Biomedical subjects

M Zhou

Publications and source records attributed to M Zhou.

At least 235 records · Page 13Linked to original sources

PubMed1997

Analysis of AMPA receptor properties during postnatal development of mouse hippocampal astrocytes.

Glial cells in the mammalian brain express various types of voltage- and ligand-gated ion channels, including glutamate receptors (GluRs) of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-subtype. In the present study we followed developmental changes in the functional properties of AMPA receptor (AMPA-R) channels expressed by astrocytes of the mouse hippocampus between postnatal days (P) 5-35 to learn more about the physiological significance of these glial receptors. A fast concentration clamp technique was applied to cells acutely isolated from the CA1 stratum radiatum subregion to quantitatively analyze rapidly activating and desensitizing receptor responses. The equilibrium responses of glutamate and kainate differed between P5 and P12. Although the maximum current induced by kainate was almost the same at all developmental stages, a steep rise in the maximum glutamate response was observed within the same time range. Between P5 and P12 there was an increase in the potentiation of AMPA-R currents with cyclothiazide (CTZ); at the same time, the dissociation kinetics of CTZ became significantly slower. These changes in the pharmacological properties suggested a variation in splice variant expression. With proceeding maturation, we observed an increase in the degree of desensitization of the glutamate- and AMPA-induced receptor currents. In addition to the shift in flip/flop splicing, these findings could hint at a developmental regulation of RNA editing in the arginine/glycine site. Altogether, the present results demonstrate changes in astrocytic AMPA-R functioning early in postnatal development, although after P12 the receptor properties remained almost constant. Although the overall Ca2+ permeability did not vary during development, the prolonged receptor opening in the early postnatal period causes an enhanced Na+/Ca2+ influx into the immature astrocytes. This could influence glial proliferation and differentiation during CNS ontogenesis.

Animals↗

PubMed1997

Morphometric comparison of the motor trigeminal neurons.

Comparative morphological and morphometric studies of the motor trigeminal nucleus (MTN) were carried out on the brains of an alligator, a human being and a rat for the first time. Differences in neurons regarding sizes, areas, numbers, column volumes, neuropil indices and circulatory ratios were found. The results showed that the positions and shapes of the MTN were different, and the shapes of motor neurons were different, too. The average area of motor trigeminal neurons was the largest in the alligator, compared with the area in the human being, and the rat; the number of neurons and the column volume of MTN were the largest in the human being. As for the neuropil indices, the value was in descending order: alligator, human being and rat; whereas for the circulatory ratio of neuronal cell bodies, the order was rat, alligator, and human being. We conclude that the size of motor neurons in the MTN may be related to the power of masticatory muscles, and there may be a connection between jaw sizes and shapes and sizes of the motor neurons in the MTN.

Alligators and Crocodiles↗

PubMed1997

Morphometric analyses of axons in the lateral corticospinal tract with ageing process.

Morphometric analyses were carried out to reveal a relation between age and axonal changes in the lateral corticospinal tract (LCST) at the L1 level of the human spinal cord. Histological preparations of the spinal cord were made after embedding in celloidin to stain with Luxol fast blue-periodic acid-Schiff-hematoxylin or Klüver-Barrera methods. The number, average transverse area, total area and diameter of axons of the LCST were counted and measured using an image-analyser combined with a computer. The morphometric analyses revealed that (1) there was a significant decrease in the axonal number of the LCST with age (p < 0.001); (2) the axons were not partially nor completely accompanied by surrounding myelin sheaths, and increased in number with age; (3) the diameter and average area of axons in the LCST became significantly reduced with age (p < 0.01); (4) the total area decreased significantly with age in a unit area of 2,700 microns2; and (5) the circularity ratio showed no significant change with age.

Adult↗

PubMed1997

[The significance of detecting Epstein-Barr virus BNLF1 fragment and its expression in Hodgkin's disease in the Guangdong area].

OBJECTIVE: To study the association between Epstein-Barr virus (EBV) and lymphoma. METHODS: PCR, in situ hybridization and immunohistochemistry were used to detect the presence of EBV in 51 cases of Hodgkin's disease in the Guang dong area. RESULTS: The detection rate of EBV-BNLF1 fragment by PCR was 80.4%, significantly higher than that of reactive hyperplasia of lymph nodes (RHLN). Cloning and sequence analysis revealed the PCR product to be BNLF1 fragment, but no mutation was found. In situ hybridization (ISH) demonstrated EBV in the nuclei of malignant and non-malignant cells in 15 of the 41 PCR-positive cases. The expression product of BNLF1 gene-latent membrane protein (LMP1) was detected in 25 of the 51 cases of HD (49%) and the staining was restricted to the tumor cells. The detection rates of BNLF1 fragment and its expression in the 15 cases of HD under 20 years of age were much higher that those in HD over 20 years of age and RHLN of the same age group (P < 0.01). CONCLUSION: There was EBV infection and expression of its latent membrane protein in the tumor cells in half of the HD cases and may play a role in the genesis and development of HD. The results also suggest that HD in children and adolescence being more closely correlated with EBV latent infection.

Adolescent↗

PubMed1997

[Effects of EDRF on the vasoconstrictor action of phenylephrine in rat aorta].

The influence of endothelium-derived relaxing factor (EDRF) on the vasoconstrictor effect of phenylephrine on rings of rat aorta was studied in this paper. Rings of rat aorta, with or without endothelium, were suspended in organ chambers for the measurement of contractive force and contractive speed. All experiments were performed in the presence of indomethacin (10 mumol/L) to prevent the production of vasoactive prostanoids. When the preparations with intact endothelium were treated with methylene blue (10 mumol/L), an inhibitor of the target enzyme of EDRF, or NG-nitro-L-arginine (30 mumol/L), an inhibitor of EDRF formation, dose-contractive force curves of phenylephrine shifted to left: the EC30 value decreased 5-fold and the maximal response ratios were 1.6 +/- 0.4 and 1.6 +/- 0.5 (n = 8) respectively. These results were similar to those observed after mechanical removal of the endothelium: a 3-fold decrease in the EC30 value and the maximal response ratio was 1.0 +/- 0.2 (n = 8), The latter results may be related to a little EDRF produced by vascular smooth muscle. Our results suggest that the vasoconstrictive effect induced by phenylephrine may also be regulated by EDRF production from vascular endothelium and smooth muscle.

Animals↗

PubMed1997

Acupuncture methods for hemiplegic spasm.

Remitting hemiplegic spasticity in apoplexy (HSA) is an important problem in today's clinical study. Through teaching and clinical practice, the authors summed up the effective acupuncture methods for remitting HSA: puncture deeply the acupoints on the superior-spasm side (SSS) by filiform needles so as to obtain the intensive needling sensations in the deep tissues (ISDT) until the superior spasm is immediately remitted; tap the skin on the inferior-spasm side (ISS) by skin needles until the corresponding muscle contracts. The methods have showed a significant immediate and long-term therapeutic effect.

Acupuncture Therapy↗

PubMed1997

[The distribution of motoneuronotrophic factor 1 (MNTF1) and its receptor-like substance in the spinal cord and limb muscles of mice with motoneuron disease].

Using a monoclonal antibody for the motoneuronotrophic factor 1 (MNTF1) and its idiotypic antibody we have detected immunohistochemically the changes in the expression of the positive immunoreactivities for the MNTF1 and its receptor-like substance in the cervical and lumbar spinal cord regions as well as in the limb muscles of the wobbler mice, as the disease progressed from the first to the fourth stage. The results indicated that the positive immunoreactivities for the MNTF1 and its receptor-like substance were mainly located in the soma and neurites of the anterior born motoneurons at spinal layers VIII and IX and in the sarcoplasm of the skeletal muscles of the fore- and hind-limbs, and whereas their nuclei were immunoreactively negative. In the first stage (3 weeks) of the disease there were fewer in numbers of cells containing positive immunoreactivities (P < 0.01) and lesser in their relative amount of immunoreactivities per cell (P < 0.01) in the cervical and lumbar spinal cord as well as in the fore- and hind-limbs muscles of the wobbler mice as compared to those of the normal littermates. In the fourth stage (3 months) of the disease these differences between the wobbler mice and the normal littermates were even more distinct (P < 0.01 and P < 0.01). These results suggested that as syntheses of the skeletal muscle target cell-derived MNTF1 and its receptor-like substance were reduced to levels which were not enough to ensure the survival of motoneurons and consequently leading to muscular atrophy, as the motoneuron disease in wobbler mice deteriated.

Animals↗

PubMed1997

[The changes of glutamate receptor and free Ca2+i in hypoxic-ischemic cerebral injury: experimental study].

This experiment was designed to explore the pathogenesis in hypoxic-ischemic encephalopathy (HIE). Sixteen newborn pigs were divided into two groups: (Group A) normal control and (Group B) HIE 24 hours. The glutamate receptor (Glu R) in forebrain crude synaptic membrane (SPM) and free Ca2+i in RBC were tested respectively. The results revealed that the binding sites (Bmax) of Glu R in Group B was much lower than that in Group A, but the affinity (Kd) showed no statistic difference between Group A and Group B. In addition, free Ca2+i of RBC in Group B was much higher than that in Group A. This study demonstrates that the changes of Glu R and Ca2+i are involved in the pathogenesis of hypoxic-ischemic cerebral injury in newborn animals.

Animals↗

PubMed1997

Segmented assimilation: issues, controversies, and recent research on the new second generation.

"The segmented assimilation theory offers a theoretical framework for understanding the process by which the new second generation--the children of contemporary immigrants--becomes incorporated into the system of stratification in the host society and the different outcomes of this process. This article examines the issues and controversies surrounding the development of the segmented assimilation theory and reviews the state of recent empirical research relevant to this theoretical approach. It also highlights main conclusions from recent research that bear on this theory and their implications for future studies." The geographical focus is on the United States.

Acculturation↗

PubMed1997

[Anti-inflammatory effect of total flavonoidal glycosides of Swainsona salsula].

Total flavonoidal glycosides (SSTFG) was extracted from Swainsona salsula (Pall.) Taub.. The anti-inflammtory effect of SSTFG was investigated. The results indicated that SSTFG inhibited markedly dimethylbenzene-induced inflammation in the ears of mice and albumen--caused swell in the feet of mice. SSTFG also exhibited a significant antagonism against increase in permeability of the peritoneal capillary of mice caused by acetic acid.

Acetic Acid↗

PubMed1997

[Relationship between bcl-X(L) expression and sensitivity to chemotherapy in acute myeloid leukemic cells].

OBJECTIVE: To investigate the characteristics and regulation of apoptosis in acute myeloid leukemic cells. METHODS: Flow cytometry, DNA electrophoresis and Northern blot were used to analyze the expression of bcl-X(L) before and after Vp16 treatment, and the relationships between bcl-X(L) expression and apoptotic sensitivity, clinical features and prognosis were also analyzed. RESULTS: Most of the leukemic cells from AML patients overexpressed bcl-X(L) mRNA. The expression of bcl-X(L) was still maintained high level after Vp16 treatment in patients with pretreatment overexpression. These patients were resistant to apoptosis, poor responsed to chemotherapy and associated with adverse prognostic features, such as high WBC counts, local leukemic infiltrations. Bone marrow cells from long-term remission AML patients and normal controls also showed bcl-X(L) downregulation after in vitro Vp16 treatment, but the apoptotic rates were lower than that in nonremissive AML. CONCLUSION: Overexpression of bcl-XL played an important role in leukemogenesis and drug resistance. Downregulation of bcl-X(L) was necessary but not sufficient to initiate apoptosis.

Adolescent↗

PubMed1997

Oxidative and malondialdehyde modification of low-density lipoprotein: a comparative study.

Low-density lipoprotein (LDL) was modified with copper ions (Cu2+) and malondialdehyde (MDA), and the differences were compared. The results show that both oxidative and MDA modification produce a decrease in free amino groups in LDL and enhance its electrophoretic mobility on agarose gel, and that these observations are linked. However, differences produced by the two forms of modification were observed. Oxidative modification of LDL involves free radical-mediated lipid peroxidation which produces large amounts of thiobarbituric acid-reactive substances (TBARS) and conjugated dienes. In addition, vitamin E was reduced considerably and cholesterol lowered, and apolipoprotein B (apo B) fragmentation and aggregation were seen. Similar changes were not seen with MDA modification which does not involve lipid peroxidation. Fluorescence emission spectra of both forms of modified LDL show that emission intensity increases gradually as the modification progresses, but maximum emission wavelength and spectrum patterns are not the same. These findings may be of some significance in the study of the antigenicity, scavenger receptor multiplicity and toxic effects of modified LDL.

Copper↗

PubMed1997

[Effects of induction of anti-embryonation and anti-fecundity immunity on liver granuloma formation in mice infected with Schistosoma japonicum].

OBJECTIVE: To investigate the effect of anti-fecundity and anti-embryonation immunity on liver granuloma formation in mice immunized with soluble immature egg antigen (SIEA) of schistosoma japonicum. METHOD: BALB/c mice were immunized with the crude SIEA or 26,000-28,000 molecular antigen derived from SIEA and compared the size in schistosoma japonicum egg granulomas in the liver after challenge infection both the immunized mice and unimmunized controls. RESULTS: The number and size of egg granuloma were significantly decreased in mice immunized with SIEA and SIEA 26-28,000, by 29.26% and 49.64%, respectively. The inhibitive effects on granuloma formation and spleen weights in the group immunized with SIEA 26-28,000 were stronger than those in the group immunized with the crude SIEA. However, mean granuloma size and spleen weights in the group immunized with SEA or SIEA-1 fraction were not different from unimmunized control. CONCLUSION: SIEA and SIEA 26-28,000 antigenic molecule play an important role in inhibition on liver granuloma formation through their anti-embryonation and anti-fecundity immunity effects.

Animals↗

PubMed1996

A fluorogenic substrate for beta-glucuronidase: applications in fluorometric, polyacrylamide gel and histochemical assays.

We have developed a fluorogenic substrate, ELF-97 beta-D-glucuronide, that provides significant advantages over existing substrates in detecting beta-glucuronidase activity. ELF-97 beta-D-glucuronide allows the detection of enzymatic activity in situ, yielding a hydrolytic product that exhibits maximal fluorescence within the physiological pH range. This substrate yields a hydrolytic product that demonstrates a more than 100 nm Stokes shift, which minimizes interference from autofluorescence in plant tissue. With the commercial enzyme, ELF-97 beta-D-glucuronide can detect less than 2 x 10(-4) U/ml of beta-glucuronidase activity in solution, and 5 x 10(-4) U per lane in polyacrylamide gels. Assays using transgenic Arabidopsis, whole leaf extracts of GUS-positive, but not GUS-negative plans, show significant GUS activity upon incubation with ELF-97 beta-D-glucuronide. Furthermore, the ability of this substrate to form insoluble precipitates at the sites of enzymatic activity makes it suitable for in situ localization of GUS activity in tissue samples of higher plants.

Electrophoresis, Polyacrylamide Gel↗

PubMed1996

Evidence that a rapidly turning over protein, normally degraded by proteasomes, regulates hsp72 gene transcription in HepG2 cells.

Heat shock protein 72/73 (Hsp70) is a cytosolic molecular chaperone that carries out fundamental roles under both normal and stress situations. There is great interest in delineating the mechanisms whereby Hsp70 levels are regulated. We observed that N-acetyl-leucyl-leucyl-norleucinal (ALLN), a synthetic aldehydic tripeptide that inhibits proteasomes, markedly induced Hsp70 levels (up to 30-fold above base line in HepG2 cells and human endothelial cells). Induction of Hsp70 by ALLN was dose-dependent and not related to cell toxicity. ALLN selectively increased Hsp70 levels without affecting Hsp25, Hsp27, Hsp60, Hsp86, Hsp90, Hsp104, or Bip (immunoglobulin heavy chain binding protein) in HepG2 cells. ALLN induced Hsp70 not only by stabilizing the protein but also by dramatically increasing its synthesis. The modulation of Hsp70 synthesis by ALLN resulted from a rapid and marked increase in transcription of the hsp72 gene, since the induction of hsp72 mRNA was blocked in cells co-treated with actinomycin D. hsp72 mRNA levels were affected in a time-dependent manner by exposure to ALLN; significant elevations occurred within 60 min of treatment, and a decline to background levels was observed by 7 h of recovery. The ALLN-induced increase in hsp72 gene expression was associated with trimerization of the heat shock transcriptional factor (HSF1). ALLN did not affect the steady-state level of HSF1 protein. The effects of ALLN appeared to require de novo protein synthesis, since the induction of both HSF1 trimerization and hsp72 transcription was blocked by co-treatment with cycloheximide. When we tested a series of protease inhibitors, only the related aldehydic tripeptides, N-acetyl-leucyl-leucyl-methioninal and the proteasome inhibitor, Cbz-leucyl-leucyl-leucinal, induced Hsp70 levels. The specific proteasome inhibitor, lactacystin, which has a different structure, also induced Hsp70 levels. Overall, our results suggest that a rapidly turning over protein that is normally degraded by proteasomes may be involved in the regulation of Hsp70 synthesis via effects on the hsp70 transcriptional factor, HSF1.

Biopolymers↗

PubMed1996

Chromatography of hydroxysteroid dehydrogenases.

The structure-function study of hydroxysteoid dehydrogenases has stimulated the development of their chromatography, which in turn reveals more mechanisms of these enzymes. Due to the various membrane associations and mild hydrophobic nature of most of the enzymes studied up to now, hydrophobic interaction chromatography has played a crucial role in their purification, using media such as phenyl-Superose or Sepharose-PEG. At the same time, affinity chromatography, especially the dye-containing columns, proves very efficient for these dehydrogenases, as the latter utilizes adenylyl-containing cofactors. Elution by their specific ligand facilitates their purification. In this paper, the use of detergents in the purification of these enzymes is also reviewed. Hydroxysteroid dehydrogenase preparation is further improved by rapid purification which facilitates the elimination of protein microheterogeneity, caused in vitro by oxidation, reduction or partial proteolysis. This process was shown to increase the crystallizability of the enzymes [Lin et al., J. Cryst. Growth, 122 (1992) 242-245; Zhu et al., J. Mol. Biol., 234 (1993) 242-244]. The fast purification permitted a simpler procedure and better combination of various columns than conventional chromatography. This leads to even higher efficiency, yielding homogeneous and highly active preparations.

Animals↗

PubMed1996

Demonstration of a physical interaction between microsomal triglyceride transfer protein and apolipoprotein B during the assembly of ApoB-containing lipoproteins.

Microsomal triglyceride (TG) transfer protein (MTP) is an endoplasmic reticulum lumenal protein consisting of a 97-kDa subunit and protein disulfide isomerase. It is believed that MTP delivers TG to nascent apoB molecules during the assembly of lipoprotein particles in the secretory pathway. Although in vitro studies have established the mechanism of TG transfer between donor and acceptor membranes, the mechanism of action of MTP in vivo remains unknown. The present studies were undertaken to examine whether or not the transfer of TG to nascent apoB in the endoplasmic reticulum involves the physical interaction between MTP and apoB. HepG2 cells were labeled with [3H]leucine, lysed in a nondenaturing homogenizing buffer, and immunoprecipitated with anti-MTP antiserum. We found that labeled apoB and protein disulfide isomerase were co-immunoprecipitated by this procedure. In addition, we were able to detect the 97-kDa subunit of MTP in these immunoprecipitates by immunoblot. The association of MTP and apoB, as assessed in pulse-labeled cells by co-immunoprecipitation, was transient; apoB was prominent on fluorgraphy at 10 min of chase but minimal thereafter. Oleic acid treatment, which protects apoB from rapid intracellular degradation by increasing TG availability, increased both the degree and the duration of association between MTP and apoB dramatically. Inhibition of TG synthesis by Triacsin D, on the other hand, significantly decreased the MTP-apoB binding. N-Acetyl-leucyl-leucyl-norleucinal, a cysteine protease inhibitor, which directly protects apoB from rapid intracellular degradation but does not affect TG synthesis, increased the interaction between MTP and apoB only slightly, although it did prolong it. Our results suggest that direct interaction between MTP and apoB occurs during the assembly of apoB-containing lipoproteins in HepG2 cells.

Apolipoproteins B↗

PubMed1996

The infectious bronchitis virus nucleocapsid protein binds RNA sequences in the 3' terminus of the genome.

The infectious bronchitis virus (IBV) nucleocapsid protein was expressed as a bacterial fusion protein which differed from the native protein only in the addition of six amino terminus histidine residues. Using RNA overlay protein blot assays, the recombinant protein was shown to bind to RNA fragments specific for the positive sense 3' noncoding end of the IBV genome. At greater concentrations of sodium chloride, the native and fusion nucleocapsid proteins similarly bound to G RNA, representing the terminal 1805 3' nt of the genome, whereas bovine serum albumin and allantoic fluid protein did not bind to labeled G RNA. Competitive gel shift assays with labeled G RNA indicated that the protein interacted with several unlabeled RNA representing sequences at the 3' noncoding end of the IBV genome. Cache Valley virus (a bunyavirus) mRNA transcribed from the small segment cDNA also inhibited the interaction with IBV G RNA to approximately the same extent as homologous unlabeled G RNA, whereas reactions with bovine liver RNA and yeast tRNA were considerably weaker. Whereas yeast tRNA did not inhibit the interaction with the labeled large G RNA, interactions of the fusion protein with EF, a region from 78 to 217 nt from the 3' terminus of the IBV genome, were also apparently weaker than interactions with fragment CD which consisted of the 3' terminal 155 nt. On a molar basis, the latter interacted in an identical nature to a RNA consisting of CD and an additional 1053 nt of plasmid sequences. Compared to bovine liver RNA, unlabeled G specifically inhibited binding to the two smaller labeled IBV fragments in gel shift assays. The binding of IBV nucleocapsid protein with RNA probably requires specific sequences and/or structures that are present on the genome, and may represent a common mechanism used by similar viral nucleoproteins whose functions depend on binding to RNA.

Binding, Competitive↗