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Biomedical subjects

A Pascual

Publications and source records attributed to A Pascual.

At least 145 records · Page 8Linked to original sources
PubMed1991

Effect of antimicrobial agents on the uptake of ofloxacin and its optically active isomer (-)-ofloxacin by human polymorphonuclear leucocytes.

The effect of several antimicrobial agents, active against Gram-positive cocci, anaerobes or fungi on the intracellular penetration of ofloxacin and its optically active isomer (-)-ofloxacin into human polymorphonuclear leucocytes (PMNs) was studied. In the presence of therapeutic extracellular concentrations of these drugs, both ofloxacin and (-)-ofloxacin reached high intracellular concentrations (cellular to extracellular ratio (C/E greater than 3). Ofloxacin and (-)-ofloxacin uptake by PMNs was higher when cells were stimulated with opsonized zymosan (C/E greater than 5). It is concluded that none of the antimicrobial agents studied significantly affected the uptake of both quinolones by human PMNs.

Anti-Bacterial Agents↗
PubMed1991

Kinetics of adherence of mucoid and non-mucoid Pseudomonas aeruginosa to plastic catheters.

The adherence of six non-mucoid and three mucoid strains of Pseudomonas aeruginosa to polyvinyl chloride (PVC), polyurethane (PU) and siliconised latex (SL) was evaluated by a radiometric method and scanning electronmicroscopy. Initially greater numbers of mucoid than non-mucoid strains adhered to all three materials. Hydrophobic non-mucoid strains adhered more efficiently than hydrophilic strains. Numbers of adherent non-mucoid P. aeruginosa cells increased with time, reaching a peak, which was different for each strain, at 1-4 h for PU, 4 h-2 days for SL and 2-3 days for PVC; thereafter a gradual decrease was observed, maximal and final values of adherence being higher with PVC and SL than with PU. Adherence of mucoid strains increased with time in 3-5 days, until a steady state was reached. We conclude that although non-mucoid strains of P. aeruginosa initially colonise plastic surfaces better than mucoid strains, mucoid strains also persist on these surfaces.

Bacterial Adhesion↗
PubMed1991

Effect of plastic catheter material on bacterial adherence and viability.

The kinetics of adherence of single isolates of Staphylococcus aureus, S. epidermidis, Pseudomonas aeruginosa and Escherichia coli to catheters made of polyvinyl chloride (PVC), Teflon, siliconised latex, polyurethane and Vialon was evaluated by a radiometric assay. Radiolabelled bacteria (10(8) cfu/ml) were incubated in vials containing 1-cm lengths of catheter for up to 3 days. The peak of maximal adherence to each biomaterial was reached after 24 h for P. aeruginosa and after 72 h for the other strains. Bacterial adherence to PVC and siliconised latex was significantly higher (2-6 times; p less than 0.05) than to the other biomaterials for all the strains. The lowest values of adherence were observed with polyurethane and Vialon for the staphylococci but with Teflon for E. coli and P. aeruginosa. Bacterial viability and growth was evaluated in eluates obtained from incubation of segments of each catheter in buffer for 24 h. None of the eluates affected the viability of the staphylococci. However, all of them, significantly increased the growth of E. coli and P. aeruginosa with the exception of the eluate from siliconised latex, in which the inoculum count was reduced to an undetectable level for E. coli. We conclude that bacterial adherence to catheters may depend in part on the nature of the biomaterial and that certain substances eluted from the catheters may affect the viability and growth of different micro-organisms.

Bacterial Adhesion↗
PubMed1991

Effect of preincubation of Pseudomonas aeruginosa in subinhibitory concentrations of amikacin, ceftazidime and ciprofloxacin on adherence to plastic catheters.

The effect of preincubation of Pseudomonas aeruginosa in subinhibitory concentrations (1/4 x minimum inhibitory concentration) of amikacin, ceftazidime and ciprofloxacin on the expression of surface hydrophobicity and adherence to polyvinyl chloride, siliconized latex and polyurethane was evaluated. None of the antimicrobials significantly altered the expression of surface hydrophobicity. Subinhibitory concentrations of amikacin did not significantly reduce the adherence of P. aeruginosa to any of these 3 biomaterials. A significant inhibition of the adherence of polyvinyl chloride and siliconized latex but not to polyurethane was induced by both ceftazidime (p less than 0.05 to p less than 0.01 in different times) and ciprofloxacin (p less than 0.01). The effect of ceftazidime was present only for the first 4 h of bacteria-biomaterial interaction, whereas that of ciprofloxacin persisted throughout the study period (72 h).

Amikacin↗
PubMed1991

Effect of ampicillin/sulbactam on human polymorphonuclear leukocyte function.

The effect of ampicillin and sulbactam on the interaction in vitro of human polymorphonuclear leukocytes (PMN) with Staphylococcus aureus was examined. The exposure of a non-penicillinase-producing S. aureus strain to one fourth the MIC of ampicillin but not of sulbactam significantly increased the uptake of bacteria by human PMN. This effect was also observed when bacteria were exposed to the MIC0.25 of different combinations of ampicillin and sulbactam (2/1, 1/1, 1/4, 1/8 and 1/32). These effects were not observed when a penicillinase-producing strain was used. The production of superoxide and hydrogen peroxide radicals by human PMN was not affected by the presence of these antimicrobials. Ampicillin and sulbactam, neither alone nor in combination, showed intracellular activity against S. aureus within human PMN.

Ampicillin↗
PubMed1991

[Effect of miocamycin and erythromycin on the activity of human neutrophils against Staphylococcus aureus].

We evaluate the effect of two macrolide drugs (miocamycin and erythromycin) on human neutrophil cells (PMNs) against S. aureus strains. We studied: a) S. aureus pre-treatment effect, using subinhibitory concentrations of the two drugs, on its phagocytosis by human PMN's; b) effect of the drugs on superoxide production by PMN's; c) intracellular activity of the two drugs against S. aureus. Prior treatment of S. aureus with subinhibitory concentrations (25% of the MIC) increases significantly the phagocytosis of opsonized bacteria by human PMN's. Using non-opsonized bacteria, the registered effect was only statistically significant for miocamycin. Pre-incubation of human PMN's with 1, 10 and 25 mg/L concentrations of each drug did not influence superoxide production of the cells. Both drugs showed slight intracellular activity against S. aureus inside human PMN's, although this only achieves statistically significant difference with higher concentrations (25 mg/L) of miocamycin. In summary, both drugs influence directly human PMN's phagocytosis of S. aureus, changing the opsonic requirements of the microorganism. At therapeutic levels, neither erythromycin nor miocamycin hampered phagocytic and bactericidal mechanisms of human PMN's. At higher concentration, miocamycin showed good intracellular activity against S. aureus.

Erythromycin↗
PubMed1991

[Effect of subinhibitory concentrations of beta-lactams on the production of slime, surface hydrophobicity and adhesion of Staphylococcus epidermidis].

The activity of subinhibitory concentrations of oxacillin, imipenem, cefalotin, cefuroxime, cefotaxime and amoxycillin-clavulanic acid upon slime production, surface hydrophobicity and polystyrene adherence of S. epidermidis was evaluated. Slime production and polystyrene adherence of three Staphylococcus epidermidis strains was assessed using test tube (safranin stained film) or in microtiter plate. The surface hydrophobicity was determined using a biphasic system (water/p-xylene). Using one-half and one-quarter of MIC for all antibiotics tested, a reduction in slime production and polystyrene adherence was observed in all three strains used. Regarding surface hydrophobicity, in one of the strains used we have observed a rise in surface hydrophobicity values as compared to control strains whenever one-half of MCI was used for all six antimicrobial agents and also with one-quarter of amoxicillin-clavulanate MCI. Subinhibitory MCI of all six antibiotics tested inhibits slime production and adherence of Staphylococcus epidermidis. This inhibitory effect is not related to changes in surface hydrophobicity.

Anti-Bacterial Agents↗
PubMed1991

[Evaluation of the Mycoscreen technique for the detection and quantification of genital mycoplasmas].

A total of 161 samples from genital sources were evaluated using two different methods for genital Mycoplasma isolation: inoculation to urea broth, arginine broth and A7 solid media (standard method) and a new enzymatic method (Mycoscreen Oxoid). The isolation rates for Ureaplasma urealitycum were 42% (standard method) and 49% (Mycoscreen) (sensitivity: 100%; specificity: 88%). The isolation rates for Mycoplasma hominis were 13% (standard method) and 14% (Mycoscreen) (sensitivity: 80%; specificity: 95%). Using the enzymatic method, manufacturer's positive result is defined as a count greater than 10,000 UCC-ml at 24 hours. When we compare the 24 hours results, the concordance rates was 84% (Ureaplasma urealyticum) and 62% (Mycoplasma hominis). Mycoscreen method is a valid and fast technique for the isolation and identification of genital Mycoplasma. It also allows a fast screening of pathologic counts of Ureaplasma urealyticum in genital exudates.

Bacteriological Techniques↗
PubMed1990

Regulation by butyrate of the cAMP response to cholera toxin and forskolin in pituitary GH1 cells.

In pituitary GH1 cells, a rat growth hormone-producing cell line, butyrate elicited a dose-dependent increase in cholera toxin receptors as measured by an increased binding of 125I-labeled cholera toxin to the intact cells. Butyrate did not alter the affinity of cholera toxin binding, the dissociation constant being 0.4 nM for both control and butyrate-treated cells. Despite the increased binding, the cAMP response to cholera toxin was strongly reduced after exposure to butyrate. This reduction was dose-dependent and with butyrate 1--5 mM, intracellular and extracellular (medium) cAMP levels were decreased by more than 70% in cells incubated for 24 h with 1 nM cholera toxin. Forskolin (30 microM) elicited a cAMP response similar to that found with the toxin, and a similar inhibition of cAMP was also found after incubation of GH1 cells with butyrate. Butyrate also affected basal cAMP levels which were reduced by 40--60% in cells cultured for 24--48 h with the fatty acid. In order to study whether butyrate influenced cAMP synthesis and/or cAMP degradation, adenylyl cyclase and phosphodiesterase activities were determined in control cells and in cells incubated for 24 h with cholera toxin or forskolin. Butyrate had a dual effect since, besides activating phosphodiesterase by more than twofold, it also inhibited the cyclase by 40--50% in all groups. The in vitro response of adenylyl cyclase to stimulatory (NaF) and inhibitory (carbachol and adenosine) effectors was also examined. The absolute activity of the cyclase was always 40--50% lower in the cells incubated with butyrate, but the percentage change of activity obtained in butyrate-treated and untreated cells was unaltered. In addition, ADP-ribosylation of the guanine nucleotide stimulatory component of the cyclase (Gs) was not affected in the cells incubated with butyrate. These results suggest that the catalytic (C) subunit of adenylyl cyclase and/or its interaction with the regulatory components might be altered in butyrate-treated GH1 cells. The inhibition of the cAMP response in GH1 cells was accompanied by an inhibition of a biological action of the nucleotide, namely growth hormone (somatotropin) production which is primarily controlled by thyroid hormones in these cells. Forskolin alone did not affect the somatotropin levels but potentiated the growth hormone response to triiodothyronine. Butyrate produced a dose-dependent inhibition of this response, which was totally abolished at concentrations of butyrate higher than 1 mM.

Adenylyl Cyclases↗
PubMed1990

Regulation of thyroid hormone receptor and c-erbA mRNA levels by butyrate in neuroblastoma (N2A) and glioma (C6) cells.

Butyrate produced a biphasic modulation of the thyroid hormone receptor in neuroblastoma N2A cells increasing receptor number by 20-35% at concentrations 0.25-0.75 mM and decreasing receptor levels by 30-55% at 2-4 mM. The half-life of the receptor, as assessed by its disappearance after incubation with 18 microM cycloheximide was 8.4 hr in control cells and 10.3 hr and 5.0 hr in cells incubated with 0.25 and 4 mM butyrate, respectively. This compound increased the abundance of multyacetylated forms of histone H4 from 30% in control cells to almost 70% with butyrate 4 mM. In glioma C6 cells, the fatty acid produced a dose-dependent increase of receptor levels (up to 3-4-fold with 2-5 mM butyrate) and had little effect in increasing multiacetylation (from 30% in controls to 42-46% with 2-5 mM butyrate). Recent studies have shown that the c-erbA proto-oncogen codes for the thyroid hormone receptor. In N2A and C6 cells, 2 c-erbA-related mRNAs, one measuring 2.6 kb and the other 6 kb, were detected. Both forms were differently regulated by butyrate. This compound decreased the abundance of the 2.6 kb forms in both cell types, even at the concentrations at which there was an elevation of receptor levels. Only the largest mRNA correlated with receptor concentration increasing by 2-3-fold after treatment of C6 cells with butyrate, and undergoing a smaller but biphasic change in N2A cells. Our data suggest that modification of chromatin structure probably secondary to acetylation induces changes in thyroid hormone receptor levels in neuroblastoma and glioma cells by affecting both receptor stability and receptor mRNA levels.

Animals↗
PubMed1990

Effect of plastic catheters on the phagocytic activity of human polymorphonuclear leukocytes.

The effect of five kinds of plastic catheters (polyvinyl chloride, Teflon, polyurethane, Vialon and siliconized latex) on the phagocytic and bactericidal function of human polymorphonuclear leukocytes was evaluated. In the presence of the polyvinyl chloride, Teflon and siliconized latex catheters, superoxide radical production by polymorphonuclear leukocytes was significantly inhibited. The effect of the siliconized latex catheter was presumably mediated by products eluted from the catheter into the medium, since the incubation of polymorphonuclear leukocytes in eluates obtained from the incubation of this catheter in buffer induced a similar inhibitory effect. This phenomenon was not observed with polyurethane or Vialon catheters. Neither the catheters evaluated nor their eluates affected the uptake of opsonized Staphylococcus aureus by human polymorphonuclear leukocytes. It is concluded that the polyvinyl chloride, Teflon and siliconized latex catheters used in this study could impair the respiratory burst of human polymorphonuclear leukocytes.

Catheterization↗
PubMed1990

Effect of three plastic catheters on survival and growth of Pseudomonas aeruginosa.

The effect of polyvinylchloride (PVC), polyurethane (PU) and siliconized latex (SL) catheters on the survival and growth of six non-mucoid and three mucoid strains of Pseudomonas aeruginosa was evaluated. Pseudomonas aeruginosa (1 x 10(8)) was incubated in PBS alone (control) or with 30 1-cm length segments of each catheter and the number of viable microorganisms was determined after 8 h, 1, 2, 5, 7 and 10 days. The presence of PVC catheters significantly favoured the survival and growth of non-mucoid strains in comparison to the control (P less than 0.05 at 5 days, P less than 0.01 at 7 days and thereafter); a similar result was observed with SL catheters (P less than 0.05 at 2 days, P less than 0.01 at 5 days and thereafter). No differences were observed with PU catheters. The number of mucoid microorganisms decreased with time in all controls and suspensions containing segments of catheter, but non-mucoid revertants appeared and quickly increased in the presence of PVC and SL (but not PU) catheters. Eluates of PBS previously containing PVC or SL segments induced a 100- to 500-fold increase in the growth of a non-mucoid strain in comparison with PBS alone. It is concluded that some plastic catheters can release substance(s) that favour the viability of P. aeruginosa.

Bacterial Adhesion↗
PubMed1990

Uptake and intracellular activity of an optically active ofloxacin isomer in human neutrophils and tissue culture cells.

The penetration of an optically active ofloxacin isomer [(-)-ofloxacin] into human neutrophils and different tissue culture cells (HEp-2, McCoy, MDCK, and Vero) was studied and compared with that of ofloxacin by a fluorometric assay. The cellular-to-extracellular-concentration ratios (C/E) of (-)-ofloxacin were always higher than 6, significantly greater than those of ofloxacin at extracellular concentrations of 5 and 10 mg/liter. The penetration of (-)-ofloxacin and ofloxacin was doubled when neutrophils were stimulated by phorbol myristate acetate but not affected after ingestion of opsonized Staphylococcus aureus. The C/E ratios of (-)-ofloxacin and ofloxacin for different tissue culture epithelial cells and fibroblasts were lower than those of neutrophils but still higher than 2. Both compounds produced a significant reduction in viable intraphagocytic S. aureus during 3 h of exposure to antimicrobial agents. We conclude that (-)-ofloxacin appears to reach higher intracellular concentrations than ofloxacin, remaining active inside the neutrophils.

Cells, Cultured↗
PubMed1990

Intratumoral variation of estrogen and progesterone receptors in breast cancer: relationship with histopathological characteristics of the tumor.

Estrogen (ER) and progesterone (PR) receptors were assayed in the center and the periphery of 24 primary breast cancers and correlated with seven morphological features of the tumors. Quantitative variations in ER and PR contents between center and periphery were not significant, and the major discordance rate of the receptor status was only 8.3% for ER and 12.5% for PR. Among all morphological features studied, only tumor cellularity was correlated with steroid receptors; thus 18 out of 19 ER-positive samples (p less than 0.005) and 15 out of 16 PR-positive samples (p less than 0.025) were tumor cellularity 2-3, and higher ER (p less than 0.003) and PR (p less than 0.007) levels were found in tumor cellularity 2-3. Our results indicate that steroid receptors should be assayed in samples with a high content of tumor cellularity, whether the sample is taken from the center or the periphery of the tumor.

Adult↗
PubMed1990

Effect of azithromycin, roxithromycin and erythromycin on human polymorphonuclear leukocyte function against Staphylococcus aureus.

The effect of three macrolides (azithromycin, roxithromycin and erythromycin) on the interaction in vitro of human polymorphonuclear leukocytes (PMNs) with Staphylococcus aureus was examined. The exposure of S. aureus to 0.25 MIC of roxithromycin and erythromycin but not of azithromycin significantly increased the uptake of opsonized bacteria by human PMNs. The preincubation of PMNs with 1, 10 and 25 mg/l of the three antimicrobial agents did not affect either the uptake of S. aureus or the superoxide radical production by human PMNs. At these same concentrations the three agents showed slight but not significant intracellular activity in PMNs against S. aureus. It is concluded that treatment of S. aureus with subinhibitory concentrations of roxithromycin and erythromycin enhanced phagocytosis by PMNs, but the three macrolides tested did not directly affect the functions of human PMNs against S. aureus.

Azithromycin↗