Injury of mitochondrial respiration and membrane potential during iron/ascorbate-induced peroxidation

First functional events during peroxidation in mitochondria consisted in a progressive inhibition of the phosphorylating and uncoupled respiration with succinate and glutamate/malate as substrates, whereas the resting state respiration during the same period was virtually not influenced. The membrane potential registered at a time with the respiration rates was capable of being built up for a relatively long time interval with only minor decreases, and broke down rather promptly when the active respiration was highly diminished. Inhibition of respiration proceeded mainly during the initiation phase of peroxidation. Lag phases of varied length, of malondialdehyde formation which were predominantly attributed to the iron/protein ratios correlated closely with different time intervals needed to attain maximal inhibition of respiration and decrease in glutathione. Hence, the lessening of respiration, drop of membrane potential and loss of the antioxidant, glutathione, represent early stages in the causal chain of events which precede the onset of intensive lipid peroxidation.     

Inhibition of IAA-induced elongation in Avena coleoptile segments by lead: a physiological and an electron microscopic study.

A high resolution growth measuring apparatus was used to demonstrate the inhibition of auxin-induced cell elongation in oat coleoptile segments (Avena sativa L. var Holden) by lead at concentrations ranging from 2 x 10-6 M to 2 x 10-3 M. The inhibition was immediate, having no measurable lag period. Electron micrographs of lead-treated and control segments revealed that in the treated material, lead became localized as electron-dense granules in the cell walls and in vesicles associated with dictyosomes. These granules were found to be lead hydroxide phosphate by electron diffraction techniques. The possible significance of this localization and identification with regard to phosphatase activity is discussed.     

Characterization of ribonucleolytic activity of angiogenin towards tRNA

Yeast tRNA is a convenient substrate for the assay of the ribonucleolytic activity of human angiogenin. The optimal pH, [NaCl], and temperature for tRNA cleavage by angiogenin are approximately 6.8, 15-30 mM, and approximately 55 degrees C, respectively, as compared with approximately 8.0, 100-200 mM, and approximately 65 degrees C, respectively, for RNase A. Polyanions and metals both inhibit angiogenin and RNase A but to different extents.     

In vitro metabolism or testosterone by breast microcysts

Breast microcysts are considered to be a normal findings in the adult female breast without any increased risk of developing carcinomatous change. Breast cysts fluid contains steroid but not studies have been reported on the ability of breast microcysts to metabolise steroid hormones. It was, therefore, the aim of this study to identify the metabolites formed on incubation of radiolabelled testosterone with microcysts. In all instances dihydrotestosterone and androstenedione were formed. Oestrogens were not identified. Tis study, therefore, provides evidence for th presence of 5-alpha-reductase and 17-oxidoreductase enzyme systems in breast microcysts.     

Cloning of nisin resistance determinant and replication origin on 7.6-kilobase EcoRI fragment of pNP40 from Streptococcus lactis subsp. diacetylactis DRC3

The nisin resistance determinant and an origin of replication on pNP40, a plasmid of about 60 kilobases that is present in Streptococcus lactis subsp. diacetylactis DRC3, was cloned on a 7.6-kilobase EcoRI fragment. When self-ligated, this fragment existed as an independent replicon (pFM011) and contained a 2.6-kilobase EcoRI-XbaI fragment encoding nisin resistance.     

Structure determination of the 2:1 derivatives of copper(I) bromide and iodide with bis(diphenylphosphino)methane. A simple structural scheme for the formation of (CuX)nLm species

The structures of the complexes (CuX)₂DPM (X = Br, I; DMP = bis(diphenylphosphino)methane) were determined from three dimensional X-ray data collected by counter methods. The iodine derivative crystallizes in the space group Pbca with eight units in a cell defined by a = 17.128(9), b = 18.306(9) c, = 16.508 (8) Å. The structure was refined by the least-squares method to a final R factor of 0.054 for 1336 non-zero independent reflections. The bromine derivative crystallizes in the space group P2₁/c with eight units in a cell defined by a = 23.707(1), b = 17.805(9), c = 16.991(1) Å, β = 136.10(5)°. The final least-squares refinement, based on 2489 non-zero independent reflections, gave an R factor of 0.074.Both the compounds have similar structures with a centrosymmetric (CuX)₄ core, in which two copper atoms have a tetrahedral geometry, while the other two are trigonal.The above structures are compared with those already reported for other compounds (CuX)_nL_m and a single scheme is proposed to rationalize the different geometries of the (CuX)_n core on the basis of steric and electronic effects.     

Turnover of hepatic phosphofructokinase in normal and diabetic rats. Role of insulin and peptide stabilizing factor.

Earlier work demonstrated that the activity of liver phosphofructokinase (PFK-L2) and immunoreactive PFK-L2 were decreased in diabetic rats and increased to normal or super-normal amounts following insulin treatment (Dunaway, G.A., and Weber, G., (1974) Arch. Biochem. Biophys. 162, 629-637). This report indicates that the decrease in levels of PFK-L2 in diabetic rats is a result of an accelerated degradation rate while the synthetic rate remains nearly normal. Following insulin treatment, the rate of PFK-L2 synthesis is enhanced 2-fold, whereas the rate of degradation appears to be greatly diminished. An inverse relationship is shown to exist between the PFK-L2 levels and the rates of PFK-L2 degradation, suggesting that the levels of PFK-L2 are primarily regulated by degradation rate. In addition, the levels of the PFK-L2 peptide stabilizing factor are inversely proportional to rates of PFK-L2 degradation. These results indicate that insulin mediates the rate of degradation of PFK-L2 by controlling the level of the peptide stabilizing factor.