Effect of aflatoxin-B1 on rat cerebellar cortex: light and electron microscopic study

Introduction: Aflatoxin contamination of foods is a worldwide problem, especially in developing countries. The effects of aflatoxins on the cerebellum are not well studied

Aim of the study: The aim of the present study was to evaluate the possible neurotoxic effects of aflatoxin B1 on the cerebellar cortex of adult male albino rats

Materials and methods: A total of 30 adult female albino rats were used. They were divided into two groups. Group I [10 animals] was allowed water ad libitum and fed a standard diet [negative control]. Group II [20 animals] was administered 5 ml aflatoxin B1 orally by a gastric tube every week for 8 consecutive weeks. Samples from the cerebella were taken and processed for light and electron microscopic investigation

Results: Light microscopic examination of the cerebellar cortex of aflatoxin-treated animals showed its prominent neurotoxic effect on the Purkinje cell layer, with less effect on the granular and molecular layers. Glial fibrillary acidic protein-positive cells were more abundant in the three cortical layers of treated animals compared with the control animals. Ultrastructural study of the cerebellum of the aflatoxin-treated group showed dilated Golgi complex and accumulation of secondary lysosomes in association with nuclear shrinkage and irregularity within Purkinje cells. Many myelinated nerve fibers and nerve cell processes in the molecular and granular layer belonging to the affected nerve cells showed degenerative changes

Conclusion: It could be concluded according to this study that aflatoxin B1 has a neurotoxic effect on the cerebellar cortex of adult female albino rats

Chronic effect of aspartame versus stevioside on the cerebellar cortex of the adult albino rat: a histological and immunohistochemical study

Sweeteners have evolved rapidly over the last 20 years and are added to a wide variety of food items, drinks, drugs, and hygiene products. Aspartame is the most frequently used artificial sweetener. In contrast, stevioside is a sweet herb that seemed to be a promising natural candidate to replace artificial sweeteners but was found to have hazardous effects on the male reproductive system. The aim of this work was to compare between the histological changes in the cerebellar cortex of adult rats after administration of aspartame and stevioside for 6 months. The reversibility of these changes was also evaluated. A total of 25 albino rats aged 3 months were used in this study. They were divided into five groups comprising five rats each. The first group was the control group. Rats in the second group were given stevioside at a dose of 8.6 mg/day for 6 months. Rats in the third group were given stevioside for 6 months and were then allowed 1 month for recovery. Rats in the fourth group were given aspartame at a dose of 20 mg/day for 6 months. Rats in the fifth group were given aspartame for 6 months and were then allowed 1 month for recovery. Specimens of the cerebellar cortex were processed for H and E and subjected to immunohistochemical staining for glial fibrillary acidic protein [GFAP] and caspase-3 and electron microscopic study. Morphometric and statistical analyses were performed to count the number of Purkinje cells, the number of granular cells, and the number of GFAP and caspase-3 immunostained cells. The present study showed degenerative changes in the Purkinje and granular cell layers in both the aspartame-treated and stevioside-treated groups. This was confirmed by a significant increase in caspase-positive cells and a significant decrease in cell number. Moreover, there was marked increase in the number of astrocytes in areas of degeneration. This was confirmed by a significant increase in GFAP immunostaining. Recovery from stevioside was better than that from aspartame, as evidenced by the normal histological appearance of Purkinje cells and less vacuolated neuropils. This was supported by a significant increase in the number of neurons, significant decrease in caspase-positive cells, and significant decrease in GFAP immunostaining in the recovery group from stevioside compared with the recovery group from aspartame. Cessation of stevioside gives better results and leads to better improvement of the histological picture of the cerebellar cortex compared with cessation of aspartame

Effect of aluminum on the histological structure of rats' cerebellar cortex and possible protection by melatonin

Aluminum [AL] is toxic to the central nervous system, and melatonin [MEL] reduces lipid peroxidation by its antioxidant activity. This study was carried out to investigate the histological changes in the cerebellar cortex of rats after AL treatment and to detect any possible protective role of MEL when given concomitantly with AL. This study used 50 adult male albino rats, randomly divided into five equal groups. Group I: control group; group II: received daily intraperitoneal [i.p.] injection of 1/2 ml 0.9% saline containing 2% ethanol; group III: received daily i.p. injection of MEL at 10 mg/kg bw dissolved in 1/2 ml 0.9% saline plus 2% ethanol; group IV: received daily i.p. injection of aluminum chloride at 10 mg/kg bw dissolved in 1/2 ml saline; group V: received both AL and MEL. After 2 months of treatment, the cerebellum was dissected out from each animal and was processed for light and electron microscopic studies. Morphometric and statistical analysis were conducted. After AL administration, the cerebellum exhibited significant reduction in the number of Purkinje cells and prominent peri neuronal spaces in the molecular layer around basket and stellate cells. Ultrastructurally, some of the few encountered Purkinje cells were shrunken with dense cytoplasm, ill-distinct nuclei, and swollen mitochondria with ruptured membranes and cristae. Granule cells revealed increased condensation of their nuclear chromatin. Concomitant administration of MEL with AL displayed an observable protection against these changes. MEL may have a protective role against AL-induced cerebellar toxicity

Toxic effect of cisplatin on cerebellar cortex and spinal cord of adult male albino rat and the possible role of vitamin E: light and electron microscopic study

The nervous system is frequently the site of symptomatic toxicity of antineoplastic agents, cisplatin is a widely used potent chemotherapeutic agent that is highly neurotoxic. It has been proven that it is able to generate reactive oxygen species and inhibit the activity of antioxidant enzymes. This study was carried out to demonstrate the neurotoxic effects of cisplatin on the structure of adult rat cerebellum and spinal cord, and the role of vitamin E which has been shown to ameliorate hephro, oto and neurotoxicities induced by cisplatin. Thirty adult male albino rats weighing 200-250 gm were divided into three groups: Group one: kept as a control. Group two: animals treated with cisplatin at a dose of 4mg/kg twice weekly by intraperitoneal injection, for one month. Group three: animals treated with vitamin E at a dose of 100mg/kg by intramuscular injection in concomitant with cisplatin twice weekly for one month. Animals were sacrificed and their cerebella and spinal cords were processed for light and electron microscopy. Morphometrical and statistical study was done for the mean number, as well as the mean surface area of Purkinje cells and mean surface area of their nuclei. The histological approach revealed marked degenerative changes in the Purkinje cells and motor ceurons of cisplatin treated animals [Group II]. Some of these cells appeared irregular with deeply stained cytoplasm and pykontic nuclei. Ultrastructural examination showed Purkinje cells with cellular shrinkage, damaged organelles and irregular nuclei with electron dense karyoplasms. Significant degenerative changes in the motor neurons and blood capillaries of the anterior horn of the spinal cord in the same group were frequently observed. Morphometric evaluations demonstrated significant decrease in the mean number and the mean surface area of nuclei and cell bodies of Purkinje cells. These structural and morphometrical alterations were much less observed in concomitant use of vitamin E with cisplatin [Group III]. Cerebellum and spinal cord are considered the target areas of cisplatin neurotoxicity, while vitamin E, when used in combination with cisplatin displays a protective action against neurotoxicity

Effects of postnatal exposure to static magnetic field on the development of the cerebellar granule cells

Many studies were performed to evaluate the effects of static magnetic fields [SMFs] on the processes of proliferation and migration of cerebellar cells to their final postnatal destinations. Granule cells are the most abundant interneurons in the cerebellum. Progenitors of these neurons actively proliferate during the first 2 postnatal weeks in external granular layer [EGL]. The granule cells in the EGL migrate inwards to form the internal granular layer [IGL], and the EGL disappears. So the postnatal development of the cerebellum depends on their postnatal proliferation and migration which is vulnerable to any micro-environmental insult. to evaluated the light and electron microscopic changes occurred to the cerebellar granule cells of the pups after postnatal exposure to SMF [20 mT]. Postnatal exposure to SMFs showed that there was a significant thinning in the EGL at the beginning of the study at postnatal thy 4, this significant decrease in thickness progressed in the first week. At two weeks when normally the EGL starts to disappear, it showed persistent increase in its thickness indicating delayed migration. At all ages of exposed group [P], EGL contained many apoptotic cells and some degenerated cells. IGL showed significant decrease in its cellular density till the postnatal day 15 concomitant with the period of delayed migration in the EGL. At the postnatal days 22, the cells in IGL began to regain its near normal cellular density but the IGL showed disarrangement of its crowded granule cells with absence of appearance of regular glomeruli among them with appearance of some degenerated cells among the granule cells. Many cells of the IGL also showed areas of cytoplasmic vacuolation. Postnatal exposure to SMFs produces some delay in the development and appearance of more apoptotic cells. But some of these changes in different stages of the postnatal development of the cerebellar cortex began to be less apparent with advancement of age

Further observations on cerebellar climbing fibers. A study by means of light microscopy, confocal laser scanning microscopy and scanning and transmission electron microscopy

The intracortical pathways of climbing fibers were traced in several vertebrate cerebella using light microscopy, confocal laser scanning microscopy, scanning and transmission electron microscopy. They were identified as fine fibers up to 1(micron thick, with a characteristic crossing-over bifurcation pattern. Climbing fiber collaterals were tridimensionally visualized forming thin climbing fiber glomeruli in the granular layer. Confocal laser scanning microscopy revealed three types of collateral processes at the interface between granular and Purkinje cell layers. Scanning electron microscopy showed climbing fiber retrograde collaterals in the molecular layer. Asymmetric synaptic contacts of climbing fibers with Purkinje dendritic spines and stellate neuron dendrites were characterized by transmission electron microscopy. Correlative microscopy allowed us to obtain the basic three-dimensional morphological features of climbing fibers in several vertebrates and to show with more accuracy a higher degree of lateral collateralization of these fibers within the cerebellar cortex. The correlative microscopy approach provides new views in the cerebellar cortex information processing.

Correlative microscopy of cerebellar Golgi cells

The cerebellar Golgi cells of mouse, teleost fish, primate and human species have been studied by means of light and Golgi light microscopic techniques, confocal laser scanning microscopy, slicing technique, ethanol-cryofracturing and freeze-fracture methods for scanning electron microscopy and ultrathin sectioning and freeze-etching replicas for transmission electron microscopy. The Golgi cells appeared in the granular layer as polygonal, stellate, round or fusiform macroneurons surrounded by the granule cell groups. They exhibited ascending dendrites toward the molecular layer and horizontal dendrites and a short beaded axonal plexus confined to the granular layer. Scanning electron microscopy revealed their three-dimensional neuronal geometry and smooth outer surfaces. Freeze-fracture method for SEM showed the stereospatial cytoplasmic arrangement of endoplasmic reticulum, cell organelles and nuclear envelope. By means of transmission electron microscopy the asymmetric synaptic connections of Golgi cell horizontal dendrites--with mossy fiber rosettes at the cerebellar glomerulus--and of Golgi cell axons--with granule cell dendrites at the periphery of glomerular region--were identified. At the molecular layer, Golgi cell ascending dendrites exhibited short neckless spines establishing asymmetric contacts with granule cell axons or parallel fibers. Shaft asymmetric axodendritic and axospinodendritic contacts between Golgi cell dendrites and climbing fibers were also found in the molecular layer.

Utility of silver-colloidal staining method in the diagnosis of medulloblastoma.

Histopathological features of medulloblastomas are usually distinctive. However in rare instances, a distinction between the neoplastic cells of medulloblastoma and the neurones in the cerebellar internal granular layer becomes difficult at light microscopic level. In order to distinguish presence of argyrophilic Nucleolar Organizer Regions (Ag-NORs) was analysed in the paraffin sections of medulloblastoma as well as in the cerebellar internal granular layer. The neoplastic cells in medulloblastoma contained a mean 4.78 Ag-NOR per nucleus while the neurones in cerebellar internal granular layer contained a mean Ag-NOR 0.90 +/- 0.12 per nucleus. Compound Ag-NORs were present in the cells of medulloblastoma while they were absent in the neurones of cerebellar internal granular layer. The results of this study indicate that Ag-NOR technique may be useful in an uncommon situation, where a histopathological distinction between cells of medulloblastoma and neurones in the cerebellar internal granular layer becomes difficult.