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G M Besser

Publications and source records attributed to G M Besser.

At least 163 records · Page 9Linked to original sources
PubMed1993

Melatonin and its analogs inhibit the basal and stimulated release of hypothalamic vasopressin and oxytocin in vitro.

The secretion of neurohypophyseal hormone and ACTH in the rat has been shown to exhibit circadian rhythms, with high values during the day and low values throughout the night. The neurohypophyseal hormone daily rhythm is altered by exposure to constant light and by pinealectomy. It was, thus, proposed that the observed fall in vasopressin (AVP), oxytocin, and ACTH over the hours of darkness could be related to the release of melatonin seen at this time. Therefore, a study was performed to determine the effect of melatonin on AVP, oxytocin, and CRH-41 release from the isolated rat hypothalamus in vitro. Employing a previously validated technique, rat hypothalami were incubated in either medium alone or medium containing melatonin or one of two melatonin analogs. Hormone release was measured by RIA, and the ratios were calculated and compared by Student's t test, with Dunnett's correction for multiple comparisons. Melatonin showed a dose-dependent inhibition of both basal and stimulated AVP and oxytocin release in the concentration range 4.3 x 10(-10) to 2.5 x 10(-3) M, while having no significant effect on the release of CRH-41. The two melatonin analogs, 2-iodomelatonin and 5-methoxy-N-isobutanoyltryptamine, were also found to inhibit both basal AVP and oxytocin release, indicating that this effect probably depends upon the presence of melatonin receptors in the hypothalamus. This inhibitory modulation of AVP, in the absence of any effect on CRH-41, suggests that melatonin may affect water balance by means of directly inhibiting hypothalamic AVP release. Furthermore, circadian rhythmicity in pituitary-adrenal activity may depend on melatonin modulation of AVP, rather than changes in CRH-41.

Animals↗
PubMed1993

Plasma catecholamine levels in porcine Escherichia coli septicaemia and following treatment with buprenorphine or naloxone.

Changes in plasma catecholamine levels in response to the induction of shock and following treatment with buprenorphine or naloxone were determined in a porcine model of Escherichia coli septicaemia. Thirty animals were anaesthetised with alpha-chloralose and infused with live E. coli over 2 hr. One hour after starting the infusion, cardiac index, mean arterial pressure, and pH had decreased significantly (P < 0.001), and there was a significant increase in mixed venous blood lactate concentrations (P < 0.001). This was associated with significant increases in plasma concentrations of adrenaline and noradrenaline (P < 0.001). There was a strong correlation between the extent of the increase in circulating catecholamines and the severity of shock (as reflected by haemodynamic changes and lactic acidosis) as well as significantly higher peak plasma catecholamine concentrations (P < 0.01) and dramatic terminal increases in circulating catecholamines in nonsurviving animals. Animals were randomly divided into three groups and received either naloxone or buprenorphine or an equivalent volume of normal saline and were monitored for a further 3 hr. Both naloxone and buprenorphine produced significant improvements in cardiac index (P < 0.05) and limited the development of acidosis (P < 0.05). This was not associated with any further increase in plasma catecholamine concentrations; indeed, catecholamine levels tended to decrease in treated animals but continued to increase in controls. In summary, we have shown a correlation between the increase in plasma catecholamines and the severity of shock in this model. In addition, we observed that the beneficial effects of treatment with buprenorphine or naloxone were not accompanied by any further increase in plasma catecholamine concentrations.

Animals↗
PubMed1992

Effect of 12-hour infusion of naloxone on mood and cognition in normal male volunteers.

The effects of a 12-hour naloxone infusion on mood, cognition, and plasma cortisol levels were evaluated in eight normal subjects. The dosage used was a 10 mg dose plus 7 mg/hr (total = 94 mg). Naloxone induced a significant rise in serum cortisol and also induced cognitive impairment, as shown by increased choice reaction time, reduced ability to recall the order of letters and numbers, and reduced accuracy of spatial orientation. The rise in cortisol induced by naloxone was significantly correlated with the rise in the Profile of Mood Scale (POMS) score, indicative of dysphoria. Finally, performance on the spatial orientation task was highly negatively correlated with the peak POMS score after naloxone. From these data and previous studies it is concluded that opioid receptors of low sensitivity to naloxone may mediate a common mechanism regulating the pituitary-adrenal axis' mood, and cognitive function during stress. Personality traits may account for the large individual variability reported in previous studies.

Adult↗
PubMed1992

Octreotide.

Explore the source record for details and available documents.

Acromegaly↗
PubMed1992

Gallstones during octreotide therapy.

Gallbladder stones (GBS) are found in up to 50% of patients receiving octreotide, but the reported prevalence of cholecystolithiasis in patients treated with octreotide is variable and little is known about gallstone incidence, composition, pathogenetic mechanisms, dissolvability, and primary prevention. Octreotide treatment apart, in industrialised societies most GBS are mixed in composition, cholesterol-rich (arbitrarily greater than 70% cholesterol by weight), radiolucent (70%), and, given a patent cystic duct (70%), dissolvable in bile rendered unsaturated in cholesterol by oral ursodeoxycholic (UDCA) +/- chenodeoxycholic (CDCA) acid treatment. They form when (1) GB bile becomes supersaturated with cholesterol (as the molar ratio of cholesterol to phospholipids in biliary vesicles approaches 1:1, the vesicles become unstable); (2) there is an imbalance between pro- and anti-nucleating factors, which favors cholesterol crystal precipitation; and (3) there is stasis within the GB as a result of altered motor function and/or excess mucus that traps the crystals. These changes may be associated with altered (4) biliary bile acid composition (more DCA and less CDCA than normal), and/or (5) phospholipid fatty acid composition (arachidonyl-rich lecithin acting as a substrate for mucosal prostaglandin synthesis which, in turn, may influence both gallbladder motility, and mucus glycoprotein synthesis and secretion). During octreotide treatment, meal-stimulated cholecystokinin (CCK) release is impaired leading to GB hypomotility, but little is known about the effects of octreotide on biliary cholesterol saturation, crystal nucleation time, mucus glycoprotein concentration, bile acid or phospholipid fatty acid composition. Most, but not all, reports suggest that the prevalence of GBS in octreotide-treated patients is considerably greater than that in age-, sex-, and weight-matched controls, but proof (by pre-treatment and on-treatment ultrasound) that the GBS were absent before, but developed during, therapy is not always available. Furthermore, there are few data on analysis of GBS composition in patients developing stones during treatment, although initial reports suggest that octreotide-associated GBS are also radiolucent, cholesterol-rich, and dissolve with oral bile acid treatment. Maximum GBS attenuation values, measured in Hounsfield Units (HU) by localized computerized tomography scanning of the GB, predict stone composition and dissolvability: GBS with scores of less than 100 HU are cholesterol-rich and dissolve well with oral bile acid treatment. However, preliminary results in 11 acromegalic patients treated with 200 to 600 micrograms octreotide/d for 29 to 68 months show that the HU scores range from 23 to 490 (mean +/- SEM, 116 +/- 41), suggesting that at least four of these 11 patients have non-cholesterol stones.(ABSTRACT TRUNCATED AT 400 WORDS)

Acromegaly↗
PubMed1992

Proceedings of the workshop, "Practical approaches to the diagnosis and treatment of acromegaly".

Practical approaches to the management of acromegaly are discussed. The roles of surgery, radiotherapy, and medical treatment with oral dopamine agonists such as bromocriptine or the long-acting somatostatin analogue octreotide given subcutaneously are reviewed. Most cases need surgery, but cure is rare in patients with macroadenomas, although common with microadenomas. Radiotherapy should be considered in surgical failures, but takes several years to be effective. Medical treatment with octreotide is effective in the majority, for whom it represents a major advance, but it needs to be administered subcutaneously and the development of gallstones and gastritis in long-term treatment are problems. Bromocriptine is usually less effective, but occasionally still plays a role in the therapeutic program. Combinations of the different modalities are usually required in the management of acromegalic patients.

Acromegaly↗
PubMed1992

Pituitary imaging using a labelled somatostatin analogue in acromegaly.

OBJECTIVE: A number of neoplasms are known to express somatostatin receptors, and the use of somatostatin receptor imaging in their localization has recently been described. We have looked at the use of an 123I-labelled Tyr3-octreotide analogue of somatostatin in the visualization and functional characterization of growth hormone-secreting pituitary adenomas. PATIENTS: Fifteen patients with biochemically-proven acromegaly were scanned using this agent. In eight of these we also assessed acute GH responses to octreotide in order to correlate these responses with tumour uptake characteristics. MEASURES: Planar and single-photon-emission computerized tomographic (SPECT) images of the head were obtained using a gamma-camera at 10 minutes, and 4 and 24 hours, after injection of the radiopharmaceutical. Blood for serum GH was sampled for 12 hours after administration of a single dose of 100 micrograms octreotide. RESULTS: Twelve of the acromegalic subjects showed significant uptake of the radiopharmaceutical in the pituitary fossa. Of the eight patients in whom we assessed acute GH responses, five demonstrated a significant fall in GH in response to octreotide. These subjects also showed positive uptake in the pituitary on scanning. The three patients who had no fall in GH had no uptake on scanning. CONCLUSIONS: Uptake of 123I-labelled Tyr3-octreotide in the pituitary fossa appears to correlate closely with the presence of a therapeutic response to octreotide.

Acromegaly↗
PubMed1992

Interleukin-6, a growth promoting cytokine, is present in human pituitary adenomas: an immunocytochemical study.

OBJECTIVE: The aim of this study was to investigate the presence of interleukin-6 (IL-6) in human pituitary adenomas. DESIGN: Immunocytochemistry was performed in 15 cases of pituitary adenomas obtained at transsphenoidal surgery. PATIENTS: Fifteen cases of pituitary adenomas were examined; these included five GH-secreting adenomas, four prolactinomas, four ACTH-secreting adenomas and two null-cell ('functionless') adenomas. MEASUREMENTS: Each tumour was stained for the presence of IL-6 by means of the avidin-biotin-peroxidase complex (ABC) technique, and was also stained for GH, prolactin, ACTH and alpha-subunit by conventional immunocytochemistry. RESULTS: Fourteen of the 15 tumours examined, excepting one GH-secreting tumour, demonstrated clusters of IL-6 positively stained cells; the specificity of the staining was established by a significant decrease in staining in parallel sections of all tumours studied when the anti IL-6 antibody was preabsorbed with recombinant human IL-6. CONCLUSIONS: It is concluded that IL-6 immunoreactivity is present in human pituitary tumours, and is independent of the specific secretory cell product. The role of this cytokine in the pathogenesis of such tumours requires further investigation.

Adenoma↗
PubMed1992

Prevalence of gastritis in patients with acromegaly: untreated and during treatment with octreotide.

OBJECTIVE: It has previously been suggested that acromegalic patients treated with the somatostatin analogue octreotide invariably have chronic gastritis. We have examined the prevalence of gastritis in a large group of acromegalic patients, untreated and during treatment with octreotide. DESIGN: We studied three groups of acromegalic patients: (A) untreated; (B) octreotide-treated; (C) a subgroup of these studied both before and during octreotide therapy. PATIENTS: Forty-eight patients, grouped as above, with active acromegaly were examined for the presence of gastritis. MEASUREMENTS: Gastroscopy and histological examination of gastric biopsies for the presence of gastritis and Helicobacter organisms were undertaken. The principal outcome was quantification of the prevalence of gastritis in the various study groups. RESULTS: Group A: 10 of the 33 patients (30%) had gastritis before any therapy with octreotide. Group B: 17 of 36 patients (47%) on octreotide treatment for 6-59 months (mean 20.5) had gastritis, and this was present in five out of the sub-group of eight patients (62%) treated for over 3 years. Group C: three of 21 patients (14%) developed gastritis during treatment with octreotide for between 6 and 23 months (mean 12.4). There was a highly significant association between the presence of gastritis and the presence of Helicobacter pylori organisms. CONCLUSIONS: Octreotide therapy of acromegaly may predispose to the development of gastritis, but this remains statistically unproven. Certainly, gastritis is not an invariable consequence of octreotide therapy, even after prolonged periods of treatment. The presence of gastritis is associated with H. pylori infection.

Acromegaly↗
PubMed1992

Mania in association with hydrocortisone replacement for Addison's disease.

A 32 year old woman with untreated primary adenocortical insufficiency presented with prominent depressive symptoms. Upon treatment with physiological doses of glucocorticoids she developed a self-limiting acute manic illness. We suggest that up-regulation of hippocampal glucocorticoid receptors as a consequence of prolonged hypocortisolaemia resulted in increased cerebral sensitivity to exogenous corticosteroids, which are known to precipitate manic symptoms in some normal individuals when given in supraphysiological doses.

Acute Disease↗
PubMed1992

Effect of metyrapone on the pituitary-adrenal axis in depression: relation to dexamethasone suppressor status.

It has been suggested that the well-documented hypercortisolaemia found in a proportion of patients with severe depression occurs either in response to excessive secretion of corticotrophin-releasing hormone-41 (CRH-41) from the hypothalamus, or as a consequence of up-regulation of pituitary CRH-41 receptors. The attenuation of the normal ACTH response to CRH-41 in these subjects is thought to result from inhibition of corticotrophin secretion by elevated cortisol levels. We tested these hypotheses by examining ACTH responses to metyrapone, an 11 beta-hydroxylase inhibitor which blocks the formation of cortisol, followed by CRH-41 in 15 severely depressed in-patients diagnosed according to DSM-IIIR criteria. Patients were assigned to two groups according to their response to overnight administration of 1 mg dexamethasone: suppressors (8) and nonsuppressors (7). A third group consisted of 6 healthy matched controls. Metyrapone 750 mg was given 4-hourly for 24 h and samples were taken for cortisol and ACTH. Six of the original 15 patients (3 from each group) were given a bolus dose of 100 micrograms human CRH-41 intravenously after 24 h of metyrapone, and ACTH levels were measured over 2 h. Falls in circulating cortisol in response to metyrapone were similar in all three groups. However, we found exaggerated rises in ACTH amongst the nonsuppressors, as compared to the suppressors and the control group, after metyrapone.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Cortex Hormones↗
PubMed1992

Differential effects of neuroexcitatory amino acids on corticotropin-releasing hormone-41 and vasopressin release from rat hypothalamic explants.

We have investigated the direct effects of different neuroexcitatory amino acids (EAA) on the secretion of CRH-41 and arginine vasopressin (AVP) from the rat hypothalamus maintained in vitro. CRH-41 and AVP released in the medium were assayed by RIA before and after incubation with N-methyl-D-aspartate (NMDA), N-methyl-D,L-aspartic acid, kainate (KA), and quisqualate in the concentration range 1 nM to 1 mM in either the absence or the presence of 1 mM Mg2+ in the medium. In the case of NMDA, the effect of the addition of glycine (1 and 10 microM) to the incubation medium was also studied. Finally, we investigated whether different periods of exposure (up to 100 min) of hypothalamic explants to NMDA and KA would affect CRH-41 release. While no EAA was able to induce CRH-41 release under any of the above conditions, 20-min incubations with NMDA in the dose range of 1 nM to 1 mM in the absence of added Mg2+ significantly stimulated AVP release in a dose-related fashion; the maximum effect occurred at a concentration of 1 mM [ratio of stimulated collection/basal collection: NMDA, 1.51 +/- 0.10, controls, 0.86 +/- 0.05 (mean +/- SEM); P < 0.001]. KA also showed a dose-related stimulatory effect in the dose range of 1 nM to 1 mM, with maximal AVP stimulation at 10 microM (KA, 1.91 +/- 0.28; controls, 0.90 +/- 0.03; P < 0.01). The effects of both NMDA and KA on AVP were completely reversed by the competitive antagonists D,L-2-amino-5-phosphonovaleric acid and 6-cyano-7-nitroquinoxaline-2,3 dione, respectively, at doses 10 times higher than those of the agonists. N-Methyl-D,L-aspartic acid stimulated AVP secretion only at a dose of 10 mM (P < 0.01), whereas quisqualate was ineffective at any concentration. The addition of 1 mM Mg2+ to the medium blocked the effect of NMDA, while attenuating AVP stimulation induced by KA. The stimulatory effect of KA on AVP was significantly reduced by D-L-2-amino-5-phosphonovaleric acid (P < 0.05), suggesting that KA may also act through NMDA receptors. Moreover, the presence of glycine in the incubation medium did not result in any effect of NMDA on CRH-41 secretion, nor did it appear to potentiate NMDA-induced AVP release.(ABSTRACT TRUNCATED AT 400 WORDS)

2-Amino-5-phosphonovalerate↗
PubMed1992

The effect of a met-enkephalin analogue on growth hormone, prolactin, gonadotropins, cortisol and thyroid stimulating hormone in healthy elderly men.

The aim of the study was to evaluate the effect of the guanyl derivative of the opioid analogue D-ala2,MePhe4-Met-enkephalin-(o)-ol (G-DAMME) on pituitary secretion in healthy elderly men. Nine healthy elderly men (65-88 years) and 10 young adults (20-30 years) were studied. GH, PRL, gonadotropins, cortisol (to evaluate the effect on ACTH) and TSH were measured after G-DAMME (0.25 mg iv) or placebo administration. In elderly men, the GH response to G-DAMME was reduced or absent, while prompt GH release was found in all young men. G-DAMME lowered LH levels in young men but not in elderly men. No significant variations in FSH levels after G-DAMME and placebo were noted in either group of subjects. A similar and significant rise in PRL and TSH, and a fall in cortisol, after G-DAMME was observed in both elderly and young adults. We have demonstrated that the sensitivity to opioid modulation by G-DAMME on PRL, TSH and cortisol secretion is unchanged with aging. On the other hand, the data indicate that LH and GH responsiveness to G-DAMME change with age.

Adult↗
PubMed1992

A comparison of the clearance of ovine and human corticotrophin-releasing hormone (CRH) in man and sheep: a possible role for CRH-binding protein.

A specific binding protein for human corticotrophin-releasing hormone (hCRH), which does not bind to the ovine hormone (oCRH), has recently been demonstrated in human plasma. No such binding protein has been found in sheep plasma. We have investigated the half-life of human and ovine CRH in man and in sheep. Peptides were measured directly in plasma with two-site immunoradiometric assays, as these assays are unaffected by the presence of inactivated peptide fragments. In man, the half-life of hCRH (30.5 +/- 3.3 min; mean +/- S.E.M.) was significantly (P less than 0.001) less than that of oCRH (42.8 +/- 6.4 min). In sheep, there was no significant difference between the half-life of hCRH (46.5 +/- 7.2 min) and that of oCRH (39.8 +/- 10.1 min); these half-lives were also significantly (P less than 0.001) longer than that of hCRH in man. One possible explanation for the shorter half-life of hCRH in man is that the clearance of hCRH is enhanced by CRH-binding protein, although other binding proteins often have the opposite effect. Peak ACTH and cortisol responses occurred earlier in sheep than in man, although no differences were found in the response times to oCRH or hCRH within either species. The responses were more sustained in sheep than in man, and the previously reported biphasic response was only seen in some of the sheep and not in man. Absolute responses to either peptide were greater in sheep than in man; however, in man an 8.1-fold rise in ACTH was measured in response to oCRH, while hCRH gave a significantly (P = 0.043) smaller 4.4-fold response.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗
PubMed1992

Pyridostigmine partially reverses dexamethasone-induced inhibition of the growth hormone response to growth hormone-releasing hormone.

The GH response to insulin-induced hypoglycaemia and growth hormone-releasing hormone (GHRH) has been shown to be impaired in subjects with Cushing's syndrome and in healthy volunteers given oral glucocorticoids. Pyridostigmine is an anticholinesterase that stimulates GH secretion, probably by inhibition of hypothalamic somatostatin secretion. This work was designed to study the site of action of glucocorticoids in inhibiting the secretion of GH. Eight healthy male volunteers were studied on three occasions in random order. They took 2 mg oral dexamethasone or placebo at precisely 6-hourly intervals for 48 h before receiving 120 mg oral pyridostigmine or placebo, followed 60 min later by GHRH (100 micrograms) i.v. Samples for measuring GH were obtained at 15 min intervals for 2 h. The 'area under the curve' (AUC) for each of the treatments was significantly different: dexamethasone-pyridostigmine-GHRH (mean +/- S.E.M., 1938 +/- 631 mU/min per l), dexamethasone-placebo-GHRH (634 +/- 211) and placebo-placebo-GHRH (4267 +/- 1183) (P < 0.02, Wilcoxon test). In conclusion, dexamethasone given for 48 h significantly inhibited the AUC for GH following treatment with GHRH. However, pretreatment with pyridostigmine significantly reversed the inhibition although this was still partial. Our data suggested that this short-term suppressive effect of dexamethasone was independent of GHRH, and most probably relates to stimulation of the release of somatostatin.

Depression, Chemical↗