Response to 13 generations of selection for increased 8-week body weight in lines of mice carrying a sheep growth hormone-based transgene

The purpose of this study was to evaluate selection in lines of transgenic mice. Two replicates of lines that either carried or did not carry the sheep metallothionein-1a sheep growth hormone transgene (oMt1a-oGH) were established. The host lines had been previously selected for rapid growth or selected randomly. Within-litter selection for increased 8-wk body weight was carried out for 13 generations. The frequency of oMt1a-oGH was monitored in all generations in the transgenic lines, but no genotypic information regarding the transgene was used as an aid to selection. The oMt1a-oGH was activated from weaning, at 3 wk, until 8 wk of age by adding ZnSO4 to the drinking water. Zinc stimulation of the transgene was not done during mating, gestation, or lactation. Data on body weights and weight gains were analyzed with a conventional mixed model and with an animal model. Genetic progress was achieved in all lines subjected to directional selection. In the control background, response to selection for 8-wk body weight was larger in the nontransgenic lines than in the transgenic lines, whereas no difference was found in the selected background. The frequency of the transgene was increased from the initial .5 to .62 in the randomly selected background but decreased to .04 in lines from a selected background. The REML estimates of variance components and genetic gain estimates varied greatly between the two methods. In general, there was better agreement between the realized heritability estimates and the heritability estimates obtained from the conventional mixed model analysis than between realized heritability estimates and results obtained using the animal model. Favorable correlated responses were obtained for 3- and 6-wk body weights and on 3- to 6- and 6- to 8-wk weight gains. Correlated responses to selection were larger in the selected than in the nonselected background but were not affected by the presence of the transgene. Results suggest that constructs similar to the oMt1a-oGH, which allow tight regulation, may be successfully incorporated into commercial livestock and should have larger effects in populations that have not been subject to selection.     

Correlated changes in fertility and fitness traits in lines of oMt1a‐oGH transgenic mice selected for increased 8‐week body weight*

Correlated responses in fitness and fertility traits were compared in transgenic and nontransgenic lines of mice selected for increased 8‐week body weight. Two replicates of lines which either carried or did not carry the sheep metallothionein‐1a sheep growth hormone transgene (oMt1a‐oGH) were established. Host lines had been previously selected for rapid growth or selected randomly. Within‐litter selection was carried out for 13 generations, and a randomly selected control line was kept for each set of replicate lines. Mice were genotyped every generation for the presence of the transgene, but this information was not used in selection decisions. The oMt1a‐oGH construct was activated by adding 25 mm ZnSO₄ to the drinking water from 3 weeks (weaning) until 8 weeks of age. Zinc stimulation of the transgene was not carried out during mating, gestation and lactation. Correlated responses in fitness traits were measured by regression of least‐squares means (as deviations from the control lines) on generation number. Two fitness indexes were defined to combine the information on individual fitness traits. The proportion of infertile matings was higher in generations 7 to 13 than in generations 0 to 6. Correlated responses to selection showed an increase in the cohabitation to littering interval in nontransgenic lines and an increase in litter sizes in lines from the selected background. Preweaning pup survival did not change over generations. Overall fitness increased in the transgenic line from the selection background whereas no changes were observed in the transgenic line from the control background. The initial frequency of 0.5 of the transgene was reduced to less than 0.10 in the selected background, but increased to an average of 0.62 in the control lines. The comparison of specific mating groups involving transgenic and nontransgenic mates revealed that the only consistent disadvantage in having a transgenic parent was the increase in the length of the cohabitation to littering interval. Major fitness problems were not associated with the oMt1a‐oGH transgene, which makes this construct a potential choice for use in livestock breeding programmes.     

Correlated responses to selection for large body size in oMt1a-oGH mice: growth, feed efficiency and body composition

Correlated responses were determined for growth, feed consumption, feed efficiency and body composition following short‐term selection for large 8‐week body weight in transgenic and nontransgenic mice. Replicate lines which either carried or did not carry the sheep metallothionein 1a‐sheep growth hormone transgene (oMt1a‐oGH) were established. The lines carrying the transgene at an initial frequency of 0.5 came from a high‐growth (TM) and a randomly selected (TC) background. The respective nontransgenic lines were identified as NM and NC. Control replicates (CC) came from the randomly selected background. During the selection process the transgene was activated by adding 25 mm ZnSO₄ to the drinking water of all mice. Correlated responses were measured with (Z) and without (C) the addition of zinc. After seven and eight generations of selection, the frequency of transgenic mice in line TM had fallen sharply, whereas transgene frequency had risen moderately in TC. The reduced frequency of oMt1a‐oGH in the high‐growth genetic background may have been caused by a lower additive effect compared with the randomly selected background combined with a fitness disadvantage of the transgene. Therefore, the utility of a transgene in improving a quantitative trait may depend in part on genetic background. Correlated responses for most traits in NC were similar for Z and C. In contrast, correlated responses in TC showed marked differences in C compared with Z. For example, daily gain and feed efficiency showed no significantly correlated responses under C and positive responses (p < 0.001) under Z, and the reverse was found for indicators of body fat percentage. These line by environment (Z versus C) interactions may represent a genetic correlation of less than one between a trait expressed in two distinct environments. Thus, in developing lines with a transgene that can be regulated, a critical question is whether selection for quantitative trait(s) should be conducted when the transgene is activated or not activated.     

Components of growth in mice hemizygous for a MT/bGH transgene.

The objective of this study was to determine the effects of a metallothionein/bovine GH transgene on duration and rate of growth of lean and fat in mice. Mice were produced by mating hemizygous transgenic males to nontransgenic females. Ten weights and six measurements of total body electrical conductivity to estimate body composition were taken on 147 progeny between birth and 84 d of age. Growth traits for fat-free mass (FFM) and body fat mass (FM) were obtained by fitting FFM and FM to a logistic curve y = A/(1 + exp(k(b - t))), where y is FFM or FM, A is asymptotic mass, k and b are curve parameters, and t is time in days. The function and its first, second, and third derivatives for FFM and FM were used to model growth. A mixed model was used with animal and litter as random effects and trans-genotype, sex, and transgenotype x sex as fixed effects in analyses of growth traits. Estimates of transgeno-type and transgenotype x sex interaction were tested by using their corresponding standard errors. Males had greater response to the transgene than females in final FFM and growth rate during the entire growth period. Transgenic males and females had greater duration of lean growth than nontransgenics. Transgenic males began to accumulate fat later, but they eventually gained more fat than transgenic females.     

Evaluation of Nutritional Equivalency of Corn Grain from DAS-Ø15Ø7-1 (Herculex* I) in the Diets of Laying Hens

Grain from transgenic corn line TC1507 (Herculex* I) from Pioneer Hi-Bred International Inc. and Dow AgroSciences LLC, which expresses the Cry1F protein from Bacillus thuringiensis to provide protection from lepidopteran pests of corn, was compared with its isoline equivalent and 2 conventional corn strains in a 16-wk laying hen feeding trial. Egg production and production efficiency of hens fed the diet formulated with transgenic grain TC1507 were similar to those of hens fed diets formulated with isoline or nontransgenic conventional corns. Hens fed TC1507 had similar egg qualities as those fed nontransgenic grain diets. Diet × phase interactions were noted for Haugh unit and Roche color fan score. Hens fed conventional corn 2 had a poorer Haugh unit score compared with hens fed the other 3 diets. Conventional corn 1 had greater levels of xanthophylls compared with the other corn treatments, resulting in increased Roche color fan score for eggs produced by hens fed this diet. Overall, hens fed the transgenic Herculex* I corn grain containing the Cry1F protein performed as well as hens fed the isoline equivalent of Herculex* I and hens fed the conventional corn grains.     

Effect of dietary alpha-lipoic acid on growth, body composition, muscle pH, and AMP-activated protein kinase phosphorylation in mice

The effects of alpha-lipoic acid (ALA) on the growth, body composition, postmortem AMP-activated protein kinase (AMPK) activation, and 24-h muscle pH were investigated. Thirty male C57BL/6J mice were fed diets containing 0, 0.5, or 1.0% ALA (DM basis). At the end of the 3-wk feeding trial, carcass weights decreased (P < 0.05) 14 and 30% for mice fed 0.5 and 1.0% ALA, respectively, compared with the 0% group, with decreases in BW as the levels of dietary ALA increased. This change in carcass weight occurred because carcass fat content for mice receiving 0.5 and 1.0% ALA was 7.32 and 8.09% lower (P < 0.05), respectively, than for the 0% ALA treatment, and because gonadal fat decreased (P < 0.05) 85% in mice fed 1.0% ALA compared with those fed 0% ALA. Dietary ALA caused a slight increase (P < 0.05) in carcass moisture content, with no (P = 0.07) effect on protein and ash content. Furthermore, ALA supplement decreased (P < 0.05) ADFI (DM basis) from 4.3 g/d for 0% ALA-fed mice to 3.4 g/d for 1.0% ALA-fed mice. At 20 min postmortem, pH was greater (P < 0.05) in muscle of mice fed 1.0% ALA than in muscle of mice fed 0% ALA. Ultimate (24-h) pH values differed (P < 0.05) among treatments, and mean values were 5.83, 6.08, and 6.29 for 0, 0.5, and 1.0% ALA, respectively. Phosphorylation of AMPK alpha subunit at Thr172, an indicator of AMPK activation, was decreased (P < 0.05) in muscle of ALA-treated mice at 20 min postmortem. Because AMPK has a crucial role in the control of glycolysis, the reduction in AMPK activation decreases glycolysis, and thereby increases the ultimate pH of postmortem muscle. In summary, dietary ALA supplement can decrease fat accumulation in mice, and because ALA increased muscle pH at 20 min and 24 h postmortem, these results suggest that dietary ALA supplementation might decrease carcass fatness and prevent the development of PSE pork and poultry. However, further research is required to test the effects of ALA in swine and poultry.     

Selection for increased adult body weight in mouse lines with and without the rat growth hormone transgene

SUMMARY: Four lines of mice with and without the rat growth hormone (rGH) transgene were developed to measure responses to selection for increased 42-day body weight and evaluate fitness of mice with and without the rGH transgene. Each line contained selected and unselected (control) sublines. At the last three generations of selection (Generations 12-14), selected sublines differed from unselected controls by 3.8 to 4.7 g (14.8 to 19.8%) in 42-day weight, -0.5 to -8.3% in fertility, and 0.5 to 1.6 in litter size at birth. The origin of the lines (W: previously selected for 42-day weight and C: unselected) affected 42-day weight, i. e. 42-day weight of mice originating from W was significantly (P < 0.01) heavier than that of mice originating from C. Responses to selection, as measured by the deviation of the selected subline from the control, continued to be positive over 14 generations. Realized heritability of 42-day weight ranged from 0.30 to 0.42. The rGH transgene that increased 63-day weight by 54% was not found at Generation 12. The unexpected loss of rGH transgene was due to poor fitness of mice with the rGH transgene. Mice with the transgene had lower fertility rate than those without the transgene (50.0 to 73.7% vs. 95.0%), smaller litter size (6.8 to 7.8 vs. 8.6) and poorer survival of the progeny (69.2 to 74.5% vs. 88.3%). Based on these data, selective advantage/disadvantage of the rGH transgene in the fitness traits was estimated quantitatively. The results from the study on growth and reproductive traits suggest that desirable effects of gene transfer on a specific trait (42- and 63-day weight in the present study) might be offset by undesirable effects on other traits (e. g., reproduction and survival) in some cases of transgenic animals. ZUSAMMENFASSUNG: Selektion auf hohes adultes Gewicht in M?uselinien mit und ohne Rattenwachstumshormon-Transgenen Vier M?uselinien mit und ohne das Rattenwachstumshormon (rGH) Transgen wurden zur Messung des Selektionserfolges auf gesteigertes 42-Tage-K?rpergewicht entwickelt, um auch Fitne? zu prüfen. Jede Linie bestand aus einer selektierten und aus einer unselektierten (Kontroll-)Unterlinie. In den drei letzten Selektionsgenerationen (Generationen 12-14) unterschieden sich die selektierten Unterlinien um 3,8 bis 4,7 g (14,8 bis 19,8%) im 42-Tage-Gewicht, -0,5 bis -8,3% in Fruchtbarkeit und 0,5 bis 1,6 in Wurfgr??e bei Geburt. Der Ursprung der Linien (W: früher auf 42-Tage-Gewicht selektiert, C: unselektiert) beeinflu?te das 42-Tage-Gewicht. M?use aus der ersten waren signifikant (p < 0,01) schwerer als jede aus C. Selektionserfolg gemessen als Abweichung von der Kontrolle war über 14 Generationen positiv, realisierte Heritabilit?t variierte von 0,3 bis 0,42. Das rGH-Transgen steigerte das 63-Tage-Gewicht um 54%, aber war in der Generation 12 nicht mehr vorhanden. Der unerwartete Verlust des RGH-Transgens war auf schlechte Fitne? der besitzenden M?use zurückzuführen. Transgene M?use hatten geringere Fruchtbarkeit als jene ohne das Transgen (50 bis 73,7% im Vergleich zu 95%), kleinere Wurfgr??e (6,8 bis 7,8 gegenüber 8,6) und schlechtere überlebensrate der Nachkommen (69,2 bis 74,5% im Vergleich zu 88,3%). Die Ergebnisse erlauben die quantitative Sch?tzung der selektiven Vorteile/Nachteile des rGH-Transgens im Bezug auf Fitne?. Erwünschte Wirkungen von Gentransfer auf spezifische Merkmale (41- und 63-Tage-Gewicht in dieser Untersuchung) k?nnen durch unerwünschte Wirkungen von Transgenen auf andere Merkmale (Reproduktion und überleben) neutralisiert werden.     

Elliptical selection experiment for the estimation of genetic parameters of the growth rate and feed conversion ratio in rabbits

Two elliptical selection experiments were performed in two contemporary sire lines of rabbits (C and R) in order to optimize the experimental design for estimating the genetic parameters of the growth rate (GR) and feed conversion ratio (FCR). Twelve males and 19 females from line C, and 13 males and 23 females from line R, were selected from an ellipse defined by a quadratic index based on these traits. Data from 160 rabbits of each of the parental generations of lines C and R and their offspring (275 and 266 animals, respectively) were used for the analysis. A Bayesian framework was adopted for inference. Marginal posterior distributions of the genetic parameters were obtained by Gibbs sampling. An animal model including batch, parity order, litter size, and common environmental litter effects was assumed. Posterior means (posterior standard deviations) for heritabilities of GR and FCR were estimated to be 0.31 (0.10) and 0.31 (0.10), respectively, in line C and 0.21 (0.08) and 0.25 (0.12) in line R. Posterior means of the proportion of the variance due to common litter environmental effects were 0.14 (0.06) and 0.21 (0.06) for GR and FCR, respectively, in line C and 0.17 (0.06) and 0.22 (0.06) in line R. Posterior means of genetic correlation between both traits were -0.49 (0.25) in line C and -0.47 (0.32) in line R, indicating that selection for GR was expected to result in a similar correlated response in FCR in both lines.     

Effects of thyrotropin-releasing hormone and a thyrotropin releasing hormone analog on growth and selected plasma hormones in lambs

An 8-wk growth trial was conducted to assess the effects of continuous infusion of thyrotropin-releasing hormone (TRH) and an active TRH analog less than Aad-His-Pro-NH2 (the less than Aad is L-pyro-alpha-aminoadipic acid) on growth trial performance, carcass composition and hormone profiles of growing lambs. Both drugs were infused at 600 micrograms X lamb -1 X d -1 with 16 lambs/treatment. Both TRH and less than Aad-His-Pro-NH2 decreased average daily gain (ADG; P less than .01) and increased feed conversion (FC; P less than .01) compared with saline infused controls. Average daily feed intake was not altered. Carcasses of lambs given TRH or less than Aad-His-Pro-NH2 contained fewer kilograms of moisture (P less than .05) and appeared to contain fewer kilograms of protein. Thyrotropin-releasing hormone and less than Aad-His-Pro-NH2 increased thyroid gland weights (P less than .05), but pituitary gland weights were not different. Plasma thyrotropin (TSH) concentrations were increased by both drugs compared with control lambs, peaking at 4 to 7 d after initiating infusion. However, by 14 d, TSH concentrations returned to control levels. Triiodothyronine (T3) and thyroxine (T4) were elevated by both drugs over the entire 8-wk trial, with peak levels reached at 10 d and maintained for the duration of the study. Both TRH and less than Aad-His-Pro-NH2 increased prolactin over the entire period. Growth hormone levels were not altered by either drug. The effects of less than Aad-His-Pro-NH2 infusion on growth trial performance, carcass composition and hormone profiles of growing lambs were very similar to TRH. The negative effects of TRH and less than Aad-His-Pro-NH2 infusion on ADG, FC and carcass protein appear to be the result of elevated T3 and T4 levels.     

转Cecropin B抗菌肽基因柑橘对溃疡病的离体抗性评价

本文对转Cecropin B抗菌肽基因的锦橙植株进行了表达检测以及柑橘溃疡病病原菌的接菌实验。分别用喷雾法和针刺法进行离体接菌实验,用Real-time PCR和Southern blot进一步检测分析了在转基因植株中Cecropin B基因的表达、整合情况。结果显示与喷雾法相比,针刺接种处理的离体叶片开始显症时间短,且发病率高,便于统计分析。针刺接种6天后,大部分转基因株系发病率与非转基因植株无显著差异,其中,PR8、PR11、AAT8 和AAT14株系的发病率分别为67%、63%、68%和54%,显著低于非转基因植株。Real-time PCR表达分析结果表明,转基因株系中Cecropin B基因表达量明显高于对照株系。Southern blot结果显示PR8和AAT14株系中转基因为单拷贝, PR11和AAT8株系中转基因分别为两个拷贝和三个拷贝。实验结果表明转Cecropin B抗菌肽基因提高了对柑橘溃疡病的抗性。     

Investigations on genetically modified maize (Bt-maize) in pig nutrition: fattening performance and slaughtering results.

A grower finisher performance trial with forty-eight pigs was designed to compare the growth performance of pigs fed diets containing either genetically modified (GM) Bt-maize (NX6262) or its parental maize (Prelude) line. During the experiment, the pigs were fed with a grower and a finisher diet both containing 70% maize investigated in a previously study which showed that they contained similar ME values and digestibility of crude nutrients. The pigs with an initial live weight of 23.9 +/- 3.0 kg were allotted to single boxes. During a 91 days growing period the pigs of both groups recorded equal performance in daily weight gain (AW) 815 +/- 93 vs. 804 +/- 64 g/d depending on equal amounts of feed intake 1.95 +/- 0.15 vs. 1.94 +/- 0.15 kg/d (parental vs. transgenic). The results confirm equal performance among growing-finishing pigs fed parental or genetically modified maize containing diets. For slaughtering the pigs were divided into 4 groups with a different duration of the finishing period. After slaughtering the carcass characteristic were registered.     

Selection for postweaning gain in rats: I. Correlated response in feed utilization and body composition

Response to selection for up (U) and (D) 3- to 9-wk gain in rats on average daily gain (ADG), average daily feed intake (ADI), gain/feed (G/F), body composition (BC), fasting metabolic rate per unit metabolic size (MR) and partial efficiency of weight gain (ADG/Fg) was evaluated after 34 generations of mass selection. At 3-wk weaning, 120 litters representing F1 crosses of two replicates within each of the U, D and control (C) selection lines were divided within sexes between bulk-feeder and tube-feeder cage types for recording feed intake until 9 wk of age. Rats from tube-feeder cages representing 16 litters/line were utilized for MR and BC data. Response in ADG was asymmetrical; 16% higher for U line but only 8% lower in D line, compared with C line. Correlated responses were positive and significant in both U and D lines for ADI (6% and -3%) and G/F (5% and -5%). Line differences in MR were not significant but both selected lines were slightly higher than C line in MR at 6 wk of age, and the reverse at 9 wk of age. Over the period of 6 to 9 wk of age, maintenance requirements per unit metabolic size and ADG/Fg were 1 and 5% above for the U and -1 and -4% for D lines, relative to C line. Females of both selected lines were fatter than C line (P less than .05) at 9 wk of age, but only D line males were fatter than C line.     

Metallothionein expression and tumor growth in the transplantable pregnancy-independent mouse mammary tumor.

In various human tumors, a metal binding protein, metallothionein (MT) is reported to play an important role in carcinogenesis. In the present preliminary study, MT expression and tumor growth were investigated in transplantable pregnancy-independent mammary tumors (TPIMT) derived from pregnancy-independent mammary tumors (PIMT) in GR/A mice, in order to study the possible role of MT in mammary carcinogenesis. TPIMT as well as PIMT showed MT expression in tumor cells in all of the successive transplantations. A negative correlation was observed between MT expression in transplanted tumor tissues and their growth in the hosts (r=-0.53, p<0.05). The present study indicates that MT is a useful marker of tumor progression in TPIMT.     

Fractionation of fiber and crude protein in fresh forages during the spring growth

The composition of the fiber and CP of alfalfa, bromegrass, and endophyte-free and -infected tall fescue forages was compared during the spring growth from vegetative to reproductive stages. Forages were sampled from April 27 to June 6 in 1994, and from April 27 to June 11 in 1995, with 11 and 12 harvest dates, respectively. Total dietary fiber (TDF) was fractionated into insoluble and soluble fiber (SF). The CP of the forages was fractionated into nonprotein N (A), soluble CP (B1), insoluble CP that was soluble in neutral detergent (B2), CP insoluble in neutral detergent but soluble in acid detergent (B3), and CP insoluble in acid detergent (C). Effects of year, forage species, and harvest dates (day as a covariable) were included in the model. Across harvest dates, alfalfa (A) had lower (P < .01) TDF and higher (P < .01) SF concentrations than grasses (GR) (A: 49.9 and 14.4% and GR: 60.4 and 4.5% [OM basis] for TDF and SF, respectively). Alfalfa had higher (P < .01) CP (20.6% DM) than GR (15.3%). The rate of decrease in CP (% DM) across days was higher (P < .01) for bromegrass (-.4%/d) than for the other forages (-.29%/d). Fraction A (% of CP) was not different (P = .24) among forages (22.5%), but B1 was higher (P < .01) in A (17.1%) than in GR (13.2%). The B2 fraction (% of CP) was higher (P < .01) in A compared with GR (51.6 vs 45.9%, respectively). Alfalfa had lower (P < .01) B3 (3.0% of CP) than bromegrass (18.6%) and tall fescue (13.2%). Fraction C was not different (P = .23) among forages (3.8%). Fractions A, B1, and C (% of CP) did not change (P > .05) across days for all forages. Fraction B2 (% of CP) decreased across days in A (-.21%/d) but was not affected in GR. Fraction B3 (% of CP) increased (P < .05) in A (.1%/d), decreased in endophyte-infected tall fescue (-.20%/d), and did not change (P > .05) in the other forages. Crude protein and fiber composition were affected more by forage species than by maturity. The CP and NDF concentrations were more affected by maturity. Insoluble fractions but not soluble fractions of CP were affected by maturity.     

不同氨基酸限量水平对肉鸭的生长性能和胴体特征的影响

本研究旨在评估日粮不同氨基酸水平对1～56 d肉鸭生长性能和胴体特征的影响。将平均初始体重为（55.92±0.56）g的800只1日龄肉鸭随机分为5组,每组4个重复,每个重复40只。各组肉鸭在1～21 d时饲喂赖氨酸、蛋氨酸+胱氨酸、苏氨酸水平分别为0.90%+0.75%+0.70%、1.0%+0.80%+0.80%、1.10%+0.90%+0.85%、1.20%+1.0%+0.95%、1.30%+1.10%+1.0%的日粮,22～56 d时饲喂赖氨酸、蛋氨酸+胱氨酸、苏氨酸水平分别为0.75%+0.65%+0.55%、0.80%+0.70%+0.60%、0.90%+0.75%+0.65%、0.95%+0.80%+0.70%、1.0%+0.85%+0.75%的日粮。结论：T4和T5组较T1和T2组显著提高了21 d肉鸭的体重（P＜0.05）,T1组1～21 d肉鸭的平均日增重最低（P＜0.05）,而料重比最高（P＜0.05）。T2、T3和T4组肉鸭的胸肌相对重量显著高于其他各组（P＜0.05）,但日粮氨基酸限量水平对肉鸭胴体重、肝脏、腹脂和腿肌相对重量及肉色、pH、蒸煮损失、系水力的影响均不显著（P＞0.05）。结论：在肉鸭生长早期,随着日粮氨基酸水平的升高,日增重表现为显著升高,但氨基酸水平对肉鸭生长后期的生长性能和胴体特征影响很小。 [关键词]氨基酸|肉鸭|生长性能|胴体特征     

Insulin-like growth factor binding proteins initiate cell death and extracellular matrix remodeling in the mammary gland

We have demonstrated that insulin-like growth factor binding protein-5 (IGFBP-5) production by mammary epithelial cells increases dramatically during forced involution of the mammary gland in rats, mice and pigs. We proposed that growth hormone (GH) increases the survival factor IGF-I, whilst prolactin (PRL) enhances the effects of GH by decreasing the concentration of IGFBP-5, which would otherwise inhibit the actions of IGFs. To demonstrate a causal relationship between IGFBP-5 and cell death, we created transgenic mice expressing IGFBP-5, specifically, in the mammary gland. DNA content in the mammary glands of transgenic mice was decreased as early as day 10 of pregnancy. Mammary cell number and milk synthesis were both decreased by approximately 50% during the first 10 days of lactation. The concentrations of the pro-apoptotic molecule caspase-3 was increased in transgenic animals whilst the concentrations of two pro-survival molecules Bcl-2 and Bcl-x were both decreased. In order to examine whether IGFBP-5 acts by inhibiting the survival effect of IGF-I, we examined IGF receptor- and Akt-phoshorylation and showed that both were inhibited. These studies also indicated that the effects of IGFBP-5 could be mediated in part by IGF-independent effects involving potential interactions with components of the extracellular matrix involved in tissue remodeling, such as components of the plasminogen system, and the matrix metallo-proteinases (MMPs). Mammary development was normalised in transgenic mice by R3-IGF-I, an analogue of IGF-I which binds weakly to IGFBPs, although milk production was only partially restored. In contrast, treatment with prolactin was able to inhibit early involutionary processes in normal mice but was unable to prevent this in mice over-expressing IGFBP-5, although it was able to inhibit activation of MMPs. Thus, IGFBP-5 can simultaneously inhibit IGF action and activate the plasminogen system thereby coordinating cell death and tissue remodeling processes. The ability to separate these properties, using mutant IGFBPs, is currently under investigation.     

Effects of dietary fat type and non-starch-polysaccharide-hydrolysing enzyme addition to rye-based diets on muscle protein turnover in broilers

1. Muscle protein turnover was measured in broilers fed on rye-based diets containing either beef tallow (T) or soybean oil (S) at an inclusion rate of 100 g/kg. Each of these diet types was tested either in the absence (S[-], T[-]) or presence (S[+], T[+]) of a xylanase-containing enzyme preparation. Protein turnover was measured in gastrocnemius muscle (GM) and pectoralis major muscle (PM). 2. Fractional rate of protein synthesis (FSR) was measured by the large dose technique using [15N]-labelled phenylalanine whereas fractional protein growth rate (FGR) was estimated by regressing tissue protein content over time. Fractional breakdown rates (FBR) were calculated by the difference between FSR and FGR. 3. In PM, FSR (%/d) was 22.1, 23.4, 21.5 and 24.4 in groups S[-], S[+], T[-] and T[+], respectively, and FBR (%/d) was 8.3, 9.8, 4.5 and 10.8 with the xylanase effect being significant. The FGR of 17.0%/d calculated for the broilers fed on the T[-] diet tended to be higher than for the other groups (13.6 to 13.8%/d). No significant effects were detected for these parameters in the GM. 4. The absolute amounts of protein which were synthesised daily and accreted in both muscles were significantly higher with xylanase supplementation in both fat type diets but at a significantly higher level when soybean oil was the dietary fat type. 5. The observed effects on protein turnover have to be seen in the context of an overall adverse effect of dietary soluble pentosans from rye in combination with tallow on physico-chemical chyme conditions, digestion and absorption of energy and nutrients and tissue-specific metabolic changes.     

长枝木霉对白三叶种子发芽及幼苗抗逆性研究

在室内条件下,用不同浓度的长枝木霉孢子悬浮液对白三叶种子进行处理,研究了其种子发芽率、根芽长及抗逆性酶活变化,以及长枝木霉对白三叶种子的促生作用及抗逆性的影响。结果表明,长枝木霉孢子悬浮液浓度在5.0×105个/mL~1.0×107个/mL时能促进白三叶种子活性,在孢子浓度为1.0×106个/mL时,发芽率为93%,与对照80%相比提高了16.25%;胚根长1.93cm,与对照1.26cm相比增长了53.1%;胚芽长1.33cm,与对照1.04cm相比增长了27.8%。抗逆性结果表明,长枝木霉孢子悬浮液能够提高白三叶种子抗病害及不良环境的能力,降低MDA含量,提高PAL、POD的活性。其中,孢子悬浮液浓度为5.0×105个/mL时,PAL活性最高,为2.157U/(g·min)FW;孢子浓度为1.0×106个/mL时POD的活性最高,为29.875U/g FW;孢子悬浮液浓度5.0×105个/mL时,MDA含量最低,为1.012μmol/g FW。     

Improved development of somatic cell cloned bovine embryos by a mammary gland epithelia cells in vitro model

Previous studies have established a bovine mammary gland epithelia cells in vitro model by the adenovirus-mediated telomerase (hTERT-bMGEs). The present study was conducted to confirm whether hTERT-bMGEs were effective target cells to improve the efficiency of transgenic expression and somatic cell nuclear transfer (SCNT). To accomplish this, a mammary-specific vector encoding human lysozyme and green fluorescent protein was used to verify the transgenic efficiency of hTERT-bMGEs, and untreated bovine mammary gland epithelial cells (bMGEs) were used as a control group. The results showed that the hTERT-bMGEs group had much higher transgenic efficiency and protein expression than the bMGEs group. Furthermore, the nontransgenic and transgenic hTERT-bMGEs were used as donor cells to evaluate the efficiency of SCNT. There were no significant differences in rates of cleavage or blastocysts or hatched blastocysts of cloned embryos from nontransgenic hTERT-bMGEs at passage 18 and 28 groups (82.8% vs. 81.9%, 28.6% vs. 24.8%, 58.6% vs. 55.3%, respectively) and the transgenic group (80.8%, 26.5% and 53.4%); however, they were significantly higher than the bMGEs group (71.2%, 12.8% and 14.8%), (p < 0.05). We confirmed that hTERT-bMGEs could serve as effective target cells for improving development of somatic cell cloned cattle embryos.     

Temporal patterns of growth hormone, prolactin and thyrotropin secretion in Targhee rams selected for rate and efficiency of gain

Thirteen Targhee rams selected for rate and efficiency of gain for 4 yr (1.5 generations) were compared with 10 rams from a Targhee line with no selection for over 20 yr to determine if selection for these traits would be associated with changes in the secretion of growth hormone (GH), thyrotropin (TSH) and(or) prolactin (PRL). Selected rams exhibited greater birth weight, average daily gain (ADG) and feed consumed/day during a 6-wk individual feeding regimen, and exhibited greater overall ADG during a 16-wk feeding trial as compared with the unselected rams. Temporal blood plasma samples were collected at 15-min intervals for 8 h from each of the 23 rams for hormone analysis. Selected rams exhibited greater overall mean GH (6.1 +/- .4 vs 4.6 +/- .5 ng/ml), overall mean TSH (8.6 +/- 1.2 vs 6.2 +/- .7 ng/ml) and baseline mean TSH (8.0 +/- 1.1 vs 5.6 +/- .5 ng/ml) than the unselected rams. Although the adjusted GH spike amplitude value was higher in the selected line (12.1 +/- 3.0 vs 7.4 +/- .8 ng/ml), this difference was not significant. No differences were observed with any of the variables of PRL secretion. In addition, there were no significant correlations between any of the hormone variables and any of the feed or gain data. These data support the hypothesis that Targhee rams selected for rate and efficiency of gain exhibit higher plasma levels of GH and TSH than unselected rams of the same breed.