Many thanks to Silke Kipper, Sarah Kiefer, Michael Wei&#223;, Conny Bartsch and Silke Voigt-Heucke for enthusiastic sample collection in the field, to Janett Birkenfeld for continued assistance, to Ulla Kobalz for the beautiful gels and to Tobias Krause for moral support.

All procedures were performed in compliance with the German law for animal protection (TierSchG).
1. Preparation of Reagents and Consumables
<ol>
	<li>Prepare a 5% (w/w) Chelex-100 solution in molecular grade water. Prepare aliquots of 200 &#181;l in standard 1.5 ml reaction tubes. As the Chelex resin precipitates fast from the suspension it is necessary to re-homogenize the suspension constantly during the preparation of the aliquots. It's advisable to prepare 50 ml or more in one batch and keep the suspension homogenized using a magnetic stirrer. The Chelex solution can be stored for years at ambient conditions.</li>
	<li>Cut pieces of Whatman paper with a width smaller than the beak width of the bird to be tested. The length of the paper depends on the method to take the sample:
	<ol>
		<li>Using forceps, the piece should be long enough to enable sample collection without the forceps being inserted into the beak of the bird. As a rough estimate, for a beak length of 0.5 cm a piece of paper with the length of 1 cm should be fine.</li>
		<li>If not using forceps, the piece must be longer, but the stiffness of the piece should still allow sampling of epithelial cells.</li>
	</ol>
	</li>
	<li>Prepare one aliquot of PCR premix for each sample to be analyzed. For a PCR in a total volume of 25 &#181;l the mix contains 0.18 mM dNTPs, 2 mM MgCl2, 70 mM Tris-HCl, 17.25 mM ammonium sulfate , 0.1% Tween-20, 0.32 &#956;M P2 primer (TCTGCATCGCTAAATCCTTT), 0.32 &#956;M P8 primer (CTCCCAAGGATGAGRAAYTG)16 and 2 units Taq polymerase. Homemade Taq polymerase17 can be used. To allow addition of the maximum amount of DNA-solution, a 6 &#181;l premix can be prepared and stored at -20 &#176;C for several weeks.</li>
</ol>
2. Sample Collection
Wearing gloves is not essential for avian sex determination as the PCR primers cannot anneal to human DNA. For other genotyping purposes it might be advisable.
<ol>
	<li>Capture the bird of interest and gently hold it in one hand e.g. with the 'ringer's grip'18. Make sure not to squeeze the bird.</li>
	<li>Hold a piece of Whatman paper with a forceps and swipe it several times across the inside of the cheeks, the tongue and the choana. Usually samples are obtained within less than 30 seconds.
	<ol>
		<li>Adult animals: depending on the species it might be difficult to get the bird to open its beak. Usually touching the side of the beak and applying gentle pressure will work.</li>
		<li>Nestlings: Sampling from hatchlings or nestlings is especially easy using this technique, as their begging behavior provides easy access to the inside of the beak. It might even be possible to obtain the sample without handling them at all, as they readily beg e.g. when their nestbox is opened.</li>
	</ol>
	</li>
	<li>Immediately store the paper in a prepared reaction tube containing 200 &#181;l of the 5% (w/w) Chelex-100 solution.</li>
</ol>
If you also intend/need to mark the chicks, do so now as described in section 6.
3. Storage of Samples Before DNA Extraction
<ol>
	<li>If working in the lab, store samples at -20 &#176;C. If this is not possible or difficult (e.g. in the field) store samples at ambient temperatures.</li>
	<li>Samples can be stored for more than 3 years at temperatures ranging from room temperature to -20 &#176;C.</li>
</ol>
4. DNA Extraction
<ol>
	<li>If the sample is frozen, thaw it at room temperature.</li>
	<li>Ensure that the piece of paper is on the bottom of the tube submerged in the Chelex-100 solution.</li>
	<li>Incubate samples for 15 min at 56 &#176;C.</li>
	<li>Vortex briefly and spin down the content of the tube.</li>
	<li>Incubate the samples for 8 min at 100 &#176;C.</li>
	<li>Spin the samples at 15,000 x g for 3 min.</li>
	<li>Use the supernatant for subsequent genotyping.</li>
</ol>
5. Molecular Sex Determination
<ol>
	<li>Prepare one PCR tube with 6 &#181;l premix per sample plus two additional tubes for the negative (mandatory) and positive control (optional). For routine sex determination include a sample from the last successful sexing as a positive control.</li>
	<li>Add 19 &#181;l of the supernatant from the DNA extraction to the PCR premix. Make sure to pipette from the surface of the solution to avoid carryover of Chelex beads. This is crucial, as Chelex is a cation exchanger and thus severely inhibits all enzymatic reactions.</li>
	<li>Run the following PCR program: Incubation at 94 &#176;C for 3 min, 45 cycles each with a 30 sec melting step 94 &#176;C, followed by a 30 sec annealing step at 55 &#176;C, followed by a 45 sec elongation step at 72 &#176;C. In a final chase off step, the reactions are incubated for 5 min at 72 &#176;C.</li>
	<li>Prepare a 2% standard TBE or TAE agarose gel to separate the PCR products.</li>
	<li>Run the agarose gel with appropriate voltage settings.</li>
	<li>Visualize the bands under UV light and take a picture. Make sure the two bands in the samples originating from females are well separated.</li>
	<li>Distinguish male from female samples by the presence of one (male) or two (female) bands.</li>
</ol>
6. Marking Nestlings
<ol>
	<li>Check nests for newly hatched chicks on a schedule appropriate for the species/study (e.g. daily checks in the mornings are advised as most chicks hatch then).</li>
	<li>Cut the down feathers of each chick within a nest at a different characteristic location. In zebra finches tufts of downs grow at four characteristic and distinct areas across the nestling's body (Figure 4A). For each chick cut one area (Figure 4B). If there are more than four chicks within one nest, the unique four 'haircuts' can be combined.</li>
</ol>
For zebra finches: Apply leg bands at ten days post hatching when down feathers become hard to detect and nestling size allows ringing.

<ol>
	<li>Russell, W. M. S., Burch, R. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+principles+of+humane+experimental+technique.">The principles of humane experimental technique.</a> , (1959).</li><li>Robertson, B. 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=Molecular+sexing+of+individual+kakapo,+Strigops+habroptilus+Aves,+from+feces.">Molecular sexing of individual kakapo, Strigops habroptilus Aves, from feces.</a> Mol. Ecol. 8, 1349-1350 (1999).</li><li>Yannic, G., 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=Description+of+microsatellite+markers+and+genotyping+performances+using+feathers+and+buccal+swabs+for+the+Ivory+gull+(Pagophila+eburnea).">Description of microsatellite markers and genotyping performances using feathers and buccal swabs for the Ivory gull (Pagophila eburnea).</a> Mol. Ecol. Resour. 11, 877-889 (2011).</li><li>Bello, N., 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=Isolation+of+genomic+DNA+from+feathers.">Isolation of genomic DNA from feathers.</a> J. Vet. Diagn. Invest. 13, 162-164 (2001).</li><li>Handel, C. M., 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=Use+of+buccal+swabs+for+sampling+DNA+from+nestling+and+adult+birds.">Use of buccal swabs for sampling DNA from nestling and adult birds.</a> Wildl. Soc. Bull. 34, 1094-1100 (2006).</li><li>Brubaker, J. L., 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=A+noninvasive,+direct+real-time+PCR+method+for+sex+determination+in+multiple+avian+species.">A noninvasive, direct real-time PCR method for sex determination in multiple avian species.</a> Mol. Ecol. Resour. 11, 415-417 (2011).</li><li>Arima, H., Ohnishi, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Usefulness+of+avian+buccal+cells+for+molecular+sexing.">Usefulness of avian buccal cells for molecular sexing.</a> Ornithological Science. 5, 139-143 (2006).</li><li>Seki, S. -. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+sexing+of+individual+Ryukyu+Robins+Erithacus+komadori+using+buccal+cells+as+a+non-invasive+source+of+DNA.">Molecular sexing of individual Ryukyu Robins Erithacus komadori using buccal cells as a non-invasive source of DNA.</a> Ornithological Science. 2, 135-137 (2003).</li><li>Wellbrock, A. H. J., 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=Buccal+swabs+as+a+reliable+source+of+DNA+for+sexing+young+and+adult+Common+Swifts+(Apus+apus).">Buccal swabs as a reliable source of DNA for sexing young and adult Common Swifts (Apus apus).</a> J. Ornithol. 153, 991-994 (2012).</li><li>Marion, W. R., Shamis, J. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Annotated-Bibliography+of+Bird+Marking+Techniques.">Annotated-Bibliography of Bird Marking Techniques.</a> Bird Banding. 48, 42-61 (1977).</li><li>Scharff, C., Adam, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neurogenetics+of+birdsong.">Neurogenetics of birdsong.</a> Curr. Opin. Neurobiol. , (2012).</li><li>Griffith, S. C., Buchanan, 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=The+Zebra+Finch:+the+ultimate+Australian+supermodel.">The Zebra Finch: the ultimate Australian supermodel.</a> Emu. 110, 5-12 (2010).</li><li>Fee, M. S., Scharff, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+songbird+as+a+model+for+the+generation+and+learning+of+complex+sequential+behaviors.">The songbird as a model for the generation and learning of complex sequential behaviors.</a> Ilar J. 51, 362-377 (2010).</li><li>Honarmand, M., 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=Stressful+dieting:+nutritional+conditions+but+not+compensatory+growth+elevate+corticosterone+levels+in+zebra+finch+nestlings+and+fledglings.">Stressful dieting: nutritional conditions but not compensatory growth elevate corticosterone levels in zebra finch nestlings and fledglings.</a> PLoS On. 5, (1371).</li><li>Krause, E. T., 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=Zebra+finch+nestlings+beg+more+under+better+nutritional+conditions.">Zebra finch nestlings beg more under better nutritional conditions.</a> Behaviour. 148, 1239-1255 (2011).</li><li>Griffiths, 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=A+DNA+test+to+sex+most+birds.">A DNA test to sex most birds.</a> Mol. Ecol. 7, 1071-1075 (1998).</li><li>Pluthero, F. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+purification+of+high-activity+Taq+DNA+polymerase.">Rapid purification of high-activity Taq DNA polymerase.</a> Nucleic Acids Res. 21, 4850-4851 (1993).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Joint+Working+Group+on+Refinement.+Laboratory+birds:+refinements+in+husbandry+and+procedures.+Fifth+report+of+BVAAWF/FRAME/RSPCA/UFAW+Joint+Working+Group+on+Refinement.">Joint Working Group on Refinement. Laboratory birds: refinements in husbandry and procedures. Fifth report of BVAAWF/FRAME/RSPCA/UFAW Joint Working Group on Refinement.</a> Lab Anim. 35, 1-163 (2001).</li></ol>

The authors have nothing to disclose.

Sexing from buccal swabs using Chelex showed an extremely high success rate. Cutting hatchling's down feathers enabled differentiation between nestlings until leg banding was possible.
Chelex-DNA extraction from buccal swabs yielded enough DNA to successfully perform molecular sexing. Sex determination was 100% correct as validated by sexually dimorphic plumage. The success rate reported here is markedly higher than the rate reported by two previous studies7,9. The DNA extraction wi...

Individual recognition, sexing and genotyping are fundamental prerequisites in a variety of experimental studies. Obtaining DNA bearing material and marking subjects unambiguously (even at an early age) should have minimal impact on physiology, behavior, and survival. Whenever possible, invasive procedures should be avoided according to the RRR principle1.
Non-invasive methods are not only beneficial for the animal but also might improve the obtained data as animals are less affected by the treatments.
In birds, DNA sexing can be performed on a number of non-invasively obtainable materials as droppings2, feathers3,4 or buccal swabs3,5,9. Regardless of subject&#180;s condition and age buccal swabs are the method of choice for avian sexing, because they are easy to perform, rarely fail and handling is short.
So far, DNA from buccal swabs was either extracted with commercially available kits3,6 or time consuming standard DNA extraction protocols3,6-8. Kits are not only rather expensive, but their protocols can impose challenges for field work. Some procedural details, e.g. drying and incubation of samples, are not practical in the field. Especially in a setting where experimental protocols require sex dependent treatment from as early as a few minutes post hatching, there is urge for a quick, non-invasive, reliable and easy method to obtain results.
Across the avian taxa a considerable toolbox for marking individuals has been developed10. The wide array of available techniques accounts for the variety of research objectives, species and budgets. However, marking small nestlings has confronted researchers with additional challenges. In some species (e.g. passerines) chicks are too small to apply leg bands and require alternative methods, which do not alter parent-offspring behavior. As awareness and interest in improving animal welfare and techniques in field and laboratory studies is growing, the use of non-invasive techniques is strongly encouraged and preferred.
This protocol provides a non-invasive, quick, easily recognizable and persistent method to individually mark very young nestlings before applying leg bands is feasible. This marking method is introduced on one of the most important avian laboratory model species, the Zebra Finch (Taeniopygia guttata)11-13. The protocol complies with all of the previously published objectives for individual marking techniques10 and has been already successfully applied14,15.

<table border="0" cellpadding="0" cellspacing="0" width="702">
	<tbody>
		<tr height="75">
			<td height="75" style="height:75px;width:191px;">Whatman 3MM Chromatography paper</td>
			<td style="width:163px;">e.g. Fisher Scientific</td>
			<td style="width:269px;">No.:3030-153</td>
			<td style="width:80px;"></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:191px;">Chelex 100 Resin</td>
			<td style="width:163px;">Biorad</td>
			<td style="width:269px;">#143-2832</td>
			<td></td>
		</tr>
		<tr height="50">
			<td height="50" style="height:50px;width:191px;">Taq polymerase</td>
			<td style="width:163px;">addgene</td>
			<td style="width:269px;">http://www.addgene.org/25712/</td>
			<td></td>
		</tr>
		<tr height="75">
			<td height="75" style="height:75px;width:191px;">leg band (Flexi number rings for birds, diameter 2,5 mm)</td>
			<td style="width:163px;">Horst Stengel &#38; Sohn</td>
			<td style="width:269px;"></td>
			<td></td>
		</tr>
	</tbody>
</table>

who is who? non-invasive methods to individually sex and mark altricial chicks

Many experiments require early determination of offspring's sex as well as early marking of newborns for individual recognition. According to animal welfare guidelines, non-invasive techniques should be preferred whenever applicable. In our group, we work on different species of song birds in the lab and in the field, and we successfully apply non-invasive methods to sex and individually mark chicks. This paper presents a comprehensive non-invasive tool-box. Sexing birds prior to the expression of secondary sexual traits requires the collection of DNA-bearing material for PCR. We established a quick and easy method to sex birds of any age (post hatching) by extracting DNA from buccal swabs. Results can be obtained within 3 hours. For individual marking chick's down feathers are trimmed in specific patterns allowing fast identification within the hatching order. This set of methods is easily applicable in a standard equipped lab and especially suitable for working in the field as no special equipment is required for sampling and storage. Handling of chicks is minimized and marking and sexing techniques are non-invasive thereby supporting the RRR-principle of animal welfare guidelines.

Buccal swabs can be used to obtain DNA for sex determination in a variety of small birds
Samples were collected from Zebra Finches (Taeniopygia guttata, 99 individuals, age 0 days - 5 years), Canaries (Serinus canaria), Bengalese Finches (Lonchura striata), Nightingales (Luscinia megarhynchos), Great Tits (Parus major) and Blackbirds (Turdus merula) (for all other species: sample size 1-3, age unknown) (Figure 1).
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Watch this Scientific Journal Video about Who is Who? Non-invasive Methods to Individually Sex and Mark Altricial Chicks at JoVE.com

Who is Who? Non-invasive Methods to Individually Sex and Mark Altricial Chicks

This protocol provides a convenient set of methods, which enables extremely fast, easy, non-invasive, reliable and low-cost, molecular sex determination of birds and their non-invasive, quick, safe and easily recognizable marking shortly after hatching. Only limited handling of chicks is required. This convenient toolbox of methods complies entirely with the RRR-guidelines.

Many experiments require early determination of offspring's sex as well as early marking of newborns for individual recognition. According to animal ...

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18.3K Views.  Freie Universität Berlin.  Questo protocollo fornisce un insieme di metodi conveniente, che consente estremamente veloce, semplice, non invasivo, affidabile ea basso costo, determinazione del sesso molecolare degli uccelli e la loro non-invasivo, rapido, sicuro e facilmente riconoscibile marcatura poco dopo la schiusa. È necessaria solo la gestione limitata dei pulcini. Questo comodo toolbox di metodi del tutto conforme alle RRR linee guida. 

Video: Who is Who? Non-invasive Methods to Individually Sex and Mark Altricial Chicks

Labeling hESCs and hMSCs with Iron Oxide Nanoparticles for Non-Invasive in vivo Tracking with MR Imaging

In recent years, stem cell research has led to a better understanding of developmental biology, various diseases and its potential impact on regenerative medicine. A non-invasive method to monitor the transplanted stem cells repeatedly in vivo would greatly enhance our ability to understand the mechanisms that control stem cell death and identify trophic factors and signaling pathways that improve stem cell engraftment. MR imaging has been proven to be an effective tool for the in vivo depiction of stem cells with near microscopic anatomical resolution. In order to detect stem cells with MR, the cells have to be labeled with cell specific MR contrast agents. For this purpose, iron oxide nanoparticles, such as superparamagnetic iron oxide particles (SPIO), are applied, because of their high sensitivity for cell detection and their excellent biocompatibility. SPIO particles are composed of an iron oxide core and a dextran, carboxydextran or starch coat, and function by creating local field inhomogeneities, that cause a decreased signal on T2-weighted MR images. This presentation will demonstrate techniques for labeling of stem cells with clinically applicable MR contrast agents for subsequent non-invasive in vivo tracking of the labeled cells with MR imaging.

For the evaluation of new stem cell therapies it is important to non-invasively track the injected cells in vivo. This video will show you how to label human mesenchymal and embryonic stem cells with iron oxide based contrast agents in vivo for subsequent MR imaging in vivo.

In recent years, stem cell research has led to a better understanding of developmental biology, various diseases and its potential impact on regenerative ...

Labeling Stem Cells with Fluorescent Dyes for non-invasive Detection with Optical Imaging

Optical imaging (OI) is an easy, fast and inexpensive tool for in vivo monitoring of new stem cell based therapies. The technique is based on ex vivo labeling of stem cells with a fluorescent dye, subsequent intravenous injection of the labeled cells and visualization of their accumulation in specific target organs or pathologies. The presented technique demonstrates how we label human mesenchymal stem cells (hMSC) by simple incubation with the lipophilic fluorescent dye DiD (C67H103CIN2O3S) and how we label human embryonic stem cells (hESC) with the FDA approved fluorescent dye Indocyanine Green (ICG). The uptake mechanism is via adherence and diffusion of the lypophilic dye across the phospholipid cell membrane bilayer. The labeling efficiency is usually improved if the cells are incubated with the dye in serum-free media as opposed to incubation in serum-containing media. Furthermore, the addition of the transfection agent Protamine Sulfate significantly improves contrast agent uptake.

This video shows techniques for labeling of human embryonic stem cells and mesenchymal stem cells with fluorescent dyes. This technique can be used for an in vivo tracking of transplanted stem cells with optical imaging and for histopathological correlations with fluorescence microscopy.

Optical imaging (OI) is an easy, fast and inexpensive tool for in vivo monitoring of new stem cell based therapies. The technique is based on ex vivo ...

Non-invasive 3D-Visualization with Sub-micron Resolution Using Synchrotron-X-ray-tomography

Little is known about the internal organization of many micro-arthropods with body sizes below 1 mm. The reasons for that are the small size and the hard cuticle which makes it difficult to use protocols of classical histology. In addition, histological sectioning destroys the sample and can therefore not be used for unique material. Hence, a non-destructive method is desirable which allows to view inside small samples without the need of sectioning.
We used synchrotron X-ray tomography at the European Synchrotron Radiation Facility (ESRF) in Grenoble (France) to non-invasively produce 3D tomographic datasets with a pixel-resolution of 0.7&micro;m. Using volume rendering software, this allows us to reconstruct the internal organization in its natural state without the artefacts produced by histological sectioning. These date can be used for quantitative morphology, landmarks, or for the visualization of animated movies to understand the structure of hidden body parts and to follow complete organ systems or tissues through the samples.

We used synchrotron X-ray tomography at the European Synchrotron Radiation Facility (ESRF) to non-invasively produce 3D tomographic datasets with a pixel-resolution of 0.7&micro;m. Using volume rendering software, this allows the reconstruction of internal structures in their natural state without the artefacts produced by histological sectioning.

Little is known about the internal organization of many micro-arthropods with body sizes below 1 mm. The reasons for that are the small size and the hard ...

A Magnetic Tether System to Investigate Visual and Olfactory Mediated Flight Control in Drosophila

It has been clear for many years that insects use visual cues to stabilize their heading in a wind stream. Many animals track odors carried in the wind. As such, visual stabilization of upwind tracking directly aids in odor tracking. But do olfactory signals directly influence visual tracking behavior independently from wind cues? Also, the recent deluge of research on the neurophysiology and neurobehavioral genetics of olfaction in Drosophila has motivated ever more technically sophisticated and quantitative behavioral assays. Here, we modified a magnetic tether system originally devised for vision experiments by equipping the arena with narrow laminar flow odor plumes. A fly is glued to a small steel pin and suspended in a magnetic field that enables it to yaw freely. Small diameter food odor plumes are directed downward over the fly s head, eliciting stable tracking by a hungry fly. Here we focus on the critical mechanics of tethering, aligning the magnets, devising the odor plume, and confirming stable odor tracking.

Here we describe how to tether a fly in an olfactory magnetic-tether (OMT) apparatus. We describe how to align the rare-earth magnets and odor ports, and how to set mass flow rates for both the stimulus delivery and vacuum suction to achieve optimal odor tracking.

It has been clear for many years that insects use visual cues to stabilize their heading in a wind stream. Many animals track odors carried in the wind. ...

Cell Block Preparation from Cytology Specimen with Predominance of Individually Scattered Cells

This video demonstrates Shidham's method for preparation of cell blocks from liquid based cervicovaginal cytology specimens containing individually scattered cells and small cell groups. This technique uses HistoGel (Thermo Scientific) with conventional laboratory equipment.
The use of cell block sections is a valuable ancillary tool for evaluation of non-gynecologic cytology. They enable the cytopathologist to study additional morphologic specimen detail including the architecture of the lesion. Most importantly, they allow for the evaluation of ancillary studies such as immunocytochemistry, in-situ hybridization tests (FISH/CISH) and in-situ polymerase chain reaction (PCR). Traditional cell block preparation techniques have mostly been applied to non-gynecologic cytology specimens, typically for body fluid effusions and fine needle aspiration biopsies.
Liquid based cervicovaginal specimens are relatively less cellular than their non-gynecologic counterparts with many individual scattered cells. Because of this, adequate cellularity within the cell block sections is difficult to achieve. In addition, the histotechnologist sectioning the block cannot visualize the level at which the cells are at the highest concentration. Therefore, it is difficult to monitor the appropriate level at which sections can be selected to be transferred to the glass slides for testing. As a result, the area of the cell block with the cells of interest may be missed, either by cutting past or not cutting deep enough. Current protocol for Shidham's method addresses these issues. Although this protocol is standardized and reported for gynecologic liquid based cytology specimens, it can also be applied to non-gynecologic specimens such as effusion fluids, FNA, brushings, cyst contents etc for improved quality of diagnostic material in cell block sections.

Shidham's method for preparation of cell blocks with AV-marker from cytology specimens containing individually scattered cells and small cell groups.

This video demonstrates Shidham's method for preparation of cell blocks from liquid based cervicovaginal cytology specimens containing individually ...

A Practical Approach to Genetic Inducible Fate Mapping: A Visual Guide to Mark and Track Cells In Vivo

Fate maps are generated by marking and tracking cells in vivo to determine how progenitors contribute to specific structures and cell types in developing and adult tissue. An advance in this concept is Genetic Inducible Fate Mapping (GIFM), linking gene expression, cell fate, and cell behaviors in vivo, to create fate maps based on genetic lineage.
GIFM exploits X-CreER lines where X is a gene or set of gene regulatory elements that confers spatial expression of a modified bacteriophage protein, Cre recombinase (CreERT). CreERT contains a modified estrogen receptor ligand binding domain which renders CreERT sequestered in the cytoplasm in the absence of the drug tamoxifen. The binding of tamoxifen releases CreERT, which translocates to the nucleus and mediates recombination between DNA sequences flanked by loxP sites. In GIFM, recombination typically occurs between a loxP flanked Stop cassette preceding a reporter gene such as GFP.
Mice are bred to contain either a region- or cell type-specific CreER and a conditional reporter allele. Untreated mice will not have marking because the Stop cassette in the reporter prevents further transcription of the reporter gene. We administer tamoxifen by oral gavage to timed-pregnant females, which provides temporal control of CreERT release and subsequent translocation to the nucleus removing the Stop cassette from the reporter. Following recombination, the reporter allele is constitutively and heritably expressed. This series of events marks cells such that their genetic history is indelibly recorded. The recombined reporter thus serves as a high fidelity genetic lineage tracer that, once on, is uncoupled from the gene expression initially used to drive CreERT.
We apply GIFM in mouse to study normal development and ascertain the contribution of genetic lineages to adult cell types and tissues. We also use GIFM to follow cells on mutant genetic backgrounds to better understand complex phenotypes that mimic salient features of human genetic disorders.
This video article guides researchers through experimental methods to successfully apply GIFM. We demonstrate the method using our well characterized Wnt1-CreERT;mGFP mice by administering tamoxifen at embryonic day (E)8.5 via oral gavage followed by dissection at E12.5 and analysis by epifluorescence stereomicroscopy. We also demonstrate how to micro-dissect fate mapped domains for explant preparation or FACS analysis and dissect adult fate-mapped brains for whole mount fluorescent imaging. Collectively, these procedures allow researchers to address critical questions in developmental biology and disease models.

A Practical Approach to Genetic Inducible Fate Mapping: A Visual Guide to Mark and Track Cells In Vivo

Genetic Inducible Fate Mapping (GIFM) marks and tracks cells with fine spatial and temporal control in vivo and elucidates how cells from a specific genetic lineage contribute to developing and adult tissues. Demonstrated here are the techniques required to fate map E12.5 mouse embryos for epifluorescent and explant analysis.

Fate maps are generated by marking and tracking cells in vivo to determine how progenitors contribute to specific structures and cell types in developing ...

A Reversible, Non-invasive Method for Airway Resistance Measurements and Bronchoalveolar Lavage Fluid Sampling in Mice

Airway hyperreactivity (AHR) measurements and bronchoalveolar lavage (BAL) fluid sampling are essential to experimental asthma models, but repeated procedures to obtain such measurements in the same animal are generally not feasible.  Here, we demonstrate protocols for obtaining from mice repeated measurements of AHR and bronchoalveolar lavage fluid samples.  Mice were challenged intranasally seven times over 14 days with a potent allergen or sham treated.  Prior to the initial challenge, and within 24 hours following each intranasal challenge, the same animals were anesthetized, orally intubated and mechanically ventilated.  AHR, assessed by comparing dose response curves of respiratory system resistance (RRS) induced by increasing intravenous doses of acetylcholine (Ach) chloride between sham and allergen-challenged animals, were determined.  Afterwards, and via the same intubation, the left lung was lavaged so that differential enumeration of airway cells could be performed.  These studies reveal that repeated measurements of AHR and BAL fluid collection are possible from the same animals and that maximal airway hyperresponsiveness and airway eosinophilia are achieved within 7-10 days of initiating allergen challenge.  This novel technique significantly reduces the number of mice required for longitudinal experimentation and is applicable to diverse rodent species, disease models and airway physiology instruments.  

Repeated measurements of rodent respiratory physiology and sampling of airway inflammatory cells are desirable, but generally not feasible. Here we describe a repeatable method for orally intubating mice that permits repeated measurements of airway hyperreactivity and sampling of airway inflammatory cells.

Airway hyperreactivity (AHR) measurements and bronchoalveolar lavage (BAL) fluid sampling are essential to experimental asthma models, but repeated ...

Using Unfixed, Frozen Tissues to Study Natural Mucin Distribution

Mucins are complex and heavily glycosylated O-linked glycoproteins, which contain more than 70% carbohydrate by weight1-3. Secreted mucins, produced by goblet cells and the gastric mucosa, provide the scaffold for a micrometers-thick mucus layer that lines the epithelia of the gut and respiratory tract3,4. In addition to mucins, mucus layers also contain antimicrobial peptides, cytokines, and immunoglobulins5-9. The mucus layer is an important part of host innate immunity, and forms the first line of defense against invading microorganisms8,10-12. As such, the mucus is subject to numerous interactions with microbes, both pathogens and symbionts, and secreted mucins form an important interface for these interactions. The study of such biological interactions usually involves histological methods for tissue collection and staining. The two most commonly used histological methods for tissue collection and preservation in the clinic and in research laboratories are: formalin fixation followed by paraffin embedding, and tissue freezing, followed by embedding in cryo-protectant media.
Paraffin-embedded tissue samples produce sections with optimal qualities for histological visualization including clarity and well-defined morphology. However, during the paraffin embedding process a number of epitopes become altered and in order to study these epitopes, tissue sections have to be further processed with one of many epitope retrieval methods13. Secreted mucins and lipids are extracted from the tissue during the paraffin-embedding clearing step, which requires prolong incubation with organic solvents (xylene or Citrisolv). Therefore this approach is sub-optimal for studies focusing on the nature and distribution of mucins and mucus in vivo.
In contrast, freezing tissues in Optimal Cutting Temperature (OCT) embedding medium avoids dehydration and clearing of the sample, and maintains the sample hydration. This allows for better preservation of the hydrated mucus layer, and thus permits the study of the numerous roles of mucins in epithelial biology. As this method requires minimal processing of the tissue, the tissue is preserved in a more natural state. Therefore frozen tissues sections do not require any additional processing prior to staining and can be readily analyzed using immunohistochemistry methods.
We demonstrate the preservation of micrometers-thick secreted mucus layer in frozen colon samples. This layer is drastically reduced when the same tissues are embedded in paraffin. We also demonstrate immunofluorescence staining of glycan epitopes presented on mucins using plant lectins. The advantage of this approach is that it does not require the use of special fixatives and allows utilizing frozen tissues that may already be preserved in the laboratory.

Unfixed frozen tissue samples embedded in Optimal Cutting Temperature medium (OCT) can be used to study natural distribution and glycosylation of secreted mucus. In this approach tissue processing is minimal and the natural presentation of glycolipids, mucins and glycan-epitopes is preserved. Tissue sections can be analyzed by immunohistochemistry using fluorescence or chromogenic detection.

Mucins are complex and heavily glycosylated O-linked glycoproteins, which contain more than 70% carbohydrate by weight1-3. Secreted mucins, produced by ...

Fecal Glucocorticoid Analysis: Non-invasive Adrenal Monitoring in Equids

Adrenal activity can be assessed in the equine species by analysis of feces for corticosterone metabolites. During a potentially aversive situation, corticotrophin releasing hormone (CRH) is released from the hypothalamus in the brain. This stimulates the release of adrenocorticotrophic hormone (ACTH) from the pituitary gland, which in turn stimulates release of glucocorticoids from the adrenal gland. In horses the glucocorticoid corticosterone is responsible for several adaptations needed to support equine flight behaviour and subsequent removal from the aversive situation. Corticosterone metabolites can be detected in the feces of horses and assessment offers a non-invasive option to evaluate long term patterns of adrenal activity. Fecal assessment offers advantages over other techniques that monitor adrenal activity including blood plasma and saliva analysis. The non-invasive nature of the method avoids sampling stress which can confound results. It also allows the opportunity for repeated sampling over time and is ideal for studies in free ranging horses. This protocol describes the enzyme linked immunoassay (EIA) used to assess feces for corticosterone, in addition to the associated biochemical validation.

Adrenal activity can be assessed in the equine species by analysis of feces for corticosterone metabolites. The method offers a non-invasive option to assess long term patterns in both domestic and free ranging horses. This protocol describes the enzyme linked immunoassay involved and the associated biochemical validation.

Adrenal activity can be assessed in the equine species by analysis of feces for corticosterone metabolites. During a potentially aversive situation, ...

Methods to Discover Alternative Promoter Usage and Transcriptional Regulation of Murine Bcrp1

Gene expression in different tissues is often controlled by alternative promoters that result in the synthesis of mRNA with unique &#8212; usually untranslated &#8212; first exons. Bcrp1 (Abcg2), the murine orthologue of the ABC transporter Breast Cancer Resistance Protein (BCRP, ABCG2), has at least four alternative promoters that are designated by the corresponding four alternative first exons produced: E1U, E1A, E1B, and E1C. Herein, in-silico protocols are presented to predict alternative promoter usage for Bcrp1. Furthermore, reporter assay methods are described to produce reporter constructs for alternative promoters and to determine the functionality of putative promoters upstream of the alternative first exons that are identified.

With the murine ABC transporter Bcrp1 (Abcg2) as an example, in-silico protocols are presented to detect alternative promoter usage in genes expressed in mouse tissues, and to evaluate the functionality of the alternative promoters identified using reporter assays.