Morphogenesis of the hatching gland of Atlantic halibut (Hippoglossus hippoglossus)

Summary The halibut hatching gland (HG) cells are first observed as a cellular disc in front of the embryonic head around the midpoint of intra ovo development. The disc is subsequently transformed into a loop of increasing diameter as the HG cells migrate over the anterior part of the yolk sac. When the HG disc is transformed into a loop, the density of HG cells is highest at the migratory front. Some HG cells lag behind the migrating front at the early stages of HG development. At maturity, all cells are contained in a narrow belt which is about 10 cells wide. The HG belt structure consists of a monolayer of HG cells, and is maintained while the cells migrate between the two epidermal cell layers. Migration is halted about 2 days before normal hatching when the HG cells reach a destination at about a right angle to on the embryonic axis. Under the scanning electron microscope, the differentiating HG cells protrude as a ridge the yolk sac surface. The HG cells immunostain with antiserum to hatching enzyme when the HG is observed as a crescent structure around the embryonic head. By counting the number of immunostaining cells in composite photos of the entire yolk sac membrane, we found that the HG belt consists of approximately 2000 secretory cells at maturity. This cell number stays fairly constant throughout the period of HG cell migration. Accordingly, mitoses of the halibut HG cells have generally ceased prior to morphogenesis, and cytodifferentiation is already quite advanced when cell migration starts. Offprint requests to: J.V. Helvik     

über die Verschiebung der Vererbungsrichtung unter dem Einflu\ von KohlensÄure

Ohne Zusammenfassung     

Die Vegetation und der Canal auf dem Isthmus von Suez

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Zwei Fehlerquellen bei Merogonieversuchen und die Entwicklungsfähighkeit merogonischer und partiellmerogonischer Seeigelbastarde

Ohne Zusammenfassung Mit 3 Tafeln     

Über die Zweikernigkeit der Leberzellen

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Calcineurin controls growth, morphology, and pathogenicity in Aspergillus fumigatus

Calcineurin is implicated in a myriad of human diseases as well as homeostasis and virulence in several major human pathogenic microorganisms. The fungus Aspergillus fumigatus is a leading cause of infectious death in the rapidly expanding immunocompromised patient population. Current antifungal treatments for invasive aspergillosis are often ineffective, and novel therapeutic approaches are urgently needed. We demonstrate that a mutant of A. fumigatus lacking the calcineurin A (cnaA) catalytic subunit exhibited defective hyphal morphology related to apical extension and polarized growth, which resulted in drastically decreased filamentation. The delta cnaA mutant lacked the extensive lattice of invading hyphae seen with the wild-type and complemented strains. Sporulation was also affected in the delta cnaA mutant, including morphological conidial defects with the absence of surface rodlets and the added presence of disjunctors creating long conidial chains. Infection with the delta cnaA mutant in several distinct animal models with different types of immunosuppression and inoculum delivery led to a profound attenuation of pathogenicity compared to infection with the wild-type and complemented strains. Lung tissue from animals infected with the delta cnaA mutant showed a complete absence of hyphae, in contrast to tissue from animals infected with the wild-type and complemented strains. Quantitative fungal burden and pulmonary infarct scoring confirmed these findings. Our results support the clinical observation that substantially decreasing fungal growth can prevent disease establishment and decrease mortality. Our findings reveal that calcineurin appears to play a globally conserved role in the virulence of several pathogenic fungi and yet plays specialized roles in each and can be an excellent target for therapeutic intervention.