Biomedical subjects

R V Lloyd

Publications and source records attributed to R V Lloyd.

At least 145 records · Page 8Linked to original sources

PubMed1993

Differentiation of human pituitary adenomas determines the pattern of chromogranin/secretogranin messenger ribonucleic acid expression.

The distribution of chromogranin/secretogranin (Cg/Sg) mRNAs, determined by Northern and in situ hybridization, was analyzed in 14 cultured pituitary adenomas characterized by immunohistochemistry and hormone secretion in a defined medium in vitro. There were 5 functional GH adenomas, 1 silent GH adenoma, 7 null cell adenomas, and 1 oncocytoma. The null cell adenomas, oncocytoma, and silent GH adenomas were also analyzed by electron microscopy. Most null cell adenomas and the oncocytoma secreted FSH and LH into the culture medium. GH adenomas, which are examples of well differentiated tumors based on morphological examination, expressed significantly more SgIII mRNA compared to the null cell adenomas and oncocytoma (70 +/- 6% vs. 22 +/- 5%; P < 0.001). GH adenomas also expressed significantly less CgA mRNA compared to the less well differentiated null cell adenomas and oncocytoma (27 +/- 6% vs. 67 +/- 4%; P < 0.001), which could be considered less well differentiated based on ultrastructural morphological features. After treatment with phorbol 12-myristate 13-acetate (10(-7) M) for 7 days, there was an increase in the mRNA for CgB and SgII mRNAs in GH and null cell tumors, while dexamethasone treatment for 7 days increased CgA mRNA in GH and null cell adenomas. GnRH treatment for 7 days increased CgB mRNA in null cell adenomas. Phorbol 12-myristate 13-acetate also decreased the percentage of immunoreactive GH cells and GHm RNA, determined by in situ and Northern hybridization analyses. These results indicate that pituitary adenomas have a distinct pattern of Cg/Sg mRNA expression, which appears to be related to the degree of morphological differentiation of these neoplasms, and suggest that the effects of secretagogues on various Cg/Sg mRNA levels may be related to the stimulation of hormone secretion.

Adenoma↗

PubMed1993

Effects of estrogen and epidermal growth factor on prolactin and Pit-1 mRNA in GH3 cells.

The effects of epidermal growth factor (EGF) and 17 beta-estradiol (E2) on the expression of prolactin (PRL), the transcription factor Pit-1/GHF-1 (Pit-1), and on dopamine D2 receptor mRNA in GH3 cells were analyzed by immunocytochemistry, in situ hybridization, and Northern analysis in a defined serum-free cell culture medium. Radioimmunoassay was used to determine PRL secretion. Both EGF and E2 stimulated PRL mRNA and PRL secretion, although the effects of EGF were more rapid than those of E2. Pit-1 mRNA levels were not significantly changed in spite of the 2- to 8-fold increases in PRL mRNA levels and significant increases in PRL secretion. Analysis of dopamine D2 receptor mRNA by in situ hybridization and Northern hybridization detected expression of dopamine receptor in GH3 cells, but the receptor mRNA levels were not modified by EGF or E2 treatment in complete serum or in serum-free media. These observations suggest that EGF and E2 modulate PRL mRNA levels and PRL secretion significantly in vitro, while the mRNA levels of Pit-1 do not change significantly in GH3 cells cultured in a defined culture medium.

Animals↗

PubMed1993

Immunohistochemical assessment of proliferative activity in adrenocortical neoplasms.

Although many histologic criteria have been utilized to help distinguish benign from malignant adrenocortical tumors, it still may be difficult to assess the biologic potential of a given tumor. We evaluated 19 adenomas and 15 primary carcinomas with the avidin-biotin complex peroxidase method utilizing formalin-fixed, paraffin-embedded tissues with monoclonal antibodies for proliferating cell nuclear antigen (PC10) and Ki-67 (MIB 1) to determine if staining for these antigens could be used to help differentiate benign from malignant adrenocortical neoplasms. We also evaluated whether these markers could be used as prognostic indicators. Labeling indices for both PCNA and Ki-67 were determined by enumerating 1000 tumor cells, and expressed as a percentage of cells with nuclear staining. A PCNA and a Ki-67 score was obtained by the product of the staining intensity (0-3+) and the extent of nuclear staining, expressed as an estimate of the percentage of cells staining. Both PCNA and Ki-67 score and labeling index were correlated with mitotic counts, histologic diagnosis, and clinical outcome. Follow-up period for patients ranged from 4 months to 12 years with a mean of 25 months. Mitotic counts correlated with histologic diagnosis and clinical outcome. Both Ki-67 score and labeling index were significantly higher in malignant than in benign tumors, and correlated with mitotic counts and clinical outcome. There was a strong correlation between Ki-67 score and labeling index, indicating that Ki-67 score may be a more rapid and equally accurate method of estimating proliferative index of a tumor. PCNA score and labeling index did not correlate with histologic diagnosis or clinical outcome.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenoma↗

PubMed1993

Primary renal carcinoid. Case report and literature review.

We report a case of primary renal carcinoid, which is a very rare neoplasm: to our knowledge, only 19 cases have been previously reported. The tumor displayed histologic features typical of carcinoid tumors from other sites, including growth in nests and ribbons, uniform cells with finely granular, eosinophilic cytoplasm, and stippled chromatin. Electron microscopy confirmed the presence of membrane-bound dense-core granules. Immunohistochemical analysis revealed staining for chromogranin A, neuron-specific enolase, Leu-7, and synaptophysin, as well as pancreatic polypeptide. An interesting finding was the positive staining for prostatic acid phosphatase, while staining for prostate-specific antigen was negative. Although prostatic acid phosphatase is commonly seen in primary gastrointestinal hindgut carcinoids, in this case a primary hindgut carcinoid was ruled out by clinical examination and endoscopy. The patient developed metastases to the liver, but was well and without symptoms 15 months after diagnosis.

Acid Phosphatase↗

PubMed1993

Pituitary specific transcription factor messenger ribonucleic expression in adenomatous and nontumorous human pituitary tissues.

BACKGROUND: The pituitary-specific transcription factor, Pit-1/GHF-1 (Pit-1) is a member of the POU family of homeobox genes. This transacting factor has a role in the development and expression of selected anterior pituitary cells including prolactin, growth hormone (GH), and thyrotropin, cell types in rodent pituitary. The expression of Pit-1 mRNA in human pituitaries has not been previously analyzed and the role of specific secretagogues in the regulation of Pit-1 transcripts in human pituitary adenomas has not been examined. Analysis of Pit-1 expression in normal and neoplastic human pituitaries may provide insight into the specificity of this transcription factor for pituitary cell types and the role of Pit-1 in human pituitary function. EXPERIMENTAL DESIGN: In situ and Northern hybridization analyses were used to study the expression of Pit-1 mRNA in surgically removed human pituitary adenomas and nontumorous pituitaries obtained within 6 hours postmortem. A cultured GH surgically removed adenoma was used to analyze the regulation of GH and Pit-1 in vitro. RESULTS: In situ hybridization localized Pit-1 mRNA in all pituitary adenomas, although the mRNA levels in GH and prolactin adenomas were significantly higher than those in ACTH, null cell and gonadotroph tumors. Northern hybridization analysis revealed a 2.4 and a 1.2 kb mRNA transcript for Pit-1. Although GH mRNA transcript was markedly changed by dexamethasone and phorbol 12-myristate 13-acetate in vitro, Pit-1 mRNA transcripts were not changed significantly by these secretagogues. CONCLUSIONS: Pit-1 mRNA transcripts are expressed mainly in prolactin and GH pituitary adenomas, but are also found in other adenomas and in the nontumorous adult human pituitary. Pit-1 mRNA transcript levels are not readily modulated in cultured GH adenoma cells by various secretagogues in vitro compared with the marked modulation of GH mRNA transcripts by these same secretagogues.

Adenoma↗

PubMed1993

Reexamination of the microsomal transformation of N-hydroxynorcocaine to norcocaine nitroxide.

Cocaine is known to be associated with hepatotoxicity in laboratory animals, and there is recent evidence that it also induces liver damage in humans. In both cases an N-oxidative pathway is responsible. Cocaine (NCN) is first N-demethylated to norcocaine, followed by oxidation to N-hydroxynorcocaine (NCNOH) and norcocaine nitroxide (NCNO.). On the basis of ESR studies of NCNOH with rat liver microsomes, it has been proposed that NCNO. induces hepatotoxicity by futile redox cycling between NCNO. and NCNOH at the expense of NADPH. The reaction is reported to be accompanied by formation of superoxide and lipid peroxyl radicals. It has also been reported that the same toxic sequence occurs with rat brain microsomes, leading to the formation of reactive free radicals in the brain. We have reexamined the microsomal metabolism of NCNOH to investigate the mechanism more thoroughly. Spin traps [5,5-dimethyl-1-pyrroline N-oxide and alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone] were used to investigate the formation of reactive free radicals, including superoxide, in liver and brain microsomal incubations. In agreement with the literature, we detected a six-line spectrum of a radical adduct of alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone from liver microsome incubations. In contrast, our results showed that brain microsomes were completely inactive, contrary to the literature. In addition, we did not find any NCNO.- or NCNOH-dependent formation of superoxide with either brain or liver microsomes.

Animals↗

PubMed1993

Protein kinase C (PKC) activity and PKC messenger RNAs in human pituitary adenomas.

Protein kinase C (PKC) is involved in the differentiation and growth regulation of a variety of tissues including anterior pituitary gland cells. To determine the distribution of PKC in different types of adenomas, PKC activity was analyzed in human pituitary tumors and the effects of hypothalamic hormone stimulation on PKC activity were examined in cultured adenoma cells. Gonadotroph (LH/FSH) and null cell adenomas had significantly higher levels of particulate, soluble, and total PKC activity compared with growth hormone (GH) adenomas (P < 0.05). Chronic stimulation of null cell adenomas with gonadotropin hormone-releasing hormone or of one GH adenoma with GH-releasing hormone for 7 days did not significantly alter total PKC activity in pituitary cells cultured in serum-free medium. Localization of the calcium-dependent PKC isozymes (alpha, beta and gamma) by immunohistochemistry and in situ hybridization revealed predominantly PKC alpha in all adenomas and variable expression of PKC beta and gamma in some tumors. When the calcium-independent PKC isozymes (delta, epsilon, and zeta) were localized by in situ hybridization, normal and neoplastic pituitaries expressed abundant mRNA for PKC epsilon, whereas some tumors and one normal pituitary had a few cells positive for PKC zeta mRNA as evaluated by grain density and the number of cells labeled. These results indicate that there is a variable distribution of PKC mRNA isozymes in human pituitary adenomas and that normal pituitaries and pituitary adenoma cells express the mRNA for both the calcium-dependent and some of the calcium-independent PKC isozymes. Chronic treatment with the hypothalamic gonadotropin hormone-releasing hormone and GH-releasing hormone, which increased LH/FSH and GH secretion, respectively, did not increase PKC activity in cultured adenoma cells. The presence of calcium-dependent and calcium-independent PKC isozymes in normal and neoplastic pituitary cells indicates that PKC probably plays a major role in signal transduction in the human pituitary adenomas examined in this study.

Adenoma↗

PubMed1993

Detection of prolactin messenger RNA in mammary and other normal and neoplastic tissues by polymerase chain reaction.

BACKGROUND: Although prolactin (PRL) is produced predominantly by the anterior pituitary gland, recent studies have found PRL in normal brain tissues and in various neoplasms. Many of these studies have used immunohistochemical methods to detect PRL production, so the distinction between de novo synthesis and uptake by tissues with PRL receptors was not possible with these approaches. PRL production by various neoplasms has been designated as ectopic, since it was assumed that non-neoplastic cells were not producing this hormone. EXPERIMENTAL DESIGN: The reverse transcriptase polymerase chain reaction technique (RT-PCR) was used to detect PRL mRNA in various normal rat tissues and normal and neoplastic human tissues. The sensitivity of RT-PCR to detect amplified products starting with very low amounts of total RNA was also determined. Amplified DNA was detected by ethidium bromide staining, Southern hybridization with 32P-labeled probes and with a chemiluminescent method. RESULTS: PRL expression was readily detected in normal rat brain and pituitary. One fg of starting total pituitary RNA was sufficient to detect PRL expression with RT-PCR. PRL was detected in human hypothalamus, cerebellum, and normal breast tissues (3/4 cases) as well as in breast carcinomas (5/7 cases). A lung, an endometrial and a medullary thyroid carcinoma also expressed PRL. The chemiluminescent detection system was as sensitive as 32P-labeled probes in detecting the amplified PCR product. CONCLUSIONS: These results indicate that PRL gene expression is present in normal and neoplastic mammary and other tissues and can be readily detected by RT-PCR.

Animals↗

PubMed1993

Protein kinase C activity and messenger RNA modulation by estrogen in normal and neoplastic rat pituitary tissue.

BACKGROUND: Estrogens stimulate pituitary cell growth by prolactin cell hyperplasia in normal rat pituitaries while inhibiting growth of transplantable rat pituitary tumors in vivo and in vitro. The mechanisms by which estrogens stimulate proliferation of normal and hyperplastic pituitary tissues while inhibiting growth of established transplantable tumors is unknown. Protein kinase C (PKC) is involved in proliferation and differentiation of many cells including those of the anterior pituitary gland. PKC has a major role in regulating pituitary hormone synthesis and secretion. Analysis of PKC activity in normal, hyperplastic and transplantable pituitary tumors may provide insight into the mechanism of estrogen action on tumor growth and differentiation in pituitary tissues. EXPERIMENTAL DESIGN: Normal female rats and female rats with transplantable pituitary tumors were treated with estradiol 17 beta (E2) in vivo and subsequently analyzed for PKC activity. Rats with GH3 pituitary tumors were treated with E2 in vivo and a GH3 pituitary cell line maintained in vitro were also analyzed for PKC activity after estrogen treatment. The calcium-dependent and calcium-independent PKC isozymes were analyzed by in situ and Northern hybridization in normal and neoplastic pituitary tissue using specific oligonucleotide probes to characterize the subtypes of PKCs present in pituitary tissues. The calcium-dependent PKCs were also analyzed by immunohistochemistry using specific antibodies to PKC alpha, beta and gamma. RESULTS: Estrogen treatment increased total PKC activity significantly in normal pituitaries, but did not change total PKC activity in transplantable MtT/F4 and MtT/W15 tumors or in GH3 cells in vivo or in vitro. The mRNAs for PKC alpha and beta were detected in normal and neoplastic pituitary tissues and were increased after estrogen treatment in normal pituitary and MtT/F4 tumors, but not in MtT/W15 tumors. The calcium-independent PKC delta, epsilon and zeta were also detected in normal pituitary and in transplantable pituitary tumors and in GH3 cells by Northern hydridization and the levels of these PKCs were also regulated by estrogens. CONCLUSIONS: Estrogen modulates PKC levels in pituitary cells with an increase in total PKC activity in hyperplastic pituitaries but not in transplantable pituitary tumors. Estrogen also regulates the mRNA levels of the calcium-dependent and calcium-independent PKC isozymes.

Animals↗

PubMed1992

Studies of composite grafts of fetal pancreas (FP) and fetal liver (FL) in the streptozotocin-induced diabetic rat.

A hepatotrophic effect of pancreatic islets on co-transplanted hepatocytes has been described recently by Ricordi et al. We investigated a possible reciprocal effect of co-transplanted fetal liver (FL) on fetal pancreas (FP) isografted into streptozotocin diabetic rats. FL was co-transplanted with FP in three sites: the new intramural small bowel (ISB) site, the conventional renal subcapsular (RSC) site, and the historically inhospitable intramuscular (IM) site. Overall, as compared to grafts of FP alone, composite FP/FL grafts consistently provided earlier restoration of normoglycemia in streptozotocin diabetic recipients (24 +/- 8 vs. 67 +/- 43 days P = 0.001). The proportion of recipients rendered normoglycemic and the clearance of glucose was site-dependent. For FP and FP/FL recipients respectively, the ISB site resulted in 100% normoglycemia in both groups (19/19 and 6/6), the RSC site resulted in 71% (5/7) and 40% (2/5) and the IM site resulted in 14% (1/7) and 67% (6/9). In normoglycemic recipients, glucose clearance was normal or supraphysiologic except for the RSC site. Composite isografts brought about normoglycemia in 75% (6/8) of recipients treated with beta-cell toxic doses of cyclosporine that prevented reversal of diabetes in recipients of FP alone. Co-transplantation of FL benefits FP through paracrine mechanisms mediated by unknown factor(s). Thus, as compared to grafts of FP alone, composite FP/FL grafts established normoglycemia more rapidly, mitigated cyclosporine toxicity and corrected diabetes when transplanted in the small bowel site. There are several mediators that may be responsible for these paracrine effects between the liver cells and the pancreas. IGF-1 elaborated by FL is the most likely trophic factor.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Pituitary lactotrophs and somatotrophs in pregnancy: a correlative in situ hybridization and immunocytochemical study.

Lactotroph hyperplasia is a prominent finding in the adenohypophyses of pregnant women. In order to elucidate the morphogenesis of this change, pituitaries from 16 women in various phases of pregnancy were collected at autopsy and studied by histology, immunocytochemistry and in situ hybridization. The results showed that the increase in the amount of prolactin (PRL) mRNA paralleled the progressive lactotroph hyperplasia. The presence of mitoses in PRL-immunoreactive cells provided evidence that proliferation of preexisting lactotrophs contribute to lactotroph accumulation. Growth hormone (GH) immunoreactive cells showed a marked reduction in GH mRNA indicating that GH synthesis was inhibited. In many GH-immunoreactive cells, PRL mRNA became apparent. These findings demonstrate that GH is stored following discontinuation of GH synthesis. It appears that, when PRL is secreted in excess during pregnancy, somatotrophs are recruited to produce PRL. These somatotrophs begin to express PRL mRNA, transform to bihormonal mammosomatotrophs and possibly later to lactotrophs, contributing to PRL production. Mature somatotrophs may be regarded as reserve cells in the adenohypophysis, having the potential to switch hormone synthesis and to convert to mammosomatotrophs and possibly lactotrophs.

Adolescent↗

PubMed1992

Effects of cotransplanted fetal liver on fetal pancreas isografts.

Ricordi et al. described a hepatotrophic effect mediated by pancreatic islets on cotransplanted hepatocytes. We found a reciprocal salutary effect of fetal liver (FL) on fetal pancreas (FP) in the intramural small bowel (ISB) site. To further investigate this intriguing finding, composite FP/FL isografts were transplanted to the conventional renal subcapsular (RSC) site and the accessible but historically inhospitable intramuscular site in streptozotocin-diabetic Lewis rats. A comparison of recipients of FP/FL and FP alone found the proportion rendered normoglycemic was site dependent. All recipients of either composite FP/FL grafts or FP alone transplanted in the ISB site became normoglycemic. The proportion of normoglycemic recipients was lower in the RSC site (71% FP and 40% FP/FL) and the i.m. site (14% FP and 67% FP/FL). Importantly, regardless of site, normoglycemia was established with an accelerated time course in recipients of FP/FL versus FP alone (24 +/- 8 vs. 67 +/- 43 days; P = 0.001). Normal (or more rapid) glucose clearance after challenge was achieved in all normoglycemic recipients except those transplanted in the RSC site. On histological examination of excised FP/FL grafts, hepatocytes were present in association with islets. Cyclosporine-induced islet toxicity could not be overcome in 6 recipients of FP alone, but 6 of 8 recipients of FP/FL became normoglycemic (P less than 0.01). To assess the effect of FP on hepatocytes, allografts (Wistar donors) of FP or FP/FL were cotransplanted in the ISB of enzyme-deficient jaundiced Gunn rats. Immunosuppression consisted of rapamycin (0.8 mg/kg/day) infused intravenously for 4 weeks. In the FP/FL group (n = 4), the mean serum bilirubin level decreased from 8.6 to 4.9 mg/dl at 6 weeks after transplantation. This was a significant difference as compared with the increased mean serum bilirubin from 6.9 to 7.8 mg/dl (P less than 0.05; paired Student's t test) in recipients of FL alone (n = 4). In conclusion, we found a mutual paracrine effect on islets and hepatocytes transplanted as a composite FP/FL graft. FL hastened the establishment of normoglycemia following transplantation of FP in diabetic rats, and FP enhanced FL transplant function in Gunn rats.

Animals↗

PubMed1992

Molecular approaches for the analysis of chromogranins and secretogranins.

Recent molecular analyses have contributed to our knowledge about the chromogranin/secretogranin (Cg/Sg) family and their utility in diagnostic pathology. The genes for five of these proteins have been cloned, and the deduced amino acid sequences have provided insights into the structure and possible functions of the Cgs/Sgs, including their role as prohormones. Northern hybridization and in situ hybridization histochemistry have provided a great deal of information about the tissue distribution of the Cg/Sg gene products. Some neoplasms such as small cell lung carcinomas, which have little stored Cg/Sg protein, have abundant cytoplasmic mRNAs that can be readily detected by hybridization studies. Some other neoplasms such as neuroblastomas have decreased CgA and increased SgII mRNAs during maturation to ganglioneuromas. There is also a differential expression of Cgs/Sgs in some endocrine neoplasms such as parathyroid adenomas, which express abundant CgA mRNA and little CgB mRNA, and in pituitary prolactinomas, which express CgB mRNA but not CgA mRNA. The mRNA for CgA has been found unexpectedly in some neoplasms such as 15% of colonic adenocarcinomas. Thus, molecular approaches in the analysis of Cgs/Sgs should contribute to the diagnosis of endocrine neoplasms and may provide support for a molecular classification of neoplasms in diagnostic pathology.

Animals↗

PubMed1992

Double adenomas of the pituitary: a clinicopathological study of 11 tumors.

Of more than 3000 cases of surgically removed pituitary adenomas, 11 were defined as "double adenomas," i.e., 2 morphologically or immunocytologically distinct tumors. In 8 cases, the lesions exhibited differing histological features and immunophenotypes; in 2 specimens, distinct ultrastructural features were noted as well. In another instance, despite histological and immunocytological uniformity, the two neoplastic components demonstrated distinct ultrastructure. In yet another case, the two adenomas were consecutively removed; despite similar histological features, they differed in immunocytological and ultrastructural characteristics. Last, in one case, the adenoma was histologically uniform, but a portion of the mass exhibited immunoreactivity by ultrastructural features distinct from those of the remainder of the lesion. Hormonal excess attributed to both tumors could be correlated with endocrine manifestations in two cases. Double adenomas of the pituitary occur infrequently. In routine histological sections of surgical material, they are often difficult if not impossible to identify. Presented herein are clinical and endocrinological data on 10 cases of double pituitary adenomas correlated with morphological and immunocytochemical results. The literature regarding multiple adenomas is reviewed as are the diagnostic and therapeutic difficulties associated with these rare lesions.

Acromegaly↗

PubMed1992

Analysis of gastrinomas by immunohistochemistry and in situ hybridization histochemistry.

Gastrinomas from 25 patients were examined by immunohistochemistry (IHC) and in situ hybridization histochemistry (ISH). Most patients (84%) presented with the Zollinger-Ellison syndrome. Six had multiple endocrine neoplasia type I (MEN-I). Twelve patients (48%) had duodenal primaries and 11 of 12 of these had metastases to regional lymph nodes and/or liver in spite of the small sizes of the primary tumors (mean size of 0.9 cm). Five patients had pancreatic gastrinomas and eight patients had metastatic tumor in regional lymph nodes or liver at surgery but a primary was not found. IHC and ISH analyses showed that all cases were positive for gastrin protein and 24 of 25 (96%) expressed gastrin mRNA that was easily detected in formalin-fixed, paraffin-embedded tissue sections. Both benign and malignant tumors expressed alpha subunit of human chorionic gonadotropin protein (alpha-HCG). However, only malignant gastrinomas (29%) expressed adrenocorticotropic hormone protein or proopiomelanocortin (POMC) mRNA. ISH and Northern hybridization analysis revealed that chromogranin A mRNA was the most common member of the chromogranin/secretogranin (Cg/Sg) family which was expressed in both benign and malignant gastrinomas. These results indicate that duodenal gastrinomas are common in both sporadic and MEN-1-associated cases, and small duodenal primaries may be associated with extensive regional lymph node and liver metastases. Expression of ACTH/POMC protein and mRNA was consistently associated only with malignant gastrinomas while gastrin protein, gastrin mRNA and Cgs/Sgs mRNAs were readily detected in both benign and malignant gastrinomas.

Adrenocorticotropic Hormone↗

PubMed1992

Chromogranin A, chromogranin B and secretogranin II mRNAs in the pituitary and adrenal glands of various mammals. Regulation of chromogranin A, chromogranin B and secretogranin II mRNA levels by estrogen.

BACKGROUND: The chromogranin/secretogranin (Cg/Sg) acidic proteins are widely distributed in vertebrate species. They are thought to play a role in hormone packaging within secretory granules, in hormone secretion, and serve as prohormones for various proteolytic cleavage products. The genes for most members of the Cg/Sg family have been cloned, so hybridization analysis can be used to analyze the distribution and regulation of Cg/Sg mRNAs in various vertebrate species. EXPERIMENTAL DESIGN: The method of in situ hybridization was used to localize chromogranin A, chromogranin B, and secretogranin II in adrenal and pituitary tissues from laboratory animals and from humans in order to analyze the distribution of various Cg/Sg mRNAs in these tissues. To gain some insight into the regulation and possible functions of specific Cg/Sg members, female rats were ovariectomized for different periods with and without estrogen replacement and the pituitaries were subsequently analyzed by in situ hybridization and Northern hybridization analyses. Combined ISH and immunohistochemistry were used to localize the specific cell types in normal rat pituitary that expressed the mRNA for chromogranin A, chromogranin B, and secretogranin II. RESULTS: All three Cg/Sg mRNAs were detected in pituitary and adrenal tissues of rats, mice, dogs, monkeys, and humans. Combined in situ hybridization and immunohistochemistry using rat pituitary revealed that the glycoprotein hormone-secreting cells expressed all three Cg/Sg mRNAs in approximately equal amounts. Ovariectomy followed by estrogen replacement resulted in decreased levels of CgA and SgII mRNAs. In contrast, the level of CgB mRNA, that was not changed by ovariectomy, was increased after estrogen treatment, probably secondary to prolactin cell hyperplasia. CONCLUSIONS: The three principal Cg/Sg mRNAs are present in the adrenal and pituitary of various vertebrates. Estrogen plays a significant role in regulating the mRNA levels of different Cgs/Sgs suggesting functional and regulatory differences in Cg/Sg proteins.

Adrenal Glands↗

PubMed1992

Morphologic effects of hGRH gene expression on the pituitary, liver, and pancreas of MT-hGRH transgenic mice. An in situ hybridization analysis.

Morphologic changes in the pituitary, liver, and pancreas of mice with the metallothionein-human growth hormone--releasing hormone (MT-hGRH) transgene were analyzed by in situ hybridization histochemistry (ISH). There was progression from somatotroph hyperplasia to neoplasia in pituitaries of transgenic mice. Pituitary neoplasms were present between 9 to 12 months of age in some mice. Magnetic resonance imaging (MRI) readily identified enlarged pituitaries in MT-hGRH transgenic mice. Serum mouse GH and hGRH levels were marked elevated in MT-hGRH transgenic mice. In situ hybridization histochemistry showed mRNA for hGRH in liver, pituitary, pancreas, spleen, and in most other tissues examined. Combined ISH and immunohistochemistry in the pituitary gland showed that some of the GH cells also produced hGRH, and ultrastructural immunohistochemical analysis of pituitaries showed that GH and hGRH were localized in the same cell and within the same secretory granules. Liver cells of MT-hGRH transgenic mice showed evidence of hypertrophy, and the pancreatic islets were hyperplastic with significant increases in the islet cell areas. The morphologic changes in the liver were distinctive enough to separate control littermates from MT-hGRH transgenic mice in all cases. The enlarged pancreatic islets had increased numbers of insulin-producing cells. Immunoreactive hGRH and hGRH mRNA were both localized in islet cells, and an intense hybridization signal of hGRH mRNA, but only weak staining for hGRH protein, were detected in the liver of transgenic mice. These results indicate that excessive hGRH production leads to distinct morphologic changes in various organs in MT-hGRH transgenic mice and that there is temporal progression from hyperplasia to adenomatous somatotrophs in pituitaries with chronic stimulation by hGRH that involves paracrine, endocrine, and autocrine mechanisms.

Adenoma↗

PubMed1992

The effects of estrogen on prolactin gene methylation in normal and neoplastic rat pituitary tissues.

The effects of estrogen treatment on rat prolactin (PRL) gene methylation were analyzed in normal pituitaries and in three transplantable rat pituitary tumors. Northern analysis showed increased PRL mRNA expression in estrogen-treated pituitary and in MtT/F4 and MtT/F-DMBA tumors. Prolactin mRNA amounts in MtT/W15 tumor were decreased by estrogen treatment. There was an inverse relationship between changes in PRL mRNA expression and changes in gene methylation in the coding regions of the PRL gene after estrogen treatment. The amounts of the 4.6-Kb and 1.8-Kb restriction fragments generated by HpaII digestion in pituitary tissues were influenced by estrogen, with an increase in these fragments in normal pituitary, MtT/F4, and MtT/F-DMBA tumors after estrogen treatment. In contrast, the amounts of the 4.6-Kb and 1.8-Kb fragments were decreased in MtT/W15 tumors after estrogen treatment. Most of the internal -CCGG- sites in the PRL gene were methylated in the liver, and the PRL gene was not expressed in the liver. These data suggest that there is a tissue-specific pattern of DNA methylation of the PRL gene and that PRL gene methylation is influenced by estrogen in vivo in normal and tumorous pituitary tissues. These results also suggest that estrogen may influence PRL expression by multiple mechanisms, including changes in the level of DNA methylation.

Animals↗