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81.
Frank A. Pedersen 《Human nature (Hawthorne, N.Y.)》1991,2(3):271-291
Secular change in sex ratios is examined in relation to experience in the family. Two theoretical perspectives are outlined: Guttentag and Secord’s (1983) adaptation of social exchange theory, and sexual selection theory. Because of large-scale change in number of births and typical age differentials between men and women at marriage, low sex ratios at couple formation ages existed in the U.S. between 1965 and the early 1980s. The currently high sex ratios, however, will persist until the end of the century. High sex ratios appear to be associated with lower divorce rates, male commitment to careers that promise economic rewards, male willingness to engage in child care, higher fertility, and higher rates of sexual violence. Sexual selection theory calls attention to intrasexual competition in the numerically larger sex. 相似文献
82.
Complementation between urokinase-producing and receptor-producing cells in extracellular matrix degradation. 总被引:11,自引:0,他引:11 下载免费PDF全文
P H Quax N Pedersen M T Masucci E J Weening-Verhoeff K Dan? J H Verheijen F Blasi 《Molecular biology of the cell》1991,2(10):793-803
The respective roles of urokinase plasminogen activator (u-PA) and the u-PA receptor in extracellular matrix degradation was investigated. Human pro-u-PA and the human u-PA receptor were expressed independently by two different mouse LB6 cell lines. The matrix degradation capacity of these cell lines individually or in coculture was studied. Although pro-u-PA-producing cells alone degrade the matrix in the presence of plasminogen, u-PA-receptor producing cells do not. Cocultivation of a small fraction of pro-u-PA-producing cells with the receptor-producing cells increases the rate of matrix degradation at least threefold. By immunoprecipitation it was shown that cocultivation of the two cell lines increases the conversion of the inactive pro-u-PA to the active two chain u-PA. The enhancement of matrix degradation and of pro-u-PA activation requires actual binding of pro-u-PA to its receptor because it is inhibited by u-PA-receptor antagonists. The u-PA receptor must be cell associated, as binding of pro-u-PA to a receptor solubilized from the cell surface with phosphatidyl-inositol specific phospholipase C did not enhance the activation of pro-u-PA in the presence of plasminogen. The finding that activity of u-PA is enhanced when it is bound to its receptor, even when the receptor is produced by a different cell, might have important implications for the mechanisms of u-PA-induced extracellular proteolysis in vivo. 相似文献
83.
M Del Rosso N Pedersen G Fibbi M Pucci G Dini E Anichini F Blasi 《Experimental cell research》1992,203(2):427-434
We have shown the presence of surface receptors for the amino-terminal fragment (ATF) of human urokinase-type plasminogen activator (u-PA) on an in vitro-established cell line of human epidermal origin by both radio-binding assays with human 125I-u-PA-ATF and transmission electron microscopy of a gold-u-PA complex. On the basis of cross-linking experiments with 125I-u-PA-ATF and subsequent autoradiography of the gels we have observed that such receptors are not spontaneously released into the culture medium. The treatment with phosphatidylinositol-specific phospholipase C induces the release of the receptor, which behaves as a glycosyl phosphatidyl inositol(GPI)-anchored protein. Phase-partitioning experiments on cell lysates have shown that the receptor partitions into the detergent phase. By detaching cell monolayers with the chelating agent EDTA we have prepared the cell-substratum contact sites of these cells, which represent only the 3.5% of the surface membrane of monolayered cells. Such plasma membrane remnants are highly selected since they contain about 43% of total u-PA-ATF binding sites. Such binding sites show the same biochemical and morphological characteristics of u-PA-ATF receptors observed in the monolayered cells, thus indicating that u-PA is selectively concentrated at the level of cell-substratum contacts. This is likely to enable directional proteolysis for cell migration and invasion. 相似文献
84.
P Berkowitz N W Huh K E Brostrom M G Panek D J Weber A Tulinsky L G Pedersen R G Hiskey 《The Journal of biological chemistry》1992,267(7):4570-4576
45Ca(II) binding studies (equilibrium dialysis) on the kringle domain of bovine prothrombin fragment 1 were conducted using a mixture of peptides (residues 43-156 and 46-156) resulting from limited alpha-chymotryptic hydrolysis of fragment 1. Analysis of the Scatchard plot of these data indicates a single, low affinity Ca(II)-binding site to be present. Similar results were obtained from studies on the decarboxylated fragment 1 derivative, 10-gamma-MGlu-fragment 1. Acetylation of bovine fragment 1 in the absence of Ca(II) or Mg(II) ions results in the loss of the metal ion-promoted quenching of the intrinsic Trp fluorescence of the protein and the Ca(II)-mediated binding to phosphatidylserine/phosphatidylcholine (PS/PC) vesicles. The acetylation of the NH2 alpha-group of Ala-1 has been shown (Welsch, D. J., and Nelsestuen, G. L. (1988) Biochemistry 27, 4946-4952) to abolish the PS/PC binding property of fragment 1. The present study demonstrates that acetylation of a second site possibly Ser-79 or Thr-81 using the conditions described in the preceding paper results in loss of both the fluorescence transition and the Ca(II)-mediated PS/PC binding of the resulting protein derivative. Removal of the O-acetyl group at the Ser-79/Thr-81 site is accomplished by aminolysis with 0.2 M hydroxylamine, pH 10, 50 degrees C; the fluorescence transition is partially restored. PS/PC binding is partially restored if the NH2 alpha-group of Ala-1 is trinitrophenylated but is not restored if the NH2 alpha-group of Ala-1 is acetylated. We conclude that the Ser-79/Thr-81 site may represent a portion of the metal ion-binding site within the kringle domain of fragment 1. Occupancy of this site by a Ca(II) ion appears to be important in the binding of the protein to PS/PC vesicles. 相似文献
85.
D J Weber P Berkowitz M G Panek N W Huh L G Pedersen R G Hiskey 《The Journal of biological chemistry》1992,267(7):4564-4569
Chemical modification of bovine prothrombin fragment 1 according to the procedure of D. J. Welsch and G. L. Nelsestuen (1988) [Biochemistry 27, 4946-4952 and ealier papers] provided a series of fragment 1 derivatives in which various nitrogen-containing side chains were N-acetylated and/or N-2,4,6-trinitrophenylated. In addition the des-[Ala-1,Asn-2]- and des-[Ala-1,Asn-2,Lys-3]-fragment 1 derivatives were prepared by limited enzymatic hydrolysis of fragment 1 using cathepsin C and plasmin, respectively. Quantitative studies on the Ca(II) binding of these proteins have been accomplished using 45Ca(II) equilibrium dialysis. Binding of these fragment 1 derivatives to phosphatidylserine/phosphatidylcholine (PS/PC) vesicles (25:75) in the presence of Ca(II) ions has been studied using the light-scattering technique. Acylation of the 5 lysine residues of fragment 1 by the action of acetic anhydride (500-fold molar excess) in the presence of 75 mM Ca(II), pH 8.0, results in loss of positive cooperativity in Ca(II) binding (Scatchard plot) and an increase in the number of Ca(II) ions bound. The Ca(II)-dependent PS/PC binding of the acylated protein is reduced. Removal of 2 and 3 residues from the amino terminus likewise leads to loss of positive cooperativity in Ca(II) binding and reduced binding affinity to PS/PC vesicles. The important role of the amino-terminal 1-10 sequence is discussed. We conclude that positive cooperativity in Ca(II) binding is not a prerequisite for the Ca(II)-dependent binding of bovine prothrombin fragment 1 to PS/PC vesicles. 相似文献
86.
Molecular cloning of osteoma-inducing replication-competent murine leukemia viruses from the RFB osteoma virus stock. 下载免费PDF全文
L Pedersen W Behnisch J Schmidt A Luz F S Pedersen V Erfle P G Strauss 《Journal of virology》1992,66(10):6186-6190
We report the molecular cloning of two replication-competent osteoma-inducing murine leukemia viruses from the RFB osteoma virus stock (M. P. Finkel, C. A. Reilly, Jr., B. O. Biskis, and I. L. Greco, p. 353-366, in C. H. G. Price and F. G. M. Ross, ed., Bone--Certain Aspects of Neoplasia, 1973). Like the original RFB osteoma virus stock, viruses derived from the molecular RFB clones induced multiple osteomas in mice of the CBA/Ca strain. The cloned RFB viruses were indistinguishable by restriction enzyme analysis and by nucleotide sequence analysis of their long-terminal-repeat regions and showed close relatedness to the Akv murine leukemia virus. 相似文献
87.
L. Mario Amzel Mario A. Bianchet Peter L. Pedersen 《Journal of bioenergetics and biomembranes》1992,24(5):429-433
It has been proposed that during ATP synthesis/hydrolysis F1 ATPases experience a complex pattern of nucleotide binding and release during the catalytic cycle (binding change mechanism). This type of mechanism has implications that can be correlated with the structure of the enzyme. F1-ATPases (stoichiometry 33) are essentially a symmetrical trimer of pairs of the major subunits ( and ); the minor subunits (, and ) are in single copies and interact with the trimer in an asymmetrical fashion. The asymmetry introduced by the minor subunits has important structural and functional consequences: (1) it introduces differences between the potentially equivalent binding and catalytic sites in the major subunits, (2) it restricts the ways in which a binding change mechanism can occur, and (3) it governs the way in which the F1 interacts with the (asymmetrical) F0 sector. 相似文献
88.
Krishan K. Arora David M. Parry Peter L. Pedersen 《Journal of bioenergetics and biomembranes》1992,24(1):47-53
Hexokinase plays an important role in normal glucose-utilizing tissues like brain and kidney, and an even more important role in highly malignant cancer cells where it is markedly overexpressed. In both cell types, normal and transformed, a significant portion of the total hexokinase activity is bound to particulate material that sediments upon differential centrifugation with the crude mitochondrial fraction. In the case of brain, particulate binding may constitute most of the total hexokinase activity of the cell, and in highly malignant tumor cells as much as 80 percent of the total. When a variety of techniques are rigorously applied to better define the particulate location of hexokinase within the crude mitochondrial fraction, a striking difference is observed between the distribution of hexokinase in normal and transformed cells. Significantly, particulate hexokinase found in rat brain, kidney, or liver consistently distributes with nonmitochondrial membrane markers whereas the particulate hexokinase of highly glycolytic hepatoma cells distributes with outer mitochondrial membrane markers. These studies indicate that within normal tissues hexokinase binds preferentially to non-mitochondrial receptor sites but upon transformation of such cells to yield poorly differentiated, highly malignant tumors, the overexpressed enzyme binds preferentially to outer mitochondrial membrane receptors. These studies, taken together with the well-known observation that, once solubilized, the particulate hexokinase from a normal tissue can bind to isolated mitochondria, are consistent with the presence in normal tissues of at least two different types of particulate receptors for hexokinase with different subcellular locations. A model which explains this unique transformation-dependent shift in the intracellular location of hexokinase is proposed. 相似文献
89.
90.
Mineralization of 2,4-dichlorophenoxyacetic acid (2,4-D) by two Alcaligenes eutrophus strains and one Pseudomonas cepacia strain containing the 2,4-D degrading plasmids pJP4 or pRO101 (=pJP4::Tn1721) was tested in 50 g (wet wt) samples of non-sterile soil. Mineralization was measured as 14C-CO2evolved during degradation of uniformly-ring-labelled 14C-2,4-D. When the strains were inoculated to a level of approximately 108 CFU/g soil, between 20 and 45% of the added 2,4-D (0.05 ppm, 10 ppm or 500 ppm) was mineralized within 72 h. Mineralization of 0.05 ppm and 10 ppm, 2,4-D by the two A. eutrophus strains was identical and rapid whereas mineralization by P. cepacia DBO1(pRO101) occurred more slowly. In contrast, mineralization of 500 ppm 2,4-D by the two A. eutrophus strains was very slow whereas mineralization by P. cepacia DBO1 was more rapid. Comparison of 2,4-D mineralization at different levels of inoculation with P. cepacia DBO1(pRO101) (6×104, 6×106 and 1×108 CFU/g soil) revealed that the maximum mineralization rate was reached earlier with the high inoculation levels than with the low level. The kinetics of mineralization were evaluated by nonlinear regression analysis using five different models. The linear or the logarithmic form of a three-half-order model were found to be the most appropriate models for describing 2,4-D mineralization in soil. In the cases in which the logarithmic form of the three-half-order model was the most appropriate model we found, in accordance with the assumptions of the model, a significant growth of the inoculated strains.Abbreviations 2,4-D
2,4-dichlorophenoxyacetic acid
- CFU
colony forming units
- PTYG
peptone, tryptone, yeast & glucose
- DPM
disintegrations per minute 相似文献