Functional role of phenylacetic acid from metapleural gland secretions in controlling fungal pathogens in evolutionarily derived leaf-cutting ants

Fungus-farming ant colonies vary four to five orders of magnitude in size. They employ compounds from actinomycete bacteria and exocrine glands as antimicrobial agents. Atta colonies have millions of ants and are particularly relevant for understanding hygienic strategies as they have abandoned their ancestors'' prime dependence on antibiotic-based biological control in favour of using metapleural gland (MG) chemical secretions. Atta MGs are unique in synthesizing large quantities of phenylacetic acid (PAA), a known but little investigated antimicrobial agent. We show that particularly the smallest workers greatly reduce germination rates of Escovopsis and Metarhizium spores after actively applying PAA to experimental infection targets in garden fragments and transferring the spores to the ants'' infrabuccal cavities. In vitro assays further indicated that Escovopsis strains isolated from evolutionarily derived leaf-cutting ants are less sensitive to PAA than strains from phylogenetically more basal fungus-farming ants, consistent with the dynamics of an evolutionary arms race between virulence and control for Escovopsis, but not Metarhizium. Atta ants form larger colonies with more extreme caste differentiation relative to other attines, in societies characterized by an almost complete absence of reproductive conflicts. We hypothesize that these changes are associated with unique evolutionary innovations in chemical pest management that appear robust against selection pressure for resistance by specialized mycopathogens.     

Effects of the administration of cadmium and zinc on the concentration of zinc in the thymus of rats

The zinc content of thymus glands of male Wistar rats has been determined during five weeks of treatment with ZnCl₂ and CdCl₂, and compared with a group of control rats. THymus gland extracts were chromatographed on columns of Sephadex G-75 and the zinc content of the one hundred fractions obtained were determined by atomic absorption spectrophotometry. The rats treated with ZnCl₂ showed an increase in the thymus concentration of zinc bound to high and low molecular weight proteins. The rats treated with CdCl₂ showed an increase in zinc concentration, as opposed to the control group, during the first three weeks of treatment, and thereafter show a toxic effect of cadmium on the gland, with ulterior regression of the latter, and a decrease in the concentration of zinc.     

A cryptic RNA-binding domain in the Pol region of the L-A double-stranded RNA virus Gag-Pol fusion protein.

The Pol region of the Gag-Pol fusion protein of the L-A double-stranded (ds) RNA virus of Saccharomyces cerevisiae has (i) a domain essential for packaging viral positive strands, (ii) consensus amino acid sequence patterns typical of RNA-dependent RNA polymerases, and (iii) two single-stranded RNA binding domains. We describe here a third single-stranded RNA binding domain (Pol residues 374 to 432), which is unique in being cryptic. Its activity is revealed only after deletion of an inhibitory region C terminal to the binding domain itself. This cryptic RNA binding domain is necessary for propagation of M1 satellite dsRNA, but it is not necessary for viral particle assembly or for packaging of viral positive-strand single-stranded RNA. The cryptic RNA binding domain includes a sequence pattern common among positive-strand single-stranded RNA and dsRNA viral RNA-dependent RNA polymerases, suggesting that it has a role in RNA polymerase activity.     

Gross (mesoscopic) and applied anatomy of the anterior inferior cerebellar artery in man with special reference to its course through the cerebellopontine angle region.

In the present paper, we describe anatomical variants of the anterior inferior cerebellar artery in man for applicative purposes. Our goal was to provide the surgeon with a detailed anatomical view of the region. This is similar to what he may observe through the surgical microscope using modern microsurgical techniques. We have focused our attention on the segments of the artery comprising its origin, its course until it reaches the cerebellum and its main collateral branches. Our results confirm the great variability of the elements under study, but enable the establishment of a few basic variational patterns. These patterns together with their relative frequency may be helpful in microsurgery.     

Ferralterin: An iron-sulfur protein functional in enzyme regulation in photosynthesis

The chloroplast new protein factor that was recently shown to link light to the activation of fructose 1,6-bisphosphatase was identified as a previously unrecognized iron-sulfur protein. This protein, given the name “ferralterin,” was purified to homogeneity from spinach leaves and from the blue-green alga (cyanobacterium) Nostoc muscorum. Ferralterin from both sources showed a visible absorption peak at 410nm, a molecular weight of about 30,000 and (provisionally) 4 g-atoms per mole each of nonheme iron and acid labile sulfide. The homogeneous ferralterin preparations catalyzed a light-dependent activation of chloroplast fructose 1,6-bisphosphatase that was dependent only on chlorophyll-containing membranes.     

On the conformational dependence of the proton chemical shifts in nucleosides and nucleotides III. Proton chemical shifts of 5′-nucleotides as a function of different conformational parameters

The variation of the chemical shift of the protons of 5′-UMP and 5′-AMP is calculated as a function of χ_CN, ψ and ? torsion angles. The shift of H8 of 5′-AMP and H6 of 5′-UMP is found to be very sensitive to the value of χ_CN. For the anti conformations the shift of these protons is more sensitive to the value of the rotation about CS′-05′ than about C4′-CS′. For the protons of the ribose the calculations show that for the C2′-endo pucker H3′ and H2′ undergo the largest chemical shift variations when ? and ψ vary. The calculated variations are considered in relation with the role of the conformation of the nucleotides in the chemical shift variation between mono and polynucleotides and between the different helical structures of polynucleotides.