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Biomedical subjects

R Steinherz

Publications and source records attributed to R Steinherz.

52 records · Page 3Linked to original sources
PubMed1984

Hypernatremic dehydration as a sign leading to the diagnosis of glucose-galactose malabsorption in breast-fed neonates.

Hypernatremic dehydration is described in a case of a breast-fed infant with glucose-galactose malabsorption. Hypernatremic dehydration in general is uncommon in normal breast-fed infants. The finding of hypernatremic dehydration in breast-fed infants with watery diarrhea and sugar in the stool should lead to the consideration of monosaccharide intolerance such as glucose-galactose malabsorption.

Carbohydrate Metabolism, Inborn Errors↗
PubMed1983

Effects of cysteamine and other thiols on cystine egress from isolated lysosome-rich fractions of cystinotic and normal leucocytes.

After loading isolated normal and cystinotic white blood cell lysosomes with radioactive amino acid methyl esters, egress of the corresponding amino acids was measured in the presence or absence of reducing agents. Cysteamine greatly enhanced disposal of cystine- and, to a lesser extent, cysteine-loaded lysosomes, resulting in final similar rates of radioactive clearance. Cysteamine did not alter leucine egress. Cysteamine comparably accelerated cystine egress from normal and cystinotic lysosomes. Reduced glutathione, ascorbic acid, coenzyme A and acetylcoenzyme A, which are much less effective cystine-depleting agents on intact cystinotic cells than cysteamine, failed to increase egress rates from isolated lysosomes loaded with cystine. We believe this in vitro system can help in the future in evaluating drug efficacy in reducing cystine content in cystinotics in addition to the already existing tissue culture technique.

Amino Acids↗
PubMed1982

Patterns of amino acid efflux from isolated normal and cystinotic human leucocyte lysosomes.

This study describes the first direct measurements of amino acid efflux from human lysosomes. Isolated leucocyte lysosomes can be loaded with radioactive amino acids by exposure to low concentrations of the corresponding labeled amino acid methyl esters. Efflux of amino acid from the loaded lysosomes can then be determined. Conditions during loading are adjusted for each ester to permit its adequate intralysosomal hydrolysis and subsequent accumulation of the free amino acid. Relative rates of efflux were leucine approximately equal to phenylalanine greater than methionine greater than tryptophan much greater than cystine. Efflux of leucine, tryptophan, or cystine was independent of exogenous cation, ATP, or amino acid concentrations under the conditions tested. Leucine efflux was similar in normal and cystinotic lysosomes, providing strong evidence that isolated cystinotic lysosomes do not manifest a generalized defect in amino acid efflux. In both normal and cystinotic lysosomes, cystine efflux was much slower than efflux of leucine or other amino acids from human or rat liver lysosomes. Significant differences in mean cystine efflux between isolated normal and cystinotic lysosomes were not apparent in the present test system, although the possibility of differences in rats could not be excluded.

Alanine↗
PubMed1982

Cystine accumulation and clearance by normal and cystinotic leukocytes exposed to cystine dimethyl ester.

Upon exposure to 0.25 mM cystine dimethyl ester, normal and cystinotic leukocytes accumulate substantially more intracellular cystine than is present endogenously in cystinotic cells. Leukocytes loaded by exposure to cystine dimethyl ester may have abnormally lucent and distended lysosomes, and the cystine is compartmentalized within the granular fraction of the cells. After the cells are exposed to cystine dimethyl ester, cystine clearance from normal leukocytes is much faster than from cystinotic cells. The ratios of labeled cysteine-N-ethylmaleimide to cystine are also greater in normals than in cystinotics 60 min after termination of loading. No overlap in ranges of cystine clearance half-times or cystine-N-ethylmaleimide to cystine ratios was observed in normal compared to cystinotic leukocytes. Limited experiments with fibroblasts exposed to cystine dimethyl ester suggest a correspondingly prolonged cystine clearance for cystinotic cells. These experiments provide evidence for defective clearance of cystine from cystinotic lysosomes in situ.

Cystine↗
PubMed1981

Association of certain human leukocyte antigens with nephropathic cystinosis in the absence of linkage between these loci.

The HLA phenotypes of 41 patients (22 males and 19 females) with classical nephropathic cystinosis were analyzed and compared with those reported from a control group of 1,465 Americans of Caucasian origin. There was a significantly increased association of cystinosis with HLA B7, and a reduced association with A9. The calculated A3B7 and A1B7 haplotypes were also significantly increased in cystinosis. Lod score analysis of five families indicated that linkage between the gene(s) for cystinosis and the HLA loci is unlikely. While associations of other genetic diseases with specific HLA types should be sought, such relationships, as documented here, do not imply true genetic linkage.

Cystinosis↗
PubMed1980

Reduced chronic hemolysis during high-dose vitamin E administration in Mediterranean-type glucose-6-phosphate dehydrogenase deficiency.

The observation that high-dose oral vitamin E supplementation (800 IU per day) improved red-cell survival in two rare disorders associated with increased red-cell susceptibility to oxidative stress prompted a similar trial in 23 patients with Mediterranean glucose-6-phosphate dehydrogenase (G6PD) deficiency. Three months of vitamin E administration resulted in decreased chronic hemolysis as evidenced by improved red-cell life span (P less than 0.025), with an improvement in red-cell half-life from 22.9 +/- 0.7 days to 25.1 +/- 0.6 days (mean +/- S.E.M.), increased hemoglobin concentration (P less than 0.001), and decreased reticulocytosis (P less than 0.001) as compared with base-line values. Evaluation after one year of vitamin E administration demonstrated sustained improvement in all these indexes. Controlled clinical trials of vitamin E supplementation may be warranted to examine its efficacy in ameliorating acute hemolytic crises or in reducing morbidity from neonatal jaundice in this relatively common genetic disorder.

Administration, Oral↗
PubMedDate not supplied

A comparison of insulin receptors in the developing fetal lung in normal and in streptozotocin-induced diabetic pregnancies.

Insulin receptors from fetal rat lungs of normal and streptozotocin-induced diabetic pregnancies were examined for their binding capacities and association constants. Sprague-Dawley rats, given a single dose of streptozotocin at 7 days' gestation, became hypoinsulinemic and hyperglycemic within 48 hours, although they remained healthy enough to carry fetuses to term. The fetuses of the streptozotocin-treated pregnancies had hyperglycemia (3,750 +/- 400 micrograms glucose/ml vs 390 +/- glucose/ml for control subjects), but were not hyperinsulinemic. Insulin receptor binding capacities of fetal lungs from control pregnancies increased as a function of gestational age from 16 to 21 days. Receptor binding capacities of lungs from streptozotocin-treated pregnancies also increased with gestational age until 21 days, when they dropped to 50% of control values. It was demonstrated in organ culture that fetal lung receptors from normal pregnancies of 20 days' gestation could be down-regulated in the presence of insulin and that this down-regulation is coupled to a biologic effect of insulin, hexose transport. It was concluded that fetal lung insulin receptors can be regulated by insulin concentrations in vitro and by experimental diabetic pregnancies in vivo.

Animals↗