Differential effects of inhibitors of cyclooxygenase (cyclooxygenase 1 and cyclooxygenase 2) in acute inflammation

The anti-inflammatory activity of drugs more selective for cyclooxgenase isoform inhibition (cyclooxygenase 1, cyclooxygenase 2), were compared in rat carrageenin-induced pleurisy. Suppression of inflammation by cyclooxygenase 2-selective inhibitors, NS-398 (N-[-2-cyclohexyloxy]-4-nitrophenyl methanesulphonamide) and nimesulide (4-nitro-2-phenoxy-methanesulfonanilide), and by piroxicam and aspirin, more selective for cyclooxygenase 1, was measured. Piroxicam and aspirin significantly inhibited inflammatory cell influx, exudate and prostaglandin E2 formation, 6 h after carrageenin injection. Cyclooxygenase 2 inhibitors had little effect on these parameters with NS-398 alone reducing prostaglandin E2 levels, but increasing levels of leukotriene B4. In contrast, at 3 h after carrageenin injection, cyclooxygenase 2 inhibitors significantly inhibited all inflammatory parameters however suppression with piroxicam and aspirin was greater, and more pronounced than at 6 h. NS-398 and nimesulide dosing did not reduce thromboxane B2 production from platelets isolated from rats with carrageenin-induced pleurisy, demonstrating that at the doses used, cyclooxygenase 2 inhibitors did not inhibit cyclooxygenase 1, as platelets contain only this isoform. Therefore, in the rat carrageenin-induced pleurisy, drugs more selective for the inhibition of cyclooxygenase 1 attenuate inflammation over a wider time frame than cyclooxygenase 2-selective drugs, suggesting a significant role for cyclooxygenase 1 in this model. Inhibition of cyclooxygenase 2 by NS-398 however, resulted in an increase in the potent chemoattractant leukotriene B4.     

Antiasthmatic activity of the second-generation phosphodiesterase 4 (PDE4) inhibitor SB 207499 (Ariflo) in the guinea pig

We evaluated the airway activity of the novel phosphodiesterase type 4 inhibitor SB 207499 [Ariflo; c-4-cyano-4-(3-cyclopentyloxy-4-methoxyp henyl-r-1-cyclohexane carboxylic acid)], in the guinea pig. Ovalbumin (OA)-induced contractions of guinea pig isolated tracheal strips were inhibited by SB 207499 with an EC50 of 1 microM but had little or no effect on exogenous agonist-induced contraction, which suggests that its effect on OA-induced contraction in vitro is primarily due to inhibition of mediator release from mast cells. In anesthetized guinea pigs, SB 207499 inhibited OA-induced bronchoconstriction with i.v. and p.o. ID50 values of 1.7 and 17 mg/kg, respectively. At 1, 3 and 6 hr after SB 207499 (30 mg/kg p.o.), OA-induced bronchospasm was inhibited by 92%, 70% and 58%, respectively, corresponding to elevated plasma concentrations of 1.62 +/- 0.19, 1.65 +/- 0.29 and 0. 93 +/- 0.24 microg/ml, respectively, of SB 207499. SB 207499 also inhibited house dust mite-induced bronchoconstriction (ID50 = 0.9 mg/kg i.v. and 8.9 mg/kg p.o.). In contrast to its lack of bronchorelaxant activity in vitro, SB 207499 inhibited bronchospasm induced by i.v. leukotriene D4 (LTD4) [ID50 = 3 mg/kg i.v.]. The bronchorelaxant effect of i.v.-administered SB 207499 was at least additive with that of salbutamol in reversing infused histamine-enhanced airway tone, but it did not alter base line or enhance salbutamol-induced cardiovascular effects. In conscious guinea pigs, SB 207499 (10 or 30 mg/kg p.o.), 1 hr before antigen or LTD4 challenge, markedly reduced bronchospasm and subsequent eosinophil influx as measured by bronchoalveolar lavage 24 hr after provocation. SB 207499 administered after OA or LTD4 challenge also reduced airway eosinophilia measured at 24 hr after OA challenge or 96 hr after LTD4 challenge. These results, coupled with the broad anti-inflammatory activity of SB 207499 previously described (Barnett et al., 1998), suggest that SB 207499 will be useful in the treatment of asthma and other inflammatory disorders.     

Factors associated with suicide attempts among patients with schizophrenia

This study explored the association between psychosocial variables and symptoms among patients with schizophrenia-spectrum disorders who have attempted suicide and those who have not attempted suicide. Of 336 patients with a DSM-III-R diagnosis of schizophrenia or schizoaffective disorder who were consecutively evaluated at a university-affiliated clinical research center, 98, or 29.2 percent, reported one or more suicide attempts. Compared with patients who had not attempted suicide, patients who had made an attempt had a greater number of lifetime depressive episodes, an earlier age of onset of their illness, and an earlier age at first hospitalization.     

Efficacy of clindamycin hydrochloride capsules for the treatment of deep pyoderma due to Staphylococcus intermedius infection in dogs

Clindamycin hydrochloride capsules (11 mg/kg body weight, q24 h) were administered orally to 20 dogs with deep staphylococcal pyoderma. Response to therapy was excellent in 100% of the dogs. Duration of therapy varied from 21 to 91 d, with an average duration of 45 d. Relapses occurred in 25% of the dogs within a 3-month period. One dog vomited when the clindamycin was given on an empty stomach. Under the conditions of the study, clindamycin was an effective, safe, and convenient antibiotic for the treatment of deep staphylococcal pyoderma in dogs.     

Development of orally active oxytocin antagonists: studies on 1-(1-[4-[1-(2-methyl-1-oxidopyridin-3-ylmethyl)piperidin-4-yloxy]-2- methoxybenzoyl]piperidin-4-yl)-1,4-dihydrobenz[d][1,3]oxazin-2-one (L-372,662) and related pyridines

The previously reported oxytocin antagonist L-371,257 (2) has been modified at its acetylpiperidine terminus to incorporate various pyridine N-oxide groups. This modification has led to the identification of compounds with improved pharmacokinetics and excellent oral bioavailability. The pyridine N-oxide series is exemplified by L-372,662 (30), which possessed good potency in vitro (Ki = 4.1 nM, cloned human oxytocin receptor) and in vivo (intravenous AD50 = 0.71 mg/kg in the rat), excellent oral bioavailability (90% in the rat, 96% in the dog), good aqueous solubility (>8.5 mg/mL at pH 5.2) which should facilitate formulation for iv administration, and excellent selectivity against the human arginine vasopressin receptors. Incorporation of a 5-fluoro substituent on the central benzoyl ring of this class of oxytocin antagonists enhanced in vitro and in vivo potency but was detrimental to the pharmacokinetic profiles of these compounds. Although lipophilic substitution around the pyridine ring of compound 30 gave higher affinity in vitro, such substituents were a metabolic liability and caused shortfalls in vivo. Two approaches to prevent this metabolism, addition of a cyclic constraint and incorporation of trifluoromethyl groups, were examined. The former approach was ineffective because of metabolic hydroxylation on the constrained ring system, whereas the latter showed improvement in plasma pharmacokinetics in some cases.     

Synchronous period-doubling in flicker vision of salamander and man

Periodic flashes of light have long served to probe the temporal properties of the visual system. Here we show that during rapid flicker of high contrast and intensity the eye reports to the brain only every other flash of light. In this regime, retinal ganglion cells of the salamander fire spikes on alternating flashes. Neurons across the entire retina are locked to the same flashes. The effect depends sharply on contrast and flash frequency. It results from a period-doubling bifurcation in retinal processing, and a simple model of nonlinear feedback reproduces the phenomenon. Pharmacological studies indicate that the critical feedback interactions require only cone photoreceptors and bipolar cells. Analogous period-doubling is observed in the human visual system. Under bright full-field flicker, the electroretinogram (ERG) shows a regime of period-doubling between 30 and 70 Hz. In visual evoked potentials from the occiput, the subharmonic component is even stronger. By analyzing the accompanying perceptual effects, we find that retinal period-doubling begins in the periphery of the visual field, and that it is the cause of a long mysterious illusory flicker pattern.     

Increased density of microtubule associated protein 2-immunoreactive neurons in the prefrontal white matter of schizophrenic subjects

Recent studies have suggested that schizophrenia may be related to prenatal disturbances in the cortical subplate, a transient but essential structure in the formation of cerebral cortical circuitry. Although most subplate neurons die during later development, some remain as the interstitial neurons of the adult white matter. In this study we used a monoclonal antibody against the cytoskeletal protein, microtubule associated protein-2 (MAP2), to quantify the density and distribution of labeled neurons in postmortem brain specimens containing the prefrontal white matter from five schizophrenic cases and matched controls. In both schizophrenics and matched controls, the density of white matter neurons decreased with increasing white matter depth. However, the mean density of MAP2-immunoreactive neurons was greater in the superficial white matter of the schizophrenic subjects compared to the matched controls. In contrast, no difference in the density of labeled neurons was seen in the deeper white matter. These findings are consistent with an abnormality in the development of the cortical subplate in at least some cases of schizophrenia.     

Characteristics of cation binding to the I domains of LFA-1 and MAC-1. The LFA-1 I domain contains a Ca2+-binding site

The crystal structures of the I domains of integrins MAC-1 (alphaM beta2; CD11b/CD18) and LFA-1 (alphaL beta2; CD11a/CD18) show that a single conserved cation-binding site is present in each protein. Purified recombinant I domains have intrinsic ligand binding activity, and in several systems this interaction has been demonstrated to be cation-dependent. It has been proposed that the I domain cation-binding site represents a general metal ion-dependent adhesion motif utilized for binding protein ligands. Here we show that the purified recombinant I domain of LFA-1 (alphaLI) binds cations, but with significantly different characteristics compared with the I domain of MAC-1 (alphaMI). Both alphaLI and alphaMI bind 54Mn2+ in a conformation-dependent manner, and in general, cations with charge and size characteristics similar to Mn2+ most effectively inhibit 54Mn2+ binding. Surprisingly, however, physiological levels of Ca2+ (1-2 mM) inhibited 54Mn2+ binding to purified alphaLI, but not to alphaMI. Using 45Ca2+ and 54Mn2+ in direct binding studies, the dissociation constants (KD) for the interactions between these cations and alphaLI were estimated to be 5-6 x 10(-5) and 1-2 x 10(-5) M, respectively. Together with the available structural information, the data suggest differential affinities for Mn2+ and Ca2+ binding to the single conserved site within alphaLI. Antagonism of LFA-1, but not MAC-1, -mediated cell adhesion by Ca2+ may be related to the Ca2+ binding activity of the LFA-1 I domain.