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Biomedical subjects

S Kaufman

Publications and source records attributed to S Kaufman.

At least 397 records · Page 22Linked to original sources
PubMed1977

Partial purification and characterization of rat liver phenylalanine hydroxylase phosphatase.

A phosphatase which catalyzes the release of 32Pi from 32P-labeled phenylalanine hydroxylase has been purified about 50-fold from rat liver extracts. The phosphatase is able to catalyze the removal of only 70 to 80% of the 32Pi leaving about the same amount of Pi still bound to the hydroxylase as was originally present in the native enzyme. Dephosphorylation is accompanied by a corresponding loss in phenylalanine hydroxylase activity when the activity is measured with the natural cofactor, tetrahydrobiopterin, but not when measured with the synthetic cofactor, 6-methyltetrahydropterin. The partially purified phosphatase has very low activity toward p-nitrophenylphosphate, histone phosphate, and phosphorylase a. The activity toward these substrates has not been purified to the same extent as the phenylalanine hydroxylase phosphatase activity.

Animals↗
PubMed1977

Bovine adrenal tyrosine hydroxylase: purification and properties.

Bovine adrenal tyrosine hydroxylase has been obtained in a form that is 85 to 90% pure. Sodium dodecyl sulfate-gel electrophoresis and density gradient centrifugation studies have established that the subunit molecular weight of the chymotrypsin-solubilized enzyme is 34,000. The presence of iron in the purified enzyme (0.50 to 0.75 mol of iron/mol of enzyme) has been established. Crude particulate tyrosine hydroxylase can be activated by the phospholipid, phosphatidyl-L-serine, or by exposure to enzymatic phosphorylating conditions. Both forms of activation lower the Km of the enzyme for its 2-amino-4-hydroxypteridine cofactor. By contrast, tyrosine hydroxylase that has been solubilized by chymotrypsin cannot be activated by either of these methods.

Adrenal Medulla↗
PubMed1977

Cellular and extracellular dehydration, and angiotensin as stimuli to drinking in the common iguana Iguana iguana.

1. After water deprivation, the iguana promptly drank slightly more than enough water to restore the body fluids to isotonicity even under conditions of hypervolaemia. 2. In response to systemic injections of hypertonic solutions of NaCl and sucrose, the iguana drank and retained enough water to dilute the injected load to isotonicity irrespective of whether water was offered immediately or after 3 hr, and irrespective of whether the solute was administered I.V. or I.P. 3. Hypertonic solutions to glucose, urea, sorbitol and KCl caused little drinking. 4. The long latencies to drinking after hypertonic loads, which were not dependent on the nature of the solute, the route of administration or the dosage, were shown not to be a result of slow distribution of the solute throughout the body fluids. 5. Clearance of injected solutes via renal and extra-renal (nasal salt gland) routes was negligible during the 6 hr experimental period. 6. Measurements of plasma [Na], haematocrit, osmotic pressure and inulin space showed that the iguana drank, in response to cellular dehydration, enough water to restore the intracellular fluid volume to normal. 7. We conclude that, in response to substances which dehydrate cells, the iguana regulates its body osmolality precisely and efficiently provided it is able to do so by drinking. In this respect the responses of the iguana are similar to those of the nephrectomized rat since, in the short term, both rely exclusively on drinking to restore cellular water to normal. 8. The iguana also drinks in response to extracellular dehydration produced by hyperoncotic peritoneal dialysis, and in response to I.P. angiotensin II.

Angiotensin II↗
PubMed1977

[3H]inositol incorporation into phosphatidyl-inositol in work-induced growth of rat muscle.

Unilateral tenotomy of the gastrocnemius muscle in normal rats caused rapid hyptertrophy of the soleus and plantaris muscles. The phospholipid content of hypertrophied muscles increased; the increase was proportional to the extent of hypertrophy and was distributed proportionally among the major phospholipid components. During the growth process, the hypertrophying muscles incorporated [3H]inositol into phosphatidyl-inositol more rapidly than did the contralateral, control limb muscles. The increased incorporation was evident 2 h after the operation and cannot be explained solely by an increased uptake of [3H]inositol. After growth had ceased, the incorporation of [3H]inositol into phosphatidyl-inositol gradually returned toward control levels. The increase in incorporation after tenotomy was prevented by simultaneous spinal section to abolish activity in the tenotomized limb muscles. By contrast, in rats that had been forced to swim for prolonged periods of time, there was no increased incorporation of [3H]inositol into phosphatidyl-inositol. It is concluded that the increased incorporation of [3H]inositol into phosphatidyl-inositol is related to increased muscle activity sufficient to produce compensatory hypertrophy.

Adaptation, Physiological↗
PubMed1977

Atypical phenylketonuria with normal phenylalanine hydroxylase and dihydropteridine reductase activity in vitro.

A child with phenylketonuria had normal phenylalanine hydroxylase activity in vitro. In addition, all known components of the phenylalanine hydroxylating system were within the normal range. Despite early treatment with a phenylalanine-restricted diet, the patient developed severe neurological symptoms. Although the primary molecular defect in this child is not known, there are indications that the defect lead to disturbances in phenylalanine metabolism and the biosynthesis of L-dopa and L-5-hydroxytryptophan. The administration of these two precursors of neurotransmitters brought a notable improvement in the patient's neurological symptoms.

5-Hydroxytryptophan↗
PubMed1976

Studies on phenylalanine and tyrosine hydroxylation by rat brain tyrosine hydroxylase.

Tyrosine hydroxylase (EC1.14.16.2), presumably the rate-limiting enzyme in the biosynthesis of catecholamines, is known to catalyze the hydroxylation of both phenylalanine and tyrosine. Using both an isolated enzyme preparation and a synaptosomal preparation, where some architectural integrity of the tissue has been preserved, we have attempted to evaluate the manner in which these two substrates are hydroxylated by rat brain tyrosine hydroxylase. In the presence of tetrahydrobiopterin the isolated enzyme catalyzes the hydroxylation of phenylalanine to 3,4-dihydroxyphenylalanine with the release of free tyrosine as an obligatory intermediate. In contrast, the rat brain striatal synaptosomal preparation in the presence of endogenous cofactor converts phenylalanine to 3,4-dihydroxyphenylalanine without the release of free tyrosine.

Animals↗
PubMed1976

In vitro activation of rat liver phenylalanine hydroxylase by phosphorylation.

Essentially pure phenylalanine hydroxylase from rat liver can be activated between 2.5- and 3.0-fold by treatment with Mg2+, ATP, protein kinase, and cyclic AMP. The activation is seen when the hydroxylase is assayed in the presence of tetrahydrobiopterin, but not in the presence of 2-amino-4-hydroxy-6,7-dimethyltetrahydropteridine. In the presence of [gamma-32P]ATP, activation is accompanied by incorporation of 32P into the protein to the extent of 0.7 mol/mol of hydroxylase subunit (Mr = 50,000). Cehmical analysis of the untreated enzyme shows that it already contains about 0.3 mol of Pi/mol of hydroxylase. These results suggest that the activity of the hydroxylase may be regulated by phosphorylation.

Adenosine Triphosphate↗
PubMed1976

Activation of tyrosine hydroxylase by polyanions and salts. An electrostatic effect.

The activity of a partially purified preparation of tyrosine hydroxylase (EC 1.14.16.2) from the bovine caudate nucleus was increased by heparin, chondroitin sulfate, phosphatidylserine, polyacrylic acid, polyvinyl sulfuric acid and both poly-D-, and poly-L-glutamic acids, all polyanions. A variety of salts both activated the enzyme and prevented the activation by the polyanions. The observations that activity is increased when the enzyme interacts with salts and with macromolecules of high negative charge density are used to infer a model for these interactions and for the structural change in the enzyme that accompanies activation.

Animals↗
PubMed1976

Carcinocythemia (carcinoma cell leukemia). An acute leukemia-like picture due to metastatic carcinoma cells.

Observation of a unique population of cells on a Wright-stained blood smear of a patient with metastatic breast carcinoma prompted a study to determine their origin. The primary carcinoma contained a marker, the presence of "signet cells." These were demonstrated in direct peripheral smears and buffy coat preparation of peripheral blood and confirmed histochemically by showing positive periodic acid-Schiff, alpha-napthol and beta-glucuronidase reactions. "Carcinocythemia" is suggested as a name for this unusual process observed over a six month period. Studies of the patient's immunocompetence, of circulating cell surface immunoglobulins and karyotype analysis were made. Postmortem examination revealed retroperitoneal fibrosis, splenic atrophy and extensive metastatic carcinoma but no evidence of leukemia. The cells will be contrasted to those seen in a second patient who appeared to have acute myelocytic leukemia complicating extensive cancer involving the bone marrow. The observations suggest that a leukemia-like blood picture due to circulating cancer cells may occur during the course of metastatic breast carcinoma.

Acute Disease↗
PubMed1976

Hyperphenylalaninemia due to dihydropteridine reductase deficiency. Assay of the enzyme in fibroblasts from affected infants, heterozygotes, and in normal amniotic fluid cells.

Two infant siblings with modest elevations of serum phenylalanine concentrations had seizures and developmental regression: they died in their second year. Dihydropteridine reductase activity, which can be measured in normal cultured skin fibroblasts, was measured in the younger sibling and was absent. Parents of the two siblings and parents of a previously reported patient all showed 50% or less of the normal dihydropteridine reductase activity in their cultured fibroblasts. Dihydropteridine reductase activity is also present in normal cultured amniotic fluid cells, offering the possibility of prenatal diagnosis. Absence of dihydropteridine reductase results not only in a defect in the conversion of phenylalaning to tyrosine, but also in the biosynthesis of the neurotransmitters, dopamine, norephinephrine, and serotonin. Since deficiencies in these neurotransmitters would not be alleviated by a phenylalanine-restricted diet, it is important to establish the nature of the enzymatic defect in all suspected variants of phenylketonuria.

Adult↗
PubMed1976

Hepatic phenylalanine 4-monooxygenase is a phosphoprotein.

Phenylalanine hydroxylase [phenylalanine 4-monooxygenase; EC 1.14.16.1; L-phenylalanine, tetrahydropteridine:oxygen oxidoreductase(4-hydroxylating)] isolated from rat liver is a phosphoprotein containing approximately 0.31 mumol of protein-bound phosphate per mumol of subunit (50,000 molecular weight). When the enzyme is further phosphorylated in the presence of ATP and a 3'5'-cyclic-AMP-dependent protein kinase (EC 2.7.1.37; ATP:protein phsophotransferase), an additional 0.7 mumol of phosphate per mumol of subunit is introduced, bringing the total phosphate content up to about 1 mumol/mumol of subunit. This phosphorylation of the enzyme in vitro is accompanied by a 2.6-fold increase in hydroxylase activity when the activity is assayed in the presence of tetrahydrobiopterin. Partial proteolytic digestion of phenylalanine hydroxylase, which previously had been shown to activate the enzyme 20- to 50-fold [Fisher, D.B. & Kaufman, S. (1973) J. Biol. Chem. 248, 4345-4353], removes almost all of the phosphate from the enzyme.

Animals↗
PubMed1976

NIH conference. Dopamine- -hydroxylase. Basic and clinical studies.

Dopamine-beta-hydroxylase, the enzyme responsible for conversion of dopamine to norepinephrine, is released along with catecholamines from the adrenal medulla and from sympathetic nerve endings. The properties and mechanisms of the enzyme's action are discussed and its distribution described. Dopamine-beta-hydroxylase is a valuable indicator of exocytosis as a mechanism for neurotransmitter release. The enzyme is present in plasma, but its levels vary widely between individuals. This variation seems to be related more to genetic factors than to sympathetic nerve activity. Abnormally high or low plasma levels are associated with several diseases. However, the relation of these levels to disease pathogenesis rather than to genetic determinants is unclear. Levels of the enzyme are elevated in patients with pheochromocytoma and decline after removal of the tumor. Dopamine-beta-hydroxylase levels seem to be normal in hypertensive patients. Inhibition of dopamine-beta-hydroxylase provides a useful pharmacologic approach to evaluating the role of norepinephrine in psychiatric disorders.

Adolescent↗