The repolarization phase of cardiac action potential is prone to aberrant excitation that is common in cardiac patients. Here, we demonstrate that this phase is markedly sensitive to Ca 2؉ because of the surprising existence of a Ca 2؉ -activated K ؉ currents in cardiac cells. The current was revealed using recording conditions that preserved endogenous Ca 2؉ buffers. The Ca 2؉ -activated K ؉ current is expressed differentially in atria compared with ventricles. Because of the significant contribution of the current toward membrane repolarization in cardiac myocytes, alterations of the current magnitude precipitate abnormal action potential profiles. We confirmed the presence of a small conductance Ca 2؉ -activated K ؉ channel subtype (SK2) in human and mouse cardiac myocytes using Western blot analysis and reverse transcription-polymerase chain reaction and have cloned SK2 channels from human atria, mouse atria, and ventricles. Because of the marked differential expression of SK2 channels in the heart, specific ligands for Ca 2؉ -activated K ؉ currents may offer a unique therapeutic opportunity to modify atrial cells without interfering with ventricular myocytes.Cardiac action potentials (APs) 1 are shaped predominantly by the interplay between transient inward Na ϩ , Ca 2ϩ , and outward K ϩ currents (1). While the repolarization phase of the AP can be wrought by the kinetics of the principal currents, small and sustained outward currents also define this phase, rendering this region prone to irregular membrane excitation.In humans, delineation of the outward currents that confer the late repolarization phase of the cardiac AP is crucial for our understanding of the etiology of arrhythmias. We provide a novel report that demonstrates that the repolarization phase of cardiac AP shows marked sensitivity toward apamin, an exclusive ligand for a small conductance Ca 2ϩ -activated K ϩ channel (2).Ca 2ϩ -activated K ϩ channels (K Ca ) are present in most neurons and mediate the afterhyperpolarizations following AP (3, 4). However, functional significance of K Ca in the heart has not previously been documented. K Ca channels can be divided into three main subfamilies (3, 5-7). These include the large-conductance Ca 2ϩ -and voltage-activated K ϩ channels (BK), the intermediate-conductance K Ca channels (IK), and the smallconductance K Ca channels (SK), which are sensitive to apamin and scyllatoxin. Among the SK channels, they are encoded by at least three genes, SK1, SK2, SK3 (4, 6), with differential sensitivity toward apamin. SK2 is highly sensitive to apamin, with a half-blocking concentration (IC 50 ) of 60 pmol/liter, whereas SK1 channels are not affected by 100 nmol/liter apamin (2). SK3 channels are intermediate.Here, we report for the first time, the presence of I K,Ca (Ca 2ϩ -activated K ϩ current) in cardiac myocytes that plays a crucial role in cardiac AP profile. Using a combination of electrophysiological recordings and biochemical and molecular biological techniques, we have identified the presence of SK2...

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Abstract-We directly examined the role of the Ca v 1.3 (␣ 1D ) Ca 2ϩ channel in the sinoatrial (SA) node by using Ca v 1.3 Ca 2ϩ channel-deficient mice. A previous report has shown that the null mutant (Ca v 1.3 Ϫ/Ϫ ) mice have sinus bradycardia with a prolonged PR interval. In the present study, we show that spontaneous action potentials recorded from the SA nodes show a significant decrease in the beating frequency and rate of diastolic depolarization in Ca v 1.3

Chronic heart failure (HF) and erectile dysfunction (ED) are 2 highly prevalent disorders that frequently occur concomitantly. Coronary artery disease, HF, and ED share several common risk factors, including diabetes mellitus, hypertension, smoking, and dyslipidemia. Additionally, the distinct physiologic sequelae of HF create unique organic and psychologic factors contributing to ED in this patient population. Standard HF therapy with beta-receptor blockers, digoxin and thiazide diuretics may worsen sexual dysfunction owing to medication side effects. This may, in turn, lead to noncompliance in misguided efforts to retain satisfactory sexual activity, with secondary worsening of cardiac capacity. This review describes the unique aspects of ED in the HF population.

BackgroundWe have observed that dry eye redness is characterized by a prominence of fine horizontal conjunctival vessels in the exposed ocular surface of the interpalpebral fissure, and have incorporated this feature into the grading of redness in clinical studies of dry eye.AimTo develop an automated method of grading dry eye-associated ocular redness in order to expand on the clinical grading system currently used.MethodsNinety nine images from 26 dry eye subjects were evaluated by five graders using a 0–4 (in 0.5 increments) dry eye redness (Ora Calibra™ Dry Eye Redness Scale [OCDER]) scale. For the automated method, the Opencv computer vision library was used to develop software for calculating redness and horizontal conjunctival vessels (noted as “horizontality”). From original photograph, the region of interest (ROI) was selected manually using the open source ImageJ software. Total average redness intensity (Com-Red) was calculated as a single channel 8-bit image as R – 0.83G – 0.17B, where R, G and B were the respective intensities of the red, green and blue channels. The location of vessels was detected by normalizing the blue channel and selecting pixels with an intensity of less than 97% of the mean. The horizontal component (Com-Hor) was calculated by the first order Sobel derivative in the vertical direction and the score was calculated as the average blue channel image intensity of this vertical derivative. Pearson correlation coefficients, accuracy and concordance correlation coefficients (CCC) were calculated after regression and standardized regression of the dataset.ResultsThe agreement (both Pearson’s and CCC) among investigators using the OCDER scale was 0.67, while the agreement of investigator to computer was 0.76. A multiple regression using both redness and horizontality improved the agreement CCC from 0.66 and 0.69 to 0.76, demonstrating the contribution of vessel geometry to the overall grade. Computer analysis of a given image has 100% repeatability and zero variability from session to session.ConclusionThis objective means of grading ocular redness in a unified fashion has potential significance as a new clinical endpoint. In comparisons between computer and investigator, computer grading proved to be more reliable than another investigator using the OCDER scale. The best fitting model based on the present sample, and usable for future studies, was C4=−12.24+2.12C2HOR+0.88C2RED:C4 is the predicted investigator grade, and C2HOR and C2RED are logarithmic transformations of the computer calculated parameters COM-Hor and COM-Red. Considering the superior repeatability, computer automated grading might be preferable to investigator grading in multicentered dry eye studies in which the subtle differences in redness incurred by treatment have been historically difficult to define.

Chronic heart failure (HF) is an increasingly common cardiovascular disorder. The goal of healthcare providers is to optimize quality of life in this population, including sexual health. Up to 75% of patients with HF report erectile dysfunction (ED). As HF is a condition with distinct physiologic sequelae, some unique organic and psychological factors contributing to ED in this patient population have been identified, along with risk factors common to the development of coronary artery disease, HF and ED. This review describes contributing factors to ED in the setting of HF and highlights treatment considerations for this distinct patient population.

Phosphodiesterase-5 (PDE-5) inhibitors selectively inhibit PDE-5 enzymes that are present in various tissues like penile tissue, platelets, vascular, and smooth muscle tissue. The drug's actions on these tissues have lead to the successful therapeutic use in patients suffering from conditions such as erectile dysfunction (ED) and pulmonary hypertension. PDE-5 inhibitors (PDE-5i) act on the erectile tissue causing penile smooth muscle relaxation and vasodilatation leading to penile erection. In addition, in particular when used in conjunction with prostaglandin inhibitors, PDE-5i cause vasodilatation in pulmonary vasculature hence decreasing both the pulmonary arterial pressure and resistance. PDE-5i have also shown to mildly decrease blood pressure, increase cardiac index, and increase coronary blood flow in experimental animals as well as in human studies. The Food and Drug Administration (FDA) has approved three PDE-5i for the treatment of ED: sildenafil (Viagra), vardenafil (Levitra), and tadalafil (Cialis) and one for pulmonary hypertension: sildenafil (Revatio). These agents are highly selective for PDE-5 enzymes as compared to other subclasses of PDE enzymes and have the almost identical pharmacological action but slightly different pharmacokinetics. Only little data exist about long-term use of PDE-5i and their effects on different organ system. This paper reviews the current information available on chronic PDE-5 inhibitor use.

A greater understanding of the hypersensitivity and curability of testicular germ cell tumors (TGCTs) has the potential to inform strategies to sensitize other solid tumors to conventional chemotherapies. The mechanisms of cisplatin hypersensitivity and resistance in embryonal carcinoma (EC), the stem cells of TGCTs, remain largely undefined. To study the mechanisms of cisplatin resistance we generated a large panel of independently derived, acquired resistant clones from three distinct parental EC models employing a protocol designed to match standard of care regimens of TGCT patients. Transcriptomics revealed highly significant expression changes shared between resistant cells regardless of their parental origin. This was dominated by a highly significant enrichment of genes normally repressed by H3K27 methylation and the polycomb repressive complex 2 (PRC2) which correlated with a substantial decrease in global H3K27me3, H2AK119 ubiquitination, and expression of BMI1. Importantly, repression of H3K27 methylation with the EZH2 inhibitor GSK-126 conferred cisplatin resistance to parental cells while induction of H3K27 methylation with the histone lysine demethylase inhibitor GSK-J4 resulted in increased cisplatin sensitivity to resistant cells. A gene signature based on H3K27me gene enrichment was associated with an increased rate of recurrent/progressive disease in testicular cancer patients. Our data indicates that repression of H3K27 methylation is a mechanism of cisplatin acquired resistance in TGCTs and that restoration of PRC2 complex function is a viable approach to overcome treatment failure.