Allometric Scaling of Patrolling Rate and Nest Volume in Constrictotermes cyphergaster Termites: Hints on the Settlement of Inquilines

Structural and functional traits of organisms are known to be related to the size of individuals and to the size of their colonies when they belong to one. Among such traits, propensity to inquilinism in termites is known to relate positively to colony size. Larger termitaria hold larger diversity of facultative inquilines than smaller nests, whereas obligate inquilines seem unable to settle in nests smaller than a threshold volume. Respective underlying mechanisms, however, remain hypothetical. Here we test one of such hypotheses, namely, that nest defence correlates negatively to nest volume in Constrictotermes cyphergaster termites (Termitidae: Nasutitermitinae). As a surrogate to defence, we used ‘patrolling rate’, i.e., the number of termite individuals attending per unit time an experimentally damaged spot on the outer wall of their termitaria. We found that patrolling rate decayed allometrically with increasing nest size. Conspicuously higher patrolling rates occurred in smaller nests, while conspicuously lower rates occurred in larger nests presenting volumes in the vicinity of the threshold value for the establishment of inquilinism. This could be proven adaptive for the host and guest. At younger nest age, host colonies are smaller and presumably more vulnerable and unstable. Enhanced defence rates may, hence, prevent eventual risks to hosts from inquilinism at the same time that it prevents inquilines to settle in a still unstable nest. Conversely, when colonies grow and maturate enough to stand threats, they would invest in priorities other than active defence, opening an opportunity for inquilines to settle in nests which are more suitable or less risky. Under this two-fold process, cohabitation between host and inquiline could readily stabilize.     

Ammonia assimilating enzymes from cyanobacteria: in situ and in vitro assay using high-performance liquid chromatography

Assay systems for ammonia assimilating enzymes in cyanobacteria are reported. Glutamine synthetase, glutamate synthase, and glutamate dehydrogenase can be easily assayed in situ, after the cells are made permeable to the reagents, or in vitro. The method is based upon the quantitation of glutamine or glutamate after the separation, when needed, of their o-phthaldialdehyde derivatives by reverse-phase high-performance liquid chromatography on a C18 column. The isocratic elution and the fluorometric detection of the amino acid derivatives make the method fast, simple, sensitive, and free of the assay artifacts which can be produced in coupled assays or when spectrophotometric measurements are carried out in the turbid samples employed for in situ assays.     

Mixed infection, Trichinella spiralis and Trichinella britovi, in a wild boar hunted in the Province of Cáceres (Spain)

The etiological agents of human trichinellosis are distributed worldwide in domestic and wild animals. In Spain, two morphologically indistinguishable Trichinella species have been described—Trichinella spiralis and Trichinella britovi—that are perpetuated in both domestic and sylvatic cycles. The present work reports a double natural infection involving these species in a wild boar killed by hunters in the Province of Cáceres, Spain. After artificial digestion of the boar’s muscles, nine larvae/g were collected. These were characterized by multiplex-PCR and Western-blotting using the Trichinella-specific monoclonal antibodies US5 and US9, and both T. spiralis and T. britovi were detected. The mechanism by which this wild boar came to acquire a mixed infection remains unclear.     

Proteomics, networks and connectivity indices

Describing the connectivity of chemical and/or biological systems using networks is a straight gate for the introduction of mathematical tools in proteomics. Networks, in some cases even very large ones, are simple objects that are composed at least by nodes and edges. The nodes represent the parts of the system and the edges geometric and/or functional relationships between parts. In proteomics, amino acids, proteins, electrophoresis spots, polypeptidic fragments, or more complex objects can play the role of nodes. All of these networks can be numerically described using the so-called Connectivity Indices (CIs). The transformation of graphs (a picture) into CIs (numbers) facilitates the manipulation of information and the search for structure-function relationships in Proteomics. In this work, we review and comment on the challenges and new trends in the definition and applications of CIs in Proteomics. Emphasis is placed on 1-D-CIs for DNA and protein sequences, 2-D-CIs for RNA secondary structures, 3-D-topographic indices (TPGIs) for protein function annotation without alignment, 2-D-CIs and 3-D-TPGIs for the study of drug-protein or drug-RNA quantitative structure-binding relationships, and pseudo 3-D-CIs for protein surface molecular recognition. We also focus on CIs to describe Protein Interaction Networks or RNA co-expression networks. 2-D-CIs for patient blood proteome 2-DE maps or mass spectra are also covered.     

Low Tryptophan and Protein in the Diet During Development Increase the Susceptibility to Convulsions in Adult Rats

Tryptophan (TRY) is the precursor for serotonin (5-HT) synthesis. Common maize has low protein content with low concentration of TRY and lysine. A diet based on two strains of corn differing in their TRY content were given to adult female rats, prior mating, during pregnancy and lactation. Same diets were offered to their male offspring after weaning until reaching 60-days old. The pattern and severity of the convulsive phenomenon induced by monosodium glutamate (MSG) in a well established model of Status epilepticus were evaluated in comparison with data from animals of two control groups: (a) rats fed a hypoproteic (8% protein) diet, and (b) rats fed a normal Purina chow diet (23% protein). Significant increased susceptibility to convulsions was observed in both groups of rats fed the corn-based diets. However, the animals fed the common corn-based diet (8–9% protein; 0.058% TRY) showed a higher susceptibility to convulsions than what was registered in animals fed a Quality Protein Maize (QPM)-based diet (8–9% protein; 0.1% TRY). It is concluded that low TRY concentration in the diet during development, produces lower rate of brain 5-HT synthesis, affecting development and maturation of GABAergic inhibitory cortical interneurons, with alteration of cortical excitability, contributing in part, to the increased susceptibility to convulsions, as shown in the experiments here reported. Special issue article in honor of Dr. Ricardo Tapia.     

Properties of the recombinant ferredoxin-dependent glutamate synthase of Synechocystis PCC6803. Comparison with the Azospirillum brasilense NADPH-dependent enzyme and its isolated alpha subunit

The properties of the recombinant ferredoxin-dependent glutamate synthase of Synechocystis PCC6803 were determined by means of kinetic and spectroscopic approaches in comparison to those exhibited by the bacterial NADPH-dependent enzyme form. The ferredoxin-dependent enzyme was found to be similar to the bacterial glutamate synthase alpha subunit with respect to cofactor content (one FMN cofactor and one [3Fe-4S] cluster per enzyme subunit), overall absorbance properties, and reactivity of the FMN N(5) position with sulfite, as expected from the similar primary structure of ferredoxin-dependent glutamate synthase and of the bacterial NADPH-dependent glutamate synthase alpha subunit. The ferredoxin- and NADPH-dependent enzymes were found to differ with respect to the apparent midpoint potential values of the FMN cofactor and of the [3Fe-4S] cluster, which are less negative in the ferredoxin-dependent enzyme form. This feature is, at least in part, responsible for the efficient oxidation of L-glutamate catalyzed by this enzyme form, but not by the bacterial NADPH-dependent counterpart. At variance with earlier reports on ferredoxin-dependent glutamate synthase, in the Synechocystis enzyme the [3Fe-4S] cluster is not equipotential with the flavin cofactor. The present studies also demonstrated that binding of reduced ferredoxin to ferredoxin-dependent glutamate synthase is essential in order to activate reaction steps such as glutamine binding, hydrolysis, or ammonia transfer from the glutamine amidotransferase site to the glutamate synthase site of the enzyme. Thus, ferredoxin-dependent glutamate synthase seems to control and coordinate catalytic activities taking place at its subsites by regulating the reactions of the glutamine amidotransferase site. Association with reduced ferredoxin appears to be necessary, but not sufficient, to trigger the required activating conformational changes.     

Systematic screening of reactive cysteine proteomes

Redox signalling constitutes a topic within the field of cellular signal transduction which is attracting increasing interest. A major challenge is to identify the components of redox signalling pathways. Proteins containing cysteines that may reversibly form disulphides are principal candidates as transmitters of redox signals. Thioredoxins are small proteins containing a highly reactive dithiol. Here we present a simple procedure to isolate and separate proteins that contain redox active cysteines using a site-directed, histidine-tagged mutant of thioredoxin, which forms stable mixed disulphides with its targets.     

The oligomerization domain of VP3, the scaffolding protein of infectious bursal disease virus,plays a critical role in capsid assembly

Infectious bursal disease virus (IBDV) capsids are formed by a single protein layer containing three polypeptides, pVP2, VP2, and VP3. Here, we show that the VP3 protein synthesized in insect cells, either after expression of the complete polyprotein or from a VP3 gene construct, is proteolytically degraded, leading to the accumulation of product lacking the 13 C-terminal residues. This finding led to identification of the VP3 oligomerization domain within a 24-amino-acid stretch near the C-terminal end of the polypeptide, partially overlapping the VP1 binding domain. Inactivation of the VP3 oligomerization domain, by either proteolysis or deletion of the polyprotein gene, abolishes viruslike particle formation. Formation of VP3-VP1 complexes in cells infected with a dual recombinant baculovirus simultaneously expressing the polyprotein and VP1 prevented VP3 proteolysis and led to efficient virus-like particle formation in insect cells.