The plant's capacity in regulating resource demand

Regulation of resource allocation in plants is the key to integrate understanding of metabolism and resource flux across the whole plant. The challenge is to understand trade-offs as plants balance allocation between different and conflicting demands, e.g., for staying competitive with neighbours and ensuring defence against parasites. Related hypothesis evaluation can, however, produce equivocal results. Overcoming deficits in understanding underlying mechanisms is achieved through integrated experimentation and modelling the various spatio-temporal scaling levels, from genetic control and cell metabolism towards resource flux at the stand level. An integrated, interdisciplinary research concept on herbaceous and woody plants and its outcome to date are used, while drawing attention to currently available knowledge. This assessment is based on resource allocation as driven through plant-pathogen and plant-mycorrhizosphere interaction, as well as competition with neighbouring plants in stands, conceiving such biotic interactions as a "unity" in the control of allocation. Biotic interaction may diminish or foster effects of abiotic stress on allocation, as changes in allocation do not necessarily result from metabolic re-adjustment but may obey allometric rules during ontogeny. Focus is required on host-pathogen interaction under variable resource supply and disturbance, including effects of competition and mycorrhization. Cost/benefit relationships in balancing resource investments versus gains turned out to be fundamental in quantifying competitiveness when related to the space, which is subject to competitive resource exploitation. A space-related view of defence as a form of prevention of decline in competitiveness may promote conversion of resource turnover across the different kinds of biotic interaction, given their capacity in jointly controlling whole plant resource allocation.     

Roles of thioredoxin reductase during the aerobic life of Lactococcus lactis

Thiol-disulfide bond balance is generally maintained in bacteria by thioredoxin reductase-thioredoxin and/or glutathione-glutaredoxin systems. Some gram-positive bacteria, including Lactococcus lactis, do not produce glutathione, and the thioredoxin system is presumed to be essential. We constructed an L. lactis trxB1 mutant. The mutant was obtained under anaerobic conditions in the presence of dithiothreitol (DTT). Unexpectedly, the trxB1 mutant was viable without DTT and under aerated static conditions, thus disproving the essentiality of this system. Aerobic growth of the trxB1 mutant did not require glutathione, also ruling out the need for this redox maintenance system. Proteomic analyses showed that known oxidative stress defense proteins are induced in the trxB1 mutant. Two additional effects of trxB1 were not previously reported in other bacteria: (i) induction of proteins involved in fatty acid or menaquinone biosynthesis, indicating that membrane synthesis is part of the cellular response to a redox imbalance, and (ii) alteration of the isoforms of the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GapB). We determined that the two GapB isoforms in L. lactis differed by the oxidation state of catalytic-site cysteine C152. Unexpectedly, a decrease specific to the oxidized, inactive form was observed in the trxB1 mutant, possibly because of proteolysis of oxidized GapB. This study showed that thioredoxin reductase is not essential in L. lactis and that its inactivation triggers induction of several mechanisms acting at the membrane and metabolic levels. The existence of a novel redox function that compensates for trxB1 deficiency is suggested.     

Brief exposure to -2 Gz reduces cerebral blood flow velocity during subsequent +2 Gz acceleration

In order to determine the implication of the cerebral vasoconstriction occurring under -Gz acceleration in the mechanism of the push-pull effect, four healthy male non-pilots were submitted to a control centrifugation at +2 Gz, and then to an experimental run with identical +2 Gz plateau, but preceded by -2 Gz exposure. Cerebral blood flow velocity (CBFV), pulsatility index, and resistance index (RI) were continually measured with a transcranial Doppler instrument. The decrease in blood pressure and in CBFV was more important during the experimental run, when the change in RI was not different. We concluded that the cerebral vasoconstriction occurring under -2 Gz exposure seems not to be a major contributor in the mechanism of the push-pull effect appearing during subsequent +2 Gz acceleration.     

Unique biochemical and behavioral alterations in Drosophila shibire(ts1) mutants imply a conformational state affecting dynamin subcellular distribution and synaptic vesicle cycling

Dynamin is a GTPase protein that is essential for clathrin-mediated endocytosis of synaptic vesicle membranes. The Drosophila dynamin mutation shi(ts1) changes a single residue (G273D) at the boundary of the GTPase domain. In cell fractionation of homogenized fly heads without monovalent cations, all dynamin was in pellet fractions and was minimally susceptible to Triton-X extraction. Addition of Na(+) or K(+) can extract dynamin to the cytosolic (supernatant) fraction. The shi(ts1) mutation reduced the sensitivity of dynamin to salt extraction compared with other temperature-sensitive alleles or wild type. Sensitivity to salt extraction in shi(ts1) was enhanced by GTP and nonhydrolyzable GTP-gammaS. The shi(ts1) mutation may therefore induce a conformational change, involving the GTP binding site, that affects dynamin aggregation. Temperature-sensitive shibire mutations are known to arrest endocytosis at restrictive temperatures, with concomitant accumulation of presynaptic collared pits. Consistent with an effect upon dynamin aggregation, intact shi(ts1) flies recovered much more slowly from heat-induced paralysis than did other temperature-sensitive shibire mutants. Moreover, a genetic mutation that lowers GTP abundance (awd(msf15)), which reduces the paralytic temperature threshold of other temperature-sensitive shibire mutations that lie closer to consensus GTPase motifs, did not reduce the paralytic threshold of shi(ts1). Taken together, the results may link the GTPase domain to conformational shifts that influence aggregation in vitro and endocytosis in vivo, and provide an unexpected point of entry to link the biophysical properties of dynamin to physiological processes at synapses.     

Development of a minimal chemically-defined medium for the exponential growth of Streptococcus thermophilus

AIMS: The present work aimed to define a minimal chemically-defined medium which could sustain the growth of most (if not all) strains of Streptococcus thermophilus. METHODS AND RESULTS: A minimal medium containing 20 components, including one carbohydrate source, six amino acids, two metallic ions, six vitamins and urea allowed for growth of 13 out of 15 Strep. thermophilus strains. Growth of the two last strains required the presence of additional amino acids, the number of which depended on the strain. Growth rates of the strains in the minimal medium ranged from 0.38 to 0.64 h(-1), and final populations were about 10(8) cfu ml(-1). CONCLUSIONS: Streptococcus thermophilus appears much less demanding than other lactic acid bacteria. SIGNIFICANCE AND IMPACT OF THE STUDY: The definition of such a growth medium will be very useful for metabolic flux studies as well as peptide transport studies.     

La majorité des couples procréant par don de sperme envisagent d’informer l’enfant de son mode de conception, mais la plupart souhaitent le maintien de l’anonymat du donneur

Semen donation is anonymous by law since 1994 in France but has been abolished in various countries. We present the results of a study that has been conducted in 14 Cecos in 2006, including 534 couples who were waiting for the assisted procreation, were under treatment, or had already at least one child with donor semen. The results were very similar between men and women and in the various groups. Over 90% of the men and the women are in agreement with donors’ anonymity and less than 10% would like the law to be changed on this point. Approximately 25% of them would give up their parental project if the law was going to change. Almost one-third would like information on the semen donor, mainly on his health, to be transmitted to themselves and to the children. The couples who plan to become parents through semen donation make a clear distinction between donor anonymity and child disclosure on its conception circumstances.     

Treatment of Gross Obesity by Jejunal Bypass

Jejunal bypass operations were performed on 47 grossly obese patients. The results were disappointing in three patients who had a standard “14 in/4 in” Payne and DeWind procedure and therefore a more radical operation was performed, joining four inches (10·2 cm) of proximal jejunum to 10 inches (24·4 cm) of terminal ileum. Two years after the modified operation a mean of 44·2 kg had been lost and the weight tended to stabilize. This weight loss was due mainly to inadequate calorie intake. The appetite became more controlled so that if weight was regained this was small in amount. Metabolic sequelae and their symptoms also settled by two years. The physical, psychological, and social outcome was good. The postoperative period was stormy and required close medical and psychiatric supervision. There were two deaths.     

Synthesis and Biological Evaluation of Polyaminated 2′,3′-Dideoxy-3′-thiacytidine Prodrugs

Abstract

The syntheses and biological evaluation of polyaminated 2′,3′-dideoxy-3′-thiacytidine have been performed. A new lead was found to increase the in vitro antiviral potency (syncitia formation on MT-4 cell line) of two order magnitude greater than the parent nucleoside drug. Moreover, the in vitro activity on HIV macrophages was found to be more than 3 log greater than the activity of the parent drug 1.