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Biomedical subjects

J Thornton

Publications and source records attributed to J Thornton.

At least 55 records · Page 3Linked to original sources
PubMed2000

Body composition changes during Tanner stage 5.

Clinicians use the combination of Tanner stage 5 (T5) of puberty, final height, and epiphyseal fusion to define maturity. We tested the hypothesis that changes in body composition related to age are identifiable during T5. Asian, Black, Hispanic, and White T5 adolescents (n = 148, 72 females) had measurements taken of their height, weight, total body potassium by 40K counting, total body water by D2O dilution; and total body bone mineral, fat-free mass, and fat mass by dual-energy X-ray absorptiometry. The relative increases with age in lean body components were greater than those in height and weight, and were greater in males. Age was a significant determinant of all body components in males, but of only bone mineral in females. The effect of age was independent of ethnicity. These findings suggest an independent effect of age on body composition during T5, especially in males. We propose that peak levels of lean body components should be included in the definition of maturity in certain clinical and metabolic situations.

Absorptiometry, Photon↗
PubMed2000

Total body calcium in obese women. Validation of dual-energy X-ray absorptiometry against in vivo neutron activation analysis.

In vivo neutron activation analysis (IVNA) allows in vivo measurement of total body calcium and is considered the gold standard technique. Dual-energy X-ray absorbtiometry (DXA) estimates total body calcium. Although there are a few comparisons of the two techniques, there are none with obese women. The present study compared the estimation of total body calcium by DXA with the measurement of Ca by IVNA in 69 obese women. Sixty-nine obese women (age 44 +/- 10 years, body weight [BW] 93 +/- 10.4 kg, body mass index [BMI] 35 +/- 4, fat mass 42 +/- 7 kg, 48 pre- and 21 postmenopausal, 30 Caucasian and 39 African-American) were recruited for a six-month body composition study without weight loss intervention. Total body (TB) Ca was measured by IVNA (CaIVNA) and by DXA (CaDXA) at baseline (n = 69) and again at six months (n = 40). At baseline, CaDXA was significantly higher than CaIVNA (1018 +/- 130 g vs. 706 +/- 92 g, p = 0.0001). The difference remained after six months (1028 +/- 153 g vs. 715 +/- 96 g). There was a small but significant increase in TBCa at six months by both DXA (16.5 +/- 40, p < 0.02) and IVNA (8 +/- 22 g, p < 0.03). However, this change was not significantly different between the two methods (p = 0.2365). The correlation between the two methods was very high (r = 0.937) and was independent of either race or menopausal status (p = 0.5163). We generated a regression equation: CaIVNA = 0.659 x CaDXA + 34.77; SEE = 32.2, R = 0.937. We present a model integrating the effect of weight and height on the relationship between CaIVNA and CaDXA. The higher the BMI, the bigger the difference between CaIVNA and CaDXA. In our population with a mean BMI of 35.3, CaIVNA = 69% CaDXA.

Absorptiometry, Photon↗
PubMed2000

Effect of the microclimate on horses during international air transportation in an enclosed container.

OBJECTIVE: To determine if the microclimate is detrimental to horses during international air transportation in an enclosed container. PROCEDURE: On each of two 12 h and two 24 h flights three horses were transported in an enclosed container designed to prevent exposure to insect vectors. Heart rates were monitored throughout and blood samples were collected periodically. Air in the container was sampled for bacteria and fungal spores and the temperature and relative humidity were recorded inside and outside the container periodically during the flight. On the two 12 h flights similar observations were made on three horses transported in regular open containers, which were used as controls. RESULTS: Heart rates during the flights reflected any agitation of the horses. Agitation was only mild and generally associated with take-off and landing. There were no changes in haematological or blood biochemical values that suggested any detrimental effects of the flights. The temperature in the Airstable was relatively constant during each flight (means ranged from 18.7 to 23.4 degrees C) and was significantly warmer than in the cargo hold (range 13.9 to 18.3 degrees C). Relative humidity fluctuated more widely and reflected the ambient humidity during airport stops. The numbers of bacteria and fungal spores in the Airstable air varied during the flights but were of no apparent significance to the horses' health. CONCLUSION: The Airstable proved a convenient means to transport horses on international flights and caused no discernible ill effects on the horses studied.

Air Microbiology↗
PubMed2000

Bone mineral in prepubertal children: gender and ethnicity.

Previous reports of gender and ethnic differences in bone mineral in prepubertal children have been inconsistent due to different methodologies, the problematic nature of bone density by dual-energy X-ray absorptiometry (DXA) calculated as the ratio of bone mineral mass to projected bone area (BA), and the generally small study populations. The aim of this study was to test the hypothesis that gender and ethnic differences in bone mineral by DXA are present in prepubertal children. The subjects were 336 healthy Asian, black, and white prepubertal children (172 females and 164 males). Total body bone mineral content (TBBMC) was adjusted for total body BA (TBBA), age, height, and weight. Adjusted mean TBBMC was greater in males than in females (p = 0.01). The gender difference was independent of ethnicity. Adjusted mean TBBMC was different for black compared with nonblack children (p = 0.001). The ethnic difference was a function of TBBA and weight. This study in a multiethnic population of prepubertal children shows (1) a gender difference in TBBMC and (2) an ethnic difference in TBBMC.

Absorptiometry, Photon↗
PubMed1999

Comparison of digital subtraction angiography with gadolinium-enhanced magnetic resonance angiography in the diagnosis of renal artery stenosis.

Renal artery stenosis (RAS) is a treatable cause of hypertension and renal failure for which no ideal screening technique is currently available. We evaluated the use of dynamic gadolinium-enhanced magnetic resonance angiography (MRA) for the diagnosis of RAS. Sixty-two patients with secondary hypertension were enrolled in the study. All patients had conventional renal angiography and gadolinium enhanced MRA. The sequence used was a 3D FMP SPGR sequence with the following parameters (TR: 26 ms, TE: 6.9 ms, flip angle 40 degrees, field of view 36 x 36 cm, matrix 246 x 256, 1 excitation). Gadolinium 0.3 mmol/kg was administered and 60 1. 5-mm-thick partitions were obtained over a duration of 3.5 min. The MRA images were then compared with conventional digital subtraction angiography (DSA) images. Conventional DSA demonstrated 138 renal arteries, whereas gadolinium-enhanced MRA demonstrated 129 (93 %). Twenty-one renal artery stenoses and four occluded arteries were seen at conventional DSA. Gadolinium-enhanced MRA had a sensitivity of 88 %, specificity of 98 %, accuracy of 96 %, positive predictive value of 92 % and negative predictive value of 97 % when compared with conventional DSA. Gadolinium-enhanced MRA is an accurate technique for identifying patients with RAS. It is less sensitive in picking up accessory renal arteries.

Angiography, Digital Subtraction↗
PubMed1999

Maternal body fat and water during pregnancy: do they raise infant birth weight?

OBJECTIVE: Our purpose was to determine the relation to infant birth weight of maternal fat and lean tissue during early and late pregnancy. DESIGN: Total and net maternal pregnancy weight, fat, and water were determined from measurements of total body water, body density, and bone mineral mass in 200 women, with the use of a multicompartment model for body fat estimation in early and late pregnancy. Regression modeling was used to determine the relation of maternal body composition to birth weight, with control for maternal age, height, parity, and race and for infant gestational age and sex. RESULTS: Maternal weight and body water at term were significantly associated with infant birth weight, but maternal body fat at term was not. These relations remained when maternal net values were used for weight, fat, and water to eliminate the contribution of the conceptus to these components. CONCLUSION: In well-nourished women delivering at term, maternal body fat near term does not contribute significantly to infant birth weight, but maternal body water does.

Adipose Tissue↗
PubMed1999

A Heideggerian investigation into the lived experience of humour by nurses in an intensive care unit.

A literature search revealed no systematic enquiry into the experience of humour by nurses in the intensive care setting, suggesting that there was a need for such studies (Astedt-Kurki & Liukkonen 1994). This phenomenological study was undertaken using an interpretive human science approach of phenomenology grounded in the hermeneutics of Heidegger. The task was to investigate and describe the concept of humour in an intensive care unit (ICU) from an inductive-descriptive perspective, seeking to identify the essence of the phenomenon through an accurate description of the lived experience of humour. A sample of eight nurses with at least one year's intensive care experience was randomly selected. Semi-structured interviews were conducted, audiotaped, transcribed into text, checked for transcription errors, and returned to participants for checking to ensure reliability and validity. Main core themes were identified and categorized, then Colaizzi's seven steps were used for analysis. Themes and categories identified in the collected data were rich and varied, allowing for lengthy discussions on thoughts and experiences. The study revealed a rich experience of humour in the ICU, suggesting that humour is central to nursing, and therefore worthy of deeper analysis using the same methodology.

Adaptation, Psychological↗
PubMed1999

Motif-based searching in TOPS protein topology databases.

MOTIVATION: TOPS cartoons are a schematic ion of protein three-dimensional structures in two dimensions, and are used for understanding and manual comparison of protein folds. Recently, an algorithm that produces the cartoons automatically from protein structures has been devised and cartoons have been generated to represent all the structures in the structural databank. There is now a need to be able to define target topological patterns and to search the database for matching domains. RESULTS: We have devised a formal language for describing TOPS diagrams and patterns, and have designed an efficient algorithm to match a pattern to a set of diagrams. A pattern-matching system has been implemented, and tested on a database derived from all the current entries in the Protein Data Bank (15,000 domains). Users can search on patterns selected from a library of motifs or, alternatively, they can define their own search patterns. AVAILABILITY: The system is accessible over the Web at http://tops.ebi.ac.uk/tops

Algorithms↗
PubMed1999

Percutaneous placement of biliary stents for the treatment of high risk patients with jaundice due to common bile duct stones.

OBJECTIVE: Percutaneous treatment of eight high risk patients with jaundice due to common bile duct stones who were unfit for, or refused surgery and in whom endoscopic therapy failed. METHODS: Fine needle percutaneous cholangiography was followed by catheterization of the bile duct and insertion of a 10-Fr double pigtail Teflon stent in seven cases and a metal stent in one patient with bile duct stones and noncalculous lower common bile duct obstruction. RESULTS: Stent insertion was successful in all patients. Two patients showed pus in the common bile duct. Stent insertion in these relieved the jaundice, but one patient died from sepsis at 72 h. The other patient died from renal and respiratory failure 3 wk after stent insertion with resolution of the jaundice. In six patients, stent therapy relieved the jaundice for periods up to 3 yr or death from other causes. CONCLUSIONS: These findings suggest that percutaneous transhepatic stent insertion is a reasonable alternative for the management of common bile duct stones when endoscopic stent insertion fails.

Aged↗
PubMed1998

Iditis: protein structure database.

The validation, enrichment and organization of the data stored in PDB files is essential for those data to be used accurately and efficiently for modelling, experimental design and the determination of molecular interactions. The Iditis protein structure database has been designed to allow the widest possible range of queries to be performed across all available protein structures. The Iditis database is the most comprehensive protein structure resource currently available, and contains over 500 fields of information describing all publicly deposited protein structures. A custom-written database engine and graphical user interface provide a natural and simple environment for the construction of searches for complex sequence- and structure-based motifs. Extensions and specialized interfaces allow the data generated by the database to used in conjunction with a wide range of applications.

Database Management Systems↗
PubMed1998

Informed consent for clinical trials: in search of the "best" method.

OBJECTIVE: To review the literature on comparisons between different methods of obtaining informed consent for clinical trials. DESIGN: Eight hundred and twelve articles were traced, in the process of conducting a systematic review of the ethics of clinical trials, by searching a number of sources: bibliographic databases (Medline, Psychlit and BIDS science and social science indices), hand searches, personal contacts, an original collection and a systematic follow-up of reference lists. Fourteen research reports were found which provided comparative data on different methods of obtaining informed consent. Eleven of these used a randomised design. Studies were classified according to three outcome measures (anxiety, consent rate and understanding). RESULTS: The results of the various studies suggest that giving people more information and more time to reflect tends to be associated with a lower consent rate. There seems to be an optimal level of information about side-effects such that patients are not overburdened by detail, while grasping the most important risks. More information in general is associated with greater awareness of the research nature of the trial, voluntariness of participation, right to withdraw and (available) alternative treatments. This result does not, however, extend to explanations of the concept of randomisation on which the literature is contradictory--sometimes more information is associated with increased understanding of the concept and sometimes it is not. Although divulging less information seems to be associated with less anxiety, there is evidence of an interaction with knowledge--high levels of knowledge are significantly associated with less anxiety, irrespective of consent method. The more that patients know before they are invited to participate in a trial, the better equipped they are to cope with the informed consent procedure. CONCLUSION: There is some evidence to suggest that there is an optimal amount of information which enhances patient understanding and which might, in turn, reduce anxiety. However. the studies were not altogether conclusive. More work needs to be carried out, especially on public understanding of science and on how different ways of explaining scientific concepts affect that understanding.

Clinical Trials as Topic↗
PubMed1998

Merosin-deficient congenital muscular dystrophy and cortical dysplasia.

Congenital muscular dystrophy (CMD) encompasses a heterogenous group of muscle disorders with autosomal recessive inheritance, characterized by muscular weakness and hypotonia at birth or within the first few months of life and developmental delay. Merosin-deficient CMD is a clinically distinct form which may be associated with significant abnormalities of the brain detectable by neuroimaging. We report two siblings of consanguineous parents with merosin-deficient CMD in an Irish family who in addition to the characteristic white matter abnormalities on neuroimaging, had occipital dysplasia. Clinical, electrophysiological muscle biopsy findings and neuroimaging were very similar in both cases. Although merosin-deficient CMD with white matter abnormalities on neuroimaging is well documented in the literature, the association with occipital dysplasia has only rarely been reported. The appearance of an identical cortical defect in these siblings suggests an underlying genetic mechanism.

Biopsy↗
PubMed1998

Ferrets (Mustela putoius furo) inefficiently convert beta-carotene to vitamin A.

The ferret has recently been used as a model to evaluate the absorption and metabolism of several carotenoids; however, little is known about the vitamin A (VA) requirements of this species or the ability of ferrets to convert dietary beta-carotene (betaC) to VA. Three studies were conducted to estimate the daily utilization of VA in ferrets and to determine the effect of prior VA status on the ability of ferrets to utilize betaC as a source of VA. Weanling male ferrets were fed a pelleted, low carotenoid, semipurified diet either with (+VA) or without VA (-VA) for 21- to 35-d prefeeding periods. Upon initiation of the experiments, several ferrets were killed to determine base-line VA status. The remaining ferrets were fed VA, betaC, or VA and betaC in pelleted feed (Studies 1-3) or liquid carrier (Study 3) for 16-21 additional days. Hepatic VA and betaC concentrations were used as the primary indicators of VA status, although serum and adrenal VA and betaC also were measured. The results showed the following: 1) provision of betaC at up to a 15:1 weight ratio of betaC to VA in pelleted feed or liquid carrier was not sufficient to maintain hepatic VA stores after a -VA prefeeding period; 2) the daily utilization rate of VA by ferrets ranged from 80 to 171 microg in the three studies; 3) the ferret was confirmed to be a species that has the majority of its serum VA in ester form; and 4) feeding -VA diets significantly reduced serum retinyl esters but had less effect on serum retinol. We conclude that although ferrets can convert betaC to VA, the process is inefficient. The ferret model can be most appropriately used when studying the biological effect of tissue betaC stores on VA status and is less appropriate for the evaluation of dietary betaC conversion to VA.

Adrenal Glands↗
PubMed1998

The impact of true partnership between a university Level I trauma center and a community Level II trauma center on patient transfer practices.

OBJECTIVE: To examine the effect of a clinical and administrative partnership with an academic urban Level I trauma center on the patient transfer practices at a suburban/rural Level II center. METHODS: Data for 2 years before affiliation (PRE) abstracted from inpatient charts and the trauma registry were compared with that for 2 years after (POST). The following data were collected: number of, reason for, and destination and demographics of transfers. Chi(2) test and t test analyses were used; p < 0.05 defined significance; data are mean +/- SEM. RESULTS: Transfer rate increased from 4% PRE to 6.9% (p = 0.001) POST with no significant difference in age, Glasgow Coma Scale score, Injury Severity Score, or Revised Trauma Score. Repatriation occurred in 12.8% POST (none PRE). The current Level I facility accepted 1.8% of all transfers PRE and 36.4% POST (p = 0.0001). PRE/POST rates by reason are as follows: pediatric, 14.6%/9.0% (p = 0.04); intensive care unit, 0.4%/1.7% (p = 0.13); complex orthopedic, 100%/0% (p = 0.005); vascular, 50%/0% (p = 0.008); spinal cord injury, 100%/100%; and ophthalmologic, 0%/100% (p = 0.005). CONCLUSIONS: In this experience of Level I/II partnership (1) transfer patterns were altered, (2) select patient cohort transfers decreased (pediatric, complex orthopedic, vascular), whereas others increased (aortic work-up), and (3) repatriation rates were low.

Hospitals, Community↗