Morphologic der seeigelzähne II. Die gekielten Zähne der echinacea (Echinodermata,echinoidea)

Structure and growth of a keeled tooth are discussed with Paracentrotus lividus as the main example. The microscopic structure of the tooth skeletons of other sea urchins was compared, considering at least one member of each family with the exception of Saleniidae. Attention is called to the necessary revision of the system of sea urchins.

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Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Ueber den stand der Agrarmeteorologischen Forschung in der Deutschen Demokratischen Republik

Ohne Zusammenfassung     

Elektronenmikroskopische Untersuchungen über Glaskörperrindenzellen und Zonulafasern

Zusammenfassung Es werden folgende Befunde zur Feinstruktur des Glaskörpers beim 16 Tage alten Rattenembryo und der Glaskörperrinde beiderseits der Ora serrata beim 3 Jahre alten, an Retinoblastom erkrankten Kind mitgeteilt:Der Glaskörper des Rattenembryos und die Glaskörperrinde des kindlichen Auges enthalten Fibroblasten. Sie unterscheiden sich nicht von den im Bindegewebe vorkommenden Fibroblasten. Im embryonalen Rattenglaskörper wurden außerdem faserbildende Zellen mit wabiger Struktur des Zytoplasmas beobachtet.Die Fibroblasten der Glaskörperrinde bilden die Fibrillen des Glaskörpergerüstes und der Zonulafasern. Diese Fibrillen zeigen eine deutliche Querstreifung. Die Streifung ist unregelmäßig oder periodisch. Die Länge der Perioden beträgt in unseren Schnitten bei den Glaskörperfibrillen des Rattenembryos und des kindlichen Auges meist etwa 120, seltener 210 A. An den Fibrillenbündeln einer Zonulafaser des kindlichen Auges wurden Perioden von 90–120, 400, 440 und 630 A beobachtet.Die Fibroblasten der Glaskörperrinde des kindlichen Auges liegen im Bereich der Pars plana corporis ciliaris auch tief in den Buchten und Falten des Ciliarepithels. Hierdurch wird eine maximal große Anheftungsfläche für die von ihnen produzierten Fibrillen der Zonulafasern gewährleistet.Die Pars plana corporis ciliaris des kindlichen Auges ist von einem dichten Netz von Fibroblastenfortsätzen überzogen. Auch vereinzelte Makrophagen finden sich hier.Unsere elektronenmikroskopischen Befunde bestätigen die Angaben von Balazs über das Vorkommen von Fibrocyten (Fibroblasten) und Makrophagen in der Glaskörperrinde. Ferner bestätigen sie die bereits von früheren Autoren lichtmikroskopisch gewonnenen Erkenntnisse, wonach es sich beim Glaskörper um mesenchymales Gewebe, bei den Zonulafasern im Bindegewebsfasern handelt.

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Summary The following electron microscopical findings in the vitreous body of 16-day-old rat embryos and in the vitreoretinal border layer on both sides of the ora serrata in a 3-year-old child are reported:The vitreous body of the rat embryo and the vitreoretinal border layer of the infant eye contain fibroblasts. These fibroblasts do not differ from those present in connective tissue. The embryonic vitreous body of the rat contains fibre-forming cells, which show an alveolar structure of the cytoplasm.The fibroblasts in the cortical tissue layer of the vitreous body form the fibrils of the stroma of the vitreous body and the zonula fibres. These fibrils show a marked cross striation. The striation is either irregular or shows periodicity. In the vitreous body of the rat embryo and of the infant eye the lenght of these periods has been measured with 120 and 210 A. Periods of 90–120, 400, 440 and 630 A could be shown in the fibrillar bundles of a zonula fibre of the infant eye. In the region of the pars plana corporis ciliaris the fibroblasts of the cortical tissue layer of the vitreous body of the infant eye are also found deep down in the sinus and folds of the ciliary epithelium. Thus they guarantee an as large as possible area for the attachment of the fibrils of the zonula fibres which they produce.The pars plana corporis ciliaris of the infant eye is covered with a dense network of fibroblast processes. Also cells of the macrophage type may be found in this region.Our electron microscopical findings confirm those of earlier light microscopists and lately by Balazs. The vitreous body of the eye is formed by mesenchymal tissue, whereas the zonula fibres are formed by connective tissue.

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Mit dankenswerter Unterstützung durch den Schweizerischen Nationalfonds zur Förderung der Wissenschaftlichen Forschung.     

Regulation of urokinase- and tissue-type plasminogen activator gene expression in the rat seminiferous epithelium

The secretion of plasminogen activator by seminiferous tubules at defined stages of the epithelial cycle is influenced both by neighboring spermatogenic cells and by hormones. We have used cRNA probes for urokinase-type (uPA) and tissue-type (tPA) plasminogen activators to analyze their mRNA levels in different stages of the epithelial cycle. Urokinase-type PA mRNA was most abundant in stages VII-VIII, while tPA mRNA levels showed smaller variations between the different stages. Both FSH and (Bu)2cAMP increased the steady-state level of tPA mRNA and tPA production without affecting those of uPA in stages VII-IX in vitro, whereas retinoic acid treatment selectively increased the concentration uPA mRNA and uPA production in stages II-VI. The results show that the expression of the uPA and tPA genes is differentially regulated in specific stages of the rat seminiferous epithelium.     

Microbial oxidation of ebastine

The microbial oxidation of ebastine to carebastine was investigated. Among the 15 micro-organisms examined, only theCunninghamella strains showed the desired biotransformation.Cunninghamella blakesleeana oxidised the substrate within 7 days, via the intermediates alcohol and aldehyde, mainly to carebastine, the corresponding carboxylic acid. Optimisation of the culture conditions increased the yield from initially 10% up to a reproducible 40%. For the synthesis of carebastine a substrate concentration of 200 mg/l, a starting pH of 5.0 and the addition of 1% poly(vinyl alcohol) is favourable. The results achieved in experiments with shaking flasks are transferable to the fermentation scale and yielded 270 mg carebastine in a 3-l fermentation of 600 mg ebastine. The progress of the reaction was detected by TLC and HPLC, the products were identified by mass spectrometry and NMR.     

Xylitol production by immobilized recombinant Saccharomyces cerevisiae in a continuous packed-bed bioreactor

Continuous xylitol production with two different immobilized recombinant Saccharomyces cerevisiae strains (H475 and S641), expressing low and high xylose reductase (XR) activities, was investigated in a lab-scale packed-bed bioreactor. The effect of hydraulic residence time (HRT; 1.3-11.3 h), substrate/cosubstrate ratio (0.5 and 1), recycling ratio (0, 5, and 10), and aeration (anaerobic and oxygen limited conditions) were studied. The cells were immobilized by gel entrapment using Ca-alginate as support and the beads were treated with Al(3+) to improve their mechanical strength. Xylose was converted to xylitol using glucose as cosubstrate for regeneration of NAD(P)H required in xylitol formation and for generation of maintenance energy. The stability of the recombinant strains after 15 days of continuous operation was evaluated by XR activity and plasmid retention analyses. Under anaerobic conditions the volumetric xylitol productivity increased with decreasing HRT with both strains. With a recycling ratio of 10, volumetric productivities as high as 3.44 and 5.80 g/L . h were obtained with the low XR strain at HRT 1.3 h and with the high XR strain at HRT 2.6 h, respectively. However, the highest overall xylitol yields on xylose and on cosubstrate were reached at higher HRTs. Lowering the xylose/cosubstrate ratio from 1 to 0.5 increased the overall yield of xylitol on xylose, but the productivity and the xylitol yield on cosubstrate decreased. Under oxygen limited conditions the effect of the recycling ratio on production parameters was masked by other factors, such as an accumulation of free cells in the bioreactor and severe genetic instability of the high XR strain. Under anaerobic conditions the instability was less severe, causing a decrease in XR activity from 0.15 to 0.10 and from 3.18 to 1.49 U/mg with the low and high XR strains, respectively. At the end of the fermentation, the fraction of plasmid bearing cells in the beads was close to 100% for the low XR strain; however, it was significantly lower for the high XR strain, particularly for cells from the interior of the beads. (c) 1996 John Wiley & Sons, Inc.