Formation of recombinants between snowshoe hare and La Crosse bunyaviruses.

Wild-type recombinants were obtained at high frequency from coinfections of BHK cells involving temperature-sensitive, conditional-lethal mutants of snowshoe hare (SSH) and La Crosse (LAC) bunyaviruses. Analyses of two of the recombinants indicated that they have the genome compositions SSH/LAC/SSH and SSH/LAC/LAC for their respective L, M, and S virion RNA species. This evidence, together with that for the genetic stability of the recombinants, indicates that they were derived by segment reassortment of the competent genome pieces of the parental viruses. The SSH/LAC/SSH recombinant appears, from polypeptide analysis, to have the SSH type of nucleocapsid protein (N), whereas the SSH/LAC/LAC recombinant has the LAC nucleocapsid protein, suggesting that the viral S RNA codes for the N protein.     

Regulatory characteristics of a fructose bisphosphatase from the blue-green bacterium Anacystis nidulans.

A specific fructose 1,6-bisphosphatase (EC 3.1.3.11) has been partially purified from the obligately autotrophic blue-green bacterium Anacystis nidulans. It was most active at pH 8.0. The K_m for fructose 1,6-bisphosphate was 0.088 mm at pH 8.0 and 0.105 mm at pH 7.0; the K_m for MgCl₂ was 0.95 mm at pH 8.0. Activity at netural pH was particularly sensitive to the MgCl₂ concentration. AMP was an allosteric inhibitor, 50% inhibition being exerted by 0.058 mm AMP at pH 7.0 and 0.085 mm AMP at pH 8.O. The way in which changes in intracellular pH and the concentrations of Mg²⁺ and AMP might influence the activity of the enzyme in the Calvin cycle, the oxidative pentose phosphate pathway and in glycolysis and gluconeogenesis is discussed.     

Semisyngeneic hybrid resistance to murine teratocarcinoma cells

Resistance to two cultured lines of murine embryonal carcinoma was studied in F₁ hybrids constructed between the tumor-syngeneic mouse strain 129/J and several allogeneic strains. Three of four such hybrid strains were significantly more resistant to the multipotent embryonal carcinoma line PCC3 than the tumor-syngeneic 129/J parent strain. All hybrid strains tested showed significantly higher resistance to the nullipotent embryonal carcinoma line F9 than the syngeneic strain.Hybrid resistance to embryonal carcinoma lines does not require a hybridH-2 complex.Several kinds of evidence indicate that this hybrid resistance has an immunological basis.     

Semisyngeneic hybrid resistance to murine teratocarcinoma cells

Resistance to two cultured lines of murine embryonal carcinoma was studied in F1 hybrids constructed between the tumor-syngeneic mouse strain 129/J and several allogeneic strains. Three of four such hybrid strains were significantly more resistant to the multipotent embryonal carcinoma line PCC3 than the tumor-syngeneic 129/J parent strain. All hybrid strains tested showed significantly higher resistance to the nullipotent embryonal carcinoma line F9 than the syngeneic strain. Hybrid resistance to embryonal carcinoma lines does not require a hybrid H-2 complex. Several kinds of evidence indicate that this hybrid resistance has an immunological basis.     

Monolayer properties of chloroplast lipids

The properties of seven monogalactosyldiacylglycerols and six digalactosyldiacylglycerols, isolated from photosynthetic membranes and possessing different levels of fatty acid unsaturation, have been studied by the monolayer technique and compared with those of the fully saturated compounds. In addition, the monolayer properties of sulphoquinovosyldiacylglycerols and phosphatidylglycerols from higher plant chloroplasts, and several hexadecenoic acids have been measured.Monogalactosyldiacylglycerols containing saturated fatty acids form a condensed monolayer similar to that of saturated phosphatidylcholines. The naturally occurring monogalactosyldiacylglycerols, of which the double bond index ranged from 0.6 to 3.9, possessed comparable force-area curves suggesting that headgroup interactions play a more important role in packing behaviour than in phosphatidylcholines. Although digalactosyldiacylglycerols containing fully saturated fatty acids form a more expanded monolayer than the corresponding monogalactosyldiacylglycerols, the degree of expansion of the monolayer due to the presence of unsaturated fatty acids in the naturally occurring digalactosyldiacylglycerols is much less than in monogalactosyldiacylglycerols. Monogalactosyldiacylglycerols and digalactosyldiacylglycerols from a single species have very similar monolayer properties, and the presence of sulphoquinovosyldiacylglycerols and phosphatidylglycerols in the proportions in which they occur in higher plant chloroplasts does not have any condensing effect on a monolayer of galactolipids     

A DNA sequence cleaved by restriction endonuclease R.EcoRI in only one strand.

Restriction endonuclease EcoRI cuts both strands of the DNA sequence

generating two separate frayed ends (Hedgpeth et al., 1972). Here it is shown that under standard digestion conditions, the enzyme also attacks the sequence

but cuts only one strand. The resulting nick is an efficient initiation point for DNA synthesis by Escherichia coli DNA polymerase I, allowing the selective labelling of one strand of the DNA duplex.In buffers of low molarity and high pH (8.5), EcoRI cleaves sequences with the form

(Polisky et al., 1975). Thus it seems that under both sets of conditions the enzyme recognises the four-base-pair core sequence

and that its ability to cleave different adjacent phosphodiester bonds varies with pH and ionic strength.     

Assignment of the large oligonucleotides of vesicular stomatitis virus to the N, NS, M, G, and L genes and oligonucleotide gene ordering within the L gene.

Analyses of prototype vesicular stomatitis (VSV, Indiana serotype) mRNA-32P-labeled viral RNA duplexes have established the assignments of 65 of the 72 large oligonucleotides that are recovered by two-dimensional electrophoresis of RNase T1 digests of the viral RNA. Fifty of the oligonucleotides are recovered in the L RNA duplex, four each in the N, M, and NS duplexes, and three in the G RNA duplex. Studies of three small defective-particle RNA species indicate that they have only L gene oligonucleotides in addition to three of the seven unassigned oligonucleotides. Some L gene ordering of oligonucleotides can be postulated from the defective-particle RNA sequence analyses. Analyses of naturally occurring alternate isolates of VSV Indiana have established that by comparison to the prototype virus strain, the alternate isolates minimally have genome sequence differences in L, G, N, NS and/or unassigned regions of the genome. Changes in the genome have also been induced by vitro high-level mutagenesis of the prototype virus.     

Adenosine triphosphate-activated adenylate deaminase from marine invertebrate animals. Properties of the enzyme from lugworm (Arenicola cristata) body-wall muscle.

Adenylate deaminase (AMP aminohydrolase, EC 3.5.4.6) from lugworm (Arenicola cristata) body-wall muscle was partially purified by extraction in KCl solutions and chromatography on phosphocellulose. Enzyme activity was eluted from the column at two salt concentrations. Both forms show co-operative binding of AMP (Hill coefficient, h, 2.85) with s0.5 values of 20 mM and 15.6 mM. ATP and ADP act as positive effectors lowering h to 1.07 and s0.5 to 2mM. The apparent Ka (activation) for ATP was 1.5mM. GTP is an inhibitor with an apparent Ki of 0.12 mM. In vivo the ATP-activated adenylate deaminase is in the active form and may be regulated by changes in GTP concentrations. Adenylate deaminase may act as a primary ammonia-forming enzyme in ammonotelic marine invertebrates with the purine nucleotide cycle.     

Location ofMls locus on mouse chromosome 1

Linkage between theMls locus and the chromosome 1 markersDip-1 andald was detected using two sets of recombinant inbred strains. Linkage betweenMls andDip-1 was confirmed in the fifth and sixth backcross generations of an incipient congenic strain. The AKXL data indicate that the gene order isDip-1-ald-Mls. The recombination frequency betweenald andMls is estimated to be 0.07 ±0.05, based on the AKXL data. The recombination frequency betweenDip-1 andMls is estimated to be 0.18 ±0.04, based on all the available data.