Spatial relationships among the cellular tapetum, visual streak and rod density in dogs

Abstract

The dog visual system is well suited to dim light conditions due to rod-dominated retina and the reflective tapetum. The topographical distributions of rods and thickness of the tapetum of the dog were quantified in retinal whole mounts stained with thionine, and spatial relationships among the tapetum, rod density and visual streak of high ganglion cell density were elucidated. The relationship between the retina and tapetum was analyzed in parasagittal sections stained with thionine or hematoxylin-eosin. The tapetum was thick in its center, and the thickest part consisted of 9 to 12 tapetal cell layers. Rod density ranged from 200,000 to 540,000/mm2. Maximum rod density was found in the area dorsal to the visual streak, and the density in that area was significantly higher than the rod density in the visual streak and accorded spatially with the thickest part of the tapetum. The horizontal visual streak was found over the horizontal line through the optic disc in the temporal half and extended slightly into the nasal half. The central area of the highest density of ganglion cells was approximately located midway between the nasal and temporal ends of the visual streak. The visual streak was located within the tapetal area, but ventrally to the thick part of the tapetum.

Retinal photoreceptor and ganglion cell types and topographies in the red fox (Vulpes vulpes) and Arctic fox(Vulpes lagopus)

“…Act., predominant diel activity pattern: N = nocturnal; C = cathemeral; D = diurnal (data mostly from Nowak, ). Photoreceptor data: red fox and Arctic fox, present study; wolf, Peichl et al, ; dog cones, Mowat et al, ; Klein et al, ; dog rods, Yamaue, Hosaka, & Uehara, ; ferret cones, Calderone & Jacobs, ; ferret rods, Jeffery, Darling, & Whitmore, ; wild mink, Steffen, ; cat, Steinberg, Reid, & Lacy, ; Linberg et al, ; lynx and cheetah, Ahnelt, Fernández, et al, ; Ahnelt, Schubert, Kuebber‐Heiss, & Anger, ; Ahnelt, Schubert, Kübber‐Heiss, Schiviz, et al, ; raccoon and coati, Peichl & Pohl, ; hyena, Calderone et al, ; cusimanse, Coimbra, Kaswera‐Kyamakya, Gilissen, Manger, & Collin, …”

Scientific and Regulatory Policy Committee Points to Consider: Fixation, Trimming, and Sectioning of Nonrodent Eyes and Ocular Tissues for Examination in Ocular and General Toxicity Studies

“…Cone-dense visual streaks have been identified in all commonly utilized nonrodent laboratory species—rabbits, dogs, and minipigs. 16,23- 27 In the past, there have been some discrepancies in the terminology used in nonprimate species; some publications refer to the visual streak as the area centralis. In this article, we use the term area centralis specifically to describe the small, focal subregion of the visual streak with the highest cone density, which (among the nonprimate species commonly used in ocular toxicity studies) is present only in the dog.…”

Selected Aspects of Ocular Toxicity Studies With a Focus on High-Quality Pathology Reports: A Pathology/Toxicology Consultant’s Perspective

“…A total of 5 sections or more should allow adequate evaluation of a full range of ocular tissues including the cone-rich visual streak/macula which varies by species as diagramed in Figure 1.8 by Vezina. 88 The visual streak (macula equivalent) is inferior to the optic disc in rabbits, 89,90 superior/temporal to the optic disc in dogs, 91,92 and superior to the optic disc in domestic pigs and minipigs [93][94][95] and inadvertently referred to as area centralis in domestic pigs and minipigs by several laboratories. 96,97 Sagittal (vertical) trimming with 2-step H & E-stained sections for temporal (200-500 mm apart) and central calottes (500-1000 mm apart) and 1 H&E-stained section for the nasal calotte should be made for eyes from these species, which should capture the visual streak identified by high ganglion cell density in retina from multiple sagittal sections from all 3 species.…”