Electron microscopical morphometry of GH producing pituitary adenomas in comparison with normal GH cells

Summary GH producing adenomas of patients with acromegaly (undifferentiated acidophil adenomas and well differentiated GH cell adenomas) were studied at the ultrastructural level and analysed morphometrically by the point counting method. They were compared with identically prepared GH cells of normal pituitaries from patients undergoing surgery for metastasizing cancer of the prostate. In the well differentiated GH cell adenomas significantly more points were counted on nucleoli, unorganized cytoplasm, rough endoplasmic reticulum, immature secretory granules, Golgi areas and on the plasma membranes, than in normal GH cells. Comparison of normal GH cells with tumour cells in undifferentiated acidophil adenomas demonstrated significantly larger volumes of nuclei, rough endoplasmic reticulum, Golgi fields, immature secretory granules and of the cell membranes, and also of nucleoli and of the mitochondria. Secretory granules and lysosomes were observed more frequently than in normal GH cells. In a comparison of both adenoma types, the well differentiated acidophil adenomas contained significantly larger volumes of the unorganized cytoplasm, secretory granules and of cell membranes, whereas more points were counted on the rough endoplasmic reticulum and on the mitochondria in undifferentiated acidophil adenomas. The differences between the normal GH cells and the GH cell in undifferentiated adenomas (mainly larger nucleoli, larger volumes of the rough endoplasmic reticulum and the lower volumes of secretory granules) indicate a higher secretory activity in the adenomas. The significant differences between the well differentiated and the undifferentiated adenomas (mainly the increased volumes of mitochondria and of the unorganized cytoplasm in the undifferentiated tumours) indicate a lower grade of differentiation and may be interpreted as signs of increased proliferation.This publication contains results from the thesis submitted by Karin Rübenach-Gerz (Hamburg 1986)Dedicated to Prof. Dr. Klaus-Joachim Hempel on the occasion of his 60th birthday     

Electron microscopical morphometry of pituitary adenomas. Comparison of tumours in acromegaly and hyperprolactinemia

By electron microscopical morphometry (point counting method) 4 groups of adenomas were compared in order to identify the source of prolactin in hyperprolactinemia. The 4 types of adenomas were characterized by the following features: Group I: acromegaly without hyperprolactinemia (GH positive and PRL negative on the immunohistochemical level); Group II: acromegaly with hyperprolactinemia and/or galactorrhea (GH positive and PRL positive on the immunohistochemical level); Group III: adenomas with hyperprolactinemia without acromegaly (GH negative and PRL positive on the immunohistochemical level); Group IV: adenomas with hyperprolactinemia without acromegaly (GH and PRL negative on the immunohistochemical level). Morphometry was performed in order to analyse the relative amount of the following cellular structures: nuclei, nucleoli, rough endoplasmic reticulum, Golgi fields, immature secretory granules, mature secretory granules, lysosomes, mitochondria, unorganized cytoplasm, and cellular membranes. Significant differences (Student t-test, Wilcoxon test; 2 p less than 0.05) were found for the following compartments: rough endoplasmic reticulum and Golgi fields in group III had significantly larger volumes than in group IV. The volume of secretory granules of group II and group IV was larger than of group III. The volume of mitochondria of group IV was larger than in group I, and it was larger in group I and group III than in group II. Despite these differences a distinctive morphometrical pattern of the different subgroups could not be established. The quantitative data are valuable for interpretation of high or low functional activity but not for differential diagnoses. Therefore, if only the source of PRL in hyperprolactinemia has to be identified, immunocytochemistry is the best and simpler method.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ultrastructural morphometry of the rat pituitary intermediate zone after stimulation and suppression

The intermediate zone of the rat pituitary was studied after stimulation for 3 weeks with the adrenostatic drugs metyrapone and aminogfutethimide and after suppression for 3 weeks with the glucocorticoid 6α-methylprednisolone using morphometry by the point-counting method on electron micrographs. After metyrapone, intermediate cells showed a significant (P <.05) increase in volume percentages of the smooth endoplasmic reticulum, the Golgi apparatus, and the lucent immature secretory granules, as well as a significant decrease in the lucent secretory granules, the vacuoles, the lysosomes, and the cell membranes in comparison with the untreated controls. After aminoglutethimide, the volume percentages of the nuclei, the smooth endoplasmic reticulum, and the dense and lucent immature secretory granules were significantly increased in comparison with the controls, whereas the unorganized cytoplasm, the lucent secretory granules, the vacuoles, and the lysosomes were significantly decreased. The morphological changes after both adrenostatic drugs clearly indicate the pathophysiologically expected increase of secretory activity. After 6α-methyfprednisolone, the rough endoplasmic reticulum, the vacuoles, and the lysosomes significantly decreased in comparison with the controls, and the smooth endoplasmic reticulum, the Golgi fields, and the immature secretory granules were increased. These changes cannot be interpreted without certain reservations as the first alterations indicate decreased activity, whereas the increased Golgi fields and immature secretory granules are usually signs of increased secretory activity, which cannot be expected after glucocorticoid treatment. The possible causes are discussed.     

Ultrastructural morphometry of different adrenal adenoma types

Twelve surgical specimens of adrenal tumors (3 mainly compact cell adenomas and 2 mainly spongiocytic adenomas of Cushing’s syndrome, 4 adenomas of Conn’s syndrome, 1 androgen-secreting adenoma, and 2 hormonally inactive tumors) were studied by ultrastructural morphometry, using the point-counting method. All groups were compared with regard to the statistical differences among the different cell organelles. Compact cell adenomas and spongiocytic adenomas in Cushing’s syndrome revealed differences in the volume fraction of the following cell organefles: nuclei, smooth endoplasmic reticulum, mitochondria, Golgi zones, and unorganized cytoplasm, as well as in the fraction of lipid vacuoles. Compact cell adenomas in Cushing’s syndrome were different from Conn’s adenomas with respect to nuclei, smooth endoplasmic reticulum, rough endoplasmic reticulum, lysosomes, Golgi zones, and unorganized cytoplasm. Spongiocytic adenomas in Cushing’s syndrome were different from adenomas in Conn’s syndrome with respect to organized cytoplasm and lysosomes. Further data are given concerning the differences between Cushing’s syndrome, adenomas in androgen-producing tumors, and inactive tumors. The statistically significant data were correlated with the functional expression of the different tumors. The morphometric studies confirmed the visually established ultrastructural features of adrenal tumors and provided further significant differences. Finally, these examinations obviously yielded specific patterns of the different adrenal adenoma types.     

Light and electron microscopical morphometry of pituitary adenomas in hyperprolactinemia

Two highly differentiated acidophil prolactin-cell adenomas with hyperprolactinemia (group I), 8 large cell chromophobe adenomas with hyperprolactinemia (group II), and 2 small cell chromophobe adenomas (group III), one of which was combined with hyperprolactinemia, were studied immunohistologically. Morphometry was performed on the light- and electron microscopical level. The 11 active adenomas were immunohistologically positive for prolactin, the 12th adenoma with normal prolactin plasma level was negative for prolactin. Light microscopical morphometry displayed significantly more cells of smaller size in the "small cell chromophobe" adenomas, whereas the large cell chromophobe adenomas and the highly differentiated prolactin cell adenomas were not different. Ultrastructural morphometry demonstrated significant differences between highly differentiated prolactin cell adenomas (group I), and large cell chromophobe adenomas (group II). The latter contain smaller "relative volumes" of nucleoli and of secretory granules, whereas the rough endoplasmic reticulum, the Golgi fields and the nuclei were not different. Comparison of large cell chromophobe adenomas (group II), and small cell chromophobe adenomas (group III) revealed significantly larger relative volumes of nuclei and of mitochondria but smaller volumes of rough endoplasmic reticulum and of Golgi fields in the small cell chromophobe adenomas. Significant differences between the active and the inactive adenoma of small cell chromophobe type in the group III were not found. In spite of the low quantity of small cell chromophobe adenomas and of acidophil prolactin cell adenomas, our data demonstrate that there exist distinct and significant light microscopical and ultrastructural differences between the three adenoma types.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pituitary adenomas with hyperfunction of TSH

Summary In a collection of 564 surgically removed pituitary adenomas, 4 cases were found to have had elevated TSH plasma levels. One of these tumors (case 1) could be classified as a highly differentiated mucoid TSH cell adenoma presenting histochemical reactions typical of, as well as electron microscopical features identical to, normal TSH cells. Immunoenzymatic studies failed to demonstrate TSH in the tumor cells. Two further adenomas (case 2 and 3) were similarly structured in many areas, but showed regions of poorer differentiation in which cells with distinct pleomorphism, irregular secretory granules, increased numbers of ribosomes and a well developed rough endoplasmic reticulum were present. In 10% of the tumor cells GH could be demonstrated immunoenzymatically, but there was no TSH. The fourth adenoma was an undifferentiated acidophilic adenoma showing pleomorphic cells having slight acidophil and partly mucoid granulations. The ultrastructure showed convoluted nuclei, increased numbers of free ribosomes as well as abundant rough endoplasmic reticulum and secretory granules which were different in size and number but distinctly of the TSH cell type. Immunoenzymatically, TSH was found in some cells, with GH in more cells. Endocrinologically, elevated levels of GH were measured in cases 2, 3 and 4 with LH being increased in case 1. Clinical and morphological correlations are discussed.Supported by the Sonderforschungsbereich 34 (Endocrinology) of the Deutsche ForschungsgemeinschaftDedicated to Professor Dr. Gerhard Seifert on the occasion of his 60th birthday     

Ultrastructural localization of prolactin in the human pituitary prolactinomas and its changes by bromocriptine treatment

Fourteen human prolactinomas, four of which received bromocriptine treatment, were studied by immunoelectron microscopy to observe the intracellular localization of prolactin (PRL). In the untreated cases two different patterns of PRL localization were noted. In the first type (Type I) PRL was seen in Golgi saccules, single stacks of rough endoplasmic reticulum (RER), and a few secretory granules and in the second type (Type II) it was present in the predominant parallel arrays of RER. Type II cells were observed more frequently in the cases with higher serum prolactin levels. In the treated cases with normalized serum prolactin levels, the tumor cells showed accumulation of secretory granules. This finding suggested secretory inhibition. RER and Golgi saccules were inconspicuous in these cells and this might indicate decreased production of PRL. In a case which was resistant to the bromocriptine treatment, most tumor cells were similar in ultrastructural localization of PRL to those cells in the untreated cases and this might suggest the lack of dopamine receptor.     

Heterogeneity of the MtTW15 mammosomatotropic tumor. II. Characterization of parenchymal cells by superimposition immunocytochemistry and electron microscopy

Large MtTW₁₅ tumors, which secrete growth hormone (GH) and prolactin (PRL), are composed of ovoid, elongated, and angular cells which demonstrated interdigitating processes and junctional complexes. The majority of the cells were essentially agranular, but two types of granulated cells were identifiable. One class of granulated cells contained moderate to sparse populations of round dense-cored granules measuring up to 250 nm in diameter. Rod-shaped to filamentous mitochondria with an electron-dense matrix were characteristic of a second class of granulated cells with pleomorphic granules of various sizes and electron densities. Images of exocytotic release of the round dense-cored granules were frequently seen, but were not observed with the pleomorphic granules, many of which were judged to be lysosomes. Superimposition immunocytochemistry revealed hormones only in the granulated cells with round to ovoid granules. Morphometry indicated that hormone specific subpopulations of tumor cells can be identified since PRL secretory granules were significantly smaller than GH secretory granules (149 ± 6 nm for PRL versus 221 ± 9 nm for GH, P < 0.001). The vast majority of immunopositive cells contained only GH or PRL, but a few were observed containing both hormones. Ovoid to irregular-shaped nuclei, large lipid inclusions, numerous free ribosomes and polyribosomes, moderate development of the rough endoplasmic reticulum, and prominent Golgi profiles were characteristics of all cell types. Irrespective of the presence or absence of cytoplasmic granular elements, particles resembling viruses were encountered in many tumor cells, and these frequently appeared to be budding into the cisternae of the endoplasmic reticulum.     

Morphology of a GHRH producing pancreatic islet cell tumour causing acromegaly

Summary A 54 year old woman suffered from acromegaly due to a pancreatic islet cell tumour producing GHRH. The tumour was demonstrated on CT scan. The diagnosis was established from elevated plasma levels of GHRH, GH and prolactin, and by the lack of signs of a pituitary adenoma in trans-sphenoidal surgery. Acromegaly was cured by tumour removal. Light microscopically, the tumour showed a medullary and microlobular pattern. The cells were large and often cuspidal. Small granules were found in semi-thin sections. Small aggregations of amyloid fibres were seen, mostly around capillaries. Immunocytochemistry revealed GHRH, NSE, neurotensin, serotonin, VIP and PP. S 100 was positive only in nerve fibres. Staining for GH, ACTH, calcitonin, -HCG,-HCG, insulin, glucagon, gastrin, substance P, bombesin and somatostatin was negative. Ultrastructure showed oval partly lobulated nuclei with small nucleoli, moderate amounts of rough endoplasmic reticulum, many free ribosomes, some large Golgi fields and small numbers of secretory granules measuring 150 nm or, in a few cells, 650 nm.Only 4 other cases of pancreatic endocrine tumours causing acromegaly by ectopic GHRH secretion are described in the literature and these were similar to our case in many respects.     

Prolactin-secreting adenomas. A light and electron microscopical study.

The microscopical and ultrastructural findings in twenty-five prolactin-secreting pituitary adenomas removed by transsphenoidal surgery have been analyzed and compared with previously published cases. Under the light microscope, these adenomas could easily be confused with chromophobe adenomas. However, in eight cases a small number of cells contained erythrosinophilic granules of the type found in prolactin cells. Electron microscopical study of the tumor cells showed scarce secretory granules frequently undergoing exocytosis, a prominent rough endoplasmic reticulum, and a large Golgi area containing immature granules. Cytoplasmic bundles and aggregates of filaments, as well as myelin figures and glycogen within the mitochondria were occasionally found. Comparison with prolactin cells during lactation, in pituitary autografts, and under in vitro stimulation shows that the tumor cells are actively secreting.     

Propylthiouracyl-induced hypothyroidism results in reversible transdifferentiation of somatotrophs into thyroidectomy cells. A morphologic study of the rat pituitary including immunoelectron microscopy

Two-month-old female Fischer-344 rats were rendered hypothyroid by ingestion of propyl-thiouracyl (PTU) (0.1% in drinking water) and sacrificed 3, 7, 14, and 28 days after the start of PTU administration as well as 3, 7 and 14 days after interruption of a 14-day PTU treatment. Controls received no PTU. The pituitaries were studied by histology, immunohistochemistry, electron microscopy, and immunoelectron microscopy, using the immunogold double-labeling technique. In the course of hypothyroidism, pituitary thyrotrophs had undergone the well-known thyroidectomy change. In addition, a contingent of growth hormone (GH) cells lost their large secretory granules, enlarged, displayed progressive dilation of rough endoplasmic reticulum, thereby transforming into thyroidectomy cells. These bihormonal thyrosomatotrophs contained gH in their secretory granules and thyrotropin in the dilated rough endoplasmic reticulum as documented by the immunogold double-labeling method for GH and thyrotropin. After discontinuation of PTU treatment, a rapid increase in size, number and GH labeling of secretory granules and simultaneous involution of distended rough endoplasmic reticulum with reduction of thyrotropin labeling took place in thyrosomatotrophs. A practically complete restitution of normal pituitary structure was seen in 2 weeks. Results implicate that, contrary to previously accepted concepts, adenohypophysial cells may not be irreversibly committed to one morphologically recognizable cell line.     

Pituitary chromophobe adenomas consisting of prolactin cells

Summary Morphologic studies of pituitary neoplasms removed by surgery from 36 human patients revealed 8 chromophobe adenomas which differed clearly from the remaining tumors. The cytoplasm of the adenoma cells failed to stain with PAS, aniline blue, aldehyde fuchsin, aldehyde thionin, orange G or light green, but positively stained granules were found by using erythrosine or carmoisine. Immunoperoxidase technique disclosed the presence of prolactin in the cytoplasm of some adenoma cells. The adenoma cells exhibited distinct ultrastructural features such as well developed rough surfaced endoplasmic reticulum with Nebenkern formation, prominence of Golgi apparatus, presence of misplaced exocytosis as well as pleomorphism of secretory granules with a considerable variation of size ranging from 130 to 500 nm in diameter. Thus, by electron microscopy the adenoma cells showed a close resemblance to prolactin cells of the non-tumorous pituitary glands except for the reduced size and number of secretory granules.These chromophobe adenomas are regarded as representing a distinct pathological entity clearly distinguishable from other forms of pituitary neoplasms. In view of the morphologic findings and the elevation of blood prolactin level (measured in 3 patients) the term, sparsely granulated prolactin producing pituitary adenoma, appears to be the most appropriate one to designate these tumors.The authors wish to thank Dr. H. Friesen for providing the anti-human prolactin and Dr. L. A. Sternberger for the peroxidase-anti-peroxidase complex. The excellent technical assistance of Mrs. Gezina Ilse and Miss Nancy Macphail and the valuable secretarial help of Mrs. Maureen Rowling are appreciated.The work was supported in part by MA-552 grant of the Medical Research Council of Canada and by the St. Michael's Hospital Research Society.     

Sparsely granulated prolactin cell adenomas of the pituitary gland

Summary The possible relationship between the preoperative plasma prolactin levels of patients having a sparsely granulated prolactin cell adenoma of the pituitary gland and the morphology of the tumors was studied by means of quantitative electron microscopy. To this end, a number of ultrastructural variables were chosen which are generally regarded to be indicative of cellular activity and which could be determined in a quantitative or semiquantitative way. These variables were determined in 19 adenomas from 17 patients and plotted against the corresponding prolactin levels. It appeared that marked endocrine activity was associated with a small number of granules per cell, a high frequency of exocytosis, and a marked development of the rough endoplasmic reticulum. Granule size and development of Golgi apparatus and lysosomes were not at all, or only poorly correlated with the plasma hormone levels. Finally, the number of mitochondria per cell showed a totally unexpected inverse correlation with endocrine activity. Due to the close mutual correlation existing between several of the variables investigated, combining them in a multivariate analysis did not significantly improve the correlation with the hormone level.     

Immunhistochemical and electron microscope analysis of adenomas of the thyroid gland

Summary Histological, immunhistochemical and electronmicroscopic studies of 12 human, scintigraphically cold, thyroid adenomas with specific cytological differentiation identified four different cell types: oxiphil cell, clear cell, ergastoplasm-rich cell and mitochondrion-rich cell.The oxiphil tumor cell can be recognized light-microscopically by its large size and its eosinophilic granular cytoplasm. Most of these cells do not produce thyroglobulin. The ultrastructural characteristics of oxyphil cells are principally mitochondria in great numbers and many large lysosomes. Clear cell adenomas show a trabecular growth pattern. The tumor cells have an abundance of cytoplasm which contains small acidophilic granules. Immunhistochemically we were able to demonstrate thyroglobulin in small amounts within cytoplasmic granules and more extensively within the follicle lumina. Electronmicroscopically we observed a large number of smooth surfaced vacuoles of varying size, extraordinary large lysosomes and occasional cisternae of rough endoplasmic reticulum, the latter probably corresponding to the immune-histochemically identified thyroglobulin granules. The ergastoplasm-rich-cell adenomas, which to the best of our knowledge have not been previously described, show a predominantly micro-to normofollicular architecture histologically without intrafollicular colloid. The cytoplasm of the ergastoplasm-rich cells reveales a strong positive thyroglobulin-staining reaction. The fine structure of these cells is characterized by the abundance of cisternae of the rough endoplasmic reticulum. The mitochondrion-rich-cell adenomas exhibited a microfollicular structure with an intensive acidophilic granular staining at the basal part of the tumor cells. Immunhistochemically and electronmicroscopically we found some morphologic and functional features which differentiate these cells from the oxyphil cell. Thyroglobulin was located predominantly in the apical portion of the cytoplasm in the mitochondrion-rich cells without sharp demarcation from the luminar thyroglobulin. Electron microscopically fewer basal and laterally located mitochondria were seen in mitochondrion-rich cells compared with oxyphil cells. As we could not find any sign of functional activity in the oxyphilic, clear cell and ergastoplasm-rich cell adenomas we analysed those aspects of the lysosomal system not concerned with the enzymatic digestion of thyroglobulin.     

The ultrastructure of the pars intermedia and the subdivision of its glandular cells in the young sheep pituitary

The ultrastructures of the pituitary pars intermedia of 11 male sheep about 1-13 months of age were observed. The following cells were distinguished in the sheep pars intermedia: pars intermedia glandular cells, marginal cells, interstitial cells, follicular cells, pars distalis-like granular cells, degenerating cells and mast cells. The pars intermedia glandular cells contain a well-developed Golgi apparatus and many mitochondria. The secretory granules had various densities and sizes (100-425 nm in diameter). No image of exocytosis was found. The pars intermedia glandular cells were classified into the following three subtypes: "PI-I, PI-II and PI-III type cells." PI-I type cells contain rather few secretory granules, but their rough endoplasmic reticulum is well developed in parallel arrays. PI-II type cells contain a few secretory granules, and the rough endoplasmic reticulum consists of scattered short strands. PI-III type cells contain abundant secretory granules of high density mixed with a few granules with low density. The rough endoplasmic reticulum is scattered strands. This type of cell was distinguished from granular cells like those of the pars distalis, although the granular cells also contained many dense granules. The marginal cells contacted the glandular cells directly, not being separated by a basal lamina. The degenerating cells were filled with myelinated lysosomes. Mast cells were often found in the interlobular connective tissue.     

Ultrastructural morphometry of prolactin secreting adenomas treated with dopamine agonists

19 macroprolactinomas and 1 microprolactinoma were analysed by light microscopical, immunohistological and ultrastructural as well as morphometrical methods. 8 adenomas were removed from patients who were treated preoperatively with bromocriptine and/or Lisurid for different periods. 18 of 20 adenomas were positive for PRL on the immunohistological level. One case was negative. This patient showed a good response to the pharmacological treatment. The ultrastructure of this case revealed many secretory granules. A morphometric analysis of the ultrastructure could be performed in 19 cases; 1 case had to be excluded because of large necrotic areas. The following qualitative significant alterations after the treatment could be established: Reduction of the volume density of the rough endoplasmatic reticulum; Reduction of the size of the granula diameter; Increase of the volume density of the more irregular and indented nuclei. Other alterations were as follows: Reduction of the nuclear size; Increase of the number of secretory granules and of the volume density of lysosomes. These changes were to be observed in most of those tumors which responded to the dopamine agonist treatment. The non-responding adenomas and one which was removed 6 days after having discontinued a successful preoperative medical therapy were similar to the untreated adenomas. The results display the influence of dopamine agonist on the hormone synthesis, release and degradation in PRL secreting adenoma cells.     

Quantitative changes in the morphology of the aging canine prostate

Stereological methods at the light and electron microscopic levels were used to examine the morphological changes in the beagle prostate associated with increasing age and with the occurrence of spontaneous benign hyperplasia. Analyses of semithin sections of tissue embedded in plastic revealed that proliferation of prostatic glandular and stromal components, increase in epithelial cell numbers, and increase in epithelial cell size all contributed to the dramatic increase in prostate weight seen in aging dogs. Analyses at the electron microscopic level revealed that the volume densities of rough endoplasmic reticulum and secretion granules were significantly lower in epithelial cells of the immature prostate than in the prostate of mature dogs (greater than 1.5 years of age). In contrast, no significant differences were seen in the volume densities of rough endoplasmic reticulum, free ribosomes, secretion granules, smooth endoplasmic reticulum, or mitochondria in randomly selected prostatic epithelial cells of dogs 1.5 to 9 years of age, whether or not the prostates were hyperplastic.     

Estrogen-induced hyperplasia and neoplasia in the rat anterior pituitary gland. An immunohistochemical study

Diethylstilbestrol (DES) treatment of weanling F344 female rats resulted in enlarged pituitary glands and diffuse pituitary prolactin (PRL) cell hyperplasia in all animals after 9 and 12 weeks of treatment. Serum PRL was significantly greater than in control rats (P less than 0.001). Immunohistochemical studies showed that most of the pituitary gland cells consisted of PRL cells. Ultrastructural studies showed increased numbers of PRL cells with hyperplasia of the rough endoplasmic reticulum and decreased numbers of secretory granules. There was a decrease in the relative number of growth hormone (GH) and other cell types in the anterior pituitary. Pituitary tumors and normal pituitary glands were dissociated with trypsin and maintained in culture for 3 weeks. The numbers of PRL and GH cells decreased with time in both groups, and there was an increase in the number of fibroblasts. Staining of the culture cells with neuron-specific enolase showed that the anterior pituitary cells were positive for this enzyme, while the fibroblastic cells were negative. When dissociated pituitary cells were cultured in the presence of 10(-9) M DES for 7 days, there was a 42% increase in the number of immunoreactive PRL cells. These results indicate that DES-treated rats provide an excellent model for study of the in vivo and in vitro regulation of pituitary hyperplasia and neoplasia.     

Secretory process in Brunner's glands during recovery from stimulation with a single dose of pilocarpine

The secretory pathway and kinetics of the secretory process were studied in Brunner's glands of mice after stimulation of secretion with a parasympatho-mimetic drug. Adult male mice were injected with pilocarpine, while unstimulated controls received saline. The animals were subsequently administered an intravenous injection of 3H-threonine, and tissue was prepared for electron microscope autoradiography at intervals ranging from 5 minutes to 2 hours after injection of the radioactive precursor. Stimulation with pilocarpine resulted in discharge of secretory granules, which was reflected in a significantly lower percentage of the cell volume occupied by granules. In both control and stimulated mice, at 5 minutes after injection of 3H-threonine, the highest percentage of silver grains was found over the rough endoplasmic reticulum. The proportion of silver grains over the rough endoplasmic reticulum declined at later intervals, and a peak of labeling was observed over the Golgi apparatus at 1 hour. Labeling of the secretory granules increased in the 1- and 2-hour samples from both control and stimulated mice, although the relative concentration of radioactivity in both Golgi-associated and apical secretory granules was greater in stimulated than control glands at 1 hour. The results suggest that the secretory protein produced by Brunner's glands was synthesized by the rough endoplasmic reticulum and transported to the Golgi apparatus where secretory granules were formed in both stimulated and control glands. Depletion of secretory granules by prior stimulation resulted in no change in the kinetics of arrival of radioactivity in the cell organelles involved in the secretory process. However, the drainage of the radioactive label from the rough endoplasmic reticulum was significantly slower in the stimulated glands than in the controls. The existence of two subcompartments within the rough endoplasmic reticulum is among the possible explanations for the latter observation.