A mathematical model that uses Gaussian distribution to analyze the germination of Manfreda brachystachya (Agavaceae) in a thermogradient

Germination of nondormant seeds of Manfreda brachystachya (Agavaceae) was analyzed at temperatures ranging from 11–35°C. Maximum germination (95%) occurred at 25°C. An exponential sigmoid relationship was found between time and cumulative germination. Germination rate for every subpopulation (10–90% germination) was estimated by means of a normal distribution analysis. The kurtosis indicated die amplitude of the range of temperatures where the highest germination rates were concentrated, and the skew indicated sharply inhibitory temperatures in the range of temperatures used. Based on analysis of the normal distribution models for each subpopulation, we calculated a theoretical function which described germination rate over the temperature range considered: F(T,x) = A × exp[-B(C−1)²], where A is the function that describes germination rate for each subpopulation (characterized by the percentage [x] at optimal temperature); B is a shape parameter, 1/(σ²); and C is the ratio between each germination temperature (T) and the optimal germination temperature. The Gaussian curves were used to calculate thermal time, and base and ceiling temperatures. Germination thermal time ranged from 1333 to 2373°C h, and base and ceiling temperatures were 10.44 ± 0.7°C and 39.54 ± 0.7°C, respectively. There was a linear relationship between thermal time and cumulative percentage of germination of the subpopulations. Based on fitted curves for each subpopulation, the use of a general model for all the subpopulations has been proven: F8 = A × exp[−5.9437(C−1)²], where changes in the curves for each subpopulation depended on temperature only.     

Purification and characterization of limonoate dehydrogenase from Rhodococcus fascians.

Limonoate dehydrogenase from Rhodococcus fascians has been purified to electrophoretic homogeneity by a procedure that consists of ion-exchange, hydrophobic, and affinity chromatography. The native enzyme has a molecular mass of around 128,000 Da and appears to be composed of four similar subunits (30,000 Da each). The isoelectric point is 4.9 as determined by isoelectric focusing. The homogeneous enzyme was used to determine the NH2-terminal amino acid sequence. The enzyme was purified from cells grown in either fructose or limonoate as a carbon source. Limonoate dehydrogenase activity was higher in limonoate-grown cultures. Additionally, the enzyme preparations differed in their affinity for limonoids but not for NAD+. In all cases limonoate dehydrogenase exhibited a higher catalytic rate and stronger affinity for limonoate A-ring lactone than for disodium limonoate, the limonoid traditionally used for in vitro activity assays. Our data confirm previous reports proposing that limonoate A-ring lactone is the physiological substrate for limonoate dehydrogenase. The increase in limonoate dehydrogenase activity observed in limonoate-grown cultures appears to be caused by a rise in protein levels, since chloramphenicol prevented such an effect.     

High-frequency rearrangements in Rhizobium leguminosarum bv. phaseoli plasmids.

High-frequency genomic rearrangements affecting the plasmids of Rhizobium leguminosarum bv. phaseoli CFN42 were analyzed. This strain contains six large plasmids ranging in size from 200 to 600 kb. In the absence of any selective pressure, we found 11 strains from 320 analyzed colonies that presented different kinds of plasmid-borne rearrangements, including sequence amplification, deletion, cointegration, and loss of plasmids. These data support the concept that the R. leguminosarum bv. phaseoli genome is a dynamic structure and imply that strains are mixtures of similar but not identical cells.     

Creatine supplementation in health and disease. Effects of chronic creatine ingestion in vivo: Down-regulation of the expression of creatine transporter isoforms in skeletal muscle

Interest in creatine (Cr) as a nutritional supplement and ergogenic aid for athletes has surged over recent years. After cellular uptake, Cr is phosphorylated to phosphocreatine (PCr) by the creatine kinase (CK) reaction using ATP. At subcellular sites with high energy requirements, e.g. at the myofibrillar apparatus during muscle contraction, CK catalyzes the transphosphorylation of PCr to ADP to regenerate ATP, thus preventing a depletion of ATP levels. PCr is thus available as an immediate energy source, serving not only as an energy buffer but also as an energy transport vehicle. Ingestion of creatine increases intramuscular Cr, as well as PCr concentrations, and leads to exercise enhancement, especially in sprint performance. Additional benefits of Cr supplementation have also been noticed for high-intensity long-endurance tasks, e.g. shortening of recovery periods after physical exercise.The present article summarizes recent findings on the influence of Cr supplementation on energy metabolism, and introduces the Cr transporter protein (CreaT), responsible for uptake of Cr into cells, as one of the key-players for the multi-faceted regulation of cellular Cr homeostasis. Furthermore, it is suggested that patients with disturbances in Cr metabolism or with different neuro-muscular diseases may benefit from Cr supplementation as an adjuvant therapy to relieve or delay the onset of symptoms. Although it is still unclear how Cr biosynthesis and transport are regulated in health and disease, so far there are no reports of harmful side effects of Cr loading in humans. However, in this study, we report that chronic Cr supplementation in rats down-regulates in vivo the expression of the CreaT. In addition, we describe the presence of CreaT isoforms most likely generated by alternative splicing.     

Pyrazolopyrimidines as highly potent and selective,ATP-competitive inhibitors of the mammalian target of rapamycin (mTOR): Optimization of the 1-substituent

A series of pyrazolopyrimidine mammalian Target Of Rapamycin (mTOR) inhibitors with various substituents at the 1-position have been prepared, resulting in compounds with excellent potency, selectivity and microsomal stability. Combination of a 1-cyclohexyl ketal group with a 2,6-ethylene bridged morpholine in the 4-position and a ureidophenyl group in the 6-positon resulted in compound 8a, that selectively suppressed key mTOR biomarkers in vivo for at least 8 h following iv administration and showed excellent oral activity in a xenograft tumor model.     

Both the Extracellular Leucine-Rich Repeat Domain and the Kinase Activity of FLS2 Are Required for Flagellin Binding and Signaling in Arabidopsis

In Arabidopsis, activation of defense responses by flagellin is triggered by the specific recognition of the most conserved domain of flagellin, represented by the peptide flg22, in a process involving the FLS2 gene, which encodes a leucine-rich repeat serine/threonine protein kinase. We show here that the two fls2 mutant alleles, fls2-24 and fls2-17, which were shown previously to confer insensitivity to flg22, also cause impaired flagellin binding. These features are rescued when a functional FLS2 gene is expressed as a transgene in each of the fls2 mutant plants, indicating that FLS2 is necessary for flagellin binding. The point mutation of the fls2-17 allele lies in the kinase domain. A kinase carrying this missense mutation lacked autophosphorylation activity when expressed in Escherichia coli. This indicates that kinase activity is required for binding and probably affects the stability of the flagellin receptor complex. We further show that overexpression of the kinase-associated protein phosphatase (KAPP) in Arabidopsis results in plants that are insensitive to flagellin treatment, and we show reduced flg22 binding in these plants. Furthermore, using the yeast two-hybrid system, we show physical interaction of KAPP with the kinase domain of FLS2. These results suggest that KAPP functions as a negative regulator of the FLS2 signal transduction pathway and that the phosphorylation of FLS2 is necessary for proper binding and signaling of the flagellin receptor complex.     

Purification and characterization of murine beta-nerve growth factor

Beta-nerve growth factor (β-NGF) is a trophic factor in the nervous system. We aimed to isolate and characterize this protein in view of its potential therapeutic use in neurodegenerative diseases. For purification a two-step ion-exchange procedure was followed. The characterization was performed using separation and immunological techniques, as well as a biological assay. These studies showed that the obtained protein consisted of a mixture of β-NGF molecules, intact at their NH₂-terminal extreme, and molecules which have lost the NH₂-terminal octapeptide and exhibit modifications increasing its hydrophobicity. All these molecular species were recognized immunologically and showed biological activity.     

Identification of nucleoli in the early branching protist Giardia duodenalis

Giardia duodenalis has been described as 'anucleolated'. In this work we analysed the subcellular distribution of several nucleolar markers in Giardia nuclei using silver and immunostaining techniques for electron and confocal laser microscopy as well as expression of epitope-tagged proteins in transgenic trophozoites. We identified anteronuclear fibrogranular structures corresponding to nucleolar organising regions with recruited ribonucleoprotein complexes, rRNA and epitope-tagged fibrillarin and rRNA-pseudouridine synthase (CBF5). Recombinant fibrillarin and CBF5 were targeted to this subcompartment. This study demonstrates the presence of nucleoli in G. duodenalis and provides a model to analyse minimal requirements for nucleolar assembly and maintenance in eukaryotic cells.     

Le Paléolithique Supérieur dans la moyenne vallée de l’Ebre

After 30 years of research, we begin to perceive an incipient outline of the Upper Palaeolithic in the central Ebro Valley. The assembled data permit us to speak of human occupation on the Southern face of the Pyrenees, but also on the borders of the Iberian Mountains and of the Ebro basin. All these sites seem to mark the passageways from and to the neighbour territories, emphasizing the communication pathway role of the Iberian basin.