Genetic structure of a widespread alpine shrub Rhododendron aureum (Ericaceae) across East Asia

Journal of Plant Research - The vast territory of East Asia, including southwestern Beringia, is considered to have been almost ice free during the Pleistocene. Cold-resistant flora may have...     

A mathematical model of periodic processes in membranes (with application to cell cycle regulation)

A mathematical model of the regulation of the cell cycle by the plasma membrane is suggested. The model is based on the hypothesis that structural transitions of the cell membrane play an important role in the regulation of cell division. Conditions of transition from the proliferating state to the resting state and back are investigated. Possible qualitative differences between models of the cell cycle of a normal and a tumour cell are pointed out.     

On the possibility of reduction of dissipative structure models to a simple form

A multicomponent reaction-diffusion system containing two different space scales (contrasting system) is considered. It is shown that if the system answers several conditions enumerated, it can be reduced to a bicomponent system which describes a dissipative structure either of a peak or of a step type. While in the first case the original and the final systems are equivalent only in the neighbourhood of zero, in the second case the equivalence is more general as the solution of these systems does not leave the region for which the procedure of reduction was developed.     

On the possible mechanism of cell cycle synchronization

The influence of exchanges of lipids and antioxidants (AO) between the cells on the cell proliferation is studied in the frame of the membrane model of the cell cycle. It is shown theoretically that the easy-oxidative lipids exchange favours the synchronization of cell division, while the AO exchange leads to desynchronization. The analytical consideration and some numerical estimations are carried out. The qualitative consequences accessible to experimental verification are discussed.     

Development of magnocellular neurosecretory neurons in embryonic hypothalamic tissue transplanted into the cavity of the 3d cerebral ventricle of adult rats

Magnocellular neurosecretory cell (MSC) ontogenesis was comparatively assessed in normal rat hypothalamus and in fetal hypothalamic tissue transplanted into the third ventricle of the adult rat brain. 3H-thymidine uptake has shown that the time of origin of NSC in grafted tissue and supraoptic nucleus of normal rat fetuses was similar. NSC pericarions in grafts were well developed and contained neurosecretory material (NSM). Nuclear and nucleolar volumes did not differ from those in adult animals. Water deprivation was followed by a significant increase in nuclear and nucleolar volumes and NSM content in pericarions of grafted tissue, which suggests that raised synthetic activity was not accompanied by an increased NSM release. It is concluded that proliferation and specific differentiation of NSC precursor cells are invariably determined by genetic factors. The origin of neurosecretory nuclei and their specific connections is considerably influenced by conditions of tissue surroundings.