Functional assessment of morphological homoplasy in stem-gnathostomes

Osteostraci and Galeaspida are stem-gnathostomes, occupying a key phylogenetic position for resolving the nature of the jawless ancestor from which jawed vertebrates evolved more than 400 million years ago. Both groups are characterized by the presence of rigid headshields that share a number of common morphological traits, in some cases hindering the resolution of their interrelationships and the exact nature of their affinities with jawed vertebrates. Here, we explore the morphological and functional diversity of osteostracan and galeaspid headshields using geometric morphometrics and computational fluid dynamics to constrain the factors that promoted the evolution of their similar morphologies and informing on the ecological scenario under which jawed vertebrates emerged. Phylomorphospace, Mantel analysis and Stayton metrics demonstrate a high degree of homoplasy. Computational fluid dynamics reveals similar hydrodynamic performance among morphologically convergent species, indicating the independent acquisition of the same morphofunctional traits and, potentially, equivalent lifestyles. These results confirm that a number of the characters typically used to infer the evolutionary relationships among galeaspids, osteostracans and jawed vertebrates are convergent in nature, potentially obscuring understanding of the assembly of the gnathostome bodyplan. Ultimately, our results reveal that while the jawless relatives of the earliest jawed vertebrates were ecologically diverse, widespread convergence on the same hydrodynamic adaptations suggests they had reached the limits of their potential ecological diversity—overcome by jawed vertebrates and their later innovations.     

Impact of carbon and phosphate starvation on growth and programmed cell death of maritime pine suspension cells

Programmed cell death is a fundamental aspect of plant development and defense. In suspension cultures of maritime pine (Pinus pinaster Ait.), cell death was associated with the simultaneous depletion of sugar and phosphate. This present work suggests that sugar rather than phosphate deprivation induced programmed cell death events, including degradation of nuclear DNA and remobilization of phosphate. However, phosphate starvation may have a synergistic effect on programmed cell death mediated by the lack of carbon source. Sugar and phosphate analogs were used to evaluate the nature of signaling events, and results suggested that programmed cell death induction by sugar starvation occurs downstream of hexokinase-based sugar sensing mechanisms, and that the synergistic effect of lack of phosphate is independent of phosphate sensing.     

Assessing the need for adaptive radiotherapy in head and neck cancer patients using an automatic planning tool

BackgroundUnbiased analysis of the impact of adaptive radiotherapy (ART) is necessary to evaluate dosimetric benefit and optimize clinics’ workflows. The aim of the study was to assess the need for adaptive radiotherapy (ART) in head and neck (H&N) cancer patients using an automatic planning tool in a retrospective planning study.Materials and methodsThirty H&N patients treated with adaptive radiotherapy were analysed. Patients had a CT scan for treatment planning and a verification CT during treatment according to the clinic’s protocol. Considering these images, three plans were retrospectively generated using the iCycle tool to simulate the scenarios with and without adaptation: 1) the optimized plan based on the planning CT; 2) the optimized plan based on the verification CT (ART-plan); 3) the plan obtained by considering treatment plan 1 re-calculated in the verification CT (non-ART plan). The dosimetric endpoints for both target volumes and OAR were compared between scenarios 2 and 3 and the SPIDERplan used to evaluate plan quality.ResultsThe most significant impact of ART was found for the PTVs, which demonstrated decreased D98% in the non-ART plan. A general increase in the dose was observed for the OAR but only the spinal cord showed a statistical significance. The SPIDERplan analysis indicated an overall loss of plan quality in the absence of ART.ConclusionThese results confirm the advantages of ART in H&N patients, especially for the coverage of target volumes. The usage of an automatic planning tool reduces planner-induced bias in the results, guaranteeing that the observed changes derive from the application of ART.     

Purification and characterization of trypsin from Luphiosilurus alexandri pyloric cecum

Trypsin from L. alexandri was purified using only two purification processes: ammonium sulfate precipitation and anion exchange liquid chromatography in DEAE-Sepharose. Trypsin mass was estimated as 24 kDa through SDS-PAGE, which showed only one band in silver staining. The purified enzyme showed an optimum temperature and pH of 50 °C and 9.0, respectively. Stability was well maintained, with high levels of activity at a pH of up to 11.0, including high stability at a temperature of up to 50 °C after 60 min of incubation. The inhibition test demonstrated strong inhibition by PMSF, a serine protease inhibitor, and Kinetic constants km and kcat for BAPNA were 0.517 mM and 5.0 S^?1, respectively. The purified enzyme was also as active as casein, as analyzed by zymography. Therefore, we consider trypsin a promising enzyme for industrial processes, owing to its stability in a wide range of pH and temperature and activity even under immobilization.     

Interaction of Curcumin with Manganese May Compromise Metal and Neurotransmitter Homeostasis in the Hippocampus of Young Mice

Manganese (Mn) exposure is related to industrial activities, where absorption by inhalation has high relevance. Manganism, a syndrome caused as a result of excessive accumulation of Mn in the central nervous system, has numerous symptoms similar to those seen in idiopathic Parkinson disease (IPD). Some of these symptoms, such as learning, memory, sensorial, and neurochemical changes, appear before the onset of motor deficits in both manganism and IPD. The aim of this study was to evaluate the possible neuroprotective effects of curcumin against behavioral deficits induced by Mn toxicity in young (2 months old) Swiss mice. We evaluated the effect of chronic inhalation of a Mn mixture [Mn(OAc)₃ and MnCl₂ (20:40 mM)], 1 h/session, three times a week, over a 14-week period on behavioral and neurochemical parameters. Curcumin was supplemented in the diet (500 or 1,500 ppm in food pellets). The Mn disrupted the motor performance evaluated in the single-pellet reach task, as well as the short- and long-term spatial memory evaluated in the step-down inhibitory avoidance task. Surprisingly, curcumin also produced similar deleterious effects in such behavioral tests. Moreover, the association of Mn plus curcumin significantly increased the levels of Mn and iron, and decreased the levels of dopamine and serotonin in the hippocampus. These alterations were not observed in the striatum. In conclusion, the current Mn treatment protocol resulted in mild deficits in motor and memory functions, resembling the early phases of IPD. Additionally, curcumin showed no beneficial effects against Mn-induced disruption of hippocampal metal and neurotransmitter homeostasis.

Heterospecific Acoustic Interference: Effects on Calling in Oophaga pumilio

Call rate suppression is a common short-term solution for avoiding acoustic interference in animals. It has been widely documented between and within frog species, but the effects of non-anuran calling on frog vocalizations are less well known. Heterospecific acoustic interference on the calling of male Oophaga pumilio (formerly Dendrobates pumilio) was studied in a lowland, wet tropical forest in SE Nicaragua. Acoustic playback experiments were conducted to characterize the responses of O. pumilio males to interfering calls of cicadas, two species of crickets, and a sympatric dendrobatid frog, Phyllobates lugubris. Call rate, call bout duration, percent of time calling, dominant frequency, and latency to first-call were analyzed. Significant call rate suppression was observed during all stimulus playbacks, yet no significant differences were found in spontaneous call rates during pre- and postplayback trials. Dominant frequency significantly decreased after P. lugubris playback and first-call latency significantly decreased in response to both cicada and tree cricket playbacks. These results provide robust evidence that O. pumilio males can dynamically modify their calling pattern in unique ways, depending on the source of the heterospecific acoustic interference.     

Ion hydration in nanopores and the molecular basis of selectivity

Using a simple model, it is shown that the cost of constraining a hydrated potassium ion inside a narrow pore is smaller than the cost of constraining hydrated sodium or lithium ions in pores of radius around 1.5 A. The opposite is true for pores of radius around 2.5 A. The reason for the selectivity in the first region is that the potassium ion allows for a greater distortion of its hydration shell and can therefore maintain a better coordination, and the reason for the reverse selectivity in the second region is that the smaller ions retain their hydration shells in these pores. This is relevant to the molecular basis of ion selective channels, and since this mechanism does not depend on the molecular details of the pore, it could also operate in all sorts of nanotubes.     

Selection of allosteric beta-lactamase mutants featuring an activity regulation by transition metal ions

Libraries of phage-displayed beta-lactamase mutants in which up to three loops have been engineered by genetic introduction of random peptide sequences or by randomization of the wild-type sequence have been submitted to selection protocols designed to find mutants in which binding of transition metal ions to the engineered secondary binding site leads to significant effects on the enzymatic activity. A double-selection protocol was applied: The phage-displayed libraries were first selected for transition metal ions affinity by panning on IMAC support, then a second selection step was applied to isolate mutants that have retained significant catalytic activity. The analysis of the kinetic properties of mutants in the presence of nickel, copper, or zinc ions allowed isolation of a few mutants whose activity was either enhanced or inhibited by factors up to three and >10, respectively, in a metal-specific manner. A remarkable mutant exhibiting differential allosteric regulation depending on the metal was found. Its activity was activated by nickel ion binding, inhibited by cupric ion binding, and nearly unaffected by zinc ions. These observations point to an interesting potential for up- or down-regulation of activity within a monomeric enzyme by binding to an "allosteric site" relatively remote from the active site.     

Effects of concentration and sniff flow rate on the rat electroolfactogram

Previous reports using the electroolfactogram (EOG) to study the spatial and temporal aspects of response in the rodent olfactory epithelium had focused on high odorant concentrations that gave large responses. This investigation has used lower concentrations to test the difference between responses in the rat dorsomedial and lateral recesses with a range of nasal flow rates and a range of chemical properties. The responses to a highly polar, more hydrophilic odorant changed more steeply with flow rate than responses to a very nonpolar, hydrophobic odorant. With low flow rates there was a response delay in the lateral recess, which is consistent with the models indicating lower flow rates in that region. We observed significant volume conduction effects in which large responses in the dorsomedial region obscured smaller initial portions of the lateral responses. These effects could be removed by destroying the dorsomedial response with a high concentration of a low molecular weight ester. We caution that investigators of EOG recordings from the intact epithelium must attend to the possible presence of volume conduction, which can be assessed by attention to the selectivity of odorant response, response waveform, and response latency.     

<Emphasis Type="Italic">In vivo</Emphasis> assessment of the impedance ratio method used in electronic foramen locators

Background  

The results of an in vivo study on the "ratio method" used in electronic foramen locators (EFL) are presented. EFLs are becoming widely used in the determination of the working length (WL) during the root canal treatment. The WL is the distance from a coronal reference point to the point at which canal preparation and filling should terminate. The "ratio method" was assessed by many clinicians with the aim of determining its ability to locate the apical foramen (AF). Nevertheless, in vivo studies to assess the method itself and to explain why the "ratio method" is able to locate the apical foramen and is unable to determine intermediate distances were not published so far.