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S Bao

Publications and source records attributed to S Bao.

At least 109 records · Page 6Linked to original sources
PubMed1995

The effects of brefeldin A on the glucose transport system in rat adipocytes. Implications regarding the intracellular locus of insulin-sensitive Glut4.

Insulin activates glucose transport by recruiting Glut4 glucose transporters from an intracellular pool to plasma membrane (PM). To localize intracellular translocating Glut4, we studied the effects of brefeldin A (BFA), which disassembles Golgi and prevents trans-Golgi vesicular budding, on the glucose transport system. Isolated rat adipocytes were treated with and without both BFA (10 micrograms/ml) and insulin. BFA did not affect maximal rates of either 2-deoxyglucose or 3-O-methyl-glucose transport or the insulin:glucose transport dose-response curve but did increase basal transport by approximately 2-fold (p < 0.05). We also measured Glut4 in PM, low (LDM) and high density microsome subfractions. In basal cells, BFA increased PM Glut4 by 58% concomitant with a 18% decrease in LDM (p < 0.05). Insulin alone increased PM Glut4 by 3-fold concomitant with a 56% decrease in LDM. BFA did not affect insulin-induced changes in Glut4 levels in PM or LDM. Most intracellular Glut4 was localized to sub-PM vesicles by immunoelectron microscopy in basal cells, and BFA did not affect insulin-mediated recruitment of immunogold-labeled Glut4 to PM. In summary, 1) in basal cells, BFA led to a small increase in glucose transport activity and redistribution of a limited number of transporters from LDM to PM; 2) BFA did not affect insulin's ability to stimulate glucose transport or recruit normal numbers of LDM Glut4 to PM; and 3) insulin action is predominantly mediated by a BFA-insensitive pool of intracellular Glut4, which localizes to sub-PM vesicles. Thus, the major translocating pool of Glut4 in rat adipocytes does not involve trans-Golgi.

3-O-Methylglucose↗
PubMed1995

Ubiquitin fusion proteins are overexpressed in colon cancer but not in gastric cancer.

A cDNA clone (AF3) encoding the ubiquitin A gene 52 amino acid extension fusion protein (UbA52) was isolated from a subtracted cDNA library of human colorectal carcinoma minus adjacent normal mucosa. In Northern hybridization the mRNA signal for UbA52 was greater in surgical samples of colonic carcinoma (T) than in paired adjacent normal (N) tissues in 24 of 29 cases (T/N = 3.4 +/- 0.5, P < 0.01). An oligonucleotide probe specific for only the 52 amino acid extension confirmed the overexpression of UbA52. In contrast, there was no overexpression of UbA52 mRNA in gastric cancer samples (n = 7, T/N = 1.0 +/- 0.3). The mRNA of several ribosomal proteins, and of another ubiquitin A gene fusion protein, UbA80, with an 80 amino acid extension of ribosomal protein S27a, have been reported to be over-expressed in colon cancer, but not as yet at the protein level. Using rabbit antisera to the ribosomal protein component S27a we demonstrate over-expression of S27a at the protein level in colonic (n = 5), but not gastric (n = 6) carcinomas. Therefore it is likely that both UbA80 and UbA52 are overexpressed in colon cancer, but not in gastric cancer.

Base Sequence↗
PubMed1995

IgA production by peritoneal cavity B cells is IL-6 independent: implications for intestinal IgA responses.

We have shown previously both in vitro and in vivo that IL-6 is an important factor for the development of IgA-producing B cells. However, despite the lack of this cytokine in mice with targeted disruption of the interleukin (IL)-6 gene (gene knockout mice), a substantial number of IgA-producing plasma cells occur in their intestinal mucosa. The experiments reported here indicate that there is a population of IgA-producing B cell precursors originating from the peritoneal cavity, distinguished from conventional Peyer's patch-derived precursors by their expression of CD5, and that IgA secretion by these cells is IL-6-independent. Further, there is an increase in CD5 expression among brightly staining IgA-producing cells obtained from the intestinal lamina propria of IL-6 gene-disrupted mice compared to normal controls. These data suggest an explanation for the persistence of IgA-producing plasma cells in the intestinal mucosa of IL-6-depleted mice and indicate the importance of IL-6 for development of conventional precursors of IgA-producing B cells, but not those derived from the peritoneal cavity pool.

Animals↗
PubMed1995

Analysis of feline dual lymphocyte populations observed by flow cytometry.

Two discrete lymphocyte populations were observed commonly on flow cytometric analysis (FCM) of feline lymphocyte subsets. The identity of these populations as small and large lymphocytes was established by correlating data from FCM with that from peripheral blood films. Dual lymphocyte populations were more likely to be seen in feline immunodeficiency virus-positive (FIV(-)+ ve) cats but their occurrence was not affected by health status, age, gender or breed. FIV(-)+ ve cats had a significantly higher proportion of large lymphocytes than FIV-negative (FIV(-)- ve) cats. However, FIV(-)+ ve cats had significantly fewer small lymphocytes than FIV(-)- ve cats but similar numbers of large lymphocytes. Lymphocyte subset analysis revealed that small lymphocytes had a greater proportion of CD4+ cells than large lymphocytes, regardless of the FIV or health status of the cat. In FIV(-)- ve cats, small lymphocytes had a greater proportion of Pan T + lymphocytes than large lymphocytes, but the converse was seen in FIV(-)+ ve cats. The proportion of CD8 + cells was higher in small lymphocytes than large lymphocytes in well FIV(-)- ve cats but this distinction was not seen in sick FIV(-)- ve cats or FIV(-)+ ve cats of any health status. Regardless of health status, FIV(-)+ ve cats had a lower absolute count of small lymphocytes which were T cells (due to lower numbers of both CD4 + and CD8 + cells) than FIV(-)- ve cats. The numbers of small B cells were similar for both FIV(-)+ ve and FIV(-)- ve cats. However, there were no differences between FIV(-)+ ve and FIV(-)- ve cats in the absolute values of any subset of the large lymphocytes, which suggested that FIV may affect only small lymphocytes. Statistically, the inclusion or exclusion of the large lymphocyte population for routine lymphocyte subset analysis did not affect the overall results. However, because there were significant differences in subset distribution between small and large lymphocytes, analysis of both groups should be included in studies examining the role of lymphocytes in disease.

Animals↗
PubMed1995

Cytokine mediated effects in mucosal immunity.

The predominance of IgA antibodies in mucosal sites reflects a combination of high rate IgA isotype switching among precursor cells in induction sites, their selective localization in mucosal effector tissues and vigorous proliferation of these cells after extravasation. Each of these steps leading to IgA expression at the mucosa is under cytokine control. This paper will address the role of cytokines in induction and expression of IgA responses and strategies for manipulating cytokine expression. Therapeutic interventions based on this information may not only lead to improved vaccination responses and correction of immunodeficiencies but also, by invoking the phenomenon of oral tolerance, may assist in the management of autoimmune, allergic and alloreactive disease.

Animals↗
PubMed1994

Ontogeny of major histocompatibility complex antigen expression on cultured human embryonic skeletal myoblasts.

Human embryonic myoblasts isolated from 13- to 19-week embryos were treated for 24 to 144 hr with 0.1-500 U/ml IFN-gamma and the constitutive and IFN-gamma-inducible MHC expression was examined by flow cytometry. Low levels of constitutive MHC I were expressed that increased with both developmental age and incubation time. In contrast, no constitutive MHC II was detected on human embryonic myoblasts at any age or incubation time. Both classes of MHC can be induced by IFN-gamma. Maximal MHC I induction increased in parallel with age, i.e., maximal induction occurred on 19-week myoblasts, while MHC II induction peaked at 17 weeks. IFN-gamma-induced expression of MHC I and II also increased with incubation time. Induced expression of MHC I antigen reached plateau levels at 72 hr of IFN-gamma incubation, whereas MHC II increased to a plateau level at 120 hr. The immunological importance of these findings for myoblast transfer therapy is discussed.

Cells, Cultured↗
PubMed1994

Molecular cloning of chick cardiac muscle tensin. Full-length cDNA sequence, expression, and characterization.

Here we describe the molecular cloning of 7.1-kilobase cDNA encoding chick cardiac muscle tensin. It contains an open reading frame of 1,744 amino acid (aa) residues. Sequence analysis reveals that, in addition to the previously noted SH2 domain (Davis, S., Lu, M. L., Lo, S. H., Lin, S., Butler, J. A., Druker, B. J., Roberts, T. M., An, Q., and Chen, L. B. (1991) Science 252, 712-715), tensin contains virtually all of the known sequence (362 aa) of insertin, an actin-capping protein that allows actin monomer to be "inserted" (Schroer, E., and Wegner, A. (1985) Eur. J. Biochem. 153, 515-520). Moreover, tensin shares partial homology with actin (46.7% identity in 30 aa), beta-spectrin's actin-binding consensus (40% identity in 26 aa), BCR (40% identity in 25 aa), catenin alpha (35% identity in 45 aa), synapsin Ia (25.6% identity in 156 aa), IL-3 receptor (20.2% identity in 384 aa), and IL-2/EPO receptors (14% identity in 20 aa). Recombinant full-length tensin, tagged with an influenza-derived epitope, was over-expressed by a baculovirus system and purified to apparent homogeneity. It migrates as a 200-kDa protein in SDS-polyacrylamide gel electrophoresis, similar to the native tensin. The structure of the tensin molecule has been characterized by light scattering, electron microscopy, and gel filtration. Nine monoclonal antibodies recognizing different regions of tensin have been prepared and characterized. The epitope-tagged recombinant tensin gene was subcloned into a pRcCMV vector and transfected into NIH 3T3 cells. Immunofluorescence stainings with monoclonal antibodies specific for chick tensin (not cross-reactive with mouse tensin) showed that the expressed protein is indeed localized at focal contacts, as that of native tensin.

3T3 Cells↗
PubMed1994

The role of interleukin-6 in mucosal IgA antibody responses in vivo.

In mice with targeted disruption of the gene that encodes interleukin-6 (IL-6), greatly reduced numbers of immunoglobulin A (IgA)-producing cells were observed at mucosae and grossly deficient local antibody responses were recorded after mucosal challenge with either ovalbumin or vaccinia virus. The IgA response in the lungs was completely restored after intranasal infection with recombinant vaccinia viruses engineered to express IL-6. These findings demonstrate a critical role for IL-6 in vivo in the development of local IgA antibody responses and illustrate the effectiveness of vector-directed cytokine gene therapy.

Animals↗
PubMed1994

Na(+)-dependent high affinity uptake of L-glutamate in primary cultures of human fibroblasts isolated from three different types of tissue.

Cultured human fibroblasts isolated from embryonic muscle, skin and peripheral nerve tissues were found to accumulate [3H]L-glutamate by a Na(+)-dependent uptake process strongly inhibited by several glutamate/aspartate analogues including D- and L-aspartate, D- and L-threo-3-hydroxyaspartate and L-trans-pyrrolidine-2,4-dicarboxylate but not D-glutamate. It was also reduced by elevated concentrations of K+, Rb+ and Cs+. The values of Km's were 5-20 microM, well within the 'high affinity' region. Variations in the capacity (Vmax) of [3H]L-glutamate uptake did not correlate with the origin (muscle, skin or nerve tissue) of the fibroblasts. The uptake characteristics suggest that it is mediated by a transport system similar to that commonly observed only in brain tissue.

Aspartic Acid↗
PubMed1994

Cytokine regulation of mucosal responses: a rational basis for new vaccine delivery strategies.

In this review, cytokine regulation of mucosal responses is discussed in relation to the mucosal immune network and regulation of IgA responses. Based on this understanding, aspects of gene therapy for manipulation of the host environment and vaccine delivery systems are discussed. Although evidence obtained in vitro is briefly reviewed the general focus of this article is on evidence obtained from models in vivo.

Animals↗
PubMed1994

Biological actions of insulin are differentially regulated by glucose and insulin in primary cultured adipocytes. Chronic ability to increase glycogen synthase activity.

We have shown previously that prolonged exposure to insulin and glucose impairs the insulin-responsive glucose transport system in primary cultured adipocytes. To assess the ability of insulin and glucose to regulate other cellular insulin actions, epididymal rat adipocytes were cultured in media containing 0-15 mM D-glucose and with or without insulin (50 ng/ml). After 24 h, cells were washed and basal and maximally insulin-stimulated rates of 2-deoxy-D-glucose uptake, L-leucine incorporation into protein, glucose oxidation to CO2, glucose incorporation into lipids, and glycogen synthase activity were measured. The results confirmed that glucose potentiates insulin's chronic ability to decrease basal and maximal glucose transport rates by approximately 50% at 5 mM glucose and by approximately 70% at 15 mM glucose compared with control cells. However, neither glucose nor insulin, alone or in combination, affected rates of leucine incorporation into protein. In addition, basal and maximal rates of glucose oxidation and of glucose incorporation into lipids were not regulated by glucose, and maximal responses declined approximately 50% over 24 h only when insulin was not present during preincubation (i.e., chronic insulin exposure was necessary to maintain full maximal responses). Glycogen synthase activity was measured in a cell-free system (0.5 mM UDP-glucose, with 10 or 0.01 mM glucose-6-phosphate) after exposing intact cells to glucose and insulin. Both short-term (1 h) and long-term (24 h) exposure to glucose alone led a dose-dependent increase in I-form and D-form glycogen synthase activity. Chronic exposure to insulin also increased total glycogen synthase activity (I- plus D-form) but did not affect absolute rates of maximally stimulated I-form activity. Glucose (but not insulin) increased the cellular content of immunoreactive glycogen synthase by 70% after 1 h. These results show that 1) chronic exposure to glucose and insulin impairs insulin responsiveness of the glucose transport system but does not affect rates of amino acid incorporation into protein; 2) the chronic presence of insulin is necessary for the maintenance of normal maximally stimulated rates of glucose oxidation and of glucose incorporation into lipids in cultured cells; and 3) glucose increases both D-form and I-form glycogen synthase activity, in part by increasing the amount of synthase protein, whereas chronic insulin exposure increases total glycogen synthase activity without altering maximal absolute rates of I-form activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Adipocytes↗
PubMed1993

Structure of parasternal intercostal muscles in the adult hamster: topographic effects.

The parasternal intercostals are primary inspiratory muscles like the costal and crural diaphragm. However, the structure of the rib cage and its impedance to inspiration and expiration varies regionally. We questioned whether topographic differences in rib cage structure and impedance were associated with regional differences in parasternal intercostal muscle structure. Therefore, we examined the size and percentage of histochemically stained fibers in the parasternal intercostal muscles in the first, second, third, fourth, and sixth interspaces in the hamster. We observed a rostrocaudal gradient in the percentage and size of slow oxidative (SO), fast oxidative-glycolytic, and fast glycolytic (FG) fibers in the parasternal intercostal muscles. In particular, the percentage of SO decreased while the percentage of FG increased in a rostrocaudal direction in the first through sixth interspaces. In addition, the size of SO and FG fibers increased from the first to sixth interspace. Furthermore, changes in the size and percent of the three fiber types produced, in a rostrocaudal direction, significant reductions in the relative mass of the parasternal intercostal muscle made up of SO fibers and increases in the mass of fast fibers. We speculate that topographical differences in the size and percentage of fast and slow twitch fibers in the parasternal intercostal are likely to alter force-generating capacity of the parasternal muscles in a rostrocaudal direction and likely reflect regional differences in muscle load and/or activity.

Analysis of Variance↗
PubMed1993

Localization of IFN-gamma and IL-6 mRNA in murine intestine by in situ hybridization.

Previous studies have highlighted the importance of CD4+ T cells in regulation of IgA responses and have indicated a functional heterogeneity among these cells between inductive (Peyer's patch) and effector (lamina propria) sites in the intestine. To determine whether these functional differences could be accounted for by differences in cytokine profile of cells in each of these sites, the distribution of mRNA for interferon-gamma (IFN-gamma) and interleukin-6 (IL-6) was investigated by in situ hybridization techniques using 35S-labelled riboprobes. Whereas message for IL-6 is abundant in all regions of the lamina propria from the base of the mucosa to the tips of the villi, very little is expressed in Peyer's patches or in the epithelium. In contrast, message for IFN-gamma is expressed predominantly by cells localized only in the base of the lamina propria and, as with IL-6, very little message was detected in Peyer's patches although occasional strongly positive IFN-gamma cells were observed in the epithelium. These results indicate that, at least in the absence of deliberate intestinal stimulation, functional expression of these cytokines is restricted to effector rather than induction sites in the intestine. This is consistent with our previous observations demonstrating a requirement for T-cell signals in promoting post-extravasation differentiation and proliferation of IgA-committed B cells in vivo and the implications of these findings to the role of the Th1 and Th2 subsets of CD4+ cells in mucosal immune responses is discussed.

Animals↗
PubMed1992

Increased expression of human ribosomal phosphoprotein P0 messenger RNA in hepatocellular carcinoma and colon carcinoma.

To search for differentially expressed gene products in selected cancers of endodermal origin, cDNA libraries derived from mRNA in human hepatocellular carcinoma and adjacent grossly normal tissue were generated. From these parent libraries, subtracted cDNA libraries of tumor minus normal and normal minus tumor tissues were constructed. After screening these subtracted libraries by +/- hybridization, a cDNA clone that is overexpressed in hepatocellular carcinoma and encodes the human acidic ribosomal phosphoprotein P0 (P0) was identified. We then evaluated the expression of this phosphoprotein P0 in human colon carcinoma samples. Surgical specimens of primary tumors and liver metastases were examined by Northern hybridization of total RNA with one of 2 32P-labeled P0 probes. The mRNA level of the P0 was greater in primary colon carcinoma than in paired adjacent normal colonic epithelium in 36 of 38 cases; the mean tumor/normal ratio was 2.7 (range, up to 13). The tumor/normal ratio, when plotted against the Dukes' stage of disease, gave evidence for increasing P0 expression with increasing stage of colon carcinoma (P = 0.02). In all 8 cases of paired colon carcinoma metastatic to liver and 2 cases of paired primary hepatocellular carcinoma, the P0 mRNA level was greater in tumor than in adjacent normal liver tissue. The mean tumor/normal ratio was 4.0 (range, up to 11) for the colon cancers metastatic to liver and 4.2 for the primary hepatocellular carcinoma samples. These findings support a common increased expression of selected gene products in different tumors of endodermal origin and suggest that increased P0 expression, in line with certain other ribosomal proteins, may be associated with human colorectal cancer progression and biological aggressiveness.

Blotting, Northern↗
PubMed1992

Flavivirus induces MHC antigen on human myoblasts: a model of autoimmune myositis?

Infection of human embryonic myoblasts by West Nile virus (WNV), a flavivirus, caused significant upregulation of class I and II MHC expression as determined by flow cytometry. After 48 hours at a multiplicity of infection of 5 pfu/cell, a sixfold increase in MHC class I expression was induced from initially low levels of expression. In contrast, MHC class II was induced de novo to five times the control fluorescence level. At least 70% of the cells were infected as determined using fluorescence microscopy and anti-WNV antibody labeling. Myoblasts were > 90% pure as shown by anti--Leu-19 labeling. MHC class I (but not class II) was increased threefold after exposure to virus-inactivated supernatant from 48-hour--infected cells, indicating the presence of factor(s) contributing to the MHC class I increase. These findings may be important in establishing a link between viral infection of human cells and induction of inflammatory autoimmune disease. We discuss the possibility of using WNV as an in vivo model.

Autoimmune Diseases↗
PubMed1991

[Experimental and clinical studies of using Nd: YAG laser via domestic metal cap and sapphire tip delivery systems].

Sixteen segments of normal human cadaver aorta were irradiated by Nd: YAG laser beam delivered via domestic metal cap and sapphire tip fiber systems. Results revealed that the adherence to target tissue and tissue damage were more apparent with metal caps than those with sapphire tips. Furthermore, the latter had smoother edges of ablation crater less carbonization layers and smaller thermal necrotic zones. The delivery systems were used to perform laser angioplasty in 2 iliac and 5 coronary atherosclerotic arteries and all achieved immediate recanalization.

Aged↗
PubMed1989

The promises and problems of ergonomics application in the People's Republic of China.

Ergonomics or human factors, as an applied science concerning the design of interfaces between man, machine and the working environment, has shown its great capacities and potentials for improving working conditions and efficiency during its applications in most industrially developed countries (IC). As a means of improving the economy, industrialisation has been initiated in many industrially developing countries (DC). Knowledge and technology available in ICs have been transferred to DCs in order to increase the process of industrialisation. Ergonomics as a western discipline has also been transferred to many DCs during the technology transfer process. As an example of the transfer and development of ergonomics in industrially developing countries, this paper examines the development of ergonomics and its various areas of application in the People's Republic of China. After reviewing the current ergonomics situation and its applications in China from various points of view - i e, from organisation, research, education and industrial application - promises and problems associated with the development of this new area of science are discussed.

Journal Article↗