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Biomedical subjects

S Wu

Publications and source records attributed to S Wu.

At least 505 records · Page 28Linked to original sources
PubMed1991

Green tea extract inhibits nucleoside transport and potentiates the antitumor effect of antimetabolites.

The present study provides evidence that green tea extract (GTE), consisting of polyphenol components, is a highly active nucleoside transport inhibitor. GTE markedly inhibited radiolabeled thymidine and uridine transport in mouse leukemia L1210 cells, with IC50 values of 3.2 and 8.0 mumol/L, respectively. GTE blocked the rescue effect of exogenous nucleosides and enhanced the cytotoxicity of AraC and MTX to L1210 cells and human hepatoma BEL-7402 cells. GTE markedly potentiated the inhibitory effect of AraC on leukemia L1210 and P388 in mice. These results indicate that GTE is potentially useful when combined with antimetabolites in cancer chemotherapy.

Animals↗
PubMed1991

Effect of ginsenopolypeptide on the 3H-TdR integration of human blood lymphocyte.

This paper reports the study of the effect of ginsenopolypeptide on 3H-TdR integration in normal human blood lymphocytes in vitro with micro-blood culture method of 3H-TdR integration. The results showed that the effect of ginsenopolypeptide on 3H-TdR integration in normal human peripheral blood lymphocytes which can be activated by phytoagglutinin was enhanced at low dosage and inhibited at high dosage, and its stimulating spike was 10(-6) micrograms/ml (P less than 0.01).

Adjuvants, Immunologic↗
PubMed1991

High-sensitivity laser-induced fluorescence detection for capillary electrophoresis.

Capillary electrophoresis provides very high efficiency separations of biological molecules. Laser-induced fluorescence produces very high sensitivity detection. The combination of the two techniques results in an analytical tool with unprecedented properties: separations with more than a million theoretical plates and detection limits of a few hundred analyte molecules. This paper considers the design of high-sensitivity laser-induced fluorescence detection for capillary zone electrophoresis separation of labeled amino acids and capillary gel electrophoresis separation of DNA sequencing fragments.

Amino Acids↗
PubMed1991

[Effects of semen Ziziphis Spinosae oil and Ziziphis Spinosae extract on the decrease of serum lipoprotein and inhibiton of platelet aggregation].

Our experiments have shown that oral administration of Semen Ziziphis Spinosae oil(SZSO) or Ziziphis Spinosae extract (ZSE) given to quails for 53 days can significantly reduce their TC, LDL and TG and markedly subdue the fatty degeneration in their livers. Also, SZSO pressed into the stomach of rats for five days can conspicuously inhibit their platelet aggregation, while ZSE cannot.

Animals↗
PubMed1991

Alcohol and pyruvate cardioplegia. Twenty-four-hour in situ preservation of hamster hearts.

Isolated hamster hearts were first perfused with a normal Krebs-Henseleit medium to demonstrate comparable viability of hearts before perfusing and storing them for 24 hours in one of three solutions. The three solutions were a physiologic saline with pyruvate as the substrate and 4% alcohol to arrest the heart (group 1), a standard cardioplegic solution (group 2), and an alcohol-free physiologic saline with pyruvate as the substrate (group 3). Recovery in terms of rate/pressure product and oxygen consumption after 30 minutes of reperfusion was 81% and 93%, respectively, for group 1, 13% and 32% for group 2, and 70% and 72% for group 3. Percent of physiologic recovery was not related to recovery of adenosine triphosphate. The adenosine triphosphate level returned to approximately 40% control level in all three groups, and in all three groups inorganic phosphate remained approximately 320% over control level after 30 minutes of reperfusion. Phosphocreatine level significantly higher in groups 1 and 3 than in group 2, as a result of improved oxygen consumption. Intracellular pH, determined by phosphorous 31 nuclear magnetic resonance spectroscopy, was physiologic in groups 1 and 3 but alkaline in group 2. This alkalinity may have been caused by leaky membranes. Pyruvate helped preserve mitochondrial function during depressed oxygen delivery, such as was seen during the 24-hour storage period. Four percent alcohol arrested the heart; combined with pyruvate plus alcohol solution were better than a standard cardioplegic solution for maintaining functional capability.

Animals↗
PubMed1990

Determination of phosphonoformic acid in human plasma and urine by high-performance liquid chromatography with electrochemical detection.

Trisodium phosphonoformate (foscarnet) is used in the treatment of cytomegalovirus infections in immunocompromised patients, such as bone marrow and renal transplant recipients, as well as patients with the acquired immune deficiency syndrome. A simple high-performance liquid chromatographic assay is described using an electrochemical detector. The method is accurate, precise and reproducible. Hydrochlorothiazide is used as the internal standard. This assay allows measurement of foscarnet in biological fluids at concentrations as low as 33 microM. This method is being used for the analysis of samples in clinical trials and is important in the evaluation of the pharmacokinetic disposition of the drug.

Cathartics↗
PubMed1990

Predicting progression to AIDS: combined usefulness of CD4 lymphocyte counts and p24 antigenemia.

PURPOSE: To investigate the combined usefulness of CD4 lymphocyte counts and human immunodeficiency virus type 1 (HIV-1) p24 antigen in predicting progression to the acquired immunodeficiency syndrome (AIDS). PATIENTS AND METHODS: CD4 lymphocyte counts and HIV-1 p24 antigen status were evaluated over a 4-year period in 518 HIV-1-seropositive men enrolled in the Multicenter AIDS Cohort Study in Chicago. RESULTS: Twenty-six percent (134 of 518) of the HIV-1-seropositive cohort had detectable p24 antigen during the study period. Men with p24 antigenemia experienced a more rapid decline in CD4 lymphocyte counts than men who were persistently p24 antigen-negative (p less than 0.01). Mean CD4 lymphocyte counts at first detection of p24 antigen were 406 and 455 cells/microL for men with incident and prevalent antigenemia, respectively. Antigen was detected in 61% (63 of 103) of the men who progressed to AIDS and in only 17% (71 of 415) of the men who did not (p less than 0.0001). The 4-year estimated cumulative AIDS incidence was 86%, 63%, and 21% for men with entry CD4 counts less than 200, 200 to 399, and 400 or more cells/microL, respectively. Presence of p24 antigenemia was strongly associated with more rapid disease progression within each of these CD4 groupings (p less than 0.0001). CONCLUSION: Our data indicate that p24 antigenemia can first be detected with moderate CD4 cell depletion, is associated with a more rapid decline in the CD4 lymphocyte population, and combined with CD4 lymphocyte counts is useful in identifying individuals at significantly greater risk of disease progression. Our findings provide important information for assessing HIV-1 disease prognosis over a 4-year period.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Ethanol protects the heart against the calcium paradox injury.

Rat hearts were depleted of Ca2+ (less than 10(-9) M) for 10 min, followed by 15 min of Ca2+-repletion. The calcium paradox injury occurs during Ca2+-repletion, after a period of calcium depletion. The calcium paradox injury was assessed by percent recovery (hemodynamics, [Ca2+]i, and energy levels) during Ca2+-repletion. A decrease in Na+ concentration during Ca2(+)-depletion did not allow for recovery during Ca2(+)-repletion, however 2.5% and 5% ethanol during Ca2(+)-depletion allowed for an approximate 50% recovery during Ca2(+)-repletion. A combination of ethanol (2.5% or 5%) with a low extracellular Na+ concentration (88 mM) allowed for complete recovery. Ethanol prevented a depletion of diastolic [Ca2+]i during Ca2(+)-depletion, and allowed for a return of normal diastolic [Ca2+]i during Ca2(+)-repletion. Ethanol modulates the activity of the Na+/Ca2+ exchanger and protects against the Ca2(+)-paradox injury.

Animals↗
PubMed1990

Mechanism of acetylcholine-induced inhibition of Ca current in bullfrog atrial myocytes.

The mechanism of the anti-beta-adrenergic action of acetylcholine (ACh) on Ca current, ICa, was examined using the tight-seal, whole-cell voltage clamp technique in single atrial myocytes from the bullfrog. Both isoproterenol (ISO) and forskolin increased ICa dose dependently. After ICa had been enhanced maximally by ISO (10(-6) M), subsequent application of forskolin (50 microM) did not further increase ICa, suggesting that ISO and forskolin increase ICa via a common biochemical pathway, possibly by stimulation of adenylate cyclase. ACh (10(-5) M) completely inhibited the effect of low doses of forskolin (2 x 10(-6) M), as well as ISO, but it failed to block the effects of high doses of forskolin (greater than 5 x 10(-5) M). Intracellular application of cyclic AMP (cAMP) also increased ICa. ACh (10(-5) M) failed to inhibit this cAMP effect, indicating that the inhibitory action of ACh occurs at a site proximal to the production of cAMP. ACh (10(-5) M) also activated an inwardly rectifying K+ current IK(ACh). Intracellular application of a nonhydrolyzable GTP analogue, GTP gamma S (5 X 10(-4) M), activated IK(ACh) within several minutes; subsequent application of ACh (10(-5) M) did not increase IK(ACh) further. These results demonstrate that a GTP-binding protein coupled to these K+ channels can be activated maximally by GTP gamma S even in the absence of ACh. Intracellular application of GTP gamma S also strongly inhibited the effect of ISO on ICa in the absence of ACh. Pertussis toxin (IAP) completely prevented both the inhibitory effect of ACh on ICa and the ACh-induced activation of IK(ACh). GTP gamma S (50 microM-1 mM) alone did not increase ICa significantly; however, when ISO was applied first, GTP gamma S (5 x 10(-4) M) gradually inhibited the ISO effect on ICa. These results indicate that ACh antagonizes the effect of ISO on ICa via a GTP-binding protein (Gi and/or Go). This effect may be mediated through a direct inhibition by the alpha-subunit of Gi which is coupled to the adenylate cyclase.

Acetylcholine↗
PubMed1990

Calcium inhibition of glycolysis contributes to ischaemic injury.

STUDY OBJECTIVE: The purpose of the study was to confirm that [Ca2+]i and .[H+]i increase during ischaemia in hypertensive hearts but not in thyrotoxic hearts, and that the rise in [Ca2+]i and [H+]i inhibits glycolysis, causing a rise in phosphomonoester sugars and thereby influencing postischaemic recovery. DESIGN: Rats were made hypertensive by aortic banding and thyrotoxic by injection of L-thyroxine. [Ca2+]i was studied in isolated hearts by surface fluorometry assessing calcium dependent changes in the fluorescent dye INDO-1, while [pH]i and phosphomonoester sugars were studied by 31P nuclear magnetic resonance (NMR). Global ischaemia was carried out by turning off all flow to the heart for 30 min. Hearts were then reperfused for 30 min. SUBJECTS: 72 Sprague-Dawley rats, weight 500-600 g, were used. Left ventricular hypertrophy was generated by aortic banding in 36, half of which were treated with verapamil. Eighteen were injected with L-thyroxine and there were 18 controls. MEASUREMENTS AND RESULTS: With all groups, developed pressure immediately declined after the onset of global ischaemia. During ischaemia the phosphomonoester sugars rose less in the hearts of thyrotoxic rats and the verapamil treated aortic constricted rats than in those of untreated aortic constricted and normal rats. During ischaemia there was no significant difference in [pH]i among the four groups. During ischaemia intracellular calcium rose least in thyrotoxic and verapamil treated aortic constricted rats, and most in untreated aortic constricted and normal rats. Intracellular calcium rose 10-15 min after the onset of ischaemia in verapamil treated pressure overload and control hearts; calcium rose immediately after the onset of ischaemia in the untreated aortic constricted hearts, but negligibly in hearts from thyroxine treated animals. Verapamil treatment of the aortic constricted hearts prevented the rise in intracellular calcium, and attenuated phosphomonoester sugar accumulation. Postischaemic recovery was complete in hearts in thyroxine treated and verapamil treated aortic constricted rats, but not in hearts from untreated aortic constricted and normal rats. Postischaemic recovery was inversely related to ischaemic diastolic [Ca2+]i and phosphomonoester sugar levels, but was not related to ischaemic values for [pH]i. CONCLUSIONS: Postischaemic recovery may depend on the ability of the cell to maintain mitochondrial activity as evidenced by oxygen consumption, thereby controlling the voltage of the cell, and influencing the ability of the myocardium to maintain its calcium homeostasis.

Animals↗
PubMed1990

Nitrogen fixation of nodulation mutants of soybean as affected by nitrate.

It was previously reported that three soybean (Glycine max [L.] Merr.) nodulation mutants (NOD1-3, NOD2-4, and NOD3-7) were partially tolerant to nitrate when nitrate was supplied simultaneously with inoculation at the time of transplanting. The current study evaluated the effect of short-term nitrate treatment on nitrogenase activity (C(2)H(2) reduction per plant and per nodule weight) and on relative abundance of ureides when nitrate application was delayed until plants were 3 weeks old and nodules were fully developed. Nitrogenase activity of the mutants was similar to that of Williams after an initial 3-week growth period, prior to nitrate treatment. Application of 5 millimolar nitrate resulted in greater inhibition of nitrogenase activity in Williams than in the three mutants. NOD1-3 was most tolerant of nitrate among the mutants tested and showed the highest relative abundance of ureides. Although C(2)H(2) reduction activity per plant for NOD1-3 was higher than for Williams in the presence of nitrate, C(2)H(2) reduction activity per gram of nodules was lower for NOD1-3 than for Williams in the presence and absence of nitrate. Compared to Williams, NOD1-3 had higher nodule ureide concentration and had similar glutamine synthetase activity in nodule tissue, indicating its nodules have normal nitrogen assimilation pathways. Nitrate application resulted in ureide accumulation in nodule tissue as well as in all plant parts assayed. Unexpectedly, nitrate treatment also increased the rate of ureide degradative capacity of leaves in both NOD1-3 and Williams. The data confirmed that nitrogenase activity of the selected nodulation mutants was more, but still only partially, tolerant of nitrate compared with the Williams parent.

Journal Article↗
PubMed1990

[Effects of tetrandrine on platelet aggregation, platelet adhesion and coagulation].

We examined the effect of tetrandrine on platelet aggregation, platelet adhesion and coagulation in vitro. The results showed that tetrandrine markedly inhibited the platelet aggregation induced by ADP or collagen. Tetrandrine also markedly inhibited platelet adhesion and thrombosis, but didn't change thrombin coagulation time and plasma coagulation time obviously.

Alkaloids↗