Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P61278 (somatostatin)
 22,083 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The rat pheochromocytoma cell line PC12 forms neurites in response to nerve growth factor (NGF), and it was also reported to extend processes in the presence of somatostatin (somatotropin release-inhibiting factor, SRIF), a neuroactive peptide that seems to act as a morphogenetic factor in the developing nervous system. In the present study, we re-evaluated the effects of SRIF on PC12 cell differentiation. Our results indicate that SRIF alone is ineffective in promoting neurite outgrowth. Instead, SRIF or its analogue, octreotide (a SRIF agonist on the receptor subtypes 2, 3 and 5), potentiates neurite extension induced by NGF. These results suggest that SRIF enhances neurite formation in PC12 cells without directly promoting neurite outgrowth. SRIF potentiation of NGF-induced neurite outgrowth persists at least in part in the presence of pertussis toxin (PTX), suggesting the involvement of PTX-insensitive G-proteins. In addition, protein kinase-dependent pathways are likely to mediate SRIF effects on NGF-induced differentiation.
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PMID:Somatostatin enhances neurite outgrowth in PC12 cells. 983 28

It has been proposed that neurotransmitters and neuromodulators may function as neurotrophic factors during the development of the nervous system. Somatostatin (SS) was known to increase neurite outgrowth in PC12 cells, rat pheochromocytoma cell line, and cerebellar granule cells as well as Helisoma neuron. To further investigate a neurotrophic role of SS, voltage-dependent K+ and Ca2+ channel expression was studied using whole-cell patch-clamp in PC12 cells and the effect of SS was compared to that of nerve growth factor (NGF). Cyclic AMP (cAMP) level and mitogen-activated protein (MAP) kinase phosphorylation were also studied following the treatment with SS and/or NGF. Whereas NGF (50 ng/ml) increased continually the current density of the voltage-dependent K+ channel throughout 8 days treatment, SS (1 microM) increased the K+ current density on day 2 to the peak. K+ current density was decreased thereafter and was not different on day 6 from that of undifferentiated cells. Although SS did not increase voltage-dependent Ca2+ current density, it potentiated NGF-induced increase of voltage-dependent Ca2+ channel current density as well as the K+ current density. cAMP level was decreased by NGF and/or SS treatment. An increased phosphorylation of MAP kinase induced by NGF was not changed by SS treatment. These results support functionally that SS may function as a neurotrophic factor in developing nervous system.
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PMID:Somatostatin potentiates voltage-dependent K+ and Ca2+ channel expression induced by nerve growth factor in PC12 cells. 987 77

Although in situ hybridization has been used to examine the distribution of messenger RNA for somatostatin receptor subtypes (sst) in human tumors, the cellular localization of sst1 and sst2A receptors has not been reported. In this study, we describe the cellular localization of human sst1 and sst2A receptor proteins in both cryostat- and paraffin-embedded sections of 25 human tumor tissues using two recently developed polyclonal antibodies. Six somatostatin (SS) receptor (SSR) positive tumors (two gastrinomas, three carcinoids, one pheochromocytoma) and one SSR negative tumor (renal cell carcinoma), selected by positive and negative SSR autoradiography, respectively, were studied by both immunohistochemistry and Western blot analysis. The six SSR positive tumors expressed sst2A, while 4 of 5 expressed sst1 as well. The SSR negative tumor did not express either sst1 or sst2A. Western blot analysis of wheat germ agglutinin purified membrane proteins confirmed the presence of the sst1 and sst2A glycosylated receptors. The paraffin-embedded sections gave best information with respect to the subcellular localization. Sst1 immunoreactivity was observed both on the membrane and in the cytoplasm, while sst2A showed predominantly membrane-associated immunoreactivity. This subcellular distribution of sst1 or sst2A receptors was confirmed in paraffin-embedded sections of 8 additional intestinal carcinoids, 5 gastrinomas and 5 pheochromocytomas. Sst1 receptors were detected in 7 out of 8 carcinoids, in all gastrinomas, and in 4 out of 5 pheochromocytomas, while 6 out of 8 carcinoids, all gastrinomas, and 3 out of 5 pheochromocytomas expressed sst2A receptors. In conclusion, sst1 and sst2A receptors show a differential subcellular localization in human SSR positive tumors. The use of SSR subtype selective antibodies to detect the subcellular distribution of SSR subtypes in individual tumor cells is an important step forward to understand more about the pathophysiological role of the different SSR subtypes in human tumors.
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PMID:Immunohistochemical detection of somatostatin receptor subtypes sst1 and sst2A in human somatostatin receptor positive tumors. 1002 52

Somatostatin (SS) and SS analogues inhibit the growth of various kinds of endocrine and exocrine cells via the SS receptor (SSTR). Carcinoid tumor is representative of the tumors treatable by SS analogues. We examined the expression of SSTR2A by immunohistochemical and in situ hybridization methods with a specific antibody against a synthesized 20-amino acid peptide of the COOH terminus of human SSTR2A and oligonucleotide probes in 62 endocrine tumors of various kinds: pancreatic endocrine tumor; carcinoid; neuroendocrine carcinoma; medullary thyroid carcinoma; pheochromocytoma; and small cell carcinoma of the lung, neuroblastoma, and ganglioneuroma. SSTR2A was expressed in 87% of these tumors and at both primary and metastatic sites. The immunohistochemical reactivity of SSTR2A was strong on the cell membrane and less intense in the cytoplasm of the tumor cells. SSTR2A mRNA was also detected in the tumor cells. The results indicate the usefulness of SSTR2A analogues for the treatment of neuroendocrine tumors, even metastatic ones: metastatic carcinoids, metastatic pheochromocytomas, tumors that adhered to large vessels, and neuroendocrine carcinomas.
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PMID:Immunohistochemical expression of somatostatin type 2A receptor in neuroendocrine tumors. 1058 62

The preoperative evaluation and safe anesthetic treatment of patients with endocrine gland tumors mandate an understanding of the physiologic dysfunctions attributable to these tumors. Some patients will exhibit various signs and symptoms characteristic of the MEN syndromes. In the patient with acromegaly, a fiberoptic-guided intubation of the trachea to secure the airway before induction of general anesthesia must be anticipated. Anesthetic treatment of the patient with hyperadrenocorticism requires knowledge of the physiologic effect of excess cortisol. In the patient with severe hyperparathyroidism, we attempt to correct the markedly elevated plasma calcium levels and maintain adequate hydration and urine output perioperatively. Following thyroidectomy for MCT, 2 potential problems of concern are upper airway obstruction and aspiration resulting from injury (unilateral or bilateral) to the recurrent laryngeal nerve and the superior laryngeal nerve, respectively. The major focus during excision of an insulinoma is prevention of wide swings in blood glucose concentrations. In the gastrinoma patient, the anesthesiologist not only must correct any intravascular fluid volume deficit or electrolyte imbalance but must also consider the patient to have a full stomach at the time of anesthetic induction. Correction of hypokalemia and control of hypertension may be required in the preoperative preparation of the patient with an adrenal cortex tumor. Preoperative alpha-adrenergic blockade must be initiated in the patient with a pheochromocytoma to prevent dangerous elevations in blood pressure during anesthesia and surgery for the tumor's removal. Vasodilators with rapid onset and short duration are used to treat intraoperative hypertension. After ligation of the tumor's blood supply, falls in blood pressure may require treatment with fluids and vasopressors. Carcinoid syndrome patients should be treated with somatostatin to prevent stimuli such as anxiety, abdominal scrubbing, or tumor manipulation from precipitating severe hypotension, hypertension, bronchospasm, or tachycardia. In both pheochromocytoma and carcinoid patients, a smooth anesthetic induction and tracheal intubation plus avoidance of drugs that release histamine or activate the sympathetic nervous system may also prevent intraoperative crises.
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PMID:Anesthetic implications for surgical patients with endocrine tumors. 1081 14

Sensitive, specific radiopharmaceuticals are available for scintigraphic diagnosis and internal radiotherapy of neuroendocrine tumors. (123)I-MIBG (metaiodobenzylguanidine) scintigraphy is the examination of choice for visualizing tumor sites of pheochromocytoma. In the event of malignant pheochromocytoma or carcinoid tumor, this examination allows assessment of the presence or absence of tumor uptake and can guide radiotherapy with (131)I-MIBG. The peptides secreted by neuroendocrine tumors can be radiolabeled for targeting of their specific receptors. Scintigraphy using a (111)In-labeled somatostatin analog (octreotide) is the examination of choice for diagnosis of the spread of gastroenteropancreatic and carcinoid tumors, as it is more sensitive than morphologic imaging techniques. It can also guide radiotherapy performed with the same pharmaceutical vector. These same two agents (MIBG and octreotide) can be used therapeutically by replacing (123)I with (131)I and (111)In by (90)Y. A transient palliative effect is obtained for a variable number of tumors (most often large ones) that take up the radiopharmaceutic agent well. There is general consensus that, for relatively radioresistant solid tumors, this type of radiotherapy is efficient only in the event of small tumor targets (a few millimeters in diameter) whose uptake is maximal, allowing more homogeneous distribution than that achieved with large tumors. Thus for optimal control of the disease it is recommended first to use scintigraphic imaging to confirm that the tumor takes up the radiopharmaceutical agent in question ((123)I-MIBG or (111)In-octreotide) and then reduce the tumor burden surgically before injecting high therapeutic activity (possibly with reinjection of peripheral stem cells). This treatment can be repeated three times every 3 months before evaluating the response. In these conditions, internal radiotherapy can be beneficial or even determinant for controlling disease progression.
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PMID:Nuclear medicine applications for neuroendocrine tumors. 1103 95

Selecting the appropriate approach for resection and follow-up of pheochromocytomas (PCCs) is highly dependent upon reliable localization and exclusion of multifocal, bilateral, or metastatic disease. Metaiodobenzylguanidine (MIBG) scintigraphy was developed for functional localization of catecholamine-secreting tissues. Somatostatin receptor imaging (SRI) has a high sensitivity for localizing head and neck paragangliomas, but studies of intraabdominal PCCs are rare. In this study we review our experience of [(123)I]MIBG and SRI, performed since 1983 and 1989, respectively, in the work-up of primary and recurrent PCCs. Scintigraphic results were correlated with catecholamine secretion, size and site, malignancy, associated tumor syndromes, and morphological features. [(123)I]MIBG scans were performed in a total of 75 patients, in 70 cases before resection of primary PCCs and in 5 cases because of recurrent disease. Ninety-one PCCs were resected. The overall detection rates were 83.3% and 89.8% for PCCs larger than 1.0 cm. Multifocal disease was detected in 4 patients with [(123)I]MIBG. [(123)I]MIBG uptake correlated with greater size of PCC (r = 0.33; P = 0.008) and greater concentration of plasma epinephrine (r = 0.32; P = 0.006). [(123)I]MIBG-negative PCCs (n = 14) had significantly (P = 0.01) smaller diameters than [(123I)]MIBG-positive tumors. Furthermore, [(123)I]MIBG uptake was significantly higher in unilateral (P = 0.02), benign (P = 0.02), sporadic (P = 0.02), intraadrenal (P = 0.02), and capsular invasive (P = 0.03) PCCs than in bilateral, malignant, MEN2A/2B-related, extraadrenal, and noninvasive PCCs, respectively. The detection rate of SRI was only 25% (8 of 32) for primary benign PCCs. In 14 patients metastases occurred, which were effectively visualized with [(123)I]MIBG in 8 of 14 cases. SRI was able to detect metastases in 7 of 8 cases, including 3 [(123)I]MIBG-negative metastatic cases. In addition, [(123)I]MIBG and SRI detected 2 recurrences. In conclusion, [(123)I]MIBG uptake is correlated with the size, epinephrine production, and site of PCCs. Its role in bilateral and MEN2A/2B-related PCCs seems limited. In cases of recurrent elevation of catecholamines, localization of metastases and/or recurrence should be attempted with [(123)I]MIBG scintigraphy. In suspicious metastatic PCCs, SRI might be considered to supplement [(123)I]MIBG scintigraphy.
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PMID:[(123)I]metaiodobenzylguanidine and [(111)In]octreotide uptake in begnign and malignant pheochromocytomas. 1115 32

Medullary thyroid carcinoma (MTC) originates in the parafollicular cells (C cells) of the thyroid, secreting both calcitonin and CEA. Genetic and biochemical testing allow early pre-clinical identification of familial forms. Sporadic MTC usually presents as a solitary palpable thyroid nodule and in most cases the definitive diagnosis is established only at the time of surgery. Nuclear medicine procedures, which play a minor role in the preoperative evaluation of MTC, are essential in postoperative follow-up to detect residual and/or recurrent tumor. A number of radiopharmaceuticals are able to visualize MTC lesions with considerable advantages in diagnosis and prognosis, some of them having also a therapeutic role. Among them, 99mTc[V]DMSA shows the highest diagnostic sensitivity and is considered by many authors the radiopharmaceutical of choice in the postoperative work-up of MTC. Radioiodinated MIBG, in spite of its high specificity has a poor sensitivity (30%); however it is useful for the identification of pheochromocytoma and, in patients showing MIBG uptake in tumoral lesions, high activities of 131I-MIBG may be used for therapy. 111In labeled octreotide detects lesions which express somatostatin receptors; a positive scintigraphic result seems to give also prognostic information (higher uptake in slow-growing lesions) and provides the basis for treatment with octreotide or lanreotide and 111In or 90Y-labeled octreotide analogues. Interesting perspectives are offered by 18F-FDG PET and monoclonal anti-CEA labeled antibodies; the latter may be also used for therapy.
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PMID:Role of nuclear medicine in the diagnosis and therapy of medullary thyroid carcinoma. 1137 May 45

This is a consensus statement from an international group, mostly of clinical endocrinologists. MEN1 and MEN2 are hereditary cancer syndromes. The commonest tumors secrete PTH or gastrin in MEN1, and calcitonin or catecholamines in MEN2. Management strategies improved after the discoveries of their genes. MEN1 has no clear syndromic variants. Tumor monitoring in MEN1 carriers includes biochemical tests yearly and imaging tests less often. Neck surgery includes subtotal or total parathyroidectomy, parathyroid cryopreservation, and thymectomy. Proton pump inhibitors or somatostatin analogs are the main management for oversecretion of entero-pancreatic hormones, except insulin. The roles for surgery of most entero-pancreatic tumors present several controversies: exclusion of most operations on gastrinomas and indications for surgery on other tumors. Each MEN1 family probably has an inactivating MEN1 germline mutation. Testing for a germline MEN1 mutation gives useful information, but rarely mandates an intervention. The most distinctive MEN2 variants are MEN2A, MEN2B, and familial medullary thyroid cancer (MTC). They vary in aggressiveness of MTC and spectrum of disturbed organs. Mortality in MEN2 is greater from MTC than from pheochromocytoma. Thyroidectomy, during childhood if possible, is the goal in all MEN2 carriers to prevent or cure MTC. Each MEN2 index case probably has an activating germline RET mutation. RET testing has replaced calcitonin testing to diagnose the MEN2 carrier state. The specific RET codon mutation correlates with the MEN2 syndromic variant, the age of onset of MTC, and the aggressiveness of MTC; consequently, that mutation should guide major management decisions, such as whether and when to perform thyroidectomy.
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PMID:Guidelines for diagnosis and therapy of MEN type 1 and type 2. 1205 Feb 90

A 35-year-old woman was admitted to our hospital with the following complaints, headache, sweating, anxiety, dizziness, nausea, vomiting and severe hypertension. The technical images (abdominal CT, scintigraphic octreotide scan and renal arteriography) revealed the presence of a left adrenal pheochromocytoma and stenosis of the renal artery. Ten days following adrenalectomy, watery diarrhea appeared. The long-acting somatostatin analogue octreotide (LAR, 30 mg/month, i.m.), was started, and after 2 weeks diarrhea decreased and gradually disappeared. In conclusion, we were confronted with an unusual case of pheochromocytoma associated with renal artery stenosis and the appearance of watery diarrhea some days after surgical treatment. Treatment with octreotide brought about the remission of diarrhea in this patient.
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PMID:A case of pheochromocytoma with renal artery stenosis and post-surgical watery diarrhea. 1184 76


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