Pierluigi Gambetti

Synapses and malnutrition: Quantitative ultrastructural study of rat cerebral cortex

In a previous study we have found that synaptosomal fractions from cerebral cortex of 24-day-old rats malnourished from late gestation yielded more protein and higher enzyme activities than the controls, suggesting that presynaptic endings may be relatively “spared” during malnutrition. In order to explore further the effect of malnutrition on presynaptic endings, we have carried out a quantitative ultrastructural study of the lamina pyramidalis from the somatosensory cortex of rats identical in age and method of malnutrition to those used in the previous study. The fractional area of the cortex occupied by cell bodies was 53% larger in the malnourished animals than in the controls. This increase was due to a higher density rather than a larger size of the cell bodies. Neurons accounted for almost all the increase of cellularity while no conclusion could be reached for the glia. The fractional area occupied by neuropil was decreased by 7.4%. The fractional area of the neuropil occupied by presynaptic endings was 18.3% smaller in malnourished animals. This decrease was the result of a diminished size (−11.8%) as well as density (−7.4%) of the presynaptic endings. Furthermore, in malnourished animals, about 72% of the area occupied by presynaptic endings was accounted for by presynaptic profiles measuring 0.375 μm2 or less, while in the controls presynaptic endings of the same size accounted for about 57% of the presynaptic endings area. Possible explanation for the apparent inconsistency of biochemical and morphologic data are presented.

Familial spongy degeneration of the central nervous system (Van Bogaert-Bertrand disease) - An ultrastructural study

SummaryLight and electron microscopy study of skeletal muscle and cerebral biopsies from a case of spongy degeneration of central nervous system is reported. The multiple vacuoles present in cerebral gray and white matter correspond to (a) clefts within myelin sheaths resulting from splitting at the intraperiod line and (b) swollen astrocytic perikarya and processes. Unusual mitochondria containing crystalline-like material were observed only in astrocytes. The ultrastructural findings are consistent with cerebral edema. It is suggested that the astrocytes play a primary role in the fluid accumulation while the myelin swelling is a secondary lesion. The possible role of the abnormal astrocytic mitochondria is discussed.ZusammenfassungEs wird über licht- und elektronenoptische Untersuchungen an Muskel-und Hirnbiopsien eines Falles von spongiöser Degeneration des ZNS berichtet. Die in der grauen und weißen Hirnsubstanz enthaltenen Vacuolen entsprechen a) Spalten in den Markscheiden infolge Aufsplitterung an der intraperiodischen Linie und b) geschwollenen Astrocytenperikaryen und-fortsätzen. Ungewöhnliche Mitochondrien mit Gehalt an kristallinem Material fanden sich nur in Astrocyten. Die ultrastrukturellen Befunde entsprechen denen des Hirnödems. Es wird angenommen, daß die Astroglia eine primäre Rolle in der Flüssigkeitsansammlung spielt, während die Markscheidenschwellung als eine Sekundärläsion aufgefaßt wird. Die mögliche Bedeutung abnormer Astrocyten-Mitochondrien wird diskutiert.

Puromycin: Action on Neuronal Mitochondria

Puromycin, in dosages that inhibit cerebral protein synthesis and expression of memory in mice, produces swelling of neuronal mitochondria. Acetoxycycloheximide, which inhibits cerebral protein synthesis to the same extent as puromycin, fails to produce swelling of neuronal mitochondria. Puromycin and heximide mixtures produce severe inhibition of protein synthesis, but result in a minimal swelling of neuronal mitochondria and in a decrease of peptidylpuromycin complexes to a level of 30 percent of that following the injection of puromycin alone. It is concluded that swelling of neuronal mitochondria in the presence of puromycin is not due to inhibition of cerebral protein synthesis per se, but is related to a specific action of puromycin on ribosomal protein synthesis. The findings are consistent with the hypothesis that peptidyl-puromycin complexes are responsible for mitochondrial swelling.

RNA and axonal flow. Biochemical and autoradiographic study in the rabbit optic system

Summary The movement of RNA and its precursors was studied in the rabbit optic system at various time intervals after intraocular injection of [ 3 H]uridine. A proximo-distal gradient of both precursors and RNA was found, with the 3 H precursors always preceding the appearance of [ 3 H]RNA. By autoradiography, most of the RNA in the optic nerve was found to be outside the axons, mainly in glial cells. Actinomycin D administered intracranially after intraocular injection of [ 3 H]uridine produced a 70–80% diminution in synthesis of labeled RNA in the optic nerve, without affecting the retina. Instead, when this drug was injected intraocularly before [ 3 H]uridine, it had no effect on the optic nerves, in spite of a severe inhibition of RNA synthesis in the retina. It is concluded that most of the RNA found in the nerve is synthesized locally, and since both precursors and RNA follow very closely the axonal pathway, it is suggested that the labeled precursors migrate intraaxonally and are taken up by adjacent glial cells where they are incorporated into RNA.

The significance of cytoplasmic inclusions in late infantile and juvenile amaurotic idiocy - An ultrastructural Study

SummaryThe electron microscopic findings of cerebral biopsies from two siblings with late infantile-juvenile amaurotic idiocy are presented. One patient had a mixture of “fingerprint” and multilamellar inclusions, often in the same cytosome. The second patient had only “fingerprint” inclusions.Electron microscopic findings in autopsied tissues from two other cases of late infantile-juvenile amaurotic idiocy with multilamellar cytosomes are also presented. Evolution of the multilamellar cytosomes into lipofuscin was not observed. We concluded that cases of late infantile-juvenile amaurotic idiocy with multilamellar and “fingerprint” inclusions should be distinguished from cases with lipofuscin.

Synapses and malnutrition. Morphological and biochemical study of synaptosomal fractions from rat cerebral cortex

Abstract Malnutrition from the last week of gestation resulted in significant diminution in weight and total protein content of cerebral cortex of 12- and 24-day-old rats. In synaptosomal fractions from cerebral cortices of 24-day-old malnourished rats the recovery of protein and of acetylcholinesterase and choline acetyltransferase activity per gram of fresh tissue was higher than in the controls. Quantitative morphologic studies showed no difference in the composition of synaptosomal fractions from malnourished and control rats. The higher yield in protein. AChE and ChAc of synaptosome fractions may indicate that presynaptic endings are relatively spared by perinatal malnutrition, however, the possibility that these results are due to an altered distribution of the presynaptic endings among the various subcellular fractions cannot be ruled out.

Status spongiosus of rat central nervous system induced by actinomycin D.

SummaryThe effect on central myelin of Actinomycin D, an RNA — and, secondarily, a protein-synthesis inhibitor, has been studied by light and electron microscopy. The intracranial injection of this drug produced an extensivestatus spongiosus of the white matter in the cerebrum, cerebellum, brain stem and optic nerve within 48 h.The status spongiosus was due to vacuole formation within the myelin sheath and to enlargement of the extracellular space. Three types of vacuoles were observed: (a) the most common varieties formed between the inner tongue and the remainder of the myelin sheath; (b) a second variety formed by enlargement of the periaxonal space with separation of the axon from its myelin sheath, and (c) a less common type of vacuolization was due to splitting of the myelin lamellae at the interperiod line to form large intramyelinic vacuoles. Myelinic vacuoles were preceded by nuclear and cytoplasmic changes in oligodendrocytes, which included nucleolar segregation, disaggregation, and diminution in number of ribosomes. These changes were similar to those previously reported in a variety of cells exposed to Actinomycin D. It is suggested that myelin vacuoles result secondarily from the Actinomycin D inhibitory effect on oligodendroglial RNA — and protein-synthesis, rather than from a direct effect of this drug on the myelin sheath.

Distribution of puromycin peptides in mouse entorhinal cortex.

Abstract The distribution of [ 3 H] puromycin peptides (PP) in mouse entorhinal cortex was investigated by ultrastructural autoradiography after intracerebral injections of [ 3 H] puromycin. Neuronal nuclei, postsynaptic elements, and neuronal perikarya had the highest densities of silver grains related to PP with 7.1, 6.9, and 5.5 grains/100μ 2 , respectively, while the presynaptic endings had a significantly lower grain density of 3.2 grains/100μ 2 . The grain density over the remaining cerebral cortical parenchyma was 2.7 grains/100μ 2 . Most of the radioactivity present in neuronal perikarya was related to perikaryal mitochondria. These findings are discussed in light of existing evidence that PP are responsible for the suppression of memory and for morphological and functional alteration of brain mitochondria.

Accumulation of smooth cisterns, multivesicular bodies and "zebra" bodies in neurons - A case of peculiar storage condition

SummaryThe ultrastructural and biochemical study of cerebral and liver biopsies from a two-year-old boy with 20 month history of psychomotor retardation, hypotonia and hyporeflexia is presented. Although the case cannot be considered, at the present time, as a separate entity in view of the failure of the biochemical studies of identifying the stored material, the ultrastructural features, which include clustered agranular cisterns of endoplasmic reticulum and numerous multivesicular bodies and “zebra” bodies in neurons, indicate a storage disorder morphologically different from those reported to date. In the present case, morphological and cytochemical findings suggest that the agranular endoplasmic reticulum may give trise to multivesicular bodies which, in turn, may become dense bodies and “zebra” bodies.