A partially purified preparation of the heatstable enterotoxin of EsMherichia coli caused a rapid and persistent increase in electric potential difference and short-circuit current when added in vitro to the luminal surface of isolated rabbit ileal mucosa. As little as 1 ng/ml produced an easily detectable response. Under short-circuit condition, the enterotoxin abolished net Cl-absorption; this change was half that produced by theophylline, which stimulated net secretion. The enterotoxin did not change cyclic AMP concentration but caused large and persistent increases in cyclic GMP concentration. The electrical and nucleotide responses exhibited similar and unusually broad concentration-ependences and maximal effects could not be demonstrated. Theophylline elevated cyclic GMP concentration 3fold both in the presence and absence of the enterotoxin, suggesting no effect of the toxin on cyclic GMP hosphodiesterase. Guanylate cyclase [GTP pyrophosphatelyase~cycizing); EC 4.6.1.21 activity in a crude membrane fraction from intestinal epithelial cells was stimulated 7-fold by the enterotoxin. These results suggest that guanylate cyclase stimulation is the basis for the toxin's diarrheagenic effect.Two enterotoxins have been identified among the extracellular products of Escherichia colh isolated from humans and other mammals with diarrheal disease-one heat-labile (1, 2) and the other heat-stable (1, 3, 4). The former is immunologically crossreactive with cholera toxin (5) and, like cholera toxin, stimulates adenylate cyclase (6). The latter acts more rapidly (7) and has a lower molecular weight [5000 or less (8) been equilibrated with 99% methanol/1% acetic acid. A broad peak of toxin activity appeared just behind the void volume.The eluate was reconcentrated and again filtered on Sephadex LH-20 that had been equilibrated with water. Toxin was then eluted with water and the eluate was stored in a refrigerator with preservatives. Even when stored for 6 wk at room temperature, no loss of activity could be detected. The final material was 200-to 1000-fold purified but still gave several peaks on silica gel chromatography. A detailed description of this procedure will be published elsewhere (W. J. Laird and D. M. Gill, unpublished data).Enterotoxin activity was assayed in suckling mice (9). Fifty-microliter aliquots of toxin in water were introduced by transabdominal injection into the stomachs of 2 to 4-day-old suckling mice (CD-1 Swiss white from Charles River Laboratories, Boston, MA). After 60 min the mice were killed with CHC13 and ratios of total intestinal weight to total body weight were determined. Control ratios were about 0.06 and maximal ratios were about 0.13. A mouse unit was defined as the amount of toxin producing a half-maximal increase in ratio. Serial 1:1 dilutions of toxin were assayed; three mice were used for each dilution.Three separately prepared batches of toxin were used for various phases of the present study. An aliquot from one of these batches was lyophilized and weighed: one mouse ...

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The Forkhead Box m1 (Foxm1 or Foxm1b) transcription factor (previously called HFH-11B, Trident, Win, or MPP2) is an important positive regulator of DNA replication and mitosis in a variety of cell types. Global deletion of Foxm1 in Foxm1 ؊/؊ mice is lethal in the embryonic period, causing multiple abnormalities in the liver, heart, lung, and blood vessels. In the present study, Foxm1 was deleted conditionally in the respiratory epithelium (epFoxm1 ؊/؊ ). Surprisingly, deletion of Foxm1 did not alter lung growth, branching morphogenesis, or epithelial proliferation but inhibited lung maturation and caused respiratory failure after birth. Maturation defects in epFoxm1 ؊/؊ lungs were associated with decreased expression of T1-␣ and aquaporin 5, consistent with a delay of type I cell differentiation. Expression of surfactant-associated proteins A, B, C, and D was decreased by deletion of Foxm1. Foxm1 directly bound and induced transcriptional activity of the mouse surfactant protein B and A (Sftpb and Sftpa) promoters in vitro, indicating that Foxm1 is a direct transcriptional activator of these genes. Foxm1 is critical for surfactant homeostasis and lung maturation before birth and is required for adaptation to air breathing.epithelial cells ͉ Foxm1 ͉ lung development ͉ surfactant proteins

Glial fibrillary acidic protein (GFAP), a protein that is associated with 9-nm filaments of astrocytes, was observed to be increased in the astrocytes surrounding senile plaques in patients with Alzheimer dementia and in aged subjects without dementia. A few GFAP-positive fibers were seen in the centers of plaques. These results emphasized the selectivity of senile changes; whereas some cells seemed to undergo degeneration or dysfunction, other cells--astrocytes--maintain their capacity for reaction and may increase the formation of at least one protein, GFAP.

We have found that three phenotypically dissimilar mouse B16 melanoma subclones are competent recipients for DNA-mediated gene transfer. Two of these approach and a third, amelanotic clone B78H1, surpasses mouse LTK cells in frequencies of transferent colony formation after treatment with either of two codominantly selectable plasmid vectors, pSV2gpt or pGCcos3neo. Melanoma transferents incorporate both selectable plasmid-homologous sequences and substantial amounts of unselected donor DNA into their cellular DNAs. In addition they retain the distinctive states of differentiation characteristic of the untreated clones. Frequencies of pGCcos3neo-mediated transfer of neo gene-encoded antibiotic resistance into B78H1 can reach 10(-2) in response to treatment with as little as 15 ng plasmid/ml coprecipitate/dish. B78H1 cells readily give rise to "secondary" transferents for the neo gene after treatment with DNA from a "primary" B78H1 neo transferent. This gene transfer system has potential applications for study of regulation of melanoma and neural crest differentiation and malignancy.