The surface-tension-driven flow of blood from a droplet into a capillary tube

In tissue, medical, or dental engineering, when blood comes into contact with a new artificial material, the flow may be influenced by surface tension between the blood and the surface of the material. The effect of surface tension on the flow of blood is significant, especially in microscale. The leading edge of the flowing blood is the triple point where the blood, the material surface, and a stationary gas orfluid meet. The movement of the triple point, i.e., the advancing front of the flow, is driven by surface tension, resisted by viscous shear stress, and balanced by the inertial force (-mass x acceleration). In this article, the dynamics is illustrated in detail in the case of blood flowing into a capillary tube by contact. The capillar, tube draws the blood into it. It is shown theoretically that initially the flow of blood in the capillary has a large acceleration, followed by a relatively large deceleration over the next short period of time, then the acceleration becomes small and oscillatory. The velocity history appears impulsive at first, then slows down. The history of the length of blood column appears smooth after integration. Existing solutions of the Navier-Stokes equation permit the analysis of simpler cases. Further fluid mechanics development is needed to meet the practical needs of bioengineering. The importance of experimental study of surface tension and contact angle over a biological surface or a man-made material as a future direction of research is pointed out.     

The reduction of a nitroxide spin label as a probe of human blood antioxidant properties

The kinetics of reduction of the radical R*, 5-dimethylaminonaphthalene-1-sulfonyl-4-amino-2,2,6,6-tetramethyl-1-piperidine-oxyl by blood and its components were studied using the EPR technique. The results demonstrate that R* is adsorbed to the outer surface of the membrane and does not penetrate into the erythrocytes. A series of control experiments in PBS demonstrate that ascorbate is the only natural reducing agent that reacts with R*. The observed first order rate of disappearance of the nitroxide radical k, is: k(blood) > k(eryth) > k(plasma) and k(blood) approximately = k(eryth) + k(plasma). The results demonstrate that: a. The erythrocytes catalyze the reduction of R* by ascorbate. b. The rate of reduction of the radical is high though it does not penetrate the cells. c. In human erythrocytes there is an efficient electron transfer route through the cell membrane. d. The study points out that R* is a suitable spin label for measuring the reduction kinetics and antioxidant capacity in blood as expressed by reduction by ascorbate.     

Deformation of leukocytes on a hematological blood film

Human leukocytes in a blood film exhibit a significantly larger diameter than in the circulation. This is due to the fact that white cells are highly deformed during preparation of a blood film. Instead of having the usual spherical shape, the cells are compressed to "pancake" forms with a thickness of about 1 micron. Hematological investigation is usually performed on these compressed cells, but in the circulation they are not observed. The deformation of the cells on a blood film is due to compression by the glass edge used to spread the blood. After deformation leukocytes do not have enough time to recover since the blood film usually dries in a shorter period than is needed for cell recovery. The shape and size of the leukocyte on the blood film is not only determined by cell volume but also by the cell membrane area. This is shown for each kind of leukocyte by independent prediction of the pancake dimensions from previous measurements of cell volume and membrane area. Leukocytes which are strongly compressed during blood film preparation may exhibit mechanical damage with rupture of membranes.     

Blood group change in a patient with blastic transformation of a myelodysplastic syndrome

Loss of certain red blood cell antigens has been described in patients with acute myelocytic leukemia (AML). This paper describes the loss of blood group A antigen in a patient with AML. The acute leukemia in this patient was preceded by a myelodysplastic syndrome for several months. At the time of diagnosis the patient's red cells showed the 0 Rh(D)+ phenotype. After induction of complete remission with two courses of Daunorubicin, Cytosin-arabinosid, and Etoposid his blood group reverted to A2. Serological studies including saliva analysis revealed that the original blood group was very likely A.     

Secondary polycythemia: a boon or a burden?

The development of a secondary erythrocytosis is usually considered a compensatory effort to counteract tissue hypoxia. However, the associated increase in viscosity tends to decrease blood flow and in theory should augment rather than relieve tissue hypoxia. Clinical observations have supported this concern and phlebotomies have been used to treat cardiopulmonary patients with high hematocrits and to prepare acclimatized mountain climbers for strenuous exercises. Direct measurements of tissue tension in rats and mice have shown that a moderate increase in hematocrit does increase the tissue tension of oxygen, probably due to a concomital increase in blood volume, and only severe increases in hematocrit are detrimental. In contrast, it was found that erythropoietin production in mice and man is decreased at even the most extreme hematocrits, suggesting that the tissue tension in the kidneys is not affected by high hematocrits and sluggish blood flow. This lack of renal hypoxia at high blood viscosities appears to serve an important purpose by preventing a vicious circle in which hypoxia will cause erythrocytosis leading to more hypoxia and more erythrocytosis and so on. However, well maintained secondary erythrocytosis cannot always be considered optimal for overall oxygen transport and has to be evaluated clinically for its potential benefit or harm.     

Hypotensive activity of the plasma proteins in a normovolemic blood exchange transfusion

The effect of post-hemotransfusion protein fractions on blood pressure, microcirculation and physiologically active substances has been studied in stimulated blood replacement by homologous animal blood. The in vivo and in vitro experiments have revealed that subfraction of hemotransfusion plasma macromolecular proteins has a prominent antihypertensive effect, leading to blood flow slowing in the microvascular bed. Hemotransfusion plasma proteins possess high serotonin-releasing activity. The involvement of blood proteins and physiologically active substances into the generation of the recepient's response to homologous blood transfusion from several donors and its role in the genesis of post-transfusion complications are discussed.     

Zinc metabolism in male rats with a transplanted ovary]

Results of the research on the concentration of zink ions in the blood serum and prostate tissue, urine excretion level by means of heterotropic transplantation of the ovary to castrated rats (males) are presented. The degree of the organism estrogenization was assessed by determining the estradiol concentration in the blood serum by the radio-immune method. The research has shown that castration leads to a zink concentration decrease in the blood serum and its reduced excretion with the urine. A significant rise in the concentration of estradiol in the blood serum did not influence the zink metabolism in the organism.     

The Mz variety of the St(a+) phenotype--a variant of glycophorin A exhibiting a deletion

The NeuNAc level of erythrocyte membranes from two related donors exhibiting the Mz variety of St(a+) phenotype within the MNSs blood group system was found to be decreased by about 16%. The quantity of glycophorin A was decreased by about 38%, whereas that of glycophorin B was not significantly different from normal. Mz erythrocyte membranes were also found to contain an abnormal component (molar ratio to glycophorin A about 0.89:1.0) with an apparent molecular mass of about 24,000 Da. Immunoblotting experiments and amino-acid sequence analysis revealed that the novel component (and glycophorin A in one of the donors) carries blood group M activity. Blood group N activity was demonstrable for glycophorin A and glycophorin B from both donors. Amino-acid sequence analysis of chymotryptic, tryptic and cyanogen bromide peptides demonstrated that the novel molecule exhibits the typical structure of a Sta-active molecule. However, since it exhibits blood group M activity, it appears to represent a variant of glycophorin A lacking the residues 27-58 (encoded by exon three of the glycophorin A gene) rather than a glycophorin B-glycophorin A-hybrid molecule of the anti-Lepore type. Since one of the Mz heterozygotes was found to exhibit both M- and N activity on glycophorin A, the Mz gene complex appears to encode a blood group N-active glycophorin A apart from the novel component and a blood group s-active glycophorin B, although the level of glycophorin A in the erythrocyte membranes is decreased by about half.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pergolide: a potent dopaminergic antihypertensive.

Pergolide, a potent centrally acting dopamine agonist, lowered both blood pressure and heart rate of spontaneously hypertensive rats and normotensive rats. Its blood pressure-lowering activity in both types of rats was more potent than that of lergotrile, a weaker dopamine agonist. The parallelism between the antihypertensive activity and the dopaminergic potency of the two compounds and the complete antagonism of the antihypertensive activity of pergolide by haloperidol, a dopaminergic blocker, indicate the involvement of dopaminergic mechanisms in maintaining the homeostasis of blood pressure and perhaps in the pathology of hypertension such as that in spontaneously hypertensive rats.     

Transient relative motion of two cells in a channel flow

The hydrodynamic interaction of a red blood cell and a white blood cell in microvessels is studied, by use of a two-dimensional numerical model. The red blood cell, modeled as a small rigid circular cylinder, and the white blood cell, modeled as a larger rigid circular cylinder, are immersed in an incompressible Newtonian fluid in a two-dimensional channel. It is assumed that no external force or moment acts on the model cells, and the effect of inertia forces on the motion of the fluid and the cells is neglected. The velocity field of the suspending fluid and the instantaneous velocities of the two model cells are computed by the finite element method. Using the translational velocities of the model cells obtained, the trajectories of their relative motion are determined, for various initial positions. It is shown that the cells may or may not pass each other or separate, depending on the initial positions. The present results compare well to the experimental results.     

Forces on a Wall-Bound Leukocyte in a Small Vessel Due to Red Cells in the Blood Stream

As part of the inflammation response, white blood cells (leukocytes) are well known to bind nearly statically to the vessel walls, where they must resist the force exerted by the flowing blood. This force is particularly difficult to estimate due to the particulate character of blood, especially in small vessels where the red blood cells must substantially deform to pass an adhered leukocyte. An efficient simulation tool with realistically flexible red blood cells is used to estimate these forces. At these length scales, it is found that the red cells significantly augment the streamwise forces that must be resisted by the binding. However, interactions with the red cells are also found to cause an average wall-directed force, which can be anticipated to enhance binding. These forces increase significantly as hematocrit values approach 25% and decrease significantly as the leukocyte is made flatter on the wall. For a tube hematocrit of 25% and a spherical protrusion with a diameter three-quarters that of the vessel, the average forces are increased by ∼40% and the local forces are more than double those estimated with an effective-viscosity-homogenized blood. Both the enhanced streamwise and wall-ward forces and their unsteady character are potentially important in regard to binding mechanisms.     

Purification of a human plasma membrane glycoprotein from human red blood cells by affinity chromatography using a monoclonal antibody

Using the monoclonal antibody LICR-LON-Fib75.1 coupled to Sepharose as an affinity chromatography column, a membrane glycoprotein with an apparent molecular weight of 18,000 on sodium dodecyl sulfate-polyacrylamide gels has been purified from human red blood cells. The purified protein contained 25% carbohydrate by weight, the predominant sugars being galactose, mannose, and glucosamine. Amino acid analysis indicated that the protein was relatively rich in aspartate, glutamate, valine, and leucine and had a low proline and methionine content. The molecule could be removed from intact red blood cells by trypsin and could be labeled with iodine by lactoperoxidase-catalyzed cell surface iodination of red blood cells. The protein could also be labeled using the lipidsoluble photoactivatable reagent 3-(trifluoromethyl)-3-(m-[125I]iodophenyl) diazirine) and partitioned into the lower phase of the phase-separable detergent Triton X-114. During size-exclusion chromatography in different detergents alterations were observed in the apparent molecular weight of the protein. These results suggest that this Fib75.1-binding protein is an external red blood cell membrane glycoprotein which is capable of binding detergent. Proteins with a similar molecular weight have also been isolated from two human tumor cell lines by immunoprecipitation with this monoclonal antibody.     

Leukocyte-depleted blood: a comparison of available preparations.

Febrile nonhemolytic transfusion reactions due to leukoagglutinins are frequently seen in patients who have been given multiple blood transfusions. To prevent or reduce the severity of these reactions, leukocyte-poor blood (that containing fewer than 0.3 X 10(9) leukocytes per unit) is frequently requested by clinicians. Four methods commonly used in Canada to produce leukocyte-poor blood were examined for their relative effectiveness and appropriate use. The mean total leukocyte count per unit was reduced to 0.22 X 10(9) in buffy-coat-poor red blood cell preparations produced by centrifugation with the blood bag inverted, to 0.19 X 10(9) by perfusion through an Imugard filter, to 0.21 X 10(9) by the use of an IBM 2991 automated cell washer and to 0.13 X 10(9) with the use of frozen blood. The proportion of red cells recovered varied from 62% with the inverted-spin method to 85% with the use of frozen blood. Comparison of these data and the percentage of leukocytes removed, the shelf life of the product, the cost of supplies and the preparation time indicated that the use of sophisticated machinery, such as the IBM cell washer, or of glycerolization plus washing of frozen cells is not warranted for most patients. Instead, patients who have febrile nonhemolytic transfusion reactions should initially be treated with a leukocyte-poor red cell preparation produced by the inverted-spin method; only if such reactions recur should the blood bank be requested to provide filtered, washed or frozen red cells.     

Finite element analysis of stresses developed in blood sacs of a pusherplate blood pump

Mechanical circulatory support (MCS) devices are blood pumps that support or replace the function of the native heart. It is important to minimize the material stresses in the flexing blood sac or diaphragm in order to increase the duration of support these devices can provide. An axisymmetric finite element model of a pusherplate blood pump was constructed to evaluate the effect of various design parameters on the material stresses in a segmented poly(ether polyurethane urea) seamless blood sac. The design parameters of interest were the sac thickness, pump case wall taper, and radius of the sac between the pusherplate and pump case wall. The analysis involved a quasi-static analysis of the systolic ejection phase of the pump. The finite element solution suggested that the principal stresses and strains increased almost linearly with sac thickness. The pump case wall taper had the largest effect; decreasing the peak principal stresses by approximately 35% when the pump case was straight versus tapered. Lastly, the model demonstrated that the radius of the blood sac between the pusherplate and pump case wall had little or no effect on the magnitude of the blood sac stresses. Therefore, this study suggests that in order to minimize the stresses in a blood sac of a pusherplate blood pump, a straight pump case should be chosen with the thinnest sac.     

Blood volume as a controlling factor for body water homeostasis inHirudo medicinalis

Summary Raising the blood volume in leeches by blood transfusion from donor leeches resulted in temporarily increased urinary flow. Displacement of the blood within the leech by massage, produced temporarily increased urinary flow in segments with elevated blood volume and seemed to decrease urinary flow in segments with lowered blood volume. It is suggested that blood volume and body water homeostasis are controlled by a feed-back system.     

Direct polymerase chain reaction (PCR) from human whole blood and filter-paper-dried blood by using a PCR buffer with a higher pH

We described a novel approach to directly amplify genomic DNA from whole blood and dried blood spotted on filter paper without any DNA isolation by using the PCR buffer with a higher pH, which was optimized as pH 9.1-9.6. Direct PCR on blood treated with various anticoagulants showed that the buffer worked well with the blood treated by citrate, EDTA, or heparinate. DNA fragments with different lengths could be efficiently amplified directly from various forms of blood samples. By coupling the buffer with tetra-PCR, a "true" single-tube genotyping was realized by using whole blood or paper-dried blood as starting material.     

Calibration in dogs of a subcutaneous miniaturized glucose sensor using a glucose meter for blood glucose determination.

The feasibility of calibrating a glucose sensor by using a wearable glucose meter for blood glucose determination and moderate variations of blood glucose concentration was assessed. Six miniaturized glucose sensors were implanted in the subcutaneous tissue of conscious dogs, and the parameters used for the in vivo calibration of the sensor (sensitivity coefficient and extrapolated current in the absence of glucose) were determined from values of blood glucose and sensor response obtained during glucose infusion. (1) Venous plasma glucose level and venous total blood glucose level were measured simultaneously on the same sample, using a Beckman analyser and a Glucometer II, respectively. The regression between plasma glucose (x) and whole blood glucose (y) was y = 1.12x-0.08 mM (n = 114 values, r = 0.96, p = 0.0001). The error grid analysis indicated that the use of a Glucometer II for blood glucose determination was appropriate in dogs. (2) The in vivo sensitivity coefficients were 0.57 +/- 0.11 nA mM-1 when determined from plasma glucose, and 0.51 +/- 0.07 nA mM-1 when determined from whole blood glucose (t = 1.53, p = 0.18, n.s.). The background currents were 0.88 +/- 0.57 nA when determined from plasma glucose, and 0.63 +/- 0.77 nA when determined from whole blood glucose (t = 0.82, p = 0.45, n.s.). (3) The regression equation of the estimation of the subcutaneous glucose level obtained from the two methods was y = 1.04x + 0.56 mM (n = 171 values, r = 0.98, p = 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)     

All clinically-relevant blood components transmit prion disease following a single blood transfusion: a sheep model of vCJD

Variant CJD (vCJD) is an incurable, infectious human disease, likely arising from the consumption of BSE-contaminated meat products. Whilst the epidemic appears to be waning, there is much concern that vCJD infection may be perpetuated in humans by the transfusion of contaminated blood products. Since 2004, several cases of transfusion-associated vCJD transmission have been reported and linked to blood collected from pre-clinically affected donors. Using an animal model in which the disease manifested resembles that of humans affected with vCJD, we examined which blood components used in human medicine are likely to pose the greatest risk of transmitting vCJD via transfusion. We collected two full units of blood from BSE-infected donor animals during the pre-clinical phase of infection. Using methods employed by transfusion services we prepared red cell concentrates, plasma and platelets units (including leucoreduced equivalents). Following transfusion, we showed that all components contain sufficient levels of infectivity to cause disease following only a single transfusion and also that leucoreduction did not prevent disease transmission. These data suggest that all blood components are vectors for prion disease transmission, and highlight the importance of multiple control measures to minimise the risk of human to human transmission of vCJD by blood transfusion.     

Blood cell telomere length is a dynamic feature

There is a considerable heterogeneity in blood cell telomere length (TL) for individuals of similar age and recent studies have revealed that TL changes by time are dependent on TL at baseline. TL is partly inherited, but results from several studies indicate that e.g. life style and/or environmental factors can affect TL during life. Collectively, these studies imply that blood cell TL might fluctuate during a life time and that the actual TL at a defined time point is the result of potential regulatory mechanism(s) and environmental factors. We analyzed relative TL (RTL) in subsequent blood samples taken six months apart from 50 individuals and found significant associations between RTL changes and RTL at baseline. Individual RTL changes per month were more pronounced than the changes recorded in a previously studied population analyzed after 10 years' follow up. The data argues for an oscillating TL pattern which levels out at longer follow up times. In a separate group of five blood donors, a marked telomere loss was demonstrated within a six month period for one donor where after TL was stabilized. PCR determined RTL changes were verified by Southern blotting and STELA (single telomere elongation length analysis). The STELA demonstrated that for the donor with a marked telomere loss, the heterogeneity of the telomere distribution decreased considerably, with a noteworthy loss of the largest telomeres. In summary, the collected data support the concept that individual blood cell telomere length is a dynamic feature and this will be important to recognize in future studies of human telomere biology.