1-Methoxypyrene and 1,6-dimethoxypyrene: two novel metabolites in fungal metabolism of polycyclic aromatic hydrocarbons

The metabolism of pyrene by Penicillium glabrum strain TW 9424, a strain isolated from a site contaminated with polycyclic aromatic hydrocarbons (PAHs) was investigated in submerged cultures. The metabolites formed were identified as 1-hydroxypyrene, 1,6- and 1,8-dihydroxypyrene, 1,6- and 1,8-pyrenequinone, and 1-pyrenyl sulfate. In addition, two new metabolites were isolated and identified by UV, ¹H nuclear magnetic resonance, and mass spectroscopy as 1-methoxypyrene and 1,6-dimethoxypyrene. Experiments with [methyl-³H]S-adenosyl-l-methionine (SAM) revealed that SAM is the coenzyme that provides the methyl group for the methyltransferase involved. To our knowledge, this is the first time that methoxylated metabolites of PAHs have been isolated from fungal cultures. Received: 27 August 1996 / Accepted: 8 January 1997     

Catabolite inactivation of phosphoenolpyruvate carboxykinase in spheroplasts from Saccharomyces Cerevisiae

Catabolite inactivation of phosphoenolpyruvate carboxykinase was studied in yeast spheroplasts using 0.9 M mannitol or 0.6 M potassium chloride as the osmotic support. In the presence of potassium chloride the rate of catabolite inactivation was nearly the same as that occurring in intact yeast cells under different conditions of incubation. However, in the presence of mannitol, catabolite inactivation in spheroplasts was prevented. The mannitol inhibition of catabolite inactivation was released by addition of ammonium or phosphate ions. At a concentration of 0.3 M ammonium or 0.06 M phosphate ions, the maximum rate of catabolite inactivation in spheroplasts suspended in mannitol was achieved and was comparable with that observed in spheroplasts incubated in 0.6 M potassium chloride as the osmotic stabilizer. Sodium sulfate (0.04 and 0.4 M) or potassium chloride (0.06 and 0.6 M) did not release the mannitol inhibition of catabolite inactivation in spheroplasts. In intact yeast cells, 0.9 M mannitol, 0.08 M ammonium or 0.1 M phosphate ions did not influence the rate of catabolite inactivation. The nature of the effects of mannitol, ammonium and phosphate ions on catabolite inactivation in yeast spheroplasts is disscussed.     

The innervation of the uterus in Salamandra salamandra (L.) (Amphibia,Urodela)

The innervation of the uterus in the ovoviviparous urodele Salamandra salamandra was studied. In whole mount preparations of the thin-walled uterus of pregnant females, a dense adrenergic network was demonstrated using a modified glyoxylic acid fluorescence technique. Based on vesicle type and cytochemical reactivity after chromate/dichromate fixation for electron microscopy at least two types of neural process were distinguished and classified as adrenergic and cholinergic. Both types are preferentially situated above or between the smooth muscles of the uterine tissue. Adjacent to the muscles in the walls of arterioles mainly adrenergic fibers are seen. Using high performance liquid chromatography with electrochemical detection in tissue homogenates of uterus a considerable amount of noradrenaline could be identified. The significance of the dense innervation is discussed with respect to the function of the uterus during pregnancy and birth.     

Effect of anabolic steroids on rat heart muscle cells

Summary Long-term treatment of female rats with the anabolic steroid hormone Methandrostenolone results in a conspicuous increase of intermediate sized, nonmyofibrillar filaments in muscle cells of the left cardiac ventricle, as revealed by electron microscopy. These filaments, measuring 70–110 Å in diameter, form a characteristic network at the Z-level of the sarcomere, either encircling or penetrating the Z-bands, and appear to insert into the nuclear membrane. The T-system is accompanied by the filaments adjacent to the site of the couplings. Here they are attached to subsarcolemmal electron-dense patches, which may be Z-line precursor material. The filaments may function as a cytoskeleton, to provide passive support in the mechanism of contraction and to mediate nucleo-sarcolemmal and nucleomyofibrillar exchange.The author wishes to thank Prof. Dr. C. Stang-Voss for advice and discussion     

How many is enough? exploring the myosin repertoire in the model eukaryoteDictyostelium discoideum

The cytoplasm of eukaryotic cells is a very complex milieu and unraveling how its unique cytoarchitecture is achieved and maintained is a central theme in modern cell biology. It is crucial to understand how organelles and macro-complexes of RNA and/or proteins are transported to and/or maintained at their specific cellular locations. The importance of filamentous-actindirected myosin-powered cargo transport was only recently realized, and after an initial explosion in the identification of new molecules, the field is now concentrating on their functional dissection. Direct connections of myosins to a variety of cellular tasks are now slowly emerging, such as in cytokinesis, phagocytosis, endocytosis, polarized secretion and exocytosis, axonal transport, etc. Unconventional myosins have been identified in a wide variety of organisms, making the presence of actin and myosins a hallmark of eukaryotism. The genome ofS. cerevisiae encodes only five myosins, whereas a mammalian cell has the capacity to express between two and three dozen myosins. Why is it so crucial to arrive at this final census? The main questions that we would like to discuss are the following. How many distinct myosin-powered functions are carried out in a typical higher eukaryote? Or, in other words, what is the minimal set of myosins essential to accomplish the multitude of tasks related to motility and intracellular dynamics in a multicellular organism? And also, as a corollary, what is the degree of functional redundancy inside a given myosin class? In that respect, the choice of a model organism suitable for such an investigation is more crucial than ever. Here we argue thatDictyostelium discoideum is affirming its position as an ideal system of intermediate complexity to study myosin-powered trafficking and is or will soon become the second eukaryote for which complete knowledge of the whole repertoire of myosins is available.     

Differential effects of light quantity and spectral light quality on growth, morphology and development of two stoloniferous Potentilla species

Plant species from open habitats often show pronounced responses to shading. Apart from a reduction in growth, shading can lead to marked changes in morphology and architecture, and it may affect the rate of plant development. Natural shade comprises two basically different features, a reduction in light quantity (amount of radiation) and changes in the spectral light quality. The first aspect represents changes in resource availability, while the latter acts as a source of information for plants and can prompt morphogenetic responses. A greenhouse experiment was carried out to study the effects of changes in light quality and quantity on the growth, morphology and development of two stoloniferous Potentilla species. Individual plants were subjected to three light treatments: (1) full daylight (control); and two shade treatments, in which (2) light quantity (photon flux density) and (3) light spectral quality (red/far-red ratio) were changed independently. Plant development was followed throughout the study. Morphological parameters, biomass and clonal offspring production were measured at the end of the experiment. Morphological traits such as petiole length, leaf blade characteristics and investment patterns into spacers showed high degrees of shade-induced plasticity in both species. With a few exceptions, light quality mainly affected morphological variables, while production parameters were most responsive to changes in light quantity. Potentilla anserina allocated resources preferentially to established rosettes at the cost of stolon growth and branching, while in P. reptans, all parameters related to development and allocation were slowed down to the same extent by light limitation. Light quality changes also positively affected biomass production via changes in leaf allocation. Changes in the spectral light quality had major effects on the size of modular structures (leaves, ramets), whereas changes in light quantity mainly affected their numbers. Received: 12 December 1997 / Accepted: 8 July 1998     

The Hfr status of Pseudomonas aeruginosa is stabilized by integrative suppression

Summary A temperature-sensitive mutant (dna-11) with the phenotype of a mutant defective in the initiation of DNA replication, was isolated from an Hfr-like FP2 donor of Pseudomonas aeruginosa. Reversion of its temperature-sensitive character was achieved by integrative suppression rather than by backmutation or an additional suppressor mutation. The dna-11 mutant proved to be helpful in stabilizing the Hfr status of the original host.     

Spatial structure of stoloniferous herbs: an interplay between structural blue-print, ontogeny and phenotypic plasticity

Plant form and spatial structure reflect the basic architectural blue-print of a plant. In most plant species, the expression of the structural blue-print is systematically altered during ontogeny resulting in predictable changes in the allometry of plant structures and in the types of structures that are produced. The expression of the structural blue-print or the timing of ontogenetic changes is also frequently altered by environmental conditions. This latter source of variability, referred to as phenotypic plasticity, is manifested through changes in the timing and rates of meristem initiation and development, the likelihood that meristems will remain dormant or commit to different demographic fates (i.e., vegetative vs. reproductive structures), or the size and structure of the organs formed. Complex interactions among these components can result in considerable differences in form and spatial structure among individuals of the same species. This paper focuses on the importance of these different components in determining the architecture of clonal plants with long internode connections between ramets.A case study is presented that attempts to separate ontogenetic variation and phenotypic plasticity in two stoloniferous species with different structural blue-prints, in their responses to shading. In both species the rate of ontogenetic development responded to intermediate shading levels, but only at very low levels of light availability did plastic changes in branch formation occur. Under shaded conditions the two species achieved similar changes in their architecture in conspicuously different ways. We discuss how different mechanisms leading to a given architecture can be distinguished and what the ecological implications of this are.