118 



A. MAAS 



alcohol-methacrylate mixtures. Since the cell out- 

 growth is predominantly in monolayers, the respective 

 periods during which the tissue has to stay in the 

 various media from fixation to embedding may be 

 comparatively short. Cells were damaged by staying 

 too long in alcohol of a higher percentage, e.g. over 

 night. No shrinkage of cells was noticed by light 

 microscopic examination. The tissue was detached 

 from the bottle in the non-polymerized methacrylate 

 mixture, by means of a rubber-coated, bent glass 

 rod. By centrifuging the cell suspension at about 

 300-500 rpm for five minutes one gets a compact 

 sediment. When properly fixed, its color is a dirty 

 brown. 



Sedimentation was already effected in a butyl- 

 methyl-methacrylate mixture (4:1) with 2 % dichlor- 

 benzoylperoxide (3). The methacrylate mixture was 

 not polymerized preliminarily; however, the filled 

 gelatine capsules were evacuated for five minutes 

 before being deposited in the incubator in order to 

 ensure removal of gas pockets, which are easily 

 formed in sediments. Incubation was carried out at 

 48X for about 30 hrs. 



The ultrathin sections were prepared with an 

 ultra-microtome (Fernandez-Moran) placed at my 

 disposal by courtesy of Messrs. E. Leitz at Wetzlar. 

 The knife used is a diamond built into a container 

 to receive the sections. The container was filled with 

 an alcoholic solution of 25 %. The sections appeared 

 in the shape of an uninterrupted band and spread 

 out properly on the water surface within 15 minutes. 

 By heating the water it was possible to speed up this 



process without the quality of the sections deterio- 

 rating. The sections themselves showed grey-white 

 interference colors. The bands of sections were re- 

 ceived by mesh copper grids with a formvar film. 



The sections (fig. 1) were observed and photo- 

 graphs were taken in a Siemens electron microscope 

 Cm 100 c with stigmator and an aperture of 30 n 

 and an accelerating voltage of 60 kV. 



The examinations carried out have proved that it 

 is possible to obtain results which can easily be 

 reproduced by a simple method of preparation, such 

 as the preparation of sediments by trimming of the 

 cells from the culture containers. It enables both 

 infected and non-infected tissue cultures to be ex- 

 amined by electron microscopy. 



These investigations were kindly supported by Drs. 

 Grehn and Walter, Wetzlar. I also wish to extend my 

 thanks to Miss M. Hahn of the Behring-Werke for her 

 cooperation in preparing the sections and taking the 

 electron micrographs. 



References 



1. DuLBECco, R. and Vogt, M., /. Expil. Med. 99, 167 



(1954). 



2. Harford, C. G., Hamlin, A., and Parker, E., /. E.xptl. 



Med. 101, 6, 577 (1955). 



3. Newmann, S. B., Borysko, E., and Swerdlow, M., 



/. Research Nat. Bur. Standards 4, 43, 183 (1949). 



4. Stuart, D. C, Ann. Report 26 (1954). 



5. YouNGNER, J. S., Proc. Soc. E.xptl. Biol. Med. 85, 202 



(1954). 



Eine einfache Vorrichtung 

 ZLim Anspitzen von plexiglaseingebetteten Objekten 



A. Maas 



ZentraUaboratorimu fiir angewandte Ubermikroskopie dcr Universitat Bonn 



L)as vor dem Schneidcn auf dem Mikrotom not- 

 wendige Anspitzen plexiglaseingebetteter Objekte, 

 das unter mikroskopischer Beobachtung von Hand 

 mit einer Rasierklinge vorgenommen wird, ist bei 

 kleiner ObjektgroBe sowie bei groBer Hiirte des 

 Plexiglases mit Schwierigkeiten verbunden. Im fol- 

 genden soil iiber eine Vorrichtung berichtet werden, 

 die es gestattet, plexiglaseingebettete Objekte bis zu 

 einer Dimension von einigen // in die Spitze einer 

 Pyramide zu legen, deren Spitzen- und Fliichenwinkel 

 exakt definiert sind. 



Das Objekt wird in iiblicher Weise in das halb- 

 kugelformige Ende eines zylindrischen Plexiglas- 

 blockes eingeschlossen. Der Plexiglasblock wird so- 

 dann in eine Haltevorrichtung (Blockhalter) einge- 

 spannt. Die sich beim Anspitzen des Plexiglasblockes 



ergebende Form des angespitzten Objektes ist mit- 

 bestimmend fiir die GroBe und Giite der spateren 

 Ultra-Diinnschnitte. Durch die GroBe des Spitzen- 

 winkels wird die statische Festigkeit des Objektes 

 beim Schneidevorgang festgelegt. Auf Grund der im 

 Objekt beim Schneiden auftretenden Zug- und 

 Druckspannungen wird somit die Giite des erhalte- 

 nen Ultra-Schnittes beeinfiuBt. 



Mit Hilfe einer Rasierklinge wird der Plexiglas- 

 block so angespitzt, daB sich das Objekt in der 

 Spitze einer Pyramide befindet. Das Prinzip der 

 Anordnung ist in Abb. 1 im schematischen Grundriss 

 dargestellt. Der Plexiglasblock ist um eine Achse An 

 um definierte Winkelbetriige drehbar und in der 

 Liingsrichtung der Achse verschiebbar angeordnet. 

 Das eingebettete Objekt kann mittels eines spater 



