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Biomedical subjects

E Bailey

Publications and source records attributed to E Bailey.

At least 217 records · Page 12Linked to original sources
PubMed1970

Factors involved in changes in hepatic lipogenesis during development of the rat.

1. Changes in the activities of acetyl-CoA carboxylase (EC 6.4.1.2), phosphofructokinase (EC 2.7.1.11), aldolase (EC 4.1.2.13), extramitochondrial aconitate hydratase (EC 4.2.1.3) and NADP-dependent isocitrate dehydrogenase (EC 1.1.1.42) have been measured in the livers of developing rats from late foetal life to maturity. 2. The effect of altering the weaning time on some enzymes associated with lipogenesis has been studied. Weaning rats at 15 days of age instead of 21 days results in an immediate increase in the activity of ;malic' enzyme (EC 1.1.1.40) whereas the activities of glucose 6-phosphate dehydrogenase (EC 1.1.1.49) and ATP citrate lyase (EC 4.1.3.8) did not increase until 4-5 days and acetyl-CoA carboxylase 2-3 days after early weaning. Weaning rats on to an artificial-milk diet led to complete repression of the rise in activity of hepatic enzymes associated with lipogenesis normally found on weaning, except for ;malic' enzyme, which increased in activity after 20 days of age. 3. The effect of intraperitoneal injections of glucagon, cortisol, growth hormone and thyroxine on the same hepatic enzymes has been investigated. Only thyroxine had any effect on enzyme activities and caused a 20-fold increase in ;malic' enzyme activity and a twofold increase in ATP citrate lyase activity. 4. The activities of hepatic glucose 6-phosphate dehydrogenase and ;malic' enzyme are higher in adult female than in adult male rats and it has been shown that this sex difference in enzyme activities is due to both male and female sex hormones. 5. Hepatic malate, citrate, pyruvate, glucose 6-phosphate and phosphoenolpyruvate concentrations have been measured throughout development. 6. The results are discussed in relation to the dietary and hormonal control of hepatic enzyme activities during development.

Animals↗
PubMed1970

Fatty acid utilization during development of the rat.

1. In the absence of added carnitine pronounced changes occur during development, in the degradation of [U-(14)C]palmitate to (14)C-labelled acid-soluble material (predominantly ketone bodies) and (14)CO(2) by liver homogenates. The formation of both products by liver homogenates of 5-day-old rats is considerably higher than in foetal livers. This high value is maintained during the suckling period and falls after weaning to adult values which are similar to those of the foetus. Addition of carnitine stimulates production of acid-soluble material throughout development. The effect of added carnitine on CO(2) production varies with age, stimulating in foetal and post-weaning age groups but inhibiting during the suckling period. 2. The degradation of [U-(14)C]palmitate to acid-soluble material and CO(2) by heart homogenates also varies during development. Formation of both products is highest 5 days after birth and thereafter decreases steadily to adult values. Addition of carnitine stimulates the production of both CO(2) and acid-soluble material at all ages. 3. The activity of carnitine palmitoyltransferase in liver increased after birth to reach maximum activity at 2-5 days of age. Thereafter the activity of the enzyme decreased until day 15 of life and then remained constant until day 30, decreasing after this time to adult values which were about one half of the foetal liver activities.

Animals↗
PubMed1969

A comparison of the properties of the pyruvate kinases of the fat body and flight muscle of the adult male desert locust.

1. The pyruvate kinases of the desert locust fat body and flight muscle were partially purified by ammonium sulphate fractionation. 2. The fat-body enzyme is allosterically activated by very low (1mum) concentrations of fructose 1,6-diphosphate, whereas the flight-muscle enzyme is unaffected by this metabolite at physiological pH. 3. Flight-muscle pyruvate kinase is activated by preincubation at 25 degrees for 5min., whereas the fat-body enzyme is unaffected by such treatment. 4. Both enzymes require 1-2mm-ADP for maximal activity and are inhibited at higher concentrations. With the fat-body enzyme inhibition by ADP is prevented by the presence of fructose 1,6-diphosphate. 5. Both enzymes are inhibited by ATP, half-maximal inhibition occurring at about 5mm-ATP. With the fat-body enzyme ATP inhibition can be reversed by fructose 1,6-diphosphate. 6. The fat-body enzyme exhibits maximal activity at about pH7.2 and the activity decreases rapidly above this pH. This inactivation at high pH is not observed in the presence of fructose 1,6-diphosphate, i.e. maximum stimulating effects of fructose 1,6-diphosphate are observed at high pH. The flight-muscle enzyme exhibits two optima, one at about pH7.2 as with the fat-body enzyme and the other at about pH8.5. Stimulation of the enzyme activity by fructose 1,6-diphosphate was observed at pH8.5 and above.

Adenine Nucleotides↗
PubMed1969

A comparison of the properties of the phosphofructokinases of the fat body and flight muscle of the adult male desert locust.

1. Phosphofructokinase was isolated, and partially purified by ammonium sulphate fractionation, from the fat body and flight muscle of the desert locust. 2. Ammonium sulphate appears to stabilize the enzymes, but does not activate them. 3. Both flight-muscle and fat-body enzymes give sigmoidal hexose monophosphate concentration-activity curves, which are characteristic of regulatory enzymes. 4. At low ATP concentrations both the enzyme activities increase rapidly with increasing ATP concentrations, but above an optimum concentration ATP becomes inhibitory. This optimum concentration is 0.2mm for the fat-body enzyme and 0.1mm for the flight-muscle enzyme. 5. AMP activates both the enzymes; half-maximal activation occurs at 10mum in each case, the effect being independent of substrate concentration. 6. 3',5'-(cyclic)-AMP (0.5mm) and P(i) (1mm) activate the flight-muscle enzyme, but have no effect on the fat-body enzyme. 7. FDP (1mm) inhibits both enzymes, and with the flight-muscle enzyme this inhibition is increased by increasing the ATP concentration. 8. Citrate, phosphoenolpyruvate and alpha-glycerophosphate have no effect on either enzyme under the assay conditions used. 9. The properties of phosphofructokinases from the locust are compared with those of phosphofructokinases from other sources.

Adenine Nucleotides↗
PubMed1968

Regulation of rat liver pyruvate kinase. The effect of preincubation, pH, copper ions, fructose 1,6-diphosphate and dietary changes on enzyme activity.

1. Preincubation of partially purified rat liver L-type pyruvate kinase at 25 degrees for 10min. causes a marked increase in co-operativity with respect to both the substrate, phosphoenolpyruvate, and the allosteric activator, fructose 1,6-diphosphate. 2. The results are consistent with the existence of two forms of liver L-type pyruvate kinase, designated forms L(A) and L(B). It is postulated that form L(A) has a low K(m) for phosphoenolpyruvate (about 0.1mm) and is not allosterically activated, whereas form L(B) is allosterically activated by fructose 1,6-diphosphate, exhibiting in the absence of the activator sigmoidal kinetics with half-maximal activity at about 1mm-phosphoenolpyruvate. In the presence of fructose 1,6-diphosphate, form L(B) gives Michaelis-Menten kinetics with K(m) less than 0.1mm. It is further postulated that preincubation converts form L(A) into form L(B). 3. The influence of pH on the preincubation effect was studied. 4. The inhibition of pyruvate kinase by Cu(2+) was studied in detail. Though phosphoenolpyruvate and fructose 1,6-diphosphate readily protect the enzyme against Cu(2+) inhibition, little evidence of significant reversal of the inhibition by these compounds could be found. 5. The effects of starvation, fructose feeding and preincubation on the pyruvate kinase activity of crude homogenates of various tissues of the rat were also studied.

Animals↗