Search PubMed⌕ Search

Biomedical subjects

R C Marshall

Publications and source records attributed to R C Marshall.

86 records · Page 5Linked to original sources
PubMed1973

Interaction of 13 CO 2 and bicarbonate with human hemoglobin preparations.

Formation of (13)C-resonances attributable to carbamino derivatives has been observed in human erythrocyte hemolysate preparations equilibrated with (13)CO(2) at 33 degrees . Carbamino formation is most marked in deoxyhemoglobin and at alkaline pH, and is very largely inhibited by the addition of 2,3-diphosphoglycerate or conversion to oxyhemoglobin. The prominent carbamino resonance at 30.0 ppm upfield of CS(2) is visible in the spectrum of packed, deoxygenated erythrocytes equilibrated in (13)CO(2). This chemical shift falls close to that observed with sperm-whale myoglobin and within 2 ppm upfield of that seen with simple amino acids and peptides. The bicarbonate-carbonate resonance near 33 ppm is broad in the hemoglobin preparations, which always contain some carbonic anhydrase, but becomes narrow in the presence of the carbonic anhydrase inhibitor, acetazolamide. The nuclear magnetic resonance condition of intermediate exchange rate with dissolved CO(2) (68.4 ppm) obtains in the absence of inhibitor. The process has marked consequences in reducing the spin-lattice relaxation time, T(1), of the bicarbonate resonance by more than 10 times. The deoxyhemoglobin carbamino resonance has a T(1) value of 700 msec, indistinguishable from that of the protein carbonyl resonance envelope.

Acetazolamide↗
PubMedDate not supplied

Quantitative gated blood pool SPECT for the assessment of coronary artery disease at rest.

BACKGROUND: Planar gated blood pool imaging (GBPI) has long proven to be useful for the noninvasive assessment of ventricular function. From a practical viewpoint, gated blood pool single photon emission computed tomography (GBPS) acquisition can be accomplished in the same time as a three-view planar series, with the benefit of a tomographic perspective that avoids chamber overlap. METHODS AND RESULTS: Quantitative gated blood pool SPECT was applied to 10 patients who underwent coronary arteriography, contrast ventriculography, and planar gated blood pool imaging. For each patient, the mid-short axis oblique slice was divided into 4 discrete segments using 4 different reference models and 2 forms of segmentation. A center of mass (counts) fixed in the end-diastolic frame and segmentation that bisected the ventricular septum proved to have the highest sensitivity and specificity for determining regional wall motion abnormalities at rest in myocardium supplied by severely diseased coronary arteries (>75 %). GBPS correctly identified 19 of 21 abnormal segments (90%), with good specificity (95%), whereas ventriculography identified 12 (57%) and planar GBPI identified 9 (43%) of the segments supplied by diseased coronaries. CONCLUSION: Quantitative GBPS appears to be a sensitive method for assessing coronary artery disease at rest in myocardium perfused by severely diseased coronary arteries.

Aged↗
PubMedDate not supplied

Technical competency in flexible sigmoidoscopy.

BACKGROUND: Family practice residencies offer training in flexible sigmoidoscopy; however, there are no objective recommendations for determining competency in learners. We describe a longitudinal study designed to determine the mean procedure time and depth of insertion for family practice residents. METHODS: During a 21-month period, data were collected for 421 patients undergoing flexible sigmoidoscopy. Second- or third-year family medicine residents supervised by family medicine faculty did all procedures. The data were analyzed with simple descriptive statistics, t test, and linear and logistic regression. RESULTS: The mean procedure time was 18+/-9.3 minutes (17.2 - 19.6, 95% confidence interval [CI]). The mean insertion depth was 51.4+/-12.4 cm (50.4 - 52.6 cm, 95% CI). Performing a biopsy was associated with an increase in procedure time (17.0 vs 27.3 minutes, P < .0001). Women with a history of pelvic surgery had less depth of insertion than did those who had no history of pelvic surgery (47 vs 53 cm, P = .002, t test). CONCLUSION: Procedural competency consists of knowledge, technical skills, and attitudes. Knowledge and attitudes can be assessed with other items, such as examinations and observation. Primary care faculty can now use these standards of insertion depth and procedure time when determining technical skill proficiency for their residents in flexible sigmoidoscopy.

Attitude of Health Personnel↗