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Biomedical subjects

S J Rowland

Publications and source records attributed to S J Rowland.

15 recordsLinked to original sources
PubMed2004

Biosynthesis of unusual monocyclic alkenes by the diatom Rhizosolenia setigera (Brightwell).

Novel, polyunsaturated monocyclic sester- and triterpenes isolated from the diatom Rhizosolenia setigera (Brightwell), are biosynthesised mainly via the mevalonate pathway. The experiments involved incubation of the alga with [1-(13)C]acetate, isolation of the alkenes by extraction and silver ion HPLC, followed by determination of the labelling pattern of one of the monocyclic triterpenes by (13)C-NMR spectroscopy. In addition, the extent of (13)C incorporation was also measured by mass spectrometry which revealed that the involvement of the mevalonate route in the biosynthesis of these cyclic compounds was less than for the co-occurring acyclic highly branched isoprenoid alkenes.

Acetates↗
PubMed2002

Liquid chromatography/electrospray ionisation mass spectrometric investigations of imidazoline corrosion inhibitors in crude oils.

The so-called imidazolines (2-alkyl-1-[ethylalkylamide]-2-imidazolines and 2-alkyl-1-ethylamine-2-imidazolines) are a group of surface-active compounds, complex mixtures of which are used by various industries as surfactants and corrosion inhibitors. Although their industrial synthesis was reported over 100 years ago, few methods for the determination of individual imidazolines in mixtures, including industrial matrices such as crude oils, have been reported. Here we demonstrate that spiking of crude oils with synthetic imidazolines followed by solid-phase extraction and liquid chromatography/electrospray ionisation multistage mass spectrometry (LC/ESI - MS(n)) allows an estimation of low (<10) parts per million concentrations of individual imidazolines in crude oils. Whilst non-optimised at present, the method is a significant advance and may prove useful not only for improving an understanding of the mechanisms of industrial imidazoline synthesis and for monitoring downhole and topside oilfield operations, but also for the determination of the fate of imidazoline-based oilfield corrosion inhibitors and surfactants in the environment.

Journal Article↗
PubMed2001

Investigations of cholesterol transformation during sewage treatment: relevance to estrogen formation pathways?

There is currently a great deal of concern over the observation of so-called estrogenic effects (specifically increases in the concentrations of the egg yolk precursor, vitellogenin) in male fish living in some UK rivers. The effects have been attributed to chemicals, including estrogenic steroids, which enter the rivers via sewage effluents. The origins of these estrogenic steroids in sewage may include contributions from the influents and possibly in situ transformation processes of other steroids occurring during sewage treatment. The present study examined the latter possibility. The bacterial metabolism of radiolabelled cholesterol during laboratory-simulated aerobic sewage treatment was studied by reverse phase radio-high performance liquid chromatography (rHPLC) and radio-gas chromatography (rGC) to examine the hypothesis that cholesterol could undergo A-ring aromatisation to form first, 19-norcholest-1,3,5(10)-trien-3-ol (NCT) and hence, by known bacterial pathways, the estrogenic steroid, estrone. The results showed that, to the contrary, much of the cholesterol (approx. 50% in 96 h) underwent rapid mineralisation to carbon dioxide, consistent with A-ring rupture (rather than aromatisation) and beta-oxidation of the alkyl side chain as major transformation routes. Some polar (early-eluting) rHPLC products were observed, possibly steroidal conjugates and/or fatty acids. Among the minor metabolites detected by rGC and GC-mass spectrometry (GC-MS) were cholest-3,5-diene and a second cholestadiene isomer. However, since alkenes were unexpected in this rHPLC fraction, they may arise as artefacts from thermal decomposition of cholesteryl esters, indicating that some cholesterol esterification had also occurred. In the alcohol rHPLC fractions, cholestadienol was identified by GC and GC-MS but neither NCT or estrone were detected. This suggests that, at least under these simulated conditions, in situ aromatisation of cholesterol to NCT and formation of estrone from NCT were not major processes.

Animals↗
PubMed2001

Effects of temperature on polyunsaturation in cytostatic lipids of Haslea ostrearia.

Unusual chemicals produced by the-'blue oyster' diatom, Haslea ostrearia, include the water-soluble blue pigment marennine and numerous polyunsaturated sesterterpene oils or haslenes. Aqueous extracts of the alga exhibit in vitro and in vivo activities against human lung cancer cells and anti-HIV effects. Here we report that three haslenes also demonstrate in vitro cytostatic action against a human lung cancer cell line. The most active haslene is the most unsaturated and unsaturation in the haslenes increases with increasing algal growth temperature.

Alkenes↗
PubMed2001

Factors influencing the distributions of polyunsaturated terpenoids in the diatom, Rhizosolenia setigera.

Polyunsaturated highly branched isoprenoid (HBI) hydrocarbon distributions of laboratory cultures of five strains of the planktonic diatom Rhizosolenia setigera (Brightwell) are shown herein to be highly variable. Some strains produced both haslenes with from three to five double bonds and rhizenes. The haslenes comprised not only Delta5 alkenes but also those with C7(20) unsaturation, including hasla-7(20),9E,Z, 23-trienes and hasla-7(20),9E,Z-13, 23-tetraenes. The rhizenes contained C7(25) unsaturation and the vinyl moiety common to all algal haslenes so far characterised. The effects of temperature and salinity on HBI composition, along with isotopic content, were determined in strain CS 389/A. Increase in growth temperature from 18 to 25 degrees C increased the degree of unsaturation in the haslenes and E to Z isomerisation in the triene. There was also an increase in unsaturation in the rhizenes at the highest growth temperature, with hexaenes dominant over the pentaenes but in the rhizenes, Z to E isomerisation increased. Increased salinity from 15 to 35 psu increased cell growth and rhizene production but decreased haslene production. Unsaturation in haslenes was not changed by increased salinity but unsaturation in the rhizenes decreased. These may reflect growth rate differences. The carbon isotopic compositions of the haslenes and rhizenes were similar to that of the major sterol at 18 degrees C, but the major HBI isomers were 3-4 per mil depleted relative to phytol released by saponification from chlorophyll a. This suggests biosynthesis of HBIs from a different isotopic pool of isopentenyl biphosphate to that from which phytol is biosynthesised. At 25 degrees C, further isotopic differences were observed. The variables controlling HBI distributions in R. setigera are still not fully understood and rationalisation of the environmental controls on the sedimentary distributions of the HBIs from R. setigera may only be possible once such factors are established.

Alkenes↗
PubMed2001

Analysis of oilfield produced waters and production chemicals by electrospray ionisation multi-stage mass spectrometry (ESI-MSn).

Large quantities of diverse polar organic chemicals are routinely discharged from oil production platforms in so-called produced waters. The environmental fate of many of these is unknown since few methods exist for their characterisation. Preliminary investigations into the use of multistage electrospray ionisation ion trap mass spectrometry (ESI-MSn) show its potential for the identification and quantification of compounds in specialty oilfield chemicals (corrosion inhibitors, scale inhibitors, biocides and demulsifiers) and produced waters. Multiple stage mass spectrometry (MSn) with both positive and negative ion detection allows high specificity detection and characterisation of a wide range of polar and charged molecules. For example, linear alkylbenzenesulfonates (LAS), alkyldimethylbenzylammonium compounds, 2-alkyl-1-ethylamine-2-imidazolines, 2-alkyl-1-[N-ethylalkylamide]-2-imidazolines and a di-[alkyldimethylammonium-ethyl]ether were all identified and characterised in commercial formulations and/or North Sea oilfield produced waters. The technique should allow the marine environmental effects and fates of some of these polar compounds to be studied.

Environmental Monitoring↗
PubMed2001

Haslea salstonica sp. nov. and Haslea pseudostrearia sp. nov. (Bacillariophyta), two new epibenthic diatoms from the Kingsbridge estuary, United Kingdom.

Two new diatom species, Haslea salstonica and Haslea pseudostrearia are described in light and electron microscopy and compared with two well-known members of Haslea. Scanning electron microscope observations confirm that the new species belong to the genus Haslea. This study extends previous observations on the genus, particularly with respect to the development of a pseudostauros. The characteristic features of the genus are discussed briefly.

Diatoms↗
PubMed2001

Investigations of the origins of estrogenic A-ring aromatic steroids in UK sewage treatment works effluents.

The present preliminary study describes an investigation of a putative aromatisation pathway in sewage from cholesterol through the corresponding A-ring aromatic steroid, norcholest-1,3,5(10)-trienol (NCT) to estrone. The synthesis and analytical characterisation of NCT and of the trimethyl silyl ether by gas chromatography-mass spectrometry, is described. The analytical properties of synthetic NCT were used to direct a search for the compound over several months in 1998 in the effluents of two sewage treatment works (STW; Deephams and Harpenden, north London). The study was prompted by the earlier findings that increased vitellogenin concentrations in the plasma of caged male rainbow trout held in the STW effluents (so-called fish 'feminisation') could be attributed to the presence of A-ring steroids such as estrone. Until now it has been assumed that these steroids originate from the STW influents and it is not clear to what extent, if at all, aromatisation of steroids might occur during STW operation. NCT was only detected in the solid particles associated with the effluents on one occasion in 8 months. This suggests that the hypothesised pathway is not a major one. Confirmation of previous reports of estrone and 17 beta-estradiol was also obtained using a published analytical method and by a simple modification of the method these reports were extended to include a regular occurrence of the weaker estrogen, 16 alpha-estriol in the case of Harpenden STW effluents in 1998.

Environmental Monitoring↗
PubMed2001

A simple method for SEM examination of sectioned diatom frustules.

We describe an innovative yet straightforward method to obtain high quality thin sections of diatom exoskeletons for observation by scanning electron microscopy (SEM). The use of this new technique allows for clear observations of some ultrastructural valve features, including the raphe, which are generally difficult to observe and describe accurately using transmission electron microscopy analysis of thin sections or SEM of randomly fractured diatom valves. In addition, because this method involves the complete removal of the organic content of the diatom cells, resulting in clean and mostly undisturbed skeletal thin cross-sections, even the intact valvar structures of weak girdle bands can be studied.

Diatoms↗
PubMed1995

Tn552 transposase purification and in vitro activities.

The Staphylococcus aureus transposon Tn552 encodes a protein (p480) containing the 'D,D(35)E' motif common to retroviral integrases and the transposases of a number of bacterial elements, including phage Mu, the integron-containing element Tn5090, Tn7 and IS3. p480 and a histidine-tagged derivative were overexpressed in Escherichia coli and purified by methods involving denaturation and renaturation. DNase I footprinting and gel binding assays demonstrated that p480 binds to two adjacent, directly repeated 23 bp motifs at each end of Tn552. Although donor strand cleavage by p480 was not detected, in vitro conditions were defined for strand transfer activity with transposon end fragments having pre-cleaved 3' termini. Strand transfer was Mn(2+)-dependent and appeared to join a single left or right end fragment to target DNA. The importance of the terminal dinucleotide CA-3' was demonstrated by mutation. The in vitro activities of p480 are consistent with its proposed function as the Tn552 transposase.

Base Sequence↗
PubMed1994

Characterisation of sin, a potential recombinase-encoding gene from Staphylococcus aureus.

The staphylococcal beta-lactamase (Bla) transposon Tn4002 has previously been reported to have a high level of insertional specificity for a 1.8-kb region on the plasmid pSK1. Nucleotide sequences of this region and of a related region on plasmid pI9789 were determined. Sequence analysis revealed that these two plasmids contain sin, a gene whose deduced product shows similarity to a family of DNA recombinases. Southern hybridisation analysis indicated that sin is located on alpha-, beta- and gamma-families of Bla plasmids and on pSK1 family plasmids. A region of dyad symmetry located upstream from sin on pSK1 and pI9789 was identified as the site of insertions of Tn552 and Tn4002 in separate isolates.

Amino Acid Sequence↗
PubMed1990

Tn552, a novel transposable element from Staphylococcus aureus.

Tn552, one of several closely related beta-lactamase-encoding transposons from Staphylococcus aureus, has a novel set of putative transposition functions. Each is homologous with a well-characterized function from a different type of mobile genetic element. Thus, Tn552 encodes: (i) resL-binL, a co-integrate resolution system homologous with those of Tn3 family elements; (ii) p480, a potential transposase significantly homologous with the DNA integrases of eukaryotic retroviruses and retrotransposons; and (iii) p271, a potential ATP-binding protein that shows homology with the B protein of phage Mu. The 3' terminal nucleotides of Tn552 (CA), adjacent to which p480 might cleave, are the same as those of retroviruses, retrotransposons and phage Mu. The presumptive resolvase (BinL) is very closely related to BinR, which was identified as a DNA invertase and is now shown to resolve an artificial co-integrate in vivo. Furthermore, the structure of the derivative of Tn552 found in the staphylococcal plasmid pI258 can be explained by a BinL (or BinR)-mediated site-specific deletion ('resolution') event. Thus, pI258 contains only the right-hand half of Tn552, which encodes the beta-lactamase and two regulatory proteins. The latter are homologous with the beta-lactamase gene repressor and co-inducer of Bacillus licheniformis. Interestingly, the order of the regulatory genes is reversed in S. aureus compared with Bacillus licheniformis.

Amino Acid Sequence↗
PubMed1989

Characterization of the staphylococcal beta-lactamase transposon Tn552.

The staphylococcal beta-lactamase transposon Tn552 is a member of a novel group of transposable elements. The organization of genes in Tn552 resembles that of members of the Tn21 sub-group of Tn3 family transposons, which transpose replicatively by cointegrate formation and resolution. Thus, a possible resolution site ('resL') and a resolvase gene (tnpR or 'binL') have been identified. However, consistent with the fact that Tn552 generates 6 bp (rather than 5 bp) flanking direct repeats of target DNA, neither the putative transposase protein, nor the terminal inverted repeats of Tn552 are homologous to those of Tn3 elements. Tn552, like phage Mu and retroelements, is defined by the terminal dinucleotides 5' TG .. CA 3'. A naturally occurring staphylococcal plasmid, pI9789, contains a Tn552-derived resolution system ('resR-binR') that acts as a 'hotspot' for Tn552 transposition; insertion creates a segment of DNA flanked by inversely repeated resolution sites, one (resR) on pI9789 and the other (resL) on Tn552. The putative Tn552 resolvase, the most closely related of known resolvases to the homologous DNA invertases, initially was identified as a DNA invertase ('Bin') as a result of its ability to mediate efficient inversion of this segment in vivo.

Amino Acid Sequence↗
PubMedDate not supplied

Design and development of a new cryosurgical instrument utilizing the Peltier thermoelectric effect.

Warts and some other dermatological conditions may be treated by the application of intense cold. This freezing has to be so severe as to form ice crystals which will rupture the cell membranes. The initial part of this project was to investigate the feasibility of using Peltier thermoelectric coolers (TECs) to cool down a suitable hand-held treatment tip to a temperature of approximately -50 degrees C. The results of these initial experiments showed how this could be accomplished and a prototype cryosurgical instrument, suitable for clinical trials, was designed and constructed. This new design is freestanding, self-contained and is operated from a standard 230 V mains supply. Unlike existing systems it does not use any disposable gases or liquids. A cryoprobe of this new design would allow reliable cryosurgery to be performed in a GP's treatment room where supplies of liquid nitrogen, nitrous oxide or carbon dioxide are not readily available. The design also has a built-in thermometer to measure the treatment tip temperature thus ensuring consistency in treatment. Clinical trials are being conducted at a number of GP practices to evaluate this new design.

Cryosurgery↗