On zero-order hold equivalents of distributed parameter systems

Various connections are established between linear time-invariant distributed parameter continuous-time systems and their zero-order hold discrete-time equivalents. These connections are established in both the time and frequency domains. The time-domain connections relate various growth constants and norm bounds of the continuous-time systems considered to those of their zero-order hold discrete-time equivalents. The frequency-domain connection provides an upper bound on the difference between the frequency response of a continuous-time system and that of its zero-order hold discrete-time equivalent     

An Iterative O‐Methyltransferase Catalyzes 1,11‐Dimethylation of Aspergillus fumigatus Fumaric Acid Amides

S‐adenosyl‐l ‐methionine (SAM)‐dependent methyltransfer is a common biosynthetic strategy to modify natural products. We investigated the previously uncharacterized Aspergillus fumigatus methyltransferase FtpM, which is encoded next to the bimodular fumaric acid amide synthetase FtpA. Structure elucidation of two new A. fumigatus natural products, the 1,11‐dimethyl esters of fumaryl‐l ‐tyrosine and fumaryl‐l ‐phenylalanine, together with ftpM gene disruption suggested that FtpM catalyzes iterative methylation. Final evidence that a single enzyme repeatedly acts on fumaric acid amides came from an in vitro biochemical investigation with recombinantly produced FtpM. Size‐exclusion chromatography indicated that this methyltransferase is active as a dimer. As ftpA and ftpM homologues are found clustered in other fungi, we expect our work will help to identify and annotate natural product biosynthesis genes in various species.     

Structured singular values with nondiagonal structures. I.Characterizations

The purpose of this two-part series is to provide a robustness analysis framework for a class of problems with highly structured modeling uncertainties. This framework is more general than that of the usual block, diagonally structured uncertainties, and it corresponds to a structure consisting of block-by-block matrix perturbations. We study the structured singular value with respect to this structure, and we establish a number of novel results for this notion. This paper contains a study on the properties of the structured singular value. We give an alternative characterization of this notion as the solution of a smooth optimization problem. Furthermore, we show that under a certain circumstance the structured singular value reduces to a vector-induced matrix norm     

Molecular cloning of the murine IL-1 beta converting enzyme cDNA

IL-1 beta is a potent modulator of immune and inflammatory responses. Murine IL-1 beta is initially synthesized as an inactive 33-kDa pro-molecule that is activated by proteolytic cleavage between Asp-117 and Val-118 to generate the 17-kDa mature IL-1 beta protein. This cleavage is catalyzed by a specific protease that has been designated the IL-1 beta converting enzyme (or IL-1 beta convertase). We have used a human IL-1 beta convertase cDNA to isolate murine convertase cDNA from a WEHI-3 library. These cDNA predicted that the murine convertase is a 402-residue protein. Overall, the murine convertase showed 71% nucleotide and 62% predicted amino acid sequence identity with the human convertase. Southern blot analysis of interspecific backcross mice indicated that the murine IL-1 beta convertase is encoded by a single copy gene located on murine chromosome 9. The murine convertase showed broad constitutive expression, being detected in mononuclear phagocyte and T lymphocyte cell lines as well as in spleen, heart, brain, and adrenal glands. The expression of the murine convertase in mononuclear phagocytes was up-regulated by treatment with LPS or rIFN-gamma. These studies establish that the IL-1 beta convertase is an evolutionarily conserved, widely expressed enzyme that can be regulated at a pretranslational level.     

Effects of bovine follicular fluid and passive immunization against gonadotropin-releasing hormone (GnRH) on messenger ribonucleic acid for GnRH receptor and gonadotropin subunits in ovariectomized ewes

In cultured ovine pituitary cells, inhibin increases concentrations of mRNA encoding GnRH receptor and numbers of GnRH receptors. The objective of this study was to test the hypothesis that inhibin increases concentrations of ovine GnRH receptor mRNA in vivo. Ovariectomized ewes were used to eliminate effects of endogenous ovarian hormones, and passive immunization against GnRH was employed to avoid possible confounding influences of GnRH on GnRH receptor gene expression. Two groups of ewes (n = 5/group) were treated with 50 ml GnRH antiserum on Days 0 and 3 of the experiment. One group of immunized ewes received 10 ml charcoal-extracted bovine follicular fluid (bFF) as a source of inhibin every 8 h for 48 h on Days 4-6 of the experiment. A third group of ewes was not passively immunized and was treated only with bFF, and control ewes received no treatments. Anterior pituitary glands were collected from all ewes on Day 6. Passive immunization against GnRH, alone or in combination with treatment with bFF, decreased mean concentrations of LH (p < 0.01) and LH pulse amplitude (p < 0.001). In ewes treated only with GnRH antiserum, number of LH pulses was also reduced (p < 0.03). Circulating concentrations of FSH tended to be lower (p = 0.06) in passively immunized ewes compared to controls. Treatment with bFF, alone or in combination with GnRH antiserum, reduced circulating concentrations of FSH (p < 0.02) and amounts of FSHbeta subunit mRNA (p < 0.001) to less than 30% and 10% of control values, respectively. Despite effects of bFF on concentrations of FSHbeta mRNA and secretion of FSH, concentrations of GnRH receptor mRNA were similar among controls, ewes treated with bFF alone, and passively immunized ewes treated with bFF. Passive immunization against GnRH did not affect concentrations of GnRH receptor mRNA but resulted in a reduction (p < 0.05) in amount of LHbeta mRNA. Treatment with bFF did not affect amounts of either alpha subunit or LHbeta subunit mRNA except when combined with treatment with antiserum, when amounts of both alpha and LHbeta subunit mRNA were reduced (p < 0.05). These results do not support the hypothesis that inhibin increases concentrations of GnRH receptor mRNA in the ewe, and they provide evidence that inhibin is not an acute regulator of ovine GnRH receptor gene expression in vivo.     

Verläßlichkeit – Grundlage zur Beherrschung komplexer Rechensysteme

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