Biomedical subjects
Publications and source records attributed to E Meyer.
Sliding friction between the tip of a friction force microscope and NaCl(100) was studied to deduce the velocity dependence of friction forces on the atomic scale. A logarithmic dependence of the mean friction force is revealed at low velocities. The experimental data are interpreted in terms of a modified Tomlinson model which is based on reaction rate theory.
Activation-induced cell death (AICD) in T cells is mediated by CD95 ligand (CD95L)/receptor interaction, which has also been implicated in apoptosis induction by some anticancer agents. In this article we show that both anti-CD3-triggering (AICD) and doxorubicin treatment led to the production of a functionally active CD95L in the CD3+/T-cell receptor-positive (TCR+) T leukemia cell line H9. CD95L-expressing H9 cells killed CD95-sensitive J16 or CEM target cells, but not CD95-resistant CEM or J16 cells overexpressing dominant negative FADD (J16/FADD-DN). By immunoprecipitation, CD95L was physically bound to CD95, suggesting that AICD and doxorubicin-induced apoptosis involve CD95L-mediated CD95 aggregation, thereby triggering the CD95 death pathway. CD95 aggregation was associated with the recruitment of FADD and caspase-8 to the CD95 receptor to form the CD95 death-inducing signaling complex (DISC), resulting in caspase-8 activation and cleavage of the effector caspase-3 and PARP. Blocking of the CD95L/receptor interaction by antagonistic antibodies to CD95 or to CD95L also blocked AICD and inhibited the early phase of doxorubicin-induced apoptosis, though cell death induced by doxorubicin eventually proceeded in a CD95-independent manner. These findings may explain some conflicting data on the role of death receptor systems in drug-induced apoptosis. Thus, in cells with an inducible CD95 receptor/ligand system, drug-induced apoptosis may be mediated by CD95L-initiated DISC formation and activation of downstream effector programs similar to AICD in T cells. (Blood. 2000;95:301-308)
Six microsatellite - or short tandem repeat (STR) - systems with uniform repetitive sequences (HumTH01, HumCD4, HumFES/FPS, HumF13B, HumTPO, HumLPL) and three compound repeat systems (HumVWA, HumFIBRA, D21S11) were used, including data from the literature, to determine genetic distances among eight populations worldwide. The TH01- and VWA homologous loci in nonhuman primates (chimpanzees, gorillas, orangutans, rhesus monkeys, ring-tailed lemurs) were compared and found to be shorter than in humans. Microsatellites of lower complexity were most efficient for the separation of major ethnic groups. The loci of higher complexity showed a leveling of the diversity differences among populations, which could be attributed to higher mutation rates.
There are many causes of pericardial effusion and it is useful to classify them etiologically, since this disorder is the most common pathologic process involving the pericardium. This report details our experience with pericardioscopy and epicardial biopsy in 101 patients with pericardial effusions in whom pericardioscopy was performed. By means of clinical data and polymerase chain reaction we tried to elucidate the etiology of the pericardial effusion which were classified as follows: we found 41 effusions to be induced by primary malignant tumors or tumors metastatic to the pericardium. Specific diagnosis of viral and bacterial pericarditis was established in 17 patients by examination of the pericardial effusion with PCR, where we found 3 patients positive for adenovirus, 5 patients positive for cytomegalovirus, 2 patients positive for enterovirus-RNA and 5 patients positive for borrelia Burgdorferi-DNA. Additionally, idiopathic effusions (lymphocytic and autoreactive) were seen in 35 patients. In summary immunological and molecular biology investigations seem to provide an additional tool in the diagnostic of pericardial effusion with unknown etiology. If we focus on the ELISA results, there is some evidence, that the demonstration [table: see text] of activation markers and soluble mediators of inflammation such as Il-6, Il-8 and IFN-gamma in pericardial effusion and the simultaneously lack of these mediators in sera of the patients first may be helpful in the discrimination of autoreactive and lymphocytic effusion. Second, this cytokine pattern or distribution indicates a possible local inflammatory process, where these cytokines were all released from activated T lymphocytes present in lymphocytic effusion. In the future, this may have therapeutic implications.
BACKGROUND: Gas embolism is a potential hazard during laparoscopic procedures. The aim of this study was to evaluate the effects of nitrous oxide (N(2)O) inhalation in the case of gas embolism with carbon dioxide (CO(2)) and helium during pneumoperitoneum. METHODS: For this study, 20 anesthetized pigs were ventilated with N(2)O (67% inspired) in O(2) (n = 10) or with halothane (0.7-1.5 inspired) in O(2) (n = 10). In each group, CO(2) (n = 5) or helium (n = 5) pneumoperitoneum was established and gas embolism induced at different rates (CO(2) at 0.5, 1, or 2 ml/kg/min; helium at 0.025, 0. 05, or 0.1 ml/kg/min) through the left femoral vein a maximum of 10 min while all hemodynamic parameters were continuously monitored. RESULTS: In the CO(2) group without N(2)O, all the animals tolerated rates of 0.5 and 1 ml/kg/min over the 10 min, whereas only 3 of 4 animals in the CO(2) group with N(2)O tolerated a rate of 0.5 ml/kg/min, and 2 of 4 animals a rate of 1 ml/kg/min. In the helium group without N(2)O, all the animals tolerated gas embolism at all rates, whereas in the helium group with N(2)O, 4 of 5 animals needed to be resuscitated at a rate of 0.1 ml/kg/min and one death occurred. CONCLUSIONS: Inhalation of N(2)O worsens the negative cardiovascular effects of venous CO(2) or helium gas emboli and increases the risk of emboli-induced death when CO(2) or helium are used to establish pneumoperitoneum. The volume of venous venous helium gas emboli causing such effects is substantially smaller than that for venous CO(2) gas emboli.
Finite element analysis (FEA) is used to study the effect of geometric variations on the properties of rectangular cantilevers and U-shaped Joule-heated cantilevers. Simulations of locally thinned cantilevers as well as of cantilevers modified by the implementing of a hole or a side cut are compared with fabricated cantilevers, which are tuned by focused ion beam (FIB) milling. By locally thinning the cantilevers, the resonance frequency and the spring constant are reduced. For a hole, the internal stress is increased while for a side cut, the lateral spring constant is decreased. Good agreement between the measured and the simulated resonance frequencies is observed. Simulations of the current density and the temperature distributions attained during the passage of current through a doped silicon layer are performed to optimize the design of Joule-heated cantilevers (U-shaped) for thermal gravimetric applications. A very uniform temperature distribution over a region near the apex can be realized by slitting the U-shaped cantilever. In such a way, the heating power can be minimized by effecting only a small variation in the geometry of a U-shaped cantilever. A simple fabrication process for the fabrication of Joule-heated cantilevers is presented, which consists mainly of a uniform conductive p-doped layer.
We present quantitative and qualitative detection of analyte vapors using a microfabricated silicon cantilever array. To observe transduction of physical and chemical processes into nanomechanical motion of the cantilever, swelling of a polymer layer on the cantilever is monitored during exposure to the analyte. This motion is tracked by a beam-deflection technique using a time multiplexing scheme. The response pattern of eight cantilevers is analyzed via principal component analysis (PCA) and artificial neural network (ANN) techniques, which facilitates the application of the device as an artificial chemical nose. Analytes tested comprise chemical solvents, a homologous series of primary alcohols, and natural flavors. First differential measurements of surface stress change due to protein adsorption on a cantilever array are shown using a liquid cell.
Paramecium internal eliminated sequences (IESs) are short AT-rich DNA elements that are precisely eliminated from the germ line genome during development of the somatic macronucleus. They are flanked by one 5'-TA-3' dinucleotide on each side, a single copy of which remains at the donor site after excision. The timing of their excision was examined in synchronized conjugating cells by quantitative PCR. Significant amplification of the germ line genome was observed prior to IES excision, which starts 12 to 14 h after initiation of conjugation and extends over a 2- to 4-h period. Following excision, two IESs were shown to form extrachromosomal circles that can be readily detected on Southern blots of genomic DNA from cells undergoing macronuclear development. On these circular molecules, covalently joined IES ends are separated by one copy of the flanking 5'-TA-3' repeat. The similar structures of the junctions formed on the excised and donor molecules point to a central role for this dinucleotide in IES excision.
OBJECTIVE: This study considered the cost effectiveness of misoprostol prophylaxis for nonsteroidal anti-inflammatory drug (NSAID)-induced gastrointestinal damage, using data from the Misoprostol Ulcer Complications Outcomes Safety Assessment (MUCOSA) trial. The initial aim was to gain listing of misoprostol on the Australian National Formulary. DESIGN: The economic evaluation followed a 2-stage approach in considering the cost effectiveness of misoprostol, a 'within-trial' analysis followed by a simple modelled analysis which explored the implications of the trial results for life-years saved beyond the trial setting. The perspective of the evaluation is that of the healthcare system. SETTING: Three different populations were considered: the total trial population; patients with a history of peptic ulcer disease; and patients over 65 years of age. STUDY POPULATION: Patient data were taken from the MUCOSA trial, which involved 8843 patients receiving continuous NSAID therapy for the control of rheumatoid arthritis. INTERVENTIONS: Misoprostol plus any NSAID therapy was compared with placebo (no misoprostol) plus any NSAID therapy. MAIN OUTCOME MEASURES AND RESULTS: The study found the incremental cost per definite serious gastrointestinal complication avoided with misoprostol was 39,603 Australian dollars ($A) for the total trial population, $A5599 for patients with a history of peptic ulcer disease and $A35,405 for patients over 65 years of age. The incremental cost per life-year saved with misoprostol was $A41,866 for the whole group, $A6244 for patients with a history of peptic ulcer disease and $A40,322 for patients over 65 years of age. CONCLUSIONS: The study found misoprostol to be cost effective in this setting.
UNLABELLED: To increase the signal-to-noise ratio (S/N) of H2(15)O bolus PET activation images, we designed and tested a data acquisition protocol that alters the relative distribution of tracer in the uptake and washout phases of the input function. This protocol enhances the S/N gains obtained with conventional switched protocols by combining task switching and the use of a large bolus of blood free of tracer (cold bolus). The cold bolus is formed by sequestering blood in the lower limbs with a double cuff before tracer injection. METHODS: The effect of a combined cold-bolus, switched protocol on the signal from activation images was first simulated using a compartmental model of the uptake of H2(15)O into the brain. Then, the effectiveness of the protocol was investigated in 4 healthy volunteers performing a language task. Each volunteer underwent scanning 12 times: 3 activation/ baseline and 3 baseline/activation scans using the conventional switched protocol and 3 activation/baseline and 3 baseline/activation scans using the combined cold-bolus, switched protocol. The S/N changes introduced when using the cold bolus were analyzed by comparing, across protocols, the magnitude and statistical significance of the activation foci associated with the execution of the language task identified in the averaged subtracted images, and by comparing image noise levels. RESULTS: In the simulated datasets, the combined protocol yielded a substantial increase in the activation signals for scan durations greater than 60 s, in comparison with equivalent signals yielded by the switched protocol alone. In the PET experiments, activation foci obtained using the combined protocol had significantly higher t statistic values than did equivalent foci detected using the conventional switched protocol (mean improvement, 36%). Analysis of the S/N in the averaged subtracted images revealed that the improvements in statistical significance of the activation foci were caused by increases in the signal magnitudes and not by decreases in overall image noise. CONCLUSION: We designed a data acquisition protocol for H2(15)O bolus PET activation studies that combines the use of a tracer-free bolus with a switched protocol. Simulated and experimental data suggest that this combined protocol enhances the S/N gains obtained with a conventional switched protocol. Implementation of the combined protocol in H2(15)O bolus activation studies was easy.
A current hypothesis claims that an increase of blood flow is required for oxygen consumption to rise during neuronal excitation (activation). Chronic progressive external ophthalmoplegia is a mitochondrial disease associated with deletions of mtDNA or by point mutation of tRNA genes. We tested the hypothesis that the cerebral metabolic rate of oxygen (CMRO2) may not rise in this disorder if the accompanying cerebral blood flow increase is insufficient. Two patients with progressive external ophthalmoplegia were visually stimulated with a colored checkerboard pattern reversing as different frequencies. When stimulated, Patient 1 had a small increase of cerebral blood flow, while Patient 2 had no cerebral blood flow increase. In the visually active state, the patients had no significant change of CMRO2, while healthy subjects had a pronounced increase of CMRO2 in the pericalcarine visual cortex at 4 Hz and a further slight increase at 8 Hz during activation.
Cerebral blood flow (CBF) was measured with PET during rudimentary singing of a single pitch and vowel, contrasted to passive listening to complex tones. CBF increases in cortical areas related to motor control were seen in the supplementary motor area, anterior cingulate cortex, precentral gyri, anterior insula (and the adjacent inner face of the precentral operculum) and cerebellum, replicating most previously seen during speech. Increases in auditory cortex were seen within right Heschl's gyrus, and in the posterior superior temporal plane (and the immediately overlying parietal cortex). Since cortex near right Heschl's has been linked to complex pitch perception, its asymmetric activation here may be related to analyzing the fundamental frequency of one's own voice for feedback-guided modulation.
Cerebral blood flow (CBF) was measured with PET during rudimentary singing of a single pitch and vowel, contrasted to passive listening to complex tones. CBF increases in cortical areas related to motor control were seen in the supplementary motor area, anterior cingulate cortex, precentral gyri, anterior insula (and the adjacent inner face of the precentral operculum) and cerebellum, replicating most previously seen during speech. Increases in auditory cortex were seen within right Heschl's gyrus, and in the posterior superior temporal plane (and the immediately overlying parietal cortex). Since cortex near right Heschl's has been linked to complex pitch perception, its asymmetric activation here may be related to analyzing the fundamental frequency of one's own voice for feedback-guided modulation.
The matrix metalloproteinases are crucial in the physiological and pathological degradation of the mammalian extracellular matrix, including breast tumours, and osteoarthritic cartilage. These enzymes are classified according to their matrix substrate specificity. Collagenase-3 (MMP-13) is a member of this family and preferentially cleaves type II collagen, cartilage, fibronectin and aggrecan. Collagenase-3 is normally expressed in hypertrophic chondrocytes, periosteal cells, and osteoblasts during bone development. The structure of the catalytic domain of recombinant mouse collagenase-3, complexed to the hydroxamate inhibitor (RS-113456), is reported at 2.0 A resolution. Molecular replacement and weak phasing information from a single derivative determined the structure. Neither molecular replacement nor derivative methods had a sufficient radius of convergence to yield a refinable structure. The structure illuminates the atomic zinc ion interactions with functional groups in the active site, emphasizing zinc ligation and the very voluminous hydrophobic P1' group for the inhibitor potency. The structure provides insight into the specificity of this enzyme, facilitating design of specific inhibitors to target various diseases.
Aminoimidazole ribonucleotide (AIR) synthetase (PurM) catalyzes the conversion of formylglycinamide ribonucleotide (FGAM) and ATP to AIR, ADP, and P(i), the fifth step in de novo purine biosynthesis. The ATP binding domain of the E. coli enzyme has been investigated using the affinity label [(14)C]-p-fluorosulfonylbenzoyl adenosine (FSBA). This compound results in time-dependent inactivation of the enzyme which is accelerated by the presence of FGAM, and gives a K(i) = 25 microM and a k(inact) = 5.6 x 10(-)(2) min(-)(1). The inactivation is inhibited by ADP and is stoichiometric with respect to AIR synthetase. After trypsin digestion of the labeled enzyme, a single labeled peptide has been isolated, I-X-G-V-V-K, where X is Lys27 modified by FSBA. Site-directed mutants of AIR synthetase were prepared in which this Lys27 was replaced with a Gln, a Leu, and an Arg and the kinetic parameters of the mutant proteins were measured. All three mutants gave k(cat)s similar to the wild-type enzyme and K(m)s for ATP less than that determined for the wild-type enzyme. Efforts to inactivate the chicken liver trifunctional AIR synthetase with FSBA were unsuccessful, despite the presence of a Lys27 equivalent. The role of Lys27 in ATP binding appears to be associated with the methylene linker rather than its epsilon-amino group. The specific labeling of the active site by FSBA has helped to define the active site in the recently determined structure of AIR synthetase [Li, C., Kappock, T. J., Stubbe, J., Weaver, T. M., and Ealick, S. E. (1999) Structure (in press)], and suggests additional flexibility in the ATP binding region.
Suicide gene therapy systems such as the herpes simplex thymidine kinase/ganciclovir system (TK/GCV) may kill cancer cells by apoptosis through as yet undefined mechanisms. Here we show that TK/GCV treatment induces p53 accumulation and increases cell surface expression of CD95 and tumor necrosis factor receptor, which is likely to involve p53-mediated translocation of CD95 to the cell surface. TK/GCV-induced apoptosis involves CD95-L-independent CD95 aggregation leading to the formation of a Fas-associated death domain protein (FADD) and caspase-8-containing, death-inducing signaling complex. Dominant negative FADD, the caspase-8 inhibitor zIETD-fmk [Z-Ile-Glu(OMe)-Thr-Asp(OMe)-fluoromethylketone], and zVAD-fmk (Z-Val-Ala-Asp-fluoromethylketone) partially abrogate TK/GCV-induced apoptosis. In addition to apoptosis induction, TK/GCV treatment strongly sensitizes for CD95-L-, TNF-, and TNF-related, apoptosis-inducing, ligand (TRAIL)-induced cell death in constitutively resistant cells. These findings may be used to increase the efficacy of TK/GCV and other suicide gene therapy systems for the treatment of cancer.
In a multicentric retrospective clinical study with 16 pediatric centres we identified 103 cases of histologically confirmed early childhood cirrhosis (ECC) in Germany for the years 1984-1994. The most prominent diagnoses were congenital bile duct anomalies (47.5%), inborn metabolic disorders (17.5%) and unclear etiologies (17.5%). Chronic and excessive intake of copper might be discussed as an etiological factor in 8 other cases. 5 of these were proven to have coincided with very high hepatic copper contents and copper plumbing/acid well water. Their connection with copper exposure must be considered as probable, whereas 3 others were only suspected copper cases, mainly due to reliable exclusion of other etiologies. High corrosivity (base capacity) values and copper levels in the water for infants formula of 9-26.4 mg/L were determined in those probable cases for which exposure conditions could be exactly reproduced. Additional reports on copper associated ECC, either Indian Childhood Cirrhosis (ICC) from outside India or so-called Idiopathic Copper Toxicosis ( ICT ), originate from Austria, Australia, Germany, Ireland, USA.
Formation of 4-carboxy-5-aminoimidazole ribonucleotide (CAIR) in the purine pathway in most prokaryotes requires ATP, HCO3-, aminoimidazole ribonucleotide (AIR), and the gene products PurK and PurE. PurK catalyzes the conversion of AIR to N5-carboxyaminoimidazole ribonucleotide (N5-CAIR) in a reaction that requires both ATP and HCO3-. PurE catalyzes the unusual rearrangement of N5-CAIR to CAIR. To investigate the mechanism of this rearrangement, [4,7-13C]-N5-CAIR and [7-14C]-N5-CAIR were synthesized and separately incubated with PurE in the presence of ATP, aspartate, and 4-(N-succinocarboxamide)-5-aminoimidazole ribonucleotide (SAICAR) synthetase (PurC). The SAICAR produced was isolated and analyzed by NMR spectroscopy or scintillation counting, respectively. The PurC trapping of CAIR as SAICAR was required because of the reversibility of the PurE reaction. Results from both experiments reveal that the carboxylate group of the carbamate of N5-CAIR is transferred directly to generate CAIR without equilibration with CO2/HCO3- in solution. The mechanistic implications of these results relative to the PurE-only (CO2- and AIR-requiring) AIR carboxylases are discussed.