Name: quantification of ethanol levels in zebrafish embryos using head space gas chromatography
Uploaded: 2020-02-11T14:00:00
Description: Watch this Scientific Journal Video about Quantification of Ethanol Levels in Zebrafish Embryos Using Head Space Gas Chromatography at JoVE.com

The research presented in this article was supported by previous grants from National Institutes of Health/National Institute of Dental and Craniofacial Research (NIH/NIDCR) R01DE020884 to J.K.E. and National Institutes of Health/National Institute on Alcohol Abuse and Alcoholism (NIH/NIAAA) F32AA021320 to C.B.L. and by the current grant from National Institutes of Health/National Institute on Alcohol Abuse (NIH/NIAAA) R00AA023560 to C.B.L. We thank Rueben Gonzales for providing and assisting with gas chromatograph analysis. We thank Tiahna Ontiveros and Dr. Gina Nobles writing assistance.

All zebrafish embryos used in this procedure were raised and bred following established IACUC protocols27. These protocols were approved by the University of Texas at Austin and the University of Louisville.
NOTE: The zebrafish line Tg(fli1:EGFP)y1 was used in this study28. All water used in this procedure is sterile reverse osmosis water. All statistical analyses were performed using Graphpad Prism v8.2.1.
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R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ethanol+concentration+in+56+refillable+electronic+cigarettes+liquid+formulations+determined+by+headspace+gas+chromatography+with+flame+ionization+detector+(HS-GC-FID).">Ethanol concentration in 56 refillable electronic cigarettes liquid formulations determined by headspace gas chromatography with flame ionization detector (HS-GC-FID).</a> Drug Testing and Analysis. 9 (10), 1637-1640 (2017).</li><li>Heit, C., 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=Quantification+of+Neural+Ethanol+and+Acetaldehyde+Using+Headspace+GC-MS.">Quantification of Neural Ethanol and Acetaldehyde Using Headspace GC-MS.</a> Alcoholism: Clinical and Experimental Research. 40 (9), 1825-1831 (2016).</li><li>Chun, H. J., Poklis, J. L., Poklis, A., Wolf, C. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+and+Validation+of+a+Method+for+Alcohol+Analysis+in+Brain+Tissue+by+Headspace+Gas+Chromatography+with+Flame+Ionization+Detector.">Development and Validation of a Method for Alcohol Analysis in Brain Tissue by Headspace Gas Chromatography with Flame Ionization Detector.</a> Journal of Analytical Toxicology. 40 (8), 653-658 (2016).</li><li>Schlatter, J., Chiadmi, F., Gandon, V., Chariot, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simultaneous+determination+of+methanol,+acetaldehyde,+acetone,+and+ethanol+in+human+blood+by+gas+chromatography+with+flame+ionization+detection.">Simultaneous determination of methanol, acetaldehyde, acetone, and ethanol in human blood by gas chromatography with flame ionization detection.</a> Human and Experimental Toxicology. 33 (1), 74-80 (2013).</li><li>Schier, C. J., Mangieri, R. A., Dilly, G. A., Gonzales, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microdialysis+of+ethanol+during+operant+ethanol+self-administration+and+ethanol+determination+by+gas+chromatography.">Microdialysis of ethanol during operant ethanol self-administration and ethanol determination by gas chromatography.</a> Journal of Visualized Experiments. (67), e4142 (2012).</li><li>Adalsteinsson, E., Sullivan, E. V., Mayer, D., Pfefferbaum, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+quantification+of+ethanol+kinetics+in+rat+brain.">In vivo quantification of ethanol kinetics in rat brain.</a> Neuropsychopharmacology. 31 (12), 2683-2691 (2006).</li><li>Quertemont, E., Green, H. L., Grant, K. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Brain+ethanol+concentrations+and+ethanol+discrimination+in+rats:+effects+of+dose+and+time.">Brain ethanol concentrations and ethanol discrimination in rats: effects of dose and time.</a> Psychopharmacology. 168 (3), 262-270 (2003).</li><li>Flentke, G. R., Klinger, R. H., Tanguay, R. L., Carvan, M. J., Smith, S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+evolutionarily-conserved+mechanism+of+calcium-dependent+neurotoxicity.">An evolutionarily-conserved mechanism of calcium-dependent neurotoxicity.</a> Alcoholism: Clinical and Experimental Research. 38 (5), 1255-1265 (2014).</li><li>Reimers, M. J., Flockton, A. R., Tanguay, R. 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As a developmental model system, zebrafish are ideally suited to study the impact of environmental factors on development. They produce large numbers of externally fertilized embryos, which allows for precise timing and dosage paradigms in ethanol studies. This, combined with the live imaging capabilities and the genetic and developmental conservation with humans, make zebrafish a powerful model system for teratology studies. Described is a protocol for measuring embryonic ethanol concentrations in developing zebrafish e...

Fetal Alcohol Spectrum Disorders (FASD) describes a wide array of neurological impairments and craniofacial dysmorphologies associated with embryonic ethanol exposure1. Multiple factors, including timing and dosage of ethanol exposure and genetic background, contribute to the variation of FASD2,3. In humans, the complex relationship of these variables makes studying and understanding the etiology of FASD challenging. Animal models have proven crucial in developing our understanding of the mechanistic basis of ethanol teratogenicity. A wide variety of animal model systems has been used to study multiple aspects of FASD and results have been remarkably consistent with what is found in exposure in humans4. Rodent model systems are used to examine many aspects of FASD, with mice being the most common5,6,7. The majority of this work has focused on developmental defects to early ethanol exposure8, though later exposure to ethanol has been shown to cause developmental anomalies as well9. Moreover, the genetic capabilities of mice have greatly aided in our ability to probe the genetic underpinnings of FASD10,11. These studies in mice strongly suggest that there are gene-ethanol interactions with the sonic hedgehog pathway, retinoic acid signaling, Superoxide dismutase, Nitric oxide synthase I, Aldh2 and Fancd28,10,11,12,13,14,15,16,17,18,19,20,21. These studies show that animal models are critical to advancing our understanding of FASD and its underlying mechanisms.
The zebrafish has emerged as a powerful model system to examine many aspects of ethanol teratogenesis22,23. Due to their external fertilization, high fecundity, genetic tractability, and live imaging capabilities, zebrafish are ideally suited to study factors such as timing, dosage, and genetics of ethanol teratogenesis. Ethanol can be administered to precisely staged embryos and the embryos can then be imaged to examine the direct impact of ethanol during developmental processes. This work can be related directly to humans, because the genetic programs of development are highly conserved between zebrafish and humans and can therefore help guide FASD human studies24. While zebrafish have been used to examine ethanol teratogenesis, a lack of consensus in reporting embryonic ethanol concentrations makes comparison to humans difficult25. In mammalian systems, blood-alcohol levels correlate directly to tissue ethanol levels26. Many of the zebrafish studies treat embryos before complete formation of their circulatory system. With no maternal sample to examine, a process to assess ethanol concentrations is required to quantify ethanol levels within the embryo. Here we describe a process to quantify ethanol concentrations in a developing zebrafish embryo using head space gas chromatography.

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			<td>Air</td>
			<td></td>
			<td></td>
			<td>Provided by contract to the university</td>
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		<tr>
			<td>Analytical Balance</td>
			<td>VWR</td>
			<td>10204-962</td>
			<td></td>
		</tr>
		<tr>
			<td>AutoSampler, CP-8400</td>
			<td>Varian</td>
			<td></td>
			<td>Gas Chromatograph Autosampler</td>
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		<tr>
			<td>Calcium Chloride</td>
			<td>VWR</td>
			<td>97062-590</td>
			<td></td>
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		<tr>
			<td>Ethanol</td>
			<td>Decon Labs</td>
			<td>2701</td>
			<td></td>
		</tr>
		<tr>
			<td>Gas chromatograph vial with polytetrafluoroethylene/silicone septum and plastic cap 2 mL</td>
			<td>Agilent</td>
			<td>8010-0198</td>
			<td>Can reuse the vials after cleaning, but not the caps/septa</td>
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			<td>Gas Chromatograph, CP-3800</td>
			<td>Varian</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Helium</td>
			<td></td>
			<td></td>
			<td>Provided by contract to the university</td>
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		<tr>
			<td>HP Innowax capillary column</td>
			<td>Agilent</td>
			<td>19095N-123I</td>
			<td>30 m x 0.53 mm x 1.0 &#956;m film thick</td>
		</tr>
		<tr>
			<td>Hyrdogen</td>
			<td></td>
			<td></td>
			<td>Provided by contract to the university</td>
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			<td>Magnesium Sulfate (Heptahydrate)</td>
			<td>Fisher Scientific</td>
			<td>M63-500</td>
			<td></td>
		</tr>
		<tr>
			<td>Microcentrifuge tube 1.5 mL</td>
			<td>Fisher Scientific</td>
			<td>2682002</td>
			<td></td>
		</tr>
		<tr>
			<td>Micropipette tips 10 &#956;L</td>
			<td>Fisher Scientific</td>
			<td>13611106</td>
			<td></td>
		</tr>
		<tr>
			<td>Micropipette tips 1000 &#956;L</td>
			<td>Fisher Scientific</td>
			<td>13611127</td>
			<td></td>
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		<tr>
			<td>Micropipette tips 200 &#956;L</td>
			<td>Fisher Scientific</td>
			<td>13611112</td>
			<td></td>
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			<td>Petri dishes 100 mm</td>
			<td>Fisher Scientific</td>
			<td>FB012924</td>
			<td></td>
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			<td>Pipetman L p1000L Micropipette</td>
			<td>Gilson</td>
			<td>FA10006M</td>
			<td></td>
		</tr>
		<tr>
			<td>Pipetman L p200L Micropipette</td>
			<td>Gilson</td>
			<td>FA10005M</td>
			<td></td>
		</tr>
		<tr>
			<td>Pipetman L p2L Micropipette</td>
			<td>Gilson</td>
			<td>FA10001M</td>
			<td></td>
		</tr>
		<tr>
			<td>Polytetrafluoroethylene/silicone septum and plastic cap</td>
			<td>Agilent</td>
			<td>5190-7021</td>
			<td>Replacement caps/septa for gas chromatograph vials</td>
		</tr>
		<tr>
			<td>Potassium Chloride</td>
			<td>Fisher Scientific</td>
			<td>P217-500</td>
			<td></td>
		</tr>
		<tr>
			<td>Potassium Phosphate (Dibasic)</td>
			<td>VWR</td>
			<td>BDH9266-500G</td>
			<td></td>
		</tr>
		<tr>
			<td>Pronase</td>
			<td>VWR</td>
			<td>97062-916</td>
			<td></td>
		</tr>
		<tr>
			<td>Silica Beads .5 mm</td>
			<td>Biospec Products</td>
			<td>11079105z</td>
			<td></td>
		</tr>
		<tr>
			<td>Silica Beads 1.0 mm</td>
			<td>Biospec Products</td>
			<td>11079110z</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium Bicarbonate</td>
			<td>VWR</td>
			<td>BDH9280-500G</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium Chloride</td>
			<td>Fisher Scientific</td>
			<td>S271-500</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium Phosphate (Dibasic)</td>
			<td>Fisher Scientific</td>
			<td>S374-500</td>
			<td></td>
		</tr>
		<tr>
			<td>Solid-phase microextraction fiber assembly Carboxen/Polydimethylsiloxane</td>
			<td>Millipore Sigma</td>
			<td>57343-U</td>
			<td>Replacement fibers</td>
		</tr>
		<tr>
			<td>Star Chromatography Workstation</td>
			<td>Varian</td>
			<td></td>
			<td>Chromatography software</td>
		</tr>
		<tr>
			<td>Thermogreen Low Bleed (LB-2) Septa</td>
			<td>Millipore Sigma</td>
			<td>23154</td>
			<td>Replacement inlet septa</td>
		</tr>
	</tbody>
</table>

quantification of ethanol levels in zebrafish embryos using head space gas chromatography

Fetal Alcohol Spectrum Disorders (FASD) describe a highly variable continuum of ethanol-induced developmental defects, including facial dysmorphologies and neurological impairments. With a complex pathology, FASD affects approximately 1 in 100 children born in the United States each year. Due to the highly variable nature of FASD, animal models have proven critical in our current mechanistic understanding of ethanol-induced development defects. An increasing number of laboratories has focused on using zebrafish to examine ethanol-induced developmental defects. Zebrafish produce large numbers of externally fertilized, genetically tractable, translucent embryos. This allows researchers to precisely control timing and dosage of ethanol exposure in multiple genetic contexts and quantify the impact of embryonic ethanol exposure through live imaging techniques. This, combined with the high degree of conservation of both genetics and development with humans, has proven zebrafish to be a powerful model in which to study the mechanistic basis of ethanol teratogenicity. However, ethanol exposure regimens have varied between different zebrafish studies, which has confounded the interpretation of zebrafish data across these studies. Here is a protocol to quantify ethanol concentrations in zebrafish embryos using head space gas chromatography.

Blood ethanol levels cannot be determined in early embryonic zebrafish, because they lack a fully formed circulatory system. To determine the level of ethanol concentration in the zebrafish embryos, the ethanol levels are measured directly from homogenized embryonic tissue. To properly measure the embryonic ethanol concentrations, the embryonic volume has to be taken into account. The embryo (yolk attached) sits inside the chorion (eggshell) surrounded by extraembryonic fluid (Figure 1). Any...

Watch this Scientific Journal Video about Quantification of Ethanol Levels in Zebrafish Embryos Using Head Space Gas Chromatography at JoVE.com

Quantification of Ethanol Levels in Zebrafish Embryos Using Head Space Gas Chromatography

This work describes a protocol to quantify ethanol levels in a zebrafish embryo using head space gas chromatography from proper exposure methods to embryo processing and ethanol analysis.

Fetal Alcohol Spectrum Disorders (FASD) describe a highly variable continuum of ethanol-induced developmental defects, including facial dysmorphologies ...

This protocol is significant because it helps in understanding the pharmacokinetics of ethanol in developing zebrafish embryos and this will help standardize ethanol exposure regimes in zebrafish studies. The main advantage of our technique is that it allows researchers to rapidly and reproducibly measure ethanol levels during embryonic development, particularly in embryos where blood supply is not available. This method can be easily applied to other model systems as well as other environmental factors assuming proper technique and equipment setup.I would expect individuals performing this protocol for the first time to struggle with the speed necessary to prevent ethanol evaporation during embryo processing. Begin by transferring 10 embryos with extra embryonic fluid into 1.5 milliliter microcentrifuge tubes marked with a line at a volume of 250 microliters. Add water to the fill line.Prepare additional microcentrifuge tubes for dechorionated samples. To remove the chorion, incubate the embryos in a 100 millimeter Petri dish with two milligrams per milliliter of protease cocktail in embryo media for 10 minutes. Gently swirl the dish every few minutes to break the chorion.Once all the embryos are free of the chorion, remove them from the protease cocktail and wash them twice with fresh media. Then transfer the embryos to a fresh 100 millimeter dish. When all samples are ready for volume measurement, use a P200 micropipette with the smallest tip possible to carefully remove all liquid from around the embryos.Weigh the water with a scale with less than 0.1 milligram precision, then determine the volume of the 10 embryos by subtracting the weight of the removed water from 250 microliters. To determine the volume of a single embryo, divide the difference by 10. Gather the embryos from the mating tanks and place them in a standard 100 millimeter Petri dish then incubate the dish at 28.5 degrees Celsius.At six hours post fertilization, transfer up to 100 embryos to a new dish with embryo media and 1%ethanol or media alone. Cover but to not seal the Petri dishes and place them in a 28.5 degree Celsius incubator for 18 hours or until they reach 24 hours post fertilization. Use two P200 micropipettes set to 50 microliters and aspirate the protease cocktail solution into one and water into the second.Then quickly place 10 embryos in a 1.5 milliliter microcentrifuge tube using a glass pipette and close the cap. Repeat this process for all samples to be tested, controls and ethanol treated embryos. Working with one sample at a time, quickly open the cap and aspirate all residual embryo media with a P200 micropipette set to 200 microliters.Rapidly but gently add and remove the 50 microliters of water, then add the 50 microliters of protease cocktail and close the tube cap. Let the sample sit for 10 minutes at room temperature then quickly add 450 microliters of five molar sodium chloride and close the tube cap. Homogenize the sample by vortexing for 10 minutes and transfer two microliters of supernatant to a gas chromatography vial.Seal the vial with a polytetrafluoroethylene cap. After completing the startup method, load 436 current SPME ethanol two to five-minute RG run. meth from the methods menu in the analysis software for each sample on the sample list.Fill out the sample list starting with the air, water, and five molar sodium chloride protease cocktail blanks. Then enter in the ethanol standards in order from 0.3125 to 40 millimolar. Follow the standards with the second round of blanks.Enter all homogenized embryo supernatant samples to be tested from lowest to highest predicted ethanol concentration and finish by entering a third round of blanks. Add the gas chromatography vials to the autosampler in the order in which the samples were entered and allow them to warm for 10 to 15 minutes. Then start the sample runs using the software.After all runs are completed, activate the shutdown method by adding a final sample in the sample list and running standby.meth. Back up all data acquired during the sample run. Once the shutdown method is complete, click on open chromatogram and open the folder with the results.Samples are automatically integrated in this program. In the results, make sure the correct peaks have been integrated. Once all samples have been confirmed, print or export the results.Plot the peak height of the ethanol standards on a graph, then calculate the slope, y-intercept, and r squared values. Obtain the ethanol value for each sample by subtracting the peak height of the sample from the y-intercept of the standards and dividing this value by the slope of the standards. To calculate the ethanol concentration in the embryos, calculate the dilution factor for each sample and multiply the sample ethanol value by this dilution factor.Finally, calculate media reference samples by multiplying the media ethanol value by a dilution factor of 10. To properly calculate the embryonic ethanol concentrations, the volumes of embryos both in their chorion and removed from their chorion were measured. In this analysis, the embryo comprised 56%of the total volume inside the chorion.Based on previously published work, 73.6%was used as the embryonic water content for all the presented analyses. This resulted in water comprising 0.82 microliters of the 1.1 microliters of embryonic volume. Of the total water volume, 49%is contained in the embryo and 51%is in the extraembryonic fluid.For the gas chromatography analysis, two groups of 15 samples and the media with which they were treated measured five times per group were analyzed. Media ethanol levels were 143.6 millimolar for group one and 133.6 millimolar for group two. The ethanol concentrations of the embryos averaged 63.5 millimolar and 53.1 millimolar for groups one and two respectively.A ratio of embryonic ethanol concentration to media levels of ethanol for each sample was calculated. Group one had 44%of the media ethanol levels while group had 40%of the media ethanol levels. Untreated control embryos were measured at zero millimolar media ethanol concentration.The most important thing to remember when attempting this procedure is that processing the embryos for GC analysis properly is critical as ethanol is volatile and will evaporate quickly. The best way to perform this step is described, but it needs to be practiced to develop proper muscle memory. This procedure will help standardize ethanol treatment regimes in zebrafish and allow future work to dissect the genetic and cellular mechanisms of ethanal teratogenicity.

Research

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