Studies on salmonellosis in the house mouse, Mus musculus.

Salmonellae were isolated from the faeces from 17 of 170 (10%) wild house mice. Salmonella typhimurium was isolated from 10, S. typhimurium, var. Copenhagen from 2, S. thompson from 1, and S. muenchen from 4. It was concluded that house mice could be a reservoir of infection and play an important role in human and animal salmonellosis.     

Esterase-13 of the rat (Rattus norvegicus) and its homology with esterase-3 of the house mouse (Mus musculus)

A new allele of esterase-13 was detected in various laboratory inbred strains of Rattus norvegicus and designated Es-13c. The activity of ES-13 towards a range of chromogenic substrates, inhibitor profile, isoelectric points and retardation coefficients on polyacrylamide gel electrophoresis were determined. The organ specific expression of ES-13 alleles was investigated and it was shown that kidney homogenates contained a factor which modified the liver enzyme banding pattern in vitro. The features of ES-13 from the rat indicated homology between this esterase and ES-3 from the house mouse, Mus musculus domesticus.     

Two erythrocytic lactate dehydrogenase variants in the house mouse, Mus musculus

Two erythrocytic LDH variants have been found in the house mouse, Mus musculus. One, involving the presence and absence of the next to the slowest electrophoretically separable isozyme, is controlled by a regulatory locus which may be similar to Ldr-1 (Shows and Ruddle, 1968). The second appears to be indirectly controlled by the Hbb locus and may be attributed to the accumulation of a storage product in the lysates. Ldr-1 is polymorphic in natural populations of the house mouse.     

Genetic differences in alteration of albumin in the house mouse,Mus musculus

Two strains of mice were shown to differ in relative proportion of two major protein bands of liver under acid conditions of electrophoresis. Genetic control was autosomal and by a pair of dominant and recessive genes. The difference was observed only if liver homogenates were extracted by treating with dilute acid and alkali. The two protein bands were identified as albumin on the basis of electrophoretic migration, molecular weight, and immunological response. No differences were found between strains in relative amounts of comparable bands of plasma. However, in studies with extraction of mixtures, liver homogenates of one strain but not another were capable of converting a large proportion of albumin from several sources to a faster-migrating form. It was concluded that the strains differ in a factor in liver capable of causing a secondary modification of the albumin molecule.     

Linkage of the locus for serum albumin in the house mouse,Mus musculus

An electrophoretic variant for serum albumin in Mus musculus has been used to map the structural gene for this protein to chromosome 5.     

Purification and characterization of esterase 2B of the house mouse, Mus musculus

The N-terminal tryptic peptide of Crithidia oncopelti cytochrome c557 X-Pro-Me3Lys-Ala-Arg in which X represents an unknown N-terminal blocking group was characterized by electrophoresis at pH 2 and by 1H and 13C nuclear magnetic resonance. 1H-NMR spectra of the tryptic peptide suggested that the blocking group X was N,N-dimethylproline although the electrophoretic mobility of the peptide suggested a larger molecular weight. The peptides X-Pro-Me3Lys and X-Pro were generated by treatment of the tryptic peptide with thermolysin and carboxypeptidase and the free blocking group X was prepared by acid hydrolysis. Comparison of the 1H-NMR spectra of these peptides with spectra of synthetic N,N-dimethylproline and N,N-dimethylprolylproline demonstrated that the blocking group was indeed N,N-dimethylproline. The 13C-NMR spectrum of the tryptic peptide was consistent with this conclusion although unambiguous assignments to all resonances could not be obtained because of the small amount of material available. The origin of the dimethylproline blocking group is discussed.     

Epigenetic formation of lactate dehydrogenase isozymes in the house mouse, Mus musculus.

The origin of mouse lactate dehydrogenase (LDH) sub-bands was investigated by using our miniaturized polyacrylamide gel electrophoretic apparatus. Mouse LDH isozymes are generated by combinations of three types of A subunit, the primary type and two epigenetically modified forms. These are designated A1, A2, and A3 in the order of their electrophoretic mobilities towards the anode. The A1 subunit arises from the covalent binding of molecules of glutathione through disulfide bonds to the original subunit, A3. The A2 subunit arises from the covalent binding of molecules of cysteine through disulfide bonds to the A3 subunit. All isozymes can be explained as tetramers composed of the three kinds of A subunit (A1, A2, or A3) in combination with B subunits to yield a total of 35 isozymes. The kinetic properties of these sub-bands were also examined. There was no difference between A24 and A34 in the Km for pyruvate and for lactate. Thermostability at 56 degrees C was greater for A34 than for A24. The activities of tetramers at the electrophoretic position of A3B1 and A4 in extracts containing all five isozymes were increased by treatment of the extracts with high concentrations of reduced glutathione or cysteine with the concomitant disappearance or decrease in activity of tetramers at the position of B4 and A3B1. These results suggest that, in the presence of reduced glutathione or cysteine, LDH isozymes containing the B subunit are first dissociated and then the A subunits are preferentaially recombined.     

Of mice and 'convicts': origin of the Australian house mouse, Mus musculus

The house mouse, Mus musculus, is one of the most ubiquitous invasive species worldwide and in Australia is particularly common and widespread, but where it originally came from is still unknown. Here we investigated this origin through a phylogeographic analysis of mitochondrial DNA sequences (D-loop) comparing mouse populations from Australia with those from the likely regional source area in Western Europe. Our results agree with human historical associations, showing a strong link between Australia and the British Isles. This outcome is of intrinsic and applied interest and helps to validate the colonization history of mice as a proxy for human settlement history.     

Ejaculate allocation under varying sperm competition risk in the house mouse, Mus musculus domesticus

A common mechanism through which males can enhance their successin postcopulatory contests over paternity is to inseminate moresperm than their rivals. However, ejaculate production is costlyand the evolution of prudent sperm allocation strategies sensitiveto variation in local levels of sperm competition has now beendemonstrated in diverse taxa, including mammals. Theory predictsan increased sperm allocation in response to an elevated riskof sperm competition, but here we show that male house mice(Mus musculus domesticus) instead ejaculate fewer sperm perejaculate when mating in the presence of a rival male. Thissurprising sperm allocation pattern may be a necessary consequenceof adaptive changes in copulatory behavior, enabling males toachieve more rapid sperm transfer and/or to ejaculate repeatedlyunder risk of sexual competition. The size of a second ejaculatecomponent, the copulatory plug, is unaffected by sperm competitionrisk. Our results highlight how the often complex interplaybetween different reproductive traits can affect the evolutionof sperm competition phenotypes.     

Structural differences between albumin A and albumin C of the house mouse,Mus musculus

Two albumins, albumin A from C3H mice and albumin C isolated from descendents of the wild mice in which the variant was first uncovered, were found to differ in their electrophoretic properties. Albumin C was shown to bind two more H⁺ ions than albumin A at pH 5.4. Peptide mapping after trypsin digestion revealed that albumin C had three peptides (TP-C1, TP-C2, and TP-C3) which were missing in albumin A. The latter likewise had a peptide (TP-A1) which was not found in albumin C. An amino acid analysis of the variant peptides suggests that TP-A1 had been split into TP-C1 and TP-C2 on digestion with trypsin, because a glutamic acid in TP-A1 was replaced by a lysine. This change would also appropriately alter the electrophoretic properties of albumin C. No obvious counterpart was discovered for TP-C3 of albumin C in albumin A.This work was supported by a grant from the National Research Council of Canada.     

Genomic analyses of the Formosan harvest mouse (Micromys minutus) and comparisons to the brown Norway rat (Rattus norvegicus) and the house mouse (Mus musculus)

The harvest mouse, Micromys minutus (MMIN), has a very wide range of distribution (from the British Isles across the Euroasian continent to Japan and Taiwan). We studied an isolated population of MMIN in Taiwan, which is at the southeastern margin of the species’ geographic distribution, and compared its genetic complement with those of the same species previously reported from other geographic locations and with two model rodent species, the house mouse (Mus musculus) and the brown Norway rat (Rattus norvegicus). The diploid number (2N) of MMIN was 68, consistent with that reported for other populations. However, variations were noted in the fundamental number (FN) and the shape and banding patterns of the individual chromosomes among populations. The FN of MMIN was estimated to be 72, including 2 bi-armed autosomes, 31 one-armed autosomes, and one pair of one-armed sex chromosomes. Here, we propose the first ideogram for MMIN. C-banding, Ag-NOR, and the locations of 18S rRNA gene sequences (MMIN chromosomes no. 10, 14, 19, 29, 31, 33, and X) mapped by fluorescence in situ hybridization (FISH) are also reported. Additionally, we compared the 18S rDNA sequences and performed cross-species X chromosome painting (FISH) for M. minutus, M. musculus, and R. norvegicus. The results indicate that both genetic elements are rather conserved across species. Thus, implications for the phylogenetic position of Micromys were limited.     

Diet of the house mouse (Mus musculus) on Guillou Island, Kerguelen archipelago, Subantarctic

The diet of the house mouse (Mus musculus domesticus), introduced to the Kerguelen archipelago in the 1800s, was studied at monthly intervals from August 1997 to July 1998 in the closed communities of Acaena magellanica, the main habitat of mice on Guillou Island. The analysis of 291 stomach contents showed that this opportunistic rodent included a variety of items in its diet: earthworms (Dendrodrilus rubidus tenuis, Microscolex kerguelensis), caterpillars of a flightless moth (Pringleophaga kerguelensis), weevil adults and larvae (Ectemnorrhinus spp.), seeds of Acaena magellanica, and floral parts of dandelion (Taraxacum officinale). The animal prey were dominant in its diet all year round, except in summer. Based on the presence of chaetae in the stomach contents, our results show that earthworms are an important prey for the house mouse at Kerguelen. The consequences of these food habits for the invertebrate communities of the subantarctic islands are discussed.     

Dynamics of non-specific esterase during fat resorption in the jejunum of the house mouse,Mus musculus

Summary The dynamics of non-specific esterase in the upper duodenum of the house mouse was studied electron microscopically at various intervals following a fat meal. Enterocytic esterase became associated with lipid droplets during fat resorption and formation of primary chylomicrons. Esterase activity remained associated with the primary chylomicrons throughout the process of extrusion into the extracellular space at the lateral interdigitations, and during subsequent transport into the lymph vessels. It is suggested that certain isozymes of non-specific esterase participate in lipid transport.Supported by the Deutsche Forschungsgemeinschaft (SFB 46). This is contribution no. 37 of a research program devoted to the cellular distribution and genetics of non-specific esterase