Vertical migrations in two hygrophilous species of micro‐snails in relation to time of the year and habitat type

The aim of this study was to investigate vertical migration behaviors in two species of hygrophilous micro‐snails, Vertigo moulinsiana and Vertigo angustior, in relation to the time of the year (spring and summer) at two sites that differ in ground water level (periodically inundated site and non‐inundated site). The study shows different patterns of vertical migrations in the studied species. Vertigo angustior demonstrated a strong affinity to the litter layer (a weak tendency for vertical movements), independent of the time of year and site studied. By contrast, V. moulinsiana showed a clear tendency for vertical migrations, which differed depending on the time of year and site. These differences may be related to the spatial segregation of microhabitats used by these two species at the sites studied and to differences in the ability to resist inundation. Vertigo angustior is associated with microhabitats which are not subjected to prolonged inundation and tolerates a brief submersion. The periodic character of vertical migrations may suggest the effect of endogenous factors related to reproduction in V. moulinsiana. Some plasticity of this behavior in relation to habitat conditions demonstrated by this species may be an adaptation to live in unpredictably flooded environments.     

NPY and stress 30 years later: the peripheral view

Almost 30 years ago, neuropeptide Y (NPY) was discovered as a sympathetic co-transmitter and one of the most evolutionarily conserved peptides abundantly present all over the body. Soon afterward, NPY's multiple receptors were characterized and cloned, and the peptide's role in stress was first documented. NPY has proven to be pivotal for maintaining many stress responses. Most notably, NPY is known for activating long-lasting vasoconstriction in many vascular beds, including coronary arteries. More recently, NPY was found to play a role in stress-induced accretion of adipose tissue which many times can lead to detrimental metabolic changes. It is however due to its prominent actions in the brain, one of which is its powerful ability to stimulate appetite as well as its anxiolytic activities that NPY became a peptide of importance in neuroscience. In contrast, its actions in the rest of the body, including its role as a stress mediator, remained, surprisingly underappreciated and not well understood. Our research has focused on that other, "peripheral" side of NPY. In this review, we will discuss those actions of NPY on the cardiovascular system and metabolism, as they relate to adaptation to stress, and attempt to both distinguish NPY's effects from and integrate them with the effects of the classical stress mediators, glucocorticoids, and catecholamines. To limit the bias of someone (ZZ) who has viewed the world of stress through the eyes of NPY for over 20 years, fresh insight (DH) has been solicited to more objectively assess NPY's contributions to stress-related diseases and the body's ability to adapt to stress.     

Production of transmitochondrial cybrids containing naturally occurring pathogenic mtDNA variants

The human mitochondrial genome (mtDNA) encodes polypeptides that are critical for coupling oxidative phosphorylation. Our detailed understanding of the molecular processes that mediate mitochondrial gene expression and the structure–function relationships of the OXPHOS components could be greatly improved if we were able to transfect mitochondria and manipulate mtDNA in vivo. Increasing our knowledge of this process is not merely of fundamental importance, as mutations of the mitochondrial genome are known to cause a spectrum of clinical disorders and have been implicated in more common neurodegenerative disease and the ageing process. In organellar or in vitro reconstitution studies have identified many factors central to the mechanisms of mitochondrial gene expression, but being able to investigate the molecular aetiology of a limited number of cell lines from patients harbouring mutated mtDNA has been enormously beneficial. In the absence of a mechanism for manipulating mtDNA, a much larger pool of pathogenic mtDNA mutations would increase our knowledge of mitochondrial gene expression. Colonic crypts from ageing individuals harbour mutated mtDNA. Here we show that by generating cytoplasts from colonocytes, standard fusion techniques can be used to transfer mtDNA into rapidly dividing immortalized cells and, thereby, respiratory-deficient transmitochondrial cybrids can be isolated. A simple screen identified clones that carried putative pathogenic mutations in MTRNR1, MTRNR2, MTCOI and MTND2, MTND4 and MTND6. This method can therefore be exploited to produce a library of cell lines carrying pathogenic human mtDNA for further study.     

Major groove width variations in RNA structures determined by NMR and impact of <Superscript>13</Superscript>C residual chemical shift anisotropy and <Superscript>1</Superscript>H–<Superscript>13</Superscript>C residual dipolar coupling on refinement

Ribonucleic acid structure determination by NMR spectroscopy relies primarily on local structural restraints provided by ¹H– ¹H NOEs and J-couplings. When employed loosely, these restraints are broadly compatible with A- and B-like helical geometries and give rise to calculated structures that are highly sensitive to the force fields employed during refinement. A survey of recently reported NMR structures reveals significant variations in helical parameters, particularly the major groove width. Although helical parameters observed in high-resolution X-ray crystal structures of isolated A-form RNA helices are sensitive to crystal packing effects, variations among the published X-ray structures are significantly smaller than those observed in NMR structures. Here we show that restraints derived from aromatic ¹H– ¹³C residual dipolar couplings (RDCs) and residual chemical shift anisotropies (RCSAs) can overcome NMR restraint and force field deficiencies and afford structures with helical properties similar to those observed in high-resolution X-ray structures.     

Glycosyl hydroperoxides derived from 2-deoxysugars

Oxidation of 3,4,6-tri-O-benzyl-2-deoxy-d-glucose and d-galactose or their t-butyl glycosides to the corresponding glycosyl hydroperoxides can be performed with hydrogen peroxide in the presence of an acid catalyst. Several reaction conditions and their influence on the effectiveness of the oxidation are discussed. Separation of the α - and β-anomers of the glycosyl hydroperoxides was achieved through mixed peroxide formation by reaction of the hydroperoxide group with 2-methoxypropene and subsequent deprotection.     

An RNA Structural Switch Regulates Diploid Genome Packaging by Moloney Murine Leukemia Virus

Retroviruses selectively package two copies of their RNA genomes via mechanisms that have yet to be fully deciphered. Recent studies with small fragments of the Moloney murine leukemia virus (MoMuLV) genome suggested that selection may be mediated by an RNA switch mechanism, in which conserved UCUG elements that are sequestered by base-pairing in the monomeric RNA become exposed upon dimerization to allow binding to the cognate nucleocapsid (NC) domains of the viral Gag proteins. Here we show that a large fragment of the MoMuLV 5′ untranslated region that contains all residues necessary for efficient RNA packaging (Ψ^WT; residues 147-623) also exhibits a dimerization-dependent affinity for NC, with the native dimer ([Ψ^WT]₂) binding 12 ± 2 NC molecules with high affinity (K_d = 17 ± 7 nM) and with the monomer, stabilized by substitution of dimer-promoting loop residues with hairpin-stabilizing sequences (Ψ^M), binding 1-2 NC molecules. Identical dimer-inhibiting mutations in MoMuLV-based vectors significantly inhibit genome packaging in vivo (∼ 100-fold decrease), whereas a large deletion of nearly 200 nucleotides just upstream of the gag start codon has minimal effects. Our findings support the proposed RNA switch mechanism and further suggest that virus assembly may be initiated by a complex comprising as few as 12 Gag molecules bound to a dimeric packaging signal.