Enhanced sample filling and discretization in thermoplastic 2D microwell arrays using asymmetric contact angles.

Sample filling and discretization within thermoplastic 2D microwell arrays is investigated toward the development of low cost disposable microfluidics for passive sample discretization. By using a high level of contact angle asymmetry between the filling channel and microwell surfaces, a significant increase in the range of well geometries that can be successfully filled is revealed. The performance of various array designs is characterized numerically and experimentally to assess the impact of contact angle asymmetry and device geometry on sample filling and discretization, resulting in guidelines to ensure robust microwell filling and sample isolation over a wide range of well dimensions. Using the developed design rules, reliable and bubble-free sample filling and discretization is achieved in designs with critical dimensions ranging from 20 µm to 800 µm. The resulting devices are demonstrated for discretized nucleic acid amplification by performing loop-mediated isothermal amplification for the detection of the mecA gene associated with methicillin-resistant Staphylococcus aureus.

Predictors of antiretroviral treatment-associated tuberculosis in Ethiopia: a nested case-control study.

Little is known about the predictors of antiretroviral treatment (ART)-associated tuberculosis (TB) in developing nations. The objective of this study was to determine predictors of ART-associated TB in adults with HIV infection at Jimma University Hospital, Ethiopia. A nested case-control study was conducted in October 2009. The study population consisted of adults with HIV infection (aged >14 years) who developed active TB in the first six months since ART initiation and controls that did not develop active TB. Data were collected using a structured and pretested questionnaire. Cox proportions hazards analysis was done to determine predictors of ART-associated TB. A total of 357 patients (119 cases and 238 controls) participated in the study. After six months of follow-up, cumulative incidence of ART-associated TB was 5.2% (123/2355). Forty (33.6%) cases were lost to follow-up after they developed ART-associated TB and 11 (9.2%) died. Fifty-one (21.4%) controls interrupted ART and 11 (4.6%) died. A CD4 lymphocyte count increase >0.5/µL/day (adjusted hazard ratio [AHR] = 19.80, 95% confidence interval [CI]: 9.52, 41.12, P < 0.001), a base-line CD4 lymphocyte count <200 cells/µL (AHR = 9.59, 95% CI: 2.36, 39.04, P = 0.002), World Health Organization (WHO) clinical stage 3 or 4 (AHR = 3.04, 95% CI: 1.62, 5.69, P < 0.001), night sweats during ART initiation (AHR = 1.53, 95% CI: 1.06, 2.21, P < 0.001) and high ART adherence (AHR = 1.30, 95% CI: 1.13, 1.50, P < 0.001) were independent predictors of ART-associated TB. HIV-infected adults with these risk factors should be followed cautiously for the development of ART-associated TB. Good ART adherence and a good immunological response during ART were associated with ART-associated TB, most likely because of an immune reconstitution inflammatory syndrome unmasking the TB.

Characterizing variation in mycorrhiza effect among diverse plant varieties.

Exploitation of arbuscular mycorrhizal fungi may be an important approach for development of reduced-input agriculture. We discuss the use of linear models to analyze variation in mycorrhiza response among diverse plant varieties in order to assess the value of mycorrhizas. Our approach allows elimination of variation linked to differences in plant performance in the absence of mycorrhizas and the selection of plant lines that might harbor genetic variation of use to improve the mycorrhizal symbiosis in agriculture. We illustrate our approach by applying it to previously published and to novel data. We suggest that in dealing with a relative trait such as mycorrhiza effect, the choice of measure used to quantify the trait greatly affects interpretation. In the plant populations under consideration, we find evidence for a greater potential to increase mycorrhiza benefit than previously suggested.

Topographically modified surfaces affect orientation and growth of hippocampal neurons.

Extracellular matrix molecules provide biochemical and topographical cues that influence cell growth in vivo and in vitro. Effects of topographical cues on hippocampal neuron growth were examined after 14 days in vitro. Neurons from hippocampi of rat embryos were grown on poly-L-lysine-coated silicon surfaces containing fields of pillars with varying geometries. Photolithography was used to fabricate 1 microm high pillar arrays with different widths and spacings. Beta(III)-tubulin and MAP-2 immunocytochemistry and scanning electron microscopy were used to describe neuronal processes. Automated two-dimensional tracing software quantified process orientation and length. Process growth on smooth surfaces was random, while growth on pillared surfaces exhibited the most faithful alignment to pillar geometries with smallest gap sizes. Neurite lengths were significantly longer on pillars with the smallest inter-pillar spacings (gaps) and 2 microm pillar widths. These data indicate that physical cues affect neuron growth, suggesting that extracellular matrix topography may contribute to cell growth and differentiation. These results demonstrate new strategies for directing and promoting neuronal growth that will facilitate studies of synapse formation and function and provide methods to establish defined neural networks.