Teratogenic effects induced in tail ofBufo arenarum tadpoles following treatment with carcinogens

Riassunto Si descrivono gli effetti teratogeni indotti nella coda del girino delBufo arenarum in uno stadio premetamorfosico, come conseguenza dell'impianto di cristalli di idrocarburi cancerigeni. Tanto il MC come il BP o il DMBA producono alette sopranumerarie che ripetono le strutture istologiche delle alette normali; ed inoltre il DMBA induce la formazione di una seconda notocorda parallela alla normale.

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Career investigator of Argentine CNICT.

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Fellow of Argentine CNICT.     

Nitrogenase activity in a transfilter culture of rhizobia with a non-leguminous plant callus culture: Transfer of fixed15N2 from bacteria toPortulaca callus

Summary A transfilter culture of the non-leguminous plantPortulaca grandiflora var. JR andRhizobium sp. cowpea 32H1 was established. Using¹⁵N₂-analysis we demonstrated that¹⁵N-containing substances produced by the bacteria passed through the membrane and¹⁵N was enriched in the plant cells.Acknowledgment. The authors wish to express their gratitude to Prof. H. Marschner and Dr G. Hentschel for the determination of the nitrogen-content of our samples by the Dumasmethod and for advice on the optic emission method. Drs J. Burton, Milwaukee, Wisc., and Tjepkema, Oregon State University, are thanked for generous gifts ofRhizobium sp. cowpea 32H1. This work was supported by the DFG.     

Transfilter associations of nonleguminous plants with rhizobia: Channelling of N2 fixed by rhizobia into the nitrogen-metabolism ofPortulaca grandiflora callus tissues

Summary In transfilter associations ofPortulaca grandiflora callus tissues withRhizobium sp. cowpea 32H1 the nitrogenium fixed by the bacteria was channelled into the normal pathway of nitrogen metabolism of higher plants. In associations kept in an¹⁵N₂ containing atmosphere 10% of the¹⁵N taken up into the plant cells was incorporated intoPortulaca proteins. The results demonstrate that cells of nonleguminous plants are profiting from the quasi-symbiotic situation.     

Effect of carbobenzoxy,phenylacetyl and phenylpropionyl derivatives of amino acids on mammalian and bacterial asparaginase

Zusammenfassung Während Acylderivate von Aminosäuren mit mehr als einer aromatischen Gruppe (wie z.B. N-Phenylacetyl-S-benzyl-l-cystein) auf Rattenleberasparaginase eine stark hemmende Wirkung ausüben, werden Asparaginase ausEscherichia coli undErwinia cartovora durch solche Verbindungen nicht gehemmt.     

Effect of carbobenzoxy derivatives of amino acids on glutamine synthesis and γ-glutamyl transfer

Zusammenfassung Carbobenzoxyderivate von aromatischen Aminosäuren mit einer zusätzlichen aromatischen Gruppe hemmen die Glutaminsynthetase und-Glutamyl-Transferase aus Schafshirn sowie die Glutaminsynthetase aus Rattenleber stark.     

Telomeres and meiosis in health and disease

The aim of this review is threefold. First, we want to report on recent observations on the role of telomeres in the alignment of homolog and non-homologues in the yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe and the relationship of early telomere clustering to later recombination events. Second, we compare the similarities and differences between synaptic and asynaptic yeasts. Third, we report on the increasing evidence of the effect of meiosis on telomeric sequences that suggest an induction of a specific form of recombination processes termed telomere rapid deletion.     

Electrostatic trapping of ammonia molecules

The ability to cool and slow atoms with light for subsequent trapping allows investigations of the properties and interactions of the trapped atoms in unprecedented detail. By contrast, the complex structure of molecules prohibits this type of manipulation, but magnetic trapping of calcium hydride molecules thermalized in ultra-cold buffer gas and optical trapping of caesium dimers generated from ultra-cold caesium atoms have been reported. However, these methods depend on the target molecules being paramagnetic or able to form through the association of atoms amenable to laser cooling, respectively, thus restricting the range of species that can be studied. Here we describe the slowing of an adiabatically cooled beam of deuterated ammonia molecules by time-varying inhomogeneous electric fields and subsequent loading into an electrostatic trap. We are able to trap state-selected ammonia molecules with a density of 10(6) cm(-3) in a volume of 0.25 cm3 at temperatures below 0.35 K. We observe pronounced density oscillations caused by the rapid switching of the electric fields during loading of the trap. Our findings illustrate that polar molecules can be efficiently cooled and trapped, thus providing an opportunity to study collisions and collective quantum effects in a wide range of ultra-cold molecular systems.