Methodologic aspects of genomic fingerprinting in population studies]

Use of DNA fingerprinting in population studies is complicated by a number of methodical problems caused by the necessity to work with a large amount of experimental data and insufficient reproducibility of the results. In this work, possible approaches to overcome methodical difficulties faced by the authors during elaboration of the experimental technique are discussed.     

动物行为学实验带教探索与实践

目的：为提高实验教学和科研工作的质量和效果,结合国家重点实验室有利条件,从行为学实验培训角度以培养实验技术人员基本实验技能为重点。方法：安排学生学习行为医学发展史、熟练行为学动物生命观、基本实验仪器操作以及鼓励实验技术人员自行研制行为检测制仪器等课程。结果：实验技术人员了解了现代行为学的发展,掌握常规的实验方法,培养了科学的思维方式,同时也激发了实验技术人员发挥主观能动性,实现理论和技术的结合。结论：多途径带教培训有利于实验技术人员行为学实验工作打下牢固的基础。     

Effect of aerobic training on the plasma ACTH response to exercise

The purpose of this study was to reexamine the effect of training on plasma adrenocorticotropin (ACTH) levels during exercise. Ten adult volunteers were split into a control and an experimental group. The experimental group participated in a 12-wk training program that resulted in a significant 11% increase in their mean maximal O2 uptake. The plasma ACTH response to a 150-W work rate was measured in both groups before and after the training program. The experimental group demonstrated a significant reduction in the ACTH response (11 vs. 4 pg/ml) to the work rate, whereas the control group demonstrated an unchanged response (16 vs. 13 pg/ml) over the course of the study. These data suggest that the ACTH response to an absolute submaximal work rate is blunted after training.     

Comparative systemic analysis of experimental models of chemical hepatic carcinogenesis in the rat

The aim of this work is to compare several experimental protocols inducing hepatocarcinogenesis in the rat. The results show that the experimental protocols using an initiator and a promotor are not equivalent (in term of latency period and premalignant lesions) to experimental protocols using a chronic administration of one carcinogenic compound.     

Quantitative studies of bacterial chemotaxis and microbial population dynamics

Although there is a long history of conjecture regarding the role and significance of bacterial chemotaxis in microbial ecology, only recently has a significant body of work appeared attempting to address this issue. The purpose of this paper is to provide a concise overview of this work, which combined mathematical modeling of bacterial population migration and experimental measurement of the model parameters with modeling of competitive microbial population dynamics in a nonmixed environment. Predictions from the population dynamics models, based on experimental estimates of the various motility and growth parameter values, are related to the small number of experimental observations available to date dealing with the effects of bacterial motility on competition in a nonmixed environment. Current results indicate that cell motility and chemotaxis properties can be as important to population dynamics as cell growth kinetic properties, so that greater attention to this aspect of microbial behavior is warranted in future studies of microbial ecology.     

Multiplicity of steady states in a bioreactor during the production of 1,3-propanediol by <Emphasis Type="Italic">Clostridium butyricum</Emphasis>

In recent decades, the production of compounds from microorganisms has increased significantly. Glycerol as a source of substrate appears to have great potential, due to its large supply because of the increase in biodiesel production. This paper will discuss the multiplicity of steady states for the production of 1,3-propanediol from glycerol by Clostridium butyricum, employing a model that takes into account inhibition by fermentation products. The theoretical study of bifurcation enabled us to make a qualitative adjustment to the various experimental steady states, using the theoretical steady states obtained from the AUTO2007 program. The theoretical model parameters were varied to fit qualitatively the values of the experimental steady states. In addition, this work is a qualitative study, using experimental steady states that can be used as an initial study for more advanced work on optimizing the production of 1,3-propanediol.     

Protein balance: a fundamental question of cell biology needing reappraisal

Although protein synthesis and protein degradation are two independent processes that are firmly regulated, how they maintain a balance of protein in the non-growing cell remains to be established. In work in the 1980s, the author suggested a self-regulating mechanism. However, experimental work on this interesting and fundamental problem is needed for a better understanding of 'protein balance' in cells.     

Shoulder muscle co-ordination during chronic and acute experimental neck-shoulder pain. An occupational pain study

Little is known about the mechanisms leading to chronic neck-shoulder musculoskeletal disorders (MSD). The aim of the present study was to investigate and compare motor function during controlled, low load, repetitive work together with chronic or acute experimental neck-shoulder pain. The clinical study was performed on workers with (n = 12) and without (n = 6) chronic neck-shoulder pain. In the experimental study, experimental muscle pain was induced in healthy subjects by intra-muscular injection of hypertonic saline into the trapezius muscle (n = 10). The assessed parameters related to motor performance were: work task event duration, cutting forces, surface electromyogram (EMG) activity in four shoulder muscles, displacement of the centre of pressure, and arm and trunk 3D movements. For controlled cutting force levels, chronic and acute experimental pain provoked a series of changes: a decreased working rhythm and a protective reorganisation of muscle synergy (experimental study), higher EMG frequency contents which may indicate altered motor unit recruitment, and greater postural activity and a tendency towards increased arm and trunk movements. These pain-related changes can play a role in the development of MSD. The present clinical and experimental study demonstrated similar interactions between motor co-ordination and neck-shoulder pain in occupational settings. We therefore suggest that this experimental model can be used to study mechanisms related to MSD. Information on such modulatory processes may help in the design of new strategies aimed at reducing the development of MSD.     

Adaptable individuals and innovative lineages

This paper suggests (i) that while work on animal innovation has made good progress in understanding some of the proximate mechanisms and selective regimes through which innovation emerges, it has somewhat neglected the role of the social environment of innovation; a neglect manifest in the fact that innovation counts are almost always counts of resource-acquisition innovations; the invention of social tools is rarely considered. The same is true of many experimental projects, as these typically impose food acquisition tasks on their experimental subjects. (ii) That neglect is important, because innovations often pose collective action problems; the hominin species were technically innovative because they were also socially adaptable. (iii) In part for this reason, there remains a disconnect between research on hominin innovation and research on animal innovation. (iv) Finally, the paper suggests that there is something of a disconnect between the theoretical work on innovation in hominin evolution (based on theories of cultural evolution) and the experimental tradition on human innovation. That disconnect is largely due to the theoretical work retreating from strong claims about the proximate mechanisms of human cultural accumulation.     

Flow of a blood analogue fluid in a compliant abdominal aortic aneurysm model: Experimental modelling

The aim of this work is to develop a unique in vitro set-up in order to analyse the influence of the shear thinning fluid-properties on the flow dynamics within the bulge of an abdominal aortic aneurysm (AAA). From an experimental point of view, the goals are to elaborate an analogue shear thinning fluid mimicking the macroscopic blood behaviour, to characterise its rheology at low shear rates and to propose an experimental device able to manage such an analogue fluid without altering its feature while reproducing physiological flow rate and pressure, through compliant AAA. Once these experimental prerequisites achieved, the results obtained in the present work show that the flow dynamics is highly dependent on the fluid rheology. The main results point out that the propagation of the vortex ring, generated in the AAA bulge, is slower for shear thinning fluids inducing a smaller travelled distance by the vortex ring so that it never impacts the anterior wall in the distal region, in opposition to Newtonian fluids. Moreover, scalar shear rate values are globally lower for shear thinning fluids inducing higher maximum stress values than those for the Newtonian fluids. Consequently, this work highlights that a Newtonian fluid model is finally inadequate to obtain a reliable prediction of the flow dynamics within AAA.     

Interferons and the tumor cell

Optimal use of interferons (IFNs) for the treatment of tumor disease requires experimental work in order to precisely define IFN actions. We have pointed out three modes of such actions relevant for the antitumor efficacy exerted by IFNs: effects on apoptosis, effects on genes involved in malignant transformation and effects on angiogenesis. These are but three selected areas forming a basis for the development of optimal IFN therapy. Further experimental work, undertaken in these and additional IFN areas, is mandatory for the most effective clinical use of IFNs for the treatment of tumor disease.Abbreviations IFN interferon - FGF basic fibroblast growth factor     

Non-ideal tracer sedimentation equilibrium: a powerful tool for the characterization of macromolecular interactions in crowded solutions

Non-ideal tracer sedimentation equilibrium is a technique devised to quantify the effect of high concentrations of unrelated macromolecules on the self- or hetero-associations of dilute macromolecules. Principles and experimental techniques are reviewed, and previous experimental work summarized. A new analysis of experimental data is presented that requires no a priori assumptions regarding the nature of weak repulsive interactions between solute species and the concentrated (crowding) species.     

Evaluation of a Hill based muscle model for the energy cost and efficiency of muscular contraction

The purpose of this study was to evaluate a Hill-based mathematical model of muscle energetics and to disclose inconsistencies in existing experimental data. For this purpose, we simulated iso-velocity contractions of mouse fast twitch EDL and slow twitch SOL fibers, and we compared the outcome to experimental results. The experimental results were extracted from two studies published in the literature, which were based on the same methodology but yielded different outcomes (B96 and B93). In the model, energy cost was modeled as the sum of heat and work. Parameters used to model heat rate were entirely independent of the experimental data-sets. Parameters describing the mechanical behavior were derived from both experimental studies. The model was found to accurately predict the muscle energetics and mechanical efficiency of data-set B96. The model could not, however, replicate the energetics and efficiency of SOL and EDL that were found in data-set B93. The model overestimated the shortening heat rate of EDL but, surprisingly, also the mechanical work rate for both muscles. This was surprising since mechanical characteristics of the model were derived directly from the experimental data. It was demonstrated that the inconsistencies in data-set B93 must have been due to some unexplained confounding artifact. It was concluded that the presented model of muscle energetics is valid for iso-velocity contractions of mammalian muscle since it accurately predicts experimental results of an independent data-set (B96). In addition, the model appeared to be helpful in revealing inconsistencies in a second data-set (B93).     

To err and win a nobel prize: Paul Boyer,ATP synthase and the emergence of bioenergetics

Paul Boyer shared a Nobel Prize in1997 for his work on the mechanism of ATPsynthase. His earlier work, though (whichcontributed indirectly to his triumph),included major errors, both experimental andtheoretical. Two benchmark cases offer insightinto how scientists err and how they deal witherror. Boyer's work also parallels andillustrates the emergence of bioenergetics inthe second half of the twentieth century,rivaling achievements in evolution andmolecular biology. This revised version was published online in July 2006 with corrections to the Cover Date.     

The relative changes in isometric force and work during fatigue and recovery in isolated toad sartorius muscle

Toad sartorius muscle was subjected to sinusoidal varying length changes at 2 Hz to measure work. Both isometric tetanic force and work per cycle were measured before, during, and after a 3-min fatigue. Both isometric tetanic force and positive work, the work done by the muscle during the shortening part of the cycle, rapidly decreased in parallel in the first 40 s of fatigue. Thereafter, force continued to decrease, but at a slower rate, to about 10% of prefatigue values, whereas positive work levelled off at about 30% of prefatigue values. Negative work, the work done on the muscle during the lengthening part of the cycle, increased during fatigue to the extent that net work became negative. This was due to a prolonged relaxation, which resulted in active force still being generated while the muscle was being stretched. Work and force recovered at about the same rate. Isometric force measurements alone do not give any clear indication that net work will be negative under a particular set of experimental conditions.     

Computational technique for plasma parameters determination using Langmuir probe data

In the present work, we consider a new numerical method for processing the experimental information on the electron energy distribution function obtained with a Langmuir probe in a low-pressure plasma. This method offers the possibility to establish the temperature and concentration of the electrons for different forms of the distribution function. Some specific difficulties of the previous methods used to do such estimations are surpassed using the method proposed in this work.     

Devitrification in glass-forming aqueous solutions

The process by which a metastable glass, or the supercooled liquid obtained by heating the glass above its glass transition temperature, forms the stable crystalline phase or phases is generally termed devitrification. In aqueous-solution glasses the devitrification process has been found to consist mainly of the nucleation and growth of a large number of ice particles and is often most rapid at compositions near the water-rich edge of the glass-forming region of concentrations. This, unfortunately, is also the main regions of interest in the cryobiological application of these glass-forming solutions, and hence a knowledge of devitrification and how best to minimize or avoid it becomes important to this work. In this paper our experimental and theoretical knowledge of the devitrification process in aqueous and other glass-forming systems will be reviewed. Recent experimental and theoretical simulation work will also be discussed. In principle devitrification can be substantially avoided by sufficiently rapid heating; hence the purpose of the simulations is to allow the extrapolation of the experimental data into regions of high heating rates (> 100 °C min⁻¹) which are inaccessible to current experimental observation but may nonetheless be useful in the cryobiological application.     

A phenomenological model and validation of shortening-induced force depression during muscle contractions

History-dependent effects on muscle force development following active changes in length have been measured in a number of experimental studies. However, few muscle models have included these properties or examined their impact on force and power output in dynamic cyclic movements. The goal of this study was to develop and validate a modified Hill-type muscle model that includes shortening-induced force depression and assess its influence on locomotor performance. The magnitude of force depression was defined by empirical relationships based on muscle mechanical work. To validate the model, simulations incorporating force depression were developed to emulate single muscle in situ and whole muscle group leg extension experiments. There was excellent agreement between simulation and experimental values, with in situ force patterns closely matching the experimental data (average RMS error <1.5 N) and force depression in the simulated leg extension exercise being similar in magnitude to experimental values (6.0% vs. 6.5%, respectively). To examine the influence of force depression on locomotor performance, simulations of maximum power pedaling with and without force depression were generated. Force depression decreased maximum crank power by 20–40%, depending on the relationship between force depression and muscle work used. These results indicate that force depression has the potential to substantially influence muscle power output in dynamic cyclic movements. However, to fully understand the impact of this phenomenon on human movement, more research is needed to characterize the relationship between force depression and mechanical work in large muscles with different morphologies.     

A 6-hour working day--effects on health and well-being

The effect of the total amount of work hours and the benefits of a shortening is frequently debated, but very little data is available. The present study compared a group (N = 41) that obtained a 9 h reduction of the working week (to a 6 h day) with a comparison group (N = 22) that retained normal work hours. Both groups were constituted of mainly female health care and day care nursery personnel. The experimental group retained full pay and extra personnel were employed to compensate for loss of hours. Questionnaire data were obtained before and 1 year after the change. The data were analyzed using a two-factor ANOVA with the interaction term year*group as the main focus. The results showed a significant interaction of year*group for social factors, sleep quality, mental fatigue, and heart/respiratory complaints, and attitude to work hours. In all cases the experimental group improved whereas the control group did not change. It was concluded that shortened work hours have clear social effects and moderate effects on well-being.     

地衣标本的采集、制作与保存

详细论述了地衣标本的采集、制作和保存方法及注意事项,同时阐明了在采集标本的同时进行共生菌和光合共生物分离培养的重要性。