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.     

Wide-Inhibitory Spectra Bacteriocins Produced by Lactobacillus gasseri K7

The aim of our study was to determine the genetic characterization and classification of Lb. gasseri K7 bacteriocins, comparison with bacteriocins of the Lb. gasseri LF221 strain and other related strains. Bacteriocin-encoding genes were amplified by PCR, subjected to DNA sequencing, and BLAST sequence analysis was performed to search the database for homologous peptides. Lb. gasseri K7 produces two two-peptide bacteriocins, named gassericin K7 A and gassericin K7 B. Their nucleotide sequences were deposited at GenBank, under accession numbers EF392861 for the gassericin K7 A and AY307382 for the gassericin K7 B. Analysis of gene clusters of bacteriocins in Lb. gasseri K7 strain revealed a 100 percent sequence identity with bacteriocins in LF221 strain. An active peptide of gassericin K7 B is homologous to the complementary peptide of gassericin T, and a complementary peptide of gassericin K7 B is homologous to the active peptide of gassericin T. Another surprising finding was that the sakacin T-beta peptide is partly homologous to the active peptide of gassericin K7 A, while the other sakacin T peptide (alfa) is partly homologous to the complementary peptide of gassericin K7 B. Gassericins of Lb. gasseri K7 strain were both classified as two-peptide bacteriocins. Human probiotic strains Lb. gasseri K7 and LF221 are different isolates but with identical bacteriocin genes. They produce wide-inhibitory spectra bacteriocins that are new members of two-peptide bacteriocins with some homologies to other bacteriocins in this group. Described bacteriocins offer a great potential in applications in food industry, pharmacy and biomedicine.     

Development of the ethmoidal structures of the endocranium in Discoglossus pictus (Anura: Discoglossidae)

We use histological techniques and computer‐aided three‐dimensional reconstructions made from serial histological sections to describe the ontogeny of the ethmoidal endocranium of discoglossid frog Discoglossus pictus. We identify a pattern of development for the suprarostral cartilage that differs from previous findings and probably represents the ancestral anuran pattern. The nasal cartilages, including the inferior prenasal cartilage, are de novo adult structures. The only larva‐derived structures of the adult nasal capsules are the posterior aspects of the solum nasi and septum nasi. We also identify patterns of development for the ethmoid plate and postnasal wall that occur during early in ontogenesis. These patterns are associated with development events during metamorphic climax. The pattern of timing of chondrification of the anterior nasal cartilages more closely coincides with that of the neobatrachian species than that recorded for the pelobatid frog Spea. In addition, this study supports a sister taxon relationship between Discoglossus and Alytes. J. Morphol. 271:1078‐1093, 2010. © 2010 Wiley‐Liss, Inc.     

Molecular Evidence for Polyphyletic Origin of the Primary Symbionts of Sucking Lice (Phthiraptera,Anoplura)

Based on 16S rDNA analyses, the primary symbionts of sucking lice were found to form a polyphyletic assemblage of several distant lineages that have arisen several times within Enterobacteriaceae and at least once within Legionellaceae. Another independent lineage of endosymbiotic enterobacteria inhabits a sister group of the sucking lice, Rhynchophthirina. The inspection of 16S rDNA supports the symbiotic nature of the investigated bacteria; they display a typical trait of degenerative processes, an increased AT content (Adenine–Thymine content) in comparison with free-living bacteria. The calculation of divergence time between the closest anopluran and rhynchophthirine symbionts further support their independent origin. The results shown here, together with evidence from other groups, indicate that the significance of primary symbionts for blood-feeding insects should be reconsidered.