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Biomedical subjects

S J Thomas

Publications and source records attributed to S J Thomas.

At least 37 records · Page 2Linked to original sources
PubMed2001

Total body irradiation using a modified standing technique: a single institution 7 year experience.

We describe a simple standing technique for delivering total body irradiation (TBI) using large horizontal fields, made possible by the off-centre installation of a non-dedicated treatment unit in a pre-existing bunker. Patients are treated using anterior and posterior fields with customized lung compensators. This technique enables the dose to the lung to be accurately calculated and modified to avoid overdose and to minimize the risk of pneumonitis. From February 1991 to December 1997, 94 patients with a variety of haematological malignancies were given fractionated TBI using this technique prior to allogenic or autologous bone marrow transplantation. Patients received a total dose of 14.4 Gy given in eight fractions over 4 days, with at least 6 h between fractions. The prescribed dose to the lungs was reduced to 12 Gy in eight fractions. The technique was well tolerated, took less than 10 min to set up and did not disrupt the daily routine use of the machine. Doses to all measured points on the trunk and head were within +/-6% of the prescribed dose. Doses to the lungs were within +/-5% of the prescribed dose. There were no early respiratory deaths in the 37 autologous transplant patients. There were 10 (17%) respiratory deaths in the 57 allogeneic transplant patients, 3 of confirmed infectious aetiology.

Adolescent↗
PubMed2000

The anatomical relationship between the posterior interosseous nerve and the supinator muscle.

Understanding the anatomical relationships in the region of the supinator muscle is crucial in limiting surgical morbidity. The course, length, and muscular innervations of the posterior interosseous nerve, as well as a detailed dissection of the supinator muscle, were described and recorded in 31 specimens from 16 adult cadavers. In our study, the radial nerve bifurcated into the posterior interosseous nerve and superficial radial nerve 8.0 +/- 1.9 cm distal to the lateral intermuscular septum. The bifurcation of the radial nerve occurred 3.6 +/- 0.7 cm proximal to the leading edge of the supinator, with the posterior interosseous nerve exiting the supinator muscle 3.8 +/- 0.9 cm distal to the proximal margin. The arcade of Frohse was membranous in 68% of our specimens and tendinous in 32%. The supinator had one semicircular head or layer in 71% of specimens and 2 distinct heads or layers, as defined by diverging muscle fibers, in 29%. With 2 heads, or layers, the superficial layer extended to the lateral epicondyle while the deep layer extended to the ulna, below the radial notch.

Adult↗
PubMed2000

Comparison of exertional indices following moderate training in collegiate athletes.

BACKGROUND: To better understand the inflammatory response to two divergent training modalities: running and weight training. METHODS EXPERIMENTAL DESIGN: prospective, repeat measures, observational study of subjects over the course of 8-10 weeks of training. Data analysis was consonant with this design and included a repeat measures ANOVA with multiple posthoc comparisons. The level of significance was set at 0.05. SETTING: collegiate athletic training facilities. PATIENTS: twenty-two subjects comprised the study group. These included both male and female collegiate athletes, ages 17-22 years of age with a mean height of 178.6 cm, a mean weight of 77.5 kg and a mean lean body mass of 67.2 kg. Exclusion criteria consisted of hemophilia or chronic conditions requiring anti-inflammatory medication. INTERVENTIONS: training for runners (n=11) consisted of multiple 5-km runs throughout the course of a 60-75 minute workout. For a comparable time period, weight trainers participated in multiple joint, total body strengthening workouts. MEASURES: four exertional indices were examined. These included serum levels of creatine kinase, lactate, Interleukin-6, and C-reactive protein. Assessments of these markers were made immediately before and after each training session. Three sessions were monitored over an 8-10 week period. RESULTS: The data show that moderate exertion is accompanied by modest increases in these markers. Mean serum values did not exceed 125 U/L for serum creatine kinase, 5 mM/I for lactates, and 2.6 pg/ml for IL-6. C-reactive protein was sporadically detectable in weight lifters only. These increases were detected immediately postexercise. Each training modality produced a unique profile for creatine kinase and IL-6, suggestive of a training effect. CONCLUSIONS: Overall, the levels for all exertional markers reported herein are well below those reported for exhaustive exercise. As consistent exhaustive efforts can catalyze overtraining syndromes, periodic assessments of these exertional indices could help to document the appropriateness of the training stimulus.

Adolescent↗
PubMed1999

Ischaemic pre-conditioning in organotypic hippocampal slice cultures is inversely correlated to the induction of the 72 kDa heat shock protein (HSP72).

In vivo, preconditioning with a sublethal insult can confer resistance to normally lethal episodes of cerebral ischaemia. This phenomenon has been linked with the induction of the 72 kDa heat shock protein (HSP72), but this has not been clearly demonstrated in vitro. We have used organotypic hippocampal slice cultures to investigate whether tolerance to lethal ischaemia is dependent on HSP72. Cultures were maintained in vitro for 14 days, and neuronal damage assessed using propidium iodide fluorescence. Prolonged neuronal HSP72 upregulation occurred following exposure to 30 min ischaemia, 45 min hypoxia and 1 microM kainate, but not 1 microM NMDA or 20 min ischaemia, all sublethal insults. Preconditioning with ischaemia, kainate or hypoxia 24 h prior to lethal ischaemia (45 min) was not protective, and when the delay was increased to 48 h, damage in the CA3 pyramidal cell region was significantly increased compared to cultures exposed to 45 min ischaemia alone. Preconditioning with 20 min ischaemia had no effect on the severity of ischaemic damage. Preconditioning with 1 microM NMDA significantly reduced neuronal damage produced by either 45 or 60 min ischaemia when the delay between insults was 48 h. NMDA pre-treatment also prevented neurotoxicity produced by glutamate (5-10 mM) but not NMDA (10-30 microM). These data suggest that in vitro, the increased expression of HSP72 following some sublethal insults should be considered as a marker of cell stress prejudicial to the survival of neurones subsequently exposed to ischaemia, while tolerance can be produced through mechanisms independent of HSP72 induction.

Animals↗
PubMed1999

Role of Nr13 in regulation of programmed cell death in the bursa of Fabricius.

Apoptotic cell death is developmentally regulated in the chicken bursa of Fabricius. Although apoptosis is low in the embryonic bursa, cell death increases markedly after hatching. The expression of Bcl2 family cell death antagonists was examined to identify the genes that regulate bursal cell apoptosis. The expression of Bcl-xL, A1, and Mcl1 was detected in both embryos and hatched birds, whereas Nr13 was expressed at high levels in embryonic bursa, and decreased significantly after hatching, correlating inversely with apoptosis. The oncogene v-reland phorbol myristate acetate, two known inhibitors of bursal cell apoptosis, induced Nr13 expression. Overexpression of Nr13 in DT40 bursal lymphoma cells protected them from low serum-induced apoptosis. The mechanism of inhibition of apoptosis by Nr13 is likely to involve a critical BH4 domain and interaction with death agonist Bax. Deletion of the BH4 domain converted Nr13 into a death agonist. Bax coimmunoprecipitated with Nr13 and Bax was induced, whereas Nr13 levels diminished when bursal lymphoblasts were induced to apoptosis by dispersion. Bursal transplantation studies demonstrated that Nr13 could prevent the in vivo programmed elimination of bursal stem cells after hatching, suggesting that Nr13 plays a role in maintaining bursal stem cells.

Amino Acid Sequence↗
PubMed1999

Relative electron density calibration of CT scanners for radiotherapy treatment planning.

Several authors have reported data on the variation of Hounsfield numbers with electron density in CT scanners. The data can be fitted with a double straight line approach. For non-bone tissues (or phantom materials with similar atomic numbers) the data from all authors can be fitted to a single straight line. For bone-like materials the line varies between authors. The method used to measure electron density has a greater effect than the differences between scanners, or the kilovoltage used on a given scanner. The effect of variation of these slopes on the accuracy of radiotherapy treatment planning is analysed. For typical radiotherapy beams, to produce a 1% error in dosimetry would require errors of over 8% in bone electron density. Using a single pair of calibration lines for all the scanners reported would give dosimetric errors of under 0.8%. A formula is recommended as a default for use in planning systems in circumstances where no data are available for a particular scanner.

Calibration↗
PubMed1999

What variety of attention is automatically captured by peripheral cues?

Previous studies have shown that the voluntary allocation of attention to a location in space can influence accuracy in two ways. First, additional processing resources can be allocated to the attended location, leading to an improvement in perceptual quality for objects presented at that location. Second, decision processes can be restricted to information arising from the attended location, which improves accuracy without influencing the perceptual representation. The present study examined the operation of these two attentional mechanisms when nonpredictive peripheral cues were used to capture attention automatically. Experiment 1 showed that, like predictive cues, nonpredictive cues influence accuracy by summoning perceptual resources and also by influencing decision processes. However, both the cues and the targets in this experiment were defined by luminance increments, making it possible that the cuing effects were mediated by a task-controlled attentional set rather than being fully automatic. Experiments 2 and 3 examined this possibility by using luminance-defined cues and color-defined targets; evidence was again obtained for both perceptual-level and decision-level attention effects. The capture of attention by a nonpredictive peripheral cue thus appears to influence both perceptual resource allocation and postperceptual decision processes.

Attention↗
PubMed1998

Effect of providing fortified meals and between-meal snacks on energy and protein intake of hospital patients.

This study aimed to evaluate whether food fortification and snacks could increase the energy and protein intakes of hospital patients. The control group of 82 consecutive admissions on medical, elderly care and orthopaedic wards ate freely from the hospital menu. Subsequently, an intervention group of 62 patients were offered fortified food and snacks, providing an extra 22.2|g protein/day and 966 kcal/day in addition to the standard menu. Fortification significantly increased energy intake in the intervention group (P = 0.007, independent samples t-test), having the greatest effect on groups with the lowest energy intake, that is male and female orthopaedic, female medical and female elderly patients (84 cent of total). The increases in energy intake were 21.3 cent, 21.4 cent, 23 cent and 19.6 cent respectively. Although the increased energy and protein intake represented 25.6 cent and 22.5 cent respectively, of the supplements given, and suggested that wastage was high, it was nevertheless sufficient to remove energy deficit. We therefore propose that provision of fortified food and snacks is a convenient method of improving the nutritional intakes of hospital patients.

Adult↗
PubMed1998

The efficacy and safety of a pharmacologic protocol for maintaining coronary artery bypass patients at a higher mean arterial pressure during cardiopulmonary bypass.

A recent randomized trial of higher versus lower mean arterial pressure (MAP) during cardiopulmonary bypass (CPB) showed that higher MAP on CPB was associated with a lower incidence of overall cardiac and neurologic morbidity and mortality in coronary artery bypass graft surgery (CABG) patients. Cardiopulmonary bypass MAP was controlled pharmacologically while CPB flow was held constant for any given period. The objective of the present study was to assess the efficacy and safety of this pharmacologic protocol. Two hundred forty-eight patients participated in the study; the mean age was 65.8 +/- 9.4 years, 20% were women, and the mean preoperative ejection fraction was 48%. The low-flow corrected CPB MAP attained for the low and high MAP groups was 56.7 +/- 5.0 mmHg and 77.7 +/- 7.1 mmHg, respectively (p = 0.0001). Major cardiac and neurologic outcomes, postoperative blood loss, renal dysfunction, intensive care unit (ICU) stay, and duration of intubation were not found to be significantly associated with any drug in the pharmacologic protocol. These findings support that the pharmacologic protocol used to maintain CABG patients at higher MAP on CPB is both efficacious and safe.

Aged↗
PubMed1997

Genetic factors in the aetiology of mouth ulcers.

The aetiology of mouth ulcers is uncertain, and prior research has indicated both environmental and genetic factors. In this study, information on mouth ulcer incidence was collected for 290 twin pairs--127 monozygous (MZ) and 163 dizygous (DZ)--and their parents, a total of 1,160 people. Self-reported data on mouth ulcer incidence were available for the twins, and in each family the mother also reported on the mouth ulcer incidence in the twins, the twins' father, and herself. A structural equation model--combining a measurement model, a rater bias model, and a model including genetic and environmental influences--was used to explain variation in mouth ulcers. The fitted model explained the variation in a latent phenotype of mouth ulcer incidence for the twins in terms of an additive genetic factor (64%), a common environment factor (26%), and a specific environment factor (10%). The mothers' ratings showed a significant positive bias.

Bias↗
PubMed1997

Orthovoltage applicator design: its effect on a transmission monitor chamber.

In the Pantak DXT300, the applicators are mounted immediately below a transmission monitor chamber. Changing the metals used in applicator construction can cause variations of up to 22% in calibration factor (cGy MU(-1)) and apparent dose rate (MU min(-1)), but has no effect on radiation dose rate (cGy min(-1)). The results are consistent with being caused by backscatter from the applicator to the monitor chamber.

Calibration↗
PubMed1997

Computerized data collection in the operating room during coronary artery bypass surgery: a comparison to the hand-written anesthesia record.

OBJECTIVE: To investigate variability between hand-written and computerized anesthesia records and evaluate any associated bias. DESIGN AND MEASUREMENTS: A computer system that was used to collect intraoperative data for a study of hemodynamic management during coronary artery bypass graft surgery is described. The system collected and recorded hemodynamic data automatically downloaded from the anesthesia monitor as well as surgical events and drug administration data entered through menu options. The system then combined, summarized, and graphed the data as well as formatted it for export to a commercially available database program. In a sample of 14 patients, blood pressure data collected by the computer system was compared with the blood pressure data charted in the hand-written anesthesia record. MAIN RESULTS: Although general linear models controlling for within-patient variation and randomization assignment for mean arterial pressure range on cardiopulmonary bypass showed a significant relationship; low R2 values indicated that much of the variability could not be explained and that there was, therefore, poor agreement between the two records. Furthermore, a systematic bias in the hand-written anesthesia record was found when the computer system record was compared with the hand-written record and to the difference of the two records, so that extremes seen in the computer system record tended to be minimized in the hand-written anesthesia record. CONCLUSIONS: Because of the lack of explained variability between the computer system and hand-written anesthesia records and the bias in the hand-written anesthesia record, the hand-written anesthesia record should not be relied on as a source of accurate data for research purposes.

Anesthesia↗
PubMed1997

Familial Burkitt's lymphoma in Papua New Guinea.

A study of Burkitt's lymphoma (BL) in Papua New Guinea for the years 1958-87 revealed four instances of familial BL. Incident cases occurred within 1 year of each other in the four families. Personal follow-up was possible for three of these families whose pedigrees showed that two or more siblings were affected. There was no significant variation of the incidence of BL by year of diagnosis or month of onset. There was significant variation in annual average incidence of BL between the three provinces studied, with the highest incidence in the Nuku and Lumi census districts (of the West Sepik Province). This is the first report of familial BL outside Africa.

Burkitt Lymphoma↗
PubMed1996

Severity of aortic atheromatous disease diagnosed by transesophageal echocardiography predicts stroke and other outcomes associated with coronary artery surgery: a prospective study.

Advanced atheromatous disease of the thoracic aorta identified by transesophageal echocardiography (TEE) is a major risk factor for perioperative stroke. This study investigated whether varying degrees of atherosclerosis of the descending aorta, as assessed by TEE, are an independent predictor of cardiac and neurologic outcome in patients undergoing coronary artery bypass grafting (CABG). Intraoperative TEE of the descending aorta was performed on 189 of 248 patients participating in a randomized controlled trial of low (50-60 mm Hg) or high (80-100 mm Hg) mean arterial pressure during cardiopulmonary bypass for elective CABG. Aortic atheromatous disease was graded from I to V in order of increasing severity by observers blinded to outcome. Measured outcomes were death, stroke, and major cardiac events assessed at 1 wk and 6 mo. Nine of the 189 patients with TEE examinations had perioperative strokes by 1 wk. At 1 wk, no strokes had occurred in the 123 patients with atheroma Grades I or II, while the 1-wk stroke rate was 5.5% (2/36), 10.5% (2/19), and 45.5% (5/11) for Grades III, IV, and V, respectively (Fisher's exact test, P = 0.00001). For 6-mo outcome, advancing aortic atheroma grade was a univariate predictor of stroke (P = 0.00001) and death (P = 0.03). By 6 mo there were one additional stroke, three additional deaths, and one additional major cardiac event. Atheromatous disease of the descending aorta was a strong predictor of stroke and death after CABG. TEE determination of atheroma grade is a critical element in the management of patients undergoing CABG surgery.

Aged↗