PubMed Health⌕ Search

Biomedical subjects

M R Hardeman

Publications and source records attributed to M R Hardeman.

At least 37 records · Page 2Linked to original sources
PubMed1992

Decrease of erythrocyte deformability in cyclosporine-treated renal transplant patients: correction with fish oil as well as corn oil.

Twenty-nine renal transplant recipients with good, stable transplant function were included in a double-blind cross-over study to investigate the effects of different immunosuppressive treatment modalities and also the effects of fish oil and corn oil supplementation on erythrocyte deformability. Ten patients were treated with cyclosporine (CyA) only, 10 patients with CyA and prednisolone, and 9 patients with azathioprine and prednisolone. Erythrocyte deformability, as measured by an ektacytometric technique, was significantly decreased in both CyA-treated groups compared with the azathioprine-prednisolone-treated group, and this decrease was corrected with fish oil and with corn oil. The cause and the clinical significance of less deformable erythrocytes due to CyA are not yet clear. However, less deformable erythrocytes could play a role in the genesis of the complications of CyA.

Adult↗
PubMed1992

The clinical importance of erythrocyte deformability, a hemorrheological parameter.

Hemorheology, the science of the flow behavior of blood, has become increasingly important in clinical situations. The rheology of blood is dependent on its viscosity, which in turn is influenced by plasma viscosity, hematocrit, erythrocyte aggregation, and erythrocyte deformability. In recent years it has become apparent that the shape and elasticity of erythrocytes may be important in explaining the etiology of certain pathological situations. Thus, clinicians have become increasingly interested in hemorheology in general and erythrocyte deformability in particular. In the course of time, many clinical studies have been performed, but no concise review has thus far been published. This article encompasses a review of the clinically based literature on this subject.

Blood Viscosity↗
PubMed1992

Effects of epidural and spinal anesthesia on blood rheology.

This study was designed to compare the influence of epidural and spinal anesthesia on blood viscosity. We studied 22 patients, ASA classification I, who underwent elective knee or ankle arthroscopy and received epidural (n = 11) or spinal (n = 11) anesthesia with plain bupivacaine, and 10 control volunteers, who did not undergo surgery or receive anesthesia. There were significant decreases in hematocrit, plasma viscosity, and whole-blood viscosity at high (70 s-1), medium (0.5 s-1), and low (0.05 s-1) shear rates. The magnitude of changes was similar in all groups but occurred earlier in the control group (between 10 and 30 min) and after spinal administration (between 10 and 30 min) rather than after epidural administration (between 30 and 60 min) of bupivacaine. Only spinal anesthesia was associated with a decrease in erythrocyte deformability. The observed rheologic changes are attributed to hemodilution from the intravenous administration of fluids and the redistribution of fluid in the intravascular and extravascular compartments after sympathetic blockade and to postural changes rather than the effect of bupivacaine on blood elements.

Adult↗
PubMed1992

Blood and plasma viscosity in diabetes: possible contribution to late organ complications?

It has been postulated that an increased whole blood and plasma viscosity contribute to diabetic organ complications. Blood viscosity was measured in 30 controls and four groups of insulin-dependent diabetic patients at three shear rates: 70 sec-1, 0.5 sec-1 and 0.05 sec-1. Results were compared before and after correction for a haematocrit of 0.45. Twenty-five patients without organ complications, 21 with microalbuminuria, 13 with overt nephropathy and 12 patients with leg ulcerations were studied. Blood and plasma viscosity were normal in the patients without organ complications and with microalbuminuria. Plasma viscosity was significantly elevated in the diabetic patient with nephropathy and leg ulceration. After correction for haematocrit blood viscosity was also higher in these two groups, although this was only significant in the group with leg ulceration. In conclusion blood and plasma viscosity were only elevated in the patients with major organ complications and not in the patients without or with early complications. Therefore it is unlikely that an elevation of blood or plasma viscosity contributes early in the pathogenesis of diabetic organ damage.

Adult↗
PubMed1991

The effect of low-osmolar ionic and nonionic contrast media on human blood viscosity, erythrocyte morphology, and aggregation behavior.

The effects of three low-osmolar radiographic contrast media (CM)--two nonionic (iohexol, iopamidol) and one ionic (ioxaglate)--on red blood cell (RBC) morphology and aggregation behavior, as well as on blood and plasma viscosity, have been studied. Blood taken from normal, healthy individuals and from patients with uremia was investigated. The authors controlled for the effects of dilution, ionic and nonionic hyperosomolality, and specific chemotoxicity. With ioxaglate, the normal biconcave RBC morphology was fairly well maintained. Iohexol produced a mixture of more-or-less normal cells and echinocytes, while iopamidol yielded only echinocytes. Irregular RBC aggregates have been frequently associated with the presence of echinocyte morphology. In the case of ioxaglate, the capacity of normal blood for rouleaux formation was preserved. This appeared to be compatible with an only moderate decrease in low shear viscosity values. In comparison to the normal control group, RBCs from patients with uremia were clearly more sensitive for hyperosmolar stress. It can be concluded that, in contrast to the nonionic CM, the ionic dimeric compound ioxaglate seems to protect human RBCs against hyperosmolar stress by a mechanism unknown at the present.

Blood Viscosity↗
PubMed1989

Transient aggregation resistance of human blood platelets in fresh plasma. I. Methodology.

A novel analytical method, using turbidometry, for reporting the time-dependent decay in the threshold concentration of adenosine diphosphate (ADP), required to elicit a secondary aggregation response in fresh human citrated platelet-rich plasma (PRP), is described. The phenomenon, called "transient aggregation resistance" (TAR) ends, usually within one hour after venepuncture, in a steady state or "baseline aggregation resistance" (BAR). Back extrapolation of the mathematically transformed data to t = 0, yields a maximal threshold concentration of ADP, representing the initial aggregation resistance (TARmax) at the time of blood withdrawal, which threshold is usually many orders of magnitude higher than the BAR-value. The exponential decay of TAR can be characterized by its half-life (t1/2). Mixing fresh, rapidly prepared, plasma with PRP, kept long enough to show only the stable low BAR-value, could restore the initial high (transient) aggregation resistance found in fresh PRP, suggesting that it concerns a natural, labile plasmatic factor. One hour old PRP, deliberately made refractory to ADP, did not show the TAR phenomenon again, but had a higher BAR-value. It is suggested that the level of clinical relevance of these early in vitro aggregation measurements is higher than that of classical, delayed aggregometry (e.g. BAR-values).

Humans↗
PubMed1989

Transient aggregation resistance of human blood platelets in fresh plasma. II. Physiological relevance: influence of fish oil.

In order to evaluate the physiological relevance of the blood platelet "transient aggregation resistance" (TAR) test we studied the effect on this test of two different amounts of fish oil, corresponding to .75 g g (2.5 mmol) and 1.5 g (5 mmol) of eicosapentaenoic acid respectively, added in a cross-over design to the normal diet of 16 healthy male volunteers. It appeared that the "baseline aggregation resistance" (BAR), equivalent to the classic platelet aggregation ADP-threshold, was not influenced by Maxepa while, in contrast, a significant prolongation of TAR occurred. Apparently platelet aggregation analysed early after blood withdrawal, measures aspects of physiological relevance which, due to their short half life, are missed in the original method.

Docosahexaenoic Acids↗
PubMed1988

Clumping of labeled leukocyte suspension. A simple measure for avoiding it.

Leukocytes in "mixed" suspensions can clump together, resulting in cell clusters which are responsible for false positive hot spots in lungs of patients, in the case of abscess localization studies using 111In labeled leukocytes. Addition of extra ACD (acid-citrate-dextrose) in those labeled leukocyte suspensions prevented cell clumping and avoided occurrence of focal radioactivity accumulation in lungs. The acidification did not interfere in leukocyte migration under agar.

Citric Acid↗
PubMed1987

Laser diffraction ellipsometry of erythrocytes under controlled shear stress using a rotational viscosimeter.

An ektacytometric extension for the Contraves LS-30 viscosimeter is described, as well as the procedure to measure erythrocyte deformability and rouleau formation with this combination. The method error (coefficient of variation) for the measurements of the erythrocyte elongation index appeared to be less than 1%, while both intra- and interindividual variation were around 2%. Preliminary clinical experiments performed on blood from different patient groups (i.e., diabetes, uraemia, sickle cell anaemia) clearly demonstrated more rigid erythrocytes than normal. It can be concluded that it is possible now to analyse with 1 instrument: plasma viscosity, whole blood viscosity at shear rates from 0.01 to 236 s-1, erythrocyte deformability and rouleau formation.

Blood Viscosity↗
PubMed1987

The influence of maternal whole blood viscosity on fetal growth.

To explore the relevance of the rheological properties of maternal blood in pregnancy to fetal growth a study of whole blood viscosity (WBV) was conducted in the early third trimester of 138 pregnancies. A significant negative correlation was found between WBV at low shear rate and birthweight centile. As the rheological parameters were found to be negatively correlated with the placenta coefficient, an independent role for maternal WBV seems likely. When WBV, placental weight and degree of infarction accounted for significant contributions in a logistic regression model, diastolic blood pressure data did not assist in the correct prediction of occurrence of a low birthweight centile (less than 10th). A simplified model is proposed, to explain the mechanisms by which some clinical variables may express their influence on fetal growth. In conclusion, it is suggested that WBV might be considered one of the factors which determine the efficacy of placental perfusion on the maternal side. However, as this variation in efficacy of placental perfusion is only weakly reflected in variations in birthweight, the influence of WBV on fetal growth cannot be very important.

Adolescent↗
PubMed1987

Relationship between blood viscosity and cerebral ischemia after surgical treatment of ruptured intracranial aneurysms.

To determine the role of blood viscosity after surgical treatment of ruptured intracranial aneurysms, the relationship between blood viscosity and clinical condition was examined in 17 patients. A total of 213 blood samples were analyzed. An inverse correlation was found between blood viscosity and level of consciousness; in addition, blood viscosity was higher when focal neurologic deficit was observed. Hematocrit was similarly related to clinical condition, although the correlations observed were less strong. Postoperative plasma viscosity was higher in patients with focal neurologic deficit. Regular blood viscosity measurements are of value in patients at risk for developing cerebral ischemia.

Blood Viscosity↗
PubMed1985

Demonstration of labile platelet desaggregation-promoting substance(s) in human blood, using the donor's own blood platelets ("DOP assay") as indicator cells, with special reference to the possibility of measuring diet-induced alterations.

A method is described for the semi-quantitative biological determination of labile platelet desaggregation-promoting substance(s) in human platelet suspensions and in platelet-free fresh plasma by using the donor's own platelets ("DOP assay"). Using the donor as his own control it is possible to demonstrate a dose-related increase of the platelet desaggregation-promoting potency in response to cod-liver oil. The labile platelet desaggregation-promoting activity can also be observed in fresh platelet-free plasma. Circumstantial evidence is presented for the prostaglandin-like nature of these labile platelet desaggregation-promoting substance(s).

Adenosine Diphosphate↗
PubMed1984

Dynamic studies of lymphocytes labelled with indium-111 during and after treatment with monoclonal anti-idiotype antibody in advanced B cell lymphoma.

The migration pattern of lymphocytes labelled with indium-111 was followed in a patient with B cell non-Hodgkin's lymphoma treated with a murine monoclonal anti-idiotype antibody. During the early phase of continuous infusion of antibody rapid fluxes of labelled lymphocytes into and out of the blood were seen. Dynamic scanning showed immediate uptake in the lungs; thereafter activity decreased in the lungs and increased in the liver. Studies of labelled and unlabelled cells in the circulation showed that treatment resulted in the removal of lymphocytes from the blood which was repopulated from an extravascular compartment. Tumour cells were shown to be cleared from the blood by the reticuloendothelial system in the liver. Indium-111 should be used circumspectly because it may cause chromosomal damage in labelled cells, but it is clearly useful as a radiolabel for following the migration pathways of lymphocytes in vivo.

Aged↗
PubMed1984

Blood cell labelling techniques: state of the art.

A critical survey has been given of recent developments in the technique of cell labelling. The ideal characteristics of the radionuclide, as well as the complexing substance, carrying the nuclide inside the cell are formulated. The importance of limiting the radiation dose, cellular radiosensitivity, as well as the quality control of the final cellular suspension are emphasized.

Blood Cells↗
PubMed1983

Labeling with indium-111 has detrimental effects on human lymphocytes: concise communication.

When lymphocytes from human peripheral blood were labeled with In-111 oxinate, several of their properties appeared to be affected. The spontaneous release of the radionuclide was found to be relatively high. Labeled lymphocytes showed a decreased proliferative capacity, dependent on the dose of the label. Cytogenetic studies revealed that In-111 oxinate induces severe chromosomal aberrations. These results emphasize the need for great caution in the use of the In-111 label for studies on lymphocyte traffic in humans.

Cell Division↗