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Biomedical subjects

S E Mackinnon

Publications and source records attributed to S E Mackinnon.

At least 145 records · Page 8Linked to original sources
PubMed1993

Walking track analysis: utilization of individual footprint parameters.

Functional assessment of rat sciatic, tibial, and peroneal nerve injuries was performed using walking track analysis. Individual walking print length (PL), toe spread (TS), and intermediate toe spread (ITS) values were measured up to 24 weeks after specific nerve transection, with or without repair. Sciatic and tibial nerve manipulation initially affected all footprint measurements, consistent with loss of intrinsic and extrinsic motor function. After sciatic repair, TS demonstrated partial recovery without any substantial recovery in PL or ITS, compared with sciatic transection values. By contrast, after tibial repair, PL values recovered dramatically, between 16 and 24 weeks, to levels not significantly different from control subjects. This was not observed after tibial transection without repair. TS recovered partially, whereas ITS recovered to control levels by 20 weeks after tibial repair. Peroneal transection resulted in multiple contractures, rendering this group unmeasurable at 4 weeks. After peroneal repair, only the PL reflected significant loss of function at 2 weeks, recovering to control values by 8 weeks. Manual TS measurements in nonwalking rats did not reflect functional nerve regeneration. Thus, individual PL measurements alone can be used to characterize functional recovery after tibial and peroneal nerve injury, whereas TS reflected recovery after sciatic nerve injury.

Animals↗
PubMed1993

Duration of contact time alters cutaneous pressure threshold measurements.

Semmes-Weinstein monofilaments (SWMs) are standard measures used to assess hand sensibility. The purpose of this study was to evaluate the effect of varying contact time on the measurement of cutaneous pressure thresholds. Thirty-two healthy adult subjects were evaluated with a 20-filament SWM test kit. The index finger of the dominant hand was assessed with the following four distinct monofilament contact times: 0.5, 1.5, 5.0, and 30.0 seconds. With increased duration of monofilament contact time, there was a significant increase in the cutaneous pressure threshold measures (p < 0.05). That is, to perceive a stimulus for a longer period of time, a heavier filament was required. With increasing age, significantly higher pressure thresholds were obtained particularly for the sustained contact time (> 5.0 seconds). Pressure thresholds vary significantly with SWM contact time, emphasizing the importance of maintaining a consistent SWM application protocol.

Adult↗
PubMed1993

Correlation of two-point discrimination and hand function following median nerve injury.

Two-point discrimination (2pd) (moving and static) and object identification were assessed in 43 patients after median nerve repair and graft in the middistal forearm. The mean age was 37 years (range, 16-78 yr). Twenty-six patients underwent primary median nerve repair and 17 had secondary median nerve grafts. The minimum follow-up time was 2 years. The values of moving 2pd and static 2pd ranged from 2 to > 16 mm. Both moving 2pd and static 2pd had strong correlational relationships with hand function as measured by object identification. Correlation coefficients for the relationship between 2pd (moving and static) and total objects identified ranged from 0.66 to 0.74.

Adolescent↗
PubMed1993

Women surgeons. Results of the Canadian Population Study.

OBJECTIVE: A national survey of women surgeons in Canada was undertaken to evaluate their ability to combine career with personal and family life. SUMMARY BACKGROUND DATA: Despite increasing numbers of women entering the medical profession, women continue to select nonsurgical careers. Although there are many reports regarding women in medical specialties there is little information available regarding women who choose surgical careers. Such data will be useful in increasing the enrollment of women in surgical training programs. METHODS: A 93-item questionnaire was mailed in July 1990 to the 459 eligible female surgeons. The survey was conducted using a modified Dillman 5-step computerized method. The study was closed in May 1991. RESULTS: Of the 459 surgeons who were located, 419 (91.3%) responded. Most surgeons (65.5%) were married. Only 6.5% were separated or divorced. The majority married another professional (91.4%). One quarter married another surgeon. Of all women who married at least once, 70.9% had at least one child. Most surgeons delayed child bearing until after they had completed their surgical training. The majority of respondents were in active surgical practice (82.3% full-time, 6.0% part-time). The most common surgical subspecialty was obstetrics and gynecology (40.9%), followed by ophthalmology (21.2%), and general surgery (12.1%). Surgeons were rarely dissatisfied (4-9%) with career, marriage, health, friendships, financial status, and hobbies. Overall, 88.3% were happy with their decision to pursue a career in surgery. CONCLUSIONS: Women surgeons practicing in Canada are able to combine productive careers with rewarding family lives and are satisfied with their decision to do so despite the compromises involved.

Adult↗
PubMed1993

Development of a new measure of fine sensory function.

With the loss of sight, the blind individual must rely on tactile senses for function, and yet assessment of hand sensibility is not routinely integrated into evaluations of the blind. The available sensory measures lack the sensitivity to differentiate higher levels of hand sensibility, and therefore, a new more sensitive measure of fine sensory function was developed. A 3 x 3 braille dot cell was developed, and pattern variation was utilized to assess higher discriminatory abilities. Thirty blind and sighted subjects were evaluated, and intertester reliability of fine sensory function (braille pattern identification) was established (r = 0.95). Comparison between braille identification and measures of threshold and innervation density revealed the strongest correlational relationship with two-point discrimination. This study supports the assessment of fine sensory function with braille pattern identification.

Activities of Daily Living↗
PubMed1993

Establishment of reliability in the evaluation of hand sensibility.

Evaluation of hand sensibility using measures of threshold and tactile discrimination are standard assessment methods following nerve injury. Many of the available sensory measures for the quantification of hand sensibility lack verification of intertester reliability. Intertester reliability of vibration threshold, cutaneous pressure threshold, two-point discrimination, object identification, and texture identification was established. The intraclass correlation coefficient ranged from 0.96 to 0.99 for all variables except texture identification (r = 0.77). Comparisons were made between the sensory measures and each functional measure. The strongest correlational relationship was between two-point identification and object identification. Based on the results of this study, evaluation of hand sensibility may be attained with measurement of vibration and cutaneous pressure threshold, two-point discrimination, and object identification.

Adult↗
PubMed1993

Verification of a free vascularized nerve graft model in the rat with application to the peripheral nerve allograft.

We report a vascularized sciatic nerve graft in the rat, based upon the femoral popliteal superior muscular artery pedicle. The pedicle may be raised from the common femoral artery via the popliteal artery, with accompanying venous drainage to the femoral vein. We have characterized two vessels: the middle tibial artery to the posterior tibial nerve and the arteria comitas nervus peroneus to the peroneal nerve. Plastic monomer and Evans blue labeled albumin injections established the anatomic model. The graft was reliably perfused at the time of isolation and 24 hours post-transplantation. The model was used to evaluate regeneration across allogeneic (ACI to Lewis, n = 12) versus syngeneic (Lewis to Lewis, n = 6) nerve grafts. Electrophysiologic and histomorphometric assessments demonstrated that the vascularized immunosuppressed allograft was similar to the vascularized syngeneic graft. Both were superior to the vascularized allograft without immunosuppression.

Action Potentials↗
PubMed1993

Effect of cold preservation on lymphocyte migration into peripheral nerve allografts in sheep.

Lymphocyte migration into fresh and preserved peripheral nerve allografts was quantitated to assess the effect of cold preservation and freeze-thawing pretreatment on the local immunological response to nerve allografts. Out-bred ewes received multiple 1.5-cm subcutaneous heterotopic peroneal nerve autografts, fresh allografts, and pretreated allografts, implanted within the same recipient. Lymphocyte migration was studied at 7 days by injecting autologous 111indium-labeled lymphocytes intravenously. After 3 hr of recirculation, lymphocyte migration into graft tissue was quantitated by a gamma counter (epm/g, mean +/- SEM). Lymphocyte traffic into fresh nerve allografts (21,623 +/- 3783) increased an average 9.4-fold over the autograft value (2918 +/- 377, P < 0.04). Histologic studies illustrated a marked lymphocytic infiltrate of CD4+ and CD8+ cells and enhanced class I and II MHC expression in fresh allografts, but not in autografts. Short-term cold preservation, for 6 and 12 hr (5 degrees C), enhanced lymphocyte entry into pretreated allograft tissue. Conversely, cold preservation for longer periods (1 and 3 weeks) dramatically reduced lymphocyte migration to values below corresponding autograft levels (783 +/- 100 and 1,252 +/- 120, respectively, P < 0.01). A comparable reduction in lymphocyte migration into nerve allografts was observed after freeze-thawing pretreatment (P < 0.01). Cold preservation of donor allogeneic lymphocytes inhibited their capacity to induce intradermal host lymphocyte migration, implicating passenger lymphocytes as a potential cold-sensitive allogeneic component of the nerve allograft. Assessment of the local response to ovine peripheral nerve allografts, utilizing radiolabeled autologous lymphocytes, demonstrated that cold preservation and freeze-thawing pretreatment significantly reduced lymphocyte migration into nerve allografts. The mechanism(s) of reduced lymphocyte migration may involve inactivation or death of antigen-presenting cells, including passenger lymphocytes.

Animals↗
PubMed1993

Facial sensibility in patients with unilateral facial nerve paresis.

This study evaluated facial sensibility in 29 patients with unilateral lower motoneuron facial nerve paresis using standard clinical tests of sensory evaluation used at other anatomic sites, most commonly the hand. Vibratory and cutaneous pressure thresholds and moving and static two-point discrimination were measured. Statistically significant differences were found between the affected and unaffected sides of the face, with vibration threshold, cutaneous pressure threshold, and static two-point discrimination being greater on the affected side. Vibration thresholds and two-point discrimination (moving and static) progressively decreased, moving down the face from the forehead to the cheek, chin, and then the lip. Sensibility thresholds are altered in patients with unilateral lower motor neuron facial nerve paresis. These findings document a relationship between sensory disturbance and lower motoneuron facial nerve paresis. The potential functional significance of this relationship has clinical significance for patients undergoing rehabilitation training.

Adolescent↗
PubMed1993

Comparison of regeneration across nerve allografts with temporary or continuous cyclosporin A immunosuppression.

The efficacy of short-term immunosuppression in a nerve allograft model was examined by comparing regeneration across peripheral nerve allografts with either temporary (12 weeks) or continuous (30 weeks) cyclosporin A treatment. One-hundred fifty Lewis rats received 2-cm nerve grafts from allogeneic ACI or syngeneic Lewis rat donors and were allocated to the following groups: allogeneic grafts and continuous cyclosporin A, with 18 weeks (20 rats) or 30 weeks (20 rats) of survival after graft placement; allogeneic grafts and temporary cyclosporin A, with 12 weeks (10 rats), 18 weeks (20 rats), or 30 weeks (20 rats) of survival; and control rats with allogeneic and syngeneic grafts, no cyclosporin A, with 12, 18, or 30 weeks (10 rats each) of survival. Functional regeneration across the nerve grafts was serially assessed with walking-track analysis. Endpoint evaluations included electrophysiological, histological, and morphometric studies. Both walking-track and electrophysiological function reached a plateau at a significantly worse level in nonimmunosuppressed allograft recipients than in syngeneic or treated allograft recipients. The group with temporary therapy experienced significant worsening in both motor and electrophysiological function at Week 18, 6 weeks after cyclosporin A withdrawal, compared to the group with continuous treatment. At Week 30, motor and electrophysiological function in the temporary-treatment group recovered to levels similar to those of the syngeneic and continuous cyclosporin A groups. Histological assessment of the graft segments from the temporary cyclosporin A group at 18 weeks showed evidence of rejection, with mononuclear cell infiltration and demyelination; morphometric evaluation demonstrated significantly decreased numbers of nerve fibers in the distal host segment. These histological and morphometric changes were no longer present in the nerves from the temporarily immunosuppressed rats at Week 30. Withdrawal of immunosuppression after successful regeneration through nerve allografts results in short-term graft rejection. Eventual restoration of graft histological and function parameters is comparable to continuously immunosuppressed rats. Temporary immunosuppression of nerve allograft recipients is feasible.

Analysis of Variance↗
PubMed1992

Subcutaneous injection of oral cyclosporin A solution.

Cyclosporin A (CyA) is the agent of choice for immunosuppression in the majority of rodent organ and tissue allotransplantation experiments. Subcutaneous injection of suitably dissolved pure CyA powder preparation is the acceptable standard of drug administration. We investigated the possibility of using oral CyA solution in an injectable form and compared its availability with that of the standard solution in a rat model. Oral CyA solution diluted in placebo (olive oil) and standard solution prepared from pure compound were injected subcutaneously at a dose of 5 mg/kg/day to two groups of rats. Trough whole blood CyA concentrations were measured on day 10 following initiation of treatment. Blood CyA levels of the standard solution group (1,167 +/- 246 micrograms/liter, mean +/- SD) were virtually identical to those of the oral solution group (1,105 +/- 179 micrograms/liter; P greater than 0.05). In addition, the oral solution was easier to prepare and caused less injection site morbidity than the standard solution. We conclude that placebo-diluted oral CyA solution may be safely injected subcutaneously to rats and results in consistent blood levels, comparable to those achieved with standard solution prepared from pure compound.

Administration, Oral↗
PubMed1992

Chronic cyclosporin A therapy in rats.

We investigated the pharmacokinetics of cyclosporin A (CsA) blood levels and drug toxicity in a chronic rat study in which long-term (30 weeks) CsA was administered. Ninety Lewis rats received subcutaneous CsA at 5 mg/kg/day for 12 weeks, at which time CsA injections were stopped in 50 animals. The remaining 40 rats were maintained on 5 mg/kg CsA daily until week 18 and then switched to an alternate day dosing until week 30. All rats were observed daily and weighed weekly. Whole blood CsA levels were determined by a commercially available radioimmunoassay kit. The daily dosing regimen resulted in greatly elevated trough CsA levels (greater than 1,600 micrograms/liter) and substantial chronic systemic toxicity, with weight loss and death in eight animals. Alternate day dosing reduced trough levels (mean 1,311 micrograms/liter) and decreased toxicity. Chronic administration by the subcutaneous route resulted in a considerable depot effect, with constancy of drug levels over a 48 hr dosing interval and a slow decline of drug levels (15 days) upon cessation of treatment. These results underscore the importance of monitoring both body weight and blood CsA levels in rodent studies when CsA is employed. Investigators should be aware of drug accumulation with chronic therapy and the consequent need to modify dosing to prevent toxicity.

Animals↗
PubMed1992

Provocative sensory testing in carpal tunnel syndrome.

This study reports the relationship between three clinical tests in the diagnosis of carpal tunnel syndrome and the stages of nerve compression. Assessments of 158 patients with carpal tunnel syndrome were reviewed retrospectively. 77% of patients had at least one of the clinical signs present. The incidence of positive pressure-provocative and Phalen's tests were similar and more likely to occur in combination than separately. Tinel's sign was more likely to be positive in the later stages of nerve compression. Our results suggest that the presence or absence of a provocative test is dependent upon the severity of the nerve compression.

Adult↗
PubMed1992

An assessment of regeneration across peripheral nerve allografts in rats receiving short courses of cyclosporin A immunosuppression.

While peripheral nerve reconstruction could benefit from the use of nerve allografts, long term immunosuppression for non-vital organ transplantation is controversial. This study investigated the effectiveness of short course Cyclosporin A immunosuppression. Fourteen Lewis (RT1l) rats were the recipients of 3 cm sciatic nerve grafts from ACI (RT1a) donors, repaired to the transected sciatic nerve of the recipient animal. Animals were treated with Cyclosporin A (5 mg/kg/day) for eight weeks. Neuromuscular function was assessed every two weeks by sciatic function index determinations until 20 weeks. Electrophysiological, histological and morphological evaluations were performed at 14 (n = 6) and 20 weeks (n = 8) postengraftment. Rats had significantly improving functional studies from four to eight weeks (P = 0.01). Function decreased following cessation of Cyclosporin A treatment. Rats evaluated at 14 weeks had histological evidence of graft rejection with inflammatory cell infiltration, extensive demyelination and remyelination, and some Wallerian degeneration. Rats demonstrated improvement in morphological parameters and motor function from 14 to 20 weeks after engraftment. In this sciatic nerve allograft model, short course Cyclosporin A immunosuppression, although resulting in an initial episode of graft rejection, was successful in permitting good long term functional regeneration of neuromuscular function.

Animals↗
PubMed1992

Reinnervation of distal sensory nerve environments by regenerating sensory axons.

This study investigated the specificity of sensory nerve regeneration in a primate model. In adult cynomolgus monkeys, the femoral nerve was explored in the groin and two sensory branches identified. A sensory branch was sectioned and introduced into the proximal channel of a Y-shaped silicone chamber. This proximal sensory nerve stump was given distal choices of distal sensory nerve graft or distal sensory nerve which was intact to the distal sensory cutaneous receptors. After eight months, histological analysis confirmed axonal growth directed towards both the distal nerve graft and the distal nerve intact to the distal cutaneous receptors. However, the number of nerve fibres directed towards the distal nerve was significantly greater than the number of nerve fibres directed towards the nerve graft (P less than 0.004). These results suggest that while both distal nerve graft and distal intact nerve act as specific targets to regenerating proximal primate nerve, the presence of an intact distal end-organ positively enhances sensory regeneration.

Animals↗
PubMed1992

Sensory recovery after median nerve grafting.

Fourteen patients were evaluated prospectively after median nerve grafts. Twelve male and two female patients with a mean age of 41 years were included. Mean time since surgery was 4 years. Detailed sensory evaluations were completed. Statistical evaluation analyzed relationships between object identification, sensory tests, and graft length. According to the S-0 to S-4 grading system, 11 patients were considered to be S-3+ or greater. Recovery of moving two-point discrimination of 2 to 3 mm. was achieved by 50% of the patients. Strong correlations were found between object identification and static two-point discrimination, moving two-point discrimination, and graft length. Cutaneous pressure threshold and vibration threshold correlated weakly with object identification.

Adult↗
PubMed1992

Continuous intravenous regional anesthesia.

This study evaluates the effectiveness of continuous intravenous regional anesthesia for prolonged operations on the upper extremity. The factors evaluated include patient's sex and age, number of procedures performed, tourniquet on and off times, anesthetic doses, adjunctive drugs used, technical complications, and side effects. Seventy-two procedures were done on 34 patients. The first tourniquet time averaged 58 minutes. Off time averaged 10 minutes. Second tourniquet time averaged 33 minutes, and the mean total tourniquet time was 91 minutes. The mean first anesthetic dose was 275 mg. Mean second anesthetic dose was 128 mg. Mean total anesthetic dose was 402 mg. There were two (6%) technical complications and two (6%) patients had side effects. Continuous intravenous regional anesthesia offers the prolonged anesthesia of brachial plexus block or general anesthesia and the safety, reliability, and ease of intravenous regional anesthesia. Continuous intravenous regional anesthesia should be considered an alternative choice of anesthetic method in upper extremity surgery.

Adult↗