All experiments complied with all applicable laws, National Institutes of Health guidelines, and were approved by the University of Colorado Anschutz Institutional Animal Care and Use Committee.
1. Animals
2. Tissue preparation
3. Staining
Figure 1: CARS imaging can be combined with immunofluorescent imaging. The graphs shows that CARS imaging occurs at 660/640 nm red signal spectrum26. This wavelength is sufficiently far removed from the green, blue, or UV range, allowing for combination of the CARS signal with immunofluorescence in these ranges. Specifically, the graph also indicates the excitation and emission for Nissl tagged with blue fluorophore, which was combined with CARS during the collection of representative results for this publication. Please click here to view a larger version of this figure.
4. Imaging
NOTE: The CARS laser set up contains a fiber laser that provides the 80 MHz clock, and an OPO (Optical Parametric Oscillator) laser with a tunable range of 770-990 nm with the Stokes beam fixed at 1031 nm, which are needed for collecting the CARS signal. There is one aperture for both beams.
Figure 2: CARS instrument diagram showing CARS lasers (red arrows) and non-descanned (NDD) epi and forward detection incorporated onto a laser scanning confocal. In forward NDD we acquire CARS for C-H bonds (dark red arrows) and SHG (second harmonic generatioin) at 515 nm (orange arrow). In epi NDD, we acquire CARS for C-H bonds (dark red arrows) and 2PE (two-photon emission) autofluorescence (light blue arrow). Sequentially, fluorescence confocal images can be acquired (green arrows for visible laser, blue arrows for confocal detection). Please click here to view a larger version of this figure.
Figure 3: CARS can illuminate myelin (magenta) in brain tissue (brainstem) while also imaging Nissl (cyan) or fluorescent markers. The two panels show representative results from a Mongolian gerbil (single image M. unguiculatus, Figure 3A,C,E) and mouse (z-stack max projection M. musculus, Figure 2B,D,F) brain, indicating that this technique can be used across species. Figure 3A,B showing Nissl in cyan, C,D show the CARS signal in magenta, E,F combine the Nissl and CARS signals with each panel for gerbil or mouse, respectively. Both sets of images show a section of the medial nucleus of the trapezoid body (MNTB) in the brain stem. Neurons in the MNTB receive inputs from heavily myelinated axons, which terminate in the calyx of held, a type of giant synapse27. Scale bar is 20 µm. Please click here to view a larger version of this figure.
One of the biggest advantages of CARS microscopy over other techniques is the compatibility with fluorescent imaging23. Figure 1 shows the CARS spectra compared to Nissl tagged with immunofluorescent marker showing little/no overlap in spectra. Figure 2 illustrates the laser set up for CARS in combination with confocal microscopy. Figure 3 demonstrates two representative images, one as a single stack and one z-stack max projection from gerbil and mouse that might be obtained using CARS imaging showing both cell bodies (cyan) and myelin signal (magenta).
Anesthetic: | |||
1 mL disposable syringe with needle 27 GA x 0.5" | Exel int | 260040 | |
Fatal + | Vortech | ||
Surgery: | |||
Spring Scissors – 8mm Cutting Edge | Fine Science Tools | 15024-10 | |
Standard tweezers | Fine Science Tools | 11027-12 | |
Perfusion: | |||
4% Paraformaldehyde | Fisher Chemical | SF994 (CS) | |
Fine Scissors – Sharp | Fine Science Tools | 14063-11 | |
Kelly hemostats | Fine Science Tools | 13019-14 | |
Millipore H2O | |||
Needle tip, 23 GA x 1" | BD precision glide | 305193 | |
Phosphate buffered saline (PBS): | |||
Potassium chloride | Sigma | P9333 | |
Potassium phosphate monobase | Sigma | P5655 | |
pump with variable flow or equivalent | |||
Sodium chloride | Fisher Chemical | s271-1 | |
Sodiumphosphate dibasic | Sigma | S7907 | |
Dissection: | |||
50 mL vial with 4% PFA | |||
Bochem Chemical Spoon 180mm | Bochem | 230331000 | |
Fine Scissors – Sharp | Fine Science Tools | 14063-11 | |
Noyes Spring Scissors | Fine Science Tools | 15011-12 | |
Pair of fine (Graefe) tweezers | Fine Science Tools | 11050-10 | |
Shallow glass or plastic tray, approximately 10" x 10" | |||
Standard tweezers | Fine Science Tools | 11027-12 | |
Surgical Scissors – Blunt | Fine Science Tools | 14000-20 | |
Slicing: | |||
Agar, plant | RPI | 9002-18-0 | |
Vibratome | Leica | VT1000s | |
well plate | Alkali Sci. | TPN1048-NT | |
Staining: | |||
AB Media: | 1n 1,000 mL of Millipore H2O | ||
Phosphate buffered (PB): | |||
Potassium Phosphate Monobase | Sigma | P5655 | |
Sodium Phosohate Dibasic | Sigma | S7907 | |
BSA (Bovine serum albumin) | Sigma life science | A2153-100g | |
Sodium Chloride | Fisher Chemical | s271-1 | |
Triton X-100 | Sigma – Aldrich | x100-500ml | |
Nissl 435/455 | Invitrogen | N21479 | |
CARS: | |||
APE picoemerald laser | Angewandte Physik & Elektronik GmbH | ||
bandpass filter (420-520 nm) | Chroma Technology | HQ470/100m-2P | |
bandpass filter (500-530 nm) | Chroma Technology | HQ515/30m-2P | |
bandpass filters (640-680 nm) | Chroma Technology | HQ660/40m-2P | |
Confocal microscope | Olympus | FV1000 | |
Cut Transfer pipet | Fisher | 13-711-7M | |
dichroic longpass 565 nm | Chroma Technology | 565dcxr | |
dichroic longpass 585 nm | Chroma Technology | 585dcxr | |
dichroic shortpass 750 nm | Chroma Technology | T750spxrxt | |
glass bottom culture dish | MatTek | P35G-0-10-C | |
glass weight (10 mm x 10 mm boro rod) | Allen Scientific Glass Inc | ||
multiphoton shortpass emission filter 680 nm | Chroma Technology | ET680sp-2p8 | |
PBS |
Coherent anti-Stokes Raman spectroscopy (CARS) is a technique classically employed by chemists and physicists to produce a coherent signal of signature vibrations of molecules. However, these vibrational signatures are also characteristic of molecules within anatomical tissue such as the brain, making it increasingly useful and applicable for Neuroscience applications. For example, CARS can measure lipids by specifically exciting chemical bonds within these molecules, allowing for quantification of different aspects of tissue, such as myelin involved in neurotransmission. In addition, compared to other techniques typically used to quantify myelin, CARS can also be set up to be compatible with immunofluorescent techniques, allowing for co-labeling with other markers such as sodium channels or other components of synaptic transmission. Myelination changes are an inherently important mechanism in demyelinating diseases such as multiple sclerosis or other neurological conditions such as Fragile X Syndrome or autism spectrum disorders is an emerging area of research. In conclusion, CARS can be utilized in innovative ways to answer pressing questions in Neuroscience and provide evidence for underlying mechanisms related to many different neurological conditions.
Coherent anti-Stokes Raman spectroscopy (CARS) is a technique classically employed by chemists and physicists to produce a coherent signal of signature vibrations of molecules. However, these vibrational signatures are also characteristic of molecules within anatomical tissue such as the brain, making it increasingly useful and applicable for Neuroscience applications. For example, CARS can measure lipids by specifically exciting chemical bonds within these molecules, allowing for quantification of different aspects of tissue, such as myelin involved in neurotransmission. In addition, compared to other techniques typically used to quantify myelin, CARS can also be set up to be compatible with immunofluorescent techniques, allowing for co-labeling with other markers such as sodium channels or other components of synaptic transmission. Myelination changes are an inherently important mechanism in demyelinating diseases such as multiple sclerosis or other neurological conditions such as Fragile X Syndrome or autism spectrum disorders is an emerging area of research. In conclusion, CARS can be utilized in innovative ways to answer pressing questions in Neuroscience and provide evidence for underlying mechanisms related to many different neurological conditions.
Coherent anti-Stokes Raman spectroscopy (CARS) is a technique classically employed by chemists and physicists to produce a coherent signal of signature vibrations of molecules. However, these vibrational signatures are also characteristic of molecules within anatomical tissue such as the brain, making it increasingly useful and applicable for Neuroscience applications. For example, CARS can measure lipids by specifically exciting chemical bonds within these molecules, allowing for quantification of different aspects of tissue, such as myelin involved in neurotransmission. In addition, compared to other techniques typically used to quantify myelin, CARS can also be set up to be compatible with immunofluorescent techniques, allowing for co-labeling with other markers such as sodium channels or other components of synaptic transmission. Myelination changes are an inherently important mechanism in demyelinating diseases such as multiple sclerosis or other neurological conditions such as Fragile X Syndrome or autism spectrum disorders is an emerging area of research. In conclusion, CARS can be utilized in innovative ways to answer pressing questions in Neuroscience and provide evidence for underlying mechanisms related to many different neurological conditions.