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Results for “Intracellular quantification”

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At least 505 records · Page 28Linked to original sources

PubMed2003

Regulation of pancreatic stellate cell function in vitro: biological and molecular effects of all-trans retinoic acid.

Pancreatic stellate cells (PSCs) are essentially involved in the development of pancreatic fibrosis, a constant feature of chronic pancreatitis and pancreatic cancer. Profibrogenic mediators, such as ethanol metabolites and cytokines, induce a PSC activation process that involves proliferation, enhanced production of extracellular matrix proteins and a phenotypic transition towards myofibroblasts which includes a loss of the characteristic retinoid-containing fat droplets. Here, we have analysed how exogenous all-trans retinoic acid (ATRA) affects activation of rat PSCs induced by sustained culture. Bromodeoxyuridine-incorporation assays indicated an ATRA-dependent inhibition of DNA synthesis. In contrast, ATRA did not affect expression of alpha-smooth muscle actin, a protein typical for myofibroblasts. Quantification of [3H]proline incorporation revealed a diminished collagen production in ATRA-treated PSCs. Furthermore, zymography experiments showed that supernatants of ATRA-exposed PSC cultures contained higher levels of matrix metalloproteinase-9 but not of matrix metalloproteinase-2 than untreated controls. At the level of intracellular signalling, ATRA had no effect on extracellular signal-regulated kinase activation after incubation of PSCs with the mitogen platelet-derived growth factor (PDGF). In addition, PDGF-induced DNA binding of activator protein-1 (AP-1) transcription factors was not inhibited by ATRA treatment. Luciferase reporter gene assays, however, revealed an ATRA-dependent transrepression of AP-1 in PDGF-stimulated PSCs. Together, the results indicate that exogenous ATRA displays inhibitory effects on PSC proliferation and collagen synthesis but does not block phenotypic transition towards myofibroblasts. We hypothesise that inhibition of AP-1 signalling may be involved in the mediation of biological effects of ATRA on PSCs.

Actins↗

PubMed1982

Nuclear magnetic resonance studies of forearm muscle in Duchenne dystrophy.

The forearms of six patients with Duchenne dystrophy were examined by the painless and non-invasive technique of high-resolution nuclear magnetic resonance spectroscopy. The phosphorus spectrum was abnormal in that the ratios of phosphocreatine to adenosine triphosphate and to inorganic phosphate were reduced. Absolute quantification under the conditions of this experiment was not possible but it was probable that in dystrophy the concentration of phosphocreatine in muscle was appreciably reduced. A signal in the phosphodiester region of the spectrum was recorded consistently in patients with dystrophy but not in controls. The intracellular pH of the muscle in the dystrophic patients was abnormally alkaline. The clinical application of nuclear magnetic resonance spectroscopy remains to be proved, but it appears to be a promising non-invasive technique for investigating biochemical abnormalities of muscle disease.

Adenosine Triphosphate↗

PubMed2004

Determination and modeling of kinetics of cancer cell killing by doxorubicin and doxorubicin encapsulated in targeted liposomes.

Various mathematical approaches have been devised to relate the cytotoxic effect of drugs in cell culture to the drug concentration added to the cell culture medium. Such approaches can satisfactorily account for drug response when the drugs are free in solution, but the approach becomes problematic when the drug is delivered in a drug delivery system, such as a liposome. To address this problem, we have developed a simple model that assumes that the cytotoxic potency of a drug is a function of the intracellular drug level in a critical compartment. Upon exposure to drug, cell death commences after a lag time, and the cell kill rate is dependent on the amount of drug in the critical intracellular compartment. The computed number of cells in culture, at any time after exposure to the drug, takes into account the cell proliferation rate, the cell kill rate, the average intracellular drug concentration, and a lag time for cell killing. We have applied this model to compare the cytotoxic effect of doxorubicin (DOX), or DOX encapsulated in a liposome that is targeted to CD44 on B16F10 melanoma cells in culture. CD44 is the surface receptor that binds to hyaluronan and is overexpressed on various cancer cells, including B16F10. We have shown previously that the drug encapsulated in hyaluronan-targeted liposomes was more potent than was the free drug. The model required the determination of the cell-associated DOX after the cells were incubated with various concentrations of the free or the encapsulated drug for 3 h, and the quantification of cell number at various times after exposure to the drug. The uptake of encapsulated drug was greater than that of the free drug, and the ratio of cell association of encapsulated:free drug was 1.3 at 0.5 micro g/ml and increased to 3.3 at 20 micro g/ml DOX. The results demonstrate that the enhanced potency of the encapsulated drug could stem from its enhanced uptake. However, in certain cases, where larger amounts of the free drug were added, such that the intracellular amounts of drug exceeded those obtained from the encapsulated drug, the numbers of viable cells were still significantly smaller for the encapsulated drug. This finding demonstrates that for given amounts of intracellular DOX, the encapsulated form was more efficient in killing B16F10 cells than the free drug. The outcome was expressed in the kinetic model as a 5-6-fold larger rate constant of cell killing potency for the encapsulated drug versus the free drug. The model provides a quantitative framework for comparing the cytotoxic effect in cultured cells when applying the drug in the free form or in a delivery system.

Animals↗

PubMed2004

Surface EMG crosstalk evaluated from experimental recordings and simulated signals. Reflections on crosstalk interpretation, quantification and reduction.

OBJECTIVES: Surface EMG crosstalk is the EMG signal detected over a non-active muscle and generated by a nearby muscle. The aim of this study was to analyze the sources of crosstalk signals in surface EMG recordings and to discuss methods proposed in the literature for crosstalk quantification and reduction. METHODS: The study is based on both simulated and experimental signals. The simulated signals are generated by a structure based surface EMG signal model. Signals were recorded with both intramuscular and surface electrodes and single motor unit surface potentials were extracted with the spike triggered averaging approach. Moreover, surface EMG signals were recorded from electrically stimulated muscles. RESULTS: From the simulation and experimental analysis it was clear that the main determinants of crosstalk are non-propagating signal components, generated by the extinction of the intracellular action potentials at the tendons. Thus, crosstalk signals have a different shape with respect to the signals detected over the active muscle and contain high frequency components. CONCLUSIONS: Since crosstalk has signal components different from those dominant in case of detection from near sources, commonly used methods to quantify and reduce crosstalk, such as the cross-correlation coefficient and high-pass temporal filtering, are not reliable. Selectivity of detection systems must be discussed separately as selectivity with respect to propagating and non-propagating signal components. The knowledge about the origin of crosstalk signal constitutes the basis for crosstalk interpretation, quantification, and reduction.

Action Potentials↗

PubMed2003

Determination of tricarboxylic acid cycle acids and other related substances in cultured mammalian cells by gradient ion-exchange chromatography with suppressed conductivity detection.

An ion-exchange chromatography method was established for simultaneously analyzing the tricarboxylic acid (TCA) cycle acids and other related substances in cultured mammalian cells, including citrate, cis-aconitate, isocitrate, alpha-ketoglutarate, succinate, malate, fumarate, oxaloacetate, trans-aconitate, phosphate, lactate and pyruvate. A Dionex 600 ion chromatograph with an ion suppressor and a conductivity detector, and an IonPac AS11-HC analytical column were employed. An NaOH gradient elution containing 13.5% methanol contributed to sufficient separation of target substances. The stability of carboxylic acids was investigated and oxaloacetate was found to be extremely unstable especially at pH 3. TCA cycle acids and other related substances in Chinese hamster ovary (CHO) cells were separated completely, and lactate, malate, phosphate, citrate and cis-aconitate were quantified due to their higher concentrations. In the quantification of the five substances, detection limits (S/N=3) ranged from 0.12 to 0.48 microM, the correlation coefficients from 0.9982 to 1.0000 in their linear ranges of concentration, and the recoveries from 87 to 95%. The metabolic status of CHO cells was analyzed on the basis of the intracellular concentrations of TCA cycle acids.

Animals↗

PubMed2004

Peptide-linked molecular beacons for efficient delivery and rapid mRNA detection in living cells.

Real-time visualization of specific endogenous mRNA expression in vivo has the potential to revolutionize medical diagnosis, drug discovery, developmental and molecular biology. However, conventional liposome- or dendrimer-based cellular delivery of molecular probes is inefficient, slow, and often detrimental to the probes. Here we demonstrate the rapid and sensitive detection of RNA in living cells using peptide-linked molecular beacons that possess self-delivery, targeting and reporting functions. We conjugated the TAT peptide to molecular beacons using three different linkages and demonstrated that, at relatively low concentrations, these molecular beacon constructs were internalized into living cells within 30 min with nearly 100% efficiency. Further, peptide-based delivery did not interfere with either specific targeting by or hybridization-induced fluorescence of the probes. We could therefore detect human GAPDH and survivin mRNAs in living cells fluorescently, revealing intriguing intracellular localization patterns of mRNA. We clearly demonstrated that cellular delivery of molecular beacons using the peptide-based approach has far better performance compared with conventional transfection methods. The peptide-linked molecular beacons approach promises to open new and exciting opportunities in sensitive gene detection and quantification in vivo.

Amino Acid Sequence↗

PubMed1991

Electron probe X-ray microanalysis of intracellular element concentrations in cryosections in the presence of changes in cell volume.

The interpretation of element concentration data for X-ray microanalyses of biological tissues, which are subjected to some experimental treatment, can be complicated by changes in cell volume and total cell dry matter induced by the treatment. We have examined the manner in which such changes would affect the values measured in frozen-dried cryosections of soft tissues, and how they may be taken into account in the interpretation of the results. The element content (mass per unit dry weight) measured by the peak-to-continuum or Hall method is independent of changes in cell volume, but is sensitive to a change in the local dry mass. Conversely, intracellular concentrations in terms of mass per unit volume, as determined by the peripheral or internal standard technique, are dependent on volume changes but independent of dry mass. The estimated dry weight fraction is affected by changes in both volume and dry mass. The results obtained from both quantification methods can therefore provide information on the combination of changes in cellular element levels, volume and total dry mass that may occur following the experimental treatment. In a study of the late effect of the drug cisplatin on electrolyte concentrations in kidney proximal tubules, both quantification methods have been used to obtain wet weight and dry weight concentrations. By applying the above considerations, the analytical results have been interpreted as a combination of changes in element levels and a shrinkage of the tubule cells. Cell shrinkage was confirmed by morphometric analysis of tubular cross-sections.

Animals↗

PubMed2004

Extracellular calcium antagonizes forskolin-induced aquaporin 2 trafficking in collecting duct cells.

BACKGROUND: Urinary concentrating defects and polyuria are the most important renal manifestations of hypercalcemia and the resulting hypercalciuria. In this study, we tested the hypothesis that hypercalciuria-associated polyuria in kidney collecting duct occurs through an impairment of the vasopressin-dependent aquaporin 2 (AQP2) water channel targeting to the apical membrane possibly involving calcium-sensing receptor (CaR) signaling. METHODS: AQP2-transfected collecting duct CD8 cells were used as experimental model. Quantitation of cell surface AQP2 immunoreactivity was performed using an antibody recognizing the extracellular AQP2 C loop. Intracellular cyclic adenosine monophosphate (cAMP) accumulation was measured in CD8 cells using a cAMP enzyme immunoassay kit. To study the translocation of protein kinase C (PKC), membranes or cytosol fractions from CD8 cells were subjected to Western blotting using anti-PKC isozymes antibodies. The amount of F-actin was determined by spectrofluorometric techniques. Intracellular calcium measurements were performed by spectrofluorometric analysis with Fura-2/AM. RESULTS: We demonstrated that extracellular calcium (Ca2+ o) (5 mmol/L) strongly inhibited forskolin-stimulated increase in AQP2 expression in the apical plasma membrane. At least three intracellular pathways activated by extracellular calcium were found to contribute to this effect. Firstly, the increase in cAMP levels in response to forskolin stimulation was drastically reduced in cells pretreated with Ca2+ o compared to untreated cells. Second, Ca2+ o activated PKC, known to counteract vasopressin response. Third, quantification of F-actin demonstrated that Ca2+ o caused a nearly twofold increase in F-actin content compared with basal conditions. All these effects were mimicked by a nonmembrane permeable agonist of the extracellular CaR, Gd3+. CONCLUSION: Together, these data demonstrate that extracellular calcium, possibly acting through the endogenous CaR, antagonizes forskolin-induced AQP2 translocation to the apical plasma membrane in CD8 cells. In hypercalciuria, this mechanism might blunt water reabsorption and prevent further calcium concentration, thus protecting against a potential risk of urinary calcium-containing stone formation.

Actins↗

PubMed2006

Metabolic flux analysis of a glycerol-overproducing Saccharomyces cerevisiae strain based on GC-MS, LC-MS and NMR-derived C-labelling data.

This study focuses on unravelling the carbon and redox metabolism of a previously developed glycerol-overproducing Saccharomyces cerevisiae strain with deletions in the structural genes encoding triosephosphate isomerase (TPI1), the external mitochondrial NADH dehydrogenases (NDE1 and NDE2) and the respiratory chain-linked glycerol-3-phosphate dehydrogenase (GUT2). Two methods were used for analysis of metabolic fluxes: metabolite balancing and (13)C-labelling-based metabolic flux analysis. The isotopic enrichment of intracellular primary metabolites was measured both directly (liquid chromatography-MS) and indirectly through proteinogenic amino acids (nuclear magnetic resonance and gas chromatography-MS). Because flux sensitivity around several important metabolic nodes proved to be dependent on the applied technique, the combination of the three (13)C quantification techniques generated the most accurate overall flux pattern. When combined, the measured conversion rates and (13)C-labelling data provided evidence that a combination of assimilatory metabolism and pentose phosphate pathway activity diverted some of the carbon away from glycerol formation. Metabolite balancing indicated that this results in excess cytosolic NADH, suggesting the presence of a cytosolic NADH sink in addition to those that were deleted. The exchange flux of four-carbon dicarboxylic acids across the mitochondrial membrane, as measured by the (13)C-labelling data, supports a possible role of a malate/aspartate or malate/oxaloacetate redox shuttle in the transfer of these redox equivalents from the cytosol to the mitochondrial matrix.

Carbon↗

PubMed1993

Expression of oncoprotein 18 in human leukemias and lymphomas.

Oncoprotein 18 (Op18) is an 18 kDa intracellular phosphoprotein that appears to be up-regulated in certain neoplastic cells. In the present report we have analysed the expression of Op18 in samples of human hematopoietic disorders, mainly leukemias and lymphomas. For this purpose we have developed reagents allowing quantitative Western-blot analysis, and quantification of Op18 on the single cell level by flow cytometric analysis. The data demonstrates that a significant fraction of all lymphoma and leukemia cases express Op18 at levels that are several-fold higher than the Op18 levels ever found in benign proliferating tissue, such as bone marrows in remission and reactive lymph nodes. Thus, the results establish on the single cell level that Op18 is frequently expressed at abnormal levels in lymphoid and myeloid malignancies. Flow cytometric analysis revealed a striking qualitative and quantitative heterogeneity in Op18 expression between patients with lymphoma or leukemia. Moreover, our analysis demonstrates that the abnormal cellular levels of Op18 expression frequently found in high grade lymphoma and acute leukemia samples do not correlate with an increased fraction of cells in S phase. Finally, we also present an example of dramatic changes in Op18 expression pattern in bone marrow cells during the progression of a chemo-resistant acute leukemia.

Acute Disease↗

PubMed1990

An improved double fluorescence flow cytometry method for the quantification of killer cell/target cell conjugate formation.

We have developed an improved method to analyse stable associations (conjugate formation) between effector and target cells. Hydroethidine (red) stained lymphoblastoid target cells were cocentrifuged with carboxyfluorescein diacetate acetoxymethylester (green) stained human IL-2 activated cytotoxic cells (LAK). In the present studies either enriched or purified CD3 negative large granular lymphocytes (LGL) were used as cytotoxic cells. These fluorescent vital dyes localize intracellularly and therefore do not modify the cell to cell contact which eventually leads to the lytic events. Both dyes can be excited at a common wavelength (488 nm) using a single argon laser. Effectors firmly bound to target(s) (stable conjugates) were detected as two color fluorescent events (red and green). This method has several features: (a) the number of conjugates is recorded with reference to a fixed number of target cells; (b) the composition of conjugates (number of effectors or targets per conjugate) can be studied by analysis of the fluorescence intensities (red or green); (c) conjugate formation can be studied at E:T ratios comparable to those used in the classical 51Cr release cytotoxic assay; (d) it gives reproducible results and permits the study of very weak differences in binding properties. This method was used to study conjugate formation between human IL-2-activated cytotoxic cells (or purified CD3 negative LGL) and various lymphoblastoid target cells. We were able to demonstrate that cell lines susceptible to lysis formed more conjugates and were surrounded by more LAK effectors than their resistant counterparts and that no conjugate contained more than one target.

Cell Adhesion↗

PubMed2002

Pressure-induced endothelial Ca(2+) oscillations in lung capillaries.

Endothelial second messenger responses may contribute to the pathology of high vascular pressure but remain poorly understood because of the lack of direct in situ quantification. In lung venular capillaries, we determined endothelial cytosolic Ca(2+) concentration [Ca(2+)](i) by the fura 2 ratioing method. Pressure elevation increased mean endothelial [Ca(2+)](i) by Ca(2+) influx through gadolinium-inhibitable channels and amplified [Ca(2+)](i) oscillations by Ca(2+) release from intracellular stores. Endothelial [Ca(2+)](i) transients were induced by pressure elevations of as little as 5 cmH(2)O and increased linearly with higher pressures. Heptanol inhibition of [Ca(2+)](i) oscillations in a subset of endothelial cells indicated that oscillations originated from pacemaker endothelial cells and were propagated to adjacent nonpacemaker cells by gap junctional communication. Our findings indicate the presence of a sensitive, active endothelial response to pressure challenge in lung venular capillaries that may be relevant in the pathogenesis of pressure-induced lung microvascular injury.

Animals↗

PubMed2002

cAMP binding protein assay for widespread use in cell signaling studies.

cAMP plays a critical role in intracellular signaling pathways that regulate proliferation or differentiation. The cAMP binding protein assay, using a naturally derived cAMP binding protein, is one of the most widely used methods for cAMP determination. The major steps of this binding assay include purification of the binding protein, cAMP extraction from samples, and quantification of the cAMP Most purification methods of the cAMP binding protein were published before 1975, and many of the materials and methods are outdated. Here we describe an updated method of purification of cAMP binding protein from bovine skeletal muscle with the advantages of simplicity, low cost, and high yield The isolation procedures can be completed in two days using commercially available materials and equipment. The cAMP binding properties of the isolated protein can be utilizedfor more than two years. Binding protein isolatedfrom 1 kg bovine muscle is sufficientfor at least 3 x10(4) assay tubes. Furthemore, we describe the techniques of cAMP extraction and quantification that have been used successfully in studying parathyroid hormone signaling as an example of a G protein-linked seven transmembrane domain receptor that signals through the protein kinase A pathway.

Adenylyl Cyclases↗

PubMed1994

Flow cytometric detection of anti-neutrophil cytoplasmic autoantibodies.

An intracytoplasmic immunofluorescence staining technique which allows the detection and quantification of anti-neutrophil cytoplasmic autoantibodies (ANCA) by flow cytometry is described. A polymorph neutrophil population from human peripheral blood was used in this study as indicator cells. These were fixed and permeabilized by paraformaldehyde, Tween 20 and saponin, to allow ANCA in the patients sera to reach their intracellular antigen targets. The numbers of indicator cells remained unaltered by the permeabilization protocol and no cell aggregation or loss of intracellular antigenicity was observed. An excellent agreement (91% (207/228)) between ANCA detection by immunofluorescence microscopy (IF) and flow cytometry was noted. Compared with IF assay, the flow cytometric method has a sensitivity of 93% (42/45) and a specificity of 90% (165/183). Although not able to discriminate between P-ANCA or C-ANCA, this flow cytometric method has the advantage of providing an objective, reproducible and quantitative measure of ANCA, which makes it an ideal technique for screening of patients sera for ANCA reactivities.

Antibodies, Antineutrophil Cytoplasmic↗

PubMed1993

Movement of the free catalytic subunit of cAMP-dependent protein kinase into and out of the nucleus can be explained by diffusion.

The catalytic (C) subunit of cyclic AMP (cAMP) dependent protein kinase (PKA) has previously been shown to enter and exit the nucleus of cells when intracellular cAMP is raised and lowered, respectively. To determine the mechanism of nuclear translocation, fluorescently labeled C subunit was injected into living REF52 fibroblasts either as free C subunit or in the form of holoenzyme (PKA) in which the catalytic and regulatory subunits were labeled with fluorescein and rhodamine, respectively. Quantification of nuclear and cytoplasmic fluorescence intensities revealed that free C subunit nuclear accumulation was most similar to that of macromolecules that diffuse into the nucleus. A glutathione S-transferase-C subunit fusion protein did not enter the nucleus following cytoplasmic microinjection. Puncturing the nuclear membrane did not decrease the nuclear concentration of C subunit, and C subunit entry into the nucleus did not appear to be saturable. Cooling or depleting cells of energy failed to block movement of C subunit into the nucleus. Photobleaching experiments showed that even after reaching equilibrium at high [cAMP], individual molecules of C subunit continued to leave the nucleus at approximately the same rate that they had originally entered. These results indicate that diffusion is sufficient to explain most aspects of C subunit subcellular localization.

Animals↗

PubMed1993

Combined use of surface electromyography and 31P-NMR spectroscopy for the study of muscle disorders.

This article describes the use of combining spectral electromyographic signal techniques with phosphorus magnetic resonance (31P-NMR) spectroscopy for the purpose of studying muscle disorders. The quantification of muscle fatigue by electromyographic spectral variables such as the median frequency is summarized. Its development as a laboratory and clinical tool is presented, with an emphasis toward its potential as an assessment procedure. Similarly, the use of 31P-NMR spectroscopy for noninvasive measurement of phosphate metabolites and intracellular pH during fatigue are described. The limitations of this procedure are presented and compared with surface electromyographic techniques. Suggestions are made for combining these techniques for the purpose of monitoring muscle metabolic and electrophysiologic changes in situ during fatiguing exercises. A recent study in which these techniques were combined to evaluate the underlying mechanisms of fatigue in patients with fibromyalgia is described.

Adult↗

PubMed1996

Heparin-induced overexpression of basic fibroblast growth factor, basic fibroblast growth factor receptor, and cell-associated proteoheparan sulfate in cultured coronary smooth muscle cells.

Basic fibroblast growth factor (bFGF), a potent mitogen for arterial smooth muscle cells (SMCs), plays a pivotal role in the pathogenesis of arteriosclerosis and restenosis. Heparin in nanogram quantities may promote or even be required for binding of bFGF to its cognate receptor. Conversely, heparin in microgram doses is a strong inhibitor of arterial SMC replication in vitro and in vivo. Bovine coronary SMCs (cSMCs) express bFGF, bFGF receptor (FGF-R1), and cell membrane-integrated proteoheparan sulfate (HSPG). These three molecules are known to form a trimolecular complex that promotes signal transduction and mitogenesis. The bFGF synthesized by cSMCs is distributed to an intracellular and a pericellular compartment. Resting cultured cells retain about 80% of their bFGF intracellularly; 20% is found in the pericellular region. During proliferation, 70% to 80% of total bFGF is expressed in the pericellular compartment. Trypsinization generates soluble forms of the complex of bFGF with the ectodomains of the bFGF receptor and cell membrane-integrated HSPG in the pericellular compartment, thus allowing quantification of pericellular bFGF by a highly specific enzyme immunoassay. Standard heparin inhibits the proliferation of cSMCs by up to 80% in a concentration range between 10 and 100 micrograms/mL medium in a dose-dependent manner but increases the protein content of cSMCs compared with proliferating control cells. The heparin-induced increase in cellular protein content includes a 60% to 100% increase in the expression of pericellular bFGF, FGF-R1, and cell membrane-integrated HSPG. Thus, under heparin treatment, the heparan sulfate side chains of cell membrane-integrated HSPG incorporate more [35S]sulfate, and the proportion of [35S]heparan sulfate among total glycosaminoglycans increases from 36% to 52%. Fluorescence-activated cell sorting analysis and [3H]thymidine incorporation experiments provide evidence for multiple effects of heparin, including blocks at early and late checkpoints of the cell cycle in heparin-treated cells. These results indicate that heparin, despite its anti-proliferative potency, stimulates the expression of all components of the bFGF system even in coronary SMCs in which growth is inhibited.

Animals↗

PubMed1997

[Interactions between biospecific polymers and MCF7 cells: modulation of cellular proliferation and expression of estrogen receptors].

Numerous studies on interactions between insoluble polymers and cell membrane receptors indicated modulation of cellular proliferation and cell phenotype by these polymers considered as biospecific. We synthesized several biospecific polymers in order to investigate the interactions between polymers and intracellular receptors as estrogen receptors considered as tumoral indicator of breast cancer. Biospecific polymers were obtained by random substitutions of crosslinked polystyrene beads with suitable chemical groups (sulfonate and amino acid sulfamides). These polymers were used as microcarriers for culture of MCF7 cells, a cellular model of human breast cancer. Quantification of MCF7 cell estrogen receptors was determined by radioligand binding assay for different days of cellular proliferation. The data obtained with MCF7 cells cultured on biospecific polymers show an inverse relationship between polymer induced inhibition of cell proliferation and polymer induced increase of estrogen receptors. Similar inverse relationship was obtained with MCF7 cell cultured on standard polystyrene tissue culture plates. The various interaction between insoluble polymers and MCF7 cells could be related to the proportion and the nature of the substitutive chemical groups. These biospecific polymers could presents sites of interaction with cell membrane receptors leading to modulation of cell biological activity. The different insoluble polymers were used as preliminary models: a practical application could be a methodology of cellular selection using soluble biospecific polymers (for example chemically modified dextrans).

Binding, Competitive↗