Impurity profiling quality control testing of synthetic peptides using liquid chromatography-photodiode array-fluorescence and liquid chromatography-electrospray ionization-mass spectrometry: the obestatin case

Clinically used low molecular weight heparins (LMWH) are anticoagulants of choice and are phenomenally complex mixtures of millions of distinct natural and unnatural polymeric sequences. The FDA recommends that each LMWH be considered as an independent drug with its own activity profile, placing significant importance on the biophysical characterization of each intact LMWH. We report a robust protocol for fingerprinting these pharmaceutical agents. Capillary electrophoresis of three LMWHs, enoxaparin, tinzaparin, and a Sigma preparation, under reverse polarity conditions in the presence of selected linear alkyl polyamines gives an electrophoretic pattern that is characteristic of the nature of the starting material. The buffers that best provided optimal resolution without compromising sensitivity and speed of analysis were 50 mM sodium phosphate, pH 2.3, and 100 mM ammonium formate, pH 3.5. Resolution was strongly dependent on the structure of polyamine with pentaethylenehexamine being most effective for enoxaparin and Sigma LMWH. In contrast, tinzaparin could be best resolved with tetraethylenepentamine. Cyclic polyamines were ineffective. Resolution was also dependent on the concentration of resolving agents and displayed a narrow window that provides optimal resolution. These features suggest a strong structural origin of the fingerprint pattern. Overall, the simple protocol will find special use in assessing LMWH quality and batch-to-batch variability.     

The ecology of primate material culture

Tool use in extant primates may inform our understanding of the conditions that favoured the expansion of hominin technology and material culture. The ‘method of exclusion’ has, arguably, confirmed the presence of culture in wild animal populations by excluding ecological and genetic explanations for geographical variation in behaviour. However, this method neglects ecological influences on culture, which, ironically, may be critical for understanding technology and thus material culture. We review all the current evidence for the role of ecology in shaping material culture in three habitual tool-using non-human primates: chimpanzees, orangutans and capuchin monkeys. We show that environmental opportunity, rather than necessity, is the main driver. We argue that a better understanding of primate technology requires explicit investigation of the role of ecological conditions. We propose a model in which three sets of factors, namely environment, sociality and cognition, influence invention, transmission and retention of material culture.     

Interactions of antifungal plant defensins with fungal membrane components

Plant defensins are small, basic, cysteine-rich peptides that are generally active against a broad spectrum of fungal and yeast species at micromolar concentrations. Some of these defensins interact with fungal-specific lipid components in the plasmamembrane. Structural differences of these membrane components between fungal and plant cells probably account for the selective activity of plant defensins against fungal pathogens and their nonphytotoxic properties. This review will focus on different classes of complex lipids in fungal membranes and on the selective interaction of plant defensins with these complex lipids.     

The Aerodynamic Cost of Head Morphology in Bats: Maybe Not as Bad as It Seems

At first sight, echolocating bats face a difficult trade-off. As flying animals, they would benefit from a streamlined geometric shape to reduce aerodynamic drag and increase flight efficiency. However, as echolocating animals, their pinnae generate the acoustic cues necessary for navigation and foraging. Moreover, species emitting sound through their nostrils often feature elaborate noseleaves that help in focussing the emitted echolocation pulses. Both pinnae and noseleaves reduce the streamlined character of a bat’s morphology. It is generally assumed that by compromising the streamlined charactered of the geometry, the head morphology generates substantial drag, thereby reducing flight efficiency. In contrast, it has also been suggested that the pinnae of bats generate lift forces counteracting the detrimental effect of the increased drag. However, very little data exist on the aerodynamic properties of bat pinnae and noseleaves. In this work, the aerodynamic forces generated by the heads of seven species of bats, including noseleaved bats, are measured by testing detailed 3D models in a wind tunnel. Models of Myotis daubentonii, Macrophyllum macrophyllum, Micronycteris microtis, Eptesicus fuscus, Rhinolophus formosae, Rhinolophus rouxi and Phyllostomus discolor are tested. The results confirm that non-streamlined facial morphologies yield considerable drag forces but also generate substantial lift. The net effect is a slight increase in the lift-to-drag ratio. Therefore, there is no evidence of high aerodynamic costs associated with the morphology of bat heads.     

The Effect of Morphine on Regional Cerebral Blood Flow Measured by 99mTc-ECD SPECT in Dogs

To gain insights into the working mechanism of morphine, regional cerebral blood flow (rCBF) patterns after morphine administration were assessed in dogs. In a randomized cross-over experimental study, rCBF was estimated with ^99mTc-Ethylcysteinate Dimer single photon emission computed tomography in 8 dogs at baseline, at 30 minutes and at 120 minutes after a single bolus of morphine. Perfusion indices (PI) in the frontal, parietal, temporal and occipital cortex and in the subcortical and cerebellar region were calculated. PI was significantly decreased 30 min after morphine compared to baseline in the right frontal cortex. The left parietal cortex and subcortical region showed a significantly increased PI 30 min after morphine compared to baseline. No significant differences were noted for the other regions or at other time points. In conclusion, a single bolus of morphine generated a changing rCBF pattern at different time points.     

An integrated proteomics and genomics analysis to unravel a heterogeneous platelet secretion defect

Eight patients with clinical bleeding problems have evidence for platelet storage pool disease as they present with impaired platelet aggregation and secretion with low concentrations of ADP and collagen and an absence of second phase aggregation with epinephrine. Electron microscopy analysis further showed a reduced but not absent amount of platelet dense granules, and CD63 staining was decreased compared to healthy controls. The presence of alpha granules and CD62P expression after platelet activation was normal. This work aimed at identifying differentially expressed proteins in the platelet releasate and its remaining pellet after activation with A23187 and TRAP in patients and controls using DIGE-based proteomic technology. We identified 44 differentially expressed proteins in patients and the altered expression for some of them was confirmed by immunoblot analysis. Most of these proteins belong to the class of cytoskeleton-related proteins. In addition, 29 cytoskeleton-related genes showed an altered expression in platelet mRNA from patients using a real-time PCR array. In conclusion, our study shows that the dense granule secretion defect in patients with platelet storage pool disease is highly heterogeneous with evidence of an underlying cytoskeleton defect.     

Information generated by the moving pinnae of Rhinolophus rouxi: tuning of the morphology at different harmonics

Bats typically emit multi harmonic calls. Their head morphology shapes the emission and hearing sound fields as a function of frequency. Therefore, the sound fields are markedly different for the various harmonics. As the sound field provides bats with all necessary cues to locate objects in space, different harmonics might provide them with variable amounts of information about the location of objects. Also, the ability to locate objects in different parts of the frontal hemisphere might vary across harmonics. This paper evaluates this hypothesis in R. rouxi, using an information theoretic framework. We estimate the reflector position information transfer in the echolocation system of R. rouxi as a function of frequency. This analysis shows that localization performance reaches a global minimum and a global maximum at the two most energetic frequency components of R. rouxi call indicating tuning of morphology and harmonic structure. Using the fundamental the bat is able to locate objects in a large portion of the frontal hemisphere. In contrast, using the 1st overtone, it can only locate objects, albeit with a slightly higher accuracy, in a small portion of the frontal hemisphere by reducing sensitivity to echoes from outside this region of interest. Hence, different harmonic components provide the bat either with a wide view or a focused view of its environment. We propose these findings can be interpreted in the context of the foraging behaviour of R. rouxi, i.e., hunting in cluttered environments. Indeed, the focused view provided by the 1st overtone suggests that at this frequency its morphology is tuned for clutter rejection and accurate localization in a small region of interest while the finding that overall localization performance is best at the fundamental indicates that the morphology is simultaneously tuned to optimize overall localization performance at this frequency.     

An ideal-observer model of human sound localization

In recent years, a great deal of research within the field of sound localization has been aimed at finding the acoustic cues that human listeners use to localize sounds and understanding the mechanisms by which they process these cues. In this paper, we propose a complementary approach by constructing an ideal-observer model, by which we mean a model that performs optimal information processing within a Bayesian context. The model considers all available spatial information contained within the acoustic signals encoded by each ear. Parameters for the optimal Bayesian model are determined based on psychoacoustic discrimination experiments on interaural time difference and sound intensity. Without regard as to how the human auditory system actually processes information, we examine the best possible localization performance that could be achieved based only on analysis of the input information, given the constraints of the normal auditory system. We show that the model performance is generally in good agreement with the actual human localization performance, as assessed in a meta-analysis of many localization experiments (Best et al. in Principles and applications of spatial hearing, pp 14–23. World Scientific Publishing, Singapore, 2011). We believe this approach can shed new light on the optimality (or otherwise) of human sound localization, especially with regard to the level of uncertainty in the input information. Moreover, the proposed model allows one to study the relative importance of various (combinations of) acoustic cues for spatial localization and enables a prediction of which cues are most informative and therefore likely to be used by humans in various circumstances.