Sex- and strain-dependent histological features of the proximal convoluted tubular epithelium of mouse kidney: association with lysosomes containing apolipoprotein B

In the present study, we performed comparative histological observations of ICR, BALB/c, C57BL/6, C3H/HeN and DBA/2 mice kidneys. Sex and strain differences were observed in the appearance of vacuolar structures of the proximal convoluted tubules (toluidine blue-positive granules in osmium-postfixed epoxy-resin sections). These features were especially remarkable in male DBA/2 mice. The vacuolar structures in male DBA/2 mice showed heterogeneous staining with Sudan B in frozen sections and appeared under an electron microscope as multilammelar giant dense bodies. In addition, these dense bodies showed heterogeneous acid phosphatase reactions. Immunohistochemical analyses of these structures for apolipoprotein B showed strong positive reactions. These results suggested that vacuolar structures in the proximal convoluted tubules, which were remarkable in male DBA/2 mice, were giant lysosomes containing apolipoprotein B.     

Strain differences of ether susceptibility in mice

The susceptibility to ether in the following six strains of mice was tested: C57BL/6, DBA/2, BALB/c, C3H/He, ICR and ddY. Mice of 4 weeks old were exposed to a flow of air containing various concentrations of ether for 90 min and the mortalities were assessed. The C57BL/6 strain was the most resistant and the C3H/He strain was the most sensitive to the lethal effect of ether. The susceptibilities of the closed colony mice, ICR and ddY, were intermediate between those of C57BL/6 and C3H/He mice. The DBA/2 and BALB/c strains were more sensitive than these closed colony mice and made up a sensitive group with the C3H/He strain. The LD50 values for ether in male mice of C57BL/6 and C3H/He were 6.0 and 3.1% atm, and in female mice of these strains were 6.6 and 3.2% atm, respectively. The ED50 value of ether which was accompanied by loss of righting reflex after exposure for 10 min was also higher in male C57BL/6 mice than in male C3H/He mice.     

Sex and strain differences in the hepatotoxic response to acute cocaine administration in the mouse

Cocaine-induced hepatotoxicity was examined in vivo in a dose-responsive manner in C57BL/6Ibg, DBA/2Ibg, C3H/2Ibg, and Balb/cJ mice. Serum glutamic-pyruvic transaminase (SGPT) activities were determined 24 hours after intraperitoneal (IP) administration of cocaine (20 to 100 mg/kg). Significant elevations (100- to 150-fold) in SGPT were observed in male mice receiving cocaine. Significant differences in sensitivity to cocaine-induced hepatotoxicity were found among males of the inbred strains, with Balb being most sensitive and C57BL being least sensitive and C3H and DBA strains exhibiting intermediate sensitivity. Female mice of the four inbred strains were more resistant than males to cocainemediated hepatotoxicity, as indicated by only twofold to tenfold elevations in SGPT values. Among the females, sensitivity of the four inbred strains—as indicated by dose response curves—fell into two categories: the sensitive strains (C3H and C57BL) and the resistant strains (Balb and DBA). Pretreatment of males of the four inbred strains with the P-450 inducer phenobarbital resulted in enhancement of cocaine-mediated hepatotoxicity in the C57BL and Balb but not the C3H and DBA mice. Phenobarbital pretreatment of females of the four inbred strains resulted in enhancement of the hepatotoxic response to cocaine in the C3H, DBA, and Balb mice. Phenobarbital-pretreated C57BL females exhibited a 100% mortality rate after the acute cocaine dose, and thus no determination of hepatotoxicity could be established for them. These data demonstrate sex and strain differences in cocaine-induced hepatotoxicity and suggest that phenobarbital pretreatment does not uniformly enhance the hepatotoxicity of cocaine.     

Studies on vertebrate kidney. V. PAS-positive lipids in kidneys of fishes from different habitats.

Five fish species living in different habitats, i.e. fresh water, estuarine and marine, were studied for the distribution of PAS-positive materia in various regions of the kidney, 10 minutes' oxidation with 0-5 per cent. HIO4 being employed prior to treatment with Schiff's reagent. PAS-positive material was detected in different sites of the kidney, i.e. brush border of proximal tubules, proximal tubule cells' cytoplasm, distal tubule cells' cytoplasm, glomerulus, basal cell border of proximal tubules and the interstitial cells. Of these sites, the brush border of the proximal tubule of Scoliodon sorrakowah showed the presence of PAS-positive lipids. Elsewhere the PAS-positive reaction was due to carbohydrates. Free aldehyde groups were absent. In Tilapia mossambica and Labeo rohita, PAS staining was enhanced after chloroform-methanol extraction, particularly in the brush border of the proximal tubule. The significance of these findings is discussed.     

Homo- and heterotetrameric forms of the membrane-bound metalloendopeptidases meprin A and B

Meprin A and B are disulfide-linked, tetrameric metalloendopeptidases in renal brush border membranes. Meprin A contains 90-kDa subunits (alpha subunits) and is expressed in random-bred and some inbred strains of mice. Meprin B contains subunits of 110 kDa (beta subunits) in situ, and the enzyme from C3H mice, a strain that does not express alpha subunits, has been characterized. Evidence from this and previous studies indicate that beta subunits are expressed in all mouse strains. The tetrameric organization of these meprins was examined in brush border membrane fractions from a random-bred strain (ICR) and two inbred strains of mice (C57BL/6 and C3H/He). Lectin blotting using biotinylated concanavalin A revealed that membranes from the random-bred strain contained three oligomeric complexes of approximately 390, 440, and 490 kDa as determined after sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) in the absence of reducing agents. The subunits in all three oligomers were linked by disulfide bridges. Western blotting using an anti-alpha monoclonal antibody indicated that alpha subunits (90 kDa) were present in the 390- and 440-kDa complexes. Western blotting with a polyclonal antibody specific for beta subunits (110 kDa) indicated the presence of these subunits in the 440- and 490-kDa complexes. Electroelution of the individual oligomers followed by SDS-PAGE under reducing conditions confirmed that the 390- and 490-kDa molecules are homotetramers of alpha and beta subunits, respectively, and that the 440-kDa molecule is a heterotetramer consisting of disulfide-bridged alpha and beta subunits. C57BL/6 mice expressed both alpha and beta subunits and contained tetramers composed of alpha 4 and alpha 2 beta 2. C3H/He mice expressed only the 110-kDa beta subunits and the beta 4 oligomer. This type of multimeric organization of disulfide-linked subunits is unique for the known endopeptidases.     

A sex-limited serum protein variant in the mouse: Hormonal control of phenotypic expression

The sex-limited protein (Slp) antigen of the mouse is first detected in the serum of strain DBA/2J males at 5–6 weeks of age and reaches full adult levels by 10 weeks. This antigen is normally absent in females. Immature DBA/2J males castrated at 3 1/2 weeks of age failed to develop Slp antigen, while DBA/2J females treated with testosterone propionate starting at 3 1/2 weeks developed normal adult male levels of Slp antigen. Similar hormone-influenced effects were demonstrated in adult males and females of the same strain. Experiments indicated that testosterone does not act directly in the serum to expose Slp antigenic sites. Testosterone treatment of both males and females of strain C57BL/10JSf, which does not carry the gene for the presence of the Slp antigen, failed to stimulate the appearance of the antigen. Thus, the presence of Slp antigen in the serum is dependent on both the proper genotype and the presence of male hormone.Supported by U.S.P.H.S. Research Grant GM-15419, U.S.P.H.S. Training Grant 2T01-GM-00071 (H.C.P.), and U.S.P.H.S. Career Development Award K3-HE-24,980 (D.C.S.).     

Influence of the concentration of sperm on the percentage of eggs fertilized for three strains of mice

This study was conducted to determine the optimal concentration of sperm to use for the insemination of females to detect differences among strains of mice in the percentage of eggs fertilized. Female ICR mice were inseminated with sperm of concentrations ranging from 0.25 to 8 × 10⁶/50 μl from males of either DBA/2N, CF1, or C57BL/6N strains. Differences among strains were detected only when approximately 50% of the eggs were fertilized but not when each of the strains fertilized either a high or low percentage of eggs. The optimal concentration of sperm therefore was the concentration that gave approximately 50% fertilized eggs.     

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.     

Strain differences in histamine release from mouse peritoneal mast cells induced by compound 48/80 or A23187

Strain differences among BALB/c, BDF1, CDF1, C3 H/He, C57 BL/6, DBA/2, ddy and ICR mice were investigated with respect to the ratios of histamine release from mouse peritoneal mast cells induced by compound 48/80, a Ca2+ dependent histamine releaser, and the Ca2+ ionophore A23187. The ratios of histamine release from mouse peritoneal mast cells induced by compound 48/80 were found to be high in BALB/c, ddY and ICR mice, but low in BDF1, CDF1, C3 H/He, C57 BL/6 and DBA/2 mice. Those induced by Ca2+ ionophore A23187 were high in BALB/c, BDF1, CDF1, C3 H/He, DBA2, ddy and ICR mice but low in C57 BL/6 mice. These results indicate that differences in histamine release from mouse peritoneal mast cells are strain dependent.     

不同品系小鼠对实验感染念珠状链杆菌敏感性的观察

本文通过念珠状链杆菌（Ｓｔｒｅｐｔｏｂａｃｉｌｕｓｍｏｎｉｌｉｆｏｒｍｉｓ,Ｓ．ｍ．）实验感染昆明、Ｃ５７ＢＬ／６Ｊ、ＢＡＬＢ／ｃ、ＩＣＲ、ＮＩＨ、ＤＢＡ共６个品系小鼠,观察其对Ｓ．ｍ．敏感性的差异。其中昆明、Ｃ５７ＢＬ／６Ｊ两个品系在腹腔接种后表现出明显的临床、病理改变。昆明小鼠发病率和死亡率分别为９２％和８０％;Ｃ５７ＢＬ／６Ｊ分别是８０％和１２％。昆明小鼠较之Ｃ５７ＢＬ／６Ｊ小鼠起病急、病情严重,多数动物死于感染的急性期。其余品系的发病率为：ＮＩＨ８％、ＢＡＬＢ／ｃ和ＤＢＡ４％,没有动物死亡;ＩＣＲ在接种后无任何临床病理改变。在实验感染后临床病理改变方面,昆明小鼠和Ｃ５７ＢＬ／６Ｊ小鼠间有较大不同。昆明小鼠以末梢血管淤血、四肢尾部水肿、关节炎、截瘫、腹泻为主,而Ｃ５７ＢＬ／６Ｊ小鼠则以注射部位和其它部位皮下脓肿、化脓性关节炎为主。本研究提示,中国昆明小鼠对Ｓ．ｍ．敏感性最高,可以将其作为“哨兵动物”用于实验大鼠Ｓ．ｍ．的常规监测;不同品系小鼠不仅对实验感染Ｓ．ｍ．的敏感性不同,而且表现出不同的临床病理改变。     

Cyclophosphamide-Induced IN VIVO Sister Chromatid Exchanges (Sce) in MUS MUSCULUS. III. Quantitative Genetic Analysis

In vivo cyclophosphamide (CP)-induced sister chromatid exchanges (SCEs) were evaluated in females from five genetic strains of mice (C57BL/6J, C3H/S, 129/ReJ, BALB/c and DBA/2) and their F₁ hybrids. Baseline (noninduced) SCE values differ significantly among strains, 129/ReJ having the lowest and DBA/2 having the highest mean SCE per cell values. In general, the baseline SCE of a given F₁ is within the range of its corresponding parental strains or near the lower parental value. Furthermore, there is a genotype-dependent increase in mean SCEs per cell with CP dose. Strain differences in SCE induction are noted particularly at the two higher CP doses (4.50 and 45.0 mg/kg). In general, F₁ hybrids involving a strain with high induced SCEs and a strain with low induced SCEs exhibit mean SCE values that are closer to the value of the lower strain. F₁ s involving two strains with high SCEs or two strains with low SCEs yield SCEs not different from parental strains. The method of diallel cross analysis showed the order of dominance of these strains in SCE induction to be 129/ReJ BALB/c C3H/S DBA/2 C57BL/6J. These results support the involvement of predominantly nonadditive genetic factors as major gene(s) in SCE induction. In addition, involvement of random and independent events in SCE induction is suggested by the distribution of SCEs which follows a Poisson distribution.     

不同群系小鼠胚胎玻璃化冷冻保存技术的研究

利用 EFS40 ,二步法对近交系 C5 7BL/6、DBA/2和远交群 ICR小鼠囊胚玻璃化冷冻保存 ,并对冷冻后胚胎体内、外发育效果进行比较。结果表明 ,相同条件下鲜胚经培养 ,近交系 C5 7BL /6小鼠的囊胚发育率 ( 93% )与 ICR( 1 0 0 % )相比差异不显著 ( P>0 .0 5 ) ;而两近交系的囊胚孵化率明显低于 ICR( P<0 .0 1 )。 C5 7BL/6、DBA/2小鼠囊胚冷冻后发育率 ( 93% ,96% )和孵化率 ( 5 2 % ,46% )与各自对照组 ( 1 0 0 % ,1 0 0 %和 61 % ,62 % )相比均无显著差异 ( P>0 .0 5 ) ;并且与 ICR冷冻组发育率和孵化率 ( 94% ,5 3% )之间也无显著差异 ( P>0 .0 5 )。两近交系冻胚移植妊娠与各自对照组和 ICR冷冻组比较均无显著差异 ( P>0 .0 5 )。C5 7BL/6胚胎移植产仔率 ( 35 % )与对照组 ( 5 1 % )之间差异显著 ( P<0 .0 1 ) ,而 DBA/2胚胎移植产仔率 ( 4 7% )与对照组和 ICR冷冻组 ( 39% ,5 8% )相比差异不显著 ( P>0 .0 5 )。     

Cryopreservation of mouse spermatozoa in the presence of raffinose and glycerol

When mouse epididymal spermatozoa were rapidly frozen in two steps (37 to -70 degrees C for solid CO2 and -70 to -196 degrees C for liquid nitrogen) as pellets, 18% raffinose provided the greatest protection to ICR mouse spermatozoa against cold-shock; sperm motility and fertilizing ability were 43% and 22.4%, respectively. A small proportion of spermatozoa frozen with 10% sucrose was motile but incapable of fertilizing ovulated oocytes. Glycerol and dimethylsulphoxide were less effective at any concentration examined. However, the fertilizing ability of frozen-thawed ICR spermatozoa was significantly improved (35.5%) by addition of glycerol (1.75% final concentration) to medium containing 18% raffinose. Spermatozoa from one outbred (ddY) and 5 inbred (C57BL/6N, C3H/HeN, DBA/2N, BALB/c and kk) strains of mice were successfully frozen in the presence of 18% raffinose and 1.75% glycerol, although the fertilization rates of frozen-thawed spermatozoa varied among strains (13% for C57BL/6N to 64% for DBA/2N). A small fraction of mouse eggs resulting from fertilization by frozen-thawed spermatozoa developed normally in vitro (37% in C57BL/6N to 71% in ICR) to the blastocyst stage and in vivo (19% for C57BL/6N spermatozoa and ddY oocytes) to Day 18 of gestation.     

Behavioral profiles of inbred strains on novel olfactory,spatial and emotional tests for reference memory in mice

Studying the behavior of genetic background strains provides important information for the design and interpretation of cognitive phenotypes in mutant mice. Our experiments examined the performance of three commonly used strains (C57BL/6J, 129S6, DBA/2J) on three behavioral tests for learning and memory that measure very different forms of memory, and for which there is a lack of data on strain differences. In the social transmission of food preference test (STFP) all three strains demonstrated intact memory for an odor-cued food that had been sampled on the breath of a cagemate 24 hours previously. While C57BL/6J and 129S6 mice showed good trace fear conditioning, DBA/2J mice showed a profound deficit on trace fear conditioning. In the Barnes maze test for spatial memory, the 129S6 strain showed poor probe trial performance, relative to C57BL/6J mice. Comparison of strains for open field exploratory activity and anxiety-like behavior suggests that poor Barnes maze performance reflects low exploratory behavior, rather than a true spatial memory deficit, in 129S6 mice. This interpretation is supported by good Morris water maze performance in 129S6 mice. These data support the use of a C57BL/6J background for studying memory deficits in mutant mice using any of these tasks, and the use of a 129S6 background in all but the Barnes maze. A DBA/2J background may be particularly useful for investigating the genetic basis of emotional memory using fear conditioning.     

Cryopreservation of mouse strains by ultrarapid freezing

Two-cell mouse embryos from four different inbred strains (BALB/c, C3H/He, C57BL/6 and DBA/2) and one closed colony (Slc:ICR) were frozen by direct placement into liquid nitrogen after a 10-15 sec exposure to a highly concentrated solution (DAP 213: 2 M dimethyl sulphoxide, 1 M acetamide, 3 M propylene glycol in PB 1), and later thawed in a 37 degrees C waterbath. The percentages of morphologically normal embryos were 80.7-92.6% on thawing. Morphologically normal embryos were then transferred to the oviducts of pseudopregnant recipients, and 7.4-60.0% of the embryos developed into normal young (BALB/c; 34.3%, C3H/He; 30.6%, C57BL/6; 60.0%, DBA/2; 7.4%, and Slc:ICR; 24.3%).     

Genetic differences in leverpress escape/avoidance conditioning in seven mouse strains

Studies of inbred mouse strains can provide us with important information about the genetic basis of learning and memory. The present experiment studies the acquisition of a leverpress escape/avoidance task in six commonly studied inbred mouse strains (C57BL/6NCrlBR, DBA/2NCrlBR, C3H/HeJ, FVB/NJ, BALB/cByJ and 129S6/SvEvTac), and one outbred strain, the CD1. Results indicated that the strains formed three discrete performance clusters. The C57BL/6NCrlBR, C3HeB/FeJ, BALB/cByJ, and CD1 strains acquired the avoidance response comparably to Sprague-Dawley rats, avoiding approximately 40% of shocks by the fourth and final training session. The 129S6/SvEvTac and FVB/NJ were extremely poor at the avoidance task throughout training. The FVB/NJ strain remained in an escape mode, while the 129S6/SvEvTac animals performed few responses of any type. Finally, the DBA/2NCrlBR strain performed exceptionally well, avoiding over 90% of the shocks by the final session. Results are discussed in terms of genetic differences in learning and how the nigrostriatal dopamine system may mediate the observed differences.     

Dimethylnitrosamine metabolism: II. In vitro activation of dimethylnitrosamine by hepatic and renal tissues from crosses among BALB/c, DBA and C57BL mice

Crosses among BALB/c, C57BL and DBA mice were performed to investigate the genetic mechanisms involved in metabolism of DMN by renal and hepatic tissues. Liver S-9 fractions from parental strain DBA had the greatest potential to activate DMN and liver fractions from parental strain BALB/c had the lowest. No age or sex-related differences were observed within strain. Crossing of either C57BL or DBA to BALB/c mice resulted in F1 hybrids with liver microsomal enzymes that gave results similar to the BALB/c parental strain. There were no sex or age differences within crossbred strains in the potential of liver to activate DMN. In contrast male DBA and C57BL parental mice renal S-9 fractions did not differ significantly from each other but did differ significantly from male BALB/c renal fractions and from female and immature animals of all strains. Crossing of either DBA or C57BL mice with BALB/c mice resulted in male F1 hybrids whose renal S-9 fractions did not differ significantly from males of the parental BALB/c strain. In all instances, male renal S-9 fractions had a significantly greater potential to activate DMN than female or immature animals. F1 DBA X C57BL hybrids had renal S-9 fractions that did not differ significantly from the parental strains. These data suggest that the gene(s) for low DMN metabolism of BALB/c mice are apparently dominant over the genes from both DBA and C57BL. The exact genetic or physiological mechanism needs further elucidation.     

Strain specificity and cholinergic modulation of visuospatial attention in three inbred mouse strains

The tremendous increase in the use of mouse inbred strains and mutant mice to study the molecular basis of psychiatric disorders urges for a better understanding of attentional performance in mice. To this aim, we investigated possible strain differences in performance and cholinergic modulation of visuospatial attention in three widely used mouse inbred strains (129S2/SvHsd, C57BL/6JOlaHsd and DBA/2OlaHsd) in the five-choice serial reaction time task. Results indicated that after extended training, performance of 129S2/SvHsd mice was superior to that of C57BL/6JOlaHsd and DBA/2OlaHsd mice in terms of attention, omission errors, inhibitory control and latencies to correct choice. Increasing the attentional load resulted in comparable decrements in attention in all strains and inhibitory control impairments that were most pronounced in DBA/2OlaHsd mice. Further pharmacological evaluation indicated that all strains showed attentional impairments after treatment with the muscarinic and nicotinic antagonists scopolamine and mecamylamine, respectively. 129S2/SvHsd mice were less sensitive, whereas DBA/2OlaHsd mice appeared more sensitive to the detrimental effects of mecamylamine. In addition, subchronic, but not acute, nicotine treatment slightly improved attentional performance in all strains to the same extent. In conclusion, our data indicate strain specificity with particularly good performance of 129S2/SvHsd mice and strong cholinergic involvement in visuospatial attention in mice.     

The induction of cytochrome P-450 by isosafrole and related methylenedioxyphenyl compounds

Using sucrose gradients, the Ah receptor and a 3-4S binding peak were measured in hepatic cytosol from Dub: ICR, C57BL/6, and DBA/2 male mice. Isosafrole, piperonyl butoxide, and 5-t-butyl-1,3-benzodioxole were unable to displace 2,3,7,8-tetrachlorodibenzo-p-dioxin or 3-methylcholanthrene from either the Ah receptor or the 3-4S binding peak, in vitro. In in vivo experiments, treatment of C57BL/6 mice with 3-methylcholanthrene caused a 4-fold reduction in Ah receptor binding 2 h after i.p. injection; whereas, isosafrole caused a 2-fold enhancement of the Ah receptor after 24 h. This increase in the Ah receptor binding following isosafrole treatment may be due to induction. 3-Methylcholanthrene treatment of C57BL/6 mice also caused a 3-fold reduction in the 3-4S binding peak 2 h after i.p. injection; isosafrole treatment had little or no effect on the 3-4S peak in C57BL/6 or DBA/2 mice. Both in vivo and in vitro data appear to demonstrate that there is no direct role for the Ah receptor or the 3-4S protein in the regulation of cytochrome P-450 by methylenedioxyphenyl compounds. Using Sephadex G-100 chromatography, a cytosolic protein fraction was obtained from C57BL/6 and Dub:ICR mice which was previously implicated by others as a carrier in the metabolism of benzo[a]pyrene (B[a]P). This fraction was applied to sucrose gradients and sedimented in the 3-4S region. Hence it appears that the 3-4S binding peak may be the carrier described by these workers.     

Strain variation in the susceptibility and immune response to Clonorchis sinensis infection in mice

Mice have shown various susceptibility to infection by Clonorchis sinensis. To compare the intra-specific variation in the host-parasite relationship of C. sinensis, 6 strains of mice (ICR, BALB/c, C57BL/6, DDY, CBA/N, and C3H/HeN) with 3 different haplotypes were evaluated on their susceptibility. The worm recovery rate and immunological responses were observed after 4 and 8 weeks of infection with 30 metacercariae. The highest worm recovery rate was observed as 20.7% in the C3H/HeN strain after 4 weeks of infection along with histopathological changes. The rate was 10.0% in C57BL/6 mice after 8 weeks. ICR, BALB/c, and CBA/N showed elevated levels of IgE at both time points when compared to the rest of the strains. The serum IgG1 and IgG2a levels were elevated in most of the strains; however, the C57BL/6 strain showed a lower level of IgG2a that indicated the IgG1 predominance over IgG2a. The production of IL-4 after concanavalin-A stimulation of splenocytes slightly increased among the mouse strains except C3H/HeN after 4 or 8 weeks of infection, but each strain produced high levels of IFN-γ after 8 weeks, which implied mixed Th1/Th2 responses. ICR, DDY, CBA/N, and C3H/HeN strains showed a significantly increased level of IL-10 after 8 weeks as compared to C57BL/6. All of the strains showed an increased level of IL-13 and suggested fibrotic changes in the mice. In conclusion, mice are insusceptible to infection with C. sinensis; however, the C57BL/6, BALB/c and ICR strains are relatively susceptible after 8 weeks of infection among the six strains. Worm expulsion may be one of the causes of low susceptibility of C3H/HeN mice strain at the 8th week. Elevated IgE, IFN-γ, and IL-13 of infected mice suggest both Th1 and Th2 responses that may be related to the low host susceptibility.