Variations de salinité chez les anguilles. Modifications duQO2 et des teneurs en cations des tissues hépatiques et rénaux

Summary Respiratory and ionic contents (Na, K, Ca) measurements were performed on hepatic and renal tissues extracted from yellow eels or silver eels.The increase of hepatic O₂ uptake observed on yellow eels when kept in salt water may be the result of water balance disequilibrium.     

Influence de la salinité sur la respiration tissulaire chez les Téléostéens

Summary Respiratory measurements by the Warburg method were performed on hepatic, renal and branchial tissues extracted from fishes (tench and eels), kept in either salt or fresh water. The oxygen consumption of hepatic tissues of both tench and eels increased when the fishes were transferred from fresh to salt water. No difference was observed for renal and branchial tissues.     

Serotonin levels in fish brain: Effects of hydrostatic pressure and water temperature

Summary The contents of serotonin (5 HT) and its metabolite 5 hydroxy indoleacetic acid (5 HIAA) have been measured (HPLC technique) in the brains of eels exposed to different conditions of hydrostatic pressure and temperature (HP=1 or 101 ATA in winter, Tw=14°C, and in summer, Tw=19°C). It appears that an increase of Tw induces a significant increase of the 5 HT/5 HIAA ratio. In contrast, eels exposed at 101 ATA of HP for 1 h do not exhibit any modification in the 5 HT/5 HIAA brain ratio at a given temperature. The involvement of 5 HT under the conditions studied is discussed.     

Pressure acclimation of the eel and liver membrane composition

Homeoviscous adaptation of membrane fluidity is known to exist in fish living at great depths. Is this adaptation also present in fish living near the surface but experimentally acclimated to high pressure? The composition of mitochondria-rich fractions extracted from the livers of eels acclimated for 15 days at 101 ATA was determined. The results show that pressure induced a significant increase (+100%) of total phospholipids (PL) and cholesterol without a change in their ratio. The increase of PL content was accompanied by a decrease in phosphatidylcholine in favour of phosphatidyl ethanolamine which, due to its preference for the H₁₁ form, is able to compensate for the loss in fluidity induced by pressure.     

The role of orientation experiments in discovering mechanisms

Many types of experiments have been recognized in the literature. One important type we discuss in this article is the orientation experiment. While orientation experiments are like other types of experiments in that they are tests for causal relevance, they also have other qualities. One important (but not the only) goal of these experiments is to offer a rough, qualitative characterization of the mechanism responsible for a capacity of interest, effectively constraining future research. This makes them particularly useful during the early stages of investigation, when an explanandum-phenomenon has just been identified and several (often competing) hypotheses as to the qualitative character of the mechanism responsible for it are proposed. We illustrate our claims, and explicate a number of additional aims that orientation experiments can sometimes serve, by considering three case studies from different era's, namely the discovery of the mechanisms responsible for i) the capacity of eels to produce numbing sensations (17th and 18th century), ii) puerperal fever in Semmelweis' Vienna Maternity Hospital (19th century), and iii) the capacity of pigeons to home (20th century).     

Séparation chromatographique et dosage de l'arginine-vasotocine et de l'isotocine de l'hypophyse et du noyau préoptique chez l'Anguille de Mer du Nord (Anguilla anguilla L.)

Summary Thin-layer chromatographic separation and bioassay of arginin-vasotocin and ichtyotocin of hypophyseal and preoptic nucleus extracts from North Sea eels show that the hypophysis is much richer in arginin-vasotocin than in ichtyotocin. Analogous results have been observed in the preoptic nucleus fractions.

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Avec la collaboration technique de M. G.Hoeltzel.     

Proliferationen der Fischepidermis nach der Einwirkung von inhibitoren des glykolytischen Energiestoffwechsels

Summary When fluoride-ions or monoiodoacetate is added to the ambient medium, there occur in fish larvae after 12 h, and in eels after 24 h, in some places, solid epidermal proliferations. The effect of glycolysis inhibitors on epidermal mitotic activity might be due to an impairment of energy metabolism as it is nullified by a simultaneous application of inorganic diphosphate or by doubled O₂ partial pressure of 320 mm Hg.     

Experimentelle Reversion von Tumorzellen in vivo

Summary European eels with fast growing epidermal papillomas (cauliflower disease) were treated with quinine-sulphate. At concentrations of 15 to 60 mg/l and after 8 weeks of treatment, there occurred newly formed mucous cells and club cells in the tumor tissue. Tight contact between all cells was reestablished. The nucleus-plasma-relation had evidently decreased. Electron microscopical studies showed a restauration of degenerated cell organelles, especially of the outer membrane. Growth rate of the tumors was reduced, and at a concentration of 60 mg/l the tumor tissue ceased growing from the beginning of treatment.     

Toxicity of Temik (aldicarb) for a fresh water teleost,Barbus conchonius Hamilton

Summary The toxic effects of Temik (aldicarb) on a fresh water Himalyan lake teleost,Barbus conchonius were investigated in hard and soft water. The 48-, 72- and 96-h TL_m-values in mg/l were 8.99, 2.39 and 2.42 respectively in the hard-water test and 3.30, 0.62 and 0.46 in the soft-water test. The toxicity of Temik toB. conchonius increases many fold in soft water.One of us (S. C. P.) is grateful to U. G. C., for the award of a senior research fellowship.     

NMR structures of the C-terminal end of human complement serine protease C1s

Synthetic peptides derived from the C-terminal end of the human complement serine protease C1s were analysed by circular dichroism and nuclear magnetic resonance (NMR) spectroscopy. Circular dichroism indicates that peptides 656-673 and 653-673 are essentially unstructured in water and undergo a coil-to-helix transition in the presence of increasing concentrations of trifluoroethanol. Two-dimensional NMR analyses performed in water/trifluoroethanol solutions provide evidence for the occurrence of a regular α-helix extending from Trp659 to Ser668 (peptide 656-673), and from Tyr656 to Ser668 (peptide 653-673), the C-terminal segment of both peptides remaining unstructured under the conditions used. Based on these and other observations, we propose that the serine protease domain of C1s ends in a 13-residue α-helix (656Tyr-Ser668) followed by a five-residue C-terminal extension. The latter appears to be flexible and is probably locked within C1s through a salt bridge involving Glu672. Received 19 November 1997; accepted 24 November 1997     

Enhancement of fluorescence of pyrene-containing lipids by polar media, detergents and phospholipids

The fluorescence intensities of a medium-chain fatty acid and of several amphiphilic lipids, each containing pyrene in covalent linkage, were enhanced considerably by: 1) Dissolving in mixtures of a polar solvent (e.g. methanol, ethanol, tetrahydrofuran or dimethylsulfoxide) and water; for each individual compound, a certain ratio of solvent to water provided maximal fluorescence intensity. 2) Incorporating into micelles of reduced Triton X-100; an excess of detergent was used so that, statistically, only one molecule of lipid resided in one micelle of the Triton X-100. 3) Incorporating into liposomes of egg phosphatidylcholine; maximal fluorescence was observed using a large excess of phosphatidylcholine. When related to the fluorescence intensities in chloroform/methanol (2:1, by vol.) or water, the enhancement of fluorescence in the above three systems was about 2-6-fold or up to 60-fold, respectively.     

The influence of different nutrients on plasma cholecystokinin levels in the rat

Isocaloric and isovolemic amounts of protein (casein), fat (intralipid) and carbohydrate (saccharose) and an isovolemic control solution of water were administered intragastrically to conscious rats. The plasma CCK levels, determined by a sensitive and specific radioimmunoassay, showed an increment of 6.3 +/- 0.6, 2.7 +/- 0.5, 1.7 +/- 0.4 and -0.9 +/- 0.4 pM, respectively (basal value 2.5 +/- 0.3 pM). The threshold increment of plasma CCK to stimulate pancreatic enzyme secretion by exogenous CCK was found to be 1.5 pM. It is therefore concluded that casein is a potent stimulus for CCK secretion and pancreatic secretion, but that fat and even carbohydrate, although less potent, also produce a CCK increment above the threshold for pancreatic secretion.     

Water in keratin: electrical conductivity measurements]

Measurements of electrical conductivity of keratin fibers show that, for weak hydration (0-5%) interaction between water and protein is strong. This decreases the probability of charges-exchange taking place between them. During the first percentages of elongation, an increase of the percentage of "intermediate water" appears.     

Enhancement of fluorescence of pyrene-containing lipids by polar media,detergents and phospholipids

Summary The fluorescence intensities of a medium-chain fatty acid and of several amphiphilic lipids, each containing pyrene in covalent linkage, were enhanced considerably by: 1) Dissolving in mixtures of a polar solvent (e.g. methanol, ethanol, tetrahydrofuran or dimethylsulfoxide) and water; for each individual compound, a certain ratio of solvent to water provided maximal fluorescence intensity. 2) Incorporating into micelles of reduced Triton X-100; an excess of detergent was used so that, statistically, only one molecule of lipid resided in one micelle of the Triton X-100. 3) Incorporating into liposomes of egg phosphatidylcholine; maximal fluorescence was observed using a large excess of phosphatidylcholine. When related to the fluorescence intensities in chloroform/methanol (21, by vol.) or water, the enhancement of fluorescence in the above three systems was about 2-6-fold or up to 60-fold, respectively.     

Inversion of the female sexual phenotype at high temperature in the urodelian amphibian, Pleurodeles waltii Michah]

Breeding of Pleurodeles waltii larvae with female gentotype was carried out in 29,5-30 degrees C tap water within 4 months after hatching. 11 out of 15, 1 year old animals, exhibited all the characteristics of male sexual maturity. Mating one of the neo-males (ZW) thus obtained, with a standard female (ZW) results in a sex-ratio of the offspring consistent with theoretical expectation.     

Isolation of an antifreeze peptide from the Antarctic sponge <Emphasis Type="Italic">Homaxinella balfourensis</Emphasis>

Polar plants and animals survive in subzero waters (-2 degrees C) and many of these marine organisms produce antifreeze proteins (AFPs) to better adapt themselves to these conditions. AFPs prevent the growth of ice crystals which disrupt cellular membranes and destroy cells by inhibiting crystallization of water within the organism. The hydrophilic extract of an Antarctic sponge Homaxinella balfourensis exhibited a non-colligative freezing point depression effect on the crystal morphology of water. The extract was purified by repeated reverse phase high-pressure liquid chromatography, then assayed and shown to contain several AFPs. The major peptide was isolated, analyzed using matrix-assisted laser desorption ionization mass spectrometry and the partial structure of the peptide identified through amino acid sequencing. AFPs have potential applications in agriculture, medicine and the food industry.     

Effects of Ca2+ and Mg2+ on motility of sea urchin spermatozoa

Summary Swimming speed of sea urchin spermatozoa, measured by a light scattering technique, did not change with 0-20 mM Ca²⁺ in the medium. The speed was maximum at the normal concentration of Mg²⁺ (49 mM) in sea water.Supported by grants-in-aid from the Ministry of Education, Science and Culture, Japan, and a grant from the Ford Foundation.     

The influence of cold or isolation stress on resistance of mice to West Nile virus encephalitis

The effect of cold or isolation stress on mortality rate and brain virus level were investigated in mice infected with West Nile virus (WNV). Exposure of mice for 5 min/day to cold water (1 +/- 0.5 degrees C) for 8-10 days resulted in 92% mortality as compared to 47% in control mice (p less than 0.001). Mice housed in individual cages (isolation stress) were also more susceptible to WN viral infection, as shown by increased mortality rate reaching 85% as compared to 50% in mice housed 6 per cage (p less than 0.01). Cold or isolation stress increased blood brain and spleen virus levels as early as 2 days after inoculation. After 8 days of isolation or cold stress, mice inoculated with WNV had 8.9 and 9.0 log10 plaque forming units in the brain, respectively, as compared to 6.9 in the control (p less than 0.01-0.001). Furthermore, lymphoid organs such as spleen and thymus showed severe mass loss. These data suggest that physical or non-physical stress situations enhance WNV encephalitis by accelerating virus proliferation and increase mortality in mice.     

Determination of odour affinities based on the dose-response relationships of the frog's electro-olfactogram

Summary Electro-olfactograms (EOG's) recorded from the frog's olfactory epithelium for 11 substances were used to calculate dissociation constants which in turn serve as an index for the affinity between odorant and receptor site. These constants were calculated with and without a correction for the odour partition between water and air. For a homologous series of 7 n-alcohols these values decrease up to 1-heptanol. The dose-response relationships were based on the peaks of the EOG's since the peak/plateau-ratio was concentration-dependent for some of the substances.This work was supported by Z.W.O. grant number 12-24-12 of the Dutch Government.     

The effect of skim milk on plasma cholesterol in rats.

From the 15th day of birth, newborn rats were offered rat chow mixed with water or skim milk. The former also received tap water, the latter skim milk. In the latter group, plasma cholesterol was lowered in 43- and 64-day-old males and in 64-day-old females.