Search PubMed⌕ Search

Biomedical subjects

A R Green

Publications and source records attributed to A R Green.

At least 37 records · Page 2Linked to original sources
PubMed2002

Effect of NXY-059 on infarct volume after transient or permanent middle cerebral artery occlusion in the rat; studies on dose, plasma concentration and therapeutic time window.

1. The efficacy of the free radical trapping agent NXY-059 in reducing the infarct volume following both transient and permanent focal ischaemia has been examined in rats. 2. In the transient ischaemia model, rats were subjected to a 2 h occlusion of the middle cerebral artery (MCA). Intravenous infusion of NXY-059 (1, 10 and 30 mg kg(-1) h) for 21.75 h starting 2.25 h after the occlusion, produced a dose-dependent decrease in both neurological impairment and the histologically measured infarct volume (a mean 59% decrease at 10 mg kg(-1) h). 3. In the permanent ischaemia model, animals were injected (s.c.) with a loading dose of NXY-059 of 32.5, 53.8 or 75.4 mg kg(-1) and osmotic minipumps were implanted which had been primed to deliver respectively 30, 50 or 70 mg kg(-1) h. When treatment was initiated 5 min after MCA occlusion there was a dose dependent protection of both cortical and sub-cortical tissue (cortex: 63% at the mid-range dose). Protection was related linearly to plasma concentration (plasma unbound NXY-059 concentration at 1 h: 37+/-16 micromol l(-1) at the mid-range dose). 4. When the mid range dose was administered between 5 min - 4 h after MCA occlusion, a marked and statistically significant protection was seen at all time points (44% protection in cortex at 4 h). 5. These data demonstrate the substantial neuroprotective efficacy of NXY-059 at plasma concentrations that can be achieved clinically and indicate that NXY-059 also has a therapeutic window of opportunity that is clinically relevant.

Administration, Cutaneous↗
PubMed2002

Protection against 3,4-methylenedioxymethamphetamine-induced neurodegeneration produced by glutathione depletion in rats is mediated by attenuation of hyperthermia.

3,4-Methylenedioxymethamphetamine (MDMA) administration produces neurotoxic degeneration of serotonin terminals in rat brain. These effects occur only after systemic administration and not after central injection, suggesting that peripheral metabolism, possibly hepatic, is required for toxicity. Glutathione is one of the principal cellular defence mechanisms, but conjugation with glutathione can, on some occasions, increase the reactivity of certain molecules. Previous studies have shown that central administration of glutathione adducts of a MDMA metabolite produces a neurotoxicity profile similar to that of systemic MDMA. In the present study, depletion of peripheral (hepatic) glutathione by 43% with dl-buthionine-(S,R)-sulfoximine (an inhibitor of glutathione synthesis) did not attenuate MDMA-induced neurotoxicity as indicated by the 34% loss of [(3) H]paroxetine binding to the serotonin uptake sites in Dark Agouti rats treated with the inhibitor. However, a more profound depletion (92%) of glutathione by diethylmaleate (direct conjugation) administration significantly reduced the serotonergic neurotoxicity produced by MDMA. This depletion protocol also attenuated the hyperthermic response to MDMA. A combination protocol utilising both buthionine-(S,R)-sulfoximine and diethylmaleate that did not alter the hyperthermic response of the rats given MDMA also failed to attenuate the neurotoxicity. These findings indicate that glutathione depletion does not offer specific protection against MDMA-induced serotonin neurotoxicity in Dark Agouti rats.

Animals↗
PubMed2002

Galactic and solar radiation exposure to aircrew during a solar cycle.

An on-going investigation using a tissue-equivalent proportional counter (TEPC) has been carried out to measure the ambient dose equivalent rate of the cosmic radiation exposure of aircrew during a solar cycle. A semi-empirical model has been derived from these data to allow for the interpolation of the dose rate for any global position. The model has been extended to an altitude of up to 32 km with further measurements made on board aircraft and several balloon flights. The effects of changing solar modulation during the solar cycle are characterised by correlating the dose rate data to different solar potential models. Through integration of the dose-rate function over a great circle flight path or between given waypoints, a Predictive Code for Aircrew Radiation Exposure (PCAIRE) has been further developed for estimation of the route dose from galactic cosmic radiation exposure. This estimate is provided in units of ambient dose equivalent as well as effective dose, based on E/H x (10) scaling functions as determined from transport code calculations with LUIN and FLUKA. This experimentally based treatment has also been compared with the CARI-6 and EPCARD codes that are derived solely from theoretical transport calculations. Using TEPC measurements taken aboard the International Space Station, ground based neutron monitoring, GOES satellite data and transport code analysis, an empirical model has been further proposed for estimation of aircrew exposure during solar particle events. This model has been compared to results obtained during recent solar flare events.

Aerospace Medicine↗
PubMed2001

Deletions of the derivative chromosome 9 occur at the time of the Philadelphia translocation and provide a powerful and independent prognostic indicator in chronic myeloid leukemia.

Chronic myeloid leukemia (CML) is characterized by formation of the BCR-ABL fusion gene, usually as a consequence of the Philadelphia (Ph) translocation between chromosomes 9 and 22. Large deletions on the derivative chromosome 9 have recently been reported, but it was unclear whether deletions arose during disease progression or at the time of the Ph translocation. Fluorescence in situ hybridization (FISH) analysis was used to assess the deletion status of 253 patients with CML. The strength of deletion status as a prognostic indicator was then compared to the Sokal and Hasford scoring systems. The frequency of deletions was similar at diagnosis and after disease progression but was significantly increased in patients with variant Ph translocations. In patients with a deletion, all Ph(+) metaphases carried the deletion. The median survival of patients with and without deletions was 38 months and 88 months, respectively (P =.0001). By contrast the survival difference between Sokal or Hasford high-risk and non-high-risk patients was of only borderline significance (P =.057 and P =.034). The results indicate that deletions occur at the time of the Ph translocation. An apparently simple reciprocal translocation may therefore result in considerable genetic heterogeneity ab initio, a concept that is likely to apply to other malignancies associated with translocations. Deletion status is also a powerful and independent prognostic factor for patients with CML. The prognostic significance of deletion status should now be studied prospectively and, if confirmed, should be incorporated into management decisions and the analysis of clinical trials.

Adult↗
PubMed2001

Regulation of the stem cell leukemia (SCL) gene: a tale of two fishes.

The stem cell leukemia (SCL) gene encodes a tissue-specific basic helix-loop-helix (bHLH) protein with a pivotal role in hemopoiesis and vasculogenesis. Several enhancers have been identified within the murine SCL locus that direct reporter gene expression to subdomains of the normal SCL expression pattern, and long-range sequence comparisons of the human and murine SCL loci have identified additional candidate enhancers. To facilitate the characterization of regulatory elements, we have sequenced and analyzed 33 kb of the SCL genomic locus from the pufferfish Fugu rubripes, a species with a highly compact genome. Although the pattern of SCL expression is highly conserved from mammals to teleost fish, the genes flanking pufferfish SCL were unrelated to those known to flank both avian and mammalian SCL genes. These data suggest that SCL regulatory elements are confined to the region between the upstream and downstream flanking genes, a region of 65 kb in human and 8.5 kb in pufferfish. Consistent with this hypothesis, the entire 33-kb pufferfish SCL locus directed appropriate expression to hemopoietic and neural tissue in transgenic zebrafish embryos, as did a 10.4-kb fragment containing the SCL gene and extending to the 5' and 3' flanking genes. These results demonstrate the power of combining the compact genome of the pufferfish with the advantages that zebrafish provide for studies of gene regulation during development. Furthermore, the pufferfish SCL locus provides a powerful tool for the manipulation of hemopoiesis and vasculogenesis in vivo.

Amino Acid Sequence↗
PubMed2001

3,4-Methylenedioxymethamphetamine induces monoamine release, but not toxicity, when administered centrally at a concentration occurring following a peripherally injected neurotoxic dose.

RATIONALE: There is good evidence that 3,4-methylenedioxymethamphetamine (MDMA)-induced neurotoxicity results from free radical formation. However, it is unclear whether it is the presence of MDMA or a metabolite in the brain that initiates this process. OBJECTIVE: We wished to measure the concentration of MDMA in the brain following peripheral administration of neurotoxic doses and examine the effect on acute monoamine release and the subsequent neurotoxic loss in 5-hydroxytryptamine (5-HT) content when a high concentration of MDMA was infused into cerebral tissue. METHODS: Selectively placed microdialysis probes were used to determine both the concentration of MDMA in the brain following peripheral injection and the degree of 5-HT release. Monoamines in dialysate and tissue were measured with standard HPLC techniques. RESULTS: MDMA, administered intraperitoneally, at doses of 10 and 15 mg/kg, which produce neurodegeneration, resulted in an estimated cerebral extracellular concentration of MDMA of 11 and 20 microM, respectively. When MDMA (100-400 microM) was perfused through a selectively placed microdialysis probe it dose-dependently increased 5-HT release in the hippocampus and dopamine release in the striatum. Seven days after perfusion of MDMA the concentration of 5-HT and its metabolite, 5-hydroxyindoleacetic acid was unchanged in the ipsilateral side of the brain of normothermic rats and also in the brains of animals made hyperthermic to mimic the acute effect of MDMA given peripherally. In contrast, perfusion with 5,7-dihydroxytryptamine (400 microM) markedly decreased the cerebral 5-HT content. A second probe, also placed in the hippocampus at a distance of 1 mm from the main probe, revealed that during the perfusion of MDMA (400 microM) the estimated extracellular concentration of MDMA in the hippocampus was between 10.4 and 19.5 microM, i.e. in the range of concentrations observed after systemic injection of neurotoxic doses of MDMA. CONCLUSIONS: These data demonstrate that MDMA when injected directly into the brain produces 5-HT release but no neurotoxicity, suggesting that it must be metabolised peripherally in order to produce compounds that induce free radical formation and neurotoxicity in the brain.

3,4-Dihydroxyphenylacetic Acid↗
PubMed2001

A neurotoxic dose of 3,4-methylenedioxymethamphetamine (MDMA; ecstasy) to rats results in a long-term defect in thermoregulation.

RATIONALE: 3,4-Methylenedioxymethamphetamine (MDMA; "ecstasy") administration to rats produces damage to cerebral 5-HT nerve endings; however, the long-term functional consequences of this damage are poorly understood. OBJECTIVE: To confirm that MDMA administration produces a long-term effect on thermoregulation and investigate the mechanisms involved. METHODS: Male Dark Agouti rats were injected with a neurotoxic dose of MDMA (12.5 mg/kg i.p.). Five to 6 weeks later, they were exposed to high ambient temp (30 degrees C) for 60 min followed by a return to normal temp (20 degrees C), with rectal temperature being measured under both conditions. Further groups of MDMA-pretreated rats were challenged with 8-OH-DPAT and their temperature response measured. RESULTS: MDMA administration produced acute hyperthermia. Rectal temperature had normalised 24 h later and was similar to saline-injected controls over the following 15 days. MDMA administration produced a 37% loss in hypothalamic 5-HT content 18 days later. When MDMA-pretreated rats were subjected to high ambient temperature 33 days posttreatment, they displayed both a faster rise in rectal temperature and sustained hyperthermia when returned to normal conditions. There was no difference in their hypothermic response to the 5-HT1A agonist 8-OH-DPAT. CONCLUSIONS: A neurotoxic dose of MDMA resulted in impaired thermoregulation when rats were exposed to high ambient temperature. 5-HT1A receptor mechanisms were unaltered. Impaired serotonergic function following MDMA presumably alters the neurotransmitter balance, thereby compromising thermoregulation. Heavy recreational users of MDMA may also have impaired thermoregulation and thus be at greater risk of an acute adverse response to MDMA in a hot crowded dance environment.

Amphetamines↗
PubMed2001

Studies on the neuroprotective effect of the enantiomers of AR-A008055, a compound structurally related to clomethiazole, on MDMA ("ecstasy")-induced neurodegeneration in rat brain.

RATIONALE: 3,4-Methylenedioxymethamphetamine (MDMA, "ecstasy") administration produces neurotoxic degeneration of 5-HT nerve endings in several regions of rat brain. Administration of the GABAmimetic drug clomethiazole protects against this damage. OBJECTIVE: We wished to see whether the enantiomers of AR-A008055 (1-4-methyl-5-thiazolyl-1-phenyl-methylamine), a compound structurally related to clomethiazole, were also neuroprotective against MDMA-induced degeneration. METHODS: (R)-(+)-AR-A008055 or (S)-(-)-AR-A008055 (100 mg/kg IP) was injected 5 min prior to and 55 min after MDMA (15 mg/kg IP) administration to Dark Agouti rats. Rectal temperature was measured during this time and the concentration of 5-HT and 5-HIAA measured in hippocampus, cortex and striatum 7 days later. [3H]-Paroxetine binding was also measured in cortex. RESULTS: Both enantiomers abolished the acute MDMA-induced hyperthermia and attenuated the subsequent neurotoxic loss of 5-HT, 5-HIAA and [3H]-paroxetine binding. When rats given the enantiomer plus MDMA were warmed to keep their rectal temperature elevated to near that of animals given only MDMA, the neuroprotective effect of (S)-(-)-AR-A008055 was still seen, while the effect of (R)-(+)-AR-A008055 was abolished. Protection was also seen when (S)-(-)-AR-A008055 (50 mg/kg) was given, a dose which produced only a modest attenuation of MDMA-induced hyperthermia. CONCLUSIONS: The current data suggest that a major proportion of the neuroprotective action of (S)-(-)-AR-A008055 did not involve an attenuating effect on MDMA-induced hyperthermia. The protection afforded by (R)-(+)-AR-A008055, which is not a GABA agonist, appears to be solely due to its action on body temperature, strengthening the contention that abolishing the acute MDMA-induced hypothermia can produce neuroprotection. Since (S)-(-)-AR-A008055 has a similar pharmacology to clomethiazole, these data suggest that drugs which increase GABAA receptor channel opening are neuroprotective against MDMA-induced damage.

Animals↗
PubMed2001

Effect of GBR 12909 and fluoxetine on the acute and long term changes induced by MDMA ('ecstasy') on the 5-HT and dopamine concentrations in mouse brain.

We examined the long term effect of 3,4 methylenedioxymethamphetamine (MDMA, 10, 20 and 30 mg/kg, i.p.) on the cerebral 5-hydroxytryptamine (5-HT) and dopamine content in Swiss Webster mice. Three injections of MDMA (20 or 30 mg/kg, i.p.) given 3 h apart produced a marked depletion in the striatal content of dopamine and its metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) 7 days later. None of the doses administered altered the concentration of 5-HT or its metabolite 5-hydroxyindoleacetic acid (5-HIAA) in several brain areas. Pre-treatment with the dopamine uptake inhibitor GBR 12909 (10 mg/kg, i.p.), 30 min before each of the three MDMA (30 mg/kg, i.p.) injections, completely prevented the long term loss in the striatal catechol concentrations. However, GBR 12909 (10 mg/kg, i.p.) not only failed to prevent the acute effects induced by MDMA (30 mg/kg x 3, i.p.) on dopamine metabolism 30 min later, but in fact potentiated them. The 5-HT uptake inhibitor, fluoxetine (10 mg/kg, i. p.) failed to prevent both the acute and long term dopaminergic deficits. MDMA (30 mg/kg x 3) altered the body temperature of the mice biphasically, producing a rapid hyperthermia followed by prolonged hypothermia. In contrast, MDMA (20 mg/kg x 3) produced an initial hypothermia followed by hyperthermia. The present experiments therefore appear to rule out any direct relationship between the neurotoxic effects of MDMA and its acute effects on body temperature in mice. Fluoxetine administered 30 min before each MDMA (30 mg/kg) injection prevented these temperature changes, while GBR 12909 was without effect. This suggests that the neuroprotective effect of GBR 12909 against MDMA-induced neurotoxicity is not directly related to its ability to inhibit the MDMA-induced acute effects on dopamine metabolism or alter the MDMA-induced temperature change. The data illustrate major differences in the neurotoxic profile of MDMA in mice and rats.

3,4-Dihydroxyphenylacetic Acid↗
PubMed2001

Efficacy of disodium 4-[(tert-butylimino)methyl]benzene-1,3-disulfonate N-oxide (NXY-059), a free radical trapping agent, in a rat model of hemorrhagic stroke.

Because free radical mechanisms may contribute to brain injury in hemorrhagic stroke, the effect of the free radical trapping agent disodium 4-[(tert-butylimino)methyl]benzene-1,3-disulfonate N-oxide (NXY-059) was investigated on outcome following intracerebral hemorrhage (ICH) in rat. ICH was induced in 20 adult rats by infusion of collagenase into the caudate-putamen. Thirty minutes later rats were treated with NXY-059 (50 mg/kg subcutaneous plus 8.8 mg/kg/h for 3 days subcutaneous delivered via implanted osmotic pumps) or saline (equivalent volumes). Magnetic resonance imaging 24 h after ICH confirmed that the hemorrhage was uniform in the two groups, and subsequent imaging at 7 and 42 days post-ICH showed that the hematoma resolved similarly in the two groups. Behavioral testing on days 1, 3, 7, 14, and 21 after ICH showed that rats treated with NXY-059 had significantly decreased neurological impairment at all times. Deficits in skilled forelimb use 4-5 weeks post-ICH, and in striatal function 6 weeks post-ICH, were not reduced by treatment with NXY-059. Treatment with NXY-059 significantly reduced the neutrophil infiltrate observed 48 h post-hemorrhage in the vicinity of the hematoma, and the number of TUNEL-positive cells 48 h post-hemorrhage at the hematoma margin. However, by 6 weeks there were no differences in neuronal densities in treated and control rats.

Animals↗
PubMed2001

Neuroprotective efficacy of AR-A008055, a clomethiazole analogue, in a global model of acute ischaemic stroke and its effect on ischaemia-induced glutamate and GABA efflux in vitro.

We have investigated the neuroprotective properties of AR-A008055 [(+/-)-1-(4-methyl-5-thiazolyl-1-phenyl-methylamine], a novel compound structurally related to clomethiazole. Administration (i.p.) of (+/-)-AR-A008055 60 min after 5 min of global cerebral ischaemia in gerbils produced a dose-dependent protection of the hippocampus from damage. Both enantiomers [(R)-(+)-AR-A008055 and (S)-(-)- AR-A008055] at 600 micromol/kg produced similar protection to that following clomethiazole (600& micromol/kg) and both produced similar and sustained neuroprotection, at 4, 7 and 21 days post-insult. When infused intravenously over a 2-h period, both enantiomers produced concentration-dependent neuroprotection, with the enantiomers providing similar protection at every plasma concentration (50-200 nmol/ml). The efficacy of (S)-(-)-AR-A008055 was similar to clomethiazole, but it was slightly less potent. Ischaemia-induced glutamate efflux from rat brain cortical prisms in vitro was inhibited by both isomers (100 microM). The inhibitory effect of (R)-(+)-AR-A008055 was blocked by bicuculline (10 microM) and picrotoxin (100 microM), while the effect of (S)-(-)-AR-A008055 was only antagonised by picrotoxin. This indicated that (S)-(-)-AR-A008055, like clomethiazole, is able to open the GABA(A)-chloride channel in the absence of endogenous GABA. (R)-(+)-AR-A008055 was more potent than (S)-(-)-AR-A008055 in enhancing the concentration of GABA in the medium following 30 min exposure of tissue to the ischaemic conditions, suggesting that it is an effective GABA uptake inhibitor. This action may explain both its effect on glutamate efflux in vitro and its neuroprotective effect in vivo.

Animals↗
PubMed2001

The interaction of AR-A008055 and its enantiomers with the GABA(A) receptor complex and their sedative, muscle relaxant and anticonvulsant activity.

AR-A008055 [(+/-)-1-(4-methyl-5-thiazolyl)-1-phenylmethylamine] is structurally related to clomethiazole and has been used to probe the mechanism of the neuroprotective effect of clomethiazole. Clomethiazole, (+/-)-AR-A008055 and (S)-(-)-AR-A008055 all displaced [35S]-t-butyl-bicyclophosphorothionate ([35S]TBPS) from rat cerebral cortex tissue (IC50 values: GABA, 8.1+/-0.04 microM; clomethiazole, 130+/-30 microM; (+/-)-AR-A008055, 494+/-7 microM; (S)-(-)-AR-A008055, 221+/-14 microM. (R)-(+)-AR-A008055 was without significant effect (IC50>1000 microM). None of the compounds interacted with NMDA or AMPA receptors or with sodium or calcium (N, P/Q) channels. Brain penetration of both enantiomers following their i.p. administration was excellent, with brain and plasma concentrations being similar. Clomethiazole dose-dependently inhibited spontaneous locomotor activity in rats and was approximately 10 times more sedative than either enantiomer of AR-A008055. Clomethiazole was more potent than (S)-(-)-AR-A008055 in the "pull-up" test (muscle relaxation) and in producing loss of righting reflex, while (R)-(+)-AR-A008055 had little effect. The time animals remained on a Rota-rod was of the order: clomethiazole<(S)-(-)-AR-A008055<(R)-(+)-AR-A008055. (S)-(-)-AR-A008055 (210 micromol/kg) raised seizure threshold to pentylenetetrazole (i.v.) by 119+/-21%. The (R)-(+)- enantiomer was not anticonvulsant. Overall, (S)-(-)-AR-A008055 exhibited a similar pharmacology to clomethiazole. However, its sedative and muscle relaxant effects were substantially less than clomethiazole, emphasising that these properties are not directly related to neuroprotective efficacy. The current data suggest that the proposed GABA uptake inhibitory property of (R)-(+)-AR-A008055 fails to produce significant sedative, myorelaxant or anticonvulsant activity.

Animals↗
PubMed2001

The mechanisms involved in the long-lasting neuroprotective effect of fluoxetine against MDMA ('ecstasy')-induced degeneration of 5-HT nerve endings in rat brain.

1. It has been reported that co-administration of fluoxetine with 3,4-methylenedioxymethamphetamine (MDMA, 'ecstasy') prevents MDMA-induced degeneration of 5-HT nerve endings in rat brain. The mechanisms involved have now been investigated. 2. MDMA (15 mg kg(-1), i.p.) administration produced a neurotoxic loss of 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) in cortex, hippocampus and striatum and a reduction in cortical [3H]-paroxetine binding 7 days later. 3. Fluoxetine (10 mg kg(-1), i.p., x2, 60 min apart) administered concurrently with MDMA or given 2 and 4 days earlier provided complete protection, and significant protection when given 7 days earlier. Fluvoxamine (15 mg kg(-1), i.p., x2, 60 min apart) only produced neuroprotection when administered concurrently. Fluoxetine (10 mg kg(-1), x2) markedly increased the K(D) and reduced the B(max) of cortical [3H]-paroxetine binding 2 and 4 days later. The B(max) was still decreased 7 days later, but the K(D) was unchanged. [3H]-Paroxetine binding characteristics were unchanged 24 h after fluvoxamine (15 mg kg(-1), x2). 4. A significant cerebral concentration of fluoxetine plus norfluoxetine was detected over the 7 days following fluoxetine administration. The fluvoxamine concentration had decreased markedly by 24 h. 5. Pretreatment with fluoxetine (10 mg kg(-1), x2) failed to alter cerebral MDMA accumulation compared to saline pretreated controls. 6. Neither fluoxetine or fluvoxamine altered MDMA-induced acute hyperthermia. 7. These data demonstrate that fluoxetine produces long-lasting protection against MDMA-induced neurodegeneration, an effect apparently related to the presence of the drug and its active metabolite inhibiting the 5-HT transporter. Fluoxetine does not alter the metabolism of MDMA or its rate of cerebral accumulation.

Animals↗
PubMed2001

A study of the mechanisms involved in the neurotoxic action of 3,4-methylenedioxymethamphetamine (MDMA, 'ecstasy') on dopamine neurones in mouse brain.

1. Administration of 3,4-methylenedioxymethamphetamine (MDMA, 'ecstasy') to mice produces acute hyperthermia and long-term degeneration of striatal dopamine nerve terminals. Attenuation of the hyperthermia decreases the neurodegeneration. We have investigated the mechanisms involved in producing the neurotoxic loss of striatal dopamine. 2. MDMA produced a dose-dependent loss in striatal dopamine concentration 7 days later with 3 doses of 25 mg kg(-1) (3 h apart) producing a 70% loss. 3. Pretreatment 30 min before each MDMA dose with either of the N-methyl-D-aspartate antagonists AR-R15896AR (20, 5, 5 mg kg(-1)) or MK-801 (0.5 mg kg(-1)x3) failed to provide neuroprotection. 4. Pretreatment with clomethiazole (50 mg kg(-1)x3) was similarly ineffective in protecting against MDMA-induced dopamine loss. 5. The free radical trapping compound PBN (150 mg kg(-1)x3) was neuroprotective, but it proved impossible to separate neuroprotection from a hypothermic effect on body temperature. 6. Pretreatment with the nitric oxide synthase (NOS) inhibitor 7-NI (50 mg kg(-1)x3) produced neuroprotection, but also significant hypothermia. Two other NOS inhibitors, S-methyl-L-thiocitrulline (10 mg kg(-1)x3) and AR-R17477AR (5 mg kg(-1)x3), provided significant neuroprotection and had little effect on MDMA-induced hyperthermia. 7. MDMA (20 mg kg(-1)) increased 2,3-dihydroxybenzoic acid formation from salicylic acid perfused through a microdialysis tube implanted in the striatum, indicating increased free radical formation. This increase was prevented by AR-R17477AR administration. Since AR-R17477AR was also found to have no radical trapping activity this result suggests that MDMA-induced neurotoxicity results from MDMA or dopamine metabolites producing radicals that combine with NO to form tissue-damaging peroxynitrites.

Animals↗
PubMed2001

Variant Philadelphia translocations in chronic myeloid leukaemia can mimic typical blast crisis chromosome abnormalities or classic t(9;22): a report of two cases.

A range of fluorescent in situ hybridization techniques have been used to reveal hidden variant Philadelphia translocations in two cases of Ph-positive chronic-phase chronic myeloid leukaemia. In one patient, a highly complex variant Ph translocation affecting four chromosomes had resulted in the formation of structures with the appearance of i(17q) and +8. Misinterpretation of these karyotypes has direct clinical relevance. Our findings illustrate that even established cytogenetic abnormalities may contain cryptic abnormalities beyond the resolution of conventional cytogenetic methods.

Aged↗
PubMed2001

Mutation and methylation analysis of the transforming growth factor beta receptor II gene in polycythaemia vera.

Polycythaemia vera (PV) is a myeloproliferative disorder (MPD) thought to result from transformation of a haemopoietic stem cell. Transforming growth factor beta1 (TGF-beta1) is a negative regulator of haemopoietic stem cells, an effect mediated by direct binding to TGF-beta receptor II (TGF-beta RII). Reduced levels of TGF-beta RII mRNA or protein have been reported in several MPDs including PV, suggesting a role for TGF-beta RII in PV. No mutational analysis of the TGF-beta RII gene has yet been performed in PV. To investigate whether genetic or epigenetic alteration of the TGF-beta RII gene contributes to the pathogenesis of PV, we performed mutation and methylation analysis in 15 PV patients. The promoter, all seven exons and all intron/exon junctions were studied using single-strand conformation polymorphism (SSCP) and heteroduplex analysis (HA). In total, three single nucleotide polymorphisms (SNPs) were identified. These were located in the promoter, intron 2 and exon 5. No acquired mutations were detected in any patient sample. We also present a novel method, termed methylation-specific strand extension (MSSE), for the detection of methylated CpG dinucleotides. The combination of bisulphite modification and MSSE permits rapid analysis of the methylation status of CpG dinucleotides in multiple samples. We analysed the methylation status of the promoter and of a CpG island within exon 1 in 15 PV patients. No aberrant methylation was detected in either of these regions. These data demonstrate that neither mutation nor abnormal methylation of the TGF-beta RII gene is associated with the pathogenesis of PV. Furthermore, MSSE is a rapid and robust approach for assessing the methylation status of a given genomic region.

Adult↗
PubMed2001

Myeloproliferative disorders.

The myeloproliferative disorders (MPDs) are a group of pre-leukaemic disorders characterized by proliferation of one or more lineages of the myelo-erythroid series. Unlike the Philadelphia chromosome in chronic myeloid leukaemia, there is no pathognomonic chromosomal abnormality associated with the MPDs. Chromosomal abnormalities are seen in 30-40% of patients with polycythaemia vera (PV) and idiopathic myelofibrosis (IMF) and seem to indicate a poor prognosis. On the other hand, chromosomal abnormalities are rare in essential thrombocythaemia. Consistent acquired changes seen at diagnosis include deletion of the long arm of chromosome 20, del(13q), trisomy 8 and 9 and duplication of parts of 1q. Furthermore del(20q), trisomy 8 and dupl(lq) all arise in multipotent progenitor cells. Molecular mapping of 20q deletions and, to some extent, 13q deletions has identified a number of candidate target genes, although no mutations have yet been found. Finally, translocations associated with the rare 8p11 myeloproliferative syndrome and other atypical myeloproliferative disorders have permitted the identification of a number of novel fusion proteins involving fibroblast growth factor receptor-1.

Chromosome Aberrations↗