Frequency of congenital defects and dominant lethals in the offspring of male mice treated with methylnitrosourea

ICR strain male mice were injected intraperitoneally with daily doses of MNU (5-25 mg/kg) for 5 days and mated to untreated virgin females of the same strain on days 1-7, 8-14, 15-21 and 64-80 after the last dose. Copulations during these periods involve, respectively, spermatozoa, late spermatids, early spermatids, and spermatogonial stem cells at the time of the last treatment. The uterine contents were examined on day 18 of pregnancy for post-implantation losses (dominant lethality). Fetuses were examined for external and skeletal abnormalities. In contrast to the results reported for specific-locus mutations, MNU treatment of either postmeiotic cells or spermatogonial stem cells caused dose-dependent significant increases in the incidence of congenital defects and of dominant lethals over the control levels. The relative sensitivity of germ cells sampled on days 1-7, 8-21 and 64-80 to MNU-induced congenital defects was 1:1.6:2. For the induction of dominant lethals, the sensitivity ratio was 1:1.8:0.5. It is proposed that congenital defects in the offspring of mice following paternal treatment with MNU may represent mostly chromosomal rather than genic changes. Cleft palate was the most frequent of the external abnormalities, which were significantly induced in every treatment series; fused ribs were the most frequent of the skeletal abnormalities, which were significantly induced in the treatment series for spermatogonial stem cells.

Quantitative genetics and the evolution of ontogeny. III. Ontogenetic changes in correlation structure among live-body traits in randombred mice

Ontogenetic series of phenotypic, additive genetic, maternal and environmental correlation matrices are presented and interpreted in the light of recent models for the Ontogenetic origin and variation in correlation between traits. A total of 432 mice from 108 full-sib families raised in a cross-fostering design were used to estimate the various components of phenotypic correlation for five live-body traits at eight ages. The level of genetic and phenotypic correlation decreased with age, while levels of maternal and environmental correlation remained more or less constant. Genetic correlations probably decreased due to compensatory growth. Phenotypic correlations decreased primarily due to the relative decrease in importance of highly correlated maternal effects and consequent increase in poorly correlated environmental effects as portions of phenotypic variation. The effect of compensatory growth on genetic correlation was also responsible for a portion of the decline in phenotypic correlation. Phenotypic correlation patterns remained constant over the ages studied here. It also seems likely the genetic, maternal and environmental correlation patterns do not change with age for the characters analysed.

Genetic analysis of size-scaling patterns in the mouse mandible

The relationship between multidimensional form of the adult mouse mandible and body size is examined from an ontogenetic perspective. The origin and ontogeny of phenotypic correlations are described in terms of genetic and environmental covariance patterns between adult skeletal morphology and growth in body weight. Different ontogenetic patterns are observed in the genetic correlations, and these can be related to the developmental as well as the functional aspects of mandibular form. The quantitative genetic aspects of craniomandibular growth and morphogenesis are explored, together with an examination of the impact of ontogenetic changes in the genetic variance-covariance structure on morphogenetic integration and evolution by selection.

Genetics of mandible form in the mouse

The underlying determination of phenotypic variability and covariability is described for 14 traits that define the morphological size and shape of the mature mouse mandible. Variability is partitioned into components due to direct additive and dominance genetic effects, indirect maternal additive genetic effects, genetic covariance between direct additive and indirect maternal additive effects and common and residual environmental effects. Multivariate analyses of the dimensionality of genetic variability indicate several complex and independent genetic components underlie the morphological form of the mandible. The multidimensional nature of the genetic components suggests a complex picture with regard to the consequences of selection on mandibular form.

'Heterosis' in litter size of chimaeric mice

Aggregation chimaeras were made from embryos of C57BL/6 and BALB/c mice. Chimaeric and control females were mated with ICR males at 8 weeks of age and their litter sizes were evaluated over a 5-month period after the first mating. Progeny tests showed that 18 of 27 chimaeras produced oocytes of both genotypes. The mean litter sizes of C57BL/6, BALB/c and their F1crosses (C57BL/6 × BALB/c and BALB/c × C57BL/6) were 8·14, 9·36, 13·38 and 13·40, respectively. The mean for chimaeras was 11·54 and chimaeric heterosis was evident, but it was not as much as heterosis in the F1When the chimaeras were classified into the mixed and single-genotype progeny chimaeras, chimaeric heterosis was observed only in the mixed-progeny chimaeras. Quantitative GPI analyses in ten organs showed that the degree of chimaerism in the mixed-genotype progeny chimaeras was higher than that in most of the single-genotype progeny chimaeras and that the degree of chimaerism in the ovaries was positively correlated with litter size in the mixed-genotype progeny chimaeras. On the other hand, such correlation was not observed in the single-genotype progeny chimaeras.

[Growth of human tumor transplanted into nude mice with various genetic backgrounds]

Nude mice with different genetic backgrounds were used for the experiment to evaluate the growth of human and murine tumors in the different hosts. Twelve human tumors including 5 gastric carcinomas (St-4, St-10, St-15, St-40, KS-1), 2 colon carcinomas (Co-3, Exp-42), 1 breast carcinoma (MX-1), 1 bile duct carcinoma (Ch-1), 1 hepatocellular hepatoma (Li-4) and 2 hemangiosarcomas (LC-27-R, LC-27-UR), and one murine tumor spontaneously arisen from C3H/HeN nu/+ mouse were transplanted into the subcutaneous tissue of nude mice with genetic backgrounds of BALB/cA, DDD and ICR (CD-1). BALB/cA-nu was originated from the Central Institute for Experimental Animals, DDD-nu was supplied from the Institute of Medical Science, University of Tokyo and ICR (CD-1)-nu was supplied from Charles River Co., Ltd. Tumors were measured by the width (W) and length (L) three times a week by the same person. The tumor volume (V) was estimated by the formula V = W2 X L/2. Tumor doubling time (Td) during the exponential growth phase was compared between the nude mice with different genetic backgrounds. It was found that Td of MX-1 in DDD-nu mice and Td of St-40 and Exp-42 in BALB/cA-nu mice were shortened in comparison with those of tumors transplanted into nude mice with the other strains. However, no statistically significant differences were observed when t-test of matched pairs and coefficients of correlation were applied to compare Td in the other kinds of nude mice. Nude mice with genetic backgrounds of DDD and ICR (CD-1) were thought to be also useful for various kinds of therapeutic experiments in human tumor xenografts/nude mice system.

Additive, nonadditive and maternal genetic effects on adiposity in mice fed different levels of fat

Polygenic obese (M16), nonobese (ICR) and reciprocal crossbred (M16 male x ICR female and ICR male x M16 female) mice were fed ad libitum diets containing 1, 5 or 25% fat from 3 to 10 weeks of age. Epididymal and subcutaneous fat depot weights (E, S) and depot weights as a proportion of empty body weight (E%, S%) were used as measures of adiposity at 6 and 10 weeks of age. Genetic differences in adiposity among the four populations were partitioned into average direct (a), average maternal (m) and direct heterotic (h) effects. Line M16 was greater than ICR at both 6 and 10 weeks in E (81% at 6 weeks and 114% at 10 weeks), S (82%, 73%), E% (27%, 37%) and S% (26%, 12%). Average direct genetic effects, as determined by a, accounted for 60% of the M16 vs. ICR line difference in E and S at six weeks, the remainder of the difference being due to m. The major portion of the line difference in E% and S% at 6 weeks was accounted for by m. At ten weeks of age, most of the line difference in E, S, E% and S% was due to additive direct genetic effects while the contribution of maternal genetic effects was negligible. Heterosis was sizeable for all measures of adiposity, varying from 10.8% in S% at 10 weeks to 26.8% in E at six weeks, possibly indicating the presence of directional dominance. E and E% increased significantly with the increase in dietary fat percent, but S and S% were not affected. Interactions of genotype with level of dietary fat percent were not significant for the epididymal or subcutaneous fat depot weights or proportional weights.

Ethanol intoxication as a function of genotype dependent responses in three inbred mice strains

Three strains of mice, ICR Swiss, DBA/2J and C57Bl/6J were compared for initial sensitivity, recovery from intoxication, and acute tolerance development to ethanol. The The C57Bl/6J mice were found to be less sensitive and to recover more rapidly from the effects of the same dose of ethanol than the other two strains treated. None of the strains tested demonstrated acute tolerance to ethanol when given the same dose 3 hours later.

Selection for serum cholesterol, voluntary physical activity, 56-day body weight and feed intake in randombred mice. I. Direct responses

A five-generation selection experiment was conducted with randomly bred ICR mice. Lines were developed for high (CH) and low (CL) serum cholesterol (SC), voluntary physical activity (lines AH and AL), 56-day body weight (lines WH and WL), and feed intake (lines IH and IL). An unselected randomly bred control line was maintained with each pair of selection lines (CC, AC, WC and IC, respectively). Selection was based on individual performance in SC, activity and weight lines, and on within-sex, among full-sib family selection in intake lines. Genetic responses (selected line generation means deviated from control line generation means and regressed on generation number) were different from zero (P less than 0.05) in CH males and females, CL males, AH males and females, AL males, WH males and females, WL males and females, and IH females. Realized heritabilities which did not differ (P less than 0.05) between sexes were: 0.43 +/- 0.05 (line CH), 0.37 +/- 0.06 (line CL), 0.26 +/- 0.08 (line AH), 0.16 +/- 0.04 (line AL), 0.33 +/- 0.05 (line WH), 0.40 +/- 0.05 (line WL), 0.42 +/- 0.06 (line IH). In Line IL heritabilities of males and females differed (P less than 0.05) from each other (0.08 +/- 0.06 and 0.29 +/- 0.06, respectively).

Selection for serum cholesterol, voluntary physical activity, 56-day weight and feed intake in randombred mice. II. Correlated responses

Randomly bred ICR mice were selected for five generations for high and low serum cholesterol (SC), voluntary physical activity, 56-day body weight and feed intake. An unselected, randomly bred control line was maintained with each pair of selection lines. Significant increases in mature body weight occurred in males of high weight and high intake lines and in females of high SC, high weight and high intake lines. Significant decreases in mature body weights occurred in males of low weight line and in females of low SC and low weight lines. Both high and low selected SC lines had greater (P less than 0.05) activity scores and consumed more feed than the SC control. Mice selected for high activity consumed more (P less than 0.05) feed than mice selected for low activity. Mice selected for high 56-day body weight consumed more (P less than 0.05) feed and had higher SC than mice selected for low 56-day body weight. Mice selected for high feed intake were heavier (P less than 0.05) and more active (P less than 0.05) than low feed intake mice but had significantly lower SC levels.

Molecular cloning of DNA complementary to a mouse alpha-fetoprotein mRNA sequence

DNA complementary to mouse yolk sac messenger RNA has been inserted at the PstI site of the plasmid pBR322 by annealing of the oligo(dG)-tailed plasmid DNA with the oligo(dC)-tailed mouse DNA. Transformation of Escherichia coli strain RRI with this annealed DNA yielded clones bearing recombinant plasmids. The clones were screened for DNA complementary to mouse alpha-fetoprotein (AFP) messenger RNA sequences by hybridization with a cDNA probe transcribed from an AFP mRNA of over 90% purity. Out of nine plasmids that were isolated and analyzed by restiction mapping, all had homologous insert DNA of various lengths. The plasmid with the longest insert, pAF6, contained 1.65 kb of added DNA, which is about 70% of the AFP mRNA. This clone was positively identified by a hybridization-translation procedure to contain a cDNA sequence for AFP. A restriction map of this clone and the orientation of the message are presented.

Induction of sister chromatid exchanges in mouse fetuses resulting from maternal alcohol consumption during pregnancy

Mice were force-fed ethyl alcohol at different doses, administration rates, and durations during pregnancy. A tablet of 5-bromodeoxyuridine (BrdU) was implanted subcutaneously in the animals between the 16th and 18th day of gestation. Twenty-one hours later, the animals were killed, the fetuses removed, and the fetal liver cells treated to exhibit sister chromatid exchanges (SCE's). The following conclusions were drawn: (1) Ingestion of alcohol by pregnant mice induced SCE's in the liver cells of their fetuses. (2) The number of exchanges in the fetal cells was directly proportional to the amount of alcohol consumed by the dam in the period when BrdU was present in her blood. (3) The induction of exchanges above control level was due entirely to alcohol ingestion and was independent of exposure to BrdU, any other drug, or any dietary deficiency.