Biomaterial Database

Light and electron microscopic study on the pineal complex of the coelacanth, Latimeria chalumnae Smith. 1977

M A Hafeez, and M E Merhige

The pineal complex of the coelacanth, Latimeria chalumnae was studied light and electron microscopically. It consists of two vesicles representing parapineal and pineal organs. Both occur intracranially and openly communicate with each other and the brain ventricle. The entire complex shows a striking photoreceptor morphology with sensory, ependymal and nerve cells. The last cell type is more abundant in the parapineal vesicle than in the pineal organ. The following ultrastructural details of the parapineal are noteworthy: 1. The sensory cells possess large inner and outer segments protruding freely in the vesicular cavity. The outer segments measure 8-10 mum in length and consist of as many as 275 lamellae. The basal processes of these cells terminate in neuropil-like regions. Occasionally, dense granules (500-1000 A) of uncertain identity occur in the perinuclear and inner segment cytoplasm of the cells. 2. The supporting cells are of the ependymal type. Their cytoplasm contains a filamentous feltwork and pinocytotic vesicles, but lacks secretory granules. Cytosomes are particularly abundant in cell processes in the neuropil-like zones. The basal end-feet of these cells isolate the receptor and nerve cells from the perivascular space. 3. In the neuropil-like regions, terminals of sensory cells make synaptic contacts with neuronal dendrites. Synaptic ribbon-like profiles in the terminals characterize the contact zones. Only unmyelinated nerve fibers could be observed in the small area of the tissue examined. The results are discussed with regard to photoreceptive and secretory functions of the pineal complex and its evolution in lower vertebrates.

UI	MeSH Term	Description	Entries
D008854	Microscopy, Electron	Microscopy using an electron beam, instead of light, to visualize the sample, thereby allowing much greater magnification. The interactions of ELECTRONS with specimens are used to provide information about the fine structure of that specimen. In TRANSMISSION ELECTRON MICROSCOPY the reactions of the electrons that are transmitted through the specimen are imaged. In SCANNING ELECTRON MICROSCOPY an electron beam falls at a non-normal angle on the specimen and the image is derived from the reactions occurring above the plane of the specimen.	Electron Microscopy
D009474	Neurons	The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the NERVOUS SYSTEM.	Nerve Cells,Cell, Nerve,Cells, Nerve,Nerve Cell,Neuron
D010786	Photoreceptor Cells	Specialized cells that detect and transduce light. They are classified into two types based on their light reception structure, the ciliary photoreceptors and the rhabdomeric photoreceptors with MICROVILLI. Ciliary photoreceptor cells use OPSINS that activate a PHOSPHODIESTERASE phosphodiesterase cascade. Rhabdomeric photoreceptor cells use opsins that activate a PHOSPHOLIPASE C cascade.	Ciliary Photoreceptor Cells,Ciliary Photoreceptors,Rhabdomeric Photoreceptor Cells,Rhabdomeric Photoreceptors,Cell, Ciliary Photoreceptor,Cell, Photoreceptor,Cell, Rhabdomeric Photoreceptor,Cells, Ciliary Photoreceptor,Cells, Photoreceptor,Cells, Rhabdomeric Photoreceptor,Ciliary Photoreceptor,Ciliary Photoreceptor Cell,Photoreceptor Cell,Photoreceptor Cell, Ciliary,Photoreceptor Cell, Rhabdomeric,Photoreceptor Cells, Ciliary,Photoreceptor Cells, Rhabdomeric,Photoreceptor, Ciliary,Photoreceptor, Rhabdomeric,Photoreceptors, Ciliary,Photoreceptors, Rhabdomeric,Rhabdomeric Photoreceptor,Rhabdomeric Photoreceptor Cell
D010870	Pineal Gland	A light-sensitive neuroendocrine organ attached to the roof of the THIRD VENTRICLE of the brain. The pineal gland secretes MELATONIN, other BIOGENIC AMINES and NEUROPEPTIDES.	Epiphysis Cerebri,Pineal Body,Corpus Pineale,Gland, Pineal,Pineal Bodies,Pineal Glands
D004805	Ependyma	A thin membrane that lines the CEREBRAL VENTRICLES and the central canal of the SPINAL CORD.	Ependymas
D005075	Biological Evolution	The process of cumulative change over successive generations through which organisms acquire their distinguishing morphological and physiological characteristics.	Evolution, Biological
D005399	Fishes	A group of cold-blooded, aquatic vertebrates having gills, fins, a cartilaginous or bony endoskeleton, and elongated bodies covered with scales.
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
D013569	Synapses	Specialized junctions at which a neuron communicates with a target cell. At classical synapses, a neuron's presynaptic terminal releases a chemical transmitter stored in synaptic vesicles which diffuses across a narrow synaptic cleft and activates receptors on the postsynaptic membrane of the target cell. The target may be a dendrite, cell body, or axon of another neuron, or a specialized region of a muscle or secretory cell. Neurons may also communicate via direct electrical coupling with ELECTRICAL SYNAPSES. Several other non-synaptic chemical or electric signal transmitting processes occur via extracellular mediated interactions.	Synapse