Many transcription factors are critical for ensuring proper embryonic development of the endocrine pancreas and normal islet function. The transcription factor pancreatic duodenal homeobox 1 (PDX-1) is uniformly expressed in early pancreatic buds of embryos as well as the beta and delta cells of the islets of Langerhans. PDX-1 has also been found in dispersed endocrine cells of the duodenum in adults and plays a key role in pancreas formation. It has been reported that null mutation of PDX-1 in mice results in a failure of the pancreatic bud to expand; thus, the mice die 2-3 days after birth from hyperglycemia and dehydration. Heterozygous PDX-1 mice developed a pancreas but were diabetic. It has been shown that PDX-1 is required for maintaining the pancreatic islet functions by activating gene transcriptions including insulin, somatostatin (SST), islet amyloid polypeptide, glucose transporter type 2, and glucokinase. PDX-1 serves a dual role in pancreatic development. It initially contributes to pancreatic formation during embryogenesis and subsequently regulates the pancreatic islet cell physiology in mature islet cells. Understanding the underlying molecular mechanisms of pancreas formation, especially the function of PDX-1, may contribute to the enhanced treatment and prevention of debilitating diseases such as diabetes, insulinomas, and pancreatic carcinomas.

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New variations of minimum noise and correlation energy (MINACE) filters are considered for detection and recognition of objects and rejection of clutter in synthetic aperture radar (SAR) data. We present initial very attractive results that aid different modules in an SAR automatic target recognition (ATR) processor. For four class test set data, we show detection performance of P D Ͼ99.8% with P FA Х0.026/km 2 ; for classification we show P C Ͼ96.6% with P FA Х0.026/km 2 . Selected tests with noise and obscurations present and of several objects in large real SAR background are also included. All results used full shift-invariance tests. © 1997 Society of Photo-Optical Instrumentation Engineers.[S0091-3286 (97)01410-4]

The activity of the retinoblastoma protein pRB is regulated by phosphorylation that is mediated by G 1 cyclinassociated cyclin-dependent kinases (CDKs). Since the pRB-related pocket proteins p107 and p130 share general structures and biological functions with pRB, their activity is also considered to be regulated by phosphorylation. In this work, we generated phosphorylationresistant p107 and p130 molecules by replacing potential cyclin-CDK phosphorylation sites with nonphosphorylatable alanine residues. These phosphorylation-resistant mutants retained the ability to bind E2F and cyclin. Upon introduction into p16INK4a -deficient U2-OS osteosarcoma cells, in which cyclin D-CDK4/6 is dysregulated, the phosphorylation-resistant mutants, but not wild-type p107 or p130, were capable of inhibiting cell proliferation. Furthermore, when ectopically expressed in pRB-deficient SAOS-2 osteosarcoma cells, the wild-type as well as the phosphorylation-resistant pRB family proteins were capable of inducing large flat cells. The flat cell-inducing activity of the wild-type proteins, but not that of the phosphorylation-resistant mutants, was abolished by coexpressing cyclin E. Our results indicate that the elevated cyclin D-or cyclin E-associated kinase leads to systemic inactivation of the pRB family proteins and suggest that dysregulation of the pRB kinase provokes an aberrant cell cycle in a broader range of cell types than those induced by genetic inactivation of the RB gene.