Influence of general anaesthesia on slow waves of intracranial pressure.

OBJECTIVE: Slow vasogenic intracranial pressure (ICP) waves are spontaneous ICP oscillations with a low frequency bandwidth of 0.3-4 cycles/min (B-waves). B-waves reflect dynamic oscillations in cerebral blood volume associated with autoregulatory cerebral vasodilation and vasoconstriction. This study quantifies the effects of general anaesthesia (GA) on the magnitude of B-waves compared to natural sleep and conscious state. MATERIALS AND METHODS: The magnitude of B-waves was assessed in 4 groups of 30 patients each with clinical indications for ICP monitoring. Normal pressure hydrocephalus patients undergoing Cerebrospinal Fluid (CSF) infusion studies in the conscious state (GROUP A) and under GA (GROUP B), and hydrocephalus patients undergoing overnight ICP monitoring during physiological sleep (GROUP C) were compared to deeply sedated traumatic brain injury (TBI) patients with well-controlled ICP during the first night of Intensive Care Unit (ICU) stay (GROUP D). RESULTS: A total of 120 patients were included. During CSF infusion studies, the magnitude of slow waves was higher in conscious patients ( GROUP A: 0.23+/-0.10 mm Hg) when compared to anaesthetised patients ( GROUP B: 0.15+/-0.10 mm Hg; p = 0.011). Overnight magnitude of slow waves was higher in patients during natural sleep (GROUP C: 0.20+/-0.13 mm Hg) when compared to TBI patients under deep sedation (GROUP D: 0.11+/- 0.09 mm Hg; p = 0.002). CONCLUSION: GA and deep sedation are associated with a reduced magnitude of B-waves. ICP monitoring carried out under GA is affected by iatrogenic suppression of slow vasogenic waves of ICP. Accounting for the effects of anaesthesia on vasogenic waves may prevent the misidentification of potential shunt-responders as non-responders.This is the author accepted manuscript. The final version is available from Taylor & Francis via http://dx.doi.org/10.1080/01616412.2016.1189200

Sulfide geochronology along the Endeavour Segment of the Juan de Fuca Ridge

Forty-nine hydrothermal sulfide-sulfate rock samples from the Endeavour Segment of the Juan de Fuca Ridge, northeastern Pacific Ocean, were dated by measuring the decay of 226Ra (half-life of 1600 years) in hydrothermal barite to provide a history of hydrothermal venting at the site over the past 6000 years. This dating method is effective for samples ranging in age from ∼200 to 20,000 years old and effectively bridges an age gap between shorter- and longer-lived U-series dating techniques for hydrothermal deposits. Results show that hydrothermal venting at the active High Rise, Sasquatch, and Main Endeavour fields began at least 850, 1450, and 2300 years ago, respectively. Barite ages of other inactive deposits on the axial valley floor are between ∼1200 and ∼2200 years old, indicating past widespread hydrothermal venting outside of the currently active vent fields. Samples from the half-graben on the eastern slope of the axial valley range in age from ∼1700 to ∼2925 years, and a single sample from outside the axial valley, near the westernmost valley fault scarp is ∼5850 ± 205 years old. The spatial relationship between hydrothermal venting and normal faulting suggests a temporal relationship, with progressive younging of sulfide deposits from the edges of the axial valley toward the center of the rift. These relationships are consistent with the inward migration of normal faulting toward the center of the valley over time and a minimum age of onset of hydrothermal activity in this region of 5850 years

Influence of mild-moderate hypocapnia on intracranial pressure slow waves activity in TBI

Funder: University of CambridgeAbstract: Background: In traumatic brain injury (TBI) the patterns of intracranial pressure (ICP) waveforms may reflect pathological processes that ultimately lead to unfavorable outcome. In particular, ICP slow waves (sw) (0.005–0.05 Hz) magnitude and complexity have been shown to have positive association with favorable outcome. Mild-moderate hypocapnia is currently used for short periods to treat critical elevations in ICP. Our goals were to assess changes in the ICP sw activity occurring following sudden onset of mild-moderate hypocapnia and to examine the relationship between changes in ICP sw activity and other physiological variables during the hypocapnic challenge. Methods: ICP, arterial blood pressure (ABP), and bilateral middle cerebral artery blood flow velocity (FV), were prospectively collected in 29 adult severe TBI patients requiring ICP monitoring and mechanical ventilation in whom a minute volume ventilation increase (15–20% increase in respiratory minute volume) was performed as part of a clinical CO2-reactivity test. The time series were first treated using FFT filter (pass-band set to 0.005–0.05 Hz). Power spectral density analysis was performed. We calculated the following: mean value, standard deviation, variance and coefficient of variation in the time domain; total power and frequency centroid in the frequency domain; cerebrospinal compliance (Ci) and compensatory reserve index (RAP). Results: Hypocapnia led to a decrease in power and increase in frequency centroid and entropy of slow waves in ICP and FV (not ABP). In a multiple linear regression model, RAP at the baseline was the strongest predictor for the decrease in the power of ICP slow waves (p < 0.001). Conclusion: In severe TBI patients, a sudden mild-moderate hypocapnia induces a decrease in mean ICP and FV, but also in slow waves power of both signals. At the same time, it increases their higher frequency content and their morphological complexity. The difference in power of the ICP slow waves between the baseline and the hypocapnia period depends on the baseline cerebrospinal compensatory reserve as measured by RAP

Zebrafish ProVEGF-C Expression, Proteolytic Processing and Inhibitory Effect of Unprocessed ProVEGF-C during Fin Regeneration

BACKGROUND: In zebrafish, vascular endothelial growth factor-C precursor (proVEGF-C) processing occurs within the dibasic motif HSIIRR(214) suggesting the involvement of one or more basic amino acid-specific proprotein convertases (PCs) in this process. In the present study, we examined zebrafish proVEGF-C expression and processing and the effect of unprocessed proVEGF-C on caudal fin regeneration. METHODOLOGY/PRINCIPAL FINDINGS: Cell transfection assays revealed that the cleavage of proVEGF-C, mainly mediated by the proprotein convertases Furin and PC5 and to a less degree by PACE4 and PC7, is abolished by PCs inhibitors or by mutation of its cleavage site (HSIIRR(214) into HSIISS(214)). In vitro, unprocessed proVEGF-C failed to activate its signaling proteins Akt and ERK and to induce cell proliferation. In vivo, following caudal fin amputation, the induction of VEGF-C, Furin and PC5 expression occurs as early as 2 days post-amputation (dpa) with a maximum levels at 4-7 dpa. Using immunofluorescence staining we localized high expression of VEGF-C and the convertases Furin and PC5 surrounding the apical growth zone of the regenerating fin. While expression of wild-type proVEGF-C in this area had no effect, unprocessed proVEGF-C inhibited fin regeneration. CONCLUSIONS/SIGNIFICANCES: Taken together, these data indicate that zebrafish fin regeneration is associated with up-regulation of VEGF-C and the convertases Furin and PC5 and highlight the inhibitory effect of unprocessed proVEGF-C on fin regeneration

Bottom pressure signals at the TAG deep-sea hydrothermal field : evidence for short-period, flow-induced ground deformation

Author Posting. © American Geophysical Union, 2009. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 36 (2009): L19301, doi:10.1029/2009GL040006.Bottom pressure measurements acquired from the TAG hydrothermal field on the Mid-Atlantic Ridge (26°N) contain clusters of narrowband spectral peaks centered at periods from 22 to 53.2 minutes. The strongest signal at 53.2 min corresponds to 13 mm of water depth variation. Smaller, but statistically significant, signals were also observed at periods of 22, 26.5, 33.4, and 37.7 min (1–4 mm amplitude). These kinds of signals have not previously been observed in the ocean, and they appear to represent vertical motion of the seafloor in response to hydrothermal flow - similar in many ways to periodic terrestrial geysers. We demonstrate that displacements of 13 mm can be produced by relatively small flow-induced pressures (several kPa) if the source region is less than ∼100 m below the seafloor. We suggest that the periodic nature of the signals results from a non-linear relationship between fluid pore pressure and crustal permeability

Stochastic analysis of exit fluid temperature records from the active TAG hydrothermal mound (Mid-Atlantic Ridge, 26°N) : 1. Modes of variability and implications for subsurface flow

Author Posting. © American Geophysical Union, 2007. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 112 (2007): B07101, doi:10.1029/2006JB004435.Yearlong time series records of exit fluid temperature from the active TAG hydrothermal mound (Mid-Atlantic Ridge, 26°N) reveal a complex space-time pattern of flow variability within the mineral deposit. Exit fluid temperatures were measured every 8–10 min from 17 sites distributed across the upper terrace of the mound from June 2003 to June 2004. High-temperature records were obtained using Deep Sea Power and Light SeaLogger® probes deployed in fractures discharging ∼360°C black smoker fluids, and low-temperature records were obtained using VEMCO Ltd. Minilog probes deployed in cracks discharging ∼20°C diffuse flow fluids. The temperature records are considerably more variable than those acquired from vent fields on the fast spreading East Pacific Rise and exhibit a complex mix of both episodic and periodic variability. The diffuse flow records alternate between periods of discharge and periods of what I infer to be recharge when fluid temperatures are equal to background water column levels (∼2.7°C) as ambient seawater is drawn into the seafloor. The space-time patterns of these episodic variations suggest that they represent reorganizations of the secondary circulation system driving diffuse discharge on the upper terrace of the mound on timescales from a few hours to a few days, most likely in response to permeability perturbations. Harmonic temperature oscillations were observed over a range of periods, with the principal lunar semidiurnal tidal period (M2) being most dominant. During certain times, exit fluid temperatures at diffuse sites pulse at diurnal and semidiurnal tidal periods when they are hovering near background water column levels, which I interpret as flow reversals associated with the vertical displacement of a fluid boundary layer at the seafloor interface when the local net flux is near zero. The pulsing behavior is predicted by poroelastic models of tidal loading but is not consistent with effects from tidal currents, which demonstrates that poroelastic effects from tidal loading modulate shallow subsurface flow at the active TAG mound.This work was supported by the National Science Foundation (OCE-0137329)

Self-reported data: a major tool to assess compliance with anti-malarial combination therapy among children in Senegal

Background: Although there are many methods available for measuring compliance, there is no formal gold standard. Different techniques used to measure compliance were compared among children treated by the anti-malarial amodiaquine/sulphadoxine-pyrimethamine (AQ/SP) combination therapy, in use in Senegal between 2004 and 2006. Methods: The study was carried out in 2004, in five health centres located in the Thies region (Senegal). Children who had AQ/SP prescribed for three and one day respectively at the health centre were recruited. The day following the theoretical last intake of AQ, venous blood, and urine samples were collected for anti-malarial drugs dosage. Caregivers and children above five years were interviewed concerning children's drug intake. Results: Among the children, 64.7% adhered to 80% of the prescribed dose and only 37.7% were strict full adherent to the prescription. There was 72.7% agreement between self-reported data and blood drug dosage for amodiaquine treatment. Concerning SP, results found that blood dosages were 91.4% concordant with urine tests and 90% with self-reported data based on questionnaires. Conclusion: Self-reported data could provide useful quantitative information on drug intake and administration. Under strict methodological conditions this method, easy to implement, can be used to describe patients' behaviors and their use of new anti-malarial treatment. Self-reported data is a major tool for assessing compliance in resource poor countries. Blood and urine drug dosages provide qualitative results that confirm any drug intake. Urine assays for SP could be useful to obtain public health data, for example on chemoprophylaxis among pregnant women

Crustal structure of the Trans-Atlantic Geotraverse (TAG) segment (Mid-Atlantic Ridge, 26°10′N) : implications for the nature of hydrothermal circulation and detachment faulting at slow spreading ridges

Author Posting. © American Geophysical Union, 2007. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 8 (2007): Q08004, doi:10.1029/2007GC001629.New seismic refraction data reveal that hydrothermal circulation at the Trans-Atlantic Geotraverse (TAG) hydrothermal field on the Mid-Atlantic Ridge at 26°10′N is not driven by energy extracted from shallow or mid-crustal magmatic intrusions. Our results show that the TAG hydrothermal field is underlain by rocks with high seismic velocities typical of lower crustal gabbros and partially serpentinized peridotites at depth as shallow as 1 km, and we find no evidence for low seismic velocities associated with mid-crustal magma chambers. Our tomographic images support the hypothesis of Tivey et al. (2003) that the TAG field is located on the hanging wall of a detachment fault, and constrain the complex, dome-shaped subsurface geometry of the fault system. Modeling of our seismic velocity profiles indicates that the porosity of the detachment footwall increases after rotation during exhumation, which may enhance footwall cooling. However, heat extracted from the footwall is insufficient for sustaining long-term, high-temperature, hydrothermal circulation at TAG. These constraints indicate that the primary heat source for the TAG hydrothermal system must be a deep magma reservoir at or below the base of the crust.This research was supported by NSF grant OCE-0137329

IgG responses to the gSG6-P1 salivary peptide for evaluating human exposure to Anopheles bites in urban areas of Dakar region, Sénégal

<p>Abstract</p> <p>Background</p> <p>Urban malaria can be a serious public health problem in Africa. Human-landing catches of mosquitoes, a standard entomological method to assess human exposure to malaria vector bites, can lack sensitivity in areas where exposure is low. A simple and highly sensitive tool could be a complementary indicator for evaluating malaria exposure in such epidemiological contexts. The human antibody response to the specific <it>Anopheles </it>gSG6-P1 salivary peptide have been described as an adequate tool biomarker for a reliable assessment of human exposure level to <it>Anopheles </it>bites. The aim of this study was to use this biomarker to evaluate the human exposure to <it>Anopheles </it>mosquito bites in urban settings of Dakar (Senegal), one of the largest cities in West Africa, where <it>Anopheles </it>biting rates and malaria transmission are supposed to be low.</p> <p>Methods</p> <p>One cross-sectional study concerning 1,010 (505 households) children (n = 505) and adults (n = 505) living in 16 districts of downtown Dakar and its suburbs was performed from October to December 2008. The IgG responses to gSG6-P1 peptide have been assessed and compared to entomological data obtained in or near the same district.</p> <p>Results</p> <p>Considerable individual variations in anti-gSG6-P1 IgG levels were observed between and within districts. In spite of this individual heterogeneity, the median level of specific IgG and the percentage of immune responders differed significantly between districts. A positive and significant association was observed between the exposure levels to <it>Anopheles gambiae </it>bites, estimated by classical entomological methods, and the median IgG levels or the percentage of immune responders measuring the contact between human populations and <it>Anopheles </it>mosquitoes. Interestingly, immunological parameters seemed to better discriminate the exposure level to <it>Anopheles </it>bites between different exposure groups of districts.</p> <p>Conclusions</p> <p>Specific human IgG responses to gSG6-P1 peptide biomarker represent, at the population and individual levels, a credible new alternative tool to assess accurately the heterogeneity of exposure level to <it>Anopheles </it>bites and malaria risk in low urban transmission areas. The development of such biomarker tool would be particularly relevant for mapping and monitoring malaria risk and for measuring the efficiency of vector control strategies in these specific settings.</p