Search PubMed⌕ Search

Biomedical subjects

T Schmidt

Publications and source records attributed to T Schmidt.

At least 145 records · Page 8Linked to original sources
PubMed1998

Isolation and characterization of the rat huntingtin promoter.

Huntington's disease (HD) is a neurodegenerative disorder caused by a (CAG)>37 repeat expansion in a novel gene of unknown function. Although the huntingtin gene is expressed in neuronal and non-neuronal tissues, the disease affects nerve cells of selected regional areas of the central nervous system. To gain insight into the regulation of the HD gene we analysed 1348 bp of the rat huntingtin promoter region. This region lacks a TATA and a CAAT box, is rich in GC content and has several consensus sequences for binding sites for SP1, PEA3, Sif and H2A. The stretch between nucleotides -56 and -206 relative to the first ATG is highly conserved between human and rodents and it harbours several potential binding sites for transcription factors. We analysed deletion mutants fused with the chloramphenicol acetyltransferase reporter gene in transfected, HD-expressing neuronal (NS20Y, NG108-15) and non-neuronal Chinese hamster ovary cell lines. Hence these cells should contain the required trans-acting factors necessary for HD gene expression. Partial deletion of the evolutionarily conserved part of the promoter significantly decreases the activity in both neuronal and non-neuronal cells, indicating that the core promoter activity is located between nucleotides -332 and -15. DNase I footprinting and electrophoretic mobility-shift assays were used to define the nucleotide positions and binding affinity of DNA-protein interactions.

Animals↗
PubMed1998

[A 44-year-old patient with cardial carcinoma and paraneoplastic orbital disease].

HISTORY AND CLINICAL FINDINGS: Bilateral orbital involvement with chemosis, protrusion and reduced vision developed in a 44-year-old man 12 weeks after carcinoma of the cardia with lymph node metastases and peritoneal carcinomatosis had been diagnosed and palliative chemotherapy with a cycle of leucovorin and 5-fluorouracil had been concluded. INVESTIGATIONS: Computed tomography excluded a retrobulbar metastasis. Thyroid hormone concentration was normal as was the thyroid autoantibody titre. There was also no evidence on sonography of endocrine orbital disease. These findings established the diagnosis of paraneoplastic orbital myositis. TREATMENT AND COURSE: The symptoms briefly regressed on initial treatment with systemically administered high doses of corticosteroids. Renewed marked eyeball protrusion with incipient visual loss was treated with conjunctival drainage and tarsorrhaphy, as well as radiotherapy to the retrobulbar space. This achieved significant improvement. Shortly thereafter the patients died of acute bleeding from the primary tumour. CONCLUSION: In patients with an underlying malignancy and symptoms of orbital myositis orbital involvement as part of a paraneoplastic syndrome should be diagnosed once other causes have been excluded.

Adenocarcinoma↗
PubMed1998

Evidence implicating Gfi-1 and Pim-1 in pre-T-cell differentiation steps associated with beta-selection.

After rearrangement of the T-cell receptor (TCR) beta-locus, early CD4(-)/CD8(-) double negative (DN) thymic T-cells undergo a process termed 'beta-selection' that allows the preferential expansion of cells with a functional TCR beta-chain. This process leads to the formation of a rapidly cycling subset of DN cells that subsequently develop into CD4(+)/CD8(+) double positive (DP) cells. Using transgenic mice that constitutively express the zinc finger protein Gfi-1 and the serine/threonine kinase Pim-1, we found that the levels of both proteins are important for the correct development of DP cells from DN precursors at the stage where 'beta-selection' occurs. Analysis of the CD25(+)/CD44(-,lo) DN subpopulation from these animals revealed that Gfi-1 inhibits and Pim-1 promotes the development of larger beta-selected cycling cells ('L subset') from smaller resting cells ('E subset') within this subpopulation. We conclude from our data that both proteins, Pim-1 and Gfi-1, participate in the regulation of beta-selection-associated pre-T-cell differentiation in opposite directions and that the ratio of both proteins is important for pre-T-cells to pass the 'E' to 'L' transition correctly during beta-selection.

Animals↗
PubMed1998

Enhanced B-1 cell development, but impaired IgG antibody responses in mice deficient in secreted IgM.

The role of endogenous natural IgM in promoting the adaptive Ab response was investigated in newly constructed mutant mice in which B cells do not secrete IgM but still express surface IgM and IgD and undergo class switching to express other Ig isotypes. While the mutant mice had relatively normal numbers of conventional B (B-2) cells in all tissues examined, unexpectedly, B-1 cells in the peritoneum and spleen were approximately threefold more abundant. The elevated levels of B-1 cells were already detectable at 4 wk of age and were stably maintained throughout life. The levels of serum IgG2a, IgG3, and IgA were also elevated in the mutant mice at an early age. IgG2a response to a T cell-independent Ag was augmented, whereas IgG Ab responses to suboptimal doses of a T cell-dependent Ag were impaired. The latter defect was associated with fewer splenic germinal centers, impaired Ab affinity maturation, and less Ag trapping on follicular dendritic cells. Together, these findings demonstrate a physiologic role of natural IgM in the feedback regulation of B-1 cell development, the regulation of IgG2a production, and the promotion of efficient B-2 cell Ab responses.

Animals↗
PubMed1998

[Lead poisoning caused by a Greek ceramic cup].

HISTORY AND ADMISSION FINDINGS: A 24-year-old woman, an administrative employee, was admitted with colicky abdominal pain and constipation, as well as breathing-related chest pain of recent onset with cough and sometimes blood-streaked sputum. She had previously been unsuccessfully treated for gastritis and adnexitis. On physical examination revealed diffuse, ill-defined abdominal pain on pressure and mild tachycardia, but was otherwise unremarkable. INVESTIGATIONS: Electrocardiogram, chest radiogram, lung scintigraphy, abdominal sonography, oesophago-gastro-duodenoscopy and gynaecological examination indicated nothing abnormal. Laboratory tests showed microcytic anemia, slight leucocytosis and anisocytosis, as well as polychromasia and basophilic stippling of erythrocytes. The 24-h urinary porphyrin concentration was elevated. DIAGNOSIS TREATMENT AND COURSE: Precise differentiation of porphyrins in urine, stool and erythrocytes by enzymatic measurement first raised the suspicion of lead poisoning. Whole-blood lead concentration was markedly raised to 600 micrograms/l (normal up to 90 micrograms/l) and 170 micrograms/dl in urine (normal up to 80 micrograms/dl). A ceramic cup from Greece was traced as the source of the lead, the patients having regularly for over 2 1/2 months drunk lemon instant-tea from it. She was treated with oral doses of DMPS (sodium salt of 2,3-dimercapto-1-propanesulphonic acid), 5-10 mg/kg 3x daily for 2 days, followed by 2.5 mg/kg 2 x daily, until lead concentrations in blood and urine had become normal, when all symptoms disappeared: detoxification was complete within 4 months. CONCLUSION: This case impressively illustrates how difficult it can be to diagnose lead poisoning and identify its source. Oral DMPS is a practicable and efficacious form of treatment.

Abdominal Pain↗
PubMed1998

Identification of redox-sensitive cysteines in GA-binding protein-alpha that regulate DNA binding and heterodimerization.

The transcription factor GA-binding protein (GABP) is composed of two subunits, GABPalpha and GABPbeta. The DNA-binding subunit, GABPalpha, is a member of the Ets family of transcription factors, characterized by the conserved Ets-domain that mediates DNA binding and associates with GABPbeta, which lacks a discernible DNA binding domain, through ankyrin repeats in the NH2 terminus of GABPbeta. We previously demonstrated that GABP is subject to redox regulation in vitro and in vivo through four COOH-terminal cysteines in GABPalpha. To determine the roles of individual cysteines in GABP redox regulation, we generated a series of serine substitution mutants by site-directed mutagenesis and identified three redox-sensitive cysteine residues in GABPalpha (Cys388, Cys401, and Cys421). Sulfhydryl modification of Cys388 and Cys401 inhibits DNA binding by GABPalpha, whereas, modification of Cys421 has no effect on GABPalpha DNA binding but inhibits dimerization with GABPbeta. The positions of Cys388 and Cys401 within the known Ets-domain structure suggest two very different mechanisms for redox regulation of DNA binding. Sulfhydryl modification of Cys388 could directly interfere with DNA binding or might alter the positioning of the DNA-binding helix 3. Modification of Cys401 may inhibit DNA binding through stabilization of an inhibitory helix similar to that described in the Ets-1 protein. Thus, GABP is regulated through at least two redox-sensitive activities, DNA binding and heterodimerization.

Alkylation↗
PubMed1998

A triple-crystal diffractometer for high-energy synchrotron radiation at the HASYLAB high-field wiggler beamline BW5.

The triple-crystal diffractometer installed at HASYLAB beamline BW5 with a high-field wiggler of critical energy 27 keV for DORIS III, operated at 4.5 GeV electron energy, is described. Samples can be mounted in large cryostats or furnaces normally used in neutron scattering experiments. The instrument has been successfully applied to measure structure factors S(Q) in liquids and amorphous materials, to collect full data sets of highly accurate structure factors for charge-density work, to measure the spin component of the ground-state magnetization in transition-metal and rare-earth compounds, to study the diffuse scattering from stacking faults and dislocation loops in Si single crystals, and for the investigation of various aspects of structural phase transitions: critical scattering in SrTiO3, oxygen order and stripe order in high-To materials. A crossed-beam technique allows for local studies of texture, internal strain and phase changes in the bulk of materials.

Journal Article↗
PubMed1998

Is Hylamer adequate for use in alloarthroplasties?

In the present study ultrahigh molecular weight polyethylene (UHMWPE) implants from different manufactures were evaluated by differential scanning calorimetry (DSC), infrared spectroscopy (IRS) and wide-angle X-ray scattering (WAXS). With DSC measurements the crystallinity of all evaluated implants ranged between 58.2% and 73.2%. The highest crystallinity was documented in Hylamer with 73.2%. These results were checked and confirmed by infrared spectroscopy. According to WAXS studies Hylamer had an orthorhomboid phase as well as a monocline phase. After remelting the orthorhomboid phase was no longer detectable. We do not recommend using UHMWPE implants which have been secondarily modified. The product Hylamer clearly demonstrates how the original crystal structure of UHMWPE can be altered. The described changes in Hylamer implants will probably lead to an increased failure rate.

Calorimetry, Differential Scanning↗
PubMed1998

[Consequences of the latest Euratom directive 96/29 ("basic standard") regarding radiotherapy].

AIM: The Council Directive 96/26 will be brought into force by the Member States of the EC until the year 2000. What practical consequences on both mounting and holding radiotherapeutical facilities should be considered? METHODS: Regarding the Council Directive, facts on workers' actual occupational exposure in medicine and representative calculations on structural shielding the consequences will be evaluated. RESULTS: Increasing both total number of occupationally exposed workers and number of Category A workers but also enforced structural shielding should be expected. Working in any protected area during pregnancy will be strictly prohibited now. CONCLUSIONS: With respect to the generally sufficient structural shielding no restrictions for existing radiotherapeutical facilities are to be expected. But it is emphasized to carry out further mountings on base of the latest Council Directive 96/26 Euratom.

Environmental Monitoring↗
PubMed1998

[Changes in crystallinity by sterilization and processing of ultrahigh molecular polyethylene used in endoprosthetics].

PURPOSE OF THE STUDY: We wanted to analyze crystallinity changes during sterilization in raw and in UHMWPE components for total joint arthroplasty manufactured. MATERIALS AND METHODS: To analyze the crystallinity DSC measurements and to determine the relative crystallinity infrared spectroscopy was performed. The DSC measurements were based on a comparison between the melting enthalpy of one known material to the unknown material. RESULTS: The raw manufactured non-sterilized sample showed a value for the DSC-measured crystallinity of 55.5%; the sample after gamma-sterilization without air was 56.0%, and with air 56.5%. The crystallinity after ethylene-oxide sterilization was 57.7% and after autoclavation 57.9%. The manufacturing time from the raw to the arthroplasty part showed some what different results. The average crystallinity of the samples differed between 55.4% and 61.6%. The best results were achieved in ETO-sterilized samples and one gamma-sterilized sample without air. The highest values were seen for the Hylamer. CONCLUSION: In summary, the best values for crystallinity were seen in both raw and completed arthroplasty products with ETO sterilization. For medical use cancerogenous factors must be excluded. Gamma-sterilization without air can be accepted as well. Increasing the crystallinity too much can lead to more wear debris.

Crystallization↗
PubMed1998

Direct observation of ligand colocalization on individual receptor molecules.

We have exploited the novel methodology of far-field fluorescence microscopy at the single molecule level to study colocalization of two different ligand molecules on an individual receptor. The use of dual-wavelength single molecule imaging allows discrimination between isolated and colocalized ligands with an accuracy of 40 nm. In the case of very close proximity of the two ligands, below 7 nm, single pair Forster energy-transfer was observed. The latter finding unequivocally demonstrates colocalization of two ligands on an individual receptor.

Binding Sites↗
PubMed1998

The genomic organization of non-LTR retrotransposons (LINEs) from three Beta species and five other angiosperms.

We have isolated and characterized conserved regions of the reverse transcriptase gene from non-LTR retrotransposons, also called long interspersed nuclear elements (LINEs), from Beta vulgaris, B. lomatogona and B. nana. The novel elements show strong homology to other non-LTR retrotransposons from plants, man and animals. LINEs are present in all species of the genus Beta tested, but there was variation in copy number. Analysis by Southern hybridization and fluorescent in situ hybridization revealed the clustered organization of these retroelements in beet species. PCR amplification using degenerate primers to conserved motifs of the predicted LINE protein sequence enabled the cloning of LINEs from both Monocotyledonae (Allium cepa, Oryza sativa and Secale cereale) and Dicotyledonae (Nicotiana tabacum and Antirrhinum majus) indicating that LINEs are a universal feature of plant genomes. A dendrogram of fifteen new and six previously isolated sequences showed the high level of sequence divergence while revealing families characteristic of some genera. The genomic organization of non-LTR retrotransposons was examined more detailed in A. majus and O. sativa.

Amino Acid Sequence↗
PubMed1998

The role of osmolality in the absorption of a nutrient solution.

BACKGROUND: Loss of water during enteral nutrition following massive intestinal resection may be severe. Low osmolality of oral rehydration solutions has recently been shown to mediate an increase in water absorption. AIM: To evaluate the effect of osmolality of a nutrient solution on the intraluminal duodenojejunal water flow, and the net absorption rates of total nitrogen and carbohydrate. METHODS: Eight healthy volunteers with a mean age of 27 (range 25-29) years participated in the study. Enteral nutrition (17% protein, 59% carbohydrate, 24% lipid plus 5 g/L PEG 4000) was infused (5 mL/min 2.64 kcal/min) into the descending duodenum either as a hypotonic (160 mOsmol/kg) or as an isotonic solution in a random order. Intestinal samples were aspirated 20 and 45 cm distally to the infusion point. RESULTS: Intraluminal water flow rates were significantly lower with the hypotonic solution than with the isotonic solution, both in the duodenum (4.9 +/- 0.3 vs. 6.7 +/- 0.5 mL/min; P < 0.02) and the upper jejunum (3.0 +/- 0.1 vs. 3.9 +/- 0.2 mL/min; P < 0.005). The net absorption rates of total nitrogen and carbohydrate were similar with both solutions. CONCLUSION: Low osmolality of a nutrient solution decreases intraluminal water flow rates in the upper intestine without affecting the absorption rates of total nitrogen and carbohydrate. Compared with an isotonic solution, the use of a hypotonic solution might lower the water loss in patients with extensive short bowel intestinal resection.

Adult↗
PubMed1998

Discrimination of irritable bowel syndrome by non-linear analysis of 24-h jejunal motility.

Conventional analysis of ambulatory longterm manometry of the small intestine has revealed abnormalities in patients with the irritable bowel syndrome (IBS). The aim was to use methods from non-linear dynamics, in particular the concepts of symbolic dynamics and entropy, in order to discriminate motility in IBS from healthy subjects. 24-h jejunal motility was recorded in 30 IBS patients and 30 healthy subjects. Computerized analysis of contraction amplitudes and intercontractile intervals was performed. Both time series were analysed by symbolic dynamics and entropy to quantify the degree of randomness inherent in the signal. During phase II IBS patients exhibited significantly increased entropies for the intercontractile intervals (IBS: 0.978 +/- 0.016, C: 0.965 +/- 0.020, P = 0.004) and for the contraction amplitudes (IBS: 0.978 +/- 0.008, C: 0.970 +/- 0.026, P = 0.05) compared with healthy subjects. In addition, a significantly increased mean contraction amplitude (mmHg) was found in patients (IBS: 25.2 +/- 4.8, C: 22.2 +/- 3.1, P = 0.003). Considering a combination of both parameters, a diagnostic accuracy of 82% was achieved. We conclude that phase II motility of the small intestine is more random in IBS than in health. Symbolic dynamics seems to be a promising new concept for the analysis of long-term gastrointestinal motility recordings.

Adult↗
PubMed1998

Role of Staphylococcus aureus surface-associated proteins in the attachment to cultured HaCaT keratinocytes in a new adhesion assay.

Colonization of human skin with Staphylococcus aureus is a common feature in a variety of dermatologic diseases. In order to reproducibly investigate the adherence of Staphylococcus aureus to human epidermal cells, an in vitro assay was established using the biotin/streptavidine labeling system and the HaCaT cell line. This assay was used to define the role of several Staphylococcus aureus surface proteins with regard to their function in the staphylococcal adhesion process. Our studies included the standard laboratory strain Newman as well as its genetically constructed mutants DU5873, DU5852, DU5854, and DU5886 generated by allele replacement or transposon mutagenesis, which are deficient in the elaboration of staphylococcal protein A (spa), clumping factor (clfA), coagulase (coa), and the fibronectin-binding proteins A and B (fnbA/B), respectively. In comparison with strain Newman all mutants showed remarkably reduced adherence to the HaCaT keratinocyte cell line in our assay, yielding only between 43% and 60% of the adherence capacity of strain Newman after 60 min. Bacterial adherence could be re-established by introducing the cloned wild-type genes for the surface proteins on shuttle plasmids into the chromosomally defective mutants, thus suggesting a pathogenetic role of these proteins in the attachment of Staphylococcus aureus to human keratinocytes. Bacterial adherence was additionally enhanced by alkaline pH-values that are characteristic for skin conditions with epidermal barrier dysfunction. The use of Staphylococcus aureus mutant strains, deficient in the elaboration of defined proteins, allows specific investigation of colonization and virulence factors of this dermatologic relevant microorganism.

Bacterial Adhesion↗
PubMed1998

Isolation of cDNA clones coding for IgE autoantigens with serum IgE from atopic dermatitis patients.

Recently we demonstrated that a high percentage of atopic dermatitis (AD) patients displayed specific immunoglobulin E reactivity to human proteins. Here we show that IgE autoreactivity is found predominantly in AD patients with severe skin manifestations and reveal the molecular nature of four IgE autoantigens. An expression cDNA library constructed from a human epithelial cell line (A 431) was screened with serum IgE from two AD patients. DNA sequence analysis of three IgE-reactive clones identified the alpha-chain of the nascent polypeptide-associated complex, cytokeratin type II, and the BCL7B oncogen as atopy-related IgE autoantigens (ara). The fourth cDNA coded for an IgE autoantigen containing a typical calcium binding motif that occurred in histogenetically different cells and tissues (keratinocytes, muscle, brain). Recombinant Escherichia coli-expressed IgE autoantigens bound IgE from AD but not from patients with other immunologically mediated disorders (graft vs. host disease, systemic lupus erythematosus) and elicited immediate type skin reactions in AD patients. In serum samples collected from an AD patient over a period of 5 years, IgE anti-ara NAC antibody levels peaked during disease exacerbation. Our finding that ara BCL7B was detected in serum bound to IgE antibodies suggests that intracellular IgE autoantigens can become released after tissue damage and may occur as IgE immune complexes. Via binding to antigen presenting cells as well as to effector cells, IgE autoantigen immune complexes may contribute to exacerbation and/or perpetuation of severe atopic diseases even in the absence of exogenous allergens.

Amino Acid Sequence↗
PubMed1998

Effects of amlodipine once or twice daily on circadian blood pressure profile, myocardial hypertrophy, and beta-adrenergic signaling in transgenic hypertensive TGR(mREN2)27 rats.

The effects of amlodipine on blood pressure profiles, cardiac hypertrophy, and beta-adrenergic signal transduction were studied in transgenic hypertensive TGR(mREN2)27 rats (TGRs), which are characterized by an inverse circadian blood pressure rhythm. Cardiovascular parameters were monitored by radiotelemetry; beta-adrenoceptor density and function were measured by radioligand binding and by determination of beta-adrenergic stimulation of adenylyl cyclase. Ventricular weight and the activity of cardiac sarcolemmal 5-nucleotidase were used as measures of hypertrophy. Acute i.p. injection of amlodipine (1, 3, 10 mg/kg body weight) either at 8:00 or at 20:00 h dose-dependently reduced blood pressure irrespective of the dosing time. For long-term treatment, TGRs were divided into three groups: untreated; amlodipine, once-daily, 5 mg/kg; and amlodipine, twice daily, 2.5 mg/kg. Both treatment schedules resulted in decreased 24 h means in systolic and diastolic blood pressure and a reduction in ventricular hypertrophy but had no effects on cardiac beta-adrenergic signaling. Once-daily dose of amlodipine at 8:00 h decreased blood pressure predominantly during the daily resting period of the rats, whereas twice-daily dosing induced a bimodal blood pressure pattern. However, even after 5 weeks of treatment, typical circadian profiles could not be observed with either treatment, indicating a short duration of action of amlodipine in rats. Thus it remains an open question whether pharmacologic normalization of the circadian blood pressure pattern in TGRs will more effectively reduce myocardial hypertrophy and restore beta-adrenergic signaling than a reduction in 24-h blood pressure per se.

Adenylyl Cyclases↗