Application of the disulfide trapping approach to explain the antiparallel assembly of dimeric rabbit uteroglobin: A preliminary study using short peptide models

The spontaneous air oxidation of the peptides H-GICPRFAHVIENLL- NH2 and Ac-LPQTTRENIMKLTEKIVKSPLCM-OH, whose sequences correspond to the helicoidal fragments 1–14 and 48–70 of the monomer of rabbit uteroglobin, was studied. While no oxidation products were observed in the absence of trifluoroethanol, the heterodimer was formed selectively in the presence of the structuring agent. Head-to-head and tail-to-tail homodimers were not detected under these conditions. These results suggest that the N- and C- terminal extremes of the monomer of uteroglobin might contain enough structural information to govern dimerization with a head-tail topology, through a selective helix-to-helix recognition process.     

Effects of experimental stress factors on probing behaviour by aphids

Probing behaviour of Aphis fabae Scopoli and Rhopalosiphum padi (L.) was tested in different stress situations normally occurring in aphid-plant studies such as interruption of feeding or starvation, transfer to a new plant, and attachment to the electrode wire. The DC electrical penetration graph (EPG) technique and a honeydew clock were used to collect data on behavioural effects of these stress conditions. As a general effect, an interruption of feeding behaviour acted as a reset, i.e., the same sequence and time course of probing events were shown, irrespective the interruptions duration, from 1–100 min. Nevertheless, some minor differences were found, especially in A. fabae. Increased interruption times (deprivation from the host plant) stimulated the aphids to insert their stylets earlier. When A. fabae was put back on its host plant after a one min interruption phloem feeding started earlier than with longer interruption times, but only when it was put back to the same plant and feeding site on which it fed before. It is concluded that this effect is at least partly due to memory of previous probing/feeding experience on the plant as it vanishes with longer interruption times. This explanation also holds for phloem salivation (E1) before starting sustained sap ingestion, which was reduced on the previous feeding site, but only after the one min interruption in A. fabae. The aphid-plant specificity appeared high in these effects. Both aphids were somewhat affected by wiring, resulting in earlier probing, longer total pathway phase, and less and later phloem feeding (as reflected by honeydew excretion). Thus confirming, that the evaluation of EPG results can be improved with supplementary data from free aphids.     

Synthesis and SAR of alpha-acylaminoketone ligands for control of gene expression

A lead discovery library and a follow-up focused library of alpha-acylaminoketones were designed based on known dibenzoylhydrazine ecdysone agonists, including GS(TM)-E. The compounds were assayed in mammalian cells expressing the ecdysone receptor from Bombyx mori for their ability to cause expression of a reporter gene downstream of an ecdysone response element. The most potent alpha-acylaminoketones were comparable to GS(TM)-E in this assay.     

The hernandez and fernandez genes of Drosophila specify eye and antenna

The formation of different structures in Drosophila depends on the combined activities of selector genes and signaling pathways. For instance, the antenna requires the selector gene homothorax, which distinguishes between the leg and the antenna and can specify distal antenna if expressed ectopically. Similarly, the eye is formed by a group of "eye-specifying" genes, among them eyeless, which can direct eye development ectopically. We report here the characterization of the hernandez and fernandez genes, expressed in the antennal and eye primordia of the eye-antenna imaginal disc. The predicted proteins encoded by these two genes have 27% common amino acids and include a Pipsqueak domain. Reduced expression of either hernandez or fernandez mildly affects antenna and eye development, while the inactivation of both genes partially transforms distal antenna into leg. Ectopic expression of either of the two genes results in two different phenotypes: it can form distal antenna, activating genes like homothorax, spineless, and spalt, and it can promote eye development and activates eyeless. Reciprocally, eyeless can induce hernandez and fernandez expression, and homothorax and spineless can activate both hernandez and fernandez when ectopically expressed. The formation of eye by these genes seems to require Notch signaling, since the induction of ectopic eyes and the activation of eyeless by the hernandez gene are suppressed when the Notch function is compromised. Our results show that the hernandez and fernandez genes are required for antennal and eye development and are also able to specify eye or antenna ectopically.     

Mutagenesis analysis of the yeast Nha1 Na+/H+ antiporter carboxy-terminal tail reveals residues required for function in cell cycle

The yeast Nha1 Na(+),K(+)/H(+) antiporter may play an important role in regulation of cell cycle, as high-copy expression of the NHA1 gene is able to rescue the blockage at the G(1)/S transition of cells lacking Sit4 protein phosphatase and Hal3 activities. Interestingly, this function was independent of the role of the antiporter in improving tolerance to sodium cations, it required the integrity of a relatively large region (from residues 800 to 948) of its carboxy-terminal moiety, and was not performed by the fission yeast homolog antiporter Sod2, which lacks a carboxy-terminal tail. Here we show that a hybrid protein composed of the Sod2 antiporter fused to the carboxy-terminal half of Nha1 strongly increased sodium tolerance, but did not allow growth at high potassium nor did rescue growth of the sit4 hal3 conditional mutant strain. Deletion of Nha1 residues from 800 to 849, 900 to 925 or 926 to 954 abolished the function of Nha1 in cell cycle without affecting sodium tolerance. A screening for loss-of-function mutations at the 775-980 carboxy-terminal tail of Nha1 has revealed a number of residues required for function in cell cycle, most of them clustering in two regions, from residues 869 to 876 (cluster A) and 918 to 927 (cluster B). The later is rather conserved in other related antiporters, while the former is not.     

NSL a Neuro-Symbolic Language for a Neuro-Symbolic Processor (NSP)

A Neuro-Symbolic Language for monotonic and non-monotonic parallel logical inference by means of artificial neural networks (ANNs) is presented. Both the language and its compiler have been designed and implemented in order to translate the neural representation of a given problem into a VHDL software, which in turn can set devices such as FPGA. The result of this operation leads to an electronic circuit that we call NSP (Neuro-Symbolic Processor).     

Heterotrophic microbial activity and organic matter degradation in coastal lagoons of Colombia

In this study we measured the community respiration and the bacterial respiration as part of the overall degradation process of organic material. Additionally, the turnover rates of the pools of dissolved free glucose and acetate as representatives of the fraction of easily degradable low molecular organic solutes were determined. The study was performed in several coastal lagoons of the "Outer Delta of the Río Magdalena" in northern Colombia. The lagoons can be separated into two groups: The first group contains highly productive brackish lagoons with chl a concentrations ranging from 62-130 micrograms/l. The second group consists of less productive freshwater lagoons with chl a between 5.5-19 micrograms/l. Turnover rates of glucose and acetate were very fast in the highly productive lagoons resulting in turnover times of less than 20 min for both compounds. In the less productive systems the cycling of glucose and acetate was much slower. Here the mean values of the turnover times were 2 hr for glucose and 1.5 hr for acetate. The rates of bacterial DNA-formation measured as thymidine incorporation differed significantly between both groups of lagoons, being very high (1.86-2.76 nmol/l/hr) in the highly productive and relatively low (0.073-0.55 nmol/l/hr) in the less productive group. Water column community respiration ranged between 122 and 16 micrograms C/l/hr with means of 88 micrograms C/l/hr in the highly and 19 micrograms C/l/hr in the less productive group. In the first group the mean values of the bacterial contribution to community respiration amounted to 37% and in the second group to 18%. The bacterial respiration was determined in an indirect way via bacterial biomass production and assuming a growth efficiency of 50%. It is discussed whether this relatively high growth efficiency allows reasonable results in both groups of lagoons.     

In vivo topography of Rap1p-DNA complex at Saccharomyces cerevisiae TEF2 UAS(RPG) during transcriptional regulation

We have analyzed in detail the structure of RAP1-UAS(RPG) complexes in Saccharomyces cerevisiae cells using multi-hit KMnO(4), UV and micrococcal nuclease high-resolution footprinting. Three copies of the Rap1 protein are bound to the promoter simultaneously in exponentially growing cells, as shown by KMnO(4) multi-hit footprinting analysis, causing extended and diagnostic changes in the DNA structure of the region containing the UAS(RPG). Amino acid starvation does not cause loss of Rap1p from the complex; however, in vivo UV-footprinting reveals the occurrence of structural modifications of the complex. Moreover, low-resolution micrococcal nuclease digestion shows that the chromatin of the entire region is devoid of positioned nucleosomes but is susceptible to changes in accessibility to the nuclease upon amino acid starvation. The implications of these results for the mechanism of Rap1p action are discussed.