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This study shows the application of AI image generators with fine-tuning to the Kansei engineering design process. Kansei engineering is a method for surveying and analyzing users' latent feelings and preferences to product and service development (Nagamachi, 1991, 2011).. There are several common difficulties in applying Kansei engineering, including a lack of variety in evaluation samples, the need for non-designers to participate in the design process, and the fact that designers are often too busy to fully engage in the design process. In order to address these challenges, we have applied an AI image generator, StableDiffusion (Rombach et al. 2021),to the Kansei engineering design process. The "Hypernetworks" framework to fine-tune StableDiffusion in order to make better representation of the shape and appearance of milk cartons. Based on previous Kansei engineering study on milk cartons (Ishihara et al., 1996) , several attempts are shown to use AI-generated designs to create innovative and visually appealing milk carton designs, including designs incorporating red and blue colors and abstract shapes, and a design inspired by the abstract paintings of Jackson Pollock. The authors conclude that the use of AI technology can be a valuable tool in boosting innovative design through Kansei engineering, and that further research is needed to explore the potential for interaction between humans and AI in the design process.

Introduction Quantitative measurement of anti-A/-B antibody titers is important during ABO-incompatible living kidney transplantation (ABOi-LKT). Methods We conducted a multi-institutional study to measure the antibody titers using the automated column agglutination technique (auto-CAT) and tube test (TT) method in ABOi-LKT recipients. Statistical analysis was performed to evaluate the two methods. Results We examined 111 samples from 35 ABOi-LKT recipients at four institutions. The correlation coefficient of the two methods was >0.9; the concordance rate and clinically acceptable concordance rate for the IgG titers were 60.4% and 88.3%, respectively. Perioperative status did not influence the statistical significance. Parallel changes were observed in the IgG antibody titers measured using the auto-CAT or TT technique by desensitizing therapy in time-course monitoring. Conclusion Auto-CAT is comparable with the TT technique and is feasible for IgG anti-A/B antibody titration in ABOi-LKT recipients. This article is protected by copyright. All rights reserved.

This article seeks to characterize the seed husk fiber of Moringa oleifera and understand its influence when added to a cementitious composite, in terms of mechanical performance. Moringa fibers were chemically and physically tested and were added to a cementitious composite. Specimens were molded for Ultrasonic Speed Pulse test and Uniaxial Compression Strength test, and subsequent observation in SEM. The results show a fiber with high lignin content and high absorption of water. Adding fiber to the composite, the water in the mixture is absorbed, which reduces the formation of hydrated cement compounds over time. Consequently, it results in a composite with low mechanical strength. The fiber/matrix interface analyzed in the micrographs is porous, has microcracks and a high concentration of calcium hydroxide. Despite this, the same lignin content that impairs mechanical strength in this composite is what makes the fiber resistant to weathering. More studies regarding the effectiveness of this quality should be carried out.

Strong inward rectifier K+ (sKir) channels determine the membrane potentials of many types of excitable and nonexcitable cells, most notably the resting potentials of cardiac myocytes. They show little outward current during membrane depolarization (i.e., strong inward rectification) because of the channel blockade by cytoplasmic polyamines, which depends on the deviation of the membrane potential from the K+ equilibrium potential (V – EK) when the extracellular K+ concentration ([K+]out) is changed. Because their open-channel conductance is apparently proportional to the “square root” of [K+]out, increases/decreases in [K+]out enhance/diminish outward currents through sKir channels at membrane potentials near their reversal potential, which also affects, for example, the repolarization and action-potential duration of cardiac myocytes. Despite its importance, however, the mechanism underlying the [K+]out dependence of the open sKir channel conductance has remained elusive. By studying Kir2.1, the canonical member of the sKir channel family, we first show that the outward currents of Kir2.1 are observed under the external K+-free condition when its inward rectification is reduced and that the complete inhibition of the currents at 0 [K+]out results solely from pore blockade caused by the polyamines. Moreover, the noted square-root proportionality of the open sKir channel conductance to [K+]out is mediated by the pore blockade by the external Na+, which is competitive with the external K+. Our results show that external K+ itself does not activate or facilitate K+ permeation through the open sKir channel to mediate the apparent external K+ dependence of its open channel conductance. The paradoxical increase/decrease in outward sKir channel currents during alternations in [K+]out, which is physiologically relevant, is caused by competition from impermeant extracellular Na+.

The human ability to texture pattern recognition is very high and precise. Although details of texture significantly affect Kansei, grasping texture features in quantitative methods have been difficult. We have analyzed wallpaper texture patterns and Kansei, with Principal Component Analysis, 2-dimensional FFT (Fast Fourier Transfer) and Convolutional Neural Networks. Principal Component Analysis showed the Kansei structure on wallpapers. 2D FFT results are used for revealing specific relations between spectrum features and Kansei evaluation. Convolutional neural networks have learned to be Kansei visual recognition system and integrative feature analyzer. 2DFFT was used to analyze 3 significant samples that differ only on texture. Square staggered texture, small and large rhombus textures have different FFT patterns. The planar frequency patterns suggest different Kansei perceptions. CNN has learned as “transfer learning” based on pre-trained networks. Pattern perception and relations between Kansei structures were successfully learned. Interpolations for unlearned patterns were also investigated.

BACKGROUND Inward rectifier K channels of the Kir2.x subfamily are widely expressed in neuronal tissues, controlling neuronal excitability. Previous studies reported that local anesthetics (LAs) do not affect Kir2 channels. However, the effects have not been studied at large concentrations used in regional anesthesia. METHODS This study used the patch-clamp technique to examine the effects of bupivacaine and lidocaine on Kir2.1, Kir2.2, and Kir2.3 channels expressed in human embryonic kidney 293 cells. RESULTS When applied extracellularly in whole-cell recordings, both LAs inhibited Kir2.x currents in a voltage-independent manner. Inhibition with bupivacaine was slow and irreversible, whereas that with lidocaine was fast and reversible. Kir2.3 displayed a greater sensitivity to bupivacaine than Kir2.1 and Kir2.2 (50% inhibitory concentrations at approximately 5 minutes, 0.6 vs 8-10 mM), whereas their sensitivities to lidocaine were similar (50% inhibitory concentrations, 1.5-2.7 mM). Increases in the charged/neutral ratio of the LAs at an acidic extracellular pH attenuated their inhibitory effects, and a permanently charged lidocaine derivative QX-314 exhibited no effects when applied extracellularly. Inside-out experiments demonstrated that inhibition of Kir2.1 with cytoplasmic lidocaine and QX-314 was rapid and reversible, whereas that induced by bupivacaine was slow and irreversible. Furthermore, dose-inhibition relations for the charged form of bupivacaine and lidocaine obtained at different cytoplasmic pHs could be approximated by a single relation for each LA. CONCLUSIONS The results indicate that both LAs at clinical concentrations equilibrated rapidly with the intracellular milieu, differentially inhibiting Kir2.x channel function from the cytoplasmic side.

Inward rectifier K + channels of the Kir2.x subfamily play important roles in controlling the neuronal excitability. Although their cellular localization in the brain has been extensively studied, only a few studies have examined their expression in the spinal cord and peripheral nervous system. In this study, immunohistochemical analyses of Kir2.1, Kir2.2, and Kir2.3 expression were performed in rat dorsal root ganglion (DRG) and spinal cord using bright-field and confocal microscopy. In DRG, most ganglionic neurons expressed Kir2.1, Kir2.2 and Kir2.3, whereas satellite glial cells chiefly expressed Kir2.3. In the spinal cord, Kir2.1, Kir2.2 and Kir2.3 were all expressed highly in the gray matter of dorsal and ventral horns and moderately in the white matter also. Within the gray matter, the expression was especially high in the substantia gelatinosa (lamina II). Confocal images obtained using markers for neuronal cells, NeuN, and astrocytes, Sox9, showed expression of all three Kir2 subunits in both neuronal somata and astrocytes in lamina I–III of the dorsal horn and the lateral spinal nucleus of the dorsolateral funiculus. Immunoreactive signals other than those in neuronal and glial somata were abundant in lamina I and II, which probably located mainly in nerve fibers or nerve terminals. Colocalization of Kir2.1 and 2.3 and that of Kir2.2 and 2.3 were present in neuronal and glial somata. In the ventral horn, motor neurons and interneurons were also immunoreactive with the three Kir2 subunits. Our study suggests that Kir2 channels composed of Kir2.1–2.3 subunits are expressed in neuronal and glial cells in the DRG and spinal cord, contributing to sensory transduction and motor control.

We developed a bedsore-prevention mattress and wheel chair cushion. Throughout development, we made numerous body pressure measurements on different mattresses and cushions. Such measurements required much time and effort. Simulation of body pressure has the potential to estimate the pressure distribution caused by physical parameters of different mattresses. In this study, we show attempts to model the body and estimate the pressure on its transverse plane. The computation was based on a non-linear finite element method with hyperelastic materials, such as muscle, skin and fat. Because the model simulates different tissues, we can estimate the pressure not only on the surface, but also that inside the trunk. The simulated results agreed well with actual pressure measurement results. Differences in physical properties of the mattresses were also modeled.

Expression of hyperpolarization-activated cyclic nucleotide-gated channels (HCN1-4) on distal dendrites of neurons is suggested to modify synaptic integration in the central nervous system. However, the mechanisms of dendritic localization are not fully understood. Recent studies have revealed that S-palmitoylation plays an important role in the enrichment of various molecules at the postsynaptic membrane. Thus, we performed an acyl-biotinyl exchange assay, and found that HCN1, HCN2, and HCN4, but not HCN3, were S-palmitoylated in HEK293 cells. Mutation of multiple intracellular cysteine residues at the N-terminus of HCN2 was required for complete inhibition of S-palmitoylation. However, this mutagenesis had a minimal effect on surface expression of HCN2 proteins or electrophysiological properties of HCN2 current when expressed in HEK293 cells or in Xenopus oocytes. These findings provide insight into the physiological roles of S-palmitoylation of HCN channels in native neurons.

The conductance of the strong inward rectifier K+ channel depends on the “square root” of the extracellular K+ concentration. The present study shows that this physiologically important phenomenon is caused by a channel blockade by extracellular Na+, which is competitive with extracellular K+., Strong inward rectifier K+ (sKir) channels determine the membrane potentials of many types of excitable and nonexcitable cells, most notably the resting potentials of cardiac myocytes. They show little outward current during membrane depolarization (i.e., strong inward rectification) because of the channel blockade by cytoplasmic polyamines, which depends on the deviation of the membrane potential from the K+ equilibrium potential (V – EK) when the extracellular K+ concentration ([K+]out) is changed. Because their open-channel conductance is apparently proportional to the “square root” of [K+]out, increases/decreases in [K+]out enhance/diminish outward currents through sKir channels at membrane potentials near their reversal potential, which also affects, for example, the repolarization and action-potential duration of cardiac myocytes. Despite its importance, however, the mechanism underlying the [K+]out dependence of the open sKir channel conductance has remained elusive. By studying Kir2.1, the canonical member of the sKir channel family, we first show that the outward currents of Kir2.1 are observed under the external K+-free condition when its inward rectification is reduced and that the complete inhibition of the currents at 0 [K+]out results solely from pore blockade caused by the polyamines. Moreover, the noted square-root proportionality of the open sKir channel conductance to [K+]out is mediated by the pore blockade by the external Na+, which is competitive with the external K+. Our results show that external K+ itself does not activate or facilitate K+ permeation through the open sKir channel to mediate the apparent external K+ dependence of its open channel conductance. The paradoxical increase/decrease in outward sKir channel currents during alternations in [K+]out, which is physiologically relevant, is caused by competition from impermeant extracellular Na+.

We have conducted a series of experiments aimed at improving the design of body brush handles. This study recruited eight female and 13 male university students between the ages of 19 and 21. Three prototype body brushes (A, C, and D), and an existing commercial design (B) were tested. The prototype handles were made from two parallel stainless-steel wires and a plastic base, and each design was uniquely curved. The existing product, B, had a straight wooden handle. Electromyography (EMG) was recorded at the biceps brachii and flexor digitorum profundus while the participants aligned the brush head with the centers of their backs. A significantly lower EMG integral was measured with prototype C, and prototypes A and C both received positive Kansei evaluations. Then, two new designs (samples E and F) based on A were compared with B. Six men between the ages of 30 and 60 years participated in these second experiments. A final design was selected based on the results and the refined model will be marked in July 2017.

ObjectiveMolecular epidemiology is a promising tool for understanding tuberculosis transmission dynamics but has not been sufficiently utilised in Asian countries including Japan. The aim of this study was to estimate the proportion of TB cases attributable to recent transmission and to identify risk factors of genotype clustering and the development of large clusters within 3 years in an urban setting in Japan.Design and settingLong-term cross-sectional observational study combining the characteristics of patients with culture-positive TB notified in Shinjuku City, Tokyo (2002–2013), with genotype data ofMycobacterium tuberculosis.Primary outcome measureGenotype clustering rate and association between genotype clustering status and explanatory variables.ResultsAmong 1025 cases, 515 were localised within 113 genotype clusters. The overall clustering rate was 39.2%. Significantly higher rates were found in patients aged ConclusionOur results indicated that a large proportion of patients with culture-positive TB were involved in the recent TB transmission chain. Foreign-born persons still have a limited impact on transmission in the Japanese urban setting. Intensified public health interventions, including the active case finding, need to focus on individuals with socioeconomic risk factors that are significantly associated with tuberculosis transmission and clusters with shorter registration intervals between the first two cases.

We report a case of rheumatoid arthritis in which the earliest symptom was bilateral paratendonitis of the Achilles tendons, followed by paratendonitis of a finger extensor. A series of musculoskeletal ultrasonograms revealed a progression from paratendonitis of the extensor tendon to erosive synovitis of the adjacent metacarpophalangeal joint. High-resolution ultrasonography combined with power Doppler imaging seems to be a useful and convenient tool both for diagnosing paratendonitis early and for closely monitoring the progressing inflammation.

The natural product austocystin D was identified as a potent cytotoxic agent with in vivo antitumor activity and selectivity for cells expressing the multidrug resistance transporter MDR1. We sought to elucidate the mechanism of austocystin D's selective cytotoxic activity. Here we show that the selective cytotoxic action of austocystin D arises from its selective activation by cytochrome P450 (CYP) enzymes in specific cancer cell lines, leading to induction of DNA damage in cells and in vitro. The potency and selectivity of austocystin D is lost upon inhibition of CYP activation and does not require MDR1 expression or activity. Furthermore, the pattern of cytotoxicity of austocystin D was distinct from doxorubicin and etoposide and unlike aflatoxin B(1), a compound that resembles austocystin D and is also activated by CYP enzymes to induce DNA damage. Theses results suggest that austocystin D may be of clinical benefit for targeting or overcoming chemoresistance.

The aim of this study was to characterize the pathological conditions of symptomatic ankles in patients with rheumatoid arthritis (RA) using power Doppler sonography (PDS). We analyzed 17 consecutive ultrasonography (US) records of RA patients with symptomatic ankles who underwent B-mode ultrasonography (BUS) combined with PDS of their ankles in our department because of clinical need. Correlations between US findings and clinical and serological data were assessed. The diagnostic capabilities of BUS and PDS were also compared. Common US findings were talocrural synovitis (76%), subtalar synovitis (71%), and talonavicular synovitis (59%). Tenosynovitis around the ankle was detected in ten patients (59%), including several cases of tenosynovitis of tibialis posterior (41%) and tenosynovitis of peroneus longus and brevis (35%). Achilles tendon enthesitis was detected in six patients, and retrocalcaneal bursitis was detected in five. Compared with BUS, PDS offers demonstrably superior diagnostic capability for the detection of rheumatoid ankle diseases, especially subtalar joint synovitis and peroneal tenosynovitis. Rheumatoid factor (RF) levels were significantly higher in patients with tenosynovitis than in patients without tenosynovitis. PDS is an excellent modality for diagnosing both intra- and extracapsular synovitis in rheumatoid ankles. Using PDS, we found positive association between ankle tenosynovitis and RF levels in RA patients.

Heteromultimerization of different pore-forming subunits is known to contribute to the diversity of inward rectifier K(+) channels. We examined if the subunits belonging to different subfamilies Kir2 and Kir3 can co-assemble to form heteromultimers in heterologous expression systems. We observed co-immunoprecipitation of Kir2.1 and Kir3.1 as well as Kir2.1 and Kir3.4 in HEK293T cells. Furthermore, analyses of subcellular localization using confocal microscopy revealed that co-expression of Kir2.1 promoted the cell surface localization of Kir3.1 and Kir3.4 in HEK293T cells. In electrophysiological experiments, co-expression of Kir2.1 with Kir3.1 and/or Kir3.4 in Xenopus oocytes and HEK293T cells did not yield currents with distinguishable features. However, co-expression of a dominant-negative Kir2.1 with the wild-type Kir3.1/3.4 decreased the Kir3.1/3.4 current amplitude in Xenopus oocytes. The results indicate that Kir2.1 is capable of forming heteromultimeric channels with Kir3.1 and with Kir3.4.

PurposeGift flowers should be chosen to depict a message with the sender's kansei and are bound by nature of flowers and social manners, to maintain social relationship between the sender and the recipient. Few buyers, but most florists, have expert knowledge of the flowering time, scent, price, and nature of each flower, and are experts in arranging flowers that meet a given purpose. The purpose of this paper is to incorporate handling constraints into the inference process of a kansei engineering system.Design/methodology/approachThe paper collected the expert knowledge concerning nature of flowers, composing flower arrangements and social manners on gifts from specialists of flower arrangements including a florist and special books. At the same time, kansei evaluation experiments on the kinds of flowers and colors were conducted. The expertise and the results of kansei experiments were organized into a flower database and inference rules for choice of a main flower, arrangement shapes and combination flowers. The rules were implemented as server‐side programs. Users input information about the recipient, purpose of the arrangement and purchase information using a web browser. The system outputs a solution; a list of main flowers, combination flowers, greens and the shape of arrangement.FindingsTraditional kansei engineering studies revealed the relationships between design elements and kansei with developing new analyzing methods. Different constraints come into the actual product design and manufacturing should be integrated with findings obtained from the kansei evaluation to successfully utilize kansei engineering for product development.Practical implicationsThe inference rules will be able to tell the reasons for choosing the main‐ and combination flowers and arrangement shapes to satisfy the customers.Originality/valueThe proposed system suggests the original arrangement of flowers unlike most online florists selling ready‐made arrangements. The paper shows a solution to incorporate different constraints underlying in a real production process into the inference process based on the result of kansei analysis.

The outward component of the strong inward rectifier K+ current (IKir) plays a pivotal role in polarizing the membranes of excitable and non-excitable cells and is regulated by voltage-dependent channel block by internal cations. Using the Kir2.1 channel, we previously showed that a small fraction of the conductance susceptible only to a low-affinity mode of block likely carries a large portion of the outward current. To further examine the relevance of the low-affinity block to outward IKir and to explore its molecular mechanism, we studied the block of the Kir2.1 and Kir2.2 channels by spermine, which is the principal Kir2 channel blocker. Current–voltage relations of outward Kir2.2 currents showed a peak, a plateau and two peaks in the presence of 10, 1 and 0.1 μm spermine, respectively, which was explained by the presence of two conductances that differ in their susceptibility to spermine block. When the current–voltage relations showed one peak, like those of native IKir, outward Kir2.2 currents were mediated mostly by the conductance susceptible to the low-affinity block. They also flowed in a narrower range than the corresponding Kir2.1 currents, because of 3- to 4-fold greater susceptibility to the low-affinity block than in Kir2.1. Reducing external [K+] shifted the voltage dependences of both the high- and low-affinity block of Kir2.1 in parallel with the shift in the reversal potential, confirming the importance of the low-affinity block in mediating outward IKir. When Kir2.1 mutants known to have reduced sensitivity to internal blockers were examined, the D172N mutation in the transmembrane pore region made almost all of the conductance susceptible only to low-affinity block, while the E224G mutation in the cytoplasmic pore region reduced the sensitivity to low-affinity block without markedly altering that to the high-affinity block or the high/low conductance ratio. The effects of these mutations support the hypothesis that Kir2 channels exist in two states having different susceptibilities to internal cationic blockers.

The strong inward rectification of the whole cell Kir2.1 current, which is very similar to the cardiac inward rectifier K+ current (IK1), is caused by voltage-dependent blockade of outward currents by the intracellular polyamines spermine and spermidine. We recently showed that macroscopic Kir2.1 currents obtained from inside-out patches in the presence of various concentrations of cytoplasmic polyamines are well explained by the sum of the currents through two populations of channels that show differing susceptibilities to polyamine blockade. The outward currents obtained with 5–10 μm cytoplasmic spermine showed current–voltage relationships similar to those of IK1 and were considered to flow mostly through a small population of channels exhibiting lower spermine sensitivity. Here we used inside-out patches to examine the blockade of macroscopic Kir2.1 currents by cytoplasmic Mg2+ in the absence and presence of cytoplasmic spermine. Outward currents were blocked by 0.6 and 1.1 mm Mg2+ in a concentration-dependent manner, but a small fraction (∼0.1) of the macroscopic conductance was resistant to Mg2+ at those concentrations, suggesting there are two populations of Kir2.1 channels with different sensitivities to Mg2+. Furthermore, at those concentrations, Mg2+ blocked inward currents by inducing a shallow blocked state that differed from the deeper state causing the inward rectification. In the presence of 1.1 mm Mg2++ 5 μm spermine, Mg2+ blocked a substantial current component during depolarizing pulses and generated transient outward components, which is consistent with findings from earlier whole-cell experiments. In the steady state, Mg2+ blocked the currents at voltages around and negative to the reversal potential and induced sustained outward components. The steady-state and time-dependent current amplitudes and the fractional blockades caused by spermine and Mg2+ could be quantitatively explained by a model in which Mg2+ competes with spermine to block the high-affinity channel and induces three conductance states. The present results suggest that the outward IK1 flows through two populations of channels with different sensitivities to cytoplasmic blockers.

The outward component of the strong inward rectifier potassium current, I(K1), is significantly larger in ventricles than in atria of the heart, resulting in faster repolarization at the final phase of the action potential in ventricles. However, the underlying mechanism of the difference in I(K1) remains poorly understood. I(K1) channels are composed of subunits from the Kir2 subfamily, and I(K1) amplitude is determined by the voltage-dependent blockade of the channel by the intracellular polyamines spermine and spermidine, and by Mg(2+). Using a perforated patch-clamp method, which minimizes changes in the intracellular polyamine and Mg(2+) concentrations, we detected repolarization-induced outward I(K1) transients, which are caused by competition between Mg(2+) and spermine to block the channel, in ventricular but not in atrial myocytes from guinea-pig heart. The contribution of the Kir2.3 subunit to the I(K1) channel was found to be minor in the guinea-pig heart, because the activation time course of the Kir2.3 currents was approximately 10-fold slower than those of I(K1), and the marked external pH sensitivity of the Kir2.3 currents was not found in I(K1). Both the Kir2.1 and Kir2.2 currents recorded from inside-out patches exhibited outward transients similar to those of ventricular I(K1) in the presence of 5-10 microM spermine and 0.6-1.1 mM Mg(2+), and their amplitudes were diminished by increasing the spermine or spermidine concentrations. The total and free polyamine concentrations in guinea-pig cardiac tissues were higher in atria than ventricles. These results strongly suggest that different intracellular polyamine concentrations are responsible for the difference in atrial and ventricular I(K1) of the guinea-pig heart.

A questionnaire study was undertaken of more than 2800 elderly people aged 60 years and over and living at home, to investigate the relationship between their performance of some instrumental activities of daily living (IADLs) and their visual abilities. The IADL measured the ability of elderly participants to pick up coins, manage monthly financial matters, use the telephone and take medication as recommended. Visual abilities were assessed by means of each subject's answers to questions relating to resolution, focus, adaptation to bright or to dim lighting, dynamic acuity, distance perception and colour vision. The types of visual functions that, together with age and gender, contribute to determining the level of independence in the performance of IADL activities were identified using logistic regression analysis. The results indicated that elderly participants who had problems with either distance perception or yellowish vision also tended to have difficulties in picking up coins, using the telephone ...

The strong inward rectifier K+ current, IK1, shows significant outward current amplitude in the voltage range near the reversal potential and thereby causes rapid repolarization at the final phase of cardiac action potentials. However, the mechanism that generates the outward IK1 is not well understood. We recorded currents from the inside-out patches of HEK 293T cells that express the strong inward rectifier K+ channel Kir2.1 and studied the blockage of the currents caused by cytoplasmic polyamines, namely, spermine and spermidine. The outward current–voltage (I–V) relationships of Kir2.1, obtained with 5–10μm spermine or 10–100μm spermidine, were similar to the steady-state outward I–V relationship of IK1, showing a peak at a level that is ∼20mV more positive than the reversal potential, with a negative slope at more positive voltages. The relationships exhibited a plateau or a double-hump shape with 1μm spermine/spermidine or 0.1μm spermine, respectively. In the chord conductance–voltage relationships, there were extra conductances in the positive voltage range, which could not be described by the Boltzmann relations fitting the major part of the relationships. The extra conductances, which generated most of the outward currents in the presence of 5–10μm spermine or 10–100μm spermidine, were quantitatively explained by a model that considered two populations of Kir2.1 channels, which were blocked by polyamines in either a high-affinity mode (Mode 1 channel) or a low-affinity mode (Mode 2 channel). Analysis of the inward tail currents following test pulses indicated that the relief from the spermine block of Kir2.1 consisted of an exponential component and a virtually instantaneous component. The fractions of the two components nearly agreed with the fractions of the blockages in Mode 1 and Mode 2 calculated by the model. The estimated proportion of Mode 1 channels to total channels was 0.9 with 0.1–10μm spermine, 0.75 with 1–100μm spermidine, and between 0.75 and 0.9 when spermine and spermidine coexisted. An interaction of spermine/spermidine with the channel at an intracellular site appeared to modify the equilibrium of the two conformational channel states that allow different modes of blockage. Our results suggest that the outward IK1 is primarily generated by channels with lower affinities for polyamines. Polyamines may regulate the amplitude of the outward IK1, not only by blocking the channels but also by modifying the proportion of channels that show different sensitivities to the polyamine block.

Arginine residue at position 285 (R285) in the intracellular C-terminal domain of inward rectifier potassium channel Kir2.2 is conserved in many species, but missing in previously reported human Kir2.2 sequences. We here identified the human Kir2.2 gene in normal individuals, which contained R285 in the deduced amino-acid sequence (hKir2.2/R285). All 30 individuals we examined were homozygous for Kir2.2/R285 gene. The hKir2.2/R285 was electrophysiologically functional in both mammalian cells and Xenopus oocytes. However, the hKir2.2 missing R285 was functional only in Xenopus oocytes, but not in mammalian cells. Thus, R285 in Kir2.2 is important for its functional expression in mammalian cells.