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Biomedical subjects

M Shi

Publications and source records attributed to M Shi.

At least 19 recordsLinked to original sources
PubMed2002

Nestin-containing cells express glial fibrillary acidic protein in the proliferative regions of central nervous system of postnatal developing and adult mice.

We are interested in the expression patterns of nestin, an embryonic intermediate filament that represent a neural precursor marker, in the mammalian central nervous system. With an immunohistochemical approach, distribution of nestin-containing cells and their colocalization with glial fibrillary acidic protein (GFAP) or neuronal nuclear specific protein (NeuN) were studied in adult and postnatal days 2-30 (P2-30) mice. Nestin-immunoreactivity was predominately distributed in certain proliferative regions, such as cerebral cortex, hippocampus, hypothalamus, subfornical organ, cerebellar cortex, area postrema, midline raphe glial structures, as well as ependymal and subependymal zones of the brain and spinal cord. The majority of nestin-immunoreactive cells, characterized by astroglial profiles of multiple and radial processes, showed a partial overlapping distribution with that of GFAP-immunoreactive astroglial cells. Double immunofluorescence confirmed that about 77% of these nestin-immunoreactive cells exhibited GFAP-immunoreactivity, indicating that a large percentage of nestin-expressing cells may have committed to astroglial cells. In developing mice, down-regulation of nestin expression was observed between P7 and P14. Although co-expression of nestin and NeuN occurred in cortical neurons of P2-7 mice, nestin-containing cells showing NeuN-immunoreactivity disappeared in CNS in older animals. Our results reveal the distribution pattern of nestin-containing neural precursors in the postnatal CNS and provide evidence on their differentiation fate to neurons and astrocytes, suggesting that nestin-containing glial cells may play an important role in remodeling and repairing in the postnatal and adult central nervous system.

Aging↗
PubMed2001

Self-assembly of novel [3]- and [2]rotaxanes with two different ring components: donor-acceptor and hydrogen bonding interactions and molecular-shuttling behavior.

Three of the first kind of hetero[3]rotaxanes, which comprise one linear component and one neutral and one tetracationic ring component, have been assembled by using the intermolecular hydrogen bonding and donor-acceptor interactions. Three neutral [2]rotaxanes and three tetracationic [2]rotaxanes have also been synthesized as intermediate products or for the sake of property comparison. The linear molecules are incorporated with two glycine subunits, for templating the formation of the neutral tetraamide cyclophane, and one or two hydroquinone subunits, for inducing the formation of the tetracationic cyclophane. Variable-temperature (1)H NMR investigation reveals that the shuttling behavior of the tetracationic ring component along the linear component is substantially influenced by the existence of the neutral ring component. The spatial repelling interaction of the neutral ring on the electron-deficient tetracationic ring simultaneously weakens the latter's "positioning" tendency at both electron-rich hydroquinone sites of the linear component. As a result, the activation energy associated with the shuttling process of the tetracationic ring between the two hydroquinone sites is remarkably reduced in comparison to that of the shuttling process of the corresponding neutral ring-free [2]rotaxanes. For the first time, the rotation of the dipyridinium subunit around the axis formed by the two methylene groups connecting them within the tetracationic cyclophane has been investigated by variable-temperature (1)H NMR spectroscopy and the associated kinetic data have also been successfully obtained. Furthermore, the UV-vis and fluorescent properties of the new [2]- and [3]rotaxanes have been studied. The results demonstrate that [3]rotaxanes with different ring components possess unique kinetic features that are not available in [3]rotaxanes with identical ring components.

Journal Article↗
PubMed2001

Lewis base effects in the Baylis-Hillman reaction of imines with cyclohex-2-en-1-one and cyclopent-2-en-1-one.

In the Baylis-Hillman reaction of N-benzylidene-4-methyl-benzenesulfonamide with cyclohex-2-en-1-one or cyclopent-2-en-1-one, we found that, in the presence of a catalytic amount of DMAP, the Baylis-Hillman reaction can be greatly accelerated to give the normal Baylis-Hillman adduct 1 or 3 in good or very high yields: moreover, using PBu3 as a Lewis base in the reaction of N-benzylidene-4-methylbenzenesulfonamide with cyclopent-2-en-1-one, the normal Baylis-Hillman adducts 3 could be obtained in very high yields within 5 h, however, using PBu3 or DBU as a Lewis base in the reaction of N-benzylidene-4-methyl-benzenesulfonamide with cyclohex-2-en-1-one, beside the normal Baylis-Hillman adduct 1 abnormal Baylis-Hillman adduct 3-aryl-2-[(4-methylphenyl)sulfonyl]-2-azabicyclo[2.2.2]octan-5-one 2 was formed at the same time; the substituent's effects were also examined.

Journal Article↗
PubMed2001

Antibody-induced shedding of CD44 from adherent cells is linked to the assembly of the cytoskeleton.

CD44 is a widely expressed integral membrane glycoprotein that serves as a specific adhesion receptor for the extracellular matrix glycosaminoglycan hyaluronan. CD44 participates in a variety of physiological and pathological processes through its role in cell adhesion. Under appropriate conditions, the ectodomain of CD44 is proteolytically removed from the cell surface. In this study we show that excessive CD44 shedding can be induced in mouse fibroblasts and monocytes upon exposure of these cells to a CD44-specific Ab immobilized on plastic, whereas treatment with phorbol ester induces significantly enhanced CD44 release from the monocytes only. CD44 shedding proceeds normally in fibroblasts and monocytes deficient in TNF-alpha converting enzyme (TACE), a sheddase involved in the processing of several substrates. Conversely, activation of the CD44 protease has no effect on the release of TNF-alpha from TACE-expressing cells, although the same metalloprotease inhibitor effectively blocks both TACE and the CD44 sheddase. Concomitant with anti-CD44 Ab- or phorbol ester-induced CD44 shedding, dramatic changes are observed in cell morphology and the structure of the actin cytoskeleton. Disruption of actin assembly with cytochalasin reduces CD44 shedding, but not the release of TNF-alpha. Moreover, pharmacological activation of Rho family GTPases Rac1 and Cdc42, which regulate actin filament assembly into distinct cytoskeletal structures, has a profound effect on CD44 release. We conclude that the CD44 sheddase and TACE are distinct enzymes, and that Ab- and phorbol ester-enhanced cleavage of CD44 is controlled in a cell type-dependent fashion by Rho GTPases through the cytoskeleton.

ADAM Proteins↗
PubMed2001

Titanium(IV) chloride and quaternary ammonium salt promoted Baylis-Hillman reaction.

The Baylis-Hillman reaction of aldehydes with alpha,beta-unsaturated ketones can be drastically affected by the reaction temperature and Lewis bases. When the reaction was carried out at -78 degrees C using catalytic amounts of quaternary ammonium salts (R4N+X-, X = Cl, Br, I) as Lewis bases, in the presence of titanium(IV) chloride, the chlorinated aldol adduct 1 was obtained as the major product. Quaternary ammonium bromides and iodides (R4N+X-, X = Br, I) have higher catalytic activity than corresponding chlorides (R4N+Cl-). Quaternary ammonium fluorides (R4N+F-) do not have activity at all. The amounts of Lewis acid and quaternary ammonium salts used affect the reaction rate and product. A plausible reaction mechanism is proposed. If the reaction was carried out at room temperature (about 20 degrees C) in the presence of titanium(IV) chloride and quaternary ammonium salts (R4N+X-, X = Cl, Br, I), the elimination product 3, derived from 1, was formed as the major product.

Journal Article↗
PubMed2001

Lymphocyte subpopulations in the caecum mucosa of rats after infections with Eimeria separata: early responses in naive and immune animals to primary and challenge infections.

This study aimed to characterise the local (intestinal) immune response of rats after primary and challenge infections with Eimeria separata. Naive rats and rats which had been immunised by two moderate infections were exposed to a heavy infection with 100000 oocysts per animal. Necropsies were performed 0, 24 and 48 h after infection and lymphocyte subpopulations were microscopically quantified in the caecum mucosa after marking by immunohistological techniques. There was no difference between naive and immune rats concerning the number of CD45R(+) (B) cells, whereas significantly more CD3(+) (T) cells were found in the caecum wall of the immune rats. CD4(+) T cells predominated in animals after primary infection, whereas CD8(+) T cells represented the major T-cell subset in challenged rats. The proportion of TCRgammadelta(+) T cells did not differ in the mucosa between the groups examined, whereas challenged rats showed significantly increased numbers of TCRalphabeta(+) T cells in the caecum wall when compared with animals after a primary infection. Thus, CD4(+) T cells may be particularly involved in the immune response to a primary infection of rats with E. separata whereas immunity to a challenge infection seems to be mediated predominantly by CD8(+) and TCRalphabeta(+) T cells.

Animals↗
PubMed2001

Overexpression of agouti protein and stress responsiveness in mice.

Ectopic overexpression of agouti protein, an endogenous antagonist of melanocortin receptors' linked to the beta-actin promoter (BAPa) in mice, produces a phenotype of yellow coat color, Type II diabetes, obesity and increased somatic growth. Spontaneous overexpression of agouti increases stress-induced weight loss. In these experiments, other aspects of stress responsiveness were tested in 12-week-old male wild-type mice and BAPa mice. Two hours of restraint on three consecutive days produced greater increases in corticosterone and post-stress weight loss in BAPa than wild-type mice. In Experiment 2, anxiety-type behavior was measured immediately after 12 min of restraint. This mild stress did not produce many changes indicative of anxiety, but BAPa mice spent more time in the dark side of a light-dark box and less time in the open arms of an elevated plus maze than restrained wild-type mice. In a defensive withdrawal test, grooming was increased by restraint in all mice, but the duration of each event was substantially shorter in BAPa mice, possibly due to direct antagonism of the MC4-R by agouti protein. Thus, BAPa mice showed exaggerated endocrine and energetic responses to restraint stress with small differences in anxiety-type behavior compared with wild-type mice. These results are consistent with observations in other transgenic mice in which the melanocortin system is disrupted, but contrast with reports that acute blockade of central melanocortin receptors inhibits stress-induced hypophagia. Thus, the increased stress responsiveness in BAPa mice may be a developmental compensation for chronic inhibition of melanocortin receptors.

Adrenocorticotropic Hormone↗
PubMed2001

Role of placental tissues in the intrauterine transmission of hepatitis B virus.

OBJECTIVE: The purpose of this study was to determine the mechanism of intrauterine transmission of hepatitis B virus. STUDY DESIGN: Placental tissues from 158 pregnant women who tested positive for hepatitis B surface antigen were examined for hepatitis B virus markers, Fc gamma receptors, and hepatitis B surface antigen-anti-hepatitis B surface antigen in different layers of cells. RESULTS: It was shown that the hepatitis B virus infection rate among different layers of placental cells gradually decreased from the maternal side to the fetal side. Furthermore, the closer the infected cell layer was to the fetal side, the higher the risk of intrauterine hepatitis B virus infection. Fc gamma receptors were found on cells of both hepatitis B surface antigen positive and negative placentas; Fc gamma receptors III were found on trophoblastic cells and villous mesenchymal cells, and Fc gamma receptors II were found on only villous mesenchymal cells. Hepatitis B surface antigen-antibodies to hepatitis B surface antigen was detected in the cytoplasm and on the membrane of trophoblastic cells and villous mesenchymal cells in 2 hepatitis B surface antigen-positive placentas. CONCLUSION: The results support the hypothesis that intrauterine hepatitis B virus transmission could be caused through "cellular transfer" in the placenta. One of the means of cellular transfer could be through Fc gamma receptor III-mediated entry of hepatitis B surface antigen-antibodies to hepatitis B surface antigen into cells.

Adolescent↗
PubMed2001

A novel vascular smooth muscle chymase is upregulated in hypertensive rats.

While greater than 80% of angiotensin II (Ang II) formation in the human heart and greater than 60% in arteries appears to result from chymase activity, no cardiovascular cell-expressed chymase has been previously reported. We now describe the cloning of a full-length cDNA encoding a novel chymase from rat vascular smooth muscle cells. The cDNA encompasses 953 nucleotides, encodes 247 amino acids, and exhibits 74% and 80% homology in amino acid sequence to rat mast cell chymase I and II, respectively. Southern blot analysis indicates that the rat vascular chymase is encoded by a separate gene. This chymase was induced in hypertrophied rat pulmonary arteries, with 11-fold and 8-fold higher chymase mRNA levels in aortic and pulmonary artery smooth muscle cells from spontaneously hypertensive than in corresponding tissues from normotensive rats. We assayed the activity of the endogenous enzyme and of a recombinant, epitope-tagged chymase in transfected smooth muscle cells and showed that Ang II production from Ang I can be inhibited with chymostatin, but not EDTA or captopril. Spontaneously hypertensive rats show elevated chymase expression and increased chymostatin-inhibitable angiotensin-converting activity, suggesting a possible role for this novel enzyme in the pathophysiology of hypertension.

Amino Acid Sequence↗
PubMed2001

[Determination of protocatechualdehyde in yu xue bi granula].

The content of Protocatechualdehyde in YuXueBi granula was determined by HPLC. The chromatographic column was packed with ODS-2 (particle size 5 microns). The mobile phase was MeOH-H2O-H3PO4(17:83:0.003) adjusted to pH 3 with N(C2H5)3. The detection wavelength was 280 nm. The velocity of flow was 1.0 ml/min. The average recovery rate was 96.14%, RSD was 1.16%. The method was simple and stable.

Benzaldehydes↗
PubMed2001

[Genotype polymorphism and its implications of mannose-binding protein allele in 5 Chinese nationalities].

OBJECTIVE: To detect the genotypes and sequences of the exon 1 of human mannose-binding protein (MBP) allele in 5 Chinese nationalities. METHODS: The genotypes of MBP gene of 5 Chinese nationalities were detected by polymerase chain reaction-restriction fragment length polymorphism(PCR-RFLP). The exon 1 of the MBP gene of 22 Chinese Hans was analyzed by using ABI 310 genetic analyzer. RESULTS: The DNA sequences of exon 1 of Chinese MBP gene were acquired. The allele frequencies of the codon 54 of the MBP gene (MBP-54) of 5 Chinese nationalities were 0.181(Hans), 0.128(Uygurs), 0.181(Mongols), 0.179(Tibetans) and 0.181(Yis). The allele distribution for MBP-54 mutation of 5 Chinese nationalities was in good agreement with Hardy-Weinberg equilibrium. Compared with the Hans, Uygurs had a lower MBP-54 mutation rate. There were no differences in the allele frequencies between the chronic hepatitis B patients and health controls in Chinese Hans. The mutations of the codons 52 and 57 were not detected in this study. CONCLUSION: A higher prevalence of MBP-54 mutation was found in 5 Chinese nationalities, MBP-54 mutation was not associated with the persistence of hepatitis B.

Adolescent↗
PubMed2001

High-throughput genomic and proteomic analysis using microarray technology.

BACKGROUND: High-density microarrays are ideally suited for analyzing thousands of genes against a small number of samples. The next step in the discovery process is to take the resulting genes of interest and rapidly screen them against thousands of patient samples, tissues, or cell lines to further investigate their involvement in disease risk or the response to medication. METHODS: We used a microarray technology platform for both single-nucleotide polymorphisms (SNPs) and protein expression. Each microarray contains up to 250 elements that can be customized for each application. Slides contained either a 16- or 96-microarray format (4000-24,000 elements per slide), allowing the corresponding number of samples to be rapidly processed in parallel. RESULTS: Results for SNP genotyping and protein profiling agreed with results of restriction fragment length polymorphism (RFLP) analysis or ELISA, respectively. Genotyping analyses, using the microarray technology, on large sample sets over multiple polymorphisms in the NAT2 gene were in full agreement with traditional methodologies, such as sequencing and RFLP analysis. The multiplexed protein microarray had correlation coefficients of 0.82-0.99 (depending on analyte) compared with ELISAs. CONCLUSIONS: The integrated microarray technology platform is adaptable and versatile, while offering the high-throughput capabilities needed for drug development and discovery applications.

Arylamine N-Acetyltransferase↗
PubMed2001

[Adenovirus-mediated transfer of human wild-type p53, GM-CSF, and B7-1 genes efficiently produces growth suppression and apoptosis of hepatocellular cells in vitro].

OBJECTIVE: To investigate the tumor suppressor activity of recombinant adenovirus vector expressing the human wild-type p53, GM-CSF, and B7-1 proteins (designated as BB-102) in human hepatocellular carcinoma cells (HCC) in vitro. METHODS: The wild-type p53 BEL-7402, mutant p53 HLE, and HuH-7 HCC cell lines were infected with BB-102 at MOI of 50 in vitro. Immunohistochemical assay was used to determine p53 expressed by BB-102. Tumor suppressor activity of the expressed p53 was identified by terminal deoxynucleotidy I transferase (TdT) assay in BB-102-infected HCC cell lines. RESULTS: p53 protein was found to express in a dose-dependent manner in BB-102-infected HCC cell lines. The proliferation of HCC cell lines were suppressed significantly at the average rates of 58.5%, 81.5%, and 71.1% for BEL-7402, HLE, and HuH-7 respectively from 4 to 10 days, accompanying inducing apoptosis in BB-102-infected HCC cell lines. CONCLUSIONS: Besides the expression of B7-1 and GM-CSF, BB-102 is able to express p53 protein in independent manner and exerts its anti-tumor activity, which suggests that BB-102 may be useful for gene therapy against HCC in vivo.

Adenoviridae↗
PubMed2001

[Study on donor-specific antigens in inducing immunological tolerance].

OBJECTIVE: To compare the effects of different donor-specific antigens, through different pathways, on the inducement of immunological tolerance. METHODS: After the establishment of a stable rat cervical heterotopic heart transplantation model, donor specific transfusion (DST), donor specific spolenocyte (DSSL) and donor specific bone marrow (DSBM) were given to recipients 3-14 days prior to the transplantation through peripheral vein, portal vein and intrathymic injection respectively. Low dose CsA 5 mg/(kg.d) was given from the 3rd-14th day pre-transplantation to the 28th day post-transplantation. The survival time of cardiac grafts was monitored, meanwhile, the donor specific mixed lymphocyte reaction (MLR) and the subsets of T lymphocytes CD8+ were determined. RESULTS: DSBM and the administrative pathway of intrathymic injection achieved the best effects on the inducement of immunological tolerance and the improvement of graft survival. CONCLUSION: The donor specific antigens can induce the donor-specific immunological tolerance. It may be a practicable approach for the clinical experiments in the future.

Animals↗
PubMed2000

Titanium(IV) chloride and the amine-promoted baylis-hillman reaction

In the Baylis-Hillman reaction, we found that, when the reactions of arylaldehydes with methyl vinyl ketone were carried out at <-20 degrees C using a catalytic amount of amine as a Lewis base in the presence of titanium(IV) chloride, the chlorinated compounds 1 could be obtained as the major product in very high yields for various arylaldehydes. In addition, acrylonitrile could undergo the same reaction to give the corresponding chlorinated product in moderate yield.

Journal Article↗
PubMed2000

An unexpected carbon dioxide insertion in the reaction of trans-2, 4-disubstituted azetidine, trans-2,5-disubstituted pyrrolidine, or trans-2,6-disubstituted piperidine with diphenylthiophosphinic chloride and diphenylselenophosphinic chloride

In the reaction of trans-2,4-disubstituted azetidine, trans-2, 5-disubstituted pyrrolidine, or trans-2,6-disubstituted piperidine with diphenylthiophosphinic chloride or diphenylselenophosphinic chloride in acetonitrile in the presence of potassium carbonate at room temperature, an unexpected carbon dioxide insertion produced carbamic diphenylthiophosphinic or diphenylselenophosphinic anhydride in good yield. The same product could be also obtained when the reaction was carried out under carbon dioxide atmosphere using potassium hydroxide or triethylamine as a base. This is a very simple reaction process related to the fixation of carbon dioxide without a metal catalyst.

Journal Article↗