A one-drop cryoscope: The tonicity of frog and goldfish sera

Zusammenfassung Es wird eine einfache Modifikation eines Kryoskopes zur objektiven Messung von Gefrierpunktserniedrigungen im Bereiche von 20 µl beschrieben. Das Instrument eignet sich u.a. zur Bestimmung der Gefrierpunktserniedrigungen des Wirbeltierblutes.

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This work was supported by Grant 619A from the Damon Runyon Memorial Fund for Cancer Research, Publication No. 109 of the Department of Biology, Wayne State University.     

Effect of vitamin A on tumor development in burned, unburned, and glucocorticoid-treated mice inoculated with an oncogenic virus.

High doses of vitamin A decreased the severity of tumor development in mice inoculated with a murine sarcoma virus; the same doses of vitamin A had no effect on the increased tumorigenesis seen in animals severely stressed with thermal injury or the increased tumorigenesis induced by exogenous glucocorticoid administration.     

Maternal regulation of zerknüllt: a homoeobox gene controlling differentiation of dorsal tissues in Drosophila

The homoeobox gene zerknüllt (zen) plays an important role in the differentiation of dorsal tissues during Drosophila development. zen- embryos show transformations in the dorsal-most regions of the fate map, and lack several tissues that normally derive from these regions, including the amnioserosa and optic lobe. zen displays a simple dorsal on/ventral off pattern as early as cleavage cycle 10-11 (ref. 2). We have prepared a polyclonal antibody against a full-length zen protein, and used this to examine its pattern of expression in mutants that disrupt dorsal-ventral polarity. Most or all of the maternally expressed genes that are involved in this process have been previously identified and fall into two classes, so called 'dorsalizers' and 'ventralizers' (see refs 4-7, reviewed in ref. 8). On the basis of our analysis of zen expression in each of these maternal mutants we propose that one or more of the dorsalizing genes encodes a repressor which inhibits the expression of zen in ventral regions of developing embryos. The ventralizing gene cactus might play an important role in restricting the activity of this repressor to ventral regions, thereby permitting the activation of zen in those dorsal tissues where its function is critically required.