Immunoelectron microscopy of corticotropes and melanotropes in the pituitary gland of the European ferret, Mustela putorius furo

The superimposition technique and protein A-gold method of immunoelectron microscopy were employed to study the ultrastructure of corticotropes as well as melanotropes in the ferret pituitary gland. This is the first study ever elucidating the ultrastructural heterogeneity of melanotropes in mammalian pars intermedia on an immunocytochemical basis. Morphological heterogeneity of pars distalis corticotropes has also been elucidated. It is suggested that the different subtypes may represent stages of development (histogenesis), or functional phases of a single cell type. In addition, the occurrence and distribution of both corticotropes and melanotropes in different hypophyseal components have been studied by light-microscopic immunocytochemistry.

The fine structure of dexamethasone-induced growth hormone cells in the anterior pituitary gland of the rat fetus

The effect of synthetic glucocorticoid, dexamethasone (DEX), on the fine structure of the fetal growth hormone (GH) cell was examined in rats on Days 17-19 of gestation by the protein A-gold method of immuno-electron microscopy. GH cells appeared on Day 19 in the control fetuses. The DEX-induced GH cells of Day 17 fetuses displayed more immature features than those of Day 18, which closely resembled GH cells found in the control fetus on Day 19. Cytological changes which indicate increased secretory activity such as the development of the rough endoplasmic reticulum or enlargement of the Golgi complex, and an accumulation of secretory granules were evident only in the DEX-treated fetuses on Day 19. It is concluded that DEX not only accelerates the development of GH cells, as observed on Day 17 or 18, but also brings them to a functionally stimulated state by Day 19.

Growth hormone and nutrition interact to regulate expressions of kidney IGF-I and IGFBP mRNAs

The effects of growth hormone (GH) and fasting on renal insulin-like growth factor-I (IGF-I) and IGF-binding proteins (IGFBP)-1, -2, -3, -4, -5 were examined in spontaneous dwarf rats (SDR) which have a complete and specific lack of GH among pituitary hormones. Renal expression of the mRNA which encodes IGF-I was reduced in these rats, and IGFBP-1 and IGFBP-4 were found to be elevated. Administration of GH restored expression of IGF-I and IGFBP-1 mRNA, suggesting that GH is, among other pituitary hormones, more specifically associated with renal expression of these genes. The elevation in the IGFBP-4 mRNA level, however, was not attenuated by GH administration, indicating that this hormone may not be directly related to the regulation of expression of this gene. Fasting for 48 hours resulted in a reduction of IGF-I mRNA and an increase in IGFBP-1 mRNA in SDRs as well as in normal rats, suggesting that a cause other than a reduced serum GH is responsible for these fasting-induced changes. Fasting resulted in little change in levels of other IGFBP-2, -3, -4, -5 mRNAs. When these results were compared with those obtained using liver, IGFBP mRNA expression was shown to be regulated differently in different tissues. Based on our finding that IGFBP-1 modulates the mitogenic action of IGF-I, a full understanding of nutrition-related growth processes in the kidney must take this relationship into consideration as well as that which exists between GH and IGF-I.

Tubular hypertrophy due to work load induced by furosemide is associated with increases of IGF-1 and IGFBP-1

We have examined the expression of insulin-like growth factor 1 (IGF-1), IGF binding protein-1 (IGFBP-1), and IGF binding protein-3 (IGFBP-3) in the rat distal nephron during increased cell work load and hypertrophy, induced by the diuretic, furosemide. Furosemide was given for six days to increase distal sodium delivery and uptake. To mitigate salt loss, the animals drank 0.8% NaCl and 0.1% KCl. Control rats were infused with vehicle (0.9% saline) and drank tap water. Furosemide increased urinary volume (13-fold) and sodium excretion (eightfold), and decreased urine osmolarity (fourfold). By immunocytochemistry, staining for IGF-1 and IGFBP-1 was markedly increased in distal convoluted tubules and cortical collecting ducts; both segments also underwent hypertrophy. Increased staining for the peptides was evident early (1 hr, 18 hr) after furosemide, prior to hypertrophy of cells. Whereas transcripts of IGF-1 and IGFBP-3 mRNA showed little or no increase in extracts from furosemide-treated kidney cortices, IGFBP-1 mRNA was increased threefold 18 hours after furosemide. Alterations of IGF-1 and IGFBP-1 were independent of changes in plasma aldosterone, glucocorticoids or arginine vasopressin. That IGFBP-1 mRNA increased threefold without significant changes in IGF-1 mRNA suggests that hypertrophic stimuli might initially induce the synthesis of IGF binding protein followed by the trapping of extracellular IGF-1. The present study raises the possibility of IGF-1 and IGFBP-1 being involved in processes that lead to tubular hypertrophy. IGFBP-1 may regulate these effects by binding to and interaction with IGF-1.

Regulation of growth hormone expression in fetal rat pituitary gland by thyroid or glucocorticoid hormone

The regulation of growth hormone (GH) cell development by thyroid and glucocorticoid hormones in the fetal rat pituitary gland was examined. Dexamethasone (Dex) treatment of dams induced GH and GH mRNA accumulation in the fetal pituitary gland on day 17 or 18 of gestation when substantial GH expression has not yet occurred in the control fetus. The additional thyroxine injections apparently enhanced the effect of Dex, whereas it exhibited no effect when given alone. The reduction of fetal thyroid hormone level by methimazole suppressed either the Dex induction of GH expression on day 18 or the spontaneous onset of GH expression on day 19 of gestation. The results suggest that 1) thyroid hormone exerts its stimulatory action on fetal GH gene expression only in the presence of glucocorticoid, 2) this synergistic action of these two hormones is evident as early as day 17 of gestation, and 3) rapid maturation of GH cells seen on day 19 in the normal fetus is considered to be induced by concomitant increase in both serum thyroid and glucocorticoid hormone levels.

Intrauterine growth retardation due to growth hormone deficiency in rats

The effect of growth hormone (GH) on fetal growth was examined in the spontaneous dwarf rat (SDR) with the isolated GH deficiency. A 328-bp GH gene fragment containing the site of SDR mutation was amplified from fetal liver genomic DNA using PCR and digested with restriction enzyme SauI to distinguish the fetal genotype. When heterozygote (dr/+) males and females were crossed, a significant reduction in body weight of dr/dr fetuses was observed on days 20 and 21 (92 and 89% that of +/+ fetuses, respectively). Body weight reduction was also noticed on day 21 in dr/dr fetuses (80%) in comparison with that of dr/+ fetuses crossed from dr/dr females and dr/+ males. Unexpectedly, the body weight of dr/+ fetuses was found to be significantly less than that of +/+ fetuses on days 19 (94%) and 20 (97%), which reached the level of +/+ fetuses by day 21 of gestation. The fetal tail length was not affected by the GH status. These results provide direct evidence for the involvement of pituitary GH in the regulation of fetal body weight during late gestation, but not in fetal skeletal growth.

IGF-I and IGF-binding protein gene expressions in spontaneous dwarf rat

Effects of growth hormone (GH) and fasting on hepatic expressions of insulin-like growth factor I (IGF-I) and IGF-I-binding protein (IGFBP)-1, -2, -3, and -4 were examined in spontaneous dwarf rats (SDR), which completely and specifically lack GH among pituitary hormones. The hepatic expressions of mRNA encoding IGF-I and IGFBP-3 were reduced and IGFBP-1 mRNA was elevated in the SDR. Both chronic and acute administration of GH restored these changes, indicating the association of GH but not other pituitary hormones with hepatic expressions of these genes. In addition, the present examination revealed that mRNA level of IGFBP-2 was elevated in SDR, which could not be attenuated by exogenous GH, and that GH may not be directly relevant to the regulation of hepatic IGFBP-4 expression. Fasting for 2 days reduced IGF-I mRNA level and increased IGFBP-2 mRNA level in the SDR, as well as in the normal rat, suggesting the presence of factors other than reduced serum GH responsible for fasting-induced alteration in the expression of these mRNAs. On the other hand, fasting resulted in little change or even a reduction of IGFBP-1 mRNA level in the SDR.

Bone dysplasia in a child born to parents with osteogenesis imperfecta and pseudoachondroplasia

We report on a boy born to a mother with pseudoachondroplasia and a father with osteogenesis imperfecta (Sillence type III). At birth, the boy was found to have osteogenesis imperfecta type III. Although clinical findings of pseudoachondroplasia were not manifested at the age of 8 months, roentgenographic findings showed characteristics of pseudoachondroplasia in addition to those of osteogenesis imperfecta. He died of respiratory distress at age 15 months.

Cell function during chondrogenesis and osteogenesis induced by bone morphogenetic protein enclosed in diffusion chamber. Biochemical studies on native products derived from outside differentiating cells

A diffusion chamber containing rabbit bone morphogenetic protein (BMP) was implanted in the abdominal muscle of a Sprague-Dawley rat. Outside of the chamber, cartilage differentiated one to two weeks after implantation, and bone replaced the cartilage three to four weeks after implantation. The interstitial fluid inside the chamber contained only biologic substances produced by cells proliferating and differentiating outside of the chamber. To investigate the cell function during chondrogenesis and osteogenesis, alkaline phosphatase activity and the amounts of S-100 alpha protein, S-100 beta protein, creatine kinase subunits M (CK-M), creatine kinase subunits B (CK-B), hyaluronic acid (HA), and chondroitin sulfate (CS) were measured in the supernatant of interstitial fluid inside the chamber. Alkaline phosphatase activity increased two to four weeks after implantation. The amount of S-100 beta protein acutely increased during the fourth week. The amount of CK-B also increased during the fourth week. The increased levels of HA and CS were also observed after two to four weeks. The examination of such native products may help not only to clarify the mechanisms of cartilage and bone development, but also to develop a sensitive bioassay for BMP.

A case of bilateral dysplasia epiphysealis hemimelica associated with polydactyly and syndactyly

Dysplasia epiphysealis hemimelica (DEH) on bilateral medial malleoli occurred in a boy who had polydactylies and syndactylies of all four limbs. Cases with both bilateral and symmetrical DEH affection as in this case seem not to have been reported previously in the literature. Dysplasia epiphysealis hemimelica complicated by congenital anomalies is extremely rare. A one-month-old boy of normal delivery had polydactylies of thumbs, small fingers, and great toes, and had symmetrical syndactylies of fingers and toes. At age eight, the patient reported swelling and tenderness on bilateral medial malleoli. Radiographs showed small blotches of radiopacity. Two years later, the radiopacities had enlarged to become typical of DEH.

Light- and electron-microscopic immunocytochemistry of somatotropes in the anterior pituitary gland of European ferret, Mustela putorius furo

Light-microscopic immunocytochemistry of ferret anterior pituitary revealed the localization of somatotropes in the pars distalis, but no immunoreactive cells were detected in the pars tuberalis. Ultrastructural studies by superimposition immunocytochemistry and immuno-electron microscopy, elucidated the morphological heterogeneity of these somatotropic cells. They were classified into 2 subtypes on the basis of size of the secretory granules. Type-I cells with small granules (mean diameter, 192 nm), were considered to be the immature somatotrop, while Type-II cells, with comparatively larger secretory granules (mean diameter, 257 nm), were considered to be the matured form of Type-I cells and the typical somatotropic cell-type, and were much more predominant than the Type-I cells. The fact that Type-II cells had a distinct Golgi zone and many mitochondria, while in Type-I cells the intracellular organelles were generally less developed, supports this suggestion. In addition to these two extreme subtypes, several intermediate forms were also encountered that may represent different transitional phases during the conversion of Type I to Type II. Protein A-gold immuno-electron microscopy illustrated the specific localization of growth hormone over the granules, with no labelling over any other cytoplasmic organelles of the 2 somatotrope subtypes.

Microvascular and cellular defects of the periosteum of osteogenesis imperfecta

Periosteum stripped from fragments of diaphyseal long bones from osteogenesis imperfecta (OI) patients was examined both in vivo and in vitro. The OI periosteum was thickened and characteristic finding was a defective microvascular system. The vascular walls of arterioles and capillaries were thick and the lumina of many of these vessels were narrowed or occluded by hypertrophic endothelial cells and multiplication of smooth muscle cell layers. Circulatory deficiency in the OI periosteum might be regarded as one of the causes of the slender, osteopenic diaphyseal bone characteristic of the disorder. A higher proliferative activity was observed in cultured OI periosteal cells, but the cytoplasmic structure showed increased myelinoid bodies and smooth endoplasmic reticulum and decreased lysosomes and rough endoplasmic reticulum. These findings may be related to the abnormal metabolic activity of OI periosteal cells.

Repair of bone defect with cultured chondrocytes bound to hydroxyapatite

Cultured chondrocytes were bound to hydroxyapatite (HA) and implanted in surgically created bone defects in the ulna of the rabbit. Chondrocytes were obtained from the iliac crest cartilage of the rabbit and were cultured on the HA block for two weeks before implantation. Scanning electron micrographs showed that pores of the HA surface and the inside of the block were filled with cultured cells. After cultivation for two weeks, the expression of chondrocyte-specific characteristics was confirmed in these cells by an implanted diffusion of chondrocyte-specific characteristics was confirmed in these cells by an implanted diffusion chamber experiment. The HA without chondrocytes served as a control. At two weeks postimplantation, proliferating chondrocytes were observed on the surface and in the inside pores of the HA-chondrocyte blocks but not the HA controls. At four and six weeks postimplantation, in the central region of the implants, there was a significant increase in the amount of bone formation in the HA with cultured chondrocytes. At 13 weeks post-implantation, the implants were partially resorbed and completely enveloped in lamellar bone, including bone marrow.

Dexamethasone induces advanced growth hormone expression in the fetal rat pituitary gland in vivo

The effects of dexamethasone (DEX) on the onset of GH expression in the fetal rat pituitary gland were studied. Pregnant rats received oral administration of DEX dissolved in drinking water (25 mg/liter) for 40 h before killing on days 16-19 of pregnancy. The number of immunoreactive GH cells in the control fetus on day 18 was very small, whereas it was remarkably increased by DEX to a compatible value obtained from control fetuses on day 19. The effect of DEX on the induction of immunoreactive GH cells was found to be less potent on day 17 and not evident on day 16. The population of GH cells on day 19 was doubled, and they stained more intensely by GH antiserum after DEX treatment. In situ hybridization revealed that there were many GH messenger RNA (mRNA)-positive cells in the pituitary gland of a DEX-treated fetus at day 18, whereas they were negligible in number in the age-matched control. Northern blot analysis revealed that DEX induced accumulation of small amounts of GH mRNA in the fetal pituitary gland on day 17, whereas it induced a marked elevation of GH mRNA level on day 18. Reducing the levels of endogenous glucocorticoids by the administration of metyrapone (0.5 mg/ml in drinking water) to the pregnant rats from day 17-19 resulted in the significant reduction in the number of GH cells at day 19. Short-term treatment of DEX (duplicate sc injections at 18 h and 6 h before killing) also induced immunoreactive GH cells on day-18 fetuses but not on day-17 fetuses. Immunoreactive GH cells appeared on day 17 only after quadruplicate injections of DEX during last 40 h, suggesting that there is a difference in fetal sensitivity to DEX between days 17 and 18. These results indicate that immunoreactive GH cells and GH mRNA are inducible by DEX at an earlier stage of the fetal life than they normally appear. It is suggested that glucocorticoids play an important role in the development of GH cells in the fetal pituitary gland in vivo.

Increased population of nonhormone-producing cells suggests the presence of dysfunctional growth hormone cells in the anterior pituitary gland of the spontaneous dwarf rat

Anterior pituitary gland of the spontaneous dwarf rat (SDR) with isolated growth hormone (GH) deficiency was studied using immunocytochemistry, cell count and in situ hybridization. The standard immunocytochemistry of five anterior pituitary hormones [adrenocorticotropic hormone (ACTH), luteinizing hormone, thyroid-stimulating hormone, prolactin (PRL) and GH] and S-100 protein failed to detect any cytological difference between normal rats and SDRs, except for the size of different types of cells which were smaller in SDR than in normal rats, and GH cells which were undetectable in the SDR. The cell count study again showed lack of immunoreactive GH cells in the SDR. The population of PRL cells was significantly reduced in the SDR by 40% in male and 30% in female when compared to those of the control. The population of ACTH cells was larger in the male SDR. The population of the immunonegative cells was calculated by subtracting the sum of the percentages of immunopositive cells from 100, and it was found to be remarkably increased in the SDR. The population of immunonegative cells was about 55% in both male and female SDRs, whereas it was calculated to be 18.7% (male) or 10.2% (female) in the control rats. In situ hybridization study using GH cRNA indicated the presence of a considerable number of cells which express GH mRNA in the SDR as well as in the control rats. These results taken as a whole suggest the presence of a number of dysfunctional GH cells in the SDR.(ABSTRACT TRUNCATED AT 250 WORDS)

[Prognosis of intractable asthma]

Forty-nine intractable asthma patients from January 1981 were divided into three groups. Group I consisted of patients still alive after ten years (January 1991) who were receiving decreased doses of steroids or no steroids at all. Group II patients were also alive, but the doses of steroids they were receiving were unchanged. Group III consisted of patients who had died during the ten years. Of the 49 patients, nine were in Group I, 13 in Group II and 17 in Group III. The condition of the other 10 patients was unknown. The mortality rate of the known 39 patients over 10 years was 43.6%, a very high rate. The groups of living patients (I + II) were younger than the patients in the dead group (III) and the latter patients had more obstructive ventilatory dysfunction in the stable state (FEV1.0/FVC%, and %FEV1.0 were 56.1% and 52.8%) in 1980. In the therapy carried out over the 10 years, antiallergic drugs and inhaled steroids were administered in order to decrease oral steroids in both Group I, II and III. In Group I, however, more patients had received immunotherapy (hyposensitization) or gold therapy than in Group II and III. There were more complications due to steroids during the ten years in Group II and III than in Group I. Aging and obstructive ventilatory dysfunction may be factors which worsen the prognosis of intractable asthma, and decreasing of the doses of oral steroids may be important to prevent complications.

Coffin-Lowry syndrome associated with calcium pyrophosphate crystal deposition in the ligamenta flava

Clinical and ultrastructural study of four cases of Coffin-Lowry syndrome (CLS), a heritable disorder with peculiar facies, stooped posture, vertebral changes, and mental retardation, is reported. Three of the four cases had myelopathy caused by calcification of the ligamenta flava in early adulthood. These patients demonstrated that CLS is a calcium pyrophosphate dihydrate crystal deposition disease, and it is postulated that a metabolic abnormality in collagen and in proteoglycans are responsible for some aspects of CLS.

Immunohistochemistry of the pituitary pars distalis of the musk shrew, Suncus murinus

Immunocharacteristics of the pituitary pars distalis cell types of the musk shrew, Suncus murinus, were studied by the unlabeled antibody enzyme technique, using peroxidase-antiperoxidase or avidin-biotin-peroxidase complex. The thyrotropin (TSH)-, gonadotropin (GTH)-, corticotropin (ACTH)-, prolactin (PRL)-, and growth hormone (GH)-secreting cells of the PD were identified on the basis of their immunoreactivity with different heterologous antisera. The TSH cells showed specific immunoreactivity with antisera against human (h) TSH beta and rat (r) TSH beta. Cells showing immunoreactivity with the antisera against hLH beta and ovine (o) LH beta were designated as GTH cells as no immunoreactivity was observed with antisera against hFSH beta and oFSH beta. The ACTH cells as well as the cells of the pars intermedia were revealed by anti-ACTH1-24 and anti-ACTH1-10 sera. Whereas the PRL cells were recognized by their immunoreactivity with antisera against hPRL and oPRL, the GH cells were identified with anti-hGH, anti-oGH, and anti-bovine (b) GH sera. TSH and GTH, TSH and ACTH, GTH and ACTH, ACTH and GH, ACTH and PRL, and GH and PRL cells were visualized in the same section using the dual immunoperoxidase technique. Comparison of the immunohistochemically identified cells with those described histochemically reveals several discrepancies, which expose the limitations of the latter techniques identifying adenohypophysial cells.

Zonal and age-related difference in the amounts of creatine kinase subunits in cartilage

Energy metabolism in cartilage may affect the morphogenetic events of skeletal growth. Investigating enzymes responsible for energy metabolism in cartilage, such as creatine kinase (CK), can provide clues to an understanding of pathogenesis and treatment of osteochondrodysplasias. In this study levels of CK subunits M (muscle type) and B (brain type) were measured by a highly sensitive enzyme immunoassay system in growth and resting cartilages of the rat rib at various ages. CK-M was predominant, but there was no statistically significant difference in its quantity of CK among cartilages of various ages or between resting and growth cartilage. In contrast, although CK-B levels were low, they showed a significant decrease with advancing age and a significant increase in growth cartilage as compared with resting cartilage. The results of this study suggest that CK in cartilage, especially CK-B, may play an important role in skeletal growth.

Bioassay of chondrocyte differentiation by bone morphogenetic protein

For sensitive bioassay of cartilage development in response to bone morphogenetic protein (BMP), the supernatant of interstitial fluid containing crud BMP was obtained from an implanted diffusion chamber, applied to a cellulose acetate film, and stained with Alcian blue. The optical density of the Alcian blue-stained spot was measured by a densitometer for quantitative analysis. Density of the Alcian blue-stained spot was markedly increased when cartilage developed outside the chamber. Occurrence of cartilage-specific proteoglycan-H (PG-H) and Type II collagen was seen in this intensely stained spot by dot-blot analysis. Electron microscopic examination revealed that the residue of interstitial fluid in the implanted diffusion chamber contained many collagen fibrils and proteoglycan granules.

Allelic association of human dopamine D2 receptor gene in alcoholism

In a blinded experiment, we report the first allelic association of the dopamine D2 receptor gene in alcoholism. From 70 brain samples of alcoholics and nonalcoholics, DNA was digested with restriction endonucleases and probed with a clone that contained the entire 3' coding exon, the polyadenylation signal, and approximately 16.4 kilobases of noncoding 3' sequence of the human dopamine D2 receptor gene (lambda hD2G1). In the present samples, the presence of A1 allele of the dopamine D2 receptor gene correctly classified 77% of alcoholics, and its absence classified 72% of nonalcoholics. The polymorphic pattern of this receptor gene suggests that a gene that confers susceptibility to at least one form of alcoholism is located on the q22-q23 region of chromosome 11.

Molecular mechanism of growth hormone (GH) deficiency in the spontaneous dwarf rat: detection of abnormal splicing of GH messenger ribonucleic acid by the polymerase chain reaction

The spontaneous dwarf rat (SDR) is an experimental model for pituitary dwarfism with an autosomal recessive mode of inheritance. In the pituitary of the SDR, neither GH cells nor GH protein were detected by immunological methods, but SDR pituitary has a very small amount of GH mRNA. In the present study the effects of GH-releasing factor and an analog of its second messenger, (Bu)2cAMP, on the total accumulation and secretion of GH were studied in primary cultures from SDR pituitaries. GH-releasing factor and (Bu)2cAMP increased the amount of GH mRNA, but neither accumulation nor secretion of immunoreactive GH was detected. These results suggested that the mutation is not manifest during transcription, but at a later stage. The GH gene of SDR was cloned, and its sequence was determined. A point substitution was found in the consensus sequence of the 3' splice site of the third intron. Judging from this point mutation, one would predict an abnormal splicing and a 1-base deletion in the GH mRNA. Therefore, the fragment of SDR GH cDNA in which the deletion was predicted was amplified by the polymerase chain reaction. Its sequence analysis confirmed that the SDR GH mRNA had 1 base deletion which must cause a premature translational termination of GH mRNA. These results demonstrate that GH deficiency in SDR is caused by a point mutation in the GH gene producing an abnormal splicing of GH mRNA.

Electron-microscopic study on the anterior pituitary gland of spontaneous dwarf rats

The spontaneous dwarf rat is a novel experimental model animal on the study of pituitary dwarfism. The fine structure of the anterior pituitary cells was studied in the immature and mature dwarf rats. Pituitary glands were removed from 5-, 10-, 20-day-old immature dwarfs, adult (45 days-16 weeks) dwarfs and normal 3-month-old rats and processed for electron-microscopic observation. In the control animals, growth hormone cells were readily identified by their ultrastructural characteristics, such as the presence of numerous electron-dense secretory granules, 300-350 nm in diameter, well developed rough endoplasmic reticulum and a prominent Golgi complex. In contrast, growth hormone cells were not found in the anterior pituitary gland of the spontaneous dwarf rat at any age examined. Other pituitary cell types, i.e., luteinizing hormone/follicle stimulating hormone, thyroid stimulating hormone, adrenocorticotropic hormone and prolactin cells, appeared similar in their fine structure to those found in the control rats. In the pituitary gland of dwarf rats, a number of polygonal cells were observed either with no or relatively few secretory granules. The rough endoplasmic reticulum was arranged in parallel cisternae and the Golgi complex was generally prominent in these cells. In addition, many were found to have abundant lysosomes. A few minute secretory granules were occasionally observed; however, the immunogold technique failed to localize growth hormone or prolactin in the granules. The nature of these cells remained obscure in this study.(ABSTRACT TRUNCATED AT 250 WORDS)