Search PubMed⌕ Search

Biomedical subjects

G F Johnson

Publications and source records attributed to G F Johnson.

140 records · Page 8Linked to original sources

Hepatic lysosomal copper protein in dogs with an inherited copper toxicosis.

Hepatic copper overload inherited as an autosomal recessive trait in Bedlington Terriers is characterized by the presence of hepatocellular lysosomal granules of unusually high specific gravity and electron density which contain at least two thirds of the total hepatic copper. Fractionation of homogenates of liver from such affected Bedlington Terriers yielded a low-speed pellet which contained the lysosomal granules. This fraction was used for isolation of a copper-binding protein by alkaline-reduction, solubilization, fractional acetone precipitation, and gel filtration. The purified protein yielded a single band on polyacrylamide gel electrophoresis and resembled other metallothioneins in containing 15 cysteine residues and 7 to 8 atoms of copper (but no zinc) per 54 amino acid residues. No methionine, histidine, or any aromatic amino acid was present. The accumulation of this lysosomal copper protein appears to be related to the primary genetic defect which underlies the hepatic copper toxicosis of the Bedlington Terrier.

Animals↗

Racial background and lidocaine pharmacokinetics.

The pharmacokinetics of lidocaine were investigated in 17 healthy young adult volunteers seven Caucasians, five Orientals, and five Blacks). With the assumption of a one-compartment open model and linear pharmacokinetics, analysis of the data determined that there were no significant differences in the volume of distribution, clearance, elimination half-life, and serum protein binding of lidocaine among these racial groups. Our finding that lidocaine clearance and protein binding are not significantly different in young adult Caucasians and Orientals is consistent with our previous hypothesis that drugs metabolized in the body by N-dealkylation (lidocaine and diphenhydramine) area cleared at similar rates in young adult Caucasians and Orientals when protein binding is taken into account.

Adult↗

Plasma dexamethasone and the dexamethasone suppression test. Initial and follow-up tests in depressed patients.

Plasma dexamethasone concentrations following oral dexamethasone administration were examined in 78 patients with major depression prior to and during treatment. The test-retest stability of plasma dexamethasone levels within patients was satisfactory with an overall significant positive correlation between tests for each patient. However, significant variability was noted in individual patients. Change in pre-DST cortisol and plasma dexamethasone levels were the two variables, in that order of importance, contributing to change in DST status. In studies examining the clinical utility of serial dexamethasone suppression tests as a guide to recovery from depression, the effect of variability in plasma dexamethasone concentrations should be taken into account.

Adult↗

The effect of age on cortisol and plasma dexamethasone concentrations in depressed patients and controls.

The aim of this study was to identify any relationships between various patient factors such as age, gender and concurrent medication that may affect plasma cortisol or dexamethasone (DEX) concentrations. Multiple regression analysis was used to formulate an equation to predict plasma DEX levels to identify factors that may influence DEX bioavailability. Pre- and post-DST cortisol levels did not increase with age, but DEX levels were higher in elderly depressed patients. Neither gender nor psychotropic medication affected plasma cortisol or DEX levels. There was no indication that pre-DST cortisol levels influenced plasma DEX levels to account for the lower DEX values in non-suppressors. Age was the only significant factor found in this study to influence DEX levels and it could be argued that the dose of DEX should be lowered when administering the DST to elderly patients to reduce plasma DEX variability.

Adult↗