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排序方式: 共有180条查询结果,搜索用时 15 毫秒
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S. Jakovcic J. Haddock G. S. Getz M. Rabinowitz H. Swift 《The Biochemical journal》1971,121(2):341-347
THE DEVELOPMENT OF THE INNER MITOCHONDRIAL MEMBRANE IN FOETAL AND NEONATAL RAT LIVER WAS STUDIED BY FOLLOWING THREE PARAMETERS: (1) the activity of several respiratory enzymes in homogenates and purified mitochondria, (2) the spectrophotometric determination of cytochrome content in the mitochondria and (3) the cardiolipin content in both homogenates and purified mitochondria. Respiratory-enzyme activities of homogenates of foetal liver were one-quarter to one-twentieth of those of homogenates of adult liver, and the enzyme specific activities in purified mitochondria from foetal liver were one-half to one-eighth of those in mitochondria from adult liver. The cardiolipin content of liver homogenates increased approximately twofold during the development period, but there was no significant change in the cardiolipin content of purified mitochondria. It is concluded that cell mitochondrial content approximately doubles in the immediate postnatal period. There was no evidence for an increase in the relative amount of cristae protein in mitochondria during this period to account for increases in mitochondrial enzyme specific activity, since cardiolipin and cytochrome concentrations remained unchanged and electron micrographs revealed no differences. The cause of the lower respiratory-enzyme specific activity in foetal liver mitochondria is unclear. Qualitative differences in respiratory units in foetal and mature animals are suggested. 相似文献
3.
R C Haddock M L Spell C D Baker J R Grammer J M Parks M Speidel F M Booyse 《The Journal of biological chemistry》1991,266(32):21466-21473
Recombinant human single-chain urokinase (rscu-PA), two-chain urokinase (tcu-PA), and diisopropyl-fluorophosphate-treated tcu-PA (DFP-tcu-PA) bound to cultured human and porcine endothelial cells in a rapid, saturable, dose-dependent and reversible manner. Analysis of specific binding results in cultured human umbilical vein endothelial cells (HUVECs) gave the following estimated values for Kd and Bmax: 0.57 +/- 0.08 nM (mean +/- S.E.) and 188,000 +/- 18,000 sites/cell for 125I-labeled rscu-PA; 0.54 +/- 0.10 nM and 132,000 +/- 23,900 sites/cells for 125I-labeled tcu-PA; 0.89 +/- 0.14 nM and 143,000 +/- 30,300 sites/cell for 125I-labeled DFP-tcu-PA, respectively. Values for Kd were similar for primary and subcultured (six passages) HUVECs, but Bmax values were lower in subcultured HUVECs. Similar Kd values were found in cultured porcine endothelial cells; however, Bmax values varied depending on the endothelial cell type. All 125I-labeled urokinase forms yielded similar cross-linked approximately 110-kDa ligand-receptor complexes with cultured HUVECs, and 125I-labeled DFP-tcu-PA bound to a single major approximately 55-kDa protein in whole-cell lysates (ligand blotting/autoradiography), suggesting the presence of a single major approximately 55-kDa urokinase receptor in cultured HUVECs. The approximately 55-kDa urokinase receptor, isolated from several separate batches of cultured HUVECs (3-5 micrograms of protein, approximately 1 x 10(9) cells), by ligand affinity chromatography, exhibited the following properties: retained biologic activity as evidenced by its ability to bind 125I-labeled rscu-PA by ligand blotting/autoradiography and formation of a cross-linked 125I-labeled approximately 110-kDa rscu-PA-receptor complex; single-chain approximately 55-kDa protein, following reduction; complete conversion to and formation of a single major deglycosylated approximately 35-kDa protein, following treatment with N-glycanase. 相似文献
4.
Use of chlC-lac fusions to determine regulation of gene chlC in Escherichia coli K-12. 总被引:1,自引:0,他引:1 下载免费PDF全文
Gene fusions between the lac structural genes and the chlC locus were isolated, and the regulation of lac gene expression was studied. The fused lac genes were induced by nitrate anaerobically and repressed by the presence of oxygen. 相似文献
5.
The characteristics and transparent exopolymer particle (TEP) content of marine snow formed from thecate dinoflagellates 总被引:3,自引:0,他引:3
Abundant marine snow containing diatoms and detritus, but dominatedby large, bioluminescent thecate dinoflagellates and their temporaryvegetative cysts, especially several species of the genus Gonyoulax,was observed at six stations in the Santa Barbara Channel, California,in 1989 and 1994. These aggregates were unusually cohesive andmucus rich, and contained 24 times more mass, particulateorganic carbon (POC), particulate organic nitrogen (PON) andchlorophyll a per unit aggregate volume than more common typesof marine snow formed from diatoms, fecal matter, larvaceanhouses or miscellaneous detritus. However, the relationshipbetween aggregate size and the concentration of TEP (transparentexopolymer particles which form the mucus matrix of most marinesnow) was similar to that of other types of aggregates, suggestingthat much of the copious gel-like material within dinoflagellateaggregates was not TEP. While this is the first report of abundantthecate dinoflagellates occurring within large, rapidly sinkingmarine aggregates, the data do not support the conclusion thatmass aggregation and subsequent sedimentation of blooms is partof the life history adaptations of thecate dinoflagellates,as it is for some diatoms. The high abundance of free-livingdinoflagellate cells and temporary cysts, and the similar proportionof dinoflagellates relative to other algal and chemical componentsin both aggregates and the surrounding seawater, indicate thatthe dinoflagellates were not differentially aggregating. Evenso, passive accumulation of dinoflagellates in marine snow throughaggregation processes may result in more rapid transport ofdinoflagellate-generated material to the deep ocean, alter thenature of sinking particulate matter following dinoflagellateblooms, and increase the nutritional value of marine snow asa food source for zooplankton and fish. 相似文献
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The pelagic realm of the ocean is characterized by extremelyclear water and a lack of surfaces. Adaptations to the visualecology of this environment include transparency, fluorescence,bioluminescence, and deep red or black pigmentation. While thesignals that pelagic organisms send are increasingly well-understood,the optical capabilities of their viewers, especially for predatorswith camera-like vision such as fish and squid, are almost unknown.Aquatic camera-like vision is characterized by a spherical lensfocusing an image on the retina. Here, we measured the resolvingpower of the lenses of eight species of pelagic cephalopodsto obtain an approximation of their visual capabilities. Wedid this by focusing a standard resolution target through dissectedlenses and calculating their modulation transfer functions.The modulation transfer function (MTF) is the single most completeexpression of the resolving capabilities of a lens. Since theoptical and retinal capabilities of an eye are generally well-matched,we considered our measurements of cephalopod lens MTF to bea good proxy for their visual capabilities in vivo. In general,squid have optical capabilities comparable to other organismsgenerally assumed to have good vision, such as fish and birds.Surprisingly, the optical capability of the eye of Vampyroteuthisinfernalis rivals that of humans. 相似文献
8.
Background
Many high-throughput genomic experiments, such as Synthetic Genetic Array and yeast two-hybrid, use colony growth on solid media as a screen metric. These experiments routinely generate over 100,000 data points, making data analysis a time consuming and painstaking process. Here we describe ScreenMill, a new software suite that automates image analysis and simplifies data review and analysis for high-throughput biological experiments. 相似文献9.
Alain Gagnon Matthew S. Miller Stacey A. Hallman Robert Bourbeau D. Ann Herring David JD. Earn Joaquín Madrenas 《PloS one》2013,8(8)
The worldwide spread of a novel influenza A (H1N1) virus in 2009 showed that influenza remains a significant health threat, even for individuals in the prime of life. This paper focuses on the unusually high young adult mortality observed during the Spanish flu pandemic of 1918. Using historical records from Canada and the U.S., we report a peak of mortality at the exact age of 28 during the pandemic and argue that this increased mortality resulted from an early life exposure to influenza during the previous Russian flu pandemic of 1889–90. We posit that in specific instances, development of immunological memory to an influenza virus strain in early life may lead to a dysregulated immune response to antigenically novel strains encountered in later life, thereby increasing the risk of death. Exposure during critical periods of development could also create holes in the T cell repertoire and impair fetal maturation in general, thereby increasing mortality from infectious diseases later in life. Knowledge of the age-pattern of susceptibility to mortality from influenza could improve crisis management during future influenza pandemics.
“The war is over – and I must go” Egon Schiele, 1890–1918.相似文献
10.
Penezina OP Fomovskaia GN Haddock TF Davenport RD 《Ukrainski? biokhimicheski? zhurnal》1999,71(6):56-61
L-selectin (CD62L) is the principal leukocyte adhesion molecule for the high endothelial venules of peripheral lymph nodes. This adhesion has an absolute requirement for calcium ions. Nevertheless, some studies have shown carbohydrate adhesion receptor interactions on lymphocytes and neutrophils, including the L-selectin molecule, that are Ca-independent. In the present study fucoidan, a reportedly Ca2+ independent ligand of L-selectin, and Mabs to human CD62L were coupled to magnetic polystyrene beads (MPB), as a model of leukocyte-surface interactions, and the efficiency of human leukocyte separation was investigated. 30% of Ficoll-purified human mononuclear cells and 75% of dextran-purified human leukocytes (DPHL) were specifically bound by fucoidan-modified MPB in the presence of Ca2+; 55% of dextran-purified leukocytes were specifically bound in the absence of Ca2+. The specific binding was inhibited by an excess of free fucoidan. The data obtained show the presence of Ca-independent adhesion determinants, specific to fucoidan on human leukocytes. No significant specific binding of leukocytes to fucoidan-modified MPB was found after the incubation with fresh human Ca(2+)-depleted whole blood. More than 90% of DPHL were specifically bound to MPB modified with Mabs to human CD62L irrespective of Ca2+ presence. The same degree of separation was achieved after the incubation with fresh human Ca(2+)-depleted-whole blood with anti-CD62L modified beads. 相似文献