Effect of dietary supplements containing antioxidants on attenuation of muscle damage in exercising sled dogs.

OBJECTIVE: To determine whether dietary antioxidants would attenuate exercise-induced increases in plasma creatine kinase (CK) activity in sled dogs. ANIMALS: 41 trained adult sled dogs. PROCEDURE: Dogs, randomly assigned to 2 groups, received the same base diet throughout the study. After 8 weeks on that diet, 1 group (21 dogs) received a daily supplement containing vitamins E (457 U) and C (706 mg) and beta-carotene (5.1 mg), and a control group (20 dogs) received a supplement containing minimal amounts of antioxidants. After 3 weeks, both groups performed identical endurance exercise on each of 3 days. Blood samples were collected before and 3 weeks after addition of supplements and after each day of exercise. Plasma was analyzed for vitamins E and C, retinol, uric acid, triglyceride, and cholesterol concentrations, total antioxidant status (TAS), and CK activity. RESULTS: Feeding supplements containing antioxidants caused a significant increase in vitamin E concentration but did not change retinol or vitamin C concentrations orTAS. Exercise caused significantly higher CK activity, but did not cause a significant difference in CK activity between groups. Exercise was associated with significantly lower vitamin E, retinol, and cholesterol concentrations and TAS but significantly higher vitamin C, triglyceride, and uric acid concentrations in both groups. CONCLUSIONS AND CLINICAL RELEVANCE: Use of supplements containing the doses of antioxidants used here failed to attenuate exercise-induced increases in CK activity. Muscle damage in sled dogs, as measured by plasma CK activity, may be caused by a mechanism other than oxidant stress.

Effects of dietary antioxidant supplementation on oxidative damage and resistance to oxidative damage during prolonged exercise in sled dogs.

OBJECTIVES: To determine effects of dietary antioxidant supplementation on plasma concentrations of antioxidants, exercise-induced oxidative damage, and resistance to oxidative damage during exercise in Alaskan sled dogs. ANIMALS: 62 Alaskan sled dogs. PROCEDURE: Dogs were matched for age, sex, and ability and assigned to 1 of 3 groups: sedentary and nonsupplemented (control [C]; n = 21), exercised and supplemented (S; 22), and exercised and nonsupplemented (N; 19). Dogs in group S were given 400 units of alpha-tocopherol acetate, 3 mg of beta-carotene, and 20 mg of lutein orally per day for 1 month, then dogs in groups S and N completed 3 days of exercise. Blood samples were collected before and after 1 and 3 days of exercise and after 3 days of rest. Plasma antioxidant concentrations were determined, and oxidative damage to DNA (plasma 7,8 dihydro-8-oxo-2'deoxyguanosine [8-oxodG] concentration) and membrane lipids (plasma hydroperoxide concentration) and resistance of plasma lipoproteins to oxidation were assessed. RESULTS: Supplementation increased plasma concentrations of alpha-tocopherol, beta-carotene, and lutein. Plasma concentration of alpha-tocopherol increased and concentration of lutein decreased in group S with exercise. Concentration of 8-oxodG decreased in group S but increased in group N during and after exercise. Lag time of in vitro oxidation of lipoprotein particles increased with exercise in group S only. CONCLUSIONS AND CLINICAL RELEVANCE: Dietary supplementation with antioxidants resulted in increased plasma concentrations of antioxidants. Moreover, supplementation decreased DNA oxidation and increased resistance of lipoprotein particles to in vitro oxidation. Antioxidant supplementation of sled dogs may attenuate exercise-induced oxidative damage.

Oxidant stress in sled dogs subjected to repetitive endurance exercise.

OBJECTIVE: To determine whether repetitive endurance exercise in sled dogs was associated with substantial lipid peroxidation, decreases in antioxidant capacity of the serum, and skeletal muscle damage. ANIMALS: 24 lightly trained sled dogs. PROCEDURE: 16 dogs completed a 58-km run on each of 3 consecutive days; the other 8 dogs (control) did not exercise during the study. Blood samples were collected before the first exercise run and after the first and third exercise runs. Plasma isoprostane and serum vitamin E concentrations, total antioxidant status of plasma, and serum creatine kinase activity were measured. RESULTS: Plasma isoprostane concentrations in dogs in the exercise group were significantly increased after the first exercise run and further significantly increased after the third exercise run. Serum vitamin E concentration was significantly decreased after the first exercise run in dogs in the exercise group, and this change persisted after the third exercise run. There was a significant linear relationship between plasma isoprostane concentration and the logarithm of serum creatine kinase activity (adjusted ? = 0.84). CONCLUSIONS AND CLINICAL RELEVANCE: Results demonstrate that repetitive endurance exercise in dogs is associated with lipid peroxidation and a reduction in plasma antioxidant concentrations. We interpret these results as indicating that the antioxidant mechanisms of minimally trained dogs may, in some instances, be inadequate to meet the antioxidant requirements of repetitive endurance exercise.

Metabolizable energy intake and sustained energy expenditure of Alaskan sled dogs during heavy exertion in the cold.

OBJECTIVE: To measure energy expenditures of Alaskan sled dogs at rest and during racing under frigid conditions, using the doubly labeled water (DLW) technique. ANIMALS: 18 fit Alaskan sled dogs. PROCEDURE: Energy expenditure was measured in 9 dogs during a 490-km sled dog race by use of the DLW technique, whereby dogs were administered water enriched with nonradioactive isotopes of hydrogen and oxygen. Energy intake was determined by dietary analysis. Changes in background abundance of the isotopes 2H and 18O were monitored in 5 dogs that did not receive isotope-enriched water. RESULTS: Dogs completed the 490-km race at an average speed of 7 km/h at ambient temperature of -35 to -10 C. Total energy expenditure, measured by the DLW technique, was 47,100 +/- 5,900 kJ/d (4,400 +/- 400 kJ.kg-0.75/d), and metabolizable energy intake was 44,600 kJ/d (4,100 kJ.kg-0.75/d) during the 70-hour race. CONCLUSIONS: The sustained metabolic rate for these sled dogs during racing was extraordinarily high for a large mammal. This study validated use of the DLW technique in dogs with exceptionally high energy expenditure associated with prolonged exercise in the cold.

Effect of postexercise carbohydrate supplementation on muscle glycogen repletion in trained sled dogs.

OBJECTIVE: To evaluate the effect of immediate postexercise carbohydrate supplementation on muscle glycogen (MG) repletion during the first 4 hours of recovery in sled dogs. ANIMALS: 24 Alaskan Huskies. PROCEDURE: Dogs were assigned to 1 of 3 treatment groups, and a muscle biopsy specimen was obtained 1 hour before and immediately (group A) or 4 hours (groups B and C) after a 30-km run. Immediately after exercise, dogs in group A and group C were given water; dogs in group B were given a glucose polymer solution (1.5 g/kg of body weight) in water. RESULTS: At 4 hours after exercise, MG concentration was significantly greater in group-B than in group-C dogs; the value in group-C dogs was not different from the value in group-A dogs immediately after exercise. Assuming similar rates of glycogen depletion between treatment groups, during the first 4 hours of recovery, group-B dogs replaced 49% of the glycogen used during exercise. Plasma glucose concentration was significantly greater in group-B than in group-A and group-C dogs at 100 minutes after exercise. CONCLUSIONS: Immediate postexercise carbohydrate supplementation in sled dogs leads to increased glucose concentration, which in turn promotes more rapid rate of MG repletion in the first 4 hours of recovery than is observed in dogs not given supplements. CLINICAL RELEVANCE: For dogs running in multiple heats on a single day or over several consecutive days, immediate postexercise carbohydrate supplementation may promote more rapid and complete recovery between bouts of exercise.

Exercise-associated hyponatremia in Alaskan sled dogs: urinary and hormonal responses.

Exercise-associated hyponatremia occurs in horses and humans, both species that sweat, and in sled dogs, which do not sweat. To investigate the mechanism of exercise-associated hyponatremia in sled dogs, we measured water turnover, serum electrolyte concentrations and osmolality, plasma renal hormone concentrations, and urine composition of 12 fit Alaskan sled dogs before, during, and after a 490-km sled dog race (Ex group). Water turnover and serum electrolyte concentrations were measured in six similarly fit dogs that did not run (Sed group). Water turnover was significantly larger (P < 0.001) in Ex [190 +/- 19 (SD) ml . kg-1 . day-1] than in Sed dogs (51 +/- 13 ml . kg-1 . day-1). There were significant (P < 0.001) decreases in serum sodium concentration (from 148.6 +/- 2.8 to 139.7 +/- 1.9 mmol/l) and osmolality (from 306 +/- 9 to 296 +/- 5 mosmol/kgH2O) of Ex, but not Sed, dogs during the race. Plasma concentrations of arginine vasopressin decreased, whereas aldosterone and plasma renin activity increased significantly (P < 0. 01) during the race. Urine osmolality was unchanged, whereas urine sodium, potassium, and chloride concentrations decreased significantly (P < 0.05) and urine urea concentration increased (P = 0.06). These results demonstrate increased water turnover associated with hyponatremia and renal sodium conservation with maintained high urine osmolality in exercising Alaskan sled dogs.

Serum biochemical values in sled dogs before and after competing in long-distance races.

OBJECTIVE: To measure and compare blood values in sled dogs before and after long-distance racing. DESIGN: Prospective study. ANIMALS: 17 adult sled dogs in the 1991 Iditarod Trail Sled Dog Race and 21 in a simulated sled dog race. PROCEDURE: Blood samples were obtained from 17 dogs 7 days before they began and after they finished (finisher group) or were eliminated from (nonfinisher group) the Iditarod Trail Sled Dog Race. Blood samples were also obtained from 21 dogs before and after a simulated sled dog race. RESULTS: In finisher-group dogs, BUN and uric acid (UA) concentrations were increased after racing; nonfinisher-group dogs had significantly lower postrace BUN and UA concentrations. Significant increases in creatine kinase (CK) and aspartate transferase (AST) activities were detected in all dogs after racing, and postrace values were higher in nonfinisher-group dogs, compared with finisher-group dogs. Mean alkaline phosphate activities were significantly increased after racing in nonfinisher-group dogs only. In dogs that ran the simulated race, postrace values for serum albumin, total protein, calcium, and potassium concentrations, as well as Hct, hemoglobin concentration, and RBC count, were significantly lower than prerace values. Postrace values for alkaline phosphate, alanine transaminase, AST, lactate dehydrogenase, CK, BUN, and UA were significantly higher than prerace values. CLINICAL IMPLICATIONS: High CK activities are indicative of severe muscle degeneration and, in sled dogs, may represent a degree of muscle breakdown beyond which a dog cannot continue to work. Markedly high CK, and possibly AST, serum activities may be indicators of performance failure in sled dogs competing in long-distance races.

Effect of racing on serum sodium and potassium concentrations and acid-base status of Alaskan sled dogs.

OBJECTIVE: To examine the effect of participation in a long-distance race on serum electrolyte concentrations, estimated exchangeable cation content, and acid-base status of Alaskan sled dogs. DESIGN: Prospective study. ANIMALS: 9 male and 5 female, sexually intact, physically fit Alaska sled dogs between 18 and 48 months old. PROCEDURE: Body weight was recorded, and blood samples were collected from dogs before, during, and after a 300-mile race. RESULTS: Serum sodium and potassium concentrations decreased during the race, as did serum total protein, albumin, and globulin concentrations and PCV. Effects on acid-base status were minimal. Body weight and estimated total exchangeable cation content in dogs also decreased significantly during the race. CLINICAL IMPLICATIONS: Prolonged running is associated with decreases in serum cation concentration and estimated total exchangeable cation content in dogs, as in human beings and horses. However, the mechanism of the decrease in serum cation concentration likely differs among species. Clinical abnormalities associated with cation depletion were not observed in the dogs in this study.

Clock drawing as an assessment tool for dementia.

Clock drawing has recently been shown to lie useful in differentiating Alzieimer's disease patients from normal controls. Our procedure for clock drawing differed from other published reports in that a copy condition was employed and patients were asked to set clock hands to read "ten after eleven". We found both clock drawing procedures to be correlated with tests related to executive and visuospatial functioning. In both conditions, nondemented controls performed significantly better than demented patients. In the command condition there was no difference between Alzheimer patients and patients with cerebrovascular dementia. In the copy condition, patients with cerebrovascular dementia performed significantly worse than Alzheimer patients. The inclusion of a copy condition appears to greatly expand the utility of this test. Although our scoring system did not differentiate between various dementing disorders in the command condition, if clock drawing is used as a screening instrument, lack of improvement in the copy condition in comparison to the command condition may be a sign of a vascular involvement.

Lateralized cognitive style and self-description.

A scale of hemispheric preference in cognitive style was related to self-report measures of emotional functioning, with the hypothesis that persons who rely on cognition characteristic of one hemisphere may also manifest emotional characteristics of that hemisphere. In two studies, university students characterizing themselves as preferring a cognitive style representative of right hemisphere processes endorsed more positive emotional orientations. This finding may suggest a more optimistic attitude, but may also reflect a tendency to deny negative traits; a right hemispheric cognitive style was associated with a positive self-report bias. These observations in normals have interesting parallels to the changes in emotional orientation and self-description bias that follow lateralized brain lesions or temporal lobe epilepsy.

Multivariate analysis of EEG coherence: stability of the metric, individual differences in patterning and response to arousal.

When coherence is computed among all pairs of a multichannel EEG, the resultant matrix can be de-structured with conventional multivariate analysis procedures to characterize the patterning of electrophysiologic information at each frequency band of the EEG across brain regions. Six right-handed young men had EEG data recorded from left and right frontal, temporal, parietal, and occipital locations during three visits to the laboratory at one week intervals. During each session, data were recorded during a relaxation period, an alert resting period, and as loud white noise was presented. Factor analysis of coherence matrices showed a model pattern of a large posterior factor and an anterior factor, both of which were right-lateralized, plus a residual factor that was most often left-lateralized. Four of the six men showed this pattern on each occasion, particularly for the delta and the theta bands. Two men showed variant patterns, which were also stable over time. A priori de-structuring of the matrix into partial multiple intrahemispheric and inter-hemispheric coherences also showed generally higher coherences on the right side, with the exception of left occipital inter-hemispheric values. Effects of arousal manipulations were not striking, but the factor patterns suggested increases in right hemisphere coherence for the alpha and beta bands during high arousal.

Longitudinal study of brain function and depletion of iron stores in individual subjects.

Seven men living in a controlled research unit showed decrements in iron stores due to repeated phlebotomy. For each subject, weekly measures of cognitive task performance, electroencephalographic (EEG) power and Event-Related Potentials (ERPs) were examined in relation to serum ferritin level. No reliable relationships of ferritin level to cognitive performance ability were observed. Some EEG findings appeared similar to previous observations on EEG data and iron status in cross-sectional research. For four of the seven subjects, asymmetries of EEG power in the occipital electrodes appeared related to the decline in iron status over time.