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Biomedical subjects

M P Stewart

Publications and source records attributed to M P Stewart.

17 recordsLinked to original sources
PubMed2001

Exciton-mediated hydrosilylation on photoluminescent nanocrystalline silicon.

A novel white light-promoted reaction using photoluminescent nanocrystalline silicon enables the hydrosilylation of alkenes and alkynes, providing stabilization of the porous silicon without significant loss of the photoemissive qualities of the material. Photopatterning and lithographic fabrication of isolated porous silicon structures are made possible. Experiments and observations are presented which indicate that the light promoted hydrosilylation reaction is unique to photoluminescent silicon, and does not function on nonemissive material. Hydrosilylation using a reactive center generated from a surface-localized exciton is proposed based upon experimental evidence, explaining the photoluminescence requirement. Indirect excitons formed by light absorption mediate the formation of localized electrophilic surface states which are attacked by incoming alkene or alkyne nucleophiles. Supra-band gap charge carriers have sufficient energy to react with nucleophilic alkenes and alkynes, thereupon causing Si-C bond formation, an irreversible event. The light-promoted hydrosilylation reaction is quenched by reagents that quench the light emission from porous silicon, via both charge transfer and energy transfer pathways.

Journal Article↗
PubMed2001

Penetrating missile injuries of the brachial plexus.

We studied a consecutive series of 58 patients with penetrating missile injuries of the brachial plexus to establish the indications for exploration and review the results of operation. At a mean of 17 weeks after the initial injury, 51 patients were operated on for known or suspected vascular injury (16), severe persistent pain (35) or complete loss of function in the distribution of one or more elements of the brachial plexus (51). Repair of the nerve and vascular lesions abolished, or significantly relieved, severe pain in 33 patients (94%). Of the 36 patients who underwent nerve graft of one or more elements of the plexus, good or useful results were obtained in 26 (72%). Poor results were observed after repairs of the medial cord and ulnar nerve, and in patients with associated injury of the spinal cord. Neurolysis of lesions in continuity produced good or useful results in 21 of 23 patients (91%). We consider that a vigorous approach is justified in the treatment of penetrating missile injury of the brachial plexus. Primary intervention is mandatory when there is evidence of a vascular lesion. Worthwhile results can be achieved with early secondary intervention in patients with debilitating pain, failure to progress and progression of the lesion while under observation. There is cause for optimism in nerve repair, particularly of the roots C5, C6 and C7 and of the lateral and posterior cords, but the prognosis for complete lesions of the plexus associated with damage to the cervical spinal cord is particularly poor.

Adolescent↗
PubMed1999

A novel leukocyte adhesion deficiency caused by expressed but nonfunctional beta2 integrins Mac-1 and LFA-1.

In the leukocyte adhesion deficiency (LAD)-1 syndrome, there is diminished expression of beta2(CD18) integrins. This is caused by lesions in the beta2-subunit gene and gives rise to recurrent bacterial infections, impaired pus formation, and poor wound healing. We describe a patient with clinical features compatible with a moderately severe phenotype of LAD-1 but who expresses the beta2 integrins lymphocyte function- associated molecule (LFA)-1 and Mac-1 at 40%-60% of normal levels. This level of expression should be adequate for normal integrin function, but both the patient's Mac-1 on neutrophils and LFA-1 on T cells failed to bind ligands such as fibrinogen and intercellular adhesion molecule (ICAM)-1, respectively, or to display a beta2-integrin activation epitope after adhesion-inducing stimuli. Unexpectedly, divalent cation treatment induced the patient's T cells to bind to ICAM-2 and ICAM-3. Sequencing of the patient's two CD18 alleles revealed the mutations S138P and G273R. Both mutations are in the beta2-subunit conserved domain, with S138P a putative divalent cation coordinating residue in the metal ion-dependent adhesion site (MIDAS) motif. After K562 cell transfection with alpha subunits, the mutated S138P beta subunit was coexpressed but did not support function, whereas the G273R mutant was not expressed. In summary, the patient described here exhibits failure of the beta2 integrins to function despite adequate levels of cell-surface expression.

Adolescent↗
PubMed1998

LFA-1-mediated adhesion is regulated by cytoskeletal restraint and by a Ca2+-dependent protease, calpain.

The activity of integrins on leukocytes is kept under tight control to avoid inappropriate adhesion while these cells are circulating in blood or migrating through tissues. Using lymphocyte function-associated antigen-1 (LFA-1) on T cells as a model, we have investigated adhesion to ligand intercellular adhesion molecule-1 induced by the Ca2+ mobilizers, ionomycin, 2, 5-di-t-butylhydroquinone, and thapsigargin, and the well studied stimulators such as phorbol ester and cross-linking of the antigen-specific T cell receptor (TCR)-CD3 complex. We report here that after exposure of T cells to these agonists, integrin is released from cytoskeletal control by the Ca2+-induced activation of a calpain-like enzyme, and adhesive contact between cells is strengthened by means of the clustering of mobilized LFA-1 on the membrane. We propose that methods of leukocyte stimulation that cause Ca2+ fluxes induce LFA-1 adhesion by regulation of calpain activity. These findings suggest a mechanism whereby engagement of the TCR could promote adhesion strengthening at an early stage of interaction with an antigen-presenting cell.

Calcium↗
PubMed1997

Total shoulder replacement in rheumatoid disease: 7- to 13-year follow-up of 37 joints.

We made a prospective study of 58 consecutive Neer II total shoulder replacements in 49 rheumatoid patients. Cemented glenoid and press-fit humeral components had been used. After a mean follow-up of 9.5 years (7 to 13), 11 patients (15 shoulders) had died, one shoulder had been arthrodesed and five patients (five shoulders) had been lost to follow-up. Of the remaining 37 shoulders 29 were painfree or had only slight discomfort, four had pain on unusual activity, and four had moderate or severe pain. There were satisfactory improvements in the mean range of active elevation (53 degrees to 75 degrees) and external rotation (5 degrees to 38 degrees); satisfactory performance of the activities of daily living had been maintained throughout follow-up. Radiographs showed loosening in ten shoulders of nine glenoid and nine humeral components but of these only three had significant symptoms. Three loose glenoid components and two loose humeral components required revision. We consider that the Neer total shoulder replacement provides a reasonable medium to long-term outcome in rheumatoid arthritis, but recommend that the humeral component should be routinely cemented.

Adult↗
PubMed1996

T cell adhesion to intercellular adhesion molecule-1 (ICAM-1) is controlled by cell spreading and the activation of integrin LFA-1.

Many leukocyte integrins require activation before they can adhere to their ligands. For example, stimulation of T cells enables the integrin LFA-1 to bind to ligand. This study compares two well known protocols for inducing T cell LFA-1 mediated adhesion to intercellular adhesion molecule-1 (ICAM)-1. We how that treatment with high concentrations of the divalent cation Mg2+ induces a high affinity state of LFA-1, which is reflected in the binding of soluble ICAM-1 and correlates with the expression of the epitope recognized by mAb 24. The second stimulation protocol with the phorbol ester phorbol-12,13-dibutyrate (PDBu) does not induce a high affinity state of LFA-1, and in this situation, adhesion is dependent on cell spreading and intracellular events involving protein kinase C, [Ca2+]i, and actin polymerization. These low affinity LFA-1 receptors are responsible for the initial contact with immobilized ligand because, unlike the Mg2+-stimulated receptors, adhesion is not blocked by soluble ICAM-1. Finally, we used a third method of inducing LFA-1-mediated adhesion by stimulation of T cells through the TCR/CD3 complex. This procedure, which is considered to be a more physiologic trigger for LFA-1 activation, resembles the phorbol ester protocol in that high affinity LFA-1 receptors are not induced and cell adhesion depends on involvement of the cytoskeleton and cell spreading.

Antibodies, Monoclonal↗
PubMed1996

Fractional allele loss data indicate distinct genetic populations in the development of non-small-cell lung cancer.

Allelic imbalance or loss of heterozygosity (LOH) has been widely used to assess genetic instability in tumours, and high LOH on chromosome arms 3p, 9p and 17p has been considered to be a common event in non-small-cell lung cancer (NSCLC). We have investigated allelic imbalance in 45 NSCLCs using 92 microsatellite markers on 38 chromosome arms. LOH of 38% was observed on 3p using nine markers, 58% on 9p using 15 markers and 38% on 17p using five markers. Fractional allele loss (FAL) has been calculated for each tumour (FAL is the number of chromosome arms showing LOH/number of informative chromosome arms) and a median FAL value of 0.09 was obtained in the 45 NSCLCs studied. The LOH data were examined on the basis of FAL scores: low FAL (LFAL) (0.00-0.04), medium FAL (MFAL) (0.05-0.13) and high FAL (HFAL) (0.14-0.45) based symmetrically around the median FAL value of 0.09. Tumours with HFAL values showed a very clear polarisation of the LOH data on chromosome arms 3p, 9p and 17p, such that 80% showed loss on 3p, 80% on 9p and 73% on 17p. These incidences of LOH were significantly higher than would be expected, since overall genetic instability in these HFAL tumours ranged from 14% to 45% LOH. Nine of the 14 patients in the LFAL group were found to have no LOH on 3p, 9p or 17p, but five of these had LOH at other sites: i.e. LOH on 5p, 5q, 8p, 13q, 16q and 19q. These results indicate that LFAL patients form a new subset of NSCLC tumours with distinct molecular-initating events, and may represent a discrete genetic population.

Adenocarcinoma↗
PubMed1993

Gulf war wounds: application of the Red Cross wound classification.

The Red Cross wound classification was applied to 63 casualties requiring surgery in the recent Gulf war. The majority of wounds affect only soft tissue, caused predominantly by antipersonnel fragments. Bullet wounds were fewer but tended to be more severe, often involving a fracture or vascular damage. We recommend minor modification to the classification to include scoring of significant neurological injury. Further, we feel that by recording the distribution of all wounds as well as scoring the casualty's two worst injuries, the incidence and pattern of multiple wounds are ascertained, which is useful in military surgical research. We believe that the Red Cross wound classification is valuable in assessing a wound as part of a secondary survey, but that this wound score has little part to play in triage. It may help to decide management of individual wounds in clinical practice and is useful for recording the nature of wounds for future analysis.

Evaluation Studies as Topic↗
PubMed1993

Shotgun wounds of the limbs.

Shotgun blasts may cause devastating injuries in civilian trauma practice. We have reviewed 23 consecutive patients with 28 deliberate shotgun wounds to limbs treated over a 4-year period. Wounds were categorized using the Red Cross wound classification. Twenty wounds were high-energy transfer grade 2 and 3 injuries: eight involved only the soft tissues (five category 2ST, three category 3ST), 10 wounds involved fractures (two category 2F, seven category 3F, one category 3VF), and three wounds involved major vessel injury (two category 3V, one category 3VF). Category 2ST and 3ST wounds were managed successfully with thorough wound excision of devitalized tissue, fasciotomy, and early wound closure. The more complex category 3F, 3V and 3VF wounds required a multidisciplinary approach to their management. Three lower limbs (category 3F, 3V, and 3VF wounds) with associated major nerve injury were amputated at the first operation; there were no cases of secondary amputation. Of the salvaged limbs, those with category 3F injury at or below the level of the elbow or knee had poor functional results.

Adult↗
PubMed1992

Effects of a videotape feedback package on the peer interactions of children with serious behavioral and emotional challenges.

Peer interactions are among the greatest challenges experienced by children who have severe emotional and behavioral problems. This study evaluated an intervention package designed to increase the ratio of these children's desirable to undesirable interactions. The package included three principal components: (a) observation of videotapes following regularly scheduled peer activity sessions; (b) self-evaluation of the children's peer interactions observed on the videotapes; and (c) delayed feedback and reinforcement for desirable peer interactions. Five students from two elementary schools participated. Multiple baseline designs and one reversal were used to evaluate the effects of the intervention package. The results showed that the intervention produced lower levels of undesirable peer interactions and higher ratios of desirable to undesirable interactions for all participants. The results are discussed in regard to their conceptual and applied implications and in terms of specific directions for future research.

Affective Symptoms↗
PubMed1991

Penetrating missile injuries in the Gulf war 1991.

During the recent Gulf war 63 patients with penetrating missile injuries (including 29 Iraqi prisoners of war) underwent operation in a British Army Field Hospital. Their injuries and initial operative management are reported. Fifty-one casualties (81 per cent) suffered an average of nine wounds (range 1-45) due to fragmentation weapons, and 12 casualties sustained bullet wounds. All wounds were explored following the established principles of war surgery. The extremities were involved in 48 patients (76 per cent). Eight compound long bone fractures were managed with external skeletal fixators applied at the time of initial operation. Laparotomy was performed on seven patients, one of whom died. The average duration of operation was 77 min for shrapnel wounds and 85 min for bullet wounds.

Abdominal Injuries↗
PubMed1991

Ciguatera fish poisoning: treatment with intravenous mannitol.

Intravenous mannitol was given to 16 patients with acute ciguatera fish poisoning requiring hospital admission. Thirteen patients (81%) presented with sensory and neuromuscular symptoms; paraesthesiae and pain and weakness in the lower limbs were predominant features. Mannitol had little effect upon gastrointestinal manifestations, but a marked reduction was observed in the expected duration of neurological symptoms. Although these results are empirical and uncontrolled, they suggest that mannitol infusion may be effective in altering the clinical course of acute ciguatera fish poisoning.

Adolescent↗
PubMed1987

Tension pneumothorax complicating pulmonary hydatid disease in childhood.

The case of a 3-year-old girl with bilateral pulmonary hydatid disease presenting as a tension pneumothorax is described. This is a rare but serious complication of hydatid disease in the pediatric age group which may arise as a result of rapid growth of the cyst in the lung and low resistance to its expansion. Prompt relief of the pneumothorax with intercostal drainage is advocated, followed by early surgical removal of any suspected cyst to avoid further complication.

Bronchial Fistula↗
PubMed1985

Treatment of acute abscesses by incision, curettage and primary suture without antibiotics: a controlled clinical trial.

One hundred and thirty-seven consecutive acute superficial abscesses were randomly allocated to incision, curettage and primary suture without parenteral antibiotics (64 cases) or to conventional treatment with incision, drainage and dressings (73 cases). Wound healing was faster; 7.0 days: 25.1 days (P less than 0.01, Wilcoxon's rank sum test), the number of hospital visits was smaller; 3.8 visits: 11.1 visits (P less than 0.01) and the time off work was shorter; 4.0 days: 14.1 days (P less than 0.01) in the group treated by primary closure compared with those managed conventionally. In this study no complications attributable to the withholding of antibiotics occurred. Incision and primary closure of abscesses is safe and more economic than conventional drainage. Routine antibiotic cover is not necessary.

Abscess↗
PubMed1984

Infection after abdominal surgery: five year prospective study.

A total of 1504 consecutive abdominal operations were studied prospectively over a five year period. The incidence of wound (2.8%) and intraperitoneal (0.8%) infections was low compared with contemporary reports. It is difficult to justify modifying existing practice on the basis of small controlled clinical trials when information from accurate audit discloses results superior to those of experimental studies.

Abdomen↗