Estimation of aboveground biomass in conserved areas of Stipa tenacissima L. stands in the high steppes of western Algeria by mean of the Landsat 8 imagery‐based vegetation indices

The main aim of this paper was to evaluate the use of OLI spectral data as a tool to assess the steppe vegetation in a conservation context. The field sampling was conducted for two specific areas of treatment (a) an exclosure area and (b) a free grazing area. After testing several vegetation indices (VIs), the optimal results were obtained for the Normalised Difference Vegetation Index (NDVI)‐based aboveground biomass model with r² = 0.61 and r² = 0.72 for total and perennial biomass, respectively. No difference between observed and predicted total and perennial biomass was found (p = 0.700 and p = 0.306, respectively). The comparison between the two treatments using the field sampling revealed a significant difference on total plant cover (p = 0.016) and total biomass (p = 0.005), with a plant cover of 50.6% and a biomass of 325.771 kg dry matter per hectare (kg DM ha^?1) on average in grazed area and 66.9%, 1,407.869 kg DM ha^?1 in exclosure. Finally, a concordance is noted between the results obtained by the NDVI‐based biomass model and the field sampling‐based biomass.     

Cellular adaptation of the trapezius muscle in strength-trained athletes

 The aim of this study was to elucidate the cellular events that occur in the trapezius muscle following several years of strength training. In muscle biopsies from ten elite power lifters (PL) and six control subjects (C), several parameters were studied: cross-sectional area of muscle fibres, myosin heavy chain composition (MHC) and capillary supply [capillaries around fibres (CAF) and CAF/fibre area]. A method was also developed for counting the number of myonuclei and satellite cell nuclei. The proportion of fibres expressing MHC IIA, the cross-sectional area of each fibre type and the number of myonuclei, satellite cells and fibres expressing markers for early myogenesis were significantly higher in PL than in C (P<0.05). A significant correlation between the myonuclear number and the cross-sectional area was observed. Since myonuclei in mature muscle fibres are not able to divide, we suggest that the incorporation of satellite cell nuclei into muscle fibres resulted in the maintenance of a constant nuclear to cytoplasmic ratio. The presence of small diameter fibres expressing markers for early myogenesis indicates the formation of new muscle fibres. Accepted: 17 November 1998     

Contrasting use of CCR5 structural determinants by R5 and R5X4 variants within a human immunodeficiency virus type 1 primary isolate quasispecies

Macrophagetropic R5 human immunodeficiency virus type 1 (HIV-1) isolates often evolve into dualtropic R5X4 variants during disease progression. The structural basis for CCR5 coreceptor function has been studied in a limited number of prototype strains and suggests that R5 and R5X4 Envs interact differently with CCR5. However, differences between unrelated viruses may reflect strain-specific factors and do not necessarily represent changes resulting from R5 to R5X4 evolution of a virus in vivo. Here we addressed CCR5 domains involved in fusion for a large set of closely related yet functionally distinct variants within a primary isolate swarm, employing R5 and R5X4 Envs derived from the HIV-1 89.6(PI) quasispecies. R5 variants of 89.6(PI) could fuse using either N-terminal or extracellular loop CCR5 sequences in the context of CCR5/CXCR2 chimeras, similar to the unrelated R5 strain JRFL, but R5X4 variants of 89.6(PI) were highly dependent on the CCR5 N terminus. Similarly, R5 89.6(PI) variants and isolate JRFL tolerated N-terminal CCR5 deletions, but fusion by most R5X4 variants was markedly impaired. R5 89.6(PI) Envs also tolerated multiple extracellular domain substitutions, while R5X4 variants did not. In contrast to CCR5 use, fusion by R5X4 variants of 89.6(PI) was largely independent of the CXCR4 N-terminal region. Thus, R5 and R5X4 species from a single swarm differ in how they interact with CCR5. These results suggest that R5 Envs possess a highly plastic capacity to interact with multiple CCR5 regions and support the concept that viral evolution in vivo results from the emergence of R5X4 variants with the capacity to use the CXCR4 extracellular loops but demonstrate less-flexible interactions with CCR5 that are strongly dependent on the N-terminal region.     

Stimulation of cellular signaling and G protein subunit dissociation by G protein betagamma subunit-binding peptides

We previously developed peptides that bind to G protein betagamma subunits and selectively block interactions between betagamma subunits and a subset of effectors in vitro (Scott, J. K., Huang, S. F., Gangadhar, B. P., Samoriski, G. M., Clapp, P., Gross, R. A., Taussig, R., and Smrcka, A. V. (2001) EMBO J. 20, 767-776). Here, we created cell-permeating versions of some of these peptides by N-terminal modification with either myristate or the cell permeation sequence from human immunodeficiency virus TAT protein. The myristoylated betagamma-binding peptide (mSIRK) applied to primary rat arterial smooth muscle cells caused rapid activation of extracellular signal-regulated kinase 1/2 in the absence of an agonist. This activation did not occur if the peptide lacked a myristate at the N terminus, if the peptide had a single point mutation to eliminate betagamma subunit binding, or if the cells stably expressed the C terminus of betaARK1. A human immunodeficiency virus TAT-modified peptide (TAT-SIRK) and a myristoylated version of a second peptide (mSCAR) that binds to the same site on betagamma subunits as mSIRK, also caused extracellular signal-regulated kinase activation. mSIRK also stimulated Jun N-terminal kinase phosphorylation, p38 mitogen-activated protein kinase phosphorylation, and phospholipase C activity and caused Ca2+ release from internal stores. When tested with purified G protein subunits in vitro, SIRK promoted alpha subunit dissociation from betagamma subunits without stimulating nucleotide exchange. These data suggest a novel mechanism by which selective betagamma-binding peptides can release G protein betagamma subunits from heterotrimers to stimulate G protein pathways in cells.     

Characterization of recombinant diaminopropionate ammonia-lyase from Escherichia coli and Salmonella typhimurium

Diaminopropionate ammonia-lyase gene from Escherichia coli and Salmonella typhimurium was cloned and the overexpressed enzymes were purified to homogeneity. The k(cat) values, determined for the recombinant enzymes with DL-DAP, D-serine, and L-serine as substrates, showed that the enzyme from S. typhimurium was more active than that from E. coli and the K(m) values were found to be similar. The purified enzymes had an absorption maximum (lambda(max)) at 412 nm, typical of PLP dependent enzymes. A red shift in lambda(max) was observed immediately after the addition of 10mM DL-DAP, which returned to the original lambda(max) of 412 nm in about 4 min. This red shift might reflect the formation of an external aldimine and/or other transient intermediates of the reaction. The apoenzyme of E. coli and S. typhimurium prepared by treatment with L-cysteine could be partially (60%) reconstituted by the addition of PLP. The holo, apo, and the reconstituted enzymes were shown to be present as homo dimers by size exclusion chromatography.     

Modified apoptotic molecule (BID) reduces hepatitis C virus infection in mice with chimeric human livers

Hepatitis C virus (HCV) encodes a polyprotein consisting of core, envelope (E1, E2, p7), and nonstructural polypeptides (NS2, NS3, NS4A, NS4B, NS5A, NS5B). The serine protease (NS3/NS4A), helicase (NS3), and polymerase (NS5B) constitute valid targets for antiviral therapy. We engineered BH3 interacting domain death agonist (BID), an apoptosis-inducing molecule, to contain a specific cleavage site recognized by the NS3/NS4A protease. Cleavage of the BID precursor molecule by the viral protease activated downstream apoptotic molecules of the mitochondrial pathway and triggered cell death. We extended this concept to cells transfected with an infectious HCV genome, hepatocytes containing HCV replicons, a Sindbis virus model for HCV, and finally HCV-infected mice with chimeric human livers. Infected mice injected with an adenovirus vector expressing modified BID exhibited HCV-dependent apoptosis in the human liver xenograft and considerable declines in serum HCV titers.     

Evolution of competitive fitness in experimental populations of E. coli: What makes one genotype a better competitor than another?

An important problem in microbial ecology is to identify those phenotypic attributes that are responsible for competitive fitness in a particular environment. Thousands of papers have been published on the physiology, biochemistry, and molecular genetics of Escherichia coli and other bacterial models. Nonetheless, little is known about what makes one genotype a better competitor than another even in such well studied systems. Here, we review experiments to identify the phenotypic bases of improved competitive fitness in twelve E. coli populations that evolved for thousands of generations in a defined environment, in which glucose was the limiting substrate. After 10000 generations, the average fitness of the derived genotypes had increased by 50% relative to the ancestor, based on competition experiments using marked strains in the same environment. The growth kinetics of the ancestral and derived genotypes showed that the latter have a shorter lag phase upon transfer into fresh medium and a higher maximum growth rate. Competition experiments were also performed in environments where other substrates were substituted for glucose. The derived genotypes are generally more fit in competition for those substrates that use the same mechanism of transport as glucose, which suggests that enhanced transport was an important target of natural selection in the evolutionary environment. All of the derived genotypes produce much larger cells than does the ancestor, even when both types are forced to grow at the same rate. Some, but not all, of the derived genotypes also have greatly elevated mutation rates. Efforts are now underway to identify the genetic changes that underlie those phenotypic changes, especially substrate specificity and elevated mutation rate, for which there are good candidate loci. Identification and subsequent manipulation of these genes may provide new insights into the reproducibility of adaptive evolution, the importance of co-adapted gene complexes, and the extent to which distinct phenotypes (e.g., substrate specificity and cell size) are affected by the same mutations.     

Tridimensional evaluation and optimization of the orthotic treatment of adolescent idiopathic scoliosis

Adolescent idiopathic scoliosis involves complex tridimensional deformities of the spine, rib cage and pelvis. Moderate curves generally are treated using an orthosis. This paper presents different studies performed over the last fifteen years related to the biomechanical evaluation and optimization of the orthopedic treatment of scoliotic deformities. Patient specific 3D models of the spine, pelvis and rib cage are computed from calibrated radiographs, and are used to calculate 2D and 3D clinical indices. The torso shape is acquired using surface topography. With such internal and external 3D models, the efficacy of the most frequently used orthoses can be analyzed and new treatments can be developed. Pressures generated by a brace on the patient's trunk were measured using a flexible matrix of pressure sensors and displayed over the patient's internal geometry in order to analyze the brace efficacy. Patient specific finite element models have been developed, including the osseo-ligamentous structures as well as the muscles, the neuro-control, trunk growth and its adaptation to the stress. These models were used to analyze the effects of the Boston brace. The electro-myographic activity also was measured to analyze the < active > correction mechanisms. Adjustment techniques and software are used to help the orthotists with real time feedback when the brace is being fabricated and adjusted to the patient. Residual growth potential is also being added to the computer model to simulate the long term effect of a brace. The improvement of the orthotic treatments of scoliotic deformities is very encouraging. The exploitation of such tools is expected to allow reaching optimal treatment personalized to each patient. double dagger.