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A D Postle

Publications and source records attributed to A D Postle.

68 records · Page 4Linked to original sources
PubMed1990

CTP:cholinephosphate cytidylyltransferase in human and rat lung: association in vitro with cytoskeletal actin.

CTP:cholinephosphate cytidylyltransferase activities were compared in saline homogenates of immature fetal (15-16 weeks gestation) and adult human lung. There were no differences in subcellular enzyme distribution, in Vmax activity, or in the phosphatidylglycerol-mediated stimulation of soluble enzyme activity. These results provide no support for a developmental translocation of cytidylyltransferase from a cytosolic to a microsomal location in human lung, such as that proposed to accompany the maturation of pulmonary surfactant phosphatidylcholine biosynthesis in rat. Soluble cytidylyltransferase activity from human but not rat lung was increased after manipulation in vitro. Resolution of human H form (greater than 10(3) kDa) and L form (200 kDa) enzyme by gel filtration led to an activity increase of 200%. Incubation at 37 degrees C for 2 h increased soluble enzyme recovery, although prior centrifugal removal of generated actin-rich aggregates was necessary in adult lung fractions. In contrast, 85% of soluble rat lung cytidylyltransferase was actin aggregate-associated after incubation. The apparent heteroassociation of rat and human lung enzyme with actin in the presence of poly(ethylene glycol) at 4 degrees C strongly suggested close in vitro and potential in vivo linkage. A partial co-purification of adult human lung cytidylyltransferase with actin was also consistent with this idea. We propose that some reported cytidylyltransferase translocation phenomena may be mediated by cytoskeletal interactions in vitro.

Actins↗
PubMed1990

Erythrocyte fatty acid profiles in childhood malignancy.

The erythrocyte fatty acid composition was determined for 79 children using gas chromatography. The stearic:oleic acid ratio (SOR) was significantly lower in those children with newly diagnosed malignancies than in a reference group of healthy children. However, a control group of children with chronic, non-malignant conditions were also found to have a low SOR. These results suggest that the erythrocyte SOR cannot be used as a tumour marker in children.

Adolescent↗
PubMed1988

A comparison of the specificity of phosphatidylcholine synthesis by human fetal lung maintained in either organ or organotypic culture.

Human fetal lung (14-18 weeks gestation) was maintained in either organ or organotypic culture. By 4 days in organ culture or 14 days in organotypic culture, epithelial cells within both culture systems exhibited well-developed apical microvilli and possessed numerous intracellular lamellar bodies characteristic of surfactant phospholipid stores. However, analysis of the pattern of synthesis of individual molecular species of phosphatidylcholine by [14C]choline incorporation and reversed-phase h.p.l.c. showed that this apparent maturation was not paralleled by an increased synthesis of the dipalmitoyl species in either culture system. By contrast, the fractional synthesis of dipalmitoyl phosphatidylcholine, expressed as a percentage of total [14C]choline incorporation, decreased with time in both organ and organotypic culture. Moreover, these fractions were not significantly different from those measured in parallel monolayer cultures of mixed human fetal lung cells that displayed mainly fibroblast morphology. These results suggest that the synthesis pattern of phosphatidylcholine species by lung cells in culture is determined principally by their incubation conditions and not by their state of apparent maturation.

Cells, Cultured↗
PubMed1987

Method for the sensitive analysis of individual molecular species of phosphatidylcholine by high-performance liquid chromatography using post-column fluorescence detection.

Conditions are described for the efficient resolution by reversed-phase high-performance liquid chromatography on octadecylsilica stationary phases of individual molecular species of phosphatidylcholine on the basis of their fatty acyl composition. The effects are described of varying stationary phase carbon loading, mobile phase polarity and column temperature. Eluted peaks were detected by a sensitive post-column fluorescence system using the fluorescent probe 1,6-diphenyl-1,3,5-hexatriene. This detection system permitted direct quantitation of phosphatidylcholine species irrespective of the degree of acyl unsaturation and eliminated the need for elaborate pre-column derivatization. The techniques were applied to the analysis of phosphatidylcholine isolated from rat liver and lung.

Animals↗
PubMed1985

The proteins of human lung surfactant.

Human pulmonary surfactant was purified from bronchoalveolar lavage of patients. The proteins present in surfactant were analyzed by SDS-polyacrylamide gel electrophoresis into serum and non-serum components. One non-serum surfactant protein (Mr = 43 000) was then identified in the 100 000 X g supernatant of a lung homogenate on the basis of phospholipid binding. This lung protein was purified and partially characterized. The presence of 3-methyl histidine and reaction in Western blot analysis with antibody against chicken muscle actin both strongly suggested that the 43 000 Da protein of human surfactant is indeed cytoplasmic actin. It is proposed that this surfactant protein is involved in the secretion and not necessarily in the function of surfactant.

Amino Acids↗
PubMed1982

The induction of synthesis of L-type pyruvate kinase in cultured rat hepatocytes.

Hepatocytes were isolated from preweaned neonatal and adult rats and maintained in primary monolayer culture. Cells from preweaned newborns possessed no L-type pyruvate kinase, nor did they synthesize the enzyme. Incubation for 48-72 h in culture medium supplemented with 2 mM-fructose and 0.1 microM-insulin induced the synthesis of L-type pyruvate kinase, as judged by increased enzyme activity and the increased incorporation of [3H]leucine into immunoprecipitable L-type pyruvate kinase. Hepatocytes isolated from 48 h-starved adult rats incorporated less [3H]leucine into L-type pyruvate kinase than did cells isolated from high-carbohydrate-diet-fed rats. The rate of enzyme synthesis by cells from 48 h-starved rats was increased by the inclusion of fructose and insulin in the incubation medium, after a lag phase of 24-48 h. After 4 days in culture in the presence of fructose and insulin, hepatocytes from 48 h-starved rats synthesized L-type pyruvate kinase at similar rates to hepatocytes isolated from high-carbohydrate-diet-fed rats.

Age Factors↗
PubMed1982

Glucocorticoid hormones have a permissive role in the phosphorylation of L-type pyruvate kinase by glucagon.

The incorporation of [32P]phosphate into L-type pyruvate kinase in response to glucagon was studied in hepatocytes isolated from control and adrenalectomized rats. In control cells, pyruvate kinase phosphorylation was maximally stimulated by 210% by glucagon. Adrenalectomy reduced both the basal extent of phosphorylation and the response to glucagon to 25% of those measured in control hepatocytes. This impaired pyruvate kinase phosphorylation was associated with altered kinetic properties of L-type pyruvate kinase. Glucagon injected in vivo (1 mg/kg) into adrenalectomized rats did not increase the substrate-co-operativity of L-type pyruvate kinase. These results suggest a molecular basis for the well-recognised glucocorticoid hormone-dependence for the stimulation by glucagon of hepatic gluconeogenesis. Further effects of this defective enzyme regulation on hepatic metabolism are suggested by the observation that adrenalectomy abolished the ability of glucagon to inhibit hepatic fatty acid biosynthesis both in vivo and in isolated hepatocytes.

Adrenalectomy↗
PubMed1982

Lipid metabolism in pregnancy.

Serum cholesterol and triglyceride concentrations in 34 normal women were monitored before, during and after pregnancy. All women displayed an initial fall in both substances during the first trimester. The concentrations increased to maximum values during the third trimester. There was a considerable variation in the time required for this hyperlipidaemia to decline after delivery. Lactation appeared to be an important factor in this variation; women who bottle-fed their infants maintained an elevated serum triglyceride level for three times longer than those who breast-fed their infants.

Adult↗
PubMed1980

The use of tritiated water to measure absolute rates of hepatic glycogen synthesis.

Glucogen synthesis in rat liver in vivo was measured by the incorporation of 3H from 3H2O into glycogen. In meal-fed rats incorporation and the incorporation of 3H into glycogen was linear up to 100 min. Before feeding glycogen concentration and the incorporation of 3H were both low; and both rose on feeding to give maximal values after 2-3h. The glycogen concentration was maintained for a further 5h but the incorporation of 3H rapidly declined to pre-feeding values. This shows that glycogen turnover was low in the post-prandial rat. Streptozotocin diabetes decreased the rise in glycogen concentration on feeding and had a similar effect on 3H2O incorporation. Both effects were reversed by insulin administration. The number of 3H atoms incorporated per glycogen glucose moiety formed in biosynthetic experiments (2.84 +/- 0.47) was relatively constant and allowed absolute biosynthetic rates to be calculated. Degradation of glucose from glycogen labelled by 3H2O showed that most of the 3H was located at C-2 and C-5. The incorporation would arise by rapid equilibration of hexose phosphates through phosphoglucose isomerase, transaldolase and triose phosphate isomerase.

Animals↗
PubMed1979

Regulation of cholesterol synthesis in skin fibroblasts derived from old people.

Sterol synthesis from radioactive acetate and the suppression of this synthesis by human low density lipoprotein (LDL) have been investigated in skin fibroblast strains derived from infant donors and from donors over the age of 70 years. The activity of the enzyme hydroxymethylglutaryl-CoA reductase and its repression by LDL has also been investigated in these fibroblast strains and in senescent cells of the foetal lung cell strain MRC-5. No age-related differences could be detected either in repression of [3H]acetate incorporation by LDL, or in repression of HMG-CoA reductase activity.

Aged↗
PubMed1978

Double pre-beta lipoprotein in ischaemic heart disease.

The presence or absence of a double pre-beta lipoprotein (pre-beta 1+ or pre-beta 1-) peak on agarose gel electrophoresis was recorded in: a) 77 survivors of myocardial infarction, b) their first-degree relatives, and c) 148 controls. Thirty-nine percent of myocardial infarction survivors and 24% of controls had pre-beta 1+ (P less than 0.05). The segregation of pre-beta 1+ in the families of myocardial infarction survivors was consistent with autosomal dominant inheritance. In the control group, fasting serum cholesterol and triglyceride values were higher in the pre beta 1+ subjects, but the differences were not significant. We conclude that the presence of double pre-beta lipoprotein peak on electrophoresis is associated with an increased risk of myocardial infarction.

Cholesterol↗
PubMed1978

Comparison of three automated methods of serum tirglyceride analysis.

Two new automated methods for serum triglyceride analysis are described and compared with each other and with an established chemical method. They are a chemical method requiring no glycerol blank correction and a commercially available fully enzymatic method requiring no prior lipid extraction. Both methods had higher quality control precision and faster sampling rates than the established method. Comparison of duplicate analyses of a random series of serum samples by all three methods gave a closer correlation between the new methods than between either and the conventional method.

Adult↗