Transanal single-port laparoscopic total mesorectal excision in the treatment of rectal cancer.

Our objective was to report of our first experience with transanal total mesorectal excision (TME) of rectal cancer using single-port equipment, a pure natural orifice transluminal endoscopic surgery (NOTES) procedure, and to discuss the advantages and disadvantages of the technique. A patient with rectal cancer was selected according to preoperative evaluation criteria. Purse-string sutures were placed into the rectum distal to the tumor using the procedure of prolapse and hemorrhoids (PPH) anoscope. A full-thickness incision of the rectal wall was made circumferentially below the purse string and a three-channel cannula was inserted. The artificial orifice was insufflated. The entire mesorectum was dissected upward according to the principles of TME. Pneumoperitoneum was created by opening the rectouterine pouch. The sigmoid colon and its mesentery were dissected, and the inferior mesenteric vessels were ligated and divided. After dissection of a sufficient length of sigmoid colon, the PPH anoscope and the three-channel cannula were removed. The rectum and sigmoid colon were brought out through the anus. The tumor was resected. After removal of the specimens, a stapled end-to-end anastomosis was fashioned between the rectum and the sigmoid colon. Operative time was 300 min. The mesorectum was completely removed with negative distal and circumferential margin. The final pathological stage was pT3N1M0, with one positive lymph node (1/12). The patient recovered uneventfully after surgery. Pure-NOTES performed as transanal single-port laparoscopic TME for rectal cancer appears to be feasible and safe.

[Summary of best evidence for pulse contour cardiac output monitoring in severe burn patients].

Objective: To summarize the best evidence for pulse contour cardiac output (PiCCO) monitoring in severe burn patients. Methods: A bibliometric approach was used. Foreign language databases including UpToDate, BMJ Best Practice, Joanna Briggs Institute Evidence-Based Practice Database, Cochrane Library, PubMed, Web of Science, Embase, Medline, and Guideline International Network, as well as Chinese databases such as China National Knowledge Infrastructure, Wanfang Database, and VIP Database were systematically retrieved to obtain all the publicly published evidence on PiCCO monitoring in severe burn patients in each database from the establishment of each database to May 2022, including guidelines, expert consensus, evidence summary, systematic review, and original research. The literature was screened and evaluated for the quality, from which the evidences were extracted, evaluated, and classified to summarize the best evidences. Results: Three guidelines, two expert consensuses, one evidence summary (with two systematic reviews being traced), two systematic reviews, three randomized controlled trials, one cohort study, and one case-control study were retrieved and included, with good quality of literature. Totally 37 pieces of best evidences about PiCCO monitoring in severe burn patients were summarized from the aspects of pre-operation evaluation, pipe placement and operation, monitoring system establishment, pipeline maintenance, and supervision and education. Conclusions: Totally 37 pieces of best evidences about PiCCO monitoring in severe burn patients are summarized from 5 aspects, providing a basis for the clinical implementation of scientific and standardized PiCCO monitoring and nursing management.

Detection of patients presenting with adverse drug events in the emergency department.

BACKGROUND: Adverse drug events (ADE) have been studied widely in hospitalised and emergency department (ED) patients. Less is known about the ED visits of drug-related injury in Taiwan. This study seeks to determine the incidence, risk and patient outcomes of ADE in an ED population. METHODS: We conducted a prospective observational cohort study of patients 18 years and older presenting to the ED of an urban, tertiary medical centre. ED visits between 1 March 2009 and 28 February 2010 identified by investigators for suspected ADE were further assessed by using the Naranjo Adverse Drug Reaction probability scale. Outcomes (ED disposition, injury severity and preventability) and associated variables (triage, gender, drug category, number of drugs, Charlson comorbidity index score and ADE mechanism) were measured. RESULTS: Of 58,569 ED visits, 452 patients (0.77%) had physician-documented ADE. 24% of patients with ADE were hospitalised with life-threatening conditions, with a mortality rate of 10.0%. The majority of ADE were considered preventable (73.4%), and the unintentional overdose was the most common cause. Cardiovascular agents accounted for the most ADE (25.8%) and consisted of 65.3% of ADE in patients aged 65,years and older. Risk factors for ADE-related hospitalisation were elderly age (odds ratio (OR) 1.9, 95% confidence interval (CI) 1.1-3.4), severity of ADE (OR 6.9, 95% CI 3.3-14.5) and higher Charlson comorbidity index scores (OR 3.4, 95% CI 2.0-5.7). CONCLUSION: ADE-related ED visits are not uncommon in Taiwan and many cases are preventable. ED-based surveillance may provide useful information for monitoring outpatient ADE.

Pollution extents of organic substances from a coal gangue dump of Jiulong Coal Mine, China.

This paper addresses the distribution and occurrence of harmful organic substances in coal gangue dump from Jiulong Coal Mine and its influence on the environment. The samples were taken from the coal gangue dump and coal waste water stream and analyzed by organic geochemical methods. The results indicate that the coal gangues contain abundant harmful organic substances like polycyclic aromatic hydrocarbons. The TOC and sulfur contents of the samples are much higher than those of the background sample except Sample JL7. The contents of organic bulk parameters are relatively high. Ten carcinogenic PAHs were identified and these harmful organic substances have influenced the surrounding area. Along the waste water stream, organic substances pollute at least 1,800 m far from the coal gangue dump.

Ras reduces L-type calcium channel current in cardiac myocytes. Corrective effects of L-channels and SERCA2 on [Ca(2+)](i) regulation and cell morphology.

Heart failure is associated with dysregulation of intracellular calcium ([Ca(2+)](i)), reduction in myofibrils, and increased activation of Ras, a regulator of signal-transduction pathways. To evaluate the potential effects of Ras on [Ca(2+)](i), we expressed constitutively active Ras (Ha-Ras(V12)) in cardiac myocytes and monitored [Ca(2+)](i) via fluorescence and electrophysiological techniques. Ha-Ras(V12) reduced the magnitude of the contractile calcium transients. Unexpectedly, however, calcium loading of the sarcoplasmic reticulum was increased, suggesting that Ha-Ras(V12) introduces a defect in excitation-calcium release coupling. Consistent with this idea, L-channel calcium currents were reduced by Ha-Ras(V12), which also downregulated the activity of the L-channel gene promoter. Coexpression of L-channels and SERCA2 largely corrected Ha-Ras(V12)-induced dysregulation of [Ca(2+)](i). Furthermore, whereas Ha-Ras(V12) downregulated myofibrils, this effect was blocked by coexpression of L-channels. These results suggest that Ras downregulates L-channel expression, which may play a pathophysiological role in cardiac disease.

Effects of elevating [Na]i on membrane currents of canine ventricular myocytes: role of intracellular Ca ions.

OBJECTIVES: Our first objective was to study how elevating [Na]i can modify the background membrane conductance in canine ventricular myocytes (CVM). In particular, we wanted to find evidence for a Nai-activated K current (IK,Na) in these cells. The second objective was to compare the effects of elevating [Na]i on membrane currents without and with intracellular Ca buffering. METHODS: Whole-cell currents were recorded and [Na]i was elevated either by using a pipette perfusion device that allowed [Na] in the pipette solution to be varied (from 0 to 50 mM), or by 50 microM ouabain. RESULTS: Although an outward current attributable to IK,Na was confirmed in guinea-pig ventricular myocytes (GPVM) under our recording conditions, no such current was seen in 29 CVM examined. With Cai buffering, the main effect of elevating [Na]i on CVM was an increase in inward current around and negative to the resting membrane potential. Based on the dependence of this Nai-induced inward current on K ions and its pharmacological properties, especially the effects of low concentrations of external Ba ions (< or = 5 microM) at strongly hyperpolarized voltages, we hypothesize that this current was carried by extracellular K ions through the inward rectifier (IK1) channels that had been modified by the high level of [Na]i. With Cai buffering, elevating [Na]i by ouabain had few or no effects on the L-type Ca channel current (ICa) or the slow delayed rectifier current (IKs). Without Cai buffering, ouabain induced a rapid reduction of both currents along with an increase in a time-independent outward current at voltages positive to -60 mV. CONCLUSION: Our data suggest that there are species variations in K channel expression and/or K channel modulation by intracellular Na ions. Furthermore, intracellular Ca ions play a crucial role in mediating the effects of Nai loading on membrane currents in canine ventricular myocytes.

Heterogeneous changes in K currents in rat ventricles three days after myocardial infarction.

OBJECTIVE: After coronary artery occlusion, surviving myocardium in and around the infarct zone plays an important role in arrhythmogenesis. Understanding the mechanisms for derangements in cardiac electrical activity at the cellular and molecular levels is important for the design of effective therapeutic strategies. METHODS: To provide part of that understanding, we studied changes in K channel function and expression in rat ventricular myocardium three days after occluding the left major coronary artery. The epicardium and endocardium of infarcted region in the left ventricle and the free wall of right ventricle were separated for myocyte isolation, followed by whole-cell voltage clamp studies. Myocytes were also isolated from corresponding regions of control and sham-operated hearts and studied under the same conditions. RESULTS: We found that the transient outward (Ito), delayed rectifier (IK) and inward rectifier (IKI) currents have different distribution patterns in normal rat ventricular myocardium. Sham-operation did not affect any of these K currents in left ventricular myocytes, but coronary artery occlusion caused a reduction of all three. For Ito and IKI the reduction was greater in epicardial than in endocardial myocytes, but IK was reduced equally in these two cell groups. Unexpectedly, Ito and IK as well as cell capacitance were increased in right ventricular myocytes from infarcted as well as sham-operated hearts. Western blot analysis indicated that the level of Kv4 channel proteins (Kv4.2 + Kv4.3) was reduced in infarcted left ventricular myocardium, consistent with the reduction in Ito. CONCLUSION: Our data suggest that the distribution of K channels and changes in them induced by coronary artery occlusion are heterogeneous in ventricular myocardium. Understanding the molecular mechanisms for this heterogeneity and its implications in arrhythmogenesis poses a challenge in designing effective antiarrhythmic therapy for myocardial infarction patients.

Concerning the independence of the basis of hypertension due to ACTH or renovascular constriction.

Administration of ACTH to four sheep with chronic renovascular hypertension resulted in an increase in blood pressure which was at least as high as that described in normotensive sheep and could be completely accounted for by an increase in cardiac output.

Inter-relationships between sodium and potassium intake and the blood pressure effects of ACTH in sheep.

These studies examine the effect of sodium (Na) and potassium (K) intake on the pressor and metabolic actions of ACTH (20 micrograms/kg/day) in sheep. After 21 days on each of five regimens in which Na and K intake varied from 0 to 100 mmol/day, no simple relationship between Na and K intake and blood pressure was found. After five days of ACTH treatment, mean arterial pressure (MAP) rose + 5 mmHg in sheep on 0 mmol Na, 0 mmol K (expressed as 0 Na 0 K); + 13 mmHg on 10 Na 100 K; + 5 mmHg on 0 Na 100 K; + 20 mmHg on 100 Na 0 K and + 24 mmHg on 100 Na 100 K. Plasma [K] was unchanged by ACTH on 0 Na 0 K but fell in sheep on the other electrolyte regimens. Water intake increased with ACTH on all regimens except 100 Na 0 K. Blood aldosterone concentration was high in sheep maintained on 0 Na regimens but lower after five days of ACTH treatment in all groups. Blood cortisol and corticosterone concentrations increased with ACTH on all regimens studied.

Kinetic effects of FPL 64176 on L-type Ca2+ channels in cardiac myocytes.

To characterize the effects of the Ca2+ channel agonist FPL 64176 on L-type Ca2+ current in isolated rat ventricular myocytes, certain of its effects were compared with those of a better known agonist, S (-) Bay K 8644. Both drugs enhance currents elicited by depolarizing pulses and enhance and slow the decay of tail currents elicited by subsequent repolarization. Both drugs shift the voltage dependence of activation and of inactivation approximately 10 mV in the negative direction, but FPL 64176 slows the rate of both activation and the decline of Ca2+ current during a depolarization, whereas Bay K 8644 accelerates the rate of current decay under the same conditions. In single channel studies in on-cell recording mode, FPL 64176 produced a great lengthening of the channel open time, produced very long openings when the channels were repolarized after a depolarizing stimulus, and had only modest effects on mean closed times and on first latency distributions. FPL 64176 and Bay K 8644 also had minimal effects on L-type channel "on" gating currents, while the "off" gating currents were slowed, particularly at positive potentials. However, the effects on gating currents were too small to account for the prolonged tails observed in FPL 64176. Once the channel is open, FPL 64176 slows transitions to closed or inactivated channel states.

Role of inward and delayed rectifier currents in generation of early afterdepolarization in guinea pig ventricular myocytes under K(+)-free or low K+ superfusion.

Early afterdepolarization (EAD) was studied in isolated ventricular myocytes of guinea pig heart. Under K(+)-free's treatment, most of the myocytes showed hyperpolarization in resting potential and the duration of action potential was prolonged, eventually leading to the appearance of EAD with the second plateau of -76 +/- 3 mV. TTX (10 microM) and verapamil (10 microM) or normal Tyrode's solution abolished the EAD. The background I-V curve showed inward rectifying with a crossover in the level of -80 to -30 mV and the reversal potential shifted from -80 to -120 mV when normal Tyrode's solution was changed to K(+)-free solution. The changes of I-V relationship of inward current IK) were similar to the background ones except without crossover. The delayed rectifier current (IK) was inhibited significantly under K(+)-free treatment. Low K+ (2.7 mM) superfusion was able to induce EAD in only a few cases (4/15). Adding Cs+ (5.0 mM) into low K+ solution, EAD was induced in almost every case. The background I-V curve was inhibited slightly under low K+ superfusion, but was inhibited significantly with a remarkable crossover under low K+ and Cs+ treatment. The changes of I-V curve IK1 under low K+ or low K+ and Cs+ treatment were similar to the changes of background ones. There were no significant changes in the IK under low K+ superfusion while a remarkable inhibition occurred under low K+ and Cs+ treatment. It was suggested that both IK1 and IK were involved in the induction of EAD under K(+)-free or Cs+ treatment in guinea pig ventricular myocytes.

[Effects of panaxatriol saponins (PTS) isolated from panax notoginseng on the action potential and delayed rectifier current (Ix) in sheep cardiac Purkinje fibers].

The electrophysiological effects of PTS in sheep cardiac Purkinje fibers were studied. PTS was shown to increase the duration of action potential (APD30, APD50 and APD90) at the concentrations of 2.5 micrograms/ml and 5.0 micrograms/ml. However, the amplitude of action potential (APA) remained unchanged. The result of using double microelectrode voltage clamp method showed that PTS (1.25-10.0 micrograms/ml) depressed the delayed (outward) rectifier current (Ix) in time- and dose-dependent manners, when the holding potential was held at +20 mV, the command potential was held at +10 mV, 0.2 Hz and the clamping time at 1-1.5 s. It may be concluded that the effect of PTS on APD is mainly related to blocking the delayed rectifier potassium channel.

Perforated patch recording with beta-escin.

Perforated patch recording with nystatin, amphotericin B and gramicidin can be more difficult in the hands of some investigators than others. In addition, it is difficult to introduce low molecular weight substances such as dyes into the cytoplasm in such experiments. We have determined that beta-escin represents a convenient, easy-to-use alternative to less water-soluble ionophores.

One calcium ion may suffice to open the tetrameric cardiac ryanodine receptor in rat ventricular myocytes.

1. The release of Ca2+ from sarcoplasmic reticulum in response to Ca2+ entering through L-type Ca2+ channels was studied in isolated voltage clamped rat ventricular myocytes at room temperature using the fluorescent Ca2+ indicators fluo-3 and Oregon Green 488 Bapta 5N. 2. Depolarizations to positive potentials elicited fluo-3 Ca2+ transients with rates of rise that were linearly related to the magnitude of the peak measured Ca2+ current in the presence of Cs+-containing pipette solutions. 3. Further experiments utilizing prepulses to preactivate a constant number of channels also revealed a linear relationship between the Ca2+ transient rate of rise and the magnitude of entering Ca2+ current at positive potentials. Under these conditions as well, the maximal rates of rise of global myoplasmic Ca2+ transients were due primarily to Ca2+ release from the sarcoplasmic reticulum as revealed by effects of ryanodine and caffeine on the Ca2+ transients. Using such prepulses, linearity between the Ca2+ transient rate of rise and the magnitude of the peak Ca2+ current was found under a variety of pulse protocols. 4. Using one such pulse protocol, linearity between the Ca2+ transient rate of rise and the magnitude of the peak Ca2+ current was also found when Ca2+ currents assessed at one potential were reduced in magnitude during the onset of block by application of Co2+. Using the same pulse protocol, linearity between the Ca2+ transient rate of rise and the magnitude of the peak Ca2+ current was also found when use of Cs+ was avoided by blocking K+ currents with extracellular TEA and 4-aminopyridine. Linearity in the relationship between the Ca2+ transient rate of rise and the magnitude of the peak Ca2+ current was also found when Ca2+ transients were measured using the low affinity Ca2+ indicator Oregon Green 488 Bapta 5N in place of fluo-3. 5. These results appear to indicate that the cardiac ryanodine receptor is capable of being activated by only one calcium ion. Alternative interpretations of the data are discussed.

The relationship between strength and function in females with juvenile rheumatoid arthritis.

OBJECTIVE: To describe the relationship between isokinetic concentric and eccentric quadriceps strength and function in females with juvenile rheumatoid arthritis (JRA). METHODS: Twenty girls with JRA aged 6 to 16 years participated in the study. Function and strength were measured on one occasion. Isokinetic concentric and eccentric quadriceps torque was measured on the Kin-Com dynamometer. Function was measured with the Childhood Health Assessment Questionnaire (CHAQ) and the Canada Fitness Award 50 m run. Pain and joint count were taken as measures of disease activity. Pain was assessed on a visual analog scale through parent- and self-report. Correlations between function, standardized torque values, pain, and joint count were determined. Stepwise multiple regression analyses with function as the predicted variable were performed. RESULTS: Correlations between standardized torque and CHAQ scores were moderate (r = -0.48, p = 0.03 for concentric torque and r = -0.43, p = 0.06 for eccentric). Correlations between torque and run scores were also moderate (r = -0.48, p = 0.03 for concentric, r = -0.31, p = 0.19 for eccentric). Pain and total joint count were the best predictors of CHAQ score (r2 = 0.80), while concentric torque was the best predictor of running ability (r2 = 0.23). CONCLUSION: Quadriceps torque was moderately correlated to function in girls with JRA. Function as determined on the CHAQ was best predicted from measures of disease activity, while function as determined on the 50 m run was best predicted from concentric quadriceps torque. Further research is required to determine a cause-effect relationship between strength and function in girls with JRA.

A peptide corresponding to residues Asp177 to Asn208 of human cyclin A forms an alpha-helix.

Cyclins are essential activators of eukaryotic cell cycle-regulating enzymes called cyclin-dependent kinases (CDKs). The binding of cyclins to CDKs is mediated by a structural motif comprising a five-helix bundle called the cyclin fold and an additional helix (the N-terminal alpha-helix) located N-terminal to the cyclin fold. In this work, we examine, using CD and NMR spectroscopy, the structure of a 32-residue synthetic peptide derived from the segment (Asp177 to Asn208) corresponding to the N-terminal alpha-helix of human cyclin A. CD spectroscopic analysis of the peptide revealed that trifluoroethanol (TFE) can induce the peptide to assume a stable alpha-helix conformation. Two-dimensional 1H NMR spectroscopy showed that the alpha-helix is formed by the Asp181 to Cys193 segment of the peptide. The alpha-helical structure of the peptide in the TFE/H2O cosolvent was found to be identical to that in the crystal structure of intact cyclin A. Taken together, these results suggest that the N-terminal alpha-helix of cyclins may exist as an independent structural unit that plays essential functional roles in activating CDKs.

Interdomain chaperoning between PSD-95, Dlg, and Zo-1 (PDZ) domains of glutamate receptor-interacting proteins.

The multiple PSD-95, Dlg, and Zo-1 (PDZ) domain protein, glutamate receptor-interacting protein (GRIP), is involved in the clustering and trafficking of the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptor by directly binding to the cytoplasmic tail of the receptor's GluR2 subunit. Both the forth and fifth PDZ domains (PDZ4 and PDZ5) of GRIP are required for effective binding to the receptor. Using NMR and circular dichroism spectroscopic techniques, we show that PDZ5 is completely unstructured in solution. Freshly prepared PDZ4 is largely folded, but the domain can spontaneously unfold. Neither PDZ4 nor PDZ5 binds to GluR2 in solution. Unexpectedly, when PDZ4 and PDZ5 are covalently connected (i.e. PDZ45), both PDZ domains become well folded and stable in solution. The covalent linkage of the two PDZ domains is essential for proper folding of the tandem PDZ domains and its effective binding to GluR2. The interdomain chaperoning effect observed in the PDZ domains of GRIP represents a previously uncharacterized function of PDZ domains.

Measurement of extracellular fluid volume and blood volume in sheep.

Methods are described for the simultaneous measurement of extracellular fluid volume (ECFV) and plasma volume (PV) in sheep using dilution of 82Br (as sodium bromide) and 131I-labelled ovine gamma globulin. Following injection of 82Br (100 micronCi), equilibrium in blood was reached after 3 h at which time only 4% of the injected dose was in rumen water. The ECFV was measured as the mean of the 2- and 3-h bromide space after correction for the relative water content of plasma, the Gibbs-Donnan factor and the loss of 82Br into red blood cells. 131I-labelled ovine gamma globulin (20 micronCi) was injected after the 3-h 82 Br space was obtained and blood samples were taken at 10, 20, 30 and 40 min. In 16 determinations in 11 sheep (25-47 kg body weight) the mean (+/- s.e.m.) ECFV was 9112 +/- 289 ml (or 245 +/- 9 ml/kg). The mean PV for 16 observations in 11 sheep measured together with ECFV was 1597 +/- 62 ml (or 42-8 +/- 1-8 ml/kg). Although there was no relationship between body weight and PV there was a significant correlation between ECFV and body weight and also significant negative correlations between body weight and ECFV or PV when these were expressed as a function of body weight. The variation in ECFV measured on four occasions over 7-10 days in four sheep was 3-5% (range 2-6-4-6%). For PV measured in two animals on two consecutive days at the same time as ECFV the coefficient of variation was 1-5 and 2-1%. Acute sodium depletion (250-670 mmol) by parotid duct cannulation in three sheep resulted in a fall in ECFV which would account for only 15-20% of the sodium deficit. The remainder is presumably derived from ruminal sodium stores.

Formation of a native-like beta-hairpin finger structure of a peptide from the extended PDZ domain of neuronal nitric oxide synthase in aqueous solution.

Neuronal nitric oxide synthase (nNOS) is targeted to the cell membrane via interactions of its extended PDZ domain with PDZ domains of membrane-associated proteins including PSD-95 and alpha1-syntrophin. The formation of heterodimers between the nNOS PDZ domain and the PDZ domains of nNOS-binding proteins requires a stretch of continuous amino-acid residues C-terminal to the canonical nNOS PDZ domain. In this work, we show that a 27-residue peptide comprising the C-terminal extension of the extended nNOS PDZ domain is capable of binding to PSD-95. The structure of the 27-residue peptide in aqueous solution was determined using multidimensional NMR-spectroscopic techniques. The free peptide adopts a native-like beta-hairpin finger structure in aqueous solution. The results indicate that the C-terminal extension peptide of the nNOS PDZ domain may represent a relatively independent structural unit in the mediation of the interaction between nNOS and PDZ domain-containing proteins including PSD-95 and alpha1-syntrophin.

Effects of outer mouth mutations on hERG channel function: a comparison with similar mutations in the Shaker channel.

The fast-inactivation process in the hERG channel can be affected by mutations in the pore or S6 domain, similar to the C-type inactivation in the Shaker channel. However, differences in the kinetics and voltage dependence of inactivation between these two channels suggest that different structural determinants may be involved. To explore this possibility, we mutated a serine in the outer mouth region of hERG (S631) to residues of different physicochemical properties and compared the resulting changes in the channel's inactivation process with those resulting from mutations of an equivalent position in the Shaker channel (T449). The most dramatic differences are seen when this position is occupied by a charged residue: S631K and S631E disrupted C-type inactivation in hERG, whereas T449K and T449E facilitate C-type inactivation in Shaker. S631K and S631E also disrupted the K selectivity of hERG pore, a change not seen in T449K or T449E of Shaker. To further study why there are such differences, we replaced S631 with cysteine. This allowed us to manipulate the properties of thiol groups at position 631 and correlate side-chain properties here with changes in channel function. S631C behaved like the wild-type channel when the thiol groups were in the reduced state. Oxidizing thiol groups with H2O2 or modifying them with MTSET or MTSES disrupted C-type inactivation and K selectivity, similar to the phenotype of S631K and S631E. The same thiol-modifying maneuvers did not affect the wild-type channel function. Our results suggest differences in the outer mouth structure between hERG and Shaker, and we propose a "molecular spring" hypothesis to explain these differences.