Neurites show pathway specificity but lack directional specificity or predetermined lengths in Xenopus embryos

The earliest outgrowth of nerve fibers from identified spinal neurons labeled with horseradish peroxidase (HRP) was traced along surgically rearranged pathways in the central nervous system (CNS) of Xenopus embryos. Parts of the CNS were misaligned or inverted rostrocaudally by grafting a segment of labeled spinal cord in place of the same or different spinal cord segment of an unlabeled embryo or by joining two rostral half embryos (head-to-head) or two caudal half embryos (tail-to-tail), one half of which was derived from a labeled embryo in each combination. Donor embryos were labeled by injection of HRP into a selected blastomere at the 16- or 32-cell stage. Host embryos were unlabeled. Grafts from labeled donors to unlabeled host embryos were made at early neural tube stages before outgrowth of any nerve fibers had started (Jacobson and Huang, 1985). Routes taken by labeled nerve fibers growing into unlabeled CNS were observed at later stages, and the rates of nerve fiber elongation were calculated. Labeled nerve fibers were normal in appearance, and elongated without branching, at normal rates (22-71 micron/h). In head-to-head and tail-to-tail embryos and in embryos with inverted spinal cord grafts, nerve fibers continued elongating without branching in the direction opposite to normal in the CNS. Many fibers reached lengths that were far greater than normal. No reorientation of such maldirected nerve fibers was seen. These results indicate that nerve fiber elongation is not guided by axially polarized pathway cues or markers and that nerve fibers do not grow to predetermined lengths. However, neurites preferred to grow along stereotyped nerve fiber pathways even when forced to grow in the wrong direction or when confronted with nonneural tissue.     

Further characterization of the vesicular stomatitis virus temperature-sensitive O45 mutant: intracellular conversion of the glycoprotein to a soluble form.

Reexamination of the viral products of tsO45, a glycoprotein mutant of vesicular stomatitis virus, showed that at 39 degrees C there was a conversion of the glycoprotein (G) to a truncated, soluble form, Gs, which subsequently appeared in the extracellular medium. The half-life for this intracellular conversion and extracellular appearance was about 2 h at 39 degrees C. Gs was precipitated by a monoclonal antibody to the ektodomain but not by an antipeptide serum made against the first 15 amino acids at the carboxy terminus of G. Gs was also resistant to endoglycosidase H digestion. On the basis of pulse-chase experiments, the generation of Gs most probably occurred in the rough endoplasmic reticulum. This additional phenotype of the tsO45 mutant provides another approach for studying the generation and subsequent transport of a secreted protein in fibroblast cells.     

Purification and properties of epithelial growth inhibitor (EGI) from human platelets: its separation from type beta transforming growth factor (TGF-beta)

We previously reported that sera from various kinds of animals contain a protein(s) capable of inhibiting the growth of the non-malignant epithelial cell line derived from Buffalo rat liver (BRL). In the present study, a similar epithelial cell-specific growth inhibitor (EGI) was purified to homogeneity from an acid-ethanol extract of human platelets. During purification, EGI was separated from the major component of type beta transforming growth factor (TGF-beta), which can stimulate the colony formation of the non-malignant fibroblastic cell line derived from rat kidney (NRK) in soft agar in the presence of epidermal growth factor (EGF). The purified EGI had an Mr of 27,000, and was composed of two subunits identical in Mr. It significantly inhibited the growth in monolayer cultures of three non-malignant epithelial cell lines, BRL, MDCK (from Madin-Darby canine kidney) and BSC-1 (from African green monkey kidney), at doses lower than 40 pg/ml in medium containing 10% fetal calf serum. Its inhibitory activity was stable against heating at 90 degrees C for 3 min, but not against treatment with 50 mM dithiothreitol. In addition, TGF-beta was also partially purified from the same extract. The purified TGF-beta did not show any inhibitory activity toward the growth of BRL, MDCK, BSC-1, or NRK.     

Calcium/phospholipid-dependent kinase recognizes sites in microtubule-associated protein 2 which are phosphorylated in living brain and are not accessible to other kinases

Microtubule-associated protein 2 (MAP-2) purified after microtubule assembly cycles from bovine brain had been shown to contain about 10 esterified phosphates (mol/mol), which were relatively phosphatase resistant and essentially confined to the projection domain which contributes to the visible arms on microtubules. The kinase responsible for phosphorylating these sites had not been identified. We have approached this question by using a phosphatase that releases the bulk of these residues and then determining which kinase can now add additional residues corresponding to those released. Three kinases were chosen because of their abundance in brain and/or proximity to microtubules. Of these only Ca/phospholipid-dependent kinase was able to recognize the previously occupied sites. We also found that MAP-2 isolated from rat brain without assembly cycles contained more phosphate than previously recognized, greater than 30 mol/mol, suggesting that 20 of these had been inadvertently released by phosphatase during assembly cycles. All 3 kinases (Ca/phospholipid-dependent, cAMP-dependent, and Ca/calmodulin-dependent kinase II) recognized more sites in the bovine than in the rat MAP-2.     

豚鼠冰水游泳应激后血浆、肾上腺髓质和脑内组织的亮—脑啡肽含量变化

豚鼠冰水游泳应激3min后,用放射免疫法测定血浆、肾上腺髓质和脑内三个脑区组织的亮—脑啡肽(Leu-enkephalin,LEK,)含量和血浆的血管紧张肽Ⅱ(Angiotensin Ⅱ,ATⅡ)浓度变化。结果表明:在冰水中游泳应激组豚鼠的血浆、肾上腺髓质、下丘脑和纹状体组织的LEK含量和血浆的ATⅡ浓度,均较对照组豚鼠明显升高(P值均<0.01)。提示:豚鼠在冰水中紧张、剧烈游泳后,可能激活了中枢神经和周围组织内的脑啡肽能神经元和血管紧张肽原酶—血管紧张肽Ⅱ系统,从而促进LEK和ATⅡ的释放增加。     

北京东郊作物土壤系统中重金属的迁移、分布、积累

 本文研究了北京东郊污灌区重金属在作物—土壤中的迁移、分布、积累规律,证实本区蔬菜中汞含量比粮食作物约大3—15倍,比水果约大6—200倍。麦粒、糙米中的Cu、Hg、Cd、Pb、Ni的含量与土壤含量相关性不显著。架豆中重金属含量与土壤中重金属含量的相关性,只有Zn,Pb达显著水平。白菜土有机质含量与重金属含量相关性达显著水平,而白菜的重金属含量与土壤的重金属含量相关性却不显著。说明除了土壤中重金属的总量外,有效态含量的多少,是影响本区作物吸收积累重金属的主要因素。 本区施污泥的土壤和生长的作物Cd／Zn大部小于1%、盆栽试验证明：施用本区污泥污水对水稻生长发育的影响比施污泥灌清水的影响大些,因此,施用含重金属污泥时,最好不要超过5000斤／亩。大田和室内模拟试验证明：重金属从土壤中迁移到植物,由植物带走输出的量极少,其中以带走输出的Hg、Cd,As相对较多,带走输出的Pb、Cr相对的少些。     

HBsAg合成肽段的免疫源性和抗肽血清与天然HBsAg的结合测定

我们将三种乙型肝炎表面抗原的合成肽段在联结载体或不接载体的情况下,分别制备成4种免疫原对兔子进行了免疫。大部分兔子都产生了抗肽抗体。其中抗P_(122-48)(auw)与抗P_(122-148)(adw)都能与天然HBsAg反应,而抗P_(122-148)(adw)的抗HBs活力比文献报道的都高,通过结构分析表明:含有天然蛋白上免疫显性区域的免疫原是合成疫苗的理想选者。     

Uptake of lung surfactant subfractions into lamellar bodies of adult rabbit lungs

The goals of this investigation were to determine whether subfractions of alveolar surfactant that have different physical and biochemical properties are preferentially taken up from the alveolar air space into lamellar bodies and to correlate the magnitude of the uptake with the properties of the fractions. Radiolabeled subfractions were obtained by differential centrifugation of lavage fluid from rabbits that had been intravenously injected with radioactive palmitate. The subfractions were P (pellet) 3 (1,000 g, 20 min), P4 (60,000 g, 60 min), P5 (100,000 g, 16 h). Subfractions were instilled into the lungs of anesthetized spontaneously breathing adult rabbits, and lavage and lamellar body fractions were isolated at later times. P3 and P4 were taken up to a larger extent than was P5 or liposomes prepared from a P4 lipid extract. The fractions that were preferentially taken up (P3 and P4) contained surfactant apoprotein (APO) 36, tubular myelin, multilamellar vesicles, and were rapidly adsorbed to an air-water interface. P3 also contained APO 10. These results demonstrate that different forms of surfactant are recycled at different rates and suggest that there is specificity in the recycling process.     

A subset of cells in the nerve net of Hydra oligactis defined by a monoclonal antibody: its arrangement and development

A monoclonal antibody, termed JD1, was generated that bound to a subset of the nerve cells in the hypostome and tentacles of Hydra oligactis. Using a whole-mount technique the spatial pattern of the subset of nerve cells and their processes could be clearly visualized using indirect immunofluorescence. The subset largely corresponds to the epidermal sensory cells. Using the same technique the development of the pattern during head regeneration and budding was examined. The appearance of the nerve cells coincides with the formation of both the tentacles and hypostome. When head regeneration does not occur, JD1+ cells do not appear suggesting the differentiation of JD1+ cells is an integral event in head formation dependent on antecedent patterning processes.     

Stimulatory effect of 1 alpha, 25-dihydroxyvitamin D3 on the formation of skin tumors in mice treated chronically with 7,12-dimethylbenz[a]anthracene

The effect of 1 alpha, 25-dihydroxyvitamin D3 (1 alpha, 25-(OH)2D3) and its 24,24-difluoro analog on the formation of skin tumors in mice was evaluated in a complete carcinogenesis model using 7,12-dimethylbenz[a]anthracene (DMBA) as the carcinogen. Twice weekly topical application of 0.25-0.50 nmol of 1 alpha, 25-(OH)2D3 or 0.05-0.10 nmol of the difluoro analog of 1 alpha, 25-(OH)2D3 1 hour prior to treatment with 50 nmol DMBA stimulated tumor formation several fold compared to animals receiving DMBA alone. Topical application of 0.50 nmol of 1 alpha, 25-(OH)2D3 24 hours after treatment with DMBA, or half of this dose of the vitamin D3 metabolite, applied 1 hour before and 24 hours after treatment with DMBA, also stimulated tumor formation several fold. These results are in marked contrast to the potent inhibitory effect of 1 alpha, 25-(OH)2D3 and its difluoro analog on the formation of skin tumors in mice promoted by 12-O-tetradecanoylphorbol-13-acetate.