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Aqueous Humor Dynamics of the Brown-Norway Rat.

ABSTRACT: Purpose:The study aimed to provide a quantitative description of aqueous humor dynamics in healthy rat eyes. Methods:One eye of 26 anesthetized adult Brown-Norway rats was cannulated with a needle connected to a perfusion pump and pressure transducer. Pressure-flow data were measured in live and dead eyes by varying pump rate (constant-flow technique) or by modulating pump duty cycle to hold intraocular pressure (IOP) at set levels (modified constant-pressure technique). Data were fit by the Goldmann equation to estimate conventional outflow facility (C) and unconventional outflow rate (Fun). Parameter estimates were respectively checked by inserting a shunt of similar conductance into the eye and by varying eye hydration methodology. Results:Rat IOP averaged 14.6 ± 1.9 mm Hg at rest. Pressure-flow data were repeatable and indistinguishable for the two perfusion techniques, yielding C = 0.023 ± 0.002 ?L/min/mm Hg and Fun = 0.096 ± 0.024 ?L/min. C was similar for live and dead eyes and increased upon shunt insertion by an amount equal to shunt conductance, validating measurement accuracy. At 100% humidity Fun dropped to 0.003 ± 0.030 ?L/min. Physiological washout was not observed (-0.35 ± 0.65%/h), and trabecular anatomy looked normal. Conclusions:Rat aqueous humor dynamics are intermediate in magnitude compared to those in mice and humans, consistent with species differences in eye size. C does not change with time or death. Evaporation complicates measurement of Fun even when eyes are not enucleated. Absence of washout is a notable finding seen only in mouse and human eyes to date.

SUBMITTER: Ficarrotta KR

PROVIDER: S-EPMC5967599 | biostudies-literature | 2018 May

REPOSITORIES: biostudies-literature

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Aqueous Humor Dynamics of the Brown-Norway Rat.

Ficarrotta Kayla R KR Bello Simon A SA Mohamed Youssef H YH Passaglia Christopher L CL

Investigative ophthalmology & visual science 20180501 6

<h4>Purpose</h4>The study aimed to provide a quantitative description of aqueous humor dynamics in healthy rat eyes.<h4>Methods</h4>One eye of 26 anesthetized adult Brown-Norway rats was cannulated with a needle connected to a perfusion pump and pressure transducer. Pressure-flow data were measured in live and dead eyes by varying pump rate (constant-flow technique) or by modulating pump duty cycle to hold intraocular pressure (IOP) at set levels (modified constant-pressure technique). Data were ...[more]

PMID: 29847660

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Project description:PurposeRetinoblastoma (Rb) is the most common primary intraocular cancer in children. Unlike with most solid tumors, direct biopsy is contraindicated due to risk of tumor dissemination. However, recent therapeutic techniques have allowed for the safe extraction of aqueous humor (AH) from eyes undergoing therapy, providing the unique opportunity to use AH as a liquid biopsy for Rb. Although the extraction of AH in Rb eyes undergoing therapy is new, the consideration of whether there are tumor biomarkers in the AH is not. The current manuscript is a systematic review of all studies that have examined biomarkers in the AH of Rb eyes. The authors hypothesized that AH sampling and analysis of tumor biomarkers may have new clinical relevance for the diagnosis, prognosis, and/or management of Rb.MethodsA comprehensive database search (PubMed, Web of Science, Embase, and Cochrane Databases) was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement to identify articles on AH markers in Rb eyes. Inclusion criteria included English language articles with original reports on AH markers in the eyes of patients with confirmed Rb. Data on marker type, number of eyes, marker means and ranges, and when available, control values and clinicopathological correlations were collected. Articles were stratified based on marker type, and assessed quantitatively and qualitatively.ResultsAn initial database search produced 325 articles, and an additional 11 articles were identified through searching citations. After removing duplicates and applying the eligibility criteria, we selected 27 articles to be included in the current review. A total of 463 eyes with histologically confirmed Rb were included in this review. The various markers and their values, with comparison to controls and clinicopathological correlations, are discussed.ConclusionsAH sampling and tumor biomarker analysis in eyes without undergoing enucleation have the potential to revolutionize the management of Rb.Translational relevanceAlthough previous studies evaluated markers in the AH only after enucleation and not at diagnosis or during therapy, the clinical relevance of these markers was limited. However, recent changes in the management of Rb have allowed for safe sampling of the aqueous during therapy and, thus, correlation of tumor biomarkers with disease course. Thus, the authors felt it important to revisit previous research to evaluate whether these markers may now be applicable for the diagnosis, prognosis, or management of Rb.

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Aqueous Humor Dynamics of the Brown-Norway Rat.

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Aqueous Humor Dynamics of the Brown-Norway Rat.

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