Floor Of Third Ventricle Research Articles

Neural regeneration and neuronal migration following injury I. The endocrine hypothalamus and neurohypophyseal system

Central to this investigation are several basic hypotheses that are designed to test the role of nitric oxide (NO) in the complex process of central regeneration and plasticity in a well established model system of the mammalian brain. We have employed histochemical techniques at the light and ultrastructural level coupled with correlative scanning electron microscopy, ommunoelectron microscopy, and in situ hybridization in order to determine the functional significance of the increased expression of nitric oxide synthase (NOS) in neurons of the supraoptic (SON) and paraventricular (PVN) nuclei which accompanies regeneration of their axotomized neurites following hypophysectomy. The aim of this investigation was to determine the potential role and temporal up-regulation of NOS in this basic regenerative process and to establish the ultrastructural and neuroanatomical correlates during critical periods of regeneration and regrowth of SON and PVN axons following hypophysectomy in the endocrine hypothalamus of the rat. Our data support the hypothesis that NO may serve as a second messenger molecule that may act in some fashion to govern not only the process of central regeneration and regrowth of magnocellular (SON/PVN) axons into the median eminence, neural stem, and neural lobe (the neurohypophyseal system) but may also influence the regeneration of neurites into new neuroanatomical domains such as the adjacent lumen of the third cerebral ventricle. We have demonstrated a distinct temporal relationship between injury (axotomy) of SON/ PVN axons and the establishment of new neurovascular zones following hypophysectomy with the up-regulation of NOS. This up-regulation appears to correlate well with successful regeneration in the mammalian neurohypophyseal system. We have also successfully inhibited axonal regeneration with the use of nitroarginine, a competitive antagonist of NO. NOS up-regulation attendant to regeneration of SON and PVN axons may have inestimable clinical implications, particularly with respect to closed head injury and cerebral contusion that involves the mechanical shearing of the infundibular stalk. In addition, this investigation has reaffirmed that large numbers of bona fide neurons migrate and emerge upon the floor of the adjacent third cerebral ventricle shortly following hypophysectomy (within 2 weeks). The origin and mechanisms of neuronal migration and plasticity following hypohysectomy are the subject of interpretation and discussion in this investigation.

Pituitary Hemorrhage Extending into the Third Ventricle

A case of pituitary apoplexy causing pituitary hemorrhage with extension into the third ventricle is reported. The patient was a 73-year-old, obese female admitted with sudden onset of vomiting and impaired consciousness. Neurological examination revealed that she was stuporous, with marked neck stiffness and a dilated left pupil. A plain skull X-ray showed sellar enlargement and destruction of the dorsum sellae. Computed tomography demonstrated a high-density area in the third and lateral ventricles and a round, high-density mass in the suprasellar cistern. The patient died the next day. Autopsy revealed a large tumor in the sellar and suprasellar areas. The tumor and the hematoma within it compressed the floor of the third ventricle and passed through the lamina terminalis and the hypothalamic region. Histological examination disclosed a basophilic adenoma. The pituitary hemorrhage appeared to be the result of ischemia and necrosis within the pituitary adenoma caused by its acute expansion. The extension of the hematoma into the third ventricle was attributable to the large size of the tumor and its close adhesion to the floor of third ventricle.

Electron microscopic demonstration of a supraependymal cluster of neuronal cells and processes in the hamster third ventricle.

A supraependymal cluster of neuronal cells and processes consistently present on the floor of the hamster third ventricle was identified and characterized by means of correlative scanning (SEM) and transmission (TEM) electron microscopy. SEM revealed each cluster to be ovoid with the majority of its surface covered by dome-shaped protrusions and fine beaded fibers. A number of processes traveling individually or in groups also entered or exited from the cluster at its base. As these processes passed over the ventricular surface, they contributed to an extensive network on the floor and ventral aspect of the ventricular wall. Some processes terminated on the ependymal surface in bulbous endings while others penetrated the ependyma. The neuronal nature of these clusters and their associated processes was confirmed at the TEM level. The dome-shaped protrusions visible on the surface of the cluster in SEM corresponded to apical surfaces of neurons confined to the peripheral aspect of a core of loosely arranged processes. These cells exhibited a prominent nucleolus, stacks of rough endoplasmic reticulum (RER), polyribosomes, Golgi cisternae, mitochondria and microtubules (MT) and gave rise to dendritic processes which extended into the core. These dendrites gave off branches at acute angles and contained polyribosomes, single cisternae of RER and evenly spaced MT. Other profiles of processes within the core shared these characteristics, suggesting that they also were branches of the peripheral cells. Axons present within the core and on the cluster's surface exhibited vesicle-filled varicosities which frequently established synaptic contact with the peripheral cells and their processes. The presence of an intraventricular cluster of neurons which potentially communicates with centers extrinsic to the ventricle may have important implications in the hypothesized role of cerebrospinal fluid and tanycytic ependyma in the neuroendocrine regulation of anterior pituitary function.

The sheep third ventricle: scanning electron microscopy of estrous, anestrous and estrogen-progesterone-treated anestrous ewes.

Surface features of the third ventricle in estrous, anestrous and anestrous estrogen-progesterone (E2+P)-treated ewes were examined with scanning electron microscopy (SEM). To ensure uniformly good preparations, a procedure for rapid perfusion of sheep brains was developed as well as the use of critical point drying. Ependymal surfaces on the dorsal aspects of the lateral walls as viewed by SEM were heavily ciliated while the ventral aspect of the lateral walls and ventral floor were not. In all groups, the appearance of the lateral walls was similar while that of the ventral floor-median eminence appeared to vary with the absence or presence of gonadal steroids. In estrous ewes there were numerous stubby microvilli and miniblebs on ependyma of the ventrolateral wall-floor, many of which are presumed to be tanycytes. This contrasted with the appearance of similar regions in anestrous ewes where there were patchy smooth bare areas on ependymal surfaces with fewer microvilli and small surface protrusions. Anestrous E2+P-treated ewes showed an appearance intermediate between the other two groups. The SEM data support a correlation between reproductive status and the relative presence or absence of surface modifications on the ventral floor of the sheep third ventricle.

Effects of unilateral section of the brain stem after mesial cerebral incision.

Recently, seven young, healthy chimpanzees were subjected to an experimental surgical procedure known as mesial cerebral incision.! This procedure consists of incision and separation of corpus callosum, lamina terminalis, floor of third ventricle, pineal region, pons, cerebellum, and medulla oblongata. Actually, it is staged in two parts. The first, a parasagittal craniotomy, provides access to corpus callosum, the third ventricle and its floor, as well as the pineal regions. In this first stage, the diaphragma sellae can be visualized if care is taken during the incision of the third ventricular floor (FIGURE 1). Some time after recovery, a suboccipital craniectomy is performed (FIGURE 2). This is the second stage of mesial cerebral incision and provides exposure of vermis and medulla, both of which are incised under direct vision (FIGURE 1). The pons must be separated indirectly through the rostral apex of the suboccipital craniectomy on the caudal part of the exposure provided in stage 1. The basilar artery can be felt pulsating at the lowest extremity of this incision. In all stages and parts of mesial cerebral incision, gentle blunt separation of white fibers with the Sachs dissector permits almost bloodless access to the various anatomical levels and structural areas. For example, the dissector is introduced into the full depth of the callosum through a small incision in the pia. Then it is drawn slowly backward (or forward) with pressure sufficient to separate the white fibers but not to tear blood vessels. The resistance of the latter is greater, and, with some practice, vessels can be spared in a series of fenestrations while the surrounding fibers are clearly and cleanly cut. Five more chimpanzees have undergone this procedure since the original report, bringing the total to twelve. The techniques of mesial cerebral incision have been extended by microdissection in the macaque so as to expose the contents of the third ventricle and thus expose the anterior and mesial parts of the thalamus.2 Thereafter, the rostral thalamus was sucked out by micropipette. This local unilateral microexcision resulted in a chronic epileptic animal, which has been described in detail by Milhorat and Baldwin.2,3 The primates subjected to mesial cerebral incision recover promptly and can return to usual cage or run activity within ten days after either operative stage. These chimpanzees have exhibited normal bilateral synergistic motor activity except in two cases, in which a monoparesis of right or left upper extremity occurred. Five such animals that did not show any neurological deficit after mesial cerebral incision were also subjected to unilateral incisions of the brain stem on right or left sides. The incision was made just below the inferior colliculus and calculated so as to extend to, but not across, the midline, while sparing the cerebral peduncle. In order to accomplish this brain-stem section, the animal was carefully anesthetized with endotracheal halothane and, after shaving of the head, was postured for a left (or right) occipitoparietal craniotomy. Following aseptic preparation, the scalp was infiltrated with 111,500 nupercaine solution containing

Third ventriculostomy by puncture of the lamina terminalis and the floor of third ventricle.

Third ventriculostomy by puncture of the lamina terminalis and the floor of third ventricle.

Symposium on pituary tumours (4) Unusual pathological features

Some aspects of tumour pathology in the pituitary region are discussed. Material from 83 cases of anterior lobe tumours is reviewed and the range of histological appearances illustrated. The massive suprasellar extension of the chromophobe adenomas, often more to one side than the other, is stressed. Eosinophil and basophil adenomas were encountered infrequently. Of the tumours of the posterior lobe, a few gliomas have been described, whilst those resembling in structure the infundibulum, involve the pituitary stalk and adjacent floor of the third ventricle, into which they protrude. Intrasellar and suprasellar cystic tumours form the third group in this review and evidence is presented confirming the similarity in pathogenesis of craniopharyngioma to other intracranial epidermoids.