EphrinB2 and GRIP1 stabilize mushroom spines during denervation-induced homeostatic plasticity

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Molecular characterisation of Hanseniaspora species

The sequences of the internal transcribed spacers (ITS regions) and the 5.8S rRNA gene, together with the electrophoretic karyotypes of 27 strains representative of the six species belonging to the genus Hanseniaspora, were examined. From the analysis of the 5.8S rRNA gene and the ITS regions, the genus Hanseniaspora is monophyletic and can be divided into two subgroups. This subdivision was supported by electrophoretic chromosome patterns. Hanseniaspora guilliermondii, H. uvarum and H. valbyensis show 6–7 bands (8 to 9 chromosomes), while the second group comprises the species H. occidentalis, H. osmophila and H. vineae which have only 5 chromosomes.     

The Significance of the Vestibular Cell in Trap Nesting Wasps (Hymenoptera: Crabronidae): Does its Presence Reduce Mortality?

In a study carried out with the trap-nesting solitary wasp Trypoxylon attenuatum (Hymenoptera: Crabronidae) in 2000, we analysed the significance of different nest characteristics, like the vestibular cell and empty intercalary cells, and its role in the reduction of mortality. Analysis of the presence of the vestibular cell suggested that it represents a nest completion structure, whose presence reduces mortality in the initial stages (M1) but does not affect that due to chrysidid parasitoids (MP). The length of such vestibular cell was found to depend mainly on the space between the last provisioned cell and the exterior, pointing to a possible role in the reduction of the remaining space that could be used by other females to establish a nest exterior to the completed one. The empty intercalary cells were smaller than the vestibular cells, did not affect M1 or MP mortality rates in the nest, and exhibited an “aggregated” pattern of occurrence. This suggests that they could be the result of “abnormal” behaviour by the female owning the nest. The total mortality rate decreased with the increase in the number of cells in the nests, also being greater in nests established at low heights above the ground. M1 was lower in the innermost cells, while MP increased towards the interior and in the nests with more cells. The distribution in the nests of cells parasitized by Trichrysis cyanea (the main natural enemy found in the wasp population studied) reflects an “aggregated” pattern, suggesting repeated attacks against certain nests.     

Toward minimal bacterial cells: evolution vs. design

Recent technical and conceptual advances in the biological sciences opened the possibility of the construction of newly designed cells. In this paper we review the state of the art of cell engineering in the context of genome research, paying particular attention to what we can learn on naturally reduced genomes from either symbiotic or free living bacteria. Different minimal hypothetically viable cells can be defined on the basis of several computational and experimental approaches. Projects aiming at simplifying living cells converge with efforts to make synthetic genomes for minimal cells. The panorama of this particular view of synthetic biology lead us to consider the use of defined minimal cells to be applied in biomedical, bioremediation, or bioenergy application by taking advantage of existing naturally minimized cells.     

Isolation and partial characterization of three histone-specific acetyltransferases from Artemia

The specificity of the histone-H4-specific, protease-activated protein kinase (H4-PK) was examined using two series of synthetic peptides corresponding to the phosphorylation sites in histone H4 and pyruvate kinase. Optimum kinetic constants for phosphorylation were observed using the peptide Val-Lys-Arg-Ile-Ser-Gly-Leu. Peptides in which the Lys was replaced by Arg or the Lys-Arg sequence was transposed were phosphorylated with less favorable kinetics. Peptides with either basic residue deleted did not serve as substrates. Only the H4 peptide, containing an Arg-Arg sequence, was phosphorylated by the cyclic-AMP-dependent protein kinase (CA-PK). Distinct specificity determinants for H4-PK and CA-PK were also observed using the pyruvate kinase peptide (Leu-Arg-Arg-Ala-Ser-Leu-Gly). Collectively the data indicated that the primary substrate specificity determinants for H4-PK are Lys-Arg-Xaa-Ser whereas the CA-PK selectively phosphorylates the sequence Arg-Arg-Xaa-Ser.     

The specificity of induction of α-galactosidase from Saccharomyces carlsbergenensis

A number of sugars and derivatives have been tested for their ability to induce the synthesis of α-galactosidase from Saccharomyces carlbergensis. Besides galactose and the substrates of the enzyme melibiose, raffinose and stachyose, D-galacturonic acid, L-arabinose, D-tagatose, methyl-α-D-galactoside, lactose and isopropyl-β-D-thiogalactoside were able to act as inducers. Of these, metyl-α-D-galactoside, lactose, isopropyl-β-D-thiogalactoside and L-arabinose have been shown to be gratuitous inducers with which kinetic studies of induction have been carried out. Lactose was the most efficient inducer, giving a maximal differential rate of synthesis of the enzyme of 110 mU/10⁷ cells at a concentration of 190 mM, followed by L-arabinose (60 mU/10⁷ cells at a concentration of 180 mM, followed by L-arabinose (60 mU/10⁷ cells at 40 mM), isopropyl-β-D-thiogalactoside (43 mU/10⁷ cells at 60 mM) and metyl-α-D-galactoside (25 mU/10⁷ cells at 150 mM). The concentration of inducer required to obtain half-maximal induction was similar for lactose, L-arabinose and isopropyl-β-D-thiogalactoside and about 5-fold higher for methyl-α-D-galactoside. The property of the compounds to act as inducers was compared to their ability to interact with the enzyme and the results discussed in terms of the molecular structures which are recognized by the enzyme and by the induction machinery.