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Biomedical subjects

M Buchanan

Publications and source records attributed to M Buchanan.

At least 19 recordsLinked to original sources
PubMed1999

Arrays of multielement ultrasound applicators for interstitial hyperthermia.

Arrays of multielement ultrasound applicators for interstitial hyperthermia have been developed and tested both in vitro and in vivo. The system includes multielement applicators, a 64 channel RF driving unit, a power measuring unit, a 112 channel multisensor temperature measuring unit, and a water cooling unit. Ninety-five arrays of single-element and nine arrays of three-element ultrasound applicators were designed, built, and characterized by measuring transducer efficiency and ultrasound field distribution. Improved uniformity in the azimuthal direction was achieved by using multiple driving frequencies. In addition, production of ultrasound in a desired sector of the transducer was possible by selecting a suitable frequency. Both in vitro and in vivo experiments showed that 92% of monitored temperature points within the target volume of 30 mm x 30 mm x 35 mm achieved a therapeutic temperature rise (above 5 degrees C) when an array of five three-element applicators were used. These results indicated that the arrays of multielement ultrasound applicators have distinct advantages over present interstitial hyperthermia modalities in terms of the capability to control the temperature distribution with a large catheter spacing. As a conclusion, the feasibility of a practical arrays of multielement ultrasound applicators for interstitial hyperthermia was demonstrated.

Animals↗
PubMed1996

A primary intraosseous carcinoma of the anterior maxilla. Report of a new case.

The case of a primary intraosseous carcinoma occurring in the maxilla is presented. The classification; clinical, radiologic, and light microscopic features; and treatment are described. These rare lesions should be considered among the diagnostic possibilities when patients present with atypical cysts of the jaws.

Diagnosis, Differential↗
PubMed1996

Electromyographic activity during windsurfing on water.

Electromyographic activity and the electrocardiogram were recorded during windsurfing on the water in six subjects (three females and three males). 'Beating' and 'reaching' (both with continuous pumping), 'running' and 'uphauling' were performed in light to moderate winds. The physiological signals were transmitted to a shore base by radio telemetry and recorded with synchronized video and audio information of movement. Heart rates were similar for the beating, reaching and running activities within the individuals, but varied between individuals (means of 145 to 173 beats min-1), due to performance conditions and related muscle activity levels. During beating and reaching, the trapezius, flexor carpi ulnaris, extensor carpi radialis, biceps brachii and tibialis anterior were very active, with the gluteus maximus being particularly important in beating. Running involved less general muscle activity, though the role of the tibialis anterior increased. Differences in technique were identified between the subjects, notably in the order of muscle recruitment to participate in the activities.

Electromyography↗
PubMed1996

Electromyographic activity of beating and reaching during simulated boardsailing.

This study examined the responses of six competitive boardsailors (three males, three females) during laboratory-based simulation tasks while the electromyographic activity of up to 13 muscles was recorded. A sailboard, mounted in a steel frame and resting on a waterbed, allowed simulation of roll and pitch movements. Wind force was simulated by attaching the boom to a weight stack with a hydraulically controlled buffered release phase. The progression of the simulation test was controlled by the sailor copying movements on an edited video of each subject boardsailing on the open water. Analysis of individual pumping movements for mean peak percentage of maximal enveloped voluntary contraction (%MEVC) in 'beating' and 'reaching' showed that muscular activity in the arm (flexor carpi ulnaris, extensor carpi radialis and biceps brachii) was greatest (66-94% MEVC), with considerable activity (58-75% MEVC) in the deltoid and trapezius shoulder muscles, but much less activity in the leg muscles (16-40% MEVC). For the combined upper and lower body muscles there was a significant difference (P < 0.001) between 'beating' and more physically demanding 'reaching' pumping activity. Electromyographic activity was higher than reported previously during simulation, reflecting the current dynamic nature of the sport.

Adult↗
PubMed1996

Dermatofibrosarcoma protuberans.

BACKGROUND: Dermatofibrosarcoma protuberans (DFSP) is a locally aggressive soft tissue sarcoma in which recurrences are common. It usually affects middle-aged individuals with the most common location being the trunk. Sex distribution varies among published series. Mohs surgery is the treatment of choice. Immunostaining for CD34 facilitates the diagnosis of DFSP and aids in indicating the surgical margins of the tumor; however, the sensitivity of this marker is variable. MATERIALS AND METHODS: This is a retrospective review of 16 cases of DFSP treated with Mohs surgery at Duke University Medical Center between 1981 and 1994. Clinical and histologic features are analyzed. Immunohistochemical stains for CD34 were performed in one case. RESULTS: Twelve of the 16 patients were women with four younger than 20 years. The most common location was the trunk. No recurrences following Mohs surgery have been documented. The average number of stages during Mohs surgery was 3.3. Surgical wounds were repaired by complex layered closure in 11 cases. Stains for CD34 were negative on the initial biopsy, but were positive on frozen sections. CONCLUSIONS: Both sexes and all age groups are affected by DFSP. Mohs surgery is the treatment of choice and offers a significant improvement in cure rates with the cosmetic advantage of smaller postoperative wounds. Immunostains for CD34 appear to be an important adjunct to facilitate tumor removal, but the variable expression of CD34 antigen by DFSP tumors can lead to variable staining patterns.

Adolescent↗
PubMed1995

Health and cancer prevention: knowledge and beliefs of children and young people.

OBJECTIVE: To collect information from children and young people about their knowledge of and attitudes towards cancer and their understanding of health and health related behaviours to inform future health promotion work. DESIGN: Questionnaire survey of 15-16 year olds, and interviews with play materials with 9-10 year old children. SETTING: Six inner city, suburban, and rural schools. SUBJECTS: 226 children aged 15-16 years and 100 aged 9-10 years. MAIN OUTCOME MEASURES: Knowledge about different types of cancer; beliefs about health; sources of information; quality of research data obtainable from young children about cancer and health. RESULTS: Both samples knew most about lung cancer, but there was also some knowledge of breast and skin cancer and leukaemia. Smoking, together with pollution and other environmental factors, were seen as the dominant causes of cancer. Environmental factors were mentioned more often by the inner city samples. Television and the media were the most important sources of information. Young people were more worried about unemployment than about ill health. More than half the young people did not describe their health as good, and most said they did not have a healthy lifestyle. Children were able to provide detailed information about their knowledge and understanding by using drawings as well as interviews. CONCLUSIONS: Children and young people possess considerable knowledge about cancer, especially about lung cancer and smoking, and show considerable awareness of predominant health education messages. Despite this knowledge, many lead less than healthy lifestyles. Health is not seen as the most important goal in life by many young people; the circumstances in which many children and young people live are not experienced as health promoting.

Adolescent↗
PubMed1995

Human recombinant stem-cell factor induces melanocytic hyperplasia in susceptible patients.

BACKGROUND: Recombinant human stem-cell factor (SCF), a cytokine acting on hematopoietic progenitor cells, has potential for the treatment of several hematologic and oncologic disorders. In a hematology-oncology phase I trial of SCF, several patients had cutaneous hyperpigmentation at the SCF subcutaneous injection sites. OBJECTIVE: Our purpose was to investigate the pathogenesis of this hyperpigmentation phenomenon. METHODS: Skin biopsy specimens were obtained before, at the completion of, and after SCF therapy and were processed for histology, immunohistology, and electron microscopy. RESULTS: Skin at the site of SCF injection had an increased number of melanocytes, increased melanocytic dendrite extension, and melanin as compared with noninjected tissue. Immunohistochemical stains revealed an increase in staining with melanocyte-specific monoclonal antibodies HMB-45 and NKI/beteb, and a monoclonal antibody to the receptor for SCF, c-kit. CONCLUSION: Subcutaneous injection of SCF results in hyperplasia of melanocytes. SCF may be useful in the treatment of melanocytopenic disorders, but caution may be necessary in patients with disorders of melanocyte proliferation.

Antibodies, Monoclonal↗
PubMed1994

Cyclopiazonic acid stimulates Ca2+ influx through non-specific cation channels in endothelial cells.

A non-specific cation channel in cultured human umbilical vein endothelial cells was obtained by cell-attached patch-clamp study. This channel showed a conductance of 28 pS when both pipette and bath contained 140 mM potassium chloride. when pipette solution was changed into 140 sodium chloride with 5 mM calcium chloride, the conductance was 26 pS. when 120 mM calcium chloride was used as the only cation in the pipette, a conductance of 6 pS was obtained. Bath application of cyclopiazonic acid, an inhibitor of the sarcoplasmic reticulum Ca2+ pump in smooth muscle and other tissues, dose dependently activates this non-specific cation channel. It is assumed that cyclopiazonic acid by blockade of the refilling of Ca2+ stores depletes the rapidly exchanging intracellular Ca2+ stores and this action stimulates Ca2+ influx through the non-specific cation channels in human umbilical vein endothelial cells.

Calcium↗