P.C. Braga

Lack of opiate receptor involvement in centrally induced calcitonin analgesia

Abstract Calcitonin (CT) injected into the brain ventricles (ICV) of conscious rabbits induced an analgesia not reversable by naloxone which could be repeatedly elicited (for 5 days), while tolerance to morphine developed. CT and morphine synergized in vivo when administered ICV in combination. CT did not alter electrically-induced contractions of guinea-pig myenteric plexus-longitudinal muscle and no displace of 3 H-dihydromorphine by CT was observed in brain opiate receptor preparations. We have concluded that the mechanism of centrally induced CT analgesia may be opiate-independent.

Inhibitory activity of thymol against the formation and viability of Candida albicans hyphae.

As the capacity of Candida albicans to produce hyphae is considered an important virulence factor in the pathogenesis of candiasis, the aim of this study was to investigate whether thymol, the major component of thyme oil, can interfere with the filamentous forms of Candida albicans and their viability. The morphological transition from yeasts to filamentous forms was investigated by analysing the morphological index (MI), which classifies the differentiated forms and blastoconidia; viability was investigated by means of fluorescence microscopy using a new SYTO‐9 and propidium iodide method previously used to stain only blastoconidia. Without thymol, there was an average of 94.00 ± 3.06% hyphal forms. After 6 h of incubation with 1x MIC (125 μg ml−1), 1/2x MIC and 1/4x MIC of thymol, filamentation was, respectively, 14.33 ± 8.25%, 28.33 ± 7.17% and 45.67 ± 8.09% in comparison with control (all statistically significant). In the absence of thymol, viable cells accounted for an average of 93.00 ± 4.00% whereas, after 6 h of incubation with 1x MIC, 1/2x MIC and 1/4x MIC of thymol, the presence of 54.33 ± 1.86%, 29.00 ± 3.61% and 23.00 ± 2.52% of yellow–orange coloured forms indicated damaged membranes and reduced viability. Our findings show that thymol interferes with the formation and viability of hyphae. This can be attributed to the characteristics of thymol disturbing Candida cell membranes and metabolism, probably by affecting fungal cell‐wall synthesising enzymes.

Decreased antinociceptive effect of morphine in rats treated intraventricularly with prostaglandin E1

The administration of prostaglandin E1 intracerebrally through a cannula implanted in a lateral ventricle, antagonizes morphine analgesia in rats.An electrical stimulation technique was adopted on the rats tail to measure the antinociceptive activity of morphine. Some hypotheses are advanced in order to explain the sensitizing activity of prostaglandin E1.

Antioxidant activity of bisabolol: inhibitory effects on chemiluminescence of human neutrophil bursts and cell-free systems.

Human polymorphonuclear neutrophils (PMN), reactive oxygen species (ROS) and inflammatory reactions are closely interrelated, and increasing attention is being given to the search for new synthetic or natural antioxidant agents, capable of reducing ROS and consequent inflammation. It has been claimed that bisabolol (a monocyclic sesquiterpene alcohol) has an antioxidant/anti-inflammatory activity, but this has almost exclusively been investigated using chemical or biochemical tests. We studied the ability of bisabolol to interfere with ROS production (luminol-amplified chemiluminescence, LACL) during human PMN respiratory bursts induced by both corpusculate(Candida albicans)and soluble stimulants (N-formyl-methionyl-leucyl-phenylalanine, fMLP). LACL was also used to test cell-free systems (SIN-1 and H2O2/HOCl– systems) in order to investigate the presence of scavenging activity. After C. albicans stimulation, significant concentration-dependent LACL inhibition was observed at bisabolol concentrations ranging from 7.7 to 31 μg/ml; after the fMLP stimulus, significant LACL inhibition was observed at bisabolol concentrations ranging from 3.8 to 31 μg/ml. A similar effect was observed in the SIN-1 and H2O2/HOCl– systems. These findings draw the attention to the possible medical use of bisabolol as a means of improving the antioxidant network and restoring the redox balance by antagonising oxidative stress.

Antioxidant Activity of Calendula officinalis Extract: Inhibitory Effects on Chemiluminescence of Human Neutrophil Bursts and Electron Paramagnetic Resonance Spectroscopy

There is growing interest in natural chemical compounds from aromatic, spicy, medicinal and other plants with antioxidant properties in order to find new sources of compounds inactivating free radicals generated by metabolic pathways within body tissue and cells, mainly polymorphonuclear leukocytes (PMNs) whose overregulated recruitment and activation generate a large amount of reactive oxygen species (ROS) and reactive nitrogen species (RNS), leading to an imbalance of redox homeostasis and oxidative stress. The aim of this study was to examine whether a propylene glycol extract of Calendula officinalis interferes with ROS and RNS during the PMN respiratory bursts, and to establish the lowest concentration at which it still exerts antioxidant activity by means of luminol-amplified chemiluminescence. Electron paramagnetic resonance (EPR) spectroscopy was also used in order to confirm the activity of the C. officinalis extract. The C. officinalis extract exerted its anti-ROS and anti-RNS activity in a concentration-dependent manner, with significant effects being observed at even very low concentrations: 0.20 μg/ml without L-arginine, 0.10 μg/ml when L-arginine was added to the test with phorbol 12-myristate 13-acetate and 0.05 μg/ml when it was added to the test with N-formyl-methionyl-leucyl-phenylalanine. The EPR study confirmed these findings, 0.20 μg/ml being the lowest concentration of C. officinalis extract that significantly reduced 2,2-diphenyl-1-picrylhydrazyl. These findings are interesting for improving the antioxidant network and restoring the redox balance in human cells with plant-derived molecules as well as extending the possibility of antagonizing the oxidative stress generated in living organisms when the balance is in favor of free radicals as a result of the depletion of cell antioxidants.

Inhibitory Effects of Metabolite I of Erdosteine on the Generation of Nitric Oxide and Peroxynitrite Chemiluminescence by Human Neutrophils

Polymorphonuclear neutrophils (PMNs) can generate superoxide anions and nitric oxide (NO), which is not only an important mediator of various cellular activities, but can also react with superoxide anions to produce peroxynitrite anions (ONOO–). Peroxynitrite is a potent and potentially toxic oxidant that damages various types of biomolecules. It preferentially mediates the oxidation of thiolic groups in protein and non-protein molecules, thus altering their functions. The aim of this study was to examine whether, in addition to its ability to reduce the respiratory bursts of human PMNs, the SH metabolite I (Met I) of erdosteine, can interfere with NO and NO-derived peroxynitrite production, thus extending its antioxidant activity. This was done by means of the luminol amplified chemiluminescence (LACL), which has been widely used to detect the production of reactive oxidant species (ROS) by PMNs under various conditions. At 5 and 10 µg/ml, Met I significantly reduced LACL after fMLP and PMA stimulation. When L-Arg was added to the reaction medium, as a NO donor, the chemiluminescence of fMLP increased by up to 67% and that of PMA by up to 132%, but was once again significantly reduced by 5 and 10 µg/ml of Met I. In a cell-free system, the use of linsidomine (SIN-1) makes it possible to investigate the behavior of LACL induced by peroxynitrite release, which was significantly reduced by Met I concentrations ranging from 1.25 to 10 µg/ml. Our findings indicate that Met I, a molecule with a SH group, reacts with ROS, NO and NO-derived peroxynitrite, and has both antioxidant and scavenging activity. This is of interest for the strategy of protecting against damage induced by radical species in the pulmonary cell environment, in which they can induce a phlogogenic loop, and suggests that adding exogenous thiols may be useful in antagonizing the toxic effects of reactive molecules on endogenous thiols.

Therapies in development for community-acquired pneumonia

The current use of antimicrobials has become more complex due to the extensive emergence of antibiotic resistance. The single most important approach in resistance control is probably the judicious use of chemotherapeutic agents. New agents that may be of use in the treatment of community-acquired pneumonia are currently in development. Antimicrobials can be grouped according to their mechanism of action. These include protein synthesis inhibitors (ketolides, oxazolidinones, streptogramins and glycylcyclines), nucleic acid synthesis inhibitors (fluoroquinolones), peptidoglycan synthesis inhibitors (β-lactams and glycopeptides) and agents interfering with membrane function (cationic peptides and lipopeptides). Among those agents under development, only the oxazolidinones, the cationic peptides and the lipopeptide antibiotics can be truly regarded as structurally novel inhibitors as the other agents are analogues of existing compounds which have been in clinical use for many years.

The in vitro effects of ceftibuten on the host defense mechanism

The in vitro effects of ceftibuten on human polymorphonuclear leukocyte (PMN) chemotaxis, phagocytosis and chemiluminescence were investigated. PMN from healthy adult donors were incubated for 1 h in medium alone or in medium containing increasing concentrations of ceftibuten (4, 8 and 40 times the MIC for Escherichia coli). Up to 40 MIC ceftibuten did not significantly interfere with the function of PMN.

Staphylococcus aureus and Escherichia coli adhesion to human cells is reduced by sub-MICs of gemifloxacin

Abstract This study was designed to investigate the capacity of subinhibitory concentrations of the newly developed fluoroquinolone antibiotic gemifloxacin to interfere with the mechanism of bacterial adhesion. Human buccal epithelial cells were incubated with Staphylococcus aureus and Escherichia coli, and grown in the presence of serial dilutions of gemifloxacin from 1/2 MIC to 1/128 MIC. A significant decrease in the adhesion of both S. aureus and E. coli was observed from 1/2 MIC to 1/32 MIC. Morphological changes including filamentous forms of E.coli and cluster formation and swelling of S. aureus were also observed, mainly from 1/2 MIC to 1/8 and 1/16 MIC. These findings are discussed in terms of dose-effect relationships and the interpolation of this pharmacodynamic data with the pharmacokinetics curve of gemifloxacin.

Influence of Brodimoprim on Polymorphonuclear Leukocyte Phagocytosis and Oxidant Radical Production

Antibiotics not only reach the site of infection, but also penetrate cyclically, during a treatment, into polymorphonuclear leukocytes (PMNs) and may influence their functions positively or negatively. With reference to these aspects, the influence of brodimoprim (BMP), a dimethoxybenzylpyrimidine recently entered into clinical use, on human PMN phagocytosis and oxidant radical production (chemiluminescence) was investigated. PMNs from healthy adult donors were incubated for 50 min in medium alone or in medium containing increasing concentrations (3.7, 7.5, 15, and 30 micrograms/ml) of BMP and trimethoprim (TMP). In unwashed PMNs, phagocytosis was not modified by BMP, but was significantly reduced by 30 micrograms/ml TMP; chemiluminescence was significantly reduced by 15 and 30 micrograms/ml BMP and by all concentrations of TMP. When PMNs were washed after incubation, phagocytosis was unaffected and chemiluminescence was significantly restored. BMP at therapeutic concentrations did not influence PMNs and was less toxic than TMP.