Non-linear filtering with discontinuous observations and applications to life sciences

In various applications one faces the problem of estimating a signal from discontinuous observations. For example, in biomedical applications the signal may be the ‘state’ of a given organ and one observes through an external counter the amount of radioactivity sequestered by the organ after injection of a radioactive tracer. Here the problem is studied in the context of nonlinear filtering when the signal can be modelled as either a random variable or a diffusion process, and the observations have a continuous and a purely discontinuous component; both components may be affected by the signal. When the signal is a random variable an explicitly computable solution is obtained; for the diffusion case the solution is given as a sequence of approximating filters that can be computed recursively.     

A phylogenetic analysis of Legionella

Four species of Legionella, L. pneumophila NCTC 11192, L. bozemanii NCTC 11368, L. micdadei NCTC 11371 and L. jordanis ATCC 33623 have been characterized by oligonucleotide cataloguing of their 16S ribosomal RNA. All four species are phylogenetically closely related, while no specific relationship could be detected with any other group of organisms investigated so far with respect to this method. At a low level of relationship legionellae are members of the broad group of purple photosynthetic bacteria and their non-phototrophic relatives, in which Legionella form an independent line of descent.     

Proteins of the sieve-tube exudate of Cucurbita maxima

Summary Sieve-tube exudate which appears on cut surfaces of stems of Cucurbita maxima as distinct droplets has been depicted in electron micrographs of longitudinal sections of the phloem. The exudate, which was produced from mature sieve tubes only, contained filaments of P-protein, but no mitochondria or vesicles of endoplasmic reticulum. The water-soluble part of the exudate contained at least 12 proteins, as shown by disc-electrophoresis. Enzymic activity was found for peroxidases, acid phosphatases, and aldolases. Color tests and assays for other enzymes, including ATPase, fructokinase, several dehydrogenases, and UDP-glucose: D-fructose-2-glucosyl transferase, gave negative results. With repeated cutting of a stem, the protein content of the exudate increased, while the amount of exudate decreased.Supported by Deutsche Forschungsgemeinschaft and Stiftung Volkswagenwerk. During part of this investigation the senior author held a U.S. National Science Foundation Senior Foreign Scientist Fellowship at the University of Wisconsin.     

Two Pathways of Glutamate Fermentation by Anaerobic Bacteria

Two pathways are involved in the fermentation of glutamate to acetate, butyrate, carbon dioxide, and ammonia-the methylaspartate and the hydroxyglutarate pathways which are used by Clostridium tetanomorphum and Peptococcus aerogenes, respectively. Although these pathways give rise to the same products, they are easily distinguished by different labeling patterns of the butyrate when [4-(14)C]glutamate is used as substrate. Schmidt degradation of the radioactive butyrate from C. tetanomorphum yielded equally labeled propionate and carbon dioxide, whereas nearly all the radioactivity of the butyrate from P. aerogenes was recovered in the corresponding propionate. This procedure was used as a test for the pathway of glutamate fermentation by 15 strains (9 species) of anaerobic bacteria. The labeling patterns of the butyrate indicate that glutamate is fermented via the methylaspartate pathway by C. tetani, C. cochlearium, and C. saccarobutyricum, and via the hydroxyglutarate pathway by Acidaminococcus fermentans, C. microsporum, Fusobacterium nucleatum, and F. fusiformis. Enzymes specific for each pathway were assayed in crude extracts of the above organisms. 3-Methylaspartase was found only in clostridia which use the methylaspartate pathway, including Clostridium SB4 and C. sticklandii, which probably degrade glutamate to acetate and carbon dioxide by using a second amino acid as hydrogen acceptor. High levels of 2-hydroxyglutarate dehydrogenase were found exclusively in organisms that use the hydroxyglutarate pathway. The data indicate that only two pathways are involved in the fermentation of glutamate by the bacteria analyzed. The methylaspartate pathway appears to be used only by species of Clostridium, whereas the hydroxyglutarate pathway is used by representatives of several genera.     

Interactions between Plants and Epiphytic Bacteria Regarding Their Auxin Metabolism VI. The Influence of the Epiphytic Bacteria on the Content of Extractable Auxin in the Plant

Sterile plants of maize, pea, and cucumber contain less auxin (extracted with methanol or ether) than nonsterile ones. The auxin content is restored within one day by reinfecting sterile plants (or only the shoots, with roots and culture medium remaining sterile) with epiphytic bacteria strains able to produce IAA or with soaking water of nonsterile seeds. Reinfection with bacteria, strains unable to produce IAA is ineffective. — The possibility of a bacterial auxin production during methanol extraction was excluded.     

Beziehungen zwischen submikroskopischer Chloroplastenstruktur und Art der Kohlenstoffquelle unter phototrophen Ernährungsbedingungen bei Chlamydobotrys stellata

Zusammenfassung Die Chloroplasten von photo-autotroph (Licht + CO₂) oder photo-heterotroph (Licht + Acetat) gewachsenen Chlamydobotrys stellata werden elektronenmikroskopisch untersucht. Es wird eine nahe Beziehung zwischen der Chloroplasten-Feinstruktur und der Ernährungsart gefunden. Die Thylakoide der Chloroplasten photo-heterotroph kultivierter Algen sind im allgemeinen durch Stroma voneinander getrennt und nur zu wenigen gestapelt. In photo-autotrophen Organismen kommt es durch Bildung einer charakteristischen Faltungsstruktur von Thylakoidmembranen zur Bildung von Grana (Pseudo-Grana).Die Ergebnisse werden im Hinblick auf die Photosynthese und Photoassimilation von Acetat bei Chlamydobotrys stellata diskutiert.

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Relationship between submicroscopic chloroplast structure and type of carbon nutrition of Chlamydobotrys stellata

Summary Chloroplasts from Chlamydobotrys stellata grown photo-autotrophically (light + CO₂) or photo-heterotrophically (light + acetate) have been investigated by means of electronmicroscopy. A close relationship between chloroplast fine structure and type of nutrition could be observed. Thylakoids in chloroplasts from photo-heterotrophically cultivated algae are generally separated from each other by stroma and only few thylakoid packages are present. In photo-autotrophic organisms, however, characteristic folding structure of thylakoid membranes results in the formation of grana (pseudo-grana).These results are discussed in respect to chloroplast function in photosynthesis and photoassimilation of acetate in Chlamydobotrys stellata.

     

Das geruchsorgan der rezenten Actinistia und Dipnoi (Pisces)

The olfactory organs of all recent genera from the Actinistia (Latimeria) and Dipnoi (Neoceratodus, Lepidosiren, Protopterus) were studied morphologically, and compared with each other. Whereas the olfactory organ of Latimeria resembles that of the Brachiopterygii, the olfactory organ of the Dipnoi is similar to that, of the Elaemohra.nnhii and ArtinnnfarAraii

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Nit dankenswerter Unterstützung durch die Deutsche Forschungsgemeinschaft.