Population fluctuations, reproduction and survival in the Striped fieldmouse Rhabdomys pumilio on the Cape Flats, South Africa

A wild population of Striped fieldmice was studied for a continuous period of five years in an area of alien Acacio bush about 24 km from Cape Town, South Africa. Mice were live-trapped, marked by toe-clipping and released on a 60-station grid, and also kill-trapped in a separate area. Marked annual fluctuations in the population size were correlated with a 6–8 month summer breeding season. There were also marked inter-annual differences in peak population size. The age of sexual maturity of females was determined from the first pregnancy which occurred at 6–7 weeks old; and of males from the presence of visible spermatozoa in the vas deferens which occurred at about 11 weeks old. Litter size was affected by both the age and the body mass of the female. It appeared that mean survival from birth was only approximately 1.5 months and that survival from first capture was about 1.9–2.5 months. This high mortality appeared to be the major reason for the sharp seasonal fluctuations in population size and may also have been responsible for the interannual differences since marked changes in survival were recorded between some years.     

Plasma esterase polymorphism in the Bank vole, Clethrionomys glareolus, in Britain

Three hundred and eighty-three Clethrionomys glareolus from 20 localities in England, Wales and Scotland were typed for plasma esterase and a genetic polymorphism was discovered. The esterase was named Es-1. Breeding tests suggested that three alleles were segregating: Es-1^o when homozygous results in complete absence of enzyme activity. The active alleles Es-1^f and Es-1^s code for enzyme variants which migrate more rapidly and less rapidly, respectively, under starch gel electrophoresis. Of these active alleles, Es-1^f is morc common in the north of Britain and Es-1⁸ in the south. A 23-month field study on two areas at Wicken Fen, Cambridgeshire, suggested that animals possessing Es-1^s survived less well at high population densities, perhaps through their being more likely to emigrate.     

Selective protection of in vitro synthesized cDNA against nucleases by incorporation of phosphorothioate-analogues.

The conditions for the stepwise synthesis of single- (ss) and double-stranded (ds) cDNA using thio-analogues instead of dNTPs are described in this paper. RNA of paramyxovirus Sendai (strain 6/94) serves as template in these experiments. The increased resistance of this alpha S-modified cDNA against several nucleases, like S1-Nuclease, DNase I, Exonuclease III, snake venom Phosphodiesterase (PDE) and the combination of DNase I and PDE is demonstrated.     

Structure of viral DNA in a rat cell line transformed by the cloned EcoRI-C fragment of adenovirus 12.

A DNA segment carrying viral DNA was cloned from a rat cell line transformed by the cloned EcoRI-C fragment (0 to 16.4 map units) of human adenovirus type 12(Ad12), and the viral sequence in the clone was analysed. The cloned segment contained the region from nucleotide positions 118 to 3520 of the Ad12 genome in the middle. No unique structure was found at the viral and non-viral DNA junctions. When examined the transforming activity, the conserved viral sequence was able to transform rat 3Y1 cells efficiently. Southern blotting analysis of the viral sequence in five re-transformed cell lines showed that the viral sequence was inserted at different sites of cellular DNA. These results indicate that (I) the Ad12 DNA moiety from the enhancer-promoter region of the E1A gene to the end of the E1B gene contains enough information for efficient transformation of the rat cell, and (II) integration of the viral sequence at unique cellular sites is not prerequisite for transformation.     

Structure of the human alpha 1-acid glycoprotein gene: sequence homology with other human acute phase protein genes.

We have determined the sequence coding for human alpha 1-acid glycoprotein from two independently isolated cDNA clones and a genomic clone. The aminoacid sequences deduced from the three clones, deriving from three different individuals, are identical. Southern blot analysis on human DNA indicates that there are at least two genes coding for alpha 1-AGP. We propose that alpha 1-AGP found in plasma is a mixture of the products of these two different genes. This is the simpler explanation for the heterogeneity in the aminoacid composition in purified alpha 1-AGP observed by Schmid et al. (1). DNA sequence comparison with cDNA clones coding for human alpha 1-antitrypsin and haptoglobin shows a conserved sequence within the 5' untranslated region which may play a role in the acute phase response.     

Direct-acting mutagenicity of N4-aminocytidine derivatives bearing alkyl groups at the hydrazino nitrogens.

To investigate the mechanism of N4-aminocytidine-induced mutagenesis, N'-alkyl-N4-aminocytidines and N4-alkyl-N4-aminocytidines were prepared and their mutagenicity on bacteria were assayed. N'-Methyl-N4-aminocytidine, N'-(2-hydroxyethyl)-N4-aminocytidine and N',N'-dimethyl-N4-aminocytidine showed direct-acting mutagenicity on S. typhimurium TA100 and E. coli WP2 uvrA, tester strains that are sensitive to base-pair substitutions. In contrast, N4-methyl-N4-aminocytidine, N4-(2-hydroxyethyl)-N4-aminocytidine and N4,N'-dimethyl-N4-aminocytidine were not mutagenic on these bacteria. Since N'-methyl-N4-aminocytidine does not form hydrazones, the possibility that N4-aminocytidine causes mutation due to its reactivity with carbonyl compounds has been excluded. Furthermore, the fact that only those alkyl N4-aminocytidines having a hydrogen on the nitrogen at position 4 are mutagenic is consistent with the previously proposed mechanism in which the tautomerization between the amino and the imino forms of N4-aminocytosine allowing an ambiguous base pairing is the cause of the mutagenesis.     

Dependence of secretion and assembly of type 1 fimbrial subunits of Escherichia coli on normal protein export.

The export of fimbrial subunits was found to be diminished at the restrictive temperature in a strain bearing a secA(Ts) mutation. Likewise, export was inhibited in a strain harboring a malE-lacZ protein fusion upon induction of hybrid protein synthesis. Both conditions resulted in the accumulation of a precursor protein ca. 2,000 daltons larger than the mature fimbrial subunit.     

Simultaneous release of penicilloic acid and phenylacetyl glycine by penicillin-binding proteins 5 and 6 of Escherichia coli.

Penicillin-binding proteins (PBPs) 5 and 6 of Escherichia coli released the bound penicilloyl moiety at an intermediate rate relative to, e.g., Staphylococcus aureus PBPs 4 (rapid) and 1 or 2 (slow). Each of these E. coli PBPs released the bound penicilloyl moiety as both penicilloic acid (hydrolysis) and phenylacetyl glycine (scission of the C-5--C-6 bond followed by hydrolysis).     

Ectopic integration of chromosomal genes in Streptococcus pneumoniae.

When a DNA fragment containing a marker gene was ligated to random chromosomal fragments of Streptococcus pneumoniae and used to transform a recipient strain lacking that gene, the gene was integrated at various locations in the chromosome. Such ectopic integration was demonstrated for the malM gene, and its molecular basis was analyzed with defined donor molecules consisting of ligated fragments containing the malM and sul genes of S. pneumoniae. In a recipient strain deleted in the mal region of its chromosome, these constructs gave Mal+ transformants in which the malM and sul genes were now linked, with malM located between duplicate sul segments. Ectopic integration was unstable under nonselective conditions; mal(sul) ectopic insertions were lost at a rate of 0.05% per generation. Several possible mechanisms of ectopic integration were examined. The donor molecule is most likely to be a circular form of ligated homologous and nonhomologous fragments that, after entry into the cell, undergoes circular synapsis with the recipient chromosome at the site of homology, followed by repair and additive integration.     

Molecular cloning and genetic organization of C4-dicarboxylate transport genes from Rhizobium leguminosarum.

Cosmids containing C4-dicarboxylate transport (dct) genes were identified from a gene bank of Rhizobium leguminosarum DNA made in the broad-host-range vector pLAFR1 by their ability to complement R. trifolii dct mutants. The dct genes were further characterized by subcloning, restriction site mapping, and transposon Tn5 and Tn7 mutageneses. Three dct loci were identified within a 5.5-kilobase region of DNA, in the order dctA-dctB-dctC. The results suggested that dctA encoded a structural component necessary for C4-dicarboxylate transport, whereas dctB and dctC encoded positive regulatory elements, and that dctA was transcribed divergently from dctB and dctC. Expression of dctA and dctC was obtained from vector promoters in some pLAFR1- and pSUP106-based plasmids.