Radicaux libres et spermatozoïdes humains: physiologie et physiopathologie

The role of reactive oxygen species in the physiopathology of human sperm function has been emphasized in recent years. Their production in semen has been associated with loss of motility, decreased capacity for spermoocyte fusion and loss of fertility. In semen preparations, there are two major sources of reactive oxygen species: leucocytes and spermatozoa themselve. It has been proposed that reactive oxygen species production by human spermatozoa was dependent upon a membrane-bound NADPH oxidase or a mitochondrial diaphorase. Hydrogen peroxide produced by the dismutation of superoxide anion has been recognized as the most toxic oxidizing species for human spermatozoa. Owing to their high content of polyunsaturated fatty acids, it has been proposed that lipid peroxidation of the sperm plasma membrane is largely responsible for defective sperm function. Reactive oxygen species also affect the sperm axoneme as a result of ATP depletion, inhibit mitochondrial functions, and synthesis of DNA, RNA and proteins, produce cytoskeletal modifications and inhibit sperm-oocyte fusion. Human spermatozoa possess enzymatic defence systems such as superoxide dismutase, glutathion peroxidas/reductase and catalase to counteract the toxic effects induced by reactive oxygen species. Correlations have been reported between their effectiveness and the duration of sperm motility. If the excessive production of reactive oxygen species is detrimental for human spermatozoa, they could also participate in the physiological function of the spermatozoa when present at low concentrations. Indeed, reactive oxygen species have been shown to be involved in the activation of several enzymes. Furthermore, sperm capacitation, acrosome reaction and sperm-zona interaction would be enhanced by reactive oxygen species.     

Risques et valorisation des insectes dans l’alimentation humaine et animale

In a context of dwindling lands and resources, associated with a strong dependence on protein for feed and food, new methods of production and/or new food must be developed without affecting the quality of food, natural habitat and biodiversity of animal and vegetable species. As such, insects appear more and more as a solution of the future. To date, the consumption of insects is indicated by the term “entomophagy”, from the Ancient Greek “entomos” meaning insect and “phagos” meaning food. In such a context, a global evaluation of entomophagy seems essential before allowing the introduction of this practice in animal and human feed. Firstly, through this review, elements concerning the potentialities of insect valorization and their nutritional qualities will be brought. Secondly, the environmental impact of such a practice as well as the biological, chemical, physical or sanitary risks and even the potential presence of allergens and antinutritional factors will be approached. Thirdly, a review of the current European regulations will be proposed. Finally, reflections will be brought on the economic perspectives of entomophagy.     

Malposition épididymaire et oligospermie

In the course of investigation of men suffering from severe oligospermia the author has met with cases were spermatogenesis was normal in testicular biopsies, contrasting with repeatedly severe oligospermia, the situation being accompanied by an obvious malposition of the epididymis. The main anomaly of the epididymis was the absence of its habitual caudal structure. There is no clear physiopathological explanation for biopsy/sperm discrepancy linked to epididymal malposition, but experimental work concerning cryptepididymal situations may offer a clue.     

Apoptose et spermatogenèse

Onset of spermatogenesis is associated with a wave of apoptosis, which limits its efficacy during the first cycles in most mammals. After the first cycles, the actual efficacy of spermatogenesis always remains below the theoretical yield. Among the germinal cells, spermatogonia are the main targets of physiological apoptosis. This physiological apoptosis partly depends on the relationships between germ cells and Sertoli cells. The impact of the Sertoli cell/germ cell number ratio on the efficacy of spermatogenesis is well accepted, the concept of density-dependent regulation in the seminiferous tubule was proposed in the early eighties. Since the steps of spermatogenesis require a continuous progression of the cell cycle rather than an arrest, germ cells might therefore be more sensitive to apoptosis. This may also lead to severe disturbances between proliferation and cell death. The first experiments designed to elucidate the mechanisms of germ cell apoptosis were based on hormonal deprivation or cryptorchidism. However, the link between hormonal or cellular action and cell survival remained to be established. Analysis of signal transduction pathways involved in germ cell apoptosis and their regulation were the next steps. The involvement of bcl-2 family genes has been confirmed, although the expression of some of its members remains more controversial. Data derived from overexpression of some genes (Bcl-2, Bcl-xl) or resulting from gene inactivation (Bax) at the testicular level have highlighted the role of these genes in the control of germ cell apoptosis and have also provided some evidence for the strict requirement for density-dependent regulation of spermatogenesis. More recently, variations in the pattern of expression of these genes or proteins helped to explain some of the discrepancies in the literature. The place of the Fas/Fas ligand system during the first cycle of spermatogenesis remains a matter of debate, with controversies concerning the precise site of expression of this oncogene and its receptor. Conversely, its role in the testis after chemotoxic or radiotoxic treatments is well established. However, the normal fertility of animals with a spontaneous inactivation of Fas or Fas L genes does not support a physiological role of these factors during spermatogenesis. While factors involved in TNF/TNF R1 (Tumor Necrosis Factor) are under study, some data have been reported concerning the role of TRAIL (TNFalpha Related Apoptosis Inducing Ligand) and its active or decoy receptors in the testis. Among the oncogenes which may modulate the apoptotic process, Kit/Stem Cell Factor is particularly interesting, as Kit is expressed in some germ cells and Leydig cells, whereas SCF is expressed by Sertoli cells. Its impact during gonadal development and in the survival and proliferation of differentiated spermatogonia has been clearly established. Using a transgenic mice model, in which the Kit gene was inactivated by the insertion of a nls-lacZ sequence in its first exon, we showed that one single copy of the gene was unable to sustain physiological spermatogenesis and fertility in male mice. Our results also suggest that the Kit gene might be expressed at different steps of spermatogenesis, with different signal transduction pathways and biological actions. Finally, analysis of the signal transduction pathways involved in testicular apoptosis and their mechanisms of control is one of the key steps to a better understanding of both impairment of spermatogenesis and the pathogenesis of certain germ cell tumours.     

Radiopharmaceutiques et réglementations

The radiopharmaceuticals are products that combine two very stringent regulatory requirements from two different authorities: as medicine from a pharmaceutical point of view (Afssaps) and as radioactive source with specific authorization (ASN). This article discusses the different regulatory constraints imposed by these authorities but suggests also that legislation is supposed to be modified in the coming years in collaboration with nuclear physicians and their Society (SFMN).     

Acta Biochimica et Biophysica Sinica

Acta Biochimica et Biophysica Sinica (Acta Biochim Biophys,Sin,ISSN 0582-9879)is a leading scientific journalpublishing original papers,short communications and mini reviews in the fields of biochemistry,molecular biology andbiophysics in China.It has been published monthly for 35 years.Acta Biochim Biophys Sin is sponsored by the     

Illustrations pratiques — Pièges et artefacts/Trucs et astuces

Artifacts result from discrepancy between the estimated density values coming from the reconstructed CT image and the real value. They may come from many reasons (patient, device, algorithm, RX physical) and lead to deterioration of image quality and bad attenuation correction for SPECT or PET.     

Cannabis et fertilité masculine

Cannabis is the most used recreational drug in the world. One of the major concerns of exposure to the cannabis is its negative effect on the reproductive function. The discovery of the endocannabinoid system, composed of multiple endogenous lipid ligands, their receptors and their metabolic enzymes, highlights the importance of the signaling pathways of this system in multiple events of reproduction. The objective of this study is to review the impact of the cannabis on male reproductive function. The limits and the perspective possible studies to evaluate the effects of the cannabis on male fertility are discussed in this study on the basis of the studies carried out on men and animals.     

Identité masculine et transsexualisme

Transsexualism is a phenomenon of our culture. In the past, there were men and women who could not accept their innate sex. What is new is linked to our modern medical technology which offers patients a so-called «change of sex» using hormones and surgery; in fact it is a change in appearance, allowing the individual to «pass» as a member of the other sex. Some societies had and still have a social status for a third gender, but our transsexuals do not want to be treated as members of a third gender, they want to belong to the other gender Male-to-female and female-to-male transsexuals have the same mental functioning, characterized by splitting and denial. But there are differences, in part because society is more intolerant of feminine behaviors in men than of masculine behaviors in women. Male-to-female transsexualism includes a subgroup of subjects who, after failing in school, are unable to earn their living and live on welfare, even after surgical sex reassignment. We have learned from the study of intersexed and transsexual subjects that the feeling of belonging to a gender is a belief, a construction, in which psychological factors (interactions between the parents, the environment and the child) play an important role. Masculine or feminine identities have their roots in the sexual difference, but they are defined by each culture. A man is a male who accepts at least part of his culture’s stereotypes regarding masculinity. Even if biological factors play a role, they cannot explain the whole of gender identity and sexual orientation.     

Blessures dans la filiation et infertilité masculine : étude comparative et psychodynamique

The family history of a set of infertile men was the aim of the present study, through a filiation events grid based on a psychoanalytical approach. During the genetic counselling before ICIS procedure, the family chart was established and the filiation grid applied to a group of 30 infertile men requiring assisted reproductive procedures, as well as to a control group of 30 fertile men recruited in a maternity hospital after birth of their child. The filiation events differed significantly between two groups. It can be therefore assumed that difficulties in the past generation may play a part in some cases of infertility. A psychodynamic approach is then developed to highlight the hypothesis of a link between the traumatic impact of these filiation events on these men and its translation as a somatic expression.     

Cryptorchidie et température testiculaire

The testis migrates to a scrotal location before birth. This physiological descent is associated with a reduction in the temperature of the testicular environment since the temperature of the scrotal cavity is lower than that of the body one. This leads to the etablishment of a themperature gradient between the testis and the body which already exists in prepubertal boys. In cases of testicular maldescent (cryptorchidism), the temperature of the testis in its cryptorchid location is much higher than that of the normally descended contrlateral testis. However, there are no data obtained from human studies to establish wether the increased temperature of a cryptorchid testis is responsible for the spermatogenic perturbations typically observed. Nor do we know wether the relocation of a cryptorchid testis to the scrotum permits re-establishment of a normal testicular temperature. Adult men with a history of cryptorchidism constitute about 10% of infertile men, and among these previously cryptorchid infertile men 45% have an abnormally elevated scrotal temperature. This abnormal increase in scrotal temperature is a negative risk factor for fertility: these men have smaller testicular volumes, a more severely impaired spermatogenesis and a higher prevalence of primary infertility than previously cryptorchid infertile than previously cryptorchid infertile men with normal scrotal temperature. However, data provided until now do not allow to know whether elevated temperature is due to the decreased testicular size (hypotrophy) or is a consequence of cryptorchidism per se.     

Synthèses et réductions de sucres fonctionnels mono et diinsaturés

Attempts to prepare 1,2:5,6 and 2,3:5,6 di-unsaturated sugars starting from 3,4,6-tri-O-acetyl-1,5-anhydro-1,2-dideo xy-d-arabino-hex-1-enitol or from ethyl 4,6-di-O-acetyl-1,5-anhydro-2,3-dideoxy-α-d-erythro-hex-2-enopyranoside led to 1,5-anhydro-1,2,6-trideoxy-l-threo-hex-5-enitol and its 3,4-diacetate. Hydrogenation and hydrogenolysis of the unsaturated chloro and fluoro derivatives afforded 1,5-anhydro-1,2,6-trideoxy-d-arabino-hexitol and ethyl 4-O-acetyl-2,3,6-trideoxy-α-d-erythro-hexopyranoside.     

Protéomique et marqueurs cardiaques

Cardiovascular diseases are the major causes of morbidity and mortality in western countries and the molecular mechanisms responsible are greatly unknown unless a genetic defect or genes/proteins alteration. The biological complexity has shown that one gene did not encode for one protein but for several, due to mRNA splicing and post-translational modifications. Proteomic analysis is a technology that can provide a global approach to study protein modulation and study by differential comparison various samples. Surface-enhanced laser desorption ionization–time of flight (SELDI–TOF) analysis is a technique, based on combination of chromatography of proteins on proteinchip arrays and mass spectrometry, allowing the comparison of protein profiles from various biological samples. This technology has been particularly used for plasma/serum analysis. We will take, as example, the comparative proteomic analysis of plasma from patients having a myocardial infarction by the SELDI approach in describing the principle, the problems linked to the study of plasma, the protein identification and the validation of the technology using other techniques. These approaches have been proved to be interesting for studying cardiovascular diseases in order to better understand the molecular mechanisms involved and identifying protein interactions and new biological factors/biomarkers involved in cardiovascular.