Fractlonation and characterization of cell nuclei from rat neocortex by protein-DNA ratios

Zusammenfassung Die Kerne des Rattenneocortex wurden mit einer nachBurdman modifizierten Methode auf einem diskontinuierlichen Saccharosegradienten in zwei Populationen aufgetrennt. Die Kerne werden durch das Protein/DNA-Verhältnis charakterisiert: kleine Kerne 1.5; grosse Kerne 3.9. Die morphologische Differenzierung im Phasenkontrastmikroskop erwies sich als ungenügend.

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This investigation was supported by grant No. 89 of the Fritz Hoffmann-La Roche Foundation.     

The development of pyruvate kinase,glycerol kinase and phosphoenolpyruvate carboxykinase activities in liver and adipose tissue of the rat

Zusammenfassung Es wird gezeigt, dass in der Leber die Aktivität der PEP-Kinase und der Glycerolkinase nachgeburtlich ansteigt. Im braunen Fettgewebe fällt die PEP-Kinaseaktivität nach dem 40. Tag ab. Sie fehlt im weissen Fettgewebe. Die Pyruvatkinaseaktivität fällt in der Leber nach der Geburt ab, während sie im braunen Fettgewebe ansteigt.     

L23 protein functions as a chaperone docking site on the ribosome

During translation, the first encounter of nascent polypeptides is with the ribosome-associated chaperones that assist the folding process--a principle that seems to be conserved in evolution. In Escherichia coli, the ribosome-bound Trigger Factor chaperones the folding of cytosolic proteins by interacting with nascent polypeptides. Here we identify a ribosome-binding motif in the amino-terminal domain of Trigger Factor. We also show the formation of crosslinked products between Trigger Factor and two adjacent ribosomal proteins, L23 and L29, which are located at the exit of the peptide tunnel in the ribosome. L23 is essential for the growth of E. coli and the association of Trigger Factor with the ribosome, whereas L29 is dispensable in both processes. Mutation of an exposed glutamate in L23 prevents Trigger Factor from interacting with ribosomes and nascent chains, and causes protein aggregation and conditional lethality in cells that lack the protein repair function of the DnaK chaperone. Purified L23 also interacts specifically with Trigger Factor in vitro. We conclude that essential L23 provides a chaperone docking site on ribosomes that directly links protein biosynthesis with chaperone-assisted protein folding.     

The postnatal development of hormone sensitive lipase in brown and white adipose tissue of the rat

Zusammenfassung Die Aktivität hormonsensitiver Lipasen im weissen und braunen Fettgewebe der Ratte steigt zwischen dem 10. und 18. Tag nach der Geburt. Corticosteronzufuhr verursacht bei 10tägigen Ratten einen Aktivitätsanstieg. Adrenalin und Noradrenalin haben im braunen Fettgewebe keinen Effekt.     

Measurement of collateral flow in experimental coronary occlusion

Zusammenfassung Es wird ein Verfahren zur autoradiographischen Darstellung der intramyocardialen Durchblutungsverteilung nach experimenteller Coronarocclusion angegeben. Im Versorgungsbereich akut verschlossener Coronararterien wird eine inhomogene Reduktion der Durchblutung beobachtet, wobei die Innenschichten regelmässig stärker als die subepicardialen Myocardanteile betroffen sind.     

The role of kinesin, dynein and microtubules in pancreatic secretion

The regulated secretion of pancreatic zymogens depends on a functional cytoskeleton and intracellular vesicle transport. To study the dynamics of tubulin and its motor proteins dynein and kinesin during secretion in pancreatic acinar cells, we infused rats with 0.1 μg/kg/h caerulein. Electron and fluorescence microscopy detected neither dynein nor kinesin at the apical secretory pole, nor on the surface of mature zymogen granules. After 30 min of secretagogue stimulation, kinesin and the Golgi marker protein 58 K were reallocated towards the apical plasma membrane and association of kinesin with tubulin was enhanced. Disruption of acinar cell microtubules had no effect on initial caerulein-induced amylase release but completely blocked secretion during a second stimulus. Our results suggest that mature zymogen granule exocytosis is independent of intact microtubules, kinesin and dynein. However, microtubule-dependent mechanisms seem to be important for the replenishment of secretory vesicles by redistribution of Golgi elements towards the apical cell pole. J. Schnekenburger and I.-A. Weber have contributed equally to this work.     

The Pendulum Swings Again: A Mathematical Reassessment of Galileo's Experiments with Inclined Planes

 After over 300 years of scrutiny, the subject of Galileo continues to be pursued with unabating intensity. Dava Sobel's Galileo's Daughter points to the popular interest in the man and his legacy. The Catholic Church, understandably interested in dispelling the notion that its censure of Galileo centuries ago is proof positive that religious faith and science as well as ecclesiastical authority and free pursuit of scholarship are irreconcilable, continues to offer explanations. New books, articles and conferences probe both in breadth and in depth the magnetic field charged by Galileo, science, and the Church. Galileo's analysis of the physics of motion has also received considerable attention. In particular, a great deal has been written during the past thirty years about the structure and objectives of three experiments with inclined planes. Galileo had carried them out in Padua and recorded them in his working papers. The assessments of the three experiments differ widely in points of detail, but all regard them as sophisticated, ingenious, and remarkable. This article presents a new critical study of these experiments. Its conclusion is that one of the experiments is indeed a success, but that the other two fail and are abandoned because Galileo did not have a firm enough grip on the underlying physical principles and mathematical relationships.