Role of human liver cytochrome P4503A in the metabolism of etoricoxib, a novel cyclooxygenase-2 selective inhibitor

Etoricoxib, a potent and selective cyclooxygenase-2 inhibitor, was shown to be metabolized via 6'-methylhydroxylation (M2 formation) when incubated with NADPH-fortified human liver microsomes. In agreement with in vivo data, 1'-N'-oxidation was a relatively minor pathway. Over the etoricoxib concentration range studied (1-1300 microM), the rate of hydroxylation conformed to saturable Michaelis-Menten kinetics (apparent K(m) = 186 +/- 84.3 microM; V(max) = 0.76 +/- 0.45 nmol/min/mg of protein; mean +/- S.D., n = 3 livers) and yielded a V(max)/K(m) ratio of 2.4 to 7.3 microl/min/mg. This in vitro V(max)/K(m) ratio was scaled, with respect to yield of liver microsomal protein and liver weight, to obtain estimates of M2 formation clearance (3.1-9.7 ml/min/kg of b.wt.) that agreed favorably with in vivo results (8.3 ml/min/kg of b.wt.) following i.v. administration of [(14)C]etoricoxib to healthy male subjects. Cytochrome P450 (P450) reaction phenotyping studies-using P450 form selective chemical inhibitors, immunoinhibitory antibodies, recombinant P450s, and correlation analysis with microsomes prepared from a bank of human livers-revealed that the 6'-methyl hydroxylation of etoricoxib was catalyzed largely (approximately 60%) by member(s) of the CYP3A subfamily. By comparison, CYP2C9 (approximately 10%), CYP2D6 (approximately 10%), CYP1A2 (approximately 10%), and possibly CYP2C19 played an ancillary role. Moreover, etoricoxib (0.1-100 microM) was found to be a relatively weak inhibitor (IC(50) > 100 microM) of multiple P450s (CYP1A2, CYP2D6, CYP3A, CYP2E1, CYP2C9, and CYP2C19) in human liver microsomes.

Persistent sodium channel activity mediates subthreshold membrane potential oscillations and low-threshold spikes in rat entorhinal cortex layer V neurons

Entorhinal cortex layer V occupies a critical position in temporal lobe circuitry since, on the one hand, it serves as the main conduit for the flow of information out of the hippocampal formation back to the neocortex and, on the other, it closes a hippocampal-entorhinal loop by projecting upon the superficial cell layers that give rise to the perforant path. Recent in vitro electrophysiological studies have shown that rat entorhinal cortex layer V cells are endowed with the ability to generate subthreshold oscillations and all-or-none, low-threshold depolarizing potentials. In the present study, by applying current-clamp, voltage-clamp and single-channel recording techniques in rat slices and dissociated neurons, we investigated whether entorhinal cortex layer V cells express a persistent sodium current and sustained sodium channel activity to evaluate the contribution of this activity to the subthreshold behavior of the cells. Sharp-electrode recording in slices demonstrated that layer V cells display tetrodotoxin-sensitive inward rectification in the depolarizing direction, suggesting that a persistent sodium current is present in the cells. Subthreshold oscillations and low-threshold regenerative events were also abolished by tetrodotoxin, suggesting that their generation also requires the activation of such a low-threshold sodium current. The presence of a persistent sodium current was confirmed in whole-cell voltage-clamp experiments, which revealed that its activation "threshold" was negative by about 10mV to that of the transient sodium current. Furthermore, stationary noise analysis and cell-attached, patch-clamp recordings indicated that whole-cell persistent sodium currents were mediated by persistent sodium channel activity, consisting of relatively high-conductance ( approximately 18pS) sustained openings. The presence of a persistent sodium current in entorhinal cortex layer V cells can cause the generation of oscillatory behavior, bursting activity and sustained discharge; this might be implicated in the encoding of memories in which the entorhinal cortex participates but, under pathological situations, may also contribute to epileptogenesis and neurodegeneration.

Evaluation of oxidative stress before and after haemodialysis in chronic renal failure

OBJECTIVE

To evaluate the oxidative stress before and after haemodialysis in chronic renal failure patients.

METHODS

A prospective study comprising of 22 patients of CRF who have to receive their first haemodialysis. All patients were subjected to standard four hours haemodialysis. The parameters of oxidative stress i.e. erythrocyte malonaldehyde (MDA), reduced glutathione (GSH) and superoxide dismutase (SOD) were measured before and after haemodialysis.

RESULTS

The value of mean erythrocyte MDA (9.40 +/- 3.36 mumol/L) and SOD (617 +/- 64.33 units/ml) were significantly higher in patients of CRF before haemodialysis than in controls (p < 0.001). The mean GSH levels were significantly lower (451 +/- 63.91 micrograms/ml) in patients than in controls before haemodialysis (p < 0.001). After haemodialysis MDA levels further increased (12.27 +/- 4.38 mumol/L), SOD levels decreased (458 +/- 69.58 EU/ml) and GSH levels further decreased (396 +/- 41.41 micrograms/ml) (p < 0.001).

CONCLUSIONS

There was an evidence of oxidative stress in patients of CRF before haemodialysis which increased further after haemodialysis, the mechanisms of which is not delineated. The procedural factors may be contributing in the increased oxidative stress after haemodialysis.

Negative regulation of dorsoventral signaling by the homeotic gene Ultrabithorax during haltere development in Drosophila

Growth and patterning during Drosophila wing development are mediated by signaling from its dorsoventral (D/V) organizer. In the metathorax, wing development is essentially suppressed by the homeotic selector gene Ultrabithorax (Ubx) to mediate development of a pair of tiny balancing organs, the halteres. Here we show that expression of Ubx in the haltere D/V boundary down-regulates its D/V organizer signaling compared to that of the wing D/V boundary. Somatic loss of Ubx from the haltere D/V boundary thus results in the formation of a wing-type D/V organizer in the haltere field. Long-distance signaling from this organizer was analyzed by assaying the ability of a Ubx(-) clone induced in the haltere D/V boundary to effect homeotic transformation of capitellum cells away from the boundary. The clonally restored wing D/V organizer in mosaic halteres not only enhanced the homeotic transformation of Ubx(-) cells in the capitellum but also caused homeotic transformation of even Ubx(+) cells in a genetic background known to induce excessive cell proliferation in the imaginal discs. In addition to demonstrating a non-cell-autonomous role for Ubx during haltere development, these results reveal distinct spatial roles of Ubx during maintenance of cell fate and patterning in the halteres.

The occurrence of toothwear in users of Ecstasy (3,4-methylenedioxymethamphetamine)

Ecstasy users have reported that dry mouth, jaw tension and tooth grinding were common side effects of its use although the influence of these effects upon toothwear have not been previously investigated.

OBJECTIVE

This study aimed to compare incisal and occlusal toothwear in Ecstasy users and a group of non-users of Ecstasy but users of other drugs.

METHODS

Groups were established by a snowball peer information network from visitors to the "drop-in" Maryland Centre in Liverpool. Volunteers completed a questionnaire about social life, drug use and diet. Clinical examination for wear on the incisal edges and on canine tips was conducted with a mirror and probe, whereas occlusal wear was recorded in impressions and subsequently scored from stone replica casts. The degree of toothwear was scored according to the criteria of the Tooth Wear Index (Smith & Knight, Br Dent J 1984;157:16).

RESULTS

Ecstasy users (n = 30) were compared with non-users (n = 28). Toothwear through the enamel into the underlying dentine occurred in 18 (60%) Ecstasy users but in only three (11%) non-users. The overall mean toothwear score in Ecstasy users was 0.63 compared with 0.16 in non-users (t = 4.34, P < 0.001). Dry mouth was reported by 93% of Ecstasy users whilst 89% stated that they clenched or ground their teeth after taking the drug. Tooth grinding commonly continued into the following morning. Carbonated (acidic) beverages were consumed by 93% of the users with a mean of three cans per "trip".

CONCLUSION

The severity of toothwear and the number of teeth affected were greater in Ecstasy users than in a group of non-users. The occlusal surfaces were more commonly affected than the incisal, which may indicate jaw clenching rather than grinding as a feature of Ecstasy-induced muscle hyperactivity.

Endosulfan poisoning in Northern India: a report of 18 cases

Eighteen cases of endosulfan poisoning by accidental overexposure during spray, admitted between October 1995 to September 1997, were observed and analyzed. These accounted for approximately one third of the total number of poisoning cases admitted in our unit during this period. Nausea, vomiting abdominal discomfort, tonic and clonic convulsions, confusion, disorientation, and muscular twitchings were cardinal manifestations. None of the patients succumbed to their illness. Analysis of various incriminating factors revealed that accidental overexposure was due to failure to adhere to the instructions for spray either due to ignorance or due to illiteracy. All the patients avoided preventive measures and developed toxicity both due to inhalation and absorption through skin. Endosulfan (a chlordiene derivative) poisoning is gaining up momentum in this part of world and has become an important matter for public health in India.

IRT-1, a novel interferon-gamma-responsive transcript encoding a growth-suppressing basic leucine zipper protein

Interferon-gamma (IFN-gamma) inhibits proliferation of vascular smooth muscle cells (VSMCs) in culture and reduces arterial restenosis post-balloon angioplasty. The identification and characterization of IFN-gamma-specific transcripts in VSMCs are an important approach to discern the molecular mechanisms underlying vascular proliferative disease. In this report, we describe IRT-1, a novel mRNA transcript constitutively expressed in a number of human tissues, but expressed in human VSMCs only when they are stimulated with IFN-gamma. This mRNA expression is induced >200-fold 72 h after IFN-gamma treatment. IRT-1 mRNA is also acutely expressed in rat carotid arteries that are injured by balloon angioplasty. The IRT-1 cDNA transcript encodes a basic protein that contains a leucine zipper motif, a core nuclear localization sequence, and a single strongly hydrophobic region. Constitutive IRT-1 mRNA expression in human peripheral blood lymphocytes is reduced when these cells are stimulated to proliferate. Overexpression of IRT-1 protein in VSMCs alters their morphology and dramatically reduces their proliferative capacity. This study suggests that IRT-1 is an IFN-gamma-inducible factor that may regulate the progression of vascular proliferative diseases.

An association between the regular use of 3,4 methylenedioxy-methamphetamine (ecstasy) and excessive wear of the teeth

AIMS

This study was established to determine if users of ecstasy had greater tooth wear than a comparison group of non-users.

DESIGN

The study involved a direct comparison between two groups of young people gathered by a peer information network and divided by the response to the question "Do you take ecstasy?"

SETTING

The information network was established at the Maryland Centre in Liverpool (UK). Besides offering advice on drug and sex-related problems this centre distributes free condoms and is therefore visited by many young people who would not consider themselves to have these problems.

PARTICIPANTS

There were 30 users and 28 non-users with no significant difference in the gender ratio. Age was not recorded to maintain absolute confidentiality, but all the participants appeared to be of student age.

MEASUREMENTS

Tooth wear was measured using the index of Smith & Knight. The social and drug-taking profile of the two groups was ascertained by questionnaire.

FINDINGS

It was found that the mean (+/- STD) tooth wear score for the back teeth was 0.96 +/- 0.16 in the users compared with 0.12 +/- 0.08 for the comparison group. These values were significantly different (p < 0.001). The values for the front teeth were not significantly different. Many users were aware of clenching their teeth 12 or even 24 hours after taking the drug.

CONCLUSION

Taking ecstasy results in an increased likelihood of tooth wear on the back teeth. This is likely to result from clenching the teeth in the acidic environment caused by carbonated (fizzy) drinks.

Aneurysms of sinus of Valsalva eroding into the interventricular septum: etiopathology and surgical considerations

OBJECTIVE

To evaluate and discuss etiopathology, clinical manifestations and surgical outcome of a rare subset of unruptured aneurysm of the sinus of Valsalva which erodes into the interventricular septum.

METHODS

Between 1989 and 1995, seven cases of unruptured aneurysm of the sinus of Valsalva eroding into the interventricular septum underwent surgical correction at the King Edward VII Memorial Hospital, Bombay. The origin of all these aneurysms was from the right coronary sinus. The mean age of presentation was 31 years. All patients were male. Calcification of the aneurysm was seen in three. Three patients presented without aortic regurgitation; all had complete heart block. Four patients presented with aortic regurgitation and in addition, two had complete heart block. Preoperative left ventricular function was poor in patients with aortic regurgitation (Ejection fraction range; 30-42%), when compared to those without aortic regurgitation (Ejection fraction range; 48-52%). Of those without aortic regurgitation at initial presentation, one patient developed progressive aortic regurgitation after 3 years requiring surgery. While two other patients were operated at earliest for closure of aneurysm, even in the absence of aortic regurgitation. All those with aortic regurgitation required surgery for aortic valve replacement and closure of aneurysm. Aneurysm was closed by direct suturing of the ostium in two patients and by patch closure in five patients. Permanent pacemaker was implanted in five patients.

RESULT

There was no operative death. Patients who underwent aortic valve replacement required postoperative ionotropic support. Two patients, who underwent surgery in absence of aortic regurgitation, remain free of aortic regurgitation at the end of 36 and 42 months of follow-up. One of the patients with calcific aneurysmal sac underwent successful re-replacement of the aortic valve for paravalvar leak after a 2 year interval.

CONCLUSION

Unruptured aneurysm of the sinus of Valsalva eroding into the interventricular septum should be operated at the earliest, which makes surgery simple and prevents development of complications such as aortic regurgitation and heart block.

Effect of active-site modification on the terminal marking deamidation of triosephosphate isomerase

The conformational change which results from the opening and closing of the hinged lid over the catalytic center of triosephosphate isomerase is transmitted to the subunit interface of the dimer and eventually leads to the spontaneous, specific deamidation of Asn71. This is followed by the deamidation of Asn15 approximately 5 A away on the neighboring subunit and leads to destabilization of the protein and degradation. However, it has not been established whether this molecular wear and tear occurs via an intra-subunit or inter-subunit transmission of the conformational change. We have studied this first step in the terminal marking by reacting the active-site Glu165 with the substrate analog 3-chloroacetol phosphate (CAP) which immobilizes the hinged lid. Under mild deamidation conditions (pH 9.5, 24 h, 30 degrees C) the native homodimer readily deamidated. In contrast, the CAP-modified homodimers were resistant to deamidation. Heterodimers composed of one native subunit and one CAP subunit showed intermediate deamidation. When the native and CAP-labeled subunits were resolved by electrophoresis in urea gels, it was found that the unlabeled subunit had preferentially deamidated. These data coupled with molecular modeling considerations show that restricting movement of the hinged lid prevents deamidation of Asn71 on that subunit, but that the other subunit with the free hinged lid functions independently and still deamidates. Thus, the conformationally induced wear and tear appears to be largely intra-subunit. These observations clearly link catalysis with terminal marking of the protein and suggest a general mechanism for how other enzymes may wear out.

Pseudohexabothrium taeniurae n. sp. (Monogenea: Hexabothriidae) from the gills of Taeniura lymma (Dasyatididae) from the Great Barrier Reef, Australia

Pseudohexabothrium taeniurae n. sp. is proposed for a hexabothriid monogenean found on the gills of Taeniura lymma (Forsskål) off Heron Island, Great Barrier Reef, Queensland, Australia. Pseudohexabothrium taeniurae is distinguished from Pseudohexabothrium rajae Brinkmann, 1952, the type and only species of the genus, by the morphology of the sucker sclerites and eggs, and by the size of the hamuli, pharynx, and the "false" oral sucker. The generic diagnosis of Pseudohexabothrium is revised. A phylogenetic analysis places Pseudohexabothrium as the sister group to the rest of the family except Hexabothrium.

Neoplastic transformation and aberrant cell-cell interactions in genetic mosaics of lethal(2)giant larvae (lgl), a tumor suppressor gene of Drosophila

Homozygosity for lethal(2)giant larvae (lgl), a mutation in a tumor suppressor gene of Drosophila, induces neoplasia of the imaginal discs. To explore the developmental capacities of lgl mutant cells, we have investigated their growth and differentiation in genetic mosaics. Adult wings mosaic for lgl displayed abnormal growth and differentiation of the lgl mutant and neighboring wild-type cells, suggesting aberrant cell-cell interactions during development. lgl mutant clones also straddled the anteroposterior boundary of the wing imaginal disc, apparently due to failure of the cells of the anterior and the posterior compartment to segregate at the boundary. To further test if anteroposterior compartmentalization takes place in the neoplastic imaginal discs of lgl mutant larvae, we studied the expression of an engrailed (en)-specific lacZ reporter gene during progressive stages of their tumorous growth. Our results show that en is activated in the posterior compartments of the neoplastic imaginal discs. However, during later stages of tumorous overgrowth, the en-expressing and nonexpressing cells appear to show extensive intermixing. These observations suggest that neoplastic transformation of imaginal discs involves loss of their normal cell-cell interactions and signaling.

Epithelial hyperplasia of imaginal discs induced by mutations in Drosophila tumor suppressor genes: growth and pattern formation in genetic mosaics

Lethal mutations in the giant discs (lgd) and fat (ft) tumor suppressor genes of Drosophila cause epithelial hyperplasia in all imaginal discs. By contrast, mutations in the vestigial (vg) gene adversely affect cell viability in the wing imaginal discs and consequently cause loss of pattern in the adult wings. However, combining homozygous lgd or ft mutations with homozygous vg1 increases the size of the wing imaginal discs and partially restores the bristle pattern in the wings of pharate adults. Comparable pattern restoration in vg1 wings is also induced by a newly isolated weak hypomorphic lgd3 allele. Further, mosaic analysis revealed that whereas lgd clones generated by the Minute technique display abnormal differentiation, those induced in a homozygous vg1 background exhibit autonomous restoration of wing pattern. These results suggest that pattern restoration in vg1 wings can serve as an assay for hyperplasia induced by mutations in Drosophila tumor suppressor genes.

Mitochondrial gene expression during bovine cardiac growth and development

The expression of both mitochondrial and nuclear genes encoding enzymes involved in electron transport and oxidative phosphorylation was examined in bovine cardiac tissue during early growth, development and aging. The steady state level of mRNAs for mitochondrial genes including ATPase 6. COXII and cyt b increased 2.5-4-fold relative to early fetal levels in late fetal and young adult tissues and showed a marked decline (30-50%) in older adult tissues. Similar results were found with the nuclear genes, COXVB and ATP-beta synthase showing coordinate regulation of the two genomes. An increase in mtDNA copy number correlated with the increase in transcript level. Enzyme activity levels for NADH dehydrogenase and cytochrome c oxidase showed a similar trend, albeit of lesser magnitude. These activity levels contrasted with the activity level of an entirely nuclear-encoded mitochondrial enzyme, citrate synthase, which increased not only throughout development but in the older adult tissue. This study indicates that there is a pattern of increasing mitochondrial and nuclear gene expression for OXPHOS enzymes in developing cardiac tissue and decreasing OXPHOS gene expression in the aging heart.

Misoprostol but not antacid prevents endotoxin-induced gastric mucosal injury: role of tumor necrosis factor-alpha

Many of the complications of septic shock are believed to be a consequence of elevated circulating levels of tumor necrosis factor (TNF), which is an important mediator of tissue injury. Prostaglandins (PGs) of the E series have recently been reported to inhibit TNF production in vitro. We investigated the in vivo effect of misoprostol, a PGE1 analog, on endotoxin-induced gastric mucosal injury and TNF production. For the gastric mucosal injury studies, groups of animals were pretreated with intragastric misoprostol (100 and 200 micrograms/kg) or with antacid (2 ml/animal of Maalox Plus) 30 min prior to a challenge with intravenous E. coli lipopolysaccharide (LPS) at 5.0 mg/kg. Stomachs were examined 3 hr after LPS. Systemic endotoxin alone induced microscopic edema, vascular congestion, and polymorphonuclear (PMN) infiltration of the gastric mucosa. Pretreatment with misoprostol, but not with antacid, significantly and dose-dependently reduced the gastric mucosal injury. For the TNF studies, groups of rats were given either misoprostol (100 or 200 micrograms/kg, intragastric), or saline 1 hr prior to LPS challenge. Serum samples were obtained 1.5 hr after LPS challenge. Misoprostol dose-dependently and significantly (P less than 0.01) inhibited TNF activity. We conclude that misoprostol is a potent inhibitor of TNF systemic production and inhibits the gastric mucosal injury induced by endotoxemia. These studies suggest a potentially important therapeutic role for misoprostol in inflammatory diseases in which TNF exerts a contributory role.