Modulation of acute and chronic inflammatory processes by cacospongionolide B, a novel inhibitor of human synovial phospholipase A2. (1/742)

1. Cacospongionolide B is a novel marine metabolite isolated from the sponge Fasciospongia cavernosa. In in vitro studies, this compound inhibited phospholipase A2 (PLA2), showing selectivity for secretory PLA2 (sPLA2) versus cytosolic PLA2 (cPLA2), and its potency on the human synovial enzyme (group II) was similar to that of manoalide. 2. This activity was confirmed in vivo in the 8 h zymosan-injected rat air pouch, on the secretory enzyme accumulating in the pouch exudate. Cacospongionolide B, that is bioavailable when is given orally, reduced the elevated levels of sPLA2 present in paw homogenates of rats with adjuvant arthritis. 3. This marine metabolite showed topical anti-inflammatory activity on the mouse ear oedema induced by 12-O-tetradecanoylphorbol acetate (TPA) and decreased carrageenin paw oedema in mice after oral administration of 5, 10 or 20 mg kg(-1). 4. In the mouse air pouch injected with zymosan, cacospongionolide B administered into the pouch, induced a dose-dependent reduction in the levels of eicosanoids and tumour necrosis factor alpha (TNFalpha) in the exudates 4 h after the stimulus. It also had a weak effect on cell migration. 5. The inflammatory response of adjuvant arthritis was reduced by cacospongionolide B, which did not significantly affect eicosanoid levels in serum, paw or stomach homogenates and did not induce toxic effects. 6 Cacospongionolide B is a new inhibitor of sPLA2 in vitro and in vivo, with anti-inflammatory properties in acute and chronic inflammation. This marine metabolite was active after oral administration and able to modify TNFalpha levels, and may offer an interesting approach in the search for new anti-inflammatory agents.  (+info)

Effects of praeruptorine C on the intracellular free calcium in normal and hypertrophied rat ventricular myocytes. (2/742)

AIM: To study the intracellular free calcium ([Ca2+]i) in normal and hypertrophic left ventricular myocytes isolated from adult rat hearts and the effects of praeruptorine C (Pra-C) on them. METHODS: [Ca2+]i of single myocyte was measured with Fura 2-AM. RESULTS: The resting [Ca2+]i was 87 +/- 4 nmol.L-1 in normal left ventricular myocytes, 123 +/- 7 nmol.L-1 in hypertrophied myocytes. After exposure to KCl (20, 40, and 60 mmol.L-1), the [Ca2+]i were increased by 66%, 141%, and 268% in normal myocytes, and 77%, 185%, and 243% in hypertrophic myocytes, respectively. Pra-C (1, 10, and 100 mumol.L-1) concentration-dependently inhibited the [Ca2+]i elevation caused by KCl (35 mmol.L-1) or norepinephrine (20 mumol.L-1) in both normal and hypertrophied myocytes. All of the effects of Pra-C were similar to that of nifedipine. CONCLUSION: [Ca2+]i of hypertrophied myocytes was higher than that of normal ones and Pra-C decrease the [Ca2+]i elevation in left ventricular myocytes resulted from its calcium channel blockade.  (+info)

Salinomycin-induced polyneuropathy in cats: morphologic and epidemiologic data. (3/742)

In April 1996, an outbreak of toxic polyneuropathy in cats occurred in the Netherlands. All cats had been fed one of two brands of dry cat food from one manufacturer. Chemical analyses of these foods, stomach contents, and liver and kidney of affected cats revealed contamination with the ionophor salinomycin. Epidemiologic and clinical data were collected from 823 cats, or about 1% of the cats at risk. In 21 affected cats, postmortem examination was performed. The affected cats had acute onset of lameness and paralysis of the hindlimbs followed by the forelimbs. Clinical and pathologic examination indicated a distal polyneuropathy involving both the sensory and motor nerves.  (+info)

New actin mutants allow further characterization of the nucleotide binding cleft and drug binding sites. (4/742)

We have generated 9 site-specific mutations in Saccharomyces cerevisiae actin. These mutants display a variety of phenotypes when expressed in vivo, including slow actin filament turnover, slow fluid-phase endocytosis, and defects in actin organization. Actin mutation D157E confers resistance to the actin-sequestering drug, latrunculin A. Latrunculin A inhibits nucleotide exchange on wild-type yeast actin but not on D157E actin, suggesting that this residue is part of the latrunculin A binding site. We have refined our earlier map of the phalloidin binding site on actin, demonstrating a requirement for residue G158 in addition to D179 and R177. The nine new actin mutants as well as a large collection of existing actin mutants were also used to identify the putative binding site of another actin binding drug, tolytoxin, on actin. The actin alleles that result in decreased sensitivity to this drug cluster at a site near the nucleotide-binding pocket. Actin purified from one of these mutants has a reduced affinity for tolytoxin. In addition, tolytoxin causes a 2.4-fold increase in the t1/2 of ATP exchange, further suggesting that this drug binds near the nucleotide-binding pocket of actin. We note that the binding sites for latrunculin A, phalloidin, and tolytoxin all map close to the actin nucleotide binding pocket.  (+info)

Reactivity of Cl-P(+)-Cl toward cyclic organic ethers. (5/742)

The dichlorophosphenium ion (Cl-P(+)-Cl) undergoes a variety of reactions with cyclic organic ethers in the gas phase in a Fourier-transform ion cyclotron resonance mass spectrometer. Most of the reactions are initiated by Cl-P(+)-Cl-induced heterolytic C-O bond cleavage. However, the observed final products depend on the exact structure of the ether. For saturated ethers, e.g., tetrahydropyran, tetrahydrofuran, and 2-methyltetrahydrofuran, the most abundant ionic product corresponds to hydroxide abstraction by Cl-P(+)-Cl. This unexpected reaction is rationalized by a multistep mechanism that involves an initial heterolytic C-O bond cleavage accompanied by a 1,2-hydride shift, and that ultimately yields a resonance-stabilized allyl cation and HOPCl2. The process is estimated to be highly exothermic (AM1 calculations yield delta H = -(33-38) kcal mol(-1) for the ethers mentioned above). However, the adducts formed from most of the unsaturated ethers are unable to undergo hydride shifts and hence cannot react via this pathway. In some of these cases, e.g., for 2,5-dihydrofuran and 2,5-dihydro-3,4-benzofuran, the C-O bond heterolysis is followed by oxygen/chlorine exchange to yield the O=PCl radical and a resonance-stabilized carbocation (AM1 calculations yield delta H = -14 kcal mol(-1) for the reaction of 2,5-dihydro-3,4-benzofuran). Hydride abstraction by Cl-P(+)-Cl also yields an abundant product for these two ethers. On the other hand, the ethers with low ionization energies, such as 2,3-dihydrofuran and 2,3-dihydrobenzofuran, react with Cl-P(+)-Cl by electron transfer. Finally, a unique pathway, addition followed by elimination of HCl, dominates the reaction with furan. The observed reactions are rationalized by thermochemical data obtained from semiempirical molecular orbital calculations.  (+info)

Vimentin dephosphorylation by protein phosphatase 2A is modulated by the targeting subunit B55. (6/742)

The intermediate filament protein vimentin is a major phosphoprotein in mammalian fibroblasts, and reversible phosphorylation plays a key role in its dynamic rearrangement. Selective inhibition of type 2A but not type 1 protein phosphatases led to hyperphosphorylation and concomitant disassembly of vimentin, characterized by a collapse into bundles around the nucleus. We have analyzed the potential role of one of the major protein phosphatase 2A (PP2A) regulatory subunits, B55, in vimentin dephosphorylation. In mammalian fibroblasts, B55 protein was distributed ubiquitously throughout the cytoplasm with a fraction associated to vimentin. Specific depletion of B55 in living cells by antisense B55 RNA was accompanied by disassembly and increased phosphorylation of vimentin, as when type 2A phosphatases were inhibited using okadaic acid. The presence of B55 was a prerequisite for PP2A to efficiently dephosphorylate vimentin in vitro or to induce filament reassembly in situ. Both biochemical fractionation and immunofluorescence analysis of detergent-extracted cells revealed that fractions of PP2Ac, PR65, and B55 were tightly associated with vimentin. Furthermore, vimentin-associated PP2A catalytic subunit was displaced in B55-depleted cells. Taken together these data show that, in mammalian fibroblasts, the intermediate filament protein vimentin is dephosphorylated by PP2A, an event targeted by B55.  (+info)

Safety and efficacy of intravenous zanamivir in preventing experimental human influenza A virus infection. (7/742)

Zanamivir is a potent inhibitor of influenza A and B virus neuraminidases and is active topically in experimental and natural human influenza. We conducted this double-blinded, placebo-controlled study to evaluate the safety and efficacy of intravenously administered zanamivir. Susceptible volunteers were randomized to receive either saline or zanamivir (600 mg) intravenously twice daily for 5 days beginning 4 h prior to intranasal inoculation with approximately 10(5) 50% tissue culture infectious doses (TCID50) of influenza A/Texas/36/91 (H1N1) virus. Reductions in the frequency of viral shedding (0% versus 100% in placebo, P < 0.005) and seroconversion (14% versus 100% in placebo, P < 0.005) and decreases in viral titer areas under the curve (0 versus 11.6 [median] log10 TCID50. day/ml in placebo, P < 0.005) were observed in the zanamivir group, as were reductions in fever (14% versus 88% in placebo, P < 0.05), upper respiratory tract illness (0% versus 100% in placebo, P < 0.005), total symptom scores (1 versus 44 [median] in placebo, P < 0.005), and nasal-discharge weight (3.9 g versus 17.5 g [median] in placebo, P < 0.005). Zanamivir was detectable in nasal lavage samples collected on days 2 and 4 (unadjusted median concentrations, 10.5 and 12.0 ng/ml of nasal wash, respectively). This study demonstrates that intravenously administered zanamivir is distributed to the respiratory mucosa and is protective against infection and illness following experimental human influenza A virus inoculation.  (+info)

Efficacy and safety of the neuraminidase inhibitor zanamivirin the treatment of influenza A and B virus infections. (8/742)

The efficacy and safety of zanamivir, administered 2x or 4x daily over 5 days, was evaluated in the treatment of influenza infections. A total of 1256 patients entered the study; 57% of those randomized had laboratory-confirmed influenza infection. The primary end point, "alleviation of major symptoms," was created to evaluate differences in clinical impact. In the overall population with or without influenza infection, zanamivir reduced the median number of days to reach this end point by 1 day (P=.012 2x daily vs. placebo; P=.014 4x daily vs. placebo). The reduction was greater in patients treated within 30 h of symptom onset, febrile at study entry, and in defined high-risk groups. Zanamivir reduced nights of disturbed sleep, time to resumption of normal activities, and use of symptom relief medications. It was well tolerated. These results suggest that zanamivir can significantly reduce the duration and overall symptomatic effect of influenza.  (+info)