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W R Lusby

Publications and source records attributed to W R Lusby.

At least 19 recordsLinked to original sources
PubMed1995

Degradation of pheromone biosynthesis-activating neuropeptide (PBAN) by hemolymph enzymes of the tobacco hornworm, Manduca sexta, and the corn earworm, Helicoverpa zea.

The tritium-labeled bis-norleucine analog of Helicoverpa zea pheromone biosynthesis-activating neuropeptide ([3H]NLPBAN) was incubated in vitro with hemolymph from Manduca sexta or H. zea adult females. The incubations resulted in the formation of several tritium-labeled degradation products. At a [3H]NLPBAN concentration of 0.9 microM the degradation proceeded at a very slow but physiologically plausible rate (2-10 fmol/min/microliters hemolymph). The primary [3H]NLPBAN degradation reaction in M. sexta hemolymph was not inhibited by 20 microM leupeptin, 0.1 mM amastatin, 1 mM EDTA, 1 mM EGTA, 1 mM 1,10-phenanthroline, or 2 mM 4-(2-aminoethyl)benzenesulfonyl fluoride; but secondary reactions may have been affected, as some of the inhibitors changed the radio-HPLC profile of the degradation products. It is concluded that hemolymph of M. sexta and H. zea contains peptidase(s) capable of inactivating circulating PBAN.

Amino Acid Sequence↗
PubMed1995

The glycosylceramides of the nematode Caenorhabditis elegans contain an unusual, branched-chain sphingoid base.

Caenorhabditis elegans was cultured in semi-defined medium containing yeast extract, soy peptone, glucose, hemoglobin, Tween 80, and sitosterol. Monoglycosylceramides were chromatographically purified from nematode extracts. Their structures were elucidated with mass spectrometry, nuclear magnetic resonance spectroscopy, and analysis of methanolysis products of the parent cerebrosides. The glycosylceramides were unusual in that the only long-chain sphingoid base detected was an iso-branched compound with a C-4 double bond (i.e., 15-methyl-2-aminohexadec-4-en-1,3-diol). Glucose was the only sugar moiety detected. The fatty acids consisted of a series of primarily straight-chain, saturated, 2-hydroxylated C20-C26 acids; some iso-branched analogs also occurred. The sphingomyelins of C. elegans were also hydrolyzed, and the same iso-branched C17 compound was the only sphingoid base detected. This is the first structural analysis of a nematode glycosphingolipid and the first report of an organism in which the long-chain sphingoid bases are entirely iso-branched.

Animals↗
PubMed1995

Synthesis of a selenomethionine peptide and a preliminary study of transport into Escherichia coli monitored by high-performance liquid chromatography.

The tripeptide Gly-SeMet-Gly has been synthesized by a combination of solution and solid-phase methods. Increase in weight of the resin was very nearly theoretical, and purification was straightforward. Its absorption was compared to that of the corresponding peptide, Gly-Met-Gly, in E. coli using HPLC ion-exchange separation and fluorometric determination of the disappearance of peptides in the culture medium and the appearance of methionine and selenomethionine in the same culture medium. As E. coli are not known to possess extracellular peptidases, and in fact have been shown to possess transport systems for peptides, this absorption is interpreted as transport of the peptide through the cell wall and membrane into the cytoplasm, endohydrolysis of the peptide, and efflux of the peptides' amino acids. Uptake of both peptides was approximately equal, but was slowed when both peptides were present simultaneously.

Amino Acid Sequence↗
PubMed1992

Isolation and structural elucidation of the geometrical isomers of lutein and zeaxanthin in extracts from human plasma.

All-E-(3R,3'R,6'R)-lutein, all-E-(3R,3'R)-zeaxanthin, all-E-(3R,3'S,6'R)-3'-epilutein and some geometrical isomers of the former two dihydroxycarotenoids have been separated from an extract of human plasma by semipreparative high-performance liquid chromatography on a silica-based nitrile-bonded column. In the order of chromatographic elution, the isolated fractions were identified as all-E-lutein, all-E-zeaxanthin, all-E-3'-epilutein, 9Z-lutein, 9'Z-lutein, a mixture of 13Z-lutein and 13'Z-lutein, 9Z-zeaxanthin, 13Z-zeaxanthin and 15Z-zeaxanthin. The structures of all compounds, including the relative configuration at C(3') and C(6') of the luteins and the position of the stereomutated double bonds in the geometrical isomers, were unambiguously established by 1H nuclear magnetic resonance spectroscopy. The absolute configuration of the three all-E compounds was derived by circular dichroism and is also assumed to be valid for the geometrical isomers. The ultraviolet-visible absorption and mass spectra of each of the individually isolated compounds were also in agreement with the proposed structures.

Carotenoids↗
PubMed1992

Separation and identification of carotenoids and their oxidation products in the extracts of human plasma.

Eighteen carotenoids as well as vitamin A and two forms of vitamin E (gamma- and alpha-tocopherol) have been separated from extracts of human plasma by high-performance liquid chromatography (HPLC) on reversed-phase and sillca-based nitrile-bonded columns. In the order of chromatographic elution on a C18 reversed-phase column, the carotenoids were identified as (3R,3'R,6'R)-beta, epsilon-carotene-3,3'-diol [(3R,3'R,6'R)-lutein], (3R,3'R)-beta, beta-carotene-3,3'-diol [(3R,3'R)-zeaxanthin], 5,6-dihydroxy-5,6-dihydro-psi,psi-carotene, 3-hydroxy-2',3'-didehydro-beta,epsilon-caroten-3-ol, 3-hydroxy-beta-carotene,psi,psi-carotene, 7,8-dihydro-psi,psi-carotene, beta,psi-carotene, 7,8,7',8'-tetrahydro-psi,psi-carotene, beta,epsilon-carotene, beta,beta-carotene, 7,8,11,12,7',8'-hexahydro-psi,psi-carotene, and 7,8,11,12,7',8'-11',12'-octahydro-psi,psi-carotene. The polar carotenoids, which eluted in the vicinity of lutein and were unresolved on the C18 column, have been separated on a nitrile-bonded column employing isocratic HPLC conditions. In the order of elution, the carotenoids were epsilon,epsilon-carotene-3,3'-dione, 3'-hydroxy-epsilon,epsilon-caroten-3-one, 5,6-dihydroxy-5,6-dihydro-psi,psi-carotene, 3-hydroxy-beta,epsilon-caroten-3'-one, (all-E,3R,3'R,6'R)-lutein, (all-E,3R,3'R)-zeaxanthin, and (all-E,3R,3'S,6'R)-beta,epsilon-carotene-3,3'-diol (3'-epilutein) followed by several geometrical isomers of lutein and zeaxanthin.

Carotenoids↗
PubMed1991

Comparison of known and suspected pheromonal constituents in males of African ticks, Amblyomma hebraeum Koch and Amblyomma variegatum (Fabricius).

Three low molecular weight compounds were found in hexane:diethyl ether extracts of fed males of the African ticks, Amblyomma variegatum (tropical bont tick) and A. hebraeum (bont tick), namely, o-nitrophenol, methyl salicylate and 2,6-dichlorophenol. These same compounds were also fond in a rinse of fed A. variegatum males, but were absent or present in only trace amounts in a rinse of fed A. hebraeum males, o-Nitrophenol and methyl salicylate were present in much higher concentrations (i.e., amounts/tick) in A. variegatum than in A. hebraeum. 2,6-Dichlorophenol was also more abundant in A. variegatum than in A. hebraeum, but the differences were not as great as with the former two compounds. Extraction in hexane over a 3-week period revealed four additional compounds, benzaldehyde, benzyl alcohol, benzothiazole and nonanoic acid. The first three compounds were found in males of both species; nonanoic acid was found only in A. hebraeum males. Published reports consistently show strong attraction by o-nitrophenol and methyl salicylate for both sexes of the two bont tick species; 2,6-dichlorophenol and benzaldehyde have been reported to be attractive to both sexes of A. hebraeum. The possible roles of these compounds, as well as others occasionally reported from A. hebraeum and A. variegatum, as components of the aggregation/attachment pheromone or other pheromones is discussed.

Animals↗
PubMed1991

Metabolism of plant sterols by nematodes.

Parasitic nematodes do not biosynthesize sterols de novo and therefore possess a nutritional requirement for sterol, which must be obtained from their hosts. Consequently, the metabolism of phytosterols by plant-parasitic nematodes is an important process with potential for selective exploitation. The sterol compositions of several species of plant-parasitic nematodes were determined by capillary gas chromatography-mass spectrometry and compared with the sterol compositions of their hosts. Saturation of the phytosterol nucleus was the major metabolic transformation performed by the root-knot nematodes Meloidogyne arenaria and M. incognita and the corn root lesion nematode, Pratylenchus agilis. In addition to saturation, the corn cyst nematode, Heterodera zeae, dealkylated its host sterols at C-24. Because free-living nematodes can be cultured in sterol-defined artificial medium, they have been successfully used as model organisms for investigation of sterol metabolism in plant-parasitic nematodes. Major pathways of phytosterol metabolism in Caenorhabditis elegans, Turbatrix aceti and Panagrellus redivivus included C-24 dealkylation and 4 alpha-methylation (a pathway unique to nematodes). C. elegans and T. aceti introduced double bonds at C-7, and T. aceti and P. redivivus saturated the sterol nucleus similarly to the plant-parasitic species examined. Several azasteroids and long-chain dimethylalkylamines inhibited growth and development of C. elegans and also the delta 24-sterol reductase enzyme system involved in the nematode C-24 dealkylation pathway.

Animals↗
PubMed1988

Glucosylations of pregn-5-ene-3 beta,20R-diol.

The four possible monoglucosides of the pregn-5-ene-3 beta,20R-diol were synthesized along with a mixture of the four possible 3,20-diglucosides. The glucosides were characterized by HPLC and mass spectrometry.

Chemical Phenomena↗
PubMed1987

Metabolism of sterols of varying ring unsaturation and methylation by Caenorhabditis elegans.

The metabolism of three dietary 4,4-desmethylsterols and two 4 alpha-methylsterols was investigated in the free-living nematode Caenorhabditis elegans. Dietary cholestanol was converted mostly to lathosterol. Dietary lathosterol, 7-dehydrocholesterol, 4 alpha-methylcholest-7-enol and 4 alpha-methylcholest-8(14)-enol each remained largely unchanged. An absolute requirement for a substantial quantity of 7-dehydrocholesterol in C. elegans did not exist. C. elegans was unable to remove a 4 alpha-methyl group or introduce a double bond at C-5 and also demonstrated the lack of a delta 7-reductase. Its nutritional sterol requirement was satisfied by cholestanol, lathosterol or 7-dehydrocholesterol; growth was comparable to that obtained previously in media containing delta 5-sterols. However, the two 4 alpha-methylsterols appeared to be unsatisfactory sterol nutrients. The possible physiological importance of 4 alpha-methylsterols is discussed briefly.

Animals↗
PubMed1985

Biosynthesis of a C21 steroid conjugate in an insect. The conversion of [14C]cholesterol to 5-[14C]pregnen-3 beta,20 beta-diol glucoside in the tobacco hornworm, Manduca sexta.

Following injection into Manduca sexta (L.) female pupae (day 16), [14C]cholesterol was converted to a C21 steroid conjugate, 5-[14C]pregnen-3 beta,20 beta-diol glucoside. The conjugate was isolated from ovaries and eggs and contained three glucose units at least one of which is attached to C-20. The distribution of the other two glucose units remains to be determined. Other than the dealkylation of C-24 alkane or alkene substituents, side-chain cleavage of sterols is uncommon to insects. Here we report the first definitive proof of the biosynthesis of a C21 steroid conjugate from cholesterol in an insect species. The capability of M. sexta to so readily convert cholesterol to a C21 steroid suggests a physiological role for 5-pregnen-3 beta,20 beta-diol in this species.

Animals↗
PubMed1985

Inhibition of C28 and C29 phytosterol metabolism by N,N-dimethyldodecanamine in the nematode Caenorhabditis elegans.

Effects on the metabolism of campesterol and stigmasterol in Caenorhabditis elegans were investigated using N,N-dimethyldodecanamine, a known inhibitor of growth, reproduction and the delta 24-sterol reductase of this nematode. 7-Dehydrocholesterol was the predominant sterol (51%) of C. elegans grown in stigmasterol-supplemented media, whereas addition of 25 ppm amine resulted in a large decrease in the relative percentage of 7-dehydrocholesterol (23%) and the accumulation of a substantial proportion (33%) of delta 24-sterols (e.g., cholesta-5,7,24-trienol) and delta 22,24-sterols (e.g., cholesta-5,7,22, 24-tetraenol) but yielded no delta 22-sterols. Dealkylation of stigmasterol by C. elegans proceeded in the presence of the delta 22-bond; reduction of the delta 22-bond occurred prior to delta 24-reduction. Addition of 25 ppm amine to campesterol-supplemented media altered the sterol composition of C. elegans by increasing the percentage of unmetabolized dietary campesterol from 39 to 60%, decreasing the percentage of 7-dehydrocholesterol from 26 to 12%, and causing the accumulation of several delta 24-sterols (6%). C. elegans also was shown to be capable of dealkylating a delta 24 (28)-sterol as it converted 24-methylenecholesterol to mostly 7-dehydrocholesterol. The proposed role of 24-methylenecholesterol as an intermediate between campesterol and 7-dehydrocholesterol was supported by the results.

Amines↗
PubMed1984

Comparative effects of growth inhibitors on sterol metabolism in the nematode Caenorhabditis elegans.

An analogous series of dimethylalkyl compounds, consisting of four amines, an amide, and a phosphonate ester, inhibited motility and reproduction of the nematode Caenorhabditis elegans. Dimethylamines with straight-chain lengths of 12, 14, or 16 carbon atoms were equally active nematicides, causing greater than 80% population growth inhibition at a concentration of 25 ppm. The C12 straight-chain amine and its corresponding amide produced similar inhibition and were much more potent than either the corresponding C12 phosphonate or a C12 branched-chain amine. Inhibition of the delta 24-sterol reductase system was exhibited by all four amines, but not by the amide or phosphonate, in the following order of activity: C12 branched-chain amine greater than C12 straight-chain amine greater than C14 amine greater than C16 amine. The C12 branched amine also blocked the C-24(28)-dehydrogenase system in the conversion of sitosterol to fucosterol, the initial step in sitosterol dealkylation.

Amides↗
PubMed1983

Novel nuclear methylation of sterols by the nematode Caenorhabditis elegans.

Caenorhabditis elegans possesses a unique sterol methylation pathway not reported to occur in any other organism and also removes the C-24 ethyl group of sitosterol (a plant sterol). This nematode produced substantial quantities of 4 alpha-methyl-5 alpha-cholest-8(14)-en-3 beta-ol and smaller amounts of lophenol from dietary cholesterol, desmosterol or sitosterol. When C. elegans was propagated in media containing sitosterol plus 25-azacoprostane hydrochloride (25-aza-5 beta-cholestane hydrochloride), an inhibitor of delta 24-sterol reductase in insects, its 4 alpha-methylsterol fraction largely consisted of equal amounts of 4 alpha-methyl-5 alpha-cholesta-7,24-dien-3 beta-ol and 4 alpha-methyl-5 alpha-cholesta-8(14),24-dien-3 beta-ol. Thus 25-azacoprostane hydrochloride inhibited both a delta 24-sterol reductase and a delta 7-sterol isomerase in C. elegans.

Animals↗
PubMed1982

Synthesis of brassinosteroids and relationship of structure to plant growth-promoting effects.

A number of brassinosteroids with and without hydroxyl groups or an alkyl substituent in their side chain were synthesized. The alkyl substituent at C-24 highly influenced the oxidation of the C-22 double bond with osmium tetroxide and, hence the ratio of the 22 beta,23 beta- and 22 alpha,23 alpha-glycolic isomers obtained. Two different bean bioassays used to compare the plant growth-promoting capabilities of these compounds and of brassinolide and its three side chain 22,23-cis-glycolic isomers showed that brassinolide was the most active. The next most active brassinosteroids were generally those with 22 alpha-OH, 23 alpha-OH orientation and a beta-methyl or alpha-ethyl substituent at C-24. Similarly, of the synthetic precursor tetrahydroxy ketones of the brassinosteroids, those with 22 alpha-OH, 23 alpha-OH orientation (like brassinolide) and an alkyl group at C-24 were also the most active in both bioassays. The results indicate stringent structural features are required for a steroid to induce brassin activity. The structural requirements are: a trans A/B ring system (5alpha-hydrogen), a 6-ketone or a 7-oxa-6-ketone system in ring B, cis alpha-oriented hydroxyl groups at C-2 and C-3, cis hydroxy groups at C-22 and C-23 as well as a methyl or ethyl substituent at C-24.

Biological Assay↗