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Biomedical subjects

Y Ma

Publications and source records attributed to Y Ma.

At least 415 records · Page 23Linked to original sources
PubMed1996

Structural and functional roles of the amino-terminal region and collagen-like domain of human serum mannan-binding protein.

The serum mannan-binding protein (S-MBP) is a Ca(2+)-dependent C-type animal lectin specific for mannose and N-acetylglucosamine, which plays an important role in first-line host defense. To study the structure and function relationship of the lectin, a full-length human S-MBPcDNA was expressed in Sf9 insect cells using a baculovirus expression system, and a cDNA encoding the carbohydrate recognition domain (CRD) of human S-MBP was expressed in E. coli. The properties of the recombinant S-MBP and recombinant S-MBP-CRD were compared with those of the native human S-MBP and the CRD of the native S-MBP. The results indicated that functional human S-MBP can be successfully expressed in Sf9 cells and functional S-MBP-CRD in E. coli. In addition, the amino-terminal region and collagen-like domain are required for higher oligomer formation and play important roles in complement activation.

Animals↗
PubMed1996

Two components of the chloroplast protein import apparatus, IAP86 and IAP75, interact with the transit sequence during the recognition and translocation of precursor proteins at the outer envelope.

The interactions of precursor proteins with components of the chloroplast envelope were investigated during the early stages of protein import using a chemical cross-linking strategy. In the absence of energy, two components of the outer envelope import machinery, IAP86 and IAP75, cross-linked to the transit sequence of the precursor to the small subunit of ribulose-1, 5-bisphosphate carboxylase (pS) in a precursor binding assay. In the presence of concentrations of ATP or GTP that support maximal precursor binding to the envelope, cross-linking to the transit sequence occurred predominantly with IAP75 and a previously unidentified 21-kD polypeptide of the inner membrane, indicating that the transit sequence had inserted across the outer membrane. Cross-linking of envelope components to sequences in the mature portion of a second precursor, preferredoxin, was detected in the presence of ATP or GTP, suggesting that sequences distant from the transit sequence were brought into the vicinity of the outer membrane under these conditions. IAP75 and a third import component, IAP34, were coimmunoprecipitated with IAP86 antibodies from solubilized envelope membranes, indicating that these three proteins form a stable complex in the outer membrane. On the basis of these observations, we propose that IAP86 and IAP75 act as components of a multisubunit complex to mediate energy-independent recognition of the transit sequence and subsequent nucleoside triphosphate-induced insertion of the transit sequence across the outer membrane.

Animals↗
PubMed1996

Susceptibility locus for inflammatory bowel disease on chromosome 16 has a role in Crohn's disease, but not in ulcerative colitis.

In the Western world, chronic inflammatory bowel disease (IBD) presents as two major clinical forms, Crohn's disease (CD) and ulcerative colitis (UC) [Targan, S.R. and Shanahan, F. (1994). In Retford, D.C (ed.), Inflammatory Bowel Disease: From Bench to Bedside. Williams and Wilkins, Baltimore]. Genetic epidemiological studies, the occurrence of rare syndromes associated with IBD, and animal models suggest that inherited factors play significant roles in the susceptibility to both forms of IBD [Yang, H.-Y. and Rotter, J.I. (1995) In Kirsner, J.B. and Shorter, R.G. (eds). Genetic Aspects of Idiopathic Inflammatory Bowel Disease. Williams and Wilkins, Baltimore, pp.301-331]. Recently, a genome-wide search on European families with multiple affected members with CD identified a putative susceptibility locus in the centromeric region of chromosome 16 [Hugot, J.-P. et al. (1996) Nature, 379, 821-823]. We have now tested this region in an independent set of US families, confirmed that this region is likely to contain a gene predisposing to CD, and further refined the chromosomal location of this gene. Most importantly with respect to this locus, our data also seem to indicate that there is heterogeneity both within the CD group, and between the CD and UC groups with respect to this locus. The susceptibility locus appears to be involved only in non-Jewish CD sibpairs and not in our Ashkenazi Jewish CD sibpairs. Additionally, we have tested sibpairs having either only UC or both UC and CD for involvement of this locus, and have found no evidence that this region predisposes to IBD in these patients.

Chromosome Mapping↗
PubMed1996

Reduction of Saccharomyces cell adhesion by liquid mechanical vibration.

The effect of liquid mechanical vibration on the adhesion of Saccharomyces cerevisiae cells to the internal glass surface of a pipette was studied using a 25 Hz vibration source. The maximum vibration amplitude was 1.06 mm (peak to peak) along the pipette direction. Relative movements between the pipette and yeast suspension in it were produced by vibration and reduced the cell adhesion. The reduction in adhesion was affected by both vibration amplitude and suspension pH. Analysis showed that in routine cell counts, cell adhesion to the pipette wall was a significant error source. The construction of a vibration device for routine cell count work appears feasible.

Cell Adhesion↗
PubMed1996

Irreversible paraben inhibition of glycolysis by Streptococcus mutans GS-5.

Parabens were found to inhibit irreversibly glycolysis by the cariogenic dental plaque bacterium Streptococcus mutans GS-5 and to decrease the capacity of the bacterium to lower the pH in dense cell suspensions containing excess glucose. The hierarchy of effectiveness was butyl > propyl > ethyl > methyl paraben. Results of studies of the nature of glycolytic inhibition by butyl paraben indicated that it could act at millimolar concentrations as an irreversible inhibitor of the phosphotransferase system for sugar uptake and was lethal for the bacterium at these same levels. Butyl paraben acted also as a reversible inhibitor of the F-ATPase of the organism. Overall, it appeared that the lethal actions of parabens can be interpreted at least in part as due to irreversible damage to key enzymes, such as those of the phosphotransferase system.

Food Preservatives↗
PubMed1996

Multiple glucan-binding proteins of Streptococcus sobrinus.

Several proteins from culture supernatants of Streptococcus sobrinus were able to bind avidly to Sephadex G-75. The proteins could be partially eluted from the Sephadex by low-molecular-weight alpha-1,6 glucan or fully eluted by 4 M guanidine hydrochloride. Elution profiles were complex, yielding proteins of 16, 45, 58 to 60, 90, 135, and 145 kDa, showing that the wild-type strain possessed multiple glucan-binding proteins. Two mutants of Streptococcus sobrinus incapable of aggregation by high-molecular-weight alpha-1,6 glucan were isolated. One mutant was spontaneous, from a cell suspension to which glucan had been added, whereas the other was induced by ethyl methanesulfonate. Both mutants were devoid of a 60-kDa protein, as shown by gel electrophoresis of culture supernatants and whole cells. Amino acid analysis showed that the 58- to 60-kDa protein and the 90-kDa protein were distinct, although both were N-terminally blocked. Both mutants retained their ability to adhere to glass in the presence of sucrose and to ferment mannitol and sorbitol. Both mutants retained their glucosytransferase activities, as shown by activity gels. Western blots (immunoblots), employing antibody against a glucan-binding protein of Streptococcus mutans, failed to reveal cross-reactivity with S. sobrinus proteins. The results show that even though S. sobrinus produces several proteins capable of binding alpha-1,6 glucans, the 60-kDa protein is probably the lectin needed for glucan-dependent cellular aggregation.

Amino Acids↗
PubMed1996

Structure, function, and evolution of adenovirus-associated RNA: a phylogenetic approach.

To explore the structure and function of a small regulatory RNA, we examined the virus-associated (VA) RNA species of all 47 known human adenovirus serotypes and of one simian virus, SA7. The VA RNA gene regions of 43 human adenoviruses were amplified and sequenced, and the structures of 10 representative VA RNAs were probed by nuclease sensitivity analysis. Most human viruses have two VA RNA species, VA RNA, and VA RNAII, but nine viruses (19%) have a single VA RNA gene. Sequence alignments classified the RNAs into eight families, corresponding broadly to the known virus groups, and three superfamilies. One superfamily contains the single VA RNAs of groups A and F and the VA RNAI species of group C; the second contains the VA RNAI species of groups B1, D, and E and the unclassified viruses (adenovirus types 42 to 47), as well as the single VA RNAs of group B2; and the third contains all VA RNAII species. Fourteen regions of homology occur throughout the molecule. The longest of these correspond to transcription signals; most of the others participate in RNA secondary structure. The previously identified tetranucleotide pair, GGGU:ACCC, is nearly invariant, diverging slightly (to GGGU:ACCU) only in the two group F viruses and forming a stem in the central domain that is critical for VA RNA structure and function. Secondary structure models which accommodate the nuclease sensitivity data and sequence variations within each family were generated. The major structural features-the terminal stem, apical stem-loop, and central domain-are conserved in all VA RNAs, but differences exist in the apical stem and central domains, especially of the VA RNAII species. Sequence analysis suggests that an ancestral VA RNA gene underwent duplication during the evolution of viruses containing two VA RNA genes. Although the VA RNAII gene seems to have been lost or inactivated by secondary deletion events in some viruses, the high degree of homology among the VA RNAII species implies that this RNA may play an undiscovered role in virus survival. We speculate that the VA RNA genes originated from cellular sequences containing multiple tRNA genes.

Adenoviridae↗
PubMed1996

T lymphocytes play a critical role in the development of cyclosporin A-induced osteopenia.

The T lymphocyte suppressor, cyclosporin A, has been shown to cause high turnover osteoporosis. We postulated that cyclosporin A may exert its effects via the T cell rather than direct activity on bone. In this study we administered cyclosporin A (15 mg/kg.day by gavage) to 11 10-week-old Rowett athymic nude rats and to 12 age-matched immunocompetent Sprague-Dawley rats. Placebo was administered to control groups (n = 12 for both). After 28 days of treatment, the Sprague-Dawley rats displayed high turnover bone loss, but the nude rats were largely unaffected by the drug. Sprague-Dawley treated rats had less than half the percent trabecular area of their controls as measured at the secondary spongiosa of the proximal tibial metaphysis (P < 0.001; strain by treatment, P = 0.007). The same pattern was evident for trabecular number, separation, and thickness (strain by treatment, P = 0.034, P = 0.001, and P = 0.021, respectively). Only the Sprague-Dawley rats had an elevated percent eroded perimeter and an elevated bone area referent bone formation rate (strain by treatment, P = 0.002 and P = 0.0003, respectively). Mass, glucose, ionized calcium, PTH, osteocalcin, 1,25-dihydroxyvitamin D, and creatinine all responded similarly to cyclosporin A regardless of strain. T Lymphocytes thus appear to be a prerequisite for the development of cyclosporin A-induced osteopenia.

Animals↗
PubMed1996

Expression of Fas ligand by human cytotrophoblasts: implications in placentation and fetal survival.

Recent data indicated that local production of Fas ligand (FasL) by cells of the eye and testis may confer immune tolerance at these sites. In the present study, we examined the in vivo and in vitro patterns of expression of FasL in the human placenta to provide a potential mechanism through which the fetus is afforded protection against the cytolytic actions of lymphocytes present within maternal decidua across gestation. Immunohistochemical staining of first trimester human placental tissue sections revealed the presence of FasL in cytotrophoblasts in free floating villi, anchoring villi, and cytotrophoblastic islands. FasL staining was also pronounced in syncytiotrophoblasts of term placenta indicating that FasL expression is maintained across gestation. Multiple molecular forms of FasL, suggestive of altered patterns of glycosylation, were detected in extracts of term placenta, amnion and chorion by Western blotting. In addition, in vitro expression of FasL was demonstrated to increase 2 to 3-fold during differentiation of primary cultures of cytotrophoblasts isolated from human term placentas. Local production of FasL by human cytotrophoblasts provides a mechanism through which cytotrophoblasts may induce immune tolerance and self-regulate survival during invasion and subsequent placentation.

Antigens, Surface↗
PubMed1996

A novel subunit of vacuolar H(+)-ATPase related to the b subunit of F-ATPases.

The subunit structure of the vacuolar H(+)-ATPase (V-ATPase) membrane sector is not entirely known. The proteolipid is the only subunit that has been implicated in the mechanism of energy transfer in the enzyme. We have identified a protein (M16) that co-purifies with the V-ATPase complex from bovine chromaffin granules. Information obtained from the amino acid sequence of a proteolytic fragment of M16 was used to clone a bovine adrenal cDNA encoding this protein. The cDNA encodes a hydrophilic protein of 118 amino acid residues with a calculated molecular mass of 13682Da. Amino acid sequence analysis revealed that M16 exhibits a significant homology to subunit b of F-ATPases. M16 is smaller than subunit b and contains no apparent transmembrane segment in its N terminus. The remainder of subunit b is related to M16 not only by its amino acid sequence but also in its predicted structure of helix-turn-helix. The structural and evolutionary implications of these findings are discussed.

Adrenal Medulla↗
PubMed1996

[Glutamine dipeptide enriched nutritional solutions attenuate bacterial translocation in rats after 60% intestinal resections].

OBJECTIVE: To investigate the effects of alanyl-glutamine dipeptide (Ala-Gln) enriched parenteral nutrition solution on intestinal mucosa or gut barrier since traditional parenteral nutrition leads to bacterial translocation. METHODS: The moderate operation stress was induced by 60% resection of small intestine. Qualified rats distributed in three groups: Chow group (n = 10) received standard rat chow, PN group (n = 10) received traditional parenteral nutrition solution only, and Ala-Gln group (n = 10) received glutamine dipeptide enriched nutritional solutions (3% Ala-Gln). Rats were maintained on their respective diets for 7 days. RESULTS: Chow group and Ala-Gln group maintained serum glutamine concentration, villus height and mucosal thickness. The bacterial translocation rate in Chow group and Ala-Gln group was 20% and in PN group 70%. CONCLUSION: Results demonstrate that Ala-Gln enriched nutritional solutions maintain intestinal adaptation and gut barrier function after massive intestinal resection.

Animals↗
PubMed1996

Secondary and tertiary structure in the central domain of adenovirus type 2 VA RNA I.

The small (160 nt) adenovirus RNA, VA RNAI, antagonizes the activation of the cellular protein kinase PKR (also known as DAI), a key regulator of gene expression. VA RNA consists of two stems separated by a complex region, the central domain, that is essential for its function. A notable feature of the central domain is a pair of tetranucleotides, GGGU and ACCC, which are mutually complementary and phylogenetically conserved. To investigate their role in the structure and function of VA RNA, we generated three sets of mutations designed to disrupt the putative stem and to restore it with different nucleotides. Substitutions in either of the tetranucleotides abrogated VA RNA function in two independent PKR-based assays, demonstrating the importance of these sequences in vivo. Compensating mutants restored function, indicating that the two tetranucleotides pair in the cell, but all of the compensating mutants were less active than wild-type VA RNA. The effects of the mutations on RNA structure were probed by nuclease sensitivity analysis. Pronounced changes in two loops in the central domain correlated closely with the formation and disruption of the stem, suggesting that the tetranucleotide stem defines a critical element in the structure of the central domain through tertiary interactions with the two loops. A model for the central domain is presented that accommodates these findings and also accounts for the known sites of PKR interaction.

Adenoviruses, Human↗
PubMed1996

Soluble cytokine receptors as carrier proteins: effects of soluble interleukin-4 receptors on the pharmacokinetics of murine interleukin-4.

Soluble interleukin-4 (IL-4) receptors (sIL-4R) can have either enhancing or inhibitory effects on the activity of IL-4 in vivo, depending on the relative concentration ratios of sIL-4R to IL-4. Whereas competition with membrane IL-4 receptors is the basis for their inhibitory action, the mechanisms responsible for the potentiation of IL-4 activity are not completely clear but may involve alterations in the half-life and biodistribution of IL-4 in vivo. To better understand the basis for the enhancing effect of sIL-4R, we have analyzed their effects on the pharmacokinetic properties of IL-4. Studies with radiolabeled recombinant IL-4 demonstrated that, when injected alone, IL-4 was rapidly cleared from the circulation and eliminated through the kidneys in a proteolytically degraded form. Administration of IL-4 in combination with increasing concentrations of sIL-4R resulted in a dose-dependent enhancement in the blood levels of IL-4 and a concomitant reduction in its clearance from circulation and excretion in the urine. Differences between measurements of IL-4 concentrations based on radioactivity and enzyme-linked immunosorbent assays indicated that the injected IL-4 was rapidly inactivated in vivo and that the presence of sIL-4R diminished this process. The inactivation of IL-4 was mediated through the membrane IL-4 receptors and required receptor internalization and intact lysosomal function. Taken together, these results suggest that sIL-4R are able to alter the pharmacokinetic properties of IL-4, prolonging its half-life in the circulation and reducing its clearance through diminished renal excretion and/or interference with inactivation. These effects are consistent with the ability of sIL-4R to potentiate IL-4 activity in vivo.

Animals↗
PubMed1996

[A human bone marrow cell line (B3HM) inducing leukemia in mouse].

Human bone marrow mononuclear cells were cultured on a layer of stromal cells derived from bone marrow of a patient with esophageal cancer. After five-week cultivation, the mononuclear cells could grow independently of stromal cells in liquid culture and had been passaged over 50 generations with a doubling time of 48 hours. The cell line thus established is called B3HM. The growth of B3HM appeared anchorage independent in semi-solid culture and produced 423 +/- 87.7 colonies per 5 X 10(4) cells. Immunofluorescence analysis showed that the cells were CD19+, CD20+, CD13+, CD15+, with both B cell and granulocyte surface markers. The cells or cell homogenate could induce leukemia when inoculated in nude mice and "615" inbred mice. The induced mouse leukemia was transplantable and L3T4 positive in more than 80% of the leukemic cells. The pathogenesis of the induced mouse leukemia is worthy of further investigation.

Aged↗
PubMed1996

[Preparation of huichun zhibao oral liquid (HZOL)].

The formulation, preparing method, quality standards, pharmacodynamic experinents and toxicological experiments of HZOL are described. The content of icariin, which is and effective component of epimedium herb as well as one of the main ingredients in HZOL, was successfully determined through HPLC, with an average recovery of 98.98% and RSD = 1.53%.

Animals↗
PubMed1996

[Detection of lipoarabinomannan-IgG in serum for the diagnosis of pulmonary tuberculosis].

OBJECTIVE: To ascertain the value of lipoarabinomannan-IgG (LAM-IgG) determination in the diagnosis of pulmonary tuberculosis. METHOD: LAM-IgG in sera obtained from 90 patients with active pulmonary tuberculosis, 53 patients with lung cancer and 30 healthy individuals were detected by using rapid enzyme-linked immunosorbent assay (ELISA). RESULTS: The positive rate was 82% in tuberculosis group, and the false positive rates were 8% and 3% in cancer group and healthy controls respectively. CONCLUSION: The results suggested that rapid ELISA and LAM-IgG detection was a useful supplementary tool for diagnosis of pulmonary tuberculosis.

Enzyme-Linked Immunosorbent Assay↗