Feulgen positive nucleoli in Epon semithin sections: Fact or artifact?

Summary Epon semithin sections from glutaraldehyde fixed tissues show stained nucleoli after treatment with the Schiff's reagent. The possibility that aldehyde groups already present could account for this positive staining reaction is briefly discussed.This work was partially supported by a grant from the Comisión Asesora de Investigación Científica y Técnica, Spain. The author is greatly indebted to O.D. Colman and O. Partearroyo for valuable collaboration.     

Chromatin fluorescence by pyronin staining

Summary Human, chicken and mouse cells from different tissues show a bright red-orange fluorescence of the chromatin after staining with pyronin Y. The possibility that intercalation of the dye into double helical nucleic acids accounts for this fluorescence pattern is briefly discussed.This work was partially supported by a grant from the Comisión Asesora de Investigación Científica y Técnica, Spain.     

A note on the polytene nuclei in the fat body ofDrosophila larvae

Resumen Los nucleos de las células grasas de larvas deDrosophila melanogaster, contienen cromosomas politénicos cuya ultrastructura es similar a la que presentan los cromosomas en las glandulas salivales. Bandas gruesas, finas, y algunas «minibandas» se hallan separadas por regiones claras compuestas por fibrillas con un diametro de 60–80 Å. El nucleolo constituido por elementos granulares periféricos y fibrilares centrales, presenta un aspecto similar al nucleolo de glandulas salivales.

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The work reported in this paper was undertaken during the tenure of a research fellowship awarded by the Instituto Nacional de Farmacología y Bromatología, Argentine.

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This work was supported by a research grant from the Population Council. Inc. New York.     

Nucleolar structure in root-tip cells ofAllium cepa

Resumen La tinción con plata y con fucsina básica del nucleolo en células meristemáticas deAllium cepa permite detectar la localización de dos componentes de distinta afinidad tintorial. El componente de mayor argentofilia aparece en forma de gránulos, distribuídos en el interior de una matriz contínua que presenta marcada basofilia.

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The work reported in this paper was undertaken during the tenure of a Research Training Fellowship awarded by the International Agency for Research on Cancer.