Water Stress-Induced Responses in the Growth,Cuticular Wax Composition,Chloroplast Pigments and Soluble Protein Content,and Redox Metabolism of Two Genotypes of Ricinus communis L.

Journal of Plant Growth Regulation - The aim of this study was to investigate the physiological and biochemical responses to three different water regimes in two castor bean genotypes (BRS Energia...     

Biosynthesis of a thermostable gellan lyase by newly isolated and characterized strain of Geobacillus stearothermophilus 98

The thermophilic strain able to degrade gellan was isolated from Bulgarian hot spring. According to its morphological and biochemical properties and by partial sequencing of its 16S rDNA, it was classified as Geobacillus stearothermophilus. It grew in a synthetic medium with gellan as the only carbon source with a specific growth rate of 0.69 h⁻¹ and generation time of 60 min. The strain produced thermostable gellan lyase extracellularly during exponential phase. Its synthesis was inducible; the enzyme was not registered in culture liquid without gellan. The enzyme activity was increased tenfold in conditions of continuous cultivation compared to data from batch fermentations and enzyme productivity was almost sixfold higher. The enzyme showed optimal activity at 75°C in a very large pH area 4–8.5. This enzyme is the first reported thermostable gellan lyase, its residual activity was 100% after 24 h incubation at 60°C and its half-life was 60 min at 70°C.     

Regulation of endothelin-converting enzyme-1 expression in human neuroblastoma cells

In recent years endothelin-converting enzyme (ECE-1) has been suggested to play an important role in amyloid-beta peptide metabolism as one of the amyloid-degrading enzymes. In this connection, the analysis of the levels of expression and distribution of ECE-1 in the brain under normal and pathologic conditions could be important in neurodegeneration and pathogenesis of Alzheimer disease. In our previous studies, we have demonstrated that expression of ECE-1 was significantly reduced in the cortex of adult rats after 15 mins of global ischemia. It was also significantly reduced in the striatum of rats subjected to prenatal hypoxia. In the present study, we analyzed effects of hypoxia and oxidative stress on ECE-1 in human neuroblastoma NB7 cells and effects of the cholinergic agonist carbachol and the phorbol ester, phorbol 12-myristate 13-acetate (PMA). We have found that chronic (24 hrs) hypoxia and oxidative stress resulted in 30% and 20% decrease in expression of ECE-1 at the protein level, respectively, although at the level of ECE-1 mRNA there were no statistically significant changes. Serum withdrawal from the incubation medium as well as addition of carbachol or PMA for 24 hrs also led to a significant reduction of the levels of ECE-1 protein in NB7 cells. Further study of the downstream signaling cascades involved in downregulation of ECE expression in NB7 cells and primary neuronal cells might provide us with new insights into possible therapeutic strategies for prevention or treatment of Alzheimer disease in elderly patients and those who suffer from stroke or cerebrovascular disorders.     

Endocrine changes in male stumptailed macaques (Macaca arctoides) as a response to odor stimulation with vaginal secretions

In mammalian species, social chemosignals are important in modulating endocrine reproductive functions. In nonhuman primates, previous studies have described a high frequency of mounting behavior by females in the follicular and periovulatory phases of the menstrual cycle. Stumptailed macaque females do not signal receptivity by means of sexual swellings, as do others macaques, therefore providing a good model in which to study chemical signaling of reproductive status. We exposed anesthetized stumptailed males to vaginal secretions of either late follicular or menses phase or to saline solution to determine the endocrine changes promoting male sexual behavior. In males exposed to follicular secretions, plasma testosterone concentrations were sustained up to 120 min after exposure. Such an effect was not observed in animals exposed to menses or saline odor sources. A luteinizing hormone surge, occurring 30 minutes after exposure to late follicular phase secretion swabs, preceded this sustained testosterone effect. The fact that late follicular scents induce sustained testosterone concentrations provides support to the idea that stumptailed males draw information concerning female reproductive status from the female's vaginal odor.     

Kinetics of the interaction of desAABB-fibrin monomer with immobilized fibrinogen

The soluble and stable fibrin monomer-fibrinogen complex (SF) is well known to be present in the circulating blood of healthy individuals and of patients with thrombotic diseases. However, its physiological role is not yet fully understood. To deepen our knowledge about this complex, a method for the quantitative analysis of interaction between soluble fibrin monomers and surface-immobilized fibrinogen has been established by means of resonant mirror (IAsys) and surface plasmon resonance (BIAcore) biosensors. The protocols have been optimized and validated by choosing appropriate immobilization procedures with regeneration steps and suitable fibrin concentrations. The highly specific binding of fibrin monomers to immobilized fibrin(ogen), or vice versa, was characterized by an affinity constant of approximately 10(-8)M, which accords better with the direct dissociation of fibrin triads (KD approximately 10(-8) -10(-9) M) (J. R. Shainoff and B. N. Dardik, Annals of the New York Academy of Science, 1983, Vol. 27, pp. 254-268) than with earlier estimations of the KD for the fibrin-fibrinogen complex (KD approximately 10(-6) M) (J. L. Usero, C. Izquierdo, F. J. Burguillo, M. G. Roig, A. del Arco, and M. A. Herraez, International Journal of Biochemistry, 1981, Vol. 13, pp. 1191-1196).     

Biochemical and NMR study on the competition between proteins SC35, SRp40, and heterogeneous nuclear ribonucleoprotein A1 at the HIV-1 Tat exon 2 splicing site

The human immunodeficiency virus, type 1, Tat protein plays a key role in virus multiplication. Because of its apoptotic property, its production is highly controlled. It depends upon the A3 splicing site utilization. A key control of site A3 activity is the ESS2 splicing silencer, which is located within the long stem-loop structure 3 (SLS3), far downstream from site A3. Here, by enzymatic footprints, we demonstrate the presence of several heterogeneous nuclear ribonucleoprotein (hnRNP) A1-binding sites on SLS3 and show the importance of the C-terminal Gly domain of hnRNP A1 in the formation of stable complexes containing several hnRNP A1 molecules bound on SLS3. Mutations in each of the UAG triplets in ESS2 strongly reduce the overall hnRNP A1 binding, showing the central role of ESS2 in hnRNP A1 assembly on SLS2-SLS3. Using NMR spectroscopy, we demonstrate the direct interaction of ESS2 with the RNA recognition motifs domains of hnRNP A1. This interaction has limited effect on the RNA two-dimensional structure. The SR proteins SC35 and SRp40 were found previously to be strong activators of site A3 utilization. By enzymatic and chemical footprints, we delineate their respective binding sites on SLS2 and SLS3 and find a strong similarity between the hnRNP A1-, SC35-, and SRp40-binding sites. The strongest SC35-binding site only has a modest contribution to site A3 activation. Hence, the main role of SR proteins at site A3 is to counteract hnRNP A1 binding on ESS2 and ESE2. Indeed, we found that ESE2 has inhibitory properties because of its ability to bind hnRNP A1.     

Murine models based on acute myeloid leukemia-initiating stem cells xenografting

Acute myeloid leukemia(AML) is an aggressive malignant disease defined by abnormal expansion of myeloid blasts. Despite recent advances in understanding AML pathogenesis and identifying their molecular subtypes based on somatic mutations, AML is still characterized by poor outcomes, with a 5-year survival rate of only 30%-40%, the majority of the patients dying due to AML relapse. Leukemia stem cells(LSC) are considered to be at the root of chemotherapeutic resistance and AML relapse. Although numerous studies have tried to better characterize LSCs in terms of surface and molecular markers, a specific marker of LSC has not been found, and still the most universally accepted phenotypic signature remains the surface antigens CD34+CD38- that is shared with normal hematopoietic stem cells. Animal models provides the means to investigate the factors responsible for leukemic transformation, the intrinsic differences between secondary post-myeloproliferative neoplasm AML and de novo AML, especially the signaling pathways involved in inflammation and hematopoiesis. However, AML proved to be one of the hematological malignancies that is difficult to engraft even in the most immunodeficient mice strains, and numerous ongoing attempts are focused to develop "humanized mice" that can support the engraftment of LSC. This present review is aiming to in-troduce the field of AML pathogenesis and the concept of LSC, to present the current knowledge on leukemic blasts surface markers and recent attempts to develop best AML animal models.     

Introgressive hybridization and morphological transgression in the contact zone between two Mediterranean Solea species

Hybrid zones provide natural experiments where new combinations of genotypes and phenotypes are produced. Studying the reshuffling of genotypes and remodeling of phenotypes in these zones is of particular interest to document the building of reproductive isolation and the possible emergence of transgressive phenotypes that can be a source of evolutionary novelties. Here, we specifically investigate the morphological variation patterns associated with introgressive hybridization between two species of sole, Solea senegalensis and Solea aegyptiaca. The relationship between genetic composition at nuclear loci and individual body shape variation was studied in four populations sampled across the hybrid zone located in northern Tunisia. A strong correlation between genetic and phenotypic variation was observed among all individuals but not within populations, including the two most admixed ones. Morphological convergence between parental species was observed close to the contact zone. Nevertheless, the samples taken closest to the hybrid zone also displayed deviant segregation of genotypes and phenotypes, as well as transgressive phenotypes. In these samples, deviant body shape variation could be partly attributed to a reduced condition index, and the distorted genetic composition was most likely due to missing allelic combinations. These results were interpreted as an indication of hybrid breakdown, which likely contributes to postmating reproductive isolation between the two species.     

Expression of full-length human pro-urokinase in mammary glands of transgenic mice

Human pro-urokinase expressed in the mammary glands of transgenic animals is quickly activated and converted to urokinase by proteases that are present in the milk. Thus, it is nearly impossible to isolate full-sized pro-urokinase from the milk of transgenic animals. To solve this problem, we constructed transgenic mice that express human pro-urokinase and modified ecotin, which is a potent serine protease inhibitor from E. coli, in their mammary glands. The gene encoding ecotin was modified so as to enhance its specificity for the human urokinase-type plasminogen activator. Co-expression of modified ecotin and human pro-urokinase in the mammary glands allows for purification of full-length human pro-urokinase from these transgenic mice. The results described here suggest a general way of preventing the activation of zymogens that are expressed in the mammary glands of transgenic animals by co-expression of a zymogen along with a protease inhibitor.