1. We have compared the mechanisms involved in sodium nitroprusside (SNP)-induced relaxation and [Ca2+]i reduction in isolated piglet pulmonary (PA) and mesenteric (MA) arteries. 2. SNP (10(-8) M-3x10(-5) M) evoked a concentration-dependent relaxation of PA and MA (pD2=6.66+/-0.06 and 6.74+/-0.14, respectively) stimulated by noradrenaline, which was markedly reduced by the guanylate cyclase inhibitor ODQ. In fura 2-incubated PA and MA, SNP produced a parallel reduction in contractile force and in [Ca2+]i, expressed as the ratio of emitted fluorescence at 340 and 380 nm (F340/F380). 3. The inhibition of the Na+/K+-ATPase after the incubation in a K+-free medium or the exposure to ouabain (10(-6) M) inhibited SNP-induced relaxation in MA but not in PA. SNP-induced relaxation was not attenuated by 80 mM KCl plus nifedipine (10(-6) M) but was inhibited by thapsigargin (2x10(-6) M; pD2=5.69+/-0.19 and 5.89+/-0.19 for PA and MA, respectively). 4. Pretreatment of PA with thapsigargin and MA with thapsigargin plus ouabain induced a stronger inhibition on the reduction in [Ca2+]i than on the relaxation induced by SNP, indicating the existence of Ca2+-independent mechanisms. 5. The activation of the Na+/K+-ATPase by the addition of KCl after the incubation in a K+-free medium similarly reduced [Ca2+]i in PA and MA, whereas it relaxed with much less efficacy PA than MA. 6. We conclude that SNP reduces [Ca2+]i and causes relaxation through the activation of SERCA in PA and SERCA and Na+/K+-ATPase in MA. However, Ca2+-independent mechanisms also contribute to SNP-induced effects.

Animals↗

PubMed2001

Propafenone modulates potassium channel activities of vascular smooth muscle from rat portal veins.

We have studied the effects of the class Ic antiarrhythmic propafenone on K+ currents in freshly isolated smooth muscle cells from rat portal veins and on the spontaneous contractions in whole tissues. Under Ca2+-free conditions, when cells were clamped at -80 mV (whole-cell configuration) depolarizing steps from -80 to +50 mV induced a family of K+ currents (I(Ktotal)) that mainly comprised the delayed rectifier current [I(K(V))], whereas when held at -10 mV only small-amplitude, noninactivating, currents (I(NI)) were recorded. Propafenone (10 microM) markedly inhibited I(Ktotal), but at potentials positive to +30 mV it also induced a noisy outwardly rectifying current [I(BK(Ca))] that was abolished by iberiotoxin (0.1 microM). Inhibition of I(Ktotal) by propafenone was concentration-dependent (EC50 = 0.059 +/- 0.009 microM). Propafenone also inhibited the transient outward current [I(K(A))] and ATP-sensitive potassium current [I(K(ATP))] induced by levcromakalim (10 microM). Inhibition of I(K(V)), I(K(A)), and I(K(ATP)) by propafenone was voltage-independent. In Ca(2+)-containing conditions propafenone inhibited I(K(V)) and I(BK(Ca)) and immediately abolished spontaneous outward transient K+ currents. In whole veins, propafenone behaved as the K(V) inhibitor 4-aminopyridine, increasing the amplitude and duration of spontaneous contractions. Propafenone also inhibited the inhibitory effects of the K(ATP) channel opener levcromakalim on spontaneous contractions. These results indicate that in vascular smooth muscle cells, propafenone inhibits K(V), K(A), BK(Ca), and K(ATP) channels. These actions correlated with its effects on mechanical activity in whole portal veins.

Animals↗

PubMed2000

[The activity of eight fluoroquinolones versus biolayers of Escherichia coli and Pseudomonas aeruginosa in siliconized latex urinary catheters].

OBJECTIVE: To evaluate the in vitro activity of eight fluoroquinolones against Escherichia coli and Pseudomonas aeruginosa biofilms on siliconized latex urinary catheters. MATERIAL AND METHODS: The MICs and MBCs of norfloxacin, ciprofloxacin, ofloxacin, levofloxacin, clinafloxacin, sparfloxacin, trovafloxacin, and moxifloxacin for two strains of E. coli (CBR-3 and CBR-4) and two strains of P. aeruginosa (HUS-3 and PBR-2) were determined according to the NCCLS guidelines. The susceptibility of bacteria attached to siliconized latex catheters to fluoroquinolones was also evaluated. Catheter segments containing 6 or 24 hours old biofilms were used as inocula for the studies of antimicrobial activity against bacterial biofilms. RESULTS: MICs of ciprofloxacin for planktonic and attached bacteria were equal. MICs values for the others fluoroquinolones increased two or more times when bacterial biofilms were used as inocula, except for ofloxacin and E. coli CBR-4, trovafloxacin and E. coli CBR-3, and levofloxacin and trovafloxacin and P. aeruginosa PBR-4; in these cases the MIC values for planktonic and attached bacteria were similar. When bacteria attached to siliconized latex were used as inocula, MBCs values increased 8-> 4,096-fold for all the fluoroquinolones evaluated. CONCLUSIONS: E. coli and P. aeruginosa biofilms on siliconized latex were more resistant to the bactericidal activity of fluoroquinolones than planktonic bacteria.

Anti-Infective Agents↗

PubMed1999

Distribution of trace metals in different tissues in the rock oyster Crassostrea iridescens: seasonal variation.

Explore the source record for details and available documents.

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 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↗

PubMedDate not supplied

Effect of a siliconized latex urinary catheter on bacterial adherence and human neutrophil activity.

The effect of a siliconized latex urinary catheter on the in vitro adherence and growth of Pseudomonas aeruginosa and Escherichia coli and on the activity of human polymorphonuclear leukocytes (PMNs) was assessed. The adherence of P. aeruginosa to latex catheters was significantly greater than that of E. coli, being 30 times higher at 6 hr of incubation. The survival of E. coli (10(8) CFU/ml) in phosphate-buffered saline (PBS) containing segments of siliconized latex catheters was lower than in the controls. This effect seems to be due to a toxic effect produced by substances eluted into the medium from the catheters, as the viability of E. coli (10(3) CFU/ml) in eluates obtained from the incubation of catheters in PBS (24 hr; 37 degrees C) was significantly lower than in the controls. These phenomena were not observed with P. aeruginosa. The incubation of human PMNs with either catheter segments or eluates did not affect the uptake of opsonized E. coli but significantly decreased the production of superoxide radicals by these phagocytes. It is concluded that the adherence of P. aeruginosa to these catheters is higher than that of E. coli and that the latex urinary catheter used herein elutes substances that are in vitro toxic for E. coli and the oxygen-dependent bactericidal mechanisms of human PMNs.

Bacterial Adhesion↗