PubMed Health⌕ Search

Biomedical subjects

X Y Ma

Publications and source records attributed to X Y Ma.

At least 37 records · Page 2Linked to original sources
PubMed1996

Calcium channel blockade and anti-free-radical actions of panaxatriol saponins in cultured myocardiocytes.

AIM: To identify the calcium channel blockade and anti-free-radical actions of panaxatriol saponins Re, Rf, Rg1, Rg2, Rh1, and oleanolic acid saponin Ro. METHODS: On ventricular myocytes of Wistar rats, single channel activities of B, L, and T type calcium channels were recorded with the cell-attached configuration of patch-clamp technic, and free radical contents were measured with electron spin resenance method. RESULTS: Re, Rg1, Rg2, and Rh1 shortened the open times, prolonged the close times, and reduced the open-state probabilities of B, L, and T type calcium channels; Rf shortened the open time, prolonged the close time and reduced the open-state probability of L type calcium channel; Ro did not influence the activity of calcium channels (60 mumol.L-1). Re, Rg1, Rg2, and Rh1 antagonized the increase of free radical content induced by xanthine 0.42 mmol.L-1-xanthine oxidase 5.3 nmol.L-1; Ro and Rf had no effect (30 mumol.L-1). CONCLUSION: Re, Rg1, Rg2, and Rh1 had both the calcium channel blockade and antifree-radical actions. Rf had blockade action on L type calcium channel.

Animals↗
PubMed1995

[Vasopressin facilitates aortic baroreceptor activity in the rat].

Effect of arginine vasopressin (AVP) on the aortic baroreceptor activity of anesthetized rats was studied in 25 aorta arch-aortic nerve preparations. The results obtained were as follows: (1) By perfusing the isolated aortic arch with AVP (10(-8) mol/L), at constant intra-aortic pressure (IAP) of 13.3 kPa, the integrated aortic nerve activity (IANA) was increased by 40 +/- 4.7% (P < 0.0001), and the stepwise increase or decrease of IAP were accompanied correspondingly by changes of IANA. The function curve of aortic baroreceptor was shifted to the left and upward, and the peak into grated value (PIV) of the curve was increased from 621 +/- 85 to 711 +/- 81%.kPa-1 (P < 0.01). There were no changes in threshold pressure (TP), saturation pressure (SP), operating range (OR) and peak slope (PS). After washing out of AVP, the IANA returned to the control level. (2) The above effects of AVP were abolished by pretreatment with V1-antagonist [d (CH2)5Tyr- (Me) AVP, 10(-7) mol/L]. (3) By perfusing the aorta-arch preparation with five different concentrations of AVP (10(-11)-10(-7) mol/L), at the same constant IAP, IANA were respectively 190%, 160%, 150%, 130% and 103% of the control. After pretreatment with V2-antagonist [d (CH2) (d-Ile2Abu4] AVP (10(-7) mol/L), the perfusions with five different concentrations of AVP increased the IANA respectively to 130%, 150%, 160%, 170% and 180% of the control. When the V2-receptor-mediated vasodilating effect of AVP was blocked, the facilitatory effect of AVP on aortic baroreceptors via V1 receptors was significantly exhibited in a dose-dependent manner.(ABSTRACT TRUNCATED AT 250 WORDS)

Afferent Pathways↗
PubMed1994

Cysteine residues in the Vif protein of human immunodeficiency virus type 1 are essential for viral infectivity.

The infectivity factor of human immunodeficiency virus type 1 (HIV-1), Vif, contains two cysteine residues which are highly conserved among animal lentiviruses. We introduced substitutions of leucine for cysteine residues in the vif gene of a full-length HIV-1 clone to analyze their roles in viral infection. Mutant viruses containing substitutions in either Cys-114, Cys-133, or both displayed a vif-negative infection phenotype similar to that of an isogeneic vif deletion mutant, namely, a cell-dependent complete to partial loss of infectivity. The vif defect could be complemented by cotransfection of mutant viral DNA with a Vif expression vector, and there was no evidence that recombination contributed to the repair of the vif deficiency. The viral protein profile, as determined by immunoblotting, in cells infected with cysteine substitution mutants and that in wild-type virus were similar, including the presence of the 23-kDa Vif polypeptide. In addition, immunoblotting with an antiserum directed against the carboxyl terminus of gp41 revealed that gp41 was intact in cells infected with either wild-type or vif mutant HIV-1, excluding that Vif cleaves the C terminus of gp41. Our results indicate that the cysteines in HIV-1 Vif are critical for Vif function in viral infectivity.

Amino Acid Sequence↗
PubMed1994

Effects of vitamins and methionine on blastogenic response of splenocytes and lipid peroxidation in lung and liver of mice exposed to SiO2 dust.

We studied the effects of nutrients such as vitamin C, E, B6, niacin, and methionine on the blastogenic response of splenocytes and lipid peroxidation (LPO) in lung and liver of mice exposed to SiO2 dust. The results showed that after treatment with SiO2, the blastogenic response of splenocytes decreased significantly (p < 0.001), whereas the LPO level in lung and liver increased remarkably (lung p < 0.05; liver p < 0.001). Vitamin E, C, and niacin strongly enhanced the blastogenic response of T and B splenic lymphocytes to concanavalin-A and to lipopolysaccharide (p < 0.001). The effects of methionine and B6 were much less intense. Other supplied nutrients have been shown to inhibit LPO in lung and liver of mice exposed to SiO2 (p < 0.001).

Animals↗
PubMed1994

Effects of dietary supplementation on the function of alveolar macrophages of silicosis rats, on the blastogenic response of lymphocytes and on the peroxidase activity in blood of silicosis patients.

We studied the effects of a nutrient supplemented diet on the function of alveolar macrophages of silicosis rats and on the blastogenic response of lymphocytes, glutathione peroxidase (GSH-PX) activity, and lipid peroxidase (LPO) activity in the blood of silicosis patients. The results showed that a nutrient supplemented diet increased the phagocytosis rate (p < 0.01) and index (p < 0.05) of alveolar macrophages of silicosis rats. A nutrient supplemented diet also enhanced significantly the GSH-PX activity (p < 0.001) and the blastogenic response of lymphocytes (p < 0.01), and decreased substantially the LPO content (p < 0.05) in the blood of silicosis patients. We conclude that a nutrient supplemented diet may play an important role in antilipid peroxidation, decreased free radical reaction, stabilizing cell membrane, delaying lung fibrosis, and enhancing immune functions of the body.

Animals↗
PubMed1994

[Effects of atrial natriuretic peptide on aortic baroreceptor activity in rats].

Effects of atriopeptin III (AP III) on the aortic baroreceptor activity in rats were studied in the isolated aorta arch-aortic nerve preparation in situ. By perfusing the isolated aortic arch with AP III (2.0 micrograms/ml) in rats, at constant intra-aortic pressure (IAP) of 13.3 kPa, the integral of aortic nerve activity (IANA) was increased by 64 +/- 27% (P < 0.001), the stepwise increases and decreases of IAP were correspondingly accompanied by increase and decrease in IANA, while the saturation pressure (SP) and the operating range (OR) of aortic baroreceptor activity were decreased from 22.5 +/- 0.5 to 21.3 +/- 0.5 kPa (P < 0.05) and 12.1 +/- 0.4 to 10.6 +/- 0.4 (P < 0.05), respectively, and the threshold pressure (TP) did not show any changes. The function curve of aortic baroreceptor was shifted to left and upward, and the peak integral value (PIV) and the peak slope (PS) of the curve were increased from 508 +/- 66 to 730 +/- 52% (P < 0.05), 55.6 +/- 7.5 to 93.2 +/- 6.8%.kPa-1 (P < 0.05), respectively. After washing out of AP III, the IANA returned to the control level. By perfusing the aortic arch with sodium nitroprusside (NP, 1.0 microgram/ml), at constant intra-aortic pressure (IAP) of 13.3 kPa, although the IANA was decreased as compared with the control, there was no statistical significance (P > 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

In vivo neutralization of P-selectin protects feline heart and endothelium in myocardial ischemia and reperfusion injury.

The cardioprotective effects of an mAb to P-selectin designated mAb PB1.3 was examined in a feline model of myocardial ischemia (MI) and reperfusion. PB1.3 (1 mg/kg), administered after 80 min of ischemia (i.e., 10 min before reperfusion), significantly attenuated myocardial necrosis compared to a non-blocking mAb (NBP1.6) for P-selectin (15 +/- 3 vs 35 +/- 3% of area at risk, P < 0.01). Moreover, endothelial release of endothelium derived relaxing factor, as assessed by relaxation to acetylcholine, was also significantly preserved in ischemic-reperfused coronary arteries isolated from cats treated with mAb PB1.3 compared to mAb NBP1.6 (67 +/- 6 vs 11 +/- 3, P < 0.01). This endothelial preservation was directly related to reduced endothelial adherence of PMNs in ischemic-reperfused coronary arteries. Immunohistochemical localization of P-selectin was significantly upregulated in the cytoplasm of endothelial cells that lined coronary arteries and veins after 90 min of ischemia and 20 min of reperfusion. The principal site of intracytoplasmic expression was in venous vessels. mAb PB1.3 significantly decreased (P < 0.01) adherence of unstimulated PMNs to thrombin and histamine stimulated endothelial cells in a concentration-dependent manner in vitro. These results demonstrate that PMN adherence to endothelium by P-selectin is an important early consequence of reperfusion injury, and a specific monoclonal antibody to P-selectin exerts significant endothelial preservation and cardioprotection in myocardial ischemia and reperfusion.

Animals↗
PubMed1993

[Influence of 11 ginsenoside monomers on action potentials of myocardiocytes].

Eleven ginsenoside monomers were added to cultured myocardiocytes of neonatal Wistar rats in a concentration of 20 micrograms.ml-1. And the action potentials (AP) were led with microelectrodes. Rb1, Rb2, Rb3, Rc, Rg1, Rg2, Re, and Rh1 inhibited AP, decreasing APA by 20%, 13%, 5%, 18%, 30%, 37%, 28%, and 23%, respectively. The potency of the most effective monomer Rg2 20 micrograms.ml-1 was similar to that of the calcium channel blocker nimodipine 1.25 micrograms.ml-1. Rd, Rf, and Ro had no significant influence on AP. The average potency of the panaxatriol saponin (PTS) monomers were greater than that of the panaxadiol saponin (PDS) monomers. The above demonstrate the reason why the calcium channel blockade action of PTS is stronger than that of PDS results from the summation of monomer drug effects.

Action Potentials↗
PubMed1993

[Antioxidative action of soyasaponin monomers I, A1, A2, and their inhibitory effects on action potential and beating of myocardiocytes in culture].

Ventricular myocardiocytes from newborn Wistar rats were cultured. Soyasaponin monomers I, A1, A2 2 micrograms.ml-1 added to the culture medium, like nimodipine 1.25 microgram.ml-1, decreased the number of spontaneously beating clusters and the action potential parameters of myocardiocytes, which restored after washing out and were reversed by Ca2+ 80 micrograms.ml-1 or epinephrine 10 micrograms.ml-1, indicating the Ca2+ channel blockade action of the saponin monomers. Adding xanthine 0.42 mmol.L-1 and xanthine oxidase 5.4 nmol.L-1 into culture medium led to the increase of free radical content of the myocardiocytes and the decrease of action potential parameters, which were reversed by I 2 micrograms.ml-1, indicating the antioxidative action of saponin monomer I.

Action Potentials↗
PubMed1993

[Photodegradation assay method of nifedipine and its application to studies on percutaneous absorption].

A new method of analysis for low concentrations nifedipine was developed according to the principle of a photodegradation analytical method that has been reported by the authors previously, and was used to study percutaneous absorption. The absorbance of sample solution was measured before and after light irradiation at 237 nm for 2 h. In this method, calibration graph was linear in the range of 1-20 micrograms/ml for delta A237. The average recovery for nifedipine was 98.80%. No interference from propylene glycol, azone, m-nifedipine, nitrendipine, verapamil and propranolol was observed. It is shown that azone can promote markedly percutaneous absorption of nifedipine.

Animals↗
PubMed1992

Influences of ginsenosides Rb1, Rb2, and Rb3 on electric and contractile activities of normal and damaged cultured myocardiocytes.

Free radical damage to the cultured myocardiocytes of Wistar rat was induced by adding xanthine 0.42 mmol.L-1 and xanthine oxidase 5.3 nmol.L-1 to the culture medium. 30 micrograms.ml-1 of Rb1, Rb2 or Rb3 extracted from the leaf and stem of Panax ginseng C A Meyer restored the action potentials (AP) of free radical damaged cells to normal, indicating their antioxidative action. On normal myocardial cells, Rb1, Rb2, Rb3 20 micrograms.ml-1 inhibited the AP and spontaneous contractility, (suggesting the Ca channel blockade action of panaxadiol saponins). The degrees of their inhibitory effects were found to be Rb1 > Rb2 > Rb3. Their effects against X-XO were basically the same.

Action Potentials↗
PubMed1992

[The photodegradation-assay method of sodium nitroprusside and its application to studies on percutaneous absorption].

A new method of quantitative analysis of sodium nitroprusside (SNP) was developed according to the principle of a photodegradation analytical method that has been reported by the authors previously. After irradiated of solution of SNP under fluorescent lamp, the increase in absorbance at 394 nm belonged to nonlinear kinetics, but the absorbance increment with concentration was linear in certain concentration range of SNP. When irradiated for 30 min or 60 min, SNP in solution can be quantitated accurately by delta A394. The standard curve of this method was linear from 50 to 1000 mg/L. The within-day and day-to-day precisions (RSD) were 1.9% and 2.6% respectively, with recoveries of 99.0-100.1%. No interference from small amount of serum protein, stearyl alcohol, propylene glycol, azone, m-nifedipine, nitrendipine and verapamil was observed. This method has been successfully applied to study percutaneous absorption.

Animals↗
PubMed1992

[Determination of m-nifedipine and its pharmacokinetic study in rabbits by high-pressure liquid chromatography].

A high-pressure liquid chromatographic method was developed for determination of m-nifedipine in plasma using a chemical bonded C-18 phase column (YWG-C18 10 microns, made in China) with nitrendipine as internal standard. To increase life of the YWG-C18 column a mixture of methanol and 5 mmol.L-1 phosphate buffer (70:30 vol/vol) was selected as mobile phase with a flow rate of 0.8 ml.min-1. The method was sensitive to m-nifedipine 3 ng.ml-1 plasma and the standard curve was linear from 10 to 1000 ng.ml-1 with correlation coefficient of 0.99. The within-day and day-to-day precisions (CV) of this method were 4.5% and 7.0%, respectively, with recoveries of 95-102% (10-1000 ng.ml-1). There was no interference with nifedipine, amiodarone, propranol, and verapamil. A pharmacokinetic study on m-nifedipine was carried out in 8 rabbits. A better computer fitted to a two-compartment model was observed using 3P87 program. The parameters obtained were as follow: Vc 6.3 L.kg-1, Cl 0.021 L.kg-1.min-1, T1/2 alpha 30 min, T1/2 beta 230 min, AUC 102 micrograms.min.ml-1.

Animals↗
PubMed1991

Mass screening for rectal neoplasm in Jiashan County, China.

Jiashan county is a rural area in China with very high incidence and mortality rates of colorectal cancer. From 1980 to 1984, we conducted a mass screening for rectal neoplasm in the 11 people's communes in this county. Of the 72,879 individuals who were eligible for screening, 60,496 participated, representing an overall participation rate of 83.0%. Both the fecal occult blood (OB) test and rectoscopy were performed on 47,560 of the participants, and rectoscopy only was performed on the remaining 12,936 individuals. From the mass screening, 15 rectal cancers, 3 carcinoids, 899 polyps, 98 ulcers, and 7 inflammatory tumors were detected, a total of 1022 cases. Eight of the 15 detected cases of rectal cancer were in Dukes' stage A. We did not find any evidence for an association between schistosomiasis and colorectal cancer. Results from the OB test were found to have a negative correlation with results from rectoscopy (odds ratio = 0.8, 95% CI = 0.6, 1.1). The OB test had a high false positive rate of 32.7%, and a poor positive predictive value of 3.5%. Both its positive and negative predictive powers were below 1.0, in other words, its positive likelihood ratio was below 1.0 and negative likelihood ratio was above 1.0, indicating that the OB test is not informative and has a poor predictive accuracy for rectal neoplasm. In addition, there were a number of practical problems concerning the use of the OB test for mass screening in the rural community.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Recombinational analysis of a natural noncytopathic human immunodeficiency virus type 1 (HIV-1) isolate: role of the vif gene in HIV-1 infection kinetics and cytopathicity.

Two molecularly cloned coisolates of human immunodeficiency virus type 1 (HIV-1) have been found to exhibit different phenotypes of viral expression, either rapid and cytopathic (N1T-A virus) or delayed and noncytopathic (N1T-E virus [X. Ma, K. Sakai, F. Sinangil, E. Golub, and D. J. Volsky, Virology 176:184-194, 1990]). To identify the viral genetic elements responsible for these phenotypes, we prepared reciprocal recombinants in different regions of N1T-A and N1T-E viral genomes. Infectivity experiments with the recombinant viruses revealed that the rapid/cytopathic (N1T-A-like) phenotype assorted cleanly with the V1f-coding region and Vif expression. The smallest HIV-1 DNA region that conferred the complete phenotypic switch was a 284-bp NdeI-StuI fragment within the vif open reading frame. Nucleotide sequence analysis revealed a 35-bp deletion starting at nucleotide 218 in the N1T-E vif gene. A 23-kDa Vif protein was detected by immunoblotting using Vif-specific antiserum in extracts of cells infected with N1T-A but not N1T-E virus. No detectable vif protein was found in association with sedimented particles of either virus. Cotransfection of a eucaryotic vif expression plasmid with N1T-E DNA complemented the N1T-E defect; rapid/cytopathic infection similar to that in N1T-A-transfected cells was observed. We conclude that Vif controls the rate, and consequently the cytopathic outcome, of HIV-1 infection.

Amino Acid Sequence↗