Janet E. Steiss

Temporal-spatial gait analysis by use of a portable walkway system in healthy Labrador Retrievers at a walk

OBJECTIVE To establish a protocol to collect temporal-spatial gait analysis variables by use of a portable walkway system in Labrador Retrievers at a walk and to determine reference values. ANIMALS 56 healthy Labrador Retrievers. PROCEDURES 6 passes across the walkway (3 passes in each direction) were recorded. Inclusion criteria for a pass were that the dog was at a walk (velocity, 60.0 to 90.0 cm/s) and had minimal head turning. The first 3 passes that met the inclusion criteria were analyzed for each dog. RESULTS Mean stride length was 88.4 cm. Mean stance time (ST) of forelimbs and hind limbs was 0.62 and 0.56 seconds, respectively. Mean stance time percentage (ST%; proportion of stance time to total gait cycle time) for forelimbs and hind limbs was 55.6% and 50.2%, respectively. Mean total pressure index (TPI) of forelimbs and hind limbs was 27.1 and 17.4, respectively. Mean number of sensors (NS) activated by each paw strike of forelimbs and hind limbs was 17 and 13, respectively. Mean forelimb-to-hind limb symmetry ratios were 1.11 (ST), 1.10 (ST%), 1.62 (TPI), and 1.37 (NS). Symmetry ratios for left limbs to right limbs, left forelimb to right forelimb, and left hind limb to right hind limb were 1.00. CONCLUSIONS AND CLINICAL RELEVANCE A protocol for collection of temporal-spatial gait analysis variables with a portable walkway system in Labrador Retrievers at a walk was developed, and reference values for variables and symmetry ratios were reported. Further research will determine the extent to which symmetry ratios differ in dogs with orthopedic disorders.

Concomitant brainstem axonal dystrophy and necrotizing myopathy in vitamin E-deficient rats

The purpose of this study was to simultaneously evaluate in rats the effects of vitamin E depletion on tissue alpha-tocopherol (alpha-T) concentrations, electrophysiologic measurements and histopathology. Rats (21-day-old male Wistar) were fed either vitamin E-deficient or supplemented (control) diets (n = 6/group) for 10, 16, and 61 weeks. At these times, electrophysiologic tests (electromyography, spinal and somatosensory evoked potentials, and motor nerve conduction velocity) were performed, the rats were killed and alpha-T concentrations of adipose tissue, sciatic nerve, and cervical and lumbar spinal cord were measured along with histopathologic evaluation of skeletal muscles and the nervous system. By 61 weeks, depletion of alpha-T from adipose tissue and peripheral nerve was more severe (< 1% of controls) than from cervical and lumbar spinal cord (15 and 8% of controls, respectively). Electrophysiologic tests were normal at all times. Histopathologic evaluation at 61 weeks revealed normal peripheral nerve structure, but necrosis of type 1 muscle fibers and increased numbers of spheroids in the gracile and cuneate nuclei. Our results confirm that low alpha-T concentrations in tissues precede histologic changes in peripheral nerves and skeletal muscle. Furthermore, pathologic changes associated with vitamin E deficiency occur independently in muscle and nervous tissue of rats.

α-tocopherol concentrations of the nervous system and selected tissues of adult dogs fed three levels of vitamin E

The effects of dietary vitamin E levels on tissue α-tocopherol (α−T) concentrations in different parts of the nervous system are largely unknown. Therefore, we measured the α−T contents of nervous and other tissues obtained from beagle dogs fed for two years a vitamin E-deficient diet (−E, 0.05±0.02 mg vitamin E/kg diet, n=2), a vitamin E-supplemented diet (+E, 114±14 mg/kg, n=2), or a standard chow diet (En, 74±6 mg/kg, n=3). Brain regions and spinal cords of +E dogs contained about double the α−T concentrations of En dogs, and about 10-fold those of −E dogs. The various brain regions of −E dogs, compared with En dogs, retained 12–18% of the α−T concentrations, with the exception of the caudal colliculus, which retained 48%. Peripheral nerve α−T concentrations in +E dogs (67 ng/mg wet weight) were nearly 5-fold higher than in En dogs (13.4±5.9 ng/mg) and 80-fold higher than in −E dogs (0.8 ng/mg). Within each dietary group, the lowest α−T concentrations in the central nervous system (CNS) were in the spinal cord. Peripheral nerves were the most susceptible to vitamin E repletion or depletion: in +E dogs, nerves contained higher concentrations of α−T than most brain regions; in En dogs, they contained similar concentrations; but in −E dogs, they contained less α−T than most brain regions. Muscles and other tissues of −E dogs retained from 1 to 10% of En values. The studies demonstrate that the CNS conserved α−T compared to peripheral nerves and nonnervous tissues in adult dogs, but contained lower absolute concentrations of α−T compare with most other tissues.

Depletion of adipose tissue and peripheral nerve α-tocopherol in adult dogs

To assess the relationship between tissue α-tocopherol depletion and histopathologic or functional changes in nervous tissue, a longitudinal study of male 1-year-old beagle dogs, two fed a vitamin E-deficient diet (0.05±0.02 mg α-tocopherol/kg;—E dogs) and two fed a vitamin E-supplemented diet (114±14 mg α-tocopherol/kg; +E dogs), was carried out. Plasma and adipose tissue α-tocopherol concentrations neurological examinations, and sensory and motor nerve conduction velocities were determined at approximately 8-wk, intervals over 109 wk. Tibial nerve α-tocopherol concentrations were measured at 65 and 109 wk; adjacent sections were examined for histologic changes. In the two—E dogs, plasma α-tocopherols declined linearly on a semilog plot to <0.1 μg/mL by 109 wk. Plasma α-tocopherol concentrations were depleted to half of the initial concentrations in approximately 87 d. Adipose tissue α-tocopherol concentrations (based on wet weight, cholesterol or triglyceride) also declined linearly on semilog plots, and were deleted to half of the initial concentrations in approximately 120 d. Tibial nerve α-tocopherols (ng/μg cholesterol) in—E dogs decreased to 16% of average +E at 65 wk, and to 2% at 109 wk. neurologic examinations, histologies and nerve conduction velocities were normal in all dogs throughout the study. Our results demonstrate in dogs that depletion of plasma, adipose tissue and nerve α-tocopherol precedes histologic and functional changes in peripheral nerves during vitamin E deficiency.

Respiratory alkalosis and primary hypocapnia in Labrador Retrievers participating in field trials in high-ambient-temperature conditions.

OBJECTIVE To determine whether Labrador Retrievers participating in field trials develop respiratory alkalosis and hypocapnia primarily in conditions of high ambient temperatures. ANIMALS 16 Labrador Retrievers. PROCEDURES At each of 5 field trials, 5 to 10 dogs were monitored during a test (retrieval of birds over a variable distance on land [1,076 to 2,200 m]; 36 assessments); ambient temperatures ranged from 2.2 degrees to 29.4 degrees C. For each dog, rectal temperature was measured and a venous blood sample was collected in a heparinized syringe within 5 minutes of test completion. Blood samples were analyzed on site for Hct; pH; sodium, potassium, ionized calcium, glucose, lactate, bicarbonate, and total CO2 concentrations; and values of PvO2 and PvCO2. Scatterplots of each variable versus ambient temperature were reviewed. Regression analysis was used to evaluate the effect of ambient temperature (< or = 21 degrees C and > 21 degrees C) on each variable. RESULTS Compared with findings at ambient temperatures < or = 21 degrees C, venous blood pH was increased (mean, 7.521 vs 7.349) and PvCO2 was decreased (mean, 17.8 vs 29.3 mm Hg) at temperatures > 21 degrees C; rectal temperature did not differ. Two dogs developed signs of heat stress in 1 test at an ambient temperature of 29 degrees C; their rectal temperatures were higher and PvCO2 values were lower than findings in other dogs. CONCLUSIONS AND CLINICAL RELEVANCE When running distances frequently encountered at field trials, healthy Labrador Retrievers developed hyperthermia regardless of ambient temperature. Dogs developed respiratory alkalosis and hypocapnia at ambient temperatures > 21 degrees C.

Neuromuscular effects of acute 2,4-dichlorophenoxyacetic acid (2,4-D) exposure in dogs ☆

2,4-Dichlorophenoxyacetic acid (2,4-D) was administered once orally to adult female mongrel dogs at 0, 25, 50, 75, 100 or 125 mg/kg of body weight (n = 4 per group). Clinical neurological examinations, electromyography (EMG) and motor nerve conduction velocity measurements were carried out before exposure, and on days 1, 3, 7, 14, 21 and 28 post-exposure. On day 7, two dogs per group were killed. Samples of the medial and lateral plantar nerves were removed for teased fiber and semi-thin section analysis; samples of appendicular muscles were removed for histology and histochemistry. Necropsy included histopathological examination of the brain and spinal cord at multiple levels. Remaining dogs were killed on day 28 and their tissues were processed similarly. Transient generalized myotonic discharges were found in skeletal muscles of dogs receiving 50 mg/kg or more of 2,4-D. A few dogs in the higher dosage groups also had mild muscle stiffness, myotonic dimpling and/or lethargy, lasting up to 3 days post-exposure. Other parameters remained within normal limits.

Vitamin E deficiency in dogs does not alter preferential incorporation ofRRR-α-tocopherol compared withall rac-α-tocopherol into plasma

The plasma and lipoprotein transport ofRRR andall rac-α-tocopherols, labeled with different amounts of deuterium [2R,4′R,8′R-α-[5-C2H3]tocopheryl acetate (d3RRR-α-tocopheryl acetate] and 2RS, 4′RS, 8′RS-α-[5,7-(C2H3)2]tocopheryl acetate (d5all rac-α-tocopheryl acetate), was studied in adult beagle dogs that had been fed a vitamin E-deficient (−E; two dogs) or supplemented (+E; two dogs) diet for two years. We set out to test the hypothesis that the activity of the hepatic tocopherol binding protein (which is thought to preferentially incorporateRRR-α-tocopherol into the plasma) is up-regulated by vitamin E deficiency. Labeled α-tocopherols increased and decreased similarly in plasma of both −E and +E dogs. Irrespective of diet,d3RRR-α-tocopherol was preferentially secreted in plasma. Thus, vitamin E deficiency in dogs does not markedly increase the apparent function of the hepatic tocopherol binding protein. We also studied vitamin E transport in a German Shepherd dog with degenerative myelopathy (DM). Based on the coincident appearance ofd3RRR-α-tocopherol in plasma and chylomicrons, we suggest that the abnormality in DM may be associated with abnormal vitamin E transport resulting from an impaired function of the hepatic tocopherol binding protein.

Comparison of four erythrocyte fragility tests as indicators of vitamin E status in adult dogs

Plasma alpha-tocopherol (alpha-T) concentrations, erythrocyte osmotic fragility and detergent sensitivity were measured at 8 week intervals in two 1-year-old male beagle dogs fed a vitamin E-deficient diet (< 0.08 mg per kg alpha-T) and in two control beagles fed the same diet supplemented with vitamin E (> 90 mg per kg alpha-T). Beginning at 24 weeks, dialuric acid haemolysis and spontaneous haemolysis were evaluated also. In the vitamin E-deficient dogs, plasma alpha-T concentrations declined progressively from baseline values of 20.5 and 31.3 micrograms per ml to 0.11 and 0.07 micrograms per ml, respectively, by 90 weeks. The supplemented dogs maintained alpha-T concentrations between 18.3 and 38.4 micrograms per ml. Both dialuric acid haemolysis (R = -0.89) and spontaneous haemolysis (R = -0.91) increased with declining plasma alpha-T concentration. In the dialuric acid haemolysis assay, 50 per cent haemolysis occurred when plasma alpha-T declined to 1.7 micrograms per ml, compared with spontaneous haemolysis in which 50 per cent haemolysis occurred when plasma alpha-T declined to 0.5 micrograms per ml. Osmotic fragility and detergent sensitivity remained unchanged in the vitamin E-deficient dogs throughout the study. Of the four tests, dialuric acid haemolysis was the most sensitive in-vitro assay for vitamin E deficiency in adult dogs.

Dog Gait Analysis Using the Center of Pressure

In this study we evaluate the applicability of nonlinear mathematical techniques to describe and define normal dog gait. A commercially available walkway 2-dimensional motion analysis system was utilized to acquire kinematic data from healthy dogs. The kinematic data of the center of pressure (COP) of the dog during walking were analyzed. The ability to analyze COP on individual dogs has the potential to provide insight into normal and abnormal gait in dogs, and early detection of subtle lameness. This is especially important in working and athletic dogs.Copyright