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Biomedical subjects

C Christmann

Publications and source records attributed to C Christmann.

At least 19 recordsLinked to original sources
PubMed2003

Remote activation of referred phantom sensation and cortical reorganization in human upper extremity amputees.

Phantom limb sensation, whether painful or not, frequently occurs after peripheral nerve lesions. It can be elicited by stimulating body parts adjacent to the amputation site (referred to as phantom sensation) and it is often similar in quality to the stimulation at the remote site. The present study induced referred phantom sensations in two upper limb amputees. Neuroelectric source imaging (ESI) as well as functional magnetic resonance imaging (fMRI) was used to assess reorganization in primary somatosensory cortex (SI). Whereas recent studies found mislocalization of sensation related to stimulation mainly in regions adjacent and ipsilateral to the amputation site, we report here the elicitation of phantom sensation in the arm by stimulation in the lower body part both ipsi- and contralateral to the amputation in two arm amputees. The fMRI evaluation of one patient showed no shift in the location of the foot whereas ESI revealed major reorganization of the mouth region in primary somatosensory cortex in both patients. These data suggest that cortical structures other than SI might be contributing to the phenomenon of referred sensation. Candidate structures are the thalamus, secondary somatosensory cortex, posterior parietal cortex and prefrontal cortex.

Adult↗
PubMed1999

Disturbance of myocardial energy metabolism in experimental virus myocarditis by antibodies against the adenine nucleotide translocator.

OBJECTIVE: The adenine nucleotide translocator (ANT) of the inner mitochondrial membrane is an autoantigen in myocarditis and in dilated cardiomyopathy. Clinical and experimental studies showed that specific autoantibodies inhibit the transmembrane nucleotide transport. In isolated hearts of guinea pigs immunized with the ANT, energy metabolism is disturbed. This metabolic disorder is related to functionally active specific antibodies and to a reduced heart function. This study tests whether similar immunological, metabolical and functional responses also occur in experimental virus myocarditis. METHODS AND RESULTS: Experimental virus myocarditis was induced in A.SW/SnJ-mice by Coxsackie B3 virus infection. Specific antibodies against the ANT were detected by Western Blot in 14 out of 19 infected animals. In the isolated perfused hearts of five of these 14 mice cytosolic and mitochondrial ATP/ADP-ratios, determined by nonaqueous fractionation, were significantly altered, signalling a reduced ANT function [cytosolic ATP/ADP: 59 +/- 18 vs. 136 +/- 20 (controls), mitochondrial ATP/ADP: 4.2 +/- 1.0 vs. 1.1 +/- 0.3], all P < 0.05. Also, left ventricular pressure [43 +/- 9 vs. 78 +/- 6 mmHg (noninfected controls)], rate-pressure product (15.8 +/- 3.2 vs. 30.5 +/- 3.0 mmHg/min/1000), dp/dt (2410 +/- 222 vs. 3250 +/- 118 mmHg/s), and oxygen consumption (4.7 +/- 0.9 vs. 7.3 +/- 0.7 mumol/g/min), all P < 0.05, were lowered. CONCLUSION: The data support the hypothesis that a virus infection alters cardiac energy metabolism and function by an antibody-mediated modulation of the function of the ANT.

Adenosine Diphosphate↗
PubMed1999

In vitro susceptibilities of Aeromonas genomic species to 69 antimicrobial agents.

A total of 217 strains representing all 14 currently described genomic species in the genus Aeromonas were tested for susceptibility to 69 antimicrobial agents by a microdilution method. All species were susceptible to tetracyclines, quinolones, chloramphenicol, and most of the aminoglycosides and the cephalosporins, but were resistant to lincosamides, vancomycin, teicoplanin and some penicillins. In general, no significant differences were found that correlated with the taxonomic designation or the origin of the isolates tested. The microdilution method proved to be easy to perform allowing susceptibility testing of extensive strain collections for a large number of antimicrobial agents.

Aeromonas↗
PubMed1979

[Experimental studies on the development of human skull fractures].

Pressure tests were performed on certain well-defined points in the median-sagittal plane of soft part covered skulls of 40 human corpses. It was found that the elastic behaviour of the skull obeys Hooke's law, thus the modulus of elasticity is the Ist differential quotient in the stress-strain diagram. Beside the vectorial nature of the compression force the point of application is also of decisive importance. The globe-ellipsoid theories do not correspond to the structure of human skulls. Autopsy revealed over 50% more confirmed fractures than the X-ray pictures. This contradiction in the diagnosis of fractures on the human skull can be reduced by series of X-ray pictures. The lines of the fractures run to the most part along the Benninghoff--Goerttler pillars of strength. Additional biostatic parameters (maximum load before breaking, coefficient of elasticity, stress, elongation etc.) were also obtained which permit an insight into the specific mechanic structure of the human skull and its load-bearing ability.

Biomechanical Phenomena↗
PubMed1978

[The mechanisms of fracture in the human skull under static loads while still covered by tissue (author's transl)].

Static compression tests were undertaken on 40 human skulls while still covered by tissue. The compression tests were performed on the median sagittal part of the calotte. It was found that the skull, like the tubular bones, is fully elastic. Dissection revealed considerably more fractures, particularly in the basal region, than were shown on x-ray pictures (50%). With regard to the mechanisms of fracture, Fig. 2 shows that fractures occur only while the last third of the load is being applied. The following parameters were determined: maximum stress upon fracture, strain, elongation, elasticity module and elasticity coefficient.

Biomechanical Phenomena↗
PubMed1978

[Contribution to three-dimensional consideration of surfaces of joints of condyli femoris (author's transl)].

There were laid sections in a difference of 1 cm across the condyli femoris of 5 human formalin-fixed femora and was looked for the curvature of the areas of joints at their marks. In comparing with literature was to be seen that corresponding dats failed at the orientation of the bone. Model conceptions used in case of compensation can't be accepted. Exact calculations of the three-dimensional curvature of surface are presumed for taking into account the mechanism of transfer of forces in the knee joint.

Aged↗
PubMed1978

[Rare thoracic injuries (biomechanics, diagnosis and therapy) (author's transl)].

Thoracic injuries caused by direct or indirect power action involve various injury effects. The extent of injury depends on the force and the direction of the acting power, on the biomechanical properties of the partial structures of the thorax, and on genetically determined variations of form and structure. These correlations are demonstrated by special examples of rare thoracic injuries. The motto for the diagnostic and the choice of the therapeutical procedure is: "Inter vulnerationem thoracis diagnosis incipiat".

Accidents, Traffic↗
PubMed1977

[Eigen-frequencies and lines of nodes from skulls (author's transl)].

The skull has a system of vibration with characteristic Eigen-frequencies and oscillation modes. Macereted and non-macereted skulls showed lines of nodes of a typical manner which is specific for the hominides. Specially the mod of vibration of the 2. Eigen-frequency is strongly correlated with the state of the skull. Defined fractures of the base causes the Eigen-frequency shifting in rostral direction. Patterns of fracture, diaphanoscopic and x-ray investigation showed no correlations to the mod of vibration of all the Eigen-frequencies. In the clinical practice this findings give a diagnostic possibility in immediate identification of the fractures and infractures.

Animals↗
PubMed1977

[Low frequency vibration on human hollow bone (author's transl)].

With the aid of a stable fixation and a hammer system was removed the bone in vibrations which was registered. The vibrations have relations to the regions of the bone and have a practical connexion to the knowledge of the fracturation of the bone.

Biomechanical Phenomena↗
PubMed1977

[High frequency vibrations of human hollow bone (author's transl)].

For study of the functional structures in hollow bone were applicated longitudinal waves in form of ultrasonics. The findings have a great signification for the practical medicine, because we can demonstrate the elastic modul of the bone, the absorption of the longitudinal waves in the bone by a thickness more than 5 cm and the transformation of the ultrasonic amplitude in the bone.

Biomechanical Phenomena↗
PubMed1977

[Theoretic considerations on the vibration of human skulls (author's transl)].

Using a computer program for the evaluating of free eligible rotation-symmetrical cylinder shells the number of magnitude of the natural-frequencies were estimated. Assuming the skull of being annulary fixed the calculated values doe in the same range as those got from deat bodies or macerated skulls respectively. Modeling the vibration conditions for the non-fixed border of the skull, the mode shifts into a singulaer point on the rotations axis. In fact the mode in exactly known basis fractures tends to go to the vertex.

Biomechanical Phenomena↗
PubMed1977

[On the estimation of the vibration of human skulls (author's transl)].

The skull as a biosystem capable vibration shows characteristic oscillation modes with specific Eigen-frequencies. For the calculation of the these values we used a test method. The 4 lowest Eigen-frequencies are in the range of 1-3 KHz(f1 = 1,03 +/- 0,35KHz;f2 = 1,71 +/- 0,13KHz;f3 = 2,16 +/- 0,12 KHz and f4 = 2,57 +/- 0,11 KHz;n = 13). The shifting of the vibration mode is of diagnostic value in estimating of skull-basis-fractures.

Biomechanical Phenomena↗
PubMed1977

[Characteristic Biomechanical values for the hip joint (author's transl)].

Four human hip joints which had been fixed informaldehyde taken from human corpses (average age at death: 72 years) were subjected to pressure along defined axes and tested for static strength and elasticity, the hip joint being regarded as a system. The stress-strain curve reveals no definite linearity. The deviations from Hooke's elasticity found in this way have been explained by the fact that not only completely elastic bone, but also plastic components (cartilage of the joint) were tested. The maximum breaking strain, the modulus of elasticity and the elasticity coefficient were also determined. Only about 50% of all fractures observed on the test set-up were diagnosticised radiologically. The parameters which have, in the past, been determined only on models have thus been replaced by experimental results obtained on actual hip joints.

Biomechanical Phenomena↗
PubMed1977

[The influence of inhomogenity on strength of bones (author's transl)].

The authors experiments (n = 50) and calculation (n = 1000) with human hollow bone revealed physical and chemical data which were compared. It was shown that the physical and chemical properties are different in the diaphysis and epiphysis. These regularities are the consequence of the physical and chemical inhomogenities. These findings can be explained as a mechanism of protection.

Biomechanical Phenomena↗