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S J Lewis

Publications and source records attributed to S J Lewis.

233 records · Page 13Linked to original sources
PubMed1982

No major thermogenic role for (Na+ + K+)-dependent adenosine triphosphatase apparent in hepatocytes from hyperthyroid rats.

(Na+ + K+)-dependent ATPase activity, heat production and oxygen consumption were increased by 59%, 62% and 75% respectively in hepatocytes from tri-iodothyronine-treated rats. Ouabain at concentrations of 1 and 10 mM decreased oxygen uptake by 2--8% in hepatocytes from euthyroid rats and by 5--15% in hepatocytes from hyperthyroid animals. Heat output was decreased by 4--9% with the glycoside in isolated liver parenchymal cells from the control animals and by 11% in the cells from the tri-iodothyronine-treated animals. These results do not support the hypothesis that hepatic (Na+ + K+)-ATPase plays a major role in increased heat production in hepatocytes from hyperthyroid rats.

Animals↗
PubMed1982

Intracardiac electrophysiologic study of intravenous diltiazem and combined diltiazem-digoxin in patients.

Fifteen patients without sinoatrial (SA) or atrioventricular (AV) node dysfunction underwent electrophysiologic study (EPS) before and after intravenous diltiazem: 0.20 mg/kg bolus followed by 0.0007 mg/kg/min infusion (seven patients) or 0.25 mg/kg bolus followed by 0.0012 mg/kg/min infusion (eight patients). In six patients intravenous digoxin (0.018 mg/kg) was given and 45 minutes later EPS was repeated while the diltiazem infusion continued. Diltiazem prolonged sinus cycle length (+7%, p less than 0.01), lengthened AH conduction time (+22% in constant rate atrial paced rhythm, p less than 0.001), prolonged AV node functional and effective refractory periods (+6%, p less than 0.01 and +16%, p less than 0.05, respectively), lengthened AV node Wenckebach cycle length (+13%, p less than 0.001), shortened atrial functional refractory period (-3%, p less than 0.05), and reduced mean arterial pressure (-8%, p less than 0.005 in constant rate atrial paced rhythm). Subsequently, intravenous digoxin further prolonged sinus cycle length (+12%, p less than 0.05), AH conduction time (+17%, p less than 0.05), AV node Wenckebach cycle length (+9%, p less than 0.05), and AV node functional refractory period (+7%, p less than 0.05), shortened atrial effective refractory period (-7%, p less than 0.05) and ventricular effective refractory period (-6%, p less than 0.05), and increased systolic arterial pressure (+6%, p less than 0.05). Diltiazem and digoxin have additive depressant effects on SA and AV node function without significant adverse effects.

Adult↗
PubMed1982

Disparate effects of heparin on free thyroxine as measured by two radioimmunoassays: concise communication.

Free thyroxine (FT4) has been measured in two groups of patients, before and after heparin, using equilibrium dialysis (ED) and two radioimmunoassays, RIA-I and RIA-II. In Group A, nine patients were tested before and after 12-24 hr of intravenous heparin, FT4 (ED) rose from 1.9 +/- 0.5 to 2.8 +/- 3.0 ng/dl, and RIA-I from 1.37 +/- 0.37 to 1.89 +/- 1.21 ng/dl, whereas RIA-II results fell from 0.97 +/- 0.38 to 0.66 +/- 0.32 ng/dl. In Group B, ten patients were tested before and after 15 min of intravenous heparin. FT4 (ED) rose from 1.7 +/- 0.7 to 3.2 +/- 1.6 ng/dl (p less than 0.02), and RIA-I rose from 1.3 +/- 0.46 to 2.02 +/- 0.01 ng/dl (P less than 0.05), whereas RIA-II results fell from 1.07 +/- 0.38 to 0.63 +/- 0.31 ng/dl (P less than 0.02). The correlation coefficient between FT4 (ED) and RIA-I in 38 paired results was 0.96, but there was no correlation between FT4 (ED) and RIA-II results.

Adult↗
PubMed1981

Fluorometric determination of peripheral tissue histamine levels using Bio-Rex 70.

Bio-Rex 70, a weak cation exchange resin, has been incorporated into a column chromatographic extraction procedure for the determination of peripheral tissue levels of histamine. The extracted histamine is quantified fluorometrically after condensation with o-phthaldialdehyde (OPT). The sensitivity of the procedure allows for the chromatographic extraction, using Bio-Rex 70, of 10 ng histamine to give fluorescence twice that of the blank. Because this extraction procedure does not separate histamine from spermidine it cannot be applied in determining levels of brain histamine. However, because spermidine in concentrations of up to 400 times that of histamine does not interfere with OPT-histamine fluorescence, the histamine levels of all peripheral tissues (including nerves) and fluids may be confidently examined. The relative simplicity of the procedure allows for the determination of 30 tissue samples within a working day. The method has been applied to determine peripheral tissue levels of histamine in naïve Wistar rats and the effects of compound 48/80 on these levels in several selected tissues have been investigated. Compound 48/80 decreased the levels of histamine in the heart, kidney and ileum, whereas these levels were initially elevated in the liver and lung without subsequent depletion. Since the reliability of existing histamine extraction procedures is questionable under certain conditions, it is suggested that the use of Bio-Rex 70 is a valuable addition in evaluating the possible physiological role(s) of tissue histamine.

Animals↗
PubMed1981

The persisting (P) cell: histamine content, regulation by a T cell-derived factor, origin from a bone marrow precursor, and relationship to mast cells.

Histamine was detected at levels of 100 ng/10(6) cells in the metachromatic granules of the persisting (P) cell, which appears in cultures of murine lymphoid or bone marrow cells and is capable of long-term growth in vitro in the presence of a T cell-derived growth factor. This factor, which we termed P-cell stimulating factor, was distinct from t-cell growth factor and had an apparent molecular weight of 25,000-30,000. P cells did not originate from Thy.1-positive cells nor was the thymus necessary for the development of their precursors. Moreover, P cells grew directly from colonies generated in agar cultures of bone marrow cells, the nature of the colonies indicating that P cells shared a common precursor with hemopoietic cells. Mutant Wf/Wf mice, although deficient in certain mast cells, possessed P-cell precursors. It is hypothesized that P cells are related to a specialized subset of mast cells, derived from a bone marrow progenitor but regulated by activated T cells.

Animals↗
PubMed1980

A modified method for the isolation and determination of brain histamine using the Bio-Rex 70.

Bio-Rex 70, a weak cation exchange resin, has been used to specifically isolate histamine from rat brain tissue. This method compares favourably to other extraction procedures with respect to selectivity, reproducibility and time taken to perform the procedure. However, because it combines the optimum of these properties, it appears more adaptable for routine laboratory use. Following isolation, histamine is quantified fluorometrically after condensation with o-phthaldialdehyde (OPT). The sensitivity of the procedure allows for the chromatographic isolation, using Bio-Rex 70, of 12.5 ng histamine to give fluorescence twice that of blank. In addition, the use of Bio-Rex 70 enables the selective separation of histamine from fluorescent contaminants such as spermidine. The stability and the reproducibility of the adsorption and elution characteristics of Bio-Rex 70 enables the determination of 30 brain samples in a working day. This method has been applied to determine whole brain and regional brain levels of histamine in control and L-histidine-treated rats. The whole brain level of histamine, which was 50 ng/g, was increased by L-histidine and the highest concentration of histamine was found in the hypothalamus. Since the reliability of existing histamine extraction procedures is questionable, under certain conditions, it is suggested that the use of Bio-Rex 70 is a valuable addition in evaluating the possible physiological role of brain histamine.

Animals↗
PubMed1980

Methods to quantify silver in autoradiographs.

The developed silver in specially prepared photographic films (PF) and autoradiographs (AR) of radiolabeled arterial tissue was quantified by direct grain counting (GC), microdensitometry (OD), and by electron probe X-ray microanalysis (EPA). The EPA data was proportional to the OD data with a very small variance. The GC data increased with the EPA data, but showed a large variance. The EPA signal was shown 1) to be reproducible even after multiple traverses across the specimen, 2) to be directly proportional to the electron beam current and emulsion silver concentration, and 3) to be insensitive to a) beam size, b) current density, c) energy above 17 keV, or d) nonuniformities in the thickness of the conductive coating on the specimen.

Autoradiography↗
PubMed1980

Quantitative microautoradiography of arteries: comparison of radioactivity to silver.

The local concentration of silver in developed aortic transmural microautoradiographs was compared to the corresponding 125I-labeled albumin radioactivity concentration [ci(x)] in the subjacent tissue. Silver [s(x)] was measured by electron probe X-ray microanalysis (EPA) and the corresponding ci(x) by direct gamma-ray counting. The results show 1) that the relationship between volume-averaged values of radioactivity (ci) and EPA signal (s) is adequately described by ci = Ks, where K is a proportionality constant, and 2) that ci(x) measured by EPA [i.e., Ks(x)] agrees closely with ci(s) measured direcly from en face microtomy slices of corresponding unfixed tissue specimens.

Animals↗
PubMed1978

Atypical pyoderma gangrenosum with leukemia.

Pyoderma gangrenosum (PG) has been increasingly reported in association with myeloproliferative disorders. Monoclonal gammaopathy, myeloma, myeloid metaplasia, and polycythemia have all been found in association with PG. Recently, seven cases of PG in association with leukemia have been described: three cases with acute myeloblastic leukemia, two cases with chronic myelogenous leukemia, one case with acute lymphoblastic leukemia, and one case with acute leukemia of either plasma cell or myeloblast origin. To these we add two cases of PG with acute myeloblastic leukemia. These patients often have an atypical clinical presentation for PG, with bullae and relatively superficial involvement obscuring the correct diagnosis.

Acute Disease↗
PubMed1978

Sebum composition: a comparison of thin-layer chromatography and infrared reflectance spectroscopy.

Thin-layer chromatography and infrared reflectance spectroscopy were compared as methods for measuring sebum composition. Solutions of varying known concentrations of free fatty acids and triglycerides were analyzed by both methods. Skin surface lipid samples were similarly analyzed. Infrared spectroscopy produced more variable data than thin-layer chromatography with photodensitometry. This was particularly true at low concentrations of free fatty acids. It is concluded that thin-layer chromatography with photodensitometry is a more accurate method for the measurement of sebum composition.

Chromatography, Thin Layer↗
PubMedDate not supplied

Regional brain concentrations of neurotensin following amygdaloid kindled and cortical suprathreshold stimulation-induced seizures in the rat.

There is now considerable evidence that putative neuropeptides are involved in epileptogenic processes. Neurotensin (NT), which affects neuronal excitability in many parts of the CNS, is potentially relevant to the kindling phenomenon, but has not previously been studied in the kindling model of epilepsy. This study compared the short term (24 hr) and long term (3 wk) effects of amygdaloid kindled seizures, and the short term effects of non-kindled seizures (cortical suprathreshold stimulation-induced seizures, STS), on the concentrations of NT in 13 brain regions in the rat. Whereas kindled seizures produced neither short term nor long term changes in NT, the STS resulted in altered NT concentrations, with a decrease in the cortex and increases in the hippocampus and cervical spinal cord. These results reveal seizure-type specific changes in NT in 3 brain regions; and indicate that although NT does not appear to be involved in kindling, it may be important in the neurochemical mechanisms underlying STS.

Animals↗
PubMedDate not supplied

Isolation and determination of tissue spermidine using Bio-Rex 70.

Bio-Rex 70, a weak cation exchange resin, has been used to extract spermidine from rat tissues. This method compares favourably to other extraction procedures with respect to selectivity, reproducibility and time needed to perform the procedure and, because it combines the optimum of these procedures, it appears more adaptable for routine laboratory use. Following extraction, spermidine is quantified fluorometrically after condensation with o-phthaldialdehyde (OPT). The sensitivity of the present procedure allows for the chromatographic isolation of 20 ng spermidine to give fluorescence twice that of blank. The procedure is selective for spermidine because the fluorescence of other OPT-reactive substances has been eliminated by either the extraction or the assay procedures. The stability and reproducibility of the adsorption and elution characteristics of Bio-Rex 70 enables the determination of 30 tissue samples in a working day. This procedure has been used to determine the levels of spermidine in whole and regional brain areas. In addition, the concentration of spermidine in peripheral tissues was also determined. Of the brain regions, the medulla oblongata/pons had the highest level of spermidine (68.24 +/- 7.67 microgram/g), and in peripheral tissues the highest level of this polyamine was found in the heart (48.59 +/- 4.32 microgram/g).

Animals↗