Intracellular appearance of nitrite and nitrate in nitrogen-starved cells of Ankistrodesmus braunii

Summary The occurrence of heterotrophic nitrification in nitrogen-starved cells of Ankistrodesmus braunii was confirmed. The levels of nitrate and nitrite were measured over a period of four weeks. The validity of quantitative determinations in the presence of highly active nitrate and nitrite reductases is discussed. Whereas free hydroxylamine as an intermediate could not be detected, increased hydroxylamine oxidase activity was found in nitrogen-starved cultures. Nitrite reductase and hydroxylamine oxidase can be assigned to particles by sucrose density gradient centrifugation. The possible involvement of microbodies, which were found to be present in Ankistrodesmus, in metabolic processes during nitrogen starvation is discussed.Abbreviations NR nitrate reductase - NiR nitrite reductase - NNEDA N-(1-naphthyl)ethylenediaminedihydrochloride - DCPIP 2,6-dichlorophenolindophenol - EDTA ethylenediaminetetraacetic acid - TCA trichloroacetic acid - DAB 3,3-diaminobenzidine - AT 3-amino-1H-1,2,4-triazole - AMP 2-amino-2-methyl-1,3-propanediol     

Genetische Untersuchungen zur Inkompatibilität im Culex-pipiens-Komplex

Zusammenfassung Bei Kreuzungen zwischen Culex pipiens-Populationen verschiedener geographischer Herkunft werden drei Kreuzungstypen festgestellt: normale Kreuzbarkeit, reduzierte Kreuzbarkeit und Inkompatibilität (Nichtkreuzbarkeit). Die drei Kreuzungstypen sind mit Hilfe der Embryonierungsrate, der Schlüpfrate und der entstehenden Nachkommenschaft gegeneinander abgrenzbar. Bei Inkompatibilität sind 99.9% der sich entwickelnden Embryonen letal und etwa 0.1% der Tiere schlüpfen und sind fertile, diploide Weibchen. Die Aktivierung des Eies erfolgt durch das Spermium. Es liegt induzierte, meiotische Parthenogenese vor. Die diploiden, parthenogenetischen Weibchen gehen aus einer Oocyte 2. Ordnung oder aus Teilungsprodukten einer Oocyte 2. Ordnung hervor. Bei den letalen, haploiden Embryonen beteiligt sich das Spermium nicht am Aufbau des Embryos.

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Genetic investigations on the incompatibility in the Culex pipiens complex

Summary In crosses between populations of the mosquito Culex pipiens of different geographical origin three crossing types have been found (1) crosses with normal offspring (2) crosses with reduced offspring and (3) crosses that show almost total incompatibility. In the case of incompatible crosses 99.9% of the developing embryos are lethal and only about 0.1% of the embryos hatch and develop into fertile diploid females. The origin of the exceptional diploid females has been investigated by means of the marker genes Kuf, r, w, var, y and ru. These females develop from a diploid oocyte or from a diploid nucleus that originated by fusion of the pronucleus and the last polar body. This has been concluded from the frequency of homozygous and heterozygous offspring from heterozygous females, the frequency of equational separation of different genes and the distribution of cross-over gametes in the exceptional females. Based on the genetical data it is argued that induced meiotic parthenogenesis takes place. The sperm does not play any part in the production of the diploid females and the lethal embryos. After the activation of the egg the sperm moves to the center of the egg but it does not succeed to fuse with the pronucleus. As a result the pronucleus starts to develop into a haploid embryo in about 99.9% and only in a few cases is the diploidy restored by a change in the meiotic process in the egg.

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Teil einer Dissertation der Math.-Nat. Fakultät der Universität Mainz

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Danksagung: Herrn Prof. Dr. H. Laven danke ich für die Bereitstellung des Untersuchungsmaterials sowie für die Anregungen bei der Durchführung der Arbeit.

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Angenommen durch H. Stubbe     

Die Schnecken(Gastropoda Prosobranchia) der deutschen Meeresgebiete und brackigen Küstengewässer

Zusammenfassung 1. Im Anschluß an eine frühere taxonomische Bearbeitung der Muscheln oder Bivalvia (Ziegelmeier 1957) werden Bestimmungsschlüssel für die Schnecken (Gastropoda Prosobranchia) der deutschen Meeresgebiete und brackigen Küstengewässer vorgelegt.2. Die Bestimmungsschlüssel basieren auf Schalenmerkmalen. Sie werden durch 20 Tafeln und 7 Abbildungen illustriert.3. Eine kurze Einführung in die äußere Anatomie der Gastropoda und Erläuterungen technischer Termini sollen auch dem jungen Studenten und interessierten Laien eine Bestimmung ermöglichen.

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The snails (Gastropoda Prosobranchia) of the German marine areas and brackish coastal waters

Following a systematic treatment of the Bivalvia (Ziegelmeier 1957), this paper presents a taxonomic survey of the Gastropoda species found in marine and coastal waters near Germany; it includes species known from other countries bordering the North Sea and Baltic Sea. Employing taxonomic keys and numerous photographic illustrations, determinations are based on shell structures. Definitions of technical terms and explanations of pertinent details of gastropod anatomy are given in order to make determinations possible also for beginning students and interested laymen.

     

Leaf wax constituents of some myrtaceous species

Eucalyptin and 8-desmethyleucalyptin have been isolated from the leaf wax coatings of several species of Eucalyptus, from Syncarpia glomulifera, Lophostemon confertus and an Angophora hybrid indicating that C-methylated flavones may be fairly distinctive of the family Myrtaceae. Ursolic acid has been isolated from the leaf waxes of E. youmanii, S. glomulifera, Leptospermum petersonii and Melaleuca quinquenervia, friedelin from Lophostemon confertus and 4,6-dimethoxy-2-hydroxyacetophenone from E. michaeliana.     

Effect of nitrite and nitrate on chlorophyll fluorescence in green algae

Summary The influence of nitrite and nitrate on chlorophyll fluorescence, a very sensitive indicator for the redox state of the primary acceptor of photosystem II of photosynthesis, was studied in green algae (several species of Chlorella, and Ankistrodesmus braunii). In phosphate solution under an atmosphere of nitrogen (i.e., in the absence of O₂ and CO₂, and without nitrite or nitrate), fluorescence shows a pronounced induction and then rises to a high steady-state level. In the presence of nitrite, however, fluorescence decreases after a rather short induction peak to a much lower steady-state. Nitrate, on the other hand, does not have any influence on either induction or steady-state of fluorescence. These results clearly demonstrate that nitrite reduction in the light is very closely coupled to the photosynthetic electron transport system, whereas nitrate is not reduced photosynthetically in vivo.     

Physical and morphological aspects of the eye of the manatee trichechus inunguis natterer 1883: (Sirenia: Mammalia)

The eyes and aspects of vision of the Amazonian manatee Trichechus inunguis NATTERER 1883: (Sirenia: mammalia) have been examined in five animals, in relation to previous findings for sirenians. This paper presents a review of previous findings confirming those upon gross ocular anatomy, retinal histology and ocular refraction. The confirmation of a primarily rod retina, high receptor: ganglion cell ratio and low refractive error under water were of note. A visual pigment based upon vitamin A₁ and a difference spectrum of λ max at 505 nm was in agreement with Dartnalls nomogram. The findings suggest a retina more suited to low light levels and at best, moderate visual acuity, though motion perception appears present and a low degree of binocular vision possible.     

Adaptive Mutation in Saccharomyces cerevisiae

ABSTRACT

Adaptive mutation is a generic term for processes that allow individual cells of nonproliferating cell populations to acquire advantageous mutations and thereby to overcome the strong selective pressure of proliferation-limiting environmental conditions. Prerequisites for an occurrence of adaptive mutation are that the selective conditions are nonlethal and that a restart of proliferation may be accomplished by some genetic change in principle. The importance of adaptive mutation is derived from the assumption that it may, on the one hand, result in an accelerated evolution of microorganisms and, on the other, in multicellular organisms may contribute to a breakout of somatic cells from negative growth regulation, i.e., to cancerogenesis. Most information on adaptive mutation in eukaryotes has been gained with the budding yeast Saccharomyces cerevisiae. This review focuses comprehensively on adaptive mutation in this organism and summarizes our current understanding of this issue.