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101.
PEX11alpha is required for peroxisome proliferation in response to 4-phenylbutyrate but is dispensable for peroxisome proliferator-activated receptor alpha-mediated peroxisome proliferation 下载免费PDF全文
Li X Baumgart E Dong GX Morrell JC Jimenez-Sanchez G Valle D Smith KD Gould SJ 《Molecular and cellular biology》2002,22(23):8226-8240
The PEX11 peroxisomal membrane proteins promote peroxisome division in multiple eukaryotes. As part of our effort to understand the molecular and physiological functions of PEX11 proteins, we disrupted the mouse PEX11alpha gene. Overexpression of PEX11alpha is sufficient to promote peroxisome division, and a class of chemicals known as peroxisome proliferating agents (PPAs) induce the expression of PEX11alpha and promote peroxisome division. These observations led to the hypothesis that PPAs induce peroxisome abundance by enhancing PEX11alpha expression. The phenotypes of PEX11alpha(-/-) mice indicate that this hypothesis remains valid for a novel class of PPAs that act independently of peroxisome proliferator-activated receptor alpha (PPARalpha) but is not valid for the classical PPAs that act as activators of PPARalpha. Furthermore, we find that PEX11alpha(-/-) mice have normal peroxisome abundance and that cells lacking both PEX11alpha and PEX11beta, a second mammalian PEX11 gene, have no greater defect in peroxisome abundance than do cells lacking only PEX11beta. Finally, we report the identification of a third mammalian PEX11 gene, PEX11gamma, and show that it too encodes a peroxisomal protein. 相似文献
102.
Ferbeyre G de Stanchina E Lin AW Querido E McCurrach ME Hannon GJ Lowe SW 《Molecular and cellular biology》2002,22(10):3497-3508
Oncogenic activation of the mitogen-activated protein (MAP) kinase cascade in murine fibroblasts initiates a senescence-like cell cycle arrest that depends on the ARF/p53 tumor suppressor pathway. To investigate whether p53 is sufficient to induce senescence, we introduced a conditional murine p53 allele (p53(val135)) into p53-null mouse embryonic fibroblasts and examined cell proliferation and senescence in cells expressing p53, oncogenic Ras, or both gene products. Conditional p53 activation efficiently induced a reversible cell cycle arrest but was unable to induce features of senescence. In contrast, coexpression of oncogenic ras or activated mek1 with p53 enhanced both p53 levels and activity relative to that observed for p53 alone and produced an irreversible cell cycle arrest that displayed features of cellular senescence. p19(ARF) was required for this effect, since p53(-/-) ARF(-/-) double-null cells were unable to undergo senescence following coexpression of oncogenic Ras and p53. Although the levels of exogenous p53 achieved in ARF-null cells were relatively low, the stabilizing effects of p19(ARF) on p53 could not explain the cooperation between oncogenic Ras and p53 in promoting senescence. Hence, enforced p53 expression without oncogenic ras in p53(-/-) mdm2(-/-) double-null cells produced extremely high p53 levels but did not induce senescence. Taken together, our results indicate that oncogenic activation of the MAP kinase pathway in murine fibroblasts converts p53 into a senescence inducer through both quantitative and qualitative mechanisms. 相似文献
103.
Maroun Abi Moussa François Guillé Georges Kyriakou Jean François Griveau Dominique Le Lannou Bernard Lobel 《Andrologie》2003,13(2):122-127
Objective
To assess the efficacy and safety of percutaneous testicular biopsy to provide sperm cells for ICSI in male patients with azoospermia not amenable to surgical treatment.Materials and methods
From October 1995 to December 2001, 175 biopsies were performed in men with azoospermia to provide material for intracytoplasmic sperm injection. Azoospermia was obstructive (OA) in 41 cases and non-obstructive (NOA) in 134 cases. Open biopsy was performed in the first 15 patients in the series and percutaneous biopsy was performed on an outpatient basis, under local anesthesia, with a Biopty Gun® (14G needle), in the subsequent patients as the first step in management. Open surgical biopsies were performed in another 15 patients following a sperm cell-negative percutaneous biopsy.Results
All biopsies performed for OA were positive, but only 51/134 biopsies (38%) were positive in the NOA group. The material provided by percutaneous biopsy, when positive for sperm cells, was always sufficient to perform ICSI. When percutaneous biopsy was negative, open surgical biopsy failed to give better results. Five men developed minor complications (acute hematocele) following percutaneous biopsies requiring reoperation for hemostasis (3.12%). No major complications were observed. Results were comparable in terms of fertilization and pregnancy rates whether fresh or frozen-thawed sperm was used.Conclusion
Percutaneous testicular sperm extraction is a safe, well-tolerated and cost-effective procedure in the management of male-factor infertility related to azoospermia. 相似文献104.
Trostchansky A Ferrer-Sueta G Batthyány C Botti H Batinić-Haberle I Radi R Rubbo H 《Free radical biology & medicine》2003,35(10):1293-1300
We have studied the role of three Mn(III)porphyrins differing in charge, alkyl substituent length and reactivity, on LDL exposed to low fluxes of peroxynitrite (PN) in the presence of uric acid. Mn(III)porphyrins (5 microM, MnTE-2-PyP(5+), MnTnOct-2-PyP(5+), and MnTCPP(3-)) plus uric acid (300 microM) inhibited cholesteryl ester hydroperoxide formation, changes in REM as well as spared alpha- and gamma-tocopherol. MnTnOct-2-PyP(5+), the more lipophilic compound, was the most effective in protecting LDL lipids, while MnTCPP(3-) exerted the lesser protection. Mn(III)porphyrins react fast with PN ( approximately 10(5)-10(7) M(-1) s(-1)) to yield a O=Mn(IV) complex. The stoichiometry of uric acid consumption was approximately 1.7 moles per mol of PN, in agreement with reactions with both the O=Mn(IV) complex and nitrogen dioxide. A shift from an anti- to a pro-oxidant action of the Mn(III)porphyrin was observed after uric acid was significantly consumed, supporting competition reactions between LDL targets and uric acid for the O=Mn(IV) complex. Overall, the data is consistent with the catalytic reduction of PN in a cycle that involves a one electron oxidation of Mn(III) to Mn(IV) by PN followed by the reduction back to Mn(III) by uric acid. These antioxidant effects should predominate under in vivo conditions having plasma uric acid concentration range between 150 and 500 microM. 相似文献
105.
Ruso JM Besada L Martínez-Landeira P Seoane L Prieto G Sarmiento F 《Journal of liposome research》2003,13(2):131-145
An investigation on the dependence of electrophoretic mobilities of unilamellar vesicles of phosphatidylcholine-cholesterol-phosphatidylinositol (PC-Chol-PI) on the concentration of several cations with variations in the relation charge/radius in the range Na+, K+, Cs+, Mg2+, Ca2+, Ba2+, Al3+, and La3+ has been realized. Plots of zeta potential against ion concentration exhibit a maximum for all the cations under study, the position of the maximum is greatly affected by the charge of the ion. From the feature of these plots two phenomenon were observed: an initial binding of cations into the slipping plane for ion concentration below the maximum and a phenomenon of vesicle association for concentration above the maximum. To confirm these observations measurements on dynamic light scattering were performed to obtain the corresponding size distribution of the liposomes at different ion concentrations. Finally the ability of the Stern isotherm to describe the adsorption of the cations to vesicles was tested by two methods. The two main parameters of the theory: the total number of adsorption sites per unit area, N1, and the equilibrium constant, K; (and consequently the free energy of adsorption, deltaG0ads) were calculated for the different ions, showing good agreement. The equilibrium constants of adsorption have been found to obey a linear relationship with ion radius the slope of which decreases with the ion charge. 相似文献
106.
The normal processing of biological samples for Scanning Electron Microscopy, includes treatment with aldehyde (1 to 2 hours), postfixation with Osmium (1 hour), followed by dehydration in a ascending grade of ethanol (30 a 100%), 10 to 15 minutes in each step, and finally drying. This procedure takes at least 8 hours. In this work, samples of mosquitoes (Aedes), protozoa (Tritrichomonas muris), bacteria (Clostridium oceanicum), murine liver, and small intestine were processed in the same manner in a domestic microwave oven for two minutes at 20% of its maximum power. The complete procedure from the initial fixation to dehydration in 100% ethanol was reduced to one hour with good preservation of the ultrastructural details of the specimens. 相似文献
107.
Phylogenetic Relationships of Acanthocephala Based on Analysis of 18S Ribosomal RNA Gene Sequences 总被引:3,自引:0,他引:3
García-Varela M Pérez-Ponce de León G de la Torre P Cummings MP Sarma SS Laclette JP 《Journal of molecular evolution》2000,50(6):532-540
Acanthocephala (thorny-headed worms) is a phylum of endoparasites of vertebrates and arthropods, included among the most
phylogenetically basal tripoblastic pseudocoelomates. The phylum is divided into three classes: Archiacanthocephala, Palaeacanthocephala,
and Eoacanthocephala. These classes are distinguished by morphological characters such as location of lacunar canals, persistence
of ligament sacs in females, number and type of cement glands in males, number and size of proboscis hooks, host taxonomy,
and ecology. To understand better the phylogenetic relationships within Acanthocephala, and between Acanthocephala and Rotifera,
we sequenced the nearly complete 18S rRNA genes of nine species from the three classes of Acanthocephala and four species
of Rotifera from the classes Bdelloidea and Monogononta. Phylogenetic relationships were inferred by maximum-likelihood analyses
of these new sequences and others previously determined. The analyses showed that Acanthocephala is the sister group to a
clade including Eoacanthocephala and Palaeacanthocephala. Archiacanthocephala exhibited a slower rate of evolution at the
nucleotide level, as evidenced by shorter branch lengths for the group. We found statistically significant support for the
monophyly of Rotifera, represented in our analysis by species from the clade Eurotatoria, which includes the classes Bdelloidea
and Monogononta. Eurotatoria also appears as the sister group to Acanthocephala.
Received: 12 October 1999 / Accepted: 8 February 2000 相似文献
108.
Adherence of Bilophila wadsworthia to the cultured human embryonic intestinal cell line, Intestine 407 (Int 407), varied among the strains tested from strongly adherent (76-100% cells positive for one or more adherent bacteria) to non- or weakly adherent (0-25% positive cells). Although negative staining revealed that infrequent cells of an adherent strain, WAL 9077, the adherent type-strain, WAL 7959, and a non-adherent strain, WAL 8448, expressed loosely associated fimbrial structures, a role for these structures in adhesion could not be confirmed with either scanning or thin-section electron micrography. Ruthenium red staining of thin-section preparations and subsequent electron microscopy failed to reveal an extensive extracellular polysaccharide layer. SDS-PAGE analysis of crude outer membrane fractions of WAL 9077 and WAL 8448 demonstrated clear differences in their major and minor outer membrane protein components. Thus, we postulate that the adherence of B. wadsworthia to Int 407 cells is mediated by an outer membrane or cell wall component. 相似文献
109.
Botrytis cinerea is a pathogenic filamentous fungus, which infects more than 200 plant species. The enzymes secreted by B. cinerea play an important role in the successful colonization of a host plant. Some of the secreted enzymes are involved in the degradation of pectin, a major component of the plant cell wall. A total of 126 proteins secreted by B. cinerea were identified by growing the fungus on highly or partially esterified pectin, or on sucrose in liquid culture. Sixty‐seven common proteins were identified in each of the growth conditions, of which 50 proteins exhibited a SignalP motif. Thirteen B. cinerea proteins with functions related to pectin degradation were identified in both pectin growth conditions, while only four were identified in sucrose. Our results indicate it is unlikely that the activation of B. cinerea from the dormant state to active infection is solely dependent on changes in the degree of esterification of the pectin component of the plant cell wall. Further, these results suggest that future studies of the B. cinerea secretome in infections of ripe and unripe fruits will provide important information that will describe the mechanisms that the fungus employs to access nutrients and decompose tissues. 相似文献
110.