Ultrastructure of 6-aminonicotinamide (6-AN)-induced lesions in the central nervous system of rats. III. Alterations of the spinal gray matter lesion with aging

Animal models of multiple sclerosis: Focus on experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is a chronic, progressive disorder of the central nervous system (CNS) that affects more than two million people worldwide. Several animal models resemble MS pathology; the most employed are experimental autoimmune encephalomyelitis (EAE) and toxin- and/or virus-induced demyelination. In this review we will summarize our knowledge on the utility of different animal models in MS research. Although animal models cannot replicate the complexity and heterogeneity of the MS pathology, they have proved to be useful for the development of several drugs approved for treatment of MS patients. This review focuses on EAE because it represents both clinical and pathological features of MS. During the past decades, EAE has been effective in illuminating various pathological processes that occur during MS, including inflammation, CNS penetration, demyelination, axonopathy, and neuron loss mediated by immune cells.

Effect of 6-aminonicotinamide on metabolism of astrocytes and C6-glioma cells

Brain tissue cells have been shown to use two predominant pathways for energy production. The first of these is the pentose phosphate shunt, and the second is glycolysis, followed by the TCA cycle. Inhibition of these pathways can result in a reduction of ATP, and changes in the concentration of various metabolites. In the present study, the acute and chronic effect of 6-aminonicotinamide (6-AN) (0.01, 0.02, and 0.03 mg/ml) was examined on astrocytes and C6-glioma cells. Following this treatment, glucose, lactate, glutamate, ATP, and PCr were assayed according to the procedures of Lowry and Passonneau. Our data indicated that following 15 minutes treatment of astrocytes and C6-glioma with 6AN there was no significant difference in the concentration of metabolites measured. However, following 24 hours treatment there was a significant increase in glucose concentration and significant reduction in the concentration of ATP, PCr, lactate and glutamate in both cell types. Morphological changes appeared later following 48 hours treatment with 6-AN in both cell types. Glucose accumulation can be explained by the fact that it is the precursor to both glycolysis and the pentose phosphate shunt. If these processes are inhibited, glucose will obviously accumulate and products like ATP, PCr, lactate and glutamate will decrease. Additionally, there was significant differences in concentration of glucose and lactate between astrocytes and C6-glioma cells. The significance of these differences has been discussed.

Fine structural changes in the rat arcuate nucleus by forced running stress

The forced running stress in male rats induced some fine structural changes in the arcuate nucleus. By inducing stress for 2 days, the number of multilamellar astrocytic wrappings and endoplasmic reticular (ER) whorls increased significantly. After a stress of 12 days, half of the rats remained inactive for several weeks, and the other half regained their normal activity. In the inactive group, the ER whorls were partially degenerated at 2 weeks after the stress. These degenerative changes remained for 14 weeks after the stress with the increased lysosomes and the disorganization of r-ER. These findings may suggest that long-term stress induces degenerative changes in the arcuate nucleus neurons and that some of these changes persist with some aging-like morphological changes.

Aqueductal lesions in 6-aminonicotinamide-treated suckling mice

Suckling mice which received a single intraperitoneal injection of 6-aminonicotinamide on the 5th postnatal day, consistently developed hydrocephalus. During the early stages of hydrocephalus (7-9 days after injection), aqueductal lesions were characterized by edematous ependymal and subependymal cells, and spongy changes in the periaqueductal area, which resulted in aqueduct stenosis. Later stages (after 20 days post-injection) showed that these edematous changes totally subsided, leaving an obliterated aqueduct which was similar to that of human congenital hydrocephalus. At the completely obliterated area, ultrastructural investigation disclosed a normal-looking neuropil but no aqueductal lumen. In the remaining ependymal cell, increased intermediate filaments and lipid droplets occurred. These data suggest that acute ependymal cell degeneration during the perinatal period may result in the profile of aqueduct "agenesis" in human congenital hydrocephalus.

Nuclear membrane indentations in Huntington's chorea

Electron-microscopical examination of the nucleus accumbens, caudate nucleus and frontal cortex was performed in 21 patients with Huntington's disease (HD) and 21 age-matched controls. In HD, nuclear membrane indentations (NMI) were found in 25%, 29% and 20%, respectively, of the neurons of these areas. In the control group these figures were 4%, 4% and 38%, respectively. Possible pathogenetic mechanisms of the NMI are discussed.

Neuropathologic changes in suckling and weanling rats with pyrithiamine-induced thiamine deficiency

Pregnant and nursing Wistar rats were fed a thiamine-deficient diet, and their offspring were injected daily with pyrithiamine. The pathologic lesions in the suckling rats were examined at different times of development. There were distinct changes at 22 days of age, by which time the rats are weaned, and the morphogenesis of the cerebellum is almost completed. Before 22 days of age, there were no pathologic changes except for scattered petechial hemorrhages in the brain. After 22 days of age, acute pathologic changes were observed, in decreasing order of severity, in the vestibular nuclei, inferior olivary nuclei, mammillary body, periventricular gray matter, thalamus, and quadrigeminal plates. The initial changes were swelling of post-synaptic dendrites and distension of the periaxonal space of myelinated axons in the parenchyma and ring-shaped hemorrhages in the perivascular space. Pyrithiamine injections into the offspring of rats fed a thiamine-deficient diet probably induce disturbance of the electrolyte permeability of the neuronal excitable membrane, resulting in swelling of this element. These changes were followed by the filtration of erythrocytes and plasma into the parenchyma and astrocytic swelling, which may be a secondary effect of neuronal changes on the brain vascular permeability.