Morphological restoration of gonadotrope population by thymulin gene therapy in nude mice.

The integrity of the thymus during the first week of life is necessary for a proper maturation of the pituitary-gonadal axis as revealed by the significantly reduced levels of circulating gonadotropins in congenitally athymic (nude) mice. In the present work we studied the impact of athymia and the effect of neonatal thymulin gene therapy on the pituitaries of adult nude mice. Also circulating thymulin and gonadotropin levels were evaluated. We used an adenoviral vector expressing a synthetic gene for the thymic peptide thymulin (metFTS) termed RAd-FTS. On postnatal day 1, each experimental heterozygous (nu/+) and homozygous (nu/nu) pup of both sexes received a single bilateral i.m. injection of RAd-FTS or RAd-GFP/TK, a control vector expressing green fluorescent protein. On postnatal days 51-52, mice were bled and sacrificed, their pituitaries were immediately dissected, fixed and immunostained. Morphometry was performed by means of an image analysis system. The following parameters were calculated: volume density (VD: cell area/reference area), cell density (CD: number of cells/reference area), and cell size (expressed in microm(2)). Serum thymulin levels were measured by a bioassay and gonadotropin levels were assayed by RIA. It was observed that neonatal thymulin gene therapy in the athymic mice restored their serum thymulin levels and prevented the reduction in circulating gonadotropin levels. The histometrical analysis revealed that the treatment prevented the reduction in gonadotrope CD and the VD in athymic mice. Our data suggest that thymulin gene therapy may be an effective strategy to approach reproductive deficits associated with endocrine thymus dysfunction.

Morphometric and ultrastructural analysis of different pituitary cell populations in undernourished monkeys.

Undernutrition elicited by a low-protein diet determines a marked reduction of hypophyseal activity and affects the function of the respective target organs. The objective of the present investigation was to study the ultrastructural and quantitative immunohistochemical changes of the different pituitary cell populations in undernourished monkeys that had been previously shown to have significant changes in craniofacial growth. Twenty Saimiri sciureus boliviensis monkeys of both sexes were used. The animals were born in captivity and were separated into two groups at one year of age, i.e., control and undernourished animals. The monkeys were fed ad libitum a 20% (control group) and a 10% (experimental group) protein diet for two years. Pituitaries were processed for light and electron microscopy. The former was immunolabeled with anti-GH, -PRL, -LH, -FSH, -ACTH, and -TSH sera. Volume density and cell density were measured using an image analyzer. Quantitative immunohistochemistry revealed a decrease in these parameters with regard to somatotrophs, lactotrophs, gonadotrophs and thyrotrophs from undernourished animals compared to control ones. In these populations, the ultrastructural study showed changes suggesting compensatory hyperfunction. On the contrary, no significant changes were found in the morphometric parameters or the ultrastructure of the corticotroph population. We conclude that in undernourished monkeys the somatotroph, lactotroph, gonadotroph, and thyrotroph cell populations showed quantitative immunohistochemical changes that can be correlated with ultrastructural findings.

Morphometric and ultrastructural analysis of different pituitary cell populations in undernourished monkeys

Undernutrition elicited by a low-protein diet determines a marked reduction of hypophyseal activity and affects the function of the respective target organs. The objective of the present investigation was to study the ultrastructural and quantitative immunohistochemical changes of the different pituitary cell populations in undernourished monkeys that had been previously shown to have significant changes in craniofacial growth. Twenty Saimiri sciureus boliviensis monkeys of both sexes were used. The animals were born in captivity and were separated into two groups at one year of age, i.e., control and undernourished animals. The monkeys were fed ad libitum a 20 percent (control group) and a 10 percent (experimental group) protein diet for two years. Pituitaries were processed for light and electron microscopy. The former was immunolabeled with anti-GH, -PRL, -LH, -FSH, -ACTH, and -TSH sera. Volume density and cell density were measured using an image analyzer. Quantitative immunohistochemistry revealed a decrease in these parameters with regard to somatotrophs, lactotrophs, gonadotrophs and thyrotrophs from undernourished animals compared to control ones. In these populations, the ultrastructural study showed changes suggesting compensatory hyperfunction. On the contrary, no significant changes were found in the morphometric parameters or the ultrastructure of the corticotroph population. We conclude that in undernourished monkeys the somatotroph, lactotroph, gonadotroph, and thyrotroph cell populations showed quantitative immunohistochemical changes that can be correlated with ultrastructural findings

Sexual dimorphism in the age changes of the pituitary lactotrophs in rats.

It is known that aging is associated with alterations in hypothalamic and pituitary functions. In the present study, we have undertaken a quantitative immunohistochemical assessment of the lactotroph cell population as well as prolactin (PRL) secretion, in male and female rats of different ages. Pituitaries from young (3 months), old (20 months) and senescent (29 months) male and female Sprague-Dawley rats were processed for the immunohistochemical detection of lactotrophs. Serum PRL was measured by a homologous RIA. Additionally, the in vitro PRL secretory activity was estimated by perifusion of pituitary cells from senescent animals. Analysis of morphometric parameters revealed age-related changes of PRL cell population in animals of both sexes. The cell density (CD), surface density (SD) and volume density (VD) decreased with age in both male and female rats. However, CD as well as SD appeared to have increased in females when compared to males, either in young or old animals, while VD was higher only in old females. The pituitaries of senescent females displayed chromophobic microadenomas on a background of diffuse PRL cell hyperplasia. Prolactin serum levels showed a marked increase with age in females, but only a modest elevation in males. In senescent females, PRL production per cell was reduced. We conclude that in rats, there exists a clear sexual dimorphism in the age-related changes of pituitary PRL cells.