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Biomedical subjects

M Voigt

Publications and source records attributed to M Voigt.

At least 73 records · Page 4Linked to original sources
PubMed1995

The influence of tendon Youngs modulus, dimensions and instantaneous moment arms on the efficiency of human movement.

The purpose of the study was to examine the influence of passive tendon work on the gross mechanical efficiency of human whole body movement. Seven male subjects participated in the study. They performed repetitive jumps (like skipping) of three different intensities. Metabolic costs and work rates were recorded to obtain mechanical efficiencies. Net joint moments were calculated from film recordings using inverse dynamics. A general stress-strain relationship for tendons was modelled using a quadratic function, including Youngs elastic modulus of tendon tissue and tendon dimensions. Instantaneous tendon moment arms for the largest leg extensor muscles (m. triceps surae and m. quadriceps femoris) were calculated using joint angle-moment arm transfer functions obtained from the literature (cadaver studies) and the tendon work was calculated from the net joint moments. Gross efficiency values of 0.65-0.69 and efficiency values of 0.77-0.80 at the approximate level of the muscle-tendon complexes were observed. The tendons performed 52-60% of the total work. The enhancement of the muscle-tendon efficiency over the maximal theoretical efficiency of the contractile machinery (0.30) could exclusively be explained by the contribution of the tendon work. A clear negative relationship between repetitive jumping with high mechanical efficiency and running economy at 12 km h-1 was found. Using model calculations the gross efficiency and the muscle-tendon efficiency were shown to be sensitive to tendon Youngs modulus, dimensions and moment arms. The efficiencies were most sensitive to changes in the tendon moment arms. A 10% decrease in tendon moment arms resulted in a 13% increase in the gross efficiency. Optimization or minimisation of the mechanical efficiency by changing the tendon variables 5% was followed by changes in mechanical efficiency of +14% and -10%, respectively.

Adult↗
PubMed1995

Excitability of the soleus H reflex during graded walking in humans.

The excitability of the soleus Hoffmann (H) reflex was measured in five healthy male subjects during graded treadmill walking. Uphill and downhill walking at an 8% grade as well as level walking were used to vary the demands for lengthening and shortening contractions of the soleus muscle. These changes were assumed to cause differences in control of the afferent input in the spinal cord and the voluntary output to the soleus muscle. The H reflex was strongly modulated in all three walking conditions, high during the stance phase and low or absent during the swing phase. The shape of the modulations was, however, different. At uphill walking the reflex increased gradually during the whole stance phase and seemed to follow the soleus electromyogram (EMG) pattern closely. In the downhill condition the reflex excitability increased rapidly at heel strike like the soleus EMG and co-contraction of the anterior tibial muscle was observed. At level walking a fast rise in reflex excitability was seen just after heel strike with low or absent soleus EMG. Mean soleus EMG was lower during downhill than during uphill or level walking, but the mean H reflex amplitude was similar in all three conditions. However, when the H reflex was related directly to the EMG activity by linear regression the reflex gain was lower during uphill walking than in the two other conditions. Furthermore, the ratio between H reflex and EMG amplitude was high during the first half of the stance phase at level walking indicating an elevated reflex excitability independent of the voluntary motor output. It is therefore concluded that the modulation of reflexes during walking cannot be interpreted in terms of the idea of automatic gain compensation. The reflexes must be controlled specifically and independently during the different phases of the motor output to meet the mechanical requirements of the movement task. Most explicitly this was seen during downhill walking, where an elevated reflex excitability together with co-contraction at the ankle joint seem to provide increased joint stiffness and security, when the kinetic energy of the body has to be brought under control at heel strike.

Adult↗
PubMed1995

Bone-on-bone forces during loaded and unloaded walking.

Joint moments and bone-on-bone forces in the ankle, knee and hip joint were studied in 7 healthy male subjects during unloaded and loaded walking. The subjects walked across a force platform while they were filmed at 200 Hz. Loaded walking was examined at 10 and 20 kg load carried symmetrically in the hands. Peak joint moments and peak bone-on-bone forces increased from unloaded to loaded walking for the ankle and hip joint (p < 0.05). The lowest bone-on-bone forces were found at the ankle joint (3,318 +/- 390 N) during unloaded walking and the highest at the hip joint (6,399 +/- 1,517 N) during 20 kg loading. Expressed relative to body weight (BW) these values corresponded to 4.2 +/- 0.50 and 8.0 +/- 1.78 BW). However, the individual values showed that 2 of the 7 subjects differed remarkably from the other 5, especially with respect to the hip joint loadings. During loaded walking (20 kg) these 2 subjects showed 14.4 and 15.1 BW peak compression force in the hip joint while the remaining subjects were all below 6.3 BW, which could be explained by the 2 subjects' low ankle joint moments and higher knee and hip joint moments. Apparently, a total 'leg moment' formed by the three major joints is required to support the body and maintain the locomotion, although the relative contribution from each joint can differ among individuals. The peak joint moments were the most dominant contributor to the peak bone-on-bone forces. Therefore, it is concluded that interindividual differences in walking style can lead to pronounced differences in peak bone-on-bone forces. It remains unclear how these interindividual differences are related to joint degradation.

Adult↗
PubMed1994

Topographical distribution of synaptic-associated proteins in the neuritic plaques of Alzheimer's disease hippocampus.

Studies of the molecular composition of the abnormal neuritic processes of the plaques in Alzheimer's disease (AD) have shown that these structures are immunoreactive with antibodies against growth-related molecules, synaptic/axonal proteins, and cytoskeletal proteins. These studies suggest that a subpopulation of abnormal neurites in the plaque are sprouting axons that eventually degenerate. To test this hypothesis further we studied the regional distribution of plaques in the hippocampus using a panel of monoclonal antibodies against synaptic proteins. With these antibodies we found a greater proportion of immunoreactive plaques compared to previous studies where a monoclonal antibody against synaptophysin was used. The most sensitive antibodies to detect neuritic plaques were SP11 and anti-p65, and the largest number of positive plaques was found in the entorhinal cortex and CA1 region. These results further support the theory that synaptic and axonal damage are involved in plaque formation in AD.

Aged↗
PubMed1994

[Undetected esophageal foreign body aspiration in a patient with seizures].

We report an oesophageal foreign body in a patient with a seizure disorder secondary to encephalitis disseminata who was transferred to our department of neurosurgery because of rising intracranial pressure. He presented with confusion, motor aphasia, and dysphagia. However, the diagnosis of increased intracranial pressure could not be confirmed clinically or by computed tomography. A routine chest X-ray film showed a dental prosthesis projecting on the area of the hypopharynx. Bronchoscopy and oesophagoscopy showed the denture to be lodged in the hypopharynx, but it was impossible to remove it endoscopically. Therefore, an oesophagopharyngotomy was performed and the foreign body extracted. The postoperative course was complicated by pneumonia, which responded well to antibiotic treatment. The patient made an otherwise uneventful recovery and was able to eat without difficulty.

Adult↗
PubMed1994

[Nosocomial infections with the detection of Staphylococcus aureus in an average hospital--an 11-year analysis].

Nosocomial infections over an 11 years period were monitored prospectively in a district hospital. A total of nosocomial infections among 162.197 patients discharged from 1980-1990 were analyzed. The incidence rate of nosocomial infections was 3.6%. The predominant isolates were Escherichia coli and Staphylococcus aureus (11%). The highest rates of S. aureus infections were established in wound infections and skin and mucosal infections at surgery, gynaecology and paediatrics departments. The number of multiply resistant S. aureus strains has decreased and those of sensitive isolates has increased. 72% of 652 S. aureus isolates have been typed by phage typing and biotyping. Statistical analysis could not establish a significant relationship between phage patterns and nosocomial infections. The spectrum of phage patterns of these nosocomial strains was the same as those of the endogenous colonization of men. Nosocomial outbreaks could not been realized.

Bacteriophage Typing↗
PubMed1994

Helicopters as part of a regional EMS system--a cost-effectiveness analysis for three EMS regions in Germany.

With increasing health care costs the use of rescue helicopters is being questioned on the grounds of expense. No data exist on the cost-effectiveness of the use of rescue helicopters as part of a regional EMS. The end-point of this study was to analyse the cost-effectiveness of a 15 min response time (state regulation) of advanced life support (ALS) equipment provided by helicopter (1,575,000 DM annual costs) versus a ground-based ambulance (1,004,000 DM annual costs) in three EMS systems (50 km radius) with differing demographic and geographic features in Germany. The effect of varying the ratio of helicopters to ground-based vehicles (ALSC) has also been considered using two additional models. In model 1 each region was allocated one additional helicopter and had six ALS cars removed (daytime only). This improved the response times and saved nearly 1,500,000 DM per year. In model 2 each region had its existing helicopter withdrawn and replaced with six ALS cars. This made response times longer and increased expenditure. In conclusion, the additional use of rescue helicopters in EMS regions (50 km radius) remains cost-effective up to an ALSC:helicopter cost ratio of 1:6.

Air Ambulances↗
PubMed1992

Complementation of formyl peptide receptor-mediated signal transduction in Xenopus laevis oocytes.

Formyl-methionine-containing peptides (e.g. fMet-Leu-Phe) stimulate a variety of neutrophil functions by interacting with specific cell surface receptors which are coupled via G-proteins to stimulation of phospholipase C. Two markedly distinct cDNAs coding for formyl peptide receptors have recently been isolated from a rabbit and a human cDNA library respectively. To examine the hitherto unknown signal transduction properties of the formyl peptide receptor encoded by the human cDNA, we have used the PCR to clone this cDNA from poly(A)+ RNA of myeloid differentiated human leukaemia (HL-60) cells, and have injected the cDNA-derived receptor cRNA into Xenopus laevis oocytes. Receptor activity was determined electrophysiologically by measuring the agonist-dependent opening of intracellular Ca2+ concentration ([Ca2+]i)-independent Cl- channels. Injection of pure formyl peptide receptor cRNA did not lead to peptide-dependent changes in membrane current. In contrast, marked alterations of membrane current were observed in response to formyl peptides when the receptor cRNA was supplemented with poly(A)+ RNA isolated from undifferentiated HL-60 cells. Injection of the latter RNA did not lead to formyl-peptide-dependent alterations of membrane current. Binding studies using a radioiodinated formyl peptide revealed that injection of formyl peptide receptor cRNA alone led to expression of the formyl peptide receptor on the oocyte surface, and that co-injection of poly(A)+ RNA from undifferentiated HL-60 cells did not alter the level of receptor expression. Size fractionation of poly(A)+ RNA from undifferentiated HL-60 cells showed that the mRNA required to complement formyl-peptide-dependent signal transduction in oocytes had a size of approx. 3-3.5 kb. These results strongly suggest that the human formyl peptide receptor requires a specific cofactor(s), which is lacking in Xenopus oocytes but is present in undifferentiated HL-60 cells, to activate the second messenger pathway in oocytes. Identification of this factor will provide important information about the molecular mechanisms by which G-protein-coupled granulocyte-activating receptors stimulate phospholipase C.

Amino Acid Sequence↗
PubMed1991

Cloning of a putative high-affinity kainate receptor expressed predominantly in hippocampal CA3 cells.

Kainic acid is a potent neurotoxin for certain neurons. Its neurotoxicity is thought to be mediated by an excitatory amino-acid-gated ion channel (ionotropic receptor) possessing nanomolar affinity for kainate. Here we describe a new member of the rat excitatory amino-acid receptor gene family, KA-1, that has a 30% sequence similarity with the previously characterized alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor subunits GluR-A to -D. The pharmacological profile of expressed recombinant KA-1 determined in binding experiments with [3H]kainate is different from that of the cloned AMPA receptors and similar to the mammalian high-affinity kainate receptor (kainate greater than quisqualate greater than glutamate much greater than AMPA) with a dissociation constant of about 5 nM for kainate. The selectively high expression of KA-1 messenger RNA in the CA3 region of the hippocampus closely corresponds to autoradiographically located high-affinity kainate binding sites. This correlation, as well as the particular in vivo pattern of neurodegeneration observed on kainate-induced neurotoxicity, suggests that KA-1 participates in receptors mediating the kainate sensitivity of neurons in the central nervous system.

Amino Acid Sequence↗
PubMed1991

[Postoperative hemorrhage].

Postoperative hemorrhage is the second most frequent indication for early relaparotomy. The incidence depends on the level of care in a given hospital. It is highest, therefore, in institutions delivering maximal care with many trauma cases. We performed 3443 laparotomies from January 1988 to March 1991. 214 (5.9%) patients had to be reoperated, 48 of them because of postoperative bleeding. This amounts to 1.3% of the total number of laparotomies. Bleeding was identified through drains, ultrasonography or endoscopy, ultrasonography having the highest sensitivity and specificity. Total mortality was 30%. Analysis of the literature shows that mortality is lowest when relaparotomies are performed on 3%-6% of patients.

Abdominal Injuries↗
PubMed1991

Dynamic control of muscle stiffness and H reflex modulation during hopping and jumping in man.

1. The objective of the study was to evaluate the functional effects of reflexes on muscle mechanics during natural voluntary movements. The excitability of the H (Hoffmann) reflex was used as a measure of the excitability of the central component of the stretch reflex. 2. We recorded EMG, ground reaction forces and the H reflex in the soleus muscle in humans while landing from a downward jump, during drop jumping and during hopping. The movements were also recorded by high-speed cinematography. 3. The EMG pattern was adapted to the motor task. When landing the EMG in the soleus muscle and in the anterior tibial muscle showed preinnervation and alternating activity after touch down. When hopping there was little preinnervation in the soleus muscle, and the activity was initiated about 45 ms after touch down by a peak and continued unbroken until lift off. In the drop jumps the EMG pattern depended on the jumping style used by the subject. 4. The H reflex in the soleus muscle was strongly modulated in a manner appropriate to the requirements of the motor task. During landing from a downward jump the H reflex was low at touch down whereas while hopping it was high at touch down. During drop jumping it was variable and influenced by the jumping technique. 5. Muscle stiffness in the ankle joint was negative after touch down when landing, but always positive when hopping. 6. It is suggested that during landing the alternating EMG pattern after touch down was programmed and little influenced by reflexes. During hopping reflexes could contribute to the initial peak and the EMG during lift off. 7. The programmed EMG activity and the suppression of the H reflex while landing probably contribute to the development of the negative stiffness and change the muscles from a spring to a damping unit.

Adult↗
PubMed1991

[Variability of percentile values of body measurements of newborn infants (with special reference to body weight)].

The percentile curves for fetal growth between the 25th and 42nd week of gestation calculated for more than 52,000 newborns in East Germany in 1985 were compared with the rates defined for the same population in 1973-74 and showed a significantly lower mean birth weight. Besides methodological differences (primarily a more precise estimation of gestational age in the new study by using ultrasound fetometry), the differences seem to be mainly the result of changes in the reproductive behaviour of the population over that period (decrease in parity). When comparing different populations independently of ethnic specificities, a number of modifying factors have to be taken into account which significantly influence the birth weight, namely: parity, spacing, age and stature of the mother. These variables have also to be remembered when assessing the maturity of newborns in order to standardize the birth weight in relation to mortality and morbidity. As a basis for calculating percentile curves the cumulative frequency distribution should be preferred, rather than assuming a normal distribution, since fetal diseases or developmental anomalies result in an uneven distribution with an over-representation of small for date fetuses. The selection of data for calculating normal values must be rejected because of the arbitrary decisions which this entails.

Anthropometry↗
PubMed1991

[Gestational age related correction of birth weight by parity. Body height and weight of the mother].

Corrections to the real birthweight of infants are proposed from the 28th to 42nd week of pregnancy. These take account of the influence of parity and maternal height and weight. The effect of these three characteristics on the birthweight is calculated both one and two dimensionally by combining the characteristics with the actual duration of pregnancy. Thus, for example, after 40 full weeks of pregnancy 560g of the birthweight would be considered the weight correction. For newborn infants of relatively short light-weight mothers, this account should be added to the real birthweight ascertained, and for the babies of relatively tall, heavy mothers it would be subtracted. Only after this correction can the two dimensional classification of neonates into hypotrophic, eutrophic or hypertrophic take place according to birthweight and duration of gestation.

Adult↗
PubMed1990

Changes in muscle strength and speed of an unloaded movement after various training programmes.

The effect of three different training programmes on the maximal speed of an unloaded movement (a karate punch) was studied. Three movement variables were selected: maximal speed of the hand (Vh,max), maximal speed of the shoulder (Vs,max) and elbow extension speed (theta E) simultaneous with Vh.max. The programmes were: training group 1 (TG 1, n = 8) - karate students, dynamic heavy progressive resistance exercise (incline situp and incline bench press) + punch bag exercise; training group 2 (TG 2, n = 8)-karate students, punch bag training; training group 3 (TG 3, n = 5)-no karate experience, dynamic heavy progressive resistance exercise (as in TG 1). The movement variables were calculated from chrono-cyclo photographic recordings of the punches (100 Hz). The level of significance was set at 5%. Sixteen weeks of training gave the following results: significant increases in dynamic strength in all the training groups (14%-53%). In TG 1 the Vh.max increased significantly from 8.49 m.s-1, SD 1.19 to 9.35 m.s-1, SD 1.29 (10%); Vs.max increased significantly in TG 1 by 32% (2.18 m.s-1, SD 0.56 to 2.87 m.s-1, SD 0.98) and in TG 2 by 14% (2.40 m.s-1, SD 0.61 to 2.74 m.s-1, SD 0.52), and in TG 3 theta E at Vh,max increased significantly from 28.6 rad.s-1, SD 4.3 to 32.2 rad.s-1, SD 4.5 (13%). No significant relationships between the changes in maximal muscle strength and the changes in movement speed were found.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

[New aspects of assessment of physical development of children and adolescents by preventive examinations].

The results of the examinations of a representative cross-section were used as the basis for bringing up to date the standard values and ranges of variability of the body measurements of newborns according to gestational age, of head circumference up to the 3rd year and of body height and weight from 0-18 years. Tables and somatograms were also drawn up for the evaluation of body weight in relation to specific types of build, and standard values for skinfold thickness and total body fat were worked out in order to permit a biologically meaningful assessment of the physical development and nutritional status of children and adolescents. Alongside the description of the individual stages in the development of selected characteristics of maturation used in assessing sexual maturity, percentiles for the average age on reaching each of these stages of development will be available, together with a new series of photographs of breast, pubes and genital development.

Anthropometry↗
PubMed1990

[Birth weight of newborn infants in relation to body height and body weight of parents with special reference to duration of pregnancy].

Using the data of the 1985 GDR somatogram standards (birthweight percentiles calculated from 51,570 liveborn singletons) the impact of parental weight and length on the birthweight were calculated. Peristatic factors in combination with the genetic 'anlage' act first of all via maternal weight. Body height and/or length of mother and father are more representative for the genetic constitution. Their impact on neonatal weight seems to be less significant, however statistically calculable. The paternal 'anlage' is relatively modified by the intrauterine environment (maternal constitution).

Birth Weight↗
PubMed1990

[Neonatal percentile values for the GDR--1985. Correlation of body weight and length in newborn infants (calculation of birth weight/body length in cm. with reference to gestational age)].

Taking account of the gestational age (28th to 42nd completed week of pregnancy) the sex-related ratio of birth weight to length (g/cm) for newborn infants is reported. This shows that observation of the correlation between birth weight and length with reference to gestational age makes a more accurate classification of newborn infants possible, rather than using a two dimensional classification (birth weight week of gestation).

Birth Weight↗