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Biomedical subjects

R W Hanson

Publications and source records attributed to R W Hanson.

At least 181 records · Page 10Linked to original sources
PubMed1969

Measurement of adipose-tissue metabolites in vivo.

1. The concentrations of glucose, pyruvate, lactate, citrate, glutamate, malate and aspartate were measured in epididymal adipose tissue from starved, fed and starved-re-fed rats. 2. To measure these intermediates it was necessary to correct for their concentration in the extracellular tissue space, which was considered to be most satisfactorily equated with the glucose space. This space in vivo was 7.42, 4.90 and 7.54ml./100g. wet wt. of tissue in adipose tissue taken from starved, fed and starved-re-fed rats respectively. After correction for the glucose space, the concentrations of metabolites (nmoles/g. of cells) in epididymal adipose tissue of fed rats were: pyruvate, 8.5; lactate, 50.3; citrate, 18.5; glutamate, 100.0; malate, 6.4; aspartate, 34.2. 3. Starvation for 72hr. resulted in a fall in pyruvate and aspartate concentrations to 3.57 and 25.1nmoles/g.; starvation for 72hr. followed by re-feeding for 72hr. caused an increase in glutamate and aspartate concentrations to 140 and 67.6nmoles/g. 4. These changes are interpreted with regard to the simultaneous alteration in lipogenesis that occurs during the starvation-re-feeding cycle.

Adipose Tissue↗
PubMed1969

Dietary protein and the control of fatty acid synthesis in rat adipose tissue.

Fatty acid synthesis in adipose tissue normally proceeds at a high rate when fasted animals are refed a diet containing carbohydrate, protein, and low levels of fat. This study investigated the effect of omitting protein from the refeeding diet. Rats were fasted for 48 hr and refed either a protein-free diet or a balanced diet, and the rate of fatty acid synthesis from glucose, pyruvate, lactate, and aspartate was measured. Refeeding the animals a diet devoid of protein resulted in a low rate of fatty acid synthesis from each of these substrates as well as a reduction in carbon flow over the citrate cleavage pathway. The activities of glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, NADP-malate dehydrogenase, and ATP-citrate lyase were also reduced in epididymal fat pads from these rats. On the other hand, adipose tissue phosphoenolpyruvate carboxykinase activity was five times as great as that in tissue from animals refed a balanced diet. This difference could be eliminated if actinomycin D was injected coincident with refeeding. Refeeding rats diets high in carbohydrate is not, therefore, capable of inducing high rates of fatty acid synthesis in adipose tissue in the absence of dietary proteins. Thus, liver and adipose tissue respond differently to dietary protein.

Adipose Tissue↗
PubMed1968

Citrate, pyruvate, and lactate contaminants of commercial serum albumin.

Commercial serum albumin was found to contain lactate, pyruvate, and especially citrate in addition to fatty acids. Glucose, aspartate, and alpha-ketoglutarate were also present but at lower concentrations. Charcoal treatment followed by prolonged dialysis was effective in removing most of these contaminants.

Animals↗
PubMed1967

Changes in lipid synthesis in rat liver during development.

1. Lipogenesis, as measured by the incorporation of (14)C-labelled glucose or acetate into fatty acids in liver slices, is high in foetal and adult rat liver but is low in the liver of the suckling rat, especially with glucose as substrate. 2. The rate of synthesis of non-saponifiable lipids from glucose is about 15 times as great in the liver of the 18-day foetus as in adult liver. Activity in the newborn is negligible. 3. Glucose incorporation into fat is strongly concentration-dependent in liver slices from the adult and 2-week-old rat, but less markedly so in liver slices from the foetus. 4. Changes in the activity of hepatic citrate-cleavage enzyme (ATP-citrate lyase) occur in parallel with the changes in the extent of fatty acid formation, supporting the participation of this enzyme in lipogenesis. However, NADP-malate dehydrogenase, a potential source of reduced nucleotide coenzyme for lipogenesis in the adult, could not be detected in foetal rat liver.

Journal Article↗
PubMed1967

Phosphoenolpyruvate carboxykinase and pyruvate carboxylase in developing rat liver.

1. Phosphoenolpyruvate carboxykinase and pyruvate carboxylase were measured in foetal, newborn and adult rat liver extracts by a radiochemical assay involving the fixation of [(14)C]bicarbonate. 2. Pyruvate-carboxylase activity in both foetal and adult liver occurs mainly in mitochondrial and nuclear fractions, with about 10% of the activity in the cytoplasm. 3. Similar studies of the intracellular distribution of phosphoenolpyruvate carboxykinase show that more than 90% of the activity is in the cytoplasm. However, in the 17-day foetal liver about 90% of the activity is in mitochondria and nuclei. 4. Pyruvate-carboxylase activity in both particulate and soluble fractions is very low in the 17-day foetal liver and increases to near adult levels before birth. 5. Phosphoenolpyruvate-carboxykinase activity in the soluble cell fraction increases 25-fold in the first 2 days after birth. This same enzyme in the mitochondria has considerable activity in the foetal and adult liver and is lower in the newborn. 6. Kinetic and other studies on the properties of phosphoenolpyruvate carboxykinase have shown no differences between the soluble and mitochondrial enzymes. 7. It is suggested that the appearance of the soluble phosphoenolpyruvate carboxykinase at birth initiates the rapid increase in overall gluconeogenesis at this stage.

Aging↗
PubMed1967

The relative significance of acetate and glucose as precursors for lipid synthesis in liver and adipose tissue from ruminants.

1. The incorporation of labelled glucose into lipid by liver slices from sheep and cows is considerably less than that by liver slices from the rat, although oxidation to carbon dioxide occurs to a similar extent. ATP citrate lyase and NADP malate dehydrogenase are inactive in both sheep and cow liver but active in rat liver. The absence of the citrate-cleavage pathway of lipogenesis in ruminant liver has been confirmed by the negligible amounts of C-3 of aspartate incorporated into fatty acids. 2. Considerable amounts of [(14)C]acetate are incorporated into fatty acids and non-saponifiable lipid in rat and ruminant liver. Acetyl-CoA synthetase, the initial enzyme in the metabolism of acetate, has a high activity in liver from rat and ruminants. 3. In adipose tissue from ruminants more acetate than glucose is converted into lipids, whereas the converse is true in rat adipose tissue. The greater incorporation of [(14)C]acetate into fatty acids in adipose tissue from the ruminant as compared with the non-ruminant may be caused, in part, by the higher activity of acetyl-CoA synthetase activity in the ruminant. 4. The results suggest that, in both liver and adipose tissue from ruminants, acetate is a more important source of lipid than glucose. 5. Two enzymes of the hexose monophosphate shunt, glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase, are active in both tissues and from the three species.

Acetates↗
PubMed1967

Pyridine nucleotide synthesis by rat adipose tissue in vitro.

The synthesis of NAD and NADP by rat adipose tissue was measured in vitro. Nicotinamide-7-(14)C and NaH(2)(32)PO(4) were incorporated together into NAD with a (32)P/(14)C ratio of 1.82 and nicotinic-7-(14)C acid and NaH(2)(32)PO(4) with a ratio of 1.94. Nicotinic acid stimulated, by 90%, lipogenesis from glucose-U-(14)C by rat adipose tissue in vitro. Glucose plus insulin and refeeding for 48 hr after a 48 hr fast markedly increased the incorporation of nicotinic-7-(14)C into NAD in rat epididymal fat pads in vitro, but neither fructose, L-glutamine, nor insulin alone increased the synthesis of NAD in this tissue. Glucose-1-(14)C, ribose-1-(14)C, and to a greater extent glucose-6-(14)C are incorporated into the NAD of rat adipose tissue. Fasting followed by refeeding sharply increased the radioactivity of NAD-(14)C formed from glucose-1-(14)C and glucose-6-(14)C but not from ribose-1-(14)C. Increasing the ribose concentration from 2 mM to 10 mM increased its incorporation into adipose tissue NAD twofold. The nicotinic-7-(14)C acid incorporation into NAD increased over the 1st hr of incubation and remained constant for the next 3 hr. The concentration of NAD in the fat pads showed a similar response to the time of incubation. NADP concentrations increased over the entire 4 hr incubation period as did the incorporation of nicotinic-7-(14)C acid into NADP. The results of this study suggest that NAD is synthesized de novo by rat adipose tissue in vitro and that this synthesis is increased by factors which stimulate lipogenesis.

Adipose Tissue↗
PubMed1967

The citrate cleavage pathway and lipogenesis in rat adipose tissue: replenishment of oxaloacetate.

Fatty acid synthesis via the citrate cleavage pathway requires the continual replenishment of oxaloacetate within the mitochondria, probably by carboxylation of pyruvate. Malic enzyme, although present in adipose tissue, is completely localized in the cytoplasm and has insufficient activity to support lipogenesis. Pyruvate carboxylase was found to be active in both the mitochondria and cytoplasm of epididymal adipose tissue cells; it was dependent on both ATP and biotin. Alteractions in dietary conditions induced no significant changes in mitochondrial pyruvate carboxylase activity, but the soluble activity was depressed in fat-fed animals. The possible importance of the soluble activity in lipogenesis lies in its participation in a soluble malate transhydrogenation cycle with NAD malate dehydrogenase and malic enzyme, whereby a continual supply of NADPH is produced. Consequently, the pyruvate carboxylase in adipose tissue both generates mitochondrial oxaloacetate for the citrate cleavage pathway and supplies soluble NADPH for the conversion of acetyl-CoA to fatty acid.

Adipose Tissue↗