Phylogeography and sympatric differentiation of the Arctic charr Salvelinus alpinus (L.) complex in Siberia as revealed by mtDNA sequence analysis.

Sequence variation in the mtDNA control region of Arctic charr Salvelinus alpinus and Dolly Varden Salvelinus malma from 56 Siberian and North American populations was analysed to assess their phylogeographic relationships and the origins of sympatric forms. Phylogenetic trees confirm the integrity of phylogroups reported in previous mtDNA studies except that the Siberian group does not separate as a single cluster. Haplotype network analysis indicates the proximity of Siberian and Atlantic haplotypes.

A model of self-maintenance of in vivo malignant growth not dependent on tumour type or origin: syndrome of everlasting wound healing.

The common mechanism of permanent growth maintenance in all types of malignant tumours is proposed. According to the model, the main event, stimulating tumour growth is the stochastic but permanent death of a proportion of tumour cells as a result of inherent genetic instability of tumour cell genome (chromosome fragility). Dead cells trigger the complex and multicomponent process of wound healing, manifesting in stimulation of cell proliferation, angiogenesis, cell migration and other events.

Neocortical grafts receive functional afferents from the same neurons of the thalamus which have innervated the visual cortex replaced by the graft in adult rats.

Electrophysiological and anatomical studies were carried out in parallel to investigate the ability of lateral geniculate body neurons to regenerate axons damaged by the removal of the primary visual cortex and to innervate graft neurons functionally after transplantation of fetal neocortical tissue to a lesion cavity in the brain of adult rats. In electrophysiological experiments neurons of a large portion of the transplants (14/35) displayed visual responses with characteristics resembling closely those of normal primary visual cortex; these transplants also displayed a different degree of restoration of topographically organized visual field representations on them. To demonstrate anatomical regeneration of inputs from the host lateral geniculate body to the graft, injections of FluoroGold were made before grafting into the intact visual cortex for retrograde labeling of the lateral geniculate body neurons.

Retinal afferents innervate functionally tectal but not neocortical grafts placed in lesioned superior colliculus of adult rats.

Solid pieces of tectum or occipital neocortex derived from 17-day rat fetuses were placed over the lesioned right superior colliculus (SC) in adult rats as sheets retaining the internal structure of the embryonal tissue. The upper laminae of the recipient's SC (approximately up to stratum opticum) were removed by aspiration after the neocortex overlying the SC was aspirated out. Two to 5 months after the operation a microelectrode study of the neuronal electrical activity in the grafts was performed.