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Biomedical subjects

H Yang

Publications and source records attributed to H Yang.

At least 847 records · Page 47Linked to original sources
PubMed1994

A logical state model of circus movement atrial flutter role of anatomic obstacles, anisotropic conduction and slow conduction zones on induction, sustenance, and overdrive paced modulation of reentrant circuits.

Mapping studies of atrial flutter in both the canine sterile pericarditis model and the right atrial enlargement model commonly reveal single loop reentrant circuits in the lower posterior part of the right atrium. Functional bidirectional conduction block and natural anatomical obstacles comprise the central obstacle for reentrant impulse during circus movement atrial flutter. Because the relative roles of anatomical obstacles, in combination with functional barriers, anisotropic conduction, and slow conduction can not be readily assessed with current electrophysiological techniques, an atrial activation model was developed to study the mechanisms of circus movement atrial flutter. A discrete state model consisting of 4096 logically connected cardiac elements was used to simulate atrial activation; an inexcitable region simulating the inferior vena cava (IVC) was also incorporated in the model. Atrial flutter was induced by programmed premature stimulation. Anisotropic conduction velocity properties, regional variations in slow conduction, regional refractory gradients and stimulation parameters were specified for each simulation. The reentrant circuit generally consisted of a single reentrant impulse which circulated around a continuous line of functional bidirectional conduction block joined to the IVC. Rapid pacing, 5-30 ms shorter than the spontaneous reentrant cycle length, was applied to entrain and/or terminate the rhythm. The results of this study demonstrate that patterns of initiation, entrainment, termination and reinitiation of circus movement atrial flutter mimic results from in vivo activation mapping studies. We find that sustained circus movement atrial flutter circuits depend on: 1) natural anatomical obstacles to stabilize reentrant circuits, and 2) anisotropic conduction properties to reduce the degree of functional conduction block needed to maintain circus movement. Rapid pacing of simulated circus movement atrial flutter demonstrated that the entrainment criteria can be satisfied in a two-dimensional syncytium.

Animals↗
PubMed1994

Differentiation of sinus tachycardia from ventricular tachycardia with 1:1 ventriculoatrial conduction in dual chamber implantable cardioverter defibrillators: feasibility of a criterion based on the atrioventricular interval.

Tachycardia discrimination in future implantable cardioverter defibrillators (ICDs) is likely to be enhanced by the addition of an atrial sensing/pacing lead. However, differentiation of sinus tachycardia (ST) from ventricular tachycardia (VT) with 1:1 VA conduction will remain problematic. We assessed the use of the AV interval as a potential criterion for correctly differentiating ST from VT. Incremental V pacing at the right ventricular (RV) apex served as a "VT" model in each of 41 patients with 1:1 VA conduction to pacing cycle lengths < or = 450 msec. High right atrial and RV apical electrograms during normal sinus rhythm (NSR) and during incremental V pacing were digitized (simulating ICD sensing). From these signals, AV interval versus pacing cycle length plots were computer generated to identify crossover cycle lengths, each defined as the cycle length at which the AV interval during V pacing equals the AV interval during NSR. At cycle lengths longer than the crossover value, the AV interval during "VT" exceeds the AV interval during NSR. In contrast, the AV interval during ST is physiologically shorter than the AV interval during NSR. Thus, ST can be readily differentiated from "VT" over a range of cycle lengths greater than the crossover value. The overall mean calculated crossover cycle length was 371 +/- 52 msec. In 11 patients paced multiple times, each crossover cycle length was reproducible (mean coefficient of variation was 1.2% +/- 0.9% per patient). AV intervals measured at the RV apex were also analyzed with incremental V pacing during catecholamine stimulation (isoproterenol, n = 5) and during alternate site "VT" (RV outflow tract [n = 8] and left ventricle [n = 2]). In all these cases, the new "VT" plots of AV interval versus pacing cycle length coincided with or fell to the left of those obtained during control RV apical pacing and recording (i.e., these AV interval values crossed the NSR baseline at cycle lengths < or = the crossover cycle length). Thus, the cycle length range for recognizable differentiation of ST from "VT" remained valid. The data suggest that the described AV interval criterion relying on the crossover cycle length: (1) is a promising approach to improve differentiation of ST from relatively slow VTs with 1:1 VA conduction, and (2) can readily be automated in future dual chamber ICDs, given its computational simplicity.

Defibrillators, Implantable↗
PubMed1994

Recombinant Mycobacterium bovis BCG secreting functional interleukin-2 enhances gamma interferon production by splenocytes.

Mycobacterium bovis BCG was genetically engineered to express and secrete mouse interleukin-2 (IL-2) and rat IL-2. Genes encoding IL-2 were inserted into an Escherichia coli-BCG shuttle plasmid under the control of the BCG HSP60 promoter. To facilitate study of proteins produced in this system, the IL-2 gene product was expressed (i) alone, (ii) with the mycobacterial alpha-antigen secretion signal sequence at the amino terminus, (iii) with an influenza virus hemagglutinin epitope tag at the amino terminus, and (iv) with both the secretion signal sequence and the epitope tag. When expressed with the alpha-antigen signal sequence, biologically active IL-2 was secreted into the extracellular medium. Western blot (immunoblot) analysis of the intracellular IL-2 and extracellular IL-2 revealed that the secretion signal was appropriately cleaved from the recombinant lymphokine upon secretion. To assess the ability of recombinant BCG to stimulate cytokine production in a splenocyte population, mouse splenocytes were cultured together with wild-type or IL-2-producing BCG. IL-2-secreting BCG clones stimulated substantial increases in gamma interferon production, which could be reproduced by the addition of exogenous IL-2 to BCG. Levels of IL-6, IL-10, tumor necrosis factor alpha, and granulocyte-macrophage colony-stimulating factor were not significantly changed, while IL-4 and IL-5 remained undetectable (less than 50 pg/ml). The enhanced production of gamma interferon in response to IL-2-secreting BCG was strain independent. Recombinant BCG expressing mammalian cytokines provides a novel means to deliver cytokines and may augment the immunostimulatory properties of BCG in immunization and cancer therapy.

Animals↗
PubMed1994

Anabolic effect of IGF-I coinfused with total parenteral nutrition in dexamethasone-treated rats.

We determined the anabolic effects of recombinant human insulin-like growth factor I (rhIGF-I, 800 micrograms/day) coinfused with total parenteral nutrition (TPN) in male Sprague-Dawley rats (230-250 g), with and without dexamethasone (Dex, 70 micrograms/day)-induced catabolism for 6 days. Dex without IGF-I increased serum insulin concentrations 300% and glucose concentrations 20%; IGF-I plus Dex significantly reduced serum insulin and glucose concentrations to TPN control levels. Animals given Dex without IGF-I lost 30 +/- 3 g; IGF-I plus Dex reduced the weight loss to 9 +/- 3 g, P < 0.001. IGF-I without Dex resulted in a weight gain of 14 +/- 2 g compared with a gain of 4 +/- 1 g in TPN controls, P < 0.01. Determination of nitrogen balance and body composition confirmed that changes in body weight were due to corresponding changes in nitrogen excretion and total body protein content. IGF-I significantly reduced TPN-induced intestinal atrophy, resulting in a 30% increase in weight of the small intestine plus colon compared with TPN without IGF-I. These results indicate that coinfusion of rhIGF-I with TPN counteracts Dex-induced insulin resistance and has a significant net anabolic effect when given with or without Dex in rats.

Analysis of Variance↗
PubMed1994

Role of peripheral capsaicin-sensitive neurons and CGRP in central vagally mediated gastroprotective effect of TRH.

We investigated in conscious rats the role of capsaicin-sensitive neurons and alpha-calcitonin gene-related peptide (CGRP), the form preferentially expressed in capsaicin sensory neurons, in mediating intracisternal thyrotropin-releasing hormone (TRH) analogue-induced vagal muscarinic gastroprotection against ethanol lesions. The TRH analogue RX-77368 (1.5 ng ic) reduced by 78 and 66% gastric hemorrhagic lesions induced by intragastric intubation of 60 and 80% ethanol, respectively. alpha-CGRP (1 nmol/kg iv) inhibited by 88% gastric lesions induced by 60% ethanol, and this peptide action was blocked by the CGRP antagonist, CGRP-(8-37) (128 nmol/kg iv). The protective effect of RX-77368 against 60% ethanol was completely abolished by the CGRP monoclonal antibody 4901 (4.8 mg/kg iv), CGRP-(8-37) (128 nmol/kg iv), and capsaicin pretreatment (125 mg/kg). Gastric lesions induced by 60% ethanol were not altered by the CGRP antagonist or antibody alone but were enhanced by capsaicin pretreatment. These results suggest that the gastroprotection induced by intracisternal TRH analogue involves an interaction between central vagal efferent pathways and splanchnic sensory afferent terminals containing CGRP.

Animals↗
PubMed1994

[Studies on the constituents of the roots of Acorus calamus L].

A new tricyclic sesquiterpene, named calamenone (1), and two known sesquiterpenes, calamendiol (2) and isocalamendiol (3), were isolated from the roots of Acorus calamus L. The structure of the new compound was elucidated on the basis of spectral and X-ray diffraction data.

Drugs, Chinese Herbal↗
PubMed1994

[CD5+B cells and autoimmune diseases].

By using two colour flow cytometric analysis, we examined the proportion of B lymphocytes bearing CD5 surface antigen (CD5+B cell). The level of CD5+B cells was markedly increased in active chronic ITP and active hyperthyroid patients with Graves' disease. There was an inverse correlation between the percentage of circulating CD5+B cells and platelet counts, and a positive correlation between the level of CD5+B cells in peripheral blood and serum T3 level. These results suggested that the level of CD5+B cells might play a role in producing autoantibodies in some autoimmune diseases.

Adolescent↗
PubMed1994

[Role of EcoRI-BclI fragment at the promoter upstream region on the expression of alpha-amylase gene].

A series of plasmids derived from pNL201 with the promoter upstream region of alpha-amylase gene of B. licheniformis have been constructed. In the meantime, a series of plasmids derived from pAmy41 with full alpha-amylase gene have also been constructed and they have different promoter upstream region with the EcoRI-BclI fragment deleted or partial destroyed. The alpha-amylase activity of the engineering strains carrying alone or double plasmids has been determined. The statistical results show that the EcoRI-BclI fragment possesses negative regulation in the expression of alpha-amylase gene in B. subtilis.

Deoxyribonuclease EcoRI↗
PubMed1994

[Measles surveillance in a rural area: assessment of a passive reporting system].

Comparison of the data provided by the passive epidemic reporting system (PERS) with those of epidemicologic investigation during the outbreak of measles in a rural area, Rongshui County, from November 26, 1992 to May 10, 1993 indicated that the PERS delayed the report one month during the outbreak, failed to describe the time, place and age distributions correctly. The main drawbacks of the PERS were tediousness and delay. The reformed active surveillance system with diagnostic recipe made the reporting precedures much simpler and well acceptable by the physicians.

Adolescent↗
PubMed1994

[Characteristics of reversed optic cupping in glaucoma after reduction of intraocular pressure].

Quigley's hypothesis indicates that the dense connective tissue is the least and the pores of the lamina cribrosa are the largest at the superior and inferior poles of the lamina cribrosa, therefore they are the most vulnerable locations to be involved by the characteristic glaucomatous optic nerve damage. To get clinical evidences of the hypothesis, the reversal or contraction of glaucomatous optic cup after reduction of intraocular pressure (IOP) was examined (The change is primarily caused by intraocular hypertension--induced distortion and posterior ectasia of the lamina cribrosa which moves forward reversely, leading to dilated optic cup contraction.). The method of examination was a stereoscopic flicker comparison with a computerized image system, alternatively displaying superposed 2 serial stereo pairs rapidly and the changing part presenting jumping appearance. Under stereoscopic observations, the changes of 3-dimension optic cup end be seen and the false positive phenomena caused by photographic angle variation, vascular pulsation, etc. can be differentiated from the characteristic changes of the cup. Stereo fundus photographs were taken from 31 eyes with high intraocular pressures before and after treatment for reduction of IOPs which was either diamox administration or trabeculectomy. The results show that the reversal of optic cups after reduction of IOPs are mostly asymmetrical, especially at the superior and/or inferior poles. By multiple stepwise regression, it is known that the amount of the change is only correlated with the initial IOP.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Ultrastructural observations of the anterior chamber angle tissues in congenital glaucoma.

Eighteen trabeculectomy specimens of congenital glaucoma were examined by light and transmission electron microscopy. The results showed that the primary anomalies in congenital glaucoma included the developmental defects of trabecular meshwork, excessive collagen fibrils in the trabecular matrix, shifting forward of ciliary muscle fibres and persistent mesenchymal tissues in the anterior-chamber angle. The authors also pointed out the importance of the secondary lesions of the trabecular meshwork in the pathogenesis of congenital glaucoma.

Anterior Chamber↗
PubMed1994

[Free thyroxine in burn patient and its clinical significance].

Using radioimmunoassay serum FT3 and FT4 and S-TSH were determined in 42 patients with different sizes of burn. The results were all in the normal range, indicating that there was only sufficient amount of thyroxine in trauma patients to maintain the lowest basal metabolism for living. The changes in the total T3 and T4 did not conform to that reported elsewhere. It deserves further clinical observation and study.

Adolescent↗
PubMed1994

[In vitro sensitivity of Plasmodium falciparum to mefloquine, quinine, amodiaquine, chloroquine, pyronaridine and sulfadoxine/pyrimethamine in south Yunnan].

The sensitivity of P. falciparum to mefloquine, quinine, amodiaquine, chloroquine, pyronaridine, and sulfadoxine/pyrimethamine (MEF, QNN, AMO, CHL, PYR, S/P) was tested using in vitro microtest in south Yunnan Province in 1992. The ID50 were 46, 480, 52, 150, 15 and 2 x 10(4)/25 x 10(2) nmol/L, respectively; ID95 were 160, 1,536, 292, 680, 60 and 24 x 10(5)/3 x 10(5) nmol/L, respectively. All the isolates (30) were sensitive to MEF and QNN; 100% (30/30) and 96.7% (29/30) isolates were found to be resistant to AMO and CHL, the cross-resistance rate was 100% to the two drugs. One of 5 isolates exhibited resistance to PYR. The results suggest that the P. falciparum was susceptible to MEF and QNN, but was resistant to AMO, CHL and S/P. CHL-resistant P. falciparum showed a marked cross-resistance to AMO, but not to MEF, QNN, and S/P; AMO-resistant P. falciparum exhibited cross-resistance to CHL, but not to MEF, QNN, and S/P.

Amodiaquine↗
PubMed1994

[Transcription of HSP 70 gene induced by pressure overload in left ventricule of rats].

The changes of heat shock protein 70 (HSP70) messenger RNA was examined in rats after abdominal aortic partial ligation. Four hours after ligation, the systemic arterial pressure was increased and thereafter maintained at a high level. The ratio of left ventricule weight to body weight began to increase at the third day and increased by 59%, comparing with that of the sham-operated rats at 4 w. Accumulation of HSP 70 mRNA was observed at 4 h and maintained at high level at 1 d, 2 d, 1 w and then gradually disappeared there after. The above experimental results suggest that transcription of HSP 70 gene was induced at an early stage of cardiac hypertrophy caused by pressure overload.

Animals↗
PubMed1994

[Detection of isoferritin level in breast cancer tissue and serum].

ELISA (double-determinant) was used to evaluate the isoferritin level in the breast cancer tissue. The isoferritin concentration was measured in cytosol extracts of 25 breast cancer tissues (BCT), 6 cancer surrounding tissues (CST) and 8 normal breast tissues (NBT). With the results of 16,023 +/- 15,732, 2467 +/- 1360 and 1382 +/- 647 ng/mcp (milligrams of ontosol protein), respectively. The isoferritin concentrations of BCT and CST were 11.6 and 1.8 times as much as that of NBT, and the differences were statistically significant (P < 0.001 and 0.05). The serum isoferritin level was also measured in 96 healthy persons and 68 breast cancer patients (mean 58.7 +/- 35.8 and 473.3 +/- 297.3 ng/ml) with the difference as big as 8.1 times. The results have demonstrated that the level of cytosol isoferritin in BCT is an important parameter of breast tissue malignance and may be also responsible for the serum isoferritin increase. Therefore we think that serum isoferritin may be used as a marker for early diagnosis of breast cancer.

Biomarkers, Tumor↗