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C A Koch

Publications and source records attributed to C A Koch.

At least 37 records · Page 2Linked to original sources
PubMed2001

Genetic aspects of pheochromocytoma.

We here review the literature on genetics related to pheochromocytoma. About 10 percent of these neuroendocrine tumors are hereditary and are most often associated with multiple endocrine neoplasia type 2 (MEN 2), von Hippel-Lindau disease, and neurofibromatosis type 1 (NF 1). Hereditary tumor syndromes such as the aforementioned ones, are ideal to study the molecular pathogenesis of tumorigenesis as opposed to sporadic tumors in which genetic alterations often merely represent epigenetic tumor progression phenomena. Recent advances in molecular genetics, especially of RET, VHL, NF1, and SDHD, helped better understand the pathogenesis of pheochromocytoma. In this paper, we not only summarize key points of genetic discoveries related to pheochromocytoma, but also report in table format all known RET germline mutations related to pheochromocytoma.

Drosophila Proteins↗
PubMed2001

Abnormal ACTH-stimulation test in a patient with AIDS: adrenal insufficiency or toxoplasmosis?

We here report a 32-year old homosexual man with AIDS who had an abnormal ACTH stimulation test while taking megestrol actetate (megace). On further evaluation, he was found to have recurrent Non-Hodgkin lymphoma (spleen) and intracranial toxoplasmosis, perhaps imitating or aggravating symptoms suggestive of adrenal insufficiency (AI). We diagnosed secondary AI due to megace treatment and tapered this medication under simultaneous hydrocortisone replacement therapy. After the patient's intracranial toxoplasmosis had been treated with intravenous bactrim, his symptoms disappeared. We conclude that patients with AIDS on megace therapy should receive special attention in regards to the potential development of AI, especially in stress situations such as infections or pain.

Acquired Immunodeficiency Syndrome↗
PubMed2001

Adrenal androgens regulation and adrenopause.

Adrenal androgens (AA) are mainly produced by the human adrenal cortex. ACTH is the major regulator of their secretion. However, other factors, such as gonadal sex steroids, insulin, growth hormone, prolactin, hypothalamic peptides and growth factors have been involved in AA regulation. More recently, it has become well accepted that, besides systemic factors, AA secretion is under the control of the "sympathoadrenal system" and "immunoadrenal system". Here we review the extraadrenal and intraadrenal mechanisms of AA regulation and how they may relate to endocrinoimmunosenescence.

Adrenal Glands↗
PubMed2000

Duplication of the mutant RET allele in trisomy 10 or loss of the wild-type allele in multiple endocrine neoplasia type 2-associated pheochromocytomas.

Inherited mutations of the RET proto-oncogene are tumorigenic in patients with multiple endocrine neoplasia type 2 (MEN 2). However, it is not understood why only few of the affected cells in the target organs develop into tumors. Genetic analysis of nine pheochromocytomas from five unrelated patients with MEN 2 showed either duplication of the mutant RET allele in trisomy 10 or loss of the wild-type RET allele. Our results suggest a "second hit" causing a dominant effect of the mutant RET allele, through either duplication of the mutant allele or loss of the wild-type allele, as a possible mechanism for pheochromocytoma tumorigenesis in patients with MEN 2.

Adrenal Gland Neoplasms↗
PubMed2000

Somatic von Hippel-Lindau gene mutations detected in sporadic endolymphatic sac tumors.

Endolymphatic sac tumors (ELSTs) occur sporadically or in association with an autosomal dominantly inherited tumor syndrome, von Hippel-Lindau (VHL) disease. In VHL disease, a germline mutation of the VHL tumor suppressor gene is inherited, and loss of function of the wild-type allele occurs through genetic deletion with subsequent development of neoplastic growth. Genetic alterations associated with sporadic ELSTs are less well understood. In this study, we used tissue microdissection to selectively analyze neoplastic cells from four sporadic ELSTs. In two cases, we detected somatic mutations involving VHL gene exons 1 and 2, respectively. Additionally, one of these cases revealed deletion of the VHL gene locus. Two cases did not reveal VHL gene mutation; one of these two cases showed VHL gene deletion. These results suggest that mutations and allelic deletions of the VHL tumor suppressor gene play a role in the tumorigenesis of sporadic ELSTs.

Adult↗
PubMed2000

The guanine nucleotide exchange factor CNrasGEF activates ras in response to cAMP and cGMP.

Small GTPase proteins such as Ras are key regulators of cellular proliferation and are activated by guanine nucleotide exchange/releasing factors (GEFs/GRFs). Three classes of Ras GRFs have been identified to date, represented by Sos1/2, Ras-GRF1/2 and Ras-GRP. Here, we describe a novel candidate Ras activator, cyclic nucleotide rasGEF (CNrasGEF), which contains CDC25, Ras exchange motif (REM), Ras-association (RA), PDZ and cNMP (cAMP/cGMP) binding (cNMP-BD) domains, two PY motifs and a carboxy-terminal SxV sequence. CNrasGEF can activate Ras in vitro, and it binds cAMP directly via its cNMP-BD. In cells, CNrasGEF activates Ras in response to elevation of intracellular cAMP or cGMP, or treatment with their analogues 8-Br-cAMP or 8-Br-cGMP, independently of protein kinases A and G (PKA and PKG). This activation is prevented in CNrasGEF lacking its CDC25 domain or cNMP-BD. CNrasGEF can also activate the small GTPase Rap1 in cells, but this activation is constitutive and independent of cAMP. CNrasGEF is expressed mainly in the brain and is localized at the plasma membrane, a localization dependent on the presence of intact PDZ domain but not the SxV sequence. These results suggest that CNrasGEF may directly connect cAMP-generating pathways or cGMP-generating pathways to Ras.

Animals↗
PubMed2000

[Primary pigmented nodular adrenocortical dysplasia (PPNAD) within the scope of Carney complex as the etiology of Cushing syndrome].

BACKGROUND: Primary pigmented adrenocortical dysplasia (PPNAD) represents a rare disorder of the adrenal glands and frequently occurs in patients with the so-called Carney complex. Carney complex is an autosomal dominant neoplasia syndrome including skin and mucosal lentigines, myxomas, and PPNAD. CASE REPORT: A 37-year-old woman suffered from several episodes of weight gain/depression and weight loss/mania indicating cyclic hypercortisolism. Finally, she developed a full-blown Cushing's syndrome (CS) treated by bilateral adrenalectomy. She had PPNAD in the setting of Carney complex. CONCLUSION: PPNAD may lead to different clinical manifestations: 1. subclinical hypercortisolism, 2. intermittent hypercortisolemia, and 3. full-blown CS. It can be diagnosed with the 6-day Liddle test that typically shows a paradoxical stimulation of cortisol secretion after dexamethasone administration. The treatment of choice for PPNAD is bilateral adrenalectomy in order to prevent devastating long-term effects of hypercortisolism.

Adrenal Cortex↗
PubMed2000

Do glucocorticoids cause spinal epidural lipomatosis? When endocrinology and spinal surgery meet.

Here, we report pathogenetic aspects of spinal epidural lipomatosis (SEL) based on a literature review. SEL is a rare entity but can cause significant morbidity. Its symptoms can be identical to those of more common disorders such as vertebral and disc disease, and cord lesions (for example, transverse myelitis, multiple sclerosis and syringomyelia). Therefore, it often goes undiagnosed. In addition, SEL occurs in patients on glucocorticoid therapy, which can lead to myopathy, thereby mimicking the motor symptoms of SEL. Glucocorticoids seem to play a major role in the development of SEL, although idiopathic SEL has also been reported. The latter occurs almost exclusively in obese individuals who may have concurrent hypercortisolism. Once clinically suspected, SEL is best diagnosed by magnetic resonance imaging (MRI). Treatment of SEL is directed at reducing body weight in patients with idiopathic SEL, and at decreasing glucocorticoid excess in patients with endogenous or exogenous hypercortisolism. In severe cases, decompressive laminectomy might become necessary to alleviate the neurological symptoms caused by spinal cord compression.

Epidural Space↗
PubMed2000

Ectopic lingual thyroid: an otolaryngologic emergency beyond childhood.

Ectopic thyroid is rare and occasionally presents suddenly in childhood. Adult patients with thyroid ectopy who develop local symptoms commonly have an enlarged ectopic gland and hypothyroidism. We describe the first case of an adult patient who sudden presented with sudden dysphagia and dyspnea caused by a large lingual thyroid in clinical and biochemical euthyroidism. Treatment consisted of surgical removal of the ectopic gland and thyroid hormone replacement therapy.

Adolescent↗
PubMed2000

Calmodulin-independent coordination of Ras and extracellular signal-regulated kinase activation by Ras-GRF2.

Ras-GRF2 (GRF2) is a widely expressed, calcium-activated regulator of the small-type GTPases Ras and Rac. It is a multidomain protein composed of several recognizable sequence motifs in the following order (NH(2) to COOH): pleckstrin homology (PH), coiled-coil, ilimaquinone (IQ), Dbl homology (DH), PH, REM (Ras exchanger motif), PEST/destruction box, Cdc25. The DH and Cdc25 domains possess guanine nucleotide exchange factor (GEF) activity and interact with Rac and Ras, respectively. The REM-Cdc25 region was found to be sufficient for maximal activation of Ras in vitro and in vivo caused Ras and extracellular signal-regulated kinase (ERK) activation independent of calcium signals, suggesting that, at least when expressed ectopically, it contains all of the determinants required to access and activate Ras signaling. Additional mutational analysis of GRF2 indicated that the carboxyl PH domain imparts a modest inhibitory effect on Ras GEF activity and probably normally participates in intermolecular interactions. A variant of GRF2 missing the Cdc25 domain did not activate Ras and functions as an inhibitor of wild-type GRF2, presumably by competing for interactions with molecules other than calmodulin, Ras, and ligands of the PH domain. The binding of calmodulin was found to require several amino-terminal domains of GRF2 in addition to the IQ sequence, and no correlation between calmodulin binding by GRF2 and its ability to directly activate Ras and indirectly stimulate the mitogen-activated protein (MAP) kinase ERK in response to calcium was found. The precise role of the GRF2-calmodulin association, therefore, remains to be determined. A GRF2 mutant missing the IQ sequence was competent for Ras activation but failed to couple this to stimulation of the ERK pathway. This demonstrates that Ras-GTP formation is not sufficient for MAP kinase signaling. We conclude that in addition to directly activating Ras, GRF2, and likely other GEFs, promote the assembly of a protein network able to couple the GTPase with particular effectors.

Animals↗
PubMed2000

Neurosurgical implications of Carney complex.

OBJECT: The authors present their neurosurgical experience with Carney complex. Carney complex, characterized by spotty skin pigmentation, cardiac myxomas, primary pigmented nodular adrenocortical disease, pituitary tumors, and nerve sheath tumors (NSTs), is a recently described, rare, autosomal-dominant familial syndrome that is relatively unknown to neurosurgeons. Neurosurgery is required to treat pituitary adenomas and a rare NST, the psammomatous melanotic schwannoma (PMS), in patients with Carney complex. Cushing's syndrome, a common component of the complex, is caused by primary pigmented nodular adrenocortical disease and is not secondary to an adrenocorticotropic hormone-secreting pituitary adenoma. METHODS: The authors reviewed 14 cases of Carney complex, five from the literature and nine from their own experience. Of the 14 pituitary adenomas recognized in association with Carney complex, 12 developed growth hormone (GH) hypersecretion (producing gigantism in two patients and acromegaly in 10), and results of immunohistochemical studies in one of the other two were positive for GH. The association of PMSs with Carney complex was established in 1990. Of the reported tumors, 28% were associated with spinal nerve sheaths. The spinal tumors occurred in adults (mean age 32 years, range 18-49 years) who presented with pain and radiculopathy. These NSTs may be malignant (10%) and, as with the cardiac myxomas, are associated with significant rates of morbidity and mortality. CONCLUSIONS: Because of the surgical comorbidity associated with cardiac myxoma and/or Cushing's syndrome, recognition of Carney complex has important implications for perisurgical patient management and family screening. Study of the genetics of Carney complex and of the biological abnormalities associated with the tumors may provide insight into the general pathobiological abnormalities associated with the tumors may provide insight into the general pathobiological features of pituitary adenomas and NSTs.

Acromegaly↗