1,720,999 research outputs found
Effects of different culture conditions and leptin on GH mRNA expression and GH secretion by pig pituitary cells.
No full textGrowth hormone (GH) is enhanced in malnutrition; physiological increments in GH secretion seem to play an important role in regulating metabolism during fasting. Leptin has also been shown to play a role, amongst others, in modulating the somatotropic axis. In this study, we investigated how the composition of culture media could influence basal and leptin-stimulated GH secretion and expression in pig pituitary cells. Pituitary cells from 8-month-old sows were incubated for 48 h in presence and absence of 10% fetal calf serum, either in DMEM/Ham's F12, in arginine-free DMEM/Ham's F-12, or in DMEM/Ham's F12 Salts. Cells were then treated for 24 h with GHRH or recombinant human leptin (rhLep) individually or in association with GHRH; cell proliferation, nitric oxide (NO) production and GH expression and secretion were determined. The absence of nutritional factors induced a decrease in cell proliferation, but stimulated both GH secretion and expression. Furthermore, rhLep significantly increased GH expression and secretion irrespective of culture conditions. NO production was only significantly enhanced by leptin under DMEM/Ham's F12 culture conditions. These observations lead us to hypothesize that the adaptive capabilities of pituitary cells may overcome the negative effects of undernutrition; in this context, leptin does not seem to depend on NO pathways in modulating GH secretion
Effect of duration of altrenogest treatment on farrowing rate and litter size of gilts
No full textThe objective of the present study was to compare two common durations of altrenogest (ALT) feeding during different periods of the year on the fertility of gilts after ALT withdrawal. During a 12-month period gilt replacements that were assumed to be cyclic were subjected to oestrus synchronisation with 15 mg/day ALT administered for 18 days (ALT-18; n = 268) or 14 days (ALT-14; n = 153) whereas 275 non-treated gilts served as controls. Fewer ALT-14 than ALT-18 gilts expressed oestrus by 7 days after last ALT treatment (79.1% vs 88.8%; P < 0.05). Farrowing rate was lower (P < 0.05) for ALT-14 than for the other groups (81%, 91% and 92% for ALT-14, ALT-18, and Control, respectively) but farrowing rates were not affected by time of year. Control litter sizes were not different from ALT-14 except during September to November when Control litter sizes were larger than either ALT treatments (13.6 ` 0.33, 12.3 ` 0.65 and 12.7 ` 0.39 for Control, ALT- 14 and ALT-18, respectively; P < 0.05). The ALT-18 gilts had larger litter sizes during January to August. The present data suggest that the appropriate duration of ALT feeding to synchronise oestrus in gilts is 18 days
Effects of chronic melatonin administration on pregnancy rate in dairy cows submitted to a fixed-time AI protocol during summer and winter seasons
No full textThe aim of this study was to assess the effect of chronic melatonin treatment before calving in summer (long-day photoperiod, LDP, 16 h of light and 8 h of darkness) or winter (short-day photoperiod, SDP, 8 h of light and 16 h of darkness) on pregnancy rate after calving in lactating dairy cows. Before calving 60 cows were treated with melatonin and another 60 cows were not treated with melatonin thus functioning as a control group. In each group, 30 cows were treated during summer and 30 during winter. At 60 days after calving, all animals were submitted to a cosynch-ovsynch plus progesterone protocol and had fixed time artificial insemination (FTAI). The pregnancy rate at day 30 after FTAI was no different between groups (50% and 48% in treatment and in control groups, respectively, P = 0.66). Pregnancy losses during the first trimester of gestation (day 90 after FTAI) were 10% in cows treated with melatonin and 6% in the control group (P = 0.35). Considering the season of treatment there were no differences in either pregnancy rate (P = 0.70) or embryonic losses (P = 0.30) between the treatment and control groups. The results of this study indicate that in dairy cows submitted to a cosynch-ovsynch plus progesterone protocol and FTAI, the treatment with melatonin before calving did not compromise either pregnancy rate or embryo losses in both summer and winter
Seasonal variations of pituitary and gonadal activity and responsiveness to GnRH in the male goat
No full textEffect of IL-1ß, IL-6 AND TNFa alone or in association with GHRP-6 or Galanin, on GH expression and release from pig pituitary cells
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Leptin levels and leptin and its receptor expresion in pig placenta.
No full textLeptin, an adipocyte hormone involved in energy homeostasis, plays a role in the control of reproduction and pregnancy. The objective of this study was to unravel a possible relationship between maternal plasma leptin concentrations and leptin receptor gene expression in swine. A total of 15 crossbred multiparous sows aging 24 - 36 months with an average weight of 160  10 kg were used. Blood samplings started 2 weeks before A.I. and were carried out every 15 dd until 45 dd of gestation; thereafter, blood samples were obtained weekly until 1 month post-partum. Leptin plasma levels were measured by the Linco Multi-Species Leptin Assay Kit; total RNA was extracted from placental tissue and RT-PCR was carried out with specific primers. Maternal leptin levels significantly (p<0.05) increased during the last third of gestation; they weren’t related with neither piglet number nor weight. Results of RT-PCR studies evidenced the expression of both leptin and receptor long (but not short) form; the long form had been predicted to be the predominantly functional receptor. The co-presence of hormone and receptor in the same organ implies a possible autocrine/paracrine effect. These results suggest that leptin may be involved in placental endocrine function
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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