Senescent erythrocytes: modification of rheologic properties, antigenic expression and interaction with monocytes.

Human erythrocytes have a well-defined lifespan of 120 days. Their eventual removal from circulation is a complex process affected by many cellular parameters, making them susceptible to sequestration in the spleen and other organs. The purpose of this study was to investigate putative changes in rheologic properties, antigenic expression and interaction with monocytes of senescent erythrocytes (SE).

[Vascular disease and cellular activation: exploration of cell adhesion phenotype by quantitative flow cytometry].

The pathogenesis of atheromatous and/or thrombotic vascular diseases involves rheological parameters, soluble mediators and cellular agents. The many studies that have tried to establish correlations between plasma factors, shear stress and the risk of ischemia have left some questions unanswered. Current exploration methods are now focusing on the determining role of cells.

Linear and nonlinear elastic modelling of the deformation of vasa vasorum.

The authors present analytical and numerical approaches of the deformation of venous and arterial vessels vasa vasorum. An elastic behaviour of the vessel wall is supposed. It is shown that a normal range of intraluminar pressure induces a small deformation in the vasa vasorum in arteries.

Adhesion Probability of Colloidal Particles with Repulsive Soft Interaction.

Computer simulations of the irreversible adhesion of charged colloidal particles at a solid/liquid interface are performed to determine whether the distribution of particles in the vicinity of a preadsorbed (also charged) one follows the Boltzmann law applied to an a priori uniform adhesion probability, as first assumed by Adamczyk et al. (J. Colloid Interface Sci.

Hoof size, shape, and balance as possible risk factors for catastrophic musculoskeletal injury of Thoroughbred racehorses.

Objective: To evaluate hoof size, shape, and balance as risk factors for catastrophic musculoskeletal injuries (CMI), including suspensory apparatus failure (SAF) and cannon bone condylar fracture (CDY) in Thoroughbred racehorses.

Animals: 95 Thoroughbred racehorses that died between 1994 and 1996.

Procedure: 38 quantitative measures of hoof size, shape, and balance were obtained from orthogonal digital images of the hoof and were compared between case horses with forelimb CMI (70), SAF (43), and CDY (10) injuries and control horses whose death was unrelated to the musculoskeletal system (non-CMI, 25).

Shear stress abnormalities contribute to endothelial dysfunction in hypertension but not in type II diabetes.

Background: The relative contribution of the various hemodynamic and metabolic mechanisms leading to endothelial dysfunction may be different in specific vascular diseases. Since shear stress is one of the main mechanical stimuli of endothelial cells, the aim of this study was to investigate its contribution to endothelial dysfunction in two distinct vascular diseases, hypertension and type II diabetes.

Subjects And Methods: We measured the radial artery diameter at baseline, after ischemic vasodilation and after nitroglycerin vasodilation in 16 untreated patients with high blood pressure, in 15 type II normotensive diabetic patients and in 17 healthy controls.

Molecular rotors as fluorescent probes for biological studies.

Molecular rotors, which structure can be 4-(N,N-dimethylamino)-benzene, -benzylidene and -cinnamylidene derivatives and, also, coumarine-like compounds, have photophysical characteristics which strongly depend on the environmental parameters (polarity, viscosity, temperature, etc.). In this paper, a basic knowledge on molecular fluorescent rotors will be reminded and two fields of applications using molecular fluorescent rotors as optical sensors will be described: firstly, in polymer and, more particularly to detect the formation of hydrophobic microdomains, in the case of the aggregation of amphiphilic polymers (as models for globular proteins and/or enzymes) and, secondly, in cell biology, especially in liposomes (as models for biological membranes) to follow their thermotropic behavior and in endothelial cells under 3D fluorescence microscopy.

[New automatic test for the study of platelet response to variations in osmotic pressure: application in the evaluation of the viability of platelet concentrates].

Studying the osmotic resistance or swelling of platelets has often been suggested as a global test to assess the viability of those cells. A number of authors have also analysed the behaviour of platelets in hypotonic media by a variety of complementary methods (cell count, morphology, determinations of substances released, photometric measurement of aggregation induced by aggregating agents, etc). Most studies are currently based on the so-called "osmotic shock response" test, which measures according to time the light transmitted through platelet-rich plasma (PRP) after dilution in distilled water.

[Modeling of elastic deformation and vascular resistance of arterial and venous vasa vasorum].

As in most living tissues, a network of nutritional vessels, the so-called vasa vasorum, irrigates the vessel wall under physiological conditions. An alteration or obstruction of this network can induce severe lesions. Most normal arteries and veins are irrigated by a vasa vasorum network located mainly in the adventice.

A new simple cone-plate viscometer for hemorheology.

The aim of this work was to evaluate a new automatic cone-plate viscometer (LBY-N6, PRECIL, Beijing, China) which was designed for clinical measurements of blood and plasma viscosities. Standard calibrating oils of viscosity varying from 1.85 to 20.

[Myocardial infarction due to spontaneous coronary dissection during the postpartum period].

The authors report the case of a 34 year old woman, admitted to hospital because of myocardial infarction two months after delivery of her fifth child. The infarction was caused by spontaneous dissection of the left main coronary and left anterior descending arteries. Twenty-three months later, the patient was well with medical therapy.

Photodecontamination of blood components: advantages and drawbacks.

Photochemical methods using photosensitizing photoactive drugs are very promising for blood product decontamination. Depending on the nature of virus - or parasite - bound photosensitizers, direct photochemical addition to virus components (DNA, proteins and lipids) occurs or the photosensitizer produces singlet oxygen inactivating viruses or parasites. The main advantage of this method is the lack of dark toxicity of presently used photosensitizers (psoralens, methylene blue, merocyanine 540, porphyrins/chlorins, phthalocyanines).

Dermal carcinogenicity in transgenic mice: relative responsiveness of male and female hemizygous and homozygous Tg.AC mice to 12-O-tetradecanoylphorbol 13-acetate (TPA) and benzene.

Assessment of the carcinogenic potential of chemical agents continues to rely primarily upon the chronic rodent bioassay, a resource-intensive exercise. Recent advances in transgenic technology offer a potential resource conserving approach to carcinogen detection. Incorporation of oncogenes with known roles in the development of neoplasms into the genomes of laboratory rodents may provide new models with the potential of quickly and accurately separating carcinogenic from noncarcinogenic chemicals.

Calcium antagonists and thiazide diuretics have opposite effects on blood rheology and radial artery compliance in arterial hypertension: a randomized double-blind study.

In addition to their effects on blood pressure, antihypertensive agents may produce additional effects on blood rheology and arterial compliance abnormalities which may play a role in target-organ damage. However, these effects may depend only on the specific pharmacological properties of certain antihypertensive agents, and may be partly unrelated to blood pressure lowering action. We compared the effects of nitrendipine 20 mg once daily to hydrochlorothiazide 25 mg once daily in 33 mildly to moderately hypertensive and otherwise healthy patients, in a double blind parallel group trial.

[Myocardial infarction in a pregnant woman during salbutamol therapy].

The authors report the case of a 31 year old woman at 30 weeks' gestation who developed a non-Q wave postero-lateral myocardial infarction during treatment with salbutamol. There were no complications and delivery took place at term normally. Coronary angiography was performed 3 months post-partum and was normal: the Methergin test was negative.

Relationship between race start characteristics and risk of catastrophic injury in thoroughbreds: 78 cases (1992).

Objective: To investigate relationships of several racehorse characteristics and race conditions with risk of a catastrophic musculoskeletal injury (CMI) resulting in euthanasia in Thoroughbreds during racing in California in 1992.

Design: Retrospective longitudinal study.

Animals: Thoroughbreds that incurred CMI during racing and all California race entrants in 1992.

Hemorheology and therapeutic hemapheresis.

Rheological parameters (plasma and blood viscosities, erythrocyte aggregation and deformability) are very relevant to a better understanding of the changes inflicted on the properties of blood in various hematological diseases (monoclonal gammopathies in particular). This study reports the measurement of rheological parameters (plasma and blood viscosity, RBC aggregation and deformability) in hematological disorders where abnormal blood properties have been described. All these diseases are treated by means of blood separators (therapeutic haemapheresis:plasma exchange, plasma processing, or erythrocyte exchange).

The effect of rouleaux formation on blood coagulation.

The coagulation of whole blood resulting a blood clot is initiated in vitro for studying the effect of rouleaux formation on the kinetics of coagulation and clot formation. The clot formation is monitored in the rotational viscosimeter and in the erythroaggregometer using a light backscattered technique. The intensity of flow as well as hematocrit were changed in a way to determine a tendency in the effect of rouleaux size on the rate of coagulation.

Rheologic characterization of vegetal lectins by dissociation of induced erythrocyte agglutinates.

Energy evolved from hemagglutination reaction or spent in dissociating erythrocyte agglutinates has been proved to be an excellent parameter for analyzing cell-cell interactions mediated by bridging molecules such as antibodies or lectins. We developed a new rheo-optical method to estimate the energy of dissociation of red blood cell agglutinates. In a Couette shear field agglutinates can be dissociated until a suspension of monodispersed cells is obtained.

Red blood cell adhesion on a solid/liquid interface: comparison of two models.

Discoid red blood cells (RBCs) deposited irreversibly on a horizontal glass surface are studied by means of optical microscopy and image analysis. The relative surface covered by the RBCs, as well as the variance of this surface coverage as a function of the cell concentration, are analyzed and compared to the results derived from the ballistic deposition (BD) model. This model describes the irreversible deposition of spherical particles under the influence of an infinitely large gravitation force and does not allow for overlaps between adsorbed particles.

Multicenter study of an erythro-aggregometer: quality control and standardization.

There is a need for quality assurance procedures in hemorheology, especially for clinical and pharmacological studies, which require reliable and well-calibrated instruments to be interpretable and comparable. Preliminary investigations allowed preparation of standardized SM (normal NS and hyperaggregable HS), and checking of storage conditions (in accordance with the guidelines of the SSC of ISTH) of RBC in nutritive SAG mannitol for at least 2 or 3 weeks with subsequent washings and resuspension in SM. In our study, we compared erythro-aggregometers of the same brand in 6 laboratories, using the same red blood cells (RBC) and suspending media (SM) for each series of tests.

Effect of glutaraldehyde on hemoglobin-dependent quenching of pyrene fluorescence. Application to oxygen diffusion in erythrocyte.

In the present study, we investigate the effect of glutaraldehyde incorporation on the erythrocyte deformability, membrane fluidity and process of molecular oxygen diffusion. The erythrocyte deformability variations were inversely related with the glutaraldehyde concentration incorporated. The membrane fluidity, as assessed by a method based on the kinetics of pyrene dodecanoic acid excimers formation, decreased as the glutaraldehyde concentration increased.

Coagulation and hemorheology.

The application of principles of hemorheology on a process of blood coagulation was suggested by H.H. Hartert - inventor of the thromboelastograph which he introduced in 1947.

Effect of fibrin polymerzation on flow properties of coagulating blood.

The evolution of stress in coagulating blood is described by aMaxwell-like constitutive model. The evolution is essentiallyaffected by conversion of fibrinogen to fibrin monomer, fibrinpolymerization and its crosslinking. The modifying effects of theprocess result from the active constituents of blood plasma,blood cell concentration and intensity of flow.