湿地松与茶树间作根系分布状况的研究

湿地松(Pinus elliottii)是阳性乔木,茶树(Camellia sinensis)是阴性灌木。这两种树种间作,形成针阔、乔灌两层树冠结构的茶园复合生态系统,可以改善茶树生态条件,提高茶叶的产量和品质。但间作存在胁地现象。一般认为这是上层树木的过度遮荫和根系间的竞争造成的。为了解这两种树种根系的分布状况和相互关系,并为间作茶园的合理配置和加强这种茶园的耕作管理提供依据,我们进行了湿地松与茶树间作根系分布状况的研究。     

沙地草场植物根系化学元素含量的特征

 本文报道了内蒙古沙地草场不同植物根系的化学元素含量特征。结果表明：51种植物根系的N、P、K、Si、Na、Fe和灰分的平均含量分别为1.08%、0.104%、0.686%、0.811%、0.049%、0.030%和6.416%。其中相同植物根系的N、P、K、Na和灰分的含量低于其地上部分的平均含量,而Si和Fe相反,根系的平均含量高于其地上部分。     

Evidence for two distinct conformations of the Escherichia coli mannitol permease that are important for its transport and phosphorylation functions

Column chromatography of the Escherichia coli mannitol permease (mannitol-specific enzyme II of the phosphotransferase system) in the presence of deoxycholate has revealed that the active permease can exist in at least two association states with apparent molecular weights consistent with a monomer and a dimer. The monomeric conformation is favored by the presence of mannitol and by the phosphoenolpyruvate (PEP)-dependent phosphorylation of the protein. The dimer is stabilized by inorganic phosphate (Pi), which also stimulates phospho-exchange between mannitol and mannitol 1-phosphate (a partial reaction in the overall PEP-dependent phosphorylation of mannitol). Kinetic analysis of the phospho-exchange reaction revealed that Pi stimulates phospho-exchange by increasing the Vmax of the reaction. A kinetic model for mannitol permease function is presented involving both conformations of the permease. The monomer (or a less-stable conformation of the dimer) is hypothesized to be involved in the initial mannitol-binding and PEP-dependent phosphorylation steps, while the stably associated dimer is suggested to participate in later steps involving direct phosphotransfer between the permease, mannitol and mannitol 1-phosphate.     

Artificial Feeding Systems for Plant-Parasitic Nematodes

Feeding of an "obligate" plant-parasitic nematode (nonfungal feeder), Pratylenchus scribneri, in the absence of plant tissue was demonstrated in an artificial system consisting of liquid media and indicator dyes including amaranth and various nontoxic food colors. Among the compounds tested, sucrose, dextrose, Gamborg''s B5 medium, and DL-methionine stimulated a small percentage of feeding (12-36%). A high percentage of feeding (90-100%) occurred in a filtrate from excised corn roots cultured in Gamborg''s B5 medium. This feeding system has the potential to develop an artificial medium for plant-parasitic nematodes and to screen novel nematicides that are stomach poisons.     

Binding of the J 1 Adhesion Molecules to Extracellular Matrix Constituents

The J1 glycoproteins can be obtained in multiple forms in the soluble fraction of developing and adult mouse brain tissue. They are recovered as two forms of apparent molecular weights of 160,000 and 180,000 (J1-160) from adult mouse brain and as forms of apparent molecular weights of 200,000 and 220,000 (J1-220) from developing brain. J1-160 and J1-220 share common epitopes but are considered as separate entities, with J1-220 being immunochemically closely related if not identical to tenascin. Based on the observation that J1 immunoreactivity appears on basement membrane and interstitial collagens after denervation of the neuromuscular junction in adult rodents, we became interested in investigating the binding properties of J1 glycoproteins to extracellular matrix constituents in vitro. Both J1-160 and J1-220 bound to collagens type I-VI and IX but not to laminin, fibronectin, bovine serum albumin, or gelatin under hypotonic buffer conditions. Under isotonic buffer conditions, J1-220 bound to all collagen types, whereas J1-160 bound only to collagen types V and VI with values that could be examined by Scatchard analysis. Binding of J1-220 to collagens displayed two binding constants (KD) between 1.5 and 4.4 X 10(-9) and 1.8 and 5.5 X 10(-8) M, respectively, under hypotonic buffer conditions and a single KD of 2.1-8.0 X 10(-8) M under isotonic buffer conditions. Binding of J1-160 to collagens had an apparent KD of 1.9-8.0 X 10(-9) M under hypotonic buffer conditions. Under isotonic buffer conditions, binding constants of J1-160 to collagen types V and VI were approximately 2 X 10(-8) M. Binding of J1-220 to collagen type I could be inhibited by J1-220, J1-160, and collagen type VI but not by fibronectin or gelatin. Conversely, binding of J1-160 was inhibited by J1-220, J1-160, and collagen type VI (in order of decreasing efficacy of competition). J1-160 and J1-220 were retained on a heparin-agarose column and eluted in a salt gradient at approximately 0.5 M NaCl. The formation of the J1-heparin complexes was inhibited 100-fold more efficiently by heparin than by chondroitin sulfate. These experiments show that J1 glycoproteins resemble in many respects the extracellular matrix constituents fibronectin, laminin, vitronectin, and von Willebrand factor.     

Isolation and Biochemical Characterization of a Neural Proteoglycan Expressing the L5 Carbohydrate Epitope

The monoclonal L5 antibody reacts with an N-glycosidically linked carbohydrate structure which is present on the neural cell adhesion molecule L1, neural chondroitin sulfate proteoglycans, and other not yet identified glycosylated proteins. Using this antibody, we isolated and characterized proteoglycans from adult mouse brain and cultured astrocytes biosynthetically labeled with Na2 35SO4 and a 3H-amino acid mixture. Our data suggest that the L5 proteoglycans of both sources are identical in their biochemical properties. The apparent molecular mass of the L5 proteoglycan is approximately 500 kDa. Digestion of the iodinated L5 proteoglycan from mouse brain and of the [35S]methionine-labeled L5 proteoglycan from cultured astrocytes with proteinase-free chondroitinases ABC and AC revealed three major core proteins with apparent molecular masses of approximately 380, 360, and 260 kDa. These represent molecularly distinct protein cores.     

Interleukin-1 Hyperproduction by In Vitro Activated Peripheral Macrophages from Cerebellar Mutant Mice

Several mutations in mice produce complex patterns of neuronal degeneration of the cerebellum and of its afferent pathways. In the staggerer (sg/sg) mutant, atrophy of the lymphoid organs and immunological abnormalities have been described. To search for a possible link between the neurological and the immune disorders in this mutant, we studied the production by its peripheral macrophages of interleukin-1 (IL-1), which roles in both immune and nervous systems are well established. Suspensions of peritoneal and/or spleen macrophages from mutants and their appropriate controls were stimulated in vitro by lipopolysaccharide. Northern and dot blots, performed with murine IL-1 cDNA probes, revealed a clear-cut hyperexpression of IL-1 mRNA in staggerer macrophages. An IL-1 bioassay using the IL-1-responsive D10.G4 cell line also revealed a sixfold increase of IL-1 activity in the macrophage supernatants of staggerer mutant mice. The hyperproduction was found in 3-week to 1-year-old staggerer and also in heterozygous (+/sg) mice. A similar phenomenon existed in cerebellar mutants lurcher, Purkinje cell degeneration (pcd), and to a lesser extent reeler and wobbler, but was absent in the neurological mutants weaver, jimpy, and motor end plate disease (medH). These observations establish that in several point mutations in mice, central nervous degeneration is associated with dysregulation of IL-1 production by peripheral macrophages.     

Isolation and reconstitution of furosemide-binding proteins from Ehrlich ascites tumor cells

Summary Furosemide-binding proteins were isolated from cholate-solubilized membranes of Ehrlich ascites tumor cells by affinity chromatography, using furosemide as ligand. Solubilized proteins retarded by the affinity material were eluted by furosemide. In reducing and denaturing gels, the major proteins eluted by furosemide were 100 and 45 kDa. In nonreducing, nondenaturing gels, homodimers of both polypeptides were found, whereas no oligomeric proteins containing both polypeptides were seen. It is concluded that the furosemide gel binds two distinct dimeric proteins. The isolated proteins were reconstituted into phospholipid vesicles and the K⁺ transport activity of these vesicles was assayed by measurement of⁸⁶Rb⁺ uptake against a large opposing K⁺ gradient. The reconstituted system was found to contain a K⁺ transporting protein, which is sensitive to Ba²⁺ like the K⁺ channel previously demonstrated to be activated in intact cells after cell swelling.     

咖啡碱对椎实螺胚增长的影响

作者采用简单的螺胚生长抑制法,证明软体动物细胞具有DNA复制后修复功能,并受咖啡碱抑制。在没有其他诱变剂的参与下,咖啡碱并不损伤DNA,但也没有保护作用。     

Glial uptake system of GABA distinct from that of taurine in the bullfrog sympathetic ganglia

The kinetics and specificity of GABA and taurine uptake were studied in the bullfrog sympathetic ganglia. GABA uptake system consisted of simple saturable component and taurine uptake system consisted of two saturable components exclusive of non-saturable influx. Taurine unaffected GABA uptake while GABA inhibited taurine uptake competitively with theK _i/K_m ratio of 38. GABA (5.14 M) uptake was inhibited by -aminovaleric acid and slightly by 2,4-diaminobutyric acid (5 mM, each) among ten structural analogs. Taurine uptake under high-affinity conditions was most strongly suppressed by hypotaurine and -alanine competitively with theK _i/K_m ratio of 1.0 and 1.9, respectively. Autoradiography showed that glial cells were heavily labeled by both [³H]GABA and [³H]taurine. These results suggest that GABA is transported by a highly specific carrier system distinct from the taurine carrier and that taurine, hypotaurine, and -alanine may share the same high-affinity carrier system in the glial cells of the bullfrog sympathetic ganglia.