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Biomedical subjects

G A Hegreberg

Publications and source records attributed to G A Hegreberg.

At least 19 recordsLinked to original sources
PubMed1991

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 of DL-2-(9-anthroyl)-stearic acid and DL-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.

Animals↗
PubMed1990

Skeletal muscle changes associated with equine myotonic dystrophy.

A progressive neuromuscular disorder in young horses, clinically apparent as early as 1 month of age, is characterized by generalized myotonia, muscle stiffness, muscle weakness and atrophy. Myotonia is identified by percussion dimpling and myotonic EMG discharges. Changes in one case included testicular hypoplasia, cataract formation, and glucose intolerance, indicating a systemic involvement. Pathologic changes in skeletal muscles from three affected foals were examined. Sarcoplasmic masses, ringed fibers, internal positioning of sarcolemmal nuclei, and nuclear rowing were among the primary histologic changes noted. Variation in fiber diameter size, especially atrophy, and type I predominance were also prominent changes. A neurogenic involvement was indicated by type grouping changes in several muscles.

Animals↗
PubMed1990

Congenital skin diseases.

The purpose of this chapter is to review some of the common congenital and hereditary skin diseases in domestic animals. Alopecia, abnormalities in pigmentation, and structural defects of the dermis are addressed in a problem-solving format. Features of other miscellaneous congenital and hereditary skin diseases are discussed. Specific breed and species involvement and the ages of onset are identified. Modes of inheritance and information on recognizing patterns of inheritance by pedigree analysis are presented. Clinical and pathologic findings important to differential diagnosis of these conditions are summarized. Advanced diagnostic techniques useful in further characterizing these conditions are presented.

Animals↗
PubMed1988

Progressive myotonia in foals resembling human dystrophia myotonica.

A severe and progressive neuromuscular disorder accompanied by clinical, electrophysiological, and pathological features resembling human dystrophia myotonica was observed in three foals. This disorder was apparent as early as 1 month of age and involved progressive skeletal muscle dysfunction, initially characterized by proximal muscle hypertrophy and hypertonicity with subsequent muscle stiffness, weakness, and atrophy. Multisystem involvement was manifested in one case by testicular hypoplasia, early cataract formation, and borderline glucose intolerance. Prolonged dimpling of these large rear-limb muscles was elicited by percussion. Myotonic discharges were identified by electromyography. Percussion dimpling and the typical myotonic discharges persisted after neuromuscular blockade. Distinctive histologic muscle changes included ring fibers, sarcoplasmic mass formation, variation in fiber diameter size, and internally positioned nuclei.

Animals↗
PubMed1987

Electromyographic evaluation of adult Labrador retrievers with type-II muscle fiber deficiency.

Labrador Retrievers with type-II muscle fiber deficiency were examined electrodiagnostically. Electromyographic changes consisted of positive sharp waves, fibrillation potentials, bizarre high-frequency discharges, and, rarely, myotonic-like discharges. Fasciculation potentials were recorded infrequently. Fibrillation potentials and bizarre high-frequency discharges were the most commonly observed electromyographic changes. Bizarre high-frequency discharges were prominent in muscles of the head and neck, proximal muscles of the thoracic limbs, and the thoracolumbar paraspinal musculature. Marked abnormalities were not observed in the motor nerve conduction velocity. Decremental responses of the evoked compound muscle action potential to repetitive nerve stimulation were not observed.

Animals↗
PubMed1985

Inhibition of rat peritoneal mast cell histamine secretion by protoporphyrin and incandescent light.

Rat peritoneal mast cells (RPMC) exposed to protoporphyrin (PP) and incandescent light (IL) become refractory to the stimulatory effects of compound 48/80. Once initiated, this refractory state continues to develop even after removal of the light source and is essentially complete within 30 min. While this state of unresponsiveness appears to be relatively permanent in the dark, prolonged incubation in the light (greater than 80 min) induces cell lysis. We have shown that the resistant state is not specific for the mast cell stimulator compound 48/80. Mast cells passively sensitized with IgE and illuminated for 30 min in the presence of 100 ng/ml PP also fail to release histamine upon stimulation by anti-rat IgE, anti-rat F(ab')2, concanavalin-A (Con-A), and the calcium ionophore A23187. The inability to respond to immunological stimuli could not be ascribed to the reversible loss of membrane-bound IgE from its receptor. While the binding of either the inducer to IgE or IgE to its receptor may actually be impaired in refractory cells, the significance of such impairments on the development of the resistant state in these cells is precluded by the inability of A23187 to either increase intracellular 45Ca2+ levels or induce histamine release. The data suggest that the RPMC refractory state develops as a result of covalent inter- and/or intramolecular cross-linking of membrane proteins. Furthermore, this cross-linking may involve sulfhydryl or amino groups essential to either stimulus transduction, or the histamine secretory process itself.

Animals↗
PubMed1985

Familial canine dermatomyositis: clinical, electrodiagnostic, and genetic studies.

Three Collies with a skin disorder, 6 progeny from a breeding of 2 of the Collies (incross litter), and the 4 progeny from the breeding of an affected Collie male and a normal Labrador Retriever female (outcross litter) were examined. By 7 to 11 weeks of age, all 6 dogs in the incross litter developed a qualitatively similar, but variably severe, dermatitis of the ears, face, lips, tip of the tail, and over bony prominences of limbs. Later, myopathic signs characterized by bilaterally symmetrical skeletal muscle atrophy of the head, neck, trunk, and extremities; facial palsy; decreased jaw tone; stiff gait; and hyperreflexia were observed in the dogs more severely affected by the dermatitis. Of the 4 dogs in the outcross litter, 3 had similar, but milder, clinical manifestations of the dermatitis and myopathy. Cutaneous lesions consisted of intraepidermal and subepidermal vesicles or pustules with intradermal infiltration by leukocytes. Muscle lesions included myositis; myofiber degeneration, regeneration, and atrophy; and fibrosis. A generalized myopathy in the severely affected dogs was indicated by abnormal readings on needle electromyograms and normal motor nerve conduction velocities. Spontaneous needle electromyogram abnormalities were fibrillation potentials, positive sharp waves, and bizarre high-frequency discharges. Retrospective and prospective genetic analyses disclosed a definite familial tendency and indicated the condition has an autosomal dominant component.

Animals↗
PubMed1984

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.

Journal Article↗
PubMed1984

Familial canine dermatomyositis. Initial characterization of the cutaneous and muscular lesions.

Familial canine dermatomyositis is a recently identified disease of collie dogs that resembles human juvenile dermatomyositis. The lesions in the skin and muscles obtained by biopsy from two litters of dogs were characterized for the purpose of determining the similarity of the lesions to those of human dermatomyositis. The cutaneous lesions began between 7 and 11 weeks of age and were present on the face, lips, ears, and skin over bony prominences of the limbs, feet, sternum, and tip of the tail. Histologically the cutaneous lesions frequently consisted of vesicles, pustules, and ulcers on the lips, face, and ears. Neutrophils, lymphocytes, mast cells, and macrophages were present throughout the dermis. Neutrophils and lymphocytes were also present in and around vessels. Between 13 and 19 weeks of age generalized muscle atrophy was noted. The muscle lesions consisted of interstitial lymphocyte, plasma cell, macrophage, and neutrophil accumulation; myofiber degeneration, regeneration, and atrophy; and fibrosis. Perivascular neutrophils, lymphocytes, and plasma cells were also seen. Histologically, the lesions resembled those present in human juvenile dermatomyositis; and these observations, coupled with clinical, immunologic, and clinical pathologic observations presented elsewhere, suggest that familial canine dermatomyositis is an appropriate and potentially useful model for human juvenile dermatomyositis.

Animals↗
PubMed1983

Congenital myasthenia gravis in 13 smooth fox terriers.

In 13 Smooth Fox Terriers with a congenital form of myasthenia gravis, clinical signs included intermittent, progressive muscle weakness that became more pronounced with exercise; muscle wasting; megaesophagus; and aspiration pneumonia. Neurologic abnormalities were apparent only during periods of weakness and included inability to retract the fore- and hindlimbs from painful stimuli. A decrement of the compound muscle action potential was evident during repetitive supramaximal nerve stimulation. Intravenous injection of a short-acting cholinesterase inhibitor evoked immediate improvement of clinical and electromyographic signs. Intracellular microelectrode studies of a biopsied external intercostal muscle revealed reduced amplitude of miniature end-plate potentials, as occurs in acquired myasthenia gravis. However, in contrast to acquired myasthenia gravis, antibodies directed against acetylcholine receptors were not demonstrable in serum and were not bound to acetylcholine receptors in muscle. Despite lack of complexing with immunoglobulin, the amount of acetylcholine receptor protein in biopsied external intercostal muscles from 9 affected pups was less than 25% of the amount in 5 unaffected littermates. The latter finding accounted for the reduction in amplitude of miniature end-plate potential and the failure of neuromuscular transmission. Treatment with a long-acting cholinesterase inhibitor in 6 cases resulted in temporary improvement in muscle strength.

Animals↗
PubMed1983

Decreased osmotic fragility in heritable canine myopathy.

Osmotic fragility was examined in red blood cells from dogs with a heritable muscle disorder that clinically resembles a muscular dystrophy. Several erythrocyte abnormalities have been reported in patients with certain forms of muscular dystrophy and it is thought that these changes reflect genetically induced alterations in the plasma membrane. It is believed that the examination of erythrocytes may eventually lead to the understanding of membrane involvement in muscle disorders. In this study, the mean osmotic fragility was found to be significantly lower in affected cells than in normal cells. These differences were maintained regardless of changes in incubation temperature (5 degrees, 20 degrees, or 35 degrees C) and pH (6.5, 7.0, 7.5, or 8.0). Quantitative analysis of glycolytic metabolites and adenine nucleotide concentrations revealed little variance between erythrocytes from normal and affected animals. Similarly, the pattern of membrane protein phosphorylation in intact erythrocytes from affected animals did not differ from that observed when erythrocytes from normal animals were examined. Of the red cell indices measured, the erythrocyte count in affected animals was moderately increased, but both the mean corpuscular volume and mean corpuscular hemoglobin content were significantly reduced. From these data it is concluded that the decrease in osmotic fragility cannot be explained by differences in cell metabolism or energy production. However, the decrease in affected cell mean corpuscular volume and mean corpuscular hemoglobin content may be correlated with the decrease in osmotic fragility in a manner similar to that observed in the hemolytic disorder of beta-thalassemia.

Adenine Nucleotides↗
PubMed1983

Comparative pathology of connective tissue diseases.

Selected examples of animal models for human connective tissue diseases are reviewed, with emphasis on those which can be verified by genetic, immunologic, and biochemical studies. Desnick et al. have stated that the study of animal models in inborn errors of metabolism will "have a dramatic impact on the future development and evaluation of effective therapies for a variety of human enzyme diseases." It is hoped that these discussions, including comments on the importance of animal models for specific human diseases of the connective tissue, will yield significant benefits in human health.

Animals↗
PubMed1981

Inheritance of a neuromuscular disorder of Labrador retriever dogs.

A heritable neuromuscular disorder of Labrador Retrievers was demonstrated to be transmitted by a simple autosomal recessive mode. The pathologic changes were confined to affected dogs, and a method for identifying the unaffected carrier was not found. The disorder was first recognized in 4 litters submitted for clinical examination, then was studied in 6 additional litters to determine the mode of inheritance. Although the disorder appeared widespread, its prevalence was thought to be low.

Animals↗
PubMed1980

Dermatosparaxis in a Himalayan cat: I. Biochemical studies of dermal collagen.

Dermatosparaxis, a genetic disease, results from the deficiency of the NH2 procollagen peptidase, an enzyme which removes the NH2-terminal nontriple-helical extensions from procollagen. We have identified a Himalayan cat which has deficient amino terminal procollagen peptidase activity. The partially processed precursor chains pNalpha 1 (110,000 daltons) and pNalpha 2 (99,000 daltons) were identified by sodium dodecyl sulfate electrophoresis. In contrast to that from a normal animal, the 20,000 xg supernatant of a skin homogenate failed to convert pNcollagen to collagen. Amino acid analysis of pNalpha 1 and pNalapha 2 chains demonstrated the presence of cysteine and a lower percentage of hydroxyprolyl and glycyl residues due to the presence of the amino terminal extensions. The disorder in this animal is milder than that in sheep and cattle which is reflected in the longer survival and relatively smaller proportion of pNalpha chains in skin. The defect was also demonstrated by skin fibroblasts in culture.

Amino Acids↗
PubMed1980

Dermatosparaxis in a Himalayan cat: II. Ultrastructural studies of dermal collagen.

Dermatosparaxis is a connective tissue disease, primarily of sheep and cattle, that results from deficient activity of the NH2-terminal procollagen peptidase. It is characterized by fragile, loose skin that is easily torn with minor trauma. We have identified a cat twith a defect in this procollagen peptidase which affects only a small proportion of the collagen molecules; the majority of the collagen is processed normally. Nonetheless, as seen by transmission and scanning electron microscopy, this population of aberrant collagen molecules significantly alters the structure of individual collagen fibrils, the assembly of fibrils into fiber bundles and the integration of fiber bundles into a normal, woven network in the reticular dermis of skin. Although the clinical findings are less severe than those in sheep and cattle where the enzymatic defect is more complete, the ultrastructural abnormalities are marked and demonstrate that a minority of abnormal collagen molecules cn have a major effect on the structure and function of connective tissues.

Animals↗
PubMed1980

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, seizures was performed. Amino acid profiles of serum, cerebrospinal fluid (CEF), and biopsied cerebral cortex from epileptic dogs were compared with those seizure-free siblings. No differences also 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 correlations 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.

Amino Acids↗