Linked Life Data

9394501

Source:http://linkedlifedata.com/resource/pubmed/id/9394501

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:dateCreated
1998-3-3
pubmed:abstractText
The topography and spectral characteristics of mammalian photoreceptors correlate with both, the present ecological demands and the evolutionary history. The South American Opossum is a marsupial mammal with unspecialized habitus and crepuscular lifestyle. A sparse population of cones (max. = 3000/mm2) can be differentiated into four subtypes by morphological, topographical and immunocytochemical criteria. In spite of this unusual diversity the cone types can be split into two functional groups: The population of single cones labeled by antibody OS-2 for short wavelength sensitive pigments was ubiquitous but at very low densities (200/mm2). The single cones labeled by antibody (COS-1) against long wavelength sensitive pigments constitute the dominant population in the area centralis (2300/mm2). These two single cone types correlate with the pair typically present in placental mammals. Discrimination of spatial and color contrast may be provided by this "modern" set. The COS-1 labeled double and single cones bearing an oil droplet, display a different pattern by being restricted to the inferior (non-tapetal) half of the retina (max = 800/mm2). This additional set of cones with oil droplets and long wavelength pigments is a conservative feature of the opossum retina and other marsupials. As an accessory cone system it is possibly providing enhanced sensitivity at mesopic conditions. During the early evolution of nocturnal mammals with its prominent expansion of rod vision these cone types were conserved but then were lost in placental mammals. Thus the unique features of mammalian retinas are the result of two evolutionary steps: first a reduction of cone based vision, followed by a secondary differentiation of photopic vision and behaviour relying on the remaining set of cones.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:status
MEDLINE
pubmed:month
Dec
pubmed:issn
0034-7108
pubmed:author
pubmed:issnType
Print
pubmed:volume
56 Su 1 Pt 2
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
199-207
pubmed:dateRevised
2010-11-18
pubmed:meshHeading
pubmed:year
1996
pubmed:articleTitle
The opossum photoreceptors--a model for evolutionary trends in early mammalian retina.
pubmed:affiliation
Department of General & Comparative Physiology, School of Medicine, University of Vienna, Austria.
pubmed:publicationType
Journal Article, Review, Research Support, Non-U.S. Gov't