Biochemical characterization of enkephalin-like immunoreactive peptides of adrenal glands

The total enkephalin-like immunoreactive peptide content of adrenal glands from dog, cattle, guinea pig and rat was investigated by radioimmunoassay using a (met⁵)-enkephalin antiserum. Dog adrenals contain the highest amount of peptides, cattle and guinea pig adrenals contain lesser amounts, and the rat adrenals had the least amount (0.05% that of the dog). Comparison of the (met⁵)-enkephalin content of the adrenal cortex and medulla with that of whole bovine adrenal gland indicates that the peptides are concentrated in the medulla. Analysis of the chromaffin granules from bovine adrenal medulla indicates this to be the primary storage site for (met⁵)-enkephalin-like peptides. Gel chromatography reveals a molecular heterogeneity of the immunoreactive peptides in all species tested; high molecular weight peptides account for a larger proportion of the immunoreactivity when compared with the low molecular weight peptides.     

The regulation of ionic nickel uptake and cytotoxicity by specific amino acids and serum components

The effects of serum components and amino acids on the uptake and cytotoxicity of NiCl₂ were examined in cultured Chinese hamster ovary (CHO) cells. CHO cells maintained in a minimal salts/glucose medium accumulated 10-fold more⁶³Ni than did cells maintained in complete medium supplemented with 10% fetal bovine serum. Cell-surface binding of⁶³Ni appeared to account for the majority of this increased accumulation of cell-associated nickel observed in the simple maintenance medium since such increases were reduced 70% by trypsin treatment. The addition of the Ni²⁺-binding amino acids cysteine or histidine to the salts/glucose medium markedly decreased⁶³Ni accumulations, an effect not observed following addition of any of several amino acids that do not bind Ni²⁺. Supplementation of the salts/glucose medium with fetal bovine serum decreased in a concentration dependent fashion both the⁶³Ni²⁺ uptake and cell detachment caused by Ni²⁺, while dialyzed (amino acid-free) serum was 3–5-fold less effective than undialyzed serum at reducing⁶³Ni²⁺ uptake and similarly exhibited only a slight protective effect against nickel-induced cytotoxicity. Supplementation of dialyzed serum with cysteine at levels approximating those in whole serum partially restored its inhibitory activity toward nickel uptake by cells and restored completely its inhibition of nickel's cytotoxicity, indicating the predominant role of specific amino acids over serum proteins in regulating the uptake and subsequent cytotoxicity of Ni²⁺. Addition of cysteine to the salts/glucose medium during a 2 h exposure of cells to either 100 μM HgCl₂ or 1 mM NiCl₂ masked the cytotoxic effects of these metal ions. These results demonstrate the importance of extracellular small molecular weight metal ion chelators in altering the biological effects of metal ions at the level of metal uptake.     

Effect of psoralen-induced photodermatitis on tryptophan metabolism in rats

Tryptophan metabolism ‘via kynurenine’ has been studied in rats before and after induction of experimental light-conditioned dermatitis with psoralen. Tryptophan load in animals during the acute phase of dermatitis (one day after induction) causes a markedly increased urinary excretion of total metabolites in comparison with that obtained before dermatitis. During this phase of the skin disease tryptophan pyrrolase activity is significantly increased and kynureninase activity significantly decreased in liver in respect to the control animals. Kynurenine aminotransferase activity shows no significant variations in both liver and kidneys. After 6 days of dermatitis, when the skin damage is in repair, both the excretory values of the urinary metabolites after L-tryptophan load and the enzymic activities are similar to those before dermatitis.     

Cyclic AMP-dependent and -independent protein kinases of the water mold, Blastocladiella emersonii.

Protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37) and cyclic adenosine 3',5'-monophosphate binding activities have been identified in zoospore extracts of the water mold Blastocladiella emersonii. More than 75% of these activities is found in the soluble fraction. Soluble protein kinase activity is resolved in three peaks(I, II and III) by DEAE-cellulose chromatography. Peak I is casein dependent and insensitive to cyclic AMP. Peak II is histone dependent and cyclic AMP independent; this enzyme is inhibited by the heat-stable inhibitor from bovine muscle. Peak III utilizes histone as substrate and is activated by cyclic AMP.     

Differential effects of manganese ions on Blastocladiella emersonii adenylate cyclase.

Adenylate cyclase (ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1) activity in Blastocladiella emersonii is associated with particulate subcellar fractions. Solubilization after treatment with detergent suggests its localization in a membrane fraction of the zoospore homogenate. The enzyme specifically requires Mn2+ for activity and is not stimulated by NaF. The kinetic characteristics of substrate utilization by B. emersonii adenylate cyclase were investigated with various concentrations of ATP and Mn2+, and in the presence of inhibitors. Plots of enzyme activity versus the actual concentration of the MnATP2- complex give sigmoid curves. An excess of Mn2+ activates the enzyme at low concentrations of substrate and leads to a modification of the enzyme kinetics. The nucleotides 5'-AMP and GTP were shown to be competitive inhibitors of the enzyme. In addition, kinetic data, obtained under conditions in which an inhibitor (ATP) is added in constant proportion to the variable substrate (MnATP2-) concentration, produced reciprocal plots that were linear and intersecting to the right of the ordinate, and secondary replots that were hyperbolic. These kinetic patterns support a model in which: MnATP2- is the substrate; free Mn2+ is an activator at low substrate concentrations, but an inhibitor at high substrate concentrations; and free ATP is not an efficient inhibiyor (Ki greater than 1.10(-4) M).     

Changes in cyclic AMP binding and protein kinase activities during growth and differentiation of Blastocladiella emersonii.

Multiple protein kinases in the water mould Blastocladiella emersonii are described. A cyclic AMP-independent protein kinase which prefentially phosphorylates casein remains unchanged during vegetative growth of the cells and in the two phases of differentiation: germination and sporulation. In contrast, cyclic AMP-dependent protein kinase activity and cyclic AMP binding components are induced during the sporulation.     

Nuclear inclusions in the nerve cells of the sphenopalatine ganglion of the dog

Summary Large numbers of nuclear inclusions have been found in the nerve cells of the sphenopalatine ganglia of six healthy adult dogs. Their morphological characteristics are similar to those previously described elsewhere. The presence of simple and granular bodies in normal cells seems to support the hypothesis that these nuclear structures might be considered as normal nuclear organelles related to cellular metabolic activity.     

The presence of aromatic L-amino acid decarboxylase in certain intestinal nerve cells

Summary The presence of aromatic 1-amino acid decarboxylase (AADC) in nerve cell bodies of the intrinsic plexuses of the guinea-pig small intestine was demonstrated by incubating segments of intestine with 1-dopa in the presence of an inhibitor of monoamine oxidase, pargyline. After such incubation, some nerve cell bodies gave a fluorescence histochemical reaction indicative of the presence of a decarboxylated product of 1-dopa, probably dopamine. No fluorescence reaction occurred in the unincubated control or if the inhibitor of AADC, RO 4-4602, was included in the incubation mixture. The AADC-containing cell bodies apparently do not take up and store dopamine, because no fluorescence could be detected after incubation with dopamine and a monoamine oxidase inhibitor. The AADC-containing cells were found in about half of the ganglia of the submucous plexus of the guinea-pig small intestine, but were considerably less frequent in the myenteric plexus. They were also found in the other areas examined in this study, that is, in both enteric plexuses of the guinea-pig distal colon and of the small intestines of rabbits and rats.     

Induction of mutants in Saccharomyces cerevisiae by guanidine hydrochloride II. Conditions that prevent induction

The induction of ⁻ “petite” mutants by guanidine hydrochloride (GuHCl) is inhibited in several conditions. Anaerobiosis inhibited the induction either with or without cell multiplication. Both nalidixic acid (NA) and cycloheximide (CH) inhibited the induction of mutants. On the other hand, chloramphenicol (CAP) produced a dual effect: at low concentration it stimulated, at high concentration it inhibited, the induction. The effect of these different inhibitors on the transformation of ⁺ mother cells into ⁻ by GuHCl is discussed.