Aspects of development of bone marrow in male albino rats: Light and electron microscope study

Twenty five healthy male albino rats were utilized in this study to throw more light on the histological and ultra structural changes in femur's bone marrow at different ages in albino rats. They were classified into five groups [5 animals each]: group A, [prenatal, 17-19 days of gestation], group B [newborn, I-day old], group C [one week old], group D [adult, 3-6 months old], and group E [senile, more than I8-months old]. The animals were sacrificed and small pieces of femurs were taken and processed for light and electron microscopes examination. The bone marrow was consisted of vascular and non vascular elements. The vascular elements of the prenatal group showed small capillaries and many dilated blood sinusoids. They were lined with flat endothelial cells with little cytoplasm. Large cells[adventitial cells] with large nuclei, pale cytoplasm and long processes were noticed on the abluminal side of dilated sinusoids in the marrow of the newborn. The marrow arterioles of 1 week- old and adult groups were lined with cuboidal lining cells and surrounded by pericytes with flat nuclei and long processes. However, in the senile group, multiple thick walled arterioles with narrow lumen were detected. The non vascular elements of the marrow were formed of hemopoietic and non hemopoietic cells. In the prenatal group, some cells showed small electron dense nuclei, dense cytoplasm and irregular cell membrane [apoptotic cells]. Many large macrophages with eccentric nuclei were seen in cIose relation with the apoptotic cells. Giant cells with multiple nuclei and vacuolated cytoplasm [osteoclasts] were noticed adjacent to calcified spicules. Many hemopoietic cells at different stages of development were noticed at 1-day of age. Apoptotic neutrophils with dark nuclei and muddy cytoplasmin together with mitotic cells were also observed. Hemopoietic cells were markedly increased at the age of I-week, adult, till senile. Fat cells and many megakaryocytes were also marked. The megakaryocytes appeared as large cells with multilobulated nuclei and numerous electron dense granules in their cytoplasm. Also, intracytoplasmic canaliculi appeared as elongated vesicles which may branch. These canaliculi were of smooth surface and enclosed empty cores. With senility, there was marrow hypocellularity. Most of the cells were apoptotic. In conclusion, bone marrow started its function as a hemopoietic organ postnatally. In senile group apoptosis predominated mitosis. Predominance of mitosis in young ages making them more recommended as a potent source for bone marrow transplantation

effect of exposure to cold on epidermal permeability barrier in albino rat [light and electron microscope study]

This study was carried out on 15 adult albino rats to determine the effect of cold exposure on epidermal permeability barrier. Rats were divided into two groups [a control group and an experimental group] and their soles were treated with topical acetone to disrupt epidermal barrier. The experimental group was subdivided into two subgroups [animals left in empty cages and animals subjected to a steady contact with ice]. The examination of both semithin and ultrathin sections showed that epidermis of soles of the control animals consisted of thick stratum corneum formed of very flat, heavily keratinized cells. After four hours, the acetone treated soles showed relatively paler stratum corneum in semithin sections and empty spaces between the horny cells in the ultrastructure examination. The animals whose soles were treated with acetone and left for four hours in contact with ice showed broken down stratum corneum in large areas in the semithin sections. Electron microscopy revealed abnormally empty or early empty vacuoles [disorganized lamellar bodies] in both stratum granulosum and stratum spinosum

Observations on the vascular barrier of the thymus in albino rat

A light and electron microscope study was performed to provide further information on the blood thymic barrier. Ten thymus glands were obtained from ten male albino rats ranging in age from 4 to 8 weeks. Paraffin sections were prepared. stained by Fix. and E. and examined by light microscope. Other specimens were processed for transmission electron microscope examination. The haematoxylin and eosin stained sections showed the thymic lobules consisting of cortex and medulla where the lymphocytes were condensely packed in the cortex but sparsely arranged in the medulla. Hassall's corpuscles appeared in the medulla and high endothelial venules were observed at the corticomedullary junction. The transmission electron microscope revealed lymphocytes in different sizes. The reticular cells appeared between the lymphocytes as large polygonal cells with large pale nuclei and vesicular cytoplasm. Macrophages also were observed. Two types of capillaries were detected. The first type showed less irregular endothelial lining with few internal projections; outer collagenous fibers were lacking and the endothelial cells were surrounded by retincular cells. The other type showed a highly irregular endothelial lining and an outer investment of a prominent collagenous coat. The epithelial investment of the first type and the collagenous coat of the other type were suggested to share in the hemato-thymic barrier around both types of thymic capillaries

Light and electron [SEM and TEM] microscope study of the fourth ventricle ependymal lining in rabbit

The ependymal structure of the floor of the fourth ventricle of adult rabbit was investigated using light, scanning and transmission electron microscopy. Eight adult healthy male rabbits were anaesthetized with ether and sacrificed. Small pieces of the floor of fourth ventricle were taken. They were processed for preparation of paraffin sections, stained with Hx and E and examined by L/M. Other minute pieces of them were processed for scanning and transmission electron microscope study. The ependymal cells of the fourth ventricle were seen forming a single row of cuboidal cells with prominent rounded nuclei. Scanning electron microscope showed that the floor of the fourth ventricle exhibited different zones separated by prominent grooves. The ependymal cells exhibited a dense netweek of long cilia. These cilia gradually decreased towards the median sulcus where the ependymal cells were devoid of cilia, but instead they had microvilli on their luminal surfaces. Also pit-like holes appeared in the ependymal lining along the median sulcus, globular supra-ependymal surface projections were noticed. The transmission electron microscope showed that the cells apart from the median sulcus had long and profuse network of interwoven microvilli and cilia over their luminal surface. The cell bodies exhibited supranuelear Golgi complexes, few electron dense granules and multivesiculated bodies. These features suggested a secretory and/or absorptive role