Fixed Dystonia in Complex Regional Pain Syndrome: a Descriptive and Computational Modeling Approach

Background  

Complex regional pain syndrome (CRPS) may occur after trauma, usually to one limb, and is characterized by pain and disturbed blood flow, temperature regulation and motor control. Approximately 25% of cases develop fixed dystonia. Involvement of dysfunctional GABAergic interneurons has been suggested, however the mechanisms that underpin fixed dystonia are still unknown. We hypothesized that dystonia could be the result of aberrant proprioceptive reflex strengths of position, velocity or force feedback.     

Characterization of Site-Specific Mutations in a Short-Chain-Length/Medium-Chain-Length Polyhydroxyalkanoate Synthase: In Vivo and In Vitro Studies of Enzymatic Activity and Substrate Specificity

Saturation point mutagenesis was carried out at position 479 in the polyhydroxyalkanoate (PHA) synthase from Chromobacterium sp. strain USM2 (PhaC_Cs) with specificities for short-chain-length (SCL) [(R)-3-hydroxybutyrate (3HB) and (R)-3-hydroxyvalerate (3HV)] and medium-chain-length (MCL) [(R)-3-hydroxyhexanoate (3HHx)] monomers in an effort to enhance the specificity of the enzyme for 3HHx. A maximum 4-fold increase in 3HHx incorporation and a 1.6-fold increase in PHA biosynthesis, more than the wild-type synthase, was achieved using selected mutant synthases. These increases were subsequently correlated with improved synthase activity and increased preference of PhaC_Cs for 3HHx monomers. We found that substitutions with uncharged residues were beneficial, as they resulted in enhanced PHA production and/or 3HHx incorporation. Further analysis led to postulations that the size and geometry of the substrate-binding pocket are determinants of PHA accumulation, 3HHx fraction, and chain length specificity. In vitro activities for polymerization of 3HV and 3HHx monomers were consistent with in vivo substrate specificities. Ultimately, the preference shown by wild-type and mutant synthases for either SCL (C₄ and C₅) or MCL (C₆) substrates substantiates the fundamental classification of PHA synthases.     

The Outcome of Prophylactic Intravenous Cefazolin and Ceftriaxone in Cirrhotic Patients at Different Clinical Stages of Disease after Endoscopic Interventions for Acute Variceal Hemorrhage

Antibiotic prophylaxis with norfloxacin, intravenous ciprofloxacin, or ceftriaxone has been recommended for cirrhotic patients with gastrointestinal hemorrhage but little is known about intravenous cefazolin. This study aimed to compare the outcome of intravenous cefazolin and ceftriaxone as prophylactic antibiotics among cirrhotic patients at different clinical stages, and to identify the associated risk factors. The medical records of 713 patients with acute variceal bleeding who had received endoscopic procedures from were reviewed. Three hundred and eleven patients were entered for age-matched adjustment after strict exclusion criteria. After the adjustment, a total of 102 patients were enrolled and sorted into 2 groups according to the severity of cirrhosis: group A (Child’s A patients, n = 51) and group B (Child’s B and C patients, n = 51). The outcomes were prevention of infection, time of rebleeding, and death. Our subgroup analysis results failed to show a significant difference in infection prevention between patients who received prophylactic cefazolin and those who received ceftriaxone among Child’s A patients (93.1% vs. 90.9%, p = 0.641); however, a trend of significance in favor of ceftriaxone prophylaxis (77.8% vs. 87.5%, p = 0.072) was seen among Child’s B and C patients. More rebleeding cases were observed in patients who received cefazolin than in those who received ceftriaxone among Child’s B and C patients (66.7% vs. 25.0%, p = 0.011) but not in Child’s A patients (32% vs. 40.9%, p = 0.376). The risk factors associated with rebleeding were history of bleeding and use of prophylactic cefazolin among Child’s B and C patients. In conclusion, this study suggests that prophylactic intravenous cefazolin may not be inferior to ceftriaxone in preventing infections and reducing rebleeding among Child’s A cirrhotic patients after endoscopic interventions for acute variceal bleeding. Prophylactic intravenous ceftriaxone yields better outcome among Child’s B and C patients.     

Chromosomal context and epigenetic mechanisms control the efficacy of genome editing by rare-cutting designer endonucleases

The ability to specifically engineer the genome of living cells at precise locations using rare-cutting designer endonucleases has broad implications for biotechnology and medicine, particularly for functional genomics, transgenics and gene therapy. However, the potential impact of chromosomal context and epigenetics on designer endonuclease-mediated genome editing is poorly understood. To address this question, we conducted a comprehensive analysis on the efficacy of 37 endonucleases derived from the quintessential I-CreI meganuclease that were specifically designed to cleave 39 different genomic targets. The analysis revealed that the efficiency of targeted mutagenesis at a given chromosomal locus is predictive of that of homologous gene targeting. Consequently, a strong genome-wide correlation was apparent between the efficiency of targeted mutagenesis (≤ 0.1% to ≈ 6%) with that of homologous gene targeting (≤ 0.1% to ≈ 15%). In contrast, the efficiency of targeted mutagenesis or homologous gene targeting at a given chromosomal locus does not correlate with the activity of individual endonucleases on transiently transfected substrates. Finally, we demonstrate that chromatin accessibility modulates the efficacy of rare-cutting endonucleases, accounting for strong position effects. Thus, chromosomal context and epigenetic mechanisms may play a major role in the efficiency rare-cutting endonuclease-induced genome engineering.     

Redefining the role of metallothionein within the injured brain: extracellular metallothioneins play an important role in the astrocyte-neuron response to injury

A number of intracellular proteins that are protective after brain injury are classically thought to exert their effect within the expressing cell. The astrocytic metallothioneins (MT) are one example and are thought to act via intracellular free radical scavenging and heavy metal regulation, and in particular zinc. Indeed, we have previously established that astrocytic MTs are required for successful brain healing. Here we provide evidence for a fundamentally different mode of action relying upon intercellular transfer from astrocytes to neurons, which in turn leads to uptake-dependent axonal regeneration. First, we show that MT can be detected within the extracellular fluid of the injured brain, and that cultured astrocytes are capable of actively secreting MT in a regulatable manner. Second, we identify a receptor, megalin, that mediates MT transport into neurons. Third, we directly demonstrate for the first time the transfer of MT from astrocytes to neurons over a specific time course in vitro. Finally, we show that MT is rapidly internalized via the cell bodies of retinal ganglion cells in vivo and is a powerful promoter of axonal regeneration through the inhibitory environment of the completely severed mature optic nerve. Our work suggests that the protective functions of MT in the central nervous system should be widened from a purely astrocytic focus to include extracellular and intra-neuronal roles. This unsuspected action of MT represents a novel paradigm of astrocyte-neuronal interaction after injury and may have implications for the development of MT-based therapeutic agents.     

Exercise therapy for prevention of falls in people with Parkinson's disease: A protocol for a randomised controlled trial and economic evaluation

Background

People with Parkinson's disease are twice as likely to be recurrent fallers compared to other older people. As these falls have devastating consequences, there is an urgent need to identify and test innovative interventions with the potential to reduce falls in people with Parkinson's disease. The main objective of this randomised controlled trial is to determine whether fall rates can be reduced in people with Parkinson's disease using exercise targeting three potentially remediable risk factors for falls (reduced balance, reduced leg muscle strength and freezing of gait). In addition we will establish the cost effectiveness of the exercise program from the health provider's perspective.

Methods/Design

230 community-dwelling participants with idiopathic Parkinson's disease will be recruited. Eligible participants will also have a history of falls or be identified as being at risk of falls on assessment. Participants will be randomly allocated to a usual-care control group or an intervention group which will undertake weight-bearing balance and strengthening exercises and use cueing strategies to address freezing of gait. The intervention group will choose between the home-based or support group-based mode of the program. Participants in both groups will receive standardized falls prevention advice. The primary outcome measure will be fall rates. Participants will record falls and medical interventions in a diary for the duration of the 6-month intervention period. Secondary measures include the Parkinson's Disease Falls Risk Score, maximal leg muscle strength, standing balance, the Short Physical Performance Battery, freezing of gait, health and well being, habitual physical activity and positive and negative affect schedule.

Discussion

No adequately powered studies have investigated exercise interventions aimed at reducing falls in people with Parkinson's disease. This trial will determine the effectiveness of the exercise intervention in reducing falls and its cost effectiveness. This pragmatic program, if found to be effective, has the potential to be implemented within existing community services.

Trial registration

The protocol for this study is registered with the Australian New Zealand Clinical Trials Registry (ACTRN12608000303347).