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Biomedical subjects

M K Youssef

Publications and source records attributed to M K Youssef.

9 recordsLinked to original sources
PubMed2000

Skeletal muscle reinnervation by reduced axonal numbers results in whole muscle force deficits.

Patients sustaining a peripheral nerve injury will frequently experience residual muscle weakness after muscle reinnervation, even if the nerve repair is performed under optimal circumstances to allow rapid muscle reinnervation. The mechanisms responsible for this contractile dysfunction remain unclear. It is hypothesized that after peripheral nerve injury and repair, a reduced number of axons are available for skeletal muscle reinnervation that results in whole muscle force and specific force deficits. A rat model of peroneal nerve injury and repair was designed so that the number of axons available for reinnervation could be systematically reduced. In adult rats, the peroneal nerve to the extensor digitorum longus muscle was either left intact (sham group, n = 8) or divided and repaired with either 50 percent (R50 group, n = 7) or 100 percent (R100 group, n = 8) of the axons in the proximal stump included in the repair. Four months after surgery, maximal tetanic isometric force was measured and specific force was calculated for each animal. Mean tetanic isometric force for extensor digitorum longus muscles from R50 rats (2765.7 +/- 767.6 mN) was significantly lower than sham (4082.8 +/- 196.5 mN) and R100 (3729.0 +/-370.2 mN) rats (p < 0.003). Mean specific force calculations revealed significant deficits in both the R100 (242.1 +/- 30 kN/m2) and R50 (190.6 +/- 51.8 kN/m2) rats compared with the sham animals (295.9 +/- 14 kN/m2) (p < 0.0005). These data support our hypothesis that after peripheral nerve injury and repair, reinnervation of skeletal muscle by a reduced number of axons results in a reduction in tetanic isometric force and specific force. The greater relative reduction in specific force compared with absolute force production after partial nerve repair may indicate that a population of residual denervated muscle fibers is responsible for this deficit.

Animals↗
PubMed1996

Management of facial contour deformities with deepithelialized lateral intercostal free flap.

Ten cases suffering from facial contour deformities caused by loss of subcutaneous tissue are presented. Three cases had hemifacial microsomia, 3 had postmaxillectomy collapsed cheek, while the remaining 4 patients had Romberg's disease. All cases were treated by the insertion of a deepithelialized, revascularized lateral intercostal flap. The flaps used had dimensions ranging from 9 cm x 6 cm to 12 cm x 14 cm. The vascular pedicle of the flap is the lateral cutaneous branch of one of the lower four posterior intercostal bundles (usually the tenth or the eleventh). The flap is designed to have the pedicle in its center, thus allowing defattening of the edges at the primary surgery and minimizing the need for secondary debulking. Nine flaps were successful and one failed. All successful flaps gave a permanent and satisfactory correction of the deformity. The difficulties and advantages of the flap are presented.

Adolescent↗
PubMed1996

Acetaminophen plasma level after oral administration in liver cirrhotic patients suffering from schistosomal infection.

Hepatosplenic schistosomal infection is a common parasitic liver disease in Egypt, resulting in the formation of granuloma followed by fibrosis which leads to the chronic liver disease. Plasma level of acetaminophen (AAP) and its glucuronide and sulfate metabolites after oral administration at a dose of 1 g was determined in liver-cirrhotic younger (9 - 25 years old) and elderly patients (45 - 65 years old) suffering from schistosomal infection. These levels of AAP and its metabolites in patient groups were compared with those in corresponding healthy subject groups. Examinations for participants in the present study by physicians indicated the more severe cirrhosis in elderly patients compared to younger patients and the formation of collateral circulation and the renal insufficiency in elderly patients. The elimination of AAP from plasma was significantly prolonged in both younger and elderly patient groups. In elderly patients plasma concentration of AAP in early stage (before the time to reach Cmax) was significantly higher, indicating the partial avoidance of first-pass metabolism due to the formation of hepatic shunt pathway. Plasma concentration of AAP-glucuronide was greatly decreased in both patient groups, whereas no significant difference in the plasma concentration of AAP-sulfate compared to those in corresponding healthy subject groups. These results will suggest that with repeated dosing of AAP special care must be taken in schistosomal patients since the elimination of AAP from plasma is remarkably reduced.

Acetaminophen↗
PubMed1980

Karyological study of Gallus domesticus macrochromosomes.

After an incubation period of four days and colchicine pretreatment (air-cell method), clear metaphase figures were obtained from a cell suspension of the allantoic sacs. It was only by shortening the colchicine application to one hour that sufficiently elongated chromosomes suitable for karyological studies could be prepared. The total arm length and the arm length indices are given of the six pairs of macrochromosomes - including the Z chromosome - and of the three largest microchromosomes. Different from the previous findings as reported in the literature, the two largest macrochromosomes are described as submetacentric and not as metacentric. The findings on the seven chromosomes following agree with those given in the literature.

Animals↗
PubMed1978

Paper chromatographic determination of chlortetracycline.

Chlortetracycline was successfully separated from its degradation products and from other tetracyclines on a paper chromatogram previously impregnated with a mixture of edetate disodium and urea solution in pH 5.0 McIlvaine buffer. Chlortetracycline separation from its degradation products and from both tetracycline and oxytetracycline was attributed primarily to the complexation of these antibiotics with urea and edetate on the chromatogram. The separated spots were located under UV light, and their Rf values were calculated. Chlortetracycline recovery from the paper chromatogram was satisfactory (98.3 +/- 0.002%). The developed method was successfully applied to the determination of chlortetracycline in various dosage forms. In addition, the method was adequate for monitoring chlortetracycline hydrochyloride stability in aqueous solutions.

Chlortetracycline↗