Histological study on the effect of tobramycin dosage regimens on renal proximal tubular cells in the rats

The present study was undertaken to show the potential nephrotoxicity of tobramycin, given in two different dosage regimens, on the proximal convoluted tubules by using the light and transmission electron microscopic techniques. Thirty-five rats were divided into three groups: Group I served as control, Group II received tobramycin at 4mg/Kg of body weight intraperitoneally every 8 hours for ten days, and Group III received once-daily dosing of intraperitoneal injection of tobramycin at 12mg/Kg of body weight for ten days. The rats were sacrificed 3 days after the last injection. Small pieces of the right kidneys of all the animals were processed for light and electron microscopic examination. The study showed that tobramycin resulted in certain structural and ultrastructural changes in the proximal convoluted tubules. These changes included vacuolar degeneration in the epithelial cells, increased number of lysosomes with variably sized myeloid bodies, mitochondrial oedema, and loss of apical microvilli. These changes were clearly evident following multiple-daily dosing and were less obvious following once-daily dosing. Furthermore, regenerating tubular epithelial cells were evident following once-daily dosing administration. The experimental tobramycin toxicity can be reduced by administering equivalent amounts of the antibiotic in a once-daily dosing as opposed to multiple-daily injections. It is hoped that this study will contribute in the selection of a more appropriate dosing regimen for tobramycin in human beings

Tripartite Os Inca: an embryological and morphological study

Inca bone [Os Inca] or os interparietale is an interesting developmental cranial variation. It is the portion of the squamous part of the occipital bone that lies superior to the highest nuchal line when this portion remains separate throughout life. In one hundred and ten human adult skulls examined in this study an Inca bone was found in only one specimen; it was tripartite. In this presentation the embryological background and morphological features of this anomaly are discussed

histological study of the dura mater using light and electron microscope

The present study has been undertaken to investigate the ultrastructure of the dura mater so as to correlate its structure with its mechanical function. This study aimed also to contribute further to the understanding of the functional morphology of the barrier formed by the mesothelial lining of the arachnoid mater to find a satisfactory explanation of the mechanism of bulk outflow of cerebrospinal fluid from the subarachnoid space into the dural sinuses. The clinical implication of this study in lumbar puncture procedure is also discussed. Six young adult sheep, eight rats, and four monkeys were used in this study. Specimens of 7 human lumbar dura and arachnoid were obtained during surgical treatment of disc herniation. Dura and arachnoid specimens were prepared for light and electron microscopy. Human Lumbar dura mater is divided into three parts: outer, middle and inner. In the outer part of the dura, collagen appears to be running in a longitudimal direction. Few elastic fibers and nerve fibers are also present. In the middle part, the collagen fibers are arranged in various directions with few elastic fibers in between. The inner part is less dense with collagen running mainly in a longitudinal direction. Numerous fibroblasts are present. The outer arachnoid is lined by a single layer of mesothelial cells. Below this are dark cells. The inner spinal human arachnoid is composed of groups of clear cells As regards spinal dura and arachnoid in the sheep, collagen fibers appear, in the outer dura, to be running in a longitudinal direction. In the middle dura, collagen is arranged in various directions. The inner dura is composed of collagen fibers running longitudinally and obliquely. Dark and light cells are present in the arachnoid. The collagen in the rat's dura is running mainly in a longitudinal direction in the outer part of the dura and in various directions in the inner part. The dural-arachnoid interface is readily identified by the presence of electron-dense granular material. At places, the arachnoid cells approximate that dense band thus diminishing the subdural space. The arachnoid is composed of fibrous connective tissue with numerous trabeculae. The arachnoid dark cells are characterized by dark nuclei with abundant heterochromatin. The dura of the monkey is composed of dense fibrous connective tissue consisting of collagen bundles and fibroblasts. The inner dura is highly cellular containing elongated fibroblasts. The collagen is loosely arranged in the inner dura. The subdural space is observed at the dural arachnoid interface in places however, this space was obliterated by the close approximation of the dural and arachnoid walls. The arachnoid is composed of two types of cells, clear and dark. The dura is composed of dense flbroblastic connective tissue and the collagen fibers are its major structural component. They have the strongest mechanical properties. Thus, the orientation of collagen fibers may explain the mechanical properties observed in different tissues. It has been previously indicated that the collagen fibers are arranged in a longitudinal and this explains the strong mechanical properties of the dura when subjected to stretching and deforming forces during movements and postural changes. Hopefully, increased understanding may open the way for new approaches in the evaluation of dural lesions produced by different needle bevels and the relationship of dural lesions to the production of postural headache