Cyclic GMP does not inhibit protein kinase C-mediated enzyme secretion in rat pancreatic acini

In pancreatic acini, cGMP can be increased by secretagogues such as cholecystokinin (CCK), cholinergic agents, and bombesin, whose actions on enzyme secretion are believed to be mediated by protein kinase C. However, the role of cGMP in acinar cell function has been unclear. A recent paper by Rogers et al. (Rogers, J., Hughes, R.G., and Matthews, E. K. (1988) J. Biol. Chem. 263, 3713-3719) reported that two analogues of cGMP, N2,O2-dibutyl guanosine 3':5'-monophosphate (Bt2cGMP) and 8-bromoguanosine 3':5'-monophosphate (8Br-cGMP), at concentrations in the nanomolar range, inhibited the stimulation of amylase secretion caused by CCK-8, bethanechol, bombesin, and 12-O-tetradecanoylphorbol-13-acetate (TPA). Rogers et al. also reported that sodium nitroprusside inhibited the stimulation of enzyme secretion caused by CCK-8 or TPA. These authors concluded that cGMP inhibits protein kinase C-mediated secretion in pancreatic acini. In the present study we attempted to confirm the findings of Rogers et al., We found, however, that Bt2cGMP inhibited CCK-8-stimulated amylase release only at concentrations of the nucleotide above 10 microM. Moreover, there was a close correlation between the ability of Bt2cGMP to inhibit CCK-8-stimulated amylase release and its ability to inhibit binding of 125I-CCK-8. Bt2cGMP, at concentrations as high as 3 mM, did not alter the stimulation of amylase release caused by carbachol, bombesin, TPA, or A23187. 8Br-cGMP, at concentrations up to 1 mM, did not inhibit the stimulation of amylase release caused by CCK-8 or TPA. At concentrations above 0.1 mM, 8Br-cGMP augmented the stimulation of amylase release caused by CCK-8, carbachol, bombesin, or TPA. Sodium nitroprusside, at a concentration that causes a 60-fold increase in cGMP, did not inhibit the stimulation of amylase release caused by CCK-8, carbachol, bombesin, or TPA. Our results do not confirm the findings of Rogers et al. and indicate that cGMP does not inhibit protein kinase C-mediated secretion in pancreatic acini.     

A study of variance in measurements of tank-treading frequency in populations of normal human red cells

The statistical variance in rheoscopic measurements of tank-treading frequency ( TTF ) of normal human red cells has been investigated and the sources of this variance analyzed. Experiments were designed to expose the influence of donor, the stability of a donor's cells over a 2-month period, storage time from venipuncture to testing, cell age, applied shear rate and variations in the rheoscope gap due to trial-to-trial manipulation. The results show that the TTF varies linearly with applied shear rate within the range 20 to 180 s-1 and is strongly dependent on cell age. The slope of the TTF characteristic is not significantly different in cells taken from different, but hematologically normal adults nor does it change significantly over time in a particular donor. TTF measurements may be useful in distinguishing rheologically abnormal cell populations which differ from normal cells by at least 10%.     

Characterization of genome structure of amphotropic and ecotropic wild mouse retroviruses.

We studied the RNA genomes of several wild mouse type C retroviruses by using RNase T1-oligonucleotide fingerprinting. The amphotropic and ecotropic viruses of field strain 1504 produced very similar oligonucleotide fingerprints, but each also had several unique oligonucleotides. All of these unique oligonucleotides were located in the env gene region and were probably responsible for the host range differences between these viruses, as well as the lymphomagenic and paralytogenic properties of the viruses. We obtained similar results with the amphotropic and ecotropic viruses of another field strain (4070), which was isolated from a mouse from a different trapping area. The amphotropic viruses of several field strains (strains 1504, 4070, and 1313) were more closely related than the ecotropic viruses of different strains (strains 1504, 4070, and 4996). These findings suggested that the genetic sequences of the amphotropic viruses are more conserved than those of ecotropic viruses isolated from the same wild mice.     

Variations in cancer mortality among local authority areas in England and Wales: relations with environmental factors and search for causes.

Geographical variations in specific causes of mortality among the 1366 local authority areas of England and Wales as defined at 1971 were studied by examining extracts from death certificates held on computer tape. Five items of information on each death--year of death, age at death, sex, local authority area of residence, and the underlying cause of death, during the 11 years 1968-78--permitted a more detailed investigation than had been possible before. Analysis of some early results of the study--including maps of mortality for pleural mesothelioma, nasal cancer and bladder cancer--suggested that, despite the known limitations of death certification, systematic study of the mortality of small areas may give clues to aetiological factors in the environment. Analyses relating mortality to the distribution of environmental factors and examining disease profiles of each area may also provide clues. These will be followed up by other methods of study, such as case-control techniques.     

Mechanism of action of ATP on intestinal epithelial cells. Cyclic AMP-mediated stimulation of active ion transport

ATP, ADP and AMP but not adenosine increased cyclic AMP in dispersed enterocytes prepared from guinea pig small intestine. This action of ATP was augmented by IBMX and was reproduced by App(NH)p or App(CH2)p. ATP also increased the formation of cyclic [14C]AMP in enterocytes that had been preincubated with [14C]adenine. Gpp(NH)p and NaF each caused persistent activation of adenylate cyclase in plasma membranes from enterocytes and ATP caused significant augmentation of this persistent activation. In addition to increasing cellular cyclic AMP and augmenting Gpp(NH)p and NaF-stimulated persistent activation of adenylate cyclase, ATP increased the Isc across mounted strips of small intestine and inhibited net absorption of fluid and electrolytes in segments of everted small intestine. These results indicate that intestinal epithelial cells possess a receptor that interacts with ATP and other adenine nucleotides and that receptor occupation by ATP causes activation of adenylate cyclase, increased cyclic AMP and changes in active ion transport across intestinal mucosa.     

Mechanism of action of ATP on intestinal epithelial cells: Cyclic AMP-mediated stimulation of active ion transport

ATP, ADP and AMP but not adenosine increased cyclic AMP in dispersed enterocytes prepared from guinea pig small intestine. This action of ATP was augmented by IBMX and was reproduced by App(NH)p or App(CH₂)p. ATP also increased the formation of cyclic [¹⁴C]AMP in enterocytes that had been preincubated with [¹⁴C]adenine. Gpp(NH)p and NaF each caused persistent activation of adenylate cyclase in plasma membranes from enterocytes and ATP caused significant augmentation of this persistent activation. In addition to increasing cellular cyclic AMP and agumenting Gpp(NH)p and NaF-stimulated persistent activation of adenylate cyclase, ATP increased the I_sc across mounted strips of small intestine and inhibited net absorption of fluid and electrolytes in segments of everted small intestine. These results indicate that intestinal epithelial cells possess a receptor that interacts with ATP and other adenine nucleotides and that receptor occupation by ATP causes activation of adenylate cyclase, increased cyclic AMP and changes in active ion transport across intestinal mucosa.     

Analysis of mini-F plasmid replication by transposition mutagenesis

Derivatives of a mini-F plasmid in which Tn3 is inserted in F deoxyribonucleic acid were obtained, and the sites of insertion for 40 of the derivatives were mapped. Tn3 was found to insert at many sites within mini-F, but most insertions were within the 43.0- to 43.7-kilobase (kb), 44.2- to 44.7-kb, and 45.9- to 46.3-kb segments. Hence, these segments are unnecessary for mini-F replication. Most of the Tn3 derivatives were similar to their parent miniplasmid with respect to copy number, stability, and incompatibility. Insertions at 45.15 kb and near 46.0 kb caused a moderate disruption of copy number control, and insertion at 47.6 kb resulted in unstable maintenance. Deletion derivatives lacking deoxyribonucleic acid between 40.3 and 44.76 kb and between 45.92 and 49.4 kb were obtained. This observation suggests either that mini-F contains a third origin, in addition to those already reported to be at 42.6 and 44.4 kb, or that the reported position of the secondary origin, 44.4 kb, is incorrect and that this origin is between 44.76 and 45.92 kb.