Deletion of an rRNA gene set in Bacillus subtilis

One of the 10 rRNA gene sets found in a wild-type strain of Bacillus subtilis 168 was deleted, apparently by recombination between two tandemly repeated rRNA gene sets. The deletion strain grew as well as the wild-type strain under a variety of growth conditions and also showed no change in the sporulation efficiency.     

The complete nucleotide sequence of the I-E alpha d immune response gene.

We have isolated and sequenced the complete murine I-E alpha immune response gene of the H-2db haplotype. The I-E alpha d gene consists of 5300 basepairs and is organized into five or possibly six exons that correspond to different domains of the alpha chain. The amino acid sequence deduced from the I-E alpha gene shows 75% homology to its human counterpart, the HLA-DR alpha chain. The absence of I-E antigen in H-2 mice is due to lack of E alpha chain synthesis. We show here that this defect is caused by a deletion in the 5' end of the I-E alpha b gene.     

Isolation and analysis of (Gp)nXp sequences of rat liver 5S RNA by means of restricted ribonuclease T2 hydrolysis

Essentual difficulties arise when base number in oligoguanylic blocks and location of these blocks along the polynucleotide chain need to be determined in the course of determination of the nucleotide sequences in ribonucleic acids. To overcome this difficulty it is suggested to take advantage of a recently discovered resistance of phosphodiester bond between kethoxalated G and its 3′-neighbour against T₂ RNase hydrolysis 1,2. The approach is illustrated by analysis of 5S RNA from rat liver. Sequences of general formula (Gp)_nXp were isolated from T₂ RNase hydrolysate of 5 S RNA rapidly and quantitatively. The information obtained greatly facilitates the whole procedure of sequencing. It is expected that the method proposed would be effective for analysis of 5 S and 4 S RNA and for highmolecular weight fragments of ribosomal and viral RNAs.     

The size heterogeneity of rat insulin-like growth factor-I mRNAs is due primarily to differences in the length of 3'-untranslated sequence

Previous studies have revealed multiple size classes of rat insulin-like growth factor-I (IGF-I) of estimated size 7.5-7.0, 1.9-1.5, and 1.2-0.9 kilobases (kb). Available sequence information accounts for only 2.1 kb of the 7.5-7.0 kb IGF-I mRNAs. We used oligomer directed ribonuclease H (RNase H) mapping to define the extent to which the unknown sequence in the large molecular weight mRNAs lies 5' or 3' to known sequence. Rat liver polyadenylated RNAs were incubated with oligomer probes complementary to internal rat IGF-I precursor (E domain) coding sequences. RNase H was used to hydrolyze IGF-I mRNAs at the point of annealment with the oligomers. Resultant 5' and 3'-IGF-I mRNA fragments were analyzed on Northern blots. A probe specific for type 1 (class C) 5'-sequences (the most predominant of multiple 5'-sequence types found on rat IGF-I mRNAs) identifies intact IGF-I mRNAs of 7.5-7.0, 1.9-1.5 and 1.2-0.9 kb but, after oligomer directed RNase cleavage of these mRNAs, identified only a single IGF-I mRNA 5'-fragment. Major differences in the length of sequence 5' to the IGF-I coding sequence therefore, do not account for the multiple size classes of type 1 (class C) IGF-I mRNAs. The size of the 5'-fragment suggests that the extent of sequence 5' to the IGF-I coding sequence is 0.4-0.7 kb in type 1 (class C) IGF-I mRNAs. Identification of multiple 3'-fragments of IGF-I mRNAs demonstrated heterogeneity in the 3'-ends of rat IGF-I mRNAs.(ABSTRACT TRUNCATED AT 250 WORDS)     

Iscoms in parasitological research

During the history of vaccine development, a number of adjuvants and adjuvant formulations have been tested and evaluated for their ability to increase the immunogenicity of different antigens. In this review, Anna Lundén, Karin L?vgren Bengtsson, Anders Sj?lander and Arvid Uggla focus on iscoms (immune stimulating complexes), their characteristics and applications to different types of parasitic antigens.     

The effect of nisin on Listeria monocytogenes in culture medium and long-life cottage cheese

M.A.S.S. FERREIRA AND B.M. LUND. 1996. The sensitivity to nisin of 27 strains of Listeria monocytogenes , four of L. innocua and one of L. ivanovii was estimated at pH 6.8 and pH 5.5. Strains of L. monocytogenes showed differences in sensitivity which were not correlated with serotype. Strains of L. innocua were as resistant as the most resistant strains of L. monocytogenes , whereas the strain of L. ivanovii was relatively sensitive. Two of the most resistant strains of L. monocytogenes multiplied in aerated liquid medium adjusted to pH 5.0 with HCl, incubated at 20°C; nisin, 500 IU ml^-1, prevented multiplication and caused death. Following inoculation of a resistant strain into long-life cottage cheese, pH 4.6–4.7, the number of viable L. monocytogenes decreased approximately 10-fold during storage at 20°C for 7 d; addition of nisin, 2000 IU g^-1, to the cottage cheese increased the rate of inactivation to approximately a 1000-fold decrease in 3 d.