Biomedical subjects

T Arzberger

Publications and source records attributed to T Arzberger.

At least 19 recordsLinked to original sources

PubMed2006

How a neuropsychiatric brain bank should be run: a consensus paper of Brainnet Europe II.

The development of new molecular and neurobiological methods, computer-assisted quantification techniques and neurobiological investigation methods which can be applied to the human brain, all have evoked an increased demand for post-mortem tissue in research. Psychiatric disorders are considered to be of neurobiological origin. Thus far, however, the etiology and pathophysiology of schizophrenia, depression and dementias are not well understood at the cellular and molecular level. The following will outline the consensus of the working group for neuropsychiatric brain banking organized in the Brainnet Europe II, on ethical guidelines for brain banking, clinical diagnostic criteria, the minimal clinical data set of retrospectively analyzed cases as well as neuropathological standard investigations to perform stageing for neurodegenerative disorders in brain tissue. We will list regions of interest for assessments in psychiatric disorder, propose a dissection scheme and describe preservation and storage conditions of tissue. These guidelines may be of value for future implementations of additional neuropsychiatric brain banks world-wide.

Brain↗

PubMed2004

Differential expression of menin in sporadic pituitary adenomas.

Pituitary adenomas represent one of the key features of multiple endocrine neoplasia type 1. The gene involved in this syndrome (MEN1) is a putative tumor suppressor, that codes for a 610-amino acid nuclear protein termed 'menin'. Analyses of sporadic pituitary adenomas have so far failed to reveal MEN1 mutations or defects in MEN1 transcription in these tumors. In the present study we detected menin protein expression in a panel of normal and tumoral pituitary tissues, using a monoclonal antibody against the carboxy-terminus of menin. In the normal human pituitary gland, strong nuclear staining for menin was detectable in the majority of the endocrine cells of the anterior lobe, without a clear association with a particular hormone-producing type. In sporadic pituitary adenomas, menin expression was variable, with a high percentage of cases demonstrating a significant decrease in menin immunoreactivity when compared with the normal pituitary. Interestingly, metastatic tissues derived from one pituitary carcinoma had no detectable menin levels. Altogether, our data provide the first information regarding the status of menin expression in human normal and neoplastic pituitary as determined by immunohistochemistry (IHC).

Adenoma↗

PubMed2004

Expression of epidermal growth factor receptor in neoplastic pituitary cells: evidence for a role in corticotropinoma cells.

The oncogenic effects of epidermal growth factor (EGF) have long been established. EGF receptor (EGFr) is overexpressed in many types of tumors and constitutes a target for cancer treatment. The pituitary gland is a target of EGF action and it is very likely that EGFr plays a role in pituitary tumor formation and progression. However, there is a controversy in the literature concerning EGFr expression in the different types of pituitary adenomas. In the present study we investigated the expression pattern of the wild type EGFr (EGFrWT) and the constitutively active variant III (EGFrvIII) at the mRNA and protein levels in a large series of pituitary tumors. EGFrWT was found in a high percentage of hormone-secreting tumors, but only in a small fraction of non-functioning pituitary adenomas, while no expression of the EGFrvIII could be detected by nested RT-PCR in any tumor. Among the hormone-secreting adenomas, the highest incidence of EGFr expression was found in Cushing's pituitary adenomas. Furthermore, immunohistochemistry for the phosphorylated EGFr revealed the presence of activated EGFr in most Cushing's adenomas, compared with most pituitary adenomas. Taking into account that downregulation of p27/Kip1 plays a significant role in corticotrope tumorigenesis and that EGFr mitogenic signaling results in decreased p27/Kip1, we searched for a correlation between EGFr expression and p27/Kip1 levels in corticotropinomas. Low p27/Kip1 immunoreactivity was observed in corticotropinomas expressing EGFr. On the other hand, somatotropinomas expressing EGFr had high p27/Kip1 immunoreactivity. These data suggest a corticotrope-specific phenomenon and indicate that EGFr may have a role in the unbalanced growth of corticotrope tumoral cells.

Adenoma↗

PubMed2003

Dopamine receptor agonists in current clinical use: comparative dopamine receptor binding profiles defined in the human striatum.

The aim of this study was to compare dopamine receptor binding affinities of all currently approved dopamine receptor agonist treatments for Parkinson's disease (PD) in human brain tissue. Alpha-dihydroergocryptine and lisuride displayed higher comparative affinities (Ki=35.4 and 56.7 nM, respectively) for D1 receptors, than the D1/D2 dopamine agonist pergolide (Ki=447 nM). The second generation non-ergot dopamine receptors agonists pramipexole and ropinirole demonstrated no affinity for D1 receptors at concentrations up to 10(-4) M. The ergoline dopamine agonists cabergoline and lisuride displayed the highest affinities for the D2 receptor (Ki=0.61 and 0.95 nM, respectively). Surprisingly, the second generation non-ergot dopamine receptors agonists pramipexole and ropinirole only weakly inhibited binding to D2 receptors (Ki=79.5 and 98.7 microM, respectively using [3H]spiperone). Interestingly we also found that the affinities of cabergoline (Ki=1.27 nM), lisuride (Ki=1.08 nM) and pergolide (Ki=0.86 nM) for the D3 receptor subtype were comparable to that of pramipexole (Ki=0.97 nM). The present results thus support the hypothesis that the antiparkinsonian effect of dopamine receptor agonists is mediated by a more complex interactions with dopamine receptor subtypes than currently believed.

Aged↗

PubMed2002

The role of endothelins in the regulation of pituitary function.

The different members of the endothelin peptide family exhibit potent, long-lasting vasoconstrictive effects and thus play a central role in blood pressure regulation. However, endothelins have also been shown to modulate renal, cardiac and immune functions under physiological and pathophysiological conditions. In addition, endothelins are thought to be involved in the progression of some types of tumours. Soon after their discovery in 1988, it was shown that endothelins affect hormone release in the pituitary. Moreover, the intrapituitary production and expression of both endothelins and endothelin receptors have been described. This review summarises the present day knowledge concerning the expression and regulation of intrapituitary endothelins and their receptors. In addition, the effects of endothelins on hormone production by anterior, intermediate and posterior pituitary cell types are reviewed and their importance for pituitary physiology and pathophysiology is discussed.

Animals↗

PubMed2002

Retention of dopamine 2 receptor mRNA and absence of the protein in craniospinal and extracranial metastasis of a malignant prolactinoma: a case report.

OBJECTIVES: The case presented here describes the clinical evolution of a malignant prolactinoma with occurrence of intra- and extra-cranial metastases. In this case, the presence of dopamine 2 receptor (D2R) was studied at the mRNA and protein level, in order to understand the pathological background of the resistance to treatment with different dopamine agonists. DESIGN: Together with an extensive description of the clinical history of this case, a combination of in vitro and in vivo techniques was performed to provide the basis of the dopamine resistance developed in the course of the disease. METHOD: A comparison of the D2R was performed in specimens obtained at presentation of the disease compared with autoptic specimens derived from local invasion and metastasis using in situ hybridization and immunohistochemical techniques. RESULTS: Intact D2R mRNA was found in the primitive tumor and metastatic tissues, whereas protein for the same receptor was present only in the tissues derived from neurosurgical operations and not in the metastases obtained post-mortem. CONCLUSION: This is the first report of the absence of D2R protein despite the retention of the transcript in an advanced stage of a malignant prolactinoma. The findings of this single case suggest the hypothesis that postranscriptional mechanisms may contribute to the development of dopamine resistance in prolactinomas.

Brain Neoplasms↗

PubMed2002

Characterization of the human and mouse genes encoding the tuberoinfundibular peptide of 39 residues, a ligand of the parathyroid hormone receptor family.

The polypeptide TIP39 (tuberoinfundibular peptide of 39 residues) is a potent activator of the parathyroid hormone (PTH)-2 receptor (P2R) and an antagonist of the PTH-1 receptor (P1R). To clarify its possible physiological function(s), we studied its interaction with the human P1R and P2R and examined the expression of TIP39 in man and mouse. To find out possible sites of this ligand interaction in the organism, we identified the genes encoding the TIP39 protein precursors of Homo sapiens and Mus musculus in the databases of the human and mouse genome projects respectively. We then obtained the full-length cDNAs of both species by RACE-PCR. The deduced TIP39 preprohormones consist of an N-terminal 30 amino acid (aa) signal peptide followed by a 29 aa TIP39 precursor-related peptide, an Arg-Arg processing site, and the actual 39 aa TIP39 sequence. The first 23 aa of the actual TIP39 sequence, thought to contain the P2R receptor activation site, are identical in man and mouse and thus phylogenetically conserved. By contrast, the 16 aa C-terminal portion showed a higher degree of diversity (75% aa identity). By using RT-PCR, TIP39 was found to be highly expressed in human central nervous system tissues, trachea, fetal liver, and, to a lesser degree, in human heart and kidney. Using in situ hybridization, TIP39 mRNA expression was revealed in various areas of the mouse brain. In a homologous human cell model using human embryonic kidney 293 cells stably transfected with human P1R and P2R, human TIP39 did bind to P1R with moderate affinity (IC(50) approximately 10(-7)-10(-6 )M), but showed higher affinity binding to P2R (IC(50) approximately 10(-8)M), comparable to the affinity of human N-terminal PTH (hPTH(1-34)) to this receptor. In P2R-transfected cells, the cAMP pathway was activated more efficiently ( approximately 10-fold) by TIP39 as a ligand compared to hPTH(1-34). In P1R-transfected cells, only hPTH(1-34) but not TIP39 was able to elicit a cAMP response, but TIP39 was able to directly antagonize the cAMP-stimulating effect of hPTH(1-34) on this receptor. In conclusion, we could show a possible function of TIP39 for the human organism as a potent activator of P2R (e.g. in brain) as well as an antagonist of the action of PTH and/or PTH-related protein on P1R (e.g. in bone and kidney). The physiological role of TIP39 in calcium metabolism with regard to these actions remains to be determined. The tools developed in this work will allow us to investigate the possible role of TIP39 as a locally or systemically secreted ligand modulating the function of the PTH receptor family.

Animals↗

PubMed2001

Normal human pituitary gland and pituitary adenomas express cannabinoid receptor type 1 and synthesize endogenous cannabinoids: first evidence for a direct role of cannabinoids on hormone modulation at the human pituitary level.

Little is known about the expression and function of cannabinoid receptor type 1 (CB1) in the human pituitary gland. The aim of this study was to investigate CB1 expression in human normal and tumoral pituitaries by in situ hybridization and immunohistochemistry using an antibody against CB1. CB1 was found in corticotrophs, mammotrophs, somatotrophs, and folliculostellate cells in the anterior lobe of normal pituitary. After examination of 42 pituitary adenomas, CB1 was detected in acromegaly-associated pituitary adenomas, Cushing's adenomas, and prolactinomas, whereas faint or no expression was found in nonfunctioning pituitary adenomas. Experiments with cultured pituitary adenoma cells showed that the CB1 agonist WIN 55,212--2 inhibited GH secretion in most of acromegaly-associated pituitary adenomas tested and that the CB1 antagonist SR 141716A was generally able to reverse this effect. Moreover, WIN 55,212--2 was able to suppress GHRH-stimulated GH release, and this effect was not blocked by coincubation with SR 141716A, possibly indicating a non-CB1-mediated effect. In contrast, WIN 55,212--2 was ineffective on GH-releasing peptide-stimulated GH release. In four Cushing's adenomas tested, WIN 55,212--2 was not able to modify basal ACTH secretion. However, simultaneous application of CRF and WIN 55,212--2 resulted in a synergistic effect on ACTH secretion, and this effect could be abolished by SR 141716A, demonstrating a CB1-mediated effect. In the single case of prolactinomas tested, WIN 55,212--2 was able to inhibit basal secretion of PRL. Finally, the presence of endocannabinoids (anandamide and 2-arachidonoylglycerol) was investigated in normal and tumoral pituitaries. All tumoral samples had higher contents of anandamide and 2-arachidonoylglycerol compared with the normal hypophysis. Moreover, endocannabinoid content in the different pituitary adenomas correlated with the presence of CB1, being elevated in the tumoral samples positive for CB1 and lower in the samples in which no or low levels of CB1 were found. The results of this study point to a direct role of cannabinoids in the regulation of human pituitary hormone secretion.

Adenoma↗

PubMed2000

The expression of the antiproliferative gene ZAC is lost or highly reduced in nonfunctioning pituitary adenomas.

The ZAC gene encodes a new zinc-finger protein that concomitantly induces apoptosis and cell cycle arrest and localizes to chromosome 6q24-q25, a well-known hot spot related to cancer. ZAC is highly expressed in the anterior pituitary gland, and its ablation by antisense targeting promotes pituitary cell proliferation. Here we investigate ZAC status in pituitary tumors to evaluate its role in pituitary tumorigenesis. Interest ingly, a strong reduction or absence of ZAC mRNA and protein expres sion was detected in nonfunctioning pituitary adenomas, whereas in clin ically active pituitary neoplasias, the decrease in ZAC expression was variable. Loss of expression was not associated with a mutation of the ZAC gene. Our observations suggest that alternative mechanisms of gene inactivation and/or altered regulation of the ZAC gene occur in nonfunctioning pituitary adenomas.

Adenoma↗

PubMed2000

Celloidin mounting (embedding without infiltration) - a new, simple and reliable method for producing serial sections of high thickness through complete human brains and its application to stereological and immunohistochemical investigations.

Celloidin mounting (embedding without infiltration) of the human central nervous system (CNS) proved to be superior to gelatin embedding for the production of serial sections ranging in thickness from 220 to 500 microm. After gallocyanin-staining, a comprehensive neuroanatomical as well as neuropathological survey of the human brain is possible, including diagnosis of Alzheimer's disease. Details of a fractionator analysis of the total striatal neuron number are described and the possible quantitative analysis of parallel immunohistochemically stained sections is discussed.

Adult↗

PubMed2000

Thyrotrophin receptor protein expression in normal and adenomatous human pituitary.

Thyrotrophin (TSH) synthesis and secretion is under the positive control of thyrotrophin releasing hormone and under the negative control of the thyroid hormones. However, it is hypothesised that TSH has a direct effect on the regulation of its own synthesis through an intrapituitary loop mediated by pituitary TSH receptors (TSH-R). The aim of this investigation was to study the expression of TSH-R in normal human pituitary at mRNA and protein levels, and to compare the pattern of protein expression between different pituitary adenomas. Using RT-PCR we were able to detect TSH-R mRNA in the normal pituitary, and immunohistochemical studies showed TSH-R protein expression in distinct areas of the anterior pituitary. Double immunostaining with antibodies against each of the intrapituitary hormones and S100 revealed that TSH-R protein is present in thyrotrophs and folliculostellate cells. Examination of 58 pituitary adenomas, including two clinically active and two clinically inactive thyrotroph adenomas, revealed TSH-R immunopositivity in only the two clinically inactive thyrotroph adenomas. This study shows, for the first time, the presence of TSH-R protein in the normal anterior pituitary and in a subset of thyrotroph adenomas. The expression of TSH-R in the thyrotroph and folliculostellate cell subpopulations provides preliminary evidence of a role for TSH in autocrine and paracrine regulatory pathways within the anterior pituitary gland.

Adenoma↗

PubMed1999

Progressive degeneration of dopamine system functions after transient cerebral oligemia in rats.

A reduction in cerebral blood flow to oligemic levels was achieved in pentobarbital-anesthetized adult rats by clamping both carotid arteries (BCCA) for 60 min. To assess the extent to which the animals' dopaminergic system was affected over an increasing time span, their spontaneous locomotor activity in an unfamiliar environment and in response to the subcutaneous administration of apomorphine was tested at various times after either BCCA or sham operation. Eight to 14 days after the operation, it was possible to observe a diminished locomotor activity in response to apomorphine injection in BCCA as compared with sham-operated animals, while oral stereotypical behavior such as licking was increased. At 3 months, there was only a subtle decrease in apomorphine-induced locomotor activity, and stereotypical behavior was similar in both groups. At 7 months, the BCCA rats covered shorter distances than sham-operated controls during the habituation phase; after apomorphine injection, more stereotypic movements, such as, e.g., sniffing, were observed, and less running. Twelve months after surgery, no further differences could be observed between the two groups during the habituation phase, but the injection of apomorphine led to increased stereotypic sniffing movements, rearing and locomotor activity in BCCA animals to a greater extent than in the controls. At 12 months, sensorimotor disturbances elicited by the rota rod test, which were only transiently observed at 11 weeks and 7 months, did not appear any different from the normal age-related motor decline of the sham-operated controls. The animals' motor co-ordination in the chimney test was not significantly disturbed during the time between 7 and 12 months after surgery. At 15 months, nocturnal locomotor activities in BCCA rats were significantly decreased. In situ hybridization (ISH) histochemistry revealed decreased D1 receptor mRNA (D1RmRNA) in striatal neurons 19 months after surgery, while D2 receptor mRNA (D2RmRNA) and the neuronal number remained the same. The present results show that just as is already known for the immature rat brain, the adult rat brain, too, reacts to a transient decrease in its blood supply by appearance of long-lasting alterations in function, and that even a single oligemic episode is capable of inducing progressive dopaminergic dysfunctions and ultimately the partial loss of striatal D1RmRNA.

Animals↗

PubMed1999

Inhibition of Zac1, a new gene differentially expressed in the anterior pituitary, increases cell proliferation.

Zac1 is a new zinc finger protein that concomitantly controls apoptosis and cell cycle arrest through separate pathways. The mouse Zac1 gene is mainly expressed in the pituitary gland and in different brain areas. In this study regional and cellular expression of Zac1 in the pituitary gland was determined by in situ hybridization. Zac1 messenger RNA was abundantly expressed in the anterior pituitary lobe compared with that in the intermediate and posterior lobes. Zac1 transcripts were found in all hormone-secreting cell types, with the highest levels in GH- and PRL-producing cells. To investigate the impact of Zac1 in pituitary cell proliferation, we ablated the endogenous Zac1 gene by antisense treatment in two murine cell types, AtT-20 and TtT/GF, that are representative of granular and agranular cell lineages, respectively. The decline in Zac1 protein levels under antisense treatment was accompanied by increased DNA synthesis in clonal corticotroph and folliculo-stellate cells, as demonstrated by enhanced [3H]thymidine incorporation (36% and 50%, respectively). Antisense oligonucleotides against Zac1 controlled cell proliferation in a dose-dependent way, and mutagenized antisense oligonucleotides were inert. Conclusively, our data provide the first evidence of a role for Zac1 in pituitary growth control.

Animals↗

PubMed1998

Heterogeneous dopamine D2 receptor subtype messenger ribonucleic acid expression in clinically nonfunctioning pituitary adenomas.

Little is known about differences in the expression, localization, and function of the two dopamine D2 receptor subtypes, D2short and D2long (D2s and D2l), in either normal or adenomatous pituitary. We investigated the messenger RNA (mRNA) expression of the D2 receptor (D2R) subtypes in clinically nonfunctioning pituitary adenomas by in situ hybridization using subtype-specific oligonucleotides. The five normal pituitaries studied expressed similar ratios of D2R subtypes mRNA with a predominant expression of the D2l isoform. In 2 of 18 clinically inactive adenomas no D2R mRNA was found, whereas in 16 a heterogeneous expression of D2R isoforms was observed. Six adenomas expressed only the D2l and 2 adenomas only the D2s subtype mRNA; the remaining 8 expressed extremely varying proportions of the two subtypes. The D2R was found only in a subset of the nonfunctioning adenoma cells. In gonadotropin-immunopositive adenomas, the D2R was mainly localized in LH- and FSH-immunopositive cells. Probably because of the heterogeneous D2R subtype expression, suppression of cell proliferation was observed in only 3 of 9 adenoma cell cultures in which the growth inhibitory effect of bromocriptine was studied. Although there is some evidence that the presence of the D2s receptor subtype favors the growth inhibitory response to bromocriptine, further studies with a larger number of inactive adenomas are needed to confirm this speculation.

Adenoma↗

PubMed1997

Changes of NMDA receptor subunit (NR1, NR2B) and glutamate transporter (GLT1) mRNA expression in Huntington's disease--an in situ hybridization study.

The distribution of NMDA receptor subunit (NR1, NR2B) and glia-bound glutamate transporter (GLT1) mRNAs was investigated in postmortem brains of Huntington's disease (HD) patients and controls by means of in situ hybridization using radiolabeled deoxyoligonucleotides. In the neostriatum of HD, NR1, NR2B and GLT1mRNA decreased in correlation to disease severity. GLT1mRNA was not as low as NR1/NR2BmRNA. Losses were more prominent in putamen than in the distinctly atrophied caudate. NR1/NR2BmRNA decreased corresponding to neuronal loss, GLT1mRNA due to reduced cellular expression. The number of GLT1mRNA expressing cells identified as astrocytes increased in the neostriatum (astrogliosis). In contrast to controls, most of these astrocytes contained glial fibrillary acidic protein. NR1/NR2B and GLT1mRNA expression was not homogeneously lower in the neostriatum; zones with stronger hybridization signals corresponded to the matrix compartment and consisted of a larger number of cells with high mRNA levels. Early in the disease, cellular NR1/ NR2BmRNA levels were higher in these zones than in controls. These findings indicate a loss of neurons with NMDA receptors in the neostriatum of HD. A concomitant proliferation of astrocytes with GLT1 transcripts may represent a compensatory mechanism protecting neostriatal neurons from glutamate excitotoxicity.

ATP-Binding Cassette Transporters↗

PubMed1996

Immunohistochemical and electrophysiological evidence for omega-conotoxin-sensitive calcium channels in unmyelinated C-fibres of biopsied human sural nerve.

In vitro electrophysiological measurements of Ca2+ potentials in human sural nerve fascicles revealed that Ca2+ conductances might be present on unmyelinated C-fibres. Furthermore, these Ca2+ potentials were partially blocked by omega-conotoxin, a calcium antagonist for the N-type Ca2+ channels. Therefore, immunohistochemical staining with indirect immunofluorescent omega-conotoxin GVIA was used to localize N-type Ca2+ channels in intact and in enzymatically dissociated human sural nerve fascicles. Densities of toxin binding sites were highly heterogeneous throughout the different nerve fascicles investigated and putative N-type Ca2+ channels were localized in about 20% of the unmyelinated C-fibres. Myelinating Schwann cells as well as enzymatically demyelinated axons displayed no specific binding indicating the absence of N-type Ca2+ channels.

Calcium Channel Blockers↗

PubMed1996

Patch-clamp study on membrane properties and transmitter activated currents of rabbit area postrema neurons.

Using the patch-clamp technique in combination wit sliced tissue preparation the membrane properties of newborn rabbit area postrema neurons were investigated. The neurons responded upon depolarization with a fast Na+-current followed by an inactivating and non-inactivating K+-current. GABA-activated currents were investigated resulting in a large C1-(-)conductance, indicating the expression of GABAA-receptors. The expression of glutamate receptor mRNA was studied by in situ hybridization and electrophysiological measurements of these receptors by means of the patch-clamp technique. As a main result it was found that ionotropic glutamate receptors in the area postrema are composed of "flop" variants of the GluA-, GluB- and GluC-subunits.

Animals↗

PubMed1995

Expression and localization of endothelin-1 and endothelin receptors in human meningiomas. Evidence for a role in tumoral growth.

In addition to its well-known homoeostatic actions in the cardiovascular system, ET-1 has been shown to constitute a potent growth regulatory peptide in various tissues. We have studied the expression of ET-1 and its receptors (ET-Ar and ET-Br) in human meningiomas (n = 35) as well as their involvement in cellular growth. By PCR of reverse-transcribed RNA we detected ET-1 mRNA in 91% (32 of 35), ET-Ar mRNA in 82% (29 of 35), and ET-Br mRNA in 42% (15 of 35) of human meningiomas examined. The localization of ET-1 mRNA, ET-Ar mRNA, and ET-1 peptide in tumoral cells was observed by in situ hybridization and immunohistochemistry, whereas ET-Br mRNA was expressed at low level only in cells belonging to blood vessels. In addition, we found that ET-1 stimulated [3H] thymidine incorporation in primary cell cultures of 20 meningiomas and that this effect could be blocked by BQ-123, a specific antagonist for ET-Ar. In contrast, RES-701-3, an antagonist of ET-Br, did not block the proliferative effect of ET-1. In conclusion, our data provide evidence that ET-1 constitutes an important growth factor for meningiomas acting via ET-Ar. We can hypothesize that ET-1, acting in concert with other growth factors and cytokines, is involved in the meningioma tumorigenesis.

Adult↗