The ipsilateral human motor cortex can functionally compensate for acute contralateral motor cortex dysfunction

What promotes motor recovery from stroke? To date, studies of recovery from stroke have shown alterations in function in various cortical areas, including the contralesional (unaffected) motor cortex (M1). However, whether these changes contribute to recovery or are mere epiphenomena remains unclear. We therefore sought evidence that the ipsilateral M1 can compensate for dysfunction of the contralateral M1. We recorded the change in force production during a finger-tapping task in response to acute disruption of M1 function by repetitive transcranial magnetic stimulation (rTMS). Neither control (occipital) nor ipsilateral M1 rTMS lead to a change in tapping force. RTMS over contralateral M1 had a short-lived effect and induced changes in ipsilateral M1 excitability around the time that these behavioral effects abated, consistent with delayed compensation by the ipsilateral M1. Simultaneous bilateral M1 stimulation, designed to prevent compensation by the ipsilateral M1, had a large and prolonged effect on tapping force. This is the first demonstration that the ipsilateral primary motor cortex is capable of functionally significant compensation for focal contralateral cortical dysfunction in the adult human and provides a rational basis for interventional treatments aimed at promoting functional compensation in unaffected cortical areas after stroke.     

Cardiovascular changes and catecholamine release following anaesthesia in Chinook salmon (Oncorhynchus tshawytscha) and snapper (Pagrus auratus)

We investigated recovery from anaesthesia in Chinook salmon (Oncorhynchus tshawytscha) with and without surgery. Fish either underwent light sedation on exposure to 60 ppm AQUI-S or surgical depth anaesthesia with 120 ppm AQUI-S. Surgical depth anaesthesia experiments were replicated using New Zealand snapper (Pagrus auratus). During light sedation, there was no evidence of catecholamine release in salmon despite changes in heart rate and blood pressure. Following surgical anaesthesia both salmon and snapper released high concentrations of catecholamines into the circulation. Plasma half-life of adrenaline in salmon was 9.3+/-0.7 min (n = 7) and in snapper was 4.4+/-3.3 min (n = 7). There was no further release of catecholamines, despite attempts by both species to escape their enclosures. Though clearance of the catecholamines was rapid, the cardiovascular effects of anaesthesia were prolonged. Dorsal aortic blood pressure (P(DA)) and heart rate (HR) were high following anaesthesia, falling by 60 min in the 60 ppm exposed salmon but remaining high in the 120 ppm group. Following anaesthesia ventral aorta blood pressure (P(VA)) in snapper was positively correlated with HR, as was P(DA) and haematocrit in salmon. Recovery of cardiovascular control processes is prolonged in recovery from anaesthesia if the fish become hypoxic.     

Clinical and angiographic predictors of stroke and death from carotid endarterectomy: systematic review.

OBJECTIVE: To identify risk factors for operative stroke and death from carotid endarterectomy. DESIGN: Systematic review of all studies published since 1980 which related risk of stroke and death to various preoperative clinical and angiographic characteristics, including unpublished data on 1729 patients from the European carotid surgery trial. MAIN OUTCOME MEASURE: Operative risk of stroke and death. RESULTS: Thirty six published studies fulfilled our criteria. The effect of 14 potential risk factors was examined. The odds of stroke and death were decreased in patients with ocular ischaemia alone (amaurosis fugax or retinal artery occlusion) compared with those with cerebral transient ischaemic attack or stroke (seven studies; odds ratio 0.49; 95% confidence interval 0.37 to 0.66; P < 0.00001). The odds were increased in women (seven studies; 1.44; 1.14 to 1.83; P < 0.005), subjects aged > or = 75 years (10 studies: 1.36; 1.09 to 1.71; P < 0.01), and with systolic blood pressure > 180 mm Hg (four studies; 1.82; 1.37 to 2.41; P < 0.0001), peripheral vascular disease (one study; 2.19; 1.40 to 3.60; P < 0.0005), occlusion of the contralateral internal carotid artery (14 studies; 1.91; 1.35 to 2.69; P < 0.0001), stenosis of the ipsilateral internal carotid siphon (five studies; 1.56; 1.03 to 2.36; P = 0.02), and stenosis of the ipsilateral external carotid artery (one study; 1.61; 1.05 to 2.47; P = 0.03). Operative risk was not significantly related to presentation with cerebral transient ischaemic attack versus stroke, diabetes, angina, recent myocardial infarction, current cigarette smoking, or plaque surface irregularity at angiography. Multiple regression analysis of data from the European carotid surgery trial identified cerebral versus ocular events at presentation, female sex, systolic hypertension, and peripheral vascular disease as independent risk factors. CONCLUSIONS: The risk of stroke and death from carotid endarterectomy is related to several clinical and angiographic characteristics. These observations may help clinicians to estimate operative risks for individual patients and will also facilitate more meaningful comparison of the operative risks of different surgeons or at different institutions by allowing some adjustment for differences in case mix.     

Spontaneously Fluctuating Motor Cortex Excitability in Alternating Hemiplegia of Childhood: A Transcranial Magnetic Stimulation Study

Background

Alternating hemiplegia of childhood is a very rare and serious neurodevelopmental syndrome; its genetic basis has recently been established. Its characteristic features include typically-unprovoked episodes of hemiplegia and other transient or more persistent neurological abnormalities.

Methods

We used transcranial magnetic stimulation to assess the effect of the condition on motor cortex neurophysiology both during and between attacks of hemiplegia. Nine people with alternating hemiplegia of childhood were recruited; eight were successfully tested using transcranial magnetic stimulation to study motor cortex excitability, using single and paired pulse paradigms. For comparison, data from ten people with epilepsy but not alternating hemiplegia, and ten healthy controls, were used.

Results

One person with alternating hemiplegia tested during the onset of a hemiplegic attack showed progressively diminishing motor cortex excitability until no response could be evoked; a second person tested during a prolonged bilateral hemiplegic attack showed unusually low excitability. Three people tested between attacks showed asymptomatic variation in cortical excitability, not seen in controls. Paired pulse paradigms, which probe intracortical inhibitory and excitatory circuits, gave results similar to controls.

Conclusions

We report symptomatic and asymptomatic fluctuations in motor cortex excitability in people with alternating hemiplegia of childhood, not seen in controls. We propose that such fluctuations underlie hemiplegic attacks, and speculate that the asymptomatic fluctuation we detected may be useful as a biomarker for disease activity.     

The CaVβ Subunit Protects the I-II Loop of the Voltage-gated Calcium Channel CaV2.2 from Proteasomal Degradation but Not Oligoubiquitination

Ca_Vβ subunits interact with the voltage-gated calcium channel Ca_V2.2 on a site in the intracellular loop between domains I and II (the I-II loop). This interaction influences the biophysical properties of the channel and leads to an increase in its trafficking to the plasma membrane. We have shown previously that a mutant Ca_V2.2 channel that is unable to bind Ca_Vβ subunits (Ca_V2.2 W391A) was rapidly degraded (Waithe, D., Ferron, L., Page, K. M., Chaggar, K., and Dolphin, A. C. (2011) J. Biol. Chem. 286, 9598–9611). Here we show that, in the absence of Ca_Vβ subunits, a construct consisting of the I-II loop of Ca_V2.2 was directly ubiquitinated and degraded by the proteasome system. Ubiquitination could be prevented by mutation of all 12 lysine residues in the I-II loop to arginines. Including a palmitoylation motif at the N terminus of Ca_V2.2 I-II loop was insufficient to target it to the plasma membrane in the absence of Ca_Vβ subunits even when proteasomal degradation was inhibited with MG132 or ubiquitination was prevented by the lysine-to-arginine mutations. In the presence of Ca_Vβ subunit, the palmitoylated Ca_V2.2 I-II loop was protected from degradation, although oligoubiquitination could still occur, and was efficiently trafficked to the plasma membrane. We propose that targeting to the plasma membrane requires a conformational change in the I-II loop that is induced by binding of the Ca_Vβ subunit.     

Polyinosinic acid is a ligand for toll-like receptor 3

Innate immune responses are critical in controlling viral infections. Viral proteins and nucleic acids have been shown to be recognized by pattern recognition receptors of the Toll-like receptor (TLR) family, triggering downstream signaling cascades that lead to cellular activation and cytokine production. Viral DNA is sensed by TLR9, and TLRs 3, 7, and 8 have been implicated in innate responses to RNA viruses by virtue of their ability to sense double-stranded (ds) RNA (TLR3) or single-stranded RNA (murine TLR7 and human TLR8). Viral and synthetic dsRNAs have also been shown to be a potent adjuvant, promoting enhanced adaptive immune responses, and this property is also dependent on their recognition by TLR3. It has recently been shown that mRNA that is largely single-stranded is a ligand for TLR3. Here we have investigated the ability of single-stranded homopolymeric nucleic acids to induce innate responses by murine immune cells. We show for the first time that polyinosinic acid (poly(I)) activates B lymphocytes, dendritic cells, and macrophages and that these responses are dependent on the expression of both TLR3 and the adaptor molecule, Toll/IL-1 receptor domain-containing adaptor inducing IFN-beta (TRIF). We therefore conclude that TLR3 is able to sense both single-stranded RNA and dsRNA.     

A pre-equilibrium before nucleotide binding limits fingers subdomain closure by Klentaq1

Numerous studies have been undertaken to establish the mechanism of dNTP binding and template-directed incorporation by DNA polymerases. It has been established by kinetic experiments that a rate-limiting step, crucial for dNTP selection, occurs before chemical bond formation. Crystallographic studies indicated that this step may be due to a large open-to-closed conformational transition affecting the fingers subdomain. In previous studies, we established a fluorescence resonance energy transfer system to monitor the open-to-closed transition in the fingers subdomain of Klentaq1. By comparing the rates of the fingers subdomain closure with that of the rate-limiting step for Klentaq1, we showed that fingers subdomain motion was significantly faster than the rate-limiting step. We have now used this system to characterize DNA binding as well as to complete a more extensive characterization of incorporation of all four dNTPs. The data indicate that DNA binding occurs by a two-step association and that dissociation of the DNA is significantly slower in the case of the closed ternary complex. The data for nucleotide incorporation indicate a step occurring before dNTP binding, which differs for all four nucleotides. As the only difference between the (E x p/t) complexes is the templating base, it would suggest an important role for the templating base in initial ground state selection.     

Postinspiratory activity of the parasternal and external intercostal muscles in awake canines.

Previous studies have shown in awake dogs that activity in the crural diaphragm, but not in the costal diaphragm, usually persists after the end of inspiratory airflow. It has been suggested that this difference in postinspiratory activity results from greater muscle spindle content in the crural diaphragm. To evaluate the relationship between muscle spindles and postinspiratory activity, we have studied the pattern of activation of the parasternal and external intercostal muscles in the second to fourth interspaces in eight chronically implanted animals. Recordings were made on 2 or 3 successive days with the animals breathing quietly in the lateral decubitus position. The two muscles discharged in phase with inspiration, but parasternal intercostal activity usually terminated with the cessation of inspiratory flow, whereas external intercostal activity persisted for 24.7 +/- 12.3% of inspiratory time (P < 0.05). Forelimb elevation in six animals did not affect postinspiratory activity in the parasternal but prolonged postinspiratory activity in the external intercostal to 45.4 +/- 16.3% of inspiratory time (P < 0.05); in two animals, activity was still present at the onset of the next inspiratory burst. These observations support the concept that muscle spindles are an important determinant of postinspiratory activity. The absence of such activity in the parasternal intercostals and costal diaphragm also suggests that the mechanical impact of postinspiratory activity on the respiratory system is smaller than conventionally thought.