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Biomedical subjects

G Menzel

Publications and source records attributed to G Menzel.

At least 19 recordsLinked to original sources
PubMed2002

Expression of bacterial poly(3-hydroxybutyrate) synthesis genes in hairy roots of sugar beet (Beta vulgaris L.).

Three genes from Ralstonia eutropha necessary for poly(3-hydroxybutyrate) (PHB) synthesis were introduced into the hairy roots of sugar beet. Transformation of a vector construct harbouring the PHB genes, each fused to the coding region of the pea ribulose-bisphosphate carboxylase plastid targeting sequence, resulted in 20 transgenic hairy-root clones, producing up to 55 mg high molecular PHB/g dry weight, as identified by gas chromatography, gel permeation chromatography and HPLC. Accumulation of PHB polymer in sugar beet root leucoplasts was confirmed by transmission electron microscopy. Thus, for the first time, plastidic PHB production was demonstrated for roots of a carbohydrate-storing crop plant.

Beta vulgaris↗
PubMed2001

Transfer functions as a basis for the verification of models--variability and restraints.

OBJECTIVE: The seat-to-head transfer function of the human body reflects the biodynamic response. Based on measured data, biodynamic models have been proposed to reflect this response. They must satisfy usually the international published mean values of the seat-to-head transfer function. The question arises to what extent mean values reflect individual pattern of biodynamics. METHODS: An experimental study was performed with 39 male subjects sitting on a hard seat without back rest and with supported feet. They were exposed to random whole-body vibration at three intensities with a relaxed and an erect posture. The accelerations in the z-direction were measured at the seat and head. The seat-to-head transfer functions with the associated coherence functions were calculated. RESULTS: The biodynamic response characterised by the maximum of the seat-to-head transmissibility and the frequency of its occurrence is influenced by the posture of the subjects in a dominant way and shows an individual variability of considerable extent. The mean responses suggest a missing effect of vibration intensity, but individually different effects of the intensity were found. Repeated measurements confirmed this result. CONCLUSIONS: The application of a model validated by the comparison with mean values of the transmissibility could cause misleading conclusions, if it is used for the prediction of individual spinal loads. Models prepared for the calculation of individual loads should be validated by a mean individual transmissibility derived from repeated measurements. RELEVANCE: The results illustrate the loss of information by averaging individual transfer functions and the consequence of a limited validity and applicability in occupational health, ergonomics, and design.

Acceleration↗
PubMed2000

Amplification of cyclin D1 gene in multiple myeloma: clinical and prognostic relevance.

Approximately 30% of myeloma patients express cyclin D1 RNA and protein. The low incidence of translocation t(11; 14) detected by conventional cytogenetics suggests that the up-regulation of cyclin D1 protein might result from other mechanisms as well as from gene amplification. Therefore, the frequency and the clinical and prognostic implications of cyclin D1 amplification were examined. We highly purified myeloma cells from bone marrow by magnetic cell sorting and analysed 50 myelomas by fluorescence in situ hybridization (FISH) using probes specific for cyclin D1 and 20 samples by immunoblotting to detect cyclin D1 expression. The amplification of cyclin D1 gene was found in 19 of 50 analysed patients and was associated with expression of cyclin D1 protein. The amplification correlated significantly with the bone marrow infiltration, plasma cell morphology and labelling index as well as serum beta2-microglobulin, C-reactive protein (CRP) and creatinine levels. In univariate analysis, the amplification of the cyclin D1 gene was a significantly unfavourable parameter with regard to overall survival (P = 0.0064) and progression-free survival (P = 0. 0005). In multivariate analysis, cyclin D1 amplification and serum beta2-microglobulin were independent and well-suited parameters for predicting survival. The detection of cyclin D1 amplification seems to be of promising prognostic value in multiple myeloma.

Adolescent↗
PubMed1998

Co-expression of p53 and MDM2 in human atherosclerosis: implications for the regulation of cellularity of atherosclerotic lesions.

Atherosclerosis is a fibroproliferative disease of the arterial intima. It was recently found that wild-type p53 (wt p53) accumulates in human atherosclerotic tissue. Wt p53 is a cell cycle regulator involved in DNA repair, DNA synthesis, cell differentiation, and apoptosis and might therefore make an important contribution to the cellularity of atherosclerotic plaques. The product of the MDM2 gene is a nuclear protein which forms a complex with p53, thereby inhibiting the negative regulatory effects of wt p53 on cell cycle progression. In order to address a potential role of the interaction of p53 with MDM2 for the regulation of cellularity in atherosclerotic tissue, 22 carotid atheromatous plaques from patients undergoing endarterectomy were studied to determine the presence of p53 immunoreactivity (IR), MDM2 IR, cell proliferation as evidenced by MIB1/Ki-67 IR and DNA fragmentation by in situ terminal transferase-mediated dUTP 3' end labelling (TUNEL), as a marker for apoptosis. p53 IR localized to areas with evidence of chronic inflammation (22/22) and was observed in virtually all cell types in 68.79 +/- 7.51 per cent of the nuclei. p53 staining in the control tissue from human internal mammary arteries was present in 0.2 +/- 0.29 per cent of the cells (P < or = 0.002). MDM2 IR was present in all cases (22/22) in macrophages and smooth muscle cells (SMCs) in 60.53 +/- 8.32 per cent of the nuclei (controls: 0.8 +/- 0.65 per cent, P < or = 0.002) and co-localized with p53 IR as shown by examination of adjacent sections and by double immunofluorescence labelling. Importantly, co-immunoprecipitation and western blot analysis revealed that p53 and MDM2 were physically associated, indicating that MDM2-p53 complex formation takes place in vivo in human atherosclerotic tissue. Positive TUNEL staining and MIB1/Ki-67 IR present in 3.01 +/- 1.27 per cent of the nuclei (controls: 0 per cent, P < or = 0.002) localized to the same plaque compartments as p53 IR and MDM2 IR. Thus, the fate of cells with p53 accumulation may depend on the interaction and the stoichiometry of the p53 and MDM2 proteins. Cells were indeed found with strong p53 accumulation and nuclear morphology typical for apoptosis and there were a few MIB1/Ki-67-positive cells with co-expression of MDM2, indicating a possible role for MDM2 in reversing the negative regulatory effects of p53 for cell cycle progression. The nuclear co-localization of p53 IR with MDM2 IR and the co-immunoprecipitation assay indicate the presence of p53-MDM2 complex formation in vivo in human atherosclerotic tissue. The destiny of individual p53 and MDM2-co-expressing cells either to undergo p53-dependent apoptosis or to re-enter the cycle of cell proliferation may depend on the relative ratios of the two proteins. p53 and MDM2 may therefore play an important role in regulating cellularity and inflammatory activity in human atherosclerotic plaques.

Apoptosis↗
PubMed1997

Topographical association between the cyclin-dependent kinases inhibitor P21, p53 accumulation, and cellular proliferation in human atherosclerotic tissue.

The cell cycle is controlled by cyclin-dependent protein kinases (CDKs). The activity of these enzymes is directed by inhibitors of CDKs. The 21-kD protein product (P21) of the WAF1/CIP1 gene, which can be transactivated by the protein product of the tumor suppressor gene p53, acts as an inhibitor of cyclin-dependent kinases. To assess whether both P21 and p53 may play a role in the control of cellular proliferation in atherosclerotic lesions, the topographical association between p53, P21, and the proliferation marker MIB1/Ki-67, was analyzed by immunohistochemistry in human carotid atheromatous plaques of 26 patients. p53 immunoreactivity (IR) was present in 26 of 26 cases in the nuclei of virtually all cell types (macrophages [MPs], smooth muscle cells [SMCs], endothelial cells [ECs]) in areas with chronic inflammation in 71.08 +/- 8.28% of the nuclei. p53 staining in the control tissue from human coronary arteries was present in 0.3 +/- 0.45% of the cells (P < .002): P21-IR was present in 24 of 26 specimens in 64.38 +/- 10.13% of the cells (controls: 3.8 +/- 1.85%, P < .002) and localized to nuclei of MPs (CD68 positive) and SMCs (alpha-actin positive), as well as ECs of microvessels present in 21 specimens (21 of 21) and luminal ECs present in 18 specimens (16 of 18). As shown by double labeling, P21-IR colocalized with p53-IR in most MPs (24 of 24), intimal SMCs (22 of 24), ECs of microvessels (19 of 21), and luminal ECs (10 of 16). Interestingly, few p53-positive cells did not show simultaneous P21-IR, and, conversely, not all P21-positive cells demonstrated p53-IR. MIB1/Ki-67-positive cells were identified in 21 of 26 tissue specimens in 3.53 +/- 1.79% of the nuclei (controls: 0%, P < .002) and localized principally to MPs bordering the atheromatous lipid core (21 of 26) and to a few scattered SMCs (16 of 26), ECs of microvessels (13 of 21), and luminal ECs (2 of 18). Most importantly, none of the cells coexpressing P21 and p53 were positive for MIB1/Ki-67-IR, indicating the absence of proliferating activity. In summary, this study demonstrates that P21-IR is present in the atherosclerotic plaque and colocalizes with p53 in most MPs, SMCs, and ECs. The lack of proliferation markers in cells coexpressing p53 and P21 suggests that transcriptional activation of the WAF1/CIP1 gene by p53 may be involved in the control of cellular proliferation in advanced human atherosclerotic plaques.

Arteriosclerosis↗
PubMed1996

Identification of two MADS box genes that are expressed in the apical meristem of the long-day plant Sinapis alba in transition to flowering.

To understand the molecular mechanisms involved in the transition from vegetative to reproductive growth, the photoperiodic-controlled induction of flowering in the long-day plant Sinapis alba was used to screen for regulatory genes which are expressed upon induction in the apical meristem. By using the conserved MADS box-encoding region of the organ identity gene AGAMOUS, the genes SaMADS A and SaMADS B were identified which are expressed in transition stages of mustard. RNA blot analysis has confirmed that the transcript levels of both genes are drastically increased shortly after the induction of flowering and that both genes are expressed earlier than the known MADS box genes. In situ hybridization studies have shown that the expression of the genes is restricted to the apical meristem of induced plants during early phases of reproductive development. The expression of SaMADS A is first detectable in the central zone of the meristem, a region where the earliest changes of an evoked meristem could be detected by classical physiological methods, suggesting that SaMADS A may have an important function during the transition to flowering.

Amino Acid Sequence↗
PubMed1993

[Labeling of yeast protoplasts by neutral red and nile blue for fusion experiments].

Neutral red and Nile blue were found to be suitable for staining protoplasts from various strains of Saccharomyces cerevisiae. The absorption of stains by the protoplasts was dependent on the pH value, for both stains. At a pH of 7.9 the protoplasts of the fusion partners could be stained differently and therefore it was possible to observe the fusion between the various strains of yeast. Consequently the prerequisites were created for the following micromanipulation.

Fluorescent Dyes↗
PubMed1992

Effects of isolated and combined exposures to whole-body vibration and noise on auditory-event related brain potentials and psychophysical assessment.

Auditory event-related brain potentials (ERP) in response to two different tone stimuli (1.1 kHz or 1 kHz, 80 dB, 50 ms; given by headphones at a regular interstimulus interval of 5 s with a probability distribution of 70:30) were recorded from 12 healthy male subjects (Ss) during four different conditions with two repetitions: A-60 dBA white noise (wN), no whole-body vibration (WBV); B-60 dBA wN plus sinusoidal WBV in the az-direction with a frequency of 2.01 Hz and acceleration of 2 m.s-2 root mean square; C-80 dBA wN, no WBV; D-80 dBA wN plus WBV. Each condition consisted of two runs of about 11 min interrupted by a break of 4 min. During the break with continuing exposure, but without auditory stimuli, Ss judged the difficulty of the tone-detection task and intensity of noise by means of cross-modality matching (CMM). Vibration-synchronous activity in the electrocardiogram was eliminated by a subtraction-technique. Noise caused an attenuation of the N1 and P2 amplitudes and prolongation of P3 latencies. The WBV did not cause systematic ERP effects. Condition B was associated with higher N1 and smaller P3 amplitudes. The factor "condition" had a significant effect on the peak latencies of P3 to target stimuli and the task difficulty judged by CMM. Both effects exhibited significant linear increases in the sequence of conditions A, B, C, D. For the evaluation of exposure conditions at work, it can be suggested that noise has a strong systematic effect which can be enhanced by WBV.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed1991

[Suitability of support materials for the fixation of microfungi].

Saccharomyces cerevisiae Müller-Thurgau F and Aspergillus spec. NH, a producer of glucoamylase, were cultivated in the presence of various supporting materials (three microspherical zeolitic particles, alpha-alumina and foam corundum). The supports were microscopically tested to find out whether they are settled by microfungi or not. Whereas the yeast cells lay on the supports only loosely the hyphae of Aspergillus grew around the supports and with the exception of foam corundum enclosed them in mycelial spheres. This phenomenon may favour the separation of fungal biomass in biotechnological processes.

Aspergillus↗
PubMed1990

Changes in auditory evoked brain potentials during ultra-low frequency whole-body vibration of man or of his visual surround.

Auditory evoked brain potentials (AEP) were recorded from nine healthy male subjects during three types of condition: A - subject and visual field stationary; B - subject vibrated (z-axis, 0.6 Hz, 1.85 ms-2 rms), visual field stationary; C - subject stationary, visual field vibrated (as for B). The visual surround was confined to a checkerboard pattern in front of the subject. Auditory stimuli (1000 Hz, 86 dB, interstimulus interval 7 s) were delivered via headphones to evoke AEP. Vibration-synchronous activity in the EEG was eliminated by a subtraction technique. In comparison with condition A, conditions B and C caused an attenuation of P2 and N1P2 components of AEP together with an increased latency of N1. Effects of conditions B and C did not differ. Direct vestibular stimulation and mechanisms specific for whole-body vibration were rejected as modes of action. The AEP-changes and the subjective evaluation of experimental conditions, arousal and performance, as well as symptoms of kinetosis (motion sickness) suggest a sensory mismatch, leading to a "latent kinetosis" with de-arousal, as the dominating mechanism by which the processing of information was affected. This suggestion was supported by an additional pilot study. Under real working conditions a similar effect can be expected during relative motion between the driver and his visual surround, i.e. even with perfect vibro-isolation of the driver's seat.

Adult↗
PubMed1990

The effect of low-frequency whole-body vibration under different visual conditions on auditory evoked potentials.

Auditory evoked brain potentials (AEP) were recorded from 9 healthy males during sinusoidal whole-body vibration (WBV) in the longitudinal (+/- az) direction with 0.6 Hz, 1.85 ms-2rms (F1), 1.01 Hz, 4.27 ms-2rms (F2) and without WBV (F3) under 3 visual conditions--homogeneous bright visual field (B), normal vision (N), and complete darkness (D). The sequences of the different experimental conditions were arranged according to a 9 X 9 Latin Square design. A subtraction technique was used to eliminate vibration-synchronous activity from the EEG. The N1 and N1P2 amplitudes decreased during F1 and F2, compared to F3. The latencies of N1 and P2 increased during F1 and F2. The effects of F1 and F2 did not differ. The visual conditions exhibited no systematic effect on the AEP. The results suggest (1) F1 and F2 to be equivalent exposure conditions and (2) the dominance of vestibular-auditory interactions, compared with visual-auditory ones.

Acoustic Stimulation↗
PubMed1990

[Perioperative chemoprophylaxis in percutaneous nephrolitholapaxy].

In 48 patients suffering from giant renal calculi a percutaneous nephrolitholapaxy was done. The use of perioperative antibiotic prophylaxis using aminoglycosides or cephalosporins was effective in reduction of postoperative urinary tract infections.

Anti-Bacterial Agents↗
PubMed1989

[Laboratory studies of vibration transmission in motor vehicle seats].

Operator seats (Models 050 and 500, Möve) were examined with vertical sinusoidal whole-body vibration (WBV) in the frequency range from 1 to 40 Hz (1.5 and 3.0 ms-2rms) and with simulated stochastic vibration of combines for the harvest of sugarcane. Six male subjects volunteered for the experiments. The WBV transmitted from the seat mounting base to the seat cushion and head were compared with data of a hard experimental seat. Interindividual differences cannot be explained by different body masses only. The iolation and main resonance of the two operator seats differed. Additional resonant peaks occurred above 6 Hz. They can cause unfavourable conditions at certain applications. The operator seats tested are probably suited for the reduction of WBV exposure on combines for the harvest of sugarcane.

Adult↗
PubMed1989

[Laboratory studies on the subjective evaluation of motor vehicle seats].

Operator seats (Models 050 and 500, Möve) were examined with vertical sinusoidal whole-body vibration (WBV) in the frequency range from 1 to 40 Hz (1.5 and 3.0 ms-2 rms) and with simulated stochastic vibration of combines for the harvest of sugarcane. Six male subjects volunteered for the experiments. The subjective assessments of operator seats by cross-modality matching, paired comparisons, and questionnaires were compared with data of a hard experimental seat. Transmitted WBV and subjective evaluation correlated partially only. Suggestions are derived for the improvement of the seats tested.

Adult↗
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↗