Die elektronische Volumenbestimmung von Blutkörperchen und ihre Fehlerquellen

Advances in Resistive Pulse Sensors: Devices bridging the void between molecular and microscopic detection

Since the first reported use of a biological ion channel to detect differences in single stranded genomic base pairs in 1996, a renaissance in nanoscale resistive pulse sensors has ensued. This resurgence of a technique originally outlined and commercialized over fifty years ago has largely been driven by advances in nanoscaled fabrication, and ultimately, the prospect of a rapid and inexpensive means for genomic sequencing as well as other macromolecular characterization. In this pursuit, the potential application of these devices to characterize additional properties such as the size, shape, charge, and concentration of nanoscaled materials (10 - 900 nm) has been largely overlooked. Advances in nanotechnology and biotechnology are driving the need for simple yet sensitive individual object readout devices such as resistive pulse sensors. This review will examine the recent progress in pore-based sensing in the nanoscale range. A detailed analysis of three new types of pore sensors - in-series, parallel, and size-tunable pores - has been included. These pores offer improved measurement sensitivity over a wider particle size range. The fundamental physical chemistry of these techniques, which is still evolving, will be reviewed.

Cross-sectional study of biomarkers of exposure and biological effect on monozygotic twins discordant for smoking

BACKGROUND

The aim of this study was to investigate the possible correlation between smoking status and biomarkers of exposure (BoE) and biological effect (BoBE) in monozygotic twins discordant for smoking status (smoker and non-smoker pairs). By eliminating potential genetic variability in this manner, a clearer pattern of the effects of lifestyle and environmental exposures should become apparent.

METHODS

This was a cross-sectional study on monozygotic healthy twins (44 subjects, 26 males and 18 females) with a mean age 31.5 years. BoE to cigarette smoke and BoBE were measured in body fluids (24 h urine and blood) after medical pre-screening.

RESULTS

All BoE were significantly higher in the smoker twins. Among BoBE, 11-dehydrothromboxane B(2) (11-dehydro TBX), 2,3-dinorthromboxane B(2) (2,3-dinor TBX), 8-epi-prostaglandin F2α (8-epiPGF), hydroxyproline (OH-P), fibrinogen, white blood cell (WBC), neutrophil and lymphocyte counts and heart rate were statistically significantly increased in the smoker compared to the non-smoker twins. Moreover, statistically significant correlations between neutrophil count and 11-dehydro TBX (r=0.32), WBC and 8-epiPGF (r=0.33), OH-P and 8-epiPGF (r=0.49) and heart rate and fibrinogen (r=0.46) were observed.

CONCLUSIONS

The study results confirmed the reliability of the BoE for the evaluation of smoking status. Moreover, a subset of the BoBE, reported as being associated with inflammatory conditions and early stages of vascular disorders, has emerged as showing a consistent relationship with smoking status from the present and the previous studies. By using monozygotic twin pairs, genetic variability has been excluded as a possible source of variability in this study. These results should assist in the interpretation of other population studies using these biomarkers.

Red cell morphology and the peripheral blood film

Red cell morphology as determined by microscopic examination of a stained blood film is an old and traditional approach to the evaluation of an anemic patient. The examination of a well-made and well-stained peripheral blood film remains an important and vital tool in the evaluation of the anemic patient and provides direction for the subsequent laboratory evaluation of the patient's anemia. This article provides a review of the important red cell changes necessary for evaluation in determining the cause of anemia.

Chromate effects on red cells membranes

The modification of human erythrocyte membrane proteins by chromate previously had been investigated by kinetic (4) and electrophoretic techniques (5). In the Coulter Counter we now observed that chromate (10 mM) caused an increase in the intracellular resistivity but also an augmentation of the critical voltage where the membrane resistance breaks down owing to electroporation. Furthermore, a slight chromate-induced augmentation of echinocyte shape was observed. Also, chromate causes the intracellular pH to shift to higher values.

Evaluation of a new blood cell counter with sheath flow system

A blood cell counter with a sheath flow system has been developed to eliminate the drawback of the Coulter type blood cell counter, namely, signal distortion caused by the cells passing through the electric aperture gate. With the new system, signal distortion was low and a near-normal distribution curve for erythrocytes and resin particles was obtained. The counter has a computer program for determining the red cell distribution width, which represents an actual size difference at 20% of the relative frequency of the distribution curve. This is independent of mean cell volume, and is considered to be of clinical importance. We examined the values in 2,300 healthy subjects and patients with various hematological disorders.

Measurement of biophysical properties of red blood cells by resistive pulse spectroscopy: volume, shape, surface area, and deformability

This paper presents a simple, new approach to the determination of size, shape, surface area, and deformability information for cells, notably red blood cells. The results are obtained by combining experimental measurements from resistive pulse spectroscopy (an extension of electronic cell-sizing methodology) with theoretical calculations for model cell systems. Assuming constancy of surface area and approximating red cell shapes by both prolate and oblate ellipsoids of revolution, values are determined for cell shape factor and volume under a variety of conditions. For red blood cells under low-stress conditions, shape factor, volume, and surface area results are found to be consistent with those available from the literature, when the oblate model is used. The applicability of this approach for determination of red cell properties under altered conditions is demonstrated by results for cell volume, at varying osmotic pressure and mechanical shear (tensile) stress. By quantitating the change in cell shape with stress, a new numerical scale for measuring cell deformability is also obtained, and data are presented on its variation for red cells at different osmolalities, over the range of 140 to 500 mOsm.

Normal and homogeneous red blood cell populations over a wide range of hyper-iso-hypotonic media. III. Corrected volumes in Coulter Counter measurements

The volumes of human erythrocytes after rapid and gradual swelling in hypotonic NaCl media were measured using a Coulter Counter ZB at temperatures of +4 degrees C and +20 degrees C together with potassium leakage, the degree of hemolysis and the 'returning volume', i.e., the volume in an isotonic solution to which the cells will return from that in a hypotonic solution. The methodological and systematic errors in the volume measurements were corrected by taking into account the shape dependence of the Coulter Counter and the change in cell population during hemolysis, whereafter the measured cell volume values and the comparison between them become more reliable. The curves for cell volume as an inverse function of osmotic pressure appeared to be non-linear. The slopes were small at first but showed a rapid increase as the cells approached their maximal volume. The critical hemolytic volume was approx. 8% higher at +20 degrees C after both rapid and gradual swelling than at +4 degrees C and approx. 4% higher after a gradual swelling as compared with a rapid swelling both at +4 degrees C and +20 degrees C. A decrease in temperature resulted in an increase in the critical osmotic pressure both in rapid and gradual hemolysis, but did not greatly affect the amount of prelytic K+ leakage. The critical osmotic pressure was smaller in gradual hemolysis than in rapid hemolysis and the prelytic K+ leakage was doubled at both +4 degrees C and +20 degrees C. The shifts in osmotic fragility as a function of temperature may be due to differences in the visco-elastic properties of the cell membrane, but the shifts in osmotic fragility as a function of swelling rate may be connected with differences in potassium leakage and membrane stretch.

Osmotic hemolysis and fragility. A new model based on membrane disruption, and a potential clinical test

Red cell osmotic hemolysis has traditionally been defined by the loss of hemoglobin, in response to reduced osmotic pressure, as measured spectroscopically. Previous work from this laboratory using resistive pulse spectroscopy (RPS) has shown that in a mixed population of hemolyzing cells, ghosts can be detected as being more deformable, and hence appearing distinctly smaller, than the remaining intact cells. Other researchers using similar methods have reported detection of ghosts as apparently smaller objects, resulting from their greater sensitivity to dielectric breakdown. We now confirm both of these results, and demonstrate by kinetic studies that changes which occur in the rheological and electrical properties of ghosts are independent phenomena. We include in our analysis the explicit calculation of ghost and intact spherocyte resistivity after dielectric breakdown. The two different characterizations for ghosts are integrated into a proposed model of osmotic hemolysis based on known red blood cell membrane and cytoplasmic properties. This work provides both a theoretical and a practical foundation for RPS-based measures of osmotic fragility, including a potential new clinical test, measures which provides very early detection of the ultimate fate of osmotically stressed red cells.

[Computer-analysis of volume distribution curves of erythrocytes (author's transl)]

The erythrocyte diameter curve of Price-Jones exhibits symmetrical, normal distribution. In contrast, the volume distribution curve of erythrocytes shows an asymmetrical course with some skewness to the right, which with different haematological diseases may vary. With respect to differential diagnosis as well as to therapy it is of importance to have available an objective means of comparing curves with different shapes. We therefore developed a mathematical determination of the volume distribution curves, which derived from the overlapping of two Gaussian normal distribution curves. Volume distribution curves of erythrocytes were determined with an electronic particle counter (Coulter counter) in 271 healthy and haematologically affected children as well as in 3 adults. With only one exception all volume distribution curves of erythrocytes could be fitted using computer analysis and the constants m1, m2, s1 and s2 were calculated. Characterisation of the curves with only these 4 constants allows a simple qualitative as well as quantitative comparison of different volume distribution curves.

Analysis of velocity sedimentation techniques in cell separation. Influence of apparative and sample properties on separative power, resolution and sensitivity

In the present investigation the velocity sedimentation technique was analysed with respect to separation resolution, power and sensitivity. It was found that apparative modifications do not influence the resolution, which is a function of the contribution of apparative errors to the dispersion. A surprisingly small parameter of 0.15 was determined and it seems unlikely that this value can be improved. On the other hand an apparative modification is presented which improves the separation power and makes sample loading independent of the gradient filling. If cells (from rat bone marrow) were separated, a several times higher dispersion for a given cell volume was observed than was due to the apparative error. It was concluded that density variations were the major source of this dispersion. Since cell volume and density apparently show independent variations within a biological cell population the cell density cannot be disregarded if velocity sedimentation profiles are discussed in physical terms as is often done.

Measurement of the mean cell volume using electronic particle counters

Under carefully controlled conditions electronic cell counters, for example the Coulter Counter, Model FN, and Channelyzer, may be calibrated to give MCV values down to as small as 20 fl which agree with those derived from the centrifugation PCV (corrected for plasma trapping) and the red cell count. The MCV values will be too high if the instrument uses a high cell concentration, has a fixed lower threshold, no effective upper threshold and no edit facility. This may partly explain why the Coulter Counter, Model S, when standardized with 4C cell control gives higher MCV values than the Model FN linked to the Channelyzer. The difference is, on average, 2 fl with normal blood samples and 5 fl in cases of microcytic anaemia. It is suggested that standards of low MCV should be used together with those of normal MCV when calibrating the Model S.

Control of cell growth in bacteria: experiments with thymine starvation

When cells of Escherichia coli THU were starved for thymine, they continued to grow without division for at least two successive volume doublings at their initial rate. Within experimental error this average rate of volume increase, 0.21 mum(3) per hr, was identical with that observed in control cultures during two generations of growth in the presence of thymine. This growth rate was also independent of the age of the cells at the time of starvation. These results are consistent with the hypothesis, proposed earlier, that growth rates are controlled by uptake sites for binding, transport, or accumulation of compounds into the cell, that the number of these sites is constant throughout most of the cell cycle, and that this number doubles near or at cell division.