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Biomedical subjects

G Lee

Publications and source records attributed to G Lee.

At least 505 records · Page 28Linked to original sources
PubMed1977

Linear dose response and quantitative attenuation by potassium of the inotropic action of acetylstrophanthidin.

To evaluate the nature of the inotropic dose response of digitalis and to determine the effects of potassium on this response, isometrically contracting isolated supported right ventricular cat papillary muscles were studied relative to their peak tension and peak dT/dt increases to physiologic cumulative doses of acetylstrophanthidin (ACS) in different extracellular potassium concentrations in the muscle bath. The inotropic dose response to ACS was observed to be linear in cumulative glycoside concentrations ranging from 0.40 to 4.23 X 10(-7) M ACS in 3.5 mM K+ medium and from 1.22 to 7.47 X 10(-7) M ACS in 7.0 mM K+ medium. The influence of potassium alterations in the muscle bath from the low to the high K+ concentrations prior to ACS resulted in marked attenuation of the positive inotropic property of ACS. From these data, it is concluded that the dose inotropic response of digitalis is linear, with small doses producing proportionally the same effects as larger doses, and that extracellular potassium markedly influences this linear dose response such that higher K+ concentrations considerably attenuate the positive inotropic response of digitalis.

Animals↗
PubMed1977

Echocardiographic identification of the mitral valve prolapse syndrome.

The data presented herein would indicate that mitral valve prolapse may be represented by a variable spectrum of abnormalities on the echocardiogram. Utilizing all the abnormalities described, echographic evidence of mitral valve prolapse may be detected in most patients with this disorder. However, evidence of mitral valve prolapse may also be observed in a large contingent of asymptomatic patients without other clinical manifestations of cardiac disease. The biologic significance of these echographic abnormalities remains uncertain and constitutes an important area for future investigation.

Cineangiography↗
PubMed1977

Effects of thyrotropin on the thyroid cell membrane: hyperpolarization induced by hormone-receptor interaction.

Cultured thyroid cells accumulate the lipophilic cation triphenylmethylphosphonium, indicating that there is an electrical potential (interior negative) across the plasma membrane. Thyrotropin stimulates the uptake of the lipophilic cation 3-fold, and the proton conductor carbonylcyanide-m-chlorophenylhydrazone causes efflux of triphenylmethylphosphonium accumulated in the presence or absence of thyrotropin. The stimulatory effect of thyrotropin on triphenylmethylphosphonium accumulation is not mimicked by human chorionic gonadotropin, a glycoprotein hormone with a similar structure whose target organ is not the thyroid, and the effect is abolished if the thyrotropin-receptor activity of the cells is destroyed by treatment with trypsin. Analogous effects are observed with thyroid plasma membrane vesicles which are essentially devoid of mitochondrial and soluble enzyme activities. Triphenylmethylphosphonium uptake and stimulation by thyrotropin occurs when NaCl, KCl, or Tris.HCl concentration gradients are artifically imposed across the vesicle membrane ([salt](out) > [salt](in)). It seems likely, therefore, that triphenylmethylphosphonium uptake is driven by a chloride diffusion potential (interior negative) and that thyrotropin either increases the permeability of the membrane to anions or decreases its permeability to cations. Thyrotropin-stimulated triphenylmethylphosphonium uptake in the vesicle preparations reaches a quasi steady-state within 3 min; in contrast, thyrotropin-stimulated adenylate cyclase activity is negligible during this period of time, becomes measurable after about 4 min, and is optimal after 12-15 min. Thus, a primary mode of action of thyrotropin on the thyroid cell may be an alteration in the electrical potential across the plasma membrane. The relevance of this observation to the mechanism of action of other glycoprotein hormones, certain bacterial toxins, and interferon is discussed.

Animals↗
PubMed1977

Effects of digitalis on the exercise electrocardiogram in normal adult subjects.

Controversy continues regarding the effects of administration of digitalis upon the exercise electrocardiogram. Thus, maximal treadmill exercise tests were performed before and two weeks after administration of 0.25 mg of digoxin daily in 15 normal subjects (documented by cardiac catheterization and coronary arteriographic studies). Administration of digitalis induced abnormal findings on exercise tests in all 14 subjects with serum levels of digoxin greater than or equal to 0.5 ng/ml; however, at workloads greater than 75 to 90 percent of maximal predicted heart rate, the changes in the ST segment reverted to a normal configuration in all subjects, thereby providing differentiation of digitalis-induced ST-segment alterations from those due to myocardial ischemia at maximal treadmill stress.

Adult↗
PubMed1977

Spontaneous cytomegalovirus mononucleosis with conjunctivitis.

Cytomegalovirus (CMV) was isolated from the conjunctiva of a patient with mild unilateral catarrhal conjunctivitis associated with the typical clinical features of CMV mononucleosis syndrome in a previously healthy adult. The diagnosis was confirmed by a marked rise in the complement fixation antibody titers. Prospective studies are needed to determine the frequency of conjunctival involvement in CMV mononucleosis and the relation, if any, to sporadic cases of conjunctivitis.

Adult↗
PubMed1976

Cytological observations of the ovarian epithelium in mammals during the reproductive cycle.

We have studied the ovarian epithelijm at various stages of the reproductive cycle in a number of mammalian species utilizing light microscopy, scanning microscopy, the freeze-fracture technique, transmission microscopy and by employing specialized tracers that use lanthanum and horseradish peroxidase. We found that the epithelial cells are joined by incomplete tight junctions, gap junctions, and desmosomes. The cytoplasmic matrix contains a large irregularly shaped nucleus, few microtubules, microfilaments, mitochondria, endoplasmic reticulum and a host of coated and non-coated vesicles of varying diameters. The saccules comprising the large Golgi complex and its companion vesicles are associated with a basal body-centriole complex: some of these saccules and affiliated vesicles are acid phosphatase positive. Surface modifications of ovarian epithelial cells include numerous microvilli, some of which have a bulbous tip, and plications of the lateral plasma membrane which are thought to accomodate volume changes of the ovary during follicular development. Many coated and non-coated endocytotic caveolae were found on these cells, particularly in the basal area. These caveolae internalized exogeneously administered horseradish peroxidase. We view the marked endocytotic activity as an efficient transport mechanism for partially removing substances from the interstitium of the ovary and the peritoneum.

Animals↗
PubMed1976

Efficacy of cardioselective beta adrenergic blockade with intravenously administered tolamolol in the treatment of cardiac arrhythmias.

The efficacy of tolamolol, a cardioselective beta adrenergic blocking agent, was evaluated in the treatment of cardiac arrhythmias in 27 patients. Nineteen patients had supraventricular arrhythmias and eight had ventricular arrhythmias. Evaluation was by doulbe-blind randomized trial in 23 patients. Tolamolol was effective in reducing ventricular rate in 17 (85 percent) of 19 patients with supraventricular arrhythmias and resulted in conversion to sinus rhythm in 2 of the 17. The mean ventricular rate in 17 patients decreased from 135 to 102/min 10 minutes after initiation of administration of tolamolol and gradually decreased further to 93/min after 60 minutes. Reduction in ventricular rate was sustained for 2 hours of monitoring undergone by all patients and for 4 and 6 hours monitoring in two subgroups. Among the eight patients with ventricular ectopic beats, tolamolol reduced their frequency in four patients and had no effect in four. Six patients had chronic obstructive pulmonary disease and experienced no adverse clinical effects on respiratory function in association with administration to tolamolol. Untoward effects occurred in 10 patients, including hypotension in 3, 1 of whom required vasopressor therapy. Other side effects were sedation, nausea, dyspnea and warmth in the chest, all of which were mild and transient, requiring no treatment. Cardioselective beta adrenergic blockade with tolamolol was highly effective in controlling ventricular rate in supraventricular arrhythmias and reduced the frequency of ventricular ectopic beats in half of the small group of patients with this arrhythmia. It is particularly applicable in patients with obstructive pulmonary disease in whom cardiac beta adrenergic blockade is indicated. Hypotension is an important potential side effect.

Adrenergic beta-Antagonists↗
PubMed1976

Comparative effects of morphine, meperidine and pentazocine on cardiocirculatory dynamics in patients with acute myocardial infarction.

The cardiocirculatory effects of the commonly used parenteral analgesics, morphine sulfate 15 mg, meperidine hydrochloride 100 mg and pentazocine 60 mg, each administered intravenously, were compared in 12 patients with acute myocardial infarction during cardiac catheterization and by echocardiogram. No untoward hemodynamic effects occurred following the administration of morphine or meperidine. In contrast, pentazocine produced significant (p less than 0.01 to less than 0.05) increases in systemic and pulmonary arterial pressures, left ventricular filling pressure, systemic vascular resistance, and systolic and diastolic dimensions; and decreases in left ventricular ejection fraction and mean velocity of circumferential fiber shortening. These deleterious actions of pentazocine appeared due to peripheral vasoconstriction and negative inotropic properties. Further, pentazocine-induced increases in left ventricular preload and afterload increased myocardial oxygen demands. Since this study demonstrates that pentazocine is hazardous in myocardial infarction, morphine and meperidine are the preferred analgesics in this condition.

Adult↗
PubMed1976

Preparation and in vitro antifungal activities of some quinolizidine derived hemiaminals and beta-tert-amino sulfides.

New alpha-thiohemiaminals, 7alpha-phenylthio-7-epideoxynupharidin-6-ol, the diasteriomeric 7beta-phenylthiodeoxy-nupharidin-6-ol, and 3-methyl-3-methylthio-4-hydroxyquinolizidine, were prepared and reduced to the corresponding beta-tert-amino sulfides. The configuration at C-7 of the beta-tert-amino sulfides was determined by observing the direction of the solvent-induced shift of the C-7 methyl proton resonance. The configuration at C-7 of the new alpha-thiohemiaminals was established by correlations with the beta-tert-amino sulfides and confirmed, in the case of the deoxynupharidine derivatives, by circular dichroism and ascertaining the sterochemistry of deuteride incorporation upon sodium borodeuteride reduction of the alpha-thiohemiaminal. The in vitro antifungal activities of six compounds possessing the quinolizidine skeleton, including all the newly synthesized compounds as well as some previously reported ones, and amphotericin B were tested against several human pathogenic fungi. Besides amphotericin B, only the two deoxynupharidine alpha-thiohemiaminals were active, especially against Histoplasma capsulatum and Blastomyces dermatitidis. The observations indicate activity is derived from the 3-furyl group and the functionality from which alpha-thioimmonium ions can be produced.

Antifungal Agents↗
PubMed1976

Use of thyrotropin and cholera toxin to probe the mechanism by which interferon initiates its antiviral activity.

Thyrotropin (10 muM) inhibited the antiviral activity of interferon. When added after interferon, thyrotropin (TSH) had no effect on antiviral activity. There was also no inhibition of interferon action in cells washed with medium between incubations with TSH and interferon. 125I-Labeled TSH and 125I-labeled cholera toxin could bind to preparations of mouse L-cell plasma membranes. The binding was specific in that it was prevented by unlabeled thyrotropin or cholera toxin, but not by insulin, glucagon, prolactin, growth hormone, human chorionic gonadotropin, or luteinizing hormone. Mouse interferon inhibited 125I-labeled TSH binding to L-cell plasma membranes. The effect of mouse interferon on 125I-labeled cholera toxon binding was more complex, inhibition occurring only after an initial enhancement at low interferon concentrations. A 10-fold higher concentration of interferon was required to inhibit 125I-labeled TSH binding. Mouse interferon was also able to displace bound 125I-labeled TSH, but not bound 125I-labeled cholera toxin. The interferon interaction with cell membranes was temperature-sensitive. Human interferon could induce changes in binding of 125I-labeled TSH and 125I-labeled cholera toxin to mouse L-cell plasma membranes similar to those induced by mouse interferon. Mouse interferon induced similar changes in plasma membranes of human KB-3 cells, which are insensitive to both human and mouse interferons. In view of these results, the species specificity of interferons does not appear to reside solely at the point of the initial interaction with their binding sites.

Bacterial Toxins↗
PubMed1976

Thyrotropin-ganglioside interactions and their relationship to the structure and function of thyrotropin receptors.

Gangliosides inhibit 125I-labeled thyrotropin binding to the thyrotropin receptors on bovine thyroid plasma membranes, on guinea pig retro-orbital tissue plasma membranes, and on human adipocyte membranes. This inhibition by gangliosides is critically altered by the number and location of the sialic acid residues within the ganglioside structure, the efficacy of inhibition having the following order: GD1b greater than GT1 greater than GM1 greater than GM2 = GM3 greater than GD1a. The inhibition results from the interaction of thyrotropin and gangliosides, rather than the interaction of membrane and gangliosides. Fluorescence studies show that the inhibition is associated with a distinct conformational change of the thyrotropin molecule and that the progression from a "noninhibitory conformation" to an "inhibitory conformation" parallels exactly the order of effectiveness in inhibiting 125I-labeled thyrotropin binding. The ganglioside inhibition of 125I-labeled thyrotropin binding appears to be hormonally specific in that it is not affected by albumin, glucagon, insulin, prolactin, follicle-stimulating hormone, growth hormone, or corticotropin. The possibility that a ganglioside or ganglioside-like structure is a component of the thyrotropin receptor is suggested by the finding that gangliosides more complex than N-acetylneuraminylgalactosylglucosylceramide are present in bovine thyroid membranes in much higher quantities than have been previously found in extraneural tissue. The finding that the B component of cholera toxin, which also interacts with gangliosides, has a peptide sequence in common with the beta subunit of thyrotropin, suggests that thyrotropin and cholera toxin may be analogous in their mode of action on the membrane.

Adipose Tissue↗
PubMed1976

Cholera toxin interactions with thyrotropin receptors on thyroid plasma membranes.

Unlabeled cholera toxin inhibits [125I]thyrotropin binding to thyrotropin receptors on thyroid plasma membranes. Maximal inhibition by cholera toxin does not exceed 40%, whereas unalbeled thyrotropin completely inhibits [125I]thyrotropin binding to these same membranes. Kinetic analyses of the binding data are compatible with the view that the cholera toxin decreases the number of receptor sites available to thyrotropin and that the mechanism by which the cholera toxin inhibits [125I]thyrotropin binding to these receptor sites involves both competitive and noncompetitive elements.

Adenylyl Cyclases↗