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Biomedical subjects

R L Peiffer

Publications and source records attributed to R L Peiffer.

At least 19 recordsLinked to original sources
PubMed2002

Diabetes mellitus and bilateral cataracts in a kitten.

An 18-week-old male domestic long-hair kitten was presented with a history of polyuria and polydipsia for several weeks. The general condition was unremarkable, but the kitten was considerably smaller than expected for the age and showed cataracts in both eyes. Serum glucose concentrations were persistently elevated and based on clinical findings and an elevated serum fructosamine concentration, a diagnosis of diabetes mellitus was established. Diabetes mellitus is not commonly diagnosed in young kittens, nor are cataracts recognised as a frequent feature of this disease in cats. The cataracts progressed in spite of the insulin therapy and the kitten was euthanised 10 weeks after referral. Histopathological examination of the pancreas revealed few and small islets of Langerhans compared to the examination of pancreas from a healthy kitten of the same age. Histopathological changes in the eyes included cataracts affecting both cortex and nucleus.

Animals↗
PubMed2002

Pathology of canine cataract surgery complications.

AIM: To compare pathological complications arising from 2 methods of canine cataract surgery, manual extracapsular cataract extraction (MECCE) and the more automated phacoemulsification and aspiration (PA). METHODS: Case material presented to the Comparative Ophthalmic Pathology Laboratory, University of North Carolina over the previous 20 years (1979-1999) was searched for cases with a history of prior cataract surgery. Data were obtained from the pathology accession forms, and submitting veterinarians were contacted to verify and complete missing data where possible. The slides were re-examined, histological features of surgical complications were noted and secondary changes recorded. RESULTS: Fourteen canine post-cataract-surgery cases were reviewed, the average age of the group being 7.7 years. Of the 14 eyes, 7 had surgery performed using MECCE, and 7 using PA. Of the 7 eyes that underwent MECCE surgery, 5 were enucleated and diagnosed on both clinical and pathological grounds with glaucoma. Of the 7 eyes that underwent PA, 4 were diagnosed with infectious endophthalmitis. CONCLUSIONS: Complications observed were related to the surgical technique performed. Failures of manual extracapsular surgical procedures were more commonly associated with postoperative synechia and glaucoma, compared with failures of phacoemulsification, which were more commonly associated with infection and rhegmatogenous retinal detachments. CLINICAL RELEVANCE: To minimise post surgical complications, MECCE should be accompanied by rigorous efforts to reduce surgically induced inflammation, while PA should be performed using excellent aseptic technique. It is important with both techniques to totally remove cortical material while maintaining the integrity of the posterior capsule.

Journal Article↗
PubMed2000

Morphologic alterations in the anterior lens capsule of canine eyes with cataracts.

OBJECTIVE: To examine the morphologic changes in the anterior lens capsule and lens epithelium of canine eyes with cataracts. SAMPLE POPULATION: Anterior lens capsules from the eyes of 25 dogs with cataracts and from an additional 10 canine globes with lenses subjectively assessed to be normal. PROCEDURE: Thickness of each anterior lens capsule was measured by use of a digital microscopic camera and imaging software. All 25 capsules from eyes with cataracts were submitted for light microscopy; 4 were also submitted for electron microscopy. RESULTS: Thickness of the anterior lens capsule increased with age for the normal lenses and the lenses with cataracts; the change with age was similar for both groups. Light microscopy revealed fibrous metaplasia of lens epithelial cells in 7 of 25 anterior lens capsules with focal thickenings of the posterior aspect of the capsule. Electron microscopy revealed deposition of collagen and basement membrane-like material by fibroblast-like cells. CONCLUSIONS: Results indicate that thickness of the anterior lens capsule in dogs increases with age and that this increase in thickness is not significantly different between normal lenses and lenses with cataracts. In addition, epithelial cells from lenses with cataracts may undergo metaplasia to form plaques composed of fibrous tissue and ectopic basement membrane produced by epithelial cells.

Aging↗
PubMed2000

Assessment of ascorbate ocular disposition in the conscious rabbit: an approach using the microdialysis technique.

PURPOSE: This study was performed to evaluate the transport kinetics of ascorbate in aqueous humor of conscious rabbits. METHODS: Following the development of a spectrophotometric assay for ascorbate in serum, aqueous humor and microdialysate, and preliminary studies of ascorbate systemic disposition in the rabbit, microdialysis probes were placed into the anterior chamber of one eye, and the posterior chamber of the contralateral eye, of four New Zealand white rabbits. After a one-month recovery period, conscious rabbits were placed in restraining devices, and marginal ear veins were cannulated for repeat blood sampling and ascorbate administration. A tracer i.v. bolus of (14)C-ascorbate, followed by stepwise increasing i.v. infusions of unlabelled ascorbate, was administered. Estimates of basal ascorbate transport into aqueous were determined by analysis of tracer ( 14)C-ascorbate in microdialysis probe effluent and serum. Kinetic modeling was employed to assess ascorbate disposition during infusion. RESULTS: Systemic disposition of exogenously administered ascorbate was well characterized by a two-compartment model. Kinetic modeling returned physiologically realistic volumes for the posterior chamber, and reliable estimates governing ascorbate flux into, between, and from the posterior and anterior chambers. CONCLUSIONS: In vivo assessment of ascorbate kinetics in aqueous humor and blood of the rabbit was facilitated by the microdialysis technique. Contrary to reports in the literature, ascorbate saturable uptake from blood to aqueous was not observed at physiologic blood concentrations ( approximately 11 to 30 mg/L).

Animals↗
PubMed1999

Primary corneal papilloma and squamous cell carcinoma associated with pigmentary keratitis in four dogs.

Squamous cell carcinoma (SCC) and squamous papilloma are rarely reported as primary lesions of the cornea in dogs. One case of corneal papilloma and 3 cases of SCC, each arising as a primary central corneal neoplasm rather than spreading from adjacent limbal conjunctiva, were reviewed. The most common cause of SCC in animals is chronic exposure of lightly pigmented epithelium to UV light; however, all dogs in this study had a history of chronic pigmentary keratitis. Three of the 4 dogs were of brachycephalic breeds with naturally proptotic eyes and oversized palpebral fissures that may have exposed the cornea to greater excessive solar radiation. Alternatively, mechanical factors that caused chronic changes in the cornea may have been causative factors for induction of primary dysplastic or neoplastic changes. Primary corneal neoplasia should be considered in the differential diagnosis of corneal masses.

Animals↗
PubMed1999

Microdialysis evaluation of the ocular pharmacokinetics of propranolol in the conscious rabbit.

PURPOSE: This study was conducted to assess the effects of anesthesia and aqueous humor protein concentrations on ocular disposition of propranolol. METHODS: Rabbits were anesthetized and a microdialysis probe was inserted into the anterior chamber of one eye; the contralateral eye served as a control. At timed intervals after probe placement, a 100-microl sample of aqueous humor was aspirated from each eye to determine protein concentration. In vitro protein binding parameters were used to simulate the impact of protein concentration on propranolol disposition. To assess the influence of anesthesia, probes were implanted in the anterior chamber of each eye. After >5-day stabilization, conscious and anesthetized rabbits (n = 3/group) received a 200-microg topical dose of [3H]DL-propranolol in each eye; propranolol was assayed in probe effluent. RESULTS: Changes in aqueous humor protein concentrations were observed following probe insertion. Simulations demonstrated that the unbound propranolol AUC (approximately 2.4-fold) in aqueous humor should be reduced due to protein influx. Intraocular propranolol exposure in anesthetized rabbits was approximately 8-fold higher than in conscious rabbits, and approximately 1.9-fold higher than in rabbits without a post-surgical recovery period. CONCLUSIONS: Anesthesia and time-dependent aqueous humor protein concentrations may alter ocular pharmacokinetics, and must be taken into account in the design of microdialysis experiments.

Adrenergic beta-Agonists↗
PubMed1998

Ocular infections with dematiaceous fungi in two cats and a dog.

Pigmented fungi were identified in ocular tissues from 2 cats and 1 dog. The first cat was euthanatized because of acute anterior uveitis that was unresponsive to treatment. On histologic examination, intraocular structures had been obliterated and replaced by a gray coagulum of inflammatory infiltrates and fungal elements. The second cat was treated for unilateral glaucoma that was unresponsive to treatment. A large retrobulbar mass, discovered and removed during an enucleation procedure, contained plant-origin foreign material. Keratitis, episcleritis, and orbital cellulitis with fungal elements were found on examination of the enucleated globe. The dog, examined because of a presumed corneal scratch of 2 weeks' duration that was unresponsive to treatment, had a corneal lesion subsequently removed by lamellar keratectomy that contained fungi on histologic examination. Infections caused by dematiaceous fungi are not common in domestic animals, and, to our knowledge, such infections in the eye have not been described.

Animals↗
PubMed1998

Evaluation of microdialysis sampling of aqueous humor for in vivo models of ocular absorption and disposition.

The dynamics of beta-adrenergic-associated reductions in aqueous humor production for treatment of elevated intraocular pressure are not well understood. In particular, the relationship between ocular pharmacokinetics and pharmacodynamics has yet to be established. This study was undertaken to develop a procedure for examining the ocular absorption and disposition of topically administered ophthalmic beta-adrenergic antagonists in individual animals. Dogs were anesthetized with isoflurane and a microdialysis probe was implanted in the anterior chamber of one eye and perfused with 0.9% saline at a rate of 2 microliters min-1. 3H-propranolol was administered by intracameral injection or topically. Each dog received intracameral and topical propranolol, in alternate eyes on separate days, in a randomized cross-over fashion. Microdialysis probe effluent was collected every 5 min for > or = 2.5 h; concentrations of propranolol were determined by liquid scintillation spectroscopy and were corrected for probe recovery of the substrate as determined by in vivo retrodialysis (approximately 46%) to estimate aqueous humor concentrations. In separate experiments in rabbits, microdialysis probes were implanted in each eye. 3H-propranolol was administered topically to one eye; the contralateral eye received intracameral 3H-propranolol. Model-independent pharmacokinetic parameters for each treatment phase were calculated. The mean +/- S.D. times to peak concentration of propranolol in aqueous humor were 86.6 +/- 47.6 min in the dog and 54.1 +/- 20.4 min in the rabbit. The terminal rate constant was 0.0189 +/- 0.00429 min-1 in the dog vs. 0.00983 +/- 0.00546 min-1 in the rabbit. Intraocular tissue availability of propranolol differed markedly between the dog (n = 3) and rabbit (n = 3) (approximately 0.056 in the dog vs. approximately 0.55 in the rabbit). These results demonstrate the utility of microdialysis sampling for examination of ocular pharmacokinetics.

Absorption↗
PubMed1998

The organophosphate pesticide chlorpyrifos affects form deprivation myopia.

PURPOSE: The effects of the anti-cholinesterase organophosphate pesticide chlorpyrifos (CPF) on the refractive development of the eye were examined. Form deprivation was used to induce eye growth to address the previously reported relationship between organophosphate pesticide use and the incidence of myopia. METHODS: Chickens, a well-established animal model for experimental myopia and organophosphate neurotoxicity, were dosed with chlorpyrifos (3 mg/kg per day, orally, from day 2 to day 9 after hatching) or corn oil vehicle (VEH) with or without monocular form deprivation (MFD) over the same period. The set of dependent measures included the refractive state of each eye measured using retinoscopy, axial dimensions determined with A-scan ultrasound, and intraocular pressure. RESULTS: Dosing with CPF yielded an inhibition of 35% butyrylcholinesterase in plasma and 45% acetylcholinesterase in brain. MFD resulted in a significant degree of myopia in form-deprived eyes resulting from significant lengthening of the vitreal chamber of the eye. CPF significantly reduced the effect of MFD, resulting in less myopic eyes (mean refraction: VEH-MFD = -16.2 +/- 2.3 diopters; CPF-MFD = -11.1 +/- 1.8 diopters) with significantly shorter vitreal chambers. Nonoccluded eyes were, on average, slightly hyperopic. Treatment with CPF for 1 week in the absence of MFD led to no significant change in ocular dimensions or refraction relative to controls. CONCLUSIONS: The use of form deprivation as a challenge suggests that CPF treatment interferes with the visual regulation of eye growth.

Animals↗
PubMed1997

Internal sclerostomy with a mechanical trephine versus the neodymium:YAG laser in dogs.

BACKGROUND AND OBJECTIVES: To experimentally compare and contrast the internal sclerostomy produced using a mechanical trephine with that made by an Nd:YAG laser, and to evaluate the healing patterns, efficacy, and technical advantages of each method. MATERIALS AND METHODS: Four healthy dogs with normal eyes were used in this study. The left eye of each dog had an internal sclerostomy performed with an automated mechanical trephine. The right eye of each dog had an internal sclerostomy performed with an Nd:YAG laser. Postoperatively, the intraocular pressure of each eye was measured at regular intervals. The dogs were euthanized successively at 1, 2, 3, and 4 weeks postoperatively, and the morphology of the surgical sites was studied. RESULTS: The Nd:YAG laser was easier to manipulate and technically less demanding than the mechanical trephine. However, the Nd:YAG laser induced more prominent corneal edema and conjunctival hyperemia compared with the automated trephine. Morphology of the tissue response showed tissue necrosis and greater inflammation with the Nd:YAG laser than with the automated trephine. CONCLUSIONS: These two techniques demonstrate differences in technical demands and tissue response. Both are characterized by minimal reactive fibrosis of the episcleral and Tenon's capsule fibroblast.

Animals↗
PubMed1996

Experimental evaluation of a hydroxylapatite reservoir tube shunt in rabbits.

BACKGROUND AND OBJECTIVES: Anterior chamber tube shunts of various design are of increasing importance in the surgical management of refractory glaucoma. However, the reservoirs that are commonly used today are made of a silicone or an acrylic material that may become enveloped by a fibrous capsule, which in turn may impede aqueous resorption. In this study, the authors investigated the properties of hydroxylapatite (HA) as a reservoir in gonioimplants, using three different types of HA reservoir designs. It has been demonstrated that HA orbital implants become vascularized, and the authors hypothesized that this feature of HA might modify the development of the fibrous capsule, enhancing the efficacy and decreasing the size of the implants. MATERIALS AND METHODS: HA reservoirs with Silastic tube shunts were implanted in the right eyes of six Dutch-belted rabbits. Clinical examinations were performed and intraocular pressure was measured periodically for 16 weeks postoperatively. Prior to euthanasia, fluorescein-labeled latex microspheres were injected into the anterior chamber to demonstrate implant patency. Light microscopy was used to study the tissue response to the implants and the pathways of aqueous flow. RESULTS: In general, the authors found a granulomatous inflammatory response to the HA accompanied by neovascularization into the implant and minimal fibrous encapsulation of the reservoir. CONCLUSIONS: The use of HA as a suprascleral reservoir has several advantages, the major one being a theoretical increase in the functional lifetime of the implant.

Animals↗
PubMed1996

Feline ocular epithelial response to growth factors in vitro.

OBJECTIVE: To examine the proliferative abilities of growth factors known to participate in wound healing on feline lens, iris pigment, ciliary, and retinal pigment epithelium cultured in vitro. ANIMALS: 8 clinically normal cats. PROCEDURE: Iris pigment, lens, ciliary, and retinal pigment epithelia of normal eyes of cats were isolated and cultured. Morphologic characteristics of primary cell cultures were studied by light and electron microscopy. Subcultures of epithelial cells were exposed to media supplemented with 0.5% fetal bovine serum plus various combinations of insulin and/or growth factors, including transforming growth factor-alpha, epidermal growth factor, acidic fibroblast growth factor, and basic fibroblast growth factor. Growth promoting effects were evaluated by counting with an electronic cell counter. RESULTS: Cells retained many of the morphologic characteristics of in vivo cells. Cell proliferation assays indicated that transforming growth factor-alpha stimulated lens and ciliary epithelial cell growth, and epidermal growth factor enhanced lens and iris pigment epithelial cell growth. Acidic fibroblast growth factor had proliferative effects on lens, iris pigment, and ciliary epithelium. Basic fibroblast growth factor was the most potent stimulator of all mitogens used, and caused substantial proliferation in all cell types. Insulin alone stimulated lens and ciliary epithelial proliferation but, combined with other growth factors, had a synergistic effect with those causing cell proliferation, except acidic fibroblast growth factor with iris pigment epithelium. CONCLUSION: Morphologic studies support the argument that pigment-producing cells are involved in feline ocular sarcoma. Growth factor studies indicated that ciliary epithelium has the most profound proliferative effect of all growth factors used. These data may help guide future studies in determining the cell of origin for feline ocular sarcoma.

Analysis of Variance↗
PubMed1994

Lens expression of TGF alpha in transgenic mice produces two distinct eye pathologies in the absence of tumors.

Transgenic mice carrying the rat TGF alpha minigene linked to the alpha A crystallin promoter were generated to investigate the effects of expression of this growth factor in the lens of the eye. All transgenic mice exhibited eye abnormalities in the absence of overt tumors, and two distinct and heritable phenotypes were observed. Five lineages produced 'squinting' transgenic mice characterized by microphthalmic eyes with severe lens and retinal dysplasia, and four lineages produced 'bulged' transgenic mice with eyes that exhibited enlarged globes, lens epithelial hyperplasia, anterior segment dysgenesis, and in some cases retinal dysplasia. The eye perturbations of both phenotypes were evident histologically by 1 week of age, and the eyes of squinting mice were abnormal during embryonic development. The squinting phenotype was dominant over the bulged phenotype in intercrosses, suggesting that position effects from the transgene integration site resulted in differences in TGF alpha expression between the two phenotypes. In situ hybridization showed that TGF alpha transgene expression was confined to the lens or lens rudiment of all transgenic eyes despite the involvement of non-lenticular tissues in the pathology. These results show that inappropriate expression of TGF alpha in the eye can disrupt the communication required to coordinate normal eye development.

Animals↗
PubMed1993

TGF alpha deficiency results in hair follicle and eye abnormalities in targeted and waved-1 mice.

To explore the physiological roles of transforming growth factor alpha (TGF alpha), we disrupted the mouse gene by homologous recombination in embryonic stem cells. Homozygous mutant mice were viable and fertile, but displayed pronounced waviness of the whiskers and fur, accompanied by abnormal curvature, disorientation, and misalignment of the hair follicles. Homozygous and, to a lesser extent, heterozygous mice displayed eye abnormalities of variable incidence and severity, including open eyelids at birth, reduced eyeball size, and superficial opacity. Histological examination revealed eyelid and anterior segment dysgenesis, corneal inflammation and scarring, and lens and retinal defects. Although TGF alpha deficiency affected skin and eyes, wound healing in these tissues was not impaired. Similar hair and eye defects have been previously associated with the recessive mutation waved-1 (wa-1), and Northern analysis revealed reduced expression of TGF alpha in wa-1 mice. Crosses between wa-1 homozygotes and TGF alpha-targeted mice confirmed that wa-1 and TGF alpha are allelic.

Alleles↗
PubMed1993

Ocular and associated neuropathologic observations in suspected whiplash shaken infant syndrome. A retrospective study of 12 cases.

We examined the eyes of 12 infants who died with the clinical and pathologic diagnosis of the shaken baby syndrome. The ocular histopathologic findings and the neuropathologic findings were compared. Preretinal, intraretinal, and subretinal hemorrhages were observed; hemorrhages of the superficial retinal layers and subsensory retinal space predominated. Retinal hemorrhages were found in 12 cases, intracranial hemorrhage was found in 11 cases, and cerebral edema was found in 10 cases. The intraretinal and periretinal hemorrhages were most prevalent at the posterior pole. Five cases had retinal folds. There was a low incidence of optic disc edema and choroidal hemorrhage.

Brain Edema↗
PubMed1993

Pathology of corneal endothelium in keratoconus.

Keratoconus is characterized by stromal thinning and conical deformity of the cornea that affects a small but significant portion of the population. Although keratoconus has been well studied, endothelial changes have not been extensively investigated. We studied the endothelium of 14 keratoconus corneal buttons obtained over the past 6 years by penetrating keratoplasty using light microscopy, scanning electron microscopy and transmission electron microscopy. Observations were correlated with patient history. Corneas demonstrated: endothelial cell pleomorphism and polymegathism (6 corneas); endothelial cell degeneration (13), and evidence of anterior chamber inflammation (4). Patterns of endothelial damage were variable ranging from isolated cell membranolysis to denudement of Descemet's membrane. Less damage was present at the apex of the cones than that observed in a circumferential pattern at the bases. In general the damage observed correlated with the severity and duration of the keratoconus with 9 years being the dividing time between mild and severe endothelial cell damage. These observations support other studies that implicate contact lens wear as a cause of pleomorphism and polymegathism in these patients. Endothelial cell alterations are likely a secondary event occurring due to mechanical stresses.

Adolescent↗
PubMed1992

Fibronectin as a component of pseudophakic acellular membranes.

Avidin-biotin immunohistochemical staining for fibronectin was used to study 17 aphakic intraocular lens implanted globes and 12 explanted intraocular lenses. Fibronectin was identified as a component of acellular pseudophakic membranes and was also observed within lens epithelial cells and macrophages.

Cataract Extraction↗