Search PubMed⌕ Search

Biomedical subjects

Q Zhang

Publications and source records attributed to Q Zhang.

At least 631 records · Page 35Linked to original sources
PubMed1997

Evidence that late preconditioning against myocardial stunning in conscious rabbits is triggered by the generation of nitric oxide.

Recent studies in conscious pigs and rabbits have demonstrated that a series of brief coronary occlusions renders the heart relatively resistant to myocardial "stunning" 24 hours later (late preconditioning [PC] against stunning). The mechanism of this powerful cardioprotective response is unknown. The goal of the present study was to test the hypothesis that the development of late PC against stunning is triggered by increased generation of NO during the first ischemic challenge. Conscious rabbits underwent a sequence of six 4-minute coronary occlusion/4-minute reperfusion cycles for 3 consecutive days (days 1, 2, and 3). On day 1, rabbits received either an intravenous infusion of the NO synthase inhibitor NG-nitro-L-arginine (L-NA, 13 mg/kg before the first occlusion) (group II, n = 10) or vehicle (group I [control], n = 10). In the control group, on day 1 systolic wall thickening (WTh) in the ischemic/reperfused region remained significantly depressed for 4 hours after the sixth reperfusion, indicating myocardial stunning. On days 2 and 3, however, the recovery of WTh improved markedly, so that the total deficit of WTh decreased by 60% on day 2 and 55% on day 3 compared with day 1 (P < .01). In the L-NA-treated group, the total deficit of WTh on day 1 was similar to that observed in the control group. On day 2, however, the total deficit of WTh was not significantly different from that observed on day 1 and was 132% greater than that observed in control rabbits on day 2 (P < .01). On day 3, the total deficit of WTh was 66% less than that noted on day 2 (P < .01). Thus, in L-NA-treated rabbits the sequence of six coronary occlusions and reperfusions performed on day 1 failed to precondition against stunning on day 2, but the same sequence performed on day 2 did precondition against stunning on day 3. Another group of rabbits (group III, n = 6) received L-NA on day 1 in the absence of ischemia and was subjected to the occlusion/ reperfusion sequence on days 2 and 3. In these animals, the total deficit of WTh on day 2 did not differ from that observed in control rabbits on day 1, indicating that administration of L-NA did not exacerbate the severity of myocardial stunning 24 hours later; therefore, the absence of late PC against stunning on day 2 in group II cannot be ascribed to a delayed deleterious action of L-NA on WTh. In conclusion, these results demonstrate that the NO synthase inhibitor L-NA completely blocks the development of late PC against myocardial stunning in conscious rabbits, indicating that NO generated as a result of the PC ischemia triggers the development of the cardioprotective response observed 24 hours later. NO is known to exert numerous biological actions resulting in rapid but transient physiological responses. The present observations support a novel pathophysiological paradigm in which NO also plays a key role in the delayed myocardial adaptations to ischemic stress, acting as a signaling step in the transduction pathway that leads to increased resistance to subsequent ischemic injury.

Animals↗
PubMed1997

The protective effect of late preconditioning against myocardial stunning in conscious rabbits is mediated by nitric oxide synthase. Evidence that nitric oxide acts both as a trigger and as a mediator of the late phase of ischemic preconditioning.

Seventy-four conscious rabbits undergoing a sequence of six 4-minute coronary occlusion/4-minute reperfusion cycles for 3 consecutive days (days 1, 2, and 3) were assigned to nine groups. In group I (controls, n = 8), the recovery of systolic wall thickening (WTh) after the sixth reperfusion was markedly improved on days 2 and 3 compared with day 1, indicating late preconditioning (PC) against myocardial stunning; the total deficit of WTh after the sixth reperfusion was reduced by 56% on day 2 and 50% on day 3 compared with day 1 (P < .01). Administration on day 2 of the nonselective NO synthase (NOS) inhibitor N omega-nitro-L-arginine (L-NA) (group II, n = 8) or of the selective inducible NOS inhibitors aminoguanidine (AG) (group IV, n = 8) and S-methylisothiourea sulfate (SMT) (group VI, n = 6) completely abrogated late PC against stunning on day 2. On day 3, the expected PC effect became manifest in all groups. Administration of L-NA, AG, or SMT on day 1 (groups III [n = 7], V [n = 6], and VII [n = 5], respectively) had no discernible effect on the deficit of WTh on day 1, indicating that these agents do not augment the severity of myocardial stunning in nonpreconditioned myocardium. In group VIII (n = 7), the abrogation of late PC by SMT on day 2 was completely reversed by the concomitant administration of L-arginine (595 mg/kg IV), indicating that it was not due to nonspecific NOS-unrelated actions. Administration of L-arginine alone on day 2 (group IX [n = 5]) had no effect on the deficit of WTh. Furthermore, administration of L-NA on day 1 (group III) prevented the appearance of the PC effect on day 2, whereas AG (group V) and SMT (group VI) did not, suggesting that the development of late PC on day 1 is triggered by the endothelial (type III) isoform of NOS. This study demonstrates that three structurally different NOS inhibitors (L-NA, AG, and SMT), given 24 hours after the PC ischemia, consistently abrogate late PC against myocardial stunning in conscious rabbits, indicating that this cardioprotective effect is mediated by the activity of NOS. The results obtained with AG and SMT specifically implicate the inducible (type II) isoform as the mediator of the protection on day 2. Previous studies have shown that NO triggers the development of late PC. The present results indicate that NO plays a dual role in late PC against stunning, acting initially as the trigger and subsequently as the mediator of the protection.

Animals↗
PubMed1997

Regulation of prostaglandin endoperoxide H synthase 1 and 2 by estradiol and progesterone in nonpregnant ovine myometrium and endometrium in vivo.

PG endoperoxide H synthase-2 (PGHS-2) messenger RNA (mRNA) and protein levels are increased dramatically in ovine myometrium and endometrium during both glucocorticoid-induced premature labor and spontaneous term labor. In this study, we examined estradiol and progesterone regulation in vivo of PGHS-1 and PGHS-2 expression at both mRNA and protein levels using a nonpregnant ovariectomized sheep model. We determined the differential distribution of PGHS-2 and PGHS-1 in ovine myometrium and endometrium with immunocytochemistry. Twenty ovariectomized ewes were treated with saline (n = 5) or estradiol infused i.v. for 2 days (50 microg/day; n = 5) or an intravaginal progesterone sponge for 10 days (containing 0.3 g progesterone; n = 5) or an intravaginal progesterone sponge for 10 days with estradiol (50 microg/day) administered on days 9 and 10 with the progesterone sponge still in place (EP; n = 5). PGHS-1 and -2 mRNA and protein were measured by Northern and Western blot analyses, respectively. PGHS-2 mRNA and protein abundance increased significantly in myometrium after estradiol treatment (P < 0.01). In contrast, progesterone was a more potent stimulator than estradiol of PGHS-2 protein abundance in endometrium (P < 0.01). PGHS-1 concentration did not change after estradiol and/or progesterone administration (P > 0.05). PGHS-2 was immunolocalized in myometrial cells and endometrial glandular epithelial cells, whereas immunoreactive PGHS-1 was located in the myometrial cells, endothelial and smooth muscle cells of blood vessels, as well as epithelial cells of glands and stromal cells in endometrium. Estradiol-dependent activation of PGHS-2 gene expression resulted in increased PGHS-2 levels in sheep myometrium in vivo. Progesterone did not have any effect on PGHS-2 gene expression in the myometrium. In contrast, progesterone was a more potent stimulator of endometrial PGHS-2 abundance than estradiol. Estradiol and progesterone did not regulate PGHS-1 expression in either endometrium or myometrium. The distribution and differential regulation of PGHS-1 and -2 in myometrium and endometrium are consistent with the differential functions of both enzymes.

Animals↗
PubMed1997

Evaluation of dementia: a systematic study of the usefulness of the American Academy of Neurology's practice parameters.

OBJECTIVE: This study examined the usefulness of the "Practice Parameters for the Evaluation of Dementia," published by the Quality Standards Subcommittee of the American Academy of Neurology (1994). The Practice Parameters are stratified according to three levels of certainty (standards, guidelines, and options), and suggest indications for the use of neuroimaging studies. METHODS: We reviewed 119 consecutive cases referred for assessment of memory loss to a university-affiliated interdisciplinary clinic. We assessed the diagnostic value of laboratory, neuropsychological, and neuroimaging studies above the standard history, neurologic, and mental status examinations. We also assessed the sensitivity and specificity of four clinical indicators (i.e., early symptom onset, noninsidious course, focal neurologic signs or symptoms, and gait disturbance) for predicting the diagnostic utility of neuroimaging studies. RESULTS: The largest changes in diagnostic categories between the standard and the comprehensive diagnostic process was a 9% decrease in the diagnosis of Alzheimer's disease, a 6% increase in the diagnosis of mixed dementia (due largely to laboratory studies), and a 4% increase in the diagnosis of vascular dementia (due to neuroimaging). The clinical indicators were 82% sensitive and 50% specific in predicting that neuroimaging studies would change the diagnosis. In six cases, meaningful neuroimaging findings were not associated with any clinical indicator (5% false negatives). In 43 cases, neuroimaging provided no significant clinical findings despite the presence of an indicator (36% false positives). CONCLUSIONS: In this convenience sample, diagnostic accuracy was improved to a comparable degree by laboratory and neuroimaging studies, although at a significant difference in cost. Use of the four clinical indicators would have reduced the frequency of neuroimaging studies by 33% but missed clinically meaningful information in 5%. Although imperfect, the Practice Parameters represent a first step toward improving the cost effectiveness of the dementia work-up.

Aged↗
PubMed1997

Citrate uptake by isolated rat renal brush border membrane vesicles in cadmium-intoxicated rats.

Epidemiological Studies have reported that the formation of renal stones is often observed in workers exposed to cadmium (Cd). Citrate is known to be a protective factor against renal stone formation. We previously reported that direct exposure to high-level cadmium impaired the citrate uptake by the brush border membrane vesicles (BBMV), which may mean that the formation of renal stones from exposure to Cd could be prevented. In the present study, to clarify the mechanism of Cd-induced renal stone formation, the characteristics of BBMV-induced citrate uptake were determined in Cd-intoxicated rats. Cd intoxication was induced by daily subcutaneous injections of CdCl2 at a dose of 2 mg Cd/kg body wt per day for 17 to 20 days. The BBMV were prepared by the divalent cation precipitation method. Citrate uptake was measured by the Millipore rapid membrane filtration technique. The citrate uptake per mg protein was not significantly different between the two groups. The volume of BBMV was significantly reduced (50%) in Cd-intoxicated rats compared with that of control rats. Percentages of the equilibrium value were also significantly inhibited in Cd-intoxicated rats.

Animals↗
PubMed1997

Direct effect of inorganic mercury on citrate uptake by isolated rat renal brush border membrane vesicles.

Occupational exposure to mercury has long been associated with renal proximal injury and an increased incidence of proteinuria, as has such exposure to cadmium. Renal citrate excretion is very important with respect to acid-base balance since the metabolism of citrate generates three bicarbonate ions. In this study, we exposed isolated rat renal brush border membrane vesicles (BBMV) to mercury (Hg2+) and examined their citrate uptake characteristics. BBMV were prepared by the divalent cation precipitation method. Citrate uptake was measured by the Millipore rapid membrane filtration method. The preincubation of BBMV with 0.5 and 2 mM HgCl2 for 1 min significantly inhibited citrate uptake compared with that of BBMV without Hg preincubation. The analysis of the time course of citrate uptake during a 30-min preincubation of BBMV with 0.1 mM Hg2+ also revealed a significant reduction in the uptake compared with that of the control BBMV without preincubation. These findings indicate that the preincubation of BBMV with mercury results in a time- and concentration-dependent inhibition of citrate uptake.

Animals↗
PubMed1997

Ethylene oxide does not extinguish the osteoinductive capacity of demineralized bone. A reappraisal in rats.

We examined the influence of ethylene oxide (EO) and gamma irradiation on the osteoinductive capacity of demineralized bone. Demineralized bone powder prepared from Wistar rats was exposed to EO (55 degrees C or 40 degrees C) or gamma irradiation (25 KGy) or was preserved in ethanol. Sterilely-prepared bones served as controls. The powder was packed in a gelatin capsule and implanted for 6 weeks in muscles of 6-week-old female rats. Exposure of demineralized bone particles to EO 55 degrees C resulted in an almost complete loss of osteoinductivity. Irradiated bones lost about 40% of their osteoinductive capacity, while sterilization with EO at 40 degrees C resulted in only a slight alteration of the osteoinductivity, as assessed by the recovered weight ratio, calcium content, alkaline phosphatase activity measurements and histomorphometry. Ethanol treatment had no influence on the new bone yield when compared to controls. As EO exposure at 40 degrees C is a true sterilization procedure, it can be recommended in a clinical setting for its small effect on osteoinductive capacity as assessed experimentally in rats.

Alkaline Phosphatase↗
PubMed1997

[Alterations of p53 gene in human ovarian tumor].

Using polymerase chain reaction--single strand conformational polymorphisms and EB staining techniques, 43 ovarian tumors were detected in the exons 5-8 of p53 gene. The results showed that alterations of p53 gene were 0/10(0%) in benign, 1/3(33.3%) in borderline, 14/30 (46.6%) in malignant ovarian neoplasms. In our series, the alterations of p53 gene were present in bordline tumor and stage I to stage i.v. cancer. The results suggest that the alterations of p53 gene are closely correlated with initiation of ovarian cancer and may be involved in the pathogenesis of ovarian carcinoma. It may be an early event and play an improtant role in the progression of human ovarian carcinoma.

Adenocarcinoma, Mucinous↗
PubMed1997

[Study on antimutagenic effect of lanthanum carbonate in CA test, UDS test and MN test].

Antimutagenic effect of Lanthanum carbonate [La2 (CO3)3] has been evaluated by means of unscheduled DNA synthesis (UDS) test, chromosomal aberration (CA) test in vitro human embryofibroblast (HEF) and micronucleus (MN) test in mouse bonemarrow polychromatic erythrocyte (PCE) induced by four different mutagens, i.e., short wave ultraviolet (UV), hydrochloric acid nitrogen mustard (NH2HCl), arsenic sodium oxide (NaAsO2) and cyclophosphamide (CP). The results of this study indicated that the antimutagenic effect of La2(CO3)3 was obvious in multiple antimutagenic systems in which mutation was induced by UV, NH2HCl and CP, but the effect of La2(CO3)3 on the decrease of CA frequencies induced by NaAsO2 had no statistical significance.

Animals↗
PubMed1997

[Preliminary application of mRNA differential display technique in the isolation of genes possibly associated with tumor metastasis].

We have previously reported that in vitro treatment with interferons of MA891, a spontaneous mouse mammary tumor capable of metastasizing to the lungs upon subcutaneous inoculation, could modulate its metastatic potential. IFN-gamma increases while IFN-alpha decreases lung metastasis. Identifying the genes differentially expressed in MA891 cells separately treated with IFN-alpha and IFN-gamma. MA891 cells were treated in vitro with 200 U/ml IFN-alpha or IFN-gamma respectively for 48 h. Total RNA was isolated with the single step method of acid guanidinium thiocyanate. After being digested by DNase I, the two RNA samples were differentially displayed with T12MA/T/C/G x 20 arbitrary primer pairs. Most of the RT-PCR were done twice. The differentially expressed cDNA bands were isolated, reampliated and cloned. Ten differentially expressed cDNA bands were identified: T2 alpha, T2 gamma, C4 alpha, T6 alpha, T11 gamma, G15 gamma, T16 gamma, T5 alpha 1, T5 alpha 2, T17 alpha, T15 alpha, T15 gamma, named according to the type of IFN and primer pairs used. The total RNA samples of MA891 cells treated by IFN-alpha and IFN-gamma were differentially displayed with T12MA/T/C/G x 20 arbitrary primer pairs. Theoretically they can cover 95% mRNAs. It is anticipated that one or more of the ten cDNA clones may be related to the metastatic potential of MA891 cells.

Animals↗
PubMed1997

[DNA polymorphisms of apolipoprotein A I gene in Chinese endogenous hypertriglyceridemics].

The restriction fragment length polymorphisms (RFLPs) of apolipoprotein(apo) A I gene were studied using polymerase chain reaction (PCR) in 69 endogenous hypertriglyceridemics (HTG) and 74 healthy subjects from a population of Chinese Han nationality in Chengdu area. The loci studied included Msp 1 within intron 3 of the apo A I gene; Xmn I, 5' to the apo A I gene; and Pst I, 3' to the apo A I gene. The results showed that both in HTG group and control group M1, X1 and P1 alleles were the major alleles and homozyous M1M1, X1X1 and P1P1 genotypes were the most frequent ones. The frequencies of rare M2 and X2 alleles in Chinese were significantly higher than those in European Caucasians (0.293 vs 0.111, P < 0.0006, 0.286 vs 0.130, P < 0.004), but no differences were found in the frequency of rare P2 allele (0.071 vs 0.046, P > 0.05). The frequency of rare M2 tended to increase in the HTG group when compared with the control group (0.353 vs 0.275, P > 0.05). Both in the HTG group and control group, subjects with genotype M2M2 had a higher serum mean concentration of TC, apo C II and higher serum TG/HDL-C ratio compared with the subjects with the genotypes M1M1 and M1M2 (P = 0.05, P < 0.03, P < 0.04), and the serum TG, apo C II and apo E levels had a tendency to increase. The subjects with the genotypes P1P2 and P2P2 had a higher serum apo A II levels compared with the subjects with the genotype P1P1 (P < 0.04). The data show that the only Msp I RFLP within the intron 3 of apo A I gene is associated with endogenous hypertriglyceridemia to some extent in Chinese population.

Adult↗
PubMed1997

[Studies on the essential oil constituents of the stem bark of Magnolia obovata].

For the extensive studies of the chemical constituents of Magnollis obovata, the essential oil from Magnolia obovata was obtained by steam distillation. The chemical components of the oil were examined by means of capillary gas chromatography and gas chromatography-mass spectrometry. 29 of the 75 separated constituents were identified. The content of each component identified was determined by area normalization method, which showed the content of 9 compounds was higher than 1%.

Gas Chromatography-Mass Spectrometry↗
PubMed1997

[Clinical significance of galactose oxidase-Schiff reaction in the detection of carcinoma and precancerous lesions of large intestine].

OBJECTIVE: To study the clinical value of galactose oxidase-Schiff (GO-S) reaction to test carcinoma and precancerous lesions of large intestine. METHODS: 127 patients who had symptoms and signs of digestive tract diseases and 10 normal controls were studied, with their samples of rectum mucus smears stained. The histological sections of 73 cases of carcinoma and precancerous lesions of large intestine were stained with GO-S reaction. RESULTS: The positive rates of GO-S reaction in carcinoma and precancerous lesions of large intestine were over 80%. The specificity and sensitivity of GO-S reaction to detect carcinoma and precancerous lesions of large intestine were 98% and 86%, respectively. The positive predictive value was 90%. CONCLUSION: GO-S reaction, being satisfactory and sensitive marker of carcinoma and precancerous lesions of large intestine, can be used for screening and general survey of these lesions.

Adolescent↗
PubMed1997

[Apoptosis of nasopharyngeal carcinoma cells induced by topoisomerase I inhibitor].

PURPOSE: To determine if the topoisomerase I inhibitor Camptothecin (CPT) can induce apoptosis in vitro in a human nasopharyngeal carcinoma (NPC) cell line with low differentiation (CNE-2Z). METHODS: The light microscopy, flow cytometry and agarose gel electrophoresis were used to examine the morphological changes, cell cycle distribution, hypodiploid cells and DNA fragmentation. RESULTS: After exposure to CPT for a certain period, CNE-2Z cells underwent obvious morphological changes with characteristics of apoptosis such as decrease in cell volumes condensation of chromatin and the formation of apoptotic bodies. Flow cytometry (FCM) test showed that when CNE-2Z cells were treated with 2-10 mumol/L CPT for 12 or 24 hours, hypodiploid cells accounted for 30% and 50% respectively. Cell cycle analysis by FCM revealed that changes in CNE-2Z cell cycle distribution were apparent 24 hours after treatment with various doses of CPT, showing no obvious dose-dependent relationship. Compared with controls, the percentage of cells in G2/M phase decreased markedly while those in G1 and S phases increased moderately. CONCLUSION: The results demonstrated that DNA topoisomerase I inhibitor Camptothecin can induce apoptosis in CNE-2Z cells in vitro.

Antineoplastic Agents, Phytogenic↗
PubMed1997

[Partial laryngectomy for treatment of the laryngeal cancer of T3 and T4 categories].

Between 1980 to 1993, 31 patients (27 men and 4 women) with squamous cell carcinoma of the larynx with T3,4 categories undergone partial largngectomy. The 3- and 5-year survival rates were 64.5% and 59.3% respectively. The extubation rate was 71.0% and recurrence rate 19.4%. After opration, the 31 patients have acquired speech function of different degrees and the swallow function returned to normal. The authors concluded that in selected patients with T3,4 laryngeal cancers, partial laryngectomy is feasible and acceptable, which preserves all laryngeal functions and improves life quality.

Adult↗
PubMed1997

[Transsphenoidal microscopic removal of invading pituitary adenoma].

Eighteen cases of invading pituitary adenoma were removed via the approach of transsphenoidal microscopical operation. Among them 4 cases had insulin dependent diabetes. The pituitary adenoma were near-totally removed in 15 cases, partially removed in 3, and 10 cases were treated by supplement radiotherapy postoperatively and 5 cases by oral bromocriptin postoperatively. The average time of follow-up was 3.8 years. There were 3 cases(16.6%) had postoperative recurrence of the tumor which were finally cured by transfrontal craniotomy. The feasibility of the transsphenoidal microscopic approach for the invading pituitaty adenoma was discussed.

Adenoma↗