血管内皮舒张因子在氧自由基所致慢性缺氧大鼠肺内动...

The role of endothelium-derived relaxing factor (EDRF) on the effect of oxygen-derived free radicals (generated by xanthine-xanthine oxidase system) on intrapulmonary arterial in chronic hypoxic rats was studied by a microbioassay method. Intrapulmonary artery rings with intact or denuded endothelium of hypoxic (5,000 m, 10 days) and normoxic rats were prepared for observation of oxygen-derived free radicals induced contraction. It was shown that oxygen-derived free radicals induced contractions of intrapulmonary arterial rings with intact endothelium were obviously augmented in hypoxic rats than in normoxic controls. The augmented responses could be further potentiated by the addition of EDRF inactivator reduced hemoglobin (RHb), but diminished or even abolished by applying superoxide dismutase (Cu-Zn SOD). However, no effect on denuded rings was observed when RHb or SOD was added. It is concluded that chronic hypoxia may attenuate the action of EDRF in the enhancement of the reactivity of intrapulmonary artery to oxygen-derived free radicals.     

磁场对大豆共生固氮的效应

恒定磁场处理慢生大豆根瘤菌“005”和接种后的大豆植株,发现磁场可以提高根瘤的固氮活性。在一定的磁场强度(70—100mT)下,固氮活性平均可以提高4—5倍,植株的结瘤数和根瘤重量平均提高2—3倍。从这样的根瘤中所分离出的根瘤菌,由慢生型转变成快生型,在100植株中有17株的根瘤分离出快生菌。生长世代时间和培养溶液中的pH值与慢生型不同,而与快生型相同。     

Colocalization of the genes for the alpha 3(IV) and alpha 4(IV) chains of type IV collagen to chromosome 2 bands q35-q37.

Each type of basement membrane in man contains between two and five genetically distinct type IV collagens: alpha 1(IV)-alpha 5(IV). Genes for alpha 1(IV), alpha 2(IV), alpha 3(IV), and alpha 5(IV) have been isolated. We have recently isolated partial cDNAs for the fifth member of the family, designated alpha 4(IV). On the basis of comparison of the deduced peptide sequences of all five chains, the type IV collagens can be divided into two families: alpha 1-like, comprising alpha 1(IV), alpha 3(IV), and alpha 5(IV); and alpha 2-like, comprising alpha 2(IV) and alpha 4(IV). Genes encoding the alpha 1(IV) and alpha 2(IV) chains (COL4A1 and COL4A2) both map to human chromosome 13q34 and have been shown to be transcribed from opposite DNA strands using a common bidirectional promoter that allows coordinate regulation of the two chains. Indeed, these two chains are commonly found together in basement membrane and form [alpha 1]2.[alpha 2] heterotrimers. Whereas alpha 1(IV) and alpha 2(IV) have been found in all basement membranes studied hitherto, it has been shown that alpha 3(IV) and alpha 4(IV) are found in only a subset of basement membranes. In basement membranes where either of these molecules is present, however, they are found together. In view of this relationship and the structural similarities between alpha 1(IV) and alpha 3(IV) and between alpha 2(IV) and alpha 4(IV), we hypothesized that COL4A3 and COL4A4, the genes encoding alpha 3(IV) and alpha 4(IV), respectively, have a genomic organization similar to that of COL4A1 and COL4A2.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

The trk proto-oncogene encodes a receptor for nerve growth factor.

Two classes of receptors with distinct affinities for nerve growth factor (NGF) have been identified. The low affinity receptor (Kd approximately 10(-9) to 10(-8) M) is a cysteine-rich glycoprotein encoded by the previously characterized LNGFR gene. The structural nature of the high affinity receptor (Kd approximately 10(-11) to 10(-10) M) has yet to be established. In this study we show that the product of the human trk proto-oncogene (gp140trk) binds NGF with high affinity. Moreover, NGF could be chemically cross-linked to the endogenous gp140trk present in rat PC12 pheochromocytoma cells as well as to gp140trk ectopically expressed in mouse fibroblasts and in insect Sf9 cells. High affinity binding of NGF to gp140trk can occur in the absence of low affinity LNGFR receptors, at least in nonneural cells. Addition of NGF to PC12 cells elicits rapid phosphorylation of gp140trk on tyrosine residues and stimulates its tyrosine kinase activity. These results indicate that gp140trk is a functional NGF receptor that mediates at least some of the signal transduction processes initiated by this neurotrophic factor.     

Oxidation of tyrosine by peroxidase isozymes derived from peanut suspension culture medium and by isolated cell walls

A comparative study on tyrosine oxidation was made with a pure cationic and anionic peroxidase from peanut cell culture medium. The results showed that both isozymes possessed almost identical capacity to oxidize tyrosine to dityrosine, isodityrosine and polytyrosine with the main difference being the pH optimum (pH 4 for the anionic and pH 7 for the cationic isozyme). Variation of reaction time after 1.5 h incubation had little effect on the quantity and quality of the oxidation products. On the other hand, increase of enzyme units correspondingly increased tyrosine-oxidation. The removal of heme and carbohydrate moieties from the holoenzyme arrested the reaction thereby suggesting the role played by these moieties in stabilizing the active site of peroxidase isoenzymes. Isolated cell wall extracts catalyzed the tyrosine-oxidation equally well as the purified peroxidase. Even though polyclonal antibodies against anionic peroxidase inhibited the in vitro tyrosine reaction they did not affect the tyrosine oxidation by the cell walls, while the cationic antibodies did.Abbreviations A.PRX anionic peanut peroxidase - C.PRX cationic peanut peroxidase - PcAb polyclonal antibodies - ELISA enzyme-linked-immuno-sorbent-assay - TFMS trifluoromethane sulfonic acid     

高胆固醇血症家兔红细胞在交、直流电场中的电泳行为

本文对高胆固醇血症家兔红细胞在交、直流电场中的电泳行为进行了多指标测定,结果显示,高脂组与正常组相比红细胞聚集能力增强,变形能力及膜流动性下降,表明高脂血症可能较易导致血栓形成。中药有效成分8501有对抗高脂引起的红细胞上述改变的作用,提示8501可能对血栓和动脉粥样硬化斑块形成有防治作用。     

根分泌物及其生态效应

根分泌物是个古老而年轻的研究领域。早在18,19世纪,人们(Plenk,1795;Decandolle,1830)就观察到根分泌物对邻近植株的促生和抑制作用,1904年Hilter提出“根际”的概念,标志着人们对根分泌物及其生态效应的进一步认识。此后人们对根分泌物研究逐步展开。Lyon和Willson(1920)发现,生长于无菌水培液中的植物能释放有机物,为深入研究奠定了基础。但很长一段时间这个研究领域一     

辐射增敏剂甲硝唑氨酸对坪期V_(79)细胞DNase活力的影响

研究了辐射增敏剂甲硝唑氨酸(CM)对受照前后坪期V_(79)细胞DNase活力的影响。结果表明CM在一定浓度范围内(1—10mmol/L)对DNase的激活作用有浓度依赖关系。细胞经6—12Gyγ线照后DNase活力亦增高,若照射合并CM处理后,则对DNase激活有相加作用。还就DNase活力升高与DNA链断裂间的可能关系进行了讨论。