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Biomedical subjects

S Powell

Publications and source records attributed to S Powell.

At least 19 recordsLinked to original sources

Recall for self and other in autism: children's memory for events experienced by themselves and their peers.

Research on memory processing suggests that memory for events that an individual experiences should be superior to that for similar events that someone else experiences (e.g., Baker-Ward et al., 1990). However, such predictions may not be applicable to individuals with autism. There are already suggestions that individuals with autism have specific difficulties in remembering (Boucher & Lewis, 1989). In addition, they are known to have more general difficulties involving processes related to the "self." If children with autism have difficulties in encoding information about themselves this could result in a deficit in personal episodic memory. The studies reported here compare memory for personally experienced events with that of memory for events experienced by a peer. An adaptation of a method devised by Boucher and Lewis has been employed to assess recall. Two separate studies were conducted to investigate whether children with autism are impaired at recalling personal events. Two groups of children took part in Study 1, a group of children with autism and a control group of typical children matched for verbal mental age. A group of children with moderate learning difficulties were employed in the second study to investigate whether the findings also occur in other groups of individuals who have learning disabilities. Findings indicate that, in the group with autism, events performed by the individual were recalled significantly less well than the observed events performed by a peer. However, the results for the nonautistic children in both studies showed that the opposite was true. Theoretical claims are discussed in the light of these findings.

Adolescent↗

Identification of endothelial cell binding sites on the laminin gamma 1 chain.

The laminins belong to a family of trimeric basement membrane glycoproteins with multiple domains, structures, and functions. Endothelial cells bind laminin-1 and form capillary-like structures when plated on a laminin-1-rich basement membrane matrix, Matrigel. Laminin-1 is composed of 3 chains, alpha1, beta1, and gamma1. Because laminin-1 is known to contain multiple biologically active sites, we have screened 156 synthetic overlapping peptides spanning the entire laminin gamma1 chain for potential angiogenic sequences. Only 7 of these peptides, designated as C16, C25, C30, C38, C64, C75, and C102, disrupted the formation of capillary-like structures by human umbilical vein endothelial cells on Matrigel. Dose-response experiments in the presence of 50 to 200 microg/mL showed that tube formation was prevented by most peptides at 150 and 200 microg/mL, except for C16, which showed strong activity at all concentrations. Active peptides promoted vessel sprouting from aorta rings and angiogenesis in the chick chorioallantoic membrane assay. In addition, the active peptides also promoted endothelial cell adhesion to dishes coated with 0.1 microg of peptide and inhibited attachment to laminin-1 but not to plastic or fibronectin. Four of the active peptides, C25, C38, C75, and C102, may have cell-type specificity with endothelial cells, since they did not promote PC12 neurite outgrowth or adhesion of B16-F10 melanoma and human submandibular gland cells. These results suggest that specific laminin gamma1-chain peptides have angiogenic activity with potential therapeutic applications.

Allantois↗

Ritualized conflict in Odontomachus brunneus and the generation of interaction-based task allocation: a new organizational mechanism in ants.

Intracolonial conflict among ant workers can establish a reproductive hierarchy, with top-ranking individuals often securing oviposition opportunities. Here we show that in the ant Odontomachus brunneus, reproduction-based dominance interactions control worker movement and location, and that this, in turn, mechanistically governs task allocation within the colony and establishes a division of labour for nonreproductive tasks. Movement made by a worker towards the brood is mostly preceded by winning a pairwise dominance interaction, and movement away from the brood is mostly preceded by losing a pairwise interaction. Consequently, workers are distributed within the colony such that the more subordinate the individual, the more peripheral her location with respect to the reproductive centre of the nest. Behavioural roles are naturally restricted to particular zones of the colony, therefore, allocation to a particular zone, through dominance interaction, ensures role specialization. This represents a new organizational mechanism, which we call 'interaction-based task allocation'. In characterizing the dominance interactions of this species, we also identify two new behaviours: (1) 'subordinate driving', which involves a dominant individual physically manoeuvring a subordinate, by way of continued aggression, away from the reproductive centre of the nest; and (2) 'antennal shivering', which describes the antennal movements made by a subordinate immediately preceding and during subordinate driving. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗

The prevalence of corticosteroid allergy in two U.K. centres: prescribing implications.

Allergic contact dermatitis to topical corticosteroids is a common problem, seen in up to 6% of patients undergoing patch testing. Rates of steroid allergy vary widely both within and between countries. It has previously been shown that non-fluorinated steroids degrade and react with arginine more rapidly in an in vitro system and may therefore be more likely to sensitize than fluorinated steroids. We have compared the rates of steroid allergy and corticosteroid prescribing habits in two different areas in England to observe the relationship between these factors. The results suggest that predominant use of non-fluorinated corticosteroids (hydrocortisone, hydrocortisone-17-butyrate and budesonide) results in a higher prevalence of corticosteroid contact allergy in comparison with those areas using a greater proportion of fluorinated corticosteroids.

Administration, Topical↗

Correlation between androgen receptor expression and FGF8 mRNA levels in patients with prostate cancer and benign prostatic hypertrophy.

AIM: To investigate the correlation between androgen receptor expression and fibroblast growth factor 8 (FGF8) mRNA levels. METHODS: 39 human prostate cancers and 14 benign prostatic hypertrophy specimens were examined immunohistochemically for androgen receptor expression and by in situ hybridisation and reverse transcription polymerase chain reaction for FGF8 expression. RESULTS: In 39 tumours there was a statistically significant negative correlation between tumour grade and FGF8 expression and a positive correlation between FGF8 and androgen receptor expression. All 14 benign hypertrophy specimens expressed moderate to high levels of FGF8 and androgen receptor. CONCLUSIONS: Loss of FGF8 may be a factor involved in the development of prostatic cancer.

Fibroblast Growth Factor 8↗

Detecting single base substitutions, mismatches and bulges in DNA by temperature gradient gel electrophoresis and related methods.

Temperature gradient gel electrophoresis (TGGE) and related methods can separate DNA fragments that differ by a single base pair or defect. This article describes the basic features of TGGE, and reviews the theoretical model of DNA unwinding and its ability to predict DNA mobility in a temperature gradient gel. Recent applications of TGGE and related methods that were directed at detecting point mutations, and evaluating the effects of single site defects are also reported.

Animals↗

Clonidine potentiates the neuropathic pain-relieving action of MK-801 while preventing its neurotoxic and hyperactivity side effects.

Antagonists of NMDA glutamate receptors have been shown to alleviate neuropathic pain in rats and humans. However, NMDA antagonists can cause significant side effects ranging from behavioral disturbances to injury of neurons in the posterior cingulate/retrosplenial (PC/RS) cortex. We have found that alpha-2 adrenergic agonists prevent the PC/RS neurotoxic side effects of NMDA antagonists. In the present study of adult female rats subjected to sciatic nerve ligation (Bennett neuropathic pain model) and tested for paw withdrawal latency (PWL) following a thermal stimulus, we evaluated the ability of the NMDA antagonist, MK-801, to alleviate neuropathic pain either by itself or when administered together with the alpha-2 adrenergic agonist, clonidine. We found that MK-801, at a dose (0.05 mg/kg s.c.) that is known to cause mild hyperactivity but is subthreshold for producing PC/RS neurotoxic changes, relieved the neuropathic pain state associated with sciatic nerve ligation. However, the relief at this dose was very transient, and no neuropathic pain-relieving effect was observed at a lower dose (0. 025 mg/kg s.c.) of MK-801. Clonidine, at a dose (0.05 mg/kg s.c.) that prevents the cerebrocortical neurotoxic effects of MK-801, decreased sensitivity to the thermal stimulus equally under all conditions (ligated, sham ligated, unoperated), but did not specifically relieve neuropathic pain in the ligated limb. Combining this dose of clonidine with an ineffective dose (0.025 mg/kg s.c.) of MK-801 provided specific, complete and long lasting (up to 4 h) relief from neuropathic pain. Rats receiving this drug combination did not display hyperactivity or any other behavioral disturbance typically associated with MK-801 treatment, nor show neurotoxic changes in cerebrocortical neurons. In separate experiments on normal unoperated rats, we found that clonidine (0.05 mg/kg s.c.) counteracted the hyperactivity induced by MK-801 (0.05 mg/kg s.c.) and returned activity levels to a normal range. These findings signify that clonidine, which does not specifically relieve neuropathic pain, can potentiate the neuropathic pain-relieving action of MK-801, while also protecting against neurotoxicity and hyperactivity side effects of MK-801. The potentiation is of a sufficient magnitude that it permits cutting the MK-801 dose requirement in half, thereby achieving prolonged neuropathic pain relief while doubling the margin of safety against any type of side effect that might be mediated by blockade of NMDA receptors.

Adrenergic alpha-Agonists↗

Spontaneous play in children with autism: a reappraisal.

Much controversy remains regarding the ability of children with autism to engage in spontaneous play. In this study children with autism, Down syndrome and typical development with verbal mental ages of approximately 2 years were assessed for play abilities at three data points. Even in this group of children with autism, who had relatively low verbal mental ages, symbolic play skills were not totally absent. However, it was possible to distinguish their pattern of play behaviors from the other two groups. Consequentially, it is argued that there are unusual features in early spontaneous play in children with autism and these atypical patterns are not restricted to their difficulties in the production of symbolic play. Such differences in early spontaneous play raise interesting questions about the etiology of autism, the direction of future research, and the theoretical models that can account for the condition.

Autistic Disorder↗

Nitrous oxide (laughing gas) is an NMDA antagonist, neuroprotectant and neurotoxin.

Extensive research has failed to clarify the mechanism of action of nitrous oxide (N2O, laughing gas), a widely used inhalational anesthetic and drug of abuse. Other general anesthetics are thought to act by one of two mechanisms-blockade of NMDA glutamate receptors or enhancement of GABAergic inhibition. Here we show that N2O, at anesthetically-relevant concentrations, inhibits both ionic currents and excitotoxic neurodegeneration mediated through NMDA receptors and, like other NMDA antagonists, produces neurotoxic side effects which can be prevented by drugs that enhance GABAergic inhibition. The favorable safety record of N2O may be explained by the low concentrations typically used and by the fact that it is usually used in combination with GABAergic anesthetics that counteract its neurotoxic potential.

Animals↗

Users evaluate LupusLine, a telephone peer counseling service.

OBJECTIVE: To assess the impact of LupusLine during its pilot phase of operation by determining patterns of utilization and user satisfaction. LupusLine is a peer counseling service designed to provide ongoing emotional support from home to home by telephone appointment. METHODS: One hundred fifty-three respondents were surveyed, using a 72-item structured questionnaire administered over the telephone by interviewers separately trained and hired specifically for this purpose. The questionnaire was pilot tested on 10 volunteers with systemic lupus erythematosus (SLE), and a panel of related health professionals reviewed the questionnaire for face validity. RESULTS: Most users were women (94.5%) who had SLE themselves (87.5%) and who called the service because of recent changes in their physical functioning and reported feelings of depression and anxiety about their illness. Forty-one percent of respondents made 6 or more calls to their assigned peer counselor. Respondents reported high levels of satisfaction across 5 highly correlated measures, with 92% of callers reporting at least moderate satisfaction with the service. Over 60% of respondents who reported a change in 6 "feeling" categories attributed this change to using LupusLine. Fewer users reported a change in 4 specific behaviors since using the service, but more respondents attributed changes, when they occurred, to LupusLine. CONCLUSIONS: Based on these initial findings, we believe that telephone networks similar to the LupusLine model may be able to offer substantial benefit to people coping with the complex, ongoing psychosocial challenges of SLE. Further, the at-home accessibility and low cost of such volunteer-based interventions may play an ever more needed role in the present health care environment.

Adult↗

Imitation of pretend play acts by children with autism and Down syndrome.

Although there has recently been considerable research interest in the difficulties that children with autism have engaging in pretend play, little attention has been paid to the ability of these children to imitate pretend play acts. Furthermore, suggestions that children with Down syndrome have relatively advanced abilities in pretend play have not been accompanied by an examination of their capacity to imitate pretend play. Three groups of children: autistic, Down syndrome, and normally developing were studied for their capacity to imitate single pretend acts and a series of pretend acts that formed scripts. While the children with autism were surprisingly better than the other two groups on the single-scheme task, they demonstrated specific difficulties on the multischeme task. Results are discussed in relation to current theories of autism and the notion of imitation.

Adolescent↗

Effect of diuretics on urinary oxalate, calcium, and sodium excretion in very low birth weight infants.

OBJECTIVE: To study the effect of diuretic drugs on urinary oxalate excretion in premature infants, and to examine the relationship between urinary calcium and sodium excretion in premature infants. METHODOLOGY: We measured urinary oxalate, calcium, and sodium excretion in 32 premature infants at approximately 34 weeks gestational age. Seven infants were receiving furosemide, 5 infants were receiving thiazide, 8 infants were receiving furosemide plus thiazide, and 12 infants who were not receiving diuretics served as controls. RESULTS: Urinary oxalate to creatinine ratios in infants receiving furosemide (0.48 +/- .26), thiazide (0.54 +/- .20), furosemide plus thiazide (0.44 +/- .19), and control infants (0.51 +/- .43) were similar by analysis of variance (ANOVA). Data expressed as oxalate concentration gave similar results. Urinary calcium to creatinine ratios in infants receiving furosemide (0.81 +/- .30), thiazide (0.54 +/- .25), furosemide plus thiazide (0.75 +/- .49), and control infants (0.37 +/- .25) were similar by ANOVA. The urinary calcium concentration in infants receiving furosemide plus thiazide (0.085 +/- 0.042 mg/mL) was different from control infants (0.044 +/- .023) by ANOVA and Student-Newman-Keuls test. Urinary calcium to creatinine ratio was correlated with sodium to creatinine ratio (r = .751). CONCLUSION: Urinary oxalate excretion in premature infants is not affected by diuretic drugs. Urinary sodium and calcium excretion are closely linked in sodium supplemented premature infants receiving diuretics. The calciuric effect of furosemide is not decreased by the addition of thiazide in premature infants receiving sodium supplements.

Analysis of Variance↗

Effects of choosing academic assignments on a student with attention deficit hyperactivity disorder.

The effects of choosing academic assignments on the undesirable behaviors manifested by a second-grade student with attention deficit hyperactivity disorder were analyzed. This study extended Dunlap et al.'s (1994) research on choice making as a form of antecedent control. A reversal design showed that undesirable behaviors decreased when the student was given a choice of academic assignments.

Attention↗

Ruptured bacterial intracranial aneurysm in pregnancy. A case report.

BACKGROUND: Rupture of a documented infectious cerebral aneurysm is a rare complication of infectious endocarditis, with a high morbidity and mortality rate. The only previously reported case was associated with maternal and neonatal mortality. No known report exists of a ruptured bacterial intracranial aneurysm complicating an ongoing pregnancy with maternal or fetal survival. CASE: A 38-year-old, white woman, gravida 9, para 4, at 18 weeks' gestation, developed infectious endocarditis with peripheral and cerebral emboli secondary to intravenous drug abuse, causing renal failure and cortical strokes. She required hemodialysis and also suffered a subarachnoid hemorrhage due to rupture of cerebral bacterial aneurysms. A team approach to her care was necessary. At 28 weeks' gestation she delivered by cesarean section for abruptio placentae. Both the mother and neonate recovered. CONCLUSION: Rupture of mycotic aneurysms can be catastrophic and is often managed surgically. The patient described here was severely affected, and though indicated, surgical intervention was not possible. An aggressive team approach provided a good maternal and fetal outcome.

Adult↗