Biomedical subjects

M B Wood

Publications and source records attributed to M B Wood.

At least 37 records · Page 2Linked to original sources

PubMed1996

Endothelin induces vasoconstriction in the bone vasculature in vitro: an effect mediated by a single receptor population.

The aim of this study was to define the types of endothelin receptors present in the canine tibial vasculature. Endothelin receptor agonists and antagonists were used in two different models: isolated nutrient tibial arteries in organ bath and in vitro-perfused canine tibial bones. In isolated nutrient tibial arteries, endothelin-1 caused concentration-dependent contractions of rings with and without endothelium. BQ-123, a selective endothelin-A antagonist, induced a significant rightward shift of endothelin-1 concentration-response curves. No contractions were observed with sarafotoxin S6c, a selective endothelin-B agonist. The responses of endothelin-1 were not affected by the presence of NG-monomethyl-L-arginine acetate plus indomethacin or by removal of the endothelium. In perfused tibial bones, endothelin-1 was more potent than endothelin-3 in causing concentration-dependent contractions. Neither endothelin-1, endothelin-3, nor sarafotoxin S6c caused relaxations. Neither the inhibition of nitric oxide nor the inhibition of prostaglandins significantly altered contractions to endothelin-1. These concordant data indicate that endothelin is a vasoconstrictor in the bone vasculature, an effect that appears to be mediated only through endothelin-A receptors.

Animals↗

PubMed1996

Endothelin-A receptors mediate vascular smooth-muscle response to moderate acidosis in the canine tibial nutrient artery.

Perfusate pH may influence the tone of vascular smooth muscle by affecting the release of endothelium-derived vasoactive factors or by directly modulating function of the smooth muscle. This study was designed to investigate the role of endothelium-derived factors on acidosis-induced responses of isolated canine tibial nutrient artery suspended in an organ chamber for the measurement of isometric contractile force. To investigate the specific role of the endothelium in half the rings, the endothelium was removed mechanically. Concentration-response curves to KCl were obtained in the absence or presence of inhibition of two important endothelium-derived relaxing factors, nitric oxide and prostacyclin, and an inhibitor of receptors for the endothelium-derived contracting factor, endothelin-1. Acidification of the perfusate from pH 7.45 to 7.0 significantly attenuated the contractions to KCl in arterial rings with endothelium (the mean of the effective concentration causing 50% of the maximal response for KCl at pH 7.45 and 7.0 was 12.31 +/- 0.40 nM and 14.60 +/- 0.55 nM, respectively). This difference was abolished by mechanical removal of the endothelium. In rings with endothelium, inhibition of nitric oxide or prostacyclin did not abolish the attenuation of KCl-induced contractions occurring with acidosis (the mean of the effective concentration causing 50% of the maximal response for KCl at pH 7.45 and 7.0 was 11.18 +/- 0.60 nM and 13.60 +/- 0.60 nM, respectively). Inhibition of endothelin-A receptors did not alter contractions to KCl at pH 7.45. However, the acidosis-induced attenuation of contractions with KCl was abolished by the endothelin-A-receptor antagonist BQ-123 (the mean of the effective concentration causing 50% of the maximal response at pH 7.45 and 7.0 was 13.8 +/- 1.34 nM and 13.2 +/- 1.34 nM, respectively). These results suggest that acidosis-induced relaxation of canine tibial nutrient artery is endothelium dependent and that activation of endothelin-A receptors during acidosis is coupled to a release of an endothelium-derived relaxing factor.

Acidosis↗

PubMed1996

Effect of human adrenomedullin on a canine tibial perfusion model in the absence of vascular endothelium.

The effect of human adrenomedullin was investigated using an ex vivo perfused canine tibial model in the absence of vascular endothelium. Adrenomedullin is a novel peptide with known vasodilator properties. In this model, a 0.1 ml bolus injection of 10(-5) M of either acetylcholine or adrenomedullin decreased vascular resistance in tibial preparations precontracted with prostaglandin F2 alpha by 88.3 +/- 3.0% and 92.8 +/- 2.8%, respectively, in the presence of vascular endothelium. Conversely, a 0.1 ml bolus injection of 10(-5) M acetylcholine produced a constrictor response after removal of vascular endothelium. A 0.1 ml bolus injection of 10(-5) M adrenomedullin decreased the baseline perfusion pressure in a dose-dependent manner for a duration of 20 minutes and also attenuated the pressor response to exogenous norepinephrine injection for at least 10 minutes compared with the control study (p < 0.05) in the absence of vascular endothelium. These data suggest that human adrenomedullin relaxes blood vessels in bone by a direct action on vascular smooth-muscle cells. In addition, the attenuation effect of human adrenomedullin on pressor responses to exogenous norepinephrine injection is independent of vascular endothelium.

Acetylcholine↗

PubMed1995

Cellular schwannoma. A clinicopathologic, DNA flow cytometric, and proliferation marker study of 70 patients.

BACKGROUND: A clinicopathologic study of 70 cases of cellular schwannoma was performed to assess their distribution, response to therapy, and rate of recurrence relative to modern prognostic indicators. METHODS: Seventy-one cellular schwannomas from 70 patients were retrieved from the files of the Mayo Clinic Tissue Registry. The significance of mitotic index, proliferative marker staining (proliferating cell nuclear antigen and MIB1), immunochemical p53 expression, and DNA ploidy were assessed relative to tumor behavior, particularly recurrence. All parameters were subject to statistical analysis (Student's t test). RESULTS: Cellular schwannomas represented 4.6% of benign peripheral nerve tumors operated on at the Mayo Clinic. In 15% of the cases, an initial diagnosis of malignancy had been made. The median patient age was 47.7 years (range, 15-80 years) and the female-to-male ratio was 1.6:1. The principle tumor locations were the para- and intraspinal regions, including the sacrum (64%), extremities (25%), and intracranial space (8%). All tumors consisted primarily of hypercellular, compact, Antoni A tissue. Mitoses (< or = 4/10 hPF]) were observed in 71% of the cases. Foci of necrosis were noted in 11% of cases. Ultrastructural studies and immunohistochemistry clearly demonstrated features of schwannian differentiation. Surgery was the treatment in all cases. Excision was intralesional to gross total in the majority; total resection with wide margins was undertaken in three tumors, each of which had initially been considered malignant. Follow-up in 47 patients (67%) ranged from 1 to 29 years (mean, 7.7 years) and revealed recurrences in 11 patients (23.4%): no patient experienced metastasis or died of tumor. Although no correlation existed between recurrence and DNA ploidy, percent S-phase determinations, proliferation marker (PCNA, MIB1) staining, or the frequency of p53 immunoreactivity, a statistically significant correlation (P < 0.001) was observed, however, between recurrence and mitotic indices. CONCLUSION: Proliferation indices, as defined by immunochemical analysis, are not useful predictors of recurrence in cellular schwannoma. In lesions not completely resected, tumor recurrence is significantly correlated with mitotic count. The significant overall frequency of recurrence in this series is attributable to a high proportion of intraspinal and intracranial tumors. Our study confirms the benign nature of cellular schwannoma and underscores the necessity of distinguishing them from malignant peripheral nerve sheath tumors, lesions that often require adjuvant therapy.

Adolescent↗

PubMed1995

Reperfusion injury in vascularized bone allografts.

A vascularized allograft canine tibia was used to evaluate the preservation of the osseous microcirculation. Six pairs of adult tibiae were harvested, and a vascular washout was performed with mannitol solution. The bones then were perfused continuously (0.03 ml/min at 5 degrees C) for 20 hours with University of Wisconsin solution. Following storage, each pair of bones was transplanted, by microvascular anastomosis, to a recipient dog, and bone blood flow was estimated using the radiolabeled microsphere method. Adrenoreceptor control mechanisms were evaluated in one specimen, and endothelial function was evaluated in the contralateral specimen. Alpha 1-adrenoreceptor blockade produced a significant increase (89 +/- 80%) in bone blood flow (p < 0.05). A further increase (99 +/- 56%) was observed with the addition of alpha 2-blockade (p < 0.01). Acetylcholine produced a decrease (65 +/- 65%) in blood flow (p < 0.01). This effect was inhibited by L-NG-monomethyl-arginine, which resulted in an increase (53 +/- 47%) in bone blood flow (p < 0.05). The no-reflow phenomenon was observed in two vascularized allografts. These results demonstrate that smooth muscle adrenoreceptors were preserved successfully for 24 hours. In contrast, endothelial function was abnormal. There was no evidence that the endothelium was producing endothelium-derived relaxing factor, and the results suggest that an endothelium-derived constricting factor dependent on L-arginine was produced during reperfusion. It is concluded that University of Wisconsin solution does not preserve normal endothelial function in the microcirculation of bone.

Anastomosis, Surgical↗

PubMed1995

Evaluation of influence of 24-hour cold preservation on endothelin production and on endothelin receptors in the bone vasculature.

Endothelin-1 is a vasoactive peptide produced by the vascular endothelium. It is one of the most potent endogenous vascular smooth muscle constrictors. Two subtypes of the endothelin receptor have been cloned and sequenced and denoted endothelin-A and endothelin-B. The aim of this study was to define the influence of cold ischemia on the production of endothelin-1 and on the endothelin receptors. Two different preservation techniques (cold storage only and cold storage with microperfusion with University of Wisconsin solution) also were compared. The study was performed in an in vitro bone perfusion model to isolate the vascular endothelium from blood components. The production of endothelin-1 by the bone vasculature was not altered after 24 hours of cold ischemia. No contractions were observed with S6c, a selective endothelin-B agonist, and this effect was not influenced by cold ischemia. The response mediated by the endothelin-A receptor was increased significantly, an effect that was not influenced by preservation with University of Wisconsin solution. This latter finding was the only significant alteration in the vascular function detected in the in vitro model after 24 hours of cold ischemia. With regard to the pharmacologic properties of endothelin-1, this mediated response could be implicated in the pathogenesis of vasospasm.

Animals↗

PubMed1995

Comparison of vascularised iliac crest and vascularised fibula transfer for reconstruction of segmental and partial bone defects in long bones of the lower extremity.

The results and complications of lower extremity bone reconstruction using microvascular fibula transfer were retrospectively compared with reconstruction using microvascular iliac crest transfer. Seventeen patients matched as much as possible in regard to location of defect (femur, tibia, ankle) and aetiology (traumatic defect, osteomyelitis) were studied in each group. Data collected included number of prior operative procedures, length of bony defect, presence or absence of associated soft tissue loss, the final clinical and radiographic result, technique of bone immobilisation and duration to union, complications including patency of microvascular anastomoses (if known) and nature and number of additional operative procedures. The outcome of this study suggests that, for reconstruction of the femur or tibia bridging a defect greater than 10 cms, fibula transfer yielded a satisfactory outcome. For defects less than 10 cms resulting from debridement for osteomyelitis, iliac crest transfer yielded a more favourable result. Moreover, the iliac crest appeared to be more optimal than the fibula for reconstruction about the ankle regardless of aetiology.

Bone Remodeling↗

PubMed1995

Clinical results of the one-bone forearm.

Between 1973 and 1991, 19 patients underwent creation of a one-bone forearm at our institution as treatment for radioulnar instability secondary to trauma ("type 1" patients) or tumor resection or congenital deformity ("type 2" patients). Seventeen had failed previous reconstruction attempts. Ten one-bone forearms were constructed in neutral rotation, and nine in varying pronation (mean, 24 degrees). The distal ulna was absent or excised at the time of surgery in nine patients, partially excised in two, and shortened in one. At a mean follow-up interval of 42 months, the primary union rate was 68%, and the secondary rate was 74%. Using a rating scale devised for this study, 37% excellent, 32% good, 26% fair, and 5% poor results were noted. Poor results were statistically associated with previous trauma (type 1 patients), infection, severe nerve injury, and multiple previous surgical procedures. This is a retrospective study, and because of the limitations of such studies, no correlation of results with forearm rotational position, preoperative wrist or elbow dysfunction, fusion location, distal ulna excision or synostosis union was noted. Significant complications were noted in 10 patients, with a higher rate in type 1 patients. Although one-bone forearm construction remains a viable salvage option for forearm instability in selected patients, results may be less predictable than previously reported.

Adult↗

PubMed1995

Prosthetic usage in major upper extremity amputations.

Patterns of use of contemporary prostheses by 135 patients with major upper extremity amputations were evaluated by questionnaire. Eighty-four percent of the patients were male and 16% were female. Amputation levels represented were below elbow, 44%; above elbow, 40%; and shoulder disarticulations or forequarter amputations, 16%. The follow-up interval averaged 12 years (range, 1-67 years). One hundred and thirteen patients were fitted with either a myoelectric or body-powered prosthesis. The overall rejection rate was 38%. Thirty-nine of 42 in the below-elbow amputation group used the prosthesis and appeared to benefit the most. Eight of 141 in the wrist disarticulation group used the prosthesis: as did 9 of 21 in the above-elbow amputation group. In contrast, all bilateral amputees used their prostheses. Stiff shoulders and brachial plexus injury were both predictors for poor prosthetic usage.

Amputees↗

PubMed1995

Levator scapulae transfer and fascia lata fasciodesis for chronic spinal accessory nerve palsy.

A retrospective evaluation of the functional results after reconstructive treatment with levator scapulae transfer and scapulo-spinal fasciodesis by fascia lata slings for complete chronic trapezius palsy is presented. Five patients (ages 6 to 40 years) were operated on between 1988 and 1991 because of incapacitating pain and/or functional limitations. Treatment was recommended after failure to alleviate symptoms by a shoulder-girdle muscle-strengthening program or after unsuccessful nerve graft. The descriptions of the results are drawn from the last follow-up evaluation available for each patient (minimum: 14 months post-operative). They are expressed in terms of functional recovery, residual pain, and patient satisfaction. Three patients had an excellent result, with at least 80 percent of normal abduction and forward elevation of the arm, no residual pain, and a high satisfaction rate. One patient showed good improvement in function, with 90 percent of normal shoulder function, but complained of some residual pain. The last patient was not improved by the surgery. Levator scapulae transfer and scapulo-spinal fasciodesis by fascia lata slings, substitute for the function of the upper trapezius and enhance the function of the serratus anterior, thus helping to relieve pain and to improve shoulder function after chronic trapezius palsy. The procedure warrants consideration in patients who are not candidates for nerve repair and reconstruction.

Accessory Nerve↗

PubMed1995

Arthrodesis of the knee with a vascularized fibular rotatory graft.

We retrospectively reviewed the records of thirteen patients who had been managed with an arthrodesis of the knee with use of a vascularized graft from the ipsilateral fibula and fixation with an intramedullary rod. The indications for the operation included a large skeletal defect secondary to the resection of a tumor about the knee in eight patients, an infection at the site of an arthroplasty in four (with failure of a previous conventional arthrodesis in three of the four), and severe rheumatoid gonarthrosis as well as a persistent non-union of the distal part of the femur in one. The average age of the patients at the time of the operation was forty-three years (range, twenty-six to seventy-six years). Most of the patients had had multiple previous procedures (thirty-three operations had been performed in ten patients). Twelve of the thirteen patients had a solid fusion and a successful result after an average duration of follow-up of fifty-one months (range, eight to ninety-three months). The remaining patient, who had had four previous arthroplasties, had a recurrence of an infection seven months after the operation and was managed with an amputation. Six complications--including two superficial wound infections, one deep wound infection, one deep venous thrombosis, one transient peroneal-nerve palsy, and one delayed union--occurred in three patients.

Adult↗

PubMed1995

Arthrodesis of the ankle with a free vascularized autogenous bone graft. Reconstruction of segmental loss of bone secondary to osteomyelitis, tumor, or trauma.

Reconstruction after massive loss of bone about the ankle is difficult because of the limited amount of surrounding soft tissue and because of technical factors pertaining to adequate internal or external fixation. Conventional techniques are often unsuccessful because of the frequency of associated deep infection and of previous operative procedures. In this report, we describe eleven patients with a large defect of the distal aspect of the tibia who were managed at our institution with arthrodesis of the ankle with free vascularized bone graft. The defect was related to a tumor resection; an acute open fracture with bone and soft-tissue loss caused by a shotgun injury; or osteomyelitis, either alone or in combination with septic arthritis, with chronic non-union following a fracture of the ankle. A free fibular graft was used in osseous defects that were larger than four centimeters, and a free iliac-crest graft was used in smaller defects. Osteocutaneous or osteomuscular flaps were constructed to cover accompanying soft-tissue defects when necessary. A successful fusion was obtained in nine of the eleven patients. The results in the remaining two were regarded as clinical failures, and a below-the-knee amputation was performed. One amputation was done because of recurrent infection and the other, because of failure of the fracture to unite after four years.

Adolescent↗

PubMed1994

Chronic peripheral nerve pain treated with direct electrical nerve stimulation.

Chronic somatic peripheral nerve pain was treated prospectively in 24 nonrandomized patients by a program of direct electrical nerve stimulation. Patients qualified for the program if anesthetic (lidocaine) nerve block of the involved cutaneous zone of the peripheral nerve relieved symptoms and transcutaneous electrical nerve stimulation transiently improved and did not exacerbate somatic pain. Results were judged according to a pain score. Patients noted improved sleep and complete absence of the need for narcotic pain medication. On the basis of subjective and objective criteria, 18 patients had good or excellent results and 6 had implant failures. Of the six patients with failures, three failed the trial period and did not have implantation, and three had no significant pain relief and were judged as treatment failures. Three patients had late equipment failure after initial good results. Most patients had some relief of pain, which increased their quality of life and eliminated the need for narcotic analgesia. Direct electrical nerve stimulation should be considered for somatic peripheral nerve pain that has not been ameliorated with other methods. It will reduce, although not necessarily eliminate, pain and pain behavior in most patients.

Adolescent↗

PubMed1994

Intercostal nerve transfer for brachial plexopathy.

Thirteen patients with traumatic brachial plexopathy underwent intercostal nerve transfer to the biceps motor branch (9 patients) or combined gracilis muscle and intercostal nerve transfer (4 patients; 3 for elbow flexion and 1 for elbow extension). Follow-up time ranged from 12 to 48 months (mean, 25 months) on 12 patients. Useful elbow flexion or extension was obtained in a total of 9 patients. Comparison of pre- and postoperative spirometry in 4 patients demonstrated a mild decline in pulmonary function, although there was no subjective change in respiratory status. Intercostal nerve transfer and combined gracilis muscle and intercostal nerve transfer are viable, although technically demanding, alternatives for restoring active elbow motion in patients with irreparable brachial plexus lesions when conventional tendon transfers are not feasible. The morbidity of intercostal nerve harvest with respect to pulmonary function is minimal.

Adult↗

PubMed1994

Flexor carpi radialis tendinitis. Part II: Results of operative treatment.

We retrospectively reviewed the results of decompression of the flexor carpi radialis tunnel in ten patients (six women and four men) who had tendinitis. The average age of the patients at the time of the operation was forty-five years (range, twenty-five to fifty-eight years). The average duration of follow-up was forty-four months (range, twenty-eight to seventy-six months). The primary symptom was pain, localized to the proximal aspect of the trapezium, that was accentuated by resisted flexion of the wrist and radial deviation. The diagnosis was confirmed in five patients when Xylocaine (lidocaine), injected into the area of the tenderness, decreased the pain. Two patients had evidence of idiopathic tendinitis, which one patient believed to be associated with activities involving repetitive flexion of the wrist. The tendinitis developed after fracture of the scaphoid in two patients, fracture of the distal aspect of the radius in one, excision of a ganglion in two, carpometacarpal arthrodesis in one, and blunt trauma in two. The mean duration of symptoms before the operative intervention was sixteen months (range, one to forty-three months). The intraoperative findings included adhesions in six patients, attrition or rupture of a tendon in four, exostosis in three, stenosis in three, and an anomalous tendon in one patient. Additional procedures, such as excision of a ganglion, removal of an exostosis, tendon transfer, or application of a fat graft, were performed in seven patients. Nine of the ten patients had relief of the symptoms and were able to resume their preoperative employment and leisure activities. One patient continued to be symptomatic.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1994

Canine bone blood flow measurements using serial microsphere injections.

The objective of this study was to determine the reproducibility of serial bone blood flow (BBF) quantitation using multiple microsphere injections. Three consecutive estimates of BBF were obtained, using 15-mu radionuclide-labeled microspheres from 21 anesthetized adult dogs. A dose of 3 million spheres/kg was used in seven dogs (Cohort 1); a dose of 0.5 million spheres/kg was used in the remaining 14 dogs (Cohorts 2 and 3). Estimates of BBF were made at an average of 129, 153, and 175 minutes after the animals had been anesthetized in the first two cohorts and 179, 203, and 225 minutes in Cohort 3. The dogs in Cohort 1 had no surgical intervention; the dogs in Cohorts 2 and 3 had increasingly complex surgical interventions. Despite stabilization of cardiovascular status, BBF was found to vary by 33.4% in Cohort 1, 25.7% in Cohort 2, and 42.5% in Cohort 3 over the three injections. Cortical BBF fell by 13.9%, 12.1%, and 12.4% between the first and second, and by 31.0%, 11.2%, and 29.9% between the second and third estimates for Cohorts 1, 2, and 3, respectively. Variation in right to left blood flow was used as an overall measure of error caused by technique and did not consistently increase between the first, second, or third BBF estimates in any cohort. Cortical BBF data were found to be significantly more reliable than cancellous data (p < 0.01); error caused by technique was least in the midshaft femoral or midshaft humeral cortical samples. Increasing the dose of spheres administered from 0.5 to 3 million/kg for three serial microsphere injections increased the number of reliable samples and did not lead to increased technical error or shunting. This study demonstrates that there is a significant decrease in BBF over time in the anesthetized dog; therefore, serial estimates of BBF can only be interpreted if the results are normalized or if a control group of animals is included.

Animals↗

PubMed1993

Adrenergic control mechanisms of blood flow in a vascularized canine tibial allograft.

A vascularized canine tibial allograft was used to study the alpha-adrenoreceptor subtypes of the microcirculation of bone. Bone transplantation was performed on six dogs, and the bone blood flow was estimated with the use of serial injections of radiolabeled 15 microns microspheres. After microvascular anastomosis, the mean cortical blood flow in the allografted tibia was 3.6 +/- 2.1 ml/100 g/min. Alpha 1-adrenoreceptor blockade, with prazosin, caused an increase in normalized blood flow in five allografts and a slight decrease in one allograft. The mean increase was 32 +/- 48%, but this was not statistically significant (p < 0.2). The addition of an alpha 2-adrenoreceptor blockade, with rauwolszin, resulted in a significant increase (132 +/- 88%) in normalized blood flow in all allografts (p < 0.02). This ex vivo experiment confirms that both alpha 1 and alpha 2 adrenergic mechanisms play a role in controlling bone blood flow in centrally denervated allografts.

Animals↗

PubMed1993

Effect of ischemic storage on endothelium in canine bone.

The limits of room temperature (24 degrees C) and hypothermic (4 degrees C) storage for preservation of endothelial eccrine function were investigated with use of an ex vivo perfusion apparatus model of the cannulated canine tibia. Norepinephrine-induced contraction of smooth muscles in both the presence and absence of acetylcholine was compared, with and without selective blockade of endothelial-derived relaxing factor (EDRF). At room temperature, release of EDRF deteriorated after 24 h and was absent after 48 h of storage. At 4 degrees C, endothelial eccrine activity appeared unimpaired for as long as 72 h of storage. From 96-192 h of storage at 4 degrees C, release of EDRF was suggested, but with an attenuation of its effect on smooth muscle. At 216 and 504 h of storage at 4 degrees C, no endothelial eccrine activity was demonstrated.

Acetylcholine↗