Ubels, J. L. | bioRxiv Science

bioRxiv2019

Patch-Clamp Recording of K+ Current from Lacrimal Gland Duct Cells

Electrophysiologic studies have characterized ion channels in lacrimal gland acinar cells, but due to relative paucity and inaccessibility, such studies on lacrimal gland duct cells are challenging. The duct cells are believed to secrete the high level of K+ that is present in tears. The goal of this project was to develop a method for isolation of viable, single duct cells, demonstrate their utility for patch-clamp recording and characterize the K+ channels expressed by duct cells. Exorbital lacrimal gland slices from Sprague-Dawley rats were incubated with collagenase. Under a microscope, the ducts were microdissected from the glands and then incubated with elastase and collagenase. Dispersed duct cells were plated on a cover slip coated with BD Cell-Tak. Duct cells were distinguished from acinar cells by their smaller size and lack of granularity. Whole-cell K+ currents were recorded from duct cells using the perforated-patch technique and pipettes with resistances of less than 10 M{Omega}. EGTA and CaCl2 in the pipette solution were adjusted to give 1 uM free Ca++. When held at -80 mV, duct cells showed K+ currents that activated at command voltages near 0 mV and reached amplitudes near 1 nA at +100 mV. Currents reached peak amplitude less than 20 ms after depolarization and did not inactivate. These currents were inactivated by holding the cells at 0 mV. Currents were blocked reversibly by TEA in the presence of Ca2+, but were not blocked by TEA in the absence of Ca2+. Currents were not affected by clotrimazole (10 uM) or Ba2+ (5 mM). A method has been established for isolation and dissociation lacrimal gland duct cells for electrophysiologic studies. These cells express a voltage-activated K+ channel that is dependent on the presence of intracellular Ca2+ and may correspond to the IKCa1 channel expressed on the apical membranes of lacrimal gland ducts.

physiology↗

bioRxiv2019

Prevalence of Refractive Error and Need for Corrective Lenses in Medically Underserved Residents of Tijuana, Mexico

PurposeThe population of Tijuana, Mexico is growing rapidly, with a current official population estimate of 1.7 million. Nearly 80,000 people migrate to Tijuana each year, resulting in the rise of neighborhoods with substandard housing, lack of services and inadequate access to health care, including eye care. This study describes refractive errors and the need for corrective lenses among participants attending free clinics in these neighborhoods where they received free eye exams and glasses during January 2016. Methods: This is a retrospective observational chart review of de-identified data collected from intake forms that were filled out for each participant at the clinics. Subjects were self-selected in response to announcements in the neighborhoods where clinics were conducted. Subjects with presenting uncorrected visual acuity 20/30 OU or worse were examined with an autorefractor to measure spherical refractive error. Either prescription or reading glasses were then distributed to participants who had refractive errors. Epi Info, an open source program provided by the CDC, was used to analyze demographic, visual acuity and refractive error data. Results: Presenting visual acuity was evaluated in 1209 people. Of these patients, 70% had a visual acuity of 20/30 or worse. Only 23% of these patients had glasses. Among the patients who were given refractions, 13% had clinically significant myopia (-0.75 D or worse in at least one eye). In participants 20 years old and younger, only 8% had clinically significant myopia. Clinically significant hyperopia (+0.75 D or worse in at least one eye) was detected in 25% of participants. Astigmatism (-1.5 D or worse in at least one eye) was present in 18% of participants. Prescription glasses were given to 542 participants and 396 of these people received their first glasses. Reading glasses were given to 386 people. Among students only 15% presented at the clinics with glasses, while it was determined that 56% of student participants needed glasses. Conclusion: The high levels of uncorrected refractive error in this study suggest limited access to affordable eye care in neighborhoods where clinics were conducted. Prevalence of myopia among adolescents and young adults is increasing in many parts of the world. In contrast, a relatively high prevalence of hyperopia was observed in this age group in Tijuana. The data demonstrate an urgent need for eye care and correction of refractive error in the study group.

epidemiology↗