The ultrastructure of the rat central nervous system in chronic undernutrition

Time scale and extent of neuronal and synaptic loss in the hippocampal formation of malnourished adult rats

We have demonstrated that a prolonged low-protein diet induces neuronal and synaptic loss in the hippocampal formation of the adult rat. Because 6 months of protein deprivation was the shortest period analyzed in the previous investigations, in the present study we have evaluated the length of the treatment period necessary to induce significant changes in the numbers of neurons and synapses. Groups of 2-month-old rats were analyzed: (1) and (2) malnourished for 1 and 3 months with a low-protein diet (8% casein): (3) and (4) age-matched control rats fed with a standard diet. Stereological methods were employed to estimate the total number of granule, hilar, CA3 and CA1 pyramidal cells and the volume of the respective cell layers, the volume of the mossy fiber system and the number and related quantitative features of mossy fiber-CA3 synapses. No differences in the number of cells or synapses were found between 1-month malnourished rats and the respective controls. However, in rats treated for 3 months the total number of granule cells. CA3 and CA1 pyramidal cells was reduced, as was the total number of synapses. These findings indicate that the changes induced by protein deprivation progressively increase during the early phases of treatment and that they are already evident after 3 months of protein deprivation.

Effects of hyperbilirubinaemia on glutathione S-transferase isoenzymes in cerebellar cortex of the Gunn rat

The glutathione S-transferases (GSTs) are a family of isoenzymes involved in the detoxication of a variety of electrophilic xenobiotics. The present investigation demonstrates that GST activity and the concentration of cytosolic GSTs in cerebellar cortex of Gunn rats were increased in hyperbilirubinaemic animals compared with non-jaundiced controls. Age-dependent and region-specific increases in GST isoenzymes were seen in three regions of the cerebellar cortex of jaundiced Gunn rats, whereas GST concentrations were not altered in the brainstem, thalamus/hypothalamus, cortex or liver. Cytosolic GST activity was increased 1.3-fold in the flocculus and lateral hemispheres of 20-day-old and 1.7-fold in the flocculus, lateral hemispheres and vermis of 60-day-old jaundiced (jj; homozygous) Gunn rats compared with non-jaundiced (Jj; heterozygous) Gunn rats. H.p.l.c. was used to determine the GST subunit protein concentrations in cytosolic fractions isolated from liver and brain regions of jaundiced and non-jaundiced animals. In all regions of the cerebellum from 20-day-old animals, the levels of Alpha-class GST subunits 2 (Yc1; 3.0-fold) and 8 (Yk; 2.0-fold) were increased in jaundiced rats. In 60-day-old animals, the concentrations of Alpha-class GST subunits 2 (Yc1; 5.0-fold) and 8 (Yk; 3.0-fold), Mu-class subunit 11 (Yo; 2.5-fold) and Pi-class subunit 7 (Yp; 2.0-fold) were increased in all regions of cerebellar cortex of jaundiced animals. In cerebellum of 10-, 20- and 60-day-old non-jaundiced and jaundiced Gunn rats, the flocculus had the highest concentration of Mu-class GST subunit 4 (Yb2) and vermis the lowest; hyperbilirubinaemia increased the concentration of subunit 4 (Yb2; 3- to 5-fold) in the flocculus and lateral hemispheres, but not the vermis, of 20- and 60-day-old rats. Intraperitoneal injection of sulphadimethoxine, a long-acting sulphonamide which displaces bilirubin from its albumin-binding sites and increases the bilirubin levels in tissues, further increased the already elevated concentrations of GST subunits in the lateral regions of cerebellar cortex of hyperbilirubinaemic rats. For example, the concentration of subunit 4 (Yb2) was increased 2.2-fold (compared with non-jaundiced controls) in Gunn rats injected with saline and 7.4-fold in rats injected with 100 mg of sulphadimethoxine/kg body weight. In contrast, GSTs in the vermis of jaundiced animals were not affected by sulphadimethoxine injection. Sulphadimethoxine had no effect on GST concentrations in lateral regions and vermis of heterozygous (Jj) Gunn rats.(ABSTRACT TRUNCATED AT 400 WORDS)

Cell loss in the cerebellum and hippocampal formation of adult rats after long-term low-protein diet

Whereas quite a number of previous reports have shown that the developing brain is vulnerable to protein deprivation, the mature CNS is usually considered resistant to this condition. To explore this assumption the present experimental model was built on groups of 2-month-old rats fed with a low-protein diet (8% casein) for 6, 12, and 18 months and respective age-matched controls fed for the same periods with a standard laboratory chow (27% casein). The numerical density of cerebellar granule cells was estimated using three different stereological procedures (classical, unfolding, and disector). By all methods a significant cell loss was demonstrated. In the hippocampal region the numerical densities of dentate gyrus granule cells and the CA3 pyramidal cells were estimated using the unbiased disector method. A significative and progressive loss of neurons was likewise found. The occurrence of cell loss after lengthy periods of undernutrition in adulthood is thus an issue of paramount importance if extrapolation can be made to the human brain.

Presynaptic inclusions in mossy fibre terminals of the cerebellar cortex following long-term undernutrition in adult rats

Past work on the C.N.S. of nutritionally deprived immature rats shows widespread structural and functional alterations that were not found in nutritionally deprived adults. In the present work we studied cerebellar mossy fibre terminals of adult rats, given a 8% casein diet for periods of 6, 12 and 18 months. After 12 months of the diet, mossy fibre terminals presented a large number of spherical or disc-shaped membrane-free inclusions herein referred to as presynaptic inclusions, with diameters up to 1.3 micron and formed by fine-textured subunits, compacted into 3 nm strands. This material is an extension of the cytoplasmic network of the terminal. No special relationship was observed with the active zones; synaptic vesicles found in the proximity or embedded in these inclusions were often of the flat type, whereas those close to the active zones always appeared spherical. These results show that even in adult rats synaptic terminals are areas sensitive to protein deprivation.

Impeded cerebellar development and reduced serum thyroxine levels associated with fetal alcohol intoxication

Pregnant albino rats were placed on a complete liquid diet (Ensure) containing either 9% ethanol or an isocaloric amount of sucrose between the third and twentieth day of gestation. The pups born to these rats were sacrificed either day 11 or day 14 postnatum and morphometrical, histological and biochemical analyses were done on their cerebellums and cerebrums. Pups that were exposed to ethanol in utero had significantly smaller body weights, cerebrums and cerebellums than pair-fed controls. The cerebellar mass was reduced by 10% and the cerebral weight by 3% in the pups exposed to alcohol when body weights were normalized to that of pair-fed controls. Cerebellar aspartyl aminotransferase (EC 2.6.1.1) activity was reduced at day 11 and 14 in ethanol treated pups compared with controls. Serum T4 levels were also reduced in the ethanol treated group. Histological analyses revealed that the external granule cell (EGC) layer of ethanol treated pups was significantly thicker at 11 and 14 days postnatum than that of pair-fed control pups. Cerebellar ornithine decarboxylase (ODC, EC 4.1.1.17) activity was higher at day 11 in the ethanol treated pups than in controls. The reduced mass, AAT activity, T4 serum levels and the increased thickness of the ECG layer indicate a delayed or impeded maturation of cerebellum in ethanol treated pups. These data are considered from the viewpoint that ethanol, other drugs such as methadone and prenatal stress (malnutrition) may cause delayed cerebellar maturation by reducing serum T4 levels in the early postnatal period (day 5-14).