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61.
62.
Inorganic tin (SnCl4·H2O) is toxic to microbial populations obtained from estuarine sediments plated on nutrient medium solidified with either agar or purified agar. The use of gelatin as a gelling agent decreased the apparent toxicity of tin, and toxicity was markedly reduced in medium solidified with silica gel. There was no evidence that toxic agar-tin complexes were involved. Cd, Cu, Pb, Ni, and Zn exhibited similar toxicity patterns; therefore, toxicity levels determined in the laboratory should be extrapolated to the environment with caution. The addition of cysteine to the medium had no effect on tin toxicity. Serine or 3-hydroxyflavone enhanced toxicity, while humic acids or gelatin inhibited toxicity. Replacement of SO42− with NO3 did not alter tin toxicity, but replacement of Cl with NO3 decreased tin toxicity. Thus, the toxic effect(s) of tin depend as much on the chemical speciation of the metal as on the total concentration of the metal in the medium.  相似文献   
63.
Dihydrofolate reductase from Lactobacillus casei and its complexes with NADPH and methotrexate yield well-resolved Raman spectra. The 1685-cm?1 Raman band assigned to the carboxamide of NADPH persists in the NADPH-enzyme binary complex but is absent from the NADPH-methotrexate-enzyme ternary complex. This is ascribed to stabilization of the polarized form of the carboxamide by H bonding to the NH and CO groups of Ala 6 and Ile 13 of the peptide backbone.  相似文献   
64.
Eight male patients with insulin-dependent diabetes mellitus (IDDM) without residual beta-cell function were studied on two occasions in random order. In one experiment hypoglycemia was induced by a constant rate iv infusion of insulin (0.034 U/kg/h) during 150 minutes. At the other occasion an identical infusion of insulin was given, but this time euglycemia was maintained by a variable iv infusion of glucose. Plasma levels of free insulin were almost identical during the two experiments indicating that insulin clearance is not influenced by hypoglycemia in patients with IDDM.  相似文献   
65.
Isidrogalvia longiflora, a new combination based onAsagraea longiflora, is proposed. It is the first record ofIsidrogalvia from Bolivia.  相似文献   
66.
In 1843 S. B. Buckley (1809–1884) traveled up the St. Johns River, Florida in search of plants, shells, and possibly other natural history objects. Buckley encountered many difficulties in interior Florida and his trip did not live up to his original expectations. It was unfortunate that the took years to distribute his plant specimens, since few botanists or naturalists had preceded him into that poorly explored region.  相似文献   
67.
In 1843 S. B. Buckley (1809–1884) traveled up the St. Johns River, Florida in search of plants, shells, and possibly other natural history objects. Buckley encountered many difficulties in interior Florida and his trip did not live up to his original expectations. It was unfortunate that the took years to distribute his plant specimens, since few botanists or naturalists had preceded him into that poorly explored region.  相似文献   
68.
Summary The properties of surfactin, a biosurfactant lipopeptide, were highly modified in the presence of inorganic cations. The micellization of surfactin was favoured by monovalent and, especially by divalent cations with a modification of the molecular area at the air-water interface. Haemolysis of erythrocytes by surfactin was enhanced by low concentrations of divalent cations with an increase of the binding of the lipopeptide to membrane. Inorganic ions induced conformational rearrangements probably due to ion-surfactin associations which modify the surface-active properties.  相似文献   
69.
Two individual glycoprotein components from human milk-fat-globule membranes (MFGM) has been purified by selectively extracting the membrane glycoproteins followed by lectin affinity chromatography and gel filtration on Sephadex G-200 in the presence of protein-disaggregating agents. The purified glycoprotein components, termed 'epithelial-membrane glycoprotein' (EMGP-155 and EMGP-39) have estimated molecular weights of 155 000 and 39 000 respectively, and yield a single band under reducing conditions on sodium dodecyl sulphate/polyacrylamide gel. EMGP-155 and EMGP-39 contain 21.0% and 7.0% carbohydrate by weight, with fucose (13.5%, 12.4%), mannose (3.7%, 6.2%), galactose (28.5%, 22.6%), N-acetylglucosamine (17.8%, 7.4%) and sialic acid (36.4%, 51.4%) of the carbohydrate moiety respectively. For both the glycoprotein components, aspartic and glutamic acid and serine are the major amino acid residues.  相似文献   
70.
Granulosa cells isolated from mature Graafian follicles of swine produced significant quantities of immunoreactive 6-keto-PGF1α under chemically defined conditions in vitro. Luteinizing hormone elicited a dose-dependent stimulation of 6-keto-PGF1α accumulation, but follicle stimulating hormone, prolactin, L-epinephrine, estradiol-17B, or PGE2 were devoid of effect. The time-dependent in vitro production of 6-keto-PGF1α by ovarian cells was susceptible to inhibition by indomethacin, U-51506, cycloheximide, and actinomycin D. These observations implicate granulosa cells in the specific and hormonally regulated production of prostacyclin.  相似文献   
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