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Biomedical subjects

S M Lewis

Publications and source records attributed to S M Lewis.

At least 199 records · Page 11Linked to original sources
PubMed1980

Use of 111Indium-labeled platelets to measure spleen function.

The distribution of 111In-labelled platelets following intravenous bolus injection has been studied using a gamma camera and computer system. Liver uptake, which accounted for about 10% of the dose, was completed between 6 and 10 min after injection. Blood pool and splenic 111In, which accounted for the remainder of the dose, reached constant levels simultaneously about 20 min after injection. The kinetics of splenic uptake are consistent with a two compartmental model in which circulating and splenic platelets are in dynamic equilibrium with each other. From analysis of the kinetics, splenic blood flow and the mean transit time of platelets through the spleen have been calculated in normal subjects and in patients with haematological disorders. Blood flow, which was about 200 ml per min in normals, tended to increase with increasing spleen size. Transit time was not dependent on spleen size; it was about 10 min in all but one of the subjects.

Blood Platelets↗
PubMed1980

Radionuclide distribution following injection of 111Indium-labelled platelets.

Platelets labelled with 111In displayed similar survival curves after incubation with 111In-oxine in plasma, plasma-saline and dextrose saline media. The use of autologous red cells to cushion platelets during high-speed centrifugation facilitated platelet resuspension without greatly affecting the duration of the labelling procedure. Quantitative scanning after reinjection of labelled platelets in haematologically normal subjects showed that, initially, splenic indium amounted to about 35% of the injected dose and hepatic indium about 12%; these levels rose only slightly over the subsequent duration of the platelet life span. Subtraction of the signal from indium in platelets thought to be normally pooled within the spleen from the total indium signal gave splenic indium uptake curves which reflected splenic platelet destruction. Initially, the sum of indium levels in spleen, liver and blood equalled 100% of the dose. Thereafter, the sum fell progressively at a rate thought to be approximately equal to the rate of bone marrow uptake.

Blood Platelets↗
PubMed1980

Cell volume studies in B-cell leukaemia.

Leucocyte volume histograms were obtained in 12 cases of B-chronic lymphocytic leukaemia (B-CLL), two cases of B-prolymphocytic leukaemia (B-PLL) and two cases of hairy-cell leukaemia (HCL) by means of a Coulter model ZBl linked to a channelyser. Visual examination of the histograms showed differences between the cases which were confirmed by measurement of the modal volume (MV) and the sigma value (SD of log-volume). The MV of the cells in B-CLL ranged from 153.8 to 244.2 fl (mean 198.24 fl) and was lower than the MV in the cases of HCL (427.5 and 465.6 fl). One case of B-PLL had cells with an MV within the B-CLL range while in the other the MV was greater (317.9 fl). The histogram in one of two cases of B-CLL in 'prolymphocytoid' transformation showed a relatively high sigma value, thus suggesting heterogeneity in cell size. The volume histogram is a simple method of sizing the predominant cell in the peripheral blood in lympho-proliferative disorders and permits an objective comparison between cell sizes in different diseases.

B-Lymphocytes↗
PubMed1980

Interlaboratory comparison of serum vitamin B12 assay.

The results have been compared of microbiological and radioisotope dilution (RID) assay of serum vitamin B12 by participants in national interlaboratory trials in Britain. There was wide variation between the individual participants, especially marked in the L. leichmannii microbiological assay and in the RID methods, whereas excellent correlation, reproducibility, and recovery were obtained in reference laboratories by microbiological assay with both E. gracilis and L. leichmannii. In general, RID gave higher results than microbiological assay. The need for suitable reference sera is emphasised.

Biological Assay↗
PubMed1980

End-tidal CO2 response to low levels of inspired CO2 in awake beagle dogs.

The steady-state end-tidal CO2 tension (PCO2) was examined during control and 1% CO2 inhalation periods in awake beagle dogs with an intact airway breathing through a low dead-space respiratory mask. A total of eight experiments were performed in four dogs, comprising 31 control observations and 23 CO2 inhalation observations. The 1% inhaled CO2 produced a significant increase in the steady-state end-tidal PCO2 comparable to the expected 1 Torr predicted from conventional CO2 control of ventilation. We conclude that 1% inhaled CO2 results in a hypercapnia. Any protocol that is to resolve the question of whether mechanisms are acting during low levels of inhaled CO2 such that ventilation increases without any change in arterial PCO2 must have sufficient resolving power to discriminate changes in gas tension in magnitude predicted from conventional (i.e., arterial PCO2) control of ventilation.

Animals↗
PubMed1980

Effect of plasma carbonic anhydrase on ventilation in exercising dogs.

Recent studies suggest pH sampled by arterial chemoreceptors may not equal that sampled by external pH electrodes, because the uncatalyzed hydration of CO2 in plasma is a slow reaction (t 1/2 approximately 9 S). The importance of this reaction rate to ventilatory control (particularly during exercise) is not known. We studied the effect of catalyzing the CO2-pH reaction in three awake exercising dogs with chronic tracheostomies and carotid loops; the dogs were trained to run on a treadmill. Respiration frequency, tidal volume, total ventilation, and end-tidal partial pressure of CO2 (PCO2) were continuously monitored. Periodically, carotid artery blood was drawn and analyzed for partial pressure of O2 (PO2), PCO2, pH, and plasma carbonic anhydrase (CA) activity. Measurements were made during steady-state exercise (3 mph and 10% grade), during a control period, after injection of a 5 ml bolus of saline, and after injection of 5 mg/kg of bovine CA dissolved in 5 ml of saline. This dose of CA increased the reaction rate by more than 80-fold. Neither the control nor the CA injections significantly altered the ventilatory parameters. Saline and CA date differed by less than 5% in ventilation, 1 Torr in arterial PCO2, 0.01 in pH units, and 1.5 Torr in end-tidal PCO2. Thus the of CO2 hydration in plasma is not a significant factor in ventilatory control.

Animals↗
PubMed1980

Ferrokinetic studies and prognosis in aplastic anaemia.

In a study of 16 patients with aplastic anaemia, an attempt has been made to relate ferrokinetic data to haematological measurements and clinical course. There was a positive relationship of cellularity on trephine biopsy with plasma iron clearance and erythrocyte iron turnover, but not with red cell utilisation. Bone marrow aspirate provided less reliable information on erythropoietic function than did trephine biopsy. There was good correlation between all the ferrokinetic parameters and reticulocyte count, but not between reticulocyte count and marrow cellularity, even by trephine. Patients whose ferrokinetic studies indicate a less severe erythroid depression (i.e., plasma clearance T 1/2 less than 200 min and red cell utilisation greater than 35%) are more likely to survive without transplantation than those with more abnormal ferrokinetic results, but such studies alone are of only limited value in clinical management of the individual patient.

Anemia, Aplastic↗
PubMed1979

Transitional myeloproliferative disorder.

Eleven patients have been observed with clinical features of both polycythaemia vera and myelofibrosis. Detailed follow-up and repeated haematological and isotopic investigations, including the assessment of erythropoietic distribution by 52Fe scanning, over a 10 year period, have indicated that patients who initially present with this syndrome may remain in a steady state for several years and that this transitional syndrome does not necessarily imply an active or irreversible transformation into classical myelofibrosis. Therapy with iron, folic acid, alkylating agents, splenectomy or splenic irradiation may reduce the extramedullary component of myeloproliferation and allow occasional patients to revert to more classical polycythaemia vera. Radioactive phosphorus (32P) therapy may be inappropriate in polycythaemic patients with dominant extramedullary erythropoiesis, as this form of therapy has a preferential medullary action and may selectively encourage extramedullary myeloproliferation.

Adult↗
PubMed1979

Platelet counting-development of a reference method and a reference preparation.

A reference method has been defined for platelet counting by counting chamber haemocytometry, and a procedure has been developed, using platelet rich plasma (PRP) and a Coulter ZBI counter which provides a reliable, rapid and relatively simple method for platelet counting which is closely comparable to the reference method and can thus be used both as a secondary reference method and a routine method. The optimal method for obtaining PRP from EDTA blood was by augmented sedimentation with Boyum's methyl cellulose-metrizoate mixture at sp. gr. 1.08. This was shown to yield a platelet suspension which reflects closely the platelet content of the original blood. Calibration of electronic counters for platelet counting requires material which is stable and which parallels natural human platelets in size, distribution and other physical characteristics. A suspension of glutaraldehyde-fixed human platelets in glycerol appears to be suitable as a reference preparation. Its method of production is described.

Calibration↗
PubMed1979

Draft protocol for testing calibration and quality control material used with automatic blood-counting apparatus.

A large number of commercial preparations are now available for calibrating or checking the stability of automatic blood counters. Most of these preparations are supplied with 'stated' values though the methods for assigning these values are not described in sufficient detail to allow for an adequate assessment of the validity. The Haemocytometry Panel of the British Committee for Standards in Haematology are therefore proposing a draft protocol for testing calibration and quality control materials. Comments on the draft protocol are invited, either as letters to the Editor of Clinical and Laboratory Haematology or in confidence to the Chairman of the Haemocytometry Panel.

Automation↗
PubMed1979

Autonomous erythropoietin induced erythrocytosis.

Erythrocytosis in a young Sinhalese man is described. The patient was known to have had a raised Hb and PCV for at least 10 years. Subsequent investigations failed to support the diagnosis of polycythaemia vera or to reveal a cause for secondary polycythaemia. Blood erythropoietin values were raised, but no cause for inappropriate secretion could be identified. Although there was no evidence of erythrocytosis in the family, the findings in this patient appear to be those of a condition which has been called familial polycythaemia. The spleen was unusually large and was associated with hypersplenism and thrombocytopenia. Problems of diagnosis and management are described. Phlebotomy appears to be the treatment of choice, with a regimen of regular venesection for the control of symptoms due to hyperviscosity and vascular occlusion.

Adult↗
PubMed1978

Cell junctions in dyserythropoiesis.

Erythroid cell junctions have previously been reported in some cases of dyserythropoietic anaemia. This study has demonstrated that they are a relatively common occurrence in dyserythropoiesis. They range from apposition of cellular membranes with preservation of the intercellular space, to membrane confluence, to interdigitation and septate-like junctions. By special staining with colloidal lanthanum, ruthenium red and tannic acid, together with studies of the effect of proteolytic enzymes, their structural composition has been identified and it was confirmed that they are not artefact. The role of cell junctions in dyserythropoiesis is discussed.

Anemia↗