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Biomedical subjects

M Spira

Publications and source records attributed to M Spira.

At least 37 records · Page 2Linked to original sources
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

Human amnion collagen for soft tissue augmentation--biochemical characterizations and animal observations.

As bovine collagen is currently being scrutinized as to its immunogenicity in clinical use, a human source collagen, human amnion collagen (HAC), has been developed in our laboratory as an injectable biomaterial for soft tissue augmentation. Pepsin-extracted human amnion collagen was highly purified and reconstituted. Gamma irradiation was employed to ensure complete sterility and to produce cross-linking in collagen chains to improve implant persistence without the use of chemical additives. The purity and characteristics of human amnion collagen were proven by amino acid assay, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, immune blotting, and collagenase digestion. Animal studies comparing both irradiated and nonirradiated amnion collagen to bovine collagen (Zyderm and Zyplast) were carried out in a rat model. Humoral immunity was evaluated by examining the sera for antibody reactivity towards the implanted human collagen by the ELISA test. Insignificant antibody levels against human amnion collagen were found. Animal observation revealed fibroplasia, vascular infiltration, and the development of adipocytes with the implant as well as a lack of inflammatory response following up to 12 months of implantation. The persistence rate of our human amnion collagen was equal to, or even longer than, that of both types of bovine collagen implants.

Amino Acids↗
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

Keratoacanthoma: when to observe and when to operate and the importance of accurate diagnosis.

Although keratoacanthoma regresses spontaneously, treating physicians seldom allow these lesions to progress through their natural course. We describe two cases of skin lesions, the first being a keratoacanthoma, which enlarged rapidly and then involuted with minimal scarring. The second lesion was initially misdiagnosed and failed to respond to medical management. An accurate diagnosis of squamous cell carcinoma was not made until the lesion had become deeply invasive. These two lesions have helped clarify our thoughts about the observation of keratoacanthomas, the need for frequent patient follow-up when a lesion is not surgically ablated, and the importance of providing the pathologist with an adequate biopsy specimen for diagnostic purposes.

Adult↗
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↗
PubMed1994

Mouse antibody response following repetitive injections of gamma-irradiated human placenta collagen.

Injectable bovine collagen has been used clinically for years. But both the necessity of repeated injections to maintain corrections and the question of adverse allergic reactions developing from the use of a xenogenic collagen have been an area of serious concern. To overcome these adverse effects, we have developed injectable collagen preparations from human placenta. Gamma irradiation was used for sterilization and crosslinking of the collagen. We observed the mouse immune response to gamma-irradiated human placenta soluble and insoluble collagen following multiple injections. After six injections of these materials, no total IgG level increase was found, nor was antibody specifically directed against human collagen found. Mouse antibody levels were also observed following Zyderm II and Zyplast repetitive injections and following repetitive implantations of coated vicryl and chromic gut. No humoral immune response was found in this heterologous type system.

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↗
PubMed1993

A simple technique for harvesting standardized skin grafts in the rodent.

A simple technique for harvesting skin grafts of predetermined size, shape, and thickness in rodents is described. In this technique, the donor skin is immobilized and tensed by means of a tongue depressor, or similar template, inserted into the loose areolar tissue below the panniculus, stretching the overlying skin to permit easy dermatome harvesting of a skin graft.

Animals↗
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

Cartilage warping: an experimental model.

Cadaveric cartilage was cut into blocks with a newly devised cartilage cutter. Over one-hundred pieces of cartilage were used to define a kinetics curve of cartilage warping. Kinetics curves were developed for a control group of cartilage blocks placed in saline-soaked gauze (n = 46). In addition, kinetics curves were developed for cartilage placed in hypotonic saline (n = 14), hypertonic saline (n = 14), and cyanoacrylate glue (n = 6). Photographs of all groups were taken at timed intervals in order to plot the cartilage warping. It was found that pieces of cartilage which were cut peripherally (n = 6) warped twice as much as those cut centrally (n = 40). This was significant to p = 0.001. Within 15 minutes, centrally cut pieces of cartilage warped to approximately 90 percent of their end warpage; on the other hand, peripherally cut pieces of cartilage required 30 minutes to warp 90 percent of their destined warpage. The variables used did not significantly alter the kinetics curves as compared with control.

Cadaver↗
PubMed1993

Injectable soft tissue substitutes.

Historical and modern advances in the development of an injectable soft tissue substitute are reviewed. Nonbiologic alloplastic and biologic injectables are described. The authors' experiences, as well as those of others, employing presently available materials in terms of specific indications and special techniques are delineated. The search for a safe, effective, easy-to-use, and long-lasting soft tissue substitute continues.

Adipose Tissue↗
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↗