Biomedical subjects

M G Davidson

Publications and source records attributed to M G Davidson.

At least 37 records · Page 2Linked to original sources

PubMed1998

Transferrin in after-cataract and as a survival factor for lens epithelium.

The Fe-transport protein, transferrin (Tf), is synthesized and secreted by whole lenses and cultured lens epithelial cells. Because of Tf's central role in cell growth and proliferation, its participation in lens cell proliferation following cataract extraction was explored using a rabbit model of after-cataract. Varying amounts of the central anterior lens capsule were removed (0, 35, or 80%) following extraction of the lens. The Tf content of and secretion by after-cataract lens capsular sacs containing regenerated lens tissue was determined ex vivo at 0, 3, 5, 7 and 9 weeks post-surgery. In all cases Tf content of and secretion by the lens sacs was higher than that of their contralateral controls (whole lenses). Tf secretion was up to 5-fold higher and metabolic labeling studies indicated secretion of newly synthesized Tf. The sacs contained up to 10 times the concentration of Tf as the control lenses. Human lens after-cataract capsular bags also secreted Tf. The function of Tf as a survival factor was tested on cultured lens epithelial cells. Cells cultured in serum-free medium had a survival rate of only 20-34% if the medium was changed each day. If the medium was never changed during this period, the survival rate was 43-52%, suggesting secretion of essential growth factors by these cells. Addition of 200 microg ml-1 Tf to the medium during each daily change increased survival to levels attained when the medium was not changed. Addition of Tf antibodies to the culture medium during each daily change decreased cell survival to 14%. Apparently Tf acts as a survival factor for lens epithelia and its synthesis is up-regulated in after-cataract lens sacs. These factors suggest that Tf may play an important role in the pathogenesis of lens epithelial cell proliferation and after-cataract formation following cataract surgery.

Animals↗

PubMed1998

The lens influences aqueous humor levels of transforming growth factor-beta 2.

BACKGROUND: Transforming growth factor-beta 2 (TGF-beta 2) is a pluripotent cytokine which has been suggested to play a number of roles in ocular physiologic and pathologic states. Intraocular fluid (i.o.f.) levels of TGF-beta 2 are quite high. Although the sources of ocular TGF-beta are not completely defined, the retinal pigment epithelium, the epithelium of the ciliary body and trabecular meshwork cells all secrete it. In this study we utilized canine lens and rabbit ciliary pigmented epithelial cell cultures to quantitate the in vitro secretion of TGF-beta 2. In addition, the effects of aphakia or the presence of cataractous lenses on IOF TGF-beta 2 levels were determined. METHODS: Lens and ciliary body epithelial cell culture supernatants and aqueous humors were assayed for total TGF-beta 2 levels by ELISA and bioassay. RESULTS: TGF-beta 2 accumulated in the media bathing lens epithelial cell cultures (0.7 +/- 0.03 ng/ml at day 2) and ciliary pigmented epithelial cell cultures (0.8 +/- 0.06 ng/ml at day 2) in a time-dependent manner. Surprisingly, aqueous humor from aphakic rabbit eyes contained significantly higher levels of TGF-beta 2 than their contralateral phakic controls. Furthermore, aqueous humor from canine eyes with cataracts also contained significantly higher levels of TGF-beta 2 than normal eyes. CONCLUSIONS: These results suggest that the lens secretes TGF-beta 2 and that the presence and status of the lens may influence IOF TGF-beta 2 levels.

Animals↗

PubMed1998

Elevated interleukin-10-to-interleukin-12 ratio in feline immunodeficiency virus-infected cats predicts loss of type 1 immunity to Toxoplasma gondii.

Similar to human immunodeficiency virus, feline immunodeficiency virus (FIV) induces immunodeficiency and enhanced susceptibility to secondary pathogens. To explore cytokine alterations in lentivirus immunodeficiency, constitutive mRNA expression was measured in lymph nodes of healthy and FIV-infected cats before and after challenge with Toxoplasma gondii. Cytokine mRNA expression was similar in control and FIV-infected cats during the first 10 weeks after infection. At 16 weeks, interferon (IFN)-gamma, tumor necrosis factor-alpha, and interleukin (IL)-10 mRNA were increased in FIV-infected cats. Challenge with T. gondii induced an increase in IL-2, IFN-gamma, and IL-12 in the lymph nodes of control cats, whereas IFN-gamma and IL-10 but not IL-2 or IL-12 increased in the lymph nodes of FIV-T. gondii coinfected cats. These results indicate that FIV immunodeficiency may derive from a failure to generate an IL-12-dependent type 1 response and that an elevated level of IL-10 mRNA expression is a predictor of lentivirus immunodeficiency.

Animals↗

PubMed1998

Keratometry, ultrasonic biometry, and prediction of intraocular lens power in the feline eye.

OBJECTIVE: To determine ocular dimensions (using A-scan ultrasound biometry) and corneal curvature (using keratometry) in the feline eye and to calculate the appropriate dioptric power for a prototype posterior chamber intraocular lens (IOL) necessary to achieve emmetropia in the eyes of cats undergoing lens extraction. ANIMALS: 25 clinically normal adult mixed-breed cats and 10 eyes from 10 clinically normal adult mixed-breed cat cadavers. PROCEDURE: A-scan ultrasonic biometry was performed on both eyes of each live cat. Cats were tranquilized, and keratometry was performed on each eye. Biometry was performed on the cadaver eyes. Five of the cadaver eyes had the lens extracted and an IOL, designed for use in dogs, was implanted. Biometry was repeated to estimate postoperative IOL position. Using 3 theoretical IOL formulas, data from biometry, keratometry, and postoperative IOL position were used to predict IOL strength required to achieve emmetropia after lens extraction in cats. RESULTS: Mean axial length of eyes in live cats was 20.91 +/- 0.53 mm. Mean preoperative anterior chamber depth (ACD) was 5.07 +/- 0.36 mm, and mean lens thickness was 7.77 +/- 0.23 mm. Predicted postoperative ACD was calculated to be 10.84 mm. Measured postoperative ACD in the 5 cadaver eyes was 8.28 mm. Required IOL strength calculated, using the predicted postoperative ACD, was 73 to 76 diopters. The required IOL strength calculated, using the measured postoperative ACD, was 53 to 55 diopters. CONCLUSIONS AND CLINICAL RELEVANCE: An IOL of substantially higher diopter strength than that needed in dogs is required to achieve emmetropia after lens extraction in average cats; an IOL strength of approximately 53 to 55 diopters will likely be required.

Animals↗

PubMed1998

Experimental implantation of posterior chamber prototype intraocular lenses for the feline eye.

OBJECTIVE: To measure postoperative anterior chamber depth (ACD), corneal curvature, and refractive state of feline eyes after lens removal and implantation of a prosthetic intraocular lens (IOL) and determine appropriate IOL use in cats. ANIMALS: 8 clinically normal adult cats. PROCEDURE: A-scan ultrasonic biometry, keratometry, and streak retinoscopy were performed on both eyes of each cat before and after lens removal and implantation of a prosthetic IOL. Three diopter (D) IOL strengths were used: 48, 51, and 60 D. Measurements were recorded for 12 weeks after surgery. RESULTS: IOL were well tolerated by cats, with no serious complications attributable to implantation or presence of the IOL. The ACD was significantly greater after (8.30 mm) than before (4.97 mm) surgery; however, it became slightly more shallow during the 4 weeks after surgery, suggesting that the IOL shifted anteriorly in the eye. Significant difference in corneal curvature was not detected before or after surgery among eyes with various IOL. Twelve weeks after surgery, eyes with 48-, 51-, and 60-D IOL had mean +/- SD refractive state of +2.1 +/- 0.49, +0.42 +/- 0.20, and -2.6 +/- 0.78 D, respectively. Linear regression analysis of refractive state on IOL power for all eyes at 12 weeks after surgery predicted that +52.8-D IOL was necessary to best approximate emmetropia in these cats. CONCLUSION AND CLINICAL RELEVANCE: IOL of substantially higher diopter strength than that needed in dogs was required to achieve emmetropia after lens extraction in cats. A 52- to 53-D IOL is required to correct feline eyes to near emmetropia after lens removal.

Animals↗

PubMed1997

Neodymium:yttrium-aluminum-garnet laser treatment of cystic granula iridica in horses: eight cases (1988-1996).

OBJECTIVE: To determine clinical features of cystic granula iridica in horses and outcome of horses treated with an ophthalmic neodymium:yttrium-aluminum-garnet (Nd:YAG) laser. DESIGN: Retrospective study. ANIMALS: 8 horses. PROCEDURE: An ophthalmic Nd:YAG laser was used to deflate cysts in all horses. RESULTS: Horses were examined because of visual impairment (n = 5), decreased jumping performance (2), or head shaking (1). Clinical signs associated with cysts resolved in all horses after treatment. Short- and long-term complications did not develop, and cysts did not recur. CLINICAL IMPLICATIONS: Cystic granula iridica may cause vision impairment in horses. Treatment with an ophthalmic Nd:YAG laser appears to be safe and effective.

Aluminum↗

PubMed1997

Cytologic identification of Toxoplasma gondii in bronchoalveolar lavage fluid of experimentally infected cats.

OBJECTIVE: To determine whether it was possible to retrieve organisms, by means of bronchoalveolar lavage (BAL), from cats inoculated with Toxoplasma gondii. DESIGN: Experimental study. ANIMALS: 27 cats. Sixteen of the 27 were experimentally infected with feline immunodeficiency virus. PROCEDURE: All cats were inoculated with T gondii tachyzoites. Cats were grouped on the basis of feline immunodeficiency virus status and route (IV or intra-arterial) and number of tachyzoites administered. Bronchoalveolar lavage was performed by means of a standard technique. Lavage fluid was evaluated cytologically for tachyzoites. RESULTS: Clinical signs of toxoplasmosis varied widely among individual cats, but were generally most pronounced in group-1 and -2 cats (n = 5 each) and less pronounced in group-3 (n = 5) cats. Group-4 and -5 cats (n = 6 each) did not have clinical signs of toxoplasmosis. In 14 of the 15 cats in groups 1, 2, and 3, tachyzoites were detected in BAL fluid collected 7 days after inoculation. Tachyzoites were detected 14 days after inoculation in the single cat without tachyzoites 7 days after inoculation. A necropsy was performed on 9 of these cats, and tachyzoites were identified histologically in 4 of the 9. Tachyzoites were not detected in BAL fluid collected 3 days (n = 6) or 7 days (n = 6) after inoculation from the 12 cats in groups 4 and 5. Tachyzoites were not identified histologically in any of these 12 cats. CLINICAL IMPLICATIONS: BAL may be useful in the diagnosis of toxoplasmosis, particularly in cats with signs of pulmonary involvement.

Animals↗

PubMed1997

Prednisolone at anti-inflammatory or immunosuppressive dosages in conjunction with doxycycline does not potentiate the severity of Rickettsia rickettsii infection in dogs.

Dogs were experimentally inoculated with Rickettsia rickettsii to determine if anti-inflammatory or immunosuppressive dosages of prednisolone, when administered in conjunction with an antirickettsial antibiotic (doxycycline), induced therapeutically relevant pathophysiological consequences that ultimately influence disease outcome. Although the duration of rickettsemia was prolonged in dogs receiving immunosuppressive, but not anti-inflammatory, corticosteroids, concurrent administration of doxycycline and corticosteroids conferred no other detected detrimental effects. Treatment with doxycycline or doxycycline in conjunction with prednisolone resulted in decreased R. rickettsii-specific antibody titers; however, examination of appropriately timed acute- and convalescent-phase serum samples would have facilitated an accurate diagnosis of Rocky Mountain spotted fever (RMSF) in all 16 dogs. We conclude that the concurrent use of anti-inflammatory or immunosuppressive doses of prednisolone in conjunction with doxycycline, early in the course of experimental RMSF, confers no clinically relevant detrimental effects and that additional studies might be indicated to detect possible beneficial effects in cases of severe or potentially fulminant RMSF. However, because the illness induced in these dogs was of mild to moderate severity, the results of this study should definitely not be construed as supporting the safety or efficacy of prednisolone for treatment of severe canine or human RMSF.

Animals↗

PubMed1996

Photocoagulation of limbal melanoma in dogs and cats: 15 cases (1989-1993).

OBJECTIVE: To evaluate immediate clinical effects and long-term results of neodymium:yttrium-aluminum-garnet laser treatment of limbal melanoma in dogs and cats. DESIGN: Retrospective case series. ANIMALS: 13 dogs and 2 cats. RESULTS: At the time of treatment, 9 tumors were progressively enlarging and 4 were static. Recent growth characteristics of 2 tumors were not reported. Total energy applied ranged from 7.5 to 572 J. In all eyes, pigmented tissue shrank after treatment; however, 3 tumors recurred, 1 at 3 months and 2 at 1 year after treatment. CLINICAL IMPLICATIONS: Photocoagulation may be an effective means of treating limbal melanoma in dogs and cats.

Animals↗

PubMed1996

Paradoxical effect of clindamycin in experimental, acute toxoplasmosis in cats.

Cats were experimentally inoculated parenterally with the ME49 strain of Toxoplasma gondii to characterize the efficacies of two different dosages of orally administered clindamycin hydrochloride in the treatment of ocular toxoplasmosis. Concentrations of clindamycin hydrochloride at levels previously suggested to be inhibitory to T. gondii replication in vitro were achieved in the serum and aqueous humor but not in the cerebrospinal fluid. Antibiotic therapy, initiated 7 days after inoculation, resulted in no significant difference in the morphometric severity of ocular posterior segment lesions compared with that in the control groups. Treatment appeared to blunt T. gondii-specific immunoglobulin M production but had no significant effect on immunoglobulin G titers. Paradoxically, clindamycin administration was associated with increased morbidity and mortality from hepatitis and interstitial pneumonia, which are characteristic of generalized toxoplasmosis. Serum tumor necrosis factor alpha activity was detected at moderate levels in all groups of cats and correlated with the severity of clinical disease. The results of the study suggest that clindamycin, when administered at this specific time interval following inoculation, does not ameliorate ocular lesions and has a detrimental effect on the clinical course of acute, experimental toxoplasmosis in cats. The factors responsible for and the relevance of this detrimental effect to naturally occurring toxoplasmosis in humans and pet cats were not clear from the study but may relate to an antibiotic-associated decrease in the antitoxoplasmic activity of phagocytic cells responsible for the control of T. gondii.

Acute Disease↗

PubMed1996

Molecularly cloned feline immunodeficiency virus NCSU1 JSY3 induces immunodeficiency in specific-pathogen-free cats.

A full-length feline immunodeficiency virus NCSU1 (FIV-NCSU1) genome (JSY3) was cloned directly from FIV-NCSU1-infected feline CD4+ lymphocyte (FCD4E) genomic DNA and identified by PCR amplification with 5' long terminal repeat, gag, env, and 3' long terminal repeat primer sets. Supernatant from FCD4E cells cocultured with JSY3-transfected Crandell feline kidney (CrFK) cells was used as an inoculum. Cell-free JSY3 virus was cytopathogenic for FCD4E lymphocytes but did not infect CrFK cells in vitro. To determine in vivo infectivity and pathogenesis, six young adult specific-pathogen-free cats were inoculated with cell-free JSY3 virus. Provirus was detected at 2 weeks postinfection (p.i.) and was still detectable at 25 weeks p.i. as determined by gag region PCR-Southern blot analysis of peripheral blood mononuclear cell lysates. Infectious virus was recovered from peripheral blood mononuclear cells at 6 and 25 weeks p.i., and an antibody response to FIV was detected by 4 weeks. In the acute phase of infection, JSY3 provirus was found only in the CD4+ lymphocyte subset; however, by 14 weeks p.i., the greatest provirus burden was detected in B lymphocytes. All six cats were panlymphopenic at 2 weeks p.i., CD4+/CD8+ ratios were inverted by 6 weeks p.i., and five of the six cats developed lymphadenopathy by 10 weeks p.i. To determine if the JSY3 molecular clone caused immunodeficiency similar to that of the parental wild-type FIV-NCSU1, the cats were challenged with the low-virulence ME49 strain of Toxoplasma gondii at 29 weeks p.i. Five of six cats developed clinical signs consistent with generalized toxoplasmosis, and three of six cats developed acute respiratory distress and required euthanasia. Histopathologic examination of the severely affected cats revealed generalized inflammatory reactions and the presence of T. gondii tachyzoites in multiple tissues. None of the six age- and sex-matched specific-pathogen-free cats inoculated with only T. gondii developed clinical disease. Our results suggest that the pathogenesis of the molecularly cloned NCSU1 JSY3 is similar to that of wild-type FIV-NCSU1.

Animals↗

PubMed1995

Evaluation of the pathogenic potential of Rickettsia canada and Rickettsia prowazekii organisms in dogs.

An unusual pattern of seroreactivity to antigens of rickettsial organisms (Rickettsia rickettsii, R rhipicephali, R montana, and R bellii), particularly to R bellii antigen, was detected in 3 dogs during a 2-month period. Thus, studies were initiated to clarify the pathogenic potential of the more distantly related rickettsial organisms (R canada and R prowazekii) in dogs. Because R bellii are nonpathogenic rickettsiae that share numerous common properties with spotted fever-group and typhus-group rickettsiae, and because closely related pathogenic relatives of R bellii have not been identified, we examined the pathogenic potential of these typhus-group rickettsiae by testing stored serum samples, by attempting rickettsial isolation from febrile dogs, and by experimentally inoculating dogs with R canada and R prowazekii. Evaluation of results of a serosurvey of acute and convalescent serum samples from 80 dogs in which Rocky Mountain spotted fever had been considered as a differential diagnosis, but seroconversion to R rickettsii had not been documented, identified 1 dog with a fourfold increase in antibody titer to R rhipicephali and 3 dogs with fourfold increases in antibody titer to 1 or more antigens of typhus-group rickettsial organisms. A study of 15 dogs that were febrile during summer months failed to identify serologic or tissue culture evidence of typhus-group rickettsial infection or typhus-group rickettsemia, but did result in isolation of R rickettsii and Ehrlichia canis, respectively, from 1 dog each. In our final study, after experimentally inoculating 6 dogs with R canada and R prowazekii, all dogs seroconverted to the respective rickettsiae, but rickettsemia or clinical and hematologic evidence of disease was not observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

Effects of topically applied mitomycin-C on intraocular pressure, facility of outflow, and fibrosis after glaucoma filtration surgery in clinically normal dogs.

The effects of mitomycin-C on intraocular pressure (IOP), facility of outflow (C), and Tenon's capsule fibrosis were studied over 60 days in 10 clinically normal dogs. A-1-piece, silicone glaucoma implant was surgically implanted into both eyes; the filtration site of one eye was treated with a single, 5-minute intraoperative application of mitomycin (0.5 mg/ml), and the fellow eye was treated in a similar manner with balanced salt solution. There were no significant differences in preoperative IOP or C-values between treatment groups. Mean IOP in eyes of both groups initially decreased from the preoperative value, but returned to the baseline value by day 21. Mean facility of aqueous outflow (C-value) increased in all eyes during the first 14 days (mitomycin-C-value = 2.26 +/- 0.72; control C-value = 2.38 +/- 0.81), then reached a plateau that was significantly higher than the baseline value in mitomycin (P = 0.039) and control (P = 0.041) eyes. Histologic evaluation revealed all implants surrounded by a connective tissue capsule composed of regular dense collagen and fibroblasts that was significantly (P = 0.003) thinner in the mitomycin-treated (scleral side = 167 +/- 62 microns; conjunctival side = 122 +/- 41 microns) than the control (scleral side = 261 +/- 92 microns; conjunctival side = 180 +/- 48 microns) group. There were, however, no significant differences in IOP or C-values between groups at any postoperative time interval. Results of this study indicate that intraoperative treatment with mitomycin suppresses, but does not prevent fibrosis around silicone filtering implants.

Animals↗

PubMed1993

Clinical and laboratory findings in chronic conjunctivitis in cats: 91 cases (1983-1991).

Clinical findings and laboratory test results from 91 cats with chronic conjunctivitis were studied to determine the causes of the disease and the sensitivity of diagnostic procedures used, and to identify correlations between results of various diagnostic procedures and clinical or signalment variations. Mean age of affected cats was 2.9 +/- 2.7 years (+/- SD), with a range from 1 month to 11 years. Conjunctivitis was more likely to be bilateral (56 cats) than unilateral (35 cats). In cats tested for FeLV or feline immunodeficiency virus infection, 15 and 8.5%, respectively, of the results were positive, compared with 4 and 2.6% for the general hospital population. Culturing or immunofluorescent assay (IFA) for feline herpesvirus 1 (FHV-1) and Chlamydia psittaci IFA resulted in identification of pathogens (positive test results) in 19% (FHV-1) and 18% (C psittaci) of tested cats. For FHV-1, culturing was more sensitive than was IFA, yielding positive results in 19 vs 8.8% of cases. In only 1 cat were FHV-1 and chlamydiae recovered. The probability of positive test results for FHV-1 or chlamydiae was unrelated to concurrent corneal disease, unilateral vs bilateral involvement, or age. Cause of conjunctivitis could not be definitively determined in the remaining 35 cases tested for both agents. Bacterial species considered to be potentially pathogenic were isolated from conjunctival sac specimens in only 1 of 38 attempts. Cytologic changes considered compatible with chlamydial or FHV-1 infection (intracytoplasmic inclusions or multinucleated epithelial cells, respectively) were found in 8 and 5 cases, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Hyphema associated with retinal disease in dogs: 17 cases (1986-1991).

We evaluated the medical records of 17 dogs with hyphema of presumed retinal origin to evaluate the clinical, laboratory, ultrasonographic, and histologic features as well as known complications. The mean age of the dogs was 11.5 years. Routine hematologic and biochemical evaluation failed to identify an underlying cause in any dog. Retinal detachments, however, were identified in 10 of 13 dogs evaluated by ultrasonography and 5 of 6 globes evaluated histologically. In 1 dog, hyphema was associated with retinal vascular disease, presumed to be caused by hypertension. The prognosis for vision in geriatric dogs with hyphema, secondary to retinal disease, was found to be grave, as 10 dogs developed secondary glaucoma. The outcome for all dogs was loss of vision.

Animals↗

PubMed1993

Feline immunodeficiency virus predisposes cats to acute generalized toxoplasmosis.

This study was designed to examine the effects of a pre-existing, clinically asymptomatic feline immunodeficiency virus (FIV) infection on a primary challenge with Toxoplasma gondii. Parenteral challenge of FIV-infected cats with tachyzoites of the ME49 strain of T. gondii caused a precipitous drop in all lymphocytes (CD4+, CD8+, and B cells) and generalized severe toxoplasmosis. The predominant postmortem lesions included acute and often fatal interstitial pneumonia, dominated histologically by macrophages, and multifocal to coalescing hepatic necrosis. Immunohistochemistry revealed numerous T. gondii antigen and tachyzoites in macrophages and other cell types in the lung lesions. The proliferative response of peripheral blood mononuclear cells to specific (T. gondii antigen) and nonspecific (Concanavalin A) mitogens was defective in the dually infected cats, suggesting marked immunosuppression. In contrast to the dually infected cats, cats infected only with T. gondii developed a transient, mild clinical disease characterized by anorexia, lethargy, and multifocal chorioretinitis. Lymphocyte changes in T. gondii-infected cats included an early pan-lymphopenia followed by reestablishment of all lymphocyte subset profiles. These cats also showed a reduced proliferative response to Concanavalin A at 1 week after challenge, but a measurable in vivo response to T. gondii antigens, as evidenced by in vitro lymphocyte proliferation in the absence of a mitogenic stimulus. These results show that infection of cats with FIV-NCSU, markedly enhances their susceptibility to a primary T. gondii infection and provides a model to study the mechanisms of the underlying immunological defect(s) occurring early after HIV infection that may predispose individuals to development of acquired immunodeficiency syndrome and associated diseases.

Animals↗

PubMed1993

A feline model of ocular toxoplasmosis.

UNLABELLED: PURPOSE. This study was performed to characterize the clinical, serologic, histopathologic, and immunohistochemical features of an experimental model of ocular toxoplasmosis in cats. METHODS: Seven specific pathogen-free cats were inoculated in the right carotid artery with 5 x 10(3) tachyzoites of the ME49 strain of Toxoplasma gondii. Control cats received heat-killed tachyzoites. RESULTS: Progressive, bilateral, multifocal retinal, and choroidal inflammatory foci developed in the principal cats, beginning 5 to 8 days postinoculation (PI). Lesion development peaked 3 weeks PI, and the lesions varied in size from pinpoint to 5 mm, had a predilection for the central tapetal fundus, and were more numerous ipsilateral to the side of inoculation. Resolution of the lesions 21 to 70 days PI was characterized by foci of tapetal destruction and retinal degeneration. Fluorescein angiography showed disruption of the blood-retinal barrier at the level of the retinal pigmented epithelium, and occasional retinal vasculitis and perivasculitis. Mild anterior uveitis developed in four cats 10 to 13 days PI. Aside from a slight febrile response 2 to 3 days PI, no physical abnormalities were observed. T. gondii antigens were detected intermittently in the serum of four of seven cats as early as 8 days PI. T. gondii-specific immunoglobulin M titers were present on day 7 PI and continued to increase until 28 days PI. Immunoglobulin G production was documented on day 13 PI, and titers continued to increase throughout the study. Evidence of anterior uveal antibody production (mean Goldmann-Witmer coefficient [C value], 80.7; range, 13.4 to 236.6) was present in 11 of 14 eyes on day 70 PI. On histopathologic evaluation 70 days PI, multifocal granulomatous chorioretinitis, with retinal degeneration, retinal vasculitis, and lymphocytic-plasmacytic anterior uveitis, was documented. Tissue cysts in the retina and choroid were found with mouse inoculation of tissue suspensions, immunohistochemical studies, and histopathologic examination. CONCLUSIONS: This nonfatal, noninvasive method of inducing ocular toxoplasmosis may prove to be a useful model for investigation of toxoplasmi retinochoroiditis, particularly with the recent characterization of a naturally occurring, immunosuppressive feline lentivirus with properties similar to human immunodeficiency virus.

Animals↗

PubMed1993

Refractive state of aphakic and pseudophakic eyes of dogs.

Streak retinoscopy was performed by 5 ophthalmologists on 256 eyes (191 dogs) to determine their postoperative refractive state after cataract extraction. Aphakic and pseudophakic eyes that had been implanted with 1 of 5 intraocular lenses (IOL) with dioptric powers ranging from +14.5 to +38 diopters (D) were studied. By use of ANOVA, breed and body type of dog and individual performing refraction were found to have no detectable effect on final refractive state. Mean refractive state of aphakic eyes was +14.4 +/- 2.10 D. Mean refractive state for different IOL powers was as follows: +14.5 D IOL = +11.54 +/- 1.18 D (n = 13); +30 D IOL = +5.15 +/- 1.18 D (n = 105); +34.0 D IOL = +3.5 D (n = 1); +36 D IOL = +2.34 +/- 0.73 D 9 (n = 61); and +38 D IOL = +1.41 +/- 0.56 D (n = 28). Residual hyperopia ranged from +0.5 D to +2.5 D with +38 D IOL, and no eyes were myopic (overcorrected) by use of any of the IOL studied. Linear regression analysis of refractive state on IOL power for all dogs predicted that dioptric strength of +41.53 D was necessary to best approximate emmetropia for the population as a whole. Body type of the dog had only slight effect (< 1.0 D) on predicted optimal IOL power. Further linear regression analysis of the 7 breeds studied predicted variations from +39.62 to +43.14 D in IOL powers necessary to approximate emmetropia.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗