Mesure des déclins de l'intensité et de l'anisotropie de fluorescence du pérylène en présence de membranes d'érythrocyte de pigeon: Comparaison avec un milieu isotrope visqueux

Using synchrotron radiation as the excitation light, we studied the fluorescence parameters of perylene incubated with pigeon erythrocyte membranes and with an isotropic viscous medium, the Primol 342 oil.From 4 to 37°C, we observed a single lifetime of 4.5 ns in the oil and two with the membrane (τ₁ = 1−1.4 ns and τ₂ = 5.4−6.1 ns). The dependence upon temperature of the rotation correlation time of perylene () in the oil was characteristic of an isotropic medium, whereas the limiting value of anitropy (r ∞) was zero. With the membrane, γ ∞ decreased from 0.14 to 0.06 and from 2.9 to 0.5 ns, indicating a greater amplitude and frequency of molecular motions.The addition of chlorpromazine, indomethacine, tetracaine, n-octylamine, octanol or octanoic acid to the membrane decreased the τ₁ and τ₂ values. This would stem from the desorganization of the membrane induced by the drugs.     

Etude “in vitro” des acides gras synthétisés dans les microsomes de cerveaux de souris normales et “quaking”

Radiogas chromatographic studies of the products of fatty acid biosynthesis in mice brain microsomes confirm the existence of a «de novo system from acetyl-CoA and malonyl-CoA and of a least two elongating systems for long chain fatty acids, involving malonyl-CoA. The possibility of an intermediary system leading from C₁₈ to C₂₀ fatty acids has been evoked.Comparison between non mutant and quaking mice indicates that all the microsomal fatty acid biosynthetic systems are depressed. The biosynthetic system elongating fatty acids from C₁₈ is the one which is the most modified quantitatively and qualitatively in quaking. Microsomal and soluble «de novo systems are qualitatively intact.     

“Laughter” and “Smile” in Barbary Macaques (Macaca sylvanus)

In an observational study on semi-free Barbary macaques it was investigated whether the phylogenetic roots of human laughter and smile can be traced back to the genus Macaca. On the basis of morphological similarity a ‘relaxed open-mouth display’ as the phylogenetic precursor of the laughter, and a ‘silent bared-teeth display’ as the possible ancestor of the smile can be distinguished in the repertory of the Barbary macaque. Behavioural sequences from focal animal protocols were analyzed in order to establish message and meaning of both displays. Relaxed open-mouth display is regularly observed in the play interactions of juveniles. It is associated with partner-directed behaviour, it is frequently answered by a relaxed open-mouth display of the receiver, and accompanied by a special vocalization. Although up to 50% of the juvenile's play partners were higher ranking than themselves voluntary participation was the rule. Most characteristically, the behaviour patterns shown by both play partners are highly symmetrical and synchronized. Silent bared-teeth display is typically accompanied by evasive or submissive body movements, and occurs primarily in dyadic interactions, mainly by the lower ranking individual. It is not an unidirectional sign of a linear dominance hierarchy, though. Silent bared-teeth display is a frequent answer to aggressive behaviour shown by the receiver. After its performance, an increase of body contact between sender and receiver was observed. Behavioural sequences of senders and receivers are complementary, but lose their asymmetry after occurrence of the display. It is concluded that these results further support Van Hooff 's (1972) view that human laughter and smile have different phylogenetic roots: while silent bared-teeth display is a signal of submission and appeasement, relaxed open-mouth display is rightly called the ‘play face’, and is an expression of fun.     

Effets sur le spermatozoïde humain du Diuron (3-(3,4-dichlorophényl)-1,1-diméthyl-urée) et de l’un de ses produits de transformation, la 3,4-dichloroaniline (3,4-DCA) (Etude préliminaire)

Diuron belongs to the family of halogenophenylureas, one of the main groups of herbicides used for more than 40 years. These herbicides absorb sunlight and can be photochemically transformed in the environment (herbicides are transformed on the soil surface exposed to sunlight) or biotransformed by microorganisms present in soil or in water. The metabolites (chlorohydroxyphenylurea, chlorophenylaniline, respectively) are more toxic than the parent compound, as demonstrated by a bioluminescence inhibition assay performed with a marine bacterium (Vibrio fischeri toxicity test). The lipophilicity of these pesticides makes the cell membrane a target for their action, especially the spermatozoa cell membrane. The aim of this study is to use human spermatozoa to evaluate the effect of this urea pesticide and its biotransformed product on the spermatozoa membrane. We investigated the structural and functional effects of these environmental pollutants on spermatozoa. Three million spermatozoa purified on a 95/47.5% Percoll gradient were suspended in 250 μl of modified Earle’s medium (without phenol red) supplemented with 7.5% of human decomplemented serum. Pesticides (Diuron or 3,4-dichloroaniline (3,4-DCA)) were added at a final concentration of 0.1; 1 and 5 mM. Samples were incubated at room temperature for 24 hours. We show that both Diuron and 3,4-DCA decrease motility and vitality of spermatozoa incubated with the highest concentration of pesticides. Our preliminary results show that the effects are more rapid and more intense with the biotransformed product (3,4-DCA) than with Diuron. Addition of herbicide to human spermatozoa increases membrane fluidity, assessed by measuring the fluorescence polarisation anisotropy with a fluorescent probe: 1,6-diphenyl-1,3,5-hexatriene (DPH). Changes in membrane fluidity may be a primary toxic effect of these herbicides. These results suggest that human spermatozoa may constitute a valuable indicator of the toxic effects of pesticides.     

Etude préliminaire des effets de la mise en eau du Réservoir de LG-2 (Territoire de la Baie James,Québec) sur le seston grossier et le zooplancton des rivières et des lacs inondés

Preliminary Study of the Effects of Impoundment of LG-2 Reservoir (James Bay Territory, Quebec) on the Net Seston and the Zooplankton of Impounded Rivers and Lakes The effects of impoundment on the biomass of net seston and zooplankton in lakes and rivers of Northern Quebec were investigated from 1978 to 1980, before, during and after the completion of LG2 Reservoir on the River La Grande (53° 54′ N, 76° 78′ W). In lotic stations, a 41–77% decrease in net seston was observed due to sedimentation of mineral particles (36–80 mg/m³ in 1978 to 10–21 mg/m³ in 1979). The ratio of organic to total seston increased from an average of 0.18 before the impoundment to 0.65 after. The flooding phase brought about a trophic upsurge; the biomass of the zooplankton increased by one to two orders of magnitude at the various sites; the greatest increases occurred in the central stations near the dam, the smallest in the upper stations near the inflow. In lake stations, no significant difference between years could be detected; the mean zooplankton biomass for all three years ranged from 6.59 mg/m³ to 34.34 mg/m³. Spatial variations between lakes were however significant. Results are compared with those in other natural lakes in Canada and reservoirs in the United States. Comparative examination of phytoplankton biomass before and after impoundment of LG2 Reservoir suggests that bacterioplankton and allochthonous organic material are key elements in the pelagic food chain after impoundment.     

Detección de Aedes (Stegomyia) albopictus (Skuse) en ovitrampas en Mérida,México

IntroducciónEl programa de enfermedades transmitidas por vectores en México tiene una red establecida de ovitrampas para la vigilancia entomológica de Aedes spp. Los servicios de salud del estado de Yucatán, en respuesta a reportes de Aedes albopictus en la periferia de Mérida, capital del estado, incrementaron la especificidad de dicha vigilancia.ObjetivoDescribir la presencia y distribución de Ae. albopictus en Mérida y su abundancia relativa comparada con Aedes aegypti, en ovitrampas del programa de control de vectores.Materiales y métodosDurante octubre de 2019, se seleccionaron al azar 91 ovitrampas en 31 barrios de Mérida. Los mosquitos adultos se obtuvieron del insectario de la Unidad Colaborativa para Bioensayos Entomológicos de la Universidad Autónoma de Yucatán a partir de huevos recolectados en campo. Se determinó la abundancia relativa de individuos adultos de cada especie identificada y por barrios evaluados.ResultadosEn el 32% de los barrios muestreados, se detectó Ae. albopictus y, en todos ellos, Ae. aegypti. Se recolectaron 28 adultos de Ae. albopictus (10 hembras y 18 machos) en las ovitrampas. No se observó correlación entre la abundancia de adultos ni de hembras Ae. aegypti y Ae. albopictus por barrio (p>0,05).ConclusionesLos resultados confirmaron que Ae. albopictus estaba coexistiendo con Ae. aegypti en Mérida en el momento del estudio. La baja abundancia relativa sugiere que Ae. albopictus se encontraba en la fase inicial de invasión.Palabras clave: Aedes, mosquitos vectores, control de vectores, enfermedades transmitidas por vectores, México     

Sneaker “jack” males outcompete dominant “hooknose” males under sperm competition in Chinook salmon (Oncorhynchus tshawytscha)

In a variety of taxa, males deploy alternative reproductive tactics to secure fertilizations. In many species, small “sneaker” males attempt to steal fertilizations while avoiding encounters with larger, more aggressive, dominant males. Sneaker males usually face a number of disadvantages, including reduced access to females and the higher likelihood that upon ejaculation, their sperm face competition from other males. Nevertheless, sneaker males represent an evolutionarily stable strategy under a wide range of conditions. Game theory suggests that sneaker males compensate for these disadvantages by investing disproportionately in spermatogenesis, by producing more sperm per unit body mass (the “fair raffle”) and/or by producing higher quality sperm (the “loaded raffle”). Here, we test these models by competing sperm from sneaker “jack” males against sperm from dominant “hooknose” males in Chinook salmon. Using two complementary approaches, we reject the fair raffle in favor of the loaded raffle and estimate that jack males were ~1.35 times as likely as hooknose males to fertilize eggs under controlled competitive conditions. Interestingly, the direction and magnitude of this skew in paternity shifted according to individual female egg donors, suggesting cryptic female choice could moderate the outcomes of sperm competition in this externally fertilizing species.     

Etude ultrastructurale comparée du processus de dégradation de l'hémoglobine par P. berghei (Vincke et Lips, 1948) en fonction de l'état de maturité de la cellule hǒte1

By serial sectioning and 3D reconstruction we have been able to demonstrate that the type of system for hemoglobin digestion in two strains of Plasmodium berghei, N and RC, is dependent on the maturity of the host cell. In parasites growing in erythrocytes, both systems for the endocytosis of hemoglobin—micropinocytosis and the cytostomal system (i.e. a cytostome budding a cytostomal tube that releases food vacuoles)—are fully functional and produce a great quantity of residual pigment. Parasites growing in reticulocytes have a disrupted cytostomal system; no tube is formed and only food vacuoles are visible in their cytoplasm. Residual pigment is smaller in size and in quantity. The reduced quantity of pigment in reticulocytes is explained by our observation of the exocytosis of pigment. We propose a hypothesis that relates the process of degradation of hemoglobin to the maturity of the host cell and a possible mechanism of protection against chloroquine, a drug known for its affinity for malarial pigment.