ENZYMES OF PHOSPHOINOSITIDE METABOLISM DURING RAT BRAIN DEVELOPMENT

—The activities of four enzymes concerned with inositol lipid metabolism have been determined in homogenates of rat brains of different ages. The enzymes are CDP-diglyceride inositol phosphatidate transferase, phosphatidylinositol kinase, diphosphoinositide kinase and triphosphoinositide phosphomonoesterase. The activities of all the enzymes increased with age. Phosphatidylinositol kinase activity rose most sharply well before myelination, reaching a maximum at about 6 days of age. Diphosphoinositide kinase and triphosphoinositide phosphomonoesterase activities increased most rapidly during myelination. The increase in CDP-diglyceride inositol phosphatidate transferase showed no definite association with any period of development. It is concluded that triphosphoinositide metabolism is associated with myelin or a closely related structure.     

单克隆抗体γ3重链可变区cDNA的合成与克隆

用异硫氰酸胍法从分泌单克隆抗体的杂交瘤细胞中提取总RNA,经oligo(dT)-纤维素柱亲和层析获得poly(A)~ RNA后,用恒定区5′端第122—125号氨基酸密码的互补序列3′A-T-A-G-G-T-G-A-C-C 5′做为引物,进行逆转录酶反应,合成双链cDNA,大小为300bp左右,与重链可变区基因的长度相符。用dC:dG接尾的方法,将ds-cDNA插入pUC19质粒,转化E.coli HB101。分离出重组体之后,经菌落原位杂交,酶切重组质粒DNA及Southern印迹,证明插入片段是重链可变区基因。     

几个生态因子对黄盖鲽的影响

黄盖鲽(Psuedopleuronectes yokohameGünther)是鲽科中的冷温性鱼类,广泛分布在日本、朝鲜及我国的东海、黄海和渤海。地方种群多,洄游范尉小,适应能力强,既是底栖生物食性,又可耐较低的温度,虽非名贵鱼种,却具有一定的经济价值,在开展近海增殖时,不存在越冬和效益外流问题。因此,早在60年代,日本山口县和大分县的学者们,便开始着手该品种的人工孵化和增殖放流试验。80年代初已达年放流2—3cm的稚鱼苗7.0×10~6尾的水平。为了在渤海开展增殖工作,建立综     

Virological survey of rhesus monkeys in China

A virological survey of rhesus monkeys captured in China for 13 viruses and/or antibodies was performed. Antigens used were SFV, SF40, HSV-1, Sa11, measles, vaccinia, epidemic or simian hemorrhagic fever, Langat, Kunming, poliomyelitis, HIV, SV41 and rubella. Monkeys were from Sichuan, Hunan, Guizhou, Yunnan and Guangxi provinces. Antibody was detected to all the listed viruses except HIV, SV41 and rubella. Both SFV and SV40 were recovered from monkeys, but H. simiae, LCM and coxsackieviruses were not.     

A comparative study of bark lectins from three elderberry (Sambucus) species

Three elderberry lectins isolated from the bark of three different species of the genus Sambucus which are native to Europe (S. nigra), North America (S. canadensis), and Japan (S. sieboldiana) were studied comparatively with regard to their carbohydrate binding properties and some structural features. All three lectins contained two identical carbohydrate binding sites per molecule and showed a very high specificity for the Neu5Ac(alpha 2-6)-Gal/GalNAc sequence. However, relative affinities for various oligosaccharides were significantly different among them, suggesting differences in the detailed structure of the carbohydrate binding sites of these lectins. The three lectins were immunologically related, but not identical, and all were composed of hydrophobic and hydrophilic subunit regions, although the molecular sizes of these subunits were slightly different among the three lectins. N-terminal sequence analysis of the subunits of these lectins suggested that they have a very similar structure in this region but also indicated the occurrence of N-terminal processing such as the deletion of several amino acid residues at the N-termini for both hydrophobic and hydrophilic subunits of all three lectins. Tryptic peptide mapping of the three lectins showed a similar pattern for all of them but also showed the presence of some unique peptides for each lectin.     

Induction of rat hepatic N-nitrosodimethylamine demethylase by acetone is due to protein stabilization

The N-nitrosodimethylamine demethylase (P450I-IE1) is induced severalfold in liver by giving rats ethanol, acetone, pyrazole, and other related small molecular weight compounds. This induction is not the result of an increase in IIE1 mRNA, but could be due to either an increase in translation rate or a decrease in protein degradation. To determine the mechanism of induction, we measured IIE1 synthesis and degradation rates in untreated and acetone-treated rats. This was accomplished by immunopurification of radiolabeled IIE1 protein using a specific monoclonal antibody subsequent to in vivo labeling of total cellular protein with either NaH14CO3 or [3H]leucine. We found that in rats fed acetone, the rate of IIE1 synthesis was not changed; however, IIE1 degradation was markedly altered. In untreated rats, IIE1 protein was degraded via a biphasic pathway consisting of both a rapid and slow component with approximate half-lives of 7 and 37 h, respectively. However, in acetone-treated rats, only a monophasic curve with a half-life of 37 h was observed. The abolition of the rapid degradation component of the IIE1 turnover cycle indicates that induction of IIE1 by acetone is primarily due to specific stabilization of IIE1 protein. Since acetone is also metabolized by IIE1, we believe that this may be a substrate-induced enzyme stabilization.     

Construction of a chimeric series of Bacillus cyclomaltodextrin glucanotransferases and analysis of the thermal stabilities and pH optima of the enzymes

The cyclomaltodextrin glucanotransferase (CGTase, EC 2.4.1.19) gene from the alkalophilic Bacillus sp. strain no. 17-1 was cloned in Escherichia coli. The cloned CGTase gene consisted of a single open reading frame which would encode a polypeptide of 713 amino acids, and the first 27 amino acid residues comprised a signal peptide. The nucleotide sequence and the amino acid sequence of this CGTase (CGTase 17-1) gene had strong homology with those of the CGTase (CGTase 38-2) gene previously cloned in our laboratory from the alkalophilic Bacillus sp. strain no. 38-2, although the enzymic properties of the CGTase 17-1 were distinct from those of the CGTase 38-2. To analyse those enzymic properties further, we constructed 12 chimeric CGTases using three restriction nuclease sites and compared the enzymic properties of the chimeric CGTases. The N-terminal part of the enzyme was important for heat stability, and the pH-activity profile was influenced by both the N- and the C-terminal parts. A third segment was less important for enzymic properties.     

Consequences of herbivory in the mountain birch (Betula pubescens ssp tortuosa): importance of the functional organization of the tree

Summary Three types of experiments indicate that the functional organization of the mountain birch may influence the ways in which the tree responds to simulated or natural herbivory. The first experiment showed that herbivory to both short and long shoot leaves affects plant development but, because growth largely proceeds by resources of the previous year, is manifested only in the year following the damage. The second experiment showed that even partial damage to a single long shoot leaf caused the axillary bud of that leaf to produce a shorter shoot the next year. Therefore, the value of a leaf depends also on the organ which it is subtending. In the third experiment we manipulated the apical dominance of shoots in ramets and caused improvement to leaf quality in extant shoots. Ramets within a tree responded individually, probably mediated by disturbance of the hormonal control because removal of apical buds elicited the response although removal of the same number of basal buds did not. Induced amelioration is a different response to induced resistance. The two responses are triggered by different cues and may occur in the same plant. By altering hormonal balance of shoots it is potentially possible for herbivores to induce amelioration of food quality. The ways in which herbivory is simulated may explain variability of results obtained when herbivory-induced responses in plants have been studied.