Search PubMed⌕ Search

Biomedical subjects

S Johansen

Publications and source records attributed to S Johansen.

At least 91 records · Page 5Linked to original sources
PubMed1980

Adamantinoma tibiae. A report of a new case.

This report describes a new case of adamantinoma of the tibia which is a rare primary malignant bone tumour. Just over 100 cases have been reported. The symptoms, treatment and problems of diagnosis are briefly discussed.

Aged↗
PubMed1980

The kinetics of sodium-dependent phenylalanine influx in the intestine of the dog: a comparison between ileum and colon.

The kinetics of sodium-dependent phenylalanine influx into samples of dog ileal and colonic mucosa in vitro have been compared and contrasted. The data were evaluated by non-linear regression analysis, on the assumption that the total influx of the amino-acid is made up of the sum of a single saturable and a diffusive component. In both mucosae, the principal effect of changing the sodium concentration in the incubation medium was to alter the Kt for phenylalanine influx. The results were compatible with a general non-compulsory model for the formation of a ternary complex between the carrier, a phenylalanine molecule and a sodium ion which can be formed from either binary complex, i.e., either species can combine first with the carrier. Within the context of this model, it was shown that the Vmax for phenylalanine influx was substantially smaller in the colon than in the ileum. In addition, the constants governing the dissociation of the ternary complex into either binary complex were both significantly smaller in the colon, whilst the dissociation constants of the binary complexes were similar in the two regions of the intestine.

Animals↗
PubMed1979

Unfolding and refolding of phospholipase C from Bacillus cereus in solutions of guanidinium chloride.

1. Protein-fluorescence studies indicated that phospholipase C from Bacillus cereus is denatured in solutions of guanidinium chloride. The denaturation was not thermodynamically reversible and followed biphasic kinetics. 2. Guanidinium chloride solutions released the structural Zn2+ from the enzyme and rendered all histidine residues chemically reactive. In the presence of free Zn1+ the enzyme was much more resistant to denaturation. Also, the addition for free Zn2+ to the denatured enzyme induced refolding. 3. The Zn2+-free apoenzyme was much more sensitive to guanidinium chloride than was the native enzyme and the denaturation appeared to be thermodynamically reversible. 4. Guanidinium chloride denaturation was associated with a reversible inactivation of the enzyme. Heat-inactivated, coagulated enzyme was substantially re-activated on dissolution in guanidinium chloride solutions followed by dialysis against a Zn2+-containing buffer.

Apoenzymes↗
PubMed1977

Kinetics of ethanol inhibition of galactose elimination in perfused pig liver.

The effect of ethanol (5--25 mM) on the galactose elimination kinetics in the intact liver was studied in the isolated perfused pig liver, using the steady-state infusion technique. Ethanol reduced galactose-Vmax on average to 0.07 mmol/min kg liver in six experiments from 0.43 mmol/min kg obtained in control experiments without ethanol. Also Km was significantly reduced from 0.23 mmol/l plasma water to 0.03 mmol/l. Ethanol increased UDP-galactose ten-fold simultaneous with a rise in hepatic outflow ratio of lactate to pyruvate to about 300 from 10; this indicates that ethanol inhibits epimerase. In experiments with increasing galactose elimination rates, the concentration of galactose-1-P increased much less than the concentration of galactose, and the phosphorylation of galactose therefore seems to be rate-limiting. In vitro galactokinase is inhibited by galactose-1-P. In the present study ethanol increased galactose-1-P five to ten times, and the reduction of Vmax and Km by ethanol could be explained by uncompetitive inhibition by galactose-1-P with Ki about 0.1 mmol/l. Ethanol decreased UDP-glucose to about 40% and UTP to less than 5%, probably due to trapping as UDP-galactose. This may depress the forward transferase reaction, and therefore the other co-substrate galactose-1-P rises--and inhibits galactokinase.

Adenosine Diphosphate↗
PubMed1976

Michaelis-Menten kinetics of galactose elimination by the isolated perfused pig liver.

The relation between galactose elimination rates and blood concentrations in the isolated perfused pig liver was analyzed by a mathematical kinetic model. It assumes that the substrate, under steady-state conditions, is removed from the blood that flows through the sinusoids by an irreversible process which follows Michaelis-Menten (i.e., saturation) kinetics. The experiments consisted of successive periods with constant infusions of galactose. The model fitted the data to within the experimental uncertainty. The estimated maximal rate (Vmax) ranged from 0.34 to 0.57 mmol-min(-1)-kg(-1) liver, and the Michaelis constant, Km, ranged from 0.12 to 0.30 mmol-liter(-1) plasma water in nine experiments. The ratio between the galactose concentration in hepatocyte water and plasma water was not significantly different from 1.0, indicating that membrane transport is not rate limiting for the elimination of galactose. In experiments with increasing concentrations of galactose in hepatocyte water and approximately saturated elimination rates, the concentrations of galactose 1-phosphate, UDPgalactose, and UDPglucose remained essentially constant. This indicates that the phosphorylation of galactose to galactose 1-phosphate is the rate-determining process.

Animals↗