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Biomedical subjects

B Leijnse

Publications and source records attributed to B Leijnse.

At least 37 records · Page 2Linked to original sources
PubMed1987

Reflections on the standardization of total bilirubin in neonatal serum.

A study is described on the standardization of the determination of neonatal total bilirubin. A wide variation in results was shown in surveys held in The Netherlands and Germany and the reasons for this variation were sought. The suitability of commercial bilirubin standards and direct reading instruments, widely used in the neonatal field, was tested by comparing all measurements with those obtained with the candidate reference method. We found differences between the stated values and those obtained by the reference method. However, a bias was also shown to exist between the results measured with the direct reading instruments and those obtained with the reference method, explaining at least qualitatively, the variation seen in the surveys. In addition, problems in the calibration of the DuPont ACA are discussed.

Adult↗
PubMed1986

Hydrophobic properties of alkaline phosphatases.

The butanol extraction method of Morton (1950), a routine step in enzyme purification, is discussed with special reference to a hydrophobic form of alkaline phosphatase from human liver tissue. This form slowly precipitates from butanol-extracted liver tissue homogenates stored at 4 degrees C. Furthermore, it is lost when acetone precipitation is applied as a purification procedure. The soluble form in liver tissue is shown to have a higher relative hydrophobicity than the serum liver/bone isoenzyme. The use of sodium cholate in the isolation of the hydrophobic form produces an artefact in isoelectric focusing, which can be abolished by dialysis prior to focusing.

Alkaline Phosphatase↗
PubMed1986

Basic principles and problems of haemocytometry.

After some brief remarks on counting chambers, references to the ICSH-recommended haemoglobin-determination are given. The microhaematocrit of normal blood is advocated as a potential routine calibration method. Comments are given on discrepancies between centrifugal and flow haemocytometry haematocrits of abnormal and artificial bloods. Flow haemocytometry instruments are classified into analogue and digital instruments or into electrical and optical instruments. Their hydrodynamic properties are discussed. The principles and problems of electrical and optical cell counting and sizing are dealt with. The importance of the refractive index and of flow-induced cell shape changes for the MCV determinations is stressed. It is argued that MCV and haematocrit values are exaggerated at both low and high values and consequently MCHC is erroneously constant. Various prevailing red cell distribution width (RDW) and platelet distribution width (PDW) definitions bring about considerable confusion. The major features of the counting and sizing of white blood cells and platelets are described.

Blood Cell Count↗
PubMed1986

Alkaline phosphatase and cholestasis.

The process of cholestasis in both man and rat leads in the majority of cases to the appearance of a biliary band in the electrophoresis of alkaline phosphatase isoenzymes. In this article, the biochemical nature and mode of formation of the biliary band is discussed, with reference to its appearance in cholestasis and other hepatobiliary diseases.

Alkaline Phosphatase↗
PubMed1986

Determination of serum triglycerides by capillary on-column gas chromatography.

We report an accurate method, based on capillary on-column gas chromatography, for determining triglycerides in human serum. After serum extraction and chemical hydrolysis, glycerol is directly measured by gas chromatography (GC). With our extraction method no free glycerol is extracted from serum. The accuracy of this method was compared with that of a method based on the original procedure of Carlson (J. Atheroscler. Res. 3, 334-336 (1963)) and which is standardized by the Centers for Disease Control (CDC, Atlanta, U.S.A.). Orthogonal regression analysis of the GC method (y) and the CDC reference method (X) resulted in y = 0.996 X + 0.000 with a correlation coefficient of 0.999. The variances of analytical data, collected over a two month period showed that, for the GC method, the within-day coefficient of variation (CV) was less than 1.43%; the between-day CV less than 1.35%. The data for the CDC method were less than 3.36% (within-day) and less than 6.38% (between-days). The CDC method is linear up to 3.7 mmol/l and the GC method to 22 mmol/l.

Chromatography, Gas↗
PubMed1986

Minimizing interlaboratory variation in routine assays of serum cholesterol through the use of serum calibrators.

A cholesterol standardization program was developed in The Netherlands for clinical laboratories that use their analytical results as indicators of cardiovascular risk. Participants with sufficient precision but inaccurate results are encouraged to use serum-based calibrators as a means to decrease bias. A regional pilot survey and thereafter a national one were carried out in 31 and 138 laboratories, respectively, to investigate whether use of the serum-calibration procedure could improve routinely performed cholesterol measurements. To participants in our national quality-control surveys were mailed three calibrators (pooled human serum) and five human-serum controls, for analysis of cholesterol on four different days. Reference method values had been assigned to the calibrators by the Netherlands Reference Laboratory, applying the U.S. Centers for Disease Control modification of the Abell-Kendall procedure. Using the calibration curves based on results for the serum calibrators decreased the between-laboratory variation (SD) by at least 50%, with improved accuracy for non-enzymatic methods. The initial within-laboratory precision was generally good, and improvements in it were small. To our knowledge, standardization results involving so many routine hospital laboratory procedures have not been previously reported.

Calibration↗
PubMed1985

Isoelectric focusing of alkaline phosphatases in agarose gel.

An isoelectric focusing technique in agarose gel is presented which is suitable for alkaline phosphatases from both serum and tissue sources. An anomaly in the literature about isoelectric focusing of serum alkaline phosphatase from liver origin is discussed and a possible explanation is proposed. The presented technique is used to demonstrate some differences in behaviour of serum liver and bone isoenzymes towards neuraminidase treatment.

Alkaline Phosphatase↗
PubMed1985

Spinal fluid protein revisited: a reappraisal of the biuret procedure.

In this study our previously described selected method, a biuret procedure with deproteinization, for the determination of spinal fluid protein is thoroughly discussed against the background of the results found with a number of Lowry modifications. The use of various separation techniques, i.e. deproteinization, ultrafiltration and chromatography (HPLC), for protein analysis led to the question as to whether low molecular weight proteins in cerebrospinal fluid play an important role or not with respect to the choice of a selected method for the determination of total protein.

Biuret Reaction↗
PubMed1985

Comparison of the rheological behavior of hemocytometry controls and fresh patient EDTA-anticoagulated blood specimens.

For rheological reasons high viscosity specimens are more sensitive to deficiencies, if any, in the aspiration systems of whole blood flow cytometers and consequently are more likely to give erroneous values. For this reason the rheological behavior of hemocytometry controls was compared with that of patient blood specimens. It is shown that the behavior of controls and patient specimens of comparable hematocrit is similar at shear rates that are probably occurring during aspiration (exceeding approximately 40 s-1). The hematocrit is shown to be a major determinant of the viscosity of both controls and patient specimens. The results suggest that from the rheological point of view the fundamental IFCC premise is met, "that errors detected by means of control specimens exactly mirror errors occurring with patients' specimens", provided their hematocrits are taken into account.

Anticoagulants↗
PubMed1984

Outdated blood and redundant buffy-coats as sources for the preparation of multiparameter controls for Coulter-type (resistive-particle) hemocytometry.

Outdated, buffy-coat depleted, CPDA-1 blood and redundant buffy-coats were used as sources for the laboratory preparation of controls for Coulter-type (resistive-particle) hemocytometry. Deteriorated white blood cells and platelets and potentially interfering microaggregates with volumes not exceeding 400 fl are shown to be virtually completely removed by centrifugation and filtration. Addition of fixed red blood cells as white blood cell substitutes and of isolated, fixed platelets enable the preparation of multiparameter controls of short-to-medium-term stability. The availability of these simple, inexpensive controls can contribute significantly to optimal internal quality control in hemocytometry.

Blood Banks↗
PubMed1984

Laboratory preparation and evaluation of a multiparameter hemocytometry control.

A protocol for the laboratory preparation of a multiparameter hemocytometry control is given. Human platelets, stabilized by a basically simplified and inexpensive fixation procedure, are added to our previously described white and red blood cell control. Evaluation of this multiparameter control shows good precision characteristics and acceptable mechanical stability for at least 7 weeks, as measured in the Coulter counter Model S Plus-II. The control can basically contribute to the realization of the essence of internal quality control: continuous self-auditing and continuous attempts at improvement of performance.

Blood Platelets↗
PubMed1984

Iron uptake by Chinese hamster fibroblasts from human transferrin.

The manner of uptake or iron by Chinese hamster fibroblasts, type DON, from human transferrin was investigated by means of replacement studies, in which the cells that were incubated with 125I-labelled human transferrin were chased with non-radioactive transferrin for only a few minutes. The results did not support the reversible endocytosis hypothesis for the uptake of iron from transferrin. The uptake of iron measured as 59Fe during several cell divisions was found to be a function of time and cell number. It was found that the total uptake of iron in the harvests was directly proportional to the incubation, and that the uptake per 10(6) cells levelled off in the course of time.

Animals↗
PubMed1984

The introduction of bromocresol purple for the determination of serum albumin on SMAC and ACA, and the standardization procedure.

The bromocresol purple methods for the determination of serum albumin on the Technicon SMAC and the DuPont ACA systems were evaluated and compared with the corresponding bromocresol green methods, a radial immunodiffusion (RID) and an electrophoresis technique. The linearity and precision of the dye binding methods were comparable. The bromocresol purple methods were more influenced by lipaemia and to a lesser extent by high bilirubin concentrations. The specificity of the bromocresol purple methods was superior to that of the bromocresol green methods and showed excellent correlations with the radial immunodiffusion method: bromocresol purple: SMAC = 1.03 (RID) + 0.32; bromocresol purple: ACA = 1.00 (RID) + 1.27. The bromocresol purple methods intercorrelated better than the bromocresol green methods. Freeze-dried sera can be used for albumin standardization. Analysis of the albumin fractions of freeze-dried and liquid sera by high-performance liquid chromatography (HPLC) did not reveal significant differences in albumin polymerization. Purified albumin reacted, irrespective of the degree of polymerization, very differently in the dye-binding methods. The bromocresol purple methods showed an overestimation of purified albumin, the bromocresol green methods an underestimation. The reason for these differences is unclear. Non-human albumin reacted poorly with bromocresol purple in contrast with bromocresol green.

Animals↗
PubMed1984

Multicentre study of a new enzymatic method of cholesterol determination.

A new enzymatic method for the determination of cholesterol in serum and plasma was evaluated in 8 separate laboratories in comparison with routine and reference methods. Investigation of the analytical reliability in the 2-26 mmol/l measurement range showed the following results: At the set reading points (10 min at 25 degrees C and 5 min at 37 degrees C) the reaction shows complete substrate conversion. The colour complex is stable over a period of 60 min. The response to cholesterol is linear up to 26 mmol/l. Precision within the series was 0.6-2.8% in 20 determinations (coefficient of variation). Day to day precision was 0.5-3.3% in triple determinations of 10 days (coefficient of variation). Accuracy was studied with 2 samples (assigned value: 3.52 and 6.70 mmol/l respectively). In the case of sample 1 the mean for the 8 laboratories was 3.44, with a median of 3.44; for sample 2 the values were 6.68 and 6.72. The results demonstrate an excellent transferability. In comparison with other enzymatic procedures, the values found with the new test were 5-10% higher; these results agree at all concentration ranges with the reference methods of Abell & Kendall and with those from mass spectrometry.

Cholesterol↗
PubMed1984

Surveys of neonatal bilirubin. An evaluation.

Experience in surveying the neonatal bilirubin determination in the Netherlands is described. Initially it was organized as a local activity (the Rotterdam area), then later enlarged to a national scale (some 150 participants). A number of items is discussed i.e. the initial improvements, which stabilized at an interlaboratory imprecision of about 8%, and further changes that could improve this rather high imprecision.

Bilirubin↗
PubMed1984

Sterile, medium scale age fractionation of human red blood cells.

After sterile removal of white blood cells and the majority of platelets from blood in a regular transfusion bag, the remaining red blood cells were separated under sterile conditions into a relatively young and a relatively old fraction. Making use of the different densities of old and young red blood cells, the separation occurs in a double transfusion bag by centrifugation, after the cells have been carefully layered on top of Percoll of "tailor-made" density. The successful results of this simple and inexpensive technique are assessed by comparing the creatine concentration and the acetylcholinesterase activity in both fractions. Thus, this medium scale fractionation technique yields hundreds of ml of sterile, young red blood cells.

Cell Fractionation↗
PubMed1983

A stable human platelet-white blood cell control for the Coulter Model S-Plus II.

The preparation and evaluation of a human platelet-white blood cell control of at least 5 months' stability, as measured in the Coulter Counter Model S-Plus II, is described. In some preparations minor departures from log normal platelet (PLT) distributions were found, impeding the generation of values for mean PLT volume (MPV) and PLT distribution width (PDW). In many cases, however, excellent linearity for PLT and white blood cell (WBC) counts and low coefficients of variation for PLT and WBC counts and PDW were found. Some possible factors causing the large coefficient of variation found for MPV values are mentioned.

Erythrocyte Count↗