Biomedical subjects

G Y Mustafa

Publications and source records attributed to G Y Mustafa.

6 recordsLinked to original sources

PubMed1989

Influence of an experimental hindlimb maldevelopment on axon number and nodal spacing in the rat sciatic nerve.

In neonatal rat pups the femoral and tibial epiphyseal cartilages on the left side were coagulated with a microcautery device. The subsequent femoral and tibial growth in length was markedly restricted on the left side, but the foot and the pelvic region exhibited normal longitudinal growth. After 6 months the sciatic nerves were removed from both sides. Electron microscopic analysis of nerve specimens from the stunted side revealed that the number of axons was 20% less compared to control specimens. Light microscopic examination of teased preparations showed a normal nodal spacing in the pelvic segment but abnormally short internodes in the femoral segment of the left sciatic nerve. These results suggest that the number of axons in the rat sciatic nerve adapts to a target maldevelopment that sets in neonatally, and that internodal elongation during development proceeds according to the local growth in length of the nerve rather than to the length growth of the whole nerve.

Animals↗

PubMed1987

Nodal spacing along regenerated axons following a crush lesion of the developing rat sciatic nerve.

The relation between internodal length (L) and fibre diameter (D) was examined light microscopically in teased specimens from normal developing rat sciatic nerves, and from rat sciatic nerves which had regenerated following crush lesions at various postnatal ages. In newborn rat pups virtually all sciatic nerve axons are unmyelinated and myelination is an essentially postnatal event. Between 2 weeks and 6 months maximal L increases from 500 microns to 1400 microns and maximal D increases from 6-8 microns to 16 microns. The increase in L matches the length growth of the hindlimb. Signs of myelin sheath remodelling are absent during normal development. Examination of regenerated nerves showed that the lengths of the internodes along large-medium-sized axons, are strongly dependent on crush age. In neonatally crushed nerves, the slope is close to normal. With increasing crush age the inclination of the regression line gradually decreases. Signs of myelin sheath remodelling are not seen in regenerated nerves crushed at birth or 1-2 weeks after birth. However, such signs are present in regenerated nerves crushed 3 weeks or more after birth. These observations support the view that myelin sheath remodelling in regenerated rat sciatic nerves is directly related to a deficient length growth following myelination.

Age Factors↗

PubMed1986

Remodelling of internodes in regenerated rat sciatic nerve: electron microscopic observations.

Twelve adult rats received a crush lesion of the left sciatic nerve in the upper thigh. Following survival times of 2 weeks to 6 months, the animals were perfused with glutaraldehyde. Longitudinal thin sections from regenerated nerve segments were examined by electron microscopy. At survival periods of 2 weeks to 1 month, exceptionally short internodes composed of a Schwann cell lacking myelin, a more or less wrinkled Schwann cell-myelin sheath unit, or Schwann cell cytoplasm containing lamellated bodies and lipid droplets, were found intercalated between conventional regenerated myelin sheaths. Such intercalated sheaths were always bordered by sites with a nodal differentiation. Although much less frequent, short distorted myelin sheaths were also found at regeneration times of 2 and 3 months, but they have not been found in sections from 6-month specimens. In the long-term regenerated nerves many paranodes were distorted by prominent myelin folds and some nodes of Ranvier exhibited abnormal axon-Schwann cell networks and adaxonal Schwann cell protrusions. These observations show that internodes in regenerated rat sciatic nerves are subject to extensive remodelling. This includes internodal shortening and nodal migration, myelin sheath breakdown and demyelination, elimination of redundant Schwann cells and nodal fusion. These morphological changes may have important physiological implications.

Animals↗

PubMed1983

Critical performance analysis of rotating resident doctors in Iraq.

The present study was undertaken to evaluate the competence of rotating residents in handling clinical problems, falling under the purview of the major clinical disciplines, which they come across during their routine work. Three hundred and one rotating residents (55% of the total) who graduated in June 1981 from the four universities of Iraq, namely, Mustansiryia, Basrah, Mosul and Baghdad, and were currently undergoing their residency posting in the various hospitals of Iraq were selected for the study. Two approaches were used to assess the level of competence: first, on the basis of the resident's responses to fifty simulated patient-management problems and, secondly, their critical performance in patient care adjudged by their respective supervisors. A minimum passing level (MPL) was fixed for patient management problems (PMP). The score for the consultant's observations could range from -70 to +100 to represent the very poor and the very good performance. Only 2% of the residents were found to have reached the minimum pass level of competence taking their overall performance in the various disciplines. No significant variation in performance was observed in relation to the university of graduation. None of the residents could reach the MPL in the case of obstetrics and gynaecology. In the case of medicine and medical emergency the findings were almost similar. The residents put up a much better performance in orthopaedics and paediatrics (45.0% and 27.5% respectively). According to the supervisors' assessment nearly two-thirds of the residents secured at least 50% of the maximum score. The study underscores the need to redefine our educational objectives specifically, with aim of developing competences at a defined level in the learner befitting the needs of the health system through a competency-based curriculum.

Clinical Competence↗

PubMed1979

Changes in axonal numbers in developing human trochlear nerve.

Complete axonal counts have been made in the intracranial parts of trochlear nerves from human fetuses of 9.2, 10 and 24 cm crown-rump length. A count was also made in the intraorbital part of the nerve from the 10 cm specimen. Schwann cell nuclei were also counted in typical cross sections, but do not necessarily reflect very accurately the schwann cell contents of the nerves. Axonal numbers conform to the propositions (1) that they do not all grow out at once, (2) do not all survive and (3) that degeneration may occur before or after myelination has begun. It seems inevitable that some loss of Schwann cells occurs in relation to the degeneration of myelinated axons, but there is no evidence for or against such a loss in relation to the degeneration of unmyelinated axons. Overall, however, Schwann cell numbers tend to increase as the number of myelinated axons increases.

Axons↗

PubMed1978

Observations on the development of the connective tissues of developing human nerve.

Trochlear nerves from two human fetuses, and digital nerves from a third, have been examined by electron microscopy. Very marked differences in maturation were found between trochlear nerves of fetuses of ages differing only by 2--3 weeks, and between proximal and distal parts of the same trochlear nerve. Immaturity was reflected in paucity of endoneurial space and collagen and in the rarity, or virtual absence, of endoneurial fibroblasts. Circumstantial evidence of collagen formation by Schwann cells has been presented and discussed.

Axons↗