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Biomedical subjects

R C Carter

Publications and source records attributed to R C Carter.

At least 19 recordsLinked to original sources
PubMed2000

Ex vivo delineation of placental angioarchitecture with the microbubble contrast agent Levovist.

OBJECTIVE: The aim of this study was to delineate placental vasculature with the microbubble contrast agent Levovist (99.9% galactose and 0.1% palmitic acid; Schering AG, Berlin, Germany), with the ultimate goal of delineating placental vascular anatomy in utero. STUDY DESIGN: A placental lobule from each of 11 term human placentas was perfused on the fetal side of the circulation under physiologic conditions. Randomly assigned dose-concentration combinations of Levovist were administered through a chorionic artery into the corresponding placental lobule, and the resultant echoenhancement with power Doppler imaging was recorded for digital analysis. Interplacental variability was corrected for by averaging the results of three injections at each dose-concentration combination. RESULTS: Echoenhancement was seen at all dose-concentration combinations in the injected lobule but not in adjacent control lobules. The three dose-concentration combinations that achieved optimal maximal integrated intensity and duration of action for both chorionic vessel and villus enhancement were 100 microL/kg of 400-mg/mL Levovist, 200 microL/kg of 400-mg/mL Levovist, and 400 microL/kg of 200-mg/mL Levovist. CONCLUSION: Microbubble contrast injection into the fetal vasculature enabled power Doppler imaging echoenhancement both in chorionic vessels and within the villus tree. We speculate that fetal injection of contrast agent may be applied to the delineation of placental lesions or areas of interfetal transfusion, although its applicability will be hindered by the need for fetal blood sampling.

Blood Vessels↗
PubMed1999

Risk factors for seizure-related motor vehicle crashes in patients with epilepsy.

OBJECTIVE: We identified clinical risk factors for seizure-related motor vehicle crashes in patients with epilepsy. BACKGROUND: Current US laws permit epilepsy patients with controlled seizures to drive. These laws attempt to balance the important economic and social value of driving with the risk to public safety from seizure-related crashes. Various clinical factors are considered in these laws, particularly the seizure-free interval. Driving restrictions range from 3 to 18 months, however, and studies have not established how these various seizure-free intervals and other clinical factors influence the risk for seizure-related motor vehicle crashes. METHODS: We performed a retrospective case-control study to determine the influence of clinical risk factors associated with seizure-related motor vehicle crashes. Both "case" and "control" patients had epilepsy, drove, and were from the same clinic, but the cases differed in having had seizure-related crashes. RESULTS: Fifty patients with epilepsy who crashed during seizures and 50 matched control patients were compared. Factors that significantly decreased the odds of patients with epilepsy having motor vehicle crashes due to seizures were: long seizure-free intervals, reliable auras, few prior nonseizure-related accidents, and having had their antiepileptic drugs (AEDs) reduced or switched. For example, patients who had seizure-free intervals > or = 12 months had a 93% reduced odds for crashing compared to patients with shorter intervals. Other findings were: 25% of patients had more than one seizure-related crash and 20% had missed an AED dose just prior to their crash. The majority (54%) of patients who crashed were driving illegally, with seizure-free intervals shorter than legally permitted. CONCLUSION: Seizure-free intervals, the presence of reliable auras, AED therapy modifications, and a history of nonseizure-induced crashes should be considered when counseling patients with epilepsy on driving and when formulating driving regulatory policy. Case control studies of crashes due to seizures can help in assessing and monitoring such risks.

Accidents, Traffic↗
PubMed1999

Is phase-specific, community-oriented treatment of early psychosis an economically viable method of improving outcome?

OBJECTIVE: The Early Psychosis Prevention and Intervention Centre (EPPIC) provides a comprehensive 'real-world' model of early intervention to young people experiencing an emerging psychotic disorder. A prospective study has already provided evidence of improved clinical outcome at 12 months after entry. The present study examined whether the service was also cost-effective. METHOD: A cost-effectiveness analysis compared EPPIC with its immediate precursor service, from the perspective of the government funding agency. Only direct costs were included. RESULTS: EPPIC proved to be more cost-effective. The weighted average cost per patient for the first 12 months was cheaper (by $AUD 7110 per patient), while treatment outcomes were superior. The savings were due to the marked reduction in in-patient costs outweighing substantial increases in the costs of community care. CONCLUSION: These results, while encouraging in terms of the further development of integrated, phase-specific intervention programmes for early psychosis, are not conclusive, and further research is required.

Adult↗
PubMed1995

Evaluation of a series of N-alkyl benzomorphans in cell lines expressing transfected delta- and mu-opioid receptors.

Transfection of individual opioid receptors in Chinese hamster ovary (CHO) cells provides a pure, homogeneous population of receptors for screening drug candidates, and an alternative to the use of selective ligands. To evaluate the potential of this system, we chose a series of (-)-5,9 alpha-dimethyl-2-hydroxy-N-substituted-6,7-benzomorphans, for which the receptor selectivity and in vivo activity had been characterized recently, and tested them in CHO cells stably transfected with either the rat delta-opioid receptor or the mouse mu-opioid receptor. [3H]Diprenorphine was used to measure opioid receptors in P2 membrane preparations. A Bmax of 7.58 +/- 0.8 pmol/mg protein and a Kd of 0.42 +/- 0.04 nM was obtained in the mu-opioid receptor expressing cell line used in these studies. In addition, [3H]naltrindole was used to confirm the delta-specificity of the cloned receptor. Both compounds gave a Bmax of 1.2 pmol/mg in the CHO cells expressing the rat delta-opioid receptor. Displacement assays were performed with eleven (-)-N-alkyl-benzomorphans in the absence and presence of 150 mM NaCl, as well as known delta- and mu-selective agonists. Sodium reduced agonist affinity in the transfected cell lines. The benzomorphan compounds displayed a range of affinities in the mu- and delta-opioid receptor expressing cell lines. Good correlations were found between their affinities at the cloned mu- and delta-opioid receptors and those in rat brain and monkey cortex (r2 from 0.73 to 0.89, P < 0.001). Comparative analysis of Ki values with in vivo potency in the mouse tail flick test indicated a high degree of correlation between antinociception and affinity in the mu-opioid receptor cell line (r2 = 0.83, p < 0.0001). Lesser correlations were found between antinociception in the mouse and affinity at the rat mu-opioid receptor (r2 = 0.6610) and at the monkey mu-opioid receptor (r2 = 0.695). In sum, these studies indicate that the cell lines expressing the cloned mu- and delta-opioid receptors are appropriate models for determining the binding affinities of this class of opioid compounds. The diminishing correlations found between species when comparing in vitro and in vivo activity suggest that caution should be taken when extrapolating binding data to pharmacological activity among species.

Animals↗
PubMed1986

Performance Evaluation Tests for Environmental Research (PETER): evaluation of 114 measures.

The goal of the Performance Evaluation Tests for Environmental Research (PETER) Program was to identify a set of measures of human capabilities for use in the study of environmental and other time-course effects. 114 measures studied in the PETER Program were evaluated and categorized into four groups based upon task stability and task definition. The Recommended category contained 30 measures that clearly obtained total stabilization and had an acceptable level of reliability efficiency. The Acceptable-But-Redundant category contained 15 measures. The 37 measures in the Marginal category, which included an inordinate number of slope and other derived measures, usually had desirable features which were outweighed by faults. The 32 measures in the Unacceptable category had either differential instability or weak reliability efficiency. It is our opinion that the 30 measures in the Recommended category should be given first consideration for environmental research applications. Further, it is recommended that information pertaining to preexperimental practice requirements and stabilized reliabilities should be utilized in repeated-measures environmental studies.

Adolescent↗
PubMed1983

Performance Evaluation Tests for Environmental Research (PETER): Moran and computer batteries.

This investigation was directed at evaluating nine cognitive ability tasks for repeated measures applications and inclusion in the Performance Evaluation Tests for Environmental Research (PETER) battery. In the first study, five tasks from the Moran Battery, which were adapted from the French kit of factor-referenced tests, were administered to 18 subjects daily for 13 workdays. In the second study, four tasks from the Carter and Sbisa Computer Generated Battery were administered daily to 17 subjects (12 in common with first study) for 15 workdays. Examination of the means, variances, and interday reliabilities, together with factor analysis of the cross-task correlations, led to the recommendation of four tasks. Tasks recommended for repeated measures applications were Vertical Addition, Perceptual Speed, Grammatical Reasoning, and Flexibility of Closure.

Adult↗
PubMed1982

Visual search with color.

Three experiments were conducted to discover how rapidly people can find a particular target when they know the color of the target. The subjects searched for specific-colored three-digit numbers among other three-digit numbers on a circular display screen. Three factors had profound effects on search speed. Search time increased dramatically (and approximately linearly) as the number of display items of the target's color increased from one to all of the items on the display. Search time also increased with the number of items not of the target's color (background items), if the color of those background items was sufficiently similar to that of the target. If the color of those background items was dissimilar to that of the target, then the background items had no effect. An effect of patterned versus random placement of target-colored items was also demonstrated.

Color Perception↗
PubMed1981

Color and conspicuousness.

The principle that things are easier to find if they contrast with their environment is expressed quantitatively. Two indices of conspicuousness, relative fixation rate and search time, are shown to be related to the color difference between the target and background objects. The color difference equations used are CIELAB, CIELUV, and the Judd modification of the index of fading. None of the equations is superior to the others. Furthermore, neither Judd's modification nor Semmelroth's adjustment accounts for effects of surround lightness. It is suggested that color difference be used as a tool for design and evaluation of visual displays, for construction of color codes to optimize search time, and as a generalization of chromatic contrast in psychophysical research.

Adolescent↗
PubMed1976

Gap junctions in thyroid epithelium of the rat.

Gap junctions were observed on the lateral plasma membrane of the typical thyroid epithelial cell in freeze-fracture preparations of rat thyroid gland. The gap junctions were 0.1 to 0.4 mum in diameter and were composed of closely packed, approximately 80 nm particles. They were located from 1 to 6 mum from the apical surface of the cell.

Animals↗
PubMed1975

Changes in tight junctions of thyroid epithelium with changes in thyroid activity.

The morphology of the tight junction of rat thyroid epithelium was examined in freeze-fractured material fixed in glutaraldehyde and briefly glycerinated. In normal thyroids the overall appearance of this junctional specialization resembled that of other cell types in many respects. Short-term changes in thyroid activity and hypophysectomy for 3 wk did not obviously affect the appearance of tight junctions. Feeding of the goitrogen, thiouracil, which stimulates secretion of thyroid-stimulating hormone, resulted in the appearance of some very narrow and some very wide, tight junctions or sometimes junctions with both wide and narrow regions within the same cell.

Animals↗