76
|
Ollivier FJ, Brooks DE, Komaromy AM, Kallberg ME, Andrew SE, Sapp HL, Sherwood MB, Dawson WW. Corneal thickness and endothelial cell density measured by non-contact specular microscopy and pachymetry in Rhesus macaques (Macaca mulatta) with laser-induced ocular hypertension. Exp Eye Res 2003; 76:671-7. [PMID: 12742349 DOI: 10.1016/s0014-4835(03)00055-1] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE Sustained increase in intraocular pressure (IOP) in humans results in a loss of corneal endothelial cells and an increase of corneal thickness. The effects of chronically elevated IOP on the corneal endothelium of monkeys with laser-induced ocular hypertension, a commonly used animal model of human glaucoma have not been documented. This study examined the central corneal thickness (CCT), the corneal endothelial cell density (ECD), and the corneal endothelial cell size (ACS) in Rhesus monkeys with experimental ocular hypertension. Materials and methods. Ten male monkeys with argon laser-induced ocular hypertension in one eye for an average duration of 2.4+/-0.7 years, were sedated with ketamine hydrochloride, and the CCT, ECD, and ACS measured at the center of the cornea of both eyes with a Topcon SP-2000P non-contact specular microscope (Topcon America Corporation((R)), Paramus, NJ, USA). CCT was also measured using a DHG-500 Pachette ultrasonic pachymeter (DHG Technology Inc., Exton, PA, USA). Mean and standard deviation (S.D.) of CCT, ECD and ACS for each eye was calculated and statistically compared.Results. Mean CCT in the hypertensive and normal eyes measured by specular microscopy was 0.477+/-0.023mm and 0.468+/-0.020 mm, respectively. Mean ECD in the hypertensive and normal eyes was 2601.7+/-631.8 and 3990.2+/-402.9 cells mm(-2), respectively. The mean size of the endothelial cells was 252.4+/-23.9 micro m(2) in the normal eye and 408.7+/-115.0 microm m(2) in the hypertensive eye. No significant difference in the measurement of CCT was observed between the specular microscope and the pachymeter (p=0.46). No significant difference in the mean CCT was observed between the two eyes (p=0.4820), whereas the mean ECD was significantly lower in the hypertensive eye than in the normal eye (p<0.001). The ECD was inversely related to the length of IOP elevation (p<0.001). CONCLUSIONS No difference in the corneal thickness measurement was observed between the specular microscopy and the pachymetry techniques. Chronic ocular hypertension did not significantly affect the CCT, but caused a significant loss of endothelial cells in the center of the cornea of the laser treated eyes compared to the normotensive eyes. The duration of elevated IOP was the most important factor affecting the ECD.
Collapse
|
77
|
Komaromy AM, Brooks DE, Kallberg ME, Dawson WW, Sapp HL, Sherwood MB, Lambrou GN, Percicot CL. Passive attenuation of cortical pattern evoked potentials with increasing body weight in young male rhesus macaques. Doc Ophthalmol 2003; 106:231-8. [PMID: 12737499 DOI: 10.1023/a:1022966113655] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The purpose of our study was to determine changes in amplitudes and implicit times of retinal and cortical pattern evoked potentials with increasing body weight in young, growing rhesus macaques (Macaca mulatta). Retinal and cortical pattern evoked potentials were recorded from 29 male rhesus macaques between 3 and 7 years of age. Thirteen animals were reexamined after 11 months. Computed tomography (CT) was performed on two animals to measure the distance between the location of the skin electrode and the surface of the striate cortex. Spearman correlation coefficients were calculated to describe the relationship between body weights and either root mean square (rms) amplitudes or implicit times. For 13 animals rms amplitudes and implicit times were compared with the Wilcoxon matched pairs signed rank test for recordings taken 11 months apart. Highly significant correlations between increases in body weights and decreases in cortical rms amplitudes were noted in 29 monkeys (p < 0.0005). No significant changes were found in the cortical rms amplitudes in thirteen monkeys over 11 months. Computed tomography showed a large increase of soft tissue thickness over the skull and striate cortex with increased body weight. The decreased amplitude in cortical evoked potentials with weight gain associated with aging can be explained by the increased distance between skin electrode and striate cortex due to soft tissue thickening (passive attenuation).
Collapse
|
78
|
Komáromy AM, Andrew SE, Sapp HL, Brooks DE, Dawson WW. Flash electroretinography in standing horses using the DTL microfiber electrode. Vet Ophthalmol 2003; 6:27-33. [PMID: 12641840 DOI: 10.1046/j.1463-5224.2003.00261.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
PURPOSE The goal of our study was the evaluation of a practical method for the recording of flash electroretinograms (ERGs) in sedated, standing horses with the DTL microfiber electrode. METHODS The horses were sedated intravenously with detomidine hydrochloride (0.015 mg/kg). The pupil was dilated and the auriculopalpebral nerve was blocked. The ERGs were recorded with the active electrode on the cornea (DTL), the reference electrode near the lateral canthus, and the ground electrode over the occipital bone. The light intensities of the white strobe light were 0.03 cd x s/m2 (scotopic) and 3 cd x s/m2 (scotopic and photopic). Photopic and scotopic single flash and flicker responses to Ganzfeld stimulation were recorded. During the 20-min dark adaptation period the retina was stimulated every 5 min with the 0.03 cd x s/m2 single flash. RESULTS The median b-wave amplitudes and implicit times were 38 microV and 33 ms (photopic cone-dominated response), 43 microV and 63 ms (5-min dark adaptation), 72 microV and 89 ms (10 min), 147 microV and 103 ms (15 min), 188 microV and 109 ms (20 min, 0.03 cd x s/m2, rod response), and 186 microV and 77 ms (20 min, 3 cd x s/m2, maximal combined rod-cone response). A steady increase in amplitude and implicit time was noted during dark adaptation. No oscillatory potentials could be isolated. CONCLUSIONS The use of detomidine hydrochloride sedation and the DTL microfiber electrode allowed the recording of good quality ERGs. This protocol should permit the detection of functional problems in the retina without the risk involved with general anesthesia.
Collapse
|
79
|
Rosa M, Cardozo LM, da Silva Pereira J, Brooks DE, Martins ALB, Florido PSS, Stussi JSP. Fungal flora of normal eyes of healthy horses from the State of Rio de Janeiro, Brazil. Vet Ophthalmol 2003; 6:51-5. [PMID: 12641843 DOI: 10.1046/j.1463-5224.2003.00267.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The conjunctival fungal flora of 32 adult horses with normal eyes (n = 64) from the State of Rio de Janeiro in Brazil was identified in the fall of 2000 using horses of different breeds, both genders and aged 5-19 years old. The culture samples were taken from the conjunctival sac of both eyes with a sterile cotton swab wetted with saline solution, seeded in Sabouraud's dextrose agar with chloramphenicol, and incubated for 5 days at an average temperature of 25 degrees C. The number of fungal colonies per eye varied between 0 and 250 colony forming units (CFUs). There were often differences in colony types between eyes of the same animal. Filamentous fungi of genera were isolated and identified in the following proportion of the total genera of fungal colonies isolated: Aspergillus (32.2%), Penicillium (25.8%), Scopulariopsis (15.9%), Trichoderma (11.2%), Cladosporium (5.6%), Mucor (2.1%), Syncephalastrum (2.1%), Eurotium (1.7%), Geotrichum (0.9%), Rhizopus (0.9%), Gliomastix (0.4%), Fusarium (0.4%), Staphylotrichum (0.4%) and Verticillium (0.4%). Yeast genera represented 9% of the total isolates. Over half the horses had at least one normal eye with either Aspergillus, Penicillium, Trichoderma or Scopulariopsis isolated, which is a departure from other studies of the normal horse eye.
Collapse
|
80
|
Andrew SE, Nguyen A, Jones GL, Brooks DE. Seasonal effects on the aerobic bacterial and fungal conjunctival flora of normal thoroughbred brood mares in Florida. Vet Ophthalmol 2003; 6:45-50. [PMID: 12641842 DOI: 10.1046/j.1463-5224.2003.00265.x] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To evaluate seasonal effects on the presence or absence of fungal and aerobic bacterial flora of the conjunctival fornix of normal Florida Thoroughbred horses. SAMPLE POPULATION Both eyes of 100 horses. PROCEDURE Horses with normal anterior segment ophthalmic examinations from three farms in north central Florida were included. Each animal had the ventral conjunctival fornix of each eye swabbed with sterile culturettes. Samples were taken in October, January, April, and July (1999-2000). Aerobic and fungal cultures were plated. Bacterial cultures were reviewed at 24 and 48 h. Fungal cultures were reviewed weekly for 4 weeks. Logistic regression analysis with season as a factor and age of the horse as a covariate was performed. Statistical significance was set at P < 0.01. RESULTS Horses ranged from 3 to 24 years of age, with a median age of 9 years. Twenty-four genera of bacteria and 35 genera of fungi were recovered. Corynebacterium sp., Staphylococcus sp., Bacillus sp. and Moraxella sp. were the bacteria most frequently isolated. Mold species, dematiaceous mold species, Chrysosporium sp., Cladosporium sp., and Aspergillus sp. were the most frequently recovered fungi. Season did not have a significant effect on the presence of microorganisms isolated for individual horses adjusted for age. Younger horses had an increased incidence of gram-negative rods and fungal isolates. The number of bacteria and fungi isolated are not uniform across seasons. CONCLUSION There were no significant differences between the number or type of organisms cultured during the sampling seasons in normal Florida horses. A large range of normal bacterial and fungal flora were isolated from these horses. The number of bacteria and fungi isolated are not uniform across seasons. The likelihood of detecting an organism depends on the horses' age.
Collapse
|
81
|
Andrew SE, Clippinger TL, Brooks DE, Helmick KE. Penetrating keratoplasty for treatment of corneal protrusion in a great horned owl (Bubo virginianus). Vet Ophthalmol 2002; 5:201-5. [PMID: 12236872 DOI: 10.1046/j.1463-5224.2002.00246.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A young adult great horned owl (Bubo virginianus) was examined following presumed trauma. The owl had soft tissue injury to its left wing as well as corneal protrusion, lens subluxation, and iridodialysis of the right eye. The bird's eye was treated surgically with a large, rectangular penetrating keratoplasty. Following escape from housing, the bird was found with partial wound dehiscence and iris prolapse 12 days post operation. Surgical repair was performed and healing progressed for 14 days, at which time the transplant dehisced and the globe was exenterated. The patient rehabilitated well until escaping from its cage again 4 weeks later, at which time it sustained an open comminuted humeral fracture and was euthanized.
Collapse
|
82
|
Komáromy AM, Brooks DE, Dawson WW, Källberg ME, Ollivier FJ, Ofri R. Technical issues in electrodiagnostic recording. Vet Ophthalmol 2002; 5:85-91. [PMID: 12071864 DOI: 10.1046/j.1463-5224.2002.00229.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Electroretinogram (ERG) and visual-evoked potentials (VEPs) are used in veterinary ophthalmology to assess the functional integrity of the retina and the central visual pathway. The interpretation of altered electrophysiologic potentials in diseases can be of great diagnostic value, although it is important to be aware of technical factors and the limitations of these techniques which may result in over-interpretation and misinterpretation of the recordings, such that they are similar to those found in disease-related electrophysiologic changes. The recorded potentials represent the differences in voltage between the active and reference electrodes. The ground electrode serves as zero. A differential or instrumentation amplifier selectively amplifies signals of interest while rejecting noise. Differences between inputs are amplified, whereas common signals are rejected in a process called common mode rejection (CMR). In order for CMR to be most effective in reducing noise, the electrode impedances should be balanced. Filters are part of the differential amplifier as they remove unwanted noise of a certain frequency. The frequency bandwidth, or passband, is the range of frequencies between low- and high-frequency filter settings that are not filtered out. Major sources of noise that cause interpretation artifacts are power lines, amplifier noise, physiologic activity, electrochemical electrode noise and circular grounds. Noise reduction is achieved with high amplifier input impedance, balanced electrode impedances, CMR, filters and signal averaging. Maintaining electrodes in good condition, achieving proper contact between electrode and animal, and keeping electrode leads short aid in achieving noise reduction.
Collapse
|
83
|
Källberg ME, Brooks DE, Garcia-Sanchez GA, Komàromy AM, Szabo NJ, Tian L. Endothelin 1 levels in the aqueous humor of dogs with glaucoma. J Glaucoma 2002; 11:105-9. [PMID: 11912357 DOI: 10.1097/00061198-200204000-00005] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE Endothelin 1 is a small peptide that is involved in regulation of intraocular pressure and modulation of ocular circulation. To investigate the role of endothelin 1 in canine glaucoma, the authors measured aqueous humor levels of endothelin 1 in healthy dogs and in dogs with hypertensive glaucoma. METHODS Aqueous humor samples were obtained with general anesthesia from the eyes of healthy dogs (n = 5) and dogs with hypertensive glaucoma (n = 10). Measurements were made by enzyme immunoassay for endothelin 1. RESULTS The endothelin 1 aqueous humor range was 1.12 - 3.63 pg/mL for healthy dogs and 1.97 - 14.97 pg/mL for glaucomatous dogs. The healthy and glaucomatous canine endothelin 1 aqueous levels (mean +/- SD) were 2.33 +/- 0.90 and 8.11 +/- 5.03 pg/mL, respectively. A two-way analysis of variance indicated that this difference was significant (P = 0.0084). The effect of age on endothelin 1 levels was not significant (P = 0.6283). The large variability found within the glaucomatous group could be explained by the degree of damage of the retina (P = 0.0006). There was no significant correlation between intraocular pressure and endothelin 1 aqueous humor levels within the glaucomatous group (P = 0.29). CONCLUSIONS The aqueous humor of dogs with hypertensive glaucoma contains significantly higher levels of endothelin 1 than that of healthy dogs.
Collapse
|
84
|
Biros DJ, Brooks DE, Brown MP, Merritt KA, Kubilis PS. Regional and zonal variations in the sulfation patterns of chondroitin sulfate in normal equine corneal stroma. Am J Vet Res 2002; 63:143-7. [PMID: 16206796 DOI: 10.2460/ajvr.2002.63.143] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To determine regional and zonal variation in sulfation patterns of chondroitin sulfate in normal equine corneal stroma. SAMPLE POPULATION 22 normal eyes from 11 horses. PROCEDURE Corneas were collected within 24 hours of death from equine necropsy specimens. After papain-chondroitinase digestion of corneal tissue, disaccharides deltaDi4S and deltaDi6S were quantified by use of capillary zone electrophoresis in the superficial, middle, and deep zones of central and peripheral regions of the cornea. RESULTS For the 2 regions combined, deltaDi6S/deltaDi4S values were significantly lower in the deep and middle zones, compared with that of the superficial zone. In the central region, deep and middle zones had significantly lower deltaDi6S/deltaDi4S values than the superficial zone did. In the peripheral region, the deep zone had significantly lower deltaDi6S/deltaDi4S values, compared with superficial and middle zones. In the deep zone, the peripheral region had significantly lower deltaDi6S/deltaDi4S values than the central region did. CONCLUSIONS AND CLINICAL RELEVANCE Distribution of deltaDi6S/deltaDi4S values follows a gradient across the healthy equine cornea, being smallest in the deep and middle zones of the central region and the deep zone of the peripheral region. Regional and zonal differences in the distribution of stromal deltaDi6S and deltaDi4S may influence the role of glycosaminoglycans in health, disease, and wound repair of the equine cornea.
Collapse
|
85
|
|
86
|
Whigham HM, Brooks DE, Andrew SE, Gelatt KN, Strubbe DT, Biros DJ. Treatment of equine glaucoma by transscleral neodymium:yttrium aluminum garnet laser cyclophotocoagulation: a retrospective study of 23 eyes of 16 horses. Vet Ophthalmol 2001; 2:243-250. [PMID: 11397272 DOI: 10.1046/j.1463-5224.1999.00083.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Contact neodymium:yttrium aluminum garnet (Nd:YAG) laser transscleral cyclophotocoagulation (TSCP) was performed on 23 eyes of 16 horses for treatment of glaucoma. The mean highest preoperative IOP was 51 +/- 17 mmHg. Follow-up evaluation was available for 19 eyes 1 day after surgery, 14 eyes from 1 to 2 weeks, 16 eyes from 4 to 6 weeks, 9 eyes from 12 to 16 weeks, and 10 eyes greater than 20 weeks after laser treatment. The mean intraocular pressure (IOP) the day following surgery was 34 +/- 13 mmHg. The mean IOP for each follow-up period was: one to two weeks postoperative, 23 +/- 9 mmHg; four to six weeks, 24 +/- 7 mmHg; 12-16 weeks, 28 +/- 10 mmHg; and >/= 20 weeks, 22 +/- 9 mmHg. IOP measurements were significantly different from pretreatment values for all follow-up intervals except for weeks 12-16 (P < 0.05). Treatment success was defined as maintenance of IOP < 30 mmHg. Treatment success was achieved in 93%, 88%, 78%, and 70% of the treated eyes at the 1-2 weeks, 4-6 weeks, 12-16 weeks, and the >/= 20 weeks re-evaluation, respectively. No significant difference was found between the number of eyes visual at presentation (52.2%) and visual at 20 weeks (60%). The most common laser complications were conjunctival hyperemia (21.7%) and corneal ulcers (13.0%). Results of this study indicate that Nd:YAG TSCP is an effective method of controlling IOP and preserving vision in horses with glaucoma. An effective Nd:YAG laser protocol for TSCP in the equine glaucomatous eye is a power setting of 11 W, duration of 0.4 s, applied 5 mm posterior to the limbus at 60 sites, resulting in a total energy dose of 264 J.
Collapse
|
87
|
Sironi G, Riccaboni P, Mertel L, Cammarata G, Brooks DE. p53 protein expression in conjunctival squamous cell carcinomas of domestic animals. Vet Ophthalmol 2001; 2:227-231. [PMID: 11397270 DOI: 10.1046/j.1463-5224.1999.00086.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The expression of p53 protein was investigated in eight formalin-fixed, paraffin-embedded conjunctival squamous cell carcinomas of five horses and one cow, dog and cat each by an immunohistochemical procedure in order to evaluate protein overexpression. Anti-human p53 protein mouse monoclonal antibodies known to be cross-reactive with p53 protein of the animal species examined were used. Positive p53 nuclear immunostaining was detected in five equine, one bovine and one feline cases. Conversely, no p53 immunostaining was found in the only canine case examined. These results demonstrate a frequent p53 overexpression in conjunctival squamous cell carcinoma that could be related to UV-induced mutations of the p53 tumor suppressor gene.
Collapse
|
88
|
Andrew SE, Tou S, Brooks DE. Corneoconjunctival transposition for the treatment of feline corneal sequestra: a retrospective study of 17 cases (1990-1998). Vet Ophthalmol 2001; 4:107-11. [PMID: 11422991 DOI: 10.1046/j.1463-5224.2001.00181.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To describe and evaluate the use of corneoconjunctival transposition as a surgical treatment for corneal sequestra in cats. ANIMALS STUDIED Fifteen cats (17 eyes) of various breeds and ages with corneal sequestra treated surgically with corneoconjunctival transposition. PROCEDURE Retrospective medical records study. RESULTS Median age was 39 months. Eight patients were castrated males, five were spayed females, and two were intact females. The left eye was affected in eight cats, the right eye was affected in five cats, and both eyes were affected in two cats. Mean (+/- SD) sequestrum diameter was 4.4 +/- 2.4 mm (range 1-10 mm) and the sequestrum was located centrally in all cases. Sequestra occurred in the superficial stroma in 8/17 corneas, in the anterior one third of the stroma in 3/17 corneas, and in the middle one third of the stroma in 6/17 corneas. Median duration of clinical signs prior to presentation was 39 days (range 14-1095 days). Median time to healing, defined as the number of days from surgery to cessation of medical treatment, was 34 days (range 25-86 days). There were no recurrences and minimal scar formation. CONCLUSIONS Corneoconjunctival transposition is a valid procedure for surgical treatment of corneal sequestra in cats. The procedure results in excellent cosmesis and functional vision with no recurrences.
Collapse
|
89
|
DeJong ES, DeBerardino TM, Brooks DE, Nelson BJ, Campbell AA, Bottoni CR, Pusateri AE, Walton RS, Guymon CH, McManus AT. Antimicrobial efficacy of external fixator pins coated with a lipid stabilized hydroxyapatite/chlorhexidine complex to prevent pin tract infection in a goat model. THE JOURNAL OF TRAUMA 2001; 50:1008-14. [PMID: 11426113 DOI: 10.1097/00005373-200106000-00006] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
BACKGROUND Pin tract infection is a common complication of external fixation. An antiinfective external fixator pin might help to reduce the incidence of pin tract infection and improve pin fixation. METHODS Stainless steel and titanium external fixator pins, with and without a lipid stabilized hydroxyapatite/chlorhexidine coating, were evaluated in a goat model. Two pins contaminated with an identifiable Staphylococcus aureus strain were inserted into each tibia of 12 goats. The pin sites were examined daily. On day 14, the animals were killed, and the pin tips cultured. Insertion and extraction torques were measured. RESULTS Infection developed in 100% of uncoated pins, whereas coated pins demonstrated 4.2% infected, 12.5% colonized, and the remainder, 83.3%, had no growth (p < 0.01). Pin coating decreased the percent loss of fixation torque over uncoated pins (p = 0.04). CONCLUSION These results demonstrate that the lipid stabilized hydroxyapatite/chlorhexidine coating was successful in decreasing infection and improving fixation of external fixator pins.
Collapse
|
90
|
Gelatt KN, van der Woerdt A, Ketring KL, Andrew SE, Brooks DE, Biros DJ, Denis HM, Cutler TJ. Enrofloxacin-associated retinal degeneration in cats. Vet Ophthalmol 2001; 4:99-106. [PMID: 11422990 DOI: 10.1046/j.1463-5224.2001.00182.x] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE The objective of this study was to evaluate the possible relationship between the administration of parenteral and/or oral [corrected] enrofloxacin and the onset of acute retinal degeneration in cats. The animals studied included 17 cats that received systemic enrofloxacin and developed retinal degeneration soon thereafter. PROCEDURES In this retrospective clinical study, cats that received parenteral and/or oral [corrected] enrofloxacin and developed acute blindness were identified. Parameters recorded included breed, age, sex, enrofloxacin dosage (daily dose and number of days administered), medical condition for which the antibiotic had been prescribed, ophthalmic signs, examination results, and the visual outcome. Fundus photographs were obtained in seven cats, and electroretinography was performed in five cats. Histopathology was performed on two eyes from one cat (case 1) that received enrofloxacin 5 months previously and developed retinal degeneration. RESULTS All cats were the domestic shorthair breed; seven were females (one neutered) and ten were males (seven castrated). Ages ranged from 3 to 16 years old (mean +/- SD; 8.8 +/- 4.6 years). The medical disorders for which enrofloxacin was administered ranged from lymphoma and pancreatitis to otitis and dermatitis, and eight cats had urinary diseases. The daily and total dosage of enrofloxacin and number of days of administration were also highly variable. Presenting clinical signs were most often mydriasis and acute blindness. All cats had diffuse retinal degeneration as evidenced by increased tapetal reflectivity and retinal vascular attenuation. Absence of recordable electroretinographic responses suggested diffuse and extensive outer retinal disease. Vision returned in a few cats, but the retinal degeneration persisted or even progressed. Histopathology of two eyes revealed primarily outer retinal degeneration, with diffuse loss of the outer nuclear and photoreceptor layers, and hypertrophy and proliferation of the retinal pigment epithelium. CONCLUSION Parenteral and/or oral [corrected] enrofloxacin is potentially retinotoxic in some cats, and may result in acute and diffuse retinal degeneration. Blindness often results, but some cats may regain vision. Practitioners should adhere closely to the manufacturer's current enrofloxacin dosage recommendation (5 mg/kg q 24 h), and continue clinical observations for this drug toxicity in cats.
Collapse
|
91
|
Andrew SE, Ramsey DT, Hauptman JG, Brooks DE. Density of corneal endothelial cells and corneal thickness in eyes of euthanatized horses. Am J Vet Res 2001; 62:479-82. [PMID: 11327451 DOI: 10.2460/ajvr.2001.62.479] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To determine density of corneal endothelial cells and corneal thickness in eyes of euthanatized horses. SAMPLE POPULATION 52 normal eyes from 26 horses. PROCEDURE Eyes were enucleated after horses were euthanatized. Eyes were examined to determine that they did not have visible ocular defects. Noncontact specular microscopy was used to determine density of corneal endothelial cells. Corneal thickness was measured, using ultrasonic pachymetry or specular microscopy. RESULTS Mean density of corneal endothelial cells was 3,155 cells/mm2. Cell density decreased with age, but sex did not affect cell density. Values did not differ significantly between right and left eyes from the same horse. Cell density of the ventral quadrant was significantly less than cell density of the medial and temporal quadrants. Mean corneal thickness was 893 microm. Sex or age did not affect corneal thickness. Dorsal and ventral quadrants were significantly thicker than the medial and temporal quadrants and central portion of the cornea. We did not detect a correlation between corneal thickness and density of endothelial cells in normal eyes of horses. CONCLUSIONS AND CLINICAL RELEVANCE Density of corneal endothelial cells decreases with age, but corneal thickness is not affected by age or sex in normal eyes of horses. The technique described here may be useful for determining density of endothelial cells in the cornea of enucleated eyes. This is clinically relevant for analyzing corneal donor tissue prior to harvest and use for corneal transplantation.
Collapse
|
92
|
Janzen J, Elliott TG, Carter CJ, Brooks DE. Detection of red cell aggregation by low shear rate viscometry in whole blood with elevated plasma viscosity. Biorheology 2000; 37:225-37. [PMID: 11026942] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
The viscosity of whole blood measured at low shear rates is determined partly by shear resistance of the red cell aggregates present, stronger aggregation increasing the viscosity in the absence of other changes. Effects of cell deformability can confound interpretation and comparison in terms of aggregation, however, particularly when the plasma viscosity is high. We illustrate the problem with a comparison of hematocrit-adjusted blood from type 1 diabetes patients and controls in which it is found the apparent and relative viscosities at a true shear rate of 0.20 s-1 are lower in the patient samples than age matched controls, in spite of reports that aggregation is increased in such populations. Because the plasma viscosities of the patients were higher on average than controls, we performed a series of experiments to examine the effect of plasma protein concentration and viscosity on normal blood viscosity. Dilution or concentration by ultrafiltration of autologous plasma and viscosity measurements at low shear on constant hematocrit red cell suspensions showed (a) suspension viscosity at 0.25 and 3 s-1 increased monotonically with plasma protein concentration and viscosity but (b) the relative viscosity increased, in concert with the microscopic aggregation grade, up to a viscosity of approximately 1.25 mPa-s but above this the value the relative viscosity no longer increased as the degree of aggregation increased in concentrated plasmas. It is suggested that in order to reduce cell deformation effects in hyperviscous pathological plasmas, patient and control plasmas should be systematically diluted before hematocrit is adjusted and rheological measurements are made. True shear rates should be calculated. Comparison of relative viscosities at low true shear rates appears to allow the effects of red cell aggregation to be distinguished by variable shear rate viscometry in clinical blood samples.
Collapse
|
93
|
Campbell AA, Song L, Li XS, Nelson BJ, Bottoni C, Brooks DE, DeJong ES. Development, characterization, and anti-microbial efficacy of hydroxyapatite-chlorhexidine coatings produced by surface-induced mineralization. JOURNAL OF BIOMEDICAL MATERIALS RESEARCH 2000; 53:400-7. [PMID: 10898881 DOI: 10.1002/1097-4636(2000)53:4<400::aid-jbm14>3.0.co;2-z] [Citation(s) in RCA: 113] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The surface-induced mineralization (SIM) technique was used to produce hydroxyapatite (HAP) coatings on external fixation pins with the antimicrobial agent, chlorhexidine, incorporated within the coating. The SIM process involved surface modification of the substrate with organic functional groups followed by immersion in aqueous supersaturated calcium phosphate solutions. X-ray diffraction spectra confirmed that hydroxyapatite coatings were formed. Chlorhexidine was incorporated into the coating by placing the substrate into various chlorhexidine solutions in between mineralization cycles. Total uptake was measured by dissolution of the coating into a 0.1 M nitric acid solution and measuring the chlorhexidine concentration using UV spectroscopy at 251 nm. Release rates were measured by submersion of coated substrates into saline solutions and measuring chlorhexidine UV absorbency at 231 nm as a function of time. Results show an initial rapid release followed by a period of slower sustained release. The anti-microbial efficacy of the HAP-chlorhexidine coatings was evaluated in vitro using a Staphylococcus aureus cell culture. Initial results show a large "inhibition zone" formed around the chlorhexidine/HAP coating vs. coatings with HAP only. This preliminary work clearly demonstrates that SIM HAP coatings have great potential to locally deliver antimicrobial agents such as chlorhexidine at implantation sites, which may greatly reduce the incidence of pin tract infection that occurs in external fixation.
Collapse
|
94
|
Brooks DE, Haynes CA, Hritcu D, Steels BM, Müller W. Size exclusion chromatography does not require pores. Proc Natl Acad Sci U S A 2000; 97:7064-7. [PMID: 10852951 PMCID: PMC16499 DOI: 10.1073/pnas.120129097] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Separation of macromolecules on the basis of their molecular weight by size exclusion chromatography has long been considered to be caused by the geometry-dependent partition of macromolecules between a continuous phase and the porous interior of a gel or cross-linked bead. The volume of a pore accessible to a solute is limited by its relative dimensions, so larger molecules will have access to a smaller volume and will remain in a bead for a shorter time than smaller solutes. Our recent alternate picture proposes that the partition coefficient can be calculated from a thermodynamic model for the free energy of mixing of the solute with the gel phase. Size-dependent exclusion caused by the unfavorable entropy of mixing associated with the partition is predicted; the magnitude of the effect is modified by enthalpic interactions between the solute and the gel phase. This concept is extended here to describe the partition of macromolecules into a layer of terminally attached polymer chains grafted onto a solid bead. Both simple mean field and self-consistent field theory calculations predict size-dependent entropic exclusion. Experimental results obtained with neutral polymer chains grafted onto solid polystyrene latex beads confirm the predictions.
Collapse
|
95
|
Biros DJ, Gelatt KN, Brooks DE, Kubilis PS, Andrew SE, Strubbe DT, Whigham HM. Development of glaucoma after cataract surgery in dogs: 220 cases (1987-1998). J Am Vet Med Assoc 2000; 216:1780-6. [PMID: 10844971 DOI: 10.2460/javma.2000.216.1780] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To examine postoperative ocular hypertension (POH) and other variables as predictors of the risk of developing glaucoma after cataract surgery in dogs. DESIGN Retrospective study. ANIMALS 220 dogs that had cataract surgery. PROCEDURE Medical records of 220 dogs (346 eyes) that had extracapsular cataract removal or phacoemulsification of cataracts were reviewed. With respect to glaucoma development, 8 variables were analyzed, which included development of POH, breed, sex, age at time of surgery, eye (right vs left), phacoemulsification time, intraocular lens (IOL) placement (yes or no), and stage of cataract development. Eyes developed glaucoma within 6 or 12 months of surgery or did not have signs of glaucoma at least 6 or 12 months after cataract surgery. RESULTS Of 346 eyes, 58 (16.8%) developed glaucoma after surgery. At 6 months, 32 of 206 (15.5%) eyes examined had glaucoma; at 12 months, 44 of 153 (28.8%) eyes examined had glaucoma. Median follow-up time was 5.8 months (range, 0.1 to 48 months). Mixed-breed dogs were at a significantly lower risk for glaucoma, compared with other breeds. Eyes with IOL placement were at a significantly lower risk for glaucoma, compared with eyes without IOL placement. Eyes with hypermature cataracts were at a significantly higher risk for glaucoma, compared with eyes with mature or immature cataracts. CONCLUSIONS AND CLINICAL RELEVANCE Multiple factors appear to contribute to the onset of glaucoma in dogs after cataract surgery. Complications prohibiting IOL placement during cataract surgery may lead to a high risk of glaucoma development.
Collapse
|
96
|
Brooks DE. Introduction and dedications for the equine issue of Veterinary Ophthalmology. Vet Ophthalmol 2000. [DOI: 10.1046/j.1463-5224.2000.32300552.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
|
97
|
Brooks DE. Can cytoplasm exist without undergoing phase separation? INTERNATIONAL REVIEW OF CYTOLOGY 1999; 192:321-30. [PMID: 10610362 DOI: 10.1016/s0074-7696(08)60532-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Studies on such systems as the lens of the eye and theoretical considerations suggest that phase separation may well occur in cytoplasm. In this chapter, several issues relevant to this question are raised. It is suggested that while the interaction between water and the macromolecules in a mixture is proving crucial to their phase separation behavior, the abnormal water that is widely observed in cytoplasm and concentrated protein solutions is unlikely to constitute a thermodynamic phase in the sense of phase separation studies. The role of fixed structures in the cytoplasm, the likelihood that the volume of separated phases would be small and subject to spreading over the fixed structures and the expectation that much of the phase volume could be occupied and dominated by properties of the interface are also discussed. Finally, some experimental approaches to studying the existence of liquid-liquid phases in cytoplasm are proposed. While there is no proof that phase separation exists in cytoplasm, application of some of the techniques outlined might well provide more positive evidence for its presence.
Collapse
|
98
|
Johansson HO, Brooks DE, Haynes CA. Macromolecular crowding and its consequences. INTERNATIONAL REVIEW OF CYTOLOGY 1999; 192:155-70. [PMID: 10553278 DOI: 10.1016/s0074-7696(08)60525-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/14/2023]
Abstract
Incompatible pairs of polymers separate into two phases in aqueous solution above a few percentage points total concentration. Protein pairs can also produce phase separation, but at somewhat higher concentrations. In this chapter, we explore the effect of high background concentrations of macromolecules on phase separation of pairs of species which would not be at sufficiently high concentration to separate in the absence of the uninvolved species. Effects produced by such high background concentrations are known as macromolecular crowding. Dramatic enhancements in various association reactions due to crowding have been predicted and observed but its effects on phase separation in biological mixtures typical of the cytoplasm have not been examined. Here, we describe a calculation based on the Flory-Huggins treatment of concentrated polymer solutions that sheds some light on this issue. We find that a background of 20 wt % of a high molecular weight species greatly reduces the concentrations needed to produce phase separation in a mixture of two incompatible macromolecules if one is more hydrophobic than the other. Given the high total concentration of macromolecules in cytoplasm, it is perhaps surprising that phases have not been observed. This issue is discussed and some explanations offered.
Collapse
|
99
|
Brooks DE, Roberge RJ, Spear A. Clinical nuances of pediatric methadone intoxication. VETERINARY AND HUMAN TOXICOLOGY 1999; 41:388-90. [PMID: 10592949] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/14/2023]
Abstract
Pediatric methadone intoxication may present with clinically unusual findings which could cause confusion to the inexperienced practitioner. We present a case of pediatric methadone overdose, address clinical nuances pertinent to these overdoses, and discuss measures aimed at limiting these potentially catastrophic exposures.
Collapse
|
100
|
Taylor DC, Brooks DE, Ryan JB. Anabolic-androgenic steroid administration causes hypertrophy of immobilized and nonimmobilized skeletal muscle in a sedentary rabbit model. Am J Sports Med 1999; 27:718-27. [PMID: 10569356 DOI: 10.1177/03635465990270060601] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Although the use of anabolic agents in athletics has generated extensive publicity and controversy, the potential therapeutic benefits of these drugs have not been fully investigated. This randomized, blinded experimental study investigated whether short-term administration of an anabolic-androgenic steroid can limit immobilization-induced muscle atrophy in a rabbit model. We casted one hindlimb each in 48 New Zealand White rabbits and randomly assigned the rabbits to two groups. The treated group received weekly intramuscular injections of the anabolic-androgenic steroid, nandrolone decanoate (15 mg/kg). Immobilization significantly decreased muscle weights in both the treated rabbits and controls. Compared with controls, the body weights of the treated rabbits increased significantly at 2, 4, and 8 weeks. At 4 and 8 weeks, wet weights, dry weights, and contractile forces were significantly greater in both the casted and noncasted tibialis anterior muscle-tendon units of the treated group. Dry weights and casted contractile forces of the extensor digitorum longus muscle unit at 4 weeks and all measures at 8 weeks were greater in the treated rabbits than in controls. These results are contrary to previously accepted views that anabolic-androgenic steroid use leads to muscle hypertrophy only in conjunction with strength training. This study adds to the growing evidence that anabolic-androgenic steroids can produce significant skeletal muscle hypertrophy in sedentary populations.
Collapse
|