Effect of dietary protein on lean body wasting in dogs: correlation between loss of lean mass and markers of proteasome-dependent proteolysis.

To determine the effect of dietary protein intake on lean body wasting in adult canines a study was undertaken to investigate the Ubiquitin Proteasome (UP) pathway and concurrent changes in lean and fat body mass of canines fed variable sources and concentrations of dietary protein. Purpose-bred, intact female canines (56) between the ages of 2 and 3 years were fed either 12 or 28% protein diet for 10 weeks. Each diet contained variable amounts of corn gluten meal and chicken protein sources in ratios of 100 : 0, 67 : 33, 33 : 67 and 0 : 100 per cent (w/w), respectively. All diets were isocaloric with calories coming from protein : fat : carbohydrate at the respective ratios of 12 : 40 : 48% for the 12% diets, and 28 : 40 : 32% for the 28% diets. Standard dual energy X-ray absorptiometry was performed to assess total body lean and fat mass at weeks 0 and 10 of the dietary trial. Muscle biopsies were also taken and processed for protein determination and standard gel electrophoresis with subsequent Western blotting for 20S proteasome and PA700 regulatory cap subunit p31. Statistical analysis revealed a moderate degree of correlation between increasing quantities of corn gluten, which is low in essential amino acids (i.e. lysine, tryptophan), and increasing loss of lean body mass over the 10-week study (R = 0.56). Furthermore, a moderate degree of correlation was observed between increasing concentrations of corn gluten protein and decreased expression of the p31 subunit of the 26S proteasome (R = 0.49). Additionally, the dogs consuming the 12% protein diets had a significant increase in fat mass regardless of the protein source. These findings suggest that lean body wasting in adult canines can be associated with the consumption of low protein diets consisting of predominantly corn gluten, which is likely due to imbalances or subclinical deficiencies of specific essential amino acids, and that low protein diets may augment accumulation of adipose tissue. Although the mechanisms remain unclear, alteration of molecular targets of skeletal muscle proteolysis, specifically involving the UP pathway occur.

Nitrogen balance in clinically normal dogs receiving parenteral nutrition solutions.

OBJECTIVE: To determine nitrogen balance in clinically normal dogs receiving parenteral nutrition solutions. ANIMALS: 8 clinically normal female Beagles. PROCEDURE: Dogs were randomly assigned to receive 4 treatments in random order. Treatment A consisted of IV administration of nonlactated Ringer's solution. Treatments B, C, and D consisted of IV administration of isocaloric parenteral solutions containing 0, 1.36, and 2.04 g of amino acids/kg of body weight/d, respectively, for 7 consecutive days. Urine and feces were collected on days 5, 6, and 7 of each treatment period, and Kjeldahl analysis was used to determine nitrogen balance. RESULTS: Mean nitrogen balance was negative with treatments A and B but was not significantly different from 0 with treatments C and D. Dogs had the lowest nitrogen balance values and lost the most weight while receiving treatment A. Dogs were able to conserve protein and had higher nitrogen balance values when receiving treatment B, compared with treatment A. Dogs lost the least amount of weight while receiving treatment D. Regression analysis indicated that an IV amino acid intake of 2.32 g/kg/d (95% confidence interval, 2.00 to 2.81 g/kg/d), as supplied by the commercial product used in this study, would result in zero nitrogen balance in clinically normal dogs. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that IV amino acid requirement of clinically normal dogs is approximately 2.3 g/kg/d.

Effect of protein intake during training on biochemical and performance variables in sled dogs.

OBJECTIVE: To determine effects of protein intake on blood variables, plasma volume, and maximal oxygen uptake (VO2max) in sled dogs undergoing rigorous training. ANIMALS: 32 Alaskan sled dogs, between 2 and 6 years old. PROCEDURE: Dogs were assigned to 1 of 4 groups on the basis of age, sex, and ability. Isocaloric diets containing 18% (diet A), 23% (diet B), 29% (diet C), or 35% (diet D) of energy as protein were assigned randomly to each group and fed 1 month before and during a 12-week training period. Maximal oxygen uptake was measured at 0 (before training) and 12 weeks. Body weight, protein and energy intake, plasma volume, PCV, hemoglobin concentration, and serum biochemical variables were measured at 0, 8, and 12 weeks. RESULTS: Serum biochemical variables, PCV, and hemoglobin concentration remained within reference ranges for all dogs. Dogs fed diet A had a decrease in VO2max and a greater rate of soft tissue injury throughout training, compared with dogs fed the other diets. At 12 weeks, dogs fed diets C and D had greater serum sodium concentration and hemoglobin concentration than did dogs fed diet A. Dogs fed diet D also had more plasma volume at 12 weeks than did dogs of any other group. CONCLUSIONS AND CLINICAL RELEVANCE: Consumption of a diet with 18% dietary protein on an energy basis (3.0 g of protein/kg of body weight) is insufficient to meet the metabolic requirements of sled dogs in training. For intense interval work, a diet with 35% dietary protein as energy (6.0 g of protein/kg) may provide a performance advantage by promoting an increase in plasma volume.

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.

Effect of diet and training on muscle glycogen storage and utilization in sled dogs.

Two groups of eight Alaskan huskies fed either a high-fat (HFD; 60% kcal from fat and 15% kcal from carbohydrate) or a high-carbohydrate diet (HCD; 60% kcal from carbohydrate and 15% kcal from fat) performed standard aerobic (1 h at 4 m/s on a 0% slope) and anaerobic (3 min at 6.7 m/s on a 10% slope) tests before and after training. Before and immediately after each exercise test, venous blood samples were collected and analyzed for lactate and pyruvate, and muscle biopsies were obtained under local anesthesia from the semitendinosus muscle and analyzed for total muscle glycogen (TMG) concentration. Training was associated with a significant increase in preexercise TMG in both diet groups; this effect was most marked in the HCD. There was no effect of diet or training on TMG utilization during the aerobic tests. The rate of TMG utilization during the anaerobic tests was between 20 and 40 times greater than that measured during the aerobic tests. The pre- to postexercise change in TMG was dependent on preexercise TMG in the HCD and HFD for both anaerobic tests (HCD: P < 0.01, r = 0.81; HFD: P < or = 0.03, r = 0.66). It is concluded that the increased glycogen storage associated with the HCD was more than offset by the more rapid rate of glycogen utilization in this group. HFD facilitated carbohydrate sparing during intense exercise and should thus be a better dietary strategy for endurance in sled dogs.

Scintigraphy for diagnosis of avulsions of the origin of the suspensory ligament in horses: 51 cases (1980-1993).

The medical records of 34 horses with a diagnosis of avulsion of the origin of the suspensory ligament that had been admitted to the veterinary medical teaching hospital between 1980 and 1993 were identified. In addition to clinical examination, 21 of 34 horses had scintigraphy and radiography performed during their examination. The usefulness of scintigraphy and radiography were assessed by comparing the initial findings reported in the medical record to those obtained in a retrospective review of the images. Thirty other horses with scintigraphic lesions of the proximal aspect of the third metacarpal/metatarsal bone but with a confirmed diagnosis other than avulsion of the suspensory ligament served as controls for lesion specificity. Scintigraphy (bone phase, n = 21) revealed increased uptake in all horses in both reviews. Only 14 of 21 (67%) horses radiographed, however, had at least 1 lesion during the initial radiographic evaluation that was reported to be suggestive of avulsion. When the radiographs were reviewed retrospectively, the radiologist identified 18 of 21 (86%) horses with lesions consistent with avulsion. The interpretation of scintigraphy appeared to be a more repeatable and sensitive diagnostic method than radiography. However, though scintigraphy was sensitive in identifying inflammation of the proximal aspect of the metacarpal/metatarsal region, no specific diagnosis of avulsion could be made without coincident radiography; the specificity of scintigraphy in diagnosing avulsion of the suspensory ligament was only 41% (21/51).(ABSTRACT TRUNCATED AT 250 WORDS)

New approach to percutaneous muscle biopsy in dogs.

The size and quality of muscle specimens obtained by use of a percutaneous biopsy technique were studied. All biopsies were performed under local anesthesia, using an 11-gauge biopsy needle. The mean +/- SEM size of specimens obtained from 128 biopsies of the semitendinosus muscles of 16 Alaskan Huskies was 23.8 +/- 4.4 mg. All biopsy specimens were of sufficient quality to permit histochemical differentiation of the fiber types by use of myosin ATPase staining. An additional 8 biopsy specimens were obtained from 1 dog and analyzed for muscle glycogen content. These specimens contained 50.6 +/- 7.2 mmol of glucose/kg of muscle wet weight. This modified biopsy procedure was free of notable complications, and repeatable use produced specimens of adequate size and quality for histologic and biochemical analysis. It is concluded that this procedure is a safe and reliable alternative to open biopsy for diagnosis and management of neuromuscular, metabolic, and nutritional myopathies.

Lipid metabolite responses to diet and training in sled dogs.

Two groups of Alaskan Huskies were fed either a high fat (HFD) or a high carbohydrate diet 4 wk before and during an 8-wk conditioning program. Aerobic bouts of exercise were performed before and after conditioning. Blood samples taken before and after each exercise test were analyzed for serum concentrations of free fatty acids (FFA), triglycerides (TG), vitamin E, glucose and serum lipase activity. The post-exercise FFA and TG values were greater in the HFD group both before and after training. There were no significant differences in plasma vitamin E or in serum lipase activity between diet groups. It is concluded that after an adequate period of adaptation, prolonged feeding of a HFD safely enhances the availability of local and peripheral lipid stores during exercise. Although the elevated levels of FFA and TG associated with HFD suggest enhanced potential for performance, further study of more prolonged and possibly more intense exercise is necessary to confirm this theory.

Use of scintimetry to assess effects of exercise and polysulfated glycosaminoglycan on equine carpal joints with osteochondral defects.

Combined blood pool and delayed images produced by use of 99mTc-methylene diphosphonate (99mTcMDP) were evaluated as an objective measurement of the response of equine joints with osteochondral defects to postoperative exercise and intra-articularly administered polysulfated glycosaminoglycan (PSGAG). Osteochondral defects (approx 2.4 x 0.9 cm) were induced arthroscopically in the dorsodistal radial carpal bones of 18 ponies. These ponies were randomized (while balancing for age [range 2 to 15; median, 5.0; mean, 5.1 years]) to 2 treatment groups. Nine ponies were assigned to be exercised, and 9 were stall-rested. Six ponies in each group were administered PSGAG (250 mg) in 1 joint (medicated) and lactated Ringer's solution (LRS) in the contralateral joint. The 3 remaining ponies in each group were administered LRS in both joints (nonmedicated). Medication was given at surgery, then weekly for 4 weeks. The exercise protocol (begun at postoperative day 6 and conducted twice daily) started with 30 minutes walking (approx 0.7 m/s), and, by postoperative month 3, the ponies were being walked for 15 minutes and trotted (approx 1.6 m/s) for 25 minutes. Simultaneous dorsal images of both carpi were made 2 to 3 minutes after IV administration of 99mTcMDP (blood pool image) and 90 to 120 minutes later (delayed image). Scintimetry, in counts per minute per pixel per millicurie, was done before, and at 1, 2, 4, 8, 10, 13, and 17 weeks after surgery, prior to euthanasia. Radionuclide uptake on blood pool images decreased faster than that on delayed images, in which uptake remained high for 17 weeks. This indicated that bone was metabolically active for at least 17 weeks after surgery. Exercise significantly (P < 0.05) decreased uptake on the blood pool images of medicated joints up to 1 month after surgery. Thus, exercise (in the presence of PSGAG) probably had a transient, beneficial effect on soft tissues of the joint. Exercise, without PSGAG, promoted increased bone remodeling, because the highest uptake on delayed images was observed in exercised, nonmedicated ponies up to 3 months after surgery. This was consistent with development of osteoarthritis in these ponies. Medication alone stimulated bone remodeling, and data indicated that an identical effect may take place in contralateral LRS-injected joints, because of systemic circulation of the drug. However, the combination of exercise and medication appeared to moderate the independent effects of each. The combination of exercise and medication in individual joints resulted in notably (P < 0.05) decreased bone remodeling.(ABSTRACT TRUNCATED AT 400 WORDS)

Humeral skeletal development and plasma constituent changes in fetuses of ewes maintained on a low calcium diet from 60 days of gestation.

The objective of this study was to evaluate the effects of a long-term, low-calcium diet on fetal calcium metabolism and fetal skeleton development in ewes. Eleven pregnant sheep were assigned to two groups, fed either a diet low in calcium (0.26% total dry matter) or normal in calcium (0.8% total dry matter) for 2 months, starting at 60 days gestational age. The ewes fed the low calcium diet showed lower plasma levels of calcium and higher plasma levels of hydroxyproline, parathyroid hormone, and 1,25(OH)2D compared with the ewes fed the normal calcium diet. There were no differences in these variables between the two groups of fetuses. These observations suggest that the plasma components of calcium homeostasis measured in the fetal lamb in the present study are independent of the ewe and are not significantly affected by the presence of lowered maternal calcium for many weeks during pregnancy. Despite the ability of the fetus of the ewe on the low calcium diet to maintain relatively normal circulating plasma components of calcium homeostasis, long-term maternal hypocalcemia delayed fetal skeletal ossification as shown by histological examination of the fetal humerus. The fetal humerus from low calcium-fed ewes showed a lower proportion of bone versus cartilage (45.6 +/- 5.9 versus 57.4 +/- 4.6%, mean +/- SD) lower ash content (15.4 +/- 1.5 versus 17.4 +/- 1.0%), and lower specific gravity (1.19 +/- 0.2 versus 1.22 +/- 0.02) (P < 0.05) than the humerus from fetuses of normal calcium-fed ewes. This study shows that the long-term calcium intake of the ewe does affect fetal skeletal development, despite a lack of observable effects on fetal plasma concentrations of calcium or known calcium regulating hormones such as 1,25(OH)2D or parathyroid hormone.

Functional analysis of ectopic parathyroid activity in cats.

The ability of ectopic parathyroid tissue to support calcium homeostasis was evaluated by measuring serum concentrations of calcium, phosphorus, albumin, magnesium, and parathyroid hormone before and for 12 weeks after bilateral thyroparathyroidectomy in 14 cats. During the immediate postoperative period, significant decrease was observed in serum calcium, magnesium, and parathyroid hormone (PTH) concentrations. Serum PTH concentration remained subnormal and did not significantly increase during the 12-week observation period. Despite persistent hypoparathyroidism, serum calcium and magnesium concentrations gradually increased. Ectopic parathyroid tissue is not capable of maintaining normal serum calcium concentration immediately after thyroparathyroidectomy. Serum calcium concentration gradually normalizes after thyroparathyroidectomy, apparently by means of a PTH-independent mechanism.

Dietary taurine deficiency and dilated cardiomyopathy in the fox.

Taurine deficiency has been implicated as a potential cause of dilated cardiomyopathy. However, the relationship between taurine and myocardial function is presently unclear. The purpose of this study was to determine whether dilated cardiomyopathy in the fox is associated with dietary taurine deficiency. A total of 68 foxes from farms with a history of death caused by dilated cardiomyopathy and 14 foxes from a farm with no history of dilated cardiomyopathy were studied. Dilated cardiomyopathy was diagnosed by echocardiography in 48% of the foxes from one farm with a positive history and in none of the foxes from the control farm. Foxes less than 9 months of age were more commonly affected than older foxes (p = 0.03). Plasma taurine concentrations were significantly less (p less than 0.01) in foxes that had dilated cardiomyopathy (26.8 +/- 16.4 nmol/ml) than in the control foxes (99.3 +/- 60.2 nmol/ml). A significantly higher (p less than 0.01) incidence of dilated cardiomyopathy was present in foxes with a history of a sibling or offspring that died of dilated cardiomyopathy than in foxes without a family history of cardiac death. In one fox with dilated cardiomyopathy that was tested, the myocardial taurine concentration was lower (1.7 mumol/gm wet weight) than that of control foxes (7.3 +/- 1.6 mumol/gm wet weight). Hepatic cysteinesulfinic acid decarboxylase activity was significantly less (p less than 0.001) in foxes with dilated cardiomyopathy (0.97 +/- 0.2 nmol/mm.mg protein) than in control foxes (2.11 +/- 0.07 nmol CO2/mm.mg protein).(ABSTRACT TRUNCATED AT 250 WORDS)

Osteochondrosis in fetuses of ewes overfed calcium.

Ewes were fed ad libitum (up to maximum of 2.5 kg/day) a complete feed containing either 1.52% calcium (High Ca) or 0.59% calcium (Normal Ca) on a dry matter basis from day 50 of pregnancy, and the fetuses were removed at 133-135 days. Thyroid C cells, identified by indirect immunofluorescence, were more numerous (P less than 0.001) and plasma levels of 24,25-dihydroxycholecalciferol [24,25(OH)2D] were higher (P less than 0.09) in fetuses of High Ca ewes. These fetuses also had retarded cartilage differentiation in the proximal humeral epiphysis and metaphysis as well as transverse trabeculation in the epiphysis. These entities are two of the hallmarks of osteochondrosis. It was shown that feeding high dietary calcium to pregnant ewes caused osteochondrosis in their fetuses. Hypercalcitoninism and/or an adverse effect of supraphysiological levels of 24,25-dihydroxycholecalciferol may have been contributory to the skeletal abnormalities.

Severe masseter myonecrosis in a horse.

A 6-year-old Quarter Horse was examined because of acute, severely swollen masseter muscles (palpation of which elicited pain response), exophthalmos, severe chemosis, and protrusion of the third eyelids. Blood selenium and vitamin E concentrations, and results of feed analysis and muscle biopsy supported a diagnosis of nutritional myopathy. The horse was treated and was clinically normal 2 weeks after discharge from the hospital.

Factors associated with the development of equine degenerative myeloencephalopathy.

A case-control study was done to identify factors associated with the development of equine degenerative myeloencephalopathy (EDM). Questionnaires were mailed to the owners of 146 horses admitted to the New York State College of Veterinary Medicine between November 1978 and June 1987 and diagnosed as having EDM by histologic examination. Questionnaires also were sent to owners of 402 clinically normal horses admitted to the college during the same period. Data were compared between the EDM-affected and control groups (56 and 179 questionnaires returned, respectively). Risk factors identified included the use of insecticide applied to foals, exposure of foals to wood preservatives, and foals frequently spending time on dirt lots while outside. Foals spending time outside on green pastures was a protective factor. Foals from dams that had had an EDM-affected foal were at higher risk of developing EDM than were foals from other dams.

An experimental model of chronic renal disease in dogs by infusion of microspheres into the renal arterial circulation.

The feasibility of renal arterial infusion of nonbiodegradable microspheres as a model of chronic renal disease in dogs was evaluated. Resin-coated, styrene-divinyl benzene copolymer microspheres were infused into the kidneys of healthy adult Beagles by direct injections of both renal arteries in a single surgical procedure. Injections of 25-microns diameter microspheres had minimal effect on either the clinical status or serum values of the dogs. Histologic examination revealed the majority of the microspheres lodged within the capillary beds of the glomeruli, and little change to the kidneys. However, injections of 50-microns diameter microspheres caused significant increases in serum concentrations of urea nitrogen and creatinine. Histologically, the larger microspheres obstructed afferent arterioles and small arteries, which caused diffuse glomerular necrosis and nephron damage. With doses ranging from 1 to 3 million microspheres/dog, a correlation between the quantity of microspheres injected and severity of renal damage was observed. The optimal dose for producing a model of moderate renal disease was determined to be 1.8 million microspheres/dog (0.9 million microspheres/kidney). During long-term studies, microsphere-injected dogs fed a moderately restricted protein ration remained relatively azotemic, compared with control dogs on the identical ration. During the 5-month postsurgical period, the serum urea nitrogen concentration averaged 18.41 +/- 1.59 mg/dl (mean +/- SE) for the microsphere-injected dogs vs 9.31 +/- 0.38 for the control dogs (P less than 0.001). Similarly, the mean serum creatinine value was significantly higher (P = 0.020) for the microsphere-injected dogs, compared with the controls (1.23 +/- 0.12 mg/dl vs 0.94 +/- 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)

Local anesthetics and nuclear medical bone images of the equine fore limb.

The effects of two local anesthetic agents on the diagnostic quality of nuclear medical bone images (NMBIs) of distal parts of the equine fore limb were investigated. Local effects on bone uptake of technetium 99m methylene diphosphonate (99mTc-MDP) 4 and 24 hours after perineural and intraarticular injection of mepivacaine hydrochloride and bupivacaine hydrochloride were evaluated in the carpal and metacarpophalangeal regions of 12 horses and ponies. Neither mepivacaine hydrochloride nor bupivacaine hydrochloride significantly altered the diagnostic quality of the NMBIs. The injection and subsequent action of local anesthetics do not appear to influence local bone uptake of 99mTc-MDP significantly.