| 1. |
- Gagnon, Yakir, et al.
(author)
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Adjusting a light dispersion model to fit measurements from vertebrate ocular media as well as ray-tracing in fish lenses.
- 2010
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In: Vision Research. - : Elsevier BV. - 1878-5646 .- 0042-6989. ; 50:9, s. 850-853
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Journal article (peer-reviewed)abstract
- Color dispersion, i.e., the dependency of refractive index of any transparent material on the wavelength of light, has important consequences for the function of optical instruments and animal eyes. Using a multi-objective goal attainment optimization algorithm, a dispersion model was successfully fitted to measured refractive indices of various ocular media and the longitudinal chromatic aberration determined by laser-scanning in the crystalline lens of the African cichlid fish, Astatotilapia burtoni. The model describes the effects of color dispersion in fish lenses and may be applicable to the eyes of other vertebrates as well.
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| 2. |
- Gagnon, Yakir, et al.
(author)
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Effects of the peripheral layers on the optical properties of spherical fish lenses
- 2008
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In: Journal of the Optical Society of America A. - 1084-7529. ; 25:10, s. 2468-2475
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Journal article (peer-reviewed)abstract
- We created a computational optical model of spherical fish lenses that takes into account the effects of the peripheral layers that differ in cellular composition from the bulk of the lens. A constant refractive index, except for the lens capsule, in the outer about 6 % of lens radius made it possible to uniquely infer the refractive index gradient in more central layers from a known or desired longitudinal spherical aberration curve using the inverse Abel transform. Since the zone of constant refractive index is wider than necessary to make the solution unique and for optimal optical performance of the lens, we propose that its width is set by the metabolic needs of the lens.
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| 3. |
- Gagnon, Yakir, et al.
(author)
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Optical advantages and function of multifocal spherical fish lenses
- 2012
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In: Journal of the Optical Society of America A. - 1084-7529. ; 29:9, s. 1786-1793
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Journal article (peer-reviewed)abstract
- The spherical crystalline lenses in the eyes of many fish species are well-suited models for studies on how natural selection has influenced the evolution of the optical system. Many of these lenses exhibit multiple focal lengths when illuminated with monochromatic light. Similar multifocality is present in a majority of vertebrate eyes, and it is assumed to compensate for the defocusing effect of longitudinal chromatic aberration. In order to identify potential optical advantages of multifocal lenses, we studied their information transfer capacity by computer modeling. We investigated four lens types: the lens of Astatotilapia burtoni, an African cichlid fish species, an equivalent monofocal lens, and two artificial multifocal lenses. These lenses were combined with three detector arrays of different spectral properties: the cone photoreceptor system of A. burtoni and two artificial arrays. The optical properties compared between the lenses were longitudinal spherical aberration curves, point spread functions, modulation transfer functions, and imaging characteristics. The multifocal lenses had a better balance between spatial and spectral information than the monofocal lenses. Additionally, the lens and detector array had to be matched to each other for optimal function. (C) 2012 Optical Society of America
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| 4. |
- Kröger, Ronald Heinz Herbert, et al.
(author)
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Rhinarium temperature dynamics in domestic dogs
- 2017
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In: Journal of Thermal Biology. - : Elsevier BV. - 0306-4565. ; 70, s. 15-19
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Journal article (peer-reviewed)abstract
- Many mammals have specialized nose-tips with glabrous and often wet skin, called rhinaria. The function of the rhinarium is unknown in most species. Rhinaria differ not only in shape and skin structure, but also in skin temperature. They are considerably colder in carnivorans than in herbivorous artio- and perissodactyls. Domestic dogs are carnivorans and their noses often feel cold, such that they can be used as an abundant and easily accessible model species. We performed a study on rhinarium temperature in dogs under various ambient temperatures as well as in different behavioral and physiological contexts, breeds, and age groups. The rhinaria of adult, alert, and comfortable dogs are colder than ambient temperature from 30 °C (approximately 5 °C colder) down to a break point at about 15 °C. At an ambient temperature of 0 °C, rhinarium temperature is approximately 8 °C and the decrease in skin surface temperature with decreasing ambient temperature has not yet leveled off. The dog rhinarium warms up under a number of circumstances. In contrast to the continuously warm rhinaria of herbivores, our results suggest strongly that the cold state is the operating state of the dog rhinarium.
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| 5. |
- Bálint, Anna, et al.
(author)
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Dogs can sense weak thermal radiation
- 2020
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In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10:1
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Journal article (peer-reviewed)abstract
- The dog rhinarium (naked and often moist skin on the nose-tip) is prominent and richly innervated, suggesting a sensory function. Compared to nose-tips of herbivorous artio- and perissodactyla, carnivoran rhinaria are considerably colder. We hypothesized that this coldness makes the dog rhinarium particularly sensitive to radiating heat. We trained three dogs to distinguish between two distant objects based on radiating heat; the neutral object was about ambient temperature, the warm object was about the same surface temperature as a furry mammal. In addition, we employed functional magnetic resonance imaging on 13 awake dogs, comparing the responses to heat stimuli of about the same temperatures as in the behavioural experiment. The warm stimulus elicited increased neural response in the left somatosensory association cortex. Our results demonstrate a hitherto undiscovered sensory modality in a carnivoran species.
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| 6. |
- Elofsson, Rolf, et al.
(author)
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A complex sensory organ in the nose skin of the prosimian primate Lemur catta.
- 2015
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In: Journal of Morphology. - : Wiley. - 1097-4687 .- 0362-2525. ; 276:6, s. 649-656
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Journal article (peer-reviewed)abstract
- Most mammals have nose tips covered by glabrous skin, a labronasal area, or rhinarium. The surface of the rhinarium of Lemur catta has a dermatoglyphic pattern consisting of epidermal domes. Below the domes, epidermal pegs dip down into the dermis. In and below the tip of the epidermal peg, a complex sensory organ is found. It consists of an association of innervated Merkel cells, lamellate (Pacini-like) bodies with a central nerve, and a ring of unmyelinated nerve endings in the epidermis. The Merkel cells are situated basally in the epidermis and the lamellated bodies just below the epidermis. The unmyelinated nerve endings related to the organ ascend in a circle straight through the epidermis ending below the corneal layer. From these nerve terminals, horizontal spikes enter the keratinocytes. The three components occur together forming an organ and are innervated from a common nerve plexus. The morphology of the complex sensory organ of the lemur shares most crucial components with Eimer's organs in moles, echidna, and platypus, while some structures are lacking, for example, the specific central pillar of keratinocytes, the cuticular cap, and a central unmyelinated fiber. The presence of the essentials of an Eimer's organ in many mammals suggests that a wider definition is motivated. J. Morphol., 2015. © 2015 Wiley Periodicals, Inc.
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| 7. |
- Elofsson, Rolf, et al.
(author)
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A new type of somatosensory organ in the nasolabila skin of the dog
- 2020
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In: Journal of Morphology. - : Wiley. - 1097-4687 .- 0362-2525. ; 281, s. 413-419
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Journal article (peer-reviewed)abstract
- A new morphological type of somatosensory organ is described. It is found in the glabrous skin of the dog nose (rhinarium or planum nasale) and situated in dermis papillae. The otherwise thick epidermis forms a thin window above the organ. There are only a few layers of keratinocytes in the window and the corneocytes are much thinner than elsewhere. The organ consists of highly branching cells that wrap naked nerve endings emanating from myelinated nerve fibers originating in the outer dermal nerve plexus. The structure entirely fills the top of the dermal papilla. The intercellular spaces of the organ and its surroundings are occupied by an extended areolar basal lamina.
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| 8. |
- Elofsson, Rolf, et al.
(author)
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A novel ultrastructure on the corneocyte surface of mammalian nasolabial skin.
- 2016
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In: Journal of Mammalogy. - : Oxford University Press (OUP). - 0022-2372 .- 1545-1542. ; 97:5, s. 1288-1294
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Journal article (peer-reviewed)abstract
- In many mammals, the skin of the rhinarium includes a thick epidermal layer. The skin surface can be smooth but can also display a structure formed of domes, ridges, and polygonal areas: a dermatoglyphic or rhinoglyphic pattern. Each structure consists of an easily visible, large area of the epidermis. The abdominal epidermis may or may not have a dermatoglyphic pattern. The abdominal skin examined in our study had no pattern and was consequently unstructured and smooth. The ultrastructural surface pattern is formed in the granular and corneous regions of nasal epidermis by desmosome protrusions projecting into adjacent keratinocytes. Complete retraction of the keratinocyte protrusions with desmosomes in the abdominal epidermis creates an unstructured, smooth surface. The cornification process differs morphologically in nasolabial and abdominal skin. In this study, we report a novel structure in the nose skin. It is related only to the surface of a single corneocyte (keratinocyte) and consists of submicrometer pores or furrows, an ultrastructure pattern. It is not related to the rhinoglyphic pattern. The nose skin can thus have 2 unrelated patterns. This structure seems to be widespread among the Mammalia. We suggest the function of the structure is to keep the rhinarium evenly moist.
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| 9. |
- Elofsson, Rolf, et al.
(author)
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A variation of pigmentation in the glabrous skin of dogs
- 2018
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In: Journal of Morphology. - : Wiley. - 0362-2525. ; 279:8, s. 1194-1198
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Journal article (peer-reviewed)abstract
- The usual pigmentation pattern in mammalian skin consists of fixed melanocytes in the basal layer of the epidermis, supplying keratinocytes with melanosomes. We observed that the glabrous skin (rhinaria and footpads) of dogs deviates from this pattern. In dogs, melanocytes are found in both the dermis and epidermis. The epidermal melanocytes are situated in the intercellular spaces of the basal and spinous layers. They are characterized by a quantity of cytoplasm containing a centriole, also developing melanosomes, and in some cases annulate lamellae. There is a high frequency of closely apposed melanocytes in the epidermis. Melanosomes in different stages of formation are also abundant. The morphology of the glabrous skin of dogs suggests transport of melanocytes from the dermis into the epidermis and formation of melanosomes in the epidermis. A distributed and intense pigment formation may be necessary to achieve the black noses of many dog breeds and wild canids, as well as dark footpads despite heavy abrasion and rapid skin renewal.
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| 10. |
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