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991.
Seventeen species ofHibiscus sectionFurcaria are native to the New World, of which 12 (one diploid, nine tetraploids, one octoploid and one decaploid) have been studied cytotaxonomically. New chromosome counts (2n=4x=72) are reported forH. cucurbitaceus, H. flagelliformis, H. kitaibelifolius, andH. laxiflorus. Seventeen types of tetraploid interspecific hybrids (seven new to this study) all showed complete meiotic chromosome homology (genome formulaGGPP) and normal floral development. That all hybrids were nevertheless almost completely sterile suggests a cytoplasmic component to the genetic differentiation of the species. The diversification of the tetraploid species in habits, habitats and geographical ranges is considerable, despite their similar genome constitutions. A key to 17 native and four introduced African species is presented.Hibiscus cerradoensis sp. nov. is described. 相似文献
992.
R Rothrock S T Perry K R Isham K L Lee F T Kenney 《Biochemical and biophysical research communications》1983,113(2):645-649
Rat fetuses of 20 days gestational age were treated in utero with the inhibitor of DNA methylation, 5-azacytidine. The liver enzyme tyrosine aminotransferase, normally expressed at very low levels until several hours after birth, was increased by the drug in the fetal livers after a lag period of about 9 hours, reaching a level 70-fold above control levels 18 hours after treatment. The high levels attained after 5-azacytidine treatment are comparable to those of glucocorticoid-treated adult livers, and were not further increased by administration of hydrocortisone to dams carrying treated fetuses. Cytidine and two other analogs, cytosine arabinoside and 6-azacytidine, were essentially without effect. 相似文献
993.
(1) Exposure of phospholipids at the outer surface of activated and control platelets was studied by incubation with a mixture of phospholipase A2 from Naja naja and bee venom, solely or in combination with sphingomyelinase from Staphylococcus aureus, using conditions under which cell lysis remained below 10%. (2) Incubation with phospholipase A2 alone revealed a markedly increased susceptibility of the phospholipids in platelets activated by a mixture of collagen plus thrombin, by the SH-oxydizing compound diamide, or by calcium ionophore A23187, as compared to control platelets or platelets activated separately by collagen or thrombin. (3) Collagen plus thrombin, diamide, and ionophore treated platelets revealed an increased exposure of phosphatidylserine at the outer surface accompanied by a decreased exposure of sphingomyelin, as could be concluded from incubations with a combination of phospholipase A2 and sphingomyelinase. These alterations were much less apparent in platelets activated either by thrombin or by collagen alone. (4) The increased exposure of phosphatidylserine in activated platelets is accompanied by an increased ability of the platelets to enhance the conversion of prothrombin to thrombin by coagulation factor Xa, in the presence of factor Va and calcium. (5) It is concluded that the altered orientation of the phospholipids in the plasma membrane of platelets activated by collagen plus thrombin, by diamide, or by calcium ionophore, is the result of a transbilayer movement. Moreover, the increased exposure of phosphatidylserine in platelets stimulated by the combined action of collagen and thrombin might be of considerable importance for the hemostatic process. 相似文献
994.
E.K. Rooney J.M. East O.T. Jones J. McWhirter A.C. Simmonds A.G. Lee 《生物化学与生物物理学报:生物膜》1983,728(2):159-170
We present a method by which it is possible to describe the binding of fatty acids to phospholipid bilayers. Binding constants for oleic acid and a number of fatty acids used as spectroscopic probes are deduced from electrophoresis measurements. There is a large shift in value for the fatty acids on binding to the phospholipid bilayers, consistent with stronger binding of the uncharged form of the fatty acid. For dansylundecanoic acid, fluorescence titrations are consistent with the binding constants derived from the electrophoresis experiments. For 12-(9-anthroyloxy)stearic acid, fluorescence and electrophoresis data are inconsistent, and we attribute this to quenching of fluorescence at high molar ratios of 12-anthroylstearic acid to phospholipid in the bilayer. 相似文献
995.
Jerry R. Colca Nirmala Kotagal Paul E. Lacy Michael L. McDaniel 《生物化学与生物物理学报:生物膜》1983,729(2):176-184
The properties of active or ATP-dependent calcium transport by islet-cell endoplasmic reticulum and plasma membrane-enriched subcellular fractions were directly compared. These studies indicate that the active calcium transport systems of the two membranes are fundamentally distinct. In contrast to calcium uptake by the endoplasmic reticulum-enriched fraction, calcium uptake by islet-cell plasma membrane-enriched vesicles exhibited a different pH optimum, was not sustained by oxalate, and showed an approximate 30-fold greater affinity for ionized calcium. A similar difference in affinity for calcium was exhibited by the Ca2+-stimulated ATPase activities which are associated with these islet-cell subcellular fractions. Consistent with the effects of calmodulin on calcium transport, calmodulin stimulated Ca2+-ATPase in the plasma membranes, but did not increase calcium-stimulated ATPase activity in the endoplasmic reticulum membranes. The physiological significance of the differences observed in calcium transport by the endoplasmic reticulum and plasma membrane fractions relative to the regulation of insulin secretion by the islets of Langerhans is discussed. 相似文献
996.
John Geigert Demetrios J. Dalietos Saul L. Neidleman Terry D. Lee Julie Wadsworth 《Biochemical and biophysical research communications》1983,114(3):1104-1108
Chloroperoxidase catalyzes the peroxidation of primary alcohols, specifically those that are allylic, propargylic, or benzylic. Aldehydes are the products. The reaction dislays appreciable activity throughout the entire pH range investigated, namely pH 3.0–7.0. This enzyme is the only haloperoxidase of four tested capable of carrying out the reaction. These results further establish chloroperoxidase as a unique haloperoxidase. 相似文献
997.
S S Lee J H Ye D P Jones D B McCormick 《Biochemical and biophysical research communications》1983,117(3):788-793
A substantial decrease in liver peroxisomal catalase was found during riboflavin deficiency in rats. This decrease is greater than that found among other hemoproteins and seems to follow decrease in flavin-dependent peroxisomal oxidases. This is not due to a general depression of peroxisomal enzymes, since Cu-dependent urate oxidase activity was not changed. Furthermore, the level of catalase activity as well as flavin-dependent oxidases was restored by riboflavin repletion. These results suggest that hydrogen peroxide, the substrate for catalase produced by several flavoprotein oxidases, induces catalase in mammals as has been indicated for certain bacteria. 相似文献
998.
Immunosuppression as a high-risk factor in the development of condyloma acuminatum and squamous neoplasia of the cervix 总被引:8,自引:0,他引:8
The iatrogenic immunosuppression in renal transplant recipients has been associated with an increased incidence of malignancy in these patients. Among 132 female transplant recipients at risk for the development of squamous lesions of the cervix, 11 (8.5%) developed cervical condylomas. Six (4.5%) of the 11 patients developed cervical neoplasia. The average age of the patients at the time of initial diagnosis was 32.2 years. The lag time from transplantation to the diagnosis of the condyloma was 22.4 months, and the lag time from transplantation to the diagnosis of cervical neoplasia was 38.0 months. The increased incidence of condylomas as well as of intraepithelial neoplasia of the cervix in this group of patients with an established higher risk of malignancy supports the hypothesis that condylomas may represent a precursor lesion of cervical cancer. Immunosuppression should be included among the high-risk factors in the development of cervical neoplasia. 相似文献
999.
Comparison of the Limulus amoebocyte lysate test with plate counts and chemical analyses for assessment of the quality of lean fish. 下载免费PDF全文
The quality of lean fish was assessed simply and rapidly with Limulus amoebocyte lysate. The endotoxin levels agreed with aerobic plate counts and chemical indices of spoilage. Correlation between level of endotoxin and level of total volatile bases was found to be highly significant (r = 0.8579; P less than 0.001). 相似文献
1000.
Light and Electron Microscopic Studies of Microorganisms Growing in Rotating Biological Contactor Biofilms 总被引:5,自引:4,他引:1 下载免费PDF全文
The biofilms growing in the first compartments of two rotating biological contactors used to treat municipal wastewater were examined by light and electron microscopy. The biofilms were found to contain a complex and varied microbial community that included filamentous and unicellular bacteria, protozoa, metazoa, and (possibly) bacteriophage. The predominant microorganism among these appeared to be a filamentous bacterium that was identical to Sphaerotilus in both morphological and ultrastructural characteristics. It was possible to isolate a Sphaerotilus-like bacterium from each contactor. Both the Sphaerotilus filaments and the wide variety of unicellular bacteria present tended to contain poly-β-hydroxybutyrate inclusions, a probable indication that these organisms were removing carbon from the wastewater and storing it. The microbial population of the biofilms appeared to be metabolically active, as evidenced by the presence of microcolonies and dividing cells. 相似文献