Synthesis and in vitro bioactivity of C-terminal deleted analogs of human growth hormone-releasing factor

A series of C-terminal deleted analogs of human growth hormone-releasing factor (hGRF) with either an amidated or a free carboxylic acid C-terminus were synthesized by solid phase methodology. Their capacity to release growth hormone was tested on rat anterior pituitary cells in monolayer culture. A gradual decrease of bioactivity down to 23% relative to hGRF was noted when the C-terminal amino acids were deleted to hGRF (1-34)OH. Further deletions, however, did not decrease the bioactivity because the potencies of the fragments, hGRF(1-31)NH2, (1-30)NH2 and (1-29)NH2 remained at about 50% of that of hGRF. Continual deletion of residues to hGRF(1-23)NH2, (1-22)NH2 and (1-21)NH2 still yielded bioactive fragments with full intrinsic activity despite very low potency. Only with the deletion down to hGRF(1-19)NH2 did the bioactivity completely disappear. Thus, together with the data published in a previous paper (1), the minimal biologically active core of hGRF with full intrinsic activity comprises the fragment (3-21).     

Metabolism of adenine nucleotides in thymocyte cytoplasm and subcellular fractions after treatment with concanavalin A, papaverine and adenosine

Studies with rat thymocytes labeled with [14C]adenine and fractionated by digitonin treatment revealed that the cytoplasm of these cells contains about 60% of the total adenine nucleotide pool with a higher ATP/ADP ratio and metabolic activity as compared with the structural components. The incorporation of [14C]adenine and [14C]adenosine into thymocyte adenine nucleotides results in predominant labeling of cytoplasmic ATP, in which the specific radioactivity of this nucleoside triphosphate is two and three times as high as in subcellular structures. Concanavalin A decreases the ATP level in thymocytes without changing its specific radioactivity. This compound does not influence the total content and amount labeled adenine nucleotides in the structural fraction. Papaverine accelerates the catabolism of ATP, mainly in thymocyte cytoplasm and, in a lesser degree, in its structural fraction. In each fraction the papaverine-induced catabolism of ATP is localized in the compartment which is more intensively labeled with [14C]adenine than the whole fractionation ATP pool. Adenosine markedly accelerates adenine nucleotide catabolism in the cytoplasmic and structural fractions of thymocytes; however, only in the first one of them this acceleration is due to ATP elevation. Papaverine and adenosine do not directly influence either the content or specific radioactivity of adenine nucleotides of the structural fraction isolated from [14C]adenine-labeled thymocytes.     

Colorimetric determination of phytate in unpurified extracts of seeds and the products of their processing

The addition of orthophosphate (up to 20 micrograms/ml of phosphorus) and chlorogenic acid (up to 50 micrograms/ml) does not impair the colorimetric assay of phytate based on the decoloration of Fe3+-sulfosalicylate complex (M. Latta, and M. Eskin (1980) J. Agric. Food Chem. 28, 1313-1315). Phytate was determined in 14 samples of seed meal and protein isolates containing inorganic phosphate and chlorogenic acid. There was no difference between the results of the analysis using crude extracts and those using purified extracts. It is therefore possible to avoid the preliminary purification of extracts as in the original method, thereby simplifying and accelerating the phytate assay to a considerable extent.     

Effector modeling of the action of ligands of GABA-receptor complex. Functional interaction of the hypothetic alcohol receptor with other subunits of the complex

The types of the interaction of the pharmacological effects of ethanol and barbiturate antagonists--picrotoxin, bemegride and corasol--were determined. The effect of ethanol was determined as competitive--for the convulsant effects of bicuculline, and non-competitive--for the effects of thiosemicarbazide. The indices of the anticonvulsant effects of n-aliphatic alcohols were compared. It is suggested that n-aliphatic alcohols alter the functional status of the supramolecular GABA-receptor channel ensemble. The pharmacological properties and the elements of the structural similarity of picrotoxin and n-propanol (the presumptive ligand of the GABA-receptor channel ensemble) are discussed.     

The cationic polymerization of 3-O-acetyl-β-arabinofuranose 1,2,5-orthobenzoate

Cationic polymerisation of 3-O-acetyl-β-L-arabinofuranose 1,2,5-orthobenzoate initiated by either triphenylcarbonium tetrafluoroborate or benzoylium perchlorate has been studied. The existence of living chains was demonstrated by termination of polymerisation with tritium-labelled 1-butanol. The number of growing chains reached a maximum after ≈10 min and then decreased.