Kyle G. Braund

Further characterization of the biology of Hammondia heydorni

Hammondia heydorni oocysts, recovered from the diarrheic feces of a dog suffering from corticosteroid toxicosis, were sporulated and characterized morphometrically. Sporulated H. heydorni oocysts were administered to three dogs, five goats, a calf and three guinea pigs, and tissues from these inoculated animals fed to coccidia-free dogs to determine species susceptibility to H. heydorni. Morphometric characteristics of H. heydorni oocysts were similar to previous descriptions. Oocysts were not excreted in the feces of dogs inoculated with oocysts. Dogs fed tissues from goats killed 14, 28 or 42 days after inoculation (d.a.i.) with oocysts excreted H. heydorni oocysts in their feces after consuming goat tissues. Dogs fed tissues from a calf killed at 28 d.a.i., and from goats killed 21 and 56 d.a.i., did not excrete oocysts in their feces. Developmental stages of H. heydorni were not observed in histologic sections of tissues from any of the animals.

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.

Myeloencephalopathy resembling Alexander's disease in a Scottish terrier dog

SummaryDiffuse degenerative myeloencephalopathy resembling Alexanders disease in a tetraparetic 9-month-old Scottish terrier dog is described. There were widespread deposits of Rosenthal fibers throughout brain and spinal cord in subpial, subependymal, perivascular and white matter regions. A diffuse proliferation of pleomorphic astrocytes in the white matter and subependymal areas was also seen. Demyelination was not a salient feature of the disease.

Lipid fluidity and composition of the erythrocyte membrane from healthy dogs and labrador retrievers with hereditary muscular dystrophy

Erythrocyte membranes and their liposomes were prepared from clinically normal dogs and Labrador retrievers with hereditary muscular dystrophy. The “static” and “dynamic” components of fluidity of each membrane were then assessed by steady-state fluorescence polarization techniques using limiting hindered fluorescence anisotropy and order parameter values of 1,6-diphenyl-1,3,5-hexatriene (DPH) and fluorescence anisotropy values ofdl-2-(9-anthroyl)-stearic acid anddl-12-(9-anthroyl)-stearic acid, respectively. Membrane lipids were extracted and analyzed by thin-layer chromatography and gas chromatography. The results of these studies demonstrated that the lipid fluidity of erythrocyte membranes, and their liposomes, prepared from dystrophic dogs were found to possess significantly lower “static and dynamic components of fluidity” than control counterparts. Analysis of the composition of membranes from dystrophic dogs revealed a higher ratio of saturated fatty acyl chain/unsaturated chains (w/w) and lower double-bond index. Alterations in the fatty acid composition such as decrease in levels of linoleic (18:2) and arachidonic (20:4) acids and increase in palmitic (16:0) and stearic (18:0) acids were also observed in the membranes of dystrophic animals. These associated fatty acyl alterations could explain, at least in part, the differences in membrane fluidity between dystrophic and control dogs.