Organometallic Ionic Plastic Crystals Incorporating Cationic Half-Sandwich Complexes.

Ionic plastic crystals (IPCs), characterized by nearly spherical molecular ions, exhibit remarkable solid-state characteristics including high ionic conductivity. However, most IPCs are organic onium salts. Incorporating organometallic half-sandwich complexes into IPCs is challenging owing to their low-symmetry structures. This paper introduces a novel series of IPCs composed of salts derived from half-sandwich organometallic complexes. We synthesized five salts of [Ru(Cp)(tmeda)(CO)]X (tmeda = N,N,N',N'-tetramethyl-1,2-ethanediamine, X = anion) with different anions and examined their phase behavior, crystal structures, and molecular motion in the solid-state. Salts featuring the CPFSA (= 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonimide), B(CN)4-, and FSA- (= (FSO2)2N-) anions underwent phase transitions to an IPC phase with a CsCl-type structure in the temperature range of 327-364 K. Employing smaller anions led to an increase in the transition temperature. In each salt, the coordination number, representing the number of anions surrounding one cation, remained eight in IPC and low-temperature phases. However, salts containing smaller anions (CF3BF3- and PF6-) displayed a rotator phase rather than the IPC phase. In these cases, the coordination numbers were six at low temperatures.

Neural Drive and Motor Unit Characteristics of the Serratus Anterior in Individuals With Scapular Dyskinesis.

OBJECTIVE: Scapular dyskinesis is one of the causes of shoulder disorders and involves muscle weakness in the serratus anterior. This study investigated whether motor unit (MU) recruitment and firing property, which are important for muscle exertion, have altered in serratus anterior of the individuals with scapular dyskinesis. METHODS: Asymptomatic adults with (SD) and without (control) scapular dyskinesis were analyzed. Surface electromyography (sEMG) waveforms were collected at submaximal voluntary contraction of the serratus anterior. The sEMG waveform was decomposed into MU action potential amplitude (MUAPAMP), mean firing rate (MFR), and recruitment threshold. MUs were divided into low, moderate, and high thresholds, and MU recruitment and firing properties of the groups were compared. RESULTS: High-threshold MUAPAMP was significantly smaller in the SD group than in the control group. The control group also exhibited recruitment properties that reflected the size principle, however, the SD group did not. Furthermore, the SD group had a lower MFR than the control group. CONCLUSIONS: Individuals with scapular dyskinesis exhibit altered MU recruitment properties and lower firing rates of the serratus anterior; this may be detrimental to muscle performance. Thus, it may be necessary to improve the neural drive of the serratus anterior when correcting scapular dyskinesis.

Structures, Thermal Properties, and Reactivities of Cationic Rh-cod Complexes in Solid State (cod = 1,5-Cyclooctadiene).

Cationic rhodium complexes with 1,5-cyclooctadiene (cod) ligands are important organometallic compounds that are useful as precatalysts; however, their solid-state structures and thermal properties have not been adequately investigated. In this study, we synthesized [Rh(cod)L]X (L = cod, C6H6, PhMe; X = SbF6, (FSO2)2N (= FSA), CF3BF3, CB11H12) and investigated their phase behaviors, crystal structures, and reactivities. The phase transitions of these salts result in disordered solid-state structures. Moreover, the structural disorder increases with a decrease in the cation symmetry in the SbF6 salts; [Rh(cod)(PhMe)]SbF6 exhibits a rotator phase, and the cations in other salts exhibit a dynamic rotational disorder. In contrast, a lower crystal symmetry with less cation disorder is observed for FSA salts. The thermal stabilities and reactivities of these salts were further investigated. FSA salts with arene ligands produce anion-coordinated complexes upon melting, and SbF6 salts with arene ligands produce [Rh(cod)L'2]SbF6 (L' = MeCN and SMe2) via an in situ single-crystal-to-single-crystal ligand-exchange reaction.

Movement control during one-leg standing is important for the bone mineral density maintenance or improvement.

INTRODUCTION: Both hip fracture and bone mineral density (BMD) decline on the non-fractured side are more likely to occur within 1 year. However, there are no longitudinal study reports on the factors associated with BMD maintenance or improvement within the first year after hip fracture. This study aimed to investigate the factors influencing the neck BMD maintenance or improvement in patients with hip fractures from within 2 weeks-6 months after surgery. MATERIALS AND METHODS: Patients were hip fracture after surgery and were divided into two groups: Among neck BMD changes (6 months minus 2 weeks after surgery) were calculated. Based on among neck BMD change, patients were classified into the BMD maintenance or improvement (change ≥ 0) and the BMD decrease groups (change < 0). Propensity score matching was performed to adjust for confounding factors. To predict the factors affecting neck BMD, hierarchical logistic regression analysis was performed. The dependent variable was the BMD maintenance or improvement group and the BMD decrease group. The independent variables were basic and medical information, and physical functions. RESULTS: The hierarchical logistic regression analysis results showed that movement control during one-leg standing affected femoral neck BMD independently from age, sex. The odds ratio for movement control during one-leg standing was 8.22. The discrimination rate of the model was 69.7%. CONCLUSION: This study suggested that adequate movement control during one-leg standing is important to maintain or improve neck BMD.

Association between movement control during one-leg standing and femoral BMD in patients with hip fractures.

INTRODUCTION: Prior studies have focused only on the temporal component of one-leg standing, no reports have examined the relationship between the qualitative components of one-leg standing and femoral BMD. Thus, this study investigated whether quality (i.e., movement control) of one-leg standing also associated femoral BMD. MATERIALS AND METHODS: A total of 80 patients with unilateral hip fracture were included in a cross-sectional study. Basic and medical information and physical functions including movement control during one-leg standing were assessed at admission and 2 weeks after surgery, respectively. Hierarchical multiple regression analysis was performed to identify predictors of femoral BMDs on the non-fractured side. Dependent variables included femoral neck and total hip BMDs in models 1 and 2, respectively. RESULTS: Hierarchical multiple regression analysis (standardized partial regression coefficients) in model 1 identified age (- 0.18), sex (0.38), body mass index (BMI) (0.41), movement control during one-leg standing on the non-fractured side (0.19), and life-space assessment (0.17) as factors associating femoral neck BMD. Meanwhile, hierarchical multiple regression analysis (standardized partial regression coefficients) in model 2 identified age (- 0.12), sex (0.36), BMI (0.37), and movement control during one-leg standing on the non-fractured side (0.25) as factors associating total hip BMD. The coefficients of determination adjusted for degrees of freedom (R2) were 0.529 and 0.470 for models 1 and 2, respectively. CONCLUSION: Our results suggest that improving movement control during one-leg standing may be important for maintaining and improving femoral BMD on the non-fractured side.

Factors Affecting Quality of Life at Discharge among Patients with Osteoporotic Vertebral Fractures.

OBJECTIVES: This study aimed to identify factors, including physical functions and activities that affect quality of life (QOL) at discharge among patients with osteoporotic vertebral fractures. METHODS: Patients with osteoporotic vertebral fractures were included in our prospective cohort study. Multiple regression analysis was performed to determine the predictors of QOL at discharge using two models: model 1, basic medical information and physical functions at admission, and model 2, basic medical information, physical function, and activity after 4 weeks of admission. RESULTS: Multiple regression analysis (standard partial regression coefficients) using model 1 identified L2 to L4 bone mineral density (-0.2), Visual Analog Scale for pain during activity at admission (-0.31), and Revised Hasegawa Dementia Scale (HDS-R) score at admission (0.64) as factors affecting QOL at discharge. Multiple regression analysis using model 2 identified HDS-R at admission (0.64), Pain Catastrophizing Scale score at 4 weeks (-0.34), and knee extension muscle strength at 4 weeks (0.28) as factors affecting QOL at discharge. CONCLUSIONS: Our results suggest that if patients have high bone mineral density, intense pain, and low cognitive function at admission, then low QOL at discharge will be predicted; however, improvement of pain catastrophizing and knee extension muscle strength during first the 4 weeks of admission may be able to improve QOL at discharge. Because patients in this study were Japanese only, it is important to exercise caution when applying our results to other populations.

Theoretical study of a simple rotational-echo double-resonance NMR for homonuclear spin-1/2 pairs.

We investigate theoretically intriguing aspects of a simple rotational-echo double-resonance (REDOR) NMR technique for homonuclear spin-1/2 pairs undergoing MAS. The simple technique sets Gaussian soft π pulses at every half MAS rotational period in the pulse sequence. The reduction in rotational echo amplitude (the REDOR echo reduction) is observed at the end of the evolution period te = (n + 1)Tr, where Tr is a MAS rotational period. The exact average Hamiltonians for the homonuclear REDOR (hm-REDOR) technique are calculated by dividing the evolution period into four periods. We show theoretically and experimentally that the hm-REDOR technique produces the REDOR echo reductions for homonuclear spin-1/2 pairs. In addition, the theoretical results reveal that the REDOR echo reductions are independent of the chemical-shift difference, δ, under a simple condition of κ = δ/ωr ≥ 6 and te < 10 ⋅ (1/d'), where ωr is the sample spinning frequency and d' is the dipolar coupling constant expressed in Hz. We call this simple condition the master condition. This means that the REDOR echo reductions for a homonuclear spin-1/2 pair can be calculated under the master condition by considering only d' and ωr , which is the case for a heteronuclear spin pair. Finally, we demonstrate that four-phase cycling yields the multiple-quantum filtered hm-REDOR experiment, where the appearance of the REDOR echo reductions shows that the echo reductions are definitely attributable to the homonuclear dipolar interaction even if there is a slight unwanted effect from the recovered chemical-shift anisotropy in these reductions.

Improvement of muscle quality assessed using the phase angle is influenced by recovery of knee extension strength in patients with hip fractures.

BACKGROUND AND AIMS: Studies reported that knee extension strength on the operated side in patients with hip fractures was not recovered to the level on the non-operated side 6 months after surgery or later. In a cross-sectional study, we revealed that a reduction in isometric knee extension muscle strength on the operated side in patients with hip fractures approximately 6 months after surgery was associated with not only a reduction in skeletal muscle mass but also a reduction in muscle quality, characterized by a reduction in the phase angle (PhA). Furthermore, the mechanisms of knee extension strength improvement can be clarified in more detail using the minimal significant change as the index of recovery. However, no longitudinal studies have examined the factors for knee extension strength improvement based on the minimal significant change in patients with hip fractures 6 months after surgery. This study aimed to longitudinally examine the factors influencing the recovery of knee extension strength based on the minimal significant change in patients with hip fractures between 2 weeks and approximately 6 months after surgery. METHODS: In this study, the outcomes used were basic and medical information, PhA, skeletal muscle index (SMI), pain, one-leg standing time, movement control during one-leg standing, and walking speed. For PhA, SMI, pain, one-leg standing time, movement control during one-leg standing, and walking speed, the amount of change was calculated by subtracting the data at 2 weeks from the data at 6 months. Group classification was determined by dividing the patients into two groups using a previous study as a reference: recovery group if the knee extension strength value approximately 6 months after surgery minus that 2 weeks after surgery was ≥3.3 kgf and non-recovery group if the value was <3.3 kgf. Logistic regression analysis was performed to explore the association between the recovery and non-recovery groups. RESULTS: The recovery group contained 55 patients, while the non-recovery group comprised 35 patients. The only significant factor associated with knee extension muscle strength in the recovery group was the amount of change in PhA. The odds ratio for the amount of change in PhA was 2.26. The discrimination rate of the model was 62.5%. CONCLUSIONS: Our results suggest that recovery of knee extension strength in patients with hip fractures after surgery was mainly because of improvements in muscle quality, not improvements in muscle mass or pain.

Crystal structures and phase-transition dynamics of cobaltocenium salts with bis(perfluoroalkylsulfonyl)amide anions: remarkable odd-even effect of the fluorocarbon chains in the anion.

Crystal structures and thermal properties of cobaltocenium salts with bis(perfluoroalkylsulfonyl)amide (C(n)F2(n+1)SO2)2N anions [n = 0 (1), 1 (1 a), 2 (1 b), 3 (1 c), and 4 (1 d)] and the 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonylamide anion (2) were investigated. In these solids, the cations are surrounded by four anions around their C5 axis, and stacking of these local structures forms two kinds of assembled structures. In the salts with even n (1, 1 b, and 1 d), the cation and anion are arranged alternately to form mixed-stack columns in the crystal. In contrast, in the salts with odd n (1 a and 1 c), the cations and anions independently form segregated-stack columns. An odd-even effect was also observed in the sum of the phase-change entropies from crystal to melt. All of the salts exhibited phase transitions in the solid state. The phase transitions to the lowest-temperature phase in 1, 1 a, and 2 are accompanied by order-disorder of the anions and symmetry lowering of the space group, which results in the formation of an ion pair. Solid-state (13)C NMR measurements on 1 a and 1 b revealed enhanced molecular motions of the cation in the higher-temperature phases.

Reduced upper and lower limb muscle strengths without reduced skeletal muscle in elderly patients with heart failure.

Objective: This study aimed to characterize the muscle strength and skeletal muscle mass of patients with heart failure by investigating hand-grip strength, five times sit-to-stand (5STS) results, and skeletal muscle mass index (SMI). Materials and Methods: Muscle strength was assessed based on hand-grip strength and 5STS, while skeletal muscle mass was assessed using a bioelectrical impedance analyzer. Hierarchical logistic regression analysis was performed to explore the association between patients with heart failure and healthy elderly individuals. Results: Hierarchical logistic regression analysis was performed to examine the muscle strength and skeletal muscle mass characteristics in patients with heart failure. Hand-grip strength and 5STS responses but not SMI outcomes differed significantly between the two groups. The results of the hierarchical logistic regression analysis revealed that the hand-grip strength and 5STS were significant predictors of heart failure. The odds ratios for hand-grip strength and 5STS were 1.44 and 0.53, respectively. Conclusion: Our results suggested that upper and lower limb muscle strengths (handgrip strength and 5STS) in elderly patients with heart failure worsened significantly without a decrease in skeletal muscle mass.

Frailty in elderly patients with acute heart failure increases readmission.

BACKGROUND: The readmission rate of heart failure (HF) patients has not decreased during the past few years. OBJECTIVES: The purpose of this study was to examine whether factors such as left ventricular ejection fraction (LVEF) and frailty are associated with readmission and number of readmissions in HF patients. METHODS: First, a propensity score matching method was used to adjust for confounding factors for readmission. Cox regression analysis was conducted to determine the factors that influenced readmission. Finally, multiple regression analysis was conducted to determine the factors that influenced the number of readmissions. The independent variables were basic and medical information, physical structure, physical functions, and activity for both Cox regression analysis and multiple regression analysis. RESULTS: After matching based on the propensity score, 18 out of 18 (100.0%) patients in the readmission group (age: 85.0 ± 6.9 years, female rate: 50.0%, body mass index: 21.7 ± 3.4 kg/m2) and 18 out of 51 (35.3%) patients in the nonreadmission group (age: 84.3 ± 8.6, female rate: 50.0%, body mass index: 21.8 ± 4.5 kg/m2) were eligible for analysis. Cox regression analysis (hazard ratios) showed that sex (0.16), geriatric nutritional risk index (1.02), and degree of frailty (11.44) were extracted as significant factors. Multiple regression analysis (standardized regression coefficients) showed that the estimated glomerular filtration rate (-0.40), LVEF (-0.32), and degree of frailty (0.29) were extracted as significant factors. CONCLUSION: Our results suggest that frailty is important to reduce the readmission rate and number of readmissions of the acute HF patients.

Not only muscle mass but also muscle quality is associated with knee extension muscle strength in patients with hip fractures.

Our results revealed that the decrease in isometric knee extension muscle strength on the operated and nonoperated sides in patients with hip fractures was associated with not only a decrease in skeletal muscle mass but also a decrease in muscle quality, characterized by a decreased PhA. PURPOSE: This study aimed to assess the relationship between isometric knee extension muscle strength on the operated or nonoperated sides and PhA in patients with hip fractures at approximately 6 months postoperatively. METHODS: This study was a cross-sectional study. Skeletal muscle index (SMI), PhA, knee extension muscle strength on the operated and nonoperated sides, and other physical function variables were assessed at approximately 6 months postoperatively. To identify predictors of knee extension muscle strength on the operated and nonoperated sides, hierarchical multiple regression analysis was performed. RESULTS: A total of 90 patients with hip fractures were included (mean age, 80.1 ± 6.9 years). SMI (0.45) and PhA on the operated side (0.27) were the significant associated factors extracted for isometric knee extension muscle strength on the operated side (standardized partial regression coefficients), independent of age, sex, and body mass index (BMI). Movement control during one-leg standing on the nonoperated side (0.26), SMI (0.32), and PhA on the nonoperated side (0.40) were the significant associated factors extracted for isometric knee extension muscle strength on the nonoperated side, independent of age, sex and BMI. CONCLUSIONS: Our results revealed that the decrease in isometric knee extension muscle strength on the operated and nonoperated sides in patients with hip fractures at approximately 6 months postoperatively was associated with not only a decrease in skeletal muscle mass but also a decrease in muscle quality, characterized by a decreased PhA.

Ionic liquids of cationic sandwich complexes.

Simple cationic sandwich complexes that contained alkyl- or halogen substituents provided ionic liquids (ILs) with the bis(perfluoroalkanesulfonyl)imide anion. Ferrocenium- and cobaltocenium ILs [M(C(5)H(4)R(1))(C(5)H(4)R(2))][Tf(2)N] (M=Fe, Co) and arene-ferrocenium ILs [Fe(C(5)H(4)R(1))(C(6)H(5)R(2))][Tf(2)N] were prepared and their physical properties were investigated. A detailed comparison of their thermal properties revealed the effects of molecular symmetry and substituents on their melting points. Their viscosity increased on increasing the length of the substituent on the cation and the perfluoroalkyl chain length on the anion. Upon cooling, ILs with low viscosities exhibited crystallization, whereas those with higher viscosities tended to exhibit glass transitions. Most of these salts showed phase transitions in the solid state. A magnetic-switching phenomenon was observed for the paramagnetic ferrocenium IL, which was associated with a liquid/solid transformation, based on the magnetic anisotropy of the ferrocenium cation. (57)Fe Mössbauer spectroscopy was applied to [Fe(C(5)H(4)nBu)(2)][Tf(2)N] to investigate the vibrational behavior of the iron atom in the crystal and glassy states of the ferrocenium IL.

Convergent neutral gas injection using supersonic gas puffing (SSGP) method for propellant feeding system in RF electric propulsion.

A convergent gas feeding method is proposed to alleviate neutral gas depletion near the central plasma region in typical electrodeless radio-frequency (RF)/helicon plasma thrusters. To achieve further performance improvement, the SuperSonic Gas Puffing (SSGP) system is one of the methods that is expected to overcome the above-mentioned depletion and the density limit. This study discovered that the spatiotemporal profiles of the neutral pressure and the estimated gas diffusion angle vary depending on the SSGP gas feeding condition, i.e., the nozzle size, filling pressure, and the valve opening time. Convergent gas feeding is successfully conducted using the SSGP method in a vacuum. As a preliminary study, high-density plasma is also obtained in the vicinity of the gas injection region using the developed SSGP system. The effects of the gas feeding position and an external divergent magnetic field on the plasma density are investigated. A suitable gas feeding position/region exists for plasma generation using the RF/helicon plasma thruster.

Physical Functions and Comorbidity Affecting Collapse at 4 or More Weeks after Admission in Patients with Osteoporotic Vertebral Fractures: A Prospective Cohort Study.

STUDY DESIGN: A prospective cohort study. PURPOSE: This study aimed to reveal physical functions and comorbidity affecting collapse at ≥4 weeks after hospital admission of patients with osteoporotic vertebral fracture. OVERVIEW OF LITERATURE: Only a few studies have investigated the influence of physical function and activity on collapse in patients with osteoporotic vertebral fractures. METHODS: This prospective cohort study analyzed patients with osteoporotic vertebral fractures admitted to the hospital between March 2018 and October 2019. Logistic regression analysis was performed to explore the predictors of vertebral collapse at >4 weeks after admission. Model 1 used basic medical information and physical functions at admission; model 2 used basic medical information and physical function and activity at >4 weeks after admission. RESULTS: In the model 1 results of logistic regression analysis, cardiovascular disease (odds ratio [OR], 12.27; 95% confidence interval [CI], 1.28-117.91) was extracted as a factor affecting vertebral collapse at ≥4 weeks after admission. In the model 2 results of logistic regression analysis, cardiovascular disease (OR, 34.57; 95% CI, 2.53-471.74), movement control during one leg standing at 4 weeks (OR, 7.25; 95% CI, 1.36-38.71), and Pain Catastrophizing Scale score at 4 weeks (OR, 1.11; 95% CI, 1.01-1.21) were extracted as factors affecting vertebral collapse at ≥4 weeks after admission. CONCLUSIONS: Our results indicate that physical functions and comorbidity affect collapse at ≥4 weeks after admission in patients with osteoporotic vertebral fractures.

High-resolution solid-state NMR investigation of the phase transition in decamethylferrocene-acenaphthenequinone charge-transfer complex.

A charge-transfer complex composed of decamethylferrocene (D) and acenaphthenequinone (A) was prepared. The material was a 1:1 neutral complex with a mixed-stack structure and exhibited a phase transition at -16 degrees C. High-resolution (13)C and (1)H NMR spectroscopy revealed that an inclination of A with respect to D occurs below the phase-transition temperature. The (1)H spin-diffusion rates of the complex undergoing high-speed magic-angle spinning (MAS) were measured to determine the shortest (1)H-(1)H distance r between D and A. To analyze the experimental results, we derived the analytical expression of the spin-diffusion rate W(z) for a homonuclear multispin system undergoing MAS. It was found that W(z) for the complex is proportional only to 1/r(6) under high-speed MAS conditions. On the basis of this relationship and the crystal structure at 20 degrees C, it was determined that the shortest (1)H-(1)H distance r at -27.7 degrees C (below the phase transition temperature) is 0.4 A shorter than that at 20 degrees C. Given this information, a plausible model of the low-temperature structure is discussed.

High-resolution NMR spectra of n-alkanes penetrating into carbon fibers and of protons in carbon fibers.

We present a simple NMR method for microscopically exploring the local environment in carbon fibers. The method utilizes n-alkanes as probe molecules, where the n-alkanes penetrate carbon fibers of interest. The high-resolution (1)H NMR spectra for a mixture of a carbon fiber and n-alkanes acquired by this method show a shift of the resonance line, which is due to the local structure of the fiber. The utility of this method is discussed on the basis of the (1)H NMR spectra obtained. In addition, the (1)H distribution and the local motion in the structure of the carbon fiber are revealed in view of the (1)H NMR spectra.

Sensitization of head and neck squamous cell carcinoma cells to Fas-mediated apoptosis by the inhibition of Bcl-X(L) expression.

BACKGROUND: Various types of malignant tumor cells are known to acquire resistance to Fas receptor (Fas)-mediated apoptosis. In Fas-sensitive cells, Fas-mediated apoptosis is observed when anti-Fas antibody is bound to Fas. Bcl-2 and Bcl-X(L) are representative anti-apoptosis proteins reported to be capable of suppressing Fas-mediated apoptosis. OBJECTIVE: To investigate the mechanism of resistance acquisition to Fas-mediated apoptosis in cultured human head and neck squamous cell carcinoma cells (HNSCCs). METHODS AND RESULTS: We applied an anti-Fas antibody (CH11) to Fas-expressing HNSCCs (HSC-2) and the CH11 did not induce cell death in HSC-2. Treatment with actinomycin D (ActD) converted the phenotypes of HSC-2 from CH11-resistant to CH11-sensitive. Western blot analysis showed no differences between ActD-treated and ActD-untreated HSC-2 in the expression of Bcl-2. On the other hand, the expression of Bcl-X(L) was greatly reduced in ActD-treated HSC-2. Moreover, the reduction of Bcl-X(L) by specific antisense oligonucleotide treatment enhanced the CH11-induced cell death of HSC-2. CONCLUSION: Our data suggest that Fas-signaling might be regulated by a Bcl-X(L)-inhibitable step in CH11-resistant HSC-2.

Inhibition of caspase-9 activity and Apaf-1 expression in cisplatin-resistant head and neck squamous cell carcinoma cells.

We have previously reported that cisplatin induces caspase-9 (Casp9) activation in head and neck squamous cell carcinoma cells in vitro (HNSCCs). Our purpose here was to examine whether HNSCCs selected for resistance to cisplatin fail to exhibit Casp9 activation in response to cisplatin. The cisplatin-resistant HNSCCs (HSC-2CR) were selected from cisplatin-sensitive HNSCCs (HSC-2) for growth in the presence of cisplatin. Following cisplatin treatment, protelyzed Casp9 subunits were detected in HSC-2, but not detected in HSC-2CR. Using a direct enzymatic assay measuring cleavage of the synthetic peptide substrate (LEHD-AFC), Casp9 activity in cisplatin-treated HSC-2CR was less than that in cisplatin-treated HSC-2. Apoptotic protease-activating factor 1 (Apaf-1) has been shown to participate as an adaptor molecule in Casp9 activation. In the presence of cytochrome c (Cyt c) released from mitochondria, Apaf-1 binds to Casp9 and causes its activation. HSC-2 expressed 2-fold higher levels of Apaf-1 compared with HSC-2CR. On the other hand, following cisplatin treatment, the same degree of increase in cytoplasmic Cyt c was detected in both HSC-2 and HSC-2CR. These results suggest that in a certain type of HNSCCs, the inhibition of Casp9 activity and Apaf-1 expression may represent a mechanism of acquired cisplatin resistance.