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C Schubert

Publications and source records attributed to C Schubert.

At least 19 recordsLinked to original sources
PubMed2001

A distinctive melanocytic lesion associated with melanoma-prone dysplastic naevus syndrome: the hybrid naevus.

Clinically and histologically, the concept of dysplastic nevi remains controversial. To elaborate more precise criteria for the nevi of patients with dysplastic naevus syndrome (DNS), we examined 58 nevi from seven DNS patients who developed one or several malignant melanomas. Clinical presentation and histomorphology were evaluated, and immunohistochemistry was performed using proliferation marker Ki-S5 and antibody DO-7 to the p53 protein. Sixty nevi from individuals without history of melanoma served as controls. Of the DNS nevi, 21 (36.2%) exhibited no morphological particularities. The remaining 37 nevi presented distinctive histological features consisting of a slight epidermal acanthosis, spitzoid vertically oriented nests of dyscohesive nevus cells, and single-standing atypical melanocytes in the basal cell layer of the epidermis. Immunohistochemical analysis revealed an average proliferation index of 2.5%, which significantly surpassed the mean growth fraction of conventional dysplastic nevi (<1%). No increase in p53 expression was observed. Characteristically, active proliferation was found in junctional single-standing melanocytes with or without nuclear atypia rather than in nest-shaped compounds. In conclusion, certain moles of patients with DNS possess distinctive features. The newly characterized criteria may provide a basis for the diagnosis of DNS and might help to identify patients at increased risk for malignant melanoma by examination of a single biopsy.

Adolescent↗
PubMed2001

Cilomilast: pharmacokinetic and pharmacodynamic interactions with digoxin.

BACKGROUND: Cilomilast is an orally active, selective phosphodiesterase 4 inhibitor currently in clinical development for the treatment of chronic obstructive pulmonary disease. OBJECTIVE: The purpose of this study was to examine the tolerability and steady-state pharmacokinetics of cilomilast and digoxin when coadministered at standard therapeutic doses in healthy adults. METHODS: In an initial, open-label phase, healthy young adults received cilomilast 15 mg BID for 5 days. After a 7-day washout period, subjects entered a double-blind, crossover phase during which they received oral digoxin (375 microg once daily) for 2 consecutive 14-day periods with no intervening washout period. Cilomilast 15 mg BID or placebo was coadministered during the first 14-day period. Subjects then crossed over to the alternative treatment for the second 14-day period. Blood and urine samples were collected at appropriate times for evaluation of digoxin and cilomilast steady-state pharmacokinetic parameters. The size of the study was sufficient to achieve 90% power to correctly exclude an effect of cilomilast. RESULTS: Twelve of the 16 subjects enrolled completed the study. There were 4 withdrawals--1 due to noncompliance, 1 due to a positive drug screening, and 2 due to adverse events. At steady state, cilomilast 15 mg BID had no significant effect on the steady-state pharmacokinetic parameters of digoxin, with 90% CIs for both primary end points--area under the plasma concentration-time curve (AUC) over a 24-hour dosing interval and minimum plasma concentration--completely contained within the specified interval for equivalence (0.80-1.25). A mean reduction in maximum observed plasma concentration of digoxin of 11% was observed during coadministration with cilomilast, and time to maximum concentration was delayed by a median of 1 hour, suggesting a small reduction in the rate of digoxin absorption. Digoxin did not appear to markedly affect cilomilast steady-state pharmacokinetics. The most frequently reported adverse event was headache. CONCLUSIONS: Cilomilast 15 mg BID had no clinically significant effect on steady-state AUC or on predose trough plasma concentrations of digoxin (375 microg once daily). The steady-state pharmacokinetics of cilomilast 15 mg BID were similar whether administered alone or with digoxin at steady state (375 microg once daily).

Adolescent↗
PubMed2001

Early mycosis fungoides: molecular analysis for its diagnosis and the absence of p53 gene mutations in cases with progression.

The histological diagnosis of initial mycosis fungoides (MF) and the molecular mechanisms that are responsible for its progression and transformation to the more highly malignant variants of MF remain largely unknown. Because of the rare occurrence of these tumours, the need for snap frozen skin biopsy specimens and the difficulty to obtain suitable material for karyotypic and genotypic analysis, specific cytogenetic and molecular lesions have not yet been identified. In particular the role of known oncogenes and tumour suppressor genes, including the p53 gene, in the pathogenesis and clinical progression of MF has not been extensively investigated. The present study was carried out using the polymerase chain reaction (PCR) technique combined with temperature gradient gel electrophoresis (TGGE) to detect mutations of the p53 gene in 58 patients with MF. TGGE analysis was also used in combination with clonality analysis by means of T-cell receptor gamma (TCRG) gene rearrangement studies to distinguish parapsoriasis en plaque and initial MF from patch/plaque stage MF. More than 83% of the diagnoses of initial MF could be confirmed using PCR-TGGE analysis. However, although the sensitive TGGE analysis was used for all exons, p53 gene polymorphisms were found in 4 and p53 gene mutation in only 1 of 58 biopsy specimens. It appears unlikely that p53 gene mutations play a role in either the pathogenesis of parapsoriasis and initial MF or their progression to advanced stages of MF. However, TCRG gene rearrangement studies by means of TCR-TGGE analysis may be useful for distinguishing histologically discordant cases of initial MF.

Biopsy↗
PubMed2001

Crystal structure of beta-arrestin at 1.9 A: possible mechanism of receptor binding and membrane Translocation.

BACKGROUND: Arrestins are responsible for the desensitization of many sequence-divergent G protein-coupled receptors. They compete with G proteins for binding to activated phosphorylated receptors, initiate receptor internalization, and activate additional signaling pathways. RESULTS: In order to understand the structural basis for receptor binding and arrestin's function as an adaptor molecule, we determined the X-ray crystal structure of two truncated forms of bovine beta-arrestin in its cytosolic inactive state to 1.9 A. Mutational analysis and chimera studies identify the regions in beta-arrestin responsible for receptor binding specificity. beta-arrestin demonstrates high structural homology with the previously solved visual arrestin. All key structural elements responsible for arrestin's mechanism of activation are conserved. CONCLUSIONS: Based on structural analysis and mutagenesis data, we propose a previously unappreciated part in beta-arrestin's mode of action by which a cationic amphipathic helix may function as a reversible membrane anchor. This novel activation mechanism would facilitate the formation of a high-affinity complex between beta-arrestin and an activated receptor regardless of its specific subtype. Like the interaction between beta-arrestin's polar core and the phosphorylated receptor, such a general activation mechanism would contribute to beta-arrestin's versatility as a regulator of many receptors.

Amino Acid Sequence↗
PubMed2001

[The influence of psychosocial factors on the immune system (psychoneuroimmunology) and their role for the incidence and progression of cancer].

Psychoneuroimmunological research investigates the influence of psychosocial factors on the immune systems. We reviewed clinical studies dealing with the following three topics: life events, psychological/psychopathological factors and social support, and their influence on cellular and humoral immune activity. There is strong evidence that stressful life events (especially losses) have a decreasing effect on immunity. Depression has a similar effect and may be the mediator between life events and the immune systems. Results dealing with the influence of social support on immune functions are still inconclusive. In the second part, we reviewed prospective studies concerning the role of psychosocial factors on cancer incidence and progression. Most of the life event studies reviewed have methodological problems, thus the results are heterogenous. There is some evidence that psychological/psychopathological factors can promote cancer progression. This is even more obvious in case of insufficient social support.

Antibody Formation↗
PubMed2000

An additional phosphate-binding element in arrestin molecule. Implications for the mechanism of arrestin activation.

Arrestins quench the signaling of a wide variety of G protein-coupled receptors by virtue of high-affinity binding to phosphorylated activated receptors. The high selectivity of arrestins for this particular functional form of receptor ensures their timely binding and dissociation. In a continuing effort to elucidate the molecular mechanisms responsible for arrestin's selectivity, we used the visual arrestin model to probe the functions of its N-terminal beta-strand I comprising the highly conserved hydrophobic element Val-Ile-Phe (residues 11-13) and the adjacent positively charged Lys(14) and Lys(15). Charge elimination and reversal in positions 14 and 15 dramatically reduce arrestin binding to phosphorylated light-activated rhodopsin (P-Rh*). The same mutations in the context of various constitutively active arrestin mutants (which bind to P-Rh*, dark phosphorylated rhodopsin (P-Rh), and unphosphorylated light-activated rhodopsin (Rh*)) have minimum impact on P-Rh* and Rh* binding and virtually eliminate P-Rh binding. These results suggest that the two lysines "guide" receptor-attached phosphates toward the phosphorylation-sensitive trigger Arg(175) and participate in phosphate binding in the active state of arrestin. The elimination of the hydrophobic side chains of residues 11-13 (triple mutation V11A, I12A, and F13A) moderately enhances arrestin binding to P-Rh and Rh*. The effects of triple mutation V11A, I12A, and F13A in the context of phosphorylation-independent mutants suggest that residues 11-13 play a dual role. They stabilize arrestin's basal conformation via interaction with hydrophobic elements in arrestin's C-tail and alpha-helix I as well as its active state by interactions with alternative partners. In the context of the recently solved crystal structure of arrestin's basal state, these findings allow us to propose a model of initial phosphate-driven structural rearrangements in arrestin that ultimately result in its transition into the active receptor-binding state.

Amino Acid Sequence↗
PubMed2000

Telomerase activity in melanocytic lesions: A potential marker of tumor biology.

Telomerase activation, being a cardinal requirement for immortalization, is a crucial step in the development of malignancy. With a view toward diagnostic and biological aspects in melanocytic neoplasia, we investigated the relative levels of telomerase activity in 72 nevi and 16 malignant melanomas by means of a modified telomeric repeat amplification protocol (TRAP) assay, including an internal amplification standard. We further compared telomerase activity with the expression of two different proliferation-specific proteins, Ki-67 and repp86, a protein expressed exclusively in the cell cycle phases S, G2, and M. Telomerase activity was associated with the overall growth fraction (Ki-67) but showed a closer correlation with the expression of repp86. Both telomerase activity and proliferation indices discriminated clearly between malignant melanomas and nevi, but not between common and dysplastic nevi. Nonetheless, a portion of nevi exhibited markedly elevated telomerase activity levels without proportionally increased proliferation. This was independent of discernible morphological changes. Clinicopathological correlations showed an association between high telomerase activity and early metastatic spread in melanomas, linking telomerase to tumor biology. Our results provide arguments in favor of an occasional progression from nevi to melanomas and imply that proliferation measurements in combination with telomerase assays may help to elicit early malignant transformation that is undetectable by conventional morphology.

Adolescent↗
PubMed2000

Chronic pelvic pain and previous sexual abuse.

OBJECTIVE: To determine whether there is an association between history of sexual abuse and development of chronic pelvic pain. METHODS: We studied 36 women with chronic pelvic pain, 23 with chronic low back pain, and 20 healthy women with reference to experience of sexual abuse, physical violence, and emotional neglect in childhood. Semistructured interviews were used to collect data. Assessment of severity of sexual abuse was based on Russell's criteria, and emotional and physical abuse were determined according to Briere's and Adler's definitions, respectively. RESULTS: In terms of experience of sexual abuse in general, the three groups did not differ statistically significantly from each other (P =.128). However, 22% of patients with chronic pelvic pain were sexually abused before their 15th birthdays, significantly more frequently than the other two groups (chronic low back pain 0%, P =.019, pain-free control 0%, P =.028). Women with chronic pelvic pain were exposed more frequently to physical violence (38%) and suffered more emotional neglect (25%) in their childhoods than women in the pain-free control group (physical abuse 5%, P =.012; emotional abuse 0%, P =.018). With regard to physical abuse and emotional neglect, the women with chronic pelvic pain did not differ from those with chronic low back pain (physical abuse 30.4%, P =.385; emotional abuse 21.7%, P =.571). CONCLUSION: Besides physical and emotional trauma, there is a significant association between sexual victimization before age 15 years and later chronic pelvic pain.

Adolescent↗
PubMed2000

Immune reaction links disease progression in cancer patients with depression.

Mood disturbances and depression are supposed to have a negative impact on patients' outcome in malignant tumour disease. On the other hand, poor prognosis in cancer patients is associated with chronic immune challenge which is paralleled by enhanced degradation of the essential amino acid tryptophan and thus decreased plasma tryptophan concentrations. Because tryptophan is precursor for the biosynthesis of the neurotransmitter serotonin (= 5-hydroxytryptamine, 5HT), low tryptophan concentrations will lead to decreased availability of serotonin which finally increases the susceptibility for the development of mood disturbances and depression in the patients. Thus, the development of depression in cancer patients may result from chronic cellular immune stimulation. In conclusion, a more aggressive tumour rather than depression will be responsible for worse outcome of cancer patients and will be associated with a more drastic challenge of the immune system, as a side effect leading to neurotransmitter disturbances.

Depression↗
PubMed1999

Characterization of glycosylphosphatidylinositol-linked molecule CD55/decay-accelerating factor as the receptor for antibody SC-1-induced apoptosis.

The human monoclonal antibody SC-1 induces apoptosis of stomach carcinoma cells and is currently used in a clinical Phase II trial. The antibody binds to a target molecule that is preferentially expressed on diffuse- and intestinal-type stomach cancer cells and shows a very restricted expression on other normal and malignant tissues. In this paper, we show that the SC-1 receptor is a stomach carcinoma-associated isoform of CD55 [membrane-bound decay-accelerating factor (DAF)-B] with a relative molecular mass of approximately 82 kDa. The antigenic site of SC-1 is an N-linked carbohydrate residue. Cross-linking of the DAF receptor increases apoptotic activity. SC-1 binding induces tyrosine phosphorylation of three proteins of approximately 60, 75, and 110 kDa, whereas a serine residue of an approximately 35-kDa protein is dephosphorylated. Expression of caspase-3 (CPP32) and caspase-8 (FLICE) is elevated, and activation of these caspases occurs. These data show that a tumor-specific variant form DAF is involved in apoptosis and can be used for adjuvant therapeutical purposes on gastric carcinoma.

Antibodies, Monoclonal↗
PubMed1999

Visual arrestin activity may be regulated by self-association.

Visual arrestin is the protein responsible for rapid quenching of G-protein-coupled receptor signaling. Arrestin exists as a latent inhibitor which must be 'activated' upon contact with a phosphorylated receptor. X-ray crystal structures of visual arrestin exhibit a tetrameric arrangement wherein an asymmetric dimer with an extensive interface between conformationally different subunits is related to a second asymmetric dimer by a local two-fold rotation axis. To test the biological relevance of this molecular organization in solution, we carried out a sedimentation equilibrium analysis of arrestin at both crystallographic and physiological protein concentrations. While the tetrameric form can exist at the high concentrations used in crystallography experiments, we find that arrestin participates in a monomer/dimer equilibrium at concentrations more likely to be physiologically relevant. Solution interaction analysis of a proteolytically modified, constitutively active form of arrestin shows diminished dimerization. We propose that self-association of arrestin may provide a mechanism for regulation of arrestin activity by (i) ensuring an adequate supply for rapid quenching of the visual signal and (ii) limiting the availability of active monomeric species, thereby preventing inappropriate signal termination.

Animals↗
PubMed1999

How does arrestin respond to the phosphorylated state of rhodopsin?

Visual arrestin quenches light-induced signaling by binding to light-activated, phosphorylated rhodopsin (P-Rh*). Here we present structure-function data, which in conjunction with the refined crystal structure of arrestin (Hirsch, J. A., Schubert, C., Gurevich, V. V., and Sigler, P. B. (1999) Cell, in press), support a model for the conversion of a basal or "inactive" conformation of free arrestin to one that can bind to and inhibit the light activated receptor. The trigger for this transition is an interaction of the phosphorylated COOH-terminal segment of the receptor with arrestin that disrupts intramolecular interactions, including a hydrogen-bonded network of buried, charged side chains, referred to as the "polar core." This disruption permits structural adjustments that allow arrestin to bind to the receptor. Our mutational survey identifies residues in arrestin (Arg175, Asp30, Asp296, Asp303, Arg382), which when altered bypass the need for the interaction with the receptor's phosphopeptide, enabling arrestin to bind to activated, nonphosphorylated rhodopsin (Rh*). These mutational changes disrupt interactions and substructures which the crystallographic model and previous biochemical studies have shown are responsible for maintaining the inactive state. The molecular basis for these disruptions was confirmed by successfully introducing structure-based second site substitutions that restored the critical interactions. The nearly absolute conservation of the mutagenically sensitive residues throughout the arrestin family suggests that this mechanism is likely to be applicable to arrestin-mediated desensitization of most G-protein-coupled receptors.

Animals↗
PubMed1999

The 2.8 A crystal structure of visual arrestin: a model for arrestin's regulation.

G protein-coupled signaling is utilized by a wide variety of eukaryotes for communicating information from the extracellular environment. Signal termination is achieved by the action of the arrestins, which bind to activated, phosphorylated G protein-coupled receptors. We describe here crystallographic studies of visual arrestin in its basal conformation. The salient features of the structure are a bipartite molecule with an unusual polar core. This core is stabilized in part by an extended carboxy-terminal tail that locks the molecule into an inactive state. In addition, arrestin is found to be a dimer of two asymmetric molecules, suggesting an intrinsic conformational plasticity. In conjunction with biochemical and mutagenesis data, we propose a molecular mechanism by which arrestin is activated for receptor binding.

Amino Acid Sequence↗
PubMed1999

Differences in morphology and cytoskeleton of MCF-7 and MX-1 cells after therapy with OH-tamoxifen and the pure estrogen antagonist ZM 182780. An immunofluorescence and scanning electron microscopic study.

The adjuvant endocrine therapy of breast cancer with non-steroidal antiestrogens of the triphenylethylene-type such as tamoxifen is clinically well established, and pure steroidal antiestrogens are being introduced in clinical trials to circumvent the probable occurrence of tamoxifen resistance. Nevertheless, there do still remain some unsolved questions about the exact mechanisms of these substances. We therefore investigated the different effects of 4-OH-Tamoxifen (OHT), a non-steroidal antiestrogen, versus ZM 182780, a pure steroidal antiestrogen, on the morphology and on the cytoskeleton of MCF-7 (estrogen receptor-positive) and MX-1 (estrogen receptor-negative) cells. For this purpose cells were treated for 2, 5 and 7 days with OHT, ZM182780 and different concentrations of beta-estradiol. Interestingly, in scanning electron microscopy, MCF-7 cells showed more differentiation by forming three-dimensional structures such as acini or tubule-like structures under ZM 182780 therapy than with OHT. As expected, MX-1 cells showed no effects after ZM 182780-therapy, but OHT led to a decrease in the number of these cells and produced a fibroblast-like appearance of the estrogen receptor-negative MX-1 cells. The following immunocytochemical experiments on the tubulin, vimentin, cytokeratin and actin cytoskeleton surprisingly did not show marked differences within the morphologically differentiated ZM 182780-treated population compared to the control group of MCF-7 cells. Only the OHT-treated cells of both, the ER(+) and the ER(-) cells, showed a rearrangement of actin filaments and cytokeratin which appeared even more pronounced within the ER(-) MX-1 cells. No experimental group showed morphologically detectable changes in tubulin or vimentin distribution. These data suggest a non ER-mediated OHT-effect on the cytoskeleton that also affects the ER(-) cell line MX-1.

Actins↗
PubMed1999

MAPKAP kinase 2 is essential for LPS-induced TNF-alpha biosynthesis.

MAPKAP kinase 2 (MK2) is one of several kinases that are regulated through direct phosphorylation by p38 MAP kinase. By introducing a targeted mutation into the mouse MK2 gene, we have determined the physiological function of MK2 in vivo. Mice that lack MK2 show increased stress resistance and survive LPS-induced endotoxic shock. This is due to a reduction of approximately 90% in the production of tumor necrosis factor-alpha (TNF-alpha) and not to a change in signalling from the TNF receptor. The level and stability of TNF-alpha mRNA is not reduced and TNF-alpha secretion is not affected. We conclude that MK2 is an essential component in the inflammatory response which regulates biosynthesis of TNF-alpha at a post-transcriptional level.

Animals↗
PubMed1999

Differential expression of CD34 and Ki-M1p in pleomorphic fibroma and dermatofibroma with monster cells.

Pleomorphic fibroma (PF) and dermatofibroma with monster cells (DFMC) are characterized by the presence of numerous cells with large atypical nuclei. Despite cytologic similarities, the two entities are likely to be unrelated, but their histogenesis is poorly understood. In this study, we examined six cases of PF and eleven cases of DFMC by immunohistochemistry using antibodies against vimentin, alpha-smooth muscle actin, S-100 protein, CD34, factor XIIIa, and the pan-monocytic marker Ki-M1p. Strong vimentin expression was seen in all tumors, whereas none of them expressed S-100 protein. PF consistently exhibited CD34 staining but appeared to be depleted of Ki-M1p positive cells compared with the surrounding normal skin. Conversely, all cases of DFMC contained numerous Ki-M1p positive cells including atypical multinucleate cells, but virtually no CD34 reactivity was observed. A weak staining for alpha-smooth muscle actin was occasionally seen in a subset of the cells of both entities. Our results indicate that PF and DFMC are histogenetically distinct entities that may arise from two different types of dermal dendritic cells defined by their reactivity for CD34 and Ki-M1p, respectively. Immunohistochemistry using these two antibodies permits an easy and reliable discrimination between PF and DFMC.

Actins↗