Gerald A. Hegreberg

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.

Amino acid changes in a genetic strain of epileptic beagle dogs.

A neurochemical evaluation of beagle dogs with naturally occurring spontaneous generalized convulsive seizures was performed. Amino acid profiles of serum, cerebrospinal fluid (CSF), and biopsied cerebral cortex from epileptic dogs were compared with those from seizure‐free siblings. No differences in absolute levels were noted. However, when levels were normalized as a percent of total free amino acids, the two groups differed in certain respects. Ten significant correlations between amino acid pairs appeared in epileptic dogs, but only one was seen in seizure‐free animals. Seven of these ten corretions involved glutamate or taurine. It was noted that the highly correlated amino acids (taurine, glutamate, glycine, glutamine, alanine) all utilize sodium‐dependent membrane transport processes. The sum of glutamate, aspartate, and glycine levels (competing sodium‐dependent high‐affinity systems) was significantly lower in epileptic beagles. Since this difference was noted in serum but not CSF or brain, it may indicate a diminished capacity of sodium‐dependent high‐affinity renal transport for acidic and certain small neutral amino acids.

Anticonvulsant Properties of Ropizine in Epileptic and Nonepileptic Beagle Dogs

Studies were conducted on a colony of purebred beagle dogs. Animals with spontaneous seizures were classed as epileptic beagles (EB). Those without spontaneous seizures were termed nonepileptic beagles (NEB). The median convulsant current for maximal electroshock seizure (MES) threshold was 175 (194‐158) mA for EB and 390 (417‐364) mA for NEB. Similarly the median convulsant dose of pentylenetetrazol (PTZ) was 7.9 (10.1–6.2) mg/kg for EB and 20.2 (24.2–17.6) mg/kg for NEB. Following pretreatment with graded doses of ropizine (SC 13504), the median protective dose against MES was 6.0 (9.2–3.9) mg/kg in EB and 3.2 (4.8‐2.1) mg/kg in NEB. Based on the incidence of ataxia, EB had a median toxic dose (TD50) of 14.0 (16.5–11.9) mg/kg, while in NEB it was 18.0 (23.6–13.7) mg/kg. The TD50 doses were unable to protect against a convulsive dose of PTZ. It is concluded first that ropizine may have anti‐grand mal activity but apparently lacks an anti‐petit mal action. Secondly, EB are more sensitive than NEB to the convulsive effects of electric current and PTZ, yet less responsive to the anticonvulsant actions of ropizine.

Biochemical changes of a muscular dystrophy of mink

1. Clinical pathologic studies were performed on mink affected with a progressive form of muscular dystrophy. Serum levels of muscle enzymes, including creatine phosphokinase, aldolase, and glutamic oxalacetic transaminase, of affected mink were markedly elevated. A significantly increased urinary creatine/creatinine ratio was a consistent finding in the affected mink, and this ratio was usually greater than two for affected mink as compared to a ratio of less than one for nonaffected mink. 2. Marked elevation of muscle enzymes in serum and an increase in the urinary creatine/creatinine excretion ratio are consistent clinical pathologic findings in human amyotonic forms of muscular dystrophy. On the basis of these clinical alterations, the muscular dystrophy of mink appears similar to the amyotonic forms of human muscular dystrophy.

Serum testosterone levels in young normal horses

Serum testosterone levels were measured in normal young male horses (29 to 34 weeks old). No differences were found between gelded and intact males. The values for all the horses were low. On the basis of their testosterone levels, all the horses were prepubertal.