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Biomedical subjects

H Stegmann

Publications and source records attributed to H Stegmann.

At least 19 recordsLinked to original sources
PubMed2006

First experimental test of a new monochromated and aberration-corrected 200 kV field-emission scanning transmission electron microscope.

The first 200 kV scanning transmission electron microscope (STEM) with an imaging energy filter, a monochromator and a corrector for the spherical aberration (Cs-corrector) of the illumination system has been built and tested. The STEM/TEM concept with Koehler illumination allows to switch easily between STEM mode for analytical and TEM mode for high-resolution or in situ studies. The Cs-corrector allows the use of large illumination angles for retaining a sufficiently high beam current despite the intensity loss in the monochromator. With the monochromator on and a 3 microm slit in the dispersion plane that gives 0.26 eV full-width at half-maximum (FWHM) energy resolution we have obtained so far an electron beam smaller than 0.20 nm in diameter (FWHM as measured by scanning the spot quickly over the CCD) which contains 7 pA current and, according to simulations, should be around 0.12 nm in true size. A high-angle annular dark field (ADF) image with isotropic resolution better than 0.28 nm has been recorded with the monochromator in the above configuration and the Cs-corrector on. The beam current is still somewhat low for electron energy-loss spectroscopy (EELS) but is expected to increase substantially by optimising the condenser set-up and using a somewhat larger condenser aperture.

Journal Article↗
PubMed2006

Life quality assessment among patients with atopic eczema.

BACKGROUND: Quantification of quality of life (QoL) related to disease severity is important in patients with atopic eczema (AE), because the assessment provides additional information to the traditional objective clinical scoring systems. OBJECTIVES: To measure health-related QoL (HRQoL) in patients with AE; to analyse discriminant, divergent and convergent validity by examining the association between various QoL methods; and to examine the association between disease severity assessed by an objective Severity Scoring of Atopic Dermatitis (SCORAD) and QoL. METHODS: HRQoL was assessed at two visits at a 6-monthly interval in 101 patients with AE and 30 controls with one dermatology-specific questionnaire [Dermatology Life Quality Index (DLQI) or Children's DLQI (CDLQI)], one generic instrument (SF-36) and three visual analogue scales (VASs) of severity and pruritus. Objective SCORAD was used to measure disease severity. RESULTS: Patients with AE had significantly lower QoL than healthy controls and the general population. DLQI /CDLQI, pruritus, and patient and investigator overall assessment of eczema severity were significantly (P < 0.0001) and positively correlated with SCORAD, while the generic questionnaire showed only poor correlation. A gender difference was found for the mental component score of SF-36 (P = 0.019). CONCLUSIONS: AE has an impact on HRQoL. Patients' mental health, social functioning and role emotional functioning seem to be more affected than physical functioning. A simple VAS score of patients' assessment of disease severity showed the highest and most significant correlations with most of the HRQoL methods used. There is evidence to support the ability of patients with AE to make an accurate determination of their disease severity and QoL.

Adolescent↗
PubMed1999

Presence of bleomycin-detectable free iron in the alveolar system of preterm infants.

Chronic lung disease (CLD) is a major cause of long term morbidity in preterm infants. Reactive oxygen species (ROS) play an important role in the pathogenesis of CLD. We show that a high percentage (63 to 83%) of the investigated bronchoalveolar secretions (BAS) of neonates contain bleomycin-detectable free iron concentrations (0. 04-0.124 nmol/micrograms SC, median range). Beside the presence of redox-active iron several iron-binding proteins like transferrin, ferritin and lactoferrin were determined in BAS. Comparison of protein distribution within the first three days of life showed slight differences between the group of preterm infants who developed CLD and the neonates who recovered from RDS. Because of the existence of free iron we suggest a higher risk of hydroxyl radical formation in the alveolar space. In an artificial system with addition of iron and hydrogen peroxide we were able to demonstrate OH-radical production in BAS by electron paramagnetic resonance (EPR). OH-radical formation by H2O2 and iron in buffer solution was slightly enhanced in the presence of BAS, indicating the absence of OH-radical-scavengers in BAS.

Albumins↗
PubMed1999

Quantification of total calcium in terminal cisternae of skinned muscle fibers by imaging electron energy-loss spectroscopy.

Skinned muscle fibers are ideal model preparations for the investigation of Ca2+ -regulatory mechanisms. Their internal ionic milieu can be easily controlled and distinct physiological states are well defined. We have measured the total Ca content in the terminal cisternae of such preparations using imaging electron energy-loss spectroscopy (Image-EELS) as a new approach for quantification of sub-cellular element distributions. Murine muscle fibers submitted to a standardized calcium-loading procedure were cryo-fixed with a combined solution exchanger/plunge freezing device. Energy-filtered image series were recorded from ultrathin freeze-dried cryosections of samples immobilized in either relaxed or caffeine-contracted state. From these image series, electron energy-loss spectra were extracted by digital image-processing and quantitatively processed by multiple-least-squares-fitting with reference spectra. The calculated fit coefficients were converted to Ca-concentrations by a calibration obtained from Ca-standards. Total Ca-contents in the terminal cisternae of skinned skeletal muscle fibers decreased upon caffeine-induced Ca-release from 123+/-159 (+/-11) to 73+/-102 (+/-8) mmol/kg d.w. (weighted mean +/- SD (+/-SEM)).

Animals↗
PubMed1999

A combined solution exchange/plunge-freezing device for skinned muscle fibers.

For many contractility studies, defined functional states of skinned muscle fiber preparations can be introduced by application of standardized perfusion protocols with large varieties of experimental solutions. Functionally important subcellular element distributions in the myoplasm and in the sarcoplasmic reticulum can be measured with high spatial resolution by electron microscopic microanalysis. Capturing these subcellular ion distributions requires their rapid immobilization by quick-freezing. We therefore combined a plunge-freezing device with a semiautomatic solution exchanger to reproducibly perfuse skinned muscle fiber bundles with multiple solutions. The isometric tension produced is simultaneously recorded as an indicator for the functional state. The samples can be quick-frozen at any chosen time of the tension transient. A cryoglueing technique finally delivers specimens suitable for cryoultramicrotomy.

Animals↗
PubMed1982

Comparison of prolonged exercise tests at the individual anaerobic threshold and the fixed anaerobic threshold of 4 mmol.l(-1) lactate.

Prolonged physical exercise tests (50 min) at the threshold of 4 mmol . l-1 lactate (ATc) and at the individual anaerobic threshold (IAT) were applied in 19 rowing athletes. In each of the rowers (n = 19) work loads corresponding to the IAT did not result in a gradual lactase accumulation or exhaustion within 50 min of exercise. Means of lactate concentration and heart rate at the end of exercise were 4.0 +/- 1.6 mmol . l-1 and 182 +/- 13.0 beats . min-1, respectively. In 15 of 19 rowers, the IAT corresponded to lower work loads than the ATc. In these cases, prolonged exercise tests at the ATc showed gradual increases in lactate concentrations to a mean of 9.6 +/- 1.2 mmol . l-1, associated with exhaustion at a mean working time of 14.4 +/- 6.3 min and a mean heart rate of 192 +/- 10.4 beats . min-1. In four rowers, the IAT was found at identical (n = 3) or higher (n = 1) work loads than the ATc. In these cases, after an initial increase no further rise in lactate concentrations in blood was observed, and exhaustion did not occur during the prolonged exercise tests. These findings support the conclusion derived from the lactate kinetics model that the IAT defines the work load at the maximal lactate steady state.

Adolescent↗
PubMed1982

Hormonal and metabolic consequences of prolonged running at the individual anaerobic threshold.

To examine the metabolic and hormonal responses to non-exhaustive steady-state exercise at the individual anaerobic threshold (IAT), 12 male physical education students performed treadmill exercise of 50 min duration. The treadmill speed equaled that at the IAT as assessed in a standardized progressive exercise test (75 +/- 2% of maximal oxygen uptake). Heart rate averaged 177.0 +/- 12.2 min-1 at 15 min and 184.5 +/- 11.5 min-1 at 50 min. After the initial adjustment, arterial lactate stabilized at individually different levels between 2.70 and 6.00 mmol/l without any substantial trend in the individual curves. Arterial glucose was unchanged throughout the test. Glycerol increased continuously to 157% above the preexercise value (P less than 0.001). The FFA blood level was not depressed but rather showed an increasing tendency between 25 and 50 min (P less than 0.05). Between 0 and 25 min, insulin decreased (P less than 0.01), growth hormone increased to 8 times its pre-exercise value (P less than 0.001), and cortisol did not show any significant changes. Between 25 and 50 min, no significant additional changes were detected for these hormones. At 15 min epinephrine and norepinephrine had increased 2.8- and 7-fold above the respective pre-exercise values (P less than 0.001); both catecholamines continued to increase until 50 min (P less than 0.001 and P less than 0.01). It is concluded that prolonged exercise at the IAT is associated with a steady-state condition in carbohydrate supply and turnover, as is suggested by the stable blood levels of glucose and lactate. The stably elevated blood level of lactate did not result in depression of the FFA blood level, suggesting unimpaired supply of FFA from extramuscular sources. Exercise at the IAT places a high load on aerobic metabolism without encountering progressive lactate accumulation and the associated metabolic effects.

Adult↗
PubMed1981

Lactate kinetics and individual anaerobic threshold.

Exercise with stepwise increasing work loads until exhaustion leads to a curvilinear increase of lactate in blood and typical lactate kinetics in the post-exercise period. Lactate kinetics in blood during exercise and recovery results from diffusion along gradients between muscle and blood and simultaneous elimination. Therefore, a general diffusion-elimination model is presented from which maximal rate of elimination (Em), individual anaerobic threshold (IAT), gradient between muscle and blood (deltaC-deltaCEm), muscle volume working above the IAT (Vm), individual membrane constant (Mc), quantity of lactate accounting for lactate gradient (Agrad), and whole body lactate (Anet) can be obtained. For demonstration purpose, this model was applied to a highly trained athlete. In this example, all constants and variables mentioned above as well as an equation reflecting individual lactate kinetics were calculated. Furthermore, the IAT was determined in 61 athletes participating in different events. In general, it can be demonstrated that with increasing aerobic capacity the lactate concentration at the IAT decreases. The lactate concentration at the IAT varies interindividually within broad limits, thus emphasizing the need for individual assessment.

Adolescent↗
PubMedDate not supplied

[Maintaining competence by physical activity and sports--circulatory physiologic and sports medicine prerequisites].

With increasing age, there is a change in the mitochondrial pattern of muscle tissue which leads to a loss of compliance of the arterial vessel wall and therefore to a slight change in contraction mode of the heart and also to a decrease of stroke and circulation volume. In the same way, lung function parameters such as vital capacity and forced ventilatory capacity are changes in the elderly. In addition to these, a higher incidence of general disease will change the organism, particularly heart circulation and the pulmonary system. In order to judge physical performance and sporting activity, certain physiological and pathophysiological features of aging have to be taken into consideration in the elderly. Avoiding any risks should be always above to intention of gaining a better physical condition, although this is desirable in principle.

Aged↗