Different A-type natriuretic peptide level in five strains of mice

Atrial (A-type) natriuretic peptide (ANP) is vasodilative hormone involved in the regulation of blood pressure and volume homeostasis. In this study, we examined the differences of the auricular and plasma ANP distribution by immunohistochemistry, ultrastructural morphometry, and radioimmunoassay in five strains of mice. The ANP-immunoreactivities of the auricle were most intense in ICR, and moderate in C57BL/6J and C3H/HeN, and weakest in BALB/cA and DBA/2Cr. The number of ANP-granules was greatest in ICR followed by C57BL, C3H or BALB/c, and DBA/2 mice, in this order. The auricular ANP content was highest in ICR, but the plasma ANP concentration was comparable in all strains. The present study demonstrates that there are differences in the ANP circulating system between five strains.     

Cytoplasmic genetic effects and growth of hybrid mice

Variation in cellular biochemical functions controlled by cytoplasmic genes was studied in relation to phenotypic differences between progeny of reciprocal hybrid female mice. Least squares procedures were used to test for differences in mitochondrial respiratory metabolism and in capacity for ATP synthesis, and differences in growth of progeny of hybrid dams. Under identical nuclear influences, mitochondria of A/J and C57BL/6J cytoplasms differed (P less than .10 to P less than .01) from those of BALB/cJ cytoplasm in energy conservation. No differences were detected in mitochondrial efficiency between BALB/cJ cytoplasm evaluated in different nuclear environments. Three-way cross progeny of C57BL/6J x BALB/cJ reciprocal hybrid females mated to DBA/2J males differed (P less than .05) in litter weight at weaning and 1 wk and 2 wk postweaning. The F2 progeny of reciprocal C57BL/6J x BALB/cJ dams and F2 and three-way cross progeny of reciprocal A/J x BALB/cJ dams did not differ in weight at any age measured. Across all genotypes of dam, rank correlations of mitochondrial traits with F2 litter weights were nonsignificant. Observed variation in mitochondrial functions partially controlled by cytoplasmic genes did not limit mouse growth under these experimental conditions.     

Encephalomyocarditis (EMC) virus-induced myocarditis by different virus variants and mouse strains.

The mode of occurrence of encephalomyocarditis (EMC) virus-induced myocarditis in mice was pathologically and virologically investigated using 2 virus variants (highly diabetogenic EMC-D and non-diabetogenic EMC-B) and 2 mouse strains (diabetes-susceptible BALB/c and diabetes-resistant C57BL/6). Mice were inoculated with 10(5) PFU/head of the virus intraperitoneally and observed up to 7 days post inoculation (7DPI). As compared with EMC-B-infected BALB/c and EMC-D-infected C57BL/6 mice, EMC-D-infected BALB/c mice developed marked myocarditis and exhibited a heart virus titer of more than 100 times above that of the others after 4DPI. Electron microscopically, small aggregations of virus-like particles, with 20-25 nm in diameter, were found in the cytoplasm of degenerated cardiomyocytes showing mitochondrial and myofibrillar degeneration in EMC-D-infected BALB/c mice.     

The relationship between sperm morphology and in vitro fertilization ability in mice

In vitro fertilization (IVF) is widely used in reproduction research, but the sperm of some inbred strains of mice yield low fertilization rates in IVF. To determine the cause of this problem, we examined the effect of epididymal sperm morphology, in particular, tail bending and the presence and type of cytoplasmic droplet (CD), on fertilizability in vitro. Sperm suspensions were obtained from the following five strains: C57BL/6J, BALB/cA, C3H/HeN, DBA/2J, and 129 x 1/SvJ. The sperm were fixed in 10% formalin and three parts of the sperm, namely the head, tail, and CD, were examined. We recorded the proportion of abnormal sperm heads and hairpins at the neck; tails were categorized as straight, proximal bent, or distal bent; and the CDs were categorized as none, light-type, and heavy-type. Based on these parameters, we determined the correlations between sperm morphology and fertilizability in vitro, as judged by IVF using ICR oocytes. The proportion of sperm with a hairpin neck was higher in strain C57BL/6J, while abnormal head morphology occurred significantly more often in strain BALB/cA. The percentage of sperm with a proximal bent tail was highest in strain DBA/2J and lowest in strain 129 x 1/SvJ. A heavy-type CD was observed more frequently in the 129 x 1/SvJ and C57BL/6J strains than in the other three strains in which a light-type CD predominated. The rank order of the fertilization rates was 129 x 1/SvJ < C57BL/6J < C3H/HeN < BALB/cA < DBA/2J. In addition, fertilization rate was positively correlated with a proximal bent tail, but negatively correlated with a heavy-type CD and distal bent tail. This new classification system establishes that the morphological characteristics of epididymal sperm differ among inbred strains of mice and that tail and CD morphology are closely related to fertilization ability in IVF. Thus, our results provide a novel method for assessing the quality of mouse sperm used for IVF.     

SPF级BALB/cC57BL/6小鼠繁殖性能及生长发育的比较研究

为提高SPF级实验动物的质量,选择10周龄BALB/c C57BL/6小鼠各50只（雌雄各半）,采取雌雄1？1近亲交配繁殖,并统计其生长发育和繁殖性能指标。BALB/c小鼠1～3周龄的平均窝重及离乳后的体重增长明显大于C57BL/6小鼠（p〈0.01）。第1胎交配分娩间隔,第1和第3胎离乳育成率品系间差异均有显著性（P〈0.05及P〈0.01）。BALB/c小鼠的体格比C57BL/6小鼠大,带乳能力比C57BL/6小鼠强但产仔能力比C57BL/6小鼠弱。     

Effects of diesel exhaust particles on the male reproductive system in strains of mice with different aryl hydrocarbon receptor responsiveness

Diesel exhaust particles (DEPs) contain polycyclic aromatic hydrocarbons (PAH) that bind to aryl hydrocarbon receptors (AhRs) and decrease sperm production. Since it is not clear if AhR mediates DEP toxicity, we investigated the effect of DEPs in four strains of mice that have different AhR responsiveness. We treated BALB/c, C57BL/6, ICR and DBA/2 mice with DEP suspensions and compared their toxicity in each strain. In both the vehicle- and DEP-treated groups, ethoxyresorufin-O-deethylase (EROD) activity, as an indirect index of AhR activity, was increased in the order of BALB/c > C57BL/6 > ICR > DBA/2. Only BALB/c and C57BL/6 mice had significantly lower daily sperm production (DSP) than vehicle-treated mice. All strains exhibited increased sperm abnormalities. In particular, the C57BL/6, ICR and DBA/2 mice exhibited significantly increased abnormalities. A significant correlation was found between EROD activity and DSP or incidence of morphologically abnormal sperm. These data suggest that DEP toxicity may affect the male reproductive system in an AhR-dependent manner.     

The developmental ability of vitrified oocytes from different mouse strains assessed by parthenogenetic activation and intracytoplasmic sperm injection

Assessment of the developmental ability of oocytes following freezing and thawing is an important step for optimizing oocyte cryopreservation techniques. However, the in vitro fertilization of frozen-thawed mouse oocytes is often inefficient because of incomplete capacitation of spermatozoa in the absence of surrounding cumulus cells. This study was undertaken to determine whether the oocyte cryopreservation efficiency of different strains of mice could be assessed from the development of oocytes following parthenogenetic activation and intracytoplasmic sperm injection (ICSI). Oocytes were collected from hybrid (C57BL/6 x DBA/2) F1 or inbred (C57BL/6J, C3H/HeN, DBA/2J and BALB/cA) strains and were vitrified in a solution containing ethylene glycol, DMSO, Ficoll and sucrose. In the first series of experiments, oocytes were activated parthenogenetically by Sr(2+) treatment after warming. The oocytes from the inbred strains, but not those of the F1 hybrid, were diploidized by cytochalasin treatment to obtain a sufficient number of blastocysts. In all strains tested, parthenogenetic embryos derived from vitrified oocytes developed into blastocysts at rates between 23 and 68%. In the second series of experiments, vitrified oocytes from each strain were injected with homologous spermatozoa after warming. Normal offspring were obtained from all strains at rates between 5 and 26% per embryo transferred. Thus, the feasibility of oocyte cryopreservation protocols can be assessed easily by in vitro development of parthenogenetic embryos or by in vivo development of ICSI embryos. Moreover, the oocytes of these four major inbred strains of mice can be cryopreserved safely for production of offspring.     

Fundamentals of host immune response against Brucella abortus: what the mouse model has revealed about control of infection

The studies reviewed here evaluated the role cellular immune system components play in control of brucellosis by conducting comparative studies with brucella-resistant C57BL/10 or C57BL/6 mice and susceptible BALB/c mice. We have shown by both in vitro and in vivo studies that activation of macrophages with interferon-gamma (IFN-γ) is an important factor for control of infection with B. abortus in the mouse model and that the mechanism of anti-brucella activity largely involved reactive oxygen intermediates. Differences in control of the organism by resistant and susceptible mice was not related to inherent differences in the ability of their macrophages to control infection either with or without IFN-γ activation nor was it attributable to NK cells since we found no role for them in control of brucellosis in either mouse strain. However, relative resistance to brucellosis did correlate with increased production of IFN-γ by CD4 T cells during the first weeks after infection while IL-10 contributed to susceptibility in BALB/c mice. Moreover, by 3 weeks post-infection splenocytes from the susceptible BALB/c mice failed to produce IFN-γ and relied on TNF- as well as CD8 T cells to control infection until the end of the plateau phase around 6 weeks post-infection when IFN-γ production resumed and clearance began. In contrast, IFN-γ was crucial for control throughout the infection in the more resistant C57BL/6 mice and the mice died in its absence by 6 weeks post-infection compared to 12 weeks for the more susceptible mice that relied on additional mechanisms of control. In contrast to the IFN-γ knock-out mice, both β2 microglobulin knock-out C57BL/6 mice, which do not express conventional MHC class I molecules and thus cannot present antigen to CD8 T cells, or perforin knock-out C57BL/6 mice, which have no T cell cytotoxic activity, controlled and cleared the infection as well as normal C57BL/6 mice. The hiatus of IFN-γ production in BALB/c mice correlated with very high levels of total IL-12 and it was postulated that the lack of IFN-γ was a consequence of p40 homodimer blocking activity. However, reduction of p40 IL-12 in vivo through administration of indomethacin reduced the infection without a concomitant measurable increase in IFN-γ. Current studies are aimed at elucidating the mechanism of the IFN-γ hiatus.     

The local immune response of mice after Helicobacter suis infection: strain differences and distinction with Helicobacter pylori

Helicobacter (H.) suis colonizes the stomach of pigs and is the most prevalent gastric non-H. pylori Helicobacter species in humans. Limited information is available on host immune responses after infection with this agent and it is unknown if variation in virulence exists between different H. suis strains. Therefore, BALB/c and C57BL/6 mice were used to compare colonization ability and gene expression of various inflammatory cytokines, as determined by real-time PCR, after experimental infection with 9 different H. suis strains. All strains were able to persist in the stomach of mice, but the number of colonizing bacteria at 59 days post inoculation was higher in stomachs of C57BL/6 mice compared to BALB/c mice. All H. suis strains caused an upregulation of interleukin (IL)-17, which was more pronounced in BALB/c mice. This upregulation was inversely correlated with the number of colonizing bacteria. Most strains also caused an upregulation of regulatory IL-10, positively correlating with colonization in BALB/c mice. Only in C57BL/6 mice, upregulation of IL-1β was observed. Increased levels of IFN-γ mRNA were never detected, whereas most H. suis strains caused an upregulation of the Th2 signature cytokine IL-4, mainly in BALB/c mice. In conclusion, the genetic background of the murine strain has a clear impact on the colonization ability of different H. suis strains and the immune response they evoke. A predominant Th17 response was observed, accompanied by a mild Th2 response, which is different from the Th17/Th1 response evoked by H. pylori infection.     

Infections in immunocompetent and immune-deficient mice with promastigotes of a North American isolate of Leishmania infantum

Leishmania infantum, an etiologic agent of zoonotic visceral leishmaniasis, is widespread among foxhounds in the United States. Experimental infections with a North American isolate of L. infantum were evaluated using two inoculation routes in immunocompetent and immunosuppressed mouse strains. Groups of 2-5 interferon gamma gene knockout (IFN-gamma-KO) (BALB/c-Ifng), inducible nitric oxide synthase (NOS) gene knockout (iNOS-KO) (C57BL/6), B-cell-deficient (microMT) (C57BL/6), and BALB/c mice were intravenously (i.v.) or subcutaneously (s.c.) inoculated with various doses of promastigotes of the LIVT-1 strain of L. infantum. None of the mice developed clinical signs of leishmaniasis during the 8-9 weeks of the study. Promastigotes were cultured from spleens of all i.v.-infected mice by 3 days post culture. Spleens from s.c.-infected mice inoculated with greater than 1 x 10(6) parasites became culture positive 3-24 days post culture, but promastigotes were not cultured from mice infected with 1 x 10(5) or 5 x 10(5) LIVT-1 promastigotes. Histological lesions were prominent in the livers of i.v.-infected mice but were mild to nonexistent in s.c. infection. Serological responses were low and transient determined by indirect fluorescent antibody testing in all groups. These results indicate that the i.v. route of infection is superior to the s.c. route in a mouse model of North American leishmaniasis and that mice lacking INF-gamma, iNOS or mice that are B-cell-deficient are not more susceptible to acute infection.     

Influence of Strain and Parity on the Risk of Litter Loss in Laboratory Mice

Pup mortality is a considerable problem in laboratory mouse breeding and the view that parity influence survival of newborn mice is widespread. Some evidence suggests that maternal behaviour is related to offspring mortality in mice. Parental experience is a factor that can improve maternal behaviour and offspring survival in some mammals. However, few papers report a relationship between parity and pup survival in mice. We investigated the influence of strain and parity on loss of entire litters of C57BL/6 and BALB/c mice using data from a breeding colony. In total, 344 C57BL/6 and 146 BALB/c litters were included. We found a considerable mortality rate for both strains: 32% of C57BL/6 litters and 20% for BALB/c litters were lost. There was a significant difference in survival of the first litter between strains, with 3.6 times higher odds of mortality in C57BL/6 mice (p = 0.0028). Parity or previous parental experience of litter loss did, however, not affect litter loss. The scientific literature does not provide a clear picture of perinatal mortality in laboratory mice. Very few studies report perinatal mortality, and only a handful of papers exist where mortality was systematically studied; this area is thus poorly understood. If perinatal mortality in mice is not recognized and investigated, but instead considered normal when breeding mice, a serious welfare problem might be overlooked.     

A fatty acid binding protein from Fasciola hepatica induced protection in C57/BL mice from challenge infection with Schistosoma bovis.

Three strains of mice (NMRI, C57/BL, BALB/c) were each immunized with a 12 kDa purified, native Fasciola hepatica fatty acid binding protein (Fh12) and challenged percutaneously with Schistosoma bovis cercariae. C57/BL mice immunized with Fh12 had significant reductions in S. bovis worm burden recoveries (96 and 87% reductions over controls in two separate experiments). When using NMRI or BALB/c mice, Fh12 alone or in Freund's adjuvant failed to induce significant protection against S. bovis. In C57/BL mice vaccinated against Fh 12, antibodies to the IgG2a isotype, but not to the IgG1 isotype, increased by 2 weeks after the second immunization and remained high through 8 weeks of S. bovis infection. Antibodies to S. bovis increased after 4 weeks of infection. Regarding cytokine production by spleen mononuclear cells, C57/BL mice vaccinated with Fh12 in adjuvant, and having the highest protective response against challenge infection with S. bovis, had an increase of IFN-gamma production with Concanavalin A but no increase of IL-4 in similarly stimulated cells. These results suggest that the protection obtained in this group of mice is mediated by a Th1 immune response.     

In vitro system for immunoglobulin class switching using BHK cells transfected with murine recombinant CD40 ligand.

To develop an in vitro system for mouse immunoglobulin (Ig) class switching, the expression vector of murine CD40 ligand (CD40L) which is expressed on T cells was transfected to BHK cells. By using culture plates coated with the BHK cells expressing the recombinant CD40L, Ig class switching of splenic B cells was examined. The CD40L mRNA was cloned from splenic T cells of BALB/mice activated with anti-CD3 antibody in vitro. As the No.593 base in the open reading frame sequence of the CD40L from BALB/c spleen differed from T to G, when compared with the known sequence from C57BL/6, one of the BALB/c-derived clones was reconstructed to the known CD40L by site-directed mutagenesis. Splenic B cells from BALB/c were induced secretion of Ig isotypes, IgM, IgG1 and IgE when cultured on two types of BHK cells, the transfected BHK cells with a CD40L clone from BALB/c and the transfected BHK cells with the reconstructed CD40L clone, in the presence of IL-4. However, when splenic B cells from C57BL/6 were cultured on the same systems, the B cells produced Ig isotypes, IgM, IgG1, IgG2a, IgG2b, IgG3 and IgE. In the similar experiments using the transfected BHK cells with a empty vector and the normal BHK cells, none of B cells produced any Ig isotypes other than IgM. These results indicate that Ig class switching of murine B cells can be induced by using these two types of CD40L-expressing BHK cells in vitro.     

近交系小鼠RAPD标记的观察

采用随机扩增多态性DNA技术(RAPD),分析BALB/c、C57BL/6、DBA/2、C3H/He等4个近交系小鼠的基因多态性,探讨用RAPD作为遗传标记,对近交系小鼠进行遗传检测。结果表明,4种小鼠表现出了各自不同的多态性RAPD标记,证明RAPD可作为近交系小鼠的分子标记,在DNA水平区别4种近交系小鼠。     

Morphometrical analysis of sex and strain differences in the mouse nephron.

In the present study, we investigated the sexual dimorphisms, effects of castration and sex hormone treatment, and strain differences in the morphology of mouse kidney by measuring the percentage of renal corpuscles with cuboidal cells in the parietal layer of the glomerular capsule, the diameter of renal corpuscles and the number of nuclei of epithelial cells in the proximal convoluted tubule. In ICR mice, the percentage of renal corpuscles with cuboidal cells and the diameter of renal corpuscles were larger in males than in females, and the numbers of nuclei were lower in males than in females. All of these parameters became similar to those of intact females by orchiectomy, and restored to levels similar to those in intact males after testosterone treatment to orchiectomized males. On the other hand, ovariectomy and estradiol treatment gave no effects to any of these parameters. Similar sexual dimorphisms were observed in BALB/c, C57BL/6, C3H/He and DBA/2 mice as in ICR mice, although the diameter of renal corpuscles was not significantly different between males and females in BALB/c mice. Strain differences were observed in each of these three parameters among the 5 strains. In conclusion, the present study demonstrated sexual dimorphisms, effects of castration and sex hormone treatment, and strain differences in the morphology of mouse kidney by morphometrical analysis.     

胚胎干细胞及种系嵌合体的研究进展

胚胎干细胞是着床前的囊胚内细胞团或早期胎儿的原始生殖细胞经体外分化抑制培养建立的多能性细胞系 ,具有与胚胎细胞相似的形态特征和分化潜能 ,体外培养时保持未分化状态 ,可以传代增殖。改变维持胚胎干细胞不分化的培养条件 ,胚胎干细胞可自发分化成多细胞结构。在一定诱导下 ,胚胎干细胞可向多个方向分化 ,并生成多种功能细胞。胚胎干细胞注入到胚泡期胚胎或与桑椹期胚胎聚合 ,可以参与包括性腺在内的各种组织的嵌合体的形成。胚胎干细胞在细胞分化与调控 ,胚胎发育 ,遗传病 ,肿瘤 ,免疫和组织或器官移植等研究中显示着广泛的应用前景。而种系嵌合体的获得是实现 ES细胞途径的决定步骤 ,低的种系嵌合率则是制约 ES细胞应用的关键。提高供体 PGCs在受体生殖腺中的比例 ,缩短 ES细胞的体外培养时间 ,以及注入早期发育阶段的受体胚胎等都能提高种系嵌合率。文章从多个方面综述了胚胎干细胞的最新研究成果 ,并着重以禽类 ES细胞为例论述了种系嵌合体的检测方法 ,种系嵌合率的影响因素以及提高种系嵌合率的方法     

Regional variations in the distribution of small intestinal intraepithelial lymphocytes in three inbred strains of mice

The regional variation in the intraepithelial lymphocytes (IELs) in the small intestine was examined in BALB/c male and female mice and C3H/He and C57BL/6 male mice. The small intestines were taken from 11 to 12-week-old mice and divided equally into 3 parts (the proximal, middle and distal parts). IELs were isolated from each part of the intestine and analyzed with flow cytometer. The number of IELs was highest in the proximal part and lowest in the distal part. The distribution of IEL subsets was markedly different between the proximal and the distal parts, and that in the middle part showed the intermediate pattern. The percentage of alphabeta T cells were higher in the distal part. In alphabeta T cell subset, the percentage of CD8alphaalpha T cells was higher in the proximal part, whereas those of CD4 and CD4CD8alphaalpha double positive T cells were higher in the distal part. In gammadelta T cell subset, no regional variations were found. The regional variations in the number and subsets of IELs showed almost the same patterns between male and female BALB/c mice and similar patterns among three strains of mice. This strongly suggests that the regional variations in the small intestinal IELs are common to mouse species.     

Experimental infections of mice and pigs with Streptococcus suis type 2.

Five inbred strains of mice were tested for their susceptibility to Streptococcus suis type 2 including the type strain, two isolates from meningitis in pigs and two isolates from tonsils of clinically healthy pigs. C57BL/6, ICR and ddY strain mice showed lower susceptibility to all strains of S. suis type 2 than BALB/c and SS strain mice. The type strain and the isolates from diseased pigs produced septicaemia and meningitis in BALB/c and SS mice inoculated with 10(8) colony forming unit of the bacteria and 60 to 100% of these infected mice died. On the other hand, mice inoculated with the isolates from healthy pigs showed mild clinical signs but none of them died. In BALB/c mice which died or developed nervous signs, the purulent meningo-encephalitis, myocarditis, ophthalmitis, labyrinthitis and otitis media were observed. S. suis type 2 antigen was demonstrated in these lesions by immunoperoxidase staining using rabbit S. suis type 2 antiserum. These results were similar to those in the experimentally infected pigs with these virulent and avirulent strains against mice. These results indicate that BALB/c and SS strains of mice are useful as an experimental model of S. suis type 2 infections in pigs, and that there are virulent and avirulent strains against mice and pigs among the strains of S. suis type 2.     

Mycobacterium avium infection through the alimentary tract in mice

Intestinal infection by Mycobacterium avium was investigated in C57BL/6 and BALB/c mouse strains. Single intragastric administration of a massive dose (10(8] or multiple administration of a lower dose (10(7), 10 times) established infection principally in the mesenteric lymph-node (MLN); a continuous or intermittent fecal excretion of the bacilli was detected by 6-8 weeks after the administration. Based on three criteria--isolation of the organisms from the MLN and from feces, and detection of acid-fast bacilli in sections of the MLN--germ-free (GF) BALB/c mice exhibited clearer dose-effect relations than the flora-bearing (FB) counterparts. After intragastric administration, the organisms were probably trapped in the Peyer's patch and then transferred to the MLN at an early period (by 4-7 days), persistent infection thus being established in the MLN. Systemic involvement evolved both in athymic and euthymic mice after a prolonged period of time (more than 40 weeks) showing far more severe involvement in the former regardless of the presence of floral organisms.     

Non-CpG methylation occurs in the regulatory region of the Sry gene

The Sry (sex determining region on Y chromosome) gene is a master gene for sex determination. We previously reported that the Sry gene has tissue-dependent and differentially methylated regions (T-DMRs) by analyzing the DNA methylation states at CpG sites in the promoter regions. In this study, we found unique non-CpG methylation at the internal cytosine in the 5'-CCTGG-3' pentanucleotide sequence in the Sry T-DMR. This non-CpG methylation was detected in four mouse strains (ICR, BALB/c, DBA2 and C3H), but not in two strains (C57BL/6 and 129S1), suggesting that the CCTGG methylation is tentative and unstable. Interestingly, this CCTGG methylation was associated with demethylation of the CpG sites in the Sry T-DMR in the developmental process. A methylation-mediated promoter assay showed that the CCTGG methylation promotes gene expression. Our finding shows that non-CpG methylation has unique characteristic and is still conserved in mammals.