Ruthenium ion catalysed C-C bond activation in lignin model compounds - towards lignin depolymerisation.

Lignin is the most abundant renewable feedstock to produce aromatic chemicals, however its depolymerisation involves the breaking of several C-O and C-C inter-unit linkages that connect smaller aromatic units that are present in lignin. Several strategies have been reported for the cleavage of the C-O inter-unit linkages in lignin. However, till today, only a few methodologies have been reported for the effective breaking or the conversion of the recalcitrant C-C inter unit linkages in lignin. Here we report the ruthenium ion catalysed oxidative methodology as an effective system to activate or convert the most recalcitrant inter unit linkages such as ß-5 and 5-5' present in lignin. Initially, we used biphenyl as a model compound to study the effectiveness of the RICO methodology to activate the 5-5' C-C linkage. After 4 h reaction at 22 °C, we achieved a 30% conversion with 75% selectivity towards benzoic acid and phenyl glyoxal as the minor product. To the best of our knowledge this is the first ever oxidative activation of the C-C bond that connects the two phenyl rings in biphenyl. DFT calculation revealed that the RuO4 forms a [3 + 2] adduct with one of the aromatic C-C bonds resulting in the opening of the phenyl ring. Biphenyl conversion could be increased by increasing the amount of oxidant; however, this is accompanied by a reduction in the carbon balance because of the formation of CO2 and other unknown products. We extended this RICO methodology for the oxidative depolymerisation of lignin model hexamer containing ß-5, 5-5' and ß-O-4 linkages. Qualitative and quantitative analyses of the reaction mixture were done using 1H, 13C NMR spectroscopy methods along with GC-MS and Gel Permeation Chromatographic (GPC) methods. Advanced 2D NMR spectroscopic methods such as HSQC, HMBC and 31P NMR spectroscopy after phosphitylation of the mixture were employed to quantitatively analyse the conversion of the ß-5, 5-5' and ß-O-4 linkages and to identify the products. After 30 min, >90% of the 5-5' and linkages and >80% of the ß-5' are converted with this methodology. This is the first report on the conversion of the 5-5' linkage in lignin model hexamer.

Dissociated backward priming effects in lexical decision and pronunciation tasks.

Backward priming was examined at 150- and 500-msec prime-target stimulus onset asynchronies (SOAs) using visually presented primes and targets in lexical decision and pronunciation tasks. Two kinds of backward relations were used: compound items for which targets and primes formed a word in the backward direction (e.g., prime: HOP; target: bell), and noncompound items for which targets and primes did not form a word but were associatively related in the backward but not the forward direction (e.g., prime: BABY; target: stork). Results showed that backward priming effects were equivalent for compounds and noncompounds. However, for lexical decisions, backward priming occurred at both SOAs, whereas for pronunciation, it occurred only at the 150-msec SOA. We discuss how this SOA-dissociated backward priming effect in lexical decision and pronunciation tasks poses a serious challenge for all theories of semantic priming.

Soy protein, thyroid regulation and cholesterol metabolism.

The effects of dietary protein on plasma cholesterol concentrations are well documented: animal proteins (casein) are hypercholesterolemic compared with plant proteins (soy protein). Although this effect of protein source on plasma cholesterol has been shown in many species, the mechanism is not completely understood. This paper reviews the relationship between dietary protein source and plasma thyroxine concentration. The basic premise is that feeding soy protein lowers plasma cholesterol concentration by causing an increase in plasma thyroxine concentrations. The metabolic changes involving cholesterol that occur when soy protein is fed are discussed. These changes are consistent with changes induced by elevating thyroxine. Data are presented from animal studies showing that feeding soy protein to laboratory animals consistently elevates plasma thyroxine concentrations. Furthermore, this elevation in plasma thyroxine concentrations precedes the change in plasma cholesterol concentrations: a necessary requirement for hypothesizing a causative effect. Possible mechanisms as to how a dietary protein source affects plasma thyroxine are also presented.

Failure to produce taste-aversion learning in rats exposed to static electric fields and air ions.

Taste-aversion (TA) learning was measured to determine whether exposure to high-voltage direct current (HVdc) static electric fields can produce TA learning in male Long Evans rats. Fifty-six rats were randomly distributed into four groups of 14 rats each. All rats were placed on a 20 min/day drinking schedule for 12 consecutive days prior to receiving five conditioning trials. During the conditioning trials, access to 0.1% sodium saccharin-flavored water was given for 20 min, followed 30 min later by one of four treatments. Two groups of 14 rats each were individually exposed to static electric fields and air ions, one group to +75 kV/m (+2 x 10(5) air ions/cm3) and the other group to -75 kV/m (-2 x 10(5) air ions/cm3). Two other groups of 14 rats each served as sham-exposed controls, with the following variation in one of the sham-exposed groups: This group was subdivided into two subsets of seven rats each, so that a positive control group could be included to validate the experimental design. The positive control group (n = 7) was injected with cyclophosphamide 25 mg/kg, i.p., 30 min after access to saccharin-flavored water on conditioning days, whereas the other subset of seven rats was similarly injected with an equivalent volume of saline. Access to saccharin-flavored water on conditioning days was followed by the treatments described above and was alternated daily with water "recovery" sessions in which the rats received access to water for 20 min in the home cage without further treatment. Following the last water-recovery session, a 20 min, two-bottle preference test (between water and saccharin-flavored water) was administered to each group. The positive control group did show TA learning, thus validating the experimental protocol. No saccharin-flavored water was consumed in the two-bottle preference test by the cyclophosphamide-injected, sham-exposed group compared to 74% consumed by the saline-injected sham-exposed controls (P < .0001). Saccharin-preference data for the static field-exposed groups showed no TA learning compared to data for sham-exposed controls. In summary, exposure to intense static electric fields and air ions did not produce TA learning as assessed by this particular design.

A prospective controlled investigation of the cognitive effects of amateur boxing.

Eighty six amateur boxers underwent a series of neuropsychological assessments on three occasions--pre bout, immediate post bout and follow up within two years; 31 water polo players and 47 rugby union players acted as controls. The neuropsychological tests were selected as being sensitive to subtle cognitive dysfunction and formed part of a battery of other neurological and ophthalmic assessments. No evidence of neuropsychological dysfunction due to boxing was found, either following a bout or a series of bouts at follow up. None of a range of parameters including number of previous contests, recovery from an earlier bout, number of head blows received during a bout and number of bouts between initial assessment and follow up, were found to be related to changes in cognitive functioning.

Rats avoid exposure to HVdc electric fields: a dose response study.

Rats, given the choice, avoid exposure to alternating current (ac) 60-Hz electric fields at intensities > or = 75 kV/m. This study investigated the generality of this behavior by studying the response of rats when exposed to high voltage direct current (HVdc) electric fields. Three hundred eighty male Long Evans rats were studied in 9 experiments with 40 rats per experiment and in one experiment with 20 rats to determine 1) if rats avoid exposure to HVdc electric fields of varying field strengths, and 2) if avoidance did occur, what role, if any, the concentration of air ions would have on the avoidance behavior. In all experiments a three-compartment glass shuttlebox was used; either the left or right compartment could be exposed to a combination of HVdc electric fields and air ions while the other compartment remained sham-exposed. The third, center compartment was a transition zone between exposure and sham-exposure. In each experiment, the rats were individually assessed in 1-h sessions where half of the rats (n = 20) had the choice to locomote between the two sides being exposed or sham-exposed, while the other half of the rats (n = 20) were sham-exposed regardless of their location, except in one experiment where there was no sham-exposed group. The exposure levels for the first six experiments were 80, 55, 42.5, 30, -36, and -55 kV/m, respectively. The air ion concentration was constant at 1.4 x 10(6) ions/cc for the four positive exposure levels and -1.4 x 10(6) ions/cc for the two negative exposure levels. Rats having a choice between exposure and non-exposure relative to always sham-exposed control animals significantly reduced the amount of time spent on the exposed side at 80 kV/m (P < .002) as they did at both 55 and -55 kV/m (P < .005). No significant differences between groups were observed at 42.5, 30, or -36 kV/m. To determine what role the air ion concentration might have had on the avoidance behavior at field strengths of 55 kV/m or greater, four additional experiments were conducted. The HVdc exposure level was held constant at either -55 kV/m (for three experiments) or -55 kV/m (for 1 experiment) while the air ion concentration was varied between experiments at 2.5 x 10(5) ions/cc, 1.0 x 10(4) for two of the experiments and was below the measurement limit (< +/- 2 x 10(3) ions/cc) for the other two experiments at 55 and -55 kV/m.(ABSTRACT TRUNCATED AT 400 WORDS)

Computed tomography findings in partial seizures.

The computed tomography findings in 82 children with partial seizures of unknown aetiology were reviewed. All had seizures with predominantly focal motor phenomena and none had abnormality on neurological examination. Findings on computed tomography were normal in 64 children (78%) and abnormal in 18 children (22%). Fourteen children had changes representing static pathology (mainly cerebral atrophy) which did not influence patient management but four had potentially correctable lesions (two tumours and two arteriovenous malformations). There were no correlations between seizure control, seizure duration, intellectual handicap, postictal weakness, electroencephalographic findings, and abnormality on the computed tomogram. In particular, none of these features were useful in predicting the presence of a tumour or arteriovenous malformation. It is concluded that a computed tomogram is indicated in every child with partial seizures.

Solid phase extraction of oxcarbazepine and its metabolites from plasma for analysis by high performance liquid chromatography.

A rapid, sensitive and simple-to-operate high performance liquid chromatographic method for the simulataneous determination of oxcarbazepine, 10-hydroxycarbazepine and 10,11-dihydro-10,11-trans-dihydroxy-carbamazepine in plasma is described. The drug and its metabolites were extracted from plasma using commercially available reversed phase octadecylsilane bonded-silica columns (Bond Elut C18, 1 mL capacity). Chromatographic separation of oxcarbazepine and its metabolites was achieved using a mobile phase consisting of acetonitrile/methanol/water (13:25:62 by volume) at a flow rate of 1.2 mL/min in conjunction with a Waters Associates Nova-Pak C18 column. The analytical column, in Radial-Pak cartridge form, was used in combination with a LiChrospher 5 microns C18 guard column. By measuring the UV absorbance at 214 nm, plasma levels in the region of 50-100 ng/mL for the drug and its metabolites can be detected with only 100 microL of plasma. The method has been applied to pharmacokinetic studies of oxcarbazepine and its metabolites in children with epilepsy; preliminary pharmacokinetic findings in two patients at steady-state are presented.

Daily variations in steady-state plasma concentrations of carbamazepine and its metabolites in epileptic children.

Total plasma carbamazepine, carbamazepine-10,11-epoxide (CBZ-EP) and 10,11-dihydro-10,11-trans-dihydroxy-carbamazepine (CBZ-DIOL) concentrations were measured during a 24h period in 21 patients receiving carbamazepine monotherapy, in equally divided doses, every 12h. Interdose and diurnal variations in plasma concentrations of parent drug and metabolites were assessed. Carbamazepine and both metabolites showed significant differences in mean 4h post-dose plasma concentrations between day and night dosing (p less than 0.001). Significant linear correlations were obtained between carbamazepine dose and plasma concentrations of carbamazepine, CBZ-EP and CBZ-DIOL when sampling times were standardised (p less than 0.01). Comparisons of plasma concentrations of the parent compound with those of its 2 main metabolites revealed significant linear correlations in all cases (p less than 0.01). The effects of daily fluctuations in plasma concentrations of all 3 compounds on their relative concentrations (CBZ-EP:carbamazepine, CBZ-DIOL:carbamazepine and CBZ-DIOL:CBZ-EP) during the 24h period were also determined: the plasma concentration ratios CBZ-EP:carbamazepine and CBZ-DIOL:carbamazepine were significantly related to the dose of carbamazepine at fixed sampling times (p less than 0.05, with 1 exception). The large interdose and diurnal variation in plasma carbamazepine concentrations observed in this study (approximately 40% decrease from peak to trough) has important implications both clinically and in relation to therapeutic drug monitoring.

Dissolution and relative bioavailability of two carbamazepine preparations for children with epilepsy.

The in-vitro dissolution profiles of two carbamazepine formulations (Tegretol and a generic carbamazepine) have been assessed and the bioavailability of carbamazepine compared in 12 epileptic children at steady-state. Dissolution from the generic formulation (100 and 200 mg tablets) tended to be greater than for the proprietary tablets. However, the bioavailability and pharmacokinetics of carbamazepine when assessed at steady-state were similar for the two formulations. It appears, therefore, that the breakthrough seizures and higher incidence of neurological side-effects observed when children were given generic carbamazepine in place of the proprietary formulation cannot be accounted for by differences in bioavailability or pharmacokinetics.

Dietary proteins, cholesterol and thyroxine: a proposed mechanism.

The effects of dietary protein sources on plasma cholesterol concentrations are well-documented: animal proteins are hypercholesterolemic relative to plant proteins. While this effect of dietary proteins has been shown in many species, the mechanism is not known. This review will explore the relation between dietary proteins and plasma thyroxine concentrations. Data will be presented showing that feeding dietary animal proteins consistently depresses plasma thyroxine levels. Furthermore, the effects of thyroxine on cholesterol metabolism is consistent with the effects of dietary proteins on cholesterol metabolism. Although evidence is not conclusive, data support the hypothesis that dietary proteins may affect plasma cholesterol levels through changes in plasma thyroxine concentrations. To elucidate the mechanism by which this happens will be the basis for future research.

Factors influencing plasma level/dose ratios of carbamazepine and its major metabolites in epileptic children.

The relationship between daily dose and plasma concentrations of carbamazepine (CBZ), CBZ-10,11-epoxide (CBZ-EP), and 10,11-dihydro-10,11-trans-dihydroxy-CBZ (CBZ-DIOL) was investigated in 21 children aged 7-16 years who received CBZ monotherapy, twice daily in equally divided doses. Significant linear correlations between CBZ dose and plasma levels were obtained for CBZ and its metabolites (p less than 0.01). In addition, the effects of daily dose and patients' age on the plasma level/dose ratios for CBZ, CBZ-EP, and CBZ-DIOL were evaluated. A significant negative correlation was observed between the daily dose of CBZ and the CBZ plasma level/dose ratio (p less than 0.01). By contrast, plasma level/dose ratios for CBZ-EP and CBZ-DIOL were independent of dose (p greater than 0.1). On the basis of these observations, we consider that the decrease in CBZ plasma level/dose ratio with increasing CBZ dose appears to be due to dose-dependent metabolic clearance of CBZ. The influence of age on plasma level/dose ratios for CBZ and its metabolites was not significant (p greater than 0.05). However, there was considerable interdose and diurnal variation in the plasma level/dose ratios, particularly for CBZ (28-41%); this must be taken into account when making dose adjustments based on plasma level/dose ratios.

Breakthrough seizures with generic carbamazepine: a consequence of poorer bioavailability?

The bioavailability of carbamazepine from two products (Ethical Generics and Ciba-Geigy) and their efficacy with regard to seizure control and incidence of side-effects were compared in 23 children with tonic-clonic or complex partial seizures. Mean plasma concentrations of carbamazepine, carbamazepine 10, 11-epoxide and 10,11-dihydro-10, 11-trans-dihydroxy-carbamazepine at comparable sampling times were not significantly different during treatment with the two drug preparations. The incidence of seizures and occurrence of abnormal EEGs were not significantly different during treatment with the two carbamazepine preparations, and, in addition, the overall incidence of side-effects was not significantly different during the two treatment periods. However, neurological side-effects were significantly less during treatment with the Ciba-Geigy product. On the basis of these observations we are confident that the efficacy of these two carbamazepine preparations in children at steady-state is the same.

The body-worn alarm in the treatment of childhood enuresis.

Two studies examined the effectiveness of the body-worn alarm in out-patient treatment of childhood nocturnal enuresis. The first involved 40 children, previously untreated by conditioning methods, treated with either the body-worn alarm or the traditional pad and bell alarm. The second study compared the body-worn alarm with modified dry-bed training with 48 children previously resistant to treatment. Results of both studies indicated the body-worn alarm was as effective as other methods in terms of the proportion of children successfully treated and was superior with respect to rapidity of response and consumer appeal. Such findings indicate that the body-worn alarm could become the treatment of choice for nocturnal enuresis.

The child's construing of nocturnal enuresis: a method of inquiry and prediction of outcome.

Fifty-five children with nocturnal enuresis were engaged in a structured interview prior to treatment with the body-worn alarm. The interview sought to understand how children make sense of the experience and examines the implications for becoming dry. Successful treatment outcome was found to be associated with the child both construing bedwetting psychologically, and indicating no resistance to change. The importance of establishing the child's attitude to bedwetting prior to treatment is stressed.

Prognosis after grand mal seizures: a study of 187 children with three-year remissions.

From a total group of 640 children with grand mal seizures, 187 who became seizure-free for three consecutive years on monotherapy which was then discontinued have been followed for between one and 14 years. Relapse occurred in 22 children (12 per cent) and was related to age at presentation: only four of 89 children with primary grand mal seizures who had presented after the age of three years relapsed, compared with 12 of 45 who had presented before their third birthday. Children who had had more seizures were at greater risk of relapse. EEGs were not useful in predicting prognosis, whether taken at presentation or before withdrawal of treatment.