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81.
Macrocystis pyrifera gametophytes were exposed in batch culture to varying mass concentrations of buried, sewage-contaminated, historically discharged sediment that had been sampled from two sites off Palos Verdes Peninsula, California. Significant gametophytic vegetative growth inhibition was detected in six days, using digital image analysis at sediment loadings ranging from 0.15 to 14.5 g in 500 mL nutrient-enriched seawater. Inhibition declined at low sediment loadings and increased at high loadings as cultures aged. Sediments corresponding to the historic emissions peak taken 2 km from the Joint Water Pollution Control Plant outfall inhibited vegetative growth more than did sediments sampled 13 km distant. Analysis showed elevated aqueous Cd(II), Cr(II) and p,p-DDE concentrations in high sediment-loading culture medium. Inhibition by Zn(II) alone was observed at similar concentrations in other experiments, but synergism or antagonism by other toxicants remains possible. 相似文献
82.
Antisera to vertebrate actin and actin-binding proteins were used to characterize the cytoskeleton of adult Schistosoma mansoni. Actin, alpha-actinin and tropomyosin immunoreactivities were detected in the cytoplasm of the apical tegument. Antiserum to alpha-actinin bound to the tegumental spines and this protein may be involved in cross-linking of spine actin filaments. Actin, alpha-actinin and tropomyosin antisera bound to the musculature. Strongest immunoreactivity was seen in the parenchyma. Antisera to actin, alpha-actinin, tropomyosin and spectrin bound to parenchyma cells including those of the tubercles, suggesting that these proteins are located in muscle cell bodies. The distribution of cytoskeletal proteins is discussed in relation to tegumental repair processes. 相似文献
83.
An amino-terminal signal sequence abrogates the intrinsic membrane-targeting information of mitochondrial uncoupling protein 总被引:5,自引:0,他引:5
Mitochondrial uncoupling protein, a polytopic integral protein of the inner membrane, is initially made in the cytoplasm as a soluble polypeptide (307 amino acids) lacking a cleavable targeting (signal) peptide. Earlier studies (Liu, X., Bell, A. W., Freeman, K. B., and Shore, G. C. (1988) J. Cell Biol. 107, 503-509) identified internal regions of the molecule that are critical for targeting and membrane insertion. Here, we demonstrate that the ability of uncoupling protein to insert into the inner membrane is abrogated when the molecule is fused behind the matrix-targeting signal of preornithine carbamyltransferase; the hybrid protein was imported across the inner membrane and deposited in the matrix where it was processed. In this context, however, the processed product remained in the matrix and was incapable of inserting into the inner membrane. 相似文献
84.
Characterization of cloned murine cytolytic T cell lines 总被引:1,自引:0,他引:1
H D Engers D Collavo M North H von Boehmer W Haas H Hengartner M Nabholz 《Journal of immunology (Baltimore, Md. : 1950)》1980,125(4):1481-1486
Murine cytolytic T lymphocytes can be kept in continuous culture apparently indefinitely by repeated passage in a concanavalin A-induced growth promoting medium. Some of these long-term cell lines maintain their cytolytic activity. Starting from three such populations, several cloned cytolytic T cell lines were derived and subsequently subcloned one or more times. Considerable variation in the levels of cytolytic activity was observed between different subclones; some initially active subclones lost activity with prolonged culture. In addition, one of the clones appeared to progressively lose the relative specificity demonstrated during the earlier passages of the parent cell line. 相似文献
85.
T W Meade R Chakrabarti A P Haines W R North Y Stirling 《BMJ (Clinical research ed.)》1979,1(6157):153-156
As part of a study to determine the extent to which the haemostatic system is implicated in the onset of clinically manifest ischaemic heart disease, characteristics influencing fibrinolytic activity (FA) and plasma fibrinogen concentrations were examined in 1601 men aged 18-64 and 707 women aged 18-59 in several occupational groups in North-west London. In men FA noticeably decreased till the age of about 58, when there was a small rise. In women a small increase in FA between 18 and about 40 was followed by a slightly larger fall between 40 and 59. There was a pronounced negative association of FA with obesity. FA was significantly less in smokers than non-smokers, though the effect was not large. FA increased with alcohol consumption. FA in men appeared to be greatest in the lower social classes, and men on night shift had poorer FA than those on day work. FA was greater in women using oral contraceptives than in those not using these preparations. In both sexes FA increased with exercise, but there were no associations between any of the characteristics studied and the increase. Plasma fibrinogen concentrations increase with age and obesity, are higher in smokers than non-smokers, and fall with alcohol consumption. In women the concentrations are higher in those using oral contraceptives. The general epidemiology of FA and plasma fibrinogen concentrations suggests that they may well be implicated in the pathogenesis of ischaemic heart disease. 相似文献
86.
E W Ades D J Phillips S L Shore D S Gordon M G LaVia C M Black C B Reimer 《Journal of immunology (Baltimore, Md. : 1950)》1976,117(6):2119-2123
Fluorescein-conjugated staphylococcal protein A (SPA) was complexed with either: 1) heat-aggregated IgG, 2) B cell specific antibody, or 3) T cell specific antibody and then used for an immunofluorescent analysis of mononuclear cell surfaces. Cellular Fc receptors failed to recognize the Fc region of aggregated IgG that had been blocked by SPA. Moreover, fluoresceinated SPA that had been complexed either with anti-Fab (B-cell specific) or T cell-specific antisera prevented the nonspecific binding of these reagents to the IgG-Fc receptors on mononuclear cells, thereby permitting the latter to be properly identified as B or T lymphocytes. In addition, when unconjugated SPA was added to presensitized target cells in a test for antibody-dependent cell-mediated cytotoxicity, cytolysis was abrogated. 相似文献
87.
The site of cellulose synthesis. Hormone treatment alters the intracellular location of alkali-insoluble beta-1,4-glucan (cellulose) synthetase activities 总被引:16,自引:1,他引:15 下载免费PDF全文
Membrane preparations from growing regions of 8-day old Pisum sativum epicotyls contain multiple beta-1,4-glucan (cellulose) synthetase activities (UDP- or GDP-glucose: beta-1,4-glucan-glucosyl transferase), and the levels of some of these are influenced by treatments with the growth hormone, indoleacetic acid (IAA). When membranes from control epicotyl segments (zero time) are fractionated by isopycnic sedimentation in sucrose density gradients, all of the synthetase activities are associated mainly with Golgi membrane (density 1.55 g/cm3). After decapitation and treatment of epicotyls with IAA, synthetases also appear in a smooth vesicle fraction (density 1.11 g/cm3) which is rich in endoplasmic reticulum (ER) marker enzyme. Major fractions of these synthetases are not recovered in association with plasma membrane or washed cell walls. When [14-C]sucrose is supplied in vivo to segments +/- IAA, radioactive cellulose is deposited only in the wall. Cellulose or cellodextrin precursors do not accumulate in those membranes in which synthetase activities are recovered in vitro. In experiments where tissue slices containing intact cells are supplied with [14C]sugar nucleotide in vitro, alkali-insoluble beta-1,4-glucan is synthesized (presumably outside the protoplast) at rates which greatly exceeded (20-30 times) those obtained using isolated membrane preparations. Progressive disruption of cell structure results in increasing losses of this high activity. These results are consistent with the interpretation that Golgi and ER-associated synthetases are not themselves loci for cellulose synthesis in vivo, but represent enzymes in transit to sites of action at the wall:protoplast omterface. There they operate only if integrity of cellular organization is maintained. 相似文献
88.
Robert F. Foran Ernest H. Shore Phillip M. Levin Richard L. Treiman 《The Western journal of medicine》1975,123(4):269-274
Long-term results with 52 bovine, 53 saphenous vein and 78 radial-cephalic arteriovenous fistulas (AVF) were analyzed. Side-to-end radial-cephalic AVF provided the best patency data, and remain the preferred access system for hemodialysis. Bovine AVF were next in ranking with better patency rates than for the saphenous vein AVF studied. Corrected one-year patency rates were 71 percent for bovine, 45 percent for saphenous and 91 percent for radial-cephalic AVF. The incidence of nonthrombotic complications with bovine AVF was higher than with saphenous vein AVF. Distal ischemia due to “steal” and certain bleeding and wound complications were unique to bovine AVF. Excellent dialysis blood flow rates and easy accessibility were provided by bovine grafts. When a satisfactory radial-cephalic AVF cannot be created, bovine graft AVF is an acceptable alternative for hemodialysis access. 相似文献
89.
T Ouellet C Lampron M Lussier L Lapointe A Royal 《Biochimica et biophysica acta》1990,1048(2-3):194-201
F9 embryonal carcinoma cells (F9EC) can be induced to differentiate in vitro into epithelial cells expressing keratin 8 (K8) and keratin 18 (K18). cDNAs corresponding to K8 and K18 mRNAs were cloned and used to study the change in the abundance of these mRNAs during differentiation of F9 cells into parietal endoderm-like cells by treatment with retinoic acid (RA) or with RA and dibutyryl cAMP (Bt2cAMP). Using an RNase protection assay, it was determined that K8 mRNA was induced slightly before K18 mRNA and that it accumulated to a greater extent than K18 mRNA. Furthermore, differentiation in presence of Bt2cAMP plus RA resulted in an earlier induction of the two mRNAs and a higher level of expression of K8 mRNA. These results indicate that K8 and K18 mRNAs are regulated differently in F9 cells. 相似文献
90.