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Biomedical subjects

B Tang

Publications and source records attributed to B Tang.

At least 109 records · Page 6Linked to original sources
PubMed1994

Protein tyrosine phosphorylation in the regulation of hematopoiesis by receptors of the cytokine-receptor superfamily.

Cytokines regulate the growth and differentiation of hematopoietic cells through their interaction with receptors of the cytokine receptor superfamily. This family of receptors has conserved motifs in the extracellular domain but share only limited similarity in the cytoplasmic domains. Although lacking catalytic domains, a variety of studies demonstrate that the cytokine receptors function by coupling ligand binding to induction of tyrosine phosphorylation. Recent studies have shown that the JAK family of kinases associate with cytokine receptors and are activated by ligand binding. Interaction occurs with the membrane proximal region of the cytoplasmic domain, a region that has been found to be essential for mitogenesis. One of the substrates of tyrosine phosphorylation is the receptor and, in the case of the receptor for Epo, the membrane distal region of the cytoplasmic domain is phosphorylated. Once phosphorylated, this site becomes a binding site for the amino-terminal SH2 domain of hematopoietic cell phosphatase (HCP). HCP is an important negative regulator of hematopoietic cell growth and its recruitment to the receptor complex is speculated to be important for this effect. The role of HCP is best indicated by the observation that the murine mutation, motheaten, is due to a mutation that results in the inability to make HCP. Motheaten mice die soon after birth due to the overproliferation of a variety of hematopoietic lineages. Together the results demonstrate an essential role in both protein tyrosine phosphorylation and de-phosphorylation in the growth regulation of hematopoiesis.

Animals↗
PubMed1994

[Effect of TRH and buzhong yiqi tang on natural killer cell activity and endocrine in stress mice].

Both thyrotropin-releasing hormone (TRH) and Buzhong Yiqi tang (BZYQT) were studied on their effect on splenic natural killer (NK) activity and hypothalamic-hypophyseal-thyroid (HHT) axis of stress mice. TRH (0.2 microgram/mouse/day, ip.) and BZYQT (0.2g/mouse/day, po.) had been given for 3 days before the amputation of right hind leg of mice were performed. Result showed that the TRH and BZYQT had rarely any effect on splenic NK activity and HHT axis recovery when they were used separately, but when used in combination they could increase the NK activity of splenic cells significantly in comparing with control group (from 8.32 +/- 4.50% to 15.60 +/- 4.18%, P < 0.05), while the HHT axis recovered to normal level at 24 hours after the amputation. The result suggests that there was a synergistic effect between TRH and BZYQT, and which exerted beneficial effect to the HHT axis stabilization and splenic NK activity recovery.

Amputation, Traumatic↗
PubMed1993

JAK2 associates with the erythropoietin receptor and is tyrosine phosphorylated and activated following stimulation with erythropoietin.

Erythropoietin (EPO) regulates the proliferation and differentiation of erythroid cells through interaction with its receptor (EPOR). Although EPOR is a member of the cytokine receptor superfamily and lacks a kinase domain, EPO induces tyrosine phosphorylation, which is correlated with gene transcription and mitogenesis. Here we demonstrate that EPO induces tyrosine phosphorylation of JAK2 kinase and activates its in vitro autophosphorylation. Using EPOR mutants, phosphorylation and activation of kinase activity correlate with the induction of mitogenesis. Furthermore, JAK2 physically associates with a membrane-proximal region of the EPOR cytoplasmic domain that is required for biological activity. The results support the hypothesis that JAK2 is the kinase that couples EPO binding to tyrosine phosphorylation and mitogenesis.

3T3 Cells↗
PubMed1993

Human endometrial 3 beta-hydroxysteroid dehydrogenase/isomerase can locally reduce intrinsic estrogenic/progestagenic activity ratios of a steroidal drug (Org OD 14).

In vitro conversion in human endometrial tissue of Org OD 14 [17 alpha-hydroxy-7 alpha-methyl-19-norpregn-5(10)-en-20-yn-3-one, a 3-keto-delta 5-10-19-nortestosterone derivative structurally related to norethynodrel] to its 4-ene isomer was demonstrated and measured spectrophotometrically and by chromatographic separation of the labeled metabolite from the tritiated precursor. The endometrial isomerase catalyzing this conversion is the 3 beta-hydroxy-steroid dehydrogenase/isomerase (3 beta HSD/isomerase), detected by Western blotting as a 42 kDa band, as confirmed by the inhibition of Org OD 14 isomerization with an antibody against this enzyme. The endometrial isomerase activity was found to be higher in secretory than in proliferative tissue and to be influenced by progestins, as suggested by the small but significant increase in activity resulting from exposure of proliferative endometrium to medroxyprogesterone acetate under organotypic culture conditions. In addition to the expected physiologic importance of endometrial 3 beta HSD/isomerase in the local metabolism of circulating steroids of adrenal origin, its presence in the endometrium is likely to have pharmacologic relevance, as illustrated by the local conversion of Org OD 14 to the 4-ene isomer, a metabolite with higher progestagenic and lower estrogenic potencies than those of its precursor. The local, tissue-specific, modification of the precursor would yield intracellular concentration ratios of Org OD 14 to 4-ene isomer in the endometrium significantly lower than those in blood. As a result, the estrogenic effects of Org OD 14 or of its 3-hydroxy metabolites on endometrial cell proliferation are minimized by the local formation of the progestagenic 4-ene isomer. This is a favorable feature of Org OD 14 since it selectively prevents undesirable proliferative stimulation of the endometrium in postmenopausal users while preserving its beneficial effects on other tissues, including bone.

3-Hydroxysteroid Dehydrogenases↗
PubMed1993

Direct effect of gonadotropins on decidualization of human endometrial stroma cells.

Decidualization of stromal cells isolated from proliferative human endometrium was achieved by adding to the culture medium human gonadotropins (FSH, FSH + LH, hCG). In addition to changes in the morphology of the stromal cells to the decidual phenotype, decidualization was evident from the expression of prolactin (PRL), demonstrated immunocytochemically, by Western blotting analysis, and by measuring its output into the medium through solid phase enzyme immunoassay. Gonadotropins also induced cAMP formation in the endometrial stromal cells under the same experimental conditions. This finding suggests that the mechanism by which gonadotropins promote decidualization of human endometrial stromal cells in vitro involves the introduction of cAMP, a compound that we have found to elicit the expression of PRL in this system. PRL is likely to be a key intermediate in the process of decidualization since it is by itself capable of inducing differentiation of the endometrial stromal cells to the decidual phenotype. Awareness of direct actions of gonadotropins on the endometrial cells and, in particular, of the decidualizing effects of FSH (Metrodin), FSH+LH (Pergonal) and hCG may contribute to the understanding of physiologic as well as pathophysiologic conditions relevant to endometrial functions and fertility.

Blotting, Western↗
PubMed1993

Cyclic adenosine 3',5'-monophosphate induces prolactin expression in stromal cells isolated from human proliferative endometrium.

In vitro decidualization of stromal cells isolated from human proliferative endometrium and cultured in RPMI-1640 containing 2% charcoal-treated fetal bovine serum and 0.1 U/ml insulin was achieved by adding to the medium cAMP derivatives [(Bu)2cAMP (db-cAMP) and 8-bromo-cAMP] or forskolin. PRL production under these conditions was demonstrated by documenting the synthesis of PRL mRNA (approximately 1.1 kilobase), the output of immunoprecipitable [35S]methionine-labeled PRL migrating as a single 23-kilodalton band during gel electrophoresis, and the time- and concentration-dependent secretion of PRL into the medium, measured by RIA (maximal on days 4-5 using 0.5 mM db-cAMP). Medroxyprogesterone acetate (1 microM) enhanced (1.7- to 2.5-fold) the effect of db-cAMP, 8-bromo-cAMP, or forskolin on PRL production, as evaluated by Western blotting analysis. Further evidence for a participation of db-cAMP in the decidualization process was provided by its ability to induce immunocytochemically detectable heat shock protein-27, insulin-like growth factor-binding protein-1, desmin, and laminin, all compounds produced by human decidual cells, but not expressed by stromal cells. The induction of PRL by cAMP may be a key step in the process of differentiation of fibroblast-like stromal cells to the decidual phenotype, as it has been previously reported by this laboratory that, under similar culture conditions, PRL itself is capable of inducing the production of heat shock protein-27, insulin-like growth factor-binding protein-1, desmin, and laminin in stromal cells isolated from proliferative endometrium.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1993

Expression of a novel form of Tec kinase in hematopoietic cells and mapping of the gene to chromosome 5 near Kit.

The Tec kinase was initially identified as a novel cytoplasmic protein tyrosine kinase that is preferentially expressed in the liver and is highly homologous to the Drosophila Dsrc28C src-related tyrosine kinase. In screening of interleukin 3 (IL-3)-dependent myeloid leukemia cells for protein tyrosine kinases, we observed that all cell lines examined expressed high levels of Tec transcripts. However, characterization of Tec cDNAs indicated that they differed significantly from the published sequence. Most strikingly, an insertion of 41 bp in the 5' region affects the initiation codon and results in replacing the published 13 amino acid amino-terminal sequences with 94 amino acids. Using polymerase chain reaction (PCR) analysis, only the form containing the insertion was detected in hematopoietic cells. In addition, we found an in-frame insertion of 66 bp that introduces an additional 22 amino acids into the SH3 domain. This insertion restores conserved SH3 sequences that are found in the src gene family and in the Dsrc28C gene. By PCR analysis, approximately equal levels of Tec transcripts containing the intact SH3 domain and containing the 22 amino acid deletion were found in hematopoietic cells. Lastly, by interspecies backcross analysis, we show that the Tec gene is tightly linked to the c-Kit gene on mouse chromosome 5.

Amino Acid Sequence↗
PubMed1993

[Effects of "he xiang zhuang gongfu" on respiratory function in healthy adults].

Eleven healthy adults who practised He Xiang Zhuang Gongfu (HGF) were followed for 6 months; 15 pulmonary function tests were determined before HGF practice, 2 months and 6 months after HGF practice. All 11 subjects took the HGF exercise every day for 30 minutes. Samplings were taken before subjects had ever practised HGF as control value, immediately and 30 minutes after HGF exercise. In the 2nd month and 6th month of HGF practice. The results indicated that VO2 decreased after 2 and 6 months HGF practice, and the effect even persisted to 30 minutes after HGF exercise, indicating that HGF may reduce metabolic rate and decrease the oxygen consumption of body. The possible mechanism was discussed. MVV had an up tendency after HGF practice, which suggested the possibility of strengthening respiratory muscle by HGF. HGF may be a good physical exercise and can induce a wakeful hypometabolic physiologic state.

Adult↗
PubMed1992

Cortical neurons inhibit basal and interleukin-1-stimulated astroglial cell secretion of nerve growth factor.

Primary cultures of neonatal rat cortical neurons and astrocytes synthesize and secrete nerve growth factor (NGF). Co-culturing neurons with astrocytes decreased NGF secretion in the co-cultures. The inhibition of co-culture NGF secretion was partially reversible upon selectively decreasing the number of neurons by glutamate treatment. Interleukin-1 beta (IL-1) stimulated NGF secretion from astrocytes, and the magnitude of this secretion was decreased in the co-cultures. Thus, co-culture with neurons decreases astroglial cell secretion of NGF and down-regulates astroglial responsiveness to IL-1.

Animals↗
PubMed1992

Unbalanced regulation of the ribosomal 5 S RNA-binding protein in Saccharomyces cerevisiae expressing mutant 5 S rRNAs.

A gene encoding the 5 S rRNA-binding protein (YL3) in yeast (Saccharomyces cerevisiae) was further characterized with respect to its chromosomal localization, the controlling sequence regions, and the influence of 5 S rRNA gene expression. Sequence and chromosome blot analyses localized the gene on chromosome XVI immediately downstream of a cytochrome oxidase assembly gene, COXII. S1 nuclease protection studies identified two major initiation sites, 20 and 65 nucleotides upstream of the coding sequence, and a single polyadenylation site, 98 nucleotides downstream of the stop codon. Northern blot analyses and S1 nuclease protection indicated a normal pattern of gene regulation in media supporting alternate rates of growth, but significantly unbalanced regulation was observed in the presence of mutant 5 S rRNA genes which under-produce RNA and result in reduced growth rates. The results suggest a co-ordinating regulatory mechanism which maintains appropriate levels of 5 S rRNA-protein complex; an internal control region-like sequence in the upstream region of the YL3 gene is consistent with this feedback mechanism.

Animals↗
PubMed1992

Perceptual organization and attention.

It is widely assumed that the grouping of the visual field first described by the Gestalt psychologists and the related phenomenon of texture segregation occur very early in the processing of visual information and involve preattentive processes. All the recent evidence supporting this assumption comes from visual search experiments in which the subject is actively looking for a target and attending to the stimulus. The question at issue is whether these kinds of patterns are perceived under conditions of inattention, i.e., when observers are not searching for them. We performed six experiments to determine whether texture segregation and grouping by similarity or proximity are perceived under conditions of inattention. On the first two trials subjects were asked to report the longer arm of a briefly presented cross which was surrounded by a pattern of ungrouped small elements. On the third trial and subsequent control trials these elements were configured into grouping patterns and subjects queried about them immediately following their line length reports. The results establish that neither texture segregation nor grouping by similarity of lightness or proximity are perceived under conditions of inattention. They support the conclusion that there is an earlier stage of processing than that referred to as preattentive.

Adult↗
PubMed1992

In vitro decidualization of human endometrial stromal cells.

Stromal cells isolated from proliferative human endometrium undergo morphologic and biochemical changes when exposed to a mixture of ovarian hormones, acquiring characteristics of decidual cells. In addition to the previously reported progestin-induced secretion of prolactin (PRL) by explants of human proliferative endometrium, and of PRL and laminin by stromal cells in culture, "in vitro" induction of several other decidual cell products was demonstrated in the present study, using cultures of stromal cells isolated from proliferative endometrium. Incubation of stromal cells with a mixture of estradiol, medroxyprogesterone acetate and relaxin, at a concentration reported to yield maximal stimulation of PRL production, resulted in changes from elongated to rounder cells, approx. 90% of which showed immunostaining for PRL under these conditions. Immunocytochemical procedures were carried out on cytospins of decidual cells isolated from decidual tissue adherent to fetal membranes collected at delivery (positive controls), and on stromal cells cultured in Lab-Tek chamber-slides, in the absence (negative controls) or in the presence of added hormones. Antibodies to 24K (a heat-shock protein also named HRP27), desmin (present in intermediate filaments), p29 (a protein associated with the estrogen receptor), and PP12 (an insulin growth factor-1 binding protein), did not react with stromal cells isolated from proliferative endometrium but showed immunostaining of the rounder cells obtained after hormonal treatment when tested with the peroxidase-labeled second antibody complex. In another series of similar experiments, in which the same decidualization end-points were employed, changes in 24K, desmin and PP12 expression were obtained by adding to the insulin-containing medium PRL instead of the hormonal mixture, a finding suggesting sequential steps during the decidualization process.

Culture Techniques↗
PubMed1992

Indigency, ethnicity, and hospital viability. The growth of racially diverse communities challenges Catholic providers and sponsors.

A Catholic Health Association study analyzes correlations between the ethnic and racial composition of communities served by Catholic hospitals and these hospitals' viability and capacity to serve their communities. It also describes the extent to which Catholic hospitals serve racially homogeneous communities, on the one hand, and racially and ethnically diverse communities, on the other. For comparison, the study focuses on hospitals in two groups. Group A consists of hospitals in the top quartile based on their proportion of care for the poor and top-quartile percentages of black and Hispanic residents in their local communities. Group B consists of hospitals with bottom-quartile levels of care for the poor and bottom-quartile percentages of black and Hispanic residents. The study found that, from 1985 to 1990, group A hospitals continued to provide high levels of care for the poor (between 28 percent and 32 percent on average) while average margins fell from about 4 percent to below 1 percent. During the same period, the amount of care group B hospitals provided to the poor remained between 5 percent and 6 percent; although their margins declined, these hospitals were significantly more profitable than group A hospitals. The financial stress currently being experienced by many hospitals that serve communities with relatively high percentages of ethnic and racial minorities is troubling. Without basic reform of the healthcare system, many of these facilities may have to close, leaving many in their communities without access to adequate healthcare.

Black or African American↗
PubMed1991

Age-associated increase in interleukin 6 in MRL/lpr mice.

It has been demonstrated that abnormal expression of interleukin 6 (IL-6) may be involved in the pathogenesis of a variety of autoimmune diseases and glomerulonephritis. In this study, we demonstrate an age-associated increase in IL-6 in the sera of MRL/lpr mice but not in control congenic MRL/+ mice, normal strains of BALB/c, C3H/HeN mice, and other autoimmune prone mice, such as (NZB x NZW)F1, (NZB x BXSB)F1 mice. IL-6 activity was detected in the sera of MRL/lpr mice by 3 weeks of age and it was neutralized by anti-mouse IL-6 antibody. The serum IL-6 level was gradually increased with age and reached up to 410 pg/ml around 30 weeks of age. The expression of IL-6 mRNA was detected in the spleen and lymph nodes from 8 weeks of age. Expression of IL-6 mRNA was also detected in C57BL/6-lpr mice, indicating the possible linkage of abnormal expression of the IL-6 gene and the lpr gene. Southern blot analysis demonstrated that both the promoter region and 3' untranslated region of the IL-6 gene were apparently normal, suggesting that deregulated production of IL-6 may be due to abnormal transcriptional control. The data suggest that abnormal expression of the IL-6 gene may play a key role in the development of polyclonal B cell activation and glomerulonephritis in MRL/lpr mice.

Age Factors↗
PubMed1991

Pregnancy-induced changes in drug metabolism in epileptic women.

The pharmacokinetics of antiepileptic drugs may be altered during pregnancy, resulting in decline of serum concentrations and subsequent suboptimal control of seizures. We investigated changes which may occur during pregnancy in hepatic drug handling by comparing metabolic ratios of 15 pregnant epileptic women to 15 nonpregnant epileptic women, as well as 10 pregnant nonepileptic and 10 nonpregnant nonepileptic controls. We used the caffeine test to describe several enzyme activities: P450 1A2, xanthine oxidase, n-acetyltransferase and hydroxylation. For this end, ratios were calculated among a number of metabolites of the main demethylation pathway of caffeine. In addition, we measured D-glucaric acid excretion for specific characterization of antiepileptic drug metabolism. Paired comparison of epileptic women in late pregnancy and six to eight weeks post partum revealed statistically significant decreases in P450 1A2, xanthine oxidase and n-acetyltransferase activities, and a significantly increased hydroxylation activity during pregnancy. Twenty-one of the 30 epileptic women (70%) were found to be fast acetylators, whereas the normal distribution in the nonepileptic control groups was 50%. Excretion of D-glucaric acid was significantly increased in all epileptic patient groups as compared to the matched nonepileptic control groups. Importantly, it was also significantly increased in the pregnant nonepileptic control group as compared to the nonpregnant nonepileptic women. Overall, our results suggest that enzymatic pathways involved in antiepileptic drug metabolism tend to be increased during pregnancy as a potential cause for observed lower serum concentrations of these drugs.

Adult↗
PubMed1990

Interleukin 6 and its receptor in the immune response and hematopoiesis.

Interleukin 6 (IL-6) plays critical roles in the immune response and hematopoiesis. It is a potent B cell differentiation factor inducing antibody-forming plasma cells. It enhances interleukin 3-induced proliferation of hematopoietic stem cells. Furthermore, IL-6 induces maturation of megakaryocytes. In IL-6 transgenic mice, a massive polyclonal plasmacytosis and an increase in the number of mature megakaryocytes in the bone marrow were observed. The data indicated that deregulated expression of the IL-6 gene induced a polyclonal plasmacytosis and could be involved in the oncogenesis of plasma cell neoplasias. IL-6 receptor (IL-6R) was molecularly cloned and found to be an immunoglobulin superfamily having an MW of 80 kDa. Upon the binding of IL-6 to its 80 kDa IL-6R, a second non-binding molecule, gp130 was shown to associate with IL-6R. The complex of IL-6 and soluble IL-6R lacking both transmembrane and cytoplasmic domains could bind gp130 and transduce the signal. The results indicate that the IL-6R system consists of two polypeptide chains: one is an 80 kDa ligand-binding molecule and the other is a possible signal transducer, gp130.

Animals↗
PubMed1990

The expected fraction of clonable genomic DNA.

Random clone mapping of genomic DNA is a subject of great interest in molecular biology. E. coli has just been mapped and work is progressing on some human chromosomes. In this paper we give estimates of the fraction of genomic DNA which is not clonable by partial digest with a restriction enzyme.

Cloning, Molecular↗