4Pi microscopy reveals an impaired three-dimensional mitochondrial network of pancreatic islet β-cells,an experimental model of type-2 diabetes

Insulin production in pancreatic β-cells is critically linked to mitochondrial oxidative phosphorylation. Increased ATP production triggered by blood glucose represents the β-cells' glucose sensor. Type-2 diabetes mellitus results from insulin resistance in peripheral tissues and impaired insulin secretion. Pathology of diabetic β-cells might be reflected by the altered morphology of mitochondrial network. Its characterization is however hampered by the complexity and density of the three-dimensional (3D) mitochondrial tubular networks in these cell types. Conventional confocal microscopy does not provide sufficient axial resolution to reveal the required details; electron tomography reconstruction of these dense networks is still difficult and time consuming. However, mitochondrial network morphology in fixed cells can also be studied by 4Pi microscopy, a laser scanning microscopy technique which provides an ～ 7-fold improved axial resolution (～ 100 nm) over conventional confocal microscopy. Here we present a quantitative study of these networks in insulinoma INS-1E cells and primary β-cells in Langerhans islets. The former were a stably-transfected cell line while the latter were transfected with lentivirus, both expressing mitochondrial matrix targeted redox-sensitive GFP. The mitochondrial networks and their partial disintegration and fragmentation are revealed by carefully created iso-surface plots and their quantitative analysis. We demonstrate that β-cells within the Langerhans islets from diabetic Goto Kakizaki rats exhibited a more disintegrated mitochondrial network compared to those from control Wistar rats and model insulinoma INS-1E cells. Standardization of these patterns may lead to development of morphological diagnostics for Langerhans islets, for the assessment of β-cell condition, before their transplantations.     

Correlated evolution of LTR retrotransposons and genome size in the genus <Emphasis Type="Italic">eleocharis</Emphasis>

Background  

Transposable elements (TEs) are considered to be an important source of genome size variation and genetic and phenotypic plasticity in eukaryotes. Most of our knowledge about TEs comes from large genomic projects and studies focused on model organisms. However, TE dynamics among related taxa from natural populations and the role of TEs at the species or supra-species level, where genome size and karyotype evolution are modulated in concert with polyploidy and chromosomal rearrangements, remain poorly understood. We focused on the holokinetic genus Eleocharis (Cyperaceae), which displays large variation in genome size and the occurrence of polyploidy and agmatoploidy/symploidy. We analyzed and quantified the long terminal repeat (LTR) retrotransposons Ty1-copia and Ty3-gypsy in relation to changes in both genome size and karyotype in Eleocharis. We also examined how this relationship is reflected in the phylogeny of Eleocharis.     

Road crossing in bank voles and yellow-necked mice

Roads and highways represent one of the most important anthropogenic impacts on natural areas and contribute to habitat fragmentation, because they are linear features that can inhibit animal movement, thereby causing barrier effects subdividing the populations adjacent to the roads. The paper examines to what extent a narrow (2-lane) and a wide (4-lane) highways represent barriers for two small mammal species: bank volesClethrionomys glareolus Schreber, 1780 and yellow-necked miceApodemus flavicollis Melchior, 1834, and whether displaced rodents are able to return across roads of different widths. The study was performed at four sites in the Czech Republic. The capture-mark-recapture method was used to determine crossing rates. At two sites, the animals captured close to the road were transferred to the other side and released, to compare return movements across the roads with the movements made by the non-transferred animals. We found that the narrow highway did not prevent movement of neither of the species, although voles crossed only after they had been transferred. Wide highways, on the other hand, completely prevened crossing of both species. While the narrow highways acted at individuals level, the wide highways affected the population subvision.     

Drivers of temporal changes in temperate forest plant diversity vary across spatial scales

Global biodiversity is affected by numerous environmental drivers. Yet, the extent to which global environmental changes contribute to changes in local diversity is poorly understood. We investigated biodiversity changes in a meta‐analysis of 39 resurvey studies in European temperate forests (3988 vegetation records in total, 17–75 years between the two surveys) by assessing the importance of (i) coarse‐resolution (i.e., among sites) vs. fine‐resolution (i.e., within sites) environmental differences and (ii) changing environmental conditions between surveys. Our results clarify the mechanisms underlying the direction and magnitude of local‐scale biodiversity changes. While not detecting any net local diversity loss, we observed considerable among‐site variation, partly explained by temporal changes in light availability (a local driver) and density of large herbivores (a regional driver). Furthermore, strong evidence was found that presurvey levels of nitrogen deposition determined subsequent diversity changes. We conclude that models forecasting future biodiversity changes should consider coarse‐resolution environmental changes, account for differences in baseline environmental conditions and for local changes in fine‐resolution environmental conditions.     

Three nematode species from elasmobranchs off New Caledonia

Nematode specimens of three species, Terranova scoliodontis (Baylis, 1931) (Ascaridida, Anisakidae), Echinocephalus sinensis Ko, 1975 and E. overstreeti Deardorff & Ko, 1983 (both Spirurida, Gnathostomatidae) were collected from the tiger shark Galeocerdo cuvier, the ray Aetobatus cf. narinari and the blotched fantail ray Taeniura meyeni, respectively, from the coastal waters of New Caledonia, South Pacific. Their examination, including scanning electron microscopy (SEM), made it possible to obtain some new data on their morphology, e.g. in relation to the number and arrangement of male caudal papillae in T. scoliodontis and both Echinocephalus spp., the presence of ventral cuticular ornamentations in T. scoliodontis and the number of transverse spines on the cephalic bulb in Echinocephalus spp. All these species are reported for the first time from New Caledonian waters and G. cuvier is a new host species for T. scoliodontis. SEM examination of the fourth-stage larvae of E. overstreeti from the type-host showed the presence of anterior dorsal and ventral groups of minute spines on the cephalic bulb to be an important taxonomic feature for␣the interspecific distinction of Echinocephalus larvae and questions previous data on the occurrence of E. overstreeti larvae in many elasmobranch fishes and molluscs in Australian waters.

---

Résumé Des Nématodes appartenant à trois espèces, Terranova scoliodontis (Baylis, 1931) (Ascaridida, Anisakidae), Echinocephalus sinensis Ko, 1975 et E. overstreeti Deardorff & Ko, 1983 (tous deux Spirurida, Gnathostomatidae) ont été collectés respectivement du requin tigre Galeocerdo cuvier et des raies Aetobatus cf. narinari et Taeniura meyeni, des eaux côtières de Nouvelle-Calédonie, Pacifique Sud. Leur étude, en particulier en microscopie électronique à balayage (MEB) a permis d’obtenir de nouvelles informations sur leur morphologie, par exemple sur le nombre et la disposition des papilles caudales mâles chez T. scoliodontis et␣les deux espèces d’Echinocephalus, la présence d’ornementations cuticulaires ventrales chez T. scoliodontis, et le nombre d’épines transversales sur le bulbe céphalique des Echinocephalus. Toutes ces espèces sont mentionnées pour la première fois des eaux de Nouvelle-Calédonie et G. cuvier est un nouvel hôte pour T.␣scoliodontis. L’examen au MEB de la larve de quatrième stade d’E. overstreeti, provenant de l’hôte-type, a montré que les groupes antérieurs et postérieurs de petites épines sur le bulbe céphalique sont un caractère taxonomique important pour la distinction interspécifique des larves d’Echinocephalus et met en doute des informations antérieures sur la présence de larves d’E. overstreeti chez de nombreux Élasmobranches et Mollusques des eaux d’Australie.

     

Neoascarophis macrouri n. sp. (Nematoda: Cystidicolidae) from the stomach of Macrourus berglax (Macrouridae) in the eastern Greenland Sea

A new species of parasitic nematode, Neoascarophis macrouri n. sp. (Cystidicolidae), is described from the stomach and stomach wall of the marine deep-water fish Macrourus berglax (onion-eye grenadier) in the eastern Greenland Sea (North Atlantic Ocean). The new species, studied using both light and scanning electron microscopy, is characterised mainly by the location of the vulva near the posterior end of the body (a short distance anterior to the anus), non-filamented eggs, the structure of the mouth, a short vestibule and the length of the spicules (567–615 and 144–156 μm). Metabronema insulanum Solov’eva, 1991 is transferred to Neoascarophis as N. insulana (Solov’eva, 1991) n. comb.     

New techniques for membrane protein crystallization tested on photosystem II core complex of Pisum sativum

The crystallization of a given protein is a hard task being even more complicated when the protein shows a hydrophobic behavior. In the case of photosynthetic proteins, the difficulty of the experiments increased due to the high light sensitivity. Aqueous solutions of photosystem II core complex (OEC PSII) of Pisum sativum were screened for crystallization conditions using standard crystallization methods. Crystal improvement was achieved by counter-diffusion technique in single capillaries of 0.2 mm inner diameter with a three-layer configuration. The use of this advanced crystallization technique—for the first time applied to the crystallization of membrane proteins—improves the reproducibility of the experiments allowing the initial crystal characterization, and facilitates the manipulation under light protection.     

Sex chromosomes and associated rDNA form a heterochromatic network in the polytene nuclei of Bactrocera oleae (Diptera: Tephritidae)

The olive fruit fly, Bactrocera oleae, has a diploid set of 2n?=?12 chromosomes including a pair of sex chromosomes, XX in females and XY in males, but polytene nuclei show only five polytene chromosomes, obviously formed by five autosome pairs. Here we examined the fate of the sex chromosomes in the polytene complements of this species using fluorescence in situ hybridization (FISH) with the X and Y chromosome-derived probes, prepared by laser microdissection of the respective chromosomes from mitotic metaphases. Specificity of the probes was verified by FISH in preparations of mitotic chromosomes. In polytene nuclei, both probes hybridized strongly to a granular heterochromatic network, indicating thus underreplication of the sex chromosomes. The X chromosome probe (in both female and male nuclei) highlighted most of the granular mass, whereas the Y chromosome probe (in male nuclei) identified a small compact body of this heterochromatic network. Additional hybridization signals of the X probe were observed in the centromeric region of polytene chromosome II and in the telomeres of six polytene arms. We also examined distribution of the major ribosomal DNA (rDNA) using FISH with an 18S rDNA probe in both mitotic and polytene chromosome complements of B. oleae. In mitotic metaphases, the probe hybridized exclusively to the sex chromosomes. The probe signals localized a discrete rDNA site at the end of the short arm of the X chromosome, whereas they appeared dispersed over the entire dot-like Y chromosome. In polytene nuclei, the rDNA was found associated with the heterochromatic network representing the sex chromosomes. Only in nuclei with preserved nucleolar structure, the probe signals were scattered in the restricted area of the nucleolus. Thus, our study clearly shows that the granular heterochromatic network of polytene nuclei in B. oleae is formed by the underreplicated sex chromosomes and associated rDNA.