Transfer amyloidosis: studies on the nature of the amyloid inducing factor in a murine transfer system

Transfer of amyloidosis between syngeneic mice was attempted with whole spleen cells and homogenates, nuclei, cytoplasmic fractions and various preparations of nucleic acids. Amyloidosis could be transferred from casein-treated donor mice by means of spleen cell suspensions, homogenates or crude nuclei, but not with nuclei treated with DNase, cytoplasmic fractions or five different nucleic acid samples, derived from whole spleens or crude nuclei. The transfer activity of crude nuclei was lost after storage at 0 or –20°C. The experiments indicated that the amyloid inducing factor is a labile, complex substance, possibly a nucleoprotein

Physiological Parameters Affecting the Chemosensory Response of Tetrahymena

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Small nuclear RNAs in the ciliate Tetrahymena.

We have isolated and partially characterized a family of small nuclear RNAs (snRNAs) from three different species of the protozoan Tetrahymena. We find six distinct snRNAs ranging in size from 100 to 250 nucleotides. The two largest snRNAs, as well as an abundant, heterogenous group of smaller snRNAs are found in the nucleolar RNA fraction. None of the snRNAs are transcription products of the ribosomal RNA gene or its flanking regions, as shown by hybridization tests. The snRNAs are metabolically stable as determined by pulse/chase experiments and several of them contain a number of modified nuclotides. The snRNAs from Tetrahymena all have slightly different sizes from mammalian snRNAs. The cap structure of the snRNAs from Tetrahymena differs from that of the snRNAs from mammalian cells, but has not yet been fully characterized. The relative amount of snRNAs to total RNA is less in Tetrahymena (greater than 0.1%) than in mammalian cells (2%)

Synthesis of low molecular weight RNA components A, C and D by polymerase II in alpha-amanitin-resistant hamster cells.

In an attempt to establish which RNA polymerase catalyzes the synthesis of the low molecular weight RNA components A, C and D, Ama 1 cells (mutant Chinese hamster cells) were used in experiments with addition of alpha-amanitin. Ama 1 cells contain an altered RNA polymerase II which is 800 times more resistant towards inhibition by alpha-amanitin than the wild type enzyme. Alpha-amanitin (up to 200 microgram/ml) added to these cells does not affect the synthesis of the low molecular weight RNAs A, C and D. These data together with our previous data showing that alpha-amanitin (0.5 - 5.0 microgram/ml) preferentially inhibits the synthesis of A, C and D in normal cells indicate that RNA polymerase II catalyzes the synthesis of the low molecular weight RNA components A, C and D