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Biomedical subjects

G Graber

Publications and source records attributed to G Graber.

At least 19 recordsLinked to original sources
PubMed2002

Quantitative and qualitative analysis of in vivo Doppler signal enhancement of FS-069.

RATIONALE AND OBJECTIVES: In vivo lifetime of ultrasound (US) contrast agents is still limited and thus a cause for ongoing investigations of new substances. The purpose of this study was to determine the time intensity changes of the Doppler signals obtained within the femoral vein after two different doses of a new microsphere-based ultrasound contrast agent. METHODS: Twenty-four healthy male volunteers (mean age, 29; average weight, 76 kg) were included in this study. All underwent a triplex Doppler US examination after an intravenous bolus injection of 0.3 mL and 1.0 mL Optison. To examine the signal enhancement characteristics of this contrast agent the audio signal of the pulsed-wave spectral Doppler US was measured quantitatively using an audio analyzer, whereas velocity-encoded color Doppler examinations were scored qualitatively (score 0-3). RESULTS: The mean maximal enhancement of the audio signal at a dose of 1.0 mL FS-069 was significantly higher than with a bolus of 0.3 mL FS-069 (29 +/- 2 dB vs. 26 dB +/- 2 dB, P < 0.001). The time-intensity curves after each bolus injection yielded an early peak (one minute after the injection) followed by constantly decreasing signal intensities. The scoring of the velocity-encoded color Doppler US revealed an optimal enhancement (score 2) for 3 minutes and 20 seconds (0.3 mL Optison) and for 6 minutes (1.0 mL Optison), respectively. CONCLUSIONS: This study showed the capability of triplex Doppler ultrasound signal enhancement after Optison. 1.0 mL Optison proved to be the more appropriate dose for an optimal signal enhancement than 0.3 mL Optison.

Adult↗
PubMed2000

Electrophysiological control of ventricular rate during atrial fibrillation.

Thirteen anesthetized canine subjects (17-29 kg) were used to demonstrate that mild cervical left vagal stimulation could control ventricular rate effectively during atrial fibrillation (AF). Two studies are presented. The first study used six subjects to demonstrate the inverse relationship between (manually applied) left vagal stimulation and ventricular excitation (R wave) rate during AF. As left vagal stimulation frequency was increased, ventricular excitation rate decreased. In these studies, a left vagal stimulus frequency of 0-10 per second reduced the ventricular excitation rate from > 200/min to < 50/min. The decreasing ventricular excitation rate with increasing left vagal stimulation frequency was universal, occurring in all 26 trials with the six subjects. This fundamental principle was used to construct an automatic controller for use in the second study, in which seven subjects were used to demonstrate that ventricular rate can be brought to and maintained within a targeted range with the use of an automatic (closed-loop) controller. A 45-minute record of automatic ventricular rate control is presented. Similar records were obtained in all seven subjects.

Animals↗
PubMed2000

Developing a code of ethics for human cloning.

Under what conditions might the cloning of human beings constitute an ethical practice? A tendency exists to analyze human cloning merely as a technical procedure. As with all revolutionary technological developments, however, human cloning potentially exists in a broad social context that will both shape and be shaped by the biological techniques. Although human cloning must be subjected to technical analysis that addresses fundamental ethical questions such as its safety and efficacy, questions exist that focus our attention on broader issues. Asserting that cloning inevitably leads to undesirable consequences commits the fallacy of technological determinism and untenably separates technological and ethical evaluation. Drawing from the Report of the National Bioethics Advisory Committee and Aldous Huxley's Brave New World, we offer a draft "Code of Ethics for Human Cloning" in order to stimulate discussion about the ethics of the broader ramifications of human cloning as well as its particular technological properties.

Cloning, Organism↗
PubMed1996

Retention force changes in implant-supported titanium telescope crowns over long-term use in vitro.

Titanium is used to fabricate spherical and bar attachments for overdentures on osseointegrated implants. This in vitro study investigated the long-term effects of commercially pure titanium on the retention force of telescope crowns with conical interface. Combinations of various materials for the inner and outer crowns were tested. Telescope crowns of pure titanium showed retention force characteristics comparable to telescope crowns fabricated conventionally in a precious alloy.

Chromium Alloys↗
PubMed1994

A new concept of overdentures with telescope crowns on osseointegrated implants.

Primary splinting of fixtures with bar attachments has proven to be clinically effective for overdentures on osseointegrated implants in the edentulous mandible. However, in vitro investigations indicate that a more favorable force transfer to the individual fixtures can be attained by secondary splinting of four implants with tapered telescope crowns, compared to primary splinting with rigid or jointed bar attachments. Moreover, in contrast to jointed attachments, the telescope crowns ensure a stable denture position. These results underscore the need to clinically test telescope crowns as anchors for overdentures on osseointegrated implants. Telescope crowns on four implants allow an optimal restorative concept of overdentures with the bridgelike design of the removable suprastructure.

Crowns↗
PubMed1991

[Hybrid prosthesis implant-supported superstructures in edentulous jaw. 1. Case planning].

Dental literature covers a wide range of implant-based denture supports. Based on static/dynamic as well as preventive periodontal considerations, rigidly anchoring the removable superconstruction of hybrid dentures using secondary splinting of four implants with telescope crowns or readymade cap-andpost systems, is generally appropriate in cases where the lower jaw is toothless. This makes possible an impeccable bridgeshaped design for the main part of the dentures, with wide-open inter-implant rincing areas. Clinical experience has shown that, in comparison to bridge dentures or rigid bridgework, secondary splinting in reconstructions greatly simplifies oral hygiene, particularly for elderly patients.

Aged↗
PubMed1991

[Hybrid prosthetic implant supported suprastructures in edentulous mandible. Conus crowns and shell-pin-systems on HA-Ti-implants. 2. Prosthetic construction principles].

Dental literature covers a wide range of implant-based denture supports. Based on static/dynamic as well as preventive periodontal considerations, rigidly anchoring the removable superconstruction of hybrid dentures using secondary splinting of four implants with telescope crowns or readymade cap-andpost systems, is generally appropriate in cases where the lower jaw is toothless. This makes possible an impeccable bridge-shaped design for the main part of the dentures, with wide-open inter-implant rincing areas. Clinical experience has shown that, in comparison to bridge dentures or rigid bridgework, secondary splinting in reconstructions greatly simplifies oral hygiene, particulary for elderly patients.

Crowns↗
PubMed1990

[Therapy of masticatory dysfunction].

A representative sample of patients who had presented with masticatory dysfunction at our clinic was assessed immediately as well as after longer periods following therapy. The results of this epidemiologic study indicate that those cases in which isolated stressors constituted the main etiologic factor are most responsive to therapy, but also most likely to recur. When occlusal interferences are involved, therapeutic success will depend heavily on the degree of destruction of the different articular structures. Patients presenting with psychic disorders causing somatic disturbances in the orofacial region or with primary TMJ affections such as polyarthritis or polyarthrosis are the most resistant to therapy.

Adolescent↗
PubMed1990

[The marginal accuracy of the fit of fixed adhesive ceramic inlays].

48 extracted human molars were restored with MOD inlays using 3 different ceramic systems: Dicor, Mirage and Vitadur N. For the Dicor system both the direct and indirect manufacturing procedures were used and all the necessary technical and clinical steps were performed. After being subjected to a thermal cycling stress test for 100 days, the teeth were ground sectioned for light microscopic examination. Sintered high-strength ceramic systems (Mirage and Vitadur N) displayed significantly better marginal adaptation than casted glass ceramic. In order to estimate the extent of the outer marginal gap, we measured the defective surface where the adhesive composite had disintegrated. The best possible marginal fit will certainly prolong the longevity of inlay restorations.

Ceramics↗
PubMed1989

[Construction and testing of a strain gauge for measuring masticatory force].

The main objective of this study was to establish and test a measuring system for monitoring occlusal forces and force cycles during mastication. A measuring module using strain gauge transducers was incorporated in the bridge-pontic of a three part test bridgework. A load cell was used intraorally for loading and calibration. The test bridges were incorporated in the patient's mouth and calibrated in vivo using variable loads. The recording system was a special intensifying and processing system (Alpha 3000, Hottinger-Baldwin Messtechnik, Darmstadt, West Germany). The percentage errors registered for every test bridge in various in-vitro tests were below 2%. Clinically, occlusal forces resulting during chewing of 4 types of food of different consistency were measured in 5 subjects. The results were shown as continuous force cycles which reflect cybernetic guidance patterns of the masticatory system.

Adult↗