Expression analysis of RET and the GDNF/GFRalpha-1 and NTN/GFRalpha-2 ligand complexes in pheochromocytomas and paragangliomas.

Pheochromocytoma and its extra-adrenal counterpart paraganglioma are rare catecholamine producing tumors which usually occur sporadically but may also be a part of neuroendocrine tumor syndromes such as multiple endocrine neoplasia type 2A (MEN 2A). Activating mutations of the RET proto-oncogene which is the underlying cause of MEN 2A, is also seen in approximately 10% of sporadic pheochromocytomas. Glial cell line derived neurotrophic factor (GDNF) and neurturin (NTN) have been shown to function as independent ligands to RET, binding in a complex with the membrane-bound receptors GFRalpha-1 and GFRalpha-2 respectively. Here we have investigated the mRNA expression of RET and its ligand complexes, GDNF/GFRalpha-1 and NTN/GFRalpha-2, in a panel of pheochromocytomas and paragangliomas using mRNA in situ hybridization. RET expression was evident in normal adrenal medulla, and in 13/15 pheochromocytomas, including 5/5 MEN 2A associated tumors, but only in 1/10 paragangliomas. The frequent expression of RET in the pheochromocytomas suggest that this gene might be involved in the tumorigenesis. However, no expression of GDNF/GFRalpha-1 or NTN/GFRalpha-2 could be detected in any of the 25 tumors analyzed, suggesting that these ligand complexes are not important in the development of pheochromocytoma or paraganglioma.

Comparative genomic hybridization reveals frequent losses of chromosomes 1p and 3q in pheochromocytomas and abdominal paragangliomas, suggesting a common genetic etiology.

Pheochromocytomas and abdominal paragangliomas are rare, catecholamine-producing tumors that arise from the chromaffin cells derived from the neural crest. We used comparative genomic hybridization (CGH) to screen for copy number changes in 23 pheochromocytomas and 11 abdominal paragangliomas. The pattern of copy number changes was similar between pheochromocytomas and paragangliomas, with the most consistent finding being loss of 1cen-p31, which was detected in 28/34 tumors (82%). Losses were also found on 3q22-25 (41%), 11p (26%), 3p13-14 (24%), 4q (21%), 2q (15%), and 11q22-23 (15%), and gains were detected on 19p (26%), 19q (24%), 17q24-qter (21%), 11cen-q13 (15%), and 16p (15%). Losses of 1p and 3q were detected in the majority of tumors, whereas gains of 19p and q, 17q, and 16p were seen only in tumors with six or more CGH alterations. This progression of genetic events did not correspond with the conversion to a malignant phenotype. CGH alterations involving chromosome 11 were more frequent in the malignant tumors, compared with the benign tumors (9/12 versus 3/16). In summary, we propose that pheochromocytomas and abdominal paragangliomas, which share many clinical features, also have a common genetic origin and that the loss of 1cen-p31 represents an early and important event in tumor development.

Regulation of neurotrophin signaling in aging sensory and motoneurons: dissipation of target support?

A hallmark of senescence is sensorimotor impairment, involving locomotion and postural control as well as fine-tuned movements. Sensory and motoneurons are not lost to any significant degree with advancing age, but do show characteristic changes in gene-expression pattern, morphology, and connectivity. This review covers recent experimental findings corroborating that alterations in trophic signaling may induce several of the phenotypic changes seen in primary sensory and motoneurons during aging. Furthermore, the data suggests that target failure, and/or breakdown of neuron-target interaction, is a critical event in the aging process of sensory and motoneurons.

Reciprocal changes in the expression of neurotrophin mRNAs in target tissues and peripheral nerves of aged rats.

trk receptors are downregulated in both dorsal root ganglion (DRG) and spinal motoneurons of aged rats with behavioral sensorimotor deficits. Here we provide evidence, using reverse transcription-polymerase chain reaction (RT-PCR), of decreased levels of neurotrophin (nerve growth factor, NGF; brain-derived neurotrophic factor, BDNF; neurotrophin-3, NT-3; and neurotrophin-4, NT-4) mRNAs in target muscles. Moreover, the degree of neurotrophin mRNA decrease in target muscles seems to co-vary with the extent of sensorimotor disturbances. In contrast, the peripheral nerve of aged rats showed a reciprocal regulation of neurotrophins, with increased levels of NGF, BDNF, and NT-4 mRNAs. Taken together, evidence suggest an aging-related attenuation of neurotrophin signaling between target tissues, on one hand, and DRG and motoneurons, on the other, and, furthermore, that target-derived neurotrophins regulate the expression levels of trk mRNAs in both DRG and motoneurons.

Long term experience after subtotal adrenalectomy for multiple endocrine neoplasia type IIa.

OBJECTIVE: To evaluate the long-term results after subtotal adrenalectomy in patients with multiple endocrine neoplasia type IIa (MEN IIa). DESIGN: Retrospective study. SETTING: University Hospital, Sweden. SUBJECTS: Five patients who underwent partial adrenalectomy between 1985 and 1989. INTERVENTIONS: Subtotal adrenalectomy with a rim of cortical tissue left in situ. MAIN OUTCOME MEASURES: Follow up by interview, measurement of cortisol and catecholamine excretion in urine, and cortisol concentration in serum in response to stimulation with ACTH. RESULTS: Three patients took no corticosteroids regularly, but during upper respiratory tract infections, or periods of severe stress they took 25 mg cortisone acetate daily. This is confirmed by their normal values of 24 hour urinary cortisol excretion and subnormal responses to an ACTH-stimulation test. The fourth and fifth patients had low concentrations of endogenous corticosteroids postoperatively, which is being replaced with 25 mg cortisone acetate daily. Postoperatively all five patients had low urinary adrenaline excretion. CONCLUSION: Subtotal adrenalectomy in patients with MEN IIa resulted in basal endogenous corticosteroids within the reference range in three of five patients. There was no evidence of reduced adrenocortical function with time, nor were there any signs of recurrence of the pheochromocytoma.

Evidence for increased GDNF signaling in aged sensory and motor neurons.

Several lines of evidence suggest that attenuated neurotrophin signaling may account for some of the aging-related phenotypic changes observed in motor and sensory neurons. Glial-derived neurotrophic factor (GDNF) signals through the GFRalpha-1-RET receptor complex and has trophic effects on both primary sensory neurons and, in particular, motoneurons. In this study we provide evidence using RT-PCR that GDNF, but not neurturin, is strongly up-regulated in target muscles (800%) and to a lesser extent also in peripheral supportive tissues. Results here, and in an earlier study, show that the up-regulation of GDNF in target and supportive tissues parallels an increased neuronal expression of the cognate receptors. Increased GDNF signaling may explain some of the phenotypic characteristics of aging sensory and motoneurons.

Effect of chronic endogenous hypercalcemia on prolactin and thyrotropin responsiveness in man.

To investigate whether chronic endogenous hypercalcemia influences TSH and/or PRL release from pituitary thyrotrophs and lactotrophs in man, 10 patients with endogenous hypercalcemia, due either to cancer or to primary hyperparathyroidism, were injected with 25 micrograms TRH iv. The TSH and PRL responses were compared with those obtained in an age-, sex-, and weight-matched group of patients comprised of 10 normocalcemic individuals with other diseases. The mean maximal TSH response in the hypercalcemic group (3.7 +/- 0.4 microU/ml) was 46% lower than in the normocalcemic group (6.8 +/- 1.2 microU/ml; p less than 0.02). Similarly, the mean maximal PRL response was 45% lower in the hypercalcemic (31 +/- 5 ng/ml) than in the normocalcemic patients (57 +/- 9 ng/ml; p less than 0.05). Feasible mechanisms behind this inhibitory influence of chronic endogenous hypercalcemia on TSH and PRL responsiveness are discussed.

Serum calcium decline after intravenous administration of thyrotropin-releasing hormone in man.

The influence of iv administration of 0.2 mg thyrotropin-releasing hormone (TRH) on serum calcium was examined in 20 subjects divided into three different groups: one, comprising patients with primary hypothyroidism (A), another, containing euthyroid patients with various diseases (B), and a third, including healthy volunteers (C). Ninety min after the TRH injection total serum calcium (T-Ca) had fallen by 0.19 +/- 0.03 mmol/l in group A (p less than 0.01), by 0.10 +/- 0.02 mmol/l in group B (p less than 0.01), and by 0.08 +/- 0.02 mmol/l in group C (p less than 0.02). Ionized serum calcium (I-Ca) fell in parallel with T-Ca in group A and B. In contrast, serum magnesium was unaffected in all groups. Neither the renal excretion of calcium nor the serum concentration of parathyroid hormone, glucagon or calcitonin changed significantly in response to TRH. These results indicate that TRH has a slight hypocalcemic effect in man which is not caused by plasma dilution, direct influence on the kidneys, or TRH effects on the major calcium regulating hormones. Whether TRH per se, or an increased serum TSH level, induces calcium to leave the vascular space remains to be elucidated.