Filter Dissertations and Theses By:
An ethnobotanical, ecological and LC-MS-based chemometric investigation of Phaleria nisidai, a traditional adaptogen containing diterpene esters from Palau, Micronesia
Year of Dissertation:
An ethnobotanical, ecological and LC-MS-based chemometric investigation of Phaleria nisidai, a traditional adaptogen containing diterpene esters from Palau, Micronesia Palau is a country with a rich heritage of traditional medicine still being practiced. One of the most popular and respected remedies in Palau is a tea made from fresh leaves of Phaleria nisidai Kaneh. (Thymelaeaceae). Interviews conducted to determine the use of this plant revealed that it is employed non-specifically to treat a variety of general health concerns. Its use as a prophylactic to keep away sickness, as a 'system cleaner', as well as for strength and energy indicate that it is being used as an adaptogen, a medicine taken routinely to help adapt to external pathogenic, mental or physical stress. A series of in vitro immunological assays were conducted to determine the effect of crude extracts and guide phytochemical fractionation of this plant to identify immunostimulant compounds. Phaleria nisidai is in the family Thymelaeaceae, one of two plant families known to produce diterpene ester compounds. Multivariate analysis to compare mass spectral data of active and inactive fractions allowed for the identification of several daphnane diterpene esters as tentative active marker compounds. Simplexin, the marker contributing most to differentiation of active and inactive fractions, was active when tested alone for stimulation of cytokine output by peripheral blood mononuclear cells (PBMCs). This demonstrated that a chemometric approach to active compound determination as opposed to traditional time- and resource-intensive bioactivity-guided purification methods to determine active compounds in a plant matrix was successful. This work also confirms a methanol extract of this plant and one of its constituents has activity as an immunostimulant, verifying its traditional use. This is also the first report of diterpene esters in the genus Phaleria. Simplexin and other diterpene esters have shown cocarcinogenic and irritant activity in cell and mouse models and have caused gastric and pulmonary problems in animals grazing on plants containing these compounds. However, these compounds have also shown anti-HIV and anticancer activity. To determine if Palauans are ingesting diterpene esters in traditional preparations of Phaleria nisidai, simplexin, acetoxyhuratoxin and huratoxin were quantified from methanol and aqueous extracts prepared in the lab and in aqueous infusions prepared by six traditional healers in Palau. Diterpenes were not detected in traditional aqueous extracts prepared by healers in Palau, or in aqueous extracts prepared in our lab, but were detected in the methanol extract. PBMC proliferation as well as their production of IFNγ was measured and it was found that aqueous extracts induce both PBMC proliferation as well as an increase in IFNγ production, although these effects were milder and significantly less than the activity demonstrated by the methanol extract. This further validated the traditional use of P. nisidai as an immunestimulating adaptogen and allayed concerns about public health issues with chronic ingestion of aqueous P. nisidai infusions. Levels of simplexin, acetoxyhuratoxin, huratoxin and a bioactive xanthone, mangiferin, were analyzed in leaf samples from 227 trees collected from 92 populations of Phaleria nisidai. All Rock Island populations contained minute daphnane concentrations and lower amounts of mangiferin than populations on the largest Palauan island, Babeldaob. Savannah, scrub savanna and mature forest habitats all contained populations with exceptionally high levels of daphnanes, while the mangiferin content across habitats was more homogenous. Analysis of these compounds by geographic variables can be useful to identify high-yielding chemotypes for biomedical or toxicological studies. These studies demonstrate that Palauan traditional medicine can offer a source of plant metabolites with potent biological activity that corresponds to their traditional use. The discovery of simplexin and other diterpene esters in a plant consumed daily indicates that Palauans have found a way to selectively extract beneficial compounds while minimizing exposure to potentially harmful metabolites. The possibility also exists that Palauans have uncovered a low-dose therapeutic window at which diterpene esters can provide immunostimulant benefits while avoiding toxicological risks. The pharmacological potential of simplexin and related diterpenes in Phaleria nisidai should be reevaluated in light of these findings.
The Behavioral Effects of Exposure to the Endocrine Disrupting Chemical, Ethinyl Estradiol, on Fourspine Stickleback (Apeltes quadracus)
Year of Dissertation:
There is growing evidence that endocrine disrupting chemicals polluting the environment have the potential to affect animal health and behavior. Ethinyl estradiol (EE2), the active ingredient in contraceptive pills and hormone-replacement therapies, is a particularly potent endocrine disrupting chemical found in our waterways. In this study, adult male and female fish were used to investigate the effects of a 60 day EE2 exposure on 1) ecologically relevant behaviors, 2) gonadal state, and 3) male reproductive coloration. Exposure to levels of EE2 documented in the environment (10, 70 and 100 ng/L) detrimentally altered fish behavior. Fish exposed to EE2 were less active, more aggressive, and avoided an artificial predator less often. 100 days in clean water reversed some but not all of these behavioral changes. In both males and females, gonads in exposed groups differed from controls, and included the presence of ovotestes found only in males exposed to EE2. Reproductive coloration in males was not affected by exposure. This is the first report of long-lasting behavioral aberrations caused by EE2 exposure in adult fish.
In Vitro Models to Study the Properties of the TCRα Locus Control Region
Year of Dissertation:
Locus Control Regions (LCR) are cis-acting gene regulatory elements with the unique, integration site-independent ability to transfer the characteristics of their locus-of-origin's gene expression pattern to a linked transgene. LCR activities have been discovered in numerous T cell-lineage gene loci. These elements can be adapted to the design of gene therapy vectors that direct robust therapeutic gene expression to the T cell progeny of engineered stem cells. Currently, transgenic mice provide the only experimental approach that wholly supports all the critical aspects of LCR activity. Herein, we report two cell culture models to study the properties of the T cell receptor (TCR)-α LCR. The first is an in vitro embryonic stem cell differentiation model that has been optimized to manifest all key features of mouse TCRα LCR function. High level, copy number-related TCRα LCR-linked reporter gene expression levels are cell type-restricted in this system, and are upregulated during the expected stage transition of T cell development. The ability of this LCR to overcome position effects may be due to barrier insulator-like activity within. To further explore this possibility, we established a second model that seems to support this notion. The characterization and identification of the sequences involved in this possible barrier insulator will provide an additional vertebrate model for the study of insulators. This study additionally validates a novel, tractable and more rapid approach for the study of LCR activity in T cells, and its translation to therapeutic genetic engineering.
Diet and feeding strategies of redbreast sunfish (Lepomis aurtitus) and bluegill sunfish (Lepomis macrochirus) in two suburban lakes.
Year of Dissertation:
This is a study of the feeding habits of two species of sunfish, Lepomis auritus (Linnaeus, 1758), redbreast sunfish, and Lepomis macrochirus Rafinesque, 1819, bluegill sunfish, co-occurring in two suburban lakes with different degrees of shoreline development. Since it has been well-documented that other animal species change their dietary habits during or just prior to breeding season, it seemed sensible to determine if sunfish also exhibited this behavior. The two study lakes are close in proximity in Putnam County, New York. Lake Mahopac is a more urbanized setting, close to road traffic, surrounded by homes, and has little to no vegetation due to the introduction of grass carp. Long Pond is in a more pristine setting with one side being entirely wooded. It is not close to any main roads and there are few houses on the perimeter. The vegetation is for the most part undisturbed except for a small amount removed from its beach areas. Despite the lack of vegetation, Lake Mahopac still has as much species diversity as Long Pond. Unfortunately the bluegill population in Lake Mahopac has suffered from the lack of weed beds, which are necessary for successful breeding, which has resulted in a steady decline in numbers. The redbreast sunfish population in Long Pond is very small, most likely due to the fact that redbreast sunfish prefer moving water and Long Pond is relatively stagnant. Breeding season usually starts in May and ends in August; the exact time changes from year to year based upon weather conditions. Female bluegills from Lake Mahopac exhibited a dietary shift in which they fed opportunistically during the pre-breeding season (when water temperature is below 20° C), but shifted to that of a specialist during the breeding period (when water temperature is between 20° C to 28°C) and post-breeding (when water temperature once again begins to cool). When water temperature falls below 20° C in the fall, sunfish move to deeper waters until the following spring when the water once again warms up and they move to the shoreline to breed. There is some dietary overlap between the species, especially between females during pre-breeding, as well as between male and female redbreast sunfish from Lake Mahopac and male and female bluegills from Long Pond, indicating that if food sources become scarce they could develop both interspecific competition between females and intraspecific competition between the sexes in each lake.
IMPACT OF ODORS ON PATERNAL RESPONSIVENESS AND ASSOCIATED NEURONAL ACTIVITY IN "EXPECTANT" MALE PRAIRIE VOLES (Microtus ochrogaster),
Year of Dissertation:
Dr. Maryam Bamshad-Alavi
Prairie voles (Microtus ochrogaster) are unusual mammals because they are socially monogamous. The breeding pairs form pair bonds and jointly care for offspring. Although the duration and intensity of parental behavior in male prairie voles is similar to that observed in females, there are sex differences in the onset and pattern of infant caring in this species. The factors that contribute to sex differences in parental behavior of prairie voles are unknown. As males and females show all components of active and inactive parental behaviors, it is possible that sensory inputs from infants arouse a different pattern of parental care in each sex. Males and females may also differ in the degree of attentiveness to infant sensory cues and to other environmental stimuli. Furthermore, they may focus their attention on different aspects of infant cues or perceive the same cues differently. I conducted three experiments to test these hypotheses. In the first experiment, I tested the attentiveness and sensitivity of male and female prairie voles towards infant-related odors across the reproductive period. Males and females showed increased attentiveness to infant-related odors at different times during the reproductive period. In the second experiment, I examined the impact of female sensory cues on male responsiveness towards infant odors. The data suggest that male's exposure to the female's tactile and distal cues during the gestation period elicited indirect paternal behavior in presence of infant odors. However, infant odors alone were insufficient to stimulate direct paternal responsiveness in these males. In the third experiment, I studied the neuronal activity of brain areas that could be involved in the enhanced indirect paternal behavior that was observed in males housed with their mate through mid gestation. In response to infant-related odors, males that had stayed with their mate had higher neuronal activity in the ventral tegmental area (VTA) compared to males that had stayed with their same-sex sibling. Together, these studies indicate that female sensory cues in prairie voles play an important role in enhancing indirect paternal care by increasing the male's attentiveness to odors and activating neurons in the VTA region of his brain.
Lichen Taxonomy for the 21st Century: A Revision of the Genus Lepraria s.l. in North America north of Mexico
Year of Dissertation:
The results of a series of studies of lichens are presented. These studies are hoped to codify a forward for taxonomic progress in the group. Chapter one presents a standardized morphological terminology and descriptive scheme for the sterile crustose genus Lepraria. Chapters two through seven present a series of studies where molecular phylogenetic analyses of nrITS sequence were used to resolve species boundaries in Cladonia (III), Lepraria (IV-VII), and Punctelia (II). Chapter eight reveals not all sterile crustose lichens resemble their congeners. Chapter nine presents a study in the use of molecular data to place an unknown sterile crustose lichen in higher level classification of fungi. Chapter ten uses that method to revise the circumscriptions of Lepraria and the sterile fruticose genus Leprocaulon. Finally, chapter eleven comprises a taxonomic revision of the crustose species of Lepraria s. str. that occur in North America north of Mexico.
Regulation of anti-dsDNA B-cells in mice transgenic for the heavy and light chains of an Anti-dsDNA antibody
Year of Dissertation:
Regulation of anti-dsDNA B-cells in mice transgenic for the heavy and light chains of an Anti-dsDNA antibody By Rita H. Lewis Advisor: Professor Linda A. Spatz The diversity of the B-cell repertoire is important for the development of antibodies to a multitude of pathogens. However, in the process of generating antibody diversity, B-cells arise that produce antibodies to self-antigens. These autoreactive B-cells must be kept in check lest they secrete autoantibodies that can induce autoimmune disease. There are several mechanisms inherent in the immune system for regulating autoreactive B-cells. I have been using a transgenic mouse model, in which mice were made transgenic for the R4A IgM heavy and Vê1 light chain genes of an anti-double stranded DNA (anti-dsDNA) antibody, to study the regulation of anti-dsDNA B cells. Anti-dsDNA antibodies are the hallmark of the autoimmune disease Systemic Lupus Erythematosus (SLE). I observed that the transgenic anti-dsDNA B cells are targeted to anergy in the R4A-Cì/Vê1 mice as evidenced by arrested development, receptor down modulation, and functional unresponsiveness and reduced calcium flux in response to B-cell receptor stimulation. I also observed a relatively high frequency of transgenic B cells in the T1 but not the T2 or mature stages of development. In addition, transgenic T1 B cells were observed to display features of anergy suggesting that the T1 stage may be a regulatory checkpoint where anti-dsDNA B cells are anergized and subsequently eliminated. Interestingly, transgenic B-cells that were able to transition to the T2 and T3 stages of development tended to co-express an endogenous heavy chain while the majority of mature B cells in these mice expressed the endogenous heavy chain only. Surprisingly, however, B-cells expressing only the endogenous heavy chain on their membrane were also observed to express transgenic heavy chain transcripts. These results have led me to propose a model whereby autoreactive B cells can escape a regulatory checkpoint if they express more than one heavy chain. These dual receptor expressing B-cells may have diminished autoreactivity if the level of membrane expression of the transgenic heavy chain is low relative to the level of expression of the endogenous heavy chain. Subsequent down-regulation of the transgenic heavy chain as a B-cell matures in the periphery may be a novel mechanism for averting autoreactivity.
Hyper-activated protein kinase C mediates the reduced AMPA receptor surface expression in prenatal cocaine exposed brains: the role for diacylglycerol, diacylglycerol kinase, and 3-phosphoinositide-dependent kinases.
Year of Dissertation:
Abstract Hyper-activated protein kinase C mediates the reduced AMPA receptor surface expression in prenatal cocaine exposed brains: the role for diacylglycerol, diacylglycerol kinase, and 3-phosphoinositide-dependent kinases. By Jingjing Liu Advisor: Professor Hoau-Yan Wang Prenatal cocaine exposure induced neurobehavioral and synaptic changes are in part mediated by the defected alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-type glutamatergic receptor (AMPAR) neurotransmission. This abnormality of AMPAR system is related to reduced AMPA-GluR2/3 synaptic targeting, which is resulting from sustained phosphorylation of glutamate receptor-interacting protein (GRIP) by hyper-activated protein kinase C (PKC) (Bakshi et al., 2009). The underlying molecular mechanism responsible for PKC hyper-activation, however, remains obscure. Blockade of PKC and PKC/M by their specific pseudosubstrate inhibitors restores AMPAR synaptic targeting, demonstrating that PKC is essential in producing AMPAR abnormalities in prenatal cocaine exposed animal brains. The enhanced PKC activation by prenatal cocaine exposure correlates with an elevated 3-phosphoinositide-dependent protein kinase-1 (PDK1) level, and a persistent increase of synaptic membranous diacylglycerol (DAG) level resulting from down-regulated GRIP-associated DAG kinase (DGKγ and DGKζ) subtypes. Altogether, these data provide the molecular underpinning for persistent PKC activation in prenatal cocaine-exposed brain and suggest that suppression of PKCγ and PKC/PKMζ can restore GluR2/3 synaptic targeting and AMPAR function. Importantly, the data derived from this study may provide a novel strategy to treat neurobehavioral abnormalities resulting from prenatal cocaine exposure.
Characterization of the Sinorhizobium meliloti ExoR protein
Year of Dissertation:
The soil bacterium Sinorhizobium meliloti is capable of establishing a symbiotic relationship with its leguminous plant host alfalfa by forming nitrogen-fixing root nodules through a series of signal exchanges and structural changes. The presence of a potential bacterial signal molecule, succinoglycan, is required for the invasion step of this symbiosis. The production of succinoglycan, which is inversely coupled with the production of flagella, is tightly regulated by the S. meliloti ExoR protein and the ExoS/ChvI two-component regulatory system. To better understand the regulatory function of ExoR and its relationship with the ExoS/ChvI system, I have carried out extensive genetic and biochemical analyses of ExoR and ExoS proteins. I found that ExoR is a periplasmic protein and it functions only in the periplasm. Interestingly, the C-terminal 20 amino acids appear not to be essential for the regulatory function of ExoR. Most importantly, the ExoR protein is digested in the periplasm, which appears to be the molecular mechanism regulating the amount of functional ExoR protein in the periplasm. The genetic analysis of my collection of exoR, exoS, and chvI mutants suggests that ExoR functions upstream of the ExoS/ChvI two-component signal transduction pathway. This conclusion was further supported by the analysis of the exoR expression in different genetic backgrounds, which suggests the ExoR-ExoS-ChvI pathway is feedback regulated by ExoR. The combination of biochemical and genetic analyses suggest that ExoR functions in the periplasm through interaction with the ExoS sensing domain to keep ExoS in the off state. The proteolysis of ExoR would reduce the amount of functional ExoR and lead to the activation of ExoS and the expression of the genes regulated by the pathway. With the continuous discovery of ExoR/ExoS/ChvI homologous systems in a wide range of bacteria, my findings will contribute to a better understanding of the S. meliloti-alfalfa symbiosis and the pathogenicity of some bacterial plant and animal pathogens.
Antimalarial Benzophenones and Xanthones from Garcinia species
Year of Dissertation:
Garicina, a genus in the Clusiaceae, is a source of antiparasitic and antimalarial phenolic secondary metabolites, including benzophenones and xanthones. The methanolic extracts of G. livingstonei, G. mangostana, G. spicata, and G. xanthochymus were tested in vitro for antiplasmodial activity against the P. falciparum clone D6. The crude methanolic G. mangostana extract inhibited the clone by 89%, while the G. xanthochymus extract inhibited it by 24%. Neither of the extracts showed any cytotoxicity toward Vero cells. Hexanes, EtOAc, and n-BuOH partitions of a G. xanthochymus seed extract were also screened against the P. falciparum clone D6, the hexanes partition inhibited the clone by 58%, the EtOAc and n-BuOH partitions showed no inhibitory activity. Additionally, compounds identified from Garcinia species were screened in the plasmodial lactase dehydrogenase (pLDH) activity assay. The compounds tested were: aristophenone A (1), cycloxanthochymol (2), gambogenone (3), guttiferone A (4), guttiferone E (5), guttiferone H (6), isoxanthochymol (7), xantochymol (8), xanthone (9), mangiferin (10), alloathyriol (11), alpha-mangostin (12), beta-mangostin (13), 3-isomangostin (14), 8-desoxygartanin (15), 4-methoxyxanthone (16), 1,5,6-trihydroxyxanthone (17), and 32-hydroxy-ent-guttiferone M (18). Only compounds 5, 6, 7, 12, 13, and 14 showed antiplasmodial activity. The antiplasmodial activities of compounds 5, 6, and 14 have not been previously reported. This is the first report of 7, 12, and 13 having antiplasmodial activity against the chloroquine-sensitive P. falciparum clone D6 and chloroquine-resistant clone W2. For the benzophenones 8 and 2 the absence of a terminal methylene on the C-8 side chain (cf. 5 and 7) correlates with antiplasmodial activity. Compound 6 with a terminal methylene on C-30 and a cyclohexane from C-7 to C-8 is antiplasmodial. It was concluded that, for benzophenones neither the C-5 nor the C-14 side groups affect antiplasmodial activity. The substitution pattern of both the A and B rings of the xanthones was shown to be important in determining the extent of antiplasmodial activity. An isoprenyl chain was necessary on C-8 for antiplasmodial activity (cf. 12 and 14). The results indicate that the antiplasmodial activity is determined by factors other than the hydroxylation of C-4 and C-5 alone as the current structure activity studies indicate.