Biomaterial Database

Endogenous control of spinule formation in horizontal cells of the teleost retina. 1983

R H Douglas, and H J Wagner

The process of horizontal cells invaginating teleost cone pedicles are studded with small finger-like projections which are present only in the light-adapted state. The aim of this study was to investigate whether the formation and degradation of these so-called spinules, which are thought to function as feed-back synapses onto the cones, is endogenously controlled. Three types of experiment were carried out involving fish entrained to a 12 h light/dark cycle: 1) The number of spinules was determined in goldfish at various times during exposure to either constant darkness (36 h) or constant light (57 h). 2) The time course of spinule formation and degradation in goldfish was investigated following exposure to light or darkness at various times during the light/dark cycle. 3) The time course of flash-induced spinule formation in tench following dark adaptation at noon was compared to that following dark adaptation at midnight. The results of these experiments show that spinule formation and degradation are partially under endogenous control but that they need light and full expression. This endogenous rhythm is reflected in the time courses of spinule formation and breakdown during different phases of the light/dark cycle.

UI	MeSH Term	Description	Entries
D008027	Light	That portion of the electromagnetic spectrum in the visible, ultraviolet, and infrared range.	Light, Visible,Photoradiation,Radiation, Visible,Visible Radiation,Photoradiations,Radiations, Visible,Visible Light,Visible Radiations
D012160	Retina	The ten-layered nervous tissue membrane of the eye. It is continuous with the OPTIC NERVE and receives images of external objects and transmits visual impulses to the brain. Its outer surface is in contact with the CHOROID and the inner surface with the VITREOUS BODY. The outer-most layer is pigmented, whereas the inner nine layers are transparent.	Ora Serrata
D002940	Circadian Rhythm	The regular recurrence, in cycles of about 24 hours, of biological processes or activities, such as sensitivity to drugs or environmental and physiological stimuli.	Diurnal Rhythm,Nyctohemeral Rhythm,Twenty-Four Hour Rhythm,Nycthemeral Rhythm,Circadian Rhythms,Diurnal Rhythms,Nycthemeral Rhythms,Nyctohemeral Rhythms,Rhythm, Circadian,Rhythm, Diurnal,Rhythm, Nycthemeral,Rhythm, Nyctohemeral,Rhythm, Twenty-Four Hour,Rhythms, Circadian,Rhythms, Diurnal,Rhythms, Nycthemeral,Rhythms, Nyctohemeral,Rhythms, Twenty-Four Hour,Twenty Four Hour Rhythm,Twenty-Four Hour Rhythms
D003624	Darkness	The absence of light.	Darknesses
D005399	Fishes	A group of cold-blooded, aquatic vertebrates having gills, fins, a cartilaginous or bony endoskeleton, and elongated bodies covered with scales.
D006054	Goldfish	Common name for Carassius auratus, a type of carp (CARPS).	Carassius auratus
D000222	Adaptation, Physiological	The non-genetic biological changes of an organism in response to challenges in its ENVIRONMENT.	Adaptation, Physiologic,Adaptations, Physiologic,Adaptations, Physiological,Adaptive Plasticity,Phenotypic Plasticity,Physiological Adaptation,Physiologic Adaptation,Physiologic Adaptations,Physiological Adaptations,Plasticity, Adaptive,Plasticity, Phenotypic
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia