Search PubMed⌕ Search

Biomedical subjects

J Dow

Publications and source records attributed to J Dow.

At least 37 records · Page 2Linked to original sources
PubMed1993

Determination of an acetylcholinesterase inhibitor, MDL 73745, in dog plasma and urine by combined gas chromatography/negative ion chemical ionization mass spectrometry.

A highly sensitive and specific assay has been developed for the determination of MDL 73745 [2,2,2-trifluoro-1-(3-trimethylsilyl-phenyl) ethanone] (I) and the internal standard (MDL 74398) at the nanomolar level in dog plasma and urine by gas chromatography/mass spectrometry. After a single-step extraction process, an aliquot was directly injected onto the gas chromatograph column. The mass spectrometer was run in the negative ion chemical ionization mode with ammonia as reagent gas, and was set to monitor the abundant M-. ion at m/z 246 of both compounds. The method yielded a linear response over the concentration range 0.1-10 pmol 100 microliters -1 plasma or urine. Within-day reproducibility at a concentration of 0.25, 1 and 5 pmol 100 microliters -1 plasma was 8.6%, 1.0% and 1.0%, respectively. The method was applied to the determination of I in plasma and urine after administration of 1 mg kg-1 i.v. and 10 mg kg-1 p.o. to dogs.

Acetophenones↗
PubMed1993

Pharmacokinetics of and monoamine oxidase B inhibition by (E)-4-fluoro-beta-fluoromethylene benzene butanamine in man.

MDL 72974A ((E)-4-fluoro-beta-fluoromethylene benzene butanamine HCl salt, CAS 120635-25-8) is a new irreversible inhibitor of the B form of monoamine oxidase (MAO-B). MDL 72974A's pharmacokinetic parameters were evaluated after administration of a single oral dose and after multiple oral doses. The concentration of parent drug was determined in plasma using a solid-liquid extraction method and gas chromatographic-mass spectrometric analysis. MDL 72974A produced significant inhibition of platelet MAO-B activity at all of the doses > or = 0.5 mg (> 95% after 1 h). The pharmacokinetic parameters showed a short plasma half-life (1 h) and a high total body clearance (Cltot) both probably due to extensive and rapid metabolism as suggested by the low urinary excretion of unchanged drug (< 1% of the administered dose). After the administration of multiple doses of MDL 72974A, a decrease in Cltot and a concomitant increase in the AUC and t1/2, was observed, probably due to a change in the elimination rate of MDL 72974A. Due to the once-a-day dosing schedule and the short plasma t1/2, no drug accumulation occurred.

Allyl Compounds↗
PubMed1992

Dendritic processing: using microstructures to solve a hitherto intractable neurobiological problem.

In vivo, intracellular recordings of mammalian brain stem motoneurones, followed by peroxidase staining and tridimensional reconstruction, suggest that the shape of the dendritic tree plays an important role in the processing of neural information. To test this hypothesis attempts were made to guide, in culture, the growth of neuritic branches of neurones dissociated from the hypoglossal nucleus of rat brain stem. This was performed using topographical and adhesive microstructures which were designed to control the shape of the neuritic tree. Guidance of the neuritic processes can be observed with small grooves engraved on quartz and plastic substrates, and simple shapes with few processes and bifurcations on each neurite could be obtained using adhesive microstructures. These procedures, which allow the shape of a neurone to be controlled, are very promising in the study, by means of classical electrophysiological methods as well as optical recordings, of the involvement of dendritic architecture in the processing of neural information.

Animals↗
PubMed1991

Effect of a cardioselective alpha-tocopherol analogue on reperfusion injury in rats induced by myocardial ischaemia.

Free radicals may cause some of the irreversible injury which occurs during myocardial ischaemia and reperfusion. In the present study the effects of a cardioselective, free radical scavenger, MDL 74270, which is an analogue of alpha-tocopherol, on myocardial infarct size in an anaesthetised rat model of coronary artery ligation (60 min) and reperfusion (30 min) has been evaluated. Infusion of MDL 74270 (0.3-3.0 mg/kg per h) commencing 10 min before occlusion until the end of reperfusion significantly reduced infarct size. The highest dose also caused a significant reduction in serum creatine phosphokinase levels. Similar findings have been obtained with the bromide salt of MDL 74270. Tissue distribution studies with 14C-labelled MDL 74270 and its tertiary amine analogue (MDL 74366) showed heart/blood ratios of total radioactivity, 1-6 h after i.v. administration, greater than 20 after MDL 74270 and around 1 after MDL 74366. The importance of accumulation of total radioactivity in the heart after MDL 74270 is supported by the fact that MDL 74366 was 30 times less potent as a myocardial protector in the ligation/reperfusion studies. It is concluded that MDL 74270 has potential for cardioprotective use in conditions of acute reperfusion.

Animals↗
PubMed1991

A cardioselective, hydrophilic N,N,N-trimethylethanaminium alpha-tocopherol analogue that reduces myocardial infarct size.

The alpha-tocopherol analogue 3,4-dihydro-6-hydroxy-N,N,N,2,5,7,8- heptamethyl-2H-1-benzopyran-2-ethanaminium 4-methylbenzenesulfonate (1a, MDL 73404) and its O-acetate 1b (MDL 74270) were synthesized. Compound 1a was found to be hydrophilic (log P = -0.60) and to prevent lipid autoxidation in rat brain homogenate with an IC50 of 1.7 +/- 0.9 microM. Tissue distribution studies with [14C]-1b in rats (1 mg/kg iv) showed that radioactivity accumulates in the heart (ratio 20:1 vs blood after 1 h). Infusion of 1 mg/kg per h of 1b bromide reduced infarct size by 54% in rats subjected to coronary artery occlusion for 60 min followed by reperfusion for 30 min, compared to saline-infused controls. By comparison, the tertiary amine analogue 5 was found not to accumulate in heart tissue, to be an equally effective free-radical scavenger in vitro, but to require a higher dose to reduce infarct size in rats. This shows that the cardioselectivity of compound 1 contributes to its potency in salvaging myocardial tissue in rats after ischemia and reperfusion.

Animals↗
PubMed1989

Ulcerogenic choledochoduodenal fistula.

Spontaneous choledochoduodenal fistula is a rare form of biliary enteric fistula which is usually related to peptic ulcer disease and therefore is seen more often in men. This is in contrast to the more common cholecystoduodenal fistula which is associated with calculous gall-bladder disease and occurs predominantly in women. We report two cases diagnosed by radiology following unhelpful laparotomy.

Adult↗
PubMed1986

Transfer kinetics of pefloxacin into cerebro-spinal fluid after one hour i.v. infusion of 400 mg in man.

Nine subjects (5 women) aged between 17-66 years, with hydrocephalus were studied. An external ventricular drain was introduced for diagnostic purposes. Cerebro-spinal fluid (CSF) and plasma samples were obtained at suitable intervals after 1 h infusion of 400 mg pefloxacin. In plasma, pefloxacin Cmax was 8.54 +/- 1.53 (mean +/- S.E.M.) mg/l, at the end of infusion, whereas N-desmethyl pefloxacin concentration was 0.17 +/- 0.03 mg/l. The metabolite accounted for only 2% of plasma levels of pefloxacin. In CSF, pefloxacin Cmax was 2.97 +/- 0.32 mg/l, 5-6 h after the start of infusion, whereas N-desmethyl pefloxacin Cmax varied between 0.1-0.2 mg/l. Apart from the 1 h sample, the CSF/plasma ratio of pefloxacin was 60% which is similar to the unbound fraction of pefloxacin in plasma. The apparent half-life (T1/2) of transfer of pefloxacin from plasma to CSF was 1.26 +/- 0.18 h, assuming a first order process, while the apparent elimination T1/2 in CSF was 13.40 +/- 1.76 h, which is similar to the elimination T1/2 found previously in plasma, thus accumulation of pefloxacin in CSF is unlikely. With the present dosage regimen, CSF quickly attains therapeutic levels of pefloxacin.

Adolescent↗
PubMed1985

Automated high-performance liquid chromatographic determination of spiramycin by direct injection of plasma, using column-switching for sample clean-up.

A fully automated high-performance liquid chromatographic method is described for the determination of spiramycin 1 in plasma. First, 1 ml of plasma is diluted with 1.5 ml of 4% acetonitrile containing spiramycin 2 as internal standard, and 1 ml is then injected via an automatic sampling unit. A pneumatic valve, which is remote-controlled by the programmable timer of an integrator, switches the sample, initially injected onto a precolumn for sample clean-up, to an analytical column for sample separation. This method was compared with a microbiological assay and has been successfully applied to pharmacokinetic studies on spiramycin in humans.

Chromatography, High Pressure Liquid↗