Alcaloïdes des feuilles de Voacanga thouarsii

Leaves of Voacanga thouarsii Roem. et Schult. yielded 3 indole alkaloids (ibogaine, voacangine, voacristine) and 12 ‘bis-indole’ alkaloids. Three of the latter are known (vobtusine, vobtusinelactone and subsessiline) and nine are new.     

Behavior of juvenile pink salmon (Oncorhynchus gorbuscha Walbaum) toward novel prey: influence of ontogeny and experience

Synopsis The behavior of individual, juvenile pink salmon toward novel prey (Artemia salina) under laboratory conditions is described. Two aspects of predatory behavior, namely latency time to initial prey-capture attempt and prey-capture success, are quantified in relation to chronological age and feeding experience. Initially, mean latency time declined slightly with increasing age up to Day 19 (post-emergence from gravel), but increased sharply to an asymptote with further aging. Mean percentage capture success gradually increased from 7.88% on Day 1 to 92.9% on Day 45. Prior feeding experience on the prey resulted in a decline (to a stable level) in mean latency time in experienced fish compared to control fish. Mean percentage capture success was not significantly altered by prior feeding experience on the prey.     

Air pollution due to «Do-it-yourself» activities at home

Summary Do-it-yourself work as a leisure activity contributes to air pollution in homes. The products or materials handled while working may be dispersed in the air, in the form of gas, vapors or particles which, by penetrating the organism, may represent a genuine risk of intoxication. This air pollution source is of importance for two reasons: the number of amateurs of do-it-yourself work at home is steadily increasing and the products or materials and techniques formerly reserved to professionals are now available to anybody. The most frequently used health hazard products are the solvents, which are present in paints, varnishes, glues, protective wood coatings and paint strippers. Techniques such as the stripping of paint by means of heat and autogenous or electrical welding produce metal fumes, the noxiousness of which is well-known by all specialists in occupational toxicology. The hazards of acute intoxication affecting persons exposed to a high concentration of polluting agents in the air, during a short period of time, are those occuring most frequently during craftwork at home. Nevertheless, certain particular jobs may be carried out over periods long enough to generate risks of chronic intoxication. In comparison with the intoxication hazards in the professional field, those due to craftwork at home seem to be subject to three aggravation factors: the lack of knowledge of users, insufficient technical prevention and the absence of medical or toxicological control. The prevention of toxicological hazards due to do-it-yourself jobs effectuated at home is achieved through the information of the general public and that of the general practitioners. The knowledge about the risks incurred would lead the craftsmen to take efficient preventive measures. The doctors should draw the attention of their patients to the incompatibility existing between certain pathologic conditions and the fact of handling chemical products. They should also take account of possible toxic etiologies at the moment of diagnosing.     

Étude chimiotaxonomique de quelques espéces de Hazunta

The alkaloidal composition of several species of the genus Hazuntahas been systematically studied. Among the twenty-four alkaloids isolated, ten are new.     

The differential regulation of aldosterone output in hamster adrenal by angiotensinII and adrenocorticotropin

Aldosterone was isolated from hamster adrenal cells and was identified by high performance liquid chromatography and thermospray mass spectroscopy analysis. Basal outputs from adrenal cell suspensions were of the same order of magnitude, 8.4 ± 1.9 ng and 8.0 ± 0.7 ng/2 h/50,000 cells, for aldosterone and corticosteroid, respectively. The outputs of aldosterone and corticosteroid increased with K⁺ concentrations to reach maxima of 3.3- and 1.6-fold at 10 meq/l of K⁺. Angiotensin_II (A_II) produced dose-dependent increases in aldosterone and corticosteroid outputs with maxima of 3- and 4-fold, respectively. In contrast, ACTH induced relatively no changes in aldosterone output, whereas dose-dependent increases in corticosteroid output were found. In time study experiments, with 10⁻⁸ M A_II, aldosterone and corticosteroid outputs were maximally increased after 1 h (6-fold) and 3 h (1.8-fold), respectively. At 10⁻⁸ M, ACTH had a small stimulatory effect on aldosterone output after 6 h, whereas it provoked a gradual increase in corticosteroid output (up to 7-fold after 8 h of incubation). The effects of A_II and ACTH on adrenal cytochrome P-450_11β involved in the last steps of aldosterone formation were evaluated by c combined in vivo andin vitro experiments. The P-450_11β mRNA level was increased by a low sodium intake but not by a 24 h ACTH stimulus. These results taken together indicate that ACTH and A_II differentially regulate P-450_11β. It is postulated that these two regulatory peptides regulate the hamster adrenal steroidogenesis by different P-450 genes.     

Predator inspection,shoaling and foraging under predation hazard in the Trinidadian guppy,Poecilia reticulata

Synopsis Guppies,Poecilia reticulata, living in stream pools in Trinidad, West Indies, approached a potential fish predator (a cichlid fish model) in a tentative, saltatory manner, mainly as singletons or in pairs. Such behavior is referred to as predator inspection behavior. Inspectors approached the trunk and tail of the predator model more frequently, more closely and in larger groups than they approached the predator's head, which is presumably the most dangerous area around the predator. However, guppies were not observed in significantly larger shoals in the stream when the predator model was present. In a stream enclosure, guppies inspected the predator model more frequently when it was stationary compared to when it was moving, and made closer inspections to the posterior regions of the predator than to its head. Therefore, the guppies apparently regarded the predator model as a potential threat and modified their behavior accordingly when inspecting it. Guppies exhibited a lower feeding rate in the presence of the predator, suggesting a trade-off between foraging gains and safety against predation. Our results further suggest that predator inspection behavior may account for some of this reduction in foraging. These findings are discussed in the context of the benefits and costs of predator inspection behavior.     

Living in the fast lane: effects of cost of locomotion on foraging behaviour in juvenile Atlantic salmon

Stream-dwelling, juvenile Atlantic salmon, Salmo salar L., feed mainly on drifting invertebrates, usually by swimming upstream from a stationary position to intercept individual prey items. Laboratory experiments tested the prediction that individual salmon should reduce the distance over which they would travel (attack distance) to intercept drifting food items as the energy cost of swimming increases with increasing current velocity. Attack distance varied inversely with current velocity as expected. The fish's average speed of upstream movement relative to the substrate remained constant and the duration of individual attacks therefore declined as current velocity increased. Calculated reaction distances and a second ecperiment using tethered prey drifting at speeds independent of current velocity confirmed that these relationships were due to fish actually delaying attacks on perceived prey for longer periods as current velocity increased. Using estimated metabolic rates for burst swimming, it appears that energy expenditure per attack varies little with current velocity. Therefore, by reducing their reaction and attack distances in response to increasing current velocity, the fish reduced their energy cost of travel per attack.     

Functional expression of human liver cytosolic beta-glucosidase in Pichia pastoris. Insights into its role in the metabolism of dietary glucosides.

Human tissues such as liver, small intestine, spleen and kidney contain a cytosolic beta-glucosidase (CBG) that hydrolyses various beta-d-glycosides, but whose physiological function is not known. Here, we describe the first heterologous expression of human CBG, a system that facilitated a detailed assessment of the enzyme specificity towards dietary glycosides. A full-length CBG cDNA (cbg-1) was cloned from a human liver cDNA library and expressed in the methylotrophic yeast Pichia pastoris at a secretion yield of approximately 10 mg x L-1. The recombinant CBG (reCBG) was purified from the supernatant using a single chromatography step and was shown to be similar to the native enzyme isolated from human liver in terms of physical properties and specific activity towards 4-nitrophenyl-beta-D-glucoside. Furthermore, the reCBG displayed a broad specificity with respect to the glycone moiety of various aryl-glycosides (beta-D-fucosides, alpha-L-arabinosides, beta-D-glucosides, beta-D-galactosides, beta-L-xylosides, beta-D-arabinosides), similar to the native enzyme. For the first time, we show that the human enzyme has significant activity towards many common dietary xenobiotics including glycosides of phytoestrogens, flavonoids, simple phenolics and cyanogens with higher apparent affinities (K(m)) and specificities (k(cat)/K(m)) for dietary xenobiotics than for other aryl-glycosides. These data indicate that human CBG hydrolyses a broad range of dietary glucosides and may play a critical role in xenobiotic metabolism.