Loxiglumide, a CCK-A receptor antagonist, stimulates calorie intake and hunger feelings in humans

Exogenous cholecystokinin (CCK) induces early satiety when infused into humans. Whether alimentary CCK (CCK-A) receptor blockade stimulates food intake in humans is, however, uncertain. The aim of the present investigation was, therefore, to establish the effect of CCK-A receptor blockade on satiety and eating behavior in healthy volunteers. To further explore the role of endogenous CCK, the effects of the specific CCK-A receptor antagonist loxiglumide (Lox; 22 micromol. kg(-1). h(-1)) on satiety and eating behavior were investigated in healthy men and compared with saline infusions (as placebo) in a series of randomized, double-blind, placebo-controlled, crossover studies. Lox produced a slight (7%), but not significant (P = 0.104), increase in food intake that was accompanied by a modest (10%), but significant (P < 0.004), increase in calorie intake. Fluid ingestion was not affected by Lox. Subjects experienced more hunger and delayed fullness during Lox infusion than during saline infusion (P < 0.05). This study provides further evidence that CCK is an endogenous physiological satiety signal acting through CCK-A receptor-mediated mechanisms. Repeated-dose studies comparing hunger and satiety responses after CCK-A receptor blockade in healthy subjects and patients with eating disorders may help clarify the possible involvement of endogenous CCK in these conditions.     

Genomic affinities in Arachis section Arachis (Fabaceae): molecular and cytogenetic evidence

Section Arachis is the largest of nine sections in the genus Arachis and includes domesticated peanut, A. hypogaea L. Most species are diploids (x=10) with two tetraploids and a few aneuploids. Three genome types have been recognized in this section (A, B and D), but the genomes are not well characterized and relationships of several newly described species are uncertain. To clarify genomic relationships in section Arachis, cytogenetic information and molecular data from amplified fragment length polymorphism (AFLP) and the trnT-F plastid region were used to provide an additional insight into genome composition and species relationships. Cytogenetic information supports earlier observations on genome types of A. cruziana, A. herzogii, A. kempff-mercadoi and A. kuhlmannii but was inconclusive about the genome composition of A. benensis, A. hoehnei, A. ipaensis, A. palustris, A. praecox and A. williamsii. An AFLP dendrogram resolved species into four major clusters and showed A. hypogaea grouping closely with A. ipaensis and A. williamsii. Sequence data of the trnT-F region provided genome-specific information and showed for the first time that the B and D genomes are more closely related to each other than to the A genome. Integration of information from cytogenetics and biparentally and maternally inherited genomic regions show promise in understanding genome types and relationships in Arachis.     

The simple repeat poly(dT-dG).poly(dC-dA) common to eukaryotes is absent from eubacteria and archaebacteria and rare in protozoans

Genomic DNA from a wide variety of prokaryotic and eukaryotic organisms has been assayed for the simple repeat sequence poly(dT-dG).poly(dC-dA) by Southern blotting and DNA slot blot hybridizations. Consistent with findings of others, we have found the simple alternating sequence to be present in multiple copies in all organisms in the animal kingdom (e.g., mammals, reptiles, amphibians, fish, crustaceans, insects, jellyfish, nematodes). The TG element was also found in lower eukaryotes (Saccharomyces cerevisiae, Neurospora crassa, and Dictyostelium discoideum) and at a much lower frequency in protozoans (Oxytricha fallux and Tetrahymena thermophila). The sequence was also repeated in high copy number in a higher plant (Zea mays) as well as at very high levels in a unicellular green alga (Chlamydomonas reinhardi). Although the copy number of the repeat per haploid genome was generally proportional to genome size, there was a greater-than-1,000-fold variation in the number of (TG)25/100-kb genomic DNA. By contrast, no eu-or archaebacterium--including Myxococcus xanthus, whose life cycle is very similar to that of the slime mold Dictyostelium discoideum, and Halobacter volcanii, whose genome contains other repeated sequences-- was found whose genomic DNA contained this sequence in detectable amounts. A computer search also failed to find the TG element in human mitochondrial DNA.      

Screening for microorganisms performing the stereoselective reduction of α-formyl-esters

Summary 107 Microorganisms selected from 26 genera belonging to bacteria, actinomycetes, fungi and yeasts were screened for their ability to reduce -formyl-esters stereoselectively. Eighteen strains have been found which were able to reduce at least one of 5 substrates tested with an optical purity of more than 85% ee. The best strains were Candida humicola, Aspergillus petrakii, Streptomyces hydrogenans and Streptomyces griseus. The dependence of the enantioselectivity of the reduction on the group of microorganisms and on the substituents of the formyl-esters is discussed.     

Protein evolution in different cellular environments: cytochrome b in sharks and mammals

DNA sequences for the mitochondrial cytochrome b gene were determined for 13 species of sharks. Rates and patterns of amino acid replacement are compared for sharks and mammals. Absolute rates of cytochrome b evolution are six times slower in sharks than in mammals. Bivariate plots of the number of nonsynonymous and silent transversions are indistinguishable in the two groups, however, suggesting that the differences in amino acid replacement rates are due primarily to differences in DNA substitution rates. Patterns of amino acid replacement are also similar in the two groups. Conserved and variable regions occur in the same parts of the cytochrome b gene, and there is little evidence that the types of amino acid changes are significantly different between the groups. Similarity in the relative rates and patterns of protein change between the two groups prevails despite dramatic differences in the cellular environments of sharks and mammals. Poor penetrance of physiological differences through to rates of protein evolution provides support for the neutral theory and suggests that, for cytochrome b, patterns of evolution have been relatively constant throughout much of vertebrate history.      

Selection for fresh weight in Arabidopsis thaliana under two mating systems

Summary Four races of Arabidopsis thaliana were used to produce two F ₂ populations and these constituted the base populations of an artifical selection study. All plants were grown under aseptic culture conditions in a controlled environment and the character studied was fresh weight after 15 days' growth. For one section of the study, two selection intensities were applied to each F ₂ population and the selected parents were randomly mated. In addition to the high selections a group of random selections were maintained as a control. In the second section of the study the procedure differed only in that mating was by self-fertilization.For one population the selection response was as expected for a character of low heritability. A regular response was also observed for the other population when mating was at random, but the results for selection with self-fertilization indicated the presence of dominance effects. The overall conclusion was that selection with random mating and selection with self-fertilization produced approximately equal genetic gains.

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Zusammenfassung Vier Rassen von Arabidopsis thaliana wurden verwendet, um zwei F ₂-Populationen herzustellen, die als Ausgangspopulationen für Untersuchungen über künstliche Selektion dienten. Alle Pflanzen wurden unter sterilen Kulturbedingungen in kontrollierter Umwelt gezogen, das untersuchte Merkmal war das Frischgewicht nach 15tägigem Wachstum. In einem Teil des Versuchs wurden zwei Selektionsintensitäten auf jede der F ₂-Populationen angewandt und die selektierten Eltern zufällig gepaart. Zusätzlich zur strengen Selektion wurde eine Gruppe zufallsgemäß ausgewählter Individuen als Kontrolle gezogen. Im zweiten Teil des Versuchs unterschied sich das Vorgehen vom vorigen nur dadurch, daß die zufällige Paarung durch Selbstbefruchtung ersetzt wurde.Für eine Population war der Selektionserfolg wie für ein Merkmal mit niedriger Heritabilität zu erwarten. Eine reguläre Antwort wurde auch für die andere Population beobachtet, wenn die Paarung zufällig erfolgte, jedoch zeigten die Ergebnisse der Selektion mit Selbstbefruchtung das Vorkommen von Dominanzeffekten an. Insgesamt wird gefolgert, daß Selektion verbunden mit zufälliger Paarung und Selektion verbunden mit Inzucht näherungsweise gleiche genetische Gewinne zur Folge hatten.

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Paper number 3497 of the Journal Series of the North Carolina State University Agricultural Experiment Station, Raleigh, N.C. This investigation was supported in part by Public Health Service Research Grant GM11546 from the Division of General Medical Sciences. The support for computing was provided by the National Institutes of Health Grant FR-00011. The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Experiment Station of the products named, nor criticism of similar ones not mentioned.