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Biomedical subjects

Y Yang

Publications and source records attributed to Y Yang.

At least 1,297 records · Page 72Linked to original sources
PubMed1993

Curative radiofrequency catheter ablation for permanent junctional reciprocating tachycardia.

Two patients with the permanent form of junctional reciprocating tachycardia successfully treated with the radiofrequency catheter ablation technique are described. In both patients a reentrant tachycardia utilizing a concealed slow conducting posterior septal accessory pathway for retrograde conduction was demonstrated. Radiofrequency current was delivered below the coronary sinus orifice. The procedure resulted in ablation of the accessory pathway conduction in both patients. During the follow-up, both patients remained free from tachycardia on no medication. This report demonstrates that the arrhythmogenic substrate of the permanent junctional reciprocating tachycardia can be easily suppressed by means of the radiofrequency catheter technique.

Adult↗
PubMed1993

Kinetic interactions of tazobactam with beta-lactamases from all major structural classes.

Tazobactam was shown to be a potent inhibitor of group 1, 2a, 2b, and 2b' beta-lactamases. Extended kinetic studies with class A and C serine beta-lactamases showed that the PC1, TEM-2, and P99 enzymes all were reversibly inhibited prior to inactivation of the enzymes. The CcrA metallo-beta-lactamase was less well inhibited, with a 50% inhibitory concentration at least 3 orders of magnitude less favorable than those for most serine beta-lactamases. The numbers of hydrolytic turnovers of tazobactam before inactivation were 2 for PC1, 125 for TEM-2, 50 for P99, and 4,000 for the CcrA enzyme. In spectral studies, transient intermediates were formed after reaction of tazobactam with the PC1, TEM-2, and CcrA beta-lactamases, corresponding to enzyme-associated intermediates responsible for hydrolysis of tazobactam. Chromophores absorbing at 270 nm (CcrA) and 288 nm (TEM-2 and PC1) were observed for these reaction intermediates. The P99 cephalosporinase formed a stable complex with a UV maximum at 295 nm. Incubation of tazobactam with all of the enzymes resulted in accumulation of a tazobactam reaction product with a short-wavelength absorbance. This product has characteristics similar to those of the major eucaryotic metabolite of tazobactam. Possible reaction mechanisms are presented to explain the findings. In conclusion, both serine-based and metallo-beta-lactamases were irreversibly inactivated by tazobactam following an initial transient inhibition phase.

Bacterial Proteins↗
PubMed1993

Cellular internalization in the absence of invasin expression is promoted by the Yersinia pseudotuberculosis yadA product.

The Yersinia pseudotuberculosis invasin protein is able to promote bacterial penetration into mammalian cells. Insertion mutations that eliminate production of this protein show residual internalization that is dependent on the presence of the Yersinia virulence plasmid. An enrichment procedure was used to isolate molecular clones containing regions of the virulence plasmid that confer this low-level uptake on Y. pseudotuberculosis inv mutants. All of the Y. pseudotuberculosis strains isolated from this procedure harbored plasmids containing a region encompassing the yadA gene, which encodes a previously identified adhesin associated with attachment to extracellular matrix proteins. All of the mutations isolated that affected internalization of one of the strains that survived the enrichment disrupted the yadA open reading frame. Furthermore, a strain that contained yadA sequences and no other region of the virulence plasmid was able to promote internalization of a Y. pseudotuberculosis inv mutant. Consistent with these results, an intact virulence plasmid containing an insertion mutation in yadA was as defective as a plasmid-cured strain at promoting uptake of Y. pseudotuberculosis inv mutants. These results indicate that the product of the yadA gene is responsible for the plasmid-dependent entry observed in Y. pseudotuberculosis inv mutants.

Adhesins, Bacterial↗
PubMed1993

[The effects of salvia miltiorrhiza, polysaccharide sulphate, dextran 40 and mannitol on the viscoelasticity properties of red blood cell suspension].

In vitro, the effects of Dextran 40(DX40), mannitol, salvia miltiorrhiza and polysaccharide Sulphate (PSS) on the viscoelasticity properties of red cell suspensions were studied. The results demonstrated that when the concentration of the drugs increased, mannitol increased eta 5 x 96, eta 51 x 2, eta', eta" and G', and DX 40 increased the values of eta' eta" and G', but it had no obvious effect on eta 5 x 96 and eta 51 x 2; salvia miltiorrhiza and PSS had no obvious effect on eta 5 x 96, eta 51 x 2, eta', eta'' and G'. However, the average values of eta', eta'' and G' of Salvia miltiorrhiza and PSS groups were lower than those of DX 40 and Mannitol groups. Clinically, these four drugs in treatment doses might improve viscoelasticity properties of whole blood. For treating the ischemic cerebral vascular diseases and hyperviscosity syndromes, Salvia miltiorrhiza and PSS could be infused faster, but DX40 and mannitol should be infused slowly.

Blood Viscosity↗
PubMed1993

[The role of hemorheologic disturbance in experimental acute pancreatitis].

The role of hemorheologic disturbance in experimental acute pancreatitis was studied in Wistar male rats. It was found that pancreatic duct obstruction with secretin stimulation could induce acute interstitial pancreatitis (AIP), but when high molecular dextran intravenous injection being added, acute necrotizing pancreatitis (ANP) was induced. The authors suggest that the high molecular dextran can increase blood viscosity, aggregation of erythrocytes and decrease erythrocyte deformability, which results in pancreatic microcirculatory disturbances and promotes progressive pancreatic necrosis. Hemorheologic disturbance is one of the key factors in the pathogenesis of ANP.

Acute Disease↗
PubMed1993

Effect of Astragalus membranaceus on electrophysiological activities of acute experimental Coxsackie B-3 viral myocarditis in mice.

A murine model for observing the effect of Astragalus membranaceus (AM) on electrophysiological action of the right ventricular myocardium was developed in 4-week-old male BALB/c mice infected with coxsackie B-3 virus (CB3V). The conventional microelectrode technique and a real-time data processor system were used. The survival rate in AM-treated mice was much higher and the percentage of abnormal action potential was much lower than those in infected control mice (P < 0.05, P < 0.01, respectively). Some abnormal electrophysiological parameters, such as APA, OS and Vmax, in infected myocardium were found to be improved by AM treatment. The results suggest that AM may be valuable in the prevention and treatment of acute viral myocarditis involving coxsackie B viruses.

Action Potentials↗
PubMed1993

[Application of RFLP analysis to Duchenne and Becker muscular dystrophy in Shandong Province. I. Carrier detections in females at risk].

There were eight intragenic and two flanking bridge DNA polymorphic markers used in the RFLP analysis in 21 Duchenne and Becker muscular dystrophy selected from nine different districts in Shandong Province. A total number of 173 individuals of the families were accepted for gene tracking and carrier detection, as well as prenatal diagnosis. Based on the frequency of the probe polymorphism tested in our study of 53 unrelated individuals, one to three high polymorphic probes were sequentially used and all families presented the informativeness in RFLP analysis. Some more introgenio probes were supplied for assessment of mutated sites and carrier status with the help of gene phases, if recombinations were found. Our results presented a ratio of 85.45% of carrier detection at risk females with 95% or more reliability, including 17 carriers and 30 non-carriers. It was not able to ascertain the carrier status of 8 females because of DNA absence from key family members. Finally, we proposed a diagnostic procedure for the RFLP analysis to DMD/BMD families.

Female↗
PubMed1993

Words or concepts: the features of indexing units and their optimal use in information retrieval.

Words or Concepts, which are a better choice for indexing the contents of documents? The answer depends on what method is used for retrieval. This paper studies the effects of using canonical concepts versus document words in different retrieval systems with a testing collection of MEDLINE documents. In our tests, for a retrieval system which does not use any human knowledge, using words yielded better retrieval results, while using concepts suffered from a vocabulary difference between canonical expressions of concepts and non-canonical words in queries or documents. For a system which depends on the UMLS synonym set for a mapping from queries or documents to canonical concepts, the retrieval results were slightly better than the case of not using the synonyms, but still worse than the systems using words. For the systems which automatically "learn" empirical connections between words and concepts from examples in the testing collection, the vocabulary problem was effectively solved, and the results of using concepts were competitive or better, compared to those using words.

Abstracting and Indexing↗
PubMed1993

The hypoxic moderation of systemic hypertension in spontaneously hypertensive rats.

The mechanism of hypoxic moderation of systemic systolic blood pressure was investigated in spontaneously hypertensive rats (SHR). Male SHR rats were divided into hypoxic (H, 5000 m for 15 d) and normoxic (N) groups. The systemic blood pressure of SHR-H (24.9 +/- 1.2 kPa) was found to be 3 kPa lower than that in SHR-N (27.0 +/- 1.3 kPa) (P < 0.05). This protective effect may have been related to the adaptive changes in vascular reactivity which manifested as an increase in the relaxation response of the aorta to ACh (P < 0.01) and a drop in its contraction in response to 5-HT (P < 0.05) following hypoxic exposure. The hypoxic moderating effect against the development of systemic hypertension may have also been related to the increased plasma levels of ANP observed.

Altitude↗
PubMed1993

[Determination of trace elements in several hemostatic medicinal plants and their boiling water extracts].

The experimental results indicate that the amounts of Cu, Zn, Fe and Mn in Rubia cordifolia and Agrimonia pilosa var. japonica are very small in boiling water extracts (only 6%). But after digestion they may rise to 30%. It was found that the amounts of four trace elements decreased with the increase of extracting time, but the ratios of Mn/Zn and Zn/Cu were almost the same.

Copper↗
PubMed1993

[Capillary blood viscosimeter of the microcomputer].

On the basis of specific property of non-Newtonian fluid (blood) we have worked out the formula of capillary blood viscosimeter:sheat stress tau alpha = alpha rho gh/2L shear rate f (tau alpha) = 1/pi alpha 3 [3q + h(dq/dh)] and designed and produced the prototype. Repetition experiments have indicated that the property of the instrument is stable, and a comparison of the prototype with the cone and plate viscosimeter has demonstrated the reliability of the measurements.

Blood Viscosity↗
PubMed1993

[Study on determination of gentamycin by enhanced chemiluminescent immunoassay].

Gentamycin was determined by solid antigen competition inhibition method of chemiluminescet immunoassay, in which luminol-(p-hydroxydiphenyl)-H2O2 was used a the chemiluminescence system and p-hydroxydiphenyl as the chemiluminescent enhancer. Solid antigen was synthesized by a method in which gentamycin was immobilized covalently on microcrystalline cellulose previously activated by 1,1'-carbonyldiimidazole. The rabbit anti-gentamycin IgG and the HRP-donkey anti-rabbit IgG were used as the first antibody and labelled second antibody, respectively. The linear range of the gentamycin (with blank serum) was 0.03-1 micrograms/tube and the correlation coefficient of the log-log regression equation [r[ was 0.981 +/- 0.016 with a limit of detection 3.3-11.4 ng/tube and the recovery of gentamycin 88.2 +/- 4.5%.

Biphenyl Compounds↗
PubMed1993

[Analysis of proteins and antigens in nine strains of Toxoplasma gondii by means of SDS-PAGE and immunoblotting].

The proteins and antigens of nine strains of Toxoplasma gondii were analyzed by SDS-PAGE and immunoblotting. These strains including RH strain, Zs-2 strain, CN strain and SH1, SH2, SH3, SH4, SH5, SH8 strains, were obtained from other laboratories or isolated from deformity fetus in our laboratory. SDS-PAGE analysis revealed that these strains were very close in the major bands of proteins and differences were observed only in part. There were common components in antigens of all strains using IgG antibody prepared from high-titre rabbit antisera raised against RH strain of Toxoplasma.

Animals↗
PubMed1993

Microvascular retinopathy in the Zucker diabetic fatty rat.

PURPOSE: To determine if quantifiable morphometric signs of retinopathy occur in the Zucker diabetic fatty rat (ZDF/Gmi-fa, formerly designated ZDF/Drt), a partially inbred strain in which the genetic propensity for diabetes is only expressed in obese males. METHODS: Retired diabetic (ZDF/Gmi-fa) and control lean Zucker (fa/+) breeder rats were examined for quantifiable evidence of microvascular changes of the retinal capillaries by gross examination, trypsin digestion of retinal vessels, and transmission electron microscopy. RESULTS: Gross examination of retinas and trypsin digestion of capillaries revealed no differences. Quantitative assessment of capillary cell nuclear density showed that diabetic retinas were hypercellular compared to lean rats (3.888 +/- 0.041 versus 3.304 +/- 0.046 nuclei per 100 microns (mean +/- SE), P = 0.0042). Transmission electron microscopic analysis of retinal capillary basement membrane thickness demonstrated thicker measurements in diabetic animals (mean thickness 21% greater in diabetic rats, P = 0.0307). CONCLUSIONS: This model may be useful for pharmacologic intervention studies because it is naturally and severely non-insulin-dependent diabetic, there are quantifiable retinal vascular changes, and same-sex litter mates can be used as controls.

Animals↗
PubMed1992

Empty and peptide-containing conformers of class I major histocompatibility complex molecules expressed in Drosophila melanogaster cells.

Transfected Drosophila melanogaster cells can express large quantities of class I major histocompatibility complex molecules. Such molecules lack endogenous peptides because the Drosophila cells are devoid of proteins necessary for intracellular peptide loading. The empty molecules are efficiently expressed on the cell surface and can acquire extracellular peptides. The conformation and stability of empty murine class I molecules are determined by the source of beta 2-microglobulin. All beta 2-microglobulin-induced conformers of empty heavy chains seem to be unified in a common rigid conformation on peptide binding.

Amino Acid Sequence↗