Fixation d'azote par les cyanobacteries dans les rizières du Mali

Résumé La fixation de l'azote par les cyanobactéries a été étudiée pendant un cycle végétatif dans trois rizières pluviales soudano-sahéliennes ne recevant pas d'engrais azoté. Lorsque l'illumination solaire est forte, et en l'absence de couvert végétal, l'activité réductrice de l'acétylène (ARA) présente deux maximums, en fin de matinée et au milieu de l'après-midi. Dans le cas d'une intensité lumineuse moyenne ou faible et d'une couverture dense, on constate un maximum unique en fin de matinée ou début d'après-midi. Au cours du cycle cultural, l'ARA présente deux maximums, l'un au moment du tallage, l'autre à maturation du riz. En ce qui concerne les cyanobactéries fixatrices, le premier maximum correspond à la prédominance d'espècesd'Anabaena, et le second à la prédominance d'espèces deCylindrospermum. Dans une des rizières étudiées, aucune forme fixatrice de l'azote n'a été observée. Plusieurs espèces hétérocystées non-fixatrices ont été identifiées. Des expériences en vases de végétation ont confirmé l'inhibition de TARA des cyanobactéries par les fortes intensités lumineuses. LesOscillatoria se protègent contre la lumière par phototactisme négatif (enfouissement dans le sol) et par un processus de photocinèse agrégative.

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Nitrogen fixation by cyanobacteria in paddy fields of Mali

Summary Nitrogen fixation by cyanobacteria was studied during a cropping cycle in three rain paddy fields of Mali that had not received exogenous nitrogen. Under intense sunlight and in the absence of a crop canopy, the acetylene reducing activity (ARA) showed two maxima, at the end of morning and in mid-afternoon. With medium or low intensity of light and dense plant cover, a single maximum was observed at the end of the morning. In the course of the cropping cycle, ARA showed two maxima, at the tillering period and at crop ripening. In regard to the nitrogen-fixing cyanobacteria, the first ARA peak corresponded to the predominance ofAnabaena species and the second one to the predominance ofCylindrospermum species. No nitrogen-fixing forms were observed in one of the paddy fields studied. A number of heterocystic non-fixing species have been identified. Pot experiments confirmed the inhibition of ARA in cyanobacteria by high light intensity.Oscillatoria spp. are self-protected against light by negative phototactism and by a process of photokinetic agregation.

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Fijación de nitrógeno por cianobacterias en arrozales de Malí

Resumen Le fijación de nitrógeno por cianobacterias se estudió, durante un ciclo vegetativo completo, en tres arrozales de tipo pluvial, en Malí, a los que no se aportó ningún abono nitrogenado. Cuando la intensidad de la luz solar es fuerte y en ausencia de cubierta vegetal la actividad reductora de acetileno (ARA) presenta dos máximos: el primero al final de la mañana y el segundo a media tarde. Con una intensidad luminosa media o baja y una cubierta vegetal densa se observó un único máximo al final de la mañana o principio de la tarde. Durante el ciclo del cultivo la ARA presenta dos máximos: el primero relacionado con el momento de formación de la espiga y el segundo con la maduración del arroz. En cuanto concierne a las cianobacterias fijadoras, el primer máximo corresponde a una predominancia de especies deAnabaena y el segundo a una de especies deCylindrosporum. En uno de los arrozales estudiados no se ha observado ninguna forma fijadora de nitrógeno. Se han identificado especies no fijadoras de nitrógeno aunque formadoras de heterocistes. La inhibición de ARA por fuertes intensidades luminosas se ha confirmado mediante experiencias en maceta. LasOscillatoria spp. se autoprotegen de la luz mediante fototactismo negativo (se entierran en el suelo) y gracias a un proceso de fotocinesis agregativa.

     

Les faunes terrestres quaternaires des Îles du Japon

This paper explains a brief history of research on Quaternary terrestrial mammals in Japan and fossil occurrence of taxa at major localities of each time period at first. Based on these data, then, the changing history of Quaternary terrestrial mammals in Japan is reviewed, especially on such points as (1) importance of strait in western Japan as coming over route, (2) changing history of Plio-Pleistocene terrestrial mammals in Japan, (3) two faunas during the Late Pleistocene, (4) dates of extinctions of large mammals near the end of the Late Pleistocene. Formation process of Quaternary terrestrial mammal fauna in Japan must have been affected by condition of land connection with Asian continent at seaway west to Japan and changing history of climate and vegetation in East Asia, and it should be considered by different time period, e.g. before and after ca. 1.7 Ma. The time period after 1.7 Ma is one affected by glacial sea level fluctuations. Although a new fauna came over from the west to Japan when sea level was low, this time period is basically the age of insularization, and it is presumed that the fauna was becoming endemic during this time period. During the late Late Pleistocene, there were two faunas existed in Japan, e.g. one with Palaeoloxodon naumanni having come over from the west and another with Mammuthus primigenius having come over from the north. The former dwelled mainly in deciduous broad-leaved forest and mixed forest with conifers in temperate climate, while the latter dwelled in steppe and coniferous forest in subboreal climate. Both faunas changed their ranges to north and south repeatedly as climate changed, and the extinction of large mammals of the fauna with Palaeoloxodon naumanni occurred at the same time of the beginning of the LGM (ca. 25–16 ka). On the other hand, large mammals of the fauna with Mammuthus primigenius became extinct or moved to north as climate became warm quickly after the LGM. Thus, it is suggested that the extinction of large mammals at the late Late Pleistocene occurred by “two pulses.” The extinction process of large mammals in Japan seems likely that they went extinct finally near the end of the Pleistocene going through the reduction of habitat and fragmentation of populations caused by the repeated temperature change during the late Late Pleistocene, rather than a single drastic event.     

Expression in vitro du gène de l'aromatase dans les cellules testiculaires du rat

The ability of the male gonad to convert androgens into estrogens is well known ; the microsomal enzymatic complex involved in this transformation is named aromatase and is composed of a specific cytochrome P450 aromatase (P450arom) and a ubiquitous reductase. Using a highly specific RT-PCR method we have measured the amount of P450arom mRNA in purified Leydig and Sertoli cells prepared from 20, 40 and 70–80 day-old rats. The amount of P450arom mRNA in the Leydig cells is independent of age (40 × 10⁻³ attomoles/μg of total RNA); in contrast, in the immature rat Sertoli cells, after 5 days of culture the amount of P450arom mRNA is 20-fold lower when compared to that of 20-day-old rat Sertoli cells (71 × 10⁻³ attomoles/μg of total RNA). Nevertheless, irrespective of the age, the addition of either FSH or dbcAMP for 6 h increases the level of P450arom mRNA in the rat Sertoli cell preparations. Therefore, we evidenced that during testicular maturation not only the Leydig cells but also the Sertoli cells of the rat have the capacity to express the gene for cytochrome P450 aromatase.     

Stimulation du potentiel de dégradation dans les eaux marines profondes par les bactéries barotolérantes colonisant les fèces du plancton migrateur

At a depth of 1 150 m in the northwest Mediterranean, amino acid uptake and bacterial biomass production rates increased, in a 12-day time interval, 5- and 30-fold, respectively. Simultaneously, bacterial response to pressure changes evolved from barophilic to barotolerant. During the same period, scanning electron microscope observations and in situ observations using Underwater Video Profiler showed a 2-fold increase in particle concentrations, mainly due to faecal pellet production by zooplankton. This input, nutrient rich and largely colonized with bacteria unaffected by pressure variations since they originated from organisms that regularly migrate up and down through the water column, could produce such microbial activity peaking in the deep water masses.     

Enquête sur les pratiques du spermogramme en France

An extensive investigation was performed by numerous public as well private biological laboratories. 214 answers were collected. Most of them corresponded to laboratories analysing less than 5 spermiograms per week. Only 74 of them can be considered as specialised in this field. Among the questions, those conserning sperm conservation, viscosity and motylity evaluation, spermatozoa count, rate of teratospermia, study of rund cells revealed marked differences in the routine practice. These differences can affect the diagnostic value of the spermiogram. To reach ab harmonisation of the results, some recommendations are proposed by the working group. First, treatment and microscopic examinations should be carried out at 37 °C; WHO recommendation should be followed for the motility and teratospermia rate evaluation. A common format is also proposed to present results conserning the spermiocytogram, contributing to improve the standardisation.     

Altérations environnementales du développement du testicule foetal: zoom sur les phtalates

There are great concerns about the increasing incidence of abnormalities in male reproductive function. Human sperm counts have markedly dropped, and the rate of testicular cancer has clearly increased over the past four decades. Moreover, the prevalence rates of cryptorchidism and hypospadias are also probably increasing. It has been hypothesized that all these adverse trends in male reproduction result from abnormalities in the development of the testis during foetal and neonatal life. Furthermore, many recent epidemiological, clinical and experimental data suggest that these male reproductive disorders could be due to xenobiotics termed endocrine disruptors, which are becoming more and more concentrated and prevalent in our environment. Among these endocrine disruptors, we chose to focus this review on phthalates for different reasons: 1) they are widespread in the environment; 2) their concentrations in many human biological fluids have been measured; 3) the experimental data using rodent models suggesting a reprotoxicity are numerous and are the most convincing; 4) their deleterious effects on the development and function of the rat foetal testis have been largely studied; 5) some epidemiological data in humans suggest a reprotoxic effect at environmental concentrations at least during neonatal life. However, the direct effects of phthalates on human foetal testis have never been explored. Thus, as we did for the rat in the 1990s, we recently developed and validated an organotypic culture system, which allows maintenance of the development of the different cell types of human foetal testis. In this system, the addition of 10^?4 M MEHP (mono-2-ethylhexyl phthalate), the most produced phthalate, had no effect on basal or LH-stimulated production of testosterone, but it reduced the number of germ cells by increasing their apoptosis, without modifying their proliferation. This is the first experimental demonstration that phthalates alter the development of the foetal testis in humans. Using our organotypic culture system, it is interesting to compare these results obtained in humans with the response to MEHP in the mouse and the rat testes to analyse the relevance of toxicological tests based on rodent models.     

Liste taxonomique des abeilles du genre Andrena (Hymenoptera : Apoidea : Andrenidae) du Nord-Est algérien avec les commentaires et les ajouts aux autres régions du pays

This study concerns the species list of Hymenoptera Apoidea Andrenidae belonging to Andrena genus collected during years 2002, 2005, 2006, 2007, 2008 and 2009 in the north-eastern Algeria. A total of 58 species from 27 subgenera are reported including a species described in 2011, Andrena (Parandrenella) tebessana Scheuchl, Benarfa & Louadi. Two species are new for the Algerian fauna: A. (Orandrena) monilia Warncke 1967 and A. (Suandrena) cyanomicans Pérez 1895. A. (Margandrena) quinquepalpa Warncke 1980 has been only very recently cited from Algeria from the material described here. The present study also includes the Algerian distribution of each species, flight periods and flower choices.     

Dosage du fer et de l'aluminium échangeable dans les minéraux argileux et dans les sols

Résumé Une méthode est proposée pour le dosage du fer et de l'aluminium échangeable dans les minéraux argileux et dans les sols. La méthode est basée sur l'extraction successive des oxinates de fer et d'aluminium en fonction du pH.Les conditions optimales et l'influence des divers facteurs déterminant l'extraction quantitative et sélective de ces deux éléments ont été préalablement étudiées.Publication du Centre de Chimie Biologique et Colloïdale du sol subsidié par I'I.R.S.I.A.     

Absorption de l'oxyde nitreux par les parties aeriennes du maïs

Resume Il est montré que les parties aériennes des plantules de maïs semblent capables d'absorber l'oxyde nitreux (N₂O) produit lors de la dénitrification. Cette constatation peut s'avèrer importante au cours d'expériences sur la dénitrification conduites en présence de végétaux.     

Approches de compression du signal ECG avec les polynômes orthogonaux

Nowadays, telemedicine is more and more required. Signal compression is a critical step in telemedicine systems. In this paper, we suggest the use of orthogonal polynomials for electrocardiogram signal compression. The algorithms developed were tested using the Massachussets Institute of Technology's signal database. The results of our tests were compared to those of well-established methods and were, in some cases, better and comparable in most cases.     

Hydrolyse enzymatique des protéines par les bactéries du rumen

The hydrolysis of proteins in the rumen is a process brought about mainly by bacteria, of which many species produce proteases. The majority of endopeptidases are cysteine proteases, whereas exopeptidases are mainly aminopeptidases. Prevotella ruminicola is distinguished from other bacterial species by its capacity to produce dipeptidases such as type I dipeptidyl aminopeptidase. The mechanisms controlling the synthesis of endo- and exopeptidases have been little studied. Enzyme production seems to depend on the concentrations of peptides, amino acids and carbohydrates. Proteolytic activity varies in relation to pH, and the concentrations of ions and phenolic compounds. Various works have shown that hydrolysis of a protein by enzymes depends on its three-dimensional structure and possible bonding to non-protein structures. These properties determine the peptide and amino acid concentrations that occur in the rumen. The molecular weight, hydrophobic property and primary structure of the peptides are the main factors that affect the hydrolysis and/or uptake of these compounds by rumen bacteria. The methodological problems inherent to assaying these compounds do however lead to current divergences of opinion concerning the physico-chemical characteristics of the peptides that escape rumen fermentation.     

Effet toxique du champignon ascomycèteCordyceps militaris sur les cellules du diptèreAedes albopictus cultivéesin vitro

Résumé Le filtrat de cultures du champignon entomopathogèneCordyceps militaris L. Link) est toxique pour les cellules d'Aedes albopictus (Skuse) Singh cultivéesin vitro. Cette toxicité se traduit par des altérations nucléaires marquées et une destruction rapide du tapis cellulaire après désintégration du cytoplasme.

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Summary The culture of the fungusCordyceps militaris L. (Link) produces a cytopathic effect onin vitro cultivated cells ofAedes albopictus (Skuse) Singh. The toxicity consists of several alterations in the nucleus and destruction of the cells after a cytoplasmic desintegration.

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Travail subventionné par le Conseil National de Recherches du Canada. Les auteurs remercient Mlle ColetteTrudel pour son excellente assistance.     

Observations sur une nouvelle couche pariétale dans les cellules associées aux vaisseaux du Robinier et du Sycomore

Résumé Après avoir achevé leur différenciation, les cellules associées aux vaisseaux élaborent une nouvelle couche pariétale bien distincte des parois primaires et secondaires classiques. Cette couche est située uniquement le long de la paroi commune avec un vaisseau; il n'existe pas de formation semblable le long des parois communes à deux cellules vivantes du parenchyme. Plusieurs méthodes ont été utilisées pour déterminer l'origine, la structure et la composition chimique de cette couche; en particulier, un traitement par le PATAG en révèle la nature polysaccharidique. Son rôle n'a pas été défini avec certitude: il est possible que les substances pariétales qui la composent soient utilisées lors de la formation des thylles.Ce travail a été effectué dans le cadre de l'Equipe de Recherche Associée n 179 et de l'Institut de Biologie Végétale, Université Paris VI, France.

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Observations on a new wall layer in vessel associated cells ofRobinia andAcer

Summary In mature vessel associated cells, a new wall layer is built (after cell differentiation). This layer is quite different from primary and secondary wall and is deposited only on the cell side which abuts a vessel element; no similar structures are seen along the wall separating two living parenchyma cells. Several methods were used to study the origin, structure, and composition of this layer; in particular, polysaccharides are visualized with PATAG technique. The role of this layer is discussed: the new wall materials may be used later during tylose formation.

     

Physiologie et comportement de quelques fourmis (Hym. formicidæ) du Sahara en rapport avec les principaux facteurs du climat

Résumé Etude de la perméabilité du tégument de 12 fourmis du Sahara comparées à 5 fourmis de France. Toutes transpirent dès que l'atmosphère n'est pas saturée d'humidité, mais les fourmis du Sahara perdent beaucoup moins d'eau que les espèces d'Europe placées dans les mêmes conditions.Etude du comportement vis-à-vis de la température. Il y a peu de différences entre les espèces d'un même genre, mais de provenances différentes. Les températures léthales supérieures des fourmis les plus résistantes sont beaucoup plus basses que les températures qui règnent au sol au printemps et en été.

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Summary A study of the integument permeability of 12 ants from the Sahara, compared with 5 ants from France. All of them transpire as soon as the atmosphere is no longer saturated with moisture, but the saharian ants loose much less water than the european species subjected to the same conditions.A study of the reactions to heat. There is little difference between species of a same genus, but of varied origins. The upper lethal temperatures of the most resisting ants are much lower than the temperatures that are reached on ground level in spring and summer.

     

Techniques de détection du VIH dans les milieux biologiques: Application à la recherche du virus dans le sperme

Growing numbers of HIV seronegative women want to have children with HIV infected partners by artificial insemination. The most sensitive assays for showing the presence of the virus are the coculture method and the DNA-PCR that are able to detect proviral load. HIV is detected from non spermatozoal mononuclear cells, seminal fluid but it was not found in spermatozoa fraction. But we know, by in vitro studies, that HIV can bound to and enter spermatozoa. Thus artificial insemination between HIV seropositive man and seronegative woman lead to a risk of contamination even with purified spermatozoa. Today, any virological assay is able to affirm that specimen is not infectious.     

Etude au microscope electronique de l'ultrastructure du centriole chez les vertébrés

Zusammenfassung Die Ultrastruktur des Zentralkörpers wurde beiTriton, Pleurodeles, Maus, Ratte undHühnchen elektronenmikroskopisch untersucht. In allen Fällen stellt sich dieser Körper als Hohlzylinder mit einem Durchmesser von etwa 150 m und einer Länge von 300–500 m dar. Seine Wandung, die stark osmiophil ist, besteht aus etwa 9 Röhrchen, die untereinander und zur Achse des Zylinders parallel angeordnet sind. Der Zentralkörper liegt entweder am Spindelpol von Mitosen oder in der Nähe der Nuclearmembran und des Golgiapparates im Cytoplasma von ruhenden Zellen.Die an normalen Gewebe beobachtete Ultrastruktur des Zentralkörpers wurde ebenso in verschiedenen Krebsgeweben und in Zellen, die der Wirkung von Colchicin oder Natrium-Kakodylat ausgesetzt waren, nachgewiesen.Die Spindelfasern erscheinen als kleine Kanäle mit einem Durchmesser von 20 m; sie sind bei einer großen Mehrzahl von Mitosen, die der Wirkung von Mitosegiften ausgesetzt waren, nicht nachweisbar.Die Ultrastruktur des Zentralkörpers entspricht derjenigen des Basalkörperchens des Flimmerepithels und des proximalen Zentralkörpers der Spermatozoen.Der Zentralkörper erscheint als ein hochdifferenziertes Organ, dessen Ultrastruktur, je nach den verschiedenen Anforderungen der Zellentwicklung, die Synthese von Faserproteinen möglich macht.     

Etats épididymaire,prostatique et vésiculaire en relation avec les paramètres du spermogramme chez les hommes consultant pour infertilité

The semen results from the mixture on ejaculation of various secretions from the testicle, the genital tract and the adnex glands. It consists on a cellular phase: spermatozoa and a liquidian phase: the seminal plasma. The spermogram is the first exam to make in order to set diagnosis of male infertility. It is completed with a biochemical study of the semen to find an excretory origin to infertility. In this work, we have studied the frequences of prostatic, vesicular and epididymious anomalys, through dosage of their markers in the semen, in 146 males consulting for infertility and eventual relationships between these markers and the characteristics of the spermogram. We found out that the prostate is the most hurt portion of the genital tract in infertile males and presents a dysfunctioning in 32,26% of cases, most often resulting in an inflammatory states of this gland. The epididymious obstruction is detected in 35% of azoospermia cases. In all the cases, we found out significant statistical correlation between the semen volume and the activity of alpha 1–4 glucosidase and also the pH of the semen and the seminal citric acid. For patients having a high leucospermia we didn’t find any relationship between the leucocytes rate in the semen and the different biochemical markers. If the seminal fructose rate has no effect on the initial mobility of spermatozoa, it has a statistically significant effect on their survival. In fact, the diminution of seminal fructose coincides with a bad survival of spermatozoa, which shows the importance of this spermatic substrate on the maintaining of spermatozoa mobility.