instruction:
Given a passage, construct a question on the basis of the information present in the passage. Construct the question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) it answer uses text phrases from the passage. Avoid creating questions that (i) can't be answered correctly without actually understanding the passage and (ii) uses the same words or phrases given in the passage.
question:
Class III antiarrhythmic agents exhibit reverse rate-dependent lengthening of the action potential duration (APD). In spite of the several theories developed so far to explain this reverse rate dependency (RRD), its mechanism has not yet been clarified. The aim of the present work was to further elucidate the mechanisms responsible for reverse rate-dependent drug effects.', 'Action potentials were recorded from multicellular canine ventricular preparations and isolated cardiomyocytes, at cycle lengths (CLs) varying from 0.3 to 5 s, using conventional sharp microelectrodes. APD was either modified by applying inward and outward current pulses, or by superfusion of agents known to lengthen and shorten APD. Net membrane current (I(m)) was calculated from action potential waveforms. The hypothesis that RRD may be implicit in the relationship between I(m) and APD was tested by numerical modelling. Both drug-induced lengthening (by veratrine, BAY-K 8644, dofetilide, and BaCl(2)) and shortening (by lidocaine and nicorandil) of action potentials displayed RRD, i.e. changes in APD were greater at longer than at shorter CL. A similar dependency of effect on CL was found when repolarization was modified by injection of inward or outward current pulses. I(m) measured at various points during repolarization was inversely proportional to APD and to CL. Model simulations showed that RRD is expected as a consequence of the non-linearity of the relationship between I(m) and APD.
answer:
Is reverse rate dependency an intrinsic property of canine cardiac preparations?


question:
Environmental conditions (eg, latitude) play a critical role in the susceptibility and severity of many autoimmune disorders, including multiple sclerosis (MS). Here, we investigated the mechanisms underlying the beneficial effects of immune regulatory processes induced in the skin by moderate ultraviolet B (UVB) radiation on central nervous system (CNS) autoimmunity.', 'Effects of UVB light were analyzed in a murine model of CNS autoimmunity (experimental autoimmune encephalomyelitis). Additionally, patients with relapsing-remitting MS were treated with narrowband UVB phototherapy. Immunomodulatory effects were examined in skin biopsies, serum samples, and immune cells of the peripheral blood.', 'Regulatory T cells (Tregs), which are induced locally in the skin-draining lymph nodes in response to UVB exposure, connect the cutaneous immune response to CNS immunity by migration to the sites of inflammation (blood, spleen, CNS). Here, they attenuate the inflammatory response and ameliorate disease symptoms. Treg-inducing tolerogenic dendritic cells (DCs) were further necessary for induction of this systemic immune regulation by UVB radiation, because ablation of Langerhans cells abolished the UVB-induced phenotype. MS patients treated with UVB phototherapy showed an increase in induced Tregs and tolerogenic DCs accompanied by the downregulation of the T-cell effector cytokine interleukin 21. The treatment further induced elevated serum levels of vitamin D.
answer:
Does ultraviolet B light attenuate the systemic immune response in central nervous system autoimmunity?


question:
In dialysis patients, volume overhydration is common and is related to increased risk of cardiovascular morbidity and mortality. However, it remains unclear whether volume overload imposes those detrimental effects through endothelial dysfunction.', 'In this cross-sectional study, 81 stable patients on continuous ambulatory peritoneal dialysis in a single center were recruited. Volume status was evaluated by extracellular water, assessed by bioimpedance analysis, and normalized to individual height (nECW). Endothelial function was estimated by endothelial-dependent flow-mediated dilatation (FMD) of the brachial artery and expressed as percentage change relative to baseline diameter.', 'There were 37 male and 44 female patients (mean age 61 +/- 12 years, dialysis vintage 20 +/- 23 months). FMD in female patients was significantly higher than that in male patients (9.17% +/- 6.23% vs 6.31% +/- 5.01%, p < 0.05). FMD was negatively correlated with weight (r = -0.308, p < 0.01), body mass index (r = -0.242, p < 0.05), systolic blood pressure (r = -0.228, p < 0.05), ECW (r = -0.404, p < 0.001), and nECW (r = -0.418, p < 0.001). No correlation was found between FMD and other variables. In multiple stepwise regression analysis, calcium x phosphate product (beta = 0.422, p < 0.001), nECW (beta = -0.343, p < 0.01), and dialysis vintage (beta = -0.237, p < 0.05) were independent determinants of FMD (adjusted R(2) = 0.327 for this model).
answer:

Is volume overhydration related to endothelial dysfunction in continuous ambulatory peritoneal dialysis patients?