The effects of gamma irradiation on the postnatally developing canine cerebellar cortex. II. Sequential histogenesis of radiation-induced changes

Effects of nitric oxide on blood-brain barrier permeability in common carp (Cyprinus carpio L.)

OBJECTIVE

To determine in vivo effects of nitric oxide (NO) on blood-brain barrier (BBB) permeability in common carp (Cyprinus carpio L.).

ANIMALS

148 carp. PROCEDURES Carp received glyceryl trinitrate (1 mg/kg) as an NO donor or received no treatment (control group). Nitrite and nitrate concentrations in carp sera were determined 0.25, 1, 3, 6, 8, 12, and 24 hours after treatment. In control and treatment groups, BBB permeability was analyzed by assessment of leakage of Evans blue dye into various brain areas at 6, 12, and 24 hours after glyceryl trinitrate treatment. Brain edema was determined by means of the wet-dry weight method and assessed with light microscopy on H&E-stained preparations of tissues obtained 6 and 24 hours after glyceryl trinitrate treatment.

RESULTS

Treatment with glyceryl trinitrate induced endogenous synthesis of NO, which was upregulated 6 and 8 hours after treatment. Increased NO synthesis was associated with increased permeability of the BBB, which developed 6 hours after treatment with the NO donor. Although the BBB became impermeable again by 12 hours after glycerol trinitrate treatment, brain edema still persisted 24 hours after treatment.

CONCLUSIONS AND CLINICAL RELEVANCE

In this study, treatment with an NO donor caused reversible opening of the BBB and brain edema in common carp. An intact BBB is important to prevent influx of potentially harmful substances into the brain. This investigation highlighted the possibility of BBB disarrangement caused by NO, a substance found in the CNS of all vertebrates evaluated.

Familial periventricular nodular heterotopia

We describe herein a 13-year-old girl, her 34-year-old mother and her 60-year-old grandmother who have periventricular heterotopic nodules. The mother has suffered from epileptic seizures since she was 15 years old, but the daughter and grandmother have had no epilepsy. They showed multiple uncalcified nodules on the lateral ventricular walls on CT. On MRI the intensity of the nodules was the same as that of the cerebral gray matter, suggesting heterotopia, and no other cerebral abnormalities were observed. Despite extensive examinations, neither have exhibited evidence of tuberous sclerosis. The periventricular nodular heterotopia observed in this family are a unique form of migration disorders, which may be caused by a dominant mutation.

Cytoarchitectonic investigation of the rat spinal cord following ethylnitrosourea administration at different developmental stages

We examined the histological findings and cytoarchitectonic alterations in the rat spinal cord following matrix cell degeneration caused at different developmental stages, from neural plate formation through neuroblast generation. Ethylnitrosourea (ENU) 20 mg/kg body weight was administered transplacentally to the fetuses on the 10th embryonic day (E10) to 14th. The observations were made until the 21st postnatal day. Normally, mitoses were present scatteredly in the matrix cell layer of the neural plate or neural tube on E10 or E11, and gradually restricted to the dorsal portion of the alar plate as development occurred. The localization and number of degenerative cells as well as the site and degree of neuronal decrease in the completed dysgenetic spinal cord seemed to correlate with the topography and frequency of the mitoses in the matrix cell layer at the time of ENU administration. Disorder in the pattern of cytoarchitecture of neurons was not observed. The degree of hypoplasia of the white matter was proportional to the intensity of decrease of the spinal neurons. Aberrant myelinated fibers were not seen. No reactive gliosis, fibrosis or abnormal vascularization was observed at any time.

Initial junctions between developing parallel fibers and Purkinje cells are different from mature synaptic junctions

During postnatal development of cerebellar cortex, junctions are formed between parallel fiber axons and the shafts of Purkinje cell dendrites. These shaft junctions resemble synaptic junctions on spines in thin sections, in that the axon contains a cluster of synaptic vesicles, and the pre- and postjunctional membranes are lined by electron-dense material. The shaft junctions do not have the aggregate of particles arrayed on the extracellular half of the postjunctional membrane that is characteristic of mature spine synaptic junctions in freeze-fractured preparations, however, and so presumably have a different protein composition. Shaft junctions are transient specializations, present only in developing tissue, but do not appear simply to be intermediates in the formation of mature spine synaptic junctions. In normal development, spines are formed by the Purkinje cell dendrite at sites not occupied by shaft junctions. Moreover, in certain neurological mutant mice, shaft junctions form in the absence of spine synapses, and in other systems spines develop in the absence of shaft junctions. We suggest that shaft junctions are a class of synapse formed during development which is distinguished by its capacity to dissociate, and that only some fraction of the parallel fibers forming shaft synapses with a developing Purkinje cell will have established spine synapses in the adult.

Dysplastic gangliocytoma of cerebellum in a newborn. Case report

Dysplastic gangliocytoma of the cerebellum is reported in a newborn. It is characterized by large ganglion cells in the molecular layer and premature attenuation of the external granule-cell layer. The internal granule-cell layer appears rarefied but otherwise normally organized. It appears that in this disease the migrating granule cells mature too early and become arrested in the molecular layer, because of their abnormal forms, while others continue to migrate and grow in size in their normal location in the inner granule-cell layer.

Restitution of bromodeoxyuridine-induced changes in cerebellar development

Previously, it was shown that bromodeoxyuridine (BrdU) in 2-day-old rats caused hypoplasia of the external cerebellar granular layer. Significant restitution was achieved after removal of BrdU by an increase in the rate and duration of proliferative activity of the EGL cells, but abnormal cerebellar cytoarchitecture remained detectable at 35 days of age due mainly to polarity changes in the regenerated cells. The present report concerns repair of the EGL after giving BrdU to 7-day-old rats i.p. (15 mg/100 g body weight) twice daily for 3 days and killed at 15 days-of-age. Now, the regenerative capacity of the EGL was severely curtailed. The proliferative activity of the EGL of the treated animals was similar to normal controls and there was no change in the orientation of either the EGL cells or the parallel fibers. The only noticeable differences were a decrease in the width of the molecular layer and the presence of unusually elongated primary dendrites in many Purkinje cells of the BrdU treated rats. It was concluded that lengthening of the cell cycle time had slowed down the removal of BrdU and thus reduced the regenerative potential of the EGL at this age.

Electron microscopic analysis of postnatal histogenesis in the cerebellar cortex of staggerer mutant mice

Postnatal development of the cerebellar cortex has been compared in staggerer mutant and unaffected littermate mice. From postnatal day 3 to about day 21 the external granular layer in staggerer mice is decreased in thickness and area, and the number of postmitotic granule cell neurons is reduced. Those granule cells that are generated seem to differentiate normally, with the remarkable exception that they form only primitive junctions with Purkinje cell dendritic shafts. These specialized junctions are not superseded by the normal parallel fiber:Purkinje spine synapses and disappear by the third week. Purkinje cell somata and dendrites are smaller than normal at all stages examined. The dendrites are not confined to the sagittal plane as in the normal and, unique among mutant or other animals described to date, they exhibit virtually no branchlet spines. All other cortical synaptic relations of granule and Purkinje cells, including climbing fiber:Purkinje spine synapses, appear qualitatively normal. However, by 28 days virtually all staggerer granule cells have degenerated. While the primary genetic defect remains unknown, we postulate that the morphological abnormalities may be attributable to a block in the normal developmental relationship between granule cells and Purkinje cells. The small cell size and failure to form branchlet spines suggest that the Purkinje cell abnormality may be closer to the primary effect of the mutant gene than the more flagrant hypoplasia and degeneration of granule cell neurons.

Studies on ectopic granule cells in the cerebellar cortex. III. An investigation into the restoration of the external granular layer after partial destruction

In order to strengthen a hypothesis concerning the occurrence of ectopic granule cells, one of the assumptions made was tested systematically. The reaction of the EGL to partial destruction by various single doses by hydroxyurea at various ages was followed. Under all conditions examined, re-population of the EGL takes place--rapidly after lower doses, slowly after high doses of HU. The phenomena observed are discussed with a view on the hypothesis mentioned. Re-population is beneficial, but may itself be a major pathogenetic factor in certain developmental malformations by upsetting the "time-schedule". The results are also of potential interest for an analysis of the regulation of normal cerebellar morphogenesis.