Investigation of reagent storage and electrochemical testing on filter paper

Thesis (Ph.D.)--Boston UniversityDiagnosis and detection is one of the most effective means of controlling matters that adversely affect public health and safety. Yet, in the developing world with a high burden of disease, most gold standard diagnostics remain widely inaccessible due to cost and lack of infrastructure. In recent years, one strategy to increase access to health and safety devices has been through the development of point-of-care diagnostics that are low-cost, portable, and easy-to-use for on-site analysis. In particular, paper has recently been in the spotlight as such a point-of-care (POC) platform. Compared to conventional POC tests made of glass or plastic substrates, paper itself is even thinner, light-weight, portable, disposable, and can store biological and chemical molecules for analytical measurement within its fibrous network. Several paper-based tests have demonstrated high sensitivity and specificity to detect proteins, bacteria, and metals for applications in disease diagnosis, health monitoring, and food and water safety. However, several gaps still remain in order to fully develop these paper-based analytical devices for point-of-care use in low-resource settings. First, reagent stability on filter paper is poorly understood, as well as its influence on quantitative, long-term testing. Second, the need for specialized instrumentation to perform the analytical methods on the paper devices can be a logistical and financial burden to end users in resource-limited settings. This dissertation addressed these questions through the development of quantitative paper assays for robust and point-of-care testing in low-resource settings. First, we fabricated micro-paper electrochemical devices, or µPEDs, for the amperometric detection of ethanol. This target analyte has direct applications in the global issue of road safety, which claims thousands of lives due to driving under the influence of alcohol. Also, we demonstrate that ethanol detection can provide the basis for the novel detection of substandard misoprostol, a high impact drug to save mothers from post-partum bleeding that is often the reason for maternal mortality. Second, we developed an independent method to study reagent stability on filter paper under conditions likely encountered in low-resource settings. Methods that enhanced stability were also used in the development of the µPEDs. Finally, we demonstrate that the ethanol measurements on our µPEDs could be performed with a commercial glucose meter, which operate by the same principles required to measure analyte concentrations. This integration of device and reader presents a cheap, reliable, low-power, and portable platform that can be adapted for the detection of other analytes relevant to health and safety

Signatures of selection in loci governing major colour patterns in Heliconius butterflies and related species.

BACKGROUND: Protein-coding change is one possible genetic mechanism underlying the evolution of adaptive wing colour pattern variation in Heliconius butterflies. Here we determine whether 38 putative genes within two major Heliconius patterning loci, HmYb and HmB, show evidence of positive selection. Ratios of nonsynonymous to synonymous nucleotide changes (ω) were used to test for selection, as a means of identifying candidate genes within each locus that control wing pattern. RESULTS: Preliminary analyses using 454 transcriptome and Bacterial Artificial Chromosome (BAC) sequences from three Heliconius species highlighted a cluster of genes within each region showing relatively higher rates of sequence evolution. Other genes within the region appear to be highly constrained, and no ω estimates exceeded one. Three genes from each locus with the highest average pairwise ω values were amplified from additional Heliconius species and races. Two selected genes, fizzy-like (HmYb) and DALR (HmB), were too divergent for amplification across species and were excluded from further analysis. Amongst the remaining genes, HM00021 and Kinesin possessed the highest background ω values within the HmYb and HmB loci, respectively. After accounting for recombination, these two genes both showed evidence of having codons with a signature of selection, although statistical support for this signal was not strong in any case. CONCLUSIONS: Tests of selection reveal a cluster of candidate genes in each locus, suggesting that weak directional selection may be occurring within a small region of each locus, but coding changes alone are unlikely to explain the full range of wing pattern diversity. These analyses pinpoint many of the same genes believed to be involved in the control of colour patterning in Heliconius that have been identified through other studies implementing different research methods.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are

Tsetse fly (Glossina pallidipes) midgut responses to Trypanosoma brucei challenge

Abstract Background Tsetse flies (Glossina spp.) are the prominent vector of African trypanosome parasites (Trypanosoma spp.) in sub-Saharan Africa, and Glossina pallidipes is the most widely distributed species in Kenya. This species displays strong resistance to infection by parasites, which are typically eliminated in the midgut shortly after acquisition from the mammalian host. Although extensive molecular information on immunity for the related species Glossina morsitans morsitans exists, similar information is scarce for G. pallidipes. Methods To determine temporal transcriptional responses of G. pallidipes to Trypanosoma brucei brucei challenge, we conducted Illumina based RNA-seq on midgut organ and carcass from teneral females G. pallidipes at 24 and 48 h post-challenge (hpc) with T. b. brucei relative to their respective controls that received normal blood meals (without the parasite). We used a suite of bioinformatics tools to determine differentially expressed and enriched transcripts between and among tissues, and to identify expanded transcripts in G. pallidipes relative to their orthologs G. m. morsitans. Results Midgut transcripts induced at 24 hpc encoded proteins were associated with lipid remodelling, proteolysis, collagen metabolism, apoptosis, and cell growth. Midgut transcripts induced at 48 hpc encoded proteins linked to embryonic growth and development, serine endopeptidases and proteosomal degradation of the target protein, mRNA translation and neuronal development. Temporal expression of immune responsive transcripts at 48 relative to 24 hpc was pronounced, indicative of a gradual induction of host immune responses the following challenge. We also searched for G. m. morsitans orthologous groups that may have experienced expansions in the G. pallidipes genome. We identified ten expanded groups in G. pallidipes with putative immunity-related functions, which may play a role in the higher refractoriness exhibited by this species. Conclusions There appears to be a lack of strong immune responses elicited by gut epithelia of teneral adults. This in combination with a compromised peritrophic matrix at this stage during the initial phase of T. b. brucei challenge may facilitate the increased parasite infection establishment noted in teneral flies relative to older adults. Although teneral flies are more susceptible than older adults, the majority of tenerals are still able to eliminate parasite infections. Hence, robust responses elicited at a later time point, such as 72 hpc, may clear parasite infections from the majority of flies. The expanded G. m. morsitans orthologous groups in G. pallidipes may also be functionally associated with the enhanced refractoriness to trypanosome infections reported in G. pallidipes relative to G. m. morsitans

Taurine protection of PC12 cells against endoplasmic reticulum stress induced by oxidative stress

<p>Abstract</p> <p>Background</p> <p>Taurine is a free amino acid present in high concentrations in a variety of organs of mammalians. As an antioxidant, taurine has been found to protect cells against oxidative stress, but the underlying mechanism is still unclear.</p> <p>Methods</p> <p>In this report, we present evidence to support the conclusion that taurine exerts a protective function against endoplasmic reticulum (ER) stress induced by H₂O₂ in PC 12 cells. Oxidative stress was introduced by exposure of PC 12 cells to 250 uM H₂O₂ for 4 hours.</p> <p>Results</p> <p>It was found that the cell viability of PC 12 cells decreased with an increase of H₂O₂ concentration ranging from approximately 76% cell viability at 100 uM H₂O₂ down to 18% at 500 uM H₂O₂. At 250 uM H₂O₂, cell viability was restored to 80% by taurine at 25 mM. Furthermore, H₂O₂ treatment also caused a marked reduction in the expression of Bcl-2 while no significant change of Bax was observed. Treatment with taurine restored the reduced expression of Bcl-2 close to the control level without any obvious effect on Bax. Furthermore, taurine was also found to suppress up-regulation of GRP78, GADD153/CHOP and Bim induced by H₂O₂, suggesting that taurine may also exert a protective function against oxidative stress by reducing the ER stress.</p> <p>Conclusion</p> <p>In summary, taurine was shown to protect PC12 cells against oxidative stress induced by H₂O₂. ER stress was induced by oxidative stress and can be suppressed by taurine.</p

Melanophilin and myosin Va track the microtubule plus end on EB1

In mouse melanocytes, myosin Va is recruited onto the surface of melanosomes by a receptor complex containing Rab27a that is present in the melanosome membrane and melanophilin (Mlp), which links myosin Va to Rab27a. In this study, we show that Mlp is also a microtubule plus end–tracking protein or +TIP. Moreover, myosin Va tracks the plus end in a Mlp-dependent manner. Data showing that overexpression and short inhibitory RNA knockdown of the +TIP EB1 have opposite effects on Mlp–microtubule interaction, that Mlp interacts directly with EB1, and that deletion from Mlp of a region similar to one in the adenomatous polyposis coli protein involved in EB1 binding blocks Mlp's ability to plus end track argue that Mlp tracks the plus end directly by hitchhiking on EB1. These results identify a novel +TIP and indicate that vertebrate cells possess a +TIP complex that is similar to the Myo2p–Kar9p–Bim1p complex in yeast. We suggest that the +TIP complex identified in this study may serve to focus the transfer of melanosomes from microtubules to actin at the microtubule plus end

Kinematic Evidence for Superfast Locomotory Muscle in Two Species of Teneriffiid Mites

Locomotory muscles typically operate over a narrow range of contraction frequencies, characterized by the predominant fiber types and functional roles. The highest documented frequencies in the synchronous sound-producing muscles of insects (550 Hz) and toadfish (200 Hz) far exceed the contraction frequencies observed in weight-bearing locomotory muscles, which have maximum documented frequencies below 15-30 Hz. Laws of scaling, however, predict that smaller arthropods may employ stride frequencies exceeding this range. In this study we measured running speed and stride frequency in two undescribed species of teneriffiid mites from the coastal sage scrub of southern California. Relative speeds of both species [129-133 body lengths (BL)s(-1)] are among the fastest documented for any animal. Measured stride frequencies for both species far exceed those documented for any weight-bearing locomotory muscle, with measured values for one species ranging from 93 Hz at 25 degrees C to 111 Hz at 45 degrees C. Stride frequencies either closely approximate or, for one species, exceed predicted values based on an interspecific scaling of frequency and animal mass. Consequently, while the ultra-high frequencies of these muscles must depend on appropriately scaled kinetics of the calcium transient and contraction-relaxation cycle, these do not appear to limit the operating frequencies during running. The predicted low muscle forces operating at these very high frequencies evidently suffice for locomotion, probably because of the larger relative muscle force generated by smaller animals

Antimony nanobelt asymmetric membranes for sodium ion battery

In this study, composite asymmetric membranes containing antimony (Sb) nanobelts are prepared via a straightforward phase inversion method in combination with post-pyrolysis treatment. Sb nanobelt asymmetric membranes demonstrate improved cyclability and specific capacity as the alloy anode of sodium ion battery compared to Sb nanobelt thin films without asymmetric porous structure. The unique structure can effectively accommodate the large volume expansion of Sb-based alloy anodes, prohibit the loss of fractured active materials, and aid in the formation of stable artificial solid electrolyte interphases as evidenced by an outstanding capacity retention of ∼98% in 130 cycles at 60 mA g−1. A specific capacity of ∼600 mAh g−1 is obtained at 15 mA g−1 (1/40C). When the current density is increased to 240 mA g−1, ∼80% capacity can be maintained (∼480 mAh g−1). The relations among phase inversion conditions, structures, compositions, and resultant electrochemical properties are revealed through comprehensive characterization

Comparison of Magnetic Resonance Imaging and Serum Biomarkers for Detection of Human Pluripotent Stem Cell-Derived Teratomas.

The use of cells derived from pluripotent stem cells (PSCs) for regenerative therapies confers a considerable risk for neoplastic growth and teratoma formation. Preclinical and clinical assessment of such therapies will require suitable monitoring strategies to understand and mitigate these risks. Here we generated human-induced pluripotent stem cells (iPSCs), selected clones that continued to express reprogramming factors after differentiation into cardiomyocytes, and transplanted these cardiomyocytes into immunocompromised rat hearts post-myocardial infarction. We compared magnetic resonance imaging (MRI), cardiac ultrasound, and serum biomarkers for their ability to delineate teratoma formation and growth. MRI enabled the detection of teratomas with a volume &gt;8 mm(3). A combination of three plasma biomarkers (CEA, AFP, and HCG) was able to detect teratomas with a volume &gt;17 mm(3) and with a sensitivity of more than 87%. Based on our findings, a combination of serum biomarkers with MRI screening may offer the highest sensitivity for teratoma detection and tracking