Biomedical subjects
Publications and source records attributed to M Schmidt.
Worldwide the application for a drug registration follows three basic principles: the proof of quality, efficacy and safety. In the following the applicability of these three principles on extracts from roots of the medicinal plant Kava (Piper methysticum) will be examined in the light of the current discussion of possible hepatic side effects ratio.
The coexistence of dystopic kidney and abdominal aortic aneurysm or aortoiliac occlusive arterial disease is uncommon (0.12-0.15 %) and constitutes a technical challenge to vascular surgeons. Between 1997 and 1999 we performed 249 aortoiliac reconstructions and encountered four patients (1.6 %) with dystopic kidneys. The aortoiliac reconstructions were performed successfully in all patients while maintaining renal blood supply. Aortoiliac reconstructions in patients with horseshoe or pelvic kidney show similar results as regular reconstructions on the condition that optimal preoperative diagnosis and operative technique are used considering atypical renal vessels. Nevertheless, pelvic kidneys can lead to serious complications as we describe in this report. On the basis of our patients anatomy, embryology and surgical management of this entity.
PURPOSE: Presentation of a new protocol for simultaneous acquisition of both low and high resolution T 1 -weighted images of breast lesions for dynamic contrast-enhanced MR mammography. Demonstration of possible diagnostic improvement with representative measurements in patients with suspected breast cancer by adding morphologic parameters from high resolution sequences to the analysis of the signal-time curve. MATERIALS AND METHODS: Dynamic MR imaging was performed with a 1.5 T system (Magnetom SONATA, Siemens Medical Systems, Germany) and the manufacturer's double-breast coil. Coronal T 1 -weighted 3D FLASH sequences (spatial resolution 1.25 x 1.25 mm 2; slice thickness 1.7 mm) were acquired once before and five times after administration of contrast medium (Gd-DTPA, 0.15 mmol/kg) injection. In addition, a high resolution T 1 -weighted 3D-FLASH sequence (spatial resolution, 0.63 x 0.63 mm 2) was obtained before administration of contrast medium and after the third post-contrast low-resolution sequence. Except for the acquisition matrix, all imaging parameters were identical for both 3D pulse sequences. To assure comparison of the measured signal intensities for both T 1 -weighted sequences, calibrating phantom measurements were performed using a dilution series of Gd-DTPA. RESULTS: Phantom measurements demonstrated similar signal intensities and enhancement pattern for both sequences. A combined protocol consisting of both pulse sequences can be employed and does not interfere with the signal-time curve analysis. By measuring one high resolution sequence 3:18 minutes after administration of contrast medium, morphologic features can be evaluated without interference from barely enhancing surrounding tissue. The overall study time is not increased. The improved spatial resolution slightly increases the severity of motion artifacts. CONCLUSION: The new protocol is a clever way to improve the measurement of morphologic features without relevant loss of dynamic information. It is superior to converting the entire investigation to high resolution sequences and does not add any costs by not extending or duplicating the investigation. How much the new protocol can improve the specificity or sensitivity of MR-mammography is currently investigated on a larger patient group.
OBJECTIVE: We compared immunohistological examination of endometrium biopsy specimen with the results of the immunohistological examination of tumor specimen to analyse the valence of this preoperative examination according to the clinico-pathological findings and overall-survival. MATERIAL AND METHOD: Between 1985 and 1995 193 women were treated of an endometrial carcinoma at the University hospital Mainz. In this group we evaluated 41 patients with enough preoperative endometrial biopsy material for a retrospective immunohistochemical analysis and complete follow-up data. The materials from diagnostic curettage were stained and analysed for oestrogen and progesterone receptor status and for MiB-1. The results were statistically analysed using Logrank-test for overall survival. RESULTS: The mean follow-up time was 49 months. We found a significant correlation between staining results of oestrogen (p-value = 0.0005) and progesterone (p-value=0.0003) receptor status with overall survival as well as for MiB-1 (p-value=0.05). The correlation of staining results between biopsy specimen results and tumor material from hysterectomy was 84-85 %. CONCLUSION: These well known prognostic factors are measurable on biopsy specimen material in same quality and high valence as on hysterectomy material.
Potent and safe vaccinia virus vectors inducing cell-mediated immunity are needed for clinical use. Replicating vaccinia viruses generally induce strong cell-mediated immunity; however, they may have severe adverse effects. As a vector for clinical use, we assessed the defective vaccinia virus system, in which deletion of an essential gene blocks viral replication, resulting in an infectious virus that does not multiply in the host. The vaccinia virus Lister/Elstree strain, used during worldwide smallpox eradication, was chosen as the parental virus. The immunogenicity and safety of the defective vaccinia virus Lister were evaluated without and with the inserted human p53 gene as a model and compared to parallel constructs based on modified vaccinia virus Ankara (MVA), the present "gold standard" of recombinant vaccinia viruses in clinical development. The defective viruses induced an efficient Th1-type immune response. Antibody and cytotoxic-T-cell responses were comparable to those induced by MVA. Safety of the defective Lister constructs could be demonstrated in vitro in cell culture as well as in vivo in immunodeficient SCID mice. Similar to MVA, the defective viruses were tolerated at doses four orders of magnitude higher than those of the wild-type Lister strain. While current nonreplicating vectors are produced mainly in primary chicken cells, defective vaccinia virus is produced in a permanent safety-tested cell line. Vaccines based on this system have the additional advantage of enhanced product safety. Therefore, a vector system was made which promises to be a valuable tool not only for immunotherapy for diseases such as cancer, human immunodeficiency virus infection, or malaria but also as a basis for a safer smallpox vaccine.
Recombinant allergenic proteins have been produced in a variety of different expression systems. This review gives examples of and compares prokaryotic expression systems, such as Escherichia coli, and eukaryotic systems including the yeasts, Saccharomyces cerevisiae and Pichia pastoris, baculovirus-insect cell systems, mammalian cell systems and plant systems. Important factors to consider in choosing an expression system are discussed and examples of applications are given.
Glatiramer acetate (GA) interferes with antigen recognition and modulates cytokine secretion of T cells in an antigen-specific manner. Here we analysed the capacity of GA to modulate proliferative responses and cytokine secretion of peripheral blood mononuclear cells (PBMCs) in response to antigen-independent stimuli, i.e., phytohaemagglutinin (PHA) and staphylococcal enterotoxin B (SEB) stimulation in five healthy volunteers. A significant reduction of proliferative responses, as well as interferon-gamma (IFNalpha) and tumour necrosis factor-alpha (TNFalpha) secretion, was observed at concentrations of 200 microg/ml suggesting that GA may also exert immunomodulatory effects on mitogen- and superantigen-induced T-cell stimulation in vitro. However, since systemic GA concentrations of this magnitude are highly unlikely to occur in vivo the immunomodulatory effects observed here are not likely to contribute to the therapeutic mechanisms of action under physiological conditions.
The following article reviews nuclear medicine techniques which can be used for assessment of endocrine disorders of the hypothalamic-pituitary axis. For planar and SPECT imaging somatostatin-receptor- and dopamine-D2-receptor-scintigraphy are the most widely distributed techniques. These nuclear medicine techniques may be indicated in selected cases to answer differential diagnostic problems. They can be helpful to search for presence and localization of receptor positive tissue. Furthermore they can detect metastasis in the rare cases of a pituitary carcinoma. Scintigraphy with Gallium-67 is suitable for further diagnostic evaluation in suspected hypophysitis. Other SPECT radiopharmaca do not have relevant clinical significance. F-18-FDG as PET radiopharmacon is not ideal because obvious pituitary adenomas could not be visualized. Other PET radiopharmaca including C-11-methionine, C-11-tyrosine, F-18-fluoroethylspiperone, C-11-methylspiperone, and C-11-raclopride are available in specialized centers only. Overall indications for nuclear medicine in studies for the assessment of endocrine disorders of the hypothalamic-pituitary-axis are rare. Original studies often report only about a small number of patients. According to the authors' opinion the relevance of nuclear medicine in studies of clinically important endocrinologic fields, e.g. localization of small ACTH-producing pituitary adenomas, tumor localization in ectopic ACTH syndrome, localization of recurrent pituitary tissue, assessment of small incidentalomas, can not be definitely given yet.
BACKGROUND: An accurate, noninvasive technique for the diagnosis of coronary disease would be an important advance. We investigated the accuracy of coronary magnetic resonance angiography among patients with suspected coronary disease in a prospective, multicenter study. METHODS: Coronary magnetic resonance angiography was performed during free breathing in 109 patients before elective x-ray coronary angiography, and the results of the two diagnostic procedures were compared. RESULTS: A total of 636 of 759 proximal and middle segments of coronary arteries (84 percent) were interpretable on magnetic resonance angiography. In these segments, 78 (83 percent) of 94 clinically significant lesions (those with a > or = 50 percent reduction in diameter on x-ray angiography) were also detected by magnetic resonance angiography. Overall, coronary magnetic resonance angiography had an accuracy of 72 percent (95 percent confidence interval, 63 to 81 percent) in diagnosing coronary artery disease. The sensitivity, specificity, and accuracy for patients with disease of the left main coronary artery or three-vessel disease were 100 percent (95 percent confidence interval, 97 to 100 percent), 85 percent (95 percent confidence interval, 78 to 92 percent), and 87 percent (95 percent confidence interval, 81 to 93 percent), respectively. The negative predictive values for any coronary artery disease and for left main artery or three-vessel disease were 81 percent (95 percent confidence interval, 73 to 89 percent) and 100 percent (95 percent confidence interval, 97 to 100 percent), respectively. CONCLUSIONS: Among patients referred for their first x-ray coronary angiogram, three-dimensional coronary magnetic resonance angiography allows for the accurate detection of coronary artery disease of the proximal and middle segments. This noninvasive approach reliably identifies (or rules out) left main coronary artery or three-vessel disease.
A series of models for the active site (H-cluster) of the iron-only hydrogenase enzymes (Fe-only H2-ases) were prepared. Treatment of MeCN solutions of Fe2(SR)2(CO)6 with 2 equiv of Et4NCN gave [Fe2(SR)2(CN)2(CO)4](2-) compounds. IR spectra of the dicyanides feature four nu(CO) bands between 1965 and 1870 cm(-1) and two nu(CN) bands at 2077 and 2033 cm(-1). For alkyl derivatives, both diequatorial and axial-equatorial isomers were observed by NMR analysis. Also prepared were a series of dithiolate derivatives (Et4N)2[Fe2(SR)2(CN)2(CO)4], where (SR)2 = S(CH2)2S, S(CH2)3S. Reaction of Et4NCN with Fe2(S-t-Bu)2(CO)6 gave initially [Fe2(S-t-Bu)2(CN)2(CO)4](2-), which comproportionated to give [Fe2(S-t-Bu)2(CN)(CO)5](-). The mechanism of the CN(-)-for-CO substitution was probed as follows: (i) excess CN(-) with a 1:1 mixture of Fe2(SMe)2(CO)6 and Fe2(SC6H4Me)2(CO)6 gave no mixed thiolates, (ii) treatment of Fe2(S2C3H6)(CO)6 with Me3NO followed by Et4NCN gave (Et4N)[Fe2(S2C3H6)(CN)(CO)5], which is a well-behaved salt, (iii) treatment of Fe2(S2C3H6)(CO)6 with Et4NCN in the presence of excess PMe3 gave (Et4N)[Fe2(S2C3H6)(CN)(CO)4(PMe3)] much more rapidly than the reaction of PMe3 with (Et4N)[Fe2(S2C3H6)(CN)(CO)5], and (iv) a competition experiment showed that Et4NCN reacts with Fe2(S2C3H6)(CO)6 more rapidly than with (Et4N)[Fe2(S2C3H6)(CN)(CO)5]. Salts of [Fe2(SR)2(CN)2(CO)4](2-) (for (SR)2 = (SMe)2 and S2C2H4) and the monocyanides [Fe2(S2C3H6)(CN)(CO)5](-) and [Fe2(S-t-Bu)2(CN)(CO)5](-) were characterized crystallographically; in each case, the Fe-CO distances were approximately 10% shorter than the Fe-CN distances. The oxidation potentials for Fe2(S2C3H6)(CO)4L2 become milder for L = CO, followed by MeNC, PMe3, and CN(-); the range is approximately 1.3 V. In water,oxidation of [Fe2(S2C3H6)(CN)2(CO)4](2-) occurs irreversibly at -0.12 V (Ag/AgCl) and is coupled to a second oxidation.
The number of olfactory projection neurons (OPNs) in the brain of the juvenile and adult shore crab Carcinus maenas continues to increase during the life of the animal. In vivo labeling of adult crabs with the proliferation marker bromodeoxyuridine (BrdU) revealed a group of proliferating neuronal precursor cells in the lateral soma clusters (LCs) and in the soma clusters of the hemiellipsoid bodies (HBCs). The LCs contain the cell bodies of the olfactory projection neurons and the HBCs house the cell bodies to which the OPNs project. The aim of the present study was to examine whether the input from primary olfactory afferents has any influence on the rate of proliferation and survival of the neuronal precursors in the central olfactory pathways of C. maenas. Different sets of experiments involving BrdU injection and its immunocytochemical detection combined with unilateral amputation of the antennule that houses the olfactory organ were carried out. Our results show that the missing olfactory sensory input affects the rate of proliferation and the survival of postmitotic cells in the LC and in the HBC compared with control animals. The effect on the survival of postmitotic cells tested by BrdU injection followed by unilateral ablation is lateralized. Proliferation of neuronal precursor cells tested by the reversed experimental order was drastically impaired bilaterally. We conclude that the olfactory sensory input is necessary for a normal rate of proliferation of neuronal precursors and the survival of their progeny in the LC and in the HBC of C. maenas.
BACKGROUND: Epithelioid hemangioendotheliomas are rare vascular tumors, mostly originating from soft tissue, lungs or liver. CASE REPORT: A 58-year-old woman was admitted to hospital because of upper congestion, Horner's syndrome and segmental sensory disturbance. MRI of the spine showed a spinal mass, reaching from the seventh cervical vertebra to the fourth chest vertebra. Because of worsening of upper congestion and progressive neurological impairment, the patient had to be operated twice. Unfortunately a surgical excision of the infiltrating tumor in sano was not possible and the patient died 4 weeks after the second operation. Histologic examination revealed the diagnosis of infiltrating epithelioid hemangioendothelioma, originating from the first chest vertebra. CONCLUSION: Prognosis of epithelioid hemangioendothelioma is mainly determinated by its location. In advanced stages of disease or lack of surgical cure epithelioid hemangioendotheliomas may be fatal. Therefore epithelioid hemangioendotheliomas should be considered early in the differential diagnosis of patients with uncertain bone lesions.
A time-resolved Laue X-ray diffraction technique has been used to explore protein relaxation and ligand migration at room temperature following photolysis of a single crystal of carbon monoxymyoglobin. The CO ligand is photodissociated by a 7.5 ns laser pulse, and the subsequent structural changes are probed by 150 ps or 1 micros X-ray pulses at 14 laser/X-ray delay times, ranging from 1 ns to 1.9 ms. Very fast heme and protein relaxation involving the E and F helices is evident from the data at a 1 ns time delay. The photodissociated CO molecules are detected at two locations: at a distal pocket docking site and at the Xe 1 binding site in the proximal pocket. The population by CO of the primary, distal site peaks at a 1 ns time delay and decays to half the peak value in 70 ns. The secondary, proximal docking site reaches its highest occupancy of 20% at approximately 100 ns and has a half-life of approximately 10 micros. At approximately 100 ns, all CO molecules are accounted for within the protein: in one of these two docking sites or bound to the heme. Thereafter, the CO molecules migrate to the solvent from which they rebind to deoxymyoglobin in a bimolecular process with a second-order rate coefficient of 4.5 x 10(5) M(-1) s(-1). Our results also demonstrate that structural changes as small as 0.2 A and populations of CO docking sites of 10% can be detected by time-resolved X-ray diffraction.
In order to study ternary amphiphilic mixtures, we introduce a simplistic model of hard spheres corresponding to water and hard needles corresponding to oil and amphiphilic particles, where the hydrophilic head is modeled as a hard sphere and the hydrophobic tail as an infinitely thin needle attached radially to the sphere. For this system, we construct a geometry-based density functional and perform Monte Carlo computer simulations. The equation of state derived from the theory is found to be in remarkable agreement with our simulation results. We investigate the theoretical demixing phase diagram, and find that the predicted trends strongly support the amphiphilic character of the model.
The caloric curve for Na(139)(+) has been measured from 100 K up to the temperature where the clusters are boiling hot and spontaneously emit atoms. In this limit the clusters form an evaporative ensemble, the temperature and energy of which have been determined. As the caloric curve of an atomic gas with a finite number of atoms is known, one can construct the caloric curve for this finite system below and above the boiling point. A conjecture is made on how to link the evaporative ensemble temperature of the free cluster in vacuum to the boiling temperature of a finite system at a given pressure. This allows one to determine the enthalpy of vaporization at the phase transition of the finite system.
Stratum griseum superficiale (SGS) of the superior colliculus receives a dense cholinergic input from the parabigeminal nucleus. In this study, we examined in vitro the modulatory influence of acetylcholine (ACh) on the responses of SGS neurons that project to the visual thalamus in the rat. We used whole-cell patch-clamp recording to measure the responses of these projection neurons to electrical stimulation of their afferents in the stratum opticum (SO) before and during local pressure injections of ACh. These colliculothalamic projection neurons (CTNs) were identified during the in vitro experiments by prelabeling them from the thalamus with the retrograde axonal tracer wheat germ agglutinin-apo-HRP-gold. In a group of cells that included the prelabeled neurons, EPSCs evoked by SO stimulation were significantly reduced by the application of ACh, whereas IPSC amplitudes were significantly enhanced. Similar effects were observed when the nicotinic ACh receptor agonist lobeline was used. Application of the selective GABA(B) receptor antagonist 3-[[(3,4-dichlorophenyl)-methyl]amino]propyl](diethoxymethyl)phosphinic acid blocked ACh-induced reduction in the evoked response. In contrast, the ACh-induced reduction was insensitive to application of the GABA(A) receptor antagonist bicuculline. The ACh-induced reduction was also diminished by bath application of muscimol at the low concentrations that selectively activate GABA(C) receptors. Because GABA(C) receptors may be specifically expressed by GABAergic SGS interneurons (Schmidt et al., 2001), our results support the hypothesis that ACh reduces CTN activity by nicotinic receptor-mediated excitation of local GABAergic interneurons. These interneurons in turn use GABA(B) receptors to inhibit the CTNs.
Inactivation of the retinoblastoma (Rb) protein caused by gene mutation, association with oncoproteins from small DNA viruses, mutational inactivation of p16(Ink4a), or overexpression of cyclin D is a common feature of many human cancer cells and is causally associated with the aberrant proliferation control of cancer cells; whereas normal cells maintain an integrated cell cycle machinery and are subject to cell cycle checkpoint control by cyclin-dependent kinase (CDK) inhibitors (CKIs). To determine whether this difference can be translated into a therapeutic advantage to protect normal cells from adverse cytotoxicity caused by chemotherapy, we established cell model systems for ecdysone-inducible expression of p16(Ink4a), p21(Waf1), and p27(Kip1) in one CKI-responsive cell line (A431 human vulvar epidermoid carcinoma cells with functional Rb) and one CKI-unresponsive cell line (SiHa human cervical cancer cells with nonfunctional Rb). Expression of p16(Ink4a), p21(Waf1), or p27(Kip1) in both SiHa and A431 cells strongly inhibited CDK2 activity, indicating functional expression of the CDK inhibitors in both cell lines. However, only in A431 cells did expression of p16(Ink4a), p21(Waf1), or p27(Kip1) cause Rb dephosphorylation, arrest cell cycle traversal, and potently inhibit cell proliferation. Induction of p16(Ink4a), p21(Waf1), or p27(Kip1) in SiHa cells failed to cause Rb dephosphorylation or to arrest cell cycle traversal, and such induction only minimally inhibited cell proliferation. We then compared the chemosensitivity of clones derived from these two cell lines when the CKIs were and were not induced. Induction of p16(Ink4a), p21(Waf1), or p27(Kip1) conferred strong resistance to paclitaxel- or cisplatin-mediated cytotoxicity on the CKI-responsive A431 cells but not on the CKI-unresponsive SiHa cells. Our results support a novel chemotherapy strategy for treating patients with Rb pathway-impaired cancers by concurrent administration of chemotherapy with CKIs as chemoprotective agents for normal cells.
Deregulated expression of the proto-oncogene c-myb, which results from provirus integration, is thought to be responsible for transformation in a set of murine leukemia virus (MuLV)-induced myeloid leukemias (MML). We reported recently that this transcription factor promotes proliferation by directly transactivating c-myc and inhibits cell death through its up-regulation of Bcl-2 (Schmidt et al., 2000). To understand more about how these cells become transformed we looked at how they deal with cellular pathways inducing growth arrest. Specifically, we were interested in the expression of the tumor suppressor gene Cdkn2b (p15(INK4b)) in MML because this gene is expressed during myeloid differentiation and its inactivation by methylation has been shown to be important for the development of human acute myeloid leukemia. mRNA levels for p15(INK4b) and another INK4 gene p16(INK4a) were examined in monocytic Myb tumors and were compared with expression of the same genes in c-myc transformed monocytic tumors that do not express c-Myb. The Cdkn2a (p16(INK4a)) gene was generally not expressed in either tumor type, an observation explained by methylation or deletion in the promoter region. Although Cdkn2b (p15(INK4b)) mRNA was expressed in the Myc tumors, many transcripts were aberrant in size and contained only exon 1. Surprisingly, in the majority of the Myb tumors there was no p15(INK4b) transcription and neither deletion nor methylation could explain this result. Additional experiments demonstrated that, in the presence of constitutive c-Myb expression, the induction of p15(INK4b) mRNA that accompanies differentiation of M1 cells to monocytes does not occur. Therefore, the transcriptional regulator c-Myb appears to prevent activation of a growth arrest pathway that normally accompanies monocyte maturation.