966 resultados para Biology, Molecular|Health Sciences, Pathology|Biophysics, General


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The improvement of tropical tree crops using conventional breeding methods faces challenges due to the length of time involved. Thus, like most crops, there is an effort to utilize molecular genetic markers in breeding programs to select for desirable agronomic traits. Known as marker assisted breeding or marker assisted selection, genetic markers associated with a phenotype of interest are used to screen and select material reducing the time necessary to evaluate candidates. As the focus of this research was improving disease resistance in tropical trees, the usefulness of the WRKY gene superfamily was investigated as candidates for generating useful molecular genetic markers. WRKY genes encode plant-specific transcriptional factors associated with regulating plants' responses to both biotic and abiotic stress. ^ One pair of degenerate primers amplified 48 WRKY gene fragments from three taxonomically distinct, economically important, tropical tree crop species: 18 from Theobroma cacao L., 21 from Cocos nucifera L. and 9 from Persea americana Mill. Several loci from each species were polymorphic because of single nucleotide substitutions present within a putative non-coding region of the loci. Capillary array electrophoresis-single strand conformational polymorphism (CAE-SSCP) mapped four WRKY loci onto a genetic linkage map of a T. cacao F2 population segregating for resistance to witches' broom disease. Additionally, PCR primers specific for four T. cacao loci successfully amplified WRKY loci from 15 members of the Byttneriae tribe. A method was devised to allow the reliable discrimination of alleles by CAE-SSCP using only the mobility assigned to the sample peaks. Once this method was validated, the diversity of three WRKY loci was evaluated in a germplasm collection of T. cacao . One locus displayed high diversity in the collection, with at least 18 alleles detected from mobility differences of the product peaks. The number of WRKY loci available within the genome, ease of isolation by degenerate PCR, codominant segregation demonstrated in the F2 population, and usefulness for screening germplasm collections and closely related wild species demonstrates that the WRKY superfamily of genes are excellent candidates for developing a number of genetic molecular markers for breeding purposes in tropical trees. ^

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The Inupiaq Tribe resides north of the Arctic Circle in northwestern Alaska. The people are characterized by their continued dependence on harvested fish, game and plants, known as a subsistence lifestyle (Lee 2000:35-45). Many are suggesting that they leave their historical home and move to urban communities, places believed to be more comfortable as they age. Tribal Elders disagree and have stated, "Elders need to be near the river where they were raised" (Branch 2005:1). The research questions focused on differences that location had on four groups of variables: nutrition parameters, community support, physical functioning and health. A total of 101 Inupiaq Elders ≥ 50 years were surveyed: 52 from two rural villages, and 49 in Anchorage. Location did not influence energy intake or intake of protein; levels of nutrition risk and food insecurity; all had similar rates between the two groups. Both rural and urban Elders reported few limitations of ADLs and IADLs. Self-reported general health scores (SF-12.v2 GH) were also similar by location. Differences were found with rural Elders reporting higher physical functioning summary scores (SF-12.v2 PCS), higher mental health scores (SF-12.v2 MH), higher vitality and less pain even though the rural mean ages were five years older than the urban Elders. Traditional food customs appear to support the overall health and well being of the rural Inupiaq Elders as demonstrated by higher intakes of Native foods, stronger food sharing networks and higher family activity scores than did urban Elders. The rural community appeared to foster continued physical activity. It has been said that when Elders are in the rural setting they are near "people they know" and it is a place "where they can get their Native food" (NRC 2005). These factors appear to be important as Inupiaq Elders age, as rural Inupiaq Elders fared as well or better than Inupiaq Elders in terms of diet, mental and physical health.

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In many vertebrate and invertebrate species mediators of innate immunity include antimicrobial peptides (AMPs) such as peptide fragments of histones and other proteins with previously ascribed different functions. Shark AMPs have not been described and this research examines the antibacterial activity of nurse shark (Ginglymostoma cirratum) peripheral blood leukocyte lysates. Screening of lysates prepared by homogenizing unstimulated peripheral blood leukocytes identified muramidase (lysozyme-like) and non-muramidase antibacterial activity. Lysates were tested for lysozyme using the lysoplate assays, and antibacterial (AB) activity was assayed for by a microdilution growth assay that was developed using Planococcus citreus as the target bacterium. Fractionation of crude lysates by ion exchange and affinity chromatography was followed by a combination of SDS-PAGE with LC/MS-MS and/or N-terminal sequence analysis of low molecular weight protein bands (<20 kDa). This yielded several peptides with amino acid sequence similarity to lysozyme, ubiquitin, hemoglobin, human histones H2A, H2B and H4 and to antibacterial histone fragments of the catfish and the Asian toad. Not all peptide sequences corresponded to peptides potentially antibacterial. The correlation of a specific protein band in active lysate fractions was accomplished by employing the acid-urea gel overlay assays in which AB activity was seen as zones of growth inhibition on a lawn of P. citreus at a position corresponding to that of the putative AB protein band. This study is the first to describe putative AMPs in the shark and their potential role in innate immunity.^

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Bio-molecular interactions exist ubiquitously in all biological systems. This dissertation project was to construct a powerful surface plasmon resonance (SPR) sensor. The SPR system is used to study bio-molecular interactions in real time and without labeling. Surface plasmon is the oscillation of free electrons in metals coupled with surface electromagnetic waves. These surface electromagnetic waves provide a sensitive probe to study bio-molecular interactions on metal surfaces. This project resulted in the successful construction and optimization of a homemade SPR sensor and the development of several new powerful protocols to study bio-molecular interactions. It was discovered through this project that the limitations of earlier SPR sensors are related not only to the instrumentation design and operating procedures, but also to the complex behaviors of bio-molecules on sensor surfaces that were very different from that in solution. Based on these discoveries the instrumentation design and operating procedures were fully optimized. A set of existing sensor surface treatment protocols were tested and evaluated and new protocols were developed in this project. The new protocols have demonstrated excellent performance to study biomolecular interactions. The optimized home-made SPR sensor was used to study protein-surface interactions. These protein-surface interactions are responsible for many complex organic cell activities. The co-existence of different driving forces and their correlation with the structure of the protein and the surface make the understanding of the fundamental mechanism of protein-surface interactions a very challenging task. Using the improved SPR sensor, the electrostatic interaction and hydrophobic interaction were studied separately. The results of this project directly confirmed the theoretical predictions for electrostatic force between the protein and surface. In addition, this project demonstrated that the strength of the protein-surface hydrophobic interaction does not solely depend on the hydrophobicity as reported earlier. Surface structure also plays a significant role.

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Pseudomonas aeruginosa is an opportunistic pathogen that has received attention because of its close association with cystic fibrosis (CF). Chronic pulmonary infection with the mucoid P. aeruginosa is the leading cause of mortality in CF patients. This bacterium has the ability to sense and adapt to the harsh environment in the CF lung by converting from a nonmucoid to a mucoid state. The mucoid phenotype is caused by overproduction of a polysaccharide called alginate. Alginate production is regulated by the algT/U operon containing five genes, algT/U-mucA-mucB-mucC-mucD. Alginate overproduction in CF isolates has been partially attributed to a loss-of-function mutation in mucA that results in the overexpression of algT. This mucoid phenotype is unstable, reverting to the nonmucoid form when the isolates are cultured outside of the CF lung. This study was undertaken to determine the mechanisms involved in the conversion from the mucoid to the nonmucoid form. Thirty-six spontaneous nonmucoid variants of a known mucoid isolate with a mucA mutation were analyzed. Ten of these isolates were complemented in trans by plasmids containing the algT operon and the algT gene. Chromosomal DNA was extracted and the mucA and algT genes were amplified by the polymerase chain reaction. Sequence analysis of the genes showed that these mutants retained the original mucA mutation but acquired secondary mutations in the algT gene.

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The emergence of tamoxifen or aromatase inhibitor resistance is a major problem in the treatment of breast cancer. The molecular signaling mechanism of antiestrogen resistance is not clear. Understanding the mechanisms by which resistance to these agents arise could have major clinical implications for preventing or circumventing it. Therefore, in this dissertation we have investigated the molecular mechanisms underlying antiestrogen resistance by studying the contributions of reactive oxygen species (ROS)-induced redox signaling pathways in antiestrogen resistant breast cancer cells. Our hypothesis is that the conversion of breast tumors to a tamoxifen-resistant phenotype is associated with a progressive shift towards a pro-oxidant environment of cells as a result of oxidative stress. The hypothesis of this dissertation was tested in an in vitro 2-D cell culture model employing state of the art biochemical and molecular techniques, including gene overexpression, immunoprecipitation, Western blotting, confocal imaging, ChIP, Real-Time RT-PCR, and anchorage-independent cell growth assays. We observed that tamoxifen (TAM) acts like both an oxidant and an antioxidant. Exposure of tamoxifen resistant LCC2 cell to TAM or 17 beta-estradiol (E2) induced the formation of reactive oxidant species (ROS). The formation of E2-induced ROS was inhibited by co-treatment with TAM, similar to cells pretreated with antioxidants. In LCC2 cells, treatments with either E2 or TAM were capable of inducing cell proliferation which was then inhibited by biological and chemical antioxidants. Exposure of LCC2 cells to tamoxifen resulted in a decrease in p27 expression. The LCC2 cells exposed to TAM showed an increase in p27 phosphorylation on T157 and T187. Conversely, antioxidant treatment showed an increase in p27 expression and a decrease in p27 phosphorylation on T157 and T187 in TAM exposed cells which were similar to the effects of Fulvestrant. In line with previous studies, we showed an increase in the binding of cyclin E-Cdk2 and in the level of p27 in TAM exposed cells that overexpressed biological antioxidants. Together these findings highly suggest that lowering the oxidant state of antiestrogen resistant LCC2 cells, increases LCC2 susceptibility to tamoxifen via the cyclin dependent kinase inhibitor p27.

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Fluorescent proteins (FPs) are extremely valuable biochemical markers which have found a wide range of applications in cellular and molecular biology research. The monomeric variants of red fluorescent proteins (RFPs), known as mFruits, have been especially valuable for in vivo applications in mammalian cell imaging. Fluorescent proteins consist of a chromophore caged in the beta-barrel protein scaffold. The photophysical properties of an FP is determined by its chromophore structure and its interactions with the protein barrel. Application of hydrostatic pressure on FPs results in the modification of the chromophore environment which allows a systematic study of the role of the protein-chromophore interactions on photophysical properties of FPs. Using Molecular Dynamics (MD) computer simulations, I investigated the pressure induced structural changes in the monomeric variants mCherry, mStrawberry, and Citrine. The results explain the molecular basis for experimentally observed pressure responses among FP variants. It is found that the barrel flexibility, hydrogen bonding interactions and chromophore planarity of the FPs can be correlated to their contrasting photophysical properties at vaious pressures. I also investigated the oxygen diffusion pathways in mOrange and mOrange2 which exhibit marked differences in oxygen sensitivities as well as photostability. Such computational identifications of structural changes and oxygen diffusion pathways are important in guiding mutagenesis efforts to design fluorescent proteins with improved photophysical properties.

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HIV-associated neurocognitive disorders (HAND) is characterized by development of cognitive, behavioral and motor abnormalities, and occur in approximately 50% of HIV infected individuals. Our current understanding of HAND emanates mainly from HIV-1 subtype B (clade B), which is prevalent in USA and Western countries. However very little information is available on neuropathogenesis of HIV-1 subtype C (clade C) that exists in Sub-Saharan Africa and Asia. Therefore, studies to identify specific neuropathogenic mechanisms associated with HAND are worth pursuing to dissect the mechanisms underlying this modulation and to prevent HAND particularly in clade B infection. In this study, we have investigated 84 key human synaptic plasticity genes differential expression profile in clade B and clade C infected primary human astrocytes by using RT2 Profile PCR Array human Synaptic Plasticity kit. Among these, 31 and 21 synaptic genes were significantly (≥3 fold) down-regulated and 5 genes were significantly (≥3 fold) up-regulated in clade B and clade C infected cells, respectively compared to the uninfected control astrocytes. In flow-cytometry analysis, down-regulation of postsynaptic density and dendrite spine morphology regulatory proteins (ARC, NMDAR1 and GRM1) was confirmed in both clade B and C infected primary human astrocytes and SK-N-MC neuroblastoma cells. Further, spine density and dendrite morphology changes by confocal microscopic analysis indicates significantly decreased spine density, loss of spines and decreased dendrite diameter, total dendrite and spine area in clade B infected SK-N-MC neuroblastoma cells compared to uninfected and clade C infected cells. We have also observed that, in clade B infected astrocytes, induction of apoptosis was significantly higher than in the clade C infected astrocytes. In conclusion, this study suggests that down-regulation of synaptic plasticity genes, decreased dendritic spine density and induction of apoptosis in astrocytes may contribute to the severe neuropathogenesis in clade B infection.

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Androgen receptor (AR) is commonly expressed in both the epithelium of normal mammary glands and in breast cancers. AR expression in breast cancers is independent of estrogen receptor alpha (ERα) status and is frequently associated with overexpression of the ERBB2 oncogene. AR signaling effects on breast cancer progression may depend on ERα and ERBB2 status. Up to 30% of human breast cancers are driven by overactive ERBB2 signaling and it is not clear whether AR expression affects any steps of tumor progression in this cohort of patients. To test this, we generated mammary specific Ar depleted mice (MARKO) by combining the floxed allele of Ar with the MMTV-cre transgene on an MMTV-NeuNT background and compared them to littermate MMTV-NeuNT, Arfl/+ control females. Heterozygous MARKO females displayed reduced levels of AR in mammary glands with mosaic AR expression in ductal epithelium. The loss of AR dramatically accelerated the onset of MMTV-NeuNT tumors in female MARKO mice. In this report we show that accelerated MMTV-NeuNT-dependent tumorigenesis is due specifically to the loss of AR, as hormonal levels, estrogen and progesterone receptors expression, and MMTV-NeuNT expression were similar between MARKO and control groups. MMTV-NeuNT induced tumors in both cohorts displayed distinct loss of AR in addition to ERα, PR, and the pioneer factor FOXA1. Erbb3 mRNA levels were significantly elevated in tumors in comparison to normal mammary glands. Thus the loss of AR in mouse mammary epithelium accelerates malignant transformation rather than the rate of tumorigenesis.

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The purpose of this study was to investigate the effects of 17-β-estradiol (E2)-induced reactive oxygen species (ROS) on the induction of mammary tumorigenesis. We found that ROS-induced by repeated exposures to 4-hydroxy-estradiol (4-OH-E2), a predominant catechol metabolite of E2, caused transformation of normal human mammary epithelial MCF-10A cells with malignant growth in nude mice. This was evident from inhibition of estrogen-induced breast tumor formation in the xenograft model by both overexpression of catalase as well as by co-treatment with Ebselen. To understand how 4-OH-E2 induces this malignant phenotype through ROS, we investigated the effects of 4-OH-E2 on redox-sensitive signal transduction pathways. During the malignant transformation process we observed that 4-OH-E2 treatment increased AKT phosphorylation through PI3K activation. The PI3K-mediated phosphorylation of AKT in 4-OH-E2-treated cells was inhibited by ROS modifiers as well as by silencing of AKT expression. RNA interference of AKT markedly inhibited 4-OH-E2-induced in vitro tumor formation. The expression of cell cycle genes, cdc2, PRC1 and PCNA and one of transcription factors that control the expression of these genes – nuclear respiratory factor-1 (NRF-1) was significantly up-regulated during the 4-OH-E2-mediated malignant transformation process. The increased expression of these genes was inhibited by ROS modifiers as well as by silencing of AKT expression. These results indicate that 4-OH-E2-induced cell transformation may be mediated, in part, through redox-sensitive AKT signal transduction pathways by up-regulating the expression of cell cycle genes cdc2, PRC1 and PCNA, and the transcription factor – NRF-1. In summary, our study has demonstrated that: (i) 4-OH-E2 is one of the main estrogen metabolites that induce mammary tumorigenesis and (ii) ROS-mediated signaling leading to the activation of PI3K/AKT pathway plays an important role in the generation of 4-OH-E2-induced malignant phenotype of breast epithelial cells. In conclusion, ROS are important signaling molecules in the development of estrogen-induced malignant breast lesions.

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In the new health paradigm, the connotation of health has extended beyond the measures of morbidity and mortality to include wellness and quality of life. Comprehensive assessments of health go beyond traditional biological indicators to include measures of physical and mental health status, social role-functioning, and general health perceptions. To meet these challenges, tools for assessment and outcome evaluation are being designed to collect information about functioning and well-being from the individual's point of view.^ The purpose of this study was to profile the physical and mental health status of a sample of county government employees against U.S. population norms. A second purpose of the study was to determine if significant relationships existed between respondent characteristics and personal health practices, lifestyle and other health how the tools and methods used in this investigation can be used to guide program development and facilitate monitoring of health promotion initiatives.^ The SF-12 Health Survey (Ware, Kosinski, & Keller, 1995), a validated measure of health status, was administered to a convenience sample of 450 employees attending one of nine health fairs at an urban worksite. The instrument has been utilized nationally which enabled a comparative analysis of findings of this study with national results.^ Results from this study demonstrated that several respondent characteristics and personal health practices were associated with a greater percentage of physical and/or mental scale scores that were significantly "worse" or significantly "better" than the general population. Respondent characteristics that were significantly related to the SF-12 physical and/or mental health scale scores were gender, age, education, ethnicity, and income status. Personal health practices that were significantly related to SF-12 physical and/or mental scale scores were frequency of vigorous exercise, presence of chronic illness, being at one's prescribed height and weight, eating breakfast, smoking and drinking status. This study provides an illustration of the methods used to analyze and interpret SF-12 Health Survey data, using norm-based interpretation guidelines which are useful for purposes of program development and collecting information on health at the community level. ^

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Arthritis is the most common chronic condition affecting older people and is a major cause of limited activity. Arthritis education programs in English have demonstrated a positive impact on health but these programs have not reached the Hispanic communities where arthritis is the leading cause of disability. Minorities, such as Hispanics, have traditionally been reluctant to pursue self-help programs, and have been identified as an under-served population in terms of medical care. This study examined the effectiveness of one community health adult education program targeting Hispanic older adults with arthritis, the Spanish Arthritis Self Management Education Program (SASMEP), by evaluating changes in the participants' general health, pain, disability, self-efficacy, health perceptions, frequency of physician visits, and exercise. A pre and post control group experimental design and analyses of covariance were used to determine the pre and post differences in health status and health behaviors for a group participating in the SASMEP and a group who did not using gender and age as covariates. A repeated measures design was also used, and repeated measures analyses of variance and post hoc tests were done on health status and health behavior data collected pre, post and one-year post education to determine long-term differences. ^ Results indicated the participants' health status significantly improved in general health, significantly decreased in pain, and significantly decreased in arthritic disability immediately following the education. Self-efficacy and health perceptions increased for both groups but not significantly. The participants' health behaviors showed significantly fewer physician visits and significantly increased time spent performing stretching and strengthening exercise and time spent performing aerobic exercise. No group differences were found in the frequency of arthritis physician visits. ^ The improvements seen immediately after the SASMEP participation were not reflected in the post one-year scores. No significant differences were found for the participants' health status or health behaviors one year following the education. Health status and health behaviors did not return below baseline scores after one year suggesting the participants' health, although not improved, did not deteriorate. Therefore, the SASMEP education provided short-term health benefits for older Hispanic adults with arthritis, but not long-term health benefits. ^

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Jacquemontia reclinata House (Convolvulaceae) is a federally-listed endangered species endemic to coastal strand habitat of southeastern Florida, from Palm Beach to Miami-Dade counties. Although J. reclinata is currently defined as a species, its taxonomic distinctness has never been analyzed using phylogenetic evidence. In order to assess the evolutionary distinctness of J. reclinata and identify its closest relatives, internal transcribed spacer (ITS) regions within nuclear ribosomal DNA were sequenced, and the sequence data was used to reconstruct a phylogeny of Jacquemontia. The study included the three putative relatives of J. reclinata and all other species within Jacquemontia known to occur in the Greater Antilles and Bahamas, except for three species. Results concur with previous morphological studies, which suggest that J. reclinata is closely related to J. cayensis Britton, J. curtisii Peter, and J. havanensis Urban. These three species and J. reclinata form an unresolved clade. Therefore, it is not certain which of these Caribbean species is sister to J. reclinata. The lack of resolution within the clade that includes J. reclinata implies that the taxa within the clade are evolutionarily similar. Future taxonomic studies of J. reclinata should focus in resolving relationships within the Jacquemontia reclinata clade.

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Receptor-tyrosine kinases (RTKs) are membrane bound receptors characterized by their intrinsic kinase activity. RTK activities play an essential role in several human diseases, including cancer, diabetes and neurodegenerative diseases. RTK activities have been regulated by the expression or silencing of several genes as well as by the utilization of small molecules. Ras Interference 1 (Rin1) is a multifunctional protein that becomes associated with activated RTKs upon ligand stimulation. Rin1 plays a key role in receptor internalization and in signal transduction via activation of Rab5 and association with active form of Ras. This study has two main objectives: (1) It determines the role of Rin1 in the regulation of several RTKs focusing on insulin receptor. This was accomplished by studying the Rin1-insulin receptor interaction using a variety of biochemical and morphological assays. This study shows a novel interaction between the insulin receptor and Rin1 through the Vps9 domain. Two more RTKs (epidermal growth factor receptor and nerve growth factor receptor) also interacted with the SH2 domain of Rin1. The effect of the Rin1-RTK interaction on the activation of both Rab5 and Ras was also studied during receptor internalization and intracellular signaling. Finally, the role of Rin1 was examined in two differentiation processes (adipogenesis and neurogenesis). Rin1 showed a strong inhibitory effect on 3T3-L1 preadipocyte differentiation but it seems to show a modest effect in PC12 neurite outgrowth. These data indicate a selective function and specific interaction of Rin1 toward RTKs. (2) It examines the role of the small molecule Dehydroleucodine (DhL) on several key signaling molecules during adipogenesis. This was accomplished by studying the differentiation of 3T3-L1 preadipocytes exposed to different concentrations of DhL in different days of the adipocyte formation process. The results indicate that DhL selectively blocked adipocyte formation, as well as the expression of PPARγ, and C/EBP&agr;. However, DhL treatment did not affect Rin1 or Rab5 expression and their activities. Taken together, the data indicate a potential molecular mechanism by which proteins or small molecules regulate selective and specific RTK intracellular membrane trafficking and signaling during cell growth and differentiation in normal and pathological conditions.

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Pythagoras, Plato and Euclid’s paved the way for Classical Geometry. The idea of shapes that can be mathematically defined by equations led to the creation of great structures of modern and ancient civilizations, and milestones in mathematics and science. However, classical geometry fails to explain the complexity of non-linear shapes replete in nature such as the curvature of a flower or the wings of a Butterfly. Such non-linearity can be explained by fractal geometry which creates shapes that emulate those found in nature with remarkable accuracy. Such phenomenon begs the question of architectural origin for biological existence within the universe. While the concept of a unifying equation of life has yet to be discovered, the Fibonacci sequence may establish an origin for such a development. The observation of the Fibonacci sequence is existent in almost all aspects of life ranging from the leaves of a fern tree, architecture, and even paintings, makes it highly unlikely to be a stochastic phenomenon. Despite its wide-spread occurrence and existence, the Fibonacci series and the Rule of Golden Proportions has not been widely documented in the human body. This paper serves to review the observed documentation of the Fibonacci sequence in the human body.