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Biomedical subjects

P Fletcher

Publications and source records attributed to P Fletcher.

At least 55 records · Page 3Linked to original sources
PubMed1994

Brain regions associated with acquisition and retrieval of verbal episodic memory.

It is widely held that conscious recall of past experiences involves a specific system--episodic memory. Patients with amnesia have gross impairments of episodic memory while other kinds of memory remain intact, suggesting that a separable brain system underlies episodic memory. We have used positron emission tomography (PET) to identify components of this system in normal volunteers. A dual-task interference paradigm was used to isolate brain areas associated with acquisition, and a cueing paradigm to isolate the areas concerned with retrieval from verbal episodic memory. Acquisition was associated with activity in the left prefrontal cortex and the retrosplenial area, whereas retrieval was associated with activity in right prefrontal cortex and the precuneus. Our results provide clear evidence that episodic memory involves a network of specific prefrontal and posterior structures which can be fractionated into different component processes.

Brain↗
PubMed1994

Distribution of mass to the segments of elderly males and females.

The comprehensive study of the motion of elderly men and women requires the knowledge about the distribution of the body mass to the segments. Cadaver studies are of older subjects and should provide this information. However, the small samples are primarily male and do not represent the body mass of the elderly. In this study a mathematical model which utilizes the shape of the front and side outlines to calculate segment volume, and subsequently mass, is used. Substantive modifications were made to expedite the original technique [Jensen, J. Biomechanics 11, 349-358 (1978)] by using images from two cameras and digitizing software to determine cross-sectional axes as segments are outlined. The revised technique was used in a study of 12 females and seven males, each 63-75 yr. The mean error for body mass estimation was 0.05% (S.D. 2.96%). The calculated masses were compared to estimated masses based on Dempster [Technical Report 55-159, Wright-Patterson Air Force base, Ohio (1955)], and for females, the Dempster proportions overestimated head and forearm mass and underestimated arm and thigh mass (p > 0.05). For males, the head mass was overestimated. The differences between male and female segment masses were then evaluated. Differences for all segments were significant, with the exception of the upper trunk and thigh. When body mass was considered, the female thigh and foot proportions were larger and the lower trunk, forearm and hand proportions smaller.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1994

Building community for health: lessons from a seven-year-old neighborhood/university partnership.

This article presents two case studies highlighting the role of community conflict in the process of community empowerment. A graduate program for community health nurses (CHNs) in a large Midwestern city formed a partnership with a diverse, integrated neighborhood for the dual purposes of enhancing the community's capacity to improve its own health and teaching CHNs community organizing as a means to improve health. Central to the partnership are a broad definition of health, trust developed through long-term involvement, a commitment to reciprocity, social justice, and Freire's model of adult learning. Two initiatives that gave rise to major conflicts between community groups are analyzed. Conflicts, external and internal to the community, proved to be both powerful catalysts and potential barriers to the use of Freirian themes in community organization. Both university and community participants report needing better skills in the early recognition and management of conflict. We conclude that conflict management theory must be integrated with empowerment education theory, particularly when empowerment education is applied in a diverse community.

Adolescent↗
PubMed1994

The long-term follow-up of severely malnourished children who participated in an intervention program.

18 severely malnourished children (IM) who participated in a 3-year home-visiting program were compared with 2 other comparison groups comprising 17 severely malnourished (NIM) and 19 adequately nourished children (controls). On enrollment, all the groups were in the same hospital, and both malnourished groups had lower developmental levels than the controls. The IM group received intervention for 3 years after hospitalization, consisting of weekly or 2 weekly home visits with toy demonstrations. At 7, 8, 9, and 14 years after leaving the hospital, the 3 groups were compared on tests of school achievement and IQ. The NIM group showed no sign of reducing their deficits, and at the 14-year follow-up they had markedly lower scores on the WISC verbal and performance scales, the Wide Range Achievement Test (WRAT), and the Peabody Picture Vocabulary Test (PPVT), than the controls. Throughout the follow-up the IM group's scores were intermediate between the NIM and the controls in every test. At the 14-year follow-up, their scores were significantly higher than those of the NIM group in the WISC verbal scale, and the difference approached significance in the WRAT. We conclude that psychosocial intervention should be an integral part of treatment for severely malnourished children.

Adolescent↗
PubMed1993

Lead increases inositol 1,4,5-trisphosphate levels but does not interfere with calcium transients in primary rat astrocytes.

Alteration of receptor-mediated signal transduction pathways by inorganic lead (Pb) has been postulated to contribute to the neurotoxicity of this environmental toxicant, some of these effects involving astrocytes. As Pb is known to mimic Ca2+ in various biological systems or alter Ca(2+)-mediated cellular processes, we analyzed the effect of Pb exposure on alpha 1 receptor activated astrocytic phosphoinositide metabolism and Ca2+ responses in primary astrocyte cultures prepared from cerebral cortex of 1-day-old rats. Exposure to norepinephrine (NE; 10-100 microM) resulted in a significant increase in astrocytic inositol 1,4,5-trisphosphate levels, concomitant with an increase in intracellular Ca2+ levels. Fifteen minute exposure to Pb (10 microM lead acetate) significantly increased inositol 1,4,5-trisphosphate generation compared with controls, both in the presence and absence of NE. However, the inositol 1,4,5-trisphosphate-mediated Ca2+ transients following NE stimulation was unaltered in the presence of Pb (1-100 microM). NE-evoked intracellular Ca2+ responses, both in the presence and absence of extracellular Ca2+ did not differ between control and Pb-treated astrocytes. Additional studies failed to demonstrate the occurrence of Pb influx into astrocytes within the first 12 min of exposure such that Ca2+ responses would be directly affected. It therefore appears unlikely that astrotoxic effects of Pb are mediated via direct changes in intracellular Ca2+ transients.

Animals↗
PubMed1992

Gastric bypass for treating severe obesity.

Gastric bypass (RY-GBP) has a very small gastric pouch with a 1-cm diameter Roux-Y gastrojejunostomy. RY-GBP is associated with early satiety and an aversion to sweets secondary to dumping syndrome symptoms and has a significantly better weight loss than various gastroplasty procedures, including the vertical banded gastroplasty. However, it may be associated with vitamin B-12 deficiency and iron deficiency anemia in menstruating females, preventable with prophylactic oral iron and vitamin B-12. With an 80% 5 y follow-up, RY-GBP patients lose two-thirds of their excess weight within 2 y, 60% at 5 y, and greater than 50% at 9 y. The RY-GBP can be beaten by nibbling "junk foods" (potato or corn chips). Conversion to a malabsorptive procedure may cause severe malnutrition and fat-soluble vitamin deficiencies and should be used only for "superobese" patients who fail a standard RY-GBP and have severe comorbidity. RY-GBP is the most effective procedure for morbid obesity, especially in patients addicted to "sweets."

Gastric Bypass↗
PubMed1992

Cardiac responses after norepinephrine-induced ventricular hypertrophy in rats.

The increase in norepinephrine (NE) blood levels in human heart failure correlates with prognosis. In this study, we determined whether continuous NE infusion alters the positive inotropic and chronotropic responses of isolated rat cardiac muscles. Osmotic minipumps were implanted subcutaneously (s.c.) in 43 adult male rats to deliver NE (160 micrograms/kg/h for 14 days); 42 rats were sham-operated. Isolated left and right atria and left and right ventricular (LV, RV) papillary muscles were prepared to measure positive inotropic or chronotropic responses to NE, phenylephrine, forskolin, dibutyryl cyclicAMP (dbcyclicAMP), and calcium chloride. NE infusion caused (a) a 22% increase in LV wet weight without altering atrial or RV wet weights; (b) an 18% decrease in maximal inotropic response to calcium chloride in LV papillary muscles only; (c) a significantly decreased peak response to NE [72 +/- 5 vs. 93 +/- 5% (sham rats) of calcium chloride] but not to forskolin or dbcyclicAMP in RV papillary muscles; (d) an increased incidence of ectopy at low concentrations of NE, forskolin, and dbcyclicAMP in LV papillary muscles; (e) no alteration in papillary muscle responses to phenylephrine but significantly increased left atrial inotropic responses [51 +/- 5 vs. 33 +/- 2% (sham rats) of calcium chloride] and right atrial chronotropic responses [30 +/- 2 vs. 18 +/- 4 (sham rats) beats/min]; and (f) a selective decrease in beta 1-adrenoceptor density in both ventricles. Thus, NE infusion causes selective LV hypertrophy; responses of compounds that increase intracellular cyclicAMP are affected to a greater extent in papillary muscles from the hypertrophied ventricle than in tissues from the other chambers of the heart.

Animals↗
PubMed1992

The effect of the distance from the contact point to the crest of bone on the presence or absence of the interproximal dental papilla.

This study was designed to determine whether the distance from the base of the contact area to the crest of bone could be correlated with the presence or absence of the interproximal papilla in humans. A total of 288 sites in 30 patients were examined. If a space was visible apical to the contact point, then the papilla was deemed missing; if tissue filled the embrasure space, the papilla was considered to be present. The results showed that when the measurement from the contact point to the crest of bone was 5 mm or less, the papilla was present almost 100% of the time. When the distance was 6 mm, the papilla was present 56% of the time, and when the distance was 7 mm or more, the papilla was present 27% of the time or less.

Alveolar Process↗
PubMed1991

Comparison of inotropic and chronotropic responses in rat isolated atria and ventricles.

1. The positive inotropic and chronotropic responses to adrenoceptor agonists (noradrenaline, phenylephrine), to compounds which increase cAMP by post-adrenoceptor mechanisms (forskolin, theophylline and dibutyryl cAMP) and to calcium chloride were measured in isolated rat atria and papillary muscles from both ventricles. 2. Noradrenaline produced similar maximal inotropic responses to calcium chloride in all tissues. Forskolin gave similar responses to calcium chloride in atrial but not ventricular tissues; the reverse was observed with dibutyryl cAMP. Phenylephrine and theophylline produced significantly smaller inotropic responses than calcium chloride in all tissues, especially in ventricular tissues. 3. Maximal chronotropic responses to noradrenaline, theophylline and dibutyryl cAMP were similar. Forskolin produced significantly greater responses while calcium chloride and phenylephrine produced significantly smaller responses than noradrenaline. 4. These results show that the maximal positive inotropic response of some agonists is markedly dependent on the tissue chosen. Further, chronotropic responses in right atria do not mimic inotropic responses in left atria.

Animals↗
PubMed1990

Bioelectrical impedance, anthropometry and body composition in stunted and non-stunted children.

Bioelectrical impedance (BIA) and anthropometric measurements were taken of 129 stunted and 32 non-stunted children aged 9-24 months in Kingston, Jamaica. The reliability of BIA in such young children was examined and the relationships between impedance and anthropometry were determined. The stunted children had significantly lower body mass index (BMI) and smaller triceps skinfolds than the non-stunted children, suggesting differences in body composition between the groups. Resistance was significantly higher in the stunted children than the non-stunted children and nutritional group (stunted or non-stunted) contributed significantly to the variance in resistance after controlling for length, weight, mid-upper arm circumference, triceps and subscapular skinfolds, age and sex. This suggests that there were differences in body composition and/or body shape between the groups beyond that measured by the anthropometric indices used. Total body water (TBW) was estimated using an equation for Jamaican children of comparable age. As a percentage of body weight the TBW estimates were the same for the two groups, a finding which is inconsistent with the anthropometric data.

Anthropometry↗
PubMed1989

Stunting, severe malnutrition and mental development in young children.

The association was examined between an episode of severe malnutrition, stunting in length and children's developmental levels. Twenty-nine children aged between 6 and 24 months, who had recently recovered from severe malnutrition, were compared with 29 children matched for age and height who had never had an acute episode, and who came from similar social backgrounds. Both groups were given developmental assessments on the Griffiths Test, and their developmental quotients (DQs) were not significantly different. Both groups' DQs were significantly lower than a third group of 15 non-stunted children. It was concluded that the poor developmental levels usually found in severely malnourished children may be largely explained by factors associated with stunting, rather than the acute episode.

Child Development↗
PubMed1987

Differences in mortality from acute myocardial infarction between coronary care unit and medical ward: treatment or bias?

To analyse the effectiveness of coronary care units in reducing mortality from myocardial infarction 18 hospitals ranging from large urban teaching hospitals to small country hospitals were stratified into four levels of care. Previous analysis had failed to show significant differences in the overall mortality in hospital among levels. There were significant differences in mortality, however, between those patients allocated to be cared for in the coronary care unit and those in the medical wards in the more advanced hospitals. The differences were largest in the hospitals with the most elaborate facilities (level 1) and non-existent in those with the least (level 4). Several analytical approaches to these observed differences indicated that they were: (a) reduced by adjustment for age and severity of infarction; (b) paralleled by differences in coexisting disease recorded on death certificates; (c) no longer significant at level 1 after allowing for differences in coexisting disease; and (d) not significant at any level after exclusion of patients first diagnosed at necropsy. These findings suggest that the observed differences in mortality between coronary care units and medical wards are largely due to bias in selection and diagnosis.

Age Factors↗
PubMed1987

Mortality from myocardial infarction in different types of hospitals.

Hospitals ranging from large urban teaching hospitals to small country hospitals were stratified into four levels of care and examined for their effectiveness of coronary care in relation to these levels. The crude hospital mortality among 2265 patients admitted for definite or possible acute myocardial infarction was 21% at level 1 (the most elaborate level), 22% at level 2, 21% at level 3, and 19% at level 4 (the least elaborate). Adjustment for age or other prognostic factors produced no significant differences across levels either for coronary care unit care or for combined coronary unit and ward care. Success in resuscitation was also similar across levels. These findings suggest that increased resources for coronary care units--whether for new services or for upgrading existing ones--may not be required.

Age Factors↗