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Biomedical subjects

Y Yuan

Publications and source records attributed to Y Yuan.

At least 217 records · Page 12Linked to original sources
PubMed1996

Stationary phase-associated protein expression in Mycobacterium tuberculosis: function of the mycobacterial alpha-crystallin homolog.

The majority of active tuberculosis cases arise as a result of reactivation of latent organisms which are quiescent within the host. The ability of mycobacteria to survive extended periods without active replication is a complex process whose details await elucidation. We used two-dimensional gel electrophoresis to examine both steady-state protein composition and time-dependent protein synthetic profiles in aging cultures of virulent Mycobacterium tuberculosis. At least seven proteins were maximally synthesized 1 to 2 weeks following the end of log-phase growth. One of these proteins accumulated to become a predominant stationary-phase protein. N-terminal amino acid sequencing and immunoreactivity identified this protein as the 16-kDa alpha-crystallin-like small heat shock protein. The gene for this protein was shown to be limited to the slowly growing M. tuberculosis complex of organisms as assessed by Southern blotting. Overexpression of this protein in wild-type M. tuberculosis resulted in a slower decline in viability following the end of log-phase growth. Accumulation of this protein was observed in log-phase cultures following a shift to oxygen-limiting conditions but not by other external stimuli. The protein was purified to homogeneity from overexpressing M. smegmatis in two steps and shown to have a significant ability to suppress the thermal denaturation of alcohol dehydrogenase. Collectively, these results suggest that the mycobacterial alpha-crystallin protein may play a role in enhancing long-term protein stability and therefore long-term survival of M. tuberculosis.

Antigens, Bacterial↗
PubMed1996

Acidic and basic FGFs dilate arterioles of skeletal muscle through a NO-dependent mechanism.

Fibroblast growth factors (FGFs) have been known to be potent stimulators of vascular endothelial cell proliferation and angiogenesis. Recent experimental evidence indicates that basic FGF (bFGF) is also involved in modulation of arterial pressure. In this study, we investigated the effects of acidic FGF (aFGF) and bFGF on muscle microcirculation using isolated arterioles and intact cremaster muscles of the at. In isolated microvessels, aFGF and bFGF (10(-12)-10(-8) M) significantly increased arteriolar diameter in a dose-dependent and time-dependent manner. This effect was abolished during inhibition of nitric oxide synthesis by NG-monomethyl-L-arginine (L-NMMA, 10(-4) M) but was not affected by indomethacin (10(-4) M), an inhibitor of the cyclooxygenase pathway of arachidonic acid metabolism. The vasodilation induced by FGFs was not observed in endothelium-denuded vessels. Furthermore, we studied microvascular hemodynamics in response to the growth factors in the cremaster muscle using intravital microscopy. Both aFGF and bFGF dilated arterioles of the intact cremaster muscle in a pattern similar to that observed in the isolated arterioles. At a concentration of 10(-10) M, aFGF caused a 19% increase in vessel diameter and 56% increase in blood flow. Administration of L-NMMA blocked by FGF-induced vasodilation and hyperemia. These results suggest that FGFs modulate blood flow in the skeletal muscle by acting on the endothelium of arterioles. The signaling mechanism of FGF-induced vasodilation involves the synthesis of nitric oxide by arteriolar endothelium.

Animals↗
PubMed1996

VEGF induces NO-dependent hyperpermeability in coronary venules.

The purpose of this study was to investigate the direct effect of vascular endothelial growth factor (VEGF) on microvascular permeability and its signaling mechanisms. The apparent permeability coefficient to albumin was measured in isolated coronary venules. Topical application of VEGF dose-dependently and transiently increased albumin permeability by two- to threefold. Inhibition of nitric oxide (NO) synthesis with NG-monomethyl-L-arginine abolished VEGF-induced venular hyperpermeability. Furthermore, because NO exerts vasoactive effects through stimulation of guanylate cyclase (GC) and the subsequent production of guanosine 3',5'-cyclic monophosphate (cGMP), we examined the role of GC and cGMP-dependent protein kinase (PKG) in the mediation of VEGF's action. The permeability response to VEGF was measured in the presence of the selective GC inhibitor 1H-[1,2,4]oxadiazolo[4,3-alpha]quinoxalin-1-one and the specific PKG inhibitor KT-5823. Both inhibitors reduced basal permeability and prevented the hyperpermeability response to VEGF. Therefore, we suggest that VEGF modulates microvascular permeability via a signaling cascade involving NO synthesis, GC stimulation, and PKG activation.

Alkaloids↗
PubMed1996

Non-receptor protein tyrosine kinases and phosphatases in human platelets.

There is now a large and rapidly growing body of information on the different types of non-receptor tyrosine kinases and phosphatases present within platelets. These enzymes appear to play a critical role in co-ordinating, integrating and amplifying signals from multiple cell surface receptors. Despite considerable progress in this area of research over the last decade, a coherent understanding of how these enzymes fit into the complex communication networks of platelets remains elusive. The challenge ahead will be to define the molecular interactions and hierarchies between tyrosine kinases, phosphatases and other platelet signalling enzymes, and to pinpoint the key phosphorylation reactions required for the induction of specific platelet responses.

Animals↗
PubMed1996

[Measurement of maximal inspiratory flow and forced inspiratory capacity and its clinical application].

The methods of measuring the maximal inspiratory flow (V(imax)) and the forced inspiratory capacity (FIC) via forced inspiratory capacity-time curve (FIC-t curve) were investigated. Both V(imax) and FIC were measured in 35 normal subjects and 89 patients with chronic obstructive pulmonary disease (COPD). The maximal inspiratory pressure (MIP) was measured simultaneously at function residual capacity(FRC) level by modified Black Method. The results showed that there is a linear relationship between MIP and V(imax) or FIC in both normal subjects and patients with COPD. Normal subjects had a mean V(imax) and FIC much higher than those of patients with COPD. The values of V(imax) and FIC in patients were also, significantly correlated to the severity of COPD. So we suggest that both V(imax) and FIC be used as clinical indices to reflect inspiratory muscles strength.

Adult↗
PubMed1996

[Study on the mutagenicity of salted pork from high risk area of stomach cancer and its relation to pathological changes of gastric mucosa].

To investigate the relations between salted pork (SP) from Zhuanghe (a high risk area of stomach cancer in northeast China) and stomach cancer three studies had been done, including the mutagenicity of SP, the effect of SP on the gastric mucosa of residents in Zhuanghe area who had consumed SP for 10-30 years and the mucosal lesions of dogs taking SP. The results showed that the extract of SP was a strong mutagen in strain TA98 and led to increased micro-nuclei rate (MNR) and micro-nuclei cell rate (MNCR) of V79 cell at a dose range of 20-80 mumol/ml. There were dose-effect relations between SP and MNR, MNCR. The results also indicated that pathological changes of gastric mucosa of residents who consumed SP had remarkable difference from those of the control group. In people who had consumed SP for 10 years, mucosal lesions including necrosis and erosion were seen; for those consumed SP for 10+(-)20 years, there were hyperplasia and dysplasia and those for 20+(-)30 years different degrees of dysplasia and even malignant change could be observed. The research also found that SP had damaging effect on gastric mucosa in dogs taking SP. The mucosal lesions became more severe with time of feeding SP. The conclusion is that SP is a strong mutagen, long-term exposure to SP may result in repeated gastric mucosal damage and repair, and finally in severe dysplasia and malignancy.

Animals↗
PubMed1996

[A study of treatment modalities for nonresectable primary liver cancer].

This paper reports the results of multimodality treatment in 200 patients with nonresectable primary liver carcinoma (PLC) from April 1964 to July 1993. PLC was verified histologically in all cases. They were divided into two groups according to the methods of treatment. In group 1, 115 cases received anticancer agents by hepatic artery infusion (HAI). The 1- and 2-year survival rate was 10.4% and 1.7%, respectively and only one patient survived 65 months. In group 2, 85 cases received multimodality treatments by various combinations of hepatic artery chemoembolization (HACE), hepatic artery ligation (HAL), microwave coagulation (MIC) of tumor and ethanol injection into tumor (EIT). The 1-, 2-, 3- and 5-year survival rate was 34.1%, 21.2%, 12.0% and 6.7%, respectively. Five patients had been alive for 41 to 63 months and second-stage hepatic resection performed in another 6 patients. The results suggest that multimodality treatment is an effective approach to improve the long-term survival of patients with nonresectable PLC.

Adult↗
PubMed1996

[The changes of vasoactive intestinal peptide somatostatin and pancreatic polypeptide in blood and CSF of acute cerebral infarction patients and the effect of acupuncture on them].

VIP, SS and PP which exist in gastrointestinal tract and CNS might be to play an important role in nervous system as neurotransmitters of neuromediaters. There have been a few of reports about their changes in plasma and CSF in ICVD. The effects of acupuncture, which was used in treatment of ICVD with good efficiency, on VIP, SS and PP have not been known. For researching their changes in ICVD and effects of electro-acupuncture on them, and finding the mechanism of acupuncture in treatment of ICVD, the study was performed. The levels of VIP, SS and PP in 64 patients with acute cerebral infarction were determined. The points of acupuncture were Quchi (LI 12), Waiguan (SJ 5), Huantiao (BG 30), and Zusanli (ST 36). The routine treatment included dextran, nicotinic acid, aspirin, dipyridamole and radix salviae miltiorrhizae composita. The CSF and blood were taken before the begining of treatments and after a course of treatment. The level of VIP, SS and PP were measured by radiommunoassay. Results showed the level of CSF VIP in the patients was significantly lower as compared with controls. The level of plasma SS in the patients was lower, but the difference was not significant as compared with controls, and level of plasma PP in the patients was significantly increased when it was compared with controls. After electro-acupuncture treatment, in patients with good efficiency, CSF VIP recovered to normal level and the levels of plasma and CSF SS were significantly increased, while the level of plasma PP had no significant change. The results suggest that acupuncture might regulate the disturbances of metabolism of VIP and SS in CNS.

Acupuncture Points↗
PubMed1996

[A study on plasma non-species specific antibody in employees working in a automobile engine testing workshop].

To investigate the existence of the non-species specific antibody in plasma of the employees working in an automobile engine testing workshop, and to use it as a scanning marker of various hazards, the heat-stress protein antigen method and western blot technique were used. This study showed that employees working in the automoblile engine testing workshop were affected by various hazards, such as noise, toxic chemicals (carbon monoxide, lead fume, benzene, and so on), and there existed non-species specific antibodies against protein 103,900 and 54,200 of rat liver in their plasma, which were postulated as the specific products produced by exposure to occupational hazards, such as noise, carbon monoxide, et al.

Adult↗
PubMed1996

[Cetirizine improves the resistance of airway and pulmonary function in patients with asthma].

The objective of this study was to investigate the possible anti-asthma role of Cetirizine. Forty asthmatics were randomly divided into two groups. The experimental group had 30 patients. Among them were 10 patients with simple asthma, 5 patients complicated by mild emphysema, 6 patients complicated by moderate emphysema and 9 patients complicated by severe emphysema. Vit-C (control) group had 10 cases, including 2 cases of simple asthma, 6 cases complicated by mild emphysema and 2 cases complicated by moderate emphysema. All patients had a single oral dose of 5 mg Cetirizine or 0.1 g Vit-C blindly. Before and 0.5, 1 hour after their medicines, the resistance of airway (Raw), sGaw and MEFV were examined in all patients on 6200 Plethysmograph. The measured values showed a significant improvement of Raw and sGaw after administration of Cetirizine. In half an hour after Cetirizine, the Raw decreased by 20.408%, and sGaw increased by 28.249%. In one hour after Cetirizine, Raw further decreased by 24.34% and sGaw increased by 41.153% (P < 0.001). The FVC in MEFV increased by 4.96% (P < 0.02) in one hour after Cetirizine, but other parameters in MEFV curve (PEF, FEV1, MMEF) had no significant changes. All parameters in control group had no significant changes (P > 0.05). The results indicate that Cetirizine could decrease Raw in asthmatics, improve their lung ventilatory function. Cetirizine is a new H-receptor antagonist usually used as anti-inflammatory and allergy suppression medication. It is shown that Cetirizine is a promising anti-asthma agent in treating bronchial asthma.

Adult↗
PubMed1996

[Diagnostic value of exercise diffusion capacity test on diffuse pulmonary fibrosis].

Diffusion capacity for carbon monoxide of the lung (DLCO) before-and-after exercise test and 5 routine pulmonary function tests were conducted in 16 patients with diffuse pulmonary fibrosis (DPF), 19 patients with interstitial pneumonia (IP), 17 patients with COPD, and 22 normal subjects. The data showed: in normal subjects the DLCO after exercise increased significantly compared with before (P < 0.001). But in DPF group the DLCO before exercise was below the normal range, and it went down further after exercise, the decreasing rate being 17.95% (P < 0.001). The DLCO in IP and COPD groups did not significantly change before and after the exercise. Two cases of interstitial pneumonia, who had a reduced DLCO after exercise, were followed up for 0.5-1.0 year, and both patients developed into DPF by that time. The results suggest that the DLCO measure before and after exercise test may have important value for DPF diagnosis, and a reduced DLCO after exercise test in IP patients may warn the development from IP into DPF.

Adult↗
PubMed1996

[Value of measuring resistance of airway for diagnosis of asthma].

Resistance of airway (Raw), sGaw and Maximal expiratory flowvolume curve (MEFV) were measured in 35 normal subject, 43 patients with remission asthma and 100 patients with remission chronic bronchitis (some complicated by obstructive emphysema). The measured values showed that in simple asthma Raw was significantly higher than that in normal subject and in patients with chronic obstructive bronchitis (COB), but MEFV was in normal range. In chronic bronchitis the value of Raw was higher than that in normal subject, but lower than that in asthma (0.05 > P > 0.02); however the FEV1, MMEF, V75 in the curve of MEFV were significantly decreased at the stage of COB, with the most remarkable decrease in MMEF. The results suggest that Raw is a sentitive test for diagnosis of simple asthma, in addition to MEFV measurement; it may be helpful for differential diagnosis of simple asthma and COB and may has potential value for clinical practice.

Adult↗
PubMed1996

[Clinical application of enzyme linked immunosorbent assay in testing antibodies against cochlear tissues and nerve tissues].

Fifty-two patients with idiopathic sensorineural hearing loss and 20 controls were examined by enzyme linked immunosorbent assay (ELISA) with cow cochlear antigen (CCAg) and cow cochlear nerve antigen (CCNAg). The antibody level against CCAg was 0.3811 +/- 0.743 in the control group and 0.9241 +/- 0.2408 in the experimental group (OD, x +/- 2s, P < 0.01). Compared with the x +/- 2s antibody level of the control group, the antibody level of 24 of 52 (46%) patients of the experimental group was positive. The antibody level against CCNAg was 0.2254 +/- 0.382 in the control group and 0.2331 +/- 0.656 in the experimental group (P > 0.05). Compared with the x +/- 2s antibody level of the control group, the antibody level of 6 of 52 patients (11.5%) of the experimental group was elevated. It is suggested that ELISA method can be used as quantitatively in the diagnosis of autoimmune inner ear diseases. Moreover, the serum antibodies against CCNAg detected in this experiment suggest that some of autoimmune inner diseases might be retrocochlear.

Adolescent↗
PubMed1995

An essential role for lysophosphatidylcholine in the inhibition of platelet aggregation by secretory phospholipase A2.

The release of secretory phospholipase A2 (sPLA2) into the mammalian circulation may contribute to the development of hemorrhagic and inflammatory diseases. sPLA2 has previously been shown to alter the behavior of platelets, leukocytes, and endothelial cells, although the molecular basis for these cellular effects has not been established. Our studies indicate that the inhibition of platelet aggregation by snake, bee venom, and pancreatic sPLA2 is dependent on a plasma cofactor. This cofactor resides within the lipoprotein fraction of plasma, with 54%, 31%, and 11% of the activity present in the high-density lipoprotein (HDL), low-density lipoprotein (LDL), and very low density lipoprotein (VLDL) fractions, respectively. Delipidation of HDL and LDL was associated with the complete loss of platelet-inhibitory activity. Incubation of purified sPLA2 with the HDL fraction of plasma resulted in the time-dependent generation of lysophosphatidylcholine (lysoPC). The formation of lysoPC correlated with the inhibition of platelet aggregation. Purified lysoPC (10 to 100 micrograms/mL) inhibited platelet aggregation and dense granule release induced by thrombin (0.05 U/mL), collagen (1 micrograms/mL), ionophore A23187 (2 mumol/L), ADP (12.5 mumol/L), and adrenaline (3.2 mumol/L). The inhibition of platelet aggregation by lysoPC was dose-dependent and correlated with decreased fibrinogen binding to glycoprotein IIb-IIIa. Our studies indicate that the enzymatic generation of lysoPC from plasma lipoproteins is essential for the sPLA2-mediated inhibition of platelet activation in the presence of albumin. These results raise the possibility that the toxic effects of circulating sPLA2 may be due in part to the generation of the bioactive lysophospholipid, lysoPC.

Animals↗
PubMed1995

The biosynthesis of cyclopropanated mycolic acids in Mycobacterium tuberculosis. Identification and functional analysis of CMAS-2.

The major mycolic acid produced by Mycobacterium tuberculosis contains two cis-cyclopropanes in the meromycolate chain. The gene whose product cyclopropanates the proximal double bond was cloned by homology to a putative cyclopropane synthase identified from the Mycobacterium leprae genome sequencing project. This gene, named cma2, was sequenced and found to be 52% identical to cma1 (which cyclopropanates the distal double bond) and 73% identical to the gene from M. leprae. Both cma genes were found to be restricted in distribution to pathogenic species of mycobacteria. Expression of cma2 in Mycobacterium smegmatis resulted in the cyclopropanation of the proximal double bond in the alpha 1 series of mycolic acids. Coexpression of both cyclopropane synthases resulted in cyclopropanation of both centers, producing a molecule structurally similar to the M. tuberculosis alpha-dicyclopropyl mycolates. Differential scanning calorimetry of purified cell walls and mycolic acids demonstrated that cyclopropanation of the proximal position raised the observed transition temperature by 3 degrees C. These results suggest that cyclopropanation contributes to the structural integrity of the cell wall complex.

Amino Acid Sequence↗
PubMed1995

Disparate responses to oxidative stress in saprophytic and pathogenic mycobacteria.

To persist in macrophages and in granulomatous caseous lesions, pathogenic mycobacteria must be equipped to withstand the action of toxic oxygen metabolites. In Gram-negative bacteria, the OxyR protein is a critical component of the oxidative stress response. OxyR is both a sensor of reactive oxygen species and a transcriptional activator, inducing expression of detoxifying enzymes such as catalase/hydroperoxidase and alkyl hydroperoxidase. We have characterized the responses of various mycobacteria to hydrogen peroxide both phenotypically and at the levels of gene and protein expression. Only the saprophytic Mycobacterium smegmatis induced a protective oxidative stress response analogous to the OxyR response of Gram-negative bacteria. Under similar conditions, the pathogenic mycobacteria exhibited a limited, nonprotective response, which in the case of Mycobacterium tuberculosis was restricted to induction of a single protein, KatG. We have also isolated DNA sequences homologous to oxyR and ahpC from M. tuberculosis and Mycobacterium avium. While the M. avium oxyR appears intact, the oxyR homologue of M. tuberculosis contains numerous deletions and frameshifts and is probably nonfunctional. Apparently the response of pathogenic mycobacteria to oxidative stress differs significantly from the inducible OxyR response of other bacteria.

Amino Acid Sequence↗
PubMed1995

Identification of a gene involved in the biosynthesis of cyclopropanated mycolic acids in Mycobacterium tuberculosis.

Mycolic acids represent a major constituent of the mycobacterial cell wall complex, which provides the first line of defense against potentially lethal environmental conditions. Slow-growing pathogenic mycobacteria such as Mycobacterium tuberculosis modify their mycolic acids by cyclopropanation, whereas fast-growing saprophytic species such as Mycobacterium smegmatis do not, suggesting that this modification may be associated with an increase in oxidative stress experienced by the slow-growing species. We have demonstrated the transformation of the distal cis double bond in the major mycolic acid of M. smegmatis to a cis-cyclopropane ring upon introduction of cosmid DNA from M. tuberculosis. This activity was localized to a single gene (cma1) encoding a protein that was 34% identical to the cyclopropane fatty acid synthase from Escherichia coli. Adjacent regions of the DNA sequence encode open reading frames that display homology to other fatty acid biosynthetic enzymes, indicating that some of the genes required for mycolic acid biosynthesis may be clustered in this region. M. smegmatis overexpressing the cma1 gene product significantly resist killing by hydrogen peroxide, suggesting that this modification may be an important adaptation of slow-growing mycobacteria to oxidative stress.

Amino Acid Sequence↗