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A Steele

Publications and source records attributed to A Steele.

At least 37 records · Page 2Linked to original sources
PubMed1998

Atomic force microscopy imaging of fragments from the Martian meteorite ALH84001.

A combination of scanning electron microscopy (SEM) and environmental scanning electron microscopy (ESEM) techniques, as well as atomic force microscopy (AFM) methods has been used to study fragments of the Martian meteorite ALH84001. Images of the same areas on the meteorite were obtained prior to and following gold/palladium coating by mapping the surface of the fragment using ESEM coupled with energy-dispersive X-ray analysis. Viewing of the fragments demonstrated the presence of structures, previously described as nanofossils by McKay et al. (Search for past life on Mars--possible relic biogenic activity in martian meteorite ALH84001. Science, 1996, pp. 924-930) of NASA who used SEM imaging of gold-coated meteorite samples. Careful imaging of the fragments revealed that the observed structures were not an artefact introduced by the coating procedure.

Carbonates↗
PubMed1998

Bulimia: a primary care approach.

More common than anorexia and less easily detected, bulimia typically begins as an effort to control weight. Although the prognosis is better than that for anorexia nervosa, a number of medical complications can arise related to the mode of purging. Some of these complications can have profound deleterious sequelae if not diagnosed and treated.

Adolescent↗
PubMed1997

Postoperative hyponatremia despite near-isotonic saline infusion: a phenomenon of desalination.

BACKGROUND: It is widely presumed that the development of postoperative hyponatremia (which may be severe) results from administration of hypotonic fluids while antidiuretic hormone is acting. OBJECTIVE: To show that hyponatremia would occur in patients 24 hours after surgery if only near-isotonic solutions are given and to evaluate the mechanisms responsible for hyponatremia in this setting. DESIGN: Prospective cohort study. SETTING: University medical center. PATIENTS: 22 women who were having uncomplicated gynecologic surgery with infusion of near-isotonic solutions only (sodium chloride, 154 mmol/L, or Ringer lactate [sodium, 130 mmol/L, and potassium, 4 mmol/L]). MEASUREMENTS: Plasma electrolyte levels were measured at the time of induction of anesthesia and 24 hours later. Data on the balance of water and electrolytes were obtained for the same 24-hours period. RESULTS: At the time of induction of anesthesia, the plasma sodium concentration was 140 +/- 1 mmol/L; 24 hours later, it decreased in 21 of 22 patients (mean decrease, 4.2 +/- 0.4 mmol/L [P < 0.001]; lowest level, 131 mmol/L in 2 patients). The urine remained hypertonic (peak sodium plus potassium concentration in urine, 294 +/- 9 mmol/L) in all patients for the first 16 hours after induction of anesthesia. CONCLUSIONS: Postoperative hyponatremia occurred within 24 hours of induction of anesthesia when only near-isotonic fluids were infused. Hyponatremia was generally caused by generation of electrolyte-free water during excretion of hypertonic urine-a desalination process. This electrolyte-free water was retained in the body because of the actions of antidiuretic hormone. If the pathophysiology of this hyponatremic state is understood, recommendations for its prevention and treatment can be deduced.

Adult↗
PubMed1997

Trophoblasts express Fas ligand: a proposed mechanism for immune privilege in placenta and maternal invasion.

Cross-linking of Fas (CD95, APO-1) and Fas ligand (FasL; CD95L) induces apoptosis of Fas-bearing cells. Recent evidence suggests that FasL. expression plays an important role in maintenance of immune privilege in murine testis and eye and in tumour escape from immune rejection in colon cancer, melanoma and hepatocellular carcinoma. Bcl-2 is a membrane protein that suppresses apoptosis in response to a variety of stimuli. In this paper we describe abundant expression of FasL protein and mRNA transcripts within the immune privileged environment of the placenta by immunohistochemistry and reverse transcription in-situ polymerase chain reaction methods. The syncytiotrophoblast layer, the main site of feto-maternal interface, and extravillous trophoblasts, demonstrated consistent immunoreactivity for FasL in term placentae. Co-occurrence of Fas and Bcl-2 were detected with a similar pattern of distribution with FasL. The TUNEL method revealed evidence of apoptosis in the placental tissues. We speculate that abundant presence of FasL in the trophoblast contributes to immune privilege in this unique environment, perhaps by fostering apoptosis of activated Fas-expressing lymphocytes of maternal origin. An apoptotic process mediated by FasL may also play a role in placental invasion during implantation and underscores similarities between the trophoblast and neoplastic cells.

Apoptosis↗
PubMed1997

Predictability.

Explore the source record for details and available documents.

Humans↗
PubMed1997

Congruence and predictive power of mothers' and teachers' ratings of mastery motivation in children with mental retardation.

The congruence between mothers' and teachers' ratings of mastery motivation among 3-year-old children with mental retardation was investigated. The extent to which maternal and teacher ratings of task persistence at entry to preschool are predictive of observed mastery behaviors at age 5 was tested. Results indicate that mothers rated their children's task persistence behaviors higher than did teachers. Further, once the child's cognitive level and teacher ratings were controlled for statistically, maternal ratings of the child's mastery behaviors were predictive of the child's task mastery performance 2 years subsequent. Implications for educational planning were discussed.

Child, Preschool↗
PubMed1997

Hyponatremia in the rat in the absence of positive water balance.

The purpose of this report is to determine the mechanisms that lead to hyponatremia when isotonic saline was the only fluid infused into rats given antidiuretic hormone (ADH), and what might minimize the degree of this hyponatremia. Normal rats were deprived of food and water for the 24-hr study period. They received an infusion of isotonic saline to expand their extracellular fluid (ECF) volume with and without exogenous ADH administration (N = 8 in each of the four groups). Similar studies were also carried out in 32 rats fed a low electrolyte diet for 72 hr before the experiment. An additional control group was fed the low electrolyte diet supplemented with sodium (Na), potassium (K), and chloride (Cl). Hyponatremia developed over 24 hr in rats fed their usual diet if treated with ADH and isotonic saline (fall, 13 +/- 2 mM, P < 0.01). The hyponatremia was caused by negative balance for Na + K salts. Hyponatremia did not develop after the saline + ADH treatment if rats were pretreated for 3 days with a low electrolyte diet. Two factors were required to develop this hyponatremia--generation of electrolyte-free water as a result of the excretion of a large quantity of Na + K salts at a high concentration in the urine, and prevention of the excretion of this electrolyte-free water by ADH. Increasing the avidity for Na reabsorption by the kidney prevented this type of hyponatremia from developing.

Animals↗
PubMed1996

Erythrocyte Na(+)-H+ exchanger kinetics and Na(+)-Li+ countertransport activity in essential hypertensive patients.

The authors measured Na(+)-H+ exchanger kinetics together with Na(+)-Li+ countertransport V(max) in the erythrocytes of 21 subjects with essential hypertension and 16 normotensive control subjects. Na(+)-H+ exchange V(max) appeared to be increased in patients with essential hypertension, while the Na(+)-H+ exchanger affinity for intracellular proton sites (K50%) proved to be unchanged and the index of cooperativity among intracellular proton binding sites as measured by Hill's coefficient (Hill's n) decreased as compared with normotensive control subjects. Na(+)-Li+ countertransport V(max) appeared to be higher in patients with essential hypertension than in control subjects. The authors were unable to find any correlations between Na(+)-H+ exchanger kinetic parameters and metabolic variables such as parameters of insulin resistance and plasma lipids. On the basis of the data obtained, erythrocyte Na(+)-H+ exchanger activity was found to be abnormal in two kinetic variables in essential hypertensive patients and showed no simple linear correlations with the main variables of glucose metabolism, plasma lipids, renin or aldosterone.

Adult↗
PubMed1996

Tuberculin testing in two Liverpool social clubs: the effects of a tuberculosis outbreak on background positivity.

BACKGROUND: Tuberculin testing remains the standard method for assessing infection due to tuberculosis in the UK. However, there are no data on the incidence of tuberculin positivity among the general adult population in the UK and consequently interpretation of Heaf test results is often difficult. METHODS: During the investigation of an outbreak of tuberculosis in a Liverpool social club 198 members were interviewed and Heaf tested and 171 members of a second social club in Liverpool were similarly screened as a control group. Comparisons between the results from the two populations provided both an estimate of baseline Heaf test positivity in indigenous white adults from a British inner city population, and a measure of the effect on this baseline of recent exposure to tuberculosis. RESULTS: In both club populations the proportion of positive Heaf tests increased with age. Independent of age, the tuberculosis exposed population had a higher proportion of positive Heaf grade results (40.9%) than those in the control group (26.9%). Multivariate analysis confirmed both the differences in Heaf results between clubs and between age groups but identified no other behavioural or medical factors which affected Heaf test results. CONCLUSIONS: Heaf test positivity increases with age at least up to 54 years, and recent exposure to tuberculosis increases the proportion of positive Heaf tests in each age group. Interpretation of positive Heaf tests when assessing the effects of a tuberculosis outbreak should take account of background levels of Heaf positivity.

Adolescent↗
PubMed1996

Can a severe degree of ketoacidosis develop overnight?

Insulin-dependent diabetes mellitus in poor control, alcohol intake associated with extracellular fluid volume contraction, or hypoglycemia may each lead to an increased rate of production of ketoacids. Generally, several days of illness are required before ketoacidosis becomes severe. Two clinical examples are presented to suggest that a severe degree of ketoacidosis may develop over a short period of time, literally overnight. In both examples, there was the ingestion of a modest amount of ethanol. From a quantitative analysis of factors that may influence the rate of production and removal of ketoacids, the following were deduced. Contributing factors to the very rapid development of maximal ketoacidosis could include the absence of a lag period for the conversion of ethanol to acetyl-coenzyme A in the liver and an impaired ability of the brain and kidneys to oxidize ketoacids, especially if these ketoacids are produced very rapidly and/or if less metabolic work is performed by these organs. In special settings, ketoacidosis may develop more rapidly than is generally appreciated.

Adult↗
PubMed1995

Nurses' knowledge and beliefs about AIDS: comparing nurses in hospital, community and hospice settings.

The literature reports an ongoing debate amongst nurses regarding the risk of contracting human immunodeficiency virus (HIV) through routine nursing care. An emotionally charged dilemma appears to exist for many nurses regarding what they perceive as conflict between professional obligation and personal risk. This study investigates nurses' beliefs, knowledge and perceptions of risk of contracting HIV while implementing their nursing care. The study focuses on qualified nurses in the hospice, hospital and community settings. No other similar comparative study that also focuses on hospice nurses has been identified. This quantitative study was implemented within Northern Ireland, by way of a respondent-administered questionnaire. The study's sample consisted of 45 qualified nurses and a response rate of 93% (42 respondents) was achieved. Analysis of the data involved the use of descriptive and correlational statistics. Overall findings indicated that many nurses, but particularly those who work in the hospital and community settings, hold negative and biased beliefs, and have inadequate knowledge and misguided perceptions regarding their risk of contracting HIV through the implementation of routine nursing care of clients. Many of those nurses readily admit their lack of knowledge. On the whole, hospice nurses appear more knowledgeable and exhibit a more positive approach to AIDS clients, and appear less fearful than do nurses in the other two settings. Implications for hospital management, for nurse education, for nurses themselves and for clients are discussed. This study should be seen as a springboard for future research within Northern Ireland.

Acquired Immunodeficiency Syndrome↗
PubMed1995

A molecular epidemiological study of porcine rotaviruses.

Diarrhoea in the piglet can lead to stunted growth and neonatal death, with important implications for the pig farmer. During 1993, a pilot study was initiated to monitor the epidemiology of rotavirus infection in piglets with diarrhoea. Bimonthly diarrhoeal faecal specimens were collected from scouring piglets less than 6 weeks of age on a pig farm in the Northern Transvaal. The stool specimens were examined by a commercial enzyme-linked immunosorbent assay (Rotavirus EIA, IDL, Jerusalem). In total, rotavirus antigen was detected in 24% of the litters by the ELISA, which is directed at the group A rotavirus antigen. Rotavirus was found to occur throughout the year and predominantly in piglets 4 weeks old. Polyacrylamide electrophoretic analysis of the viral RNA genomes showed the presence of four distinct strains of Group A rotaviruses circulating on this farm. This study highlights the natural diversity of rotavirus strains circulating on a single farm and may indicate the importance of rotavirus infection in piglets with diarrhoea in South Africa.

Age Factors↗
PubMed1994

The visual prognosis following HLA-matched keratoplasty for high-risk patients.

We report the clinical details of 30 HLA-matched corneal grafts with a mean follow-up of 29 months. Few of the patients were immunologically naive as almost all had received previous unmatched grafts. The two-year survival rate was 77%, comparable with other series. A majority of patients obtained good vision, and this was statistically superior to a recent large series. Almost all remained on their topical medication indefinitely. The contralateral visual acuity was surprisingly good, but there are few published data for comparison. We were unable to document an enhanced prognosis with a higher degree of HLA-A, B or DR match, possibly because of the small numbers.

Adult↗
PubMed1994

What is responsible for the diurnal variation in potassium excretion?

Potassium excretion exhibits a diurnal pattern, with most excretion occurring close to noon in humans. Each component of the K+ excretion rate [urinary K+ concentration ([K+]) and flow rate] was measured and back-calculated to reflect events in the cortical collecting duct (CCD). Our purpose was to determine to what extent each component contributed to this diurnal variation in each 2-h portion of the day. In humans, K+ excretion rose threefold from nadir (0600 h) to peak (1200-1400 h), 18 h after the principal intake of K+. The variation in K+ excretion was due almost exclusively to changes in [K+] in the terminal CCD ([K+]CCD) rather than via changes in flow rate. In rats, the bulk of K+ excretion occurred shortly after eating. Both components of K+ excretion rose after meals; the rise in the [K+]CCD (3.3-fold) predominated at earlier times, and the rise in flow rate occurred later and was primarily a result of a higher rate of excretion of urea. The rise in [K+]CCD did not correlate with aldosterone levels or administration. A very large rise in the [K+]CCD only occurred in the presence of bicarbonaturia; the transtubular potassium concentration gradient was now close to 15 in the morning and evening.

Acetazolamide↗
PubMed1993

Visual prognosis following accidental vitreous loss during cataract surgery.

Over the past 7 years there has been a change in the management of accidental vitreous loss during cataract surgery. There has been a reduction in immediate postoperative complications such as hyphaema. No immediate post-operative complications were observed during the last 18 months of the study. Whereas previously many of these patients remained aphakic, there was a change initially to anterior chamber intraocular lenses (IOLs) and now the vast majority receive capsule-supported sulcus-fixated posterior chamber IOLs. All patients had improved vision post-operatively by a mean of 4 Snellen lines, although they did not achieve the acuities of age- and sex-matched controls (p = 0.015).

Adult↗
PubMed1993

Refractive results after corneal triple procedures (PK+ECCE+IOL)

We have analysed the refractive results of corneal triple procedures (penetrating keratoplasty with extracapsular cataract extraction and posterior chamber intraocular lens implantation) in 52 eyes of 47 patients with a mean follow-up of 39 months. The patients were predominantly old and female and most received unilateral surgery. The contralateral acuity was 6/24 or worse in more than 50% of cases at the time of surgery. Many of these patients were significantly ametropic pre-operatively. Biometry does not seem to have improved the refractive results in those patients in whom it was attempted. The majority of patients were hypermetropic when their refraction stabilised, with resulting poor uncorrected visual performance. Possible improvements are discussed.

Aged↗
PubMed1993

Erythrocyte Na(+)-H+ exchange activity in essential hypertensive and obese patients: role of excess body weight.

INTRODUCTION: Several authors have described increased Na(+)-H+ exchanger activity in essential hypertension, and an increase in activity of this transport system has also been postulated in situations of hyperinsulinism, such as obesity and essential hypertension. METHODS: We measured Na(+)-H+ exchanger activity in a group of 37 subjects with essential hypertension (18 obese, 19 non-obese), in a group of nine normotensive obese subjects and in a control group of 16 healthy volunteers. Plasma insulin and glucose values during an oral glucose tolerance test were evaluated, together with other variables such as plasma aldosterone, plasma renin activity and plasma potassium. RESULTS: Na(+)-H+ exchanger system activity did not appear to be abnormally raised in the hypertensive subjects, but was significantly increased in the normotensive obese group. Upon dividing the hypertensive subjects into two subgroups on the basis of body mass index, it was noted that, whereas the non-obese hypertensives showed Na(+)-H+ exchanger activity patterns similar to those in controls, the obese hypertensive subjects exhibited increased activity of the transport system. Na(+)-H+ activity correlates with body mass index and shows a significant inverse correlation with plasma potassium. No correlations were found between Na(+)-H+ exchanger activity and the sum of plasma insulin values during the oral glucose tolerance test. CONCLUSION: Na(+)-H+ exchanger overactivity appears to be characteristic in overweight subjects, but would not appear to be a specific feature of essential hypertension. The increased Na(+)-H+ exchanger activity observed in obese subjects may be postulated to be related to the hypermineralocorticoidism characteristic of this condition.

Adult↗