Lamine C2 et spermatogenèse

Lamin A/C are intermediate filaments present in nucleus. Their roles are numerous and laminopathies are issued from LMNA gene mutations. In male germ cells, this protein family is only represented by lamin C2. The results obtained in male mice show the importance of these filaments in male meiosis and suggest the existence of a new male infertility domain involving this intermediate filament and its associated proteins.     

Apoptose au cours de la spermatogenèse et dans le sperme éjaculé

It has become clear in recent years that programmed cell death occurs spontaneously in the cycle of the seminiferous epithelium. Induced germ cell apoptosis occurs at specific stages of the spermatogenic cycle and the existence of supracellular control of germ cell death during spermatogenesis has been documented. If apoptosis is a key phenomenon in the control of sperm production, the existence and role of apoptosis in ejaculated sperm cells remain controversial. Apoptosis — as determined by DNA fragmentation (TUNEL) and ultrastructural analysis — is abnormally frequent in the sperm cells of the ejaculate of sterile men with classical biochemical and ultrastructural pattern. In this review, we discuss the possible origins of DNA damage in ejaculated human spermatozoa and the consequences of DNA damage if the apoptotic spermatozoa is used for ICSI. Percentages of DNA fragmentation in human ejaculated sperm are correlated with fertilization rates both after FIV and ICSI. Detection of DNA fragmentation in human sperm could provide additional information about the biochemical integrity of sperm and may be used in future studies for fertilization failures not explained by conventional sperm parameters. However, the analysis of other molecular markers of apoptosis (Fas, Annexine V ...) is necessary to assess the role of apoptosis in human ejaculated sperm cells.     

Cancer du testicule: BEP et spermatogenèse

The sperm characteristics of 44 men treated with two or more courses of BEP chemotherapy for non seminomatous germ cell testicular tumours were investigated before and 25.2 ± 19.4 months after chemotherapy. Before treatment, 54.5% of patients were oligozoospermic. The mean sperm characteristics did not differ before and after chemotherapy. However, following chemotherapy, the recovery of initial sperm count was more frequent after one year than before. During the first year, recovery was more frequent in patients treated with two than in those treated with more than two BEP cycles. In patients with good pre-treatment sperm count, sperm production was reduced by half after chemotherapy. In a subgroup of men who provided two sperm samples after chemotherapy, sperm production was better in the second sample than in the first. Our data suggest that sperm recovery is related to testicular function prior to therapy, to the time elapsed after chemotherapy and in the first year to the number of chemotherapy cycles. In conclusion, our study is reassuring concerning the long-term male reproductive toxicity of BEP. However, further studies are required to analyse the possible effects on sperm genetic material during the recovery period.     

La spermatogenèse et l'ovogenèse de Lepisma (Thermobia) domestica. Hétéropycnose dans un sexe homogametique

Sans résumé     

Stress et Spermatogénèse

Stress, which originates in the brain, can influence spermatogenesis hormonally or via the nervous system. The hormonal route commences with the central secretion of Corticotrophin-Releasing Factor, leading to a fall in LHRH production, a decrease in Leydig cell LH receptors and a decrease in 17 a hydroxylase activity. Thus, in the case of major, prolonged stress, testosterone secretion falls, which in turn affects spermatogenesis. However, given that the testosterone threshold required for normal seminiferous epithelium function is significantly less than the mean circulating level of this hormone, the importance of low intensity stress remains unknown. The nervous route involves catecholaminergic fibres which, in the testis, innervate the Highmore corpus, the vessels, the area adjacent to the Leydig cells, and the basement membrane of seminiferous tubules. The experimental destruction of these fibres leads a regression of the seminiferous epithelium. Moreover, the experimental ablation of the rat anterior neocortex leads to changes in spermatogenesis. Therefore, given that the endocrine system does not seem to be involved in these changes, these results indicate that the highest level of the nervous system may participate in the controlling the germinal epithelium which, all things considered, would tend to support psychosomatic influences. However, given that the number of spermatozoa varies significantly between ejaculate and independantly of the level of testosterone secretion necessary for normal spermatogenesis, it may be hypothesized that it is only when sperm production is low that temporary stress, in aggravating the situation, becomes deleterious to spermatogenesis. Since, under normal conditions, such periods are short, the role of the influence of stress on spermatogenesis can only be relative. Nevertheless, if variations occur during permanently low sperm production, the likelihood of negative effects is increased. Consequently, the impact of stress or psychological factors on spermatogenesis might well depend upon particular circumstances.     

Place des troubles de la spermatogenèse dans l’hypofertilité masculine

According to Thonneauet al., (1991), 14% of couples are subfertile. In at least 59% of the cases, a male factor was involved. This indicates that 8% (14% × 59%) of men are hypofertile. Since several causes can induce male infertility and because of the heterogeneous criteria and classifications used in the literature, the percentage of each etiologic factor has not been very precisely established. In a population of 2072 consecutive patients we identified an alteration of spermatogenesis in 52% of the cases. This indicates that about 4% of men might have a spermatogenic problem. The spermatogenic insufficiency was isolated in 43% of the cases (i.e. 23% of the total population) or associated with post-testicular causes of male infertility (infectious/inflammatory; autoimmune; obstructive) in 57% of the cases (i.e. 30% of the total population studied). An etiologic factor is clinically identified for 64% of the patients presenting with a spermatogenic insufficiency. The most relevant risk factors linked to spermatogenic alteration were history of mumps orchitis (OR [IC95%]=14,6 [3,4–62,3]), history of radiotherapy-chemotherapy (OR=14,7 [3,4–63,2]). These situations were found with a low frequency (1,4% and 1,3% of the cases respectively) but provoked a spermatogenic alteration in a large majority of cases (92,9% and 92,3% respectively). On the other hand, varicoceles (OR=3,7 [2,9–4,8]) and troubles in testicular descend (OR=2,9 [2,3–3,7]), were more frequent (20,6% and 20,1% of the cases respectively), but less frequently associated with spermatogenic insufficiency (in 73,7 and 69,6% of the cases).     

Spermatogénèse et Paraplégie

In this article, the paraplegics’ possibilities for procreation will be examined. A first chapter will deal with the testicle functioning along with the study of hormonal measuring and testicle histology (study involving 100 patients). As a result, it appears that, after a testicle biopsy, there is a testicle lesion of neurological origin that is sometimes irreversible. On the contrary, the endocrinal testicle lesions have proved reversible under stimulation or spontaneously. A second chapter will deal with the different techniques to obtain an ejaculation and the semen analysis. The techniques that were used being: massage by vibrator, electroejaculation, ejaculation through pharmacological stimulation. The study focuses on 124 ejaculatory tests among which 64 forward ejaculations (52%) and 4 bachward ejaculations (3%) were obtained. The resulting semen analysis revealed a spermatozoon count greater than 20 millions per millilitre (that is 51,5%) and smaller than 5 millions in 11 cases (16%).     

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.     

Etude cytochimique de la spermatogenèse chez Lithobius forficatus L. (Myriapode Chilopode)

Résumé L'étude cytochimique de la spermatogenèse a été envisagée, d'un point de vue qualitatif chez Lithobius forficatus L. (Myriapode Chilopode). Les cellules de la lignée mâle sont de nature essentiellement protéique. On peut distinguer trois grandes périodes: 1. la croissance spermatocytaire, caractérisée par la synthèse d'ARN et de protéines basiques, 2. les phases de division de maturation, 3. la spermiogenèse, marquée par la diminution progressive de la teneur en ARN et en histones.

---

Cytochemical study of spermatogenesis in Lithobius forficatus L. (Myriapoda Chilopoda)

Summary A qualitative cytochemical study was carried out of Spermatogenesis in Lithobius forficatus L. (Myriapoda Chilopoda). The gametes are characterized by their protein nature. Spermatogenesis can be divided into three major periods: 1. Spermatocyte growth, a phase of synthesis of RNA and basic proteins, 2. period of maturation divisions, 3. spermiogenesis, characterized by a gradual decrease in the amounts of RNA and histone.

     

Menhirs et stèles de Corse. Une hypothèse chronologique

In Corsica, the first standing stones are related to Middle Neolithic. Later, during the Bronze Age, appear characteristic massive steles with arm figurations. Between those two limits, well settled, the chronology of other megalithic monuments remains much uncertain. The Sardinian chronology, proposed by E. Atzeni showed that in this island, the evolution from “aniconic menhirs” to “statues-menhirs” with dagger was related to Middle to Final Neolithic (Vth and IVth millenniums). Some examples taken in Europe confirm this chronology. In Corsica, we consider that a metamorphosis might have happen to Aravina stele (Lévie) showing that secondary transformation may have occurred on Neolithic steles. In the first stage, the monument is characterized by its apical rostrum, the engraving of the outline of the face and the “eyes”. During Bronze Age, it was modified by the carving of a sword. The comparison with other Sardinian and Maltese steles suggests a middle Neolithic age. This phase could correspond to an ancient phase of anthropomorphism of standing stones before the emergence of Final Neolithic statues-menhirs.     

Anomalies postnatales du développement de la spermatogenèse associées aux troubles de la migration testiculaire

Cryptorchidism, a non-descended testis in its physiological intrascrotal location, is one of the most frequent congenital anomalies of the male genital system. The mechanisms of the normal descent of the testis are still unclear. Several etiological hypotheses have been proposed for cryptorchidism. Cryptorchidism is associated with a greater risk of testis cancer, and is also a cause of impairment in sperm parameters and fertility in the adult age. In this article, we review the cellular and hormonal events occurring from birth to puberty in isolated cases of congenital cryptorchidism that will later, in adulthood, alter both spermatogenesis and fertility.     

Synthèse Facile de Pyrazines Disubstituées en 2 et 31)

Corynebacterium equi IFO 3730 was found to oxidize a wide variety of sec-alcohols, including alkanols, substituted alkanols, alkenols and cyclic alcohols, in moderate to high yields. Among them, the sec-alcohols which have longer carbon chains were oxidized more smoothly than those with smaller numbers of carbon. Although both enantiomers of unsymmetrically disubstituted carbinols were oxidized, the S form of 2-dodecanol was converted to the corresponding ketone a little faster than the other enantiomer.