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Stephen Bennett

Publications and source records attributed to Stephen Bennett.

4 recordsLinked to original sources
PubMed2005

Modulation of striatal dopamine release in vitro by agonists of the glycineB site of NMDA receptors; interaction with antipsychotics.

The N-methyl-D-aspartate (NMDA) glutamate receptor possesses an obligatory co-agonist site for D-serine and glycine, named the glycineB site. Several clinical trials indicate that glycineB agonists can improve negative and cognitive symptoms of schizophrenia when co-administered with antipsychotics. In the present study we have investigated the effects of glycineB agonists on the endogenous release of dopamine from preparations of rat striatal tissue prisms in static conditions. The glycineB agonists glycine (1 mM) and D-serine (10 microM), but not D-cycloserine (10 microM), substantially increased the spontaneous release of dopamine, but significantly reduced the release of dopamine evoked by NMDA. The effect of glycine on spontaneous release was abolished by the non-competitive NMDA antagonists 5R,10S-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d] cyclohepten-5,10-imine (MK-801, 10 microM) and ifenprodil (5 microM), but was only partially suppressed by the competitive antagonist 4-(3-phosphonopropyl)-piperazine-2-carboxylic acid (CPP, 10 microM). The selective inhibitor of the glial glycine transporter GlyT1 N[3-(4'-fluorophenyl)-3-(4'-phenylphenoxy)propyl]sarcosine (NFPS, 10 microM) significantly increased the release of dopamine in an MK-801-sensitive manner. Interestingly, haloperidol (1 microM), but not clozapine (10 microM), prevented the effects of glycine. This study shows that glycineB modulators can control dopamine release by interacting with a distinctive NMDA receptor subtype with which some typical antipsychotics can interfere.

Animals↗
PubMed2004

Application of a magnetic extraction technique to assess radionuclide-mineral association in Cumbrian shoreline sediments.

An assessment has been made of the association of (239+240)Pu, 241Am and 210Po (in secular equilibrium with 210Pb) with iron minerals using a magnetic extraction technique. Grab samples of beach sand from the Cumbrian (UK) coastline were subjected to successive extractions with an approximately 0.1 T ferrite magnet and an approximately 0.3 T rare-earth magnet procedure to separate magnetic iron oxide minerals. Radionuclide concentrations in the magnetic extracts were enhanced (by approximately 4-6-fold) relative to the residue. Those in the approximately 0.1 T magnet extracts were broadly similar to those in the antiferromagnetic material extracted by the approximately 0.3 T magnet, despite the very large differences in magnetic property values between the two fractions (one to two orders of magnitude). The percentage of magnetic material in terms of mass was small and therefore, the majority of these radionuclides (on average 88%) were associated with the residue. Removal of stable Fe was incomplete. Given that the radionuclides may also bind to paramagnetic (nonmagnetic) Fe minerals, the data were extrapolated by normalising the results to quantitative Fe removal. This yielded average values of 37%, 45% and 46% for (239+240)Pu, 241Am and 210Po(210Pb), respectively, as upper limits for the fraction associated with magnetic + nonmagnetic Fe minerals. There are significant uncertainties inherent in quantifying data from this extraction technique. Nevertheless, it seems reasonable to conclude that radionuclide association with Fe minerals is unlikely to have a significant impact upon the physical dispersion of sediment contaminated by Sellafield discharges in the Irish Sea. However, it may be an important factor in governing Pu redox and redissolution behaviour.

Americium↗
PubMed2004

Ephedrine- and guaifenesin-induced nephrolithiasis.

OBJECTIVES: Ephedrine and guaifenesin are herbal supplements that have experienced increased use over the past decade. Ephedrine has been used as a stimulant and weight-loss product, guaifenesin as an expectorant and cough suppressant; both are found in combination in many antitussives and expectorants. This paper reviews the reported cases of ephedrine- and guaifenesin-induced nephrolithiasis, as well as the diagnostic techniques and treatments that have been successfully used for these stones. DESIGN: A systematic review of the literature pertaining to nephrolithiasis and the compounds ephedrine and guaifenesin was conducted. RESULTS: Ephedrine and guaifenesin use results in over 35% of urinary stones that are related to pharmaceutical metabolites, and collectively are present in 0.1% of all urinary stones. These calculi are radiolucent, requiring the use of computerized tomography (CT scan) for diagnosis. Alkalinization therapy offers an alternative to surgical intervention and may have a role in prevention of recurrence. CONCLUSIONS: Ephedrine and guaifenesin have been shown to cause nephrolithiasis in cases of abuse when taken individually or in combination. It is important for the clinician to be aware of the potential for these compounds to cause nephrolithiasis.

Antitussive Agents↗