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Biomedical subjects

S Zhu

Publications and source records attributed to S Zhu.

At least 271 records · Page 15Linked to original sources
PubMed1995

Effects of axial ligand replacement on the redox potential of cytochrome c.

The formal potentials (E0') and electron transfer numbers (n) of imidazole (Im), 1-methylimidazole (1-MeIm), and 1-ethylimidazole (1-EtIm) complexes of cytochrome c have been determined for the first time using optically transparent thin-layer spectroelectrochemistry. In comparing these results with the E0' value of the cytochrome c, their potentials at infinite dilution have been calculated, which indicate that axial replacement of methionine-80 by Im, 1-MeIm, and 1-EtIm gives rise to 426, 359, and 327 mV negative shifts relative to that of native cytochrome c, respectively. Thereby, the origins of the effects of axial substitution on redox potential are discussed.

2,6-Dichloroindophenol↗
PubMed1995

Myasthenia gravis-like syndrome induced by expression of interferon gamma in the neuromuscular junction.

Abnormal humoral responses toward motor end plate constituents in muscle induce myasthenia gravis (MG). To study the etiology of this disease, and whether it could be induced by host defense molecules, we examined the consequences of interferon (IFN) gamma production within the neuromuscular junction of transgenic mice. The transgenic mice exhibited gradually increasing muscular weakness, flaccid paralysis, and functional disruption of the neuromuscular junction that was reversed after administration of an inhibitor of acetylcholinesterase, features which are strikingly similar to human MG. Furthermore, histological examination revealed infiltration of mononuclear cells and autoantibody deposition at motor end plates. Immunoprecipitation analysis indicated that a previously unidentified 87-kD target antigen was recognized by sera from transgenic mice and also by sera from the majority of human MG patients studied. These results suggest that expression of IFN-gamma at motor end plates provokes an autoimmune humoral response, similar to human MG, thus linking the expression of this factor with development of this disease.

Animals↗
PubMed1995

Overexpression of p53 predicts organ preservation using induction chemotherapy and radiation in patients with advanced laryngeal cancer. Department of Veterans Affairs Laryngeal Cancer Study Group.

A critical research frontier in head and neck oncology involves defining the use of induction chemotherapy regimens to allow organ preservation and to avoid functionally debilitating surgical resections. Completed clinical trials in laryngeal cancer indicate that such an approach is feasible, but progress thus far has been limited by our inability to predict which patients are likely to respond to chemotherapy and preserve their larynx. Mutation of the p53 tumor-suppressor gene is the most common genetic alteration identified thus far in human cancers, and it may be important in regulation of cell proliferation and chemosensitivity. To determine whether p53 overexpression predicts chemotherapy response, organ preservation, and survival in patients with advanced laryngeal cancer, we analyzed immunohistologic expression of p53 in tissue sections from 178 patients with advanced laryngeal cancer who were entered in the Department of Veterans Affairs Laryngeal Cancer Cooperative Study, a multiinstitutional clinical trial comparing induction chemotherapy (cis-platinum and 5-fluorouracil) plus radiation therapy (94 patients) to surgery plus postoperative radiation therapy (84 patients). Larynx preservation was significantly higher in the group of patients whose tumors overexpressed p53 (74% vs. 52.5%; p = 0.03). The presence of p53 overexpression did not predict survival in either the surgery or the chemotherapy groups (p = 0.82 and p = 0.53).

Antimetabolites, Antineoplastic↗
PubMed1995

The histidyl-tRNA synthetase-related sequence in the eIF-2 alpha protein kinase GCN2 interacts with tRNA and is required for activation in response to starvation for different amino acids.

Protein kinase GCN2 is a multidomain protein that contains a region homologous to histidyl-tRNA synthetases juxtaposed to the kinase catalytic moiety. Previous studies have shown that in response to histidine starvation, GCN2 phosphorylates eukaryotic initiation factor 2 (eIF-2), to induce the translational expression of GCN4, a transcriptional activator of genes subject to the general amino acid control. It was proposed that the synthetase-related sequences of GCN2 stimulate the activity of the kinase by interacting directly with uncharged tRNA that accumulates during amino acid limitation. In addition to histidine starvation, expression of GCN4 is also regulated by a number of other amino acid limitations. Questions that we posed in this report are whether uncharged tRNA is the most direct regulator of GCN2 and whether the function of this kinase is required to recognize each of the different amino acid starvation signals. We show that GCN2 phosphorylation of eIF-2, and the resulting general amino acid control pathway, is stimulated in response to starvation for each of several different amino acids, in addition to histidine limitation. Cells containing a defective aminoacyl-tRNA synthetase also stimulated GCN2 phosphorylation of eIF-2 in the absence of amino acid starvation, indicating that uncharged tRNA levels are the most direct regulator of GCN2 kinase. Using a Northwestern blot (RNA binding) assay, we show that uncharged tRNA can bind to the synthetase-related domain of GCN2. Mutations in the motif 2 sequence conserved among class II synthetases, including histidyl-tRNA synthetases, impair the ability of this synthetase-related domain to bind tRNA and abolish GCN2 phosphorylation of eIF-2 required to stimulate the general amino acid control response. These in vivo and in vitro experiments indicate that synthetase-related sequences regulate GCN2 kinase function by monitoring the levels of multiple uncharged tRNAs that accumulate during amino acid limitations.

Amino Acids↗
PubMed1995

[Gene diagnosis of adult polycysitic kidney disease--using polymorphic microsatellite markers].

Gene diagnosis of adult polycystic kidney disease (APKD) is possible by genetic linkage analysis using linked restriction fragment length polymorphisms (RFLP) on both sides of the PKD1. This technique is laborious, expensive and sample- time- consuming. SM7 is a polymorphic microsatellite that tightly linked with the PKD1. We combined PCR with polyacrylamide gel electrophoresis and method of gel Ag+ staining to detect the allelus and genotype frequencies of the microsatellite amplificated in unrelated Chinese population. The study of 8 APKD families with SM7 demonstrated that the technique is quite simple, fast, sensitive and does not require the use of radioisotopes and ultraviolet. It could provide a powerful method for the presymptomatic and prenatal diagnosis of APKD.

Adult↗
PubMed1995

[Hepatic albumin's mRNA in nephrotic syndrome rats treated with Chinese herbs].

It was found in our previous studies that two Chinese herbs, Astragali and Angelica (A & A), with a high protein diet could protect the decrease of serum albumin and markedly increase the synthesis rate of protein by 18N-glycine metabolic study in nephrotic rats. A further experiment was designed to investigate the effects of A&A and high protein intake on the level of hepatic albumin's mRNA in nephrotic rats. Male S. D. rats were divided into 3 groups: high protein diet alone (39.7% HP); HP with nephrotic syndrome (HPN); and HPN with therapy (HPNT). Nephrotic syndrome in rat was induced by accelerated nephrotoxic nephritis, withfed A&A (2 g of each in 3 ml) daily for 14 days. At the 15th day, the serum and liver were collected and the level of serum albumin and mRNA were measured with biochemistry, Northern blot, dot blot hybridization and quantity in laser density screening. The level of serum albumin in HPNT was higher than that of HPN (3.7 +/- 0.1 vs 2.9 +/- 0.29, P < 0.01) with an unchanged urinary output. The level of hepatic albumin mRNA in HPNT was higher than HPN (2.56 +/- 0.24 vs 1.7 +/- 0.12, P < 0.01) and HP (2.56 +/- 0.24 vs 1.25 +/- 0.24, P < 0.01). We conclude that in a molecular biologic level A&A combined with high protein intake could increase the albumin synthesis in the liver of nephrotic rat.

Albumins↗
PubMed1995

[An epidemiological survey of primary angle-closure glaucoma in Doumen county Guangdong].

A comparison between the results of an epidemiological study of primary angle-closure glaucoma (PACG) in Doumen County, Guangdong in 1990 and those of a similar study in Shunyi County, Beijing in 1985 was reported. The prevalence of PACG in subjects over 45 years old was 0.64% and that, over 50 years, 0.85% in Doumen, while that, over 50 years, 1.99% in Shunyi (P < 0.05). There was significant difference in the prevalence of PACG between the two counties and the difference was discussed.

Aged↗
PubMed1995

The crystal structure of deshexapeptide (B25-B30) insulin at 0.25 nm resolution.

The determination of deshexapeptide (B25-B30) insulin (DHI) was divided into two steps. At the first step, the rough structure model of DHI molecule was determined by using the molecular replacement method associated with the molecular close-packing method at 0.30 nm resolution based on the reflection data collected on four-cycle diffractometer. At the second step, the DHI model was adjusted and refined at 0.25 nm resolution based on the data collected on Area Detector. 40 water molecules were determined during the refinement, the final R-factor is 0.185 with R.M.S. deviation of 0.002 nm for bond lengths and 1.9 degrees for bond angles. The differences in conformation and function of DHI with other insulin analogues were compared and discussed.

Insulin↗
PubMed1995

[Isolation of fusarium and extraction of its toxin from buckwheat grown in an area with "endemic breast enlargement" disease].

Fusarium was isolated and its toxin was extracted from the buckwheat grown in an epidemic area with "endemic breast enlargement" disease. The toxin was determined with thin layer chromatography and mass spectrography. Results showed there were more than four kinds of mould, including fusarium, isolated from buckwheat grown in the endemic disease area. All the buckwheat grown in the area were infected with mould and 34% with fusarium. Three kinds of toxin were extracted from the buckwheat, with rates of flow of 0.23, 0.47 and 0.90, respectively, in thin layer chromatography. And, zearalenone was extracted from the buckwheat and identified by mass spectrography.

Animals↗
PubMed1995

Epidemiological survey of primary angle-closure glaucoma in Doumen.

PURPOSE: To determine the prevalence of primary angle-closure glaucoma (PACG) in Doumen Countty, Guangdong province. METHODS: Four villages from eight districts in doumen were selected by stratified, cluster and random sampling. Of a total of 1055 people aged 45 years or over, 932 (88.62%) were examined. The examination and diagnostic criterion were similar to those of shunyi survey. RESULTS: The prevalence of PACG in subjects over 45 year of eye is 0.64%, in those over 50 years of age is 0.85% in Doumen, which is significantly lower than the corresponding figure of 1.99% in shunyi (P < 0.05). CONCLUSION: This study identifies the prevalence of PACG in Doumen is lower than in Shunyi.

Aged↗
PubMed1995

Changes of plasma beta-endorphin levels before and after percutaneous transvenous mitral commissurotomy in patients with mitral stenosis.

To clarify the contribution of left atrial pressure to the secretion of beta-endorphin, we have investigated the relation between plasma beta-endorphin levels and hemodynamic changes in 35 patients with mitral stenosis undergoing percutaneous transvenous mitral commissurotomy (PTMC). Before PTMC, plasma beta-endorphin levels obtained from the antecubital vein (28.91 +/- 5.59 pg/ml) and from the femoral vein (28.20 +/- 5.44 pg/ml) in the patients with mitral stenosis were significantly higher than those obtained from the antecubital vein in the healthy volunteers (22.59 +/- 3.86 pg/ml, n = 34, P < 0.001 for each). The levels of beta-endorphin in the femoral vein correlated well with the mean left atrial pressure (r = 0.777, P < 0.001) and the mean right atrial pressure (r = 0.450, P < 0.01) before the procedure. The antecubital venous levels of beta-endorphin in patients in New York Heart Association functional Classes II (26.45 +/- 5.39 pg/ml, n = 20) and III (32.20 +/- 4.02 pg/ml, n = 15) were significantly higher than those in control subjects (P < 0.005 and P < 0.001, respectively). The differences between Classes II and III were significant (P < 0.001). The plasma levels of beta-endorphin in the patients complicated with atrial fibrillation were also significantly higher than those in patients with normal sinus rhythm (33.31 +/- 3.22 pg/ml, n = 13 vs 26.32 +/- 5.07 pg/ml, n = 22, P < 0.001). In ten to fifteen minutes after commissurotomy, plasma levels of beta-endorphin in the femoral vein significantly increased from 28.20 +/- 5.44 to 33.14 +/- 5.72 pg/ml (P < 0.001). In seventy-two hours after the procedure, plasma beta-endorphin levels in the antecubital vein fell to 24.37 +/- 2.59 pg/ml (P < 0.001 vs before PTMC and P < 0.05 vs control subjects). Plasma beta-endorphin levels in the patients with atrial fibrillation (26.62 +/- 2.36 pg/ml, P < 0.001 vs before PTMC and P < 0.002 vs control subjects) were still higher (P < 0.001) than those in patients with normal sinus rhythm (23.05 +/- 1.65 pg/ml, P < 0.001 vs before PTMC and P > 0.50 vs control subjects. There was a significant correlation between the levels of beta-endorphin in the antecubital vein and heart rate (r = 0.502, P < 0.001), mean transmitral pressure gradient (r = 0.543, P < 0.001) or mitral valve area (r = -0.710, P < 0.001) before and 72 hours after the procedure.

Adolescent↗