Hybrid surgery for the treatment of lumbar spine surgery complicated with iliac artery pseudoaneurysm, arteriovenous fistula, and lower limb artery embolism: A rare case report.

INTRODUCTION AND IMPORTANCE: Vascular injuries during lumbar surgery are rare, but complications such as false aneurysm of the iliac artery, arteriovenous fistula, and lower limb artery embolism are even rarer. These complications can easily be misdiagnosed and result in the inability to choose an appropriate surgical approach, leading to serious consequences. CASE PRESENTATION: A 36-year-old male patient experienced swelling in both lower limbs, along with numbness, coldness, and dysfunction in his right lower limb, after undergoing a "posterior lumbar discectomy" surgery. On the 20th day post-surgery, a clear diagnosis was established through CTV: 1) Right common iliac artery injury with pseudoaneurysm formation; 2) Right iliac arteriovenous fistula; 3) Right popliteal artery embolism. The patient underwent hybrid surgery to address multiple complications simultaneously and made a good recovery after the procedure. CLINICAL DISCUSSION: Rarely, lumbar spine surgery can concurrently lead to conditions such as pseudoaneurysm, arteriovenous fistula, and lower limb artery embolism. Due to atypical symptoms and signs, it is often misdiagnosed. Hybrid surgery involves incising the femoral artery, using a thrombectomy catheter to remove clots from the iliac artery above and the popliteal artery below, and then re-implanting a covered stent to treat pseudoaneurysm and arteriovenous fistula. CONCLUSION: With a solid clinical knowledge, one can make a timely diagnosis and choose an appropriate surgical method to intervene, thereby improving the prognosis. Hybrid surgery combines the minimally invasive and safe effects of endovascular techniques with the precise effects of open surgery, and it also allows for the simultaneous treatment of multiple comorbidities.

Hemispheric asymmetry in cortical thinning reflects intrinsic organization of the neurotransmitter systems and homotopic functional connectivity.

Hemispheric lateralization and its origins have been of great interest in neuroscience for over a century. The left-right asymmetry in cortical thickness may stem from differential maturation of the cerebral cortex in the two hemispheres. Here, we investigated the spatial pattern of hemispheric differences in cortical thinning during adolescence, and its relationship with the density of neurotransmitter receptors and homotopic functional connectivity. Using longitudinal data from IMAGEN study (N = 532), we found that many cortical regions in the frontal and temporal lobes thinned more in the right hemisphere than in the left. Conversely, several regions in the occipital and parietal lobes thinned less in the right (vs. left) hemisphere. We then revealed that regions thinning more in the right (vs. left) hemispheres had higher density of neurotransmitter receptors and transporters in the right (vs. left) side. Moreover, the hemispheric differences in cortical thinning were predicted by homotopic functional connectivity. Specifically, regions with stronger homotopic functional connectivity showed a more symmetrical rate of cortical thinning between the left and right hemispheres, compared with regions with weaker homotopic functional connectivity. Based on these findings, we suggest that the typical patterns of hemispheric differences in cortical thinning may reflect the intrinsic organization of the neurotransmitter systems and related patterns of homotopic functional connectivity.

Genome-wide analyses of individual differences in quantitatively assessed reading- and language-related skills in up to 34,000 people.

The use of spoken and written language is a fundamental human capacity. Individual differences in reading- and language-related skills are influenced by genetic variation, with twin-based heritability estimates of 30 to 80% depending on the trait. The genetic architecture is complex, heterogeneous, and multifactorial, but investigations of contributions of single-nucleotide polymorphisms (SNPs) were thus far underpowered. We present a multicohort genome-wide association study (GWAS) of five traits assessed individually using psychometric measures (word reading, nonword reading, spelling, phoneme awareness, and nonword repetition) in samples of 13,633 to 33,959 participants aged 5 to 26 y. We identified genome-wide significant association with word reading (rs11208009, P = 1.098 × 10-8) at a locus that has not been associated with intelligence or educational attainment. All five reading-/language-related traits showed robust SNP heritability, accounting for 13 to 26% of trait variability. Genomic structural equation modeling revealed a shared genetic factor explaining most of the variation in word/nonword reading, spelling, and phoneme awareness, which only partially overlapped with genetic variation contributing to nonword repetition, intelligence, and educational attainment. A multivariate GWAS of word/nonword reading, spelling, and phoneme awareness maximized power for follow-up investigation. Genetic correlation analysis with neuroimaging traits identified an association with the surface area of the banks of the left superior temporal sulcus, a brain region linked to the processing of spoken and written language. Heritability was enriched for genomic elements regulating gene expression in the fetal brain and in chromosomal regions that are depleted of Neanderthal variants. Together, these results provide avenues for deciphering the biological underpinnings of uniquely human traits.

A Shifting Relationship Between Sex Hormone-Binding Globulin and Total Testosterone Across Puberty in Boys.

CONTEXT: Sex hormone-binding globulin (SHBG) is associated with levels of total testosterone (total-T), and both total-T and SHBG are associated with obesity. OBJECTIVE: We aimed to clarify the nature of the relationship between testosterone and SHBG and improve our understanding of their relationships with obesity. We hypothesize that the hypothalamic-pituitary-gonadal axis contributes to the homeostasis of testosterone by increasing the production of gonadal testosterone through a feedback mechanism that might operate differently at different pubertal stages. METHODS: We investigated the dynamics of the relationship between SHBG, total-T, and body mass index (BMI) throughout puberty (from age 9 to 17) using longitudinal data obtained in 507 males. The directionality of this relationship was explored using polygenic scores of SHBG and total-T, and a two-sample Mendelian Randomization (MR) in male adults. RESULTS: Consistent with our hypothesis, we found positive relationships between SHBG and total-T at age 15 and 17 but either no relationship or a negative relationship during the earlier time points. Such shifting relationships explained age-related changes in the association between total-T and BMI. Polygenic scores of SHBG and total-T in mediation analyses and the two-sample MR in male adults suggested an effect of SHBG on total-T but also a somewhat weaker effect of total-T on SHBG. Two-sample MR also showed an effect of BMI on SHBG but no effect of SHBG on BMI. CONCLUSION: These results clarify the nature of the relationship between testosterone and SHBG during puberty and adulthood and shed new light on their possible relationship with obesity.

Prenatal stress and its association with amygdala-related structural covariance patterns in youth.

BACKGROUND: Prenatal stress influences brain development and mood disorder vulnerability. Brain structural covariance network (SCN) properties based on inter-regional volumetric correlations may reflect developmentally-mediated shared plasticity among regions. Childhood trauma is associated with amygdala-centric SCN reorganization patterns, however, the impact of prenatal stress on SCN properties remains unknown. METHODS: The study included participants from the European Longitudinal Study of Pregnancy and Childhood (ELSPAC) with archival prenatal stress data and structural MRI acquired in young adulthood (age 23-24). SCNs were constructed based on Freesurfer-extracted volumes of 7 subcortical and 34 cortical regions. We compared amygdala degree centrality, a measure of hubness, between those exposed to high vs. low (median split) prenatal stress, defined by maternal reports of stressful life events during the first (n = 93, 57% female) and second (n = 125, 54% female) half of pregnancy. Group differences were tested across network density thresholds (5-40%) using 10,000 permutations, with sex and intracranial volume as covariates, followed by sex-specific analyses. Finally, we sought to replicate our results in an independent all-male sample (n = 450, age 18-20) from the Avon Longitudinal Study of Parents and Children (ALSPAC). RESULTS: The high-stress during the first half of pregnancy ELSPAC group showed lower amygdala degree particularly in men, who demonstrated this difference at 10 consecutive thresholds, with no significant differences in global network properties. At the lowest significant density threshold, amygdala volume was positively correlated with hippocampus, putamen, rostral anterior and posterior cingulate, transverse temporal, and pericalcarine cortex in the low-stress (p(FDR) < 0.027), but not the high-stress (p(FDR) > 0.882) group. Although amygdala degree was nominally lower across thresholds in the high-stress ALSPAC group, these results were not significant. CONCLUSION: Unlike childhood trauma, prenatal stress may shift SCN towards a less amygdala-centric SCN pattern, particularly in men. These findings did not replicate in an all-male ALSPAC sample, possibly due to the sample's younger age and lower prenatal stress exposure.

Two Facile Aniline-Based Hypercrosslinked Polymer Adsorbents for Highly Efficient Iodine Capture and Removal.

Effective capture and safe disposal of radioactive iodine (129I or 131I) during nuclear power generation processes have always been a worldwide environmental concern. Low-cost and high-efficiency iodine removal materials are urgently needed. In this study, we synthesized two aniline-based hypercrosslinked polymers (AHCPs), AHCP-1 and AHCP-2, for iodine capture in both aqueous and gaseous phases. They are obtained by aniline polymerization through Friedel-Crafts alkylation and Scholl coupling reaction, respectively, with high chemical and thermal stability. Notably, AHCP-1 exhibits record-high static iodine adsorption (250 wt%) in aqueous solution. In the iodine vapor adsorption, AHCP-2 presents an excellent total iodine capture (596 wt%), surpassing the most reported amorphous polymer adsorbents. The rich primary amine groups of AHCPs promote the rapid physical capture of iodine from iodine water and iodine vapor. Intrinsic features such as low-cost preparation, good recyclability, as well as excellent performance in iodine capture indicate that the AHCPs can be used as potential candidates for the removal of iodine from radioactive wastewater and gas mixtures.

Similarity and stability of face network across populations and throughout adolescence and adulthood.

The ability to extract cues from faces is fundamental for social animals, including humans. An individual's profile of functional connectivity across a face network can be shaped by common organizing principles, stable individual traits, and time-varying mental states. In the present study, we used data obtained with functional magnetic resonance imaging in two cohorts, IMAGEN (N = 534) and ALSPAC (N = 465), to investigate - both at group and individual levels - the consistency of the regional profile of functional connectivity across populations (IMAGEN, ALSPAC) and time (Visits 1 to 3 in IMAGEN; age 14 to 22 years). At the group level, we found a robust canonical profile of connectivity both across populations and time. At the individual level, connectivity profiles deviated from the canonical profile, and the magnitude of this deviation related to the presence of psychopathology. These findings suggest that the brain processes faces in a highly stereotypical manner, and that the deviations from this normative pattern may be related to the risk of mental illness.

Pubertal Testosterone and Brain Response to Faces in Young Adulthood: An Interplay between Organizational and Activational Effects in Young Men.

According to the organizational-activational hypothesis, the organizational effects of testosterone during (prenatal) brain development moderate the activational effects of adult testosterone on behavior. Accumulating evidence supports the notion that adolescence is another period during which sex hormones organize the nervous system. Here we investigate how pubertal sex hormones moderate the activational effects of adult sex hormones on social cognition in humans. To do so, we recruited a sample of young men (n = 507; age, ∼19 years) from a longitudinal birth cohort and investigated whether testosterone exposure during adolescence (from 9 to 17 years of age) moderates the relation between current testosterone and brain response to faces in young adulthood, as assessed with functional magnetic resonance imaging (fMRI). Our results showed that the cumulative exposure to testosterone during adolescence moderated the relation between adult testosterone and both the mean fMRI response and functional connectivity (i.e., node strength). Specifically, in participants with low exposure to testosterone during puberty, we observed a positive relationship between current testosterone and the brain response to faces; this was not the case for participants with medium and high pubertal testosterone. Furthermore, we observed a stronger relationship between the brain response and current testosterone in parts of the angry-face network associated with (vs without) motion in the eye region of an observed (angry) face. We speculate that pubertal testosterone modulates the relationship between current testosterone and brain response to social cues carried by the eyes and signaling a potential threat.SIGNIFICANCE STATEMENT Accumulating evidence supports the organizational effects of pubertal testosterone, but the body of literature examining these effects on social cognition in humans is in its infancy. With a sample of young men from a longitudinal birth cohort, we showed that the cumulative exposure to testosterone during adolescence moderated the relation between adult testosterone and both the mean BOLD signal change and functional connectivity. Specifically, we observed a positive relationship between adult testosterone and the brain response to faces in participants with low exposure to testosterone during puberty, but not in participants with medium and high pubertal testosterone. Results of further analysis suggest that sensitivity to cues carried by the eyes might underlie the relationship between testosterone and brain response to faces, especially in the context of a potential threat.

Pubertal Testosterone and the Structure of the Cerebral Cortex in Young Men.

Adolescence is a period of brain maturation that may involve a second wave of organizational effects of sex steroids on the brain. Rodent studies suggest that, overall, organizational effects of gonadal steroid hormones decrease from the prenatal/perinatal period to adulthood. Here we used multimodal magnetic resonance imaging to investigate whether 1) testosterone exposure during adolescence (9-17 years) correlates with the structure of cerebral cortex in young men (n = 216, 19 years of age); 2) this relationship is modulated by the timing of testosterone surge during puberty. Our results showed that pubertal testosterone correlates with structural properties of the cerebral cortex, as captured by principal component analysis of T1 and T2 relaxation times, myelin water fraction, magnetization transfer ratio, fractional anisotropy and mean diffusivity. Many of the correlations between pubertal testosterone and the cortical structure were stronger in individuals with earlier (vs. later) testosterone surge. We also demonstrated that the strength of the relationship between pubertal testosterone and cortical structure across the cerebral cortex varies as a function of inter-regional profiles of gene expression specific to dendrites, axonal cytoskeleton, and myelin. This finding suggests that the cellular substrate underlying the relationships between pubertal testosterone and cerebral cortex involves both dendritic arbor and axon.

Estimated Prevalence of Nonverbal Learning Disability Among North American Children and Adolescents.

Importance: Nonverbal learning disability (NVLD) is a neurodevelopmental disorder characterized by deficits in visual-spatial processing but not in reading or verbal ability; in addition, problems in math calculation, visual executive functioning, fine-motor skills, and social skills are often present. To our knowledge, there are no population-based estimates of the prevalence of NVLD in community samples. Objective: To estimate the prevalence of the NVLD cognitive profile in 3 independent samples of children and adolescents from studies centered around brain imaging in the US and Canada. Design, Setting, and Participants: This cross-sectional study used data from 2 samples recruited from the community and overselected for children with psychiatric disorders (Healthy Brain Network [HBN], January 1, 2015, to December 31, 2019, and Nathan Kline Institute-Rockland Sample [NKI], January 1, 2011, to December 31, 2018) and 1 community-ascertained population sample (Saguenay Youth Study [SYS], January 1, 2003, to December 31, 2012) overselected for active maternal smoking during pregnancy. Main Outcomes and Measures: Prevalence of NVLD. Criteria for NVLD were based on clinical records of deficits in visual-spatial reasoning and impairment in 2 of 4 domains of function (fine-motor skills, math calculation, visual executive functioning, and social skills). Sample weighting procedures adjusted for demographic differences in sample frequencies compared with underlying target populations. Inflation factor weights accounted for overrepresentation of psychiatric disorders (HBN and NKI samples). Results: Across 3 independent samples, the prevalence of NVLD was estimated among 2596 children and adolescents aged 6 to 19 years (mean [SD] age, 12.5 [3.4] years; 1449 male [55.8%]). After sample and inflation weights were applied, the prevalence of NVLD was 2.78% (95% CI, 2.03%-3.52%) in the HBN sample and 3.9% (95% CI, 1.96%-5.78%) in the NKI sample. In the SYS sample, the prevalence of NVLD was 3.10% (95% CI, 1.93%-4.27%) after applying the sample weight. Across samples and estimation strategies, the population prevalence of NVLD was estimated to range from 3% to 4%. When applied to the US population younger than 18 years, 2.2 million to 2.9 million children and adolescents were estimated to have NVLD. Conclusions and Relevance: The findings suggest that the prevalence of NVLD in children and adolescents may be 3% to 4%. Given that few youths are diagnosed with NVLD and receive treatment, increased awareness, identification of the underlying neurobiological mechanisms, and development and testing interventions for the disorder are needed.

The influence of kinship and dominance hierarchy on grooming partner choice in free-ranging Macaca mulatta brevicaudus.

In group-living animals, individuals do not interact uniformly with their conspecifics. Among primates, such heterogeneity in partner choice can be discerned from affiliative grooming patterns. While the preference for selecting close kin as grooming partners is ubiquitous across the primate order, the selection of higher-ranking non-kin individuals as grooming partners is less common. We studied a group of provisioned rhesus macaques (Macaca mulatta brevicaudus) on Hainan Island, China, to examine rank-related benefits of grooming exchanges and the influence of kin relationships. We tested four hypotheses based on Seyfarth's model: (1) there will be kin preference in grooming relationships; (2) grooming between non-kin individuals will be directed up the dominance rank; (3) grooming between non-kin individuals will reduce aggression from higher-ranking ones; and (4) non-kin individuals will spend more time grooming with adjacent ranked ones. We found that grooming relationships between kin individuals were stronger than those between non-kin individuals. For non-kin relationships, lower-ranking individuals received less aggression from higher-ranking ones through grooming; a benefit they could not derive through grooming exchanges with individuals related by kinship. Individuals spent more time grooming adjacent higher-ranking non-kin individuals and higher-ranking individuals also received more grooming from non-kin individuals. Our results supported Seyfarth's model for predicting partner choice between non-kin individuals. For relationships between kin individuals, we found results that were not consistent with prediction for the exchanges of aggression and grooming, indicating the importance to control for the influence of kinship in future studies.

The influence of age on wild rhesus macaques' affiliative social interactions.

The social relationships that individuals experience at different life stages have a non-negligible influence on their lives, and this is particularly true for group living animals. The long lifespan of many primates makes it likely that these animals have various tactics of social interaction to adapt to complex changes in environmental or physical conditions. The different strategies used in social interaction by individuals at different life stages, and whether the position (central or peripheral) or role (initiator or recipient) of an individual in the group social network changes with age, are intriguing questions that remain to be investigated. We used social network analysis to examine age-related differences in social interaction patterns, social roles, and social positions in three affiliative social networks (approach, allogrooming, and social play) in a group of wild rhesus macaques (Macaca mulatta). Our results showed that social interaction patterns of rhesus macaques differ between age classes in the following ways: i) young individuals tend to allocate social time to a high number of groupmates, older individuals prefer to focus on fewer, specific partners; ii) as they grow older, individuals tend to be recipients in approach interactions and initiators in grooming interactions; and iii) regardless of the different social interaction strategies, individuals of all ages occupy a central position in the group. These results reveal a possible key role played by immature individuals in group social communication, a little-explored issue which deserves closer investigation in future research.

Inhibitory effect and mechanism of epigallocatechin-3-gaUate on autogenous vein graft stenosis in rat models / 中国胸心血管外科临床杂志

@#Objective    To investigate the effect and mechanism of epigallocatechin-3-gallate (EGCG) on restenosis of the vein graft. Methods    Totally 90 Sprague-Dawley rats were randomly divided a the control group, a vein graft group and an EGCG+vein graft group. At week 1, 2 and 4, the intimal and tunica thickness of the venous graft wall was evaluated by hematoxylin-eosin staining, and the expression of Ki-67 was assessed by immunohistochemistry analysis, and then the expression of hairy and enhancer of split-1 (HES1) was measured by Western blot assay. Results    At week 2, the intimal thickness (46.76±4.89 μm vs. 8.93±0.82 μm, 46.76±4.89 μm vs. 34.24±3.57 μm), tunica thickness (47.28±4.37 vs. 16.33±1.52 μm, 47.28±4.37 vs. 36.27±3.29 μm), positive cell rate of Ki-67 (21.59%±2.29% vs. 1.12%±0.22%, 21.59%±2.29%vs. 15.38%±1.30%), expression of HES1 respectively increased in the experimental group than those in the control group and the EGCG+vein graft group (P<0.05, respectively). At week 4, the intimal thickness (66.38±6.23 μm vs. 8.29±0.79 μm,   66.38±6.23 μm vs. 48.39±4.23 μm), tunica thickness (63.27±6.18 μm vs. 15.29±1.49 μm, 63.27±6.18 μm vs. 44.63±4.49 μm), positive cell rate of Ki-67 (33.19%±3.03% vs. 1.09%±0.19%, 33.19%±3.03% vs. 24.37%±2.73%), expression of HES1 increased in the experimental group than those in the control group and EGCG+vein graft group (P<0.05, respectively). Conclusion    EGCG may inhibite restenosis of vein graft by inhibiting Notch signal pathway.

High-Frequency Oscillations of a Sphere in a Viscous Fluid near a Rigid Plane.

High-frequency oscillations of a rigid sphere in an incompressible viscous fluid moving normal to a rigid plane are considered when the ratio of minimum clearance to sphere radius is small. Asymptotic expansions are constructed that permit an analytical estimate of the force acting on the sphere as a result of its motion. An inner expansion, valid in the neighborhood of the minimum gap, reflects the dominance of viscous effects and fluid inertia. An outer expansion, valid outside the gap, reflects the dominance of fluid inertia with a correction for an oscillating viscous boundary layer. The results are applied to the hydrodynamics of the tapping mode of an atomic force microscope and to the dynamic calibration of its cantilevers.

Outer hair cell active force generation in the cochlear environment.

Outer hair cells are critical to the amplification and frequency selectivity of the mammalian ear acting via a fine mechanism called the cochlear amplifier, which is especially effective in the high-frequency region of the cochlea. How this mechanism works under physiological conditions and how these cells overcome the viscous (mechanical) and electrical (membrane) filtering has yet to be fully understood. Outer hair cells are electromotile, and they are strategically located in the cochlea to generate an active force amplifying basilar membrane vibration. To investigate the mechanism of this cell's active force production under physiological conditions, a model that takes into account the mechanical, electrical, and mechanoelectrical properties of the cell wall (membrane) and cochlear environment is proposed. It is shown that, despite the mechanical and electrical filtering, the cell is capable of generating a frequency-tuned force with a maximal value of about 40 pN. It is also found that the force per unit basilar membrane displacement stays essentially the same (40 pNnm) for the entire linear range of the basilar membrane responses, including sound pressure levels close to hearing threshold. Our findings can provide a better understanding of the outer hair cell's role in the cochlear amplifier.

High-frequency force generation in the constrained cochlear outer hair cell: a model study.

Cochlear outer hair cell (OHC) electromotility is believed to be responsible for the sensitivity and frequency selectivity of the mammalian hearing process. Its contribution to hearing is better understood by examining the force generated by the OHC as a feedback to vibration of the basilar membrane (BM). In this study, we examine the effects of the constraints imposed on the OHC and of the surrounding fluids on the cell's high-frequency active force generated under in vitro and in vivo conditions. The OHC is modeled as a viscoelastic and piezoelectric cylindrical shell coupled with viscous intracellular and extracellular fluids, and the constraint is represented by a spring with adjustable stiffness. The solution is obtained in the form of a Fourier series. The model results are consistent with previously reported experiments under both low- and high-frequency conditions. We find that constrained OHCs achieve a much higher corner frequency than free OHCs, depending on the stiffness of the constraint. We analyze cases in which the stiffness of the constraint is similar to that of the BM, reticular lamina, and tectorial membrane, and find that the force per unit transmembrane potential generated by the OHC can be constant up to several tens of kHz. This model, describing the OHC as a local amplifier, can be incorporated into a global cochlear model that considers cochlear hydrodynamics and frequency modulation of the receptor potential, as well as the graded BM stiffness and OHC length.

Modeling high-frequency electromotility of cochlear outer hair cell in microchamber experiment.

Cochlear outer hair cells (OHC) are critically important for the amplification and sharp frequency selectivity of the mammalian ear. The microchamber experiment has been an effective tool to analyze the OHC high-frequency performance. In this study, the OHC electrical stimulation in the microchamber is simulated. The model takes into account the inertial and viscous properties of fluids inside and outside the cell as well as the viscoelastic and piezoelectric properties of the cell composite membrane (wall). The closed ends of the cylindrical cell were considered as oscillatory rigid plates. The final solution was obtained in terms of Fourier series, and it was checked against the available results of the microchamber experiment. The conditions of the interaction between the cell and pipette was analyzed, and it was found that the amount of slip along the contact surface has a significant effect on the cell electromotile response. The cell's length changes were computed as a function of frequency, and their dependence on the viscosities of both fluids and the cell wall was analyzed. The distribution of the viscous losses inside the fluids was also estimated. The proposed approach can help in a better understanding of the high-frequency OHC electromotility under experimental and physiological conditions.

Effect of voltage-dependent membrane properties on active force generation in cochlear outer hair cell.

A computational model is proposed to analyze the active force production in an individual outer hair cell (OHC) under high-frequency conditions. The model takes into account important biophysical properties of the cell as well as constraints imposed by the surrounding environment. The biophysical properties include the elastic, piezoelectric, and viscous characteristics of the cell wall. The effect of the environment is associated with the stiffness of the constraint and the drag forces acting on the cell due to the interaction with the external and internal viscous fluids. The study concentrated on a combined effect of the transmembrane potential, frequency, and stiffness of the constraints. The effect of the voltage-dependent stiffness of the cell was particularly investigated and it was found to be twofold. First, it results in higher sensitivity and nonlinearity of the OHC active force production in the physiological range. Second, it determines smaller active forces in the hyperpolarization range. The resonant properties of the active force as functions of voltage and the constraint stiffness were also analyzed. The obtained results can be important for a better understanding of the OHC active force production and the contribution of cell electromotility to the cochlear amplification, sensitivity, and nonlinearity.

A new method to evaluate the local clearance at different annular rings inside hemodialyzers.

Recent research indicated that the dialysate flow distribution inside a hemodialyzer was not uniform ("channeling" of the dialysate flows). However, effect of the channeling on the solute clearance has not been directly and quantitatively examined. In this report, a novel experiment approach is presented to test the hypothesis that hollow fibers in different regions within a given hemodialyzer may contribute differently to the solute clearance. Water solution with urea (molecular weight 60) and creatinine (molecular weight 113) were made as "blood," and pure water was used as dialysate. Two high flux dialyzers, dialyzer A (cellulose triacetate) and dialyzer B (polyethersulfone), were used in this study. The hollow fiber potting area at the blood inlet of a dialyzer was divided into equal area concentric rings. In each experiment, only one of the rings was open for blood flow, and the other rings were blocked by epoxy. The "blood" was pumped at 120 ml/min while the dialysate flow rate (Qd) varied at 500, 800, and 1,000 ml/min, respectively. The solute clearance with a specific ring open (local clearance) was determined by measuring solute (urea/creatinine) concentration at the "blood" inlet and outlet. For dialyzer A, local clearance of urea and creatinine were significantly higher in the outer ring than in the inner ring. With increasing Qd, local solute clearance increased significantly for all rings. For dialyzer B, at any given Qd, solutes local clearance also increased from the inner to outer rings. In comparison, the effect of increasing Qd on solute clearance was greater for dialyzer B than for dialyzer A. In conclusion, using the new experimental method, the authors quantitatively evaluated the solute clearance contributed by the hollow fibers at different locations (concentric rings) in dialyzers. Hollow fibers at different locations did contribute differently to the solute clearance, which may be caused by the channeling of dialysate flow. A careful design of the dialyzer to minimize the channeling is needed.