Effects of medroxyprogesterone acetate (MAP) on ovarian antral follicle development, gonadotrophin secretion and response to ovulation induction with gonadotrophin-releasing hormone (GnRH) in seasonally anoestrous ewes

When ovulation is induced with gonadotrophin-releasing hormone (GnRH) in anoestrous ewes, a proportion of animals fail to form normal (full-lifespan) corpora lutea (CL). Progesterone treatment before GnRH prevents luteal inadequacy. It remains uncertain whether a similar effect, achieved with medroxyprogesterone acetate (MAP) from intravaginal sponges, is mediated by influences on growing ovarian follicles and/or secretion of gonadotrophic hormones, before and after GnRH treatment. Two experiments were performed, on 13 and 11 anoestrous Western white-faced ewes, respectively. Seven and six ewes, respectively, received MAP-containing sponges (60 mg) for 14 days; the remaining ewes served as untreated controls. To test the effect of timing of GnRH administration after pre-treatment with MAP-releasing sponges, GnRH injections (250 ng every 2h for 24h followed by a bolus injection of 125 microg of GnRH i.v.) were given either immediately (Experiment 1) or 24h after sponge removal in the treated ewes (Experiment 2). Ovarian follicular dynamics (follicles reaching >or=5mm in size) and development of luteal structures were monitored using transrectal ultrasonography. In Experiment 1, the mean ovulation rate (0.7+/-0.3 and 1.0+/-0.4) and proportion of ovulating ewes (57 and 67%, respectively) did not vary (P>0.05) between MAP-treated and control ewes. Normal (full-lifespan) CL were detected in 29% of treated and 67% of control ewes (P>0.05). In Experiment 2, the mean ovulation rate (2.3+/-0.2 and 1.2+/-0.6; P<0.05) and percentage of ewes with normal (full-lifespan) CL (100 and 40%, respectively; P<0.10) were greater in the treated compared to control ewes. In Experiment 1, the mean peak concentration of the GnRH-induced LH surge was lower (P<0.05) in MAP-treated than in control ewes. There were no significant differences between MAP-treated and control ewes in the characteristics of follicular waves, mean daily serum FSH concentrations, and secretory parameters of LH/FSH, based on intensive blood sampling conducted 1 day before sponging and 1 day before sponge removal. It is concluded that treatment with MAP has no effect on the tonic secretion of LH/FSH or follicular wave development in anoestrous ewes. However, the GnRH-stimulated LH discharge was attenuated in the ewes that received MAP-impregnated sponges for 14 days and were treated with GnRH immediately after sponge withdrawal. Ovulatory response and CL formation were increased when GnRH was administered 24 h after sponge removal.     

Nonylphenol alters connexin 43 levels and connexin 43 phosphorylation via an inhibition of the p38-mitogen-activated protein kinase pathway

Endocrine-disrupting chemicals are exogenous compounds that mimic or inhibit the action of estrogens or other hormones. Nonylphenol, an environmental contaminant distributed along the St. Lawrence River, has been reported to act as a weak estrogen. Previous studies from our laboratory have shown that rats that were fed fish taken from nonylphenol contaminated sites have altered spermatogenesis and decreased sperm count. The mechanism responsible for this effect is unknown. Gap junctional intercellular communication (GJIC) in the testis is critical for coordinating spermatogenesis. The objectives of the study were to determine the effects of nonylphenol on GJIC and connexin 43 (Cx43) in a murine Sertoli cell line, TM4. Cells were exposed for 24 h to different concentrations (1 to 50 microM) of either nonylphenol or 17beta-estradiol. GJIC was determined using a microinjection approach in which Lucifer yellow was injected directly into a single cell, and GJIC was assessed 3 min postinjection. Nonylphenol exposure decreased GJIC between adjacent cells by almost 80% relative to controls. A significant concentration-dependent reduction in GJIC was observed at nonylphenol concentrations between 1 and 50 microM. Cx43 immunofluorescent staining was reduced at both 10 and 50 microM doses of nonylphenol. Cx43 phosphorylation, as determined by Western blot analysis, was reduced at both 10 and 50 microM concentrations, which may explain, at least in part, the inhibition of GJIC. In contrast, no effect on GJIC or Cx43 protein was observed in cells exposed to 17beta-estradiol at these concentrations. Cx43 has been reported to be phosphorylated via the p38-mitogen-activated protein kinase (MAPK) pathway. P38-MAPK activity was assessed in both control and nonylphenol-exposed cells. A dose-dependent decrease in p38-MAPK activity was observed in nonylphenol-exposed Sertoli cells. Protein kinase C activity was also measured and was not influenced by nonylphenol. These results suggest that nonylphenol inhibits GJIC between Sertoli cells and that this is modulated via nonestrogenic pathways.     

Changes in serum luteinizing hormone (LH) concentrations in response to luteinizing hormone releasing hormone (LHRH) in bull calves that attained puberty early or late

The objectives of this study were to determine if the response to luteinizing hormone releasing hormone (LHRH) could be used to select bull calves capable of early sexual maturation and to establish the optimum route and dose of LHRH. In Trial 1, at 4, 10 and 20 week of age, 20 calves were treated iv with 2 microg/kg body weight of LHRH 1 and 5h after commencing a 9-h period of blood sampling. Bulls were separated into early and late maturing (n=10), based on age at puberty (scrotal circumference (SC) of >or=28 cm). At 4 and 20 week of age, peak serum LH concentrations and area under the LH response curve in response to LHRH were lower (P<0.05) in early- versus late-maturing bulls. In Trial 2, calves at 20 week of age were given LHRH as follows: 2 microg/kg body weight iv (n=6), im (n=6) or sc (n=6); 5 microg/kg im (n=6), or ischio-rectally (ir, n=6) or sc (n=6); and 10 microg/kg im (n=6) or sc (n=6). Serum LH concentrations were at a plateau from 30 to 165 min after treatment with 5 microg/kg of LHRH (im or ir; P>0.05). We concluded that the LH responses to LHRH in calves at 4 and 20 week of age could facilitate the development of a simple test (one blood sample prior to treatment with LHRH and a second during the period of sustained response to LHRH) to select early-maturing bulls.     

Long non‐coding RNAs in melanoma

Melanoma is the most lethal cutaneous cancer with a highly aggressive and metastatic phenotype. While recent genetic and epigenetic studies have shed new insights into the mechanism of melanoma development, the involvement of regulatory non‐coding RNAs remain unclear. Long non‐coding RNAs (lncRNAs) are a group of endogenous non‐protein‐coding RNAs with the capacity to regulate gene expression at multiple levels. Recent evidences have shown that lncRNAs can regulate many cellular processes, such as cell proliferation, differentiation, migration and invasion. In the melanoma, deregulation of a number of lncRNAs, such as HOTAIR, MALAT1, BANCR, ANRIL, SPRY‐IT1 and SAMMSON, have been reported. Our review summarizes the functional role of lncRNAs in melanoma and their potential clinical application for diagnosis, prognostication and treatment.     

Protective effect of bixin on carbon tetrachloride-induced hepatotoxicity in rats

Background

The liver is an important organ for its ability to transform xenobiotics, making the liver tissue a prime target for toxic substances. The carotenoid bixin present in annatto is an antioxidant that can protect cells and tissues against the deleterious effects of free radicals. In this study, we evaluated the protective effect of bixin on liver damage induced by carbon tetrachloride (CCl₄) in rats.

Results

The animals were divided into four groups with six rats in each group. CCl₄ (0.125 mL kg^-1 body wt.) was injected intraperitoneally, and bixin (5.0 mg kg^-1 body wt.) was given by gavage 7 days before the CCl₄ injection. Bixin prevented the liver damage caused by CCl₄, as noted by the significant decrease in serum aminotransferases release. Bixin protected the liver against the oxidizing effects of CCl₄ by preventing a decrease in glutathione reductase activity and the levels of reduced glutathione and NADPH. The peroxidation of membrane lipids and histopathological damage of the liver was significantly prevented by bixin treatment.

Conclusion

Therefore, we can conclude that the protective effect of bixin against hepatotoxicity induced by CCl₄ is related to the antioxidant activity of the compound.     

Effect of platelet activating factor on the motility and acrosome reaction of buffalo (Bubalus bubalis ) spermatozoa

Platelet activating factor (PAF; 1-0-alkyl-2 acetyl-sn-glycerol-3 phosphocholine) has been shown to have a wide range of biological activities. In this study, PAF was used to induce acrosome reactions in fresh as well as frozen-thawed buffalo spermatozoa at different incubation periods and PAF levels. As the period of incubation increased, there was a gradual decrease in motility and increase in acrosome reaction in both fresh and frozen-thawed spermatozoa. With increasing PAF levels, the motility of fresh spermatozoa decreased and acrosome reaction increased whereas in frozen-thawed semen, motility remained almost constant, and the increase in acrosome reaction was not pronounced. Differences in motility and acrosome reaction among different bulls, types of semen, periods of incubation and PAF levels were significant (P < 0.01). A PAF level of 100 microM and an incubation period of 15 min were found to be optimum for inducing acrosome reaction in buffalo spermatozoa, since at this combination acrosome reaction increased significantly (P < 0.01) over that of the control without much loss of motility.     

Ultrasonographic evaluation of the pre-pubertal development of the reproductive tract in beef heifers

To study the development of the reproductive tract in heifers, the ovaries, uterus, cervix and vagina were examined by transrectal ultrasonography every 2 weeks, from 2 to 60 weeks after birth. First ovulation occurred at 63.7 +/- 1.1 weeks of age. Ovarian dimensions increased rapidly from 2 to 14 weeks of age, and increased again after 34 weeks of age (P<0.05). The size of the largest ovarian follicles increased from 8 to 14 weeks of age, from 38 to 42 weeks of age, and finally from 52 to 60 weeks of age (P<0.05). The number of follicles > or =3 mm in diameter tended to increase from 6 to 14 weeks of age (P<0.10) and increased significantly from 6 to 60 weeks of age (P<0.05). Mean numerical pixel values of the ovarian images decreased from 4 to 26 weeks of age, and then rose to 44 weeks of age (P<0.05). Diameter of the uterine body, cervix and vagina increased from 2 to 20-24 weeks of age, and again after 32 weeks of age (P<0.05). Mean numerical pixel values for the uterus and vagina decreased initially (uterus: 4-8 weeks and vagina: 6-22 weeks of age) and then increased (uterus: 14-42 weeks and vagina: 22-32 weeks of age; P<0.05). Pixel heterogeneity showed a consistent peak at 20-22 weeks of age for the uterus, cervix and vagina (P<0.05). In summary, in the heifer calf, the marked growth of the reproductive tract in the first few months of age, and prior to first ovulation, reflects phases of increased ovarian follicle (> or =3 mm in diameter) numbers and size. Ultrasonographic image analysis revealed patterns of numerical pixel values and heterogeneity that may be useful in determining important stages of growth and differentiation of the reproductive system.     

The relationship between secretory patterns of gonadotrophic hormones and the attainment of puberty in bull and heifer calves born early or late during the spring calving season

It was suggested that an early increase in gonadotrophin secretion in calves aged between 6 and 24 weeks might be critical for initiating developmental changes culminating in puberty. An early rise in luteinizing hormone (LH) release appears to be caused by an increase in LH pulse frequency in bull calves and by an increase in LH pulse amplitude in heifer calves. Previously we have found differences in the characteristics of the LH rise between prepubertal beef calves born in spring or fall; however, age at puberty was not affected by season of birth. Here we report the LH/FSH secretory patterns in prepubertal bull and heifer calves (Hereford x Charolais), born in March or April, respectively (i.e., early or late during the spring calving season; six animals of each sex born at each time). The bull calves of both groups reached puberty (defined as an attainment of scrotal circumference of >or=28 cm) at 43.2+/-1.3 weeks of age (P>0.05). Age at puberty for March- and April-born heifer calves (defined as the age at which serum progesterone concentrations first exceeded 0.4 ng/ml) averaged 56.0+/-1.4 weeks (P>0.05). Based on blood samples taken weekly from birth to 26 weeks of age, and then every other week until puberty, bull calves born in March exceeded April-born bull calves in mean serum LH concentrations at 6, 10 and 12 weeks of age (P<0.05). Mean FSH concentrations were greater (P<0.05) in March-born compared to April-born bull calves from 34 to 32 weeks before puberty. Mean serum LH (at 40, 42 and 56 weeks) and FSH concentrations (at 2, 10, 20, 22-26, 30 and 56 weeks of age) were greater (P<0.05) in heifer calves born in April than March. On the basis of frequent blood sampling (every 12 min for 10 h), heifer calves born in April exceeded March-born animals in mean LH and FSH concentrations, at 5 and 25 weeks, and LH pulse frequency, at 5, 10 and 25 weeks of age (P<0.05). None of the parameters of LH secretion (i.e., mean concentrations of LH, LH pulse frequency and amplitude based on frequent blood collection) differed between March- and April-born bull calves in this study (P>0.05). In summary, March-born bull calves had greater mean serum LH and FSH concentrations prior to 24 weeks of age than April-born calves. April-born heifer calves had greater mean serum concentrations of LH and FSH but this difference was not confined to the early postnatal period. Although there were significant differences in absolute amounts of LH secreted, there were no differences in the frequency of LH secretory pulses amongst March- and April-born bull calves and no differences in LH pulse amplitude in heifer calves born in March or April. As these particular parameters of LH secretion, as well as age at puberty, are not affected by the time or season of birth, they may be primary hormonal cues governing sexual development in bulls and heifers, respectively.