Biliary, fecal and urinary excretion of [3H]-prostaglandins in the rat

The profiles of biliary, fecal and urinary excretion of tritium labeled prostaglandins (PG's) of differing biological activity were investigated in the rat. The PG's (10 micrograms/kg: 2 to 50 microCi/rat, in 1 ml polyethylene glycol-400) were administered intragastrically. Excretion data were expressed as a percentage of the total administered radioactivity. For the orally administered PG's 11R-methyl-16R-fluoro-15R-hydroxy-9-oxoprosta-ci s-5-trans-13-dienoic acid and its methyl ester, excretion was equally divided between urine and feces. The fecal and urinary profile of excretion of 3H after prostacyclin (PGI2) was similar to that following administration of 11R, 16, 16-trimethyl-15R-hydroxy-9-oxoprosta-cis-5-trans-13-dienoic acid (trimoprostil), a PG with antisecretory-antiulcer potential. However, PGI2 was very poorly absorbed from the intestine, while the absorption of trimoprostil was very efficient. Biliary excretion, with little entero-porto-hepatic biliary circulation, was the main route of elimination of trimoprostil, thereby resulting in rapid elimination of drug-related products and diminishing the potential for systemic liability in the rat.     

Effects of nucleotides and divalent cations on phospholipase activity in Saccharomyces cerevisiae

Divalent cations activate the lysophospholipase and transacylase reactions catalyzed by the same enzymes in the yeast Saccharomyces cerevisiae. The activation was observed at neutral pH, but not at the pH optimum of lysophospholipase/transacylase, near 3.5. Adenine nucleotides, especially AMP and ADP, are strong inhibitors of the same group of enzymes. Half maximal inhibition by AMP was found at a concentration of about 20 M. The inhibition by nucleotides in low concentrations is enhanced by divalent cations.     

Purification of a phospholipase B inhibitor from Saccharomyces cerevisiae

The phospholipase B activity of plasma membrane vesicles from Saccharomyces cerevisiae is inhibited by the 100 000 X g supernatant of mechanically disrupted yeast cells. A 1850-fold purification of the inhibitor activity was achieved by gel filtration, ion exchange chromatography with DEAE-cellulose and hydrophobic interaction chromatography with Octyl-Sepharose. SDS-polyacrylamide gel electrophoresis of the purified inhibitor revealed two main bands with an apparent Mr of 60 000 and 26 500. The phospholipase B activity was strongly reduced but not completely blocked by this preparation, while the lysophospholipase and transacylase reactions, which are catalyzed by the same membrane-bound enzymes (Witt, W. et al. (1984) Biochim. Biophys. Acta 795, 108-116), were not affected.     

Preparation and characterization of monoclonal antibodies to several frog rod outer segment proteins

Monoclonal antibodies to proteins important in phototransduction in the frog rod outer segment have been obtained. These include 6 different antibodies to rhodopsin, 50 to a guanine nucleotide binding protein (G-protein; 40,000 daltons), and 2 to cytoplasmic proteins. The antigens used were Percoll-purified rod outer segments, a rod outer segment soluble protein fraction, or a soluble plus peripheral membrane protein fraction. Antibodies were assayed by solid phase assay using a fluorogenic detection system. Proteins to which antibodies bound were assayed on Western blots, and the sensitivities of three different detection systems were compared. Most antibodies bound to only one rod outer segment protein band on Western blots. Immunofluorescence microscopy demonstrated binding of both anti-rhodopsin and anti-G-protein to isolated frog rod outer segments. Antibodies were purified from either culture supernatants or ascites fluid on protein A affinity columns. Two purified anti-G-protein antibodies have binding affinities to 125I-labeled G-protein of less than 10(-6) M-1. Of 11 antibodies to frog or bovine G-protein tested in solid phase and Western blot assays, all bind to the alpha rather than the beta or gamma subunits. Procedures developed here are being used in preparing other antibodies that affect reactions in the phototransduction pathway.     

Increased incidence of developmental anomalies among descendants of carriers of methylenebisacrylamide-induced balanced reciprocal translocations

N,N'-Methylenebisacrylamide (MBA), a dimer of the monomeric acrylamide, was studied for induction of clastogenic effects in germ cells of male mice. It was found to be effective in inducing dominant-lethal mutations and heritable translocations in maturing sperm. The semisterile translocation carriers and their normal counterparts were used to determine the health impact of transmitted chromosomal rearrangements through anatomical analysis of their immediate descendants in utero. As expected, semisterility resulted primarily from embryonic death during the periimplantation stages presumably caused by sperm segregants with unbalanced chromosome complement fertilizing some of the eggs. Among conceptuses that survived to mid- and late-gestation stages, there was an increased incidence of developmental anomalies including fetal death and phenotypic defects. These anomalies are assumed to be caused by certain types of unbalanced segregants that are compatible with survival beyond the periimplantation period. This class of unbalanced segregants represent in humans a major health problem to the mother and her conceptus.     

Springtail postmolt vulnerability to pseudoscorpion predation: Mechanisms and implications

Arthropod prey are expected to be more vulnerable to their predators immediately following molt. The effects of springtail (Isotoma carpenteri) postmolt vulnerability on interactions with a pseudoscorpion predator were examined in the laboratory. Springtails exposed to vials pretreated with pseudoscorpions (Apochthonius minimus) delayed molting compared to those prey that were exposed to vials pretreated only with springtails. Although their escape ability (measured as distance jumped) was unaffected by molt condition, postmolt springtails were more profitable in terms of reduced predator handling time following capture. Despite this,A. minimus did not distinguish between postmolt and intermolt prey presented at either end of a T-maze.     

Distribution of vasoactive intestinal peptide-like immunoreactivity in the taste organs of teleost fish and frog

Summary Using immunohistochemistry, vasoactive intestinal peptide (VIP) was visualized in taste bud cells of the carp, Cyprinus carpio, and the European catfish, Silurus glanis, by means of light and electron microscopy. Intracellular membrane systems, presumably smooth endoplasmic reticulum, of light (sensory) cells, but not of dark (supporting) cells and basal cells, were densely labelled with antibody. In the frog (four species: Rana temporaria, R. ridibunda, R. arvalis, R. pipiens), taste bud cells did not label. However, the dense basal nerve fibre plexus, some subepithelial ganglionic cells, but no ascending intragemmal fibres, were immunoreactive. In fish, the results support evidence that VIP is involved in the modulation of taste transduction at the level of receptor cells. In the frog, an indirect, possibly vasodilatatory effect on taste perception may be considered.     

Capillary recruitment and transit time in the rat lung

Presson, Robert G., Jr., Thomas M. Todoran, Bracken J. DeWitt, Ivan F. McMurtry, and Wiltz W. Wagner, Jr.Capillary recruitment and transit time in the rat lung.J. Appl. Physiol. 83(2): 543-549, 1997.Increasing pulmonary blood flow and the associated rise incapillary perfusion pressure cause capillary recruitment. The resultingincrease in capillary volume limits the decrease in capillary transittime. We hypothesize that small species with relatively high restingmetabolic rates are more likely to utilize a larger fraction ofgas-exchange reserve at rest. Without reserve, we anticipate thatcapillary transit time will decrease rapidly as pulmonary blood flowrises. To test this hypothesis, we measured capillary recruitment andtransit time in isolated rat lungs. As flow increased, transit timedecreased, and capillaries were recruited. The decrease in transit timewas limited by an increase in the homogeneity of the transit time distribution and an increased capillary volume due, in part, to recruitment. The recruitable capillaries, however, were nearly completely perfused at flow rates and pressures that were less thanbasal for the intact animal. This suggests that a limited reserve ofrecruitable capillaries in the lungs of species with high restingmetabolic rates may contribute to their inability to raiseO₂ consumption manyfold abovebasal values.