Co-ordinating retinal histogenesis: early cell cycle exit enhances early cell fate determination in the Xenopus retina

The laminar arrays of distinct cell types in the vertebrate retina are built by a histogenic process in which cell fate is correlated with birth order. To explore this co-ordination mechanistically, we altered the relative timing of cell cycle exit in the developing Xenopus retina and asked whether this affected the activity of neural determinants. We found that Xath5, a bHLH proneural gene that promotes retinal ganglion cell (RGC) fate, ( Kanekar, S., Perron, M., Dorsky, R., Harris, W. A., Jan, L. Y., Jan, Y. N. and Vetter, M. L. (1997) Neuron 19, 981-994), does not cause these cells to be born prematurely. To drive cells out of the cell cycle early, therefore, we misexpressed the cyclin kinase inhibitor, p27Xic1. We found that early cell cycle exit potentiates the ability of Xath5 to promote RGC fate. Conversely, the cell cycle activator, cyclin E1, which inhibits cell cycle exit, biases Xath5-expressing cells toward later neuronal fates. We found that Notch activation in this system caused cells to exit the cell cycle prematuely, and when it is misexpressed with Xath5, it also potentiates the induction of RGCs. The potentiation is counteracted by co-expression of cyclin E1. These results suggest a model of histogenesis in which the activity of factors that promote early cell cycle exit enhances the activity of factors that promote early cellular fates

Phase diagram at finite temperature and quark density in the strong coupling limit of lattice QCD for color SU(3)

We study the phase diagram of quark matter at finite temperature (T) and finite chemical potential (mu) in the strong coupling limit of lattice QCD for color SU(3). We derive an analytical expression of the effective free energy as a function of T and mu, including baryon effects. The finite temperature effects are evaluated by integrating over the temporal link variable exactly in the Polyakov gauge with anti-periodic boundary condition for fermions. The obtained phase diagram shows the first order phase transition at low temperatures and the second order phase transition at high temperatures separated by the tri-critical point in the chiral limit. Baryon has effects to reduce the effective free energy and to extend the hadron phase to a larger mu direction at low temperatures.Comment: 18 pages, 10 figure

Water balance in Haplic Cambisols under forest and pasture in the Bonfim watershed: mountainous region of Rio de Janeiro state.

To estimate the water volumes of the main components of BH in a Haplic Cambisol in forests and pastures in the Bonfim River basin, mountainous region of RJ. Estimar os volumes de água dos principais componentes do BH num Cambissolo Háplico em florestas e pastagens na bacia do Rio Bonfim, região serrana do RJ.Também publicado em português. Título em português: Balanço hídrico em Cambissolos Háplicos sob florestas e pastagens na bacia hidrográfica do Bonfim: região serrana do estado do Rio de Janeiro

Spin observables in three-body direct nuclear reactions

Direct nuclear reactions $\vec{d}+A$ and $\vec{p}+(An)$ are described in the framework of three-body Faddeev-type equations. Differential cross section and analyzing powers are calculated using several optical potential models and compared with the experimental data. Quite satisfactory agreement is found except for few systematic discrepancies.Comment: Expanded theory sectio

Análise de cenários com proposição de medidas de recuperação ambiental para a micro-bacia do Tijuco Preto, São Carlos-SP

O artigo objetiva analisar cenários ambientais para compor o Plano Diretor do Município de São Carlos-SP com medidas de recuperação ambiental para bacias urbanas a partir de simulações hidrológicas. As medidas propostas incluem medidas compensatórias para micro e macro-drenagem. A metodologia utiliza base regional para espacializar bacias embutidas com uma classificação de uso e ocupação do solo para os anos: 1962, 1972 e 1998. São simulados cenários retrospectivos de 50 anos, 40 anos e 15 anos, e cenários prospectivos de 10 anos, com (CPD) e sem Plano Diretor (SPD). O resultados para o planejamento ambiental (CPD) indicam melhorias na carga de poluição hídrica e prevê a recuperação das funções hidrológicas e ambientais. Recomendam-se avaliar novos cenários de planejamento e instrumentação de monitoramento para bacias sem dados, conforme o programa PUB - Predictions in Ungauged Basins (Sivapalan et al. 2003)

Enhanced bone-forming activity of side population cells in the periodontal ligament.

Regeneration of alveolar bone is critical for the successful treatment of periodontal diseases. The periodontal ligament (PDL) has been widely investigated as a source of cells for the regeneration of periodontal tissues. In the present study where we attempted to develop an effective strategy for alveolar bone regeneration, we examined the osteogenic potential of side population (SP) cells, a stem cell-containing population that has been shown to be highly abundant in several kinds of tissues, in PDL cells. Isolated SP cells from the rat PDL exhibited a superior ability to differentiate into osteoblastic cells compared with non-SP (NSP) and unsorted PDL cells in vitro. The mRNA expressions of osteoblast markers and bone morphogenetic protein (BMP) 2 were significantly upregulated in SP cells and were further increased by osteogenic induction. To examine the boneforming activity of SP cells in vivo, PDL SP cells isolated from green fluorescent protein (GFP)-transgenic rats were transplanted with hydroxyapatite (HA) disks into wild-type animals. SP cells exhibited a high ability to induce the mineralized matrix compared with NSP and unsorted PDL cells. At 12 weeks after the implantation, some of the pores in the HA disks with SP cells were filled with mineralized matrices, which were positive for bone matrix proteins, such as osteopontin, bone sialoprotein, and osteocalcin. Furthermore, osteoblast- and osteocyte-like cells on and in the bone-like mineralized matrices were GFP positive, suggesting that the matrices were directly formed by the transplanted cells. These results suggest that PDL SP cells possess enhanced osteogenic potential and could be a potential source for cell-based regenerative therapy for alveolar bone

Elastic and Inelastic Scattering of 35-MeV Neutrons by 32S

開始ページ、終了ページ: 冊子体のページ付

Non-resonant direct p- and d-wave neutron capture by 12C

Discrete gamma-rays from the neutron capture state of 13C to its low-lying bound states have been measured using pulsed neutrons at En = 550 keV. The partial capture cross sections have been determined to be 1.7+/-0.5, 24.2+/-1.0, 2.0+/-0.4 and 1.0+/-0.4 microb for the ground (1/2-), first (1/2+), second (3/2-) and third (5/2+) excited states, respectively. From a comparison with theoretical predictions based on the non-resonant direct radiative capture mechanism, we could determine the spectroscopic factor for the 1/2+ state to be 0.80 +/- 0.04, free from neutron-nucleus interaction ambiguities in the continuum. In addition we have detected the contribution of the non-resonant d-wave capture component in the partial cross sections for transitions leading to the 1/2- and 3/2- states. While the s-wave capture dominates at En < 100 keV, the d-wave component turns out to be very important at higher energies. From the present investigation the 12C(n,gamma)13C reaction rate is obtained for temperatures in the range 10E+7 - 10E+10 K.Comment: Accepted for publication in Phys. Rev. C. - 16 pages + 8 figure