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Biomedical subjects

A Wang

Publications and source records attributed to A Wang.

At least 235 records · Page 13Linked to original sources
PubMed1995

Changes of gastric acid secretion and somatostatin after Roux-en-Y cholangiojejunostomy.

The authors studied the changes of gastric acid secretion and determined the levels of somatostatin (SS) and gastrin (Gn) in blood, gastric juice and pyloric antrum in 28 patients Roux-en-Y with cholangiojejunostomy (CJR-Y). Gastric acid hypersecretion was identified, and the level of SS was found dropped while the content of Gn increased in these specimens. It was considered that the reduction of SS synthesis and secretion might have a key effect on the mechanism of secondary gastric acid hypersecretion in patients after CJR-Y.

Adult↗
PubMed1995

[Effects of Chinese ginseng root and stem-leaf saponins on learning, memory and biogenic monoamines of brain in rats].

The present investigation has shown that Ginseng root saponins (ig, 50mg/kg x 7d) facilitate the learning and memory of normal male Wistar rats, while the effect of Ginseng stem-leaf saponins (ig, 50mg/kg x 7d) on antielectrconvulsive shock-induced impairment of memory consolidation in rats is more intensive than that of root saponins. Both Ginseng root and stem-leaf saponins can significantly raise the levels of biogenic monoamines in normal rat's brain.

Animals↗
PubMed1995

The central region of the yeast U4 snRNA is not important for hammerhead catalysis, but may act as a domain spacer.

Several distinct domains of U4 small nuclear (sn)RNA interact with other components of the spliceosome and are essential for pre-mRNA splicing. We have previously shown that single point mutations (Hu et al., 1995) in the central domain of the yeast U4 snRNA do not effect cell growth. In contrast to our results, this region has been reported to possess metal-binding or catalytic activity in vitro (Yang et al., 1994). In order to test if large mutations in the central domain effect cell growth and/or in vivo splicing, we have carried out further mutational analyses of this domain. A deletion of nucleotides from 62 to 88, including all those corresponding to the invariable positions of the hypothetical hammerhead, does not affect cell growth at/or above 25 degrees C. In addition, the central region (nucleotides 69-88) can be replaced by two copies of a 38-nt spacer inserted in the same orientation without any effect on cell growth or nuclear RNA splicing. These results suggest that the central domain of U4 snRNA functions primarily to separate the 5'- and 3'- domains of the snRNA by an optimal distance.

Base Sequence↗
PubMed1995

[Regulation of purine biosynthetic genes expression in Salmonella typhimurium. III. Isolation of O+ and Oc fragments of pur JHD].

It has been known that 10 enzymatic reactions are involved in de novo biosynthesis of IMP in Salmonella typhimurium. 10 genes encoding the enzymes have been localized on the Salmonella typhimurium chromosome. Seven structure genes including pur JHD operon are negatively regulated by purR. In this study the purJHD operon containing O+ and Oc were cloned in vivo respectively. Two preliminary clones, p2-9 (O+) and pC-12 (Oc) were identified to be the hybrid plasmids carrying intact pur JHD operon by genetic complementary test and reconstruction enzyme analysis. The fragments of O+ and Oc were subcloned on to pUC19 and DNA sequence were determined directly by DNA sequencer. The DNA sequence of O+ fragment revealed that a 16 base consensus sequence (named PUR box) GCGCAAACGTTTTCGT also existed in control region of pur JHD operon in Salmonella typhimurium. The DNA sequence of Oc fragment indicated that only one base change occurred at the 14th position of PUR box(C-->T). Our result strongly support the idea that PUR box is binding region of purR protein.

Base Sequence↗
PubMed1994

Chemoprevention of 4-nitroquinoline 1-oxide-induced oral carcinogenesis by dietary curcumin and hesperidin: comparison with the protective effect of beta-carotene.

The modifying effects of two natural products, curcumin and hesperidin, given during the initiation and postinitiation phases of oral carcinogenesis initiated with 4-nitroquinoline 1-oxide (4-NQO) were investigated in male F344 rats and compared with that of beta-carotene. At 6 weeks of age, rats were divided into experimental and control groups and fed the diet containing beta-carotene, hesperidin, or curcumin at a dose of 0.5 g/kg diet (500 ppm). At 7 weeks of age, all animals except those treated with each test chemical alone and control groups were given 4-NQO (20 ppm) in the drinking water for 8 weeks to induce oral cancer. Seven days after the 4-NQO exposure, groups of animals fed the diets containing test chemicals were switched to the basal diet and continued on this diet until the end of the study. Starting 1 week after the stop of 4-NQO exposure, the groups given 4-NQO and a basal diet were switched to the diets containing beta-carotene, hesperidin, and curcumin and maintained on these diets for 22 weeks. The other groups consisted of rats given 500 ppm beta-carotene, hesperidin, or curcumin alone or untreated rats. All animals were necropsied at the termination of the experiment (week 32). The incidences of tongue neoplasms and preneoplastic lesions, polyamine levels in the tongue tissue, and cell proliferation activity estimated by bromodeoxyuridine-labeling index and by morphometric analysis of silver-stained nucleolar organizer region proteins were compared among the groups. Feeding of curcumin and beta-carotene during the initiation and postinitiation phases and hesperidin at the initiation stage caused a significant reduction in the frequency of tongue carcinoma (41-91% reduction, P < 0.05) and the order of chemopreventive efficacy was curcumin > beta-carotene > hesperidin. The incidences of oral preneoplasia in rats fed the diets mixed with these compounds were also decreased (P < 0.05). There were no such lesions in rats treated with test compounds alone or those in an untreated control group. Dietary administration of these compounds significantly decreased the labeling index of bromodeoxyuridine and the number and area of silver-stained nucleolar organizer region proteins per cell nucleus that are proliferation biomarkers, of the tongue squamous epithelium (P < 0.05). In addition, polyamine levels in the oral mucosa were lowered in rats treated with 4-NQO and three test compounds when compared to those give 4-NQO alone (P < 0.05).(ABSTRACT TRUNCATED AT 400 WORDS)

4-Hydroxyaminoquinoline-1-oxide↗
PubMed1994

Cloning and characterization of HTK, a novel transmembrane tyrosine kinase of the EPH subfamily.

Using a polymerase chain reaction based strategy, we identified a novel transmembrane tyrosine kinase in CD34+ human bone marrow cells and a human hepatocellular carcinoma cell line, Hep3B. This protein, hepatoma transmembrane kinase or Htk, shares amino acid similarity with the EPH subfamily of tyrosine kinases. The HTK gene is located on human chromosome 7. The predicted 987-amino acid sequence of Htk includes a transmembrane region and signal sequence. In the predicted extracellular domain, a cysteine-rich region and tandem fibronectin type III repeats are present while a single uninterrupted catalytic domain is present in the intracellular domain. These features are consistent with other members of the Eph subfamily. Antibodies raised against Htk extracellular domain immunoprecipitated a 120-kDa protein from either in vitro translated HTK or Hep3B cells which localized primarily to the Hep3B membrane subcellular fraction. Purified in vitro translated Htk was enzymatically active and autophosphorylated on tyrosine in kinase assays. Furthermore, antibodies against Htk ECD were agonistic, inducing Htk tyrosine phosphorylation in transfected NIH3T3 cells. Northern blot analysis demonstrated a single HTK transcript abundantly present in placenta and in a range of primary tissues and malignant cell lines. HTK appears to be expressed in fetal but not adult brain and in primitive and myeloid but not lymphoid hematopoietic cells. The novel transmembrane protein, Htk, may function as a receptor with an expression pattern suggesting a role in events mediating differentiation and development.

3T3 Cells↗
PubMed1994

Mutational analysis of the PRP4 protein of Saccharomyces cerevisiae suggests domain structure and snRNP interactions.

The PRP4 protein of Saccharomyces cerevisiae is an essential part of the U4/U6 snRNP, a component of the mRNA splicing apparatus. As an approach to the determination of structure-function relationships in the PRP4 protein, we have isolated more than fifty new alleles of the PRP4 gene through random and site-directed mutagenesis, and have analyzed the phenotypes of many of them. Twelve of the fourteen single-point mutations that give rise to temperature-sensitive (ts) or null phenotypes are located in the portion of the PRP4 gene that corresponds to the beta-transducin-like region of the protein; the remaining two are located in the central portion of the gene, one of them in an arginine-lysine-rich region. Nine additional deletion or deletion/insertion mutations were isolated at both the amino- and carboxy-termini. These data show that the amino-terminal region (108 amino acids) of PRP4 is non-essential, while the carboxy-terminal region is essential up to the penultimate amino acid. A deletion of one entire beta-transducin-like repeat (the third of five) resulted in a null phenotype. All ts mutants show a first-step defect in the splicing of U3 snRNA primary transcript in vivo at the non-permissive temperature. The effects on prp4 mutant growth of increased copy-number of mutant prp4 genes themselves, and of genes for other components of the U4/U6 snRNP (PRP3 and U6 snRNA) have also been studied. We suggest that the PRP4 protein has at least three domains: a non-essential amino-terminal segment of at least 108 amino acids, a central basic region of about 140 residues that is relatively refractile to mutation and might be involved in RNA interaction, and an essential carboxy-terminal region of about 210 residues with the five repeat-regions that are similar to beta-transducins, which might be involved in protein-protein interaction. A model of interactions of snRNP components suggested by these results is presented.

Amino Acid Sequence↗
PubMed1994

Growth modulation and proteoglycan turnover in cultured mesangial cells.

Proliferation of mesangial cells is a common feature of renal disease, and conditioned media from glomerular epithelial and endothelial cells have been found to contain heparin-like molecules that suppress proliferation of rat mesangial cells (RMC). We have partially characterized the glycosaminoglycans that are labeled with 35SO4(2-) by RMC in culture at early passage and examined their ability to inhibit mitogenic stimulation of the cells. Four chondroitin/dermatan sulfate proteoglycans (CS/DSPG) were identified, the largest and smallest of which (Kd of 0.04 and 0.26 on Superose 6) were retained in the cell layer while the other two (Kd = 0.17 and 0.22) were secreted into the medium. Heparan sulfate proteoglycans (HSPG) with Kd values of 0.09, 0.13, and 0.39 were minor components of the cell layer, while a single heparan sulfate (Kd = 0.17) was recovered from the medium. After 16 h of labeling in serum-free medium, about 60% of macromolecular 35S was cell-associated and 40% was in the medium. Cell-associated label consisted of 7% CS/DSPG, 9% HSPG, and 84% free glycosaminoglycan chains (mostly CS/DS), whereas the medium contained 52% CS/DSPG, 17% HSPG, and approximately equal amounts of free HS and CS/DS chains. Bovine lung heparin (1 microgram/ml) decreased by 45% the incorporation of [3H]-thymidine into DNA after release of serum-starved RMC from growth arrest. Heparin acted prior to the G1/S interface; arrest of the cells in early S phase with aphidicolin abrogated the heparin response. The endogenous HSPGs had a slight antimitogenic effect on the RMC, but heparan sulfate chains from both the medium and cell layer had a potent effect. On an equivalent mass basis, only the free glycosaminoglycan chains were more potent than heparin in this regard, decreasing thymidine incorporation by over 90% when present at 1 microgram/ml. These results demonstrate that heparan sulfate glycosaminoglycans derived from mesangial proteoglycans are potential negative autocrine growth regulators. Proteoglycan metabolism releases these soluble heparan sulfate chains, determining the level of this activity.

Animals↗
PubMed1994

Reduced expression of phospholipase C-delta, a signal-transducing enzyme, in rat colon neoplasms induced by methylazoxymethanol acetate.

Phospholipase C (PLC), which hydrolyzes phosphoinositides, has been implicated as a key enzyme in signal transduction. We examined the expression of an isozyme of PLC, PLC-delta, in rat colon neoplasms induced by methylazoxymethanol (MAM) acetate. Large-bowel neoplasms were observed in five of 10 rats given MAM acetate (25 mg/kg body weight, by interperitoneal injection at 6 and 7 wk of age) 40 wk after treatment. Expression of PLC-delta in the neoplasms was not detected by northern blot analysis, and a low level of expression was detected by immunoblot analysis, although PLC-delta expression was apparent in the non-neoplastic colon mucosae of MAM acetate-treated rats as well as in the colon mucosae of control rats. Furthermore, analysis by reverse transcriptase-polymerase chain reaction revealed that the ratio of the expression of PLC-delta to that of beta-actin in the neoplasms was significantly lower than the ratios in the non-neoplastic colon mucosae of carcinogen-treated and control rats (P < 0.01). However, the ornithine decarboxylase (ODC) activity in the neoplasms was significantly greater than that of the non-neoplastic and control mucosae (P < 0.001). The differences in the levels of PLC-delta expression in neoplastic and non-neoplastic tissues and the inverse correlation of PLC-delta expression with ODC activity may suggest that PLC-delta has little effect on the PLC-mediated mitogenic signaling system, at least in MAM acetate-induced colon neoplasms in rats.

Animals↗
PubMed1994

Response to thymectomy in Chinese patients with myasthenia gravis.

Myasthenia gravis was diagnosed in 48 patients between 1985 and 1991 in this Chinese community. Thymectomy was performed on 36 patients and the mean postoperative follow-up period was 49 months. Significant improvement was seen in 72% of the thymectomised patients, with 33% achieving complete remission. Patients with mild generalised myasthenia at presentation or those found to have thymic hyperplasia had the best prognosis. Patients with more severe symptoms or those with an underlying thymoma also responded favourably. Only patients with ocular myasthenia or those with a normal or atrophic thymus gland had no more than an even chance of gaining significant improvement. Although previous reports suggested a high prevalence of ocular myasthenia and of thymoma among Chinese myasthenic patients, the present study has found no evidence that they respond differently to thymectomy than their Western counterparts.

Adolescent↗
PubMed1994

Effect of 24-h blood pressure levels and circadian blood pressure rhythm on left ventricular structure and function in isolated systolic hypertension.

Forty-one participants (mean age 69 +/- 5.6 years) were examined by fully automatic blood pressure monitor and Doppler echocardiography to gain information on the ambulatory blood pressure and the left ventricular structure and function in isolated systolic hypertension. Cumulative sum (cusum)-derived statistics was used to quantify circadian blood pressure rhythm and 24-h blood pressure levels were defined as mean blood pressure values during 24 h, waking (06:00-22:00 h) and sleeping (22:00-06:00 h) periods, respectively. Most of the derivatives of ambulatory blood pressure, including cusum-derived statistics and 24-h blood pressure levels, were significantly related with the left ventricular structural (left ventricular posterior wall and interventricular septum thickness) and functional (acceleration time in the left ventricular outflow tract and early diastolic deceleration time) indexes. Among the left ventricular structural and functional indexes, interventricular septum thickness at end diastole had the strongest correlation with sleeping diastolic mean blood pressure (r = 0.41, P < 0.01), left ventricular posterior wall at end diastole, the best with 24-h systolic mean blood pressure (r = 0.41, P < 0.01), acceleration time the strongest with systolic cusum-derived circadian alteration magnitude (r = 0.49, P < 0.01) and early diastolic deceleration time the greatest with diastolic cusum-derived trough blood pressure (r = 0.45, P < 0.01). We conclude that left ventricular structural changes rely on 24-h systolic and diastolic blood pressure levels, whereas left ventricular functional variations may be more dependent upon circadian blood pressure rhythm in elderly patients with isolated systolic hypertension.

Aged↗
PubMed1994

The inhibitory effect of magnesium hydroxide on the bile acid-induced cell proliferation of colon epithelium in rats with comparison to the action of calcium lactate.

The modulating effects of magnesium hydroxide and calcium lactate on the cholic acid-induced hyperproliferation of cells in rat colon epithelium were investigated. Rats were divided into six groups (10 rats/group) and fed the following diets for 8 weeks: 0.25% cholic acid alone (group 1), cholic acid plus 0.2% magnesium hydroxide (group 2), cholic acid plus 1.18% calcium in the form of calcium lactate (group 3), calcium lactate alone (group 4), magnesium hydroxide alone (group 5) and the basal diet alone (group 6). At the end of the experiment, all rats were killed for the immunocytochemical examination of 5-bromo-2'-deoxyuridine (BrdU) incorporation in the cell nuclei of colonic epithelium. Magnesium hydroxide reduced the cholic acid-induced BrdU incorporation by 33% at the distal part and 40% at the proximal part. Calcium lactate also reduced the BrdU incorporation by 48% and 51% respectively. Exposure of magnesium hydroxide or calcium lactate alone had no influence on BrdU incorporation. The results suggest that magnesium hydroxide might exert anti-carcinogenic effects as does calcium by reducing increased cell proliferation of colonic epithelium induced by toxic effects of bile acids, which are regarded as colon tumor promoters or cocarcinogens.

Animals↗
PubMed1994

Expression of cytokines, TNF-alpha and IL-1 alpha, in MAM acetate and 1-hydroxyanthraquinone-induced colon carcinogenesis of rats.

The expression of cytokines, TNF-alpha and IL-1 alpha, was examined by means of a reverse transcription followed by PCR (RT-PCR) in rat colon carcinogenesis. Forty male F344 rats were used and divided into four groups. At the start of the experiment, 20 rats were treated with methylazoxymethanol (MAM) acetate (25 mg/kg body wt, one time, i.p.) and divided into two groups; group 1 was exposed to 1% 1-hydroxyanthraquinone (1-HAQ) and group 2 was fed a basal diet during the experiment (40 weeks). Other rats were also divided into two groups; group 3 was exposed to 1% 1-HAQ as group 1, and group 4 was used as control. Tumor incidence (100%) and multiplicity (5.00 +/- 2.05) in group 1 were significantly greater than those in group 2 (20% and 0.2 +/- 0.42) and group 3 (10% and 0.10 +/- 0.32) (P < 0.01 and P < 0.01 respectively). RT-PCR technique with RNA was applied to the tissues from colon neoplasms and mucosa in each group. Expression of TNF-alpha and IL-1 alpha in the colon neoplasms was much stronger than that in the colon mucosa of each group (P < 0.001 and P < 0.01 respectively). The expression of TNF-alpha was more remarkable in the colon mucosa of group 1 than that in corresponding tissue of groups 2 and 3 (P < 0.01). The expressions of TNF-alpha and IL-1 alpha were more increased in the colon mucosa of groups 1, 2 and 3 than that in group 4 as control (P < 0.01 and P < 0.05 respectively). The results indicate that TNF-alpha and IL-1 alpha may act as growth factors in rat colon carcinogenesis by MAM acetate and 1-HAQ. In addition, the synergistic effect of 1-HAQ with MAM acetate in colon carcinogenesis might be related to biological effects of the cytokines expressed in the inflammatory condition generated by 1-HAQ.

Adenocarcinoma↗
PubMed1994

Compliance with social and safety recommendations in an outpatient comprehensive geriatric assessment program.

BACKGROUND: A unique contribution of a comprehensive outpatient geriatric assessment is its focus on social and safety issues in the frail elderly. The impact of such programs depends on the caregiver and/or patient complying with safety and social recommendations offered by the assessment team. Compliance in this setting has not been previously described. METHODS: A telephone survey was conducted of self-reported compliance in 124 frail geriatric patients with a high prevalence of dementia 3-21 months after completing a comprehensive geriatric assessment program at the University of California, San Diego, Medical Center. RESULTS: The social and safety recommendations constituted 52.8% of all the recommendations offered. The overall compliance rate (total number of safety and social recommendations followed/total number offered x 100) was 50.2% (95% CI: 43.7-56.6). Highest compliance was achieved with recommendations to complete a prior directive for health care (80.6%) and to wear a medic-alert bracelet (57.5%). Patients complied poorly with recommendations to change a living situation (36.2%). Analysis of variance showed compliance to increase with time between the assessment and survey. Stratifying for time, we found higher compliance in patients with greater impairment in functional or cognitive status. Most noncompliance was due to disagreement with the recommendations offered or failure to implement acceptable recommendations. CONCLUSIONS: Compliance with social and safety recommendations offered in a comprehensive geriatric assessment program approximates compliance observed in other clinical settings. In this setting compliance increases over time. When controlled for time, impairment in functional or cognitive status is associated with greater compliance.

Accidents, Home↗
PubMed1994

In vitro effects of stem-cell factor or interleukin-3 on myelosuppression associated with AIDS.

OBJECTIVE: To determine whether the early-acting hematopoietic growth factors stem-cell factor (SCF) or interleukin-3 (IL-3), are able to overcome the bone-marrow suppressive effects of cytokines or drugs involved in the hematologic abnormalities that accompany HIV-1 infection. DESIGN: In vitro colony formation assays of normal human bone-marrow cells exposed to the myelosuppressive drugs, zidovudine, interferon-alpha (IFN-alpha) and ganciclovir, or the myelosuppressive cytokines, tumor necrosis factor-alpha (TNF-alpha) or transforming growth factor-beta (TGF-beta), implicated in HIV dysmyelopoiesis. RESULTS: SCF (10 ng/ml) enhanced the numbers of erythroid (BFU-E) colonies in the presence of zidovudine or ganciclovir (P < 0.05) and myeloid [colony-forming unit granulocyte macrophage (CFU-GM)] colonies in the presence of ganciclovir or IFN-alpha (P < 0.05) relative to controls. IL-3 (10 ng/ml) also improved erythroid colony numbers in the presence of zidovudine (P < 0.05) and CFU-GM in the presence of IFN-alpha (P < 0.05). Neither factor consistently altered the inhibition of TGF-beta or TNF-alpha. The 50% inhibitory concentration (IC50) of the myelosuppressive agents was altered in only one setting, using IL-3 in the presence of zidovudine. CONCLUSIONS: These data suggest that SCF or IL-3 may have a therapeutic application in overcoming hematopoietic abnormalities associated with drugs commonly used in the care of AIDS patients. However, they may have less capacity to overcome the bone-marrow inhibitory effects of the endogenous cytokines TNF-alpha and TGF-beta.

Acquired Immunodeficiency Syndrome↗