Early postnatal development of the visual cortex in mice with retinal degeneration

This study characterizes the early postnatal development of the visual neocortex in C3H/HeNRj mice. These mice are homozygous for the Pde6b mutation, which causes retinal degeneration starting from postnatal day 7 (P7). To monitor the development of the visual cortex between P3 and P28 we used eight antigens known to be expressed at different developmental stages (Nestin, tau3, β3- Tubulin, Calbindin, Doublecortin, MAP2, Parvalbumin and NeuN). Using semiquantitative analysis we traced the expression and localization of different developmental markers throughout the layers of the visual cortex. Cortical tissue sections corresponding to the first postnatal week (P3-P6) stained positively for Nestin, tau3, β3-Tubulin and Calbindin. These proteins are known to be involved in the migration of neural progenitor cells (NPCs) within the cortical plate. At the time of eye-opening (P14), Doublecortin, MAP2 and NeuN, markers for developing and maturing neurons involved in NPC differentiation are present. Between P9 and P21 Nestin and Calbindin disappear while NeuN and Parvalbumin expression increases in the course of visual neocortex development. The findings of this study provide a snapshot of the dynamic changes in cortex formation during early postnatal development. So far, it is the first investigation on the postnatal development of the mouse visual cortex. Our results indicate that in C3H/HeNRj mice retinal degeneration during these early stages may not influence the maturation of the visual cortex. Until P28 in this mouse strain, the development of the visual neocortex is in accordance with data from other mice (C57BL/6) without retinal degeneration. Whether in older individuals of the C3H/HeNRj strain the visual neocortex will show signs of functional impairment has to be shown by future work

Dynamical aspects of mean field plane rotators and the Kuramoto model

The Kuramoto model has been introduced in order to describe synchronization phenomena observed in groups of cells, individuals, circuits, etc... We look at the Kuramoto model with white noise forces: in mathematical terms it is a set of N oscillators, each driven by an independent Brownian motion with a constant drift, that is each oscillator has its own frequency, which, in general, changes from one oscillator to another (these frequencies are usually taken to be random and they may be viewed as a quenched disorder). The interactions between oscillators are of long range type (mean field). We review some results on the Kuramoto model from a statistical mechanics standpoint: we give in particular necessary and sufficient conditions for reversibility and we point out a formal analogy, in the N to infinity limit, with local mean field models with conservative dynamics (an analogy that is exploited to identify in particular a Lyapunov functional in the reversible set-up). We then focus on the reversible Kuramoto model with sinusoidal interactions in the N to infinity limit and analyze the stability of the non-trivial stationary profiles arising when the interaction parameter K is larger than its critical value K_c. We provide an analysis of the linear operator describing the time evolution in a neighborhood of the synchronized profile: we exhibit a Hilbert space in which this operator has a self-adjoint extension and we establish, as our main result, a spectral gap inequality for every K>K_c.Comment: 18 pages, 1 figur

The Comparative Osteology of the Petrotympanic Complex (Ear Region) of Extant Baleen Whales (Cetacea: Mysticeti)

Anatomical comparisons of the ear region of baleen whales (Mysticeti) are provided through detailed osteological descriptions and high-resolution photographs of the petrotympanic complex (tympanic bulla and petrosal bone) of all extant species of mysticete cetaceans. Salient morphological features are illustrated and identified, including overall shape of the bulla, size of the conical process of the bulla, morphology of the promontorium, and the size and shape of the anterior process of the petrosal. We place our comparative osteological observations into a phylogenetic context in order to initiate an exploration into petrotympanic evolution within Mysticeti.The morphology of the petrotympanic complex is diagnostic for individual species of baleen whale (e.g., sigmoid and conical processes positioned at midline of bulla in Balaenoptera musculus; confluence of fenestra cochleae and perilymphatic foramen in Eschrichtius robustus), and several mysticete clades are united by derived characteristics. Balaenids and neobalaenids share derived features of the bulla, such as a rhomboid shape and a reduced anterior lobe (swelling) in ventral aspect, and eschrichtiids share derived morphologies of the petrosal with balaenopterids, including loss of a medial promontory groove and dorsomedial elongation of the promontorium. Monophyly of Balaenoidea (Balaenidae and Neobalaenidae) and Balaenopteroidea (Balaenopteridae and Eschrichtiidae) was recovered in phylogenetic analyses utilizing data exclusively from the petrotympanic complex.This study fills a major gap in our knowledge of the complex structures of the mysticete petrotympanic complex, which is an important anatomical region for the interpretation of the evolutionary history of mammals. In addition, we introduce a novel body of phylogenetically informative characters from the ear region of mysticetes. Our detailed anatomical descriptions, illustrations, and comparisons provide valuable data for current and future studies on the phylogenetic relationships, evolution, and auditory physiology of mysticetes and other cetaceans throughout Earth's history