In vitro induction of early mouse embryo intracisternal particles (epsilon particles) in cultured cell lines.

The experimental induction of epsilon particles, retrovirus-like structures corresponding to the small IA particles of the mouse, was studied by electron microscopy in rodent-cultured cell lines. Among the chemicals tested, only IdUr was shown to be an effective inducer, but not cycloheximide, puromycin , deoxy-fluorouracil or 5-azacytidine. However, only two mouse-derived cell lines: Ki-BALB and FG 10, among 27 cell lines of mouse, rat and mink origins tested, expressed epsilon particles upon IdUr treatment. Epsilon particles thus respond to chemical inducers very differently in comparison with large IAP. Moreover, the addition of interferon previously shown to attenuate IAP production, had no effect on that of epsilon particles.     

Fluctuations and patterns of desert rodent communities under human disturbance: fluctuating tendency and sensitive response of their population

The four kinds of sites under different kinds of human disturbances, i.e. a farmland area, a rotational-grazing area, an over-grazing area and a prohibited-grazing area, were selected in the typical region of the Alashan Desert of Inner Mongolia from April to October in 2002, 2003 and 2004 respectively. The fluctuating tendency of rodent communities and the sensitive response of their populations were studied using mark-recapture and trap-day methods. The four kinds of mark-recapture samples and line samples were taken in different human disturbance areas. The area of the mark-recapturing sample was 0.95 hm2 and that of the line sample was 10 km2. The samples were collected every month in the mark-recapturing sites for four consecutive days and in line sites in April, July and October every year. The variable matrix was composed of the numbers of captured rodents of the rodent communities. The sensitive response of the populations in the communities was analyzed with principal component analysis (PCA). Results showed that there were different types of rodent communities under different kinds of human disturbance on two scales in three years. In each scale, there were large differences in both the number of species and the number of main population in the rodent communities under different kinds of human disturbance on the farmland area and over-grazing area especially. The results of PCA showed that the sensitive response of the populations of the communities was significantly different under different kinds of human disturbance on the two scales in the three years. Cricetulus barabensis was the most sensitive on the farmland area, there were no differences in sensitive response of the various rodents on the rotational-grazing area, and Dipus sagitta and Phodopus roborovskii were the most sensitive in the over-grazing area.     

Reactions to disturbances in the context of antipredatory behaviour in a solitary subterranean rodent

We investigated reactions of free-living silvery mole-rats (Heliophobius argenteocinereus) to anthropogenic disturbances. Mole-rats detected soil vibrations caused by man carefully walking at a distance of up to 6 m (proved by radio-telemetry). Occasionally, mole-rats encountered outside a nest retreated there after this type of disturbance. After having their burrows broken into, the mole-rats retreated into deep tunnels, separating themselves from the rest of the burrows by soil plugs. Trapping success of silvery mole-rats using live traps for subterranean rodents was low, which contrasts with data so far published on social bathyergids. Antipredatory function of examined behaviours is discussed.     

Novel method for evaluating the health condition of mice in space through a video downlink

Clarification of the criteria for managing animal health is essential to increase the reliability of experiments and ensure transparency in animal welfare. For experiments performed in space, there is no consensus on how to care for animals owing to technical issues, launch mass limitation, and human resources. Some biological processes in mammals, such as musculoskeletal or immune processes, are altered in the space environment, and mice in space can be used to simulate morbid states, such as senescence acceleration. Thus, there is a need to establish a novel evaluation method and evaluation criteria to monitor animal health. Here, we report a novel method to evaluate the health of mice in space through a video downlink in a series of space experiments using the Multiple Artificial-gravity Research System (MARS). This method was found to be more useful in evaluating animal health in space than observations and body weight changes of the same live mice following their return to Earth. We also developed criteria to evaluate health status via a video downlink. These criteria, with “Fur condition” and “Respiratory” as key items, provided information on the daily changes in the health status of mice and helped to identify malfunctions at an early stage. Our method and criteria led to the success of our missions, and they will help establish appropriate rules for space experiments in the future.     

Whisker exploration behaviours in the 5xFAD mouse are affected by sex and retinal degeneration

Active whisking in mice and rats is one of the fastest behaviours known in mammals and is used to guide complex behaviours such as exploration and navigation. During object contact, whisker movements are actively controlled and undergo robust changes in timing, speed and position. This study quantifies whisker movements in 6‐ to 7‐month old male and female 5xFAD mice, and their C57/SJL F1 wild‐type (WT) controls. As well as genotype, we examined sex differences and the effects of retinal degeneration (rd). Mice were filmed using a high‐speed video camera at 500 frames per second (fps), under infrared light while behaving freely in three tasks: object exploration, sequential object exploration and tunnel running. Measures of whisker position, amplitude, speed and asymmetry were extracted and analysed for each task. The 5xFAD mice had significantly altered whisker angular positions, amplitude and asymmetry during object contacts and female 5xFAD mice with rd had lower mean angular positions during object contact. There were no significant effects of genotype on sequential object exploration or on tunnel running but differences due to sex and rd were found in both tasks, with female mice making larger and faster whisker movements overall, and mice with rd making larger and faster whisker movements during object contact. There were sex differences in whisker movements during sequential object exploration and females with rd had higher whisker retraction speeds in tunnel running. These data show that measuring whisker movements can quantify genotype and sex differences and the effects of rd during exploratory behaviour in these mice.     

The effectiveness of poison bait stations at reducing ship rat abundance during an irruption in a Nothofagus forest

Abstract

Ship rats exhibit large increases in abundance (irruptions) following heavy beech seedfall in New Zealand's Nothofagus forests. Predation by rats at high density severely damages native fauna populations. In 2006 the Department of Conservation undertook a management experiment in the Eg‐linton Valley to see if they could protect endangered species during a rat irruption. Poison (0.15% 1080, followed by 0.0375% coumatetralyl, or Racumin®) was laid in bait stations, and the consequences for rat abundance and survival were estimated. All 10 radio‐tagged rats died, suggesting that 1080 had a high impact on the rat population. The two rats that made the smallest daily movements survived longer than the others. Live trapping documented a reduced abundance of rats within the poison area (450 ha) after 1 month of poisoning. However, after 4 months of poisoning, the abundance of rats had begun to recover. Further investigation is needed on acceptance of Racumin® to rats, optimum spacing of bait stations for rats, and bait competition between rats and mice when densities of both species are high.     

Evolutionary patterns of major urinary protein scent signals in house mice and relatives

Scent marks are important mediators of territorial behaviour and sexual selection, especially among mammals. The evolution of compounds used in scent marks has the potential to inform our understanding of signal evolution in relation to social and sexual selection. A major challenge in studies of chemical communication is that the link between semiochemical compounds and genetic changes is often unclear. The major urinary proteins (MUPs) of house mice provide information on sex, status and individual identity. Importantly, MUPs are a direct protein product of genes, providing a clear link between genotype and phenotype. Here, we examine the evolution of urinary protein signals among house mice and relatives by examining the sequences and patterns of mRNA expression of Mup genes related to urinary scent marks. MUP patterns have evolved among mouse species both by gene duplication and variation in expression. Notably, protein scent signals that are male specific in well‐studied inbred laboratory strains vary in sex‐specificity among species. Our data reveal that individual identity signals in MUPs evolved prior to 0.35 million years ago and have rapidly diversified through recombining a modest number of amino acid variants. Amino acid variants are much more common on the exterior of the protein where they could interact with vomeronasal receptors, suggesting that chemosensory perception may have played a major role in shaping MUP diversity. These data highlight diverse processes and pressures shaping scent signals, and suggest new avenues for using wild mice to probe the evolution of signals and signal processing.     

Plasmodium berghei: inhibitors of ornithine decarboxylase block exoerythrocytic schizogony

DL-alpha-difluoromethylornithine and DL-alpha-monofluoromethyldehydroornithine methyl ester, inhibitors of ornithine decarboxylase, blocked exoerythrocytic schizogony of Plasmodium berghei in mice and in cultured human hepatoma cells. These effects were reversed by exogenous administration of the polyamine, spermidine. The antimalarial drug, primaquine, the side chain of which is structurally analogous to a natural polyamine, did not enhance the activity of alpha-difluoromethylornithine or alpha-monofluoromethyldehydroornithine methyl ester. These results extend previous observations that polyamines influence the malaria parasite's schizogony outside the red blood cell but not within it.