Role of the tubulin-microtubule system in lymphocyte activation

The role of the tubulin-microtubule system was examined in human peripheral blood leukocytes after activation with phytohemagglutinin (PHA). Soluble tubulin and microtubules were measured with a [(3)H]colchicine-binding assay. It was found that the tubulin content of PHA-activated lymphocytes was consistently increased relative to total protein content after 36 h of culture. There was no increase in the proportion of total tubulin synthesis which was present as microtubules at 36 h. Nevertheless, as a result of increased tubulin synthesis, there was a two-to three-fold increase in total microtubular mass. Colchicine, which disrupts microtubles, was used to assess the role of microtubule assembly in the sequence of events which follow lymphocyte activation, namely lymphokine release, protein synthesis, RNA synthesis, and DNA synthesis. Colchicine consistently inhibited DNA synthesis but did not inhibit release of the lymphokine, osteoclast activating factor (OAF). Protein and RNA syntheses were inhibited much less than DNA synthesis. The fact that some effects of PHA on lymphocytes appear to require intact microtubules and at least one does not suggest that the microtubule dependent step in PHA-stimulated lymphocyte activation occurs at a stage after propagation of the signal from the membrane to the cell interior.     

Dependence of root biomass accumulation on the content and metabolism of cytokinins in ethylene-insensitive plants

Diverse functions of ethylene in plants may depend on its ability to interact with other hormones. We studied the participation of ethylene in the regulation of accumulation and metabolism of cytokinins comparing ethylene-insensitive mutant plants of arabidopsis (Arabidopsis thaliana [L.] Heynh., etr1-1) with the plants of original ecotype Columbia (Col-0). Because cytokinins can regulate growth of both leaves and roots, we determined the weights of these organs and the ratio between them. The content of zeatin and its riboside in the roots of etr1-1 plants was two times greater than in Col-0 plants, which could be accounted for by inhibition of conversion of these forms of cytokinins into 9-N-glucosides. In the leaves of mutant plants, expression of IPT3 gene responsible for the synthesis of cytokinins was more intense than in Col-0 plants, which could also contribute to a rise in the content of cytokinins. In this case, the weight of roots in etr1-1 mutants was lower than in the plants of original ecotype. Because high concentrations of cytokinins can inhibit root growth, suppression of accumulation of their biomass in mutant plants may be related to a greater content of cytokinins therein. The obtained results suggest that ethylene can suppress accumulation of cytokinins and, thereby, maintain redistribution of biomass in favor of the roots, which is important for plant adaptation to a shortage of water and ions.     

Simulated brain tumor growth dynamics using a three-dimensional cellular automaton

We have developed a novel and versatile three-dimensional cellular automaton model of brain tumor growth. We show that macroscopic tumor behavior can be realistically modeled using microscopic parameters. Using only four parameters, this model simulates Gompertzian growth for a tumor growing over nearly three orders of magnitude in radius. It also predicts the composition and dynamics of the tumor at selected time points in agreement with medical literature. We also demonstrate the flexibility of the model by showing the emergence, and eventual dominance, of a second tumor clone with a different genotype. The model incorporates several important and novel features, both in the rules governing the model and in the underlying structure of the model. Among these are a new definition of how to model proliferative and non-proliferative cells, an isotropic lattice, and an adaptive grid lattice.     

A revision of Aceratherium blanfordi Lydekker, 1884 (Mammalia: Rhinocerotidae) from the Early Miocene of Pakistan: postcranials as a key

Rhinocerotids are particularly abundant and diversified in Neogene deposits of the Indian subcontinent, but their systematics is far from being well defined. Based on the revision of old collections and new findings from the Early Miocene of the Bugti Hills and Zinda Pir, Pakistan, ‘Aceratherium blanfordi Lydekker, 1884’ is a chimera, consisting of two dentally convergent but postcranially distinct rhinocerotid taxa: Pleuroceros blanfordi and Mesaceratherium welcommi sp. nov. Postcranial features appear to be much more diagnostic than craniodental morphology in this case. A phylogenetic analysis based on 282 morphological characters scored for 28 taxa (four outgroups and ingroup including both taxa of interest and a ‘branching group’) strengthens this statement and supports Pleuroceros and Mesaceratherium as monophyletic genera within Rhinocerotinae. Both genera are recognized for the first time outside Europe. In the Bugti Hills, P. blanfordi and M. welcommi are part of an exceptionally diversified rhinocerotid fauna, with up to nine species associated in the same locality (Kumbi 4f). This rhinocerotid assemblage confirms the earliest Miocene age (Agenian/Aquitanian) of the upper member of the Chitarwata Formation as a whole. Coeval homotaxic rhinocerotid faunas from Europe (France, Czech Republic) and East Africa (Uganda, Kenya) support broad and sustainable rhinocerotid interchanges amongst South Asia, Europe, and Africa under compatible environmental conditions throughout earliest Miocene times. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 160 , 139–194.     

Immunohistological localization and quantification of IAA in studies of root growth regulation

The content and distribution of auxins were studied in gravistimulated roots of maize (Zea mays L.) and primary roots of 7-day-old wheat (Triticum durum Desf.) seedlings, which branching was enhanced by excision of adventitious roots. IAA localization was observed immunohistochemically, using specific anti-IAA antibody in combination with second (anti-species) antibody labeled with colloidal gold. Differences in the IAA content (staining intensity) were found between upper and lower parts of gravistimulated maize roots. We also observed IAA accumulation in the primary wheat root after adventitious root excision; the cells of lateral root primordia were characterized by more intense IAA staining. The role of auxin redistribution in plants for lateral root initiation and development is discussed.     

Role of auxins and cytokinins in the development of lateral roots in wheat plants with several roots removed

The removal of four of five roots of 7–8-day-old wheat plants resulted in the activation of lateral root growth and the initiation of lateral root primordia on the remained root as compared to the main root of intact plants. The extent of this growth response depended on placing cut surface above or beneath the surface of the nutrient solution. The measurement of the IAA and cytokinin contents showed accumulation of these hormones in the root of experimental plants as compared to the main root of intact plants. IAA accumulation was correlated with the number of lateral roots and their primordia. The analysis of hormonal balance and their transport from the shoot to the root permits discussing the involvement of these hormones and their interaction in the control of root growth at the stages of both primordium initiation and development and lateral root elongation.     

Characterization of the Novel Plant Growth-Stimulating Strain Advenella kashmirensis IB-K1 and Evaluation of Its Efficiency in Saline Soil

Microbiology - The strain of facultative chemolithotrophic bacteria isolated from soil within the aphotic zone of the Kinderlinskaya Cave (Southern Urals, Russia) was identified as member of the...