Expression and possible role of 20alpha-hydroxysteroid dehydrogenase in the placenta of the goat

20Alpha-hydroxysteroid dehydrogenase (20alpha-HSD) catalyzes the conversion of progesterone to its inactive form 20alpha-dihydroprogesterone (20alpha-OHP). 20Alpha-HSD is expressed in the murine placenta, suggesting a role, yet unidentified, played by this enzyme during the course of pregnancy. To elucidate the possible roles of 20alpha-HSD during pregnancy, 20alpha-HSD gene expression in the placenta was examined by Northern blot analysis, and progestin (progesterone and 20alpha-OHP) concentrations in the maternal and fetal sera and the amniotic fluid were measured by radioimmunoassay in pregnant Shiba goats. The expression of 20alpha-HSD mRNA was observed in the placenta and the intercaruncular part of the uterus during mid to late pregnancy. Analysis by in situ hybridization revealed that 20alpha-HSD mRNA was mainly localized in the endometrial epithelium of the caruncle side of the placenta. Considerable enzyme activity of 20alpha-HSD was also detected in the cytosolic fraction of the placenta and intercaruncular part of the uterus. Although concentrations of progesterone and 20alpha-OHP in the maternal serum showed similar profiles, progesterone levels in the fetal serum stayed extremely low throughout the pregnancy. The 20alpha-OHP concentration in the fetal serum was always higher than that in the maternal serum. In the amniotic fluid, the concentrations of both progesterone and 20alpha-OHP remained at very low levels throughout the pregnancy. These results support the notion that 20alpha-HSD protects the fetus from the cytotoxic effects of progesterone, and thereby maintains the normal development of the fetus.     

Immunolocalization of gastrin-releasing peptide in the bovine uterus and placenta

Gastrin-releasing peptide (GRP), a mammalian homologue of amphibian bombesin, has been suggested to be a novel regulatory peptide in the reproductive tract during pregnancy. In this study, the localization of GRP in the bovine uterus and placenta was demonstrated by immunohistochemistry. Uterine and placental samples were collected from nonpregnant and pregnant specimens, respectively. Tissue sampling was done from the caruncle and intercaruncle of the uterus, and from the placentome (caruncle and cotyledon) and intercotyledon of the placenta. In all the tissues examined, GRP was detected although its immunoreactivity was observed at various degrees. In the uterus, moderate immunoreactivity for GRP was observed in the uterine gland epithelial cells. In the placenta, strong immunoreactivity for GRP was demonstrated in the uterine gland epithelial cells; moderate in superficial epithelial cells; and weak in the trophoblasts, trophoblastic giant cells and cryptal epithelial hybrid cells. In both nonpregnant and pregnant animals, GRP was immunolocalized in the uterine gland secretions and was found predominantly in the supranuclear region of the uterine gland epithelial cells. These findings may suggest that GRP is secreted into the uterine lumen and regulates the intrauterine environment of both the nonpregnant and pregnant bovine by exocrine, autocrine and/or paracrine manner.     

Protein kinase-C activity in phorbol myristate acetate-stimulated neutrophils from newborn and adult cattle.

Neutrophils from newborn calves have been shown to be deficient in ability to generate superoxide anion (O2-) after stimulation of the respiratory burst enzyme with the phorbol ester, phorbol 12-myristate 13-acetate (PMA). This compound activates the O(2-)-generating enzyme of bovine neutrophils through a pathway involving protein kinase C (PKC). To investigate the biochemical basis underlying this functional difference between neutrophils from newborn and adult cattle, we measured and compared the activity of the enzyme PKC in nonstimulated and PMA-stimulated bovine neutrophils. Neutrophils from newborn calves (n = 5) and adult cows (n = 5) were stimulated with various concentrations of PMA (0, 10, 100, and 500 ng/ml) for 3 minutes, and PKC activity was assayed in the cytosolic and the membrane fractions. In nonstimulated cells, most PKC activity was detected in the cytosolic fraction of neutrophils from newborn and adult cattle. Activity of PKC in the cytosol was dependent on the presence of added calcium and phospholipids, whereas membrane-associated PKC in nonstimulated cells did not have such dependence. Significant differences in PKC activity were not observed between newborn and adult cattle in either the cytosolic or the membrane fractions from nonstimulated cells. Stimulation with PMA caused redistribution of PKC activity in the cell (translocation) in newborns and adults, consisting of decrease in cytosolic PKC activity and increase in membrane-associated PKC activity. Similar to that in nonstimulated cells, PKC activity in cytosolic fractions from PMA-stimulated neutrophils was dependent on the presence of cofactors (calcium and phospholipids), whereas PKC activity in the membrane did not have such requirement.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of supplemental vitamin D3 concentration on concentrations of calcium, phosphorus, and magnesium relative to protein in subcellular components of the longissimus and the distribution of calcium within longissimus muscle of beef steers

The effect of supplementing diets with various levels of vitamin D3 to provide 0, 0.5, 1, and 5 million IU/(steer x d) for 8 d before slaughter on the mineral content and localization of Ca in LM and muscle fragments was studied during the postmortem aging process. Twelve feedlot steers of three biological types were given access to the four levels of vitamin D for 8 d before slaughter. Differential centrifugation techniques were used to determine the concentrations of minerals relative to protein in different muscle fragments on d 3 and 21 postmortem. Electron microscopy visualization of bound Ca indicated that vitamin D3 mobilized Ca from the sarcoplasmic reticulum and transverse tubule system into the myofibrils. Bound Ca was concentrated near the Z-line at the A-band/I-band juncture within the sarcomere. Supplementing steers with 1 and 5 million IU/(steer x d) of vitamin D3 increased (P < 0.05) Ca, P, and Mg concentrations per unit of protein in the cytosol. Soluble cytosolic Ca concentrations were greater (P < 0.05) on d 21 than on d 3 postmortem only when steers were supplemented with 5 million IU/d. Concentrations of Ca, P, and Mg in isolated tissues were increased (P < 0.05) in nuclei and myofibrilar proteins by supplementing steers with 1 and 5 million IU/ (steer x d) of vitamin D3. All supplemental vitamin D3 treatments also increased (P < 0.001) Mg concentrations in the cytosol, regardless of aging treatment, and increased Mg concentrations (P < 0.04) within the mitochondria at d 3 postmortem. Thus, supplementation of feedlot steers with vitamin D3 at levels of 0.5 to 5 million IU/(steer x d) increased Ca concentrations within respiring muscle, resulting in increased bound tissue Ca concentrations. When the respiring muscle was converted to meat, the increased bound tissue Ca resulting from vitamin D3 treatment released Ca concentrations into the cytosol during aging (P < 0.05). Results of this study indicate that vitamin D3 supplementation increased total cytosolic Ca, P, and Mg concentrations in meat.     

Bovine Uterine,Cervical and Ovarian Cytosol Estrogen and Progesterone Receptor Concentrations in Cystic Ovarian Disease

Bovine cytosol estrogen (ERC) and progesterone receptor (PRC) concentrations were measured simultaneously in various regions of the uterus and in ovarian stromal tissue in cows with cystic ovarian disease (follicular cysts), arid the concentrations compared with those in animals with normal cycles. In cystic ovarian disease, ERC concentrations in endometrium (550 fmol/mg cytosol protein (c.p.)) and in myometrium (405) were significantly higher than in control animals. Very high PRC contents were measured in the endometrium (3115) and myometrium (2761) of cows with cystic ovarian disease. In control animals, PRC concentrations in the endometrium and myometrium were significantly lower than in diseased animals. No statistical differences were observed in ERC or PRC contents between the endometrium and the myometrium in cows with cystic ovarian disease. ERC and PRC concentrations in the uterine cervix and ovaries were low compared to those detected in the uterus. Bovine serum estradiol-17ß concentrations were higher (p<0.001) in cows with cystic ovarian disease than in control animals in postpartum anestrus or during the normal estrous cycle. Serum sex hormone-binding globulin (SHBG) concentrations were of the same magnitude as in control cows during their estrous cycles. These findings show that long standing low endogenous progesterone and elevated estradiol concentrations in serum are associated with elevated ERC and PRC concentrations in bovine uterus.     

Maternal and fetal influences on uterine and conceptus development in the cow: I. Growth of tissues of the gravid uterus.

Objectives of this study were to evaluate maternal and fetal influences on development of gravid uterine tissues of cows. Brahman cows with Brahman or Charolais fetuses and Charolais cows with Brahman or Charolais fetuses were used. Cows were killed 232 +/- .5 or 271 +/- .7 d after mating. The gravid uterus of each cow was weighed and dissected into its component parts. Weights of the fetus, fetal membranes, cotyledons, caruncles, and uterus were recorded as were weights of the fetal liver, heart, kidneys, spleen, lungs, stomach complex, intestines, and semitendinosus muscle. Ribonucleic acid, DNA, and protein concentrations in caruncles, cotyledons, liver, heart, kidney, and semitendinosus muscle were determined. Data were analyzed by analysis of variance; breed of cow (C), breed of fetus (F), day of gestation (D), and all interactions were included in the model as fixed effects. Fetal weights were influenced (P less than .003) by C, F, D, and C x D and tended (P = .07) to be influenced by C X F X D. Weight, RNA, DNA, and protein contents of selected fetal tissues followed similar patterns of significance. Thus, both maternal and fetal genotype influenced fetal growth. Greater influences of the maternal system and interrelationships between maternal and fetal systems were observed at the latter stage of gestation. Placentomal (caruncle + cotyledon) weights were greater for Charolais than for Brahman cows (P less than .02) or fetuses (P less than .001) and were greater (P less than .01) at 271 than at 232 d. Caruncular weights followed similar patterns; however, fetal genotype was the only significant source of variation in cotyledonary weight, RNA, DNA, or protein content.(ABSTRACT TRUNCATED AT 250 WORDS)     

Increased nuclear type II estradiol receptor concentrations in rat spleen during the course of pregnancy.

Estradiol receptors are classified into type I and type II receptors by their affinity and capacity for estradiol binding. The type II receptors are thought to be significant in the suppression of immune response, such as in the pregnancy-associated immunosuppression. The present study was undertaken to show the presence of type II receptors in rat spleen and to examine the change of receptor distribution after estradiol administration and during pregnancy. Scatchard analysis revealed that the type II receptors were present in rat spleen, and dissociation constants were estimated to be 3.23 x 10(-9) M for cytosol and 4.29 x 10(-9) M for nuclei. The receptors possessed specificity for estradiol and diethylstilbestrol, but not for promegestone, methyltrienolone and dexamethasone. Administration of estradiol to rats resulted in the increase of nuclear receptor concentrations with concomitant decrease of cytosolic concentrations. During pregnancy, the receptor concentrations were increased in the nuclear fraction, but were not significantly changed in the cytosolic fraction. The dissociation constants of the receptors in pregnant rat spleen (4.77 x 10(-9) M for cytosol and 7.20 x 10(-9) M for nuclei) were similar to those in the non-pregnant control, suggesting the quantitative change of the receptors during pregnancy.     

Tissue and intracellular distribution of rhodanese and mercaptopyruvate sulphurtransferase in ruminants and birds

Cyanide detoxification is catalysed by two enzymes: rhodanese [thiosulphate: cyanide sulphurtransferase, E.C. 2.8.1.1], and 3-mercaptopyruvate sulphurtransferase [3-MST, EC. 2.8.1.2]. In the present work, the activity of the two enzymes in the crude extracts of different tissues and in the mitochondrial and cytosolic fractions of tissues from some ruminants (camels, cattle and sheep) and birds (chickens and pigeons) have been compared. Rhodanese activity was almost exclusively present in the mitochondrial fraction. In ruminants and chickens the highest activity of rhodanese was found in the liver, followed by the kidney. In pigeons, however, the enzyme activity was the highest in the kidneys. In camels' tissues, the rhodanese activity was significantly (P < 0.05) lower than in cattle or sheep, and the enzyme activities in the two latter species were similar. The activity of 3-MST in the crude extract of tissues from camels was similar to that in sheep, but higher than that in cattle. The enzyme activity was equally distributed between the mitochondrial and cytosolic fractions in the liver and kidneys of camels, cattle and sheep.     

Cytosolic 20 alpha-hydroxysteroid dehydrogenase activity in spontaneous neoplasms in the dog and cat.

Steroid-producing tissues such as ovary, placenta, testis and adrenal gland and non-steroid-producing cells including lymphocytes are known to contain 20 alpha-hydroxysteroid dehydrogenase (20 alpha-HSD). In the present study, we measured and partially characterized the 20 alpha-HSD in 11 neoplastic tissues surgically removed from dogs and a cat. The tissues were pathologically classified as 4 benign and 7 malignant. The enzyme activities in the cytoplasmic fraction were positive in 6 of the 7 malignant tissues and 2 of the 4 benign ones. Following DEAE chromatography analysis of 2 malignant tumour samples, multiple forms of enzyme activities with different electric charges were detected. Furthermore, 20 alpha-HSD activity in the cytosol fraction from malignant tumours was increased dramatically by passage through the DEAE column, suggesting that the enzyme is present in the cytosol as an inactive or sequestered form.     

Modulation by sphingosine of phosphorylation of substrate proteins by protein kinase C in nuclei from cow mammary gland

Protein kinase C (PKC) is an enzyme activated by diacylglycerols such as 1-oleoyl-2-acetyl-sn-glycerol (OAG), phospholipids (in particular phosphatidylserine; PS) and Ca2+, which regulate a wide variety of intracellular functions by phosphorylating multiple substrate proteins and enzymes. The effect of sphingosine, the backbone moiety of sphingolipids, on PKC activity and phosphorylation of endogenous proteins catalyzed by PKC was investigated in nuclei of cow mammary gland. Sphingosine inhibited nuclear PKC activity when lysine-rich histone was used as the substrate. The sphingosine inhibition of the PKC activity was reversed by the excess addition of PS, but not by OAG or Ca2+. Several nuclear proteins, including 56-kDa, 43-kDa, 38-kDa and 36-kDa proteins, were shown to be substrates for PKC. Of the substrate proteins, the 38-kDa and 36-kDa proteins were identified as annexin I, the Ca2+/phospholipid-binding protein; the 56-kDa and 43-kDa proteins have not yet been identified. Sphingosine inhibited phosphorylation of the 56-kDa protein and the 36-kDa annexin I, whereas it enhanced that of the 43-kDa protein. The 38-kDa annexin I species was unaffected by sphingosine. As with the PKC activity, inhibition by sphingosine of phosphorylation of the 56-kDa protein and 36-kDa annexin I was reversed by the excess addition of PS, but not by OAG or Ca2+. In addition, by the excess addition of PS and not by OAG or Ca2+, the sphingosine-enhanced phosphorylation of the 43-kDa protein was reversed and returned to near the level in the absence of sphingosine. It is suggested that sphingosine is involved in the regulation of PKC-dependent phosphorylation in the nucleus by modulating the association of PKC or its substrates, particularly annexin I, with membrane phospholipids in cow mammary gland.     

Activities of enzymes in the malate-aspartate shuttle and the isoenzyme pattern of lactate dehydrogenase in plasma and peripheral leukocytes of lactating Holstein cows and riding horses

The activities of the enzymes involved in the malate-aspartate shuttle and lactate dehydrogenase (LDH) and the pattern of the isoenzymes of LDH were determined in plasma and peripheral leukocytes of lactating Holstein cows and thoroughbred riding horses as representative herbivorous animals. In the horse plasma, LDH activities were significantly lower and AST activities were significantly higher than those in the cow plasma. The specific activities of cytosolic malate dehydrogenase (MDH), LDH and AST in the horse leukocytes were higher than those in the cows. The cytosolic ratio of MDH/LDH activity (ML ratio) in the horse leukocytes was significantly lower than that in the cow leukocytes owing to significantly higher activities of LDH. The ML ratio was considered to reflect the difference in energy metabolism in leukocytes between cows and horses. The plasma LDH isoenzyme patterns of cow and horse showed the characteristic as herbivorous animals with dominance of LDH-1, -2 and -3. The LDH isoenzyme patterns with dominance of LDH-3 and -4 in the horse leukocytes were remarkably different from those in the cow leukocytes. There were significant differences in activities of malate-aspartate shuttle enzymes, ML ratio and LDH isoenzyme patterns in the cytosolic fractions of leukocytes between the lactating cows and the riding horses.     

Similarities of cow mammary gland cytosolic 21-kDa protein, the substrate for protein kinase C, to the 20-kDa myosin light chain from smooth muscle

In the cytosol of cow mammary gland, several proteins are phosphorylated in the presence of the protein kinase C (PKC) cofactors 1-oleoyl-2-acetyl-sn-glycerol (OAG), phosphatidylserine (PS) and Ca2+. Of the substrates, the 21-kDa protein is inferred to be a 20-kDa regulatory myosin light chain (MLC20) from smooth muscle because of its molecular mass, its distribution in the cytosol, its association with melittin and sphingosine (the PKC modulators), and phosphorylation by PKC as well as by Ca2+/calmodulin-dependent myosin light chain kinase (MLCK). The present study was undertaken to examine whether the 21-kDa protein could be identified as MLC20, by adding cow uterine MLC20 to the reaction mixture containing cytosol with or without the PKC cofactors and/or calmodulin. In the absence of MLC20, the 21-kDa protein was phosphorylated when the PKC cofactors and calmodulin were added to the reaction mixture. Phosphorylation of the 21-kDa protein was inhibited by melittin or sphingosine, and the inhibition was reversed by PS, but not by calmodulin. When MLC20 was included in the reaction mixture, it was phosphorylated in the presence of the PKC cofactors, and the phosphorylated MLC20 band overlapped that of the 21-kDa protein. The indistinguishably overlapped band of the two proteins was inhibited by melittin and by sphingosine, and their inhibition was reversed by PS, not by calmodulin. It is suggested that the 21-kDa protein is the smooth muscle MLC20 and also that the 21-kDa MLC20 is phosphorylated by PKC, but not by MLCK.     

Inhibition by sulfatide of 21-kDa protein phosphorylation by protein kinase C in cow mammary gland and its reversal by phosphatidylserine

The effect of sulfatide, a sulfated sphingolipid, on phosphorylation of endogenous proteins by protein kinase C (PKC) was examined in cow mammary gland. Several proteins, including 21-kDa, 43-kDa and 56-kDa proteins in the cytosolic fraction, were found to be substrates for PKC by phosphorylation in the absence or presence of the cofactors 1-oleoyl-2-acetyl-sn-glycerol (OAG), phosphatidylserine (PS) and Ca2+. Sulfatide inhibited the 21-kDa phosphorylation, whereas it enhanced the 56-kDa and 43-kDa phosphorylation. Experiments were then conducted to examine whether other sphingolipids, including sphingosine, dihydrosphingosine, ceramides, galactocerebrosides, psychosine and sphingomyelin, modulated phosphorylation of the PKC substrates. Sphingosine, dihydrosphingosine and psychosine did not inhibit the 21-kDa phosphorylation; however, they enhanced the 56-kDa and 43-kDa phosphorylation. Ceramides, galactocerebrosides and sphingomyelin did not inhibit the 21-kDa or enhance the 56-kDa and 43-kDa phosphorylation. The inhibition by sulfatide of the 21-kDa phosphorylation was reversed by excess addition of PS, but not by OAG or Ca2+; whereas the enhancement by sulfatide, as well as sphingosine, dihydrosphingosine and psychosine, of 56-kDa and 43-kDa phosphorylation was not affected by PS, OAG or Ca2+. It is suggested that sulfatide is involved in the regulation of PKC-dependent phosphorylation by modulating the association of PKC substrates, in particular the 21-kDa protein, with membrane phospholipids in cow mammary gland.     

Plasma concentration of estrone sulfate during pregnancy in different breeds of Japanese beef cattle

Plasma concentrations of estrone sulfate in different breeds of Japanese beef cattle and the relationship between those concentrations and feto-placental growth were examined in order to assess the possibility of monitoring abnormal growth of the fetus. Blood samples were obtained from cows from day 90 of gestation to parturition. The plasma concentration of estrone sulfate was measured by direct enzyme immunoassay. From day 180 of gestation, the mean concentration of estrone sulfate increased gradually and it was drastically elevated after day 240 of gestation with the maximum at day 285. Plasma concentrations of estrone sulfate on day 240 of gestation was significantly increased in F(1) cows (Holstein Friesian and Japanese Black) compared with those in other breeds of cow. From day 270 to 278 of gestation, estrone sulfate concentrations of Holstein Friesian cows inseminated by Holstein Friesian differed from those inseminated by Japanese Black. In the cow with retained placenta, the plasma concentration of estrone sulfate reached plateau at day 240 of gestation and did not increase thereafter. There was no significant relationship between estrone sulfate concentration and duration of gestation, calf birth weight, weight of placenta or viability of newborn calves. These results indicate that changes of plasma estrone sulfate concentration in Japanese beef cattle are very similar to those in Holstein dairy cattle. They also suggest that the plasma concentration of estrone sulfate is associated with the breed of pregnant cow and that its concentration is also affected by calf birth weight depending on the breed of bull. It seems possible to predict the incidence of retained placenta but not the calf birth weight and viability of newborn calves in Japanese beef cattle.     

Profile of Bovine Proteins in Retained and Normally Expelled Placenta in Dairy Cows

Tissue‐specific protein profile is determined by its function, structure, intensity of metabolism and usefulness. This profile remains under hormonal control. Any disturbance in the general metabolism may be reflected in changes in both protein quantity and quality. These changes can be of low or high specificity, and some can be used as clinical markers of pathological conditions. The aim of this study was to describe and to compare the protein profile of caruncle and foetal villi of bovine placenta that was either properly released or retained. Placental tissues were collected from healthy cows, divided into releasing and retaining foetal membranes, homogenized and subjected to 1D and 2D electrophoresis. Computer‐aided analysis of gel images showed essential qualitative and quantitative alterations in protein profile between tissues that were properly released and retained. Alterations concerned both the number of fractions and spots as well as the intensity of staining. This preliminary study provides a general overview of the differences in the protein profile between released and retained foetal membranes. It may allow for selecting the group of proteins or single molecules, which should be further analysed in detail as possible markers differentiating the retention of foetal membranes in cows from placentas that were released spontaneously. The continuation of the study for the identification of particular spots detected in 2D gels is necessary.     

Comparison of Milk Fat Globule Membrane Proteins in Milk Samples of Dairy Cow and Goat

In order to compare the difference of milk fat globule membrane（MFGM）proteins between dairy cow and goat milk,30 milk samples were collected in a dairy farm and a goat farm from Anhui area,respectively.Extracted proteins from the MFGM-enriched fractions were identified and quantified by LC/MS approach.The results showed that 284 and 334 proteins of MFGM from dairy cow and goat were identified,the biological processes of MFGM proteins were similar between dairy cow and goat which were mainly related to biological regulation,localization,transport,signal transduction and response to stimulus.Meanwhile,there were some differences in molecular functions,and protein binding and nucleotide binding were the most prevalent molecular functions in dairy cow MFGM proteins,while protein binding and structural molecule activity were the most prevalent molecular functions in goat MFGM proteins.And structural molecule activity was the main molecular functions among the difference proteins.Pathway analysis revealed that tight junction,axon guidance,antigen processing and presentation,complement and coagulation cascades were enrichment in dairy cow MFGM proteins,and regulation of actin cytoskeleton was enrichment in goat MFGM proteins.Those results revealed the protein expression pattern difference between MFGM protein of dairy cow and goat milk,and provide reference data for further exploring the molecular mechanism of synthetic milk fat globule.     

牛奶和山羊奶中乳脂球膜蛋白的比较研究

试验旨在分析牛奶与山羊奶中乳脂肪球膜（milk fat globule membrane,MFGM）蛋白组成及潜在的生物学功能。采集牛奶和山羊奶各30份,离心分离牛奶和山羊奶中脂肪,提取MFGM蛋白,液相色谱串联质谱分析结合数据库搜索鉴定,比较了奶牛和山羊MFGM蛋白的差异,分析了MFGM蛋白参与的生物过程、分子功能及相关代谢通路。结果显示,奶牛和山羊MFGM中分别鉴定了284和334个蛋白,奶牛和山羊中蛋白参与的生物学过程的模式非常相似,主要涉及生物调控、定位、转运、信号转导和应激反应等。分子功能方面二者存在一定的差异,奶牛MFGM蛋白主要涉及蛋白结合和核苷酸结合,而山羊MFGM蛋白主要涉及蛋白结合和结构分子活性。奶牛和山羊中差异表达的MFGM蛋白主要涉及结构分子活性。通路分析发现,奶牛和山羊MFGM蛋白涉及的生物学通路稍有差异,其中紧密接头、轴突导向、抗原加工与递呈、补体和凝血级联反应通路在奶牛MFGM蛋白中得到富集,而调节肌动蛋白细胞骨架通路在山羊奶中得到富集。研究结果展示了奶牛和山羊MFGM蛋白的表达模式及差异,为进一步探索两种奶畜乳腺合成脂肪球的分子机制的异同提供科学依据。     

Bovine uterine, cervical and ovarian androgen receptor concentrations. Correlation with estrogen and progesterone receptor concentrations.

Bovine cytosol androgen receptor (ARC) concentrations were examined simultaneously in various regions of the uterus and in ovarian tissues of cows, and were related to cytosol estrogen (ERC) and progesterone receptor (PRC) concentrations and circulating steroid levels. ERC concentrations were 3-7-fold and PRC concentrations 13-29-fold those of ARC in bovine endometrial and myometrial tissues. When serum progesterone levels were low, both endometrial and myometrial ARC, endometrial ERC, and endometrial and myometrial PRC concentrations were higher (p < 0.05) than those observed during higher progesterone concentrations. Because serum 5 alpha-dihydrotestosterone (5 alpha-DHT) concentrations were higher during the luteal phase, it is possible that ARC was down-regulated by this natural ligand at this phase of the cycle. There were no differences between uterine horns in endometrial or myometrial ARC concentrations. Bovine cervical and ovarian stromal tissue also contained ARC, and the concentrations were about the same as in the endometrium and the myometrium. The relative binding affinities (RBAs) of some steroid hormones towards ARC in vitro were: the synthetic compound R1881 (146%), 5 alpha-dihydrotestosterone (100%), testosterone (75%) while estradiol-17 beta, progesterone and dexamethasone had lower RBAs (2, < 1, < 1% respectively). Cytosol androgen receptor concentrations correlated significantly with cytosol progesterone (PRC) and estrogen receptor (ERC) concentrations, both in the endometrium and myometrium. These data show that androgens, such as 5 alpha-DHT, may participate the endocrine regulation of bovine reproductive tissues.     

Relevance of apolipoproteins in the development of fatty liver and fatty liver-related peripartum diseases in dairy cows

Most metabolic diseases in dairy cows occur during the peripartum period and are suggested to be derived from fatty liver initially developed during the nonlactating stage. Fatty liver is induced by hepatic uptake of nonesterified fatty acids that are released in excess by adipose tissues attributable to negative energy balance. The fatty accumulation leads to impairment of lipoprotein metabolism in the liver, and the impairment in turn influences other metabolic pathways in extrahepatic tissues such as the steroid hormone production by the corpus luteum. Detailed understanding of the impaired lipoprotein metabolism is crucial for elucidation of the mechanistic bases of the development of fatty liver and fatty liver-related peripartum diseases. This review summarizes results on evaluation of lipoprotein lipid and protein concentrations and enzyme activity in cows with fatty liver and those with ketosis, left displacement of the abomasum, milk fever, downer syndrome and retained placenta. Obtained data strongly suggest that decreases in serum concentrations of apolipoprotein B-100, apolipoprotein A-I and apolipoprotein C-III, a reduction in activity of lecithin:cholesterol acyltransferase and induction of haptoglobin and serum amyloid A are intimately related to the development of fatty liver and fatty liver-related diseases. Moreover, determination of the apolipoprotein concentrations and enzyme activity during the peripartum period is useful for early diagnoses of these diseases.