Cerebrospinal fluid (CSF) is generally considered to be derived from plasma through a combined process of ultrafiltration and secretion by the choroid plexus. However, the mechanisms ultimately responsible for achieving the final protein composition of CSF are uncertain. Some proteins, in particular prealbumin, are present in quantities not easily explained by usual physicochemical considerations. To investigate the possibility of de novo synthesis by choroid epithelium, we have examined human choroid plexus an ependyma for the presence of prealbumin. Using the peroxidase-antiperoxidase method at the light and electron microscopic level, as well as immunofluorescence, we localized prealbumin in choroid epithelial cytoplasm on the endoplasmic reticulum and in association with the Golgi apparatus. Ependymal cells and stroma did not reveal immunocytochemical labeling. These findings indicate that the choroid plexus epithelium contributes to the final CSF composition by de novo protein synthesis.

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The concentration of gamma globulins is greatly increased in the cerebrospinal fluid (CSF) during inflammatory and degenerative disorders of the central nervous system (CNS). The mechanism by which immunoglobulins enter the CSF under normal conditions is unknown. The extent of participation of the blood-brain barrier in protein delivery to the CSF is unclear, although the choroid plexus is known to have primary responsibility for the formation and movement of certain proteins into the CSF. To investigate the role of the choroid plexus in immunoglobulin delivery to the CSF, the authors evaluated rat brain tissue by light and electron microscopic immunohistochemical technique using the peroxidase technique of immunoglobulin (Ig)G and IgA detection. Peanut agglutinin was used to identify macrophages, cells known to have important immune functions and which have been reported as a normal component of the choroid plexus. Antisera to IgG' and IgA demonstrated diffuse surface staining of the choroidal epithelial cells with light and electron microscopy; the cytoplasm and nuclei did not contain immunoglobulins. Macrophages were not present in the choroid plexus, in contrast to previous reports. The results demonstrate that immunoglobulins do not enter the CSF via the choroid plexus, unlike other proteins in similar concentrations in the CSF. In addition, macrophages are shown to be an insignificant component of the plexus, thereby further diminishing the likelihood of participation-of the choroid plexus in the regulation of immunoglobulin entry into the CNS under normal conditions.

The authors observed the clinical course of 24 women with surgically removed prolactinomas for a mean postoperative interval of 62 months. The frequency of late tumor recurrence and probable factors responsible for the recurrence were investigated. Hyperprolactinemia recurred in 4 of 13 patients with microadenomas (31%) 3 to 9 months after removal. In the macroadenoma group, relapse of hyperprolactinemia occurred in 10 of 11 patients (91%), an average of 26 months after the initial postoperative return to normal prolactin levels. Return of hyperprolactinemia was accompanied by radiologic evidence of tumor recurrence in all patients with macroadenoma, and in one patient with microadenoma. Of 12 tumors in which adjacent dura was available for histopathologic examination, 7 showed dural invasion. Although these seven patients had significantly higher preoperative levels of serum prolactin than the five without dural invasion, there was no significant relation between dural involvement and tumor recurrence. The probabilities of tumor recurring from multifocal adenoma or paraadenomatous lactotrope hyperplasia could not be assessed using our surgical material. The most plausible reason for the high recurrence rate of prolactinomas after apparent surgical cure, in the absence of defined anatomic abnormalities within the pituitary, is a functional abnormality of hypothalamic-pituitary control resulting from a primary hypothalamic disorder.

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