Narrowing a region on rat chromosome 13 that protects against hypertension in Dahl SS-13BN congenic strains

Transfer of chromosome 13 from the Brown Norway (BN) rat onto the Dahl salt-sensitive (SS) genetic background attenuates the development of hypertension, but the genes involved remain to be identified. The purpose of the present study was to confirm by telemetry that a congenic strain [SS.BN-(D13Hmgc37-D13Got22)/Mcwi, line 5], carrying a 13.4-Mb segment of BN chromosome 13 from position 32.4 to 45.8 Mb, is protected from the development of hypertension and then to narrow the region of interest by creating and phenotyping 11 additional subcongenic strains. Mean arterial pressure (MAP) rose from 118 ± 1 to 186 ± 5 mmHg in SS rats fed a high-salt diet (8.0% NaCl) for 3 wk. Protein excretion increased from 56 ± 11 to 365 ± 37 mg/day. In contrast, MAP only increased to 152 ± 9 mmHg in the line 5 congenic strain. Six subcongenic strains carrying segments of BN chromosome 13 from 32.4 and 38.2 Mb and from 39.9 to 45.8 Mb were not protected from the development of hypertension. In contrast, MAP was reduced by ～30 mmHg in five strains, carrying a 1.9-Mb common segment of BN chromosome 13 from 38.5 to 40.4 Mb. Proteinuria was reduced by ～50% in these strains. Sequencing studies did not identify any nonsynonymous single nucleotide polymorphisms in the coding region of the genes in this region. RT-PCR studies indicated that 4 of the 13 genes in this region were differentially expressed in the kidney of two subcongenic strains that were partially protected from hypertension vs. those that were not. These results narrow the region of interest on chromosome 13 from 13.4 Mb (159 genes) to a 1.9-Mb segment containing only 13 genes, of which 4 are differentially expressed in strains partially protected from the development of hypertension.     

Restriction fragment length polymorphisms, glucocorticoid receptors, and phenytoin-induced cleft palate in congenic strains of mice with steroid susceptibility differences.

A gene that affects susceptibility to cortisone-induced cleft palate maps between H-2S and H-2D on mouse chromosome 17. Congenic mouse strains that differ at this locus, designated Cps-1 (cleft palate susceptibility-1), have been tested for the presence of several closely linked markers. All data obtained so far are consistent with a gene order of H-2S-Cps-1-BAT-5-BAT-2-TNF-H-2D. The Cps-1 gene does not appear to affect the level of glucocorticoid receptors or the susceptibility of mice to phenytoin-induced cleft palate.     

Cytogenetic analysis of X-ray-induced chromosome aberrations in spontaneously leukaemic AKR mice.

The increased frequency of numerical and structural chromosomal aberrations in spontaneously leukaemic AKR mice, compared with the values of healthy control CBA/H-T6T6 mice, induced by X-irradiation, migh be connected with the predisposition to malignant growth, probably indirectly helping the virus activation, or acting together with the immune deficiency, by creating a weaker system that is more sensitive to carcinogenic agents.     

Effects of H-2 and vitamin A on micrognathia in congenic mice.

Pregnant mice congenic with C57BL/10 (B10.A, B10.BR, B10.D2, B10.A(2R), B10.A(5R), B10.A(15R), B10.A(1R), B10.A(18R), and B10.OL) were fed Purina Mouse Chow or the same diet plus 200 IU of vitamin A daily. The pregnant dams were sacrificed on the eighteenth day of gestation, and the fetuses were sexed and examined for defects in mandibular development. On average, micrognathia occurred five times more frequently in female (1.5%) than male (0.3%) fetuses. The addition of vitamin A to the diet affected only females, reducing the frequency of this defect to that observed in males from dams fed the control diet. Micrognathia was strongly associated with micro- or anophthalmia, but not with defects of the palate. C57BL/10 fetuses had the highest frequency of micrognathia (3.2%) and B10.D2 and B10.A(5R) fetuses had the lowest (0.1%). The results suggest that a locus distal to C4 and perhaps proximal to Qa-1 may exert a moderate influence on mandibular development and a second locus proximal to E beta may have a weak effect.     

Effects of H-2 on neural tube defects in congenic mice.

Pregnant mice congenic with C57BL/10 (B10.A, B10.BR, B10.D2, B10.A[2R], B10.A[5R], B10.A[15Rd, B10.A[1R], B10.A[18R], and B10.0L) were fed Purina Mouse Chow or the same diet plus 200 IU of vitamin A daily. The pregnant dams were sacrificed on the eighteenth day of gestation, and the fetuses were sexed and examined for defects in neural tube development. The frequency of neural tube defects was low (mean frequency of all strains, 0.36%) and was not affected by the addition of vitamin A (200 IU/day) to the diet. Twenty-seven of the 29 defects observed occurred in the anterior tube (exencephaly); fourteen were identified in female fetuses, but the sex could not be determined in the other 15 cases because of fetal death and early autolysis. Variations in frequency among the strains suggest that a locus between E beta and H-2D has a moderate influence on the occurrence of neural tube defects. Strains that had H-2d alleles in this segment of the H-2 complex had relatively high frequencies, and those with H-2b or H-2k alleles had significantly lower frequencies.     

High-resolution mapping of the blood pressure QTL on chromosome 7 using Dahl rat congenic strains

It was previously shown using Dahl salt-sensitive (S) and salt-resistant (R) rats that a blood pressure quantitative trait locus (QTL) was present on rat chromosome 7. In the present work, this QTL was localized to a region less than 0.54 cM in size on the linkage map using a series of congenic strains. This region was contained in a single yeast artificial chromosome that was 220 kb long. This small segment still contained the primary candidate locus Cyp11b1 (11beta-hydroxylase), but the adjacent candidate genes Cyp11b2 (aldosterone synthase) and Cyp11b3 were ruled out. It is concluded that 11beta-hydroxylase, through its known genetic variants altering the production of 18-hydroxy-11-deoxy corticosterone, is very likely to account for the blood pressure QTL on chromosome 7 in the Dahl rat model of hypertension. This QTL accounts for about 23 mm Hg under the condition of 2% NaCl diet for 24 days.     

Effects of H-2 and vitamin A on eye defects in congenic mice.

Pregnant mice congenic with C57BL/10 (B10.A, B10.BR, B10.D2, B10.A(2R), B10.A(5R), B10.A(15R), B10.A(1R), B10.A(18R), and B10.OL) were fed Purina Mouse Chow or the same diet plus 200 IU of vitamin A daily. The pregnant dams were sacrificed on the 18th day of gestation and the fetuses were sexed and examined for defects in eye development. It was found that the frequency of microphthalmia and anophthalmia in the female progeny of mice fed Mouse Chow was 7.4-9.2% in B10.A and B10.BR, 4.0-5.5% in B10.A(18R), B10, B10.A(5R), B10.A(1R), B10.A(15R), and B10.A(2R), and 0.8% and 1.4% in B10.D2 and B10.OL mice, respectively. On average, the frequency of these defects in the female progeny was 6.2 times greater than that in males (P less than 0.001). The right eye was 5.8 times more often affected than the left (P less than 0.001). The addition of vitamin A to the diet increased the frequency of these eye abnormalities in all strains, suggesting that this effect is not mediated by loci associated with H-2, as is the case with vitamin A-enhanced cleft palate. The addition of vitamin A to the diet did not affect the ratios of affected males to females, affected right to left eye, or microphthalmia to anophthalmia. The results suggest that there are two loci on chromosome 17, one centromeric to E beta and one telemeric to C4, that interact to determine to some degree the frequency of microphthalmia and anophthalmia.     

Chronopharmacokinetics of imipramine and desipramine in rat forebrain and plasma after single and chronic treatment with imipramine.

Daily variations in the pharmacokinetics of imipramine (IMI) could contribute to circadian phase-dependent effects of the drug. Therefore, the chronopharmacokinetics of IMI and its metabolite, desipramine (DMI), were studied after single and chronic application. Male rats were synchronized to a 12:12 hour light:dark (L:D) regimen with lights on from 07:00 to 19:00 (dark, 19:00-07:00). In single-dose experiments rats were injected with IMI (10 mg/kg) i.p. or i.v. at 07:30 or 19:30 and groups of rats were killed 0-22 hours thereafter. After chronic application of IMI in drinking water (approximately 15 mg/kg/d) groups of rats were killed during the 14th day of treatment at 02:00, 08:00, 14:00, and 20:00, respectively. Brain and plasma concentrations of IMI and DMI were determined by reversed-phase high-performance liquid chromatography with ultraviolet detection. After single i.p. application of IMI, maximal brain concentrations (Cmax) of IMI and DMI were nearly twofold higher in darkness (IMI, 4.8 micrograms/g; DMI, 1.8 micrograms/g) than in light (IMI, 2.85 micrograms/g; DMI, 0.85 microgram/g). Also, the area under the curve (AUC) (0-22 hours) was about 1.6-fold greater in darkness than in light for IMI and DMI; half-lives were not circadian phase dependent. After i.v. injection of IMI, the AUC in brain was also about 30% greater in darkness than in light. After chronic application of IMI in drinking water, brain concentrations of IMI and DMI varied more than threefold within 24 hours. The data demonstrate that the pharmacokinetics of IMI and DMI are circadian phase dependent. It is assumed that circadian variations in drug distribution are more likely to contribute to the drug's chronopharmacokinetics than variations in the drug's metabolism. The 24-hour variations in the drug's concentrations after chronic IMI application in drinking water can be explained by the drinking behavior of the rats, which by itself is altered by IMI.     

Selective breeding for catalepsy changes the distribution of microsatellite D13Mit76 alleles linked to the 5-HT serotonin receptor gene in mice

Catalepsy (pronounced motor inhibition) is a natural defensive reaction against predator. Recently, the quantitative trait locus for catalepsy was mapped on mouse chromosome 13 near the 5-HT(1A) serotonin receptor gene. Here, the linkage between catalepsy and the 5-HT(1A) receptor gene was verified using breeding experiment. Selective breeding for high predisposition to catalepsy was started from backcross BC[CBA x (CBA x AKR)] generation between catalepsy-prone (CBA) and catalepsy-resistant (AKR) mouse strains. CBA and AKR strains also differed in the 5-HT(1A) receptor functional activity. A rapid increase of cataleptic percentage from 21.2% in the backcrosses to 71% in the third generation of selective breeding (S3) was shown. The fragment of chromosome 13 including the 5-HT(1A) receptor gene was marked with D13Mit76 microsatellite. Breeding for catalepsy increased the concentration of CBA-derived and decreased the concentration of AKR-derived alleles of microsatellite D13Mit76 in the S1 and S2. All mice of the S9 and S12 were homozygous for CBA-derived allele of D13Mit76 marker. Mice of the S12 showed CBA-like receptor activity. These findings indicate that selective breeding for behavior can involve selection of polymorphic variants of the 5-HT(1A) receptor gene.     

Leukemia in AKR mice: III. Size distribution of suppressor T-cells in AKR leukemia and neonatal mice

Suppression of in vitro antibody forming potential of normal cells by leukemic cells of AKR and normal neonatal mice have many similarities. In both cases the suppression is by cell contact rather than by the elaboration of soluble suppressive factors and the suppression is sensitive to both x-irradiation and mitomycin C treatment. When the size distribution of suppressing cells in thymus and spleen were compared by velocity sedimentation, both leukemic and neonatal suppressing cells had similar size distribution in each organ. Both large and small cells in the thymus suppress but only large cells (sedimentation velocity >3.5 mm/hr) in the spleen are able to suppress. Leukemic cells in lymph node have a splenic size distribution, viz., only large cells suppress. Both large and small cells of a subcutaneously growing long passage AKR lymphoma are able to suppress. While large cells contain the bulk of cells actively incorporating tritiated thymidine and thus probably in cycle, small but significant amounts of incorporation in small suppressing cells is also seen.     

The level of noradrenaline and serotonin in mice differing in behavior

Laboratory mice possessing Robertsonian translocation Rb (8, 17) 1IEM in their karyotype, reveal statistically significant ability for extrapolation of the direction of stimulus movement which disappears from animal's view. Inbred CBA mice with the same translocation are less capable, and CBA mice with normal karyotype are totally incapable of solving this task. Cortical noradrenaline levels in mice with Rb (8, 17) 1IEM were the lowest and brain stem levels the highest among the three groups investigated. Serotonin levels reveal no changes among these groups.     

Effects of MHC and gender on lupus-like autoimmunity in Nba2 congenic mice

The lupus-like disease that develops in hybrids of NZB and NZW mice is genetically complex, involving both MHC- and non-MHC-encoded genes. Studies in this model have indicated that the H2d/z MHC type, compared with H2d/d or H2z/z, is critical for disease development. C57BL/6 (B6) mice (H2b/b) congenic for NZB autoimmunity 2 (Nba2), a NZB-derived susceptibility locus on distal chromosome 1, produce autoantibodies to nuclear Ags, but do not develop kidney disease. Crossing B6.Nba2 to NZW results in H2b/z F1 offspring that develop severe lupus nephritis. Despite the importance of H2z in past studies, we found no enhancement of autoantibody production or nephritis in H2b/z vs H2b/b B6.Nba2 mice, and inheritance of H2z/z markedly suppressed autoantibody production. (B6.Nba2 x NZW)F1 mice, compared with MHC-matched B6.Nba2 mice, produced higher levels of IgG autoantibodies to chromatin, but not to dsDNA. Although progressive renal damage with proteinuria only occurred in F1 mice, kidneys of some B6.Nba2 mice showed similar extensive IgG and C3 deposition. We also studied male and female B6.Nba2 and F1 mice with different MHC combinations to determine whether increased susceptibility to lupus among females was also expressed within the context of the Nba2 locus. Regardless of MHC or the presence of NZW genes, females produced higher levels of antinuclear autoantibodies, and female F1 mice developed severe proteinuria with higher frequencies. Together, these studies help to clarify particular genetic and sex-specific influences on the pathogenesis of lupus nephritis.     

低聚果糖对慢性应激小鼠抑郁样行为及肠道菌群的影响

目的 探讨低聚果糖（FOS）对慢性应激小鼠的抑郁样行为及肠道菌群的影响。方法 选取8周龄健康雄性ICR小鼠随机分成3组,C组小鼠每天给予正常护理,S组和SF组小鼠每天随机给予1～2种应激源,持续8周,SF组小鼠在应激造模的同时经食物补充FOS。在造模4周和8周后,分别通过强迫游泳、蔗糖偏好试验评估各组小鼠抑郁样行为。造模结束后通过Western blot试验检测小鼠大脑皮层内糖皮质激素受体（GR）的表达,并收集结肠内容物进行16S rDNA扩增子测序分析。结果 应激造模8周后,C、S和SF三组小鼠的肠道菌群组成存在明显差异;与C组相比,S组小鼠强迫游泳的不动时间显著增加（t=3.970,P=0.0009）,蔗糖偏好率显著降低（t=3.890,P=0.0011）,脑内GR的表达显著降低（t=4.311,P=0.0125）;与S组相比,SF组小鼠强迫游泳的不动时间显著缩短（t=3.495,P=0.0026）,蔗糖偏好率和脑内GR表达有增加趋势。结论 益生元FOS可调节肠道菌群,改善慢性应激诱发的精神情绪异常。     

Three loci on mouse chromosome 6 influence onset and final incidence of type I diabetes in NOD.C3H congenic strains

The development of insulin-dependent diabetes mellitus in both human and mouse is dependent on the interaction between genetic and environmental factors. The analysis of newly created NOD.C3H congenic strains for spontaneous and cyclophosphamide-induced diabetes has allowed the definition of three controlling genetic loci on mouse chromosome 6. A NOD-derived susceptibility allele at the Idd6 locus strongly influences the onset of diabetes in spontaneous diabetes. A NOD-derived resistance allele at the Idd19 locus affects the final diabetes incidence observed in both models, while a novel locus, provisionally termed Idd20, appears to control Idd19 in an epistatic manner. Decreased diabetes incidence is observed in CY-induced diabetes when Idd20 is homozygous for the C3H allele, while heterozygosity is associated with an increase in diabetes incidence. The Idd20, Idd19, and Idd6 candidate regions fall respectively within genetically defined intervals of 4, 7, and 4.5 cM on mouse chromosome 6. From our YAC contig, Idd6 would appear to localize within a ca. 1.5-Mb region on distal chromosome 6.