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Biomedical subjects

J G Stewart

Publications and source records attributed to J G Stewart.

At least 19 recordsLinked to original sources
PubMed1999

Primary and revision total hip replacement in patients who are Jehovah's Witnesses.

The Jehovah's Witnesses do not accept allogeneic blood transfusion or certain types of autologous blood transfusion and, therefore, present the orthopaedic surgeon with a challenge in the management of perioperative blood loss. Accepting a patient who is a Jehovah's Witness as a surgical candidate requires the surgeon to be prepared medically to use known techniques to limit red blood cell loss or increase red blood cell mass, to resort to extraordinary means when necessary, and to be prepared philosophically to deal with catastrophic blood loss in a patient who may refuse even potentially life-saving transfusion. Issues pertinent to the management of intraoperative blood loss in the patient who is a Jehovah's Witness require careful delineation and specific treatment guidelines. The authors herein review their past and current experiences in the perioperative blood management of this patient population in an attempt to address this need.

Arthroplasty, Replacement, Hip↗
PubMed1994

Human performance evaluation of a metaphor graphic display for respiratory data.

Metaphor graphics are data displays designed to look like corresponding variables in the real world, but in a non-literal sense of "look like". Evaluation of the impact of these graphics on human problem solving has twice been carried out, but with conflicting results. The present experiment attempted to clarify the discrepancies between these findings by using a complex task in which expert subjects interpreted respiratory data. The metaphor graphic display led to interpretations twice as fast as a tabular (flowsheet) format, suggesting that conflict between earlier studies is due either to differences in training or to differences in goodness of metaphor. Findings to date indicate that metaphor graphics work with complex as well as simple data sets, pattern detection as well as single number reporting tasks, and with expert as well as novice subjects.

Computer Graphics↗
PubMed1993

Metaphor graphics to support integrated decision making with respiratory data.

Support for data integration in the intensive care unit (ICU) often includes efforts to improve the display of data. An electronic version of a flowsheet (table of numbers) with optimal line graphs is by far the most common format in current ICU computer workstation technology, yet there is little evidence that this format provides particularly good support for human integration of data. The present work introduces a new form of graphic representation, one that is far more metaphoric, far more tailored to the intensive care unit than a line graph. This graphic system, called volume rectangles represents mechanical ventilator data in such a way that is easy to keep different types of variables conceptually separated, yet easy to see how they relate in a truly integrated way. Volume rectangles are one example of a general approach to display of data called the metaphor graphic approach, which is being evaluated in this and other contexts. Metaphor graphics are custom tailored visual displays designed to look like the real world situation from which the data is collected but not in a literal sense of 'look like'. Anecdotal observation suggests that such graphics are easy to learn, are remembered over long period, and are good decision support tools when the task is finding patterns in a mass of data.

Artificial Intelligence↗
PubMed1984

Gastrointestinal blood loss and anemia in runners.

Iron deficiency, with or without anemia, occurs commonly in long-distance runners, but the cause is unknown. The recent development of a simple quantitative assay for fecal hemoglobin, HemoQuant , allowed us to study whether gastrointestinal bleeding occurs in runners. Blood and stool samples were collected from 24 runners before and after a race of 10 to 42.2 km and from age- and sex-matched, nonrunning controls. The mean blood hemoglobin level and hematocrit were significantly lower in runners than in controls. Serum ferritin levels were below normal in 4 runners but in no controls. Fecal hemoglobin levels increased in 20 of 24 runners (p less than 0.01) after a race. Mean fecal hemoglobin level was 1.08 mg/g (range, 0.11 to 2.36) in controls and 0.99 mg/g (0.18 to 2.41) in runners before a race, but peaked at 3.96 mg/g (0.37 to 43.20) after a race. Competitive long-distance running induces gastrointestinal blood loss and may contribute to iron deficiency.

Adult↗
PubMed1977

Evidence for conformeric states of rhodopsin.

Spectrophotometric measurements of metarhodopsin II appearance are made on five different kinds of rhodopsin preparations. Although the preparations differ greatly in their rhodopsin: phospholipid ratio, the meta II kinetics in all of them are strikingly similar in certain respects. Meta II appearance kinetics in all of the preparations are best described by two and only two exponentials. The ratio of these two rates is always about 5. The fast fraction: slow fraction ratio depends upon temperature. These fractions are reversibly convertible in the dark, and are interconverted on a time-scale which is long compared to the meta II appearance rate. It is shown that the kinetics of the earlier step in the bleaching sequence, viz., lumi-leads to meta I, is also described by double exponentials. Again the ratio of rates is ca. 5 and the fast-slow fractions correspond to those found in the meta I leads to meta II step. It is proposed that these facts support an hypothesis for the existence of two conformeric states of rhodopsin which are in thermal equilibrium. Thermodynamic parameters associated with this proposed equilibrium are presented.

Protein Conformation↗
PubMed1977

Re-irradiation of rat tails to necrosis at six months after treatment with a "tolerance" dose of x rays or neutrons.

Rat tails were re-irradiated to necrosis levels at about six months after various fractionated treatments with 290 kV X rays or 14 MeV neutrons. The X ray dose required to produce necrosis in half of a group of tails (ND50), which had been heavily X-irradiated six months before, was 91+/-4% of the ND50 for aged controls. After prior neutron-irradiation, however, this value was 87+/-4% (neutrons in second treatment) or 75+/-5% (X rays in second course). The "effective" oxygenation of mouse tails at this time after X-irradiation was similar to that of controls; thus these percentage dose values indicate the remarkable tolerance of this organized tissue to a second course of X-irradiation, and the presence of more residual injury in neutron-irradiated tissues.

Animals↗
PubMed1977

The tolerance of re-irradiation of heavily irradiated human skin.

The clinical course of a group of 15 female patients treated with X-ray therapy for radiation-induced hypopharyngeal tumours is reviewed. Neither acute nor late skin reactions exceeded those expected in similar radical treatments of patients not previously irradiated. One patient appeared to have been cured by the treatment and four achieved two years' palliation. It is suggested that the tolerance of skin to re-irradiation following a long period may approach normal.

Aged↗
PubMed1976

Tolerance of rodent tails to necrosis after "daily" fractionated X rays or D-T neutrons.

The rat tail has been used as a model system to study the necrosis of an organized tissue following fractionated doses of collimated D-T neutrons or 290 kV X rays. RBE values for tail tolerance - 10 per cent of tails necrosing after the early skin reactions - rise from about 1-7 (single doses) to about 3-1 (16 fractions in 22 days). Neutron tolerance doses are almost independent of fractionation from 2 to 16 fractions. The tissues at risk are shown to be rather hypoxic. Early skin reaction levels can be used to predict the fraction of tails that will necrose. Early peak reactions for a given fraction of necrotic tails were slightly higher for neutrons than for X rays, and this difference was consistent for all the dose fractionation schedules employed.

Animals↗
PubMed1975

The steepness of the dose response curve both for tumor cure and normal tissue injury.

At the Christie Hospital in Manchester, 4 MeV radiation was introduced in 1955. In consequence of a lack of knowledge of absolute dose definition and R.B.E. factor, patients were treated over a range of dosage. Three hundred fourteen patients with laryngeal cancer, treated over a time interval of three weeks, received doses over a range of 5,000 rad to 5,800 rads. Recurrence, morbidity and necrosis rates are plotted against dose. In T1 tumors there is very little variation in recurrence rate, and such tumors may be safely treated at the lower doses thus avoiding morbidity and necrosis. T3 tumors, however, show a considerable variation in recurrence rate being 68 percent at the lower end of the range, dropping to 30 percent at the high end. Necrosis nil at the lower end rises to some 8 percent at the high end. The balance of advantage of tumor sterilization versus the disadvantage of normal tissue damage is discussed.

Dose-Response Relationship, Radiation↗
PubMed1975

The management of glottic carcinoma by primary irradiation with surgery in reserve.

Four hundred nineteen cases of carcinoma of the larynx (1962-1965, Christie Hospital) treated primarily by radiation with surgery in reserve for cases where radiation failed, are reviewed. Two hundred ninety-one of these cases were glottic carcinomas and cure rates, and contribution from subsequent surgery is indicated in detail. Finally the overall results are compared with a larger series of 605 cases (1955-1961). Five-year cure rate in early cases is consistent at 89 percent; likewise in the latest cases at 30 percent, the intermediate group appear to have improved by some 8 percent over the period outlined. The overall cure rate is 70 percent.

Carcinoma, Squamous Cell↗
PubMed1975

An account of the radium collar and the Finzi Harmer implant.

Dr. J. G. Stewart of the Christie Hospital and Holt Radium Institute in Manchester gave an anecdotal account of two methods which were previously used to radiate laryngeal carcinomata and neck nodes. Both techniques have been superseded by newer irradiation techniques, but in view of their considerable success and historical interest, they are included here. The first paper concerns the radium collar which was used for the treatment of late cases of laryngeal carcinoma, and in particular for cases with neck nodes. The second is a brief account of the Finzi Harmer radium needle implant technique, which was at one time widely used.

England↗