Histology and fine structure of the pre-optic nucleus and hypothalamic tracts of the European eel Anguilla anguilla L

1969 ◽  
Vol 256 (804) ◽  
pp. 135-145 ◽  
Keyword(s):  
Electron Microscopy ◽  
Anterior Margin ◽  
Third Ventricle ◽  
Anguilla Anguilla ◽  
Structural Features ◽  
Ependymal Cells ◽  
European Eel ◽  
The Third ◽  
Secretory Products

The pre-optic nucleus and hypothalamic tracts of intact and hypophysectomized specimens of the European eel Anguilla anguilla L. have been studied in situ and by optical and electron microscopy. The in situ technique reveals a hitherto unsuspected degree of segregation of the neurosecretory axons which form up to five discrete tracts having separate origins and following distinct paths before converging, at the level of the anterior margin of the pituitary, to form a median tract. The structure of the pre-optic neurons, as revealed by several different techniques, is described and it is shown that their synthetic poles, identified by a prominent cap of endoplasmic reticulum, are precisely orientated towards the third ventricle and are separated from it by, at most, two or three layers of ependymal cells. Electron microscopy shows that the secretory products lie mainly in the axonal ends of the cells though in Bouin-fixed, wax-embedded material the entire perikaryon stains with neurosecretory dyes and this, and their proximity to the third ventricle, gives the impression that they secrete into the latter, as well as centripetally. This may well be so, but from the work described below it seems more likely that these neurons receive nutrients, or stimuli, or both, from the third ventricle. Two types of pre-optic neurons, separable by structural features as well as by the size of the elementary granules they contain have been identified; these probably give rise to two of the fibre types identified in the neurohypophysis of the eel by Knowles & Vollrath. Aggregations of neurosecretion, common in the fish pre-optic nucleus, and also, much rarer, colloid vesicles, are described and discussed.

General concepts of hypothalamus-pituitary anatomy

2011 ◽  
pp. 71-81
Author(s):  
Ignacio Bernabeu ◽  
Monica Marazuela ◽  
Felipe F. Casanueva
Keyword(s):  
Median Eminence ◽  
Third Ventricle ◽  
Optic Chiasm ◽  
Perivascular Space ◽  
Ependymal Cells ◽  
The Third ◽  
Long Time ◽  
Central Grey Matter ◽  
Imaginary Line ◽  
The Brain

The hypothalamus is the part of the diencephalon associated with visceral, autonomic, endocrine, affective, and emotional behaviour. It lies in the walls of the third ventricle, separated from the thalamus by the hypothalamic sulcus. The rostral boundary of the hypothalamus is roughly defined as a line through the optic chiasm, lamina terminalis, and anterior commissure, and an imaginary line extending from the posterior commissure to the caudal limit of the mamillary body represents the caudal boundary. Externally, the hypothalamus is bounded rostrally by the optic chiasm, laterally by the optic tract, and posteriorly by the mamillary bodies. Dorsolaterally, the hypothalamus extends to the medial edge of the internal capsule (Fig. 2.1.1) (1). The complicated anatomy of this area of the central nervous system (CNS) is the reason why, for a long time, little was known about its anatomical organization and functional significance. Even though the anatomy of the hypothalamus is well established it does not form a well-circumscribed region. On the contrary, it is continuous with the surrounding parts of the CNS: rostrally, with the septal area of the telencephalon and anterior perforating substance; anterolaterally with the substantia innominata; and caudally with the central grey matter and the tegmentum of the mesencephalon. The ventral portion of the hypothalamus and the third ventricular recess form the infundibulum, which represents the most proximal part of the neurohypophysis. A bulging region posterior to the infundibulum is the tuber cinereum, and the zone that forms the floor of the third ventricle is called the median eminence. The median eminence represents the final point of convergence of pathways from the CNS on the peripheral endocrine system and it is supplied by primary capillaries of the hypophyseal portal vessels. The median eminence is the anatomical interface between the brain and the anterior pituitary. Ependymal cells lining the floor of the third ventricle have processes that traverse the width of the median eminence and terminate near the portal perivascular space; these cells, called tanycytes, provide a structural and functional link between the cerebrospinal fluid (CSF) and the perivascular space of the pituitary portal vessels. The conspicuous landmarks of the ventral surface of the brain can be used to divide the hypothalamus into three parts: anterior (preoptic and supraoptic regions), middle (tuberal region), and caudal (mamillary region). Each half of the hypothalamus is also divided into a medial and lateral zone. The medial zone contains the so-called cell-rich areas with well-defined nuclei. The scattered cells of the lateral hypothalamic area have long overlapping dendrites, similar to the cells of the reticular formation. Some of these neurons send axons directly to the cerebral cortex and others project down into the brainstem and spinal cord.

Further observations on Calliacantha Leadbeater (Choanoflagellata), with special reference to C. simplex sp. nov. from many parts of the world

1979 ◽  
Vol 204 (1156) ◽  
pp. 287-300 ◽  
Keyword(s):  
Electron Microscopy ◽  
Type Species ◽  
Structural Features ◽  
Transmission Electron ◽  
The World ◽  
Functional Implications ◽  
Range Of Variation ◽  
A New Species ◽  
Whole Mounts

C. simplex is a new species with an unusually wide geographical range, occurring at sea temperatures as varied as 0°C under ice at Pt Barrow or – 1°C in arctic Canada, to 22°C on the equator at the Galapagos Islands. The morphology and range of variation are illustrated by means of light microscopy, transmission electron microscopy and scanning electron microscopy applied to dry whole mounts prepared in situ from freshly-gathered wild material. Among the diagnostic structural features, special interest attaches to the position of the anterior transverse costa which is located unusually far back in comparison with other members of the genus; it is also shown to be within and not outside the ring of four longitudinal costae building up the lorica chamber, although this feature can only be ascertained by scanning. The differences between this species and C. natans (type species of the genus) are shown to be greater and to involve more characters than could previously have been recog­nized, and some possible functional implications are discussed in a preliminary way.

scholarly journals Scanning and Transmission Electron Microscopy of the Ependymal Lining of the Third Ventricle

1974 ◽  
Vol 1 (1) ◽  
pp. 59-73 ◽  
Author(s):  
J.E. Bruni
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Third Ventricle ◽  
Three Dimensional ◽  
Single Layer ◽  
Ependymal Cells ◽  
Ultrastructural Studies ◽  
The Third ◽  
Functional Involvement ◽  
Scanning Electron

SUMMARYIn its simplest form, the ependyma of the third ventricle consists of a single layer of cuboidal cells. Although these typical mural cells constitute the greater part of the lining of the ventricle, a specialized variety of ependymal cell (the tanycyte) can also be distinguished within circumscribed areas of the ventricular wall. Although such cells are found scattered throughout the dorsoventral extent of the third ventricle, they are particularly numerous along the ventrolateral walls and floor. The regional variation in the surface morphology of the ventricle walls as evident with the scanning electron microscope is consistent with this pattern of tanycyte distribution. Ultrastructural studies have established that the tanycyte is a fundamentally distinct cell with a long basal process extending into the subjacent neuropil and frequently directed toward a capillary wall. This unique morphology conforms closely to its three-dimensional appearance as demonstrated with the scanning electron microscope. The significance of ependymal tanycytes particularly of the third ventricle derives largely from the connections they establish between the ventricular lumen and vasculature of the median eminence. This intriguing structural relationship has led to the suggestion that ependymal cells and cerebrospinal fluid of the third ventricle may be involved in the regulation of adenohypophysial activity. Evidence indicating the functional involvement of specialized ependymal cells in the neuroendocrine control of pituitary activity is reviewed.

scholarly journals Infant satiety depends on transient expression of cholecystokinin-1 receptors on ependymal cells lining the third ventricle in mice

2013 ◽  
Vol 591 (5) ◽  
pp. 1295-1312 ◽  
Author(s):  
Tomoya Ozaki ◽  
Shahid Mohammad ◽  
Eri Morioka ◽  
Soichi Takiguchi ◽  
Masayuki Ikeda
Keyword(s):  
Transient Expression ◽  
Third Ventricle ◽  
Ependymal Cells ◽  
The Third
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