Search PubMed⌕ Search

Biomedical subjects

C Schmidt

Publications and source records attributed to C Schmidt.

At least 91 records · Page 5Linked to original sources
PubMed2001

Lentiviral vector-mediated tyrosinase-related protein 2 gene transfer to dendritic cells for the therapy of melanoma.

Dendritic cells (DCs) are the most potent professional antigen-presenting cells (APCs), which play a vital role in primary immune responses. Introducing genes into DCs will allow constitutive expression of the encoded proteins and thus prolong the presentation of the antigens derived therefrom. In addition, multiple and unidentified epitopes encoded by the entire tumor-associated antigen (TAA) gene may enhance T cell activation. This study demonstrated that an HIV-1-based lentiviral vector conferred efficient gene transfer to DCs. The transgene, murine tyrosinase-related protein 2 (mTRP-2), encodes a clinically relevant melanoma-associated antigen (MAA), which has been found to be a tumor rejection antigen for B16 melanoma. The transfer and proper processing of mTRP-2 in DCs, in terms of RNA transcription activity and protein expression, were verified by RT-PCR and specific antibody, respectively. Administration of mTRP-2 gene-modified DCs (DC-HR' CmT2) to C57BL/6 mice evoked strong protection against tumor challenge, for which the presence of CD4+ and CD8+ cells during both the priming and challenge phase was essential. In a therapy model, our results showed that four of seven mice with preestablished tumor remained tumor free for 80 days after therapeutic vaccination. Given the results shown in this study, mTRP-2 gene transfer to DCs provides a potential therapeutic strategy for the management of melanoma, especially in the early stage of the disease.

Animals↗
PubMed2001

Fisheries. Population of origin of Atlantic cod.

Most of the world's cod (Gadus morhua) fisheries are now tightly regulated or closed altogether. Being able to link individual fish to their population of origin would assist enormously in policing regulations and in identifying poachers. Here we show that microsatellite genetic markers can be used to assign individual cod from three different populations in the northeastern Atlantic Ocean to their population of origin.

Animals↗
PubMed2001

In vitro anti-tumour activity of alpha-galactosylceramide-stimulated human invariant Valpha24+NKT cells against melanoma.

alpha-galactosylceramide (KRN 7000, alpha-GalCer) has shown potent in vivo anti-tumour activity in mice, including against melanoma and the highly specific effect of inducing proliferation and activation of human Valpha24+NKT-cells. We hypothesized that human Valpha24+NKT-cells activated by alpha-GalCer might exhibit anti-tumour activity against human melanoma. To investigate this, Valpha24+NKT-cells were generated from the peripheral blood of patients with melanoma after stimulation with alpha-GalCer pulsed monocyte-derived dendritic cells (Mo-DCs). Valpha24+NKT-cells did not exhibit cytolytic activity against the primary autologous or allogeneic melanoma cell lines tested. However, proliferation of the melanoma cell lines was markedly suppressed by co-culture with activated Valpha24+NKT-cells (mean +/- SD inhibition of proliferation 63.9 +/- 1.3%). Culture supernatants of activated Valpha24+NKT-cell cultures stimulated with alpha-GalCer pulsed Mo-DCs exhibited similar antiproliferative activities against melanoma cells, indicating that the majority of the inhibitory effects were due to soluble mediators rather than direct cell-to-cell interactions. This effect was predominantly due to release of IFN-gamma, and to a lesser extent IL-12. Other cytokines, including IL-4 and IL-10, were released but these cytokines had less antiproliferative effects. These in vitro results show that Valpha24+NKT-cells stimulated by alpha-GalCer-pulsed Mo-DCs have anti-tumour activities against human melanoma through antiproliferative effects exerted by soluble mediators rather than cytolytic effects as observed against some other tumours. Induction of local cytokine release by activated Valpha24+NKT-cells may contribute to clinical anti-tumour effects of alpha-GalCer.

Adjuvants, Immunologic↗
PubMed2001

Production of a Higgs boson accompanied by two jets via gluon fusion.

Real-emission corrections to gg-->H, which lead to H+2 jet events, are calculated at order alpha(4)(s). Contributions include top-quark triangles, boxes, and pentagon diagrams and are evaluated analytically for arbitrary top mass m(t). This new source of H+2 jet events is compared to the weak-boson fusion cross section for a range of Higgs boson masses. The heavy top-mass approximation appears to work well for intermediate Higgs-boson masses, provided that the transverse momenta of the final-state partons are smaller than the top-quark mass.

Journal Article↗
PubMed2001

Homodimerization of amyloid precursor protein and its implication in the amyloidogenic pathway of Alzheimer's disease.

We reported previously that the carbohydrate domain of the amyloid precursor protein is involved in amyloid precursor protein (APP)-APP interactions. Functional in vitro studies suggested that this interaction occurs through the collagen binding site of APP. The physiological significance remained unknown, because it is not understood whether and how APP dimerization occurs in vivo. Here we report that cellular APP exists as homodimers matching best with a two-site model. Consistent with our published crystallographic data, we show that a deletion of the entire sequence after the kunitz protease inhibitor domain did not abolish APP homodimerization, suggesting that two domains are critically involved but that neither is essential for homodimerization. Finally, we generated stabilized dimers by expressing mutant APP with a single cysteine in the ectodomain juxtamembrane region. Mutation of Lys(624) to cysteine produced approximately 6-8-fold more A beta than cells expressing normal APP. Our results suggest that amyloid A beta production can in principle be positively regulated by dimerization in vivo. We suggest that dimerization could be a physiologically important mechanism for regulating the proposed signal activity of APP.

Alzheimer Disease↗
PubMed2001

In vitro biocompatibility of resorbable experimental glass ceramics for bone substitutes.

Tricalcium phosphate ceramics (TCPs) are increasingly used as bone substitutes. They demonstrate good biocompatibility and degrade relatively slowly. New glass ceramics based on calcium alkali orthophosphates (Ca(2)KNa(PO(4))(2)) were developed that degrade faster than TCP but could have reduced biocompatibility due to their high solubility. Therefore, they were modified by a neutralizing surface treatment. The aim of this study was to evaluate the biocompatibility of some of these ceramics, GB1a, GB9, and GB14, which differ in the amount of added Na, K, Mg, or Si ions, with standard and modified surfaces. The in vitro cytotoxicity of the ceramics GB1a, GB9, and GB14 was determined by the agar diffusion and filter test and the microculture tetrazolium (MTT) assay. In order to investigate the influence of surface modification, these three ceramics were compared to their surface-treated counterparts, GB1aN, GB9N, and GB14N. GB1a, the ceramic with the highest in vitro solubility, showed the strongest toxic influence in all cell culture tests. GB9 and GB14 produced better results. In contrast, the counterparts with modified surfaces exhibited no (GB9N, GB14N) or weak (GB1aN) signs of cytotoxicity. It is concluded that the toxicity of the ceramics GB1a, GB9, and GB14 depends on their solubility. A positive influence of the surface treatment on in vitro biocompatibility was demonstrated. Therefore, the surface-treated glass ceramics could be promising materials for bone replacement.

3T3 Cells↗
PubMed2001

Single amino acid substitutions and deletions that alter the G protein coupling properties of the V2 vasopressin receptor identified in yeast by receptor random mutagenesis.

To facilitate structure-function relationship studies of the V2 vasopressin receptor, a prototypical G(s)-coupled receptor, we generated V2 receptor-expressing yeast strains (Saccharomyces cerevisiae) that required arginine vasopressin-dependent receptor/G protein coupling for cell growth. V2 receptors heterologously expressed in yeast were unable to productively interact with the endogenous yeast G protein alpha subunit, Gpa1p, or a mutant Gpa1p subunit containing the C-terminal G alpha(q) sequence (Gq5). In contrast, the V2 receptor efficiently coupled to a Gpa1p/G alpha(s) hybrid subunit containing the C-terminal G alpha(s) sequence (Gs5), indicating that the V2 receptor retained proper G protein coupling selectivity in yeast. To gain insight into the molecular basis underlying the selectivity of V2 receptor/G protein interactions, we used receptor saturation random mutagenesis to generate a yeast library expressing mutant V2 receptors containing mutations within the second intracellular loop. A subsequent yeast genetic screen of about 30,000 mutant receptors yielded four mutant receptors that, in contrast to the wild-type receptor, showed substantial coupling to Gq5. Functional analysis of these mutant receptors, followed by more detailed site-directed mutagenesis studies, indicated that single amino acid substitutions at position Met(145) in the central portion of the second intracellular loop of the V2 receptor had pronounced effects on receptor/G protein coupling selectivity. We also observed that deletion of single amino acids N-terminal of Met(145) led to misfolded receptor proteins, whereas single amino acid deletions C-terminal of Met(145) had no effect on V2 receptor function. These findings highlight the usefulness of combining receptor random mutagenesis and yeast expression technology to study mechanisms governing receptor/G protein coupling selectivity and receptor folding.

Amino Acid Sequence↗
PubMed2001

Spermine supports catalysis of hairpin ribozyme variants to differing extents.

Because of the ability to cleave RNA substrates in trans, the hairpin ribozyme has great potential for therapeutic application. Activity of a three-stranded version of the minimal truncated form is enhanced by the presence of the polyamine spermine. Since spermine is the most abundant polyamine in eucariots, improved prospects for the hairpin ribozyme as therapeutic agent were predicted. We have found that not all hairpin ribozyme variants accept spermine equally well as counter-ion. Particularly the two-stranded versions commonly used for therapeutic studies show rather decreased activity when spermine is present. We have investigated a number of hairpin ribozyme derivatives regarding their ability to carry out spermine supported catalysis. Among the studied structures a two-stranded reverse-joined hairpin ribozyme displayed the highest cleavage rates in a synergistic mixture of magnesium ions and spermine. The specific features of this ribozyme along with its potential for in vivo application are discussed.

Base Sequence↗
PubMed2001

A multiparticulate drug-delivery system based on pellets incorporated into congealable polyethylene glycol carrier materials.

As a novel alternative to the incorporation into hard gelatin capsules or tablets, extended-release (Aquacoat- or Eudragit RS-coated) or enteric (Eudragit L-coated) pellets were embedded into congealed tablet-shaped PEG-plugs of different molecular weights, which rapidly released the pellets upon contact with aqueous fluids. The lower-molecular-weight PEGs (600 and 1000) were not suitable carrier materials: they dissolved the coatings or significantly increased their permeability. The release characteristics of the original pellets were maintained after embedding the pellets into the higher-molecular-weight PEGs 4000 or 10000. The shelf-life stability was a function of storage temperature and coating material. Stored at 40 degrees C, Aquacoat-coated pellets embedded in PEG 4000 exhibited a decreased drug release because of curing effects, while storage at 20 degrees C or below resulted in stable release profiles over a 3 month period. Eudragit RS-coated pellets, stored at room temperature or above, showed an increased release, and the carrier material possibly migrated into the film, thus increasing its permeability. At 4 degrees C, the release was stable over a 6 month period.

Acrylic Resins↗
PubMed2001

Transforming growth factor-beta1 induces desmoplasia in an experimental model of human pancreatic carcinoma.

Proliferation of fibrotic tissue (desmoplasia) is one of the hallmarks of several epithelial tumors including pancreatic adenocarcinoma. This tissue reaction may be deleterious or advantageous to the host or tumor. In a systematic analysis, we identified two growth factors expressed by human pancreatic carcinoma cells that are positively correlated with the ability to induce fibroblast proliferation both in vitro and in vivo, i.e., transforming growth factor (TGF)-beta1 and fibroblast growth factor-2. Here we demonstrate that the overexpression of TGF-beta1 induced up-regulation of matrix proteins and growth factors in the TGFbeta1-transfected pancreatic tumor cells. Furthermore, transfection of PANC-1 cells induces the same change in fibroblasts in either cocultivation experiments or when they are grown in conditioned medium from TGF-beta1-transfected PANC-1 cells. TGF-beta1-transfected pancreatic tumor cells induced a rich stroma after orthotopical transplantation in the nude mouse pancreas. The transfer of a single growth factor, TGF-beta1, conveys the ability to induce a fibroblast response similar to that seen in desmoplasia in human pancreatic adenocarcinoma. This effect cannot only be attributed to direct effects of TGF-beta1 but also results from the up-regulation of several other factors including collagen type I, connective tissue growth factor, and platelet-derived growth factor.

Animals↗
PubMed2001

The membrane-extrinsic domain of cytochrome b(558/566) from the archaeon Sulfolobus acidocaldarius performs pivoting movements with respect to the membrane surface.

The orientation of the membrane-attached cytochrome b(558/566)-haem with respect to the membrane was determined by electron paramagnetic resonance spectroscopy on two-dimensionally ordered oxidised membrane fragments from Sulfolobus acidocaldarius. Unlike the other redox centres in the membrane, the cytochrome b(558/566)-haem was found to cover a range of orientations between 25 degrees and 90 degrees. The described results are reminiscent of those obtained on the Rieske cluster of bc complexes and indicate that the membrane-extrinsic domain of cytochrome b(558/566) can perform pivoting motion between two extreme positions. Such a conformational flexibility is likely to play a role in electron transfer with its redox partners.

Amino Acid Sequence↗
PubMed2001

Dental microwear evidence for a dietary shift between two nonmaize-reliant prehistoric human populations from Indiana.

Several recent studies have demonstrated the efficacy of dental microwear analysis (DMA) for dietary reconstruction among nonhuman primates, early hominids, and prehistoric humans. The current study seeks microwear evidence for a paleobotanically suggested change in the types of foods that were consumed by two temporally distinct populations of the North American eastern woodlands. This particular dietary shift between the Late Archaic and the Early/Middle Woodland periods did not include the introduction of maize or any other tropical cultigen. In contrast, most dietary reconstructions from this area have compared later populations that consumed tropical cultigens (such as maize) with those that did not. High-resolution casts of adult mandibular second molar protoconid phase II wear facets were viewed via a scanning electron microscope at 500x. Photomicrographs of the microwear features were analyzed with specialized software, Microware 2.2 (Ungar [1995] Scanning 17:57-59). Analysis of variance statistical tests were performed, with one variable requiring rank-transformation. A dietary transition is evidenced by a statistically significant increase in the mean number of pits and concomitant decreases in scratch width and scratch length from the Late Archaic to the Early/Middle Woodland. Overall, the diet became harder and less abrasive. The implication here is that dental microwear analysis is able to discern relatively subtle dietary transitions in human populations that may not be as readily accessible by other means of dietary reconstruction.

Anthropology, Physical↗
PubMed2001

Proliferation and differentiation parameters of human osteoblasts on titanium and steel surfaces.

Commercially pure titanium (cpTi), titanium alloys, and steel are often used for dental and orthopedic implants. In these applications titanium is considered the "gold standard." However, tissue reactions around titanium implants and the changing trend to leave orthopedic devices in the body have led to a new examination of the preferred material. This in vitro study tested the behavior of osteoblasts on cpTi, Ti-6Al-7Nb, and stainless steel with surface designs similar to clinical implants. After surface characterization by scanning electron microscopy and profilometry, cell proliferation and the differentiation parameters of alkaline phosphatase (ALP) activity and osteocalcin were measured. For all materials tested, the growth curves showed a similar kinetic. On Ti-6Al-7Nb, ALP activity was significantly lower when compared with steel, and cpTi and did not change over the time. ALP activity increased moderately on steel and cpTi. Osteocalcin levels were higher on both titanium materials than on steel. Based on undisturbed cell growth and the relatively high alkaline phosphatase and osteocalcin levels, we suggest that cpTi provides the best biocompatibility with regard to proliferation, in addition to more reliable early and late differentiation markers of human osteoblasts in vitro.

Alkaline Phosphatase↗
PubMed2001

Regulation of Epha4 expression in paraxial and lateral plate mesoderm by ectoderm-derived signals.

Somitogenesis in all vertebrates involves a mesenchymal to epithelial transition of segmental plate cells. Such a transition involves cells altering their morphology and their adhesive properties. The Eph family of receptor tyrosine kinases has been postulated to regulate cytoskeletal organization. In this study, we show that a receptor belonging to this family, EphA4, is expressed in the segmental plate in a region where cells are undergoing changes in cell shape as a prelude to epithelialization. We have identified the ectoderm covering the somites and the midline ectoderm as sources of signals capable of inducing EphA4. Loss of EphA4 results in cells of irregular morphology and somites fail to form. We also show that when somites fail to develop, expression of EphA4 in the lateral plate is also lost. We suggest that signaling occurs between the somites and the lateral plate mesoderm and provide evidence that retinoic acid is involved in this communication.

Animals↗
PubMed2001

Transcriptional complementarity in breast cancer: application to detection of circulating tumor cells.

BACKGROUND: We used a combination of genetic subtraction, silicon DNA microarray analysis, and quantitative PCR to identify tissue- and tumor-specific genes as diagnostic targets for breast cancer. METHODS AND RESULTS: From a large number of candidate antigens, several specific subsets of genes were identified that showed concordant and complementary expression profiles. Whereas transcriptional profiling of mammaglobin resulted in the detection of 70% of tumors in a panel of 46 primary and metastatic breast cancers, the inclusion of three additional markers resulted in detection of all 46 specimens. Immunomagnetic epithelial cell enrichment of circulating tumor cells from the peripheral blood of patients with metastatic breast cancer, coupled with RT-PCR-based amplification of breast tumor-specific transcripts, resulted in the detection of anchorage-independent tumor cells in the majority of patients with breast cancer with known metastatic disease. CONCLUSION: Complementation of mammaglobin with three additional genes in RT-PCR increases the detection of breast cancers in tissue and circulating tumor cells.

Breast Neoplasms↗
PubMed2001

Immortalized bovine pancreatic duct cells become tumorigenic after transfection with mutant k-ras.

Mutation of the K-ras gene is thought to be an early and important event in pancreatic carcinogenesis. In order to study the role of this molecular alteration in the transition from the normal to the neoplastic pancreatic cell, bovine pancreatic duct cells were first immortalized by SV40 large T antigen (Ag) complementary (c)DNA transfection and then transfected with a mutated K-ras gene. As did primary duct cells, the immortalized duct cells (more than 100 passages) expressed cytokeratins, carbonic anhydrase type-II, cystic fibrosis transmembrane conductance regulator (CFTR), and multidrug resistance (mdr). They grew as a single layer after transplantation under plastic domes and formed three-dimensional structures resembling ducts when grown on Matrigel. Cell growth was stimulated by insulin, epidermal growth factor (EGF), transforming growth factor (TGF)-alpha, but cells did not respond to gastrin and CCK-8. They did not form colonies in soft agar nor did they form tumors in nude mice. Immortalized cells transfected with mutated K-ras acquired the ability to form tumors after orthotopic injection into the nude mouse pancreas. It is concluded that SV 40 immortalized bovine pancreatic

Animals↗
PubMed2001

Pyodera gangrenosum after aortic valve replacement.

A 68-year-old male patient developed pyoderma gangrenosum after elective aortic valve replacement. Treatment with steroids and clofazimine was initiated, which resulted in rapid cessation of the necrotic process. Due to thoracic instability, stabilization of the sternum was performed followed by surgical debridement and atraumatic wound closure. Postoperatively, immunosuppression with cyclosporine A was added; the patient recovered completely. Pyoderma gangrenosum is a potential life-threatening complication that must be considered in patients with severely impaired wound healing after cardiac operation.

Aged↗