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Biomedical subjects

K Sykes

Publications and source records attributed to K Sykes.

29 records · Page 2Linked to original sources
PubMed1988

Modification of the Recalde method for the isolation of human monocytes.

A modification of the method for monocyte isolation reported by Recalde (1984. J. Immunol. Methods. 69: 71-77) is described. Application of the modified method to 36 consecutive healthy adult donors gave a monocyte purity of 73 +/- 8% monocytes with less than 1% polymorphonuclear leukocytes and a yield of 3.44 +/- 0.93 x 10(5) monocytes/ml blood. While the monocyte purity of the modified Recalde method was lower than that obtained by elutriation (method BB in Fogelman et al. 1981. J. Lipid Res. 22: 1131-1141) in 15 donors (71 +/- 10% vs. 83 +/- 6%) the monocyte yield and the viability of the cells before and after culture were similar in both methods. The modified Recalde method does not require the expensive or complicated equipment required for elutriation and permits the isolation of human monocytes for culture in autologous serum from multiple donors in a single day.

Cell Separation↗
PubMed1985

Positive end-expiratory pressure may decrease arterial oxygen tension in the presence of a collapsed lung region.

The effect of positive end-expiratory pressure (PEEP) on PaO2 during collapse of a single pulmonary lobe was investigated in seven dogs. Increasing PEEP to the ventilated region of lung increased the proportion of cardiac output flowing to the collapsed lobe and decreased PaO2 and pH. PaCO2 increased at the onset of lobar collapse but was not significantly altered by changes in PEEP. In impaired lungs, the benefits of PEEP may be offset by an increase in blood flow to the unventilated region and hence lead to a decrease in PaO2.

Analysis of Variance↗
PubMed1985

Effect of plasma colloid osmotic pressure on fluid filtration rate in isolated rabbit lungs.

The relationship between fluid filtration rate (FFR) and plasma colloid osmotic pressure (COP) was studied in isolated rabbit lungs perfused at constant flow. A 50% to 60% decrease in COP increased FFR more when left atrial pressure (LAP) was 12.8 to 15 mm Hg than when it was 7.5 to 9 mm Hg. When LAP was zero, FFR did not increase until COP had been reduced from 18.8 to 7 mm Hg. The increase in FFR produced by step increases in LAP was eliminated by similar increases in COP.

Animals↗
PubMed1976

The reproducibility of submaximal work heart rates-an interim report.

Work heart rates were taken from four subjects performing standardized bouts of work on the Monark Ergometer. Whilst a linear relationship was observed between heart rate and work intensity on any one day, it is evident that day to day variations in the position (intercept) of these lines exists. The slopes are virtually identical for all subjects and for different days, however the position of the lines differs widely both between and within subjects. The best linear regression equation developed for the prediction of heart rate after 180 seconds of work from pre-exercise heart rate and work intensity was found to have 95% confidence limits of +/- 12.7 beats. Heart rates are reproducible 95% of the time to within +/- 12.2 beats when pre-exercise heart rate is ignored.

Heart Rate↗
PubMed1967

The effect of withdrawal of visual presentation of errors upon the frequency spectrum of tremor in a manual task.

1. When a subject attempts to exert a steady pressure on a joystick he makes small unavoidable errors which, irrespective of their origin or frequency, may be called tremor.2. Frequency analysis shows that low frequencies always contribute much more to the total error than high frequencies. If the subject is not allowed to check his performance visually, but has to rely on sensations of pressure in the finger tips, etc., the error power spectrum plotted on logarithmic co-ordinates approximates to a straight line falling at 6 db/octave from 0.4 to 9 c/s. In other words the amplitude of the tremor component at each frequency is inversely proportional to frequency.3. When the subject is given a visual indication of his errors on an oscilloscope the shape of the tremor spectrum alters. The most striking change is the appearance of a tremor peak at about 9 c/s, but there is also a significant increase of error in the range 1-4 c/s. The extent of these changes varies from subject to subject.4. If the 9 c/s peak represents oscillation of a muscle length-servo it would appear that greater use is made of this servo when positional information is available from the eyes than when proprioceptive impulses from the limbs have to be relied on.

Humans↗
PubMed1967

The variation of hand tremor with force in healthy subjects.

1. Total root-mean-square (r.m.s.) error over an effectively unrestricted band, and error power spectra from 0.256 to 12.5 c/s were measured for four subjects attempting to maintain fixed forces of 1-6 Lb. (0.45-2.72 kg) on a pressure joystick. The subject could see his errors as the deflexion of a cathode ray tube spot.2. The total r.m.s. error increases linearly with force with a considerable (positive) intercept when the line is extrapolated to zero force. Hence accuracy in the sense (r.m.s. error)/(force) increases with force for this type of control.3. The rate of increase of total r.m.s. error with force is greater in subjects with prominent tremor peaks in their power spectra at 8-10 c/s.4. At each frequency the r.m.s. error per unit bandwidth also increases linearly with force. Except at the very lowest frequencies the rate of increase is greater in subjects with prominent tremor peaks at 8-10 c/s. This is thought to account for the observation described in paragraph 3.5. The frequency of the tremor peak near 8-10 c/s is almost independent of the force exerted.

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