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21.
Chandan J. Gurusinghe Michael J. Hickey John V. Hurley Bernard McC. O'Brien 《The Histochemical journal》1993,25(2):140-143
Summary An immunohistochemical method using formalin-fixed, paraffin wax-embedded sections is described for detecting strain-specific major histocompatibility complex class I antigens in knee-joint tissue from DA and Lewis strains of rat. The fixed osteochondral tissues were additionally decalcified in formic acid before processing for paraffin wax embedding. For immunohistochemistry, two monoclonal antibodies, one specific for DA class I allele RT1Aa and the other for Lewis class I allele RT1A1, were used together with the avidin-biotin immunoperoxidase procedure. It was necessary to use strain-specific normal rat serum as a diluent for the antibodies to suppress cross-strain recognition. DA-specific antibody stained positively only on DA rat sections, not on Lewis rat sections, and Lewis-specific antibody stained positively only on Lewis rat sections, and not on DA. Positive staining was localized in the bone marrow, osteochondral cells and endothelium. We propose that the use of a decalcification medium may have enhanced the immunoreactivity of the tissue. The method described can be used on sections of allografts from the two strains of rat to assess morphologically the extent of cellular replacement of the graft by the host's cells. 相似文献
22.
Wei-Min Wu Robert F. Hickey Mahendra K. Jain J. Gregory Zeikus 《Archives of microbiology》1993,159(1):57-65
Accumulation of formate to millimolar levels was observed during the growth of Methanobacterium formicicum species on H2–CO2. Hydrogen was also produced during formate metabolism by M. formicicum. The amount of formate accumulated in the medium or the amount H2 released in gas phase was influenced by the bicarbonate concentration. The formate hydrogenlyase system was constitutive but regulated by formate. When methanogenesis was inhibited by addition of 2-bromoethane sulfonate, M. formicicum synthesized formate from H2 plus HCO
inf3
sup-
or produced H2 from formate to a steady-state level at which point the Gibbs free energy (G) available for formate synthesis or H2 production was approximately -2 to -3 kJ/reaction. Formate conversion to methane was inhibited in the presence of high H2 pressure. The relative rates of conversion of formate and H2 were apparently controlled by the G available for formate synthesis, hydrogen production, methane production from formate and methane production from H2. Results from 14C-tracer tests indicated that a rapid isotopic exchange between HCOO- and HCO
inf3
sup-
occurred during the growth of M. formicicum on H2–CO2. Data from metabolism of 14C-labelled formate to methane suggested that formate was initially split to H2 and HCO
inf3
sup-
and then subsequently converted to methane. When molybdate was replaced with tungstate in the growth media, the growth of M. formicicum strain MF on H2–CO2 was inhibited although production of methane was not Formate synthesis from H2 was also inhibited. 相似文献
23.
As part of an electrophoretic study on Isoëtes, a number of Neotropical and North American species were examined for allozyme variation in TPI. Three of these species—I. storkii, I. flaccida, and I. mexicana—exhibit three distinct zones of TPI activity. The two most anodally migrating zones are comparable to the two zones found in most angiosperms and in several other species of Isoëtes. The single or three-banded phenotypes produced at these loci correspond, respectively, to the homozygous and heterozygous patterns typical of a dimeric enzyme. The most cathodal zone (zone III) differs in producing either single or two-banded phenotypes. Analyses of these three zones indicate a nearly perfect correlation between zones II and III in putative allelic constitution and relative allelic mobility. Explanations involving TPI gene duplications and/or null alleles fail to account for the peculiar banding characteristics and origin of activity zone III. An alternative hypothesis involving a protease duplication and differential post-translational modification is postulated. This hypothesis adequately explains the zone III phenotypes and fixation of the third activity zone in the species examined. Amino acid sequencing is suggested as the most direct test of this hypothesis. The taxonomic distribution of TPI III generally supports a previous, morphologically-based, hypothesis on species relationships in Isoëtes. The presence of this zone is regarded as an independent synapomorphy for a major clade of Neotropical Isoëtes. 相似文献
24.
Nucleotide Composition Bias Affects Amino Acid Content in Proteins Coded by Animal Mitochondria 总被引:16,自引:0,他引:16
We show that in animal mitochondria homologous genes that differ in guanine plus cytosine (G + C) content code for proteins
differing in amino acid content in a manner that relates to the G + C content of the codons. DNA sequences were analyzed using
square plots, a new method that combines graphical visualization and statistical analysis of compositional differences in
both DNA and protein. Square plots divide codons into four groups based on first and second position A + T (adenine plus thymine)
and G + C content and indicate differences in amino acid content when comparing sequences that differ in G + C content. When
sequences are compared using these plots, the amino acid content is shown to correlate with the nucleotide bias of the genes.
This amino acid effect is shown in all protein-coding genes in the mitochondrial genome, including cox I, cox II, and cyt b, mitochondrial genes which are commonly used for phylogenetic studies. Furthermore, nucleotide content differences are shown
to affect the content of all amino acids with A + T- and G + C-rich codons. We speculate that phylogenetic analysis of genes
so affected may tend erroneously to indicate relatedness (or lack thereof) based only on amino acid content.
Received: 3 July 1996 / Accepted: 6 November 1996 相似文献
25.
Insulin activation of phosphatidylinositol 3-kinase in human skeletal muscle in vivo 总被引:2,自引:0,他引:2
Hickey Matthew S.; Tanner Charles J.; O'Neill D. Sean; Morgan Lydia J.; Dohm G. Lynis; Houmard Joseph A. 《Journal of applied physiology》1997,83(3):718-722
Hickey, Matthew S., Charles J. Tanner, D. Sean O'Neill,Lydia J. Morgan, G. Lynis Dohm, and Joseph A. Houmard. Insulin activation of phosphatidylinositol 3-kinase in human skeletal muscle invivo. J. Appl. Physiol. 83(3):718-722, 1997.The purpose of this investigation was to determinewhether insulin-stimulated phosphatidylinositol 3-kinase (PI3-kinase)activity is detectable in needle biopsies of human skeletal muscle.Sixteen healthy nonobese males matched for age, percent fat, fastinginsulin, and fasting glucose participated in one of two experimentalprotocols. During an intravenous glucose tolerance test (IVGTT)protocol, insulin-stimulated PI3-kinase activity was determined frompercutaneous needle biopsies at 2, 5, and 15 min post-insulinadministration (0.025 U/kg). In the second group, a 2-h, 100 mU · m2 · min1euglycemic hyperinsulinemic clamp was performed, and biopsies wereobtained at 15, 60, and 120 min after insulin infusion was begun.Insulin stimulated PI3-kinase activity by 1.6 ± 0.2-, 2.2 ± 0.3-, and 2.2 ± 0.4-fold at 2, 5, and 15 min, respectively, duringthe IVGTT. During the clamp protocol, PI3-kinase was elevated by 5.3 ± 1.3-, 8.0 ± 2.6-, and 2.7 ± 1.4-fold abovebasal at 15, 60, and 120 min, respectively. Insulin-stimulatedPI3-kinase activity at 15 min post-insulin administration wassignificantly greater during the clamp protocol vs. the IVGTT(P < 0.05). These observations suggest that insulin-stimulated PI3-kinase activity is detectable inneedle biopsies of human skeletal muscle, and furthermore, that theeuglycemic, hyperinsulinemic clamp protocol may be a useful tool toassess insulin signaling in vivo. 相似文献
26.
Degradation of 4,4'-dichlorobiphenyl, 3,3',4,4'-tetrachlorobiphenyl, and 2,2',4,4',5,5'-hexachlorobiphenyl by the white rot fungus Phanerochaete chrysosporium. 总被引:2,自引:1,他引:1 下载免费PDF全文
The white rot fungus Phanerochaete chrysosporium has demonstrated abilities to degrade many xenobiotic chemicals. In this study, the degradation of three model polychlorinated biphenyl (PCB) congeners (4,4'-dichlorobiphenyl [DCB], 3,3',4,4'-tetrachlorobiphenyl, and 2,2',4,4',5,5'-hexachlorobiphenyl) by P. chrysosporium in liquid culture was examined. After 28 days of incubation, 14C partitioning analysis indicated extensive degradation of DCB, including 11% mineralization. In contrast, there was negligible mineralization of the tetrachloro- or hexachlorobiphenyl and little evidence for any significant metabolism. With all of the model PCBs, a large fraction of the 14C was determined to be biomass bound. Results from a time course study done with 4,4'-[14C]DCB to examine 14C partitioning dynamics indicated that the biomass-bound 14C was likely attributable to nonspecific adsorption of the PCBs to the fungal hyphae. In a subsequent isotope trapping experiment, 4-chlorobenzoic acid and 4-chlorobenzyl alcohol were identified as metabolites produced from 4,4'-[14C]DCB. To the best of our knowledge, this the first report describing intermediates formed by P. chrysosporium during PCB degradation. Results from these experiments suggested similarities between P. chrysosporium and bacterial systems in terms of effects of congener chlorination degree and pattern on PCB metabolism and intermediates characteristic of the PCB degradation process. 相似文献
27.
Inhibition of protein synthesis by Cl- 总被引:17,自引:0,他引:17
L A Weber E D Hickey P A Maroney C Baglioni 《The Journal of biological chemistry》1977,252(11):4007-4010
Optimum K+ concentration for protein synthesis in four eukaryotic cell-free systems is obtained with 70 to 80 mM added KCl or with 110 to 150 mM added K(OAc). The different K+ optima are due to inhibition of protein synthesis by Cl- at concentrations higher than those present in the cytoplasm of eukaryotic cells. Initiation of protein synthesis is severely inhibited with 150 mM added KCl. This inhibition results from an impairment of mRNA binding to ribosomes. The binding of initiator Met-tRNAt, however, is only slightly inhibited by 150 mM KCl. 相似文献
28.
Summary A cytochemical study involving enzymic digestions, chemical extractions and specific staining methods was made of the host-parasite interface in downy mildew infected pea plants. Enzymic hydrolysis revealed both the penetration and extrahaustorial matrices to have a proteinaceous component, possibly glycoprotein, while the extrahaustorial matrix had cellulose as an additional constituent. Intense silver proteinate staining of both matrices following a prolonged incubation in thiocarbohydrazide indicated the presence of complex carbohydrates. Carbohydrates were confirmed as constituents of both matrices following the complete suppression of silver staining using the aldehyde blocking agents dimedone and sodium borohydride. Both matrices also exhibited a marked affinity for phosphotungstic acid. Following acetylation a complete elimination of phosphotungstate staining resulted, again indicating carbohydrate as a constituent of both matrices. Digestion of the fungal cell wall using an enzyme which hydrolyses -1,3-glucans showed that these carbohydrates are important in its construction. However such enzyme treatment did not affect the structural integrity of either the penetration or extrahaustorial matrix. The extrahaustorial membrane exhibited negligible staining with phosphotungstic-chromic acid treatment, while the host plasmalemma showed a positive but variable staining reaction. A very intense staining reaction characterized the fungal plasmalemma after staining with either phosphotungstic-chromic acid, phosphotungstic acid or silver proteinate. 相似文献
29.
Subjects who stop smoking cigarettes after myocardial infarction have an improved rate of survival compared with those who continue, but to date it was not known whether the benefit persisted for more than six years. A total of 498 men aged under 60 years who had survived a first episode of unstable angina or myocardial infarction by two years were followed up by life table methods for a further 13 years. Mortality in those who continued to smoke was significantly higher (82.1%) than in those who stopped smoking (36.9%). These differences increased with time. Mortality in those who were non-smokers initially and who continued not to smoke was intermediate (62.1%). The adverse effect of continued smoking was most pronounced in those with unstable angina. Continuing to smoke increased the rate of sudden death to a greater degree in those with less severe initial attacks, while the effect of smoking on fatal reinfarctions was most apparent in those with a more complicated presentation. These findings suggest that stopping cigarette smoking is the most effective single action in the management of patients with coronary heart disease. 相似文献
30.
D R Hickey A M Berghuis G Lafond J A Jaeger T S Cardillo D McLendon G Das F Sherman G D Brayer G McLendon 《The Journal of biological chemistry》1991,266(18):11686-11694
We have determined the structures and thermodynamic stabilities of the wild type Asn-52 and unusually thermostable mutant Ile-52 yeast iso-1-cytochromes c (Das, G., Hickey, D. R. McLendon, D., McLendon, G., and Sherman, F. (1989) Proc. Natl. Acad. Sci. U.S.A. 86, 496-499). Although both structures were similar, Water-166, buried within the wild type protein, is excluded from the Ile-52 mutant, which substantially reorganizes the local hydrogen bonding. Wild type Cys-102 was replaced with alanine or serine to eliminate dimerization in vitro. The Cys-102 (wild type), Ala-102, and Ser-102 proteins were equally stable, whereas the chemically modified Cys-102-SCH3 was less stable. The order of stability observed with replacements at positions 52 and 102 was as follows: Ile-52 Ala-102 greater than Ala-52 Ala-102 greater than Asn-52 Ala-102 ("normal") greater than Gly-52 Ala-102. No significant stabilization was attributed to potential energy interactions expressed as helix-forming propensities of replacements at position 52. A high correlation between differences in free energy changes and transfer free energies suggests hydrophobic interactions are the main factor for enhancing stability in the Ile-52 mutant. Additional possible contributions to the thermostability of the Ile-52 variant are energetic effects due to packing and hydrogen bonding changes surrounding position 52. 相似文献