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We report on the wavelength and time-domain responses of a lumped or distributed fiber-optic modalmetric interferometer under a very smooth pressure ( fingerprint) disturbances in the 1530-1610 nm wavelength range. A simple method to quantify such disturbances is proposed. It is shown that the lateral offset shift of 5.9 mm between the single-mode and the multimode fiber splice makes the device even more sensitive. It was measured an electrical signal power enhancements of 3.5 and 7.5 dB for 1 m and 1.65 km multimode fiber link, respectively. [ABSTRACT FROM AUTHOR]

Pancreastatin (PST), a chromogranin A-derived peptide, has counterregulatory effects on insulin in the hepatocyte and the adipocyte, suggesting a possible role in insulin resistance. The mechanism of PST action on glucose and lipid metabolism is typical of a calcium-mobilizing hormone and involves a receptor Gq/11 protein-phospholipase C (PLC)-beta pathway. In the rat adipocyte, PST inhibits insulin-mediated glucose transport, glucose utilization, and lipid synthesis, and it has a lipolytic effect but stimulates basal and insulin-stimulated protein synthesis. We have also recently studied the PST receptor-effector system in adipocyte membranes. To further investigate the mechanisms of PST effect on insulin action, we studied the cross-talk of PST with insulin signaling in the rat adipocyte. We found that PST inhibits insulin-stimulated GLUT4 translocation to the membrane, which may explain the reported inhibition of glucose transport. Tyrosine phosphorylation of the activated insulin receptor, insulin receptor substrate (IRS)-1, and p60-70 was also blunted, preventing their association with p85 phosphatidylinositol 3-kinase (PI3K) and their activity. The mechanism of this inhibition involves the activation of the "classical" protein kinase C isoforms and the serine phosphorylation of insulin receptor and IRS-1. On the other hand, PST activates the mitogen-activated protein kinase (MAPK) signaling module and enhances the effect of insulin. This pathway may account for the described effect of PST on protein synthesis. In conclusion, PST seems to inhibit the insulin-stimulated PI3K pathway in the adipocyte, whereas it activates the MAPK pathway. These data provide some clues to the PST cross-talk with insulin signaling that may explain the PST effects on glucose metabolism and protein synthesis. [ABSTRACT FROM AUTHOR]

The tropical rain forest pioneer tree Heliocarpus donnell-smithii Rose establishes itself only in light gaps of the forest canopy. A series of experiments with fluctuating temperatures have shown that the germination is increased if the temperature rises above 31°C during a few hours each day. The laboratory experiments were complemented with determinations of the seed viability in the soil each month during one year, and with determinations of germination under the natural diurnal fluctuation of temperature in a forest gap. Germination increases under fluctuating temperatures, and the seeds can remain dormant when buried in the soil during several months. The diurnal heating of the soil of light gaps as contrasted with the almost constant temperature under undisturbed canopies may be a precise environmental indicator of appropriate conditions for germination and establishment of the pioneer heliophytes of the rain forest. [ABSTRACT FROM AUTHOR]

The tropical forest pioneer trees Cecropia obtusifolia and Piper auritum germinate and become established in large light gaps of the forest canopy in the rain forest of south-eastern Mexico. Germination of the seeds of both species is under photocontrol and is triggered when the red:far-red ratio (R:FR) of the incident light increases due to a reduction of the green canopy density. Exposure to simulated light canopies retarded and reduced germination. The light environment inside the forest inhibits germination totally. Experiments with alternate R and FR light treatments indicate the need for long periods of exposure to R light for germination, and demonstrate a strong reversibility of the R light stimulation by FR light in both species. This property of the seeds may be related to the detection of light gap size and its differentiation from the normal sunflecks of the forest. [ABSTRACT FROM AUTHOR]