The relationship between EMG and change in thickness of transversus abdominis

OBJECTIVE

To investigate the relationship between changes in thickness and EMG activity in the transversus abdominis muscle of healthy subjects and the reliability of ultrasound measurements using different modes and transducers.

DESIGN

Convenience sampling.

BACKGROUND

Chronic low back pain is associated with transversus abdominis dysfunction but EMG studies of this muscle are restricted to invasive techniques. Since the thickness of transversus abdominis changes with activity, such changes measured from ultrasound images might provide insight into this muscle's function non-invasively. In addition, little is known about the comparability of ultrasound measurements from different modes and transducers, nor the reliability of transversus abdominis measurements.

METHODS

In 9 healthy subjects (aged 29-52 years, four male) transversus abdominis was studied at rest and during activity (5-80% max) with simultaneous EMG and ultrasound (M mode, 5 MHz curvilinear transducer) measurements. Intra-rater reliability for thickness measurements was studied on 13 subjects using 7.5 MHz linear and 5 MHz curvilinear transducers in B and M modes.

RESULTS

Muscle thickness changes correlated well with EMG activity (P < 0.001, R2 = 0.87) and there were no significant differences between subjects (P > 0.05). Using 7.5 MHz head, the ICC for B mode was 0.989 and for M mode was 0.981 for between days reliability. The ICC for between transducer reliability was 0.817.

CONCLUSIONS

Changes in thickness of transversus abdominis can be used to indicate changes in the electrical activity in this muscle.

RELEVANCE

Ultrasound scanning can be used in the clinical setting to provide objective information about transversus abdominis function.

Electrophysiological, biochemical, neurohormonal and behavioural studies with WAY-100635, a potent, selective and silent 5-HT1A receptor antagonist

Although considerable progress has been made in characterising the 5-HT1A receptor using agonists, partial agonists or non-selective antagonists, further studies of 5-HT1A receptor function have been hindered by the lack of highly selective antagonists. The term 'silent' antagonist has been used for such compounds in order to distinguish them unequivocally from several 5-HT1A receptor partial agonists which were initially designated 'antagonists'. In this report we provide a comprehensive review of the biochemical, pharmacological and behavioural properties of the first potent, selective and silent 5-HT1A receptor antagonist, WAY-100635 (N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl)-N-(2- pyridinyl)cyclohexanecarboxamide trihydrochloride). WAY-100635 had an IC50 (displacement of specific [3H]8-OH-DPAT binding to 5-HT1A receptors in the rat hippocampus) of 1.35 nM and was > 100-fold selective for the 5-HT1A site relative to a range of other CNS receptors. [3H]WAY-100635 was also characterised as the first 5-HT1A antagonist radioligand, displaying the same regional distribution of binding sites as [3H]8-OH-DPAT in rat brain. As would be expected for the binding of an antagonist to a G-protein-coupled receptor, the Bmax of [3H]WAY-100635 specific binding was consistently 50-60% greater than that of the agonist radioligand, [3H]8-OH-DPAT. Mn2+, but not guanine nucleotides, inhibited [3H]WAY-100635-specific binding. [3H]WAY-100635 was also shown to bind selectively to brain 5-HT1A receptors in vivo, following intravenous administration to mice. In vitro electrophysiological studies demonstrated that WAY-100635 had no 5-HT1A receptor agonist actions, but dose-dependently blocked the effects of agonists at both the postsynaptic 5-HT1A receptor in the CA1 region of the hippocampus, and the somatodendritic 5-HT1A receptor located on dorsal raphe 5-HT neurones. In vivo, WAY-100635 also dose-dependently blocked the ability of 8-OH-DPAT to inhibit the firing of dorsal raphe 5-HT neurones, and to induce the '5-HT syndrome', hypothermia, hyperphagia and to elevate plasma ACTH levels. In the mouse light/dark box anxiety model, WAY-100635 induced anxiolytic-like effects. WAY-100635 had no intrinsic effect on cognition in the delayed-matching-to-position model of short-term memory in the rat, but reversed the disruptive effects of 8-OH-DPAT on motor motivational performance. These data clearly demonstrate that WAY-100635 is the first potent, selective and silent 5-HT1A receptor antagonist. Furthermore, [3H]WAY-100635 is the first antagonist radioligand to become available for 5-HT1A receptor binding studies both in vitro and in vivo. The positive effects of WAY-100635 in an anxiety model also indicate that a postsynaptic 5-HT1A receptor antagonist action may contribute to the anxiolytic properties of 5-HT1A receptor partial agonists.

Substrate specificity of human liver aldehyde oxidase toward substituted quinazolines and phthalazines: a comparison with hepatic enzyme from guinea pig, rabbit, and baboon

Partially purified aldehyde oxidase (EC 1.2.3.1) has been prepared from human, rabbit, guinea pig, and baboon liver by heat treatment and precipitation with ammonium sulfate. The interaction of 35 substituted quinazolines and phthalazines with human liver enzyme has been studied using a spectrophotometric assay. Fifteen quinazoline and 14 phthalazine derivatives were found to be substrates for human liver aldehyde oxidase with Km values ranging from 5 to 500 microM. The substrate specificity of the quinazolines toward rabbit, guinea pig, and baboon liver aldehyde oxidase has also been investigated; the reaction of substituted phthalazines with mammalian liver enzyme has been reported previously (Beedham et al., 1990, Biochem. Pharmacol. 39, 1213-1221). Oxidation products of 2-substituted (4-substituted) quinazolines with rabbit liver aldehyde oxidase were identified by MS as 4-oxo (2-oxo)-quinazolines, respectively. In all cases, unsubstituted compounds gave the highest oxidation rates and the presence of lipophilic substituents presumably facilitated hydrophobic binding to the enzymes. However, there were marked differences in substrate specificity between human liver aldehyde oxidase and hepatic enzyme from rabbit, guinea pig, and baboon with the size of substrate being the differentiating factor. The molecular sizes of the substrates, estimated using calculated molar refractivities, ranked the size of the binding site of aldehyde oxidase in the order rabbit < guinea pig < baboon < man. Isoelectric points of the different aldehyde oxidase isozymes ranged from pH 5.10 for rabbit to 6.40 for the human liver isozyme. These results indicate that rabbit liver aldehyde oxidase shows marked differences from the human liver enzyme in its handling of quinazoline and phthalazine substrates.

Inhibition of 8-OH-DPAT-induced elevation of plasma corticotrophin by the 5-HT1A receptor antagonist WAY100635

Numerous studies have demonstrated the stimulatory effect of 5-HT1A receptor agonists, such as 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), on plasma corticotrophin (ACTH) levels in the rat. However, until recently the lack of a selective 5-HT1A receptor antagonist has hampered mechanistic studies in this area. In this study we examined the effects of the selective 5-HT1A receptor antagonist N-[2-[4-(2-methoxyphenyl)-1- piperazinyl]ethyl]-N-(2-pyridinyl) cyclohexanecarboxamide trihydrochloride (WAY100635) on plasma ACTH levels and on the elevation of ACTH induced by the 5-HT1A receptor agonist 8-OH-DPAT in the conscious rat. The basal plasma ACTH level was 41.0 +/- 1.8 pg/ml. 8-OH-DPAT increased ACTH levels at doses of 100 and 300 micrograms/kg with maximum increases of 551 and 546% respectively occurring 10 min post-injection. WAY100635 had no effects per se on plasma ACTH at doses up to 100 micrograms/kg, indicating it has no 5-HT1A receptor agonist properties. WAY100635 dose-dependently blocked the elevation of ACTH induced by 8-OH-DPAT, the minimum effective dose being 10 micrograms/kg. The present results indicate that 8-OH-DPAT elevates plasma ACTH levels by stimulating 5-HT1A receptors, a conclusion that is consistent with the findings of previous studies using non-selective 5-HT1A receptor antagonists such as pindolol.

Effects of the selective 5-HT1A receptor antagonist WAY100135 and its enantiomers on 8-OH-DPAT-induced hyperglycaemia in conscious rats

8-Hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) increases plasma glucose levels in conscious rats probably by stimulation of central 5-HT1A receptors. We have examined the effects of WAY100135 (N-tert-butyl-3-[4-(2-methoxyphenyl)piperazin-1-yl]-2-phenylpropan amide), a selective 5-HT1A receptor antagonist and its enantiomers on plasma glucose levels and on the hyperglycaemia induced by 8-OH-DPAT. (R,S)-WAY100135 (minimum effective dose (MED) 3 mg/kg i.v.) and (S)-WAY100135 (MED 1 mg/kg i.v.) dose-dependently attenuated 8-OH-DPAT-induced hyperglycaemia. In contrast, (R)-WAY100135 at doses up to 3 mg/kg i.v. was unable to block hyperglycaemia induced by 8-OH-DPAT. When the antagonists were examined for intrinsic effects on plasma glucose levels only (S)-WAY100135 (3 mg/kg i.v.) caused a significant but transient hyperglycaemia (20% increase). These results are consistent with previous suggestions that (R,S)-WAY100135 and (S)-WAY100135 are selective 5-HT1A receptor antagonists and that 8-OH-DPAT-induced hyperglycaemia is mediated by 5-HT1A receptors. The antagonist action of WAY100135 is stereoselective, and more potent activity being observed with the (S) enantiomer.

Biotransformation of carbazeran in guinea pig: effect of hydralazine pretreatment

1. After administration of [14C]-carbazeran by oral gavage to guinea pigs, 48% of the dosed radioactivity was recovered in urine and 46% in faeces after 144 h. 2. The major urinary metabolite was identified by infrared spectroscopy and mass spectrometry as the O-glucuronide of O-desmethyl-4-oxocarbazeran, O-demethylation having taken place at the 6- or 7-position. The corresponding aglycone was identified as the major faecal metabolite. 3. A minor metabolite in urine was identified as the 4-oxo-4'-hydroxy derivative of carbazeran. 4. In animals pretreated with hydralazine, an aldehyde oxidase inhibitor, less radioactivity was extracted in the urine and a significant decrease was observed in the levels of the major urinary metabolite. 5. These results show that aldehyde oxidase plays a key role in the metabolism of carbazeran in guinea pig as it does in man. The similarity of man and guinea pig liver aldehyde oxidase has been observed previously in vitro.

Subcellular localisation of guinea pig hepatic molybdenum hydroxylases

Molybdenum hydroxylase activity in guinea pig liver has been compared with that of marker enzymes in mitochondria (succinate dehydrogenase), microsomes (glucose-6-phosphatase) and cytosol (lactate dehydrogenase). Aldehyde oxidase activity was highest in the cytosol, with about 10-fold activity of xanthine oxidase. Significant molybdenum hydroxylase activity was found in mitochondria with minimal levels in microsomes. Mitochondrial and cytosolic aldehyde oxidase varied in substrate specificity and electrophoretic mobility with two major bands in each fraction, one of which was common to cytosol and mitochondria.

1-substituted phthalazines as probes of the substrate-binding site of mammalian molybdenum hydroxylases

The interaction of a series of 1-substituted phthalazine derivatives with partially purified aldehyde oxidase from rabbit, guinea-pig and baboon liver, and with bovine milk xanthine oxidase, has been investigated. Of the 18 compounds examined, rabbit liver aldehyde oxidase metabolized 10, whereas guinea-pig and baboon liver enzyme oxidized 13 and 14, respectively. Where metabolites were characterized, oxidation was shown to occur at position four of the phthalazine ring. Km values ranged from 0.003 to 1.8 mM. In contrast, most compounds were competitive inhibitors of bovine milk xanthine oxidase with Ki values ranging from 0.015 to 1.3 mM; the cationic derivative 2-methylphthalazinium iodide was oxidized to 2-methyl-1-phthalazinone by both aldehyde oxidase and, with a much reduced affinity, by xanthine oxidase. In terms of structure-metabolism relationships, Vmax values were relatively insensitive to the electronic effects of substituents, but a trend for the more lipophilic derivatives to show increased affinities (Km and Vmax/Km) towards aldehyde oxidase could be seen. However, calculations of molecular size revealed a species-dependent cut-off threshold above which compounds were not metabolized. Results suggest that the relative size of the active site for hepatic aldehyde oxidase is in the order baboon greater than guinea-pig greater than rabbit, and that in spatial terms the active site of bovine milk xanthine oxidase is similar to that of baboon liver aldehyde oxidase. Thus, the binding site of rabbit liver aldehyde oxidase, a widely used source of the oxidase, is apparently more restricted than in some other species.

Species variation in hepatic aldehyde oxidase activity

The activity of hepatic aldehyde oxidase from rabbit, guinea pig, rat, marmoset, dog, baboon and man was investigated in vitro with charged and uncharged N-heterocyclic substrates: Km and Vmax values were determined for phthalazine, 6,7-dimethoxy-1-[-4-(ethylcarbamoyloxy)piperidino]phthalazine (carbazeran), quinine and quinidine. The oxidation of N-phenylquinolinium chloride to N-phenyl-2-quinolone and N-phenyl-4-quinolone was followed spectrophotometrically. Rat or dog liver showed low and negligible enzyme activity respectively, whereas baboon liver contained a highly active aldehyde oxidase. Enzyme from marmoset and guinea pig liver had the closest spectrum of activity to human liver aldehyde oxidase. Unlike that from man, rabbit hepatic aldehyde oxidase was refractory towards carbazeran and converted N-phenylquinolinium chloride predominantly to the 2-quinolone. N-Phenyl-4-quinolone was the major oxidation product with enzyme from guinea pig, marmoset, baboon and man.