[Enamel and dentin under the ultrasonic microscope]. / Schmelz und Dentin im Bild des Ultraschallmikroskopes.

Ultrasonic reflection scanning microscopy is a new method for imaging the known structures of dental hard tissues on the basis of a simple specimen preparation. The specimens are scanned in a physiologic humid environment. Particularly high-contrast images are obtained from enamel tufts and lamellae, dentin tubules and interglobular dentin.

A new method for the simultaneous presentation of low and high magnifications of microscopic specimens: application to in vivo studies of mesenterial capillaries.

By combining an incident light microscope (C. Zeiss) with an inverted camera microscope (ICM 405, C. Zeiss) having a common optic axis, it was possible to present simultaneously two microscope images of one object. These images were recorded by two television cameras and displayed on a single monitor with the aid of a video mixer (Pieper, Schwerte). This method was applied to intravital microscopy of mesenterial capillaries (rabbit and frog). It allowed the choice of a vascular network as an overview with the incident light microscope from which a suitable capillary segment for an electrical stimulation experiment could be selected and magnified with the transmitted light microscope. The results of its application provided proof that electrically induced constrictions in capillaries are independent of proximally or distally occurring vascular reactions. Capillaries of mesenteries in rabbits and frogs were stimulated with direct currents ranging from +0.015 micro A to +20 micro A. The constrictions were found to be reversible and reproducible. In addition capillary constrictions could also be produced by topical application of histamine and serotonin droplets applied to the surface of the mesentery. These observations may help to resolve the question of whether capillary contractility in the sense of Stricker (1865, 1876) is a biological mechanism.

Myoglobin-O2-saturation profiles in muscle sections of chicken gizzard and the facilitated O2-transport by Mb+.

It has been shown that the oxygen transport in intact muscle can be quantitatively determined using Mb as an oxygen indicator in the cryomicrophotometric method. 1) The influence of the parameters such as time, temperature, boundary PO2 and metabolism on the oxygen transport in sections of chicken gizzard could be quantitatively determined from measured MbsO2-profiles; 2) The MbsO2-profiles measured under various conditions can be reproduced using a mathematical model which considers not only the diffusion of dissolved O2 but also the facilitated diffusion as well as O2 consumption. From this mathematical results it can be concluded that the mobility of the Mb in the muscle cells is limited and that Mb in the PO2-region between 5 and 0 mmHg contributes to at most 40% to the total O2-transport in chicken gizzard.