Effect of long or short acting anabolic agents, given singly or repeated, on growth rate and carcase weight of steers

A trial was carried out using 490, 12- to 15-month-old steers which were at pasture from April to November and then housed and fed grass silage and concentrates until sold live or slaughtered. Animals were allocated at random to one of the following treatments: (i) Control; (ii) implanted with 45 mg oestradiol -17 beta in silastic rubber in April; (iii) implanted with oestradiol in April and with 300 mg trenbolone acetate in April, August and November; (iv) implanted with 36 mg zeranol in April, August and November and (v) implanted with zeranol and trenbolone acetate in April, August and November. Daily liveweight gains were 0.69, 0.75, 0.78, 0.83 and 0.86 (+/- 0.02) kg, and carcase weights were 300, 306, 311, 316 and 321 (+/- 3.4) kg, for treatments (i) to (v), respectively. All implanted animals had significantly higher daily gains than control animals and an additive response was obtained where trenbolone acetate was used with oestradiol or zeranol. Pooled results for animals treated with oestradiol plus zeranol, with or without trenbolone acetate, show that the overall response for zeranol treated animals was higher than from the animals treated with oestradiol. Daily gains after the first, second and third implant period show a reduced response from the oestradiol implant for the final 63 days of the trial. This may have been caused by loss of some oestradiol implants from animals early in the trial.     

Effect of prenatal trenbolone acetate treatment on lamb performance and carcass characteristics

Forty-three pregnant Dorset and Dorset crossbred ewes were assigned randomly to a control group or implanted with either 300 mg trenbolone acetate (Low TBA) or 1,200 mg trenbolone acetate (High TBA) between d 40 and 60 of gestation. Adjusted weaning weights for ewe lambs were 23.3% less (P less than .10) with vs without TBA treatments. Postweaning ADG of ewe lambs was lower (P less than .05) but ADG of ram lambs was greater (P less than .05) for high TBA vs low TBA. Ewe lambs receiving high TBA had 19% less (P less than .05) gain per unit of feed than those receiving low TBA. Days on test for ewe lambs was greater (P less than .05) due to TBA treatment and for high TBA vs low TBA. Days on test for ram lambs was decreased (P less than .05) due to high TBA compared to low TBA. Subcutaneous fat over the ribeye and lower rib were greater (P less than .05) for high-TBA ewe lambs vs low-TBA ewe lambs. Percentage kidney and pelvic fat of ewe lambs was lower (P less than .05) due to TBA treatments. Ribeye area per unit of carcass weight was lower (P less than .05) in high-TBA ewe lambs vs low-TBA ewe lambs. Yield grade of ewe lambs was lower (P less than .05) for low TBA vs high TBA. Prenatal trenbolone acetate treatment of ewe lambs did not improve their subsequent postnatal growth performance and carcass traits. In addition, TBA implantation of the pregnant ewe produced dystocia and less milk production, as evidenced by the need for more lambs to be grafted.     

Inhibition of prolactin in the last trimester of gestation decreases mammary gland development in gilts

Prolactin is required for mammary development in various species but its possible role for mammogenesis in pigs is not known. The goal of the present study was therefore to determine the effect of prolactin inhibition by bromocriptine during the last third of gestation on mammary gland development in gilts. Twenty-eight primigravid gilts were assigned as controls (n = 15) or received 10 mg of bromocriptine orally thrice daily (n = 13) from d 70 to 110 of gestation. Jugular blood samples were collected on d 70 of gestation and every 8 d thereafter and were assayed for prolactin, IGF-I, estradiol, and progesterone. Gilts were slaughtered on d 110 of gestation and fetuses were counted and weighed. One row of mammary glands was used for dissection of parenchymal and extraparenchymal tissues and for determination of DNA, RNA, dry matter, protein, and fat contents. Tissue from the other row was used for measures of prolactin receptor number and affinity. Concentrations of prolactin were drastically reduced throughout the bromocriptine treatment period (P < .001), whereas there was no overall treatment effect on progesterone and IGF-I levels (P > .10). Total weight and extraparenchymal tissue weight of the mammary glands were unaffected by treatment (P > or = .1), but weight of parenchymal tissue, total DNA, and total RNA decreased (P < .01) with bromocriptine treatment. Percentages of fat and dry matter in parenchymal tissue increased with bromocriptine treatment (P < .01) and the percentage of protein decreased (P < .01). Number of prolactin receptors in parenchymal tissue decreased with bromocriptine treatment (P < .001) and receptor affinity increased (P < .001). Average fetal weight was lower in gilts receiving bromocriptine than in control gilts (P = .05), but fetal number did not differ (P > .1). These results clearly demonstrate that prolactin is essential for normal mammary gland development and can affect fetal growth during the last third of gestation in gilts.     

Specific window of prolactin inhibition in late gestation decreases mammary parenchymal tissue development in gilts

Prolactin is required from d 70 to 110 of gestation for normal mammary development of gilts. The goal of the present study was to determine the effect of inhibiting prolactin with bromocriptine during specific time windows during the second half of gestation on mammary gland development in gilts. Crossbred primigravid gilts were assigned as controls (n = 12) or received 10 mg of bromocriptine orally three times daily from d 50 to 69 (BR50, n = 12), d 70 to 89 (BR70, n = 12), or d 90 to 109 (BR90, n = 12) of gestation. Jugular blood samples were collected on d 50, 70, 90, and 109 of gestation and assayed for prolactin and estradiol. Gilts were slaughtered on d 109 of gestation and fetuses were counted and weighed. One row of mammary glands was used for dissection of parenchymal and extraparenchymal tissues, and for biochemical analyses. Tissue from the other row was used for measures of prolactin receptor number and affinity. Concentrations of prolactin were decreased markedly (P < 0.001) at the end of each bromocriptine treatment period compared with controls, but there was no overall treatment effect (P > 0.1) on estradiol concentrations. Extraparenchymal tissue weight of the mammary glands was unaffected by treatments (P > 0.1), but weight of parenchymal tissue, total DNA, and total RNA were lower (P < 0.01) in BR90 than control gilts. The percentage of DM in parenchymal tissue was unaffected by treatments (P > 0.1), but percentage of fat was higher and percentage of protein lower (P < 0.01) in BR90 gilts compared with controls. Cell size, as estimated by the protein:DNA ratio, also was lower (P < 0.01) in the BR90 group. Number and affinity of prolactin receptors in parenchymal tissue were not significantly altered by treatments. In conclusion, there is a specific time period in the second half of gestation, from 90 to 109 d, during which prolactin is essential for normal mammary parenchymal tissue development.     

Steroidal hormones determine sex-related differences in opioid-induced elevation of nociceptive threshold in sheep (Ovis aries)

AIMS: As sex related differences in opioid-induced elevations of nociceptive thresholds have been observed in sheep, a study was undertaken to determine if puberty, oestrus, pregnancy or administration of the hormones oestrogen and testosterone had any effect on these differences. METHODS: Withdrawal latency to a nociceptive thermal source was measured in Romney cross sheep consisting of lambs (n = 6) prior to and after their first oestrus, ram lambs (n = 6) prior to and after puberty, non-oestrous ewes (n = 6), oestrous ewes (n = 6), pregnant and subsequently suckling ewes (n = 12), wethers (n = 6) and rams (n = 6). The effects of a kappa opioid agonist (GR 89696), oestradiol benzoate, testosterone and saline on this withdrawal latency were tested in all groups. RESULTS: GR 89696 increased withdrawal latency in all animals, compared to saline, but this was most marked in ewes, particularly those in oestrus or in late pregnancy. Testosterone and oestradiol had no effect on their own, or in combination, on the withdrawal latency seen with saline alone. Oestradiol increased the effects of GR 89696 on lambs pre-pubertal ram lambs, ewes and wethers but not on post-pubertal ram lambs nor rams. Co-administration of testosterone antagonised this oestradiol effect. CONCLUSION: The efficacy of kappa opioids appears to be affected by animal sex, an effect that can be contributed to by both oestradiol and testosterone.     

Preparation of an epithelium-free mammary fat pad and subsequent mammogenesis in ewes

The objective of this study was to develop a surgical procedure for the preparation of an epithelium-free mammary fat pad (cleared mammary fat pad; CFP) in ewes. At 7 to 10 d of age, ewe lambs (n = 43, mean BW 9.2 +/- .2 kg at 14 d) were sedated and one mammary gland was locally anesthetized. An incision circumscribing the base of the teat was made and blunt dissection was performed through the extraneous mammary fat pad tissue to enable the parenchyma and teat to be wholly removed. Failure to completely remove the epithelium enabled it to regenerate and grow into the mammary fat pad. Mean diameter of the parenchymal rudiment at 7 to 10 d of age was 8.9 +/- .5 mm (range of 5 to 16 mm). The excision site was closed with wound clips and recovered lambs returned to their dams. The contralateral mammary gland remained intact, allowing it to undergo normal development. Live weight gain was unaffected by this procedure. Ewes were subsequently slaughtered in groups at various stages of prepuberty, puberty, gestation, and lactation. Of 39 operated glands recovered, only one demonstrated epithelial outgrowth within the CFP. Parenchyma within the contralateral, intact gland underwent phases of rapid growth in prepuberty, puberty, and late gestation and was capable of milk synthesis after steroid induction or parturition. Change in weight of the CFP paralleled that of the intact mammary gland to 100 d of pregnancy. Sham CFP surgery was performed on four additional ewes wherein the parenchyma was completely excised and immediately replaced. Sham-operated epithelium populated the mammary fat pad and synthesized milk that could be expressed from the teat. A CFP in sheep will be a useful model for future investigations into the local growth regulatory mechanisms associated with ruminant mammogenesis.     

Body weight and tissue gain in lambs fed an all-concentrate diet and implanted with trenbolone acetate or grazed on alfalfa

Targhee x Hampshire lambs (average BW 23 +/- 1 kg) were used in two experiments to determine the effects of finishing on concentrate with an anabolic implant or forage grazing after concentrate feeding on growth, organ and viscera weights, and carcass tissue accretion. In Exp. 1 and 2 lambs were penned by sex and assigned for slaughter at initial (23 kg), intermediate (37 kg), or end BW (ewes, 47.7; wethers 50.4 kg). From 23 to 37 kg BW, lambs were fed all-concentrate diets in drylot (DL) or grazed on alfalfa (ALF). Experiment 1 was a 2 x 2 factorial with 28 lambs; factors were wether vs ewe lambs and unimplanted vs DL implanted with trenbolone acetate-estradiol benzoate. There were no differences in organ and viscera weights due to implant status. However, ADG (P < .03) and lean gain (P < .02) were greater for implanted than for unimplanted wethers (507 vs 357 g and 1,314 vs 656 g, respectively). Ewes did not respond to the implant. Fat accretion was not affected by implantation. Experiment 2 was a 2 x 3 factorial with 42 lambs; factors were wether vs ewe lambs and drylot during growing and finishing phases (DL-DL) vs drylot during growing and alfalfa grazing during finishing (DL-ALF) vs alfalfa grazing during growing and finishing phases (ALF-ALF). In Exp. 2, ADG of DL-DL lambs was greater (P < .01) than ADG of DL-ALF or ALF-ALF lambs. Lambs on ALF-ALF had smaller (P < .05) livers and rumen/reticulum weights but heavier (P < .04) kidney, omasum, small and large intestine, and cecum weights than those on DL. In Exp. 2, DL-ALF and ALF-ALF lambs had overall hindsaddle lean gain equal to those on DL-DL with less mesenteric fat and 100 g less separable fat. Finishing lambs on alfalfa reduced fat accretion without decreasing lean accretion, whereas trenbolone acetate implants for lambs fed concentrate increased BW gain and lean accretion without affecting fat accretion.     

Bovine pituitary, kidney, uterine and mammary gland extracts contain bovine mammary epithelium growth factors that synergise with IGF-I and fetal calf serum: indication for involvement of GTP-binding proteins

Bovine mammary undifferentiated epithelial cells from young female calves, cultured in three-dimensional collagen gels in serum-free medium exhibited ultrastructural organization that resembled the in vivo situation. Extracts of bovine pituitary, kidney, uterus and mammary gland, stimulated cell proliferation in a dose-dependent manner. This mitogenic activity strongly synergised with the existant growth factors (GFs) in FCS and with IGF-I, while the addition of EGF had only minor effect. No synergistic manifestation was found with cholera toxin but pertussis toxin inhibited the growth-promoting activity of all four extracts. Other experiments indicated that this mitogenic activity does not result from prolactin, growth hormone or fibroblast growth factor. The present and former results, in which synergism between IGF-I and cholera toxin was demonstrated, suggest therefore, that the mitogenesis of normal mammary epithelial cells regulated by several tissue derived growth factors, consists of at least two pathways which are distinct from those activated by EGF and IGF-I. One of these pathways indicates involvement of pertussis toxin-sensitive GTP-binding proteins, and the other, activation of cholera toxin-sensitive adenylate cyclase.     

Thirteen-weeks subcutaneous treatment with high dose of natural sex hormones in rats with special reference to their effect on the pituitary-gonadal axis. I. Oestradiol

A high dose of oestradiol (0.3 mg/kg/day) was administrated subcutaneously to male and female rats daily for 13 weeks. The effects of hormonal treatment on various parameters were studied. The results revealed that treatment with oestradiol resulted in alopecia, retarded hair regrowth, decreased body weight and food consumption and reduced Hb, PCV and total RBCs. Neutrophilic leucocytosis, elevated ESR, and decreased blood glucose levels were also observed. Atrophy of the ovaries, testes and secondary sex organs was also recorded. The uterus of the oestradiol treated rats displayed endometrial epithelial cell hyperplasia and hypertrophy of the myometrium. The pituitary gland of the rats with oestradiol had a significant increase in the number of PRL and ACTH cells together with cytological criteria indicative of increased secretory activity; the gonadotropin-producing cells showed involutionary changes. The mammary glands of the oestradiol treated rats showed maximal stromal and ductal proliferation and minimal acinar proliferation.     

Effect of oestradiol on mast cell number and histamine level in the mammary glands of rat

Variations of mast cell number, histamine concentration and oestrogen receptor (ER) expression in mammary glands with the fluctuation of plasma oestradiol level were identified either in the intact rats at different oestrous stages or in the ovary-ectomized rats administrated with different doses of oestradiol benzoate. The results showed that the number of mast cells and histamine concentration fluctuated concomitantly with plasma oestradiol level during the oestrous cycle. More mast cell number and higher histamine concentrations were observed in the oestrous stage than that in the prooestrous and dioestrous stages. Ovariectomy decreased the mast cell number and histamine concentration, which were reconstituted by exogenous oestradiol. ER was mainly found in the nuclear of epithelial cells and interstitial cells of mammary glands. In addition, ER was also expressed in the cytoplasm of some stromal cells. These stromal cells were verified to be mast cells. In conclusion, our results suggested that oestradiol modulated mast cell number and its degranulation in the mammary gland through the ERs pathway.     

Mammary gland development and hormone levels in pregnant Upton-Meishan and large white gilts

Genetic differences between Upton-Meishan (UM, n = 13) and Large White (LW, n = 14) gilts were studied with regard to mammary gland development and concentrations of hormones. Gilts were weighed and their backfat measured at mating, and at d 70 and 109 of gestation. Jugular blood samples were also collected at these times and assayed for prolactin, cortisol, IGF-I, insulin, glucose, progesterone, and estradiol. Gilts were slaughtered on d 110 of gestation. One row of mammary glands was used for dissection and biochemical analyses. The other row was used for determination of prolactin receptor number and affinity. UM gilts weighed less (P<0.05) and had more backfat (P<0.01) than LW gilts at all times. Parenchymal tissue weight was less (P<0.05) in UM gilts. Percent fat (P<0.001) and dry matter (P<0.001) in parenchymal tissue were greater in UM gilts while that of protein (P<0.001) was lower. Total protein weight in parenchyma was also lower in parenchyma was also lower in UM gilts (P = 0.01). Both DNA (P<0.001) and RNA (P<0.001) contents were lower in UM gilts while RNA/DNA remained similar (P>0.1). Number of prolactin receptors were lower (P = 0.06) and affinity greater (P<0.05) in UM gilts. Cortisol levels were greater (P<0.01) in UM gilts while other hormones were not affected (P> 0.1). Results clearly demonstrate genetic differences with regard to mammogenesis in gilts and suggest that the less mammary gland development in Upton-Meishan compared with Large White breed of gilts may be related to lower number of prolactin receptors.     

Effect of repeated administration of combination trenbolone acetate and estradiol implants on growth, carcass traits, and beef quality of long-fed Holstein steers

Our objective was to determine the effect of repeated use of implants on feedlot performance and carcass characteristics of Holstein cattle. Holstein steers (n = 128) weighing an average of 211 kg were blocked by weight and randomly assigned to 16 pens. At the start of the trial (d 0), pens were assigned to one of four treatments: 1) nonimplanted control (C); 2) implant on d 0, 112, and 224 (T3); 3) implant on d 112 and 224 (T2); and 4) implant on d 224 (T1). Component TE-S implants (120 mg of trenbolone acetate and 24 mg of estradiol per implant) were used for all treatments during the 291-d feeding period. Over the course of the study, T2 and T3 cattle had greater ADG and final weights than C and T1 cattle (P < 0.05). Steers were harvested at a commercial abattoir on d 291. Hot carcass weights of T3 steers were greater than those of C and T1 steers (P < 0.05). Dressing percentage, adjusted 12th-rib fat, percentage of kidney, pelvic, and heart fat, yield grade, and longissimus color were not different among treatments (P > or = 0.26). Longissimus muscle areas (LMA) of T2 and T3 carcasses were larger than LMA of C (P < 0.01). No USDA Select carcasses were produced from C cattle, whereas the percentage of Select carcasses from implanted cattle ranged from 10 to 18%. Skeletal maturity advanced (P < 0.05) progressively with each additional implant. Steaks from T3 carcasses had a higher percentage of protein than controls (P < 0.05) and were less tender than all other treatments (P < 0.05). Repeated administration of combination trenbolone acetate and estradiol implants increased ADG and resulted in heavier carcasses with larger LMA. Administration of three successive implants decreased tenderness of Holstein beef, and resulted in more advanced skeletal maturity scores.     

Trenbolone acetate in combination with 17 beta-estradiol: influence of implant supports and dose levels on animal performance and plasma metabolites

Twelve (Exp. 1) and 24 (Exp. 2) young growing bulls were used to compare the effects of long-acting, cholesterol-based implants with short-acting, lactose-based implants. Each implant contained 200 mg of trenbolone acetate and 40 mg of 17 beta-estradiol. The long-acting, cholesterol-based implants were applied once either 18 wk (early implantation) or 12 wk (late implantation) before slaughter. The lactose-based pellets were implanted once (6 wk before slaughter), twice (12 and 6 wk) or three times (18, 12 and 6 wk) before slaughter. Treated animals had higher live weight gains, a lower feed conversion ratio, a higher proportion of lean meat and a lower proportion of adipose tissue than control animals. In Exp. 1 live weight gain of bulls implanted early with a single cholesterol-based implant was similar to the gain of animals treated three times with a lactose-based implant, but in Exp. 2 the effects of the long-acting implants given early were not sustained. In Exp. 3, 24 young growing bulls were used in a 3 X 2 factorial design to compare the effects of three dose levels of trenbolone acetate (100, 200 and 300 mg) and two levels of 17 beta-estradiol (40 and 60 mg). There were no significant differences between treatment groups, but highest live weight gains were observed in animals implanted with 300 mg of trenbolone and 60 mg of estradiol. This group also yielded the highest proportion of lean meat and the lowest proportion of adipose tissue. There was a decrease in plasma urea concentration after each implantation. It appeared also that plasma trenbolone was higher with implants containing 60 mg of estradiol. There were no differences between groups in growth hormone response to arginine stimulation.     

中药王不留行增乳活性单体及催乳素对奶牛乳腺上皮细胞特异性miRNA的影响

本试验旨在研究中药王不留行增乳活性单体邻苯二甲酸二丁酯及催乳素对奶牛泌乳中期乳腺上皮细胞miRNAs表达的影响;荧光定量RT-PCR检测增乳活性单体邻苯二甲酸二丁酯及催乳素作用后乳腺上皮细胞miRNAs表达变化;王不留行增乳活性单体邻苯二甲酸二丁酯及催乳素均抑制原代培养的泌乳中期奶牛乳腺上皮细胞miRNA-143、miRNA-125和miRNA-195表达;邻苯二甲酸二丁酯可抑制miRNA-21表达,催乳素对miRNA-21表达的影响尚不确定。首次阐明中药王不留行增乳活性单体邻苯二甲酸二丁酯和催乳素能引起乳腺上皮细胞miRNAs表达变化。     

水牛PNPLA8基因编码区克隆、表达分析及催乳素对该基因的调节作用

为了探究磷脂酶patatin样域包含蛋白8（patatin-like phospholipase domain containing 8,PNPLA8）在水牛乳腺脂质代谢中的作用,试验根据GenBank中公布的奶牛PNPLA8基因序列（登录号：XM_005205444.4）设计引物,应用PCR扩增并克隆水牛PNPLA8基因编码区（CDS）,应用生物信息学软件分析序列及蛋白质结构;抽提水牛不同组织及不同泌乳期乳腺组织RNA,利用实时荧光定量PCR检测PNPLA8基因在不同组织间和不同泌乳期的表达;利用不同浓度的催乳素处理水牛乳腺上皮细胞,通过定量检测催乳素对PNPLA8基因表达的影响。结果显示,水牛PNPLA8基因CDS长2 355 bp,编码784个氨基酸,与牦牛、山羊等PNPLA8基因具有较高的同源性;PNPLA8基因在所检测的水牛11个组织中有不同水平的表达,在肺脏和乳腺中表达量相对较高,在脂肪和肌肉组织中表达量较低;在整个泌乳期内PNPLA8基因的表达呈现"低-高-低"趋势;催乳素处理水牛乳腺上皮细胞结果显示,随着催乳素浓度升高,PNPLA8基因表达量逐渐下降。本研究成功克隆了水牛PNPLA8基因,并发现PNPLA8基因是参与乳腺泌乳的一个功能基因,为进一步研究PNPLA8基因在水牛乳腺中的功能奠定基础。     

Cloning,Expression Analysis and Regulation of PNPLA8 Gene by Prolactin in Buffalo

In order to investigate the role of patatin-like phospholipase domain-containing 8(PNPLA8) in lipid metabolism of mammary gland in buffalo,the coding region (CDS) was amplified and cloned by PCR based on the sequence of Bos taurus PNPLA8 gene in GenBank (accession No.:XM_005205444.4) were analyzed using bioinformatics software.Total RNA was extracted from different tissues of buffalo and mammary glands,which were harvested from different lactating buffaloes.The expression of PNPLA8 gene mRNA in different tissues and different lactation period was detected by Real-time quantitative PCR.For buffalo mammary epithelial cell treatment,different concentrations of prolactin were used and the effect of prolactin on the expression of PNPLA8 gene was detected by Real-time quantitative PCR.The results showed that the length of the PNPLA8 gene CDS was 2 355 bp,encoding 784 amino acids.The sequence showed high homology with Bos mutes and Capra hircus.PNPLA8 gene was expressed at different levels in 11 tissues examined,with a relatively high level in the lung and mammary tissues while the low level in the fat and muscle tissues.The expression abundance of the PNPLA8 gene was variable during lactation and showed a trend of "low-high-low".Prolactin treatment showed that the expression of PNPLA8 gene decreased with the increase of prolactin concentration.In this study,PNPLA8 gene of buffalo was successfully cloned,and the expression of PNPLA8 gene in different tissues and the lactation period was analyzed.Herein,the effect of prolactin on the expression of PNPLA8 gene was studied that laid a foundation for further research on PNPLA8 gene of mammary gland in buffalo.     

Growth and hormonal response of intact and castrate male cattle to trenbolone acetate and estradiol

Effects of castration and anabolic implants on weight gain, rib soft tissue composition and serum hormones were studied in cattle using a completely random design with a 2 x 2 factorial arrangement. Half of 16 bulls and 16 steers (Angus or Angus x Brahman) aged 9 mo and weighing 290 kg were treated with an implant (200 mg trenbolone acetate and 24 mg estradiol). Half of each group were not treated with an implant. A growing diet was fed for 95 d and half the animals in each group were slaughtered. Animals in the treated groups were reimplanted with trenbolone acetate and fed a finishing diet for 84 d and slaughtered. Percentage dry matter, fat and protein were determined on soft tissue from the 9-10-11th rib. Two blood samples were collected from each animal every 2 wk. Serum was assayed for five hormones. During the growing phase, untreated and treated bulls and treated steers gained more weight and had leaner rib sections that untreated steers (P less than .05); after the finishing phase, there were no differences among groups. Untreated steers had lower insulin-like growth factor (IGF-I) and higher cortisol concentrations during both phases of growth than untreated bulls did (P less than .05). Treatment with implants increased IGF-I concentrations in steers during both phases and reduced cortisol during the finishing phase.(ABSTRACT TRUNCATED AT 250 WORDS)     

胰岛素、催乳素和孕酮对奶牛乳腺上皮细胞泌乳功能的影响

具有泌乳功能的乳腺上皮细胞系可作为乳腺发育学、乳腺病理学、泌乳生物工程学研究的细胞模型,本研究测定了激素对奶牛乳腺上皮细胞系泌乳功能的影响,为阐述泌乳机制提供工作基础。应用HPLC方法对体外培养奶牛乳腺上皮细胞的酪蛋白和乳糖的分泌情况和细胞培养液中的酪蛋白、乳糖含量进行测定,以确定胰岛素、催乳素和孕酮处理后的奶牛乳腺上皮细胞的泌乳功能。试验结果表明：奶牛乳腺上皮细胞具有酪蛋白和乳糖的分泌能力,在72h内,随着细胞培养时间延长,胰岛素处理组细胞中的酪蛋白和乳糖的升高趋势不明显,孕酮处理组升高趋势较明显,催乳素处理组升高趋势很明显;胰岛素处理组、催乳素处理组和孕酮处理组细胞培养液中酪蛋白升高趋势均很明显,乳糖含量均很高,三组激素比较而言,胰岛素处理组乳糖含量最高。此外,三组激素对乳腺上皮细胞活力影响均很大,在72h之内,总体变化为：催乳素处理组和孕酮处理组细胞活力均升高,胰岛素处理组细胞活力下降。     

Prepuberal Ovine Mammary Development is Unaffected by Ovariectomy

Crossbred ewe lambs were used in a 2 × 2 × 2 factorial design to determine the effect of ovariectomy, age, and estrogen administration on prepuberal mammary development. Intact (I, n = 20) and ovariectomized (OVX, n = 17) lambs were sacrificed at 6 and 13 wk of age after 1 wk of either estrogen 0.1 mg/kg BW/day, s.c.) or vehicle injections. Ovariectomies were performed at 10 ± 1 d of age. At sacrifice, one mammary gland was dissected into parenchymal and stromal fractions for biochemical analyses. Parenchymal explants from the remaining gland were labeled with [³H]thymidine for histoautoradiography. Neither ovariectomy nor estrogen treatment affected body weight, total gland weight, or parenchymal weight (P > 0.05). However, means for each of these variables increased between 6 and 13 wk (P < 0.01). Analysis of relative mammary growth showed significant positive deviations from isometry. However, no significant difference in parenchymal allometry was observed between I and OVX groups. Exogenous estrogen stimulated an increase (P < 0.05) in epithelial cell labeling with [³H]thymidine, but neither ovariectomy nor age at sacrifice had any effect (P > 0.2) on epithelial labeling. These results demonstrate that prepuberal allometric mammary growth in the ewe lamb does not require the presence of the ovary.     

Effects of tripeptides and lactogenic hormones on oligopeptide transporter 2 in bovine mammary gland

This study was conducted to investigate the expression of oligopeptide transporter 2 (PepT2) and its potential function in bovine mammary gland. First, the PepT2 mRNA and protein were determined in cultured mammary epithelial cells. Then the effects of lactogenic hormones (prolactin, hydrocortisone or insulin) and substrate (threonyl-phenylalanyl-phenylalanine) on PepT2 were investigated. The PepT2 mRNA and protein were successfully detected in bovine mammary epithelial cells. PepT2 gene expression was enhanced by the addition of 50, 500 and 5000 ng/ml prolactin, 10 and 100 ng/ml hydrocortisone, and 50, 500, 5000 and 50,000 ng/ml insulin. PepT2 mRNA abundance was increased when 5, 10 and 15% of threonyl-phenylalanyl-phenylalanine was included. Responses of PepT2 to lactogenic hormones and oligopeptide inferred that it may play an important role in bovine mammary gland.