Biomedical subjects

Johannes Schmitt

Publications and source records attributed to Johannes Schmitt.

12 recordsLinked to original sources

PubMed2007

Inverse correlation between serum PGE2 and T classification in head and neck cancer.

BACKGROUND: Prostaglandin E2 (PGE2) serum levels have been shown previously to be increased in tumor bearing mice as well as in patients with solid tumors; however, the impact on the course or stage of disease has not been shown. We hypothesized that PGE2 is strictly required for aggressive and especially early-stage tumors of the head and neck to provoke invasion and angiogenesis. METHODS: We analyzed the serum PGE2 levels of 100 patients with head and neck squamous cell carcinoma of different stages before and 1 year after treatment and compared the results with the serum levels of 40 healthy donors and the secretion profile of 8 different squamous cell carcinoma cell lines. RESULTS: Our investigations showed a statistically significant inverse correlation between PGE2 serum levels and tumor stage. Furthermore, this effect has been reflected by the results of our cell culture analyses, which showed an inversely regulated PGE2 secretion into the medium during the process of proliferation. Interestingly, the serum levels of PGE2 were significantly downregulated 1 year after successful treatment. CONCLUSIONS: We conclude that PGE2 serum level as an indicator for early-stage cancer of the head and neck may function as a tumor marker during the follow-up period.

Biomarkers, Tumor↗

PubMed2006

Induction of reactive oxygen species and cell survival in the presence of advanced glycation end products and similar structures.

Advanced glycation end products (AGEs) that arise from the reaction of sugars with protein side chains and the terminal amino group are supposed to be involved in the pathogenesis of several diseases and therefore the effects of AGEs on cells are the objective of numerous investigations. The effects of AGEs on cells are commonly assumed to be transduced via the receptor for AGEs (RAGE) but there are also other receptors known to interact with AGEs and they are likely to be involved in signal transduction. The primary cellular effect of AGEs on cultured cells was found to be the formation of reactive oxygen species (ROS). For the present study one murine and three human cell lines were used. The effects of a set of different highly modified AGEs and AGE-like compounds derived from the incubation of different modifiers with BSA were tested for their effects on these cells. Almost all AGEs tested induced the production of reactive oxygen species (ROS) in the different cell lines although the intensity of the detected signals varied considerably between the cell lines and are strongly dependent on the AGE used for cell activation. The most highly modified BSA-species were shown to inhibit cell growth in all cell lines, whereas a moderately modified glucose derived BSA-AGE and BSA-GA(red) did not show any inhibitory effect on cell growth even when a high ROS formation was detected.

Animals↗

PubMed2006

ADME related profiling in 96 and 384 well plate format--a novel and robust HT-assay for the determination of lipophilicity and serum albumin binding.

The failure of about half of the drug candidates is associated with poor pharmacokinetic properties leading to a huge loss of time and money [1]. Early profiling of drug like properties provides important information in order to screen out insoluble, poorly absorbed and toxic compounds. Today, large compound libraries have to be screened, and of course the total number of compounds will rise over the next years leading to a growing demand for fully automated assays. A balance between quality, speed, throughput, cost and information content can be accomplished by the careful selection of assays and experimental conditions. Here we describe a novel 384 well format assay for two important ADME related descriptors (lipophilicity and serum protein binding) as input parameters for a precise prediction of fraction absorbed, blood/organ distribution coefficients and permeability, in order to maximize the information about a compound at an early stage of discovery.

Chromatography, High Pressure Liquid↗

PubMed2006

"Just ascites"?

Explore the source record for details and available documents.

Ascites↗

PubMed2005

Two analytical methods to study the interaction of AGEs with cell surface proteins.

Advanced glycation end products (AGEs) are sugar-modified proteins that are known to appear in vivo and are suspected to be involved in the pathogenesis of several diseases. Although different cellular responses to AGEs can be measured in cell culture studies, knowledge about the nature of AGE-binding and their cell surface receptors is poor. In the present paper a method for the purification of AGE-binding proteins from membrane fractions derived from different rat organs as well as a method for assaying the binding of fluorescein labelled AGEs to the surface of cells of different cell lines are described. The presence of more than 10 proteins interacting with AGEs could be shown in membrane fractions obtained from rat organs. Additionally, binding of AGE-modified BSA to different cells could be shown using fluorescence-labelled ligands in a flow cytometric approach. The presented methods provide an option to isolate AGE-interacting proteins which is a precondition for the identification of these proteins. Furthermore, the measurement of AGE-binding to cell surfaces bears the potential to gain a deeper understanding about the nature of AGE-binding to cell surface proteins and might be applied as a preliminary test before performing cell culture studies about AGE effects.

Animals↗

PubMed2005

Characterization of advanced glycation end products: mass changes in correlation to side chain modifications.

Advanced glycation end products (AGEs) that arise from the reaction of sugars with protein side chains are supposed to be involved in the pathogenesis of several diseases; therefore, the effects of AGEs on cells are the objective of numerous investigations. Because AGE modifications are an extremely heterogeneous group of side chain modifications, the exact characterization of an AGE-modified protein is impossible. To gain a deeper understanding about AGE formation kinetics and structures, AGEs can be characterized with respect to the degree of modification, specific side chain modifications, absorbance and fluorescence characteristics, and changes in the protein structure and molecular weight. For this study, human serum albumin (HSA)-AGEs derived from different concentrations of glucose, methyl glyoxal, and glyoxylic acid were used. The molecular mass of the obtained AGEs was determined using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The mass data were compared with earlier results concerning the degree of lysine and arginine side chain modifications and AGE-specific fluorescence and absorbance data. The molecular masses were found to gradually increase with increasing concentrations of the individual modifier without reaching a plateau. The mass increase correlates very well with the AGE-specific absorbance at 360 nm and with the degree of side chain modifications. The mass spectrometric data prove, for the first time, that an increasing absorbance at 360 nm is directly correlated to a mass increase during the AGE formation process.

Glycation End Products, Advanced↗

PubMed2005

Characterization of advanced glycation end products for biochemical studies: side chain modifications and fluorescence characteristics.

Advanced glycation end products (AGEs) are known to be involved in the pathogenesis of several diseases and therefore effects of AGEs on cells are the objective of numerous investigations. Since AGEs used in biochemical studies are usually not chemically characterized, comparison of data is difficult if not impossible. To find a suitable characterization protocol, human serum albumin was reacted with different concentrations of glucose, methyl glyoxal, and glyoxylic acid. The obtained AGEs were characterized with respect to the extent of side chain modifications (lysine and arginine), the carboxymethyl lysine and carbonyl content, and the fibrillar state. Additionally, their fluorescence and absorbance characteristics were extensively studied. Although we found significant differences in the degree of modification and in AGE-specific fluorescence when using different modifiers, the results provide important information and allow comparing AGEs derived from different modifier concentrations. The results also suggest strong conformational changes within the modified proteins. In the present paper we propose a set of parameters that is sufficient to partially characterize AGEs used for biochemical studies.

Amino Acids↗

PubMed2004

Two novel LEM-domain proteins are splice products of the annotated Drosophila melanogaster gene CG9424 (Bocksbeutel).

The LEM motif is a sequence of 40-50 amino acids that has been identified in a number of non-related proteins of the inner nuclear membrane including the lamina-associated polypeptides 2 (LAP2), emerin, MAN1 and the Drosophila protein otefin. This evolutionary conserved sequence motif can mediate via the interaction with the small protein BAF the binding of LEM-domain proteins to DNA. Taking advantage of its sequenced genome we analyzed whether Drosophila possesses beside otefin additional genes coding for proteins with a LEM motif. A putative candidate gene was the annotated gene CG9424 which we named Bocksbeutel. Of all putative Drosophila LEM-domain proteins, otefin and Bocksbeutel exhibited the highest similarity in the LEM motif (53% identical amino acids). The Bocksbeutel gene can code for two isoforms of 399 and 351 amino acids that are produced by alternative splicing. In the alpha-isoform a transmembrane domain is localized close to the carboxyterminus. This segment is absent in the shorter beta-isoform. By RT-PCR we could show that in the embryo the mRNA coding for the alpha-isoform and in significantly lower amounts the mRNA coding for the beta-isoform are expressed. When expressed in transfected cells as GFP fusion proteins, the beta-isoform is localized predominantly in the nucleoplasm and the alpha-isoform is targeted to the nuclear envelope, indicating that Bocksbeutel-alpha is localized in the inner nuclear membrane. Bocksbeutel-alpha is the predominant isoform expressed in cells, larvae, and flies. Indirect immunofluorescence with Bocksbeutel-specific antibodies on tissues and cultured cells revealed that Bocksbeutel proteins are localized in the nuclear envelope and in the cytoplasm. By RNA interference we have down-regulated the expression of Bocksbeutel, BAF, otefin, and lamin DmO in Drosophila Kc167 cells. The down-regulation of Bocksbeutel and otefin had no influence on the viability of Kc167 cells and the intracellular localization of all other nuclear and nuclear envelope proteins analyzed. In contrast, when lamin DmO was reduced by RNAi the distribution of Bocksbeutel and otefin in the nuclear envelope of Kc167 cells was significantly altered. We conclude that the two LEM-domain proteins Bocksbeutel and otefin are no limiting components for the maintenance of the nuclear architecture in cultured Drosophila cells at interphase.

Alternative Splicing↗

PubMed2003

Frequent expression of immunoreactive somatostatin receptors in cervical and endometrial cancer.

OBJECTIVE: A variety of human cancers has been shown to express somatostatin receptors which can be utilized for in vivo tumor targeting. Although the somatostatin receptor status of mammary and ovarian cancer has been studied in detail, somatostatin receptors have not been examined in other gynecological malignancies such as cervical or endometrial carcinoma. METHODS: We have previously developed a panel of somatostatin receptor subtype-specific antibodies that effectively stain formalin-fixed, paraffin-embedded human tumor tissue. In the present study, we have used these antibodies to determine the somatostatin receptor status of 21 randomly selected cervical carcinomas and 28 randomly selected endometrial carcinomas. RESULTS: In cervical carcinoma, the incidence of somatostatin receptor expression was sst2A (12/21, approximately 57%) > sst3 (9/21, approximately 43%) > sst1 (8/21, approximately 38%) > sst4 (0/21, 0%) = sst5 (0/21, 0%). In endometrial carcinoma, the incidence of somatostatin receptor expression was sst3 (12/28, approximately 43%) > sst2A (11/28, approximately 39%) > sst1 (9/28, approximately 32%) > sst4 (1/28, approximately 4%) = sst5 (1/28, approximately 4%). Somatostatin receptor-like immunoreactivity was in most cases located at the plasma membrane and completely blocked with antigenic peptide. The expression of somatostatin receptor subtypes was independent of patient age, diagnosis, tumor stage, and histological grade. CONCLUSION: Our findings reveal a previously unappreciated high incidence of sst1, sst2A, and sst3 somatostatin receptors in human cervical and endometrial cancers and suggest that a subgroup of receptor-positive uterine carcinomas may be a potential target for diagnostic and therapeutic intervention with stable somatostatin analogs.

Adult↗

PubMed2003

Thymic hyperplasia following successful treatment for nodular-sclerosing Hodgkin's disease.

A young female patient showed up with mediastinal bulky disease and lymph node swelling in her left supraclavicular region. Clinical and histological investigations proved nodular-sclerosing Hodgkin's lymphoma. The patient received combined modality treatment according to the protocols of the German Hodgkin's Disease Study Group and achieved complete remission. Six months later the chest X-ray and thoracic CT-scan showed mediastinal tumor masses suggesting relapsed Hodgkin's disease. Surprisingly, the histological investigation showed thymic hyperplasia as well as the absence of any signs of Hodgkin lymphoma. Thymic hyperplasia is well known as a potential differential diagnosis of mediastinal space-occupying lesions and also as a long-term complication in patients cured of Hodgkin's disease. A detailed case report and a complete review of literature are provided.

Adult↗

PubMed2002

Immunohistochemical detection of somatostatin receptors in human ovarian tumors.

OBJECTIVE: It is well established that many human tumors can express somatostatin receptors. This is the molecular basis for the application of long-acting somatostatin analogues for therapeutic and diagnostic purposes. However, there are discrepancies in earlier studies regarding the prevalence of somatostatin receptor expression in human ovarian tumors detected using autoradiographic binding studies or reverse transcription-polymerase chain reaction. METHODS: We have previously developed a panel of somatostatin receptor subtype-specific antibodies that effectively stain formalin-fixed, paraffin-embedded human tumor tissue. In the present study, we have used these antibodies to determine the somatostatin receptor status of 47 randomly selected human ovarian tumors. RESULTS: Somatostatin receptor-like immunoreactivity was in most cases located at the plasma membrane as well as in the cytoplasm of the tumor cells and was completely blocked with antigenic peptide. The pattern of expression of somatostatin receptor subtypes varied greatly between individual tumors. Of the 47 ovarian tumor specimens analyzed, 9 tumors (approximately 19%) were positive for sst(1), 13 (approximately 28%) revealed immunoreactive sst(2A) receptors, 20 (approximately 42%) showed sst(3)-like immunoreactivity, 8 (approximately 17%) revealed immunoreactive sst(4) receptors, and 10 (approximately 21%) were positive for sst(5). Whereas 18 tumors (approximately 38%) revealed no somatostatin receptor immunoreactive staining, 14 (approximately 30%) expressed more than one somatostatin receptor subtype. The expression of somatostatin receptor subtypes was independent of patient age, diagnosis, and histological grade. CONCLUSION: We provide direct evidence of somatostatin receptor protein expression in human ovarian tumors. Our findings suggest that a subgroup of receptor-positive ovarian tumors may be a potential target for treatment with somatostatin receptor subtype-selective analogs. However, due to the wide variations in the somatostatin receptor status of similar cases, each tumor specimen must be tested individually for the presence of particular somatostatin receptor subtypes.

Adolescent↗

PubMed2002

True positive somatostatin receptor scintigraphy in primary breast cancer correlates with expression of sst2A and sst5.

UNLABELLED: [111In-DTPA-D-Phe1]-octreotide scintigraphy has been shown to reveal somatostatin receptor-positive lesions in the majority of primary breast cancers. We have recently developed a panel of somatostatin receptor subtype-specific antibodies that effectively stain formalin-fixed, paraffin-embedded breast cancer tissue. However, it is uncertain to what extend somatostatin receptors detected during immunohistochemical staining represent functional binding sites responsible for high tracer uptake during somatostatin receptor scintigraphy. PATIENTS AND METHODS: We, therefore, conducted a prospective study in which 23 patients with suspected breast tumors were included. All patients received [111In]-pentetreotide scintigraphy. After surgical removal of the tumor, the somatostatin receptor status was determined by immunohistochemistry. RESULTS: Among 20 pathologically proven malignant tumors (14 ductal and six lobular carcinomas), 13 (approximately 65%) were scintigraphically visible. Of the 20 primary breast cancer specimens analyzed, three tumors (approximately 15%) were positive for sst1, nine (approximately 45%) revealed immunoreactive sst2A receptors, eight (approximately 40%) showed sst3-like immunoreactivity, and 14 (approximately 70%) were positive for sst5. There was an excellent correlation between the outcome of somatostatin receptor scintigraphy and expression of sst2A (P = 0.025) as well as sst5 (P < 0.001) but not expression of either sst1 (P = 0.343) or sst3 (P = 0.400). CONCLUSION: Both sst2A and sst5 can be responsible for high tracer uptake during [111In]-pentetreotide scintigraphy in primary breast cancer. Thus, somatostatin receptor scintigraphy may possibly be of value in the detection of proven somatostatin receptor sst2A- and/or sst5-positive lesions in metastatic breast cancer.

Adult↗