Pollen-specific expression of theArabidopsis thaliana α1-tubulin promoter assayed by β-glucuronidase,chloramphenicol acetyltransferase and diphtheria toxin reporter genespromoter assayed by β-glucuronidase,chloramphenicol acetyltransferase and diphtheria toxin reporter genes

We have characterized the promoter specificity of theArabidopsis thaliana α₁-tubulin (α ₁-tub) gene by studying expression patterns of gene fusions between the 2.2 kbp 5′ upstream region of theα ₁-tub gene and each of three different reporters: chloramphenical acetyltransferase, β-glucuronidase or the diphtheria toxin chain A gene. Analysis of transgenic tobacco andArabidopsis plants carrying the transgene showed that the chloramphenicol acetyltransferase and β-glucuronidase activities were not detected in any vegetative or reproductive organs except mature pollen. Transgenic tobacco plants carrying the diphtheria toxin chain A gene under the control of theα ₁-tub promoter were of normal phenotype but seed fertility was drastically reduced. Furthermore, the transgene could not be transmitted to the next generation through pollen, supporting the observation that theα ₁-tub promoter is active only in pollen. It was observed that the promoter activity was most active in mature pollen and decreased significantly duringin vitro pollen germination, indicating that the promoter is inactive or subdued in germinating pollen. The promoter activity was not affected by various plant growth hormones during pollen maturation.     

Vacuolar H(+)-translocating pyrophosphatases: a new category of ion translocase.

The membrane surrounding the central vacuole of plant cells contains an H(+)-translocating ATPase (H(+)-ATPase) and an H(+)-translocating inorganic pyrophosphatase (H(+)-PPase). Both enzymes are abundant and ubiquitous in plants but the H(+)-PPase is unusual in its exclusive use of inorganic pyrophosphate (PPi) as an energy source. The lack of sequence identity between the vacuolar H(+)-PPase and any other characterized ion pump implies a different evolutionary origin for this translocase. The existence of the vacuolar H(+)-PPase, in conjunction with increasing recognition of PPi as a key metabolite in plant systems, necessitates reconsideration of ATP as the primary energy source for membrane transport in plant cells.     

记真盔甲鱼类两新属——兼论真盔甲鱼类系统发育关系

本文记述了早泥盆世真盔甲鱼类两新属:憨鱼属(Nochelaspis)和翼角鱼属(Pterogonaspis).真盔甲鱼类是盔甲鱼类的一个单系类群,现有七属十二种,文中运用分支系统学原理对其系统发育关系进行了初步探讨.     

γ-氨基丁酸、荷包牡丹碱和L-谷氨酸钠对猫和家兔同侧和对侧图形视觉诱发电位的影响

在猫和家兔大脑半球一侧视区17/18交界处施加γ—氨基丁酸(GABA)、荷包牡丹碱和L—谷氨酸钠,以及用氯化钾和冷冻阻遏的方法,记录对侧和同侧皮层相应处图形视觉诱发电位(PVEP)的变化。讨论了GABA、荷包牡丹碱和L—谷氨酸钠对猫和兔的对侧和同侧PVEP的影响。     

Effects of T-2 toxin and its congeners on membrane functions of cultured human fibroblasts

Cytotoxicity of T-2 toxin, HT-2 toxin, acetyl T-2, neosolaniol, and T-2 tetraol was compared between normal human fibroblasts and mutant I-cell human fibroblasts, which only produce 10 to 15% of lysosomal hydrolases present in normal fibroblasts. Both cleavage of 3-(4, 5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) and cell count by hemocytometer were used for evaluations. For all toxins, dose-related effects on both types of cultures were evident. Cytotoxicity of the above mycotoxins on both cell lines were similar, indicating that lysosomal enzymes were not involved in the toxicity of T-2 toxin and its congeners. An inhibitor of lysosomal cysteine proteases (E-64) did not alter the cytotoxicity of T-2 toxin. The decreasing order of toxicity was T-2 toxin, HT-2 toxin, neosolaniol, acetyl T-2 toxin, and T-2 tetraol in both cell lines. When normal human fibroblasts were loaded with the fluorescent dye Lucifer yellow CH (LY), a subsequent treatment of T-2 toxin did not disrupt lysosomal membranes. The uptake of LY was not affected by T-2 toxin, which indicated that T-2 toxin did not interfere with the endocytic pathway. Results indicate that T-2 toxin and its congeners do not exert their primary toxic effect through lysosomal enzymes, membranes, or via the endocytic pathway.     

Probing the opioid receptor complex with (+)-trans-superfit. I. Evidence that [D-Pen2,D-Pen5]enkephalin interacts with high affinity at the delta cx binding site.

A variety of data support the existence of an opioid receptor complex composed of distinct but interacting mu cx and delta cx binding sites, where "cx" indicates "in the complex." The ability of subantinociceptive doses of [Leu5]enkephalin and [Met5]enkephalin to potentiate and attenuate morphine-induced antinociception, respectively, is thought to be mediated via their binding to the delta cx binding site. [D-Pen2,D-Pen5]Enkephalin also modulates morphine-induced antinociception, but has very low affinity for the delta cx binding site in vitro. In the present study, membranes were depleted of their delta ncx binding sites by pretreatment with the site-directed acylating agent, (3S,4S)-(+)-trans-N-[1-[2-(4-isothiocyanato)phenyl)-ethyl]-3-methy l-4- piperidyl]-N-phenylpropaneamide hydrochloride, which permits selective labeling of the delta cx binding site with [3H][D-Ala2,D-Leu5]enkephalin. The major findings of this study are that with this preparation of rat brain membranes: a) there are striking differences between the delta cx and mu binding sites; and b) both [D-Pen2,D-Pen5]enkephalin and [D-Pen2,L-Pen5]enkephalin exhibit high affinity for the delta cx binding site.     

Overexpression of transforming growth factor-beta in transgenic mice carrying the human T-cell lymphotropic virus type I tax gene.

Human T-cell lymphotropic virus type I (HTLV-I) has been associated with an adult form of T-cell leukemia as well as tropical spastic paraparesis, a neurodegenerative disease. Adult T-cell leukemia patients express high levels of the type 1 isoform of transforming growth factor-beta (TGF-beta 1), which is mediated by the effects of the HTLV-I Tax transactivator protein on the TGF-beta 1 promoter. To understand further the regulation of TGF-beta 1 expression by Tax, we examined its expression in transgenic mice carrying the HTLV-I tax gene. We show that tumors from these mice and other tissues, such as submaxillary glands and skeletal muscle, which express high levels of tax mRNA selectively express high levels of TGF-beta 1 mRNA and protein. Moreover, TGF-beta 1 significantly stimulated the incorporation of tritiated thymidine into one of three cell lines derived from neurofibromas of tax-transgenic mice, which suggests that the excessive production of TGF-beta 1 may play a role in tumorigenesis and that these mice may serve as a useful model for studying the biological effects of TGF-beta in vivo.     

Regulation of nuclear membrane assembly and maintenance during in vitro maturation of mouse oocytes: role of pyruvate and protein synthesis

Summary In the absence of a suitable energy source, mouse oocytes cultured in vitro resume, but fail to complete, meiotic maturation. However, little is known about the underlying mechanisms leading to this meiotic failure. We utilized pyruvate-deficient medium to test for the role of pyruvate throughout the meiotic maturation process. Germinal vesicle-stage (GV) oocytes underwent germinal vesicle breakdown (GVBD), but failed to form a polar body when cultured continuously in pyruvate-free medium. However, when GV oocytes were preincubated for 4 h in pyruvate-free medium containing dibutyryl cyclic adenosine monophosphate (dbcAMP) and then cultured in pyruvate-free medium, GVBD was markedly inhibited. Preincubation of GV oocytes in dbcAMP and cycloheximide, followed by culture in cycloheximide only, also inhibited GVBD. A longer preincubation period was required in the cycloheximide-dbcAMP case (12 h) than in pyruvate-free-dbcAMP medium situation (4 h). Strikingly, reassembly of the nuclear membrane without polar body formation was observed following GVBD in oocytes continuously cultured in pyruvate-free medium. The reassembled nuclear membrane increased in size with continued culture, and it surrounded partially-decondensed chromatin. Nuclear membrane reassembly also occurred in oocytes which had undergone GVBD during continuous culture in medium containing only cycloheximide. Reformation of nuclear membranes after GVBD was confirmed by electron-microscopic analyses of oocytes cultured in pyruvate-free medium or in the presence of cycloheximide. We conclude that both pyruvate and protein synthesis are required for nuclear membrane disassembly, whereas lack of pyruvate or protein synthesis is associated with interruption of the metaphase state and reassembly of the nuclear membrane. The evidence suggests that assembly and maintenance of an intact nucleus and its disintegration are all amenable to regulation by pyruvate, possibly via mechanism(s) involving protein synthesis.