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PubMed1988

Stimulus-response coupling in marine sponge cell aggregation: lipid metabolism and the function of exogenously added arachidonic and docosahexaenoic acids.

Cells of the marine sponge, Microciona prolifera, the most ancient of the animal cells which clump on recognition, resemble neutrophils and platelets in undergoing stimulus-response coupling when exposed to Ca2+ ionophores and phorbol esters. We have studied lipid content and remodelling in sponge cells by thin-layer, gas-liquid, and high-performance liquid chromatography (HPLC) analyses supplemented by ultraviolet and mass spectroscopy. Phosphatidylcholine (PC) (35.6%), phosphatidylethanolamine (PE) (27.4%) and phosphatidylserine (PS) (21.4%) constituted the bulk of phospholipids detected. The major fatty acids were all polyenoic; 22:6 (22%), 26:2 (17%) and 26:3 (15%). Arachidonic acid (20:4), present as 2.7% of total phospholipid, and docosahexanoic acid (22:6) were found to elicit aggregation of sponge cells when added (10 microM) in synergy with ionomycin (1 microM), resembling in their effects those of phorbol esters (but not phorbol) and 1-oleyl-2-acetylglycerol (OAG). Moreover, 20:4 and 22:6, as well as phorbol ester and OAG, overcame the block to aggregation imposed by colchicine and vinblastine. Kinetic studies of lipid remodelling showed that aggregating cells diverted [14C]22:6 or [14C]20:4 from triacylglycerol into diacylglycerol and phospholipids; appearance of label in phosphatidic acid and phosphatidylinositol (PI) anteceded labeling of phosphatidylcholine. In unstimulated cells, [14C]22:6 was rapidly incorporated into phosphatidylcholine with little accumulation in phosphatidate. Although 22:6 and 20:4 resembled OAG and phorbol esters in overcoming the effects of colchicine and vinblastine (which had no effects on overall lipid metabolism), they did not reverse the block to aggregation of nordihydroguaiaretic acid (NDGA) (which inhibited lipid metabolism). Under none of these circumstances was 22:6 or 20:4 converted to cyclooxygenase or lipoxygenase products in the course of aggregation: all labeled acyl groups remained present as unmodified fatty acids on alkaline hydrolysis. These data not only extend the observations of Muller et al. (J. Biol. Chem. 262 (1987) 9850-9858) on the role of phosphoinositides and C kinase in marine sponge cell aggregation, but also demonstrate that sponges form diacylglycerols in the process. We suggest that exogenous 22:6 and 20:4 (like phorbol esters or OAG) can substitute for endogenous diacylglycerol in the activation of protein kinase C.

Animals↗
PubMed1998

Cellular and functional recovery of Parkinsonian rats after intrastriatal transplantation of carotid body cell aggregates.

We have tested the suitability of chromaffin-like carotid body glomus cells for dopamine cell replacement in Parkinsonian rats. Intrastriatal grafting of cell aggregates resulted in almost optimal abolishment of motor asymmetries and deficits of sensorimotor orientation. Recovery of transplanted animals was apparent 10 days after surgery and progressed throughout the 3 months of the study. The behavioral effects were correlated with the long survival of glomus cells in the host brain. In host tissue, glomus cells were organized into glomerulus-like structures and retained the ability to secrete dopamine. Several weeks after transplantation, dopaminergic fibers emerged from the graft, reinnervating the striatal gray matter. The special durability of grafted glomus cells in the conditions of brain parenchyma could be related to their sensitivity to hypoxia, which is known to induce cell growth, excitability, and dopamine synthesis. This work should stimulate research on the clinical applicability of carotid body autotransplants in Parkinson's disease.

Amphetamine↗
PubMed2003

New information from cell aggregate compression tests and its implications for theories of cell sorting.

In order to verify theories about the mechanics of cell sorting, tissue spreading and checkerboard pattern formation, it is necessary to measure certain cell properties such as surface tension and adhesiveness. The purpose of this work is to clarify the relationship between these two important properties and to use computer simulations and analytical calculations to extract additional information from parallel plate compression tests. This paper shows that compression tests can be used to determine not only the surface tension between the aggregate and the surrounding medium, but also the effective viscosity of the cell cytoplasm and the interfacial tension that acts between the cells that make up the aggregate. The findings reported here also support a novel, differential interfacial tension-based theory for cell sorting, tissue spreading and checkerboard pattern formation, and pose further challenges to current differential adhesion-based models.

Cell Adhesion↗
PubMed1997

Digital ischemia and gangrene due to red blood cell aggregation induced by acquired dysfibrinogenemia.

Digital gangrene was observed in a patient who had angiographic findings of digital arterial occlusion. The patient's blood showed a marked red blood cell aggregation with rouleaux formation in long chains, which could not be dispersed at shear rates up to 200 sec-1. Studies of the patient's blood revealed the presence of an abnormal fibrinogen capable of aggregating normal red blood cells. This fibrinogen was found by Raman spectroscopy to have an increased alpha-helical content, whereas the beta-sheet content was decreased. Defibrinogenation therapy with ancrod resulted in a dramatic symptomatic relief. The disappearance of the abnormal fibrinogen 6 months later and an absence of a family history indicate that this dysfibrinogenemia was acquired.

Arterial Occlusive Diseases↗
PubMed1983

A cell aggregation model for the protective effect of selenium and vitamin E on methylmercury toxicity.

Histotypic aggregation of embryonic neural retinal cells was chosen as a test model to evaluate mercury toxicity. After 24 h rotational culture with methylmercury (CH3HgCl) at 4 microM, aggregation was completely inhibited. A dose-response relationship between concentrations of methylmercury and final sizes of aggregates was found. Selenium (Na2SeO3) at concentrations of 1, 3 and 5 microM provided a protective effect for methylmercury (1 microM) toxicity. Vitamin E (DL-alpha-Tocopherol acetate) at concentrations 5, 7 and 10 microM also provided protection against the same concentration of methylmercury; however, it was less effective than selenium. Histotypic embryonal retinal cell aggregation may be a useful assay system for in vitro neurotoxic studies in morphogenesis.

Animals↗
PubMed2000

Circulating platelet/polymorphonuclear leukocyte mixed-cell aggregates in patients with mechanical heart valve replacement.

There is convincing evidence that cell adhesion plays an important role in cardiovascular pathology and is frequently associated to "in vivo" cellular activation. This study involves patients with mechanical heart valve replacement (MHVR patients) who have increased platelet polymorphonuclear leukocyte (PMN) reactivity. Dual-color cytometry was used to determine the expression of adhesive molecules on cellular surfaces, platelet, and PMN-bound fibrinogen as well as the presence of circulating platelet/PMN mixed-cell aggregates (MCA) in 55 MHVR patients, 49 control patients under oral anticoagulant therapy, and 22 healthy volunteers. The results demonstrated that (a) PMN from MHVR patients showed an increased PMN-bound fibrinogen (mean +/- SEM: 1,420 +/- 169 anti-fibrinogen fluorescence intensity, P= 0.0012), when compared to controls (mean +/- SEM: 747 +/- 32 anti-fibrinogen fluorescence intensity) and healthy volunteers (mean +/- SEM: 692 +/- 25 anti-fibrinogen fluorescence intensity; (b) platelet activation in MHVR patients was evidenced by the higher expression of CD62P (mean +/- SEM: 128 +/- 19 anti-CD62P fluorescence intensity, P = 0.003) compared to controls (mean +/- SEM: 65 +/- 15 and 50 +/- 10 anti CD62P fluorescence intensity) and by increased levels of platelet-bound fibrinogen (mean +/- SEM: 625 +/- 20 anti-fibrinogen fluorescence intensity, P = 0.0043 versus 496 +/- 45 and 480 +/- 30 for control patients and for healthy volunteers, respectively); and (c) the proportion of MCA in MHVR patients (15 +/- 2%) was significantly higher (P = 0.009) compared to controls (7 + 1%) and healthy volunteers (6 +/- 2%). The results indicate that the presence of stable circulating MCA represents another marker of "in vivo" PMN activation in MHVR patients.

Adult↗
PubMed2000

Expression of Otx homeodomain proteins induces cell aggregation in developing zebrafish embryos.

In the zebrafish embryo, cells fated to give rise to the rostral brain move in a concerted fashion and retain tissue coherence during morphogenesis. We demonstrate here that Otx proteins have a dramatic effect on cell-cell interactions when expressed ectopically in the zebrafish embryo. Injection of zebrafish Otx1 or Drosophila otd RNAs into a single cell at the 16-cell stage results in aggregation of descendants of the injected cell. The Otx/Otd homeodomain is necessary for aggregation and appears to be sufficient for the effect when substituted for the homeodomain of an unrelated homeodomain protein. When cells containing injected zOtx1 RNA are limited to the area that is normally fated to become the anterior brain and neural retina, the induced aggregates contribute to anterior brain and retina tissues. In many other embryonic regions, which do not express endogenous zOtx1, the aggregates appear to be incompatible with normal development and do not integrate into developing tissues. By using an activatable Otx1-glutocorticoid receptor fusion protein that results in the stimulation of cell association, we demonstrate that cell aggregates can form as a result of Otx1 activity even after gastrulation is completed. Time-lapse analysis of cell movements show that cell aggregation occurs with only a slight inhibition of the rate of convergence. These results suggest that promotion of cell adhesion or mediation of cell repulsion may be one of the normal functions of the Otx proteins in the establishment of the anterior brain.

Animals↗
PubMed2006

Scaled-up production of mammalian neural precursor cell aggregates in computer-controlled suspension bioreactors.

The clinical use of neural precursor cells (NPCs) for the treatment of neurological diseases, such as Parkinson's disease and Huntington's disease, requires overcoming the scarcity of these cells through controlled expansion. The main objective of the present study was to develop a large-scale computer-controlled bioprocess for the expansion of mammalian NPCs in suspension culture by scaling up existing reactor protocols. In order to support the oxygen demands of the maximum cell densities achieved, the volumetric mass transfer coefficient was kept above 1.10/h while scaling-up from small-scale 125 mL vessels to large-scale 500 mL bioreactors. In addition, the maximum shear stress at the impeller tip was maintained between 0.30 and 0.75 Pa to reduce damage to the cells. The resulting large-scale bioprocess achieved maximum viable cell densities of 1.2 x 10(6) cells/mL and a batch multiplication ratio of 9.1. Moreover, the process successfully maintained the NPC characteristics observed in small-scale studies.

Animals↗
PubMed1997

Cotransplantation of allogeneic islets with allogeneic testicular cell aggregates allows long-term graft survival without systemic immunosuppression.

We prepared single-cell suspensions of Lewis rat ¿RT1(1/l)¿ testicular cells and cultured these in vitro for 48 h under conditions that promoted the formation of cellular aggregates. In the absence of systemic immunosuppression, the transplantation of a sufficient quantity of these aggregates (containing 11 x 10(6) cells, (75% Sertoli cells), together with 2,000 purified Lewis rat islets, reversed the diabetic state for >95 days in 100% (5/5) of the chemically diabetic Wistar-Furth ¿RT1(u/u)¿ recipients. Similar grafts consisting of islets alone or islets plus 50% fewer testicular cell aggregates survived for only 10 days. Functioning composite allografts harvested from normoglycemic animals at approximately 100 days showed healthy beta-cells in close association with Fas ligand-expressing Sertoli cells. Because no gene therapy protocol is required, the transplantation of composite grafts consisting of purified human allogeneic islets plus human allogeneic testicular cell aggregates can be applied in clinical islet transplantation as soon as it has been proven in a large animal model.

Animals↗
PubMed1979

Ganglioside patterns and cholera toxin--peroxidase labeling of aggregating cells from the chick optic tectum.

2The ganglioside compositions of the chick optic tectum and aggregating tectal cell cultures were examined. Both showed similar trends in changes in ganglioside patterns during development. GD3 and GD1b were the predominant gangliosides early in development, while GD1a and several other multisialogangliosides increased in relative amounts with increasing age in vivo and in vitro. Four gangliosides were present early in development which have not previously been reported. These gangliosides are not present at later developmental times suggesting a possible role for them during the critical early stages of nervous tissue differentiation. Some differences were noted when comparing in vivo versus in vitro ganglioside patterns; these differences may possibly be due to the lack of normal retinotectal connections in the cultures. Cytochemical studies on the localization of the presumed cholera toxin--peroxidase binding site GM1 showed conjugate binding correlates with increasing levels of GM1 in the cultures. In older cultures, the conjugate was uniformly localized on all cells and processes in the aggregates. The conjugate also bound to synaptic membranes and intensely stained the synaptic cleft. This latter observation suggests an enrichment of GM1 in the synaptic cleft region.

Animals↗
PubMed1980

Polycyclic hydrocarbon activation and metabolism in epithelial cell aggregates prepared from human mammary tissue.

The metabolism of benz(a)anthracene (BA), 7,12-dimethylbenz(a)anthracene (DMBA) and benzo(a)pyrene (BP) by human mammary epithelial cell aggregates in culture has been investigated using non-neoplastic tissues obtained from eight patients undergoing reduction mammoplasty. All three hydrocarbons were metabolized to water-soluble and organic solvent-soluble products and the latter included both K-region and non-K-region dihydrodiols. The major dihydrodiols detected as metabolites of the parent hydrocarbons were the 8,9-dihydrodiols of BA and DMBA and the 9,10-dihydrodiol of BP. The 1,2-dihydrodiols of BA and DMBA and the 11,12-dihydrodiol of BP were not detected. The hydrocarbons also became bound to the proteins and DNA of the epithelial cells but there were wide differences in the extents of binding occurring with the different hydrocarbons and in the extents of metabolism and binding occurring with tissue preparations from different patients. Some of the hydrocarbon-deoxyribonucleoside adducts formed from DMBA and BP appeared to have arisen through reactions of "bay-region" diol-epoxides with DNA, but only very low levels of reaction with DNA were detected in tissue preparations treated with BA.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed2001

Quantitative analysis of epithelial cell aggregation in the simple metazoan Hydra reveals a switch from homotypic to heterotypic cell interactions.

Hydra, a member of the diploblastic phylum Cnidaria, exhibits the most basic type of organized metazoan tissues. Two unicellular sheets of polarized epithelial cells - ectoderm and endoderm - form a double layer throughout the body column. The double layer can be reestablished from single-cell suspensions by tissue-specific cell-sorting processes. However, the underlying pattern of interactions between ectodermal and endodermal epithelial cells responsible for double-layer formation is unclear. By analyzing cell interactions in a quantitative adhesion assay using mechanically dissociated Hydra epithelial cells, we show that aggregation proceeds in two steps. First, homotypic interactions within ectodermal epithelial cells (ecto-ecto) and within endodermal epithelial cells (endo-endo) form homotypic cell clusters. Second, at an aggregate size of about ten epithelial cells/cluster, ectodermal and endodermal clusters start to form heterotypic aggregates. Homotypic ecto-ecto interactions are inhibited by a polyclonal anti-Hydra membrane antiserum, and under these conditions homotypic endo-endo interactions do not proceed beyond a size of about ten epithelial cells/cluster. These data suggest that homotypic cell clusters reduce their initial homotypic affinity and acquire a new heterotypic affinity. A link between cell adhesion and cell signaling in early Hydra aggregates is discussed.

Animals↗
PubMed2000

Differentiated dendritic cells expressing nuclear RelB are predominantly located in rheumatoid synovial tissue perivascular mononuclear cell aggregates.

OBJECTIVE: Differentiated dendritic cells (DC) and other antigen-presenting cells are characterized by the nuclear location of RelB, a member of the nuclear factor kappaB/Rel family. To characterize and enumerate differentiated DC in rheumatoid arthritis (RA) peripheral blood (PB), synovial fluid (SF), and synovial tissue (ST), the expression and location of RelB were examined. METHODS: RelB protein expression and cellular location were determined in RA PB, SF, and ST by flow cytometry and immunohistochemical analysis of purified cells or formalin-fixed tissue. DNA-binding activity of RelB was determined by electrophoretic mobility shift-Western immunoblotting assays. RESULTS: Circulating RA PBDC resembled normal immature PBDC in that they did not express intracellular RelB protein. In RA ST serial sections, cells containing nuclear RelB (nRelB) were enriched in perivascular regions. A mean +/- SD of 84 +/- 10% of these cells were DC. The remaining nRelB+,HLA-DR+ cells comprised B cells and macrophages. Only 3% of sorted SFDC contained nRelB. However, RelB present in the nucleus of these SFDC was capable of binding DNA, and therefore capable of transcriptional activity. CONCLUSION: Circulating DC precursors differentiate and express RelB after entry into rheumatoid ST. Differentiated DC can thus be identified by immunohistochemistry in formalin-fixed ST. Signals for DC maturation may differ between RA ST and SF, resulting in nuclear location of RelB predominantly in ST. This is likely to have functional consequences for the DC in these sites.

Antigen-Presenting Cells↗
PubMed1986

A comparison of five methods for estimating red cell aggregation.

A comparison has been made of the responses of five techniques for estimating the degree of aggregation in red cell suspensions. They were the use of direct microscopic observation, the erythrocyte sedimentation rate test, low shear rate viscometry, the Myrenne Erythrocyte Aggregometer and the Paar Oscillating Capillary Rheometer. The test samples consisted of normal red cells suspended in buffer to which fibrinogen was added as an aggregating agent. Each test exhibited a fibrinogen threshold concentration before any response occurred. The range of response and sensitivity was highest for the sedimentation test, viscometry and the Paar device. However the simplicity and rapidity of operation of the Myrenne machine make it attractive in a clinical setting. Finally, inspite of its relative insensitivity, the microscopic technique has the great advantage of being the only one that produces unequivocal data since it is based on direct observation.

Blood Sedimentation↗
PubMed1985

The effect of monensin on cell aggregation of normal and dystrophic human skin fibroblasts.

Measurements of aggregation kinetics using couette viscometry show that freshly trypsinized skin fibroblasts from patients with Duchenne muscular dystrophy have values of intercellular adhesiveness approx. 40% those of normal cells. If cells are allowed to recover from the effects of trypsinization (by incubation for 2 h at 37 degrees C in serum-containing medium) the intercellular adhesiveness of both cell types increases, and normal and Duchenne cells aggregate to the same extent. Exposure to the ionophore monensin during the recovery phase leads to suppression of recovery in both cell types, and this effect of the drug is greater in Duchenne fibroblasts. These results are discussed in relation to other data on the reported differential effects of trypsin and monensin on normal and Duchenne fibroblasts.

Cell Aggregation↗