Woodinine and its Stereomers - Absolute Configuration

The synthesis of all the four stereomers of the alkaloid woodinine ( 12a )¹⁾ is described and the stereochemical conclusions of Païs³⁾ and Still⁶⁾ are discussed. The absol. configurations of woodinine ( 12a ) and its diastereomer 8b are unequivocally deduced from the pertinent piperazinediones 16 and 17 .     

Effects of horizontal cell network architecture on signal spread in the turtle outer retina. experiments and simulations

In thePseudemys turtle retina five functionally distinct, electrically coupled networks of horizontal cells distribute signals in the outer plexiform layer. These networks differ significantly in their architecture, as determined by intracellular labeling with Neurobiotin after physiological recording and identification. The density of H1 horizontal cells is highest, ranging around 1800 cells/mm² at approximately 2.3 mm eccentricity. H1 horizontal cell somata are connected via 6–10 thin, short dendrites. The H1 horizontal cell axon terminal network is composed of thick axon terminals, forming a three-dimensional, sheath-like structure. Networks of coupled H2 and H3 horizontal cells have cell densities of around 210 cells/mm² and 350 cells/mm² respectively, at the same eccentricity of 2.3 mm. Cell bodies are connected with 6–12 long, thin dendrites. Here we report for the first time H4 horizontal cell networks. Cell density is approximately 970 cells/mm² at 2 mm eccentricity, and cell bodies are connected with 6–10 thin, short dendrites. General properties of passive voltage spread were compared for three of these horizontal cell networks using NeuronC. Realistic network architectures were obtained by digitizing the intracellularly labeled networks, respectively. One network obtained from coupled H1 horizontal cell bodies, one from coupled H1 horizontal cell axon terminals, and one from H2 horizontal cells were simulated. These three realistic networks were compared with an artificial, electrically coupled regular triangular network. Passive signal spread in these networks strongly depended on the exact network architecture using otherwise identical parameters. Changes in coupling strength affected signal spread in these networks differently. As in the experimental situation, changes in synaptic conductance influenced signal spread. Some principal effects of extensively coupled horizontal cells on photoreceptor signal processing were simulated with one type of photoreceptor connected by telodendria, synapsing onto an underlying triangular network and receiving feedback synapses. Under certain conditions, spatial information is coded in single photoreceptors. This was also the case in the experimental situation. In the simulation, spatial filter adjustment for optimal spatial coding in photoreceptors can be achieved by changing coupling strength in the horizontal cell network.     

The foundation of experimental ophthalmology by Theodor Leber

Theodor Leber grew up in Heidelberg as the son of a professor of Romance languages. Initially he planned to study natural sciences. Bunsen's advice led him to medicine. During his studies he succeeded in solving a competition problem posed by Helmholtz in the medical department. A short period of practical work in the eye hospital of Knapp was unsatisfactory. In Vienna with the physiologist Carl Ludwig, he was able in 1863/64, at the age of only 24 years, to demonstrate the blood circulation of the eye by color injections into the arteries and veins. Since that time the schematic drawings of his results can be found in every textbook of ophthalmology. On the occasion of the congress of the German Ophthalmological Society in Heidelberg in 1864, Theodor Leber reported on these findings and met with immense approval. In 1864–67 he followed an invitation as coworker of Liebreich to Paris; in 1867 he became A.v. Graefe's coworker in Berlin; in 1871 he moved to Göttingen, which became the first eye clinic with a laboratory for experimental investigations.The second epoch-making discovery accomplished by Leber was the detection of the fluid exchange in the eye. These results have also been confirmed by modern methods. Therefore, Theodor Leber can be called the father of experimental ophthalmology.     

Rheo-optical fourier transform infrared spectroscopy of polyurethanes and their blends with polyolefins

Rheo-optical Fourier transform infrared spectroscopy was used to analyze the orientational behavior of hard and soft segments of thermoplastic poly(ether urethane)s (TPU-Et) and poly(ester urethane)s (TPU-Es) and their blends with a 20 mass-% contribution of either polyethylene (PE) or polypropylene with an amorphous rubber phase (PP). The blends show a reduced stress level, lower elongation-to-break and a lower degree of orientation of the segments — especially for the TPU-Es blends — compared to those of pure TPU's when uniaxially elongated. Blends of TPU-Et with PP show reduced stress but increased strain compared to pure films of TPU-Et. This is caused by an improved adhesion of the rubber phase in the polypropylene and the polyether phase of TPU-Et. Optical micrographs visualize deformed polyolefin particles in elongated films of TPU-Et/PP blends. In the TPU-Et/PP blend we could achieve equivalent orientation for the polyolefin phase and the segments of TPU-Et caused by this higher phase adhesion compared to the other blends. Orientation functions (OF's) of absorption bands which specifically represent hard or soft polyurethane segments or which are characteristic of the polyolefin phase have been calculated to monitor the molecular alignment due to the mechanical treatment.     

Max Cloetta

Ohne Zusammenfassung     

Beitrag zur Kenntnis der diffusen Sklerose (klinisch,anatomisch-histologisch,erbbiologisch)

Ohne Zusammenfassung     

Über den wert der Kongorotprobe bei Krebskranken

Zusammenfassung Es wurde auf Grund von Beobachtungen an 50 Krebskranken der Wert und die Brauchbarkeit der Kongorotprobe als Funktionsprüfung des RES. untersucht. Als Ergebnis konnte festgestellt werden, daß die Methode einen eindeutigen Beweis für den Zusammenhang zwischen RES. und der Carcjnomabwehr des Körpers liefert, daß jedoch im Einzelfall der Ausfall der Probe keine sicheren prognostischen Schlüsse zuläßt. Denn die jeweils gefundene Speicherungsfähigkeit des RES. entspricht zwar durchschnittlich dem Allgemeinzustand und der vorhandenen Abwehrkraft, aber sie vermag uns nicht mehr zu sagen als der Gesamteindruck des Kranken und die übrigen klinischen Untersuchungsmethoden. Außerdem hat die Methode eine große Variations- und hohe Fehlerbreite. Die Gründe dafür wurden näher erörtert. Die Kongorotprobe hat also zweifellos eine Bedeutung als wissenschaftliches Experiment, aber sie stellt keine praktisch brauchbare Bereicherung der Untersuchungsmethoden bei Krebskranken dar.