Decorin and collagen type I gene expression in avian low score normal pectoral muscle.

The avian Low Score Normal (LSN) genetic muscle weakness is phenotypically characterized by a reduction in the ability of the birds to right themselves from a supine position. Compared to normal skeletal muscle, LSN muscle has normal myosin isoform switching and cell-cell recognition, elevated glycosaminoglycan and decorin levels at embryonic Day 20, and a large increase in collagen crosslinking at 6 wk posthatch. To begin to determine the biological mechanism involved in the elevated decorin protein concentration at embryonic Day 20, the steady-state levels of transcripts encoding both decorin and collagen Type I at embryonic Days 14, 19, and 20, and at 1 d and 6 wk posthatch were measured. On embryonic Day 20, collagen Type I transcripts were not different from the control but there was a significant elevation in decorin transcript levels. At 1 d and 6 wk posthatch, transcript levels of decorin and collagen Type I were not different between LSN and controls. The change in decorin transcript steady-state levels is limited to late embryonic development and suggests an alteration in a signal transduction pathway regulating decorin transcription.

D-2-hydroxyglutaric aciduria.

Hydroxyglutaric aciduria is detected by gas chromatographic-mass spectrometric analysis, and the D and L forms are quantified by chemical ionization with deuterated internal standards. Patients have recently been described who accumulate the D form, and they appear to be quite different from those with the more common L form. Experience is reported with three patients and an animal model with D-2-hydroxyglutaric aciduria. The phenotype appears to include mental retardation, macrocephaly, hypotonia, seizures, and involuntary movements, although neurologic and systemic manifestations of the disorder varied considerably between individual patients, even within the same family.

Idiopathic peripheral neuropathy in a horse with knuckling.

We report the pathological findings of the skeletal muscle and peripheral nerves from a male 14-months-old thoroughbred horse showing idiopathic knuckling. The affected animal, when in staining position, presented knuckling at the fetlock joint of both forelegs, and dragged both fore- and hindlegs when attempting forward movement. The skeletal muscles demonstrated neurogenic atrophy characterized by the scattering of single angular fibers, groups consisting of five to ten angular fibers, and multiple fascicles of atrophic and hypertrophic fibers. The severity of changes tended to be a distal gradient. While there was no evidence of fiber loss on light microscopy, a diffuse scattering of myelin ovoid, Wallerian-like degeneration and onion-bulb formations were observed in almost all peripheral nerves collected. The characteristic features in electron microscope were swollen axons, which contained accumulations of organelles, especially degenerative mitochondria and neurofilamanets. Onion-bulb formations were frequently found and were associated with Schwann cell processes and occasional collagen pockets. Other prominent feature were Büngner bands which contained myelin debris and regenerating axons or sprouts. These findings suggested that the nature of this disease was a disturbance in axonal transport and were indicative of a distal axonopathy.

Neurologic diseases.

The responses of apparently healthy newborn foals to neurologic testing differ significantly from those of adult horses. These responses and the diagnostic techniques pertinent to neurologic problems are reviewed as a basis for evaluation of the compromised neonatal foal. The more frequently encountered neurologic diseases are discussed in a problem-oriented format. These clinical problems include behavioral abnormalities, convulsions, changes in consciousness, blindness, ataxia without loss of strength, ataxia with weakness and paralysis, and the floppy foal.