Structural changes, related to reproduction, in the hypothalamus and in the pars tuberalis of the rhesus monkey: Part I. The hypothalamus. Part II. The pars tuberalis

Abstract

Certain cells lining a circumscribed area of the III ventricle of the rhesus monkey differ from those cells which constitute the characteristic ependymal lining of the brain. The specialized cells studied comprise a number of types which differ in their structure, ultrastructure and staining affinities; all demonstrate features which are generally associated with active secretion and/or absorption. A group of such cells, which form a limited area of the latero-ventral walls of the anterior hypothalamus, have long processes which extend to the walls of the blood vessels in the median eminence. The evidence indicates that many of these cells, here described as Type B or tanycyte cells, secrete their products into the primary capillary network of the pituitary portal system. Another group of cells, here described as Type C and C' cells are found in a slightly more posterior position lining the floor of the ventricle; as yet there are no indications that these may secrete into blood vessels in the median eminence. Some of the specialized cells lining the III ventricle (Types B and C') showed changes in relation to reproductive activity: No such changes were observed in Type C cells nor in the characteristic ependymal cells (Type A) found elsewhere. Studies on normal and experimental male and female monkeys showed that Type B tanycyte cells differed in males and females and altered during the menstrual cycle in the female. Following ovariectomy these cells showed regressive changes but returned to a normal appearance after a single injection of oestradiol. In view of the close spatial relationship of the tanycyte ependyma to cells of the pars tuberalis it was interesting to note that pars tuberalis cells also altered in relation to the menstrual cycle. The evidence presented accords with the view that certain cells which line the III ventricle of the brain and have prolongations extending to pituitary blood vessels, thus linking the cerebrospinal fluid and the blood system in the region of the pituitary, may play a role in the regulation of pituitary function and thereby constitute an important neuro-endocrine system.

Cell organization of the rat pars tuberalis. Evidence for open communication between pars tuberalis cells, cerebrospinal fluid and tanycytes

“…A subpopulation of β 1 tanycytes crosses the basal lamina and establishes cell-to-cell contact with PT-specific secretory cells. A similar finding has been reported in an early study carried out in the rhesus monkey by Knowles and Kumar (1969). β Tanycytes have the capacity to transport compounds from the ventricular CSF to the perivascular space of the portal capillaries (Peruzzo et al 2004;Rodríguez et al 2005) and, consequently, to the intercellular channels of the PT; β tanycytes are also known to secrete, through their basal processes, biologically active compounds such as β-transforming growth factor, prostaglandin E2 or the specific protein p85 (Rodríguez et al 2005;Blázquez et al 2002;Ojeda et al 2008).…”

Cerebrospinal Fluid and Ependymal Neurophysin

“…6 (area of upper arrow at ventricle, Fig. 4 (36,37). Our studies demonstrate the specific presence of neurophysin in the CSF, in the tanycytes of the infundibular recess, in the tanycyte processes, and in the external palisade layer of the median eminence.…”

“…The studies of several investigators (33)(34)(35)(36)(37)(38) suggest that these specialized ependymal cells may play a neuroendocrine role by providing a pathway from the CSF of the third ventricle to the hypothalamic portal system. It has been shown that vasopressin placed in the third ventricle of the dog had a significant effect on adrenocortical steroid output (presumably by stimulating the release of ACTH) whereas 10 times that dose by peripheral vein had no effect (35 (33,36) have traced the tanycyte processes from the surface of the third ventricle to their termination in close proximity FIGURE 7 Ciliated ependyma of the same section shown in Fig. 6 (area of upper arrow at ventricle, Fig.…”

The Cerebrospinal Fluid as a Pathway in Neuroendocrine Integration

“…This ependyma has large bulbous protrusions projecting into the infundibular recess and the basal processes of these cells appear to contact the portal capillaries of the median eminence and the secretory cells of the pars tuberalis. Sexual differences in this type of ependyma have been found by Kumar (1968) and Knowles & Kumar (1969), who have also described cyclic changes in this ependyma of the female rhesus monkey and have related them to the menstrual cycle.…”