Eléments d'observation sur la cinématique,la dynamique et l'énergétique de la locomotion dans le courant chez une larve de Trichoptère à fourreau

Observations on the kinetics, dynamics and energetics of the locomotion in the current of a case-bearing Trichoptera larva. The locomotion of Trichoptera larvae was studied by means of films. It follows a sequence similar to that usually observed in walking insects, with protraction of legs from behind to forward (Fig. 1). The walking is slow. In a current, the sequence of protraction is often modified by supplementary protractions of the anterior and middle legs (exploration or skidding). The locomotion includes phase a (advance of the body) and phase b (case towing, with protractcion of posterior leg). These two phases are more clearly separated in a current than with a force (Fig. 4, 5). These two phases agree perfectly with the basic pattern described by Denis (1968) for the larval case construction. The current causes a decrease in the mean locomotion speed (L_m) by shortening and above all separating the towing phases, which are the only moments for the rapid advance of the case (Tabl. I). Turbulent water causes the case to vibrate and these vibrations vary in amplitude (from 0.1 to 2 mm) with water velocity, but not significantly. The frequency of the vibrations does not seem to go above 15 oscillations per second (above 20 cm/s), but it is possible that higher frequencies could not be correctly registered at 64 pictures per second. These vibrations may be the cause of the higher activity in the current than under a traction force without vibrations (Bournaud, 1973). The coefficient of resistance (C_w) of the larva-case complex is high (near 0,89) at velocities above 55 cm/s, but is much higher at velocities below 55 cm/s (Fig. 7). So the case of M. testacea is better adapted to high current velocities. The 55 cm/s limit also corresponds to the velocity for changes in aspects of the behaviour of this species: rate of activity, beginning of rheokinesis stage, disappearance of negative locomotion. The minimum quantity of energy necessary for regular locomotion is from 2.6 to 3.3 × 10⁻³ kgm/s/kg fresh weight, at the rheokinesis stage (absolute maximum: 10.2 × 10⁻³ kgm/s/kg). The real energetic expenditure (R_g), including the rate of activity, is much lower (0.03 to 1 × 10⁻³ kgm/s/kg), while the energetic expenditure during the towing phases (instantaneous rheokinesis) is much higher (up to 50 × 10⁻³ kgm/s/kg) (Tabl. II). However all these values are lower than those found in the animal kingdom, and the mean traction strength of M. testacea is very high (up to 29 times the larval weight). Therefore this species uses more of its energy in traction than in speed, the opposite to the situation in fishes. It is an ethological adaptation to life in a current, reinforced by the necessity of pulling a case which increases the force of the current. The available energy E obtained by the consumption of oxygen is 86.3 × 10⁻³ kgm/s/kg in still water. It is larger than (or equal to) the instantaneous rheokinesis (R_i) in the current. Only part of the energy E is transformed into muscular energy measured by R_i. Since a 30 cm/s current produces an increase in metabolism of about 30 × 10⁻³ kgm/s/kg, the needs for muscular energy R_i increase too fast to be covered only by the basal level of metabolism in still water. In fact, only a part of the muscular energy R_i (about 1 to 3%) is transformed into strictly locomotion R_g, so that this energy requirement needs less than 1/1000 of the energy obtained by metabolism in still water (Tabl. II).     

Les tumeurs testiculaires à cellules de Leydig: à propos de quatre cas et revue de la littérature

Introduction

Leydig cell tumors of the testis are uncommon, and represent 1 to 3% of all testicular tumors, it’s the most common of sex cord stromal tumors. They can be found in all age groups, but they mainly occur in subjects aged 15 to 50 years (50%), 25% occurring in older men and a little less than 20% in children aged 5 to 9 years. The most common revealing symptom is gynecomastia in adults, whereas in children it is isosexual pseudo-precocious puberty. They pose a problem during diagnosis, nonpalpable tumors, and during the choice of surgical treatment, because it is difficult to make a clear distinction between benign and malignant tumors.

Material and methods

We describe four different presentations of this disease. The parameters studied were: age, revealing symptom, hormonal profile, type of treatment, and mode of evolution.

Results

The average age of our patients was 37.5 years. The first revealing symptom was a unilateral increasing size of purse in two cases, a bilateral increasing size of purse in one case, and gynecomastia in the last one. In all cases testosterone was normal or low, and oestradiol was normal or elevated. Our four patients underwent an orchidectomy, associated with an enucleation of the contralateral testis in only one case. A favorable evolution was observed in every case for a mean follow-up of 15 months.

Conclusion

On the basis of four different clinical observations and the analysis of the literature, the aim of this review is to present the various clinical, biological, radiological, pathological and therapeutic aspects of Leydig cell tumors of the testis.     

Cytochrome P450 et activation génétique — de la pharmacologie à l’élimination du cholestérol et à la régression de l’athérosclérose

Background

Lipoproteins are closely associated with the atherosclerotic vascular process. Elevated levels of highdensity lipoprotein cholesterol (HDL-C) and apolipoprotein AI (apo AI) in plasma indicate a low probability of coronary heart disease (CHD) together with enhanced longevity, and elevated levels of low-density lipoproteincholesterol (LDL-C) and apo B indicate an increased risk of CHD and death. Studies linking gene activation and the induction of cytochrome P450 with elevated plasma levels of apo AI and HDL-C and lowered plasma levels of LDL-C presented a new potential approach to prevent and treat atherosclerotic disease.

Objective and methods

This is a review aimed at clarifying the effects of P450-enzymes and gene activation on cholesterol homeostasis, the atherosclerotic vascular process, prevention and regression of atherosclerosis and the manifestation of atherosclerotic disease, particularly CHD, the leading cause of death in the world.

Results

P450-enzymes maintain cellular cholesterol homeostasis. They respond to cholesterol accumulation by enhancing the generation of hydroxycholesterols (oxysterols) and activating cholesterol-eliminating mechanisms. The CYP7A1, CYP27A1, CYP46A1 and CYP3A4 enzymes generate major oxysterols that enter the circulation. The oxysterols activate — via nuclear receptors — ATP-binding cassette (ABC) A1 and other genes, leading to the elimination of excess cholesterol and protecting arteries from atherosclerosis. Several drugs and nonpharmacologic compounds are ligands for the liver X receptor, pregnane X receptor and other receptors, activate P450 and other genes involved in cholesterol elimination, prevent or regress atherosclerosis and reduce cardiovascular events.

Conclusions

P450-enzymes are essential in the physiological maintenance of cholesterol balance. They activate mechanisms which eliminate excess cholesterol and counteract the atherosclerotic process. Several drugs and nonpharmacologic compounds induce P450 and other genes, prevent or regress atherosclerosis and reduce the occurrence of non-fatal and fatal CHD and other atherosclerotic diseases.     

Contribution à la connaissance des Hymenoptera Apoidea de Nouvelle-Calédonie et de leurs relations avec la flore butinée

Seulement 21 espèces d’Apoidea sont répertoriées de Nouvelle-Calédonie. La pauvreté de cette faune est paradoxale si on la compare à la richesse et l’endémicité de la flore de l’île, mais s’expliquerait par le fait qu’elle a été isolée avant ou peu après l’apparition des Apoidea vers – 130 millions d’années. Les auteurs comparent aussi les données de plusieurs îles des océans Pacifique et Indien. Deux nouvelles espèces de Halictidae sont décrites: Homalictus cocos et Lasioglossum (Chilalictus) delobeli. Une nouvelle synonymie est établie: Homalictus risbeci (Cockerell, 1929) = Homalictus crotalariae (Cockerell, 1929). Deux taxons, Chalicodoma umbripenne et Megachile laticeps, sont signalés pour la première fois en Nouvelle-Calédonie. Les relations entre les Apoidea et les 22 espèces végétales, sur lesquelles ces insectes ont été capturés, sont présentées et commentées.     

Etude de la reponse à un stress hydrique de quelques varietés de riz pluvial et de riz irrigué

Résumé La transpiration de plants de riz cultivés sur sol en chambre de culture, est suivie en continu pendant une séquence déssèchement-irrigation. Les cycles jouraliers de transpiration sont présentés avant et pendant le stress hydrique. Quatre variétés montrent une augmentation de la transpiration nocturne qui disparait lors du stress hydrique. Il apparait que la régulation stomatique est indépendante du potentiel hydrique du sol jusqu'à une valeur seuil au-delà de laquelle la baisse de transpiration est proportionnelle à la baisse du potentiel hydrique. Cette valuer seuil est plus basse pour les variétés de type irrigué.

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Water stress response for some cultivars of upland- and lowland riceI. Effects on transpiration

Summary The transpiration of rice seedlings grown on soil in a growth chamber was observed during a soil drying/rewetting sequence. The diurnal cycles of transpiration are shown before and during the water stress period. Four cultivars showed an increase of transpiration during the night. This increase disappeared during the water stress period. The stomatal regulation appeared not to depend on the soil water potential until a certain value. Below this soil-water threshold, the decrease of transpiration was proportion to the decrease of water potential. This threshold value is lower for the rain-fed cultivars than for the irrigated cultivars.

     

Aspects moléculaires de la spermatogenèse: la réparation post-réplication de l’ADN et le système ubiquitine

Ubiquitin is a ubiquitous and highly conserved protein of 76 amino acid residues, that can be covalently attached to cellular acceptor proteins through a multi-step enzymatic pathway. Mono- or poly-ubiquitination of proteins can lead to protein degradation or modification of protein activity. The ubiquitin system is essential to all eukaryotic cells. Many components of the complex ubiquitin system show remarkable evolutionary conservation, from yeast to mammalian species. Interestingly, during gametogenesis, many specialized and important aspects of the ubiquitin system become apparent. TheHR6B gene is a mammalian, autosomal homolog of theSaccharomyces cerevisiae geneRAD6 encoding a ubiquitin-conjugating enzyme.RAD6 in yeast is required for a variety of cellular functions, including sporulation, DNA repair, and mutagenesis. Male infertility inHR6B knockout mice is associated with impairment of spermatogenesis. Components of the ubiquitin system appear to be involved in different steps and processes during gametogenesis, including control of meiosis, and reorganization of chromatin structure.     

Effets d’une exposition à la Vinclozoline et à la Génistéine de la gestation à l’âge adulte sur la fonction de reproduction du ratWistar mâle: protocole et résultats préliminaires

Current evidence indicates that endocrine disrupters (EDs) can induce adverse effects on the male reproductive tract in various mammalian species. Recent reports indicate deterioration in male reproductive health in several human populations, but the evidence for a causal link with endocrine disruption is still weak. In addition, the experimental conditions of most of the reportedin vivo studies are not representative of environmental exposures (for example, high doses, short-term exposure, a single ED) and the mechanisms by which EDs disrupt the reproductive system are poorly understood. The objective of the present study is to develop an animal model to assess the reproductive effects and study the putative cellular and molecular mechanisms involved after exposure to genistein (phytoestrogen) and vinclozolin (fungicide with a known antiandrogenic potential) alone or in combination. The study will be performed in male Wistar rats, with administration of low and high doses of the compounds from conception to adulthood and a subset of the males in each treatment group will be mated with unexposed females. We plan to assess the level of sperm production, histology of the reproductive organs, motility and morphometry of spermatozoa and hormone levels, as well as DNA fragmentation of spermatozoa and determination of the number of germ cells, Sertoli cells and the diameters of seminiferous tubules. Estrogen, androgen, progesterone and FSH receptors will be detected and quantified and the level of testicular apoptosis and several apoptosis pathways will be studied to determine the putative cellular and molecular mechanisms involved. The preliminary results confirmed the developmental effects previously reported for high doses of vinclozolin. More interestingly, they indicated a number of deleterious effects for male rats exposed to low dosages alone or mixtures of low and high dosages compared to controls and rats exposed to high dosages alone. For example, a number of developmental anomalies of the genitalia were observed and a significant decrease of sperm motility and motion and fertilizing ability were observed. These preliminary results provide evidence that chronic exposure to environmental levels of EDs or mixtures of EDs have a detrimental impact on the male reproductive tract. The next step involves assessment of the anatomical disorders and the study of some of the cellular and molecular mechanisms possibly involved.     

Contrôle de la détermination et de la différenciation des caractères sexuels somatiques de Néréidiens (Annélides polychètes)

Résumé Les modalités de la détermination et de la différenciation du dimorphisme sexuel de Néréidiens (Annélides Polychètes) ont été recherchées chezNereis pelagica L. etPerinereis cultrifera G. par des expériences de décérébration, de castration (par irradiation X), de greffes et d'injection de produits génitaux.Les caractères sexuels somatiques des cirres parapodiaux (renflement et crénelures) se développent toujours conformément au sexe génétique quel que soit l'état génital de laNereis et la nature de l'intervention. La détermination des caractères sexuels somatiques des cirres parapodiaux apparaît donc comme étant très précoce (3 mois au moins avant la différenciation génitale) et stable.Par contre, les papilles pygidiales, caractère sexuel mâle dans les conditions normales, peuvent se différencier chez les très jeunes femelles dont l'épitoquie est déclenchée prématurément par décérébration et chez les femelles de tout âge dont les transformations hétéronéréidiennes sont réalisées en présence d'un milieu mâle (injection de produits génitaux, greffe sur un mâle). Les papilles pygidiales semblent donc déterminées précocement chez les deux sexes; leur différenciation est cependant inhibée chez les femelles au cours de la maturation génitale.

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Control of determination and the differentiation of the sexual somatic characters of Nereids (Annelida Polychaeta)

Summary The modalities of determination and differentiation of sexual dimorphism of Nereids (Annelida Polychaeta) were investigated inNereis pelagica L. andPerinereis cultrifera G. with experiments involving decerebration, castration (by X irradiation), grafts or injection of genital products.The sexual somatic characters of the parapodial cirri (swelling and crenellations) always develop according to the genetic sex, whatever the genital state of the Nereis and the nature of the intervention. Therefore the determination of the sexual somatic characters of the parapodial cirri appear to be determined in a very precocious and stable way (at least 3 months before the genital differentiation).The pygidial papillae, a male sexual character in normal conditions, can be formed by very young females in which heteronereidation is realized prematurely by decerebration, and by females of any age in which heteronereid transformations are realized in a male environment (e.g. by injection of genital products, or grafting onto a male). Therefore the pygidial papillae may be determined precociously in either sex; however their differentiation is normally inhibited in females in the course of genital maturation.

     

Le cancer de la verge : à propos d’un cas et revue de la littérature

Cancer of the penis is rare. It often raises the issue of acceptability of the amputation of penis. We report a case of cancer of the penis following a late circumcision. The treatment consisted of amputation of two-thirds of the penis. The patient is alive without any local recurrence 2 years after surgery. Literature review suggests that this type of cancer is very rare. The factors associated with such cancer include lack of circumcision and infection with human papilloma virus.     

Contribution à l'analyse des structures forestières 2. Caractérisation et analyse du toit de la végétation

Data used come from point-height analysis. 100 sample points are arranged in 4 lines of 25, with 24 m between lines and 1 m between points on lines. At each point, vertical lists of species are compiled, by measurement strata. Such strata depth is 10 cm when mean vegetation height in the stand is lower than 4–5 m and 50 cm when heigher. A synthetic vegetation profile is obtained by sum of species presences in each measurement stratum for all 100 observations. When these profiles are bimodal, vegetation can be divided in two at the secondary minimum level: the upper part is the canopy, the lower the understorey. Only the canopy structure is dealt with in this tudy. Several parameters, describing vertical structure of woody vegetation, are defined and measured. They are: (1) maximum height, (2) upper and lower canopy limits, (3) canopy depth and (4) density. Delimitation of canopy is achieved by calculating the hypegeometric probability of realisation groups of vegetation presence, or absence, in the vertical line of sight. The thickness is the difference between the two previous values (2) and (3) and density the number of intercepts between them. Horizontal variations in those structural parameters are revealed by cumulative sum method which demonstrates different types of pattern. Relations between horizontal variations are studied by pairs; actual values compared by linear correlation analysis while concordance between patterns are characterised by the coefficient of simple concordance ofSokal etMitchner and by a binary autocorrelation coefficient.Shannon's formula enables an overall appreciation of canopy homogeneity. an example is applied to some stands ofNothofagus antarctica (Forest) Verst. in Southern Chile and Argentina. The upper canopy limits are the same upper vegetation intercepts so canopies are smooth. High correlation exists between upper and lower limits of the canopies, and low correlation between the latter and thickness and density, so canopies are uniform.     

Endémie bilharzienne à Schistosoma mansoni à la vallée du Kou : caractérisation du système de transmission et impact socioéconomique

Schistosomiasis is one of the waterborne diseases which benefit from environmental and behavioral changes induced by the mobilization of surface water resources in Sahelian countries, such as Burkina Faso. Studies have established the existence of human schistosomiasis in the Kou valley, one of the oldest hydro-agricultural zones in the country. However, the role of population behavior in the transmission pattern of this disease and its socioeconomic impact in this valley are poorly understood. It is in response to these questions that this study was undertaken. The objectives of this study were to identify activities that exposed most of the Valley's population to infection by schistosomiasis, and to contribute knowledge on the consequences of this disease. The study was conducted in the cold dry season at the Kou Valley, located in the South Sudanese area of Burkina Faso. It has adopted the strategy of direct observation to examine host–parasites interactions. The study of the socioeconomic consequences of the infection has been first to identify subjects that actually carry the parasite by screening the population by the Kato–Katz method. These were then subjected to a questionnaire. Data were analyzed using Epi Info 6.4. This work has revealed six activities at risk of infection for the residents of the Valley with an increased risk of factor for rice farming, household activities and swimming. In view of these activities, women and young people seem to be most vulnerable to infection. This disease causes significant economic losses as a function of socio-professional categories of infected persons.     

Polymorphisme electrophorétique de la post-albumine et de la transferrine dans les différentes sous-espèces de singes anthropoïdes

Summary The electrophoretic polymorphism of post-albumin and transferin was investigated in 46 apes of the Pan troglodytes. Gorilla gorilla and Pongo pygmaeus subspecies. This type of study enables the different subspecies to be distinguished and the ancestral from to be identified. The pattern of individual variability is found to be different between the various ape species and Homo sapiens.

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Polymorphisme electrophorétique de la post-albumine et de la transferrine dans les différentes sous-espèces de singes anthropoïdes

Résumé Le polymorphisme électrophorétique de la postalbumine et de la transferine est étudié chez 46 individus apprrtenent à diverses sous-espèces de Pan troglodytes, Gorilla gorilla et Pongo pygmaeus. Il est ainsi possible de distinguer les différentes sous-espèces et de proposer lesquelles d'entre elles sont les formes ancestrales. L'étendue du polymorphisme est différente chez les différentes espèces de singes et chez Homo sapiens.

     

La dépression et le traitement antidépresseur: de la neurotoxicité à la neurogenèse

Major depressive disorder is characterized by structural and neurochemical changes in limbic structures, including the hippocampus that regulates mood and cognitive functions. Hippocampal atrophy is observed in patients with depression: structural changes in the hippocampus associated with depression include dendritic atrophy, decreased adult neurogenesis and reduced volume. Impairment of neuroplasticity in the hippocampus, amygdala and cortex is hypothesized to be the mechanism by which cognitive function, episodic verbal memory and emotions are altered in depression. Chronic stress exposure and depression leads to hippocampal atrophy and cell loss as well as to decreased expression of neurotrophic growth factors. All types of antidepressant drugs reverse or block the effects of stress. Chronic antidepressant administration upregulates neurogenesis and neuroplasticity in the adult hippocampus and these cellular responses are required for the effects of antidepressants in animal models of depression.