The permanent cationic fluorescent probe 4-(4-dimethylaminostyryl)-N-methylpyridinium (ASP⁺) has recently been reported to be transported by the organic cation transporters in the proximal tubule of the kidney [Kidney Int 1995;47:1647-1657]. A new application for the fluorescence microscopy technique using this dye as a substrate for organic cation transport systems is described, which can be used for dynamic monitoring of organic cation transport in cultured renal cells of proximal origin (LLC-PK₁ cells). The uptake of ASP⁺ was concentration dependent and linear over the first 10 min at a concentration of 1 µmol/l. The results are compatible with a carrier-mediated transport process presenting characteristics of organic cation transport systems.

Purpose To determine herpes simplex virus (HSV) DNA prevalence and mean cycle threshold of polymerase chain reaction (PCR) in corneal tissue of patients with penetrating keratoplasty (PKP), with (HSK+) and without (HSK−) previous clinical herpetic keratitis history. Methods Retrospective review of recipient corneal buttons which were explanted through PKP between March 2010 and September 2018 at the Department of Ophthalmology, Saarland University Medical Center in Homburg/Saar, Germany. Corneal tissue samples were analysed by real‐time PCR for the presence of HSV DNA. For each subject, clinical data, including patients’ demographics and clinical diagnoses, were collected. Results In total, 2230 corneal samples (age at the time of the surgery 57.3 ± 19.2 years) of 1860 patients were analysed. HSV PCR was positive in 137 (6.1%) corneal samples, with a 30.57 ± 6.01 (range 14–39) mean cycle threshold (Ct) value. Two hundred ninety‐eight (13.4%) corneas of 266 patients were clinically HSK+, and 1932 (86.6%) corneas of 1600 patients were clinically HSK−. HSV DNA was detected significantly more frequently (p < 0.0001) in HSK+ corneal samples (108 corneal samples; 36.2%), than in HSK− corneal samples (29 corneal samples; 1.5%). Ct value was significantly lower in HSK+ than in HSK‐ corneal samples (29.8 ± 5.8 versus 32.6 ± 5.9; p = 0.008). Conclusion Our data demonstrate that a positive clinical history of HSK is related to HSV PCR positivity in about every 2.8th patient. In addition, about every 66th explanted corneal tissue is HSV PCR‐positive despite the lack of clinical suspicion. These patients may need additional local/systemic antiviral treatment to avoid newly acquired HSK following penetrating keratoplasty.

AMM containing EGF and FGFb, and IL-6 and IL-8 AMM is a potential nonsurgical treatment alternative of therapy-resistant corneal epithelial defects. However, the most effective preparation method and the optimal harvesting time point are yet to be determined.

Urea and prolactin concentrations are decreased, fT4 concentration is increased in aqueous humor of keratoconus patients, and uric acid concentration remains unchanged. Urea concentration in aqueous humor is also increased in older and male patients. Therefore, metabolic disorder and hormonal balance may both have an impact on keratoconus development. Further studies are necessary to assess the specific impact.

Recently, we introduced a new method to monitor organic cation transport using the fluorescent dye 4-(4-dimethylaminostyryl)-N-methylpyridinium (ASP⁺). We now examined properties of ASP⁺ uptake across the apical membrane of proximal tubular cells (LLC-PK₁ and IHKE1) with this new method and compared the results with characteristics of organic cation transport obtained in transport studies using radio-labeled substrates. Cimetidine and choline inhibited ASP⁺ accumulation in LLC-PK₁ cells with maximal inhibitions of 51 ± 5% (n = 6, at 1 mM) and 45 ± 14% (n = 6, at 50 mM), respectively. TMA⁺, TEA⁺ and THA⁺ showed bell-shaped concentration-response curves in LLC-PK₁ and IHKE1 cells. Maximal inhibition was achieved in LLC-PK₁ cells with 10 mMTMA⁺ (53 ± 4%, n = 6), 5 mMTEA⁺ (64 ± 4%, n = 4) and 10 µMTHA⁺ (97 ± 5%, n = 6) and in IHKE1 cells with > 50 mMTMA⁺ (51 ± 8%, n = 6), 1 mMTEA⁺ (53 ± 12%, n = 6) and 5 µMTHA⁺(100 ± 1%, n = 6). Higher concentrations of these cations led to a reduction of the inhibitory effect. ASP⁺ accumulation in LLC-PK₁ cells was reduced at pH 6.0 by 60 ± 5% (n = 7) and increased at pH 8.4 by 18 ± 6% (n = 6). Membrane depolarization induced by increases in the extracelluar K⁺ concentration to 50 or 145 mMled to a reduction of the ASP⁺ accumulation in LLC-PK₁ cells by 27 ± 7% (n = 5) or 37 ± 6% (n = 5), respectively. The data of this study demonstrate that ASP⁺ accumulation across the apical membrane of LLC-PK₁ and IHKE1 cells measured fluorimetrically has properties comparable to those reported for the H⁺/organic cation exchanger described for the luminal membrane of the proximal tubule.

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