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Biomedical subjects

T J Hine

Publications and source records attributed to T J Hine.

10 recordsLinked to original sources
PubMed2006

Intermediate and high peri-operative cardiac enzyme release following isolated coronary artery bypass surgery are independently associated with higher one-year mortality.

BACKGROUND: The relationship between cardiac enzyme (CE) release following coronary artery bypass surgery (CABG) and medium term outcome is unclear. We sought to determine the relationship between post-operative CE release and one-year survival following isolated CABG. METHODS: Over three years 3,024 consecutive patients underwent isolated CABG. Patient characteristics were prospectively recorded in a cardiac surgical database. CE release, taken as the highest single measurement recorded in the first 24 hours post-op, was abstracted from an electronic archive. All cause mortality was taken from a national registry of deaths. RESULTS: Data were complete for 2,860 (94.6%) patients. CK-MB isoenzyme (reference range 5-24 U/l) was recorded in 2,568 (89.8%), total CK in 292 (10.2%). CE release three or more times the upper limit of the reference range (ULR) were recorded in 498 (17.4%) patients, 163 (5.7%) patients had CE more than six times ULR. There were 122 deaths (4.3%). Cox proportional hazards analysis showed that CE release 3-6 times ULR (adjusted HR 2.1 [95% CI: 1.6 to 2.6], p = 0.002) and CE release six or more times the ULR (adjusted HR 5.0 [95% CI: 4.5 to 5.4], p < 0.001) were independently associated with increased one-year mortality. CONCLUSION: Cardiac enzyme release following CABG is associated with increased one-year all-cause mortality. The definition of peri-operative myocardial infarction following CABG should include elevation of CK-MB three or more times the upper limit of normal.

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PubMed2004

Automated eye tracking system calibration using artificial neural networks.

The electro-oculogram (EOG) continues to be widely used to record eye movements especially in clinical settings. However, an efficient and accurate means of converting these recordings into eye position is lacking. An artificial neural network (ANN) that maps two-dimensional (2D) eye movement recordings into 2D eye positions can enhance the utility of such recordings. Multi-layer perceptrons (MLPs) with non-linear activation functions and trained with back propagation proved to be capable of calibrating simulated EOG data to a mean accuracy of 0.33 degrees . Linear perceptrons (LPs) were only nearly half as accurate. For five subjects, the mean accuracy provided by the MLPs was 1.09 degrees of visual angle ( degrees ) for EOG data, and 0.98 degrees for an infrared eye tracker. MLPs enabled calibration of 2D saccadic EOG to an accuracy not significantly different from that obtained with the infrared tracker. Using initial weights trained on another person reduced MLP training time, reaching convergence in as little as 20 iterations.

Automation↗
PubMed1998

Motion capture and the 'Ouchi' effect.

PURPOSE: The role of motion contrast and motion capture in the 'Ouchi' effect was investigated in a simplified stimulus. METHODS: Sinewave gratings were rapidly oscillated vertically within two concentric stationary 'apertures', an inner disc surrounded by an annulus. RESULTS: A strong illusion of relative motion between the disc and annulus is observed in the horizontal direction for 8 and 12 cycles/deg given small orientation differences between the two gratings. CONCLUSION: These parameters coincide with those of the 'Ouchi' effect, suggesting a sharing of the same causal mechanism.

Adult↗
PubMed1995

An illusion of relative motion dependent upon spatial frequency and orientation.

Observers scanned a stationary pattern comprising a tilted sine-wave grating completely surrounding another grating of similar spatial frequency but tilted in the opposite direction (Fig. 2). They reported an illusory "sliding" motion of the inset grating with respect to the surround grating and the effect was clearly strongest for angles between the gratings of less than 60 degrees and for spatial frequencies between 6-11 cpd. In a second experiment, a similar pattern was moved (2.0 deg/sec) either up or down for a presentation time of 167 msec. Simultaneously, the inset grating was drifted at different speeds in each of its two directions. Using the method of constant stimuli, it was shown that the relative motion illusion could be cancelled by physically drifting the grating in the opposite direction to the illusory movement. The illusion arises because there is a failure to integrate two motion signals into the single motion vector which characterises rigid motion.

Contrast Sensitivity↗
PubMed1994

Estimation of linear detection mechanisms for stimuli of medium spatial frequency.

Detection thresholds were obtained for a circularly-symmetric Gabor profile and Craik-Cornsweet profiles presented on a large white adapting field. These stimuli possessed peak spatial power between 1 and 6 c/deg. Their contrast was represented in an L, M and S cone contrast space. Detection thresholds were obtained for many vectors close to specific but theoretically important planes within this space. These data were fitted with a model comprising independent mechanisms, each a weighted sum of cone contrasts. The fit revealed a chromatic mechanism driven by delta L/L-delta M/M with no S cone input. Within cone contrast space, this mechanism was more sensitive than both a luminance mechanism with little S cone input but considerable variation in relative L to M cone input, and a blue-yellow chromatic mechanism.

Color Perception↗
PubMed1994

Seasonal variation in serum 25-hydroxy vitamin D3 does not affect 1,25-dihydroxy vitamin D.

The seasonal variation of serum 25-hydroxy vitamin D3 and 1,25-dihydroxy-vitamin D has been investigated. Blood was taken from 27 healthy volunteers, aged 21-44 years old at 3 monthly intervals over a period of 1 year. A scrolling monthly programme with 12 quarterly (3 month) time periods was developed. A summer associated increase in 25-hydroxy vitamin D3 was significantly correlated with but lagged behind by 2 months, the increase in recorded sunlight hours. However, four individuals showed no seasonal rise but maintained constant concentrations throughout the year within the established reference range. Serum 1,25-dihydroxy vitamin D showed marked intra-individual variability with no seasonal pattern although the highest concentration (180 pmol/L) was observed in the winter and no concentration greater than 108 pmol/L in the summer.

Adult↗
PubMed1993

Multivariate analysis of cholesterol distribution for monitoring the risk of coronary heart disease.

The screening of people for potential coronary heart disease and the monitoring of subjects considered at risk have been performed for some time by measuring total serum cholesterol and its constituent lipoproteins. However, these measurements vary substantially within subjects, making such assessments imprecise. It has been suggested that greater consistency can be achieved by analysing the joint distribution of the individual lipoproteins or of transformed variables derived from them. In this paper we present the results of a laboratory experiment to investigate these ideas with a view to improving current methods of monitoring patients at risk. Nested, random-effects, multivariate analysis of variance and the log-ratio analysis of compositions are used to include information on all three lipoproteins simultaneously, and ratios of generalized variances are used to assess and compare the different response variables. The multivariate approach is seen to be far superior to the usual methods. Recommendations are made for routine monitoring and the practical implications are discussed.

Analysis of Variance↗
PubMed1991

Hypercalcaemia due to calcium binding by a polymeric IgA kappa-paraprotein.

Total serum calcium concentration was raised in a 63-year-old lady with multiple myeloma and markedly elevated serum IgA kappa-paraprotein concentration. Symptoms of hypercalcaemia were absent, and serum ionized calcium was normal, suggesting calcium binding by the abnormal protein. This was demonstrated directly after isolation of the paraprotein and characterization of the calcium/protein interaction. After reduction of the paraprotein with mercaptoethanol, sodium dodecyl sulphate polyacrylamide gradient gel electrophoresis revealed two bands corresponding to light and heavy chains, but under non-reducing conditions the isolated paraprotein migrated in a series of bands, possibly representing polymeric forms of the basic immunoglobulin moiety.

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