John K. Pollak

Endogenous free radical generation may influence proteolysis in Mitochondria

Isolated Mitochondria were allowed to incorporate radioactive amino acids into protein and proteolysis was then measured. In State 4 free radical generation was manipulated by means of respiratory chain blockers and uncouplers. Conditions of enhanced radical flux resulted in accelerated protein breakdown. We suggest that radicals influence proteolysis in cells both directly (by fragmenting proteins) and indirectly (by rendering proteins more susceptible to proteinases).

The differentiation of animal mitochondria during development

The control of biogenesis and maturation of mitochondria during animal development is brought about by signals which may act on the nuclear or mitochondrial genomes or at transcriptional or post-transcriptional levels.

Mitochondrial heterogeneity in foetal and suckling rat liver: Differential leucine incorporation into the proteins of two mitochondrial populations

14C-Leucine was incorporated into proteins of foetal, suckling and adult rats. Liver mitochondria were isolated and subfractionated by isopycnic gradient centrifugation. The differential labelling pattern obtained with two populations of hepatic mitochondria confirm the concept of mitochondrial heterogeneity. The results are compatible with the concept that the two populations represent alternate stages in a maturation and division cycle.

Determination by combustion of the total organochlorine content of tissues, soil, water, waste streams, and oil sludges.

The distribution and concentration of organochlorine pesticides have been intensively investigated, but there is much less information on the total organochlorine overburden either in the environment or in man. The reason for this paucity of information seems to be that while there were many methods available for the determination of individual organochlorines, there was no simple method which permitted the determination of the total organochlorine content of biological and environmental samples. In this communication a method is described which is suitable for measuring gram quantities of total lipid-soluble organochlorine. Chloride in tissues, tissue fluids, water, soil, liquid industrial wastes and oil sludges. The method is simple and consists of three steps. The first step is a small volume extraction procedure, which extracts organic compounds containing chlorine, but excludes inorganic chlorides. The other two steps involve the degradation of organically bound chlorine to inorganic chlorides and a colorimetric assay of these chlorides.

The adenine nucleotide translocator in foetal, suckling and adult rat liver mitochondria

Abstract The adenine nucleotide content of rat liver mitochondria was shown to increase significantly after birth. On the other hand, it was found that the ligand-binding properties of the adenine nucleotide translocator were essentially the same in foetal, suckling and adult rat liver mitochondria. These results are compatible with the proposal that the accumulation of adenine nucleotides which occurs during mitochondrial biogenesis and maturation is effected by a pathway different from the adenine nucleotide translocator.

Rapid Purification of the Unstable Enzyme Carbamoyl Phosphate Synthase by High Pressure Liquid Chromatography

Abstract Extracts of soluble proteins obtained from rat liver mitochondria by freeze-thawing and subsequent diafiltration were fractionated by HPLC on a I 250 protein column. The column was eluted either with 0.05 M phosphate buffer pH 6.85 or 0.1 M acetate buffer pH 7.15. Specific fractions obtained by elution with either phosphate or acetate buffer showed a 6.1-fold or 5.5-fold increase in the specific activity of Carbamoyl phosphate synthase when compared with that of crude mitochondrial preparations. The purification and the molecular weight of carbamoyl phosphate synthase were verified by sodium dodecyl sulphate-polyacrylamide gel electrophoresis.

The importance of strict temperature control during gradient centrifugation of osmotically active cell organelles

Abstract A temporary drop in temperature below 0°C in the rotor tube during isopycnic sucrose gradient centrifugation is not usually detectable with the available temperature gauges, but such transient sub-zero temperatures will cause mitochondria to rupture and to redistribute throughout the gradient. Swing-out titanium rotors are particularly prone to such temperature variations as titanium in relation to aluminium is a poor heat conductor.

The effect of the phenoxyacetic acid herbicides 2,4,5-trichlorophenoxyacetic acid and 2,4-dichlorophenoxyacetic acid as ascertained by direct experimentation

In a recent discussion on the social responsibility of the scientist, J. T. Edsall made the point that it is difficult to resolve disputes or issues which involve technology as well as basic science (Edsall 1981). Most public policy issues on the use of technology may be placed in this category. The problems arise because scientific facts and value judgements are so closely interwoven it is exceedingly difficult to disentangle them, and the inferences that are drawn are inconclusive (Edsall 1981).

Effects of a desealant formulation, SR-51(®) and its individual components on the oxidative functions of mitochondria.

The Royal Australian Air Force has reported that personnel involved in F-111 fuel tank maintenance were concerned that exposure to a range of chemicals during the period 1977-mid-1990s was the cause of health problems. Particular concern was directed at a desealant chemical mixture known as SR-51(®). The current study, using in vitro submitochondrial assays, was designed to investigate the relative toxicities of the four components of SR-51(®) (Aromatic 150 solvent (Aro150), dimethylacetamide (DMA), thiophenol (TP) and triethylphosphate (TEP)). Based on the EC(50) values, TP and Aro150 were the most toxic components and were markedly more toxic than TEP and DMA.