High pressure flow cytometric sorting damages sperm

Sexing sperm by high-speed flow cytometry subjects them to high pressure. The routine operating pressure of the MoFlo SX flow cytometer for sperm sorting for commercial production has been 50 pounds/square inch (psi), with a standard 70 microm standard nozzle tip. It was hypothesized that lowering the sorting pressure could reduce sperm damage. Therefore, a series of experiments using semen from six bulls, sorted with three MoFlo SX sorters, was conducted to determine optimal pressure. An additional experiment was done with stallion spermatozoa. In Experiment 1, sorting at 30 psi compared to 50 psi with the 70 microm nozzle tip increased sperm motility post-thaw at 30 min and 2h from 40.5 to 48.0% and 30.0 to 40.2%, respectively (P<0.05). In Experiment 2, 49, 43, 37, 31, and 25 psi resulted in 24.2, 32.8, 35.6, 37.5, and 39.8% progressively motile spermatozoa post-thaw (P<0.05). In Experiment 3, 3 pressures (50, 40, 30 psi)x2 sorting methods were further evaluated. At 50, 40, and 30 psi, respective mean sperm motilities at 30 min were 44.8, 48.6, and 49.6% (P<0.05), and percentage of live spermatozoa were 51.7, 55.7, and 57.8% (P<0.05). The improvement of post-sort sperm quality with lowered pressure was also evident in stallion spermatozoa. After sorting at 30, 40 and 50 psi were 40.6, 34.5 and 30.1% motile spermatozoa (P<0.1), and were 76.7, 72.5 and 67.8% (P<0.05) live spermatozoa (determined by SYBR-14/propidium iodide staining). In Experiment 4 sorter performance was evaluated with two pressures (40 and 50 psi)x2 staining concentrations of bovine spermatozoa (75 x 10(6) and 100 x 10(6)mL(-1)). Lowering pressure to 40 psi did not lower sort rate and purity when compared to 50 psi (P>0.05), and higher sperm concentration during staining increased sort rate (P<0.05). In conclusion, lowering pressure of the MoFlo SX flow cytometer for sperm sorting from 50 psi (standard pressure) to 40 psi clearly improved sperm quality without a significant decrease in sorter performance.     

A high confidence, manually validated human blood plasma protein reference set

Background

The immense diagnostic potential of human plasma has prompted great interest and effort in cataloging its contents, exemplified by the Human Proteome Organization (HUPO) Plasma Proteome Project (PPP) pilot project. Due to challenges in obtaining a reliable blood plasma protein list, HUPO later re-analysed their own original dataset with a more stringent statistical treatment that resulted in a much reduced list of high confidence (at least 95%) proteins compared with their original findings. In order to facilitate the discovery of novel biomarkers in the future and to realize the full diagnostic potential of blood plasma, we feel that there is still a need for an ultra-high confidence reference list (at least 99% confidence) of blood plasma proteins.

Methods

To address the complexity and dynamic protein concentration range of the plasma proteome, we employed a linear ion-trap-Fourier transform (LTQ-FT) and a linear ion trap-Orbitrap (LTQ-Orbitrap) for mass spectrometry (MS) analysis. Both instruments allow the measurement of peptide masses in the low ppm range. Furthermore, we employed a statistical score that allows database peptide identification searching using the products of two consecutive stages of tandem mass spectrometry (MS3). The combination of MS3 with very high mass accuracy in the parent peptide allows peptide identification with orders of magnitude more confidence than that typically achieved.

Results

Herein we established a high confidence set of 697 blood plasma proteins and achieved a high 'average sequence coverage' of more than 14 peptides per protein and a median of 6 peptides per protein. All proteins annotated as belonging to the immunoglobulin family as well as all hypothetical proteins whose peptides completely matched immunoglobulin sequences were excluded from this protein list. We also compared the results of using two high-end MS instruments as well as the use of various peptide and protein separation approaches. Furthermore, we characterized the plasma proteins using cellular localization information, as well as comparing our list of proteins to data from other sources, including the HUPO PPP dataset.

Conclusion

Superior instrumentation combined with rigorous validation criteria gave rise to a set of 697 plasma proteins in which we have very high confidence, demonstrated by an exceptionally low false peptide identification rate of 0.29%.     

Molecular defense responses in roots and the rhizosphere against Fusarium oxysporum

Plants face many different concurrent and consecutive abiotic and biotic stresses during their lifetime. Roots can be infected by numerous pathogens and parasitic organisms. Unlike foliar pathogens, root pathogens have not been explored enough to fully understand root-pathogen interactions and the underlying mechanism of defense and resistance. PR gene expression, structural responses, secondary metabolite and root exudate production, as well as the recruitment of plant defense–assisting “soldier” rhizosphere microbes all assist in root defense against pathogens and herbivores. With new high-throughput molecular tools becoming available and more affordable, now is the opportune time to take a deep look below the ground. In this addendum, we focus on soil-borne Fusarium oxysporum as a pathogen and the options plants have to defend themselves against these hard-to-control pathogens.