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M W Couch

Publications and source records attributed to M W Couch.

34 records · Page 2Linked to original sources
PubMed1977

Evidence for the lack of a carrier effect in the solvent extraction and determination of octopamine by gas chromatography mass spectrometry.

It has been shown that there is no significant carrier effect when low levels of [3H]octopamine (100 pg) are extracted by ethyl acetate from aqueous solutions containing a 10(3) or 10(6) times excess of unlabelled octopamine. It is also shown that there is no carrier effect when low levels of octopamine as the tetrakis-TMS derivative are injected with 100 times the amount of the [2H3] analogue on an SE 30 column.

Chromatography, Gas↗
PubMed1977

Chemical and radiochemical stability of the adrenal-scanning agents, 6beta-iodomethyl-19-norcholest-5(10-en-3beta-ol and 19-iodocholest-5-en-3beta-ol.

The chemical stabilities of the adrenal-scanning agents, 6beta-iodo-methyl-19-norcholest-5(10)-en-3beta-ol (6-iodomethylnorcholesterol) and 19-iodocholest-5-en-3beta-ol (19-iodocholesterol), and several of their derivatives were examined by 13C nuclear magnetic resonance. Neat 6-iodomethylnorcholesterol, sealed in glass under nitrogen and stored at 0 degrees C, remains 98 mole% chemically pure for 3 months. Neat 19-iodocholesterol, stored in the dark at 25 degrees C, remains 98 mole% chemically pure for 3 months. Either 6-iodomethylnorcholesterol-125I or-131I, informulation and stored at 5 degrees C, will remain greater than 97% radiochemically pure for at least 15 days. Labelled 19-iodocholesterol, formulated and stored under the same conditions, shows 20% decomposition after 3 weeks and 40% after 6 weeks.

Adrenal Glands↗
PubMed1977

Comparison of 19-lodocholesterol and 6-lodomethylnorcholesterol as adrenal-scanning agents.

The two adrenal-specific compounds, 19-iodocholest-5-en-3beta-ol (19-iodocholesterol) and 6beta-iodometyly-19-norcholest-5(10)-en-3beta-ol (6-iodomethylnorcholesterol), synthesized pure in gram amounts have been labeled with iodine-125 and used for tissue-distribution studies in the rat. Radioactivity from 6-iodomethylnorcholesterol is accumulated in the rat adrenal gland at least 18 times more than is radioactivity from 19-iodocholesterol at 24 hr, and 50 times more at 72 hr. The use of radioactive 6-iodomethylnorcholesterol gave superior adrenal images in rats at earlier times than did radioactive 19-iodocholesterol, and the former should be equally superior when used in humans.

Adrenal Gland Diseases↗
PubMed1976

Synthesis and purification of radioactive 6beta-iodomethyl-19-norcholest-5(10)-en-3beta-ol.

A method for the synthesis and purification of 6beta-iodomethyl-19-norcholest-5(10)-ene-3beta-ol-131I of greater than 98 mole% chemical purity and greater than 99% radiochemical purity is presented. Carbon-13 and proton NMR were used to establish the identity and purity. Discrepancies in the characterization of this compound, previously published by two other research groups, are discussed.

Cholestenes↗
PubMedDate not supplied

Carbonless copy paper: a review of its chemical components and health hazards.

The components of carbonless copy paper (CCP) and the chemistry involved in its manufacture are reviewed. Claims that the routine use of CCP can cause health problems ranging from skin, eye, and lung irritation to severe headaches and neurological damage are described; yet no definitive studies have been conducted that show correlation between CCP use and these symptoms. The toxicological properties of CCP components, many of them precursors to the dye-containing microcapsules or dye solvents that may be causing these problems, are discussed. Recommendations for the minimization of possible physiological reactions to CCP include reduction of usage time; use of the CCP in a well-ventilated area; storing large quantities of CCP, both new or archived, away from work area; and the practice good hand hygiene.

Copying Processes↗
PubMedDate not supplied

Extraction of omega- and omega-1-hydroxylauric acids with ethyl acetate results in formation of acetoxy products.

In studies of the regiospecific metabolism of lauric acid by monooxygenase enzymes, incubation medium from the reaction of [14C] lauric acid and microsomes is routinely acidified and extracted with ethyl ether. Separation of products by HPLC shows the formation of omega(12)- and omega-1(11)-hydroxylauric acids by rat liver microsomes. In a comparison of several extraction solvents, we observed that the extraction of incubation media with ethyl acetate alone was associated with the appearance of a major new metabolite peak concomitant with loss of the 12- and 11-hydroxylaurate peaks by 62 and 23%, respectively. No difference was observed between extraction procedures in the per cent recovery of radiolabel. Similar results were observed with extraction of lauric acid metabolites formed by fish liver microsomes. Acidification of the incubation media prior to ethyl acetate extraction prevented formation of the new metabolite peak. In experiments to identify the new metabolite(s), 11- and 12-hydroxylaurate products formed by rat liver microsomes were acetylated and found to show an HPLC retention time similar to that of the unknown metabolite peak formed with ethyl acetate extraction. Mass spectrometric analysis further showed that the methyl esters of 11- and 12-acetoxylauric acids were very similar to that of the methyl ester derivative of the unknown metabolite fraction. Thus, data indicate that the acetoxy derivatives of 11- and 12-hydroxylauric acids were formed by direct reaction of ethyl acetate with the laurate products formed by microsomal monooxygenase enzymes. This extraction procedure can produce a major shift in the amount and ratio of omega- and omega-1-hydroxylaurates measured in the incubation media.

Acetates↗