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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
71

Inhibition of invasive breast cancer cell growth by selected peach and plum phenolic antioxidants

Vizzotto, Marcia 12 April 2006 (has links)
Fruits and vegetables are known to play an important role in human health due to the range of phytochemicals they contain. Twenty-one peach genotypes and 45 plum genotypes with different flesh and skin color were analyzed for their antioxidant content and antioxidant activity. Anthocyanin content, phenolic content and antioxidant activity were higher in red-flesh than in light-colored flesh peaches. Carotenoid content was higher in yellow-flesh peaches. Among the peaches, the antioxidant activity was well correlated with phenolic content. The anthocyanin content among the plums increased with the red color intensity. Red-flesh plums generally had higher phenolic content than the other plums. Antioxidant activity was higher in red-flesh genotypes; however, it was strongly correlated only with the phenolic content in light-colored flesh plums. Extracts from selected genotypes of peaches and plums and their fractions were evaluated against two breast cancer cell lines (MDA-MB-435 and MCF-7) and one non-cancerous breast line (MCF-10A). The cells were cultured in the presence of peach and plum extracts and their fractions at various concentrations (0-500 µg/ml) and the cell viability and antiproliferation activity was evaluated by MTT assay and Coulter Counter. There was a dose-dependent reduction on cell viability of estrogen-negative MDA-MB-435 breast cancer cells. Only weak activity against MCF-7 was observed at high extract concentrations. There was no activity against MCF-10A after 24 h treatment. Fraction I, which consists of mainly phenolic acids such as chlorogenic acid and a caffeic acid derivative, reduces MDA-MB-435 breast cancer cell viability with the lowest IC50. The second most effective fraction was Fraction II which contained anthocyanins. Fraction III (flavonols) and Fraction IV (polymerized compounds) had no effect on the cell lines. Phenolic acids present in fraction I induced apoptosis in MDA-MB-435 estrogen receptor-negative cell line. Fraction I did not induced apoptosis in MCF-10A, a noncancerous cell line even at higher concentrations than the ones tested in MDA-MB- 435. Apoptosis induced by Fraction I was caspase 3 and PARP independent. After treatment with 50 µg of chlorogenic acid equivalent/ml there was an activation of p- ERK.
72

Effects of Anti-tumor Drugs on OC2 Human Oral Cancer Cells

Su, Hsing-Hao 03 September 2008 (has links)
The present study explored the effect of three anti-tumor drugs (cisplatin, fluorouracil, and temozolomide) on viability and cytosolic free Ca2+ concentrations ([Ca2+]i) in OC2 human oral cancer cells. The effect of cisplatin related mitogen-activated protein kinases (MAPKs) phosphorylation was also examined. Cisplatin at concentration of 25-150 £gM decreased viability in a concentration-dependent manner, and so did fluorouracil (50-1000 £gM) and temozolomide (50-600 £gM). The three anti-tumor drugs all failed to induce a [Ca2+]i increase; thus it seemed that these drugs induced cell death via Ca2+-independent pathways. Immunoblotting showed that OC2 cells have background phospho-ERK, phospho-JNK and phospho-p38 MAPKs. It was found that cisplatin influenced the phosphorylation of ERK, JNK and p38 MAPKs at different time points.
73

Numerical investigation on the use of multi-element blades in vertical-axis wind turbines

Bah, Elhadji Alpha Amadou 08 June 2015 (has links)
The interest in sustainable forms of energy is being driven by the anticipated scarcity of traditional fossil fuels over the coming decades. There is also a growing concern about the effects of fossil fuel emissions on human health and the environment. Many sources of renewable energy are being researched and implemented for power production. In particular, wind power generation by horizontal- and vertical-axis wind turbines is very popular. Vertical-axis wind turbines (VAWTs) have a relative construction simplicity compared to horizontal-axis wind turbines (HAWTs). However, VAWTs present specific challenges that may hinder their performance. For instance, they are strongly affected by dynamic stall. A significant part of the kinetic energy contained in the oncoming wind is lost in swirl and vortices. As a result, VAWTs have lower power production compared to HAWTs. First, the present work is aimed at the study of the aerodynamics of straight-bladed VAWTs (SB-VAWTs). Empirical calculations are conducted in a preliminary work. Then a two-dimensional double multiple streamtube (DMST) approach supported by a two-dimensional numerical study is implemented. The dynamic stall and aerodynamic performance of the rotor are investigated. A VAWT-fitted dynamic stall model is implemented. Computational fluid dynamics (CFD) simulations are conducted to serve as reference for the DMST calculations. This three-pronged approach allows us to efficiently explore multiple configurations. The dynamic stall phenomenon is identified as a primary cause of performance loss. The results in this section validate the DMST model as a good replacement for CFD analysis in early phase design provided that a good dynamic stall model is used. After having identify the primary cause of performance loss, the goal is to investigate the use to dual-element blades for alleviating the effect of dynamic stall, thereby improving the performance of the rotor. The desirable airfoil characteristics are defined and a parametric analysis conducted. In the present study the parameters consists of the size of the blade elements, the space between them, and their relative orientation. The performance of the rotor is calculated and compared to the baseline. The results highlight the preeminence of the two-element configuration over the single-element provided that the adequate parametric study is conducted beforehand. A performance enhancement is obtained over a large range of tip speed ratios. The starting characteristics and the operation stability are also improved. Finally, an economic analysis is conducted to determine the cost of energy and thus the financial viability of such a project. The Great Coast of Senegal is selected as site of operation. The energy need and sources of this region are presented along with its wind energy potential. The cost evaluation shows the economic viability by comparing the cost of energy to the current energy market prices.
74

Studies on cryopreservation of zebrafish (Danio rerio) oocytes using controlled slow cooling and vitrification

Guan, Mo January 2009 (has links)
Cryopreservation of gametes provides a promising method to preserve fish genetic materials, which offers many benefits to the fields of aquaculture, conservation and biomedicine. Although successful cryopreservation of spermatozoa of about 200 fish species has been achieved, systematic studies on cryopreservation of fish oocytes have only recently been undertaken. The objective of the present studies was to use zebrafish as a model system to develop a cryopreservation protocol for fish oocytes and to develop reliable viability assessment methods for monitoring zebrafish oocyte viability both before and after cryopreservation. A simple and rapid enzymatic method for zebrafish oocytes isolation was developed and the investigations on cryopreservation of zebrafish oocytes using improved controlled slow cooling and vitrification were carried out. Oocyte viability following cryopreservation was investigated by ATP assay, oocyte viability molecular signature (OVMS) and cryomicroscopic observation in addition to staining methods. The optimum conditions for oocyte enzymatic separation were identified as 0.4mg/ml collagenase or 1.6mg/ml hyaluronidase treatment for 10min at 22ºC and this method can be used for oocytes at all stages. The use of sodium free medium (KCl buffer), fast warming and 4-step removal of cryoprotectants in an improved controlled slow cooling protocol significantly enhanced oocyte viability (67.5 ± 1.7%) when compared with a previous study (16.3 ± 2.3%) in this laboratory. Mixtures of cryoprotectants (methanol, Me2SO and propylene glycol), stepwise addition and removal of cryoprotectants in combination of a new vitrification system (CVA65 vitrification system) were used in vitrification studies. Oocyte survivals after vitrification assessed by trypan blue staining were relatively high (76.5 ± 6.3%) shortly after warming in KCl buffer. Furthermore, the result of ATP assay showed that ATP levels in oocytes decreased significantly after cryopreservation indicating the bioenergetic systems of oocytes were damaged. Cryomicroscopic observations demonstrated that Intracellular ice formation (IIF) is the main factor causing injuries during cryopreservation of zebrafish oocytes. The results provided by the present study will assist successful protocol design for cryopreservation of fish oocytes in the future.
75

Structural and cytochemical studies on the scutellum and aleuronecellsof oat seeds before and after germination

陳慶讓, Chan, Hing-yeung. January 1985 (has links)
published_or_final_version / Botany / Master / Master of Philosophy
76

A seed germination study of the salt tolerance of Cynodon dactylon (L.) Pers. and Panicum antidotale Retz.

Tromble, John Merrill, 1932- January 1963 (has links)
No description available.
77

Spectroscopy Techniques for quantification of Microorganisms in Environmental Samples

Mondaca Fernandez, Iram January 2005 (has links)
Microbiological monitoring of water is of primary importance for preservation of human health, particularly in an arid zone like the U.S. southwest. In this work, infrared spectroscopic methods were developed to identify and quantify microorganisms present in water and water-related environmental samples. Focus of the work was primarily on evaluating the impact of various sterilization methods on microorganism physiology as gauged by the non-invasive approach of infrared spectroscopy. This work demonstrates that FTIR techniques can be used to identify changes in the physiology of microorganisms and that for heat treatment, a correlation between spectral changes and the viability of microorganisms can be made.
78

The In Vitro Effects of Pure and Street Methamphetamine on the proliferation and Cell Cycle of Mouse Brain Endothelial (bEnd5) cells

Mafunda, Patrick Siyambulela January 2012 (has links)
<p><font size="3"> <p>The blood-brain barrier (BBB) is an interface between the brain parenchyma and the circulating system. This barrier plays a vital role in protecting the CNS by restricting free paracellular diffusion of molecules from the systemic circulation. Methamphetamine (MA) is a highly addictive psychostimulant and has demonstrated neurotoxic properties as well as the ability to compromise the BBB. MA exposure is strongly linked with increased oxidative stress which can result in a decrease in the integrity of the BBB.<font size="3">The aim of this study was to investigate </font><i><font size="3" face="Times New Roman,Times New Roman"><font size="3" face="Times New Roman,Times New Roman">in vitro </font></font><font size="3">effects of pure and street MA &quot / tik&quot / on DNA proliferation and cell cycles in mouse brain endothelial (bEnd5) cells. <font size="3">Trypan blue was used to determine effects of MA (0.0001M-1mM) on cell viability and % cell growth. The Cell Titer Glo&reg / luminescent assay and nonradioactive analogue, 5-bromo-2'-deoxyuridine (BrdU) was used to detect ATP and DNA levels, respectively. Cell cycles (propidium iodide incorporation) were analysed using flow cytometry. Statistical analysis was performed using Wilcoxin Rank Sum Test in which P&lt / 0.05 was denoted as significant. <font size="3">Results of this study showed that:&nbsp / <font size="3">1. Viability of bEnd5 cells exposed to all selected concentrations of MA were unaffected when compared to controls (P&gt / 0.05). <font size="3">2. % Cell growth was suppressed by MA exposure at 96hrs in comparison to that of controls (P&le / 0.03). 3. Cells exposed to MA had significant higher ATP concentrations than control cells at 96hrs (P &le / .0.03) 4. DNA synthesis was markedly suppressed in cells exposed to pure MA and street MA sample 4 (P&le / 0.03), while was similar and higher in cells exposed to street MA sample 1 (P=0.39), and street MA sample 2 and 3 (P&le / 0.04), respectively at 96hrs. 5. bEnd5 cell were arrested between 72 and 96hrs at the G1-S phase. <font size="3">In conclusion, this study demonstrated pure and illicit samples of MA obtained from forensic police did not affect the viability of bEnd5 cells, however resulted in the significant suppression of their cell numbers. This growth inhibition may be due to MA-induced cell cycle arrest at the G1-S phase. The study also showed that compounds found in the samples of street MA produced results significantly different to that of pure MA. </font></font> <p>&nbsp / </p> </font>&nbsp / </font></font></font> <p>&nbsp / </p> </i></p> </font></p> <p>&nbsp / </p>
79

The In Vitro Effects of Pure and Street Methamphetamine on the proliferation and Cell Cycle of Mouse Brain Endothelial (bEnd5) cells

Mafunda, Patrick Siyambulela January 2012 (has links)
<p><font size="3"> <p>The blood-brain barrier (BBB) is an interface between the brain parenchyma and the circulating system. This barrier plays a vital role in protecting the CNS by restricting free paracellular diffusion of molecules from the systemic circulation. Methamphetamine (MA) is a highly addictive psychostimulant and has demonstrated neurotoxic properties as well as the ability to compromise the BBB. MA exposure is strongly linked with increased oxidative stress which can result in a decrease in the integrity of the BBB.<font size="3">The aim of this study was to investigate </font><i><font size="3" face="Times New Roman,Times New Roman"><font size="3" face="Times New Roman,Times New Roman">in vitro </font></font><font size="3">effects of pure and street MA &quot / tik&quot / on DNA proliferation and cell cycles in mouse brain endothelial (bEnd5) cells. <font size="3">Trypan blue was used to determine effects of MA (0.0001M-1mM) on cell viability and % cell growth. The Cell Titer Glo&reg / luminescent assay and nonradioactive analogue, 5-bromo-2'-deoxyuridine (BrdU) was used to detect ATP and DNA levels, respectively. Cell cycles (propidium iodide incorporation) were analysed using flow cytometry. Statistical analysis was performed using Wilcoxin Rank Sum Test in which P&lt / 0.05 was denoted as significant. <font size="3">Results of this study showed that:&nbsp / <font size="3">1. Viability of bEnd5 cells exposed to all selected concentrations of MA were unaffected when compared to controls (P&gt / 0.05). <font size="3">2. % Cell growth was suppressed by MA exposure at 96hrs in comparison to that of controls (P&le / 0.03). 3. Cells exposed to MA had significant higher ATP concentrations than control cells at 96hrs (P &le / .0.03) 4. DNA synthesis was markedly suppressed in cells exposed to pure MA and street MA sample 4 (P&le / 0.03), while was similar and higher in cells exposed to street MA sample 1 (P=0.39), and street MA sample 2 and 3 (P&le / 0.04), respectively at 96hrs. 5. bEnd5 cell were arrested between 72 and 96hrs at the G1-S phase. <font size="3">In conclusion, this study demonstrated pure and illicit samples of MA obtained from forensic police did not affect the viability of bEnd5 cells, however resulted in the significant suppression of their cell numbers. This growth inhibition may be due to MA-induced cell cycle arrest at the G1-S phase. The study also showed that compounds found in the samples of street MA produced results significantly different to that of pure MA. </font></font> <p>&nbsp / </p> </font>&nbsp / </font></font></font> <p>&nbsp / </p> </i></p> </font></p> <p>&nbsp / </p>
80

The In Vitro Effects of Pure and Street Methamphetamine on the proliferation and Cell Cycle of Mouse Brain Endothelial (bEnd5) cells

Mafunda, Patrick Siyambulela January 2012 (has links)
<p><span style="font-size: 11.5pt">The blood-brain barrier (BBB) is an interface between the brain parenchyma and the circulating system. This barrier plays a vital role in protecting the CNS by restricting free paracellular diffusion of molecules from the systemic circulation. Methamphetamine (MA) is a highly addictive psychostimulant and has demonstrated neurotoxic properties as well as the ability to compromise the BBB. MA exposure is strongly linked with increased oxidative stress which can result in a decrease in the integrity of the BBB. </span></p> <div><span style="font-size: 11.5pt">The aim of this study was to investigate <i>in vitro </i>effects of pure and street MA &ldquo / tik&rdquo / on DNA proliferation and cell cycles in mouse brain endothelial (bEnd5) cells. </span></div> <div><span style="font-size: 11.5pt">Trypan blue was used to determine effects of MA (0.0001M-1mM) on cell viability and % cell growth. The Cell Titer Glo&reg / luminescent assay and nonradioactive analogue, 5-bromo-2'-deoxyuridine (BrdU) was used to detect ATP and DNA levels, respectively. Cell cycles (propidium iodide incorporation) were analysed using flow cytometry. Statistical analysis was performed using Wilcoxin Rank Sum Test in which P&lt / 0.05 was denoted as significant. </span></div> <div><span style="font-size: 11.5pt">Results of this study showed that: </span></div> <div><span style="font-size: 11.5pt">1. Viability of bEnd5 cells exposed to all selected concentrations of MA were unaffected when compared to controls (P&gt / 0.05)&nbsp / </span><span style="font-size: 11.5pt">&nbsp / </span></div> <div><span style="color: windowtext / font-size: 11.5pt">2. % Cell growth was suppressed by MA exposure at 96hrs in comparison to that of controls (P&le / 0.03). </span></div> <div style="margin: 0cm 0cm 25pt"><span style="color: windowtext / font-size: 11.5pt">3. Cells exposed to MA had significant higher ATP concentrations than control cells at 96hrs (P &le / .0.03) </span><span style="color: windowtext / font-size: 11.5pt">4. DNA synthesis was markedly suppressed in cells exposed to pure MA and street MA sample 4 (P&le / 0.03), while was similar and higher in cells exposed to street MA sample 1 (P=0.39), and street MA sample 2 and 3 (P&le / 0.04), respectively at 96hrs. </span><span style="color: windowtext / font-size: 11.5pt">5. bEnd5 cell were arrested between 72 and 96hrs at the G1-S phase.&nbsp / </span></div> <div style="margin: 0cm 0cm 25pt"><span style="line-height: 115% / font-size: 11.5pt">In conclusion, this study demonstrated pure and illicit samples of MA obtained from forensic police did not affect the viability of bEnd5 cells, however resulted in the significant suppression of their cell numbers. This growth inhibition may be due to MA-induced cell cycle arrest at the G1-S phase. The study also showed that compounds found in the samples of street MA produced results significantly different to that of pure MA.</span></div>

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