http://dspace.cityu.edu.hk:80/handle/2031/729 2013-04-30T12:54:13Z http://dspace.cityu.edu.hk:80/handle/2031/6587 Title: Effects of temperature, salinity and food availability on two subtidal nassariid gastropods, Nassarius siquijorensis and Nassarius conoidalis Authors: Zhao, Qian ( 趙倩) Abstract: Owing to degradation of seabed communities by environmental stresses and human perturbations, species which have specialized diets in the local marine benthic community are gradually replaced by opportunistic species of which a number of them are scavengers. This study investigated how three major environmental factors, temperature, salinity and food availability, affected the survival, development, behaviour and physiology of the embryos, larvae and adults of two dominant subtidal scavenging gastropods, Nassarius siquijorensis and Nassarius conoidalis. Mortality and developmental rate of the embryos of N. siquijorensis and N. conoidalis were investigated at nine combinations of temperature (20, 25, and 30°C) and salinity (20, 25, 30‰). The median hatching time (HD50) was calculated using the standard logistic regression. Temperature, salinity, as well as the interaction between temperature and salinity had significant effects on both survival and HD50 for both N. siquijorensis and N. conoidalis with highest survival and fastest development at 30°C and 30‰. Larval mortality at six temperatures (10, 15, 20, 25, 30 and 35°C) and seven salinities (0, 5, 10, 15, 20, 25 and 30‰) were observed after 24 hrs and 48 hrs. Both N. siquijorensis and N. conoidalis larvae showed higher mortalities at low temperatures and salinities, especially at 10°C or at 5‰, with more than half of them died after 48 hrs. The larval mortality of N. siquijorensis under low temperatures and salinities was significantly lower than that of N. conoidalis. Respiration rate, swimming velocity, and clearance rate of the larvae of N. siquijorensis and N. conoidalis were measured at nine combinations of temperature (20, 25, and 30°C) and salinity (20, 25, 30‰). Temperature, salinity and the interaction between temperature and salinity had significant effects on oxygen consumption, clearance rate and swimming behaviour of both species. Significantly lower clearance rates and oxygen consumption rates were observed at lower salinities and temperatures, and the dispersal distance VSL was significantly higher at lower salinities. The effects of starvation on respiration, ammonia excretion, shell length, body weight, scope for growth (SFG) and body chemical composition of N. siquijorensis and N. conoidalis were studied for 32 days. During starvation, significant decreases in respiration rate and ammonia excretion rate were observed for both N. siquijorensis and N. conoidalis. Starvation, time, and the interaction between starvation and time were found to be significant in affecting SFG for both N. siquijorensis and N. conoidalis. At the end of the experiment, the unfed individuals had significantly lower percentages of protein and fat but higher percentages of carbohydrate as compared with the control for both N. siquijorensis and N. conoidalis. Significant increases in wet weight and shell length were obtained from the control for both N. siquijorensis and N. conoidalis but the differences between species were insignificant. In another experiment in which the individuals were starved for 96 days, a significantly higher mortality was obtained for N. siquijorensis as compared with N. conoidalis. The effects of starvation and distance from carrion on chemoreception were compared between N. siquijorensis and N. conoidalis. The time to reach carrion was species specific and was significantly affected by both starvation and the distance from the carrion. Under well-fed condition, mean time to detect carrion at 15 cm and 20 cm away from carrion were significantly shorter in N. siquijorensis than N. conoidalis. For the starved group, the mean time to detect carrion at 2.5 cm and 10 cm away from carrion, however, was significantly shorter in N. conoidalis than N. siquijorensis. For N. conoidalis, starved individuals were more sensitive to carrion than well-fed ones with higher percentages of individuals able to locate the carrion at 10 cm, 15 cm and 20 cm away from the carrion. In summary, embryos and larvae of N. siquijorensis are more tolerant than N. conoidalis to temperature and salinity changes. This may help explain why N. siquijorensis has a wider distribution in Hong Kong waters as compared with N. conoidalis which is restricted to southern waters where salinity is relatively constant throughout the year. Both N. conoidalis and N. siquijorensis are generalist feeders adaptive to unpredictable food supply by reducing energy expenditure through decreasing respiration and ammonia excretion when starved. In recent years, they are gradually replacing species which have specialized diets in Hong Kong waters where the benthic environment suffers from various human disturbances such as eutrophication, trawling and hypoxia which directly or indirectly affects food availability. Nevertheless, N. siquijorensis grow faster than N. conoidalis when food availability is high while N. conoidalis perfom better under starvation. Their differential responses to food availability may help explain the dominance of N. siquijorensis in Hong Kong waters where the benthic environment is highly disturbed. Notes: CityU Call Number: QL430.5.N3 Z45 2011; xviii, 195 leaves : ill. (some col.) 30 cm.; Thesis (M.Phil.)--City University of Hong Kong, 2011.; Includes bibliographical references (leaves 160-193) 2011-01-01T00:00:00Z http://dspace.cityu.edu.hk:80/handle/2031/6586 Title: Effects of andrographolide and taxifolin on cell proliferation, cell cycle progression and apoptosis of prostate carcinoma DU145 cells Authors: Zhang, Zhongrong ( 張鐘融) Abstract: Natural products have been playing a domain role in cancer chemotherapy and prevention in the past 30 years. Traditional Chinese medicine (TCM) with thousands years of history is a huge source for discovery and investigation of effective natural herbal products. A lot of compounds isolated or derived from TCM have been suggested to possess the property of inducing cell cycle arrest, cell differentiation and apoptosis in various kinds of cancer cells. Andrographolide (Andro) which is the main bioactive component from Andrographis paniculata (穿心蓮) has been reported to have many biological effects including anti-proliferative effect on several tumor cell lines. However, there is no detailed study about the biological effects of Andro on androgen refractory prostate cancer cells. Taxifolin (Taxi), a dihydroflavonol belongs to flavonoids group, together with its glycosides are commonly found in many species of medical herbs. In recent years, experimental studies have provided growing evidences for the protective effect of flavonoids against cancer because of their beneficial actions on multiple cancer-related biological pathways (e.g. carcinogen bioactivation, cellsignaling, cell cycle regulation, angiogenesis, oxidative stress, inflammation). Although the reports on flavonoids and cancer are still limited and conflicting, some protective associations have suggested flavonoid-rich food for cancer protection. Results in the present study showed that Andro inhibited cell proliferation of androgen independent prostate cancer cell line DU145 in a time and dosedependent manner, with the IC50 value (48 h) of 13.70 μM. On the other hand, Andro exhibited little growth inhibitory effect on noncancerous human fibroblast Hs27 (IC50˃500 μM, 48h). Cell cycle analysis demonstrated that, at low concentration (˂=40 μM), Andro-treated DU145 cells accumulated at G2/M phase dose-dependently. Immunoblot of Phospho-Histone H3 (Ser10) antibody (mitotic marker) further revealed that the G2/M accumulation of DU145 cell was caused by cell cycle arrest at mitotic phase. Additionally, microtubule network was visualized by immunostaining of tubulin, which suggested that Andro treatment leaded to the formation of abnormal spindle-chromosome structure resulting in cell arrest at prometaphase. However, in vitro microtubule assembly assay indicated that Andro did not interact directly with microtubule. Double staining of AnnexinV-FITC / PI showed that Andro also induced apoptosis dose-dependently, with the highest apoptotic rate after 48-hour treatment. High concentration (80 μM) of Andro treatment directly induced cell death without a marked alteration of cell cycle distribution within the first 24 hour. Western blotting analysis revealed that Andro exposure triggered several cell cycle regulation pathways, including up-regulation of cyclin B1 and cyclin-dependent kinase (CDK) inhibitor p21(Waf1/Cip1), dephosphorylation on Tyr15 of Cdc2 and phosphorylation of Wee1, Myt1 and Cdc25C, which involved in the process of cyclin B/Cdc2 complex activation and led to cell accumulation in mitosis. Andro-induced apoptosis was associated with activation and cleavage of poly (ADP-ribose) polymerase (PARP), caspase-7, caspase-9 and caspase-3 related to mitochondria apoptotic pathway. Taxi exhibited low anti-proliferative effect on DU145 cell line (IC50˃500 μM, 48 h). On the other hand, combination of 100 μM Taxi with Andro significantly enhanced the growth inhibitory effect of the latter on DU145 cells. It was found that combinated treatments of 100 μM Taxi and Andro (10-40 μM) markedly increased G2/M accumulation in DU145 cells compared to treatments with Andro-alone, through rising of mitotic index (approximately twice with 20 μM Andro treatment). Quantification of apoptosis with flow cytometry revealed that Andro-induced apoptosis and cell death was also promoted potently by synchronous treatment of Taxi, whereas exposure to Taxi alone did not exhibit marked alteration on cell morphology, cell cycle distribution or cell viability. Western blotting analysis revealed that the mitotic rate increased by combination treatment was related to upregulation of cyclin B/Cdc2 mitotic complex and CDK inhibitor p21; the enhanced apoptosis was associated with increases of PRAP, caspase-7, and caspase-9 activation. The increase of twisted and elongated mitotic spindle after the combined treatment suggested that anti-microtubule activity of the two combined compounds was involved as a remarkable enhanced microtubule polymerization was observed. This study investigated the biological effect of Andro and Taxi on cell morphology proliferation, cell cycle, apoptosis in androgen-independent prostate cancer cell DU145, and the synergetic/additive anticancer effect with combination treatment. Hence, Andro might be effective on prostate cancer treatment and low cytotoxic Taxi might be a promising additive in combined drug treatment of prostate cancer. This study also provided experimental evidences for the potential treatment of cancer by dietary-flavonoid in combination with anti-cancer compounds. Notes: CityU Call Number: RC280.P7 Z45 2011; xviii, 198 leaves : ill. (some col.) 30 cm.; Thesis (M.Phil.)--City University of Hong Kong, 2011.; Includes bibliographical references (leaves 175-198) 2011-01-01T00:00:00Z http://dspace.cityu.edu.hk:80/handle/2031/6582 Title: Relating estradiol and telomeres to longevity in marine medaka Oryzias melastigma Authors: Yip, Wun Piu ( 葉煥彪) Abstract: Longevity gender gap (LGG) (females living longer than males) exists in humans and other animals. Ample evidence in mammals has shown that a gender difference exists in telomere length (TL) (females longer than males) and the rate of telomere attrition (females slower than males). Critical shortening of telomere may induce replicative senescence and ultimately lead to tissue stem cell exhaustion, age-related tissue degeneration, organismal aging and shortened lifespan. In mammals, estradiol (E2) has been proposed as a key factor responsible for reducing telomere attrition via two pathways: (1) increase telomerase activity (TA) to replenish telomeres loss, and/or (2) reduce oxidative damage to telomeric DNA. However, the relationships between E2, TL and longevity in non-mammalian vertebrates remain largely unexplored. Marine medaka Oryzias melastigma possess a number of desirable characteristics for telomere and estrogen biology and longevity studies, including: (1) short TL (0.5-12 kb); (2) gradual senescence and telomere shortening with age; (3) known telomerase reverse transcriptase (TERT) and estrogen receptor-alpha (ERα) gene and protein sequences; (4) short lifespan (approximately 18 months), and available in large numbers under laboratory conditions; (5) estrogen biology similar to humans, and (6) distinct sexual dimorphism, the morphology of the anal fin is very prominent in O. melastigma ca. 1 month after hatching, rendering it highly desirable for gender study. In the present study, the O. melastigma was used as a model for studying the relationship between TL, E2 and longevity in non-mammalian vertebrates. The sex ratio and fish survival, plasma E2, testosterone levels of O. melastigma at 4 months (young), 8 months (middle-aged) and 12 months old (senior) were measured. Telomere length (by Southern blotting), telomerase activity (by RTQ-TRAP assay), gene expressions of telomerase reverse transcriptase (TERT) and ERα (by real time-PCR), DNA oxidation (by 8-OHdG) and protein oxidation (by protein carbonyl) were measured in the liver and gills of male and female O. melastigma at different ages. The results show that LGG also exists in O. melastigma (females living longer than males). The female O. melastigma has begun to outnumber the males by the time they reach 10 months old. With advancing age, the proportion of short TRFs length (˂2 kb) increases in the liver of female and male O. melastigma and in the gills of female O. melastigma, showing a decline of TL with age. In the liver, gender difference is clearly evident in TL, TA, TERT and ERα mRNA expressions in the young and middle-aged O. melastigma. Plasma E2 was positively correlated with liver ERα mRNA expression (p ≤ 0.001) and liver TA (p ≤ 0.05). In addition, liver ERα mRNA expression was positively correlated with liver TA (p ≤ 0.001), suggesting up-regulation of TA by E2 in the liver was possibly mediated via ERα regulated pathways: TERT gene transcription and/or TERT protein phosphorylation. In parallel, liver DNA oxidation (as measured by 8-OHdG level) and oxidative protein damage (as measured by protein carbonyl level) were found to increase with age in O. melastigma, and the levels of oxidative damage were generally lower in females than in males. In addition, plasma E2 was inversely correlated with 8-OHdG (p ≤ 0.05) and protein carbonyl content (p ≤ 0.001), respectively, suggesting E2 may enhance cellular antioxidant defense in the liver, leading to a lower oxidative damage in the females. Collectively, in the liver, E2 may prevent telomere shortening by enhancing telomerase activity and reducing oxidation damage. In the gills, gender difference in TL and TA were detected, but not for TERT mRNA expression. Given an absence of ERα mRNA expression in the gills, and a significant positive correlation between plasma E2 and gill TA (p ≤ 0.001), the activity of telomerase in the gills of O. melastigma was unlikely to be mediated via TERT transcription, but likely to be induced by E2 via the TERT protein phosphorylation pathways. Moreover, the gill 8-OHdG and protein carbonyl levels were lower in middle-aged females than in males (8 months old), possibly because females have stronger antioxidant defense capacity. When plasma E2 declined in old female O. melastigma (12 months), the antioxidant defense capacity in the female gills was weakened and the gender advantage faded out accordingly. In conclusion, the results of this study provide a comprehensive understanding of the in vivo relationship between E2, TL and longevity in O. melastigma. The present findings support the view that E2 may also protect telomeres by increasing TA and reducing cellular oxidative stress and is also a key factor contributing to a greater longevity in female O. melastigma. Given the short generation time and distinct sexual dimorphism, O. melastigma may serve as a desirable alternative model for further studies of the possible mechanisms of gender-specific longevity in vertebrates. Notes: CityU Call Number: QL638.O78 Y56 2011; xvii, 194 leaves : ill. (some col.) 30 cm.; Thesis (M.Phil.)--City University of Hong Kong, 2011.; Includes bibliographical references (leaves 123-163) 2011-01-01T00:00:00Z http://dspace.cityu.edu.hk:80/handle/2031/6574 Title: Design, synthesis and photophysical study of luminescent tetra(iscyano) rhenium(I) complexes Authors: Siu, Wai Kit ( 蕭偉傑) Abstract: This thesis presents the design, synthesis, characterization and photophysical properties of new classes of luminescent tetraisocyano rhenium(I) complexes. A new series of rhenium(I) tetra(isocyano) diimine complexes, [Re(CNR)4(N-N)]+, with various isocyanide and diimine ligands of different electronic nature (where R = 4-IC6H4, 4-BrC6H4, 4-Br-2,6-(CH3)2C6H2, 2,4,6-Cl3C6H2, 2,4,6-Br3C6H2, 2,4-Cl2-6-CH3OC6H2; N-N = 2,2'-bipyridine, 1,10-phenanthroline, 4,4'-di-tertbutyl- 2,2'-bipyridine, 4,4'-dimethoxy-2,2-bipyridine and 1-methyl-2-(2'-pyridyl)imidazole) has been synthesized and characterized. These complexes were characterized by 1H NMR, IR, mass spectrometry and elemental analysis. The X-ray crystal structures of three of the complexes [Re(4-IC6H4NC)4(phen)]ClO4, [Re(4- BrPhNC)4(bpy)]PF6 and [Re(2,6-(CH3)2PhNC)4(bpy)]PF6 were also determined. These complexes were found to show orange to red photoluminescence, which were assigned as derived from the 3MLCT [dπ(Re) → π*(N-N)] excited state origin. It has also been demonstrated that the emission properties of these complexes could be readily tuned through the substituents on the isocyanide and diimine ligands. The photophysical properties, solvatochromic behaviour and the structure-property correlation of these complexes were investigated in details by UV-vis and emission spectroscopy. It is worth paying attention that some of these complexes are extremely sensitive to the polarity and rigidity of the medium. The emissive excited state was further studied by nano-second transient absorption spectroscopy. The electrochemical properties of these complexes by cyclic voltammetry have also been described. In addition to the complexes with neutral diimine ligands, another new classes of luminescent tetra(p-bromophenylisocyano) cyclometalated rhenium(I) complexes, [Re(CNC6H4Br)4(R1-pyind)] (where R1-pyind are substituted 2-(2'-pyridyl)indoles, which is prepared by the reaction of the corresponding facial tricarbonyl cyclometalated rhenium(I) complexes fac-[Re(CO)3(H2O)(R1-pyind)] have been developed. These complexes were characterized by 1H NMR, IR, mass spectrometry and elemental analysis. The X-ray structure of one of the facial tricarbonyl cyclometalated rhenium(I) complexes has also been determined. The UV-vis absorption, emission and electrochemical properties of these tricarbonyl and tetra(pbromophenylisocyano) cyclometalated rhenium(I) complexes have also been studied. Notes: CityU Call Number: QC476.8 .S58 2010; vii, 171 leaves : ill. (some col.) 30 cm.; Thesis (M.Phil.)--City University of Hong Kong, 2010.; Includes bibliographical references. 2010-01-01T00:00:00Z