PubMed Health⌕ Search

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 469 records · Page 26Linked to original sources
PubMed2005

Plasma dependent reduction in red blood cell aggregation after dextran sulfate low-density lipoprotein apheresis--implications for rheological studies.

Red blood cell (RBC) aggregation is increased in familial hypercholesterolemia, and is reduced significantly after low density lipoprotein (LDL) apheresis. The purpose of the present study was to clarify whether this reduction depends on changes in plasma composition, RBC membrane properties, or both. RBC aggregation was determined in a computerized cell flow-properties analyzer, before and after LDL apheresis. We compared RBC aggregation in autologous plasma with aggregation in a plasma-free standard solution (0.5% of dextran 500 kDa) to define the separate contributions of plasma and cellular properties to the observed RBC aggregation. RBC aggregation in autologous plasma was reduced by 35.5% after LDL apheresis (P=0.01) but was not significantly affected when measured in dextran 500. This suggests that LDL apheresis attenuated RBC aggregation by altering plasma composition rather than RBC membrane properties. These results are relevant to the understanding of hemorheological changes which follow therapeutic apheresis in hypercholesterolemic patients.

Blood Component Removal↗
PubMed1990

Effects of tetrodotoxin on heart cell aggregates. Phase resetting and annihilation of activity.

The influence of relatively low concentrations of tetrodotoxin (TTX) on phase resetting of spontaneous activity of embryonic chick atrial heart cell aggregates by brief duration current pulses was investigated experimentally and theoretically. The maximal upstroke velocity, Vmax, of the spontaneous action potential was reduced by TTX in a concentration-dependent manner for [TTX] less than 10(-7) M. However, the beat rate was unaffected in this concentration range. Application of a depolarizing current pulse of brief duration during a critical region of the spontaneous cycle annihilated activity in some preparations exposed to [TTX] approximately 10(-7) M. These results were analyzed with the model of electrical activity described in the previous paper (Clay, J.R., R.M. Brochu, and A. Shrier. 1990. Biophys. J. 58:609-621) based on a tonic block of the INa channel by TTX with a dissociation constant, KD, of 50 nM.

Action Potentials↗
PubMed1982

Beta-adrenergic stimulation of prolactin release from superfused pituitary cell aggregates.

l-Isoproterenol (l-ISO), a specific agonist of beta-adrenergic receptors, evoked a prompt rise of prolactin (PRL) release from superfused anterior pituitary cell aggregates established in culture for 5 days. The effect was concentration-dependent between 1 and 100 nM. d-Isoproterenol was more than 2 orders of magnitude weaker than the l-isomer. When dopamine receptors were blocked with domperidone, PRL secretion was also stimulated by l-epinephrine (E) and l-norepinephrine (NE), the rank order of potency being l-ISO greater than E much greater than NE. Under the latter conditions dopamine and the alpha-adrenergic agonists, clonidine and phenylephrine, had no stimulatory effect at 1 microM. Stimulation of PRL release by l-ISO and E was blocked by the beta-receptor antagonist, propranolol, but not by the alpha-receptor blocker, prazosin.

Animals↗
PubMed1991

[The characteristics of the cell aggregation of the tectum mesencephali in chick embryos and of the cerebral cortex in newborn rats in mixed cultures].

To determine species-specific cells in mixed culture, obtained after simultaneous cultivation of dissociated cells of chick embryo midbrain tegmentum and newborn albino rat cerebral cortex, various DNA amounts were used for testing chick and rat cells. The study of cell structure of the aggregates revealed that in addition to the aggregates consisting of cells belonging to only one species of animals, chimera aggregates also exist made of cells of both species of animals, basically of chick embryo glial cells and newborn rat neurons.

Animals↗
PubMed2002

Kupffer cell aggregation and perivenular distribution in steatohepatitis.

Cytokine release from inflammatory cells, endotoxin, lipid peroxidation, and generation of reactive oxygen species are among the factors currently thought to be important in the pathogenesis of alcoholic and nonalcoholic steatohepatitis (SH). To more fully evaluate the role of mononuclear inflammatory cells in SH, 11 needle liver biopsies showing SH were selected for immunohistochemical staining to analyze the type and distribution of mononuclear inflammatory cells, including T and B lymphocytes and Kupffer cells (using immunostains for CD3, CD4, CD8; CD20; and CD68, respectively). An additional seven biopsies showing normal or fatty liver were also selected for CD68 immunostaining. Immunohistochemistry showed mild to moderate (1+ to 2+) numbers of T cells, with equal representation of CD4 and CD8 cells. T cells were found in portal tracts and in regions of SH. B cells were only rarely present. CD68 staining of simple fatty liver and normal liver showed elongated, spindle-shaped Kupffer cells diffusely distributed along the sinusoids throughout the lobules. In contrast, in cases of SH, there was prominent enlargement and aggregation of Kupffer cells in perivenular regions. Scattered large vacuoles of fat that had appeared to be within hepatocytes on routine stain were found actually to be within Kupffer cells. These results support the concept that hepatic Kupffer cells are a major immune effector cell in the pathogenesis of steatohepatitis. A potential direct Kupffer cell role in hepatic lipid processing is also postulated.

Adult↗
PubMed1982

Interaction of hyaluronate with the surface of simian virus 40-transformed 3T3 cells: aggregation and binding studies.

Previous studies have shown that the divalent-cation independent aggregation of simian virus 40-transformed 3T3 cells (SV-3T3) is mediated by the interaction of endogenous hyaluronate with binding sites on the cell surface. In the present study, the nature of the interaction of hyaluronate with the binding sites was characterized further by examining both the aggregation of SV-3T3 cells and the binding of exogenously added [3H]hyaluronate. The aggregation of SV-3T3 cells was found to be: (1) optimal at pH 7; (2) only slightly affected by variations in temperature between 0 and 40 degrees C; (3) more potently inhibited by the addition of high molecular weight preparations of hyaluronate than by lower molecular weight preparations; and (4) enhanced by increasing the ionic strength of the medium. With the exception of the effects of temperature, these characteristics correspond closely to those previously described for binding of [3H]hyaluronate. The effect of ionic strength on the binding of [3H]hyaluronate by SV-3T3 cells was found to correspond closely to its effect on lowering the viscosity of hyaluronate. Both effects (i.e. binding and reduction in viscosity) had similar dose-response curves for NaCl and MgCl2. This close correspondence between binding and the reduction of viscosity suggested that the effect of ionic strength on binding was due to a change in the structure of hyaluronate. Lowering the temperature (40 to 0 degrees C) also enhanced the binding of [3H]hyaluronate to SV-3T3 cells. However, this effect was blocked if the cells were first fixed with glutaraldehyde, suggesting that temperature mediates its effect through the binding sites. Additional experiments showed that the binding of [3H]hyaluronate by SV-3T3 cells could be prevented by preincubating the cells with several types of lectins.

Animals↗
PubMed1980

Cell aggregate suspension culture for large-scale production of biomolecules.

A method is described for the rapid reversible conversion of a number of continuous cell lines from anchorage-dependent growth to growth as aggregates of cells in suspension culture. Employing this technique, an inoculum of three 75-cm2 flasks of BALB/c SV3T3 cells was grown to 60 liters of aggregate suspension in 14 days. This yielded 120 ml of packed cells or 9.1 x 10(10) cells. Similar results were obtained for other cell lines. Biomolecules such as migration-inhibition factor (MIF) and plasminogen activator were produced from these cultures.

Animals↗
PubMed1987

Effect of temperature dependent changes in mechanical stability of red cell aggregates on relative apparent whole blood viscosity.

As the temperature dependence of relative apparent whole blood viscosity eta rel is still controversial, the relation between the temperature dependence of red cell aggregation (RCA) and that of eta rel was examined in normal donors and in patients with venous ulcers of the leg. Apparent whole blood viscosity was measured in the DEER-rheometer (0.01 Pa less than tau less than 2.9 Pa) at 10 degrees C, 20 degrees C, 30 degrees C and 37 degrees C. The instrument was calibrated for each temperature to correct for changes in viscometer geometry. Simultaneously the minimal shear stress tau Tmin to keep RCA dispersed was determined by photometric aggregometry. eta rel was found to increase with decreasing temperature. By basing the relative cold induced increase in eta rel on the state of RCA as defined by the ratio of tau/tau Tmin the relation between both features is verified: With increasing RCA the cold induced increase in eta rel is progressively enhanced.

Blood Viscosity↗
PubMed2002

Sensitivity of the ultrasonic interferometry method (Echo-Cell) to changes of red cell aggregation: application to diabetes.

The sensitivity of the ultrasonic interferometry method (Echo-Cell) to changes in red blood cell (RBC) aggregation was investigated in comparison to the Regulest erythroaggregometry known as a reference method. In experiments where different concentrations of dextrans of 40 or 70 kD molecular weights were added to normal RBCs, the Echo-Cell was proved as sensitive as erythroaggregometry. A comparative study using RBC samples from normal and diabetic subjects showed that the Echo-Cell was much more sensitive when aggregation was measured in diluted than undiluted plasma. The sensitivity of Echo-Cell measurements in diluted plasma was similar to that of erythroaggregometry. Further analysis revealed that RBC aggregation was underestimated by Echo-Cell when measurements were made in undiluted plasma containing high fibrinogen levels, implying that in that case an elevated plasma viscosity might indirectly affect the sensitivity of the Echo-Cell. The low sensitivity of the Echo-Cell to detect an abnormal RBC aggregation when suspensions were prepared in undiluted plasma, is likely related to a relatively high shear stress exerted on RBC aggregates by the suspending medium. In conclusion, the sensitivity of the Echo-Cell to detect abnormal changes in RBC aggregation can be optimized by diluting the plasma.

Adult↗
PubMed2006

Harpin mediates cell aggregation in Erwinia chrysanthemi 3937.

The hypersensitive response elicitor harpin (HrpN) of soft rot pathogen Erwinia chrysanthemi strains 3937 and EC16 is secreted via the type III secretion system and remains cell surface bound. Strain 3937 HrpN is essential for cell aggregation, but the C-terminal one-third of the protein is not required for aggregative activity.

Amino Acid Sequence↗
PubMed2002

Effect of sodium orthovanadate on glycosylation of the phosphopeptidomannans involved in the cell-cell aggregation of the yeast Kluyveromyces bulgaricus.

In studies of yeast flocculation it has been found that low concentrations of vanadium contained in sodium orthovanadate do not affect the growth and the cell-cell adhesion of the yeast Kluyveromyces bulgaricus, whereas high concentrations delay the growth of the yeasts and strongly inhibit flocculation. Moreover, higher sensitivity to Hygromycin B and calcofluor white was taken to imply altered cell wall integrity which is supported by compositional analysis of the extracted phosphopeptidomannans. Yeasts grown on sodium orthovanadate show a decrease in the percentage of phosphopeptidomannans and their compositions. It is proposed that the vanadium contained in sodium orthovanadate has a similar conformation to phosphorus and competes with phosphorus in phosphorylated compounds. The decrease of carbohydrate components and phosphorus linking to phosphopeptidomannans detected may alter their structure and modify ligand binding properties.

Cell Aggregation↗
PubMed1986

Influence of thyroid hormones on rat cerebellar cell aggregation and survival in culture.

In order to study the effect of thyroid hormones on rat cerebellar granule cells, cerebellar perikarya isolated from 5-7-day-old rats were cultured in the presence of normal fetal calf serum, fetal calf serum treated with Dowex-2 ion exchange resin to remove thyroid hormones, or ion exchange-treated serum resupplemented with physiological concentrations of T4 and T3. Granule cells grown under hypothyroid conditions showed abnormal cellular aggregation, neurite fasciculation and cell survival. Cell aggregation, which may be an in vitro correlate of cerebellar granule cell migration to the internal granule layer, was reduced by over 50% under hypothyroid conditions. The rate of protein synthesis in hypothyroid cultures was stimulated by as much as 3-fold compared to thyroid hormone-containing cultures consistent with a proposal that the normal developmental pattern of diminishing protein synthesis specific activity is delayed or prevented under hypothyroid conditions. In addition ultrastructural studies revealed abnormalities in the density of cold-stable microtubules in thyroid hormone-deficient cultures. These results demonstrate that thyroid hormones can influence granule neuron behavior in the absence of Purkinje cells. Furthermore, the observed defects bear numerous similarities to documented abnormalities within the hypothyroid cerebellum, suggesting that this in vitro culture system may serve as a useful model for studying the mechanism of action of thyroid hormones on the cells of the cerebellum.

Animals↗
PubMed1995

Stimulatory effect of perhexiline maleate on the basal and LHRH-stimulated luteinizing hormone release from rat pituitary cell aggregates in vitro.

Perhexiline maleate (PM) is an anti-anginal agent of amphiphilic character involved in lipidosis disorders. Experiments were carried out to study PM action on LH release from rat anterior pituitary cell aggregates. PM caused significant and dose-dependent increases of basal LH release when the aggregates had been previously treated with PM for 20 min, then incubated for 30 min with the same concentration of drug after renewal of the culture medium. The increases of basal LH secretion induced by PM were 69% (p < 0.001) at a concentration of 10(-7)M, 130% (p < 0.001) at a concentration of 10(-5)M and 250% (p < 0.001) at a concentration of 10(-4)M. PM also increased the LHRH-stimulated LH release by 25.5% (p < 0.05) at a concentration of 10(-5)M and by 74.5% (p < 0.01) at the concentration of 10(-4)M. The results showed that PM was more potent on basal LH release than on LH stimulated by LHRH. The mechanism of this action remains unclear. It may be due to the lipidosis property of the drug.

Animals↗
PubMed1988

Use of aggregating cell cultures for toxicological studies.

Relatively simple techniques are now available which allow the preparation of large quantities of highly reproducible aggregate cultures from fetal rat brain or liver cells, and to grow them in a chemically defined medium. Since these cultures exhibit extensive histotypic cellular reorganization and maturation, they offer unique possibilities for developmental studies. Therefore, the purpose of the present study was to investigate the usefulness of these cultures in developmental toxicology. Aggregating brain cell cultures were exposed at different developmental stages to model drugs (i.e., antimitotic, neurotoxic, and teratogenic agents) and assayed for their responsiveness by measuring a set of biochemical parameters (i.e., total protein and DNA content, cell type-specific enzyme activities) which permit a monitoring of cellular growth and maturation. It was found that each test compound elicited a distinct, dose-dependent response pattern, which may ultimately serve to screen and classify toxic drugs by using mechanistic criteria. In addition, it could be shown that aggregating liver cell cultures are capable of toxic drug activation, and that they can be used in co-culture with brain cell aggregates, providing a potential model for complementary toxicological and metabolic studies.

Animals↗