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Zusammenfassung Die pranatale Entwicklung des Cerebellums der Ratte von Tag 12–20 wurde mit Hilfe einer lichtmikroskopischen Serienschnittuntersuchung aufgezeigt. Wahrend der Proliferationsphase von Tag 12–14 tritt vor allem in der kaudalen Zwischenzone und in der Mittelzone der Cerebellumanlage eine Massenzunahme auf, wohingegen die rostrale Zwischenzone eine geringere Proliferationstendenz zeigt. In der sich anschliesenden Schichtungsphase von Tag 15–18 tritt die embryonale Kornerschicht am Tag 15 in alien unter-suchten Sdinittebenen in der kaudalen Zwischenzone gleichzeitig auf. Die innere Kornerschicht last sich zum erstenmal am Tag 16 dokumentieren. Am Tag 18 ist die Schichtung der Kleinhirnrinde in EGL (Molekularschicht) und IGL abgeschlossen. Die anschliesende Proliferationsphase am Tag 19–20 zeigt sich in einer Zunahme der einzelnen Schichten. Die Ergebnisse werden mit den Befunden anderer Autoren diskutiert. Summary The development of the cerebellum in rat embryos from day 12 to day 20 p. c. The prenatal development of the cerebellum of the rat from day 12–20 was shown with the help of a light-microscopic serial section study. During the proliferation phase from day 12–14 an increase in mass occurs especially in the caudal interzone and the middle zone of the cerebellum anlage, whereas the rostral interzone shows a small proliferation tendency. In the following stratification phase day 15–18 the embryonic granular layer appears simultaneously in the caudal interzone on day 15 in all studied sectional planes. The internal granular layer can be first documented on day 16. On day 18 the layering of the cerebellar cortex in EGL (molecular layer) und IGL has been completed. The subsequent proliferation phase day 19–20 demonstrates an increase of the various layers. The results are discussed with the findings of other authors. Resume Le developpement du Cervelet chez ľembryon de Rat du 12e au 20e jour Le developpement prenatal du cervelet du Rat a ete suivi, du 12e au 20e jour, par la methode des coupes histologiques serines, examinees en microscopic optique. Pendant la phase de proliferation, du 12e au 14e jour, un accroissement de substance apparait surtout dans la zone intermediaire cau-dale et dans la zone moyenne de ľebauche cerebelleuse, alors que la zone intermediaire rostrale ne montre qu'une tendance proliferative moindre. Au cours de la phase de stratification, qui fait suite, du 15e au 18e jour, la couche granulaire embryonnaire apparait en meme temps, dans tous les plans de coupes examines, au niveau de la zone intermediaire caudale. La couche granulaire interne devient observable, pour la premiere fois, au 16e jour. Au 18e jour, s'acheve la lamination du cortex cerebelleux en un «Stratum mole-culare» et un «Stratum granulosum». La phase ulterieure de proliferation, des 19e–20e jours, se caracterise par un epaisissement de chaque couche. Ces resultats sont discutes avec ceux ďautres auteurs. Resumen Desarrollo del cerebelo en embriones de ratas del dia 12 hasta el dia 20 Se demostro el desarrollo prenatal del cerebelo de la rata desde el dia 12 hasta el dia 20 mediante un estudio con el microscopio corriente en cortes seriados. Durante la fase de proliferation del dia 12 al 14, se presenta un aumento de la masa especialmente en la zona intermedia caudal y en la zona media del esbozo del cerebelo, mientras que la zona intermedia rostral de-muestra una menor tendencia a la proliferacion. En la siguiente fase de estratificacion del dia 15 al 18, la capa granulosa embrionaria se presenta simultaneamente el dia 15 en todos los cortes examinados de la zona intermedia caudal. La capa granulosa interna se observa por primera vez el dia 16. El dia 18 finaliza la estratificacion de la corteza cerebelosa en EGL (capa molecclar) e IGL. La fase proliferativa que sigue los dias 19 y 20, presenta un aumento de cada una de las capas. Los hallazgos se comparan con los resultados de otros autores.

Size analyses and size classifications were made of the nuclei of embryonal mouse brain cells in monolayer culture. Measurements were made by surface analysis, using the Quantimet (1,299 nuclei), and linear analysis, using the Digiscan (1,887 nuclei). Despite the different methods of measurement and different logarithmic classification, similar distribution curves were obtained, approaching the Gaussian normal distribution. The methodical problems of karyometry as well as the problems of statistical data processing are discussed.

Wistar rats were administered single doses of 16 or 50 mg/kg 6-mercaptopurine (6-MP) on day 12 of pregnancy. Necrosis in the fetal forebrain and spinal cord was studied by light microscope 6, 12, 14, 48, 72, and 81 h and 8 days afterward. The extent of necrosis was dose dependent. The first necroses were seen after 24 h, regardless of location (brain, spinal cord) or dose; but the extent was greatest after 48 h. All necrotic cells had a typical appearance; they were ballooned and often fragmented, their nuclei were darkly colored and frequently pyknotic, and they were often karyorhexic. Necroses appeared almost exclusively at sites of beginning cellular differentiation, i.e., in the intermediate zone. In the spinal cord the ventricular zone was also necrotic and the alar plate (dorsal horn) always affected. Phagocytizing cells (macrophages) appeared in the spinal cord after 48 h and in the brain after 72 h. After 81 h all the necrotic material had been phagocytized. at which time there was a massive congestion of the extra- and intracerebral vessels. Hemorrhages appeared in denned localizations. Eight days after exposure to 16 mg/kg 6-MP fetuses no longer showed any visible deviations. Fetuses exposed to 50 mg/kg showed deviations in the cytoarchitecture of the neopallium: an extremely broadened ventricular zone, few cells in the intermediate zone, and extensive rarefaction of cells in the cortical plate with no clear layer structure. In the spinal cord, cleft formations were especially noticeable in the dorsal-horn region. All fetuses showed a hydrocephalus externus after 50 mg/kg. The mechanism leading to necrosis is discussed.

Studies were carried out on the nuclear size of embryonic mouse brain monolayer cells at various cell densities. The variation in cell density resulted from different initial cell numbers. The nuclear area was measured area-analytically with the Quantimet, the determination of cell population was measured linear-analytically using the Digiscan. Nuclear size remains constant in a cell culture of 104 up to 8.3 × 104 cells ml, which corresponds to a cell density of about 25–160 cells/unit. A significant diminution in mean nuclear size of the cell nucleus occurs in the case of increased cell densities of 215 and 277 cells/unit, corresponding to a cell culture of 2.5 × 105 and 7.3 × 105 cells ml. This diminution may be connected with the accumulation of Gl cell nuclei in cultures with contact-dependent growth inhibition.

The influence of cytosine-arabinoside (ara-C) on the nuclear size of monolayer cells from mouse brains were studied by quantitative analysis with the Quantimet (area measurement) and linear analysis with the Digiscan. Ara C (0,1; 1,0; 10,0 mug/ml) causes a significant nuclear enlargement, depending on the dose of 16%, 30% and 35% respectively and at the same time a decrease in cell density and an inhibition of mitotic activity. The size-distribution graph is altered by ara-C: the graph flattens and widens at the base. Moreover, in the case of 10,0 mug ara-C/ml a pronounced graph shoulder is visible in the small nuclear size region which can be interpreted as a slight accumulation of small nuclei. The nuclear enlargement is possibly due to an accumulation of shortchain polynucleotides.

12 hrs, 1, 2, and 4 days after i.p. administration of 2, 3 or 5 mg/kg 6-AN (6-Aminonicotinamide) on postnatal day 5, the following findings were made in the sciatic nerve of the newborn rat. In the myelin-forming fibres a swelling between the axolemm and the first inner intraperiod-line of the Schwann cell develops with displacement of the otherwise intact axon. The myelin formation is not impeded. During the 4 days of control after administration of 6-AN there is continual growth of the myelin sheath with an orderly lamellar structure. Using any dose there is no demonstrable alteration in the Schwann cells--with the exception of the inner cytoplasmic tongue--either in the foetal promyelin and mature nonmyelinated fibres. These findings are discussed and compared with the known glia alterations of the spinal ganglia and dorsal radix after the application of 6-AN.

The prenatal cortex development after the application of 6-Mercaptopurine (6-MP) was studied in the rat embryo. 24 h after application of a single dose of 6-MP on day 12, 13, 14 or 15 of gestation first cell lesions occured in the form of necroses. 48 h after injection of the drug these necroses were most pronounced. Their extent and distribution pattern was, however, dependent on the developmental stage. In the early developmental phase, on days 12 and 13, massive necroses could be observed in the intermediate zone. At later stages of development (drug application on day 14 or 15) damaged cells could occasionally also be found scattered over the whole ventricular wall. The late toxic response to 6-MP treatment suggests that, after incorporation of metabolites of the agent into DNA during the S-phase, at least one additional S-phase is completed before the disturbance created in a cell is sufficient to cause necrosis. The necrosis may be a result of an action of 6-MP directly on DNA or via an affect on transcription. The different extent of the lesion during the various developmental phases suggests different growth dynamics of the cortex.

The myelin sheath and axon areas in the sciatic nerve of 20 adult rats were studied using the video-point-counting method (Quantimet). This automatic measurement procedure allows an exact and rapid determination of the above mentioned areas as a result of the differing intensities of the structures. The electron-microscopic pictures are projected at a magnification of 3500 onto the monitor through a lens system from a Vidikon-TV-tube, objective 32 mm. The areas of single nerve cross-sections, myelin sheath areas and total area are then measured. These area values are stated in picture points which can be calculated to absolute values. The statistical evaluation of both parameters shows a linear regression with a correlation coefficient of 0.94. These values are compared with the results obtained using the conventional manual methods of other authors, e.g. determination of lamellae number or myelin sheath thickness as well as axon circumference or axon diameter. The special advantages of this procedure are thereby pointed out.

Actinomycin D (AMD) inhibits the RNA-synthesis by intercalating with the DNA-helix. In monolayer culture of embryonic mouse brain cells in the 8th passage the cell nuclei were demonstrated with the Feulgen-reaction and quantitatively-morphometrically evaluated following a 48 h intoxication with AMD (0.001; 0.01; 0.1 mug/ml). The mean value of nuclear area calculated from single measurements with the Quantimet 720 is significantly larger when compared to the controls at a dose of 0.01 mug AMD/ml. At 0.1 mug AMD/ml ca. 30% of the cell nuclei are pyknotic; the non-pyknotic nuclei are enlarged significantly by appr. 20%. The linear-analytic results using a Digiscan show no enlargement of tendon length, on the contrary, at 0.1 mug AMD/ml a significant diminution versus the controls can be seen. This resutls from the pyknotic cell nuclei which are also measured in this case no single measurements were carried out. The determination of cell density using a Digiscan shows a diminution of cell number by 19, 31 or 68% dependent upon AMD-concentration.

Size analyses and size classifications were made of the nuclei of embryonal mouse brain cells in monolayer culture. Measurements were made by surface analysis, using the Quantimet (1,299 nuclei), and linear analysis, using the Digiscan (1,887 nuclei). Despite the different methods of measurement and different logarithmic classification, similar distribution curves were obtained, approaching the Gaussian normal distribution. The methodical problems of karyometry as well as the problems of statistical data processing are discussed.

Uber experimentelle Erweiterungsplastiken der Harnblase unter Verwendung von unterschiedlich vorbehandelten autologen, homologen und heterologen Vollhautlappen wurde schon fruher von der gleichen Arbeitsgruppe berichtet.