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Biomedical subjects

J Mason

Publications and source records attributed to J Mason.

At least 253 records · Page 14Linked to original sources
PubMed1982

The demonstration of protein-bound 99Mo-di- and trithiomolybdate in sheep plasma after the infusion of 99M0-labelled molybdate into the rumen.

1. Protein-bound, trichloracetic acid- (TCA) insoluble 99Mo appeared in plasma a few hours after the introduction of 99Mo-labelled molybdate (30 mg Mo) into the rumen of sheep maintained on a basic diet supplemented with elemental sulphur (3 g S/d). 2. Most of the 99Mo could be displaced from its protein carrier in vitro and the labelled compounds displaced were identified by sephadex G-25 chromatography as di- and trithiomolybdate. Tetrathiomolybdate was not detected. 3. In control experiments protein-bound, TCA-insoluble 99Mo predominated in plasma after the direct administration of [99Mo]tetrathiomolybdate, either into the rumen or intravenously. The 99Mo could be displaced in vitro and [99Mo]tetrathiomolybdate identified, although [99Mo]trithiomolybdate was also present. The study provides direct evidence of thiomolybdate synthesis and absorption in ruminants in vivo.

Animals↗
PubMed1982

Antiarrhythmic efficacy of amiodarone in recurrent ventricular tachycardia evaluated by multiple electrophysiological and ambulatory ECG recordings.

Thirty-three patients with recurrent drug-refractory ventricular tachycardia were treated with oral amiodarone during an average period of 6.1 months. In-hospital monitoring for two weeks or more, electrophysiological tests and ambulatory ECG were used to evaluate the results. Twenty patients are still using the drug with complete control of the arrhythmia. Eleven have failed the drug, ten due to recurrence of documented ventricular tachycardia. Only three patients failed after the first month of therapy. Two patients died, one suddenly. The drug was discontinued in a further two patients due to side-effects. Other side-effects were tolerable or manageable by dose adjustments alone. Five patients showed evidence of inadequate arrhythmia control between days 15 and 32 of therapy but subsequently responded to the drug for 4-9 months, giving further support to the concept that in some patients at least 30 days of therapy is necessary for the full effect of the drug to appear. In 16 of the 20 patients tested by arrhythmia induction study while on the drug, ventricular tachycardia could still be induced. Seven (44%) of these eventually failed the drug. Arrhythmia recurred in one of those four in whom tachycardia could not be induced. Amiodarone is a valuable drug in the management of recurrent ventricular tachycardia, refractory to other antiarrhythmic drugs.

Adult↗
PubMed1982

Neuroendocrine risk factors of suicidal behavior.

Three of 22 subjects in a study of neuroendocrine correlates of clinical change made serious suicide attempts, 2 of which were lethal. The suicidal subjects had significantly higher 24-hour urinary cortisol levels and significantly lower 24-hour urinary norepinephrine-to-epinephrine ratios than the nonsuicidal patients had. Although the cortisol finding confirms earlier reports, the norepinephrine-to-epinephrine ratio finding is new. The results support the concept that the clinical utility of neuroendocrine measures is enhanced by using a multihormonal profile.

Adult↗
PubMed1982

Tubular signal for the renin activity in the juxtaglomerular apparatus.

To investigate the effect of ionic composition of the tubular fluid in the macula densa segment upon the JGA renin activity, the macula densa segment was perfused with different solutions and the renin activity in the attached juxtaglomerular apparatus was measured. Increasing the sodium chloride concentration at the macula densa by perfusion with Ringer's solution or saline increased the JGA renin activity. An activation of JGA renin activity did not occur when amiloride was added to the saline or when the animals were pretreated by a high-salt diet. Perfusing the macula densa segment with a sodium-chloride-free solution, with sodium- or chloride-substituted solutions, or with mock early distal fluid, did not affect the JGA renin activity. These data are in accord with the proposition that in the tubuloglomerular feedback mechanism the renin-angiotensin salt diet. Perfusing the macula densa segment with a sodium-chloride-free solution, with sodium- or chloride-substituted solutions, or with mock early distal fluid, did not affect the JGA renin activity. These data are in accord with the proposition that in the tubuloglomerular feedback mechanism the renin-angiotensin salt diet. Perfusing the macula densa segment with a sodium-chloride-free solution, with sodium- or chloride-substituted solutions, or with mock early distal fluid, did not affect the JGA renin activity. These data are in accord with the proposition that in the tubuloglomerular feedback mechanism the renin-angiotensin system in the juxtaglomerular apparatus acts as a local, humoral mediator between the signal perceived at the macula densa and the hemodynamic response at the glomerulus. The mediation by the renin-angiotensin system, which is influenced by the sodium chloride balance, allows the sensitivity of this control of GFR to be adjusted in a homeostatically appropriate manner.

Animals↗
PubMed1981

Leucine metabolism in patients with malignant disease.

Studies of the metabolism of the amino acid, leucine, have been carried out in six patients with progressive cancer and compared to similar studies in a group of control subjects. U-14C leucine was given by the single injection technique and the disappearance of radioactive leucine from the plasma as well as the appearance of the label in expired air was determined over a 3-hour interval in both the overnight fasting state and during glucose ingestion. Plasma leucine levels in the basal state were higher in the patients with malignant disease (193 +/- 17 mumol/L vs 135 +/- 16 mumol/L) as was the flux or rate of appearance of unlabeled leucine molecules into the plasma (136 +/- 5 mumol/kg hour vs 79 mumol/kg/hour). Oxidation of leucine resulted in the appearance of about 19% of the injected label in expired CO2 of control subjects with almost twice that amount being found in progressive cancer patients. When the irreversible disposal of leucine to a metabolic fate other than oxidation was calculated (perhaps an indicator of protein synthesis), this was also increased in the progressive cancer patients. Exogenous glucose administration resulted in a fall in both leucine level and flux in the control subjects, while these parameters were less affected in three of the cancer patients. The fall in oxidation when glucose was given was more pronounced in the control subjects. These data are interpreted to mean that all aspects of leucine metabolism, presumably an example of branched chain amino acid metabolism, appear to be accelerated in subjects with cancer and weight loss. In addition, the peripheral control of the metabolism of this group of amino acids, as affected by glucose and insulin, appears to be impaired.

Body Weight↗
PubMed1981

The early phase of experimental acute renal failure. VI. The influence of furosemide.

Experiments were performed to determine whether furosemide, given in doses high enough to induce a strong diuresis and to inhibit the mechanism of tubuloglomerular feedback, offers any protection from acute renal failure induced by a nephrotoxin or ischaemia. Microperfusion of the loop of Henle revealed that a tubular furosemide concentration of 5 x 10(-5) mol x 1(-1) was necessary to fully inhibit the tubuloglomerular feedback response to a raised sodium chloride concentration at the macula densa. The infusion of furosemide systemically to achieve such concentrations in the tubule resulted in an improvement in renal function when given before or after the nephrotoxin but was without effect when given before or after ischaemia. Measurements of furosemide concentrations in the urine, however, confirmed that sufficient amounts were applied to inhibit the feedback mechanism. It is concluded from this and similar studies that furosemide is only beneficial in models of acute renal failure with an obstructive or nephrotoxic pathogenesis, in which it acts by flushing out the noxious material and not by inhibiting the mechanism of tubuloglomerular feedback.

Acute Kidney Injury↗
PubMed1981

Intracellular electrolyte composition following renal ischemia.

The technique of electron microprobe analysis was used to determine the intracellular electrolyte concentrations in proximal or distal tubular cells of the rat kidney during ischemia. When the exposed kidney was maintained in air during ischemia, the composition of the surface cells differed little from control, and the electrolyte disturbances were confined to the deeper lying cells. When maintained in nitrogen, all cells underwent changes in cellular electrolyte concentrations that were uniform, indicating that the surface cells can preserve their composition during ischemia by utilizing oxygen from the air. In the proximal tubular cells, after 20 or 60 min of ischemia in nitrogen, sodium increased from 20 to 93 or 112, chloride rose from 21 to 53 or 66, potassium fell from 141 to 65 or 42, phosphate decreased from 145 to 110 or 95 mmoles.kg-1 of wet wt, and the dry wt dropped from 22.6 to 20.3 or 17.5% of wet wt, respectively. In the distal tubular cells, 20 min of ischemia in nitrogen produced little effect on cellular composition, but after 60 min, sodium increased from 11 to 77, chloride rose from 15 to 48, potassium fell from 134 to 89, phosphate decreased from 168 to 145 mmoles.kg-1 of wet wt, and the dry wt dropped from 20.8 to 18.4% of wet wt. The disturbances in sodium and potassium are caused primarily by an inhibition of the sodium/potassium pump, whereas the changes in chloride, phosphate, and dry weight content result mainly from an influx of extracellular fluid. When blood flow was reintroducing, the electrolyte disturbances were rapidly reversed in all cells, restoration being virtually complete within 60 min, but returned in some proximal cells by 18 hr of reperfusion. Thus, the disturbance in electrolyte composition increases with the duration of ischemia, is less pronounced in the distal than proximal cells and, although initially completely reversible when blood flow is restored, reappeared in the proximal cells 1 days after the initial injury.

Animals↗
PubMed1981

The enzyme-linked immunosorbent assay (ELISA) for malaria. III. Antibody response in documented Plasmodium falciparum infections.

Serum specimens from patients in El Salvador, Central America, with slide-proven Plasmodium falciparum infections were examined for antibodies to P. falciparum using the enzyme-linked immunosorbent assay (ELISA) and the indirect fluorescent antibody (IFA) methods. Both serologic tests were positive in 78.1% of the 827 samples, both negative in 5.4%, the ELISA positive alone in 6.3%, and the IFA alone in 10.2%. Agreement between the serologic tests was better in the specimens with high positive titers (high IFA = high ELISA). Seropositivity rates and geometric mean titers were higher in the older (greater than or equal to 15 years) age groups for both ELISA and IFA; in such persons, the IFA was positive in 92% and the ELISA in 88%. The lowest seropositivity rates found by the ELISA were observed in children; 27.6% of 98 children less than or equal to 4 years of age were negative. A longer duration of infection as evidenced by the presence of gametocytes on the blood slide resulted in higher positivity rates by both ELISA and IFA. This phenomenon, particularly apparent in young children, supports the belief that the more important variable in determining the proportion of false negatives is previous malaria experience and not age. The results indicate that, while neither serologic test is appropriate as a diagnostic aid, both the ELISA and the IFA would be useful in epidemiologic investigations.

Adolescent↗
PubMed1981

Migratory silicone granuloma.

A 38-year-old woman had a migratory silicone granuloma of the left upper portion of the chest and left upper arm secondary to a ruptured breast implant. The initial diagnosis was factitial panniculitis. With the common use of silicone in cosmetic surgery, physicians should inquire into a possible history of silicone injections or implants before ascribing a factitial cause to foreign-body granulomas.

Adult↗
PubMed1980

Encainide: a new and potent antiarrhythmic agent.

Encainide is a potent Class I antiarrhythmic drug that prolongs conduction in the His-Purkinje system. It produces only minimal hemodynamic changes in the normal or depressed left ventricle. Studies to date demonstrate excellent effectiveness against ventricular arrhythmia, and in comparative studies with quinidine, encainide was superior in reducing the frequency and complexity of ventricular premature beats in patients late after myocardial infarction.

Anilides↗