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Biomedical subjects

C M Lee

Publications and source records attributed to C M Lee.

At least 271 records · Page 15Linked to original sources
PubMed1987

Inhibition of radioligand binding to A1 adenosine receptors by Bay K8644 and nifedipine.

Two dihydropyridine compounds, Bay K8644 (a calcium entry activator) and nifedipine (a calcium entry blocker), were found to inhibit the binding of [3H]phenylisopropyladenosine ([3H]PIA) to A1 adenosine receptors in rat cerebral cortex membranes with comparable potencies (IC50 10-30 microM). Scatchard analyses indicated that both Bay K8644 and nifedipine inhibited the binding of [3H]PIA by increasing the KD but without significant effect on the Bmax. When tested at 100 microM, neither Bay K8644 nor nifedipine showed a significant effect on [3H]-p-aminoclonidine ([3H]PAC; alpha 2-adrenergic receptor), [3H]dihydroalprenolol ([3H]DHA; beta-adrenergic receptor), [3H]spiperone (dopamine receptor), and [3H]nitrobenzylthioinosine [( 3H]NBMPR; nucleoside transporter) binding. In the presence of 10 mM Mg2+, the ability of 2-chloroadenosine (2-Cl-Ad, an A1 adenosine receptor agonist) to displace [3H]PIA binding was increased. Conversely, the potencies of 1,3-diethyl-8-phenylxanthine (DPX; an A1 receptor antagonist), Bay K8644 and nifedipine in inhibiting [3H]PIA binding were unchanged. It is suggested that both Bay K8644 and nifedipine may act as antagonists of adenosine A1 receptors, in addition to their well-known effects on calcium channels.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1987

Quantification of diabetic macular edema.

In a cross-sectional study, 34 diabetic patients with clinically significant macular edema underwent visual acuity testing, stereo fundus photography (graded for retinal thickening and hard exudates), fluorescein angiography (evaluated for macular leakage and the outline of the foveal avascular zone [FAZ]), and vitreous fluorophotometry (whereby posterior penetration ratios were calculated). This last ratio provided the highest single correlation with visual acuity; next highest were patient age and FAZ grading. Multivariate regression confirmed that these three variables together best predicted visual acuity. Lesser correlations with acuity were obtained with angiographic leakage and fundus photography grading. Cross-correlations among all gradings showed that indicators of breakdown of the blood-retinal barrier, ie, fluorophotometry, angiographic leakage, and retinal thickening, were significantly correlated with each other, whereas FAZ grading was independent of all these factors and correlated only with acuity. By performing vitreous fluorophotometry and fluorescein angiography, it is possible to quantitate two major components of diabetic maculopathy: breakdown of the blood-retinal barrier and macular ischemia, both of which are highly correlated with visual acuity.

Adult↗
PubMed1987

Electroretinographic findings in sickle cell retinopathy.

We obtained electroretinograms (ERGs) from normal subjects and from patients with sickle cell disease. The ERG components (a-wave, b-wave, and oscillatory potentials) obtained from normal subjects and patients without peripheral retinal neovascularization did not differ in either amplitude or implicit time. However, ERG components obtained from patients with peripheral retinal neovascularization were reduced in amplitude compared with those obtained from normal subjects or patients without neovascularization. The reduced a-wave, b-wave, and oscillatory potential amplitudes may have been due to photoreceptor dysfunction secondary to choroidal ischemia or possibly increased oxygen demands by the inner retina. Ischemia of the inner retina may also have contributed to the altered b-wave and oscillatory potentials. These results suggest that ERG provides a means of assessing the consequence of peripheral retinal ischemia to retinal cell function and could be of value in monitoring patients with sickle cell disease for the development of clinically significant peripheral retinal neovascularization.

Anemia, Sickle Cell↗
PubMed1987

Quantification of macular ischaemia in sickle cell retinopathy.

Macular ischaemia has a central role in the pathophysiology and prognosis of retinal macular disease. We attempted to quantitate two of its major components as follows: vascular nonperfusion, by measuring the foveal avascular zone (FAZ), using fluorescein angiography; and functional damage, using automated perimetry of the central 30 degrees. Sickle cell disease was chosen for study because it was considered a prototype for a purely ischaemic retinopathy without an exudative component. We found that the FAZ measurement was reproducible and that the patients with maculopathy had statistically larger FAZs than the normal controls (p = 0.016, Wilcoxon rank sum test). In addition, scotomas measured by visual field perimetry were significantly larger in the sickle cell patients with maculopathy than in those without maculopathy. Our results showed that angiography and perimetry of the central 30 degrees were more sensitive tests for the detection of ischaemic macular disease than visual acuity and that macular ischaemia could be quantified by their use.

Adolescent↗
PubMed1987

Interaction of nutrition and infection: macrophage activity in vitamin B12-deficient rats infected with Trypanosoma lewisi.

MACROPHAGE ACTIVITY WAS STUDIED IN RATS INFECTED WITH TRYPANOSOMA LEWISI IN THREE PROTOCOL GROUPS: one group was fed complete diet, a second group was given a vitamin B(12)-deficient diet, and a third group was fed a pair-fed control (calorically restricted) diet. Throughout the observational period, in animals fed complete and pairfed diets, marked increases in acid phosphatase levels in peritoneal macrophages were directly related to the degree of parasitemia. Acid phosphatase levels in rats deprived of vitamin B(12) were approximately one third that of animals with an adequate supply of the vitamin. Irrespective of the diets, the infection with T lewisi also elicited increased macrophage phagocytosis of polystyrene latex particles and macrophage spreading. Both of these activities occurred at a much slower rate in the vitamin B(12)-deficient animals.

Acid Phosphatase↗
PubMed1987

Interaction of trace metal contaminants on hematological responses: influence of infection with Trypanosoma lewisi.

The influence of trace metal contaminants (lead, cadmium, and mercury) on Sprague-Dawley rats was investigated to determine whether subclinical levels of these metals might have adverse effects on the host's ability to respond to an infective agent.In the present study, a trace metal contaminant-trypanosome system was employed to observe the hematological changes in rats infected with Trypanosoma lewisi. The animal groups were: (1) lead (Pb), (2) cadmium (Cd), (3) mercury (Hg), and (4) controls (animals not exposed to trace metals).Regardless of the trace metals, infected animals showed decreases in total erythrocyte counts and lower hematocrit values. Generally, infected animals also showed increases in total leucocyte counts, decreases in the percentages of lymphocytes and monocytes, increases in percentage of neutrophils, and no changes in percentages of eosinophils and basophils.

Animals↗
PubMed1987

A clinicopathologic study of dye laser photocoagulation on primate retina.

Chorioretinal lesions produced by dye laser photocoagulation were examined on normal monkey retinas, using angiographic and histopathologic techniques. Retinal burns produced by green (514 nm), yellow (577 nm), orange (600 nm), and red (630 nm) laser lights were placed in the posterior pole between the fovea and the major vascular arcades. When examined histopathologically 24 hours after treatment, greater damage to the inner retina and deep choroid was noted with the red laser light than with the green, yellow and orange laser lights. These differences were not detectable 31 days after treatment. There were no appreciable acute differences among the lesions caused by green, yellow and orange irradiation. Laser light at four wavelengths of the orange spectrum (590, 595, 600, and 605 nm) produced comparable chorioretinal destruction in the juxtafoveal zone when examined 24 hours and 31 days after treatment. Retinal arterioles and venules treated with yellow (577 nm) and orange (600 nm) laser light demonstrated endothelial and pericytic cell damage. Changes in the outer retina, pigment epithelium, and choriocapillaris were also present beneath the photocoagulated vessels.

Animals↗
PubMed1986

Multiple tachykinin binding sites in peripheral tissues and in brain.

Tachykinin binding sites in guinea pig urinary bladder (GPUB), rat salivary gland (RSG), hamster urinary bladder (HUB), rat vas deferens (RVD) and rat cerebral cortex (RCC) were compared using 125I-Bolton Hunter conjugates of substance P (125I-BHSP), eledoisin (125I-BHE) and neurokinin A (125I-BHNKA). In typical SP-P tissues (GPUB, RSG) and in RCC, SP was the most potent displacer of 125I-BHSP and [Glp6,D-Pro9]-SP(6-11) was 90 times less active than [Glp6,L-Pro9]-SP(6-11) while SP methyl ester (SPOMe) was 5-10 times more active than the Bolton Hunter conjugate of SPOMe (I-BHSPOMe). On the other hand, in typical SP-E tissues (HUB, RVD), neurokinin A was most potent in displacing 125I-BHE and [Glp6,D-Pro9]-SP(6-11) was over 300 times more active than [Glp6,L-Pro9]-SP(6-11) while SPOMe was 160 times less active than I-BHSPOMe. In rat cerebral cortex, the rank order of potency of tachykinins and related analogues in displacing 125I-BHE was distinct from that of peripheral SP-E sites, with neurokinin B being the most potent displacer, and SPOMe was over 1,000 times more active than I-BHSPOMe; 125I-BHE binding sites in CNS may represent a third category of tachykinin receptor, designated SP-N.

Animals↗
PubMed1986

Lipogenesis in isolated human sebaceous glands.

Lipogenesis in isolated human sebaceous glands from [U-14C]glucose, [U-14C]leucine, [U-14C]isoleucine, and [U-14C]valine has been determined by thin-layer chromatography. Total lipogenesis from 2 mmol/l [U-14C]glucose was 114.8 +/- 22.3 pmol/gland per h (mean +/- SE), with 53.8% being incorporated into triglycerides, 20.2% into squalene, 12.8% into phospholipids, 2.1% into cholesterol and 7.1% into wax monoester and cholesterol ester and 5% into di- and monoglycerides and free fatty acids. Total lipogenesis from 2 mmol/l [U-14C]leucine, 2 mmol/l [U-14C]isoleucine, and 2 mmol/l [U-14C]valine in the presence of 2 mmol/l glucose was 26, 29 and 9%, respectively, of that seen with 2 mmol/l glucose alone. The pattern of 14C distribution in the various lipid classes from the three U-14C-labelled branched-chain amino acids was not significantly different from that seen with [U-14C]glucose.

Carbon Radioisotopes↗
PubMed1986

Smooth muscle relaxant effect of dehydroindicolactone.

Dehydroindicolactone, a novel linear furanocoumarin with an 8-substituted side chain carrying a 5-member ring lactone, showed spasmolytic activity in a number of smooth muscle preparations. The spasmolytic activity seems to lie in its ability to block the dihydropyridine-sensitive calcium channel.

Animals↗