Zoltán Fülöp

NEUROGLIA IN THE INTERNAL GRANULAR LAYER OF THE DEVELOPING RAT CEREBELLAR CORTEX

Neuroglia in the internal granular layer of the developing rat cerebellar cortex

Proliferation of bergmann-glia in the developing rat cerebellum

SummaryMitotic cells in the ganglionic layer of the infant rat cerebellum were studied between 3 to 12 postnatal days. The connection of these cells with the radial glial fibers of the primitive molecular layer could be established. On this basis it was assumed that the mitotic cells studied were immature Bergmann-glial cells whose proliferative activity seemed to continue even after the formation of their characteristic radial fibers. This phenomenon might offer an explanation for the divergent views on the generation time of Bergmann-glia.

Effects of the novel NMDA receptor antagonist gacyclidine on recovery from medial frontal cortex contusion injury in rats.

Gacyclidine, a novel, noncompetitive NMDA receptor antagonist, was injected (i.v.) into rats at three different doses to determine if the drug could promote behavioral recovery and reduce the behavioral and anatomical impairments that occur after bilateral contusions of the medial frontal cortex (MFC). In the Morris water maze,contused rats treated with gacyciidine at a dosage of 0.1 mg/kg performed better than their vehicle-treated conspecifics. Rats given gacyclidine at either 0,3 or 0.03 mg/kg performed better than brain-injured controls, but not as well as those treated with 0.1 mg/kg. Counts of surviving neurons in the nucleus basalis magnoceilularis (NBM) and the medial dorsal nucleus (MDN) of the thalamus were used to determine whether gacyclidine treatment attenuated secondary cell death. In both the NBM and the MDN, the counts revealed fewer surviving neurons in untreated contused rats than in gacyclidine-treated rats. Increases in the size and number of microglia and astrocytes were observed in the striatum of gacyclidinetreated contused brains. Although most consequences of MFC contusions were attenuated, we still observed increases in ventricle dilation and thinning of the cortex. In fact, the ventricles of rats treated with 0.1 mg/kg of gacyclidine were larger than those of their vehicle treated counterparts, although we observed no behavioral impairment.

Review : Progesterone and Recovery after Traumatic Brain Injury: An Overview

After traumatic brain injury (TBI), female animals often show better cognitive and behavioral recovery than male animals. In female animals, this advantage is conferred by higher levels of systemic progesterone at the time of injury. In rats, postmortem examination of brain tissue reveals that pseudo-pregnant female rats (high progesterone, low estrogen) have virtually no cerebral edema compared with male rats and low- progesterone-state normal cycling female rats after TBI. Progesterone injections can also eliminate cerebral edema in brain-injured male rats. Sex differences in the outcome of TBI highlight the importance of consid ering the timing of therapy and hormonal fluctuations in developing safe and effective treatments for CNS injury. NEUROSCIENTIST 4:435-442, 1998

Mosaicism of the ventricular layer as the developmental basis of neocortical columnar organization

SummaryThe ratio and local distribution of intensely and weakly labelled neurons as compared with unlabelled neurons were studied in newborn mice by means of autoradiography using 3H-thymidine injected at various embryonic ages. The distribution and migrational properties of intensely labelled neurons suggest that cells contributing to any given cortical layer are not generated simultaneously but in smaller units that correspond to cortical microcolumns. This implies a mosaicity in the genetic potential of the ventricular germinative layer.

Visualization of outgrowing axons of grafted neurons by anterograde labelling with Phaseolus vulgaris leucoagglutinin in the motor cortex of the rat.

Fetal cerebral cortical tissue was transplanted into an aspirated lesion cavity made in the sensorimotor cortex of adult rats. Ten weeks after grafting, outgrowing fibers from the graft were visualized by an anterograde tracing technique using Phaseolus vulgaris leucoagglutinin (PHA-L). It was demonstrated that the efferent fibers grew into the neighboring host cortical tissue, the corpus callosum and in some cases approached caudate/putamen. Characteristic axon arborization with abundant boutons were found in the host cortical tissue, but only in close vicinity to the grafts. It is concluded that the PHA-L anterograde tracing technique can be a useful tool to assess the degree of anatomical integration of the transplants into the host tissue.

Electrophysiological and morphological properties of embryonic neocortical grafts developing in different regions of the host rat brain.

Parallel morphological and electrophysiological studies of embryonic neocortical tissue (primordia of anterior parietal–presumptive sensorimotor–cortex) grafted into different regions of the host adult brain (sensori-motor cortex, caudate-putamen, septum or thalamus) were carried out to investigate to what extent the properties of transplanted embryonic neocortex–an advanced organizational form of neuronal tissue–are affected by homotopic or heterotopic surroundings. The results point to the importance of the host tissue environment as it influences both the size, the morphological and functional properties of the implanted embryonic cortical plate tissue. The cortical grafts were smaller in size when developed homo-topically in sensorimotor cortex and grew larger in heterotopic environment (caudate-putamen, septum, thalamus). The orientation of neuronal dendrites in the grafts tends to follow that seen in the surroundings. The homotopic grafts showed a better structural integration into the host brain. Differences were seen between intracortical and subcortical transplants in the spontaneous firing rate of neurons and in the ratio of units with various types of spontaneous discharge.

Mature but not fetal or neonatal rat superior cervical ganglion transplants survive in the cortex of adult rats.

The transplantation of catecholaminergic tissues is a possible therapy for parkinsonism. Central nervous tissue is suitable for transplantation only in the immature stage, whereas peripheral nervous tissue can also be transplanted when mature. The present study compares the development of fetal (17–20 embryonic day, E17–20), neonatal (1–3 postnatal day, P1–3 and mature (5–6‐week‐old) rat superior cervical ganglia after transplantation into the cerebral cortex of adult rats. The mature transplants survived in greater proportion and preserved their structural characteristics, although a considerable proportion of the neurons died. The perinatal transplants only survived sporadically, decreased in size and the surviving remnants failed to display a structure comparable to the adult ganglion in situ. Thus, the use of adult donors is not only a possibility but a necessity when superior cervical ganglion (probably any ganglion) is transplanted. This principle is radically different from that seen in the case of central nervous tissues, and can be understood by the analysis of the time curves of cell proliferation and programmed cell death (apoptosis) observed during the perinatal development of sympathetic ganglia.

Histological alterations in the fetal mouse cerebellum after neutron irradiation: A light and electron microscopic study

Histological effects of in utero neutron irradiation (0.5 Gy) were investigated in fetal mouse cerebellum. Irradiation was performed on the 18th embryonic day. Histological alterations were examined at 2, 6 and 12 h after irradiation. The effect was most pronounced in the EGL, 6 h after irradiation. In some cells (about 24%) karyopycnosis, destruction of cytoplasmic organelles and shrinkage were observed. Remnants of destroyed cells--the pycnotic nuclei with some cytoplasmic debris around them--were rapidly phagocytized by the surrounding cells. In addition to glial elements, the EGL germinal cells also showed phagocytic activity. Dense particles appearing light-microscopically as pycnotic nuclei, proved to be mostly remnants of destroyed, phagocytized cells under electron microscope.

Transneuronal Degeneration in Different Inbred Strains of Mice: A Preliminary Study of Olfactory Bulb Events After Olfactory Nerve Lesion

Cytological analysis of the olfactory bulb was performed in two inbred strains of mice SEC/1 ReJ and C57/B16J after the lesion of the olfactory nerve. The data show an enhanced transneural degeneration in C57 mice as compared to the controls, while in the SEC mice this phenomenon did not exceed the level of spontaneous degeneration previously described by other authors. On the basis of our findings two different genetically adaptive systems are hypothesized and correlated with onto-genetical data.