The Experts below are selected from a list of 66 Experts worldwide ranked by ideXlab platform
William P. Roach - One of the best experts on this subject based on the ideXlab platform.
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Study of corneal lesions induced by 1,318-nm laser radiation pulses in Dutch Belted Rabbits (Oryctolagus cuniculus).
Comparative Medicine, 2002Co-Authors: Bryan K. Ketzenberger, Thomas E. Johnson, Yvonne A. Van Gessel, Steven P. Wild, William P. RoachAbstract:BACKGROUND AND PURPOSE: Use of high-energy near-infrared lasers is becoming more prevalent in today's industries, such as technology, medicine, and military operations. Despite wide-range use of these lasers, threshold, median effective dose (ED50), and the mechanism of laser-tissue interaction are not well defined at the 1,318-nm wavelength for human corneal exposures. The goals of the study reported here were to establish the ED50 for single-pulse, 1,318-nm laser exposures on the Dutch Belted Rabbit cornea and to characterize microscopic changes. Results of this study were then compared with those of previous corneal studies. METHODS: A neodymium:yttrium aluminum garnet (Nd:YAG) laser was used to deliver single 1,318-nm wavelength pulses to the corneas of 10 female Dutch Belted Rabbits (Oryctolagus cuniculus). Single pulses of 0.5-ms duration and radiant energy ranging from 116 to 2,250 J/cm2 irradiated the exposure sites. Sites were clinically evaluated for presence of a lesion at one hour and 24-h after exposure. Results of the 24-h evaluation were used to determine the (ED50). Corneas were subsequently collected at the 24-h endpoint for microscopic evaluation. RESULTS: The ED50 for 1,318-nm exposures to the Rabbit cornea was determined to be 382 J/cm2, as measured at the 1/e2 (0.865 times that of the peak power per unit area). At each exposure site, there was a small (< 1 mm in diameter), white, circular, well demarcated corneal lesion characterized histologically by a band of stromal coagulative necrosis and endothelial necrosis, with sparing of the anterior epithelium. In addition, there appeared some potential for damage to Descemet's membrane at the highest energy level tested. CONCLUSIONS: Findings indicate that the Rabbit corneais subject to injury at the 1,318-nm wavelength with the established ED50.
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Corneal exposures from 1540-nm laser pulses
Laser and Noncoherent Light Ocular Effects: Epidemiology Prevention and Treatment, 2001Co-Authors: William P. Roach, Thomas E. Eurell, Thomas E. JohnsonAbstract:Dutch Belted Rabbit corneas and corneal equivalent (CE) tissue were exposed to 0.8 millisecond pulses of 1540 nm laser light. We report the single pulse ED50 for Dutch Belted Rabbits and for in-vitro corneal equivalent tissues. A histological comparison between the two tissues is presented. Remarkable similarities between the two models in both location and extent of damage are noted. We postulate which cellular energy absorption mechanisms are significant at 1540 nm and how this relates to the histopathology presented.
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Femtosecond laser threshold: Retinal damage versus induced breakdown mechanisms
Laser-Tissue Interaction V; and Ultraviolet Radiation Hazards, 1994Co-Authors: Clarence P. Cain, Cynthia A. Toth, Cindy D. Stein, Gary D. Noojin, David J. Stolarski, Benjamin A. Rockwell, Stephen A. Boppart, William P. RoachAbstract:Threshold measurements at 90 femtoseconds (fs) and 600 fs have been made for minimum visible lesions (MVLs) using Dutch Belted Rabbit and Rhesus monkey eyes. Laser induced breakdown (LIB) thresholds on biological materials including vitreous, normal saline, tap water, and ultrapure water are reported along with irradiance calculations utilizing nonlinear transmission properties including self-focusing. At both pulsewidths the ED50 dose required for the Rhesus monkey eye was less than half the value determined for the Dutch Belted Rabbit eye, all thresholds being 1 microjoule ((mu) J) or less. Measurements on the Rhesus eye at 600 fs found the ED50 dose (0.26 (mu) J) to be much lower than the ED50 dose at 90 fs (0.43 (mu) J). But for these two pulsewidths, almost the same energy level was determined for the Dutch Belted Rabbit eye (0.94 (mu) J vs. 1.0 (mu) J). LIB threshold measurements at 100 fs and 300 fs using a simulated eye with isolated vitreous found the ED50 dosages to be 3.5 and 6.0 (mu) J respectively. We found in all cases that the ED50 dosages required to produce MVLs in 24 hours for Rabbit and monkey eyes were less than the ED50 values measured for LIB in vitreous or saline or any other breakdown values reported. Also observed was the fact that many of the threshold lesions did not appear in the 1-hour postexposure check but clearly showed up at the 24-hour reading which provided for a much lower threshold dose after 24 hours. We discuss the energy levels and peak powers at which nonlinear effects can begin to occur.
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Retinal hemorrhagic lesions from femtosecond visible laser pulses
Laser-Tissue Interaction V; and Ultraviolet Radiation Hazards, 1994Co-Authors: Cindy D. Stein, Clarence P. Cain, Cynthia A. Toth, Gary D. Noojin, Benjamin A. Rockwell, Dave J. Stolarski, William P. RoachAbstract:We present our clinical evaluation of hemorrhagic and non-hemorrhagic 90 fs single pulses in Rabbits and primates. The Rabbit and primate eye present unique in vivo models for evaluation of retinal and choroidal laser induced hemorrhages with distinct differences in their retinal anatomy. We found two different hemorrhagic events to occur in the posterior pole with delivery of 90 fs pulses. First, in the Dutch Belted Rabbit, we found large amounts of energy per pulse (from 20 to 60 times ED50) were required for formation of subretinal hemorrhages. Second, in the Rhesus monkey, we found significant numbers of small intraretinal hemorrhages from relatively low energy 90 fs pulses. Both the Dutch Belted Rabbit and the Rhesus monkey failed to consistently show subretinal hemorrhagic lesions form very high pulse energies. Our findings suggest more energy absorption at the level of the retinal circulation than the choroidal circulation with our pulse parameters. The effects of the laser on the retinal circulation may be due to the use of a wavelength of 580 nm. At this wavelength the oxyhemoglobin to melanin absorption ratio is nearly at its peak (approximately 0.40), perhaps allowing improved absorption in the retinal vasculature. One precaution with this finding, however, are the distinct differences between primate and non-primate ocular systems. Further studies are required to resolve the differences in damage at the level of the RPE and choroid between Rabbits and primates.
Alton G Swennes - One of the best experts on this subject based on the ideXlab platform.
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enzootic enteropathogenic escherichia coli infection in laboratory Rabbits
Journal of Clinical Microbiology, 2012Co-Authors: Alton G Swennes, Alexis Garcia, Ellen M Buckley, Nicola M A Parry, Carolyn M Madden, Peter B Morgan, Keith M AstrofskyAbstract:Enteropathogenic Escherichia coli (EPEC) is the most important cause of persistent diarrhea in children, particularly in developing countries. Animals serve as pathogenic E. coli reservoirs, and compelling evidence for cross-species EPEC transmission exists. In this report, enzootic EPEC infection associated with up to 10.5% diarrhea-associated morbidity in a large laboratory Dutch Belted Rabbit colony was investigated. These Rabbits were obtained from a commercial vendor and had acute diarrhea following shipment. Fecal culture of 20 Rabbits yielded 48 E. coli isolates, 83% of which were eae positive. Repetitive sequence-based PCR (REP-PCR) and serologic analysis identified a single disease-associated EPEC O145:H2 strain. In sampled Rabbits, EPEC-positive culture and the presence of diarrhea were significantly associated. This strain displayed a localized adherence-like HEp-2 cell adherence pattern, as seen in diarrheic human infant EPEC isolates. Treatment was instituted with the fluoroquinolone antibiotic enrofloxacin, to which all isolates were susceptible. Preshipment parenteral enrofloxacin administration reduced diarrhea-associated morbidity 22-fold and mortality 12-fold in subsequent deliveries. This report emphasizes the zoonotic potential of animal EPEC strains and the need for virulence determinant-based screening of E. coli isolates from diarrheic animals.
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differential virulence of clinical and bovine biased enterohemorrhagic escherichia coli o157 h7 genotypes in piglet and Dutch Belted Rabbit models
Infection and Immunity, 2012Co-Authors: Smriti Shringi, Alexis Garcia, Kevin K Lahmers, Kathleen A Potter, Sureshkumar Muthupalani, Alton G Swennes, Carolyn J Hovde, Douglas R Call, Thomas E BesserAbstract:Enterohemorrhagic Escherichia coli O157:H7 (EHEC O157) is an important cause of food and waterborne illness in the developed countries. Cattle are a reservoir host of EHEC O157 and a major source of human exposure through contaminated meat products. Shiga toxins (Stxs) are an important pathogenicity trait of EHEC O157. The insertion sites of the Stx-encoding bacteriophages differentiate EHEC O157 isolates into genogroups commonly isolated from cattle but rarely from sick humans (bovine-biased genotypes [BBG]) and those commonly isolated from both cattle and human patients (clinical genotypes [CG]). Since BBG and CG share the cardinal virulence factors of EHEC O157 and are carried by cattle at similar prevalences, the infrequent occurrence of BBG among human disease isolates suggests that they may be less virulent than CG. We compared the virulence potentials of human and bovine isolates of CG and BBG in newborn conventional pig and weaned Dutch Belted Rabbit models. CG-challenged piglets experienced severe disease accompanied by early and high mortality compared to BBG-challenged piglets. Similarly, CG-challenged Rabbits were likely to develop lesions in kidney and intestine compared with the BBG-challenged Rabbits. The CG strains used in this study carried stx2 and produced significantly higher amounts of Stx, whereas the BBG strains carried the stx2c gene variant only. These results suggest that BBG are less virulent than CG and that this difference in virulence potential is associated with the Stx2 subtype(s) carried and/or the amount of Stx produced.
Alexis Garcia - One of the best experts on this subject based on the ideXlab platform.
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enzootic enteropathogenic escherichia coli infection in laboratory Rabbits
Journal of Clinical Microbiology, 2012Co-Authors: Alton G Swennes, Alexis Garcia, Ellen M Buckley, Nicola M A Parry, Carolyn M Madden, Peter B Morgan, Keith M AstrofskyAbstract:Enteropathogenic Escherichia coli (EPEC) is the most important cause of persistent diarrhea in children, particularly in developing countries. Animals serve as pathogenic E. coli reservoirs, and compelling evidence for cross-species EPEC transmission exists. In this report, enzootic EPEC infection associated with up to 10.5% diarrhea-associated morbidity in a large laboratory Dutch Belted Rabbit colony was investigated. These Rabbits were obtained from a commercial vendor and had acute diarrhea following shipment. Fecal culture of 20 Rabbits yielded 48 E. coli isolates, 83% of which were eae positive. Repetitive sequence-based PCR (REP-PCR) and serologic analysis identified a single disease-associated EPEC O145:H2 strain. In sampled Rabbits, EPEC-positive culture and the presence of diarrhea were significantly associated. This strain displayed a localized adherence-like HEp-2 cell adherence pattern, as seen in diarrheic human infant EPEC isolates. Treatment was instituted with the fluoroquinolone antibiotic enrofloxacin, to which all isolates were susceptible. Preshipment parenteral enrofloxacin administration reduced diarrhea-associated morbidity 22-fold and mortality 12-fold in subsequent deliveries. This report emphasizes the zoonotic potential of animal EPEC strains and the need for virulence determinant-based screening of E. coli isolates from diarrheic animals.
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differential virulence of clinical and bovine biased enterohemorrhagic escherichia coli o157 h7 genotypes in piglet and Dutch Belted Rabbit models
Infection and Immunity, 2012Co-Authors: Smriti Shringi, Alexis Garcia, Kevin K Lahmers, Kathleen A Potter, Sureshkumar Muthupalani, Alton G Swennes, Carolyn J Hovde, Douglas R Call, Thomas E BesserAbstract:Enterohemorrhagic Escherichia coli O157:H7 (EHEC O157) is an important cause of food and waterborne illness in the developed countries. Cattle are a reservoir host of EHEC O157 and a major source of human exposure through contaminated meat products. Shiga toxins (Stxs) are an important pathogenicity trait of EHEC O157. The insertion sites of the Stx-encoding bacteriophages differentiate EHEC O157 isolates into genogroups commonly isolated from cattle but rarely from sick humans (bovine-biased genotypes [BBG]) and those commonly isolated from both cattle and human patients (clinical genotypes [CG]). Since BBG and CG share the cardinal virulence factors of EHEC O157 and are carried by cattle at similar prevalences, the infrequent occurrence of BBG among human disease isolates suggests that they may be less virulent than CG. We compared the virulence potentials of human and bovine isolates of CG and BBG in newborn conventional pig and weaned Dutch Belted Rabbit models. CG-challenged piglets experienced severe disease accompanied by early and high mortality compared to BBG-challenged piglets. Similarly, CG-challenged Rabbits were likely to develop lesions in kidney and intestine compared with the BBG-challenged Rabbits. The CG strains used in this study carried stx2 and produced significantly higher amounts of Stx, whereas the BBG strains carried the stx2c gene variant only. These results suggest that BBG are less virulent than CG and that this difference in virulence potential is associated with the Stx2 subtype(s) carried and/or the amount of Stx produced.
Keith M Astrofsky - One of the best experts on this subject based on the ideXlab platform.
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enzootic enteropathogenic escherichia coli infection in laboratory Rabbits
Journal of Clinical Microbiology, 2012Co-Authors: Alton G Swennes, Alexis Garcia, Ellen M Buckley, Nicola M A Parry, Carolyn M Madden, Peter B Morgan, Keith M AstrofskyAbstract:Enteropathogenic Escherichia coli (EPEC) is the most important cause of persistent diarrhea in children, particularly in developing countries. Animals serve as pathogenic E. coli reservoirs, and compelling evidence for cross-species EPEC transmission exists. In this report, enzootic EPEC infection associated with up to 10.5% diarrhea-associated morbidity in a large laboratory Dutch Belted Rabbit colony was investigated. These Rabbits were obtained from a commercial vendor and had acute diarrhea following shipment. Fecal culture of 20 Rabbits yielded 48 E. coli isolates, 83% of which were eae positive. Repetitive sequence-based PCR (REP-PCR) and serologic analysis identified a single disease-associated EPEC O145:H2 strain. In sampled Rabbits, EPEC-positive culture and the presence of diarrhea were significantly associated. This strain displayed a localized adherence-like HEp-2 cell adherence pattern, as seen in diarrheic human infant EPEC isolates. Treatment was instituted with the fluoroquinolone antibiotic enrofloxacin, to which all isolates were susceptible. Preshipment parenteral enrofloxacin administration reduced diarrhea-associated morbidity 22-fold and mortality 12-fold in subsequent deliveries. This report emphasizes the zoonotic potential of animal EPEC strains and the need for virulence determinant-based screening of E. coli isolates from diarrheic animals.
Daniel Palanker - One of the best experts on this subject based on the ideXlab platform.
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improving the therapeutic window of retinal photocoagulation by spatial and temporal modulation of the laser beam
Journal of Biomedical Optics, 2011Co-Authors: Christopher Sramek, Lohshan Leung, Theodore Leng, Jefferson Brown, Yannis M Paulus, Georg Schuele, Daniel PalankerAbstract:Decreasing the pulse duration helps confine damage, shorten treatment time, and minimize pain during retinal photocoagulation. However, the safe therapeutic window (TW), the ratio of threshold powers for thermomechanical rupture of Bruch's membrane and mild coagulation, also decreases with shorter exposures. Two potential approaches toward increasing TW are investigated: (a) decreasing the central irradiance of the laser beam and (b) temporally modulating the pulse. An annular beam with adjustable central irradiance was created by coupling a 532-nm laser into a 200-μm core multimode optical fiber at a 4-7 deg angle to normal incidence. Pulse shapes were optimized using a computational model, and a waveform generator was used to drive a PASCAL photocoagulator (532 nm), producing modulated laser pulses. Acute thresholds for mild coagulation and rupture were measured in Dutch-Belted Rabbit in vivo with an annular beam (154-163 μm retinal diameter) and modulated pulse (132 μm, uniform irradiance "flat-top" beam) with 2-50 ms pulse durations. Thresholds with conventional constant-power pulse and a flat-top beam were also determined. Both annular beam and modulated pulse provided a 28% increase in TW at 10-ms duration, affording the same TW as 20-ms pulses with conventional parameters. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE). (DOI: 10.1117/1.3542045)
