Permanent URI for this collection
Browse
Recent Submissions
Publication A molecular re-examination of speciation in the intertidal red algamastocarpus stellatus(gigartinales, rhodophyta) in europe(Informa UK Limited, 2005-11-01) Zuccarello, Giuseppe C.; Schidlo, Natasha; Mcivor, Lynne; Guiry, Michael D.Mastocarpus stellatus is a common intertidal red alga in the north Atlantic. Previous work showed that the species was divided into at least two breeding groups in the northeastern Atlantic, a northern one ( absent in Spain and Portugal) and a southern one, which were almost completely inter-sterile. It also showed that, in laboratory culture, at least two types of life history were evident in this species ( a sexual one and a 'direct' one). The distribution of these life histories appeared to have a north - south distribution. We have used molecular markers to confirm these results and expand the sampling in certain populations. Organellar markers showed that the breeding groups have different plastid and mitochondria haplotypes and appear to be distributed along a north - south gradient. Populations in southern England and northern France ( Brittany) have mixed northern and southern breeding groups, except for the Rade du Brest, as was shown previously from culture studies. Results also show that most asexual plants have a plastid haplotype corresponding to the northern breeding group and a mitochondrial haplotype corresponding to the southern breeding group, a possible case of differential organellar inheritance and hybrid formation of an asexual life history. These results using molecular markers support previous conclusions and again emphasize the high levels of genetic variation in marine algae in Brittany.Publication Adenoviral-mediated overexpression of catalase inhibits endothelial cell proliferation(American Physiological Society, 2002-12-01) Zanetti, Michela; Katusic, Zvonimir S.; O'Brien, TimothyAlthough hydrogen peroxide (H2O2) induces proliferation of vascular smooth muscle cells, its role in endothelial cell proliferation is unclear. Our aim was to study the role of hydrogen peroxide in endothelial cell proliferation by overexpressing catalase. Human aortic endothelial cells were transduced with adenoviral vectors encoding beta-galactosidase (Adbetagal) or catalase (AdCat) or were exposed to diluent alone (control). Transgene expression was demonstrated by beta-galactosidase staining, Western analysis, and significantly increased enzyme activity in AdCat-transduced cells. Overexpression of catalase decreased DNA synthesis in AdCat compared with control and Adbetagal-transduced cells (536.8 +/- 31 vs. 1,875.1 +/- 132.9 vs. 1,347.5 +/- 93.7 dpm/well, respectively; P < 0.05 vs. control and Adβgal). Six days after transduction with AdCat (multiplicity of infection = 50), cell numbers were significantly reduced (AdCat: 38 +/- 1.8% of cell counts in control, P < 0.05; and 45 +/- 2% of cell count in Adbetagal, P < 0.05). Incubation with aminotriazole 10 mmol/l, an inhibitor of catalase, prevented this effect. The number of apoptotic cells was increased one- and threefold 2 and 4 days, respectively, after transduction with AdCat. Exogenous administration of low concentrations of H2O2 (50 μM) significantly increased cell proliferation, whereas it was inhibited by higher concentrations. These results suggest that H2O2 is an important modulator of endothelial cell proliferation.Publication Multivariate relationships and spatial distribution of geochemical features of soils in jamaica(Informa UK Limited, 2002-01-01) Zhang, Chaosheng; Lalor, GeraldConcentrations of 31 chemical elements in 165 soil samples from the tropical island of Jamaica were analyzed during the island-wide soil survey. Multivariate outliers were detected and remedied for quality control of the database. Multivariate analyses including principal component analysis (PCA), cluster analysis, and analysis of variance (ANOVA), and a geographic information system (GIS) were applied to study the geochemical features of element associations and sample clusters. The results show that rare earth elements, most of the heavy metals and trace elements (including As, Al, Cd, Ce, Co, Cr, Dy, Eu, Fe, Hf, Hg, La, Lu, Mn, Pb, Sb, Sc, Sm, Th, Ti, U, V, Yb, Zn) are enriched in the bauxitic soils relative to the non-bauxitic soils, and closely correlated with one another. Negative correlations between the bauxite-enriched elements and the mobile alkali and alkaline earth elements including Ca, Sr, Mg and Na are observed, showing the opposite tendencies of enrichment of the immobile elements and leaching of the mobile elements during the soil formation processes. The halogen elements of Br and I are also relatively enriched in the bauxitic soils, but they appear to be rather affected by sea-spray. Copper has poor correlations with all the other elements, which is likely to be related to mineralization. Significantly different concentrations of the bauxite-enriched elements are observed between the bauxitic and non-bauxitic soils.Publication Statistical characteristics and predictability of particle formation events at mace head(Wiley-Blackwell, 2006-01-01) Yoon, Y. J.; O'Dowd, C. D.; Jennings, S. G.; Lee, S. H.[ 1] The seasonal characteristics of coastal nucleation events at the Mace Head Atmospheric Research Station, resulting from exposure of macroalgae to the atmosphere, were analyzed for a 2-year period from August 2002 to July 2004. Nucleation events occurred on 58% of the days over the period. The seasonal variation of the number of event days and event duration show a clear cycle, with maximum values in spring and autumn and the minimum values in the winter season. The nucleation events typically start similar to 75 min prior to the occurrence of the low-tide mark and the event start time is correlated (r = 0.75) to the low-tide height. The intensity of the events, as determined by the peak particle concentrations achieved, is also positively correlated with the amount of tidal areas exposed to ambient air, as determined by the tidal height, and solar radiation. A nucleation potential index (NPI) was developed as a tool to provide a predictive capability for event prediction at Mace Head. The index was derived from normalized tidal height, solar radiation intensity, and wind direction and was compared with the occurrence of nucleation events from the database. The result shows that Mace Head particle formation events can be quite well predicted with a threshold probability of 50%.Publication In vivo gene transfer of inducible nitric oxide synthase to carotid arteries from hypercholesterolemic rabbits(Ovid Technologies (Wolters Kluwer Health), 2003-04-10) Zanetti, M.; d'Uscio, L. V.; Kovesdi, I.; Katusic, Z. S.; O'Brien, T.Background and Purpose-Hypercholesterolemia is associated with endothelial dysfunction. Inducible nitric oxide synthase (iNOS) is upregulated in atherosclerotic vessels. However, its role in the regulation of vascular function is not completely understood. We examined the effect of adenovirus-mediated gene transfer of iNOS to the hypercholesterolemic rabbit carotid artery in vivo. Methods-Rabbits were fed a high-cholesterol or chow diet for 10 weeks. Two doses (1 x 10(8) and 1 x 10(9) plaque-forming units [pfu]/mL) of adenoviral vectors encoding iNOS (AdiNOS) or beta-galactosidase (Adbetagal) were luminally delivered to the carotid arteries from chow- and cholesterol-fed animals. Vascular reactivity and superoxide levels were assessed in Adbetagal- and AdiNOS-transduced vessels from chow- and cholesterol-fed animals after 3 days. Results-Endothelium-dependent vasorelaxation was impaired in the carotid artery from cholesterol-fed animals. In AdiNOS-transduced arteries, transgene expression was demonstrated by positive immunostaining in the endothelium. Transduction with low-dose (1 x 10(8) pfu/mL) AdiNOS did not affect vascular reactivity in arteries from chow- and cholesterol-fed animals. In contrast, high-dose (1 x 10(9) pfu/mL) AdiNOS significantly reduced endothelium-dependent relaxation in vessels from cholesterol-but not chow- fed rabbits. After both low- and high-dose iNOS gene transfer, levels of O-2(.-) were significantly (P<0.05) elevated in carotid arteries from cholesterol-fed animals. Incubation with an O-2(.-) scavenger did not reverse vascular dysfunction in these arteries. Conclusions-Adenoviral- mediated overexpression of iNOS results in increased production of O-2(.-) in carotid arteries from cholesterol-but not chow- fed animals. High-dose AdiNOS gene transfer is associated with reduced endothelium-dependent and -independent relaxation in vessels from cholesterol-fed animals.Publication Modelling the contribution of sea salt and dimethyl sulfide derived aerosol to marine ccn(Copernicus GmbH, 2002-01-14) Yoon, Y. J.; Brimblecombe, P.The concentration of cloud condensation nuclei (CCN) in the marine boundary layer (MBL) was estimated from dimethyl sulfide (DMS) flux, sea salt (SS) emission, and aerosols entrained from the free troposphere (FT). Only under clean air conditions, did the nucleation of DMS derived sulfur (DMS CCN) contribute significantly to the MBL CCN. The accommodation coefficient for sulfuric acid mass transfer was found to be a very important parameter in the modeling the contribution of DMS to MBL CCN. The relationship between seawater DMS and MBL CCN was found to be non-linear mainly due to the transfer processes of sulfuric acid onto aerosols. In addition, sea salt derived CCN (SS CCN) and entrained aerosol from the FT (FT CCN) affected the MBL CCN directly, by supplying CCN, and indirectly, by behaving as an efficient sink for sulfuric acid. The SS CCN explained more than 50% of the total predicted MBL CCN when wind speeds were moderate and high. Sea salt and FT aerosol may often be more efficient sources of MBL CCN than DMS.Publication Positive solvability of systems of nonlinear hammerstein integral equations(Elsevier BV, 2005-11-01) Yang, Zhilin; O'Regan, DonalPublication Time-resolved observations of the short period cv sdss j123813.73-033933.0(EDP Sciences, 2006-03-21) Zharikov, S. V.; Tovmassian, G. H.; Napiwotzki, R.; Michel, R.; Neustroev, V.Aims. We observed a new and poorly studied cataclysmic variable ( CV) SDSS J123813.73-033933.0 to determine its classification and binary parameters. Methods. Simultaneous time-resolved photometric and spectroscopic observations were carried out to conduct period analysis and Doppler tomography mapping. Results. From radial velocity measurements of the Ha line we determined its orbital period to be 0.05592 +/- 0.00035 days (80.53 min). This period is longer than the first estimate of 76 min by Szkody et al. ( 2003), but still at the very edge of the period limit for hydrogen-rich CVs. The spectrum shows double-peaked Balmer emission lines flanked by strong broad Balmer absorption, indicating a dominant contribution by the white dwarf primary star, and is similar to the spectra of short-period low-mass transfer WZ Sge-like systems. The photometric light curve shows complex variability. The system undergoes cyclic brightening up to 0.4 mag, which are of semi-periodic nature with periods of the order of 8 - 12 h. We also detect a 40.25 min variability of similar to 0.15 mag corresponding to half of the orbital period. Amplitude of the latter increases with the cyclic brightening of the system. We discuss the variable accretion rate and its impact on the hot spot as the most probable reason for both observed processes. Conclusions. SDSS J123813.73-033933.0 is preliminary classified as a WZ Sge-like short period system with low and unstable accretion rate.Publication Multiple positive solutions of singular positone dirichlet problems with derivative dependence(Cambridge University Press (CUP), 2006-05-01) YAN, BAOQIANG; O'REGAN, DONAL; AGARWAL, RAVI P.The existence of multiple positive solutions is presented for the singular Dirichlet boundary value problems [GRAPHICS] using the fixed point index; here f may be singular at x = 0 and x' = 0.Publication Comparison of three updating schemes using artificial neural network in flow forecasting(Copernicus GmbH, 2004-01-01) Xiong, Lihua; O’Connor, Kieran M.; Guo, ShenglianThree updating schemes using artificial neural network (ANN) in flow forecasting are compared in terms of model efficiency. The first is the ANN model in the simulation mode plus an autoregressive (AR) model. For the ANN model in the simulation model, the input includes the observed rainfall and the previously estimated discharges, while the AR model is used to forecast the flow simulation errors of the ANN model. The second one is the ANN model in the updating mode, i.e. the ANN model uses the observed discharge directly together with the observed rainfall as the input. In this scheme, the weights of the ANN model are obtained by optimisation and then kept fixed in the procedure of flow forecasting. The third one is also the ANN model in the updating mode; however, the weights of the ANN model are no longer fixed but updated at each time step by the backpropagation method using the latest forecast error of the ANN model. These three updating schemes are tested for flow forecasting on ten catchments and it is found that the third updating scheme is more effective than the other two in terms of their efficiency in flow forecasting. Moreover, compared to the first updating scheme, the third scheme is more parsimonious in terms of the number of parameters, since the latter does not need any additional correction model. In conclusion, this paper recommends the ANN model with the backpropagation method, which updates the weights of ANN at each time step according to the latest forecast error, for use in real-time flow forecasting.Publication Oxidative phosphorylation and the tricarboxylic acid cycle are essential for normal development of mouse ovarian follicles(Oxford University Press (OUP), 2005-06-24) Wycherley, G.BACKGROUND: Mouse ovarian follicles are typically grown in upright drops of culture medium. Recently we found that culture of follicles at the medium-gas interface in inverted drops markedly improved follicular development, possibly due to improved access of oxygen to the follicle. In this study, we examined the importance of aerobic energy metabolism for follicle development by culturing mouse follicles (198 +/- 16.5 initial mu m diameter, mean +/- SD) in the presence of phosphorylation and tricarboxylic acid (TCA) cycle inhibitors. METHODS: All inhibitors were tested in the inverted system using 100 mu l medium drops in 96-well plates; certain inhibitors were also tested in upright drops with or without an oil overlay. RESULTS: The oxidative phosphorylation inhibitor rotenone (0.1, 0.5 and 1 mu mol/l) totally abolished follicle growth in the inverted system; cyanide (1 mmol/l) totally abolished growth in the upright with oil system but not in the inverted system (possibly due to loss of cyanide gas due to the absence of an oil overlay). The mitochondrial uncoupler 2,4-dinitrophenol (0.5 and 1 mmol/l) also abolished growth in the inverted system. The TCA cycle inhibitor monofluoroacetate (10 mmol/l), significantly inhibited growth in all three culture systems (P < 0.01) but malonate (10 mmolA) had no effect. CONCLUSIONS: Aerobic metabolism and an adequate oxygen supply are essential for normal follicular development.Publication Existence and multiplicity of solutions for some three-point nonlinear boundary value problems(Springer Nature, 2006-01-01) Xian, Xu; O'Regan, DonalWe study the existence and multiplicity of solutions for the three-point nonlinear boundary value problem u '' ( t) +lambda a(t) f (u) = 0, 0 < t < 1; u( 0) = 0 = u(1)-gamma u(eta), where eta is an element of (0,1), gamma is an element of [0,1), a(t) and f (u) are assumed to be positive and have some singularities, and. is a positive parameter. Under certain conditions, we prove that there exists lambda* > 0 such that the three-point nonlinear boundary value problem has at least two positive solutions for 0 <lambda <lambda*, at least one solution for lambda =lambda*, and no solution for lambda >lambda*.Publication A novel follicle culture system markedly increases follicle volume, cell number and oestradiol secretion(BioScientifica, 2004-06-01) Wycherley, G; Downey, D; Kane, M T; Hynes, A CThis study reports a novel, simple method for culture of mouse follicles which results in follicles with cell numbers similar to in vivo fully grown follicles. Using this method, follicles (1180-240 mum in diameter) were cultured in a 100 mul inverted drop of medium without oil and compared with culture in upright drops with and without a mineral oil overlay. Follicles, isolated from C57BL/6 x CBA/ca crossbred and MF1 inbred mice, were cultured individually at 37degreesC in 96-well round-bottomed suspension cell tissue culture plates for 6 days. Follicles grown in the inverted drop culture system reached a markedly higher final diameter (means+/- S.E.M.; 471 +/- 6.0 mum) as compared with the upright with oil (363 +/- 2.7 mum) and without oil (358 +/- 4.0) systems. There was no significant effect of mouse strain on follicle diameter. Follicular secretion of oestradiol and lactate into the medium was measured on days 2, 4 and 6 of culture. Secretion of oestradiol per follicle on day 6 was 2.49 +/- 0.45 ng in the inverted and 0.90 +/- 0.17 ng in the upright without oil system (P < 0.001). Follicular secretion of lactate on a per unit of follicle volume basis remained constant in the inverted system over days 2, 4 and 6 and was less (P < 0.001) than secretion in both the upright with and without oil systems. Follicle cell proliferation was markedly increased in the inverted as compared with the upright with oil system; the increases in cell numbers were significant on day 3 (P < 0.01) and on all subsequent days (P < 0.001). These results are discussed in relation to the supply of oxygen to the follicle in culture.Publication Comparison of four updating models for real-time river flow forecasting(Informa UK Limited, 2002-08-01) XIONG, LIHUA; O'CONNOR, KIERAN M.Four different error-forecast updating models are investigated in terms of their capability of providing real-time river flow forecast accuracy superior to that of rainfall-runoff models applied in the simulation (nonupdating) mode. The first and most widely used is the single autoregressive (AR) model, the second being an elaboration of that model, namely the auto regressive-threshold (AR-TS) updating model. A fuzzy autoregressive-threshold (FU-AR-TS) updating model is proposed as the third form of model, the fourth and final error-forecast updating model applied being the artificial neural network (ANN) model. In the application of these four updating models, the lumped soil moisture accounting and routing (SMAR) conceptual model has been selected to simulate the observed discharge series on 11 selected test catchments. As expected, it is found that all of these four updating models are very successful in improving the flow forecast accuracy, when operating in real-tithe forecasting mode. A less expected, but nonetheless welcome, result is that the three updating models having the most parameters, i.e. AR-TS, FU-AR-TS, and ANN, do not show any considerable advantages in improving the real-time flow forecast efficiency over that of the simple standard AR model. Thus it is recommended that, in the context of real-time river flow forecasting based on error-forecast updating, modellers should continue to use the AR model.Publication Unbounded solutions for singular boundary value problems on the semi-infinite interval: upper and lower solutions and multiplicity(Elsevier BV, 2006-12-01) Yan, Baoqiang; O’Regan, Donal; Agarwal, Ravi P.Publication A non-linear perturbation model considering catchment wetness and its application in river flow forecasting(Elsevier BV, 1997-12-01) Xia, J.; O'Connor, K.M.; Kachroo, R.K.; Liang, G.C.Publication Comparative genome analysis of the primary sex-determining locus in salmonid fishes(Cold Spring Harbor Laboratory, 2003-02-01) Woram, R. A.We compared the Y-chromosome linkage maps for four salmonid species (Arctic charr, Salvelinus alpinus, Atlantic salmon, Salmo salar, brown trout, Salmo trutta; and rainbow trout, Oncorhynchus mykiss) and a putative Y-linked marker from lake trout (Salvelinus namaycush). These species represent the three major genera within the subfamily Salmoninae of the Salmonidae. The data clearly demonstrate that different Y-chromosomes have evolved in each of the species. Arrangements of markers proximal to the sex-determining locus are preserved on homologous, but different, autosomal linkage groups across the four species studied in detail. This indicates that a small region of DNA has been involved in the rearrangement of the sex-determining region. Placement of the sex-determining region appears telomeric in brown trout, Atlantic salmon, and Arctic charr, whereas an intercalary location for SEX may exist in rainbow trout. Three hypotheses are proposed to account for the relocation: translocation of a small chromosome arm; transposition of the sex-determining gene; or differential activation of a primary sex-determining gene region among the species.Publication Cdna and deduced amino acid sequence of thesalmo salar(atlantic salmon) adult hemoglobin alpha chain(Oxford University Press (OUP), 1989-01-01) Wolff, Jacques P.; Gannon, FrankPublication Genetic variation in marine bivalvia (mollusca)(American Association for the Advancement of Science (AAAS), 1973-11-30) Wilkins, N. P.; Levinton, J.Publication Enterokinase in normal intestinal biopsies and those from patients with untreated coeliac disease(BMJ, 1972-11-01) Woodley, J. F.; Keane, R.