Solvation properties of ubiquinone-10 in solvents of different polarity

The solvation properties of ubiquinone-10 and ubiquinol-10 in a wide variety of solvents of polarity varying from alkanes to water are reported. Greatest solubility is observed in solvents of intermediate polarity and particularly where low polarity is combined with a pronounced tendency to interact with the benzoquinone substituent of the ubiquinone molecule. This includes solvents like chloroform and benzene. Ubiquinone-10 is somewhat less polar than ubiquinol-10 as judged by comparative solubilities of the two molecules. Proton-NMR chemical shift measurements and aggregation studies in selected solvents indicate that in ubiquinone-10 in the liquid phase and in solution in hydrocarbons like dodecane the molecules have a preferred association possibly involving stacking of the benzoquinone rings. Surface balance studies indicated that the surface-active character of ubiquinone-10 is relatively weak and only in a comparatively polar and highly structured solvent, formamide, was there evidence of an effect on surface tension of the solvent. The critical micelle concentratiom in this solvent was estimated to be about 5 M on the basis of surface tension measurements. Ubiquinone-10 is well known to form virtually insoluble monolayers at the air/water interface. Studies of the partition of ubiquinone-10 in binary mixtures of solvents suggest that the interaction of the benzoquinone ring substituent with structured polar solvents is considerably weaker than the internal cohesion between molecules of the solvent. No evidence on the basis of wide-angle X-ray diffraction measurements was obtained to indicate that solvent molecules were a component of the crystal lattice of ubiquinone-10 that had precipitated from solvent mixtures.     

Toxicity and mutual interactions of cadmium and zinc ions in normal and carcinogen-transformed mouse cells

The toxicity of chloride salts of physiological (zinc, manganese, nickel) and non physiological (cadmium) bivalent metal ions was studied in normal or carcinogen-transformed mouse embryo fibroblast cells. The dose response curves for toxicity to both types of cells exhibited similar shapes. The transformed cells, however, were about twice as sensitive to zinc toxicity as normal cells. When normal and transformed cells were grown together and incubated for several hours with an appropriate concentration of zinc, the malignant cells were selectively killed. Cadmium was much more toxic than the three other metal ions in both types of cells. Its toxic effect was reversed by simultaneous addition of zinc at nontoxic concentrations.Abbrevications CFA colony forming ability - MCA 3-methylcholanthrene     

Synthesis and maturation of cross-reactive glycoprotein in fibroblasts deficient in arylsulfatase a activity

The biosynthesis of arylsulfatase A was studied in cultured fibroblasts by pulse-chase labeling with [2-³H]mannose; the enzyme was isolated by immunoprecipitation and denaturing polyacrylamide gel electrophoresis. In normal fibroblasts, and in fibroblasts from a patient with multiple sulfatase deficiency, the enzyme was synthesized as a glycoprotein of apparent molecular weight of 59,000; half of it was processed over a period of 4 days to M_r= 57,000. The precursor chain of M_r= 59,000 was secreted in the presence of 10 mM NH₄Cl. An immunoprecipitable glycoprotein of normal size was synthesized by fibroblasts from two unrelated patients with metachromatic leukodystrophy, but this material disappeared within twenty hours. In fibroblasts from an individual with pseudodeficiency of arylsulfatase A, the immunoprecipitable precursor glycoprotein was smaller (M_r= 56,000). The synthesis of cross-reactive proteins with altered properties supports the concept of allelic mutations as the genetic basis of metachromatic leukodystrophy and of arylsulfatase A pseudodeficiency.     

Comparison of six rabbit liver cytochrome P-450 isozymes in formation of a reactive metabolite of acetaminophen

This laboratory has recently reported the isolation of an ethanol-inducible form of rabbit liver microsomal cytochrome P-450, designated isozyme 3a. In view of the reports of others that the hepatotoxicity of acetaminophen is increased in ethanol-treated animals and the human alcoholic, we have determined the activity of the six available P-450 isozymes in the activation of the drug to give an intermediate which forms a conjugate with reduced glutathione. Isozymes 3a, 4, and 6, all of which are present in significant amounts in the liver microsomes from rabbits chronically administered ethanol, exhibited the highest activities in the reconstituted enzyme system, whereas isozymes 3b and 3c were 10- to 20-fold less effective, and phenobarbital-inducible isozyme 2 was essentially inactive, even in the presence of cytochrome b5. The results obtained thus indicate that induction by ethanol of P-450 isozyme 3a (or a homologous enzyme in other species) may contribute to the toxicity of acetaminophen but that other cytochromes also play a significant role.     

The postribosomal particle of rabbit liver contains protein-synthesis factors and serum albumin mRNA

As demonstrated by indirect immunoprecipitation and polyacrylamide gel electrophoresis, an 85S particle separated by sucrose density-gradient centrifugation from the postribosomal pellet of rabbit liver, is able to synthesize serum albumin if supplemented with both ribosomal subunits and sources of energy. It is retained on heparin bound to Sepharose 4B, contains translatable mRNA and apparently all protein factors required for translation. This particle may represent a highly organized protein synthesizing machinery, the combination of which with ribosomes results in formation of new protein molecules.     

Detection of beta-adrenergic receptors on rabbit mononuclear cells isolated free of significant contamination by other cell types

In order to study rabbit mononuclear cell surface receptors, it was necessary to develop a procedure to isolate mononuclear cell preparations that are free of significant contamination by other cell types, especially platelets. Centrifugation of dextran-sedimented, anti-coagulated whole blood through Hypaque (density 1.060) at 600 X g for 5 min at 22 degrees C eliminated greater than 93% of starting platelets. A second 5-min Hypaque centrifugation of Hypaque-Ficoll-isolated mononuclear cells (MNC) (approximately 80% lymphocytes) at 450 X g for 5 min at 22 degrees C reduced platelet contamination to less than one platelet per three MNC, and resulted in the overall removal of greater than 99.5% of starting platelets. These relatively pure MNC which were isolated in less than 2 hr were identified as having beta-adrenergic receptors by radioligand binding techniques using [125I]iodohydroxybenzylpindolol [( 125I]IHYP). Binding of [125I]IHYP to intact rabbit MNC was a saturable, stereospecific, and rapid process with a dissociation constant (KD) of 0.53 +/- 0.18 nM and a binding capacity of 3,461 +/- 235 sites/cell.     

Epicuticular waxes from Agropyron dasystachyum,agropyron riparium and Agropyron elongatum

Epicuticular waxes from whole plants of Agropyron dasystachyum var. psammophylum, A. riparium and A. elongatum contain hydrocarbons (5–8 %), long chain esters (12–15%) and free acids (2–5%). The major esters are C₃₄C₅₆ esters derived from C₁₆C₃₀ acids and alcohols (1-hexacosanol is the major alcohol) but C₃₁, C₃₃ and C₃₅ esters (3–11%) are also present. The latter esters are C₁₈ and C₂₀ acid esters of C₁₃ and C₁₅ 2-alkanols. A. dasystachyum wax contains 2% free alcohols, that of A. riparium contains 17% and that of A. elongatum 11% (1-hexacosanol is the major alcohol in each). Diesters (2%), C₈C₁₂ diols esterified by (E)-2-alkenoic acids, are present in A. riparium wax. Hentriacontane-14,16-dione is present: 29% in A. dasystachyum wax and 32% in A. riparium wax, but only 5% in A. elongatum wax. 25-Oxohentriacontane-14,16-dione forms 14% of A. dasystachyum wax and 27% of A. elongatum wax but the oxo β-diketones of A. riparium wax (5%) consist of both 10-oxo- and 25-oxohentriacontane-14,16-diones in the ratio 4:1. Hydroxy β-diketones of the waxes are 25- and 26-hydroxyhentriacontane-14,16-diones; in A. dasystachyum (20%) the ratio is 3:1, in A. elongatum (20%) the ratio is 9:1 but in A. riparium (5%) it is ca 1:2. The configuration of the hydroxyl group in the 26-hydroxy β-diketone is opposite to that in the 25-hydroxy derivative. The unusual composition of the oxygenated β-diketones of A. riparium confirms that this species should be regarded as separate from A. dasystachyum. Wax from A. elongatum also contains 4-hydroxy-25-oxohentriacontane-14,16-dione (4%) and an unusual oxo-β-ketol, 18-hydroxy-7,16-hentriacontanedione (2%), both these components are probably derived biosynthetically from the 25-oxo β-diketone which is the major component of this wax. Syntheses of racemic 18-hydroxy-7,16-hentriacontanedione and of a model β-ketol, 12-hydroxy-10-pentacosanone, are described.     

Estimation of pyruvate decarboxylation in perfused rat skeletal muscle

A total of 46 E. coli strains showing mannose-resistant, P-blood-group independent hemagglutination of human erythrocytes were tested for binding to neuraminic acid. Nine of the strains completely lost their hemagglutination activity after the erythrocytes were treated with neuraminidase. To characterize the receptor structure, different neuraminic acid containing glycoproteins, their desialylated derivatives and neuraminyl oligosaccharides were tested for hemagglutination inhibition. These studies showed that the nine strains had binding specificity for alpha 2-3 linked neuraminic acid.     

In vivo interactions of acrylonitrile with macromolecules in rats

The irreversible binding of [2,3-14C]acrylonitrile (VCN) to proteins, RNA and DNA of various tissues of male Sprague-Dawley rats after a single oral dose of 46.5 mg/kg (0.5 LD50) has been studied. Proteins were isolated by chloroform-isoamyl alcohol-phenol extraction. RNA and DNA were separated by hydroxyapatite chromatography. Binding of VCN to proteins was extensive and was time dependent. Radioactivity in nucleic acids was registered in the liver and the target organs, stomach and brain. DNA alkylation, which increased by time, was significantly higher in the target organs, brain and stomach (119 and 81 pmol/mg, respectively, at 24 h) than that in the liver. The covalent binding indices for the liver, stomach and brain at 24 h after dosing were, 5.9, 51.9 and 65.3, respectively. These results suggest that VCN is able to act as a multipotent carcinogen by alkylation of DNA in the extrahepatic target tissues, stomach and brain.     

RBEs of Thermal Neutron Capture Therapy and 10B(n,α)7 Li Reaction on Melanoma-Bearing Hamsters

Using Greene's melanoma transplanted into Syrian (golden) hamsters, we determined the relative biological effectiveness (RBE) of thermal neutron capture therapy (TNCT) using ¹⁰B-paraboronophenylalanine (¹⁰B-BPA) in comparison with a 9-MeV electron beam. We also obtained the RBE of the ¹⁰B(n,α)⁷Li reaction by calculation based on summed dose data from TNCT. Throughout this study, the Kyoto University Research Reactor was used as the source for thermal neutrons; the reactor was specially altered to attain a low contamination level both for gamma-rays and fast neutrons. ¹⁰B-BPA was administered 8 hours before thermal neutron irradiation to the hamsters with melanoma. The tumor was then irradiated at 5 MW for 90 minutes. The absorbed dose from this TNCT was calculated by the method of Fairchild and Goodman (Phys. Med. Biol. 1966; 2:15–30). The RBEs of the TNCT and the ¹⁰B(n,α)⁷Li reaction obtained by the tumor growth delay time (TGDT) method were 2.22 and 2.51, respectively, at 10.5 days of TGDT. These RBE values varied with TGDT and the absorbed dose. The RBE value of TNCT had a peak at 7.0 days of TGDT; that of the ¹⁰B(n,α)⁷Li reaction was higher at a low absorbed dose level and lower at a high absorbed dose level.