Biomedical subjects

I Katz

Publications and source records attributed to I Katz.

At least 91 records · Page 5Linked to original sources

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

Symphalangism with metacarpophalangeal fusions and elbow abnormalities.

Three generations of a family manifest similar skeletal abnormalities: proximal symphalangism with several unusual features, metacarpophalangeal synostoses, massive tarsal and carpal fusions and abnormalities of the elbows (radial head dislocation, radiohumeral synostosis). Two members of this family were previously reported by Pearlman et al. as examples of the Nievergelt syndrome, but the affected individuals lack the mesomelic dysplasia that is an integral part of that entity. Moreover, the Nievergelt syndrome does not include symphalangism. The term "Nievergelt-Pearlman syndrome" should be dropped.

Abnormalities, Multiple↗

PubMed1976

Effect of phloretin on the permeability of thin lipid membranes.

Phloretin dramatically increases cation conductances and decreases anion conductances of membranes treated with ion carriers (nonactin, valinomycin, carbonyl-cyanide-m-chlorophenylhydrazone [CCCP], and Hg(C6F5)2) or lipophilic ions (tetraphenylarsonium [tphAs+] and tetraphenylborate [TPhB-]). For example, on phosphatidylethanolamine membranes, 10(-4) M phloretin increases K+ -nonactin and TPhAs+ conductances and decreases CCCP- and TPhB- conductances 10(3)-fold; on lecithin: cholesterol membranes, it increases K+-nonactin conductance 10(5)-fold and decreases CCCP- conductance 10(3)-fold. Similar effects are obtained with p- and m-nitrophenol at 10(-2) M. These effects are produced by the un-ionized form of phloretin and the nitrophenols. We believe that phloretin, which possesses a large dipole moment, adsorbs and orients at the membrane surface to introduce a dipole potential of opposite polarity to the preexisting positive one, thus increasing the partition coefficient of cations into the membrane interior and decreasing the partition coefficient of anions. (Phloretin may also increase the fluidity of cholesterol-containing membranes; this is manifested by its two- to three-fold increase in nonelectrolyte permeability and its asymmetrical effect on cation and anion conductances in cholesterol-containing membranes.) It is possible that pholoretin's inhibition of chloride, urea, and glucose transport in biological membranes results from the effects of these intense intrafacial dipole fields on the translocator(s) of these molecules.

Anti-Bacterial Agents↗

PubMed1976

Frontometaphyseal dysplasia: evidence for autosomal dominant inheritance.

Frontometaphyseal dysplasia is a syndrome that encompasses cranial hyperostosis, abnormal tubulation of cylindrical bones, and other skeletal and extraskeletal abnormalities. The most striking features are overgrowth of the supraorbital ridges which results in a Mephistophelian facial appearance and a radiographic configuration of the skull that has been likened to a soldier's helmet. Most patients have severe hearing loss, defective dentition, poorly developed musculature, and joint contractures. Dominant inheritance has been suggested in previous reports, but an appropriate pedigree has been documented in only one family. This paper describes three additional patients in two unrelated families: (1) an 8-year-old boy whose mother has mild metaphyseal dysplasia and several minor skeletal abnormalities that have occurred in patients with the syndrome; and (2) two maternal half-brothers. These cases provide additional evidence that frontometaphyseal dysplasia is an autosomal dominant trait with variable penetrance.

Abnormalities, Multiple↗

PubMed1976

Self-evaluation, social reinforcement, and academic achievement of black and white schoolchildren.

Black and white male schoolchildren covertly evaluated their own performance at a verbal task administered by black and white male experimenters. It was hypothesized that academically successful children would be predisposed to appraise themselves favorably, whereas relatively unsuccessful pupils would be biased toward self-criticism. The covert self-evaluations were assumed to represent at internalization of early experiences of predominantly positive or negative social reinforcement from adult socializing agents. The predicition for self-criticism was upheld in the white experimenter condition but not in the black experimenter condition. Relationships consistent with the theory were found between subjects' self-appraisals and their retrospective reports of positive and negative reinforcements received from parents and teachers in various typical situations. These relationships were more evident for black subjects than for white subjects. The extent to which children's self-praise and self-criticism mediated affect was assessed by means of a color conditioning technique. Contrary to predicition, possibly due to the easy nature of the experimental task.

Achievement↗

PubMed1973