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Biomedical subjects

M Biedermann

Publications and source records attributed to M Biedermann.

At least 37 records · Page 2Linked to original sources
PubMed1992

On-line coupled liquid chromatography-gas chromatography (LC-GC) and LC-LC-GC for detecting irradiation of fat-containing foods.

On-line coupled liquid chromatography-gas chromatography-flame ionisation detection (LC-GC-FID) enables efficient and unambiguous determination of irradiation for some fat-containing foods (e.g. meat). Other products, however, contain interfering components or are contaminated, e.g., with mineral oil. Since more selective detection by mass spectrometry has limited success, the determination was improved by a more selective isolation of some key components among the fat degradation products, e.g. the dienes or trienes, by LC-LC-GC-FID. Applications are shown for soup mixes, some spices, fish, and shrimps.

Alkanes↗
PubMed1992

Chronic low frequency stimulation reduces myosin phosphorylation in rabbit fast twitch muscle.

The effect of 1-12 days of electrical stimulation (10 Hz) on the ability to phosphorylate the P-light chain of myosin was studied in rabbit tibialis anterior muscle. Myosin phosphorylation was induced by exposure of the stimulated muscle and that of the contralateral leg to a single conditioning stimulus train (5 Hz) for 25 s via the motor nerve. Isometric tension was measured as were the myosin light chain composition and the activities of the enzymes responsible for phosphorylation and dephosphorylation. A computer simulation of the potential effect of a stimulation-induced disruption of Ca2+ metabolism on phosphorylation was also performed. Chronic stimulation for as little as 1 day eliminated light chain phosphorylation and reduced the myosin light chain kinase activity by approximately 36%. Conversely, phosphatase activity and light chain composition were unaffected. The model demonstrated that a slight depression in the magnitude of the Ca2+ transient could potentially attenuate phosphorylation. The data suggest that phosphorylation of myosin is extremely sensitive to prolonged muscle activity. Furthermore, it appears more likely that this sensitivity is related to regulation of intracellular free Ca2+ than to the other elements of the calmodulin-dependent system for myosin phosphorylation examined.

Animals↗
PubMed1992

[Post-traumatic impingement syndrome caused by a displaced tuberculum majus fragment].

The posttraumatic impingement-syndrome caused by displacement and retraction of the entire great tuberosity with the bony insertions of the supraspinatus or infraspinatus muscle is often diagnosed with delay. Two types are distinguished: 1. The fracture of great tuberosity with proximal and dorsal dislocation of the fragment impairs motion by impinging under the acromion and against the posterior glenoid wall. 2. The multi-fragment bony fracture at the rotator cuff insertion, usually finish in rotator cuff deficiency. The analysis of the last 22 operated patients demonstrates the important preoperative complaints, commonly during a long time before reconstruction. The excellent postoperative results show the importance of the early and generous management of proximal humeral fractures.

Fractures, Open↗
PubMed1991

Food contamination by hydrocarbons from packaging materials determined by coupled LC-GC.

Paraffins from raw extracts of foods and packing materials were isolated by LC and directly transferred to GC, applying concurrent eluent evaporation and a loop-type interface. Paraffins from various packing materials have been characterized: sisal bags, cardboard boxes, plastic films, wax-coated paper and cardboard as well as paraffin coatings. Important food contamination was found for sisal bags, cardboard boxes, and wax-coated paper/cardboard. Contamination by paraffin coatings on cheese was surprisingly small.

Aluminum↗
PubMed1990

Auditory evoked responses in awake rabbits after exposure to high intensity noise impulses.

Impulse noise effects were tested in chronic experiments on 8 awake rabbits. Alterations of cochlear potentials and evoked responses from the inferior collinulus and the medial geniculate body were studied. The rabbits were subsequently exposed to 10 noise impulses of 144 dB SPL, then (after recovery) to 10 impulses of 153 and 164 dB SPL. After exposure the amplitudes of all potentials were reduced. Time of restitution depended on the intensity of the noise, the restitution failed after exposure to 164 dB SPL impulses. Time lapses of the amplitude-reduction and restitution process were comparable for both structures of the auditory pathway. The peak latencies were prolonged significantly in only two of the rabbits after this impulse intensity. Impulses of 164 dB SPL were followed by irreversible changes of all evoked responses.

Acoustic Stimulation↗
PubMed1989

[Testis endothesis surgery. Results of an ambulatory clinical evaluation study].

Under out-patient conditions 13 testicular endotheses of silicone rubber were implanted in local anaesthesia. The mean age of the 11 patients was 44.6 years and minimum follow-up was one year. In all but one case the clinical course was uneventful, in this patient the prosthesis was rejected after a secondary intervention. The follow-up examination did show in all cases clinical, ultrasonographical and cosmetical good results with the 14 g variant for the adult patient. This prosthesis is recommended the further use because of low operative risk, uneventful follow-up and improved body image.

Adolescent↗
PubMed1987

Input-output functions of cochlear microphonics in chronic experiments on awake rabbits.

Chronically implanted electrodes were used to record cochlear microphonics (CM) in awake rabbits. Test stimuli were sine waves of 1,250, 2,500, 5,000 and 10,000 Hz, with intensities increased from 40 to 100 dB SPL. By using this long-term method for registering the CM, we have found that the form of the input-output functions recorded is in agreement with that from acute experiments as described in the literature. Our method proved to be valid for recording CM with constant amplitudes over a period of 8-10 weeks. Our present results form a basis for further investigations concerning noise overload.

Animals↗
PubMed1987

Time lapse effects of impulse noise on cochlear microphonics in rabbits observed in chronic experiments.

Cochlear microphonics (CM) were recorded from awake rabbits with chronically implanted electrodes. Test frequencies used were 1,250, 2,500, 5,000 and 10,000 Hz, with intensities increased from 40 to 100 dB SPL. The rabbits were exposed to ten noise impulses of 144 dB SPL, which were then followed by impulse intensities of 153 and 164 dB SPL for the same animal. Input-output functions before and after each noise exposure were recorded, and recovery processes of the CM were tracked. After 144 dB SPL impulses, complete recovery of CM occurred; the effects of 153 dB SPL impulses varied from restitution up to complete CM loss. Impulses of 164 dB SPL caused an irreversible CM loss in all cases. Despite inter-individual differences, the threshold for irreversible CM loss in rabbits may occur between impulse noise intensities of 153 and 164 dB SPL.

Animals↗
PubMed1987

Quantitative evaluation of myocardial stress/rest 201TL SPECT: results of a ROI-based method in 108 patients with CHD.

ROI-based polar maps (33 ROIs) were employed to evaluate quantitatively stress/rest myocardial 201Tl SPECT in 108 patients with angiographically proven coronary heart disease (CHD) in comparison with 30 controls. Sensitivity in detecting a CHD with stenoses of greater than 50% of luminal diameter was determined versus normal regional values (+/- 2.5 SD) employing vitality (VI) and wash-out corrected redistribution (RD). The method was evaluated referring to the severity of the disease, to the number of ROIs displaying changes [(a) 1 ROI, (b) greater than 2 ROIs], to validity of VI, RD or a combination thereof, and for specificity. Wash-out values were found to depend on degree of stress individually achieved and thus were not used as a threshold criterion. Sensitivity in supply areas with old myocardial infarctions was 95% (a) and 86% (b), resp. With no infarction, it was 96% (a) and 79% (b), resp. VI in stenosis greater than 75% was more sensitive than RD. However, combined evaluation of VI and RD yielded sensitivities from 91-100% (a) and 77-94% (b), resp. for different main supply areas. In stenosis less than 50% with normal VI, RD was positive in 18-31%. Specificity turned out to be 91% (a) and 97% (b), resp. We conclude that the method presented is reliable to quantify numerically 201Tl kinetics in myocardial SPECT, aimed at detecting and describing CHD.

Adult↗
PubMed1985

[Early and late reaction of the guinea pig cochlea to impulse noise].

Guinea pigs (GP) were exposed to 10 impulses of 164 dB (SPL). Measuring of cochlear microphonics (CM) at frequencies between 0.5 and 10 kHz and morphological examination of the cochlea by the surface preparation technique followed 2 hours, 2 and 6 weeks after exposure to impulse noise. During the 2 hours following noise exposure the amplitudes of CM decreased in all tested frequencies, while recovery of CM never could be observed at this time. Subsequent morphological changes in the structure of the organ of Corti could be found. They varied considerably between the tested animals. 2 and 6 weeks after exposure to 10 impulses all GP had irreversible defects in the cochlea in an extent from an incomplete pattern of outer hair cells up to a total lack of areas of the organ of Corti. Only in GP with morphological damages in a small extent CM were recordable again. A good agreement of functional and morphological results was established. It can be concluded that exposure to few single impulses with peaks of sound pressure of sufficient intensity will produce irreversible morphological defects in the cochlea, resulting in marked functional injury, if the damaged area is large enough.

Animals↗
PubMed1979

Horseradish peroxidase as a label of injured cells.

The present study is concerned with artifacts likely to occur in a horseradish peroxidase exclusion test. Incubation of murine peritoneal macrophages and lymphocytes with the peroxidase showed a close relationship between the number of living cells and the percentage of cells excluding the tracer. The penetration of the cytoplasm by horseradish peroxidase is attributed to an increase in the permeability of the cell membrane during the incubation (ranging from 10 to 120 min). It was not increased by the presence of tracer throughout the incubation period. However, concomitant fixation of the cell in the presence of horseradish peroxidase caused an increase in the influx of the tracer. The horseradish peroxidase exclusing test applied to the guinea-pig organ of Corti has proved to be valid provided that: (a) mechanical lesions prior to the tracer incubation are avoided; (b) incubation is terminated by removal of the extracellular tracer; (c) fixation is carried out as soon as possible; (d) a low concentration of horseradish peroxidase is used; and (e) specimens are incubated in diaminobenzidine-H2O2 medium for the shortest possible period. Although fixation-induced cytoplasmic infiltration by horseradish peroxidase was not detected in cochlear specimens, the findings call attention to possible sources of error and define the level of significance of the test. Horseradish peroxidase does not appear to be a cytotoxic agent under the conditions used.

Animals↗
PubMed1978

Endolymphatic leakage in case of acute loss of cochlear microphonics.

Rapid loss of cochlear microphonics in guinea-pigs previously exposed to high-energy impulse noise was shown to be related to the breakdown of the endolymphatic boundary. The cochlear duct was rendered leaky by deterioration of the reticular membrane, and damage of sensory and supporting cells.

Animals↗
PubMed1978

[Peroxidase distribution pattern and cochlear microphonics in the impulse-noise exposed cochlea of the guinea pig (author's transl)].

Morphological findings evidenced the impulse noise trauma primarily a mechanical lesion of cells. The loss of mechanically damaged sensory cells results in the initial decline of cochlear microphonics. Due to mechanical lesions many sites of leakage in the wall of the cochlear duct give way to the diffusion of components of either lymph, which will produce a general functional disturbance associated with additional decline of microphonics. The functional restoration of the inner ear requires the previous repair of the endo/perilymphatic barrier.

Animals↗
PubMed1977

[Effect of single impulses on cochlear microphone potentials of the guinea-pig cochlea].

The influence of highly intensive single impulses on the cochlea of guinea pig was studied in an acute experiment. Very short impulses of less than or equal to 0.1 ms duration were produced by a sparknoise generator. The cochlear microphonics (CM) to a test stimulus (sinus tone, 3150 Hz) were recorded from the round window and measured prior to, during, and following impulse treatment. During the impulse treatment, the greatest amplitude reduction of CM occurred after the first impulse, while the further impulses caused a decreasing reduction. At first the number of impulses was varied: 1, 3, and 5 impulses were applied at intervals of 15 s each, at an impulse sound level of 164 dB sound pressure level re. 0.002 mubar (SPL). After these impulse treatments, in all cases a continual decrease of CM amplitudes up to a constant end value without recovery was found within a 2-hrs period of observation. The height of the end value depends on the number of impulses applied. Subsequently, at an exposure to 5 impluses the impulse sound level was stepwise reduced (164, 153, 144, 139 and 133 dB SPL). Again, a characteristic decrease of CM amplitudes was observed during the 2-hrs period of observation. The height of the end value is now dependent on the impluse sound level. Impulses of 164, 153 and 144 dB SPL cause a strong decrease of CM while the effect of impulses of 139 and 133 dB SPL is distinctly lower.

Acoustic Stimulation↗