3 research outputs found
Nonlinear evolution of cylindrical gravitational waves: Numerical method and physical aspects
The effects of insulin and follicle-simulating hormone (FSH) during in vitro development of ovarian goat preantral follicles and the relative mRNA expression for insulin and FSH receptors and cytochrome P450 aromatase in cultured follicles
The actions of different concentrations of insulin alone or in combination with follicle-stimulating hormone (FSH) were evaluated by in vitro follicular development and mRNA expression of cytochrome P450 aromatase (CYP19A1) and as receptors for insulin (INSR) and FSH (FSHR) from isolated, cultured goat preantral follicles. Goat preantral follicles were microdissected and cultured for 18 days in the absence or presence of insulin (5 and 10 ng/ml or 10 mu g/ml) alone or in combination with FSH. After 18 days, the addition of the maximum concentration of insulin to the culture medium reduced follicular survival and antrum formation rates significantly compared to the other treatments. However, when FSH was added to the culture medium, no differences between these two parameters were observed. Preantral and antral follicles from the fresh control as well as from all cultured follicles still presented a normal ultrastructural pattern. In medium supplemented with FSH, only insulin at 10 ng/ml presented oocytes with higher rates of meiosis resumption compared to control, as well as oocytes in metaphase II. Treatment with insulin (10 ng/ml) plus FSH resulted in significantly increased levels of INSR and CYP19A1 mRNA compared to that with other treatments. In conclusion, 10 ng/ml insulin associated with FSH was more efficient in promoting resumption of oocyte meiosis, maintaining survival, stimulating follicular development, and increasing expression of the INSR and CYP19A1 genes in goat preantral follicles
Numerical bifurcation analysis of two coupled FitzHugh-Nagumo oscillators
The behavior of neurons can be modeled by the FitzHugh-Nagumo oscillator
model, consisting of two nonlinear differential equations, which simulates the
behavior of nerve impulse conduction through the neuronal membrane. In this
work, we numerically study the dynamical behavior of two coupled
FitzHugh-Nagumo oscillators. We consider unidirectional and bidirectional
couplings, for which Lyapunov and isoperiodic diagrams were constructed
calculating the Lyapunov exponents and the number of the local maxima of a
variable in one period interval of the time-series, respectively. By numerical
continuation method the bifurcation curves are also obtained for both
couplings. The dynamics of the networks here investigated are presented in
terms of the variation between the coupling strength of the oscillators and
other parameters of the system. For the network of two oscillators
unidirectionally coupled, the results show the existence of Arnold tongues,
self-organized sequentially in a branch of a Stern-Brocot tree and by the
bifurcation curves it became evident the connection between these Arnold
tongues with other periodic structures in Lyapunov diagrams. That system also
present multistability shown in the planes of the basin of attractions.Comment: 9 pages and 8 figure