526
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Gooding KM, Whatmore JL, Warland D, Hannemann MM, Middlebrooke AR, Paisley K, Liddell W, Lee B, Tooke JE, Shore AC. PC21 PREDICTORS OF SKIN MINIMUM VASCULAR RESISTANCE IN WOMEN. Microcirculation 2004. [DOI: 10.1080/10739680490488607] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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527
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Rao M, Arya N, Lee B, Hannon RJ, Loan W, Soong CV. Endovascular Repair of Abdominal Aortic Aneurysm in a Patient with Renal Transplant. Cardiovasc Intervent Radiol 2004; 27:523-4. [PMID: 15461978 DOI: 10.1007/s00270-004-0169-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Patients with functioning renal transplant who develop abdominal aortic aneurysm can safely be treated with endovascular repair. Endovascular repair of aneurysm avoids renal ischemia associated with cross-clamping of aorta.
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528
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Hwang YH, Choi JY, Kim S, Chung ES, Kim T, Koh SS, Lee B, Bae SH, Kim J, Park YM. Over-expression of c-raf-1 proto-oncogene in liver cirrhosis and hepatocellular carcinoma. Hepatol Res 2004; 29:113-121. [PMID: 15163433 DOI: 10.1016/j.hepres.2004.02.009] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/28/2003] [Revised: 01/05/2004] [Accepted: 02/03/2004] [Indexed: 12/18/2022]
Abstract
Liver cirrhosis accompanies at least 70% of hepatocellular carcinomas world-wide. To evaluate the dysregulation of apoptosis and the MAPK pathway in hepatocarcinogenesis, we investigated the expression profiles of the genes involved in apoptosis and MAPK pathway in cirrhosis and hepatocellular carcinoma. A total of 94 tissue specimens (61 cirrhosis and 33 hepatocellular carcinoma) obtained from 67 patients were analyzed by microarray, quantitative PCR and Western blot experiments. Of 71 apoptosis-associated genes, c-raf-1 and S6 were up-regulated in 42.9% and 32.1% of 28 cirrhosis tissues, respectively, and both genes were well correlated in a five-cluster K-means analysis. For c-raf-1 and down stream genes in the MAPK pathway, c-raf-1, MEK, and MAPK were up-regulated in 40%, 80%, and 86.7% of 45 cirrhosis specimens, respectively, and in 50%, 63.6%, and 59.1% of 22 hepatocellular carcinoma specimens, respectively. Western blot analysis showed that activated Raf-1 was over-expressed in 91.2% (52/57) of cirrhosis and in 100% (30/30) of hepatocellular carcinoma. The expression level of Raf-1 in 14 of 26 paired samples (53.8%) was significantly higher in hepatocellular carcinoma than in cirrhosis ( [Formula: see text] -fold, [Formula: see text] ). These results suggest that the activation of Raf-1 plays an important role in the development of hepatocellular carcinoma.
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529
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McFall B, Arya N, Soong C, Lee B, Hannon R. Crutch induced axillary artery injury. THE ULSTER MEDICAL JOURNAL 2004; 73:50-2. [PMID: 15244127 PMCID: PMC2475443] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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530
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Huang MK, Choi YJ, Houde R, Lee JW, Lee B, Zhao X. Effects of Lactobacilli and an acidophilic fungus on the production performance and immune responses in broiler chickens. Poult Sci 2004; 83:788-95. [PMID: 15141837 DOI: 10.1093/ps/83.5.788] [Citation(s) in RCA: 126] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Accumulated lines of evidence indicate that inactivated probiotics could have beneficial effects similar to those of live probiotics. Two strains of disrupted, cobalt-enriched, lactic acid bacteria (Lactobacillus acidophilus and Lactobacillus casei) and a disrupted fungal mycelium (Scytalidium acidophilum) were spray-mixed onto a mash basal feed, in 2 concentrations, prior to pelleting. The effects of these probiotics on production performance and immune response in broiler chickens were investigated. The production parameters, including BW, feed intake (FI), BW gain (BWG), and feed conversion ratio (FCR), were monitored weekly during a 6-wk trial. The immune response was evaluated by immunizing the birds with the antigen keyhole limpet hemocyanin (KLH) followed by a serological assay to measure blood IgA and IgG titers. Some of the production parameters were significantly improved by low L. casei (LCL; for BW and BWG), high L. acidophilus (LAH; for BW and BWG), and high fungal (FH; for BW, BWG, and FI) in comparison with the nonadditive control (NC-). However, these 3 treatments (LCL, LAH, and FH) did not enhance the measured immune responses. Instead, the titers of serum KLH-specific IgA in high L. casei (LCH) and low L. acidophilus (LAL) were significantly higher than those of NC-, 10 d after immunization. None of the probiotic treatments increased the titer of KLH-specific IgG in blood. Our results indicate that disrupted and cobalt-enriched L. acidophilus or L. casei was able to enhance production performance of broiler chickens. The fungal mycelium, S. acidophilum, when used at a high concentration, also demonstrated its potential for the first time to be used as a probiotic. In addition, the optimal concentration for administering probiotics is strain dependent. A higher dose does not always result in a better performance.
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531
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Shin TJ, Park HK, Lee SW, Lee B, Oh W, Kim JS, Baek S, Hwang YT, Kim HC, Ree M. Synthesis and characterization of new aromatic polyimides containing well-defined conjugation units. POLYM ENG SCI 2004. [DOI: 10.1002/pen.10104] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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532
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Stojadinovic O, Vouthounis C, Lee B, Stallcup M, Tomic‐Canic M. 142 ??Catenin and Carm?1 as Co?Repressors of Glucocorticoid Receptor Lead to Inhibition of Keratinocyte Migration. Wound Repair Regen 2004. [DOI: 10.1111/j.1067-1927.2004.0abstractek.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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533
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Stojadinovic O, Brem H, Lee B, Vouthounis C, Entero H, Tomic‐Canic M. 138 Molecular Pathogenesis of Chronic Wounds: The Role of ??Catenin and C?MYC. Wound Repair Regen 2004. [DOI: 10.1111/j.1067-1927.2004.0abstracteg.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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534
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535
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536
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Spealman RD, Lee B, Tiefenbacher S, Platt DM, Rowlett JK, Khroyan TV. Triggers of relapse: nonhuman primate models of reinstated cocaine seeking. NEBRASKA SYMPOSIUM ON MOTIVATION. NEBRASKA SYMPOSIUM ON MOTIVATION 2004; 50:57-84. [PMID: 15160638] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 04/29/2023]
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537
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Arya N, Rao M, Lee B, Hannon RJ, Soong CV. Treatment of co-existing thoracic and abdominal aortic aneurysms using combined endoluminal stent grafts and conventional surgery. THE ULSTER MEDICAL JOURNAL 2003; 72:126-8. [PMID: 14696828 PMCID: PMC2475434] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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538
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McLoone N, Lee B, Anderson J, McKenna K. Homozygous factor V Leiden mutation in a patient with traumatic leg ulceration. Clin Exp Dermatol 2003; 28:608-9. [PMID: 14616826 DOI: 10.1046/j.1365-2230.2003.01402.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Factor V Leiden mutation is a well-established risk factor for venous thrombosis and ulceration. We report a 20-year-old male patient who presented with a traumatic left leg ulcer that responded poorly to therapy. He had no previous medical history. Following investigation it was discovered that the patient had extensive venous thrombosis of the left leg veins and was homozygous for the factor V Leiden gene mutation. This case demonstrates the need for detailed history taking and thorough investigation of any atypical ulcer in young adults.
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539
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Pozarowski P, Huang X, Halicka DH, Lee B, Johnson G, Darzynkiewicz Z. Interactions of fluorochrome-labeled caspase inhibitors with apoptotic cells: a caution in data interpretation. Cytometry A 2003; 55:50-60. [PMID: 12938188 DOI: 10.1002/cyto.a.10074] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
BACKGROUND Fluorochrome-labeled inhibitors of caspases (FLICA, e.g., FAM-VAD-FMK, FITC-VAD-FMK) have been designed as affinity labels of the enzyme active center of caspases Their binding by apoptotic cells was interpreted as reflecting activation of caspases. We have recently observed, however, that their binding is more complex and may involve additional mechanisms. Our goal in this study was to clarify the ongoing utility of these probes. METHODS Apoptosis of HL-60, Jurkat, MCF-7 and T-24 cells was induced by the DNA topoisomerase I inhibitor, topotecan, or by oxidative stress (H(2)O(2)). Lymphocytes were induced by their mitogenic activation. Using multiparameter laser scanning and flow cytometry analysis, the correlation between FLICA binding and the number of known apoptotic indicators was examined. These included: collapse of the mitochondrial transmembrane potential; activation of caspase-3 (detected immunocytochemically); binding of annexin V; chromatin condensation; the presence of DNA strand breaks; and loss of plasma membrane capability to exclude propidium iodide (PI). FLICA binding specificity was tested by pretreatment with z-VAD-FMK or z-DEVD-FMK. RESULTS FLICA binding was subsequent to the collapse of mitochondrial transmembrane potential, nearly concurrent with caspase-3 activation, and preceded annexin V binding, chromatin condensation, DNA fragmentation and loss of plasma membrane integrity. The predominant portion of FAM-VAD-FMK, FITC-VAD-FMK or FAM-DEVD-FMK binding to apoptotic cells could not be inhibited by z-VAD-FMK or z-DEVD-FMK, respectively, when the unlabeled inhibitors were added post-induction of apoptosis. CONCLUSIONS FLICA are specific and convenient to use markers of apoptotic cells and they detect very early events of apoptosis associated with caspases activation. Assays that combine their binding with either the loss of mitochondrial potential or with exclusion of PI as a probe of plasma membrane integrity, distinguish sequential stages of apoptosis and are particularly useful to differentiate between apoptosis and necrosis. Our results conform with the published data that unlabeled caspase inhibitors, when added after induction of apoptosis, cannot prevent activation of caspases detected by binding of biotinylated inhibitors or by cleavage of fluorogenic substrates. While FLICA binding by apoptotic cells most likely is a consequence of caspase activation, these binding events may also involve other or additional mechanisms than simply their specific attachment to the active enzyme centers of caspases.
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540
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Lee B. Looking Beneath the Surface of Agricultural Safety and Health.: Dennis J Murphy. (Pp 104.) Published by American Society of Agricultural Engineers, 2003 (ASAE Pub 801M0303). ISBN 1-802769-28-X. Inj Prev 2003. [DOI: 10.1136/ip.9.3.286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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541
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Komulainen P, Brown GR, Mikkonen M, Karhu A, García-Gil MR, O'Malley D, Lee B, Neale DB, Savolainen O. Comparing EST-based genetic maps between Pinus sylvestris and Pinus taeda. TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 2003; 107:667-678. [PMID: 12827250 DOI: 10.1007/s00122-003-1312-2] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2002] [Accepted: 03/10/2003] [Indexed: 05/24/2023]
Abstract
A genetic map of Pinus sylvestris was constructed using ESTP (expressed sequence tag polymorphism) markers and other gene-based markers, AFLP markers and microsatellites. Part of the ESTP markers (40) were developed and mapped earlier in Pinus taeda, and additional markers were generated based on P. sylvestris sequences or sequences from other pine species. The mapping in P. sylvestris was based on 94 F(1) progeny from a cross between plus-tree parents E635C and E1101. AFLP framework maps for the parent trees were first constructed. The ESTP and other gene sequence-based markers were added to the framework maps, as well as five published microsatellite loci. The separate maps were then integrated with the aid of AFLPs segregating in both trees (dominant segregation ratios 3:1) as well as gene markers and microsatellites segregating in both parent trees (segregation ratios 1:1:1:1 or 1:2:1). The integrated map consisted of 12 groups corresponding to the P. taeda linkage groups, and additionally three and six smaller groups for E1101 and E635C, respectively. The number of framework AFLP markers in the integrated map is altogether 194 and the number of gene markers 61. The total length of the integrated map was 1,314 cM. The set of markers developed for P. sylvestris was also added to existing maps of two P. taeda pedigrees. Starting with a mapped marker from one pedigree in the source species resulted in a mapped marker in a pedigree of the other species in more than 40% of the cases, with about equal success in both directions. The maps of the two species are largely colinear, even if the species have diverged more than 70 MYA. Most cases of different locations were probably due to problems in identifying the orthologous members of gene families. These data provide a first ESTP-containing map of P. sylvestris, which can also be used for comparing this species to additional species mapped with the same markers.
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542
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Tiefenbacher S, Lee B, Meyer JS, Spealman RD. Noninvasive technique for the repeated sampling of salivary free cortisol in awake, unrestrained squirrel monkeys. Am J Primatol 2003; 60:69-75. [PMID: 12784287 DOI: 10.1002/ajp.10080] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The use of noninvasive measures of hypothalamic-pituitary-adrenal (HPA) axis function is of growing interest among preclinical and clinical investigators. This report describes a method for the repeated assessment of salivary free cortisol in awake, unrestrained squirrel monkeys (Saimiri sciureus) based on a saliva sampling technique previously developed for rhesus monkeys. Individually housed adult male squirrel monkeys were trained to chew on dental rope attached to a pole, from which saliva was extracted by centrifugation and analyzed for cortisol by radioimmunoassay (RIA). Eight of nine monkeys readily acquired the task, reliably providing adequate saliva samples for the assay. Salivary free cortisol levels were examined in these subjects under basal conditions and in response to two types of neuroendocrine challenge. Levels of salivary free cortisol showed relatively low intra- and interindividual variability, with mean individual morning levels ranging between 17.1 and 37.9 microg/dl. Squirrel monkeys demonstrated a consistent daily rhythm in salivary free cortisol ranging from a high of 27.4 +/- 5.2 microg/dl (mean +/- SEM) at 12 P.M. to a low of 7.5 +/- 1.6 microg/dl at 6 P.M. Intravenous (IV) challenges with 1 microg/kg ACTH, or 10 and 50 microg/kg CRF resulted in significant increases in salivary free cortisol. The described sampling technique provides a reliable and sensitive means for repeated measurement of HPA activity in unrestrained, awake squirrel monkeys. In addition, our findings illustrate several features of HPA system rhythmicity and reactivity using salivary cortisol instead of blood plasma or serum.
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543
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Russell K, Hartling L, Lee B, Crumley E, Wiebe N, Klassen TP. Early Versus Late Re-Feeding in the Treatment of Acute Gastroenteritis in Children: A Systematic Review. Paediatr Child Health 2003. [DOI: 10.1093/pch/8.suppl_b.33ba] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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544
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Edrees WK, Lau LL, Young IS, Smye MG, Gardiner KR, Lee B, Hannon RJ, Soong CV. The effect of lower limb ischaemia-reperfusion on intestinal permeability and the systemic inflammatory response. Eur J Vasc Endovasc Surg 2003; 25:330-5. [PMID: 12651171 DOI: 10.1053/ejvs.2002.1848] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVES a relationship has been demonstrated between increased intestinal permeability, endotoxaemia and the development of the systemic inflammatory response syndrome (SIRS) after aortic surgery. The aim of this study was to evaluate whether isolated lower limb ischaemia-reperfusion (I/R) injury affects intestinal mucosal barrier function and cytokine release. PATIENTS AND METHODS four groups of patients were investigated, group I, patients with critical limb ischaemia (CLI) undergoing infra-inguinal bypass surgery (n=18); group II, patients with intermittent claudication (IC) undergoing infra-inguinal bypass surgery (n=14); group III, patients with CLI unsuitable for arterial reconstruction, undergoing major amputation (n=12); and group IV, patients undergoing carotid endarterectomy for symptomatic carotid stenosis (n=13). Intestinal permeability, endotoxaemia and urinary soluble tumour necrosis factor receptors were assessed (p55TNF-R). RESULTS an increase in intestinal permeability was observed on the 3rd postoperative day only in CLI group. This was found to correlate with arterial clamp time. Patients who had a femoro-distal bypass had significantly higher intestinal permeability compared to those who had femoro-popliteal bypass. Endotoxaemia was not detected in any of the groups. Postoperative urinary p55TNF-R concentrations were significantly higher in CLI group compared to the other groups. These did not correlate with the increased intestinal permeability. CONCLUSIONS our results support the hypothesis that revascularisation of critically ischaemia limbs leads to intestinal mucosal barrier dysfunction and cytokine release. They also suggest that the magnitude of the inflammatory response following I/R injury is related to the degree of initial ischaemia.
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545
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Lee B, Shin T, Lee S, Yoon J, Kim J, Youn H, Ree M. Time-resolved X-ray scattering and calorimetric studies on the crystallization behaviors of poly(ethylene terephthalate) (PET) and its copolymers containing isophthalate units. POLYMER 2003. [DOI: 10.1016/s0032-3861(03)00130-7] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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546
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Reid JA, McConway J, Lau LL, Hannon RJ, Lee B, Soong CV. An expensive superstition--'a Saturday flit is a short sit'. IRISH MEDICAL JOURNAL 2003; 96:121-2. [PMID: 12793481] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 03/02/2023]
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547
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Bartkus JM, Juni BA, Ehresmann K, Miller CA, Sanden GN, Cassiday PK, Saubolle M, Lee B, Long J, Harrison AR, Besser JM. Identification of a mutation associated with erythromycin resistance in Bordetella pertussis: implications for surveillance of antimicrobial resistance. J Clin Microbiol 2003; 41:1167-72. [PMID: 12624047 PMCID: PMC150313 DOI: 10.1128/jcm.41.3.1167-1172.2003] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Erythromycin treatment failures and in vitro resistance of Bordetella pertussis have been reported on several occasions in the past few years, but the mechanism of resistance has not been described. One potential mechanism, genetic modification of the erythromycin-binding site on the 23S rRNA of the 50S ribosomal subunit, has been observed in other bacteria. To explore this possibility, we amplified the portion of the 23S rRNA gene encoding the central loop of domain V. DNA sequencing and restriction fragment length polymorphism of the PCR products showed that each of the four erythromycin-resistant B. pertussis strains tested contained an A-to-G transition mutation at position 2058 (Escherichia coli numbering) of the 23S rRNA gene. The mutation was not found in seven erythromycin-susceptible isolates tested. Two of the resistant isolates were heterozygous, containing at least one mutant copy and one wild-type copy of the 23S rRNA gene. These results indicate that erythromycin resistance in these strains is likely due to a mutation of the erythromycin-binding site in the 23S rRNA gene. Identification of the resistance mechanism will facilitate development of molecular susceptibility testing methods that can be used directly on clinical specimens in the absence of an isolate.
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548
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Gao H, Korbling M, Lee B, Champlin R, Reuben J. 169Mobilization of type 1 and type 2 dendritic cells by GM-CSF alone or in combination with G-CSF. Biol Blood Marrow Transplant 2003. [DOI: 10.1016/s1083-8791(03)80167-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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549
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Lee B, Couriel D, Shen D, Hinze L, Champlin R, Reuben J. 112Serum cytokine profiles of patients with acute GVHD treated with methylprednisolone alone or in combination with infliximab are different. Biol Blood Marrow Transplant 2003. [DOI: 10.1016/s1083-8791(03)80113-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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550
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Trinczek M, Gorelov A, Melconian D, Alford WP, Asgeirsson D, Ashery D, Behr JA, Bricault PG, D'Auria JM, Deutsch J, Dilling J, Dombsky M, Dubé P, Eaton S, Fingler J, Giesen U, Gu S, Häusser O, Jackson KP, Lee B, Schmid JH, Stocki TJ, Swanson TB, Wong W. Novel search for heavy nu mixing from the beta+ decay of 38mK confined in an atom trap. PHYSICAL REVIEW LETTERS 2003; 90:012501. [PMID: 12570603 DOI: 10.1103/physrevlett.90.012501] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2002] [Indexed: 05/24/2023]
Abstract
A new technique, full neutrino momentum reconstruction, is used to set limits on the admixture of heavy neutrinos into the electron neutrino. We measure coincidences between nuclear recoils and positrons from the beta decay of trapped radioactive atoms and deduce the neutrino momentum. A search for peaks in the reconstructed recoil time-of-flight spectrum as a function of positron energy is performed. The admixture upper limits range from 4 x 10(-3) to 2 x 10(-2) and are the best direct limits for neutrinos (as opposed to antineutrinos) for the mass region of 0.7 to 3.5 MeV.
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