Zur Biosynthese des Cantharidins. I

Summary In contrast to the female, the adult males ofLytta vesicatoria (Coleopt. Meloidae) produced radioactive cantharidine on injection with¹⁴C-1-acetate and¹⁴C-2-mevalonate solutions. A partial degradation of the cantharidine showed that in the acetate experiment approximately of the activity occurred at C atoms 2 + 3 whereas with mevalonate approximately of the activity was at C atoms 8 + 9 and at C atoms 10 + 11. These results show that cantharidine is not formed by a tail to tail linkage of 2 isoprene units.

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Wir danken dem Schweizerischen Nationalfonds zur Förderung der wissenschaftlichen Forschung für die Unterstützung dieser Arbeit, Herrn Dr.J. Würsch (Physikalisch-chemische Abteilung der Firma F. Hoffmann-La Roche & Co. AG, Basel) für¹⁴C-2-Mevalolacton und unserer mikroanalytischen Abteilung (LeitungH. Frohofer) für die Aktivitätsbestimmungen.     

Hydrolysis of human leucocyte phospholipids by snake venoms

Résumé Les phospholipases A des venins du serpentVipera palestinae et duNaja naja ne clivent pas des phospholipides de leucocytes intacts, sauf en présence d'un facteur lytique se trouvant dans le venin deNaja naja. L'activité des phospholipases des deux venins sur les leucocytes endommagés n'est pas la même.     

Transmembrane semaphorin signalling controls laminar stratification in the mammalian retina

In the vertebrate retina, establishment of precise synaptic connections among distinct retinal neuron cell types is critical for processing visual information and for accurate visual perception. Retinal ganglion cells (RGCs), amacrine cells and bipolar cells establish stereotypic neurite arborization patterns to form functional neural circuits in the inner plexiform layer (IPL), a laminar region that is conventionally divided into five major parallel sublaminae. However, the molecular mechanisms governing distinct retinal subtype targeting to specific sublaminae within the IPL remain to be elucidated. Here we show that the transmembrane semaphorin Sema6A signals through its receptor PlexinA4 (PlexA4) to control lamina-specific neuronal stratification in the mouse retina. Expression analyses demonstrate that Sema6A and PlexA4 proteins are expressed in a complementary fashion in the developing retina: Sema6A in most ON sublaminae and PlexA4 in OFF sublaminae of the IPL. Mice with null mutations in PlexA4 or Sema6A exhibit severe defects in stereotypic lamina-specific neurite arborization of tyrosine hydroxylase (TH)-expressing dopaminergic amacrine cells, intrinsically photosensitive RGCs (ipRGCs) and calbindin-positive cells in the IPL. Sema6A and PlexA4 genetically interact in vivo for the regulation of dopaminergic amacrine cell laminar targeting. Therefore, neuronal targeting to subdivisions of the IPL in the mammalian retina is directed by repulsive transmembrane guidance cues present on neuronal processes.     

磁处理对油体系一些性质的影响

本文研究了磁处理对油体系流变性质和结蜡性质的影响。实验证实磁处理可以使油体系的流性指数增加和稠度系数减少,说明磁处理有利于改善油体系的流动性能,最佳的磁感应强度为30～60mT。研究表明,磁处理虽然能加强含蜡煤油的结蜡倾向,但可减少原油的结蜡倾向。影响结蜡倾向的最强的磁感应强度为100mT。本文首次提出用温度指数对比油体系的结蜡倾向。     

Light dependent accumulation of macrophages at the photoreceptor-pigment epithelial interface in the retina of albino mice

Summary In the subretinal space of albino mice, macrophages appear from the time of eye opening and increase in number for 6 months; thereafter they decline with age. Dark rearing retards the accumulation of these cells, and exposure to constant light results in a rapid increase. Observations suggest that macrophages appear as a response to visual cell decay in albino mice and supplement the phagocytic activity of the pigment epithelium.We thank R.K. Hawkins for efficient management of the animal colony, H.G. Jansen for cooperation in the use of electron microscope and Ms Paula van Alphen for help in preparation of the illustrations.     

Immunocytochemical demonstration of contractile cells in the human ovarian follicle

Actin- and myosin-like immunoreactivity is found in cells located in the theca externa of the follicle wall of the human ovary, and corresponding to previously observed myoid cells. The immunocytochemical observation provides direct structural evidence that non-vascular contractile cells are also present in the follicle wall in humans. As expected, perifollicular blood vessels showed a positive immunoreaction for actin and myosin in their smooth muscle walls.     

Peripherally located adrenergic neurons innervating the vas deferens and the seminal vesicle of the guinea-pig

Zusammenfassung Samenleiter und Samenblase vom Meerschweinchen besitzen eine besonders kräftige adrenergische Innervierung, die von Nervenzellen, die in unmittelbarer Nähe der Organe liegen, ausgeht.

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This work has been supported by grants from the United States Public Health Service (NB 02854-04) and from Stiftelsen Magnus Bergvalls Minne.