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Biomedical subjects

K Maier

Publications and source records attributed to K Maier.

At least 19 recordsLinked to original sources
PubMed2001

Early functional apoptotic responses of thymocytes induced by Tri-n-butyltin.

BACKGROUND: Programmed cell death, also termed apoptosis, is the main focus of interest in a variety of scientific and clinical areas. For a better understanding of the mechanisms of apoptosis, from the onset of the cellular death program to the late stages of apoptosis or apoptotic necrosis, very early functional events have to be quantified because they might be involved in temporal and causal relationships between apoptosis-related key processes. METHODS: We have established a flow cytometric technique to quantify time-dependent signals simultaneously with high temporal resolution (Deltat = 1 s) in living cells. With this technique, the response of cells to apoptosis-stimulating agents can be analyzed over 15 min. For this purpose, a thermostatted sample tube holder for repeatable interruption-free injection of substances into the cell suspension was developed. Early detectable fluorescence and scatter parameters were related to intracellular free Ca2+ concentration, [Ca2+]i (Indo-1 fluorometry), membrane permeability (propidium iodide [PI] influx), and cell volume (forward scatter). RESULTS: A T-cell line (Jurkat) served as a model system. Apoptosis was induced by the biozid Tri-n-butyltin (TBT). Dependent on the TBT concentration (0.3-10 microM), the mean free [Ca2+]i increased by a factor of 1.2-6 during a short time interval of just 2 min. Especially after low TBT concentrations (< 0.5 microM), this [Ca2+]i increase was nearly transient during the observation time of 15 min. Higher TBT concentrations (0.5-10 microM), however, induced a transient increase of [Ca2+]i (Ca-TR) only in a fraction of the cells; in another subpopulation, a steady-state Ca2+ signal (Ca-SST) was observed. The analysis of the simultaneously registered PI signals of the Ca-SST cells showed a shift to increasing PI fluorescence (by a factor of about 4) with increasing Ca2+ concentrations. In Ca-TR cells, the PI fluorescence remained nearly unchanged. These apoptosis-related changes (increase in [Ca(2+)]i and membrane permeability) could be confirmed by the additional observation of a TBT concentration-dependent decrease in cell volume measured during the same early time period. CONCLUSIONS: The simultaneously analyzed parameters (i.e., [Ca2+]i, membrane permeability, and cell volume) suggested that, in our model system of Jurkat T-cells treated with TBT, an apoptotic cell fate was indicated very early (within 15 min) by the steady-state [Ca2+]i level.

Apoptosis↗
PubMed2001

Reversal of established delayed type hypersensitivity reactions following therapy with IL-4 or antigen-specific Th2 cells.

Delayed-type hypersensitivity reactions (DTHR) are mediated by IFN-gamma-producing CD4+ (Th1) or CD8+ T cells (Tc1) and can be prevented by steering T cells toward an IL-4-producing Th2 or Tc2 phenotype. It is currently accepted that T cells can be directed toward a Th2 or Tc2 phenotype only during the initiation of an immune response. Once established, the cytokine pattern of immune reactions is believed to be stable. Therefore, inhibition of DTHR by the induction of Th2/Tc2 responses, termed immune deviation, is considered only as a prevention but not as a therapy of harmful DTHR. Here we demonstrate that therapeutic immune deviation can reverse established contact hypersensitivity (CHS), a Th1/Tc1-mediated DTHR. One or two weeks after induction of CHS, mice received either a single cycle of IL-4 therapy or adoptive transfer of antigen-specific Th2 cells. This treatment generated a novel state of immunity that provided long-lasting protection against tissue destruction and neutrophil recruitment during subsequent antigen exposures. Therapeutic immune deviation of established CHS was dependent on CD4+ T cells and the induction of endogenous IL-4 synthesis. Thus, a population of immunoregulatory Th2 cells persists during advanced inflammatory responses that can be used for therapeutic deviation of established DTHR.

Adoptive Transfer↗
PubMed2001

Effect of caffeine on oxygen consumption and metabolic rate in very low birth weight infants with idiopathic apnea.

OBJECTIVE: Methylxanthines are among the most commonly prescribed drugs in neonatal intensive care. This study evaluates the effect of caffeine on oxygen consumption and metabolic rate in premature infants with idiopathic apnea. METHODS: Eighteen preterm infants at gestational ages from 28 to 33 weeks and birth weights of 890 to 1680 g were enrolled in the study. Nine preterm infants received caffeine therapy, and 9 served as a control group. Oxygen consumption and energy expenditure were examined before, during, and after caffeine treatment. RESULTS: Oxygen consumption increased significantly from 7.0 +/- 0.9 before caffeine to 8.8 +/- 0.7 mL/kg/min after 48 hours of caffeine therapy, and energy expenditure increased from 2.1 +/- 0.3 to 3.0 +/- 0.2 kcal/kg/hour. During the observation period of 4 weeks of caffeine treatment, oxygen consumption increased significantly in the caffeine group compared with the control patients. In the caffeine group, a lower environmental temperature was sufficient to maintain a normal body temperature. With similar caloric intake in both groups during the study period, daily weight gain in the control group was significantly higher (21 +/- 4 vs 42 +/- 2 g/d). None of the other parameters recorded changed during caffeine therapy. CONCLUSION: Long-term administration of caffeine in preterm infants is associated with an increase in oxygen consumption and with a reduction of weight gain. This may have implications for clinical practice as nutritional regimens need to be adjusted during this therapy.

Apnea↗
PubMed2000

Mast cells control neutrophil recruitment during T cell-mediated delayed-type hypersensitivity reactions through tumor necrosis factor and macrophage inflammatory protein 2.

Polymorphonuclear leukocytes (PMNs) characterize the pathology of T cell-mediated autoimmune diseases and delayed-type hypersensitivity reactions (DTHRs) in the skin, joints, and gut, but are absent in T cell-mediated autoimmune diseases of the brain or pancreas. All of these reactions are mediated by interferon gamma-producing type 1 T cells and produce a similar pattern of cytokines. Thus, the cells and mediators responsible for the PMN recruitment into skin, joints, or gut during DTHRs remain unknown. Analyzing hapten-induced DTHRs of the skin, we found that mast cells determine the T cell-dependent PMN recruitment through two mediators, tumor necrosis factor (TNF) and the CXC chemokine macrophage inflammatory protein 2 (MIP-2), the functional analogue of human interleukin 8. Extractable MIP-2 protein was abundant during DTHRs in and around mast cells of wild-type (WT) mice but absent in mast cell-deficient WBB6F(1)-Kit(W)/Kit(W-)(v) (Kit(W)/Kit(W)(-v)) mice. T cell-dependent PMN recruitment was reduced >60% by anti-MIP-2 antibodies and >80% in mast cell-deficient Kit(W)/Kit(W)(-v) mice. Mast cells from WT mice efficiently restored DTHRs and MIP-2-dependent PMN recruitment in Kit(W)/Kit(W)-(v) mice, whereas mast cells from TNF(-/)- mice did not. Thus, mast cell-derived TNF and MIP-2 ultimately determine the pattern of infiltrating cells during T cell-mediated DTHRs.

Animals↗
PubMed2000

Simultaneous recording of calcium transients and reactive oxygen intermediates of human polymorphonuclear granulocytes in response to formyl-Met-Leu-Phe and the environmental agent sulfite.

BACKGROUND: Human polymorphonuclear granulocytes (PMN) are an essential component in the immunological defense network against a variety of harmful pathogens. We have studied the effects of the airborne pollutant sulfite on the calcium metabolism and respiratory burst of these cells simultaneously. METHODS: A flow cytometric method was developed using the fluochromes Indo-1 and DHR-123. This method allowed us to investigate the real-time kinetics of intracellular free calcium and reactive oxygen intermediates in viable cells with a temporal resolution of 1 s over a time course of 17 min. An additional feature was the possibility to discriminate between reacting and nonreacting cells after treatment with defined stimuli, thus gaining additional insight into the behavior of cell subpopulations. RESULTS: We analyzed the effects of sulfite on PMN before and after stimulation with formyl-Met-Leu-Phe (FMLP). Treatment with sulfite alone (0.001-1 mM) caused a small, nontransient increase in intracellular calcium. Preincubation with sulfite reduced the maximal calcium response elicited by FMLP. A significant increase in steady-state calcium levels after stimulation with FMLP was observed after treatment with sulfite in concentrations of 10 and 100 mM. Regarding the respiratory burst, treatment with sulfite alone in concentrations of 0.001-1 mM induced a significant increase in DHR-123-derived fluorescence, whereas concentrations of 5 and 10 mM caused a significant depression of this fluorescence below baseline values. Sulfite caused a maximal twofold increase of DHR-123-derived fluorescence compared with the FMLP response. Similar results were obtained after preincubation with sulfite before treatment with FMLP, showing that the effect of sulfite on the respiratory burst was additive to the FMLP response. Regarding the fractions of responding cells, treatment with sulfite up to 1 mM induced a concentration-dependent increase of burst-reactive PMN, whereas preincubation before stimulation with FMLP showed no correlation between sulfite concentration and fraction of burst-reacting cells. CONCLUSIONS: By simultaneous registration of [Ca(2+)](i) and [H(2)O(2)](i) of PMN after treatment with FMLP and sulfite, the essential responses were already observed within a short time interval (15 min). Striking differences were found in the response of calcium as second messenger and respiratory burst in PMN treated with sulfite. Until a critical concentration (0. 5-1 mM), sulfite caused a concentration-dependent increase of [H(2)O(2)](i), in addition to the FMLP-induced response. The [Ca(2+)](i) changes induced by sulfite alone, however, were found to be small and showed no correlation with the respiratory burst response.

Air Pollutants↗
PubMed2000

Evidence for oxidative stress in bronchiolitis obliterans syndrome after lung and heart-lung transplantation. The Munich Lung Transplant Group.

Bronchiolitis obliterans syndrome (BOS) is the most serious long-term sequel of lung or heart-lung transplantation (H/LTX). Neutrophilia in the lower respiratory tract is a prominent feature of BOS. Because polymorphonuclear leukocytes (PMN) are capable of releasing large quantities of reactive oxygen species, we measured indicators of oxidative stress and glutathione levels representing antioxidant defense in H/LTX patients (HLTX, n=6; double-LTX, n=7; single-LTX, n=9). We analyzed 19 bronchoalveolar lavage (BAL) samples from 13 non-BOS patients (nine female, four male: age 39+/-4 years) and 17 BAL samples from nine BOS patients (five female, four male: age 33+/-2 years). PMN were the predominant BAL cell population in BOS (61.7+/-7.8% vs. 12.3+/-3.4%, P<0.001). Myeloperoxidase activity in the epithelial lining fluid and oxidized methionine residues in BAL-derived proteins were elevated in BOS (8.6+/-1.6 U/ml vs. 2.2+/-0.6 U/ml, P<0.01; and 12.6+/-1.1% vs. 7.7+/-0.8%, P<0.001, respectively). In addition, the concentration of reduced glutathione in epithelial lining fluid was decreased in BOS (162.6+/-20.1 microM vs. 345.8+/-57.1 microM, P<0.01), whereas the proportion of oxidized glutathione was increased (13.9+/-2.0O% vs. 6.7+/-1.2%, P<0.001). PMN, myeloperoxidase, and oxidized methionine residues were inversely correlated, whereas reduced glutathione was positively correlated with forced expiratory volume in 1 sec (P<0.05 to P<0.001). We conclude that excessive oxidative stress and a lack of glutathione are associated with BOS after H/LTX and may play relevant roles in the development of this disorder.

Adult↗
PubMed2000

Inhibition of glutamine synthetase in rabbit pneumococcal meningitis is associated with neuronal apoptosis in the dentate gyrus.

Apoptosis of dentate granular cells in the hippocampal formation during bacterial meningitis may be mediated by glutamate toxicity. For this reason, we studied the relationship between glutamine synthetase activity and regional neuronal apoptosis in rabbits with experimental pneumococcal meningitis. The duration of meningitis was 24 h, and the treatment was started 16 h after infection. Significant increases of glutamine synthetase protein concentration (P < 0.05) were found in the frontal cortex of rabbits with meningitis (n = 7) and rabbits with meningitis receiving ceftriaxone treatment (n = 12) as compared to the control animals (n = 14). No significant differences were seen in the hippocampal formation. The enzymatic activity of glutamine synthetase also was elevated in the frontal cortex (P < 0.05), but not in the hippocampal formation of rabbits with meningitis. After intravenous administration of L-methionine sulfoximine (specific inhibitor of glutamine synthetase) in rabbits with meningitis treated with ceftriaxone (n = 10), the concentration of neuron-specific enolase in CSF (P = 0.025) and the density of apoptotic neurons in the dentate gyrus quantified with the in-situ tailing reaction (P = 0.043) were higher than in meningitic animals receiving only ceftriaxone (n = 10). In conclusion, the inability of hippocampal glutamine synthetase to metabolize excess amounts of glutamate may contribute to neuronal apoptosis in the hippocampal formation during meningitis.

Animals↗
PubMed2000

Criteria for development of a database for safety evaluation of fragrance ingredients.

Over 2000 different ingredients are used in the manufacture of fragrances. The majority of these ingredients have been used for many decades. Despite this long history of use, all of these ingredients need continued monitoring to ensure that each ingredient meets acceptable safety standards. As with other large databases of existing chemicals, fulfilling this need requires an organized approach to identify the most important potential hazards. One such approach, specifically considering the dermal route of exposure as the most relevant one for fragrance ingredients, has been developed. This approach provides a rational selection of materials for review and gives guidance for determining the test data that would normally be considered necessary for the elevation of safety under intended conditions of use. As a first step, the process takes into account the following criteria: quantity of use, consumer exposure, and chemical structure. These are then used for the orderly selection of materials for review with higher quantity, higher exposure, and the presence of defined structural alerts all contributing to a higher priority for review. These structural alerts along with certain exposure and volume limits are then used to develop guidelines for determining the quality and quantity of data considered necessary to support an adequate safety evaluation of the chosen materials, taking into account existing data on the substance itself as well as on closely related analogs. This approach can be considered an alternative to testing; therefore, it is designed to be conservative but not so much so as to require excessive effort when not justified.

Administration, Cutaneous↗
PubMed2000

Construction and testing of a computer-based intraoral laser scanner for determining tooth positions.

An optical set-up for intraoral data acquisition based on the principle of laser triangulation was developed. The system consists of a pig-tailed laser with line generating optics, a stepping motor driven positioning stage, a commercial CCD (charge coupled device) camera system with frame grabber interface, a control personal computer and a mirror system compensating for the fact that there is no possibility of watching an object directly in the mouth under a certain angle except from a facial position during intraoral scanning. Due to the size of the prototype measurements were still restricted to plaster casts. In order to evaluate its accuracy, the measurements were compared with those taken with a commercial laser scanner and a coordinate measurement table. The accuracy of the prototype scanner was determined to be DeltaXYZ=0.04 mm using gauge blocks of given dimensions and proved to range between the commercial laser scanner and the coordinate measurement table (i.e., it was slightly better than that of the commercial scanner). Applications in orthodontics were demonstrated by scanning plaster casts and measuring distances on reconstructed surfaces. The measured distances showed a maximum deviation of about +/-0.2 mm compared with the data of the coordinate measurement table, which served as a reference. In addition, reconstruction of three-dimensional tooth movements was performed on the scan data. The translational and rotational parameters gained from the superimposition of scanned point clouds and describing tooth movement were also in good accordance with the reference. The achieved accuracy proved to be sufficient for further development which should include a reduction in size and the use of more precise device components.

Dental Occlusion↗
PubMed2000

Gemifloxacin is effective in experimental pneumococcal meningitis.

In a rabbit model of Streptococcus pneumoniae meningitis, 5 mg of gemifloxacin mesylate (SB-265805) per kg/h reduced the bacterial titers in cerebrospinal fluid (CSF) almost as rapidly as 10 mg of ceftriaxone per kg/h (Deltalog CFU/ml/h +/- standard deviation [SD], -0.25 +/- 0.09 versus -0.38 +/- 0.11; serum and CSF concentrations of gemifloxacin were 2.1 +/- 1.4 mg/liter and 0.59 +/- 0.38 mg/liter, respectively, at 24 h). Coadministration of 1 mg of dexamethasone per kg did not affect gemifloxacin serum and CSF levels (2.7 +/- 1.4 mg/liter and 0.75 +/- 0.34 mg/liter, respectively, at 24 h) or activity (Deltalog CFU/ml/h +/- SD, -0.26 +/- 0.11).

Animals↗
PubMed2000

Bacterial expression of G-protein-coupled receptors: prediction of expression levels from sequence.

Eleven G-protein-coupled receptors were expressed in Escherichia coli as fusion proteins with N-terminal glutathione-S-transferase and a C-terminal (His)6 tag. Expression levels varied between 0.1% and 10% of the total cellular protein. Low expression levels, as quantified by analytical nickel chelating chromatography, coincided with a toxic effect of protein expression. Multiple linear regression analysis was used to establish a correlation between the occurrence of positively charged amino acid residues in the loop regions and the expression level. Indeed, 44% of the variation in expression levels could be attributed to the positive charge content. Consequently, this sequence feature is the major determinant of expression level. Our results were supported by two mutations where positive charges were introduced into loop regions of two low-expressing receptors: As predicted, these mutations led to a considerably higher expression. A similar mutation of an olfactory receptor described previously increased expression approximately 100-fold and further supports our model. The data are discussed in the context of the "positive inside rule".

Amino Acid Sequence↗
PubMed1999

Maize glutathione-dependent formaldehyde dehydrogenase: protein sequence and catalytic properties.

Glutathione-dependent formaldehyde dehydrogenase (FDH; EC 1.2.1.1) has been purified 3900-fold from maize cell-suspension cultures to a specific activity of 4.68 mumol (mg protein)-1 min-1. The homogeneous enzyme consisted of two identical subunits with a molecular mass of 42 kDa, and an isoelectric point of 5.8. Eight tryptic peptides were sequenced and gave a perfect fit to the protein sequence derived from maize Fdh cDNA (J. Fliegmann and H. Sandermann, 1997, Plant Mol Biol 34: 843-854). There was 62% identity with the eucaryotic FDH consensus sequence. Michaelis constants of approx. 20 microns (formaldehyde), approx. 50 microns (glutathione) and approx. 31 microns (NAD+) were determined for the maize enzyme as well as for FDH partially purified from dog lung. Besides S-hydroxymethylglutathione, pentanol-1, octanol-1, and omega-hydroxy-fatty acids served as substrates for both FDH preparations. The unusual substrate specificity indicates that FDH may be involved in the detoxification of long-chain lipid peroxidation products.

Aldehyde Oxidoreductases↗
PubMed1999

Prevention of epidural fibrosis with ADCON-L in presence of a durotomy during lumbar disc surgery: experiences with a pre-clinical model.

A potential complication of lumbo-sacral surgery is the inadvertent tear of the dura mater, which sometimes eludes intra-operative detection. ADCON-L, a bioabsorbable gel used in lumbosacral laminectomies or laminotomies, is a physical barrier to post-operative epidural fibrosis. Three experimental lumbar laminectomy studies were designed to assess in vivo the effects of ADCON-L when applied in presence of dural punctures in a rat model. In the first study, the durotomy was repaired with fibrin sealant, in the second experiment the dural defect was microsurgically sutured, while in a third protocol the durotomy was left unrepaired. In each study, dural healing was assessed respectively at 4, 8, or 12 weeks post-operatively. Blinded anatomical dissection and histopathology were used to compare results between treatments (sham operated control vs. ADCON-L). In the fibrin sealant experiment, an additional treatment group (fibrin sealant used together with ADCON-L) was included. The results of these studies consistently demonstrate that ADCON-L is an effective anti-fibrotic agent, and does not interfere with the normal dural healing processes following a meningeal puncture. The application of the gel may therefore be safe in presence of dural incisions, even when they are not identified during surgery, as demonstrated in these in vivo studies.

Animals↗
PubMed1999

Health effects of sulfur-related environmental air pollution: the pulmonary surfactant system is not disturbed by exposure to acidic sulfate and neutral sulfite aerosols.

The goal of this study was to assess the impact of long-term exposure to environmental sulfur-related aerosols on the biochemical and biophysical properties of lung surfactant. Eight Beagle dogs were housed under clean air conditions for 450 days, followed by an exposure period of 400 days to 0.36 mg/m3 of sulfite (16.5 h/d) and to 5.66 mg/m3 of sulfate (6 h/d) equivalent to a pulmonary hydrogen burden of 15 mumol/m3. Other dogs kept in clean air for the whole study period were additional controls. Serial bronchoalveolar lavages (BALs) were analyzed for total phospholipid concentration, content and ratio of a surfactant-rich large aggregate (LA) fraction and a small aggregate (SA) fraction, in vitro surface area cycling of LAs into SAs as a measure of alveolar extracellular pulmonary surfactant aggregate metabolism, and surface activity of native and lipid-extracted LA. No significant changes over time and no differences between the clean air period and the exposure period were observed. Thus, long-term environmental exposure of dogs to the sulfur-related air pollution tested does not lead to alterations in the amount, extracellular metabolism, or surface-active properties of pulmonary surfactant.

Aerosols↗
PubMed1999

Determination of the centre of resistance in an upper human canine and idealized tooth model.

The purpose of this investigation was to analyse the influence of geometric and material parameters of a human canine on initial tooth mobility, and the stress and strain profiles in the periodontal ligament. While the material parameters of tooth and bony structures are known within an uncertain limit of approximately a factor of 10, values reported for the elasticity parameters of the periodontal ligament differ significantly. In the course of this study, bilinear behaviour was assumed for the mechanical property of the periodontium. The finite element model of an elliptical paraboloid was created as an approximation to the geometry of a human canine to reduce calculation time and to determine influences of the geometry on numerical results. The results were compared with those obtained for a realistic human canine model. The root length of both models was 19.5 mm. By calculating pure rotational and pure tipping movements, the centre of resistance (CR) was determined for both models. They were located on the long axis of the tooth approximately 7.2 mm below the alveolar crest for the idealized model and 8.2 mm for the canine model. Thus, the centre of resistance of a human canine seems to be located around two-fifths of the root length from the alveolar margin. Using these results, uncontrolled tipping (1 N of mesializing force and 5 Nmm of derotating momentum), as well as pure translation (additionally about 10 Nmm of uprighting momentum) were calculated. Comparing the idealized and the realistic models, the uncontrolled tipping was described by the parabolic-shaped model within an accuracy limit of 10 per cent as compared with the canine model, whereas the results for bodily movement differed significantly showing that it is very difficult to achieve a pure translation with the realistic canine model.

Computer Simulation↗
PubMed1997

Antioxidative and clinical effects of high-dose N-acetylcysteine in fibrosing alveolitis. Adjunctive therapy to maintenance immunosuppression.

In fibrosing alveolitis (FA), activated phagocytes cause excessive oxidative stress in the lower respiratory tract. Additionally, levels of glutathione, a major antioxidant of the human lung, are markedly reduced. Since N-acetylcysteine (NAC) is a known precursor for glutathione synthesis, we investigated the effect of NAC on redox balance and lung function in FA. Eighteen patients with an established diagnosis of FA were treated with 600 mg NAC three times daily for 12 wk in addition to their latest immunosuppressive therapy. Before and after NAC therapy, pulmonary function tests (PFTs) and bronchoalveolar lavage (BAL) were performed. BAL fluid was analyzed with regard to cell differential, glutathione status, and methionine sulfoxide content of BAL proteins (Met(O)), as an indicator of oxidative stress at the alveolar surface. There was an increase of total glutathione (GSHt = GSH +/- 2 x GSSG: 3.43 +/- 0.30 microM versus 4.20 +/- 0.66 microM, p < 0.05) and of reduced glutathione (GSH: 2.58 +/- 0.24 microM versus 3.42 +/- 0.54 microM, p < 0.005) in native BAL fluid and in the epithelial lining fluid (GSHt: 267.3 +/- 26.0 microM versus 367.1 +/- 36.0 microM, p < 0.005; GSH: 204.5 +/- 20.7 microM versus 302.9 +/- 32.2 microM, p < 0.005). The increase of GSH was accompanied by a decrease of Met(O) (6.83 +/- 0.71% versus 4.60 +/- 0.40%, p < 0.005). PFTs significantly improved during NAC treatment. We conclude that high-dose NAC significantly improved the antioxidant screen of the lungs by elevating GSH levels. Moreover, the decrease of Met(O) levels indicated an antioxidant effect at the alveolar surface. These biochemical changes were accompanied by an improvement of PFTs in patients under maintenance immunosuppression. NAC supplementation should, therefore, be considered as an adjunct therapy for FA.

Acetylcysteine↗