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Biomedical subjects

K Maier

Publications and source records attributed to K Maier.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1997

Comparative loss of activity of recombinant secretory leukoprotease inhibitor and alpha 1-protease inhibitor caused by different forms of oxidative stress.

Secretory leukoprotease inhibitor (SLPI) and alpha 1-protease inhibitor (alpha 1-PI) are powerful antiproteases currently under investigation for their potential to protect the lung from neutrophil elastase (NE). The aim of this study was to determine whether the recombinant form of SLPI (rSLPI) and alpha 1-PI show different grades of loss of inhibitory activity when exposed to reactive oxygen metabolites. We incubated rSLPI and alpha 1-PI with N-chlorosuccinimide (NCS), chloramines, activated polymorphonuclear leucocytes (PMNs) and activated alveolar macrophages (AMs). Under all conditions evaluated, both antiproteases were partially inactivated. The resulting anti-NE activity of rSLPI was not significantly different from that of alpha 1-PI after exposure to NCS (p > 0.5), chloramines (p > 0.6), activated PMNs (p > 0.07) and activated AMs (p > 0.9). In conclusion, recombinant secretory leukoprotease inhibitor and alpha 1-protease inhibitor lose antineutrophil elastase activity to a similar extent when exposed to conditions that may be present in inflammatory lung disorders.

Animals↗
PubMed1996

alpha 2-Antiplasmin and plasminogen activator inhibitors in healing human skin wounds.

Mechanical injury of tissues is followed by the formation of a provisional fibrin matrix, which is later replaced by granulation tissue. The fibrinolytic proteinase, plasmin, is thought to contribute to the displacement of the primary matrix. Plasmin is generated from the ubiquitous proenzyme plasminogen by plasminogen activators. The system of plasminogen activation is controlled at several levels: plasminogen activator inhibitors (PAI-1 and PAI-2) counteract the activity of plasminogen activators and alpha 2-antiplasmin inhibits the activity of plasmin. In order to elucidate the mechanisms that regulate the plasminogen activator system in healing human skin wounds, we performed the immunohistological study reported here. The plasmin inhibitor alpha 2-antiplasmin and PAI-2 were found in the primary fibrin-rich matrix and in the granulation tissue. alpha 2-Antiplasmin was diffusely distributed in the tissue and its distribution correlated with the presence and localization of plasmin(ogen) except that, in contrast to plasmin(ogen), the alpha 2-antiplasmin was apparently not cell-associated. The stainings for PAI-2 increased with time and paralleled the development of the cellular infiltrate. PAI-2 was found in association with cells, which were identified by double immunofluorescence stainings as monocytes/macrophages and fibroblasts. In line with the immunohistological data, polymerase chain reaction after reverse transcription revealed mRNA for PAI-2 in healing human skin wounds. Taken together, our findings indicate that in healing human skin wounds, PAI-2 is the primary regulator of plasminogen activators, whereas alpha 2-antiplasmin may serve to control plasmin activity.

Base Sequence↗
PubMed1995

Increased oxidation of extracellular glutathione by bronchoalveolar inflammatory cells in diffuse fibrosing alveolitis.

An unbalanced oxidative stress is thought to be an important element in the pathogenesis of diffuse fibrosing alveolitis (DFA). The purpose of our study was to investigate the role of reactive oxygen metabolites (ROMs) released from cultured bronchoalveolar inflammatory cells (BA-cells) on glutathione oxidation. We studied bronchoalveolar lavage samples from 10 healthy controls and from 20 patients with diffuse fibrosing alveolitis (all were nonsmokers). BA-cells obtained by bronchoalveolar lavage (BAL) were incubated with 50 microM of reduced glutathione (GSH). Oxidation of GSH to glutathione disulphide (GSSG) by BA-cell derived oxidants was detected as a decline of GSH in the supernatants. Total glutathione (GSHtot = GSH + 2 GSSG) and GSSG in the epithelial lining fluid (ELF), and methionine sulphoxide (Met(O)) content of BAL proteins were determined. In diffuse fibrosing alveolitis the oxidative activity of BA-cells was enhanced, GSHtot and GSH were decreased, whereas the GSSG:GSH ratio was increased. The oxidative activity of BA-cells correlated positively with the GSSG:GSH ratio, but not with the methionine sulphoxide content. The methionine sulphoxide content was elevated in diffuse fibrosing alveolitis and inversely correlated with GSHtot. The methionine sulphoxide content also correlated positively with the percentage of BAL neutrophils. We conclude that BA-cell-derived reactive oxygen species are capable of oxidizing extracellular GSH in vitro. The positive correlation between the BA-cell oxidative activity in vitro and GSSG:GSH ratio in ELF suggests that a similar oxidative effect on extracellular GSH may also occur in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Use of dreams in therapy: a survey of clinicians in private practice.

A literature review indicated a dearth of research on how dreams are used in therapeutic settings so a questionnaire was sent to a random sample of 500 members of the Florida Psychological Association to assess (a) the extent of dream use in therapy, (b) theoretical approaches applied to dream interpretation, and (c) basis for experience and expertise in dream work. Of the 500 potential clinicians, 228 returned survey forms for a response rate of 46%. Analysis indicated that 83% of the respondents used dream material at least occasionally in their practice and that Freudian and Gestalt approaches were most often used in dream interpretation. Interestingly, most respondents gained their 'experience' in dream work through self-study and continuing education workshops and seminars.

Adult↗
PubMed1994

[The use of autologous keratinocytes in ear surgery].

To date autologous keratinocyte grafts have been used successfully to treat second- or third-degree burn wounds. This method allows a thin epithelialization of surfaces to take place but has been rarely used in otologic surgery until now. This technique has two possible indications in surgery of the external ear canal and the middle ear. We have currently used this method to cover a wound bed after resection of external ear canal stenosis and to treat large mastoid cavities with chronic secretion. Various aspects of the method as well as initial results of clinical use are shown.

Adult↗
PubMed1994

[Changes in selenium status, antioxidant enzyme activity and lipid peroxide level after drinking cures in Bad Hall health resort].

61 spa patients, predominantly with heart and vascular diseases, were divided into 2 therapeutic groups. In addition to the usual balneotherapeutic program, one group (J) received a course of "iodine brine concentrate" for drinking (2 x 100 ml, daily iodine uptake approximately 9 mg), and the control group (CI) received isotonic NaCl in the same way. The patients were mostly on a reduced-fat and -calorie diet. The following parameters were determined at the beginning and at the end of the 26-day treatment period: total cholesterol, HDL-cholesterol, triglycerides, lipoprotein (a) (in serum); selenium (Se), malondialdehyde (MDA), and activities of Se-dependent, Se-independent, and total glutathione peroxidase (GSH-PX) (in plasma). In the J group, a significant increase was found in Se-independent (+17%) and total GSH-PX (+5%) and a significant decrease in total cholesterol (-6.9%) and MDA (-13.2%). At the end of the cure, Se levels were higher in the J group than in the C1 group. The only significant change in the C1 group was a decrease in HDL-cholesterol. Positive correlations were found between selenium and Se-dependent GSH-PX (r = 0.253) and between total GSH-PX and Se-dependent GSH-PX (r = 0.665). A negative correlation was obtained between Se-dependent and Se-independent GSH-PX (r = -0.331). The results are discussed with regard to the importance of antioxidant defense mechanisms in several degenerative diseases (atherosclerosis, diabetes, cataract etc.), and also respecting interactions between iodine and selenium metabolism, as well as normalization effects conditioned by the balneotherapy itself.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗