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J P Fawcett

Publications and source records attributed to J P Fawcett.

At least 19 recordsLinked to original sources
PubMed2005

Structural identification of bitespiramycin metabolites in rat: a single oral dose study.

Bitespiramycin is a macrolide antibiotic consisting of a mixture of some nine spiramycin ester derivatives. It has a similar spectrum of antibiotic activity to that of spiramycin but has superior pharmacokinetic properties. In this study, a rapid and facile LC/ESI-MSn method was applied to study the metabolism of bitespiramycin in rat following a single oral dose (80 mg kg-1). Concentrations of parent drug constituents and metabolites were determined in plasma, urine, feces and bile. Concentrations of parent drug constituents and metabolites in plasma were very low. In urine, feces and bile, parent drug constituents and 38 metabolites were identified on the basis of their chromatographic and mass spectrometric properties. The identity of 17 metabolites was confirmed by comparison with reference substances. The principal metabolites were the corresponding spiramycins formed by hydrolysis of the 4''-(3-methylbutanoate) groups. Other important metabolic pathways were: hydrolytic loss of the forosamine and mycarose sugars; aldehyde reduction; cysteine conjugation of the aldehyde group; and hydrolysis of the lactone ring. Products formed by lactone ring opening were found only in urine, and those formed by aldehyde reduction were found only in feces. Aldehyde reduction and hydrolytic loss of forosamine represent novel biotransformation pathways for spiramycin derivatives.

Administration, Oral↗
PubMed2001

The pharmacokinetics of levosalbutamol: what are the clinical implications?

Salbutamol (albuterol) is a beta2-adrenoceptor agonist used as a bronchodilator for the treatment of asthma and as a uterine relaxant for the suspension of premature labour. Salbutamol has been marketed as a racemic mixture, although beta2-agonist activity resides almost exclusively in the (R)-enantiomer. The enantioselective disposition of salbutamol and the possibility that (S)-salbutamol has adverse effects have led to the development of an enantiomerically pure (R)-salbutamol formulation known as levosalbutamol (levalbuterol). Salbutamol is metabolised almost exclusively by sulphotransferase (SULT) 1A3 to an inactive metabolite. (R)-Salbutamol is metabolised up to 12 times faster than (S)-salbutamol. This leads to relatively higher plasma concentrations of (S)- salbutamol following all routes of administration, but particularly following oral administration because of extensive metabolism by the intestine. Enantiomer concentrations are similar for the first hour following an inhaled dose, reflecting the fact that salbutamol in the lung probably undergoes little metabolism. Subsequently, (S)-salbutamol predominates due to absorption and metabolism of the swallowed portion of the inhaled dose. Following oral or inhaled administration of enantiomerically pure salbutamol, a small amount (6%) is converted to the other enantiomer, probably by acid-catalysed racemisation in the stomach. Tissue binding of salbutamol is not enantioselective and plasma protein binding is relatively low. Both enantiomers are actively excreted into the urine. Compared with healthy individuals, patients with asthma do not have substantially different pharmacokinetics of the salbutamol enantiomers, but they do appear to have less drug delivered to the lung following inhaled administration because of their narrowed airways. Levosalbutamol elicits an equal or slightly larger response than an equivalent dose of the racemic mixture. This is probably due to competitive inhibition between the enantiomers at beta-adrenoceptors. Pharmacokinetic-pharmacodynamic relationships for levosalbutamol show relatively large interindividual variations. Functionally significant genetic polymorphisms have been identified for beta2-adrenoceptors, SULT1A3 and organic action transporters, all of which affect the disposition or action of levosalbutamol. Animal, in vitro and some clinical studies have reported deleterious effects of (S)-salbutamol on smooth muscle contractility or lung function. However, well-designed clinical studies in patients with asthma have failed to find evidence of significant toxicity associated with (S)-salbutamol. The clinical consequences of relatively higher plasma concentrations of (S)-salbutamol following administration of racemate remain unclear, but in the absence of clear evidence of toxicity the clinical superiority of levosalbutamol over racemic salbutamol appears to be small.

Administration, Inhalation↗
PubMed2000

Evidence that brain-derived neurotrophic factor from presynaptic nerve terminals regulates the phenotype of calbindin-containing neurons in the lateral septum.

Brain-derived neurotrophic factor (BDNF) is transported anterogradely in neurons of the CNS and can be released by activity-dependent mechanisms to regulate synaptic plasticity. However, few neural networks have been identified in which the production, transport, and effects of BDNF on postsynaptic neurons can be analyzed in detail. In this study, we have identified such a network. BDNF has been colocalized by immunocytochemistry with tyrosine hydroxylase (TH) in nerve fibers and nerve terminals within the lateral septum of rats. BDNF-containing nerve fibers terminate on a population of calbindin-containing neurons in lateral septum that contain TrkB, the high-affinity receptor for BDNF. Overexpression of BDNF in noradrenergic neurons increased levels of calbindin in septum, as well as in whole-brain lysates. Septal levels of calbindin and BDNF partially decreased after unilateral lesions of the medial forebrain bundle (MFB), induced with 6-hydroxydopamine, a treatment that abolished TH staining. These data suggest that BDNF is anterogradely transported within the MFB in catecholaminergic neurons arising from brainstem nuclei. To determine whether BDNF affects the production of calbindin in lateral septal neurons directly, we tested the effects of BDNF on cultures of septal neurons from embryonic day 16-17 rats. BDNF promoted the expression of calbindin, as well as the arborization of calbindin-containing neurons, but BDNF had no effect on cell division or survival. Together, these results suggest that BDNF, anterogradely transported in catecholaminergic neurons, regulates calbindin expression within the lateral septum.

Age Factors↗
PubMed2000

A mammalian PAR-3-PAR-6 complex implicated in Cdc42/Rac1 and aPKC signalling and cell polarity.

Cellular asymmetry is critical for the development of multicellular organisms. Here we show that homologues of proteins necessary for asymmetric cell division in Caenorhabditis elegans associate with each other in mammalian cells and tissues. mPAR-3 and mPAR-6 exhibit similar expression patterns and subcellular distributions in the CNS and associate through their PDZ (PSD-95/Dlg/ZO-1) domains. mPAR-6 binds to Cdc42/Rac1 GTPases, and mPAR-3 and mPAR-6 bind independently to atypical protein kinase C (aPKC) isoforms. In vitro, mPAR-3 acts as a substrate and an inhibitor of aPKC. We conclude that mPAR-3 and mPAR-6 have a scaffolding function, coordinating the activities of several signalling proteins that are implicated in mammalian cell polarity.

Amino Acid Motifs↗
PubMed2000

Stereoselective glucuronidation of formoterol by human liver microsomes.

AIMS: Formoterol is a beta2-adrenoceptor agonist marketed as a racemic mixture of the active (R; R)- and inactive (S; S)-enantiomers (rac-formoterol). The drug produces prolonged bronchodilation by inhalation but there is significant interpatient variability in duration of effect. Previous work has shown that in humans formoterol is metabolized by conjugation with glucuronic acid but little is known about the stereoselectivity of this reaction. The aim of the present study was to investigate the glucuronidation of formoterol enantiomers in vitro by human liver microsomes. METHODS: The kinetics of formation of formoterol glucuronides during incubation of racemate and of single formoterol enantiomers with human liver microsomes (n=9) was characterized by chiral h.p.l.c. assay. RESULTS: The kinetics of glucuronidation of the two formoterol enantiomers obeyed the Michaelis-Menten equation. Glucuronidation of formoterol was stereoselective and occurred more than two times faster for (S; S)-formoterol than for (R; R)-formoterol. In incubations with single formoterol enantiomers, the median (n=9) Km values for (R; R)-glucuronide and (S; S)-glucuronide were 827.6 and 840.4 microm, respectively, and the median V max values were 2625 and 4304 pmol min-1 mg-1, respectively. Corresponding values determined in incubations with rac-formoterol were 357.2 and 312.1 microm and 1435 and 2086 pmol min-1 mg-1 for (R; R)- and (S; S)-glucuronide, respectively. Interindividual variation was large with the ratio of V max/Km (S; S/R; R) ranging from 0.57 to 6.90 for incubations with rac-formoterol. CONCLUSIONS: Our study demonstrates that glucuronidation of formoterol by human liver microsomes is stereoselective and subject to high interindividual variability. These findings suggest that clearance of formoterol in humans is subject to variable stereoselectivity which could explain the variation in duration of bronchodilation produced by inhaled formoterol in patients with asthma.

Aged↗
PubMed2000

Chlamydia pneumoniae serological status is not associated with asthma in children or young adults.

BACKGROUND: The factors that cause the allergic sensitization and inflammation in asthma still remain to be clarified. A role for Chlamydia pneumoniae has been suggested although serological studies have produced conflicting findings. This study aims to clarify the relationship between asthmatic variables and C. pneumoniae serological status. METHODS: A case-control study was undertaken on an asthma-enriched subset from a longitudinal birth cohort. In all, 198 subjects (96 with self-reported asthma) had C. pneumoniae serology (microimmunofluorescence [MIF] IgG, IgA) undertaken at age 11 and age 21 and assessment made in relation to a number of asthma variables. RESULTS: The only statistically significant finding was in subjects self-reporting asthma at age 21 who had evidence of lower IgG titres (P = 0.046), a finding in the opposite direction to that expected from the hypothesis. Subjects with high IgG titres (> or =128) were less likely to have reported ever having asthma; odds ratio (OR) = 0.29, (95% CI: 0.10-0.87). No association existed between symptoms suggestive of asthma in the previous 12 months and either IgG (P = 0.127) or IgA (P = 0.189) antibody titres at age 21. Likewise, no association was found between symptoms suggestive of asthma in the previous two years and C. pneumoniae IgG antibody titre (P = 0.81) at age 11. There was no evidence of an association with any of the other variables examined at either age 11 or age 21. These included use of inhaled steroids, serum IgE levels, airway responsiveness, skin test evidence of atopy, or smoking status. CONCLUSION: The results of this study suggest that C. pneumoniae infection when diagnosed by MIF serology is not a major risk factor for the development of asthma in children and young adults. The study has not, however, addressed the role this organism may play in specific asthmatic subsets or asthma exacerbations.

Adolescent↗
PubMed1999

Characterization of dopaminergic midbrain neurons in a DBH:BDNF transgenic mouse.

The neurotrophin brain-derived neurotrophic factor (BDNF) has been implicated in the survival and differentiation of central nervous system neurons, including dopaminergic cells in culture. To determine whether BDNF might play a role in the development of dopaminergic neurons in vivo, we used a previously characterized transgenic mouse (DBH:BDNF) that overexpresses BDNF in adrenergic and noradrenergic neurons as a result of fusion of the BDNF gene to the dopamine beta-hydroxylase (DBH) gene promoter. We quantified dopaminergic neuronal profiles at four midbrain coronal levels and compared DBH:BDNF transgenic animals with wild-type mice of the same genetic background. Analysis of sections immunostained with tyrosine hydroxylase (TH) showed that the mean number of dopaminergic neurons in the four selected midbrain sections was 52% greater (one-way analysis of variance, P < 0.0005) in transgenic mice (2,165 +/- 55 S. E.M., n = 4) than in control mice (1,428 +/- 71 S.E.M., n = 4). The increase in dopaminergic neuron profile count in DBH:BDNF transgenic animals was confirmed by analysis of the pars compacta of the substantia nigra on Nissl-stained sections. Surface area of the reference region of interest containing TH-immunoreactive neurons was similar in transgenic and control mice. Regional analysis of different midbrain areas containing dopaminergic neurons suggested that the increase in cell profile count occurs in a relatively homogeneous manner. Comparison of TH-immunoreactive cell size showed a tendency for smaller neurons in transgenic animals, but the difference was not statistically significant. We conclude that DBH:BDNF transgenic mice show increased number of TH-immunoreactive cells in the midbrain. We propose that BDNF rescues dopaminergic neurons from the perinatal period of developmental cell death as a consequence of increased anterograde transport of the neurotrophin via the coeruleonigral projection.

Animals↗
PubMed1999

Rapid chiral high-performance liquid chromatographic assay for salmeterol and alpha-hydroxysalmeterol. Application to in vitro metabolism studies.

A rapid and sensitive chiral high-performance liquid chromatographic (HPLC) assay for the simultaneous determination of salmeterol and its principal human metabolite alpha-hydroxysalmeterol is described. The two pairs of enantiomers were resolved on a chiral-cellobiohydrolase column and detected by electrochemical detection at +700 mV. Standard curves were linear over the concentration range 0.1 to 4.0 microM for alpha-hydroxysalmeterol enantiomers and 2.5 to 40.0 microM for salmeterol enantiomers. Intra- and inter-day coefficients of variation were < 10%. The method was applied to a study of human hepatic metabolism in vitro which showed that microsomal metabolism of salmeterol to alpha-hydroxysalmeterol is not stereoselective.

Albuterol↗
PubMed1999

Differential sorting of nerve growth factor and brain-derived neurotrophic factor in hippocampal neurons.

Nerve growth factor (NGF) is released through the constitutive secretory pathway from cells in peripheral tissues and nerves where it can act as a target-derived survival factor. In contrast, brain-derived neurotrophic factor (BDNF) appears to be processed in the regulated secretory pathway of brain neurons and secreted in an activity-dependent manner to play a role in synaptic plasticity. To determine whether sorting differences are intrinsic to the neurotrophins or reflect differences between cell types, we compared NGF and BDNF processing in cultured hippocampal neurons using a Vaccinia virus expression system. Three independent criteria (retention or release from cells after pulse-chase labeling, depolarization-dependent release, and immunocytochemical localization) suggest that the bulk of newly synthesized NGF is sorted into the constitutive pathway, whereas BDNF is primarily sorted into the regulated secretory pathway. Similar results occurred with AtT 20 cells, including those transfected with cDNAs encoding neurotrophin precursor-green fluorescent protein fusions. The NGF precursor, but not the BDNF precursor, is efficiently cleaved by the endoprotease furin in the trans-Golgi network (TGN). Blocking furin activity in AtT 20 cells with alpha1-PDX as well as increasing the expression of NGF precursor partially directed NGF into the regulated secretory pathway. Therefore, neurotrophins can be sorted into either the constitutive or regulated secretory pathways, and sorting may be regulated by the efficiency of furin cleavage in the TGN. This mechanism may explain how neuron-generated neurotrophins can act both as survival factors and as neuropeptides.

Animals↗
PubMed1999

Stereoselective urinary excretion of bupivacaine and its metabolites during epidural infusion.

A sensitive and efficient chiral assay for bupivacaine and its three principal metabolites desbutylbupivacaine, 4'-hydroxybupivacaine, and 3'-hydroxybupivacaine has been applied to urine from five male patients receiving postoperative epidural infusions of rac-bupivacaine fentanyl over 60-120 hr. The fraction of the dose of bupivacaine (total dose 840-2093 mg) accounted for in urine was 75 +/- 6%. The rate of excretion of bupivacaine enantiomers' approximated a steady state after approximately 30 hr with values of 1.27 +/- 0.26 and 0.76 +/- 0.13 mg hr-1 for (R)- and (S)-enantiomers, respectively. The fraction of the dose of bupivacaine enantiomer excreted unchanged in the urine (fe) varied from 14.3% to 39.1% for (+)-(R)-bupivacaine and 9.2% to 14.0% for (-)-(S)-bupivacaine in the five patients. The rate of excretion of all metabolites also reached a steady state after approximately 30 hr and the relative amounts of metabolites excreted into urine (fm) suggest bupivacaine is subject to regioselective and stereoselective clearance, which may vary from patient to patient.

Aged↗
PubMed1998

Iron deficiency and anaemia in a longitudinal study of New Zealanders at ages 11 and 21 years.

AIMS: To determine iron status in a longitudinal study of New Zealanders, the Dunedin Multidisciplinary Health and Development Study (DMHDS), at ages 11 (1983-4) and 21 (1993-4). METHODS: Red cell variables were measured in 553 (298 males, 255 females) and 784 (413 males, 371 females) members of the DMHDS at ages 11 and 21, respectively. A total of 456 (259 males, 197 females) members were tested at both ages. Serum ferritin was measured at age 21 only. RESULTS: The prevalence of anaemia in females (haemoglobin < 120 g/L) increased from 3.1% at age 11 to 5.8% at age 21 (pregnant women excluded). There was a significant association between low haemoglobin at age 11 and low haemoglobin at age 21. In males, prevalence of anaemia decreased from 2.3% at age 11 to 0.97% (haemoglobin < 130 g/L) at age 21. The prevalence of iron deficiency (ferritin < 12 ng/mL) at age 21 was 0.24% in men and 6.7% in women. The prevalence of iron deficiency with anaemia at age 21 was zero in men and 2.2% in women. CONCLUSIONS: The prevalences of anaemia and iron deficiency in the DMHDS appear to be low by comparison with similar populations in other countries. Anaemia appears to be a stable trait in young women and screening may be useful for its early detection.

Adult↗
PubMed1998

Functional evidence that BDNF is an anterograde neuronal trophic factor in the CNS.

In this report, we have tested the hypothesis that brain-derived neurotrophic factor (BDNF) is an anterograde neurotrophic factor in the CNS and have focused on central noradrenergic neurons that synthesize BDNF. Double-label immunocytochemistry for BDNF and dopamine-beta-hydroxylase (DBH), a marker for noradrenergic neurons, demonstrated that BDNF is partially localized to noradrenergic nerve fibers and terminals in the adult rat brain. To test the functional importance of this anterograde BDNF, we analyzed transgenic mice carrying a DBH-BDNF minigene. Increased synthesis of BDNF in noradrenergic neurons of DBH-BDNF mice caused elevated TrkB tyrosine kinase activation throughout postnatal life in the neocortex, a noradrenergic target region. This afferently regulated increase in TrkB receptor activity led to long-lasting alterations in cortical morphology. To determine whether noradrenergic neuron-expressed BDNF also anterogradely regulated neuronal survival, we examined a second noradrenergic target, neonatal facial motoneurons. One week after axotomy, 72% of facial motoneurons were lost in control animals, whereas only 30-35% were lost in DBH-BDNF transgenic mice. Altogether, these results indicate that BDNF is anterogradely transported to fibers and terminals of noradrenergic neurons, that anterogradely secreted BDNF causes activation of TrkB in target regions, and that this secretion has functional consequences for target neuron survival and differentiation. This presynaptic secretion of BDNF may provide a cellular mechanism for modulating neural circuitry, in either the developing or mature nervous system.

Age Factors↗
PubMed1998

Whole blood serotonin relates to violence in an epidemiological study.

BACKGROUND: Clinical and animal studies suggest that brain serotonergic systems may regulate aggressive behavior; however, the serotonin/violence hypothesis has not been assessed at the epidemiological level. For study of an epidemiological sample we examined blood serotonin, because certain physiological and behavioral findings suggested that it might serve as an analog marker for serotonergic function. METHODS: Whole blood serotonin was measured in a representative birth cohort of 781 21-year-old women (47%) and men (53%). Violence was measured using cumulative court conviction records and participants' self-reports. Potential intervening factors addressed were: gender, age, diurnal variation, diet, psychiatric medications, illicit drug history, season of phlebotomy, plasma tryptophan, platelet count, body mass, suicide attempts, psychiatric diagnoses, alcohol, tobacco, socioeconomic status, IQ, and overall criminal offending. RESULTS: Whole blood serotonin related to violence among men but not women. Violent men's mean blood serotonin level was 0.48 SD above the male population norm and 0.56 SD above the mean of nonviolent men. The finding was specific to violence, as opposed to general crime, and it was robust across two different methods of measuring violence. Together, the intervening variables accounted for 25% of the relation between blood serotonin and violence. CONCLUSIONS: To our knowledge, this is the first demonstration that an index of serotonergic function is related to violence in the general population.

Adult↗
PubMed1998

Seroprevalence of Helicobacter pylori in a longitudinal study of New Zealanders at ages 11 and 21.

BACKGROUND: Helicobacter pylori seroprevalence increases with age in adult life but spontaneous reversion may occur in childhood and adolescence. AIMS: To determine the seroprevalence of H. pylori in a longitudinal study of New Zealanders at ages 11 and 21. METHODS: Serum from members of the Dunedin Multidisciplinary Health and Development Study (DMHDS) at age 11 (n = 561; 303 males, 258 females) and 21 (n = 785; 413 males, 372 females) was tested for H. pylori antibodies. A large proportion of those tested at age 11 was retested at age 21 (n = 465; 262 males, 203 females). Serological status was examined in terms of gender, socioeconomic status (SES) and self-reported use of antibiotics. RESULTS: The seroprevalence of H. pylori decreased by 38% from 6.6% (37/561) at age 11 to 4.1% (32/785) at age 21. Seroprevalence at age 11 was not associated with gender or SES. For those tested at both ages, the drop in seroprevalence from 6.7% to 4.1% was statistically significant (t = 2.57, p < 0.01, paired t-test) and was much greater in females (71%) than males (12%). Of the 31 seropositive individuals at age 11, 17 (six males, 11 females) seroreverted and self-reported antibiotic use in the year preceeding age 21 was more common in females (eight/11) than males (zero/six). Of the 434 seronegative individuals at age 11, only five (four males, one female) had seroconverted at age 21. CONCLUSIONS: Seroprevalence in the DMHDS declined from age 11 to 21 predominantly in females. The decline involved a greater rate of seroreversion and lower rate of seroconversion in females than males.

Adolescent↗