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91.
Jack M. Widholm 《Plant Cell, Tissue and Organ Culture》1996,45(3):201-205
A pink-pigmented, facultative methylotrophic (PPFM) bacterium, Methylobacterium mesophilicum, which is found on the leaf surface of most plants, has been reported to be a covert contaminant of tissue cultures initiated from Glycine max (soybean) leaves and seeds by Holland and Polacco (1992). The bacteria can be detected as pink colonies when leaves are pressed or tissue culture homogenates are plated on a medium with methanol as the sole carbon source. Since the presence of contaminating bacteria can confound any biochemical results obtained with such cultures (Holland and Polacco 1992), we wanted to determine the extent of the contamination of our tissue cultures of soybean and other species. No PPFMs were detected in any soybean culture we have, and previous results describing the biochemical characteristics of ureide utilization by one of our soybean suspension cultures (27C) also indicates that PPFM bacteria were not present. Analysis of about 200 other strains of 11 different species maintained in this lab showed that only three of about 160 callus cultures, recently initiated from Datura innoxia leaves, contained PPFMs. The D. innoxia leaves did have PPFMs on their surface but in most cases they did not survive the surface disinfestation and culture regimes. Thus PPFM bacterial contamination should not be a serious problem in most plant tissue cultures.Abbreviations AMS
ammonium mineral salts medium
- PPFM
pink-pigmented facultative methylotrophic bacteria 相似文献
92.
Joanne McLaurin Geralyn C. Trudel Ivan T. Shaw Jack P. Antel Neil R. Cashman 《Developmental neurobiology》1995,26(2):283-293
We have developed a series of immortal human-human hybrid cell lines that express phenotypic characteristics of primary oligodendrocytes, by fusing a 6-thioguanine–resistant mutant of the human rhabdomyosarcoma RD with adult human oligodendrocytes by a lectin-enhanced polyethylene glycol procedure. Hybrids were selected in an aminopterin-containing media. In contrast to the tumor parent cells, a hybrid clone M03.13 expressed surface immunoreactivity for galactosyl cerebroside and intracellular immunoreactivity for myelin basic protein (MBP), proteolipid protein (PLP), and glial fibrillary acidic protein (GFAP). Serum deprivation or chronic treatment with a protein kinase C activator 4-β-phorbol 12-myristate 13-acetate (PMA), but not dibutyl cyclic adenosine monophosphate induced coordinate up-regulation or de novo induction of oligodendrocyte phenotypic markers with concomitant down-regulation of GFAP expression. Consistent with immunohistochemical studies, northern blot analysis demonstrated that both MBP and PLP mRNA were up-regulated in MO3.13 cells by PMA treatment. M03.13 cells provide an immortalized clonal model system suitable for study of gene expression subserving oligodendrocyte and astrocyte phenotypes. © 1995 John Wiley & Sons, Inc. 相似文献
93.
A Simple and Widely Applicable Method for Preparing Homogeneous and Stable Quality Control Samples in Water Microbiology 总被引:2,自引:0,他引:2 下载免费PDF全文
Test strains suspended in skim milk, quickly frozen in dry ice-ethanol, and stored at - 70°C can be used as quality control samples that are immediately available by quickly thawing at 37°C. The samples remain homogeneous and stable for at least 1 year, except for Aeromonas hydrophila, which decreases 20 to 30% in 1 year. 相似文献
94.
Richard J. Robins Jack G. Woolley Morteza Ansarin John Eagles Brian J. Goodfellow 《Planta》1994,194(1):86-94
(S)-(-)-Tropic acid is the acidic moiety of the tropane ester alkaloids, hyoscyamine and scopolamine (hyoscine). When tropic acid is fed to transformed root cultures of Datura stramonium L. or a Brugmansia (Datura) Candida x B. aurea hybrid, the formation of these alkaloids is inhibited. Phenyllactic acid, from which the tropoyl moiety is derived, is considerably less inhibitory. Label from (RS)-phenyl[1,3-13C2]lactic acid is incorporated at high levels into apoatropine, littorine, aposcopolamine, hyoscyamine, 7-hydroxyapoatropine, scopolamine and 7-hydroxyhyoscyamine when fed to these cultures. The presence of an excess concentration of unlabelled tropic acid has little influence on the specific incorporation into these products. It is concluded that free tropic acid is not an intermediate in hyoscyamine biosynthesis but rather that the rearrangement of phenyllactic acid occurs subsequent to its esterification.Abbreviations FM
fresh mass
- NMR
nuclear magnetic resonance spectroscopy
We are grateful to Drs. N.J. Walton, A.J. Parr, M.J.C. Rhodes (Institue of Food Research, Norwich) and B. Dräger (Münster, Germany) for helpful and critical discussions. We also wish to thank Dr. P. Bachmann (Braunschweig, Germany) for suggesting the use of the DB-17 column to separate littorine from hyoscyamine and for the modified Excel programme used to calculate the specific incorporations, Yannick Ford (AFRC Co-operative Award Studentship, University of Oxford) and Abigael Peerless for their able assistance, Dr. I. Colquhoun for assistance with some of the NMR spectroscopy and Drs. K. Shimomura (Tsukuba, Japan) and T. Hashimoto (Kyoto, Japan) for pure samples of 7-hydroxyhyoscyamine. J.G.W, gratefully acknowledges support from the Nuffield Foundation under the Small Grants Scheme to promote collaborative experimentation and M.A. is grateful to the Ministry of Education, Iran for a research scholarship. 相似文献
95.
Mössbauer spectroscopic studies on a heme peptide (HP) derived from cytochrome c and on the HP recombined non-covalently with the remaining cleaved section are reported. The results suggest that the environment of the heme site in the known crystal structure of cytochrome c may differ in detail from the environment of the heme in the working protein. 相似文献
96.
Presynaptic modulation by eicosanoids in cortical synaptosomes 总被引:1,自引:0,他引:1
In continuing experiments to determine the ionic basis of inhibitory presynaptic modulation, rat cortical synaptosomes were employed and receptor-activated K+ efflux was determined with a K+ sensitive electrode. When synaptosomes were sub-optimally depolarized by veratridine, the addition of agents that activated purinergic, 2, muscarinic and opioid receptors all promoted K+ efflux. With 2-chloroadenosine as a model inhibitory presynaptic modulator, the increased K+ efflux evoked by this agent was blocked by the cyclooxygenase inhibitor indomethacin suggesting that arachidonic acid or its metabolites was an intermediary in opening the channel. When arachidonic acid and PGE2 were tested, both promoted K+ efflux that was inhibited by dendrotoxin and mast cell degranulating peptide, two agents that are known to inhibit a delayed rectifier K+ current. Our results suggest that via eicosanoid second messengers, inhibitory presynaptic modulators open a sub-class of K channels that hyperpolarize nerve terminals, therefore less Ca2+ would enter per nerve impulse and thus the evoked release of neurotransmitters would be decreased.Abbreviations DTX
dendrotoxin
- MCDP
mast cell degranulating peptide
- NHGA
norhydroguairetic acid
- PGE2
prostaglandin E2 相似文献
97.
Sequence and characterization of the Escherichia coli genome between the ndk and gcpE genes 总被引:1,自引:0,他引:1
Abstract The region of the chromosome immediately upstream of the Escherichia coli gene gcpE has been cloned and sequenced. This region contains two functional open reading frames, orf 384 and orf 337, encoding proteins of 43082 and 36189 Da, respectively. Sequencing analysis (this paper) and the isolation of a DNA fragment containing a functional promoter (Talukder, A.A., Yanai, S., and Yamada, M. (1994) Biosci. Biotech. Biochem. 58, 117–120) indicate that orf 337 is in an operon with gcpE . The gene orf 384 is immediately downstream of the gene ndk , which encodes nucleoside diphosphate kinase. 相似文献
98.
99.
Weak antioxidant defenses make the heart a target for damage in copper-deficient rats 总被引:3,自引:0,他引:3
Copper deficiency causes more salient pathologic changes in the heart than in the liver of rats. Although oxidative stress has been implicated in copper deficiency-induced pathogenesis, little is known about the selective toxicity to the heart. Therefore, we examined the relationship between the severity of copper deficiency-induced oxidative damage and the capacity of antioxidant defense in heart and liver to investigate a possible mechanism for the selective cardiotoxicity. Weanling rats were fed a purified diet deficient in copper (0.4 μg/g diet) or one containing adequate copper (6.0 μg/g diet) for 4 weeks. Copper deficiency induced a 2-fold increase in lipid peroxidation in the heart (thiobarbituric assay) but did not alter peroxidation in the liver. The antioxidant enzymatic activities of superoxide dismutase, catalase, and glutathione peroxidase were, respectively, 3-, 50- and 1.5-fold lower in the heart than in the liver, although these enzymatic activities were depressed in both organs by copper deficiency. In addition, the activity of glutathione reductase was 4 times lower in the heart than in the liver. The data suggest that a weak antioxidant defense system in the heart is responsible for the relatively high degree of oxidative damage in copper-deficient hearts. 相似文献
100.
Mutant plants defective in the assimilation of nitrate can be selected by their resistance to the herbicide chlorate. In Arabidopsis thaliana, mutations at any one of nine distinct loci confer chlorate resistance. Only one of the CHL genes, CHL3, has been shown genetically to be a nitrate reductase (NR) structural gene (NIA2) even though two NR genes (NIA1 and NIA2) have been cloned from the Arabidopsis genome. Plants in which the NIA2 gene has been deleted retain only 10% of the wildtype shoot NR activity and grow normally with nitrate as the sole nitrogen source. Using mutagenized seeds from the NIA2 deletion mutant and a modified chlorate selection protocol, we have identified the first mutation in the NIA1 NR structural gene. nia1, nia2 double mutants have only 0.5% of wild-type shoot NR activity and display very poor growth on media with nitrate as the only form of nitrogen. The nial-1 mutation is a single nucleotide substitution that converts an alanine to a threonine in a highly conserved region of the molybdenum cofactor-binding domain of the NR protein. These results show that the NIA1 gene encodes a functional NR protein that contributes to the assimilation of nitrate in Arabidopsis. 相似文献