The effect of red cell aggregation on the transit time of cells and plasma through the kidney.
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Animals↗
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Results for “Cell Aggregation”
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Enhanced cell aggregation and liver functions using polymers modified with a cell-specific ligand in primary hepatocyte cultures.
Hepatocytes cultured as multicellular aggregates called spheroids exhibit enhanced liver functions and maintain them over a long period compared with monolayer culture. We previously reported the induction of hepatocyte spheroids using the synthetic polymer Eudragit (a copolymer of methacrylic acid and methylmethacrylate) as an artificial matrix in a cell suspension system (Yamada et al., J. Biochem., 123, 1017-1023, 1998). In this method, hepatocyte aggregation was promoted by the effects of electrostatic and hydrophobic interactions between cells and the polymer. To enhance the cell aggregation ability and cell-specificity of the polymer, in the present study, we prepared hepatocyte-targeting polymers containing lactone, a ligand of the asialoglycoprotein receptor. Addition of the lactone-modified polymers to the medium promoted cell aggregation and spheroid formation more effectively than unmodified Eudragit. The spheroids induced by the polymers exhibited enhanced liver functions, i.e., albumin secretion, ammonia removal, and urea synthesis, from early in the culture. We also investigated the induction of hetero-spheroids composed of various liver constitutive cells by this method. The hetero-spheroids induced by the polymers showed improved liver functions.
Journal Article↗
Ultrastructural and functional characteristics of rat pituitary cell aggregates.
Suspensions of isolated rat pituitary cells and gonadotroph- or lactotroph/somatotroph-enriched subpopulations obtained by unit gravity sedimentation were allowed to aggregate by constant gyrotory shaking, yielding aggregates of 100-150 micrometers. Within a few days, the aggregated pituitary cells became organized in a tissue-like configuration. There was no proliferation of mesenchymal cells. Glandular cells had a round to oval shape and formed specialized cell junctions. Areas of close apposition alternated with more dilated intercellular spaces. The different pituitary cell types retained their characteristic ultrastructural features and secretory granules, typical of the various cell types. Functional characteristics could be accurately studied in a superfusion system. LH, FSH, and PRL secretion showed very rapid on-off responses to nanomolar concentrations of the specific regulatory stimuli LHRH, TRH, vasoactive intestinal peptide, and dopamine. Aggregates remained highly responsive to LHRH even after 3 weeks in culture. The results indicate that isolated pituitary cells allowed to reaggregate in suspension culture form viable and functional multicellular structures which have maintained in vivo characteristics.
Animals↗
Stimulus-response coupling in sponge cell aggregation: Evidence for calcium as an intracellular messenger.
Aggregation of dissociated sponge cells has been proposed as a model for cell-cell recognition mediated by a specific proteoglycan aggregation factor (Microciona aggregation factor). To test whether sponge cells undergo stimulus-response coupling in which intracellular Ca is a messenger, aggregation of mechanically dissociated cells was studied. Changes in light transmission through cell suspensions paralleled aggregation as judged by microscopy. In the presence, but not absence, of Ca (>5 mM) partially purified Microciona aggregation factor aggregated both living and glutaraldehyde-fixed cells. Evidence for a messenger role of Ca was the following: (i) Addition of Ca to Ca-depleted cells induced aggregation that varied with [Ca]. (ii) Addition of Ca ionophores (A23187 and ionomycin) caused aggregation that varied with [Ca] and far exceeded that provoked by Ca alone. Glutaraldehyde-fixed cells did not respond to ionophores with or without Ca. (iii) Calcium antagonists inhibited aggregation. These included inhibitors of the Ca-calmodulin complex (N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride and 1-[bis(p-chlorophenyl)methyl]-3-[2,4-dichloro-beta-(2,4-dichlorobenzyloxyl)phenylethyl]imidazolinium chloride), Ca channel blockers (La, Co, Cd, and verapamil), and three nonsteroidal anti-inflammatory agents (indomethacin, ibuprofen, and piroxicam). Results indicated not only that early events of sponge aggregation can be quantified by continuous recording but that aggregation is not simply due to passive agglutination of inert cells by an extracellular proteoglycan. Rather, sponge cells recognize surface ligands to which they respond by Ca-dependent stimulus-response coupling.
Journal Article↗
Detection and clinical significance of red cell aggregation in the human subcutaneous vein using a high-frequency transducer (10 MHZ): a preliminary report.
To assess ultrasonic measurements for quantitative analysis of red cell aggregation in humans, 50 patients admitted to our hospital were examined without selection. The extent of the aggregates was a assessed by videodensitometry in the subcutaneous vein in the forearm after 2 min of occlusion by manual compression over the skin. Determinants of aggregability were also evaluated by laboratory blood testing to identify potential correlations with ultrasound data. Multiple regression analysis showed that echogenicity was significantly associated with plasma fibrinogen (p < 0.0001), serum total cholesterol (p = 0.0006) and serum protein fraction excluding albumin (p = 0.0049) and was inversely associated with serum total triglyceride (p = 0.0425), but not with age or hematocrit. Ultrasound measurements of red cell aggregation seemed to be useful for the assessment not only for a part of the rheological condition of the blood, but also concomitant changes in plasma macromolecules.
Cholesterol↗
Antigen 43 from Escherichia coli induces inter- and intraspecies cell aggregation and changes in colony morphology of Pseudomonas fluorescens.
Antigen 43 (Ag43) is a surface-displayed autotransporter protein of Escherichia coli. By virtue of its self-association characteristics, this protein is able to mediate autoaggregation and flocculation of E. coli cells in static cultures. Additionally, surface display of Ag43 is associated with a distinct frizzy colony morphology in E. coli. Here we show that Ag43 can be expressed in a functional form on the surface of the environmentally important Pseudomonas fluorescens strain SBW25 with ensuing cell aggregation and frizzy colony types. Using green fluorescence protein-tagged cells, we demonstrate that Ag43 can be used as a tool to provide interspecies cell aggregation between E. coli and P. fluorescens. Furthermore, Ag43 expression enhances biofilm formation in P. fluorescens to glass surfaces. The versatility of this protein was also reflected in Ag43 surface display in a variety of other gram-negative bacteria. Display of heterologous Ag43 in selected bacteria might offer opportunities for rational design of multispecies consortia where the concerted action of several bacterial species is required, e.g., waste treatment and degradation of pollutants.
Adhesins, Bacterial↗
GABA-mediated control of glutamate decarboxylase (GAD) in cell aggregate culture of chick embryo retina.
Glutamate decarboxylase (L-glutamate 1-carboxylase, (EC 4.1.1.15) activity increased 7-fold during the course of differentiation of retina cell aggregate cultures prepared from 8-day-old embryos. The addition of 5 mM GABA in the culture medium almost completely prevented the appearance of GAD activity normally observed during the differentiation of the aggregates. This effect was readily reversible after shifting the aggregates to a GABA-free medium. Differentiated cultures, characterized by high GAD specific activity were also sensitive to GABA treatment, which promoted 50% decrease in the enzyme activity after 7 h incubation of the aggregates in the presence of 0.01 mM GABA. Maximal inhibition was obtained at 0.1 mM GABA. However, GABA up to 10 mM concentration had no effect on GAD activity when added directly to homogenates of retinal tissue. The GABA-mediated inhibition of GAD was antagonized by picrotoxin. The ED50 for picrotoxin to revert GAD inhibition by 0.01 mM GABA was approximately 2 microM. The time course for the decay in GAD activity of cultures exposed to 5 mM GABA, revealed two first-order kinetic components. For an 8-day-old culture the first component had a T1/2 of approximately 60 min and the second decayed with a T1/2 of approximately 315 min. In 13-day-old cultures the first component of GAD decay was identical to the one observed in 8-day-old cultures. The second component, however, was insensitive to GABA inhibition.
Animals↗
CULTURE OF DISSOCIATED DROSOPHILA EMBRYOS: AGGREGATED CELLS DIFFERENTIATE AND SORT OUT.
When the cells of Drosophila embryos are dissociated and cultured in vitro, aggregation of the cells begins rapidly and movements of the cells continue for at least 5 days. Oenocytes, hypoderm, nerve, muscle, and trachea cells take up characteristic positions in the aggregates. Cells from X2 mutant embryos sort out in identically the same way as do cells from normal embryos.
Animals↗
Theory of the adhesion of cells and the spontaneous sorting-out of mixed cell aggregates.
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Blood Cells↗
Letter: Comments on "geometry and the exchange principle in cell aggregation kinetics".
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Cell Aggregation↗
Influence of implantation site of MO4 cell aggregates on the formation of metastases.
Implantation of spheroidal aggregates of virally transformed MO4 fibroblastic cells into the pinna or into the tail of syngeneic C3H mice in matched experiments produced invasive fibrosarcomas in all animals. The growth rate of primary tumours was lower in the tail than in the pinna. Histology revealed no differences between tumours at both sites of implantation. Fibrosarcomas in the tail formed spontaneous metastases in the lungs and in the ischiadic, lumbar, renal and thoracic lymph nodes in 69-85% of the mice. After comparable tumour-bearing periods, no metastases were observed in mice with tumours in the pinna. Our experiments clearly demonstrated the influence of the site of the primary tumour on the formation of metastases.
Animals↗
Red blood cell aggregation and sedimentation: the role of the cell shape.
The influence of erythrocyte shape changes on the sedimentation rate was studied in vitro and in vivo. In vitro the highest sedimentation rate was observed with a slight degree of stomatocytosis (morphological index-0.3; i.e. one red cell out of three being a stomatocyte I). With increasing degrees of stomatocytosis the sedimentation rate gradually decreased. Echinocytosis reduced the aggregation and sedimentation very drastically; the sedimentation rate was virtually zero when echinocytosis I or higher degrees were present. The influence of abnormal cell shapes occurring in vivo was studied in patients with an abnormal blood smear. It was found that a severely abnormal red cell morphology reduced the sedimentation rate in a standardized, fibrinogen-rich plasma to about half. These results indicate that the shape plays a crucial role in the aggregation and sedimentation of red cells and they may contribute to the understanding of the interaction of red cells with other cells such as endothelium.
Blood Sedimentation↗
Transfer of tumor cells between cell aggregates as a model for adhesive changes in metastasis.
A model for cell detachment which may influence metastasis in vivo is described involving the transfer of hamster melanoma cells from aggregates of those tumor cells to hamster fibroblast aggregates. The aggregates were made by the spontaneous association of cultured cells. Tumor and fibroblast aggregates were then incubated together but separated by a nylon net that allowed only single cells to pass. Melanoma cells rapidly separated from the tumor aggregates, crossed the net, and attached to the fibroblast aggregates, but fibroblast cells did not. This model of metastasis reflects the postulated role of cell-to-cell adhesion in metastasis and will allow further study of the role of cell attachments in metastasis.
Animals↗
Generation of basidiomycetous hyphal cell-aggregates by addition of the Arg-Gly-Asp motif-containing fragment of high-molecular-weight cell-adhesion protein MFBA derived from the basidiomycete Lentinus edodes.
The Arg-Gly-Asp (RGD) motif-containing fragment of high-molecular-weight cell-adhesion protein MFBA derived from Lentinus edodes caused a significant aggregation of the fragmented hyphal cells of Schizophyllum commune. This fungal cell-aggregation was inhibited by a previous treatment of the cells with the Gly-Arg-Gly-Asp-Ser-Pro peptide, but not with the Gly-Arg-Gly-Glu-Ser-Pro peptide, showing that the RGD motif is essential for the cell-aggregation activity.
Basidiomycota↗
Microrheology and light transmission of blood. III. The velocity of red cell aggregate formation.
The formation of primary (rouleaux) and secondary (rouleaux networks) RCA was studied by microcinematography (12 frames/sec) and photometry in a counterrotating "rheoscope" chamber. The blood was first subjected to rapid viscometric flow (460 sec-1, all RBC dispersed and aligned in flow) and then brought abruptly to full stop. In normal human blood, primary and secondary RCA occurred simultaneously, and were completed within 8 to 10 sec after stop. Blood from pregnant women at term, known for its pronounced red cell aggregation, shows a dissociation between the formation of short primary rouleaux (initiated even before full stop and completed 1-2 see thereafter) and secondary RCA completed 3-5 see after stop. RCA increases the light transmission of blood (measured by an increase in photovoltage V), the process and its first derivative (dV/dt equals I) can be recorded. After flow stop, there is an exponential decay of I(I equals t-I-o with e-lambda-t). The half time of this decay is recorded and correlated to the kinetics of red cell aggregate formation In human blood the half time of this process varies between 1.0 and 6.0 sec. In suspensions of human RBC in artificial plasmas, t-1/2 decreases with increasing concentration of fibrinogen and/or Dextran 250000, the second component appearing at concentrations above 500 mg-%. The method lend sitself for the quantification of RCA in small blood samples (20 mul).
Blood Viscosity↗
Power Doppler ultrasound evaluation of the shear rate and shear stress dependences of red blood cell aggregation.
The use of power Doppler ultrasound at 10 MHz is evaluated as a method to study the shear rate and the shear stress dependences of red blood cell aggregation. This evaluation was based on six in vitro experiments conducted in a 1.27-cm diameter tube under steady flow conditions. Porcine whole blood was circulated in the flow model at flow rates ranging between 125 to 1500 ml/min (mean shear rate across the tube ranging between 6 and 74 s-1). For each flow condition, the variation of the Doppler power across the tube and the velocity profile were measured by moving the Doppler sample volume across the tube diameter. For each radial position, the shear rate within the Doppler sample volume was also determined by considering the radial power pattern of the ultrasound beam. To estimate the shear stress within the Doppler sample volume, the apparent viscosity of blood samples withdrawn from the flow model was measured for each experiment. The variation of the Doppler power as a function of the shear rate within the sample volume showed a rapid reduction of the power between 1 and 5 s-1, a transition region between 5 and 10 s-1, and a very slow reduction beyond 10 s-1. Little variation of the Doppler power was measured for shear stress higher than 2 dyn/cm2. The maximum Doppler power for all flow rates was usually found near the center of the tube. Based on the ultrasonic scattering models, which predict that the Doppler power is related to the volume square of the scatterers, the method described in the present study showed a very high sensitivity to the presence of red blood cell aggregation for shear rates below 10 s-1.
Animals↗
Red blood cell aggregation during cardiopulmonary bypass: a pathogenic cofactor in endothelial cell activation?
OBJECTIVE: The bio-incompatibility of the cardiopulmonary bypass (CPB) circuit and the use of artificial colloids trigger massive defense reaction that involves endothelial cells and several blood cells: platelets, neutrophils, monocytes, red blood cells (RBC) and lymphocytes. Investigating the effects on RBC aggregation and endothelial cells activation, the present study addresses two different prime solutions commonly used in the clinical practice. METHODS: RBC aggregation was measured by means of Laser-assisted Optical Rotation Cell Analyzer, in an in vitro study designed to mimic the human blood-material interactions during extracorporeal circulation. A clinical study investigating endothelial activation was conducted in 20 patients undergoing elective coronary bypass surgery, randomly assigned for CPB using two different priming solutions: HAES-steril 6% (HES 200/0.5) and Voluven 6% (HES 130/0.4). RESULTS: Circulation trough a Chandler loop of HES-blood mixes altered significantly RBC aggregability. The use of HES 130/0.4 resulted in marked decrease in RBC aggregation (aggregation index (AI) before and after circulation was 23.5+/-3.8 and 18+/-2.9, respectively), no significant differences being found when compared with Ringer's lactate group. The use of HES 200/0.5 resulted in better maintained RBC aggregation (AI 39.7+/-5.9 and 29.7+/-4.7 before and after circulation, respectively). The AI measured for the whole blood (control) sample was 61.9+/-4.9 before circulation, and 58.1+/-4 after. Markers of endothelial activation (von Willebrand factor (vWF), thrombomodulin (TM), tissue plasminogen activator (tPA) and E-selectin) significantly increased during CPB. Differences between HES treatment groups were evident post-bypass. While the markers of endothelial activation returned to baseline in HES 200/0.5 group, HES 130/0.4 was associated on the first post-operative day with further increase of vWF and tPA. CONCLUSION: RBC aggregation significantly drooped as consequence of blood dilution and blood-material interaction. We reason that low RBC aggregation added to plasma viscosity reduction and non-physiologic flow conditions during extracorporeal circulation are important factors contributing to loss of shear stress at the venous endothelial wall. The loss of shear stress triggers complex signaling leading to endothelial activation. Additional fundamental research is needed in order to verify the hypothesis introduced by the present study. Characterizing the impact of rheologic parameters on endothelial function could prove to be valuable in patients undergoing CPB.
Adult↗
Recovery of chronic parkinsonian monkeys by autotransplants of carotid body cell aggregates into putamen.
We have studied the effect of unilateral autografts of carotid body cell aggregates into the putamen of MPTP-treated monkeys with chronic parkinsonism. Two to four weeks after transplantation, the monkeys initiated a progressive recovery of mobility with reduction of tremor and bradykinesia and restoration of fine motor abilities on the contralateral side. Apomorphine injections induced rotations toward the side of the transplant. Functional recovery was accompanied by the survival of tyrosine hydroxylase-positive (TH-positive) grafted glomus cells. A high density of TH-immunoreactive fibers was seen reinnervating broad regions of the ipsilateral putamen and caudate nucleus. The nongrafted, contralateral striatum remained deafferented. Intrastriatal autografting of carotid body tissue is a feasible technique with beneficial effects on parkinsonian monkeys; thus, this therapeutic approach could also be applied to treat patients with Parkinson's disease.
Animals↗