Name: sperm collection of differential quality using density gradient centrifugation
Uploaded: 2018-11-29T15:00:00
Description: Watch this Scientific Journal Video about Sperm Collection of Differential Quality Using Density Gradient Centrifugation at JoVE.com

All methods described here have been approved by the Institutional Animal Care and Use Committee (IACUC) of the University of Georgia.
1. Washing using Traditional Centrifugation
<ol>
	<li>Prepare phosphate buffer solution (PBS). Add 8.0 g of NaCl, 0.2 g of KCl, 1.44 g of Na2HPO4 and 0.24 g of KH2PO4 to 800 mL of distilled water (dH2O). Adjust the pH to 7.4 using 0.1 N HCl and bring the solution to 1 L using dH2O.</li>
	<li>Pr...

<ol>
	<li>Spargo, S. C., Hope, R. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evolution+and+nomenclature+of+the+zona+pellucida+gene+family.">Evolution and nomenclature of the zona pellucida gene family.</a> Biology Reproduction. 68, 358-362 (2003).</li><li>Okamura, F., Nishiyama, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+passage+of+spermatozoa+through+the+vitelline+membrane+in+the+domestic+fowl,+Gallus+gallus.">The passage of spermatozoa through the vitelline membrane in the domestic fowl, Gallus gallus.</a> Cell and Tissue Research. 188 (3), 497-508 (1978).</li><li>Henkel, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sperm+function+and+assisted+reproduction+technology.">Sperm function and assisted reproduction technology.</a> Reproductive Medicine and Biology. 4, 7-30 (2005).</li><li>Reddy, R. P., Bakst, M. R., Wishart, G. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Artificial+Insemination+of+broilers:+Economic+and+management+implications.">Artificial Insemination of broilers: Economic and management implications.</a> Proceedings of 1st International Symposium on Artificial Insemination of Poultry. Poultry Science Association. , 73-89 (1995).</li><li>Howarth, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+Examination+for+Sperm+Capacitation+in+the+Fowl.">An Examination for Sperm Capacitation in the Fowl.</a> Biology of Reproduction. 3, 338-341 (1971).</li><li>Menkveld, R., Holleboom, C. A. G., Rhemrev, J. P. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measurement+and+significance+of+sperm+morphology.">Measurement and significance of sperm morphology.</a> Asian Journal of Andrology. 13, 59-68 (2011).</li><li>Kumaresan, A., Johannisson, A., Al-Essawe, E. M., Morrell, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sperm+viability,+reactive+oxygen+species,+and+DNA+fragmentation+index+combined+can+discriminate+between+above-+and+below-average+fertility+bulls.">Sperm viability, reactive oxygen species, and DNA fragmentation index combined can discriminate between above- and below-average fertility bulls.</a> Journal of Dairy Science. 100, 5824-5836 (2017).</li><li>Froman, D. P., McLean, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Objective+measurement+of+sperm+motility+based+upon+sperm+penetration+of+Accudenz.">Objective measurement of sperm motility based upon sperm penetration of Accudenz.</a> Poultry Science. 75, 776-784 (1996).</li><li>Zaneveld, L. J., De Jonge, C. J., Anderson, R. A., Mack, S. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Human+sperm+capacitation+and+the+acrosome+reaction.">Human sperm capacitation and the acrosome reaction.</a> Human Reproduction. 6 (9), 1265-1274 (1991).</li><li>Ahammad, M. U., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Acrosome+reaction+of+fowl+sperm:+Evidence+for+shedding+of+acrosomal+cap+in+intact+form+to+release+acrosomal+enzyme.">Acrosome reaction of fowl sperm: Evidence for shedding of acrosomal cap in intact form to release acrosomal enzyme.</a> Poultry Science. 92 (3), 798-803 (2013).</li><li>Ahammad, M. U., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Maturational+changes+in+motility,+acrosomal+proteolytic+activity,+and+penetrability+of+the+inner+perivitelline+layer+of+fowl+sperm,+during+their+passage+through+the+male+genital+tract.">Maturational changes in motility, acrosomal proteolytic activity, and penetrability of the inner perivitelline layer of fowl sperm, during their passage through the male genital tract.</a> Theriogenology. 76 (6), 1100-1109 (2011).</li><li>Chalah, T., Brillard, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+assessment+of+fowl+sperm+viability+by+eosin-nigrosin+and+dual+fluorescence.">Comparison of assessment of fowl sperm viability by eosin-nigrosin and dual fluorescence.</a> Theriogenology. 50 (3), 487-493 (1998).</li><li>Aitken, R. J., West, K. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+the+relationship+between+reactive+oxygen+species+production+and+leukocyte+infiltration+in+fractions+of+human+semen+separated+on+Percoll+gradients.">Analysis of the relationship between reactive oxygen species production and leukocyte infiltration in fractions of human semen separated on Percoll gradients.</a> International Journal of Andrology. 13, 433-451 (1990).</li><li>Mortimer, D., Mortimer, S. T., Carrell, D., Aston, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Density+Gradient+Separation+of+Sperm+for+Artificial+Insemination.">Density Gradient Separation of Sperm for Artificial Insemination.</a> Spermatogenesis. Methods in Molecular Biology (Methods and Protocols. , 927 (2013).</li><li>Qingling, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Processing+of+semen+by+density+gradient+centrifugation+selects+spermatozoa+with+longer+telomeres+for+assisted+reproduction+techniques.">Processing of semen by density gradient centrifugation selects spermatozoa with longer telomeres for assisted reproduction techniques.</a> Reproductive BioMedicine Online. 31, 44-50 (2015).</li><li>Moohan, J. M., Lindsay, K. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spermatozoa+selected+by+a+discontinuous+Percoll+density+gradient+exhibit+better+motion+characteristics,+more+hyperactivation,+and+longer+survival+than+direct+swim-up.">Spermatozoa selected by a discontinuous Percoll density gradient exhibit better motion characteristics, more hyperactivation, and longer survival than direct swim-up.</a> Fertility and Sterility. 64 (1), 160-165 (1995).</li><li>Paulson, J. D., Polakoski, K. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+glass+wool+column+procedure+for+removing+extraneous+material+from+human+ejaculate.">A glass wool column procedure for removing extraneous material from human ejaculate.</a> Fertility and Sterility. 28, 178-181 (1977).</li><li>Ahammad, M. U., Chiaki, N., Tatemoto, H., Kawamoto, Y., Nakada, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Utilization+of+the+swim-up+migration+sedimentation+technique+to+separate+viable+and+progressively+motile+fowl+spermatozoa.">Utilization of the swim-up migration sedimentation technique to separate viable and progressively motile fowl spermatozoa.</a> World's Poultry Science Association Proceedings. , (2010).</li><li>Lucena, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recovery+of+motile+sperm+using+the+migration-sedimentation+technique+in+an+in+vitro+fertilization-embryo+transfer+programme.">Recovery of motile sperm using the migration-sedimentation technique in an in vitro fertilization-embryo transfer programme.</a> Human Reproduction. 4 (2), 163-165 (1989).</li><li>Henkel, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sperm+Processing+for+IVF.">Sperm Processing for IVF.</a> Clinical Embryology: A Practical Guide. , (2013).</li><li>Sherman, J., Paulson, D., Liu, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+glass+wool+filtration+on+ultrastructure+of+human+spermatozoa.">Effect of glass wool filtration on ultrastructure of human spermatozoa.</a> Fertility and Sterility. 36, 643-647 (1981).</li><li>Freund, M., Carol, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Factors+affecting+haemocytometer+counts+of+sperm+concentration+in+human+semen.">Factors affecting haemocytometer counts of sperm concentration in human semen.</a> Journal of Reproduction and Fertility. 8, 149-155 (1964).</li><li>Bakst, M. R., Wishart, G. J., Brillard, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oviducal+sperm+selection,+transport+and+storage+in+poultry.">Oviducal sperm selection, transport and storage in poultry.</a> Poultry Science Review. 5, 117-143 (1994).</li><li>Ahammad, M. U., Okamoto, S., Kawamoto, Y., Nakada, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effects+of+regular+fluid+secretion+from+the+uterus+of+laying+hens+on+the+longevity+and+fertilization+ability+of+fowl+sperm+in+the+oviduct.">The effects of regular fluid secretion from the uterus of laying hens on the longevity and fertilization ability of fowl sperm in the oviduct.</a> Poultry Science Journal. 1 (1), 13-22 (2013).</li><li>Ahammad, M. U., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Maturational+changes+in+the+survivability+and+fertility+of+fowl+sperm+during+their+passage+through+the+male+reproductive+tract.">Maturational changes in the survivability and fertility of fowl sperm during their passage through the male reproductive tract.</a> Animal Reproduction Science. 128 (1-4), 129-136 (2011).</li><li>Choi, K. H., Emery, D. A., Straub, D. E., Lee, C. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Percoll+process+can+improve+semen+quality+and+fertility+in+turkey+breeders.">Percoll process can improve semen quality and fertility in turkey breeders.</a> Asian-Australasian Journal of Animal Sciences. 12 (5), 702-707 (1999).</li><li>Chen, M. J., Bongso, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparative+evaluation+of+two+density+gradient+preparations+for+sperm+separation+for+medically+assisted+conception.">Comparative evaluation of two density gradient preparations for sperm separation for medically assisted conception.</a> Human Reproduction. 14 (3), 759-764 (1999).</li></ol>

Fertility not only determines the profitability of animal production but also acts as a means of natural selection of species for existence. The ultimate function of a sperm cell is to fertilize an ovum. The oviduct of a female selects only those fittest sperm in order to ensure fertilization of the ovum23,24. In vitro studies have also revealed a close correlation between qualitative sperm traits and fertilization success4,<...

In vertebrates, male gametes undergo intense selective pressure; therefore reproductive fitness of a male is pivotal for achieving successful fertilization. Males of any given vertebrate species must be able to produce sperm cells in large quantities and of sufficient quality in order to meet the needs of fertilization. Sperm cells, having both a sperm head and a flagellum, are the most polarized cells in the body. They are also very heterogeneous in quality of sperm (live and dead, morphologically normal and abnormal, and immobile, low mobile and high mobile), which is revealed through the wide variation in reproductive efficiency of the males. The larger the proportion of high-quality sperm, the fewer the number of matings required to successfully fertilize the ovum. However, to achieve fertility, morphologically normal sperm cells rely on propulsive forces generated by their flagella to reach the site of fertilization as well as to penetrate the zona pellucida1 (ZP; in the case of mammals) or inner perivitelline layer2 (IPVL; in the case of birds and reptiles) of the ovum following natural mating or artificial insemination (AI). Determining sperm quality is necessary for use in assisted reproductive technologies3 (ART) and selection of breeding males to be used in AI programs4. On the other hand, the success of ART solely relies upon the accurate evaluation of sperm quality. A number of laboratory tests have been developed to determine the functional characteristics of sperm. The most important parameters are sperm morphology, viability, mobility, capacitation (avian sperm do not require capacitation5), acrosome reaction (AR; exocytosis and release of a proteolytic enzyme from the acrosome of the sperm head), sperm penetration of ZP or IPVL, and fertilization6,7,8,9,10,11. Measures of fertility alone do not provide an accurate evaluation of the fertilizing ability of a sperm population11. Measures of the several events leading up to fertilization of an egg allow for an appropriate representation of the performance of individual spermatocytes7.
The methodology developed for measuring sperm function is primarily species-specific. For example, in avian sperm, viability, mobility and penetration of IPVL are the most common parameters used to assess sperm quality8,11,12. The number of live sperm in the ejaculate plays a crucial role for the survival of sperm because the presence of a large number of dead sperm in the semen affects the quality of sperm. This enhances the production of reactive oxygen species in the semen and causes oxidative damage to the live sperm13. Sperm mobility, the capacity for flagellar movement of avian sperm against resistance at body temperature, is known to play a direct role in bringing about fertilization8. It is well established that mobility is positively correlated with fertility and is, therefore, a primary determinant of fertility8. However, a mobile sperm must also have the ability to undergo an AR and to penetrate the IPVL11. IPVL penetration assays take account for every sperm that participates in the process of fertilization11.
In the application of ART, ejaculate is usually processed in order to maximize the concentration of high-quality sperm and minimize concentration of low-quality sperm. After collection of semen, the proportion of high-quality sperm can be enriched through sperm separation procedures commonly used in both industry and research practices. Many of these procedures have been developed, all with respective benefits and limitations, but all utilize the heterogeneous nature of sperm to collect only the sperm with high fertilizing ability. These procedures include sperm migration methods, adherence column filtration and density gradient centrifugation (DGC)14,15,16,17,18,19,20. Among the available techniques, DGC has been found to be very simple, repeatable, cost-effective and efficient in isolating the maximum amount of high-quality sperm for use in ART with the goal of maximizing chance of fertilization14,15. In addition, DGC is not injurious to the sperm cell membrane. In contrast, sperm migration methods collect only progressively mobile sperm18,19, but the quantity of sperm collected is very low, making it inefficient in collecting large volumes of sperm18,20. Adherence column filtration is very efficient in filtering highly mobile sperm from semen17; however, it tends to be injurious to sperm membranes20,21.
In the DGC technique, the most commonly used substrate for generating the density gradient is Percoll, which consists of colloidal silica particles coated in polyvinylpryrolidone. Percoll density gradient centrifugation (PDGC) can either be continuous or discontinuous but a discontinuous gradient is most commonly used for high yield isolation of highly mobile sperm13,16,20. In a discontinuous gradient, lower density media floats above higher density media, creating a gradient that increases in density from the top to the bottom of a conical tube. This creates boundaries at the interface between the two media of differing density. The efficiency of PDGC is derived from two factors: 1) the propulsive ability of individual sperm cells and 2) the tendency of sperm cells with high structural integrity to have an increased density. Sperm with higher mobility are better able to cross from lower density media and penetrate into a higher density media. Lower mobility sperm are more likely to become trapped at the boundary created by the interface between media of differing density. Sperm cells with high structural integrity and mobility tend to have a higher density than dead, abnormal or low mobile sperm cells. When centrifugal force is applied in PDGC, this facilitates movement of sperm with different densities to their respective place in the gradient.
In general practice, after PDGC is performed, the soft pellet of sperm with high fertility potential at the bottom of the conical tube is collected, and the remainder is discarded. However, an underutilized advantage of this technique is its ability to separate sperm cells into several groups based on the quality differences. For research purposes, separation of sperm by degree of quality utilizing the PDGC technique allows for study of sperm quality as it pertains to physiologic, metabolomic and proteomic differences. Here, we aim to detail how this technique may be used to separate sperm by quality, as well as demonstrate these differences in quality, using the previously established eosin-nigrosin vital staining for viability, Accudenz assay for mobility, and sperm-IPVL interaction assay for penetrability.

<table border="0" cellpadding="0" cellspacing="0" style="width:824px;" width="825">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Accudenz</td>
			<td style="width:323px;">Accurate Chemical and Scientific Corporation, Westbury, NY, USA</td>
			<td style="width:119px;">AN7050</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Percoll&#160;</td>
			<td style="width:323px;">Sigma-Aldrich, Corp., St. Louis, MO, USA</td>
			<td style="width:119px;">P7828</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Schiff&#8217;s reagent</td>
			<td style="width:323px;">Sigma-Aldrich, Corp., St. Louis, MO, USA</td>
			<td style="width:119px;">3952016</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">TES</td>
			<td style="width:323px;">Sigma-Aldrich, Corp., St. Louis, MO, USA</td>
			<td style="width:119px;">T1375</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Eosin Y</td>
			<td style="width:323px;">Sigma-Aldrich, Corp., St. Louis, MO, USA</td>
			<td style="width:119px;">E4009</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Nigrosin</td>
			<td style="width:323px;">Sigma-Aldrich, Corp., St. Louis, MO, USA</td>
			<td align="right" style="width:119px;">198285</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">ST 40R Centrifuge&#160;</td>
			<td style="width:323px;">Thermo Scientific, Waltham, MA, USA</td>
			<td align="right" style="width:119px;">75004524</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">DU 530 Life Sciences UV/Vis Spectrophotometer</td>
			<td style="width:323px;">Beckman Coulter, Brea, CA, USA</td>
			<td style="width:119px;"></td>
			<td>No catalogue is found</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:216px;">Olympus IX 71 Inverted Fluorescence and Phase Contrast Microscope</td>
			<td style="width:323px;">Olympus America Inc., PA, USA</td>
			<td style="width:119px;"></td>
			<td>No catalogue is found</td>
		</tr>
	</tbody>
</table>

sperm collection of differential quality using density gradient centrifugation

In sexual reproduction, a male gamete or sperm cell fuses with a female gamete to bring about fertilization. However, a large number of sperm cells with fertilizing ability are required to interact with a female gamete to ensure fertilization. As such, the fertilizing ability of individual sperm cells is critical for successful reproduction. Density gradient centrifugation has been utilized for several decades as a reproducible, fast, efficient, effective and extremely adaptable method to collect only high-quality sperm to be used in assisted reproductive technology. The protocols we described herein focus on the utilization of the discontinuous Percoll density gradient centrifugation (PDGC) technique to isolate three distinct populations of rooster sperm by their quality. We were able to collect low-, medium- and high-quality sperm. We also describe reproducible protocols that entail determining fertility potential of sperm by assessing their viability, mobility and penetrability. Collection of sperm by their quality using PDGC technique would be useful to accurately and thoroughly characterize sperm with differential fertility potential.

The PDGC technique resulted in distinct separation of three layers of sperm by degree of quality across all parameters. Sperm separates into a high-quality layer below the higher density solution, a medium-quality layer between the higher and lower density solution and a low-quality layer above the lower density solution. These differences in quality are evidenced by clear differences in viability (Figure 4), mobility (Figure 5) ...

Watch this Scientific Journal Video about Sperm Collection of Differential Quality Using Density Gradient Centrifugation at JoVE.com

Sperm Collection of Differential Quality Using Density Gradient Centrifugation

In this paper, we aim to describe the performance of the density gradient centrifugation technique and its application in sperm physiology research.

In sexual reproduction, a male gamete or sperm cell fuses with a female gamete to bring about fertilization. However, a large number of sperm cells with ...

This method can help answer key questions in the field of sperm physiology, such as the chemical determinates of sperm quality. The main advantage of this technique is it's ability to separate large quantities of sample by quality, as well as adaptability when compared to alternative methods. Though this method can provide insight in the differences in sperm quality, it can also be applied to other samples such as mixed cell types or subcellular components with different densities.To begin, make two 3 milliliter Percoll dilutions in two separate tubes. In a clean test tube, dilute 1 milliliter of semen sample with 2 milliliters of PBS. Pipe it gently to mix the solution.Add 3 milliliters of the lower density Percoll sollution to a sterile conical tube. Then, carefully pipette 3 milliliters of the higher density Percoll solution beneath the lower density Percoll solution. While tilting the conical tube at a 45 degree angle, pipette 3 milliliters of the diluted semen sample on top of the Percoll density gradient.After preparing a blank tube, centrifuge both tubes at 1500 Gs for 20 minutes. Insure that three distinct layers of semen have formed in the tub after centrifugation. Using a pipette collect the three layers of semen, starting with the top layer, followed by the middle layer, and ending with the hard pellet at the bottom of the tube.Transfer each of the layers to a sterile micro centrifuge tube. Dilute each of the semen samples with 1.5 milliliters of PBS and centrifuge the samples at 1500 Gs for ten minutes. Finally, pour off the supernatant and reconstitute the pellets with motility buffer.In this protocol, the Percoll density gradient centrifugation technique, or PDGC, was used to separate a semen sample into three distinct layers. Sperm separates into a high quality layer below the higher density solution, a medium quality layer between the higher and lower density solutions, and a low quality layer above the lower density solution. These differences in sperm quality are evidenced by differences in viability, mobility, and penetrability.While attempting this procedure, it's important to remember that samples need to be brought to room temperature. The success of PDGC is reliant upon careful preparation of the gradient as well as careful collection of the isolated layers. After it's development, this technique paved the way for our research in the field of sperm perdiomics to explore bio markers of fertility in avian species.

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Introduction to Separation Methods

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Harvesting Sperm and Artificial Insemination of Mice

Rodents of the genus Peromyscus (deer mice) are the most prevalent native North American mammals. Peromyscus species are used in a wide range of research including toxicology, epidemiology, ecology, behavioral, and genetic studies. Here they provide a useful model for demonstrations of artificial insemination. 

Methods similar to those displayed here have previously been used in several deer mouse studies, yet no detailed protocol has been published. Here we demonstrate the basic method of artificial insemination. This method entails extracting the testes from the rodent, then isolating the sperm from the epididymis and vas deferens. The mature sperm, now in a milk mixture, are placed in the female&#x2019;s reproductive tract at the time of ovulation. Fertilization is counted as day 0 for timing of embryo development. Embryos can then be retrieved at the desired time-point and manipulated.

Artificial insemination can be used in a variety of rodent species where exact embryo timing is crucial or hard to obtain. This technique is vital for species or strains (including most Peromyscus) which may not mate immediately and/or where mating is hard to assess. In addition, artificial insemination provides exact timing for embryo development either in mapping developmental progress and/or transgenic work. Reduced numbers of animals can be used since fertilization is guaranteed. This method has been vital to furthering the Peromyscus system, and will hopefully benefit others as well.

This protocol demonstrates methods for extracting sperm from the testes of males and then inseminating female mice. This procedure is useful when precise time is needed in developmental studies as well as transgenic work.

Rodents of the genus Peromyscus (deer mice) are the most prevalent native North American mammals.  Peromyscus species are used in a wide range of research ...

DNA Extraction from 0.22 &mu;M Sterivex Filters and Cesium Chloride Density Gradient Centrifugation

This method is used to extract high molecular weight genomic DNA from planktonic biomass concentrated on 0.22 &mu;M Sterivex filters that have been treated with storage/lysis buffer and archived at -80&deg;C, and to purify this DNA using a cesium chloride density gradient.  The protocol begins with two one-hour incubation steps to liberate DNA from cells and remove RNA.  Next, a series of Phenol:Chloroform and Chloroform extractions are performed followed by centrifugation to remove proteins and cell membrane components, collection of the aqueous DNA extract, and several buffer exchange steps to wash and concentrate the extract.  Part Five describes the optional purification via cesium chloride density gradient.  It is recommended to work with less than 15 samples at one time to avoid confusion and cut down protocol time. The total time required for this protocol depends on the number of samples to be extracted. For 10-15 samples and assuming the proper centrifugation equipment is available, this entire protocol should take 3 days. Make sure you have the hybridization ovens set to temperature at the outset of the process.

DNA Extraction from 0.22 &amp;mu;M Sterivex Filters and Cesium Chloride Density Gradient Centrifugation

We describe a method for extraction of high molecular weight genomic DNA from planktonic biomass concentrated on 0.22 &mu;m Sterivex filters, followed by cesium chloride density gradient centrifugation for purification.

This method is used to extract high molecular weight genomic DNA from planktonic biomass concentrated on 0.22 &mu;M Sterivex filters that have been ...

In-vivo Centrifugation of Drosophila Embryos

A major strategy for purifying and isolating different types of intracellular organelles is to separate them from each other based on differences in buoyant density. However, when cells are disrupted prior to centrifugation, proteins and organelles in this non-native environment often inappropriately stick to each other. Here we describe a method to separate organelles by density in intact, living Drosophila embryos. Early embryos before cellularization are harvested from population cages, and their outer egg shells are removed by treatment with 50% bleach. Embryos are then transferred to a small agar plate and inserted, posterior end first, into small vertical holes in the agar. The plates containing embedded embryos are centrifuged for 30 min at 3000g. The agar supports the embryos and keeps them in a defined orientation. Afterwards, the embryos are dug out of the agar with a blunt needle. Centrifugation separates major organelles into distinct layers, a stratification easily visible by bright-field microscopy. A number of fluorescent markers are available to confirm successful stratification in living embryos. Proteins associated with certain organelles will be enriched in a particular layer, demonstrating colocalization. Individual layers can be recovered for biochemical analysis or transplantation into donor eggs. This technique is applicable for organelle separation in other large cells, including the eggs and oocytes of diverse species.

In-vivo Centrifugation of Drosophila Embryos

We describe a method to separate organelles by density in living Drosophila embryos. Embryos are embedded in agar and centrifuged. This technique yields reproducible separation of major organelles along the anterior-posterior embryo axis. This method facilitates colocalization experiments and yields organelle fractions for biochemical analysis and transplantation experiments.

A major strategy for purifying and isolating different types of intracellular organelles is to separate them from each other based on differences in ...

Two Types of Assays for Detecting Frog Sperm Chemoattraction

Sperm chemoattraction in invertebrates can be sufficiently robust that one can place a pipette containing the attractive peptide into a sperm suspension and microscopically visualize sperm accumulation around the pipette1. Sperm chemoattraction in vertebrates such as frogs, rodents and humans is more difficult to detect and requires quantitative assays. Such assays are of two major types - assays that quantitate sperm movement to a source of chemoattractant, so-called sperm accumulation assays, and assays that actually track the swimming trajectories of individual sperm.
Sperm accumulation assays are relatively rapid allowing tens or hundreds of assays to be done in a single day, thereby allowing dose response curves and time courses to be carried out relatively rapidly. These types of assays have been used extensively to characterize many well established chemoattraction systems - for example, neutrophil chemotaxis to bacterial peptides and sperm chemotaxis to follicular fluid. Sperm tracking assays can be more labor intensive but offer additional data on how chemoattractancts actually alter the swimming paths that sperm take. This type of assay is needed to demonstrate the orientation of sperm movement relative to the chemoattrractant gradient axis and to visualize characteristic turns or changes in orientation that bring the sperm closer to the egg.
Here we describe methods used for each of these two types of assays. The sperm accumulation assay utilized is called a "two-chamber" assay. Amphibian sperm are placed in a tissue culture plate insert with a polycarbonate filter floor having 12 &mu;m diameter pores. Inserts with sperm are placed into tissue culture plate wells containing buffer and a chemoatttractant carefully pipetted into the bottom well where the floor meets the wall (see Fig. 1). After incubation, the top insert containing the sperm reservoir is carefully removed, and sperm in the bottom chamber that have passed through the membrane are removed, pelleted and then counted by hemocytometer or flow cytometer.
The sperm tracking assay utilizes a Zigmond chamber originally developed for observing neutrophil chemotaxis and modified for observation of sperm by Giojalas and coworkers2,3. The chamber consists of a thick glass slide into which two vertical troughs have been machined. These are separated by a 1 mm wide observation platform. After application of a cover glass, sperm are loaded into one trough, the chemoattractant agent into the other and movement of individual sperm visualized by video microscopy. Video footage is then analyzed using software to identify two-dimensional cell movements in the x-y plane as a function of time (xyt data sets) that form the trajectory of each sperm.

Eggs and the extracellular coatings around eggs frequently release peptides, proteins and small molecules that communicate with sperm to guide them to the egg thereby promoting fertilization. Using frog sperm we describe and compare two classes of assays used to detect sperm chemoattraction &#x2013; sperm accumulation assays and sperm tracking assays.

Sperm chemoattraction in invertebrates can be sufficiently robust that one can place a pipette containing the attractive peptide into a sperm suspension ...

Mouse Sperm Cryopreservation and Recovery using the I&middot;Cryo Kit

Thousands of new genetically modified (GM) strains of mice have been created since the advent of transgenesis and knockout technologies. Many of these valuable animals exist only as live animals, with no backup plan in case of emergency. Cryopreservation of embryos can provide this backup, but is costly, can be a lengthy procedure, and generally requires a large number of animals for success. Since the discovery that mouse sperm can be successfully cryopreserved with a basic cryoprotective agent (CPA) consisting of 18&#37; raffinose and 3&#37; skim milk, sperm cryopreservation has become an acceptable and cost-effective procedure for archiving, distributing and recovery of these valuable strains.
 Here we demonstrate a newly developed I&bull;Cryo kit for mouse sperm cryopreservation. Sperm from five commonly-used strains of inbred mice were frozen using this kit and then recovered. Higher protection ratios of sperm motility (&gt; 60&#37;) and rapid progressive motility (&gt; 45&#37;) compared to the control (basic CPA) were seen for sperm frozen with this kit in 5 inbred mouse strains. Two cell stage embryo development after IVF with the recovered sperm was improved consistently in all 5 mouse strains examined. Over a 1.5 year period, 49 GM mouse lines were archived by sperm cryopreservation with the I&bull;Cryo kit and later recovered by IVF.

Mouse Sperm Cryopreservation and Recovery using the I&amp;middot;Cryo Kit

Here we demonstrate the newly developed I&#x2022;Cryo kit for mouse sperm cryopreservation. Two-cell stage embryo development with frozen-thawed sperm was improved consistently in 5 mouse strains with the use of this kit. Over a 1.5 year period, 49 genetically modified mouse lines were archived by sperm cryopreservation with the I&#x2022;Cryo kit and later successfully recovered by IVF.

Thousands of new genetically modified (GM) strains of mice have been created since the advent of transgenesis and knockout technologies.  Many of these ...

Determination of Protein-ligand Interactions Using Differential Scanning Fluorimetry

A wide range of methods are currently available for determining the dissociation constant between a protein and interacting small molecules. However, most of these require access to specialist equipment, and often require a degree of expertise to effectively establish reliable experiments and analyze data. Differential scanning fluorimetry (DSF) is being increasingly used as a robust method for initial screening of proteins for interacting small molecules, either for identifying physiological partners or for hit discovery. This technique has the advantage that it requires only a PCR machine suitable for quantitative PCR, and so suitable instrumentation is available in most institutions; an excellent range of protocols are already available; and there are strong precedents in the literature for multiple uses of the method. Past work has proposed several means of calculating dissociation constants from DSF data, but these are mathematically demanding. Here, we demonstrate a method for estimating dissociation constants from a moderate amount of DSF experimental data. These data can typically be collected and analyzed within a single day. We demonstrate how different models can be used to fit data collected from simple binding events, and where cooperative binding or independent binding sites are present. Finally, we present an example of data analysis in a case where standard models do not apply. These methods are illustrated with data collected on commercially available control proteins, and two proteins from our research program. Overall, our method provides a straightforward way for researchers to rapidly gain further insight into protein-ligand interactions using DSF.

Differential scanning fluorimetry is a widely used method for screening libraries of small molecules for interactions with proteins. Here, we present a straightforward method to extend these analyses to provide an estimate of the dissociation constant between a small molecule and its protein partner.

A wide range of methods are currently available for determining the dissociation constant between a protein and interacting small molecules. However, most ...

Isolation of Intact Mitochondria from Skeletal Muscle by Differential Centrifugation for High-resolution Respirometry Measurements

Mitochondria are involved in cellular energy metabolism and use oxygen to produce energy in the form of adenosine triphosphate (ATP). Differential centrifugation at low- and high-speed is commonly used to isolate mitochondria from tissues and cultured cells. Crude mitochondrial fractions obtained by differential centrifugation are used for respirometry measurements. The differential centrifugation technique is based on the separation of organelles according to their size and sedimentation velocity. The isolation of mitochondria is performed immediately after tissue harvesting. The tissue is immersed in an ice-cold homogenization medium, minced using scissors and homogenized in a glass homogenizer with a loose-fitting pestle. The differential centrifugation technique is efficient, fast and inexpensive and the mitochondria obtained by differential centrifugation are pure enough for respirometry assays. Some of the limitations and disadvantages of isolated mitochondria, based on differential centrifugation, are that the mitochondria can be damaged during the homogenization and isolation procedure and that large amounts of the tissue biopsy or cultured cells are required for the mitochondrial isolation.

Here, a quadriceps muscle specimen is taken from an anaesthetized pig and mitochondria are isolated by differential centrifugation. Then, the respiratory rates of mitochondrial respiratory chain complexes I, II and IV are determined using high-resolution respirometry.

Mitochondria are involved in cellular energy metabolism and use oxygen to produce energy in the form of adenosine triphosphate (ATP). Differential ...

Avian Semen Collection by Cloacal Massage and Isolation of DNA from Sperm

Collection of semen may be useful for a wide range of applications including studies involving sperm quality, sperm telomere dynamics, and epigenetics. Birds are widely used subjects in biological research and are ideal for studies involving repeated sperm samples. However, few resources are currently available for those wishing to learn how to collect and extract DNA from avian sperm. Here we describe cloacal massage, a gentle, non-invasive manual technique for collecting avian sperm. Although this technique is established in the literature, it can be difficult to learn from the available descriptions. We also provide information for extracting DNA from avian semen using a commercial extraction kit with modifications. Cloacal massage can be easily used on any small- to medium-sized male bird in reproductive condition. Following collection, the semen can be used immediately for motility assays, or frozen for DNA extraction following the protocol described herein. This extraction protocol was refined for avian sperm and has been successfully used on samples collected from several passerine species (Passer domesticus, Spizella passerina, Haemorhous mexicanus, and Turdus migratorius) and one columbid (Columba livia).

This protocol describes cloacal massage, a non-invasive manual technique for collecting semen from birds, and DNA extraction from avian sperm using a commercial extraction kit with modifications.

Collection of semen may be useful for a wide range of applications including studies involving sperm quality, sperm telomere dynamics, and epigenetics. ...

Fish Sperm Assessment Using Software and Cooling Devices

For gamete quality evaluation, there are innovative, rapid, and quantitative techniques that can provide useful data for aquaculture. Computerized systems for sperm analysis were developed to measure several parameters and one of the most commonly measured is the sperm motility.
Initially, this computer technology was designed for mammalian species, although it can also be used for fish sperm analysis. Fish have specific features that can affect sperm assessment such as a short motility time after activation and, in some cases, adaptation to lower temperatures. Thus, it is necessary to modify both software and hardware components to make motility analysis more efficient for fish sperm analysis. For mammalian sperm, the heating plate is used to maintain optimal temperatures of spermatozoa. However, for some fish species, it is advantageous to use a lower temperature to prolong the duration of motility, since the sperm remain active for less than 2 min. Therefore, cooling devices are necessary to refrigerate samples at constant temperature over the time of analysis, including on the optical microscope. This protocol describes the analysis of fish sperm motility using software for sperm analysis and new cooling devices to optimize the results.

The present protocol describes a procedure of fish sperm assessment using computer-assisted sperm analysis and cooling devices. The software gives a rapid, accurate and quantitative analysis of fish sperm quality based on spermatozoa motility, which can be a useful tool in aquaculture to improve reproduction success.

For gamete quality evaluation, there are innovative, rapid, and quantitative techniques that can provide useful data for aquaculture. Computerized systems ...

Field Identification of Matricaria chamomilla using a Portable qPCR System

Quality control in botanical products begins with the raw material supply. Traditionally, botanical identification is performed through morphological assessment and chemical analytical methods. However, the lack of availability of botanists, especially in recent years, coupled with the need to enhance quality control to combat the stresses on the supply chain brought by increasing consumer demand and climate change, necessitates alternative approaches. The goal of this protocol is to facilitate botanical species identification using a portable qPCR system on the field or in any setting, where access to laboratory equipment and expertise is limited. Target DNA is amplified using dye-based qPCR, with DNA extracted from botanical reference materials serving as a positive control. The target DNA is identified by its specific amplification and matching its melting peak against the positive control. A detailed description of the steps and parameters, from hands-on field sample collection, to DNA extraction, PCR amplification, followed by data interpretation, has been included to ensure that readers can replicate this protocol. The results produced align with traditional laboratory botanical identification methods. The protocol is easy to perform and cost-effective, enabling quality testing on raw materials as close to the point of origin of the supply chain as possible.

Field Identification of Matricaria chamomilla using a Portable qPCR System

Presented here is a protocol for field identification of Matricaria chamomilla using a portable qPCR system. This easy-to-perform protocol is ideal as a method to confirm the identity of a botanical species at locations where access to laboratory equipment and expertise is limited, such as farms and warehouses.

Quality control in botanical products begins with the raw material supply. Traditionally, botanical identification is performed through morphological ...