Biomedical subjects

D J Collins

Publications and source records attributed to D J Collins.

At least 55 records · Page 3Linked to original sources

PubMed1991

A comparison of in vivo and in vitro 31P NMR spectra from human breast tumours: variations in phospholipid metabolism.

An in vivo 31P NMR spectrum was obtained from each of four human breast tumours. The phosphomonoester and phosphodiester region of each spectrum consisted of a broad peak. Chemical extracts from samples of each of the tumours obtained at resection were examined on a high field strength NMR system. The phosphomonoester region in the spectrum from each extract resolved into three peaks consisting of phosphocholine, phosphoethanolamine and a nucleoside monophosphate. The phosphodiester region resolved into two components, glycerophosphorylcholine and glycerophosphorylethanolamine. Comparing the in vivo and in vitro data from each tumour showed that the contribution of phosphodiester was much lower in the in vitro spectra. We believe this to be a consequence of phospholipid, which would not appear in the aqueous extract, contributing to the phosphodiester peak in vivo.

Breast Neoplasms↗

PubMed1989

In-vivo 31P magnetic resonance spectroscopy for monitoring treatment response in breast cancer.

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Antineoplastic Combined Chemotherapy Protocols↗

PubMed1983

The structure and function of oestrogens. VI. The quinone methide hypothesis: stability of the benzylic hydrogen atoms of meso-hexoestrol during oestrogenic stimulation in mice.

A new hypothesis for oestrogen action at the molecular level is that the phenolic moiety of an oestrogen is oxidized to the corresponding quinone methide which is rapidly reduced with, say, NADPH to regenerate the oestrogen; the feedback from the rapid consumption of oxidant and/or reductant in the target organs might be responsible for the local increase in RNA synthesis, and its consequent phenomena. This hypothesis requires continuous removal and replacement of a benzylic hydrogen atom (H9 alpha of oestradiol) in an oestrogen at the receptor site. When a physiological dose of a mixture meso-(2-14C)- and meso-(2,3,4,5-3H4)hexoestrol was administered intravaginally in mice, the 14C:3H ratio in the phenolic portion of the vaginal extracts was essentially the same as that of the pure test mixture. This indicates that there was no net exchange of benzylic hydrogen in meso-hexoestrol during its stimulation of the mouse vagina.

Animals↗

PubMed1983

The structure and function of oestrogens. VII. The use of (9,12,12-2H3)- and (11xi,12,12-2H3) oestradiol in a test of the quinone methide hypothesis for oestrogen action.

Ovariectomized mice were injected intravaginally with a physiological dose of (9,12,12-2H3)oestradiol (3), and a control group was similarly injected with (11xi,12,12-2H3)oestradiol (4). Gas-liquid chromatography/mass spectrometry (g.l.c./m.s.) analysis of the oestradiols recovered from the vaginae of the two sets of mice showed that the content and distribution of deuterium were the same as in the respective pure trideuterated oestradiols (3) and (4). This proved conclusively that the 9 alpha-hydrogen of oestradiol is not exchanged during residence in and stimulation of the vagina. It therefore appears unlikely that reversible quinone methide formation in oestradiol is the trigger mechanism for stimulation of RNA synthesis, unless a hydrogen transfer relay system permits repetitive removal and replacement of the hydrogen atom at C9 during the oxidation-reduction cycle.

Animals↗

PubMed1981

Analysis of isomeric ethynylestradiol glucuronides in urine.

A method for separation and analysis of conjugates of ethynylestradiol in urine is described. Steroid conjugates are separated on a lipophilic strong anion exchanger (triethylaminohydroxypropyl Sephadex LH-230), and phenolic steroids released by enzyme hydrolysis or solvolysis ar isolated by chromatography on the same ion exchanger. Steroids carrying an ethynyl group are isolated by chromatography on SP-Sephadex (Ag+). Ethynylestradiol is analyzed by gas chromatography-mass spectrometry of the trimethylsilyl ether, using [9,11,11,12,12-(2)H5] ethynylestradiol and internal standard.

Ethinyl Estradiol↗

PubMed1978

Serum methionine: its rapid determination by continuous-flow colorimetry.

A rapid automated method for the determination of serum methionine is presented for use with the Technicon AutoAnalyzer system. It is based on the decolorisation of halide platinates by organic sulphides, including methionine. The 5--95% reference range from 249 sera from hospital patients (excluding those with liver and renal diseases and diabetes) was 20--60 mumol/l, mean 35 mumol/l. The S.D. of the method for 40 duplicate samples was 2.2 mumol/l. Recoveries ranged from 101--105%. This measurement facilitates the clinical evaluation of liver disease, especially acute liver failure, kidney disease and diabetes mellitus.

Autoanalysis↗

PubMed1976