A toxic substance produced by Nocardia otitidiscaviarum isolated from cutaneous nocardiosis

During our studies on toxic substances from clinically isolated Nocarida, a new isolate identified as Nocardia otitidiscaviarum from cutaneous nocardiosis was found to produce a toxic substance called HS-6 that had strong in vitro as well as in vivo toxicity. The mouse intraperitoneal LD₅₀ value was 1.25 mg/kg and the ED₅₀ value for L1210 cultured cells was 0.3 ng/ml. The structure of HS-6 was determined and found to belong to the 16-membered macrocyclic group with a molecular formula of C₄₃H₆₈O₁₂. HS-6 also showed activity against pathogenic fungi such as Cryptococcus neoformans.     

罗汉果组培苗的栽培研究

本文报道罗汉果组培苗的栽培研究结果,为罗汉果在生产上推广应用组培苗栽培,提供有效的技术措施。     

An in-vivo measurement and analysis of viscoelastic properties of the spinal cord of cats

An in-vivo experimental technique was employed to determine the linear and nonlinear characteristics of viscoelastic properties of the spinal cord of anesthetized cats. The stress relaxation and recovery curves were reproducible in a group of cat experiments. The data of linear viscoelastic properties were used to develop a power law model with Boltzmann's convolution integral. The model was capable of predicting a prolonged stress relaxation and recovery curve. For larger deformation, the results were quantified using a nonlinear analysis of viscoelastic response of the spinal cord under the uniaxial experiment.     

转铁蛋白结构与功能的研究——骆驼血清转铁蛋自的分离纯化及其含单一铁结合部位的结构域的制备和鉴定

分离纯化获得的骆驼血清转铁蛋白由分子量为73,000和63,000两个组分组成。两者至少N-端五肽顺序相同(Met-Pro-Asp-Lys-Thr)。骆驼血清转铁蛋白在生理pH下不能与人胎盘转铁蛋白受体结合。用胰蛋白酶酶解骆驼转铁蛋白可以同时得到两个合单一铁结合部位的结构域,分别来自转铁蛋白分子的N-端称N-端结构域(分子量34,700和40,700)和C-端称C-端结构域(分子量35,100)。在上述结果的基础上指出并讨论了反刍动物转铁蛋白在结构和功能上存在更多的共同性,而与其它哺乳动物的转铁蛋白有着明显的区别。     

Alport syndrome: a genetic study of 31 families

Thirty one families with Alport syndrome including 3 families with associated syndromes were studied. The location of the COL4A5 gene, responsible for the Alport syndrome, was determined by linkage analysis with eight probes of the Xq arm and by a radiation hybrid panel. Concordant data indicated the localization of the Alport gene between DXS17 and DXS11. Four deletions and one single base mutation of the COL4A5 gene were detected. Homogeneity tests failed to show any evidence of genetic heterogeneity superimposed on clinical heterogeneity for ophthalmic signs and end-stage renal disease age.     

Evolution of the expression of the Gld gene in the reproductive tract of Drosophila.

During the preadult development of Drosophila melanogaster, the GLD (glucose dehydrogenase) gene (Gld) is expressed in a variety of tissues, including the immature reproductive tract. At the adult stage the expression of Gld becomes largely restricted to the reproductive tract of males and females. We examined the expression of GLD in the adult reproductive tract of 50 species in the genus Drosophila, as well as in those of a few representative species from four other closely related genera. GLD exhibits considerable organ-specific diversity in the reproductive tract of males and females. Among these species, five male GLD phenotypes and six female GLD phenotypes were found. In contrast, the preadult expression of GLD in representative species from each distinct adult pattern type was determined and found to be highly conserved in both the immature reproductive tract and non-reproductive organs. Moreover, the set of reproductive organs that express GLD during preadult development is equivalent to the sum of the five male and six female adult GLD phenotypes. To initially define the contribution of cis- versus trans-acting factors responsible for differences in adult GLD expression between two of these species--D. melanogaster and D. pseudoobscura--we transferred the D. pseudoobscura Gld to the genome of D. melanogaster and investigated its expression. GLD expression patterns of these transformants displayed characteristics that are unique to both species, suggesting the presence of both cis- and trans-acting differences between these two species.     

Gastric effects of thyrotropin-releasing hormone microinjected into the dorsal vagal nucleus in cats

We investigated the gastric acid secretory and motility responses to microinjection of thyrotropin-releasing hormone (TRH) into the dorsal motor nucleus of the vagus (DMV) in anesthetized cats. Gastric acid output was collected every 15 min through a gastric cannula after saline flush and titrated to pH 7.0. Antral and corpus contractions were continuously recorded by extraluminal force transducers. TRH dissolved in 200 nl of saline and microinjected unilaterally into the DMV induced a dose-dependent (50-200 ng) increase in gastric acid secretion. The acid secretory response began in the first 15 min collection and lasted 45 min. TRH frequently increased the force of contractions of the antrum and corpus within one minute of microinjection. The minimal effective dose for eliciting increased motility was lower than for inducing acid secretion. These results demonstrate that TRH acts in the DMV of cats to stimulate gastric acid secretion and contractions.     

The trk tyrosine protein kinase mediates the mitogenic properties of nerve growth factor and neurotrophin-3.

The product of the trk proto-oncogene encodes a receptor for nerve growth factor (NGF). Here we show that NGF is a powerful mitogen that can induce resting NIH 3T3 cells to enter S phase, grow in semisolid medium, and become morphologically transformed. These mitogenic effects are absolutely dependent on expression of gp140trk receptors, but do not require the presence of the previously described low affinity NGF receptor. gp140trk also serves as a receptor for the related factor neurotrophin-3 (NT-3), but not for brain-derived neurotrophic factor. Both NGF and NT-3 induce the rapid phosphorylation of gp140trk receptors and the transient expression of c-Fos proteins. However, NT-3 appears to elicit more limited mitogenic responses than NGF. These results indicate that the product of the trk proto-oncogene is sufficient to mediate signal transduction processes induced by NGF and NT-3, at least in proliferating cells.     

The trkB tyrosine protein kinase is a receptor for brain-derived neurotrophic factor and neurotrophin-3.

trkB is a tyrosine protein kinase gene highly related to trk, a proto-oncogene that encodes a receptor for nerve growth factor (NGF) and neurotrophin-3 (NT-3). trkB expression is confined to structures of the central and peripheral nervous systems, suggesting it also encodes a receptor for neurotrophic factors. Here we show that brain-derived neurotrophic factor (BDNF) and NT-3, but not NGF, can induce rapid phosphorylation on tyrosine of gp145trkB, one of the receptors encoded by trkB. BDNF and NT-3 can induce DNA synthesis in quiescent NIH 3T3 cells that express gp145trkB. Cotransfection of plasmids encoding gp145trkB and BDNF or NT-3 leads to transformation of recipient NIH 3T3 cells. In these assays, BDNF elicits a response at least two orders of magnitude higher than NT-3. Finally, 125I-NT-3 binds to NIH 3T3 cells expressing gp145trkB; binding can be competed by NT-3 and BDNF but not by NGF. These findings indicate that gp145trkB may function as a neurotrophic receptor for BDNF and NT-3.