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Biomedical subjects

S Shenaq

Publications and source records attributed to S Shenaq.

At least 19 recordsLinked to original sources
PubMed2000

Increased axonal regeneration through a biodegradable amnionic tube nerve conduit: effect of local delivery and incorporation of nerve growth factor/hyaluronic acid media.

The authors emphasize the possible pharmacological enhancement of axonal regeneration using a specific growth factor/ extracellular media incorporated in a biodegradable nonneural nerve conduit material. They investigated the early effects on nerve regeneration of continuous local delivery of nerve growth factor (NGF) and the local incorporation of hyaluronic acid (HA) inside a newly manufactured nerve conduit material from fresh human amnionic membrane. Human amnionic membrane contains important biochemical factors that play a major neurotrophic role in the nerve regeneration process. The process of manufacturing a nerve conduit from fresh human amnionic membrane is described. This nerve conduit system was used in rabbits to bridge a 25-mm nerve gap over 3 months. NGF was released locally, over 28 days, at the distal end of the tube via a system of slow release, and HA was incorporated inside the lumen of the tube at the time of surgery. NGF/HA treatment promoted axonal regeneration across the amnionic tube nerve conduit (8,962 +/- 383 myelinated axons) 45% better than the nontreated amnionic tube group (6,180 +/- 353 myelinated axons). The authors demonstrate that NGF/HA media enhances additional axonal regeneration in the amnionic tube nerve conduit. This result is secondary to the effect of the amnion promoting biochemical factors, in combination with the NGF/HA effect on facilitating early events in the nerve regeneration process.

Amnion↗
PubMed2000

Modulation of peripheral nerve regeneration: a tissue-engineering approach. The role of amnion tube nerve conduit across a 1-centimeter nerve gap.

A new type of a biodegradable nerve graft conduit material, the amnion tube, has been developed in our laboratory. To test the tube in the peripheral nerve regeneration process, it was initially applied across a 1-cm sciatic nerve gap in rats and was compared with other nerve conduit materials. We used male Sprague-Dawley rats as our animal model. The experiment included 66 rats that were randomly assigned into five groups: autograft (n = 17), amnion tube (n = 19), silicone tube (n = 20), no repair (n = 7), and sham group (n = 3). The process of peripheral nerve regeneration was evaluated at 2, 4, 10, and 17 weeks following injury and repair by using morphologic and functional assessments of the outcome of nerve regeneration in each animal. Nerve regeneration across the amnion tube nerve conduit was comparable with that seen in autograft and superior to that of the silicone group. A uniform nerve tissue was seen filling and crossing the amnion conduit, and the regenerated nerve from the proximal stump reached the distal end and was undifferentiated from the normal nerve tissues. At 4 months, the amnion tube biodegraded and no longer could be identified and differentiated from the nerve tissues. The amnion tube animal group showed a number of axons very close to that in the nerve autograft group (37,157 versus 33,054). Functional recovery at a 2- to 4-week interval was significantly statistically higher only in the amnion tube animal group (p = 0.01). However, the improvement disappeared between 10 and 17 weeks. In conclusion, the amnion tube is a potential ideal nerve conduit material secondary to its unique characteristics: it contains important neurotropic factors, is biodegradable, provokes a very weak immune response, is semiflexible, is readily available, and is easily manufactured into different sizes and diameters.

Amnion↗
PubMed2000

Augmentation of adipofascial flaps using the long-term local delivery of insulin and insulin-like growth factor-1.

The adipofascial flaps currently described in the literature frequently lack the volume requirements for reconstructive goals. In this study, the authors examined the use of long-term local delivery of insulin and insulin-like growth factor-1 (IGF-1) using polylactic-coglycolic acid/polyethylene glycol (PLGA/PEG) microspheres to augment inguinal adipofascial flaps based on the inferior epigastric vessels in the rat. Two flap models, the island flap and the limited dissection flap, were used to demonstrate simultaneous treatment and pretreatment modalities, respectively. Experimental groups received 12.5 mg of insulin microspheres (carrying 1 IU of insulin) plus 12.5 mg of IGF-1 microspheres (carrying 2.5 microg of IGF-1). A group undergoing the operation only (no treatment with microspheres) and a group treated with blank microspheres (no growth factor) served as external controls for the surgical procedure and the drug delivery device, respectively. In all groups (n = 5 animals in each), the contralateral flap served as an internal control. Upon harvest on postoperative day 28, the insulin and IGF-1-treated flaps in both models weighed statistically more than the internal control flaps and the two external control flaps. Likewise, on gross inspection, the adipogenic growth factor-treated flaps had greater volumes than the internal control flap groups and both of the external control flap groups (operation only and blank microspheres). Other intergroup comparisons suggested the absence of a systemic insulin and IGF-1 effect on adiposity. A histomorphometric analysis suggested (1) that insulin and IGF-1 treatment does not alter flap cell composition and (2) that flap augmentation is secondary to the stimulation of cell proliferation and adipocytic differentiation rather than the hypertrophy of mature adipocytes. Further evidence in favor of cell proliferation and differentiation was the discovery of nonanatomic, ectopic fat islands on the pedicle sheath of the treated flaps and the lack of variation in cell size distribution among groups. The authors concluded that the long-term local delivery of insulin and IGF-1 with PLGA/PEG microspheres is an effective method of adipofascial flap augmentation; this method increases the number of mature adipocytes rather than increasing the size of preexisting cells.

Adipose Tissue↗
PubMed1999

Endoscopic technique for harvesting the intercostal nerve as a nerve graft: a feasibility preliminary study in cadavers.

Endoscopic surgical procedures in plastic surgery have been applied in numerous aesthetic and reconstructive surgical techniques. The use of the endoscopic video-assisted technique in peripheral nerve surgery is one of the most recent advances in reconstructive surgery. In this preliminary report, the seventh intercostal nerve, in fresh human cadavers, was harvested with the aid of endoscopy through a single 2-cm transverse incision. The anatomy of the intercostal nerve and the endoscopic surgical technique are described in this report. Multiple intercostal nerve grafts of adequate size, number, and length could be harvested, with less donor site morbidity, and used for future reconstruction of the injured peripheral nerve. The advantages of using an endoscopic technique to harvest the intercostal nerve include a magnified, clear, and illuminated visualization; a better remote access incision site; and an atraumatic technique, which may be proven particularly applicable in clinical procedures in patients who are prone to hypertrophic scars such as in women and children.

Cadaver↗
PubMed1998

Endoscopic-assisted temporoparietal fascial flap dissection and harvesting: a feasibility preliminary cadaveric study.

Endoscopic procedures in plastic surgery have been applied in various aesthetic and reconstructive surgical techniques. The authors describe, in this preliminary report, a new surgical technique of endoscopic dissection of the temporoparietal fascial flap. A series of 6 fresh human cadavers (12 flaps) were dissected endoscopically. The surgical incisions, flap anatomy applicable to endoscopy, endoscopic surgical technique, and type of endoscopic setup is standardized for all flaps, allowing direct identification of the temporoparietal fascial layers and the major vascular pedicle. This endoscopic manipulation of the flap, without the traditional large scalp incision, permits local and free transfer of the temporoparietal fascial flap. Exposure of the flap by means of the conventional T or Y temporal incisions has several possible disadvantages, including an increased risk of blood loss, alopecia, and facial nerve injury. Endoscopic dissection and mobilization of the temporoparietal fascial flap can obviate the direct flap incision and yield a flap accessible to dissection and mobilization for additional clinical applications. This new, innovative, and minimally invasive endoscopic procedure may prove particularly applicable to future clinical applications of this type of fascial flap.

Cadaver↗
PubMed1998

The intradermal anatomy of the inframammary fold.

The anatomy of the inframammary fold has been a subject of controversy. This report describes the anatomic location and the histologic structure of the inframammary fold on the basis of caderveric dissections and microscopic examination. Ten breast cadaver dissections were performed on female cadavers (ages 35 to 72). Twenty specimens after en bloc resections of the inframammary fold and subcutaneous tissue, including the pectoralis muscle, were harvested. Specimens were examined for gross collagen stricture by using India ink to highlight the collagenous aspects of the subcutaneous soft-tissue networks. The inframammary fold skin and dermis from the contralateral breast and control samples of skin and dermis from the upper chest and the abdomen were collected for microscopic studies. These samples were stained with Sirius red and examined microscopically by polarized light. On histologic examination, regular arrays of collagen were found running parallel with the inframammary fold, and the control sections showed random patterns of collagen deposition. On gross examination, a condensation of the superficial fascial system was observed. This formed a zone of adherence between the skin and the underlying pectoralis fascia. The conclusion of this study is that the inframammary fold is an intrinsic dermal structure consisting of regular arrays of collagen held in place by a zone of adherence that is a specialized area of the superficial fascial system. The clinical significance of this study is that the intradermal structure of the inframammary fold should be preserved in any breast procedure for natural aesthetic results.

Adult↗
PubMed1997

Central venous catheters coated with minocycline and rifampin for the prevention of catheter-related colonization and bloodstream infections. A randomized, double-blind trial. The Texas Medical Center Catheter Study Group.

BACKGROUND: Central venous catheters are a principal source of nosocomial bloodstream infections, which are difficult to control. OBJECTIVE: To determine the efficacy of catheters coated with minocycline and rifampin in preventing catheter-related colonization and bloodstream infections. DESIGN: Multicenter, randomized clinical trial. SETTING: Five university-based medical centers. PATIENTS: 281 hospitalized patients who required 298 triple-lumen, polyurethane venous catheters. INTERVENTION: 147 catheters were pretreated with tridodecylmethyl-ammonium chloride and coated with minocycline and rifampin. Untreated, uncoated catheters (n = 151) were used as controls. MEASUREMENTS: Quantitative catheter cultures, blood cultures, and molecular typing of organisms to determine catheter-related colonization and bloodstream infections. RESULTS: The group with coated catheters and the group with uncoated catheters were similar with respect to age, sex, underlying diseases, degree of immunosuppression, therapeutic interventions, and risk factors for catheter infections. Colonization occurred in 36 (26%) uncoated catheters and 11 (8%) coated catheters (P < 0.001). Catheter-related bloodstream infection developed in 7 patients (5%) with uncoated catheters and no patients with coated catheters (P < 0.01). Multivariate logistic regression analysis showed that coating catheters with minocycline and rifampin was an independent protective factor against catheter-related colonization (P < 0.05). No adverse effects related to the coated catheters or antimicrobial resistance were seen. An estimate showed that the use of coated catheters could save costs. CONCLUSIONS: Central venous catheters coated with minocycline and rifampin can significantly reduce the risk for catheter-related colonization and bloodstream infections. The use of these catheters may save costs.

Adolescent↗
PubMed1997

Functional assessment of tibial-nerve recovery in the cat using gait analysis: preliminary study.

The purpose of this study was to investigate gait-pattern changes after complete tibial nerve lesion in the cat, and to observe whether nerve repair could reverse some of the changes. In six cats, a 5-cm segment of the tibial nerve was transected. The nerve gap was then repaired with nerve autograft in three animals and was unrepaired in three as controls. The walking patterns of the cats were videotaped, and the hip, knee, ankle, and metatarsophalangeal joint angles were measured at the beginnings of the F, E1, E2, and E3 phases of the step cycle. Two weeks after surgery, abnormal gait patterns were observed, and four gait parameters (E3.Hip, E3.Ankle, E3.M-P, and F.Ankle) were found to be statistically significantly different from normal. Six months after surgery, the nerve-graft group had gait-parameter values approaching normal, while the control group showed no measurable improvement. Correspondingly, electrophysiologic testing revealed considerable nerve regeneration in the nerve-graft group but not in the control group. It was concluded that these gait parameters can be used as valid functional indices to evaluate the degree of tibial nerve recovery in the cat model.

Action Potentials↗
PubMed1997

Augmentation of random-flap survival by implantation of vascularized fascia allografts and temporary immunosuppression: implications for flap fabrication.

The purpose of this study was to explore the possible use of an allogeneic vascular source for flap fabrication. Epigastric fascia with its superficial epigastric vessel pedicle was harvested from the donor rat and microsurgically revascularized in the recipient rat across a major histocompatibility barrier. ACI rats (Rtl-a) served as donors, and Lewis rats (Rtl-1) served as recipients. The recipient rat was immunosuppressed with a daily dose of 2 mg/kg cyclosporin A plus 5 mg/kg prednisone for 4 weeks. Three experiments were performed for skin, muscle, and bone studies. In experiment 1 (20 Lewis rats), placement of the allotransplanted fascia underneath the epigastric skin significantly improved the survival of a random epigastric skin flap raised 3 weeks later (7.35 +/- 0.65 cm2 versus 6.09 +/- 0.90 cm2, p < 0.05). Immunosuppression was discontinued 10 days after flap elevation with no observable additional skin necrosis. In experiment 2 (13 Lewis rats) and experiment 3 (14 Lewis rats), segments of isogeneic muscle and bone were grafted successfully on the allotransplanted fascia, respectively. The survival of these grafts was confirmed by metabolic bone activity, bone labeling, microangiography, and histologic studies and further confirmed 2 weeks after cessation of immunosuppression. An allotransplanted fascia as a vascular source proved in this model its capability to improve the survival of a random skin flap and to accept a free bone or muscle graft with temporary immunosuppression. These findings hold promise for possible use of an allogeneic vascular source in flap fabrication.

Animals↗
PubMed1996

Ankle stance angle: a functional index for the evaluation of sciatic nerve recovery after complete transection.

This study attempted to develop a motor functional index, ankle stance angle (ASA), to assess rat sciatic nerve regeneration subsequent to autografting. ASA, 50 degrees in normal rats, is the ankle joint angle at the mid-stance phase of the gait cycle. In a nerve graft group, a 1-cm segment of the right sciatic nerve was transected and then repaired with nerve autograft. In an ungrafted group, the nerve gap was left unrepaired. ASA measured 4 months after surgery was statistically significantly larger in the nerve graft group (36 degrees) than in the ungrafted group (22 degrees). The results suggest that ASA is more sensitive than sciatic function index in detecting functional recovery after a complete sciatic nerve lesion. ASA also showed a significant correlation with the passive range of ankle joint motion and gastrocnemius muscle weight. The study concluded that ASA is a reliable index for assessment of regeneration of rat sciatic nerve after a complete lesion. The intra-rater reliability (r = 0.97 and 0.90) and inter-rater reliability (r = 0.85) tests performed support the conclusions.

Animals↗
PubMed1995

Hypothermia and cardiopulmonary bypass during resection of extensive arteriovenous malformation followed by microvascular reconstruction.

A patient is presented in whom hypothermic hypoperfusion and cardiopulmonary bypass were used to aid in resection of a mandibular arteriovenous malformation. This was followed by immediate microvascular reconstruction using a fibular osteocutaneous microvascular free tissue transfer. Prior attempted resection after highly selective embolization had proved inadequate. We found that the operative field, using hypothermic hypoperfusion was bloodless and enabled safe, rapid excision of the malformation. After patient rewarming, microvascular reconstruction was readily performed. No neurologic sequelae resulted, and no recurrence of the malformation has been noted.

Adolescent↗
PubMed1995

Prefabrication of a secondary TRAM flap.

A secondary TRAM flap was prefabricated in a rat model using the rectus muscle. The right rectus muscle was elevated as an inferiorly pedicled muscle flap in one experimental group (n = 6) and as a superiorly pedicled muscle flap in a second group (n = 5) and then sandwiched between a silicone sheet and the abdominal skin. Two weeks later, the abdominal skin and attached rectus muscle were elevated over the silicone sheet as a secondary TRAM flap. The surviving skin paddle areas of these prefabricated TRAM flaps were compared with superiorly (n = 7) and inferiorly (n = 8) pedicled TRAM flaps in a control group. One-way analysis of variance did not show significant differences between groups (p = 0.07). TRAM flap prefabrication in the rat model yields a skin paddle survival area comparable to that of a conventional TRAM flap, and it is possible to perform this procedure without using the anterior rectus sheath.

Abdominal Muscles↗
PubMed1994

A comparison of soft-tissue substitutes.

The fate of the Zyderm II, Zyplast, Vicryl, and chromic gut was histologically examined up to 1 year following subcutaneous implantation into rats. Our data demonstrated both Zyderm II and Zyplast to be inert materials without inflammatory response; there was no difference in long-term persistence between these two collagens. Both Vicryl and chromic gut implants caused an intense inflammatory response at 1 month, and Vicryl was completely resorbed before 6 months. The degree of inflammation associated with chromic gut diminished over time, and approximately 67% of the material persisted without reaction up to 1 year.

Animals↗
PubMed1994

Study of the delay phenomenon in the rat TRAM flap model.

Partial flap necrosis is frequently associated with the pedicled TRAM flap in the clinical setting. We created a TRAM flap model in rats (one control group and four delay groups; n = 8 in each group) and used a variety of flap delay techniques and vascular manipulations in an effort to increase the surviving area of the flap. The areas of surviving skin paddles in the five groups ranged from 4.4 cm2 in the control group to 9.9 cm2 in one of the delay groups. Analysis of variance and Tukey's pairwise comparisons indicated that delay groups II, III, and IV differed significantly from the control group (ANOVA F = 15.99, p < 0.001; Tukey experimental ER = 0.05, individual ER = 0.0068; critical value = 4.07). Ligation of the superficial inferior epigastric vessels and deep superior epigastric vessels (dominant pedicle) 1 week before TRAM flap surgery increased the area of survival of the skin paddle significantly in the rat model. The procedure is relatively easy to perform, and our laboratory findings should be readily reproducible in clinical practice.

Animals↗
PubMed1994

Development of a TRAM flap model in the rat and study of vascular dominance.

To investigate the suitability of the rat TRAM flap model for human TRAM flap research, we designed four different TRAM flaps with 10 x 3 cm rectangular skin paddles in rats: type 1 (n = 6), superior TRAM flap with unilateral superior rectus muscle pedicle; type 2 (n = 6), superior TRAM flap with unilateral inferior rectus muscle pedicle; type 3 (n = 6), inferior TRAM flap with unilateral superior rectus muscle pedicle; and type 4 (n = 6), inferior TRAM flap with unilateral inferior rectus muscle pedicle. We elevated and sutured back the TRAM flaps and measured the survival skin paddle areas. Our study demonstrated that in the rat TRAM flap model, the superior deep epigastric vessels are a more important source of vascularity for the skin paddle than the inferior deep epigastric vessels. A 5-cm lateral extension from the midvertical line was enough to cause some distal necrosis in every flap. A cephalically placed, inferiorly pedicled rat TRAM flap (type 2) has the smallest area of skin paddle survival; we concluded, therefore, that this flap placement is the most suitable for TRAM flap research.

Animals↗
PubMed1993

An anatomical, morphological and electrophysiological study of the rabbit facial nerve in the temporal bone.

Anatomical, histological and electrophysiological features of the rabbit facial nerve in the temporal bone are described for research purposes. Based upon the findings the rabbit intratemporal facial nerve is surgically accessible and consists of a constant axon number and myelin sheath thickness. As a valid model the rabbit intratemporal nerve can be readily utilized for research studies in nerve regeneration pertinent to the facial nerve in this region.

Animals↗
PubMed1993

Vascularized nerve tube: an experimental alternative for vascularized nerve grafts over short gaps.

Multilayered tubes fabricated from human amnion were placed subcutaneously and/or longitudinally in contact with an axial artery and vein in rats. Histologic evaluation at the third postoperative week showed that the tubes had incorporated with the surrounding fibrovascular tissue. New capillary formation within the tube wall was well demonstrated by microangiography. Vascularized amnion tubes were then used to bridge a 1-cm-long femoral nerve gap in an artificially-created, relatively avascular bed in rats. An avascular bed was created by wrapping the corresponding nerve segment with a thin silicone sheet. After 3 months, nerve regeneration was assessed using morphometric analysis. The vascularized amnion conduits showed comparable nerve regeneration to vascularized nerve grafts (p > 0.05), and superior nerve regeneration when compared to nonvascularized amnion conduits and nonvascularized nerve grafts as well (p < 0.05). This suggests that, in the rat model, a conduit can be neovascularized and used as a prefabricated tissue, to bridge short nerve gaps in a compromised bed.

Amnion↗