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Hunt KM, Brooker SL, Sanz‐Fernandez MV, Gabler NK, Baumgard LH, McGuire MA. The effects of heat stress and Zn intake on the microbial communities in the stomach, ileum, colon and feces of pigs. FASEB J 2013. [DOI: 10.1096/fasebj.27.1_supplement.356.7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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77
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Chan KH, Ghosh J, McGuire MA. Over 150 potentially low‐value health care practices: an Australian study. Med J Aust 2013; 198:84. [DOI: 10.5694/mja12.11807] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Accepted: 01/03/2013] [Indexed: 11/17/2022]
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78
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Hunt KM, Williams JE, Shafii B, Hunt MK, Behre R, Ting R, McGuire MK, McGuire MA. Mastitis is associated with increased free fatty acids, somatic cell count, and interleukin-8 concentrations in human milk. Breastfeed Med 2013; 8:105-10. [PMID: 22283504 PMCID: PMC3568962 DOI: 10.1089/bfm.2011.0141] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
BACKGROUND Research in bovine lactation has demonstrated that milk produced by a mammary gland displaying inflammation-based symptoms of mastitis has increased levels of free fatty acids (FFAs) compared with milk produced by a contralateral asymptomatic gland. However, the effects of mastitis on lipid classes in milk have not been investigated in humans. METHODS The study described here compared milk collected from the symptomatic breast of women with mastitis (n=14) with that collected from the contralateral asymptomatic breast to determine if mastitis caused alterations in the quantity of total lipids, FFAs, and phospholipids (PLs), as well as the fatty acid profiles of these lipid classes. To assess their efficacy as biomarkers of mastitis, samples were also analyzed for selected markers of local inflammation: sodium, somatic cell count (SCC), and interleukin-8 (IL-8). RESULTS FFAs were higher in milk from the mastitic breast compared with that from the healthy breast (1.31 vs. 1.07 ± 0.10 g/100 g of lipid, p<0.05). Similarly, SCC and IL-8 were elevated roughly 10-fold in milk from mastitic breasts, compared with milk from healthy breasts, and sodium tended to be higher in milk from mastitic breasts (p<0.10). However, there were no differences in total lipid, PLs, or fatty acid profiles within each lipid class. CONCLUSIONS In summary, mastitis is associated with increased lipolysis in the human breast but not alterations in milk fat synthesis, as evidenced by a lack of alteration in total milk lipids. Additionally, these results indicate that SCC and IL-8 may be better indicators of mammary inflammation than sodium content.
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79
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Ritzenthaler KL, Shahin AM, Shultz TD, Dasgupta N, McGuire MA, McGuire MK. Dietary intake of c9,t11-conjugated linoleic acid correlates with its concentration in plasma lipid fractions of men but not women. J Nutr 2012; 142:1645-51. [PMID: 22833652 DOI: 10.3945/jn.111.156794] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The c9,t11-18:2 isomer of conjugated linoleic acid (c9,t11-CLA) represents the main dietary CLA form with putative health benefits. Whereas CLA intake influences the tissue CLA concentration, little is known about the association between dietary CLA and the CLA content of plasma lipid fractions. This study was designed to document fasting and nonfasting plasma c9,t11-CLA concentrations in a population of free-living adults (n = 94) and relate these concentrations to c9,t11-CLA intake. We also determined the c9,t11-CLA content of the primary plasma lipid fractions in a subset (n = 50) of our participants, related these to c9,t11-CLA intake, and determined whether c9,t11-CLA intake or plasma c9,t11-CLA was correlated with plasma cholesterol. Mean fasting plasma c9,t11-CLA concentrations were 0.46 ± 0.01 and 0.54 ± 0.01% (wt:wt) of total fatty acids for men and women, respectively (P < 0.05); nonfasting concentrations were 0.28 ± 0.01 and 0.38 ± 0.01% of total fatty acids, respectively (P < 0.001). All major esterified plasma lipid fractions contained c9,t11-CLA; TG had the highest percentages. In men, c9,t11-CLA intake correlated (r = 0.47; P < 0.05) with TG c9,t11-CLA content, suggesting that TG c9,t11-CLA may serve as a biomarker for c9,t11-CLA intake. In females, there were no correlations between c9,t11-CLA intake and the c9,t11-CLA content of any esterified plasma lipid fraction. In neither sex was there a relation between dietary c9,t11-CLA or plasma c9,t11-CLA concentration and circulating lipoprotein cholesterol concentration. The influence of sex on circulating c9,t11-CLA content and further validation of biomarkers of c9,t11-CLA intake warrant further investigation.
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80
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Lu T, Park JY, Parnell K, Fox LK, McGuire MA. Characterization of fatty acid modifying enzyme activity in staphylococcal mastitis isolates and other bacteria. BMC Res Notes 2012; 5:323. [PMID: 22726316 PMCID: PMC3434086 DOI: 10.1186/1756-0500-5-323] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2012] [Accepted: 06/08/2012] [Indexed: 05/05/2023] Open
Abstract
Background Fatty acid modifying enzyme (FAME) has been shown to modify free fatty acids to alleviate their bactericidal effect by esterifying fatty acids to cholesterol or alcohols. Although it has been shown in previous studies that FAME is required for Staphylococcus aureus survival in skin abscesses, FAME is poorly studied compared to other virulence factors. FAME activity had also been detected in coagulase-negative staphylococci (CNS). However, FAME activity was only surveyed after a bacterial culture was grown for 24 h. Therefore if FAME activity was earlier in the growth phase, it would not have been detected by the assay and those strains would have been labeled as FAME negative. Results Fifty CNS bovine mastitis isolates and several S. aureus, Escherichia coli, and Streptococcus uberis strains were assayed for FAME activity over 24 h. FAME activity was detected in 54% of CNS and 80% S. aureus strains surveyed but none in E. coli or S. uberis. While some CNS strains produced FAME activity comparable to the lab strain of S. aureus, the pattern of FAME activity varied among strains and across species of staphylococci. All CNS that produced FAME activity also exhibited lipase activity. Lipase activity relative to colony forming units of these CNS decreased over the 24 h growth period. No relationship was observed between somatic cell count in the milk and FAME activity in CNS. Conclusions Some staphylococcal species surveyed produced FAME activity, but E. coli and S. uberis strains did not. All FAME producing CNS exhibited lipase activity which may indicate that both these enzymes work in concert to alter fatty acids in the bacterial environment.
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81
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Williams J, Wilcox J, Meehan CL, Brooker SL, Hunt KM, McGuire MA, McGuire MK. Macronutrient composition of milk produced by Ngandu and Aka women in the Central African Republic. FASEB J 2012. [DOI: 10.1096/fasebj.26.1_supplement.624.5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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82
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Hunt KM, Brooker SL, Williams JE, McGuire MK, McGuire MA. Elevated dairy fat intake by lactating women increases milk fat and alters fatty acid profile, but does not change gene expression in the milk fat globule transcriptome. FASEB J 2012. [DOI: 10.1096/fasebj.26.1_supplement.390.4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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83
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Hunt KM, Preuss J, Nissan C, Davlin CA, Williams JE, Richardson AD, McGuire MK, Bode L, McGuire MA. Human milk oligosaccharides enhance the growth of
Staphylococci. FASEB J 2012. [DOI: 10.1096/fasebj.26.1_supplement.268.8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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84
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Cordina RL, Celermajer DS, McGuire MA. Systemic venous anatomy in congenital heart disease: implications for electrophysiologic testing and catheter ablation. J Interv Card Electrophysiol 2011; 33:143-9. [PMID: 22015428 DOI: 10.1007/s10840-011-9624-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2011] [Accepted: 09/04/2011] [Indexed: 11/29/2022]
Abstract
INTRODUCTION Cardiac arrhythmias are a significant problem in patients with congenital heart disease. Many patients with congenital heart disease have abnormal systemic venous anatomy which can complicate electrophysiologic testing, catheter ablation and pacemaker and defibrillator implantation. We reviewed the systemic venous anatomy in a cohort of patients undergoing electrophysiologic testing and catheter ablation. METHODS AND RESULTS We reviewed all electrophysiologic studies performed in patients with adult congenital heart disease (n = 80) at our institution between January 1998 and October 2009. Ten patients (13%) had a congenital systemic venous anomaly. Of these, seven (9%) had a left superior vena cava and four (5%) had infrahepatic interruption of the inferior vena cava (two had both anomalies). One patient's inferior vena cava was connected to a left-sided atrium; she had right atrial isomerism. In four patients (40%), systemic venous abnormalities were discovered at the time of electrophysiologic testing. CONCLUSIONS Systemic venous anomalies occur frequently in the congenital heart disease population and may complicate electrophysiologic testing and catheter ablation. Pre-procedural imaging may assist in facilitating a successful procedure.
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85
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Hunt KM, Foster JA, Forney LJ, Schütte UME, Beck DL, Abdo Z, Fox LK, Williams JE, McGuire MK, McGuire MA. Characterization of the diversity and temporal stability of bacterial communities in human milk. PLoS One 2011; 6:e21313. [PMID: 21695057 PMCID: PMC3117882 DOI: 10.1371/journal.pone.0021313] [Citation(s) in RCA: 456] [Impact Index Per Article: 35.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2011] [Accepted: 05/25/2011] [Indexed: 01/30/2023] Open
Abstract
Recent investigations have demonstrated that human milk contains a variety of bacterial genera; however, as of yet very little work has been done to characterize the full diversity of these milk bacterial communities and their relative stability over time. To more thoroughly investigate the human milk microbiome, we utilized microbial identification techniques based on pyrosequencing of the 16S ribosomal RNA gene. Specifically, we characterized the bacterial communities present in milk samples collected from 16 women at three time-points over four weeks. Results indicated that milk bacterial communities were generally complex; several genera represented greater than 5% of the relative community abundance, and the community was often, yet not always, stable over time within an individual. These results support the conclusion that human milk, which is recommended as the optimal nutrition source for almost all healthy infants, contains a collection of bacteria more diverse than previously reported. This finding begs the question as to what role this community plays in colonization of the infant gastrointestinal tract and maintaining mammary health.
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86
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Delaire O, Ma J, Marty K, May AF, McGuire MA, Du MH, Singh DJ, Podlesnyak A, Ehlers G, Lumsden MD, Sales BC. Giant anharmonic phonon scattering in PbTe. NATURE MATERIALS 2011; 10:614-9. [PMID: 21642983 DOI: 10.1038/nmat3035] [Citation(s) in RCA: 174] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2011] [Accepted: 04/22/2011] [Indexed: 05/24/2023]
Abstract
Understanding the microscopic processes affecting the bulk thermal conductivity is crucial to develop more efficient thermoelectric materials. PbTe is currently one of the leading thermoelectric materials, largely thanks to its low thermal conductivity. However, the origin of this low thermal conductivity in a simple rocksalt structure has so far been elusive. Using a combination of inelastic neutron scattering measurements and first-principles computations of the phonons, we identify a strong anharmonic coupling between the ferroelectric transverse optic mode and the longitudinal acoustic modes in PbTe. This interaction extends over a large portion of reciprocal space, and directly affects the heat-carrying longitudinal acoustic phonons. The longitudinal acoustic-transverse optic anharmonic coupling is likely to play a central role in explaining the low thermal conductivity of PbTe. The present results provide a microscopic picture of why many good thermoelectric materials are found near a lattice instability of the ferroelectric type.
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87
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Hunt KM, Nissan C, Bode L, McGuire MK, McGuire MA. Correlations between human milk bacteria and oligosaccharide concentrations. FASEB J 2011. [DOI: 10.1096/fasebj.25.1_supplement.104.3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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88
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Uhoya WO, Montgomery JM, Tsoi GM, Vohra YK, McGuire MA, Sefat AS, Sales BC, Weir ST. Phase transition and superconductivity of SrFe(2)As(2) under high pressure. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:122201. [PMID: 21389565 DOI: 10.1088/0953-8984/23/12/122201] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
High pressure x-ray diffraction and electrical resistance measurements have been carried out on SrFe(2)As(2) to a pressure of 23 GPa and temperature of 10 K using a synchrotron source and designer diamond anvils. At ambient temperature, a phase transition from the tetragonal phase to a collapsed tetragonal (CT) phase is observed at 10 GPa under non-hydrostatic conditions. The experimental relation that T-CT transition pressure for 122 Fe-based superconductors is dependent on ambient pressure volume is affirmed. The superconducting transition temperature is observed at 32 K at 1.3 GPa and decreases rapidly with a further increase of pressure in the region where the T-CT transition occurs. Our results suggest that T(C) falls below 10 K in the pressure range of 10-18 GPa where the CT phase is expected to be stable.
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89
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Sonier JE, Huang W, Kaiser CV, Cochrane C, Pacradouni V, Sabok-Sayr SA, Lumsden MD, Sales BC, McGuire MA, Sefat AS, Mandrus D. Magnetism and disorder effects on muon spin rotation measurements of the magnetic penetration depth in iron-arsenic superconductors. PHYSICAL REVIEW LETTERS 2011; 106:127002. [PMID: 21517343 DOI: 10.1103/physrevlett.106.127002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2010] [Indexed: 05/30/2023]
Abstract
It is shown that attempts to accurately deduce the magnetic penetration depth λ of overdoped BaFe(1.82)Co(0.18)As₂ single crystals by transverse-field muon spin rotation (TF μSR) are thwarted by field-induced magnetic order and strong vortex-lattice disorder. We explain how substantial deviations from the magnetic field distribution of a nearly perfect vortex lattice by one or both of these factors is also significant for other iron-arsenic superconductors, and this introduces considerable uncertainty in the values of λ obtained by TF μSR.
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90
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Rezamand P, McGuire MA. Effects of trans fatty acids on markers of inflammation in bovine mammary epithelial cells. J Dairy Sci 2011; 94:316-20. [PMID: 21183041 DOI: 10.3168/jds.2010-3289] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2010] [Accepted: 10/06/2010] [Indexed: 11/19/2022]
Abstract
Trans fatty acids (tFA) contribute to inflammation. The objective was to investigate the effects of tFA on mRNA expression of proinflammatory markers in cultured bovine mammary epithelial cells (MAC-T cell line). Bovine mammary epithelial cells were grown in Dulbecco's Modified Eagle Medium containing 10% fetal bovine serum. Cells were then subcultured in a medium lacking fetal bovine serum, to which incremental concentrations (up to 90 μM) of elaidic acid (trans-9 C18:1) or linoleidic acid (trans-9, trans-12 C18:2) were added. Bovine serum albumin (fatty acid-free) solutions were added and cells were collected at specific time points over 48 h. Then, RNA was extracted and converted to complementary DNA for quantitative real-time PCR analysis of proinflammatory gene expression. Presence of elaidic acid caused increases in mRNA expression of interleukin (IL)-1β (3.4-fold; dose-independently over a 6-h period) and intercellular adhesion molecule (ICAM)-1 (up to 1.4-fold) relative to that for cells treated with no tFA, whereas expression of IL-6 and IL-8 was reduced 0.75- and 0.85-fold, respectively. Presence of linoleidic acid reduced mRNA expression of IL-6 and IL-8 relative to that for control (0.95- and 0.87-fold, respectively). Trans mono- and dienoic fatty acids upregulated mRNA expression of IL-1β and ICAM-1, whereas expression of IL-6 and IL-8 was downregulated in MAC-T cells. Because these genes are ultimately involved in inflammation, elaidic or linoleidic acid, either directly fed or formed in the rumen during biohydrogenation, may alter the risk for mastitis in vivo.
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91
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Gofryk K, Sefat AS, McGuire MA, Sales BC, Mandrus D, Imai T, Thompson JD, Bauer ED, Ronning F. Effect of annealing on the specific heat of optimally doped Ba(Fe0.92Co0.08)2As2. ACTA ACUST UNITED AC 2011. [DOI: 10.1088/1742-6596/273/1/012094] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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92
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Fernandes RM, VanBebber LH, Bhattacharya S, Chandra P, Keppens V, Mandrus D, McGuire MA, Sales BC, Sefat AS, Schmalian J. Effects of nematic fluctuations on the elastic properties of iron arsenide superconductors. PHYSICAL REVIEW LETTERS 2010; 105:157003. [PMID: 21230930 DOI: 10.1103/physrevlett.105.157003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2009] [Indexed: 05/30/2023]
Abstract
We demonstrate that the changes in the elastic properties of the FeAs systems, as seen in our resonant ultrasound spectroscopy data, can be naturally understood in terms of fluctuations of emerging nematic degrees of freedom. Both the softening of the lattice in the normal, tetragonal phase as well as its hardening in the superconducting phase are consistently described by our model. Our results confirm the view that structural order is induced by magnetic fluctuations.
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93
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Park JY, Fox LK, Seo KS, McGuire MA, Park YH, Rurangirwa FR, Sischo WM, Bohach GA. Comparison of phenotypic and genotypic methods for the species identification of coagulase-negative staphylococcal isolates from bovine intramammary infections. Vet Microbiol 2010; 147:142-8. [PMID: 20667671 DOI: 10.1016/j.vetmic.2010.06.020] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2009] [Revised: 06/21/2010] [Accepted: 06/23/2010] [Indexed: 11/26/2022]
Abstract
Coagulase-negative staphylococci (CNS) are the most frequently isolated pathogens from cows with intramammary infection (IMI). Although API STAPH ID 20, a commercially available identification system, and PCR-restriction fragment length polymorphism (PCR-RFLP) of the gap gene (gap PCR-RFLP) have been successfully applied for the identification of CNS isolates from human specimens, their accuracy in the identification of veterinary isolates has not been fully established. In this study, we identified 263 CNS isolates from bovine IMI at species level by partial 16S rRNA gene sequence analysis as the definitive test. Species identification obtained using partial 16S rRNA gene sequence analysis was compared to results from the API STAPH ID 20 and gap PCR-RFLP analysis. Eleven different CNS species were identified by partial 16S rRNA gene sequence analysis. Only 76.0% (200/263) of the species identification results obtained by API STAPH ID 20 matched those obtained by partial 16S rRNA gene sequence analysis, whereas 97.0% (255/263) of the species identification results obtained by the gap PCR-RFLP analysis matched those obtained by partial 16S rRNA gene sequence analysis. The gap PCR-RFLP analysis could be a useful and reliable alternative method for the species identification of CNS isolates from bovine IMI and appears to be a more accurate method of species identification than the API STAPH ID 20 system.
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94
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Park JY, Fox LK, Seo KS, McGuire MA, Park YH, Rurangirwa FR, Sischo WM, Bohach GA. Detection of classical and newly described staphylococcal superantigen genes in coagulase-negative staphylococci isolated from bovine intramammary infections. Vet Microbiol 2010; 147:149-54. [PMID: 20667668 DOI: 10.1016/j.vetmic.2010.06.021] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2009] [Revised: 06/21/2010] [Accepted: 06/23/2010] [Indexed: 10/19/2022]
Abstract
The coagulase-negative staphylococci (CNS) are the most prevalent mastitis pathogen group yet their virulence characteristics have not been well described. We investigated the presence of 19 classical and newly described staphylococcal superantigen (SAg) genes in CNS isolates from bovine intramammary infections (IMI). A total of 263 CNS representing 11 different Staphylococcus spp. were examined, and 31.2% (n=82) of CNS isolates had one or more SAg genes; there were 21 different SAg gene combinations. The most prevalent combination of SAg genes (seb, seln and selq; n=45) was found in S. chromogenes, S. xylosus, S. haemolyticus, S. sciuri subsp. carnaticus, S. simulans and S. succinus. The genes for SAgs appear to be widely distributed amongst CNS isolated from bovine IMI.
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95
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Hunt KM, Williams JE, Hunt MK, Ting R, Behre R, McGuire MK, Shafii B, McGuire MA. Concentration of milk free fatty acids is increased during lactational mastitis. FASEB J 2010. [DOI: 10.1096/fasebj.24.1_supplement.556.21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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96
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Hunt KM, Foster JA, Forney LJ, Schütte UM, Beck DL, Williams JE, Collier NN, McGuire MK, McGuire MA. The human milk microbiome: a potential influence on mammary health and bacterial colonization of the infant gut. FASEB J 2010. [DOI: 10.1096/fasebj.24.1_supplement.206.5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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97
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Cordina R, McGuire MA. Maternal cardiac arrhythmias during pregnancy and lactation. Obstet Med 2010; 3:8-16. [PMID: 27582834 PMCID: PMC4989762 DOI: 10.1258/om.2009.090021] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/11/2009] [Indexed: 11/18/2022] Open
Abstract
Arrhythmias occurring during pregnancy can cause significant symptoms and even death in mother and fetus. The management of these arrhythmias is complicated by the need to avoid harm to the fetus and neonate. It is useful to classify patients with arrhythmias into those with and without structural heart disease. Those with a primary electrical problem, but an otherwise normal heart, often tolerate rapid heart rates without compromise whereas patients with problems such as rheumatic heart disease, congenital heart disease or cardiomyopathy may quickly decompensate during an arrhythmia.
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98
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Ning FL, Ahilan K, Imai T, Sefat AS, McGuire MA, Sales BC, Mandrus D, Cheng P, Shen B, Wen HH. Contrasting spin dynamics between underdoped and overdoped Ba(Fe1-xCox)2As2. PHYSICAL REVIEW LETTERS 2010; 104:037001. [PMID: 20366674 DOI: 10.1103/physrevlett.104.037001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2009] [Indexed: 05/29/2023]
Abstract
We report the first NMR investigation of spin dynamics in the overdoped nonsuperconducting regime of Ba(Fe1-xCox)2As2 up to x=0.26. We demonstrate that the absence of interband transitions with large momentum transfer Q{AF} approximately (pi/a,0) between the hole and electron Fermi surfaces results in complete suppression of antiferromagnetic spin fluctuations for x greater than or approximately 0.15. Our experimental results provide direct evidence for a correlation between T{c} and the strength of Q{AF} antiferromagnetic spin fluctuations.
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99
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Christianson AD, Lumsden MD, Nagler SE, MacDougall GJ, McGuire MA, Sefat AS, Jin R, Sales BC, Mandrus D. Static and dynamic magnetism in underdoped superconductor BaFe1.92Co0.08As2. PHYSICAL REVIEW LETTERS 2009; 103:087002. [PMID: 19792749 DOI: 10.1103/physrevlett.103.087002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2009] [Indexed: 05/28/2023]
Abstract
We report neutron scattering measurements on single crystals of BaFe1.92Co0.08As2. The magnetic Bragg peak intensity is reduced by 6% upon cooling through TC. The spin dynamics exhibit a gap of 8 meV with anisotropic three-dimensional interactions. Below TC additional intensity appears at an energy of approximately 4.5(0.5) meV, similar to previous observations of a spin resonance in other Fe-based superconductors. No further gapping of the spin excitations is observed below TC for energies down to 2 meV. These observations suggest the redistribution of spectral weight from the magnetic Bragg position to a spin resonance, demonstrating the direct competition between static magnetic order and superconductivity.
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100
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Nascimento VB, Li A, Jayasundara DR, Xuan Y, O'Neal J, Pan S, Chien TY, Hu B, He XB, Li G, Sefat AS, McGuire MA, Sales BC, Mandrus D, Pan MH, Zhang J, Jin R, Plummer EW. Surface geometric and electronic structures of BaFe2As2(001). PHYSICAL REVIEW LETTERS 2009; 103:076104. [PMID: 19792665 DOI: 10.1103/physrevlett.103.076104] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2009] [Indexed: 05/28/2023]
Abstract
BaFe2As2 exhibits properties that are characteristic of the parent compounds of the newly discovered iron (Fe)-based high-T(C) superconductors. By combining real-space imaging of scanning tunneling microscopy and spectroscopy (STM+STS) with momentum-space quantitative low-energy electron diffraction (LEED), we have identified the surface plane of cleaved BaFe2As2 crystals as the As terminated Fe-As layer-the plane where superconductivity occurs. LEED and STM+STS data on the BaFe2As2(001) surface indicate an ordered arsenic (As) terminated metallic surface without reconstruction or lattice distortion. It is surprising that STM images the different Fe-As orbitals associated with the orthorhombic structure, but not the As atoms in the surface plane.
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