Search PubMed⌕ Search

Biomedical subjects

W R Lusby

Publications and source records attributed to W R Lusby.

24 records · Page 2Linked to original sources
PubMed1982

Mineral composition of muscles of 1- to 6-year-old steers.

The diaphragm, longissimus, psoas major, semitendinosus and transversus abdominus muscles from eight or nine Angus steers were evaluated at each age of slaughter including 12, 18, 24, 30, 36, 48, 60 and 72 mo. The content of K, Fe, and Zn varied (P less than .01) with age of the steers. Ca, Na and Mg were not affected. The K content on a fat-free basis decreased from a high of 392 mg/100 g wet tissue at 24 mo of age to a low of 332 mg/100 g at 72 mo. Fe content increased with age from 2.00 mg/100 g of tissue at 12 mo to 3.73 mg/100 g at 72 mo. Concentrations of all minerals varied (P less than .01) among the five muscles evaluated. Feeding regimen had a significant effect on K, Fe and Zn, Steers fed entirely ad libitum had a higher K (17 mg/100 g more) and Fe (.19 mg/100 g more) content in their muscles than did the steers that were fed to gain .45 kg/d or those fed ad libitum for the last 6 mo before slaughter. Where significant, the magnitude of the difference in mineral content among age groups, muscles and feeding regimens was large enough to require that maturity, muscle and feeding regimen be specified when values for mineral content were reported.

Abattoirs↗
PubMed1981

Synthesis and biological activity of brassinolide and its 22 beta, 23 beta-isomer: novel plant growth-promoting steroids.

Brassinolide (2 alpha, 3 alpha, 22 alpha, 23 alpha-tetrahydroxy-24 alpha-methyl -B-homo-7-oxa-5 alpha-cholestan-6-one), a novel plant growth-promoting steroid isolated from rape pollen, and its hitherto unknown 22 beta, 23 beta-isomer were synthesized from a C-24 epimeric 60:40 mixture of 22-dehydroxampesterol (24 alpha-methyl) and brassicasterol (24 beta-methyl) from oysters. The method of synthesis favored the formation of the 22 beta, 23 beta-isomer by better than 4:1. Comparative plant growth-promoting capabilities of brassinolide, both natural and synthetic, and its three side chain cis-glycolic isomers in the bean second internode bioassay showed that the natural and synthetic brassinolides were equally active and caused splitting of the internode at the 0.1 microgram level. The least active was the 22 beta, 23 beta-isomer of brassinolide. The isomers with the 22 alpha, 23 alpha and 24 alpha, and the 22 beta, 23 beta and 24 beta configurations were highly active and were required at about 10 times the concentration of brassinolide to cause the same physiological response. In the bean first internode bioassay, an auxin-induced growth test system which employs isolated bean plant segments, the isomer with 22 beta, 23 beta and 24 beta configuration caused a greater response than brassinolide. Two of the four tetrahydroxy ketones obtained in the synthesis of the isomers were also active in both assays.

Biological Assay↗
PubMedDate not supplied

24-Methyl-23-dehydrocholesterol: a new sterol intermediate in C-24 demethylation from the nematodes Panagrellus redivivus and Caenorhabditis elegans?

Panagrellus redivivus produced 24-methyl-23-dehydrocholesterol as 4.0% of the 4-desmethylsterols when propagated in a medium containing campesterol as the dietary sterol. The re-examination of previous data revealed that Caenorhabditis elegans produced 1.8% 24-methyl-23-dehydrocholesterol when propagated in medium containing campesterol. 24-Methyl-23-dehydrocholesterol was not detected when the nematodes were propagated in medium containing 22-dihydrobrassicasterol or 24-methylenecholesterol. This may be a result of the greater efficiency of dealkylation of the latter two sterols. This is the first report of the natural occurrence of this sterol in a non-photosynthetic organism, and the first report in organisms that dealkylate 24-alkylsterols.

Acetylation↗
PubMedDate not supplied

Metabolism of [14C]cholesterol to C-20 isomeric [14C]pregn-5-ene-3,20-diols in the tobacco hornworm, Manduca sexta.

After injection into male and female fifth-instar larvae of Manduca sexta, [14C]cholesterol was converted to C21 steroids, [14C]pregn-5-ene-3 beta,20-diols. These metabolites were isolated from 8-day-old pupae and were identified by TLC, HPLC, and GC-MS as the C-20 isomers of pregnene-3 beta,20-diol. They also were isolated from male and female meconium fluid (of 16-day-old pupae) following injection of [14C]cholesterol into 14-day-old pupae.

Animals↗