Neuropathy Target Esterase: Rates of Turnover In Vivo Following Covalent Inhibition with Phenyl Di-n-Pentylphosphinate

Phenyl di-n-pentylphosphinate is a reasonably stable easily synthesized inhibitor of neuropathy target esterase (NTE) with low anticholinesterase activity. Like phenylmethylsulphonyl fluoride it protects hens against neuropathic effects of compounds such as diisopropylphosphorofluoridate. At intervals up to 15 days after dosing hens (10 mg/kg s.c. to inhibit 90% NTE) assays were made of catalytically active and of phosphinylated NTE in autopsy tissue. The sum of these components was always within the range of catalytic activity in undosed controls. However, the half-life of reappearance of active NTE was 2.07 days +/- 0.13 (SD, n = 6) for brain and 3.62 days +/- 0.23 (SD, n = 6) for spinal cord--shorter than after dosing with phenylmethylsulphonyl fluoride. It is proposed that: (1) The physiological turnover mechanism cannot distinguish between catalytically active and di-n-pentylphosphinylated NTE although initiation of organophosphate-induced delayed polyneuropathy might involve recognition of aged di-alkyl-phosphorylated NTE as "foreign". (2) The short half-lives indicate a slow spontaneous dephosphinylation of inhibited NTE occurs in vivo as well as de novo synthesis. The difference in half-lives for brain and spinal cord NTE may be due to different rates of synthesis de novo or (more likely) to different rates of spontaneous reactivation of the inhibited NTE in the two tissues.     

Naloxone reverses L-dopa induced overstimulation effects in a Parkinson's disease animal model analogue

Chronic L-DOPA treatment of Parkinson's disease frequently leads to the development of motoric overstimulation and hyperkinetic movements. To investigate this problem in the laboratory, rats surgically altered by unilateral 6-hydroxydopamine lesions (6-OHDA) were chronically treated with one L-DOPA (10 mg/kg i.p.) injection per day for 20 days. In this 6-OHDA rotation model, the unilateral dopamine denervation results in a profound contralateral sensory-motor neglect and the animals spontaneously rotate in a direction ipsilateral to the dopamine depleted hemisphere. Initially, the L-DOPA treatment did not alter the response bias but after several weeks, the response bias was reversed and the animals rotated in the formerly akinetic direction, contralaterally, at a significantly higher level. Using this overstimulation effect as an analogue of the clinically observed L-DOPA overstimulation, animals were given naloxone in conjunction with the L-DOPA treatment. Naloxone (0.10, 0.25 and 0.50 mg/kg i.p.) produced a dose related decrease in the L-DOPA induced contralateral rotation. Consistent with an expected selective effect on the L-DOPA induced rotation, a dose related increase in ipsilateral rotation was observed. These results suggest that naloxone can attenuate the overstimulation effect of L-DOPA and that this effect is not attributable to non-specific response suppression effects.     

Genetic and physical mapping of the patatin genes in potato and tomato

Summary Genes for the major storage protein of potato, patatin, have been mapped genetically and physically in both the potato and tomato genomes. In potato, all patatin genes detected by the cDNA clone pGM01 map to a single locus at the end of the long arm of chromosome 8. By means of pulsed field gel electrophoresis (PFGE) it was possible further to delimit this locus, containing 10–15 copies of the gene, to a maximum size of 1.4 million base pairs. Hybridizations with class-specific clones suggest that the locus is at least partially divided into domains containing the two major types of patatin genes, class I and II. In tomato, patatin-homologous sequences were found to reside at the orthologous locus at the end of chromosome 8. The approximately three copies in tomato were localized by PFGE to a single fragment of 300 kilobases. Whereas the class II-specific 5 promoter sequences reside in tomato at the same locus as the coding sequences, the single class I-specific copy of the 5 promoter sequences was localized on chromosome 3 with no coding sequence attached to it. A clone from this chromosome 3 locus of tomato was isolated and by restriction fragment length polymorphism mapping it could be further shown that a similar class I-specific sequence also exists on chromosome 3 of potato. As in tomato, this copy on chromosome 3 is not linked to a coding sequence for patatin. The results are discussed with respect to genome evolution and PFGE analysis of complex gene families.     

Metabolic changes following eccentric exercise in trained and untrained men

The effects of one 45-min bout of high-intensity eccentric exercise (250 W) were studied in four male runners and five untrained men. Plasma creatine kinase (CK) activity in these runners was higher (P less than 0.001) than in the untrained men before exercise and peaked at 207 IU/ml 1 day after exercise, whereas in untrained men the maximum was 2,143 IU/ml 5 days after exercise. Plasma interleukin-1 (IL-1) in the trained men was also higher (P less than 0.001) than in the untrained men before exercise but did not significantly increase after exercise. In the untrained men, IL-1 was significantly elevated 3 h after exercise (P less than 0.001). In the untrained group only, 24-h urines were collected before and after exercise while the men consumed a meat-free diet. Urinary 3-methylhistidine/creatinine in the untrained group rose significantly from 127 mumol/g before exercise to 180 mumol/g 10 days after exercise. The results suggest that in untrained men eccentric exercise leads to a metabolic response indicative of delayed muscle damage. Regularly performed long distance running was associated with chronically elevated plasma IL-1 levels and serum CK activities without acute increases after an eccentric exercise bout.     

Influence of dilution on the physical state of model bile systems: NMR and quasi-elastic light-scattering investigations

Multinuclear (1H and 31P) nuclear magnetic resonance (NMR) spectroscopy and quasi-elastic light scattering have been used to characterize molecular aggregates formed in dilute sodium taurocholate--egg lecithin solutions. When mixed micelles (1.25 g/dL) are diluted with 150 mM aqueous sodium chloride, light-scattering measurements suggest a transformation from mixed micelles to unilamellar vesicle species. Decreased 1H NMR line widths for bile salt resonances are consistent with predominance of a monomer form. The concurrent appearance of a second phospholipid choline methyl resonance indicates two types of phospholipid environment in slow chemical exchange: this behavior is consistent with small unilamellar vesicles. The appearance of bilayer vesicles in dilute model bile solutions is confirmed by addition of a lanthanide shift reagent (Pr3+), which splits the 1H or 31P head-group peak into two components with distinct chemical shift sensitivities. These mixed micelle and vesicle aggregates are also distinguished by their susceptibility to the lipolytic enzyme phospholipase A2 from cobra venom.     

Coassimilation of dietary fat and benzo(a)pyrene in the small intestine: an absorption model using the killifish

Benzo(a)pyrene (BP) was dissolved in dietary fat and fed in a single dose to killifish (Fundulus heteroclitus). Fluorescence microscopic examinations of small intestinal content and frozen sections of whole small intestine revealed that during fat digestion BP was codispersed in liquid crystalline product phases produced during lipolysis (1979. Patton, J. S., and M. C. Carey, Science. 204: 145-148) and then coabsorbed with dietary lipid followed by its reappearance in intracellular fat droplets. During the time that the absorbed fat remained in the enterocytes, BP fluorescence was initially concentrated in the intracellular fat droplets and then spread throughout the cytosol of the enterocytes. Tissue analyses showed that BP was rapidly metabolized in the intestine and transported to the gallbladder. These studies show that separation of a dissolved hydrophobic carcinogen from dietary fat occurs primarily after the fat has been digested, dispersed, absorbed, and reassembled in the enterocyte. The inability of the enterocyte to discriminate between dietary fat and dissolved carcinogenic compounds may be a partial explanation of the observed link between high fat diets and the incidence of some cancers. In vertebrates, the intestine and not the liver, appears to be the major site of metabolism of dietary polycyclic aromatic hydrocarbons (PAHs).     

Large scale selection of aluminum-resistant mutants from plant cell culture: expression and inheritance in seedlings

Summary A large number of aluminum-resistant variants, selected from non-mutagenized homozygous diploid cell cultures of Nicotiana plumbaginifolia Viv., are characterized. Of 115 variants cloned and reselected from single cells, 67 retained Al resistance in callus cultures after 6–9 months of growth in the absence of Al. There was no association between Al resistance and callus growth in the absence of Al, suggesting that the Al-resistant phenotype is not detrimental in the absence of Al challenge and that Al resistance is not the result of increased vigor. Plants regenerated from initially resistant callus lines that subsequently lost their resistance failed, with one exception, to transmit resistance to their seedling progeny. Fertile plants were regenerated from 40 of the 67 variants that retained stable Al resistance in callus culture. All 40 transmitted Al resistance to their seedling progeny (selfed and backcrossed) in segregation ratios expected for a single dominant mutation. The selfed progeny of many variants also segregated for recessive lethal mutations which were attributed to independent mutations that occurred during cell culture.     

Comparative ontogeny of photobehavioural responses of charrs (Salvelinus species)

Synopsis The development of photobehavioural responses in brook (Salvelinus fontinalis) and lake (S. namaycush) charr was studied by monitoring the intrasubstrate movements and concurrent photoresponse behaviour of incubated embryos and alevins. Photoresponse behaviour of both F-1 hybrids of the parent species was also recorded. All embryos initially moved downward in the substrate, however brook charr descended farther and faster into the substrate than did lake charr. Photoresponse tests demonstrated a similar pattern of photoresponse transformation from a photonegative to a photopositive state in both species. However, photoresponse reversal was faster, more extensive and occurred later in brook charr than in lake charr. Patterns of photoresponse change in F-1 hybrids were intermediate between those of the parent species. Photoresponse shifts preceded the onset of alevin emergence in both species. occurring when differential development of various morphological characters existed. Developmental states of characters were synchronously maximal towards the end of alevin emergence. Intermediate measures of morphological development were observed for F-1 hybrids. Possible functions and mechanisms of photoresponse transitions are discussed in relation to ecological differences between the species.     

Mathematical model of biliary lipid secretion: a quantitative analysis of physiological and biochemical data from man and other species

We propose a simple mathematical model to account for the coupling of secretion rates of bile salts, lecithin, and cholesterol into bile. The model assumes that: 1) molecules of "biliary" lecithin and cholesterol enter a functional compartment located in the endoplasmic reticulum of the hepatocyte from which they are secreted into bile, and in the case of cholesterol, also catabolized to bile salts; 2) the rates at which lecithin and cholesterol enter the "secretory" compartment are regulated independently by feedback loops that control their synthesis and/or uptake; 3) lecithin secretion is coupled by an unknown transport mechanism, possibly micellar or vesicular, to the flux of bile salts passing through the compartment; 4) cholesterol secretion is coupled by a similar mechanism to lecithin secretion and not to bile salt secretion directly; and 5) bile salt synthesis is proportional to the cholesterol content of the compartment. The model predicts that in the steady state the dependences, lecithin secretion vs bile salt secretion; cholesterol secretion vs lecithin secretion; and cholesterol secretion vs bile salt secretion, will all have the form of rectangular hyperbolae. Four independent parameters related to the postulated mechanisms of biliary lipid synthesis, uptake, and transport determine the quantitative features of these hyperbolae. These four "secretion parameters" also determine how the biliary lipid composition of hepatic and "fasting" gallbladder bile varies with bile salt secretion rate. A quantitative analysis of biochemical and physiological data on biliary lipid secretion in rat, dog, and man confirms the general predictions of the model. Deductions of the secretion parameters are made for each species and are compared with other relevant data on biliary lipid metabolism. From this analysis, we offer new insights into: i) the species differences in biliary lipid secretion and bile composition; ii) the influence of obesity on biliary lipid secretion in man; and iii) the causes of cholesterol super-saturation in fasting gallbladder bile.     

Expression of a Lactose Transposon (Tn951) in Zymomonas mobilis

The potential utility of Zymomonas mobilis as an organism for the commercial production of ethanol would be greatly enhanced by the addition of foreign genes which expand its range of fermentable substrates. We tested various plasmids and mobilizing factors for their ability to act as vectors and introduce foreign genes into Z. mobilis CP4. Plasmid pGC91.14, a derivative of RP1, was found to be transferred from Escherichia coli to Z. mobilis at a higher frequency than previously reported for any other plasmids. Both tetracycline resistance and the lactose operon from this plasmid were expressed in Z. mobilis CP4. Plasmid pGC91.14 was stably maintained in Z. mobilis at 30°C but rapidly lost at 37°C.