Sugar transport: effect of temperature on concentrative uptake of alpha-methylglucoside by kidney cortex slices

The ability of renal cortical slices to accumulate a monosaccharide is enhanced at temperatures below 37 degrees C. Increase in concentration gradients occurs despite a decrease in total sugar flux. The apparent explanation for this paradox is a proportionally greater inhibition of efflux.

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.

Effects of thyroid disease on glucose oxidative metabolism in man. A compartmental model analysis

Glucose oxidation to CO(2) in man at the fasted, steady state has been investigated in normal, hypothyroid, patients by monitoring the specific activity of plasma glucose and expired CO(2) after intravenous injection of glucose-1-(14)C, glucose-6-(14)C, and sodium bicarbonate-(24)C in tracer amounts. Making certain stoichiometric assumptions about the oxidation of the C-1 and C-6 carbons of glucose to CO(2), the data are incorporated into a multicompartmental model describing the kinetics of plasma glucose, plasma bicarbonate, and the conversion of glucose to CO(2) by the hexose monophosphate pathway and all other series and parallel pathways which oxidize glucose carbon to CO(2) (EMP-TCA). This formulation separates the distribution kinetics of glucose and bicarbonate from the kinetics of glucose oxidation to CO(2). It allows the calculation of a minimal fraction (varphi(t)) of glucose irreversibly oxidized to CO(2) which is based entirely on the duration of the experimental data. This calculation is independent of the extrapolative implications of the model beyond the experimental interval and of the particular model chosen to fit the data. All modeling and data fitting were performed on a digital computer with the SAAM program. Based on a 300 min experiment the analysis suggests that in hypothyroidism there is a decrease in the rate of glucose metabolized irreversibly (rhoG). There is also a decrease in the minimal fraction (varphi(300)) which is completely oxidized to CO(2) by way of the EMP-TCA. rhoG and varphi(300) are 0.56 and 0.42 mmole/min respectively as compared to 0.89 and 0.50 mmole/min respectively in normals. However, the fraction of the C-1 of glucose metabolized irreversibly which undergoes oxidation to CO(2) by the hexose monophosphate pathway (Psi) is not different from normal (0.07 and 0.07 respectively). The hyperthyroid studies suggest that rhoG and varphi(300) are within the normal range (1.01 and 0.46 mmoles/min respectively as compared to 0.89 and 0.50 mmole/min respectively in normals). However, Psi is decreased to less than half the normal value (0.03 as compared to 0.07 in normals).

Separate transport systems for sugars and amino acids in developing rat kidney cortex

The ability of renal cortical slices of newborn and young rats to accumulate a nonmetabolizable sugar, alpha-methylglucoside, is slight and does not reach adult capacity until 25 days of age. However, a rudimentary sugar transport system is present, as indicated by a further decrease in accumulation in the presence of phlorizin or absence of sodium ion.Amino acid uptake in immature kidney tissue is not deficient; on the contrary, the tissue took up and concentrated more glycine and lysine than adult tissue. Decreased amino acid efflux from the immature cells appears to be the explanation. Concentration dependence of amino acid uptake was the same in 5-day-old and adult tissue. These differences between the transport characteristics of a model sugar and representative amino acids during development indicate separate transport systems for the two types of substrate.

Human Cystinosis: Intracellular Deposition of Cystine

Membrane-limited inclusions were found in the cytoplasm of cells of the rectal mucosa, leukocytes, and cultured fibroblasts from two humans with cystinosis. Most of the inclusions contained amorphous material, presumably cystine. In cells of the rectal mucosa the material appeared frequently crystallized. This was rarely seen in leukocytes, and never in cultured fibroblasts. The fact that acid phosphatase could be demonstrated consistently in the organelles responsible for sequestration of cystine indicates that they are lysosomes.

In vitro induction of a primary response to the dinitrophenyl determinant

Primary antibody response against the dinitrophenyl group has been elicited in vitro after the stimulation of normal mouse spleen explants with 2,4-dinitrophenyl (DNP)-hemocyanin or alpha-DNP-poly-L-lysine (PLL). Antibodies were detected in the culture medium by the inactivation of DNP-T4 phage. The specificity of the reaction was manifested by the lack of the capacity of the medium to inactivate the unmodified bacteriophage and by the inhibition of the inactivation of DNP-T4 with DNP-lysine.

Delineation of cystine and cysteine transport systems in rat kidney cortex by developmental patterns

The impaired ability of neonatal rat kidney cortex slices to take up L-cystine at a time when the ability to accumulate cysteine is similar to that of adult tissues indicates the separate nature of the transport processes for these amino acids. Dissimilarities in dependence on oxygen and temperature are also indicative of different transport systems. The intracellular form of the amino acid was largely cysteine when either cystine or cysteine was the transported substrate although significant amounts of both were incorporated into reduced glutathione. No difference in intracellular forms was found between neonatal and adult tissue.

The intracellular ratio of cysteine and cystine in various tissues

1. The cysteine-cystine ratio was measured in rat kidney cortex, diaphragm, jejunum, liver and brain. 2. This ratio was determined by incubating these tissues in buffer containing [(35)S]cystine and then homogenizing the tissue in a buffered solution of N-ethylmaleimide. The products of this reaction were separated by high-voltage electrophoresis and the radioactivity in the cystine and 2-(l-2'-amino-2'-carboxyethylthio)-N-ethylsuccinimide regions was determined. 3. In these tissues cyst(e)ine was mainly present in the reduced form. 4. After incubation of [(35)S]cystine with rat jejunal segments it was found that 36% of the cystine in the medium has been reduced. 5. Anaerobiosis, Na(+)-free media, glucose and high concentrations of cystine and lysine were found not to affect significantly the cysteine-cystine ratio in rat kidney-cortex slices.

Microdetermination of Phosphatases Employing Phenolphthalein Diphosphate as Substrate

A micromethod is described for the determination of acid and alkaline phosphatases. Phenolphthalein diphosphate is used for substrate and may be prepared by a modified method of Huggins and Taltalay (1). The technics employed are simple, and the results bear a close relationship to units of Bodansky (2, 3). The substrates may be used for the preparation of test paper for a screening test.