Tangent simple systems method applied to a precise study of viscoelastic behaviour of human blood

The tangent simple systems (TSS) method, proposed in (1), is applied in order to study the viscoelastic behaviour of human blood in transient flow for a rectangular low shear rate step. The tangent simple systems which were used are Maxwell liquids. These systems allow one to obtain plots of variations of instantaneous values of viscosity coefficient mu, elasticity modulus G and retardation time tau = mu/G of the studied blood samples, as a function of flow duration. Variations of both parameters mu and G versus time are represented by two exponential functions which involve three couples of parameters (mu o, mu infinity), (Go, G infinity) and (tau mu, tau G). These parameters can be considered as the characteristics of each blood sample. Another representation of the results, called the dual rheogram, is also indicated. The dual rheogram enables one to follow the evolution of the blood structure. Several examples of application of the TSS method to normal blood sample and to suspensions of artificially modified red blood cells (RBC) are given.     

Serological researches in the south of Moldavia in connection with the problem of the ethnogeny of the Gagauzes, the Moldavians and the Bulgarians

With the aid of data of frequencies of genetically determined blood group systems, the authors have tried to show the basic ethno-genetic directional patterns in Southern Moldavia and in the Dniester-Carpathian-Danubian region in its entirety. Blood Groups A1A27B0, RHESUS, MN, and KELL have been determined in six random samples from four Gagauz villages (n = 330), one Moldavian village (n = 101) and one Bulgarian village (n = 96). The analysis of gene frequencies demonstrates genetic homogeneity of the total Gagauz population. Statistically reliable differentiation is observed only for the RHESUS system. It is possible now to suppose that the haemotological types of modern Gagauz and Bulgarian populations have been developed on the basis of the Balcanic serogenetic types, partially transformed under influence of gene flow from probably Central Asian or other eastern centers. The position of the Moldavians on the serogenetic map of Europe is less certain, due to a considerable ambiguity in the allele frequencies of the various blood group systems. Founder effects may account for these observations. However, the genetic distance and cluster analyses carried out on the frequencies of the surveyed blood group systems have shown the affinity of Moldavians with the Romanians and Eastern European populations.     

Differences in the concentration of erythrocytes and the hematocrit value in the blood in relation to the location of the vessels and the intensity of the blood flow

The experiments in adult rabbits revealed that in the blood flowing in cerebral veins the red cell concentration and hematocrit are much greater than in the veins of hind legs of the same animals. In blood samples taken from the heart these values are higher than in those taken from the hind leg, but usually lower than in blood samples taken from the brain. Under conditions of reduced cerebral blood flow (ischemia) the red cell concentration and hematocrit in the brain vessels decrease significantly as compared to the control conditions. Thus, the red cell distribution in arterial branching sequence is irregular, depending both on the localization of the vascular bed and the blood flow rate in it.     

One-round determination of seven leukocyte subsets in rhesus macaque blood by flow cytometry

BACKGROUND: Rhesus macaques are frequently used in biomedical research as experimental models for studying infectious diseases and for preclinical vaccination trials. The infection of these monkeys with simian immunodeficiency viruses (SIV) or simian-human immunodeficiency viruses (SHIV) reproduces the clinical and immunological characteristics of human infection by human immunodeficiency virus (HIV). Evolution of the immune response in the infected animals is generally analyzed by determining the lymphocyte subsets on blood samples using flow cytometry but requiring multiple, blood consuming, determinations. METHODS: Cell subsets present in whole-blood samples were labeled with a combination of anti-human monoclonal antibodies to CD2, CD20, CD4, CD8, and CD14 coupled to FITC or PE and analyzed by flow cytometry. RESULTS: In one round, we obtained the precise determination of macaque blood cell composition by flow cytometry. Monocytes, granulocytes, eosinophils, B lymphocytes, helper, and cytotoxic T lymphocytes were distinguished. Results obtained correlated strongly with those obtained with conventional blood cell differential systems and with separate staining of lymphocytes. The analysis of blood from healthy rhesus macaques and SHIV-infected animals demonstrated the accuracy of the determination even in very pathological situations such as macaques with simian AIDS. CONCLUSIONS: Our method allows fast determination of the blood cell composition and will be particularly useful to evaluate the cell subset evolution of macaques involved in large-scale experimental trials.     

Effect of microrheology of blood on the apparent flow instability in a rotational viscometer

Flow instability (formation of vortices and a concurrent increase in the apparent viscosity) was studied in the rotational rhombospheroid viscometer of 3 degrees, 5 degrees and 10 degrees gaps over a range of speeds from 10 to 300 r.p.m.. Comparisons between different blood systems were carried out mainly at 250 r.p.m. Experiments were carried out on blood samples obtained directly from human subjects, or from the Blood Bank, or from horses. Reconstituted suspensions of red cells in albumin or dextran were also used. Apparent flow instability was found to be not solely a function of blood viscosity, but a multiple function of many viscosity factors or blood subphases, including instability-decreasing factors such as haematocrit and aggregation of red cells; and instability-increasing factors such as rigidity of red cells; and thus specific to and characteristic of individual blood samples. Apparent instability can be described by multiple regressions as a function, Z, of red cell rigidity, Tk, blood viscosity, napp, and aggregation of red cells, AG; for example: Z = -28.29 + 26.24 Tk + 0.109 napp (r = 0.816; P less than 0.001), or Z = 5.90 - 0.0165 AG - 0.752 napp (r = 0.573; P less than 0.05). The apparent instability can be seen only in one-third of blood samples obtained from horses, and in more than half of blood samples obtained from human donors; majority of human donors shows apparent instability below 3 per cent.     

Cost analysis of various low pathogenic avian influenza surveillance systems in the Dutch egg layer sector

Background

As low pathogenic avian influenza viruses can mutate into high pathogenic viruses the Dutch poultry sector implemented a surveillance system for low pathogenic avian influenza (LPAI) based on blood samples. It has been suggested that egg yolk samples could be sampled instead of blood samples to survey egg layer farms. To support future decision making about AI surveillance economic criteria are important. Therefore a cost analysis is performed on systems that use either blood or eggs as sampled material.

Methodology/Principal Findings

The effectiveness of surveillance using egg or blood samples was evaluated using scenario tree models. Then an economic model was developed that calculates the total costs for eight surveillance systems that have equal effectiveness. The model considers costs for sampling, sample preparation, sample transport, testing, communication of test results and for the confirmation test on false positive results. The surveillance systems varied in sampled material (eggs or blood), sampling location (farm or packing station) and location of sample preparation (laboratory or packing station). It is shown that a hypothetical system in which eggs are sampled at the packing station and samples prepared in a laboratory had the lowest total costs (i.e. € 273,393) a year. Compared to this a hypothetical system in which eggs are sampled at the farm and samples prepared at a laboratory, and the currently implemented system in which blood is sampled at the farm and samples prepared at a laboratory have 6% and 39% higher costs respectively.

Conclusions/Significance

This study shows that surveillance for avian influenza on egg yolk samples can be done at lower costs than surveillance based on blood samples. The model can be used in future comparison of surveillance systems for different pathogens and hazards.     

An alternative method for calculating changes in arterial calf blood flow at rest. An initial study

In 20 patients we studied the changes in calf arterial blood flow (AF) following spinal and epidural blocks, using venous occlusion strain gauge plethysmography (SGP). AF was calculated both in the conventional way by drawing a tangent to the initial upslope of the curve, and by a new method which measures the time to the point when 50% of venous capacity is reached (tVC50). The statistical differences within and between the spinal and epidural groups for AF and tVC50 were determined. In measuring the post-block changes in AF as compared with the control values, a statistically significant correlation (rs = -0.85, p less than 0.01) was observed between the two methods. We conclude that the new variable, tVC50, seems to be potentially useful in calculating changes in arterial blood flow at rest, and could be used, for example, in connection with surgical and pharmacological interventions, especially when the initial upslope of the SGP curve is equivocal.     

Novel system for real-time ex vivo lactate monitoring in human whole blood

The objective of the study was to evaluate the performance of an amperometric enzyme based lactate sensor and to investigate the possibility of replacing a double lumen catheter based blood withdrawal system with a heparin coated single lumen system. The inner lumen of a double lumen catheter which was placed in a peripheral vein was perfused with heparin solution. The outer lumen was used to collect heparinized blood samples at a defined flow rate. The single lumen system was attached to a heparinized catheter which was also placed in a peripheral vein. The undiluted blood samples were collected at a specified flow rate. A sensor flow chamber incorporating an amperometric thin-film lactate microbiosensor was placed in the sampling line for real-time lactate monitoring. Plasma lactate concentrations were measured during frequently performed hyperlactatemia bicycle ergometer experiments in six healthy volunteers (age 25.8±2.8 years, BMI 22.7±1 kg/m²). Additionally, plasma lactate was measured in real-time using the lactate sensors. The first three experiments were performed with a double lumen based catheter system whereas the following three experiments were performed with a heparin coated catheter system. The correlation coefficients of sensor readings and laboratory analyzer results in all six experiments were between 0.93 and 0.99, respectively (P<0.001). The miniaturized lactate sensors showed a linear range up to 25 mmol/l lactate concentration and 95% response times <30 s in undiluted serum. During the experiments maximum lactate concentrations of 14 mmol/l were achieved. Improvements of system performance using heparin coated catheter systems could be shown. The overall SD of the sensor readings compared to laboratory results using three double lumen catheter based systems was 0.91 mmol/l whereas the SD using three heparin coated systems was 0.65 mmol/l. In summary, real-time monitoring of lactate in human whole blood is feasible with such a device and can be improved by using heparin coated catheter systems.     

A comparison of model linear chain molecules with constrained and flexible bond lengths under planar Couette and extensional flows

We compare directly under flow two commonly used coarse grained models of linear polymers, namely the flexible finitely extensible nonlinear elastic (FENE) chain, and the freely jointed tangent sphere chain, otherwise known as the freely jointed chain. The comparison is based on viscometric, structural and dynamical properties. We use non-equilibrium molecular dynamics to simulate steady-state systems under planar Couette flow and planar extensional flow. Computed properties include shear and elongational viscosities, normal stresses, radius of gyration and end-to-end distances, order parameters, alignment angles and spin angular velocities. In all computed properties we observe very little difference between the two molecular models. Therefore, the choice of either model is suitable, though there is a computational advantage in the use of the FENE model.     

Development of wall surface tangent DPIV measurement techniques for arterial branch models.

Experimental techniques for measuring unsteady flow in a glass arterial bifurcation model have been developed to aid in quantifying three-dimensional wall shear fluctuations associated with arterial disease. The unique feature of the current technique is the use of a "curved" laser sheet, which was everywhere tangent to the inner wall of a daughter tube in an arterial bifurcation model. Surface tangent velocity vector field measurements were made to demonstrate the potential of this technique. Ensemble-averaged data showing weak secondary flows as well as statistical distributions of flow angles are presented. Measurements of this type may be used to estimate mean and instantaneous wall shear magnitude and direction, data that are necessary for understanding the importance of circumferential motions on arterial disease.     

Special features of water structure formation in biosystems according to dielkometric data

Experimental data on dielectric function and dielectric loss tangent in living and non-living water-containing systems have been discussed from the viewpoint of our earlier concept on energy transfer in living systems and the role of water in this process. Estimates have been made of a mean length of fractal quasi-crystals, representing the form of biomolecules hydration in the living system; the expected lengths of these quasicrystals are of order of 1000 H₂O molecules. It is concluded that the peaks at the curve of frequency dependence of dielectric loss tangent in living systems is due to water sub-system, but not biomolecular vibrations.     

An improved cannulation technique for prolonged blood sampling of the American bullfrog.

A T-cannula was used to collect serial blood samples from the sciatic artery of the American bullfrog (Rana catesbeiana). The horizontal arm of the cannula was implanted in the artery and the vertical arm employed to collect blood samples. The T-cannula allowed blood flow to continue in the cannulated artery and provided long-term, repetitive blood samples from conscious, caged, but otherwise unrestrained and undisturbed animals. The cannula functioned for at least 14 days, the maximum period investigated. Athough developed for studies on amphibians and reptiles, the technique appeared to be applicable, with appropriate modifications, to a variety of small animals.     

The sample processing time interval as an influential factor in flow cytometry analysis of lymphocyte subsets

The objective of this paper is to propose a protocol to analyze blood samples in yellow fever 17DD vaccinated which developed serious adverse events. We investigated whether or not the time between sample collection and sample processing could interfere in lymphocyte subset percentage, for it is often impossible to analyze blood samples immediately after collection due to transport delay from collection places to the flow cytometry facility. CD4+CD38+ T, CD8+CD38+ T, CD3+ T, CD19+ B lymphocyte subsets were analyzed by flow cytometry in nine healthy volunteers immediately after blood collection and after intervals of 24 and 48 h. The whole blood lysis method and gradient sedimentation by Histopaque were applied to isolate peripheral blood mononuclear cells for flow cytometry analyses. With the lysis method, there was no significant change in lymphocyte subset percentage between the two time intervals (24 and 48 h). In contrast, when blood samples were processed by Histopaque gradient sedimentation, time intervals for sample processing influenced the percentage in T lymphocyte subsets but not in B cells. From the results obtained, we could conclude that the whole blood lysis method is more appropriate than gradient sedimentation by Histopaque for immunophenotyping of blood samples collected after serious adverse events, due to less variation in the lymphocyte subset levels with respect to the time factor.     

Detection and isolation of circulating melanoma cells using photoacoustic flowmetry

Circulating tumor cells (CTCs) are those cells that have separated from a macroscopic tumor and spread through the blood and lymph systems to seed secondary tumors(1,2,3). CTCs are indicators of metastatic disease and their detection in blood samples may be used to diagnose cancer and monitor a patient's response to therapy. Since CTCs are rare, comprising about one tumor cell among billions of normal blood cells in advanced cancer patients, their detection and enumeration is a difficult task. We exploit the presence of pigment in most melanoma cells to generate photoacoustic, or laser induced ultrasonic waves in a custom flow cytometer for detection of circulating melanoma cells (CMCs)(4,5). This process entails separating a whole blood sample using centrifugation and obtaining the white blood cell layer. If present in whole blood, CMCs will separate with the white blood cells due to similar density. These cells are resuspended in phosphate buffered saline (PBS) and introduced into the flowmeter. Rather than a continuous flow of the blood cell suspension, we induced two phase flow in order to capture these cells for further study. In two phase flow, two immiscible liquids in a microfluidic system meet at a junction and form alternating slugs of liquid(6,7). PBS suspended white blood cells and air form microliter slugs that are sequentially irradiated with laser light. The addition of a surfactant to the liquid phase allows uniform slug formation and the user can create different sized slugs by altering the flow rates of the two phases. Slugs of air and slugs of PBS with white blood cells contain no light absorbers and hence, do not produce photoacoustic waves. However, slugs of white blood cells that contain even single CMCs absorb laser light and produce high frequency acoustic waves. These slugs that generate photoacoustic waves are sequestered and collected for cytochemical staining for verification of CMCs.     

Effect of pulmonary blood flow on leukocyte uptake and release by dog lung

The effect of pulmonary blood flow on leukocyte uptake and release by the lung was examined in 10 anesthetized spontaneously breathing dogs. Pulmonary arterial and pulmonary venous blood was sampled with catheters placed into the right ventricle and aorta, respectively. Pulmonary blood flow was lowered by inflating a balloon catheter located in the inferior vena cava. In five experiments simultaneous blood samples were drawn from the right ventricle and aorta at 10-s intervals during a control period, a 2- to 3-min period of low flow, and a recovery period. In five additional experiments, less frequent samples were taken over periods of 15-60 min. Total leukocyte concentrations and differential counts were determined for each blood sample. The study shows that large numbers of leukocytes become sequestered within the lung when pulmonary blood flow is low and that an equivalent number of cells are released from the lung after deflation of the balloon catheter. Both the polymorphonuclear leukocytes and the lymphocytes were taken up by the lung when pulmonary blood flow was reduced. We conclude that pulmonary blood flow has a marked effect on the uptake and release of leukocytes by the dog lung.     

High-speed bubble-segmented blood sampler for the rat

An arterial blood sampler for use in the conscious rat is described. With this apparatus it is possible to obtain small (10 microliter) whole-blood or plasma samples as frequently as 1/s and to derive accurate arterial time-concentration curves in the first 60-120 s after compounds are injected for regional blood flow or pharmacokinetic measurements. The blood is withdrawn from an implanted arterial catheter into polyethylene tubing at a constant rate while bubbles are introduced at regular intervals via a side channel into the column of blood. Although some dispersion of blood samples occurs as the tubing is traversed, this can be mathematically corrected. However, correction is unnecessary if the information of interest is the area under the time-concentration curve.     

Study of the luteinizing hormone-induced increase of ovarian blood flow during the estrous cycle in the rat

CYF rats were anesthetized on various days of the 4-day cycle and blood samples were collected at 5-min interals from the ovarian vein before and after i.v. administration of 5 micrograms/100 g BW of luteinizing hormone (LH). Ovarian venous outflow, blood pressure and hematocrit were continuously recorded, and from the blood samples progesterone (P) and 17 beta-estradiol (E2) were determined by radioimmunoassay (RIA). Ovarian blood flow and P secretion showed a parallel increase on Day 1 (estrus), on Day 2, and on the afternoon of Day 4 (proestrous). LH increased ovarian blood flow each day of the cycle together with P and E2 secretion; however, no relationship was seen between the initial value of hormone secretion and the LH-induced increase of ovarian blood flow. Inhibition of hormone secretion by cycloheximide prevented the LH-induced increase of ovarian blood flow; moreover, a decrease in ovarian blood flow parallel with the diminution of hormone secretion was observed. Indomethacin pretreatment abolished the hyperemic effect of LH and partially inhibited the LH-induced increase of hormone secretion. Propranolol blocked the LH-induced increase of ovarian blood flow and blunted the effect of LH on hormone secretion. It was concluded that in LH-induced hyperemia, cAMP, prostaglandins and other vasoactive metabolites released during the process of hormone synthesis, and also a beta-adrenergic mechanism, are involved in the regulation of ovarian blood flow.     

Phenotypic variations in blood and milk of the Somali camel

132 blood samples and 54 milk samples obtained from Somali camel were analysed for red blood cell antigens with the cattle reagents and for Hb, Ca, X proteins, Tf, Alb, Am, SOD, alpha-La, beta-Lg and casein systems respectively. Positive lytic reactions were obtained with the anti-B, -Q, -Q', -W, -F1 and -J reagents. No biochemical polymorphism was observed except for Hb, X protein and beta-Lg systems.     

A rapid response microviscosimeter

An in vitro instrument is described which is designed to measure effective viscosity of blood in arteriolar size tubes at physiologically nominal flow rates, mimicking flow in the microcirculation. The 41-micron microviscosimeter is accurate within 2% when tested against viscosity standards and is reproducible within 2% using blood samples. Because the full-scale instrument response time is 3 s, either fresh or anticoagulated blood samples may be used. Measured over the nominal range of blood flow rate (Q), effective blood viscosity was found to be an increasing, decreasing, or flat function of Q, depending upon the particular individual being tested. A reference group of 81 young, healthy subjects was used to define viscous resistance (VR), a new parameter that provides for quantitative viscosity comparisons between individuals or groups without hematocrit manipulation of blood samples. As examples of the microviscosimeter's use, a group of 118 subjects was used to test for VR variation between various group subsets. No difference in VR was found between men and women; exercisers had lower VR than nonexercisers; and overweight subjects had more viscous blood than non-overweight subjects. The instrument will be useful for in vitro investigations of effective viscosity and viscous resistance in the microcirculation.     

Adrenomedullary origin of the hindquarter vasodilation during the transposition response of the rat

Transposing a rat from the home cage to a new cage produces a cardiovascular response (transposition response) characterized by an increase in hindquarter blood flow with unchanged systemic arterial pressure. Arterial blood samples were collected from rats before and during this response for radioenzymatic assay of catecholamines. During the transposition response, the concentration of adrenaline and noradrenaline in plasma increased about six- and two-fold, respectively. Ablation of the adrenal medulla prevented these changes in plasma catecholamine concentration. Constant i.v. infusion of adrenaline, at rates producing a hindquarter flow approximately matching that observed during the transposition response, evoked an increase in plasma adrenaline concentration also approximately matching the increase observed during the transposition response. It is concluded that the increase in plasma adrenaline secreted from the adrenal medulla is the main cause of the increase in hindquarter blood flow in the transposition response.