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Biomedical subjects

S Hong

Publications and source records attributed to S Hong.

At least 163 records · Page 9Linked to original sources
PubMed1994

Effects of thyroid hormone on the calcium current and isoprenaline-induced background current in rabbit ventricular myocytes.

The majority of previous studies have been performed to explain the effects of thyroid hormone on the heart in chronic hyperthyroidism that was usually induced by eight to 10 daily injections of thyroid hormones. However, it is unclear whether or not the electrophysiological effects result from the chronic manifestations of hyperthyroidism and whether thyroid hormone acts directly or indirectly on cardiac myocytes to alter cardiac electrophysiological properties. In order to examine the acute term electrophysiological effects of thyroid hormone applied in vitro and the mechanisms responsible for some of these effects, we investigated the modulatory effects of thyroid hormone on the calcium current and isoprenaline-induced background current in L-triiodothyronine-treated ventricular myocytes of the rabbit. The major findings were as follows. Over 5 h (range, 5-24 h) after treatment of L-triiodothyronine (1 microM) in vitro, the calcium current was increased significantly. Isoprenaline (1 microM) and cyclic AMP (100 microM) caused an increase in the calcium current in both euthyroid and hyperthyroid myocytes. The hyperthyroid myocytes were more sensitive to the effect of beta-adrenergic stimulation on the calcium current and isoprenaline-activated background current. In euthyroid myocytes, acetylcholine (1 microM) produced no or little changes in the amplitude of the calcium current. In hyperthyroid myocytes, acetylcholine markedly reduced the calcium current, however, acetylcholine was ineffective in the presence of sufficient intracellular cyclic AMP (100 microM). Our results suggest that thyroid hormone can affect the cardiac myocytes directly. Furthermore, our results demonstrate that thyroid hormone affects the calcium current and isoprenaline-activated background current. These electrophysiological changes may explain, at least in part, the occurrence of positive inotropy and cardiac arrhythmias that is associated with hyperthyroidism.

Acetylcholine↗
PubMed1994

Association of factor VII genotype with plasma factor VII activity and antigen levels in healthy Indian adults and interaction with triglycerides.

Plasma factor VII activity (factor VIIc) is one of the independent risk factors for coronary artery disease and is controlled by both genetic and environmental factors. Several studies in healthy Caucasian subjects have revealed an association of a common genetic polymorphism at residue 353 (Arg-->Gln) of the factor VII gene with plasma factor VIIc. We have investigated the influence of this polymorphism (factor VII Arg/Gln353) on fasting plasma factor VIIc and antigen (factor VIIag) levels and its interaction with triglyceride levels in 185 healthy Dravidian Indians of both sexes (128 men, 57 women). The frequency of Gln353 has been found to be significantly higher in Dravidian Indians (0.29; confidence interval, 0.27 to 0.30) than in Caucasians (0.10). The distribution of factor VII Arg/Gln353 genotypes was at Hardy-Weinberg equilibrium. The carriers of the Gln353 allele had significantly lower plasma factor VIIc and factor VIIag in men (P < .05). The factor VII Arg/Gln353 polymorphism explained 13% and 11% of the total variance of plasma factor VIIc and factor VIIag, respectively, in men (P < .001) and 6% and 9% in women (P > .1). The genotype-specific correlation of factor VIIc and factor VIIag with triglyceride levels was stronger in carriers of the Gln353 allele (r = .38 and .41; P < .001) than in Arg353 homozygotes (r = .09 and .27; P = .19 and .005, respectively).

Adult↗
PubMed1993

The phonetic interpretation of tone in Igbo.

This article presents a preliminary study of the phonetic interpretation of tone in Igbo, a Kwa language of southeastern Nigeria. The experimental method varies the speaker's pitch range orthogonally with variation in tonal material, and fits a model to measurements of maxima and minima in the resulting F0 contour. A new interpretation of downstep is proposed as a result.

Female↗
PubMed1993

Validity of family history data on severe headache and migraine.

This study evaluated the validity of family history data on severe headache and migraine obtained from adult probands with epilepsy in a family study of seizure disorders. We compared the probands' reports of severe headaches and migraines in their parents and full siblings with symptom-based diagnoses based on self-reports. Overall sensitivity was 48% for severe headache and 44% for migraine. When we used reports of severe headaches to screen for migraine headaches in the relatives, sensitivity was 56%. These results indicate that severe headache and migraine are underreported in family history interviews with first-degree relatives. To obtain accurate information on headaches in families for clinical practice and genetic research, direct interviews with each relative may be required.

Adult↗
PubMed1993

Reliability of seizure classification using a semistructured interview.

Methods for standardized classification of epileptic seizures are important for both clinical practice and epidemiologic research. In this study, we developed a strategy for standardized classification using a semistructured telephone interview and operational diagnostic criteria. We interviewed 1,957 adults with epilepsy ascertained from voluntary organizations. To confirm and expand the seizure history, we also interviewed a first-degree relative for 67% of subjects and obtained medical records for 59%. Three lay reviewers used all available information to classify seizures. To assess reliability, each reviewer classified a sample of subjects assigned to the others. In addition, an expert physician classified a sample of subjects assigned to two of the reviewers. Agreement was "moderate-substantial" for generalized-onset seizures, both for the comparisons between pairs of lay reviewers and for the neurologist versus lay reviewers. Agreement was "substantial-almost perfect" for partial-onset seizures, both for pairs of lay reviewers and for the neurologist versus lay reviewers. These results suggest that seizures can be reliably classified by lay reviewers, using operational criteria applied to symptoms ascertained in a semistructured telephone interview.

Adolescent↗
PubMed1992

Electrically evoked motile responses of mammalian type I vestibular hair cells.

Vestibular hair cells, type I and II, with membrane potentials around -64 mV were prepared from guinea pig ampullar cristae and maculae. In type I cells, current injection, application of voltage steps during membrane patch-clamping, or extracellular alternating current (ac) fields evoked fast length changes of 50 nm to 500 nm of the cell "neck." Mechanical responses were determined by computerized video techniques with contrast-enhanced digital image subtraction (DIS) and interpeak pixel counts (IPPC) or by double photodiode measurements. These techniques allowed spatial resolutions of 300 nm, 120 nm, and 50 nm, respectively. In contrast to measurements of high-frequency movements of auditory outer hair cells (OHCs), the mechanical responses of type I VHCs were restricted to low frequencies below 85 Hz. In addition to recently reported slow motility of VHCs, the present results suggest that fast mechanical VHC responses could significantly influence macular and cupular mechanics. Isometric and isotonic variants are discussed. The observed frequency maxima gap between VHCs and OHCs is suggested to contribute to a clear separation of the auditory and the vestibular sensory modality.

Animals↗
PubMed1991

Effect of marine coral prostanoids, clavulones, on spontaneous beating rate of cultured myocardial cells from fetal mouse hearts.

We examined effects of newly discovered marine coral prostanoids, clavulones, isolated from the Japanese stolonifer Clavularia viridis, on the spontaneous beating rate of cultured myocardial cells from fetal mouse hearts. Clavulone caused positive chronotropic action at 2-5 min after addition of clavulone (0.45 microM) to the reaction media of cardiac cells. This effect induced by clavulone was clearly different from the positive inotropic effects of ouabain (10 microM) and Bay K 8644 (0.1 microM) as judged by photoelectric recordings of beating. These results suggest a new biological action of clavulone that has positive chronotropic action on the cultured mouse myocyte preparation.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1989

Limitations of the lipid state hypothesis for atherosclerosis are revealed by X-ray diffraction measurements.

The lipid state hypothesis proposes that liquid crystalline states of cholesteryl esters play a role in the development and persistence of the fatty streak lesions characteristic of atherosclerosis. We have tested several corollaries suggested by this hypothesis and find that the ensemble of droplets in atherosclerotic tissue are predominantly in the isotropic (fluid) state at 37.0 degrees C. Furthermore, the liquid-crystalline state transition behavior of these droplets is not influenced significantly by the distribution of component cholesteryl ester species. There are no significant correlations between the transition behavior of the droplets and the age, sex, or race of the subjects from which tissue samples were taken. These results show that the lipid state hypothesis is weak, and that the origin and persistence of fatty streak lesions in humans is probably dominated by other factors.

Adolescent↗
PubMed1985

Interventional radiologic procedures in the management of the renal transplant patient.

Interventional radiologic procedures have become an important adjunct to the management of the renal transplant patient. Numerous problems can be dealt with, and in our experience these have included the diagnosis and treatment of ureteric obstruction, dilatation of renal artery stenoses, drainage of abscesses, hematomas and lymphoceles, management of complications of pancreatitis and treatment of bleeding due to fistulas and pseudoaneurysms.

Adult↗