Gastrin: A Distinct Fate of Neurogenin3 Positive Progenitor Cells in the Embryonic Pancreas

Neurogenin3+ (Ngn3+) progenitor cells in the developing pancreas give rise to five endocrine cell types secreting insulin, glucagon, somatostatin, pancreatic polypeptide and ghrelin. Gastrin is a hormone produced primarily by G-cells in the stomach, where it functions to stimulate acid secretion by gastric parietal cells. Gastrin is expressed in the embryonic pancreas and is common in islet cell tumors, but the lineage and regulators of pancreatic gastrin+ cells are not known. We report that gastrin is abundantly expressed in the embryonic pancreas and disappears soon after birth. Some gastrin+ cells in the developing pancreas co-express glucagon, ghrelin or pancreatic polypeptide, but many gastrin+ cells do not express any other islet hormone. Pancreatic gastrin+ cells express the transcription factors Nkx6.1, Nkx2.2 and low levels of Pdx1, and derive from Ngn3+ endocrine progenitor cells as shown by genetic lineage tracing. Using mice deficient for key transcription factors we show that gastrin expression depends on Ngn3, Nkx2.2, NeuroD1 and Arx, but not Pax4 or Pax6. Finally, gastrin expression is induced upon differentiation of human embryonic stem cells to pancreatic endocrine cells expressing insulin. Thus, gastrin+ cells are a distinct endocrine cell type in the pancreas and an alternative fate of Ngn3+ cells

Relaxed excited state structure and luminescence of thallium-doped caesium chloride and bromide.

Four bands, all belonging to the main thallium centres, have been detected in the emission spectra of CsCl:Tl and CsBr:Tl crystals. Their spectral, polarization and kinetic characteristics have been studied from 0.45 up to 360 K. It has been shown that the new model proposed by us recently for the relaxed excited state (RES) structure of the luminescence centre in CsI:Tl crystals is valid for CsCl:Tl and CsBr:Tl crystals as well. Two ultraviolet emission bands excited mainly in the A absorption band of Tl+ centres are ascribed to electronic transitions from trigonal and tetragonal Jahn-Teller minima of the tripler RES of Tl+. Two visible bands excitable mainly in the higher energy absorption bands of CsCl:Tl and CsBr:Tl are connected with two different off-centre configurations of self-trapped exciton perturbed by the Tl+ ion. The parameters of the corresponding excited state minima have been calculated. The mixing of the impurity and halogen excited states has been shown to decrease markedly in the sequence of anions I- --> Br- --> Cl-

Peculiarities of the triplet relaxed excited state structure in thallium-doped cesium halide crystals.

Four bands, all belonging to the main thallium centre, are detected in the tripler luminescence spectrum of thallium-doped cesium halides under excitation in impurity absorption bands. Their spectral, polarization and kinetics characteristics are studied at 0.35 to 360 K. The parameters of the corresponding relaxed excited states (RES) minima are calculated. Two ultraviolet emission bands are ascribed to electronic transitions from trigonal and tetragonal Jahn-Teller minima of the triplet RES of Tl+ ion. Two visible bands are assumed to arise from two different off-centre configurations of a self-trapped exciton perturbed by Tl+ ion

Peculiarities of the triplet relaxed excited-state structure and luminescence of a CsI:Tl crystal

Four emission bands, all belonging to the main thallium centres, have been detected in CsI:Tl, and their spectral, polarization and kinetic characteristics have been studied at 0.35-320 K. A new model is proposed for the excited states responsible for the luminescence of thallium-doped caesium iodide. In this model, the main thallium centre is considered as a cluster consisting of a Tl+ ion and at least 12 I- and 11 Cs+ ions. Two weak ultraviolet emission bands of CsI:TI (3,31 and 3.09 eV) are ascribed to electronic transitions from trigonal and tetragonal Jahn-Teller minima of the tripler relaxed excited state, whose structure is similar to that of Tl+ centres in Fee alkali halides. Two intense visible bands (2.55 and 2.25 eV) are assumed to arise from two different ('weak' and 'strong') off-centre configurations of a self-trapped exciton perturbed by the Tl+ ion. The minima responsible for all the emission bands are located on the same adiabatic potential energy surface. The excitonic-like nature of visible emission could explain the high scintillation efficiency of CsI:Tl

Luminescence and decay kinetics of relaxed bound excitons and impurity states in CsX:Tl+ (X=Cl, Br, I).

Luminescence, decay kinetics and polarization properties of single Tl+-based centres in CsX hosts (X = Cl, Dr, I) are described in a wide temperature interval 0.3 - 400 K. It is shown that four emission bands co-existing at the same relaxed excited state surface belong to this centre. At sufficiently high temperatures all the relaxed excited state minima are mutually connected by the thermally stimulated transitions

Cryogenic particle detectors with superconducting phase transition thermometers

A tungsten superconducting phase transition thermometer on a 32 g sapphire crystal has given an energy resolution of 100 eV (FWHM) for 1.5 keV X-rays, increasing to 440 eV at 14 keV. A possibility to obtain similar resolution in much larger crystals by using Al films as phonon collectors is presented