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Biomedical subjects

S Shenaq

Publications and source records attributed to S Shenaq.

33 records · Page 2Linked to original sources
PubMed1993

Nerve regeneration in a bony bed: vascularized versus nonvascularized nerve grafts.

In a rabbit model, regeneration of the intratemporal facial nerve was studied as vascularized and nonvascularized nerve grafts. Fifteen New Zealand white rabbits weighing 4 to 4.5 kg were used. A 1-cm gap was created in the intratemporal facial nerve. In the vascularized nerve graft group (group 1), the facial nerve was repaired with a vascularized median nerve graft (n = 6), while in the nonvascularized nerve graft group (group 2), the median nerve was used as a nonvascularized graft (n = 6). In group 3, the facial nerve gap was left unrepaired (n = 3). At 3 months postoperatively, electrophysiologic testing, morphologic nerve study, and morphometric muscle analysis were performed. Although the mean numerical values of axonal counting, nerve conduction, and morphometric muscle study results were slightly better in the vascularized nerve graft group, the differences between the two grafted groups were not statistically significant (p > 0.05). Morphometric nerve analysis, i.e., axon diameter and myelin sheath thickness, showed significant differences in nerve regeneration between the two groups (p < 0.05). These results suggest that a bony bed is not optimal for neovascularization of a nerve graft. We conclude that vascularized nerve grafts are superior to nonvascularized nerve grafts when nerve regeneration occurs in a bony recipient bed. This might be of clinical importance in the repair of facial nerve lesions within the temporal bone.

Animals↗
PubMed1993

Ultraviolet-A induced delayed wound contraction and decreased collagen content in healing wounds and implant capsules.

Chronic exposure to ultraviolet-A radiation causes changes in the biochemistry of dermal connective tissue. To investigate its effects on wound healing, we irradiated Sprague-Dawley rats for 4 months using a black ray ultraviolet-A radiation source (560 J/cm2). Full thickness skin wounds of 2 cm in diameter were then created on the back of each animal and silicone cubes were implanted subcutaneously into the irradiated area of the back. Wound contraction in the irradiated animals (n = 28) was significantly slower than that of the controls (n = 29) (p < 0.001). Postoperatively, the hydroxyproline content of the contracted wounds and the implant capsules was assessed at 6 and 12 weeks, respectively. In the irradiated animals, it was found to be significantly less than that of the controls (p < 0.001). A delay in wound contraction and a decrease in hydroxyproline content of healing wounds and implant capsules, reflecting an alteration in collagen metabolism, are two effects of prolonged intermittent ultraviolet-A radiation pretreatment.

Animals↗
PubMed1993

Neurosurgical correction of upper brachial plexus birth injuries.

The authors review the cases of 116 infants treated consecutively for birth-related brachial plexus injuries. Twenty-eight infants with upper brachial plexus lesions who showed no neurological improvement by 4 months of age were selected for early surgical reconstruction (at a mean age of 5 months). Neurological improvement of the affected arm was observed in more than 90% (p < 0.05) of the children examined longer than 9 months after brachial plexus reconstruction. A conservatively managed control subgroup of 44 children, first examined at less than 3 months of age, demonstrated neurological improvement by 4 months of age and continued to show improvement at 1 year of age. Early surgical reconstruction is recommended for infants with birth-related upper brachial plexus injury who show no neurological improvement by the age of 4 months.

Birth Injuries↗
PubMed1992

A new vascularized nerve graft model in the rabbit.

The macro- and microanatomy of the rabbit median nerve were studied for the purpose of developing a vascularized nerve graft (VNG) model. A segment of median nerve was then designed as a vascularized graft to serve as a model. This model consists of a 1-cm long median nerve segment and its accompanying brachial artery and vein 3 cm in length, with an arteriovenous fistula created distally. The model was tested by using the VNG to repair an intratemporal facial nerve defect and proven to be reliable. Its monofascicular pattern and diameter match those of the reconstructed facial nerve, making this model unique, compared to other models previously described.

Animals↗
PubMed1992

Reconstruction of calvarial defects.

We subdivide the calvarium into three zones, each with its special reconstructive requirements. Based on our experience with calvarial defects in 13 patients, we favor use of autogenous material, especially in the face of previous infection or a scarred recipient bed. Alloplasts give excellent forehead contour but alloplastic reconstruction should be delayed for 1 year after injury. Vascularized bone grafts maintain contour well. They are best suited to large periorbital defects. At other locations we favor split calvarial free bone grafts. Occasionally, the defect may be so large as to warrant grafts from multiple donor sites. Use of vascularized muscle helps eradicate infection, provides a vascularized bed for free bone grafts, and fills dead space. The frontal sinus is managed either by cranialization (if the posterior wall is involved) or by mucosal stripping with obliteration of the nasofrontal duct. Additional technical considerations include rigid bone fixation, surgical exposure through a bicoronal incision, and meticulous handling of bone grafts.

Adolescent↗
PubMed1992

Management of residual cranial vault deformities.

The aims of calvarial reconstruction are to restore anesthetic contour and to provide protection for the underlying central nervous system structures. The authors present their algorithm of reconstructive options. Important considerations are the anatomic location of the defect and the duration since the original injury.

Adult↗
PubMed1991

Study of microcirculation of rat femoral nerve and development of a new vascularized nerve graft model.

This study was designed to investigate the microcirculation of the rat femoral nerve and to develop a vascularized nerve graft (VNG) model which is reliable, consistent, and simple. The rat was chosen for considerations of cost and simplicity of the model. One and 2 cm long femoral nerve segments were transected proximally and distally and left attached to the femoral artery and vein in all animals. Experimental groups included the following procedures: 1) the femoral artery and vein were ligated distally and an arteriovenous (AV) fistula just proximal to the ligature was constructed; 2) distal ligation only of the femoral artery and vein was done; 3) ligation of the femoral artery and vein was done both distally and proximally; 4) control: no ligation or construction of an AV fistula were done. Neurovascular segments in all groups were wrapped with a thin silicone sheath to prevent neurovascularization from the surrounding tissues. At seven days postoperatively, viability of the segments was assessed by fluorescein dye and microangiography studies, followed by histologic evaluation. Results showed that a 1- or 2-cm long femoral nerve segment, when left attached to distally ligated femoral vessels and an intact neurovascular sheath, is a simple design to reproduce and can serve reliably as a VNG model in the rat.

Animals↗
PubMed1991

A new flap model in the rat.

Standardized skin flap models in the rat, such as the McFarlane and Finseth flaps, have suggested placement on the rat of only a single flap. The single flap, because of variations in skin vasculature among rats, may be problematic and require prohibitively large numbers of rats to obtain statistically significant results. In this study of 60 Sprague-Dawley rats, we have developed a flap model designed to be paired in a single rat and standardized to serve as the experimental flap and the control. At the level of the symphysis pubis, symmetrical, three-sided, caudally based, bilateral skin flaps, 2 cm in width, were extended to different bony landmarks. Only the length of the flaps was varied. The inferior epigastric pedicle was then divided. The flap length, which optimally produced predictable and persistent necrosis, was found midway between the xiphoid and the sternal notch. The model was pharmacologically manipulated with the injection of superoxide dismutase through the epigastric vein before division of the inferior epigastric pedicle; this scavenger did not effect the survival of the random pattern flaps.

Animals↗
PubMed1991

The trauma of suction-assisted lipectomy cannula on flap circulation in rats.

The effect of suction-assisted lipectomy on cutaneous blood vessels of inguinal skin flaps was studied and compared in 191 rats. Different types of cannula tips were used; the number of passes was standardized. In one experiment, following suctioning, 3 X 2 cm groin island flaps based on inferior epigastric pedicles were raised and then reattached. Fluorescein dye study and microangiography were performed to evaluate flap viability. Flap survival was determined clinically and by histologic examination on the fifth postoperative day. Three-sided inguinal random-pattern flaps were raised in a second experiment and reattached following suctioning. On the fifth postoperative day, surviving flap areas were measured using standard photographs and an imaging computer and were compared with controls. Results showed that cannula passes accompanied by vacuum are harmful to vessels, while those unaccompanied by vacuum are not. The greater the number of suctioning passes, the more trauma there is to vessels and the greater is the likelihood of flap necrosis. Conical and spatula tips were more harmful to vessels than spherical, cobra, keel cobra, or Fournier tips. These results support the conclusion that suction-assisted lipectomy enhances the possibility of skin necrosis by traumatizing the vascular pedicle of a flap, especially when it is used as an adjunct to flap elevation.

Animals↗
PubMed1991

Brachial plexus birth injury.

Brachial plexus birth injuries occur at a frequency of 1-2 per 1000 births. Many of these injuries spontaneously resolve. Should spontaneous recovery not occur within the first 4-6 months of life, the prognosis for attaining movement and function of the affected appendage is significantly impaired. The child demonstrates a lifelong disfiguring and functional handicap. With advances in technology, diagnosis and microsurgical techniques, surgical exploration of the brachial plexus has been revived. A multidisciplinary approach has provided dynamic results. At present only one institution in the United States utilizes this innovative protocol. This article addresses the collaborative perioperative nursing implications for a child with brachial plexus birth injury.

Birth Injuries↗
PubMedDate not supplied

Gene expression and apoptosis in the spinal cord neurons after sciatic nerve injury.

To demonstrate a dependence of spinal cord motoneurons on the communication with their targets, the expression of immediate early gene c-fos and neurotrophin genes in the lumbar (L3-L6) spinal cord neurons was examined in Sprague-Dawley rats (male > or = 9-weeks-old) with unilateral sciatic nerve transection. Using in situ hybridization, we detected the expression of c-fos mRNA in the motoneurons of the spinal cord segments within 45 min to 3 h of peripheral nerve transection (n = 4 in each time point). The expression of c-fos mRNA was also correlated positively with the expression of Fos antigen using immunohistochemistry, while no change in calbindin and parvalbumin antigens were noted. The expression of BDNF mRNA increased at 90 min after sciatic nerve transection. However, no detectable enhancement in the expression of NGF mRNA was observed. DNA fragmentation in neurons was observed using the incorporation of digoxigenin-dUTP by terminal transferase into 3'-OH terminals of DNA fragments in the ipsilateral section of the spinal cords 48h after nerve injury. Nuclei that exhibited DNA fragmentation were not observed in the spinal cord of the control animals. Lastly, we observed that the majority of astrocytes did not have DNA fragmentation. Because the detection of DNA fragmentation using this assay is one of early detections of apoptosis or programmed cell death, the result suggested we could detect early cell death in spinal cord, and indicated a target dependence of the neurons in the spinal cord after transection of sciatic nerve.

Animals↗