Unsuccessful trial of gene replacement in arginase deficiency

The Shope virus following cutaneous inoculation produces skin papillomas in rabbits and induces a virus-coded arginase in the squameous epithelium of these papillomas. The only discernible effect of the virus inoculated intravenously in rabbits and other animals was a decrease of the serum arginine concentration. Intravenous injection in 3 hyperargininemic patients, however, did not influence the underlying metabolic disease.

Developmental aspects of galactose-1-phosphate uridylytransferase in rat intestine

Kinetic and developmental characteristics of rat jejunal galactose-1-phosphate uridylyltransferase have been examined. Km values for the substrates galactose-1-phosphate and uridine diphosphate (UDP) glucose were the same for both the newborn and adult rat enzymes, although the Vmax of the enzyme in newborns was about threefold higher than that of the adult rat. Equal enzyme activity was present in the villus, crypt cells and the muscularis of adult jejunum. The specific activity of the enzyme remained relatively uniform (V about 20 nmoles/min/mg protein) until 18 days of age when the velocity of the reaction began to decrease. The adult value at 42 days of age is about one fifth of that in the young. The pattern of change of specific activity was compared with that for galactokinase and UDP-galactose-4-epimerase, and the observations suggest separated regulatory factors for each enzyme. The total activity of the galactose-metabolizing enzymes in jejunum was also calculated. In the young, transferase has the highest activity, but in the adult, epimerase activity is highest. Jejunal galactokinase activity is low throughout the developmental period which suggests that phosphorylation of galactose may be the limiting step in intestinal metabolism of the sugar.

Some evidence for the existence of turgor pressure gradients in the sieve tubes of willow

Sieve tube sap was collected either from the severed stylets of Tuberolachnus salignus (Gmelin) or via incisions made into the phloem of small willow trees or potted cuttings. Measurements of the osmotic potential (O.P.) of sap samples showed a gradient to exist in the presumed direction of assimilate transport, ie from apex to base of the stem.In most experiments samples of phloem tissue were taken after the collection of sieve tube sap, the water potential of these pieces of tissue being measured in a psychometer. Although a water potential gradient existed in the opposite sense to the O.P. gradient in the sap (lowest water potential at the apex of the stem), the difference between O.P. and W.P. indicated the turgor of the sieve tubes to be higher at the apex than at the base of the stem. The magnitude of the turgor gradient measured in this way lay between 0.5 and 2.7 atm m(-1).In other experiments severed stylets only were used to determine whether a hydrostatic gradient can exist in willow sieve tubes. After measurement of flow rates from stylets sited at the apex and base of willow stems, the Poiseuille expression was used to calculate the pressure at the point of stylet puncture. These experiments gave values for the pressure gradient (in the presumed direction of assimilate flow) of between 1.9 and 4.7 atm m(-1).

Induction of arginase activity with the Shope papilloma virus in tissue culture cells from an argininemic patient

Inoculation of the Shope virus in tissue cultures of human fibroblasts from a patient with a deficiency of the enzyme arginase results in an induction of arginase activity, apparently virus coded.

Change in the structure of Shope papilloma virus-induced arginase associated with mutation of the virus

The change in the state of the virus-induced enzyme associated with a mutation in the virus provides additional evidence that the enzyme is synthesized from virus rather than rabbit genetic information. This change in structure results in differences in stability of polymerization, degree of optical rotary dispersion (ORD) specific rotation, change in elution characteristics from carboxymethyl cellulose, and a reduction in specific activity of the arginase. Liver arginase differs markedly in ORD characteristics from the virus-induced enzyme. In contrast to the virus-induced enzyme, it showed no negative Cotton effect at 233 nm until it was activated with manganese. Manganese had no influence on the ORD spectrum of virus-induced arginase. In addition, liver arginase is denatured by 4 M urea, while the virus-induced enzyme requires 10 M urea for denaturation.

Liver galactose-1-phosphate uridyl transferase: activity in normal and galactosemic subjects

The kinetic characteristics of galactose-l-phosphate uridyl transferase have been determined in homogenates of human liver biopsies obtained from control subjects and in 50-fold purified enzyme preparations from liver obtained at autopsy. A standardized assay procedure employing linear kinetics was used to assess the enzyme activity in homogenates of liver biopsy specimens from five control subjects and four patients with congential galactosemia with demonstrated absence of the enzyme activity in red blood cells. Activity of control specimens ranged from 11.8 to 17.2 mmumoles of UDPgalactose formed per min mg of protein. Liver of two galactosemic patients, both Caucasian, possessed no detectable enzyme activity (less than 1-2% of normal). The tissue of two others, both Negro, who are known to be capable of metabolizing intravenously administered galactose, contained easily detectable enzyme at approximately 10% of the controls. No alternate enzymatic activity for formation of UDPgalactose was found in the liver of Negroes with galactosemia that was as active as the residual galactose-l-phosphate uridyl transferase. The data suggest that the residual liver enzyme activity accounts for the ability of Negroes with galactosemia to metabolize limited but significantly large quantities of galactose.