Article

Fluoro-Gold: A new retrograde axonal tracer with numerous unique properties

Department of Anatomy, School of Medicine, University of California, Irvine, CA 92717 U.S.A.
Brain Research (Impact Factor: 2.84). 08/1986; 377(1):147-54. DOI: 10.1016/0006-8993(86)91199-6
Source: PubMed

ABSTRACT

A new fluorescent dye, Fluoro-Gold, has been demonstrated to undergo retrograde axonal transport. Its properties include intense fluorescence, extensive filling of dendrites, high resistance to fading, no uptake by intact undamaged fibers of passage, no diffusion from labeled cells, consistent and pure commercial source, wide latitude of survival times and compatibility with all other tested neuro-histochemical techniques.

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    • "FG was also shown to label neurons within 48 h of exposure (Schmued and Fallon, 1986; Baranowski et al., 1992; Richmond et al., 1994). Fluorogold is a fluorescent hydroxystilbamidine tracer and uptake and retrograde transport may be facilitated by diffusion through the cell membrane where it is trapped by lysosomes and then transported to the cell body (Wessendorf, 1991) and active endocytic vesicular uptake (Schmued and Fallon, 1986). While not all fluorescent tracers have identical transport characteristics, all retrograde labeling is dependent on either the active or passive movement of dye from the point of exposure retrograde towards the cell body. "
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    ABSTRACT: Background: Retrograde labeling permits the investigation of the number, distribution and axonal projections of neurons in the peripheral nervous system. The well technique for labeling peripheral nerves consists of incubating the exposed peripheral nerve in a well for one-hour, a time intensive technique. However, other techniques that inject tracers directly into the nerve or muscle may result in variable labeling depending on nerve preparation and location of injection. New method: We describe a method of retrograde labeling peripheral nerves that increases tracer uptake and improves labeling efficiency. This technique utilizes a silicone cap over the nerve that is kept in place with fibrin glue, permitting closure of the incision with the cap in place, mitigating the need to wait one hour for back-labeling as with the standard well technique. Results: In the rat common peroneal nerve, the new silicone cap technique, compared to the standard well technique, labeled 405±11 (SEM) vs. 378±21 motoneurons and 953±40 vs. 948±57 sensory neurons. These counts were not statistically different. Labeling intensity was greater in DRG neurons with the silicone cap technique, but this difference was not evident in motoneurons. Comparison with existing method: Retrograde-labeling with silicone caps labels an equal number of motor and sensory neurons in comparison with the standard well technique and labels sensory neurons with greater intensity. Conclusions: Retrograde-labeling with silicone caps reliably labels neurons and significantly decreases the time required for labeling, reducing anaesthetic exposure and improving the efficiency of the technique.
    Full-text · Article · Nov 2015 · Journal of Neuroscience Methods
    • "3.1.2. Fluoro-gold™ Fluoro-gold™ (FG, Fluorochrome, LLC; generic name: hydroxystilbamidine , OHSt) is a widely used neuronal tracer that shows persistent RGC labeling (Abdel-Majid et al., 2005; Berkelaar et al., 1994; Schmued and Fallon, 1986; Wessendorf, 1991). FG travels from the SC to RGC somata in rodents within a week and persists for several weeks allowing for reliable quantification of RGC density (Berkelaar et al., 1994; Salinas-Navarro et al., 2009a, 2009b). "
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    ABSTRACT: Glaucoma is a disease characterized by progressive axonal pathology and death of retinal ganglion cells (RGCs), which causes structural changes in the optic nerve head and irreversible vision loss. Several experimental models of glaucomatous optic neuropathy (GON) have been developed, primarily in non-human primates and, more recently and commonly, in rodents. These models provide important research tools to study the mechanisms underlying glaucomatous damage. Moreover, experimental GON provides the ability to quantify and monitor risk factors leading to RGC loss such as the level of intraocular pressure, axonal health and the RGC population. Using these experimental models we are able to gain a better understanding of GON, which allows for the development of potential neuroprotective strategies. Here we review the advantages and disadvantages of the relevant and most often utilized methods for evaluating axonal degeneration and RGC loss in GON. Axonal pathology in GON includes functional disruption of axonal transport (AT) and structural degeneration. Horseradish peroxidase (HRP), rhodamine-B-isothiocyanate (RITC) and cholera toxin-B (CTB) fluorescent conjugates have proven to be effective reporters of AT. Also, immunohistochemistry (IHC) for endogenous AT-associated proteins is often used as an indicator of AT function. Similarly, structural degeneration of axons in GON can be investigated via changes in the activity and expression of key axonal enzymes and structural proteins. Assessment of axonal degeneration can be measured by direct quantification of axons, qualitative grading, or a combination of both methods. RGC loss is the most frequently quantified variable in studies of experimental GON. Retrograde tracers can be used to quantify RGC populations in rodents via application to the superior colliculus (SC). In addition, in situ IHC for RGC-specific proteins is a common method of RGC quantification used in many studies. Recently, transgenic mouse models that express fluorescent proteins under the Thy-1 promoter have been examined for their potential to provide specific and selective labeling of RGCs for the study of GON. While these methods represent important advances in assessing the structural and functional integrity of RGCs, each has its advantages and disadvantages; together they provide an extensive toolbox for the study of GON. Copyright © 2015. Published by Elsevier Ltd.
    No preview · Article · Jun 2015 · Experimental Eye Research
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    • "In the visual system fluorogold (FG) has become the tracer of choice for many laboratories. This compound is actively and retrogradely transported from the axons to the RGC somas where it accumulates without leaking (Schmued and Fallon, 1986; Wessendorf, 1991; reviewed in Kobbert et al., 2000). Thus, 3 days after its application on the optic nerve stump, all the RGCs are traced (Nadal-Nicolas et al., 2012; Salinas-Navarro et al., 2009b, 2009c), while when applied onto both SCi approximately one week is needed to label 98.4% and 97.8% of the RGC population in albino and pigmented rats, respectively (Danias et al., 2002; Salinas- Navarro et al., 2009b, 2009c). "

    Full-text · Article · Dec 2014 · Experimental Eye Research
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