Intramitochondrial reductive carboxylation of 2-oxoglutarate in adipose tissue and its contribution to fatty acid synthesis

• 1.1. The reductive carboxylation of 2-oxoglutarate was found to proceed in mitochondria of rat epididymal fat pads and rabbit perirenal adipose tissue at a rate similar to that in liver mitochondria.
• 2.2. In rat fat pads the incorporation of ¹⁴C from [5-¹⁴C]2-oxoglutarate into fatty acids via the carboxylation was suppressed by butylmalonate by 30%.
• 3.3. 2-Oxoglutarate and glutamate stimulated the incorporation into fatty acids of ¹⁴C from [2-¹⁴C]acetate in rat fat pads with the simultaneous reduction of tissue NADP. These effects persisted after inhibition of succinate dehydrogenase by malonate.
• 4.4. It is concluded that in adipose tissue 2-oxoglutarate carboxylation proceeds in both the cytoplasm and mitochondria. Therefore, it can supply carbon atoms as well as NADPH for fatty acid synthesis.

     

Comparative studies of glucose metabolism on mammals' red blood cells

• 1.1. Glucose utilization was measured in human, pig, cow, rabbit, mouse and rat red blood cells. Mean values are variable from species to species and range from 0.27 μmol/hr/ml RBC for pig erythrocytes to 2.85 μmol/hr/ml RBC in mouse red cells.
• 2.2. The amount of glucose metabolized through the pentose phosphate pathway ranges from 2.1 to 7.0% of the total glucose utilized.
• 3.3. Variable recycling values have been obtained for the red blood cells of the species studied but with the exception of mouse (14 nmol/hr/ml RBC) all the other values do not show great differences.
• 4.4. The hexokinase levels of the erythrocytes studied when correlated with the glucose utilization and the pentose phosphate pathway show that this enzyme could play a central role in the regulation of glucose metabolism.

     

Characterization of the blood volume and iron kinetics in the three-toed sloth,Bradypus tridactylus

• 1.1. Blood volume and iron kinetics were determined in three specimens of Bradypus tridactylus which were obtained in the coastal north-east regions of Brazil.
• 2.2. The average blood volume, circulating red cell volume and plasma volume were 54.9, 19.5 and 35.4 ml/kg body weight, respectively.
• 3.3. The average plasma iron disappearance half-time was 150.6min; the red cell radioiron uptake was 62% and the serum iron was 74.3 μg/100 ml.
• 4.4. From these figures the plasma iron turnover rate was calculated to be 165.6 μg/kg per day and the red cell iron turnover rate 102.7 μg/kg per day.

     

A comparison of tissue lipoprotein lipase activities determined in either fresh or defatted tissue preparations

• 1.1. Lipoprotein lipase activities were determined in either fresh aqueous homogenates or homogenates of acetone-diethyl ether dried powders of adipose tissue, heart, skeletal muscle and lung tissue taken from both fed and 24 hr starved rats.
• 2.2. The total tissue enzyme activities detectable in powder preparations were considerably higher than those of fresh preparations in all the tissue except lung.
• 3.3. The identity of the enzyme activity was more clearly demonstrable with homogenates of solvent-dried powders.
• 4.4. The use of both types of preparation in an experiment where rats were injected with either saline or colchicine further demonstrated the advantages of the acetone-diethyl ether-dried tissue preparation in total tissue lipoprotein lipase activity determinations.

     

Purification and characterization of lipoprotein lipase from the white adipose,skeletal muscle,cardiac muscle,mammary gland and lung tissues of the rat

• 1.1. Lipoprotein lipase (LPL) was isolated from five rat tissues: white adipose, skeletal muscle, cardiac muscle, mammary gland and lung.
• 2.2. Specific activity of the preparations varied from 75 U/mg for skeletal muscle and 720 U/mg for adipose.
• 3.3. The preparations were further analysed using SDS-PAGE and a single component identified. The mol. wt of 61,000 Da of this component was consistent for all five of the tissue sources.
• 4.4. Significant differences in the values of the isoelectric points of the enzyme species were revealed. The values varied from 7.23 (SEM 0.022) for cardiac and lung to 7.51 (SEM 0.037) for mammary.
• 5.5. Two-dimensional electrophoresis, using isoelectric focusing in the first dimension and SDS-PAGE in the second revealed differences in the patterns of stained material derived from the five tissue sources.

     

A novel inhibitor of glycogen phosphorylase from crayfish hepatopancreas

• 1.1. A novel glycogen phosphorylase inhibitor was partially purified from crayfish hepatopancreas.
• 2.2. The inhibitor was found only in two species of crayfish examined, and not in lobster, fresh and salt water clams, mussels or cockroaches.
• 3.3. The inhibitor is a small protein (M_r = 23,000) which did not show proteolytic activity.
• 4.4. Preliminary kinetic analysis of the inhibitory mechanism indicated that it bound to both glycogen and the glycogen phosphorylase protein.
• 5.5. Inhibitor binding to glycogen resulted in a competitive inhibition pattern with respect to glycogen phosphorylase (inhibition constant of ca 10 μg/ml).
• 6.6. The inhibitor also bound glycogen phosphorylase directly with a binding coefficient of 100 μg/ml resulting in a partially non-competitive inhibition pattern with respect to phosphate.

     

Is the lipolytic response in porcine adipose tissue slices equivalent to the lipolytic response in isolated adipocytes?

• 1.1. In most cases, when isolated adipocytes and adipose tissue slices from the same animal were stimulated with various lipolytic agents (adrenergie agonists, theophylline, adenosine deaminase), the qualitative response was similar.
• 2.2. There were, however, numerous exceptions; e.g. quinterenol did not affect isolated adipocytes whereas it was a partial agonist for adipose slices from the same animal.
• 3.3. The adipocytes present in slices were larger than those isolated from slices by collagenase digestion.
• 4.4. Isolated adipocytes were not more sensitive than tissue slices to stimulation by lipolytic agents.

     

Insulin administration induces capillary growth in brown adipose tissue of heat-exposed rats

• 1.1. An apparent effect of insulin administration on enlargement of interscapular brown adipose tissue (BAT) was found in heat-exposed rats, but not in warm-adapted or cold-acclimated rats.
• 2.2. BAT extracts from the heat-acclimated/insulin-treated (HI) rats notably increased the capillary growth in an in vitro angiogenesis model in which microvascular fragments and myofibroblastic (Mf) cells isolated from lipid tissues were grown in co-culture, although a direct effect of insulin was not high.
• 3.3. BAT extracts from the HI rats stimulated the production of endothelial cell growth factor and collagen by Mf cells.
• 4.4. It is probable that an increased angiogenic activity contributes to the capillary growth and tissue growth in BAT of HI rats.

     

Identification of human acetyl-CoA carboxylase isozymes in tissue and in breast cancer cells

• 1.1. In the rat, acetyl-CoA carboxylase (ACC), a rate-limiting enzyme in fatty acid metabolism, exists as at least two different isozymes (M_r 265,000 and 280,000) that display distinct tissue-specific distribution and regulation.
• 2.2. Based on the study of human tissue and human-derived breast cancer cell lines by enzyme isolation and protein blotting techniques, we have now identified two human isoforms of M_r 265,000 (HACC 265) and 275,000 (HACC 275), each of which is homologous to one of the rat isozymes.
• 3.3. Human breast carcinoma cell lines show variable expression of these two isoforms, mirrored in the estimation of ACC acetyl-CoA kinetics.

     

The development of thermoregulation in the marsupial brushtail possum Trichosurus vulpecula

• 1.1. The adult possums showed a circadian rhythm of body temperature with a peak in temperature around midnight and a nadir at noon.
• 2.2. The young possum within the pouch displayed a circadian rhythm with the highest temperatures during the day and the lowest in the early evening.
• 3.3. Although the body temperature of the young possum exceeded that of the mother occasionally, for the major part of the 24 hr the body temperature of the young was lower than that of the mother.
• 4.4. The young possum could maintain a steady body temperature between 140 and 167 days post partum. A circadian rhythm of temperature was observed between 157–190 days post partum.
• 5.5. All adipose tissue examined with the light and electron microscope had the morphology of white adipose tissue.

     

Changes in serum immunoglobulin M (IgM) concentrations during early development of chum salmon (Oncorhynchus keta) as determined by sensitive elisa technique

• 1.1. A specific and sensitive sandwich enzyme-linked immunosorbent assay (ELISA) was developed for the measurement of low levels of serum immunoglobulin M (IgM) of chum salmon Oncorhynchus keta.
• 2.2. In this assay, 5 μl serum was enough to measure the concentration of IgM and the minimum detectable concentration of serum IgM was about 5 ng/ml.
• 3.3. Coefficients of variation within and between assays ranged from 2.90 to 9.61%.
• 4.4. IgM concentrations remained at low level (< 300 ng/ml) until 40 days after hatching and then increased rapidly at the period of emergence (48 days after hatching).

     

Interaction of lipogenic substrates in porcine adipose tissue in vitro

• 1.1. Porcine adipose tissue was incubated with radiolabeled glucose, acetate or lactate. Saturation curves indicated that lactate > glucose > acetate in providing two-carbon units for fatty-acid synthesis.
• 2.2. Competition between individual substrates indicated that lactate was the best lipogenic substrate.
• 3.3. Incubation of all three substrates at concentrations observable in serum indicated that at 5.56mM, glucose was the preferred lipogenic substrate in the presence of 0.1 mM acetate and 1.0 mM lactate.
• 4.4. At elevated concentrations (18.52mM glucose, 1.0 mM acetate and 10.0 mM lactate), acetate and lactate were preferred to glucose as lipogenic substrates.

     

Effects of the nonsteroidal anti-inflammatory drug piroxicam on energy metabolism in the perfused rat liver

• 1.1. The actions of piroxicam, a nonsteroidal and noncarboxylic anti-inflammatory drug, on the metabolism of the isolated perfused rat liver were investigated. The main purpose was to verify if piroxicam is also active on glycogenolysis and energy metabolism, as demonstrated for several carboxylic nonsteroidal anti-inflammatories.
• 2.2. Piroxicam increased oxygen consumption in livers from both fed and fasted rats.
• 3.3. Piroxicam increased glucose release and glycolysis from endogenous glycogen (glycogenolysis).
• 4.4. Gluconeogenesis from lactate plus pyruvate was inhibited.
• 5.5. The action of piroxicam on oxygen consumption was blocked by antimycin A, but not by atractyloside.
• 6.6. The action of piroxicam in the perfused rat liver metabolism seems to be a consequence of its action on mitochondria.
• 7.7. It can be concluded that inhibition of energy metabolism and stimulation of glycogenolysis are not specific properties of carboxylic nonsteroidal anti-inflammatory drugs.

     

Differential post-receptor responses of adenylate cyclase in white and brown adipose tissue membranes of rats fed high-energy diets

• 1.1. Adenylate cyclase activity was determined in membranes of white and brown adipose tissue (WAT and BAT, respectively) from rats fed a high-energy diet (EXP group) vs those fed a nutritionally balanced one (CON group).
• 2.2. The isoproterenol- and guanine nucleotide-induced adenylate cyclase activity in WAT membranes of EXP rats was lower than that in CON rats.
• 3.3. Relative adenylate cyclase activity in like treated BAT membranes was higher in EXP than in CON rats.
• 4.4. It is concluded that feeding high-energy diets to rats induces similar post-receptor modifications of adenylate cyclase as found in genetic obese rodents.

     

Bovine serum sialic acid: Age-related changes in type and content

• 1.1. The sialic acid content of newborn calf serum (4.8 μmol/ml) is approx. 3-fold higher than that of mature animals (1.4 μmol/ml) and decreases to 2.4 μmol/ml at 20 days of age. Colostrum-fed and colostrum-deprived calves have similar levels of sialic acid from birth to 14 days of age.
• 2.2. The high level of sialic acid in newborn calf serum is due predominantly to N-acetylneuraminic acid, since this sialic acid accounts for 93% of the total and since <5% of the sialic acid is O-acetylated.
• 3.3. Comparison of day 0 and day 20 serum by gel filtration and by SDS polyacrylamide gel electrophoresis demonstrates that the increase in sialic acid is associated with increased production and/or sialylation of components with MW of 45–60 kDa.
• 4.4. A high percentage (64%) of the sialic acid in newborn calf serum is detected with the lipid-linked sialic acid assay, relative to 20 day old (25%) or mature (18%) animals.
• 5.5. This indicates that the glycoproteins of newborn calf serum are more efficiently extracted under the conditions of this assay than glycoproteins of mature serum.

     

Histochemical staining of cadmium taken up by the midge larva,Chironomus yoshimatsui (diptera,chironomidae)

• 1.1. The midge larva (Chironomus yoshimatsui) exposed to cadmium (10 μg Cd/ml) for 2 days was histochemically stained with benzothiazolylazo-β-naphthol.
• 2.2. A large portion of cadmium taken up by the larvae was distributed to the digestive tract, epithelial tract and fat bodies.
• 3.3. Cadmium accumulated in the fat bodies was discharged slowly relative to cadmium in the tract contents when the larvae were placed in control water.
• 4.4. Glycogen in the fat bodies of cadmium-exposed larvae was insensitive to PAS staining.

     

Combined effect of adenosine,alpha adrenergic and adenosine antagonists on serum insulin and insulin secretion from rat pancreatic islets

• 1.1. The effect of adenosine separately or in combination with alpha-1 adrenergic antagonist prazosin and alpha-2 adrenergic antagonist yohimbine as well as adenosine antagonists 8-phenyltheophylline and xanthine amine conjugate on glucose-induced insulin secretion from isolated rat pancreatic islets was studied.
• 2.2. Their in vivo effects on serum glucose and insulin levels were also investigated. Adenosine at 10 and 100 μM inhibited significantly, insulin secretion from the isolated islets whereas at 10 mM slightly increased the secretion of insulin.
• 3.3. Prazosin used at 100 μM inhibited insulin secretion. When it combined with adenosine (10 μM) it augmented the inhibitory effect of adenosine.
• 4.4. In vivo prazosin (21 mg/kg bodywt) caused a hyperglycaemia which was accompanied by hypoinsulinaemia.
• 5.5. Concurrent administration of this drug with adenosine neither affect the hyperglycaemic nor the hypoinsulinaemic effects of adenosine.
• 6.6. On the other hand, yohimbine (100 μM) has no effect neither separately nor in combination with adenosine (10 μM) in modulating the inhibitory effect of adenosine on insulin secretion.
• 7.7. When Yohimbine administered at 19.5 mg/kg body wt it did not alter serum glucose but it markedly increased the serum insulin level. Its combined administration with adenosine reduced the hyperglycaemic effect of adenosine with a remarkable increase in serum insulin.
• 8.8. Both adenosine-antagonists were ineffective in alteration of insulin secretion.
• 9.9. However, combination of 8-phenyltheophylline with adenosine (10 μM) totally blocked the inhibitory effect of adenosine on insulin secretion while xanthine amine conjugate failed to prevent this effect of adenosine.
• 10.10. These results indicate that the inhibitory effect of adenosine on insulin secretion is neither mediated via alpha-1 nor alpha-2 adrenoceptors. It might be via activation of specific adenosine receptors on rat islets which are sensitive to blockade by 8-phenyltheophylline.

     

The metabolic output of avian (Sturnus vulgaris,Calidris alpina) adipose tissue liver and skeletal muscle: Implications for BMR/body mass relationships

• 1.1. The oxygen uptake rate of avian adipose tissue, liver and skeletal muscle slices were measured.
• 2.2. The energy consumption of fat was less than one tenth that of liver and muscle.
• 3.3. Thus, interspecific allometric equations for the prediction of basal metabolic rate from body mass will not be accurate throughout the avian annual cycle unless changes in body composition are taken into account.

     

The synthesis of pyridoxal phosphate in rat brain regions

• 1.1. The concentration of pyridoxal phosphate in various areas of brain was non-uniform, ranging from 0.86–1.97 μg/g tissues.
• 2.2. Similarly, the activity of pyridoxal kinase showed an uneven distribution, ranging from 94–248 mμ moles pyridoxal phosphate formed/g tissue per hr.