Echogenic regional anaesthesia needles: a comparison study in Thiel cadavers.

Ultrasound guidance is now the standard procedure for regional nerve block in anesthesiology. However, ultrasonic visualisation of needle manipulation and guidance within tissues remains a problem. Two new echogenic needles (Pajunk and Braun) have been introduced to anesthesiology clinical practice but evaluation has been restricted to preserved animal tissue. In this study, the visibility of both echogenic needles was compared with a standard nonechogenic needle in a Thiel cadaver model. A total of 144 intramuscular injections were made in the upper arm in-plane and out-of-plane to the ultrasound beam at four angles (30°, 45°, 60° and 75°). The visibility of the needle was assessed by two independent, blinded observers using a 5-point Likert ordinal scale. Weighted κ for interobserver agreement was 0.77 (95% confidence interval [CI]: 0.68-0.86). The Pajunk echogenic needle was more visible than the Braun standard needle in-plane (p = 0.04), and the Braun standard and Braun echogenic needles out-of-plane (p = 0.02). Independent predictors of visibility using logistic regression were needle (p < 0.001) and plane of insertion (p = 0.08), receiver operator characteristic (ROC) area under the curve 0.90. In conclusion, the Pajunk echogenic needle offers the best visibility for ultrasound-guided regional anesthesia.

Zeolitic materials with hierarchical porous structures.

During the past several years, different kinds of hierarchical structured zeolitic materials have been synthesized due to their highly attractive properties, such as superior mass/heat transfer characteristics, lower restriction of the diffusion of reactants in the mesopores, and low pressure drop. Our contribution provides general information regarding types and preparation methods of hierarchical zeolitic materials and their relative advantages and disadvantages. Thereafter, recent advances in the preparation and characterization of hierarchical zeolitic structures within the crystallites by post-synthetic treatment methods, such as dealumination or desilication; and structured devices by in situ and ex situ zeolite coatings on open-cellular ceramic foams as (non-reactive as well as reactive) supports are highlighted. Specific advantages of using hierarchical zeolitic catalysts/structures in selected catalytic reactions, such as benzene to phenol (BTOP) and methanol to olefins (MTO) are presented.

Association of BoLA DRB3 and DQA1 alleles with susceptibility to Neospora caninum and reproductive outcome in Quebec Holstein cattle.

The BoLA DRB3 and DQA1 genes are part of the major histocompatibility complex (MHC) class II in cattle. These genes are highly polymorphic and have been associated with resistance to several diseases, such as mastitis, Bovine Leukemia Virus (BLV) and dermatophilis. Sequenced based typing of these genes has been carried out extensively from blood samples; however it is often impractical or expensive to obtain such samples. Repositories of well-characterized serum from cattle are readily available in many veterinary research facilities. This paper reports a retrospective analysis of BoLA class II genotypes of cattle obtained from stored serum samples from Holstein cattle from Québec dairy farms, which were obtained as part of a previous study on bovine neosporosis. It was possible to genotype 56 cattle with known infection status for Neospora caninum. We identified 14 different DRB3 and 10 different DQA1 alleles in this population. The allele frequency distribution was consistent with previously studied cattle populations, and alleles known to be associated with BLV and mastitis were present. No association was found between allele frequency distribution of DRB3 or DQA genes and infection with N. caninum. However, an association of allele DRB3*1001 and allele DRB3*2703 with resistance and susceptibility to pregnancy loss, irrespective of infection status, was identified.

Effect of sternotomy and extracorporeal circulation on pulmonary neutrophil kinetics in pigs.

Pulmonary margination of neutrophils may contribute to lung damage after extracorporeal circulation for cardiac surgery. We evaluated single-pass pulmonary neutrophil kinetics using the multiple indicator-dilution technique in control pigs (n = 10), after sternotomy alone (sterno, n = 10) or after 30 min of observation following a period of 90 min extracorporeal circulation (n = 7). Blood neutrophils increased in the control and sterno groups (p < 0.05) but remained unchanged in the extracorporeal circulation group. The transfer coefficient for neutrophil margination from the circulating to the lung-marginated pool (k(c-m)) and pulmonary neutrophil clearance (Cl(c-m)) were similar between the three groups. There was an inverse correlation between k(c-m) and the degree of lung tissue perfusion evaluated from the tracer-accessible extravascular lung water (r = -0.54, p < 0.01). There was no arterio-venous gradient of neutrophils in any of the groups, suggesting a dynamic equilibrium of the margination/demargination processes. We conclude that extracorporeal circulation does not significantly modify single pass pulmonary neutrophil kinetics 30 min after reperfusion. The rate of neutrophil margination to the tracer-accessible lung tissue suggests that lung tissue de-recruitment is associated with increased neutrophil margination.

Reduction in hepatic endothelin-1 clearance in cirrhosis.

Circulating endothelin-1 (ET-1) levels are increased in cirrhosis. The liver is an important site for circulating ET-1 clearance through the ET(B) receptor. We evaluated ET-1 kinetics in cirrhosis to determine if a reduced liver clearance contributes to this process. Cirrhosis was induced by carbon tetrachloride in rats. Hepatic ET-1 clearance was measured in isolated perfused livers using the single bolus multiple indicator-dilution technique. Plasma ET-1 levels doubled in cirrhosis from 0.49+/-0.04 fmol/ml (mean+/-S.E.M.) to 1.0+/-0.18 fmol/ml ( P <0.01). Liver ET-1 extraction was reduced from 81+/-1% (mean+/-S.E.M.) in controls to 50+/-6% in cirrhosis ( P <0.01). Kinetic modelling revealed a major irreversible binding site for ET-1 that is blocked by the selective ET(B) receptor antagonist BQ788 and a minor non-specific reversible binding site that cannot be blocked with BQ788 or the selective ET(A) antagonist BQ123. Reduced hepatic clearance correlated with the biochemical markers of cirrhosis, portal vein perfusion pressure ( r =-0.457; P <0.001) and the increase in ET-1 levels ( r =-0.462; P =0.002). Immunohistofluorescence with specific anti-(ET(B) receptor) antibodies revealed a preponderant distribution of ET(B) receptors on hepatic stellate cells, which was increased in cirrhosis. We conclude that cirrhosis reduces ET-1 clearance probably by capillarization of hepatic sinusoids and reduced access to ET(B) receptors. This relates to the severity of cirrhosis and may contribute to the increase in circulating ET-1 levels.

Moment analysis of metabolic heterogeneity: conjugation of benzoate with glycine in rat liver studied by multiple indicator dilution technique.

Metabolic zonation was assessed with the multiple indicator dilution (MID) technique in the single-pass perfused rat liver with use of moment analysis of the formed metabolite (M) data. During single-pass, retrograde rat liver perfusion with 17 Awake M benzoate, a bolus containing tracer preformed metabolite (PM) [(3)H]hippurate was injected rapidly into the hepatic vein at 20 min postperfusion, followed by injection of a second bolus containing [(14)C]benzoate at 30 min. Both doses also contained noneliminated reference indicators ((51)Cr-labeled RBCs, (125)I-labeled albumin, [(14)C]- or [(3)H]sucrose, and (2)H(2)O). The steady-state extraction ratio of benzoate, the area under the curve (AUC) and its mean transit time (MTT) during retrograde flow were identical to those previously observed for prograde flow. Values of AUC(PM) and MTT(PM) and AUC(M) were also similar to previously published prograde data, but the MTT(M) with retrograde perfusion was smaller than that for prograde perfusion. This, according to theory based on the tubes-in-series model, was consistent with perivenous enrichment of glycination activity when transport of drug was even and when the ratio of drug influx/efflux coefficient exceeded that for metabolite. Similar benzoate transport in periportal, homogeneous and perivenous isolated rat hepatocytes existed, and the influx/efflux coefficients (partition ratio) of benzoate from MID indeed exceeded that of hippurate. However, metabolism by zonal hepatocytes failed to reveal the anticipated metabolic zonation, and this is likely due to the shallow gradient of metabolic activity. The study demonstrates that moment theory is useful in delineating the perivenous enrichment of glycine conjugation activity.

Kinetic analysis of pulmonary neutrophil retention in vivo using the multiple-indicator-dilution technique.

Multiple-indicator-dilution experiments were performed in the lungs of 13 anesthetized dogs by simultaneous bolus injection of 111In-labeled neutrophils, 51Cr-labeled red blood cells, and Evans blue-labeled albumin. Concomitant counts of unlabeled neutrophils were similar in pulmonary artery and aortic blood samples, demonstrating a dynamic balance across the lungs in the physiological state. Outflow profiles of labeled neutrophils were analyzed on the basis of a recirculatory pharmacokinetic model of labeled albumin. The outflow profiles of the recovered neutrophils were composed of a throughput component of circulating neutrophils and a component of reversibly marginated neutrophils. They were interpreted by a model incorporating neutrophil margination (transfer coefficient = 0.195 +/- 0.081 s-1), rapid demargination (0.054 +/- 0.027 s-1), and transfer to a slow marginated pool (0.023 +/- 0.018 s-1). It will be interesting to apply the analysis in future studies aimed at determining whether it could be a useful research tool to investigate the interactions between the pulmonary endothelium and neutrophils in physiological and diseased states.

In vivo measurement of coronary circulation angiotensin-converting enzyme activity in humans.

Angiotensin-converting enzyme (ACE) is present on the luminal surface of the coronary vessels, mostly on capillary endothelium. ACE is also expressed on coronary smooth muscle cells and on plaque lipid-laden macrophages. Excessive coronary circulation (CC)-ACE activity might be linked to plaque progression. Here we used the biologically inactive ACE substrate (3)H-labeled benzoyl-Phe-Ala-Pro ([(3)H]BPAP) to quantify CC-ACE activity in 10 patients by means of the indicator-dilution technique. The results were compared with atherosclerotic burden determined by coronary angiography. There was a wide range of CC-ACE activity as revealed by percent [(3)H]BPAP hydrolysis (30-74%). The atherosclerotic extent scores ranged from 0.0 to 66.97, and the plaque area scores ranged from 0 to 80 mm(2). CC-ACE activity per unit extracellular space (V(max)/K(m)V(i)), an index of metabolically active vascular surface area, was correlated with myocardial blood flow (r = 0.738; P = 0.03) but not with measures of the atherosclerotic burden. These results show that CC-ACE activity can be safely measured in humans and that it is a good marker of the vascular area of the perfused myocardium. It does not, however, reflect epicardial atherosclerotic burden, suggesting that local tissue ACE may be more important in plaque development.