Aspen wood-wool is preferred as a resting place, but does not affect intracage fighting of male BALB/c and C57BL/6J mice

Aspen wood-wool, provided as nesting material, was evaluated as a possible improvement of cage environment for 10-14-week-old inbred male mice maintained in groups of six (BALB/c n = 72 and C57BL/6J n = 36). The daily behaviour of mice was video recorded and their body weight, food consumption, weights of some organs and serum corticosterone concentrations were measured. Aggressive interactions between cage mates and against a strange intruder as well as the number of wounds on the back of the animals was monitored in order to evaluate the effect of nesting material on intermale aggression. Nesting material did not affect the daily active/passive behaviour patterns of mice, although animals clearly preferred it as a resting place. BALB/c mice given nesting material showed less weight gain and smaller brown adipose tissue weights than animals without nesting material. The other characteristics measured were not affected by the presence of nesting material in either strain. The presence of nesting material had no effect on fighting in cages. C57BL/6J mice were more aggressive than BALB/c mice according to the number of wounded animals in a cage. Wounded BALB/c mice had enlarged spleens and decreased epididymal adipose tissue weights. In conclusion, the nesting material used in this study did not adversely affect the animals. On the other hand, the material was clearly preferred to conventional bedding as a resting place. These findings suggest that nesting material may improve the cage environment of laboratory mice. Furthermore, there was an indication of strain differences in aggressive behaviour. It could be suggested that C57BL/6J mice are less tolerant towards intruders and housing six mice per cage is not suitable for this strain.     

Pregnancy rates, prenatal and postnatal survival of offspring, and litter sizes after reciprocal embryo transfer in DBA/2JHd, C3H/HeNCrl and NMRI mice

Success of embryo transfer is often a limiting factor in transgenic procedures and rederivation efforts, and depends on the genetic background of the donor and recipient strains used. Here we show that embryo transfer to DBA/2J females is possible, and present data on pre- and postnatal success rates after reciprocal embryo transfer using the inbred DBA/2J and C3H/HeN, and outbred NMRI strains. The highest embryo yield was achieved in outbred NMRI females, but embryo yields were similar in DBA/2J and C3H/HeN mice following superovulation despite poor estrus cycle synchronization in DBA/2J females. In-strain transfer of DBA/2J blastocysts (transfer of embryos to recipients from the same strain) resulted in pregnancy rates (57.1%) similar to those obtained following in-strain transfer of C3H/HeN (60.0%) and NMRI mice (83.3%), although the prenatal survival rate of blastocysts was low. Moreover, from the pups born only half survived the postnatal period after transfer of DBA/2J and C3H/HeN blastocysts to DBA/2J recipients. These problems were not observed when transferring NMRI-blastocysts to C3H/HeN and DBA/2J mothers. The number of blastocysts transferred also had a positive effect on the success of embryo transfer. In conclusion, C3H/HeN and DBA/2J females can be used as recipients for embryo transfer procedures for certain donor strains like NMRI, as one major determinant seems to be the genetic background of the embryos transferred. We also recommend to increase the number of DBA/2J blastocysts transferred, and to foster the DBA/2J pups to other DBA/2J mothers postnatally for in-strain transfer of DBA/2J mice.     

The activity of alkaline phosphatase in the sera of DBA/2NCrj and CBA/BrA mice with calcified tongue lesions

Spontaneously occurring calcified lesions were found in the tongues of DBA/2NCrj and CBA/BrA mice. In the DBA/2NCrj strain, the frequency of the lesion was 80% (males) and 88% (females). The youngest age of a mouse with this lesion was 18 days after birth, and 3-4 lesions were found in the tongue of 6- to 8-week-old mice. In CBA/BrA mice, 20% of females and 48% of males had the lesions. No significant differences were found in the serum calcium concentrations in high and low lesion-developing strains, but the alkaline phosphatase activities in the high-developing DBA/2NCrj, DBA/LiA, and CBA/BrA strains were higher than in strains with no calcified lesions.     

An optimal embryo transfer condition for the effective production of DBA/2J mice.

The DBA/2J mouse strain is a standard laboratory strain that is widely used for biomedical research. This strain, however, suffers from poor reproductive performance. In addition, the conditions for reliable embryo transfer (ET) of this strain have not been elucidated. The intention of this study was to determine the optimal number of embryos for transfer that allow the effective production of DBA/2J offspring. In the experiment, 7 to 15 embryos per oviduct were transferred into pseudopregnant ICR females. A relatively high success rate for pup production was observed when a large number of DBA/2J embryos (30 embryos per female) were transferred. This result shows that the ET efficiency of the DBA/2J strain can be improved by increasing the number of transferred embryos.     

Sex-specific constitutive expression of the pre-neoplastic marker glutathione S-transferase, YfYf, in mouse liver.

Hepatic glutathione S-transferase isoenzyme content has been investigated in both sexes of three inbred strains of mice (DBA/2, C3H/He, C57BL6). A polypeptide (Mr 24,800), which is immunologically related to Yf purified from rat lung, was found to be expressed as a major form in all male mouse livers but represented only a minor enzyme form in female mouse liver. Glutathione S-transferases comprising subunits with molecular masses of 25,800 (Ya) or 26,400 (Yb) were present in males and females of the three strains under investigation. Cytosolic isoenzymes from all strains and sexes were purified to apparent homogeneity and no significant inter-strain differences in the properties of the individual forms were observed. In addition, no differences were detected in the microsomal glutathione S-transferase content of the different strains or sexes.     

Sex and strain differences in the brush border and PAS-positive granules and giant bodies of the mouse renal S3 segment cells.

We recently demonstrated sexual dimorphism in the S3 segment of the ICR mouse kidney, as differences in periodic acid Schiff (PAS) staining on the brush border and the number and size of PAS-positive granules. However, whether these sex dependent features in the S3 segment of the mouse kidney occur only in the ICR strain or are a general feature also observed in other strains is unclear. In the present study, we examined the renal S3 segment of the ICR, BALB/c, C57BL/6, C3H/He and DBA/2 mice strains, which are commonly used in laboratory experiments. PAS staining of the brush border in females of all strains was more intense than that of males, and PAS-positive granules were detected in all females. In male groups, PAS-positive granules were detected in the DBA/2 strain only, but their number was very few. In addition, PAS-positive giant bodies, larger than the nuclear size, were detected in females except those of the C57BL/6 strain. Histometrical investigation demonstrated apparent strain differences in a number of PAS-positive granules and PAS-positive giant bodies. The ultrastructural and cytochemical investigations suggest that the PAS-positive granules and PAS-positive giant bodies were multilamellar lysosomes. We propose that the present findings are significant for comparative morphology in laboratory animal science.     

Life expectancy, its relation to sexual activity and body weight in male inbred mice.

Body weight of male mice of five inbred strains caged in groups of five was determined three times between the ages of 80 and 100 days, representing the individual fully grown body weight. Sexual activity of each mouse (number of ejaculations and intromissions) was estimated under competitive conditions between the ages of 120 and 150 days in eleven repetitions. Within all inbred strains only about half of the males displayed sexual activity when confronted with an estric female. The other do not. The animals remained in their cage groups until natural death after 727 +/- 215 days (C57BL/6), 638 +/- 260 days (BALB/c), 630 +/- 187 days (CBA), 560 +/- 230 days (DBA/2) and 317 +/- 62 (AKR) days. Only amongst the sexually active animals did individual life span correlate with the number of ejaculations. This was seen in C57BL/6, CBA and DBA/2. Particularly sexually successful animals, carrying out the most ejaculations, live 10-20% longer than their (subdominant) competitors displaying less sexual success. Sexually inactive males (characterised by no ejaculations and less other sexual activities) show that this characteristic of their personalities imposes no limitation upon their life expectancy. Fully grown body weight and the individual life span correlates within the strains DBA/2, C57BL/6 and BALB/c. Medium-sized animals have a greater life expectancy than small or large ones.     

Comparison of lung virus titers in susceptible and resistant inbred mouse strains against Sendai virus infection

Susceptibility of inbred mouse strains to Sendai virus (Mol strain) infection was studied. Although some mouse strains showed age differences in susceptibility between 3-to 4-week-old and 7-to 8-week-old mice, such age differences in susceptibility were not observed in susceptible DBA/2N and resistant BALB/cA mice. In 7-to 8-week-old mice, remarkable strain differences were observed in mortality and intensity of the lung lesions, but not in lung virus titers and serum antibody, between resistant BALB/cA and susceptible DBA/2N mice.     

Long-term effects of husbandry procedures on stress-related parameters in male mice of two strains

In socially unstable groups of male laboratory mice, individuals may experience a chronic stress situation. Previous experiments have shown that the transfer of specific olfactory cues during cage cleaning, and the provision of nesting material decrease aggression and stress in group-housed male mice. In this study, the combined effect of these husbandry procedures were tested for their long-term effect on stress in groups of moderately aggressive (BALB/c) and severely aggressive (CD-1) male mice. The physiological and behavioural stress-related parameters used were body weight, food and water intake, spleen and thymus weight, adrenal tyrosine hydroxylase activity, urine corticosterone levels and behaviour in a cage emergence test. Long-term provision of nesting material and its transfer during cage cleaning was found to influence several stress-related physiological parameters. Mice housed in cages enriched with nesting material had lower urine corticosterone levels and heavier thymuses, and they consumed less food and water than standard-housed mice. Furthermore, marked differences were found between strains. CD-1 mice were less anxious in the cage emergence test, weighed more, ate and drank more, and had heavier thymuses but lighter spleens and lower corticosterone levels than BALB/c mice. We conclude that the long-term provision of nesting material, including the transfer of nesting material during cage cleaning, reduces stress and thereby enhances the welfare of laboratory mice.     

Genetic analysis of the diabetes-prone C57BLKS/J mouse strain reveals genetic contribution from multiple strains

The C57BLKS/J (BKS) inbred mouse strain is a widely used animal model of type 2 diabetes. In the presence of the diabetes (db) mutation, obese BKS-db mice develop severe diabetes. Genetic studies of diabetes-susceptibility in this strain are facilitated by the fact that BKS is a genetic composite between the diabetes-resistant C57BL/6J (B6) and susceptible DBA/2J (DBA) strains. On this basis, it has been hypothesized that diabetes-susceptibility in BKS is conferred by DBA-derived alleles. However, recent studies revealed non-B6/non-DBA genetic material in BKS. To identify the origin of this genetic component, we generated a genomic map of BKS using 537 microsatellite markers. Our results demonstrate that, in addition to B6 and DBA, BKS contains alleles from at least three other strains, including 129, C57BL/10 and an unidentified mouse strain. We also analyzed two congenic strains, B6-db and BKS-db, which are widely used for the genetic mapping of diabetes-susceptibility loci. We identified several donor-derived genomic regions introduced during the generation of these congenic strains. In summary, our study reveals novel aspects of the genetic fine-structure of BKS and related strains and facilitates the identification of diabetes-susceptibility loci in this mouse model.     

Relationship between Numerous Mast Cells and Early Follicular Development in Neonatal MRL/MpJ Mouse Ovaries

In the neonatal mouse ovary, clusters of oocytes called nests break into smaller cysts and subsequently form individual follicles. During this period, we found numerous mast cells in the ovary of MRL/MpJ mice and investigated their appearance and morphology with follicular development. The ovarian mast cells, which were already present at postnatal day 0, tended to localize adjacent to the surface epithelium. Among 11 different mouse strains, MRL/MpJ mice possessed the greatest number of ovarian mast cells. Ovarian mast cells were also found in DBA/1, BALB/c, NZW, and DBA/2 mice but rarely in C57BL/6, NZB, AKR, C3H/He, CBA, and ICR mice. The ovarian mast cells expressed connective tissue mast cell markers, although mast cells around the surface epithelium also expressed a mucosal mast cell marker in MRL/MpJ mice. Some ovarian mast cells migrated into the oocyte nests and directly contacted the compressed and degenerated oocytes. In MRL/MpJ mice, the number of oocytes in the nest was significantly lower than in the other strains, and the number of oocytes showed a positive correlation with the number of ovarian mast cells. The gene expression of a mast cell marker also correlated with the expression of an oocyte nest marker, suggesting a link between the appearance of ovarian ? 4mast cells and early follicular development. Furthermore, the expression of follicle developmental markers was significantly higher in MRL/MpJ mice than in C57BL/6 mice. These results indicate that the appearance of ovarian mast cells is a unique phenotype of neonatal MRL/MpJ mice, and that ovarian mast cells participate in early follicular development, especially nest breakdown.     

Mouse strain difference in bile duct lesions induced by swine serum injections

The mouse strain difference in bile duct lesions was studied on male A/J, BALB/c, C57BL/6, C3H/He, DBA/2 and DDY mice 4 weeks old given intraperitoneal injections of swine serum (0.05 or 0.2 ml per mouse) twice a week for 4 weeks. The hepatic lesions were restricted to the portal tract. Biliary epithelial cells showed hypertrophy and hyperplasia, and eosinophilic and homogeneous or needle-shaped material appeared in the cytoplasm of such hypertrophied epithelial cells and in the ductular lumen. Around these damaged biliary epithelia, eosinophil leukocyte and plasma cell infiltration with proliferation of collagen fibres was commonly detected. These changes became more apparent with increasing size of bile duct. Such histopathological characteristics of hepatic lesions were essentially the same in all strains, but the severity showed a clear strain difference: the lesion was marked in the DDY, A/J and BALB/c strains, moderate in C3H/He and slight in C57BL/6 and DBA/2. A high production of anti-swine-serum antibodies associated with a marked increase in the number of mouse IgG-producing lymphocytes in the spleen was detected in the strains showing the marked hepatic lesions.     

Genetics of dystrophic epicardial mineralization in DBA/2 mice

The genetics of dystrophic epicardial mineralization in mice was studied using 6 to 8-week-old hybrids and recombinant inbred strains derived from DBA/2J (high prevalence) and C57B1/6J (low prevalence) mice. DBA/2J mice of both sexes were uniformly affected. No cases were seen among 32 F1 mice and 82 F2 mice. Six out of 31 backcross progeny obtained from F1 females backcrossed to DBA/2J males were affected. Two out of 25 recombinant inbred strains were affected. These results suggest that dystrophic epicardial mineralization is determined by three or four unlinked autosomal recessive alleles.     

The nesting biology and population dynamics of the Seychelles potter wasp Eumenes alluaudi Perez

Abstract. 1. The nesting biology of the solitary potter wasp Eumenes alluaudi was studied on Cousin Island, Seychelles.
2. Although the rainy season was from October to April there was no indication of strong seasonality in the wasps' nesting.
3. Females tended to nest close to where other females were nesting.
4. The mean number of cells per nest was 3.71, the mean number of nests made per female 135, and the percentage of cells from which adults emerged 65.87; thus the mean number of adult wasps emerging from the nest(s) of each breeding female was 3.29.
5. Male-producing eggs were laid before female-producing eggs and the estimated sex ratio at emergence was, at 1:2.52, female biassed. It is possible that inbreeding occurred.
6. Daily mortality of nesting females was estimated as 0.088.
7. The mean interval between a female's emergence and her starting to nest was 19.7 days.
8. Marking showed that only 26.7 ± 6.3% of females emerging from cells in the study area returned to breed there. Since the number of emerging daughters per breeding female was only 5.01 times 0.66 times 0.72 = 2.36 (fecundity x proportion emerging x proportion of females emerging), the number of returning females would be only 236 times 0.267 = 0.63, and hence, in order to maintain numbers over many generations, 037 females must have been immigrants.     

Behavioral, physiological, and molecular differences in response to dietary restriction in three inbred mouse strains

Food restriction paradigms are widely used in animal studies to investigate systems involved in energy regulation. We have observed behavioral, physiological, and molecular differences in response to food restriction in three inbred mouse strains, C57BL/6J, A/J, and DBA/2J. These are the progenitors of chromosome substitution and recombinant inbred mouse strains used for mapping complex traits. DBA/2J and A/J mice increased their locomotor activity during food restriction, and both displayed a decrease in body temperature, but the decrease was significantly larger in DBA/2J compared with A/J mice. C57BL/6J mice did not increase their locomotor activity and displayed a large decrease in their body temperature. The large decline in body temperature during food restriction in DBA/2J and C57BL/6J strains was associated with a robust reduction in plasma leptin levels. DBA/2J mice showed a marked decrease in white and brown adipose tissue masses and an upregulation of the antithermogenic hypothalamic neuropeptide Y Y(1) receptor. In contrast, A/J mice showed a reduction in body temperature to a lesser extent that may be explained by downregulation of the thermogenic melanocortin 3 receptor and by behavioral thermoregulation as a consequence of their increased locomotor activity. These data indicate that genetic background is an important parameter in controlling an animal's adaptation strategy in response to food restriction. Therefore, mouse genetic mapping populations based on these progenitor lines are highly valuable for investigating mechanisms underlying strain-dependent differences in behavioral physiology that are seen during reduced food availability.     

Role of the genetic-physiological interrelationships of mother-progeny in establishing the viability and fertility of mammals. II. The weight of the embryos of BALB, CBA and DBA strain mice developing from transplanted blastocysts

The weights of embryos and their placentas obtained by blastocysts of CBA/LacY and DBA/2 mouse strains transfer in recipient females of BALB/c strain and also by blastocysts of BALB/c mouse strain transfer in recipient females of CBA/LacY strain were analysed on the 16th gestation day. It is shown that placental weights are determined by genotypic peculiarities of embryos, although comparative placental weights of different strain embryos could also depend on females fertility. The weight of allogenic embryos (developed from transferred blastocysts) significantly excessed the weight of singenic embryos, and most significant differences were noted in females with small number of embryos. The possibilities to solve some applied and fundamental problems of mammalian reproduction given by the method of interstrain and interbreed early stage embryos transfer are discussed.     

Effect of enrichment on variation and results in the light/dark test

Several confounding factors may influence the outcome of an experiment and the extent of inter-individual variation. The aim of this study was to investigate if cage enrichment induces an effect on experimental mean values and on inter-individual variation in the light/dark paradigm using diazepam as the anxiolytic drug. The behaviour of 216 naive adult male mice of two different strains (BALB/c and C57BL/6) was studied. The animals were housed in groups of four in 'non-enriched', 'enriched' (nesting material) or 'super-enriched' (nest-box, nesting material, wooden gnawing stick and PVC tube) cages. After 5 weeks the animals were assigned to one of three treatments: control (no injection), sham (saline injection i.p.) or diazepam (1 mg/kg bw i.p.) and tested in the light/dark test for 5 min. Variation data were analysed using three different methods (mean absolute deviation, coefficient of variation and power analysis). The C57BL/6 mice scored higher than BALB/c mice in activity related measurements and showed a less 'emotional' behaviour profile in the pharmacological control situation of the light/dark test. In this study the anxiolytic effect of diazepam was clear in BALB/c mice but absent in C57BL/6 mice. Mice housed in enriched and super-enriched cages gained more weight than mice in non-enriched cages, although food intake was not affected. Generally, the strain of mouse had the greatest impact on both mean values and variation. However, there was no consistent increase for one particular strain. The choice of statistical method for analysing variation may influence the interpretation of within-group variability, but none of the methods showed any significant differences between standard and enriched conditions on variability in any of the parameters measured.     

T cell recognition of Mlsc,x determinants

Among a large number of cow insulin-specific T cell clones derived from both C57BL/10 and B10.A strains, several were found to react to non-MHC-linked gene products of a number of allogeneic strains. The stimulatory moiety for three of these clones correlates, in part, with expression of Mlsc, as defined by mouse strains C3H/HeJ and A/J. In addition, all three of these clones are stimulated by cells from strain PL/J, which has the poorly defined Mlsx allele. The data strongly suggest that Mlsx may, in fact, be Mlsc or is, at least, highly cross-reactive with Mlsc. Segregation analysis by using (B10.D2 X PL/J)F2 mice demonstrates that the Mlsx gene is genetically independent of the Mlsa linked Ly-9 marker on chromosome 1. Further studies with the use of these Mlsc,x-reactive clones reveal that they also recognize a gene product present in many mouse strains including DBA/2 which were previously phenotyped as Mlsa. However, testing of BxD recombinant inbred lines excludes Mlsa as being the stimulatory moiety. We therefore propose reclassification of the Mls phenotypes of several mouse strains based upon a two-locus model for Mls.     

Effect of n-3 and n-6 polyunsaturated fatty acids on hare reproductive performances

The study was carried out on 42 breeder couples (42 males and 42 females) of European brown hare (Lepus europaeus), divided into three groups fed three different experimental diets (14 couples/treatment). Two diets were supplemented with n-3 and n-6 polyunsaturated fatty acids (PUFAs; 2% of linseed oil and soybean oil, respectively) and were compared with a control diet supplemented with a monounsaturated fatty acids (2% of olive oil). During the experimental period (from 15 April to 30 September), the following parameters were recorded: days from the beginning of trial to the first parturition, parturition interval, number of parturitions, number of leverets born (alive and dead), dead during suckling, the total number of leverets weaned and feed intake per cage (of males, females and leverets until weaning). Feed intake was not influenced by treatments. In hares fed n-3 and n-6 diets, the days from the beginning of the trial to the first parturition and the parturition interval were similar and were lower compared with control group (63.1 v. 70.6 days, and 37.8 v. 40.9 days, respectively; P < 0.05). Hares from n-6 group had a higher (P < 0.05) number of parturitions per cage during the experimental period than the n-3 and control group that showed a similar value (3.00 v. 2.36, respectively). The total number of leverets born per cage and parturition in n-6 and n-3 groups increased with respect to those fed control diet (P < 0.05). The leverets' mortality rate at birth was higher in n-6 than in n-3 and control group (3.50 v. 2.17, respectively; P < 0.05). In control group, leverets' mortality rate during suckling was lower with respect to n-3 (P < 0.05) and n-6 (P < 0.05), showing the highest value for the latter (P < 0.05). In spite of this higher mortality, the number of leverets weaned per cage and parturition was higher (P < 0.05) in n-6 compared with n-3 group, being the latter higher than the control group (3.12, 2.79 and 2.43, respectively). Our results show that the dietary PUFAs, particularly n-6 supplementation, have a positive influence on the reproductive performances of the European brown hare.     

Cerebral, cerebellar, and brain stem gangliosides in mice susceptible to audiogenic seizures

Abstract— The quantitative and qualitative distribution of gangliosides was investigated in the cerebrum, cerebellum and brain stem of audiogenic seizure resistant (C57BL/6J) and susceptible (DBA/2J) mice at 21 days of age. The concentration of gangliosides (μg/unit weight) was higher in the DBA cerebrum and brain stem, but lower in the DBA cerebellum compared to the concentration in C57 mice. In general, the brain water content was lower in DBA mice than in C57 mice. The distributions of a number of gangliosides were found to be different between the two strains and the differences were often in the same direction across the three brain regions. The most consistant and significant difference in ganglioside pattern observed between the strains was the higher concentration of G_M1 in all three regions of the DBA brain. These results suggest that DBA mice have a more heavily myelinated CNS than C57 mice. The relationship of these observations to inherent audiogenic seizure susceptibility is discussed.