鲥鱼的驯养与生物学研究Ⅰ.O+龄幼鱼的生长与食性

本文主要描述池塘养殖条件下鲥鱼幼鱼的生长与食性。1)1987-1989年8月至11月幼鱼生长迅速,快于同期珠江天然个体的生长速度;2)体长26.6-94.9mm的幼鱼主要摄食浮游动物,轮虫和浮游植物出现率随个体增大而减少。食物共有18个属种,摄食频度为100%;3)幼鱼的平均饱满指数为75.70‰。各类食物重量百分比的顺序为:桡足类>枝角类>无节幼体>虾类溞状幼体>轮虫>藻类。     

Roles of the respiratory Na+ pump in bioenergetics of Vibrio alginolyticus

Bioenergetic characteristics of Na+ pump-defective mutants of a marine bacterium Vibrio alginolyticus were compared with those of the wild type and revertant. Generation of membrane potential and motility at pH 8.5 in the mutants were completely inhibited by a proton conductor, carbonylcyanide m-chlorophenylhydrazone, whereas those in the wild type or revertant were resistant to the inhibitor. Motility and amino acid transport were driven by the electrochemical potential of Na+ not only in the wild type or revertant but also in the mutants. In the absence of the proton conductor, motility and amino acid transport of the mutants did not significantly differ from those of the wild type or revertant even at pH 8.5, where the Na+ pump has maximum activity. Therefore, the electrochemical potential of Na+ in the mutants seemed to be maintained at a normal level by a respiration-dependent H+ pump and Na+/H+ antiporter. On the other hand, growth of the mutants became defective as the medium pH increased, especially on minimal medium. These results indicate that the Na+ pump is an important energy-generating mechanism when nutrients are limited at alkaline pH.     

Studies on the development of water maze-learning ability in rats (3). Effect of the learning schedule on learning acquisition

The effect of different learning schedules massed or distributed practice conditions (3 trials a day for 3 days), on water-filled multiple T-maze learning ability of 8-week-old SPF Wistar-Imamichi rats was investigated. Although the mean number of errors decreased day by day in both groups, the number of errors in a given day and the total number of errors in 3 days did not differ significantly between the two groups. A tendency toward a decrease in the number of errors was observed as the trials proceeded in the group with distributed practice but not in the group with massed practice. The result suggests that a certain time period for rest after each trial is necessary to acquire the memory.     

利用单克隆抗体鉴定人甲胎蛋白(HAFP)抗原结构可分性

本文利用两株针对HAFP分子不同抗原决定簇的单克隆抗体,鉴定HAFP酶解片断的抗原抗体反应性质,并同完整HAFP分子进行比较。结果表明,酶解片断上失去了一株单克隆抗体所对应的分子部份,完整保留着另一株单克隆抗体所识别的抗原决定簇,从而证实HAFP分子某些抗原结构之间具有可分割性。     

Evidence for unique homologous peptide sequences around the glycosylated seryl and threonyl residues in polysialoglycoproteins isolated from the unfertilized eggs of the Pacific salmon Oncorhynchus keta

Structures of glycopeptides obtained by exhaustive Pronase digestion of high molecular weight (1.7 X 10(5)) salmon egg polysialoglycoprotein have been elucidated. Six principal glycopeptides isolated by gel chromatography and DEAE-Sephadex A-25 chromatography in the absence or presence of borate ion were analyzed for their carbohydrate and amino acid composition, as well as amino acid sequence, and found to be of two distinct types: glycotripeptides, Thr*-Ser*-Glu, and glycotetrapeptides, Thr*-Gly-Pro-Ser, where an asterisk indicates the amino acid residues to which either the Gal beta 1----3GalNAc or Fuc alpha 1----3GalNAc beta 1----3Gal beta 1----4Gal beta 1----3GalNAc chain is attached. Their final yield corresponds to 64% of the original desialylated glycoprotein. In view of the simple amino acid composition of salmon egg polysialoglycoprotein (molar ratio Asp2Thr2Ser3Glu1Pro1Gly1Ala3) and the result of alkaline beta-elimination indicating three carbohydrate units linked to two of two threonine and one of three serine residues, a unique primary structure comprising repetitive sequences of the above two types of glycopeptides, which are interspersed by short nonglycosylated peptides consisting of alanine and aspartic acid, has been proposed for the core protein. The molecular secondary ion mass spectra of underivatized glycopeptides were used to obtain their structural information. The anomeric configuration of the proximal sugar-peptide linkages was proven to be alpha by proton nuclear magnetic resonance spectroscopy. This is the first systematic reported study of O-glycosidically linked glycopeptides by these instrumental methods.     

Purification and properties of extracellular glucosyltransferase synthesizing 1,6-, 1,3-alpha-D-glucan from Streptococcus mutans serotype a

An extracellular glucosyltransferase (sucrose: 1,6-, 1,3-alpha-D-glucan 3-alpha- and 6-alpha-D-glucosyltransferase, EC 2.4.1.-) of Streptococcus mutans HS6 (serotype a) was purified from culture supernatant by DEAE-Sepharose chromatography and preparative isoelectric focusing. The molecular weight measured by SDS-PAGE was 159 000 and the isoelectric point was pH 4.9. The specific activity was 89.7 i.u. (mg protein)-1 and the optimum pH was 6.0. The Km value for sucrose was 4.9 mM and the enzyme activity was not stimulated by exogenous dextran T10. Glucan was synthesized de novo from sucrose by the purified enzyme and consisted of 49.1 mol% 1,6-alpha-linked glucose and 33.9 mol% 1,3-alpha-linked glucose, with 13.6 mol% terminal glucose and 3.3 mol% 1,3,6-alpha-branched glucose.     

Partial purification of two distinct enkephalin-degrading aminopeptidases from human cerebrospinal fluid

In human cerebrospinal fluid, aminopeptidase, dipeptidyl aminopeptidase, dipeptidyl carboxypeptidase, and carboxypeptidase which were capable of hydrolyzing enkephalins were detected. Among these enzymes, two distinct aminopeptidase, designated C-AP1 and C-AP2, were partially purified. These enzymes were not purified thoroughly, but the characteristics of C-AP2 were similar to those of an aminopeptidase purified from monkey brain. But the inhibitory activity of amastatin on C-AP2 was stronger, and that of substance P was negligible. On the other hand, characteristics of C-Ap1 were extremely differ from those of C-AP2 or an aminopeptidase purified from monkey brain. C-AP1 had an optimum pH more in the acidic range (the highest at pH 6.0) and was not inhibited by any of the protease inhibitor tested including bestatin and amastatin.