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Biomedical subjects

K S Soh

Publications and source records attributed to K S Soh.

12 recordsLinked to original sources
PubMed2005

Influence of exposure to electromagnetic field on the cardiovascular system.

1 We examined whether extremely low frequency electromagnetic fields (ELF-EMF) affect the basal level of cardiovascular parameters and influence of drugs acting on the sympathetic nervous system. 2 Male rats were exposed to sham control and EMF (60 Hz, 20 G) for 1 (MF-1) or 5 days (MF-5). We evaluated the alterations of blood pressure (BP), pulse pressure (PP), heart rate (HR), and the PR interval, QRS interval and QT interval on the electrocardiogram and dysrhythmic ratio in basal level and dysrhythmia induced by beta-adrenoceptor agonists. 3 In terms of the basal levels, there were no statistically significant differences among control, MF-1 and MF-5 in PR interval, QRS interval, mean BP, HR and PP. However, the QT interval, representing ventricular repolarization, was significantly reduced by MF-1 (P < 0.05). 4 (-)-Dobutamine (beta1-adrenoceptor-selective agonist)-induced tachycardia was significantly suppressed by ELF-EMF exposure in MF-1 for the increase in HR (DeltaHR), the decrease in QRS interval (DeltaQRS) and the decrease in QT (DeltaQT) interval. Adrenaline (nonselective beta-receptor agonist)-induced dysrhythmia was also significantly suppressed by ELF-EMF in MF-1 for the number of missing beats, the dysrhythmic ratio, and the increase in BP and PP. 5 These results indicated that 1-day exposure to ELF-EMF (60 Hz, 20 G) could suppress the increase in HR by affecting ventricular repolarization and may have a down-regulatory effect on responses of the cardiovascular system induced by sympathetic agonists.

Animals↗
PubMed2005

Changes in ultraweak photon emission and heart rate variability of epinephrine-injected rats.

Ultraweak photons which are spontaneously emitted from a living body may be applicable as a non-invasive tool to characterize the physiological state of the living body. We investigated changes in the intensity of ultraweak photon emission, body temperature and the cardiovascular autonomic activity induced by epinephrine injection to rats. A high dose of epinephrine can make changes to the cardiovascular autonomic activity or body temperature. Photon emission of the dorsal part, rectal temperature and heart rate variability (HRV) were measured from eight Sprague-Dawley rats. The intensities of photon emissions for saline injections, which were used as a control, decreased from 13042+/-71 counts/min at the start of measurements to 8709+/-915 counts/min at 1 h after the injections. In the case with epinephrine injections, the intensity of photon emission reduced slowly from 13361+/-354 counts/min to 11040+/-433 counts/min. Rectal temperature increased in both saline- and epinephrine-injected rats, but one hour after the injections the temperature in the epinephrine case was slightly higher than that in the saline case. The standard deviation of the QRS wave complex interval (RR interval) increased from 1 to 4 (p<0.05) and the spectral ratio of the low frequency component to the high frequency component in the HRV data LF (0.19 approximately 0.74 Hz) / HF (0.78 approximately 2.50 Hz) decreased from 0.81 to 0.26 (p<0.05) in the case of epinephrine injection while no change was found in the case of saline injection. Thus, ultraweak photon emission was closely related to the cardiovascular autonomic activity.

Animals↗
PubMed2000

Exact wave functions in a noncommutative field theory.

We consider the nonrelativistic field theory with a quartic interaction on a noncommutative plane and compute the 2-->2 scattering amplitude within perturbative analysis to all orders. We regain the results of the perturbative analysis by finding the scattering and the bound state wave functions of the two particle Schrodinger equation. These wave functions unusually have two center positions in the relative coordinates, whose separation is transverse to the total momentum and scales linearly with its magnitude, exhibiting the stringy nature of the noncommutative field theory.

Journal Article↗
PubMed1999

Synchronization and resonance in a driven system of coupled oscillators.

We study the noise effects in a driven system of globally coupled oscillators, with particular attention to the interplay between driving and noise. The self-consistency equation for the order parameter, which measures the collective synchronization of the system, is derived; it is found that the total order parameter decreases monotonically with noise, indicating overall suppression of synchronization. Still, for large coupling strengths, there exists an optimal noise level at which the periodic (ac) component of the order parameter reaches its maximum. The response of the phase velocity is also examined and found to display resonance behavior.

Journal Article↗
PubMed1995

Effects of des-Asp-angiotensin I on the electrically stimulated contraction of the rabbit pulmonary artery.

In the presence of 3 x 10(-6) M captopril, 5 x 10(-7) M des-Asp-Angiotensin I was found to inhibit the electrically (1 and 2 Hz) induced contraction of the rabbit pulmonary artery but had no significant effect on the noradrenaline-stimulated contraction. 2.8 x 10(-6) M indomethacin and 10(-6) M losartan but not 10(-6) M (S) 1-([4-(dimethylamino)-3-methylphenyl]methyl)-5-(diphenylacetyl)-4, 5,6,7- tetrahydro-1H-imidazo(4,5-c]pyridine-6-carboxylic acid, ditrifluoroacetate, dihydrate (PD123319) attenuated the inhibition. The inhibition of the electrically stimulated contraction by 5 x 10(-7) M des-Asp-angiotensin I coincided with a significant drop in the accompanying evoked 3H overflow from re-uptaken [3H]noradrenaline. The results indicate that des-Asp-angiotensin I acts presynaptically on a subtype of angiotensin receptor that involves the release of prostaglandin(s). In addition, this receptor subtype is susceptible to blockade by angiotensin AT1- but not AT2-specific receptor antagonists. It was suggested that this receptor subtype is identifiable with the recently described angiotensin AT1B receptor subtype found in the brain, pituitary and adrenal glomerulosa. These findings demonstrated a direct action of sub-micromolar concentrations of des-Asp-angiotensin I on a blood vessel and indicate that the nonapeptide is an active angiotensin per se.

Angiotensin I↗
PubMed1978

The effects of replacing ester by amide on the biological properties of compounds related to acetylcholine.

1 Replacement of ester by amine in series of derivatives of diphenylacetic acid reduces the affinity for muscarine-sensitive acetylcholine receptors of the guinea-pig ileum from 40- to 100-fold. With similar series of phenylacetic acid the reduction is only 2- to 4-fold. In both series changes in the composition of the onium group produce similar changes in the affinity of amides and esters and it appears that the stiffness of the amide bond reduces the binding of the phenyl groups at the far end of the molecule from the onium atom. 2 Replacement of ester by amide in similar series of acetyl compounds reduces activity on the guinea-pig ileum over 1000-fold and on the frog rectus over 50-fold. Compounds with larger onium groups are antagonists on both preparations with log affinity constant around 3. The amides have similar affinity for electric eel acetylcholinesterase. 3 The amides are slightly bigger than the esters in solution and slightly more hydrophilic. 4 Replacement of ester by amide in acetylcholine reduces the proportion of gauche conformer about the C--C--bond from 100% to 39%. 5 The ability of acetylcholine to activate receptors is thought to depend on some degree of flexibility in the --CO--0--bond, though the hydration of the bond may also be important.

Acetylcholine↗
PubMed1976

A comparison of affinity constants for muscarine-sensitive acetylcholine receptors in guinea-pig atrial pacemaker cells at 29 degrees C and in ileum at 29 degrees C and 37 degrees C.

1 The affinity of 17 compounds for muscarine-sensitive acetylcholine receptors in atrial pacemaker cells and ileum of the guinea-pig has been measured at 29 degrees C in Ringer-Locke solution. Measurements were also made at 37 degrees C with 7 of them. 2 Some of the compounds had much higher affinity for the receptors in the ileum than for those in the atria. For the most selective compound, 4-diphenylacetoxy-N-methylpiperidine methiodide, the difference was approximately 20-fold. The receptors in the atria are therefore different the structure from those in the ileum. 3 The effect of temperature on affinity are not the same for all the compounds, tested indicating different enthalpies and entropies of adsorption and accounting for some of the difficulty experienced in predicting the affinity of new compounds.

Acetylcholine↗
PubMedDate not supplied

Pulse type classification by varying contact pressure.

We introduced a new technique of quantification of pulse characteristics in connection with contact pressure. We provided data only for illustrative purposes, deferring statistical analysis of samples of a larger population. This quantification can be useful for diagnostic purposes; for example, by detecting changes of the three quantities according to the health condition or particular disease of a patient, or by analyzing correlations among these quantities and other physiological variables.

Adult↗