Effects of a new cholecystokinin antagonist (GE 410) on the smooth muscle of the guinea pig ileum

Summary Suc-Tyr-(SE)-Met-Gly-Trp-Met-Asp--phenethylamide (GE 410) competitively antagonized the contractions of smooth muscle strips from guinea pig ileum (pA₂=7.6, n=0.95) induced by cholecystokinin-octapeptide (CCK8). GE 410 inhibited the electrically-induced cholinergically mediated contractile responses and the [³H]ACh release in the ileum, as well as the CCK-stimulated electrical contractile responses and the [³H]ACh release in the cholinergic nerve terminals. The results suggest the existence of CCK-receptors not only in the smooth muscles but also on the neurons.     

Metabolism of 3β-hydroxycholest-5-en-26-oic acid in hamsters

Summary Metabolism of 26-hydroxycholesterol to 3-hydroxychol-5-en-24-oic acid and other C24-bile acids has been expected to occur by way of 3-hydroxycholest-5-en-26-oic acid in studies in vitro. 3-Hydroxycholest-5-en-26-oic acid was infused intravenously into bile fistula hamsters and the following C24-bile acids were identified: 3-hydroxychol-5-en-24-oic acid, lithocholic acid, chenodeoxycholic acid, and a small amount of cholic acid.     

Evidence from carbon isotope measurements for diverse origins of sedimentary hydrocarbons

The organic matter found in sedimentary rocks must derive from many sources; not only from ancient primary producers but also from consumers and secondary producers. In all of these organisms, isotope effects can affect the abundance and distribution of 13C in metabolites. Here, by using an improved form of a previously described technique in which the effluent of a gas chromatograph is continuously analysed isotopically, we report evidence of the diverse origins of sedimentary organic matter. The record of 13C abundances in sedimentary carbonate and total organic carbon can be interpreted in terms of variations in the global carbon cycle. Our results demonstrate, however, that isotope variations within sedimentary organic mixtures substantially exceed those observed between samples of total organic carbon. Resolution of isotope variations at the molecular level offers a new and convenient means of refining views both of localized palaeoenvironments and of control mechanisms within the global carbon cycle.     

2-Methoxybenzoyl phosphate: a new substrate for continuous fluorimetric and spectrophotometric acyl phosphatase assays

A new aromatic acyl phosphate, 2-methoxybenzoyl phosphate, has been synthesized. The compound shows an intrinsic fluorescence; it displays an intense emission band at 390 nm upon excitation in the near UV region. This band practically disappears after hydrolysis of the product. On the other hand, the product displays differences in the near UV absorption spectra measured before and after hydrolysis. The at 301 nm is 2720 M^–1 cm^–1, a value that is 4.3-fold higher than that of benzoyl phosphate (the usual substrate for acylphosphatase assay) at 283 nm. The main kinetic parameters of three different acylphosphatase molecular forms (the muscular isoenzyme and two subtypes of the organ common isoenzyme) were determined using both benzoyl phosphate and 2-methoxybenzoyl phosphate as substrates, and then compared. These kinetic data and the UV absorption and fluorescence properties of 2-methoxybenzoyl phosphate sugest that this compound has better substrate features than benzoyl phosphate, and can be used for both high sensitivity continuous fluorimetric and UV absorption spectrophotometric assays of acylphosphatase.     

Population biology of bryozoans: correlates of sessile,colonial life histories in freshwater habitats

Bryozoans are common, often abundant, sessile, colonial invertebrates of freshwaters. By reviewing what is known of their general ecology and considering in further detail the population biology of specific groups, we provide evidence that 1) populations are locally ephemeral and regional persistence is attained via a dynamic equilibrium between dispersal and colonization, and 2) sex may often be infrequent and a high degree of clonality obtains at both local and regional scales. On the basis of these characteristics we discuss how the group offers exceptional opportunities for investigating a number of fundamentally important ecological and evolutionary questions.The highly curious modification of the Molluscan type which the Polyzoa [=Bryozoa] present... the great beauty of their forms, and the facility with which they can in general be observed in a living state, cannot but render them special favorites for every lover of Nature; and for the more profound student must confer on them a peculiar significance, and invest their study with a scientific interest which is scarcely surpassed by that of any other group of animals.... (Allman 1856)     

Presence of hsp65 in bacterial extracts (OM-89): A possible mediator of orally-induced tolerance?

Heat shock proteins (HSP) have been implicated in rodent models of autoimmunity, particularly arthritis, and there is suggestive though inconclusive evidence that they may also play a role in human autoimmune disease. The simplest hypothesis is based on molecular mimicry due to the amino-acid sequence homology between mammalian and microbial HSP. Recently OM-89, an extract of several strains ofEscherichia coli, has shown some efficacy in the treatment of rheumatoid arthritis (RA) when taken orally. Using species-specific antibodies, we show here that OM-89 contains the 65 kDa HSP (hsp65), while hsp65 was not detected in another bacterial extract containing other microorganisms, includingStaphylococcus aureus (OM-85). We suggest that if the human homologue of hsp65 is a relevant target antigen in the human disease, the efficacy of the preparation could be due to induction of oral tolerance or to switching the Th1 response towards Th2. Alternatively, even if the human hsp65 is not a target molecule in RA joints, OM-89 may evoke bystander suppression of joint inflammation via induction of TGF-secreting effector cells. These hypotheses should be tested in further studies.     

Energy flow and community structure in freshwater ecosystems

The goal of this article is twofold: 1) It aims at providing an overview on some major results obtained from energy flow studies in individuals, populations, and communities, and 2) it will also focus on major mechanisms explaining community structures. The basis for any biological community to survive and establish a certain population density is on the one hand energy fixation by primary producers together with adequate nutrient supply and the transfer of energy between trophic levels (bottom-up effect). On the other hand, predator pressures may strongly control prey population densities one or more trophic levels below (top-down effect). Other interpopulation effects include competition, chemical interactions and evolutionary genetic processes, which further interact and result in the specific structuring of any community with respect to species composition and population sizes.     

Sex pheromone of the pine sawflyDiprion pini (Hymenoptera: Diprionidae): Chemical identification,synthesis and biological activity

The main component of the sex pheromone secretion of femaleDiprion pini L. (Hymenoptera: Diprionidae) from insects collected both in Finland and in France has been identified as athreo-3,7-dimethyl-2-tridecanol (8 ng per female) stereoisomer by GC-MS and synthesis. The secretion also contains lower and higher homologues in small amounts (1–4% of the main component). Combined gas chromatographic-electroantennographic detection showed activity in both natural and esterified extracts (acetates and propionates); the esters of the main component gave the largest responses. The acetates and propionates of the eight stereoisomers of 3,7-dimethyl-2-tridecanol were synthesized from enantiomerically highly enriched (>99% ee) building blocks. The stereochemistry of the main component was established to be (2S,3R,7R)-3,7-dimethyl-2-tridecanol by GC analysis of the natural material. It was purified by liquid chromatography prior to the GC analysis of both its pentafluorobenzoates and its isopropylcarbamates on a non-chiral polar column (ECD) and a chiral column (NPD), respectively. Field tests demonstrated that both the acetate and propionate of the main component (100 g of each applied on cotton roll dispensers) were active in attracting males, with or without the presence of several of the minor compounds. Experiments with smaller amounts of the acetate and the propionate (1 g in France and 50 g in Finland) demonstrated that the propionate was more active than the acetate, and that it also caught more males than a blend of the two compounds.