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1.
Two experiments were conducted to test for the recovery of brucella organisms from uterine flushings and harvested embryos of sero-positive embryo donor females. In Experiment I, 16 sero-positive cows were superovulated with FSH treatments and artificially inseminated at 12, 24 and 36 hours following the onset of estrus with brucella-free semen. At 48 hours after the onset of estrus, one half the potential donor females were administered an intrauterine inoculation of 3.3 to 4.6 × 104Brucellaabortus (strain 2308) organisms while the remainder received a control inoculation. In Experiment II, the same 16 cows were similarly administered superovulatory treatments and inseminated following estrus. The uterine inoculation was increased to 1.5 to 2.5 × 108 organisms administered 48 hours following estrus. Samples of recovered flushing medium and homogenized embryo residues were placed into a validated invitro culture system to detect the presence of brucella bacteria. Uterine flushings and embryos recovered from 31 females exhibiting estrus following FSH treatments were free from either field strain or the inoculated B.abortus (strain 2308) contamination. The flushings obtained from a single female, which did not respond with estrus following FSH treatment but was inoculated at appointment, did contain B.abortus which was identified as the inoculated strain 2308 and not field strain organisms. These results indicate that brucella contamination of flushing media and harvested embryos will not likely be incurred when collecting embryos from sero-positive donor females. These findings offer further encouragement for the use of embryo transplantation as a method to produce brucella-free offspring from infected cows.  相似文献   

2.
The specific synthesis of argF mRNA directed by the argF gene carried on the specialized transducing bacteriophage λh80C1857dargF, performed in vitro, is described with the use of an S180 extract from a strain carrying argR?. Synthesis of argF mRNA is biphasic at approximately 7 minutes. The regulation of argF mRNA synthesis by the specific arginine holorepressor present in an S180 extract prepared from a strain carrying the argR+ allele is described.  相似文献   

3.
4.
When Escherichiacoli strain CSH50(R6K) is lysed so as to preserve the folded chromosome structure approximately 9 of the 11 R6K molecules maintained per chromosomal equivalent cosediment with the host nucleoid on a neutral sucrose gradient; the remaining 2 plasmids sediment at their normal rate. When cells are briefly labeled with [3H]thymidine, the majority of plasmid replicative intermediates and nascent mature plasmids are found in the plasmid subpopulation that cosediments with host folded chromosomes. This finding suggests that plasmid replication occurs in a restricted cellular locus, perhaps even while in association with its host's folded chromosome.  相似文献   

5.
The GDH (NADPH) mutant strain am-1 of N. crassa has sizable pools of glutamine and glutamate under ammonium-limited conditions for which requires an elevated glutamine synthetase activity. Glutamine in the pres ence of 2-oxoglutarate, stimulated nicotinamide nucleotide oxidation by crude and purified extracts of the am-1 strain and led to a reductant dependent formation of two molecules of glutamate. Aminooxyacetate did not have any effect on the reaction, whereas azaserine inhibited it completely. It is concluded that in N. crassa glutamine synthetase and glutamate synthase are responsible for the assimilation of low ammonium concentrations.  相似文献   

6.
The sialic acid binding loctin carcinoscorpin agglutinates Escharichiacoli K12 andSalmonellaminnesots R595 cells. This interaction can be inhibited by the saccharides namely 2-keto-3-deoxyoctonate and the disaccharide D-(N-acetylneuraminyl) (2→6)2-acetamide-2-deoxy-D-galactitol. N-acetylneuraminic acid is shown to be a poor inhibitor. The same behaviour is seen when purified lipopolysaccharides from these two Gram negative bacteria are used. Vibriocholerae, a Grum negative bectarium devoid of 2-keto-3-deoxyoctonate and Staphylococcussureus a typical Gram positive bacterium failed to agglutinate in the presence of the lectin. The results suggest that the 2-keto-3-deoxyoctonate residues might represent the physiological substrate for the sialic acid binding lectin from the horseshoa crab.  相似文献   

7.
Active transport of inorganic phosphate into whole cells of a strain (AB3311) derived from Escherichia coli K12 was found to be partially resistant to 50 μM carbonyl cyanide m-chlorophenyl hydrazone (CCCP), a powerful uncoupler of oxidative phosphorylation. The presence of 10 mM dithiothreitol (DTT) before the addition of CCCP completely prevented the inhibition of phosphate uptake caused by the uncoupler. The addition of DTT to the CCCP-inhibited system restored phosphate uptake to the control rate even when added 5 min after the phosphate transport assay was started. This uncoupler resistant transport is insensitive to anaerobiosis, or the addition of 10 mM KCN which reduces oxygen consumption to less than 1% that of aerobic controls. Additional studies of transport in a mutant (CBT302) deficient in membranebound Ca2+-, Mg2+-ATPase activity also demonstrated the retention of appreciable inorganic phosphate uptake under anaerobic conditions.  相似文献   

8.
An inhibitor of Streptococcus,mutans endodextranase was detected in proteins prepared from batch cultures of S.,mutans strains representing serotypes a through g. Affinity chromatography of strain 6715-49 proteins, which apparently were free of endodextranase activity, yielded an active endodextranase and, in a separate peak, the endodextranase inhibitor. The presence of the inhibitor in culture fluids accounts for the absence of endodextranase activity in batch-grown cultures of S.,mutans known to produce this enzyme.  相似文献   

9.
A mutant strain (PL pT 1143) of Pseudomonasputida PL, has been isolated for its inability to growth with p-cymene as carbon source. The mutant oxidizes p-cymene (and p-cumate) to a compound (λmax 293 nm) which is readily converted to 3-hydroxy-p-cumate by acid. 4-Trifluoromethylbenzoate is oxidized by the mutant to an acid-stable intermediate (λmax 277nm) that has been crystallized. The spectral properties (u.v., i.r., NMR and mass) of this metabolite are consistent with those expected for a 2,3-dihydro-2,3-dihydroxy derivative of 4-trifluoromethylbenzoate. Further support of this structure was provided by elemental analysis and the properties of two derivatives of the metabolite, 4-trifluoromethyl-3-hydroxybenzoate and an acetonide formed with 2,2-dimethoxypropane. The stability of a product obtained by treatment of the dihydrodiol metabolite with triacetylosmate indicates that it is the cis-isomer.  相似文献   

10.
We have studied the kinetics of ionophore X-537A-mediated transport of manganese ions into small unilamellar vesicles formed from dipalmitoylphosphatidylcholine. To follow the transport we used the paramagnetic effect of manganese on the 1H-NMR signal from choline trimethylammonium groups on the inner phospholipid monolayer. The transport of only one manganese ion produces an intravesicular concentration which is high enough (approx. 1 mM) to substantially broaden this signal. The observed signal thus arises predominantly from those vesicles which contain no manganese. Therefore, as manganese is transported into the vesicles the observed signal decreases in intensity, but does not broaden. The initial time-dependence of the intensity of the signal, S(t), can be approximated by the simple first-order rate law: S(t) = S(O)exp(?K′t), where K′ is the probability per unit time for the transport of a manganese ion from the external medium to the intravesicular space. From the dependence of K′ on the ionophore X-537A concentration we conclude that manganese is transported into the vesicles via both 1 : 1 and 2 : 1 complexes with ionophore X-537A. At low ratios of ionophore X-537A to vesicles transport via the 1 : 1 complex predominates; at high ratios transport via the 2 : 1 complex predominates. From the dependence of K′ on manganese concentration we determined that under our conditions the equilibration of ionophore X-537A between vesicles is much faster than the transport of manganese through the vesicles. Lastly, from the dependence of K′ on temperature, we conclude that the ionophore X-537A-mediated transport of manganese into the dipalmitoylphosphatidylcholine vesicles is very sensitive to the gel-liquid crystalline phase transition.  相似文献   

11.
Lipopolysaccharide and an acidic polysaccharide were extracted with phenol-water from a rough strain of Escherichia coli (LP1092). The polysaccharide portion of lipopolysaccharide contained galactose, glucose, L-glycero-D-mannoheptose, small amounts of mannose and an unusually high proportion of 3-deoxy-D-manno-octulosonic acid; this polysaccharide was shown to represent the complete coli R2 core. The acidic polysaccharide, which functioned as a K antigen, contained large amounts of a 2-keto-3-deoxy sugar acid. On colorimetric and chromatographic evidence this acid appeared to be 3-deoxy-D-manno-octulosonic acid.  相似文献   

12.
The transducing phage λdarg14, carrying a portion of the E. coli chromosome including argECBH, is derived from the heat-inducible, lysis-defective strain λy199, which has the b519 and b515 deletions. Cleavage of λy199 DNA by EcoRI endonuclease, followed by agarose slab gel electrophoresis, results in bands corresponding to the known C, D, E, and F segments of λ, and a segment A′ (A plus B minus b519 minus b515, the cleavage site between A and B being eliminated). Cleavage of λdarg14 DNA by EcoRI yields the expected D, E, and F segments of λ and four other segments, termed 14-1 through 14-4, whose length is 17.5, 6.2, 3.0, and 2.0 kilobases, respectively, as determined by electron microscopy and corroborated by electrophoretic mobility. Heteroduplex analysis shows that the E. coli argECBH cluster is on the 14-1 segment.  相似文献   

13.
The technique of laser Doppler electrophoresis was applied for the study of the surface charge properties of (Na+,+)-ATPase containing microsomal vesicles derived from guinea-pig kidney. The influence of pH, the screening and binding of uni- and divalent cations and the binding of ATP show: (1) one net negative charge per protein unit with a pK = 3.9; (2) deviation from the Debye relation between surface potential and ionic strength for univalent cations, with no difference in the effect of Na+ and K+; (3) Mg2+ binds with an association constant of Ka = 1.1 · 102M?1 while ATP binds with an apparent Ka = 1.1 · 104M?2 for 1 mM Nacl, 0.2 mM KCI, 0.1 mM MgCl2, 0.1 mM Tris-HCI (pH 7.3). The binding is weaker at higher Mg2+ concentrations. There is no ATP binding in the absence of Mg2+. In addition, the average vesicle size derived from the linewidth of the quasi-elastic light scattering spectrum is 203.7 ± 15.2 nm. In the presence of ATP a reduction in size is observed.  相似文献   

14.
Dystrophic mice of the C57B1 dy2Jdy2J strain and of the ReJ 129 dydy strain and littermate controls were used to prepare met-tRNAfMet binding factors. The tissues were homogenized and fractions were obtained which contained ribosomes. The binding factors were assayed by the binding of [35S]methionyl-tRNA to control liver ribosomes. The binding, i.e. eukaryotic initiation factor 2 (elF 2) activity, was measured in brain, liver and muscle and in all of these tissues there was a significant decrease in the dystrophic mice. This decrease in initiation factor activity of hindleg muscle resembled, in the direction of the effect, the decrease in elongation factor activity of hindleg muscle resembled, in the of dydy mice previously reported by our laboratory. Thus these two defects, taken together may help to explain the marked wasting of the muscles. The decrease in brain in both strains provides evidence for nervous tissue involvement in genetic dystrophy.  相似文献   

15.
The linkage pattern of the K6-antigen was investigated using material from the urinary pathogen, Escherichia coli LP 1092. The polysaccharide consists of ribose and 3-deoxy-D-manno-2-octulosonate (KDO) in a ratio of 2:1. Colorimetric procedures, Smith degradation, methylation analysis, and nuclear magnetic resonance spectroscopy were applied to the whole polysaccharide and to a trisaccharide “repeating unit” obtained by mild-acid catalyzed hydrolysis. Together, the data are compatible only with a branched chain structure …3Ribfβ1→7KDOpβ2→3Ribfβ
  相似文献   

16.
Atomic coordinates and backbone torsion angles are tabulated for ferricytochrome c2 of Rhodospirillum rubrum.  相似文献   

17.
The nematode Trichinella spiralis is rejected from the intestine at a time that is characteristic for each inbred strain of mouse. Previous work (R. G. Bell et al. 1982a) had empirically identified strong, intermediate, and weak phenotypes (NFR, CHHe, and C5710 mice, respectively) in mice infected with 400 muscle larvae. It is shown that this classification applies to another eight inbred strains: SWR, DBA2, DBA1, LP, BubBn—all intermediate, and NZBBIN, C57L, A, and Mus molossinus—all weak. This phenotypic classification consistently applies with infections of 400–800 muscle larvae. Below doses of 300 muscle larvae, the strain designation of phenotype does not consistently apply. By this it is meant that the relative rejection rate changes for certain strains so that eventually some strains that were strong (NFR) or intermediate (AKR) responders to 400 muscle larvae become weak responders to 50 muscle larvae. Other strains increase their relative rejection time (B10 · BR, B10 · Q) while many do not change (NFS, C3HebFe, DBA2, DBA1). The phenomenon is most apparent in inbred parental strains rather than in F1 crosses, and it represents a phenotypic variation in rejection time that is dependent on dose. It is also demonstrated that time of rejection is directly proportional to dose in all inbred and F1 mouse strains that we have examined. Analysis of F1 crosses shows that most have the rejection time of the strongest responding parental line, suggesting simple genetic control of strong, intermediate, and weak responses. Two F1 crosses invalidated this theory. The DBA1 × C3HHe (intermediate × intermediate) showed a strong response. The additive effects of parental rejection phenotype indicated that these lines could not be genetically identical for intermediate responsiveness. Similarly, the NFR (strong) × B10 · BR (weak) F1 showed intermediate rejection, indicating partial dominance of C57B110 genes over the strong responder NFR strain. Neither the primary expulsion time phenotype, phenotypic variation to low doses, or the rejection characteristics of F1 crosses could be ascribed to genes linked to the major histocompatibility complex.  相似文献   

18.
The ability of various bacterial lipopolysaccharides and mycoplasmal lipopolysaccharides (lipoglycans) to induce macrophage-mediated tumor cell killing and Limulus amebocyte lysate clotting was determined. Lipoglycans from the mycoplasma Acholeplasmaaxantum or Acholeplasmagranularum had no activity or 104 to 105 less activity than lipopolysaccharides from Escherichiacoli 0128:B12, Escherichiacoli K235, or Salmonellaminnesota R595 in causing Limulus lysate clotting and tumor cell killing by peritoneal macrophages from normal or bacillus Calmette-Guérin-infected mice. Previous studies have shown that the lipid A portion of bacterial lipopolysaccharide is responsible for the effects on macrophage-mediated tumor cell killing and Limulus lysate clotting. The known differences in the lipid structures of bacterial lipopolysaccharides and mycoplasmal lipopolysaccharides (lipoglycans) may account for the noted differences in the biologic potencies observed here.  相似文献   

19.
Uterine stage embryos collected from the hamster (8-cell) and cow (morula, early blastocyst) were monitored for development invitro (embryo culture) and invivo (embryo transfer) following premature removal of the zona pellucida.Removal of the zona pellucida did not significantly affect invitro development to the blastocyst stage of (1) 8-cell hamster embryos (zonae removed by a combined enzymic-mechanical procedure), (2) bovine morulae (zonae removed by mechanical means only) (3) early bovine blastocysts (zonae removed by the enzymic-mechanical technique).Zona-free hamster embryos formed significantly fewer viable fetuses than did zona-intact embryos. The lower incidence of fetal development observed following transfer of zona-free 8-cell hamster embryos may have resulted in part from the formation of chimeras by fusion of these embryos inutero. Such fusion was observed to occur invitro between zona-free embryos placed in close proximity. The proportion of pregnancies resulting from transfer of bovine blastocysts cultured from zona-free morulae was similar to that of zona-intact embryos.In this study we have demonstrated that (1) enzymic and mechanical procedures used to remove zonae pellucidae from uterine-stage hamster and bovine embryos do not adversely affect subsequent development of these embryos invitro and invivo and (2) zonae pellucidae are not required for normal development of these embryos. These findings have implications for microsurgery of mammalian embryos and for embryo transfer.  相似文献   

20.
When BALBc mice were given BALBc mouse-derived cysticercoids (cysts) of Hymenolepis nana, only 143 mice became autoinfected, whereas most (3138) of dd mice given the same infection became massively autoinfected with mature worms. When BALBc mice initially given cysts were challenged with eggs on Day 7, just before the patency of the primary infection, there was normal development into cysts, but almost none of them developed into adult worms. Thus, the failure of autoinfection of H. nana in BALBc mice was not a result of failure of eggs to differentiate into cysts in the intestinal tissue, but a result of failure of these cysts to develop into adult worms in the lumen. The reasons why autoinfection does occur in dd and other strains of mice and not in the BALBc strain are discussed in terms of the difference in onset of the late response in these strains of mice, ie., the response that is acquired after egg inoculation, and is directed against the lumen phase of cyst challenges. It is strongly suggested that (1) the lumen phase which follows cyst inoculation is highly immunogenic, but clearly differs from tissue phase which follows egg inoculation, (2) the autoinfection which occurs in some strains of mice is therefore not a result of no or poor immunogenicity of the lumen phase but is due to a delay of onset of the late response with the result that a secondary generation may mature, and (3) in other strains of mice, including BALBc, which acquire the late response within 15 days of initial egg inoculation, autoinfection normally does not occur after cyst infections.  相似文献   

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