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.

Q: 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.

A: Is reverse rate dependency an intrinsic property of canine cardiac preparations?
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Q: The 6-min walk test (6MWT) has prognostic value in various pulmonary disorders including idiopathic pulmonary fibrosis (IPF). We determined the individual prognostic accuracy of distance walked and oxygen saturation during the 6MWT in patients with IPF. We defined a new composite index, the distance-saturation product (DSP), which is the product of distance walked and lowest oxygen saturation during the 6-min walk test. We compared the performance of the DSP to the individual 6MWT parameters in predicting mortality.', 'We evaluated pulmonary function tests, 6-min walk parameters and the DSP between survivors and non-survivors. The ability of each measure to discriminate outcomes was determined by receiver operator curves.', '81 patients (48 survivors, 33 non-survivors) were included. Pulmonary function tests were similar and did not correlate with survival. Desaturation was greater (89.4% versus 83.7%, P<0.001) and distance walked was lower (406.9 versus 181.3m, P = 0.005) in non-survivors. The DSP was significantly lower among non-survivors (364.8 versus 153.5m%, P < 0.001) and predicted mortality more accurately than either individual 6MWT component (P = 0.035 versus desaturation, P=0.040 versus distance). A DSP <200 m% was associated with a seven-fold greater risk of 12-month mortality and an 18.0% shorter median survival compared with a DSP > 200 m% (P < 0.001).

A: Does the distance-saturation product predict mortality in idiopathic pulmonary fibrosis?
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Q: In colorectal cancer (CRC), as in most of other malignancies, heat shock proteins (HSPs) are overexpressed and are associated with apoptosis, cancer cell proliferation, differentiation, invasion, and metastasis. HSP70 is one of the HSPs and has a promising future in cancer studies for both diagnostic and therapeutic applications. In this study, we tried to evaluate the serum levels of HSP70 in CRC patients, and to evaluate its predictive value of detecting CRC.', 'This prospective study was consisted of 33 patients diagnosed with CRC and 31 healthy subjects who were matched for age. Enzyme-linked immunosorbent assays (ELISA) were used to evaluate the serum levels of HSP70 in patients with CRC and in the healthy control group. A cut-off value for HSP70 was also determined using receiver operating characteristic (ROC) curve analysis.', 'Patients with CRC had significantly higher HSP70 concentrations compared with the control group (4.52 ± 1.83 vs 1.22 ± 0.48 ng/ml, p=0.001), the cut-off value was ≥2.25 ng/ml (95% CI 0.993-1.003, p<0.001). The sensitivity and specificity of elevated serum HSP70 in the CRC group were 96.77 and 96.96%, respectively. Also, HSP70 levels were significantly higher with rectal disease localization (p=0.01).

A:
Is heat shock protein 70 a useful marker for predicting colorectal cancer?
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