Model instability in predictive exchange rate regressions

In this paper we aim to improve existing empirical exchange rate models by accounting for uncertainty with respect to the underlying structural representation. Within a flexible Bayesian framework, our modeling approach assumes that different regimes are characterized by commonly used structural exchange rate models, with transitions across regimes being driven by a Markov process. We assume a time-varying transition probability matrix with transition probabilities depending on a measure of the monetary policy stance of the central bank at home and in the USA. We apply this model to a set of eight exchange rates against the US dollar. In a forecasting exercise, we show that model evidence varies over time, and a model approach that takes this empirical evidence seriously yields more accurate density forecasts for most currency pairs considered.     

Zuchtmethode und semisynthetische Nährmedien für Apfelwickler

Summary A method for the individual rearing of the codling mothLaspeyresia pomonella is described. The method allows the collection of exactly dated eggs and the rearing of a large number of larvae in a small space. By using the second medium described, it is possible to watch all developmental stages at any time without disturbing them. The average larval survival rate is 70–80%.     

Kinetik der hepatischen Farbstoffaufnahme von Indocyaningrün. Einfluss von Bilirubin und Natriumglykocholat

Summary Kinetics of hepatic uptake of indocyanine green, a dye which is used for evaluation of liver function, were studied in the rat. The results indicate that the relationship between ICG-dose and initial hepatic dye uptake obeys Michaelis-Menten kinetics suggesting an interaction of the dye with a carrier or fixed site in the liver cell. Thus it was possible to calculate maximum ICG-uptake (v _max ) and the Michaelis constant (K _m ) of this transport system from several submaximal values.v _max was 7.65 (6-06-9.65)²² mg per 100 g liver/min and K _m 0.56 (0.31–0.81)²². Under the influence of substances which inhibit the elimination of dyes by the liver the parametersv _max and K _m showed changes which allowed characterization of the type of inhibition. While sodium glycocholate had no influence on maximum hepatic ICG-uptake and the Michaelis constant bilirubin caused a significant increase of K _m to 1.29 (0.68–1.90)²² without significantly changingv _max . These data suggest that bilirubin interferes with hepatic uptake of indocyanine green by competitive inhibition and that uptake of bile acids is dependent on a different mechanism.     

Scotopic luminosity curve as obtained by the visual evoked response in man

Zusammenfassung Eine visuell evozierte Antwort kann durch Stimulation der zentralen retinalen Anteile mit skotopischen Reizen nach Dunkeladaptation aufgenommen werden. Die spektrale Empfindlichkeit wurde für eine konstante Antwort (Latenz=210 msec) gemessen und stimint mit der dunkeladaptierten Empfindlichkeit des menschlichen Auges in der spektralen Verteilung überein. Der zeitliche Verlauf der Amplitudenzunahme des VERs während der Dunkeladaptation ist der sensorischen Empfindlichkeit ähnlich. Das VER ist eine Antwort der zentralen retinalen Anteile, kann aber neben photopischen auch Eigenschaften des skotopischen Systems aufweisen.     

Structure and evolution of the genetic code viewed from the perspective of the experimentally expanded amino acid repertoire in vivo

Much effort has been devoted recently to expanding the amino acid repertoire in protein biosynthesis in vivo. From such experimental work it has emerged that some of the non-canonical amino acids are accepted by the cellular translational machinery while others are not, i.e. we have learned that some determinants must exist and that they can even be anticipated. Here, we propose a conceptual framework by which it should be possible to assess deeper levels of the structure of the genetic code, and based on this experiment to understand its evolution and establishment. First, we propose a standardised repertoire of 20 amino acids as a basic set of conserved building blocks in protein biosynthesis in living cells to be the main criteria for genetic code structure and evolutionary considerations. Second, based on such argumentation, we postulate the structure and evolution of the genetic code in the form of three general statements: (i) the nature of the genetic code is deterministic; (ii) the genetic code is conserved and universal; (iii) the genetic code is the oldest known level of complexity in the evolution of living organisms that is accessible to our direct observation and experimental manipulations. Such statements are discussed as our working hypotheses that are experimentally tested by recent findings in the field of expanded amino acid repertoire in vivo. Received 30 June 1999; accepted 9 July 1999     

Über die Ursache des gegensätzlichen geotropischen Verhaltens von Sproß und Wurzel

Ohne Zusammenfassung     

Identification of mutations in CUL7 in 3-M syndrome

Intrauterine growth retardation is caused by maternal, fetal or placental factors that result in impaired endovascular trophoblast invasion and reduced placental perfusion. Although various causes of intrauterine growth retardation have been identified, most cases remain unexplained. Studying 29 families with 3-M syndrome (OMIM 273750), an autosomal recessive condition characterized by severe pre- and postnatal growth retardation, we first mapped the underlying gene to chromosome 6p21.1 and then identified 25 distinct mutations in the gene cullin 7 (CUL7). CUL7 assembles an E3 ubiquitin ligase complex containing Skp1, Fbx29 (also called Fbw8) and ROC1 and promotes ubiquitination. Using deletion analysis, we found that CUL7 uses its central region to interact with the Skp1-Fbx29 heterodimer. Functional studies indicated that the 3-M-associated CUL7 nonsense and missense mutations R1445X and H1464P, respectively, render CUL7 deficient in recruiting ROC1. These results suggest that impaired ubiquitination may have a role in the pathogenesis of intrauterine growth retardation in humans.     

Crystal structure of DegP (HtrA) reveals a new protease-chaperone machine

Molecular chaperones and proteases monitor the folded state of other proteins. In addition to recognizing non-native conformations, these quality control factors distinguish substrates that can be refolded from those that need to be degraded. To investigate the molecular basis of this process, we have solved the crystal structure of DegP (also known as HtrA), a widely conserved heat shock protein that combines refolding and proteolytic activities. The DegP hexamer is formed by staggered association of trimeric rings. The proteolytic sites are located in a central cavity that is only accessible laterally. The mobile side-walls are constructed by twelve PDZ domains, which mediate the opening and closing of the particle and probably the initial binding of substrate. The inner cavity is lined by several hydrophobic patches that may act as docking sites for unfolded polypeptides. In the chaperone conformation, the protease domain of DegP exists in an inactive state, in which substrate binding in addition to catalysis is abolished.     

Filamentous phage integration requires the host recombinases XerC and XerD

Many bacteriophages and animal viruses integrate their genomes into the chromosomal DNA of their hosts as a method of promoting vertical transmission. Phages that integrate in a site-specific fashion encode an integrase enzyme that catalyses recombination between the phage and host genomes. CTX phi is a filamentous bacteriophage that contains the genes encoding cholera toxin, the principal virulence factor of the diarrhoea-causing Gram-negative bacterium Vibrio cholerae. CTX phi integrates into the V. cholerae genome in a site-specific manner; however, the approximately 6.9-kilobase (kb) CTX phi genome does not encode any protein with significant homology to known recombinases. Here we report that XerC and XerD, two chromosome-encoded recombinases that ordinarily function to resolve chromosome dimers at the dif recombination site, are essential for CTX phi integration into the V. cholerae genome. The CTX phi integration site was found to overlap with the dif site of the larger of the two V. cholerae chromosomes. Examination of sequences of the integration sites of other filamentous phages indicates that the XerCD recombinases also mediate the integration of these phage genomes at dif-like sites in various bacterial species.