Assessing forest availability for wood supply in Europe.

The quantification of forests available for wood supply (FAWS) is essential for decision-making with regard to the maintenance and enhancement of forest resources and their contribution to the global carbon cycle. The provision of harmonized forest statistics is necessary for the development of forest associated policies and to support decision-making. Based on the National Forest Inventory (NFI) data from 13 European countries, we quantify and compare the areas and aboveground dry biomass (AGB) of FAWS and forest not available for wood supply (FNAWS) according to national and reference definitions by determining the restrictions and associated thresholds considered at country level to classify forests as FAWS or FNAWS. FAWS represent between 75 and 95 % of forest area and AGB for most of the countries in this study. Economic restrictions are the main factor limiting the availability of forests for wood supply, accounting for 67 % of the total FNAWS area and 56 % of the total FNAWS AGB, followed by environmental restrictions. Profitability, slope and accessibility as economic restrictions, and protected areas as environmental restrictions are the factors most frequently considered to distinguish between FAWS and FNAWS. With respect to the area of FNAWS associated with each type of restriction, an overlap among the restrictions of 13.7 % was identified. For most countries, the differences in the FNAWS areas and AGB estimates between national and reference definitions ranged from 0 to 5 %. These results highlight the applicability and reliability of a FAWS reference definition for most of the European countries studied, thereby facilitating a consistent approach to assess forests available for supply for the purpose of international reporting.

SPR biosensor for quantification of fetuin-A as a promising multibiomarker.

Early diagnosis of ongoing malignant disease is crucial to improve survival rate and life quality of the patients and requires sensitive detection of specific biomarkers e.g. prostate-specific antigen (PSA), carcinoembryonic antigen (CEA), alpha-fetoprotein (AFP), etc. In spite of current technological advances, malignant diseases are still identified in rather late stages, which have detrimental effect on the prognosis and treatment of the disease. Here, we present a biosensor able to detect fetuin-A, a potential multibiomarker. The biosensing platform is based on polymer brush combining antifouling monomer units of N-(2-hydroxypropyl)methacrylamide (HPMA) and carboxybetaine methacrylamide (CBMAA), statistically copolymerized by surfaceinitiated atom transfer radical polymerization. The copolymer poly(HPMA-co-CBMAA) exhibits excellent non-fouling properties in the most relevant biological media (i.e. blood plasma) as well as antithrombogenic surface properties by preventing the adhesion of blood components (i.e. leukocytes; platelets; and erythrocytes). Moreover, the polymer brush can be easily functionalized with biorecognition elements maintaining high resistance to blood fouling and the binding capacity can be regulated by tuning the ratio between CBMAA and HPMA units. The superior antifouling properties of the copolymer even after biofunctionalization were exploited to fabricate a new plasmonic biosensor for the analysis of fetuin-A in real clinical blood plasma samples. The assay used in this work can be explored as labelfree affinity biosensor for diagnostics of different biomarkers in real clinical plasma samples and to shift the early biomarker detection toward novel biosensor technologies allowing point of care analysis.

Protein interactions with quaternized chitosan/heparin multilayers.

Understanding the behavior of single proteins at the polyelectrolyte multilayer film/solution interface is of prime importance for the designing of bio-functionalized surface coatings. In the present paper, we study the adsorption of the model proteins, albumin and lysozyme, as well as basic fibroblast growth factor (FGF-2) on a polysaccharide multilayer film composed of quaternized chitosan and heparin. Several analytical methods were used to describe the formation of the polysaccharide film and its interactions with the proteins. Both albumin and lysozyme adsorbed on quaternized chitosan/heparin films, however this process strongly depended on the terminating polysaccharide. Protein adsorption was driven mainly by electrostatic interactions between protein and the terminal layer of the film. The effective binding of FGF-2 by the heparin-terminated film suggested that other interactions could also contribute to the adsorption process. We believe that this FGF-2-presenting polysaccharide film may serve as a biofunctional surface coating for biologically-related applications.

Fibrin nanostructures for biomedical applications.

Fibrin is a versatile biopolymer that has been extensively used in tissue engineering. In this paper fibrin nanostructures prepared using a technique based on the catalytic effect of fibrin-bound thrombin are presented. This technique enables surface-attached thin fibrin networks to form with precisely regulated morphology without the development of fibrin gel in bulk solution. Moreover, the influence of changing the polymerization time, along with the antithrombin III and heparin concentrations on the morphology of fibrin nanostructures was explored. The binding of bioactive molecules (fibronectin, laminin, collagen, VEGF, bFGF, and heparin) to fibrin nanostructures was confirmed. These nanostructures can be used for the surface modification of artificial biomaterials designed for different biomedical applications (e.g. artificial vessels, stents, heart valves, bone and cartilage constructs, skin grafts, etc.) in order to promote the therapeutic outcome.

Molecular Composition and Volatility of Organic Aerosol in the Southeastern U.S.: Implications for IEPOX Derived SOA.

We present measurements as part of the Southern Oxidant and Aerosol Study (SOAS) during which atmospheric aerosol particles were comprehensively characterized. We present results utilizing a Filter Inlet for Gases and AEROsol coupled to a chemical ionization mass spectrometer (CIMS). We focus on the volatility and composition of isoprene derived organic aerosol tracers and of the bulk organic aerosol. By utilizing the online volatility and molecular composition information provided by the FIGAERO-CIMS, we show that the vast majority of commonly reported molecular tracers of isoprene epoxydiol (IEPOX) derived secondary organic aerosol (SOA) is derived from thermal decomposition of accretion products or other low volatility organics having effective saturation vapor concentrations <10(-3) µg m(-3). In addition, while accounting for up to 30% of total submicrometer organic aerosol mass, the IEPOX-derived SOA has a higher volatility than the remaining bulk. That IEPOX-SOA, and more generally bulk organic aerosol in the Southeastern U.S. is comprised of effectively nonvolatile material has important implications for modeling SOA derived from isoprene, and for mechanistic interpretations of molecular tracer measurements. Our results show that partitioning theory performs well for 2-methyltetrols, once accretion product decomposition is taken into account. No significant partitioning delays due to aerosol phase or viscosity are observed, and no partitioning to particle-phase water or other unexplained mechanisms are needed to explain our results.

Conformational flexibility of the agonist binding jaw of the human P2X3 receptor is a prerequisite for channel opening.

BACKGROUND AND PURPOSE: It is assumed that ATP induces closure of the binding jaw of ligand-gated P2X receptors, which eventually results in the opening of the membrane channel and the flux of cations. Immobilization by cysteine mutagenesis of the binding jaw inhibited ATP-induced current responses, but did not allow discrimination between disturbances of binding, gating, subunit assembly or trafficking to the plasma membrane. EXPERIMENTAL APPROACH: A molecular model of the pain-relevant human (h)P2X3 receptor was used to identify amino acid pairs, which were located at the lips of the binding jaw and did not participate in agonist binding but strongly approached each other even in the absence of ATP. KEY RESULTS: A series of cysteine double mutant hP2X3 receptors, expressed in HEK293 cells or Xenopus laevis oocytes, exhibited depressed current responses to α,ß-methylene ATP (α,ß-meATP) due to the formation of spontaneous inter-subunit disulfide bonds. Reducing these bonds with dithiothreitol reversed the blockade of the α,ß-meATP transmembrane current. Amino-reactive fluorescence labelling of the His-tagged hP2X3 receptor and its mutants expressed in HEK293 or X. laevis oocytes demonstrated the formation of inter-subunit cross links in cysteine double mutants and, in addition, confirmed their correct trimeric assembly and cell surface expression. CONCLUSIONS AND IMPLICATIONS: In conclusion, spontaneous tightening of the binding jaw of the hP2X3 receptor by inter-subunit cross-linking of cysteine residues substituted at positions not directly involved in agonist binding inhibited agonist-evoked currents without interfering with binding, subunit assembly or trafficking.

Attachment of human endothelial cells to polyester vascular grafts: pre-coating with adhesive protein assemblies and resistance to short-term shear stress.

Cardiovascular prosthetic bypass grafts do not endothelialize spontaneously in humans, and so they pose a thrombotic risk. Seeding with cells improves their performance, particularly in small-caliber applications. Knitted tubular polyethylene-terephthalate (PET) vascular prostheses (6 mm) with commercial type I collagen (PET/Co) were modified in the lumen by the adsorption of laminin (LM), by coating with a fibrin network (Fb) or a combination of Fb and fibronectin (Fb/FN). Primary human saphenous vein endothelial cells were seeded (1.50 × 10(5)/cm2), cultured for 72 h and exposed to laminar shear stress 15 dyn/cm(2) for 40 and 120 min. The control static grafts were excluded from shearing. The cell adherence after 4 h on PET/Co, PET/Co +LM, PET/Co +Fb and PET/Co +Fb/FN was 22%, 30%, 19% and 27% of seeding, respectively. Compared to the static grafts, the cell density on PET/Co and PET/Co +LM dropped to 61% and 50%, respectively, after 120 min of flow. The cells on PET/Co +Fb and PET/Co +Fb/FN did not show any detachment during 2 h of shear stress. Pre-coating the clinically-used PET/Co vascular prosthesis with LM or Fb/FN adhesive protein assemblies promotes the adherence of endothelium. Cell retention under flow is improved particularly on fibrin-containing (Fb and Fb/FN) surfaces.

Accessory subunits alter the temperature sensitivity of Kv4.3 channel complexes.

In human atrial myocytes the transient outward current I(to) develops a conspicuous faster inactivation with increasing temperatures. Since ß-subunits are known to modulate I(to) current kinetics, we hypothesized that the temperature sensitivity of I(to) is not only determined by the property of the ion-passing α-subunit Kv4.3 but also by its interaction with accessory ß-subunits. We therefore studied the influence of the transmembrane ß-subunits KCNE1, KCNE2 and DPP6 on Kv4.3/KChIP2 channels in CHO cells at room temperature and at physiological temperature. Exposure to 37°C caused a significant acceleration of the channel kinetics, whereas current densities and voltage dependences remained unaltered at 37°C compared to 23°C. However, Kv4.3/KChIP2 channels without transmembrane ß-subunits showed the strongest temperature sensitivity with considerably increased rates of activation and inactivation at 37°C. KCNE2 significantly slowed the current kinetics at 37°C compared to Kv4.3/KChIP2 channels, whereas KCNE1 did not influence the channel properties at both temperatures. Interestingly, the accelerating effects of DPP6 on current kinetics described at 23°C were diminished at physiological temperature, thus at 37°C current kinetics became remarkably similar for channel complexes Kv4.3/KChIP2 with and without DPP6 isoforms. A Markov state model was developed on the basis of experimental measurements to simulate the influence of ß-subunits on Kv4.3 channel complex at both temperatures. In conclusion, the remarkably fast kinetics of the native I(to) at 37°C could be reproduced by co-expressing Kv4.3, KChIP2, KCNE2 and DPP6 in CHO cells, whereas the high temperature sensitivity of human I(to) could be not mimicked.

Respiratory symptoms in preterm infants: burden of disease in the first year of life.

OBJECTIVE: While respiratory symptoms in the first year of life are relatively well described for term infants, data for preterm infants are scarce. We aimed to describe the burden of respiratory disease in a group of preterm infants with and without bronchopulmonary dysplasia (BPD) and to assess the association of respiratory symptoms with perinatal, genetic and environmental risk factors. METHODS: Single centre birth cohort study: prospective recording of perinatal risk factors and retrospective assessment of respiratory symptoms during the first year of life by standardised questionnaires. MAIN OUTCOME MEASURES: Cough and wheeze (common symptoms), re-hospitalisation and need for inhalation therapy (severe outcomes). PATIENTS: 126 preterms (median gestational age 28.7 weeks; 78 with, 48 without BPD) hospitalised at the University Children's Hospital of Bern, Switzerland 1999-2006. RESULTS: Cough occurred in 80%, wheeze in 44%, re-hospitalisation in 25% and long term inhalation therapy in wheezers in 13% of the preterm infants. Using logistic regression, the main risk factor for common symptoms was frequent contact with other children. Severe outcomes were associated with maximal peak inspiratory pressure, arterial cord blood pH, APGAR- and CRIB-Score. CONCLUSIONS: Cough in preterm infants is as common as in term infants, whereas wheeze, inhalation therapy and re-hospitalisations occur more often. Severe outcomes are associated with perinatal risk factors. Preterm infants who did not qualify for BPD according to latest guidelines also showed a significant burden of respiratory disease in the first year of life.

Normative data for lung function and exhaled nitric oxide in unsedated healthy infants.

Despite association with lung growth and long-term respiratory morbidity, there is a lack of normative lung function data for unsedated infants conforming to latest European Respiratory Society/American Thoracic Society standards. Lung function was measured using an ultrasonic flow meter in 342 unsedated, healthy, term-born infants at a mean ± sd age of 5.1 ± 0.8 weeks during natural sleep according to the latest standards. Tidal breathing flow-volume loops (TBFVL) and exhaled nitric oxide (eNO) measurements were obtained from 100 regular breaths. We aimed for three acceptable measurements for multiple-breath washout and 5-10 acceptable interruption resistance (R(int)) measurements. Acceptable measurements were obtained in ≤ 285 infants with high variability. Mean values were 7.48 mL·kg⁻¹ (95% limits of agreement 4.95-10.0 mL·kg⁻¹) for tidal volume, 14.3 ppb (2.6-26.1 ppb) for eNO, 23.9 mL·kg⁻¹ (16.0-31.8 mL·kg⁻¹) for functional residual capacity, 6.75 (5.63-7.87) for lung clearance index and 3.78 kPa·s·L⁻¹ (1.14-6.42 kPa·s·L⁻¹) for R(int). In males, TBFVL outcomes were associated with anthropometric parameters and in females, with maternal smoking during pregnancy, maternal asthma and Caesarean section. This large normative data set in unsedated infants offers reference values for future research and particularly for studies where sedation may put infants at risk. Furthermore, it highlights the impact of maternal and environmental risk factors on neonatal lung function.

The interaction of osteoblasts with bone-implant materials: 1. The effect of physicochemical surface properties of implant materials.

This comparative study of various surface treatments of commercially available implant materials is intended as guidance for orientation among particular surface treatment methods in term of the cell reaction of normal human osteoblasts and blood coagulation. The influence of physicochemical surface parameters such as roughness, surface free energy and wettability on the response of human osteoblasts in the immediate vicinity of implants and on the blood coagulation was studied. The osteoblast proliferation was monitored and the expression of tissue mediators (TNF-alpha, IL-8, MMP-1, bone alkaline phosphatase, VCAM-1, TGF-beta) was evaluated after the cell cultivation onto a wide range of commercially available materials (titanium and Ti6Al4V alloy with various surface treatments, CrCoMo alloy, zirconium oxide ceramics, polyethylene and carbon/carbon composite). The formation of a blood clot was investigated on the samples immersed in a freshly drawn whole rabbit blood using scanning electron microscope. The surfaces with an increased osteoblast proliferation exhibited particularly higher surface roughness (here R(a) 3.5 microm) followed by a high polar part of the surface free energy whereas the effect of wettability played a minor role. The surface roughness was also the main factor regulating the blood coagulation. The blood clot formation analysis showed a rapid coagulum formation on the rough titanium-based surfaces. The titanium with an etching treatment was considered as the most suitable candidate for healing into the bone tissue due to high osteoblast proliferation, the highest production of osteogenesis markers and low production of inflammatory cytokines and due to the most intensive blood clot formation.

Electrophysiological classification of P2X7 receptors in rat cultured neocortical astroglia.

BACKGROUND AND PURPOSE: P2X7 receptors are ATP-gated cation channels mediating important functions in microglial cells, such as the release of cytokines and phagocytosis. Electrophysiological evidence that these receptors also occur in CNS astroglia is rare and rather incomplete. EXPERIMENTAL APPROACH: We used whole-cell patch-clamp recordings to search for P2X7 receptors in astroglial-neuronal co-cultures prepared from the cerebral cortex of rats. KEY RESULTS: All the astroglial cells investigated responded to ATP with membrane currents, reversing around 0 mV. These currents could be also detected in isolated outside-out patch vesicles. The results of the experiments with the P2X [alpha,beta-methylene ATP and 2'-3'-O-(4-benzoyl) ATP] and P2Y receptor agonists [adenosine 5'-O-(2-thiodiphosphate), uridine 5'-diphosphate, uridine 5'-triphosphate (UTP) and UDP-glucose] suggested the involvement of P2X receptors in this response. The potentiation of ATP responses in a low divalent cation or alkaline bath, but not by ivermectin, made it likely that a P2X7 receptor is operational. Blockade of the ATP effect by the P2X7 antagonists Brilliant Blue G, calmidazolium and oxidized ATP corroborated this assumption. CONCLUSIONS AND IMPLICATIONS: Rat cultured cortical astroglia possesses functional P2X7 receptors. It is suggested that astrocytic P2X7 receptors respond to high local ATP concentrations during neuronal injury.

Limited effects of selenium substitution in the prevention of radiation-associated toxicities. results of a randomized study in head and neck cancer patients.

OBJECTIVE: The substitution of selenium activates the selenium-dependent enzyme glutathione peroxidase, which is important for scavenging free radicals. To date, only limited data are available about the clinical impact of selenium regarding the toxicities due to free radical producing therapies, e.g. irradiation or chemotherapy, and therefore the objective of this study was to investigate the clinical impact of selenium in such therapies. PATIENTS AND METHODS: 39 patients (8 female, 31 male) with advanced head and neck cancer were included in a randomised phase II study. The mean age was 63.52+/-9.31 years. Tumour localizations: oral cavity 15 patients, oropharynx 19 patients, hypopharynx 5 patients, carcinoma of unknown primary 1 patient. Group A (n=22) received 500 microg sodium selenite on the days of radiotherapy and 300 microg sodium selenite on days without radiotherapy. Group B (17) was irradiated without any selenium substitution. Both groups were well balanced according to age, gender, localization and stage of the tumour. The RTOG grade of radiation-associated toxicities was evaluated once per week. RESULTS: The following serious toxicities were observed (group A vs. group B): dysphagia 22.7% vs. 35.3%, loss of taste 22.7% vs. 47.1%, dry mouth 22.7% vs. 23.5%, and stomatitis 36.4% vs. 23.5%. A statistical trend (Fisher's exact test) was only seen for the loss of taste (p=0.172). The weekly patient analysis (Student's t-test) showed a significant reduction of dysphagia in the selenium group (Group 1) at the last week of irradiation. CONCLUSION: This small randomised trial showed limited effects of selenium in the prevention of ageusia (loss of taste) and dysphagia due to radiotherapy of head and neck cancer.

Interaction of blood plasma with antifouling surfaces.

Nonspecific adsorption of proteins is a crucial problem in the detection of analytes in complex biological media by affinity sensors operating with label-free detection. We modified the gold surface of surface plasmon resonance (SPR) sensors with three types of promising antifouling coatings: self-assembled monolayers (SAM)s of alkanethiolates terminated with diethylene glycol and carboxylic groups, poly(ethylene glycol) (PEG) grafted onto the SAMs, and zwitterionic polymer brushes of poly(carboxybetaine methacrylate), poly(sulfobetaine methacrylate), and poly(phosphorylcholine methacrylate). Using SPR, we compared the efficacy of the coatings to reduce nonspecific adsorption from human blood plasma and from single-protein solutions of human serum albumin, immunoglobulin G, fibrinogen, and lysozyme. There was no direct relationship between values of water contact angles and plasma deposition on the coated surfaces. A rather high plasma deposition on SAMs was decreased by grafting PEG chains. Fouling on PEG was observed only from plasma fractions containing proteins with molecular mass higher than 350 000 Da. The adsorption kinetics from plasma collected from different healthy donors differed. Poly(carboxybetaine methacrylate) completely prevented the deposition from plasma, but the other more hydrophilic zwitterionic polymers prevented single-protein adsorption but did not prevent plasma deposition. The results suggest that neither wettability nor adsorption of the main plasma proteins was the main indicator of deposition from blood plasma.

Hemodialysis access surgery--is there an increased risk of acquiring hepatitis C virus compared to other elective vascular interventions?

BACKGROUND: To evaluate whether dedicated access surgeons might have a significantly higher risk of acquiring hepatitis C infection compared to other vascular surgeons by assessing the prevalence of hepatitis C patients who are on chronic hemodialysis and to compare the frequency to patients undergoing elective vascular interventions. PATIENTS AND METHODS: A retrospective chart and data analysis of all patients on chronic hemodialysis was conducted. As a comparative group, the prevalence of anti-HCV antibodies and positive HCV RNA PCR among patients admitted for elective vascular surgery was assessed. RESULTS: Of 285 patients on chronic hemodialysis, 202 (71%) were had both tests (antibody test for HCV and specific HCV RNA PCR testing). 5% (n = 11; CI 95 = 3-10%) were antibody positive, and 4% (n = 8; CI 95 = 2-8%) were also PCR positive and therefore infectious. One patient was acutely infected. Of 4963 vascular surgical patients, 1141 (23%) had an anti-HCV antibody ELISA test and specific HCV RNA PCR testing. 0.4% (n = 4; CI 95 = 0.1-1%) were antibody positive and 0.2% (n = 2; CI 95 = 0.03-0.7%) were also PCR positive and hence infectious. No acutely infected patient was detected in this population. The chance of operating on a HCV positive and infectious patient among hemodialysis patients was almost 27 times higher than among elective vascular surgical patients (P < 0.0001; OR = 26.56; CI 95 = 5.42-253.40). CONCLUSIONS: Dedicated hemodialysis access surgeons have a higher risk to acquire hepatitis C infection compared to vascular surgeons performing all other elective vascular surgical interventions. To identify early infected surgeons operating on high risk HCV patient collectives and to start rapid treatment, PCR testing at regular intervals would be advisable.

Comparison of the Bayer VERSANT HCV RNA 3.0 and the Roche COBAS Amplicor HCV Monitor, Version 2.0, assays in HCV genotype 4 infection.

Prediction of treatment response is clinically important in chronic hepatitis C virus (HCV) genotype 4 infection. Early viral kinetics is useful in this respect for genotype 1 but interpretation is dependent on assay linearity and reproducibility. The VERSANT HCV RNA 3.0 (bDNA-3.0) and the COBAS Amplicor HCV Monitor 2.0 (HCM-2.0) have been widely used quantitative assays. We wanted to comparatively evaluate the two tests in a large genotype 4 sample. Genotyping was performed by NS5b sequencing. Viral load was tested in parallel in 32 patients at least six times on antiviral therapy with interferon alpha (IFNalpha). Totally, 198 samples within a quantitative range from undetectable to about 7 x 10(6) IU/mL (bDNA-3.0) were obtained and compared. Twenty-two samples with viral load above 500 000 IU/mL tested by HCM-2.0 were 1:100 diluted and retested. Quantitative values were fitted to a third order polynomial (M = 0.118303 + 1.07503 x V+ 0.0112128 x V(2) - 0.0055504 x V(3); M...HCM-2.0, V...bDNA-3.0, both log IU/mL) showing progressive nonlinearity of HCM-2.0 above 100 000 IU/mL but better clinical sensitivity with respect to bDNA-3.0. Dilution lead to a gain of at least a factor of 2.7 and thus, overestimation compared with bDNA-3.0. Deviation from linearity and overestimation upon dilution by HCM-2.0 are similar with HCV genotype 4, compared with other HCV genotypes. Differences in test performance were not detected for subtypes but for individual patients possibly related to specific quasi-species patterns. The interpretation of viral kinetic data becomes difficult due to overestimation upon dilution of baseline values by HCM-2.0.

Optimized temperature and deadspace correction improve analysis of multiple breath washout measurements by ultrasonic flowmeter in infants.

BACKGROUND: Assessment of lung volume (FRC) and ventilation inhomogeneities with ultrasonic flowmeter and multiple breath washout (MBW) has been used to provide important information about lung disease in infants. Sub-optimal adjustment of the mainstream molar mass (MM) signal for temperature and external deadspace may lead to analysis errors in infants with critically small tidal volume changes during breathing. METHODS: We measured expiratory temperature in human infants at 5 weeks of age and examined the influence of temperature and deadspace changes on FRC results with computer simulation modeling. A new analysis method with optimized temperature and deadspace settings was then derived, tested for robustness to analysis errors and compared with the previously used analysis methods. RESULTS: Temperature in the facemask was higher and variations of deadspace volumes larger than previously assumed. Both showed considerable impact upon FRC and LCI results with high variability when obtained with the previously used analysis model. Using the measured temperature we optimized model parameters and tested a newly derived analysis method, which was found to be more robust to variations in deadspace. Comparison between both analysis methods showed systematic differences and a wide scatter. CONCLUSION: Corrected deadspace and more realistic temperature assumptions improved the stability of the analysis of MM measurements obtained by ultrasonic flowmeter in infants. This new analysis method using the only currently available commercial ultrasonic flowmeter in infants may help to improve stability of the analysis and further facilitate assessment of lung volume and ventilation inhomogeneities in infants.

Deadspace estimation from CO2 versus molar mass measurements in infants.

BACKGROUND: Estimation of respiratory deadspace is often based on the CO2 expirogram, however presence of the CO2 sensor increases equipment deadspace, which in turn influences breathing pattern and calculation of lung volume. In addition, it is necessary to correct for the delay between the sensor and flow signals. We propose a new method for estimation of effective deadspace using the molar mass (MM) signal from an ultrasonic flowmeter device, which does not require delay correction. We hypothesize that this estimation is correlated with that calculated from the CO2 signal using the Fowler method. METHODS: Breath-by-breath CO2, MM and flow measurements were made in a group of 77 term-born healthy infants. Fowler deadspace (Vd,Fowler) was calculated after correcting for the flow-dependent delay in the CO2 signal. Deadspace estimated from the MM signal (Vd,MM) was defined as the volume passing through the flowhead between start of expiration and the 10% rise point in MM. RESULTS: Correlation (r = 0.456, P < 0.0001) was found between Vd,MM and Vd,Fowler averaged over all measurements, with a mean difference of -1.4% (95% CI -4.1 to 1.3%). Vd,MM ranged from 6.6 to 11.4 ml between subjects, while Vd,Fowler ranged from 5.9 to 12.0 ml. Mean intra-measurement CV over 5-10 breaths was 7.8 +/- 5.6% for Vd,MM and 7.8 +/- 3.7% for Vd,Fowler. Mean intra-subject CV was 6.0 +/- 4.5% for Vd,MM and 8.3 +/- 5.9% for Vd,Fowler. Correcting for the CO2 signal delay resulted in a 12% difference (P = 0.022) in Vd,Fowler. Vd,MM could be obtained more frequently than Vd,Fowler in infants with CLD, with a high variability. CONCLUSIONS: Use of the MM signal provides a feasible estimate of Fowler deadspace without introducing additional equipment deadspace. The simple calculation without need for delay correction makes individual adjustment for deadspace in FRC measurements possible. This is especially important given the relative large range of deadspace seen in this homogeneous group of infants.

Influence of extracellular monovalent cations on pore and gating properties of P2X7 receptor-operated single-channel currents.

Using the patch-clamp method, we studied the influence of external alkali and organic monovalent cations on the single-channel properties of the adenosine triphosphate (ATP)-activated recombinant human P2X(7) receptor. The slope conductance of the hP2X(7) channel decreased and the reversal potential was shifted to more negative values as the ionic diameter of the organic test cations increased. From the relationship between single-channel conductance and the dimensions of the inward current carrier, the narrowest portion of the pore was estimated to have a mean diameter of approximately 8.5 A. Single-channel kinetics and permeation properties remained unchanged during receptor activation by up to 1 mM ATP(4-) for >1 min, arguing against a molecular correlate of pore dilation at the single P2X(7) channel level. Substitution of extracellular Na(+) by any other alkali or organic cation drastically increased the open probability of the channels by prolonging the mean open time. This effect seems to be mediated allosterically through an extracellular voltage-dependent Na(+) binding site with a K(d) of approximately 5 mM Na(+) at a membrane potential of -120 mV. The modulation of the ATP-induced hP2X(7) receptor gating by extracellular Na(+) could be well described by altering the rate constant from the open to the neighboring closed state in a C-C-C-O kinetic receptor model. We suggest that P2X(7) receptor-induced depolarization and associated K(+)-efflux may reduce Na(+) occupancy of the regulatory Na(+) binding site and thus increase the efficacy of ATP(4-) in a feed-forward manner in P2X(7) receptor-expressing cells.