Biomedical subjects

M Richter

Publications and source records attributed to M Richter.

At least 109 records · Page 6Linked to original sources

PubMed2000

Effects of eicosanoids, neuromediators and bioactive peptides on murine airways.

The effects of several mediators including prostanoids, neuromediators, bioactive peptides and leukotrienes were investigated on the trachea, upper bronchi, lower bronchi and lung parenchyma of selected strains of mice mounted in a cascade superfusion system. The upper airways (trachea, upper bronchi) responded with greater maxima than lower airways (lower bronchi, lung parenchyma). Acetylcholine, carbachol, serotonin and 9, 11-dideoxy-9alpha,11alpha-epoxymethano-prostaglandin F(2alpha)serotonin>/=acetylcholine. Prostaglandins E(2), F(2alpha) and D(2)90% relaxation in some cases. The rank order of potency for the prostaglandins was E(2)>/=F(2alpha)D(2) with the exception of the lower bronchi on which prostaglandins had the following order of potency: F(2alpha)>/=E(2)D(2). The effects of prostaglandins were similar in four commonly used strains of mice (CD-1, BALB/c, C57BL/c6 and C3H) with some variations in efficacy. Iloprost was a weak mouse airway relaxant. It had the greatest effect on the trachea and bronchi of BALB/c and C57BL/c6 mice, whereas it had little or no effect on the airways of the CD-1 and C3H mouse strains. Vasoactive intestinal peptide potently relaxed the carbachol and precontracted the mouse trachea and bronchi. However, vasopressin, another bioactive peptide, potently and efficaciously contracted the mouse trachea and upper bronchi but had little effect on the lower bronchi. Vasopressin was the most potent and efficacious contractile agonist tested in this study. Contractions were observed with endothelins-1, -2 and -3 on mouse trachea and bronchi, but marked tachyphylaxis was present. Sarafotoxin s6c followed the same pattern suggesting the presence of endothelin ET(B) receptors on the mouse airways. Of all leukotrienes assayed (B(4), C(4), D(4) and E(4)) only leukotriene C(4) weakly contracted the mouse trachea and upper bronchi, but tachyphylaxis was most evident.

Animals↗

PubMed2000

Computer-assisted surgery in posterior instrumentation of the cervical spine: an in-vitro feasibility study.

Transarticular C1/2 screws are widely used in posterior cervical spine instrumentation. The use of pedicle screws in the cervical spine remains uncommon. Due to superior biomechanical stability compared to lateral mass screws, pedicle screws can be used, especially for patients with poor bone quality or defects in the anterior column. Nevertheless there are potential risks of iatrogenic damage to the spinal cord, nerve roots or the vertebral artery associated with both posterior cervical spine instrumentation techniques. Therefore, the aim of this study was to evaluate whether C1/2 transarticular screws as well as transpedicular screws in C3 and C4 can be applied safely and with high accuracy using a computer-assisted surgery (CAS) system. We used 13 human cadaver C0-C5 spine segments. We installed 1.4-mm Kirschner wires transarticular in C 1/2, using a specially designed guide, and drilled 2.5-mm pedicle holes in C3 and C4 with the assistance of the CAS system. Hole positions were evaluated by palpation, CT and dissection. Forty-eight (92%) of the 52 drilled pedicles were correctly positioned after palpation, imaging and dissection. The vertebral artery was not injured in any specimen. All of the 26 C1/2 Kirschner wires were placed properly after imaging and dissection evaluations. No injury to vascular or bony structures was observed. C /2 transarticular screws as well as transpedicular screws in the cervical spine can be applied safely and with high accuracy using a CAS system in vitro. Therefore, this technique may be used in a clinical setting, as it offers improved accuracy and reduced radiation dose for the patient and the medical staff. Nevertheless, users should take note of known sources of possible faults causing inaccuracies in order to prevent iatrogenic damage. Small pedicles, with a diameter of less than 4.0 mm, may not be suitable for pedicle screws.

Aged↗

PubMed2000

[Herpes simplex virus type 1-induced rising dbl quote, left (low)tumor" in the nasal vestibule. The problem of resistance development of herpes simplex in a patient with chronic lymphatic B-cell leukemia].

Herpes simplex viruses are known to be among the most common disease-causing microorganisms. Their prevalence can exceed 90% depending on the socioeconomic status of the population. Since the number of immunocompromised patients has increased because of the increased incidence in the acquired immunodeficiency syndrome and an increase in organ transplantation, herpes virus infection may have a greater clinical significance. While treatment of otherwise healthy individuals will not usually cause any clinical problems herpes infection in an immunocompromised patient can have severe consequences. Additionally, development of viral resistance can be observed that may require alternative drugs in treatment. We present a case history of a man with a B-cell chronic lymphocytic leukemia that was associated with a very unusual herpes simplex virus infection in the nasal vestibule. Possible causes for the development of resistance in herpes infections and the use of famciclovir and forscarnet as two therapeutic alternatives to aciclovir are discussed.

Antiviral Agents↗

PubMed2000

[Acceleration related injury of the cervical spine in restrained car drivers. Frequency, causes and long-term results].

In an analysis of 3,838 restrained car drivers, the proportion of acceleration related injury of the cervical spine increased from under 10 % in 1985 to over 30 % in 1997. These injuries occurred mainly in the case of head-on or multiple collisions. Letters were sent to 1,136 of the injured persons, and of the 138 patients who returned the questionnaires, 121 (88 %) were still suffering from their symptoms. It was a question of pain (74 %), tension (6 %) and stiffness (5 %) in the head (27 %), neck (55 %) and shoulder (8 %) area. The duration of the complaints was the longest after multiple collisions. In addition to a slight influence of the accompanying injuries on the duration of complaints, the individual constitution seems to be an important determining factor. In order to resolve the difficulties of conducting of this retrospective study, prospective studies are necessary which include documentation of diagnosis, treatment protocols, duration and type of complaints.

Accidents, Traffic↗

PubMed2000

[Mechanism of pelvic girdle injuries in street traffic. Medical-technical accident analysis].

During 1985 and 1993, 7,410 persons were injured in traffic accidents in the area of Hanover. Of these, 306 (4.1%) sustained a pelvic girdle injury. In 139 cases (45%), the pelvic girdle injuries were further classified (Pennal and Tile) and a technical reconstruction of the accident situation was performed. 52% were type A, 27% type B and 21% type C injuries. Some 47% of the casualties were vehicle occupants, 31% pedestrians, 12% motorcyclists and 10% cyclists. In restrained vehicle occupants pelvic girdle injuries occurred mostly in accidents with a delta-v of more than 30 km/h, whereas in unrestrained vehicle occupants, pedestrians and cyclists they also occurred with lower delta-v or collision speed. The percentage of type B and C injuries increased with higher velocities. In addition to further improvements in passive safety, lower collision speed or delta-v is necessary to reduce or prevent pelvic girdle injuries. The reconstruction of pelvic girdle injury mechanism in traffic accidents is possible, when both technical and medical parameters are considered.

Acceleration↗

PubMed2000

[Fractures of the upper extremity in restrained automobile front seat passengers. Injury pattern and incidence in relation to accident mechanism].

During 1985 and 1995, 3,260 restrained car drivers (1,228 front seat passengers) were injured in 9,380 crashes involving cars. 179 (5.5%) (front seat passengers: 53, 4.3%) of those sustained fractures, of the arm. Among the 384 single fractures the hand (25%), wrist (23%) and forearm (23%) were affected most often, elbow (9%), upper arm (10%) and shoulder (10%) rather seldom. Half of the evaluated fractures of the long tubular bones were type A-fractures due to the AO classification and the other two quarters, respectively type B- and C-injuries in each case. 16% were open fractures. No considerable differences of the injury mechanism were found comparing drivers and front seat passengers. Since over half of all fractures resulted from a direct impact to the hand and/or arm, modifications are necessary in order to improve the energy absorption by means of padding the dashboard and the inner door. The use of side- and front-airbags could serve as an additional auxiliary equipment, as long as it doesn't induce a supplemental stress, through unfolding of the airbag.

Accidents, Traffic↗

PubMed2000

Biomechanical evaluation of a new modular rod-screw implant system for posterior instrumentation of the occipito-cervical spine: in-vitro comparison with two established implant systems.

Posterior instrumentation of the occipito-cervical spine has become an established procedure in a variety of indications. The use of rod-screw systems improved posterior instrumentation as it allows optimal screw positioning adapted to the individual anatomic situation. However, there are still some drawbacks concerning the different implant designs. Therefore, a new modular rod-screw implant system has been developed to overcome some of the drawbacks of established systems. The aim of this study was to evaluate whether posterior internal fixation of the occipito-cervical spine with the new implant system improves primary biomechanical stability. Three different internal fixation systems were compared in this study: the CerviFix System, the Olerud Cervical Rod Spinal System and the newly developed Neon Occipito Cervical System. Eight human cervical spine CO/C5 specimens were instrumented from C0 to C4 with occipital fixation, transarticular screws in C1/C2 and lateral mass or pedicle screws in C3 and C4. The specimens were tested in flexion/extension, axial rotation, and lateral bending using pure moments of +/- 2.5 Nm without axial preload. After testing the intact spine, the different instrumentations were tested after destabilising C0/C2 and C3/C4. Primary stability was significantly increased, in all load cases, with the new modular implant system compared to the other implant systems. Pedicle screw instrumentation tended to be more stable compared to lateral mass screws; nevertheless, significant differences were observed only for lateral bending. As the experimental design precluded any cyclic testing, the data represent only the primary stability of the implants. In summary, this study showed that posterior instrumentation of the cervical spine using the new Neon Occipito Cervical System improves primary biomechanical stability compared to the CerviFix System and the Olerud Cervical Rod Spinal System.

Biomechanical Phenomena↗

PubMed2000

Load-displacement properties of the normal and injured lower cervical spine in vitro.

The objective of this study was to determine which discoligamentous structures of the lower cervical spine provide significant stability with regard to different loading conditions. Accordingly, the load-displacement properties of the normal and injured lower cervical spine were tested in vitro. Four artificially created stages of increasing discoligamentous instability of the segment C5/6 were compared to the normal C5/6 segment. Six fresh human cadaver spine segments C4-C7 were tested in flexion/extension, axial rotation, and lateral bending using pure moments of +/- 2.5 Nm without axial preload. Five conditions were investigated consecutively: (1) the intact functional spinal unit (FSU) C5/6; (2) the FSU C5/6 with the anterior longitudinal ligament and the intertransverse ligaments sectioned; (3) the FSU C5/6 with an additional 10-mm-deep incision of the anterior half of the anulus fibrosus and the disc; (4) the FSU C5/6 with additionally sectioned ligamenta flava as well as interspinous and supraspinous ligaments; (5) the FSU C5/6 with additional capsulotomy of the facet joints. In flexion/extension, significant differences were observed concerning range of motion (ROM) and neutral zone (NZ) for all four stages of instability compared to the intact FSU. In axial rotation, only the stage 4 instability showed a significantly increased ROM and NZ compared to the intact FSU. For lateral bending, no significant differences were observed. Based on these data, we conclude that flexion/extension is the most sensitive load-direction for the tested discoligamentous instabilities.

Aged↗

PubMed2000

Whiplash-type neck distortion in restrained car drivers: frequency, causes and long-term results.

An analysis was made of 1176 whiplash-type neck distortions taken from a total of 3838 restrained car driver incident reports. The percentage of whiplash-type neck distortion among injured drivers increased from less than 10% in 1985 to over 30% in 1997. Most occurred in head-on crashes or crashes with multiple collisions; only 15% occurred in rear-end collisions. More than 1,000 questionnaires were sent to the injured to find out about the duration and type of complaints caused by their cervical spine injury. Although only 138 (12%) returned the questionnaire, which may not be a representative sample, a further analysis was carried out. Of the 138, 121 (88%) indicated that they had suffered or were still suffering from their symptoms. The percentages of the various complaints were as follows: pain (74%), tension (6%) and stiffness (5%) in the head (27%), neck (55%) and shoulder (8%). The duration of the complaints was longest after multiple collisions and when the onset of complaints was longer than 24 h after trauma. Women and elderly persons predominated slightly in the group with longer duration of complaints. A correlation between the severity of the accompanying injuries and duration of complaints was found. Lack of adequate follow-up for patients with less severe injuries posed considerable difficulties for this retrospective study. In order to better evaluate this problem, prospective studies are necessary, with documentation including diagnosis, treatments, complaint duration and type.

Accidents, Traffic↗

PubMed2000

Functional magnetic resonance imaging with intermolecular multiple-quantum coherences.

For the first time, we demonstrate here functional magnetic resonance imaging (fMRI) using intermolecular multiple-quantum coherences (iMQCs). iMQCs are normally not observed in liquid-state NMR because dipolar interactions between spins average to zero. If the magnetic isotropy of the sample is broken through the use of magnetic field gradients, dipolar couplings can reappear, and hence iMQCs can be observed. Conventional (BOLD) fMRI measures susceptibility variations averaged over each voxel. In the experiment performed here, the sensitivity of iMQCs to frequency variations over mesoscopic and well-defined distances is exploited. We show that iMQC contrast is qualitatively and quantitatively different from BOLD contrast in a visual stimulation task. While the number of activated pixels is smaller in iMQC contrast, the intensity change in some pixels exceeds that of BOLD contrast severalfold.

Brain↗

PubMed2000

New approach in the therapy of chronic rejection? ACE- and AT1-blocker reduce the development of chronic rejection after cardiac transplantation in a rat model.

BACKGROUND: Angiotensin II is one of the most potent mitogens of smooth muscle cell proliferation and plays a central role in the development of accelerated coronary artery disease (ACAD), which remains a serious consequence after heart transplantation and limits long-term survival. We investigated the effect of an angiotensin-II blocker, Losartan (angiotensin II Type 1 [AT(1)]-blocker), and an angiotensin-converting enzyme (ACE) inhibitor, Enalapril, on experimental ACAD in a rat cardiac transplant model (Fisher to Lewis). METHODS: After grafting, recipients were treated with 10 mg/kg/day per os Losartan or 40 mg/kg/day per os Enalapril. Two groups of animals received additional pre-treatment with Losartan or Enalapril 7 days before transplantation. All study groups, including the control group, received immunosuppression with cyclosporine (3 mg/kg/day sub-cutaneously). We assessed the extent of ACAD of large and small arteries 80 days after grafting using digitizing morphometry. RESULTS: We observed significant reduction of neointimal proliferation in small arteries in Losartan pre- and post-treated and in Enalapril pre-treated recipients compared with the cyclosporine-treated group (p < 0.05). In epicardial arteries, Enalapril pre- and post-treatment as well as Losartan post-treatment significantly reduced neointimal formation compared with the control group. Reduction of neointima by Enalapril post-treatment in small arteries and Losartan pre-treatment in large arteries trended toward but failed statistical significance. CONCLUSIONS: Our results suggest the important role of the renin-angiotensin system in neointimal proliferation, which can be reduced equally with ACE inhibitors or the angiotensin-II blocker. Therefore AT(1) blockade with Losartan is a useful therapeutic strategy for inhibition of ACAD after cardiac transplantation.

Angiotensin II↗

PubMed2000

[Is appendectomy really performed too frequently? Results of the prospective multicenter study of the Swiss Society of General Surgery].

Scientific publications and provoking criticism from the lay press have recently pointed out, that appendices may be surgically removed too frequent and without indisputable necessity. In an attempt to verify these questionable statements, the Swiss Society for General Surgery (SGAC) initiated a prospective controlled multi center trial. From September 1997 to December 1998, hundred and twenty-five institutions documented 4603 appendectomies performed due to a suspected appendicitis. Histological investigation of all specimens revealed a 7% rate of normal appendices, 7.2% for patients with national health service (NHS) and 5.9% for patients with private insurances respectively. Compared to the results of the literature, where a frequency of normal appendices around 15% is judged as standard, these results are excellent. In 17.2% of the patients (15.9% NHS and 23.6% privately insured patients) an "appendicitis perforata" was observed. This percentage remains in the range reported by other authors. The analysis of time of admission (i.e. day or night) and the delay from admission to surgery shows a distribution independent to the insurance of the patients. Therefore, the planned appendectomy for patients with private insurances does not exist. A different choice of the surgical technique could be observed depending on the insurance status. In 30.4% of the private insured patients a laparoscopic appendectomy was performed as compared to 22.6% of patients with NHS. Surprisingly, an identical median hospitalization time can be observed for both groups (laparoscopic 5.5 days, open surgery 5.5 days).

Adolescent↗

PubMed2000

Probing protein-protein interactions in real time.

We have used a prototype small cantilever atomic force microscope to observe, in real time, the interactions between individual protein molecules. In particular, we have observed individual molecules of the chaperonin protein GroES binding to and then dissociating from individual GroEL proteins, which were immobilized on a mica support. This work suggests that the small cantilever atomic force microscope is a useful tool for studying protein dynamics at the single molecule level.

Aluminum Silicates↗

PubMed2000

Improvement of pain and function after arthroscopy and arthrocentesis of the temporomandibular joint: a comparative study.

In 1993 and 1994, 720 patients with pain in the temporo-mandibular joint area were examined and treated. The authors describe their therapeutic protocol. Sixty-two patients were not relieved by conservative nonsurgical therapy and were treated by arthroscopy or arthrocentesis. In both groups the differences in functional result and in pain control were analysed. Results show that both arthroscopy and lavage are useful in improving function and diminishing pain. Arthroscopy shows better results for functional treatment whereas arthrocentesis and arthroscopy show similar results in pain control.

Adolescent↗

PubMed2000

[Osteosynthesis with resorbable hemi-cerclage in metacarpal fractures].

The use and results of biodegradable hemicerclages for metacarpal fracture fixation were reviewed retrospectively. A total of 92 metacarpal fractures in 78 patients were treated with polyglycolic or polydioxanon sutures. Study parameters included time for bony union, duration of immobilisation, total active range of motion, and complications. The hemicerclage achieved rigid fracture fixation and permitted early mobilisation exercises without jeopardizing bony union. Immobilization of metacarpals was performed for a median of 3.4 (1.5 to 6) weeks. There were no complications of wound healing. Adequate bony union was achieved after a median of 4.5 weeks (3.5 to 7 weeks). In one case, premature loading of the fracture led to displacement and delayed union. At the end of treatment (6.1 [4 to 7.5] weeks), total active range of motion was 98 (85 to 100)%. Ideal indications are oblique or torsion fractures of the metacarpals. In these cases, immobilisation up to wound healing is sufficient.

Adolescent↗

PubMed2000

Effects of indoor painting and smoking on airway symptoms in atopy risk children in the first year of life results of the LARS-study. Leipzig Allergy High-Risk Children Study.

INTRODUCTION: The Leipzig Allergy High-Risk Children Study (LARS) is a prospective nested cohort control study about the influence of chemical indoor exposure in dwellings on the health outcome of atopy-risk children during the first years of life. DESIGN AND METHODS: 475 premature children and children with allergic risk factors have been selected out of the 1995/1996 birth cohort in the city of Leipzig. Twenty-five volatile organic compounds (VOC) were measured in the infant's bedrooms using passive sampling systems for 4 weeks after birth. The babies underwent a medical examination at the age of six weeks and 1 year. The parents answered a questionnaire. RESULTS: Correlations between VOC exposures and infections were calculated by multiple logistic regression. Selected VOC show a direct association to actually painted dwellings (OR = 2.4; 95% Cl 1.1-5.3). An increase of risk of pulmonary infections was observed in infants aged 6 weeks if restoration (painting OR 5.6; 95% Cl 1.3-24.0) or flooring connected with painting had occurred during the pregnancy period. Higher concentration of styrene (> 2.0 micrograms/m3, indicator for flooring) elevated the risk of pulmonary infections in six-week-old infants (OR = 2.1; 95% Cl 1.1-4.2). Environmental benzene > 5.6 micrograms/m3 increased the risk of airway infections in six-week-old babies (OR = 2.4; 95% Cl 1.28-4.48). Smoking in the dwelling (OR = 2.0; 95% Cl 1.1-3.5) as well as restoration (OR = 1.9; 95% Cl 1.1-3.5) are also risk factors of the development of wheezing in the one-year-old child. CONCLUSIONS: The data give indications in order to prevent allergies and chronic lung diseases in atopy risk children exposure to chemicals from indoor air should be minimised from birth on.

Air Pollution, Indoor↗

PubMed2000

Upper extremity fractures in restrained front-seat occupants.

BACKGROUND: The aim of our study was to analyze the injury mechanism of upper extremity fractures in car crashes, to create a basis for developing prophylactic devices. METHODS AND RESULTS: During 1985-1995, 3,260 restrained car drivers (1,228 front-seat passengers) were injured in 9,380 crashes involving cars. A total of 179 drivers (5.5%) (front-seat passengers: n = 53, 4.3%) sustained fractures of the arm. The hand (25%), wrist (23%), and forearm (23%) were affected most often, and the elbow (9%), upper arm (10%), and shoulder (10%) were seldom affected. No considerable differences of the injury mechanism were found comparing drivers with front-seat passengers. Fractures were mainly caused by head-on collisions (n = 119, 51%) or multiple collisions (n = 78, 34%). In 73% of the crashes (n = 166), delta-v exceeded 30 km/h (18.6 mph). A lower Delta-v resulted mainly in fractures affecting the shoulder and wrist. CONCLUSION: Because more than half of the upper extremity fractures resulted from a direct impact to the hand, arm, or both, modifications to improve the energy absorption by padding dashboard and inner door or by additional airbags are promising.

Abbreviated Injury Scale↗

PubMed2000

Albumin-mediated regulation of cellular glutathione and nuclear factor kappa B activation.

Human serum albumin (HSA) is a cystine-rich serum protein taken up by many cells through receptor-mediated and fluid-phase endocytosis. We hypothesized that HSA may play a role in modulating cellular antioxidant redox signaling. Lung epithelial cells (A549), fibroblasts (HFL1), and blood lymphocytes had increased glutathione (GSH) levels after 8 h incubation with HSA. Similar GSH increases were observed with either plasma-derived or recombinant HSA. Serum depleted of HSA had no effect on cellular GSH. The GSH increase was also observed in normal murine lungs upon in vivo airway instillation of HSA. GSH enhancement was not related to the redox state of the free cysteine residue (Cys-34) on HSA, however, reduction of disulfide bonds in HSA inhibited the increase in cellular GSH. In addition, the albumin-mediated increase in GSH was inhibited by the vacuolar (H(+))-ATPase inhibitors, bafilomycin A(1) and concanamycin, as well as by the membrane pH-disrupting ionophore monensin, but not by 20 mM NH(4)Cl. The degree to which albumin increased GSH levels was sufficient to protect cells against H(2)O(2)-mediated cytotoxicity and to decrease TNF-alpha-mediated NF-kappaB activation. We conclude that albumin specifically modulates cellular GSH levels, an effect sufficient to protect cells against oxidant injury and regulate NF-kappaB activation.

Cell Line↗