Characterization of Course and Terrain and Their Effect on Skier Speed in World Cup Alpine Ski Racing

World Cup (WC) alpine ski racing consists of four main competition disciplines (slalom, giant slalom, super-G and downhill), each with specific course and terrain characteristics. The International Ski Federation (FIS) has regulated course length, altitude drop from start to finish and course setting in order to specify the characteristics of the respective competition disciplines and to control performance and injury-related aspects. However to date, no detailed data on course setting and its adaptation to terrain is available. It is also unknown how course and terrain characteristics influence skier speed. Therefore, the aim of the study was to characterize course setting, terrain geomorphology and their relationship to speed in male WC giant slalom, super-G and downhill. The study revealed that terrain was flatter in downhill compared to the other disciplines. In all disciplines, variability in horizontal gate distance (gate offset) was larger than in gate distance (linear distance from gate to gate). In giant slalom the horizontal gate distance increased with terrain inclination, while super-G and downhill did not show such a connection. In giant slalom and super-G, there was a slight trend towards shorter gate distances as the steepness of the terrain increased. Gates were usually set close to terrain transitions in all three disciplines. Downhill had a larger proportion of extreme terrain inclination changes along the skier trajectory per unit time skiing than the other disciplines. Skier speed decreased with increasing steepness of terrain in all disciplines except for downhill. In steep terrain, speed was found to be controllable by increased horizontal gate distances in giant slalom and by shorter gate distances in giant slalom and super-G. Across the disciplines skier speed was largely explained by course setting and terrain inclination in a multiple linear model.     

Kinetic analysis of ski turns based on measured ground reaction forces

The objective of this study was to devise a method of kinetic analysis of the ground reaction force that enables the durations and magnitudes of forces acting during the individual phases of ski turns to be described exactly. The method is based on a theoretical analysis of physical forces acting during the ski turn. Two elementary phases were defined: (1) preparing to turn (initiation) and (2) actual turning, during which the center of gravity of the skier-ski system moves along a curvilinear trajectory (steering). The starting point of the turn analysis is a dynamometric record of the resultant acting ground reaction force applied perpendicularly on the ski surface. The method was applied to six expert skiers. They completed a slalom course comprising five gates arranged on the fall line of a 26° slope at a competition speed using symmetrical carving turns (30 evaluated turns). A dynamometric measurement system was placed on the carving skis (168 cm long, radius 16 m, data were recorded at 100 Hz). MATLAB procedures were used to evaluate eight variables during each turn: five time variables and three force variables. Comparison of the turn analysis results between individuals showed that the method is useful for answering various research questions associated with ski turns.     

Impaired mitochondrial function and reduced viability in bone marrow cells of obese mice

Bone marrow cells (BMCs) are the main type of cells used for transplantation therapies. Obesity, a major world health problem, has been demonstrated to affect various tissues, including bone marrow. This could compromise the success of such therapies. One of the main mechanisms underlying the pathogenesis of obesity is mitochondrial dysfunction, and recent data have suggested an important role for mitochondrial metabolism in the regulation of stem cell proliferation and differentiation. Since the potential use of BMCs for clinical therapies depends on their viability and capacity to proliferate and/or differentiate properly, the analysis of mitochondrial function and cell viability could be important approaches for evaluating BMC quality in the context of obesity. We therefore compared BMCs from a control group (CG) and an obese group (OG) of mice and evaluated their mitochondrial function, proliferation capacity, apoptosis, and levels of proteins involved in energy metabolism. BMCs from OG had increased apoptosis and decreased proliferation rates compared with CG. Mitochondrial respiratory capacity, biogenesis, and the coupling between oxidative phosphorylation and ATP synthesis were significantly decreased in OG compared with CG, in correlation with increased levels of uncoupling protein 2 and reduced peroxisome proliferator-activated receptor-coactivator 1α content. OG also had decreased amounts of the glucose transporter GLUT-1 and insulin receptor (IRβ). Thus, Western-diet-induced obesity leads to mitochondrial dysfunction and reduced proliferative capacity in BMCs, changes that, in turn, might compromise the success of therapies utilizing these cells.     

Stochastic 16-state model of voltage gating of gap-junction channels enclosing fast and slow gates

Gap-junction (GJ) channels formed of connexin (Cx) proteins provide a direct pathway for electrical and metabolic cell-cell interaction. Each hemichannel in the GJ channel contains fast and slow gates that are sensitive to transjunctional voltage (Vj). We developed a stochastic 16-state model (S16SM) that details the operation of two fast and two slow gates in series to describe the gating properties of homotypic and heterotypic GJ channels. The operation of each gate depends on the fraction of Vj that falls across the gate (VG), which varies depending on the states of three other gates in series, as well as on parameters of the fast and slow gates characterizing 1), the steepness of each gate's open probability on VG; 2), the voltage at which the open probability of each gate equals 0.5; 3), the gating polarity; and 4), the unitary conductances of the gates and their rectification depending on VG. S16SM allows for the simulation of junctional current dynamics and the dependence of steady-state junctional conductance (gj,ss) on Vj. We combined global coordinate optimization algorithms with S16SM to evaluate the gating parameters of fast and slow gates from experimentally measured gj,ss-Vj dependencies in cells expressing different Cx isoforms and forming homotypic and/or heterotypic GJ channels.     

Inhibition of prostaglandin synthesis in human endothelial cells treated with metabolic inhibitors.

Endothelial cell injury is often associated with increased synthesis of prostaglandin (PG)I2. We observed, however, that endothelial cells treated with metabolic inhibitors which reduce cellular ATP content develop an injury pattern characterized by reduced PGI2 synthesis. This study examined the relationship between cell injury, arachidonic acid metabolism and ATP content in human umbilical vein endothelial cells treated with 2-deoxyglucose (2DG), a glycolytic inhibitor, and oligomycin (OG), a respiratory chain inhibitor. Either inhibitor alone significantly reduced cellular ATP concentrations, but only OG reduced basal PG synthesis. The combination of 2DG and OG, however, was more effective than either agent alone in reducing cellular ATP content (greater than or equal to 50% of control) and inhibiting basal and agonist-stimulated PGI2 synthesis. This reduced PGI2 synthesis preceded 51chromium release, lactic dehydrogenase release and was not associated with a net release of arachidonic acid from cell membranes. Histamine, A23187 and bradykinin stimulated PGI2 synthesis in untreated but not in 2DG and OG treated cells. Exogenous arachidonic acid increased PGI2 synthesis to a similar extent in both 2DG and OG treated and untreated cells. Therefore, reduced PG synthesis in 2DG and OG treated endothelial cells is not due to inhibition of cyclooxygenase. Furthermore, reduced PG synthesis in these cells occurs prior to cell injury and is not strictly associated with cellular ATP depletion.     

The Effect of Local Delivery Doxycycline and Alendronate on Bone Repair

The aim of the present study was to investigate the local effect of 10% doxycycline and 1% alendronate combined with poly(lactic-co-glycolic acid) (PLGA) on bone repair. Thirty rats were divided into three groups, as follows: control group (CG), drug group (DG), and vehicle-PLGA group (VG). Bone defect was created in the right femur and filled with the following: blood clot (CG); PLGA gel, 10% doxycycline and 1% alendronate (DG); or vehicle-PLGA (VG). The animals were euthanized 7 or 15 days after surgery. Bone density, bone matrix and number of osteoclasts were quantified. At 7 days, the findings showed increased density in DG (177.75?±?76.5) compared with CG (80.37?±?27.4), but no difference compared with VG (147.1?±?41.5); no statistical difference in bone neoformation CG (25.6?±?4.8), VG (27.8?±?4), and DG (18.9?±?7.8); and decrease osteoclasts in DG (4.6?±?1.9) compared with CG (26.7?±?7.4) and VG (17.3?±?2.7). At 15 days, DG (405.1?±?63.1) presented higher density than CG (213.2?±?60.9) and VG (283.4?±?85.8); there was a significant increase in percentage of bone neoformation in DG (31.5?±?4.2) compared with CG (23?±?4), but no difference compared with VG (25.1?±?2.9). There was a decreased number of osteoclasts in DG (20.7?±?4.7) and VG (29.5?±?5.4) compared with CG (40?±?9.4). The results suggest that the association of 10% doxycycline and 1% alendronate with PLGA-accelerated bone repair.     

Inhibition of prostaglandin synthesis in human endothelial cells treated with metabolic inhibitors

Endothelial cell injury is often associated with increased synthesis of prostaglandin (PG)I₂. We observed, however, that endothelial cells treated with metabolic inhibitors which reduce cellular ATP content develop an injury pattern characterized by reduced PGI₂ synthesis. This study examined the relationship between cell injury, arachidonic acid metabolism and ATP content in human umbilical vein endothelial cells treated with 2-deoxyglucose (2DG), a glycolytic inhibitor, and oligomycin (OG), a respiratory chain inhibitor. Either inhibitor alone significantly reduced cellular ATP concentrations, but only OG reduced basal PG synthesis. The combination of 2DG and OG, however, was more effective than either agent alone in reducing cellular ATP content (≥ 50% of control) and inhibiting basal and agonist-stimulated PGI₂ synthesis. This reduced PGI₂ synthesis preceded ⁵¹ chromium release, lactic dehydrogenase release and was not associated with a net release of arachidonic acid from cell membranes. Histamine, A23187 and bradykinin stimulated PGI₂ synthesis in untreated but not in 2DG and OG treated cells. Exogenous arachidonic acid increased PGI₂ synthesis to a similar extent in both 2DG and OG treated and untreated cells. Therefore, reduced PG synthesis in 2DG and OG treated endothelial cells is not due to inhibition of cyclooxygenase. Furthermore, reduced PG synthesis in these cells occurs prior to cell injury and is not strictly associated with cellular ATP depletion.     

The 28th Conference of the International Society for Chronobiology (ISC) will be held in Bucharest (Romania), at Ramada Parc Hotel on 4–8 June 2014

The eclosion rhythm of a laboratory population of Drosophila melanogaster was studied under 12h light, 12h dark (LD 12:12) cycles. Although most of the flies were found to eclose just after “lights on” in LD 12:12, termed within gate (WG) flies, a few flies were found to eclose nearly 10h after peak eclosion, termed outside gate (OG) flies. The circadian parameters of the clocks controlling oviposition rhythms in the WG and the OG flies were estimated to understand the cause of such differences in the timing of eclosion. The distribution of the fraction of individual flies exhibiting single, multiple, and no significant period in the WG flies was significantly different from distribution in the OG flies. Compared to the WG flies, more OG flies were found to exhibit oviposition rhythm with multiple periodicity, whereas more WG flies exhibited an oviposition rhythm with a single significant period. The fraction of flies with arrhythmic oviposition was similar in both the WG and the OG flies. Free-running period τ in constant darkness (DD) and the phase angle difference ψ in LD 12:12 for the oviposition rhythm of WG and OG flies were significantly different. These results suggest that the differences in the time of eclosion between the flies eclosing within the gate and outside the gate of eclosion are probably due to differences in the circadian system controlling eclosion, which is reflected by the differences in their oviposition rhythm. (Chronobiology International, 18(4), 601–612, 2001)     

Does the difference in the timing of eclosion of the fruit fly Drosophila melanogaster reflect differences in the circadian organization?

The eclosion rhythm of a laboratory population of Drosophila melanogaster was studied under 12h light, 12h dark (LD 12:12) cycles. Although most of the flies were found to eclose just after “lights on” in LD 12:12, termed within gate (WG) flies, a few flies were found to eclose nearly 10h after peak eclosion, termed outside gate (OG) flies. The circadian parameters of the clocks controlling oviposition rhythms in the WG and the OG flies were estimated to understand the cause of such differences in the timing of eclosion. The distribution of the fraction of individual flies exhibiting single, multiple, and no significant period in the WG flies was significantly different from distribution in the OG flies. Compared to the WG flies, more OG flies were found to exhibit oviposition rhythm with multiple periodicity, whereas more WG flies exhibited an oviposition rhythm with a single significant period. The fraction of flies with arrhythmic oviposition was similar in both the WG and the OG flies. Free-running period τ in constant darkness (DD) and the phase angle difference ψ in LD 12:12 for the oviposition rhythm of WG and OG flies were significantly different. These results suggest that the differences in the time of eclosion between the flies eclosing within the gate and outside the gate of eclosion are probably due to differences in the circadian system controlling eclosion, which is reflected by the differences in their oviposition rhythm. (Chronobiology International, 18(4), 601-612, 2001)     

Quantitation of binding, recovery and desalting efficiency of peptides and proteins in solid phase extraction micropipette tips

Micropipette-tip solid phase extraction (SPE) systems are common in proteomic analyses for desalting and concentrating samples for mass spectrometry, removing interferences, and increasing sensitivity. These systems are inexpensive, disposable, and highly efficient. Here, we show micropipette-tip solid phase extraction is a direct sample preparation method for (14)C-accelerator mass spectrometry (AMS), removing salts or reagent from labeled macromolecules. We compared loading, recovery and desalting efficiency in commercially available SPE micro-tips using (14)C-labeled peptides and proteins, AMS, and alpha spectrometry ion energy loss quantitation. The polypropylene in the tips was nearly (14)C-free and simultaneously provided low-background carrier for AMS. The silica material did not interfere with the analysis. Alpha spectrometry provided an absolute measurement of desalting efficiency.     

Electrostatic state of the cytoplasmic domain influences inactivation at the selectivity filter of the KcsA potassium channel

KcsA is a proton-activated K⁺ channel that is regulated at two gates: an activation gate located in the inner entrance of the pore and an inactivation gate at the selectivity filter. Previously, we revealed that the cytoplasmic domain (CPD) of KcsA senses proton and that electrostatic changes of the CPD influences the opening and closing of the activation gate. However, our previous studies did not reveal the effect of CPD on the inactivation gate because we used a non-inactivating mutant (E71A). In the present study, we used mutants that did not harbor the E71A mutation, and showed that the electrostatic state of the CPD influences the inactivation gate. Three novel CPD mutants were generated in which some negatively charged amino acids were replaced with neutral amino acids. These CPD mutants conducted K⁺, but showed various inactivation properties. Mutants carrying the D149N mutation showed high open probability and slow inactivation, whereas those without the D149N mutation showed low open probability and fast inactivation, similar to wild-type KcsA. In addition, mutants with D149N showed poor K⁺ selectivity, and permitted Na⁺ to flow. These results indicated that electrostatic changes in the CPD by D149N mutation triggered the loss of fast inactivation and changes in the conformation of selectivity filter. Additionally, the loss of fast inactivation induced by D149N was reversed by R153A mutation, suggesting that not only the electrostatic state of D149, but also that of R153 affects inactivation.     

Vesicle-micelle transition of phosphatidylcholine and octyl glucoside elucidated by cryo-transmission electron microscopy.

Vesicle-micelle transition structures of egg phosphatidylcholine (PC) and octyl glucoside (OG) mixtures were observed in the vitrified hydrated state by cryo-transmission electron microscopy (cryo-TEM) and correlated with the macroscopic and molecular changes previously associated with micellization monitored by 90 degrees light scattering and resonance energy transfer between fluorescent lipid probes. Several distinct structural changes occurred as OG was added to the PC vesicles. First, the average vesicle size decreased from 160 nm to less than 66 nm with no apparent change or decrease in optical density (OD). Then, associated with a small rise in OD, samples with open vesicles were observed coexisting with pieces of lamellae and long cylindrical micelles; more micelles were seen at higher [OG]. This mixture of vesicles and cylindrical micelles occurred in the region of the phase diagram previously attributed to vesicle opening, and possibly vesicle size increase. At higher [OG], small spheroidal micelles coexisting with cylindrical micelles correlated with a decrease in OD and changes in the fluorescence signal. At high [OG] when the solution appeared clear, spheroidal micelles were the dominant structure. By using cryo-TEM, a technique which preserves the original microstructure of fluid systems and provides direct images at 1 nm resolution, we have elucidated the vesicle-micelle transition and identified intermediates not known previously in the PC/OG system.     

The effect of time of day on short-term maximal performance in obese and non-obese young men

The purpose of this study was to examine time-of-day effects on short-term performance in obese young men. In a balanced study design, 30 boys were divided into two groups: obese (OG; n = 15) and non-obese (CG; n = 15) groups. Both groups performed anaerobic tests of strength and power (squat-Jump, SJ; counter-movement jump, CMJ; 10-m sprint; and 30-m sprint) at 08:00 and 17:00 h on separate days. The results showed morning–evening differences in all variables in CG, with significant increases at 17:00 h (around the time of peak temperature) in comparison with 08:00 h (p < 0.01) for OG. However, such morning-evening differences were not found in the OG, except for the 30-m sprint. Obesity affects the diurnal variation on performances of 30-m sprint with a significant decrease in the evening for OG of 1.23% (p < 0.01). A correlation between anaerobic performance and oral temperature was observed only in the 30-m sprint test. In conclusion, the findings of the present study indicated that obesity is a problem that can affect circadian rhythms and performance in obese young men; therefore, preventing childhood obesity should become a top priority in efforts to improve performance and health.     

Cow traffic in relation to social rank and motivation of cows in an automatic milking system with control gates and an open waiting area

Cow traffic in automatic milking (AM) systems can be controlled with gates at the entrances to feeding areas, where cows are either let through (gate opens) or redirected (gate remains closed) to an open waiting area in front of the milking unit (MU). The motivation of a cow to enter the MU after a redirection is assumed to be reflected in redirection time, which is the elapsed time from a redirection in a control gate (CG) until the next registration in the MU (i.e. CG → milking in MU/passage through MU). In order to study the possibility of guiding cows in this kind of system and to increase the understanding for the emergence of redirection time, a behavior study was performed at the Swedish University of Agricultural Sciences, Uppsala, Sweden. Two groups of 12 cows each (high and low social rank, respectively) in an AM-system with control gates and an open waiting area were used as focal cows. After a redirection in a CG, the location of each focal cow was continuously observed until entrance in the MU or during a maximum observation time of 1 h. This was repeated five times for each focal cow, generating 120 observations in total. The social rank of the cows was established from registered visits to roughage stations. Cows of high social rank spent, on an average, 13 min in the waiting area during the observation period, compared to 20 min for cows of low social rank. In 22% of all observations, the cows entered cubicles in a resting area during the 1 h observation period and when they did, they, on an average, spent 41 min of the 1 h long observation time in the cubicles. Both time since last feeding and time since last milking were in negative relationship to redirection time. The number of cows in the waiting area significantly prolonged the redirection time. Redirection time was influenced by individual characteristics, such as social rank and by situation-specific factors, such as time since last feeding, time since last milking and the number of cows in the waiting area.     

Multi-year monitoring to facilitate adult salmon passage through a temperate tidal marsh

Adult Chinook salmon, Oncorhynchus tshawytscha, were ultrasonically tagged to monitor their movements past a tidally operated salinity control-gate structure that spans the width of Montezuma Slough, an important migration pathway for anadromous fish in the Sacramento Delta. The structure consists of a section of removable flashboards, three radial gates and a boat lock. Previous studies showed that movement through Montezuma Slough was delayed or hindered for many of the tagged salmon due to installation of the flashboards and the gate closures. Three gate configurations were tested as future mitigation options to facilitate salmon movement through the gates: full open with the boat lock closed; full operation with the boat lock open; and full operation with the boat lock closed. During October to November of 2001–2004, approximately 200 adult fall-run Chinook salmon were tagged annually and monitored for passage success during different gate configurations. Relative to the closed boat lock configuration, the full open configuration had a significantly higher passage rate in 2004 only, and a significantly shorter passage time in 2001. Relative to the closed boat lock configuration, the full operation with the boat lock open configuration was correlated with improved passage rates in 2 out of 4 years, with shorter passage times in 2001, and with longer passage times in 2002. The findings from this study suggest that the open boat lock can provide additional salmon passage at the salinity control gates, but that further multi-year studies using biotelemetry to track fish movement through Montezuma Slough should be addressed in future research.     

Blm10 binds to pre-activated proteasome core particles with open gate conformation

Blm10 is bound to the yeast proteasome core particle, a crucial protease of eukaryotic cells [corrected]. Two gates, at both ends of the CP, control the access of protein substrates to the catalytic cavity of the CP. Normally, substrate access is auto-inhibited by a closed gate conformation unless regulatory complexes are bound to the CP and translocate protein substrates in an ATP-dependent manner. Here, we provide evidence that Blm10 recognizes pre-activated open gate CPs, which are assumed to exist in an equilibrium with inactive closed gate CP. Consequently, single-capped Blm10-CP shows peptide hydrolysis activity. Under conditions of disturbed CP assembly, as well as in open gate mutants, pre-activated CP or constitutively active CP, respectively, prevail. Then, Blm10 sequesters disordered and open gate CP by forming double-capped Blm10(2)-CP in which peptide hydrolysis activity is repressed. We conclude that Blm10 distinguishes between gate conformations and regulates the activation of CP.     

Effects of fucoidan on diabetic rat testicular tissue

Increased reactive oxygen species (ROS) resulting from hyperglycemia and inadequate endogenous antioxidant systems are responsible for the complications of diabetes. ROS accumulate in the cell and stimulate apoptosis, which compromises sperm quality and function. We investigated the possible effects of fucoidan, a potent antioxidant with a regulatory effect on blood glucose homeostasis, on the testicular tissues of rats with experimental diabetes. Diabetes was induced by administering 40 mg/kg streptozotocin (STZ) on five consecutive days. Twenty-four Wistar albino male rats were divided into four groups: group 1, control group (CG); group 2, diabetes group (DG); group 3, early fucoidan group (EFG) treated with 50 mg/kg fucoidan after diabetes induction; group 4, late fucoidan group (LFG) treated with the same dose of fucoidan 15 days after diabetes induction. Fucoidan was administered intraperitoneally every two days for four weeks. Basement membrane thickness and Johnsen scores were higher in the DG than in the CG; no difference was found for either the EFG or LFG compared to the CG. Seminiferous tubule diameters of EFG were significantly greater than for the DG. Apoptotic tubule and apoptotic cell indexes were significantly greater in the DG and significantly less in the EFG and LFG groups compared to the CG. Early use of fucoidan in diabetic individuals may minimize damage to testicular tissue.     

Design and analysis of a robust genetic Muller C-element

This paper presents results on the design and analysis of a robust genetic Muller C-element. The Muller C-element is a standard logic gate commonly used to synchronize independent processes in most asynchronous electronic circuits. Synthetic biological logic gates have been previously demonstrated, but there remain many open issues in the design of sequential (state-holding) logic operations. Three designs are considered for the genetic Muller C-element: a majority gate, a toggle switch, and a speed-independent implementation. While the three designs are logically equivalent, each design requires different assumptions to operate correctly. The majority gate design requires the most timing assumptions, the speed-independent design requires the least, and the toggle switch design is a compromise between the two. This paper examines the robustness of these designs as well as the effects of parameter variation using stochastic simulation. The results show that robustness to timing assumptions does not necessarily increase reliability, suggesting that modifications to existing logic design tools are going to be necessary for synthetic biology. Parameter variation simulations yield further insights into the design principles necessary for building robust genetic gates. The results suggest that high gene count, cooperativity of at least two, tight repression, and balanced decay rates are necessary for robust gates. Finally, this paper presents a potential application of the genetic Muller C-element as a quorum-mediated trigger.     

Crystal structure of the mammalian GIRK2 K+ channel and gating regulation by G proteins, PIP2, and sodium

G protein-gated K(+) channels (Kir3.1-Kir3.4) control electrical excitability in many different cells. Among their functions relevant to human physiology and disease, they regulate the heart rate and govern a wide range of neuronal activities. Here, we present the first crystal structures of a G protein-gated K(+) channel. By comparing the wild-type structure to that of a constitutively active mutant, we identify a global conformational change through which G proteins could open a G loop gate in the cytoplasmic domain. The structures of both channels in the absence and presence of PIP(2) suggest that G proteins open only the G loop gate in the absence of PIP(2), but in the presence of PIP(2) the G loop gate and a second inner helix gate become coupled, so that both gates open. We also identify a strategically located Na(+) ion-binding site, which would allow intracellular Na(+) to modulate GIRK channel activity. These data provide a structural basis for understanding multiligand regulation of GIRK channel gating.     

Fast and slow gating relaxations in the muscle chloride channel CLC-1

Gating of the muscle chloride channel CLC-1 involves at least two processes evidenced by double-exponential current relaxations when stepping the voltage to negative values. However, there is little information about the gating of CLC-1 at positive voltages. Here, we analyzed macroscopic gating of CLC-1 over a large voltage range (from -160 to +200 mV). Activation was fast at positive voltages but could be easily followed using envelope protocols that employed a tail pulse to -140 mV after stepping the voltage to a certain test potential for increasing durations. Activation was biexponential, demonstrating the presence of two gating processes. Both time constants became exponentially faster at positive voltages. A similar voltage dependence was also seen for the fast gate time constant of CLC-0. The voltage dependence of the time constant of the fast process of CLC-1, tau(f), was steeper than that of the slow one, tau(s) (apparent activation valences were z(f) approximately -0. 79 and z(s) approximately -0.42) such that at +200 mV the two processes became kinetically distinct by almost two orders of magnitude (tau(f) approximately 16 micros, tau(s) approximately 1 ms). This voltage dependence is inconsistent with a previously published gating model for CLC-1 (Fahlke, C., A. Rosenbohm, N. Mitrovic, A.L. George, and R. Rüdel. 1996. Biophys. J. 71:695-706). The kinetic difference at 200 mV allowed us to separate the steady state open probabilities of the two processes assuming that they reflect two parallel (not necessarily independent) gates that have to be open simultaneously to allow ion conduction. Both open probabilities could be described by Boltzmann functions with gating valences around one and with nonzero "offsets" at negative voltages, indicating that the two "gates" never close completely. For comparison with single channel data and to correlate the two gating processes with the two gates of CLC-0, we characterized their voltage, pH(int), and [Cl](ext) dependence, and the dominant myotonia inducing mutation, I290M. Assuming a double-barreled structure of CLC-1, our results are consistent with the identification of the fast and slow gating processes with the single-pore and the common-pore gate, respectively.