RT-qPCR reveals opsin gene upregulation associated with age and sex in guppies (Poecilia reticulata) - a species with color-based sexual selection and 11 visual-opsin genes

Background  

PCR-based surveys have shown that guppies (Poecilia reticulata) have an unusually large visual-opsin gene repertoire. This has led to speculation that opsin duplication and divergence has enhanced the evolution of elaborate male coloration because it improves spectral sensitivity and/or discrimination in females. However, this conjecture on evolutionary connections between opsin repertoire, vision, mate choice, and male coloration was generated with little data on gene expression. Here, we used RT-qPCR to survey visual-opsin gene expression in the eyes of males, females, and juveniles in order to further understand color-based sexual selection from the perspective of the visual system.     

Quantitative proteomics analysis of phosphorylated proteins in the hippocampus of Alzheimer's disease subjects

Phosphorylation on tyrosine, threonine and serine residues represents one of the most important post-translational modifications and is a key regulator of cellular signaling of multiple biological processes that require a strict control by protein kinases and protein phosphatases. Abnormal protein phosphorylation has been associated with several human diseases including Alzheimer's disease (AD). One of the characteristic hallmarks of AD is the presence of neurofibrillary tangles, composed of microtubule-associated, abnormally hyperphosphorylated tau protein. However, several others proteins showed altered phosphorylation levels in AD suggesting that deregulated phosphorylation may contribute to AD pathogenesis. Phosphoproteomics has recently gained attention as a valuable approach to analyze protein phosphorylation, both in a quantitative and a qualitative way. We used the fluorescent phosphospecific Pro-Q Diamond dye to identify proteins that showed alterations in their overall phosphorylation in the hippocampus of AD vs. control (CTR) subjects. Significant changes were found for 17 proteins involved in crucial neuronal process such as energy metabolism or signal transduction. These phosphoproteome data may provide new clues to better understand molecular pathways that are deregulated in the pathogenesis and progression of AD.     

Neurotoxicity and oxidative stress in D1M-substituted Alzheimer's A beta(1-42): relevance to N-terminal methionine chemistry in small model peptides

Small model peptides containing N-terminal methionine are reported to form sulfur-centered-free radicals that are stabilized by the terminal N atom. To test whether a similar chemistry would apply to a disease-relevant longer peptide, Alzheimer's disease (AD)-associated amyloid beta-peptide 1-42 was employed. Methionine at residue 35 of this 42-mer has been shown to be a key amino acid residue involved in amyloid beta-peptide 1-42 [A beta1-42]-mediated toxicity and therefore, the pathogenesis of AD. Previous studies have shown that mutation of the methionine residue to norleucine abrogates the oxidative stress and neurotoxic properties of A beta(1-42). In the current study, we examined if the position of methionine at residue 35 is a criterion for toxicity. In doing so, we tested the effects of moving methionine to the N-terminus of the peptide in a synthetic peptide, A beta(1-42)D1M, in which methionine was substituted for aspartic acid at the N-terminus of the peptide and all subsequent residues from D1 to L34 were shifted one position towards the carboxy-terminus. A beta(1-42)D1M exhibited oxidative stress and neurotoxicity properties similar to those of the native peptide, A beta(1-42), all of which are inhibited by the free radical scavenger Vitamin E, suggesting that reactive oxygen species may play a role in the A beta-mediated toxicity. Additionally, substitution of methionine at the N-terminus by norleucine, A beta(1-42)D1Nle, completely abrogated the oxidative stress and neurotoxicity associated with the A beta(1-42)D1M peptide. The results of this study validate the chemistry reported for short peptides with N-terminal methionines in a disease-relevant peptide.     

Frequency and length-dependent effects of Botulinum toxin-induced muscle weakness

While the pathogenesis of Botulinum toxin type A (BTX-A)-induced muscle weakness has been systematically researched, little is known about the effects of motor fibre paralysis on the mechanical properties of skeletal muscle. Here, the long-term effect of BTX-A injection on the force-length and force-frequency properties of rabbit knee extensors is investigated. BTX-A-induced muscle weakness was greater at short compared to long muscle lengths and at low compared to high stimulation frequencies four weeks following intervention. Therefore, we conclude that the paralysing effects of BTX-A are not uniform, and must be considered in biomechanical models of musculoskeletal rehabilitation in which BTX-A is used therapeutically, as for example in patients with cerebral palsy. Although the present results could be explained through a variety of mechanisms, this study does not allow for drawing firm conclusions about the length and frequency-dependent effects of BTX-A.     

Is the force-length relationship a useful indicator of contractile element damage following eccentric exercise?

Eccentric exercise has been shown to have a measurable effect on the force-length relationship (FLR), as peak force is shifted to longer muscle lengths following exercise. Recently, this shift in the FLR has been proposed as a "simple, reliable indicator" for assessing contractile element damage following eccentric exercise. However, eccentric exercise causes fatigue and damage, and there is evidence that fatigue alone may also cause a shift in the FLR. The purpose of this paper was to assess the role of fatigue on the FLR (as measured by a torque-joint angle relationship) following isometric and eccentric exercise in the New Zealand white (NZW) rabbit. Six NZW rabbits were divided into two groups for eccentric or isometric contractions of the hindlimb dorsiflexor muscles. Pre- and post-exercise torque-joint angle relationships were measured, and the shift from the pre- to the post-exercise relationship was measured as the change in joint angle at which peak torque was produced. Eccentric exercise resulted in a rightward shift of seven degrees; isometric exercise, which is thought to not cause damage, resulted in a shift of four degrees. Furthermore, torque production was reduced to a greater extent at short compared to long muscle lengths for the eccentric and isometric exercise, resulting in a post-exercise torque-joint angle relationship that was altered in shape. We conclude from these results, that the shift in peak torque may not be a simple and reliable indicator of muscle damage, but is caused by a combination of damage and post-exercise fatigue.     

Protection against amyloid beta-peptide (1-42)-induced loss of phospholipid asymmetry in synaptosomal membranes by tricyclodecan-9-xanthogenate (D609) and ferulic acid ethyl ester: implications for Alzheimer's disease

Amyloid-beta (1-42) [Abeta (1-42)] deposition in the brain is a hallmark of Alzheimer's disease (AD) and has been shown to induce apoptosis and disrupt cellular ion homeostasis. Abeta (1-42) induces membrane lipid peroxidation, and 4-hydroxynonenal (HNE) and 2-propenal (acrolein) are the two reactive products of lipid peroxidation, which structurally modify proteins by covalent interaction and inhibit enzyme function. Phosphatidylserine (PS), an aminophospholipid, is sequestered in the inner leaflet of the plasma membrane in nonstimulated cells. An early signal of synaptosomal apoptosis is the loss of phospholipid asymmetry and the appearance of phosphatidylserine in the outer leaflet of the membrane. The ATP-requiring enzyme, flippase, maintains phospholipid asymmetry of PS. Here, we have investigated the inactivation of the transmembrane enzyme aminophospholipid-translocase (or flippase) by Abeta (1-42). Flippase activity depends on a critical cysteine residue, a putative site of covalent modification by the Abeta (1-42)-induced lipid peroxidation products, HNE or acrolein. The present study is aimed to investigate the protective effects of tricyclodecan-9-xanthogenate (D609) and ferulic acid ethyl ester (FAEE) on Abeta (1-42) induced modulation in phospholipid asymmetry in the synaptosomal membranes. Pretreatment of synaptosomes with D609 and FAEE significantly protected Abeta (1-42)-induced loss of phospholipid asymmetry in synaptosomal membranes. Our results suggest that D609 and FAEE exert protective effects against Abeta (1-42) induced apoptosis. The increase in intracellular Ca(2+) might not be the sole cause for the loss of flippase activity. Rather, other mechanisms that could modulate the function of flippase might be important in the modulation of phospholipid asymmetry. The results of this study are discussed with relevance to neuronal loss in the AD brain.     

Increased formation of short-chain organic acids after chronic ethanol administration and its interaction with the carnitine pool in rat

Organic acidurias are genetic disorders of mitochondrial metabolism that lead to the accumulation of organic acids in tissues and biological fluids. It has been demonstrated that interaction of carnitine with the cellular coenzyme A (CoA) pool, through the production of acyl-carnitines, is potentially critical for maintaining normal cellular metabolism under condition of impaired acyl-CoA use and that exposure of humans and other mammals to ethanol leads to impairment of mitochondrial function. The aim of the present study was to evaluate the role of chronic administration of ethanol on urinary excretion of short-chain organic acids and endogenous carnitines in rats. The data reported show that chronic administration of ethanol significantly increases urinary excretion of propionate, methylmalonate, as well as free acetate, butyrate, pyruvate, lactate, and beta-hydroxybutyrate. Chronic administration of propranolol abolished ethanol-dependent accumulation of propionate, suggesting involvement of beta-adrenergic mechanisms. Increased formation of propionate and methylmalonate was associated with decreased plasma carnitine levels and with increased excretion of specific acyl-carnitines, corresponding to the accumulating acyl groups. Our data indicate that chronic alcohol ingestion induces increased excretion of selected organic acids and that the endogenous carnitine pool might exert a protective role against the deleterious effects of accumulating short-chain organic acids.     

In vivo administration of D609 leads to protection of subsequently isolated gerbil brain mitochondria subjected to in vitro oxidative stress induced by amyloid beta-peptide and other oxidative stressors: relevance to Alzheimer's disease and other oxidative stress-related neurodegenerative disorders

Tricyclodecan-9-yl-xanthogenate (D609) has in vivo and in vitro antioxidant properties. D609 mimics glutathione (GSH) and has a free thiol group, which upon oxidation forms a disulfide. The resulting dixanthate is a substrate for glutathione reductase, regenerating D609. Recent studies have also shown that D609 protects brain in vivo and neuronal cultures in vitro against the potential Alzheimer's disease (AD) causative factor, Abeta(1-42)-induced oxidative stress and cytotoxicity. Mitochondria are important organelles with both pro- and antiapoptotic factor proteins. The present study was undertaken to test the hypothesis that intraperitoneal injection of D609 would provide neuroprotection against free radical-induced, mitochondria-mediated apoptosis in vitro. Brain mitochondria were isolated from gerbils 1 h post injection intraperitoneally (ip) with D609 and subsequently treated in vitro with the oxidants Fe(2+)/H(2)O(2) (hydroxyl free radicals), 2,2-azobis-(2-amidinopropane) dihydrochloride (AAPH, alkoxyl and peroxyl free radicals), and AD-relevant amyloid beta-peptide 1-42 [Abeta(1-42)]. Brain mitochondria isolated from the gerbils previously injected ip with D609 and subjected to these oxidative stress inducers, in vitro, showed significant reduction in levels of protein carbonyls, protein-bound hydroxynonenal [a lipid peroxidation product], 3-nitrotyrosine, and cytochrome c release compared to oxidant-treated brain mitochondria isolated from saline-injected gerbils. D609 treatment significantly maintains the GSH/GSSG ratio in oxidant-treated mitochondria. Increased activity of glutathione S-transferase, glutathione peroxidase, and glutathione reductase in brain isolated from D609-injected gerbils is consistent with the notion that D609 acts like GSH. These antiapoptotic findings are discussed with reference to the potential use of this brain-accessible glutathione mimetic in the treatment of oxidative stress-related neurodegenerative disorders, including AD.     

Hooking some stem-group "worms": fossil lophotrochozoans in the Burgess Shale

The fossil record plays a key role in reconstructing deep evolutionary relationships through its documentation of the early diverging stem groups leading to extant phyla. In the middle Cambrian Burgess Shale, two famously problematic worms, Odontogriphus and Wiwaxia, have recently been reinterpreted as stem-group molluscs based on their shared expression of a putative radula and putative ctenidia in Odontogriphus. More detailed analysis of these fossil structures, however, reveals pronounced anatomical and histological discrepancies with molluscan analogues, such that they are more reliably interpreted as primitive features of the superphylum Lophotrochozoa. In the absence of any obviously derived characters, Odontogriphus could be placed in the stem group of the Lophotrochozoa or on the stem of any of its constituent phyla, whereas the dorsal covering of chaetae in Wiwaxia identifies it as a stem-group polychaete. Despite their close relationship, these two jawed, segmented worms could conceivably represent the early stages of two separate phyla.