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Biomedical subjects

W Bartley

Publications and source records attributed to W Bartley.

At least 19 recordsLinked to original sources
PubMed1974

The effect of storage on enzyme activities in tissues.

The stability to storage at -20 degrees C of 29 enzymes of rat tissues was measured for periods of up to 100 days. The enzymes could be divided into four groups: (1) those that increased in activity with storage; (2) those that showed transient rises subsequently declining to the original activity or below; (3) those that showed no significant change; (4) those that declined in activity. Details of methods used and of results obtained have been deposited as Supplementary Publication SUP 50038 (19 pages) at the British Library (Lending Division) (formerly the National Lending Library for Science and Technology), Boston Spa, Yorks. LS23 7BQ, U.K., from whom copies can be obtained on the terms indicated in Biochem.J. (1973), 131, 5.

Animals↗
PubMed1973

Changes in enzyme activities in tissues of rats exposed to hypoxia.

Rats were exposed to various degrees of hypoxia and enzyme activities in their tissues were determined. In general, oxidative metabolism was not increased in response to hypoxia, nor was anaerobic metabolism. Physiological and anatomical changes were concluded to be more important than changes in cellular enzyme activities in the overall adaptation to acute hypoxia.

Animals↗
PubMed1973

Oxaloacetate decarboxylases of rat liver.

1. Two oxaloacetate decarboxylases of rat liver are described; one is mitochondrial with no metal ion requirement and activity in the alkaline pH region; the other is cytoplasmic with Mn(2+) or Mg(2+) requirement and activity around pH5. 2. A method for the partial purification of the mitochondrial enzyme is described. 3. The apparent K(m) of the mitochondrial enzyme is 0.23mm. 4. Inhibition of the mitochondrial enzyme by substrate, CoA, acetyl-CoA, citrate and phosphoenolpyruvate is described.

Acetyl Coenzyme A↗
PubMed1972

The effect of oxygen concentration on the growth and metabolism of Saccharomyces cerevisiae grown with excess of potassium or in potassium-deficient media.

1. Saccharomyces cerevisiae cells grown in limiting K(+) concentration have their growth inhibited by O(2) concentrations above 40%. With these conditions the cells grow very large and are unable to maintain ionic gradients when washed with water. 2. Cells grown in excess of K(+) showed the same pattern of change in cell size with change in O(2) concentration, but the magnitude of the changes was much less. Cells grown in excess of K(+) were not leaky. 3. Cell death, growth and development of ;leakiness' were not correlated in the cells grown in limiting K(+) concentration. 4. The activities of both alcohol dehydrogenase and cytochrome oxidase were higher in K(+)-deficient cells than in the cells grown with excess of K(+). The differences were much larger when the measurements were made on a cellular basis than when made on a protein basis. 5. In 100% O(2) 3mm-K(+) in the medium was sufficient to produce normal yeast cells.

Aerobiosis↗
PubMed1971

Properties of yeast grown anaerobically in media limiting in potassium.

1. Saccharomyces cerevisiae was grown anaerobically in media with different concentrations of K(+) down to less than 1mm. Below 3.2mm the K(+) concentration limited the growth rate and yield. 2. Yeast extract was essential for maximum growth. The yield of cells when the medium contained 0.83mm-K(+) was only 30% of the yield with 90mm-K(+). 3. At the end of anaerobic growth the cells grown in 0.83mm-K(+) had a higher concentration of oxidative enzymes than cells grown in 90mm-K(+). 4. The cells grown anaerobically in 0.83mm-K(+) could adapt to aerobic conditions if K(+) was present in the adaptation medium, but not otherwise. 5. The enzyme pattern of the yeast grown aerobically in 0.83mm-K(+) was very similar to the anaerobically grown cells and did not change markedly after the glucose was consumed.

Alcohol Oxidoreductases↗
PubMed1969

Adenosine phosphates and the control of glycolysis and gluconeogenesis in yeast.

1. Changes in dry weight, protein, RNA and DNA were measured in yeast during adaptation to glycolytic metabolism. 2. Only RNA increased significantly during the lag phase, but during the exponential phase all these cellular components increased in parallel. 3. The concentrations of ATP, ADP, AMP and glucose 6-phosphate were measured in respiring yeast and during the transition to glycolytic metabolism. 4. In respiring cells the concentration of AMP was at its highest and that of ATP was at its lowest; this relationship was reversed in glycolysing cells. 5. ADP concentration was similar in respiring and glycolysing cells, but glucose 6-phosphate concentration was much higher in the glycolysing cells. 6. A possible reason for mitochondrial repression is suggested. 7. It is concluded that adenosine phosphates do not control the direction of glycolytic flux in yeast and an alternative control of glycolysis and gluconeogenesis by enzyme activation and inactivation is suggested.

Adenine Nucleotides↗
PubMed1969

The localization of proteolytic activity in rat liver mitochondria and its relation to mitochondrial swelling and aging.

1. On storage of rat liver mitochondria at 0 degrees , water content, total amino acid content and leakage of protein all rose steadily over a 72hr. period. The initial ratio of intramitochondrial to extramitochondrial amino acid concentration lay between 18 and 24. Initially this rose, but it then fell to 1.9 at the end of storage. The concentration gradient between internal and external amino acids was relatively constant throughout the period. These processes were accentuated at 22 degrees and 40 degrees , the concentration gradient reaching 70mumoles/ml., water content rising to 8.3mg./mg. dry wt. and protein leakage reaching 42% of total mitochondrial protein. ;Swelling agents' produced no correlated changes in amino acid production and swelling. 2. Added glutamate was not concentrated within the pellet of whole or disrupted mitochondria. Endogenous amino acids were distributed evenly between the pellet and the supernatant of disrupted mitochondria. It is concluded that amino acids are produced within mitochondria and that adsorption and uptake from the medium do not contribute significantly to amino acids in the pellet. 3. beta-Glycerophosphate, a lysosome protectant, increased amino acid production by rat liver mitochondria. Treatment with Triton X-100 and disruption by freezing and thawing showed that 56% of proteolytic activity was ;free' in whole mitochondria, whereas only 11% of acid phosphatase activity, a lysosomal enzyme, was ;free'. 4. ;Light' mitochondria contained 30% more neutral proteolytic activity but 300% more acid phosphatase activity than ;heavy' mitochondria. 5. Electron micrographs of mitochondrial preparations showed less than one particle in 500 that could be identified as a lysosome. Treatment with Triton X-100 disrupted the structure of roughly 50% of the mitochondria; the rest appeared to retain their membrane, cristae and ground substance. Freezing and thawing caused gross swelling and loss of ground substance and rupture of external membranes. 6. Of the recovered proteolytic activity, 81% at pH7.4 and 70% at pH5.8 were found in the high-speed supernatant of broken mitochondria. A further fivefold increase in specific activity was found in the first protein fraction obtained by Sephadex G-50 gel filtration. 7. Between 60 and 80% of proteolytic activity was found in the 40-60%-saturated ammonium sulphate precipitate. Almost all of the soluble-fraction proteolytic activity could be recovered in a pH5.0 supernatant. 8. The results give no support to the view that mitochondrial neutral proteolytic activity reflects lysosomal content. 9. The possible role of intramitochondrial amino acid production and the proteolysis of internal barriers in passive swelling of mitochondria is discussed.

Acid Phosphatase↗
PubMed1969

The effect of age and sex on glutathione reductase and glutathione peroxidase activities and on aerobic glutathione oxidation in rat liver homogenates.

1. Changes in liver glutathione reductase and glutathione peroxidase activities in relation to age and sex of rats were measured. Oxidation of GSH was correlated with glutathione peroxidase activity. 2. Glutathione reductase activity in foetal rat liver was about 65% of the adult value. It increased to a value slightly higher than the adult one at about 2-3 days, decreased until about 16 days and then rose after weaning to a maximum at about 31 days, finally reaching adult values at about 45 days old. 3. Weaning rats on to an artificial rat-milk diet prevented the rise in glutathione reductase activity associated with weaning on to the usual diet high in carbohydrate. 4. In male rats glutathione peroxidase activity in the liver increased steadily up to adult values. There were no differences between male and female rats until sexual maturity, when, in females, the activity increased abruptly to an adult value that was about 80% higher than that in males. 5. The rate of GSH oxidation in rat liver homogenates increased steadily from 3 days until maturity, when the rate of oxidation was about 50% higher in female than in male liver. 6. In the liver a positive correlation between glutathione peroxidase activity and GSH oxidation was found. 7. It is suggested that the coupled oxidation-reduction through glutathione reductase and glutathione peroxidase is important for determining the redox state of glutathione and of NADP, and also for controlling the degradation of hydroperoxides. 8. Changes in glutathione reductase and glutathione peroxidase activities are discussed in relation to the redox state of glutathione and NADP and to their effects on the concentration of free CoA in rat liver and its possible action on ketogenesis and lipogenesis.

Age Factors↗
PubMed1969

A negative correlation between oxygen uptake and glutathione oxidation in rat liver homogenates.

GSH added to rat liver homogenates inhibited respiration and increased GSSG formation approximately proportionally to the amount of GSH added; the effect was increased by added magnesium chloride. Added NADPH and citrate decreased GSSG formation and increased respiration; 6.0mm-nicotinamide prevented GSSG formation and increased respiration. There was a negative correlation between GSSG formation and oxygen uptake. It is suggested that the decrease in oxygen uptake is mainly due to GSSG concentration and also that in vivo a GSH-GSSG steady state occurs.

Animals↗
PubMed1969

The nature of the sex-linked differences in glutathione peroxidase activity and aerobic oxidation of glutathione in male and female rat liver.

1. Glutathione peroxidase activity in the livers of sham-operated female rats was about 60% higher than in similarly treated male rats. The value in the ovariectomized female was about the same as that in the castrated or sham-operated male. 2. Glutathione peroxidase activity changed during the oestrous cycle. The highest value was in oestrus, and was about 50% higher than the lowest activity, which was found in dioestrus. The activity in proestrus and in metoestrus was respectively about 20 and 30% higher than in dioestrus. 3. In the pregnant female 1 or 2 days before term, glutathione peroxidase activity was about 20% higher than that in the female in oestrus. 4. Subcutaneous implants of both oestra-diol and progesterone in the gonadectomized rats increased the glutathione peroxidase activity approximately to the values found in the female at oestrus. 5. The rate of aerobic oxidation of GSH in the female rat liver was about 80% higher than in the male and about 110% higher than in the gonadectomized rats. Treatment of gonadectomized rats with subcutaneous implants of oestradiol and of progesterone increased the rate of oxidation of GSH by about 100%. 6. In the presence of azide the rate of GSH oxidation in the male and in the female was respectively about 3.5- and 2.1-fold that in the absence of azide. In castrated or ovariectomized rats the increase due to the presence of azide was about 2.4-fold. In the gonadectomized rats treated with oestradiol or progesterone the rate of GSH oxidation in the presence of azide was about 2.2-fold that in its absence. 7. The rate of lipid peroxidation in female was 15-30-fold that in male or in gonadectomized rats. Treatment of the gonadectomized rats with oestradiol or with progesterone increased the rate of lipid peroxidation up to values that were even higher than in the female. In the presence of GSH the formation of malonaldehyde from peroxides was virtually eliminated. 8. The results suggest that the sex-linked differences in glutathione peroxidase activity, in the rate of GSH oxidation and in the rate of lipid peroxidation are due to the female sex hormones. 9. It is suggested that both the catalase activity and the rate of hydrogen peroxide formation are higher in the male than in the female. 10. Sex-linked changes in glutathione peroxidase, in the rate of GSH oxidation and in the rate of lipid peroxide formation are discussed in relation to the metabolism of oestrogens in the liver and also to the possible nature of those sex-linked changes.

Aldehydes↗