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I Shimon

Publications and source records attributed to I Shimon.

At least 37 records · Page 2Linked to original sources
PubMed1998

Mutation and expression analysis of the cyclin-dependent kinase inhibitor gene p27/Kip1 in pituitary tumors.

By regulating cyclin-cyclin-dependent kinase (CDK) complex activity, individual CDK inhibitors (CDKIs) are potential tumor suppressors. One of the CDKIs, p27/Kip1, binds to a variety of CDK-cyclin complexes. A link between loss of p27/Kip1 function and development of pituitary tumors was suggested by the formation of pituitary tumors in almost all mice with germline deletion of the p27/Kip1 gene. However, genetic aberrations in the p27/Kip1 locus have not been analyzed in human pituitary tumors. We investigated eighteen non-functioning and GH-secreting pituitary tumor samples for p27/Kip1 mutations by single-strand conformational polymorphism (SSCP) following PCR. We found five abnormally migrating samples on the PCR-SSCP analysis. The sequence of these samples revealed a polymorphism of codon 109 (Val-->Gly), which has been previously described. No other structural changes of p27/Kip1 were found in these pituitary tumors within the coding region. In addition, no difference in p27/Kip1 protein levels in pituitary tumor tissues compared with normal pituitary tissues was demonstrated by immunostaining. These data suggest that both p27/Kip1 mutations and decreases in p27/Kip1 protein levels are infrequent in the development of pituitary tumors.

Cell Cycle Proteins↗
PubMed1997

Somatostatin receptor (SSTR) subtype-selective analogues differentially suppress in vitro growth hormone and prolactin in human pituitary adenomas. Novel potential therapy for functional pituitary tumors.

Previously, we have shown somatostatin receptor (SSTR) subtype-specific regulation of growth hormone (GH), thyroid-stimulating hormone, and prolactin (PRL) secretion in human fetal pituitary cultures, where GH and thyroid-stimulating hormone are mediated by both SSTR2 and SSTR5, whereas SSTR2 preferentially mediates PRL secretion. We now tested SSTR subtype-selective analogues in primary human GH- and PRL-secreting pituitary adenoma cultures. Analogue affinities determined by membrane radioligand binding in cells stably expressing human SSTR forms were either SSTR2 or SSTR5-selective. Analogues preferential either for SSTR2, including octreotide, lanreotide, and novel compounds with improved affinity for SSTR2, or new SSTR5-selective compounds suppressed GH in tumor cell cultures (up to 44% of control; P < 0.0005). However, novel analogues from both groups were 30-40% more potent than octreotide and lanreotide in suppressing GH (P < 0.05). Heterologous analogue combinations containing both SSTR2- and SSTR5-selective compounds were more potent in decreasing GH than analogues used alone (P < 0.05), or than combinations of compounds specific for the same receptor subtype (P < 0.005). In contrast, SSTR2-selective analogues did not suppress PRL release from six cultured prolactinomas studied. However, new SSTR5-selective analogues suppressed in vitro PRL secretion (30-40%; P < 0.05) in four of six prolactinomas. These results suggest that both SSTR2 and SSTR5 are involved in GH regulation in somatotroph adenoma cells, whereas SSTR5 exclusively regulates PRL secretion from prolactinoma cells. Thus, somatostatin analogues with improved selective binding affinity for these receptor subtypes may be effective in the treatment of either GH- or PRL-secreting adenomas.

Adenoma↗
PubMed1997

Cytokine-dependent gp130 receptor subunit regulates human fetal pituitary adrenocorticotropin hormone and growth hormone secretion.

We have shown recently that leukemia inhibitory factor (LIF) and oncostatin M (OSM), two members of the gp130-dependent cytokine family, stimulate murine proopiomelanocortin (POMC) transcription and adrenocorticotropin hormone (ACTH) secretion. LIF and corticotropin-releasing hormone (CRH) also synergistically induced in vivo ACTH secretion in fetal nonhuman primates. To elucidate the role of the gp130-related cytokines in human pituitary hormone regulation, we tested expression of gp130-related cytokine receptors in human fetal pituitaries. Using RT-PCR, mRNA expression of receptors for LIF, IL-6, and CRH, and the gp130 subunit, were all detected in fetal pituitaries of 18- and 31-wk gestation. Recombinant human IL-6, LIF, and OSM treatments of primary human fetal pituitary cultures (16-31 wk) increased ACTH secretion by up to 48% (P < 0.05) using doses of 1 nM, and when fetal cultures were cotreated with CRH, ACTH was induced five- to sixfold as compared to CRH alone (three- to fourfold; P = 0.01). Incubation with gp130-specific antibody suppressed basal and cytokine-stimulated ACTH secretion (alone or with CRH) from human fetal cells. Human POMC promoter -879/+6 fused to the luciferase reporter gene and transfected into AtT-20 cells, was stimulated by LIF (7-fold), which also exerted strong (22-fold) synergy with CRH on POMC transcription. Growth hormone (GH) release from fetal cultures was modestly stimulated (15-31%, P < 0.05), while other anterior pituitary hormones were not altered by these cytokines. Thus, physiologic concentrations of the gp130-related cytokines have direct effects on ACTH and GH regulation in the human pituitary, indicating that gp130-dependent signals serve as a paracrine system controlling early human pituitary function.

Adrenocorticotropic Hormone↗
PubMed1997

Somatostatin receptor subtype specificity in human fetal pituitary cultures. Differential role of SSTR2 and SSTR5 for growth hormone, thyroid-stimulating hormone, and prolactin regulation.

Somatostatin (SRIF), a hypothalamic inhibitor of pituitary growth hormone (GH) and thyroid-stimulating hormone (TSH) secretion, binds to five distinct receptor (SSTR) subtypes. We therefore tested SSTR subtype-specific SRIF analogs in primary human fetal pituitary cultures (23-25-wk gestation) to elucidate their role in regulating human pituitary function. Using reverse transcription-PCR, mRNA expression of SSTR2 and SSTR5 were detected in fetal pituitary by 25 wk. SRIF analog affinities were determined by membrane radioligand binding in cells stably expressing the human SSTR forms. GH secretion was suppressed equally (40-60%, P < 0.005) by analogs preferential for either SSTR2 (IC50 for receptor binding affinity, 0.19-0.42 nM) or SSTR5 (IC50, 0.37 nM), and compounds with enhanced affinity for SSTR2 were more potent (EC50 for GH suppression, 0.05-0.09 nM) than Lanreotide (EC50, 2.30 nM) and SRIF (EC50, 0.19 nM). Similarly, analogs with high affinity for SSTR2 or SSTR5 decreased TSH secretion (30-40%, P < 0.005). However, prolactin was effectively inhibited only by compounds preferentially bound to SSTR2 (20-30%, P < 0.05). Luteinizing hormone was modestly decreased (15-20%) by SSTR2- or SSTR5-specific analogs. An SSTR5-specific analog also exclusively inhibited GH in acromegalic tumor cells. Thus, SRIF regulation of GH and TSH in primary human fetal pituitary cells is mediated by both SSTR2 and SSTR5, both of which are abundantly expressed by 25 wk. In contrast, suppression of prolactin is mediated mainly by SSTR2. These results indicate that SSTR5 is critical for physiologic regulation of GH and TSH. SRIF analogs with selective affinity for this receptor may therefore be more effective in the treatment of hormone-secreting pituitary adenomas.

Adrenocorticotropic Hormone↗
PubMed1997

A pituitary mass and hypopituitarism: improvement after corticosteroid therapy.

Lymphocytic hypophysitis of the anterior pituitary is a rare autoimmune disease, invariably diagnosed either by surgical biopsy of the adenohypophysis or at autopsy. The current report describes the rapid development of hypopituitarism in a 42-year-old nulliparous woman with a large sellar mass, who did not undergo pituitary surgery. Transient regression of the sellar mass and partial improvement of the hypopituitarism was induced by treatment with corticoids. We suggest that the diagnosis of lymphocytic hypophysitis can be established clinically and that conservative treatment with corticoids should be considered prior to surgical intervention.

Adult↗
PubMed1997

Structure and function of somatostatin receptors in growth hormone control.

This new generation of SRIF analogs offer exciting opportunities to improve hormone hypersecretion in patients with GH- and TSH-secreting pituitary adenomas and possibly even in patients harboring prolactinomas and non-functioning tumors. Future development of novel analogs with improved affinity for both SSTR2 and SSTR5 may have even greater potency to suppress pituitary hormone hypersecretion and block adenoma growth.

Adenoma↗
PubMed1996

Heparin-binding secretory transforming gene (hst) facilitates rat lactotrope cell tumorigenesis and induces prolactin gene transcription.

We have shown previously that human prolactinomas express transforming sequences of the heparin-binding secretory transforming gene (hst) which encodes fibroblast growth factor-4 (FGF-4). To elucidate the role of hst in pituitary tumorigenesis we treated primary rat pituitary and pituitary tumor cell cultures with recombinant FGF-4 and also stably transfected pituitary cell lines with full-length human hst cDNA. Transfectants were screened for hst mRNA expression and FGF-4 production. FGF-4 (0.1-50 ng/ml) caused a dose-dependent 2.5-fold increase of prolactin (PRL) secretion (P < 0.001) in GH4 cells and up to 60% (P < 0.05) in primary cultures, while decreasing growth hormone release (P < 0.001). GH4 hst transfectants displayed markedly enhanced basal PRL secretion (threefold, P < 0.001) and also proliferated faster (P < 0.001). FGF-4 treatment of wild-type GH4 cells, transiently transfected with an expression construct (rPRL.luc) containing a luciferase reporter driven by the rPRL promoter, resulted in a dose-dependent increase of up to 3.3-fold in PRL transcriptional activity. Tumors derived from in vivo subcutaneous injection of GH4 hst-transfected cells strongly expressing FGF-4 grew more aggressively as assessed by histologic invasiveness and proliferating cell nuclear antigen staining (P < 0.01). The results indicate that hst overexpression mediates lactotrope tumor growth and potently stimulates PRL synthesis. Thus, hst may directly facilitate prolactinoma development via paracrine or autocrine action of its secreted protein, FGF-4.

Animals↗
PubMed1996

Transient normal platelet counts and decreased requirement for interferon during pregnancy in essential thrombocythaemia.

We report on the remarkable decrease in the platelet counts during pregnancy in two women with essential thrombocythaemia following treatment with recombinant interferon-alpha (r-IFN-alpha). Prior to pregnancy, the first patient was treated for 10 months with r-IFN-alpha 3 x 10(6) units/d six times per week, and the platelet count ranged between 750 and 800 x 10(9)/l. Starting from the sixth week of gestation, the platelet count decreased to normal levels and remained so, resulting in a lower r-IFN-alpha requirement. Following successful delivery of a healthy newborn an abrupt rise of the platelet count to pre-gestation values was observed, necessitating increased r-IFN-alpha dosage before pregnancy. The second patient when she became pregnant had been treated with r-IFN-alpha 3 x 10(6) units/d six times per week for 10 weeks. Starting from the 24th week of gestation the platelet count decreased, and despite reduction in the dose of r-IFN-alpha reached normal values at the time of delivery. The exact mechanism for the platelet count normalization during pregnancy is unclear, and several possibilities are discussed.

Female↗
PubMed1996

Insulin-like growth factor I and its binding proteins 3 and 4 are increased in Human inflammatory synovial fluid.

OBJECTIVE: To measure insulin-like growth factor I (IGF-I) and its binding proteins (IGFBP) in human synovial fluid (SF), as IGF-I resistance in the chondrocyte was implicated in the pathogenesis of inflammatory arthritis. METHODS: Ten patients with inflammatory arthritis and 7 controls were evaluated. IGF-I and IGFBP-3 were measured by radioimmunoassay while all IGFBP were evaluated by Western ligand blotting. RESULTS: Serum IGF-I did not differ between patients and controls (22.3 +/- 2.9 vs 22.0 +/- 3.0 nmol/l), while significantly higher values were found in inflammatory SF compared with noninflammatory SF (14.7 +/- 1.5 vs 10.2 +/- 1.2 nmol/l; p = 0.05). IGFBP-3 and IGFBP-4 were the most prominent bands found in inflammatory SF by Western ligand blotting. The 24 kDa IGFBP-4 band appeared faintly in 2 noninflammatory effusions and was nearly absent in others. IGFBP-3 levels in sera from the 2 groups did not differ (2.9 +/- 0.3 vs 2.5 +/- 0.3 mg/l), but were significantly higher in inflammatory compared with noninflammatory effusions (1.5 +/- 0.2 vs 0.9 +/- 0.2 mg/l; p = 0.05). CONCLUSION: The pattern of IGFBP in SF differs in inflammatory versus noninflammatory joints.

Adult↗
PubMed1995

Prolactinoma in 53 men: clinical characteristics and modes of treatment (male prolactinoma).

The data of 53 men treated for hyperprolactinemia were reviewed retrospectively to determine the efficacy of the medical and surgical treatment. The clinical assessment, radiological and neuro-ophthalmological investigations and hormonal measurements were performed before treatment as well as during the follow-up period. Imaging evaluation included computed tomography and/or nuclear magnetic resonance of the pituitary. The hormonal profile examined was PRL, FSH, LH and testosterone, as well as TSH, T4, T3 and cortisol. Thirty patients were treated solely by dopamine agonists (DA), twenty-two men had pituitary surgery in addition to DA treatment, and one patient was operated with no need for medical treatment. Decreased sexual function was the most frequent presenting symptom (85% of the men). Most of the patients had large invasive macroadenomas, with suprasellar extension. More than 40% had visual field defects. Baseline PRL (mean +/- SE) was 51,842 +/- 9,292 mU/L and decreased to a level below 575 mU/L in 70% of the patients after DA therapy. Mean testosterone, FSH, and LH levels increased slightly but significantly from the low baseline values. Complete clinical response to DA was achieved in 49% of the men and the tumor mass disappeared entirely in 21%, and incompletely in 42%. The surgical success rate (transsphenoidal or trans-cranial operation) was low--only one of the 23 patients operated recovered completely, and most of the patients were left with hormonal deficits and hyperprolactinemia. These findings indicate that continuous medical treatment with DA should be the preferred mode of treatment for male prolactinomas. Removal of these large tumors is recommended only when the tumors are life-threatening or if drug resistance or severe adverse reactions to DA develop.

Adolescent↗
PubMed1995

The insulin-like growth factor system in regulation of normal and malignant hematopoiesis.

The published data available on the insulin-like growth factor (IGF) family of peptides, its receptors and binding proteins in connection with normal and neoplastic hematopoietic processes are reviewed. It is found that nearly all the different hematopoietic cells, either normal or neoplastic, express IGF receptors. The IGFs are involved in normal erythropoiesis, granulopoiesis and lymphopoiesis. IGFs, especially IGF-1, are mitogenic for cell lines of myeloid and lymphoid leukemias and Burkitt's lymphoma. Differentiation of certain immature malignant cell lines is associated with a decrease in the number and affinity of IGF receptors. It might be concluded that the IGFs have an important role in the physiologic and neoplastic processes of the hematopoietic system, and the expanding knowledge of this issue will contribute to the understanding of proliferation and differentiation processes in specific hematologic disorders.

Animals↗
PubMed1995

Improved left ventricular function after thiamine supplementation in patients with congestive heart failure receiving long-term furosemide therapy.

PURPOSE: We have previously found thiamine (vitamin B1) deficiency in patients with congestive heart failure (CHF) who had received long-term furosemide therapy. In the present study, we assessed the effect of thiamine repletion on thiamine status, functional capacity, and left ventricular ejection fraction (LVEF) in patients with moderate to severe CHF who had received furosemide in doses of 80 mg/d or more for at least 3 months. PATIENTS AND METHODS: Thirty patients were randomized to 1 week of double-blind inpatient therapy with either i.v. thiamine 200 mg/d or placebo (n = 15 each). All previous drugs were continued. Following discharge, all 30 patients received oral thiamine 200 mg/d as outpatients for 6 weeks. Thiamine status was determined by the erythrocyte thiamine-pyrophosphate effect (TPPE). LVEF was determined by echocardiography. RESULTS: TPPE, diuresis, and LVEF were unchanged with i.v. placebo. After i.v. thiamine, TPPE decreased (11.7% +/- 6.5% to 5.4% +/- 3.2%; P < 0.01). LVEF increased (0.28 +/- 0.11 to 0.32 +/- 0.09; P < 0.05), as did diuresis (1,731 +/- 800 mL/d to 2,389 +/- 752 mL/d; P < 0.02), and sodium excretion (84 +/- 52 mEq/d to 116 +/- 83 mEq/d, P < 0.05). In the 27 patients completing the full 7-week intervention, LVEF rose by 22% (0.27 +/- 0.10 to 0.33 +/- 0.11, P < 0.01). CONCLUSIONS: Thiamine repletion can improve left ventricular function and biochemical evidence of thiamine deficiency in some patients with moderate-to-severe CHF who are receiving longterm furosemide therapy.

Aged↗
PubMed1995

Chronic myeloid leukaemia following 131I treatment for thyroid carcinoma: a report of two cases and review of the literature.

Leukaemia is an uncommon late complication of exposure to the ionizing radiation of radioactive iodine (131I). Most cases reported have been of acute leukaemias developing after high doses of 131I. Only a few cases of chronic myeloid leukaemia (CML) have been reported in this setting to date. We report two new cases of CML after low dose radioactive iodine and review the literature. We present an analysis of the minimal relative risk of CML developing in thyroid cancer patients treated with 131I in Israel. Two male patients, 35 and 51 years old, developed CML following low dose 131I therapy for metastatic mixed papillary and follicular carcinoma of the thyroid. Both had undergone thyroidectomy and neck dissection and thyroid ablation with 131I (total dose: 56 and 130 mCi respectively). Four and 10 years later, respectively, a leucocytosis was noticed with typical blood smears, and CML was diagnosed either by Philadelphia translocation or bcr-abl gene rearrangement. Thyroid cancer at that time was in remission. Estimated minimal relative risk of CML after 131I therapy where the population considered at risk comprised all thyroid cancer patients detected during the years 1981-1991 in Israel was 8.95 (95% confidence limits 2.26-35.16). Literature review disclosed five additional similar cases. The mean radioiodine dose given to the seven CML patients was 11416MBq (range 1134-32130 MBq), considerably lower than the dose given to patients reported in the literature who subsequently developed acute leukaemias (mean 34965, range 3856-54810 MBq). We suggest that CML is a potential complication of low dose 131I therapy given for thyroid carcinoma even at the lower end of the dose range used for this indication. Leucocytosis appearing in these patients should raise the suspicion of secondary CML.

Adult↗
PubMed1995

Home monitoring of 17 alpha-hydroxyprogesterone levels by filter paper blood spots in patients with 21-hydroxylase deficiency.

BACKGROUND: 21-Hydroxylase (21-OH) deficiency is characterized by an excess of androgen in both sexes and premature skeletal maturation resulting in short adult stature and male infertility. To achieve optimal height in children and fertility in adults, the replacement treatment of 21-OH deficiency with glucocorticoids should be regulated in order to adequately reduce the excess of androgens while minimizing the dose of glucocorticoids required. Neonatal screening for 21-OH deficiency is based on the measurement of the 17 alpha-hydroxyprogesterone (17-OHP) level from blood spotted on filter paper. The aim of this study was to examine whether repeated daily blood sampling on filter paper can assist in improving the monitoring of, and compliance to, 21-OH deficiency treatment. METHODS: During a 5-year period (1989-1994) we instructed 8 patients with 21-OH deficiency (2 males with salt losing, 2 males and 1 female simple virilizing, and 1 male and 2 females with nonclassical 21-OH deficiency) aged 1.3-36 years to sample blood on filter papers 1-4 times a day and send the papers to our neonatal screening laboratory by mail. On 62 occasions we measured both serum and filter paper 17-OHP levels in order to assess the degree of correlation between the two methods. RESULTS: Comparison between the filter paper and serum 17-OHP levels showed a correlation coefficient of r = 0.87. The filter paper levels were almost always higher than the serum levels. The serum 17-OHP levels were < 1 ng/ml whenever the filter paper levels were < 3 ng/ml. On long-term follow-up of 17-OHP filter paper levels we observed major diurnal and day-to-day fluctuations which might not have been noticed on routine follow-up clinic visits. CONCLUSIONS: Filter paper follow-up of 17-OHP levels can assist in optimizing the replacement treatment in patients with 21-OH deficiency while reinforcing compliance and decreasing the need for frequent clinic visits and hospitalizations. By adjusting the glucocorticoid type, dose, and time of administration to each patient we should be able to achieve optimal growth without bone age acceleration in children, to avoid overtreatment, and to improve fertility in adults.

17-alpha-Hydroxyprogesterone↗