Browsing by Subject "Hamster"
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Item Chemopreventive effects of curcumin and green tea on B[a]P-induced carcinogenesis in the hamster cheek pouch(Texas A&M University, 2005-08-29) Brandon, Jimi LynnThe present study was carried out to examine the chemopreventive effects of curcumin and green tea polyphenols on the hamster cheek pouch carcinogenesis model. This model of oral carcinogenesis has been widely used in chemoprevention studies, however, these studies have been limited to the use of DMBA as the carcinogenic agent. We have developed a protocol of carcinogenesis in the hamster cheek pouch using B[a]P, a broadly distributed environmental carcinogen, formed as a by-product of the combustion of organic materials including cigarette smoke. B[a]P- induced tumors in the hamster cheek pouch are primarily endophytic squamous cell carcinomas that closely resemble squamous cell carcinomas of the human oral mucosa. The cheek pouch of male Syrian hamsters were treated topically for eight weeks with 0.6% curcumin, 6.0% curcumin, 2.5% green tea polyphenols, or 5.0% green tea polyphenols, 3 times per week 30 minutes prior to the application of 2.0% B[a]P. The animals were sacrificed 24 hours and 72 hours after the last treatments. Short-term mechanistic markers of malignant progression were used to determine effects of each compound. Cellular proliferation, assessed by bromodeoxyuridine (Brdu) incorporation, p53 protein accumulation, and apoptotic activity were evaluated. The results of the present study demonstrated that 0.6% curcumin and 2.5% green tea polyphenols had strong inhibitory effects on cellular proliferation and p53 protein accumulation. And 6.0% curcumin and 5.0% green tea polyphenols appeared to induce apoptosis. Our data suggest that curcumin and green tea polyphenols may have a plausible chemopreventive effect on oral carcinogenesis in the hamster cheek pouch model.Item Citrus limonoids and flavonoids: extraction, antioxidant activity and effects on hamster plasma cholesterol distribution(Texas A&M University, 2005-11-01) Yu, JunFour in vitro models were used to measure the antioxidant activity of 11 citrus phytochemicals. The citrus limonoids and bergapten showed very weak antioxidant activity. The flavonoids demonstrated mild, to moderate, to strong antioxidant activity. In addition to some other commonly accepted structural features our data indicated that the hydroxyl group in position 6 of ring A could also increase the antioxidant activity of flavonoids. Compared with the active flavonoids, limonoids are highly oxygenated triterpenoids, with fewer hydroxyl groups to stabilize unpaired electrons (or scavenge free radicals). Bergapten lacks a hydroxyl group. This is the first report on the antioxidant activity of limonoids and neoeriocitrin. A feeding study using Syrian hamsters was followed to determine the effect of citrus limonoids and flavonoids on plasma cholesterol. Hamsters fed with limonin, limonin 17-Beta-D-glucopyranoside and grapefruit pulp significantly inhibited the increase of LDL/HDL-cholesterol (36.6%, 52.9% and 57% respectively) compared with the basal control (65.8%) and the pectin control (70%). Furthermore, hamsters fed with limonin had significantly larger LDL particle size (21.21 nm) compared with the control group (19.96 nm). Further studies demonstrated that LDLs from hamsters fed with limonin and limonin 17-Beta-D-glucopyranoside were less susceptible to oxidation. These data suggest that limonin, limonin 17-Beta-D-glucopyranoside and grapefruit pulp have potential inhibitory effects against atherogenesis. Supercritical CO2 (SC-CO2) was attempted to extract limonoids from grapefruit seeds and molasses. Limonin aglycone was successfully extracted with SC-CO2 directly from grapefruit seeds with the yield of 6.3 mg/g seeds at 48.3 MPa, 50˚C and 60 min with CO2 top feeding; and the limonin glucoside was extracted using SC-CO2 and ethanol as co-solvent from the defatted seeds with the yield of 0.73 mg/g seeds at 42 MPa, 52˚C, 45% ethanol (XEth=0.45) and 40 min with CO2 top feeding; and limonin glucoside also was extracted using SC-CO2 and ethanol with the yield of 0.61mg/g grapefruit molasses at 48.3 MPa, 50˚C and 10% ethanol (XEth=0.1), 40 min with CO2 top feeding. CO2 flow rate was around~5 l/min in experiments. The results demonstrated SC-CO2 extraction of limonoids from citrus juice industry byproducts has practical significance for future commercial production.Item Repeated social stress and the maturation of sexual behavior in juvenile male golden hamsters(2011-08) Bastida, Christel Celeste; Delville, Yvon; Duvauchelle, Christine; Dominguez, Juan; Gonzalez-Lima, Francisco; Gore, AndreaIn certain species, puberty is thought to be a period of susceptibility to various stressors, resulting in pathological behavioral and physiological changes subsequent to exposure during this period. However, juvenile male golden hamsters appear to be fairly resilient to pubertal stress, as compared to adult hamsters and many other species. In these experiments, repeatedly stressed juvenile male hamsters were found to be avoidant of aggressive adult male social stimuli, but did not display anxious behavior outside of a social context. In addition, several long-term changes in neural activity were associated with social stress during early puberty. The medial preoptic area and medial preoptic nucleus, and ventral tegmental area showed decreased neural activity in subjugated juveniles than in naïve individuals. Since these brain areas are involved in the expression of motivated behaviors, specifically sexual behavior, and reward pathways, we next investigated sexual behavior in virgin juveniles. When placed in a confined space with receptive females, consummatory behavior in subjugated juveniles was similar to those observed in naive juveniles. Appetitive aspects of sexual behavior were also tested in a Y-maze to allow subjects to choose whether to approach a social stimulus. When given a choice between a sexually receptive and non-receptive female social stimulus, socially stressed individuals showed anxiety related behaviors and did not show a preference. However, naïve hamsters preferred the non-receptive female. Interestingly, this effect was less significant in naïve animals tested during late puberty and early adulthood, and a preference for sexually receptive females was not observed. In addition, stressed hamsters tested with harnessed females at mid-puberty were slower to approach females, indicating altered motivation to approach adult conspecifics. This research is unique in that it is the first to suggest the disconnect between the development of consummatory and appetitive aspects of sexual behavior. Together, these data examine the effects of stress on the development of pubertal social behaviors.