Basis for the cardiac-related rhythm in muscle sympathetic nerve activity of humans

We tested the hypothesis that the cardiac-related rhythm in muscle sympathetic nerve activity (MSNA) of humans reflects entrainment of a central oscillator by pulse-synchronous baroreceptor nerve activity. Partial autospectral analysis was used to mathematically remove the portion of cardiac-related power in MSNA autospectra that was attributable to its linear relationship to the ECG. In 54 of 98 cases, > or =15% of cardiac-related power remained after partialization with the ECG; peak residual cardiac-related power was often at a frequency different than heart rate. When assessed on a cardiac-related burst-by-burst basis, there was a progressive and cyclic change in the ECG-MSNA interval (delay from R wave to peak of cardiac-related burst) on the time scale of respiration in four subjects. In these subjects, as well as in some in which the interval appeared to change randomly, there was an inverse relationship between the ECG-MSNA interval and cardiac-related burst amplitude. However, in 45% of the cases, these parameters were not related. These results support the view that the cardiac-related rhythm in MSNA reflects forcing of a nonlinear oscillator rather than periodic inhibition of unstructured, random activity.     

Assessing nitrate leaching during the three‐first years of Miscanthus × giganteus from on‐farm measurements and modeling

Miscanthus × giganteus is often regarded as one of the most promising crops to produce sustainable bioenergy. This perennial crop, renowned for its high productivity associated with low input requirements, in particular regarding fertilizers, is thought to have low environmental impacts, but few data are available to confirm this. Our study aimed at assessing nitrate leaching from Miscanthus × giganteus crops in farmers' fields, thus including a wide range of soil and cropping system conditions. We focused on the first years of growth after planting as experimental studies have suggested that Miscanthus × giganteus, once established, results in low nitrate leaching. We combined on‐farm measurements and modeling to estimate drainage, leached nitrogen, and nitrate concentration in drainage water in 38 fields located in Center‐East France during two winters (November 2010 to March 2011, November 2011 to March 2012). Nitrate leaching and nitrate concentration in drainage water were on average very low. Nitrate leaching averaged 6 kg N ha^?1 whereas nitrate concentration averaged 12 mg l^?1. These low values are attributable to the low estimates of drainage water (mean = 166 mm) but also to the low soil mineral nitrogen contents measured at the beginning of winter (mean = 37 kg N ha^?1). Our results were, however, very variable, mainly due to the crop age: nitrate leaching and nitrate concentration were critically higher during the winter following the first growth year of Miscanthus × giganteus, reflecting the low development of the crop. This variability was also explained by the range of soil and cropping conditions explored in the on‐farm design: shallow and/or sandy soils as well as fields where establishment failed had a higher risk of nitrate leaching.     

Immunoelectrophorecal differences between phytopathogenic Fusarium species

Immunoelectrograms of certain tested Fusarium spp revealed that each has a characteristic pattern and showed the relatedness between F. oxysporum on the one hand and F. culmorum and F. semitectum on the other. The B₄ protein fraction is common to the former pair, while α_1a protein fraction links the second.     

Carotid baroreflex regulation of sympathetic nerve activity during dynamic exercise in humans

We sought to determine whether carotid baroreflex (CBR) control of muscle sympathetic nerve activity (MSNA) was altered during dynamic exercise. In five men and three women, 23.8 +/- 0.7 (SE) yr of age, CBR function was evaluated at rest and during 20 min of arm cycling at 50% peak O(2) uptake using 5-s periods of neck pressure and neck suction. From rest to steady-state arm cycling, mean arterial pressure (MAP) was significantly increased from 90.0 +/- 2.7 to 118.7 +/- 3.6 mmHg and MSNA burst frequency (microneurography at the peroneal nerve) was elevated by 51 +/- 14% (P < 0.01). However, despite the marked increases in MAP and MSNA during exercise, CBR-Delta%MSNA responses elicited by the application of various levels of neck pressure and neck suction ranging from +45 to -80 Torr were not significantly different from those at rest. Furthermore, estimated baroreflex sensitivity for the control of MSNA at rest was the same as during exercise (P = 0.74) across the range of neck chamber pressures. Thus CBR control of sympathetic nerve activity appears to be preserved during moderate-intensity dynamic exercise.     

Caramelization of maltose solution in presence of alanine

Summary. Two solutions of maltose in water were used to prepare caramels. Alanine as a catalyst was added to one of these solutions. The caramelization was conducted at 130°C for total time period 90 minutes. Convenient samples were taken of each caramel solution every 30 min and subjected to sensory analysis and isolation of volatile components. The odour and colour sensory tests were evaluated according to the international standard methods (ISO). The results showed that, the presence of alanine gave rise to a high significant (P < 0.01) decrease in acid attributes and remarkable increase in the sweet and caramel attributes, which are the most important caramel notes. On the other hand the increase in heating time in presence of alanine as a catalyst resulted in a high significant (P < 0.01) increase in the browning rate of caramel solution. The new technique Solid Phase Micro Extraction (SPME) was used for trapping the volatile components in the headspace of each caramel samples followed by thermal desorption and GC and GC – MS analysis. The 5-hydroxymethyl-2-furfural (HMF), the main characteristic caramel product, showed its highest value in sample containing alanine after heating for 60 minutes. The best sensory results of the sample contains alanine were confirmed by the presence of high concentrations of the most potent odorants of caramel besides to the formation of some volatile compounds have caramel like flavours such as 2-acetyl pyrrole, 2-furanones and 1-(2-furanyl)1,2-propandione. Received April 26, 2000 Accepted February 8, 2001     

Clostridium symbiosum as a cause of bloodstream infection in an immunocompetent patient

Bloodstream infection caused by Clostridium symbiosum was previously reported in only one case, from a highly immunocompromised patient with metastic colon cancer. We describe the second case of clinical bacteraemic sepsis caused by C. symbiosum from a previously healthy man, which underlines the pathogenicity of this species.     

Crystallographic studies on the binding of isonicotinyl-NAD adduct to wild-type and isoniazid resistant 2-trans-enoyl-ACP (CoA) reductase from Mycobacterium tuberculosis

The resumption of tuberculosis led to an increased need to understand the molecular mechanisms of drug action and drug resistance, which should provide significant insight into the development of newer compounds. Isoniazid (INH), the most prescribed drug to treat TB, inhibits an NADH-dependent enoyl-acyl carrier protein reductase (InhA) that provides precursors of mycolic acids, which are components of the mycobacterial cell wall. InhA is the major target of the mode of action of isoniazid. INH is a pro-drug that needs activation to form the inhibitory INH-NAD adduct. Missense mutations in the inhA structural gene have been identified in clinical isolates of Mycobacterium tuberculosis resistant to INH. To understand the mechanism of resistance to INH, we have solved the structure of two InhA mutants (I21V and S94A), identified in INH-resistant clinical isolates, and compare them to INH-sensitive WT InhA structure in complex with the INH-NAD adduct. We also solved the structure of unliganded INH-resistant S94A protein, which is the first report on apo form of InhA. The salient features of these structures are discussed and should provide structural information to improve our understanding of the mechanism of action of, and resistance to, INH in M. tuberculosis. The unliganded structure of InhA allows identification of conformational changes upon ligand binding and should help structure-based drug design of more potent antimycobacterial agents.     

Confidence interval construction for relative toxicity endpoints such as LD50 or LD90 ratios

A common measure of the relative toxicity is the ratio of median lethal doses for responses estimated in two bioassays. Robertson and Preisler previously proposed a method for constructing a confidence interval for the ratio. The applicability of this technique in common experimental situations, especially those involving small samples, may be questionable because the sampling distribution of this ratio estimator may be highly skewed. To examine this possibility, we did a computer simulation experiment to evaluate the coverage properties of the Robertson and Preisler method. The simulation showed that the method provided confidence intervals that performed at the nominal confidence level for the range of responses often observed in pesticide bioassays. Results of this study provide empirical support for the continued use this technique.     

Enhanced open-loop but not closed-loop cardiac baroreflex sensitivity during orthostatic stress in humans

The neural interaction between the cardiopulmonary and arterial baroreflex may be critical for the regulation of blood pressure during orthostatic stress. However, studies have reported conflicting results: some indicate increases and others decreases in cardiac baroreflex sensitivity (i.e., gain) with cardiopulmonary unloading. Thus the effect of orthostatic stress-induced central hypovolemia on regulation of heart rate via the arterial baroreflex remains unclear. We sought to comprehensively assess baroreflex function during orthostatic stress by identifying and comparing open- and closed-loop dynamic cardiac baroreflex gains at supine rest and during 60° head-up tilt (HUT) in 10 healthy men. Closed-loop dynamic "spontaneous" cardiac baroreflex sensitivities were calculated by the sequence technique and transfer function and compared with two open-loop carotid-cardiac baroreflex measures using the neck chamber system: 1) a binary white-noise method and 2) a rapid-pulse neck pressure-neck suction technique. The gain from the sequence technique was decreased from -1.19 ± 0.14 beats·min(-1)·mmHg(-1) at rest to -0.78 ± 0.10 beats·min(-1)·mmHg(-1) during HUT (P = 0.005). Similarly, closed-loop low-frequency baroreflex transfer function gain was reduced during HUT (P = 0.033). In contrast, open-loop low-frequency transfer function gain between estimated carotid sinus pressure and heart rate during white-noise stimulation was augmented during HUT (P = 0.01). This result was consistent with the maximal gain of the carotid-cardiac baroreflex stimulus-response curve (from 0.47 ± 0.15 beats·min(-1)·mmHg(-1) at rest to 0.60 ± 0.20 beats·min(-1)·mmHg(-1) at HUT, P = 0.037). These findings suggest that open-loop cardiac baroreflex gain was enhanced during HUT. Moreover, under closed-loop conditions, spontaneous baroreflex analyses without external stimulation may not represent open-loop cardiac baroreflex characteristics during orthostatic stress.