Biomedical subjects

G Chen

Publications and source records attributed to G Chen.

At least 775 records · Page 43Linked to original sources

PubMed1993

Relationship between tissue calcium content and duodenal ulcer in the rat.

Since the effect of cellular calcium on cell injury has been in question, this study focused on the relationship between tissue calcium content and cysteamine-induced duodenal ulcer. Rats treated with cysteamine showed a high frequency and severity of duodenal ulcer, and the calcium content in the duodenal mucosa was elevated. Furthermore, the level of calcium content in duodenal mucosa was positively associated with the severity of the duodenal lesion. Whereas administration of calcium increased duodenal ulcerative response to cysteamine, verapamil afforded protection against ulceration. We conclude that calcium accumulation in duodenal mucosa is related to duodenal ulceration induced by cysteamine.

Animals↗

PubMed1993

Production of prostacyclin and thromboxane A2 in mononuclear cells from preeclamptic women.

OBJECTIVE: Although the changes in prostacyclin and thromboxane A2 levels in preeclampsia have been well studied, little work has previously been done on mononuclear cells, and the cause of the changes in unclear. We determined the prostacyclin and thromboxane A2 production in mononuclear cells and investigated the effect of preeclamptic serum on this production. STUDY DESIGN: The production of prostacyclin and thromboxane A2 was measured by enzyme immunoassay in 16 normal pregnant women, nine preeclamptic women with proteinuria, and six preeclamptic women without proteinuria. Sera from these three groups of women were investigated to see whether the sera have any effect on prostaglandin production. RESULTS: The levels of thromboxane A2 in preeclamptic patients were found to be much higher than those of normal pregnancy, whereas the levels of prostacyclin tended to be lower. Such changes lead to a markedly increased ratio of thromboxane A2 to prostacyclin in preeclamptic patients. There was no difference in the levels of prostacyclin and thromboxane A2 between the preeclamptic patients with and without proteinuria. Serum from preeclamptic patients with proteinuria slightly reduced prostacyclin synthesis in normal pregnancy but significantly increased increased thromboxane A2 production, resulting in a ratio of thromboxane A2 to prostacyclin similar to that of preeclampsia. However, serum from preeclamptic patients without proteinuria failed to exert such effects. CONCLUSION: The imbalance between prostacyclin and thromboxane A2 occurs in mononuclear cells from preeclamptic women, and there is a factor(s) in proteinuric-preeclamptic serum to contribute, in part, to these changes. Our findings also suggested that the cause of abnormal prostaglandin production in preeclampsia was complicated and multifactorial.

6-Ketoprostaglandin F1 alpha↗

PubMed1993

Cocaine modulation in vitro of tumor necrosis factor production by macrophages from retrovirally infected mice.

The effect of cocaine and LP-BM5 murine leukemia retrovirus infection on tumor necrosis factor (TNF) production were investigated. Three types of macrophages were used 1) peritoneal macrophage (PM), 2) thioglycollate induced peritoneal macrophage (TPM), and 3) alveolar macrophage (AM). Cells were cultured with and without cocaine during in vitro stimulation by lipopolysaccharide (LPS) and gamma-interferon (IFN). Retroviral infection enhanced the TNF production by PM and AM, but not by TPM. Intraperitoneal cocaine injection reduced TNF production by PM, but increased TNF production by AM and TPM. TNF production by AM from cocaine injected mice was stimulated by cocaine applied in vitro. In contrast, 100 micrograms/ml of cocaine in vitro significantly inhibited the TNF production by TPM from uninfected and retrovirally infected mice. Thus, TNF production by macrophages is modulated by murine retroviral infection and cocaine treatment. This could play an important role in host defense.

Animals↗

PubMed1993

Prostacyclin, thromboxane and antioxidant levels in pregnancy-induced hypertension.

1. Plasma 6-keto-prostaglandin F1 alpha (6-keto-PGF 1 alpha, a major metabolite of prostacyclin), plasma thromboxane B2 (TXB2, a major metabolite of thromboxane A2) and five antioxidants (indirect markers of reactive oxygen species) namely, plasma thiol, erythrocyte lysate thiol, erythrocyte superoxide dismutase, plasma total glutathione and erythrocyte membrane thiol, were measured in 25 healthy non-pregnant women, 36 normotensive pregnant women and 35 women with pregnancy-induced hypertension (PIH). 2. The levels of TXB2 were significantly increased in normal pregnant women and PIH women with or without proteinuria compared with non-pregnant women. The concentrations of TXB2 in PIH women with proteinuria were higher than those without proteinuria (P < 0.05). 3. The levels of 6-keto-PGF1 alpha in healthy non-pregnant women and PIH women with or without proteinuria were significantly lower than that in normotensive pregnant women (all of three P < 0.01). There were no significant differences between healthy non-pregnant women and PIH women with and without proteinuria. 4. The ratio of TXB2 to 6-keto-PGF1 alpha was markedly elevated in PIH women with or without proteinuria compared with normotensive pregnant women and healthy non-pregnant women. The difference between PIH women with proteinuria and those without proteinuria was not significant (P > 0.05). 5. The levels of plasma thiol, superoxide dismutase and glutathione were significantly decreased in PIH women compared with normotensive pregnant women. 6. There were significant positive correlations between the levels of prostaglandins and antioxidant activity.(ABSTRACT TRUNCATED AT 250 WORDS)

6-Ketoprostaglandin F1 alpha↗

PubMed1993

Electrophysiological comparison of the effects of MCI-154 on smooth muscles between mesenteric artery and vein of dogs.

1. Effects of MCI-154, a cardiotonic vasodilator, on smooth muscles were compared in isolated mesenteric artery and vein of dog. 2. MCI-154 depolarized the membrane, and inhibited Ca(2+)- and K(+)-contractions more in the vein than in the artery. 3. Nerve-mediated and noradrenaline-induced contractions, and the excitatory junction potential (e.j.p.) were inhibited by MCI-154 in the vein and potentiated in the artery. 4. Compound action potentials of perivascular nerves and action potentials generated on the e.j.p. were not altered by MCI-154. 5. MCI-154 predominantly dilates venous muscles, and as a result would reduce cardiac outflow and lower systemic blood pressure.

Animals↗

PubMed1993

Increased poly(ADP-ribosyl)ation in intact cells by cisplatin treatment.

Cisplatin (DDP) is a clinically important antitumor drug that induces the formation of DNA-DNA and DNA-protein crosslinks. We have studied whether poly(ADP-ribosyl)ation, a post-translational modification of nuclear proteins that is drastically increased by the presence of DNA strand breaks and plays a role in DNA repair, is induced following DDP treatment of cell cultures. By using an immunofluorescence technique for the in situ detection of poly(ADP-ribose) in intact cells, we found spotty nuclear signals after DDP treatment of O-342 rat ovarian tumor cells or CV-1 monkey cells, but not in untreated control cells, nor in DDP-treated cells postincubated with the ADP-ribosylation inhibitor 3-aminobenzamide. Our results thus provide direct evidence for an involvement of poly(ADP-ribosyl)ation in the cell's response to DDP treatment and, more generally, illustrate the versatility of this rapid in situ method for the detection of increased poly(ADP-ribosyl)ation in living cells.

Animals↗

PubMed1993

Free phenytoin monitoring in serum and saliva of epileptic patients in China.

Twenty-three serum samples and 13 saliva samples from 14 Chinese epileptic patients treated with phenytoin (DPH) were obtained to study the correlations between total, free serum, and saliva DPH concentrations. The binding of DPH to serum protein was assessed by equilibrium dialysis, and total and free DPH concentrations were analyzed with a domestic fluorescence polarization immunoassay reagent by the TDx system. A strong correlation existed between the total and free concentrations (r = 0.90, n = 20, p < 0.001). The mean value for the DPH free fraction was 11.13 +/- 3.65%. The mean value for the saliva fraction was 9.40 +/- 2.60%. This is the first attempt to monitor free DPH concentrations in serum in Chinese patients.

Administration, Oral↗

PubMed1993

Lithium decreases membrane-associated protein kinase C in hippocampus: selectivity for the alpha isozyme.

We investigated the effects of lithium on alterations in the amount and distribution of protein kinase C (PKC) in discrete areas of rat brain by using [3H]phorbol 12,13-dibutyrate quantitative autoradiography as well as western blotting. Chronic administration of lithium resulted in a significant decrease in membrane-associated PKC in several hippocampal structures, most notably the subiculum and the CA1 region. In contrast, only modest changes in [3H]phorbol 12,13-dibutyrate binding were observed in the various other cortical and subcortical structures examined. Immunoblotting using monoclonal anti-PKC antibodies revealed an isozyme-specific 30% decrease in hippocampal membrane-associated PKC alpha, in the absence of any changes in the labeling of either the beta (I/II) or gamma isozymes. These changes were observed only after chronic (4 week) treatment with lithium, and not after acute (5 days) treatment, suggesting potential clinical relevance. Given the critical role of PKC in regulating neuronal signal transduction, lithium's effects on PKC in the limbic system represent an attractive molecular mechanism for its efficacy in treating both poles of manic-depressive illness. In addition, the decreased hippocampal membrane-associated PKC observed in the present study offers a possible explanation for lithium-induced memory impairment.

Animals↗

PubMed1993

Diet and ethanol modulate immune responses in young C57BL/6 mice.

Chronic ethanol (ETOH) ingestion adversely affects the immunocompetence of alcohol abusers. ETOH directly impairs host defense mechanisms and indirectly modulates immunocompetence by interfering with the nutritional status of the alcoholic. It is not clear from the current literature, however, to what extent ETOH, nutritional status, or the combination of the two factors modulates immune mechanisms in chronic alcoholics. To date, most animal studies investigating the immunotoxicity of ETOH have neglected the dietary factors, which may have masked additional immunotoxic effects of ETOH. To examine these dietary factors, we fed mice three liquid ETOH diets with different dietary sufficiencies for 7 weeks and investigated various immune responses. Spleen cell number and secretions of immunoreactive interleukin-2 and tumor necrosis factor were totally independent of the diet, being affected only by ETOH. Body, spleen, and thymus weights, interferon-gamma secretion, and natural killer cell and phagocytic activities were modulated by ETOH as well as by diet. Natural killer cell and phagocytic activities were also directly affected by the nutritional quality of the diet. These results suggest that animal diets used in experimental studies of ETOH-induced immunomodulation must be planned and controlled carefully in order to single out the direct effects that ETOH has on the host defense system.

Alcoholism↗

PubMed1993

Identification and baculovirus expression of the VP4 protein of the human group B rotavirus ADRV.

A complete cDNA copy of the fourth RNA segment of the human group B rotavirus adult diarrheal rotavirus (ADRV) has been cloned into lambda phage and excised into plasmid pSK Bluescript. Gene segment 4 contains 2,303 bases and encodes one long open reading frame beginning at base 16 and terminating at base 2263. The encoded protein contains 749 amino acids, with a calculated molecular mass of 84.4 kDa and a pI of 6.1. Gene 4 cDNA was inserted into a recombinant baculovirus via homologous recombination. The gene 4 polypeptide migrates at 84 kDa when expressed either by a recombinant baculovirus or in vitro in a rabbit reticulocyte lysate. The gene 4 protein is immunoprecipitable by hyperimmune serum to ADRV, human ADRV convalescent-phase serum, a porcine group B rotavirus infection serum, and a monoclonal antibody made to ADRV virion. Guinea pig hyperimmune serum to the baculovirus-expressed ADRV VP4 protein recognizes virus and immunoprecipitates an 84-kDa protein from in vitro translations of total ADRV mRNA. In addition, the gene 4-encoded protein shares significant amino acid identity and similarity with the group A rotavirus VP4 protein. This information, together with our previous identification of an 84-kDa protein present on iodinated intact virion but not EDTA-treated ADRV, suggests that gene 4 encodes the VP4 protein equivalent present on the outer capsid of ADRV. The ADRV VP4 protein is also 58% identical to the IDIR rat group B rotavirus gene segment 3 protein. The substantial differences between these two group B VP4 proteins suggests that they are distantly related and likely to define two different group B rotavirus VP4 serotypes. The baculovirus-expressed VP4 protein should be useful for developing serotyping reagents and tests for human and animal group B rotaviruses as well as for addressing the role of VP4 in ADRV neutralization.

Amino Acid Sequence↗

PubMed1993

Adaptations of myocardial beta-adrenergic receptor complex in hibernating marmots.

Properties of marmot (Marmota flaviventris) myocardial beta-adrenergic receptor complex (beta-AR) were evaluated during hibernation (H), in summer (S) animals, and in animals aroused from hibernation (C). The results obtained for S and C animals were identical, and only the results for C animals are shown. In H-animal myocardial membrane preparations assayed at 37 degrees C, isoproterenol-dependent adenylate cyclase activity (ACA) was consistently higher, whereas the synergistic contribution of 5'-guanylylimidodiphosphate [Gpp(NH)p] in this reaction was reduced. When assayed at 10 degrees C, only the ACA in H animals responded to the combination of isoproterenol and Gpp(NH)p. In contrast, at 10 degrees C, ACA in response to Gpp(NH)p alone is essentially equal in H and C animals. Hibernation did not change myocardial beta-AR receptor density or affinity. In contrast, analysis of isoproterenol displacement of [125I]iodocyanopindolol revealed that the proportion of beta-AR in the high-affinity state was substantially greater in H than in C animals, and this relationship was retained even in the presence of Gpp-(NH)p. In an evaluation of the role of the GTP binding proteins that couple the beta-AR to the effector adenyl cyclase, we determined that there was no change in the cholera toxin- or pertussis toxin-dependent ADP ribosylation patterns. Immunochemical detection of the individual GTP binding proteins revealed no change in the levels of G alpha i1, G alpha i2, or G alpha i3. In contrast, we observed a hibernation-associated decrease in G alpha o associated with the plasma membrane-enriched particulate fraction. (ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗

PubMed1993

Opposing influences of dexamethasone and retinoic acid on adenylate cyclase activity in ROS 17/2.8 cells.

Exposure of ROS 17/2.8 cells to dexamethasone (DEX) or retinoic acid (RA) increases and decreases, respectively, adenylate cyclase activity (ACA) in response to isoproterenol, forskolin, guanylylimidodiphosphate, or NaFl. Despite dramatic changes in ACA, there were no significant changes in levels of cholera toxin- or pertussis toxin (PT)-dependent ADP-ribosylation of membranes prepared from cells after DEX or RA exposure as compared to controls. Similarly, immunochemical detection of alpha S, alpha i1-3, and alpha O, as well as Northern blot analysis of messenger RNA for each of the respective GTP binding proteins, also failed to demonstrate an influence of DEX or RA when contrasted with controls. In a novel use of the cyc- reconstitution assay, wherein the influence of inhibitory guanine nucleotide binding proteins in the extracts of control, DEX-, and RA-treated membranes is removed by a previous 24-h incubation with PT in the intact cell, we demonstrate that this PT treatment markedly enhances ACA in the cyc- reconstitution assay for all three preparations, but that the fold-increase due to PT-treatment is greatest in RA-treated cells. The greater magnitude of the effect of PT on RA-treated ROS 17/2.8 cells, in the absence of any obvious quantitative changes in the levels of the PT substrates, suggests that the effect of RA on ROS 17/2.8 cells appears to be an augmentation of the influence of inhibitory guanine nucleotide binding proteins, ultimately leading to reduced ACA.

Adenosine Diphosphate Ribose↗

PubMed1993

Effect of exogenous hydrogen peroxide on iodide transport and iodine organification in FRTL-5 rat thyroid cells.

Hydrogen peroxide plays an important role in the regulation of iodination and thyroid hormone formation. In the present study, the effect of exogenous H2O2 on 125I transport and organification was investigated in FRTL-5 rat thyroid cells. Less than 20 passages after subcloning, cells in 24-well plates (6 x 10(4) cells/well) were maintained in a thyrotropin (TSH)-containing medium (6H) for 3 days. A TSH-free medium (5H) was then used for the next 7 days. A 1-h exposure to H2O2 stimulated 125I transport and 125I organification at 0.1-0.5 mmol/l H2O2 and had a toxic effect on FRTL-5 cell at 5 mmol/l. Hydrogen peroxide (0.5 mmol/l) augmented the iodide transport and iodine organification induced by TSH (333 U/l) by two- and threefold, respectively. The biphasic effect of H2O2 was blocked totally by 5-200 micrograms/l of catalase. Catalase by itself did not influence TSH-mediated 125I transport and 125I organification. Hydrogen peroxide (0.5 mmol/l) added to cells in 5H medium increased Na+K(+)-ATPase activity twofold. Ouabain (1 mmol/l), an inhibitor of Na+K(+)-ATPase, completely inhibited the twofold increase in 125I transport induced by 0.5 mmol/l H2O2 but only inhibited H2O2-induced 125I organification by 28%. Methimazole (1 mmol/l), an inhibitor of thyroid peroxidase, had no effect on H2O2-mediated 125I transport but totally blocked the fivefold rise in 125I organification induced by 0.5 mmol/l H2O2. The effect of H2O2 on intracellular cyclic adenosine monophosphate (cAMP) levels also was studied.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Midazolam pharmacokinetics and electroencephalographic changes in eight Chinese men.

Eight Chinese healthy male volunteers aged 27 +/- s 4 a were injected i.v. midazolam (Mid) 15 mg. Blood samples were collected at 0, 2, 5, 7, 10, 20, 30, 45, 60, 90, 120, 180, and 240 min. A HPLC method was established for determining the Mid concentrations in serum. The concentration-time data was fitted with biexponential curve. Pharmacokinetic parameters were: T1/2 alpha = 6.8 +2- 2.5 min, T1/2 beta = 118 +/- 27 min, Vc = 25 +/- 7 L, Cl = 393 +/- 79 ml.min-1, Vdss = 59 +/- 13 L, AUC0-infinity = 39.6 +/- 8.6 g.min.L-1. The electroencephalogram (EEG) showed a decrease in alpha activity and an increase in beta activity. The EEG pattern reverted toward baseline after 2-3 h. Pharmacokinetic and EEG findings suggest that Mid is a preferable anesthesia inducing agent.

Adult↗

PubMed1993

[Investigation on the correlation between the mortality of cerebrovascular diseases and the meteorological factors in Zhanjiang City].

The correlation of the mortality of cerebrovascular diseases in more than 1 million population from 1987 to 1989 with meteorologic phenomena (air temperature, atmospheric pressure, relative humidity) was studied using computering simple correlation analysis in Zhanjiang City which is located in subtropical area, with an average air temperature between 15 degrees C and 18 degrees C in winter. The results showed that the mortality of cerebrovascular diseases in winter was the highest. Mortality was in significant negative correlation with air temperature (r = 0.7785, P < 0.01), in significant positive correlation with atmospheric pressure (r = 0.7511, P < 0.01), and in no significant correlation with relative humidity (r = 0.1413, P > 0.05). It suggested that the mortality of cerebrovascular diseases in Zhanjiang City would significantly increase in the condition that the average air temperature is 15 degrees C-18 degrees C, and the average atmospheric pressure is 1014-1020 millibar in winter.

Cerebrovascular Disorders↗

PubMed1993

[Clinical and experimental study on effects of man-shen-ling oral liquid in the treatment of 100 cases of chronic nephritis].

A new Chinese herbal preparation, Man-Shen-Ling (MSL, consisted of medicinal herbs such as Astragalus and Rehmannia) in treating 100 cases of chronic nephritis. The effective rate was 91% in comparing to 66.7% in the control group, P < 0.001. It was markedly effective for proteinuria, hematuria, improvement and recovery of renal functions, edema, anemia, anorexia etc in comparing with the control group. It showed no adverse effects on functions of liver, kidney, heart and GI tract. Animal model of chronic nephritis was established and the effects of MSL were observed. The laboratory findings and histopathological investigation on kidney revealed and confirmed that MSL has therapeutic effects on chronic nephritis. Pharmacodynamically, MSL exhibited effects of anti-allergy, its immuno-suppressive effect corresponded to that of cyclophosphamide, with diuretic, hypotensive, proteinuria eliminating, anti-inflammatory, anti-coagulatory, renal blood flow and glomerular filtration enhancing, the excretion of urea-nitrogen, potassium and sodium promoting function; in addition, it also could promote and modulate the immunity. Acute and chronic toxicity tests on animal models neither showed toxic, mutagenic, teratogenic nor carcinogenic effects. It is a new preparation of Chinese medicinal herbs in treating chronic nephritis, it is safe and effective.

Adolescent↗

PubMed1993

[Effect of intracerebroventricular injection of caerulein on stress-induced gastric mucosal lesion in rats].

The effect of caerulein injected into cerebroventricle on the stress-induced gastric mucosal lesion of rats with tied four limbs immersed in water was investigated. Caerulein (1.0 ng/rat) reduced significantly gastric mucosal lesion, decreased gastric acid content, but increased the gastric content of the mucus and PGE2. Under electromicroscope, morphological sign of hyposecretion in the parietal cells and hypersecretion in the mucus cells could be seen. The effect of caerulein could be prevented by intraventricular injection of naloxone or subcutaneous injection of indomethacin, but not by atropine, phentolamine and propranolol. The results indicate that the protective effect of caerulein on the gastric mucosa is mediated partly by central morphine receptors and partly by enhancement of endogenous PGE2.

Animals↗

PubMed1993

Pharmacokinetics and relative bioavailability of nimodipine capsules and tablets in 8 Chinese healthy men.

A single oral dose of tablets or capsules of 239 mumol nimodipine was given to 8 healthy volunteers of Han nationality in a randomized crossover study. Plasma levels were determined with HPLC method. The plasma concentration-time curve fitted to a first order absorption, 1-compartment open model, and the T1/2K was around 2 h. Although the capsules could reach peak level faster, the bioavailability was not significantly different from that of the tablets.

Adult↗