Biology subjects

Khan, A. A.

Publications and source records attributed to Khan, A. A..

3 recordsLinked to original sources

bioRxiv2018

Glutathione-S-transferase from the arsenic hyperaccumulator fern Pteris vittata can confer increased arsenate resistance in Escherichia coli

Although arsenic is generally a toxic compound, there are a number of ferns in the genus Pteris that can tolerate large concentrations of this metalloid. In order to probe the mechanisms of arsenic hyperaccumulation, we expressed a Pteris vittata cDNA library in an Escherichia coli {Delta}arsC (arsenate reductase) mutant. We obtained three independent clones that conferred increased arsenate resistance on this host. DNA sequence analysis indicated that these clones specify proteins that have a high sequence similarity to the phi class of glutathione-S-transferases (GSTs) of higher plants. Detoxification of arsenate by the P. vittata GSTs in E. coli was abrogated by a gshA mutation, which blocks the synthesis of glutathione, and by a gor mutation, which inactivates glutathione reductase. Direct measurements of the speciation of arsenic in culture media of the E. coli strains expressing the P. vittata GSTs indicated that these proteins facilitate the reduction of arsenate. Our observations suggest that the detoxification of arsenate by the P. vittata GSTs involves reduction of As(V) to As(III) by glutathione or a related sulfhydro compound.\n\nFundingThe authors acknowledge support from the Indiana 21st Century Research and technology Fund (912010479) to DES and LNC, from the U.S. Department of Energy (grant no. DE-FG02-03ER63622) to DES, and from BBSRC-DFID (grant no. BBF0041841GJN) to AAM. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. There are no financial, personal, or professional interests that could be construed to have influenced the paper.

plant biology↗

bioRxiv2018

The global burden of trichiasis in 2016

BackgroundTrichiasis is present when one or more eyelashes touches the eye. Uncorrected, it can cause blindness. Accurate estimates of numbers affected, and their geographical distribution, help guide resource allocation.\n\nMethodsWe obtained district-level trichiasis prevalence estimates for 44 endemic and previously-endemic countries. We used (1) the most recent data for a district, if more than one estimate was available; (2) age- and sex-standardized corrections of historic estimates, where raw data were available; (3) historic estimates adjusted using a mean adjustment factor for districts where raw data were unavailable; and (4) expert assessment of available data for districts for which no prevalence estimates were available.\n\nFindingsInternally age- and sex-standardized data represented 1,355 districts and contributed 662 thousand cases (95% confidence interval [CI] 324 thousand-1.1 million) to the global total. age- and sex-standardized district-level prevalence estimates differed from raw estimates by a mean factor of 0.45 (range 0.03-2.28). Previously non-standardized estimates for 398 districts, adjusted by x0.45, contributed a further 411 thousand cases (95% CI 283-557 thousand). Eight countries retained previous estimates, contributing 848 thousand cases (95% CI 225 thousand-1.7 million). New expert assessments in 14 countries contributed 862 thousand cases (95% CI 228 thousand-1.7 million). The global trichiasis burden in 2016 was 2.8 million cases (95% CI 1.1-5.2 million).\n\nInterpretationThe 2016 estimate is lower than previous estimates, probably due to more and better data; scale-up of trichiasis management services; and reductions in incidence due to lower active trachoma prevalence.\n\nAuthor SummaryAs an individual with trichiasis blinks, the eyelashes abrade the cornea, which can lead to corneal opacity and blindness. Through high quality surgery, which involves correcting the position of the in-turned eyelid, it is possible to reduce the number of people with trichiasis. An accurate estimate of the number of persons with trichiasis and their geographical distribution are needed in order to effectively align resources for surgery and other necessary services. We obtained district-level trichiasis prevalence estimates for 44 endemic and previously-endemic countries. We used the most recently available data and expert assessments to estimate the global burden of trichiasis. We estimated that in 2016 the global burden was 2.8 million cases (95% CI 1.1-5.2 million).\n\nThe 2016 estimate is lower than previous estimates, probably due to more and better data; scale-up of trichiasis management services; and reductions in incidence due to lower active trachoma prevalence.

epidemiology↗

bioRxiv2018

Mid-infrared optoacoustic microscopy with label-free chemical contrast in living cells and tissues

We developed mid-infrared optoacoustic microscopy (MiROM), a bond-selective imaging modality that overcomes water/tissue opacity and depth limitations of mid-infrared sensing allowing uncompromised live-cell/thick-tissue mid-infrared microscopy with up to three orders of magnitudehigher sensitivity than other vibrational imaging modalities; such as Raman. We showcase the functional label-free biomolecular imaging capabilities of MiROM by monitoring the spatiotemporal dynamics of lipids and proteins during lipolysis in living adipocytes. Since MiROM, contrary to Ramanmodalities, is not only able to detect lipids and proteins, but also important metabolites such as glucose without the need of labels, here we discuss how MiROM yields novel functional label-free abilities for a broader range of analytical studies in living cells and tissues.

cell biology↗