Single and double isotope labeling of social insect colonies: Gamma-emitting radionuclides as individually identifiable markers

Gamma-emitting radionuclides were used in single and double-isotope combinations to label individual colonies of the subterranean termite Reticulitermes flavipes Kol. Each of these radionuclides produces a characteristic and identifiable energy spectrum upon decay, and using whole-body gamma spectroscopy, the characteristic spectral emission signatures of each isotope and their relative quantities were detected in workers, brachypterous nymphs, and alates.Radionuclides present in a food source were rapidly incorporated into workers, and reached detection limits within one to three days. Isotopic labels were transferable between colony members, and all individuals in laboratory colonies were labeled within 21 days of initial contact with foragers that had fed at a labeled food source.Single- and double-label nuclide markers were transferred to sexual forms (prealates and alates) by social food flow. Applications of radionuclide labeling and gamma spectroscopic analysis in insect behavioral ecology are discussed.

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Résumé Des radionucléides ont été utilisés seuls ou en combinaison par 2 pour marquer des individus de colonies de Reticulitermes flavipes. Chaque radionucléide possède ses caractères spectraux. Avec un spectroscope très sensible, pouvant contenir l'insecte entier, il est possible d'identifier les signatures spectrales de chaque isotope et les quantités relatives de chacun d'eux chez les ouvriers, les larves brachyptères et les ailés.Les radionucléides présents dans le papier consommé sont rapidement incorporés chez les ouvriers, et atteignent le seuil de détection en 1 à 3 jours. Le marquage isotopique se transmet entre les membres de la colonie; tous les habitants de colonies de laboratorie ont été contaminés en 21 jours, après des contacts avec des individus alimentés sur une source marquée.Les marqueurs isotopiques avec 1 ou 2 radionucléides sont transférés aux sexués par les échanges trophallaxiques. La discussion porte sur les applications du marquage aux radionucléides et l'analyse au spectroscope en écologie éthologique des insectes.

     

First ovarian response to gonadotrophin stimulation in rats exposed to neonatal androgen excess

This study analyzes the effects of neonatal androgenization on follicular growth and first ovulation in response to gonadotrophins, using a model of exogenous stimulation or the use of subcutaneous ovary grafts in castrated animals to replace the hypothalamus–pituitary signal. Neonatal rats (days 1–5) were treated with testosterone, dihydrotestosterone or vehicle. At juvenile period, rats were stimulated with PMSG, hCG (alone or combined) or used as ovarian donors to be grafted on castrated adult female rats. Ovulation and ovarian histology were analyzed in both groups. Animals treated with vehicle or dihydrotestosterone stimulated with gonadotrophins (pharmacological or by using an ovary graft) ovulated, showing a normal histological morphology whereas rats exposed to testosterone and injected with the same doses of gonadotrophins did not it. In this group, ovulation was reached using a higher dose of hCG. Ovaries in the testosterone group were characterized by the presence of follicles with atretic appearance and a larger size than those observed in control or dihydrotestosterone groups. A similar appearance was observed in testosterone ovary grafts although luteinization and some corpora lutea were also identified. Our findings suggest that neonatal exposure to aromatizable androgens induces a more drastic signalling on the ovarian tissue that those driven by non-aromatizable androgens in response to gonadotrophins.     

How Mitochondrial Metabolism Contributes to Macrophage Phenotype and Functions

Metabolic reprogramming of cells from the innate immune system is one of the most noteworthy topics in immunological research nowadays. Upon infection or tissue damage, innate immune cells, such as macrophages, mobilize various immune and metabolic signals to mount a response best suited to eradicate the threat. Current data indicate that both the immune and metabolic responses are closely interconnected. On account of its peculiar position in regulating both of these processes, the mitochondrion has emerged as a critical organelle that orchestrates the coordinated metabolic and immune adaptations in macrophages. Significant effort is now underway to understand how metabolic features of differentiated macrophages regulate their immune specificities with the eventual goal to manipulate cellular metabolism to control immunity. In this review, we highlight some of the recent work that place cellular and mitochondrial metabolism in a central position in the macrophage differentiation program.     

Decreasing the Expression of GABA<Subscript>A</Subscript> α5 Subunit-Containing Receptors Partially Improves Cognitive,Electrophysiological, and Morphological Hippocampal Defects in the Ts65Dn Model of Down Syndrome

Trisomy 21 or Down syndrome (DS) is the most common cause of intellectual disability of a genetic origin. The Ts65Dn (TS) mouse, which is the most commonly used and best-characterized mouse model of DS, displays many of the cognitive, neuromorphological, and biochemical anomalies that are found in the human condition. One of the mechanisms that have been proposed to be responsible for the cognitive deficits in this mouse model is impaired GABA-mediated inhibition. Because of the well-known modulatory role of GABA_A α5 subunit-containing receptors in cognitive processes, these receptors are considered to be potential targets for improving the intellectual disability in DS. The chronic administration of GABA_A α5-negative allosteric modulators has been shown to be procognitive without anxiogenic or proconvulsant side effects. In the present study, we use a genetic approach to evaluate the contribution of GABA_A α5 subunit-containing receptors to the cognitive, electrophysiological, and neuromorphological deficits in TS mice. We show that reducing the expression of GABA_A α5 receptors by deleting one or two copies of the Gabra5 gene in TS mice partially ameliorated the cognitive impairments, improved long-term potentiation, enhanced neural differentiation and maturation, and normalized the density of the GABAergic synapse markers. Reducing the gene dosage of Gabra5 in TS mice did not induce motor alterations and anxiety or affect the viability of the mice. Our results provide further evidence of the role of GABA_A α5 receptor-mediated inhibition in cognitive impairment in the TS mouse model of DS.     

ZRF1 mediates remodeling of E3 ligases at DNA lesion sites during nucleotide excision repair

Faithful DNA repair is essential to maintain genome integrity. Ultraviolet (UV) irradiation elicits both the recruitment of DNA repair factors and the deposition of histone marks such as monoubiquitylation of histone H2A at lesion sites. Here, we report how a ubiquitin E3 ligase complex specific to DNA repair is remodeled at lesion sites in the global genome nucleotide excision repair (GG-NER) pathway. Monoubiquitylation of histone H2A (H2A-ubiquitin) is catalyzed predominantly by a novel E3 ligase complex consisting of DDB2, DDB1, CUL4B, and RING1B (UV–RING1B complex) that acts early during lesion recognition. The H2A-ubiquitin binding protein ZRF1 mediates remodeling of this E3 ligase complex directly at the DNA lesion site, causing the assembly of the UV–DDB–CUL4A E3 ligase complex (DDB1–DDB2–CUL4A-RBX1). ZRF1 is an essential factor in GG-NER, and its function at damaged chromatin sites is linked to damage recognition factor XPC. Overall, the results shed light on the interplay between epigenetic and DNA repair recognition factors at DNA lesion sites.     

The price of independence: cell separation in fission yeast

The ultimate goal of cell division is to give rise to two viable independent daughter cells. A tight spatial and temporal regulation between chromosome segregation and cytokinesis ensures the viability of the daughter cells. Schizosaccharomyces pombe, commonly known as fission yeast, has become a leading model organism for studying essential and conserved mechanisms of the eukaryotic cell division process. Like many other eukaryotic cells it divides by binary fission and the cleavage furrow undergoes ingression due to the contraction of an actomyosin ring. In contrast to mammalian cells, yeasts as cell-walled organisms, also need to form a division septum made of cell wall material to complete the process of cytokinesis. The division septum is deposited behind the constricting ring and it will constitute the new ends of the daughter cells. Cell separation also involves cell wall degradation and this process should be precisely regulated to avoid cell lysis. In this review, we will give a brief overview of the whole cytokinesis process in fission yeast, from the positioning and assembly of the contractile ring to the final step of cell separation, and the problems generated when these processes are not precise.     

Small-Scale Assays for Studying Dissolution of Pharmaceutical Cocrystals for Oral Administration

The purpose of this study was to better understand the dissolution properties and precipitation behavior of pharmaceutical cocrystals of poorly soluble drugs for the potential for oral administration based on a small-scale dissolution assay. Carbamazepine and indomethacin cocrystals with saccharin and nicotinamide as coformers were prepared with the sonic slurry method. Dissolution of the poorly soluble drugs indomethacin and carbamazepine and their cocrystals was studied with a small-scale dissolution assay installed on a SiriusT3 instrument. Two methodologies were used: (i) surface dissolution of pressed tablet (3 mm) in 20 mL running for fixed times at four pH stages (pH 1.8, pH 3.9, pH 5.4, pH 7.3) and (ii) powder dissolution (2.6 mg) in 2 mL at a constant pH (pH 2). Improved dissolution and useful insights into precipitation kinetics of poorly soluble compounds from the cocrystal form can be revealed by the small-scale dissolution assay. A clear difference in dissolution/precipitation behaviour can be observed based on the characteristics of the coformer used.     

Studies on the advent of ureotelism. Factors that render the hepatic arginase of the Mexican axolotl able to hydrolyse endogenous arginine

1. A study was undertaken of the conditions that might operate in the synthesis and hydrolysis of arginine by axolotl liver homogenate to test a previous postulate that liver arginase of the non-metamorphosed Mexican axolotl is not able to hydrolyse arginine formed from citrulline and aspartic acid, though it can split exogenous arginine, and also that an enhanced capacity to hydrolyse endogenous arginine plays a major role in the advent of ureotelism observed during the metamorphosis of the axolotl. 2. It was found that the arginase from axolotl liver is very unstable under the conditions followed, contrary to what is observed in rat liver. 3. Axolotl arginase is able to hydrolyse endogenous arginine if preserved. 4. Mn(2+) protects the enzyme and renders it able to split endogenous arginine. 5. It is suggested that the metal ion produces a change of conformation of the enzyme that, being stable, is capable of hydrolysing the amino acid, or that the new conformation is appropriate for interaction with the sites of arginine synthesis.     

Ontogenetic allometry of the bluemouth, <Emphasis Type="Italic">Helicolenus dactylopterus dactylopterus</Emphasis> (Teleostei: Scorpaenidae), in the Northeast Atlantic and Mediterranean based on geometric morphometrics

Since the emergence of the ‘microbial loop’ concept, heterotrophic flagellates have received particular attention as grazers in aquatic ecosystems. These microbes have historically been regarded incorrectly as a homogeneous group of bacterivorous protists in aquatic systems. More recently, environmental rDNA surveys of small heterotrophic flagellates in the pelagic zone of freshwater ecosystems have provided new insights. (i) The dominant phyla found by molecular studies differed significantly from those known from morphological studies with the light microscope, (ii) the retrieved phylotypes generally belong to well-established eukaryotic clades, but there is a very large diversity within these clades and (iii) a substantial part of the retrieved sequences cannot be assigned to bacterivorous but can be assigned instead to parasitic and saprophytic organisms, such as zoosporic true fungi (chytrids), fungus-like organisms (stramenopiles), or virulent alveolate parasites (Perkinsozoa and Amoebophrya sp.). All these microorganisms are able to produce small zoospores to assure dispersal in water during their life-cycles. Based on the existing literature on true fungi and fungus-like organisms, and on the more recently published eukaryotic rDNA environmental studies and morphological observations, we conclude that previously overlooked microbial diversity and related ecological potentials require intensive investigation (i) for an improved understanding of the roles of heterotrophic flagellates in pelagic ecosystems and (ii) to properly integrate the concept of ‘the microbial loop’ into modern pelagic microbial ecology.