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1.
Controlled alkaline hydrolysis of 16α-bromo-17-keto steroids 1, 5 and 7 with potassium carbonate and tetra-n-butylammonium hydroxide (n-Bu4NOH) and synthesis of 2α-hydroxy-3-ones 11, 13 and 16 by the controlled hydrolysis of the corresponding 2α-bromo-3-ones 9, 12 and 15 are described. Treatm carbonate in aqueous acetone or with n-Bu4NOH in aqueous dimethylformamide (DMF) gave 16α-hydroxy-17-ones 3, 6 and 8 in 85–90% yield, respectively. 2α-Hydroxy-3-ones 11, 13 and 16 were obtained by hydrolysis of the corresponding bromoketones 9, 12 and 15 in high yields using the above conditions or sodium hydroxide in pyridine or DMF, respectively. Deuterium labeling experiments suggested that equilibration between the 2α-bromoketone 9 and the 2β-bromo isomer 10 precedes the formation of the ketol 11 in which the true intermediate might be the 2β-isomer 10. However, rearranged androstane derivatives, 3β-hydroxy-2-ones 18 and 20, were stereoselectively obtained by treatment of the bromoketones 12 and 15 with an excess amount of sodium hydroxide.  相似文献   

2.
History and ClinicalSigns: Herds infected with Trichomonasfetus have histories of infertility, occasional abortions, and pyometra.GrossLesions: There are no specific gross lesions in the fetus. The fetuses are usually aborted in the first half of gestation and may or may not be accompanied by the placenta.MicroscopicLesions: There are no specific microscopic lesions.CulturalProcedures: It is ordinarily not necessary to culture T.fetus in order to demonstrate its presence in placental fluids and/or abomasal contents.SerologicProcedures: There are no suitable seroligic procedures for diagnosing Trichomoniasis.SpecialProcedures: Wet mounts of abomasal contents and/or placental fluids are examined microscopically for T.fetus.PreferredDiagnosticProcedures: Demonstrate the presence of T.fetus by microscopic examination of wet mounts of placental fluids and/or abomasal contents.  相似文献   

3.
The metabolism of drobuline has been examined in the dog, rabbit, rat, guinea pig and hamster. In the dog, unlike the other species, glucuronide conjugation is the major route of metabolism. The structure of the conjugate has been established as an O-glucuronide by isolation using HPLC following by field desorption mass spectral analysis. When the separate d- and l-isomers of drobuline were administered to a series of dogs the l-isomer reached plasma levels approximately three time higher than those of the d-isomer. Deuterium labeled drobuline was synthesized and resolved by multiple crystallizations of the malate salts. Racemic mixtures containing d6-d and h6-l drobuline and d6-l and h6-d drobuline were prepared and analyzed by GC-MS as the pentafluoropropionate derivatives. When either racemic mixture was administered to dogs (10 mg/kg, p.o.) the plasma levels of the l-isomer were found to be approximately three times those of the d-isomer. Using these deuterium labeled mixtures the disposition of the two isomers has been examined in the isolated perfused dog liver, in hepatocytes and isolated microsomes. The results indicate that the difference in plasma levels of the d- and l-isomers is not dependent upon stereospecific absorption or excretion but rather it is caused by metabolism of the d-isomer at a faster rate than that of the l-isomer.  相似文献   

4.
O6-Methyl[8-3H]deoxyguanosine in a synthetic DNA polymer, poly(dC, dG, m6dG), is demethylated by cell-free extracts of EscherichiacoliBr adapted by exposure to N-methyl-N′-nitro-N-nitrosoguanidine, as shown by the appearance of 3H-labeled deoxyguanosine in hydrolysates of the recovered DNA. The demethylating activity could not be detected in extracts of nonadapted E. coli. These results provide direct evidence that a previously described inducible repair activity in E. coli acts by demethylating O6-methylguanine at the DNA level.  相似文献   

5.
6.
The replication defective transducing phage λplac5O29P3 carries a portion of the E.colilac operon in the b2 region of the lambda phage. This lac operon segment contains the lac promoter, the lac operator, and the β-galactosidase z gene, but does not contain the lac repressor i gene. The z gene can be expressed from both the inserted lac promoter and the phage promoter. When E.coli strain 594 (z?, i+) or JC6256 (Δlac) is infected by λplac5O29P3 in the absence of additional cyclic AMP, β-galactosidase synthesis is shown to be expressed from the phage promoter. When 594 (λ+) or JC6256 (λ+) is infected by λplac5O29P3 in the presence of additional cyclic AMP and IPTG, β-galactosidase synthesis is shown to be expressed from the inserted lac promoter.The ability to separate the phage promoter from the inserted lac promoter for β-galactosidase expression will simplify the interpretation whenever λplac5 is used.  相似文献   

7.
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   

8.
The site of action of the crinkled (cr) locus was determined by combining dermis and epidermis from the tail of 15-day +cr and crcr mice and by growing the recombined skins in the testes of histocompatible mice. Since crcr mice have bald tails, the presence or absence of hair in the graft was the feature used to determine gene action. Grafts of the combinations +crepidermis-+cr dermis and +crepidermis-crcr dermis grew hair, whereas grafts of the combinations crcrepidermis-+cr dermis and crcrepidermis-crcr dermis produced no hair. It was concluded that the cr locus, at least for tail skin, is active in the epidermis.  相似文献   

9.
10.
Cytochrome c1, the electron donor for cytochrome c, is a subunit of the mitochondrial cytochrome bc1 complex (complex III, cytochrome c reductase). To test if cytochrome c1 is the cytochrome c-binding subunit of the bc1 complex, binding of cytochrome c to the complex and to isolated cytochrome c1 was compared by a gel-filtration method under non-equilibrium conditions (a bc1 complex lacking the Rieske ironsulfur protein was used; von Jagow et al. (1977) Biochim. Biophys. Acta 462, 549–558). The approximate stoichiometries and binding affinities were found to be very similar. Binding of cytochrome c to isolated cytochrome b which is another subunit of the reductase was not detectable by the gel-filtration method. Further, the same lysine residues of cytochrome c were shielded towards chemical acetylation in the complexes c:c1 and c:bc1. From this we conclude that the same surface area of cytochrome c is in direct contact with cytochrome bc1 and with cytochrome c1 in the respective complexes and that therefore cytochrome c is most probably the structural ligand for cytochrome c in mitochondrial cytochrome c reductase.  相似文献   

11.
In homogenates of Macacamulatta (Rhesus) or Cebusapella amygdaloid nuclear complex, adenylate cyclase activity was approximately doubled by either 10μM dopamine or 8mM NaF. In the presence of morphine, the stimulation by dopamine was reduced. A 90–100% inhibition of the dopamine stimulation was obtained with 20μM, and a 50% inhibition, with 5μM morphine. The effects of 10μM morphine on dopamine stimulation were reversed by 10μM naloxone. Morphine itself did not significantly affect the basal adenylate cyclase activity, but in the presence of 10μM morphine the stimulation by 8mM NaF was reduced approxiamtely 50%. The data suggest an action of morphine at a receptor site which is distinct from the dopamine receptor, but which inhibits the dopamine-stimulated adenylate cyclase. In addition, the cyclic GMP content of Cebus amygdala slices was reduced by 50–75% during incubation for 5–20 minutes with morphine. Maximum effects on cyclic GMP were obtained with 10μM, and half-maximum effects, with 0.1μM morphine. The effect of morphine on amygdala cyclic GMP was not reversed by naloxone. Thus, this action of morphine may not be receptor mediated, or may involve the interaction of morphine with receptors other than the opiate receptor.  相似文献   

12.
1-Aminoglycosides, a new class of specific inhibitors of glycosidases   总被引:2,自引:0,他引:2  
1-Aminoglycosides represent a new class of specific and relatively potent inhibitors of glycosidases. These compounds are specific against those enzymes which act upon glycosides that correspond to glycone of the inhibitor. Thus α- and β-D=- are inhibited by D=-glucosidases but not by D=-galactosylamine and D=-mannosylamine. α- and D=-galactosidases are inhibited by D=-galactosylamine but not by the other two glycosylamines. D=-Mannosylamine inhibits mannosidase.  相似文献   

13.
Thiosulfate-cytochrome c-551 reductase derived from Chlorobiumthiosulfatophilum has been highly purified. The enzyme reduces cytochrome c-551 of C. thiosulfatophilum in the presence of thiosulfate while cytochrome c-555 of the organism is not reduced by the enzyme. Cytochrome c-555 reacts with the enzyme at an appreciable rate only in the presence of cytochrome c-551. However, the reduction rate of cytochrome c-551 by the enzyme is greatly enhanced on addition of a catalytic amount of cytochrome c-555. Therefore, cytochrome c-555 seems to function as an effector on thiosulfate-cytochrome c-551 reductase as well as it acts as the electron donor to the light-excited chlorobium chlorophylls.  相似文献   

14.
The synthesis of 4-ethenylidene-5α-androstane-3β, 17β-diol (5) and of 4-ethenylidene-5α-androstane-3,17-dione (4) is described. Compound 5 is a competitive inhibitor of solubilized bovine microsomal adrenal Δ5-3β-hydroxysteroid dehydrogenase, with Ki =2.7μM, and is converted by the enzyme to the corresponding 3-ketone. Compound 4 shown to irreversibly inactivate the enzyme in a time-dependent manner (t12 =31 min; 55μM; pH =7.0). The substrate, dehydroepiandrosterone, protects against inactivation by compound 4. In contrast, compound 5 is not oxidized at the 3-position by the 3β-(and 17β)-hydroxysteroid dehydrogenase from P. testosteroni, but is oxidized at the 17-position. Nevertheless, the 4-ethenylidene-3,17-diketone (4) causes irreversible time-dependent inactivation (t12 =28min; 64μM; pH =7.0) when incubated directly with this bacterial enzyme, acting as an affinity label.  相似文献   

15.
Strand resealing in the invitro excision repair of 5,6-dihydroxy-dihydrothymine in osmium tetroxide oxidized polyd(A-T) by crude E.coli extracts is accomplished by polynucleotide ligase. Osmium tetroxide oxidized polyd(A-T)_serves as a chemically well defined model substrate containing damage of the kind introduced into DNA by ionizing radiation. In the first incision step of excision repair approximately one endonucleolytic nick is introduced into the polymer by extracts of E.coli endoI? and E.coli endoI?uvrA6? per ring damaged thymine residue removed.  相似文献   

16.
R.D. Randel 《Theriogenology》1984,21(1):170-185
Reproductive function is mediated by season in the Indian breeds of cattle (Bosindicus). The reproductive endocrinology of Bosindicus cattle differs from that of Bostaurus breeds; the estrus is shorter and less intense and occurs late in relation to an estrogen stimulus. Moreover, the Bosindicus female has a smaller preovulatory surge of luteinizing hormone (LH), which occurs earlier relative to the onset of estrus, and she ovulates sooner after the onset of estrus. The corpus luteum is smaller and contains less progesterone, and the serum progesterone concentration is lower in Bosindicus females. Furthermore, they have fewer preovulatory LH surges than Bostaurus females and their luteal cells are less responsive to LH in vitro during the winter. Their fertility is lower during the late fall and winter months. For Bosindicus cattle, recovery of transferable embryos and survival of embryos in the recipient are at their maximum from July through October.  相似文献   

17.
Release of [3H]phosphatidylcholine from pulmonary Type II epithelial cells was stimulated by terbutaline, forskolin and cytochalasin D. Compound 4880 inhibited both basal and agonist-stimulated release of [3H]PC. The IC50 for inhibition by compound 4880 was 1–2 μg/ml, and was similar for inhibition of both basal and stimulated release of [3H]phosphatidylcholine. Inhibitory effects of 4880 were noted following a 1 h exposure to compound 4880 and persisted up to 3 h. The inhibitory effect of compound 4880 was entirely reversed by removing compound 4880 from the external milieu. Compound 4880 had no effect on cytosolic cyclic AMP levels or lactate dehydrogenase release. Inhibition of surfactant release produced by compound 4880 was unaffected by changes in extracellular calcium concentrations. Compound 4880 is a non-toxic inhibitor of phosphatidylcholine release from Type II epithelial cells.  相似文献   

18.
Hemin XIII 4, hemin III 5, and iron 1,4-di(β-hydroxyethyl)porphyrin6 were enzymatically oxidized by a microsomal heme oxygenase preparation from rat liver. These are all better substrates of the oxygenase than the natural substrate, hemin IX 1. The enzymatic oxidation was selective for the α-methine bridge and in every case only the α-biliverdins were obtained. The latter were readily reduced by biliverdin reductase to the corresponding α-bilirubins. The absence of isomers in addition to the α-bilirubins was established by preparing the derived azopigments and by using [α-14C]6 and [α-14C]4 as substrates. The chemical oxidation of 4, 5, and 6 gave the expected mixture of biliverdins. It is concluded that heme oxygenase is not specific for hemin IX. On the other hand, the enzyme is highly selective for the α-methine bridge, defined as the methine opposed to that flanked by the 6,7-propionic acid residues.  相似文献   

19.
20.
Molecular cloning vectors derived from the CoLE1 type plasmid pMB1.   总被引:4,自引:0,他引:4  
F Bolívar 《Life sciences》1979,25(10):807-817
Invitro recombination via restriction endonucleases and invivo genetic translocation of an impicillin resistance gene, have been utilized for the construction of a series of cloning vehicles. These vectors have been derived by combining the essential replication properties of plasmid pMBl, a CoLEl type plasmid, with one, two or three resistance markers (tetracycline, ampicillin, chloramphenicol and colicin El production). During the construction of these vectors, the position of restriction sites used for cloning DNA fragments, relative to the antibiotic resistance genes and the origin of DNA replication, have been determined. The use of the cloning vectors pMB9, pBR313, pBR322, pBR324, pBR325 permits the molecular cloning and easy selection of Eco RI, Bam HI, Bgl II, Dpn II, Hind III, Sal I, Xho I, Xam I, Taq I, Pst I, Hinc II, Pvu I, Sma I, Xma I, Bal I, Hpa I, Ava I, Pvu II, Hae III, Alu I, Hpa II, Eco RII and virtually any blunt-ended generated DNA fragment.  相似文献   

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