2,498 research outputs found
Preliminary data on the geographical distribution of Drosophila Species within Morphoclimatic Domains of Brazil
Metabolic adjustments in two Amazonian cichlids exposed to hypoxia and anoxia.
The effects of graded hypoxia on the physiological and biochemical responses were examined in two closely related species of cichlids of the Amazon: Astronotus crassipinnis and Symphysodon aequifasciatus. Ten fish of each species were exposed to graded hypoxia for 8 h in seven oxygen concentrations (5.92, 3.15, 1.54, 0.79, 0.60, 0.34, and 0.06 mg O2 L- 1), with the aim to evaluate hypoxia tolerance and metabolic adjustments, where plasma glucose and lactate levels, hepatic and muscle glycogen contents, and maximum enzyme activities (PK, LDH, MDH and CS) in skeletal and cardiac muscles were measured. Another experimental set was done to quantify oxygen consumption (MO2) and opercular movements in two oxygen concentrations. Hypoxia tolerance differed between the two species. Astronotus crassipinnis was able to tolerate anoxia for 178 min while S. aequifasciatus was able to withstand 222 min exposure in deep hypoxia (0.75 mg O2 L- 1). Suppressed MO2 was observed during exposure to 0.34 (A. crassipinnis) and 0.79 mg O2 L- 1 (S. aequifasciatus), while opercular movements increased in both species exposed to hypoxia. Higher levels of muscle and liver glycogen and larger hypoxia-induced increases in plasma glucose and lactate were observed in A. crassipinnis, which showed a higher degree of hypoxia tolerance. Changes in enzyme levels were tissue-specific and differed between species suggesting differential abilities in down-regulating oxidative pathways and increasing anaerobic metabolism. Based on the present data, we conclude that these animals are good anaerobes and highly adapted to their environment, which is allowed by their abilities to regulate metabolic pathways and adjust their enzyme levels
Modelling Circumbinary Gas Flows in Close T Tauri Binaries
Young close binaries open central gaps in the surrounding circumbinary
accretion disc, but the stellar components may still gain mass from gas
crossing through the gap. It is not well understood how this process operates
and how the stellar components are affected by such inflows. Our main goal is
to investigate how gas accretion takes place and evolves in close T Tauri
binary systems. In particular, we model the accretion flows around two close T
Tauri binaries, V4046 Sgr and DQ Tau, both showing periodic changes in emission
lines, although their orbital characteristics are very different. In order to
derive the density and velocity maps of the circumbinary material, we employ
two-dimensional hydrodynamic simulations with a locally isothermal equation of
state. The flow patterns become quasi-stable after a few orbits in the frame
co-rotating with the system. Gas flows across the circumbinary gap through the
co-rotating Lagrangian points, and local circumstellar discs develop around
both components. Spiral density patterns develop in the circumbinary disc that
transport angular momentum efficiently. Mass is preferentially channelled
towards the primary and its circumstellar disc is more massive than the disc
around the secondary. We also compare the derived density distribution to
observed line profile variability. The line profile variability tracing the gas
flows in the central cavity shows clear similarities with the corresponding
observed line profile variability in V4046 Sgr, but only when the local
circumstellar disc emission was excluded. Closer to the stars normal
magnetospheric accretion may dominate while further out the dynamic accretion
process outlined here dominates. Periodic changes in the accretion rates onto
the stars can explain the outbursts of line emission observed in eccentric
systems such as DQ Tau.Comment: Accepted for publication in MNRA
Change in male secondary sexual characters in artificial interspecific hybrid populations.
Prognostic significance of serine-phosphorylated STAT3 expression in pT1-T2 oral tongue carcinoma
Objectives. Phosphorylated (activated) STAT3 (pSTAT3) is a regulator of numerous genes that play an essential part in the onset, development and progression of cancer; it is involved in cell proliferation and preventing apoptosis, and in invasion, angiogenesis, and the evasion of immune surveillance. This study aimed mainly to investigate the potential prognostic role of pSTAT3 expression in oral tongue squamous cell carcinoma (SCC). Methods. Phospho-ser727 STAT3 immunolabeling was correlated with prognostic parameters in 34 consecutive cases of pT1\u2013T2 tongue SCCs undergoing primary surgery. Computer-based image analysis was used for the immunohistochemical reactions analysis. Results. Statistical analysis showed a difference in disease-free survival (DFS) when patients were stratified by pN status (P=0.031). Most tumors had variable degrees (mean\ub1SD, 80.7%\ub123.8%) of intense nuclear immunoreaction to pSTAT3. Our findings rule out any significant association of serine-phosphorylated nuclear STAT3 expression with tumor stage, grade, lymph node metastasis, recurrence rate, or DFS. Conclusion. In spite of these results, it is worth further investigating the role of pSTAT3 (serine-and tyrosine-pSTAT3) in oral tongue SCC in larger series because preclinical models are increasingly showing that several anticancer strategies would benefit from STAT3 phosphorylation inhibition
Modelling Circumbinary Gas Flows in Close T Tauri Binaries
Young close binaries open central gaps in the surrounding circumbinary
accretion disc, but the stellar components may still gain mass from gas
crossing through the gap. It is not well understood how this process operates
and how the stellar components are affected by such inflows. Our main goal is
to investigate how gas accretion takes place and evolves in close T Tauri
binary systems. In particular, we model the accretion flows around two close T
Tauri binaries, V4046 Sgr and DQ Tau, both showing periodic changes in emission
lines, although their orbital characteristics are very different. In order to
derive the density and velocity maps of the circumbinary material, we employ
two-dimensional hydrodynamic simulations with a locally isothermal equation of
state. The flow patterns become quasi-stable after a few orbits in the frame
co-rotating with the system. Gas flows across the circumbinary gap through the
co-rotating Lagrangian points, and local circumstellar discs develop around
both components. Spiral density patterns develop in the circumbinary disc that
transport angular momentum efficiently. Mass is preferentially channelled
towards the primary and its circumstellar disc is more massive than the disc
around the secondary. We also compare the derived density distribution to
observed line profile variability. The line profile variability tracing the gas
flows in the central cavity shows clear similarities with the corresponding
observed line profile variability in V4046 Sgr, but only when the local
circumstellar disc emission was excluded. Closer to the stars normal
magnetospheric accretion may dominate while further out the dynamic accretion
process outlined here dominates. Periodic changes in the accretion rates onto
the stars can explain the outbursts of line emission observed in eccentric
systems such as DQ Tau.Comment: Accepted for publication in MNRA
Análise de crescimento de biótipos de amendoim-bravo (Euphorbia heterophylla) resistente e suscetível aos herbicidas inibidores da ALS.
A aplicação contínua de herbicidas do grupo químico das imidazolinonas, nas mesmas áreas de produção de soja, durante anos seguidos, no município de Cafelândia, PR, favoreceu a seleção de um biótipo resistente de amendoim-bravo (Euphorbia heterophylla) aos herbicidas inibidores da acetolactato sintase (ALS). Um estudo comparativo das características do crescimento do biótipo resistente e do suscetível foi realizado em casa de vegetação da Embrapa Soja, Londrina-PR, a fim de identificar diferenças no crescimento e no desenvolvimento das plantas e de seus órgãos. A produção de matéria seca total, a área foliar, a matéria seca dos caule, das raízes e das folhas, bem como a altura por planta, foram avaliadas em 13 vezes a intervalos regulares, iniciando aos 14 dias após a semeadura. A partir desses parâmetros, foram calculadas a taxa de crescimento relativo, a taxa assimilatória líquida, a razão de área foliar, a razão de peso foliar e a área foliar específica, que decrescem com a ontogenia das plantas de amendoim-bravo, sendo similares para ambos os biótipos. A matéria seca total acumulada pelas plantas e seus órgãos, a área foliar e a altura apresentaram comportamentos semelhantes para os biótipos resistente e suscetível. O ciclo vegetativo dos dois biótipos estudados não mostrou diferença significativa quanto ao crescimento e ao desenvolvimento
Type I planetary migration in a self-gravitating disk
We investigate the tidal interaction between a low-mass planet and a
self-gravitating protoplanetary disk, by means of two-dimensional hydrodynamic
simulations. We first show that considering a planet freely migrating in a disk
without self-gravity leads to a significant overestimate of the migration rate.
The overestimate can reach a factor of two for a disk having three times the
surface density of the minimum mass solar nebula. Unbiased drift rates may be
obtained only by considering a planet and a disk orbiting within the same
gravitational potential. In a second part, the disk self-gravity is taken into
account. We confirm that the disk gravity enhances the differential Lindblad
torque with respect to the situation where neither the planet nor the disk
feels the disk gravity. This enhancement only depends on the Toomre parameter
at the planet location. It is typically one order of magnitude smaller than the
spurious one induced by assuming a planet migrating in a disk without
self-gravity. We confirm that the torque enhancement due to the disk gravity
can be entirely accounted for by a shift of Lindblad resonances, and can be
reproduced by the use of an anisotropic pressure tensor. We do not find any
significant impact of the disk gravity on the corotation torque.Comment: 42 pages, 17 figures, accepted for publication in Ap
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