Tests of human auditory temporal resolution: preliminary investigation of ZEST parameters for amplitude modulation detection

Auditory temporal resolution plays a critical role in the everyday experience of listening to complex acoustic patterns. Amplitude modulation detection thresholds are widely used to measure auditory temporal resolution. In an attempt to develop a standardized clinical test of auditory temporal resolution, we used ZEST (Zippy Estimation by Sequential Testing, a Bayesian threshold estimation procedure, to measure amplitude modulation detection thresholds. ZEST utilizes prior knowledge about a listener’s thresholds, as represented by a probability density function of the thresholds, and psychometric functions of the listener’s responses. This paper reports a preliminary study in which ZEST parameters that could be used for measurements of amplitude modulation detection thresholds were sought. For this purpose, we created histograms of the detection thresholds for a wide range of modulation frequencies, measured the psychometric functions of amplitude modulation detection, and performed computer simulations of ZEST threshold estimation. The results suggested that, with appropriately-set parameters, ZEST allows for the accurate estimation of amplitude modulation detection thresholds within 20 trials

Effects of substitutions of glycine and asparagine for serine132 on activity and binding of human lipoprotein lipase to very low density lipoproteins

AbstractFor studying the role of Ser132 in the putative catalytic site of human lipoprotein lipase (LPL), mutant LPL cDNAs expressing LPLs with amino acid substitutions of Gly or Asn for Ser132 were obtained by site-directed mutagenesis, and were expressed in COS-1 cells. Considerable amounts of LPL enzyme protein mass were detected in the culture medium of COS-1 cells transfected with wild-type LPL, LPL-Gly132, or LPL-Asn132. LPL-Gly132 hydrolyzed Triton X-100-triolein and tributyrin as effectively as wild-type LPL, whereas LPL-Asn132 showed no activity. LPL-Asn132 bound to very low density lipoproteins as effectively as wild-type LPL

Relationship between advanced glycation end products and plaque progression in patients with acute coronary syndrome: the JAPAN-ACS Sub-study.

Background: The Japan Assessment of Pitavastatin and Atorvastatin in Acute Coronary Syndrome (JAPAN-ACS) trial demonstrated that early aggressive statin therapy in patients with ACS significantly reduces plaque volume (PV). Advanced glycation end products (AGEs) and the receptors of AGEs (RAGE) may lead to angiopathy in diabetes mellitus (DM) and may affect on the development of coronary PV. The present sub-study of JAPAN-ACS investigates the association between AGEs and RAGE, and PV.Methods: Intravascular ultrasound (IVUS)-guided percutaneous coronary intervention (PCI) was undertaken, followed by the initiation of statin treatment (either 4 mg/day of pitavastatin or 20 mg/day of atorvastatin), in patients with ACS. In the 208 JAPAN-ACS subjects, PV using IVUS in non-culprit segment > 5 mm proximal or distal to the culprit lesion and, serum levels of AGEs and soluble RAGE (sRAGE) were measured at baseline and 8-12 months after PCI.Results: At baseline, no differences in the levels of either AGEs or sRAGE were found between patients with DM and those without DM. The levels of AGEs decreased significantly with statin therapy from 8.6 ± 2.2 to 8.0 ± 2.1 U/ml (p < 0.001), whereas the levels of sRAGE did not change. There were no significant correlations between changes in PV and the changes in levels of AGEs as well as sRAGE. However, high baseline AGEs levels were significantly associated with plaque progression (odds ratio, 1.21; 95% confidence interval, 1.01 - 1.48; p = 0.044) even after adjusting for DM in multivariate logistic regression models.Conclusions: High baseline AGEs levels were associated with plaque progression in the JAPAN-ACS trial. This relationship was independent of DM. These findings suggest AGEs may be related to long-term glucose control and other oxidative stresses in ACS.Trial registration: NCT00242944. © 2013 Fukushima et al.; licensee BioMed Central Ltd

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Chemiluminescence-based quantification of the colonization rates of Lotus japonicus roots by arbuscular mycorrhizal fungi

Simple evaluation of the levels of root colonization by arbuscular mycorrhizal (AM) fungi is challenging for conventional histochemical staining because most roots show an endogenous background signal. Herein, we report a chemiluminescence-based novel method for the quantification of the relative colonization rates of AM fungi. Lotus japonicus seedlings were grown in two types of soils with different inoculum potential [i.e., the former vegetation was maize (host) or buckwheat (non-host)]. Indigenous AM fungi colonizing roots were labelled with wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP), which specifically targets the N-acetylglucosamine polymers of fungal cell walls. After the roots were removed from the soil and rinsed with water, all procedures were conducted in 24-well plates. AM fungi were detected by chemiluminescence in the presence of enhanced chemiluminescence (ECL) reagents, and the signal strengths were measured by image analyses. Post-staining of AM fungal structures in the presence of 3,3ʹ-diaminobenzidine (DAB) and H2O2 (DAB staining) revealed that even small colonization events (e.g., hyphopodia) could be detected, whereas the background signals observed in DAB staining were eliminated in the chemiluminescence method. Chemiluminescence thus provides both high sensitivity and high specificity. The chemiluminescence-based colonization levels of roots grown in maize soil were significantly higher than those of roots grown in buckwheat soil, demonstrating the feasibility for high-throughput quantification of the relative colonization rates of L. japonicus seedlings by AM fungi

A simple model system for identifying arbuscular mycorrhizal fungal taxa that actively colonize rice (Oryza sativa L.) roots grown in field soil

Even a few centimeters of roots in field soils can be colonized by genetically diverse arbuscular mycorrhizal (AM) fungi. The DNA sequences of AM fungi in roots suggest the fungal identities; however, it is difficult to determine which AM fungal taxa are physiologically active. In this study, we took advantage of the characteristics of rice (Oryza sativa L.) mycorrhizal roots, in which active colonization in roots is easily detected via histochemical staining of fungal succinate dehydrogenase activity (vital staining) and individual active colonization regions (infection units) in roots rarely coalesce. Root segments (< 3 mm) containing an active infection unit were dissected and squashed, large subunit (LSU) ribosomal RNA genes (rDNAs) were amplified using fungal universal primers and the sequences were directly determined by Sanger sequencing. All obtained sequences of colonization regions were of glomeromycotan origin. Phylogenetic analysis revealed that the levels of LSU-rDNA heterogeneity within an active colonization site were different among different clades. The methodology presented in this study offers researchers a novel tool for investigating the DNA information of physiologically active AM fungi in roots, whereas the factors that affect genetic diversity among active colonization remain to be clarified