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Biomedical subjects

J C Taylor

Publications and source records attributed to J C Taylor.

At least 19 recordsLinked to original sources
PubMed1994

Generating hypotheses about the function of student problem behavior by observing teacher behavior.

We examined whether, as predicted by research on child effects, we could generate hypotheses about the function of student problem behavior by observing the amount of attention teachers provided to students. In the first phase of the study, we observed the amount of attention teachers distributed among small groups of students who exhibited problem behavior in individual or small-group instructional settings (problem behavior presumably maintained by attention or escape). Based on the amount of attention each student received, we generated hypotheses about the function of his or her problem behavior. In the second phase of the study, we determined the accuracy of these predictions by conducting a brief functional assessment with each student. Results confirmed that, for 14 of the 15 students, we were able to generate accurate hypotheses about the function of their problem behavior. These results suggest the potential efficacy of using the amount of attention teachers distribute among groups of students to generate empirically based hypotheses about the function of student problem behavior maintained by attention and/or escape. These results also illustrate the efficiency of this procedure; by observing teacher behavior, we were able to generate hypotheses about the function of problem behavior for several students at one time.

Attention↗
PubMed1992

The effect of auxiliary conditions on intestinal unstirred layer diffusion modelled by numerical simulation.

Estimation of intestinal unstirred layer thickness usually involves inducing transmural potential difference changes by altering the content of the solution used to perfuse the small intestine. Osmotically active solutes, such as mannitol, when added to the luminal solution diffuse across the unstirred water layer (UWL) and induce osmotically dependent changes in potential difference. As an alternative procedure, the sodium ion in the luminal fluid can be replaced by another ion. As the sodium ion diffuses out of the UWL, the change in concentration next to the intestinal membrane alters the transmural potential difference. In both cases, UWL thickness is calculated from the time course of the potential difference changes, using a solution to the diffusion equation. The diffusion equation solution which allows the calculation of intestinal unstirred layer thickness was examined by simulation, using the method of numerical solutions. This process readily allows examination of the time course of diffusion under various imposed circumstances. The existing model for diffusion across the unstirred layer is based on auxiliary conditions which are unlikely to be fulfilled in the same intestine. The present simulation additionally incorporated the effects of membrane permeability, fluid absorption and less than instantaneous bulk phase concentration change. Simulation indicated that changes within the physiologically relevant range in the chosen auxiliary conditions (with the real unstirred layer length kept constant) can alter estimates of the apparent half-time. Consequently, changes in parameters unassociated with the unstirred layer would be misconstrued as alterations in unstirred layer thickness.

Gastrointestinal Contents↗
PubMed1992

Severe problem behaviors related to social interaction. 1: Attention seeking and social avoidance.

Studies concerning the functional analysis of severe problem behaviors have suggested that it is important to identify the different categories of stimuli that control problem behavior because each has unique treatment implications. The present study explored the differential effects of adult attention on the severe problem behaviors of two groups of children with developmental disabilities. A third group of nonproblem children was examined for comparison purposes. Children participated in three experimental conditions in which the level of adult attention was manipulated: noncontingent high attention, noncontingent low attention, and contingent attention. Results validated the existence of two groups of children who differed as to their social orientation: (a) One group of children commonly initiated social interactions and was most likely to exhibit problem behaviors under conditions of low adult attention, and (b) the other group of children rarely initiated social interactions and exhibited frequent problem behaviors under conditions of high adult attention. Implications of these data for escape and attention theories of child problem behavior are discussed, as are the applied implications for reinforcer assessment and teaching strategies.

Attention↗
PubMed1992

Severe problem behaviors related to social interaction. 2: A systems analysis.

The effects of problem behavior displayed by two groups of children with developmental disabilities was investigated. One group of children exhibited problem behavior under conditions of low adult attention and was referred to as the attention-seeking or AS behavior profile group. A second group of children exhibited problem behavior under conditions of high adult attention and was referred to as the socially avoidant or SA behavior profile group. A third group of nonproblem children (NP) was examined for comparison purposes. Pairs of children were placed in a teaching situation, and the effects of child problem behavior upon adult instructional behavior were measured. Results indicated that child behavior affected adult behavior and that different child behavior profiles affected adults differentially. Adults responded to the problem behaviors of the AS behavior profile group by increasing attention, providing higher levels of physical contact, and presenting academic tasks that required continuous adult-child interaction. Conversely, the same adults responded to the problem behaviors of the SA behavior profile group by reducing attention, providing lower levels of physical contact, and presenting academic tasks that required little adult-child interaction. The data indicated that these child effects were powerful, immediate, and durable. Theoretical implications concerning reciprocal social influence and the operant theory of child problem behavior are discussed. Applied implications concerning treatment selection and maintenance are also explored.

Adult↗
PubMed1992

Treatment of open fractures of the tibial shaft with the use of interlocking nailing without reaming.

Fifty open fractures of the tibial shaft that were treated with débridement and interlocking nailing without reaming were followed for an average of twelve months. Most of the fractures were the result of high-energy trauma, and 68 per cent of the fracture wounds were grade III. Forty-eight (96 per cent) of the fifty fractures united at an average of seven months; there were no malunions. There were four infections (8 per cent), all at the sites of grade-III fractures. Locking screws broke in five tibiae (10 per cent), but the breakage did not result in a loss of reduction. Three nails broke, two at the sites of ununited fractures and one at the site of a healed fracture. These results are comparable with, or better than, those obtained with other forms of fixation, including immobilization with a cast, unlocked intramedullary nailing, and external fixation.

Adolescent↗
PubMed1992

Correlations between laser flare measurements and anterior chamber protein concentrations.

The laser flare cell meter quantifies anterior chamber (AC) protein (flare) by measuring light scattering of a helium-neon laser beam in the AC. The relationship between photon count and protein concentration both in vitro and in vivo was assessed. The reproducibility of the in vitro photon count measurements was 7.3%. There was a significant linear relationship between photon count and the concentration of both albumin (r = 1.0, P = 0.0001) and immunoglobulin G (IgG, r = 0.99, P = 0.0001) in vitro, but the linear-regression formulas were different with greater light scattering by IgG than by albumin at the same concentration. Laser flare measurements were done on 22 patients (12 normal eyes, 5 eyes with Fuchs' heterochromic cyclitis, and 5 uveitic eyes) before cataract surgery. Aqueous humor obtained from these patients by paracentesis was analyzed for total protein, albumin, and IgG concentration. There was a significant linear relationship (r = 0.88, P = 0.0001) between the laser flare value (range, 5.8-107.8 photons/msec) and the total aqueous protein concentration (range, 14-388 mg/dl). Use of an in vitro albumin calibration curve to convert photon count into protein concentration was found to overestimate the actual protein concentration. This overestimation was slight in normal eyes and increased with increased blood-aqueous barrier breakdown. The use of such a calibration curve therefore is not appropriate in studies on diseased eyes. The authors recommended that laser flare results be expressed in either photons per milliseconds or converted into an equivalent protein concentration using a calibration curve based on actual AC protein measurements.

Aged↗
PubMed1991

Inhibition by Ro 31-6930 of agonist and allergen induced bronchoconstriction in anaesthetised guinea-pigs and cats.

Ro 31-6930, a potent smooth muscle relaxant from the novel class of potassium channel openers, has been compared with BRL 38227, salmeterol and theophylline in a range of models of airway function. Ro 31-6930 relaxed isolated tracheal muscle from sensitised guinea-pigs which had been contracted by ovalbumin and was equipotent with salmeterol in inhibiting antigen-induced bronchospasm in anaesthetised, sensitised guinea-pigs. In both anaesthetised guinea-pig and cat, Ro 31-6930, BRL 38227 and theophylline were more potent against 5-HT evoked increases in lung resistance than they were on falls in dynamic compliance. Although salmeterol had equivalent activity on both parameters it is unlikely that the small difference seen with the other compounds reflect a preferential effect on large airways. In addition, Ro 31-6930 was an effective bronchodilator when given by inhalation to the anaesthetised guinea-pig. In view of the protective activity of Ro 31-6930 against antigen challenge in the sensitised guinea-pig and its potency in relation to other bronchodilators, it is considered that compounds which relax airway smooth muscle by the opening of plasmalemmal potassium channels may have a role in the treatment of asthma.

Aerosols↗
PubMed1991

Mechanical characterization of femoral interlocking intramedullary nailing systems.

The most important mechanical characteristics of a nailing system are related to its stiffness (rigidity) and strength. This study evaluates the properties of three commercially available interlocking intramedullary nail systems using standardized test methods. An understanding of the mechanical properties along with the clinical data will assist the surgeon in choosing the optimum implant. Testing indicates that the bending strength and stiffness of the Grosse & Kempf, the AO/ASIF Universal, and the Russell-Taylor interlocking intramedullary nail designs are comparable. It is therefore not surprising that all of these nail systems have excellent clinical results. However, the nonslotted design is approximately 30 times more resistant to torsional loading than either the partially slotted design of the Grosse & Kempf nail or the fully slotted design of the AO/ASIF nail. The clinical relevance of the torsional values may not be known until a long-term comparison of the complication rates for these different systems is available. Analysis of screw design reveals a tradeoff in bending strength when compared to amount of bone purchase. The bending strength of fully threaded screws (allowing bicortical fixation) is less than that of partially threaded screws (allowing only unicortical fixation), which shows that for the implants tested, increased bone purchase requires a compromise in strength for similar sized screws.

Biomechanical Phenomena↗
PubMed1991

Booster response to acellular pertussis vaccine in children primed with acellular or whole cell vaccines.

Few data are available on the effect of a booster dose of acellular pertussis vaccine in children primed as infants with acellular vaccine. We administered acellular pertussis vaccine (ACV) at 19 months to children immunized in infancy with ACV or whole cell vaccine. Forty-one infants had been randomly assigned to receive either ACV or whole cell vaccine at 2, 4 and 6 months of age. Antibody titers to pertussis toxin and filamentous hemagglutinin were significantly higher in ACV than whole cell vaccine recipients at 7 months; at 15 months antibody to filamentous hemagglutinin (but not pertussis toxin) remained significantly higher among those receiving ACV. At 19 months all 41 children received an ACV booster. Local and systemic reactions were few and minor and were equally distributed between the two groups. All children responded to booster with significant increases in antibody; these increases tended to be greater for those having been primed with ACV. ACV booster immunization appears safe and immunogenic, regardless of the vaccine given for primary immunization.

Age Factors↗
PubMed1991

Antibodies to endothelial cells in systemic lupus erythematosus: a potential marker for nephritis and vasculitis.

Using an ELISA, anti-endothelial cell antibodies (AECA) have been found in sera obtained at the time of renal biopsy in 46 out of 57 patients (81%) with systemic lupus erythematosus (SLE) and nephritis (mean binding index (BI) = 84% +/- 52.8) compared with 22 out of 50 SLE patients (44%) without nephritis (mean BI = 45% +/- 35.9). Seventy normal human sera had a mean BI of 10% +/- 9.8. The highest levels were seen in patients with diffuse proliferative glomerulonephritis (WHO grade IV) and in patients with proteinuria and nephrotic syndrome. When the biopsies were assessed for activity and chronicity scores, AECA were associated with active renal lesions (P less than 0.001). AECA levels correlated with low complement levels but not with anti-DNA antibodies to extractable nuclear antigens (ENA), anti-cardiolipin or anti-neutrophil cytoplasmic antibodies. The presence of AECA conferred a positive predictive value of 0.68 for the presence of nephritis. Twenty-five patients had active vasculitis at the time of assay and the highest AECA values were seen in patients with both nephritis and vasculitis. No correlation was seen with serum immunoglobulin levels and immune complexes did not bind significantly to the endothelial surface. The possible role of these antibodies as a marker in lupus nephritis is discussed.

Adult↗
PubMed1991

The effects of severe behavior problems in children on the teaching behavior of adults.

Applied behavior analysts have focused on how adults can influence the problem behavior of children using a variety of behavior modification strategies. A related question, virtually unexplored, is how the behavior problems of children influence adults. This child-effects concept was explored empirically in a study involving 12 adults who were asked to teach four pairs of children in which one member of the pair exhibited problem behavior and the other typically did not. Results demonstrated that problem children displayed tantrums, aggression, and self-injury contingent on adult instructional attempts but not at other times, whereas nonproblem children showed little or no problem behavior at any time. Importantly, from a child-effects perspective, adults engaged in teaching activities with nonproblem children more often than with problem children. Also, when an adult worked with a problem child, the breadth of instruction was more limited and typically involved those tasks associated with lower rates of behavior problems. The implications of these results are discussed with respect to theories of escape behavior, current assessment practices, and intervention issues related to maintenance. The existence of child effects suggests that problem behavior may be better understood when it is conceptualized as involving a process of reciprocal influence between adult and child.

Adult↗
PubMed1990

Preclinical pharmacology of Ro 31-6930, a new potassium channel opener.

The present study compares the effects of Ro 31-6930, a novel potassium channel opener, with those of cromakalim and nitrendipine on blood pressure and other haemodynamic parameters. In conscious, spontaneously hypertensive rats (SHR) the oral dose of Ro 31-6930 for lowering blood pressure was 10 times lower than that of cromakalim and some 100 times lower than that of nitrendipine. In addition, the duration of antihypertensive activity of Ro 31-6930 was longer than that of cromakalim or nitrendipine. The tachycardia evoked by Ro 31-6930 and cromakalim was of shorter duration than the antihypertensive effect of either agent. In a repeat, once daily dosing experiment no tolerance was observed to the antihypertensive effect of Ro 31-6930 over a 22-day period. In conscious normotensive cats Ro 31-6930 was 10 times more potent than cromakalim and 1,000 times more potent than nitrendipine in reducing blood pressure. The duration of hypotensive activity was in excess of 5 h for each agent. In anaesthetised dogs all three agents reduced mean arterial pressure (MAP) and total peripheral resistance (TPR), while increasing cardiac output (CO) via a rise in stroke volume (SV). Both Ro 31-6930 and cromakalim significantly reduced femoral (FVR) and mesenteric vascular resistances (MVR), while only cromakalim reduced renal vascular resistance (RVR). Ro 31-6930 is a potent new antihypertensive agent that compares favourably with cromakalim and nitrendipine.

Anesthesia↗
PubMed1990

Improved outcome with femur fractures: early vs. delayed fixation.

Prior studies documented that early fixation of femur fractures results in a decreased incidence of adult respiratory distress syndrome (ARDS), fat embolism syndrome, and pneumonia. This study evaluates the impact of magnitude of injury on pulmonary complications and length of ICU and hospital stays in 339 trauma patients with femur fracture undergoing early (n = 121) vs. late (n = 218) operative fixation. Groups were similar with respect to transfusions, hypotension, and associated injuries, but more patients over age 50 years underwent early fixation. Patients were categorized according to Injury Severity Score (ISS): 1) less than 15 (n = 202), 2) 16-35 (n = 104), and 3) greater than 36 (n = 33). Delayed fixation significantly increased the incidence of pulmonary shunt in ISS (3) patients and of pneumonia in patients older than 50. Late fixation resulted in significantly longer hospital stays in all groups and more ICU days in the ISS (3) group. We believe that early femur fixation should be performed on all patients. Pulmonary complications were decreased and health care costs reduced.

Adult↗
PubMed1990

Evaluation of the bronchodilator properties of Ro 31-6930, a novel potassium channel opener, in the guinea-pig.

1. Ro 31-6930 (0.001-0.3 microM), cromakalim (0.03-3.0 microM), salbutamol (0.001-0.3 microM) and theophylline (0.3-100 microM) evoked dose-related reductions in guinea-pig spontaneous tracheal tone with IC50 values of 0.044, 0.20, 0.021 and 21.0 microM respectively. All four agents also relaxed tone supported by betahistine, carbachol, 5-hydroxytryptamine (5-HT), leukotriene D4 (LTD4), U46619 and prostaglandin D2 (PGD2). The order of potency of tracheal relaxants was always salbutamol greater than Ro 31-6930 greater than cromakalim greater than theophylline. 2. All four agents evoked dose-related reductions in 5-HT- and histamine-induced bronchoconstriction in pithed vagotomised guinea-pigs. The dose of Ro 31-6930 producing 50% inhibition of a 5-HT bronchoconstriction was 11.6 micrograms kg-1 and the dose producing 50% inhibition of a histamine bronchoconstriction was 4.4 micrograms kg-1. Salbutamol was approximately 4-5 times more potent than Ro 31-6930 whilst cromakalim was approximately 10 times less potent than Ro 31-6930 as a bronchodilator. Theophylline was markedly less potent than any of the other agents. 3. Ro 31-6930, cromakalim, salbutamol and theophylline each protected conscious guinea-pigs from histamine-induced respiratory distress. Ro 31-6930 and salbutamol were each effective at oral doses of 1.0 and 3.0 mg kg-1 whilst cromakalim was effective at oral doses of 3.0 and 10.0 mg kg-1. Theophylline showed activity only at 300 mg kg-1 p.o. 4. Ro 31-6930 is a novel potassium channel opener which is a potent relaxant of guinea-pig tracheal smooth muscle in vitro and a bronchodilator in vivo.

Albuterol↗
PubMed1990

Novel Escherichia coli K-12 mutants impaired in S-adenosylmethionine synthesis.

S-Adenosylmethionine (AdoMet) plays a myriad of roles in cellular metabolism. One of the many roles of AdoMet in Escherichia coli and Salmonella typhimurium is as a corepressor of genes encoding enzymes of methionine biosynthesis. To investigate the metabolic effects of large reductions in intracellular AdoMet concentrations in growing cells, we constructed and examined mutants of E. coli which are conditionally defective in AdoMet synthesis. Temperature-sensitive mutants in metK, the structural gene for the S-adenosylmethionine synthetase (AdoMet synthetase) expressed in minimal medium, were constructed by in vitro mutagenesis of a plasmid-borne copy of metK. By homologous recombination, the chromosomal copy was replaced with the mutated metK gene. Both heat- and cold-sensitive mutants were examined. At the nonpermissive temperature, two such mutants had 200-fold-reduced intracellular AdoMet levels and required either methionine or vitamin B12 for growth. In the presence of methionine or vitamin B12, the mutants grew at normal rates even though the AdoMet levels remained 0.5% of wild type. A third mutant when placed at nonpermissive temperature had less than 0.2% of the normal AdoMet level and did not grow on minimal medium even in the presence of methionine or vitamin B12. All of these mutants grew normally on yeast-extract-based medium in which an alternate form of S-adenosylmethionine synthetase was expressed.

Chromosomes, Bacterial↗
PubMed1989

Use and abuse of khat (Catha edulis): a review of the distribution, pharmacology, side effects and a description of psychosis attributed to khat chewing.

There have been relatively few reported cases of psychosis due to khat usage despite its heavy consumption in certain East African and Arabian countries. Four cases have been reported in the UK. We report here on three further cases of psychotic reactions to this substance in Somalian males, and emphasize the need to be aware of khat as a potential substance of abuse, with both medical and psychiatric complications. The features of khat psychoses are described and the relationship to amphetamine and ephedrine psychoses is discussed. The forensic aspects of two of the cases which involved homicide and combined homicide and suicide are highlighted, as is the possible role of social dislocation from the culture of origin.

Adult↗