Medicago truncatula stress associated protein 1 gene (MtSAP1) overexpression confers tolerance to abiotic stress and impacts proline accumulation in transgenic tobacco

Stress associated proteins (SAP) have been already reported to play a role in tolerance acquisition of some abiotic stresses. In the present study, the role of MtSAP1 (Medicago truncatula) in tolerance to temperature, osmotic and salt stresses has been studied in tobacco transgenic seedlings. Compared to wild type, MtSAP1 overexpressors were less affected in their growth and development under all tested stress conditions. These results confirm that MtSAP1 is involved in the response processes to various abiotic constraints. In parallel, we have performed studies on an eventual link between MtSAP1 overexpression and proline, a major player in stress response. In an interesting way, the results for the transgenic lines did not show any increase of proline content under osmotic and salt stress, contrary to the WT which usually accumulated proline in response to stress. These data strongly suggest that MtSAP1 is not involved in signaling pathway responsible for the proline accumulation in stress conditions. This could be due to the fact that the overexpression of MtSAP1 provides sufficient tolerance to seedlings to cope with stress without requiring the free proline action. Beyond that, the processes by which the MtSAP1 overexpression lead to the suppression of proline accumulation will be discussed in relation with data from our previous study involving nitric oxide.     

Pictures,Preparations, and Living Processes: The Production of Immediate Visual Perception (<Emphasis Type="Italic">Anschauung</Emphasis>) in late-19th-Century Physiology

This paper addresses the visual culture of late-19th-century experimental physiology. Taking the case of Johann Nepomuk Czermak (1828–1873) as a key example, it argues that images played a crucial role in acquiring experimental physiological skills. Czermak, Emil Du Bois-Reymond (1818–1896) and other late-19th-century physiologists sought to present the achievements and perspective of their discipline by way of immediate visual perception (unmittelbare Anschauung). However, the images they produced and presented for this purpose were strongly mediated. By means of specifically designed instruments, such as the cardioscope, the contraction telegraph, and the frog pistol, and of specifically constructed rooms, so-called spectatoriums, physiologists trained and controlled the perception of their students before allowing them to conduct experiments on their own. Studying the material culture of physiological image production reveals that technological resources such as telegraphy, photography, and even railways contributed to making physiological facts anschaulich. At the same time, it shows that the more traditional image techniques of anatomy played an important role in physiological lecture halls, especially when it came to displaying the details of vivisection experiments to the public. Thus, the images of late 19th century physiology stood half-way between machines and organisms, between books and instruments.This paper was written in the context of ten project, The Experimentalizaiton of Life: Configurations of Life Sciences, Art, and Technology (1830–1930). The project is based at the Max Planck Institute for the History of Science (Dept. III: Hans-Jörg Rheinberger), Berlin, and receives funding from the Volkswagen Stiftung, Hannover. A first draft of this paper was presented, accompanied by Sven Dierig on the Virtual Laboratory, at the Institute of Theater Sciences, Free university Berlin, in December 2000. I would like to thank Sven Dierig and the other members of the project as well as Nick Hopwood, Skúli Sigurdsson and the anonymous referees and the editors of this journal for their helpful comments on an earlier version of this paper. Thanks also to Laurie McLaughlin and Nancy Anderson for helping me with the English version of the text.     

Sizing up allometric scaling theory

Metabolic rate, heart rate, lifespan, and many other physiological properties vary with body mass in systematic and interrelated ways. Present empirical data suggest that these scaling relationships take the form of power laws with exponents that are simple multiples of one quarter. A compelling explanation of this observation was put forward a decade ago by West, Brown, and Enquist (WBE). Their framework elucidates the link between metabolic rate and body mass by focusing on the dynamics and structure of resource distribution networks-the cardiovascular system in the case of mammals. Within this framework the WBE model is based on eight assumptions from which it derives the well-known observed scaling exponent of 3/4. In this paper we clarify that this result only holds in the limit of infinite network size (body mass) and that the actual exponent predicted by the model depends on the sizes of the organisms being studied. Failure to clarify and to explore the nature of this approximation has led to debates about the WBE model that were at cross purposes. We compute analytical expressions for the finite-size corrections to the 3/4 exponent, resulting in a spectrum of scaling exponents as a function of absolute network size. When accounting for these corrections over a size range spanning the eight orders of magnitude observed in mammals, the WBE model predicts a scaling exponent of 0.81, seemingly at odds with data. We then proceed to study the sensitivity of the scaling exponent with respect to variations in several assumptions that underlie the WBE model, always in the context of finite-size corrections. Here too, the trends we derive from the model seem at odds with trends detectable in empirical data. Our work illustrates the utility of the WBE framework in reasoning about allometric scaling, while at the same time suggesting that the current canonical model may need amendments to bring its predictions fully in line with available datasets.     

Sexual dimorphism in clonal growth forms and ramet distribution patterns in <Emphasis Type="Italic">Rumex acetosella</Emphasis> (Polygonaceae)

We investigated clonal traits in the dioecious herb Rumex acetosella to characterize sexual dimorphism in clonal forms and to correlate below-ground clonal patterns and above-ground ramet distributions. We recorded creeping root length, branching patterns, ramet and clump (caespitose ramets from the same position on the root) sprouting patterns, and biomass allocations in three females and males. We also estimated the patch size of flowering ramets within a quadrat. No sexual dimorphism was detected in the frequencies of branches and flowering ramets per root length. Male plants allocated proportionally more biomass to below-ground organs. Total root length did not differ between the sexes. Females sprouted more clumps with fewer flowering ramets per root length than males, which sprouted fewer clumps with more flowering ramets, which meant that clump sprouting patterns were phalanx-like in females and guerrilla-like in males. Flowering ramets were aggregately distributed in both females and males and patch sizes were similar between sexes, indicating that the spreader propagations were not found in the guerrilla-like males. We assumed that sexual dimorphism occurred in response to physiological integration for higher reproductive effort in females.     

Biological control of pedological and hydro-geomorphological processes in a deciduous forest ecosystem

This study describes the effect of soil fauna and vegetation on the development of landscapes and how these actually control soil formation, geomorphological development and hydrological response. The study area is located in a semi-natural deciduous forest on marl in Luxembourg, with a strong texture contrast in the soil at 15–25 cm depth (luvic planosols). The methodology applied is both based on hydrological and geomorphological field measurements on runoff, sediment yield, perched water table dynamics, geomorphological survey, pedological survey and measurements related to in situ ectorganic horizon dynamics and litter decay, soil animal activity, as well as measurements of dynamic soil properties such as soil moisture and swelling and shrinkage. The results show that there is a positive feedback between tree type, soil fauna activity and the development of pipes, partial areas, soils and geomorphology. The landscape can be divided into two main types: Areas where Stellario-Carpinetum vegetation and partial areas are common and areas with Milio-Fagetum vegetation on dry slopes, which are differentiating more and more over time as a result of ongoing geo-ecosystem processes, and which also reflected in their sediment yield. The hydrological response is highly different for both landscape compartments as they are dominated by matrix (Beech) and pipe flow (Hornbeam) respectively. Soil fauna and tree type drive both soil and geomorphological evolution and they both can be considered as important ecosystem engineers.     

Facile development of medium optimization for antibody production: implementation in spinner flask and hollow fiber reactor

Most bio-industrial mammalian cells are cultured in serum-free media to achieve advantages, such as batch consistency, suspended growth, and simplified purification. The successful development of a serum-free medium could contribute to a reduction in the experimental variation, enhance cell productivity, and facilitate biopharmaceuticals production using the cell culture process. Commercial serum-free media are also becoming more and more popular. However, the cell line secrets its own recombinant product and has special nutritional requirements. How can the composition of the proprietary medium be adjusted to support the specific cell’s metabolism and recombinant protein? This article uses statistical strategies to modify the commercial medium. A design of experiments is adopted to optimize the medium composition for the hybridoma cell in a serum-free condition. The supplements of peptone, ferric citrate, and trace elements were chosen to study their impact on hybridoma growth and antibody production using the response surface methodology. The stimulatory effect of the developed formulation on hybridoma growth was confirmed by the steepest ascent path. The optimal medium stimulated the hybridoma growth and antibody production in three diverse systems: a static plate, an agitated spinner flask, and a hollow fiber reactor. The cells in the developed serum-free medium had a better antibody production as compared to that in the commercial medium in the hollow fiber reactor. Our results demonstrated that the facile optimization for medium and antibody production was successfully accomplished in the hybridoma cells.     

A Model for the Acrosome Reaction in Mammalian Sperm

The acrosome reaction is a complex, calcium-dependent reaction that results in an exocytotic event required for successful fertilization of the egg. It has long been thought that the acrosome reaction occurs upon sperm binding to the zona pellucida, a viscoelastic layer surrounding the oocyte. Recent studies have suggested that the reaction may even occur before the sperm encounters the zona, perhaps mediated by progesterone or some other agonist. It has been particularly difficult to understand differences between progesterone-induced and zona-induced reactions experimentally and whether one substance is the more biologically relevant trigger. Until this present work, there has been little effort to mathematically model the acrosome reaction in sperm as a whole. Instead, attention has been paid to modeling portions of the pathways involved in other cell types. Here we present a base model for the acrosome reaction which characterizes the known biochemical reactions and behaviors of the system. Our model allows us to analyze several pathways that may act as a stabilizing mechanism for avoiding sustained oscillatory calcium responses often observed in other cell types. Such an oscillatory regime might otherwise prevent acrosomal exocytosis and therefore inhibit fertilization. Results indicate that the acrosome reaction may rely upon multiple redundant mechanisms to avoid entering an oscillatory state and instead maintain a high resting level of calcium, known to be required for successful acrosomal exocytosis and, ultimately, fertilization of the oocyte.