1,720,965 research outputs found
Treatment of acromegaly with octreotide, a synthetic analog of somatostatin with extended action
No full textOctreotide, an analog of somatostatin, is a valid tool for the cure of acromegalic disease. This compound has a prolonged half-life and is more selective than native somatostatin in suppressing growth hormone (GH) secretion. Octreotide, 100 micrograms tid sc, decreases GH levels and improves clinical symptoms in about 85% of acromegalic patients, lowering GH to below 5 ng/ml in 45% and to below 2 ng/ml in 17-21%. Octreotide normalizes somatomedin-C (IGF-I) levels in 36-50% of patients. The increase of dosage up to 1500 micrograms/day does not appear useful in poor responsive patients. No adverse effects on other endocrine functions submitted to hypothalamus-pituitary control have been observed. A slight shrinkage of the pituitary tumor is observed in 30-50% of cases. Octreotide therapy is well tolerated and side effects are usually mild. However the possibility of colelithiasis, liver damage and diabetes mellitus in patients with glucose intolerance must be taken into account. In conclusion octreotide is a useful complement to therapeutic means now used for the treatment of acromegaly
Ectopic acromegaly
No full textEctopic acromegaly is a rare syndrome (less than 1% of acromegalic patients) caused by ectopic growth hormone-releasing hormone (GHRH) or growth hormone (GH)-producing tumors. Its recognition is clinically important because acromegaly may be a symptom of an aggressive tumor, and different therapeutic approaches are required. Most cases are caused by either extra- or intracranial GHRH-producing tumors, whereas in rare instances the underlying disease is an ectopic GH-secreting tumor. The routine evaluation of circulating GHRH in all acromegalic patients may allow its early recognition, because plasma levels greater than 0.3 ng/mL are virtually diagnostic of a GHRH-producing tumor (frequently a bronchial or pancreatic carcinoid), whereas suppressed levels may suggest an ectopic GH-producing tumor. In addition to classic imaging techniques, whole body scintiscan with labeled octreotide may help in the localization of ectopic tumors. Surgical removal of the ectopic tumor is the therapy of choice, but it is not always feasible because patients often present with widespread metastases. Patients with GHRH-induced acromegaly benefit from the administration of the long-acting somatostatin analog, octreotide, which reduces GH, IGF-I, and GHRH, and may shrink the ectopic tumor, its metastases, and the secondary pituitary enlargement
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Effects of propranolol on GH responsiveness to repeated GH-releasing hormone stimulations in normal subjects
No full textThe influence of beta-adrenergic blockade by oral propranolol on the variability of GH responses to GHRH and on GH responsiveness to repeated GHRH administrations was investigated. Eight normal volunteers underwent three tests on three separate occasions. Each test consisted of two administrations of 80 micrograms GHRH at 2-h intervals without other medication (test 1) or combined with oral administration of 80 mg propranolol 90 min before the first (test 2) or the second GHRH injection (test 3). In test 1 GH levels increased significantly after the first, but not the second GHRH bolus (net incremental area under the curve [nAUC], mean +/- SD: 1453 +/- 974 and 178 +/- 309 micrograms.l-1.(120 min)-1, respectively). In test 2 basal GH secretion was not influenced by propranolol administration, whereas the GH response to the first GHRH injection was significantly greater than in test 1 (2327 +/- 1814 micrograms.l-1.(120 min)-1; p less than 0.05). However, individual subjects showed the same variability of GH response as in test 1. The GH response to the second GHRH bolus remained negligible. In test 3 administration of propranolol 90 min before the second GHRH bolus led to a clear GH increase (690 +/- 1002 micrograms.l-1.(120 min)-1), not significantly different from the GH response to the first bolus (1796 +/- 1375 micrograms.l-1.(120 min)-1). However, only 4 subjects showed a marked restoration of the GH responsiveness to the second GHRH administration. In conclusion, oral administration of propranolol is able to increase GH responsiveness to GHRH without changing the great individual variability. The response to a repeated GHRH stimulation is only partially restored by propranolol
Clinical, biochemical, and morphological correlates in patients bearing growth hormone-secreting pituitary tumors with or without constitutively active adenylyl cyclase
No full textSomatic mutations in the α-chain (αs) of the stimulatory regulatory protein of adenylyl cyclase (Gs) causing constitutive activation of the enzyme have been identified in a subset of human GH-secreting pituitary adenomas. This study reports on the differences between acromegalic patients bearing tumors without (group 1; n = 51) or with (group 2; n = 29) this alteration. No difference in age, sex, clinical features, duration of the disease, or cure rate was observed between the two groups. By contrast, group 2 patients had higher basal GH levels than group 1. Moreover, a significant difference in sellar morphology was found; group 2 patients more frequently showed sellas of normal size (grade I) than group 1. Hypersecretory activity of group 2 tumors was also apparent at electron microscopy; contrary to those of group 1, cells of group 2 tumors were densely granulated and showed prominent rough endoplasmic reticulum and Golgi complex. With respect to group 1, group 2 patients were less responsive to GH-releasing hormone, while they were more sensitive to somatostatin- and dopamine-induced GH inhibition. These results suggest that patients with constitutively active adenylyl cyclase have hyperactive tumors; the sensitivity of these tumors to inhibitory agents (somatostatin and dopamine), possibly counteracting the expression of activating mutations, might explain the low rate of tumor growth
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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