Age-related differences in proprioceptive and visuo-proprioceptive function in relation to fine motor behaviour

Leversen et al. (PLoS One 7(6):e38830, 2012) emphasise the importance of understanding the principles of life-long development. In their study of motor control, they found a common tendency towards improved motor performance from childhood to adulthood and a subsequent deterioration. The aim of our study was to examine this issue further by investigating fine motor behaviour (tracing a model line) in 196 participants (age range 12–95 years old) in two sensory conditions—proprioceptive + visual (PV) and proprioceptive only—in both hands and in two types of movement, frontal and transversal. Regression analyses of line length and task performance speed in relation to age were conducted for the different test conditions. The best performance was found in middle age, and a quadratic function provided the best fit for most of the test conditions. The corresponding inflection points (the age at which graphical analysis showed a change in performance as a peak of maturation before decline due to ageing) showed earlier ages in the proprioceptive condition. For most types of movement analysed, performance speed was slower under the PV condition. Paired correlation analysis showed that the symmetry of precision performance between hands became stronger with age. The results provide information on age-dependent differences in proprioception based on fine motor performance. They may be of use in the design of preventive strategies for preserving proprioceptive function by reducing the risk of falls and accidents or diseases such as Parkinson’s.     

Heat shock protein 90 inhibition sensitizes acute myelogenous leukemia cells to cytarabine

Previous studies demonstrated that ataxia telangiectasia mutated- and Rad3-related (ATR) kinase and its downstream target checkpoint kinase 1 (Chk1) facilitate survival of cells treated with nucleoside analogs and other replication inhibitors. Recent results also demonstrated that Chk1 is depleted when cells are treated with heat shock protein 90 (Hsp90) inhibitor 17-allylamino-17-demethoxygeldanamycin (17-AAG). The present study examined the effects of 17-AAG and its major metabolite, 17-aminogeldanamycin (17-AG), on Chk1 levels and cellular responses to cytarabine in human acute myelogenous leukemia (AML) cell lines and clinical isolates. Cytarabine, at concentrations as low as 30 nM, caused activating phosphorylation of Chk1, loss of the phosphatase Cdc25A, and S-phase slowing. Conversely, treatment with 100 to 300 nM 17-AAG for 24 hours caused Chk1 depletion that was accompanied by diminished cytarabine-induced S-phase accumulation, decreased Cdc25A degradation, and enhanced cytotoxicity as measured by inhibition of colony formation and induction of apoptosis. Additional studies demonstrated that small inhibitory RNA (siRNA) depletion of Chk1 also sensitized cells to cytarabine, whereas disruption of the phosphatidylinositol 3-kinase (PI3k) signaling pathway, which is also blocked by Hsp90 inhibition, did not. Collectively, these results suggest that treatment with 17-AAG might represent a means of reversing checkpoint-mediated cytarabine resistance in AML.     

A frameshifting stimulatory stem loop destabilizes the hybrid state and impedes ribosomal translocation

Ribosomal frameshifting occurs when a ribosome slips a few nucleotides on an mRNA and generates a new sequence of amino acids. Programmed −1 ribosomal frameshifting (−1PRF) is used in various systems to express two or more proteins from a single mRNA at precisely regulated levels. We used single-molecule fluorescence resonance energy transfer (smFRET) to study the dynamics of −1PRF in the Escherichia coli dnaX gene. The frameshifting mRNA (FSmRNA) contained the frameshifting signals: a Shine–Dalgarno sequence, a slippery sequence, and a downstream stem loop. The dynamics of ribosomal complexes translating through the slippery sequence were characterized using smFRET between the Cy3-labeled L1 stalk of the large ribosomal subunit and a Cy5-labeled tRNA^Lys in the ribosomal peptidyl-tRNA–binding (P) site. We observed significantly slower elongation factor G (EF-G)–catalyzed translocation through the slippery sequence of FSmRNA in comparison with an mRNA lacking the stem loop, ΔSL. Furthermore, the P-site tRNA/L1 stalk of FSmRNA-programmed pretranslocation (PRE) ribosomal complexes exhibited multiple fluctuations between the classical/open and hybrid/closed states, respectively, in the presence of EF-G before translocation, in contrast with ΔSL-programmed PRE complexes, which sampled the hybrid/closed state approximately once before undergoing translocation. Quantitative analysis showed that the stimulatory stem loop destabilizes the hybrid state and elevates the energy barriers corresponding to subsequent substeps of translocation. The shift of the FSmRNA-programmed PRE complex equilibrium toward the classical/open state and toward states that favor EF-G dissociation apparently allows the PRE complex to explore alternative translocation pathways such as −1PRF.The ribosome is the molecular machine that synthesizes proteins by translating messenger RNAs (mRNAs); each sequence of 3 nt, 1 codon, characterizes 1 aa (1–3). Failure to maintain frame during translation occurs with a low error of 10⁻⁵ (4); however, frameshifting with high efficiency (>10⁻²) is often programmed into many mRNAs to express two or more proteins from a single mRNA (5, 6). Many RNA viruses, including HIV-1, use programmed frameshifting to produce their vital proteins at a precise ratio (7, 8). The common −1 programmed ribosomal frameshifting (−1PRF) signals are a heptanucleotide slippery sequence (X XXY YYZ, underlining denotes the zero-frame) and a downstream stimulatory secondary structure such as a stem loop or a pseudoknot. Frameshifting that takes place on the slippery sequence results in minimal base pair mismatches. Prokaryotic systems have an additional stimulatory signal, an upstream, internal Shine–Dalgarno (SD) sequence (9). The dnaX gene of Escherichia coli has the three −1PRF signals; an SD sequence, an A AAA AAG slippery sequence, and a downstream stem loop (9–12). Highly efficient (50–80%) −1PRF during translation of the mRNA results in production of the γ DNA-polymerase subunit in the −1 frame and the τ DNA-polymerase subunit in the 0 frame (10).The −1PRF signals are spaced so that the slippery sequence is positioned within the ribosomal peptidyl-tRNA–binding (P) site and aminoacyl-tRNA–binding (A) site, whereas the downstream secondary structure is positioned at the ribosomal mRNA entry channel (Fig. 1) (5–8, 13). The upstream SD sequence base pairs with 16S ribosomal RNA (rRNA) near the ribosomal tRNA exit (E) site (Fig. 1) (9). Both the SD sequence and the downstream secondary structure can cause pausing during translation (14–19). However, frameshifting efficiency is not strictly related to the pausing extent (15, 17), and it is not proportional to the thermodynamic or mechanical stabilities of the secondary structures (7, 20). Nonetheless, it does correlate with the thermodynamic stability of the first 3–4 bp of the downstream secondary structure (21), and with the conformational plasticity of this structure (7, 20). However, a mechanism by which the stimulatory secondary structure promotes efficient frameshifitng has not emerged yet.Open in a separate windowFig. 1.A programmed −1 FSmRNA construct and a schematic drawing of a ribosomal complex translating the slippery sequence. FSmRNA contains three −1PRF signals from the dnaX gene in E. coli; an SD sequence, a slippery sequence, and a downstream stem loop. ΔSL mRNA has the same sequence as FSmRNA except with the stem loop (red box) deleted. Start and stop codons are highlighted in blue. Corresponding polypeptide sequences are shown below the mRNA. A schematic drawing of the POST-(Cy5)K₁ complex shows the 50S and 30S subunits in blue and purple rectangles, respectively. The L1 stalk in the small blue rectangle is labeled with Cy3. The ribosomal complex contains fMVK-(Cy5)tRNA^Lys in the P site, where the slippery sequence is being displayed. The upstream SD sequence forms base pairs with 16S rRNA and the downstream stem loop presents at the mRNA entry channel in the 30S subunit. The orange oval denotes the biotin on a DNA primer annealed to the 5′ end of the mRNA for immobilization.A translational elongation cycle starts with selecting a correct aminoacyl-tRNA in the A site via conformational changes of the posttranslocation (POST) ribosomal complex that are triggered upon binding an EF-Tu(GTP)⋅aminoacyl-tRNA ternary complex (TC) (1). Once peptidyl transfer takes place, the resulting pretranslocation (PRE) ribosomal complex undergoes large-scale conformational changes that facilitate translocation of the tRNAs from the P and A sites into the E and P sites, simultaneously advancing the ribosome along the mRNA by 3 nt (22). In the first step of translocation, the acceptor stems of the tRNAs are repositioned within the large ribosomal (50S, in prokaryotes) subunit to move the tRNAs from their classical (P/P, A/A) state to their hybrid (P/E, A/P) states, where X and Y in the X/Y notation refer to the position of the anticodon stem loop (ASL) of the tRNA in the small ribosomal (30S, in prokaryotes) subunit and the position of the acceptor stem of the tRNA in the 50S subunit, respectively. Hybrid state (H) formation is accompanied by rotation of the 30S subunit relative to the 50S subunit (23, 24) and a closure of the L1 stalk of the 50S subunit such that it forms a direct contact with the P/E hybrid tRNA (23–25), a global conformation of the PRE complex that we refer to as “global state 2” (25). Global state 1, in contrast, contains classical state (C) tRNAs, nonrotated subunits, and an open L1 stalk (25). Single-molecule fluorescence resonance energy transfer (smFRET) studies of this step of translocation have shown that the H state forms spontaneously upon peptidyl transfer and that, in the absence of an elongation factor-G (EF-G), the H state exists in a dynamic equilibrium with the C state (25–27). Translocation is completed by movement of the ASLs of the tRNAs and the mRNA in the 30S subunit. This step, which comprises the rate-limiting step for the overall process of translocation, requires unlocking of the PRE complex, a conformational change that is thought to involve swiveling of the head domain of the 30S subunit (28, 29) and that is catalyzed by EF-G (30). smFRET and structural studies suggest that the L1 stalk–P/E hybrid tRNA interaction that is established during the first step of translocation is preserved throughout the second step of translocation and is essential for guiding the translocation of the P/E hybrid tRNA into the E site (25, 31, 32).Here, we report an smFRET study of the dynamics of ribosomal complexes programmed with the −1PRF mRNA of the E. coli dnaX gene. We used a FRET pair composed of a Cy3-labeled L1 stalk [L1(Cy3)-stalk] and a Cy5-labeled P-site tRNA^Lys [(Cy5)tRNA^Lys] on the first lysine codon in the slippery sequence. As previously demonstrated (25), this FRET pair enabled us to monitor transitions of ribosomal complexes between C and H states and the subsequent release of the translocated (Cy5)tRNA^Lys from the E site, along one round of the translational elongation cycle. Two mRNA constructs, one containing the downstream stem loop and one lacking it, were compared to study the effect of the secondary structure on the dynamics and translocation of the ribosomal complexes. Our results show that the downstream stem loop changes the dynamics of the PRE ribosomal complexes and disturbs the translocation process. We propose that frameshifting is one of the favorable paths that the ribosome can adopt during the futile EF-G–driven translocation attempts from the H state.     

Treatment of pruritus of primary biliary cirrhosis with rifampin

Pruritus can be a debilitating symptom in patients with chronic cholestasis. Based on previous reports of its efficacy, we evaluated the impact of rifampin on the pruritus associated with primary biliary cirrhosis. Fourteen patients were included in a randomized, crossover study. After a 15-day washout period, subjects were followed for three weeks. During the first and third week, patients received 600 mg of rifampin or placebo; no treatment was administered during the second week. Pruritus was subjectively scored on a scale from 0 to 100. With rifampin, pruritus disappeared in 11 patients and partially improved in three; with placebo, only two had a partial response (P<0.001). Six patients with a prior poor or no response to cholestyramine improved with rifampin. No changes in biochemical tests or side effects were observed during this period. We conclude that short-term administration of rifampin relieves pruritus in primary biliary cirrhosis. When administered over a period of eight months in an open study, the relief of pruritus was maintained, while one individual developed an allergic reaction. Rifampin appears to be a safe drug in the management of the pruritus of primary biliary cirrhosis.     

Inhibition of poly(ADP-ribose) polymerase attenuates the severity of acute pancreatitis and associated lung injury

The severity of acute pancreatitis results from the transmigration and activation of leukocytes within the pancreas and the local synthesis and release of proinflammatory-soluble mediators that transform a local injury into a systemic inflammatory response. Poly(ADP-ribose)polymerase-1 (PARP-1) is a nuclear DNA-binding protein that has been shown to play a relevant role in cell necrosis and organ failure in various diseases associated with inflammation. Therefore, we set out to investigate whether the genetic deletion of PARP-1 or PARP-2 (a new member of the PARP family) genes, or pharmacological inhibition of PARP activity might affect the development and severity of acute pancreatitis and pancreatitis-associated lung injury. Secretagogue-induced acute pancreatitis was achieved by 12 hourly intraperitoneal injections of cerulein in mice deficient in PARP-1 or PARP-2 genes, and wild-type (WT) littermate mice untreated or treated with PARP activity inhibitors. The severity of pancreatitis was assessed by measurements of serum amylase, lipase, interleukin-1beta and IL-6, pancreatic water content, histologic grading and pancreas myeloperoxidase (MPO) activity. Lung injury was evaluated by quantifying MPO activity and morphological changes. We found that the severity of acute pancreatitis and pancreatitis-associated lung injury was significantly attenuated in mice lacking PARP-1, but not PARP-2, compared with WT mice. Interestingly, administration of PARP inhibitors, 3-aminobenzamide or PJ34 (N-(6-oxo-5,6-dihydro-phenanthridin-2-yl)-N,N-dimethyacetamide HCl), in WT mice markedly decreased acute pancreatitis severity and pulmonary-associated injury in a larger extension than genetic deletion of PARP-1. Our results support the potential therapeutic application of PARP inhibitors in the development and severity of acute pancreatitis and associated lung injury.     

Identification of non-amplifying CYP21 genes when using PCR-based diagnosis of 21-hydroxylase deficiency in congenital adrenal hyperplasia (CAH) affected pedigrees

Steroid 21-hydroxylase deficiency is among the most common inborn errors of metabolism in man. Characterization of mutations in the 21- hydroxylase gene (CYP21) has permitted genetic diagnosis, facilitated by the polymerase chain reaction (PCR). The most common mutation is conversion of an A or C at nt656 to a G in the second intron causing aberrant splicing of mRNA. Homozygosity for nt656G is associated with profoundly deficient adrenal cortisol and aldosterone synthesis, secondary hypersecretion of adrenal androgens, and a severe form of congenital adrenal hyperplasia (CAH) characterized by ambiguous genitalia and/or sodium wasting in newborns. During the course of genetic analysis of CYP21 mutations in CAH families, we and others have noticed a number of relatives genotyped as nt656G homozygotes, yet showing no clinical signs of disease. A number of lines of evidence have led us to propose that the putative asymptomatic nt656G/G individuals are incorrectly typed due to dropout of one haplotype during PCR amplification of CYP21. For prenatal diagnosis, we recommend that microsatellite typing be used as a supplement to CYP21 genotyping in order to resolve ambiguities at nt656.      

Role of neuropsychologists in the evaluation and management of sport-related concussion: an inter-organization position statement

Over the past 20 years, clinical neuropsychologists have been at the forefront of both scientific and clinical initiatives aimed at developing evidence-based approaches to the evaluation and management of sport-related concussion (SRC). These efforts have directly impacted current policy on strategies for injury assessment and return-to-play by athletes after concussion. Many states are considering legislation requiring (a) education of athletes, parents, coaches, and school/organization officials on the recognition, evaluation, and management of SRCs; (b) removal from play of any youth athlete that is suspected of having sustained a concussion; and (c) not allowing the student to return to participation until the student is evaluated and cleared for return to participation in writing by an appropriate healthcare professional. It is the official position of the American Academy of Clinical Neuropsychology (AACN), American Board of Professional Neuropsychology (ABN), Division 40 (Neuropsychology) of the American Psychological Association (APA), and the National Academy of Neuropsychology (NAN) that neuropsychologists should be included among the licensed healthcare professionals authorized to evaluate, clinically manage, and provide return to play clearance for athletes who sustain a SRC.     

Polyautoimmunity and familial autoimmunity in systemic sclerosis

Characterization of the extent to which particular combinations of autoimmune diseases occur in excess of that expected by chance may offer new insights into possible common pathophysiological mechanisms. The goal of this study was to investigate the spectrum of polyautoimmunity (i.e. autoimmune diseases co-occurring within patients) and familial autoimmunity (i.e. diverse autoimmune diseases co-occurring within families) in patients with systemic sclerosis (SSc). A cross-sectional study of two convenience samples of patients with SSc, one in Canada and the other in Colombia, was performed. History of other autoimmune diseases in the SSc patients as well as a family history of autoimmunity was obtained. Of 719 patients, 273 (38%) had at least one other autoimmune disease. A total of 366 autoimmune diseases were reported, of which the most frequent were autoimmune thyroid disease (AITD, 38%), rheumatoid arthritis (RA, 21%), Sj?gren's syndrome (18%), and primary biliary cirrhosis (4%). There were 260 (36%) patients with first-degree relatives with at least one autoimmune disease, of which the most frequent were RA (18%) and AITD (9%). Having at least one first-degree relative with autoimmune disease was a significant predictor of polyautoimmunity in SSc patients. No significant differences in polyautoimmunity or familial autoimmunity were noted between diffuse and limited subsets of disease. Our results indicate that polyautoimmunity is frequent in patients with SSc and autoimmune diseases cluster within families of these patients. Clinically different autoimmune phenotypes might share common susceptibility variants, which acting in epistatic pleiotropy may represent risk factors for autoimmunity.     

The Multiple Autoimmune Syndromes. A Clue for the Autoimmune Tautology

The multiple autoimmune syndromes (MAS) consist on the presence of three or more well-defined autoimmune diseases (ADs) in a single patient. The aim of this study was to analyze the clinical and genetic characteristics of a large series of patients with MAS. A cluster analysis and familial aggregation analysis of ADs was performed in 84 patients. A genome-wide microsatellite screen was performed in MAS families, and associated loci were investigated through the pedigree disequilibrium test. Systemic lupus erythematosus (SLE), autoimmune thyroid disease (AITD), and Sj?gren??s syndrome together were the most frequent ADs encountered. Three main clusters were established. Aggregation for type 1 diabetes, AITD, SLE, and all ADs as a trait was found. Eight loci associated with MAS were observed harboring autoimmunity genes. The MAS represent the best example of polyautoimmunity as well as the effect of a single genotype on diverse phenotypes. Its study provides important clues to elucidate the common mechanisms of ADs (i.e., autoimmune tautology).     

Surface roughness mediates its effects on osteoblasts via protein kinase A and phospholipase A2

Earlier studies have shown that implant surface roughness influences osteoblast proliferation, differentiation, matrix synthesis and local factor production. Moreover, the responsiveness of osteoblasts to systemic hormones, such as 1,25-(OH)₂D₃, at the implant surface is also influenced by surface roughness and this effect is mediated by changes in prostaglandins. At present, it is not known which signaling pathways are involved in mediating cell response to surface roughness and how 1,25-(OH)₂D₃ treatment alters the activation of these pathways. This paper reviews a series of studies that have addressed this question. MG63 osteoblast-like cells were cultured on commercially pure titanium (cpTi) surfaces of two different roughnesses (R_a 0.54 and 4.92 μm) in the presence of control media or media containing 1,25-(OH)₂D₃ or 1,25-(OH)₂D₃ plus H8 (a protein kinase A inhibitor) or quinacrine (a phospholipase A₂ inhibitor). At harvest, the effect of these treatments on cell number and alkaline phosphatase specific activity was measured. Compared to cultures grown on the smooth surface, cell number was reduced on the rough surface. 1,25-(OH)₂D₃ inhibited cell number on both surfaces and inhibition of protein kinase A in the presence of 1,25-(OH)₂D₃ restored cell number to that seen in the control cultures. Inhibition of phospholipase A₂ in the presence of 1,25-(OH)₂D₃ caused a further reduction in cell number on the smooth surface, and partially reversed the inhibitory effects of 1,25-(OH)₂D₃ on the rough surface. Alkaline phosphatase specific activity was increased in cultures grown on the rough surface compared with those grown on the smooth surface; 1,25-(OH)₂D₃ treatment increased enzyme specific activity on both surfaces. Cultures treated with H8 and 1,25-(OH)₂D₃ displayed enzyme specific activity that approximated that seen in control cultures. Inhibition of phospholipase A₂ also inhibited the 1,25-(OH)₂D₃-dependent effect on the smooth surface, but on the rough surface there was an inhibition of the 1,25-(OH)₂D₃ effect as well as a partial inhibition of the surface roughness-dependent effect. The results indicate that surface roughness and 1,25-(OH)₂D₃ mediate their effects through phospholipase A₂, which catalyzes one of the rate-limiting steps in prostaglandin E₂ production. Further downstream, prostaglandin E₂ activates protein kinase A.