Expression of epidermal growth factor in the rat kidney

Summary The renal localization and the site of synthesis of epidermal growth factor (EGF) were investigated in the rat kidney by immunohistochemistry and in situ hybridization techniques. EGF was localized in the cells of the thick ascending limb of Henle (TAL) and distal convoluted tubule (DCT). At the ultrastructural level, EGF immunoreactivity was distributed on the apical membrane and trans-Golgi complex of the TAL and DCT cells. These segments of the rat nephron also hybridized to prepro-EGF cRNA probes in a specific manner, indicating that TAL and DCT are the sites of EGF synthesis in the rat kidney.     

Purification and characterization of fatty acid beta-oxidation enzymes from Caulobacter crescentus.

Acetoacetyl coenzyme A (acetoacetyl-CoA) thiolase, an enzyme required for short-chain fatty acid degradation, has been purified to near homogeneity from Caulobacter crescentus. The relative heat stability of this enzyme allowed it to be separated from beta-ketoacyl-CoA thiolase. The purification scheme minus the heating step also permitted the copurification of crotonase and 3-hydroxyacyl-CoA dehydrogenase. These activities are in a multienzyme complex in Escherichia coli, but a similar complex was not observed in C. crescentus. Instead, separate proteins differing in enzymatic activity were detected, analogous to the beta-oxidation enzymes that have been isolated from Clostridium acetobutylicum and from mitochondria of higher eucaryotes. In these cells, as appears to be the case with C. crescentus, the individual enzymes form multimers of identical subunits.     

Structures of paralytic acylpolyamines from the spider Agelenopsis aperta

The structures are given for five paralytic acylpolyamines from the venom of the funnel web spider, Agelenopsis aperta. The acyl moieties are derived from (3-indolyl)acetic acid, (4-hydroxy-3-indolyl)acetic acid, and 4-hydroxybenzoic acid. The polyamine portions of the toxins are novel. Three toxins (AG489, AG505, and AG452) contain 1, 5, 9, 13, 18, 22-hexaazadocosane which is unique as a natural polyamine because of its length and hydroxylation at the 5-aza position. The polyamine portions of two other alpha-agatoxins (AG488 and AG504) are unusual also, containing guanidinooxy moieties.     

Inhibition by glutamate of phosphate-dependent glutaminase of rat kidney.

A membrane-associated form of phosphate-dependent glutaminase was derived from sonicated mitochondria and purified essentially free of gamma-glutamyl transpeptidase activity. Increasing concentrations of phosphate cause a sigmoidal activation of the membrane-bound glutaminase. Phosphate also causes a similar effect on the rate of glutaminase inactivation by the two affinity labels, L-2-amino-4-oxo-5-chloropentanoic acid and 6-diazo-5-oxo-L-norleucine, as observed previously for the solubilized and purified enzyme. Therefore the two forms of glutaminase undergo similar phosphate-induced changes in conformation. A sensitive radioactive assay was developed and used to determine the kinetics of glutamate inhibition of the membrane-associated glutaminase. The Km for glutamine decreases from 36 to 4 mM when the phosphate concentration is increased from 5 to 100 mM. Glutamate is a competitive inhibitor with respect to glutamine at both high and low concentrations of phosphate. However, the Ki for glutamate is increased from 5 to 52 mM with increasing phosphate concentration. Therefore glutamine and glutamate interact with the same site on the glutaminase, but the specificity of the site is determined by the available phosphate concentration.     

An interactive technique for the display of nucleic acid secondary structure.

The ability to visualize nucleic acid secondary structure has become quite important since the advent of computer prediction and biochemical techniques that depict such structures. Manually drawing the conformations can be quite time consuming and tedious. Thus, the ability to draw with the aid of a computer the secondary structure of nucleic acid molecules is quite advantageous. This paper describes an interactive algorithm that permits one to generate such drawings which may then be used for further analysis and/or publications.     

Genetic analysis of Tourette syndrome suggesting major gene effect.

Data on Gilles de la Tourette syndrome are analyzed by multiple threshold models in inheritance that incorporate sex effect. The polygenic-multifactorial model is rejected. Single major locus inheritance can account for the data, although many of the occurrences of Tourette are due to nongenetic phenocopies. In both models, males and females share a common genetic environmental liability, but the less prevalent sex, that is, females, has a higher genetic loading for the disorder. The predicted population prevalences in the single major locus model are 2.3% for males and 0.8% for females. The implications for genetic and biological research in Tourette syndrome are discussed.     

Cerebroside sulfatase activator deficiency induced metachromatic leukodystrophy

Two siblings of consanguineous parents had presented with a variety of findings indicative of juvenile metachromatic leukodystrophy (MLD). However, instead of the expected profound deficiency of arylsulfatase A (ARS A), their enzyme levels were about half-normal, and enzyme from fibroblasts had properties identical with the properties of enzyme from normal fibroblasts. Nevertheless, the hydrolysis of cerebroside sulfate by growing fibroblasts was markedly attenuated. Supplementation of the fibroblasts with cerebroside sulfatase activator normalized the response in the loading test. These results imply that the fibroblasts, and by extension the patients, are deficient in activator. Although the defective catabolism of cerebroside sulfate and the clinical manifestations in these patients mimic MLD, the molecular basis is distinct from the classical forms of the disorder.     

Schistosoma mansoni: Inhibition of glucosephosphate isomerase and glycolysis by sugar phosphates

Glucosephosphate isomerase (EC 5.3.1.9) of Schistosoma mansoni is inhibited competitively by a number of tetrose, pentose, and hexose phosphates with inhibitor constant (K_i) values in the range of 0.5 to 400 μM. The most potent inhibitor is 5-phospho-d-arabinonate which resembles the cis-enediolate transition state intermediate of the reaction. These analogs were also found to be effective inhibitors of the production of lactate from glucose by suitably supplemented worm homogenates. The rank order of potency of inhibition of glycolysis was inversely related to the magnitudes of the K_i values for glucosephosphate isomerase. These K_i values were similar to those previously reported for mammalian glucosephosphate isomerase, suggesting similarities in the steric and electronic characteristics of the active sites of these isofunctional enzymes. This conclusion was further supported by the observed pH dependence of the inhibition by 5-phospho-d-arabinonate. Although glucosephosphate isomerase is not a rate-limiting enzyme of glycolysis, in the conventional sense, its selective inhibition could be of chemotherapeutic importance, in part because of the accumulation in glycolyzing systems of glucose 6-phosphate which is a potent feedback inhibitor of hexokinase.     

Changes in mouse brain diazepam receptor binding after phenobarbital administration

Specific ³H-diazepam binding was measured $\text{in vitro}$ in adult mouse (strain, Crl=CD-1) brain after four days of an inductive dose of phenobarbital pretreatment (i.p.). Sexual dimorphism was observed in ³H-diazepam brain binding, female mice had significantly higher benzodiazepine binding than males without any differences in apparent affinity constants (K_D). Phenobarbital pretreatment caused a significant decrease in the maximal number of binding sites (Bmax) as well as in dissociation rate constants in both sexes.