Expression of an ovine growth hormone transgene in mice causes organomegaly and hepatic lesions which resolve following transgene inactivation.
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Animals↗
Biomedical subjects
D Pomp
Publications and source records attributed to D Pomp.
Regulation of insulin-like growth factor-I and binding protein-3 expression in oMtla-oGH transgenic mice.
Growth hormone (GH)-transgenic mice provide a model for studying hormonal regulation of gene products responsible for efficient lean growth. Insulin-like growth factor-I (IGF-I) and IGF binding protein-3 (BP-3) are two products involved in mediating the growth promoting actions of GH. Mice carrying the ovine metallothionein la-ovine growth hormone (oMtla-oGH) transgene were used to study GH regulation of IGF-I and BP-3 expression because these mice do not exhibit elevated basal oGH levels without transgene stimulation by exogenous zinc. C57B1/6XCBA mice with (transgenic = TG) and without control = C) the oMtla-oGH transgene were activated (+ Zn) or inactivated (-Zn) by the addition or removal of 25 mM zinc sulfate in the drinking water. Plasma IGF-I and BP-3 levels were determined by radioimmunoassay and western ligand blotting, respectively. Hepatic IGF-I and BP-3 mRNA levels were determined by slot-blot analysis. TG+Zn mice had higher plasma IGF-I (p < 0.05) and hepatic IGF-I mRNA (p < 0.05) levels as compared to TG-Zn, C+Zn and C-Zn mice. Plasma IGF-I and hepatic IGF-I mRNA levels in TG-Zn mice were not different from C+Zn and C-Zn mice. Removal of Zn decreased hepatic IGF-I mRNA levels to C levels in TG mice. Plasma BP-3 and hepatic BP-3 mRNA levels in TG+Zn mice were increased (p < 0.05) as compared to TG-Zn, C-Zn and C+Zn. Plasma BP-3 and hepatic BP-3 mRNA levels did not differ between TG-Zn, C-Zn and C+Zn mice. Expression of the transgene also increased the level of plasma BP-3 during pregnancy as compared to that observed for pregnant C mice. We conclude that oGH regulates IGF-I and BP-3 expression in the oMtla-oGH transgenic mouse model system.
Animals↗
Rapid communication: PCR-based Sau96I polymorphism in the bovine Lipoprotein lipase gene.
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Alleles↗
Dependence of increased linear bone growth on age at oMT1a-oGH transgene expression in mice.
We have previously shown that growth hormone (GH) accelerates the rate and extends the duration of linear bone growth in a GH-transgenic mouse model. To determine if this GH effect was temporally regulated, bone lengths and growth plate widths were determined in transgenic mice carrying an ovine metallothionein 1a-ovine growth hormone (oMT1a-oGH) transgene. Transgene expression was initiated in oMT1a-oGH hemizygous transgenic mice by addition of 25 mM ZnSO4 to the water at 21 d of age; littermate control mice were also ZnSO4 supplemented. These mice were maintained on ZnSO4 until 70 d of age at which time the mice were killed and the ulna, humerus, and tibia were collected. Additional transgenic and control mice were stimulated at 21 d and the ZnSO4 stimulus withdrawn after 21 d of treatment and killed at 70 d or stimulated at 28 d with the stimulus withdrawn after 28 d and killed at 70 d. Continuously stimulated transgenic mice had longer bones than those of comparable control mice. The increased bone length in the transgenics was correlated with wider growth plates. Transgene expression initiated at 21 d of age increased bone length to the same or greater extent than that observed for mice with transgene expression initiated at 28 d but maintained for a longer interval thereby indicating that the age of GH initiation is more critical in bone elongation than the duration of GH exposure. The elevated GH effects were independent of circulating thyroid hormones and attainment of puberty. Elevated GH also increased the widths of all growth plate zones to the same extent by increasing cell numbers, rather than enhancing matrix production or individual cellular area.
Aging↗
The epigenetic influence of growth hormone on skeletal development.
We studied the epigenetic effect of growth hormone using mice that were transgenic for a sheep metallothionein 1a-sheep growth hormone, which was expressed beginning at 21 days postnatal age. The impact of exogenous growth hormone (GH) on various skeletal traits with special emphasis on the mandible was examined by conventional statistical analysis and finite element scaling analysis. In long bones, growth hormone enhances the proliferation rate of cartilage cells in the growth plate and should thus lead to increased lengths. Further, growth hormone is known to increase muscle mass. Our results are consistent with these developmental considerations. We found that the lengths of long bones increased in the transgenic mice compared to the control mice, while the differences in long bone width were less pronounced. In the mandible and skull, the impact of GH is most pronounced in areas of major muscle attachment, i.e., the proximal part of the mandible and the occipital and malar bones in the skull.
Animals↗
Growth hormone and insulin-like growth factor-I measurements in high growth (hg) mice.
Effects of a recessive gene causing high growth (hg) were studied on two major components of the growth axis in mice. Plasma and pituitary levels of growth hormone and plasma levels of insulin-like growth factor I (IGF-I) were measured in three lines homozygous for hg, each compared with a control line of alike genetic background but wild type for the hg locus (Hg). Line Gh (hghg) and line GH (HgHg) are from a line which had undergone long-term selection for high postweaning weight gain; line Ch (hghg) and line CH (HgHg) were extracted from the second backcross of Gh to C57BL/6J; line L54 (hghg) was from the sixth backcross to C57BL/6J (B6) (HgHg). Pituitary GH levels and plasma IGF-I levels were measured in both sexes at 3, 4.5, 6 and 9 wk of age. Plasma growth hormone was measured in 8- to 12-wk-old males at hourly intervals from 08.00 to 17.00. Body weight in lines homozygous for hg at 6 and 9 wk of age was 10-30% greater than in control lines. The ontogeny of this increased growth depended on genetic background. Pituitary growth hormone content was 52% lower in the two hghg lines measured (lines Ch and Gh) than in control lines at 4.5, 6 and 9 wk. Plasma growth hormone levels were also much lower in hg mice, with values only 20-30% of those in their respective controls. hg lines showed consistently low plasma growth hormone levels throughout the 9 hr sampling period, while control lines expressed the characteristic pulsatile hormone secretion.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Genetic variation in reproductive responses to a high-energy diet in mice.
Effects of a high-energy diet on reproduction were studied in 300 mice from lines selected for litter size and(or) 6-wk BW (L+, increased litter size; W+, increased body weight; L+W-, increased litter size and decreased body weight; L-W+, decreased litter size and increased body weight; and K, randomly selected control). Mice received a high-energy diet (HED; 3.8 kcal/g of ME) or a standard diet (STD; 3.3 kcal/g of ME) from 8 to 11 wk of age and were then mated and evaluated for ovulation rate and embryo survival through 17 d of gestation. The HED increased ovulation rate in all lines (P less than .05). The line x diet interaction was significant, with increased ovulation rate due to HED ranging from 9.9% in W+ to 24.2% in L-W+. Within-line regression coefficients of ovulation rate on ME intake (kilocalories from 10 to 11 wk) varied from .08 +/- .04 (P less than .05) in L+W- to .177 +/- .05 (P less than .01) in L+. In contrast, nonsignificant increases were observed in litter size (live fetuses at 17 d of gestation) due to HED. Effects of HED on embryo survival rate were significantly negative in L+ and L+W-; the decrease in L+ was a result of preimplantation losses, and the decrease in L+W- was due to postimplantation losses. The line x diet interaction was significant for postimplantation embryo survival. The results indicate significant genetic variation in reproductive responses to a high-energy diet in mice.
Animals↗
Organic solvents as facilitators of polymerase chain reaction.
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Animals↗
Replicate differences in lines of mice selected for body composition.
Replicate differences were studied in lines of mice selected at 12 weeks of age for high (HF1, HF2) or low (LF1, LF2) right epididymal fat pad weight as a percentage of body weight (%EFP); for high (HL1, HL2) or low (LL1, LL2) hind carcass weight as a percentage of body weight (%HC); and randomly (RC1, RC2). Correlated traits were subcutaneous fat pad weight as a percentage of body weight (%SFP), water weight in hind carcass as a percentage of hind carcass weight (%WAT), body weights at 3, 6, and 12 weeks of age, and 3- to 6-week weight gain. Individual and maternal effects contributed to significant genetic drift for selected and correlated traits. No evidence indicated that drift was greater in selection treatments than in controls. Significant heterosis in replicate crosses within selection treatments was found for %HC in HL, LL, and LF and for %EFP in HF. Heterosis was insignificant in crosses of control replicates. Divergence in parental lines and replicate crosses was similar, indicating that differences in heterosis between high and low lines were small relative to divergence. Asymmetry tended to be greater between replicate crosses and parental lines, because selected replicates have greater average heterosis than control replicates. Multivariate discriminant function and Mahalanobis distance analysis of selected traits showed that divergence between replicates within selection treatments was much less than among selection treatments.
Adipose Tissue↗
Observations on the cooling and cryopreservation of pig oocytes at the germinal vesicle stage.
This study examined the viability of pig oocytes at the germinal vesicle stage following cooling or cryopreservation. Cumulus-intact oocytes (n = 641) were collected from slaughterhouse pig ovaries and used in two experiments. In Exp. I the viability of 1) control, 2) cryoprotectant control (CC, 1.5 M glycerol/.5 M sucrose), 3) cooled (0 degrees C) and 4) cryopreserved (-196 degrees C) oocytes was assessed after no incubation or a 24-h incubation. Survivability was judged by morphological appearance, trypan blue exclusion and fluorescein diacetate staining. Survival rate of control oocytes (90%; based primarily on morphological appearance of the cumulus) incubated 0 h was greater (P less than .05) than that of all other groups, whereas survival rate of -196 degrees C oocytes (57%) was less (P less than .05) than that of all other groups. However, vital staining of 0 degrees C and -196 degrees C oocytes showed 0% survival rate as evidenced by trypan blue uptake and lack of fluorescence. The cumulus cells surrounding oocytes that were stored at 0 degrees C or -196 degrees C survived freezing as evidenced by trypan blue exclusion and intense fluorescence. Similar differences among treatment groups were found for oocytes incubated 24 h. Exp. 2 examined the temperature at which oocytes became sensitive to cooling. Oocyte death occurred when oocytes were cooled to 15 degrees C or lower. These results demonstrate that pig oocytes at the germinal vesicle stage did not survive cooling to 15 degrees C or below. When assessing the viability of cryopreserved cumulus enclosed oocytes it is important to use vital stains in conjunction with morphological appearance.
Animals↗
The impact of maternal uterine genotype on postnatal growth and adult body size in mice.
Embryo transfers were used to demonstrate that the genotype of the mother providing the uterine developmental environment significantly influences postnatal growth and adult body size of her progeny. Irrespective of their own genotype, mouse embryos transferred into the uterus of an inbred strain with large body size (C3H) had greater body weights, longer tails and higher growth rates than those transferred into the uterus of a strain with small body size (SWR). Uterine heterosis on body size was smaller than progeny heterosis, and both progeny and uterine heterosis persisted in adult mice. Uterine litter size was significantly negatively associated with body weight, tail length, growth rate and the timing of developmental events. The inbred SWR strain was more sensitive to the embryo transfer procedure than the C3H strain, but effects due to embryo transfer were moderate. Prenatal uterine effects have ramifications for biotechnologies utilizing embryo transfer as well as predictions about evolutionary change by selection.
Analysis of Variance↗
Donor and recipient genotype and heterosis effects on survival and prenatal growth of transferred mouse embryos.
Reciprocal embryo transfers amongst two inbred strains (C3HeB/FeJ and SWR/J) and their F1 cross (C3SWF1) were used to examine donor and recipient genotype and heterosis effects on survival and prenatal growth of mouse embryos. Among inbred strains, significant recipient genotype effects were detected for both embryo survival (P less than 0.01) and prenatal growth (P less than 0.05), while no donor genotype effects were observed. The recipient effect on overall embryo survival was due to a higher proportion of C3H recipients maintaining pregnancy to term than SWR recipients (P less than 0.01), rather than survival within litters. Irrespective of their own genotype, embryos developing in C3H uteri achieved larger body weights (P less than 0.01) and longer tail lengths (P less than 0.05) at birth than did embryos developing in SWR uteri. Recipient heterosis was not significant, while donor heterosis was significant for prenatal growth traits (P less than 0.001).
Animals↗
Lower sodium lactate in Whitten's medium improves in vitro developmental capacity of one-cell mouse embryos.
A modification of Whitten's medium, involving a reduced content of Na-lactate syrup (0.2 ml/100 ml; 11.65 mM) and osmolarity (251 mOsm), was compared with normal Whitten's medium (0.37 ml/100 ml; 21.6 mM) for ability to support mouse embryonic development in vitro from one-cell to the blastocyst stage. In a pilot study utilizing 10 ICR donor female mice, in vitro developmental capacity (IVDC; percentage of fertilized one-cell embryos developing to blastocysts in vitro per female donor) was significantly enhanced by the modified medium (68.0 versus 24.0%; P<0.001). In the main study, utilizing 134 ICR and 17 ICR x C57BL/6J F(1) donor females, the modified medium supported increased IVDC for both ICR (67.9 versus 51.1%; P<0.001) and F(1) females (98.5 versus 89.4%; P<0.05). A large degree of among donor-female variation in IVDC was observed for both media in the ICR stock (SD = 30.0). The beneficial role of the reduction of Na-lactate in Whitten's medium may be related to an improved provision of energy requirements for first cleavage and/or a more suitable osmolarity for development.
Journal Article↗
LH receptor induction and ovulation rate in mice selected for litter size and body weight.
Female mice from lines which had undergone long-term single trait and antagonistic index selection for litter size and body weight were analysed for ovulation rate and LH receptor induction. Compared to randomly selected controls, selection for large litter size increased ovulation rate (60%; P less than 0.001) and decreased LH receptor induction per microgram ovarian DNA (87%; P less than 0.01). Selection for large body weight increased ovulation rate (18%; P less than 0.001), but did not lead to a significant correlated response in LH receptor induction. Index selection for large litter size and small body weight increased ovulation rate (14%; P less than 0.01) and decreased LH receptor induction (72%; P less than 0.01), while index selection for small litter size and large body weight did not significantly alter either ovulation rate or LH receptor induction. LH receptor quantities in testes of males from the 5 lines did not exhibit the among-line profile which was observed in ovaries of females. These results confirm the role of ovulation rate in mediation of the positive genetic correlation between litter size and body weight in mice. Increased ovulation rate in mice selected for large litter size may be due to mechanisms associated with LH receptors as well as factors related to growth. In contrast, increased ovulation rate in mice selected for large body weight may be due exclusively to factors related to growth.
Animals↗
Cytoplasmic effects on selection response for increased growth rate in mice.
To determine if cytoplasmic effects have contributed to long-term selection response for increased growth rate in mice, reciprocal cross matings were made between an unselected control line (ICR) and a line (M16) derived from ICR by long-term selection for high postweaning weight gain from 3 to 6 wk of age. Embryos were recovered 2 to 4 d following mating and transferred to pseudopregnant F1 (DBA/2NCrlBR X C57BL/6NCrlBR) females. Thus, all embryos developed in similar uterine and postnatal maternal environments. A total of 122 M16 X ICR and 123 ICR X M16 mice was produced, representing 19 litters from each cross. Litters were standardized at birth to five to seven pups. Litter weights at birth and 1 wk were recorded. Body weights at 2, 3, 4, 5 and 6 wk and weight gain from 3 to 6 wk were obtained. Weights of liver, kidneys, and sc and epididymal fat pads of males were obtained at 6 wk. Females were mated at 8 wk, and litter size at birth was recorded. Least-squares procedures were used to test for differences between reciprocal crosses for all traits. Body weight at 4 wk was higher (P less than .05) for mice with ICR cytoplasm. No other significant differences were detected. There was no evidence that cytoplasmic effects influenced direct or correlated responses to long-term selection for increased postweaning weight gain.
Animals↗
A recessive mutation causing imperforate vagina in mice.
A recessive mutation (ipv) causing imperforate vagina was discovered in a line of mice selected for low lean tissue mass as a proportion of body weight. Two full sisters were found to have marked swelling of the perineum and complete closure of the vagina. Crosses of heterozygotes identified by progeny testing produced a female progeny ratio not different from the 3 normal: 1 affected (chi 2 = 0.695; p less than .3) expected on the basis of a recessive allele at a single autosomal locus. As a consequence of the imperforate vagina, the uterus and vagina were greatly distended by fluid. The uterus of affected females displayed a swollen uterine lumen and thin endometrial stroma and muscularis. Ovarian tissue of affected females was similar to that of normal mice, and affected females produced ova that were normal in appearance. The mutation causing an imperforate vagina may present a useful model for studying the basis of abnormal vaginal development in other species and increasing the understanding of normal vaginal development in the mouse.
Animals↗
Genetic control of survival of frozen mouse embryos.
Lines of mice selected for increased litter size (L+), increased body weight (W+), or randomly (K) were used to study genetic variation in embryo cryosurvival in response to standard cryopreservation protocols. A total of 60528-cell embryos from 400 females were used in two studies. In Study 1, embryos from L+, W+, and K were frozen by slow-cool and ultrarapid (direct-plunge) methods to evaluate effects of selection on cryosurvival and genotype X freezing method interaction. Post-thaw survival (PTS) was measured as percentage of recovered embryos developing in vitro to blastocyst per donor female. Nonfrozen control embryos developed similarly for each line. Within slow-cool freezing, lines differed (W+ greater than K, W+ = L+, L+ = K; p less than 0.05); no differences were observed within the ultrarapid freezing. However, line X method interaction effects on PTS were not significant. In Study 2, reciprocal crosses were made between L+ and K and between W+ and K. Hybrid and pure line embryos were frozen by slow-cooling. Control embryos developed similarly for all genotypes. Selection lines did not differ for overall PTS. However, hybrid embryos from L+ dams were superior to those from K dams (84 vs. 61%; p less than .001). No overall embryo heterosis was observed. Differences were not significant among embryo genotypes or treatments for cell number or in vivo survival. These results demonstrate significant correlated responses in embryo post-thaw cryosurvival due to selection, and implicate both maternal and embryonic genomes as controlling mouse embryo cryosurvival.
Animals↗
Body composition of inactivated growth hormone (oMt1a-oGH) transgenic mice: generation of an obese phenotype.
The consequences of a 42 d exposure to elevated growth hormone (GH) on adipose tissue were assessed using the regulatable ovine metallothionein- ovine GH (oMt1a-oGH) transgene in male and female GH transgenic (TG) mice. Activation of transgene expression at 21 d of age followed by inactivation of transgene expression at 63 d of age (TG-on/off) increased individual white adipose tissue (WAT) depots and total body lipid stores in both males and females. WAT, expressed as a percentage of fasted body weight, did not differ in wildtype (WT) and continuously activated TG males and females up to 105 d of age, but was increased approximately 270% following inactivation of the transgene. Inguinal depot adipocytes were more numerous in both male and female TG +/- relative to WT or TG animals. The ensuring obesity was not accompanied by a decrease in thermogenic capacity of brown adipose tissue, as indexed by uncoupling protein quantity. GH transgene expression was accompanied by elevated insulin levels that were restored to WT levels upon cessation of transgene expression (p > 0.1). Early, transient exposure to elevated GH increased total body lipid by nearly threefold independent of gender; the increased lipid content was sustained and reflected WAT hypertrophy and hyperplasia. The oMt1a-oGH mouse provides a novel model of induced obesity in response to inactivation of a GH-transgene by the withdrawal of the transgene stimulus.
Adipocytes↗