13C NMR des alcaloïdes des Strychnos: Les dérivés de l'harmane et de l'usambarensine

¹³C NMR spectra of some tertiary and quaternary indole alkaloids are recorded and the signals assigned. Graphic interpretation of off-resonance spectra and substituent shielding effects together with the effect of N_b-methylation are utilized in the spectral interpretation.     

Chimiotaxonomie des lycopodiales: distribution des alcaloïdes

The distribution of lysine-derived alkaloids in the genus Lycopodium (s.l.) supports the separation of the following taxa, Huperzia (= Urostachys), Lycopodiella s.l. (= Lepidotis, excl. L. volubile and L. deuterodensum) from Lycopodium s. str. Within the latter, the Fastigiatum group and the Complanata section (= Diphasiastrum) can be distinguished. The results obtained are in good agreement with the classification proposed by Wilce.     

Utilisation des spermatozoïdes cryoconservés: fréquence et résultats

Semen cryopreservation has become a major activity of CECOS units. In 2002, 2,323 patients were referred to a CECOS unit for semen cryopreservation prior to radiotherapy or chemotherapy. Cryopreservation of one or several semen specimens was performed for 2,124 patients, which represents a total of more than 60,000 straws per year. The two diseases mainly concerned by cryopreservation prior to treatment with a high risk of sterilization are testicular cancer (about 40% of requests) and lymphomas (about 30% of requests). Specimens are generally stored for several years. The most frequent indications are testicular cancer (40% of the patients) and lymphomas (30% of the patients). Due to the continuing improvement of treatment, the subsequent fertility prognosis of patients has improved over recent years, but often remains difficult or even impossible to predict. An assessment of the effective use of these frozen gametes and the results obtained therefore appeared to be interesting. During 2002, 304 men requested the use of their cryopreserved semen. More than 1,000 straws were thawed and used for insemination (195 insemination cycles, 12 pregnancies obtained) orin vitro fertilization (25 conventional IVF cycles, 8 pregnancies; 257 IVF-ICSI cycles, 57 pregnancies). A retrospective cumulative study conducted in 2001 with the collaboration of 15 of the 23 CECOS units calculated, for each year, among patients in whom cryopreservation could be performed, the percentage of patients who subsequently requested the use of straws between the date of cryopreservation and 2001. This percentage varied between 5% and 10%, depending on the time since freezing. Calculation of the percentage of patients for whom destruction of straws was performed, either at the patient’s request, or because of the patient’s death, was also performed according to the same methodology. The percentage of destruction because of the patient’s death varied between 5% and 9%. The percentage of destruction of straws at the patient’s request was close to or greater than 15%, when the storage time exceeded 3 years. The percentage of patients lost to follow-up remains low in these indications for cryopreservation, ranging between 3% and 6% depending on the year. These data are globally coherent with the data reported in the literature. Although the use of straws is not the most frequent outcome of semen cryopreservation, freezing of gametes must nevertheless always be proposed to patients, as their subsequent fertility often remains difficult to predict. Progress in methods of medically assisted procreation also allow a good chance of pregnancy even when few viable spermatozoa have been preserved.     

Anticorps anti-spermatozoïdes: techniques de dépistage et interprétation des résultats

Since the first publication on the detection of sperm-agglutinating antibodies in infertile men, multiple assays have been described. The most useful tests are able to detect antibodies bound to the sperm membrane of motile spermatozoa. The immunobeads test (IBT) is considered to be the most advantageous in terms of its sensitivity, the low incidence of false-positive results, and its ability to localize antibodies of different immunoglobulin classes on the sperm surface. The IBT assay can be used in parallel with the mixed antiglobulin reaction (MAR), to detect sperm-associated antibodies in the ejaculates of infertile men, the most rational way to test for antisperm antibodies (ASA) in males. In view of the high level of agreement between the two assays, MAR, the easier of the two, may be used as a first step in the detection of these antibodies. A positive MAR must be confirmed by IBT, as this assay is more specific for the detection of IgA antibodies. The clinical significance of sperm-associated antibodies is usually established according to the proportion of motile spermatozoa coated with immunobeads, its class and its localization on the sperm surface. However, binding of immunobeads does not provide any information about the antigens against which the antibodies are directed. As the functional effects of sperm-associated antibodies may vary as a function of their antigenic specificities, other assays, using purified fertilization related antigens, are necessary to establish, for each individual, the specific impact of the antibodies on the fertilization process. The indirect IBT assay has recently become the most widely used test to detect the various classes of ASA in serum and cervical mucus of infertile women and in the serum and seminal fluid of infertile men, in combination with the direct assay described above. However, in most laboratories, it is performed with only one dilution of the biological fluid tested, usually a low dilution, so that antibody levels of no significance for fertility could be detected. This may explain a recente debate (Human Reprod, 1999) on the significance of ASA as a cause of infertility. At present, and in the absence of standardized assays able to identify the antigens involved in each individual immune reaction, antibody assays, as detected by the IBT assay, in the serum and/or genital secretions of infertile subjects might provide useful clinical guidance.     

Marqueurs du tractus génital et activités glycosidasiques séminales

Seminal liquefaction corresponds to a proteolysis of glycoproteins and could also result in a lysis of linked glycans involving glycosidases. It is well known that α-1-4 glucosidase is a real epipidymal marker. The aim of this study is to point out new markers among the glycosidases and especially β-D-mannosidase, α-L-fucosidase and N-acetyl-β-D-glucosaminidase. There is no correlation between the three enzymatic activities and the sperm count. Moreover in case of azoospermia enzymatic activities were always present. The variations observed are both quantitative (β-MAN activity is significantly decreased) and qualitative (modifications of the relative proportions of the different enzymatic forms) according to the etiology of azoospermia.     

Benzyl-2 tropanes et γ-pyranotropanes,alcaloïdes de Knightia strobilina

Twelve new tropane alkaloids have been isolated from the leaves of the endemic New Caledonian plant Knightia strobilina Labill. (Proteaceae). The structure of seven of them, elucidated by spectroscopic methods, are described here.     

Inhibiteurs anti-trypsine et activités protéolytiques des Albumines de graine de Vigna unguiculata

Summary The extracellular space of tentacles of Drosera capensis L. is divided into two compartments by cuticular material between cells of an endodermoid layer and by the nonporous cuticle of the stalk and neck. The distal compartment includes the mucilaginous secretion as well as the free space of the secretory cap, since the cuticle covering the cap is perforated by numerous 0.05–0.3 m pores. The proximal compartment includes xylem and the intercellular space of the stalk. The existence of the endodermoid partition is consistent with the observation that action potentials recorded extracellularly from the head may be positive-going while those recorded extracellularly from the stalk are negative-going. The partitioning is also consistent with the hypothesis previously proposed to explain why the amplitude of action potentials recorded from the mucilage varies as a function of the amplitude of the receptor potential.The living cells are united by plasmodesmata. Unusually abundant plasmodesmata were observed in the walls between endodermoid cells and neck cells, between neck cells and the next row of outer stalk cells, in the end walls connecting the outer stalk cells, and the end walls connecting the inner stalk cells: these strategically located plasmodesmata presumably permit the electrotonic spread of receptor potentials and action potentials between cells.     

Benzyl-2 pseudotropanes et dihydro γ-pyranotropanes,alcaloïdes de Knightia strobilina

The structures of five new tropane alkaloids, isolated from the leaves of the endemic New Caledonian plant Knightia strobilina have been elucidated by spectroscopic methods.     

Spermatozoïdes,environnement et prévention

Over the last fivty years, the risk factors for infertility have increased substantially, particularly those due to the environment. Spermatogenesis and spermatozoa can be affected by physical (ionizing radiation microwaves, heat, cryopreservation) or chemical agents (antimitotics drugs, antibiotics, tranquillizers, insecticides, pesticides, industrial solvants, some heavy metals, alcohol, cannabis etc.). Some natural factors, as stress or paternal age (ageing or very youthful age relatively to about thirty) also seems to affect spermatogenesis and, particularly, the age can be joined with the previous ones. On the whole, these factors are able to decrease the male fertility through some changes about the concentration, the motility or the morphology of spermatozoa and so it is possible to describe populations subject to the risk. Moreover, these spermatogenetic changes can lead abnormalities in progeny. For instance, some antimitotic drugs as cyclophosphamide, when administrated to the male rat, lead malformations or functional anomalies as behavioral troubles. The industrial solvents lead a decrease of the birth weight and the cannabis leads an increase of the ante-or post-natal death. Moreover, the change of the paternal spermatogenesis caused by cannabis can be found again in the male progeny. The problem is similar with the lead, the benzodiazepines and the alcohol. Concerning the physical factors, some authors have shown that the children born from radiation exposed fathers presented an increase of the probability of leukemia. In animal, the postimplantation loss is increased when the father is irradiated or subjected to heat before mating. Finally, the paternal ageing is responsible for new dominant autosomic mutations. Moreover, in animal and man, paternal ageing and, in man, very youthful age, also seems responsible for a gradual lowering in the level of progency cerebral functions. On the whole, these data should lead to an preventive attitude which would be more effective before about thirty years of age than after this period.     

Les spermatozoïdes immobiles frais ou décongelés en fécondation assistée

Contrasting with sperm count or morphology, complete lack of mobile sperm may seriously impair ICSI fertilization and pergnancy rate. In three cases with flagellar skeleton abnormalities [dynein arm absence] only immobile sperm were found in the ejaculate. Following repeated ejaculations, higher rates of viable spermatozoa and even some motile spermatozoa could be found. Some times, in nonobstructive azoospermia, extensive sperm search didn't allow us to find but immobile sperm mostly, with very few motile sperm cells, not enough for the microinjection of all oocytes. The third group of immobile sperm is iatrogenic, following freezing and thawing surgically retrieved, testicular or epididymal spermatozoa in order to avoid repeated surgical retrieval. Following thawing, one find frequently very few motile spermatozoa that may be not enough for all retrieved oocytes and it might be necessary to inject some eggs with immobile spermatozoa. The outcome of ICSI using mobile and immobile sperm was compared in the three above mentioned groups: 1-immobile ejaculated sperm with flagellar defects, 2-immobile sperm discovered in the ejaculate after extensive sperm search and 3- immobile frozen-thawed testicular or epididymal spermatozoa. The results of ICSI in these groups show that fertilizing ability of fresh or frozenthawed immobile spermatozoa is not significantly different from ICSI with mobile sperm from the same origin. More over, in the first group with flagellar abnormalities, repeated ejaculations allowed us significantly increase sperm viability and fertilization ability. Finding only immobile fresh or frozen-thawed sperm the day of egg retrieval should not lead us to ICSI cancellation. Pregnancies may occur with such immobile sperm.     

Estimation du taux d’aneuploïdies des spermatozoïdes épididymaires prélevés en vue d’ICSI chez des hommes à caryotype normal

Over the last ten years, fluorescent in situ hybridization in decondensed sperm nuclei has been used to study the chromosomal constitution of human spermatozoa. Studies have estimated that the disomy rate per chromosomal pairs is between 0.15% and 0.3%. The aim of this study was to evaluate the aneuploidy rate of human epididymal spermatozoa extracted from five men with obstructive azoospermia undergoing IVF. Genetic studies (karyotypes, Y micodeletion syndrome and mutation of the CFTR gene) did not reveal any abnormality. Disomy frequencies were determined by X-Y-8 multicolour fluorescence in situ hybridisation on 18,013 epididymal spermatozoa and 20,000 spermatozoa from healthy donors (control group). No significant difference was found between epididymal and ejaculated samples. However, isolated non-significant differences were observed between one of the patients and the control group. In conclusion, the present findings suggests that there is no increased risk for de novo chromosomal aberrations after IVF therapy with epididymal spermatozoa of men with obstructive azoospermia.