Biomedical subjects

M Twohig

Publications and source records attributed to M Twohig.

4 recordsLinked to original sources

PubMed1999

Efficient isolation of the rare diarrhoeic shellfish toxin, dinophysistoxin-2, from marine phytoplankton.

The rare diarrhoeic shellfish poisoning (DSP) toxin, dinophysistoxin-2 (DTX-2), which is an okadaic acid (OA) isomer, has been isolated from a marine phytoplankton biomass that consisted mainly of Dinophysis acuta. Using a large double plankton net (length 5.9 m), bulk phytoplankton samples were collected off the south-west coast of Ireland and extracted with methanol and chloroform. Liquid chromatography coupled with ionspray mass spectrometry and tandem mass spectrometry (LC-MS, LC-MS-MS) showed the sample contained DTX-2 and OA, at a concentration of 80 pg/cell and 60 pg/cell, respectively. Flash chromatography using silica, sephadex LH20 and C18-silica, followed by preparative reversed-phase LC, separated DTX-2 from OA. The efficiency of the separation procedures was substantially improved by the use of a bioscreen to detect DSP toxins in eluate fractions and the application of a new derivatisation procedure for the chromatographic elucidation of toxin profiles with fluorimetric detection (LC-FLD). Thus, 1/1000th aliquots of eluate fractions were assayed using protein phosphatase-2A for the presence of inhibitory compounds. Positive fractions were further analysed for DSP toxins by LC-FLD following derivatisation using the hydrazine reagent, luminarine-3. The identity and purity of the free isolated DTX-2 was confirmed using flow injection analysis (FIA) and liquid chromatography (FIA-MS, LC-MS and LC-MS-MS).

Animals↗

PubMed1999

Pancreatic tuberculosis.

Tuberculosis of the pancreas is a rare gastrointestinal tract entity. This unusual manifestation of tuberculosis should be included in the differential diagnosis of high-risk patients presenting with a pancreatic mass.

Adult↗

PubMed1998

Sensitive determination of anatoxin-a, homoanatoxin-a and their degradation products by liquid chromatography with fluorimetric detection.

Cyanobacterial neurotoxins have been implicated in animal deaths resulting from drinking contaminated water. Anatoxin-a (AN) and homoanatoxin-a (HMAN) have previously been analysed using high-performance liquid chromatography (HPLC) with UV detection, but this procedure is insufficiently sensitive and is subject to interferences. A sensitive fluorimetric (FL) method for determining AN was recently developed using derivatisation with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) and this has been applied to the simultaneous determination of AN, HMAN and their epoxy and dihydro degradation products. Microscale syntheses were used to prepare the dihydro and epoxy derivatives from AN and HMAN. These compounds were produced in high yields, as confirmed by electrospray MS and HPLC-FL of their benzoxadiazole derivatives. All six NBD derivatives were readily separated using isocratic reversed-phase HPLC. The recoveries of these compounds from spiked water samples, using weak cation-exchange (WCX) solid-phase extraction (SPE), were 83.2-84.9% at concentrations of 10 micrograms/l. The R.S.D. values were 1.7-3.9% (n = 8) and the limits of detection were better than 10 ng/l for all six compounds, illustrating the high sensitivity of the method. This methodology was successfully applied to the analysis toxin degradation products in natural samples. Dihydroanatoxin-a (0.8 mg/g) was isolated from a benthic Oscillatoria bloom from Caragh Lake, Ireland, and was found to contain two isomers but their ratio was different from that found in the synthetic material.

Bacterial Toxins↗

PubMed1996

The role of birth injury and the consequences of inadequately treated hypogonadism in longstanding panhypopituitarism.

We describe a middle-aged profoundly hypogonadal man with panhypopituitarism since infancy who was treated only with glucocorticoid and thyroid replacement. A magnetic resonance imaging study (MRI) revealed absence of pituitary stalk and ectopic neurohypophysis consistent with traumatic transection, probably resulting from a traumatic birth. The hormonal consequences of this stalk lesion were recognized but inadequately treated for 45 years resulting in avoidable endocrine and psychosocial defects. Androgen replacement was started at age 45 with good initial results. The unique hormonal replacement issues at this age are discussed.

Birth Injuries↗