Water-use efficiency as a means of modelling net assimilation in boreal forests

Although the processes governing photosynthesis are well understood, scaling from shoot to canopy in coniferous forests is complex. Development of different sap-flow techniques has made it possible to measure transpiration of whole trees and thereby also of whole canopies. There is a strong link between photosynthesis and transpiration, for which reason it would be interesting to test whether measurements of canopy transpiration could also be used to estimate canopy photosynthesis. As a first step towards this, water-use efficiency (WUE) was studied at branch and canopy scales on the basis of branch gas-exchange measurements, with half-hourly and daily temporal resolution. Half-hourly and daily WUE at both branch and canopy scales showed a strong dependency on vapour-pressure deficit ('e). Branch photosynthesis modelled from branch transpiration and 'e mimicked well measured branch photosynthesis. Also, modelled photosynthesis, scaled to canopy and compared to net forest CO₂ exchange measured by the eddy-covariance technique, occasionally showed good agreement. In spite of these seemingly promising results, there was a difference in the response to 'e between branches and between years, which needs to be better understood.     

Studies on evolutionary and selective properties of hypercycles using a Monte Carlo method

Summary The most relevant properties of hypercycles were previously studied mainly from a theoretical point of view. We have developed a Monte Carlo method simulating hypercyclic organization to obtain information about the dynamics of this prebiotic organization. Nucleation, growth, and selective properties have been tested and the results obtained are in good agreement with those of the theoretical predictions. The influence of hypercyclic organization of the error threshold has also been studied. As a consequence of the emergence of a hypercycle, the value of this threshold decreases. The amount of this decrease depends on the population size. Moreover, for some interval of quality factor values, either the hypercycle organization or an error catastrophe can be produced, depending on the initial conditions. The influence of these phenomena on both the dynamic behavior and evolutionary advantages of the hypercycle, as well as their decisive roles on genome size, are discussed.Presented at the FEBS Symposium on Genome Organization and Evolution, held in Crete, Greece, September 1–5, 1986     

Histochemical characterization of glycoproteins present in jejunal and colonic goblet cells of pigs on different diets

Summary We examined the glycoprotein composition of intestinal goblet cells in jejunal and colonic biopsies obtained from pigs on different diets. Paraffin sections were stained both chemically and with the following horseradishperoxidase conjugated lectins: Canavalia ensiformis (Con-A), Limulus polyphemus (LPA), Lotus tetragonolobus (LTA), Arachis hypogaea (PNA), Ricinus communis (RCA1), Glycine max (SBA) and Triticum vulgaris (WGA). Using chemical staining procedures, only small quantitative differences were noted between the two organs. With respect to lectin staining, the mucus of the jejunum was characterized by the absence of Con-A binding sites, and colonic mucus consistently exhibited an absence of SBA affinity. After dietary modifications, O-acetyl sialic acid reactivity was lowered in the jejunum but was enhanced in the colon. In the jejunum, the glycoproteins became neuraminidase susceptible, whereas the colon became characterized by the absence of neutral mucins. The affinity for the tested lectins after the different diets was variable, but the most striking effects were observed after the fibreless diet (milk alone). Our data suggest the existence of marked regional variations in goblet-cell mucus and indicate significant differences between the glycoprotein components of the jejunal and colonic mucosa. Furthermore, the biosynthesis of mucins in both regions was altered by even only short-term feeding modifications.     

Improved media for normal human muscle satellite cells: Serum-free clonal growth and enhanced growth with low serum

Summary We have developed a serum-free medium for clonal growth of normal human muscle satellite cells (HMSC). It consists of an optimized nutrient medium MCDB 120, plus a serum-free supplement, designated SF, that contains epidermal growth factor (EGF), insulin, dexamethasone, bovine serum albumin, and fetuin. Fibroblast growth factor was needed with dialyzed fetal bovine serum (dFBS) as the only other supplement, but in media containing SF, it was only slightly beneficial, and was omitted from the final medium without significant loss. Clonal growth of HMSC in MCDB 120 plus SF is as good as with 15% serum and 0.5% chicken embryo or bovine pituitary extract. However, growth is further improved by use of a doubly-supplemented (DS) medium containing both SF and 5% dFBS. Clonal growth of HMSC in the DS medium far exceeds that in previous media with any amount of serum, and monolayer growth is at least equal to that in conventional media with higher levels of serum. Cells grown in these media exhibit little differentiation, even when grown to high densities. However, they retain the capacity for extensive fusion and synthesis of increased creatine kinase when transferred to a serum-free differentiation-promoting medium, such as Dulbecco's modified Eagle's medium plus insulin. All experiments were done with clonal cultures of HMSC to insure that observed growth responses were always those of muscle cells. This research was supported by a grant from the Muscular, Dystrophy Association. Editor's statement This article describes the optimization of both the basal nutrient medium and growth factor requirements for human muscle cells in vitro. This system is critical for studies of normal muscle cell and molecular biology, as well as for understanding diseases of muscle such as Duchenne, Muscular Dystrophy.     

Morphogenesis in leaf,hypocotyl and root explants of Digitalis thapsi L. cultured in vitro

The effects of the auxins 2,4-D, NAA and IAA either alone or in combination with kinetin or BA were investigated to assess the morphogenetic potential of leaf, root and hypocotyl explants of Digitalis thapsi. Calluses were obtained from the three explants in basal medium without the addition of growth regulators and in leaves, the calluses formed roots. Application of 2,4-D, NAA or BA increased callus formation. The presence of NAA induced root formation and that of BA induced shoot formation via callus interphase. Indole-3-acetic acid alone only induced the generation of roots in the hypocotyl callus. Kinetin was ineffective in all the explants tested. Combinations of NAA with kinetin or BA were more effective in inducing organogenesis in leaf explants. Optimum responses were obtained in hypocotyl and root explants by using IAA in combination with BA, the highest rate of shoot regeneration being observed in hypocotyl explants.Rooting of the differentiated shoots was readily achieved in media without growth regulators. Regenerated plantlets were transferred to soil and grew with a survival rate of 70%.Abbreviations BA benzyladenine - 2,4-D 2,4-dichlorophenoxyacetic acid - IAA indoleacetic acid, Kin-kinetin - NAA naphthaleneacetic acid     

The phylogenic expression of plasmolipin in the vertebrate nervous system

Plasmolipin is a plasma membrane proteolipid is a major myelin membrane component (Cochary et al., 1990). In this study we report the phylogenic expression of plasmolipin in the vertebrate nervous system. Using Western blot analysis with polyclonal antibodies, we have analyzed membrane fractions, including myelin, from elasmobranchs, teleosts, amphibians, reptiles, birds and mammals. On the basis of immune detection, plasmolipin appears to be restricted to the mammalian nervous system. Comparison of the central and peripheral nervous systems of mammals showed only minor differences in the level of plasmolipin in these two regions. Within mammals, little quantitative differences were observed when rat, human and bovine membrane fractions were compared. The late evolutionary expression of plasmolipin which results in its restriction to mammals makes it unique among the (major) myelin proteins. The potential physiologic significance of these data are discussed.Abbreviations EDTA Ethylene diamine N.,NN tetracetic acid - EGTA Ethylene glycol bis-(B-Aminoethyl Ether) N,,NN tetracetic acid - MES ([N-Morpholino] ethane sulfonic acid) DCCD, N, Dicyclohexyl carbodiimide     

Permeability behavior of liposomes prepared from fatty acids and fatty acid methyl esters

The permeability properties of liposomes prepared at pH 8.7 from a fatty acid and either methyl oleate or methyl elaidate, with or without cholesterol, were investigated. The fatty acids used were oleic acid, elaidic acid, and the selenium-containing fatty acids 9-selenaheptadecanoic acid and 13-selenaheneicosanoic acid. The liposomes trapped sucrose and carboxyfluorescein. Their volume change resulting from osmotic shock was directly proportional to the change in absorbance (light scattering). Liposomes prepared from oleic acid and either methyl oleate or methyl elaidate underwent osmotic swelling much more slowly than liposomes prepared from elaidic acid and either methyl oleate or methyl elaidate. Incorporation of cholesterol decreased the initial rate of erythritol permeation, especially in liposomes containing methyl oleate. The swelling rates of liposomes prepared with the selenium-containing fatty acids indicated that incorporation of methyl elaidate gave more tightly packed bilayers than did incorporation of methyl oleate. The effect of cholesterol on the initial rate of erythritol influx was greater in oleic acid and elaidic acid liposomes than in selenium-containing fatty acid liposomes, indicating that the large bulk of the selenium heteroatom suppresses the ability of cholesterol to interact with the hydrocarbon chain.     

Condensation of DNA by the C-terminal domain of histone H1. A circular dichroism study

The condensation of DNA by the C-terminal domain of histone H1 has been studied by circular dichroism in physiological salt concentration (0.14 M NaF). As the intact H1 molecule, its C-terminal domain induces the so-called psi state of DNA that is characterized by a nonconservative circular dichroism spectrum which is currently attributed to ordered aggregation of the DNA molecules. On a molar basis, intact H1 and its C-terminal domain give spectra of similar intensity. Neither the globular domain of H1 nor an N-terminal fragment, that includes both the globular and N-terminal domains, has any effect on the conservative circular dichroism of DNA. From these results it is concluded that the condensation of DNA mediated by histone H1 is mainly due to its C-terminal domain. The effect of the salt concentration and the size of DNA molecules on the circular dichroism of the complexes are also examined.