The external gills of anuran amphibians: Comparative morphology and ultrastructure

The external gills of anuran amphibians are transient structures, covered by the development of the operculum and regressing soon afterwards. Their functional role has been regarded as equivocal. However, detailed morphological analysis has been limited. Analysis of 21 species from six families using scanning and transmission electron microscopy revealed diversity at the anatomical and cellular levels in extent and length of gill filaments, numbers of surface ciliated cells, width of water‐blood barrier distance, and evidence of gill motility. The most highly developed external gills were found in species with delayed hatching, such as Phyllomedusa trinitatis, or in species in which hatchlings hang from the surface film of temporary ponds, such as Phrynohyas venulosa in which gills added 26–38% to body surface area. In one family, the bufonids, all four species examined had poorly developed gills, but in other families where we examined several species, the hylids and leptodactylids, there was considerable diversity of external gills, suggesting flexible adaptation to incubation and hatching environment. J. Morphol., 2008. © 2008 Wiley‐Liss, Inc.     

Testes investment and spawning mode in pipefishes and seahorses (Syngnathidae)

Externally fertilizing fishes are predicted to invest heavily in testes, because large numbers of sperm should be favoured by the high risk of sperm competition from sneaker males, and/or the dilution of ejaculates when shed into open water. Using museum specimens, we measured testes mass and body mass of 83 mature males, belonging to 21 genera of the family Syngnathidae (pipefishes and seahorses). In this family all species show paternal care, ranging in degree from eggs being attached to the skin of the male, to eggs being completely enclosed and nurtured within a brood pouch. The former, 'unprotected' group, is thought to have external fertilization, whereas in the latter, 'protected' group, males fertilize the eggs internally in their brood pouch. Smaller relative testes investment was thus predicted for genera that have protected compared with unprotected brood care. However, we found this not to be the case. Instead, all genera showed the same relationship between testes and body mass, regardless of brooding type. The possible implications of this surprising result are discussed, including the possibility that the mode of fertilization might have been misjudged for the pouchless syngnathids.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 83 , 369–376.     

A kinetic spectrophotometric method for simultaneous determination of glycine and lysine by artificial neural networks

A spectrophotometric method for simultaneous analysis of glycine and lysine is proposed by application of neural networks on the spectral kinetic data. The method is based on the reaction of glycine and lysine with 1,2-naphthoquinone-4-sulfonate (NQS) in slightly basic medium. On the basis of the difference in the rate between the two reactions, these two amino acids can be determined simultaneously in binary mixtures. Feed-forward neural networks have been trained to quantify considered amino acids in mixtures under optimum conditions. In this way, a one-layer network was trained. Sigmoidal and linear transfer functions were used in the hidden and output layers, respectively. Linear calibration graphs were obtained in the concentration range of 1 to 25microgml(-1) for glycine and 1 to 19microgml(-1) for lysine. The analytical performance of this method was characterized by the relative standard error. The proposed method was applied to the determination of considered amino acids in synthetic samples.     

Interference of 16.7-Hz electromagnetic fields on measured electrocardiogram

The extent of electromagnetic interference (EMI) from 16.7-Hz alternate current power lines in the human surface electrocardiogram (ECG) was evaluated. Results showed a direct linear correlation between mean EMI and magnetic induction of 5.8-21 microT on a railroad platform (electric field: 270 V/m). EMI inside a railroad car (10 microT, 0 V/m) was comparable to the electromagnetic field at the platform. Inside a voltage transformer substation (0 microT, 2000 V/m) EMI occurred only when the ECG device was closer to the power line than the test person. Magnetic induction caused 16.7-Hz EMI to a degree that proper diagnosis of ECG-rhythms was rendered impossible.     

食用调和油中花生油含量的近红外光谱分析

采用偏最小二乘法(PLS)等方法建立了食用调和油中花生油含量定量分析的近红外光谱定标模型。采集食用调和油样品在4 000 cm-1~10 000 cm-1范围内的近红外漫反射光谱,光谱经一阶导数处理后,采用偏最小二乘法建立样品中花生油含量的定标模型,并用Leave-one-out内部交叉验证法对模型进行验证。模型相关系数为0.99961,校正均方根RMSEC为0.830%。比较不同光谱预处理方法对定标模型的影响,结果表明一阶导数Corr.coeff最好。采用不同的化学计量学方法建立的定标模型中以偏最小二乘回归法最理想。     

Model misspecification confounds the estimation of rates and exaggerates their time dependency

While welcoming the comment of Ho et al. ( 2015 ), we find little that undermines the strength of our criticism, and it would appear they have misunderstood our central argument. Here we respond with the purpose of reiterating that we are (i) generally critical of much of the evidence presented in support of the time‐dependent molecular rate (TDMR) hypothesis and (ii) specifically critical of estimates of μ derived from tip‐dated sequences that exaggerate the importance of purifying selection as an explanation for TDMR over extended timescales. In response to assertions put forward by Ho et al. ( 2015 ), we use panmictic coalescent simulations of temporal data to explore a fundamental assumption for tip‐dated tree shape and associated mutation rate estimates, and the appropriateness and utility of the date randomization test. The results reveal problems for the joint estimation of tree topology, effective population size and μ with tip‐dated sequences using beast . Given the simulations, beast consistently obtains incorrect topological tree structures that are consistent with the substantial overestimation of μ and underestimation of effective population size. Data generated from lower effective population sizes were less likely to fail the date randomization test yet still resulted in substantially upwardly biased estimates of rates, bringing previous estimates of μ from temporally sampled DNA sequences into question. We find that our general criticisms of both the hypothesis of time‐dependent molecular evolution and Bayesian methods to estimate μ from temporally sampled DNA sequences are further reinforced.     

Lack of support for the time‐dependent molecular evolution hypothesis

There is increasing momentum surrounding the hypothesis that rates of molecular evolution between individuals within contemporary populations are high, and that these rates decrease as a function of time, perhaps over several millions of years, before reaching stationarity. The implications of this are powerful, potentially reshaping our view of how climate history impacts upon both species distribution patterns and the geographic structuring of genetic variation within species. However, our assessment of the hypothesis reveals a lack of theoretical support and empirical evidence for hypothesized magnitudes of time‐dependent rates of molecular evolution, with much of the apparent rate changes coming from artefacts and biases inherent in the methods of rate estimation. Our assessment also reveals a problem with how serial sampling is implemented for mutation rate estimation using ancient DNA samples, rendering published estimates unreliable.     

Quantitative analysis of dynamic protein-protein interactions in planta by a floated-leaf luciferase complementation imaging (FLuCI) assay using binary Gateway vectors

Dynamic protein-protein interactions are essential in all cellular and developmental processes. Protein-fragment complementation assays allow such protein-protein interactions to be investigated in vivo. In contrast to other protein-fragment complementation assays, the split-luciferase (split-LUC) complementation approach facilitates dynamic and quantitative in vivo analysis of protein interactions, as the restoration of luciferase activity upon protein-protein interaction of investigated proteins is reversible. Here, we describe the development of a floated-leaf luciferase complementation imaging (FLuCI) assay that enables rapid and quantitative in vivo analyses of protein interactions in leaf discs floating on a luciferin infiltration solution after transient expression of split-LUC-labelled interacting proteins in Nicotiana benthamiana. We generated a set of eight Gateway-compatible split-LUC destination vectors, enabling fast, and almost fail-safe cloning of candidate proteins to the LUC termini in all possible constellations. We demonstrate their functionality by visualizing the well-established homodimerization of the 14-3-3 regulator proteins. Quantitative interaction analyses of the molybdenum co-factor biosynthesis proteins CNX6 and CNX7 show that the luciferase-based protein-fragment complementation assay allows direct real-time monitoring of absolute values of protein complex assembly. Furthermore, the split-LUC assay is established as valuable tool to investigate the dynamics of protein interactions by monitoring the disassembly of actin filaments in planta. The new Gateway-compatible split-LUC destination vector system, in combination with the FLuCI assay, provides a useful means to facilitate quantitative analyses of interactions between large numbers of proteins constituting interaction networks in plant cells.     

Development and calibration of bio-kinetic model for surfactant biodegradation with combined respirometric and titrimetric measurements

Substrate removal mechanism in aerobic activated sludge processes was lately modeled using the simultaneous storage and growth (SSAG) phenomenon. The SSAG model was further refined with titrimetric components and successfully calibrated using both respirometric and titrimetric measurements for common substrate acetate. However, the improved SSAG model calibration was not verified with other organic substrates. Furthermore, very few studies are available in the literature on surfactant bio-kinetics, which generally use off-line experimental measurements with limited model-based interpretation. Therefore, the aim of this paper is to demonstrate its applicability for surfactant biodegradation using on-line measurements. Batch experiments were conducted using sodium dodecyl sulfate (SDS) as a test surfactant. Model calibration was done successfully for three different SDS concentrations using respirometric, titrimetric and combined respirometric-titrimetric measurement approaches. The parameter estimation results from all three stated combinations were statistically evaluated and found to be very close validating the model.     

Phylogenetic relationships of the Cretaceous frog Beelzebufo from Madagascar and the placement of fossil constraints based on temporal and phylogenetic evidence

The placement of fossil calibrations is ideally based on the phylogenetic analysis of extinct taxa. Another source of information is the temporal variance for a given clade implied by a particular constraint when combined with other, well-supported calibrations. For example, the frog Beelzebufo ampinga from the Cretaceous of Madagascar has been hypothesized to be a crown-group member of the New World subfamily Ceratophryinae, which would support a Late Cretaceous connection with South America. However, phylogenetic analyses and molecular divergence time estimates based on other fossils do not support this placement. We derive a metric, Δt, to quantify temporal divergence among chronograms and find that errors resulting from mis-specified calibrations are localized when additional nodes throughout the tree are properly calibrated. The use of temporal information from molecular data can further assist in testing phylogenetic hypotheses regarding the placement of extinct taxa.