Morphogenetic and cytogenetic effects of 7,12-dimethylbenz(a)anthracene onHaworthia callus in vitro

Zusammenfassung 7,12-Dimethylbenz(a)anthracen (DMBA) in verschiedenen Konzentrationen anstelle von Auxin, Kinetin und Kokosmilch im Nährmedium induziert die Bildung von Wurzeln und beblätterten Sprossen auf den Kalli vonHaworthia variegata. Dieses Ergebnis gleicht demjenigen im vollständigen Kontrollmedium ohne DMBA, mit dem Unterschied, dass unter dem Einfluss von DMBA weniger Sprosse und eine grössere Anzahl von Wurzeln gebildet werden. Cytologische Untersuchungen an Kallus- und Wurzelzellen aus dem DMBA-Medium zeigten eine normale Konstitution des Chromosomensatzes ohne chromosomale Aberrationen.

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This study was supported in part by a summer research grant from Lafayette College Faculty Research Funds.     

Halbdesmosomen bei Phytoflagellaten

Summary Half-desmosome like structures binding the cell to the theca have been found in the phytoflagellatePlatymonas. The tonofilaments are parts of the flagellar root system.     

Immunohistochemical demonstration of corticotrophic cells concentrated in the rostral zone of the pars intermedia of the mouse hypophysis

Résumé La nature corticotrope des cellules constituant la partie rostrale de la pars intermedia de l'hypophyse de souris est établie par la microscopie électronique et la cytoimmunofluorescence. Cette zone réagit positivement avec les anticorps anti-ACTH et négativement avec les anticorps anti-MSH.     

Dosis-Wirkungs-Beziehungen zwischen Koronardurchfluss und Herzfrequenz für Adenosin

Summary In the isolated guinea-pig heart, it has been found that the amount of adenosine which slows the heart rate is about 100 times greater than the amount which increases coronary flow.     

Theory agrees with experimental thermal denaturation of short DNA restriction fragments

Experimental melting transitions of several natural DNAs of known nucleotide sequences have recently been obtained. The differential melting curves of these DNAs-phi X174 DNA, fd DNA and SV40 DNA-all show distinctive sets of peaks or fine structure. Theoretical melting curves calculated from the sequences and a few a priori parameters have not accurately predicted the experimental transitions. Although calculated fine structure resembled experimental curves in some cases, the characteristic features of a DNA's differential melting curve could not generally be produced. Azbel and Gabbarro-Arpa et al. have recently obtained good agreement between calculated and experimental curves using a different theoretical approach-only ground-state configurations of DNA were considered for temperatures inside the transition region. Their results suggest that the basic model of DNA melting, common to all theoretical approaches, is accurate. We have used here an exact theoretical approach to calculated melting curves of four DNA restriction fragments of 95-301 base pairs containing the lactose promoter region (Fig. 1). Theoretical curves agree very well with the experimental transitions published by Hardies et al. and obtained in this laboratory.