Synthese der lunularsäure

A ten-step synthesis of lunularic acid, starting from phenyl β-chloropropionate is described. Detailed spectroscopic data are given for lunularic     

Pnoepyga immaculata n. sp., eine neue bodenbewohnende Timalie aus dem Nepal-Himalaya

Zusammenfassung Pnoepyga immaculata n. sp. lebt im Areal der beiden anderenPnoepyga-Artenalbiventer (Hodgson 1837) undpusilla Hodgson 1845 und wurde durch ihren markant abweichenden Territorialgesang entdeckt. Sie besitzt eine kurze silberhelle Strophe aus kurzen, in gleichmäßigen Abständen gereihten Pfiff-Elementen, die in der Frequenz leicht abfällt. Neben der Stimme liegen die wesentlichen diagnostischen Merkmale nach jetzigem Kenntnisstand gegenüber sympatrischenalbiventer in wenig größerem Schnabel, der Fleckenlosigkeit von Oberseite, Kopf und Flügeldecken, gegenüberpusilla in den größeren Körperabmessungen, gegenüber sympatrischenalbiventer undpusilla im schwachen grünlichen Schimmer der Oberseite und in der länglichen Schuppung der Unterseite. Es bestehen keine Proportionsunterschiede zwischenimmaculata undalbiventer/pusilla einerseits wie auch nicht zwischen diesen beiden andererseits. Bis jetzt wurden 4 Belegstücke (SammlungenKoelz, Diesselhorst, Martens) und eine durch Bandaufnahme gesicherte Beobachtung zwischen Dhaulagiri in Mittelwest-Nepal bis nahe der Ost-Grenze Nepals bekannt.P. immaculata lebt zur Brutzeit in enger Nachbarschaft mitP. albiventer undP. pusilla, ist jedoch vonalbiventer vertikal getrennt bei nachgewiesenem Kontakt, vonpusilla durch Bevorzugung trockeneren Waldunterwuchses abseits von Bächen. Schon jetzt mußimmaculata als gefährdete Art eingestuft werden, da Waldvegetation in der zur Brutzeit bevorzugten Höhenstufe zwischen 2100 und 3100 m in Nepal weitgehend vernichtet worden ist.

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Pnoepyga immaculata n. sp., a new ground living wren-babbler from the Nepal Himalayas (Timaliidae)

Summary P. immaculata n. sp. was discovered by its voice which strongly differs from the two other sympatric species,albiventer (Hodgson 1837) andpusilla Hodgson 1845. As a territorial song, it displays a silvery strophe arranged of short, more or less regularly spaced whistling notes (fig. 7a–d), slightly descending in pitch. The strophe is about 2 s long. Besides the distinct voice, the essential diagnostic characters in comparison toP. albiventer are the slightly larger bill, plain head, upper side and wing coverts (fig. 1a–d, 2, 4a–d), in comparison topusilla the larger body size (fig. 1i–m), in comparison to sympatricalbiventer andpusilla the slightly olive tinge of the upper side (against warm dark brown in both others, fig. 1e–m), and the more longish scaly feathers of the lower side (against stout scaly appearance in both others, fig. 1 a–d). These characters hold true at least in Central and Eastern Himalayan populations of the respective species. There do not exist proportional differences in the relations of any part of the body betweenimmaculata andpusilla and not between the latter ones as well. Heretofore, 4 museum specimens are known (Koelz Coll.,Diesselhorst Coll.,Martens Coll.) from West-central (Thakkhola, type locality) and East Nepal (Ting Sang La), 3 of them from the presumed breeding grounds (2100–3100 m), one from the winter quarters in the Terai lowlands. A field observation close to the Darjeeling border in far East Nepal is verified by a tape-recording.P. immaculata embarasses the biologist and systematist because it lives in close neighbourhood of the similar speciesalbiventer andpusilla. It must have been overlooked by its apparent scarcity and overall similarity to both other species of the genus. Slight ecological differences rather correspond to the vertical distribution ofalbiventer, which populates a higher forest belt. But both have already been found on territory at close range.P. pusilla inhabits different microbiotopes, especially the close proximity of running water in the same altitudinal belt asimmaculata. When discovered,P. immaculata is to be classified already as an endangered species. Forest vegetation of its preferred altitude is already greatly reduced in the Central and Eastern Nepal Himalayas. To get a more detailed information on its general distribution and biology in order to quickly arrange protected areas and thus to guarantee the survival ofP. immaculata, should be the urgent next step.

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Results of the Himalaya Expeditions ofJ. Martens, No. 163. — For No. 162 see: Stuttgarter Beitr. Naturkde. (A) 453: 1–46, 1990.     

Effects of glutathione and of cysteine on intestinal absorption of selenium from selenite

The influence of glutathione (1 mmol/L) (GSH) on in vitro mucosal uptake and in vivo absorption of⁷⁵Se-labeled selenite (10 μmol/L) was investigated in rat jejunum. For comparison, the effect ofl-cysteine (1 mmol/L) on in vivo absorption of⁷⁵Se-labeled selenite was also studied. In the in vitro, uptake experiments, only the mucosal surface was exposed to the incubation medium for 3 min. For the in vivo experiments, a luminal perfusion technique was employed. GSH inhibited in vitro mucosal Se uptake, whereas absorption in vivo was stimulated by GSH.l-Cysteine also stimulated in vivo Se absorption, confirming former in vitro mucosal uptake experiments. Thus, unlikel-cysteine, GSH affected in vitro and in vivo absorption of Se from selenite differently. Enzymatic cleavage of products of the reaction of selenite with GSH occuring more efficiently under in vivo than in vitro conditions may be a prerequisite for the stimulatory effect of GSH on Se absorption. This apparently does not apply to the stimulatory effect of cysteine. Since, GSH occurs in the intestinal lumen under physiological conditions, it may contribute to the high bioavailability of Se from selenite.     

Stimulation of mucosal uptake of selenium from selenite by some thiols at various sites of rat intestine

The influence of several thiols (conc. 1 mmol/L) on mucosal uptake of⁷⁵Se from⁷⁵Se-labeled selenite (conc. 10 μmol/L) across the brush border of rat jejunum and cecum was investigated in vitro using a short-term uptake technique.l-Cysteine (l-Cys) stimulated⁷⁵Se uptake in the mid- and distal jejunum and cecum, but not in the proximal jejunum. The effect was maximal in the distal jejunum.d-Cys was less effective in the jejunum and similarly effective in the cecum.l-Leucine (l-Leu) andl-glutamic acid significantly reduced the stimulatory effect ofl-Cys on Se uptake in the distal jejunum, whereas the respective effect ofd-Cys was not diminished byl-Leu. Cysteamine stimulated mucosal⁷⁵Se uptake at all intestinal sites tested, whereas the effect of mercaptopyruvate was restricted to the distal jejunum. Thioglycolate also enhanced⁷⁵Se uptake in the distal jejunum. The stimulatory effects ofl-Cys, mercaptopyruvate, and thiologlycolate were Na⁺-dependent, whereas the effect of cysteamine also occurred in the absence of Na⁺. Mercaptosuccinate,d-penicillamine, ergothioneine, and thiosulfate did not enhance mucosa⁷⁵Se uptake. It is concluded from these findings that the reaction of some thiols with selenite results in Se compounds that are rapidly absorbed by the intestinal epithelium through various Na⁺-dependent and Na⁺-independent, mechanisms. The high bioavailability of Se from selenite found by others might thus be the result of the presence of thiols in the gastrointestinal tract.     

A comparative study on the formation of citric acid and polyols and on morphological changes of three strains of free and immobilized Aspergillus niger

Summary The formation of citric acid, oxalic acid, erythritol and glycerol by three strains of Aspergillus niger immobilized in calcium alginate was investigated and compared with that of free cells when cultivated in shake flasks under phosphate limitation. Morphological changes were followed using an electron microscope. The production of acids and polyols, the consumption of glucose and fructose, and also the morphological changes were strain-dependent. The results also reflected the influence of long storage of a strain on productivity, morphological behaviour and phosphate consumption. Offprint requests to: H.-J. Rehm     

Effects of cell heterogeneity on production of polypeptide growth factors and mesoderm-inducing activity by Xenopus laevis XTC cells

The Xenopus laevis XTC cell line has been analyzed for the production of polypeptide growth factors and mesoderm-inducing activity. By the use of specific biological assays, it is shown that XTC cells produce a growth factor functionally related to the platelet-derived growth factor (PDGF) and two transforming growth factor (TGF)β-like activities. Mesoderm-inducing activity, as measured on X. laevis ectodermal explants from stage 10 embryos, was found to coelute on a Bio-Gel P-100 column with one of the TGFβ-like activities at an apparent molecular weight of 6–10 kDa. Analysis of the DNA content from XTC cells by flow cytometry demonstrated that the cell line is heterogeneous and consists of both tetraploid and diploid cells. Cloning of the XTC cells and selecting single-cell colonies on the basis of their ability to grow in soft agar resulted in the isolation of several homogeneous, morphologically different clonal derivatives. Analysis of conditioned medium from these clonal derivatives showed that only one of them, the only diploid line among six investigated, produced a strong heat- and acid-stable mesoderm-inducing activity that induced notochord and muscle formation in stage 10 X. laevis ectodermal expiants. The relation between this activity and a recently described TGFβ-like mesoderm-inducing factor obtained from XTC-conditioned medium will be discussed. In conclusion, a clonal cell line derived from X. laevis XTC cells which provides a good source for further characterization of mesoderm-inducing factors has been established.     

Dispersal of Acacia cyclops by birds

Summary In South Africa seedlings of the exotic Acacia cyclops grow in clumps. The seedlings occur beneath tall elements, or in bush clumps, of the surrounding indigenous vegetation. The tall shrubs are used as perches by birds, and the pattern of seedling distribution is a result of dispersal of seeds by birds. Germination of A. cyclops seeds was enhanced as a result of passage through the gut of a bird, or by artificial treatments simulating actions taking place in the gut of a bird. We examine properties of the seed, and the funicle which is attractive to birds, in relation to aspects of the life history of A. cyclops and the species' success as an invasive plant in South Africa.     

Rapid effects of nerve growth factor on the Na,K-pump in rat pheochromocytoma cells

Nerve growth factor (NGF) induces neuronal differentiation of rat pheochromocytoma cells (PC12). Here we show that NGF causes a stimulation of Na⁺,K⁺-pump mediated K⁺ influx, with a maximum at 30 min after addition of NGF. The stimulation of the Na⁺,K⁺-pump is completely blocked by the Na⁺-flux inhibitor amiloride (0.2 mM) and can be mimicked by the Na⁺ ionophore monensin. These results suggest that NGF causes a rapid enhancement of Na⁺ influx leading to an activation of the Na⁺,K⁺-pump, a mechanism similar to the action of other growth factors.