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Biomedical subjects

S M Lewis

Publications and source records attributed to S M Lewis.

At least 145 records · Page 8Linked to original sources
PubMed1987

Splenic haematocrit and the splenic plasma pool.

A method was established for estimation of plasma volume and splenic plasma pool by quantitative scanning using 113mIn labelled transferrin (TF). The method was used in 12 patients with various haematological disorders and degrees of splenomegaly. 113mIn-TF consistently gave about 6% over-estimation of plasma volume by comparison with the standard 125I HSA method. The splenic plasma pool ranged from 1.2% to 11.4% of the total plasma volume. By concurrent measurement of splenic red cell pool the splenic haematocrit (SHct) was obtained: mean 0.51, SD 0.08; the SHct/PCV ratio was 1.21 (SD 0.31) and the SHct/body Hct ratio was 1.30 (SD 0.30). SHct was independent of PCV and body Hct but there was a trend to a lower SHct in cases where splenomegaly was more marked. Direct measurement of splenic plasma pool may help to elucidate the cause of increased total plasma volume in such patients.

Adult↗
PubMed1987

Blood volume measurement in pseudopolycythaemia--when and why?

Upper reference limits for packed cell volume (PCV) for a hospital population were established by analysis of 14,000 consecutive blood count profiles. These were 0.50 for men and 0.45 for women. In 86 patients, pseudopolycythaemia was identified by an increased PCV with red cell mass (RCM) less than 125% of predicted normal. We have proposed a modified classification of pseudopolycythaemia and identified three subsets on the basis of RCM and plasma volume (PV) values. Although all patients had raised PCV at the time of referral, by the time of blood volume study a lower PCV value was noted in a proportion of patients. Patients with a low PV (less than 80% predicted normal, Group 1) and those with a 'high normal red cell mass' (RCM 113-125% predicted normal, Group 2) had higher and more persistently elevated PCV values on repeated measurement, compared with the patients in Group 3 ('transient pseudopolycythaemia'). These latter patients have a normal RCM and PV, and although initially fulfilling the criteria for pseudopolycythaemia on the basis of a raised PCV and normal RCM, a high proportion subsequently showed fluctuation in PCV which often fell below the upper reference limit. It is important to diagnose pseudopolycythaemia because of the associated increase in morbidity and mortality, and our observations suggest that whereas a blood volume study is essential to diagnose pseudopolycythaemia reliably, this investigation need only be performed when a patient shows a persistently increased PCV on repeated measurement.

Adult↗
PubMed1987

Use of radionuclide scanning to estimate size of spleen in vivo.

Splenic ultrasound was performed and spleen scans obtained by a rectilinear scanner after injection of In-113m-labelled heat damaged red cells on 14 patients with various haematological disorders. Correlation was assessed between the measured volume of the operatively removed spleens, their volumes as calculated from the ultrasound data, and their preoperative dimensions of length, circumference, and area on the scans. The relation of scan to volume was best defined by an equation V = 9.88A - 534, where V = volume of spleen (cm3) and A = area (cm2) on posterior scan. The mean percentage difference between calculated and actual spleen volume was 0.2 (SD 6.7)%. Average spleen density was established as 1.04 g/cm3. The formula was shown to be reliable in the range of splenic area c 73-450 cm2--that is, volume c 185-4000 cm3. This range includes the average normal sized spleens and the splenomegalies that are most often found in clinical practice. The formula is not valid when the spleen is smaller than normal. As the method depends on measurement of the spleen image shown by scintigraphs, it cannot be used when there is functional asplenia.

Adolescent↗
PubMed1987

Effects of feed intake and dietary urea concentration on ruminal dilution rate and efficiency of bacterial growth in steers.

Four multiple-fistulated steers (340 kg) were fed a diet containing 50% ground grass hay, 20% dry distillers grains, and 30% concentrate at two intakes (7.2 or 4.8 kg DM/d). Urea (.4 or 1.2% of the diet) was infused continuously into the steers' rumens. The experimental design was a 4 X 4 Latin square with a 2 X 2 factorial arrangement of treatments. Infusing urea at .4 or 1.2% of the diet resulted in ruminal NH3 N concentrations of 4.97 and 9.10 mg/dl, respectively. Feeding steers at high rather than low intake decreased ruminal and total tract digestibilities of organic matter, NDF, and ADF but did not increase ruminal escape of N. However, apparent N escape from the rumen calculated using purines, but not 15N, as a bacterial marker was higher when 1.2 vs. .4% urea was infused. Feeding at high rather than at low intake increased the total pool of viable bacteria per gram organic matter fermented in the rumen. Although ruminal fluid outflows and particulate dilution rates were greater when steers were fed at high than at low intakes, efficiencies of bacterial protein synthesis were unaffected by intake. The possibility of increased N recycling within the rumen with feeding at the higher intake is discussed.

Animal Feed↗
PubMed1986

Effects of vanadate on the rotational dynamics of spin-labeled calcium adenosinetriphosphatase in sarcoplasmic reticulum membranes.

We have studied the effects of vanadate on the rotational motion of the calcium adenosine-triphosphatase (Ca-ATPase) from sarcoplasmic reticulum (SR), using saturation-transfer electron paramagnetic resonance (ST-EPR). Vanadate has been proposed to act as a phosphate analogue and produce a stable intermediate state similar to the phosphoenzyme. This study provides evidence about the physical state of this intermediate. In particular, since ST-EPR provides a sensitive measure of microsecond protein rotational mobility, and hence of protein-protein association, these studies allowed us to ask (a) whether the vanadate-induced protein association observed in electron micrographs of SR vesicles also occurs under physiological (as opposed to fixed, stained, or frozen) conditions and (b) whether vanadate-induced changes in protein association also occur under conditions sufficient for enzyme inhibition but not for the production of large arrays detectable by electron microscopy (EM). At 5 mM decavanadate, a concentration sufficient to crystallize the ATPase on greater than 90% of the membrane surface area in EM, ST-EPR showed substantial immobilization of the spin-labeled protein, indicating protein-protein association in the unstained vesicles. Conventional EPR spectra of lipid probes showed that lipid hydrocarbon chain mobility is unaffected by decavanadate-induced protein crystallization in SR, suggesting that changes in protein-protein contacts do not involve the lipid hydrocarbon region. At 5 mM monovanadate, a concentration sufficient to inhibit the ATPase but not to form crystals detectable by EM, no changes were observed in ST-EPR or conventional EPR spectra of either protein or lipid.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Determination of serum immunoreactive erythropoietin in the investigation of erythrocytosis.

We assessed the diagnostic value of determinations of serum levels of immunoreactive erythropoietin in 90 patients referred for the investigation of a raised packed red-cell volume (hematocrit) and possible erythrocytosis (a red-cell volume greater than that predicted by weight, body-surface area, or both). The mean values for erythropoietin were 16 mIU per milliliter (range, 8 to 22) in patients with polycythemia rubra vera (n = 24), 30 mIU per milliliter (range, 14 to 123) in patients with secondary erythrocytosis (n = 12), 27 mIU per milliliter (range, 13 to greater than 400) in patients with erythrocytosis of unknown origin (n = 19), and 25 mIU per milliliter (range, 18 to 35) in normal controls (n = 25). The values in the patients with polycythemia rubra vera were lower than those in the other three groups (P less than 0.01, P less than 0.05, and P less than 0.0001, respectively). In subjects with an increased packed red-cell volume but without erythrocytosis (n = 35), the levels of serum erythropoietin were the same as those in normal controls. Among patients with erythrocytosis with an unknown cause, abnormally high serum erythropoietin levels were found in 3 of 19 subjects, and in 1 of these 3 the abnormality was intermittent. Thus, measurement of serum erythropoietin in a single sample may be misleading and may not have high discriminatory value in distinguishing between polycythemia rubra vera and secondary erythrocytosis. This assay is useful in identifying patients with secondary erythrocytosis who have inappropriate erythropoietin secretion.

Adult↗
PubMed1986

The relationship between chronic lymphocytic leukaemia and prolymphocytic leukaemia. III. Evaluation of cell size by morphology and volume measurements.

The peripheral blood WBC size distribution was assessed by morphological and volume measurements in 73 patients with B-cell chronic lymphocytic leukaemia (CLL) and prolymphocytic leukaemia (PLL). Patients with typical CLL, with less than or equal to 10% prolymphocytes, had a homogeneous major population of small cells which could be recognized both by morphology and volume (median volume 211.5 +/- 32.5 fl). In PLL, the volume of the main cell component was significantly larger than in CLL: in two-thirds of cases the major cell population was distributed in a first lognormal fitted curve of the volume histogram, with median volume 281.8 +/- 38.0 fl; in the remaining cases the main cell component showed a larger median volume (353.5 +/- 71.9 fl) contained within the second lognormal curve which was preceded by a minor peak. CLL patients with 11-55% prolymphocytes (CLL/PL) had characteristic cell volume histograms in which two lognormal curves could always be fitted: in 80% of cases the main cell component was located in a first curve with median volume of 257.9 +/- 28.6 fl; in the remaining cases the major population was represented by cells with median volume of 349.0 +/- 83.9 fl distributed in a second peak. Although in both CLL and CLL/PL the majority of cells was defined morphologically as small, the median volume of these lymphocytes was significantly larger in CLL/PL. The degree of concordance in the assessment of cell size between morphology and volume measurements was high in CLL, whereas in CLL/PL and PLL morphology underestimated the cell size of the major population, compared with its actual volume, in over 50% of cases. We conclude that the identification of prolymphocytes as larger cells in blood films may be hampered by distortions and artefacts of spreading. Volume measurements may provide a more objective indicator of the cell populations in this group of disorders.

Diagnosis, Differential↗
PubMed1986

Erythrocyte radiolabelling: in vitro comparison of chromium, technetium, and indium in undamaged and heat damaged cells.

The stability of the commonly used red cell radio labels chromium-51, indium-(111 or 113m), and technetium-99m, within intact red cells and stroma and their distribution within the cell were compared in undamaged and heat damaged red cells in relation to the clinical use of heat damaged cells in the assessment of splenic function. Chromium-51 labelled haemoglobin both in undamaged and heat damaged cells; indium predominantly labelled haemoglobin in undamaged cells but labelled stroma in heat damaged cells, even when the cells were labelled before heating; technetium-99m predominantly labelled haemoglobin in undamaged cells but only labelled stroma in heat damaged cells if these were heated before labelling. Indium was more firmly bound by stroma prepared from heat damaged cells, and technetium-99m showed a high rate of elution both from cells and stroma, although this rate was lower for heat damaged cells.

Chromium Radioisotopes↗
PubMed1985

Reliability and clinical impact of the normalization of the prothrombin times in oral anticoagulant control.

In 1983, the World Health Organization (WHO) published recommendations for normalization, in oral anticoagulant control, of the prothrombin time (PT). The common denominator is the International Sensitivity Index (ISI) of a thromboplastin, obtained by means of thromboplastin calibration. The common scale is that of the International Normalized Ratio (INR). The INR is the PT ratio (Formula: see text) which would have been found with the WHO primary international reference preparation (IRP) 67/40. The reliability of the INR depends on the extent of calibration precision, patient-specific influences, as well as inter-laboratory variation in the PT determination. Under well-controlled conditions the overall coefficient of variation (CV) of the INR is 11-13.5%, if thromboplastins of ISI congruent to 1 are used. For so-called low-sensitivity thromboplastins (ISI congruent to 2-2.5), the overall variation is larger due to a large between-laboratory variation of the measured PT-ratios. The user of thromboplastin will be provided with a chart or graph enabling him to convert the conventional terms used for expressing PTs into INRs. For quality assurance, and to prepare his own calibration chart if necessary, he should check normalization by means of control plasmas to which INRs have been assigned. There is sufficient clinical evidence to express optimal therapeutic ranges in terms of INR. Manufacturers should revise and adapt their inserts where necessary in order to conform to these requirements.

Administration, Oral↗
PubMed1985

The kinetics of unmatched and HLA-matched 111in-labelled homologous platelets in recipients with chronic marrow hypoplasia and anti-platelet immunity.

The kinetics of homologous platelets, labelled in plasma with 111In-tropolonate, have been studied in five recipients with chronic marrow hypoplasia and severe thrombocytopenia, who were refractory to platelet transfusions as a result of alloimmunization. Mean platelet life span (MPLS), recovery, plasma 111In level and splenic and hepatic uptake kinetics were studied on two occasions, one using HLA-matched platelets and the other unmatched platelets. In each case, recovery of labelled platelets at 1 h post-injection and MPLS improved with HLA matching, although this improvement was highly variable. Only two of the five subjects would have derived any significant benefit from HLA-matched as compared with unmatched platelet transfusions. It was concluded that the need exists for additional cross-matching procedures, possibly related to platelet specific antigens, in patients who remain refractory to platelet transfusion.

Adolescent↗
PubMed1985

Microbiology and ration digestibility in the hindgut of the ovine.

Contents of the terminal ilea, ceca-proximal colons, and terminal recta were obtained from nine sheep, three of which were fed 100% orchardgrass hay, three of which were fed 60% cracked corn-40% orchardgrass hay, and three of which were fed 80% cracked corn-20% orchardgrass hay. The digestibility of dry matter in the ceca was greatest when the all-hay diet was fed, whereas the percentage of cellulose digestion in the ceca increased with increasing levels of concentrate. For all diets, the total volatile fatty acid concentrations were higher in the ceca than in the other two sites. The cecal pH levels decreased with increased corn levels in the diet. The total microbiol numbers per gram of ileal and cecal contents increased in response to feeding of concentrate; however, across all diets, the ileal counts were 8% or less of the cecal counts. In contrast, the cellulolytic microbial numbers in the ilea were 50% or more of those in the ceca and were highest with the all-hay diet. Both bacterial and end product concentrations in the ceca were equivalent to those occurring in rumina. A total of 16 cellulolytic cultures were isolated and characterized from ileal and cecal contents of animals fed all three diets. Seven gram-negative-rod-shaped organisms were identified as Butyrivibrio fibrisolvens, whose capacity to digest cellulose exceeded that of several rumen strains. The guanine-plus-cytosine content of the DNA of one strain of B. fibrisolvens was 38.8 mol%, compared with the only previously reported value for this species of 41.2 mol%.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗
PubMed1985

Blood volume, erythrokinetics and spleen function in thrombocythaemia.

Essential thrombocythaemia was diagnosed in a series of 18 patients on the basis of platelet counts greater than 1,000 X 10(9)/1. Radionuclide studies have been carried out to distinguish thrombocythaemia as a primary disease from polycythaemia vera, myelofibrosis and chronic granulocytic leukaemia presenting with high platelet counts. These have included blood volume and spleen function, and radio-iron (52Fe) has been used to demonstrate the presence of extramedullary (splenic) erythropoiesis. The value of these investigations in distinguishing between the various myeloproliferative disorders associated with thrombocythaemia is illustrated.

Adult↗
PubMed1984

Hemodynamic effects of intravenous amiodarone.

Amiodarone is a potent antiarrhythmic agent that is effective in controlling both atrial and ventricular arrhythmias. Recently, intravenous administration was demonstrated to be effective in the acute management of rhythm disorders and, in addition, appeared to shorten the loading period normally required for oral drug administration. This investigation examined the hemodynamic effects of amiodarone after both acute intravenous bolus and continuous intravenous administration. Patients with a left ventricular ejection fraction greater than 0.35 experienced improved cardiac performance due to both acute and chronic peripheral vasodilation. However, patients with a lower ejection fraction developed a 20% decrease in cardiac index and clinically significant elevation of right heart pressures after acute bolus administration; these changes were variably compensated for by peripheral vasodilation when the drug was administered intravenously over 3 to 5 days continuously. Therefore, intravenous amiodarone can result in significant impairment of left ventricular performance in patients with preexisting left ventricular dysfunction.

Amiodarone↗