Biomedical subjects

R V Lloyd

Publications and source records attributed to R V Lloyd.

At least 163 records · Page 9Linked to original sources

PubMed1992

Pulmonary metastases of colonic carcinoma. Distinction from pulmonary adenocarcinoma.

Pulmonary metastases may develop in patients with colonic carcinoma. Histopathologic separation of a solitary colonic metastasis from a primary pulmonary adenocarcinoma may be problematic. With the use of a polyclonal antibody to carcinoembryonic antigen, a monoclonal antibody to cytokeratin (CAM 5.2), and a monoclonal carcinoembryonic antigen antibody (D-14), we compared 23 colonic carcinomas metastatic to the lung with 24 primary pulmonary adenocarcinomas. Both carcinomas manifested similar histologic features. However, foci of "dirty necrosis" were common in all but one of the colonic neoplasms, and foci were observed in only four of the primary lung carcinomas. The polyclonal carcinoembryonic antigen antibody did not distinguish metastatic colonic carcinoma from primary pulmonary adenocarcinoma. All colonic tumors stained with D-14, while three primary pulmonary adenocarcinomas stained diffusely, and eight stained focally. Staining with D-14 will not absolutely distinguish colonic from pulmonary adenocarcinoma. However, positive D-14 staining and the presence of dirty necrosis should identify most colonic carcinomas. True-negative D-14 staining practically excludes a colonic origin.

Adenocarcinoma↗

PubMed1991

Ultrastructure of spontaneous and transplanted pituitary tumors in laboratory animals.

The present review examines ultrastructural studies of pituitary tumors in laboratory animals. Such studies have been facilitated by the development of newer techniques such as immunocytochemistry and in situ hybridization. Using these methods it has been possible to correlate morphological features with function by characterizing specific pituitary hormones in secretory granules and analyzing the messenger ribonucleic acids produced by specific cell types. Analyses of spontaneous and experimentally induced tumors have provided a great deal of insight into the function and ultrastructure of these neoplasms. The description of tumor cells producing more than one hormone has been facilitated by immunocytochemical analyses. Studies of transgenic models of pituitary hyperplasia and tumor development are expanding our knowledge about the ultrastructure and about other aspects of pituitary tumors in a more controlled experimental setting. The production of various hormones by the same pituitary tumors and even the same tumor cells indicates that complex regulatory mechanisms must be analyzed by a combination of ultrastructural and other techniques to learn more about growth and hormone secretion in pituitary neoplasms.

Animals↗

PubMed1991

Idiopathic prolactin cell hyperplasia of the pituitary mimicking prolactin cell adenoma: a morphological study including immunocytochemistry, electron microscopy, and in situ hybridization.

Prolactin cell adenoma is the most frequently found lesion in surgically removed pituitaries of patients with hyperprolactinemia. However, in several instances, instead of prolactin cell adenoma, other lesions are encountered by morphological investigation. We report here the morphological findings in a patient with hyperprolactinemia who underwent transsphenoidal pituitary surgery for suspected prolactin cell adenoma. A morphological diagnosis of tumor could not be confirmed and massive diffuse prolactin cell hyperplasia was identified. The aim of this publication is to describe the lesion by histology, immunocytochemistry, electron microscopy, and in situ hybridization and to call attention to primary prolactin cell hyperplasia which can mimic prolactin cell adenoma.

Diagnosis, Differential↗

PubMed1991

In situ hybridization study of pro-opiomelanocortin (POMC) gene expression in human pituitary corticotrophs and their adenomas.

Pro-opiomelanocortin (POMC) mRNA was detected on paraffin sections by in situ hybridization (ISH) in corticotrophs of 12 nontumorous pituitaries, 11 functioning corticotroph, and 11 silent pituitary adenomas. ISH combined with immunocytochemistry for adrenocorticotrophic hormone (ACTH), a POMC-derived peptide, was also performed. ACTH immunoreactive cells of the anterior lobes and those invading the posterior lobe showed a high or moderate level of POMC mRNA that was not correlated with the intensity of ACTH immunoreactivity. Variable levels of POMC gene expression were present in Crooke's cells, corticotrophs suppressed by glucocorticoid excess. Most functioning corticotroph adenomas and silent subtype 1 adenomas had an intense hybridization signal and ACTH immunoreactivity. In silent subtype 2 and 3 adenomas, POMC mRNA had a diffuse low level or was absent; in these adenomas ACTH immunoreactivity was diffuse, restricted to some cells, or negative. The results indicate that POMC gene is expressed in both normal and suppressed nontumorous corticotrophs. Intense signals for POMC mRNA are found in most functioning corticotroph adenomas. The difference between POMC gene expression in silent 1 and silent 2 and 3 adenomas suggests that different mechanisms are responsible for the lack of endocrine activity.

Adenoma↗

PubMed1991

Effect of dopamine agonist medication on prolactin producing pituitary adenomas. A morphological study including immunocytochemistry, electron microscopy and in situ hybridization.

Conventional light microscopy, immunocytochemistry, electron microscopy and in situ hybridization were used to evaluate the effect of dopamine agonists (bromocriptine-LAR and bromocriptine) on the morphology of surgically removed prolactin (PRL)-producing pituitary adenomas. Dopamine agonist therapy resulted in decrease of serum PRL, clinical improvement and tumour shrinkage. Using light and electron microscopy cellular atrophy, interstitial and perivascular fibrosis were noted; in several tumours connective tissue accumulation was pronounced. The cellular response was not uniform. In some adenomas populations of large cells and small cells were distinguished. The large cells contained immunoreactive PRL and expressed the PRL gene indicating resistance to dopamine agonists. It appears that these cells retained the potential to secrete PRL and proliferate despite exposure to dopamine agonists. In the small cells, PRL immunoreactivity and PRL gene expression decreased providing evidence that both PRL release and synthesis were blocked. Small cells can persist in tumours after discontinuation of dopamine agonist medication suggesting these small cells are irreversibly suppressed and are not capable of regaining their endocrine function and proliferative capability. The formation of irreversibly suppressed PRL cells may explain why some PRL-producing adenomas do not recur after withdrawal of dopamine agonists.

Adenoma↗

PubMed1991

In situ hybridization in the study of pituitary tissues.

This presentation summarizes the use of in situ hybridization in the study of pituitary abnormalities. The basic techniques, technical problems and pitfalls in in interpretation and the application of in situ hybridization are discussed.

Adenoma↗

PubMed1991

Effects of estrogens on pituitary cell and pituitary tumor growth.

Estrogens have been known to induce PRL cell hyperplasia in the anterior pituitary of some species for many decades. Recent studies have shown variable susceptibility to estrogen-induced hyperplasia in different strains of rats. The distinction between hyperplastic pituitaries and adenomas is usually not made by most investigators in this field, although true neoplasms can usually be propagated by serial transplantation. The growth of transplantable tumors is usually inhibited by estrogen in vivo. Estrogens have a biphasic effect on pituitary cell proliferation in vitro with higher concentrations of estradiol inhibit cell growth, and lower concentrations stimulating PRL secretion. Estrogens can regulate PRL gene methylation in vivo thus affecting PRL mRNA expression. Recent studies have suggested that estrogen regulates signal transduction by stimulating protein kinase C. Estrogens also regulate specific proto-oncogenes such as c-myc and c-fos. These observations may help to explain some of the regulatory effects of estrogens on cell proliferation and tumor development.

Animals↗

PubMed1991

Detection of estrogen receptor in paraffin-embedded sections of breast carcinoma by immunohistochemistry and in situ hybridization.

Biopsy specimens of small breast carcinomas are often insufficient for both diagnosis and the biochemical determination of estrogen receptor (ER) protein. Recent reports from various laboratories have shown the utility of immunohistochemical detection of ER protein in paraffin-embedded tissue sections. We used immunohistochemical (IHC) staining with the Abbott ER antibody (H222) and in situ hybridization (ISH) analysis with a 35S-labeled and a biotinylated oligonucleotide probe to detect ER protein and messenger RNA (mRNA) in tissue sections of 53 breast carcinomas. The dextran-coated charcoal (DCC) assay of these same cases revealed positive receptor levels in 31 of 53 cases, whereas the IHC method was positive in 33 of 53 cases. ISH for detection of ER mRNA was more sensitive than IHC or the biochemical assay for estrogen binding proteins, as the isotopic probe detected ER mRNA in 47 of 53 cases, whereas the biotinylated probe detected ER mRNA in 46 of 53 cases. These results indicate that ER protein can be readily detected in enzyme-treated paraffin tissue sections and that the IHC detection of ER protein correlates highly with the DCC assay. ISH with isotopic and biotinylated probes detects ER mRNA in most cases found to be positive for ER protein and also in many cases without detectable ER protein. Although detection of ER protein in paraffin sections correlates highly with the biochemical assay in this report and in other reported studies, the clinical significance of increased sensitivity by ISH is unknown and must await clinical correlative follow-up studies.

Breast Neoplasms↗

PubMed1991

Targeted ablation of pituitary gonadotropes in transgenic mice.

LH, FSH, and TSH are heterodimeric glycoprotein hormones composed of a common alpha-subunit and unique beta-subunits. The alpha-subunit is produced in two distinct specialized cell types of the pituitary gland: gonadotropes, which synthesize LH and FSH, and thyrotropes, which synthesize TSH. We have demonstrated that 313 base pairs of the bovine-alpha subunit promoter direct expression of diphtheria toxin A chain specifically to the gonadotropes in transgenic mice. Animals carrying this transgene generally exhibit reproductive failure and lack of gonadal differentiation, consistent with gonadotrope ablation. Lack of gonadotrope activity was verified by RIA and immunohistochemical staining for LH. The phenotype of these transgenic mice is nearly identical to mice homozygous for the spontaneous mutation, hpg, which is due to a deletion in the gene encoding GnRH. Thyrotrope function was judged normal based on overall growth of the animals, appearance of their thyroids, T4 levels measured by RIA, and immunohistochemical staining for TSH. The ablation of gonadotropes but not thyrotropes suggests that separate cis-acting elements are necessary for expression of the alpha-subunit gene in these two cell types. Pituitary content of ACTH and GH was apparently normal, while PRL synthesis and storage were reduced. Thus, in a pituitary almost completely devoid of gonadotropes, most other pituitary functions were normal. This suggests that most pituitary cells are able to differentiate independently of terminal gonadotrope differentiation and can function in the absence of paracrine signaling provided by gonadotropes.

Adrenocorticotropic Hormone↗

PubMed1991

Analysis of pituitary hormones and chromogranin A mRNAs in null cell adenomas, oncocytomas, and gonadotroph adenomas by in situ hybridization.

To study the relationship between null cell adenomas, oncocytomas and gonadotroph adenomas, we analyzed 32 surgically removed formalin-fixed paraffin-embedded pituitary tumors for the expression of pituitary hormone messenger RNAs (mRNAs) by in situ hybridization (ISH). Most tumors were also analyzed for chromogranin A mRNA. To identify the cell type constituting the tumors and to assess hormone content, all tumors were investigated by histology, transmission electron microscopy and immunohistochemistry. Most null cell adenomas (6/11) and gonadotroph adenomas (9/10) expressed the mRNAs for alpha-subunit of glycoprotein hormones whereas only 2/11 oncocytomas expressed alpha-subunit mRNA. FSH beta and/or LH beta mRNA were present in most null cell and gonadotroph adenomas but only in a few oncocytomas. Prolactin (PRL) mRNA was detected in two null cell tumors and in one gonadotroph adenoma, whereas GH and POMC mRNA were present in one null cell adenoma. Chromogranin A mRNA, which codes for the major secretory granule protein, was present in 25/26 tumors including all tumors that were negative for pituitary hormone mRNAs, indicating adequate preservation of specific mRNA transcripts in the paraffin-embedded sections of tumor cells. These results indicate that null cell adenomas and gonadotroph adenomas are closely related neoplasms and that oncocytomas may represent a functionally defective form of null cell adenoma characterized by mitochondrial abundance, which has retained the capacity to synthesize the major secretory granule protein chromogranin A. Although the cytogenesis of null cell adenomas and oncocytomas is not clear, it can be suggested that these two tumor types are derived from a pluripotential precursor cell that is capable of undergoing multidirectional differentiation and synthesizing various hormones, mainly glycoproteins.

Adenoma↗

PubMed1991

Microsomal reduction of 3-amino-1,2,4-benzotriazine 1,4-dioxide to a free radical.

The drug SR 4233 (3-amino-1,2,4-benzotriazine 1,4-dioxide) is under pharmacological study as the lead compound in a new series of hypoxia-activated drugs, the benzotriazine N-oxides. However, the stable two- and four-electron-reduced metabolites of SR 4233, formed by the successive loss of the two oxygen atoms, are not pharmacologically active. In order to evaluate the possibility of an initial one-electron intermediate as the active species, we have used microsomal reduction and EPR spectroscopy to identify the first free radical reduction product. The unpaired electron is primarily centered on the 1-nitrogen, and the radical is best described as a nitroxide. Results with spin-trapping experiments show that reduction of SR 4233 to a free radical is followed by its air oxidation, resulting in the formation of the superoxide radical. Experiments with specific inhibitors suggest that the drug is being reduced by microsomal NADPH-cytochrome P-450 reductase.

Animals↗

PubMed1991

Possible role of free radical formation in clozapine (clozaril)-induced agranulocytosis.

The use of clozapine, a unique antipsychotic drug, has been restricted due to a 1-2% incidence of drug-induced agranulocytosis. Metabolic activation of clozapine in neutrophils or stem cells could be the molecular mechanism underlying this side effect. Clozapine oxidation by human myeloperoxidase and horseradish peroxidase was evident from the disappearance of the UV absorbance at 290 nm. High performance liquid chromatography analysis revealed the formation of at least four radioactive peaks as a result of clozapine metabolism, including radioactivity coeluting with the protein. The tight association of radioactivity with the enzymatic protein was metabolism-dependent. This protein binding, which correlates with the total metabolism of clozapine, was reduced in the presence of glutathione and was absent in the presence of ascorbate. Similarly, in the presence of both reducing agents, the metabolite peaks in the high performance liquid chromatography radiogram, which are not associated with protein, disappeared. In contrast, in the presence of glutathione, two additional metabolites were found that could be isolated and identified by NMR and mass spectroscopy as clozapine glutathionyl adducts. Evidence for one-electron transfer reactions or the intermediate formation of a clozapine radical during the peroxidase-mediated metabolism of clozapine stems from the observation of thiyl and ascorbyl radicals in the presence of glutathione and ascorbate, respectively. The ascorbyl radical was detected by direct ESR spectroscopy in a peroxidase system. Its steady state concentration was significantly increased in the presence of clozapine. Glutathionyl radical formation was demonstrated by radical trapping with 5,5-dimethyl-1-pyrroline N-oxide in a peroxidase system. Again, the radical adduct concentration was significantly increased in the presence of clozapine. Similarly, when oxygen consumption was measured in peroxidase systems in the presence of glutathione or NADPH, the rate of oxygen uptake was markedly enhanced upon addition of clozapine. Thus, the data support the possibility of clozapine activation to free radical metabolites, which may cause oxidative stress or lead to adduct formation. Further, it can be concluded from these data that radical scavengers such as ascorbic acid, when coadministered with clozapine to patients, may reduce oxidative stress and protein adduct formation.

Agranulocytosis↗

PubMed1991

The tall cell variant of papillary carcinoma of the thyroid gland. Comparison with the common form of papillary carcinoma by DNA and morphometric analysis.

The tall cell variant of papillary carcinoma of the thyroid manifests a more aggressive behavior than the usual form of papillary carcinoma of the thyroid. Morphometric analysis of nuclear features and DNA analysis may yield information predictive of aggressive behavior. Accordingly, the DNA content and morphometric features of the neoplastic cells of the tall cell variant were measured and compared with measurements obtained from neoplastic cells of the usual form of papillary carcinoma. Six of the 11 tall cell neoplasms were aneuploid, as were four of the eight usual papillary neoplasms. Although benign cells were separated from malignant cells in each case, differences between tall and usual papillary carcinoma cells were not observed regarding DNA content, chromatin texture, or nuclear size and shape. Differences in the clinical behavior of these neoplasms will likely need to be explained on the basis of other characteristics.

Carcinoma, Papillary↗

PubMed1991

Expression of neural cell adhesion molecule in normal and neoplastic human neuroendocrine tissues.

The neural cell adhesion molecule (N-CAM) is a group of cell surface glycoproteins involved in direct cell--cell adhesion. N-CAM expression in normal and neoplastic tissues was examined with specific antibodies and oligonucleotide probes by immunohistochemistry and in situ hybridization. Most neuroendocrine cells and tumors with secretory granules expressed N-CAM protein and mRNA. Parathyroid adenomas (4) were somewhat unusual, because N-CAM mRNA, but not protein, was detected in some of these benign neoplasms. Most non-neuroendocrine cells and tumors did not express N-CAM, although uterine smooth muscle and an adrenal cortical carcinoma were both positive. Western blots disclosed proteins of 180, 140, and 120 kd in normal adult brain, whereas two pheochromocytomas, a null cell adenoma, and a gastrinoma had proteins of approximately 180 and 140 kd. These results indicate that N-CAM protein and mRNA are widely expressed in neuroendocrine cells and neoplasms. N-CAM oligonucleotide probes as well as antibodies against N-CAM can be used as broad-spectrum neuroendocrine markers. In addition, these molecular probes can be used to examine the role of N-CAM in the development and regulation of neuroendocrine tissues.

Cell Adhesion Molecules, Neuronal↗

PubMed1990

Evidence against transition metal-independent hydroxyl radical generation by xanthine oxidase.

It is shown by the use of EPR spectroscopy that formation of the hydroxyl radical adduct with the spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO) in the xanthine-xanthine oxidase system is hydrogen peroxide-independent. Production of the DMPO-hydroxyl radical adduct is inhibited by superoxide dismutase but is unaffected by purified grades of catalase. Hydroxyl radicals are a secondary product of the decomposition of the DMPO-superoxide radical adduct and are also formed as a result of trace metals such as iron present in the buffer. These results are in contrast with a recent report (Kuppusamy, P., and Zweier, J. W. (1989) J. Biol. Chem. 264, 9880-9884) in which the assertion is made that the hydroxyl radical adduct arises from the trapping of hydroxyl radicals generated via the direct reduction of hydrogen peroxide by xanthine oxidase. It is demonstrated here that treatment of phosphate buffer with the chelator deferoxamine mesylate is not in itself sufficient to suppress the effect of contaminating adventitious metal ions in xanthine-xanthine oxidase incubations.

Catalase↗

PubMed1990

Calcitonin free oat-cell carcinoma of the thyroid gland.

Two cases of primary oat-cell carcinoma of thyroid, in a 63-year-old woman and a 73-year-old man, are described. Case 1 was a compound tumour with the oat-cell component merging with a papillary component. Both tumours, in addition to histological features consistent with oat-cell carcinoma, showed immunohistochemical positivity with anti-chromagranin A and anti-synaptophysin antisera. Negative results were obtained when anti-calcitonin and anti-thyroglobulin antisera were employed. Using in situ hybridization, chromogranin A and B messenger RNAs were localized with biotinylated oligonucleotide probes. In contrast, with in situ hybridization, no localization for calcitonin messenger RNA was seen using radioactive and biotinylated probes. It is concluded that these calcitonin-free, small-cell carcinomas should be considered separately from medullary thyroid carcinomas and be regarded as a distinct entity, probably the thyroid equivalent of oat-cell carcinomas of the lung.

Aged↗

PubMed1990

Detection of chromogranins A and B in endocrine tissues with radioactive and biotinylated oligonucleotide probes.

We analyzed the distribution of chromogranins A and B in normal and neoplastic endocrine tissues with secretory granules using 35S-labeled and biotin-labeled oligonucleotide probes by in situ hybridization (ISH). Both radioactive and nonradioactive probes detected messenger RNAs (mRNAs) in frozen and paraffin tissue sections. Endocrine tissues with variable immunoreactivities for chromogranin A protein, such as small-cell lung carcinomas, neuroblastomas, insulinomas, and parathyroid adenomas, expressed the mRNA for chromogranins A and B in most cells. Some technical problems with the biotinylated probes included nonspecific nuclear staining and endogenous alkaline phosphatase, which was not completely abolished by levamisole pretreatment. A differential distribution of chromogranins A and B was seen in pituitary prolactinomas, which expressed abundant chromogranin B but not chromogranin A mRNAs, and in parathyroid adenomas, which expressed abundant chromogranin A but only small amounts of chromogranin B mRNAs. These results indicate that ISH can be used to detect chromogranins A and B in endocrine tissues with radioactive and biotinylated oligonucleotide probes and that the mRNAs for chromogranin A and B are demonstrable in some tumors even when the chromogranin proteins cannot be detected by immunohistochemistry.

Biotin↗

PubMed1990

Gonadotropin-releasing hormone regulates gonadotropin beta-subunit and chromogranin-B messenger ribonucleic acids in cultured chromogranin-A-positive pituitary adenomas.

Chromogranin-A-positive pituitary adenomas include glycoprotein hormone-producing adenomas, null cell adenomas, and a few other pituitary adenomas. We studied the effects of GnRH, CRF, dexamethasone, and phorbol 12-myristate 13-acetate on FSH and LH secretion and on FSH beta and chromogranin-A and -B mRNA expression in 10 chromogranin-A-positive adenomas in vitro to analyze the regulation of FSH and chromogranin-A and -B expression in these neoplasms. Most adenomas responded to GnRH stimulation during 7 days in culture with a 2- to 10-fold increase in FSH and LH secretion and a 2- to 7-fold increase in FSH beta mRNA compared to control values. CRF and phorbol 12-myristate 13-acetate also stimulated FSH and LH secretion 2- to 5-fold in five of seven and three of three cases, respectively, during 7 days in culture. Dexamethasone stimulated both FSH and LH secretion in two of three cases as well as FSH beta mRNA in vitro in the one case examined. GnRH treatment consistently produced a 2-fold increase in chromogranin-B mRNA, but not in chromogranin-A mRNA, after 7 days of culture. These results indicate that many chromogranin-A-positive adenomas respond to GnRH and CRF in vitro by increased hormone secretion and that GnRH stimulation leads to increased amounts of FSH beta and chromogranin-B mRNAs. The differential response of chromogranin-A and -B mRNAs after GnRH stimulation indicates that the chromogranin genes are highly regulated in these tumors.

Adenoma↗