Biomechanical differences of Coflex-F and pedicle screw fixation combined with TLIF or ALIF – a finite element study

Lumbar interbody fusion is a common procedure for treating lower back pain related to degenerative disc diseases. The Coflex-F is a recently developed interspinous spacer, the makers of which claim that it can provide stabilisation similar to pedicle screw fixation. Therefore, this study compares the biomechanical behaviour of the Coflex-F device and pedicle screw fixation with transforaminal lumbar interbody fusion (TLIF) or anterior lumbar interbody fusion (ALIF) surgeries by using finite element analysis. The results show that the Coflex-F device combined with ALIF surgery can provide stability similar to the pedicle screw fixation combined with TLIF or ALIF surgery. Also, the posterior instrumentations (Coflex-F and pedicle screw fixation) combined with TLIF surgery had lower stability than when combined with ALIF surgery.     

Neural origins of basal diencephalon in teleost fishes: Radial versus tangential migration

Teleost fish possess large lateral diencephalic regions such as the torus lateralis, the preglomerular area, and the diffuse nucleus of the hypothalamic inferior lobe. While their developmental origins traditionally were suggested to lie in diencephalic midline ventricular proliferative zones, more remote midbrain origins were reported recently. This review focuses on the preglomerular region and summarizes the data supporting three existing hypotheses on its developmental origins. The conclusion is that lateral torus, diffuse nucleus of hypothalamic inferior lobe, and preglomerular region are part of the diencephalon, but have a multiregional origin provided by both radially and tangentially migrating cells forming these regions in question.     

Bayesian Analysis of Growth Curves Using Mixed Models Defined by Stochastic Differential Equations

Summary Growth curve data consist of repeated measurements of a continuous growth process over time in a population of individuals. These data are classically analyzed by nonlinear mixed models. However, the standard growth functions used in this context prescribe monotone increasing growth and can fail to model unexpected changes in growth rates. We propose to model these variations using stochastic differential equations (SDEs) that are deduced from the standard deterministic growth function by adding random variations to the growth dynamics. A Bayesian inference of the parameters of these SDE mixed models is developed. In the case when the SDE has an explicit solution, we describe an easily implemented Gibbs algorithm. When the conditional distribution of the diffusion process has no explicit form, we propose to approximate it using the Euler–Maruyama scheme. Finally, we suggest validating the SDE approach via criteria based on the predictive posterior distribution. We illustrate the efficiency of our method using the Gompertz function to model data on chicken growth, the modeling being improved by the SDE approach.     

Tail posterior probability for inference in pairwise and multiclass gene expression data

We consider the problem of identifying differentially expressed genes in microarray data in a Bayesian framework with a noninformative prior distribution on the parameter quantifying differential expression. We introduce a new rule, tail posterior probability, based on the posterior distribution of the standardized difference, to identify genes differentially expressed between two conditions, and we derive a frequentist estimator of the false discovery rate associated with this rule. We compare it to other Bayesian rules in the considered settings. We show how the tail posterior probability can be extended to testing a compound null hypothesis against a class of specific alternatives in multiclass data.     

A new iridescent tarantula of the genus Thrigmopoeus Pocock, 1899 from Western Ghats,India

A distinctive new species of ground burrowing tarantula from Western Ghats endemic genus Thrigmopoeus is described from Kerala State, India. Thrigmopoeus psychedelicus sp. nov. differs from putative species of the genus in the adults being black overall with a metallic blue lustre on the carapace and abdomen. Females of Thrigmopoeus psychedelicus sp. nov. exhibit polychromatism. Juveniles and sub-adults are paler with vibrant maroon colouration on its abdomen whereas adult females are much darker and lack vibrant colouration as sub-adults.     

Activation of catalase by apelin prevents oxidative stress-linked cardiac hypertrophy

Adipose tissue secretes a variety of bioactive factors, which can regulate cardiomyocyte hypertrophy via reactive oxygen species (ROS). In the present study we investigated whether apelin affects ROS-dependent cardiac hypertrophy. In cardiomyocytes apelin inhibited the hypertrophic response to 5-HT and oxidative stress induced by 5-HT- or H₂O₂ in a dose-dependent manner. These effects were concomitant to the increase in mRNA expression and activity of catalase. Chronic treatment of mice with apelin attenuated pressure-overload-induced left ventricular hypertrophy. The prevention of hypertrophy by apelin was associated with increased myocardial catalase activity and decreased plasma lipid hydroperoxide, as an index of oxidative stress. These results show that apelin behaves as a catalase activator and prevents cardiac ROS-dependent hypertrophy.     

Preliminary Studies on the Optimum Shape of Dental Bridges

Several pre-existing anterior and posterior dental bridge models using Finite elements and the new ceramic material In-Ceram have been developed. The mechanical behaviour of these models has been compared with optimised profiles obtained from a newly developed evolutionary algorithm known as Evolutionary Structural Optimisation (ESO).

The results show that the mechanical behaviour of the bridges was mainly restricted by the properties of the porcelain veneer and the design of the bridges themselves. For the case of the anterior bridge, it was found that there existed a specific thickness of veneer that minimised the maximum principal stress. This was related to peak stresses that occurred at the bridge surface. Peak stresses also occurred in the material interface between the In-Ceram and the veneer. These extreme stresses were attributed to the notch size and shape. For the case of the posterior bridge, it was concluded that the shape of the bottom of the Pontic tooth is crucial in reducing the magnitude of the maximum principal tensile stress. The ESO process produced bridge designs which have uniformly stressed bridge surfaces, and which also have significantly lower maximum principal tensile stresses compared to the pre-existing designs (up to 44%).     

Immunohistochemical localization of vasoactive intestinal peptide (VIP) in the circumventricular organs of the rat

Summary The indirect peroxidase-antiperoxidase immunohistochemical technique was used to investigate the possible presence of vasoactive intestinal peptide (VIP) in the circumventricular organs of the rat. Considerable numbers of VIP-immunoreactive fibers were seen in the pineal gland. A moderate amount of VIP-immunoreactive fibers was present in the median eminence, the posterior lobe of the pituitary and the area postrema, but only few fibers were found in the organum vasculosum laminae terminalis. No immunoreactivity was observed in the subfornical organ or the subcommissural organ. The circumventricular organs investigated were completely free of VIP-immunoreactive perikarya. In the circumventricular organs, VIP-immunoreactive fibers were visible between the parenchymal cells and in the perivascular spaces. The presence of coarse VIP-immunoreactive terminals in apposition to the portal vessels in the external layer of the median eminence indicates that VIP may be secreted directly into the pituitary portal circulation, thus influencing the anterior pituitary cells. The presence of large VIP-immunoreactive boutons in the posterior lobe of the pituitary suggests a secretion of VIP directly into the systemic circulation. In the pineal gland, a dense innervation by VIP-immunoreactive fibers was found in the peripheral superficial part of organ, with fibers penetrating into its central portion where they mainly terminate near in vicinity of the capillaries. In the area postrema, VIP-immunoreactive material was mainly found at the ventral border of the organ. In addition to the secretion of VIP into the bloodstream via the circumventricular organs, this study provides evidence that VIP exerts specific influence on the cellular elements of these organs.     

Bayesian estimation of inverse dose response

SUMMARY: Inverse dose-response estimation refers to the inference of an effective dose of some agent that gives a desired probability of response, say 0.5. We consider inverse dose response for two agents, an application that has not received much attention in the literature. Through the posterior profiling technique (Hsu, 1995, The Canadian Journal of Statistics 23, 399-410), we propose a Bayesian method in which we approximate the marginal posterior distribution of an effective dose using a profile posterior distribution, and obtain the maximum a posteriori (MAP) estimate for the effective dose. We then employ an adaptive direction sampling algorithm to obtain the highest posterior density (HPD) credible region for the effective dose. Using the MAP and HPD estimates, investigators will be able to simultaneously calibrate the levels of two agents in dose-response studies. We illustrate our proposed Bayesian method through a simulation study and two practical examples.     

A site- and time-heterogeneous model of amino acid replacement

We combined the category (CAT) mixture model (Lartillot N, PhilippeH. 2004) and the nonstationary break point (BP) model (BlanquartS, Lartillot N. 2006) into a new model, CAT–BP, accountingfor variations of the evolutionary process both along the sequenceand across lineages. As in CAT, the model implements a mixtureof distinct Markovian processes of substitution distributedamong sites, thus accommodating site-specific selective constraintsinduced by protein structure and function. Furthermore, as inBP, these processes are nonstationary, and their equilibriumfrequencies are allowed to change along lineages in a correlatedway, through discrete shifts in global amino acid compositiondistributed along the phylogenetic tree. We implemented theCAT–BP model in a Bayesian Markov Chain Monte Carlo frameworkand compared its predictions with those of 3 simpler models,BP, CAT, and the site- and time-homogeneous general time–reversible(GTR) model, on a concatenation of 4 mitochondrial proteinsof 20 arthropod species. In contrast to GTR, BP, and CAT, whichall display a phylogenetic reconstruction artifact positioningthe bees Apis mellifera and Melipona bicolor among chelicerates,the CAT–BP model is able to recover the monophyly of insects.Using posterior predictive tests, we further show that the CAT–BPcombination yields better anticipations of site- and taxon-specificamino acid frequencies and that it better accounts for the homoplasiesthat are responsible for the artifact. Altogether, our resultsshow that the joint modeling of heterogeneities across sitesand along time results in a synergistic improvement of the phylogeneticinference, indicating that it is essential to disentangle thecombined effects of both sources of heterogeneity, in orderto overcome systematic errors in protein phylogenetic analyses.