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排序方式: 共有289条查询结果,搜索用时 15 毫秒
1.
Mitochondrial DNA of the extinct quagga: Relatedness and extent of postmortem change 总被引:4,自引:0,他引:4
Russell G. Higuchi Lisa A. Wrischnik Elizabeth Oakes Matthew George Benton Tong Allan C. Wilson 《Journal of molecular evolution》1987,25(4):283-287
Sequences are reported for portions of two mitochondrial genes from a domestic horse and a plains zebra and compared to those published for a quagga and a mountain zebra. The extinct quagga and plains zebra sequences are identical at all silent sites, whereas the horse sequence differs from both of them by 11 silent substitutions. Postmortem changes in quagga DNA may account for the two coding substitutions between the quagga and plains zebra sequences. The hypothesis that the closest relative of the quagga is the domestic horse receives no support from these data. From the extent of sequence divergence between horse and zebra mitochondrial DNAs (mtDNAs), as well as from information about the fossil record, we estimate that the mean rate of mtDNA divergence in Equus is similar to that in other mammals, i.e., roughly 2% per million years. 相似文献
2.
Fura-2 was used to estimate myoplasmic [Ca2+] in intact fibers and fiber segments from normal and diseased human muscles. Small muscle bundles (20-50 fibers) were loaded with the membrane-permeant form of the dye (Fura-2 AM). High-performance liquid chromatography was utilized to study the ability of these cells to hydrolyze Fura-2 AM. Immediately after the 30 min loading period, Fura-2 (the Ca2+ indicator) was the predominant form of the dye in all preparations and the concentration within these fibers remained stable for over 4 1/2 hours. In addition, the resting myoplasmic [Ca2+] in fiber segments from normal subjects and those susceptible to malignant hyperthermia were the same. However, halothane administration (1.5%) induced correlated increases in myoplasmic [Ca2+] and force only in fibers from the susceptible patients. In contrast, caffeine administration causes correlated increases in myoplasmic [Ca2+] and force in both types of muscle, but lower concentrations were needed to do so in the fibers from the susceptible patients. The effects of halothane and caffeine were reversible. We conclude that Fura-2 can be used successfully to estimate resting levels and changes in myoplasmic [Ca2+] in human skeletal muscle. 相似文献
3.
Construction of synthetic genes using PCR after automated DNA synthesis of their entire top and bottom strands. 总被引:5,自引:2,他引:3
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A new method is described for the direct construction of synthetic genes by applying a modified version of the polymerase chain reaction (PCR) to crude oligonucleotide mixtures made by automated solid phase DNA synthesis. Construction of the HIV-1 393 bp rev gene and the 655 bp nef gene by this method is illustrated. The sequences for the entire top and bottom strands of rev were each programmed into an automated DNA synthesizer. Following DNA synthesis, the two crude oligonucleotide solutions were mixed together, specific primers were added, and the target gene was amplified by a modified PCR technique. Although the longer (greater than 200 bases) strands comprise a very small percentage of the total DNA after solid phase synthesis, this method uses PCR to 'find' and amplify such strands to create the target gene. The rev gene constructed by this method was found to contain 4 sequence errors, which were subsequently corrected by site-directed mutagenesis. In order to evaluate the source of sequence errors, several nef genes were made from the top and bottom strand DNA synthesis solutions using independent PCR's. Results suggest that sequence errors arose from both DNA synthesis and PCR. The utility of this method in producing a functional gene is demonstrated by expression of rev in E.coli. 相似文献
4.
Experience using two CT-guided stereotactic biopsy methods 总被引:1,自引:0,他引:1
D E Bullard B S Nashold D Osborne P C Burger R Byrd C Schold W J Oakes A Friedman P Triolo P Dubois 《Applied neurophysiology》1983,46(1-4):188-192
15 patients had intracranial CT-guided stereotactic biopsies. Biopsies were performed either with a Riechert-Mundinger stereotactic frame modified for use in the CT or by using the CT scan to establish the relationship of the intracranial lesion to identifiable bony landmarks, and subsequently performing the biopsy in a standard stereotactic frame. Both systems provided safe and accurate methods for obtaining intracranial tissue. 相似文献
5.
Seven regions of 16 S rRNA have been located on the surface of the 30 S ribosomal subunit by DNA-hybridization electron microscopy. This information has been incorporated into a model for the tertiary structure of 16 S rRNA, accounting for approximately 40% of the total 16 S rRNA. A structure labeled the platform ring is proposed for a region of rRNA within the central domain. This structure rings the edges of the platform and includes regions 655-751 and 769-810. Another region, the recognition complex, consists of nucleotides 500 to 545, and occupies a region on the exterior surface of the subunit near the elongation factor Tu binding site. Ribosomal proteins that have been mapped by immunoelectron microscopy are superimposed onto the model in order to examine possible regions of interaction. Good correlation between the model locations of ribosomal proteins, and regions of rRNA protected by ribosomal proteins provide independent support for this model. 相似文献
6.
Neutrophil-mediated suppression of virus replication after herpes simplex virus type 1 infection of the murine cornea. 总被引:9,自引:3,他引:6
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![点击此处可从《Journal of virology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Herpes simplex virus type 1 (HSV-1) infection of the murine cornea induces the rapid infiltration of neutrophils. We investigated whether these cells could influence virus replication. BALB/c mice treated with monoclonal antibody (MAb) RB6-8C5 experienced a profound depletion of neutrophils in the bloodstream, spleen, and cornea. In these animals, virus titers in the eye were significantly higher than those in the immunoglobulin G-treated controls at 3 days postinfection. By day 9, virus was no longer detectable in the controls, whereas titers of 10(3) to 10(6) PFU were still present in the neutrophil-depleted hosts. Furthermore, virus spread more readily to the skin and brains of MAb RB6-8C5-treated animals, rendering them significantly more susceptible to HSV-1-induced blepharitis and encephalitis. Only 25% of the treated animals survived, whereas all of the controls lived. Although MAb RB6-8C5 treatment did not alter the CD4+ T-cell, B-cell, natural killer cell, or macrophage populations, the CD8+ T-cell population was partially reduced. Therefore, the experiments were repeated in severe combined immunodeficiency mice, which lack CD8+ T cells. Again virus growth was found to be significantly elevated in the eyes, trigeminal ganglia, and brains of the MAb RB6-8C5-treated hosts. These results strongly indicate that in both immunocompetent and immunodeficient mice, neutrophils play a significant role in helping to control the replication and spread of HSV-1 after corneal infection. 相似文献
7.
8.
9.
Prior eccentric contractions impair maximal insulin action on muscle glucose uptake in the conscious rat 总被引:1,自引:0,他引:1
Asp Sven; Watkinson Allan; Oakes Nicholas D.; Kraegen Edward W. 《Journal of applied physiology》1997,82(4):1327-1332
Asp, Sven, Allan Watkinson, Nicholas D. Oakes, and Edward W. Kraegen. Prior eccentric contractions impair maximal insulin action on muscle glucose uptake in the conscious rat.J. Appl. Physiol. 82(4):1327-1332, 1997.Our aim was to examine the effect of prioreccentric contractions on insulin action locally in muscle in theintact conscious rat. Anesthetized rats performed one-leg eccentriccontractions through the use of calf muscle electrical stimulationfollowed by stretch of the active muscles. Two days later, basal andeuglycemic clamp studies were conducted with the rats in the awakefasted state. Muscle glucose metabolism was estimated from2-[14C(U)]deoxy-D-glucoseandD-[3-3H]glucose administration, and comparisons were made between the eccentrically stimulated and nonstimulated (control) calfmuscles. At midphysiological insulin levels, effects ofprior eccentric exercise on muscle glucose uptake were notstatistically significant. Maximal insulin stimulation revealed reducedincremental glucose uptake above basal(P < 0.05 in the red gastrocnemius;P < 0.1 in the white gastrocnemiusand soleus) and impaired net glycogen synthesis in all eccentricallystimulated muscles (P < 0.05). Weconclude that prior eccentric contractions impair maximal insulin action (responsiveness) on local muscle glucose uptake and glycogen synthesis in the conscious rat. 相似文献
10.
Isolation and characterization of plasma membrane-associated cortical granules from sea urchin eggs 总被引:9,自引:6,他引:3
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Cortical granules, which are specialized secretory organelles found in ova of many organisms, have been isolated from the eggs of the sea urchins Arbacia punctulata and Strongylocentrtus pupuratus by a simple, rapid procedure. Electron micropscope examination of cortical granules prepared by this procedure reveals that they are tightly attached to large segments of the plasma membrane and its associated vitelline layer. Further evidence that he cortical granules were associated with these cell surface layers was obtained by (125)I-labeling techniques. The cortical granule preparations were found to be rich in proteoesterase, which was purified 32-fold over that detected in a crude homogenate. Similarly, the specific radioactivity of a (125)I-labeled, surface glycoprotein was increased 40-fold. These facts, coupled with electron microscope observations, indicate the isolation procedure yields a preparation in which both the cortical granules and the plasma membrane-vitelline layer are purified to the same extent. Gel electrophoresis of the membrane-associated cortical granule preparation reveals the presence of at least eight polypeptides. The major polypeptide, which is a glycotprotein of apparent mol wt of 100,000, contains most of the radioactivity introduced by (125)I-labeling of the intact eggs. Lysis of the cortical granules is observed under hypotonic conditions, or under isotonic conditions if Ca(2+) ion is present. When lysis is under isotonic conditions is induced by addition of Ca(2+) ion, the electron-dense contents of the granules remain insoluble. In contrast, hypotonic lysis results in release of the contents of the granule in a soluble form. However, in both cases the (125)I-labeled glycoprotein remains insoluble, presumably because it is a component of either the plasma membrane or the vitelline layer. All these findings indicate that, using this purified preparation, it should be possible to carry out in vitro studies to better define some of the initial, surface-related events observed in vivo upon fertilization. 相似文献