PubMed Health⌕ Search

Biomedical subjects

F Walz

Publications and source records attributed to F Walz.

At least 19 recordsLinked to original sources
PubMed2003

Biomechanical assessment of soft tissue neck injuries in cases with long sick leave times.

A database was established by collecting 919 cases of claimed cervical spine disorders (CSDs) sustained in automotive accidents. All cases had a sick leave time of more than 4 weeks. Data was obtained from a major Swiss accident insurer. An assessment scheme was developed that took into account technical, medical, and biomechanical aspects. All cases were evaluated according to this scheme. The overall biomechanical assessment, that stated the extent to which the symptoms claimed could be explained by the impact, was found to be significantly influenced by the patient's history of CSD in terms of preexisting damage or preexisting symptoms. In 52% of the assessed cases, the CSD claimed could be explained with a combination of neck loading and also by considering the patient's medical history. Performing a solely technical analysis of the collision circumstances or a purely medical evaluation based on a Quebec Task Force (QTF) grade alone are insufficient to assess the accident-related explicability of claimed CSD. Biomechanically relevant individual factors have to be considered.

Accidents, Traffic↗
PubMed2003

Pressure aberrations inside the spinal canal during rear-end impact.

Minor soft tissue injuries of the cervical spine increasingly pose problems in public health. Such injuries are conveyed particularly often in rear-end automobile collisions at low impact speeds and it has been established that they may be associated with long-term impairment. As a possible cause for this type of injury it has been hypothesized that pressure pulses induced in cervical fluid compartments during the impact could damage the membrane of spinal nerve cells. To date, animal as well as cadaver experiments performed support this hypothesis. A theoretical analysis has been undertaken in order to investigate the pressure and flow pulse emerging in a cervical fluid compartment under conditions representing rear-end impacts with a Dv of 15 km/h. Using the finite element (FE) method, a three-dimensional model of the cervical spine was developed. The model consists of eight vertebrae (C1-T1), the intervertebral discs, the intervertebral joints, all the major ligaments, most of the neck muscles and the head. Additionally, a typical venous blood vessel was included. To determine the pressure behaviour inside the blood vessel, fluid-structure interaction was taken into account. For the time interval including the development of the S-shape, the pressure pulses were calculated and found to be in qualitative agreement with the reported measurements. The shear stresses acting on the vessel wall can be determined from the associated flow pulses. An extrapolation of the results into the interstitial space where nerve cells are located at this stage does not allow assessment of whether a damage threshold may be reached.

Accidents, Traffic↗
PubMed2002

Whiplash injury: cases with a long period of sick leave need biomechanical assessment.

A total of 668 cases of cervical spine disorders (CSD) sustained in automotive collisions were analysed. All cases had a minimum sick leave duration of 4 weeks. To evaluate these cases a scheme was developed that takes into account technical, medical, and biomechanical aspects. For each case, the delta-v value of the underlying collision was estimated, the medical files were analysed, and a QTF (Québec Task Force) grade was assigned. In addition, the medical history of the patient was reviewed. It was found that the QTF grade for patients with pre-existing damage of the neck or pre-existing signs differed significantly from those patients without such a history. The overall assessment, which stated the extent to which the symptoms claimed could be explained by the impact, was also found to be significantly influenced by a history of neck injury. The results of the study showed that in about 50% of the cases where the technical analysis alone would not suggest that the symptoms shown could be explained by the impact, those symptoms could be explained when patient history and the collision circumstances were taken into consideration. It also found that medical evaluation based on a QTF grade alone cannot assess the explicability of claimed CSD without taking into account the collision circumstances. Therefore, the assessment of critical individual relevant biomechanical factors is necessary.

Accidents, Traffic↗
PubMed1996

[Severe perforating eye injury caused by an air bag in a traffic skid accident].

BACKGROUND: After a penetrating injury of the eye following a car accident the driver demanded accurate investigations by the Institute for Legal Medicine of Zurich concerning the security of the equipment, especially the airbag. This led to an astonishing explication of the mechanism of the injury, not without consequences for safety measures for drivers and front seat passengers in air bag equipped cars. CASE REPORT: Due to a relatively harmless accident, the driver suffered from a severe penetrating injury of the right eye after the airbag deployed. The front seat passenger, having the seat belts fastened, was not injured. The accident was investigated by the Institute of Legal Medicine of Zurich. RESULTS: The analysis of the accident showed that the airbag had deployed properly. The cover of the airbag showed no defects of substance. With the precise examination of the interior of the car a broken tobacco pipe came to light. CONCLUSIONS: In this case not the airbag itself but a tobacco pipe held in the hand by the driver during the airbag ignition caused a severe injury of the eye. This case report illustrates the hazard of having any rigid object between the occupant and the deploying air bag. In conclusion, the drivers and front seat passengers of an airbag equipped car can only profit from the considerable security gain, if they know about these risks and adapt their behaviours to the new surroundings, but also the car manufactures have to instruct the customers properly.

Accidents, Traffic↗
PubMed1996

In vitro hydrolysis of gliadin and casein peptides: secondary defect in coeliac disease shown by organ culture.

BACKGROUND: Small-intestinal organ culture was used as an in vitro model of coeliac disease, studying biopsy specimens from patients with coeliac disease, cow's milk allergy, and controls. METHODS: Organ culture incubations were done using the pure gliadin peptide B3144 (amino acid sequences 3-56 of alpha-type gliadins) and a control peptide from casein (amino acid sequences 152-193 of alpha s1-casein). The importance of using negative controls was stressed by non-specific tissue damage. By reversed-phase high-performance liquid chromatography of organ culture supernatants, 27 specimens were further investigated. RESULTS: There was good retrieval of peptide calibration peaks after culture. Qualitative and quantitative evaluation of chromatography runs showed degradation of at least 29% of B3144 and 37% of Cas-P. Normal mucosa (controls and coeliac patients on a gluten-free diet) was able to hydrolyse peptide fractions completely, whereas incubation with damaged mucosa (coeliac disease, cow's milk allergy) left initial peptides. CONCLUSION: It is concluded, using a pure single gliadin peptide, that deficient peptide hydrolysis in coeliac disease was a secondary event.

Adolescent↗
PubMed1994

[Biomechanical aspects of cervical trauma].

The biomechanical expert opinion on the injury mechanism is necessary in few cases only. However, the judgement of these cases is extremely compromised if mechanically wrong terms are introduced in the clinical report. Since the injury mechanism in the neck is very complex the clinical physician should concentrate on the clinical findings familiar to him; usually the clinician lacks technical case documentation and specific training in injury biomechanics. The relevant mechanisms of neck injuries are an indirect trauma induced by a) a head contact leading to compression, hyperflexion, hyperextension and/or hypertranslation and b) a non-head-contact mechanism (hyperflexion or hyperextension, hypertranslation, acceleration). A non-contact mechanism occurs e.g. during a rear end impact without head restraint (hyperextension) or a frontal collision of a belted occupant (hyperflexion) without head impact. The term "whiplash" is misleading and incorrect: It presumes a virtually non existing two phase movement back and forth (or vice versa) like during the development of the crack of the whip. Secondly, it mixes the physical criterion mechanism with the anatomical or morphological criterion injury e.g. distortion, sprain etc. A (head)-contact mechanism is due to a corresponding momentum exerted from the head on the neck. Again, the anatomical or morphological terms are equal, but the mechanism is different. During a contact mechanism as well as during a non-contact mechanism not only a hyperflexion or a hyperextension can occur; in the first phase of the impact also a shearing force between the upper vertebral bodies (CO-C2) may load the intervertebral structures by hypertranslation.

Accidents, Traffic↗
PubMed1994

[Determining the status of the cervical spine after whiplash injury].

The results of medical investigations following acceleration mechanism to the cervical spine (so called "soft tissue neck injury") are to be described in common diagnostic terms. Biomechanical and legal considerations are beyond medical competence. In certain cases, the clinical examination must be completed in cooperation with specialists. Within the entire medical context, the neuropsychological and neuropsychiatric assessment may contribute to a comprehensive understanding of the consequences. In cases of litigation, the full array of facts, like the patients' previous history, and differential diagnoses, have to be drawn to attention. At present, compensation takes place only exceptionally and in a limited range, if an impairment by an accompanying brain injury is excluded.

Accidents, Traffic↗
PubMed1994

[Biomechanical aspects of injuries of the cervical vertebrae].

A biomechanical expert opinion on the injury mechanism is necessary only in a few cases. However, the judgement of these cases is extremely compromised if the mechanics of injury are described incorrectly in the clinical report. Since the mechanism of neck injuries is very complex, the physician without biomechanical training should concentrate on the familiar clinical findings; The relevant mechanisms of indirect neck trauma are (a) a non-head-contact mechanism (hyperflexion or hyperextension, hypertranslation, acceleration) and (b) head contact leading to compression, hyperflexion, hyperextension and/or hypertranslation. A non-head-contact mechanism occurs, for example, in the case of rear end impact without head restraint (hyperextension) or a frontal collision involving a belted occupant (hyperflexion), without head impact. The term "whiplash" is misleading and incorrect: It presumes a virtually non-existent two-phase movement back and forth (or vice versa), and it confuses the physical criterion mechanism and the anatomical or morphological criterion injury, e.g. distortion, sprain etc. A head-contact mechanism involves momentum exerted from the head on the neck. Again, the anatomical and morphological terms are the same, but the mechanism is different. With a contact mechanism and a non-contact mechanism, not only a hyperflexion or a hyperextension can occur; in the first phase of the impact, a shearing force between the upper vertebral bodies (C0-C2) may load the intervertebral structures by hypertranslation.

Accidents, Traffic↗
PubMed1992

Safety and economic aspects of continuous mammalian cell culture.

Mammalian cell cultures are the most appropriate host cells for recombinant DNA derived products if complex protein structures have to be synthesized in their native form. Due to their physiological behaviour they grow either adherent or in suspension. For the attachment of adherent cells, microcarriers or wire springs can be applied to increase the internal surface of the bioreactor. Both systems provide a simplified media exchange but, however, show some limitations in scale up. In contrast, suspension culture systems as homogeneous systems independent of any carrier have not shown any limitation in scale up. Because most cell lines which are of commercial interest grow in suspension, this technology is best advanced and used in batch and continuous mode. Although mammalian cell cultures are sensitive to hydrodynamic shear forces, technologies for deep tank production are developed which allow stirrer tip speed of up to 1.5 m s-1 sufficient for oxygen uptake, suspension of cells and homogeneous supply with nutrients. For long term bioprocesses without selection pressure it has to be considered that transformed cell lines might show genetic instability due to their variations of chromosomes. In addition, sterile technology becomes an important factor in long term bioprocesses. The decision as to which cell culture system should be chosen, whether batch or continuous processes should be applied essentially is based on the capital investment, the amount of material to be produced, genetic stability of the production cell line, reliability of sterile technology and the flexibility required in the production plant. Under the assumption that 20 kg of a protein have to be produced per year and the same product concentrations in the harvest fluid are reached in the batch process and for instance in the chemostat, it can be considered that the capital investment for one 10,000 l batch process and a 2 x 2,000 l continuous process, necessary to produce the amount of material, is comparable. Risk of microbial contamination or technical failure can be considered to be fairly low in the batch process. The economic risk for long term bioprocess in the chemostat can be expected to be medium and high in the perfusion system which is in the large scale not technically fully satisfactory. In addition, due to the longer down time period after contaminations and the start up of the continuous process, the annual yield of the batch process can be considered to be higher.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

[Biomechanical aspects of collisions in street traffic].

Injuries are still severe on average at Delta-v-values as low as 50 km/h with belted occupants and as low as 30 km/h with struck pedestrians. Therefore, all technical developments improving safety should not blind us to the fact that lowering vehicle speed remains the first priority in injury prevention. Small light weight cars of low energy consumption (e.g. electromobiles) constitute a major occupant safety problem unless advanced safety engineering will be applied. The extensive improvements over the last decades, both in active and passive safety, including newly developed steering systems, anti-blocking brake systems, seat belts, head restraints, etc. however have masked drivers sense and peception of danger. In research and development of sophisticated electronic warning and controlling systems, designed to help in driving, possible secondary effects of risk homoeostasis or compensation of risk reduction have to be taken into account at an early stage. Psychological and ergonomical knowledge has to complement the purely technical and biomechanical approach.

Acceleration↗
PubMed1991

[The "severity" of "whiplash injury of the cervical spine"].

The severity of the so called "whiplash injury of the neck" ("soft tissue neck injury") and the condition thereafter depends on the chosen angle of view: impact dynamics, biomechanics, pathological-anatomical considerations, clinical and apparative findings, medicolegal aspects and subjective assessment. The impact itself may not serve as a diagnosis, which latter has to be founded on the results of the medical examination. These findings seem to be appropriate for the resolution of questions in the course of litigation. At present, a universal severity may not be defined.

Accidents, Traffic↗
PubMed1990

Metabolic products of microorganisms. 255. Nikkomycins Wz and Wx, new chitin synthetase inhibitors from Streptomyces tendae.

Two new dipeptidyl nikkomycins of the Z and X type were isolated from the culture broth of Streptomyces tendae TU 901/395-11/32 and characterized. They show a variation in the amino acid moiety of the molecule. Nikkomycin Wz is composed of L-tyrosine and 5-amino-5-deoxy-D-allo-furanuronic acid N-glycosidally bound to uracil, whereas nikkomycin Wx is composed of L-tyrosine and 5-amino-5-deoxy-D-allo-furanuronic acid N-glycosidally bound to 4-formyl-4-imidazolin-2-one. The new nikkomycins are good inhibitors of chitin synthetase from Coprinus cinereus but they did not inhibit growth of fungi and yeasts.

Aminoglycosides↗
PubMed1988

Validation of biotechnological production processes.

Due to the biological synthesis of biotechnologically produced pharmaceuticals the product quality and safety of the drug is influenced by various factors. The correct nucleotide sequence and stability of the host cell/vector system provide the corresponding amino acid sequence of the protein. The posttranslational processing of the protein requires a well characterized production cell line. Suitable equipment for fermentation allowing a sterile production of the producing monoculture and consistent conditions are the basic requirements for the validation of the fermentation process. A constant specific productivity is one of the major criteria for the reproducibility of the production. For the validation of recovery and purification it is necessary to examine yield after each process step, product quality before and after each single process step and purification factors for removal of contaminating proteins, nucleic acids and potential viruses. In addition to the validation of the entire production process, reproducibility of quality of the formulated product has to be determined by a number of protein analytical, immunological and biochemical test methods concerning the identity, purity, safety and potency of the drug.

Biotechnology↗
PubMed1988

Fermentation with immobilized cell cultures.

For the production of monoclonal antibodies and complex recombinant human proteins or glycoproteins a number of immobilized cell culture systems have been developed. The advantages of such cell culture systems are that cells can be kept in small volumes of cell culture fluid and media can be changed continuously if necessary for induction of product synthesis or removal and harvest of metabolic products. Whereas the hollow fiber and the opticell culture systems can be limited in scaling up the microcarrier system, the fluidized bed bioreactor and the solid bed bioreactor are suitable for scaling up. In contrast to the other systems, the solid bed bioreactor requires no special manipulation for anchoring the cells to the wire springs. In situ cleaning is possible and the beads are reusable. With this cell culture fermentation system, production processes for interferon beta, monoclonal antibodies for interferon alfa and recombinant human tissue plasminogen activator were developed.

Antibodies, Monoclonal↗
PubMed1987

[Whiplash trauma of the cervical vertebrae in traffic: biomechanical and expert-opinion aspects].

The indirect injury mechanisms of the cervical spine should be subdivided into "non-contact injury" of the cervical spine, without head impact, by definition (hyperflexion or hyperextension), sometimes also called whiplash injury mechanism, and bending mechanism due to head contact, i.e. "contact injury" (hyperflexion, hyperextension, lateral bending, axial compression). The term "whiplash" is, in strict biomechanical terms, very often incorrect since it implies a biphasic motion (hyperextension and hyperflexion, or vice versa); in traffic collisions, however, its second phase is insignificant. The terms used for the injuries themselves should be taken from the classic morphology (fracture, luxation, distorsion etc.). The severity of the injury alone offers no hint as to the mechanical severity of the collision, which is established only by a mathematical reconstruction of the collision dynamics also taking into account such criteria as collision angle, seat belts, head restraint position etc. Significant cervical spine injury due to non-contact mechanism is very rare if car damage is only minor; however, head contact inducing cervical bending can lead to severe cervical injuries even with minor car damage. In the latter case the patient should not be treated as a malingerer. Moreover, if more than two vehicles are involved the reconstruction of the accident is greatly facilitated if the lesion can be proven to be a "contact" or "non-contact" injury (legal implications, insurance payments). The (rare) severe cervical spine injuries in seat belt wearers are not caused by the restraining effect of the belt but by bending and injuring of the neck due to head contact which often is not completely avoidable (justification of mandatory seat belt law).

Accidents, Traffic↗