3 (NT3) is required for the survival of most sympathetic neurones in postnatal rats. However, the mechanisms underlying the action of NT3 on sympathetic neurones is not known. Neither is it understood whether NT3 is retrogradely transported from peripheral tissues or acts locally in an autocrine fashion. In the present study, NT3-mRNA was quantified in sympathetic effector tissues and NT3 protein was localized in intact and lesioned sympathetic nerves in rats. NT3-mRNA is expressed and developmentally regulated in many effector tissues including mesenteric arteries, salivary gland, heart and kidney but hardly detectable in the superior cervical ganglia of adult animals. The majority of sympathetic neurones express immunoreactivity for TrkA and TrkC in both neonatal and adult rats. Sympathetic somata are normally immunoreactive for NT3, but the immunoreactivity is abolished by systemic administration of NT3 antibodies or axotomy of postganglionic neurones, suggesting an accumulation of NT3 from extraneuronal sources. Furthermore, the detection of NT3-immunoreactivity in the internal carotid nerve as early as 3 h following a compression and only on the distal side indicates endogenous NT3 is retrogradely transported by sympathetic neurones. These studies provide evidence indicating that NT3, like nerve growth factor, is an effector tissue-derived neurotrophic factor for sympathetic neurones both during development and in the adult animal. Thus, we have provided a clear example that one type of neurone derives, through a retrograde transport mechanism, two neurotrophic factors simultaneously from its peripheral effector tissues.

Adrenergic Fibers↗

PubMed1996

Detection of increased tissue concentrations of nerve growth factor with an improved extraction procedure.

Nerve growth factor (NGF) is a protein essential for the survival and normal function of sympathetic neurons. Two-site immunoassays have been developed over the past decade in several laboratories and used to estimate its endogenous concentrations in a variety of effector tissues. However, levels appear restricted to a narrow range, display only a poor correlation with innervation density, and show obvious inter- and intralaboratory variations, the origins of which are unclear. This led us to examine alternative extraction procedures for NGF before quantification. In particular, we have found treatment of tissue extracts with high and low pH in the presence of detergent results in the detection of higher NGF concentrations in immunoassays using either polyclonal or commercially available monoclonal antibodies. These increases were tissue-specific (sciatic nerve, mesenteric arteries, and thoracic aorta > heart and brain > sympathetic ganglia > abdominal aorta) and as much as 10 times greater than the amounts detected by traditional procedures. The method should also prove useful for the assay of other members of the neurotrophin family when appropriate antibodies become available.

Age Factors↗

PubMed1996

Endogenous nerve growth factor is required for regulation of the low affinity neurotrophin receptor (p75) in sympathetic but not sensory ganglia.

During development, many sympathetic and sensory neurons are dependent on nerve growth factor (NGF) for survival. The low affinity neurotrophin receptor (p75), expressed in these neurons, is regulated by exogenous NGF in vitro and in vivo. However, whether p75 expression in vivo is under the control of endogenous NGF has not been determined. The role of NGF in regulating the expression of p75 in sympathetic and sensory nerves was investigated in Sprague-Dawley rats treated with an antiserum specific for NGF. P75 was differentially regulated. P75 immunoreactivity (-ir) within sympathetic neurons in the superior cervical ganglia (SCG) was reduced after 2 days, and disappeared after 5 days, of treatment with the NGF antiserum. In contrast, a significant increase in p75-ir was detected in nerve bundles within and close to the SCG from 3 to 14 days after treatment. A similar pattern of p75 expression was observed in the stellate and coeliac ganglia. In contrast, p75 expression in nerve terminals of the mesenteric arteries and irides was reduced. However, in the same animals the expression of p75 was not significantly affected by the treatment in dorsal root, trigeminal or nodose ganglia, salivary gland or small intestine. In contrast to p75, the NGF high affinity receptor trkA was little affected in sympathetic neurons by depletion of endogenous NGF for 2 weeks. These results indicate that endogenous NGF is required in sympathetic ganglia for the expression of p75 but not trkA in neurons, but for the down-regulation of p75 in glia. In contrast, endogenous NGF is not essential for the regulation of p75 in neurons or glia within sensory ganglia.

Animals↗

PubMed1996

Effect of biocide concentration on electrorotation spectra of yeast cells.

The effect of the biocide Cosmocil (polyhexanide) at different concentrations on the electrorotation spectra of yeast cells is investigated over the frequency range from 1 kHz to 10 MHz. The dielectric properties of the yeast, before and after biocide treatment, were deduced from the electrorotation spectra using two-shell ellipsoid modelling methods that have been well tested for other heterogeneous biological systems. The results show a gradual increase in the cytoplasmic membrane conductivity with increasing biocide concentration, rather than an "all-or-nothing' breakdown of the membrane. The technique gives a quantitative analysis of the toxic damage by chemicals to cells and can be exploited in the development of new pharmacological agents.

Biguanides↗

PubMed1996

Differential expression of the p75 nerve growth factor receptor in glia and neurons of the rat dorsal root ganglia after peripheral nerve transection.

Sympathetic nerve terminals on blood vessels within the dorsal root ganglia sprout after sciatic nerve lesions in the rat. The mechanism underlying this phenomenon is not clear, but might be predicted to involve nerve growth factor or its homologs because these factors are known to trigger collateral sprouting of undamaged sympathetic noradrenergic terminals. We have found that sciatic nerve lesions lead to a decreased expression of neuronal p75, the low-affinity receptor for the neurotrophins, but an increased expression of glial p75 in ipsilateral dorsal root ganglia. Intriguingly, the increased expression of p75 was found primarily in association with glia surrounding large-diameter neurons, which are those associated with the noradrenergic sprouts. A smaller but significant glial response was also found in contralateral ganglia. The glial response in ipsilateral ganglia could be mimicked by ventral, but not dorsal, root transection. The dorsal root lesion-induced glial responses in contralateral ganglia were greater than those induced by ventral root or sciatic nerve lesions. Combined lesions of dorsal root and either ventral root or sciatic nerve did not prevent the glial responses of ipsilateral ganglia, suggesting that a peripheral signal is involved. Colocalization studies indicate that tyrosine hydroxylase-immunoreactive nerve sprouts were associated with p75-immunoreactive glial cells. Thus, increased glial synthesis of p75 might provide an explanation for the abnormal growth of sympathetic fibers in dorsal root ganglia after peripheral nerve injury.

Animals↗

PubMed1996

Neurotrophin-3 and trkC-immunoreactive neurons in rat dorsal root ganglia correlate by distribution and morphology.

Previous studies have shown that a subpopulation of large dorsal root ganglion neurons contains neurotrophin-3 (NT3)-like immunoreactivity. It is not known, however, whether these NT3 immunoreactive neurons also express the high affinity receptor for NT3, trkC. In the present study, the distribution and morphology of trkC immunoreactive neurons have been correlated with those of NT3 immunoreactive neurons in the dorsal root ganglia. Size and segmental distributions of both antigens indicate that they are present in the same group of large sensory neurons. Almost twice the number of these neurons are present in the cervical and lumbar spinal ganglia than in the thoracic. Co-localization study indicates that 94% of NT3 immunoreactive neurons express trkC. Our findings support the proposal that NT3 in these neurons is derived from their peripheral targets rather than synthesized in situ.

Animals↗

PubMed1996

Functional roles of neurotrophin 3 in the developing and mature sympathetic nervous system.

Nerve growth factor (NGF) is a potent regulator of sympathetic neuronal function in both developing and adult animals. This article reviews the evidence published in recent years indicating that another member of the NGF family, neurotrophin 3 (NT3), plays both a complementary and overlapping role in the development and maturation of sympathetic neurons. In migratory neural crest cells, expression of the high-affinity receptor, trkC, and promotion of mitosis by NT3 suggest an involvement in gangliogenesis, since sympathetic neuroblasts express both NT3 and trkC and require NT3 for their proliferation, differentiation, and survival, it has been proposed that the factor acts at this developmental stage as an autocrine or paracrine factor. However, NT3 also acts in parallel with NGF to promote the survival of postmitotic neurons during late development. Both trkC and trkA are expressed in sympathetic neurons and function as high-affinity receptors for NT3. NT3 is synthesized in sympathetic effector tissues and the endogenous factor is retrogradely transported to accumulate within the cell soma. Thus, in addition to its role in the differentiation of sympathetic neurons, NT3, like NGF, is also an effector tissue-derived neurotrophic factor for these neurons in maturity.

Animals↗

PubMed1996

Endogenous brain-derived neurotrophic factor is anterogradely transported in primary sensory neurons.

Neurotrophins are a family of proteins which act as survival and differentiative factors in the developing and mature nervous system. Extensive evidence has been provided for their retrograde action following incorporation into nerve terminals and transport to the cell body. In contrast, we now demonstrate that one neurotrophin, brain-derived neurotrophic factor, is transported anterogradely via both peripheral and central processes of spinal sensory neurons. Using newly generated antisera, we have examined the distribution of brain-derived neurotrophic factor immunoreactivity and found it to be present within a subpopulation of sensory somata, primarily those with a small-to-medium diameter. The immunoreactivity was accumulated on both the distal and proximal sides of a ligature on the sciatic nerve. The accumulation on the distal side, but not on the proximal side, was substantially reduced by pretreatment with brain-derived neurotrophic factor antibodies in vivo. In contrast to the periphery, the immunoreactivity only accumulated on the proximal side of a lesion of the dorsal root. In the spinal cord, most nerve terminals immunoreactive for brain-derived neurotrophic factor were identified in lamina II. Lesion of the dorsal root led to a reduction of these nerve terminals. These studies indicate that the factor is transported not only retrogradely to, but also anterogradely from, the spinal ganglia to terminals in the periphery and spinal cord. The findings add a new dimension to the role of neuronal growth factors, since anterograde transport has not been observed previously for any endogenous survival factor.

Animals↗

PubMed1996

Analysis of low affinity neurotrophin receptor (p75) expression in glia of the CNS-PNS transition zone following dorsal root transection.

Peripheral nerves exit from the brain through the transition zone where oligodendroyctes and astrocytes of the central nervous system (CNS) and Schwann cells of the peripheral nervous system (PNS) are in close proximity. In this zone, the same axons are ensheathed by oligo-dendrocytes and Schwann cells. We examined, in adult rats, the expression of the low affinity neurotrophin receptor (p75) in central glia and Schwann cells in response to lesion of lumbar dorsal roots. In normal rats, scattered p75-immunoreactive glial cells were present in the CNS-PNS transition zone. A marked increase of p75 immunoreactivity occurred in Schwann cells near the transition zone from 4 days to at least 3 weeks after dorsal root transection. In contrast, the p75 immunoreactivity remained unchanged in central glia. The differential expression of p75 in the two types of glial cells was sharply demarcated at the CNS-PNS border. Our results are consistent with earlier observations that axon damage is less potent in its ability to induce central glial expression of p75, and further, suggests a possible mechanism for the failure of regenerating dorsal root axons growing into the spinal cord.

Animals↗

PubMed1996

Photosensitization of bilirubin on proliferation and DNA synthesis in ascitic hepatoma cells.

AIM: To observe the effects and its mechanism of photosensitization of bilirubin on ascitic hepatoma (Hep A) cells. METHODS: After the cells were illuminated under the light (1.0 x 10(5) lx) for 10 min, deoxy[3H]thymidine was added for DNA synthesis assay. The cells were dyed with 0.5% trypan blue and were counted. RESULTS: The cell mortality of illuminated groups were much higher than that of dark groups (P < 0.01). The inhibitions of DNA synthesis of illuminated groups were stronger than that of dark groups (P < 0.01). The cell mortality and inhibition of DNA synthesis of illuminated groups were positively dependent upon the concentrations of bilirubin and illuminating time. No difference of DNA synthesis between room light illumination groups and dark groups (P < 0.05). CONCLUSION: The photosensitization of bilirubin killed Hep A cells obviously. Bilirubin under room light had no effect on inhibition of DNA synthesis. The photosensitization of bilirubin was closely related to 1O2 and H2O2 and not to OH. and O2-. Bilirubin, the end product of heme catabolism in mammals, is a potentially cytotoxic, lipid soluble waste product that needs to be excreted. However, bilirubin at micromolar concentration in vitro, efficiently scavenges peroxyl radicals. In liposomes, bilirubin suppresses the antioxidation more than alpha-tocopherol, which is regarded as the best antioxidant of lipid peroxidation. Thus bilirubin is a physiological, chain-breaking antioxidant. Bilirubin exhibited antitumor activity and acted as a photosensitizer with four pyrrole rings. Many photosensitizers have been used to treat cancer due to their photosensitization. In this paper, the photosensitization of bilirubin on DNA synthesis in ascitic hepatoma (Hep A) cells and on cell mortality were studied.

Animals↗

PubMed1995

Peripheral projections of rat primary sensory neurons immunoreactive for neurotrophin 3.

Sensory neurons can be classified into subpopulations based on a variety of characteristics, including their morphology and physiological modalities. Whether any of these classifications correlates with neurotrophic sensitivities has not been determined. We have recently reported that a subpopulation of large diameter sensory neurons of the rat contain neurotrophin 3-like immunoreactivity (NT3-ir). In this study, we have further characterised NT3-ir sensory neurons by their size, segmental localization, and peripheral projections by combined techniques of retrograde tracing and immunohistochemistry. The size distribution showed that NT3-ir was localised to a subpopulation of large-diameter neurons ranging from 560 to 3,120 microns2. Greater numbers of NT3-ir neurons reside in trigeminal (43% of total), cervical (36%), and lumbar (39%) than in thoracic spinal ganglia (13-17%). In combination with Fluoro-Gold retrograde tracing, it was found that about 30% of sensory neurons projecting to the tibial muscle were NT3-ir, compared with 39% for tendon, 50% for whisker hair follicles, 17% for subdermis or epidermis, and only 1% for kidney or adrenal gland. These studies indicate that NT3-ir sensory neurons mainly project to skin and muscles but not viscera. Thus, the characterization of NT3-ir spinal sensory neurons suggests that large sensory neurons subserving proprioception and mechanoception require NT3 for the maintenance of normal function.

Animals↗

PubMed1995

Differentiation of viable and non-viable bacterial biofilms using electrorotation.

A new technique for studying the properties of biofilms has been developed, based on the phenomenon of electrorotation. Biofilms of Klebsiella rubiacearum were formed on the surfaces of 6 microns diameter polystyrene beads, and the presence of such films was found to alter their electrorotation spectra. The effects of adding a biocide (polyhexanide) to the surrounding aqueous medium was also investigated. The dielectric properties of the beads with biofilms, before and after biocide treatment, were interpreted from the electrorotation spectra using modelling methods that have been well tested for other heterogeneous biological systems. The technique is of value in understanding the physico-chemical properties of biofilms and can be adapted for monitoring the presence of toxic chemicals and for testing the activity of biocides against biofilms.

Biofilms↗

PubMed1995

Sympathetic neurons in neonatal rats require endogenous neurotrophin-3 for survival.

Gene deletion of neurotrophin-3 (NT3) results in severe sensory and sympathetic deficits that are incompatible with postnatal life in mice. We have now addressed the question of whether NT3 plays a role in the postnatal animal. An antiserum specific for NT3 and capable of blocking the survival effect of the factor in vitro has been generated and given to neonatal rats. Antiserum administration during either or both of the first 2 postnatal weeks resulted in a 54-74% reduction in the size of the superior cervical ganglia, reflecting a loss of as many as 80% of all neurons, with a predominant effect on the neuropeptide Y containing subpopulation. The immunoreactivities of NPY, tyrosine hydroxylase, and p75 low affinity NGF receptor in nerve terminals within the mesenteric artery were also reduced, whereas that of the sensory neuron neuropeptide, calcitonin gene related peptide was less affected. These results demonstrate that the majority of sympathetic neurons of the neonatal rat are dependent on endogenous NT3 for their survival at a time when they are also dependent on another survival factor, NGF, thus apparently providing a clear example of a population of neurons requiring for their survival the simultaneous supply of more than one trophic factor.

Animals↗

PubMed1995

[Photosensitization of dicoumarol on tumor cells and enhancement by sodium diethyldithiocarbamate].

AIM: To study the photosensitization of dicoumarol (Dic) on tumor cells and any effect by sodium diethyldithiocarbamate (DDC). RESULTS: Dic, 40, 80, 120 mumol.L-1 concentration-dependently inhibited the DNA synthesis (81%-93%) and increased the mortality (50%-70.4%) of ascitic hepatoma (Hep A) cells exposed in light. These 2 indices were changed slightly by Dic alone even in non-illuminating group. DDC enhanced the photosensitization of Dic group. CONCLUSION: Photosensitization of Dic showed strong antitumor activities against Hep A cells. The mortality of Hep A and inhibition of the DNA synthesis in Dic-DDC-light group significantly stronger than in Dic-light group. Photosensitization of Dic was not due to 1O2 and OH., but closely related to O2.- and H2O2.

Animals↗

PubMed1994

Localization of neurotrophin-3-like immunoreactivity in the rat central nervous system.

Neurotropin-3 (NT3) is a nerve growth factor (NGF) homologue whose function is presently unknown. The factor promotes the survival of a subpopulation of sensory and sympathetic neurons in vitro. NT3 mRNA is widely distributed in both the peripheral and central nervous system but the distribution of NT3 has not yet been examined. In the present study we have determined the regional distribution and cellular localization of NT3-like immunoreactivity (-IR) in the central nervous system by immunohistochemistry. Both glia and neurons were stained. NT3-IR glia were distributed in corpus callosum, substantia nigra, fimbria of hippocampus, subependymal areas of the ventricles and cerebellum. In the forebrain, NT3-IR was detected in a number of neuronal cells, including pyramidal cells in the fifth layer of the cerebral cortices, subpopulations of neurons in the septal nuclei, diagonal bands of Broca, olfactory primary cortex, amygdala and islands of Calleja. In the hippocampus, pyramidal cells in the CA1, CA2 and lateral regions of CA3 and granular cells in dorsal dentate gyrus were labelled with different intensities. Neurons in the bed nuclei of the striatum terminalis, mesencephalic trigeminal nuclei and motoneurons in the brain stem and spinal cord were intensively labelled. A subpopulation of neurons in the reticular thalamic nuclei and midbrain were moderately labelled. Finally, in the cerebellum, NT3-IR was also found in Purkinje cells and neurons in the deep cerebellar nuclei. In some brain regions such as hippocampus, the distribution of NT3-IR correlates with that of mRNANT3 as described by others. In contrast in other regions such as spinal cord and brain stem, little correlation was found between protein and mRNA. The results suggest that some NT3 immunoreactive neurons in the central nervous system accumulate NT3 in accord with a neurotrophic role for their maintenance or survival, while others may synthesize and secrete the factor to provide support for innervating neurons.

Animals↗