MECHANISM OF ACTION OF β-N-OXALYL-L-α, β-DIAMINOPROPIONIC ACID, THE LATHYRUS SATIVUS NEUROTOXIN

The source of ammonia in the brain tissue of young rats treated with β-N-oxalyl-l -α, β-diaminopropionic acid (ODAP) has been studied. ODAP administration to 12-day-old rats causes a significant increase in the levels of adenylic acid deaminase in the brain. Glutaminase activity also shows an increase under these conditions. An increase in the levels of acid protease and transglutaminase is also observed in the brain of ODAP-treated animals. Glutamate dehydrogenase activity is decreased slightly. Glutamine synthetase enzyme is not affected. Aspartate-α-ketoglutarate transaminase and aspartate-pyruvate transaminase activities are enhanced in the brain tissue of ODAP-treated rats. It is held that protein degradation, especially the cleavage of free and protein-bound amide bonds, may be responsible for excess ammonia liberation in the brain of ODAP-treated young rats.     

Root exudates of rice seedlings. The influence of one variety on another

Summary In the present study attempts have been made to elucidate the composition and physiological actions of root exudates from CB-1 Rupsail and the mixed population of these two varieties. The chemical nature of the different components of root exudates was studied by means of paper chromatography, bioassay and other biochemical procedures. It was noted that exudates from CB-1 and Rupsail seedlings inhibited root/shoot growth of test seedlings of both varieties. But when these two varieties were grown together root/shoot growth of both varieties were markedly promoted. Both qualitative and quantitative differences in amino acids, carbohydrates and growth substances contents of root exudates of individual and mixed population of rice varieties were noted.     

SYNTHETIC ACTIVITIES DURING SPERMATOGENESIS IN THE LOCUST

Isolated testes of the locust Schistocerca gregaria were immersed in solutions of tritiated thymidine, cytidine, uridine, or arginine for short periods to study nucleic acid and protein synthesis during spermatogenesis. DNA synthesis in this tissue is completed prior to initiation of meiosis. Protein synthesis continues throughout the whole meiotic cycle as well as during spermatid development. Meiotic cells, except those in metaphase through early telophase, and early spermatids are also actively synthesizing RNA. The heteropycnotic X-chromosome does not produce RNA at any stage of spermatogenesis. The rates of protein and particularly RNA synthesis decrease as chromosome condensation progresses. Depression of RNA synthesis, however, is not always accompanied by cytologically detectable condensation of chromatin, since very little or no RNA is synthesized in spermatids in which chromatin condensation has barely begun.     

Identification of the pH-dependent membrane anchor of carboxypeptidase E (EC 3.4.17.10)

Carboxypeptidase E (CPE), a peptide hormone-processing enzyme, is present within secretory granules in both a soluble form and a form which is membrane-bound at pH 5.5 but soluble at neutral pH. Antisera raised against a peptide corresponding to the predicted COOH-terminus of CPE bind to the membrane-associated form of CPE but not to the soluble form. This COOH-terminal region is predicted to form an amphiphilic alpha-helix, containing several pairs of hydrophobic residues separated by hydrophilic residues. Synthetic COOH-terminal peptides 11-24 residues in length are able to bind to bovine pituitary membranes and can be extracted by conditions that extract the membrane-bound form of CPE. The influence of pH on the membrane binding of a 21-residue COOH-terminal peptide is similar to the membrane binding of CPE: at pH values less than 6 the majority of the peptide is membrane-bound, while at pH values above 8 less than 20% is membrane-bound. Both the 21-residue COOH-terminal peptide and the purified membrane form of CPE, but not the soluble form, partition into Triton X-114 only at low pH (pH less than 6). Combined polar and hydrophobic interactions of the COOH-terminal peptide appear to be responsible for the reversible, pH-dependent association of CPE with membranes.     

Effects of Vitamin A and Its Analogs on Nonenzymatic Lipid Peroxidation in Rat Brain Mitochondria

Vitamin A (retinol) and some of its analogs exhibited varying degrees of inhibition on induced iron and ascorbic acid lipid peroxidation of rat brain mitochondria. Malonyldialdehyde production was used as an index of the extent of in vitro lipid peroxidation. The fat-soluble vitamins retinol, retinol acetate, retinoic acid, retinol palmitate, and retinal at concentrations between 0.1 and 10.0 mmol/L inhibited brain lipid peroxidation. Retinol and retinol acetate were the most effective inhibitors. It is concluded from this study that retinol and its analogs can be considered as potential antioxidant factors, more potent than some of the well-known antioxidants such as alpha-tocopherol and butylated hydroxytoluene.