Mangiferin Prevents Guinea Pig Tracheal Contraction via Activation of the Nitric Oxide-Cyclic GMP Pathway

Previous studies have described the antispasmodic effect of mangiferin, a natural glucoside xanthone (2-C-β-Dgluco-pyranosyl-1,3,6,7-tetrahydroxyxanthone) that is present in mango trees and other plants, but its mechanism of action remains unknown. The aim of this study was to examine the potential contribution of the nitric oxide-cyclic GMP pathway to the antispasmodic effect of mangiferin on isolated tracheal rings preparations. The functional effect of mangiferin on allergic and non-allergic contraction of guinea pig tracheal rings was assessed in conventional organ baths. Cultured tracheal rings were exposed to mangiferin or vehicle, and nitric oxide synthase (NOS) 3 and cyclic GMP (cGMP) levels were quantified using western blotting and enzyme immunoassays, respectively. Mangiferin (0.1–10 µM) inhibited tracheal contractions induced by distinct stimuli, such as allergen, histamine, 5-hydroxytryptamine or carbachol, in a concentration-dependent manner. Mangiferin also caused marked relaxation of tracheal rings that were precontracted by carbachol, suggesting that it has both anti-contraction and relaxant properties that are prevented by removing the epithelium. The effect of mangiferin was inhibited by the nitric oxide synthase inhibitor, Nω-nitro-L-arginine methyl ester (L-NAME) (100 µM), and the soluble guanylate cyclase inhibitor, 1H-[1], [2], [4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) (10 µM), but not the adenylate cyclase inhibitor, 9-(tetrahydro-2-furyl)adenine (SQ22536) (100 µM). The antispasmodic effect of mangiferin was also sensitive to K⁺ channel blockers, such as tetraethylammonium (TEA), glibenclamide and apamin. Furthermore, mangiferin inhibited Ca²⁺-induced contractions in K⁺ (60 mM)-depolarised tracheal rings preparations. In addition, mangiferin increased NOS3 protein levels and cGMP intracellular levels in cultured tracheal rings. Finally, mangiferin-induced increase in cGMP levels was abrogated by co-incubation with either ODQ or L-NAME. These data suggest that the antispasmodic effect of mangiferin is mediated by epithelium-nitric oxide- and cGMP-dependent mechanisms.     

The role of vocal individuality in conservation

Identifying the individuals within a population can generate information on life history parameters, generate input data for conservation models, and highlight behavioural traits that may affect management decisions and error or bias within census methods. Individual animals can be discriminated by features of their vocalisations. This vocal individuality can be utilised as an alternative marking technique in situations where the marks are difficult to detect or animals are sensitive to disturbance. Vocal individuality can also be used in cases were the capture and handling of an animal is either logistically or ethically problematic. Many studies have suggested that vocal individuality can be used to count and monitor populations over time; however, few have explicitly tested the method in this role. In this review we discuss methods for extracting individuality information from vocalisations and techniques for using this to count and monitor populations over time. We present case studies in birds where vocal individuality has been applied to conservation and we discuss its role in mammals.     

Characteristics of Misclassified CT Perfusion Ischemic Core in Patients with Acute Ischemic Stroke

Background

CT perfusion (CTP) is used to estimate the extent of ischemic core and penumbra in patients with acute ischemic stroke. CTP reliability, however, is limited. This study aims to identify regions misclassified as ischemic core on CTP, using infarct on follow-up noncontrast CT. We aim to assess differences in volumetric and perfusion characteristics in these regions compared to areas that ended up as infarct on follow-up.

Materials and Methods

This study included 35 patients with >100 mm brain coverage CTP. CTP processing was performed using Philips software (IntelliSpace 7.0). Final infarct was automatically segmented on follow-up noncontrast CT and used as reference. CTP and follow-up noncontrast CT image data were registered. This allowed classification of ischemic lesion agreement (core on CTP: rMTT≥145%, aCBV<2.0 ml/100g and infarct on follow-up noncontrast CT) and misclassified ischemic core (core on CTP, not identified on follow-up noncontrast CT) regions. False discovery ratio (FDR), defined as misclassified ischemic core volume divided by total CTP ischemic core volume, was calculated. Absolute and relative CTP parameters (CBV, CBF, and MTT) were calculated for both misclassified CTP ischemic core and ischemic lesion agreement regions and compared using paired rank-sum tests.

Results

Median total CTP ischemic core volume was 49.7ml (IQR:29.9ml-132ml); median misclassified ischemic core volume was 30.4ml (IQR:20.9ml-77.0ml). Median FDR between patients was 62% (IQR:49%-80%). Median relative mean transit time was 243% (IQR:198%-289%) and 342% (IQR:249%-432%) for misclassified and ischemic lesion agreement regions, respectively. Median absolute cerebral blood volume was 1.59 (IQR:1.43–1.79) ml/100g (P<0.01) and 1.38 (IQR:1.15–1.49) ml/100g (P<0.01) for misclassified ischemic core and ischemic lesion agreement, respectively. All CTP parameter values differed significantly.

Conclusion

For all patients a considerable region of the CTP ischemic core is misclassified. CTP parameters significantly differed between ischemic lesion agreement and misclassified CTP ischemic core, suggesting that CTP analysis may benefit from revisions.     

High genetic and morphological diversity despite range contraction in the diploid Hieracium eriophorum (Asteraceae) endemic to the coastal sand dunes of south‐west France

Endemic plants inhabiting coastal sand dunes show augmented extinction risks due to the dynamic nature of dunes and strong human pressure on coastal areas. To investigate the survival strategies and threats to long‐term survival of such species, we combined genetic, morphological and biogeographical approaches, using the example of Hieracium eriophorum (Asteraceae) and its putative cryptic sister species H. prostratum, which are endemic to the longest coastal sand dune in Europe. An analysis of amplified fragment length polymorphism revealed high within‐population genetic variability, and slight isolation by distance was the only indication of genetic population structure. Thus, no signs of genetic threats to survival were found. Furthermore, genetic and morphometric data provided no evidence for the existence of two species. Therefore, we propose to synonymize H. prostratum with H. eriophorum and provide a nomenclatural overview with typification. Finally, an analysis of historical distribution records showed that, during the last 100 years, the species was lost from its range margins, where its habitat became fragmented. Taken together, our results suggest that one successful survival strategy of narrow endemics may be the achievement of large local population sizes on a small geographical scale, thus avoiding the genetic problems inherent to small and fragmented populations. Dune management policies should thus take care that the current tendencies to allow more erosion will not result in too severe fragmentation of the remaining continuous stretches of dune habitat. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169 , 365–377.     

Neural and local effects of hypoxia on cardiovascular responses to obstructive apnea.

Obstructive sleep apnea (OSA) acutely increases systemic (Psa) and pulmonary (Ppa) arterial pressures and decreases ventricular stroke volume (SV). In this study, we used a canine model of OSA (n = 6) to examine the role of hypoxia and the autonomic nervous system (ANS) in mediating these cardiovascular responses. Hyperoxia (40% oxygen) completely blocked any increase in Ppa in response to obstructive apnea but only attenuated the increase in Psa. In contrast, after blockade of the ANS (20 mg/kg iv hexamethonium), obstructive apnea produced a decrease in Psa (-5.9 mmHg; P < 0.05) but no change in Ppa, and the fall in SV was abolished. Both the fall in Psa and the rise in Ppa that persisted after ANS blockade were abolished when apneas were induced during hyperoxia. We conclude that 1) hypoxia can account for all of the Ppa and the majority of the Psa response to obstructive apnea, 2) the ANS increases Psa but not Ppa in obstructive apnea, 3) the local effects of hypoxia associated with obstructive apnea cause vasodilation in the systemic vasculature and vasoconstriction in the pulmonary vasculature, and 4) a rise in Psa acts as an afterload to the heart and decreases SV over the course of the apnea.     

Cell surface glycoproteins from Thermoplasma acidophilum are modified with an N-linked glycan containing 6-C-sulfofucose

Thermoplasma acidophilum is a thermoacidophilic archaeon that grows optimally at pH 2 and 59°C. This extremophile is remarkable by the absence of a cell wall or an S-layer. Treating the cells with Triton X-100 at pH 3 allowed the extraction of all of the cell surface glycoproteins while keeping cells intact. The extracted glycoproteins were partially purified by cation-exchange chromatography, and we identified five glycoproteins by N-terminal sequencing and mass spectrometry of in-gel tryptic digests. These glycoproteins are positive for periodic acid-Schiff staining, have a high content of Asn including a large number in the Asn-X-Ser/Thr sequon and have apparent masses that are 34-48% larger than the masses deduced from their amino acid sequences. The pooled glycoproteins were digested with proteinase K and the purified glycopeptides were analyzed by NMR. Structural determination showed that the carbohydrate part was represented by two structures in nearly equal amounts, differing by the presence of one terminal mannose residue. The larger glycan chain consists of eight residues: six hexoses, one heptose and one sugar with an unusual residue mass of 226 Da which was identified as 6-deoxy-6-C-sulfo-D-galactose (6-C-sulfo-D-fucose). Mass spectrometry analyses of the peptides obtained by trypsin and chymotrypsin digestion confirmed the principal structures to be those determined by NMR and identified 14 glycopeptides derived from the main glycoprotein, Ta0280, all containing the Asn-X-Ser/Thr sequons. Thermoplasma acidophilum appears to have a "general" protein N-glycosylation system that targets a number of cell surface proteins.     

Calcium, ATP, and ROS: a mitochondrial love-hate triangle

The mitochondrion is at the core of cellular energy metabolism, being the site of most ATP generation. Calcium is a key regulator of mitochondrial function and acts at several levels within the organelle to stimulate ATP synthesis. However, the dysregulation of mitochondrial Ca(2+) homeostasis is now recognized to play a key role in several pathologies. For example, mitochondrial matrix Ca(2+) overload can lead to enhanced generation of reactive oxygen species, triggering of the permeability transition pore, and cytochrome c release, leading to apoptosis. Despite progress regarding the independent roles of both Ca(2+) and mitochondrial dysfunction in disease, the molecular mechanisms by which Ca(2+) can elicit mitochondrial dysfunction remain elusive. This review highlights the delicate balance between the positive and negative effects of Ca(2+) and the signaling events that perturb this balance. Overall, a "two-hit" hypothesis is developed, in which Ca(2+) plus another pathological stimulus can bring about mitochondrial dysfunction.     

Effects of changes in left ventricular loading and pleural pressure on mitral flow

The cause of the fall in left ventricular (LV) stroke volume (SV) during a fall in pleural pressure (Pp1) has been in dispute for over a century. We have defined the changes in the temporal relationship between LV inflow (Qm) and outflow (Qa) in a canine preparation to test the mutually exclusive hypotheses that the fall in LVSV is caused only by changes during diastole (e.g., ventricular interdependence) or only by changes during systole (e.g., afterload). The ability of the experimental preparation to measure the results of acute changes in right heart volume or output and acute changes in LV afterload was validated in open-chest studies with and without pericardial constraint. In closed-chest studies, with a fall in Pp1 during a Mueller maneuver Qm reached both its inspiratory minimum and expiratory maximum before Qa in 80% of the Mueller maneuvers, invalidating both hypotheses, which each required that one flow lead the other in 100% of the Mueller maneuvers. Review of individual records suggested that if the rapid changes in Pp1 occurred during systole, Qa could vary in a manner independent of the preceding Qm. These studies suggest that both diastolic and systolic events may contribute to the fall in SV, while causing opposite changes in LV volumes.     

Cooling-induced contraction of guinea pig tracheal smooth muscle

Cooling of isolated guinea pig tracheal smooth muscle from 38 to 28 degrees C over 2.25 min produced a transient contraction followed by sustained relaxation. The cooling-induced contraction was blocked either by pretreatment with ouabain at concentrations of 10(-5) M or greater or by substitution of normal physiological salt solution with K-free solution. In contrast, the contractile response to cooling was not inhibited by pretreatment with phentolamine (10(-5) M), atropine (10(-5) M), tetrodotoxin (3 X 10(-7) M), diphenhydramine (10(-5) M), cromolyn sodium (10(-3) M), indomethacin (3 X 10(-7) M), nifedipine (10(-7) M), or verapamil (3 X 10(-6) M). Addition of NaHCO3 to the bath during cooling, preventing a change in pH of the physiological salt solution, did not affect the cooling-induced contraction. It is concluded that cooling of isolated guinea pig trachea produces a transient ouabain-sensitive contraction, and that the data suggest the contraction is mediated by inhibition of Na-K-ATPase in the smooth muscle rather than through neuronal stimulation or chemical mediator release.