Expression of peptide YY in all four islet cell types in the developing mouse pancreas suggests a common peptide YY-producing progenitor

The islets of Langerhans contain four distinct endocrine cell types producing the hormones glucagon, insulin, somatostatin and pancreatic polypeptide. These cell lineages are thought to arise from a common, multipotential progenitor cell whose identity has not been well established. The pancreatic and intestinal hormone, peptide YY, has been previously identified in glucagon-producing cells in islets; however, transgenic mice expressing Simian Virus 40 large T antigen under the control of the peptide YY gene expressed the oncoprotein in beta, delta and pancreatic polypeptide cells, and occasionally developed insulinomas, suggesting relationships between peptide YY-producing cells and several islet cell lineages. The four established pancreatic islet cell types were examined for coexpression of peptide YY in islets of normal and transgenic mice throughout development. Peptide YY immunoreactivity was identified in the earliest endocrine cells in the fetal pancreas and was coexpressed in each islet cell type during development. Peptide YY showed a high degree of co-localization with glucagon- and insulin-producing cells in early pancreatic development, but by adulthood, peptide YY was expressed in less than half of the alpha cells and was no longer expressed in beta cells. Peptide YY was also coexpressed with somatostatin and pancreatic polypeptide when these cell types first appeared, but most delta and pancreatic polypeptide cells continued to express peptide YY throughout development. The use of conditions that distinguish peptide YY from the related peptides, pancreatic polypeptide and neuropeptide Y, as well as the ability of the peptide YY gene to direct expression of a reporter gene in islets of transgenic mice, establishes expression of peptide YY in the earliest pancreatic endocrine cells.(ABSTRACT TRUNCATED AT 250 WORDS)     

Reversal of pretreatment hypotension and control of hemorrhage in trauma patients by a simple device

The injection of a suspension of Walker 256 carcinoma cells into the carotid artery of rats produced a model of hematogenously spread cerebral metastases. Most animals died from massive extracerebral tumors of the head and jaw; brain tumors were present in only one-quarter. External carotid artery ligation prior to tumor inoculation did not increase the incidence of fatal brain tumor. When cyclophosphamide, 15 mg/kg, was injected as a single dose on the fourteenth day after tumor inoculation, most of the extracerebral tumor disappeared. Fifty percent of the animals so treated were cured of tumor, but 90% of the remainder died of large intracerebral tumors. Severe cytopathic changes resulting from cyclophosphamide were present in extracerebral or choroid plexus tumors but were mild or nonexistent in intracerebral tumors. These selective effects of cyclophosphamide suggest that water-soluble agents are less effective against tumor in the brain than against extracerebral tumors despite the fact that metastatic tumor breaks down the blood-brain barrier.     

小井眼技术的发展与评价

本文报道了用氯化铁水合物催化肉桂酸和异戊醇的酯化作用，探讨了氯化铁催化合成肉桂酸异戊酯的条件。