Decondensation behavior of DNA chains induced by multivalent cations at high salt concentrations:Molecular dynamics simulations and experiments

Using molecular dynamics simulations and atomic force microscopy （AFM）, we study the decondensation process of DNA chains induced by multivalent cations at high salt concentrations in the presence of short cationic chains in solutions. The typical simulation conformations of DNA chains with varying salt concentrations for multivalent cations imply that the concentration of salt cations and the valence of multivalent cations have a strong influence on the process of DNA decondensation. The DNA chains are condensed in the absence of salt or at low salt concentrations, and the compacted conformations of DNA chains become loose when a number of cations and anions are added into the solution. It is explicitly demonstrated that cations can overcompensate the bare charge of the DNA chains and weaken the attraction interactions between the DNA chains and short cationic chains at high salt concentrations. The condensation-decondensation transi- tions of DNA are also experimentally observed in mixing spermidine with X-phage DNA at different concentrations of NaCl/MgCl2 solutions.

Study on Resistance of Human Sperm Chromatin to Heparin Decondensation

Resistance or human sperm chromatin to hearin decondensation was investigated by image analysis. The level of DNA decondensation was determined by measuring the at [red fluorescence/(red+green) fluorescenca]of sperm. The optima experimental conditions were incubating sperms With 1000 IU/ml of heparin at 37℃for 13 minutes and analysing the sperms with excitation F488, red fluorescence F630, green fuorescenco F530. The result showed that 72.93±14.73 percent or 20 fertile human sperms resist hoparin decondensation.

Assessment of Spermatic Chromatin Decondensation by the Toluidine Blue Assay in Infertile Patients in Cotonou

Background: A high level of sperm chromatin decondensation results in loss of DNA quality and it is associated with poor embryonic prognosis in Assisted Reproductive Technology (ART). This had lead to introduction of sperm DNA compaction testing in assessment of clinical male infertility. Toluidine blue assay is one of most commonly used tests to measure chromatin decondensation in research studies and also in clinical routine use. So the objective of our study was to assess the level of sperm chromatin decondensation by toluidine blue assay in men dealing with couple infertility. Methods: The sperm samples of 96 patients referred for infertility, over a 4-month period from September 2020 to January 2021, were stained with toluidine blue and observed under an optical microscope. These were evaluated according to the World Health Organization. Results: The 25 - 34 age group was the most represented among infertile men. There was a non-significant correlation between age and the level of spermatic chromatin condensation (r = 0.0348). Spermatic parameters had averages above standards norms, apart from that of low vitality. Spermatic chromatin decondenization affected 96% of infertile patients. Asthenozoospermia was the most common abnormality. Among standard parameters of spermogram, only the concentration of spermatozoa in the semen was weakly correlated (r = 0.18) with sperm chromatin decondensation. Conclusion: The level of sperm chromatin condensation is, on the one hand, a parameter independent of the age of the subject; on the other hand, allows to evaluate male infertility, like the classic parameters of the spermogram and spermocytogram. However, in view of the high probability of changes in the nuclear quality of sperm intrinsic to the analysis process and sperm concentration, an improvement of the toluidine blue test using the swim-up technique and associated with image processing software is possible.

Structural Features of Nuclei in Leaf Mesophyll Cells of Salt-Tolerant Artemisia marschalliana

All nuclei in mesophyll cells of Artemisia marschalliana are located in vacuoles and occupy up to 90% of their volume. The ultrastructural organization of chromatin in nuclei shows different degrees of its decondensation, up to complete separation of DNA from histones. It is possible that the separation of DNA from histones enables Artemisia to grow in soils with high salinity.

Biophysical mechanism-mediated time-dependent effect on sperm of human and monkey vas implanted polyelectrolyte contraceptive

Aim： To determine the short and long-term morphological effects on sperm as induced by intra-vas alteration of pH and electrical charge. Methods： Desired biophysical influences were obtained by injection of reversible inhibition of sperm under guidance （RISUG） into the lumen of the vas deferens of human subjects and the monkey. RISUG is a polyelectrolyte hydrogel complex of styrene maleic anhydride （SMA） and dimethyl sulfoxide （DMSO） which generates an electrostatic charge and also lowers in a near space of pH domain. The morphology of sperm was examined by light microscopy, scanning and transmission electron microscopy. Human study enabled semen collection by masturbation as early as 3 h after injection and studies extended up to 6 months, in the monkey, on vas excision after RISUG implantation, sperm characteristics were examined in serial sections. Results： Semenology in clinical studies and histological data of the monkey showed a time-sequenced sperm plasma membrane, tail mitochondria and nuclear decondensation alterations in sperm structural components, which beared marked similarity to changes in the sperm head and tail during capacitation and entry into the ovum. Conclusion： The findings provide a means of causing such changes in the sperm that inhibit the fertilizing ability before the nucleus is affected. Therefore achieving non-obstructive vas-based contraception, without genotoxic or teratogenic effects caused by infertile sperm passing into the semen, is feasible.