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Biomedical subjects

S Buchanan

Publications and source records attributed to S Buchanan.

31 records · Page 2Linked to original sources
PubMed1996

Magnetoenterography (MENG): noninvasive measurement of bioelectric activity in human small intestine.

The basic electrical rhythm (BER) of the gastrointestinal tract creates minute magnetic fields that have been measured in animals using a Superconducting QUantum Interference Device (SQUID) gradiometer. The aim of this study was to measure noninvasively the biomagnetic fields of human stomach and small intestine. Twenty-one human volunteers were studied using a 37-channel SQUID gradiometer positioned over the epigastrium and umbilicus. In one volunteer additional biomagnetic recordings were performed in order to map the spatial variation of the biomagnetic fields. Cyclical waveforms consistent with gastric BER [3.0+/-0.5 cycles per minute (cpm)] and small intestine BER (10.26+/-1.74 cpm) were seen in the epigastrium and umbilicus, respectively. The mapping study identified the expected frequency gradient (12.0 cpm in duodenum, 11.3 cpm in jejunum, to 9.7 cpm in ileum) within the small intestine. Noninvasive recordings of human gastric and small intestinal BER can be obtained using a SQUID gradiometer.

Adult↗
PubMed1992

Light-induced charge separation in Rhodopseudomonas viridis reaction centers monitored by Fourier-transform infrared difference spectroscopy: the quinone vibrations.

Static FTIR light-induced difference spectra have been recorded for reaction centers from Rhodopseudomonas viridis in the following charge-separated states: P+QA(-)-PQA, P+QB(-)-PQB, I(-)-I, I-QA(-)-IQA, and I-QA(2-)-IQA. A comparison of the I(-)-I difference spectra with the I-QA(-)-IQA difference spectra reveals new bands which can be assigned to QA- vibrations; these vibrations are also observed in the P+QA(-)-PQA and P+QB(-)-PQB difference spectra. Through an analysis of all of the static difference spectra, the electron-transfer pathway can be monitored in the infrared from the primary donor, P, to the secondary acceptor, QB, via the intermediate acceptor, I, and the primary acceptor, QA. The difference spectra are dominated by absorbance changes of prosthetic groups, with very few identifiable contributions from amino acids and little overall structural change in the protein backbone, involving only one or two residues for the various charge-separated states. Oxidation of the primary donor in the reaction center shows the characteristic absorbance changes of the 9-keto and 10-ester carbonyl groups observed upon oxidation of bacteriochlorophyll b in a non-hydrogen-bonded environment [Ballschmiter, K. H., & Katz, J. J. (1969) J. Am. Chem. Soc. 91, 2661-2677]. Reduction of the quinones in the reaction center yields absorbance changes of the carbonyls observed during reduction of quinones in a hydrogen-bonded environment [Bauscher, M., Nabedryk, E., Bagley, K., Breton, J., & Mäntele, W. (1990) FEBS Lett. 261, 191-195].(ABSTRACT TRUNCATED AT 250 WORDS)

Benzoquinones↗
PubMed1992

Bronchial carcinoid tumors: a retrospective analysis of 126 patients.

From 1970 until 1990, 8,958 cases of primary carcinoma of the lung were diagnosed at the Duke University Medical Center. During the same period, 126 patients (mean age, 53 +/- 13 years) were diagnosed with bronchial carcinoid. The overall survival was 78% for 5 years and 71% for 10 years. Surgical treatment in 106 patients included pneumonectomy (15), lobectomy (63 with 9 bronchoplastic procedures), stapled wedge resection (22), and bronchoscopic laser resection (6). The method of diagnosis was chest roentgenography (121), chest computed tomography (77), mediastinal tomography (31), bronchoscopy (81), bronchoscopic brushing and washing (50), bronchoscopic biopsy (40), transthoracic needle biopsy (27), thoracotomy (100), and autopsy (5). Univariate analysis of the medical history, presenting signs and symptoms, diagnostic test results, and pathologic data predicted improved survival (p less than 0.001) for: female sex (n = 58), asymptomatic presentation (n = 47), normal serum serotonin or urinary hydroxyindoleacetic acid levels (n = 76), peripheral location of the primary tumor (n = 50), pathologic stage I or II (n = 91), negative lymph nodes (n = 80), primary tumor 2 cm or less in diameter (n = 67), and typical histology (n = 80). No significance (p greater than 0.1) was observed for age, smoking history, race, family history of carcinoid, environmental exposure, or hemoptysis. The most important factors affecting survival defined by multivariate analysis were (p less than 0.01) pathologic stage, atypical histology, and asymptomatic presentation. Bronchial carcinoid tumors are unique, making up 1% to 2% of primary lung neoplasms and having an excellent prognosis after resection with a 95% 5-year and 93% 10-year survival for pathologic stage I disease.

Analysis of Variance↗
PubMed1985

Effect of self-administered daily irrigation with 0.02% SnF2 on periodontal disease activity.

To determine the effect on periodontal health of a daily self-administered irrigation with 0.02% stannous fluoride (SnF2) solution, 28 subjects who had moderate to advanced periodontitis were randomly divided into 3 groups: a control group (n = 9) which used no irrigation, a group (n = 8) which used a self-administered water irrigation device (Water Pik) daily with water (H2O group) and a group (n = 11) which used the Water Pik in a similar manner but with SnF2 solution (SnF2 group). All subjects were instructed in routine tooth brushing and flossing but received no other periodontal treatment. 4 study sites were selected from each patient which had pocket depths greater than 4 mm and bleeding upon probing. Plaque index, gingival index, bleeding tendency, pocket depth, loss of attachment, and microbiologic samples of subgingival plaque for morphologic determinations were collected from all study sites at baseline, 2, 6, and 10 weeks. A cross-over was then initiated for 2 additional monthly checks in which the H2O group changed to SnF2 and the SnF2 group was divided into 2 subgroups which either continued to use SnF2 or changed to H2O. The control group completed the study at the beginning of the crossover. The clinical data showed significantly more improvement in periodontal health during the first 10 weeks for the SnF2 group (p less than 0.01). After cross-over, the clinical data indicated the group that changed from H2O to SnF2 significantly improved their periodontal health, while the group that changed from SnF2 to H2O became worse. The microbiologic data showed trends which agreed with the clinical data during the first 10 weeks but were less significant. After cross-over, the %s of motile rods and spirochetes were too small (0-7%) to establish statistically significant changes considering the accuracy of the technique used.

Bacteria↗
PubMed1982

Determination of half-dose depth in skin for soft x-rays.

Unlike superficial x-rays, the soft x-rays normally used in dermatologic practice spare unaffected underlying organs during treatment of cutaneous malignancies. However, since the dose with depth from soft x-rays varies markedly, it is important to know this relationship for optimal therapeutic results. The peak kilovoltage, and thus the energy of the beam, is generally selected so that the dose to the base of the lesion is one-half the surface dose. An absorbed dose of 3,400 rads to the surface and a dose of about one-half this amount to the base of most malignant lesions is one standard protocol for optimal therapeutic results. An accurate value of half-depth dose in skin is therefore necessary and is readily obtained from ordinary half-value layer measurements using the technic described.

Aluminum↗
PubMed1980

Calcium and phosphate requirements of preterm infants who require prolonged hyperalimentation.

Preterm infants require large amounts of calcium and phosphate to maintain skeletal mineralization during prolonged hyperalimentation. It is impossible to supply the amount of calcium and phosphate normally acquired transplacentally (150 mg/kg/day of calcium and 80 mg/kg/day of phosphate) with reasonable volumes of a single hyperalimentation solution of a physiological pH. We recently encountered calcium phosphate precipitates plugging our hyperalimentation catheters as we tried to raise the calcium concentration above 20 mEq of calcium per liter of hyperalimentation solution. Such a solution supplies 50 mg/kg/day of calcium when run at 125 mL/kg/day. In an attempt to circumvent this problem, we are currently using two hyperalimentation solutions--one high in calcium and the other high in phosphates--run alternately for 12-hour periods. This regimen supplies 80 mg/kg/day of calcium.

Bone and Bones↗
PubMedDate not supplied

Intracerebral scopolamine administration attenuates Pavlovian heart rate conditioning in the rabbit.

Scopolamine hydrobromide was injected into the septum, dorsal hippocampus, or lateral ventricles of conscious rabbits via bilateral chronic indwelling cannulas. The cardiac orienting reflex (OR) and heart rate (HR) classical conditioning were assessed. A fourth group of animals received injections of the vehicle solution into these same brain areas and were otherwise similarly trained. Scopolamine had no effect on the cardiac OR produced by unreinforced tone stimuli. The OR consisted of pronounced bradycardia that habituated over successive trials in all groups. The HR change during classical conditioning also consisted of bradycardia. However, these conditional HR changes were attenuated by scopolamine injected into the septum and lateral ventricles, but were not affected by injections into the dorsal hippocampus. These results suggest that centrally applied scopolamine may affect a central nervous system associative process, and not a mechanism directly involved in primary bradycardia.

Animals↗
PubMedDate not supplied

Electrical stimulation of insular cortex elicits cardiac inhibition but insular lesions do not abolish conditioned bradycardia in rabbits.

Conscious rabbits received electrical stimulation of insular and more posterior perirhinal cortex through chronically implanted electrodes. Active sites for cardiovascular responses were found in both anterior and posterior insular cortex as well as more posterior perirhinal regions. Although differential response topographies occurred related to anterior versus posterior insular cortex, all heart rate responses consisted of bradycardia. Pharmacological manipulations revealed that this bradycardia was due to a combination of vagal and sympatho-inhibitory mechanisms. Some posterior sites yielded pressor responses, and bradycardia which was sensitive to phentolamine, suggesting that the bradycardia in these instances was due to activation of the baroreceptor reflex. All other blood pressure changes were depressor responses. In a second experiment two different groups of rabbits with lesions of either anterior or posterior agranular insular cortex were compared with a third group of animals with sham lesions in a differential Pavlovian conditioning experiment. No lesion completely abolished the classically conditioned bradycardia associated with tone/shock contingencies. However, anterior insular lesions attenuated the magnitude of the conditioned bradycardia compared to the posterior and sham lesions. Control experiments suggested that this attenuation was due to the lesion's effects on the conditioned stimulus/unconditioned stimulus association and not to its effects on unconditioned responding to the conditioned stimulus or unconditioned stimulus alone.

Animals↗