PubMed Health⌕ Search

Biomedical subjects

K Sykes

Publications and source records attributed to K Sykes.

At least 19 recordsLinked to original sources
PubMed1996

Aerobic fitness testing: an update.

This study confirms that all three tests are reliable tools for the assessment of cardiorespiratory fitness and the prediction of aerobic capacity. While this particular study consisted of active, youthful subjects, subsequent studies at University College Chester have found similar findings with larger databases and a wider cross-section of subjects. The Astrand cycle test and Chester step test are submaximal tests with error margins of 5-15 per cent and therefore, not as precise as maximal testing. However, they still give a reasonably accurate reflection of an individual's fitness without the cost, time, effort and risk on the part of the subject. The bleep test is a low-cost maximal test designed for well-motivated, active individuals who are used to running to physical exhaustion. Used on other groups, results will not accurately reflect cardiorespiratory fitness values. While all three tests have inherent advantages and disadvantages, perhaps the most important factors are the knowledge and skills of the tester. Without a sound understanding of the physiological principles underlying these tests, and the ability to conduct an accurate assessment and evaluation of results in a knowledgeable and meaningful way, then the credibility of the tests and the results become suspect. However, used correctly, aerobic capacity tests can provide valuable baseline data about the fitness levels of individuals and data from which exercise programmes may be developed. The tests also enable fitness improvements to be monitored, help to motivate participants by establishing reasonable and achievable goals, assist in risk stratification and facilitate participants' education about the importance of physical fitness for work and for life. Since this study was completed, further tests have been repeated on 140 subjects of a wider age and ability range. This large database confirms the results found in this study.

Adult↗
PubMed1993

Proline isomerases function during heat shock.

The cyclophilins (CYPs) and FK506 binding proteins (FKBPs) are two families of distinct proline isomerases that are targets for a number of clinically important immunosuppressive drugs. Members of both families catalyze cis/trans isomerization of peptidyl-prolyl bonds, which can be a rate-limiting step during protein folding in vitro and in vivo. We demonstrate in Saccharomyces cerevisiae that heat shock causes a 2- to 3-fold increase in the level of mRNA encoded by the major cytoplasmic CYP gene, CYP1. The cloned CYP1 promoter confers heat-inducible expression upon a reporter gene, and transcriptional induction is mediated through sequences similar to the consensus heat shock response element. Disruption of CYP1 decreases survival of cells following exposure to high temperatures, indicating that CYP1 plays a role in the stress response. A second CYP gene, CYP2, encodes a cyclophilin that is located within the secretory pathway. Its expression is also stimulated by heat shock, and cells containing a disrupted CYP2 allele are more sensitive than wild-type cells to heat. By contrast, expression of the FKB1 gene, which encodes a cytoplasmic member of the yeast FKBP family, is neither heat responsive nor necessary for survival after exposure to heat stress.

Alleles↗
PubMed1993

Harold Griffith Memorial Lecture. The Griffith legacy.

1992 was the anniversary of Crawford Long's use of ether in 1842, and Griffith and Johnson's introduction of Intocostrin into anaesthetic practice in 1942. Harold Randall Griffith was born in Montreal in 1894 and died in 1985. He interrupted his medical studies to serve in the first world war and was awarded the Military Medal for gallantry at the battle of Vimy Ridge. Griffith qualified from McGill University in 1922. After spending a year studying homoeopathic medicine, he joined his father's general practice and became the anaesthetist to the Homoeopathic Hospital in Montreal. He succeeded his father as Medical Director of the hospital (now renamed the Queen Elizabeth Hospital) in 1936 and retired in 1966. Griffith was a superb clinical anaesthetist. He was an early advocate of detailed anaesthetic records, and was responsible for the introduction of both ethylene and cyclopropane into Canadian practice, later teaching himself to intubate under these two agents. Griffith was one of the first to be concerned with standards of patient care. He introduced postoperative recovery and intensive care units into Canadian practice and played a major role in postgraduate teaching. He was unstinting in his support of organisations designed to further the progress of anaesthesia and was the first President of the Canadian Anaesthetist's Society. He was one of those responsible for inaugurating the World Federation of Societies of Anaesthesiology and was President of the First World Congress of Anaesthesiology in 1955. It is remarkable that the introduction of curare into anaesthetic practice was delayed until 1942, since curare had been used in anaesthesia some 30 years previously. However, it was probably Griffith's confidence in his own clinical abilities which enabled him to seize the opportunity when it was offered.

Anesthesiology↗
PubMed1993

Specific cross-linking of the proline isomerase cyclophilin to a non-proline-containing peptide.

A peptide corresponding to an efficient peroxisomal targeting sequence, the carboxy terminal 12 amino acids of PMP20 from Candida boidinii, was employed as an affinity ligand to search for a peroxisomal targeting receptor. Two proteins from yeast extracts with apparent molecular masses of 20 and 80 kDa were detected by chemical cross-linking to radioiodinated peptide. Both proteins were present in cytosolic supernatants. The 20-kDa species did not cross-link to a control peptide with reversed sequence, whereas the 80-kDa protein cross-linked to both peptides. The cross-linking assay was used to purify the 20-kDa protein from Saccharomyces cerevisiae. Partial protein sequencing identified this protein as cyclophilin, the product of the CYP1 gene. This protein, a peptidyl-prolyl cis-trans isomerase, is the yeast homologue of the protein that mediates the immunosuppressant effects of the drug cyclosporin A (CsA). Cross-linking of peptide to cyclophilin was inhibited by CsA. The cross-linking of cyclophilin to the PMP20-derived peptide was unanticipated because the peptide contains no prolines. The CYP1-encoded protein was not required to target proteins to peroxisomes because this organelle appeared to be assembled normally in a CYP1-disrupted strain. Furthermore, the final three amino acids of the peptide, which are critical for peroxisomal sorting, were not required for cross-linking to cyclophilin. We conclude that either cyclophilin is playing a nonessential facilitating role in peroxisomal targeting or that the interaction of the targeting peptide to cyclophilin is mimicking an interaction with an unidentified substrate or effector of cyclophilin.

Amino Acid Isomerases↗
PubMed1992

Structure of the CD59-encoding gene: further evidence of a relationship to murine lymphocyte antigen Ly-6 protein.

The gene for CD59 [membrane inhibitor of reactive lysis (MIRL), protectin], a phosphatidylinositol-linked surface glycoprotein that regulates the formation of the polymeric C9 complex of complement and that is deficient on the abnormal hematopoietic cells of patients with paroxysmal nocturnal hemoglobinuria, consists of four exons spanning 20 kilobases. The untranslated first exon is preceded by a G+C-rich promoter region that lacks a consensus TATA or CAAT motif. The second exon encodes the hydrophobic leader sequence of the protein, and the third exon encodes the amino-terminal portion of the mature protein. The fourth exon encodes the remainder of the mature protein, including the hydrophobic sequence necessary for glycosyl-phosphatidylinositol anchor attachment. The structure of the CD59 gene is very similar to that encoding Ly-6, a murine glycoprotein with which CD59 has some structural similarity. The striking similarity in gene structure is further evidence that the two proteins belong to a superfamily of proteins that may also include the urokinase plasminogen-activator receptor and a squid glycoprotein of unknown function.

Amino Acid Sequence↗
PubMed1992

Aerobic capacity.

Explore the source record for details and available documents.

Adolescent↗
PubMed1990

A naturally occurring gamma globin gene mutation enhances SP1 binding activity.

Transcription of the human fetal globin genes in erythroid cells is tightly regulated during different stages of development and differentiation. Two naturally occurring mutations 202 base pairs upstream of the duplicated gamma globin genes are associated with incorrectly regulated gamma globin gene gene expression; elevated levels of fetal globin are synthesized during adult life. A C-to-G base substitution upstream of the G gamma-globin gene is highly correlated with a dramatic increase in gene expression. It increases the similarity of the region to the consensus Sp1 recognition site. We determined that the mutated DNA had a 5- to 10-fold-higher affinity for Sp1 than did normal gamma globin gene sequence. We also observed a reduction in normal factor-binding activity. A different substitution at -202, C to T, upstream of the A gamma-globin gene was associated with a more moderate increase in fetal globin expression. This mutation decreased the similarity of the sequence to an Sp1 recognition site. We determined that it did not result in enhanced Sp1 binding but did alter normal factor binding. We suggest that these changes in nuclear protein-binding properties detected in vitro are responsible for the enhanced gamma globin gene expression found in -202 G gamma beta + patients with hereditary persistence of fetal hemoglobin.

Base Sequence↗
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↗