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Biomedical subjects

T Lee

Publications and source records attributed to T Lee.

At least 397 records · Page 22Linked to original sources
PubMed1979

Modulating effect of regional myocardial performance on local myocardial perfusion in the dog.

We studied the effect of regional contractile performance on regional coronary blood flow and flow distribution in 10 dogs. The left anterior descending (LAD) coronary artery was cannulated and perfused. Maximal vasodilation was obtained with adenosine. Consequently, variations of LAD flow reflected changes of extravascular resistance. Lidocaine injected in the LAD caused a localized reduction of contractile performance as shown by the absence of systolic wall thickening. Global left ventricular performance and pressure were unchanged. Coronary extravascular resistance diminished and LAD flow increased from 4.8 +/- 0.5 to 6.2 +/- 0.6 ml/min per g (P less than 0.02). The endocardial: epicardial ratio increased from 1.02 +/- 0.07 to 1.28 +/- 0.07 (P less than 0.001). Isoproterenol in the LAD augmented systolic wall thickening. Regional coronary flow diminished from 5.1 +/- 0.5 to 3.3 +/- 0.4 ml/min per g (P less than 0.001), and the endocardial:epicardial ratio diminished from 1.08 +/- 0.07 to 0.75 +/- 0.07 (P less than 0.01). These data indicate that myocardial contractility is a major component of extravascular coronary resistance and is a mechanical determinant of coronary blood flow and its transmural distribution.

Animals↗
PubMed1979

In vitro assessment of Tc-99m labeled bovine thrombin and streptokinase-activated human plasmin: concise communication.

Bovine thrombin and streptokinase-activated human plasmin have been labeled with Tc-99m using stannous reduction of pertechnetate under physiological conditions (pH 7.4). The binding efficiency of radiotechnetium to these enzymes is greater than 94%, with less than 5% of reduced but unbound Tc-99m (Sn) complex as assayed by ascending paper radiochromatography using ITLC silica gel plate. Free or unbound pertechnetate is less than 1%. In vitro enzymatic analyses of the Tc-99m-labeled enzymes demonstrate no evidence of protein denaturation or significant loss of enzymatic activity after labeling. Both labeled enzymes are biochemically active in vitro with their respective substrates.

Animals↗
PubMed1979

The prognostic value of serum immunosuppressive effect in patients with ovarian cancer.

Sixteen patients who underwent surgery and postoperative chemotherapy for carcinoma of the ovary were studied. Eleven survived more than 18 months without evidence of recurrence, and 5 died more than 5 months after surgery. Serial determinations were made preoperatively and postoperatively of the immunosuppressive effect of the serums of these patients on the response of normal lymphocytes to phytohemagglutinin stimulation. These determinations were plotted for each patient; the shapes of the curves for patients who survived are markedly different from those of patients who died. The prognostic value of these findings is discussed.

Adult↗
PubMed1978

Astrovirus gastroenteritis age distribution of antibody.

Astrovirus antibody was detected by immunofluorescence using infected primary human embryo kidney cultures as antigen. Of 87 Oxford children aged 0--10 years, only 7% in the 6 to 12-month-old group had antibody. The percentage of children having evidence of past infection rose progressively in the 1--4 age range and 75% of the 5 to 10-year-old group possessed astrovirus antibody. Fifty-four (77%) of a group of 70 young adults likewise had antibody.

Age Factors↗
PubMed1978

Ligand-induced conformation changes in Torpedo californica membrane-bound acetylcholine receptor.

A time-dependent increase in ligand affinity has been studied in cholinergic ligand binding to Torpedocalifornica acetylcholine receptor by inhibition of the kinetics of of [125I]-alpha-bungarotoxin-receptor complex formation. The conversion of the acetylcholine receptor from low to high affinity form was induced by both agonists and antagonists of acetylcholine and was reversible upon removal of the ligand. The slow ligand induced affinity change in vitro resembled electrophysiological desensitization observed at the neuromuscular junction and described by a two-state model (Katz, B., & Thesleff, S. (1957) J. Physiol. 138, 63). A quantitative treatment of the rate and equilibrium constants determined for binding of the agonist carbamoylcholine to membrane bound acetylcholine receptor indicated that the two-state model is not compatible with the in vitro results.

Acetylcholine↗
PubMed1978

Effect of haloperidol and apomorphine treatment on dopamine receptors in pituitary and striatum.

Prompted by an interest in the similarity of brain and tuberoinfundibular systems, the authors studied butaclamol-specific neuroleptic and apomorphine binding in pituitary and striatum after chronic haloperidol and acute apomorphine treatment. Striatal binding increases but pituitary binding decreases in haloperidol-treated rats. Pituitary binding changes rapidly in response to apomorphine exposure and striatal binding does not. These findings suggest that factors influencing binding differ in these two tissues.

Animals↗
PubMed1978

Immunosuppressive effect of serum in patients with ovarian carcinoma.

Cell-mediated immune response was measured in 23 patients with ovarian cystadenocarcinoma, 38 patients with benign ovarian tumor, and 44 healthy volunteers. The method used two indexes: the lymphocyte response per unit volume of peripheral blood to phytohemagglutinin (PHA) and the immunosuppressive effect of serum on the response of normal lymphocytes to PHA stimulation. The lymphocyte response per 50 microliter peripheral blood did not differ significantly between patients with ovarian cancer and healthy volunteers. The serum effect, in contrast, differed significantly between malignant and benign ovarian tumors, and was found to increase significantly even when the cancer masses were as small as about 5 x 5 x 5 cm in size, ie, in FIGO Stage I. It is our belief that the measurement of the serum effect in patients with any ovarian tumor enables the early detection of ovarian cancer.

Adult↗
PubMed1978

Dopamine receptors in the central nervous system.

Dopamine receptors in the central nervous system can be studied by measuring the specific binding of [3H]dopamine, [3H]haloperidol, d-[3H]LSD, [3H]dihydroergocryptine or [3H]apomorphine. The receptors are stereoselectively blocked by +)-butaclamol, a neuroleptic. All neuroleptics inhibit the specific binding of [3H]haloperidol in relation to their clinical potencies. The radioligand that desorbs most slowly from the receptor is [3H]apomorphine, thus making it a reliable ligand for dopamine receptors. Dopamine agonists that compete for [3H]apomorphine binding do so at concentrations that correlate with their potency in stimulating striatal adenylate cyclase. Structure-activity analysis, using [3H]apomorphine, confirms that the active dopamine-mimetic conformation is the beta rotamer of dopamine. Prolonged exposure in vitro of caudate homogenate to high concentrations of dopamine leads to increased binding of [3H]apomorphine or [3H]haloperidol, suggesting receptor "sensitization." Chronic haloperidol treatment of rats leads to an increased number of dopamine/neuroleptic receptors in the striatum, but a decrease in the pituitary.

Adenylyl Cyclases↗
PubMed1978

Centrally mediated hypotension and bradycardia induced by an aminotetralin derivative: TL-68.

An aminotetralin derivate, N,N-dipropyl-2-amino-1,2,3,4-tetrahydronaphthalene (TL-68) induced a prolonged decrease in blood pressure and heart rate when administered i.v. in anesthetized cats. The compound inhibited the blood pressure and heart rate responses induced by central stump stimulation of the sciatic nerve indicating inhibition of sympathetic transmission. TL-68 caused a weak inhibition of the positive chronotropic response induced by stimulation of the cardioaccelerator nerve. When comparatively low doses of TL-68 were injected into the left vertebral artery, a considerable dose-dependent decrease in blood pressure and heart rate developed. The same doses had only small or negligible effects on blood pressure and heart rate when given intravenously. When TL-68 was injected into a lateral cerebral ventricle of unanesthetized rats, a significant hypotension and bradycardia was observed which could be prevented by prior intraventricular injection of phentolamine. The results suggest that this compound exerts its effect through a central mechanism of action, perhaps by stimulation of alpha-adrenoreceptors.

Animals↗
PubMed1977

Differential activation by some 2-aminotetralin derivatives of the receptor mechanisms in the nucleus accumbens of rats which mediate hyperactivity and stereotyped biting.

A series of 2-aminotetralin derivatives were injected into the nucleus accumbens of rat to assess the nature of the dopamine mechanisms in this nucleus which modulate hyperactivity and stereotyped behaviour. It was shown that (1) Derivatives with either 5,6- or 6,7-dihydroxy substitutions were each able to induce hyperactivity and stereotyped behaviour, but substitutions in the 5,6-positions conferred greater potency throughout the series. This differential was emphasised by the continued activity of 2-amino-5,6-dihydroxytetralin in the absence of nialamide whilst the action of 2-amino-6,7-dihydroxytetralin was greatly reduced. (2) The hydroxyl functions in both the 5,6- and 6,7-series were essential for activity: dimethyoxy derivatives were inactive. (3) Generally, substitution of the nitrogen atom with one or two methyl groups, or with a butyl group, reduced or abolished activity. However, N-ethyl and N-propyl substitution markedly enhanced stereotypic potential in the 5,6-dihydroxy series (but not in the 6,7-series). The N-isopropyl derivative in the 5,6-series reflected the activity of the N-propyl compound but a further substitution of the N atom with the methyl group (N-isopropyl-N-methyl) greatly reduced the stereotypic potential without modification of the hyperactivity response. In contrast, N,N-dipropyl substitution abolished the hyperactivity response whilst increasing sterotypic potential. (4) alpha and beta-adrenoceptor blocking agents and alpha-methyl-p-tyrosine failed to reduce the hyperactivity induced by 2-amino-5,6-dihydroxytetralin or the stereotyped behaviour induced by 2-(N,N-dipropyl)-amino-5,6-dihydroxytetralin. Both behaviours were, however, very sensitive to blockade by haloperidol, indicating that both the hyperactivity and stereotyped responses are dopamine-dependent. It is concluded that the dopamine mechanisms in the nucleus accumbens which mediate/regulate hyperactivity and stereotyped behaviour are different. Further, it is suggested that the 2-aminotetralins may be valuable tools in studies designed to assess the topography of cerebral dopamine systems.

2-Naphthylamine↗