Characterization of Gastrin-Releasing Peptide and Its Receptor Aberrantly Expressed by Human Colon Cancer Cell Lines

ABSTRACT Gastrin-releasing peptide (GRP) is a mitogen and morphogen important in the development of human colon cancers. Although epithelial cells lining the colon do not normally express GRP or its receptor (GRP-R), most human tumors express GRP-R mRNA. Yet functional protein has only been detected in 24 to 40% of colon cancers. To elucidate the reason for the difference between the expression of GRP/GRP-R mRNA and protein, we studied nine human colon cancer cell lines. Quantitative polymerase chain reaction revealed that all colon cancer cell lines expressed similar amounts of mRNA for both GRP as well as GRP-R. Yet binding studies using 125 I-Tyr 4 -bombesin detected functional receptors on only five of the nine cell lines studied. Conformational fragment-length polymorphism analysis indicated that although mRNA for the ligand GRP was never mutated, mRNA for the GRP-R was always mutated. Sequencing revealed that the message for GRP-R contained between two and seven separate mutations at the nucleotide level. This resulted in 14 separate coding mutations, 2 of which were observed in more than one cell line. Each mutation was individually recreated by site-directed mutagenesis and studied in transiently transfected Chinese hamster ovary-K1 cells. Alteration of Pro 145 into a tyrosine, of Val 317 into a glutamic acid, and insertion of a 32-nucleotide segment resulting in a frameshift distal to Asp 137 all resulted in GRP receptors incapable of binding ligand. Thus, these data indicate that human colon cancers commonly express GRP and GRP-R mRNA but that receptor mutations account for the failure of functional protein to be generated

Analysis of the shape of x-ray diffraction peaks originating from the hexatic phase of liquid crystal films

X-ray diffraction studies of the bond-orientational order in the hexatic-B phase of 75OBC and 3(10)OBC compounds are presented. The temperature evolution of an angular profile of a single diffraction peak is analyzed. Close to the hexatic-B–smectic-A transition these profiles can be approximated by the Gaussian function. At lower temperatures in the hexatic-B phase the profiles are better fitted by the Voigt function. Theoretical analysis of the width of diffraction peaks in three-dimentional (3D) hexatics is performed on the basis of the effective Hamiltonian introduced by Aharony and Kardar. Theoretical estimations are in good agreement with the results of x-ray experiments

Structure Studies of the Bond-Orientational order and the hexatic-smectic transition in liquid crystals of various compositions

We report on the X-ray studies of freely suspended hexatic films of three different liquid crystal compounds. By applying angular X-ray cross-correlation analysis (XCCA) to the measured diffraction patterns the parameters of the bond-orientational (BO) order in the hexatic phase were directly determined. The temperature evolution of the BO order parameters was analyzed on the basis of the multicritical scaling theory (MCST). Our results confirmed the validity of the MCST in the whole temperature range of the existence of the hexatic phase for all three compounds. The temperature dependence of the BO order parameters in the vicinity of the hexatic–smectic transition was fitted by a conventional power law with a critical exponent β ≈ 0.1 of extremely small value. We found that the temperature dependence of higher order harmonics of the BO order scales as the powers of the first harmonic, with an exponent equal to the harmonic number. This indicates a nonlinear coupling of the BO order parameters of different order. We demonstrate that compounds of various compositions, possessing different phase sequences at low temperatures, display the same thermodynamic behavior in the hexatic phase and in the vicinity of the smectic–hexatic phase transition

HRSC auf Mars Express - Photogrammetrische und kartographische Auswertungen

Die High Resolution Stereo Camera (HRSC) an Bord der europäischen Raumsonde Mars Express ist die erste Kamera einer Planetenmission, die speziell für photogrammetrische und kartographische Zwecke entwickelt wurde. Seit Januar 2004 liefert die Kamera hochaufgelöste Bilddaten der Marsoberfläche in Stereo und in Farbe. Die Bilddaten bergen ein immenses Potenzial zur Ableitung präziser Digitaler Geländemodelle (DGMs) und farbiger Orthophotos sowie zur Herstellung topographischer und thematischer Karten und weiterer Produkte. Die Arbeitsgruppe für Photogrammetrie und Kartographie des internationalen HRSC-Forscherteams beschäftigt sich mit der systematischen Erstellung von Standardprodukten aus den Bilddaten und der Verfeinerung dieser Produkte mit dem Ziel, eine höchstmögliche Qualität zu erzielen. Dieser Beitrag beschreibt einige zur Verfeinerung geeignete Arbeitsschritte und illustriert den erreichten Stand anhand einer Reihe von Beispielen