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Biomedical subjects

L X Zhang

Publications and source records attributed to L X Zhang.

At least 37 records · Page 2Linked to original sources
PubMed2000

The impact of directly-observed treatment on the epidemiology of tuberculosis in Beijing.

SETTING: Fully supervised chemotherapy, or directly observed treatment (DOT), for newly detected smear-positive cases in Beijing, has been successfully implemented for two decades. OBJECTIVE: To evaluate the progress made in tuberculosis control, and in particular to evaluate the impact of DOT on tuberculosis epidemiology in Beijing. DESIGN: Epidemiological parameters on tuberculosis, consisting of mortality, prevalence, notification rate, tuberculous meningitis in children and initial drug resistance rate, were collected and analysed. Their trends were evaluated and compared with DOT implemented for new smear-positive cases in Beijing from 1978 to 1996. RESULTS: The coverage of DOT for new smear-positive pulmonary tuberculosis cases has increased from 10% in 1978 to more than 90% since 1990. Since DOT was introduced in 1978, mortality from tuberculosis has declined by an average of more than 7% per year. The reduction rate of 17.2%, and the rates of chronic cases and tuberculous meningitis in children decreased dramatically. The rate of newly registered smear-positive cases decreased from 18.9/100000 in 1986 to 7.3/100000 in 1996, giving an average annual reduction rate of 9.1 during this period. Initial resistance to isoniazid and streptomycin decreased from respectively 13.9% and 12.3% in 1978-1979 to 4.2% and 5.8% by 1996. The level of multidrug resistance was low and stable, at 0.8% in 1996. CONCLUSION: The experience of the Beijing tuberculosis control programme convincingly demonstrates that it is possible to improve the epidemiological situation rapidly in a low-income country, at very low cost and in a manner that is self-sufficient and sustainable.

Adolescent↗
PubMed2000

Cost effectiveness of DOTS and non-DOTS strategies for smear-positive pulmonary tuberculosis in Beijing.

The cost-effectiveness of DOTS (Directly Observed Treatment, short course) and non-DOTS strategies for smear-positive pulmonary tuberculosis in Beijing was evaluated. Cost calculation was based on the expenses of drugs, chest X-ray films, sputum smears and cultures for the patients. Effectiveness of the intervention was assessed in two aspects: direct benefits to the patients treated and indirect benefits to the others through reduced transmission of tuberculosis; disability adjusted life of year (DALY) was used as an index. The results showed that one DALY could be saved with 45.7 Yuan by DOTS and 471.4 Yuan by non-DOTS. DOTS is a good control strategy for smear-positive tuberculosis.

China↗
PubMed1999

[Antagonistic effects of melatonin on glutamate-induced neurotoxicity in rat hippocampal neurons].

The effects of glutamate (Glu) and melatonin (MEL) on the evoked populaion spike (PS) following stimulation of the schaffer collateral fiber were studied by extracellular recording technique in perfused slices of rat hippocampus: 5.0 mmol/L Glu decreased the PS peak values to 4.1% of control. This effect of Glu (5.0 mmol/L) on PS peak values was changed to 14.7%, 105.2% and 24.3% of control by 0.4, 0.5, 0.6 mumol/L of MEL. But when the interaction between MEL (0.5 mumol/L) and Glu (5.0 mmol/L) was entirely suppressed by CDP (0.5 mumol/L), the PS values reduced to zero. These results suggest that the inhibitory action of MEL on Glu-induced neurotoxicity may be mediated by 5-HT receptors.

Animals↗
PubMed1998

Apoptosis of hippocampal neurons after amygdala kindled seizures.

Seizure-induced neuronal damage may involve both excitotoxic and apoptotic (programmed cell death) mechanisms. In the present study, we used an amygdala kindled seizure model to study whether apoptotic cell death occurs. To evaluate apoptosis, we counted the numbers of cells that had DNA fragments labeled at the 3' end with digoxigenin using terminal transferase (ApopTag, Oncor). Additionally, the expression of Bax and Bcl-2, two genes associated with apoptotic cell death, was also measured following kindled seizures. We found that the number of ApopTag-positive cells in the hippocampus increased 30.4% after one kindled seizure and 82.5% after 20 seizures compared to sham controls. The ApopTag-labeled cells could be mainly interneurons of the hippocampal formation, although additional studies are required. Preferential vulnerability of inhibitory interneurons is consistent with previous studies on seizure-induced cell loss. These results, coupled with our findings that the ratio of Bax/Bcl-2 expression is increased in the hippocampus by seizures, suggest that apoptosis of hippocampal interneurons may lead to dysinhibition in the hippocampus and increased seizure susceptibility.

Amygdala↗
PubMed1998

Neural plasticity and emotional memory.

Posttraumatic stress disorder is the pathological replay of emotional memory formed in response to painful, life-threatening, or horrifying events. In contrast, depression is often precipitated by more social context-related stressors. New data suggest that different types of life experiences can differentially impact biochemistry, physiology, anatomy, and behavior at the level of changes in gene expression. Repeated separation of neonatal rat pups from their mother results in many long-lasting alterations in biology and behavior paralleling that in depression, including hypercortisolism. The role of the amygdala in modulating emotional memory is highlighted, as well as some of its unique properties such as metaplasticity (i.e., the differential direction of long-term adaptation, either potentiation or depression) in response to the same input as a function of the prior history of stimulation. The implications of these emerging data on the physiological and molecular mechanisms underlying emotional memory emphasize the particular importance of prevention and early intervention.

Amygdala↗
PubMed1997

Anterograde transport of endogenous brain-derived neurotrophic factor in hippocampal mossy fibers.

Neurotrophic factors such as brain-derived neurotrophic factor (BDNF) are assumed to provide trophic support via a target-derived, retrograde mechanism of action. However, recent studies suggest that neurotrophic factors can act in an autocrine fashion and perhaps even in an anterograde direction similar to neurotransmitters. To further explore this hypothesis, we compared the neuroanatomical pattern of BDNF mRNA and protein in response to electroconvulsive seizures (ECS) or kainic acid-induced seizure activity. Using in situ hybridization, we found that chronic ECS induced BDNF mRNA predominantly in the granule neurons of the dentate gyrus. However, immunohistochemistry with an anti-BDNF antibody revealed that ECS increased endogenous BDNF protein in the mossy fibers, which are composed of axons projecting from the granule neurons of the dentate gyrus to the CA3 pyramidal layer of the hippocampus. Kainic acid administration (10 mg/kg, i.p., once) was used to lesion CA3 neurons selectively, as these are a possible retrograde source of BDNF protein in mossy fibers. Three weeks later, a prolonged elevation of BDNF mRNA in granule neurons, but not elsewhere in hippocampus, was accompanied by an increase in BDNF protein in the mossy fibers. These results suggest that BDNF was transcribed and translated in granule neuron cell bodies but transported in an anterograde direction to provide trophic support of CA3 pyramidal neurons.

Animals↗
PubMed1997

Rats with decreased brain cholecystokinin levels show increased responsiveness to peripheral electrical stimulation-induced analgesia.

Using the P77PMC strain of rat, which is genetically prone to audiogenic seizures, and also has decreased levels of cholecystokinin (CCK), we examined the analgesic response to peripheral electrical stimulation, which is, in part, opiate-mediated. A number of studies have suggested that CCK may function as an antagonist to endogenous opiate effects. Therefore, we hypothesized that the P77PMC animals would show an enhanced analgesic response based on their decreased CCK levels producing a diminished endogenous opiate antagonism. We found that the analgesic effect on tail flick latency produced by 100 Hz peripheral electrical stimulation was more potent and longer lasting in P77PMC rats than in control rats. Moreover, the potency of the stimulation-produced analgesia correlated with the vulnerability to audiogenic seizures in these rats. We were able to block the peripheral electrical stimulation-induced analgesia (PSIA) using a cholecystokinin octapeptide (CCK-8) administered parenterally. Radioimmunoassay showed that the content of CCK-8 in cerebral cortex, hippocampus and periaqueductal gray was much lower in P77PMC rat than in controls. These results suggest that low CCK-8 content in the central nervous system of the P77PMC rats may be related to the high analgesic response to peripheral electrical stimulation, and further support the notion that CCK may be endogenous opiate antagonist.

Acoustic Stimulation↗
PubMed1997

Amygdala-kindled seizures increase the expression of corticotropin-releasing factor (CRF) and CRF-binding protein in GABAergic interneurons of the dentate hilus.

Kindling, a model of temporal lobe epilepsy, induces a number of neuropeptides including corticotropin-releasing factor (CRF). CRF itself can produce limbic seizures which resemble kindling in some aspects. However, tolerance to the convulsant effects of CRF develops rapidly. Hypothetically, this could be explained should seizures also induce the CRF-binding protein (CRF-BP), which has been postulated to restrict the actions of CRF. Therefore, in the present study, we used in situ hybridization to examine the effects of amygdala-kindled seizures on the mRNA levels of CRF and CRF-BP. Kindled seizures markedly elevated CRF and CRF-BP in the dentate gyrus of rats. CRF and CRF-BP were induced almost exclusively in GABAergic interneurons of the dentate hilus. The CRF and CRF-BP interneurons also expressed neuropeptide Y but not cholecystokinin. CRF appeared to have an excitatory role in the dentate gyrus as it decreased the afterhyperpolarization of dentate granule neurons. These results suggest that CRF may contribute to the development of amygdala kindling. However, the compensatory induction of CRF-BP may serve to limit the excitatory effects of CRF in the dentate gyrus.

Amygdala↗
PubMed1997

Lipofectin-facilitated transfer of cholecystokinin gene corrects behavioral abnormalities of rats with audiogenic seizures.

To evaluate the potential for lipofectin-mediated central nervous system gene transfer, the plasmid coding for cholecystokinin was administered intracerebroventricularly to rats, which have congenital audiogenic seizures and high responses to peripheral electric stimulation-induced analgesia. Previous studies had shown that low brain cholecystokinin levels may be the neurochemical variable of rat's audiogenic seizure and high responses to the analgesia because cholecystokinin is an anticonvulsant and anti-opioid neuropeptide. Gene transfer of cholecystokinin corrected the increased susceptibility to audiogenic seizures and the high responses to analgesia for about one week. Similar administration of plasmid expressing beta-galactosidase indicated that the vector mainly transfected ependymal cells lining the ventricle and pia mater cells. The increased cholecystokinin messenger RNA and immunoreactivity in the hippocampus following stereotactic intrahippocampal administration of cholecystokinin plasmid was also demonstrated with in situ hybridization and immunohistochemistry techniques. These results suggest that lipofectin-mediated gene transfer will be useful for studies of brain function, the modification of behavior and gene therapy for central nervous system disorders.

Acoustic Stimulation↗
PubMed1997

In situ investigation of Fas/FasL expression in chronic hepatitis B infection and related liver diseases.

To evaluate Fas/FasL expression in hepatitis B virus-related chronic liver disease, liver biopsies from 44 such cases were studied immunohistochemically. FasL was detected in the infiltrating lymphocytes and both FasL and Fas were found in the hepatocytes. The Fas and FasL-positive cells were mostly found at the advancing edges of interphase hepatitis, and Fas/FasL expression was closely correlated with the inflammatory activity. Unexpectedly, FasL was also expressed in liver cirrhotic nodules, particularly in those with hepatocellular carcinoma with or without inflammation. These results suggest that the factors which induce hepatocyte transformation might also trigger FasL expression and promote FasL/Fas-mediated apoptosis.

Adult↗
PubMed1997

Autolytic site mutant R105C of rat trypsin.

The autolytic site Arg105 of rat trypsin was replaced with Cys by DNA site-directed mutagenesis method. Comparison of expression and purification of R105C trypsin along with the wild type and some other Arg105 mutants indicates that R105C trypsin could be expressed as well but with a lower expression level. It is unexpected that R105C trypsin has no detectable activity toward trypsin substrate TAME, quite different from the wild type and other Arg105 mutants. Native gel electrophoresis analysis indicates that R105C trypsin has a similar mobility rate to that of wild type trypsin. FPLC also gives similar retaining time. The loss of activity of R105C trypsin may result from the conformational change around active site, but not the dimer formation.

Animals↗
PubMed1997

Cloning of the human orphan receptor germ cell nuclear factor/retinoid receptor-related testis-associated receptor and its differential regulation during embryonal carcinoma cell differentiation.

We have cloned a cDNA encoding the full-length coding region of the human homologue of the germ cell nuclear factor (GCNF)/retinoid receptor-related testis-associated receptor (RTR), from a human testis cDNA library. The amino acid sequence of human GCNF/RTR is highly homologous to that of the mouse GCNF/RTR. The largest difference between the two homologues is a 15 amino acid deletion in the human GCNF/RTR at amino acid 47. The GCNF/RTR gene was localized on human chromosome 9. Northern blot analysis using poly(A)+ RNA from different human tissues showed that GCNF/RTR mRNA is most abundantly expressed in the testis. GCNF/RTR was also highly expressed in embryonic stem cells and embryonal carcinoma cells but repressed in its differentiated derivatives. Induction of differentiation of mouse embryonal carcinoma F9 cells and human embryonal carcinoma NTERA-2 clone D1 (NT2/D1) cells by all-trans retinoic acid was accompanied by a down-regulation of GCNF/RTR. Our observations suggest that GCNF/RTR plays a role in the control of gene expression in early embryogenesis and during spermatogenesis.

Amino Acid Sequence↗
PubMed1997

Effect of tripterine on collagen-induced arthritis in rats.

AIM: To study the therapeutic effect of tripterine (Tri) on collagen-induced arthritis (CIA). METHODS: Collagen type II (Col) 1.5 mg was injected intradermally to induce CIA in rats. Hind paw volumes of rats were measured with a water displacement method. The serum anti-collagen antibody was measured by an enzyme-linked immunosorbent assay. Delayed hypersensitivity was reflected by skin response to Col. Interleukin-1 (IL-1) and interleukin-2 (IL-2) activities were evaluated by [3H]TdR uptake. Joint was evaluated histologically. RESULTS: Tri 15 and 30 mg.kg-1.d-1 given i.g. to rats 3 d after the first sign of arthritis reduced inflammatory swelling, suppressed humoral and skin response to Col, inhibited IL-2 and IL-1 production, reduced pathological progression of joint. CONCLUSION: Tri has a therapeutic effect on CIA.

Animals↗
PubMed1996

Continuous production of high degree casein hydrolysates by immobilized proteases in column reactor.

The enzymatic complete hydrolysis of casein was investigated by using immobilized endopeptidase and exopeptidase packed in the jacketed column reactors. The mass transfer efficiency of proteins was improved by using sliced shrimp chitin hull as enzyme support, which formed a network structure inside the column reactor that prevented the formation of protein precipitate and increased the line flow rate of protein solution. The specificity of the protease was of crucial importance for both the hydrolysis degree and the free amino acid content of the hydrolysates. Of the enzymes, tested, the immobilized A. oryzae protease was the most effective enzyme in breaking down the casein molecules and releasing the free amino acid from casein hydrolysates. The immobilized pancreatic and kidney exopeptidase could lead to a 20% increase of free amino acids. The free amino acid content of casein hydrolysates was 34.81% after processing and could reach to 64% if the column length was doubled, but 100% hydrolysis was impossible as the reverse reaction was also taking place. The casein hydrolysates was characterized by its high degree of hydrolysis and high content of free amino acids. It can be applied in infant formula, element diet, and as a protein ingredient for food industry.

Amino Acids↗