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M R Thomas

Publications and source records attributed to M R Thomas.

At least 37 records · Page 2Linked to original sources
PubMed2001

Pesticide usage monitoring in the United Kingdom.

The last decade has seen an increasing requirement throughout the United Kingdom (UK) for accurate, timely information on pesticide usage to satisfy government legislation and provide data as part of the registration and review process of pesticides. These data, collected by the Ministry of Agriculture, Fisheries and Food's Pesticide Usage Survey Group (PUSG), provide information on current and past usage patterns and allow the impact of use on the environment, operator and consumer to be more accurately assessed from actual usage patterns rather than worst case scenarios. Surveys of all crops grown commercially throughout the UK are undertaken at regular intervals using fully stratified samples of farmers and growers. Data are raised to provide national estimates of use but individual data sets can be derived from the sample. As such, the data are therefore also particularly suited to incorporation into probabilistic risk assessments. The methodologies used by the PUSG and some example data sets from a recent survey of arable crops are given.

Agriculture↗
PubMed2001

Short-term culture of peritoneum explants confirms attachment of endometrium to intact peritoneal mesothelium.

OBJECTIVE: To evaluate the initial adhesion of endometrium to the peritoneum. DESIGN: Descriptive study using light and confocal laser-scanning microscopy, immunohistochemistry, and transmission electron microscopy. SETTING: University-based laboratory. PATIENT(S): Women without endometriosis undergoing surgery for benign conditions. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Explants of peritoneum (n = 20), prepared from four patients, were cultured for 1 hour with mechanically dispersed proliferative or secretory endometrium. Peritoneum was cultured with endometrium from the same patient. Specimens were fixed and serially sectioned for hematoxylin and eosin stain, immunohistochemistry using an anti-cytokeratin monoclonal antibody, and transmission electron microscopy. RESULT(S): In 17 of 20 explants, endometrium was adherent to intact mesothelium. There was no evidence of transmesothelial invasion at any sites of attachment. Although in most cases endometrium was adherent to mesothelium via endometrial stroma, there were many sites of endometrial epithelium-mesothelium attachment. Confocal laser scanning microscopy demonstrated an intact monolayer of cytokeratin-positive cells below the sites of endometrial implantation. Transmission electron microscopy demonstrated intact, viable, mesothelial cells below sites of attachment. CONCLUSION(S): This study demonstrates that endometrium rapidly adheres to intact peritoneal mesothelium. In addition, this study demonstrates that endometrial epithelial cells, as well as stroma, can attach to mesothelium. Further studies are needed that characterize the mechanism of endometrial-mesothelial cell adhesion.

Cell Adhesion↗
PubMed2001

Genetic transformation of major wine grape cultivars of Vitis vinifera L.

We have developed an Agrobacterium-mediated transformation system for a number of important grapevine cultivars used in wine production. Transgenic plants were obtained for the seven cultivars: Cabernet Sauvignon, Shiraz, Chardonnay, Riesling, Sauvignon Blanc, Chenin Blanc and Muscat Gordo Blanco. Embryogenic callus was initiated from anther filaments and genotypic differences were observed for initiation and subsequent proliferation with Chardonnay responding most favourably to culture conditions. The transformation system allowed the recovery of germinating transgenic embryos 10-12 weeks after Agrobacterium inoculation and plants within 18 weeks. Examination of the expression patterns of the green fluorescent protein gene under the control of the CAMV35S promoter in leaf tissue of transgenic plants showed that for up to 35% of plants the pattern was not uniform. The successful transformation of a genetically diverse group of wine grape cultivars indicates that the transformation system may have general application to an even wider range of Vitis vinifera cultivars.

Blotting, Southern↗
PubMed2001

A cDNA from grapevine (Vitis vinifera L.), which shows homology to AGAMOUS and SHATTERPROOF, is not only expressed in flowers but also throughout berry development.

An AGAMOUS/SHATTERPROOF homologue (Vvmads1) was isolated from grapevine by differential display between berry and leaf mRNA. The predicted protein sequence of the full-length clone shows a high degree of homology to PLENA (77% identity) and to SHP1 and SHP2 (75% and 74% identity respectively), and is grouped with AGAMOUS/PLENA homologues when the conserved MADS and K domains are compared. Vvmads1 is expressed only in the later stages of flower development and throughout berry development, although expression is reduced after ripening commenced. When Vvmads1 was over-expressed in tobacco, the resulting plants display altered morphologies in the outer two floral whorls. In the most extreme cases, the inner whorls were surrounded by a carpelloid structure created by the modified sepals. Within these sepals were petals which had been split into sections and which were attached at the base of the flower by structures with the appearance of filaments. The results of this study suggest that Vvmads1 has a regulatory role in flower development before fertilisation and a role in fruit development after fertilisation.

AGAMOUS Protein, Arabidopsis↗
PubMed2001

A randomised trial of endoluminal reconstruction comparing the NIR stent and the Wallstent in angioplasty of long segment coronary disease: results of the RENEWAL Study.

BACKGROUND: The role of coronary stents in reducing the incidence of acute complications and late restenosis after angioplasty has been established in randomized studies focusing on simple, short coronary lesions. The development of long coronary stents has provided a safe and predictable means of treating long coronary lesions, but this carries with it a higher risk of restenosis. By comparing the outcome of treating long lesions with two different stent types, we aimed to assess the influence of stent design rather than the nature of long lesions per se on the relatively high restenosis rates in this subgroup. METHODS: This study was designed to assess procedural complications and 6-month restenosis rates in a randomized trial comparing a slotted tube stent with a self-expanding stent for the treatment of long coronary lesions. Randomization of vessels to either stent occurred after successful balloon angioplasty. Intravascular ultrasound (IVUS) was used to assess and optimize stent deployment. The patients were restudied angiographically and by IVUS at 6 months. RESULTS: A total of 82 patients (85 vessels) were recruited (slotted tube stent, n = 44 vessels; self-expanding stent, n = 41 vessels). Successful deployment occurred in 41 (100%) of 41 of the self-expanding stent group and 41 (93%) of 44 of the slotted tube stent group. There was no difference in lesion length between the two groups (slotted tube stent, 26.6 +/- 6.9 [SD] mm; self-expanding stent, 28.7 +/- 9.8 [SD] mm; P = .2), but the mean length of the self-expanding stent was greater than that of the slotted tube stent (41.6 +/- 18.8 [SD] mm vs 35.4 +/- 16.2 [SD] mm, respectively; P < .05). There was no significant difference in the rate of major events between the two groups at 6-month follow-up. The angiographic restenosis rate at follow-up was less in the slotted tube stent group, but this did not reach statistical significance (26% vs 46%, respectively; P = .1) and the target lesion revascularization rate was similar for both groups (7.9% vs 7.7%, respectively; P = .8). IVUS assessment of plaque/stent ratios suggested a greater plaque burden in the self-expanding stent compared with the slotted tube stent at follow-up (0.42 +/- 1.2 [SD] vs 0.3 +/- 0.08 [SD]), but this was not statistically significant (P = .1). CONCLUSIONS: Long stents can be safely and successfully deployed in long segment coronary disease, with an acceptable 6-month target lesion revascularization rate. Our results showed a trend toward lower angiographic restenosis and a lesser in-stent plaque burden at follow-up in the slotted tube stent compared with the self-expanding stent. This suggests that stent design may influence the restenotic process in long coronary lesions.

Aged↗
PubMed2001

Intravascular ultrasound-guided stenting in long lesions: an insight into possible mechanisms of restenosis and comparison of angiographic and intravascular ultrasound data from the MUSIC and RENEWAL trials.

The high restenosis rates in long stents may be related to suboptimal stent deployment. In an attempt to understand the potential components associated with restenosis in long stents, this study compares angiographic and intravascular ultrasound (IVUS) data from the MUSIC and RENEWAL studies where IVUS was used to optimize stent deployment in short (< 15 mm) and long (> 20 mm) coronary lesions, respectively. The RENEWAL study, a randomized trial, compared the NIR stent and Wallstent in long (> 20 mm) coronary lesions and used on-line visual IVUS criteria to optimize stent expansion. Detailed analysis of IVUS data was performed off line. Angiographic and IVUS data from this study was compared to that from the MUSIC study. Initial stent deployment was deemed optimal by the operator after visual angiographic and IVUS assessment in 50 of 70 lesions. In the remaining 20 lesions further balloon inflations were required to optimize stent apposition that led to an average gain in minimal in-stent luminal area (MISA) of 15.9% (P < 0.01). Off-line IVUS data analysis showed that the number reaching "MUSIC criteria" for optimal stent deployment preredilatation was 8 (11.4%) of 70 and 14 (20%) of 70 postredilatation. The ratio of MISA/MRAprox (mean proximal reference area) was 0.69 in RENEWAL. At 6-month follow-up, the angiographic restenosis rate in RENEWAL was 36% and target lesion revascularization (TLR) rate was 7.8%, compared with MUSIC's 9.7% and 4.5%, respectively. In conclusion, angiographic assessment of stent deployment in long lesions is limited. On-line visual IVUS with further balloon inflations to improve stent apposition led to a significant gain in MISA, but the MISA/MRAprox ratio remained suboptimal. Therefore, suboptimal stent deployment due to constraint by lesion resistance may be an important mechanism underlying the high restenosis rates in long stents.

Aged↗
PubMed2001

Development and validation of a Bayesian index for predicting major adverse cardiac events with percutaneous transluminal coronary angioplasty.

OBJECTIVE: To create a risk model for predicting major adverse complicating events of percutaneous transluminal coronary angioplasty (PTCA), and to test the accuracy of the model on a prospective cohort of patients SETTING: Tertiary cardiac centre METHODS: Available software can predict probabilities of events using Bayes's theorem. To establish the accuracy of these predictive tools, a Bayes table was created to evaluate major adverse complicating events (MACE)-death, emergency coronary artery bypass grafting (CABG), or Q wave infarct occurring during the in-patient episode-on the first 1500 patients in the department PTCA database (development group); the predictive value of this model was then tested with the subsequent 1000 patients (evaluation group). The following probabilities were assessed to determine their association with MACE: age, sex, left ventricular function, American Heart Association lesion morphology classification, cardiogenic shock, previous CABG, diabetes, hypertension, multivessel PTCA. MAIN OUTCOME MEASURES: To establish the discriminatory ability of the predictive index, calibration plots and receiver operating characteristic (ROC) curves were obtained to compare the development and evaluation groups. RESULTS: The ROC curve plotted to determine the discriminatory value of the Bayesian table created from the development group (n = 1500) in predicting MACE in the evaluation group (n = 1000) showed a moderately predictive area under the curve of 0.76 (SEM 0.07). This predictive accuracy was confirmed with separately constructed calibration plots. CONCLUSIONS: Accurate predictions of MACE can be identified in populations undergoing percutaneous intervention. The database used allows operators to obtain consent from patients appropriately from their own experience rather than from other published data. If a national PTCA database existed along similar lines, individual operators and interventional centres could compare themselves with nationally available data.

Age Factors↗
PubMed2001

High-speed rotational atherectomy in the treatment of bifurcation-type coronary lesions.

BACKGROUND: Bifurcational coronary lesions present a major interventional challenge. The differential cutting mechanism of high-speed rotational atherectomy (HSRA) may provide a favourable technique of treating this complex lesion subtype. METHODS: We evaluated the use of HSRA (32 lesions) compared to balloon angioplasty (BA) (118 lesions), with provisional stenting in both groups, in a non-randomised, retrospective study of 150 bifurcation-type lesions. RESULTS: The HSRA/stent group had a high primary success rate of 97%, an acceptably low in-hospital event rate of 9% and an overall major adverse cardiac event (MACE) rate at a mean follow-up period of 15 +/- 3.4 months of 22.5% with a target lesion revascularisation (TLR) rate of 18.7%. Procedural success in the BA/stent group was 81% with an in-hospital event rate of 14.4%, and the overall MACE rate at follow-up was 27.5% with a TLR rate of 23%. We achieved a greater acute gain in minimal luminal diameter and a lesser percentage of residual stenosis after intervention in the HSRA/stent group compared to the BA/stent group (p < 0.01). Outcome at follow-up favoured the HSRA/stent group, although the difference did not reach statistical significance. CONCLUSION: HSRA with provisional stenting provided a safe and effective means of treating bifurcation lesions.

Angioplasty, Balloon, Coronary↗
PubMed2001

Lack of effect of Lactobacillus GG on antibiotic-associated diarrhea: a randomized, placebo-controlled trial.

OBJECTIVES: To assess the efficacy of Lactobacillus GG in preventing antibiotic-associated diarrhea (AAD) in adults and, secondarily, to assess the effect of coadministered Lactobacillus GG on the number of tests performed to determine the cause of diarrhea. PATIENTS AND METHODS: In this prospective, randomized, double-blind, placebo-controlled trial conducted from July 1998 to October 1999, 302 hospitalized patients receiving antibiotics were randomized to receive Lactobacillus GG, 20 x 10(9) CFU/d, or placebo for 14 days. Subjects recorded the number of stools and their consistency daily for 21 days. The primary outcome was the proportion of patients who developed diarrhea in the first 21 days after enrollment. Weekly telephone follow-up was also performed. Results were analyzed in an intention-to-treat fashion. RESULTS: Diarrhea developed in 39 (29.3%) of 133 patients randomized to receive Lactobacillus GG and in 40 (29.9%) of 134 patients randomized to receive placebo (P=.93). No additional difference in the rate of occurrence of diarrhea was found between treatment and placebo patients in a subgroup analysis of those treated with beta-lactam vs non-beta-lactam antibiotics. Too few patients had stool cultures, additional laboratory tests for diarrhea, or a positive diagnosis of Clostridium difficile infection to assess between-group differences. CONCLUSION: Lactobacillus GG in a dose of 20 x 10(9) CFU/d did not reduce the rate of occurrence of diarrhea in this sample of 267 adult patients taking antibiotics initially administered in the hospital setting.

Adolescent↗
PubMed2000

The H93G myoglobin cavity mutant as a versatile template for modeling heme proteins: ferrous, ferric, and ferryl mixed-ligand complexes with imidazole in the cavity.

One of the difficulties in preparing accurate ambient-temperature model complexes for heme proteins, particularly in the ferric state, has been the generation of mixed-ligand adducts: complexes with different ligands on either side of the heme. The difference in the accessibility of the two sides of the heme in the H93G cavity mutant of myoglobin (Mb) provides a potential general solution to this problem. To demonstrate the versatility of H93G Mb for the preparation of heme protein models, numerous mixed-ligand adducts of ferrous, ferric, and ferryl imidazole-ligated H93G (H93G(Im) Mb) have been prepared. The complexes have been characterized by electronic absorption and magnetic circular dichroism (MCD) spectroscopy in comparison to analogous derivatives of wild type Mb. The starting ferric H93G(Im) Mb state spectroscopically resembles wild-type ferric Mb as expected for a complex containing a single imidazole in the proximal cavity and water bound on the distal side. Addition of a sixth ligand to ferric H93G(Im) Mb, whether charge neutral (imidazole) or anionic (cyanide and azide), results in formation of six-coordinate low-spin complexes with MCD characteristics similar to those of parallel derivatives of wild-type ferric Mb. Reduction of ferric H93G(Im) Mb and subsequent exposure to either CO, NO, or O2 produces ferrous complexes (deoxy, CO, NO, and O2) that consistently exhibit MCD spectra similar to the analogous ferrous species of wild-type ferrous Mb. Most interestingly, reaction of ferric H93G(Im) Mb with H2O2 results in the formation of a stable high-valent oxoferryl complex with MCD characteristics that are essentially identical to those of oxoferryl wild-type Mb. The generation of such a wide array of mixed-ligand heme complexes demonstrates the efficacy of the H93G Mb cavity mutant as a template for the preparation of heme protein model complexes.

Amino Acid Substitution↗
PubMed2000

Measurements of the dielectric properties of peripheral blood mononuclear cells and trophoblast cells using AC electrokinetic techniques.

The separation of trophoblast cells from the maternal circulation could provide a valuable diagnostic tool for prenatal diagnosis of genetic abnormalities. This has been attempted using antibody methods, but due to non-specificity of the antibodies, maternal cell contamination remains a problem. We have investigated the potential of dielectrophoretic separation methods as a means of isolating trophoblast cells from mixed peripheral blood mononuclear cells. To determine the potential of this method the dielectric properties of trophoblast cells and mixed peripheral blood mononuclear cells were measured using dielectrophoretic crossover and single cell electrorotation methods. Both dielectrophoretic crossover data and electrorotation data gave an average specific membrane capacitance of the peripheral blood mononuclear cells of 11.5 mF m(-2). Trophoblast cells prepared using three different methods had a higher average specific membrane capacitance in the range 13-18 mF m(-2). The differences in capacitance between the cell types could be exploited as the basis of an AC electrokinetic-based system for the separation of trophoblast cells from peripheral blood mononuclear cells.

Cell Membrane↗
PubMed2000

Comparison of cardiac troponin T and I and CK-MB for the detection of minor myocardial damage during interventional cardiac procedures.

A number of cardiac interventional procedures are available for the treatment of angina, including percutaneous transluminal coronary angioplasty (PTCA), stent insertion and rotational atherectomy (RA). Variable degrees of myocardial cell injury during PTCA and stent insertion have been observed, based on rises in creatine kinase MB isoenzyme (CK-MB) and cardiac troponin T (cTnT) 6-24 h post-procedure. As there are many variations in technique within each procedure it would be helpful to be able to determine objectively the degree of myocardial damage in order to optimize technique. We measured CK-MB, cTnT and cardiac troponin I (cTnI) to ascertain which is the most sensitive marker for minor myocardial damage in this setting. Blood samples were taken both before and 6, 14 and 24h after the procedure in 109 patients (77 men) with angina, 42 of whom had unstable angina. Of the 109 patients, 86 had a stent inserted (21 as a primary stent), nine had PTCA, eight had RA and six intracoronary brachytherapy. Using the manufacturers' recommended cut-offs--CK-MB 4 microg/L, cTnI and cTnT 0.1 microg/L--five patients were excluded from further analysis as all three markers were raised pre-procedure. Post procedure all three markers were in agreement for 68 patients (44 all normal, 24 all raised). Overall, CK-MB was raised in 28 patients, cTnT in 38 and cTnI in 58. In 19 patients CK-MB and cTnT were normal, but cTnI was raised (15 between 0.11 and 0.30 microg/L). cTnI was the most sensitive indicator of minor myocardial damage, but at the recommended cut-off of 0.1 microg/L may be overly sensitive. We await the results of our follow-up study to determine the clinical implications of these small rises in cTnI.

Angina Pectoris↗
PubMed1999

Assignment of the heme axial ligand(s) for the ferric myoglobin (H93G) and heme oxygenase (H25A) cavity mutants as oxygen donors using magnetic circular dichroism.

UV-visible absorption and magnetic circular dichroism (MCD) data are reported for the cavity mutants of sperm whale H93G myoglobin and human H25A heme oxygenase in their ferric states at 4 degreesC. Detailed spectral analyses of H93G myoglobin reveal that its heme coordination structure has a single water ligand at pH 5.0, a single hydroxide ligand at pH 10.0, and a mixture of species at pH 7.0 including five-coordinate hydroxide-bound, and six-coordinate structures. The five-coordinate aquo structure at pH 5 is supported by spectral similarity to acidic horseradish peroxidase (pH 3.1), whose MCD data are reported herein for the first time, and acidic myoglobin (pH 3.4), whose structures have been previously assigned by resonance Raman spectroscopy. The five-coordinate hydroxide structure at pH 10.0 is supported by MCD and resonance Raman data obtained here and by comparison with those of other known five-coordinate oxygen donor complexes. In particular, the MCD spectrum of alkaline ferric H93G myoglobin is strikingly similar to that of ferric tyrosinate-ligated human H93Y myoglobin, whose MCD data are reported herein for the first time, and that of the methoxide adduct of ferric protoporphyrin IX dimethyl ester (FeIIIPPIXDME). Analysis of the spectral data for ferric H25A heme oxygenase at neutral pH in the context of the spectra of other five-coordinate ferric heme complexes with proximal oxygen donor ligands, in particular the p-nitrophenolate and acetate adducts of FeIIIPPIXDME, is most consistent with ligation by a carboxylate group of a nearby glutamyl (or aspartic) acid residue.

Alanine↗
PubMed1999

Severe spasm of a radial artery coronary bypass graft during coronary intervention.

Coronary spasm is a well-recognized observation during coronary angiography. This report describes a patient who developed spasm of a radial artery bypass graft during coronary intervention. There are many reports on the angiographic follow-up to confirm the surgical results for patency in radial arterial conduits. We share our experience with this first case in the literature noted to have severe vasospasm during PTCA. Cathet. Cardiovasc. Intervent. 47:331-335, 1999.

Angioplasty, Balloon, Coronary↗
PubMed1999

Angiographic and clinical restenosis following the use of long coronary Wallstents.

This study assessed clinical and angiographic restenosis following the deployment of the long coronary Wallstent. Between May 1995 and June 1997, 182 Wallstents were deployed in 162 vessels in this unit. Forty-eight percent had an unstable coronary syndrome and 94% had AHA grade B or C lesions. The mean lesion length was 37 +/- 20 mm and the mean stent length was 48 +/- 20 mm. The procedural success rate was 99% and the primary success rate was 93%. Six in-patients suffered subacute stent thrombosis, the majority being in the era of anticoagulation rather than antiplatelet regimes. Seventy-three percent remained free of major adverse clinical events in the follow-up period, but 41% had angiographic restenosis. The Wallstent can be deployed in complex lesions with a high primary success rate and an acceptably low restenosis rate. The optimal management of in-stent restenosis remains to be defined.

Adult↗
PubMed1998

Expression of alphaB-crystallin in a mouse model of inherited retinal degeneration.

AlphaB-crystallin, which is abundantly expressed in the lens but also in a diversity of other tissues, functions as a stress-inducible molecular chaperone and is increased in brain neurodegenerative diseases. We compared retinal alphaB-crystallin expression in a model of inherited retinal degeneration, the rd mouse, and controls. Northern and in situ hybridization analysis showed alphaB-crystallin mRNA to have an altered spatio-temporal pattern with increased levels localized to glial cells in the degenerative state. Immunocytochemistry confirmed increased expression at Müller cells and astrocytes, together with transiently increased localization to the degenerating photoreceptors. These findings suggest that increased alphaB-crystallin expression is associated with glial cell reaction to neuronal damage in the retina, and may comprise part of the retina's overall defensive response to the stress of apoptotic photoreceptor cell death.

Animals↗
PubMed1998

Expression of Pax-6 mRNA in the retinal degeneration (rd) mouse.

The homeobox gene Pax-6 is expressed during eye development in both the retina and lens, and Pax-6 mutations cause ocular abnormalities including retinal defects. We investigated the pattern of Pax-6 gene expression in the rd/rd mouse model of inherited retinal degeneration in comparison with nondegenerative controls, using Northern blot, reverse-transcription (RT)-PCR and in situ hybridization analysis. We observed an increased level of Pax-6 mRNA expression in the degenerative state, which appeared to affect equally the major Pax-6 exon 5a transcriptional splice variants as detected by RT-PCR. By in situ hybridization, Pax-6 mRNA was localized to the inner nuclear and ganglion cell layers of nondegenerative retina, but showed a more diffuse signal pattern in the rd/rd retina. This modulation of Pax-6 mRNA levels and localization is suggestive of activation of expression in retinal glial cells and may reflect reorganization of cellular interactions in response to the degenerative processes.

Animals↗