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Biomedical subjects

R G Ryall

Publications and source records attributed to R G Ryall.

36 records · Page 2Linked to original sources
PubMed1985

Insensitivity of erythrocyte 2,3-bisphosphoglycerate to changes in extracellular phosphate concentration in vitro.

Erythrocytes maintained in vitro under controlled conditions at pH 7.40 were unable to respond to changes in extracellular phosphate concentrations with changes in intracellular 2,3-bisphosphoglycerate content over an 8 h incubation period. Increased extracellular phosphate concentrations did not retard the rate at which 2,3-bisphosphoglycerate concentrations fell when erythrocytes were incubated at pH 7.10. Elevated extracellular phosphate concentrations did not increase the rate of recovery of intracellular 2,3-bisphosphoglycerate concentrations when erythrocytes were returned to pH 7.40 having been incubated at pH 7.10. The rate at which 2,3-bisphosphoglycerate concentrations increased under these latter conditions was too slow to counterbalance any effect that adjustment of blood pH may have on the position of the haemoglobin-oxygen dissociation curve during treatment of diabetic ketoacidosis.

2,3-Diphosphoglycerate↗
PubMed1984

Erythrocyte 2,3-bisphosphoglycerate concentrations and haemoglobin glycosylation in normoxic Type 1 (insulin-dependent) diabetes mellitus.

Increased erythrocyte 2,3-bisphosphoglycerate concentrations are associated with increased haemoglobin glycosylation in patients with Type 1 diabetes mellitus who have no cause or symptoms of hypoxic stress. This change in 2,3-bisphosphoglycerate metabolism is additional to its response to changes in circulating haemoglobin concentration. Statistical analysis of data showed that erythrocyte 2,3-bisphosphoglycerate concentration did not correlate with the absolute concentration of circulating haemoglobin A1c, but with the proportion of haemoglobin glycosylated. This finding is consistent with the hypothesis that it is changes in the position of the erythrocyte oxygen dissociation curve which modulate the increase in 2,3-bisphosphoglycerate synthesis upon haemoglobin A1c formation.

2,3-Diphosphoglycerate↗
PubMed1983

An equilibrium model of the oxygen association curve of normal human erythrocytes under standardized conditions.

Hemoglobin-oxygen association curves of human erythrocytes were measured in metabolically stable cells under the standardized conditions of extracellular pH 7.400, carbon dioxide tension 38 mmHg (approximately 5 kPa) and temperature 37 degrees C. A model of the oxygen association curve of normal erythrocytes was subsequently developed, based on assumed equilibrium reactions between hemoglobins (Hb), oxygen, and 2,3-diphosphoglycerate (DPG). Conditional equilibrium constants were determined for reactions leading to the formation of species designated Hb-O2 (K = 0.14 mmHg-1), Hb-(O2)4 (K = 0.44 X 10(-4) mmHg-4), Hb-DPG (K = 0.30 X 10(4) L mol-1) and Hb-O2-DPG (K = 0.61 X 10(2) L mol-1 mmHg-1) for unmodified hemoglobin, and Hb-O2 (K = 0.14 mmHg-1) and Hb-(O2)4 (K = 0.44 X 10(-4) mmHg-4) for glycosylated hemoglobin. This model provides a practical means of calculating the expected oxygen association curve for a sample of erythrocytes under standardized conditions, given the intracellular concentrations of hemoglobins and 2,3-diphosphoglycerate and the assumption that the hemoglobins in those cells function normally.

Carbon Dioxide↗
PubMed1982

Theoretical constraints in the measurement of serum bilirubin binding capacity.

The large majority of methods for measuring serum unoccupied bilirubin binding capacity involve adding an exogenous ligand to a diluted serum sample. If the added ligand binds specifically to bilirubin binding sites, the extrapolation is made that the amount of ligand which becomes bound represents the previously unoccupied bilirubin binding capacity of the original sample. This simple theory ignores the labile nature of the equilibrium reactions between bilirubin binding sites and the ligands with which they interact. The present theoretical and experimental study of these equilibrium reactions shows that (a) sample dilution alone results in changes in the proportional occupancy of bilirubin binding sites by bilirubin and other endogenous ligands, so that the extent of vacancy of those binding sites becomes exaggerated; (b) addition of an exogenous ligand to the diluted sample results is further displacement of native bilirubin and other endogenous ligands from bilirubin binding sites. The amount of added ligand which becomes bound is thus likely to represent a greater extent of vacancy of bilirubin binding sites than was present in the original sample. Results from such methods can therefore only overestimate the unoccupied bilirubin binding capacity of blood plasma in vivo. In order to avoid these analytical problems, current methods must be redesigned. It is suggested from this work that the ability of a serum to sequester safety additional bilirubin may best be assessed from measurement of its bilirubin buffering capacity. This parameter is different from the total or unoccupied binding capacity currently attempted, and its measurement is within the capability of published methods for measuring free (= unbound) bilirubin, modified to analyse minimally diluted samples.

Bilirubin↗
PubMed1982

Minimal haemolytic effects from 0.8% chlormethiazole infusion in volunteer subjects. Chlormethiazole infusion and haemolysis.

A solution of 0.8% chlormethiazole ethanedisulphonate was infused into the antecubital vein of 14 healthy volunteers for periods ranging from 60 to 120 minutes to examine any haemolytic effects in vivo. Plasma haptoglobin and haemopexin concentrations were measured before, during and after infusion. No evidence of intravascular haemolysis of any clinical significance was found.

Adolescent↗
PubMed1981

Effect of total leucocyte count on whole blood filterability in patients with peripheral vascular disease.

An abnormal filterability of whole blood through micropore membranes in vitro has been reported in peripheral vascular disease and has been thought to indicate abnormal red cell deformability. Blood from 68 patients with symptomatic peripheral vascular disease of varying severity and from 32 age-matched controls without a history of peripheral vascular disease was studied by the technique of whole blood filtration. In agreement with earlier findings, whole blood filterability was significantly reduced in patients with symptoms of vascular disease, but also their total leucocyte count was significantly higher than that of the controls. Variation in leucocyte count was found to affect significantly whole blood filterability, and the abnormal filterability in peripheral vascular disease could be entirely ascribed to this factor and not to an alteration in red cell deformability. The raised leucocyte count was not due to smoking but its cause could not be explained.

Aged↗
PubMed1981

Intravenous chlormethiazole- haemolysis with concentrated solutions.

Since the current clinical concentration of chlormethiazole solutions (0.8%) may require the infusion of large volumes of fluid, it was decided to examine the effects on haemolysis of infusing higher concentrations of chlormethiazole into a central vein. Approximately one gram of chlormethiazole was infused into the inferior vena cavae of six anaesthetised greyhounds over each half hour using, successively, 0.8%, 1.2%, 2%, 5%, 10%, and 20% solutions of chlormethiazole. Free plasma haemoglobin levels were measured at five minute intervals, and blood chlormethiazole levels at 15 minute intervals. A rapidly progressive haemolysis occurred when the 5 or 10% solutions were infused. In a further four greyhounds, one gram of chlormethiazole was infused over each half hour using a 0.8% solution, whilst progressively hyperosmolar dextrose solutions were infused at the same rates in succeeding half hours as the concentrated chlormethiazole solutions had been infused in the first six dogs. No haemolysis occurred in these control animals. Chlormethiazole blood levels were similar in each group. Loss of chlormethiazole into the infusion tubing was examined and found to be 20% for the 0.8% solution, and 10% for the 1.2% solution, but was insignificant with the other subsequently infused concentrations of chlormethiazole. It is concluded that rapid progressive haemolysis occurs in association with the infusion of chlormethiazole solutions when concentrations of greater than 5 or 10% are infused into the inferior vena cavae of anaesthetised greyhounds.

Anesthesia↗
PubMed1981

Interpretation of particle growth and aggregation patterns obtained from the Coulter counter: a simple theoretical model.

We used a simple theoretical model to stimulate the changes in particle size distribution that occur when crystals grow, or disaggregate to a defined extent. The change in total particle volume was used as an index of growth, whereas aggregation and disaggregation were expressed as the change in total particle number. Indices of inhibition of growth and of aggregation in hypothetical test cases were calculated in relation to a control and compared with the inhibition index derived by the standard method of comparing the distribution of particle volume around a given arbitrary diameter on the particle distribution curve. We concluded that the expression of particle growth and aggregation in terms of total volume and number respectively is a preferable alternative to the standard technique.

Calcium Oxalate↗
PubMed1980

Glycosylated haemoglobin and relative polycythaemia in diabetes mellitus.

Sixty-five diabetic patients had a total red cell count significantly greater than 65 age and sex matched non-diabetics; (4.93 +/- 0.06 x 10(6) and 4.50 +/- 0.05 x 10(6) red cells/ul respectively; p less than 0.005). In 110 diabetic patients, total red cell count was positively correlated with the proportion of glycosylated haemoglobin (HbA1) (r = 0.32, p less than 0.001). The correlation was maintained in 60 of these patients with a mean blood glucose less than 15 mmol/l (r = 0.33, p less than 0.05), and in 49 non-smoking diabetic patients (r = 0.30, p = 0.05). It is proposed that the greater proportion of higher oxygen-affinity HbA1 in comparatively uncontrolled diabetics may be inducing sufficient tissue hypoxia to cause the demonstrated relative polycythaemia.

Diabetes Complications↗
PubMed1980

Validity of transcobalamin II-based radioassay for the determination of serum vitamin B12 concentrations.

A valid radioassay for the estimation of serum vitamin B12 in the presence of naturally occurring vitamin B12 (= cobalamin) analogues can be operated if serum transcobalamin II (TC II) is used as the binding protein. Serum samples that gave diagnostically discrepant results when their vitamin B12 content was analysed (i) by a commercial radioassay known to be susceptible to interference from cobalamin analogues, and (ii) by microbiological assay, were further analysed by an alternative radioassay which uses the transcobalamins (principally TC II) of diluted normal serum as the assay binding protein. Concordance between the results from microbiological assay and the TC II-based radioassay was found in all cases. In an extended study over a three-year period, all routine serum samples sent for vitamin B12 analysis that had a vitamin B12 content of less than 320 ng/l by the TC II-based radioassay (reference range 200-850 ng/l) were reanalysed using an established microbiological method. Over 1000 samples were thus analysed. The data are presented to demonstrate the validity of the TC II-based radioassay results in this group of patients, serum samples from which are most likely to produce diagnostically erroneous vitamin B12 results when analysed by a radioassay that is less specific for cobalamins.

Biological Assay↗
PubMed1978

A microtechnique for measuring red cell osmotic fragility of infants.

Chloramphenicol (D-threo-2-dichloroacetamido-1-p-nitrophenylpropane-1,3-diol) added to blood samples did not alter the observed shift in the red cell osmotic fragility curves as the samples were aged in vitro for 24 hours at 37 degrees C. Nor was the normal rate of loss of 2,3-diphosphoglycerate, ATP, or glutathione from the red cells affected by the presence of chloramphenicol over the same period. Consequently, this bacteriostatic agent can be added to blood samples taken under non-sterile conditions, such as from the heel of an infant, in order to preserve them from the effects of microbial contamination. In this way red cell osmotic fragility results can be obtained on non-sterile samples after their incubation at 37 degrees C for 24 hours. A miniaturisation of the standard osmotic fragility procedure is described, which allows results to be produced from the small, non-sterile samples obtained by heel-prick of infants.

Chloramphenicol↗
PubMedDate not supplied

A LISS spin enzyme method for the detection of red cell antibodies and its use in routine antibody screen procedures.

A technique for performing the enzyme phase of the antibody screen on red cells suspended in low-ionic-strength-salt solution (LISS) is described. The reliability of this LISS spin-enzyme (LSE) technique was compared with the two-stage papain-tile method, in the detection of 62 previously identified enzyme reacting antibodies. All 62 antibodies examined were detected by the LSE method, and no false-positive reactions were found. Using LSE and papain-tile methods in parallel, further assessment was obtained by screening 2000 sequential blood samples under routine service conditions. Fifty-six blood samples contained alloantibodies, of which 43 reacted by both methods, eight by the LSE method only, and five by the papain-tile method only. It was concluded that the LSE method was comparable to the papain-tile method.

Blood Group Antigens↗