56 research outputs found

    Active transport of ascorbate across the isolated rabbit ciliary epithelium

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    The transepithelial transport of ascorbate across the isolated rabbit ciliary epithelium (CE) was investigated. Unidirectional Previous studies have shown the existence of a mechanism for active ascorbate transport across the blood-aqueous barrier. " 4 In addition, Becker 3 has shown that the in vitro accumulation of ascorbate by the isolated ciliary epithelium (CE) occurs against a concentration gradient, with the tissue-to-medium ratio reaching a value as high as 20 within 1 hr. This process, which required glucose, as well as Na + , K + and Ca 2+ in the medium, exhibited typical saturation kinetics, temperature-dependence and inhibition by ouabain and various metabolic poisons. 3 These findings suggest that the ascorbate accumulation by the CE is a carrier-mediated active transport mechanism. Two studies have also shown that the efflux of ascorbate by the CE is by a process of passive diffusion. steps by which ascorbate moves across the tissue have not been identified. Furthermore, unidirectional and net fluxes have not been measured across the isolated CE in the absence of external driving forces. Since our laboratory can routinely isolate the rabbit CE in an Ussing-type chamber, 1617 the objective of this study was to further characterize the movement of ascorbate across the isolated preparation. Materials and Methods Adult female albino rabbits weighing about 3 kg were anesthetized with ketamine (Ketalar, ParkeDavis Co., Detroit, MI) and then sacrificed using air injection into a marginal ear vein. The eyes were promptly enucleated, and the CEs were dissected out and mounted between two Ussing-Zerahn-type chambers with the solution temperature kept at 37°C as previously described. 1617 Animals in this study were treated in accordance with the ARVO Resolution on the Use of Animals in Research. The basic bathing solution used during the dissection and experiments was as follows (in mM): NaCl, 118; KC1, 4.7; NaH 2 PO 4 , 0.8; glucose, 5.5; NaHCO 3 , 15; CaCl 2 , 1.8; MgCl 2 , 1.2; Hepes, 8; Hepes-Na, 8. For experiments requiring a low extracellular Na + concentration (8.8 mM), an additional solution in which NaCl and NaHCO 3 were replaced with choline Cl and choline HCO 3 , was prepared. The solutions were bubbled with either a 1% CO 2 -99% air mixture, or a 1% CO 2 -99% N 2 mixture when anoxia was required. The pH of the solutions was 7.5

    Chloride channel gene expression in the rabbit cornea

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    Purpose: The maintenance of stromal hydration by the corneal endothelium relies on active transendothelial anion transport, with bicarbonate and chloride the major anions carrying the current. However, the ion transport pathways that operate to maintain stromal hydration have yet to be fully elucidated. Methods: We used RT-PCR to identify the gene expression profile of members of the ClC family of chloride channels in freshly isolated samples of rabbit corneal endothelium, stroma, and epithelium. The expression of a separate group of genes was also examined to confirm the purity of the sample collection protocol. The expression of the ClC-2 and ClC-3 channel protein in the cornea was also evaluated by light and electron microscopic immunolabelling. Results: The mRNA for ClC-2, ClC-3, ClC-5, ClC-6, and ClC-7 were expressed in both the corneal epithelium and endothelium, and in the stroma. The mRNA for the skeletal muscle specific channel ClC-1 and the kidney specific chloride channel ClC-Ka were not detectable. ClC-4 mRNA was not detected in any rabbit tissue examined. The expression pattern of the mRNAs for collagens V, VI, VII, and VIII demonstrated the absence of contamination in epithelial and endothelial samples. ClC-2 and ClC-3 immunolabelling confirmed the presence of these proteins in corneal endothelium, stroma, and epithelium. Conclusions: Together with cystic fibrosis transmembrane conductance regulator (CFTR) and calcium activated chloride channel-1 (CLCA1), these results bring the number of chloride channel genes known to be expressed in the corneal endothelium and epithelium to seven. These channels are likely to be important for the maintenance of corneal transparency

    Manejo terapéutico y diagnóstico en equipo multidisciplinario y resultados obtenidos en gestantes con cardiopatía orgánica

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    Las enfermedades cardiovasculares afectan aproximadamente al 2% de las mujeres embarazadas, por lo que suponen un aumento del riesgo tanto para la madre como para el feto. El embarazo y el parto producen cambios fisiológicos sustanciales que requieren de una adecuada adaptación del sistema cardiovascular. Estos cambios fisiológicos que son muy bien tolerados en las gestantes sin cardiopatía, exponen a la mujer con enfermedad cardiovascular a eventos clínicos significativos. Este es un trabajo descriptivo, retrospectivo, de casos consecutivos de pacientes que acudieron a la División de Medicina Cardiovascular, del Hospital de Clínicas en un período comprendido entre Agosto de 2013 a Junio de 2014. Incluye a 5 pacientes embarazas y portadoras de cardiopatías conocidas o desconocidas. La edad promedio fue de 27 años, rango etario de 17 a 36 años. La edad gestacional al momento de la consulta fue de 34 semanas por fecha de última menstruación, menor edad gestacional 30 semanas y mayor edad gestacional 38 semanas. El síntoma principal de consulta fue la disnea (100%), edema de miembros inferiores en 3 pacientes (60%), y palpitaciones en 2 pacientes (40%). El manejo diagnóstico y terapéutico conjunto con un seguimiento detallado y adecuado por un equipo multidisciplinario de cardiólogos, clínicos, ginecólogos, anestesiólogos y cirujanos cardiovasculares facilitan una buena evolución clínica y un desenlace exitoso del embarazo y parto de la gestante con la cardiopatía orgánica. Como resultado de este manejo multidisciplinario todos los recién nacidos tuvieron buena evolución durante su permanencia en la unidad de cuidados intensivos sin inconvenientes

    Identification of Circulating Proteins associated With General Cognitive Function among Middle-Aged and Older adults

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    Identifying circulating proteins associated with cognitive function may point to biomarkers and molecular process of cognitive impairment. Few studies have investigated the association between circulating proteins and cognitive function. We identify 246 protein measures quantified by the SomaScan assay as associated with cognitive function (p \u3c 4.9E-5, n up to 7289). Of these, 45 were replicated using SomaScan data, and three were replicated using Olink data at Bonferroni-corrected significance. Enrichment analysis linked the proteins associated with general cognitive function to cell signaling pathways and synapse architecture. Mendelian randomization analysis implicated higher levels of NECTIN2, a protein mediating viral entry into neuronal cells, with higher Alzheimer\u27s disease (AD) risk (p = 2.5E-26). Levels of 14 other protein measures were implicated as consequences of AD susceptibility (p \u3c 2.0E-4). Proteins implicated as causes or consequences of AD susceptibility may provide new insight into the potential relationship between immunity and AD susceptibility as well as potential therapeutic targets

    Minimal information for studies of extracellular vesicles (MISEV2023): From basic to advanced approaches

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    Extracellular vesicles (EVs), through their complex cargo, can reflect the state of their cell of origin and change the functions and phenotypes of other cells. These features indicate strong biomarker and therapeutic potential and have generated broad interest, as evidenced by the steady year-on-year increase in the numbers of scientific publications about EVs. Important advances have been made in EV metrology and in understanding and applying EV biology. However, hurdles remain to realising the potential of EVs in domains ranging from basic biology to clinical applications due to challenges in EV nomenclature, separation from non-vesicular extracellular particles, characterisation and functional studies. To address the challenges and opportunities in this rapidly evolving field, the International Society for Extracellular Vesicles (ISEV) updates its 'Minimal Information for Studies of Extracellular Vesicles', which was first published in 2014 and then in 2018 as MISEV2014 and MISEV2018, respectively. The goal of the current document, MISEV2023, is to provide researchers with an updated snapshot of available approaches and their advantages and limitations for production, separation and characterisation of EVs from multiple sources, including cell culture, body fluids and solid tissues. In addition to presenting the latest state of the art in basic principles of EV research, this document also covers advanced techniques and approaches that are currently expanding the boundaries of the field. MISEV2023 also includes new sections on EV release and uptake and a brief discussion of in vivo approaches to study EVs. Compiling feedback from ISEV expert task forces and more than 1000 researchers, this document conveys the current state of EV research to facilitate robust scientific discoveries and move the field forward even more rapidly

    The Hyperpolarizing Region of the Current-Voltage Curve in Frog Skin

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    Excitability (action potential and refractory period) has been described by A. Finkelstein in the depolarizing region of the current-voltage (I-V) curve of the isolated frog skin. Recently Fishman and Macey interpreted this phenomenon as a consequence of a region with negative resistance that confers to the I-V curve an N shape. We have studied the I-V relation of the isolated frog skin in the hyperpolarizing region with a current-ramp system. It was found that in Na(2)SO(4) Ringer's, the resistance continuously increases in the hyperpolarizing direction. When hyperpolarization reaches 300 mv an electrical breakdown occurs, occasionally followed by a region of negative resistance. In NaCl Ringer's the breakdown was also found although the I-V relation was reasonably linear. Unidirectional Na(+) outflux was measured at different levels of voltage clamping across the skin and with different Na(+) concentrations in the solutions. The Na(+) outflux was found to be relatively independent of these parameters. Based on these results a Na(+) rectifying structure is postulated. An electrical model for active Na(+) transport including a diode and an oscillator is proposed. The effects of CO(2), nitrogen, amiloride, and ouabain on the I-V relation are described

    Surface and Volume Changes in the Lens during Accommodation

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    An Automatic Voltage Clamp Recorder for Inexcitable Membranes

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