Resynthesis of glycogen in skeletal muscle from standardbred trotters after repeated bouts of exercise.

Objective: To determine glycogen resynthesis rate and changes in plasma metabolite concentrations in horses before and after repeated exercise.

Animals: 6 clinically normal Standardbred trotters.

Procedure: Horses trotted distances of 3,000, 3,000, and 2,000 m (trial A) and 3 days later, trotted 2,100, 2,100, and 1,600 m (trial B).

Restoration of water and electrolyte balance in horses after repeated exercise in hot and humid conditions.

Nine adult riding horses performed on a treadmill a competition exercise test (CET) and 24 h later a standardised exercise test (SET) at mean temperature 28 degrees C and relative humidity 58%. Each horse performed the tests 5 times at 2 week intervals. The horses were given isotonic glucose-electrolyte solution via a nasogastric tube 30 min after the CET, except after the last trial when water was given.

Skeletal muscle characteristics of racing reindeer (Rangifer tarandus).

Samples from the middle gluteal muscle of 3-7-year-old racing reindeer were taken before (7 reindeer) and at the end of the racing season (12 reindeer) for determination of fibre type composition, activities of citrate synthase (CS), 3-hydroxyacyl-CoA-dehydrogenase (HAD) and the glycogen content. Muscle samples were also taken from 7 female and 18 male reindeer of same age for histochemical determination of muscle fibre composition. During the racing season the fibre type composition remained unchanged as did the activities of CS and HAD.

Accumulation of uric acid in plasma after repeated bouts of exercise in the horse.

Plasma concentration of uric acid, total peroxyl radical-trapping antioxidative parameter (TRAP), blood lactate concentration and plasma activity of xanthine oxidase (XO) were measured in six Standardbreed trotters after six bouts of exercise with increasing intensity on two separate days three days apart. Blood samples were taken immediately, 5, 10, 15, 30 and 60 min after each heat and 2, 4, and 6 hr after the last heat. Exercise caused an increase in TRAP and in the concentrations of lactate and uric acid.

A rhodopsin-based model for melatonin recognition at its G protein-coupled receptor.

The recent elucidation of the primary structures of different melatonin receptors as well as the deduction of the secondary structure of rhodopsin has allowed us to construct a model for melatonin recognition at its G protein-coupled receptor. To achieve this, we have used the quantum mechanics method Austin model 1 to fully optimize the structures of melatonin and several analogs. We also synthesized three compounds and used the three-dimensional analysis comparative molecular field analysis (CoMFA) to generate a model for the structure-activity relationships of melatonin and 27 melatonin-like compounds.

Exercise-induced changes in the activities of beta-glucuronidase and N-acetyl-beta-D-glucosaminidase in plasma and muscle of standardbred trotters.

The activities of lysosomal enzymes, such as beta-glucuronidase and N-acetyl-beta-D-glucosaminidase, have been shown to increase in muscle after endurance exercise. We examined whether measurable activities of lysosomal enzymes are present in equine plasma and whether the exercise-induced changes in the muscle are reflected in plasma. Six trained Standardbred trotters performed three exercise bouts with 1 h intervals and the same procedure was repeated 3 days later.

Responses of blood and plasma lactate and plasma purine concentrations to maximal exercise and their relation to performance in standardbred trotters.

Objective: To study whether end products of 2 pathways of anaerobic energy metabolism, lactate and purines, that accumulate in the blood after intense exercise indicate any relation to exercise performance.

Design: Venous blood samples were taken within 1 and 15 minutes after a trotting race of 2,100 m.

Animals: 16 Clinically healthy Standardbred trotters.

Competitive inhibition of coumarin 7-hydroxylation by pilocarpine and its interaction with mouse CYP 2A5 and human CYP 2A6.

1. We have shown earlier that pilocarpine strongly inhibits mouse and human liver coumarin 7-hydroxylase activity of CYP 2A and pentoxyresorufin O-deethylase activity of CYP 2B in vitro. Since pilocarpine, like coumarin, contains a lactone structure we have studied in more detail its inhibitory potency on mouse and human liver coumarin 7-hydroxylation.

An empirical and theoretical study on mechanisms of mutagenic activity of hydrazine compounds.

Hydrazine compounds are important industrial and laboratory chemicals. Many of them are carcinogenic in animal tests. Although the carcinogenicity is well established, the results of mutagenicity tests performed on alkylhydrazines vary greatly in different studies.

Changes in solid-state structure of cyclophosphamide monohydrate induced by mechanical treatment and storage.

The effects of mechanical treatment and various storage conditions on the structure of cyclophosphamide monohydrate were evaluated by thermal and X-ray analyses and molecular modeling. The monohydrate form of cyclophosphamide was found to convert to the anhydrous form through a metastable phase. Metastable forms were produced by mechanical treatment and by desiccation.

Exercise-induced changes in blood composition of racing reindeer (Rangifer tarandus tarandus L.).

The responses to near-maximal exercise before and after the training and racing season were examined in reindeer. The reindeer were tested when pulling a driver at a speed of 11-12 m/s for 600 m. The lactate responses were higher before than after training.

Plasma protein synthesis and serum amino acids in dry and lactating dairy cows.

Blood serum concentrations of protein, albumin, prealbumin, transferrin, amino acids and urea were measured in 31 healthy cows 0 to 6 weeks before and 3 to 8 weeks after parturition. In comparison to the precalving values the concentrations of albumin, prealbumin and transferrin were all lower after parturition. Alanine, glutamine, leucine, methionine, serine, and urea concentrations were also lower after calving.

Accumulation of allantoin and uric acid in plasma of exercising trotters.

Plasma concentrations of hypoxanthine, uric acid, and allantoin, which are breakdown products of adenine nucleotides, were measured in Standardbred and Finnhorse trotters during and after an exercise test on a high-speed treadmill, after an incremental exercise test performed on a racetrack, and after a racing competition. Fiber-type composition of the middle gluteal muscle and the muscle concentrations of adenine nucleotides and inosine monophosphate were measured after the racetrack test. Changes in the concentration of hypoxanthine were not observed in any of the tests.

Metabolic response to standardised exercise test in standardbred trotters with red cell hypervolaemia.

Plasma concentrations of lactate, amino acids, ammonia and products of purine catabolism were studied before, during and after a standardised incremental exercise test in 29 Standardbred trotters admitted to the clinic for exercise tolerance testing. According to their red cell volume the horses were divided into red cell normovolaemic and red cell hypervolaemic (polycythaemic) groups. The exercise-response curve for taurine differed significantly in the two groups, whereas all the other amino acids behaved similarly.

Localization of xanthine dehydrogenase mRNA in horse skeletal muscle by in situ hybridization with digoxigenin-labelled probe.

In situ hybridization was used to localize xanthine dehydrogenase (XDH) mRNA in horse skeletal muscle. Capillary endothelial cells were found to express XDH, but muscle cells did not give any signal. The digoxigenin-labelled probe was produced by PCR with primers based on the cDNA sequence of mouse XDH and horse lung cDNAs.

Parallel control of hepatic proteolysis by phenylalanine and phenylpyruvate through independent inhibitory sites at the plasma membrane.

Intracellular protein degradation in the rat hepatocyte is regulated by 7 amino acids of which Leu, Gln, and Tyr play major roles. Although Phe is known to inhibit proteolysis as effectively as Tyr at high concentrations, it has not been regarded as an active regulator because of its rapid hydroxylation to Tyr. We now show that proteolytic responses to Phe during liver perfusion differ strikingly from effects of the multiphasic regulators Leu, Gln, and Tyr in eliciting mirror image responses at half-normal and normal plasma concentrations.

Does a single bout of exercise cause adaptation of amino acid metabolism in pigs?

Amino acid responses to exercise stress in well-trained racehorses and human athletes are well characterised, but the knowledge of amino acid metabolism during and after exercise in inactive animal species is limited. To study this, plasma amino acid concentrations were measured in previously unexercised pigs which performed two exercise tests on a treadmill with an interval of one week. In general, the changes in amino acids were more pronounced after the second than after the first exercise bout.

Inhibition of proteolysis in the liver by chronic ethanol feeding.

Effects of chronic ethanol feeding on the volume density of lysosomes, the rate of protein degradation and the amount of protein were studied in livers perfused in situ at 07:00, 11:00, 17:00 and 23:00 h. Ethanol was given to the rats in drinking water for either 3 or 8-10 weeks. During week 3 of treatment and onwards, the average daily consumption of ethanol was 12.

Heterogenous zonal distribution of lysosomal enzymes in rat liver.

The activities of beta-N-acetylglucosaminidase, beta-glucuronidase, alpha-L-iduronidase and acid phosphatase were all significantly higher in the cell lysates from the periportal than from the perivenous region obtained by the regioselective digitonin treatment of the perfused liver. The activities of cathepsins B, H and L were only slightly higher in the periportal than in the perivenous cell lysates. These results support the view that there is little zonation of lysosomal degradation of proteins, whereas the enzymatic capacity for degradation of glycosaminoglycans may be more active in the periportal region.

Zonation of total and plasma protein turnover in rat liver: effects of chronic ethanol treatment.

To study the acinar distribution of protein turnover, rats were given a tracer dose of 14C-valine intraperitoneally. At 30 min or 20 hr later, livers were perfused in situ and periportal (pp) or perivenous (pv) cell lysates were collected after digitonin pulse infusion. In control rats the post-label radioactivity of cell lysates showed no zonation.

Dietary regulation of voluntary alcohol consumption in rats. Influence of a high protein diet and a methylene blue diet.

The importance of glucose homeostasis for high voluntary alcohol consumption was studied in alcohol-preferring (AA) and alcohol-avoiding (ANA) rats fed either a control diet, a protein-rich diet or a control diet supplemented with methylene blue. AA rats on the control diet were found to receive 13.6% of their daily energy intake from alcohol.

Exercise-induced transient hyperlipidemia in the racehorse.

Effects of graded intensity exercise on plasma lipids was studied in Standardbred and Finnishbred Trotters. The rate of lipolysis indicated by the elevated plasma concentrations of glycerol increased parallel with the intensity of the trot in the Standardbreds, but not as clearly in the Finnishbred trotters. During the exercise plasma triglyceride concentration increased significantly and the increase correlated with the intensity of the exercise as well as the activity of lipolysis.

Functional significance of aminoacyl-tRNA synthetase complex in the aminoacylation of tRNA(Leu) isoacceptors.

Aminoacyl-tRNA synthetases, partially purified from rat liver by two different methods, were used in vitro to study aminoacylation profiles of tRNA(Leu) isoacceptors. On the basis of molecular weights, one preparation was similar to the multienzyme complex of aminoacyl-tRNA synthetases, whereas the other apparently represents a partially disrupted complex. In the aminoacylation assay, the multienzyme complex produced a profile of leucyl-tRNA isoacceptors that was similar to those found in vivo and in liver perfusion experiments.

Mechanism and regulation of protein degradation in liver.

The degradation of intracellular protein and other cytoplasmic macromolecules in liver is an ongoing process that regulates cytoplasmic mass and provides amino acids for energy and other metabolic uses early in starvation. Cellular proteins are conveniently divided into two general classes according to readily discernable differences in average rates of turnover. A short-lived class, having a half-life of approximately 10 min, comprises about 0.

Hepatic carbohydrate metabolism in rats bred for alcohol preference.

The influence of ethanol on the carbohydrate metabolism was studied in two strains of rats: the AA strain with an inherited preference for alcohol and the ANA strain with an aversion to alcohol. In both strains, a single intraperitoneal dose of ethanol (1.5 g/kg body wt.