Seasonal variations in the fertilizing capacity ofBufo arenarum (Amphibia Anura) spermatozoa

Resumen La capacidad fecundante de los espermatozoides deBufo arenarum decae más rápidamente en verano que en invierno. Ello probablemente sea debido a la presencia, durante el invierno, de factores testiculares de protección.

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This work was supported by a grant from the Consejo Nacional de Investigaciones Cientificas y Técnicas de la República Argentina and by the Population Council grant No. 71.68 awarded to the Consejo Nacional de Investigaciones Cientificas y Técnicas to be administered by the Instituto de Biología, Facultad de Bioquímica, Química y Farmacia, Universidad Nacional de Tucumán.

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The author is most grateful to Dr.F. D. Barbieri for his kind discussion and helpful advice in the course of the present study.     

Inhibitory effect of antiproteoglycan serum on the biosynthesis of proteochondroitin sulfate in calf rib cartilage in vitro

Summary Incubation of calf rib cartilage slices with antiproteoglycan serum elevates CO₂-production, but inhibits biosynthesis of proteochondroitinsulfate and of total protein. Absorbing antiserum with proteoglycan abolishes these effects.Acknowledgment. This work was supported by grant K1 193/9 and 10 from the Deutsche Forschungsgemeinschaft.     

A medium to demonstrate the ligninolytic activity of some fungi

Zusammenfassung Es wird hier eine neue Methode angeführt, um die holzauflösende Fähigkeit einiger Pilze zu bestimmen. Ein milchiges, homogenes Agarmedium wird hergestellt, indem man kugelgemahlenes Buchensägemehl als hauptsächliche Kohlenstoffquelle benutzt. Wenn man in dieses Medium bestimmte holzzerstörende Pilze einpflanzt, wird sowohl ihre holzspaltende als auch ihre zellulosezerstörende Wirkung dadurch gezeigt, dass das Medium unter dem Wurzelgeflecht sich aufklärt.     

A “SYDE” effect of hierarchical phosphorylation: possible relevance to the cystic fibrosis basic defect

The motif “SYDE”, incorporating the protein kinase CK2 consensus sequence (S-x-x-E) has been found to be phosphorylated at both its serine and tyrosine residues in several proteins. Of special interest is the case of cystic fibrosis Transmembrane-conductance Regulator (CFTR), where this motif is close to the residue (F508), whose deletion is the by far commonest cause of cystic fibrosis. Intriguingly, however, CFTR S511 cannot be phosphorylated by CK2 to any appreciable extent. Using a number of peptide substrates encompassing the CFTR “SYDE” site we have recently shown that: (1) failure of CK2 to phosphorylate the S⁵¹¹YDE motif is due to the presence of Y512; (2) CK2 readily phosphorylates S511 if Y512 is replaced by a phospho-tyrosine; (3) the Src family protein tyrosine kinase Lyn phosphorylates Y512 in a manner that is enhanced by the deletion of F508. These data, in conjunction with the recent observation that by inhibiting CK2 the degradation of F508delCFTR is reduced, lead us to hypothesize that the hierarchical phosphorylation of the motif SYDE by the concerted action of protein tyrosine kinases and CK2 is one of the mechanisms that cooperate to the premature degradation of F508delCFTR.     

Some comparative studies of two alkaline phosphatases fromAspergillus niger

Summary Alkaline phosphatases (ALP I and ALP II), isolated and purified fromAspergillus niger exhibited broad specificity towards a wide variety of substrates, and consistently ALP II was more active than ALP I. It is possible that the difference in levels of activity of the 2 enzymes may be of physiological importance in the mycelia ofA. niger.     

The range of life in amber: significance and implications in DNA studies

A survey of the major fossiliferous amber deposits is provided, including ages and various categories of life forms reported from each. The frequence of occurrence of the major groups of plants and animals in these amber deposits is also given. Thus far, DNA from four insect and one plant species has been extracted from amber fossils. In the case of the stingless bee in Dominican amber, evidence of reproducibility is provided, since two independent laboratories isolated DNA from six or more different specimens of the same insect.Amber sources for DNA studies are listed together with their advantages and disadvantages. The important points are the availability of desired pieces, the proper identification of the fossil, verification of the amber deposit, the cost involved, and the feasibility of causing damage to the specimen. The availability of several types of amber (Mexican, Dominican, Baltic, Chinese, Canadian, Siberian and Lebanese) at four major sources (academic collections, commercial dealers, private collections and amber mines) is discussed. The scientific implications of obtaining DNA from amber inclusions are presented.     

Postsynaptic long-term potentiation follows coupling of dendritic glutamate application and synaptic activation

Dendritic depolarization, which seems to be involved in the induction of long-term potentiation (LTP), was elicited by localized glutamate application. When paired to low frequency synaptic activation in the same area, the subsequent changes had features in common with LTP, expressed as an increased probability of firing and shorter spike latency. The EPSP was not significantly increased.