Comparative measurements of potassium and chloride with ion-sensitive microelectrodes and x-ray microanalysis in cultured skeletal muscle fibers

Summary Data of the intracellular electrolyte concentration of potassium and chloride in cultured muscle cells measured by x-ray analysis were compared by using the different activity coefficients with intracellular potassium and chloride activities measured with double-barrelled microelectrodes. By using an activity coefficient of 0.6, 95% of the potassium microelectrode measurements are in accordance with the x-ray analysis values, in spite of a scattering of the values. Membrane potential and intracellular potassium values are linearly related. x-ray analysis and ion-sensitive microelectrodes measured the cytoplasmic chloride in the same range. Taking into account known activity coefficients, an error of 25% must be assumed with the intracellular chloride measurements. However, x-ray analysis and ion-sensitive microelectrode investigations are reliable tools to study intracellular potassium and chloride changes, which play an important role in membrane characteristics.     

A Model of Plant Hydraulics Under Non-equilibrium Conditions: I. STEMS

Oscillations in sap flux in two branches of a plant were foundto be non-synchronous but frequently phase-locked, even thoughthe branches had very different energy budgets. Time lags inthe transmission of oscillations along a stem were measured,and analysed in terms of an electrical transmission-line analogy.The equivalent ‘circuit elements’ in the stem wereidentified and their values calculated. These values were usedto derive the expected time lags of oscillations along a stem.Derived values agreed closely with those measured.     

Electric Conductivity and Internal Osmolality of Intact Bacterial Cells

Intact cells of Streptococcus faecalis and Micrococcus lysodeikticus were found to have high-frequency electric conductivities of 0.90 and 0.68 mho/m, respectively. These measured values, which reflect movements of ions both within the cytoplasm and within the cell wall space, were only about one-third of those calculated on the basis of determinations of the amounts and types of small ions within the cells. Concentrated suspensions of bacteria with damaged membranes showed similarly large disparities between measured and predicted conductivities, whereas the conductivities of diluted suspensions were about equal to predicted values. Thus, the low mobilities of intracellular ions appeared to be interpretable in terms of the physicochemical behavior of electrolytes in concentrated mixtures of small ions and cell polymers. In contrast to the low measured values for conductivity of intact bacteria, values for intracellular osmolality measured by means of a quantitative plasmolysis technique were higher than expected. For example, the plasmolysis threshold for S. faecalis cells indicated an internal osmolality of about 1.0 osmol/kg, compared with a value of only 0.81 osmol/liter of cell water calculated from a knowledge of the cell content and the distribution of small solutes. In all, our results indicate that most of the small ions within vegetative bacterial cells are free to move in an electric field and that they contribute to cytoplasmic osmolality.     

Case studies of the use of the locally adjusted polynomial regression

Firstly the operation mode of the procedures of local adjusted polynomial regression is explained by an artificial example of data. After that, the properties of these nonparametric estimation procedures of unknown continuous functions from measured data are demonstrated by some examples arising in experimental examinations. Especially the aspect is discussed how far the main task of separating the deterministic component from the random one in the course of measured values may be fulfilled by using different degrees of polynomials in connection with different values of the smoothing parameter.     

(An algorithm for determining values of parameters of the Gompertz growth function)]

In the literature some attempts were made to analyse and to construct models for biological growth processes and to describe the quantitative aspects of a growth characteristic's changes in time using the Gompertz' function y=aexp(-exp(b--ct)). In this paper differential equations are derived having the Gompertz' function as solution. The goodness of fit after adjusting a chosen analytical expression to the courses of measured values is able to give hints at the reliability of that expression as a true model. This possibility of verification was hardly practiced in past because of lacking in proper numerical procedures for performing the nonlinear regression. An ALGOL program for iterative adjusting the parameters of the GOMPERTZ' function (with or without a constant term) to measured values is given in an appendix of the present paper. Starting values for the nonlinear parameters b and c will be evaluated by Internal Least Squares using one of the derived differential equations. For this algorithm an ALGOL program is given in the appendix too. The growth of human embryo serves as an example to demonstrate the numerical procedures and related programs for evaluating the starting values of the parameters and for their iterative improvement until reaching a minimum for the remainding variance between calculated and measured courses.     

清洁级SD大鼠血液生理生化指标的测定

目的建立清洁级SD大鼠血液生理生化正常值。方法应用动物芯片血球计数仪测试常规血细胞计数;采用全自动生化测定仪对清洁级SD大鼠的血液28项生化指标进行测定,并进行统计分析雌雄差异显著性检验。结果建立了清洁级SD大鼠血液生理和28项血液生化参考值,ALB、AST/ALT、AG雌雄之间差异显著;血液血球计数雌雄差异不显著。结论比较详细的建立了清洁级SD大鼠的血液生理生化指标参考值,为其应用提供基础数据。     

Estimation of the air/sea exchange of ammonia for the North Atlantic Basin

As gas phase atmospheric ammonia reacts with acidic aerosol particles it affects the chemical, physical, and optical properties of the particles. A knowledge of the source strengths of NH₃ is useful in determining the effect of NH₃ on aerosol properties on a regional basis. Here, an attempt is made to determine the direction and magnitude of the air/sea flux of ammonia for the North Atlantic Basin from both measured and modeled seawater and atmospheric ammonia concentrations. Previously reported measured seawater concentrations range from less than 30 to 4600 nM with the highest concentrations reported for the Caribbean Sea, the North Sea, and the Belgium coast. Measured atmospheric ammonia concentrations range from 2 to 500 nmol m^–3 with the largest values occurring over the Sargasso Sea, the Caribbean Sea, and the North Sea. For comparison to the measurements, seawater ammonia concentrations were calculated by the Hamburg Model of the Ocean Carbon Cycle (HAMOCC3). HAMOCC3 open ocean values agree well with the limited number of reported measured concentrations. Calculated coastal values are lower than those measured, however, due to the coarse resolution of the model. Atmospheric ammonia concentrations were calculated by the Acid Deposition Model of the Meteorological Synthesizing Center (MSC-W) and by the global 3-dimensional model Moguntia. The two models predict similar annually averaged values but are about an order of magnitude lower than the measured concentrations. Over the North Sea and the NE Atlantic, the direction and magnitude of the air/sea ammonia flux calculated from MSC-W and Moguntia agree within the uncertainty of the calculations. Flux estimates derived from measured data are larger in both the positive and negative direction than the model derived values. The discrepancies between the measured and modeled concentrations and fluxes may be a result of sampling artifacts, inadequate chemistry and transport schemes in the models, or the difficulty in comparing point measurements to time-averaged model values. Sensitivity tests were performed which indicate that, over the range of values expected for the North Atlantic, the accuracy of the calculated flux depends strongly on seawater and atmospheric ammonia concentrations. Clearly, simultaneous and accurate measurements of seawater and atmospheric ammonia concentrations are needed to reduce the uncertainty of the flux calculations, validate the model results, and characterize the role of oceanic ammonia emissions in aerosol processing and nitrogen cycling for the North Atlantic.     

The reliability of adult self-reported height: The role of interviewers

Surveys serve as an important source of information on key anthropometric characteristics such as body height or weight in the population. Such data are often obtained by directly asking respondents to report those values. Numerous studies have examined measurement errors in this context by comparing reported to measured values. However, little is known on the role of interviewers on the prevalence of irregularities in anthropometric survey data. In this study, we explore such interviewer effects in two ways. First, we use data from the US National Health and Nutrition Examination Survey and the UK Household Longitudinal Study to evaluate whether differences between reported and measured values are clustered within interviewers. Second, we investigate changes in adult self-reported height over survey waves in two German large-scale panel surveys. Here, we exploit that height should be constant over time for the majority of adult age groups. In both analyses, we use multilevel location-scale models to identify interviewers who enhance reporting errors and interviewers for whom unlikely height changes over waves occur frequently. Our results reveal that interviewers can play a prominent role in differences between reported and measured height values and changes in reported height over survey waves. We further provide an analysis of the consequences of height misreporting on substantive regression coefficients where we especially focus on the role of interviewers who reinforce reporting errors and unlikely height changes.     

三江平原典型沼泽湿地蒸散发估测

2006年5—9月,利用涡度相关技术对三江平原典型沼泽湿地蒸散发进行了连续观测,在分析生长季内沼泽湿地蒸散发时间动态的基础上,采用Penman-Monteith（PM）和Priestley-Taylor（PT）模型分别模拟了沼泽湿地的日蒸散发,并利用实测值对两种模型的模拟精度进行了验证.结果表明：生长季内（5—9月）,研究区沼泽湿地蒸散发具有明显的季节变化,月均日蒸散量在5月最低、7月最高;生长季内平均蒸散发为1.94 mm·d^-1,总蒸散量293 mm.生长季前期和后期,与蒸散发实测值相比,PM模型的模拟值存在明显低估现象;PT模型模拟值与实测值在整个生长季内的一致性较好,且PT模型的形式简单、所需参数少,更适于沼泽湿地的蒸散发模拟.     

Development and evaluation of an optimization-based model for power-grip posture prediction

An optimization-based model for power-grip posture prediction was proposed. The model was based on the premise that the hand prehensile configuration in a power grip best conforms to the object shape. This premise was embodied by an optimization procedure that minimized the sum of distances from the finger joints to the object surface. The model was evaluated against data from an experiment that measured the grasp postures of 28 subjects having diverse anthropometry. The intra- and inter-person variabilities in grip postures were empirically assessed and used as benchmark values for model evaluation. The evaluation showed that the root-mean-square (RMS) values of angle differences between the predicted and measured postures had a 13.7 degrees grand mean (across all joints, subjects, and two cylindrical handles grasped), whereas the RMS values of the inter- and intra-person variabilities in measured postures had grand means of 13.0 degrees and 4.4 degrees , respectively. The model can be readily generalized to the prediction of postures in power-grasping objects of different shapes, and adapted for testing alternative prehensile strategies or performance criteria.     

Quantum efficiency of light-driven proton extrusion in Halobacterium halobium. pH dependence.

The quantum yield for light-induced proton extrusion in Halobacterium halobium cells pretreated with an ATPase inhibitor was measured between pH 5 and 9 using two separate spectrophotometric techniques. The transmittance of the cell suspension was measured with a spectrometer equipped with "end-on" photomultipliers, whereas the reflectance was measured using a light-integrating sphere. The potentialities of the two techniques are critically compared. These measurements are used to evaluate the intensities of light absorbed by the cells. Since the initial rates of proton release into the extracellular medium were simultaneously measured, the quantum yield values [QY(H+)] could be determined. The results obtained with the two techniques are in reasonable agreement. QY(H+) is 0.64 at pH 5.9 and decreases gradually to 0.28 at alkaline pH values.     

Human Discrimination of the Angular Velocity of the Vertical Movement of an Acoustic Image in Opposite Directions

The discrimination of the angular velocity of ventrodorsal and dorsoventral movement of an acoustic image was studied in nine test subjects. The experiments were performed using an apparent movement produced by consecutive activation of loudspeakers located along an arc in the vertical plane. The differential thresholds were measured by the minimum increment method. As the velocity of an acoustic image movement in opposite directions increased, the values of its mean absolute differential thresholds increased monotonically. Regression lines plotted by linear approximation of these values did not differ significantly.     

林冠截持降雨模型的初步研究

通过对林冠截持过程的研究,将单场降雨划分成很多个小的时段,顺序计算各小时段内降雨在林冠内的分配,建立了一个林冠降雨截持模型.模型考虑了冠层和树干干燥度对冠层雨期蒸发的影响,并在计算雨期蒸发时引入冠层叶面积指数、单位林地面积上树干表面积.运用模型对华北落叶松林的降雨截持进行模拟,结果表明,模拟穿透雨与实测穿透雨基本吻合,误差在±1 mm范围内,但在小降雨(＜6 mm)时模拟值偏低;树干茎流量模拟值偏低,茎流模拟相对误差随着降雨量增大而减小.同时模拟了穿透降雨的过程,结果与林内自动气象站实测穿透降雨的过程基本吻合,模拟效果较好.     

k-Cone analysis: determining all candidate values for kinetic parameters on a network scale

The absence of comprehensive measured kinetic values and the observed inconsistency in the available in vitro kinetic data has hindered the formulation of network-scale kinetic models of biochemical reaction networks. To meet this challenge we present an approach to construct a convex space, termed the k-cone, which contains all the allowable numerical values of the kinetic constants in large-scale biochemical networks. The definition of the k-cone relies on the incorporation of in vivo concentration data and a simplified approach to represent enzyme kinetics within an established constraint-based modeling approach. The k-cone approach was implemented to define the allowable combination of numerical values for a full kinetic model of human red blood cell metabolism and to study its correlated kinetic parameters. The k-cone approach can be used to determine consistency between in vitro measured kinetic values and in vivo concentration and flux measurements when used in a network-scale kinetic model. k-Cone analysis was successful in determining whether in vitro measured kinetic values used in the reconstruction of a kinetic-based model of Saccharomyces cerevisiae central metabolism could reproduce in vivo measurements. Further, the k-cone can be used to determine which numerical values of in vitro measured parameters are required to be changed in a kinetic model if in vivo measured values are not reproduced. k-Cone analysis could identify what minimum number of in vitro determined kinetic parameters needed to be adjusted in the S. cerevisiae model to be consistent with the in vivo data. Applying the k-cone analysis a priori to kinetic model development may reduce the time and effort involved in model building and parameter adjustment. With the recent developments in high-throughput profiling of metabolite concentrations at a whole-cell scale and advances in metabolomics technologies, the k-cone approach presented here may hold the promise for kinetic characterization of metabolic networks as well as other biological functions at a whole-cell level.     

Validity of Ellenberg indicator values judged from physico‐chemical field measurements

Abstract. The relationship between mean Ellenberg indicator values (IV) per vegetation relevé and environmental parameters measured in the field usually shows a large variation. We tested the hypothesis that this variation is caused by bias dependent on the phytosociological class. For this purpose we collected data containing vegetation relevés and measured soil pH (3631 records) or mean spring groundwater level (MSL, 1600 records). The relevés were assigned to vegetation types by an automated procedure. Regression of the mean indicator values for acidity on soil pH and the mean indicator values for moisture on MSL gave percentages explained variance similar to values that were reported earlier in literature. When the phytosociological class was added as an explanatory factor the explained variance increased considerably. Regression lines per vegetation type were estimated, many of which were significantly different from each other. In most cases the intercepts were different, but in some cases their slopes differed as well. The results show that Ellenberg indicator values for acidity and moisture appear to be biased towards the values that experts expect for the various phytosociological classes. On the basis of the results, we advise to use Ellenberg IVs only for comparison within the same vegetation type.     

Reliability of an individually molded shank shell for measuring tibial transverse rotations during the stance phase of walking

Use of a shank shell has been shown to estimate tibial transverse rotations better than skin-mounted markers. However, the day-to-day reliability of the transverse tibial rotations using an individually molded shank shell has not been previously investigated. This study examined the between-tests and trials reliability of an individually molded shank shell for measuring peak tibial internal and external rotations, time of peak values, and tibia range of motion during 5 walking trials. The trial-to-trial reliability of tibial transverse rotations was measured in 14 healthy individuals while the test-retest reliability was measured in 10 persons on two occasions. Trial-to-trial reliability for peak transverse rotations, time of peak values, and tibia range of motion ranged from ICC (3,1) 0.59-0.95. The PCA between trials showed that 88-99 % of values were within 3 degrees of agreement. Test-retest reliability for peak rotations, tibia range of motion, and time of peak values ranged from ICC (3,1) 0.70-0.89 with SEM 1.6-2.21 degrees , 0.021 %, and 0.034 %, respectively. The PCA between tests showed that 70-100 % of values were within 3 degrees of agreement. The use of an individually molded shell and the close attachment of the shank shell to the individual's shank resulted in reliable test-retest and trial-to-trial data.     

A critical examination of the maximum velocity of shortening used in simulation models of human movement

The maximum velocity of shortening of a muscle is an important parameter in musculoskeletal models. The most commonly used values are derived from animal studies; however, these values are well above the values that have been reported for human muscle. The purpose of this study was to examine the sensitivity of simulations of maximum vertical jumping performance to the parameters describing the force–velocity properties of muscle. Simulations performed with parameters derived from animal studies were similar to measured jump heights from previous experimental studies. While simulations performed with parameters derived from human muscle were much lower than previously measured jump heights. If current measurements of maximum shortening velocity in human muscle are correct, a compensating error must exist. Of the possible compensating errors that could produce this discrepancy, it was concluded that reduced muscle fibre excursion is the most likely candidate.     

Compliances of the liquid-filled lungs and chest wall during development in fetal sheep.

Our aim was to measure the compliance of the liquid-filled lungs (CL), and the compliance of the chest wall (CW) in fetal sheep in utero. CL and CW were measured in 6 fetuses. The compliance of the lungs and chest wall combined (respiratory system, Crs) was measured in 9 fetuses. Pressure differences across the lungs (PL), chest wall (PW) and respiratory system (Prs) were measured while the lungs were deflated and inflated with liquid from their resting lung liquid volume (V1). V1 was measured using an indicator dilution technique. Specific compliance values were obtained by normalizing the values of CL, CW and Crs with respect to values of V1. From values obtained during stepwise inflation from V1, specific compliances (ml/cm H2O/ml of lung liquid) were: lungs, 0.22 +/- 0.02; chest wall, 0.41 +/- 0.07; respiratory system, 0.13 +/- 0.01. Specific compliances of the lungs, chest wall and respiratory system did not change significantly with advancing gestational age from 120 to 143 days. Our baseline data will be valuable in assessing the in utero progress of the structural development of the lungs following manipulations known to cause altered lung growth.     

Measurement of erythrocytes on diagnostic slides by scanning electron microscopy

OBJECTIVE: To determine whether the measured sizes of erythrocytes in both paraffin-embedded sections and air-dried blood smears differ from values published in standard texts. STUDY DESIGN: Routinely prepared surgical pathology slides as well as an air-dried blood smear were viewed with a scanning electron microscope. Erythrocytes were measured using the instrument software. RESULTS: Erythrocyte size in the peripheral blood smear correlated well with textbook values, 7.2-7.9 microns. However, red blood cells within sectioned material from several laboratories showed a prominent decrease, ranging from 25% to 35%, as compared to textbook values, about 7 microns. CONCLUSION: Since cytologists and surgical pathologists often use the erythrocyte as a convenient marker on diagnostic slides, attention should be given to these observations in making sizing judgments.     

Variation in carbon isotope discrimination in relation to plant performance in a natural population of <Emphasis Type="Italic">Cryptantha flava</Emphasis>

Few studies of phenotypic selection have focused on physiological traits, especially in natural populations. The adaptive significance of plant water-use efficiency, the ratio of photosynthesis to water loss through transpiration, has rarely been examined. In this study, carbon isotopic discrimination, Δ, an integrated measure of water-use efficiency, was repeatedly measured in juveniles and adults in a natural population of the herbaceous desert perennial Cryptantha flava over a 4-year period and examined for plasticity in Δ, consistency between years in values of Δ, and evidence for selection on Δ phenotypes. There was significant concordance in Δ values among the 4 years for adult plants and significant correlations in Δ values measured in different years for juveniles and adults combined. The wettest year of the study, 1998, proved an exception because Δ values that year were not correlated with Δ values in any other year of the study. Consistency in Δ measured on the same plants in different years could indicate genotypic variation and/or consistency in the water status of the microhabitats the plants occupied. Two forms of plasticity in Δ were also evident; mean seasonal values were correlated with precipitation the preceding autumn, and Δ values also declined with plant size, indicating increasing water-use efficiency. Phenotypic selection was evident because in the first year of the study juvenile plants that would survive until year five averaged lower Δ values than did those that failed to survive. During the driest year, 2000, Δ was significantly negatively correlated with adult plant size, measured as the number of leaf rosettes, but the negative relationship between Δ and the number of flowering stalks, a more direct measure of fitness, was not significant. These results suggest that the direction of phenotypic selection on Δ changes as plants grow.