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1.
Purification and partial characterization of a cytotonic enterotoxin produced by Aeromonas hydrophila 总被引:2,自引:0,他引:2
This report describes the purification and partial characterization of a cytotonic enterotoxin produced by a human diarrheal isolate (SSU) of Aeromonas hydrophila. The extracellular enterotoxin was purified by (NH4)2SO4 precipitation, hydrophobic column chromatography, and chromatofocusing. The highly purified enterotoxin exhibited a molecular mass of 44 kDa and an isoelectric point in the range of 4.3 - 5.5 as determined by chromatofocusing. Western blot analysis using Aeromonas anti-enterotoxin revealed a single band at 44 kDa; however, cholera antitoxin failed to detect the enterotoxin antigen. This non-cholera toxin cross-reactive (non-CTC) enterotoxin was biologically active in vivo as determined by rabbit ligated ileal loop and rabbit skin vascular permeability assays. Biological activity also was in vitro by this toxin as measured by the elongation of Chinese hamster ovary (CHO) cells. The enterotoxic activity associated with this molecule was neutralized completely by homologous antibodies but not by cholera antitoxin. The purified toxin preparation was free of hemolytic and cytotoxic activities as determined by its inability to lyse rabbit red blood cells or damage CHO cells, respectively. Furthermore, this toxin induced the elevation of cAMP in CHO cells suggesting thereby that the mechanism of action of Aeromonas non-CTC enterotoxin may be similar to heat-labile enterotoxins of Escherichia coli and Vibrio cholerae. 相似文献
2.
Isolation, screening and characterization of thermophilic Bacillus species isolated from dairy products 总被引:1,自引:0,他引:1
Proteolytic thermophilic bacterial cultures (171 strains) were isolated from different milk and milk products. After screening these isolates for protease production in a liquid medium, fifty that exhibited enzyme activity in excess of 100 units/ml were selected and identified. Twenty-nine were Bacillus stearothermophilus (constituting 58% of the total), twelve were B. coagulans, five were B. circulans and four were B. licheniformis. Skim milk powder contributed the maximum number of B. stearothermophilus (64.7%) followed by raw milk (63.2%) and pasteurized milk (44.4%). When the culture supernatant liquids from the selected isolates were given heat treatment, five cultures retained 100% protease activity at 65 degrees C for 30 min. Protease of B. stearothermophilus RM-67 had the maximum heat resistance because it retained 87.5% of its activity at 70 degrees C for 30 min. 相似文献
3.
Analysis of tetracycline resistance encoded by transposon Tn10: deletion mapping of tetracycline-sensitive point mutations and identification of two structural genes 总被引:13,自引:6,他引:7 下载免费PDF全文
Deletions in the tet genes derived from Tn10 were formed from different tet::Tn5 insertion mutations by removing DNA sequences located between a HindIII site in Tn5 and a HindIII site adjacent to the tet genes. Tetracycline-sensitive point mutations were mapped in recombination tests with the deletions and were thus aligned with the genetic and physical map of the tet region. Plasmids carrying point mutations were tested for complementation with derivatives of pDU938, a plasmid carrying cloned tet genes derived from Tn10 which had been inactivated by Tn5 insertions. Complementation occurred between promoter-proximal tet point mutations and distal tet::Tn5 insertions, suggesting the existence of two structural genes, tetA and tetB. These results, together with the analysis of polypeptides in minicells harboring pDU938tet::Tn5 mutants, suggested that tetA and tetB are expressed coordinately in an operon. The tetB gene encodes the previously characterized 36,000-dalton cytoplasmic membrane TET protein, but the product of tetA was not identified. Point mutations in either tetA or tetB led to the defective expression of the resistance mechanism involving tetracycline efflux. It is suggested that the tetA and tetB products interact cooperatively in the membrane to express resistance. 相似文献
4.
Summary The results of studies on 49 families with 107 children and various populations of Caucasoid, Negroid and Mongoloid origin concerning the genetics and population genetics of the 2-glycoprotein I polymorphism are reported. In general the genetical model proposed by Cleve (1968) is confirmed: two autosomal alleles BgN and BgD controlling the phenotypes Bg N-N, Bg N-D and Bg D-D. However, divergences from this model were found in two families. They indicate the assumption of non-genetic factors influencing the phenotype expression rather than more complicated genetical control mechanisms. Within Caucasoid populations phenotype and gene frequencies show almost a homogeneous distribution. This racial stock is striking due to a significant higher 2-glycoprotein I concentration in serum as compared to Negroids and Mongoloids. In connection with this, these racial stocks differ obviously in the gene frequencies: Caucasoids BgN=0.937, Negroids=0.742, Mongoloids =0.780; resp. BgD=0.063, 0.258, 0.220.Supported by the Deutsche Forschungsgemeinschaft.D 77. 相似文献
5.
Efficient plant regeneration via somatic embryogenesis has been developed in chickpea cultivar C235. Leaf explants, on MS medium supplemented with 1.25 mg/l 2,4-D and 0.25 mg/l kinetin, yielded somatic embryos with high efficiency during dark incubation. MS medium supplemented with B5 vitamins, 0.125 mg/l IBA and 2 mg/l BAP was found suitable for embryo maturation. The well formed embryos germinated into plantlets on basal B5 medium supplemented with 0.25 mg/l BAP. Further development into healthy plantlets was obtained on basal B5 medium. Hardened plantlets produced normal, fertile plants upon transfer to soil.Abbreviations 2,4-D
2,4-dichlorophenoxyacetic acid
- BAP
6-Benzyl-aminopurine
- IAA
IndoIe-3-acetic acid
- IBA
Indole-3-butyric acid
- NAA
1-Naphthalene acetic acid
- Kinetin
6-furfuryl aminopurine
- Zeatin
6-(4-hydroxy-3-methylbut-2-enylamino)-purine 相似文献
6.
S. B. Narasimhulu P. B. Kirti S. R. Bhatt Shyam Prakash V. L. Chopra 《Plant cell reports》1994,13(11):657-660
Camelina sativa is a wild crucifer that is reported to be resistant to Alternaria blight. Polyethylene glycol mediated fusion was attempted between protoplasts from etiolated hypocotyls of Brassica carinata and mesophyll protoplasts of Camelina sativa. The mean frequency of heterokaryons was 6.8%. Three hybrid shoots were regenerated, each from a single fusionderived callus. These shoots failed to produce roots capable of withstanding transplantation. Confirmation of hybridity was obtained from the morphology of in vitro produced leaves, somatic chromosome number in leaf tips, and restriction fragment length polymorphism for a nuclear rDNA probe. Analysis for organelle constitution using RFLPs indicated that the hybrid contained chrloroplasts derived from the wild species and mitochondria from the cultivated Brassica species.Abbreviations 2,4-D
2,4-dichlorophenoxy-acetic acid
- IAA
Indole-3-acetic acid
- NAA
-Naphthaleneacetic acid
- IBA
Indole-3-butyric acid
- GA3
gibberellic acid
- BAP
6-Benzylaminopurine
- MS
Murashige and Skoog (1962) basal medium 相似文献
7.
Joe F. Bozeman III Shauhrat S. Chopra Philip James Sajjad Muhammad Hua Cai Kangkang Tong Maya Carrasquillo Harold Rickenbacker Destenie Nock Weslynne Ashton Oliver Heidrich Sybil Derrible Melissa Bilec 《Journal of Industrial Ecology》2023,27(2):382-394
Now is the time to refocus efforts in urban research and design. A changing climate and extreme weather events are presenting unique challenges to urban systems around the world. These challenges illuminate the social barriers that accompany disruptive events such as resource inequities and injustices. In this perspective, we provide three research priorities for just and sustainable urban systems that help to address these matters. The three research priorities are: (1) social equity and justice, (2) circularity, and (3) digital twins. Conceptual context and future research directions are provided for each. For social equity and justice, the future directions are mandatory equity analysis and inclusionary practices, understanding and reconciling historical injustices, and intentional integration with diverse community stakeholders. For circularity applications, they are better metrics for integration, more robust evaluation frameworks, and dynamic modeling at multiple spatial and temporal scales. Future directions for digital twins include developing principles to reduce complexity, integrating model and system components, and reducing barriers to data access. These research priorities are core to meeting several of the United Nations Sustainable Development Goals (i.e., 1—No Poverty, 8—Decent Work and Economic Growth, 10—Reduced Inequalities, and 11—Sustainable Cities and Communities). Useful social and technical matters are discussed throughout, where we highlight the importance of prioritizing localized research efforts, provide guidance for community-engaged research and co-development practices, and explain how these priorities interact to align with the evolving field of industrial ecology. 相似文献
8.
A series of ZnB2O4 phosphors doped with different concentrations of Eu and Dy (0.05 0.1, 0.2, 0.5, 1.0 mol%) and co-doped with Ce (1, 2, 5, 7, 10 mol%) respectively was prepared via the solid-state reaction technique and the thermoluminescence (TL) behaviour of gamma ray-irradiated samples was studied. The synthesized samples were irradiated with γ-rays for the dose range 0.03–1.20 kGy. The TL intensity variations with dose, dopant concentration, and the effect of co-doping were studied. The TL response curves for ZnB2O4:Eu3+ and ZnB2O4:Dy3+, ZnB2O4:Eu3,Ce3+ and ZnB2O4:Dy3+,Ce3+ phosphor were observed. It was revealed that ZnB2O4:Eu3+ showed a linear TL behaviour for the dose 0.03–1.20 kGy and ZnB2O4:Dy3+ showed linearity for the gamma dose range 0.03–0.10 kGy. Furthermore, fading for all the samples was observed to be less than 10% for a storage period of 30 days. In addition to this, the trapping parameters, especially activation energies were evaluated using the Ilich method and the initial rise method. The activation energy values obtained from both methods were in complete agreement with each other. 相似文献
9.
Lipid metabolism in plants provides uncommon opportunities for genetic engineering to produce plant oils suited to a variety of end-uses. These opportunities include improvement of food and nutritional value, creating specialty lipids and feedstocks for high-value products and designing custom-made materials for industry. Genetic engineering intervention for production of novel transgenic plants which elaborate the desired product has graduated from academic exercise to commercial possibilities. It is now realized that transgenic crops can serve as biological factories for upscaling production of premium lipids via molecular farming. This review is an attempt at analyzing the status in this field. 相似文献
10.