Red blood cell aggredation: mechanisms, adrenergic regulation

Red blood cell aggregation is a complex multiple-factor process and exerts a substantial effect on realization of basic blood function: oxygen transport. Insufficient knowledge about mechanisms of erythrocyte aggregation in normal conditions and, especially, in pathological conditions, complicates the control and correction of possible negative consequences of this process. On addition, red blood cell aggregation process is a suitable model for the elucidation of basic patterns of intercellular interactions. The paper presents contemporary data on mechanisms of erythrocyte aggregation and contribution of plasma and membrane erythrocyte properties to this process. Currently available data on intracellular signal pathways are discussed.     

Preparation and characteristics of Ca<Superscript>2+</Superscript>-dependent monoclonal antibodies to recoverin

Thirty-four primary hybridoma clones were prepared which expressed monoclonal antibodies to the Ca²⁺-binding protein recoverin. Among the resulting monoclonal antibodies, two Ca²⁺-dependent clones (mAb3 and mAb19) recognizing recoverin were detected by solid-phase immunoenzyme assay. In the presence of Ca²⁺, antibodies of the mAb3 and mAb19 clones bound to recoverin several times better than in the absence of Ca²⁺. The mAb3 and mAb19 antibodies recognized epitopes located inside the sequences Pro61-Met91 and Pro57-Tyr64 of the recoverin molecule, respectively. The possible mechanism of the Ca²⁺-dependent recognition of recoverin by the prepared monoclonal antibodies is discussed.Translated from Biokhimiya, Vol. 69, No. 12, 2004, pp. 1667–1674.Original Russian Text Copyright © 2004 by Tikhomirova, Goncharskaya, Senin.     

Estimation of the microcirculation state in cerebrovascular disorders using laser doppler flowmetry data and hemorheological parameters

The microcirculation state was assessed in the group of patients with ischemic stroke (n = 30) and the control group of healthy individuals (n = 27) using laser Doppler flowmetry and the wavelet analysis of the amplitude-frequency range of microvascular blood flow oscillations combined with absorption spectroscopy. The hemorheological parameters (blood and plasma viscosity, the degree of red blood cell aggregability and deformability) were assessed in both groups, as were their correlations with the microcirculation parameters. Decreased tissue perfusion (by 25%) and specific oxygen consumption (by 21%) were revealed in a cerebrovascular accident. Changes in the tone-forming regulatory mechanisms of microcirculation of vasodilating nature (decreased microvascular tone, activation of the secretory function of endothelium) may be regarded as a compensatory reaction aimed at maintaining the blood supply of organs and tissues in stroke. The blood viscosity increase in patients due to the plasma viscosity increase and increased red blood cell aggregability and their decreased deformability cause the blood flow to slow down and the wall shear stress to increase, which activates the endothelial secretory function and vasodilation of microvessels. Correlation between the rheological parameters and the passive (respiratory and cardiac) rhythm amplitudes was observed in the control group. In patients, the hemorheological parameters were correlated with the characteristics of the active factors of microvascular blood flow modulation (endothelial, neurogenic, and myogenic), which confirms the role of changed blood properties and regulatory tone-forming mechanisms in the maintenance of tissue perfusion in cerbrovascular accidents.     

Correlation between electrophoretic mobility and extent of aggregation of human red blood cells

The extent of aggregation, electrophoretic mobility, and zeta potential of human erythrocytes were measured in the presence of some hormones and prostaglandins. Catecholamines, adrenomimetics, and prostaglandins were found to significantly increase the extent of aggregation; the electrophysiological characteristics of the cells were affected in different ways.     

Formation of heat-sensitivity in the ontogenesis of a heat-resistant Drosophila strain and the relation between this property and the mutation process

In the experiments with a heat-resistant line of Drosophila melanogaster, it has been shown that organismal heat-resistance is formed during ontogenesis, prior to hatching, though it can be changed, in accordance with the temperature conditions after hatching (acclimation). Heat-resistance of germ cells is formed during the pupal stage; it depends on the development temperature and remains unchanged thereafter. The mutation rate (the frequency of dominant lethals) in oocytes depends on the development temperature and not on the temperature life conditions of imago. Therefore, it may be concluded that heat-resistance of germ cells as well as their reaction on extreme temperatures are autonomous, meaning their independence of this property in the organism.     

A new method of isolation and a new form of transketolase from baker's yeast]

A new procedure for the isolation of homogeneous transketolase from baker's yeast based on the use of enzyme-specific antibodies immobilized on a insoluble matrix has been developed. The enzyme yield is 90% of its total content in the original yeast extract. The eluate from the immunocolumn was found to contain a previously unknown form of transketolase which represents an enzyme-RNA complex.     

Aggregation of erythrocytes and their membranes flexibility in patients with cancer-associated anemia: Mechanisms of changes under the influence of epoetin alfa

The relationships between the red blood cell (RBC) membrane elasticity and RBC aggregation in healthy individuals and in patients with anemia of malignant tumors treated with human erythropoietin drug epoetin alfa (EA) were analyzed. It was found that prior to the treatment of patients, incubation of RBCs with EA was accompanied by an increase of RBC deformability and the reduction of their aggregation (RBCA). In these circumstances the two characteristics of the RBC microrheology correlated negatively with each other (r =–0.734, p < 0.05). In contrast, aggregation and deformability of RBCs from healthy individuals increased under the influence of EA and positively correlated with each other (r = 0.580, p < 0.05). After a 4-week treatment of patients with EA, aggregation response of the patients’ RBCs was increased by 29% (p < 0.05) and was close to that of healthy RBCs. This change of the RBC aggregation response may be connected with an alteration of the sensitivity of the membrane cationic channel to EA and an increase of the cell deformability. This possibility was supported by experiments with the use of Ca²⁺-channel blocker verapamil and Ca²⁺-chelating agent EDTA. Under these conditions a decrease of the RBC aggregation varied from 40 to 50% (p < 0.05). It was suggested that the effectors of calcium regulatory cascade upon exposure to EA may be membrane integrin receptors of type IIb–IIIa. This assumption was confirmed by experiments employing the inhibitors of these receptors (tirofibam and integrelin) and a preparation of monoclonal antibodies against IIb–IIIa receptors (monafram), which produced a significant decrease (20–30%, p < 0.05) of the RBC aggregation. Thus, our findings suggest that the altered aggregation response of RBCs in anemic patients with malignant tumors can be restored by the correction of anemia with epoetin alfa.     

ONTOGENETIC NICHE SHIFT IN THE BRACHIOPOD TEREBRATALIA TRANSVERSA: RELATIONSHIP BETWEEN THE LOSS OF ROTATION ABILITY AND ALLOMETRIC GROWTH

Abstract: Many articulated brachiopods experience marked life habit variations during ontogeny because they experience their fluid environment at successively higher Reynolds numbers, and they can change the configuration of their inhalant and exhalant flows as body size increases. We show that the extant brachiopod Terebratalia transversa undergoes a substantial ontogenetic change in reorientation governed by rotation around the pedicle. T. transversa′s reorientation angle (maximum ability to rotate on the pedicle) decreases during ontogeny, from 180 degrees in juveniles to 10–20 degrees in individuals exceeding 5 mm, to complete cessation of rotation in individuals larger than 10 mm. Rotation ability is substantially reduced after T. transversa achieves the adult lophophore configuration and preferred orientation with respect to ambient water currents at a length of 2.5–5 mm. We hypothesize that the rotation angle of T. transversa is determined mainly by the position of ventral and dorsal points of attachment of dorsal pedicle muscles relative to the pedicle. T. transversa shows a close correlation between the ontogenetic change in reorientation angle and ontogeny of morphological traits that are related to points of attachment of dorsal pedicle muscles, although other morphological features can also limit rotation in the adult stage. The major morphological change in cardinalia shape and the observed reduction of rotation affect individuals 2.5–10 mm in length. The position of ventral insertions of dorsal pedicle muscles remains constant, but contraction of dorsal pedicle muscles is functionally handicapped because dorsal insertions shift away from the valve midline, rise above the dorsal valve floor, and become limited by a wide cardinal process early in ontogeny (<5 mm). The rate of increase of cardinal process width and of distance between dorsal pedicle muscle scars substantially decreases in the subadult stage (5–10 mm), and most of the cardinalia shell traits grow nearly isometrically in the adult stage (>10 mm). T. transversa attains smaller shell length in crevices than on exposed substrates. The proportion of small‐sized individuals and population density is lower on exposed substrates than in crevices, indicating higher juvenile mortality on substrates prone to grazing and physical disturbance. The loss of reorientation ability can be a consequence of morphological changes that strengthen substrate attachment and maximize protection against biotic or physical disturbance (1) by minimizing torques around the pedicle axis and/or (2) by shifting energy investments into attachment strength at the expense of the cost involved in reorientation.