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181.
Phorbol esters induce morphologic and biochemical differentiation in U937 cells, a monocyte/macrophage-like line derived from a human histiocytic lymphoma. We are interested in the phorbol ester-stimulated release of arachidonic acid from cellular membranes and the subsequent synthesis of eicosanoids, as it may prove to correlate with the induced cellular differentiation. Undifferentiated log-phase U937 cells released little recently incorporated [3H]arachidonic acid, but phorbol 12-myristate 13-acetate increased its apparent rate of release to that of cells differentiated by exposure to phorbol myristate acetate for 3 days. Exposure of washed differentiated cells immediately prelabelled with [3H]arachidonic acid to additional phorbol myristate acetate did not augment the release of [3H]arachidonic acid. The basal release of nonradioactive fatty acids from differentiated cells was 5-10 times that of undifferentiated cells, and phorbol myristate acetate increased their release from both types of cell 2- to 3-fold. Differentiated cells immediately prelabelled with [3H]arachidonic acid exhibited greater incorporation into phosphatidylinositol and phosphatidylcholine, and contained more radioactive free arachidonic acid, compared with undifferentiated cells. Undifferentiated cells contained more radioactivity in phosphatidylserine, phosphatidylethanolamine and neutral lipids. Phorbol myristate acetate caused differentiated cells to release [3H]arachidonic acid from phosphatidylinositol, phosphatidylserine, phosphatidylcholine and phosphatidylethanolamine, but release from neutral lipids was reduced, and the content of [3H]arachidonic acid increased. In undifferentiated cells incubated with phorbol myristate acetate, radioactivity associated with phosphatidylserine, phosphatidylethanolamine and neutral lipid was reduced and [3H]arachidonic acid was unchanged. Synthesis of cyclooxygenase products exceeded that of lipoxygenase products in both differentiated and undifferentiated cells. Phorbol myristate acetate increased the synthesis of both types of product, cyclooxygenase-dependent more than lipoxygenase-dependent, especially in differentiated cells. The biological significance of these changes in lipid metabolism that accompany phorbol myristate acetate-induced differentiation are yet to be established. 相似文献
182.
Genotypic influences on reproductive aging of inbred female mice: effects of H-2 and non-H-2 alleles 总被引:1,自引:0,他引:1
The H-2 (major histocompatibility) complex of mice influences a variety of physiologic parameters. This study describes the influences of H-2 polymorphisms and other genetic influences on age-related changes (5-20 mo) in estrous cycles and fecundity. We monitored estrous cycles of virgin or retired-breeder mice of congenic strains on the background of C57BL/10Sn (B10):B10.BR/Sg (B10.BR) and B10.RIII/Sn (B10.RIII). For another comparison, we examined the C57BL/6J (B6) strain, which has the same H-2 haplotype as the B10. Estrous cycles were categorized by length during 10 mo of observations. From 5 to 15 mo of age, B10 and B10.RIII mice displayed a preponderance of 5-day cycles, B10.BR mice displayed a preponderance of 4-day cycles, and B6 mice had diminishing numbers of 4-day cycles. Age-related acyclicity differed with strain, particularly among retired breeders; B6 mice had an earlier onset and more rapid increase of acyclicity with age than the B10 congenic mice. Litters/female, maternal age at last litter, and total pups/female differed with strain; B10.BR and B10.RIII were similar and both had greater values than B10 mice. In conclusion, reproductive senescence of female mice was influenced by genes at the H-2 locus and elsewhere. 相似文献
183.
The development of mouse oocyte cortical reaction competence is accompanied by major changes in cortical vesicles and not cortical granule depth 总被引:3,自引:0,他引:3
The basis for the incompetence of the cortical reaction in germinal vesicle stage (GV) mouse oocytes was studied by evaluating cortical granules (CGs) and vesicles in GV and mature oocyte cortices. Dark and light CGs had a similar mean distance of 0.4-0.6 micron from the plasma membrane for GV and mature cortices. The cortex of mature oocytes had a large population of membrane-bounded, 0.1-1.0 micron (diameter) vesicles. More than three times as many vesicles were observed in the CG domains of mature oocytes as were observed in GV oocytes. This lack of cortical vesicles (with their potential to store calcium) and not CG depth may account for cortical reaction incompetence in GV oocytes. 相似文献
184.
Delivery of folates to the cytoplasm of MA104 cells is mediated by a surface membrane receptor that recycles 总被引:21,自引:0,他引:21
B A Kamen M T Wang A J Streckfuss X Peryea R G Anderson 《The Journal of biological chemistry》1988,263(27):13602-13609
MA104 cells, as well as several other rapidly dividing tissue culture cells, have a folate-binding protein associated with their cell surface. The protein has the properties of a membrane receptor: (a) 5-methyl[3H]tetrahydrofolic acid binds with high affinity (Kd approximately equal to 3 nM); (b) the protein is an integral membrane protein; (c) it appears to deliver physiological concentrations of 5-methyl[3H]tetrahydrofolic acid to the inside of the cell; (d) binding activity is regulated by the concentration of folate within the cell. To better understand the mechanism of action of this receptor, we have studied the pathway of folate internalization. We present evidence that during internalization: (a) folate binds to the membrane receptor; (b) the ligand-receptor complex moves into the cell; (c) the ligand is released from the receptor in an acidic intracellular compartment and moves into the cytoplasm; and (d) the unoccupied receptor returns to the cell surface. 相似文献
185.
The heterodimeric structure of factor VIII was demonstrated by two approaches. First, the native molecular weights of several partially purified fractions of factor VIII were determined by measurement of Stokes radii and sedimentation coefficients to be approx. 237 500, 201 000 and 141 000. These measured molecular weights correlated with those derived from polypeptide chain composition, in which each molecule would consist of a doublet polypeptide of Mr 83 000/81 000 plus one predominant high-Mr polypeptide of either 146 000, 120 000 or 93 000. In addition, immunoadsorption using a monoclonal antibody specific for the light-chain doublet removed all of the heavy chains. Separation of the heavy chains from the light chain by EDTA further illustrated the non-covalent nature of the heterodimers. All forms had coagulant activity which was potentiated 13-15-fold by an equimolar amount of human alpha-thrombin. Thrombin converted the Mr 83 000/81 000 doublet to one of Mr 73 000/71 000, and cleaved the largest polypeptides to a transient intermediate form of Mr 93 000 which was further cleaved to polypeptides of Mr 51 000 and 43 000. Potentiation of coagulant activity was correlated with proteolytic cleavage of either or both the doublet and the Mr 93 000 polypeptides. These data indicate that human factor VIII purified from plasma consists of a group of heterodimers, composed of a light chain of Mr 83 000 (81 000) and a heavy chain which varies in size between Mr 170 000 and 93 000, each form of which is similarly potentiated and cleaved by thrombin. 相似文献
186.
David R. McConville Dennis D. Anderson Rory N. Vosé Daniel B. Wilcox 《Hydrobiologia》1986,136(1):77-83
Species composition, relative abundance, distribution and physical habitat associations of submerged aquatic macrophytes in the main channel border (MCB) habitat of Pool 5A, Upper Mississippi River (UMR) were investigated during the summers of 1980 and 1983. The submerged aquatic macrophytes in Pool .5A MCB were a small and stable component of the river ecosystem. Submerged plants occurred primarily in small, monospecific clumps. Clumps in close proximity to each other formed plant patches. Plant patches were stable in location and number between 1980 and 1983; 82.5% of the patches first observed in 1980 were present in 1983. Submerged macrophytes covered about 10–12 ha of the 201 ha MCB in Pool 5A. Submerged plants were most common in the lower two-thirds of the pool. Ten species of aquatic macrophytes occurred on rock channel-training structures and eleven occurred on non-rock substrates in the MCB. The most common submerged plants, in order of abundance, were Vallisneria americana Michx., Heteranthra dubia Jacq., Potamogeton pectinatus L., Ceratophyllum demersum L. and Potamogeton americanus C. & S. 相似文献
187.
188.
Inhibitory Effect of Autoclaving Whey-Based Medium on Propionic Acid Production by Propionibacterium shermanii 总被引:3,自引:1,他引:2 下载免费PDF全文
Thomas M. Anderson Elizabeth A. Bodie Nelson Goodman Robert D. Schwartz 《Applied microbiology》1986,51(2):427-428
Propionic acid production by Propionibacterium shermanii was compared in pasteurized and autoclaved whey-based media. Propionic acid production decreased with increasing whey concentration in autoclaved media but not in pasteurized media. Increasing the yeast extract concentration from 5 to 10 g/liter greatly reduced the inhibitory effect of autoclaving. 相似文献
189.
Kinetic properties of cyanase 总被引:6,自引:0,他引:6
Cyanase is an inducible enzyme in Escherichia coli that catalyzes the hydrolysis of cyanate. Bicarbonate is required for activity, perhaps as a substrate, and the initial product of the reaction is carbamate, which spontaneously breaks down to ammonia and bicarbonate [Anderson, P. M. (1980) Biochemistry 19, 2882]. The purpose of this study was to characterize the kinetic properties of cyanase. Initial velocity studies showed that both cyanate and bicarbonate act as competitive substrate inhibitors. A number of monovalent anions act as inhibitors. Azide and acetate appear to act as competitive inhibitors with respect to cyanate and bicarbonate, respectively. Chloride, bromide, nitrate, nitrite, and formate also inhibit, apparently as the result of binding at either substrate site. Malonate and several other dicarboxylic dianions at very low concentrations display "slow-binding", reversible inhibition which can be prevented by saturating concentrations of either substrate. The results are consistent with a rapid equilibrium random mechanism in which bicarbonate acts as a substrate, bicarbonate and cyanate bind at adjacent anion-binding sites, and both substrates can bind at the other substrate anion binding site to give a dead-end complex. 相似文献
190.
K C Anderson J A Roach J F Daley S F Schlossman L M Nadler 《Journal of immunology (Baltimore, Md. : 1950)》1986,136(10):3612-3618
B cell-enriched preparations were prepared from human peripheral blood and lymphoid tissues by the depletion of T cells and monocytes. Only B cells by virtue of their staining with anti-B1 conjugated to fluorescein were additionally examined. Dual fluorescence staining and flow cytometric analysis demonstrated that the majority of "resting" human peripheral blood and splenic B cells co-express the B cell-restricted B1 and B2 antigens and lack B5, a B cell-restricted activation antigen, and interleukin 2 receptor (IL 2R). In contrast, nearly 2/3 and 1/3 of B1+ cells isolated from lymph node expressed IL 2R and B5 antigens, respectively. When B1+ B cells from peripheral blood and spleen were "activated" by anti-Ig, they lost the B2 antigen and acquired the B5 and/or IL 2R antigens. 2/3 of B1+ cells strongly expressed IL 2R, and up to 1/2 of B1+ cells co-expressed B5. Delineation of increased numbers of B1+ cells that co-express B5 and/or IL 2R within lymphoid tissues obtained from patients with diseases characterized by "activated" B cells provides in vivo confirmation that these phenotypic changes correlate with B cell activation. We believe that the identification and isolation of these and similar subsets of cells defined by differing cell surface phenotypes should further our understanding both of normal B cell activation and the pathophysiology of B cell disease states. 相似文献