Scanning microscopy of pituitary vascular casts

Abstract

Vascular casts of the pituitary-median eminence complex from seventeen adult female rabbits were examined with the scanning electron microscope. The results of this study confirm the presence of a single capillary bed common to the entire neurohypophysis. Arterial supply to the rabbit pituitary is only to the neurohypophysis. A direct supply to adenohypophysis was not found. Within the median eminence there are an external and internal capillary plexus. The internal capillary plexus is directed toward the infundibular recess of the third ventricle. It does not receive a direct arterial supply but derives its blood supply from the external plexus before draining to the adenohypophysis. Vessels of the posterior median eminence are confluent with vessels of the infundibular stem. On the basis of these studies, it is proposed that the entire neurohypophysis, not simply the median eminence, serves as the final common pathway to the glandular pituitary. It is also proposed that in the median eminence, vessels are organized to deliver blood containing hypothalamic releasing and inhibiting hormones as well as posterior lobe neural hormones (antidiuretic hormone and oxytocin) to the ventricular surface for subsequent transport to cerebrospinal fluid and distribution to the brain.

Blood vascular bed of the rat pituitary intermediate lobe, with special reference to its development and portal drainage into the anterior lobe. A scanning electron microscope study of vascular casts.

“…This vascular route between the intermediate and anterior lobes (or within the adenohypophysis) satisfies a category of the portal system, and may be ref erect to as an "intra-adenohypophyseal portal system" in contrast to the well-known neuro-adenohypophyseal portal system which originates in the median eminence/neural stalk/neural lobe (posterior lobe) and enters, from rather external aspects, into the anterior lobe (Fig. 1, 2, Table 1) (GREEN, 1951(GREEN, ,1966PAGE et al, 1976;PAGE and BREGLAND, 1977). The intra-adenohypophyseal portal system and its relation to the neuro-adenohypohyseal portal system are schematically diagramed in Figure male adult rat, right-sided latero-ventral view).…”

A monomeric methyl and hydroxypropyl methacrylate injection medium and its utility in casting blood capillaries and liver bile canaliculi for scanning electron microscopy.

“…Scanning electron microscopy (SEM) of casted samples, now considered a standard method for studying microcirculation, has unraveled the microvascular organization of many tissues and organs which previously were only poorly visualized by conventional light or transmission electron microscopy (MURAKAMI, 1971(MURAKAMI, , 1972FUJITA and MURAKAMI, 1973;NOWELL and LOHSE, 1974;LAMETSCHWANDTNER and SIMONSBERGER, 1975;LEE and DEMPSEY,1976;PAGE et al, 1976;CANNON, 1978;MORRIS and CAMPBELL, 1978;HODDE and NOWELL, 1980;BHALLA et al, 1981;OHTANI et al, 1983;OLSON, 1983;ROGERS and CANNON, 1983). Many casting or injection media (polyester, latex, rubber, etc.…”

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“…10,[12][13][14][15][16][17] However, there are exceptions as follows. The common tree shrew cerebral arterial circle is formed by the anterior cerebral arteries, posterior communicating arteries, posterior cerebral arteries and internal carotid arteries.…”

“…It has also been shown in this study that the median eminence in the tree shrew is nourished by the internal and external capillaries plexi. These vascular plexi are also illustrated in the rat 10,4 , rabbit 17 and human. 11 The capillaries in this part the hypothalamus of the common tree shrew join together to form 15 to 20 small veins called "hypophysial portal vessels".…”

“…With this technique, the vascular patterns in the pituitary-median eminence complex have been studied in the rabbit 17 and rat 8,9 . This technique has also elucidated the vascular pattern in pituitary gland of common tree shrew (Tupaia glis) 18 , the animal regarded as a primitive primate.…”