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Biomedical subjects

E C Crawford

Publications and source records attributed to E C Crawford.

At least 19 recordsLinked to original sources
PubMed1998

Evaluation of regional differences in right ventricular systolic function by acoustic quantification echocardiography and cine magnetic resonance imaging.

BACKGROUND: Accurate quantitative evaluation of right ventricular (RV) function has been limited by its complex structural geometry. Although embryological and anatomic observations suggest that the RV is composed of 2 distinct components, the RV sinus and infundibulum, most studies on RV dimensions and function viewed it as a single chamber. This study was designed to determine the volumes, relative contribution to global systolic function, and temporal course of contraction and relaxation of the RV sinus and infundibulum. METHODS AND RESULTS: Thirty-one individuals without heart disease (aged 1 month to 17 years, 16 boys and 15 girls) participated in this study. Instantaneous area over time, its derivatives, and the temporal course of contraction and relaxation were studied by acoustic quantification echocardiography and phonocardiography in 20 individuals. Global and regional RV volumes and ejection fraction were determined by cine MRI in 11 individuals. The RV sinus made up 81+/-6% of the combined RV end-diastolic volume and 87+/-4% of the combined stroke volume. The infundibulum accounted for the remaining 19+/-6% and 13+/-4%, respectively (P<0.0001). Compared with the infundibulum, the extent of RV sinus fiber shortening was significantly greater: for ejection fraction (56+/-11% versus 38+/-13%, P<0.001), fractional area change (42+/-14% versus 28+/-9%, P<0.0001), and dA/dt (27+/-17% versus 13+/-6%, P<0.0001). Analysis of temporal course of contraction and relaxation (expressed as percentage of the cardiac cycle to adjust for differences in heart rate) showed that the infundibulum follows the RV sinus: onset of contraction 53%+/-14 versus 19+/-11% of systole, time to peak systole 115+/-16% versus 97+/-19% (P< or =0.01), indicating a peristalsis-like pattern of contraction and relaxation. CONCLUSIONS: The results of this study demonstrate significant regional differences between the sinus and infundibulum components of the RV with regard to contribution to stroke volume, extent of fiber shortening, and sequence of mechanical activation. These data from normal individuals can be used in future research on RV function in pathological conditions.

Adolescent↗
PubMed1998

Autism and maternally derived aberrations of chromosome 15q.

Of the chronic mental disabilities of childhood, autism is causally least well understood. The former view that autism was rooted in exposure to humorless and perfectionistic parenting has given way to the notion that genetic influences are dominant underlying factors. Still, identification of specific heritable factors has been slow with causes identified in only a few cases in unselected series. A broad search for genetic and environmental influences that cause or predispose to autism is the major thrust of the South Carolina Autism Project. Among the first 100 cases enrolled in the project, abnormalities of chromosome 15 have emerged as the single most common cause. The four abnormalities identified include deletions and duplications of proximal 15q. Other chromosome aberrations seen in single cases include a balanced 13;16 translocation, a pericentric inversion 12, a deletion of 20p, and a ring 7. Candidate genes involved in the 15q region affected by duplication and deletion include the ubiquitin-protein ligase (UBE3A) gene responsible for Angelman syndrome and genes for three GABA(A) receptor subunits. In all cases, the deletions or duplications occurred on the chromosome inherited from the mother.

Adolescent↗
PubMed1998

FISH analysis of a complex chromosome rearrangement involving nine breakpoints on chromosomes 6, 12, 14 and 16.

We report the prenatal diagnosis of an apparently balanced de novo complex chromosome rearrangement (CCR) which involved nine breakpoints on four different chromosomes. Fluorescence in situ hybridization (FISH) and spectral karyotyping (SKY) were performed as an adjunct to G-banding for characterization of the abnormal chromosomes. The 22-week female fetus showed minor dysmorphic features including dolichocephaly, broad fingernails, tibial bowing, clubfoot, thoracolumbar scoliosis and hypoplastic toenails. Autopsy revealed gall-bladder hypoplasia and an atrial septal defect. Chromosome analysis of fetal tissue confirmed the presence of the complex rearrangement.

Abnormalities, Multiple↗
PubMed1991

The face--an orthodontic perspective.

Orthodontic treatment has the capacity of effecting many changes to patients. For better or worse, our society places a high value on physical beauty, and straight teeth make a positive contribution to facial attractiveness. We must think of our patients more as human faces rather than a set of malaligned teeth. Along with our capability of improving facial features we have an equal responsibility to avoid a deterioration. Providing basic guidelines are followed in patient assessment, treatment planning and treatment execution, orthodontic services can provide an enhancement to the faces and lives of our patients.

Cephalometry↗
PubMed1990

A review of the management of anterior open bite malocclusion.

Anterior openbite (AOB) malocclusion is considered one of the most demanding challenges for the orthodontist, as occlusal correction is difficult, facial aesthetics may be unsatisfactory and the incidence of relapse is high. A retrospective cephalometric study of 19 consecutively treated AOB patients is presented. The follow-up ranged from 12 to 48 months. Several case reports are included to demonstrate a contemporary approach combining orthodontic treatment and orthognathic surgery. The results indicate that overbite was maintained with good vertical skeletal stability. Anteroposterior position was less stable. Posterior facial height was maintained or decreased, and there was no evidence of postsurgical maxillary incisor movement. It is concluded that occlusal stability and clinical success may be anticipated when certain criteria are adhered to in all phases of treatment, and that a coordinated surgical-orthodontic treatment approach currently offers the best chance of attaining occlusal stability, improved function and satisfactory aesthetics.

Adolescent↗
PubMed1986

Elevation of the panting threshold of the desert iguana, Dipsosaurus dorsalis, during dehydration: potential roles of changes in plasma osmolality and body fluid volume.

Dehydration of the desert iguana, Dipsosaurus dorsalis, resulted in a progressive elevation in the magnitude of the skin temperature necessary to elicit thermal panting (i.e., the panting threshold). Panting threshold increased from 43.4 +/- 0.8 degrees C at 100% initial body weight (IBW) to 45.4 +/- 1.2 degrees C at 90% IBW to 45.7 +/- 0.9 degrees C at 80% IBW. Plasma osmolality showed no significant change with dehydration to 80% IBW. Changes in plasma osmolality, whether induced by NaCl or non-ionic sucrose loading, had a significant impact on panting threshold. Increasing plasma osmolality resulted in an elevation of panting threshold while decreasing plasma osmolality resulted in lower panting thresholds. Decreasing body fluid volume by exsanguination of 1 ml whole blood/100 g body weight resulted in a mean increase in panting threshold by 0.7 +/- 0.2 degrees C. Volume loading with 160 mM NaCl (approximately isosmotic) had no significant effect on panting threshold. These data suggest that plasma osmolality and decreases in body fluid volume may be potent modulators of panting threshold during periods of water deprivation. However, at least in desert iguanas, increases in plasma osmolality would not appear to be an important factor in the elevation of panting threshold during dehydration to 80% IBW.

Animals↗
PubMed1985

Control of panting in the desert iguana: roles for peripheral temperatures and the effect of dehydration.

Although it is generally held that panting is a physiological mechanism for the regulation of brain temperature during heat stress, a number of studies have pointed to the importance of peripheral input for the initiation of the panting response in a variety of animals. By presenting ambient heat loads of 47 degrees, 54 degrees, 58 degrees, and 65 degrees C, and measuring skin, ear and core temperatures of the desert iguana, Dipsosaurus dorsalis, at the onset of panting, we found that the skin temperature at panting onset was independent of ambient heat load. This suggests that skin (peripheral) temperature is the body temperature on which the central thermoregulatory center cues to initiate thermal panting. Peripheral temperature control of panting was retained when the plasma osmolality of the desert iguana was increased by 100 mOsm/kg H2O to simulate dehydration. Dehydration to 80% initial body weight (IBW) resulted in a progressive increase in panting threshold (skin) from 42 degrees C for untreated lizards to 42.5 degrees C at 90% IBW to 43.3 degrees C at 80% IBW. Injection of 80% IBW lizards with a volume of 10 mM NaCl equivalent to weight loss resulted in a decrease in panting threshold to 40.8 degrees C. Injection with 1% body weight 3000 mM NaCl produced a dramatic increase in panting threshold to 45.9 degrees C. These data suggest that the desert iguana responds to dehydration by elevating panting threshold, thus promoting water conservation. These data also suggest that changes in plasma osmolality may be involved in the "setting" of panting threshold.

Animals↗
PubMed1982

Hatching of amphibian embryos: the physiological trigger.

Marbled salamander embryos hatch in water if the environmental oxygen pressure is 86 torr or less, but do not hatch if the environmental oxygen pressure is equivalent to that of air. Under hypoxic conditions, embryos hatch in aqueous and nonaqueous media with equal success. Increasing carbon dioxide pressure does not induce hatching, but does decrease the time to hatching by altering environmental pH.

Ambystoma↗
PubMed1981

Respiratory water loss in camels.

Rates of oxygen consumption and respiratory water loss were studied in camels that were exposed to desert heat and water deprivation. We found that changes in body temperature are accompanied by considerable changes in respiratory water loss. Body temperature fluctuations are greatest in dehydrated camels (up to 7 degrees C), and in these the respiratory water loss might vary from abut 0.06 to 1.2 g/min. The respiratory frequency varied from about 4 to 28 min-1, while the metabolic rate varied less than twofold. The lowest values for respiratory water loss can be explained by the exhalation of air at temperatures far below body temperature, and, in addition, removal of water vapour from the exhaled air, resulting in exhalation of air at less than 100% relative humidity.

Animals↗
PubMed1975

Kinetics of inert gas equilibration in an exclusively skin-breathing salamander, Desmognathus fuscus.

Characteristics of cutaneous gas exchange in amphibians were studied by analysis of the equilibration kinetics of an inert test gas in salamanders which have neither lungs nor gills. Specimens of the common dusky salamander (Desmognathus fuscus, Plethodontidae, Urodela), average body mass 6.1 g were equilibrated with 20% chlorodifluoromethane (Freon 22) in oxygen. The time course of subsequent elimination of Freon 22 into atmospheric air was more rapid in living than in dead animals. This difference was attributed to convective transport by blood flow. Several alternative models were proposed, providing a basis for quantitative analysis of the data. All models yielded similar values for convective conductance due to blood flow. In order to calculate blood flow therefrom, a simplified circulation model based on anatomical evidence was used: the cardiac output is in part directed to the skin, subserving gas exchange with the environment, and in part to the internal organs; the blood returning from both skin and internal organs is mixed before reaching the heart. Depending on assumptions regarding the model and the partitioning of blood flow to the skin and to internal organs, the following range of values was calculated from the experimental data: cardiac output, 85-195 mul/(min-g body mass); cutaneous blood flow, 27-63 mul/(min-g body mass). Due to inherent assumptions these values must be considered minimum estimates.

Animals↗