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Biomedical subjects

M Buchfelder

Publications and source records attributed to M Buchfelder.

At least 109 records · Page 6Linked to original sources
PubMed1995

Pre- and postoperative investigations of hepatic glucose production and leucine turnover in Cushing's disease utilizing stable isotope techniques.

Impairment of glucose tolerance and muscle wasting indicating a disorder of glucose metabolism are characteristic features of Cushing's syndrome. We have examined glucose and amino acid metabolism in eleven patients with pituitary dependent Cushing's disease in comparison to nine healthy controls. Furthermore, the therapeutic effect of selective pituitary microsurgery was studied by repeated stable isotope measurements of hepatic glucose production and leucine turnover rates. Eight patients remitted after surgery and 3 had persistent disease. All patients were investigated prior to surgery and again 1 week and 3 months after the operation with (6,6-2H2)-glucose and (5,5,5-2H3)-leucine by means of a primed (4 mg/kg.min and 0.27 mg/kg.min), continuous (0.05 mg/kg.min and 0.005 mg/kg.min) infusion. In Cushing's disease, both the preoperatively elevated mean glucose production rate (2.34 +/- 0.63 mg/kg.min) and the reduced mean leucine turnover (0.213 +/- 0.025 mg/kg.min) were found to be linked with hepatic insulin resistance and an insulin-induced reduction in protein breakdown combined with a reduced protein synthesis. Mean glucose production and leucine flux both normalized after surgery in the remitting patients (2.18 +/- 0.15 mg/kg.min and 0.244 +/- 0.047 mg/kg.min 3 months after the operation). The metabolic disorders thus were reversible following successful correction of hormonal oversecretion by transsphenoidal surgery.

Adult↗
PubMed1995

Factors influencing the immediate and late outcome of Cushing's disease treated by transsphenoidal surgery: a retrospective study by the European Cushing's Disease Survey Group.

Hypercortisolism attributable to hypersecretion of ACTH by a pituitary adenoma is an uncommon and progressively lethal disease. Because of its rarity, it has been difficult to collect a large series of patients in order to identify the prognostic factors influencing the outcome after transsphenoidal surgery. We conducted a multicenter, retrospective analysis of the early and late results of surgical treatment of Cushing's disease. Files of patients with Cushing's disease who underwent transsphenoidal surgery between 1975 and 1990 were collected from 25 institutions throughout Europe. Data from 668 of 716 patients were suitable for statistical analyses. Surgical mortality was 1.9%, and major morbidity occurred in 97 patients (14.5%). Clinical and biochemical remission of Cushing's disease after surgery occurred in 510 cases (76.3%). Identification of the tumor by neuroradiological imaging or at operation with histopathological corroboration was associated with remission of hypercortisolism. Recurrence of the disease occurred in 65 (12.7%) of 510 patients in remission after surgery at a mean time of 39.3 months (range 6-104 months). The distribution of the recurrences did not show any apparent plateau or cluster throughout the follow-up period. Low postoperative steroid levels, absence of cortisol response to CRH, and the need for long-term glucocorticoid substitution therapy were all associated with a high probability of long-term remission. Our study demonstrates that transsphenoidal surgery is a safe and effective treatment for patients with Cushing's disease. However, after successful surgery there is a steady increase in the percentage of recurrences, which continues with time. Patients who after operation had hypoadrenocorticism and needed long-term glucocorticoid substitution therapy had the lowest risk of relapse.

Cushing Syndrome↗
PubMed1995

Biochemical characteristics of human pituitary somatotropinomas with and without gsp mutations: in vitro cell culture studies.

Gsp oncogenes are present in about 40% of somatotropinomas. They result in excessive cAMP production and have been proposed to be the cause of increased GH secretion. We have used in vitro cell culture to compare the biochemical characteristics of somatotropinomas with and without gsp oncogenes (gsp-positive and gsp-negative tumors, respectively). Of 30 somatotropinomas examined, 10 proved to be gsp positive, as determined by sequence analysis of DNA generated by the polymerase chain reaction. The somatostatin analog, octreotide, powerfully inhibited GH secretion by gsp-positive somatotropinomas, but had no effect on 8 of 13 gsp-negative tumors. Five of 20 gsp-negative and 4 of 10 gsp-positive tumors failed to respond to GHRH, whereas stimulatory effects ranging from 37-500% increases in GH secretion occurred in the remainder. However, strong stimulation (> 4-fold) occurred only in 5 of the gsp-negative tumors. The basal phosphatidylinositol turnover rate was elevated in about 25% of gsp-negative somatotropinomas. These results demonstrate similar and highly variable effects of GHRH on both types of somatotropinoma, whereas the absence of gsp oncogenes is often associated with resistance to octreotide. The phosphatidylinositol turnover data suggest that defects within this second messenger system may be present in a subset of somatotropinomas without gsp oncogenes.

Base Sequence↗
PubMed1995

Growth hormone releasing peptide (GHRP-6) stimulates phosphatidylinositol (PI) turnover in human pituitary somatotroph cells.

Growth hormone releasing peptide (GHRP-6) is a synthetic hexapeptide which specifically stimulates secretion of growth hormone (GH) by pituitary somatotrophs. The precise intracellular mechanism by which this is achieved has not been deciphered although it is known to involve protein kinase C (PKC) and Ca2+ but to be cAMP-independent. We have used cell cultures of human pituitary somatotrophinomas to demonstrate powerful effects of GHRP-6 on membrane phosphatidylinositol (PI) turnover, a second messenger system which leads to activation of PKC and mobilisation of intracellular Ca2+ reserves. Incubation of somatotrophinoma cells with GHRP-6 led to a dose-dependent stimulation of rate of PI turnover. GH secretion was increased in parallel. Effects were discernable after only 15 minutes incubation and rose to a maximum at 2 hours. PI turnover was stimulated by GHRP-6 in 8 of 8 tumours examined, effects ranging from 2.1 - 7.9 fold increases. Stimulation of GH secretion by GHRP-6 was independent of presence of gsp oncogenes, emphasising the cAMP-independent nature of its effects. These results provide evidence that the GH-stimulatory effects of GHRP-6 are achieved through activation of the PI second messenger system and thus support earlier findings that PKC and Ca2+ play central roles in mediating the effects of GHRP-6.

Calcium↗
PubMed1995

Prolactin-producing pituitary tumor: resistance to dopamine agonist therapy. Case report.

A 14-year-old girl presented with a rapidly growing, invasive prolactin-producing pituitary tumor that failed to respond to dopamine agonist medication. Histological, immunocytochemical, and ultrastructural studies of the surgically removed tissue revealed a pleomorphic, chromophobic, or slightly acidophilic pituitary tumor that was immunoreactive for prolactin and that, according to electron microscopy, consisted of atypical lactotrophs showing no evidence of cell shrinkage. In situ hybridization demonstrated large amounts of prolactin messenger ribonucleic acid (mRNA), moderate amounts of estrogen receptor mRNA and dopamine (D2) receptor mRNA, and an absence of growth hormone mRNA in the tumor cells. Because D2 receptor mRNA was present in the tumor, causes other than D2 receptor loss may have been responsible for the resistance of the lactotrophs to dopamine agonist administration.

Adenoma↗
PubMed1995

Somatostatin receptor expression in the thyroid demonstrated with 111In-octreotide scintigraphy.

Neuroendocrine tumors with somatostatin receptor expression may be localized by 111In-octreotide scintigraphy. This study examines those thyroid conditions where 111In-octreotide uptake could be observed also in the thyroid gland. 26 consecutive patients who underwent 111In-octreotide scintigraphy for tumor localization were additionally examined for thyroid disease by sonography and 99mTc-pertechnetate scintigraphy. 12 of these patients had no significant thyroid uptake and had an euthyroid normal-sized thyroid gland 14 patients with 111In thyroid uptakes had endemic goiters, two of them with thyroid autonomy and one with Graves' disease. Thus, 111In-octreotide thyroid uptake was predominantly seen in patients with endemic goiter with or without thyroid autonomy.

Adult↗
PubMed1994

In situ hybridization study of estrogen receptor messenger ribonucleic acid in human adenohypophysial cells and pituitary adenomas.

Estrogen receptor (ER) was demonstrated in nontumorous and adenomatous human pituitaries by autoradiography and biochemical assays. In the present study, we investigated ER mRNA by in situ hybridization applied on paraffin section of 9 nontumorous pituitaries obtained at surgery or autopsy and 109 surgically removed adenomas. In nontumorous pituitaries, in situ hybridization combined with immunocytochemistry revealed hybridization signal in GH-, PRL-, ACTH-, TSH-, and LH/FSH-immunoreactive cells, with the highest intensity in PRL-immunoreactive cells. ER mRNA was also localized in Crooke's cells, corticotrophs extending to posterior lobe, cells lining the pars intermedia cavities, and squamous nests of pars tuberalis. The neurohypophysis, endothelium, and connective tissue expressed no ER gene. ER mRNA was present in all adenoma types, including somatotroph, lactotroph, mixed somatotroph-lactotroph, mammosomatotroph, acidophil stem cell, functioning and silent corticotroph, thyrotroph, gonadotroph, null cell adenomas, and oncocytomas. The strongest signal was seen in some lactotroph and mammosomatotroph adenomas. In 9 lactotroph adenomas exposed to bromocriptine (long-acting repeatable injectable form), the hybridization signal was weak or absent, suggesting that suppression of ER gene plays a role in the inhibition of PRL synthesis and tumor growth.

Adenoma↗
PubMed1994

Growth hormone-prolactin-thyrotropin-secreting pituitary adenoma in atypical McCune-Albright syndrome with functionally normal Gs alpha protein.

The McCune-Albright syndrome (MAS) comprises a triad of physical signs: localized bone lesions termed polyostotic fibrous dysplasia, café-au-lait pigmentation of the skin, and autonomous hyperfunction of multiple endocrine systems, including overproduction of GH and T4. A somatic activating point mutation in the gene for the alpha-subunit of the G-protein (Gs alpha) in the affected tissue has been claimed to be the underlying defect. A 29-yr-old patient with MAS, showing polyostotic fibrous dysplasia associated with acromegalic features, underwent endocrinological studies, including oral glucose tolerance test and pituitary stimulation test, and magnetic resonance imaging, revealing elevated plasma concentrations of GH, PRL, and secondary hyperthyroidism due to pituitary macroadenoma infiltrating the sphenoid cavity and extending to the suprasellar space. Subsequently, reduction of tumor mass by a transsphenoidal and a subsequent subfrontal operation led to only marginal amelioration of the excessive hormone production. Postsurgery octreotide and bromocriptine therapy induced near-normalization of hormone concentrations. Immunohistochemistry of tumor tissue confirmed the plurihormonal character, but DNA sequence analysis did not detect any of the two known activating mutations in the Gs alpha gene. Furthermore, biochemical tests revealed normal Gs alpha function, ruling out other mutations that lead to constitutive Gs alpha activation. Our study documents that MAS is a heterogeneous disease. Some, but clearly not all, patients have oncogenic mutations of the gene coding for Gs alpha. Any gene acting down-stream of Gs can theoretically be predicted to result in the same phenotype. In addition, hyperthyroidism of MAS may be secondary to a TSH-producing pituitary macroadenoma.

Adenoma↗
PubMed1994

Octreotide exerts different effects in vivo and in vitro in Cushing's disease.

The effect of the long-acting somatostatin analog octreotide (SMS 201-995) on adrenocorticotropin (ACTH) secretion was studied in five patients with untreated Cushing's disease in vivo and in six human corticotropic adenoma cell cultures in vitro. For the in vivo study, 100 micrograms of octreotide sc was given 30 and 180 min after cannulation of the cubital vein and 100 micrograms of corticotropin-releasing hormone (CRH) was injected iv at 210 min. Serum ACTH and cortisol levels were measured for 390 min. In vivo, octreotide had no significant effect either on basal or CRH-stimulated ACTH levels and did not influence cortisol levels. The in vitro studies were conducted with corticotropic adenoma cell cultures derived from adenoma tissue obtained from six patients with Cushing's disease. In four of six cell cultures, octreotide (1 nmol/l-1 mumol/l) inhibited basal ACTH secretion in a dose-dependent manner. The inhibition ranged from 70 to 92% for 1 nmol/l octreotide to 14-46% for 1 mumol/l octreotide as compared to controls (100%). In three of three octreotide-responsive adenoma cell cultures investigated. CRH-stimulated ACTH secretion was suppressed by octreotide. Hydrocortisone pretreatment in vitro abolished the inhibitory effect of octreotide on ACTH secretion in one octreotide-responsive corticotropic adenoma cell culture. In conclusion, we showed that octreotide in most cases could inhibit the ACTH release from human corticotropic adenoma cells in vitro but had no suppressive effect on ACTH levels of patients with Cushing's disease in vivo. This discrepancy could be due to a somatostatin receptor down-regulation by cortisol at the hypercortisolemic state in vivo.

Adrenal Cortex Neoplasms↗
PubMed1994

Growth hormone gene structure in human pituitary somatotrophinomas: promoter region sequence and methylation studies.

The structure of the GH gene in human somatotrophinomas was examined in terms of promoter region sequence and degree of methylation. In six tumours, the promoter sequence did not differ from that observed in the corresponding genomic (white blood cell-derived) DNA, suggesting that it is unlikely that excessive GH production is due to a point mutation within this region. In contrast, Southern blot analysis using the methylation-sensitive restriction enzymes HpaII and HhaI revealed lower levels of methylation of the GH gene in somatotrophinomas when compared with that found in DNA derived from normal pituitary glands. We conclude that hypomethylation of the GH gene in human somatotrophinomas may play at least a partial role in excessive GH production.

5-Methylcytosine↗
PubMed1993

The role of transsphenoidal microsurgery in the management of sellar and parasellar meningioma.

We report on eight meningiomas that have been operated on via the transsphenoidal route since May 1988. Six patients harbored cavernous sinus meningiomas with intrasellar extension. The intrasellar tumor extension and the parasellar tumor portion medial to the carotid artery were removed. Decompression of the pituitary gland with normalization of prolactin levels was achieved in all patients. It is a well-tolerated approach to confirm the diagnosis and still allows the option of major transcranial surgery in the event of tumor progression. Additionally, we report complete tumor removal in two rare cases with intrasellar and suprasellar merely subdiaphragmatic meningiomas.

Adult↗
PubMed1993

Recent advances in the molecular biology of growth-hormone secreting human pituitary tumours.

The application of DNA technology has led to significant progress in our understanding of the aetiology of GH-secreting pituitary tumours. X-chromosome inactivation and RFLP analysis has revealed that GH-secreting tumours are monoclonal in origin and thus arise as a consequence of a somatic mutation within a single cell. Using PCR and sequence analysis, such a mutation has been identified in 30-40% of tumours. This is the so-called gsp mutation in which the gene for the alpha s subunit of the Gs protein is converted to an oncogene the expression of which results in constitutive adenyl cyclase activity and thus excessive cAMP production. In our own studies, we demonstrate that it is unlikely that a defect within the promoter region of the GH gene will prove to be a cause of excessive GH secretion in acromegaly. In contrast, we have shown that the GH gene is hypomethylated in tumour derived DNA and this may account, at least in part, for abnormal GH gene expression.

Clone Cells↗
PubMed1993

TRH/GnRH test in acromegaly. Long-term follow-up experience with successfully treated patients.

We investigated the rate of recurrence in acromegaly in 20 patients who were found to have a TRH and GnRH induced GH response postoperatively after primarily successful transsphenoidal selective adenomectomy in a retrospective study. All operations had been carried out by the same neurosurgeon (R.F.). Successful therapy was defined as basal GH-levels < or = 2 ng/ml and no evidence of residual tumour in the postoperative neuroradiological examination. The follow-up period ranged from 5 to 14 years (mean 7.7 years). At the last follow-up visit an OGTT was performed and SmC measured. In spite of the long-follow-up period we did not find patients with recurrent acromegaly in this investigation. We conclude that, in contrast to previous studies, a stimulation of GH in the TRH/GnRH test does not necessarily predict likely recurrence of acromegaly in patients with an adequate suppression of GH during an OGTT following operative microsurgical treatment.

Acromegaly↗
PubMed1993

Pulsatile administration of gonadotrophin releasing hormone as a diagnostic tool to distinguish hypothalamic from pituitary hypogonadism following neurosurgery.

Nine patients suffering from severe amenorrhoea following neurosurgical or radiotherapy for pituitary tumour or craniopharyngeoma were treated with pulsatile gonadotrophin releasing hormone (GnRH) administration. Seven patients did exhibit ovulatory cycles when GnRH was administered i.v. at a dose of 20 micrograms/pulse, but not at lower doses or when GnRH was administered s.c. Pulsatile GnRH administration may be used to assess the functional integrity of pituitary gonadotrophs and to distinguish pituitary from hypothalamic site of lesion resulting in hypogonadotrophic hypogonadism. It may also be used successfully for treatment of infertility in such patients.

Adolescent↗
PubMed1993

Does an analysis of the pulsatile secretion pattern of adrenocorticotropin and cortisol predict the result of transsphenoidal surgery in Cushing's disease?

The endocrinological, surgical, and histological findings of patients with ACTH-dependent Cushing's disease were correlated with the pulsatile secretion pattern of ACTH and cortisol and the outcome after transsphenoidal pituitary surgery. A total of 28 patients were studied. The preoperative pulsatile secretion of ACTH and cortisol was assessed by sampling blood at 20-min intervals over 24 h. The pulsatile pattern of secretion was analyzed by the Cluster program. In 21 patients, an ACTH-secreting pituitary adenoma was identified and resected. Of these patients, 18 underwent clinical remission, and their cortisol secretion was suppressed to a normal level by low dose dexamethasone. Histological examinations in the patients with persistent disease revealed normal pituitary in 6 cases, nodular hyperplasia in 1, and ACTH-secreting pituitary adenoma in 3 cases. Analysis of the pulsatile pattern of ACTH and cortisol secretion did not reveal significant differences in timing, frequency, and/or amplitude of ACTH and cortisol pulses in normalized patients and those with persistent disease after surgery. It is concluded that analysis of the secretory pattern is not a suitable method for predicting the outcome of transsphenoidal surgery in patients with ACTH-dependent Cushing's disease.

Adenoma↗
PubMed1993

Immunohistochemical expression of protein kinase C type III in human pituitary adenomas.

Immunohistochemical expression of the three major isozymes of protein kinase C--Types I, II, and III--was studied in 32 cases of human pituitary adenomas, and the results were compared in detail with their clinical data. Immunoreactivity for the Type I and Type II isozymes was negative in tumor cells of all pituitary adenomas. Moderate to strong cytoplasmic immunoreactivity for the Type III isozyme was constantly seen in acromegaly, Cushing's disease, and nonfunctioning adenomas, which indicated overexpression of the isozyme, since only slight cytoplasmic immunoreactivity was observed in the normal human anterior pituitary cells. Among 13 prolactinomas, 5 cases showed positive immunoreactivity for Type III in all tumor cells, whereas 8 cases showed negative immunoreactivity for the isozyme in all or more than 85% of tumor cells. The sizes of the tumors in this protein kinase C Type III negative group of prolactinomas tended to be smaller than those of the Type III positive prolactinomas. Also, the negative immunoreactivity for Type III was predominantly observed in those cases where prolactinomas were relatively well controlled by continuous oral dosage of dopamine agonists before operation. These results suggest that protein kinase C Type III is closely involved in human pituitary adenomas. The exceptional negativity for the isozyme in prolactinomas may be relevant to the suppression of tumor growth by dopamine agonists.

Acromegaly↗