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Biomedical subjects

D Barnett

Publications and source records attributed to D Barnett.

At least 109 records · Page 6Linked to original sources
PubMed1983

A GC method for the determination of sulphur dioxide in food headspaces.

A gas chromatographic procedure was developed to measure SO2 in the presence of water vapour up to saturation level in the headspace atmospheres of packaged food. A Teflon column packed with Chromosorb 108 was used to separate CO2, SO2, and H2O in that order, then SO2 was determined using an electrolytic conductivity detector operated in a non-catalytic mode. A permeation-tube apparatus, producing SO2 and modified to permit humidification of the effluent stream, was used to calibrate the instrument, and a heated syringe technique was devised which overcame problems of sampling low levels of SO2 in the presence of water vapour. In food headspaces the method was used to determine SO2 at the ng ml-1 level with relative deviations of less than 5%.

Chromatography, Gas↗
PubMed1982

2,4-dinitrophenol stimulation of renal ammoniagenesis.

The role of mitochondrial swelling in renal ammoniagenesis was studied by the administration of 10 mg.kg-1 2,4-dinitrophenol, in vivo, to normal and chronically acidotic rats. 2,4-Dinitrophenol increased ammonia excretion in in vivo and in vitro production from glutamine by renal cortical slices and isolated kidneys perfused with 1 mM L-glutamine. Ammonia production per glutamine molecule utilized rose towards 2, consistent with activation of the mitochondrial glutaminase-glutamate dehydrogenase pathway in 2,4-dinitrophenol-treated and acidotic rats. The rank order of 2,4-dinitrophenol stimulation of ammonia formation in vivo and in vitro was normal less than normal + 2,4-dinitrophenol less than acidotic less than acidotic + 2,4-dinitrophenol. 2,4-Dinitrophenol administration appears to enlarge the in situ proximal tubule mitochondrial population and to increase the number undergoing degradation, suggesting that mitochondrial alterations correlate with ammoniagenesis in vivo.

2,4-Dinitrophenol↗
PubMed1981

Nonparallel nephrotoxicity dose-response curves of aminoglycosides.

Nephrotoxicity comparisons of aminoglycosides in rats, utilizing large multiples of human doses, have indicated an advantage for netilmicin. However, no nephrotoxicity advantage of netilmicin has been demonstrated at the lower doses used in clinics. Some high-dose studies in rats have also suggested that the slope of the nephrotoxicity dose-response curve of netilmicin was less steep than the slopes of other aminoglycosides. Therefore, the slopes of the nephrotoxicity dose-response curves of gentamicin, amikacin, and netilmicin were compared in 200 rats at low multiples (one to five times) of human clinical doses. Histopathological evaluations of both kidneys from each rat revealed that netilmicin produced equivalent or greater nephrotoxicity as compared with gentamicin and amikacin and that the slope of the nephrotoxicity dose-response curve of netilmicin was approximately one-half as steep as the slopes of amikacin and gentamicin, which were parallel. The distribution of casts excreted in the urine after 2 weeks of dosing and the terminal gross observations corroborated the flatter dose-response slope of netilmicin. Nephrotoxicity advantages predicted by high-dose comparisons with netilmicin in rats are apparently a function of its less steep dose-response slope and therefore may have no relevance to lower doses.

Amikacin↗
PubMed1981

Plasma alpha-fetoprotein concentrations in pregnant cows exposed to Sarcocystis cruzi, Campylobacter fetus, or Aspergillus fumigatus.

Bovine alpha-fetoprotein (AFP) was determined in maternal plasma, using radioimmunoassay in an attempt to detect and monitor fetal distress in pregnant cows. Plasma from pregnant cows in the 4th to 5th month of the gestation which had been exposed to Sarcocystis cruzi, Campylobacter fetus, or Aspergillus fumigatus was used. Plasma AFP concentrations were determined at intervals from before the cows were exposed until they had aborted or calved. The plasma AFP concentration of the exposed pregnant cattle remained at 6.5 +/- 5.0 mg/ml until 24 to 48 hours before abortion or parturition, when the value increased to 25.0 +/- 8.0 ng/ml. This pattern was similar for cattle exposed to each of the infective agents. Unlike in persons, rats, or monkeys, fetal-maternal transfer of AFP seems to be minimal in cows even with inflammation or necrosis of the placentome, Thus, changes in AFP concentrations in bovine plasma cannot be used as a diagnostic tool for fetal distress or fetal death.

Abortion, Veterinary↗
PubMed1981

Prepartum changes of plasma concentrations of prostaglandin F and 13,14-dihydro-15-ketoprostaglandin metabolites in pregnant animals exposed to Sarcocystis cruzi or Campylobacter fetus.

Pregnant cows at 4- to 5-months' of gestation were exposed to Sarcocystis cruzi or Campylobacter fetus. Plasma prostaglandin F (PGF) and 13,14-dihydro-15-ketoprostaglandin metabolite (PGM) concentrations were determined at intervals from before exposure until abortion or parturition. The plasma PGF concentration of pregnant infected cattle remained at 0.02 +/- 0.04 ng/ml until 24 to 48 hours before abortion or parturition when it increased 5-fold to 0.11 +/- 0.12 ng/ml. The plasma PGM concentration of these cattle remained at 0.10 +/- 0.07 ng/ml until 24 to 48 hours before abortion or parturition when it increased over 10-fold to 1.36 +/- 0.60 ng/ml. This change in PGF and PGM was similar to that of cattle exposed to each of the infective agents and to that of normal cows at parturition. Thus, changes in PGF and PGM concentrations in bovine plasma cannot be used as a diagnostic tool to determine fetal distress or fetal death for these infections.

Abortion, Veterinary↗
PubMed1980

Plasma progesterone concentration in the bovine before abortion or parturition in pregnant animals exposed to Sarcocystis cruzi, Campylobacter fetus, or Aspergillus fumigatus.

Pregnant cows in the 4th and 5th month of the gestation were exposed to Sarcocystis cruzi, Campylobacter fetus, or Aspergillus fumigatus. Plasma progesterone concentrations were determined at intervals from before the cows were exposed until they had aborted or calved. The plasma progesterone concentration of the exposed pregnant cattle remained at 3.95 +/- 2.0 ng/ml until 24 to 48 hours before abortion or parturition, when it decreased to below 1.00 ng/ml. This pattern was similar for cattle exposed to each of the infective agents. Thus, changes in progesterone concentrations in bovine plasma cannot be used as a diagnostic tool for fetal distress or fetal death.

Abortion, Veterinary↗
PubMed1980

Experimental toxoplasmosis in calves and pregnant cows.

Experimental Toxoplasma gondii infections were studied in pregnant cows and in calves. In tests to compare their virulence, three strains of the toxoplasmal parasite were red to cats; then fecal oocysts were collected and given per os to calves. In tests to determine their effects, virulent tachyzoites or oocysts were given to 10 calves and to 22 pregnant cows by the oral, IV, or intraamniotic routes. Clinical signs were fever and inappetence. One cow in early gestation aborted 24 days after IV administration of tachyzoites. Gross and microscopic changes were slight and nonspecific. Toxoplasmas were isolaated from brain or liver of 4 cows, placenta of 2 cows, gastric contents of 2 near-term fetuses, and blood and tissues of calves. Toxoplasmas were not isolated from control cows.

Abortion, Veterinary↗
PubMed1978

Effect of myo-inositol on peripheral-nerve function in diabetes.

myo-Inositol, 500 mg twice a day, given to seven diabetic patients for two weeks, increased the amplitude of the evoked action potentials of the median, sural, and popliteal nerves by an average of 76%, 160%, and 40%, respectively. There was no significant change in the conduction velocities of these nerves, myo-Inositol may be valuable in the treatment of diabetic neuropathy.

Aged↗
PubMed1978

Distribution oand pharmacological release of histamine in canine lung in vivo.

We have examined the physiological effects of stored mediators released from airways by compound 48/80 aerosols in anesthetized dogs. In 13 dogs, both mast cell numbers and tissue histamine were related inversely to bronchial internal diameter (P less than 0.0001). Compound 48/80 aerosols degranulated mast cells and decreased histamine content (-29.0 +/- 10.0%; mean +/- SE) in 5-10 mm bronchi, but not in 3-4 mm bronchi or lung parenchyma. This was associated with increased plasma histamine (31.8 +/- 18.4 ng/ml), increased airflow resistance (Rrs: + 452 +/- 257%), decreased lung compliance (-28 +/- 10%), and decreased arterial blood pressure (-41 +/- 6.5%) at 2 min. The increased Rrs was reversed by beta-adrenergic agonists, indicating it was caused by bronchial smooth muscle contraction; prevented by chlorpheniramine, indicating it was caused by histamine action on H1-receptors; and augmented and prolonged by propranolol, suggesting that histamine triggered sympathetic mechanisms which modulated the effect of 48/80. This experimental approach permits the study of mechanisms in vivo which may be involved in the sequence of reactions initiated by antigen-IgE interaction. However, the latter involve not only stored mediators, but also unstored mediators, neural reflexes, and complex cellular interactions.

Aerosols↗
PubMed1977

Acebutolol, atenolol, and propranolol and metabolic responses to acute hypoglycaemia in diabetics.

In a double-blind crossover study the symptomatic and metabolic effects of propranolol, acebutolol, and atenolol were studied during insulin-induced hypoglycaemia in diabetics treated with diet or hypoglycaemic tablets. All the drugs prevented tachycardia, but did not affect the other symptoms of hypoglycaemia. Propranolol delayed the recovery of the blood glucose concentration and impaired the secondary rise in the concentrations of blood lactate and non-esterified fatty acids in diet-treated diabetics. Acebutolol potentiated the hypoglycaemic effect of insulin in tablet-treated diabetics (mean difference of blood glucose concentration 0.7 mmol/l (12.6 mg/100 ml)) and this difference was maintained during the recovery phase4 the blood lactate response was also impaired. Atenolol did not differ perceptibly from placebo in its effect on the metabolic responses to acute hypoglycaemia. The results may be explained by differences in the known pharmacological actions of these drugs. They support the hypothesis that beta-adrenoreceptor blocking drugs that are highly beta1 specific and without membrane-stabilising activity should be safer than the non-selective drugs when used in diabetic patients at risk from hypoglycaemia.

Acebutolol↗
PubMed1977

Effect of clofibrate on glucose tolerance in maturity onset diabetes.

1 Fourteen maturity onset diabetics showed improvement of glucose tolerance while on treatment with clofibrate. Fasting blood glucose levels were reduced by 20% after treatment for 14 and 28 days. 2 The effect was found to be independent of concurrent treatment with oral hypoglycaemic drugs. 3 Plasma insulin levels were also lower during clofibrate treatment. 4 Clofibrate may prove to be a useful adjunct to the treatment of maturity onset diabetes.

Blood Glucose↗
PubMed1976

Comparison of atenolol and propranolol during insulin-induced hypoglycaemia.

The effects of atenolol, a new beta1-blocking drug, on pulse rate, sweating, and blood glucose levels during insulin-induced hypoglycaemia were studied in a double-blind crossover trial in eight normal subjects using placebo and propranolol as reference agents. The intensity of induced hypoglycaemia was identical for atenolol, propranolol, and placebo. Propranolol prolonged hypoglycaemia, but atenolol did not. Atenolol may therefore be safe for use in patients receiving insulin.

Adrenergic beta-Antagonists↗