Bromobenzene causes hepatic and extrahepatic toxicity in rats. Toxicity is related to the presence of covalently bound material in these tissues. A major bromobenzene metabolite, p-bromophenol, has been shown to give rise to covalently bound material in liver, lung and kidney , but is not toxic. p-Bromophenol is formed from bromobenzene in liver, lung and kidney microsomes and is subsequently metabolized to 4-bromocatechol and covalently bound material. Bromobenzene-3, 4-oxide generated by liver microsomes, is detoxified by kidney, liver and lung cytosol. The results suggest that the kidney toxicity caused by bromobenzene is probably not mediated by either bromobenzene-3, 4-oxide or the reactive metabolites of p-bromophenol. In contrast, bromobenzene-3, 4-oxide may play a role in the lung toxicity observed after bromobenzene administration. However, the covalently bound material found in extrahepatic tissues may be derived from both bromobenzene-3, 4-oxide or the reactive metabolites of p-bromophenol, which may be formed directly by these tissues or transported there from the liver. 相似文献
Relatively large amounts of immunoreactive prolactin were measured in homogenates of human decidual tissue obtained immediately after delivery of normal term pregnancies. In order to study the release and possible synthesis of prolactin by this tissue, explants of decidua were incubated for 24 hours at 37°C in oxygenated Gey's buffer containing 20% fetal calf serum. When cycloheximide was added to the medium in concentrations sufficient to prevent protein synthesis, 85–90% of the prolactin present in the tissue was released into the medium during the first 3 hours of incubation. No additional prolactin accumulated in either the medium or the tissue during the remainder of the incubation period. In the absence of cycloheximide, the prolactin concentration in the medium increased progressively during incubation, so that after 24 hours the total amount of hormone present in the tissue and medium was significantly greater than that in the tissue and medium prior to incubation (37.6 ± 9.6 ng/ml at 0 time vs 82.2 ± 7.7 ng/ml at 24 hours). When 3H-1-leucine (100 u Ci) was supplied during incubation, radioactive proteins were detected in the medium at 24 hr, 14–20% of which were specifically precipitated by antiserum to human pituitary prolactin. When aliquots of this medium were chromatographed on Sephadex G-100, 80–95% of the 3H-proteins precipitated by antiserum to pituitary prolactin eluted in the same position as did purified, iodinated pituitary prolactin. These data indicate that a species of prolactin which is identical to pituitary prolactin by the criteria of immunoprecipitation and gel chromatography is synthesized by human decidual tissue . 相似文献
A glycoprotein from the stems and leaves of the plant that cross reacts with antibodies to the seed lectin has been found to bind to affinity columns of blood group A + H substance covalently linked to Sepharose. This binding of the cross reactive material to the affinity resin differs from that of the seed lectin in that it is easily dissociated with 0.15 M NaCl. Affinity electrophoresis using entrapped blood group A + H substance shows that the carbohydrate binding activity of the cross reactive material is weakly inhibited with N-acetyl-D-galactosamine and N-acetyl-D-glucosamine. Glucose, mannose and galactose gave no inhibition when tested at concentrations of 50 mM. These data indicate that the specificity of the cross reactive material is somewhat different from the N-acetyl-D-galactosamine specificity of the seed lectin. The significance of these findings is discussed in relation to the structural similarities of the cross reactive material and the seed lectin. 相似文献
Guanylate cyclase from crude homogenates of vegetative has been characterized. It has a pH optimum of 8.0, temperature optimum of 25°C and requires 1 mM dithiothreitol for optimal activity. It strongly prefers Mn++ to Mg++ as divalent cation, requires Mn++ in excess of GTP for detectable activity, and is inhibited by high Mn++ concentrations. It has an apparent Km for GTP of approximately 517 μM at 1 mM excess Mn++.The specific activity of guanylate cyclase in vegetative homogenates is 50–80 pmoles cGMP formed/min/mg protein. Most of the vegetative activity is found in the supernatant of a 100,000 x g spin (S100). The enzyme is relatively unstable. It loses 40% of its activity after 3 hours storage on ice. Enzyme activity was measured from cells that had been shaken in phosphate buffer for various times. It was found that the specific activity changed little for at least 8 hours. Cyclic AMP at 10?4 M did not affect the guanylate cyclase activity from crude homogenates of vegetative or 6 hour phosphate-shaken cells. 相似文献
The disruption of erythyrocyte membrane cytoskeletons brought about by treatment with (PMBS) has been followed by measurements of turbidity and the binding of 203Hg-labelled PMBS. After pretreatment with to block readily reactive sulphydryl groups, incubation with [203Hg]PMBS showed incorporation of approximately 4 moles radiolabel per mole of spectrin and one per mole of actin. The incorporation of radiolabel paralleled the decrease in turbidity, and the labelling of spectrin paralleled that of actin. The kinetics were pseudo first order, and the pH dependence of the observed rate constant indicated a normal value for the sulphydryl group involved. The calculated second-order rate constant for the reaction of the sulphydryl anion with PMBS, however, was several orders of magnitude less than expected from model compound studies. The results suggest that association between spectrin and actin may result in the steric hindrance of reactivity of a limited number of sulphydryl groups in each protein. Disruption of the spectrin-actin association may then be linked to the modification of the sulphydryl groups. 相似文献
The transducing phage λd, carrying a portion of the chromosome including , is derived from the heat-inducible, lysis-defective strain λy199, which has the and deletions. Cleavage of λy199 DNA by RI 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 minus , the cleavage site between A and B being eliminated). Cleavage of λd DNA by RI 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 cluster is on the 14-1 segment. 相似文献
The quantity of organic acids ( lactic acid, acetic acid, propionic acid and butyric acid ) in the content of the gastrointestinal tract of germ-free and conventional rats and the effects of the organic acid on the motility of the gastrointestinal tract of rats were investigated.Organic acids were detected only in the gastrointestinal contents of conventional rats but not in those of germ-free rats.Lactic acid detected in the stomach of rats stimulated the motility of both small and large bowel while acetic acid, propionic acid and butyric acid found in the cecum stimulated the motility of the large bowel but not of small bowel. 相似文献
incorporates 3H or 14C from 3H- or 14C-labeled ethanolamine into an -alkali soluble, alcohol -insoluble fraction obtained from cell walls. Dansyl ethanolamine was isolated from this alcohol-insoluble fraction following dansylation and hydrolysis. The alcohol-insoluble material was non-dialyzable and contained galactofuranosyl, glucosyl, phosphoryl, amino acyl and variable quantities of uronosyl residues. The lack of detectable quantities of mannosyl residues in this material suggests that the galactofuranosyl-containing cell wall polymer is distinct from the peptidophosphogalactomannan which is obtained from culture filtrates of . (Gander ., (1974) J. Biol. Chem. , 2063). 相似文献
The plasma membrane-bound penicillinase of has been purified. Amino acid analysis showed no significant differences in composition between the enzyme and exopenicillinase. Enzyme purified from cultures containing H333PO4 or [3H]-glycerol contained 33P or [3H]-glycerol activity and treatment with 8 M urea, 0.2% sodium dodecyl sulfate at 80° C did not remove the 3H-activity from the enzyme protein. Trypsin readily cleaved the glycerol-containing moiety from the enzyme protein, forming enzyme with molecular weight and heat stability like that of the exoenzyme. Phospholipase D and C also produced enzyme resembling the exo-form. 相似文献
The metabolism of 3H-androsterone was studied in homogenates (fortified with uridine 5'-diphosphoglucuronic acid and andenosine 3'-phosphate 5'-phosphosulfate) of eighteen breast tumors, one muscle underlying the primary breast carcinoma and metastatic axillary lymph nodes from a patient with suspected primary breast cancer. The major metabolites identified were less polar than androsterone. On saponification these lipoidal derivatives afforded androsterone as the only product (3 to 48%). Unmetabolized androsterone and lesser quantities of epiandrosterone, 5α-androstane-3α,17β-diol and 5α-androstane-3,17-dione comprised the free steroid fraction. Androsterone glucosiduronate was isolated (0.17–4.1%) from eight breast tumor homogenates and from the node tissue incubation (17%). There was no apparent correlation between glucuronyltransferase activity and histopathology or estrogen receptor content. 相似文献
, originally introduced as an inadvertent contaminant in solutions used for evaluating the stability of prostaglandins, proved to lead to the rapid disappearance of the cyclopentenone unit of PGA2 (as monitored by circular dichroic spectroscopy). The cyclopentenone unit is converted, in various metabolites, to a 9-keto, 9α or 9β-hydroxy group lacking the ring unsaturation. The major EtoAc-soluble 9-hydroxy metabolite (Compound-I) was shown to be 9α, 15α-dihydroxy-2,3,4,5-tetranor-13--prostenoic acid. Similar tetranor 9-hydroxy metabolites with one additional degree of unsaturation, and with a 9β-hydroxy group, also occur but these have not been fully characterized. Only two of the wide range of 9-keto metabolites are fully characterized by mass spectral (MS) data: 9,15-oxo-2,3,4,5-tetranorprostanoic acid and 9,15-oxo-2,3,4,5-tetranor-13--prostenoic acid. The water soluble metabolites have not been characterized further.The fully characterized metabolites together with MS data from mixtures of minor metabolites indicate that can perform the following transformations: β-oxidation, dehydrogenation at C-15, reduction of the enone carbon-carbon double bonds (both Δ10,11 and Δ13,14), reduction of the 9-ketone, and possibly migration of the cyclopentyl double bond (Δ10,11 → Δ11,12). metabolizes 15-epimeric PGA2 equally readily with the production of similar products. PGA1 affords less 9-keto metabolites with compound I constituting 33% of the product by HPLC analysis. displays some enantioselectivity, PGA2 and 15-epi-PGA2 are each metabolized more rapidly than their enantiomers. Other prostaglandins appear to be less readily metabolized. 相似文献
Three lysine residues of horse heart cytochrome were modified by reaction with methyl-4-mercaptobutyrimidate hydrochloride and the free SH group of the latter was covalently linked to p-azidophenacyl bromide yielding a photoaffinity-labeled cytochrome . The photoaffinity-labeled cytochrome was bound by irradiation into a covalent complex with cytochrome oxidase. 相似文献
Rhodotorucine which induces mating tube formation of cells in is metabolized rapidly by cells. By use of labeled rhodotorucine , the degradation was found to be proteolytic. Two peptide fragments Tyr-Pro-Glu-Ile-Ser-Trp-Thr-Arg and Asn-Gly-Cys(S-farnesyl) were identified as the metabolites. Proteolysis of the pheromone mainly occurred on the cell surface. Culture filtrate of cells at log phase did not metabolize rhodotorucine . 相似文献
Metabolic plasmids conferring on the aromatic growth phenotypes naphthalene, Nah+, salicylate, Sal+, or toluate, Tol+, have been isolated as covalently closed circular DNA in 100 μg amounts. Plasmid DNA was banded in CsCl-ethidium bromide density gradients and sedimentation rates measured in sucrose gradients and by analytical centrifuge. The plasmid sizes found, in millions, were /NAH 42, /SAL 43, /TOL 55, 42. Transformation of metabolic plasmid free with the isolated DNA confirmed the respective aromatic pathway gene contents. 相似文献
Kinetoplast DNA from the order Kinetoplastidae (trypanosomatids) exists as large associations (molecular weight 4 × 1010), made up of about 104 small, probably circular, molecules, commonly known as ‘minicircles’. These minicircles were originally thought to be identical in base composition, suggesting that the coding capacity of kinetoplast DNA is very restricted. However, linear molecules have also been observed in preparations of kinetoplast DNA, which, if they contain unique sequences, could represent additional genetic information. This linear DNA has been assumed to be derived from the kinetoplast, but the possibility of it being nuclear contamination has not been definitely ruled out. Work presented in this paper demonstrates that nuclear DNA contamination may indeed be present in kinetoplast DNA prepared by a commonly used method. 相似文献
Strain S296, isolated by screening 2000 colonies after nitrosoguanidine mutagenesis, yields extracts with less than 1% of wild-type RNase activity against (3H) poly(U). Unlike other strains, S296 grows with a doubling time of about 2 hr., both in nutrient broth and in minimal medium, and at 30°, 37° and 42°. The strain retains 10 to 20% of wild-type exonuclease activity against (3H) rRNA or T4 phage-specific mRNA; but two further mutants, made by screening mutagenized colonies of strain S296, are reduced to 3% of wild-type activity against those substrates as well. 相似文献
Cells of C thy?321 are examined for thymine residue release from DNA following gamma-irradiation from 5 to 15 krad. Experimental conditions are designed to inhibit enzyme activity that might promote base residue release. Enzyme action is restricted in order to assess the physicochemical action of radiation on cellular DNA, and to this end irradiation is done under O2, N2, and N2O saturating conditions. Both thymine and thymidine release from bacterial DNA are detected and quantitated, and three oxygen effects are noted in comparing yields of these products. No difference in effect is observed between N2 and N2O gassing conditions, suggesting that the hydroxyl radical has little effect on thymine or thymidine release from irradiated DNA . 相似文献
A doubly labeled 3-ketoceramide, [1-14C] lignoceroyl [1-3H2] 3-ketosphingosine ( ratio, 3.61) was injected into the left ventricle of rat heart. The ceramide isolated from the livers of the animals after 1 hr incubation contained an equal ratio of 3.60. This finding strongly supports the existence for direct conversion of 3-ketoceramide to ceramide in rat liver. 相似文献
Extracts of 40 hr nauplii can convert a heavy form of elongation factor 1 (EF-1H) to a light species (EF-1L). The data indicate that a protease in the extracts is responsible for this reaction, and these findings may explain the observation that extracts from nauplii have only EF-1L whereas before hatching of the embryos EF-1H is the predominant species (Slobin and M?ller [1975] Nature 258, 452–454). 相似文献
The metabolism of 3H-androstenedione (Δ4 -A) and 3H-estriol (E3) was studied in 12 human breast tumors. Part of each tumor was analyzed for estrogen receptor content. Aliquots of tumor homogenates were incubated for 2 hr separately with 3H-δ4-A and 3H-E3 in the presence of appropriate cofactors. No distinct differences emerged in the profiles of the unconjugated metabolites of 3H-δ4-A, the major compounds in the approximate order of descendence being androsterone, androstanedione, testosterone, 5α-androstane-3α,17β-diol, epiandrosterone, and dihydrotestosterone. One tumor homogenate from an infiltrating lobular carcinoma converted 3H-Δ4-A to glucosiduronate metabolites (11%), of which androsterone, 6.4%; testosterone, 1.6%; and androstanediol, 0.6% predominated. The homogenate of this tumor and two other tumors converted 3H-E3 to 3H-E3-3S. Conversions of E3 to E3-3S In the other tumor homogenates were less than 0.6%. No correlation between receptor content and the capability of the tumor to conjugate Δ4-A or E3 evolved. However, correlations between steroid hormone metabolism and tumor histopathology may exist. 相似文献