PubMed Health⌕ Search

Biomedical subjects

S Rowland

Publications and source records attributed to S Rowland.

At least 19 recordsLinked to original sources
PubMed2001

Aromatic hydrocarbon "humps" in the marine environment: unrecognized toxins?

Gas chromatographic analysis of the hydrocarbons of environmental samples often reveals that unresolved complex mixtures (UCMs) or gas chromatographic "humps" of aliphatic and aromatic hydrocarbons are most abundant--yet little consideration seems to have been given to the possible toxicological impacts of hydrocarbon "humps". Here we show, using a well-accepted bioassay, that monoaromatic components of a UCM of hydrocarbons from a crude oil elicit a sublethal toxic response in a typical marine pollution indicator organism (the mussel, Mytilus edulis). Furthermore, coastal U.K. mussels shown previously to have unexplained impaired health contained high concentrations of UCMs, including monoaromatic UCMs. These findings may have important implications for our understanding of the toxicological sublethal effects of oil residues in the environment. Given the relatively resistant nature of UCM hydrocarbons, the effects of both acute oil spills and more chronic discharges may need further consideration.

Animals↗
PubMed2001

Reduction of animal usage by serial bleeding of mice for pharmacokinetic studies: application of robotic sample preparation and fast liquid chromatography-mass spectrometry.

Typically, pharmacokinetic studies in mice require one animal per time point, thus resulting in differences due to dosing error, animal to animal variation and more importantly the euthanasia of a large number of animals. A method for the determination of pharmacokinetic data from serially bled mice to support early drug discovery is described. Sample analysis relies on liquid chromatography coupled with tandem mass spectrometry permitting robust and reproducible analysis requiring approximately 3 min per sample. Several parameters are discussed including the method of sample collection, preparation and analysis. The use of serially bled mice has lead to a remarkable reduction in animal usage and a corresponding reduction in compound required for such experiments. Using conventional methodology, a nine-point pharmacokinetic curve with four animals per time point would require 36 mice. With the method described below, only four mice in total are used and euthanasia is not required, permitting reuse after several weeks recovery and washout. Also, pharmacodynamic-pharmacokinetic correlation is possible and is demonstrated using a mouse model of diabetes.

Animals↗
PubMed2001

Variable stereochemistry in highly branched isoprenoids from diatoms.

C(25) highly branched isoprenoid (HBI) alkenes are ubiquitous lipids found in geochemical samples around the globe. The origins of these widespread geochemicals are believed to be restricted to a limited number of diatoms, including Haslea ostrearia (and related species), Rhizosolenia setigera, and Pleurosigma intermedium. The unsaturation of the HBI alkenes ranges from 2-6 in different species and cultures. The number of stereogenic centres is usually limited to two in the HBI alkenes due to double bond positions. The relative and/or absolute configurations for these have been determined for a range of HBI alkenes produced from different diatoms cultured under a number of growth conditions. These determinations have involved a combined spectroscopic and chromatographic analysis using NMR spectroscopy and chiral gas chromatography, respectively. HBIs isolated from Haslea spp. belong to a specific structural type which exhibit configurational diastereoisomerism, while those isolated from P. intermedium and R. setigera represent a different structural type and usually exist as mixtures of geometric isomers only. HBIs are reported from a new species of diatom whose stereochemical properties lie between those found for Haslea spp. and P. intermedium.

Alkenes↗
PubMed2001

Tetra-unsaturated sesterterpenoids (Haslenes) from Haslea ostrearia and related species.

The structures and distributions of C25 highly branched isoprenoid (HBI) alkenes (Haslenes) have been determined following isolation from cultures of the diatoms Haslea ostrearia, Haslea crucigera, Haslea pseudostrearia and Haslea saltstonica. The distributions of the HBIs change between Haslea species and also between different cultures of the same species. Large scale culturing of H. ostrearia and H. pseudostrearia has enabled the structures of three new tetra-unsaturated alkenes to be determined by NMR spectroscopy. The structural relationships between different Haslenes together with the potential significance of the biosynthesis of HBIs by the Haslea genus is discussed.

Alkenes↗
PubMed2001

Muc1 mucins on the cell surface are adhesion sites for Pseudomonas aeruginosa.

Recently, we cloned and characterized a full-length cDNA of the hamster Muc1 gene, the expression of which appears to be associated with secretory cell differentiation (Park HR, Hyun SW, and Kim KC. Am J Respir Cell Mol Biol 15: 237-244, 1996). The role of Muc1 mucins in the airway, however, is unknown. In this study, we investigated whether cell surface mucins are adhesion sites for Pseudomonas aeruginosa. Chinese hamster ovary (CHO) cells not normally expressing Muc1 mucin were stably transfected with the hamster Muc1 cDNA, and binding to P. aeruginosa was examined. Our results showed that 1) stably transfected CHO cells expressed both Muc1 mRNA and Muc1 mucins based on Northern and Western blot analyses, 2) Muc1 mucins present on the cell surface were degraded by neutrophil elastase, and 3) expression of Muc1 mucins on the cell surface resulted in a significant increase in adhesion of P. aeruginosa that was completely abolished by either proteolytic cleavage with neutrophil elastase or deletion of the extracellular domain by mutation. We conclude that Muc1 mucins expressed on the surface of CHO cells serve as adhesion sites for P. aeruginosa, suggesting a possible role for these glycoproteins in the early stage of airway infection and providing a model system for studying epithelial cell responses to bacterial adhesion that leads to airway inflammation in general and cystic fibrosis in particular.

Animals↗
PubMed2001

Hydrocarbon humps in the marine environment: synthesis, toxicity, and aqueous solubility of monoaromatic compounds.

A recent study has shown that some monoaromatic hydrocarbon constituents of the so-called unresolved complex mixtures (UCMs) or gas chromatographic humps, which are widespread in the marine environment, are toxic to the mussel Mytilus edulis. Here we describe the synthesis and toxicological assessment of 6-cyclohexyltetralin, 7-cyclohexyl-1-methyltetralin, and 7-cyclohexyl-1-n-propyltetralin, which contain structural features consistent with some monoaromatic UCM hydrocarbons. The compounds were all toxic to M. edulis when measured in the assay used previously to determine the toxicity of a monoaromatic UCM. The aqueous solubilities of the hydrocarbons in fresh and seawater at different temperatures were determined and found to range from about 10 to 110 microg/L (10-60 microg/L in seawater at 15 degrees C). Further studies of the aromatic UCM composition of a wide range of oils and oil residues are required to determine whether such alkylated compounds as 7-cyclohexyl-1-methyltetralin and 7-cyclohexyl-1-n-propyltetralin or their analogues are widespread in oils. If these aromatic compounds prove to be important in UCMs, toxicity experiments should be conducted with other biological end points and monitoring studies of pollutant hydrocarbons should probably include measurement of aromatic UCM hydrocarbons.

Animals↗
PubMed2000

Crystal structure of a novel germination protease from spores of Bacillus megaterium: structural arrangement and zymogen activation.

The DNA in the core of spores of Bacillus species is saturated with a group of small, acid-soluble proteins (SASP) that protect DNA from a variety of harsh treatments and play a major role in spore resistance and long-term spore survival. During spore germination, SASPs are rapidly degraded to amino acids and this degradation is initiated by a sequence-specific protease called germination protease (GPR), which exhibits no obvious mechanistic or amino acid sequence similarity to any known class of proteases. GPR is synthesized during sporulation as an inactive tetrameric zymogen termed P(46), which later autoprocesses to a smaller form termed P(41), which is active only during spore germination. Here, we report the crystal structure of P(46) from Bacillus megaterium at 3.0 A resolution and the fact that P(46) monomer adopts a novel fold. The asymmetric unit contains two P(46) monomers and the functional tetramer is a dimer of dimers, with an approximately 9 A channel in the center of the tetramer. Analysis of the P(46) structure and site-directed mutagenesis studies have provided some insight into the mechanism of zymogen activation as well as the zymogen's lack of activity and the inactivity of P(41) in the mature spore.

Amino Acid Sequence↗
PubMed2000

Configurations of polyunsaturated sesterterpenoids from the diatom, Haslea ostrearia.

The partial configurations of C25 isoprenoid alkenes isolated from the diatom Haslea ostrearia Gaillon (Simonsen) have been established. A combination of NMR spectroscopy studies of the alkenes with chiral shift reagents in conjunction with soluble silver beta-diketonate complexes and enantioselective gas chromatography of oxidation products of the alkenes was used. Unexpected differences in highly branched isoprenoid isomer configurations were observed between different laboratory cultures of the alga.

Alkenes↗
PubMed1998

LPAM-1 (integrin alpha 4 beta 7)-ligand binding: overlapping binding sites recognizing VCAM-1, MAdCAM-1 and CS-1 are blocked by fibrinogen, a fibronectin-like polymer and RGD-like cyclic peptides.

The alpha 4 integrin LPAM-1 (alpha 4 beta 7) mediates lymphocyte attachment within the extracellular matrix (ECM) by adhering to the connecting segment (CS)-1 site of fibronectin (FN). Here we reveal that very late antigen (VLA)-4 LPAM-1+ T cell lymphoma TK-1 cells bind via LPAM-1 to multiple copies of the RGD sequence engineered within an FN-like polymer. Further, the small conformationally restrained RGD-like cyclic peptides 1-adamantaneacetyl-Cys-Gly-Arg-Gly-Asp-Ser-Pro-Cys and Arg-Cys-Asp-thioproline-Cys inhibit the adhesion of TK-1 cells to immobilized CS-1 peptide, and to endothelial counterreceptors for LPAM-1, namely mucosal addressin cell adhesion molecule (MAdCAM)-1 and vascular cell adhesion molecule (VCAM)-1. Spontaneous adhesion of the VLA-4- LPAM-1+ B lymphoma cell line RPMI 8866 to CS-1 was likewise inhibited, confirming a previously undocumented ability of LPAM-1 to recognize the RGD tripeptide. The RGD-binding site in LPAM-1 either overlaps or is identical to sites required for interaction with MAdCAM-1, VCAM-1, and the CS-1. The binding of LPAM-1 and VLA-4 to RGD-containing ligands may have relevance in vivo given that fibrinogen at physiological concentrations is able to partially block the binding of TK-1 cells to MAdCAM-1. Hence fibrinogen and other vascular RGD-containing proteins may have mild anti-inflammatory activity required for maintaining effective homeostasis, analogous to the anti-thrombogenic activity of the vascular endothelium.

Amino Acid Sequence↗
PubMed1998

The relationship between hetero-oligomer formation and function of the topological specificity domain of the Escherichia coli MinE protein.

MinE is an oligomeric protein that, in conjunction with other Min proteins, is required for the proper placement of the cell division site of Escherichia coli. We have examined the self-association properties of MinE by analytical ultracentrifugation and by studies of hetero-oligomer formation in non-denaturing polyacrylamide gels. The self-association properties of purified MinE predict that cytoplasmic MinE is likely to exist as a mixture of monomers and dimers. Consistent with this prediction, the C-terminal MinE22-88 fragment forms hetero-oligomers with MinE+ when the proteins are co-expressed. In contrast, the MinE36-88 fragment does not form MinE+/MinE36-88 hetero-oligomers, although MinE36-88 affects the topological specificity of septum placement as shown by its ability to induce minicell formation when co-expressed with MinE+ in wild-type cells. Therefore, hetero-oligomer formation is not necessary for the induction of minicelling by expression of MinE36-88 in wild-type cells. The interference with normal septal placement is ascribed to competition between MinE36-88 and the corresponding domain in the complete MinE protein for a component required for the topological specificity of septal placement.

Antibodies↗
PubMed1997

General practice--a post-modern specialty?

The 'modern' view of the world is based on the premise that we can discover the essential truth of the world using scientific method. The assumption is made that knowledge so acquired has been 'uncontaminated' by the mind of the investigator. Post-modern theory, however, is concerned with the process of knowing and how our minds are part of the process, i.e. our perceptions of reality and the relationships between different concepts are important influences on our ways of knowing. The values of post-modern theory are those of uncertainty, many different voices and experiences of reality and multifaceted descriptions of truth. These values are closer to our experience of general practice than the 'modern' values of scientific rationalism and should be reflected in a new curriculum for general practice.

Curriculum↗
PubMed1996

Comparison between the phenotype and function of maturing dendritic cells from spleen and lymph nodes.

We compared the capacity of mature dendritic cells (DC) from lymph nodes and maturing DC from spleens in their capacity to stimulate responses to the small hapten picryl sulphonic acid (PIC) and to the same hapten conjugated to ovalbumin (PIC-OVA) and requiring processing. Surface expression of major histocompatibility complex (MHC) class II molecules, which are upregulated during maturation of splenic DC, were studied as an independent marker of maturation. Freshly isolated lymph node DC had a veiled appearance and high levels of class II expression. DC separated from suspensions of spleen cells expressed the DC-specific marker NLDC-145, but were small, had low levels of MHC class II molecules and expressed stem cell antigen. Those DC from spleen cells cultured for 24 and 48 hr showed the development of typical veiled DC morphology and high class II expression. Lymph node DC stimulated high levels of primary T-cell proliferation to PIC, but failed to stimulate primary responses to PIC-OVA. Splenic DC isolated immediately failed to stimulate primary responses to either antigen. More mature spleen DC stimulated responses both to PIC and PIC-OVA. Surprisingly, development of the capacity to stimulate responses to PIC preceded that of stimulating PIC-OVA responses. The capacity of the DC to process and present PIC-OVA was maintained during the culture period. The results indicate that both the form of the antigen and the source and maturity of the DC are critical in determining the responses stimulated in T lymphocytes.

Animals↗
PubMed1980

Cerium nitrate-silver sulfadiazine cream in the treatment of burns: a prospective evaluation.

In a prospective, randomized study of patients with major burns, the efficacy of cerium nitrate-silver sulfadiazine cream was compared with that of silver sulfadiazine cream alone. Sixty patients were studied, in two groups, with matching mean ages and mean burns sizes. Patients with associated injuries, smoke inhalation, or major medical illnesses were excluded from the study. The total number of deaths and the total number of deaths from sepsis were equal in both groups. The total number of patients whose quantitative burns wound biopsies indicated light (10(2) to 10(5) organisms/gm) or heavy (over 10(5) organisms/gm) colonization by microorganisms was not statistically different between the two groups. The distribution of bacterial isolates by organism was similar in both groups. In vitro sensitivity determinations indicated a comparable efficacy between the two agents. In this study no clear-cut superiority of one topical agent over the other could be demonstrated.

Adult↗
PubMed1975

Involvement of separate pathways in the repair of mutational and lethal lesions induced by a monofunctional sulfur mustard.

The mutagenic and lethal effects of a monofunctional sulfur mustard, 2-chloro-ethylethylsulfide (CEES), have been studied in a number of repair deficient variants of Escherichia coli K12, B/r and B. The results indicate that CEES induces a (pre)mutational lesion which is subject to Uvr+-excision-repair. Extensive CEES-induced mutagenesis can occur in exrA- uvrA- and recA- uvrB- variants suggesting that the majority of the mutations in Uvr-bacteria do not arise from error-prone repair. These findings are similar to results previously reported with a volatile degradation product of captan and with ethyl methanesulfonate (EMS) but differ from those reported with methyl methanesulfonate (MMS). It is hypothesized that CEES alkylates guanine at the O-6 position (R-O-6-G) and that this R-O-6-G which is Uvr+-excisable is directly mutagenic by producing G-C to A-T transitions during replication. Reduced levels of induced mutation frequencies observed in an endonuclease II-deficient variant lead us to postulate that, in constrast to Uvr- bacteria, CEES-induced mutation in wild-type cells arise from error-prone repair of apurinic sites. Analysis of the lethal actions of CEES indicates that the lesion produced is largely unexcisable by the Uvr+ system. Host-cell reactivation of CEES-treated TI bacteriophage shows that the production of the (pre)ethal lesion is dependent on both the initial dose and post-treatment incubation. The efficient repair of the (pre)ethal lesion requires both endonuclease II and polymerase I. Moreover, deficiencies of these two enzymes rendered bacteria more sensitive to the cytotoxic action of CEES. It is postulated that the lethal mechanism of CEES involves: (I) alkylation at the N-3 position of adenine and the N-7 position of guanine; (2) spontaneous depurination of these alkylated bases; and (3) production of apurinic sites which are lethal unless repaired by the endonuclease II-polymerase I excision-repair system.

Adenine↗