Evo-devo of human adolescence: beyond disease models of early puberty

Despite substantial heritability in pubertal development, much variation remains to be explained, leaving room for the influence of environmental factors to adjust its phenotypic trajectory in the service of fitness goals. Utilizing evolutionary development biology (evo-devo), we examine adolescence as an evolutionary life-history stage in its developmental context. We show that the transition from the preceding stage of juvenility entails adaptive plasticity in response to energy resources, other environmental cues, social needs of adolescence and maturation toward youth and adulthood. Using the evolutionary theory of socialization, we show that familial psychosocial stress fosters a fast life history and reproductive strategy rather than early maturation being just a risk factor for aggression and delinquency. Here we explore implications of an evolutionary-developmental-endocrinological-anthropological framework for theory building, while illuminating new directions for research

Coordination of Cell Polarity during Xenopus Gastrulation

Cell polarity is an essential feature of animal cells contributing to morphogenesis. During Xenopus gastrulation, it is known that chordamesoderm cells are polarized and intercalate each other allowing anterior-posterior elongation of the embryo proper by convergent extension (CE). Although it is well known that the cellular protrusions at both ends of polarized cells exert tractive force for intercalation and that PCP pathway is known to be essential for the cell polarity, little is known about what triggers the cell polarization and what the polarization causes to control intracellular events enabling the intercalation that leads to the CE. In our research, we used EB3 (end-binding 3), a member of +TIPs that bind to the plus end of microtubule (MT), to visualize the intracellular polarity of chordamesoderm cells during CE to investigate the trigger of the establishment of cell polarity. We found that EB3 movement is polarized in chordamesoderm cells and that the notochord-somite tissue boundary plays an essential role in generating the cell polarity. This polarity was generated before the change of cell morphology and the polarized movement of EB3 in chordamesoderm cells was also observed near the boundary between the chordamesoderm tissue and naïve ectoderm tissue or lateral mesoderm tissues induced by a low concentration of nodal mRNA. These suggest that definitive tissue separation established by the distinct levels of nodal signaling is essential for the chordamesodermal cells to acquire mediolateral cell polarity

On the ultimate shimming performance in the human brain

Purpose/Introduction: Improved shimming the human brain has attracted increasing interest in the recent years, using both conventional spherical harmonics (SH) of higher orders1 and multiple local coils2-8. Currently, the exact trade-off between the shim coil dimensions, the current and power requirements and the achievable shimming performance remains unclear. In this study we explore the impact of these factors on shimming the human brain. Subjects and Methods: B0 field map of the whole brain of one healthy volunteer was shimmed to the second order to account for the currently available shimming and define a valid starting point. The resultant field map was used as a target magnetic field. A stream function9 on a cylindrical surface of certain dimensions was then optimized to minimize the standard deviation of the residual magnetic field over the whole brain. During the optimization procedure, dissipated power of the coil was constrained by Pmax. All optimization problems were solved with the regularization tools10 for MATLAB (The MathWorks. Natick, USA). Considering the dimensions of a typical RF-shimming array, multicoil 7,8 and whole-body gradient coil, the radii of three cylindrical current-carrying surfaces were selected to be 105, 180 and 309 mm, with the lengths of 230, 300 and 503 mm, respectively. Results: Figure 1 shows the variation of standard deviations (SD) of the residual magnetic field inhomogeneity with regard to Pmax. In order to compare different shimming strategies, SDs achieved with global SH shimming are also marked by horizontal dotted lines. As seen, the variation of SDs for different shim coils present a similar tendency. Discussion/Conclusion: As seen in Fig. 1, for coils of smaller radius less power is required to achieve a certain shimming fideliy. Alternatively, given the power limit, a decision on the coil geometry can be made. The presented coil layouts demonstrate the importance of the certain areas of the current carrying surface, e.g. in the low face region or areas close to ears, which may guide future designs of shim arrays with irregularly-shaped coil elements or combined RF-shimming arrays

Design of a shim coil array matched to the human brain anatomy

Purpose The purpose of this study is to introduce a novel design method of a shim coil array specifically optimized for whole brain shimming and to compare the performance of the resulting coils to conventional spherical harmonic shimming. Methods The proposed design approach is based on the stream function method and singular value decomposition. Eighty‐four field maps from 12 volunteers measured in seven different head positions were used during the design process. The cross validation technique was applied to find an optimal number of coil elements in the array. Additional 42 field maps from 6 further volunteers were used for an independent validation. A bootstrapping technique was used to estimate the required population size to achieve a stable coil design. Results Shimming using 12 and 24 coil elements outperforms fourth‐ and fifth‐order spherical harmonic shimming for all measured field maps, respectively. Coil elements show novel coil layouts compared to the conventional spherical harmonic coils and existing multi‐coils. Both leave‐one‐out and independent validation demonstrate the generalization ability of the designed arrays. The bootstrapping analysis predicts that field maps from approximately 140 subjects need to be acquired to arrive at a stable design. Conclusions The results demonstrate the validity of the proposed method to design a shim coil array matched to the human brain anatomy, which naturally satisfies the laws of electrodynamics. The design method may also be applied to develop new shim coil arrays matched to other human organs

Design of a shimming coil matched to the human brain anatomy

We propose a novel design method of a shim coil specially optimized for the human brain. Numerical results demonstrate the validity of the method. The resulting coil layouts can pave a way towards a novel shimming coil specifically intended for human brain shimming. The proposed design method can be extended to other applications and organs