Готові списки джерел за темами / Bovine growth

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Добірка наукової літератури з теми "Bovine growth"

Автор: Grafiati
Опубліковано: 22 березня 2024

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Статті в журналах з теми "Bovine growth"

1

Lonergan, P. "Growth of Preimplatation Bovine Embryos." Acta Veterinaria Scandinavica 35, no. 4 (December 1994): 307–20. http://dx.doi.org/10.1186/bf03548303.

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2

BONINO, M. J. BISCOGLIO DE JIMENEZ, O. CASCONE, and J. A. SANTOMÉ. "TRINITROPHENYLATION OF BOVINE GROWTH HORMONE." International Journal of Peptide and Protein Research 14, no. 2 (January 12, 2009): 107–12. http://dx.doi.org/10.1111/j.1399-3011.1979.tb01733.x.

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3

FUKUSHIMA, J. G., M. J. BISCOGLIO DE JIMENEZ BONINO, O. CASCONE, and J. A. SANTOMÉ. "Ethoxyformylation of bovine growth hormone." International Journal of Peptide and Protein Research 21, no. 4 (January 12, 2009): 451–57. http://dx.doi.org/10.1111/j.1399-3011.1983.tb03126.x.

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4

Ahmad, SyedRizwanuddin. "USA: Bovine growth hormone update." Lancet 340, no. 8822 (September 1992): 782. http://dx.doi.org/10.1016/0140-6736(92)92313-5.

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5

Baird, Andre, Frederick S. Esch, Peter Bohlen, Deni Gospodarowicz, and Nicholas C. Ling. "4956455 Bovine fibroblast growth factor." Progress in Growth Factor Research 2, no. 4 (January 1990): 249. http://dx.doi.org/10.1016/0955-2235(90)90022-c.

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6

Ahmad, SyedRizwanuddin, and Vivien Choo. "Bovine growth hormone and mastitis." Lancet 341, no. 8851 (April 1993): 1018–19. http://dx.doi.org/10.1016/0140-6736(93)91098-7.

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7

Gabinaitiene, A., J. Siugzdaite, H. Zilinskas, R. Siugzda, and S. Petkevicius. "Mycoplasma bovis and bacterial pathogens in the bovine respiratory tract." Veterinární Medicína 56, No. 1 (February 8, 2011): 29–35. http://dx.doi.org/10.17221/1572-vetmed.

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Bovine respiratory disease caused by Mycoplasma bovis is a major health problem of cattle worldwide. It inflicts considerable financial losses on beef herds and is the most common cause of mortality in dairy cattle. Bacteriological examination of 35 nasal cavity samples from calves younger than three months of age identified Mycoplasma bovis in eight (22.9%) samples. These cattle were followed until 17 months of age, and repeated examination of nasal cavity samples before necropsy identified Mycoplasma bovis in four (11.4%) samples. At necropsy and lung samples for bacteriological and histological examination were collected. To identify microorganisms from the Mollicutes class isolated from the nasal cavities of cattle we used the PCR method. Furthermore, Mycoplasma bovis was identified on the grounds of biochemical characteristics and by the disk growth inhibition test. The organism was found in 5.7% of calves younger than three months of age in combination with Pasteurella spp. Mycoplasma bovis in combination with Pasteurella multocida and Mannheimia haemolytica was isolated from 5.7% and 2.9% of cattle at 17 months. However, Pasteurella multocida was common in cattle at 17 months and Mannheimia haemolytica was isolated from both age groups of cattle. Histopathological examination of lung samples revealed broncho-interstitial pneumonia in 14.3% of samples. Mycoplasma bovis was isolated from 60.0% of broncho-insterstitial pneumonia cases. The organism was isolated more frequently from the group of calves rather than from the cattle group (P < 0.05). The most common bacterial agents were Pasteurella multocida and Mannheimia haemolytica.
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8

Burton, Jeanne L., Brian W. McBride, Elliot Block, David R. Glimm, and John J. Kennelly. "A review of bovine growth hormone." Canadian Journal of Animal Science 74, no. 2 (June 1, 1994): 167–201. http://dx.doi.org/10.4141/cjas94-027.

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Unprecedented numbers of technical papers, abstracts, and short communications have been published in the past decade regarding the effects of exogenous bovine growth hormone on milk production, health, and reproductive efficiency of treated dairy cows. In well-managed dairy herds, exogenous growth hormone increases milk production without altering normal variability in milk composition. This has held true regardless of dairy breed tested, geographical location studied, or feeding management system used. Also consistent across studies is the rapidity of the galactopoietic effect of administered bovine growth hormone, which arises from altered partitioning and use of post-absorptive nutrients and increased synthetic capacity of the mammary gland. Growth hormone and its associated peptide, insulin-like growth factor-I, are now known to provide chronic lipolytic, diabetogenic, and gluconeogenic signals to target tissues culminating in increased mammary gland availability of glucose and nonesterified fatty acids. Together with yet ill-defined effects on mammary secretory tissue, this homeorhetic control of metabolism elicited by exogenous growth hormone is so efficient that treated cows are not more susceptible to metabolic disorders than untreated cows. However, some studies have reported an increased frequency of mastitis in groups of treated cows. This has been attributed mainly to increased milk volume in the mammary glands of treated cows and no convincing data are available that show decreased mammary gland immunity as a result of growth hormone treatments. On the contrary, an expanding body of evidence implicates growth hormone as a key neuroendocrine factor that is required for immunological competence. Trends of decreased reproductive efficiency in cows treated with growth hormone have also been reported, but available data imply that this is probably an indirect effect via prolonged negative energy balance in cows treated in early lactation rather than a direct negative effect on estrous cycling via altered reproductive hormone profiles. The objectives of the present review are to bring into focus and summarize pertinent biological discoveries regarding the treatment of dairy cows with recombinant bovine growth hormone, and to explore areas where additional growth hormone research is needed or warranted. Key words: Growth hormone, somatotropin, dairy cows, insulin-like growth factor-I
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Karpatkin, R. H., and E. Groth. "Another look at bovine growth hormone." Environmental Health Perspectives 102, no. 12 (December 1994): 1006. http://dx.doi.org/10.1289/ehp.941021006a.

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10

Hart-Elcock, Laura, R. D. Baker, and H. W. Leipold. "Growth of the Early Bovine Fetus." Journal of Veterinary Medicine Series A 37, no. 1-10 (February 12, 1990): 294–99. http://dx.doi.org/10.1111/j.1439-0442.1990.tb00908.x.

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Дисертації з теми "Bovine growth"

1

Liu, Qing-Ming. "A novel growth promoting activity in bovine milk." Thesis, University of Liverpool, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250434.

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2

Lott, Whitney Meghan. "Influence of Growth Factors on Bovine Embryo Development." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/34481.

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Many attempts have been made to improve the in vitro production of cattle embryos by refining in vitro maturation (IVM) and culture systems. Cysteine supplementation to IVM media of bovine oocytes increases cellular glutathione production, which reduces reactive oxygen species (ROS). Similarly, beneficial effects of growth factors for improving the rate of blastocyst development have been reported, but combined effects are unknown. This study was conducted to determine the additive effect of the antioxidant cysteine with epidermal growth factor (EGF) and/or insulin-like growth factor-I (IGF-I) on subsequent embryo development. Bovine oocytes from slaughterhouse ovaries were matured in TCM-199 (control), with or without the addition of 0.6 mM cysteine (C) at 0 or 12 h of maturation. After in vitro fertilization, embryos were allocated to culture treatments containing synthetic oviductal fluid medium. Culture treatments included fetal calf serum (FCS, 4%) alone; IGF-I (100 ng/mL); EGF (10 ng/mL); and IGF-I+EGF (100 ng/mL+10 ng/mL) for all IVM treatments. Although rates for blastocysts development were not different among treatments, an increased proportion of embryos attaining morula formation was achieved when cysteine was added to the IVM media (12 h C IGF-I+EGF, 41.4%; 0 h C EGF, 40.0%) as compared to control (FCS: 34.6%). When cysteine treatments were combined, percent cleavage was greater for IGF-I+EGF (70.8%) compared to FCS (61.2%). The abundance of mRNA from the apoptotic genes, Bax and Bcl-2, and the oxidative stress genes, copper (Cu)-zinc (Zn) superoxide dismutase (SOD; SOD1) and manganese (Mn) SOD (SOD2) in embryos was assessed. No significant treatment effect was observed on the expression of apoptotic and oxidative stress genes. Bax was expressed strongly (4-fold) in morulae with the addition of IGF-I, but was less prevalent in all other morula and blastocyst groups relative to FCS. There was slightly less expression of both SOD1 and SOD2 with treatments compared to FCS in morulae and blastocysts, indicative of low mitochondrial activity and/or a low level of oxidative stress in treatments. There was no significant treatment effect on total cell number, apoptotic nuclei, or apoptotic index. In conclusion, supplementation of cysteine during IVM of oocytes, in conjunction with growth factors could effectively be used as a replacement for FCS.
Master of Science
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3

Greene, Elizabeth Ann 1964. "The effects of growth factors on bovine satellite cells." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277202.

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This study examined the effects of basic fibroblast growth factor (bFGF), insulin-like growth factor I (IGF-I) and transforming growth factor beta (TGF-β) on the proliferation and differentiation of bovine satellite cells (BSC) in vitro. Cells were treated with serum-free defined media containing varying concentrations of bFGF, IGF-I and TGF-β. On day 3 of treatment total cell nuclei and myotube nuclei were determined. bFGF stimulated BSC proliferation in a dose-dependent fashion with half-maximal stimulation observed at a concentration of 5 ng/ml (p < .05). Similar results were found for IGF-I and TGF-β in the presence of FGF, with half-maximal stimulation observed at 5 ng/ml and 1 ng/ml, respectively. With regard to differentiation, TGF-beta inhibited myotube formation at concentrations above 0.05 ng/ml. IGF-I stimulated myotube formation at concentrations as low as 10 ng/ml (p < .05). These results demonstrate that proliferation and differentiation of BSC in vitro are affected by growth factors, and consequently, similar effects may be found in vivo. This information may prove to be useful in future methods of manipulating muscle growth in vivo.
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4

Stiening, Chad Michael. "GENOMIC REGULATION OF BOVINE MAMMARY EPITHELIAL CELL GROWTH AND DIFFERENTIATION." Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1252%5F1%5Fm.pdf&type=application/pdf.

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5

Rawlings, Stephen Roy. "Intracellular mechanisms regulating growth hormone release from the bovine somatotroph." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315241.

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6

Sun, Qiang. "Alternative splicing of bovine growth hormone pre-mRNA in vitro." Case Western Reserve University School of Graduate Studies / OhioLINK, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=case1058216813.

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7

Beswick, Naomi Simone. "The influence of recombinant bovine growth hormone and growth hormone releasing factor on fat synthesis in primiparous Holstein cows." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/mq22570.pdf.

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8

Ingram, C. D. "Cellular control of bovine prolactin and growth hormone secretion in vitro." Thesis, University of Cambridge, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373664.

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9

Hampton, James Howard. "Luteinizing hormone modulation of bovine ovarian follicular growth, selection and pathology /." free to MU campus, to others for purchase, 2003. http://wwwlib.umi.com/cr/mo/fullcit?p3101022.

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10

Woad, Kathryn Jane. "The insulin-like growth factor system in the bovine corpus luteum." Thesis, University of Edinburgh, 2001. http://hdl.handle.net/1842/23270.

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Bovine CL were collected on days 5, 10, and 15 of the oestrous cycle following synchronised oestrus. In addition, CL were collected following prostaglandin-induced luteolysis. In situ hybridisation detected luteal expression of IGF-I, -II and the type 1 IGF receptor mRNA throughout the oestrous cycle. IGF-I mRNA concentrations varied significantly during the cycle, increasing from low levels in the early luteal phase (day 5) to high levels in the late luteal phase (day 15). Concentrations were maximal 48 hours after exogenous prostaglandin. In contrast, there was no significant effect of day of the oestrous cycle on IGF-II and the type 1 IGF receptor mRNA concentrations in the corpus luteum. IGF-II mRNA expression was localised to a subset of steroidogenic luteal cells and was also associated with cells of the luteal vasculature. In addition, the relative abundance of IGF-II mRNA was greater than that of IGF-I mRNA. mRNA encoding the type 1 IGF receptor was widely expressed, in a pattern suggestive of large and small luteal cell expression. The actions of the IGFs are modulated by their association with members of a family of IGF-specific binding proteins (IGFBPs), which regulate the transport of IGFs and their presentation to specific receptors. In situ hybridisation detected mRNA encoding IGFBP-2, -3, and -4 in the bovine corpus luteum throughout the luteal phase. IGFBP-2 and -4 mRNA concentrations were low within the corpus luteum, and showed no temporal variation. In addition, a subset of large vessels in the periphery of the CL showed moderate to intense hybridisation for IGFBP-2 mRNA. IGFBP-3 mRNA concentrations were high throughout the luteal phase, and expression was localised to small luteal cells and cells of the luteal vasculature. These data demonstrate for the first time that the bovine CL is a site of IGF production, reception and regulation, and further support the hypothesis that the IGF system is important in regulating luteal function in the cow.
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Книги з теми "Bovine growth"

1

Corey, Beverly. Bovine growth hormone: Harmless for humans. [Rockville, Md: Dept. of Health and Human Services, Public Health Service, Food and Drug Administration, Office of Public Affairs, 1990.

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2

Bisaro, Rita. Bovine growth hormone and the dairy industry. Beltsville, Md: U.S. Dept. of Agriculture, National Agricultural Library, 1986.

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3

Larson, Jean A. BST-bovine growth hormone: January 1991 - December 1993. Beltsville, Md: National Agricultural Library, 1994.

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4

Larson, Jean A. BST-bovine growth hormone: January 1987 - January 1992. Beltsville, Md: National Agricultural Library, 1992.

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5

Larson, Jean A. BST-bovine growth hormone: January 1991 - December 1993. Beltsville, Md: National Agricultural Library, 1994.

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6

Larson, Jean A. BST-bovine growth hormone: January 1991 - December 1993. Beltsville, Md: National Agricultural Library, 1994.

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7

Larson, Jean A. BST-bovine growth hormone: January 1991 - December 1993. Beltsville, Md: National Agricultural Library, 1994.

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8

Larson, Jean A. BST-bovine growth hormone: January 1987 - January 1992. Beltsville, Md: National Agricultural Library, 1992.

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9

Larson, Jean A. BST-bovine growth hormone: January 1991 - December 1993. Beltsville, Md: National Agricultural Library, 1994.

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10

Larson, Jean A. BST-bovine growth hormone: January 1987 - January 1992. Beltsville, Md: National Agricultural Library, 1992.

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Частини книг з теми "Bovine growth"

1

Nagaune, Shinichi, and Shuichi Kaminogawa. "Cell Growth Regulatory Peptides from Bovine Casein." In Animal Cell Technology: Developments Towards the 21st Century, 271–75. Dordrecht: Springer Netherlands, 1995. http://dx.doi.org/10.1007/978-94-011-0437-1_42.

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2

Rottman, Fritz, Sally Camper, Edward Goodwin, Robert Hampson, Robert Lyons, Dennis Sakai, Richard Woychik, and Yvonne Yao. "Structure and Regulated Expression of Bovine Prolactin and Bovine Growth Hormone Genes." In Advances in Experimental Medicine and Biology, 281–99. Boston, MA: Springer US, 1986. http://dx.doi.org/10.1007/978-1-4684-5209-9_13.

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3

Lobb, Derek K., and Jennifer H. Dorrington. "Bovine Thecal Cells Secrete Transforming Growth Factor α and β." In Growth Factors and the Ovary, 199–203. Boston, MA: Springer US, 1989. http://dx.doi.org/10.1007/978-1-4684-5688-2_19.

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4

Winer, Martin A., and Roy L. Ax. "Heparin-Binding Proteins in Purified Plasma Membranes of Bovine Granulosa Cells." In Growth Factors and the Ovary, 309–13. Boston, MA: Springer US, 1989. http://dx.doi.org/10.1007/978-1-4684-5688-2_37.

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5

Hook, Vivian Y. H., Anahit V. Azaryan, and Timothy J. Krieger. "Proteases for Neuropeptide Precursor Processing in Bovine Adrenal Medullary Chromaffin Granules." In Growth Factors, Peptides and Receptors, 61–70. Boston, MA: Springer US, 1993. http://dx.doi.org/10.1007/978-1-4615-2846-3_7.

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6

Miretti, Silvia, Isabella Manenti, Paola Toschi, Elisabetta Macchi, Eugenio Martignani, Paolo Accornero, and Mario Baratta. "Bovine Skeletal Muscle Satellite Cells: Isolation, Growth, and Differentiation." In Methods in Molecular Biology, 165–74. New York, NY: Springer US, 2023. http://dx.doi.org/10.1007/978-1-0716-3609-1_15.

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7

Chegini, N., Z. M. Lei, and C. V. Rao. "Light and Electron Microscope Immunocytochemical Localization of Epidermal Growth Factor Receptors in Bovine Corpora Lutea of Pregnancy." In Growth Factors and the Ovary, 213–20. Boston, MA: Springer US, 1989. http://dx.doi.org/10.1007/978-1-4684-5688-2_22.

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8

Kopchick, John J., Francoise Pasleau, and Frederick C. Leung. "Expression of the Bovine Growth Hormone Gene in Cultured Rodent Cells." In Genetic Engineering of Animals, 19–37. Boston, MA: Springer US, 1986. http://dx.doi.org/10.1007/978-1-4684-5110-8_5.

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9

Deng, Chun Lin, Ying Jun Wang, Ji Yong Chen, Hua De Zheng, Hu Chen, De Gui Zhang, and Xing Dong Zhang. "Growth of Apatite in Bovine Serums on Porous HA/TCP Ceramics." In High-Performance Ceramics V, 1184–86. Stafa: Trans Tech Publications Ltd., 2008. http://dx.doi.org/10.4028/0-87849-473-1.1184.

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10

Pettmann, B., C. Gensburger, M. Weibel, F. Perraud, M. Sensenbrenner, and G. Labourdette. "Isolation of Two Astroglial Growth Factors From Bovine Brain; Comparison with Other Growth Factors; Cellular Localization." In Glial-Neuronal Communication in Development and Regeneration, 451–78. Berlin, Heidelberg: Springer Berlin Heidelberg, 1987. http://dx.doi.org/10.1007/978-3-642-71381-1_28.

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Тези доповідей конференцій з теми "Bovine growth"

1

Williams, John L., Pat D. Do, and Thomas L. Schmidt. "Tensile Properties of Bovine Proximal Tibial Growth Plate Cartilage." In ASME 1998 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/imece1998-0132.

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Abstract Seventy-one microtensile samples of bone-cartilage-bone from the lateral, central and medial portions of the proximal tibial growth plate were tested to failure at three speeds. Tensile strength, toe modulus, tangent modulus, and strain energy density varied by both location and strain rate, being stronger and stiffer on the lateral side and at higher strain rates. No differences could be detected in the ultimate strains by either region or strain rate.
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2

Hage, Ilige S., and Ramsey F. Hamade. "Distribution of Porosity in Cortical (Bovine) Bone." In ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-51703.

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Pores (namely lacunae, clusters of canaliculi, Haversian canals, and resorption cavities) are present throughout cortical bone. This paper characterizes the area fraction (AF, %)) of each type of these pores as function of distance from the bone’s geometric center while noting the region in which such pores are located: midcortical or periosteal. Optical slides (at 20X) are taken from 2 cortical bone biopsies named bone 1 and bone 2 and cut at mid-diaphysis femur from 2 different (about 2 year-old) bovine cows. The slides are collected from posterior (pericortical) and anterior (intracortical) locations. The area of each of these biopsies is about 2.5mm × 3mm located near the outer cortex of the bone. In polar coordinates from the bone’s center, the areas cover radial distance of about 3.3 mm (of radius, R) and encompass an arc of 10°. Automated segmentation is used to locate and identify all pores in the optical slides the shapes of which are best fitted into ellipses. Values of area fraction, AF (%) of said fitted ellipses are then automatically calculated in secondary osteons for both regions. Variations in values of area fraction AF (%) are related to actual areas of pores (based on their defining equations). Observations suggest that area fractions (%) of all pores (but to lesser degree for Haversian canals), to significantly decrease linearly and in a steep fashion with R (statistically significant, p < 0.01) in the anterior region where osteonal growth is expected to have continued to develop. However, in the posterior region where osteonal growth appears to have matured, area fraction (%) values seem to have reached a steady state resulting in fairly flat behavior versus R. All observations are equally applicable for biopsies collected from bone 1 and bone 2.
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Hoshikawa, N., H. Niino, J. Imura, Y. Ashihara, and K. Shirasawa. "CHEMOTAXIS OF POLYMORPHONUCLEAR LEUKOCYTES BY VASCULAR PERMEABILITY FACTOR FROM BOVINE PLATELETS." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643164.

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Bovine platelet a-granule acid extract (BPAE) contains vascular permeability factor (VPF) as human platelets. VPF plays as a mediator depending on polymorphonuclear (PMN) leukocytes and possesses a potent cell growth activity in cultured fibroblasts. This study was carried out to examine the chemotactic activity of VPF for PMN leukocytes of rabbits. For the study of chemotaxis, the PMN leukocytes were collected from the ascites after production by an injection of 0.1% oyster glycogen in 0.85% NaCl solution into the peritoneal cavity of rabbits. They were suspended in the Gey's balanced salt solution with supplementation of 2% human albumin. Partial purification of BPAE was performed by gel filteration using Sephadex G-50 so as to exclude the influence of PF-4 and 8-TG. BPAE, as the attractant solution, was prepared at the several concentration in the Gey's solution. Human serum activated with zymosan was used as the positive control. Effects of protamine sulfate, a competitive inhibitor of platelet-derived growth factor (PDGF), on the chemotactic activity of VPF were also studied. Chemotaxis of the PMN leukocytes was measured in the modified Boyden chamber with a 3jJm-pore filter. Five high power (x400) grids were counted per filter and cell migration was corrected by subtraction of blanks in which the lower compartment contained medium only. The most striking chemotactic response was obtained when BPAE was used at the concentration of 0.1μg/ml. However, the response was reduced at the concentration of more than 1μg/ml. The activity of BPAE (0.1μg/ml) was about 60% of the positive control level. The migration was reduced to 18% of the positive control by protamine sulfate (3μg/ml) at that concentration of BPAEIt is concluded that VPF induces chemotaxis to PMN leukocytes at the concentration lesser than that enhancing the vascular permeability response. Furthermore, protamine sulfate inhibits the VPF-induced migration of PMN leukocytes. Those findings may indicate that VPF acts as PDGF in function. Therefore, it is likely that the factor attracts PMN leukocytes and promotes cell growth in the inflamed region
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4

Khandaker, M., S. Ekwaro-Osire, and F. Afrin. "Evaluating the Crack-Tip Bridging Stress in a Bovine Cortical Bone." In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-43764.

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Recent experimental studies on human and bovine cortical bone shows that fracture strength of a cortical bone cannot be characterized by a single value of fracture toughness, but rather by variable crack growth resistance values. The mechanism of resistance of a crack extension in a bone is generally defined by R-curve behavior, which can be expressed as the relation between crack growth resistance values and crack extension. Crack bridging stress in front of a crack has been shown to be the main source of this resistance of the bone crack extension. The calculation of this bridging stress is important for predicting fracture stress in cortical bone material. In this study, a theoretical model based on weight function was developed to evaluate the bridging stress in front of a cortical bone crack tip. The main goal of this research was to investigate the role of specimen orientation on bridging stress. The hypothesis used was that specimen orientation has significant influence on the bridging stress. Two specific aims are developed to support this hypothesis: determination of the bridging stress along a crack length and investigation of the orientation effect on bridging stress. A weight function formulation was used to calculate crack opening displacements. The bridging stress along a crack can be found by minimizing the experimental and calculated crack opening displacements using a least square formulation. Finally, the bridging stress variation along a crack extension was examined in the specimen along two different orientations. The developed analytical model produces a gradually increasing trend of bridging stress with crack extension which depends on the orientation of the specimen extraction.
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5

Mimuro, Jun, та David J. Loskutoff. "EFFECT OF TRANSFORMING GROWTH FACTORβ(TGFβ) ON THE FIBRINOLYTIC SYSTEM OF CULTURED BOVINE AORTIC ENDOTHELIAL CELLS (BAEs)". У XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644446.

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TGFβ influences cell growth and differentiation in a variety of normal and transformed cells and was recently shown to have growth inhibitory activity toward cultured endothelium. The fibrinolytic activity of endothelial cells changes dramatically with their growth state. Experiments were thus performed to determine the effect of TGFβ on the fibrinolytic system of these cells. Confluent BAEs were incubated with increasing concentrations of purified human or porcine TGFβ for various times in the presence or absence of serum. Conditioned medium (CM) and extracellular matrix (ECM) were prepared and assayed for tissue-type plasminogen activator (tPA), urokinase-type PA (uPA) and PA inhibitor-1 (PAI-1) by immunological methods and by fibrin and reverse fibrin autography. TGFβ induced a dose and time dependent increase in PAI-1 antigen and activity. The half-maximal effect was observed at 0.5 ng/ml while the maximal effect was at 2-5 ng/ml and resulted in 100-fold increase of PAI-1 in CM and at least a 20-fold increase in ECM. 35S-methionine labeling experiments indicated that these effects (1) could be detected in CM within 3-4 hrs, (2) resulted from an increased rate of synthesis of PAI-1, (3) were also observed following transient exposure (1-2 h) of the cells to TGFβ, and (4) were relatively specific for PAI-1. TGFβ treated cells had normal amounts of tPA activity but greatly reduced levels of uPA activity. Human serum had a synergistic effect on PAI-1 production by these cells, but neither epidermal growth factor nor platelet derived growth factor altered their response to TGFβ. TGFβ also stimulated PAI-1 production by cultured human umbilical vein endothelial cells. The release of TGFβ by platelets may thus suppress the fibrinolytic system of the vascular wall.
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6

Singh, Ankur, Ajay Suri, and Avadhoot Date. "Synergistic Hydrate Inhibition by Bovine Serum Albumin With Kinetic Hydrate Inhibitors." In SPE Canadian Energy Technology Conference and Exhibition. SPE, 2023. http://dx.doi.org/10.2118/212781-ms.

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Abstract Using kinetic hydrate inhibitors (KHIs) can be technically and economically an ideal solution to achieving deep-sea hydrate risk management, but biodegradability requirements in many offshore locations, such as the North Sea, can restrict their usage. The problem could be addressed by developing so-called "green hydrate inhibitors." Many natural chemicals have been tested to achieve this goal. However, their performance has not been found to be at par with the non-biodegradable high-performing commercial KHIs. It has been shown by some studies that although natural chemicals cannot perform very well alone, they perform quite well when used as synergists with KHIs, possibly due to their large molecular structures with both hydrophilic and hydrophobic functional groups leading to increased steric hindrance to hydrate formation and their higher molecular viscosity possibly causing a reduction in the gas and water mass transfer rate to the hydrate nucleation sites. Thus, in this study, a protein prevalent in the circulatory system of bovine species called bovine serum albumin (BSA), was tested as a synergist with four KHIs used in academia for research and industry (PVP, PVCap, CKHI-1, and CKHI-2). Due to BSA's biodegradability, biocompatibility and nontoxicity, it is widely employed in the medical sector as a drug delivery agent. Standard constant cooling rate hydrate formation experiments at 1°C/h are performed to measure the induction time (delay in hydrate nucleation) and average hydrate growth rate within 1 hour of hydrate nucleation to evaluate the hydrate-inhibiting performance of various blends made of BSA and the four KHIs. The Induction time (IT) and the average hydrate growth rate (AHGR) delivered by each of the 0.5 wt % of the individual four KHIs are compared with the IT, and AHGR obtained from the blend of 0.25 wt % respective KHI mixed with 0.25 wt % BSA. It was found that the blends made from PVP, PVCap and CKHI-2 provided higher ITs (up to 66% for CKHI-2) and lower AHGRs (down to -60% for CKHI-2) compared to the ITs, and AHGRs obtained from the individual commercial KHIs at the same total dosage of 0.5 wt%. The blend CKHI-1 and BSA gave almost the same IT and AHGR as obtained from CKHI-1 alone. Along with high performance, the blended solutions also provide higher biodegradability as compared to commercial KHIs.
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7

Maciuc, Vasile, Gabriela Amaritii, Mihaela Ivancia, and Razvan Mihail Radu-Rusu. "Studiu privind evaluarea valorii genetice a unui efectiv de bovine dintr-o fermă familială." In Scientific and practical conference with international participation: "Management of the genetic fund of animals – problems, solutions, outlooks". Scientific Practical Institute of Biotechnologies in Animal Husbandry and Veterinary Medicine, 2023. http://dx.doi.org/10.61562/mgfa2023.23.

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The aim of this paper is to predict the improvement value by the BLUP methodology - the Sire Model, of some bulls used to inseminate females exploited in conditions of a farm located in N-W Moldova, Romania. After comparing the main productive characters between ancestry (MT – 5260.22 KG milk) and offspring it was observed that the descendants have a higher average production in LN1, of 5470 kg milk in LN1 and a lower production in LN2, about 5210.14 kg. Even if in the population the value of h2 is 0.64 females do not phenotypically express their genetic potential. We can say that their performances are influenced by environmental factors that primarily relate to the growth technology, fee-ding and the climate in which they grow. Among the bulls for which the estimate of improvement value was made, the one with registration number 53791 has the best improvement value of 451.1825 kg for milk production. This male is a breeder for other traits as well.
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8

Li, Ching-Wen, and Gou-Jen Wang. "Investigation of the Influences of Micro Vibrational Stimuli and Hydrophilicity of a Scaffold on a Bovine Endothelial Cell Culture." In ASME 2010 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/detc2010-28115.

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Both the hydrophilicity of the scaffold and applied sheer stress can influence the growth of cultured cells. In this study, the influences of applied shear stress and the hydrophilicity of the scaffold on the growth of bovine endothelial cells (BEC) were investigated. A piezoelectric micro vibrational stage was used to provide micro vibrational stimuli of different frequencies to generate various sheer stresses. 24-well, biodegradable lactide-co-glycolide (PLGA) scaffolds, and nanostructuresd PLGA scaffolds were used for the cell culturing. From the results of this study, it can be inferred that the vibration induced sheer stress can effectively enhance BEC growth as long as the corresponding sheer force is less than the adhesive force between a cell and the scaffold. It is also suggested that micro vibration stimulus may be a more cost and time effective solution than the nanostructured scaffold approach for the enhancement of BEC growth.
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9

Moore, Tara L. Arthur, and Lorna J. Gibson. "The Effect of Number of Cycles on Microdamage Accumulation in Bovine Trabecular Bone." In ASME 2001 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/imece2001/bed-23026.

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Abstract Microdamage, in the form of small cracks, exists in healthy bone. Microdamage can be created by an overload or by repetitive motion (fatigue) during daily activities. Usually, microdamage is repaired during bone remodeling and a steady state is maintained. However, in cases of excessive microdamage creation or slowed bone remodeling, microdamage can coalesce to create a fracture. Our previous work [1,2] has investigated microdamage accumulation with increasing strain in bovine trabecular bone loaded in monotonic compression and compressive fatigue. Specimens fatigued at relatively high load levels fail after a few loading cycles, while specimens fatigued at lower load levels may undergo thousands of cycles before failure. During high cycle fatigue, microdamage may accumulate by the growth of pre-existing microcracks, as well as by the crack initiation seen in low cycle fatigue.
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10

Long, Marianna M., John Bradford Bishop, Lawrence J. DeLucas, Tattanhalli L. Nagabhushan, Paul Reichert та G. David Smith. "Protein crystal growth in microgravity review of large scale temperature induction method: Bovine insulin, human insulin and human α-interferon". У AIP Conference Proceedings Volume 387. ASCE, 1997. http://dx.doi.org/10.1063/1.52064.

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Звіти організацій з теми "Bovine growth"

1

Bremel, Robert D., and Arieh Gertler. Effect of Bovine Placental Lactogen and other Placental Proteins on Growth and Differentiation of Cultured Bovine Mammary Cells. United States Department of Agriculture, September 1986. http://dx.doi.org/10.32747/1986.7566755.bard.

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2

Erdman, Richard, Geoffrey Dahl, Hanina Barash, Israel Bruckental, Avi Shamay, and Anthony Capuco. Management Strategies to Maximize Skeletal Growth Rate in Dairy Heifers. United States Department of Agriculture, July 2002. http://dx.doi.org/10.32747/2002.7695848.bard.

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The objectives of this study were to determine the effects of recombinant bovine somatotropin (bST) and added dietary rumen undegradable protein (RUP) on organ and tissue weights and body composition in growing dairy heifers. A total of 32 Holstein heifers, 3 months of age at the beginning of the study were used in the experiment. Eight heifers were slaughtered at 3 mo of age to determine pre- treatment body composition. The remaining heifers were randomly assigned to treatments (n=6) consisting of 0.1 mg/kg body weight per day of bST and 2% added dietary RUP (dry matter basis) applied in a 2X2 factorial design. A total of six heifers per treatment group (3 each at 5 and 10 mo of age), were slaughtered to determine body composition an organ masses. There was a trend for increased live and empty body weights (EB:W), carcass and non-carcass components for heifers treated with bST or fed RUP. Added RUP increased rumen and reticulum weights whereas administration of bST tended to increase the weights of small and large intestine at 10 months of age by 22 % and 26%, respectively. Spleen, heart, and kidney weights at 10 months of age were increased 36%, 28% and 23% for bST treatments respectively, compared with controls. Rates of ash and protein deposition between 3 and 10 months of age were increased by bST by 7.2 g/d and 28.9 g/d, respectively, while no treatment differences were observed for rates of fat and energy deposition. Bovine somatotropin significantly altered the metabolism of growing heifers in a manner that led to increased protein and ash deposition, and tended to reduce fat percentage, and there was a similar tendency observed with added RUP. This suggests that nutritional and endocrine manipulations could increase growth rates of skeletal and lean tissues without increasing fat deposition in prepubertal dairy heifers.
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3

Testroet, Eric D., Sayane Shome, James M. Reecy, Robert L. Jernigan, Meijun Zhu, Min Du, Stephanie Clark, and Donald C. Beitz. Profiling of the Exosomal Cargo of Bovine Milk Reveals the Presence of Immune- and Growth-modulatory Non-coding RNAs (ncRNA). Ames (Iowa): Iowa State University, January 2018. http://dx.doi.org/10.31274/ans_air-180814-330.

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4

Spiers, Donald, Arieh Gertler, Harold Johnson, and James Spain. An In Vitro and In Vivo Investigation of the Diverse Biological Activities of Bovine Placental Lactogen. United States Department of Agriculture, August 1993. http://dx.doi.org/10.32747/1993.7568087.bard.

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In order to understand the structure-function relationship of bovine placental lactogen (bPL) and initiate production of material for in vivo testing, 28 different bPL analogues were prepared by either truncation or site-directed mutagenesis. The effect of these mutations was determined by measuring binding capacity, ability to homodimerize extracellular domains (ECDs) of several lactogenic and somatogenic receptors, and by in vitro bioassays. Two analogues were prepared in large amounts for in vivo studies. These studies (a) identified the residues responsible for the somatogenic activity of bPL (K73, G133, T188) and for both lactogenic and somatogenic activity (N-terminus, K185, Y190); (b) allowed preparation of bPL analogues with selectively abolished or reduced somatogenic activity; and (c) provided a tool to understand the kinetic difference between lactogenic and somatogenic receptors. In vivo studies using rodent and dairy models showed that bovine growth hormone (bGH) is superior to bPL in stimulating growth and lactation. Likewise, bGH has greater somatogenic activity in different age groups and thermal environments. Initial studies of bPL analog T188 suggest that its lactogenic potential is superior to bGH. Effective experimental models have now been developed and tested for analysis of new bPL analogs.
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5

Sordillo, Lorraine, Don Wojchowski, Gary Perdew, Arthur Saran, and Gabriel Leitner. Identification of Staphylococcus aureaus Virulence Factors Associated with Bovine Mastitis. United States Department of Agriculture, February 2001. http://dx.doi.org/10.32747/2001.7574340.bard.

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Staphylococcus aureus is a major cause of mastitis in dairy cattle. The organism is able to adhere to and penetrate mammary epithelium, forming deep seated abscesses that result in chronic infections. This study was based on the observation that certain genotypes of S. aureus are isolated more frequently from field cases of bovine mastitis than others and the most prevalent genotypes of S. aureus have an increased ability to resist neutrophil phagocytosis and killing compared to the rare variants. It was hypothesized that these predominating genotypes differentially express virulence factors that allow them to overcome or suppress essential host defense mechanisms and successfully colonize mammary parenchyma. The overall objective of this study was to determine the mechanisms by which predominating S. aureus genotypes were able to resist mammary gland defense mechanisms. The following specific aims were accomplished to address the overall objectives of this project: 1. Analyze and compare cell surface and secreted protein profiles of common and rare S. aureus genotypes isolated from field cases of bovine mastitis. 2. Purify and sequence selectively synthesized proteins unique to the most prevalent genotypes of S. aureus . 3. Determine the in vitro effects of isolated proteins on essential host defense mechanisms. Results from each specific aim showed that these redominating genotypes differentially express factors that may allow them to overcome or suppress essential host defense mechanisms and successfully colonize mammary parenchyma. Using complementary approaches, both the US and Israeli teams identified differentially expressed S. aureus factors that were positively correlated with virulence as determined by the ability to modify host immune cell responses and increase disease pathogenesis. Several candidate virulence factors have ben identified at both the molecular (US team) and protein (Israeli team) levels. Components of the phosphotransferase system were shown to be differentially expressed in prevalent strains of S. aureus and to modify the growth potential of these strains in a milk microenvironment. Evidence provided by both the Israeli and US teams also demonstrated a potential role of Staphylococcal enterotoxins in the pathogenesis of mastitis. Certain enterotoxins were shown to directly affect neutrophil bactericidal activities which can profoundly affect the establishment of new intramammary infections. Other evidence suggests that S. aureus superantigens can suppress mammary defenses by enhancing lymphoid suppressor cell activity. Collectively, these data suggest that unique factors are associated with predominating S. aureus genotypes that can affect in vitro and in vivo virulence as related to the pathogenesis of bovine mastitis. The potential development of a subunit mastitis vaccine which incorporates only relevant antigenic determinants has not been investigated in depth. Experiments outlined in this proposal has identified putative virulence factors which contribute to the pathogenesis of S. aureus mastitis and which may be used to formulate an efficacious subunit mastitis vaccine. Results from these studies may lead to the development of new methods to prevent this costly disease, providing a viable alternative to less effective mastitis control procedures based on chemotherapy.
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6

Bregendahl, Kristjan, Dong U. Ahn, Darrell W. Trampel, and J. M. Campbell. Dietary Spray-Dried Bovine Plasma Protein Improves Growth Performance and Breast-Meat Yield of Broilers Raised in a High-Antigen Environment. Ames (Iowa): Iowa State University, January 2005. http://dx.doi.org/10.31274/ans_air-180814-1081.

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7

McElwain, Terry, Eugene Pipano, Guy Palmer, Varda Shkap, Stephen Hines, and Douglas Jasmer. Protection of Cattle Against Babesiosis: Immunization with Recombinant DNA Derived Apical Complex Antigens of Babesia bovis. United States Department of Agriculture, June 1995. http://dx.doi.org/10.32747/1995.7612835.bard.

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Bovine babesiosis caused by Babesia bovis continues to be a significant deterrent to global livestock production. Current control methods have both biological and technical drawbacks that have stimulated research on improved methods of vaccination. This BARD project has focused on characterization of candidate Babesia bovis vaccine antigens located in the apical complex, a unique group of subcellular organelles - including rhoptries, micronemes, and spherical bodies - involved in the invation of erythrocytes. Spherical bodies and rhoptries were partially purified and their contents characterized using monoclonal antibodies. Existing and newly developed monoclonal antibodies bound to antigens in the spherical body, rhoptry, merozoite membrane, and infected erythrocyte membrane. In an initial immunization study using biologically cloned strains, it was demonstrated that strain-common epitopes are important for inducing immune protection against heterologous challenge. Rhoptry-associated antigen 1 (RAP-1) had been demonstrated previously to induce partial immune protection, fulfilled criteria of broad interstrain B and T cell epitope conservation, and thus was further characterized. The RAP-1 gene family consists of at least two gene copies, is homologous to the RAP-1 gene family in B. bigemina, and contains significant sequence similarity to other erythroparasitic protozoan candidate vaccine antigens, including the apical membrane antigen of Plasmodium falciparum. A new RAP-1 monoclonal antibody was developed that inhibits merozoite growth in vitro, demonstrating the presence of a RAP-1 neutralization sensitive domain. Based on these observations, cattle were immunized with Mo7 (Mexico) strain recombinant RAP-1 representing one of the two gene copies. All cattle responded with variable levels of serum antibodies inhibitory to heterologous Israel strain merozoite growth in vitro, and RAP-1 specific T lymphocytes that proliferated when stimulated with either homologous or heterologous native parasite antigen. Minimal protection from clinical disease was present after virulent Israel (heterologous) strain B. bovis challenge. In total, the results support the continued development of RAP-1 as a vaccine antigen, but indicate that additional information about the native structure and function of both RAP-1 gene copies, including the relationship of conserved and polymorphic sequences to B and T cell lepitopes relevant for protection, is necessary for optimization of RAP-1 as a vaccine component.
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8

Sela, Shlomo, and Michael McClelland. Investigation of a new mechanism of desiccation-stress tolerance in Salmonella. United States Department of Agriculture, January 2013. http://dx.doi.org/10.32747/2013.7598155.bard.

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Low-moisture foods (LMF) are increasingly involved in foodborne illness. While bacteria cannot grow in LMF due to the low water content, pathogens such as Salmonella can still survive in dry foods and pose health risks to consumer. We recently found that Salmonella secretes a proteinaceous compound during desiccation, which we identified as OsmY, an osmotic stress response protein of 177 amino acids. To elucidate the role of OsmY in conferring tolerance against desiccation and other stresses in Salmonella entericaserovarTyphimurium (STm), our specific objectives were: (1) Characterize the involvement of OsmY in desiccation tolerance; (2) Perform structure-function analysis of OsmY; (3) Study OsmY expression under various growth- and environmental conditions of relevance to agriculture; (4) Examine the involvement of OsmY in response to other stresses of relevance to agriculture; and (5) Elucidate regulatory pathways involved in controlling osmY expression. We demonstrated that an osmY-mutant strain is impaired in both desiccation tolerance (DT) and in long-term persistence during cold storage (LTP). Genetic complementation and addition of a recombinantOsmY (rOsmY) restored the mutant survival back to that of the wild type (wt). To analyze the function of specific domains we have generated a recombinantOsmY (rOsmY) protein. A dose-response DT study showed that rOsmY has the highest protection at a concentration of 0.5 nM. This effect was protein- specific as a comparable amount of bovine serum albumin, an unrelated protein, had a three-time lower protection level. Further characterization of OsmY revealed that the protein has a surfactant activity and is involved in swarming motility. OsmY was shown to facilitate biofilm formation during dehydration but not during bacterial growth under optimal growth conditions. This finding suggests that expression and secretion of OsmY under stress conditions was potentially associated with facilitating biofilm production. OsmY contains two conserved BON domains. To better understand the role of the BON sites in OsmY-mediated dehydration tolerance, we have generated two additional rOsmY constructs, lacking either BON1 or BON2 sites. BON1-minus (but not BON2) protein has decreased dehydration tolerance compared to intact rOsmY, suggesting that BON1 is required for maximal OsmY-mediated activity. Addition of BON1-peptide at concentration below 0.4 µM did not affect STm survival. Interestingly, a toxic effect of BON1 peptide was observed in concentration as low as 0.4 µM. Higher concentrations resulted in complete abrogation of the rOsmY effect, supporting the notion that BON-mediated interaction is essential for rOsmY activity. We performed extensive analysis of RNA expression of STm undergoing desiccation after exponential and stationary growth, identifying all categories of genes that are differentially expressed during this process. We also performed massively in-parallel screening of all genes in which mutation caused changes in fitness during drying, identifying over 400 such genes, which are now undergoing confirmation. As expected OsmY is one of these genes. In conclusion, this is the first study to identify that OsmY protein secreted during dehydration contributes to desiccation tolerance in Salmonella by facilitating dehydration- mediated biofilm formation. Expression of OsmY also enhances swarming motility, apparently through its surfactant activity. The BON1 domain is required for full OsmY activity, demonstrating a potential intervention to reduce pathogen survival in food processing. Expression and fitness screens have begun to elucidate the processes of desiccation, with the potential to uncover additional specific targets for efforts to mitigate pathogen survival in desiccation.
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9

Wolfenson, David, William W. Thatcher, and James E. Kinder. Regulation of LH Secretion in the Periovulatory Period as a Strategy to Enhance Ovarian Function and Fertility in Dairy and Beef Cows. United States Department of Agriculture, December 2003. http://dx.doi.org/10.32747/2003.7586458.bard.

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The general research objective was to increase herd pregnancy rates by enhancing corpus luteum (CL) function and optimizing follicle development, in order to increase conception rate and embryo survival. The specific objectives were: to determine the effect of the duration of the preovulatory LH surge on CL function; to determine the function of LH during the postovulatory period on CL development; to optimize CL differentiation and follicle development by means of a biodegradable GnRH implant; to test whether optimization of CL development and follicle dynamics in timed- insemination protocols would improve fertility in high-yielding dairy cows. Low fertility in cattle results in losses of hundreds of millions of dollars in the USA and Israel. Two major causes of low fertility are formation of a functionally impaired CL, and subsequent enhanced ovarian follicle development. A functionally impaired CL may result from suboptimal LH secretion. The two major causes of low fertility in dairy cattle in US and Israel are negative energy status and summer heat stress; in both situations, low fertility is associated with reductions in LH secretion and impaired development of the ovulatory follicle and of the CL. In Florida, the use of 450-mg deslorelin (GnRH analogue) implants to induce ovulation, under the Ovsynch protocol resulted in a higher pregnancy rates than use of 750-mg implants, and pregnancy losses tended to decrease compared to controls, due probably to decrease in follicular development and estradiol secretion at the time of conceptus signaling to maintain the CL. An alternative strategy to enhance progesterone concentrations involved induction of an accessory CL by injection of hCG on day 5 after the cows were inseminated. Treatment with hCG resulted in 86% of the cows having two CLs, compared with 23% of the control cows. Conception rates were higher among the hCG-treated cows than among the controls. Another approach was to replace the second injection of GnRH analogue, in a timed-insemination protocol, with estradiol cypionate (ECP) injected 24 h after the injection of PGF₂ₐ Pregnancy rates were comparable with those obtained under the regular Ovsynch (timed- AI) program. Use of ECP induced estrus, and cows inseminated at detected estrus are indeed more fertile than those not in estrus at the time of insemination. Collectively, the BARD-supported programs at the University of Florida have improved timed insemination programs. In Ohio, the importance of the frequency of LH episodes during the early stages of the estrous cycle of cattle, when the corpus luteum is developing, was studied in an in vivo experiment in which cows were subjected to various episodic exposures to exogenous bovine LH. Results indicate that the frequent LH episodes immediately following the time of ovulation are important in development of the corpus luteum, from the points of view of both size and functionality. In another study, rates of cell proliferation and numbers of endothelial cells were examined in vitro in CLs collected from cows that received post-ovulation pulsatile LH treatment at various frequencies. The results indicate that the corpora lutea growth that results from luteal cell proliferation is enhanced by the episodes of LH release that occur immediately after the time of ovulation in cattle. The results also show that luteal endothelial cell numbers did not differ among cows treated with different LH doses. In Israel. a longer duration of the preovulatory LH surge stimulated the steroidogenic capacity of granulosa-derived luteal cells, and might, thereby, contribute to a higher progesterone output from the bovine corpus luteum. In an in vivo study, a subgroup of high-yielding dairy cows with extended estrus to ovulation interval was identified. Associated with this extended interval were: low plasma progesterone and estradiol concentrations and a low preovulatory LH surge prior to ovulation, as well as low post- ovulation progesterone concentration. In experiments based on the above results, we found that injection of GnRH at the onset of estrus increased the LHpeak, prevented late ovulation, decreased the variability between cows and elicited high and uniform progesterone levels after ovulation. GnRH at estrus onset increased conception rates, especially in the summer, and among primiparous cows and those with low body condition. Another study compared ovarian functions in multiparous lactating cows with those in nulliparous non-lactating heifers. The results revealed differences in ovarian follicular dynamics, and in plasma concentrations of steroids and gonadotropins that may account for the differences in fertility between heifers and cows.
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10

Hansen, Peter J., and Zvi Roth. Use of Oocyte and Embryo Survival Factors to Enhance Fertility of Heat-stressed Dairy Cattle. United States Department of Agriculture, August 2011. http://dx.doi.org/10.32747/2011.7697105.bard.

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The overall goal was to identify survival factors that can improve pregnancy success following insemination or embryo transfer in lactating dairy cows exposed to heat stress. First, we demonstrated that oocytes are actually damaged by elevated temperature in the summer. Then we tested two thermoprotective molecules for their effect on oocyte damage caused by heat shock. One molecule, ceramide was not thermoprptective. Another, insulin-like growth factor-1 (IGF) reduced the effects of heat shock on oocyte apoptosis and oocyte cleavage when added during maturation. We also used lactating cows exposed to heat stress to determine whether bovine somatotropin (bST), which increases IGF1 levels in vivo, would improve fertility in summer. Cows treated with bST received a single injection at 3 days before insemination. Controls received no additional treatment. Treatment with bST did not significantly increase the proportion of inseminated cows diagnosed pregnant although it was numerically greater for the bST group (24.2% vs 17.8%, 124–132 cows per group). There was a tendency (p =0.10) for a smaller percent of control cows to have high plasma progesterone concentrations (≥ 1 ng/ml) at Day 7 after insemination than for bST-treated cows (72.6 vs 81.1%). When only cows that were successfully synchronized were considered, the magnitude of the absolute difference in the percentage of inseminated cows that were diagnosed pregnant between bST and control cows was reduced (24.8 vs 22.4% pregnant for bST and control). Results failed to indicate a beneficial effect of bST treatment on fertility of lactating dairy cows. In another experiment, we found a tendency for addition of IGF1 to embryo culture medium to improve embryonic survival after embryo transfer when the experiment was done during heat stress but not when the experiment was done in the absence of heat stress. Another molecule tested, granulocyte-macrophage colony-stimulating factor (GM-CSF; also called colony-stimulating factor-2), improved embryonic survival in the absence of heat stress. We also examined whether heat shock affects the sperm cell. There was no effect of heat shock on sperm apoptosis (programmed cell death) or on sperm fertilizing ability. Therefore, effects of heat shock on sperm function after ejaculation if minimal. However, there were seasonal changes in sperm characteristics that indicates that some of the decrease in dairy cow fertility during the summer in Israel is due to using semen of inferior quality. Semen was collected from five representative bulls throughout the summer (August and September) and winter (December and January). There were seasonal differences in ion concentration in seminal plasma and in the mRNA for various ion channels known to be involved in acrosome reactions. Furthermore, the proportion of sperm cells with damaged acrosomes was higher in post-thaw semen collected in the summer than in its counterpart collected in winter (54.2 ± 3.5% vs. 51.4 ± 1.9%, respectively; P < 0.08Further examination is required to determine whether such alterations are involved in the low summer fertility of dairy cows.
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