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  • 1
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The importance of predators in controlling the densities of infaunal (〉0.5 mm) organisms was investigated in the mesohaline region of the Upper Chesapeake Bay (USA) using field experiments. The role of predators in controlling infaunal density and community characteristics varied with habitat type, season (i.e., predator abundance) and developmental or successional stage of the community. Few infaunal species were adversely affected by predator exclusion. Species that increased greatly in abundance in the absence of predators (e.g. Eteone heteropoda, Streblospio benedicti, Nereis succinea, and juvenile Macoma balthica and Mya arenaria) lived near the sediment-water interface and had major population pulses from fall through spring. Species whose abundances increased moderately or were not affected by predator exclusion were deeper burrowing organisms (e.g. Heteromastus filiformis and adult Mya arenaria), or were relatively small organisms (e.g. Paraprionospio pinnata, Scolecolepides viridis and Peloscolex gabriellae) whose principal predators could be other members of the infauna. Competition did not appear to be an important factor controlling infaunal density in these experiments.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0428
    Keywords: β-Casomorphin ; enkephalin ; naloxone ; insulin release ; exorphins ; opiates ; dog
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We have previously demonstrated that opiate-like substances in food protein (exorphins), contained in the peptic digest of gluten, stimulate insulin and glucagon release in dogs and that this effect is inhibited by the opiate antagonist naloxone. The present study was designed to evaluate the possible rôle of ingested opiate-like substances in the modulation of post-prandial insulin release. Similarly, the addition of synthetic β-casomorphins, which are the opioid-active material of bovine casein peptone, elicit a stimulation of post-prandial insulin release during a liver extract-sucrose test meal. The addition of met-enkephalin to a liver extract-sucrose test meal also augmented the post-prandial insulin response. Both stimulatory effects were reversed by oral naloxone, as was the post-prandial increase of insulin following ingestion of bovine casein peptone (casopeptone). The post-prandial insulin response to digested and undigested liver extract was not affected by naloxone, suggesting that the foregoing effects are likely to be specific to opiate-like materials contained in foodstuff (exorphins). In view of previous findings, the present data are compatible with a role of opiate-like substances contained in ingested nutrients in the regulation of post-prandial insulin secretion.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Heterodiamantanes and Structurally Related Compounds. Part IV. The Pentacyclic C12-Diethers 5, 14-Dioxapentacyclo[7.5.0.02,6.03,13.04,10]tetradecane, 4,14-Dioxapentacyclo[7.4.1.02,8.03,11.05,10]tetradecane, 3,11-Dioxapentacyclo[8.31.02,8.04,13.07,12]tetradecane, and 3,10-Dioxapentacyclo[7.3.1.14,12.02,7.06,11]tetradecane (3,10-Dioxadiamantane)In connection with the studies on heterodiamantanes and structurally related compounds the four novel pentacyclic diethers 6-9 were prepared starting from the cyclopentadienone dimer 12, All five compounds have as common features a central carbocyclic 6-membered ring with four axial alkyl substituents and two oxygen functions in 1,4-positions. The required twelfth C- atom was introduced by dichlorocarbene addition to 11 (the rnonocarbene adduct of 12) (→ 10, Scheme 2). The two three-membered rings in 10 had to be opened step wise. Controlled thermolysis of 10 yielded the chloride 13 and the acetate 14, respectively, from which the alcohols 16, 17 and 20 as well as the acetates 22 and 23 were obtained by reduction (Scheme 2). The remaining second ring was opened again thermally either to tricyclic compounds as 22 → 25 + 26, 23 → 27 + 28 or under simultaneous ether formation to tetra-cyclic compounds as 16 → 29 + 30, 17 → 32 + 33, 20 → 34 + 35 (Scheme 3). The two compounds 29 and 30 were also obtained from 37, the dichlorocarbene adduct of the tricyclic C11-ether 36 (Scheme 4). These tri- and tetracyclic compounds 25-30 and 32-35 were suitable intermediates for the syntheses of all four pentacyclic diethers 6-9.Diether 6 was prepared from 25, 26, 29 as well as 30 via 38 (Scheme 5), and from 29 by the route depicted in Scheme 6. By a procedure analogous to the latter one, diether 7 was obtained from 30 (Scheme 6). Diether 8 was the result of transformations starting from either 27, 28, 32 or 33 (Scheme 7). The synthesis of diether 9 (3,10-dioxadiamantane), the thermodynamically most stable of the four diethers 6-9, was achieved in three different ways : ring closure starting from the highly substituted tricyclic compounds 25 and 26 (Scheme 9), skeletal rearrangement of the group-A
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
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