Semen quality of young men in Switzerland: a nationwide cross-sectional population-based study

BACKGROUND

Sperm counts have been steadily decreasing over the past five decades with regional differences in the Western world. The reasons behind these trends are complex, but numerous insights indicate that environmental and lifestyle factors are important players.

OBJECTIVE

To evaluate semen quality and male reproductive health in Switzerland.

MATERIALS AND METHODS

A nationwide cross-sectional study was conducted on 2523 young men coming from all regions of Switzerland, recruited during military conscription. Semen volume, sperm concentration, motility, and morphology were analyzed. Anatomy of the genital area and testicular volume was recorded. Testicular cancer incidence rates in the general population were retrieved from Swiss regional registries.

RESULTS

Median sperm concentration adjusted for period of sexual abstinence was 48 million/mL. Comparing with the 5th percentile of the WHO reference values for fertile men, 17% of men had sperm concentration below 15 million/mL, 25% had less than 40% motile spermatozoa, and 43% had less than 4% normal forms. Disparities in semen quality among geographic regions, urbanization rates, and linguistic areas were limited. A larger proportion of men with poor semen quality had been exposed in utero to maternal smoking. Furthermore, testicular cancer incidence rates in the Swiss general population increased significantly between 1980 and 2014.

DISCUSSION

For the first time, a systematic sampling among young men has confirmed that semen quality is affected on a national level. The median sperm concentration measured is among the lowest observed in Europe. No specific geographical differences could be identified. Further studies are needed to determine to what extent the fertility of Swiss men is compromised and to evaluate the impact of environmental and lifestyle factors.

CONCLUSION

A significant proportion of Swiss young men display suboptimal semen quality with only 38% having sperm concentration, motility, and morphology values that met WHO semen reference criteria.

Arbuscular mycorrhizae increase the arsenic translocation factor in the As hyperaccumulating fern Pteris vittata L

Phytoremediation techniques are receiving more attention as decontaminating strategies. Phytoextraction makes use of plants to transfer contaminants from soil to the aboveground biomass. This research is devoted to study the effects of arbuscular mycorrhizae (AM) on growth and As hyperaccumulation in the Chinese brake fern Pteris vittata. We grew for 45 days P. vittata sporophytes, infected or not infected with the AM fungi Glomus mosseae or Gigaspora margarita, in a hydroponic system on quartz sand. As-treated plants were weekly fed with 25 ppm As. The As treatment produced a dramatic increase of As concentration in pinnae and a much lower increase in roots of both mycorrhizal and control plants. Mycorrhization increased pinnae dry weight (DW) (G. margarita = G. mosseae) and leaf area (G. margarita > G. mosseae), strongly reduced root As concentration (G. mosseae > G. margarita), and increased the As translocation factor (G. mosseae > G. margarita). The concentration of phosphorus in pinnae and roots was enhanced by both fungi (G. margarita > G. mosseae). The quantitatively different effects of the two AM fungi on plant growth as well as on As and P distribution in the fern suggest that the As hyperaccumulation in P. vittata can be optimized by a careful choice of the symbiont.

Nuclear changes in pathogen-infected tomato roots

We have investigated nuclear changes induced in tomato (Lycopersicon esculentum) plant roots by two different pathogens, a phytoplasma of the stolbur group and the soil-borne fungus Phytophthora nicotianae var. parasitica, using light and electron microscopy as well as flow cytometry. Our results show that both pathogens strongly influenced nuclear structure, causing pyknosis and chromatolysis, and induced variations in proportion of nuclear populations with different DNA content, increasing the 2C and decreasing the 4C nuclear populations. These latter results suggest a block of the endoreduplication process in the presynthetic phase of the host cell cycle. Moreover, in pathogen-infected roots, nuclei of the same DNA content were less fluorescent, and therefore had a lower DNA content, compared to those of controls, as confirmed by morphological analyses. Our findings suggest that different stimuli may evoke similar nuclear changes, and confirm the usefulness of flow cytometry as a tool to recognize the stress conditions related to the presence of a pathogen.

Morphological evidence for keratinolytic activity of Scopulariopsis spp. isolates from nail lesions and the air

The morphological expression of human hair and nail invasion in vitro by 31 isolates of nine Scopulariopsis species was studied by light microscopy on whole material and on semi-thin sections, as well as by transmission electron microscopy. Only some isolates of Scopulariopsis brumptii, S. candida, S. carbonaria and S. koningii were keratinolytically active. They came either from nail lesions or from outdoor aerosols. The most active isolate belonged to S. koningii and was recovered from a fingernail lesion. Both hair and nail degradation followed the biochemical and morphogenetic model described by the authors for other keratinolytic fungi.

The nucleus of differentiated root plant cells: modifications induced by arbuscular mycorrhizal fungi

The nuclei of plant cells show marked differences in chromatin organisation, related to their DNA content, which ranges from the type with large strands of condensed chromatin (reticulate or chromonematic nuclei) to one with mostly decondensed chromatin (chromocentric or diffuse nuclei). A loosening of the chromatin structure generally occurs in actively metabolising cells, such as differentiating and secretory cells, in relation to their high transcriptional activity. Endoreduplication may occur, especially in plants with a small genome, which increases the availability of nuclear templates, the synthesis of DNA, and probably regulates gene expression. Here we describe structural and quantitative changes of the chromatin and their relationship with transcription that occur in differentiated cells following an increase of their metabolism. The nuclei of root cortical cells of three plants with different 2C DNA content (Allium porrum, Pisum sativum and Lycopersicon esculentum) and their modifications induced by arbuscular mycorrhization, which strongly increase the metabolic activity of colonised cells, are taken as examples.

Scopulariopsis brevicaulis: a keratinophilic or a keratinolytic fungus?

The morphologic expression of human hair and nail invasion in vitro by Scopulariopsis brevicaulis isolates was studied by light microscopy on whole material and on semi-thin sections, and also by scanning and transmission electron microscopy. Only three isolates of the nine that were examined were keratinolytic, capable of both attacking keratinic substrates and demolishing their keratin. The process showed all the characteristic of enzymatic digestion and was in agreement with the biochemical and morphogenetic scheme proposed for other keratinolytic fungi during their invasion of human hair in vitro. All the active isolates were capable of developing structures related to surface erosion and radial penetration contemporaneously. However the extent and rate of keratinolysis were rather low when compared with the efficiency of other keratinolytic fungi. This finding suggests that S. brevicaulis is of secondary importance in the mineralization of keratinic substrates in natural environments. From the medical standpoint the mere demonstration of keratinolytic activity means that it may be regarded as a real cause of primary infection.

Arbuscular mycorrhizal induced changes to plant growth and root system morphology in Prunus cerasifera

We compared root system morphogenesis of micropropogated transplants of Prunus cerasifera L. inoculated with either of the arbuscular mycorrhizal (AM) fungi Glomus mosseae or Glomus intraradices or with the ericoid mycorrhizal species Hymenoscyphus ericae. All plants were grown in sand culture, irrigated with a nutrient solution that included a soluble source of phosphorus, for 75 days after transplanting. Arbuscular mycorrhizal colonization increased both the survival and growth (by over 100%) of transplants compared with either uninoculated controls or transplants inoculated with H. ericae. Arbuscular mycorrhizal colonization increased root, stem and leaf weights, leaf area, root length and specific leaf area, and it decreased root length/leaf area ratio, root/shoot weight ratio and specific root length. Both uptake of phosphorus and its concentration in leaves were increased by AM infection, although the time course of the relationships between intensity of AM infection and P nutrition were complex and suggested a role for factors other than nutrition. The time course for the development of infection varied. It was most rapid with G. mosseae, but it was ultimately higher with G. intraradices. None of the treatments significantly affected the lengths of adventitious roots or the first-, second- or third-order laterals that developed from them. Arbuscular mycorrhizal colonization increased the intensity of branching in all root orders with the effect being most obvious on first-order lateral roots where the number of branches increased from under 100 to over 300 brances m(-1). As a result, although first-order laterals made up 55% of the root systems of control plants, the comparable value was 36% in AM-infected plants. In contrast, second-order laterals represented 25% of control root systems, but 50% of AM-colonized root systems. Glomus intraradices but not G. mosseae increased root diameter. Anatomical studies revealed no changes in the overall form of the root tip, although there were changes in the diameter of the root cap, cell numbers and cell size. Hymenoscyphus ericae increased the duration of the metaphase index. Both AM fungal treatments increased the concentrations of soluble proteins in root extracts and modified the protein profiles by the elimination and addition of protein bands detected by PAGE analysis. We conclude that AM fungal inoculation influenced processes in the root system at different levels, but not all effects were due to improved P nutrition or increased physiological age.

Keratinolysis and its morphological expression in hair digestion by airborne fungi

The morphological expression of keratinolysis in fungi isolated from the air of Torino (98 isolates belonging to 36 species) was studied. Light microscopy on whole material and on semithin sections, as well as scanning electron microscopy was used. There were 19 keratinolytically active species, with seven in the genus Chrysosporium (C. indicum, C. keratinophilum, C. pannicola, C. tropicum, C. an. Arthroderma cuniculi, C. an. Pectinotrichum llanense, C. an. Renispora flavissima), four in the genus Malbranchea (M. arcuata, M. fulva, M. sulphurea, M. st. Uncinocarpus reesii), and three in the genus Trichophyton (T. mentagrophytes, T. rubrum, T. terrestre). In addition there were Aphanoascus fulvescens, Beauveria bassiana, Geomyces pannorum v. pannorum, Gymnoascus umbrinus and Myceliophthora vellerea. Most of these species were capable of developing structures related to surface erosion and radial penetration contemporaneously. However Gymnoascus umbrinus, Myceliophthora vellerea, an isolate of C. indicum, C. tropicum and Trichophyton mentagrophytes demonstrated only surface erosion. Different isolates of one species can vary in their production of invasive structures and in degree of keratinolytic activity. Thus such activity, like many biochemical activities of fungi, does not appear to be a constant or rigorously species-specific character.

Ultrastructural aspects of the demolition of human hair in vitro by Chrysosporium tropicum Carmichael

The pattern of invasion of human hair in vitro by a non-dermatophytic fungus, Chrysosporium tropicum, was studied by transmission and scanning electron microscopy. The components of the hair were attacked in sequence, depending on their level of keratinization, i.e. their content of cystine. In the cuticle, the sequence of digestion was as follows: intercellular material, cytoplasmic membrane, endocuticle, exocuticle, layer A, and a thinner layer below the inner cytoplasmic membrane of the cuticle cells. In the cortex, the order was: cementing material, plasmalemma, intermacrofibrillar material, microfibrils and matrix of the microfibrils. At the same time a different mode of attack was radial penetration of the various layers without regard to degree of keratinization. This occurred by means of perforating hyphae originating in the cuticle from structures similar to appressoria. With both modes of attack, the process showed all the characteristics of enzymatic digestion rather than physical breakdown. Ch. tropicum thus demonstrated important physiological parallels with dermatophytes in its demolition of hair in vitro. This could be of interest in predicting its ability to infect in vivo.