Physiological, Endocrine, and Genetic Bases of Anadromy in the Brook Charr, Salvelinus Fontinalis, of the Laval River (Québec, Canada)

Brook charr, Salvelinus fontinalis, often display alternate life history styles in coastal areas. In the Laval River, some brook charr remain freshwater residents, while others undergo seasonal migrations between freshwater and saltwater environments. In the present paper, we examined physiological (electrolyte concentrations, gill Na⁺, K⁺-ATPase activity, and thyroid hormone levels) as well as genetic differences (neutral genetic markers) between anadromous and river-resident fish from the Laval River. We also examined how artificial rearing conditions affected seasonal variations in the osmoregulatory physiology of a domestic strain derived from wild anadromous fish. Sympatric anadromous and resident forms of brook charr of the Laval River exhibited differences in gill Na⁺, K⁺-ATPase activity, plasma thyroxine (T₄), and triidothyronine (T₃) concentrations. In domestic anadromous charr, rearing conditions during development had no negative impact on osmoregulatory ability or on gill Na⁺, K⁺-ATPase activity. These results argued for an important hereditary component of gill Na⁺, K⁺-ATPase activity. However, the spring increase in T₄ was present only in wild fish. Significant differences observed at microsatellite loci further suggested that at least some level of reproductive isolation may have occurred between anadromous and resident charr in the Laval River.     

ZnFe2O4‐C/LiFePO4‐CNT: A Novel High‐Power Lithium‐Ion Battery with Excellent Cycling Performance

An innovative and environmentally friendly battery chemistry is proposed for high power applications. A carbon‐coated ZnFe₂O₄ nanoparticle‐based anode and a LiFePO₄‐multiwalled carbon nanotube‐based cathode, both aqueous processed with Na‐carboxymethyl cellulose, are combined, for the first time, in a Li‐ion full cell with exceptional electrochemical performance. Such novel battery shows remarkable rate capabilities, delivering 50% of its nominal capacity at currents corresponding to ≈20C (with respect to the limiting cathode). Furthermore, the pre‐lithiation of the negative electrode offers the possibility of tuning the cell potential and, therefore, achieving remarkable gravimetric energy and power density values of 202 Wh kg^?1 and 3.72 W kg^?1, respectively, in addition to grant a lithium reservoir. The high reversibility of the system enables sustaining more than 10 000 cycles at elevated C‐rates (≈10C with respect to the LiFePO₄ cathode), while retaining up to 85% of its initial capacity.     

Aggregation and Metal-Binding Properties of Mutant Forms of the Amyloid Aβ Peptide of Alzheimer's Disease

Abstract: The fibrillogenic properties of Alzheimer's Aβ peptides corresponding to residues 1–40 of the normal human sequence and to two mutant forms containing the replacement Ala²¹ to Gly or Glu²² to Gln were compared. At pH 7.4 and 37°C the Gln²² peptide was found to aggregate and precipitate from solution faster than the normal Aβ, whereas the Gly²¹ peptide aggregated much more slowly. Electron microscopy showed that the aggregates all had fibrillar structures. Circular dichroism spectra of these peptides revealed that aggregation of the normal and Gln²² sequences was associated with spectral changes consistent with a transformation from random coil to β sheet, whereas the spectrum of the Gly²¹ peptide remained almost unchanged during a period in which little or no aggregation occurred. When immobilised by spotting onto nitrocellulose membranes the peptides bound similar amounts of the radioisotope ⁶⁵Zn²⁺. Of several competing metal ions, tested at 20× the concentration of Zn²⁺, Cu²⁺ displaced >95% of the radioactivity from all three peptides and Ni²⁺ produced >50% displacement in each case. Some other metal ions tested caused lesser displacement, but Fe²⁺ and Al³⁺ were without effect. In a saturation binding assay, a value of 3.2 µM was obtained for the binding of Zn²⁺ to Aβ but our data provided no evidence for a reported higher affinity site (107 nM). The results suggest that the neuropathology associated with the Gly²¹ mutation is not due to enhanced fibrillogenic or different metal-binding properties of the peptide and that the binding of zinc to amyloid peptides is not a specific phenomenon.     

Association of ARVCF with zonula occludens (ZO)-1 and ZO-2: binding to PDZ-domain proteins and cell-cell adhesion regulate plasma membrane and nuclear localization of ARVCF

ARVCF, an armadillo-repeat protein of the p120(ctn) family, associates with classical cadherins and is present in adherens junctions, but its function is poorly understood. Here, we show that ARVCF interacts via a C-terminal PDZ-binding motif with zonula occludens (ZO)-1 and ZO-2. ARVCF and ZO-1 partially colocalize in the vicinity of the apical adhesion complex in polarized epithelial Madin-Darby canine kidney cells. ARVCF, ZO-1, and E-cadherin form a complex and are recruited to sites of initial cell-cell contact in sparse cell cultures. E-cadherin binding and plasma membrane localization of ARVCF require the PDZ-binding motif. Disruption of cell-cell adhesion releases ARVCF from the plasma membrane and an increased fraction of the protein localizes to the nucleus. Nuclear localization of ARVCF also requires the PDZ-binding motif and can be mediated by the PDZ domains of ZO-2. Thus, the interaction of ARVCF with distinct PDZ-domain proteins determines its subcellular localization. Interactions with ZO-1 and ZO-2, in particular, may mediate recruitment of ARVCF to the plasma membrane and the nucleus, respectively, possibly in response to cell-cell adhesion cues.     

Emergence of artemisinin-resistant Plasmodium falciparum with kelch13 C580Y mutations on the island of New Guinea

The rapid and aggressive spread of artemisinin-resistant Plasmodium falciparum carrying the C580Y mutation in the kelch13 gene is a growing threat to malaria elimination in Southeast Asia, but there is no evidence of their spread to other regions. We conducted cross-sectional surveys in 2016 and 2017 at two clinics in Wewak, Papua New Guinea (PNG) where we identified three infections caused by C580Y mutants among 239 genotyped clinical samples. One of these mutants exhibited the highest survival rate (6.8%) among all parasites surveyed in ring-stage survival assays (RSA) for artemisinin. Analyses of kelch13 flanking regions, and comparisons of deep sequencing data from 389 clinical samples from PNG, Indonesian Papua and Western Cambodia, suggested an independent origin of the Wewak C580Y mutation, showing that the mutants possess several distinctive genetic features. Identity by descent (IBD) showed that multiple portions of the mutants’ genomes share a common origin with parasites found in Indonesian Papua, comprising several mutations within genes previously associated with drug resistance, such as mdr1, ferredoxin, atg18 and pnp. These findings suggest that a P. falciparum lineage circulating on the island of New Guinea has gradually acquired a complex ensemble of variants, including kelch13 C580Y, which have affected the parasites’ drug sensitivity. This worrying development reinforces the need for increased surveillance of the evolving parasite populations on the island, to contain the spread of resistance.     

The human pituitary nitroproteome: detection of nitrotyrosyl-proteins with two-dimensional Western blotting, and amino acid sequence determination with mass spectrometry

Nitric oxide is an important mediator that participates in reduction-oxidation (redox) mechanisms and in cellular signal transduction pathways. Two types of post-translational modifications are induced by nitric oxide: S-nitrosylation of cysteine residues and nitration of tyrosine residues. Two-dimensional gel electrophoresis-based Western blotting was used to detect, and liquid chromatography (LC)-tandem mass spectrometry (MS/MS) to determine the amino acid sequence of, several different nitrated proteins in the human pituitary. Proteins from several 2D gel spots, which corresponded to the strongly positive anti-nitrotyrosine Western blot spots, were subjected to in-gel trypsin-digestion and LC-MS/MS analysis. MS/MS, SEQUEST analysis, and de novo sequencing were used to determine the nitration site of each nitrated peptide. A total of four different nitrated peptides were characterized and were matched to four different proteins: synaptosomal-associated protein, actin, immunoglobulin alpha Fc receptor, and cGMP-dependent protein kinase 2. Those nitrotyrosyl-proteins participate in neurotransmission, cellular immunity, and cellular structure and mobility.     

The Clp protease system; a central component of the chloroplast protease network

Intra-plastid proteases play crucial and diverse roles in the development and maintenance of non-photosynthetic plastids and chloroplasts. Formation and maintenance of a functional thylakoid electron transport chain requires various protease activities, operating in parallel, as well as in series. This review first provides a short, referenced overview of all experimentally identified plastid proteases in Arabidopsis thaliana. We then focus on the Clp protease system which constitutes the most abundant and complex soluble protease system in the plastid, consisting of 15 nuclear-encoded members and one plastid-encoded member in Arabidopsis. Comparisons to the simpler Clp system in photosynthetic and non-photosynthetic bacteria will be made and the role of Clp proteases in the green algae Chlamydomonas reinhardtii will be briefly reviewed. Extensive molecular genetics has shown that the Clp system plays an essential role in Arabidopsis chloroplast development in the embryo as well as in leaves. Molecular characterization of the various Clp mutants has elucidated many of the consequences of loss of Clp activities. We summarize and discuss the structural and functional aspects of the Clp machinery, including progress on substrate identification and recognition. Finally, the Clp system will be evaluated in the context of the chloroplast protease network. This article is part of a Special Issue entitled: Regulation of Electron Transport in Chloroplasts.     

Novel benzimidazole derivatives as selective CB2 agonists

The preparation and evaluation of a novel class of CB2 agonists based on a benzimidazole moiety are reported. They showed binding affinities up to 1nM towards the CB2 receptor with partial to full agonist potencies. They also demonstrated good to excellent selectivity (>1000-fold) over the CB1 receptor.     

Bromocriptine-induced implantation failure in mice: failure of the stud male to protect pregnancy.

The presence of the stud male failed to prevent implantation failure in newly inseminated females induced by administration of bromocriptine. This is in contrast with the ability of the stud male to prevent implantation failure in females induced by alien male exposure, and nutritional stress. Since bromocriptine is a potent inhibitor of hypophysial prolactin release by virtue of its stimulatory effect on hypothalamic dopaminergic activity, the results suggest that the stud male-originating luteotrophic stimulus is incapable of overriding the dopaminergic activity in bromocriptine-treated females.     

Formation of the sea urchin male pronucleus in vitro: Membrane-independent chromatin decondensation and nuclear envelope-dependent nuclear swelling

We demonstrate that complete sea urchin male pronuclear development in vitro is a two-step process involving membrane-independent chromatin decondensation and nuclear envelope-dependent pronuclear swelling. In the absence of cytoplasmic membrane vesicles (MVs), permeabilized sperm chromatin decondenses into a spherical nucleus of ≈4 μm in diameter. Pronuclear swelling to ≈7 μm requires an intact nuclear envelope, and the degree of swelling is limited by the amount of MVs assembled on the chromatin. Furthermore, after a nuclear envelope is formed, swelling can occur in the absence of additional cytoplasmic MVs. Nuclear swelling also requires ATP hydrolysis, Ca²⁺ and cytosolic factors, some of which are sensitive to heat and to the sulfhy-dryl alkylating agent, N-ethylmaleimide. The requirement for a nuclear envelope and the rate of pronuclear swelling are consistent with previous in vivo observations. © 1995 wiley-Liss, Inc.