Comparison of assessment of pigeon sperm viability by contrast-phase microscope (eosin-nigrosin staining) and flow cytometry (SYBR-14/propidium iodide (PI) staining) [evaluation of pigeon sperm viability]

[Computergestützte Spermaanalyse bei Großfalken (Falco spp.) und Vergleich zu den Ergebnissen konventioneller spermatologischer Untersuchungen]

OBJECTIVE

Numerous raptor species including some falcon species are facing continuous population decline in the wild and some are threatened by extinction. To support these species, captive breeding and reintroduction programs are attempted. Besides conservation, some large falcon species are commonly used in falconry and therefore bred commercially. Assisted reproduction is established in falcon breeding since the 1970s and semen analysis is an integral part to enable assessment of breeding males, inclusion or exclusion of semen donors and quality control of semen prior to artificial insemination. Conventional methods for semen analysis are widely used, but are time consuming and depend on the investigator's experience and ability. Computer-assisted semen analysis (CASA) would offer an objective, fast and reproducible alternative, but as they have not been established in large falcon species, this was the aim of this study.

MATERIAL AND METHODS

To this end, we examined in 3 breeding seasons 109 semen samples of gyr-saker hybrid falcons (n=2) and peregrine falcons (n=4) in 940 fields of view using the Minitube CASA SpermVision and compared these results to results of conventional methods of semen analysis. We used a preprogrammed setting and adapted two settings of CASA according to specific semen characteristics of falcons.

RESULTS

Sperm velocity, motility and viability parameters were recorded successfully using CASA. Correlation of conventional and computer-assisted motility analysis improved during the process of adaptation of CASA settings, but both methods differed significantly due to misinterpretation of round bodies and semen impurities by CASA. Viability values of conventional and computer assisted viability analysis using SYBR-PI correlated significantly while sperm concentration did not at all.

CONCLUSION

CASA failed to replace conventional semen analysis regarding sperm motility and sperm concentration using 3 different settings, as a reliable differentiation between spermatozoa, spermatids and round bodies was not achieved.

CLINICAL RELEVANCE

Using CASA, sperm velocity parameters were measured in spermatozoa of captive-bred large falcons for the first time and may be used as orientation values.

Integrity of Sperm Cell Membrane in the Semen of Crossbred and Purebred Boars during Storage at 17 °C: Heterosis Effects

Simple Summary

The cell membrane of spermatozoa is the main structural element of these gametes. In boars, due to its structure, it is most susceptible to various types of damage induced by various factors. Artificial insemination in pigs mainly involves the use of liquid semen preserved at 17 °C. Thus, it is important to monitor this semen during its storage. In practice, the changes that can take place in sperm during the preservation and storage of boar semen are not analysed. Furthermore, considerable variation is observed in the characteristics of boar semen, which may depend on the breed or crossbreeding variant of the boar. Crossbred boars are often used in artificial insemination, because they not only easily produce ejaculates with good parameters, but also have good libido characteristics. However, despite the benefits of artificial insemination with semen of crossbred boars, there is insufficient knowledge of the sensitivity of cell structures to conditions associated with semen storage in comparison with boars of the parent breeds. For this reason, a study was conducted to analyse changes in the integrity of sperm cell membranes taking place during the storage of semen collected from Duroc × Pietrain crossbred boars and purebred boars of the parent breeds. The sperm of Duroc × Pietrain crossbred boars were found to be less sensitive to the conditions of semen storage and to better retain cell membrane integrity than the sperm of purebred males, which was confirmed by calculating the heterosis effects for semen assessed at different hours of storage at 17 °C.

Abstract

The aim of the study was to assess changes in the integrity of sperm cell membranes during the storage of semen collected from Duroc × Pietrain crossbred boars and purebred boars of the component breeds. To compare the cell membrane integrity of sperm heads in crossbred and purebred boars, heterosis effects were estimated. The study was conducted on 48 ejaculates collected from Duroc × Pietrain crossbred boars and from purebred Duroc and Pietrain boars used for artificial insemination. Microscope slides were prepared from each ejaculate for the evaluation of the cell membrane integrity of the sperm, at 1, 24, 48, 72, and 96 h after collection of the ejaculate. Diluted ejaculates were stored at 17 °C. Sperm membrane integrity was analysed by two methods: SYBR-14/PI and eosin–nigrosin. Our results showed that the cell membrane integrity of sperm heads changed with storage time, but the extent of the changes varied depending on the genetic group of boars. The semen of Duroc × Pietrain crossbreds was clearly seen to be less sensitive to storage conditions than that of boars of the parent breeds, which was confirmed by the calculated heterosis effects. The percentage of sperm with an intact cell membrane was higher in crossbred boars than in purebred boars (p ≤ 0.05). In addition, significantly fewer moribund sperm spermatozoa and spermatozoa with a damaged cell membrane were observed in crossbred boars (p ≤ 0.05). In the semen of purebred Duroc and Pietrain boars, the cell membrane integrity of the sperm should be assessed more often during storage than in the semen of Duroc × Pietrain crossbred boars. This study provides valuable information for the development and implementation of semen quality monitoring in crossbred boars and boars of the parent breeds during storage at 17 °C with respect to the cell membrane structure of sperm heads. The evaluation methods used effectively identify damage to the cell membranes of the sperm during semen storage.

5-aminolevulinic acid improves chicken sperm motility

Objective

This study investigated the effects of 5-aminolevulinic acid (5-ALA) on the motility parameters, mitochondrial membrane depolarization, and ATP levels in chicken sperm.

Methods

The pooled semen from Barred Plymouth Rock males was used. In the first experiment, the semen was diluted 4-times with phosphate-buffered saline (PBS (-)) containing various concentrations (0, 0.01, 0.05, and 0.1 mM) of 5-ALA, and then the sperm motility parameters after incubation were evaluated by computer-assisted sperm analysis (CASA). In the second experiment, the semen was diluted 4-times with PBS (-) containing 0.05 mM 5-ALA, and then sperm mitochondrial membrane depolarization and ATP levels after 1.5 h of incubation were analyzed with the MitoPT® JC-1 Assay and ATP Assay kits, respectively. In the third experiment, the semen was removed from the seminal plasma and resuspended with the mediums of PBS (-), PBS (-) supplemented with CaCl2 and MgCl2 (PBS (+)) + 5-ALA, PBS (+) + caffeine, and PBS (+) + caffeine + 5-ALA. Then, the sperm motility parameters after incubation were evaluated by CASA. In the last experiment, the semen was treated with the mediums of PBS (-), PBS (-) + 5-ALA, 5.7% glucose, 5.7% glucose + 5-ALA after removing the seminal plasma, and then the sperm motility parameters were evaluated by CASA.

Results

The addition of 0.05 mM 5-ALA significantly increased the chicken sperm motility, progressive motility, linearity, average path velocity, curvilinear velocity, straight-line velocity, and the wobble. The sperm mitochondrial membrane depolarization was also increased by the 5-ALA treatment. The 5-ALA treatment decreased the sperm ATP levels. Both the caffeine treatment and glucose treatment decreased the sperm motility during incubation period.

Conclusion

5-ALA might increase sperm mitochondrial membrane depolarization to utilize the ATP for enhancing sperm movement.

The effects of maternal separation stress experienced by parents on male reproductive potential in the next generation

There is little information available about the effects of early-life parental stress on the reproductive potential of the next generation. The aim of this study is to examine the reproductive potential of male mice whose parents experienced maternal separation stress. In the present study, male first-generation offspring from parents were undergone of maternal separation (MS) were examined. Sperm characteristics, histological changes in testis, reactive oxygen species (ROS) production, expression of apoptotic and inflammatory genes and proteins were assessed. Findings showed that MS experienced by parents significantly decreased the morphology and viability of spermatozoa. Furthermore, significant changes in testicular tissue histology were observed. Increased production of ROS, decreased glutathione peroxidase (GPX) and adenosine triphosphate (ATP) concentrations, and affected the expression of genes and cytokines involved in inflammation. Finally, the mean percentage of caspase-1 and NLRP3 (NOD-, LRR- and pyrin domain-containing protein 3) positive cells was significantly higher in first-generation group. MS experienced by parents may negatively affect the reproduction of first generation offspring.

Viability assessment of spermatozoa in large falcons (Falco spp.) using various staining protocols

Viability assessment is an important part of semen analysis, and various live/dead staining protocols have been used in semen of avian species. Results of live/dead count differed between dyes, staining protocols and bird species, impeding comparability between studies and requiring species-specific comparisons of viability stains. In raptor semen, similar comparisons are absent. Thus, the aim of the present study was to compare eight conventional viability stains. Eosin blue 2% [EB], eosin blue 2% with the addition of 3% sodium citrate [EB2], eosin blue-nigrosin 5% [EBN5], eosin yellow-nigrosin 5% [EYN5], eosin yellow-nigrosin 10% [EYN10], eosin blue-aniline blue [EBA], eosin yellow-aniline blue [EYA] and bromophenol blue-nigrosin [BBN] were evaluated in comparison with the fluorescence stain SYBR^® Green-propidium iodide [SYBR-PI] in spermatozoa of falcons. The comparison was performed using conventional light microscopy which is applicable in breeding centres, veterinary practices and field studies. Additionally, live/dead stains were correlated to motility values of the same samples to validate sperm viability. Light microscopy using EB and using SYBR-PI enabled an effective and clear differentiation between alive and dead spermatozoa of falcons. Motility values correlated significantly and strongly with EB only (r = .629; p < .001), but not with any other stain used in the study. Therefore, our results suggest EB as the most suitable stain for viability assessment in the semen of large falcons.

Oxidative stress, inflammatory reactions and apoptosis mediated the negative effect of chronic stress induced by maternal separation on the reproductive system in male mice

Exposure to severe and long-lasting stressors during early postnatal life negatively affects development of the brain and associated biological networks. Maternal separation (MS) is a valid stressful experience in early life that adversely affects neurobiological circuits. In the present study, we aimed to evaluate the effects of MS on sperm quality and histology of the testis in adult male mice. In this study, male mice were subjected to MS during post-natal days (PND) 2-14. Sperm parameters, histological alterations in the testicular tissue, ROS production (using DCFH-DA assay), gene expression of TLR4, NLRP3, TNFα, BAX, ASC, caspase-1 and BCL-2 (using RT-PCR), protein levels of caspase-3 and caspase-8 (using western blotting), and protein levels of IL-1β, IL-18, GPx and ATP (using ELISA) as well as protein expression of caspase-1 and NLRP3 (using immunocytochemistry) were evaluated. Findings showed that MS decreased count, morphology and viability of spermatozoa. MS decreased the diameter of seminiferous tubules and decreased the thickness of seminiferous epithelium. Furthermore, MS increased the level of ROS production and decreased the concentrations of GPx and ATP. MS led to increased expression of TLR4, NlRP3, TNFα, caspase-1, ASC, IL-1β and IL-18. In addition, MS induced apoptosis as evidenced by increased BAX, caspase-3 and caspase-8 as well as decreased BCL-2 expression. We concluded that early life stress induced by MS has detrimental effects on sperm parameters and testicular tissue. Our results suggest that these effects are mediated by activation of ROS production, and alterations in mitochondrial function, inflammatory processes and apoptosis pathways.

Sperm Quality Parameters and Reproductive Efficiency in Muscovy Duck (Cairina moschata)

The in vitro sperm quality parameters (motility, M; viability, V; normal morphology, NM; plasma membrane integrity, PMI; mitochondrial function, MF) in Muscovy drakes (Cairina moschata) were evaluated by using microscopy and flow cytometry, the correlation among sperm quality parameters and results of artificial insemination was also assessed in present study. M, V and NM were detected by phase contrast microscopy assisted with eosinnigrosin staining, and PMI and MF were detected by using flow cytometry within appropriate fluorescence staining (SYBR-14/PI and R123/PI, respectively). Fertility (F), early embryonic mortality (EEM) and the survival embryo rate (SER) were assessed after the artificial insemination of Muscovy or Kaiya duck (Anas platyrhynchos) females. Sperm PMI and MF, the parameters detected by flow cytometry were positively correlated with sperm M, V, and NM, those were detected by phase contrast microscopy (P<0.05). Sperm V and PMI were negatively correlated with the percentage of early embryo mortality of Muscovy duck fertile eggs (P<0.05). The results of the present study showed the relationships among the AI results and the sperm quality parameters detected by microscopy as well as flow cytometry. In conclusion, flow cytometry assisted with microscopy can be an effective tool to evaluate in vitro sperm quality and may contribute to predict the reproductive performances of individual Muscovy drakes, which helps to improve duck production efficiency.

Acrosome integrity assessment of boar spermatozoa images using an early fusion of texture and contour descriptors

The assessment of the state of the acrosome is a priority in artificial insemination centres since it is one of the main causes of function loss. In this work, boar spermatozoa present in gray scale images acquired with a phase-contrast microscope have been classified as acrosome-intact or acrosome-damaged, after using fluorescent images for creating the ground truth. Based on shape prior criteria combined with Otsu's thresholding, regional minima and watershed transform, the spermatozoa heads were segmented and registered. One of the main novelties of this proposal is that, unlike what previous works stated, the obtained results show that the contour information of the spermatozoon head is important for improving description and classification. Other of this work novelties is that it confirms that combining different texture descriptors and contour descriptors yield the best classification rates for this problem up to date. The classification was performed with a Support Vector Machine backed by a Least Squares training algorithm and a linear kernel. Using the biggest acrosome intact-damaged dataset ever created, the early fusion approach followed provides a 0.9913 F-Score, outperforming all previous related works.

Spata6 is required for normal assembly of the sperm connecting piece and tight head-tail conjunction

"Pinhead sperm," or "acephalic sperm," a type of human teratozoospermia, refers to the condition in which ejaculate contains mostly sperm flagella without heads. Family clustering and homogeneity of this syndrome suggests a genetic basis, but the causative genes remain largely unknown. Here we report that Spata6, an evolutionarily conserved testis-specific gene, encodes a protein required for formation of the segmented columns and the capitulum, two major structures of the sperm connecting piece essential for linking the developing flagellum to the head during late spermiogenesis. Inactivation of Spata6 in mice leads to acephalic spermatozoa and male sterility. Our proteomic analyses reveal that SPATA6 is involved in myosin-based microfilament transport through interaction with myosin subunits (e.g., MYL6).

Assessment of changes in sperm cell membrane integrity occurring during the storage of semen from genetically different males using two diagnostic methods

Wysokińska, A. and Kondracki, S. 2014. Assessment of changes in sperm cell membrane integrity occurring during the storage of semen from genetically different males using two diagnostic methods. Can. J. Anim. Sci. 94: 601–606. The present study was carried out to assess changes in sperm cell membrane integrity occurring during the storage of semen collected from genetically different domestic male pigs. The study was aimed at assessing differences in the course of changes in the integrity of cell membranes in spermatozoa produced by males with different degrees of genetic diversity (pure-bred males, two-breed hybrids and multi-breed crosses) and testing the usefulness of two methods of sperm cell membrane integrity evaluation, based on material collected from genetically different males. The experiments were conducted on 56 ejaculates collected from 28 domestic male pigs. The examination of sperm cell membrane integrity was performed three times for each ejaculate, i.e., after 1 h, after 24 h and after 48 h from collection. The preparations for analysing cell membrane integrity were made using two methods: the SYBR 14/PI method and the eosin–nigrosin method. It was found that both SYBR 14/PI and eosin–nigrosin staining methods make it possible to successfully assess the integrity of the plasma membrane of domestic pig sperm cells under in vitro conditions. Hybrid pig spermatozoa, especially those from multi-breed crosses, better retain the integrity of their plasmalemmas than the spermatozoa of pure-bred boars. The ejaculates of Hypor cross-breed boars assessed after 1, 24 and 48 h of storage contain more spermatozoa with intact cell membranes than the ejaculates of pure-bred Duroc and Pietrain boars. The ejaculates of Hypor boars also show fewer decaying spermatozoa than those produced by pure-bred boars.

Dual vulnerability of TDP-43 to calpain and caspase-3 proteolysis after neurotoxic conditions and traumatic brain injury

Transactivation response DNA-binding protein 43 (TDP-43) proteinopathy has recently been reported in chronic traumatic encephalopathy, a neurodegenerative condition linked to prior history of traumatic brain injury (TBI). While TDP-43 appears to be vulnerable to proteolytic modifications under neurodegenerative conditions, the mechanism underlying the contribution of TDP-43 to the pathogenesis of TBI remains unknown. In this study, we first mapped out the calpain or caspase-3 TDP-43 fragmentation patterns by in vitro protease digestion. Concurrently, in cultured cerebrocortical neurons subjected to cell death challenges, we identified distinct TDP-43 breakdown products (BDPs) of 35, 33, and 12 kDa that were indicative of dual calpain/caspase attack. Cerebrocortical culture incubated with calpain and caspase-fragmented TDP-43 resulted in neuronal injury. Furthermore, increased TDP-43 BDPs as well as redistributed TDP-43 from the nucleus to the cytoplasm were observed in the mouse cortex in two TBI models: controlled cortical impact injury and overpressure blast-wave-induced brain injury. Finally, TDP-43 and its 35 kDa fragment levels were also elevated in the cerebrospinal fluid (CSF) of severe TBI patients. This is the first evidence that TDP-43 might be involved in acute neuroinjury and TBI pathology, and that TDP-43 and its fragments may have biomarker utilities in TBI patients.

A low membrane lipid phase transition temperature is associated with a high cryotolerance of Lactobacillus delbrueckii subspecies bulgaricus CFL1

The mechanisms of cellular damage that lactic acid bacteria incur during freeze-thaw processes have not been elucidated to date. Fourier transform infrared spectroscopy was used to investigate in situ the lipid phase transition behavior of the membrane of Lactobacillus delbrueckii ssp. bulgaricus CFL1 cells during the freeze-thaw process. Our objective was to relate the lipid membrane behavior to membrane integrity losses during freezing and to cell-freezing resistance. Cells were produced by using 2 different culture media: de Man, Rogosa, and Sharpe (MRS) broth (complex medium) or mild whey-based medium (minimal medium commonly used in the dairy industry), to obtain different membrane lipid compositions corresponding to different recovery rates of cell viability and functionality after freezing. The lipid membrane behavior studied by Fourier transform infrared spectroscopy was found to be different according to the cell lipid composition and cryotolerance. Freeze-resistant cells, exhibiting a higher content of unsaturated and cyclic fatty acids, presented a lower lipid phase transition temperature (Ts) during freezing (Ts=-8°C), occurring within the same temperature range as the ice nucleation, than freeze-sensitive cells (Ts=+22°C). A subzero value of lipid phase transition allowed the maintenance of the cell membrane in a relatively fluid state during freezing, thus facilitating water flux from the cell and the concomitant volume reduction following ice formation in the extracellular medium. In addition, the lipid phase transition of freeze-resistant cells occurred within a short temperature range, which could be ascribed to a reduced number of fatty acids, representing more than 80% of the total. This short lipid phase transition could be associated with a limited phenomenon of lateral phase separation and membrane permeabilization. This work highlights that membrane phase transitions occurring during freeze-thawing play a fundamental role in the cryotolerance of Lb. delbrueckii ssp. bulgaricus CFL1 cells.