Experimental control of the Mormon cricket,Anabrus simplex,byNosema locustae [Microspora: Microsporida], a protozoan parasite of grasshoppers [Ort.: Acrididae]

Spores ofNosema locustae Canning were applied with aerial equipment for experimental control of the Mormon cricket,Anabrus simplex Haldeman. The application resulted in infections in crickets during the season of application and the season following application. Spores were observed in cricket feces which indicated probable vertical transmission between generations. Reduced densities of crickets during the second season suggested effective control byN. locustae.     

Can tumorigenesis result from in vivo “transfection” of a normal cell with DNA escaped from disintegrating nontransformed cells?

In this paper I present a hypothetical step on the route to turmorigenesis which may be common to many of the tumorogenic events taking place in vivo. According to this hypothesis portions of DNA from normal nontransformed dying cells may escape degradation, “transfect” other cells and under appropriate conditions also induce transformation. When various high risk factors for carcinogenesis are examined this hypothesis may easily fit into each of them. In addition, recent reports of experimental “transfection” indirectly support this hypothesis. It could now be argued that aging, ionizing radiation, immunosuppressive drugs, genetic errors, defects in DNA repair, immunodeficiency states, chronic infections and chronic inflammatory diseases may all increase the availability of free DNA or the readiness of cells to accommodate “transfection” DNA, or both. Thus the risk of cancer associated with these situations may be explained by increased chance for “transfection” with DNA.It is suggested that the minimal requirements for cell transformation consist of a certain sequence of DNA which does not have to be integrated into the nucleus at once, it may instead accumulate piece by piece so that the first “transfection” of a cell may occur long before transformation takes place. If the “transfecting” DNA sequence does not fulfil the minimal requirements for maintaining a state of repetitive uncontrolled mitosis, then this cell may wait silently or remain a benign tumor until “boosted” with an ultimate complementary DNA sequence to develop into a fully fledged cancer.     

ISOLATION AND PARTIAL CHARACTERIZATION OF NITRATE ASSIMILATION MUTANTS OF DUNALIELLA TERTIOLECTA (CHLOROPHYCEAE)1

Fifteen nitrate assimilation-deficient mutants of the euryhaline green alga, Dunaliella tertiolecta Butcher were selected by their chlorate resistance. Ten mutants, unable to grow on NO₃^? but able to grow on NO₂^?, had no detectable nitrate reductase activity. Five mutants, unable to grow on either NO₃^? or NO₂^?, had depressed levels of both nitrate and nitrite reductase. A method for assaying methyl viologen-nitrate reductase in the presence of nitrite reductase is described.     

Accuracy of neuronal interspike times calculated from a diffusion approximation

The theory of neuronal firing in Stein's model is outlined as well as the corresponding theory for a diffusion approximation which has the same first two infinitesimal moments. The diffusion approximation is derived from the discontinuous model in the limit of large input frequencies and small postsynaptic potential amplitudes. A comparison of the calculated mean interspike intervals is made for various values of the threshold for firing and various input frequencies. The diffusion approximation can underestimate the interspike interval by up to 100% or severely overestimate it, depending on the input frequencies and the threshold. A general relation between the predictions of the two models is deduced.     

Mutations within an intron and its flanking sites: Patterns of novel polypeptides generated by mutants in one segment of the cob-box region of yeast mitochondrial DNA

Summary We have undertaken a systematic examination of the polypeptides accumulating in thirteen (out of 23) mutants in the intron cluster box7 and its flanking clusters box2 and box9 of the cob-box (cytochrome b) region of the mitochondrial genome of Saccharomyces cerevisiae. We have subjected these polypeptides to fingerprint analysis, both sequential and in parallel, with two proteases in order to disclose sequence homologies and differences between the different novel polypeptides themselves, and between them and the wild type product of the gene, i.e. apocytochrome b. One of our aims has been to establish the existence of possible correlations between the nature of the novel polypeptides and the fine structure genetic map of that segment of the mitochondrial genome.Our results show that all box7 mutants accumulate the following set of polypeptides not seen in wild type cells: a) a characteristic set of large polypeptides consisting of three species: p56, p42 and p35 or p34.5; b) a polypeptide p23; c) a much shorter fragment (of which the apparent molecular weight varies from 12.5 to 13, according to the mutation) with the exception of two mutants; d) in addition, the majority accumulate in varying amounts a polypeptide p30 closely related to but not identical with apocytochrome b.Moreover only two box7 mutants accumulate a polypeptide in the range of mobilities corresponding to 25–27 Kd (referred to as class p26) while such a polypeptide is seen in all box9 and box2 mutants examined with one exception in box2.Only one mutant in box2 resembles box7 mutants with respect to criterion a), and no box2 or box9 mutants resemble box7 mutants with respect to criterion c); criteria b) and d) appear to apply equally well to mutants in all three clusters.Fingerprint analysis, carried out with polypeptides p56, p42, p35, p34.5, p30, p26, p23, discloses that a) The polypeptides belonging to the same class of mobility exhibit very similar if not identical sequences in various cases. b) These polypeptide classes, except p56, p42 and p26, share considerable sequence homologies with wild type apocytochrome b, perhaps encompassing 50% or more of the wild type sequences. b) Polypeptides belonging to the classes p42 and p26 exhibit less extensive but nevertheless significant homologies with the wild type sequence. c) Sequences in polypeptides belonging to class p56 are virtually indistinguishable from ones in cytochrome oxidase subunit I.The inferences from these findings are 1) one gene can produce a multiplicity of polypeptide products that share a common sequence at the promoter-proximal (N-terminal) portion, but diverge beyond these regions of homology. 2) Both the multiplicity of products in single mutants, and the protein structure found, argue against the divergent segments to be due to frameshift terminations, and instead suggest that the novel products are consequences of mRNA processing defects (excision and/or ligation) at and near intron regions. 3) Mutations at edges and the center of an intron can generate similar polypeptide patterns, i.e. produce analoguous mRNA processing defects. 4) Mutations in exons, at their boundary with introns, can produce polypeptide patterns indistinguishable from those at the neighbouring intron; they diverge and eventually become typically exonlike in mutants localized at increasing distances from the boundary. 5) Taken together these findings argue that pre-mRNA processing extends beyond the boundaries of the intron proper and that certain exonsequences participate in excision and ligation. 6) Accumulated pre-mRNAs, resulting from defects in splicing can be translated. 7) Product p56 is formally analogous to p23, as a faulty but highly conserved partial product of the wild type protein, the former of Cox I (oxi3 gene), the latter of the cob-box gene proper. Therefore both genes may utilize identical RNA processing elements which are affected by box7 mutations. 8) A small amount of product similar to p56 may accumulate even in some wild types but not in others. This observations suggests that in certain nuclear backgrounds RNA processing may be more error-prone than in others.Publication No. XXXX from the Department of Chemistry, Indiana UniversitySupported by Research Grant GM 12228 from the National Institute of General Medical Sciences, National Institutes of Health; recipient of Research Career Award K06 05060 from the same Institute.Supported by Délégation Générale à la Recherche Scientifique et Technique grant n⁰ 78-70341     

Sucrose:sucrose fructosyltransferase and fructan:fructan fructosyltransferase from allium cepa

Sucrose: sucrose fructosyltransferase and fructan:fructan fructosyltransferase were isolated from the inner leaf bases of bulbing onion plants (Allium cepa) and separated by gel filtration on Bio-Gel P-150. Sucrose:sucrose fructosyltransferase produced only one trisaccharide, 1^F-fructosylsucrose, from sucrose. Fructan:fructan fructosyltransferase produced tetrasaccharide and higher polymers from trisaccharide. The trisaccharide found in the greatest concentration in onion, 6^G-fructosylsucrose, was produced from 1^F-fructosylsucrose by fructan:fructan fructosyltransferase and was not a product of sucrose:sucrose fructosyltransferase.