Reflectivity of transient Bragg reflection gratings in fiber laser with laser-wavelength self-sweeping: erratum.

This erratum presents a correction to the computed reflection spectra of transient fiber Bragg gratings that are spontaneously built-up in the ytterbium-doped fiber of the fiber laser with laser wavelength self-sweeping. The corrected spectra have high reflectivity reaching values up to 100%. Therefore, they still more support the conclusion drawn in the original paper that self-sweeping is an important mechanism for triggering the self-Q-switched regime with giant pulse generation.

Reflectivity of transient Bragg reflection gratings in fiber laser with laser-wavelength self-sweeping.

We present a method for the estimation of the reflection spectra of transient gratings in rare-earth doped fiber lasers having a self-sweeping of laser wavelength. We show that high reflectivities of several tens of percent can be achieved. An example of this is demonstrated through the use of an experimental Yb-doped Fabry-Perot fiber laser. The gratings' spectra are highly asymmetric due to the apodization of the refractive index modulation. The importance of the self-sweeping regime for triggering self-Q-switched laser instabilities is discussed.

Brain glucose sensing and counterregulatory response to hypoglycaemia.

An important obstacle to achieve optimal glycaemic control in diabetics on intensive insulin therapy is the frequent occurrence of insulin induced hypoglycaemic events. In healthy subjects and in diabetics without autonomic neuropathy hypoglycaemia activates the sympathetic nervous system, resulting in epinephrine and glucagon release. Both hormones increase hepatic glucose production and this counterregulatory response is of key importance of glucose homeostasis. Recent research shed light on the fact that antecedent hypoglycaemic episodes play pivotal role in hypoglycaemia associated autonomic failure (HAAF). In this condition the sympatho-adrenal response to decreased blood glucose level is blunted. The existence of HAAF clearly indicates that the nervous system contributes to glucose homeostasis in a substantial manner. This review outlines the mechanisms of both peripheral and central neuronal glucose sensing and of neural pathways involved in the counterregulatory response.

Effect of HGF-like basic hexapeptides on angiogenesis.

The interaction of glycosaminoglycans (GAG) with peptides relies on noncovalent binding to basic amino acid sequences, for which a minimal requirement is a pentapeptide region in the protein and the sulfated and carboxyl region in the GAG. Since such sequences are present in the heparin-binding angiogenic cytokines, including hepatocyte growth factor (HGF), we have postulated that such small peptides may have biological activity. Two basic peptide regions of the beta chain of HGF (RYRNKH512-516, HHRGK645-649) exhibited significant antiangiogenic activity in vivo in the chorioallantoic membrane assay and showed some antiproliferative activity in vitro on normal human brain microvessel endothelial-but not on anchorage-independent endothelial-cells (Kaposi sarcoma). Basic HIV-TAT peptides and scrambled hexapeptides did not show similar activity, except for KRKRKR, indicating sequence specificity of the phenomena. An HGF-derived basic peptide, HHRGK, modulated tumor-induced angiogenesis in vivo by interfering with the morphogenic, but not with the proliferative, phase of the process. These observations suggest small basic peptides as a new class of angiogenesis modulators.