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Biomedical subjects

Y Cheng

Publications and source records attributed to Y Cheng.

At least 109 records · Page 6Linked to original sources
PubMed2000

Reversal of repolarization gradient does not reverse the chirality of shock-induced reentry in the rabbit heart.

INTRODUCTION: Two hypotheses have been proposed to explain the mechanisms of vulnerability and related failure of defibrillation therapy: the cross-field-induced critical point hypothesis and the virtual electrode-induced phase singularity hypothesis. These two hypotheses predict the opposite effect of preshock repolarization on the chirality (direction of rotation) of shock-induced reentry. The former suggests its reversal upon reversal of repolarization, whereas the latter suggests its preservation. The aim of this study was to determine, by reversing the repolarization sequence, which of the mechanisms is responsible for internal shock-induced arrhythmia in the Langendorff-perfused rabbit heart. METHODS AND RESULTS: We used high-resolution optical mapping to assess the chirality of postshock reentry in 11 hearts. Hearts were paced at a coupling interval of 300 msec at various sites around the field of view (13.5 x 13.5 to 16.5 x 16.5 mm). Cathodal monophasic implantable cardioverter defibrillator shocks (-100 V, 8 msec) were applied during the T wave from a 10-mm coil electrode placed into the right ventricular cavity. We used 3.5 +/- 0.8 different pacing sites per heart. Change in direction of repolarization did not result in change of chirality. Chirality was constant in all 11 hearts despite the complete reversal of activation and repolarization patterns. However, the position of resulting vortices depended on transmembrane polarization gradient inverted delta Vm and amplitude of negative polarization Vm (deexcitation). Stronger gradients and deexcitation produced earlier epicardial break excitation (P = 0.04 and P < 0.0001, respectively). CONCLUSION: Virtual electrode-induced phase singularity mechanism underlies internal shock-induced arrhythmia in this model.

Animals↗
PubMed2000

Does physical activity reduce the risk of developing peptic ulcers?

BACKGROUND: Although Helicobacter pylori has been identified as a major cause of chronic gastritis, not all infected patients develop ulcers, suggesting that other factors such as lifestyle may be critical to the development of ulcer disease. AIM: To investigate the role physical activity may play in the incidence of peptic ulcer disease. METHODS: The subjects were men (8529) and women (2884) who attended the Cooper Clinic in Dallas between 1970 and 1990. The presence of gastric or duodenal ulcer disease diagnosed by a doctor was determined from a mail survey in 1990. Subjects were classified into three physical activity groups according to information provided at the baseline clinic visit (before 1990): active, those who walked or ran 10 miles or more a week; moderately active, those who walked or ran less than 10 miles a week or did another regular activity; the referent group consisting of those who reported no regular physical activity. RESULTS: With the use of gender specific proportional hazards regression models that could be adjusted for age, smoking, alcohol use, body mass index, and self reported tension, active men were found to have a significant reduction in risk for duodenal ulcers (relative hazard (95% confidence interval) for the active group was 0.38 (0.15 to 0.94) and 0.54 (0.30 to 0.96) for the moderately active group). No association was found between physical activity and gastric ulcers for men or for either type of ulcer for women. CONCLUSIONS: Physical activity may provide a non-pharmacological method of reducing the incidence of duodenal ulcers among men.

Adult↗
PubMed2000

Physical activity and peptic ulcers. Does physical activity reduce the risk of developing peptic ulcers?

BACKGROUND: Although Helicobacter pylori has been identified as a major cause of chronic gastritis, not all infected patients develop ulcers, suggesting that other factors such as lifestyle may be critical to the development of ulcer disease. OBJECTIVE: To investigate the role physical activity may play in the incidence of peptic ulcer disease. METHODS: The participants were men (n = 8,529) and women (n = 2,884) who attended the Cooper Institute for Aerobics Research, Dallas, Texas, between 1970 and 1990. The presence of gastric or duodenal ulcer disease diagnosed by a physician was determined from a mail survey in 1990. Participants were classified into 3 physical activity groups according to information provided at the baseline clinic visit (before 1990): active, those who walked or ran 10 miles or more a week; moderately active, those who walked or ran less than 10 miles a week or did another regular activity; and the referent group consisting of those who reported no regular physical activity. RESULTS: With the use of gender-specific proportional hazards regression models that could be adjusted for age, smoking, alcohol use, body mass index, and self-reported tension, active men had a significantly reduced risk for duodenal ulcers (relative hazard [95% confidence interval] for the active group, 0.38 [0.15-0.94], and 0.54 [0.30-0.96] for the moderately active group). No association was found between physical activity and gastric ulcers for men or for either type of ulcer for women. CONCLUSION: Physical activity may provide a nonpharmacologic method of reducing the incidence of duodenal ulcers among men.

Adult↗
PubMed2000

Virtual electrode polarization in the far field: implications for external defibrillation.

We recently suggested that failure of implantable defibrillation therapy may be explained by the virtual electrode-induced phase singularity mechanism. The goal of this study was to identify possible mechanisms of vulnerability and defibrillation by externally applied shocks in vitro. We used bidomain simulations of realistic rabbit heart fibrous geometry to predict the passive polarization throughout the heart induced by external shocks. We also used optical mapping to assess anterior epicardium electrical activity during shocks in Langendorff-perfused rabbit hearts (n = 7). Monophasic shocks of either polarity (10-260 V, 8 ms, 150 microF) were applied during the T wave from a pair of mesh electrodes. Postshock epicardial virtual electrode polarization was observed after all 162 applied shocks, with positive polarization facing the cathode and negative polarization facing the anode, as predicted by the bidomain simulations. During arrhythmogenesis, a new wave front was induced at the boundary between the two regions near the apex but not at the base. It spread across the negatively polarized area toward the base of the heart and reentered on the other side while simultaneously spreading into the depth of the wall. Thus a scroll wave with a ribbon-shaped filament was formed during external shock-induced arrhythmia. Fluorescent imaging and passive bidomain simulations demonstrated that virtual electrode polarization-induced scroll waves underlie mechanisms of shock-induced vulnerability and failure of external defibrillation.

Animals↗
PubMed2000

Norepinephrine reuptake, baroreflex dynamics, and arterial pressure variability in rats.

This study examined the effect of norepinephrine reuptake blockade with desipramine (DMI) on the spontaneous variability of the simultaneously recorded arterial pressure (AP) and renal sympathetic nerve activity (SNA) in conscious rats. Acute DMI administration (2 mg/kg iv) depressed AP Mayer waves ( approximately 0.4 Hz) and increased low-frequency (<0.2 Hz) components of AP variability. DMI decreased renal SNA variability, especially due to the abolition of oscillations related to Mayer waves. To examine whether DMI-induced changes in AP and renal SNA variabilities could be explained by alterations in the dynamic characteristics of the baroreceptor reflex loop, the frequency responses of mean AP to aortic depressor nerve stimulation were studied in urethan-anesthetized rats. DMI accentuated the low-pass filter properties of the transfer function without significantly altering the fixed time delay. The frequency responses of iliac vascular conductance to stimulation of the lumbar sympathetic chain were studied in an additional group of anesthetized rats. DMI did not markedly alter the low-pass filter properties of the transfer function and slightly increased the fixed time delay. These results suggest that the DMI-induced decrease in the dynamic gain of the baroreceptor reflex is responsible for the decreased spontaneous renal SNA variability and the accompanying increased AP variability. The "slowing down" of baroreflex responses cannot be attributed to an effect of DMI at the vascular neuroeffector junction.

Animals↗
PubMed2000

Regulation of the vascular extracellular superoxide dismutase by nitric oxide and exercise training.

The bioactivity of endothelium-derived nitric oxide (NO) reflects its rates of production and of inactivation by superoxide (O(2)(*-)), a reactive species dismutated by extracellular superoxide dismutase (ecSOD). We have now examined the complementary hypothesis, namely that NO modulates ecSOD expression. The NO donor DETA-NO increased ecSOD expression in a time- and dose-dependent manner in human aortic smooth muscle cells. This effect was prevented by the guanylate cyclase inhibitor ODQ and by the protein kinase G (PKG) inhibitor Rp-8-CPT-cGMP. Expression of ecSOD was also increased by 8-bromo-cGMP, but not by 8-bromo-cAMP. Interestingly, the effect of NO on ecSOD expression was prevented by inhibition of the MAP kinase p38 but not of the MAP kinase kinase p42/44, suggesting that NO modulates ecSOD expression via cGMP/PKG and p38MAP kinase-dependent pathways, but not through p42/44MAP kinase. In aortas from mice lacking the endothelial nitric oxide synthase (eNOS), ecSOD was reduced more than twofold compared to controls. Treadmill exercise training increased eNOS and ecSOD expression in wild-type mice but had no effect on ecSOD expression in mice lacking eNOS, suggesting that this effect of exercise is meditated by endothelium-derived NO. Upregulation of ecSOD expression by NO may represent an important feed-forward mechanism whereby endothelial NO stimulates ecSOD expression in adjacent smooth muscle cells, thus preventing O(2)(*-)-mediated degradation of NO as it traverses between the two cell types.

Animals↗
PubMed2000

Seasonal variations in mood and behavior among Chinese medical students.

OBJECTIVE: The goal of this study was to estimate the frequency of seasonal variations in mood and behavior among Chinese medical students. METHOD: A total of 1,358 medical students were surveyed with Chinese versions of the Seasonal Pattern Assessment Questionnaire and the Beck Depression Inventory in Jining, China. RESULTS: The mean global seasonality score was 8.3 (SD=3.6) out of a possible 24; 81.7% (N=1,110) of the subjects reported some trouble adapting to changing seasons. Summer difficulties were more common than winter difficulties by a ratio of 3:2; estimated rates of summer seasonal affective disorder and subsyndromal seasonal affective disorder were 4.4% and 8.0%, respectively, compared with corresponding winter rates of 2.4% and 5.7%. CONCLUSIONS: These results suggest that seasonal variations in mood and behavior are common in China. The predominance of summer difficulties stands in contrast to that in most Western studies and is consistent with the only other published study performed in Asia.

Adolescent↗
PubMed2000

Transient suppression of cortactin ectopically induces large telencephalic neurons towards a GABAergic phenotype.

Excitatory and inhibitory neuronal cell fates require specific expression of both neurotransmitter and morphological phenotypes. The role of the F-actin cytoskeleton in morphological phenotypes has been well documented, but its role in neurotransmitter phenotype expression remains unknown. Here we present evidence that the F-actin binding protein cortactin participates in determining both aspects of cell fate in large telencephalic neurons. We show that the expression of cortactin was upregulated early in development just prior to appearance of GABAergic neurons in the chick telencephalon at embryonic day 6. This program was faithfully maintained in primary neuronal cultures derived from E6 telencephalon, where immature neurons differentiate either to large pyramidal and large stellate excitatory neurons or to small inhibitory GABAergic neurons. Immunostaining revealed that cortactin was enriched in areas of membrane budding, growth cones, and in the cell cortex of immature neurons. With differentiation, intense punctate staining was also observed in an extraction-resistant cytosolic compartment of the soma and processes. More importantly, suppression of cortactin by inhibition of cortactin mRNA translation with antisense oligonucleotides caused permanent phenotypic changes. Specifically, a transient suppression of cortactin was achieved in immature neurons with a single exposure to antisense oligonucleotides. This inhibition first induced both the expression of mRNA and the enzymatic activity of GAD significantly earlier than in control neurons. Second, cortactin-suppressed large projectional neurons exhibited significantly shorter processes and growth cones with protrusive filopodia and an enlarged lamellipodia veil. Most importantly, this remodeling of neuritic outgrowth in projectional somata was accompanied by the ectopic induction of GABA (*-aminobutyric acid) expression. Considering this data altogether, it appears that cortactin may function to suppress concurrently several parameters of the GABAergic program in large developing neurons.

Animals↗
PubMed2000

Lanthanides enhance pulmonary absorption of insulin.

In an effort to investigate the enhancement effect of lanthanide ions (Ln3+) on the absorption of larger molecules from the pulmonary pathway, insulin (mol. wt. = 5730) was chosen as a model peptide. The absorption of insulin preadministered or coadministered with Ln3+ from the lung was investigated by means of an in situ pulmonary absorption experiment. The enhancement absorption of insulin by Ln3+ ions was evaluated by calculating the various bioavailabilities (Fr) of insulin from pulmonary absorption. Moreover, the temporal change of Gd content in serum was also investigated. Results showed that the promoting effect of Ln3+ on the bioavailability of insulin is closely related to its species, concentration, and delivery order. The effect of the median Ln3+ series was remarkably greater than that of light and heavy Ln3+. The anionic form of Gadolinium (Fr = 68.4%) seemed to be more effective compared with its cationic form (Fr = 59.5%). Coadministration of Gd3+ with insulin (Fr = 80.1%) was the most effective in increasing insulin absorption from the lung. Gd3+ was rapidly absorbed and metabolized to a normal level after 4 h. It was suggested that lanthanides in a very low concentration might become potent absorption enhancers to improve absorption of larger molecules via the pulmonary pathway.

Absorption↗
PubMed2000

Biclustering of expression data.

An efficient node-deletion algorithm is introduced to find submatrices in expression data that have low mean squared residue scores and it is shown to perform well in finding co-regulation patterns in yeast and human. This introduces "biclustering", or simultaneous clustering of both genes and conditions, to knowledge discovery from expression data. This approach overcomes some problems associated with traditional clustering methods, by allowing automatic discovery of similarity based on a subset of attributes, simultaneous clustering of genes and conditions, and overlapped grouping that provides a better representation for genes with multiple functions or regulated by many factors.

Algorithms↗
PubMed2000

[Glucose isomerase gene knock-out by denatured double-stranded DNA].

After Genetic background analysis of Streptomyces diastaticus No. 7 strain M1033, the modified conditions of M1033 protoplasts and transformation were established. Replacement plasmid for homologous recombination was also constructed by inserting tsr gene into glucose isomerase gene. The homologous recombination of GI gene in M1033 chromosomes was achieved by using denatured linearized DNA fragments and glucose isomerase deficient strain M1033LJ was obtained. It is basic for introducing mutation into M1033 chromosome and realizing site-directed molecular reformation.

Aldose-Ketose Isomerases↗
PubMed2000

Review of pre-eclampsia in Taiwan: a multi-institutional study.

BACKGROUND: Because the reported frequency of pre-eclampsia in Taiwan varies significantly, the aims of this study were to measure the current incidence of pre-eclampsia and its correlated morbidity and mortality for both mothers and fetuses in Taiwan. METHODS: We retrospectively studied all reported cases of pre-eclampsia and eclampsia from January 1, 1993 to December 31, 1997 in the 14 tertiary medical centers and regional hospitals in Taiwan. Recruiting criteria were pregnancy-induced hypertension (systolic blood pressure > or = 140 mmHg or diastolic blood pressure > or = 90 mmHg) with proteinuria (> or = 300 mg of urinary protein per 24 hours) and independent part edema. RESULTS: There were 4,193 patients with pre-eclampsia and eclampsia for a frequency of 2.03% of 206,551 deliveries during the study period. Of these, 58.9% of patients were classified as having mild pre-eclampsia while 38.4% had severe pre-eclampsia. Advanced maternal age (> 35 years) (odds ratio [OR] = 4.56; 95% confidence interval [CI] = 4.23-4.90; p < 0.001), primiparity (OR = 1.71; 95% CI = 1.61-1.82; p = 0.02) and twin pregnancy (OR = 1.92; 95% CI = 1.64-2.25; p = 0.01) were significant risk factors for developing pre-eclampsia. However, multivariate analysis showed that only advanced maternal age was a significant risk factor for pre-eclampsia (OR = 3.21; 95% CI = 2.95-3.50; p < 0.001). In contrast to mild pre-eclampsia, severe pre-eclampsia resulted in significantly worse outcomes for both mothers and fetuses. Complications in patients with severe pre-eclampsia included placental abruption, acute renal failure, pulmonary edema, postpartum hemorrhage, pleural effusion, preterm labor, intrauterine growth retardation, stillbirth, neonatal mortality and low birth weight infants, all of which occurred significantly more frequently than in patients with mild pre-eclampsia (p < 0.001). CONCLUSIONS: Pre-eclampsia remains a big challenge in modern obstetrics in Taiwan. Early diagnosis and management of patients with pre-eclampsia to prevent progression would significantly improve outcomes for mothers and fetuses.

Adult↗
PubMed2000

Cyclo-oxygenase products and atherothrombosis.

The advent of selective inhibitors of the cyclo-oxygenase (COX)-2 enzyme has afforded the opportunity to reduce the incidence of gastrointestinal complications of traditional nonsteroidal anti-inflammatory drugs (NSAIDs). The widespread use of these drugs has increased interest in their role in the cardiovascular system. Although deletion of the prostacyclin receptor (the IP) accelerates atherogenesis in the mouse, retention of one copy of the IP is atheroprotective. This is consistent with the failure of biochemically defined, selective doses of a COX-2 inhibitor to accelerate atherogenesis in the mouse, despite suppressing prostacyclin biosynthesis by roughly 60%. Inhibition of both COX isozymes, by contrast, markedly retards atherogenesis. Consistent with these observations, antagonism of the thromboxane receptor (the TP) retards atherogenesis and diminishes the proliferative response to vascular injury in the mouse. Even partial suppression of prostacyclin (without coincident inhibition of platelet COX-1-dependent thromboxane formation) by COX-2 inhibitors may be undesirable in acute vascular occlusive syndromes. However, these drugs are unlikely to accelerate progression of the underlying vascular disease. By contrast, the effects of TP antagonists, aspirin, and even traditional NSAIDs on atherosclerotic plaque progression merit further evaluation in humans.

Animals↗
PubMed2000

[The regulating mechanism of anti-fungicides on mouse oocyte development].

AIM: To study the mechanism of the effect of gonadotropin-induced oocyte maturation. METHODS: Mouse oocytes were cultured in HX-medium, and the effects of amphotericin B and ketoconazole on resumption of meiosis of mouse oocyte were examined. RESULTS: 1. FSH(10-200 IU/L) induced a dose-dependent manner of oocytes maturation in CEO. A maximum increase in GVBD was observed with 25-50 IU/L FSH. 2. Amphotericin tericim B (0.025-2.5 micrograms/L) caused significant increases in GVBD in CEO, which mimicked the function of FSH. 3. Ketoconazole (10(-7)-10(-3) mol/L) inhibited the effect of FSH on resumption of meiosis, but no effect on oocyte spontaneous maturation. CONCLUSION: Amphotericin B and ketoconazole are able to affect mouse oocyte maturation, and indicates that they have a regulation on FSH-induced synthesis of meiosis-activating sterol.

Amphotericin B↗
PubMed2000

[Cloning and expression of TTV gene fragment in E. coil and identification of the expressed protein].

OBJECTIVE: To construct a recombinant expression vector containing TTV gene fragment and identify the expressed protein. METHODS: Based on computer-aided studies, TTV ORF12 gene fragment coding protein of antigenicity was amplified by PCR from the patient serum with non-A-G hepatitis. Then the gene fragment was integrated into the multiple cloning site of pQE-30 and expressed in E coil. The expressed protein was identified by ELISA. RESULTS: The relative molecular weight of the expressed protein matches the predication and its yield was up to 22.33% of total bacterial proteins of E. coli The expressed protein was detected by ELISA. CONCLUSIONS: The recombinant vector has been constructed successfully and the expressed protein possesses antigenicity.

Adolescent↗
PubMed2000

Molecular cloning and protein expression of EC1-2 and EC3-4 epitopes of pemphigus vulgaris antigen.

OBJECTIVE: To clone and express EC1-2 and EC3-4 epitopes of PVA (pemphigus vulgaris antigen, desmoglein-3) in order to diagnose pemphigus and study the relationship between epitopes of PVA and anti-PVA antibody. METHODS: RNA was extracted from keratinocytes and the cDNA of epitopes EC1-2 and EC3-4 was synthesized by reverse transcription. Amplified genes of EC1-2 and EC3-4 were inserted into the expression plasmid, PGEX-4T-1, and transformed into E. coli BL21 by electric transduction. Recombinant fusion proteins of EC1-2 and EC3-4 epitopes were expressed by IPTG induction. These proteins were separated on SDS-PAGE gels and electroblotted to nitrocellulose to detect the anti-PVA antibody. RESULTS: The sequences of cloned EC1-2 and EC3-4 genes were identical to the sequence registered in PC/GENE. Expressed recombinant proteins reacted only to sera from patients with pemphigus vulgaris, not to sera from patients with bullous pemphigoid, systemic lupus erythematosus or normal persons. CONCLUSIONS: These recombinant proteins are very specific in antigenicity. This may provide a new method for the diagnosis of pemphigus vulgaris (PV) or the differential diagnosis of other bullous cutaneous diseases via patient sera. It is also helpful in understanding the relationship between adhesion molecules and the pathogenic mechanism of pemphigus vulgaris.

Autoantibodies↗
PubMed2000

[Jugulotympanic glomus tumors: a report of 11 cases].

OBJECTIVE: To evaluate the surgical technique in removal of jugulotympanic glomus tumor. METHODS: Retrospective analysis of surgical techniques and effects of the surgical treated 11 cases (1982-1998) of jugulotympanic glomus tumors (tympanic type I, 1, II, 1, IV, 3; jugular type I, 1, III, 5). RESULTS: The tumors of all 11 patients were removed completely and the wounds healed smoothly. Only one case had postoperative laryngeal nerve paralysis. There was no recurrence after 1-8 years follow-up. CONCLUSION: Suitable surgical techniques are available for removal of jugulotympanic glomus tumors and are chosen according to the size and location of the tumor. Postauricular incision is suitable for Glomous tympanicum Type II, III, IV. Since postauricular incision with superior and inferior extension provides a good exposure of the neck and temporal bone, it is suitable for surgical removal of Glomus jugulare type I. In case of Glomus jugulare type III, postauricular large "C" incision may be chosen for resection of the mid- and infra-temporal fosse, neck and skull base tumor.

Adult↗