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Biomedical subjects

Z G Wang

Publications and source records attributed to Z G Wang.

At least 19 recordsLinked to original sources
PubMed1992

[Synthesis and antitumor activity of 4-alkylthio-4-deoxy-4'-demethylepipodophyllotxin derivatives].

As a continuing part of our study on the chemistry and antitumor activity of podophyllotoxin, 11 new C-4 S-substituted podophyllotoxin derivatives were synthesised and screened in vitro against L1210 leukemia and KB cells. Thus, 4'-demethylepipodophyllotoxin was reacted with thiols in the presence of BF3. Et2O or trifluroacetic acid to give thioethers. In addition, 4-bromo-4-deoxy-4'-demethylepipodophyllotoxin, when reacted with thiols, also gave rise to corresponding thioether (4-alkylthio-4-deoxy-4'-demethylepipodophyllotoxins). Compounds 10 and 12 have the same activity as etoposide in the inhibition against L1210 leukemia, and compounds 9, 10, 12 and 15 also have comparable activity with etoposide against KB cells.

Animals↗
PubMed1992

[Food poisoning caused by mouldy rice contaminated with Fusarium and T-2 toxin].

An epidemic of food poisoning in human beings occurred in Tongxiang County, Zhejiang Province after eating mouldy rice contaminated with Fusarium and toxins. Continuous rainfall took place during the rice harvest season. The number of patients poisoned was 97, the rate of incidence was 58.8%. The incubation period was 10 to 30 minutes. The chief symptoms were nausea, dizziness, vomiting, chills, abdominal distension, abdominal pain and diarrhea. The fungi isolated from the mouldy rice were predominantly Fusarium heterosporum and F. graminearum. T-2 toxin was found in the mouldy rice and the highest content was 420 ppb.

China↗
PubMed1992

[Distinguishing Anopheles dirus of Hainan Province by gas chromatography of cuticular hydrocarbons].

In order to identify the members of Anopheles dirus complex of Hainan Province an analysis of relative content of cuticular saturated n-paraffins of Anopheles dirus collected from different localities and in different months in Hainan Province was performed by using gas chromatography. The difference among the cuticular hydrocarbons n-paraffins components was statistically insignificant. The values of stepwise cluster analysis (Q model) were very close for all the collected populations. These data suggested that there might be one species of Anopheles virus complex which was further confirmed by the similarities between blood preference, seasonal variation, and nocturnal activity.

Animals↗
PubMed1992

[The characteristics and changes in high altitude ventilatory response during acclimatization at 5000 meters altitude].

To assess the characteristics and changes of high altitude ventilation response during acclimatization at 5000m altitude. The poikilocapnic hypoxic ventilatory responses (PHVR) were tested on nineteen healthy men who sojourned 5000m altitude for 12 weeks. The results were that there was a linear correlation between predicated ventilations which were calculated for 5000m altitude depended on PHVR values before ascent and actual ventilations tested when arrived at altitude. The PHVR was increased at second week after ascent, but at twelth week it was dropped near the level before ascent. The authors thought that peripheral chemoreceptor function might be enhanced within a period after ascent. With the acclimatization becomes perfected, the role of compensatory hyperventilation drops gradually to secondary position. So the activity of the chemoreceptor was restored gradually. The PHVR values in Xining group were lower than that in sea level group before ascent, but opposite change appeared at second week at 5000m altitude. There were no significant difference in PHVR between with and without acute mountain sickness groups.

Acclimatization↗
PubMed1992

[Synthesis and antitumor activities of 4-acylthiol-4-deoxy-4'-demethylepipodophyllotoxin analogues].

This paper describes the synthesis and antitumor activity of 4-acylthiol-4-deoxy-4'-demethylepipodophyllotoxin analogues. 4-Mercapto-4-deoxy-4'-demethylepipodophyllotoxin prepared from 4'-demethylepipodophyllo-toxin with H2S in the presence of BF3.Et2O, was acylated with different acids using diethyl cyanophosphonate and thus, corresponding 4-acylthiol-4-deoxy-4'-demethyl epipodophyllotoxin analogues were synthesized. These compounds were screened in L1210 leukemia and KB cells, and one compound has activity similar to etoposide, and others were generally weaker than etoposide and corresponding 4-acylamido-4-deoxy-4'-demethylepipodophyllotoxin analogues.

Animals↗
PubMed1992

[Surgical treatment of superior vena cava syndrome].

Thirty-seven patients with superior vena cava (SVC) syndrome were admitted to our hospital during the recent six years. Among them, 23 were treated surgically. The approaches we used included SVC-atrial shunt plus lesion resection (1), innominate-atrial shunt without (2) or with membranotomy (1), jugular-atrial shunt (1), azygous-atrial shunt plus meso-atrial shunt (1), jugular-saphenous shunt (8), omental neck transplantation substernally (4) including one with omental-cervical vein anastomosis, and so on. Follow-up for an average of 40 months, showed marked effect in 55% of the surgical cases, improvement in 30%, and death in 10%. It is suggested to select intrathoracic operations for young, good risk, and surgically resectable patients and saphenous transplantation for elder, high risk and unresectable patients.

Adolescent↗
PubMed1992

[Identification of toxigenic mould in soft drink causing food poisoning].

In a soft drink caused food poisoning, white floccus was found and mould count was 6.0 x 10(2) CFU/ml. The Mycoflora was made of only one kind of mould which was identified as Penicillium janthinellum Biourge. This isolate can grow under anaerobic condition. The culture liquid of the isolate was fed to mice orally for toxicity test, which made the mice lose weight. An extract of the culture liquid was tested in weaned mice inaberitoneally for toxicity and all mice died in 24h. The toxic symptoms were tic, sway and paralysis of right rear-leg. Gross anatomy changes were gastrectosis, flatulence and intestinal edema. The conclusion is: the P. janthinellum isolate from the soft drink was the toxigenic mould.

Animals↗
PubMed1991

Nucleotide excision repair of DNA by human cell extracts is suppressed in reconstituted nucleosomes.

Nucleotide excision repair is a complex biochemical process that corrects DNA damage caused by a broad spectrum of physical and chemical agents. We examined the effect of the assembly of ultraviolet-irradiated plasmid DNA into nucleosomes on nucleotide excision repair supported by human cell extracts. Repair synthesis in unassembled UV-irradiated plasmid DNA was readily detected in extracts from repair-proficient human cells. In contrast, repair synthesis was markedly suppressed in UV-irradiated DNA assembled into nucleosomes (minichromosomes). This suppression occurred at a step(s) which precedes repair synthesis during nucleotide excision repair. Human cell extracts were unable to effectively assemble plasmid DNA into nucleosomes under repair synthesis conditions. The addition of purified histones to the extracts restored their capacity for nucleosome assembly and simultaneously led to the suppression of repair synthesis. We propose that the preferential repair of actively transcribed genes relative to transcriptionally silent genes may reflect altered nucleosome conformation during transcription.

Animals↗
PubMed1991

Overproduction and characterization of the uracil-DNA glycosylase inhibitor of bacteriophage PBS2.

A plasmid expression vector (pZWtac1) was constructed which allowed inducible overexpression of the uracil-DNA glycosylase (Ung) inhibitor (Ugi)-encoding gene (ugi) in Escherichia coli. In this plasmid, the ugi gene was under the control of both its own promoter and the tac promoter. Constitutive expression of the ugi was observed in the absence of isopropyl-beta-D-thiogalactopyranoside (IPTG). In the presence of 1 mM IPTG, the Ugi protein was overproduced to an approx. 16-fold higher level, and accounted for approx. 19% of the total soluble cellular proteins. Following high-level production in E. coli, the Ugi protein was purified to apparent homogeneity. Using E. coli Ung, we observed that Ugi inactivated the enzyme in a noncompetitive manner. Kinetic studies revealed a Ki value (0.14 microM) of approx. twelve-fold lower than Km value (1.7 microM) of glycosylase. Ugi did not act synergistically with free uracil to inhibit E. coli Ung suggesting that uracil and Ugi could share a similar mode of inhibition.

Bacillus subtilis↗
PubMed1991

Molecular abnormalities in the expression of HLA class-I antigens by melanoma cells.

Testing of a panel of cultured human melanoma cells with radiolabelled anti-HLA-class-I monoclonal antibodies (MAbs) in a binding assay has shown lack of reactivity of FO-I and SK-MEL-33 cells and low reactivity of SK-MEK-19 cells. SDS-PAGE analysis of the components immunoprecipitated from the 3 intrinsically radiolabelled melanoma cell lines by antibodies to the 2 subunits of HLA-class-I antigens has not detected beta 2-mu in the immunoprecipitates from melanoma cells FO-I and SK-MEL-33 and only a low level of HLA-class-I heavy chain in the immunoprecipitate from SK-MEL-19 cells. Northern blotting analysis with probes specific for HLA-class-I heavy chain and for beta 2-mu indicates that the abnormalities in HLA-class-I-antigen expression reflects a defect at the transcriptional level in FO-I cells and at the post-transcriptional level in SK-MEL-19 and in SK-MEL-33 cells. FO-I, SK-MEL-19 and SK-MEL-33 cells represent useful models to analyze the molecular mechanisms underlying the loss of HLA-class-I-antigen expression which is often associated with malignant transformation of melanocytes and to characterize the role of HLA-class-I antigens in the biology of melanoma cells and in their interactions with effector cells.

Antibodies↗
PubMed1991

Repolarization differences between guinea pig atrial endocardium and epicardium: evidence for a role of Ito.

It has long been known that ventricular epicardial action potential duration (APD) is shorter than endocardial, and recent evidence suggests that a larger transient outward current (Ito) in epicardium is responsible for the difference. To evaluate possible corresponding regional variations in atrial tissue, we studied guinea pig atrial epicardial and endocardial action potentials using standard microelectrode techniques. Epicardial APD was consistently shorter than endocardial, but the difference was greatly diminished by rapid pacing or early premature activation, situations in which Ito availability should be limited. 4-Aminopyridine (4-AP), at concentrations (0.5 mM) producing specific Ito blockade, increased APD significantly in atrial epicardium without affecting endocardium. The effect of 4-AP on APD was most marked at slow rates, at which Ito would be greatest, and was negligible at rapid rates or during premature activation, during which Ito would be largely inactivated. At larger concentrations (5 mM) 4-AP caused an equalization of epicardial and endocardial APD. The equimolar substitution of strontium for calcium did not affect APD at slow rates and increased APD (particularly in endocardium) at rapid rates, suggesting that the Ito underlying endocardial-epicardial differences was unlikely to be calcium dependent. We conclude that epicardial-endocardial differences in APD, well documented in ventricular tissue, can also occur in atrial tissue and that the underlying ionic mechanisms appear to be similar.

4-Aminopyridine↗
PubMed1991

Lack of HLA class I antigen expression by cultured melanoma cells FO-1 due to a defect in B2m gene expression.

The melanoma cell line FO-1 does not express HLA class I antigens and does not acquire them on the cell surface after incubation with IFN-gamma. Immunochemical studies showed that FO-1 cells synthesize HLA class I heavy chain, but do not synthesize beta 2-microglobulin (beta 2-mu). The latter abnormality is associated with lack of beta 2-mu mRNA which remains undetectable in FO-1 cells incubated with IFN-gamma. The defect was identified as a genetic lesion in the B2m gene, since DNA hybridization analysis detected a deletion of the first exon of the 5'-flanking region, and of a segment of the first intron of the B2m gene. HLA class I antigen expression was reconstituted on melanoma cells FO-1 after transfection with the wild-type mouse B2m gene, thereby confirming the abnormality of the endogenous B2m gene. The defect identified in FO-1 cells is distinct from that underlying the lack of HLA class I antigen expression by lymphoblastoid cells Daudi, but is remarkably similar to that causing lack of H-2 class I antigen expression by mouse lymphoblastoid cells R1 (TL-). These results suggest that genetic recombination in the 5' region of the B2m gene is a recurrent mechanism in B2m gene defects. In addition to contributing to our understanding of molecular abnormalities in HLA class I antigen expression by melanoma cells, FO-1 cells represent a useful model for analyzing the role of HLA class I antigens in the biology of melanoma cells and in their interaction with cells of the immune system.

Animals↗
PubMed1991

[Clinical and consequence study on 51 cases of hepatitis C].

All the 51 patients had history of plasma donation before onset of the illness. All had no evidences of recent infection with following viruses: HAV, HBV, CMV and EBV and were confirmed recently as hepatitis C by the Chiron C-100 EIA test. The incubation period was 35 to 90 days, with an average of 57.9 +/- 19.8 days. The ratio of icteric to anicteric was 1.0:1.55. Only a few cases had fever in the acute phase (13.7%). 36 cases showed acute onset of illness; 15 cases, however, had ALT elevation before the onset. 33 cases became chronic hepatitis after 1 year (64.7%), 14 out of the 33 cases had persistently abnormal ALT and 19 cases showed repeated elevation of ALT. The chronicity rate in 2 years was 38.6%. These results indicate that hepatitis C has the features of high chronicity rate and prolonged clinical course.

Adult↗
PubMed1991

Changes of glomerular fixed anionic charge sites in adriamycin nephrosis in rats.

A single intravenous injection of adriamycin (5 mg/kg) into rats induced nephrotic syndrome. In the various stages of the model, alterations of glomerular fixed anionic charge sites stained with colloidal iron were analyzed quantitatively by image analyzer, which is reported here for the first time. The results showed that there was a significant decrease in glomerular fixed anionic charge sites at 3 hours after administration of adriamycin as compared with the control animals (P less than 0.01). Marked loss of the anionic charge sites preceded the onset of proteinuria and steadily increased along with the progress of the disease. The results suggest that the loss of glomerular fixed anionic charge sites may play an important role in the development of proteinuria in nephrotic syndrome.

Animals↗
PubMed1990

Direct electrophysiological actions of pentobarbital at concentrations achieved during general anesthesia.

Pentobarbital and alpha-chloralose are widely used for experimental anesthesia, but their direct electrophysiological actions at anesthetic concentrations are unknown. Trough and peak concentrations measured by high-performance liquid chromatography averaged 27 +/- 3 and 45 +/- 13 mg/l (means +/- SD) for pentobarbital and 41 +/- 15 and 103 +/- 13 mg/l for alpha-chloralose in dogs receiving them for general anesthesia. The direct effects of each agent on papillary muscle action potentials obtained from guinea pigs killed by decapitation were studied in vitro. Pentobarbital increased action potential duration to 95% by 24 +/- 6 and 33 +/- 4% at 25 and 50 mg/l (P less than 0.001 for each), respectively, and caused corresponding increases in effective refractory period. Furthermore, pentobarbital reduced maximum rate of voltage change (Vmax) of phase 0 in a voltage-, rate-, and concentration-dependent fashion, suggesting use-dependent sodium channel blocking actions. The voltage dependence of Vmax was shifted by 3.7 +/- 1.7 (P less than 0.01) and 6.5 +/- 1.8 mV (P less than 0.001) by 25 and 50 mg/l pentobarbital, respectively. In canine ventricular muscle, pentobarbital caused rate- and concentration-dependent decreases in Vmax and increases in action potential duration and refractory period over a concentration range of 5-100 mg/l. alpha-Chloralose was devoid of direct electrophysiological effects in both species. We conclude that pentobarbital has potentially important electrophysiological actions on ventricular tissues at concentrations required for general anesthesia and may confound the results of in vivo studies.

Anesthesia, General↗
PubMed1990

Effects of flecainide and quinidine on human atrial action potentials. Role of rate-dependence and comparison with guinea pig, rabbit, and dog tissues.

Flecainide and other class IC antiarrhythmic drugs are effective in the prevention and termination of atrial fibrillation, but the mechanism of this action is unknown. To gain insights into potential cellular mechanisms, we evaluated the response of human atrial action potentials to equimolar therapeutic concentrations of flecainide and quinidine and compared this response to that of guinea pig, rabbit, and dog atria. Both compounds reduced Vmax more as activation rate increased, but flecainide was more potent than quinidine and had slower kinetics. The rate-dependence of Vmax reduction was similar for all species, but human tissue was more sensitive to the drugs tested. In contrast to changes in Vmax, drug-induced alterations in action potential duration showed opposite rate-dependence for the two drugs. Quinidine increased action potential duration to 95% repolarization (APD95) in human atria by 33 +/- 7% (mean +/- SD) at a cycle length of 1,000 msec, but this effect was reduced as cycle length decreased, to 12 +/- 4% (p less than 0.001) at a cycle length of 300 msec. Flecainide increased APD95 (by 6 +/- 3%) much less than quinidine at a cycle length of 1,000 msec, but its effect was increased by faster pacing, to 27 +/- 12% at a cycle length of 300 msec and 35 +/- 8% (p less than 0.001) at the shortest 1:1 cycle length. The rate-dependent response of APD to drugs was qualitatively similar but quantitatively different among species. Human tissue showed the greatest frequency-dependent drug effects on repolarization, followed by tissue from dogs and rabbits. Guinea pig atria showed the least (and statistically nonsignificant) rate-dependence of drug effect on APD. Drug-induced changes in refractoriness paralleled those in APD. We conclude that: 1) flecainide and quinidine both increase APD in human atrial tissue but with opposite rate-dependence, 2) the effects of flecainide to increase atrial APD and refractoriness are enhanced by the rapid rates typical of atrial fibrillation, and 3) animal tissues may differ importantly from human in both their sensitivity and rate-dependent response to antiarrhythmic drugs. The salutary response of atrial fibrillation to flecainide may be due to enhancement of drug action by the rapid atrial activation rates characteristic of this arrhythmia.

Action Potentials↗