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A Pessina

Publications and source records attributed to A Pessina.

At least 37 records · Page 2Linked to original sources
PubMed1997

Expression of B cell markers on SR-4987 cells derived from murine bone marrow stroma.

The murine cell line SR-4987 was originated in our laboratory from adherent cells of a long term bone marrow culture. SR-4987 cells do not express p21-ras and c-fms products on membrane whereas secrete M-CSF, evidence a fibroblast-like morphology and are vimentine positive. This line shows a very poor "in vitro" agar clonogenicity which is not modulated by the addition of different cytokines and growth factors (M-CSF, GM-CSF, G-CSF, IL-3, IL-7, alpha-TNF, PDGF, and EGF). On the contrary, a dramatic increase in clonogenicity is observed in the presence of bFGF. The RT-PCR investigation evidences the mRNA encoding for bFGF, IL-7, GM-CSF, and SCF (c-kit ligand). The analysis of CD antigen expression on SR-4987 cell membrane indicates a phenotype (CD5+, CD44+, 45R(B220)+, sIg+, 5'-nucleotidase+) that is consistent with a B cell feature. Our observations suggest that exogenous bFGF might represent an appropriate stimulus for inducing the SR-4987 cells proliferation also in the absence of cell-substrate anchorage. Further, they indicate that SR-4987 cells could represent a particular differentiation stage in which characters of "stromal cell" and "B cell" are coexpressed in agreement with the hypothesis of a common stromal-hematopoietic differentiation.

Animals↗
PubMed1997

From the monitoring of severe to a survey of mild adverse effects of current antihypertensive therapy: the hidden side of the iceberg. The Scientific Committee of the Italian Pharmacoepidemiology Survey on Antihypertensive Therapy.

One of the most important causes of the unsatisfactory results of antihypertensive therapy in current medical practice is the difficulty in evaluating individual tolerability to the various antihypertensive agents. The methods commonly used, i.e. assessment in controlled studies of limited duration, or notification to pharmacovigilance authorities, clearly underestimate the problem. In order to obtain more correct information on antihypertensive practice, an Italian pharmacoepidemiological study has recently been planned, and the results of a pilot phase of this study are reported here.

Antihypertensive Agents↗
PubMed1995

The different inhibiting effect of cholera toxin on two leukemia cell lines does not correlate with their toxin binding capacity.

The murine leukemia cell lines L1210 and WEHI-3B show a very different sensitivity to the cholera toxin (CT). The in vitro growth of L1210 is completely inhibited by 10(-8) M CT, while WEHI-3B growth shows the same inhibition at 10(-11) M. The analysis of membrane ganglioside pattern of the two cell lines shows that in L1210 cells the major component is the GM1a ganglioside while the monosialogangl oside fraction from WEHI-3B is entirely composed of gangliosides of the 'b' series among which GM1b is the more represented. The total cholera toxin binding capacity of the ganglioside extract from L1210 cells is more than hundred fold higher than that of WEHI-3B and this difference is also confirmed by the number of CT receptors/cell and by the binding of FITC-B subunit of CT on the cells. These surprising data are in conflict with the poor sensitivity to CT evidenced by L1210 compared to WEHI-3B cells. In order to clarify this discrepancy we investigated the cAMP accumulation, the cell viability and the clonogenicity of these two leukemia cell lines following the treatment with CT and forskolin (FRSK). The treatment of WEHI-3B cells with CT induces a dramatic increase of intracellular cAMP which highly correlates with cell death and the decrease of clonogenicity and this result is partially obtained by the treatment with FRSK. L1210 cells do not evidence significant cAMP accumulation neither with CT nor with FRSK treatment. These data suggest that the different inhibiting effect of CT on WEHI-3B and L1210 cells does not correlate with their different pattern of gangliosides and the related toxin binding capacity. Further they indicate that the growth inhibition of WEHI-3B cells is closely related with a cAMP-dependent cell killing mechanism, while the inhibition of L1210 growth (produced by high concentration of CT) is mediated by a cAMP independent mechanism.

Animals↗
PubMed1995

Different biological conditions influencing bacterial adherence assay.

Adherence of bacteria to animal cells is considered the first step in the pathogenesis of many infectious diseases. The most suitable techniques developed in vitro to check the capacity of bacteria to adhere to different tissues use monolayers of established cell lines. We studied the influence of incubation time (1, 2, 3 hours), cell substrates (Hep-2, H-407) and the number of bacteria per cell (1, 10, 100, 1000) on the adherence index (number of adherent bacteria per cell determined by microscopic count) of the fimbriated Escherichia coli 454 strain, Proteus rettgeri 25 and Enterobacter cloacae 10. The data were analyzed with different statistical methods and the results evidenced that all the conditions considered affect either the end-point of the test or the adherence index. Our observations indicate that the different methods used make it impracticable to compare many data from the literature and suggest the need to search for more homogeneity in this type of assay.

Bacterial Adhesion↗
PubMed1995

Loss of porins following carbapenem-resistance selection and adherence modification in enterobacteria.

The acquired resistance to the carbapenems is frequently joined to modified expression of porins or other outer membrane (OM) structures, thus bacterial adherence, that also depends on the presence of peculiar surface structures, might theoretically be influenced. In this study the ability to adhere to Hep-2 and I-407 eukaryotic cell monolayers was assayed for two susceptible strains of Serratia marcescens, one strain of Enterobacter cloacae and one of Providencia rettgeri in comparison with that of isogenic resistant mutants selected either by carbapenems or by cephalosporins. The mutants appeared slightly less adherent than the wild type strains, however, due to the high variability of this kind of assay, the differences observed in most cases could not be considered statistically significant. The data suggest that adherence, among the factors affecting the pathogenicity of the strains, remains probably unmodified in the resistant bacterial population possibly selected by a carbapenem treatment.

Bacterial Adhesion↗
PubMed1994

Outer membrane permeability of Serratia marcescens to meropenem and imipenem.

The penetration rates of meropenem and imipenem through the outer membrane (OM) of Serratia marcescens was evaluated by the method of Zimmermann and Rosselet. To this aim, two strains of the specie were transformed with the pMON-01 plasmid DNA that carries the bla S gene from Xanthomonas maltophilia encoding for the L-1 beta-lactamase. The permeability of the transformants to cephaloridine was not affected by the presence of the plasmid. Imipenem was shown to penetrate the OM of the transformants at a rate 4- to 5-fold higher than that of meropenem and close to that of cephaloridine. Meropenem appeared more active than imipenem in inhibiting the targets as inferred from the calculated concentrations of antibiotic in the cell periplasm in the presence of MIC. The calculation of the target access index (TAI) indicated that a 20- to 50-fold decrease in permeability or increase in beta-lactamase activity would be required to significantly increase the MICs of imipenem or meropenem for these strains.

Cell Membrane Permeability↗
PubMed1994

In vitro short-term and long-term cytotoxicity of fluoroquinolones on murine cell lines.

Short-term and long-term cytotoxicity of four fluoroquinolones (ciprofloxacin, rufloxacin, ofloxacin, lomefloxacin) on 7 established murine cell lines (WEHI-3B, L1210, EL4, P388D1, 32DC13, L929, SR-4987) by a microtiter MTT assay have been studied. In short-term cytotoxic test (24 hr), cell lines with a high proliferating cell rate (as leukemias) showed a greater sensitivity to quinolones than other cell lines. In long-term cytotoxic test (7 days) no different sensitivity was observed among the cell lines. In short-term test ciprofloxacin and rufloxacin were more toxic than lomefloxacin and ofloxacin whereas in the long-term test the activity of the four quinolones was similar. Ratio between IC50 on cell lines and MIC50 against gram negative bacteria evidenced remarkable differences when short-term or long-term cytotoxic tests were considered. The results confirm toxic activity of quinolones on mammalian cells evidencing that the sensitivity to quinolones, in short-term cytotoxic test, correlates with the doubling time of cell population. The results further suggest that long-term cytotoxic tests measure better the antiproliferating activity of quinolones providing a more powerful assay to investigate their in vitro toxicity.

Animals↗
PubMed1993

Topoisomerase I in multiple drug resistance.

Topoisomerase I is a nuclear enzyme able to catalyse the relaxation of supercoiled DNA by introducing single-stranded breaks in DNA molecule. Its function seems important to prepare DNA for many processes such as recombination, DNA repair and RNA transcription. The most important drugs active as inhibitors of topoisomerase I are represented by camptothecin and its derivatives which were developed as promising anticancer drugs. Since selectivity of action is essential for an antitumor drug, many studies were performed to investigate the mechanisms by which cancer cells become resistant to drug treatment by developing a condition of multiple drug resistance (MDR). This article analyses the role of topoisomerase I in cell functions, considers the cellular effects of topo I poisons and discusses the ways by which tumoral cells may become resistant to these drugs with a special attention to MDR mechanisms.

Animals↗
PubMed1992

Lack of in vitro antiviral activity of fluoroquinolones against herpes simplex virus type 2.

The antiviral activity against herpes simplex virus type 2 (HSV-2) of five fluoroquinolones (ciprofloxacin, lomefloxacin, ofloxacin, pefloxacin, rufloxacin) was tested in vitro. Their efficacy was evaluated as reduction of the cytopathic effect (CPER) exerted by HSV-2 on Vero cells in comparison with novobiocin and acycloguanosine. Our results show a very poor antiviral effect of five quinolones (CPER50 = 200 mg/l) that was comparable with their cytotoxicity (TCIC50 less than 200 mg/l). Novobiocin shows a lower toxicity (TCIC50 = 400 mg/l) and a slight antiviral activity (CPER50 = 120 mg/l). Acycloguanosine shows a TCIC50 greater than 400 mg/l and a CPER50 of 3.125 mg/l. The therapeutic indices gave values ranging from 0.12 to 2 for quinolones, of 3.3 for novobiocin, and greater than 128 for acycloguanosine. The antiviral efficacy of acycloguanosine was not affected by concentrations of quinolones active against bacteria (1-10 mg/l) whereas it was drastically reduced by higher doses of quinolones (greater than 50 mg/l). Our data suggest that fluoroquinolones cannot be considered drugs able to inhibit HSV-2 replication in vitro.

Acyclovir↗
PubMed1992

Establishment and characterization of a new murine cell line (SR-4987) derived from marrow stromal cells.

A new murine cell line designated as SR-4987 was established by treating a long-term bone marrow culture with the supernatant from Y-1 cells which actively produce viral C-particles (MuLV). The line showed a fibroblast-like morphology and its mesodermal origin was confirmed by immunocytochemical staining. Flow cytometric analysis of DNA index evidenced a tetraploid number of chromosomes whereas cell cycle analysis showed 34.8% of cells in S phase and 60.7% in G1. In vitro growth studies demonstrated a population doubling time of 14.7 h, a good plating efficiency (52.3%) and a very poor agar clonogenic capacity (0.6%). SR-4987 was tumorigenic only in syngeneic mice in which sarcomas were induced. The line produced M-CSF in the culture supernatant whereas G-CSF, IL-3 and GM-CSF were not detected. Studies are in progress to assess the production of other cytokines and to verify if same autocrine growth factor is involved in the control of SR-4987 proliferation. Our line provides a further model of stromal cells for studying the interaction between hemopoietic progenitors and their microenvironment, as well as to study factors produced by stromal cells acting as modulators of proliferation and differentiation of related cell populations.

Animals↗
PubMed1990

An improved method for the purification of myrosinase and its physicochemical characterization.

An improved high yielding procedure for the purification of myrosinase from Sinapis alba L. consisting of concanavalin A affinity chromatography followed by a chromatofocusing step is presented. The purified enzyme was homogeneous as judged by sodium dodecyl sulfate-gel electrophoresis and by analytical ultracentrifugation although the presence of at least three isoenzymes, with pI values from 5.05 to 5.15, was detected by isoelectric focusing. It was found that the enzyme has a molecular weight of 135.1 kg mol-1 and consists of two, possibly identical, subunits of molecular weight 71.7 kg mol-1. The structure of myrosinase was studied by circular dichroism. Contin analysis of the CD data indicates a mixed alpha-helix and beta-sheet conformation for the native protein a with approximately 19% alpha-helix and approximately 35% beta-sheet content. Denaturation with guanidinium chloride was found to be irreversible although the enzyme has excellent storage characteristics in aqueous solution.

Brassica↗
PubMed1990

Evaluation of the efficacy and safety of enalapril plus hydrochlorothiazide plus methyldopa vs standard triple therapy in the treatment of moderate to severe hypertension: results from a multicentre study.

We report the results of a randomized, double-blind, parallel group multicentre study in 120 patients with moderate to severe hypertension, comparing two different types of antihypertensive treatment: a) the standard 'triple therapy' with hydrochlorothiazide, propranolol and hydralazine, and b) the combination of an ACE inhibitor, enalapril with hydrochlorothiazide (HCTZ) and methyldopa. The two regimens caused similar degrees of blood pressure reductions. The only significant difference between the two groups was heart rate due to the bradycardiac effect of propranolol in the group treated with the standard 'triple therapy'. Only 3.4% of patients receiving the regimen of enalapril, HCTZ and methyldopa were withdrawn from the study for adverse reactions, against 10% of patients on HCTZ, propranolol and hydralazine. Four cases of hypokalaemia in the enalapril group and 19 in the propranolol group were reported: so enalapril seemed to ameliorate the hypokalaemic effect of HCTZ. The overall analysis of the study results shows that the treatment based on enalapril, HCTZ and methyldopa is as efficient and better tolerated than the established regimen of HCTZ, propranolol and hydralazine.

Blood Pressure↗
PubMed1989

Inhibition of murine leukemia (WEHI-3B and L1210) proliferation by cholera toxin B subunit.

Cholera holotoxin produces both stimulation and inhibition of the growth of different cell populations. These opposite effects were both attributed to the enzymatic activity of the subunit A that activates adenylate cyclase, increasing the intracellular level of cAMP. We observed that the B subunit of cholera toxin produced by itself an inhibition of the 'in vitro' growth of two murine leukemia cell lines (L1210 limphoid leukemia and WEHI-3B myelomonocytic leukemia). The sensitivity of WEHI-3B cells towards cholera toxin was about 5000-times higher than that of the L1210 cells, whereas the two leukemias showed an identical sensitivity to the B subunit (IC50 = 5.10(-10) M for L1210 and 10(-10) M for WEHI-3B). The inhibition produced by the B subunit was neutralized by GM1 and in a minor degree by type II gangliosides. The two leukemias showed a remarkable difference in their gangliosides contents (L1210 cells contained GM1 (80.6%) and GM2 (19.4%), while WEHI-3B cells contained GM1 (28.2%), Fuc-GM1 (44.9%) and a band (26.9%) with a chromatographic mobility between GD1a and GD1b). The inhibition could be explained by a competitive mechanism between the B subunit and some autocrine factor binding GM1-containing receptors. Our data strengthen the suggestion to consider gangliosides as very important pleiotropic biomodulators.

Animals↗
PubMed1989

Effect of fluoroquinolones on the in-vitro proliferation of myeloid precursor cells.

The effects of three fluoroquinolones (ofloxacin, pefloxacin and rufloxacin) on the in-vitro proliferation of murine myeloid cells were studied. Their activity was compared with that of nalidixic acid and novobiocin. Therapeutic concentrations of quinolones do not affect the physiological course of myelopoiesis. Only very high concentrations of drug (greater than 70 mg/l) affect bone marrow cell growth producing a dose-dependent inhibition. Because quinolones are active on topoisomerase II from eukaryotic cells they can modulate mammalian cell growth.

Animals↗
PubMed1987

Isolation of a colony-stimulating factor produced by L 1210 murine leukemia cells.

Murine L1210 leukemia cells spontaneously produce very low amounts of colony stimulating factor (CSF). CSF production was markedly increased by stimulating L1210 cells with lipopolysaccharide, lectins, and sheep red blood cells. From the conditioned medium of phytohemagglutinin-stimulated L1210 cells we isolated a CSF with an apparent molecular weight of approximately 27,000. This CSF promoted the proliferation and the differentiation of murine GM-CFU showing a weak differentiation-inducing activity on WEHI-3 D (+) cells.

Animals↗