Effect of feeding pattern on the sensitivity of hepatic carnitine palmitoyl-transferase to inhibition by malonyl-CoA in the rat

1. The feeding pattern influences the inhibitory effects of malonyl-CoA on carnitine palmitoyltransferase-I. 2. The sensitivity of liver carnitine palmitoyltransferase-I to malonyl-CoA is increased in rats meal-fed when compared to rats fed ad libitum. 3. Moreover, liver carnitine palmitoyltransferase-I of meal-fed rats remains more sensitive to inhibition by malonyl-CoA during a 24 hour fast than liver carnitine palmitoyltransferase-I of rats previously fed ad libitum.     

Disentangling invasion processes in a dynamic shipping-boating network

The relative importance of multiple vectors to the initial establishment, spread and population dynamics of invasive species remains poorly understood. This study used molecular methods to clarify the roles of commercial shipping and recreational boating in the invasion by the cosmopolitan tunicate, Botryllus schlosseri. We evaluated (i) single vs. multiple introduction scenarios, (ii) the relative importance of shipping and boating to primary introductions, (iii) the interaction between these vectors for spread (i.e. the presence of a shipping-boating network) and (iv) the role of boating in determining population similarity. Tunicates were sampled from 26 populations along the Nova Scotia, Canada, coast that were exposed to either shipping (i.e. ports) or boating (i.e. marinas) activities. A total of 874 individuals (c. 30 per population) from five ports and 21 marinas was collected and analysed using both mitochondrial cytochrome c oxidase subunit I gene (COI) and 10 nuclear microsatellite markers. The geographical location of multiple hotspot populations indicates that multiple invasions have occurred in Nova Scotia. A loss of genetic diversity from port to marina populations suggests a stronger influence of ships than recreational boats on primary coastal introductions. Population genetic similarity analysis reveals a dependence of marina populations on those that had been previously established in ports. Empirical data on marina connectivity because of boating better explains patterns in population similarities than does natural spread. We conclude that frequent primary introductions arise by ships and that secondary spread occurs gradually thereafter around individual ports, facilitated by recreational boating.     

Influence of phosphatidylcholine/cholesterol molar ratios in liposomes on cholesterol reactivity with cholesterol:oxygen oxidoreductase]

The reactivity of sonicated phosphatidylcholine-cholesterol liposomes with cholesterol : oxygene oxydoreductase, an enzyme which catalyses the oxidation of the 3 beta hydroxyl group of cholesterol to a ketone group, is compared with that of ternary system phosphatidylcholine-cholesterol-Thesit. Regardless to the phosphatidylcholines nature and the phosphatidylcholine/cholesterol molar ratio (R), the enzymatic oxidation rate of liposomal cholesterol is slower than when the reaction is developed in the present of Thesit, a surfactif agent which destroyes the lamellar particles. This is true whether Thesit is added during preparation of dispersions or during incubation with cholesterol oxydase. The enzymatic oxydation rate of cholesterol of ternary systems phosphatidylcholine-cholesterol-Thesit is independent of the (R) value and the phosphatidylcholine fatty acid unsaturation, whereas that of phosphatidylcholine-cholesterol dispersions depends on these two parameters. The reaction rate increases in the order: dipalmitoylphosphatidylcholine to yolk egg phosphatidylcholines, and dioleylphosphatidylcholine. The optimal conditions for cholesterol oxidation were found to be R = 0.5. This result is not affected by the phosphatidylcholines nature. In order to explain these data, various hypotheses are considered. In particular, the weak liposomal cholesterol reactivity with cholesterol oxidase could result from an inhibitory effect on the enzyme-substrate combination due to the polar phosphorylcholine groups.     

A comparison of structure-activity relationships within alpha-MSH on melanophores of Anolis carolinensis and Rana pipiens

We have compared the structure-function relationship of the tridecapeptide alpha-melanocyte stimulating hormone (alpha-MSH) on the melanophores of the lizard Anolis carolinensis and the frog Rana pipiens by determining the melanosome-dispersing potency of 15 shorter peptide sequences and 8 substituted alpha-MSH analogues. Major differences were found between the lizard and the frog in their response to alpha-MSH peptide fragments and analogues. In Anolis, the sequence Ser-Tyr-Ser- is not as important for the pigmentary response as in Rana since alpha-MSH-(4-13) was nearly as potent (89%) as alpha-MSH-(1-13) (100%), whereas in Rana alpha-MSH-(4-13) potency was reduced to 7.5%. In addition, loss of potency due to removal of residues Pro and Val was more marked in Rana (alpha-MSH-(1-11) = 0.1%) than in Anolis (alpha-MSH-(1-11) = 1%), suggesting that this C-terminal sequence is necessary for pigmentary activity in the frog melanophore. These results together with those of other peptide fragments and analogues have led us to define the minimal pigmentary sequence of alpha-MSH as alpha-MSH-(4-12) in Anolis in contrast to alpha-MSH-(1-13) in Rana. This suggests that Anolis and Rana alpha-MSH receptors recognise different message amino acids of the alpha-MSH peptide sequence even though the final response (melanosome dispersion) is the same.     

Protein kinase C in fibroblasts. Characteristics of its intracellular location during growth and after exposure to phorbol esters and other mitogens

Using an N-bromosuccinimide cleavage fragment of histone H1 as a relatively specific substrate for protein kinase C, we evaluated the partitioning of this kinase activity between soluble and particulate cellular fractions in 3T3-L1 fibroblasts. In confluent, serum-deprived cells, protein kinase C activity was approximately equally divided between soluble and detergent-extractable particulate fractions; both rapidly growing and transformed cells appeared to contain higher levels of particulate enzyme activity. Soluble protein kinase C activity and immunoreactivity decreased to virtually undetectable levels after exposure of the cells to phorbol 12-myristate 13-acetate (PMA), associated with a commensurate increase in particulate kinase activity and immunoreactivity. In intact cells, PMA appeared to cause a shift of immunoreactive protein kinase C from the cytosol to the perinuclear region, as assessed by immunofluorescent microscopy; however; subcellular fractionation revealed that PMA caused increases in the protein kinase C activity associated primarily with non-nuclear membranes. Exposure of the cells to sn-1,2-dioctanoylglycerol resulted in a modest and transient membrane association of protein kinase C, whereas platelet-derived growth factor, fibroblast growth factor, and bombesin caused no detectable increases in the membrane association of the kinase. Activation of protein kinase C by growth factors in fibroblasts may occur without the gross disturbances in intracellular kinase location which occur in response to phorbol esters.     

Identification of interferon-gamma as the lymphokine that mediates leukotriene B4-induced immunoregulation

Leukotriene B4 (LTB4) has been shown to modulate lymphocyte responses in both a positive and a negative way, depending on the particular cell subsets it interacts with. Recent evidence also indicates that LTB4 can directly affect the production of cytokines such as interleukin 1 (IL 1) or interleukin 2 (IL 2) and interferon-gamma (IFN-gamma). In this report, we present evidence that human T cells pulsed with LTB4 modulate IL 1 production by human monocytes by secreting IFN-gamma. In fact, we found that LTB4-pulsed T cells were capable of inducing a suppression of lymphocyte proliferation if allowed to interact with monocytes, but that this suppression was reversed to an enhancing effect when monocytes were treated with the cyclooxygenase inhibitor indomethacin. Furthermore, LTB4-pulsed T cells released a soluble factor that would mediate both effects. This factor was found to be IFN-gamma, because affinity-purified IFN-gamma could reproduce the effects, and a rabbit polyclonal anti-serum to human IFN-gamma could block the activities of supernatants from LTB4-pulsed T cells. LTB4 was also shown to enhance IFN-gamma production by T4+ T cells and to inhibit IFN-gamma production by T8+ T cells. These results suggest that LTB4 may regulate immune cell functions by inducing IFN-gamma production by T4+ cells.     

L-641,953 (R-8-fluoro-dibenzo[b, f]thiepin-3-carboxylic acid-5-oxide): a novel thromboxane-prostaglandin endoperoxide antagonist

The effects of L-641,953 (R-8-fluoro-dibenzo[b, f]thiepin-3-carboxylic acid-5-oxide) have been studied on pulmonary and other smooth muscle preparations in vitro and in vivo. When studied in vitro on guinea-pig tracheal chains, L-641,933 produced significant shifts in the dose-response curves to the prostaglandin endoperoxide analogues, U-44069 (pA2 7.06) and U-46619 (pA2 7.14), and prostaglandin (PG) F2 alpha (pA2 6.33) had minimal activity against contractions induced by histamine (pA2 4.38), 5-hydroxytryptamine (pA2 4.63), and acetylcholine (pA2 4.56) and slightly enhanced relaxation induced by PGE2. When tested on the guinea-pig gall bladder strip in vitro, L-641,953 antagonized contractions induced by U-44069 (pA2 7.03) but was less active against those induced by PGF2 alpha (pA2 6.03), PGE1 (pA2 5.62), and histamine (pA2 4.84). When tested in vitro on the guinea-pig pulmonary artery, L-651-953 significantly antagonized contractions induced by U-44069 (pA2 7.04), U-46619 (pA2 7.14), and PGF2 alpha (pA2 7.16) but was less effective against contractions induced by histamine (pA2 4.19). Schild analysis indicated that L-641,953 was fully competitive against contractions of either the guinea-pig tracheal chain induced by U-46619 or the guinea-pig pulmonary artery induced by U-44069 and U-46619. When tested on human platelets in vitro L-641,953 inhibited aggregation induced by U-44069 (IC50 1.3 X 10(-6) M) but not ADP.(ABSTRACT TRUNCATED AT 250 WORDS)     

Metabolism and excretion of exogenous [3H]-LTC4 in primates

Four novel omega- and beta-oxidation (from the omega end) products of peptide leukotrienes, 20-hydroxy and 20-carboxy-LTE4, 18-carboxy-19, 20-dinor-LTE4 and 16-carboxy-17,18,19,20-tetranor-14,15-dihydro-LTE4 were prepared by total synthesis and used as standards for identification of biliary and urinary metabolites in the cynomolgus monkey. After intravenous administration 14, 15-[3H] leukotriene C4 (10 microCi kg-1) was partially metabolized in and rapidly cleared from the vascular circulation. This resulted, within 24 hours, in significant urinary excretion (14.8 +/- 2.1%, n = 4), consisting largely of material more polar than LTE4 (61% of urinary excretion) as shown by reverse phase HPLC. The polar fraction demonstrated two predominant metabolites which coeluted in several HPLC solvent systems with synthetic 16-carboxytetranordihydro-LTE4 (major component) and 18-carboxydinor-LTE4 (minor component). Characterization of the major polar metabolite as 16-carboxytetranordihydro-LTE4 was substantiated by conversion to its N-acetylated derivative. The absence of the 14, 15 double bond was confirmed by product analysis of oxidative ozonolysis. In a single animal, the bile duct was cannulated, with significant biliary excretion of radioactivity demonstrated over 4 hours (58.6% recovery). The predominant polar biliary metabolites were also identified as the 18-carboxydinor and 16-carboxytetranordihydro derivatives of LTE4 mentioned above. These data suggest that beta-oxidation products generated from the omega-carboxyl end of the 20-carboxy-LTE4 are important products of [3H] LTC4 metabolism in the monkey. Quantitation of these urinary metabolites may be an important index of in vivo leukotriene production.