Effects of Vocal Fold Nodules on Glottal Cycle Measurements Derived from High-Speed Videoendoscopy in Children

The goal of this study is to quantify the effects of vocal fold nodules on vibratory motion in children using high-speed videoendoscopy. Differences in vibratory motion were evaluated in 20 children with vocal fold nodules (5–11 years) and 20 age and gender matched typically developing children (5–11 years) during sustained phonation at typical pitch and loudness. Normalized kinematic features of vocal fold displacements from the mid-membranous vocal fold point were extracted from the steady-state high-speed video. A total of 12 kinematic features representing spatial and temporal characteristics of vibratory motion were calculated. Average values and standard deviations (cycle-to-cycle variability) of the following kinematic features were computed: normalized peak displacement, normalized average opening velocity, normalized average closing velocity, normalized peak closing velocity, speed quotient, and open quotient. Group differences between children with and without vocal fold nodules were statistically investigated. While a moderate effect size was observed for the spatial feature of speed quotient, and the temporal feature of normalized average closing velocity in children with nodules compared to vocally normal children, none of the features were statistically significant between the groups after Bonferroni correction. The kinematic analysis of the mid-membranous vocal fold displacement revealed that children with nodules primarily differ from typically developing children in closing phase kinematics of the glottal cycle, whereas the opening phase kinematics are similar. Higher speed quotients and similar opening phase velocities suggest greater relative forces are acting on vocal fold in the closing phase. These findings suggest that future large-scale studies should focus on spatial and temporal features related to the closing phase of the glottal cycle for differentiating the kinematics of children with and without vocal fold nodules.     

A Theoretical Model of Glucose Transport Suggests Symmetric GLUT1 Characteristics at Placental Membranes

The process of glucose transport via the placenta is not fully deciphered. Here, we apply a theoretical model to compute glucose fluxes via the terminal villi of the human placenta for various sets of parameter values and conclude on characteristics of transport across the two bordering membranes. Based on available measured data, the spatial geometry of the terminal villi is being simulated. Within this region, glucose concentrations and fluxes are computed by a numerical scheme that solves the diffusion equation with boundary conditions that account for transporter mediated diffusion at the membranes. Feasible parameter values (ones that induce physiological glucose fluxes) are determined for four optional symmetry characteristics of the membranes. Confronting computed results with clinical knowledge reveals the most plausible scenario-symmetric activity of the transporter at the microvillous membrane. Thus, sensitivity analysis of the computed results enables deduction about micro-scale mechanisms at the bordering membranes based on macro-scale knowledge.     

Epithelial Cells Are Active Participants in Vocal Fold Wound Healing: An In Vivo Animal Model of Injury

Vocal fold epithelial cells likely play an important, yet currently poorly defined, role in healing following injury, irritation and inflammation. In the present study, we sought to identify a possible role for growth factors, epidermal growth factor (EGF) and transforming growth factor-beta 1 (TGFβ1), in epithelial regeneration during wound healing as a necessary first step for uncovering potential signaling mechanisms of vocal fold wound repair and remodeling. Using a rat model, we created unilateral vocal fold injuries and examined the timeline for epithelial healing and regeneration during early and late stages of wound healing using immunohistochemistry (IHC). We observed time-dependent secretion of the proliferation marker, ki67, growth factors EGF and TGFβ1, as well as activation of the EGF receptor (EGFR), in regenerating epithelium during the acute phase of injury. Ki67, growth factor, and EGFR expression peaked at day 3 post-injury. Presence of cytoplasmic and intercellular EGF and TGFβ1 staining occurred up to 5 days post-injury, consistent with a role for epithelial cells in synthesizing and secreting these growth factors. To confirm that epithelial cells contributed to the cytokine secretion, we examined epithelial cell growth factor secretion in vitro using polymerase chain reaction (PCR). Cultured pig vocal fold epithelial cells expressed both EGF and TGFβ1. Our in vivo and in vitro findings indicate that epithelial cells are active participants in the wound healing process. The exact mechanisms underlying their roles in autocrine and paracrine signaling guiding wound healing await study in a controlled, in vitro environment.     

A Multi-Scale Distribution Model for Non-Equilibrium Populations Suggests Resource Limitation in an Endangered Rodent

Species distributions are known to be limited by biotic and abiotic factors at multiple temporal and spatial scales. Species distribution models, however, frequently assume a population at equilibrium in both time and space. Studies of habitat selection have repeatedly shown the difficulty of estimating resource selection if the scale or extent of analysis is incorrect. Here, we present a multi-step approach to estimate the realized and potential distribution of the endangered giant kangaroo rat. First, we estimate the potential distribution by modeling suitability at a range-wide scale using static bioclimatic variables. We then examine annual changes in extent at a population-level. We define “available” habitat based on the total suitable potential distribution at the range-wide scale. Then, within the available habitat, model changes in population extent driven by multiple measures of resource availability. By modeling distributions for a population with robust estimates of population extent through time, and ecologically relevant predictor variables, we improved the predictive ability of SDMs, as well as revealed an unanticipated relationship between population extent and precipitation at multiple scales. At a range-wide scale, the best model indicated the giant kangaroo rat was limited to areas that received little to no precipitation in the summer months. In contrast, the best model for shorter time scales showed a positive relation with resource abundance, driven by precipitation, in the current and previous year. These results suggest that the distribution of the giant kangaroo rat was limited to the wettest parts of the drier areas within the study region. This multi-step approach reinforces the differing relationship species may have with environmental variables at different scales, provides a novel method for defining “available” habitat in habitat selection studies, and suggests a way to create distribution models at spatial and temporal scales relevant to theoretical and applied ecologists.     

Synchronization of Firing in Cortical Fast-Spiking Interneurons at Gamma Frequencies: A Phase-Resetting Analysis

Fast-spiking (FS) cells in the neocortex are interconnected both by inhibitory chemical synapses and by electrical synapses, or gap-junctions. Synchronized firing of FS neurons is important in the generation of gamma oscillations, at frequencies between 30 and 80 Hz. To understand how these synaptic interactions control synchronization, artificial synaptic conductances were injected in FS cells, and the synaptic phase-resetting function (SPRF), describing how the compound synaptic input perturbs the phase of gamma-frequency spiking as a function of the phase at which it is applied, was measured. GABAergic and gap junctional conductances made distinct contributions to the SPRF, which had a surprisingly simple piecewise linear form, with a sharp midcycle break between phase delay and advance. Analysis of the SPRF showed how the intrinsic biophysical properties of FS neurons and their interconnections allow entrainment of firing over a wide gamma frequency band, whose upper and lower frequency limits are controlled by electrical synapses and GABAergic inhibition respectively.     

冬小麦高产优质高效栽培决策模拟研究

在产量和品质形成规律及投入产出效益规律基础上,应用模糊集方法,构建了一个综合的冬小麦高产优质高效栽培优化决策模拟模型.并以Window XP为平台,采用VB(Visual Basic)语言编程,建立了相应的可视化决策支持系统.实现了在不同时空、自然、社会、经济、技术条件下,进行多目标、可综合、可选择、可调控的冬小麦田间水肥管理决策的目标.通过检验证明模拟模型是可行的.     

木糖高效生物转化的新出路

木糖的高效利用是影响木质纤维资源生物炼制经济效益的关键因素之一,也是构建其工业化生产体系的必要前提,但是木糖生物转化面临着重要的技术瓶颈,必须寻求新的思路。基于对木糖利用的现状及产业发展的综合分析,提出了木糖高效发酵制取木糖酸的新出路,论述了本领域首要的科学和技术问题是发酵抑制物的控制与消除;针对抑制物的问题,提出了细胞生理生化、代谢流分析及分子生物学的多层次和多尺度解析的研究方法;在此基础上,基于系统论的观点提出了菌种选育、原料预处理、抑制物控制与脱除、木糖酸高效发酵的技术集成的研究思路。     

A Cold-Sensitive Zygotic Lethal Causing High Frequencies of Nondisjunction during Meiosis I in DROSOPHILA MELANOGASTER Females

The X-linked, cold-sensitive zygotic lethal, l(1)TW-6(cs), both in homozygous and heterozygous females, induces nondisjunction of all four chromosomes at Meiosis I at both 25 degrees and 17 degrees . Nondisjunction frequencies approaching 0.5 for the X and fourth chromosomes have been observed at 16 degrees -18 degrees . The disjunction of the X chromosomes in males is not affected. The mutant causes mitotic irregularities in zygotes at both 25 degrees and 17 degrees . Mortality of all zygotes produced by the crosses 6(cs)/6(cs)x6(cs)/B(s)Y and FM7/6(cs)x6(cs)/B(s)Y is respectively 86% and 67-74% at 25 degrees and 99.8-99.9% and 94% at 17 degrees . The mortality of 6(cs) hemizygotes derived from females carrying no doses of 6(cs) (C(1)DX,y f/yx6(cs)/B(s)Y) is 45-55% at 25 degrees and 98% at 17 degrees . The length of the temperature-sensitive period for 6(cs) homo- and hemizygotes is affected by the maternal dosage of 6(cs); the shortest TSP is for zero and the longest is for two maternal doses. Mortality takes place primarily during embryogenesis with some larval and little pupal mortality. Analysis of sectioned embryos indicates that the large array of different patterns of damage observed could have arisen from abnormal cleavage divisions and the incomplete population of the blastoderm with nuclei.     

Surface Tensiometry of Apolipoprotein B Domains at Lipid Interfaces Suggests a New Model for the Initial Steps in Triglyceride-rich Lipoprotein Assembly

Apolipoprotein B (apoB) is the principal protein component of triacylglyceride (TAG)-rich lipoproteins, including chylomicrons and very low density lipoprotein, which is the precursor to LDL (the “bad cholesterol”). TAG-rich lipoprotein assembly is initiated by the N-terminal βα1 superdomain of apoB, which co-translationally binds and remodels the luminal leaflet of the rough endoplasmic reticulum. The βα1 superdomain contains four domains and is predicted to interact directly with lipids. Using drop tensiometry, we examined the interfacial properties of the α-helical and C-sheet domains and several subdomains to establish a detailed structure-function relationship at the lipid/water interface. The adsorption, stress response, exchangeability, and pressure (Π)-area relationship were studied at both triolein/water and triolein/1-palmitoyl, 2-oleoylphosphatidylcholine/water interfaces that mimic physiological environments. The α-helical domain spontaneously adsorbed to a triolein/water interface and formed a viscoelastic surface. It was anchored to the surface by helix 6, and the other helices were ejected and/or remodeled on the surface as a function of surface pressure. The C-sheet instead formed an elastic film on a triolein/water interface and was irreversibly anchored to the lipid surface, which is consistent with the behavior of amphipathic β-strands. When both domains were adsorbed together on the surface, the C-sheet shielded a portion of the α-helical domain from the surface, which retained its globular structure. Overall, the unique secondary and tertiary structures of the N-terminal domains of apoB support the intrinsic capability of co-translational lipid recruitment. The evidence presented here allows the construction of a detailed model of the initiation of TAG-rich lipoprotein assembly.     

The Quantum Yield of Photoinactivation of Photosystem II in Pea Leaves is Greater at Low Than High Photon Exposure

The quantum yield of PSII photoinactivation in pea leaves atlow photon exposure was 3 x 10^-7 mol PSII per mol photons absorbedby PSII and 2.5 x 10^-8 at high photon exposures (mol photonsm^-2), regardless of photomodulation of chloroplasts. We postulatethat the doseresponse behaviour of PSII photoinactivation, whichdepends on the number of photons absorbed, results from thebalance of light consumption with supply. (Received July 18, 1995; Accepted August 8, 1995)     

A Transforming Marker That Produces Merodiploids with High Efficiency and Stable Transformants with Low Efficiency in Streptococcus

A mutation (ery-r8) conferring a high level of resistance to erythromycin in the Challis strain of Streptoccus sanguis can be transferred to wild-type erythromycin-sensitive recipients via single molecules of donor DNA. The transformants thus produced are of two types: (1) cells slightly more resistant to erythromycin than wild-type and capable of segregating (at a frequency of 2 X 10(-4)/bacterium/generation) either wild-type or highly-resistant cells like the original donor type; (2) cells phenotypically and genotypically identical to the original donor type. The unstable diploids (ery-r8/+) occur with a frequency equivalent to that obtained with high-efficiency (HE) markers, whereas the stable donor-type (ery-r8) transformants occur with about five hundred times lower frequency. Penetration of the wild-type recipient by more than one molecule of DNA bearing the ery-r8 marker increases by as much as seven times the incidence of stable transformants. UV-irradiation of molecules bearing the ery-r8 marker diminishes their ability to cooperate in producing a stable transformant, although the UV sensitivity of stable transformant production by a single DNA molecule is not different from that of diploid production. Hence, stable transformants do not appear to be produced by a process typical of low efficiency (LE) markers, which are generally highly sensitive to ultraviolet irradiation. Moreover, stable ery-r8 transformants are produced with equally low frequencies in strains of S. pneumoniae that discriminate (hex+) and fail to discriminate (hex--) between HE and LE markers. We postulate that all transformations by the ery-r8 marker result in ery-r8/+ diploids, and that segregation results in the infrequent stable transformants of the original donor type. This hypothesis is supported by the observations that rifampin treatment of ery-r8/+ populations increases the frequency of segregation and similar treatment of wild-type recipients under-going transformation by the ery-r8 marker increases the frequency of stable transformants.--In producing the ery-r8/+ transformant the r8 allele is integrated close to the site of its wild-type homolog, since single molecules of DNA from this transformant can be shown to carry both alleles. Segregation of either the ery-r8 or + allele is not detectably enhanced by acridine orange or thymidine deprivation.--The ery-r8 marker occurs close to a site of mutation (ery-r2) which confers erythromycin resistance upon ribosomes. When the r2 and r8 markers are jointly transferred, ery-r2-r8/+ genomes are produced in which the r2 marker is stably integrated but the r8 marker is unstably adjoined to its wild-type homolog. Thus, the duplicated region can be quite short. When the ery-r8 marker is stably integrated, the region of the marker is refractory to subsequent transformation. Markers with properties like ery-r8 are not particularly rare, being found with a frequency of about 4% among spontaneous mutations to erythromycin resistance.     

Model of Solar Wind in the Heliosphere at Low and High Latitudes

The spatial distributions of the magnetic field, plasma density, and current at distances of (20–400)R_S from the Sun (where R_S is the solar radius) are investigated within a stationary axisymmetric MHD model of the solar wind (SW) at all latitudes in the inertial frame of reference with the origin at the center of the Sun. The model takes into account differential (with respect to the heliolatitude) rotation of the Sun and full corotation of plasma inside a boundary sphere of radius 20RS, which breaks down beyond this sphere. Self-consistent distributions of the plasma density, current, and magnetic field in the SW are obtained by numerically solving a set of time-independent MHD equations in spherical coordinates. It is demonstrated that the calculated results do not contradict observational data and describe a gradual transition from the fast SW at high heliolatitudes to the slow SW at low heliolatitudes, as well as the steepening of the profiles of the main SW characteristics with increasing distance from the Sun. The obtained dependences extend understanding of the SW structure at low and high latitudes and agree with the well-known Parker model in the limit of a small Ampère force.     

A Large and Deep Root System Underlies High Nitrogen-Use Efficiency in Maize Production

Excessive N fertilization results in low N-use efficiency (NUE) without any yield benefits and can have profound, long-term environmental consequences including soil acidification, N leaching and increased production of greenhouse gases. Improving NUE in crop production has been a longstanding, worldwide challenge. A crucial strategy to improve NUE is to enhance N uptake by roots. Taking maize as a model crop, we have compared root dry weight (RDW), root/shoot biomass ratio (R/S), and NUE of maize grown in the field in China and in western countries using data from 106 studies published since 1959. Detailed analysis revealed that the differences in the RDW and R/S of maize at silking in China and the western countries were not derived from variations in climate, geography, and stress factors. Instead, NUE was positively correlated with R/S and RDW; R/S and NUE of maize varieties grown in western countries were significantly greater than those grown in China. We then testified this conclusion by conducting field trials with representative maize hybrids in China (ZD958 and XY335) and the US (P32D79). We found that US P32D79 had a better root architecture for increased N uptake and removed more mineral N than Chinese cultivars from the 0-60 cm soil profile. Reported data and our field results demonstrate that a large and deep root, with an appropriate architecture and higher stress tolerance (higher plant density, drought and N deficiency), underlies high NUE in maize production. We recommend breeding for these traits to reduce the N-fertilizer use and thus N-leaching in maize production and paying more attention to increase tolerance to stresses in China.     

A Temporally Explicit Production Efficiency Model for Fuel Load Allocation in Southern Africa

Abstract We present a regional fuel load model (1 km² spatial resolution) applied in the southern African savanna region. The model is based on a patch-scale production efficiency model (PEM) scaled up to the regional level using empirical relationships between patch-scale behavior and multi-source remote sensing data (spatio-temporal variability of vegetation and climatic variables). The model requires the spatial distribution of woody vegetation cover, which is used to determine separate respiration rates for tree and grass. Net primary production, grass and tree leaf death, and herbivory are also taken into account in this mechanistic modeling approach. The fuel load model has been calibrated and validated from independent measurements taken from savanna vegetation in Africa southward from the equator. A sensitivity analysis on the effect of climate variables (incoming radiation, air temperature, and precipitation) has been conducted to demonstrate the strong role that water availability has in determining productivity and subsequent fuel load over the southern African region. The model performance has been tested in four different areas representative of a regional increasing rainfall gradient—Etosha National Park, Namibia, Mongu and Kasama, Zambia, as well as in Kruger National Park, South Africa. Within each area, we analyze model output from three different magnitudes of canopy coverage (<5, 30, and 50%). We find that fuel load ranges predicted by the model are globally in agreement with field measurements for the same year. High rainfall sustains green herbaceous production late in the dry season and delays tree leaf litter production. Effect of water on production varies across the rainfall gradient with delayed start of green material production in more arid regions.     

High Nitrogen Use Efficiency in Rice Genotypes is Associated with Higher Net Photosynthetic Rate at Lower Rubisco Content

Contrasting rice genotypes differing in leaf mass ratio (LMR) and leaf nitrogen content were screened. A strong inverse relationship was observed between ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) content and its efficiency estimated as the ratio of net photosynthetic rate (P_N) to Rubisco content. Similarly, an inverse relationship between the specific activity of fully activated Rubisco and its content was observed. This suggests that a down regulation of Rubisco may occur if the efficiency of the enzyme is superior. Genotypes IET 12989 and IET 13567 recorded higher P_N together with lower Rubisco content in comparison with other genotypes measured. These genotypes showed low LMR and low nitrogen content and hence could be considered as efficient nitrogen users. This revised version was published online in July 2006 with corrections to the Cover Date.     

Contrasting Changes of Photosystem 2 Efficiency in Arabidopsis Xanthophyll Mutants at Room or Low Temperature Under High Irradiance Stress

We compared the responses of wild type (WT) and three mutants including npq1 (lutein-replete and violaxanthin deepoxidase-deficient), lut2 (lutein-deficient), and lut2-npq1 (double mutant) to high irradiance (HI, 2 000 μmol m⁻² s⁻¹) at both low (LT, 5 °C) and room (25 °C) temperature. Xanthophyll-dependent energy dissipation was highest in the WT, followed by the lut2, npq1, and npq1-lut2. At 25 °C the relative stress tolerance expressed by F_v/F_m was consistent with the energy dissipation capacity for the first 2 h of treatment. After 3–4 h, the F_v/F_m levels in lut2 and npq1 converged. Under combined LT and HI the relative tolerance sequence was in contrast to the energy dissipation capacity being WT > npq1> lut2 > lut2-npq1. There were little or no significant change in the contents of xanthophylls and carotenes or the chlorophyll (Chl) a/b ratio in any of the materials. Thus lutein (L) substitution possibly alters the conformation/organisation of L binding proteins to enhance damage susceptibility under HI at LT. The enhanced vulnerability is not compensated for the energy dissipation capacity in the lut2 background at LT. This revised version was published online in August 2006 with corrections to the Cover Date.     

A High Dietary Glycemic Index Increases Total Mortality in a Mediterranean Population at High Cardiovascular Risk

Objective

Different types of carbohydrates have diverse glycemic response, thus glycemic index (GI) and glycemic load (GL) are used to assess this variation. The impact of dietary GI and GL in all-cause mortality is unknown. The objective of this study was to estimate the association between dietary GI and GL and risk of all-cause mortality in the PREDIMED study.

Material and Methods

The PREDIMED study is a randomized nutritional intervention trial for primary cardiovascular prevention based on community-dwelling men and women at high risk of cardiovascular disease. Dietary information was collected at baseline and yearly using a validated 137-item food frequency questionnaire (FFQ). We assigned GI values of each item by a 5-step methodology, using the International Tables of GI and GL Values. Deaths were ascertained through contact with families and general practitioners, review of medical records and consultation of the National Death Index. Cox regression models were used to estimate multivariable-adjusted hazard ratios (HR) and their 95% CI for mortality, according to quartiles of energy-adjusted dietary GI/GL. To assess repeated measures of exposure, we updated GI and GL intakes from the yearly FFQs and used Cox models with time-dependent exposures.

Results

We followed 3,583 non-diabetic subjects (4.7 years of follow-up, 123 deaths). As compared to participants in the lowest quartile of baseline dietary GI, those in the highest quartile showed an increased risk of all-cause mortality [HR = 2.15 (95% CI: 1.15–4.04); P for trend  = 0.012]. In the repeated-measures analyses using as exposure the yearly updated information on GI, we observed a similar association. Dietary GL was associated with all-cause mortality only when subjects were younger than 75 years.

Conclusions

High dietary GI was positively associated with all-cause mortality in elderly population at high cardiovascular risk.