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Biomedical subjects

U Meyer

Publications and source records attributed to U Meyer.

At least 19 recordsLinked to original sources
PubMed2007

[Causation, therapy and complications of treating mandibular fractures - a retrospective analysis of 10 years].

BACKGROUND: Fractures of the mandible are a common form of facial injury. The aetiological factors associated with mandibular fractures and the trends in these factors over a 10-year period are reported. METHODS: A retrospective survey was carried out of 724 patients presenting with a fracture of the mandible over the 10-year-period 1994-2003. Patients; records were reviewed and analyzed according to age, sex, cause of injury, anatomic site of fracture, treatment and postoperative complications. RESULTS: Over the 10-year-period the rate of mandibular fractures remained constant (mean 40,7%). There were no changes in the age group (mean 33,3 years) or in the higher prevalence in male (male-female-ratio 2,3 : 1). The major causes of fractures were assaults (38,6%) and accidental fall (27,3%). The most common fracture site was the condylar region (47,0%) followed by the angle (29,4%). Most fractures were treated by closed reduction until 2002, thereafter surgical treatment increased noticeable. The complication rate was 8,9% and the most common complications were hardware exposure and infection. CONCLUSION: Fractures of the mandible are a prevalent form of facial injury. Aetiological factors show no significant change over the 10-year-period. Complication-rate is low and will support the tendency towards surgical treatment.

Adolescent↗
PubMed2006

Maternal immune activation during pregnancy increases limbic GABAA receptor immunoreactivity in the adult offspring: implications for schizophrenia.

Prenatal exposures to a variety of infections have been associated with an increased incidence of schizophrenia. We have reported that a single injection of the synthetic cytokine releaser PolyI:C to pregnant mice produced offspring that exhibited multiple schizophrenia-related behavioral deficits in adulthood. Here, we characterized the effect of maternal inflammation during fetal brain development on adult limbic morphology and expression of GABAA-receptors. The PolyI:C treatment did not induce morphological abnormalities but resulted in a significant increase in GABAA receptor subunit alpha2 immunoreactivity (IR) in the ventral dentate gyrus and basolateral amygdala in adult treated compared to control subjects. Correlative analyses between the a2 subunit IR in the ventral dentate gyrus and the performance in the prepulse inhibition paradigm revealed a significant correlation in controls that was however absent in the pathological condition. These results suggest that prenatal immune activation-induced disturbances of early brain development result in profound alterations in the limbic expression of GABAA receptors that may underlie the schizophrenia-related behavioral deficits in the adult mice.

Analysis of Variance↗
PubMed2006

Reconstruction of large defects on the scalp and forehead as an interdisciplinary challenge: experience in the management of 39 cases.

AIMS: To describe options and indications for different surgical reconstruction techniques after resection of large skin tumours on the scalp taking into account an interdisciplinary approach of cranio-maxillofacial surgeon, dermatologist, and neurosurgeon, and to evaluate complications and postoperative outcome. PATIENTS AND METHODS: From a total of 39 patients with large skin tumour resections on the scalp and/or the forehead, treated between January 01, 1995 and June 30, 2005, a number of 42 surgical reconstructions were performed. The medical histories, the surgical treatment, postoperative complications, follow-up and outcome were evaluated. RESULTS: The excision defects measured 146 cm(2) (range: 80.6-546 cm(2)) on average. The most common methods for defect closure were multiple rotation-advancement flaps (n=19). Six patients were treated with split-thickness skin grafts after bone drilling for inducing granulation tissue to grow. Free latissimus dorsi muscle flaps were used in 8 patients and radial forearm flaps in 4 cases. Postoperative complications were rare. An algorithm for the surgical approach to large scalp defects was developed. CONCLUSION: For reconstruction of large defects on the scalp and forehead, various reliable methods may be used with regard to individual patient-specific parameters in cooperation with different medical specialties involved.

Aged↗
PubMed2006

Mineralization at the interface of implants.

Osseointegration of implants is crucial for the long-term success of oral implants. Mineralization of the bone's extracellular matrix as the ultimate step of a mature bone formation is closely related to implant osseointegration. Osteogenesis at oral implants is a complex process, driven by cellular and acellular phenomena. The biological process of the maintenance and emergence of minerals in the vicinity of oral implants is influenced to a great extent by biophysical parameters. Implant-related structural and functional factors, as well as patient-specific factors, govern the features of osteogenesis. To understand the influence of these factors in peri-implant bone mineralization, it is important to consider the basic biological processes. Biological and crystallographic investigations have to be applied to evaluate mineralization at implant surfaces at the different hierarchical levels of analysis. This review gives insight into the complex theme of mineral formation around implants. Special focus is given to new developments in implant design and loading protocols aimed at accelerating osseointegration of dental implants.

Bone and Bones↗
PubMed2006

Technical and clinical assessment of the use of a new material-based splint in orthognathic surgery.

Heat or auto-cured acrylic resins are materials that are commonly used in splint construction. Newly developed light-cured resins hold promise in view of the altered characteristics of the material. The aim of this study was to evaluate how far light-curing resin-based splints can be used in orthognathic surgery. Over a period of 1 year, 141 orthognathic surgeries were planned and performed using randomly chosen light-cured splints versus auto-polymerized splints. The performance of splint fabrication, the model planning and the clinical use were assessed by different measurements. The dental technician, the orthodontist and the surgeon evaluated objective parameters (model damage, fabrication time, accuracy of registration, adjustment time) as well as subjective criteria (handling). This study revealed that the use of light-curing splints significantly improved the accuracy (97.7% versus 81.2% in the case of acrylic materials). Less time was needed for the fabrication and adjustment of the splint. There was concomitantly less model damage to be observed when light-curing resins were used (9.2% versus 83.5%) and subjective measurements revealed significantly better handling of light-curing resin-based splints. Light-curing resin splints used in orthognathic surgery seem to be advantageous.

Acrylic Resins↗
PubMed2006

[Medical expert opinions in oral and maxillofacial medicine regarding incisor tooth trauma].

BACKGROUND: The treatment of traumatized patients plays a significant role in the everyday life of oral and maxillofacial surgeons as well as of dentists. Traumas of incisor teeth account for a considerable part. These traumas are often followed by lawsuits. The aim of this retrospective analysis was to highlight aspects of these lawsuits of special significance and to show the consequences for surgeons and general practitioners. MATERIAL AND METHODS: A total of 398 medical expert opinions were evaluated. Moreover, an online search of databases for relevant court decisions was performed. Analysis was initially based on formal aspects of the cases and reports. It was later supplemented by a differentiated assignment of the questions addressed by the courts to the expert consultants. RESULTS: In 97 (24%) medical expert opinions traumas of the incisor teeth were the main subject. In 35% the trauma was caused by traffic accidents followed by assaults. In one-third the medical expert opinion was commissioned by accident insurance companies. The compensation for pain and suffering was between 1500 and 2000 euros per lost tooth. CONCLUSION: Traumas of incisor teeth are often followed by litigations. Clinicians performing first treatment should ensure that documentation of clinical and radiological findings is detailed and complete. This documentation plays a decisive role in medical expert opinions.

Compensation and Redress↗
PubMed2006

The influence of an increased cobalt supply to dairy cows on the vitamin B status of their calves.

In the experiment the influence of an elevated oral cobalt supply (Co content in the ration 0.27 mg Co/kg DM; supplement of 0.14 mg Co/kg DM as CoSO(4)) to pregnant dairy cows on the vitamin B(12) concentration in milk, colostrum and vitamin B(12) status of their calves was tested in comparison with unsupplemented controls (0.13 mg Co/kg DM). While there was no significant difference in vitamin B(12) concentration in the at 70th day of lactation (start of the experiment; 3.77 +/- 1.41 vs. 3.66 +/- 1.03 ng/ml) and 290th day of lactation (almost drying off; 4.75 +/- 3.05 vs. 4.44 +/- 0.96 ng/ml), cobalamin concentration in the milk colostrum showed a tendency towards a higher cobalt content in the ration of the supplemented cows in comparison with the controls (21.0 +/- 8.4 vs. 16.7 +/- 11.9 ng/ml). Differences in the vitamin B(12) concentration in the serum of the newborn calves before and after ingestion of colostrum were not detected. From these results it can be concluded that cobalt content of 0.13 mg Co/kg DM in the ration based on wilted grass silage seems to be sufficient for pregnant dairy cows.

Animal Feed↗
PubMed2005

[Occupational exposures with risk of transmission of HIV, HBC and HCV in health care workers].

Health care workers are often victims of occupational injuries by contaminated sharps or projection of contaminated fluids to mucous membranes and are therefore at risk for transmission of HIV, HBV and HCV. Every technical and organisation-related measure useful to prevent injuries should be implemented and personal protection equipment must be made available to workers. Promotion of hepatitis B immunization is a key issue. Immediate evaluation of injured employee is necessary to assess the risk related to exposure and the indication for post-exposure prophylaxis (anti-retroviral therapy for HIV, immunoglobulins and vaccination for hepatitis B). When a health care worker has been exposed to one of the blood-born viruses, thorough information and follow-up should be offered by a specialist.

HIV Infections↗
PubMed2005

Principles of bone formation driven by biophysical forces in craniofacial surgery.

Biophysical forces, particularly mechanical loading and electromagnetic signals, are important regulators of bone formation. Indeed, the regenerative capacity of bony tissue is largely the result of the bone's capacity to recognise the functional environment required for the emergence and maintenance of a structurally intact bone. Biophysical methods of stimulation have therefore been introduced and have proved successful in clinical practice with craniofacial bones. Distraction osteogenesis, application of ultrasound, calculated transfer of stresses, and exposure to an electromagnetic field are some examples of biophysically driven approaches to influencing bone formation. The purpose of this review is to provide an insight into cellular and tissue models that are used to study the effects of biophysical stimuli on bone.

Bone Remodeling↗
PubMed2005

Design and performance of a bioreactor system for mechanically promoted three-dimensional tissue engineering.

There is currently considerable interest in increasing the response of mesenchymal cells to physical forces, and numerous loading devices have been used to increase the formation of skeletal tissue in vivo and in vitro. We have developed a bioreactor system to apply cyclic strains on three-dimensional specimens over a range of 0-20,000 mustrain. The piezoelectric-driven mechanism allows the precise adjustment and control over load-related deformations of tissue, as shown by finite-element calculations of deformation of a collagen gel under load. We present the design of the bioreactor and its performance in specimens of tissue containing activated osteoblasts and chondrocytes. Biaxial tissue straining at 2,000 mustrain led to a substantial increase in the number of both types of cell compared with unstimulated controls. The synthesis of cell-specific extracellular matrix proteins increased when physiological loads (2,000 mustrain) were applied in the bioreactor, whereas higher deformations (20,000 mustrain) resulted in a reduction in proliferation and differentiation of cells. The mechanisms whereby mechanical stimulation leads to a defined cell reaction are not known, but the application of physiological micromovements in extracorporeal tissue chambers is a promising approach to the formation of hard tissue.

Animals↗
PubMed2005

Basic reactions of osteoblasts on structured material surfaces.

In order to assess how bone substitute materials determine bone formation in vivo it is useful to understand the mechanisms of the material surface/tissue interaction on a cellular level. Artificial materials are used in two applications, as biomaterials alone or as a scaffold for osteoblasts in a tissue engineering approach. Recently, many efforts have been undertaken to improve bone regeneration by the use of structured material surfaces. In vitro studies of bone cell responses to artificial materials are the basic tool to determine these interactions. Surface properties of materials surfaces as well as biophysical constraints at the biomaterial surface are of major importance since these features will direct the cell responses. Studies on osteoblastlike cell reactivity towards materials will have to focus on the different steps of protein and cell reactions towards defined surface properties. The introduction of new techniques allows nowadays the fabrication of materials with ordered surface structures. This paper gives a review of present knowledge on the various stages of osteoblast reactions on material surfaces, focused on basic cell events under in vitro conditions. Special emphasis is given to cellular reactions towards ordered nano-sized topographies.

Biocompatible Materials↗
PubMed2005

[Osteoblast reaction on SLA and microgrooved implant surfaces].

The osseointegration process of dental implants depends on the tissue reaction at the tissue-implant interface. Osteoblasts are the main cells responsible for the regulation of osteoinduction. The manner and kinetics of the tissue reaction crucially depend on the interaction between osteoblasts and the morphology of the implant surface. The aim of this study was to investigate osteoblast behaviour on different implant surfaces (smooth, microgrooved, SLA) under standardized conditions. For this in vitro investigation we used primary bovine osteoblasts. Attachment kinetics, proliferation rate and synthesis of bone-associated proteins were used as parameters for cell reaction. The results demonstrate that both attachment and adhesion strength of the primary cell surface interaction was higher on the microgrooved surfaces than on SLA surfaces. The proliferation rate of cells and the synthesis of bone-specific proteins were higher on microgrooved surfaces in contrast to SLA surfaces. Ultrastructural analysis revealed phenotypic osteoblast-like cells on smooth and microgrooved surfaces, whereas cells on SLA surfaces showed a more fibroblastic appearance. This study demonstrates that the morphology of the implant surface determined the subsequent osteoblast reaction. An optimal cell reaction was found at surfaces which are smooth in the microenvironment of osteoblasts.

Animals↗
PubMed2005

Aspects of collagen mineralization in hard tissue formation.

Collagen is the dominant fibrous protein not only in connective tissues but also in hard tissues, bone, dentin, cementum, and even the mineralizing cartilage of the epiphyseal growth plate. It comprises about 80-90% (by weight) of the organic substance in demineralized dentin and bone. When collagen fibers are arranged in parallel to form thicker bundles, as in lamellar bone and cementum, interior regions may be less mineralized; in dentin, however, the collagen fibers form a network and collagen fibers are densely filled with a mineral substance. In the biomineralization of collagen fibers in hard tissues, matrix vesicles play a fundamental role in the induction of crystal formation. The mineralization of matrix vesicles precedes the biomineralization of the collagen fibrils and the intervening ground substance. In addition, immobilized noncollagenous fibrous macromolecules, bound in a characteristic way to the fibrous collagen surface, initiate, more intensely than collagen, mineral nucleation in the hard tissue matrix.

Animals↗
PubMed2005

[Fritz hauschild (1908-1974) and drug research in the 'German Democratic Republic' (GDR)].

The chemist and pharmacologist Fritz Hauschild developed the sympathomimetic agent Pervitin (metamphetamin) in the 1930s. Not only because of the abuse of the stimulant during the Second World War ("pilot's chocolate") it is one of the most controversial substances in drug history. Nearly forgotten are Hauschild's contributions to build up the drug system in the GDR. Although he was a convinced communist, the skilful pharmacologist gave very early warning of the imminent lack of innovation in the GDR pharmaceutical industry. A letter which he addressed to the Minister of Health, Max Sefrin (born 1913), did not lack explicitness.

Central Nervous System Stimulants↗
PubMed2004

Branched chain amino acids as a parameter for catabolism in treated phenylketonuria.

This study was performed to study an association between nutritional status on one hand and BCAA- and Phe-concentrations on the other hand in PKU patients free of infection. AA profiles from 70 PKU patients were measured. 9 patients (subgroup I) with elevated Phe- and BCAA-concentrations as well as 23 patients (subgroup II) with only elevated Phe-levels were included. Dietary records were obtained from both groups; low caloric intake in subgroup I was increased with Duocal or p-am ANAMIX without modifying total protein- and Phe-intake. AA profiles were controlled after 2 weeks. Additionally, we investigated AA profiles from 26 liver transplanted patients with increased carbohydrate and caloric intake as an example for anabolism. In subgroup I Phe- and Isoleu-concentrations decreased sign. After dietary intervention. Leu, Val and Tyr levels decreased not sign. Initial Phe-levels correlated negatively with protein and caloric intake. BCAA concentrations of liver transplanted patients receiving high amounts of carbohydrates were in the lower range of normal. Increased caloric intake lowered most of the elevated Phe- and BCAA- concentrations.

Adolescent↗
PubMed2004

[Peri-implant bone formation around cylindrical and conical implant systems].

BACKGROUND: The treatment of patients with early or immediately loaded dental implants has renewed interest in the behavior of osseointegration at the implant surface. Whereas it is generally accepted that peri-implant tissue formation and mineralization are dependent on the local mechanical environment in the interface zone, controversies exist concerning the impact of implant design on peri-implant bone formation. The aim of the present study was the in vivo evaluation of peri-implant bone formation by two different implant systems: cylindrical (ITI) versus conical (ILI). MATERIAL AND METHOD: A total of 60 implants (30 ITI and 30 ILI) were placed in the cranial and caudal part of the tibia of eight Göttinger minipigs. Half of the minipigs were sacrificed at 7 days and 28 days of osseointegration. Implant-containing bone specimens were prepared for histological and ultrastructural investigations. RESULTS: Histological and scanning electron-microscopic investigations showed a direct contact of bone-like minerals over the whole implant surface from day 7 of implant/bone interaction. Whereas the ILI implant showed direct contact up to the top of the crestal bone, ITI implants demonstrated a crestally located narrow gap without ossification over the whole experimental period. CONCLUSION: Our investigations support the hypothesis of an implant design-inherent emergence and maintenance of crestal bone.

Animals↗
PubMed2004

Ultrastructural characterization of the implant/bone interface of immediately loaded dental implants.

Primary stability and an optimized load transfer are assumed to account for an undisturbed osseointegration process of implants. Immediate loaded newly designed titanium dental implants inserted in the mandible of minipigs were used for the characterization of the interfacial area between the implant surface and the surrounding bone tissue during the early healing phase. Histological and electron microscopical studies were performed from implant containing bone specimens. Two different load regimens were applied to investigate the load related tissue reaction. Histological and electron microscopical analysis revealed a direct bone apposition on the implant surfaces, as well as the attachment of cells and matrix proteins in the early loading phase. A striking finding of the ultrastructural immunocytochemical investigations was the synthesis and deposition of bone related proteins (osteonectin, fibronectin, fibronectin receptor) by osteoblasts from day one of bone/biomaterial interaction. Calcium-phosphate needle-like crystallites were newly synthesized in a time-related manner directly at the titanium surface. No difference in the ultrastructural appearance of the interface was found between the two loading groups. Our experimental data suggest that loading of specially designed implants can be performed immediately after insertion without disturbing the biological osseointegration process.

Animals↗