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Biomedical subjects

M Fritz

Publications and source records attributed to M Fritz.

At least 19 recordsLinked to original sources
PubMed1995

Imaging soft samples with the atomic force microscope: gelatin in water and propanol.

We have imaged mica coated with thin gelatin films in water, propanol, and mixtures of these two liquids by atomic force microscopy (AFM). The elastic modulus (Young's modulus) can be tuned from 20 kPa to more than 0.1 GPa depending on the ratio of propanol to water. The resolution is best in pure propanol, on the order of 20 nm, and becomes worse for the softer samples. The degradation in resolution can be understood by considering the elastic indentation of the gelatin caused by the AFM tip. This indentation becomes larger and thus the contact area becomes larger the softer the sample is. Therefore this study may be used to estimate the resolution to be expected with an AFM on other soft samples, such as cells. Nondestructive imaging was possible only by imaging at forces < 1 nN. This was difficult to achieve in contact mode because of drift in the zero load deflection of the cantilever, supposedly caused by temperature drift, but straightforward in tapping mode.

1-Propanol↗
PubMed1995

Succession of putative peri-implant pathogens after root-form and plate-form implant placement in partially dentate adult monkeys.

This report describes the succession of putative peri-implant pathogens in partially dentate monkeys after dental implantation and prosthetic reconstruction. Tooth and implant (6 root-end form, 4 blade-vent implants) sites in eight monkeys were monitored microbiologically and clinically during the pre-implant stage, abutment connection stage, bridge placement stage, and three and six months after the bridge placement stage. Tooth and implant sites were cleaned monthly post-extraction. Microbiological studies included dark field microscopy, selective and non-selective culture, and primary phenotypic characterization of culture isolates. After implant surgery, the median proportion of several putative peri-implant pathogens studied were significantly elevated. Following fixture placement, P. intermedia replaced P. melaninogenica as the predominant Black Pigmented Anaerobic Bacilli (BPAB) in the mouth. After abutment connection stage, levels of P. intermedia, A. actinomycetemcomitans, F. nucleatun, Haemophilus sp. and spirochetes were significantly elevated at implant and tooth sites. Three months after bridge installations, P. intermedia and A. actinomycetemcomitans remained significantly elevated at implant sites. At six months after bridge installation, levels of P. intermedia, F. nucleatum and A. actinomycetemcomitans declined significantly relative to levels at three months. Porphyromonas sp. and spirochetes were not significantly elevated although their levels correlated with gingival redness. P. intermedia, Porphyromonas sp. and spirochetes levels correlated significantly with probing depth. Correlation was detected between P. gingivalis and spirochetes; and between A. actinomycetemcomitans and F. nucleatum. Our studies show a transitional increase in levels of several organisms resembling putative pathogens of human peri-implant infection, associated with implant placements in partially edentulous mouths and supports early prophylactic interventions to control their levels.

Aggregatibacter actinomycetemcomitans↗
PubMed1995

[Effect of vaginal estrogen therapy on urinary incontinence in postmenopause].

A depot preparation of Estriol (Ortho Gynest D; 3.5 mg Estriol, intravaginal) was applied for 3 months to 135 postmenopausal women with urinary incontinence. Before and after treatment the symptoms of incontinence were scaled by the Gaudenz questionnaire. 8 symptoms were tested for statistical significance. All of them had significantly improved after treatment. 63% of patients showed improvement of their incontinence, urinary stress incontinence improved in 50%. Dysuria was reported by 14 patients before treatment, by none after treatment. Daytime and nighttime micturition frequency both decreased significantly, also subjective impairment by incontinence. Thus the local application of Estriol ovula represents an effective mode of primary treatment (maintenance therapy, one dose per week) in postmenopausal patients with urinary incontinence.

Administration, Intravaginal↗
PubMed1995

[Standards in pediatric pacemaker therapy].

Despite differences between pediatric and adult pacing have narrowed, implantation procedures in children require special considerations. Patients are physically smaller, they often suffer from complex cardiac defects necessitating further open heart surgery procedures. As there are no pacemakers and only some electrodes designed specially for pediatric pacing, selection of appropriate systems is important. At this time we care for 18 patients with a mean age of 11.5 +/- 6.5 years (= 138.6 +/- 78.4 months, range 10 to 280 months). 50% of them received a permanent pacemaker because of surgically induced heart block, 33.3% because of congenital complete heart block and 16.7% because of sick sinus syndrome. Mean age at first pacemaker implantation was 57 +/- 42 months (Range 0 to 120 months). 72.2% of these children had their first pacing system implanted in the abdominal wall with an epicardial electrode, 27.8% had endovenous endocardial electrodes with subpectoral generator placement. 72.2% of our patients had already revisions of their pacing systems, mean longevity time of pulse generators were 36.8 +/- 21.8 months. Upgrading from single chamber pacing to physiological AV-sequential dual chamber pacing was performed at a mean age of 9.0 +/- 2.8 years (= 108.3 +/- 33.9 months, range 66 to 154 months). By reviewing our patient data we want to discuss present standards and guidelines of surgical pacemaker therapy in children and how to prevent potential complications.

Adolescent↗
PubMed1994

Direct observation of enzyme activity with the atomic force microscope.

The height fluctuations on top of the protein lysozyme adsorbed on mica were measured locally with an atomic force microscope operated in tapping mode in liquid. Height fluctuations of an apparent size of 1 nanometer that lasted for about 50 milliseconds were observed over lysozyme molecules when a substrate (oligoglycoside) was present. In the presence of the inhibitor chitobiose, these height fluctuations decreased to the level without the oligoglycoside. The most straightforward interpretation of these results is that the height fluctuations correspond to the conformational changes of lysozyme during hydrolysis. It is also possible, however, that the height fluctuations are, at least in part, the result of a different height or elasticity of the transient complex of lysozyme plus the substrate.

Adsorption↗
PubMed1994

Granula motion and membrane spreading during activation of human platelets imaged by atomic force microscopy.

The redistribution of platelet constituents during activation is essential for their physiological function of maintaining hemostasis. We report here about real time investigations of the activation of native human platelets under physiological conditions from the initial formation of filopodia to the fully spread form by atomic force microscopy. We followed the trafficking of granules and their interaction with the plasma membrane within single cells. Our results show movement of certain granula towards the lamellipodia. Analysis of this rearrangement and the subsequent enlargement of the platelet surface reveals details of the membrane spreading process. Images of living cells are presented that show the distribution of cytoskeletal components and membrane-bound filaments at a resolution of better than 50 nm. The local minimum forces between the tip and the platelets were estimated to be smaller than 60 pN. A model for the elastic contributions of the glycocalix to the tip/membrane interaction was developed using the theory of grafted polymers.

Biophysical Phenomena↗
PubMed1994

Mapping interaction forces with the atomic force microscope.

Force curves were recorded as the sample was raster-scanned under the tip. This opens new opportunities for imaging with the atomic force microscope: several characteristics of the samples can be measured simultaneously, for example, topography, adhesion forces, elasticity, van der Waals, and electrostatic interactions. The new opportunities are illustrated by images of several characteristics of thin metal films, aggregates of lysozyme, and single molecules of DNA.

Adsorption↗
PubMed1994

A dominant negative mutant of PG13 suppresses transcription from a cauliflower mosaic virus 35S truncated promoter in transgenic tobacco plants.

TGA1a and PG13 constitute a family of tobacco basic leucine zipper (bZIP) proteins that bind to activating sequence-1 (as-1), which is one of the multiple regulatory cis elements of the cauliflower mosaic virus (CaMV) 35S promoter. After truncation of the CaMV 35S promoter down to position -90 (CaMV 35S [-90] promoter), transcription stringently depends on the presence of as-1, which is recognized by nuclear DNA binding proteins called ASF-1. The role of the TGA1a/PG13 bZIP family in the formation of ASF-1 and in transcriptional activation of the CaMV 35S (-90) promoter has not yet been demonstrated in vivo. We constructed transgenic tobacco plants expressing a mutant of potato PG13, which lacks its wild-type DNA binding domain. This mutant acts as a trans-dominant inhibitor of ASF-1 formation and of expression from the CaMV 35S (-90) promoter, showing that PG13 can specifically interact with proteins necessary for these processes. Although we did not observe any other obvious phenotypic changes, these transgenic plants are a potentially valuable tool in identifying whether TGA1a and PG13 are involved in controlling promoters encoded in the plant genome.

Bacterial Proteins↗
PubMed1994

[Balloon dilatation of postoperative and congenital aortic isthmus stenoses].

From July 1987 to December 1992, 52 patients underwent balloon-angioplasty of aortic coarctation at three units of pediatric cardiology in Austria (Graz = 35 patients, Innsbruck = 15 patients, and Vienna = 2 patients). 35 patients had postoperative and 17 had native coarctation. Mean age at intervention was 7 10/12 years with 2 patients under 1 year and 5 patients over 18 years old. The mean relation balloon diameter-coarctation diameter was 2.6 +/- 0.9. The blood pressure gradient between upper and lower extremities decreased from a mean of 44 +/- 16 mm Hg to 15 +/- 13 mm Hg (p < 0.0001). The diameter of the stenosed segment was increased from 5 +/- 3 mm to 8.5 +/- 3.5 mm (p < 0.0001). Native coarctation showed a significantly better result in respect to decrease of the gradient (36 +/- 12 mm Hg) than did postoperative coarctations (25 +/- 19 mm Hg) (p < 0.03). 13 patients did not respond adequately to angioplasty. 10 patients out of this group had tubular narrowings and belonged to the group of postoperative coarctations, whereas localized stenoses in native coarctations gave the best results. Localized wall irregularities were found in 4 patients with native coarctation. Balloon angioplasty of postoperative and native coarctations in childhood and adolescence is a secure and effective means of treatment and should be considered as therapy of first choice. The best results can be found in the group of the circumscript type of stenoses in native coarctation, whereas long and tubular stenoses in the group of postoperative coarctations give less satisfying results.

Adolescent↗
PubMed1993

In vitro activation of human platelets triggered and probed by atomic force microscopy.

We report on the activation of human platelets probed by atomic force microscopy under nearly physiological conditions. We could image native platelets in different stages of activation at a resolution of about 100 nm. Intracellular structures within the platelets could be resolved without staining. Furthermore we could trigger and follow the activation process of individual platelets, demonstrating that the platelets are still intact and are not destroyed or severely harmed by this novel imaging process.

Blood Platelets↗
PubMed1993

Actin binding to lipid-inserted alpha-actinin.

The interaction of alpha-actinin with lipid films and actin filaments was investigated. First alpha-actinin was incorporated in lipid films at the air/water interface. Injection of alpha-actinin into the subphase of a lipid monolayer led to a significant increase of the surface pressure only for lipid films consisting of a mixture of a negatively charged lipid with a high proportion of diacylglycerol. These alpha-actinin-containing films were transferred onto silanized quartz slides. Photobleaching experiments in the evanescent field allowed quantification of the lateral number density of the lipid-bound alpha-actinin. In combination with the area increase from the monolayer experiments, the photobleaching measurements suggest that alpha-actinin is incorporated into the lipid film in such a way that actin binding sites are accessible from the bulk phase. Binding experiments confirmed that the alpha-actinin selectively binds actin filaments in this configuration. We also showed that, in contrast to actin filaments which are adsorbed directly onto planar surfaces, the alpha-actinin-bound actin filaments are recognized and cleaved by the actin-severing protein gelsolin. Thus we have constructed an in vitro system which opens new ways for investigations of membrane-associated actin-binding proteins and of the physical behavior of actin filaments in the close neighborhood to membranes.

Actinin↗
PubMed1993

Sub-gingival microflora in Macaca mulatta species of rhesus monkey.

The Macaca mulatta species of rhesus monkey is one of several non-human primate (nhp) models for periodontal disease. This report presents the bacteriology of the gingival sulci in M. mulatta monkeys. Three sub-gingival sites (maxillary right central incisor, the disto-buccal of the mandibular left second molar and mesio-buccal of the mandibular right second molar) of 9 monkeys were evaluated clinically before scaling and 7 days after scaling. Plaque samples were obtained from sub-gingival sites before clinical examination and studied bacteriologically by dark field microscopy, selective and non-selective culture, and by primary phenotypic characterizations of culture isolates. Several gingival sites presented with mild gingival inflammation. Anaerobic and facultatively anaerobic bacteria were the predominant flora colonizing the gingival sulci. The major microbial groups were Haemophilus species (100% of sites; percentage of total anaerobic count (TAC): 21-51), Peptostreptococcus micros (89%, 7.5-29.5), Actinomyces sp. (85%, 7-27), Fusobacterium nucleatum (90%, 5-8), Actinobacillus actinomycetemcomitans (73%, 1.3-12), black-pigmented anaerobic rods (BPAR) (80%, 0.6-6.5) and oral streptococci (80%, 0.2-1.0). Microbial groups detected less often were Wolinella sp. (66%, 0-2.6), Capnocytophaga sp. (30%), Eikenella corrodens (4.7%, 0), Campylobacter sp. (28%, 0-0.1) and spirochetes (4.7%, 0-0.07). Seven days after gingival sites were scaled, the plaque score and indices for gingival inflammation declined significantly. The gingival flora after scaling were characterized by lower proportions of the Actinomyces sp., P. micros and BPAR; and increased proportions of the oral streptococci, relative to pre-scaling levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Actinomyces↗
PubMed1992

From molecules to cells: imaging soft samples with the atomic force microscope.

Since its invention a few years ago, the atomic force microscope has become one of the most widely used near-field microscopes. Surfaces of hard sample are imaged routinely with atomic resolution. Soft samples, however, remain challenging. An overview is presented on the application of atomic force microscopy to organic samples ranging from thin ordered films at molecular resolution to living cells. Fundamental mechanisms of the image formation are discussed, and novel imaging modes are introduced that exploit different aspects of the tip-sample interaction for local measurements of the micromechanical properties of the sample. As examples, images of Langmuir-Blodgett films, which map the local viscoelasticity as well as the friction coefficient, are presented.

Actin Cytoskeleton↗
PubMed1991

An improved biomechanical model for simulating the strain of the hand-arm system under vibration stress.

In order to define relationships between the vibration stress and the strain of the human hand-arm system a biomechanical model was developed. The four masses of the model representing the hand, the forearm and the upper arm were connected by dampers and springs in two perpendicular directions. Simulating muscle activity, damped torsion springs were included additionally. The motions of the model were described by a differential matrix equation which was solved by using a 'transfer matrix routine' as well as by numerical integration. Thus, functions with harmonic or transient time courses could be selected as an excitation. The simulated vibrations were compared with those of other hand-arm models. The forces and torques transmitted between the masses, and the energy dissipated by the dampers were computed for several combinations of exciter frequencies and accelerations. The dependence of torques upon excitation agreed fairly well with the behaviour of the arm muscles under vibration as described by various investigators. At frequencies above 100 Hz the energy was dissipated mainly by the dampers between the masses near to the exciter. Transferring this result to the hand-arm system it shows that at high frequencies energy is dissipated by the hand and its palmar tissues and this might be one cause for the incidence of vibration-induced white finger disease.

Arm↗
PubMed1990

[Treatment of advanced pancreatic cancer with 5-fluorouracil, 4-epidoxorubicin and mitomycin C (FEM II). From the Chemotherapy of Gastrointestinal Tumors Group].

In a multicentre phase II trial, 20 patients with advanced pancreatic carcinoma were treated with 5-fluorouracil, 4-epidoxorubicin and mitomycin C, in which 4-epidoxorubicin was administered by escalated dose and split course (FEM II). From among 12 patients evaluable for response, 2 partial and 1 minimal remission were observed, suggesting a response rate of 25%. Four patients (30%) showed a no change and 5 progression. The median survival of all patients was 3.4 months, of the responders 8.4 months, of those with no change 5.2, and of those showing progression 3.4 months. Considerable nausea/vomiting and leukopenia was observed. The preliminary data suggest that the FEM II regimen does not offer any progress in terms of efficacy, survival and toxicity for advanced pancreatic carcinoma.

Adult↗
PubMed1990

Child health care policy and delivery in France.

Medical and social protection of mothers, infants, and children began in France more than a century ago. A number of laws and regulations have improved the system, which is discussed in detail. The discussion includes an overview of health policy, service delivery, and the financing of care. Is the current French system of Maternal and Child Health responsible for the good health of today's children? This question is addressed through selected examples. Finally, failures and short-comings of the system are described, including the persistence of underserved groups, unequal access to care, and other problems. Solutions are feasible, and some are now being implemented.

Adolescent↗
PubMed1989

[Utilization of helicopters for the prevention of secondary cerebral lesions in severe craniocerebral injuries].

The prehospital emergency treatment of craniocerebral trauma tries to avoid secondary cerebral lesions by controlling respiration and circulation. The therapy consists of heavy sedation with Midazolam, analgesia with morphine, artificial hyperventilation, PaO2 over 12 kPa and average arterial pressure above 80 mmHg. Our series of 46 patients recovered between 1982-1988 had a hospital mortality of 23%. 46% of the patients were polytraumatized. A normal neurologic state 6 months from the accident was registered in 86.4%. For 13.6% it was slightly pathological and no vigilant coma state was reported. The most effective rehabilitation method at the site of the accident has to secure the cerebral oxygen supply and reduce potential increase in intracranial pressure for avoid secondary cerebral lesions.

Adult↗