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Biomedical subjects

R Y Chen

Publications and source records attributed to R Y Chen.

At least 19 recordsLinked to original sources
PubMed1992

Role of calcitonin gene-related peptide in capsaicin-induced gastric submucosal arteriolar dilation.

The response of gastric submucosal arterioles to topical (submucosal) application of calcitonin-gene-related peptide (CGRP) or capsaicin with and without the human CGRP antagonist, hCGRP-(8-37), was studied using in vivo microscopy. CGRP (10(-11) to 10(-8) M) induced dose-dependent dilation. Topical treatment with hCGRP(8-37) (10(-6) M, for 10 min) caused a significant decrease in basal arteriolar diameter from 33 +/- 2 to 27 +/- 2 microns. hCGRP(8-37) did not alter acetylcholine- or adenosine-induced vasodilation but did significantly reduce CGRP 10(-8) M vasodilation from 97.3 +/- 10.1 to 15.9 +/- 4.4% of the maximal response. Topical capsaicin (10(-9) M to 5 x 10(-7) M) induced dose-dependent arteriolar dilation. This vasodilation was markedly attenuated by hCGRP(8-37). Selective ablation of capsaicin-sensitive sensory neurons nearly completely inhibited capsaicin-induced vasodilation, suggesting that this vasodilation is primarily neurogenic in origin. We conclude that 1) topical application of capsaicin stimulates capsaicin-sensitive sensory neurons and induces dose-dependent arteriolar dilation; 2) this vasodilation is mediated in part by CGRP; and 3) CGRP may be involved in modulating the basal tone of gastric resistance vessels.

Animals↗
PubMed1992

[Intraocular pressure and optic nerve damages in monocular early glaucoma: a comparative study of primary open angle glaucoma and low tension glaucoma].

The correlation of intraocular pressure (IOP) to optic nerve damages was studied in 17 patients of primary open angle glaucoma (POAG) and 24 patients of low tension glaucoma (LTG) both with monocular early glaucomatous damages. In the POAG group, the mean IOP was higher in the glaucomatous eye than in the other, while in the LTG group there was no significant IOP difference between the two eyes. Comparing the optic nerve damages in both groups, patients of POAG presented a concentrically enlarged cup with even disc rim and diffuse retinal nerve fiber layer defect (RNFLD), while patients of LTG exhibited a paracentrical cup with uneven disc rim and localized RNFLD. The results suggested that there could be different mechanisms of optic nerve damages in the two groups.

Glaucoma, Open-Angle↗
PubMed1992

Antinuclear antibody detection using streptavidin-biotin-peroxidase complex on HEp-2 cell substrate.

The streptavidin-biotin-peroxidase complex (SABC) technique was compared to conventional indirect immunofluorescence (IIF) for the detection of anti-nuclear antibody (ANA) on HEp-2 cell substrate. SABC showed higher specificity and predictive value and gave more reproducible titres and clearer staining patterns than IIF in sera from a series of rheumatic disease patients. Sera from 80 patients with various types of rheumatic diseases and 20 without rheumatic disease were further tested using the SABC method. All systemic lupus erythematosus (SLE) sera were positive. The overall sensitivity was 95%, specificity 90% and predictive value 97% for rheumatic disease. The rim pattern was associated with SLE and mixed connective tissue disease. The nucleolar/homogeneous pattern was associated with scleroderma and SLE in remission. ANA titre and staining pattern have limited value in the clinical assessment of rheumatic disease; however, ANA has very high sensitivity for SLE and remains an excellent screening test.

Antibodies, Antinuclear↗
PubMed1991

[Application of 2d NMR techniques in the structure determination of ganosporelactone A and B].

Structure and stereochemistry of ganosporelactone A and B isolated from the spores of Ganoderma lucidum have been elucidated by the use of 1H-1H COSY, 1H-13C COSY, 1H-13C COLOC and NOESY 2D NMR spectroscopy. Ganosporelactone A and B are two novel pentacyclic triterpenoids which may be biogenetically derived from lanostane skeleton through the construction of C16 and C23 bond.

Drugs, Chinese Herbal↗
PubMed1991

[Cerebral and carotid arterial radiograms in low tension glaucoma].

Cerebral and carotid arterial radiograms were performed for 22 healthy volunteers, 8 patients with primary open angle glaucoma(POAG), and 10 patients with low tension glaucoma (LTG). Analysis of the Time-Radioactivity Curves suggested that insufficient perfusion of the carotid artery, especially the internal carotid artery, might play an important role in the optic nerve damage of some cases of LTG.

Adult↗
PubMed1991

[Studies on the triterpenoid constituents of the spores from Ganoderma lucidum karst].

Five compounds were isolated from the ether soluble fraction of the spores of Ganoderma lucidum. On the basis of their chemical properties and spectral data (MS, UV, IR, 1H and 13CNMR), they were identified as 3,7,11,12,15,23-hexaoxo-5 alpha-lanosta-8-en-26-oic acid (I), 3 beta,7 beta-dihydroxy-11,15,23-trioxo-5 alpha-lanosta-8-en-26-oic acid (II), 7 beta-hydroxy-3,11,15,23-tetraoxo-5 alpha-lanosta-8-en-26-oic acid (III), 3,7,11,15,23-pentaoxo-5 alpha-lanosta-8-en-26-oic acid (IV), 24,25,26-trihydroxy-5 alpha-lanosta-7,9 (11)-dien-3-one (V), Compound I is a new natural product, named ganosporeric acid A. Compounds II, III, IV and V were obtained for the first time from the spores of Ganoderma lucidum.

Drugs, Chinese Herbal↗
PubMed1990

[Studies on constituents of ganoderma capense IV. The chemical structures of ganoine, ganodine and ganoderpurine].

Two novel pyrrole alkaloids--ganoine and ganodine and a novel purine alkaloid ganoderpurine have been isolated from the mycelium of Ganoderma capense (Lloyd)Teng (Polyporaceae) obtained by submerged fermentation. On the basis of spectroscopic data their structures were elucidated, ganoine is N-isopentyl-5-hydroxymethyl-pyrryl alldehyde. Ganodine is N-phenylethyl-5-hydroxymethyl-pyrryl aldehyde and ganoderpurine is N9-(alpha, alpha dimethyl-gamma-oxobutyl) adenine.

Adenine↗
PubMed1989

Effects of dextran-induced hyperviscosity on regional blood flow and hemodynamics in dogs.

In 10 pentobarbitalized dogs, plasma viscosity (Ep) was raised fourfold while apparent blood viscosity (Ea) increased about twofold by two steps of exchange transfusion of 200 ml of plasma with plasma containing high molecular weight dextran (mol wt 500,000, 20% wt/vol). Elevation of Ea was primarily caused by an increase of Ep but not red cell aggregation. As Ea increased, regional blood flow (by 15-microns microspheres) remained constant in most organs but reduced in the small intestine, spleen, and thyroid gland. Vascular hindrance (Z), which reflects the state of vascular geometry, was calculated as flow resistance per Ea. Among various organs, a reduction in Z was noted in the heart, liver, pancreas, kidney, brain, and adrenal gland. In myocardium, there was a progressive reduction of the endocardial-to-epicardial flow ratio, indicating a less profound vasodilation in endocardium than epicardium. These results indicate that dextran-induced hyperviscosity leads to a compensatory vasodilation in several vital organs thus serving to maintain blood flow and nutrient transport.

Animals↗
PubMed1989

Nutrient reabsorption of intestine in vitro: effects of ethanol and caffeine.

We studied the effect of ethanol and caffeine on the intestinal reabsorption (jejunum from SD rats) of glucose (Glu) and amino acids. Since most of the studies on the effect of ethanol utilized high concentration, we first characterized the effect of 8% (approximately 1.4 M) ethanol on the activity of Na(+)-coupled nutrient transport. Consistent with previous reports, ethanol (greater than 1 M) was found to inhibit the uptake rates of glucose and its non-metabolizable analogue 3-O-methyl-glucose (3-OMG) by 30%, while leucine (Leu) uptake was inhibited by 60%. Phloridzin, a specific inhibitor for Na(+)-coupled sugar transport, at 1 mM concentration could inhibit Glu and 3-OMG uptake by more than 60% without affecting Leu uptake. We then compared the effects of various concentrations of ethanol on about 20 intestinal segments taken from the same animal. We consistently observed transport inhibition at high concentration of ethanol but at low concentrations (up to 200 mM), there was no consistent effect, while phloridzin or low-Na media (86% of Na replaced by choline) significantly reduced the rate of nutrient uptake in the same experiment. Thus, it appeared that low concentrations of ethanol had no significant effect on Na(+)-coupled nutrient uptake. We also determined the effect of caffeine on intestinal 3-OMG uptake. At concentration of 0.05 mM, caffeine inhibited 3-OMG uptake by about 15% (p less than 0.05). The level of inhibition was not significantly different at 0.5 mM, but a slightly higher level of inhibition (20%) was reached at 5 mM. The action of caffeine could be mimicked by dibutyryl cAMP (1 mM).

3-O-Methylglucose↗
PubMed1986

Effects of blood viscosity on plasma renin activity and renal hemodynamics.

The effects of alterations in apparent blood viscosity on renal hemodynamics and plasma renin activity (PRA) were studied in dogs anesthetized with sodium pentobarbital. Blood viscosity was altered isovolemically either by changes in hematocrit (Hct) or by an increase in plasma viscosity (dextran administration). Arterial blood pressure and renal blood flow (RBF) remained relatively constant when apparent blood viscosity was elevated by changes in Hct or plasma viscosity. Thus the hyperviscosity of blood was associated with a decrease of renal vascular hindrance, resulting in an essentially unchanged renal flow resistance. The decrease in renal vascular hindrance may result from renal vasodilation. In hyperviscosity induced with dextran, the increase in PRA correlates linearly with the decrease in renal vascular hindrance, with a coefficient of correlation of 0.968 (P less than 0.005). The increase in PRA that resulted when Hct was raised from 25 to 55% also can be correlated linearly with the decrease in renal vascular hindrance, with a coefficient of correlation of 0.953 (P less than 0.005). These results suggest that the decrease in renal vascular hindrance in response to a rise in apparent blood viscosity leads to an increase in PRA.

Animals↗
PubMed1985

Effects of experimental hypotension on hemodynamics and renin secretion rate.

The effects of hypotension on systemic and renal hemodynamics, plasma renin activity (PRA), and renin secretion rate (RSR) were determined in dogs anesthetized with sodium pentobarbital plus chloralose. Renal blood flow (RBF) was determined with microspheres (15 micron) and with an electromagnetic flowmeter connected to an extra-corporeal circuit from the femoral artery to the renal artery. Hypotension was induced by nitroprusside infusion, which decreased peripheral resistance, and by hemorrhage, which reduced cardiac output. RSR increased in both forms of hypotension, but the increase following hemorrhage was greater than that after nitroprusside. Thus, when the mean arterial pressure (MAP) was reduced to 75 mmHg, RSR increased from 470 +/- 26 units/min to 990 +/- 12 units/min with nitroprusside and from 415 +/- 13 units/min to 1,509 +/- 21 units/min following hemorrhage. At MAP of 50 mmHg, RSR increased to 1,541 +/- 64 units/min with nitroprusside and to 2,254 +/- 98 units/min following hemorrhage. Nitroprusside increased renin secretion not only by an increase in sympathetic beta adrenergic activity through the baroreceptor reflex, but also by its direct vasolidatory effect in the renal circulation. In hemorrhagic hypotension, the increase in renin secretion was accompanied by renal vasoconstriction. The greater increase in RSR following hemorrhage than after nitroprusside at given levels of hypotension may be explained by a stronger beta adrenergic activation, the activation of prostaglandin and kallikrein systems, a lower microvascular pressure level, and/or smaller pulse pressure and lower sodium load in the macula densa. The comparison of renin secretion at the same degree of hypotension induced by different hemodynamic alterations serves to elucidate the mechanisms of renin secretion.

Animals↗
PubMed1984

Determination of the partition coefficient of 133xenon between oral tissues and blood in the dog.

Ostwald solubility coefficients for 133Xe in plasma (Sp), red blood cells (Sc), and selected oral tissue homogenates (St) obtained from the dog were determined at 4, 20, 27 and 37 degrees C by counting the 133Xe activity of the air phase and the sample (liquid, red cells or tissue) in the same tube following equilibration. The partition coefficient for xenon (lambda, in ml/g) between red cells and plasma (lambda cp) and that between tissues and plasma (lambda tp) were calculated from the measured Sp, Sc and St. The tissue-blood partition coefficients (lambda tb) of oral tissues for 133Xe were then calculated using lambda cp, lambda tp and the haematocrit value. The calculated values of lambda tb at 37 degrees C and 50 per cent haematocrit were 0.650 for the pulp, 0.674 for the tongue, 0.828 for the submandibular gland and 0.881 for the gingiva of the dog. lambda cp increased and lambda tp decreased as the temperature was reduced from 37 to 4 degrees C.

Animals↗