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Biomedical subjects

T J Morgan

Publications and source records attributed to T J Morgan.

18 recordsLinked to original sources
PubMed1997

Continuous measurement of gut luminal PCO2 in the rat: responses to transient episodes of graded aortic hypotension.

OBJECTIVES: To test the rapidity of a continuous PCO2 measurement system response to brief reductions in gut perfusion from transient episodes of graded aortic hypotension, and to investigate the relationship between the increase in ileal luminal PCO2 and mean aortic pressure during the episodes. DESIGN: Prospective, experimental animal study. SETTING: University research laboratory. SUBJECTS: Adult male Sprague-Dawley rats, weighing 430 to 510 g. INTERVENTIONS: Five Sprague-Dawley rats were anesthetized with intraperitoneal sodium phenobarbital and ventilated with 100% oxygen via tracheostomy to a PaCO2 of 30 to 50 torr (4.0 to 6.7 kPa). Distal aortic pressure was monitored invasively, and a sensor was inserted into the ileal lumen. Luminal PCO2 measurements were recorded every 2 secs. Normal saline was infused at 3 mL/hr, and isoflurane was titrated to a mean aortic pressure of 80 to 100 mm Hg. In each rat, paired 2-min inductions of distal aortic hypotension were induced by digital elevation of an aortic silk sling above the celiac artery to as many as possible of the following pressures (mm Hg): 60, 50, 40, 30, 20, and 10. The experiment was stopped if instability of luminal PCO2 or hypotension persisted through the intervening 8-min recovery periods. MEASUREMENTS AND MAIN RESULTS: One rat completed paired inductions of all six goal aortic pressures. Two rats completed five inductions. One rat completed four inductions, and one rat completed three inductions. The times to onset of luminal hypercapnia and to peak luminal hypercapnia were highly consistent and independent of the degree of hypotension. Onset of hypercapnia was usually detected < 1 min after aortic elevation, but peak luminal hypercapnia occurred approximately 1 min after release of the aortic sling. Regression analysis showed an inverse linear relationship between the maximum increase in luminal PCO2 above baseline and mean aortic pressure during induced hypotension (r2 = .6; p < .001). CONCLUSIONS: Continuous ileal luminal PCO2 measurement by the sensor is rapidly responsive to brief reductions in aortic pressure in a rat model. Maximum luminal PCO2 increase during such perturbations is inversely related to mean aortic pressure.

Animals↗
PubMed1996

Involving health care workers in screening for alcohol problems.

OBJECTIVES: (1) Examine physician and nursing staff compliance with conducting an alcohol screening interview; (2) Compare compliance with the interview with usual physician and nurse assessment of drinking; (3) Examine reasons why drinking information might not be collected. DESIGN: Residents and nurses were taught how to use an alcohol screening interview and were told by the director of residency training or by the Vice-President for Nursing to administer it to all admitted patients. Data on interviewed patients were compared with medical record data on a randomly selected series of 80 patients who were not interviewed. SETTING: Teaching hospital in an urban/suburban community. PATIENTS/PARTICIPANTS: Residents on internal medicine and family practice services; surgical nurses. MEASUREMENTS AND MAIN RESULTS: Compliance with conducting the interview was low (14.7% of residents' admissions; 13.53% of nurses' admissions). Review of the medical records indicated that some alcohol-related information was recorded in most patients' medical records (physicians recorded information on 94% of patients on the teaching services, nurses on the surgical unit recorded alcohol-related information on 71% of patients). Surgeons and surgical residents recorded alcohol-related information on 30% of their patients. Residents were more likely to interview male than female patients, and residents and nurses tended to interview patients with higher GGTP values. CONCLUSIONS: (1) Compliance with administering a standardized alcohol screening interview was low. (2) Nurses, and residents in family practice and internal medicine made some assessment of drinking for most patients. Surgeons assessed drinking in a minority of patients. (3) Expressed reasons for not administering the standardized interview included discomfort with the interview, viewing the interview as too time-consuming, or not part of the usual responsibilities of the nurses or residents. Other possible reasons for the low levels of compliance are discussed.

Admitting Department, Hospital↗
PubMed1996

"Video lottery" and treatment for pathological gambling. A natural experiment in South Dakota.

Four agencies which offer specialized treatment for pathological gambling provided data on the number of inquiries about gambling treatment and the actual number of gamblers treated before, during, and after the shutdown of video lottery in the state of South Dakota. A marked decrease in the number of inquiries and number of gamblers treated was seen during the time the machines were turned off as compared to the time periods when video lottery gambling was available. The results suggest that the accessibility and availability of video lottery machines is an important factor in the number of people being adversely impacted by gambling.

Adult↗
PubMed1995

Siggaard-Andersen algorithm-derived p50 parameters: perturbation by abnormal hemoglobin-oxygen affinity and acid-base disturbances.

The p50 and derived indexes, calculated by using the Siggaard-Andersen algorithm from a single measurement of arterial blood gas tensions and hemoglobin-oxygen saturation, are used to assess tissue oxygen availability in critical illness. We tested the accuracy of the Siggaard-Andersen p50 algorithm over a wide range of pathophysiologic conditions. Blood gases, cooximetry, and calculation of standard and in vivo p50 were performed at multiple saturations, CO2 tensions, and H+ concentrations on blood with normal (standard p50 of 26.1 and 26.7 mm Hg), increased (19.0 and 25.4), and reduced (33.9 and 38.2) hemoglobin-oxygen affinity, as well as on high-affinity blood from two patients with diabetic ketoacidosis (16.7 and 20.8). Log p50 in vivo/pH plots were constructed to determine the Bohr effect. Except in the normal affinity specimens (coefficient of variation < 1.7%), standard p50 values showed high variability (coefficient of variation > 5.9%), with saturation-linked bias and distortion of the Bohr effect. Standard p50 was overestimated by up to 11 mm Hg as saturation approached 97%. Although base deficit correction of the stored specimens (6.9 < pH < 7.1) restored the Bohr effect and improved the accuracy of standard p50 calculations (coefficient of variation = 4.4% and 2.9%), saturation-linked bias persisted. We conclude that Siggaard-Andersen p50 calculations may be misleading when there are disturbances of hemoglobin-oxygen affinity and acid-base balance, owing to changes in shape of the hemoglobin-dissociation curve. When metabolic acidosis occurs with high hemoglobin-oxygen affinity, as can occur in critical illness, indexes derived by the Siggaard-Andersen algorithm on arterial blood may greatly overestimate oxygen availability.

Acid-Base Imbalance↗
PubMed1990

Characterization and developmental expression of the chicken B-G heterodimer.

Monoclonal antibody R7-3 recognized an erythroid specific cell surface molecule with a m.w. of approximately 98 kilodaltons (Kd) under nonreducing conditions and molecules of 40 and 44 Kd under reducing conditions on both embryonic- and adult-derived peripheral RBC. Immunochemical characterization, including limited peptide map analyses of these molecules, provided evidence that mAb R7-3 was recognizing the MHC coded B-G heterodimer. This is the first report of a monoclonal antibody that recognizes the B-G heterodimer. Affinity binding studies suggested that mAb R7-3 preferentially recognized the 44 Kd molecule. Immune depletion analyses demonstrated the presence of a single population of B-G heterodimers. Endoglycosidase-F and neuraminidase digestions suggested that the 44 and 40 Kd molecules contained very little, if any, carbohydrate. B-G heterodimer expression was examined on primitive and definitive RBC during embryonic development. B-G heterodimer expression was not detected on RBC of other avians.

Animals↗
PubMed1989

Chicken transferrin receptor expression during erythroid differentiation and by retrovirus transformed cells.

Antiserum prepared against sucrose gradient purified reticuloendotheliosis virus (REV) recognized the chicken transferrin receptor. Molecules immunoprecipitated from red blood cells (RBC) obtained from embryonic chickens with either the anti-REV reagent or a chicken transferrin immunomatrix were demonstrated to be identical by co-migration in both reducing and nonreducing SDS-polyacrylamide gels and in two-dimensional isoelectric focusing analyses, reciprocal immunodepletion analyses and by peptide mapping. The chicken transferrin receptor was shown to be a 190,000 dalton cell surface membrane molecule consisting of two similar disulfide-bonded subunits of approximately 95,000 daltons. The chicken transferrin receptor was expressed on erythroid cell surface membranes as 95,000 dalton monomers as well as 190,000 dalton dimers. The chicken transferrin receptor was expressed on all differentiation/maturation stages, including mature RBC, of both the primitive and definitive type I erythroid cell series. In adult chickens, the transferrin receptor was expressed by immature erythroid cells in the bone marrow, but not by mature circulating RBC. REV-transformed immature lymphoid cells and avian erythroblastosis virus (AEV)-transformed erythroid cells expressed dimers composed of 95,000 and 110,000 dalton subunits. Comparisons among V8 protease derived peptides from 95,000 dalton transferrin receptors obtained from RBC and REV-transformed lymphoid cells revealed a high degree of homology; however, the 95,000 dalton molecules isolated from REV-transformed lymphoid cells exhibited a 56,000 dalton peptide that was unique. Cloned AEV-transformed erythroleukemia cells induced to differentiate by supplementation of the media with 1 mM butyric acid expressed elevated transferrin receptor levels. Both serological and peptide mapping studies demonstrated the human transferrin receptor on K562 cells and the chicken transferrin receptor to be distinct. However, chicken transferrin was shown to be capable of reacting with the human transferrin receptors on K562 cells.

Animals↗
PubMed1984

Old age and environmental docility: the roles of health, support and personality.

This study assessed the generalizability of Lawton and Simon's environmental docility hyopthesis across three domains of personal competence. The hypothesis was supported, in that a survey of 102 people (aged 60 to 92) found environmental press to be related significantly to adjustment only among less competent individuals in terms of (a) health (i.e., those with poor ratings of health, vision, and hearing, the old-old, and men); access to caregiving networks, (i.e., those who were unmarried, had infrequent contact with children and family, and lived in smaller communities); and (c) personality, (i.e., those with low self-esteem, and external locus of control, low assertiveness, and an inability to deal with the threat of dependency).

Aged↗
PubMed1982

Radiation dosimetry survey of computed tomography systems from ten manufacturers.

Profiles of the absorbed dose delivered throughout cylindrical and anthropomorphic phantoms during single scans by computed tomography systems from ten manufacturers were measured using LiF thermoluminescent dosemeters (TLD) and X-ray therapy verification film. The dose profiles demonstrate that a significant portion of the dose is delivered outside the imaged volume of a single scan. The doses measured in cylindrical Plexiglas phantoms were similar to those measured in anthropomorphic cross sections of tissue substitute materials except near the centre of the thorax section. The film results, obtained using a single calibration curve, agreed with the TLD results to within 25% for most systems.

Absorption↗
PubMed1981

An evaluation of CT systems from ten manufactures.

During the past three years, 23 computerized tomography (CT) machines from ten different manufacturers located in Europe and the USA have been evaluated. Using the same set of phantoms and measurement techniques, performance data have been derived including noise, uniformity of CT numbers, low contrast detectability, spatial resolution, modulation transfer function, effective photon energy and linearity of CT numbers. Thermoluminescent and film dosimetry were used to determine single-slice dose profiles at the periphery and centre of specialized anthropomorphic phantoms. The results of this study are presented in tabular and graphical form together with some general conclusions on their implications.

Brain↗
PubMedDate not supplied

MHC coded B-G homodimer and heterodimer heterogeneity among different chicken lines.

Chicken lines were classified into six distinct groups based on expression of B-G molecules by peripheral red blood cells (RBC). In addition to the previously reported 48 kD subunits of homodimeric B-G molecules, subunits of 60, 40, and possibly 20 kD were detected in certain of the chicken lines. Several of the chicken lines express the previously reported 40 and 44 kD subunits of heterodimeric B-G molecules; however, B21B21 chickens expressed 44 kD subunits only and B5B5 and B13B13 chickens did not express detectable levels of any heterodimeric-related molecules. These studies provide further evidence for the polymorphic nature of the B-G antigens.

Animals↗
PubMedDate not supplied

Energy dependence of correction factors for some Victoreen Model 570 Condensor R-Meter medium-energy chambers.

The energy dependence of each of six models of medium-energy Victoreen 570 Condenser R-Meter chambers was determined by measurement of the exposure correction factors over the diagnostic x-ray beam-quality range (0.4-4.1 mm A1 HVL) for several samples of each model. The results of an analysis of variance performed by model on the correction factors are reported as mean correction factors for the x-ray beams evaluated, with a relative standard error less than 0.8% in all cases. Energy-dependence curves for the six chamber models are given; their use is described.

Calibration↗
PubMedDate not supplied

Energy dependence of correction factors for some low-energy direct-reading pocket dosimeters.

The energy dependence for each of five models of low-energy direct-reading pocket dosimeters was characterized through an examination of the exposure correction factors determined over the diagnostic x-ray range (0.4-4.1-mm Al HVL) for many samples of each model. The results of an analysis of variance performed by model on the correction factors are reported as mean correction factors for the x-ray beams evaluated, the relative standard error being less than 0.8% in all cases. Energy-dependence curves for the dosimeter models are given, and their use is described.

Radiography↗
PubMedDate not supplied

Energy dependence of correction factors for two models of Keithley diagnostic ion chambers.

The energy dependence for each of two models of ionization chambers compatible with the Keithley model 35020 Digital Dosimeter, is determined by measurement of the exposure correction factors determined over the diagnostic x-ray range (0.4--4.9 mm AL HVL) for several for several samples of each model. The results of an analysis of variance performed by model on the correction factors are reported as mean correction factors for the x-ray beams evaluated, with a relative standard error of less than 1% for both cases. Energy-dependence curves for the two chamber models are given, and their use is described.

Evaluation Studies as Topic↗
PubMedDate not supplied

A technique for routine calibration of thermoluminescent dosimeters in the diagnostic energy range.

Four different techniques for calibrating lithium fluoride thermoluminescent dosimeters were compared at two beam qualities in the diagnostic energy range. The techniques included in-air, saturation backscatter, and Bureau of Radiological Health (BRH) test stand geometry with and without an ionization chamber. The results indicate that there are no statistical differences between any of the calibration techniques evaluated. Hence, the technique using the BRH test stand with an ionization chamber is a simple and reproducible calibration procedure which may be used in a routine diagnostic radiology quality assurance program.

Fluorides↗