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Biomedical subjects

H Seidel

Publications and source records attributed to H Seidel.

At least 73 records · Page 4Linked to original sources
PubMed1988

Blood-vessel wall arachidonate metabolism and its pharmacological modification in a new in vitro assay system.

Prostacyclin and thromboxane production was measured in human umbilical cord arteries bathed in clotting human blood and compared with arteries bathed in Krebs buffer or clotting blood without vessels. In comparison with the combined system, vessels in buffer generated only minute amounts of immunoreactive thromboxane B2 while blood alone generated only minute amounts of immunoreactive 6-oxo-PGF1 alpha. Incubation of vessels in blood was associated with an enhanced 6-oxo-PGF1 alpha formation at 1-2 h of incubation, demonstrating an active prostacyclin synthetase and a transfer of the platelet endoperoxide precursor to this enzyme. This new combined system was used to reevaluate the selectivity of cyclooxygenase inhibitors for vascular and platelet derived eicosanoid formation. With respect to 6-oxo-PGF1 alpha accumulation, the IC50 value [mumoles/l] for tiaprofenic acid (8.5 +/- 3.0) was significantly higher than that for diclofenac (0.14 +/- 0.03) (P less than 0.05) while acetylsalicylic acid (18.0 +/- 7.0) was less potent than diclofenac and indomethacin (2.4 +/- 1.0) (P less than 0.05). With respect to thromboxane B2 formation, the IC50 values for diclofenac (0.26 +/- 0.04), indomethacin (IC50 0.30 +/- 0.05) and tiaprofenic acid (IC50 0.71 +/- 0.08) were not significantly different from each other. Acetylsalicylic acid (7.7 +/- 1.8) was less potent than either of the other compounds (P less than 0.01). While these IC50 values might suggest different potencies for inhibition of vascular and platelet cyclooxygenases by tiaprofenic acid and, possibly, indomethacin, statistical analysis was not possible because of different slopes of the dose-response curves.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-Inflammatory Agents↗
PubMed1988

Isolated and combined effects of prolonged exposures to noise and whole-body vibration on hearing, vision and strain.

This study was carried out in order: (1) to examine the effects of isolated and combined prolonged exposures to noise and whole-body vibration on hearing, vision and subjectively experienced strain, and (2) to check the combined effects with repeated exposures. Six male subjects were exposed twice to noise (N) at 92 dBA, whole-body vibration (V) in the Z-axis at 4 Hz and 1.0 ms-2 rms, and noise and vibration (NV) for 90 min with each condition. Temporary threshold shifts of hearing (TTS) and their integrals (ITTS) were measured at 4, 6, 10, and 12 kHz. Visual acuity was examined by means of a very sensitive test. Cross-modality matching (CMM) of the handgrip force was used to judge the subjectively experienced strain. NV induced a clear tendency of higher TTS and ITTS than N, with several significant differences most pronounced at 10 kHz. With repeated exposures, the effect of NV decreased, while the reactions to N and V remained unchanged. The individual reactions to NV differed. The influence of the duration of exposures on vision depended on the condition; N caused time-dependent changes, whereas V did not. CMM-data increased with the duration of the exposure during V and NV. N was generally judged to be more straining than V; NV caused higher strain than V during the first 30 min of exposure only. Correlations between different effects suggest certain links between them. Additionally, less motivation--daily obtained by a questionnaire--often correlated with higher ITTS during N and NV. The results also illustrate the combined effects on the individual susceptibility, repetition of exposure, the kind of response, and, possibly, the actual psychic state.

Adolescent↗
PubMed1988

Myoelectric reactions to ultra-low frequency and low-frequency whole body vibration.

5 healthy males were exposed to vertical sinusoidal whole body vibration (WBV) at 5 frequencies (F1 = 0.315 Hz, F2 = 0.63 Hz, F3 = 1.25 Hz, F4 = 2.5 Hz, F5 = 5.0 Hz) and 2 intensities (I1 = 1.2 ms-2 rms, F1-F5; I2 = 2.0 ms-2 rms, F2-F5). Erector spinae EMGs were derived at the levels of the first thoracic (T1) and third lumbar (L3) spinous processes, rectified and synchronously averaged, as were the accelerations of the seat and the head. WBV induced vibration-synchronous EMG activity (T1 and L3) which exceeded the activity without WBV during enhanced gravitation and decreased during lowered gravitation from F1 to F3. At F4 and F5, these phase relations changed drastically, thus suggesting a different trigger mechanism. The extreme average EMG-amplitudes remained nearly constant at F1 to F3 and increased at higher frequencies. Maximum EMG activity was higher at I2 than at I1. WBV from F1 to F3 is supposed to cause tonic muscular activity triggered by the otoliths; at higher frequencies, stretch reflexes probably gain additional importance. The results hint at an increasing sensory conflict with decreasing frequency of WBV and are interpreted within the theoretical framework of different modes of motor control. Relations between transmissibility and muscle activity suggest the usefulness of including time-variant spring-characteristics into biomechanical models.

Adolescent↗
PubMed1988

Examination of spinal column vibrations: a non-invasive approach.

Accelerations of vertebrae during whole-body vibration (WBV) are used in occupational biomechanics for the prediction of internal stress. To avoid invasive techniques, a method for the calculation of bone accelerations was developed using measurements on the skin. The soft tissue between spinous processes L3 and T5 and miniature accelerometers stuck to the skin over them was modelled by a simple Kelvin element, whose parameters i.e. angular natural frequency omega n and critical damping zeta, describe an approximate transfer function between the bone (input) and the skin surface (output). The parameters were determined from free damped oscillations of the accelerometer-skin complex in the Z-axis, and depended significantly on the factors "subject" and "point of measurement". In one subject, the time courses of bone accelerations during sinusoidal WBV (4.5 and 8 Hz; 1.5 m.s-2 RMS) were calculated using separate transfer functions for each of 11 different spinal levels. Since the output signals on the skin were non-sinusoidal, the skin accelerations had to be treated with an inverse transfer function in the frequency domain. A comparison of accelerations measured on the skin and predicted for the bone mainly indicates that absolute peak values of bone accelerations are smaller and occur earlier. Both kinds of acceleration hint at differences in WBV-induced internal stress within the spine.

Bone and Bones↗
PubMed1988

Subjective evaluation of isolated and combined exposure to whole-body vibration and noise by means of cross-modality matching.

Cross-modality matching (CMM) were used for the evaluation of combined effects of sinusoidal whole-body vibration (WBV) in Z-axis with the frequencies 3-7 Hz, 1.5 ms-2, and two noise levels (L1 = 65 dBA; L2 = 85 dBA). CMM's were tested by means of three responses: handgrip force, length, estimation and brightness adjustment. The subjects were instructed to set different modalities to a value corresponding to their perception of vibration. The combination of WBV and L2 caused higher sensation responses than WBV and L1.

Analysis of Variance↗
PubMed1987

A Y/5 translocation in a 45,X male with cri du chat syndrome.

In a patient described as a 45,X male with cri du chat syndrome, combined cytogenetic and molecular methods revealed Y euchromatic material to be translocated onto the short arm of one chromosome 5, resulting in a chromosome der(5)(5qter----5p14::Yp11.31----Ypter). The translocated Y euchromatin comprised only the distal short arm including the pseudoautosomal region and the so-called deletion intervals 1 and 2. A review of 45,X males from the literature showed that; most of them carry a paternally transmitted Y/autosome translocations; resulting in various autosomal deletions. Depending on the segment concerned, the deletion led to congenital malformations.

Chromosome Banding↗
PubMed1987

Electromyographic evaluation of back muscle fatigue with repeated sustained contractions of different strengths.

The aim of the study was to obtain information on changes in surface electromyograms from the lumbar erector spinae muscles during fatiguing isometric contractions. Four male subjects held different target extension forces to fatique in a prone position under carefully controlled biomechanical conditions. Standard deviations of the distribution of EMG amplitudes (RMS values), autoregressive (AR) time series models of the 15th order and spectral densities were computed. At lower force levels, i.e., at about 50 to 100 Nm or 20-40% of estimated maximum voluntary contraction force (MVC), RMS values significantly decreased over time; at the highest level examined (on average 162 Nm), they increased. Over all force levels, the explained variances of AR models increased and mean power frequencies (MPF) decreased with increasing force. The first and second AR coefficients also exhibited significant changes, depending on both contraction time and strength. The AR time series structure of EMGs during short isometric test contractions at the lowest force level within 30 s after the failure point clearly indicated muscle fatigue and some differences remained in their dependence on the preceding force. The results suggest a concept of 'selective fatigue', and provide a basis for refined electromyographic evaluation of back muscle fatigue. Such an evaluation has to consider the force history preceding the failure point, or serious errors become unavoidable. The increase in RMS values does not constitute a criterion of back muscle fatigue at low force levels. AR time series models are recommended for the description of fatigue-induced electromyographic changes.

Adult↗
PubMed1987

An implant of a gonadotropin releasing hormone agonist (buserelin) which suppresses ovarian function in the macaque for 3-5 months.

Four adult female stumptailed macaque monkeys with regular menstrual cycles and one with irregular cycles and dysfunctional uterine bleeding were treated with a single implant containing 2.6 mg of the GnRH agonist buserelin in a matrix of polylactide/glycolide copolymer (75:25). The implant was used as a cylindrical rod of 0.8 X 0.12 cm and implanted sc in the abdominal wall. The insertion of the implant was followed by a modest rise in serum concentrations of LH and FSH lasting 3-4 days before falling to basal values. The release profile of buserelin from the implant was measured in urine by a radioimmunoassay detecting the intact molecule and its major metabolites. Immunoreactive buserelin in urine was high between days 1-3 after implant after which there was a rapid decline to form a plateau between days 15-70 followed by a further gradual decline. This prolonged release of buserelin suppressed ovulation for a mean of 148 days (range 105-182 days) as indicated by absence of serum progesterone rises. Serum FSH concentrations were low for at least 75 days and during this time serum oestradiol concentrations were uniformly suppressed in all monkeys. Once the buserelin release from the implant declined serum FSH concentrations began to rise. There was a variable delay of 7-60 days before this rise in FSH was associated with stimulation of ovarian oestradiol secretion followed by rises in serum progesterone concentrations indicative of ovulation. Apart from the first menses after insertion of implant, 4 of the monkeys became amenorrhoeic for the period of anovulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Interaction of procion red HE-3B and other reactive dyes with alkaline phosphatase: a study by means of kinetic, difference spectroscopic and chromatographic methods.

The interaction of alkaline phosphatase (EC 3.1.3.1) from calf intestine with different dyes, especially with Procion Red HE-3B was studied by several methods. From the kinetic analysis a nonlinear noncompetitive type of inhibition with an inhibition constant Ki = 0.03 mM for Procion Red HE-3B and Cibacron Blue F3G-A was estimated. The extent of inhibition of the two dyes at constant substrate and inhibitor concentration is 10 to 20 times higher than that of natural inhibitors like L-phenylalanine and NADH. Difference spectroscopic measurements with Procion Red HE-3B showed that the enzyme dimer possesses two binding sites for the dye. The dissociation constant of the dye-enzyme complex was estimated to be Kd = 0.01 mM. The binding of Procion Red HE-3B to the enzyme is mainly stabilized by electrostatic interactions. Large aromatic parts of a dye molecule like a combination of two naphthol ring systems or an anthraquinone ring flanked by spatially arranged charged substituents are important for the extent of specificity. The elution of the enzyme from the immobilized dye and the quenching of the dye-protein difference spectral signal by the competitive inhibitor phosphate and by substrates suggest the involvement of the active center of the enzyme in the dye binding region.

Alkaline Phosphatase↗
PubMed1986

Long-term effects of whole-body vibration: a critical survey of the literature.

The relevant literature on the long-term effects of whole-body vibration (wbv) was analyzed in order to obtain condensed information concerning a possibly higher health risk due to long-term exposure, the relationships between the quality of exposure (intensity, duration, frequency) and pathological effects, the significance of individual factors, conclusions for standard setting, and medical health care of workers exposed to wbv. Vibration exposure was characterized by measured values in one third of papers, whereas more than 30% of the publications selected did not contain any exposure data. Health data of about 43 000 workers exposed to wbv and 24 000 persons in control groups were reported. The results indicate an increased health risk of the spine and of the peripheral nervous system after intense long-term wbv. With a lower probability, the digestive system, the peripheral veins, the female reproductive organs, and the vestibular system were also affected. Long-term effects on other organs cannot be precluded. Wbv can worsen certain endogenous conditions. Specific diagnostic features of pathological changes induced by wbv with frequencies below 20 Hz do not exist. On average, the health risk increases with higher intensity or duration of exposure, however, quantitative exposure-effect relationships cannot be derived at present. Since wbv near the Exposure Limit of the International Standard IS 2631 is not completely safe, this survey provides arguments in favour of a lower limit. Contra-indications for professional exposure to wbv and further research needs are discussed.

Age Factors↗
PubMed1986

Effects of sinusoidal whole-body vibration on the lumbar spine: the stress-strain relationship.

The aim of this experimental study was to estimate the strain in the lumbar spine due to whole-body vibration (WBV). Four male subjects were exposed to vertical sinusoidal WBV with frequencies ranging from 1 to 15 Hz at two intensities (I1 = 1.5 ms-2 rms; I2 = 3.0 ms-2 rms). The compressive forces acting on the disc L3-4 during the extreme values of acceleration were predicted on the basis of anthropometric data, EMG of back muscles and the acceleration of the upper trunk, using a simple biomechanical model. The estimated mechanical activity of back muscles was not able to protect the spine under many exposure conditions. The highest compressive forces were predicted for WBV with 7.5, 8 and 4.5 Hz. The results suggest the possibility of fatigue failures at the endplates of lumbar vertebrae after intense long-term exposure to WBV.

Adaptation, Physiological↗
PubMed1986

Effect of whole-body vibration with different frequencies and intensities on auditory evoked potentials and heart rate in man.

Auditory evoked brain potentials (AEP) and electrocardiogram (ECG) were recorded from 9 healthy male subjects during sinusoidal whole-body vibration exposure (WBV) in the longitudinal (+/- az) direction with four frequencies (1 Hz, 2 Hz, 4 Hz, and 8 Hz) and two intensities as well as under non-WBV conditions. The sequences of the different experimental conditions were arranged according to a 9 X 9 Latin Square design. The sound of the electrohydraulic vibrator was masked by a constant noise level. A subtraction technique was used to eliminate vibration-synchronous activity contaminating the electroencephalogram. The AEP amplitude N1-P2 revealed systematic effects of different WBV frequencies and intensities. The amplitude decreased along with an increase in intensity (16 dB) by about 10 per cent. It diminished increasingly with a monotonic trend in the order non-WBV, WBV 8 Hz, WBV 4 Hz, WBV 2 Hz, and WBV 1 Hz. The interbeat-interval histograms computed from the ECG exhibited the highest mean values at MBV of 1 Hz, high intensity, and the lowest ones at WBV of 4 Hz, high intensity. The AEPs are reaffirmed as an informative measure for studying the WBV effect on central nervous information processing, although the modes of action are not yet fully known. Efferent influences on the acoustic input, cross-modality interaction, sensory mismatch, and changes of central nervous activation level are discussed as potential mechanisms.

Adolescent↗
PubMed1986

[Pathogenesis and therapy of rheumatoid inflammation].

By initial 3H-thymidine labelling an enhanced monocyte proliferation in the bone marrow of patients with rheumatoid arthritis is demonstrated. The significant monocyte proliferation correlates positively with the erythrocyte sedimentation rate but shows a negative correlation with age. The high significance of the mononuclear phagocyte (MNP) system in the pathogenesis of rheumatoid arthritis is seriously underlined by the experimental findings in our allergic arthritis model. Benoxaprofen as an inhibitor of the lipoxygenase pathway and of the inflammatory monocyte influx significantly suppresses the experimental allergic synovitis. These findings stress upon the important role of the MNP-system in the pathogenesis of rheumatoid arthritis and demonstrate the significance of the monocytes/macrophages as an important target-cell system for antirheumatic drugs.

Adolescent↗