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181.
R K Merkle Q Zhou T K Schultz W B Harper R D Cummings 《Archives of biochemistry and biophysics》1989,274(2):404-416
We have purified a carbohydrate-binding protein from porcine heart by affinity chromatography on asialofetuin-Sepharose and have characterized this protein with respect to its size, amino acid composition, partial amino acid sequence, and carbohydrate-binding specificity. Porcine heart lectin (PHL) has a subunit molecular mass of 14,700 and is immunologically cross-reactive with a polyclonal antibody raised against a lectin isolated from calf heart. The amino acid composition of PHL is similar to that of lectins that have been isolated from calf heart, bovine brain, and rat lung. Moreover, the primary sequences of four tryptic fragments (52 amino acids total) derived from PHL are closely related to sequences previously determined for 10 other vertebrate-derived lectins. The ability of PHL to agglutinate rabbit erythrocytes was inhibited only by oligosaccharides containing terminal beta-galactosyl residues. These data indicate that PHL is a vertebrate "S-type" lectin and provide further evidence that the structures and carbohydrate-binding specificities of these lectins are highly conserved across diverse vertebrate genera. 相似文献
182.
Interactions of Photobleaching and Inorganic Nutrients in Determining Bacterial Growth on Colored Dissolved Organic Carbon 总被引:8,自引:0,他引:8
Abstract Bacteria are key organisms in the processing of dissolved organic carbon (DOC) in aquatic ecosystems. Their growth depends on both organic substrates and inorganic nutrients. The importance of allochthonous DOC, usually highly colored, as bacterial substrate can be modified by photobleaching. In this study, we examined how colored DOC (CDOC) photobleaching, and phosphorus (P) and nitrogen (N) availability, affect bacterial growth. Five experiments were conducted, manipulating nutrients (P and N) and sunlight exposure. In almost every case, nutrient additions had a significant, positive effect on bacterial abundance, production, and growth efficiency. Sunlight exposure (CDOC photobleaching) had a significant, positive effect on bacterial abundance and growth efficiency. We also found a significant, positive interaction between these two factors. Thus, bacterial use of CDOC was accelerated under sunlight exposure and enhanced P and N concentrations. In addition, the accumulation of cells in sunlight treatments was dependent on nutrient availability. More photobleached substrate was converted into bacterial cells in P- and N-enriched treatments. These results suggest nutrient availability may affect the biologically-mediated fate (new biomass vs respiration) of CDOC. 相似文献
183.
D. Mercanti A. Angelini MT. Ciotti ML. Eboli C. Galli L. Battistini D. Merlo P. Calissano 《Cytotechnology》1993,11(Z1):S117-S119
The neurite outgrowth and adhesion complex (NOAC), isolated from rabbit sera has been dissociated in its major components by reverse-phase chromatography in HPLC by using a C18 column. SDS-PAGE analisys of the active fractions revealed the presence of three major bands of approximately 100, 70 and 50 kDa. Studies on the biological activity of NOAC were carried out on rat cerebellar granule cells. NOAC-cultured cells exhibit a marked resistance to excitotoxic stimuli carried by glutamate. 相似文献
184.
185.
Helena Mathews R. E. Litz H. D. Wilde S. A. Merkle H. Y. Wetzstein 《In vitro cellular & developmental biology. Plant》1992,28(4):172-178
Summary Somatic proembryos of mango (Mangifera indica L. cv. Hindi) were co-cultivated withAgrobacterium tumefaciens strain A208 harboring pTiT37-Se::pMON 9749 (9749 ASE). Transformed somatic proembryos capable of growing on selection medium
containing 200 μg/ml kanamycin produced the characteristic indigo blue precipitate in the presence of 5-bromo-4-chloro-3-glucuronic
acid. These proembryos were chimeral consisting of transformed (blue) and nontransformed (yellow/white) cells. A stepwise
selection strategy was found necessary to eliminate chimeras. a) Initial screening at 200 μg/ml kanamycin to enable growth
of transformed cells, b) further screening at 400 μg/ml kanamycin to reduce chimeras, and c) recovery of pure transformed
clones of proembryos in liquid selection medium with 100 μg/ml kanamycin. The integration of the NPT II and GUS genes into
mango genome was confirmed by Southern hybridization. 相似文献
186.
Cells of yellow-poplar (Liriodendron tulipifera L.) were transformed by direct gene transfer and regenerated into plants by somatic embryogenesis. Plasmid DNA bearing marker genes encoding β-glucuronidase (GUS) and neomycin phosphotransferase (NPT II) were introduced by microprojectile bombardment into single cells and small cell clusters isolated from embryogenic suspension cultures. The number of full-length copies of the GUS gene in independently transformed callus lines ranged from approximately 3 to 30. An enzyme-linked immunosorbent assay for NPT II and a fluorometric assay for GUS showed that the expression of both enzymes varied by less than fourfold among callus lines. A histochemical assay for GUS activity revealed a heterogeneous pattern of staining with the substrate 5-bromo-4-chloro-3-indoyl-β-d-glucuronic acid in some transformed cell cultures. However, cell clusters reacting positively (blue) or negatively (white) with 5-bromo-4-chloro-3-indoyl-β-d-glucuronic acid demonstrated both GUS activity and NPT II expression in quantitative assays. Somatic embryos induced from transformed cell cultures were found to be uniformly GUS positive by histochemical analysis. All transgenic plants sampled expressed the two marker genes in both root and shoot tissues. GUS activity was found to be higher in leaves than roots by fluorometric and histochemical assays. Conversely, roots expressed higher levels of NPT II than leaves. 相似文献
187.
S. A. Merkle A. T. Wiecko R. J. Sotak H. E. Sommer 《In vitro cellular & developmental biology. Plant》1990,26(11):1086-1093
Summary Embryogenic suspension cultures of the hardwood forest tree yellow-poplar (Liriodendron tulipifera) have the potential to produce millions of plantlets. However, low conversion frequencies limit the realization of this potential.
Using 4 embryogenic yellow-poplar lines, we first tested the ability of somatic embryos, selected for their similarity to
mature zygotic embryos, to convert to plantlets, then tested physical and chemical treatments for their effects on promoting
maturation of somatic embryos and subsequent plantlet production. Embryos selected based on resemblance to mature zygotic
embryos and transferred to a hormone-free basal medium without casein hydrolysate (CH) produced plantlets at a frequency of
63%. Populations of synchronized somatic embryos were obtained by repeated fractionation of liquid medium-cultured proembryogenic
masses (PEMs) on stainless steel sieves. These fractionated embryos failed to mature properly when cultured in liquid basal
medium, however. Development of embryos cultured in basal medium supplemented with 5×10−7
M abscisic acid (ABA) was slowed and embryos appeared to mature properly, with separated cotyledons and little precocious germination.
However, ABA-treated embryos only rarely converted to plantlets, possibly due to residual effects of the ABA. PEMs fractionated
on sieves, transferred to filter paper and placed on solidified basal medium gave a 60–70% synchronous population of mature
embryos 10–12 days following plating. Mature embryos transferred to basal medium without CH converted at a frequency of 72%.
The percentage of all embryos differentiating from PEMs on filter paper that formed plantlets was 32%.
This material is based upon work supported by the U. S. Department of Agriculture Cooperative State Research Service under
Agreement No. 85-FSTY-9-0117. 相似文献
188.
189.
Distribution of the molossinus allele of Sry, the testis-determining gene, in wild mice 总被引:3,自引:0,他引:3
Nagamine CM; Shiroishi T; Miyashita N; Tsuchiya K; Ikeda H; Takao N; Wu XL; Jin ML; Wang FS; Kryukov AP 《Molecular biology and evolution》1994,11(6):864-874
When the Y chromosome of the laboratory inbred mouse strain C57BL/6 (B6) is
replaced by the Y of certain strains of Mus musculus domesticus, testis
determination fails and all XY fetuses develop either as hermaphrodites or
XY females (XY sex reversal). This suggests the presence of at least two
alleles of Sry, the male-determining gene on the Y:M. m. domesticus and B6.
The B6 Y chromosome is derived from the Japanese house mouse, M. m.
molossinus and therefore carries a molossinus Sry allele. As a first step
to determine how the molossinus Sry allele evolved, its distribution
pattern was determined in wild mice. The cumulative data of 96 M. musculus
samples obtained from 58 geographical locations in Europe, North Africa,
and Asia show the molossinus Sry allele is restricted to Japan and the
neighboring Asian mainland and confirm that Japanese M. m. molossinus mice
were derived in part from a race of M. m. musculus from Korea or Manchuria.
Sry polymorphisms, as illustrated by the molossinus Sry allele, can serve
as molecular markers for studies on the evolution of wild M. musculus
populations and can help determine the role sex determination plays in
speciation.
相似文献
190.
One of the cellular defenses against virus infection is the silencing of viral gene expression. There is evidence that at
least two gene-silencing mechanisms are used against the human immuno-deficiency virus (HIV). Paradoxically, this cellular
defense mechanism contributes to viral latency and persistence, and we review here the relationship of viral latency to gene-silencing
mechanisms. 相似文献