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排序方式: 共有205条查询结果,搜索用时 15 毫秒
1.
R Masse D Goudreault 《The Journal of steroid biochemistry and molecular biology》1992,42(3-4):399-410
New metabolites of mesterolone, methenolone and stenbolone bearing a C18 hydroxyl group were isolated from the steroid glucuronide fraction of urine specimens collected after administration of single 50 mg doses of these steroids to human subjects. Mesterolone gave rise to four metabolites which were identified by gas chromatography/mass spectrometry as 18-hydroxy-1 alpha-methyl-5 alpha-androstan-3,17-dione 1, 3 alpha,18-dihydroxy-1 alpha-methyl-5 alpha-androstan-17-one 2, 3 beta,18-dihydroxy-1-alpha-methyl-5 alpha-androstan-17-one 3 and 3 alpha,6 xi,18-trihydroxy-1 alpha-methyl-5 alpha-androstan-17-one 4. These data suggest that mesterolone itself was not hydroxylated at C18, but rather 1 alpha-methyl-5 alpha-androstan-3,17-dione, an intermediate metabolite which results from oxidation of mesterolone 17-hydroxyl group. In addition to hydroxylation at C18, reduction of the 3-keto group and further hydroxylation at C6 were other reactions that led to the formation of these metabolites. It is of interest to note that in the case of both methenolone and stenbolone, only one 18-hydroxylated urinary metabolite namely 18-hydroxy-1-methyl-5 alpha-androst-1-ene-3,17-dione 5 and 18-hydroxy-1-methyl-5 alpha-androst-1-ene-3,17-dione 6 were both detected in post-administration urine specimens. These data indicate that the presence of a methyl group at the C1 or C2 positions in the steroids studied is a structural feature that seems to favor interaction of hepatic 18-hydroxylases with these steroids. These data provide further evidence that 18-hydroxylation of endogenous steroids can also occur in extra-adrenal sites in man. 相似文献
2.
E. Miot D. Hoffschir J.L. Poncy R. Masse A. Le Pape S. Akoka 《Journal of medical primatology》1995,24(2):87-93
This work describes quantitative MRI assessment of primate brain maturation. Nine young baboons were followed from the age of one to 30 months. Assessment of myelination was based on the gray/white matter contrast on MR images and the evolution of T2 relaxation time respectively. The brain maturation began in the posterior fossa and progressed to the olfactory bulbs corresponding to decreasing white matter T2 values. Relaxation parameters provide new opportunities to trace the myelination process in vivo. 相似文献
3.
R. Masse 《Radiation and environmental biophysics》1995,34(4):223-227
Stochastic radiation effects following exposure to heavy ions and other high linear energy transfer (LET) radiation in space are a matter of concern when the long-term consequences of space flights are considered. This paper is an overview of the relevant literature, emphasizing uncertainties entailed from estimates of relative biological effectiveness (RBE) for different experiment end-points, making the choice of a single weighting factor for the prediction of cancer risk in man extremely difficult. Life-span-shortening studies in mice exposed to heavy ions and ongoing large-scale experiments in monkeys exposed to protons suggest that RBEs for all cancers are lower than 5. This does not exclude a much higher RBE for rare tumors such as brain tumors in monkeys or promoted Harderian gland tumours in mice at LET >80 keV/µm. Skin cancer studies in rats exposed to neon or argon resulted in similar RBE. Exposure to fission neutrons led to high RBE in all species, not excluding values much higher than 20 for specific cancers such as lung tumors in mice and all cancers in rats. The estimate of maximal RBE is, however, extremely dependent on the hypothesis made on the shape of the dose-response curves in the lower range of doses. These results suggest that neutrons may be the most hazardous component of high-LET radiation. There is only limited evidence from cancer experiments that LET >150 keV/µm results in highly decreased efficiency, but this has been found for bone cancer induction following exposure to fission fragments.Invited paper presented at the International Symposium on Heavy Ion Research: Space, Radiation Protection and Therapy, Sophia-Antipolis, France, 21–24 March 1994 相似文献
4.
A Denjean B Arnoux R Masse A Lockhart J Benveniste 《Journal of applied physiology (Bethesda, Md. : 1985)》1983,55(3):799-804
The bronchomotor effect of intratracheal administration of PAF-acether (60 micrograms X kg -1) was investigated in 37 curarized baboons mechanically ventilated with constant volume and frequency. PAF-acether caused an immediate bronchoconstriction as assessed by a marked increase in peak inspiratory pressure with no change in static pulmonary compliance and chest X-rays. There was a concomitant fall in arterial PO2 and a significant increase in ventilated unperfused lung zones. A decrease of circulating platelets and leucocytes was also observed. Local anesthesia with lidocaine and atropine did not prevent PAF-acether-induced bronchoconstriction although both markedly reduced the bronchial response to histamine. Albuterol significantly reduced the bronchial response to PAF-acether. Pretreatment with aspirin (80 mg X kg -1 iv) did not prevent the bronchoconstriction caused by PAF-acether, and intravenous or intratracheal arachidonic acid caused no bronchial response. Thus the role of cyclooxygenase metabolites of arachidonic acid in PAF-acether-induced bronchoconstriction is unlikely. In conclusion, an acute bronchoconstriction probably not triggered by stimulation of irritant receptors of the airways and associated with aggregation of platelet takes place subsequent to intratracheal administration of PAF-acether. These data suggest that PAF-acether might play a role in the pathogenesis of human asthma. 相似文献
5.
The signal produced by fluorescence in situ hybridization (FISH) often is inconsistent among cells and sensitivity is low. Small DNA targets on the chromatin are difficult to detect. We report here an improved nick translation procedure for Texas red and Alexa Fluor 488 direct labeling of FISH probes. Brighter probes can be obtained by adding excess DNA polymerase I. Using such probes, a 30?kb yeast transgene, and the rp1, rp3 and zein multigene clusters were clearly detected. 相似文献
6.
Sylvain Hanein Mathilde Garcia Lucas Fares-Taie Valérie Serre Yves De Keyzer Thierry Delaveau Isabelle Perrault Nathalie Delphin Sylvie Gerber Alain Schmitt Jean-Marc Masse Arnold Munnich Josseline Kaplan Frédéric Devaux Jean-Michel Rozet 《Biochimica et Biophysica Acta (BBA)/General Subjects》2013
Background
Hereditary optic neuropathies (HONs) are a heterogeneous group of disorders that affect retinal ganglion cells (RGCs) and axons that form the optic nerve. Leber's Hereditary Optic Neuropathy and the autosomal dominant optic atrophy related to OPA1 mutations are the most common forms. Nonsyndromic autosomal recessive optic neuropathies are rare and their existence has been long debated. We recently identified the first gene responsible for these conditions, TMEM126A. This gene is highly expressed in retinal cellular compartments enriched in mitochondria and supposed to encode a mitochondrial transmembrane protein of unknown function.Methods
A specific polyclonal antibody targeting the TMEM126A protein has been generated. Quantitative fluorescent in situ hybridization, cellular fractionation, mitochondrial membrane association study, mitochondrial sub compartmentalization analysis by both proteolysis assays and transmission electron microscopy, and expression analysis of truncated TMEM126A constructs by immunofluorescence confocal microscopy were carried out.Results
TMEM126A mRNAs are strongly enriched in the vicinity of mitochondria and encode an inner mitochondrial membrane associated cristae protein. Moreover, the second transmembrane domain of TMEM126A is required for its mitochondrial localization.Conclusions
TMEM126A is a mitochondrial located mRNA (MLR) that may be translated in the mitochondrial surface and the protein is subsequently imported to the inner membrane. These data constitute the first step toward a better understanding of the mechanism of action of TMEM126A in RGCs and support the importance of mitochondrial dysfunction in the pathogenesis of HON.General significance
Local translation of nuclearly encoded mitochondrial mRNAs might be a mechanism for rapid onsite supply of mitochondrial membrane proteins. 相似文献7.
Uxmal and Tulum are two important Mayan sites in the Yucatan peninsula. The buildings are mainly composed of limestone and grey/black discoloration is seen on exposed walls and copious greenish biofilms on inner walls. The principal microorganisms detected on interior walls at both Uxmal and Tulum were cyanobacteria; heterotrophic bacteria and filamentous fungi were also present. A dark‐pigmented mitosporic fungus and Bacillus cereus, both isolated from Uxmal, were shown to be acidogenic in laboratory cultures. Cyanobacteria belonging to rock‐degrading genera Synechocystis and Gloeocapsa were identified at both sites. Surface analysis previously showed that calcium ions were present in the biofilms on buildings at Uxmal and Tulum, suggesting the deposition of biosolubilized stone. Apart from their potential to degrade the substrate, the coccoid cyanobacteria supply organic nutrients for bacteria and fungi, which can produce organic acids, further increasing stone degradation. 相似文献
8.
Neutral fat hydrolysis and long-chain fatty acid oxidation during anaerobic digestion of slaughterhouse wastewater 总被引:4,自引:0,他引:4
Neutral fat hydrolysis and long-chain fatty acid (LCFA) oxidation rates were determined during the digestion of slaughterhouse wastewater in anaerobic sequencing batch reactors operated at 25 degrees C. The experimental substrate consisted of filtered slaughterhouse wastewater supplemented with pork fat particles at various average initial sizes (D(in)) ranging from 60 to 450 microm. At the D(in) tested, there was no significant particle size effect on the first-order hydrolysis rate. The neutral fat hydrolysis rate averaged 0.63 +/- 0.07 d(-1). LCFA oxidation rate was modelled using a Monod-type equation. The maximum substrate utilization rate (kmax) and the half-saturation concentration (Ks) averaged 164 +/- 37 mg LCFA/L/d and 35 +/- 31 mg LCFA/L, respectively. Pork fat particle degradation was mainly controlled by LCFA oxidation rate and, to a lesser extent, by neutral fat hydrolysis rate. Hydrolysis pretreatment of fat-containing wastewaters and sludges should not substantially accelerate their anaerobic treatment. At a D(in) of 450 microm, fat particles were found to inhibit methane production during the initial 20 h of digestion. Inhibition of methane production in the early phase of digestion was the only significant effect of fat particle size on anaerobic digestion of pork slaughterhouse wastewater. Soluble COD could not be used to determine the rate of lipid hydrolysis due to LCFA adsorption on the biomass. 相似文献
9.
Masse JE Wong B Yen YM Allain FH Johnson RC Feigon J 《Journal of molecular biology》2002,323(2):263-284
NHP6A is a non-sequence-specific DNA-binding protein from Saccharomyces cerevisiae which belongs to the HMGB protein family. Previously, we have solved the structure of NHP6A in the absence of DNA and modeled its interaction with DNA. Here, we present the refined solution structures of the NHP6A-DNA complex as well as the free 15bp DNA. Both the free and bound forms of the protein adopt the typical L-shaped HMGB domain fold. The DNA in the complex undergoes significant structural rearrangement from its free form while the protein shows smaller but significant conformational changes in the complex. Structural and mutational analysis as well as comparison of the complex with the free DNA provides insight into the factors that contribute to binding site selection and DNA deformations in the complex. Further insight into the amino acid determinants of DNA binding by HMGB domain proteins is given by a correlation study of NHP6A and 32 other HMGB domains belonging to both the DNA-sequence-specific and non-sequence-specific families of HMGB proteins. The resulting correlations can be rationalized by comparison of solved structures of HMGB proteins. 相似文献
10.
Derkatch IL Bradley ME Masse SV Zadorsky SP Polozkov GV Inge-Vechtomov SG Liebman SW 《The EMBO journal》2000,19(9):1942-1952
The [PSI(+)] prion can be induced by overproduction of the complete Sup35 protein, but only in strains carrying the non-Mendelian [PIN(+)] determinant. Here we demonstrate that just as [psi (-)] strains can exist as [PIN(+)] and [pin(-)] variants, [PSI(+)] can also exist in the presence or absence of [PIN(+)]. [PSI(+)] and [PIN(+)] tend to be cured together, but can be lost separately. [PSI(+)]-related phenotypes are not affected by [PIN(+)]. Thus, [PIN(+)] is required for the de novo formation of [PSI(+)], not for [PSI(+)] propagation. Although [PSI(+)] induction is shown to require [PIN(+)] even when the only overexpressed region of Sup35p is the prion domain, two altered prion domain fragments circumventing the [PIN(+)] requirement are characterized. Finally, in strains cured of [PIN(+)], prolonged incubation facilitates the reappearance of [PIN(+)]. Newly appearing [PIN(+)] elements are often unstable but become stable in some mitotic progeny. Such reversibility of curing, together with our previous demonstration that the inheritance of [PIN(+)] is non-Mendelian, supports the hypothesis that [PIN(+)] is a prion. Models for [PIN(+)] action, which explain these findings, are discussed. 相似文献