The role of molecular biology in neurosurgery. Meeting of the Research Committee of the EANS in Hamburg, March 3-5, 1995.
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Animals↗
Biomedical subjects
R Fahlbusch
Publications and source records attributed to R Fahlbusch.
Relationship between cAMP induced inhibition of human meningioma cell proliferation and autocrine secretion of interleukin-6.
Previous studies have suggested that activation of the adenylyl cyclase - cAMP system in meningiomas results in decreased mitosis. We have used meningioma cell culture to further investigate this phenomenon and to examine the potential role played by interleukin-6 (IL6). Incubation of cultured meningioma cells for 4-6 days with cholera toxin and theophylline, both of which increase intracellular cAMP levels, markedly stimulated IL6 secretion and inhibited cell growth rate. Similar effects were observed with 8-bromo-cAMP. In contrast, a neutralising polyclonal antibody against IL6 significantly stimulated meningioma proliferation and reduced the inhibitory effects of 8-bromo-cAMP. These results support the concept that IL6 acts as an autocrine / paracrine inhibitory factor for meningioma proliferation, and that the inhibition exerted by elevated intracellular cAMP levels may be at least partially mediated via increased secretion of the cytokine.
8-Bromo Cyclic Adenosine Monophosphate↗
Acromegaly--the place of the neurosurgeon.
Over 12 years, we performed 498 operations for growth hormone (GH)-secreting pituitary adenomas (489 in acromegaly and nine for gigantism), with 479 by the trans-sphenoidal and 19 by the transcranial route. A consecutive series of 224 patients had an overall cure rate of 56%, with normalization in 71% when the criterion was only basal GH. Endocrine remission occurred in 72% of microadenomas, 50% of macroadenomas, and only 17% of giant adenomas. Seventy-three percent of the patients with preoperative GH levels less than 10 ng/mL were cured, but only 33% with GH greater than 100 ng/mL. Our cure rate for invasive adenomas was 38%. Surgical reexploration can lead to a 50% cure rate. Overall morbidity was low. Pretreatment of large adenomas with octreotide may soften them and facilitate their removal, and one third shrink. It also relieves the symptoms of acromegaly and improves the patient's general condition for surgery. Octreotide as first-line therapy is indicated in patients with risk factors for surgery, and it is becoming an alternative to radiotherapy after surgery. It is more potent than dopamine agonists in lowering GH levels. We recommend postoperative radiotherapy (+/- octreotide) if GH levels are fairly high after surgery or if the adenoma shows major invasiveness. Surgery is still the initial therapy of choice in acromegaly due to its high cure rate and low morbidity.
Acromegaly↗
Pituitary adenylate cyclase-activating polypeptide directly stimulates LH and FSH secretion by human pituitary gonadotrophinomas.
The effect of pituitary adenylate cyclase-activating polypeptide (PACAP) on LH and FSH secretion by human pituitary gonadotrophinomas in cell culture was studied. PACAP (1-38 peptide, 0.2-20 nmol/L) dose-dependently stimulated both LH and FSH secretion after 24 hours incubation. Of 11 tumours studied, PACAP (20 nmol/L) stimulated LH and/or FSH secretion by 1.7-4 fold in 9 cases. Two tumours did not respond to PACAP, although LHRH was stimulatory in these. None of the 11 tumours contained gsp mutations, excluding the possibility that these were the cause of the occassionally observed non-responsiveness to PACAP. A combination of PACAP (20 nmol/L) together with TRH (25 nmol/L) resulted in greater stimulatory effects on LH and FSH secretion than exerted by either peptide alone, but this was not observed with LHRH. In 3 tumours tested, PACAP stimulated cAMP production 2-3 fold by cultured human pituitary gonadotrophinomas but had no effect on rate of phosphatidylinositol (PI) turnover. These results indicate that PACAP can directly stimulate LH and FSH secretion by human pituitary gonadotrophs and that PACAP-receptors in gonadotrophin-secreting tumours are coupled with adenylate cyclase but not the PI second messenger system. We conclude that PACAP may play a role in controlling gonadotroph function in the human pituitary gland.
Adult↗
Dopamine D1, dopamine D2, and prolactin receptor messenger ribonucleic acid expression by the polymerase chain reaction in human meningiomas.
Previous studies have suggested the presence of high-affinity dopamine D1 receptors and prolactin receptors in human cerebral meningiomas. In this study, using the polymerase chain reaction, we report the presence of the messenger ribonucleic acid (mRNA) for the dopamine D1 and D2 receptors and the prolactin receptor in meningioma tissue specimens and cell cultures derived from meningioma tissue. Dopamine D1 receptor mRNA was present in a majority of female tissue specimens and in all male tissue specimens. D2 receptor mRNA was detected in all specimens examined. Prolactin receptor mRNA was present in a little more than half of the female and male meningioma tumor specimens. The polymerase chain reaction products were directly sequenced to confirm the identity of these receptors in meningiomas and cell cultures. Ligand binding studies confirmed the presence of the dopamine D1 receptor in meningioma tissue specimens. In contrast, receptor studies with the dopamine D2 ligand [125I]4-iodospiperone failed to detect D2 binding in meningioma membrane preparations. These results suggest the existence of active dopamine D1 receptors in cerebral meningiomas.
Adult↗
Relationship between protein kinase C and adenylyl cyclase activity in the regulation of growth hormone secretion by human pituitary somatotrophinomas.
OBJECTIVE: To determine the potential role of protein kinase C (PKC) and its relationship to adenylyl cyclase activity in controlling growth hormone (GH) secretion by human pituitary somatotrophinomas. METHODS: Twenty-eight somatotrophinomas were placed into cell culture, and the in vitro effects of the PKC activator 12-O-tetradecanoylphorbol 13-acetate (TPA) and the PKC inhibitor staurosporine on basal and GH-releasing hormone (GHRH)-stimulated GH secretion were examined. In addition, the influence of chronic exposure of cultured somatotrophinoma cells to TPA on the rate of inositol 1,4,5-trisphosphate production was determined. Each tumor was assessed for the presence of gsp oncogenes, and thus constitutive adenylyl cyclase activity, by direct sequence analysis of polymerase chain reaction-generated deoxyribonucleic acid. GH secretory responses of tumors with and without these oncogenes were compared. RESULTS: TPA consistently stimulated GH secretion by cultured somatotrophinoma cells. There was no difference in response between somatotrophinomas with and without gsp oncogenes, and the effects did not correlate with the variable stimulation exerted by GHRH. Tumors in which GHRH had no significant effect nevertheless responded to TPA. In combination, TPA and GHRH exerted additive stimulation. TPA treatment of cultured somatotrophinoma cells eventually resulted in suppression of inositol 1,4,5-trisphosphate production, probably reflecting down-regulation of membrane phosphatidylinositol hydrolysis, a second messenger system that also generates the endogenous PKC activator diacylglycerol. GHRH had no effect on phosphatidylinositol hydrolysis. In contrast to the effects of TPA, the PKC inhibitor staurosporine tended to reduce GH secretion, although this effect was not observed in all tumors examined. As with TPA, the effects of staurosporine did not correlate with presence or absence of gsp oncogenes. Furthermore, staurosporine did not reduce the stimulatory effects exerted by GHRH on GH secretion. CONCLUSION: These results demonstrate a role for the phosphatidylinositol-PKC second messenger cascade in controlling GH secretion by human pituitary somatotrophinomas. The results also show that the system operates relatively independent of intracellular adenylyl cyclase and, thus, protein kinase A.
Adenoma↗
Slow rhythmic oscillations of blood pressure, intracranial pressure, microcirculation, and cerebral oxygenation. Dynamic interrelation and time course in humans.
BACKGROUND AND PURPOSE: Various biological signals show nonpulsatile, slow rhythmic oscillations. These include arterial blood pressure (aBP), blood flow velocity in cerebral arteries, intracranial pressure (ICP), cerebral microflow, and cerebral tissue PO2. Generation and interrelations between these rhythmic fluctuations remained unclear. The aim of this study was to analyze whether stable dynamic interrelations in the low-frequency range exist between these different variables, and if they do, to analyze their exact time delay. METHODS: In a clinical study, 16 comatose patients with either higher-grade subarachnoid hemorrhage or severe traumatic brain injury were examined. A multimodal digital data acquisition system was used to simultaneously monitor aBP, flow velocity in the middle cerebral artery (FVMCA), ICP, cerebral microflow, and oxygen saturation in the jugular bulb (SjO2). Cross-correlation as a means to analyze time delay and correlation between two periodic signals was applied to a time series of 30 minutes' duration divided into four segments of 2048 data points (approximately 436 seconds) each. This resulted in four cross-correlations for each 30-minute time series. If the four cross-correlations were consistent and reproducible, averaging of the original cross-correlations was performed, resulting in a representative time delay and correlation for the complete 30-minute interval. RESULTS: Reproducible cross-correlations and stable dynamic interrelations were found between aBP, FVMCA, ICP, and SjO2. The mean time delay between aBP and ICP was 6.89 +/- 1.90 seconds, with a negative correlation in 81%. A mean time delay of 1.50 +/- 1.29 seconds (median, 0.85 seconds) was found between FVMCA and ICP, with a positive correlation in 94%. The mean delay between ICP and SjO2 was 9.47 +/- 2.21 seconds, with a positive correlation in 77%. Mean values of aBP and ICP did not influence the time delay and dynamic interrelation between the different parameters. CONCLUSIONS: These results strongly support Rosner's theory that ICP B-waves are the autoregulatory response of spontaneous fluctuations of cerebral perfusion pressure. There is casuistic evidence that failure of autoregulation significantly modifies time delay and the correlation between aBP and ICP.
Blood Pressure↗
Vasopressin receptor expression and mutation analysis in corticotropin-secreting tumors.
Vasopressin is an important regulator of hypothalamo-pituitary-adrenal axis activation, primarily acting through the V3 receptor (V3R). Many patients with ACTH-secreting pituitary adenomas, but not normal individuals, respond to desmopressin, a relatively V2-specific vasopressin agonist, with increased ACTH and cortisol levels. We have searched for mutations of the V3R gene in ACTH-secreting pituitary adenomas and one ectopic ACTH-secreting tumor. No abnormalities were found in 12 tumors studied by PCR-single strand conformation polymorphism (PCR-SSCP) analysis. We then verified by RT-PCR whether the response to desmopressin was due to overexpression of the V3R or abnormal expression of the V2R in the pituitary tumor. We found that the V2R gene was expressed in a number of corticotroph tumors and in the ACTH-secreting ectopic tumor, and that the V3R gene appears to be overexpressed in these tumors. We conclude that V3R mutations are unlikely to be present in the ACTH-secreting tumors we examined, but that the V2R gene is expressed in the majority of the samples tested, and the V3R is expressed in all of these tumors. We speculate that the response to the desmopressin test observed in patients with Cushing's disease may be due to abnormal expression of V3R or V2R in ACTH-secreting tumors.
Adrenocorticotropic Hormone↗
Protein kinase C-dependent growth hormone releasing peptides stimulate cyclic adenosine 3',5'-monophosphate production by human pituitary somatotropinomas expressing gsp oncogenes: evidence for crosstalk between transduction pathways.
The effects of the synthetic GH-releasing peptides, GHRP-2 and GHRP-6, on phosphatidylinositol (PI) hydrolysis and cAMP production have been examined in human pituitary somatotropinomas with and without adenylyl cyclase-activating gsp oncogenes. Both peptides dose-dependently stimulated the rate of PI hydrolysis and GH secretion by cell cultures of both types of somatotropinoma. GHRP-2 was considerably more potent than GHRP-6. The effects on GH secretion were reduced or abolished by phloretin, an inhibitor of protein kinase C, and W7, an inhibitor of calmodulin. However, antagonism of the GHRH-receptor and of protein kinase A with (N-Ac-Tyr1,D-Arg2)GRF-(1-29)-NH2 and Rp-adenosine-3',5'-cyclic monophosphothioate, respectively, did not alter the stimulatory effects of GHRP-2 and GHRP-6 on GH secretion. The effect of GHRP-2 and/or GHRP-6 on cAMP production was studied in 15 tumors, seven of which possessed constitutive adenylyl cyclase activity as evidenced by presence of gsp oncogenes. Both peptides stimulated cAMP production in the latter but not former types of tumor. Moreover, GHRP-2 and GHRP-6 potentiated the stimulation of cAMP production induced by GHRH and pituitary adenylate cyclase-activating polypeptide in tumors without gsp oncogenes. These results demonstrate that GHRP-2 and GHRP-6 exert identical effects on human pituitary somatotropinomas, except for differences in potency. Additionally, under conditions of adenylyl cyclase activity above basal levels (i.e. through stimulation of G2-protein coupled receptors or because of gsp oncogene expression), cAMP production can be increased even further by GHRP, providing evidence for cross-talk between the PI and adenylyl cyclase transduction systems in pituitary cells.
Base Sequence↗
Autocrine growth stimulation of human meningioma cells by platelet-derived growth factor.
The authors have previously shown that meningioma-derived conditioned medium profoundly stimulates the in vitro proliferation of meningioma cells. In this paper, self mitogenic agents found in the conditioned medium-autocrine growth-stimulatory factors actually secreted by human meningioma cells-are characterized as proteins related to the B chain of platelet-derived growth factor (PDGF) and possibly to the A chain of PDGF as well. The addition to conditioned medium of a neutralizing antibody against PDGF-BB caused a significant inhibition of the conditioned medium-stimulated DNA synthesis in all three meningioma cultures studied. A similar neutralizing effect was observed with an anti-PDGF-AA antibody in one meningioma culture studied. Gel filtration chromatography of concentrated conditioned medium from two different meningiomas using a Sephadex G-100 column revealed similar profiles from both conditioned media with a major peak of mitogenic activity against meningioma cells at a molecular weight (M(r)) of approximately 32 to 36 kD, accompanied by a minor peak at approximately 22 kD. The major peak mitogenic activity was significantly reduced by addition of an anti-PDGF-BB antibody. Western blot analysis of protein extracts from five meningioma specimens was performed using a monoclonal antibody against the B chain of PGDF, and a major band of PDGF-B immunoreactivity was detected at an M(r) of approximately 19 kD in all five meningiomas under both reducing and nonreducing conditions. Exogenous human and porcine PDGFs both exhibited a significant dose-dependent stimulation of DNA synthesis in two of three and three of five meningioma cultures examined, respectively. Although not all meningiomas investigated proved to share the biological activity associated with PDGF and these results may be preliminary, it seems that the autocrine growth-stimulatory loop established by PDGF-B-related molecules plays an important functional role in meningioma cell proliferation.
Brain Neoplasms↗
[Hormonally inactive hypophyseal adenomas: the results and late sequelae after surgery and radiotherapy].
PURPOSE: External radiation therapy for non functioning pituitary adenomas is clearly indicated in inoperable patients, after incomplete transsphenoidal microsurgery and in case of tumor progression. This retrospective analysis gives results and toxicity following surgery and postoperative radiotherapy of non-functioning pituitary adenomas. PATIENTS AND METHODS: Between 1983 and 1990, 50 patients with non-functioning pituitary adenomas received combined treatment at our institutions. Surgical approaches were transsphenoidal (61%), transcranial (24%) or a combination of both (15%) in short intervals. All 50 patients received a full-dose radiotherapy with single fractions between 1.9 and 2.1 Gy (median 1.9 Gy) and total doses between 46 and 63 Gy (median 48 Gy). Field sizes ranged between 20 and 72 cm2 (median 30 cm2). Endpoints of this study were: progression-free survival, late effects of brain, optic nerve and intracranial vessels, visual impairment and hypothalamic-pituitary dysfunction. Median follow-up was 54 months. RESULTS: Forty-seven of the 50 patients remained progression-free. Patients over age 60 years progressed more frequently (3/17) as compared to younger patients (0/33, p = 0.034). Following radiotherapy vision improved in 8 patients (16%), 14 patients (28%) experienced a visual impairment between 10% and 60% (according to the grading system of the German Ophthalmologic Society). In multivariate analysis no influence of age (p = 0.097) or biologically effective dose (BED) (p = 0.11) was seen on visual impairment. Three patients (6%) experienced late effects with optic neuropathy in 2 cases and temporal lobe necrosis in 1 case. Only the BED had a significant impact on late effects (p = 0.0094). Adrenal, thyroid and gonadal function abnormalities were present in 58%, 66% and 96% of the patients at last follow-up, respectively. CONCLUSIONS: Radiotherapy after incomplete transsphenoidal or transcranial surgery of non-functioning pituitary adenoma is an effective treatment. Future perspectives must include the better defining of high-risk patients and the reduction of late morbidity.
Adenoma↗
SEF-MEG localization of somatosensory cortex as a method for presurgical assessment of functional brain area.
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Brain↗
The growth hormone secretagogue, L-692,429, induces phosphatidylinositol hydrolysis and hormone secretion by human pituitary tumors.
L-692,429 is a non-peptidyl GH secretagogue. We examined the effects of L-692,429 on cultured human pituitary tumors removed from patients with acromegaly. Dose-dependent stimulation of GH secretion was observed, with 1 mumol/L leading to 2 or 3-fold increases. Prolactin (PRL) secretion by a mixed somatotrophic-lactotrophic tumor was also stimulated. The effects of L-692,429 were abolished by phloretin and W7 but not Rp-cAMPS. Rate of phosphatidylinositol turnover was markedly increased up to 3-fold by L-692,429. These results show that L-692,429 increases hormone secretion by human pituitary cells via a protein kinase C and Ca2+ dependent mechanism.
Acromegaly↗
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↗
Human chorionic gonadotrophin immunoactivity in cystic intracranial tumours.
BACKGROUND AND OBJECTIVE: With regard to intracranial tumours, elevated hCG in CSF or serum has been considered to be specific for germ-cell tumours. Recently however, elevated hCG has also been shown to be present in cyst fluid and CSF of patients with craniopharyngiomas. While germ-cell tumours are generally non-cystic, the aim of our study was to determine the significance of hCG in cystic intracranial lesions. DESIGN: In a prospective study, hCG immunoactivity and subunits of hCG were measured in cyst fluid, CSF, and serum of patients harbouring intracranial cyst lesions. PATIENTS AND MEASUREMENTS: hCG immunoactivity was measured in cyst fluid and serum samples of 42 patients. CSF samples were available from 12 patients with craniopharyngiomas. In order to fully characterize the hCG immunoactivity, we used immunoradiometric assays for total hCG activity (measuring both intact hCG and the free beta-subunit of hCG), and those specific for intact, dimeric hCG (hCG), free beta-subunit of hCG (hCG beta) and free alpha-subunit. Furthermore, immunostaining of tumour tissue was performed using monoclonal antibodies directed against the free beta-subunit of hCG. RESULTS: Total hCG immunoactivity was markedly elevated in cyst fluid of all 17 craniopharyngiomas (range 36.7-4558 IU/I; normal < 5 IU/I). Moderately elevated levels of hCG in cyst fluid were detected in three of four pituitary adenomas, in two metastases from lung cancer and in two arachnoid cysts. hCG beta was detected in cyst fluid from all hCG positive cysts, while specific determination of intact (dimer) hCG and alpha-subunit mostly yielded negative results. No hCG immunoactivity was found in cystic gliomas, meningiomas or haemangioblastomas. hCG was elevated in CSF of two patients with craniopharyngiomas, but no hCG immunoactivity was detected in any serum sample. Subtle immunostaining of epithelial cell groups was shown in five of ten craniopharyngiomas. Clear immunostaining for hCG beta was also found in scattered epithelial cells of one pituitary adenoma. CONCLUSIONS: hCG immunoactivity in cystic intracranial lesions is due mainly to hCG beta. Measurement of hCG immunoactivity in cyst fluid can be helpful in the differential diagnosis of intracranial cystic lesions, if surgery is restricted to cyst decompression and no histology is available. High levels suggest a craniopharyngioma.
Adenoma↗
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↗
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↗