203 resultados para Suckling


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Mode of access: Internet.

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Mode of access: Internet.

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"The ... work was not completed."--Dict. of nat. biog.

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We have previously developed replicon vectors derived from the Australian flavivirus Kunjin that have a unique noncytopathic nature and have been shown to direct prolonged high-level expression of encoded heterologous genes in vitro and in vivo and to induce strong and long-lasting immune responses to encoded immunogens in mice. To facilitate further applications of these vectors in the form of virus-like particles (VLPs), we have now generated a stable BHK packaging cell line, tetKUNCprME, carrying a Kunjin structural gene cassette under the control of a tetracycline-inducible promoter. Withdrawal of tetracycline from the medium resulted in production of Kunjin structural proteins that were capable of packaging transfected and self-amplified Kunjin replicon RNA into the secreted VLPs at titers of up to 1.6 x 10(9) VLPs per ml. Furthermore, secreted KUN replicon VLPs from tetKUNCprME cells could be harvested continuously for as long as 10 days after RNA transfection, producing a total yield of more than 1010 VLPs per 106 transfected cells. Passaging of VLPs on Vero cells or intracerebral injection into 2- to 4-day-old suckling mice illustrated the complete absence of any infectious Kunjin virus. tetKUNCprME cells were also capable of packaging replicon RNA from closely and distantly related flaviviruses, West Nile virus and dengue virus type 2, respectively. The utility of high-titer KUN replicon VLPs was demonstrated by showing increasing CD8(+)-T-cell responses to encoded foreign protein with increasing doses of KUN VLPs. A single dose of 2.5 x 10(7) VLPs carrying the human respiratory syncytial virus M2 gene induced 1,400 CD8 T cells per 10(6) splenocytes in an ex vivo gamma interferon enzyme-linked immunospot assay. The packaging cell line thus represents a significant advance in the development of the noncytopathic Kunjin virus replicon-based gene expression system and may be widely applicable to the basic studies of flavivirus RNA packaging and virus assembly as well as to the development of gene expression systems based on replicons from different flaviviruses.

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This study used supplementary feeding to test the hypothesis that fuel partitioning during the postweaning fast in grey seal pups is affected by size and composition of energy reserves at weaning, and by extra provisioning. Mass and body composition changes were measured during suckling and fasting to investigate the effect of natural differences in energy reserves at weaning on subsequent allocation of fat and protein to energy use. We fed seven pups for 5 days after weaning, to investigate the effect of increased fuel availability, and particularly protein, on fuel utilisation. After correcting for protein used during the moult, the proportional contribution of fat was 86–99% of total energy use. Pups with greater energy reserves, i.e. those that were heavier and fatter at weaning, had higher rates of fat and energy use. There was no significant relationship between adiposity at weaning and proportional contribution of fat to energy use, perhaps due to a limited sample size or range of body masses and adiposity. Supplemented individuals used energy, specifically fat, much faster and utilised proportionally less of their endogenous protein by departure than non-supplemented individuals. Fat metabolism contributed a similar percentage to daily energy use in both groups. These findings show that pups spare protein, even when energy use is dramatically increased. Pups that receive greater maternal provisioning and lay down more protein may have increased survival chances at sea. This study highlights the importance of protein reserves in first year survival of grey seal pups.

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Milk contains numerous bioactive substances including immunoglobulins, cytokines, growth factors and components that exert antibiotic and prebiotic activity (Field, 2005). Little is known about the biological effects of individual milk bioactives, despite the fact that natural milk improves intestinal development and immune system functions in neonates (Donovan et al., 1994; Field, 2005) relative to milk formula. Characterization of the biological effects of such components is important for optimal production of infant milk formulas to be used when mother’s milk is not available. Milk components with preliminary evidence of positive effects on the intestinal growth and mucosal immunity include osteopontin (OPN). Osteopontin is a phosphorylated acidic glycoprotein expressed by a number of different immune and non-immune cells and tissues (Sodek et al., 2000). It is also present in body fluids including blood, bile and milk (Sodek et al., 2000). Osteopontin is a multifunctional protein that is implicated in a wide number of biological processes including cell survival, bone remodeling, and immune modulatory functions (Sodek et al., 2000). Furthermore, Schack and colleagues (2009) demonstrated that the concentration of OPN in human milk is considerably higher than in bovine milk and infant formulas. Taken together, it is likely that OPN plays a role in the early development of gastrointestinal tract and mucosal immune responses in infants. Since the neonatal pig shares anatomical, physiological, immunological, and metabolic similarities with the human infants (Moughan, et al., 1992), they were selected as the animal model in our studies. Our first aim was to investigate the effects of OPN on piglet intestinal development. Newborn, colostrum-deprived piglets (n=27) were randomized to receive three treatments: formula with bovine OPN (OPN; 140 mg/L); formula alone (FF); or sow reared (SR) for 21 days. Body weight, intestinal weight and length, mucosal protein and DNA content, disaccharidase activity, villus morphology, and crypt cell proliferation were measured. Statistical significance was assigned at P<0.05. No significant effects of OPN were observed for body weight, intestinal weight and length. Mucosal protein content of SR piglets was lower than FF and OPN piglets in the duodenum, but higher than FF and OPN piglets in the ileum. No significant effects of diet in mucosal DNA content were detected for the three regions of the small intestine. Lactase and sucrase activities of SR piglets were higher than the two formula-fed groups in the duodenum, lower in the ileum. No significant effects of diet on lactase and sucrase activities were noted between two formula-fed groups in the duodenum and ileum. Jejunal lactase activity of FF piglets was higher than SR piglets, whereas no significant effect of diet was observed in jejunal sucrase activity among the three groups. Duodenal and ileal villus height and villus area of SR piglets were lower than two formula-fed groups, while OPN piglets did not differ from FF piglets. There was a significant effect of diet (P<0.0001) on jejunal crypt cell proliferation, with proliferation in OPN piglets being intermediate between that of FF and SR. In summary, supplemental OPN increased jejunal crypt cell proliferation, independent of evident morphological growth, and had a minor impact on disaccharidase activity in the small intestine of neonatal piglets. Rotavirus (RV) is the most common viral cause of severe gastroenteritis in infants and young children worldwide (Parashar et al., 2006). Maeno et al. (2009) reported that OPN knockout (OPN-KO) suckling mice were more susceptible to RV infection compared to wild-type (WT) suckling mice. To detect the role of OPN in intestinal immune responses of neonates, the goal of the second study was to evaluate whether supplemental OPN influenced the serum antibody responses to RV vaccination in neonatal piglets. Newborn, colostrum-deprived piglets were randomized into two dietary groups: formula with bovine OPN (OPN; 140 mg/L) and formula alone (FF) for 35 days. On d7, piglets in each dietary group were further randomized to receive rotavirus (RV) vaccination (Rotarix®) (FF+RV and OPN+RV) or remained non-vaccinated (FF+NV and OPN+NV). Booster vaccination was provided on d14. Blood samples were collected on d7, 14, 21, 28 and 35. RV-specific serum immunoglobulin (Ig) G, IgA, IgM and total serum IgG, IgA, IgM were measured by ELISA. Statistical significance was assigned at P<0.05, with trends reported as P<0.10. Body weight gain was unaffected by diet and/or vaccination. No significant effect of oral OPN supplementation was observed for RV-specific antibody responses and total Igs levels. After the combination of dietary groups, RV piglets had significantly higher RV-specific IgM concentrations compared to NV piglets. Although there were higher means of RV-specific IgG and RV-specific IgA concentrations in RV group than their counterparts in NV group, the difference did not reach statistical significance. RV-specific IgM reached a peak at d7 post booster vaccination (PBV), whereas the RV-specific IgG and IgA peaked later at PBV 14 or 21. Total Igs were unaffected by RV vaccination but were significantly increased over time, following similar pattern as RV-specific Igs. In summary, neonatal piglets generated weak antibody responses to RV vaccination. Supplemental OPN did not enhance RV-specific serum antibody responses and total serum Igs levels in neonatal piglets with or without RV vaccination. In conclusion, we observed normal developmental changes in the small intestine and serum Igs levels in neonatal piglets over time. Oral OPN supplementation showed minimal impacts on intestinal development and no effect on serum Igs levels. The role of supplemental OPN on the growth and development of infants is still inconclusive. Future studies should measure other physiological and immunological parameters by using different models of vaccination or infection.

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Seventy-one mature Brangus cows, 38 nonlactating (NL) and 33 in late stage of lactation (L) were fed for 192 days (Phase I) a low energy diet (L). During Phase II (65 days) 19 NL and 17 L cows were fed a high energy diet (H). The other nonlactating (19) and lactating (16) cows remained on the low energy diet. Energy restriction during Phase I did not affect (P> 0.05) cyclic ovarian activity although losses in body weight and condition were substantial. Rapid changes in body weight, condition, and percent empty body lipe (EBLP) during Phase II did not substantially influencefertility, although a five-fold difference in EBLP was observed (NL0H vs. L-L). Treatment groups did not differ (P> 0.05) in conception rate, days from the beginning of the breeding season to breeding and to conception, conception at first service, and number of services per conception. Values observed for these parameters for NL-H, L-H, NL-L, and L-L groups were respectively: 68,4%, `3,.2, 23.3, 36.8% and 1.68; 82,4% 12.7, 19.5, 58.8% and 1.29; 68.4%, 10.2, 17.4, 47.4%, and 1.41; 68.8%, 12.4, 19.5, 43.7%, and 1.50.