First Measurement of the Nuclear-Recoil Ionization Yield in Silicon at 100 eV.

We measured the nuclear-recoil ionization yield in silicon with a cryogenic phonon-sensitive gram-scale detector. Neutrons from a monoenergetic beam scatter off of the silicon nuclei at angles corresponding to energy depositions from 4 keV down to 100 eV, the lowest energy probed so far. The results show no sign of an ionization production threshold above 100 eV. These results call for further investigation of the ionization yield theory and a comprehensive determination of the detector response function at energies below the keV scale.

Precise Measurement of Differential Cross Sections of the Σ

The differential cross sections of the Σ^{-}p→Λn reaction were measured accurately for the Σ^{-} momentum (p_{Σ}) ranging from 470 to 650 MeV/c at the J-PARC Hadron Experimental Facility. Precise angular information about the Σ^{-}p→Λn reaction was obtained for the first time by detecting approximately 100 reaction events at each angular step of Δcosθ=0.1. The obtained differential cross sections show a slightly forward-peaking structure in the measured momentum regions. The cross sections integrated for -0.7≤cosθ≤1.0 were obtained as 22.5±0.68 [statistical error(stat.)] ±0.65 [systematic error(syst.)] mb and 15.8±0.83(stat)±0.52(syst) mb for 470

Constraints on Lightly Ionizing Particles from CDMSlite.

The Cryogenic Dark Matter Search low ionization threshold experiment (CDMSlite) achieved efficient detection of very small recoil energies in its germanium target, resulting in sensitivity to lightly ionizing particles (LIPs) in a previously unexplored region of charge, mass, and velocity parameter space. We report first direct-detection limits calculated using the optimum interval method on the vertical intensity of cosmogenically produced LIPs with an electric charge smaller than e/(3×10^{5}), as well as the strongest limits for charge ≤e/160, with a minimum vertical intensity of 1.36×10^{-7} cm^{-2} s^{-1} sr^{-1} at charge e/160. These results apply over a wide range of LIP masses (5 MeV/c^{2} to 100 TeV/c^{2}) and cover a wide range of ßγ values (0.1-10^{6}), thus excluding nonrelativistic LIPs with ßγ as small as 0.1 for the first time.

Light Dark Matter Search with a High-Resolution Athermal Phonon Detector Operated above Ground.

We present limits on spin-independent dark matter-nucleon interactions using a 10.6 g Si athermal phonon detector with a baseline energy resolution of σ_{E}=3.86±0.04(stat)_{-0.00}^{+0.19}(syst) eV. This exclusion analysis sets the most stringent dark matter-nucleon scattering cross-section limits achieved by a cryogenic detector for dark matter particle masses from 93 to 140 MeV/c^{2}, with a raw exposure of 9.9 g d acquired at an above-ground facility. This work illustrates the scientific potential of detectors with athermal phonon sensors with eV-scale energy resolution for future dark matter searches.

Cosmic-ray antinuclei as messengers of new physics: status and outlook for the new decade.

The precise measurement of cosmic-ray antinuclei serves as an important means for identifying the nature of dark matter and other new astrophysical phenomena, and could be used with other cosmic-ray species to understand cosmic-ray production and propagation in the Galaxy. For instance, low-energy antideuterons would provide a "smoking gun" signature of dark matter annihilation or decay, essentially free of astrophysical background. Studies in recent years have emphasized that models for cosmic-ray antideuterons must be considered together with the abundant cosmic antiprotons and any potential observation of antihelium. Therefore, a second dedicated Antideuteron Workshop was organized at UCLA in March 2019, bringing together a community of theorists and experimentalists to review the status of current observations of cosmic-ray antinuclei, the theoretical work towards understanding these signatures, and the potential of upcoming measurements to illuminate ongoing controversies. This review aims to synthesize this recent work and present implications for the upcoming decade of antinuclei observations and searches. This includes discussion of a possible dark matter signature in the AMS-02 antiproton spectrum, the most recent limits from BESS Polar-II on the cosmic antideuteron flux, and reports of candidate antihelium events by AMS-02; recent collider and cosmic-ray measurements relevant for antinuclei production models; the state of cosmic-ray transport models in light of AMS-02 and Voyager data; and the prospects for upcoming experiments, such as GAPS. This provides a roadmap for progress on cosmic antinuclei signatures of dark matter in the coming years.

Prognostic role of the length of tumour-vein contact at the portal-superior mesenteric vein in patients having surgery for pancreatic cancer.

BACKGROUND: The length of tumour-vein contact between the portal-superior mesenteric vein (PV/SMV) and pancreatic head cancer, and its relationship to prognosis in patients undergoing pancreatic surgery, remains controversial. METHODS: Patients diagnosed with pancreatic head cancer who were eligible for pancreatoduodenectomy between October 2002 and December 2016 were analysed. The PV/SMV contact was assessed retrospectively on CT. Using the minimum P value approach based on overall survival after surgery, the optimal cut-off value for tumour-vein contact length was identified. RESULTS: Among 491 patients included, 462 underwent pancreatoduodenectomy for pancreatic head cancer. PV/SMV contact with the tumour was detected on preoperative CT in 248 patients (53·7 per cent). Overall survival of patients with PV/SMV contact exceeding 20 mm was significantly worse than that of patients with a contact length of 20 mm or less (median survival time (MST) 23·3 versus 39·3 months; P = 0·012). Multivariable analysis identified PV/SMV contact longer than 20 mm as an independent predictor of poor survival, whereas PV/SMV contact greater than 180° was not a predictive factor. Among patients with a PV/SMV contact length exceeding 20 mm on pretreatment CT, those receiving neoadjuvant therapy had significantly better overall survival than patients who had upfront surgery (MST not reached versus 21·6 months; P = 0·002). CONCLUSION: The length of PV/SMV contact predicts survival, and may be used to suggest a role for neoadjuvant therapy to improve prognosis.

ANTECEDENTES: El valor pronóstico de la longitud del contacto del tumor de la cabeza pancreática con las venas porta y mesentérica superior (portal-superior mesenteric vein, PV/SMV) en los pacientes sometidos a cirugía pancreática sigue siendo un tema controvertido. MÉTODOS: Se analizaron los pacientes diagnosticados de un cáncer de la cabeza pancreática a los que se realizó una duodenopancreatectomía cefálica entre octubre de 2002 y diciembre de 2016. El contacto tumoral con la PV/SMV se evaluó de forma retrospectiva mediante tomografía computarizada (TC). Se identificó el valor de corte óptimo para la longitud del contacto tumoral con la PV/SMV, utilizando el valor mínimo de la P basado en la supervivencia global (overall survival, OS) después de la cirugía. RESULTADOS: De 491 pacientes incluidos, en 462 pacientes se realizó una duodenopancreatectomía cefálica por cáncer de la cabeza de páncreas. En la TC preoperatoria, se detectó contacto tumoral con la PV/SMV en 248 (53,7%) pacientes. La OS de los pacientes en los que el contacto del tumor con la PV/SMV fue > 20 mm fue significativamente peor que en aquellos cuyo contacto fue ≤ 20 mm (mediana de supervivencia (median survival time, MST) 23,3 versus 39,3 meses; P = 0,012). En un análisis multivariado se identificó el contacto tumoral-PV/SMV > 20 mm como un factor independiente predictor de mala supervivencia, pero el contacto tumor-PV/SMV > 180° no fue un factor pronóstico. En los pacientes en los que el contacto tumor-PV/SMV fue > 20 mm en el TC preoperatorio, la OS en aquellos que recibieron tratamiento neoadyuvante fue significativamente mejor en comparación con los pacientes tratados directamente con cirugía (MST, no alcanzada versus 21,6 meses, P = 0,002). Conclusión La longitud del contacto tumoral con la PV/SMV predice la supervivencia, por lo cual dicha longitud podría jugar un papel en la indicación de tratamiento neoadyuvante para mejorar el pronóstico.

Erratum: First Dark Matter Constraints from a SuperCDMS Single-Charge Sensitive Detector [Phys. Rev. Lett. 121, 051301 (2018)].

This corrects the article DOI: 10.1103/PhysRevLett.121.051301.

First Dark Matter Constraints from a SuperCDMS Single-Charge Sensitive Detector.

We present the first limits on inelastic electron-scattering dark matter and dark photon absorption using a prototype SuperCDMS detector having a charge resolution of 0.1 electron-hole pairs (CDMS HVeV, a 0.93 g CDMS high-voltage device). These electron-recoil limits significantly improve experimental constraints on dark matter particles with masses as low as 1 MeV/c^{2}. We demonstrate a sensitivity to dark photons competitive with other leading approaches but using substantially less exposure (0.49 g d). These results demonstrate the scientific potential of phonon-mediated semiconductor detectors that are sensitive to single electronic excitations.

Results from the Super Cryogenic Dark Matter Search Experiment at Soudan.

We report the result of a blinded search for weakly interacting massive particles (WIMPs) using the majority of the SuperCDMS Soudan data set. With an exposure of 1690 kg d, a single candidate event is observed, consistent with expected backgrounds. This analysis (combined with previous Ge results) sets an upper limit on the spin-independent WIMP-nucleon cross section of 1.4×10^{-44} (1.0×10^{-44}) cm^{2} at 46 GeV/c^{2}. These results set the strongest limits for WIMP-germanium-nucleus interactions for masses >12 GeV/c^{2}.

New Results from the Search for Low-Mass Weakly Interacting Massive Particles with the CDMS Low Ionization Threshold Experiment.

The CDMS low ionization threshold experiment (CDMSlite) uses cryogenic germanium detectors operated at a relatively high bias voltage to amplify the phonon signal in the search for weakly interacting massive particles (WIMPs). Results are presented from the second CDMSlite run with an exposure of 70 kg day, which reached an energy threshold for electron recoils as low as 56 eV. A fiducialization cut reduces backgrounds below those previously reported by CDMSlite. New parameter space for the WIMP-nucleon spin-independent cross section is excluded for WIMP masses between 1.6 and 5.5 GeV/c^{2}.

A predictive factor of insufficient liver regeneration after preoperative portal vein embolization.

BACKGROUND: Preoperative portal vein embolization (PVE) is performed to enhance the future remnant liver function (FRLF) and volume (FRLV). However, the volume of the nonembolized liver does not increase enough in some patients, which results in an insufficient FRLF. The aim of this study was to evaluate the predictors of insufficient FRLF after PVE for extended hepatectomy. METHODS: This retrospective study included 172 patients (107 patients with cholangiocarcinoma, 40 patients with metastatic liver cancer and 25 patients with hepatocellular carcinoma) who underwent PVE before extended hepatectomy. The total liver function was evaluated by measuring the indocyanine green plasma clearance rate (KICG). Computed tomography volumetry was conducted to evaluate the total liver volume and FRLV. The KICG of the future remnant liver (remK) was calculated using the following formula: KICG × FRLV/total liver volume. The safety margin for hepatectomy was set at remK after PVE (post-PVE remK) ≥ 0.05. RESULTS: One hundred and twenty-three patients with a post-PVE remK level of >0.05 underwent hepatectomy without postoperative liver failure [sufficient liver regeneration (SLR) group], and 9 patients with a post-PVE remK level of <0.05 did not due to insufficient FRLF [insufficient liver regeneration (ILR) group]. In the SLR group, the KICG values did not change after PVE (median, 0.144-0.146, p = 0.523); however, the %FRLV and remK increased significantly (35.0-44.3%, p < 0.001 and 0.0488-0.0610, p < 0001, respectively). In contrast, in the ILR group, the KICG values decreased significantly (0.128-0.108, p = 0.021) and the %FRLV increased marginally (27.4-32.6%, p = 0.051). As a result, the remK did not increase significantly (0.0351-0.0365, p = 0.213). A receiver operating characteristic curve demonstrated an remK value of 0.04 obtained before PVE (pre-PVE remK) to be the optimal cutoff point for defective liver regeneration. The univariate and multivariate analyses revealed that a pre-PVE remK value of <0.04 was a factor for ILR. It was also correlated with postoperative liver failure in the analysis of the patients who underwent hepatectomy. CONCLUSIONS: The patients in the ILR group did not achieve SLR after PVE due to a significant decrease in the KICG and an insufficient increase in %FRLV. A pre-PVE remK value of <0.04 is a useful predictor of insufficient regeneration of the nonembolized liver, even after PVE.

Major hepatectomy with combined vascular resection for perihilar cholangiocarcinoma.

BACKGROUND: Hepatectomy with vascular resection (VR) for perihilar cholangiocarcinoma (PHCC) is a challenging procedure. However, only a few reports on this procedure have been published and its clinical significance has not been fully evaluated. METHODS: Patients undergoing surgical resection for PHCC from 2002-2017 were studied. The surgical outcomes of VR and non-VR groups were compared. RESULTS: Some 238 patients were included. VR was performed in 85 patients. The resected vessels were hepatic artery alone (31 patients), portal vein alone (37 patients) or both (17 patients). The morbidity rates were almost the same in the VR (49.4 per cent) and non-VR (43.8 per cent) groups (P = 0.404). The mortality rates of VR (3.5 per cent) and non-VR (3.3 per cent) were also comparable (P > 0.999). The median survival time (MST) was 45 months in the non-VR group and 36 months in VR group (P = 0.124). Among patients in whom tumour involvement was suspected on preoperative imaging and whose carbohydrate antigen 19-9 (CA19-9) value was 37 U/ml or less, MST in the VR group was significantly longer than that in the non-VR group (50 versus 34 months, P = 0.017). In contrast, when the CA19-9 value was greater than 37 U/ml, MST of the VR and non-VR groups was comparable (28 versus 29 months, P = 0.520). CONCLUSION: Hepatectomy with VR for PHCC can be performed in a highly specialized hepatobiliary centre with equivalent short- and long-term outcomes to hepatectomy without VR.

The tumor diameter cut-off for predicting microscopic intrahepatic metastasis of hepatocellular carcinoma patients without treatment history differs from that of hepatocellular carcinoma patients with a treatment history.

BACKGROUND AND AIM: Intrahepatic metastasis (IM) of hepatocellular carcinoma (HCC) occurs via vascular invasion; the tumor diameter that affects the risk of micro intra-hepatic metastasis (MIM) should be larger than that which affects the risk of micro vessel invasion (MVI). The aim of the present study was to determine the optimum tumor diameter cut-off value for predicting the presence of MIM in HCC patients without treatment history and HCC patients with a treatment history and to compare these diameters between cases of MVI and MIM. METHODS: This retrospective study included 621 patients without macroscopic vessel invasion or intrahepatic metastasis on preoperative imaging who underwent hepatectomy. The cut-off tumor diameter for predicting the presence of MIM was determined by a receiver operating characteristic curves analysis. RESULTS: The optimum cut-off value for predicting the presence of MIM in HCC patients without treatment history was 43 mm. In contrast, the optimum cut-off value for predicting the presence of MIM in HCC patients with a treatment history was 20 mm. Among 46 HCC patients with MIM without treatment history, there were 20 patients with MIM without MVI who were considered to have potential multi-centric (MC) tumors rather than IM. The cumulative overall survival rates in patients with MIM without MVI (potential MC) was significantly better than that in patients with both MIM and MVI (P = 0.022). CONCLUSIONS: The tumor diameter cut-off value for predicting MIM differed between HCC patients without treatment history and with a treatment history and slightly smaller than those for predicting MVI beyond our expectation.

Association of distinct clinical subsets with myositis-specific autoantibodies towards anti-155/140-kDa polypeptides, anti-140-kDa polypeptides, and anti-aminoacyl tRNA synthetases in Japanese patients with dermatomyositis: a single-centre, cross-sectional study.

OBJECTIVE: To determine the association of distinct clinical subsets with myositis-specific autoantibodies (MSAs) towards anti-155/140-kDa polypeptides [anti-155/140 antibodies (Abs)], anti-140-kDa polypeptides (anti-140 Abs), and anti-aminoacyl tRNA synthetases (ARS Abs) in Japanese patients with dermatomyositis (DM). METHODS: We compared the clinical features and short-term prognoses of 30 DM patients whose serological status included these MSAs. The MSAs were determined by immunoprecipitation. RESULTS: Anti-155/140 Abs (n = 5), anti-140 Abs (n = 8), and anti-ARS Abs (n = 7) did not overlap each other. All of the anti-155/140 Ab-positive patients (n = 5) were complicated by malignancies, as were all of the anti-140 Ab-positive patients (n = 8), who showed rapidly progressive interstitial lung disease (ILD). The survival rate at 6 months from the diagnosis of DM was significantly lower in the anti-140 Ab-positive patients than in the other patients. CONCLUSION: This is the first study to report, in a single cohort of DM patients, that distinct clinical subsets are distributed in an anti-155/140 Ab-positive group, an anti-140 Ab-positive group, or an anti-ARS Ab-positive group. Our data also confirm previous evidence that anti-155/140 Abs are involved in malignancies and that anti-140 Abs are involved in rapidly progressive ILD.

Spatial variations of 226Ra, 228Ra, 134Cs, and 137Cs concentrations in western and southern waters off the Korean Peninsula in July 2014.

We examined the spatial distributions of 226Ra, 228Ra, 134Cs, and 137Cs concentrations (activities) in seawater off the western and southern Korean Peninsula in July 2014. Radium-228 (and 226Ra) concentrations in water samples varied widely from 5 to 14 mBq/L (2-4 mBq/L), showing a negative correlation with salinity, particularly at the surface off the western Korean Peninsula. This indicates that the seawaters in this area are fundamentally comprised of 228Ra-poor and high-saline Kuroshio Current water and 228Ra-rich and low-saline water (e.g., continental shelf water), with various mixing ratios. Although Fukushima Dai-ichi Nuclear Power Plant (FDNPP)-derived 134Cs was below the detection limit (<0.08 mBq/L) in waters off the western Korean Peninsula, low level 134Cs (0.1-0.2 mBq/L) was detected in waters off the southern Korean Peninsula accompanied by higher 137Cs concentrations (1.6-1.9 mBq/L) relative to that off the western Korean Peninsula. Combined with the lower radium concentrations, the detection of 134Cs is explained by mixing of FDNPP-derived radiocesium-contaminated Kuroshio Current water.

Propensity score-matched comparison of non-anatomical resection and radiofrequency ablation for hepatocellular carcinoma in patients with up to three tumours, each measuring up to 3 cm in diameter.

BACKGROUND: Non-anatomical liver resection (NAR) and radiofrequency ablation (RFA) are treatment options for early-stage hepatocellular carcinoma (HCC). The aim was to compare the outcomes of NAR and RFA for HCC in patients with three or fewer tumour nodules, each measuring not more than 3 cm in maximum diameter. METHODS: Eligible patients undergoing NAR or RFA with curative intent between September 2002 and December 2014 were identified. A propensity score-matching analysis was performed to reduce bias, and outcomes in these patients were analysed. RESULTS: From a total of 199 patients, 1:1 propensity score matching identified 70 matched pairs. Patients having NAR had a longer hospital stay (median 10 days versus 4 days for those who had RFA; P < 0·001) and a higher morbidity rate (24 versus 10 per cent respectively; P = 0·042). Patients who had NAR had slightly better recurrence-free survival but this failed to reach statistical significance in univariable analysis (P = 0·064). There was no significant difference in overall survival between the two groups (P = 0·475). RFA was identified as an independent risk factor for recurrence-free survival (hazard ratio (HR) 1·57; P = 0·041) in multivariable analysis. Local recurrence was significantly more common in patients receiving RFA (23 versus 1 per cent; P < 0·001). CONCLUSION: RFA was an independent risk factor for shorter recurrence-free survival, with a significantly higher local recurrence rate than NAR. Despite these differences, overall survival was not affected.

Estimation of reduced and increasing health risks by installation of urban wastewater systems.

This paper aims to propose a methodological framework for quantifying the reduction and increase of health risks associated with urban wastewater systems. A risk assessment model was used to quantify reduction in disease burden while a life cycle assessment approach was used to quantify increasing risks by environmental loading. Disability adjusted life years (DALYs) was used to quantify health risks. This framework was applied to a hypothetical watershed to evaluate health risks by installation of wastewater treatment systems. In this hypothetical case, 55 DALYs per year of health risk would be reduced for 200,000 people in the downstream community by constructing wastewater systems for 200,000 people, while a range from 1.9 to 22 DALYs per year of health risks would be generated by materials and energy consumption for construction and operation of wastewater systems. However, this result would significantly change, depending on the parameters used in this analysis. The proposed methodology should be improved to obtain more precise results, but it will suggest useful information to discuss the overall effects due to the installation of various types of urban wastewater systems.

Purification and properties of a decapping enzyme from rat liver cytosol.

A decapping enzyme has been purified about 2400-fold from rat liver cytosol. The decapping enzyme was shown to be fairly homogeneous by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The enzyme had an apparent molecular weight of 110,000 and consisted of two equal subunits. The enzyme hydrolyzed m7Guo5'PPP5'Ado to m7GMP and ADP. Analysis of the products produced from radioactively capped oligonucleotides and intact mRNA having 3H-cap suggests that the enzyme can hydrolyze capped mono- to pentanucleotides (m7Guo5'PPP5'N (where N = 1-5 nucleotides)) but not intact mRNA. The existence of methyl group at the N7 position of guanosine moiety of cap structure was necessary for the action of the decapping enzyme. This was confirmed by the comparison of the rates of hydrolysis of m7Guo5'PPP5'Ado by the enzyme in the presence of various nucleotides. The activity of enzyme was slightly stimulated by Na+, K+, NH4+, Ca2+ and polyamines. Mg2+ and Mn2+ were without effect on the enzyme activity.

Characterization of the calcium-activated chloride channel in isolated guinea-pig hepatocytes.

Macroscopic and unitary currents through Ca(2+)-activated Cl- channels were examined in enzymatically isolated guinea-pig hepatocytes using whole-cell, excised outside-out and inside-out configurations of the patch-clamp technique. When K+ conductances were blocked and the intracellular Ca2+ concentration ([Ca2+]i) was set at 1 microM (pCa = 6), membrane currents were observed under whole-cell voltage-clamp conditions. The reversal potential of the current shifted by approximately 60 mV per 10-fold change in the external Cl- concentration. In addition, the current did not appear when Cl- was omitted from the internal and external solutions, indicating that the current was Cl- selective. The current was activated by increasing [Ca2+]i and was inactivated in Ca(2+)-free, 5 mM EGTA internal solution (pCa > 9). The current was inhibited by bath application of 9-anthracenecarboxylic acid (9-AC) and 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) in a voltage-dependent manner. In single channel recordings from outside-out patches, unitary current activity was observed, whose averaged slope conductance was 7.4 +/- 0.5 pS (n = 18). The single channel activity responded to extracellular Cl- changes as expected for a Cl- channel current. The open time distribution was best described by a single exponential function with mean open lifetime of 97.6 +/- 10.4 ms (n = 11), while at least two exponentials were required to fit the closed time distributions with a time constant for the fast component of 21.5 +/- 2.8 ms (n = 11) and that for the slow component of 411.9 +/- 52.0 ms (n = 11). In excised inside-out patch recordings, channel open probability was sensitive to [Ca2+]i. The relationship between [Ca2+]i and channel activity was fitted by the Hill equation with a Hill coefficient of 3.4 and the half-maximal activation was 0.48 microM. These results suggest that guinea-pig hepatocytes possess Ca(2+)-activated Cl- channels.

Characterization of the calcium-sensitive voltage-gated delayed rectifier potassium channel in isolated guinea pig hepatocytes.

The voltage-dependent K+ channel was examined in enzymatically isolated guinea pig hepatocytes using whole-cell, excised outside-out and inside-out configurations of the patch-clamp technique. The resting membrane potential in isolated hepatocytes was -25.3 +/- 4.9 mV (n = 40). Under the whole-cell voltage-clamp, the time-dependent delayed rectifier outward current was observed at membrane potentials positive to -20 mV at physiological temperature (37 degrees C). The reversal potential of the current, as determined from tail current measurements, shifted by approximately 57 mV per 10-fold change in the external K+ concentration. In addition, the current did not appear when K+ was replaced with Cs+ in the internal and external solutions, indicating that the current was carried by K+ ions. The envelope test of the tails demonstrated that the growth of the tail current followed that of the current activation. The ratio between the activated current and the tail amplitude was constant during the depolarizing step. The time course of growth and deactivation of the tail current were best described by a double exponential function. The current was suppressed in Ca(2+)-free, 5 mM EGTA internal or external solution (pCa > 9). The activation curve (P infinity curve) was not shifted by changing the internal Ca2+ concentration ([Ca2+]i). The current was inhibited by bath application of 4-aminopyridine or apamin. alpha 1-Adrenergic stimulation with noradrenaline enhanced the current but beta-adrenergic stimulation with isoproterenol had no effect on the current. In single-channel recordings from outside-out patches, unitary current activity was observed by depolarizing voltage-clamp steps whose slope conductance was 9.5 +/- 2.2 pS (n = 10). The open time distribution was best described by a single exponential function with the mean open lifetime of 18.5 +/- 2.6 ms (n = 14), while at least two exponentials were required to fit the closed time distributions with a time constant for the fast component of 2.0 +/- 0.3 ms (n = 14) and that for the slow component of 47.7 +/- 5.9 ms (n = 14). Ensemble averaged current exhibited delayed rectifier nature which was consistent with whole-cell measurements. In excised inside-out patch recordings, channel open probability was sensitive to [Ca2+]i. The concentration of Ca2+ at the half-maximal activation was 0.031 microM. These results suggest that guinea pig hepatocytes possess voltage-gated delayed rectifier K+ channels which are modified by intracellular Ca2+.