“Characterization of Secretagogin-Immunoreactive Amacrine Cells in Marmoset Retina”. F. Weltzien, S. Dimarco, D. A. Protti, T. Daraio, P. R. Martin, U. Grünert. Journal of Comparative Neurology. 2014 Feb 1; 522(2): 435-55.
The aim of this study was to characterise a distinct group of amacrine cells that have not yet been described in detail. Amacrine cells are a diverse group of cells that are located in the eye, in an area known as the inner plexiform layer of the retina (Fig. 1). Previous studies on other animals and humans identified that there are at least 20 morphologically (structurally) different types of amacrine cells. Some of these have been studied in depth while others are lacking in detail, which led to this study being performed. However, there was no justification made as to why this study was carried out on common marmosets (Callithrix jucchus) other than that amacrine cells had not been described in detail for this species.
The authors stated that the procedures were conducted according to the Australian National Health and Medical Research Council (NHMRC)’s provisions in their code of practice for the care and use of animals. They also state that the marmosets used in the study were obtained from the NHMRC combined breeding facility. The experiment was approved by the University of Sydney Animal Care and Ethics Committee.
The study was funded by a grant received from the NHMRC, grant number 632640. This grant awarded $417,675 for the project title ‘Inhibitory microcircuits in the primate retina’.
The retinas from eight eyes were used from eight marmosets, four males and four females. The animals were killed by means of an overdose on sodium pentobarbitone, and their eyes were removed and dissected. The relevant sections of the eyes were then prepared and mounted on slides to be viewed under a microscope. The cells were stained in order to distinguish the cells that contained the secretagogin protein from other cells within the eye.
The antibodies used in this study to stain particular sections of the retina were obtained from a number of different animal sources. They were listed as: rat, mouse, human, bovine (cow), porcine (pig), carp, sheep, goat and rabbit.
Prior to being used in this study the marmosets were also used in an experiment that took electrophysiological readings from their visual brain centres. To date that experiment has not been published, so the details of what the marmosets were subjected to are unknown.
- It was found that only one kind of amacrine cell contained the secretagogin protein.
- The cells occupy the 2nd, 3rd and 4th strata of the inner plexiform layer of the retina, in between two bands made up of cholinergic amacrine cells, with majority of the cells being distributed within the inner nuclear layer of both the central retina and the peripheral retina (refer Fig. 1).
- Morphologically, the cells were typically asymmetrical and were found to have 1 or 2 main dendrites which branch numerous times. These branches have multiple dendritic spines and varicosities along them.
- Based on these results they are categorised as medium-field amacrine cells, which share a similar stratification distribution as narrow-field cells, and share a similar neurotransmitter pattern as wide-field cells.
The findings of this study are limited because, although there was some contribution towards our knowledge of the cellular makeup of the marmoset eye, this information cannot be extrapolated to other primates, let alone other species, including humans. It should also be noted that the functional role that both the amacrine cells and the secretagogin protein play within the eye is not yet known.
The authors also do not supply any reason as to why only one eye was used from each of the marmosets, requiring eight marmosets to perish for the eight eyes used in this study.
The role of any animal ethics committee is to weigh up the benefits that society receives from the research against the pain and suffering, and loss of life, that the animals within the study experience. The findings from this study do not contribute towards any type of substantial medical or therapeutic advances for humans, or for animals, which then begs to question why this study was approved by the University of Sydney Animal Care and Ethics Committee, and funded by the NHMRC.
There is no evidence that the NHMRC considered replacing (one of the three R’s in animal research) the common marmosets used in this study with that of human eyes donated for scientific/medical research. If the study had been conducted on human eyes, then the knowledge gained may have one day provided useful information to vision research and would have added to the existing information available about the cells within human retinas (for example, Davanger et al., 1991; Kolb et al., 1992; Rodieck and Marshak, 1992; Cuenca et al., 1995; Haverkamp et al., 2003; Casini et al., 2006). The authors also admit that “a full description of spiny amacrine cells in human retina is lacking” which again raises the question of why the relevant Animal Ethics Committee and NHMRC would not suggest that this study would have been better off performed using human retinas.
What you can do
NHRMC, GPO Box 142
Canberra ACT 261
Write to the Animal Ethics Committee that approved this and similar experiments:
University of Sydney Animal Care and Ethics Committee
Margaret Telfer Building (K07)
University of Sydney NSW 2006
Casini, G., Rickman, D.W. and Brecha, N.C. 2006. Expression of the y-aminobutyric acid (GABA) plasma membrane transporter-1 in monkey and human retina. Investigative Ophthalmology and Visual Science. Vol. 47. pp. 1682-1690
Cuenca, N., Juan, J.D. and Kolb, H. 1995. Substance P-immunoreactive neurons in the human retina. Journal of Comparative Neurology. Vol 356. pp. 491-504
Davanger, S., Ottersen, O.P. and Storm-Mathisen, J. 1991. Glutamate, GABA, and glycine in the humn retina: an immunocytochemical investigation. Journal of Comparative Neurology. Vol 311. pp. 483-494