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Biomedical subjects

J Pratt

Publications and source records attributed to J Pratt.

At least 73 records · Page 4Linked to original sources
PubMed1995

Inhibition of return to successively cued spatial locations.

Inhibition of return refers to a bias against returning attention to a location that has been recently attended. Experiments are reported that examined inhibition of return to multiple exogenously cued spatial locations. When 2 peripheral locations were cued in succession, inhibition was found for only the 1 most recently cued location. In addition, more inhibition occurred at the location of the most recent cue if the earlier cue had also been presented there, as compared with an earlier cue at a different location. Thus, the magnitude of the inhibition for a location appears to depend on the effectiveness of the attentional cue to that location. Other results suggest that candidate locations for inhibition are displaced by subsequent cues--they do not simply decay. The results provide an initial framework within which to study inhibition of return to multiple spatial locations.

Attention↗
PubMed1995

Temporal locus of knowledge of results: a meta-analytic review.

Meta-analysis was performed to evaluate the temporal locus of knowledge of results. An extensive literature review was conducted, yielding 17 published articles suitable for the meta-analyses. These studies were then separated into 2 general categories of acquisition and retention. These categories were subdivided further into KR delay interval, KR delay and motor interpolated activities, KR delay and verbal interpolated activities, post-KR interval, post-KR interval and motor interpolated activities, and post-KR interval and verbal interpolated activities. 6 of the 12 categories gave enough data for the meta-analyses. The categories which showed significant results were KR-delay, post-KR interval, and post-KR interval and verbal interpolated activities in acquisition. Although significant, effect sizes were comparatively small. The discussion of findings focused on effects of the temporal locus of KR and interpolated activities on performance and learning.

Humans↗
PubMed1995

Color-based inhibition of return.

The inhibition of return of visual attention based on stimulus color was examined in three experiments. In the first experiment, a discrete trial paradigm showed that subjects were slower to detect a color patch if the color matched that of a patch presented earlier in the same location. Experiment 2 showed that the inhibition only occurs if a neutral, nontarget distractor color is presented between presentation of the initial color cue and the subsequent target patch--explaining the previous failures to detect the phenomenon. Experiment 3 extended the results to a different combination of colors. Taken together, the results have important implications for the processing of stimulus attributes such as spatial location and color, and for the conditions necessary for producing inhibition of return.

Attention↗
PubMed1994

Comparative study of voltage-sensitive sodium channel blockers in focal ischaemia and electric convulsions in rodents.

This study evaluates the neuroprotective properties of some voltage-sensitive sodium channel blockers in a model of focal ischaemia. After curative treatment (0.5 and 24.5 h after insult), well known voltage-sensitive sodium channel blockers, phenytoin (2 x 100 mg/kg i.p.), carbamazepine (2 x 50 mg/kg i.p.), lamotrigine (2 x 50 mg/kg i.p.) and RP 66055 (2 x 8 mg/kg i.p.) were found to protect rats against brain damage induced by occlusion of the middle cerebral artery, by 40%, 24%, 28% and 44% respectively. These compounds were also active in protecting both mice and rats against tonic convulsions induced by electroshock, Intraperitoneal ED50 values in mice and rats respectively were of 5.2 and 12.5 mg/kg for phenytoin, 8.4 and 3.6 mg/kg for carbamazepine, 4.4 and 3.1 mg/kg for lamotrigine, 3.9 and 0.22 mg/kg for RP 66055. In contrast, lifarizine was totally devoid of activity in these three tests. This study extends an accumulation of data in the literature pointing to a therapeutic potential for voltage-dependent sodium channel blockers which penetrate the blood brain barrier. Such compounds as phenytoin, carbamazepine, lamotrigine or RP 66055 may act at sodium channels to prevent depolarization, inhibit release of neurotransmitters such as glutamate and thus protects the cortex against cellular damage induced by focal ischaemia by both pre- and post-synaptic inhibition of abnormal neurotransmission.

Animals↗
PubMed1994

Neuroprotective effects of colchicine in the gerbil model of cerebral ischaemia.

The tropolonic alkaloid colchicine significantly reduces the behavioural, electroencephalographic and histological damage seen after a 6-min occlusion of the two common carotid arteries of the Mongolian gerbil if the compound is administered at 2 or 4 mg/kg i.p. immediately upon reperfusion. A 45% increase in high-frequency ECoG activity and significant reduction of 80% in the hypermotility of the gerbils, with 63% less faults in a passive avoidance paradigm, were observed in conjunction with considerable protection of the hippocampus, after a single dose of 4 mg/kg colchicine. No adverse effects of colchicine treatment on animal movement and body weight were observable. Colchicine's possible mode of action, via inhibition of cellular transport systems, is discussed.

Animals↗
PubMed1994

Hurricane Andrew and a pediatric emergency department.

STUDY OBJECTIVE: To determine the effect of Hurricane Andrew on a pediatric emergency department. DESIGN: A retrospective analysis of ED visits through the use of computerized records and chart review. SETTING: A children's hospital in South Florida. TYPE OF PARTICIPANTS: All patients presenting to the ED during the control week and the two study weeks after the hurricane. MEASUREMENTS: Census, diagnoses, admission rate, and patient geographic origin and age. MAIN RESULTS: During week 1, there was an average daily increase of 40.7% in patient volume (P < .01) and a 3.3% decrease in the admission rate (P < .01). The increased census was due mainly to local patients, rather than those from the most devastated areas. More patients were seen with open wounds, gastroenteritis, and impetigo (all, P < .05); more were more than 18 years old (P < .05). By the second week, both census and admission rate returned to normal; cases of cellulitis (P < .05) and open wounds (P < .001) were increased. Although not statistically significant, a higher percentage of hydrocarbon and/or bleach ingestions was seen for both weeks. CONCLUSION: Following a hurricane, personnel in a pediatric ED can expect to see an increased census, with more diagnoses of open wounds, gastroenteritis, and skin infections. They may also see hydrocarbon and bleach ingestions. Alerting parents to the potential for injury and accidental poisoning in their children after a hurricane may help prevent the reported morbidity.

Adolescent↗
PubMed1994

Chemotherapy for germ cell tumours: prophylactic ciprofloxacin reduces the incidence of neutropenic fever.

To assess the value of prophylactic ciprofloxacin in reducing the incidence of neutropenic fever in men receiving intensive chemotherapy for germ cell tumours, we reviewed the case notes of 88 consecutive patients treated between January 1986 and December 1992. Nadir blood counts were performed in all patients on day 14. From 1989, prophylactic ciprofloxacin 250 mg b.d. was started when the neutrophil count was less than 1 x 10(9)/l and then prescribed for all subsequent courses of chemotherapy from day 7 to day 21. In total, 88 men received 429 courses of chemotherapy. Prophylactic ciprofloxacin was prescribed for 168 courses. This was associated with a trend towards reducing the risk of admission per course of chemotherapy from 8% (20/261) to 4% (6/168) (P = 0.08). WHO grade 3/4 neutropenia (< 1 x 10(9)/l) was documented for 240 (56%) courses of chemotherapy. The incidence of fever in these patients was significantly reduced from 15% (20/131) to 5% (6/109) (P = 0.02) with prophylactic ciprofloxacin. Two patients, one of whom had received prophylactic ciprofloxacin, died of chest infection confirmed on post-mortem. The results of this non-randomized, retrospective study suggest that prophylactic ciprofloxacin 250 mg b.d. is effective in reducing the incidence of fever complicating neutropenia during chemotherapy for germ cell tumours. To be cost effective, it should be given only to neutropenic patients.

Adolescent↗
PubMed1994

Rapid aimed limb movements: age differences and practice effects in component submovements.

Two experiments are reported in which younger and older adults practiced rapid aimed limb movements toward a visible target region. Ss were instructed to make the movements as rapidly and as accurately as possible. Kinematic details of the movements were examined to assess the differences in component submovements between the 2 groups and to identify changes in the movements due to practice. The results revealed that older Ss produced initial ballistic submovements that had the same duration but traveled less far than those of younger Ss. Additionally, older Ss produced corrective secondary submovements that were longer in both duration and distance than those of the younger subjects. With practice, younger Ss modified their submovements, but older Ss did not modify theirs even after extensive practice on the task. The results show that the mechanisms underlying movements of older adults are qualitatively different from those in younger adults.

Acceleration↗
PubMed1994

Effect of pH and CO2 on in vitro susceptibility of Pseudomonas cepacia to beta-lactams.

Inhibition of Pseudomonas cepacia (but not Pseudomonas aeruginosa) by beta-lactams was decreased in 5% CO2 in air compared with air alone. The effect of CO2 and pH (range, 6.0 to 8.0) on beta-lactam susceptibility, beta-lactamase expression, and outer membrane proteins was studied in isolates recovered from the sputum of children with cystic fibrosis. Incubation in 5% CO2 decreased the activity of piperacillin, piperacillin/tazobactam, and ceftazidime, although isolates were still clinically sensitive (minimum inhibitory concentrations < 16 mg/L). Cefpirome activity was markedly decreased from a minimum inhibitory concentration of 2.0 to greater than 64 mg/L. On highly buffered 3-(N-morpholino)-propane sulfonic acid media, beta-lactam susceptibility was eliminated at pH greater 7.5. A 2- to 13-fold increase in beta-lactamase activity was demonstrated after growth in 5% CO2 compared with basal aerobic levels for 13 of 15 clinical isolates. beta-Lactamase activity did not vary significantly with pH. Addition of imipenem to media (2.0 mg/L) resulted in hyperproduction of beta-lactamase (180-fold). Isoelectric points varied with cultural conditions, and all beta-lactamases detected were inhibited by clavulanate and tazobactam. Significant hydrolysis of piperacillin and ceftazidime could not be demonstrated. A 36-kD porin was present at all pH tested. Thus, our strains of Pseudomonas cepacia were markedly affected by cultural conditions not normally used in standardized susceptibility tests. However, such conditions may be encountered in the pathologically altered infected lung in cystic fibrosis.

Anti-Bacterial Agents↗
PubMed1993

Rapid aimed limb movements: differential effects of practice on component submovements.

Three experiments are reported in which subjects practiced rapid aimed limb movements (arm pointing and wrist rotation) toward a visible target region. Subjects were required to minimize their movement durations while still landing in the target. The movement trajectories were examined to assess the effects of practice on separate component submovements of the limb movements. The results revealed that practice improved primarily temporal, not spatial, aspects of performance. Practice reduced the overall movement durations, but had different effects on the individual submovements. Practice allowed subjects to reduce the amount of time spent performing final corrective submovements, but actually increased slightly the time needed to produce the initial ballistic submovement. The results suggest that practice in the present task primarily enhanced the ability to use feedback information, but there was also some evidence of changes in the ballistic, preprogrammed portion of the movements. The results demonstrate that analysis of submovements can reveal important details of the underlying motor control processes.

Journal Article↗
PubMed1992

Neuroprotective actions of riluzole in rodent models of global and focal cerebral ischaemia.

Riluzole (2 amino 6-trifluoromethoxybenzothiazole), when administered at 4 and 8 mg/kg i.p., 0.5, 4.5, 24 and 28 h after the initiation of ischaemia, significantly reduced the prevalence of slow wave, and increased the proportion of higher frequency activity seen in the quantified electrocorticogram (ECoG), during the weeks that followed a 6 min bilateral occlusion of the common carotid arteries in the Mongolian gerbil. In focal ischaemia, provoked in Fischer rats following the occlusion of the middle cerebral artery, administration of riluzole (8 mg/kg) at 30 min and 24.5 h post occlusion significantly reduced the volume of infarcted cortex. These activities of riluzole could be related to its inhibition of sodium channel activity, which in turn inhibits glutamate release.

Animals↗
PubMed1992

The infant mortality rate at Cherbourg aboriginal community: an update.

The infant mortality rate (IMR) at Cherbourg Aboriginal Community in south-eastern Queensland remained high from 1906 to about 1955-60, but since then has dropped from over 200/1000 live births in 1956-60 to 16/1000 live births in 1986-90, compared with the 1987 rate for Queensland (9.2/1000) and Australia (8.6/1000). The rapid improvement in the IMR was associated with the installation of a piped and chlorinated water supply, sewerage and an intensive campaign to eradicate intestinal worms. There has also been a change in community attitudes towards routine health practices and it is likely that this has been a major factor in the changes.

Humans↗
PubMed1992

Multicenter evaluation of a new enzyme immunoassay for detection of Clostridium difficile enterotoxin A.

The Premier Clostridium difficile toxin A enzyme immunoassay (PTA EIA) (Meridian Diagnostics, Inc., Cincinnati, Ohio) for rapid diagnosis of antibiotic-associated colitis (AAC) was evaluated in a multicenter study. Stool samples from 421 patients suspected of having AAC were tested for toxin A by the PTA EIA and for toxin B by three tissue culture assays (TCA) employing WI-38 cells (New England Deaconess Hospital) in conventional tubes or foreskin fibroblasts (Children's Hospital) or Vero cells (Beth Israel Hospital) in microwells. The tubes and plates were examined at 24 and 48 h for cytotoxicity. Clinical criteria, repeat testing at another site, and culture of frozen stool samples for C. difficile were used to evaluate discrepant results. Of 504 samples, 66 were positive and 409 were negative by both tests. Eight samples had indeterminate PTA EIA results and were excluded from this analysis. Of 21 discrepancies, 9 were PTA EIA positive and TCA negative and 12 were PTA EIA negative TCA positive. Following resolution of the discrepancies, 11 of 12 PTA EIA-negative-TCA-positive and 5 of 9 PTA EIA-positive-TCA-negative samples were considered true positive for AAC. The sensitivity and specificity were, respectively, 86.6 and 99.0% for the PTA EIA and 93.9 and 99.8% for TCA. The predictive values of positive and negative tests were, respectively, 94.7 and 97.4% for the PTA EIA and 98.7 and 98.8% for TCA. We conclude that the PTA EIA is a rapid, simple EIA technique whose accuracy in detecting enterotoxin A approaches that of reference TCA methods for detection of cytotoxin B.

Bacterial Proteins↗
PubMed1991

Pathways of serotonin-induced electrolyte transport in rat distal colon.

Serotinin-stimulated electrolyte transport was examined in flat-sheet preparations of rat left colon with the Ussing chamber-voltage clamp technique. Transport was studied in tissues stripped of muscularis propria and in nonstripped tissue. In nonstripped colon, the action of serotonin (5-hydroxytrytamine [5-HT]) on short-circuit current was inhibited by a factor of 60% by tetrodotoxin (P less than 0.05; t test) and was also inhibited by the 5HT2 antagonist ketanserin (p less than 0.05 vs serotonin; t test) and the 5-HT3 antagonist ICS 205-930 (p less than 0.05 vs serotonin, t test). These compounds produced corresponding inhibition of serotonin-induced sodium and chloride flux in this preparation. The tetrodotoxin-sensitive component was not inhibited by atropine, hexamethonium, phentolamine, or propranolol. Histologic analysis of the stripped preparation showed that it consisted of mucosa and musclaris mucosa only. In this stripped preparation, serotonin-induced change in short-circuit current was tetrodotoxin insensitive and inhibited by ketanserin (p less than 0.05 vs serotonin, t test) but not by ICS 205-930. Serotonin-induced sodium and chloride flux was inhibited by ketanserin in the presence of tetrodotoxin in this preparation. These results suggest that serotonin-induced electrolyte transport in rat distal colon is mediated by nonneural 5HT2 receptors in the mucosa or muscularis mucosa and by 5-HT3 receptors located on enteric nonadrenergic, noncholinergic nerves.

Analysis of Variance↗