Excitatory amino acid receptor-mediated neuronal signal transduction: modulation by polyamines and calcium

Molecular and Cellular Biochemistry - The excitatory amino acids (EAA), L-glutamate and L-aspartate were initially advanced as excitatory neurotransmitters some 30 years ago but in the past few...     

Adrenocortical suppression in workers manufacturing synthetic glucocorticoids.

A man who had worked for 16 years in the manufacture of a potent corticosteroid was found to be suffering from chronic adrenocortical insufficiency attributed to chronic absorption of the glucocorticoid. Eleven other symptom-free workers were therefore screened. Two of these workers, like the first patient, gave grossly abnormal responses to the Synacthen (tetracosactrin) test; one had been employed for only seven months. All 12 men had facial plethora, suggesting absorption of the drug in spite of their having adhered to the safety precautions. All workers manufacturing potent steroids should therfore be screened regularly by measurement of their plasma cortisol concentrations and should be moved regularly to processing other drugs.     

Glucofructosan biosynthesis in Fusarium oxysporum: Regulation and substrate specificity of fructosyl transferase and invertase

Mycelium of Fusarium oxysporum grown on a glucose-containing medium lacked fructosyl transferase and invertase activities. Synthesis of fructosyl t     

Microbial transformation of sterols

Summary Arthrobacter simplex, Serratia marcescens, Fusarium and Mycobacterium were tested for their ability to transform phytosterol to Androsta 1, 4 diene 3, 17 dione (ADD). Arthrobacter simplex ATCC 6946 was found to be more efficient than the other species tested.     

A simplified radioenzymatic assay for dihydrofolate reductase using [3H]dihydrofolate

This report describes a simple method to measure the activity of dihydrofolate reductase using the substrate [³H]dihydrofolate, which is generated by preincubation of [³H]folic acid for 10 min with dithionite before the enzymatic reaction. The procedure then measures the direct reduction of [³H]dihydrofolate to [³H]tetrahydrofolate by coprecipitating the unreduced substrate with excess unlabeled folic acid and acidified zinc sulfate. The advantage of this method is that [³H]dihydrofolate, which is not commercially available, can be generated from high specific activity [³H]folic acid, which is commercially available, immediately before initiating the enzymatic reaction. By this modification, the two important advantages of radioenzymatic assays for dihydrofolate reductase can be more easily exploited; namely, increased sensitivity because much less substrate need be used, and the ability to measure enzyme activity in crude tissue preparations without interference by precipitating proteins or nucleotide oxidases.     

Raman and infrared spectroscopic study of gramicidin A conformations

Raman scattering and infrared spectroscopic techniques were used to study the vibrational spectrum and conformation of the membrane channel protein gramicidin A in the solid state, in organic solutions and, using Raman scattering only, in a phospholipid environment. The investigation also includes measurements on head- and tail-group-modifled gramicidin A and a potassium thiocyanate-gramicidin A complex. Tentative identification of the molecular vibrations is proposed on the basis of the data on model compounds. The existence of four distinct conformations of the gramicidin A chain is established: conformation I present in the solid state, and CH₃OH and CD₃OD solutions; conformation II present in films cast from CHCl₃ solution; conformation III present in (CH₃)₂SO and (CD₃)₂SO solutions at concentrations below 0.5 m gramicidin A; and conformation IV present in the potassium thiocyanate-gramicidin A complex. The data obtainable on a gramicidin A-phospholipid suspension indicate a gramicidin A conformation in this environment corresponding either to the conformation I or II. The details of the spectra in the amide I region are shown to be consistent with a β-parallel hydrogen-bonded π_LD helix for conformational I, in terms of the polypeptide vibrational calculations of Nevskaya and co-workers. Conformation II is found to be consistent with an antiparallel double-stranded π_LD helix, while conformations III and IV probably have π-helical structures with larger channel diameters. The data on head- and tail-modified gramicidin A molecules indicate that their conformations are only slightly different from that of gramicidin A in conformation I.     

Low serum testosterone concentrations in patients with carcinoma of the pancreas

The detection of high activities of two sex-steroid biosynthetic enzymes—aromatase and 5-alpha-reductase—in pancreatic carcinoma tissue suggested the possibility that these enzymes may influence the circulating concentrations of sex-steroid hormones. Mean serum testosterone concentrations in 22 men and women with exocrine carcinoma of the pancreas were significantly lower than those in 20 healthy controls and 27 patients with other known malignancies, who were of similar age and sex composition. Low serum testosterone concentrations may be due to uptake by and metabolism within the tumour; alternatively, patients with low androgen concentrations may be at greater risk of developing pancreatic carcinoma.