Search PubMed⌕ Search

Biomedical subjects

S E Mackinnon

Publications and source records attributed to S E Mackinnon.

At least 109 records · Page 6Linked to original sources
PubMed1995

Regeneration across preserved peripheral nerve grafts.

The potential to store nerve grafts for a prolonged period of time was assessed in a rat sciatic nerve model. Three-centimeter syngeneic nerve grafts were stored in Belzer/University of Wisconsin cold storage solution at different temperatures (5 degrees C, 22 degrees C, or 37 degrees C) for varying time periods (6 h, 24 h, or 3 weeks) prior to transplantation. Functional assessment using serial walking track analyses revealed no difference between storage times and temperatures. At 14 months postengraftment, the conduction velocities and the number of myelinated fibers that had regenerated across all grafts stored at 5 degrees C for all time periods tested were superior to grafts stored at either 22 degrees C or 37 degrees C. Nerve grafts stored for up to 3 weeks at 5 degrees C acted as effective conduits for proximal regenerating fibers and resulted in histologic, electrophysiologic, and functional results equivalent to fresh nerve grafts. Nerve graft storage may be applicable to nerve allografts and potentially provide allograft material that requires reduced or no associated host immunosuppression.

Action Potentials↗
PubMed1995

Phenotypic analysis of migrant, efferent lymphocytes after implantation of cold preserved, peripheral nerve allografts.

Cold-preservation of peripheral nerve allografts in vitro (3 weeks, 5 degrees C) was performed to determine its effect on local lymphocyte migration patterns in vivo. Lymphocyte migration was assessed by continuously monitoring the cell output in the regional lymph for nearly 1 month. Cold-preservation delayed or prevented the typical biphasic increase in efferent lymphocyte output observed after fresh allograft implantation. It also decreased the output of activated lymphocytes (CD 5 and MHC class II positive) compared with that seen in the fresh allograft response. These changes suggest that the host immune response to preserved nerve allografts is altered over a prolonged period in vivo (3 weeks). Cold-preservation may be a useful method of reducing allograft immunogenicity, thereby limiting systemic immunosuppression requirements for the successful clinical utilization of peripheral nerve allografts.

Animals↗
PubMed1995

Subjective outcome following surgical management of upper extremity neuromas.

Our study used a telephone survey to evaluate long-term subjective outcome of 70 patients with 112 upper extremity neuromas treated surgically. The mean postinjury time before surgery was 9 years. The mean postsurgical followup was 5 years. Fifty-one of the patients were involved with workers' compensation (WC). Forty-five patients reported good relief of pain. Preoperatively, 46 patients were unemployed because of pain; following surgery 18 of these patients returned to work. Of the 54 patients taking analgesic medication preoperatively, 19 reported less and 10 reported no postoperative analgesic use. No significant difference was found in gender, postinjury time, postsurgical followup time, number of previous surgeries for pain relief, or site of nerve injury between patients who reported improvement versus no symptomatic improvement. Poor subjective outcome occurred in patients (p < .03), with 16 out of 19 of those not involved with WC reporting good pain relief as compared to 29 out of 51 of WC patients.

Adult↗
PubMed1995

Outcome following conservative management of thoracic outlet syndrome.

Conservative management of thoracic outlet syndrome is recommended as the initial treatment of choice, and yet few studies have evaluated patient outcome. This study evaluates patient subjective outcome following conservative management of thoracic outlet syndrome. Forty-two patients (37 women, 5 men), mean age 38 years, participated in a telephone questionnaire. Patients clinically diagnosed with thoracic outlet syndrome who had participated in physical therapy at least 6 months prior to the study were selected. Mean duration of symptoms before treatment was 38 months, and mean follow-up time after therapy was 1 year. Twenty-five patients reported symptomatic improvement, 10 were the same, and 7 had worse symptoms. Sixteen patients reported full work and recreational activities, and 8 patients reported restrictions in both work and recreational activities. Poor overall outcome was related to obesity (p < .04), workers' compensation (p < .04), and associated carpal or cubital tunnel syndrome (p < .04). Neck and shoulder symptoms were improved in 38 patients. Improvement in hand and arm pain was significantly better in those without concomitant distal nerve compression (p < .006).

Adult↗
PubMed1995

Subjective outcome following surgical management of lower-extremity neuromas.

This study evaluated the long-term subjective outcomes of 19 patients (13 females, six males), following surgical resection and proximal transposition of lower-extremity neuromas. The patient mean age was 49 years (S.D.: 18), with a mean post-injury time of 8 years and post-surgery follow-up of 4 years. Thirteen patients reported symptomatic improvement in pain, and six reported no improvement. Of ten subjects who were unemployed prior to surgery, two returned to work and four retired postoperatively. Preoperatively, 13 patients used analgesic medication and postoperatively, eight reported taking less medication; four had completely stopped taking pain medication. Symptomatic pain relief apparently can be achieved with surgical management of lower-extremity neuromas.

Adult↗
PubMed1995

Fascicular patterns of the hypoglossal nerve.

Hypoglossal-facial nerve transfer is a standard technique for facial-palsy reconstruction. The fascicular anatomy of the hypoglossal nerve may be important in determining strategies, when attempting to minimize atrophy of the tongue. The present study investigated hypoglossal fascicular anatomy by histomorphometric analysis of 10 human hypoglossal nerves. The nerve demonstrates a monofascicular topography in its proximal third and mid portions, becoming polyfascicular only in its distal third. The mean number of fascicles in the distal portion is 5.0, compared to 1.1 in the proximal and mid portions (p < .01). The mean number of myelinated axons in the hypoglossal nerve is 9200.

Humans↗
PubMed1995

Repetitive motion injuries.

Repetitive motion injuries have presented clinicians with a significant challenge over the past two and a half decades. Acceptable treatment of inflammatory disorders is well established, but compressive neuropathies and nonspecific complaints of numbness, tingling, and discomfort in the upper extremity present vexing dilemmas. Current research and experience point to multilevel problems, including posturally induced muscular imbalance. Although surgical solutions to these problems are sometimes indicated, conservative approaches successfully treat many individuals and have narrowed the scope and indications for surgical intervention. These approaches include ergonomic changes at the workstation, postural changes, and muscle stretching and strengthening to correct imbalance.

Arm↗
PubMed1995

Fast spin-echo magnetic resonance imaging for radiological assessment of neonatal brachial plexus injury.

Neurosurgical management of birth-related brachial plexus palsy involves observing the patient for a period of several months. Operative intervention is usually undertaken at 3 to 6 months of age or more in infants who have shown little or no improvement in affected muscle groups. Ancillary tests such as electromyography and nerve conduction studies are occasionally useful. No radiological study has been consistently helpful in operative planning, except for contrast computerized tomography (CT) myelography, which requires general anesthesia in infants. This is because the infant's small size exceeds the functional resolution of the imaging modalities. This report describes the use of a special sequence of magnetic resonance (MR) imaging entitled "fast spin echo" (FSE-MR). Unlike CT myelography, this technique provides high-speed noninvasive imaging that allows clinicians to evaluate preganglionic nerve root injuries without the use of general anesthesia and lumbar puncture. The utility of this technique is illustrated in three cases, two involving either infraclavicular exploration or a combination of infraclavicular and supraclavicular exposure based on FSE-MR findings. The FSE-MR imaging offers an excellent alternative to contrast CT myelography in evaluation of infants with birth-related brachial plexus injuries.

Birth Injuries↗
PubMed1995

Women surgeons: career and lifestyle comparisons among surgical subspecialties.

A national survey of 459 women surgeons yielded a 91.3 percent response rate. The largest subspecialties were obstetrics-gynecology (41 percent), ophthalmology (21 percent), and general surgery (12 percent). Representation in all "other" surgical specialties was small (26 percent). A comparison of career and lifestyle patterns among the four major subspecialties demonstrated no differences in marital status, although ophthalmologists were least likely to remain childless (32 percent) and general surgeons most likely (58 percent). Surgeons in obstetrics-gynecology worked the longest hours, and those in ophthalmology worked the shortest hours. No subspecialty differences were reported in quality-of-life parameters.

Career Choice↗
PubMed1994

Cold storage of peripheral nerves: an in vitro assay of cell viability and function.

The development of a nerve bank as a source of donor material to repair large defects in peripheral nerve injuries requires an understanding of the influence of cold storage on cell viability and function in these potential nerve grafts. Segments of peripheral nerves from both human and rat were stored in University of Wisconsin Cold Storage Solution (UW) at 4 degrees C for < 12 h, 3 days, and 1, 2, or 3 weeks. Cellular viability was initially assessed by the degree of cellular outgrowth from explants of the stored nerves placed in culture, and then further quantitated by dissociating the cultured nerve explants and calculating the type and number of cells per milligram of peripheral nerve. Rat Schwann cells (SCs) obtained from the stored (control and 1 and 2 weeks) nerves were tested for their functional ability to myelinate dorsal root ganglion (DRG) neurons in culture. Our findings indicate that human and rat peripheral nerves contain few viable SCs and fibroblasts after 3 weeks of cold storage with the quantity of viable cells within the human cold stored peripheral nerves decreasing significantly after 1 week of cold storage. Despite their reduced number, some SCs from rat nerves stored up to 2 weeks are capable of myelinating DRG axons in culture. These results suggest that short intervals (< 1 week) of cold storage will result in potential peripheral nerve grafts containing large populations of functional cells, while long-term (> or = 3 weeks) cold stored peripheral nerves will contain few viable cells.

Animals↗
PubMed1994

Isometric contractile function following nerve grafting: a study of graft storage.

In order to assess the effects of storage on nerve grafts, the isometric contractile function of the gastrocnemius muscle was assessed 14 months following sciatic nerve autografting in the rat. Three-centimeter sciatic nerve grafts were stored at either 5 degrees C or 22 degrees C for 6 h, 24 h, or 3 weeks in an organ transplant solution. Muscle mass and maximal force in the fresh control graft group returned to 47% and 36% of normal levels, respectively, which was similar to stored grafts. Storage at 5 degrees C was superior to 22 degrees C and there was no decrement in contractile function in grafts stored up to 3 weeks at 5 degrees C. These findings suggest that the storage of nerve grafts is a feasible technique that might be applied to nerve allografts, thus permitting elective reconstruction of large peripheral nerve gaps.

Analysis of Variance↗
PubMed1994

Nerve crush injuries--a model for axonotmesis.

Nerve crush is a commonly used experimental model in the rat; however, a standard method of inducing this injury has not been defined. This study examined six crush techniques that are frequently used and characterized the subsequent nerve injury. Five types of nerve crush using a No. 5 jeweler's forceps and a sixth using a 30-s single crush with a serrated hemostat were studied in the posterior tibial nerve of the Lewis rat. Regeneration was evaluated using serial walking track assessments at 1, 2, 4, 6, and 8 weeks postoperatively. Nerve conduction studies and histological examination were performed at 2 days, 2 weeks, and 8 weeks. Blood-nerve barrier breakdown was observed at 2 days and recovered by 2 weeks. By 4 weeks normal walking track patterns were obtained in all groups. A pattern of Wallerian degeneration and axonal regeneration was noted at 2 weeks, with histological recovery in all groups by 8 weeks. Nerve crush, induced by any of the six methods tested, was similar and provides a reliable model of axonotmesis.

Animals↗
PubMed1994

The regulation of collagen in fetal skin wounds: mRNA localization and analysis.

The deposition of collagen in fetal skin wounds has been shown in several animal models. The authors used a radiolabeled RNA antisense probe, complementary to the mRNA for the alpha-1 chain of human procollagen type I, to assess regulation of this collagen species in fetal and adult rabbit wounds. Dorsal skin wounds were placed on fetal and maternal animals at the beginning of the third trimester, and were harvested 3, 5, and 7 days later. In situ RNA/RNA hybridization was performed on suitable specimens, and morphometric analysis was carried out with a computerized LECO image analyzer. Fetal wounds exhibited an inflow of mesenchymal cells that produced collagen type I at levels higher than the surrounding tissue; this activity was highest on days 3 and 5 after wounding. Adult wounds had increased fibroblast presence by day 7, producing collagen type I at levels higher than those of adjacent unwounded tissue. Morphometric analysis of the signal produced by in situ hybridization and of the number of cells producing the signal in a given field showed that fetal wounds appear to produce collagen type I by an increase in the number of cells in the area of the wound--not by induction of the gene for procollagen type I. In contrast, adult wounds had both fibroblast migration and induction of procollagen type I mRNA synthesis. These findings imply multilevel regulation of collagen production in the adult and posttranslational regulation in the fetus.

Animals↗
PubMed1994

Intraneural topography of the ulnar nerve in the cubital tunnel facilitates anterior transposition.

The surgical management of cubital tunnel syndrome includes anterior transposition of the ulnar nerve. The success of all transposition procedures is dependent on placement of the nerve anterior to the medial epicondyle without tension. Fifteen cadaveric upper extremities underwent anterior transposition followed by anterior transposition with separation of the most proximal motor branches from the main ulnar nerve for a distance of 1, 2, and 3 cm. Proximal dissection of these motor branches achieved an average gain in distance from the epicondyle of 71%, with an average distance from the epicondyle of 3.6 cm. The intraneural topography of the ulnar nerve was studied in five additional cases. Cross-section analysis of the fascicular anatomy at 333 microns intervals along the length of the nerve with longitudinal reconstructions confirmed a safe dissection plane without interfascicular plexus formation. The most proximal motor branch in the forearm could be traced proximally an average of 6.7. cm within the nerve before interfascicular mingling occurred (range 6.0 to 7.5 cm). Thus, 6.0 cm represented the upper limit of safe proximal dissection in these nerves. Proximal separation may be performed without disruption of interfascicular plexus connections and will facilitate anterior transposition.

Cadaver↗