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Biomedical subjects

C A Lowe

Publications and source records attributed to C A Lowe.

17 recordsLinked to original sources
PubMed2004

A single nucleotide polymorphism identification assay for the genotypic characterisation of Neisseria meningitidis using MALDI-TOF mass spectrometry.

The ability of matrix-assisted laser desorption-ionisation time-of-flight mass spectrometry (MALDI-TOF) to identify virulent clones of meningococci quickly and accurately is investigated. A single nucleotide polymorphism (SNP) within the fumC gene which differentiates between the hypervirulent ET-15 strain and other ET-37 complex strains is used to determine the usefulness of this method. In this study, MALDI-TOF proved to be a fast, effective alternative to traditional DNA sequencing for the identification of an individual nucleotide.

Bacterial Typing Techniques↗
PubMed1994

Studies on the inheritance of repellent tolerances in Aedes aegypti.

Two laboratory strains and 6 inbred strains of Aedes aegypti were tested against deet, ethyl hexanediol, dimethyl phthalate, and Indalone. Reciprocal crosses and backcrosses of 2 inbred strains were tested against deet only. Results obtained were compatible with a quantitative genetic model in which the effects of the factors involved were multiplicative. Certain inbred strains differed significantly from cognate laboratory and/or inbred strains in tolerance to one or more test materials. Heritability in the broad sense (H2) was estimated at 0.05 for deet, 0.22 for ethyl hexanediol, 0.48 for dimethyl phthalate, and 0.51 for Indalone. Partial dominance was observed in the inheritance of tolerance to deet.

Aedes↗
PubMed1986

Pulmonary vascular resistance in the fluorocarbon-filled lung.

Pulmonary vascular resistance was investigated in the fluorocarbon-filled lung in an in situ isolated lung preparation. Lungs were perfused at constant flow (100 ml X min-1 X kg-1) with whole blood from a donor cat. left atrial pressure was held constant at zero pressure. Measurements of pulmonary arterial pressure enabled calculation of pulmonary vascular resistance. Regional changes in pulmonary blood flow were determined by the microsphere technique. During quasi-static deflation over a range of 0-30 mmHg, dependent alveolar pressure was consistently greater for a volume of fluorocarbon than for gas, with each pressure-volume curve for the fluorocarbon-filled lung shifted to the right of the curve for the gas-filled lung. In turn, pulmonary vascular resistance was found to increase linearly as a function of increasing alveolar pressure, independent of the medium in the lung. Thus, for a given volume, pulmonary vascular resistance was consistently greater in the fluorocarbon-filled lung compared with the gas-filled lung. This increase in pulmonary vascular resistance was accompanied by a redistribution of pulmonary blood flow in which blood flow to the dependent region was decreased in the fluorocarbon-filled lung compared with the gas-filled lung. Conversely, the less-dependent regions of the lung received a relatively greater percentage of blood flow when filled with fluorocarbon compared with gas. These findings suggest that pulmonary vascular resistance is increased during liquid ventilation, largely as the result of mechanical interaction at the alveolar-vascular interface.

Analysis of Variance↗
PubMed1984

Liquid ventilation: effects on pulmonary function in distressed meconium-stained lambs.

Seven lambs (0.93 term gestation) were delivered by cesarean section with evidence of meconium in the amniotic fluid, meconium staining, and respiratory distress. The initial arterial blood gas and acid-base status indicated severe hypoxemia and acidosis. Three of these lambs developed pneumothoraces and died on control gas ventilation with positive end expiratory pressure. During the control period (90 min) with ventilatory support, there were no significant alterations in mean arterial oxygen tension (PaO2) and alveolar-arterial oxygen gradient (A-aDO2). The initial hypercarbia and acidosis were effectively controlled and corrected using mechanical ventilation and bicarbonate infusion. Fifteen min after the onset of fluorocarbon ventilation mean PaO2 significantly increased and A-aDo2 decreased. After 90 min of fluorocarbon ventilation, lambs were returned to gas ventilation. During this recovery period, PaO2 and A-aDo2 remained significantly improved compared with control gas values. Dynamic lung compliance increased, alveolar and peak tracheal pressure decreased and inspiratory elastic work of breathing decreased during liquid ventilation.

Animals↗
PubMed1983

The effects of liquid ventilation on cardiopulmonary function in preterm lambs.

The effects of fluorocarbon ventilation on cardiopulmonary function were studied in 8 preterm lambs, 132-136 days gestation. After mechanical ventilation with 100% oxygen (control period), the lambs were ventilated with fluorocarbon (PIO2 = 622 torr). The liquid was then removed from their lungs and gas ventilation resumed (recovery period). During normothermic liquid breathing the alveolar-arterial O2 gradient (A-a DO2) decreased (P less than 0.01) from control by 154 torr and remained decreased (P less than 0.05) by 85 torr during recovery. Dynamic lung compliance (CL) increased 50% (P less than 0.05); PaO2 increased 50% (P less than 0.05); and PaCO2 decreased 29% (P less than 0.01) as compared to control values. The change in A-a DO2 and PaO2 before and after liquid ventilation was correlated (r = 0.79 and P less than 0.01) with control CL. There was a gradual decrease (P less than 0.01) in mean arterial pressure from 62 +/- 5.4 torr (control) to 53,1 +/- 9,3 torr (recovery); however, there were no significant alterations in mean central venous pressure, heart rate, or mean electrical axis.

Animals↗
PubMed1981

Increased pulmonary vascular resistance during liquid ventilation.

The effect of liquid ventilation on pulmonary vascular resistance was studied in an isolated cat lung preparation in situ. Lungs were perfused with whole blood from a donor cat at a constant flow of 100 ml . min-1 kg-1. Pulmonary arterial venous pressures were measured, and pulmonary vascular resistance calculated during gas ventilation (control) and ventilation with fluorocarbon, FC-80. During control ventilation at a mean tidal volume (VT) of 28 +/- 1 (SEM) ml and lung volume of 108 +/- 8 (SEM) ml, pulmonary vascular resistance was 0.07 +/- 0.01 (SEM) PRU. During liquid ventilation at similar lung volumes, pulmonary vascular resistance increased by 62% to 0.12 +/- 0.03 (SEM) PRU (P less than 0.05). At greater liquid lung volumes reflecting optimum CO2 elimination, pulmonary vascular resistance increased by 115% over control values to 0.15 +/- 0.01 (SEM) PRU (P less than 0.005). These data demonstrate significant alterations in pulmonary circulation during liquid ventilation, and suggest that further studies should be completed before hyperbaric applications in human can be considered.

Animals↗
PubMed1980

Children's use of the discounting principle: a perceptual approach.

The present study introduced a perceptual analogue technique in a developmental investigation of the discounting principle. Subjects watched animated films depicting the simultaneous movements of two triangles toward a goal--one that was pushed by an external object (facilitative cause present) and one that was not (faciliatative cause absent). Although college students understood the discounting principle (i.e., they perceived that the nonfacilitated triangle was more intrinsically motivated than the facilitated object), kindergarteners, second graders, and fourth graders surprisingly did not. However, because many children (mis) interpreted the "push" as an aversive stimulus, a second experiment illustrated a sequence in which one of two triangles was "carried" toward a goal. For this version, subjects in Grades 2, 4, and 6, and in college all made the discounting-consistent choice, and kindergarteners tended to do the same (p < .15). Age differences thus emerged only in subjects' ability to explain their responses. From these results, the development of the multiple sufficient cause schema is discussed, and methodological implications of the animated film technique are noted.

Adult↗
PubMed1979

On the development of the augmentation principle: a perceptual approach.

Previous research in the development of causal schemata has relied upon verbal descriptions of behavior to convey causally relevant information. In the present study, however, a perceptual analogue of Kelley's augmentation principle was created in animated films depicting the movements of 2 objects toward a goal--1 which overcame an obstacle (inhibitory cause present) and 1 which did not (inhibitory cause absent). Both forced-choice and scalar measures indicated that kindergarten, second, and fourth graders all perceived greater motivation (internal facilitative cause) in the inhibited than noninhibited object, but that age differences emerged in the ability to explain these responses. In a second experiment, the 2 target objects were inhibited by obstacles of different sizes. For this quantitative version of the principle, age differences emerged for all measures; fourth graders and most second graders responded in accord with augmentation-principle predictions. These results were compared with the earlier findings that kindergarten and fourth-grade children did not understand this principle. The contrasting methods of stimulus presentation were discussed and implications of this technique for attribution research were noted.

Child↗