Spongiform leukoencephalopathy in an adult mixed breed female dog

Leukoencephalomyelopathy is a nonspecific lesion characterized by widespread vacuolation of central nervous system white matter. It is mainly of genetic basis, occurring in young pure breed dogs. This report describes a neurodegenerative disease associated to demyelination in an adult mixed breed female dog. After 20 days in a kennel with12 other dogs, the dog showed progressive nervous signs with ataxia and inability to maintain balance. No other dog was affected. After 15 days, the animal was euthanized in extremis and necropsied. No macroscopic lesions of diagnostic relevance were present. Microscopically, status espongiosus was observed in white matter throughout the length of theneuroaxis, from frontal brain lobe to lumbar spinal cord. Specific stains of Kluver Barrera and immunohistochemistry for the detection of phosphorylated and non-phosphorylated neurofilaments, microglia, astrocytosis, oligodendrocytosis and myelin proteins in brain and spinal cord sections showed demyelination, axonal fragmentation and degeneration, microgliosis and decrease of oligodendrocytes. The anatomopathological study and epidemiological data suggests a primary demyelination due to decrease in number and function of oligodendrocytes, which is probably of genetic basis with lateonset.(AU)

Characterization of the spontaneous and gripping-induced immobility episodes on taiep rats.

In 1989, we described a new autosomic-recessive myelin-mutant rat that develops a progressive motor syndrome characterized by tremor, ataxia, immobility episodes (IEs), epilepsy, and paralysis. taiep is the acronym of these symptoms. The rat developed a hypomyelination, followed by demyelination. At an age of 7-8 months, taiep rats developed IEs, characterized electroencephalographically by REM sleep-like cortical activity. In our study, we analyzed the ontogeny of gripping-induced IEs between 5 and 18 months, their dependence to light-dark changes, sexual dimorphism, and susceptibility to mild stress. Our results showed that IEs start at an age of 6.5 months, with a peak frequency between 8.5 and 9.5 months. IEs have two peaks, one in the morning (0800-1000 h) and a second peak in the middle of the night (2300-0100 h). Spontaneous IEs showed an even distribution with a mean of 3 IEs every 2 h. IEs are sexually dimorphic being more common in male rats. The IEs can be induced by gripping the rat by the tail or the thorax, but most of the IEs were produced by gripping the tail. Mild stress produced by i.p. injection of physiological saline significantly decreased IEs. These results suggested that IEs are dependent on several biological variables, which are caused by hypomyelination, followed by demyelization, which causes alterations in the brainstem and hypothalamic mechanisms responsible for the sleep-wake cycle regulation, producing emergence of REM sleep-like behavior during awake periods.

Oligodendroglial cell damage and demyelination in infant hydrocephalus. An electron microscopic study.

The hydropic changes of oligodendroglial cells have been examined by means of transmission electron microscopy in seventeen cases of human, mostly infant hydrocephalus and associated pathology. Hydropic oligodendrocytes exhibited dilated endoplasmic reticulum and nuclear envelope, edematous mitochondria, enlarged and fragmented Golgi complexes, dense bodies and nuclear chromatin homogenization. A process of nuclear pore disassembly, extrusion of nuclear heterochromatin and an apoptotic-like process were observed in some swollen oligodendrocytes. Some resting or quiescent oligodendrocytes were also observed in the edematous neuropil. Oligodendrocyte cell processes appeared atrophic, degenerated and isolated in the enlarged extracellular spaces. They did not show any association with neighbouring axons, and myelinated axons were not observed in the neuropil. These observations suggest demyelination in infant hydrocephalus.