Bacillus thuringiensis delta-endotoxin: evidence that toxin acts at the surface of susceptible cells

Enzymically activated delta-endotoxin of Bacillus thuringiensis covalently bound to Sephadex beads, has the same effect on insect cells in tissue culture as free toxin. The effect is prevented by antitoxin antibody and heat denaturation and is not due to a nonspecific protein effect, the beads, or toxin released from the beads. The toxin, therefore, probably acts at the cell surface.     

Neurophysiological basis of directional hearing in amphibia

Discrete regions of neural tissue along the anterior-posterior axis of the torus semicircularis act as resonators, each one broadly tuned to a different range of frequencies, and each one responding optimally to the incident sound from a different direction. In this way, a map of auditory space is represented in the midbrain.     

Interaction of cocaine and bunaphtide on the3H-norepinephrine uptake mechanism on isolated left atrium of guinea-pig

Summary Bunaphtide induces a blockade in the³H-norepinephrine uptake and retention in the isolated guinea-pig left atrium. However, this blockade does not seems to be related with the cardiodepressant effect of the drug.     

Radioimmune, radiobinding and HPLC analysis of 2-5A and related oligonucleotides from intact cells

The enzyme (2-5A synthetase) which synthesizes ppp(A2'p)nA where n=2 to 4 (collectively referred to as 2-5A) is widely distributed in a variety of cells and tissues in amounts which increase response to interferon and vary with growth and hormone status. 2-5A activates a nuclease which inhibits protein synthesis. The non-phosphorylated 'core' of 2-5A ((A2'p)nA, n=2 to 4) can inhibit DNA synthesis and cell growth. Here we describe convenient and sensitive radioimmune (RI) and radiobinding (RB) assays for core and 2-5A. In combination with more satisfactory high performance liquid chromatography (HPCL) methods using reverse-phase C18 columns, these assays have been used to detect core and 2-5A in crude extracts from interferon-treated cells. The novel 2-5A synthetase products NAD2'p5' A2'p5'A and A5'p45'A2'p5'A2'p5'A (ref. 13), which can also be detected using the RB assay, were not found in significant amounts. The natural occurrence of core has not been described previously.     

Re-analysis of radiation-induced specific locus mutations in the mouse.

A re-analysis of published data on mouse mutation rates induced by X and gamma rays suggests that the kinetics of induction can be analysed by fitting the data to a parabolic curve. We interpret this to mean that a substantial proportion of the induced mutations results from gross chromosomal changes such as deletions, some of which are one-track and some of which are two-track. This analysis is based on the assumption that the shape of the dose curve, which in the female is concave upward, reflects the manner in which the mutations are induced rather than representing a one-track (linear) curve whose shape has been modified by differential repair.     

A new method for measuring guanidine in uremia

Riassunto Si descrive un metodo per la determinazione della guanidine nei liquidi biologici e si rileva che essa aumenta nel siero uremico fino a 30 volte la norma (valore medio normale: 1.41±0.49 g/100 ml) e che nei cani uremici la concentrazione muscolare è di quasi 3 volte superiore a quella plasmatica. La eliminazione urinaria non è diversa fra normali ed uremici: 382±221 e 459±229 g/24 h, rispettivamente.

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Aknowledgments. This investigation was supported by Public Health Service, Research Contract No. PH-43-68-1466.