SEARCH · PubMed Health

Results for “Cell Aggregation”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11Linked to original sources

PubMed1984

CHO cell aggregation induced by fibronectin-coated beads. Differences between wild-type and adhesion-variant cells.

ADvF11 (F11), a Chinese Hamster Ovary (CHO) cell variant, is defective in its ability to adhere to fibronectin (Fn)-coated substrata but will adhere to substrata coated with poly-L-lysine, conA or extracellular matrix (ECM) [1]. We have observed that both F11 and CHO wild-type (WT) cells were able to bind 3H-Fn beads in a similar manner; however, only WT cells and not F11 cells aggregate in the presence of Fn beads. Both cell types aggregated similarly in the presence of lectins. Fn-bead-mediated aggregation was blocked by low temperature and aggregation did not occur when formaldehyde-fixed WT cells were used. Colchicine, tetracaine and cytochalasin B were not effective in blocking aggregation induced by Fn beads. These results suggest that: 1. Both WT and F11 cells have surface membrane-binding sites for Fn. 2. The aggregation defect in F11 cells is distal to the initial interaction between the cell surface and Fn, but proximal to the cytoskeletal rearrangements required for cell adhesion.

Animals↗

PubMed1993

Regulatory effect of interleukin-4 (IL-4) on the expression and function of lymphocyte adhesion receptors involved in IL-2-induced cell aggregation.

Human recombinant interleukin-4 (rIL-4) was studied for its capacity to inhibit rIL-2-induced lymphoid cell aggregation. In contrast to rIL-2, rIL-4 was unable to induce cluster formation by itself. However, when added simultaneously with rIL-2 to cultures of freshly isolated peripheral blood lymphocytes (PBL), rIL-4 inhibited cell aggregation in a dose-dependent way. In contrast, PBL, preactivated by a 4-day culture in the presence of 500 U/ml rIL-2, were not inhibited in their adhesive capacity by rIL-4. Inhibition of cell aggregation was most prominent at 24 hr and virtually lost after 72 hr of culture. Phenotypical analysis revealed that rIL-4, with similar kinetics, decreased the rIL-2-mediated up-regulation of the CD2, CD54 and CD49e adhesion molecules. In addition, it was observed that up-regulation of the activation epitope on CD11a recognized by the mAb NKI-L16, was prevented. During 24hr of culture rIL-4 itself did not alter the expression of these antigens. Blocking experiments with mAb directed against adhesion structures did not reveal a direct role for CD49e, but obviously demonstrated involvement of CD11a/CD18-CD54 and CD2-CD58 interactions in the rIL-2-induced adhesion. Therefore, rIL-4 appears to inhibit the early phase of rIL-2-induced aggregation by preventing the up-regulation of CD54 and CD2 antigens and by inhibiting the generation of the activated state of the CD11a/CD18 receptor.

Cell Adhesion Molecules↗

PubMed1999

Behavior of cells in artificially made cell aggregates and tissue fragments after grafting to developing hind limb buds in Xenopus laevis.

During vertebrate limb development, the limb bud grows along the proximo-distal (P-D) direction, with the cells changing their adhesiveness. To know whether the position-related differences in cell adhesiveness are actually utilized by morphogenesis to constitute limb structures, we grafted cell aggregates made of dissociated cells derived from different positions and stages of developing hind limb buds into developing hind limb buds and observed the behavior of the cells. Cell aggregates made of dissociated mesenchymal cells from two different origins were implanted in different positions and stages of limb buds or grafted on limb stumps made by cutting. The two grafted cell populations in the aggregate always sorted out from each other, but their patterning of sorting-out was quite different according to the transplanted regions. In summary, cells in the aggregate that have closer positional identity to the transplanted site were always situated at the boundary between host and donor cells. The pattern of sorting-out seemed to be determined by the relative adhesiveness of surrounding cells to the constituent cells of the aggregates. We also transplanted fragments dissected out from different regions along the P-D axis into st. 50 limb buds. The descendants of grafted cells moved distally to the region corresponding to their positional identity and participated in the formation of more distal structures from that point. These results suggest that the difference in cell adhesiveness may probably play a role in arranging cells along the P-D axis of a developing limb bud.

Animals↗

PubMed2005

Classification of neural differentiation-associated genes in P19 embryonal carcinoma cells by their expression patterns induced after cell aggregation and/or retinoic acid treatment.

Expression of neural differentiation-associated genes was examined by RT-PCR and macroarray analyses during neural differentiation of P19 embryonal carcinoma cells induced by cell aggregation and/or retinoic acid (RA) treatment. Results revealed that the neural genes examined could be classified into 4 groups based on their expression patterns. The 1st group included the Wnt-1, Id-1, Id-3 and cdc42 genes, expression of which was altered by cell aggregation alone, but not by RA treatment alone. The 2nd group included the alphaN-catenin, Neuro D and GDNFRbeta genes, expression of which was altered by RA treatment alone, but not by cell aggregation. The 3rd group consisted of the Brn-2, TrkA, bcl-X, N-cadherin, E-cadherin and Otx-2 genes, expression of which was altered by either treatment. The 4th group included the ACTH, D4DR, NGC and Oct-3 genes, the expression of which changed only when both treatments were applied simultaneously. Expression of the Ets-1 and Fli-1 transcription factor genes was up-regulated by either treatment alone at initial stages of neural differentiation of P19 cells, although overexpression of these genes alone could not induce cell differentiation. Our results suggest that although both treatments are required for complete neural differentiation of P19 cells, cell aggregation or RA treatment alone drive differentiation to a certain extent at the gene expression level.

Animals↗

PubMed1978

Acquisition of synchronous beating between embryonic heart cell aggregates and layers.

Synchronous beating between chick embryonic heart cell aggregates and heart cell layers was used to study the relationship between intercellular adhesion and ionic coupling. Adhesion was measured by counting the proportion of aggregates which were not to be removed from cell layers by gentle washing after a 30 min incubation. Synchrony between bound aggregates and contiguous layers was assessed by phase microscopy. The first evidence of synchrony was seen 1.5 h after addition of aggregates to layers, following which there was an increase in the percentage of aggregates beating synchronously, reaching over 50% at 7 h and slowly increasing to a maximum of 65% by 24 h. Scanning electron microscopy and autoradiography of thymidine-labeled cells suggest that synchrony does not depend on cell movement at the interface between aggregate and layer. Acquisition of synchrony can be prevented completely by inhibiting protein synthesis, although pulsation of aggregates and layers continues in proportions unchanged from controls. After reversal of protein synthesis inhibition, synchrony is acquired at a rate and to an extent closely resembling that of newly adherent controls. These data indicate that ionic coupling is neither an inevitable nor an immediate consequence of adhesion. Since ionic coupling has been shown to correlate with the presence of gap junctions, the findings suggest that gap junctions are not involved in the initial events responsible for intercellular adhesion in vitro and that their formation following adhesion in this system may depend upon protein synthesis.

Animals↗

PubMed1980

Nevus cell aggregates in submandibular lymph nodes.

Nevus cell aggregates are occasionally found in the capsules and trabeculae of lymph nodes. These aggregates are similar histologically to those in typical cutaneous nevi and should be differentiated from metastatic tumor.

Carcinoma, Squamous Cell↗

PubMed1982

Effects of urea treatment on the divalent cation-independent cell aggregation of 3T3MIT fibroblasts.

Growth of nontransformed 3T3MIT fibroblasts in media containing 200 mM urea leads to the rapid acquisition of the transformed adhesive phenotype as evidenced by an increased rate of divalent cation-independent cell aggregation. The increased rate of divalent cation-independent cell aggregation of urea treated 3T3MIT cells shares many properties with the high rate of aggregation of transformed cells including a sensitivity to treatment with trypsin or hyaluronidase and a reduction in the presence of exogenously added hyaluronic acid. Reversal of the urea-induced increase in aggregation occurs within 24 hours in the absence of urea and can be blocked by 0.2 micrograms/ml cycloheximide. In the presence of cycloheximide, low rates of aggregation can be restored by the addition of urea-conditioned supernatents. The results of these experiments suggest that the loss of an aggregation-inhibitory activity during growth in media containing 200 mM urea is responsible for the increased rate of divalent cation-independent cell aggregation. After removal of this aggregation-inhibitory activity, the normally lowly adhesive 3T3MIT cells become phenotypically transformed with regards to the rate of divalent cation-independent cell aggregation.

Animals↗

PubMedDate not supplied

Red blood cell aggregation in diabetes mellitus.

The aim of this work is to study the red blood cell aggregation in diabetic patients. Investigations have been performed via rheometric technics on four various types of diabetics (diabetics with good metabolic control, diabetics with poor metabolic control, diabetics with a distal angiopathy, without clinical signs, diabetics with a distal angiopathy characterized by cutaneous trophic disorders). Results, compared with those of healthy subjects, show that the reversible phenomenon of erythrocyte aggregation is significantly modified in diabetic. Indeed, the red cell aggregation tendency is found to be increased in diabetics. This hyperaggregation becomes more important when the diabetes is characterized by a poor metabolic control or a distal angiopathy with or without cutaneous trophic disorders. Disturbances of red cell aggregation observed in this report are discussed as a result of plasma protein changes and may confirm the role of hemorheological properties in the pathogenesis of diabetic angiopathy.

Adult↗

PubMed1982

Cell aggregates in the soft agar "human tumour stem-cell assay".

We evaluated colony formation in soft agar by cells obtained after mechanical and/or enzymatic disaggregation of 455 malignant human tumours. Counting and assessment of cell colonies in the agar plates were done by inverted microscopy, computerized image analysis, and inspection of serial photomicrographs of the agar plates. Our results indicate that standard methods of tumour disaggregation did not usually produce single-cell suspensions and that aggregates of tumour cells varying greatly in size were placed in the agar. Most groupings of cells identified as colonies 1-3 weeks after plating arose from enlargement of preexisting aggregates of cells.

Agar↗

PubMed1988

Red cell aggregation during normal pregnancy.

Red cell aggregation (RCA) is responsible for the increase in whole blood viscosity at lower shear rates. RCA depends on the concentrations of red cells and plasma proteins with a high molecular weight and a large and asymmetrical spatial structure such as fibrinogen, immunoglobulin M and alpha 2-macroglobulin. During normal pregnancy, changes occur in all these concentrations. In a prospective study these changes and their influence on the resulting RCA were investigated in 24 healthy women with normal pregnancies. RCA was determined by light reflection measurement (syllectometry). RCA considerably increased during normal pregnancy in spite of the physiological haemodilution. The aggregation half time, used as a measure for RCA, decreased from an average non-pregnant value of 5.6 s to 3.3 s at 37 weeks. Multiple regression analysis showed that the increase in RCA could be mainly attributed to the raised fibrinogen concentration. However, at 37 weeks other factors, in addition to fibrinogen, contribute significantly to the increase in RCA.

Erythrocyte Aggregation↗

PubMed1987

Evidence for functional communication between folliculo-stellate cells and hormone-secreting cells in perifused anterior pituitary cell aggregates.

Dispersed anterior pituitary cells from adult female rats were separated by gradient sedimentation at unit gravity. The small-sized cell population on top of the gradient consisted of 65.6 +/- (SE) 4.2% (n = 8) cells immunoreactive to antiserum against S-100 protein, a marker of folliculo-stellate (FS) cells in rat pituitary. The corresponding fraction derived from adult male or immature female rats were also enriched in S-100 positive cells but to a lower extent. Only small numbers of S-100 positive cells were found in medium- and large-sized cell populations. Coaggregating the S-100 cell-enriched populations from adult females with other pituitary cell populations resulted in a clear-cut inhibition of the GH response to rat GH-releasing factor and beta-adrenergic agents, of the PRL response to TRH and angiotensin II (AII) and the LH response to LHRH. The magnitude of inhibition increased with the number of FS cells put into the coaggregates. In perifused aggregates prepared from different gradient fractions from immature females, there was a negative correlation between the occurrence of FS cells and the magnitude of the PRL response to AII. The low responsiveness to AII in FS cell enriched aggregates was not abolished when these aggregates were redissociated into single cells. It is suggested that FS cells constitute an intercellular messenger system for local inhibitory control of pituitary hormone secretion which is not based on direct and intimate contact between the interacting cells.

Aging↗

PubMed1985

Nevus cell aggregates associated with lymph nodes. Immunohistochemical observations.

Nevus cell aggregates occurring in association with axillary lymph nodes can be difficult to recognize and differentiate from a metastatic breast carcinoma. We believe S100-protein immunoreactivity, along with negative staining for keratin and epithelial membrane antigen, and typical geographic distribution of nevus cell aggregates in lymph nodes are helpful in providing an accurate diagnosis.

Adenocarcinoma↗

PubMedDate not supplied

Effects of sedimentation of small red blood cell aggregates on blood flow in narrow horizontal tubes.

The flow properties of aggregating red cell suspensions flowing at low flow rates through horizontal tubes are analyzed using a theoretical model. The effects of sedimentation of small aggregates, which will be formed at comparatively high flow rates, on the relative apparent viscosity are considered. In the case in which a large number of small aggregates are formed in a suspension flowing through a horizontal tube, it seems that red cells are transported as a concentrated suspension through the bottom part of the tube because of sedimentation of aggregates. A two-layer flow model is used for the distribution of red cells. It consists of plasma in the upper part and a concentrated red cell suspension in the bottom part of the tube divided by a smooth and horizontal interface. It is assumed that the suspension is a Newtonian fluid whose viscosity increases exponentially with hematocrit. The velocity distribution, the relative apparent viscosity and the flux of red cells are calculated as functions of width of plasma layer for a different discharge hematocrit. The theoretical results are compared with the results obtained from experimental data. The relative apparent viscosity increases rapidly with an increasing degree of sedimentation over a wide range of plasma layer widths.

Blood Flow Velocity↗

PubMed1985

Red cell aggregation in cardiovascular diseases and crucial role of inversion phenomenon.

Perfusion of the heart muscle remains an important area of studies fraught with great difficulties. An analogue of capillary system has been organized by using in vitro flow of blood from the heart patients in a slit-capillary photo-viscometer. The rate of aggregation of red cells and the morphology of aggregates have been observed and quantitated in representative cases. A possible role of the sludge-like aggregates is discussed from the viewpoint of the "inversion phenomenon" which amplifies resistance to flow as a function of rheology (rigidity or deformability) of cell aggregates and single cells. This pattern might be alike that of arterial spasm or can serve as a model for capillary occlusions. A description is given of the new instrument, the slit-capillary photo-viscometer, and stereological parameters obtained in macro- and micro-photography are included. Linear regressions of such parameters against stasis time are highly significant, showing correlation coefficient up to 0.99. These regressions can be compared for slopes and elevations observed in different blood samples, with significance up to 0.001.

Blood Viscosity↗

PubMed2005

Physical enviroment of 2-D animal cell aggregates formed in a short pathlength ultrasound standing wave trap.

2-D mammalian cell aggregates can be formed and levitated in a 1.5 MHz single half wavelength ultrasound standing wave trap. The physical environment of cells in such a trap has been examined. Attention was paid to parameters such as temperature, acoustic streaming, cavitation and intercellular forces. The extent to which these factors might be intrusive to a neural cell aggregate levitated in the trap was evaluated. Neural cells were exposed to ultrasound at a pressure amplitude of 0.54 MPa for 30 s; a small aggregate had been formed at the center of the trap. The pressure amplitude was then decreased to 0.27 MPa for 2 min, at which level the aggregation process continued at a slower rate. The pressure amplitude was then decreased to 0.06 MPa for 1 h. Temperature measurements that were conducted in situ with a 200 microm thermocouple over a 30 min period showed that the maximum temperature rise was less than 0.5 K. Acoustic streaming was measured by the particle image velocimetry method (PIV). It was shown that the hydrodynamic stress imposed on cells by acoustic streaming is less than that imposed by gentle preparative centrifugation procedures. Acoustic spectrum analysis showed that cavitation activity does not occur in the cell suspensions sonicated at the above pressures. White noise was detected only at a pressure amplitude of 1.96 MPa. Finally, it was shown that the attractive acoustic force between ultrasonically agglomerated cells is small compared with the normal attractive van der Waals force that operates at close cell surface separations. It is concluded that the standing wave trap operates only to concentrate cells locally, as in tissue, and does not modify the in vitro expression of surface receptor interactions.

Animals↗

PubMed1997

Contribution of red blood cell aggregation to venous vascular resistance in skeletal muscle.

The effects of red blood cell aggregation on venous vascular resistance and conductance were examined in the cat lateral gastrocnemius muscle. During perfusion with blood of normal hematocrit, venous conductance fell linearly by 41% when blood flow was reduced from 5 to 1 ml x min(-1) x 100 g tissue(-1) and increased linearly by 155% when flow was increased from 5 to 20 ml x min(-1) x 100 g tissue(-1). This effect was not seen when the muscle was perfused with an acellular solution of 12% Dextran 40 in Ringer solution and was greatly reduced or absent with a nonaggregating suspension of red blood cells in Ringer solution + Dextran 40. Also, the venous vascular conductance at a control flow of 5 ml x min(-1) x 100 g tissue(-1) during perfusion with the nonaggregating red blood cell suspension was twice that with normal blood of the same hematocrit. The effect of flow on venous conductance was significantly reduced when red blood cell aggregation was increased by addition of Dextran 250 to the blood (200 mg/kg body wt) and was also reduced in animals with systemic hematocrit >50%. These findings suggest that red blood cell aggregation contributes importantly to venous vascular resistance in resting muscle.

Animals↗

PubMed1988

The incorporation of monomethylethanolamine and dimethylethanolamine in fetal brain aggregating cell culture.

Fetal rat brain aggregating cell cultures were exposed to varying concentrations of [3H]monomethylethanolamine (MME) and [3H] dimethylethanolamine (DME). The rate of labeling of water-soluble compounds was more rapid and the amount of radioactivity present was greater than in the lipids. After a 72 hour incubation in the presence of millimolar concentrations of these nitrogenous bases, the major water-soluble products were the phosphorylated form of the bases. Little label was associated with the free bases or their cytidyl derivative. In the phospholipids, 97% of the radioactivity was recovered in phosphatidylmonomethylethanolamine (PMME) and 3% in phosphatidyldimethylethanolamine (PDME) or 95% in PDME and 5% in phosphatidylcholine (PC) after growth in presence of [3H]MME and [3H]DME respectively. The rate of formation of the radioactive products increased as function of the concentration of the nitrogenous base added up to 4 mM, the highest concentration employed. There was no significant difference in the pattern of labeling with cells grown in media devoid of methionine or choline. The turnover of the water-soluble metabolites was more rapid than in the phospholipids where an apparent half-life of 24 hours was calculated.

Animals↗

PubMed1979

Neurotransmitter synthesis, storage and release by aggregating cell cultures of rat brain.

Rotation-mediated aggregating cell cultures of mechanically dissociated fetal (15-16 days gestation) rat brains between 25 and 35 days in vitro were examined for their ability to synthesize neurotransmitters and putative neurotransmitters from radioactively labeled precursors added to the culture medium. Cultures derived from whole brain synthesized [3H]acetylcholine from [3H]choline, [3H]gamma-aminobutyric acid from L-[3H]glutamic acid, [3H]dopamine from L-[3H]tyrosine, [3H]dopamine and [3H]norepinephrine from L-[3H]dihydroxyphenylalanine, and [3H]serotonin from L-[3H]tryptophan. Veratridine increased and tetrodotoxin decreased the rate of [3H]-dopamine synthesized by aggregates derived from midbrain plus hindbrain. In chase experiments in which aggregates were incubated for 4 h with radioactively labeled precursors and then for 4 h with non-radioactively labeled precursors, addition of veratridine (50 micronM) during the second 4 h incubation significantly decreased the amounts of radioactively labeled acetylcholine, L-glutamic acid, dopamine and serotonin recovered from aggregates. Tetrodotoxin (5 micronM) present during the chase significantly increased the amounts of [3H]acetylcholine and [3H]dopamine recovered from the aggregates. In addition, reserpine (4 micronM) markedly depleted [3H]dopamine from aggregates in these experiments. These results indicate that these cultured cells synthesized neurotransmitters and in addition suggest that some of these compounds are stored by and released from electrically active cells within the aggregates.

Acetylcholine↗