The role of workers in transferring queen substances and the differences between worker castes in the leaf-cutting ant, Acromyrmex subterraneus brunneus (Hymenoptera: Formicidae)

The present study focused on the relationship between the queen and workers in Acromyrmex subterraneus brunneus colonies mediated by the possible transfer of substances from the fertile to the sterile caste. The queens were submitted to different situations of physical limitation, i.e., they were kept isolated in cages with holes that only permitted the entry of workers but left the queen isolated. A tracer (water-soluble dye) was applied to the pronotum and gaster of the queen and its dispersal among workers was analyzed. The results demonstrated that the minor sub caste (0.7-0.9 mm) passed on the dye through allogrooming and self-grooming, or transferred the dye through trophallaxis to the major sub caste (1.2-2.0 mm) when they were not in direct contact with the queen. These findings indicate the communication and probable transfer of substances from the queen to the workers, as well as a substance transfer between workers.

Chorismate synthase: An attractive target for drug development against orphan diseases

The increase in incidence of infectious diseases worldwide, particularly in developing countries, is worrying. Each year, 14 million people are killed by infectious diseases, mainly HIV/AIDS, respiratory infections, malaria and tuberculosis. Despite the great burden in the poor countries, drug discovery to treat tropical diseases has come to a standstill. There is no interest by the pharmaceutical industry in drug development against the major diseases of the poor countries, since the financial return cannot be guaranteed. This has created an urgent need for new therapeutics to neglected diseases. A possible approach has been the exploitation of the inhibition of unique targets, vital to the pathogen such as the shikimate pathway enzymes, which are present in bacteria, fungi and apicomplexan parasites but are absent in mammals. The chorismate synthase (CS) catalyses the seventh step in this pathway, the conversion of 5-enolpyruvylshikimate-3-phosphate to chorismate. The strict requirement for a reduced flavin mononucleotide and the anti 1,4 elimination are both unusual aspects which make CS reaction unique among flavin-dependent enzymes, representing an important target for the chemotherapeutic agents development. In this review we present the main biochemical features of CS from bacterial and fungal sources and their difference from the apicomplexan CS. The CS mechanisms proposed are discussed and compared with structural data. The CS structures of some organisms are compared and their distinct features analyzed. Some known CS inhibitors are presented and the main characteristics are discussed. The structural and kinetics data reviewed here can be useful for the design of inhibitors. © 2007 Bentham Science Publishers Ltd.

Orphan nuclear receptor NGFI-B forms dimers with nonclassical interface

The orphan receptor nerve growth factor-induced B (NGFI-B) is a member of the nuclear receptor's subfamily 4A (Nr4a). NGFI-B was shown to be capable of binding both as a monomer to an extended half-site containing a single AAAGGTCA motif and also as a homodimer to a widely separated everted repeat, as opposed to a large number of nuclear receptors that recognize and bind specific DNA sequences predominantly as homo- and/or heterodimers. To unveil the structural organization of NGFI-B in solution, we determined the quaternary structure of the NGFI-B LBD by a combination of ab initio procedures from small-angle X-ray scattering (SAXS) data and hydrogen-deuterium exchange followed by mass spectrometry. Here we report that the protein forms dimers in solution with a radius of gyration of 2.9 nm and maximum dimension of 9.0 nm. We also show that the NGFI-B LBD dimer is V-shaped, with the opening angle significantly larger than that of classical dimer's exemplified by estrogen receptor (ER) or retinoid X receptor (RXR). Surprisingly, NGFI-B dimers formation does not occur via the classical nuclear receptor dimerization interface exemplified by ER and RXR, but instead, involves an extended surface area composed of the loop between helices 3 and 4 and C-terminal fraction of the helix 3. Remarkably, the NGFI-B dimer interface is similar to the dimerization interface earlier revealed for glucocorticoid nuclear receptor (GR), which might be relevant to the recognition of cognate DNA response elements by NGFI-B and to antagonism of NGFI-B-dependent transcription exercised by GR in cells. Published by Cold Spring Harbor Laboratory Press. Copyright © 2007 The Protein Society.

Flexibility and security in the labour market: improving social protection for Brazilian workers

Includes bibliography

Toxicological and histopathological effects of boric acid on atta sexdens rubropilosa (Hymenoptera: Formicidae) workers

The current study compared the toxicity of different concentrations of boric acid in adult workers of Atta sexdens rubropilosa Forel (Hymenoptera: Formicidae), with toxicological bioassays, and examining the dose-dependent and time-dependent histopathological changes, of the midgut, Malpighian tubules, and postpharyngeal glands. Our results revealed the importance of conducting toxicological bioassays combined with morphological analyses of the organs of ants chronically exposed to insecticides used in commercial ant baits. In vitro bioassays showed that boric acid significantly decreases the survivorship of workers regardless of concentration, whereas the morphological data suggested progressive dose-dependent and time-dependent changes in the organs examined, which were evident in the midgut. The midgut is the first organ to be affected, followed by the postpharyngeal gland and Malpighian tubules. This sequence is in agreement with the absorption pathway of this chemical compound in the midgut, its transference to the hemolymph, possibly reaching the postpharyngeal glands, and excretion by the Malpighian tubules. These progressive changes might be due to the cumulative and delayed effect of boric acid. Our findings provide important information for the understanding of the action of boric acid in ant baits in direct and indirect target organs. © 2010 Entomological Society of America.

The migration of health care workers in the Western Hemisphere: issues and impacts

Includes bibliography

Flexible labour markets, workers' protection and the security of the wings": a Danish flexicurity solution to the unemployment and social problems in globalized economies"

Includes bibliography

Flexible labour markets, workers' protection and active labour market policies in the Caribbean

Includes bibliography

Effects of treatment of the fat body trophocytes of Melipona quadrifasciata anthidioides nurse workers and virgin queens in culture by juvenile hormone III and ecdysterone (20-HE)

The fat body (FB) consists of two types of cells: throphocytes and oenocytes. Throphocytes are related to intermediary metabolism storing lipids, carbohydrates, and proteins while oenocytes play role in the lipids and lipoproteins production. The vitellogenin is the precursor of egg yolk (vitelline) and is synthesized on FB. The aim of this work was to analyze the effects of hormones acting in bee reproduction, as juvenile hormone (JH) and ecdisteroids (20 HE) on FB cells, where vitellogenin is synthesized. For the study were chose nurse workers that in Melipona quadrifasciata anthidioides present activated ovaries and produce eggs, and virgin queens whose ovaries are not yet activated, presenting only previtellogenic follicles. FB trophocytes from these classes of bees were cultivated in media containing different amounts of JH and 20-HE. The effects on trophocytes cytoplasm reserves of lipids, proteins, and activity of acid phosphatase were compared by observing preparations from cultured FB, treated and control, by transmission electron microscopy (TEM). The results showed that the hormones effects are related to the bee's caste and functional ovary stage. The role of acid phosphatase on mobilization of the trophocyte reserves was also determined. © 2012 Wiley Periodicals, Inc.

The technical skills of information technology workers in Argentina

Includes bibliography

Toxicological and histopathological effects of hydramethylnon on Atta sexdens rubropilosa (Hymenoptera: Formicidae) workers

The leaf-cut ants are important agricultural pest, because they can cause intense defoliation in plants and destroy large areas cultivated. Although there are several works for the control of these insects by examining the toxicity of natural chemical compounds on various species of ants, few are focused on analyses of morphological changes caused in the affected organs. The aim of this study was to evaluate the effects of hydramethylnon on Atta sexdens rubropilosa workers through toxicological bioassays and morphological analysis of the post-pharyngeal glands, midgut, and Malpighian tubules of these ants. Hydramethylnon dissolved either in acetone (HA) or in a mixture of acetone and soy oil (HAO) was added to the artificial diet at a concentration of 200 μg/mL. The workers fed daily with the diet containing hydramethylnon showed higher mortality than the controls, especially when HAO was used. Moreover, light and electron microscopy revealed morphological alterations in the midgut and Malpighian tubules of workers treated with HA, whereas alterations of the post-pharyngeal glands were observed in the HAO-treated group. These results indicated that the presence of soy oil provided an alternate route for the ingestion of the formicide's active ingredient and corroborated previous studies that suggested a role for the post-pharyngeal glands in lipid metabolism. Our findings suggest that the oil may carry hydramethylnon to the gland lumen, resulting in lower quantity of the active ingredient in the intestinal lumen and Malpighian tubules that explains the lower degree of morphological alterations in these structures in the workers treated with HAO. These results may provide insight into the toxicological effects of hydramethylnon on leaf-cutting ants and the use of vegetable oil as an adjuvant in baits to control ants. © 2012 Elsevier Ltd.

Comparative study of intramandibular glands of workers, queens and males of stingless bee Scaptotrigona postica Latreille (Hymenoptera: Meliponini)

The mandibles of bees contain two types of tegumental glands whose function is not clear, despite the hypotheses put forward by several researchers. Although these glands have been found in all the bee species studied so far, observations have been confined mostly to workers of eusocial species in the forager phase. The work reported here involved a study of the morphology of the glands of newly emerged, nurse and forager workers, virgin and fecundated queens, and newly emerged and sexually mature males of Scaptotrigona postica, seeking to identify changes that may be linked to the bees life phase. Our findings indicate that the two types of glands are present in the species but not in all life phases or individual classes. The glands consisting of class I cells, the epithelial glands are present only in forager workers and fecundated queens. Glands of type III cells were studied in detail, and gland size was estimated from histological sections. The degree of development of the glands varies according to individual classes and life phases, suggesting different functions during the individuals life and from one individual to another. © Koninklijke Brill NV, Leiden, 2012.

Temporal polyethism and life expectancy of workers in the eusocial wasp polistes canadensis canadensis Linnaeus (Hymenoptera: Vespidae)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Taller sobre programas para trabajadores migratorios temporales: compilación de trabajos = Workshop on temporary migrant workers programs: compilation of works

Incluye Bibliografía