Biomedical subjects
Publications and source records attributed to John J Burke.
Since 2002, plant biologists have begun to apply mass spectrometry to the comprehensive analysis of complex lipids. Such lipidomic analyses have been used to uncover roles for lipids in plant response to stresses and to identify in vivo functions of genes involved in lipid metabolism.
Water-deficit stresses preferentially reduce shoot growth, thereby disrupting the flow of carbohydrates from source leaves to the developing sinks. Here, we use a novel stress bioassay to dissect responses of field and greenhouse-grown cotton (Gossypium hirsutum) source leaves to water-deficit stresses. Fifth main stem leaf samples were harvested at sunrise and subjected to a prolonged elevated respiratory demand in the dark. Sucrose levels are lower in nonstressed cotton at sunrise compared to water-deficit stressed cotton, potentially predisposing the nonstressed tissue to succumb more rapidly. Tissue death was determined initially using the cell viability stain 2,3,5-triphenyltetrazolium chloride, but was determined in subsequent experiments by monitoring the decline in chlorophyll fluorescence yield. Fluorescence yield measurements were obtained within minutes of harvesting and individual samples were monitored over the time course of the treatment. Analyses of the time course and magnitude of chlorophyll fluorescence yield decline in samples from irrigated and dryland plots permitted the detection of stress responses within 24 h of the cessation of irrigation. The rate of fluorescence yield decline during the elevated respiratory demand treatment slowed as the water-deficit stress increased. Upon irrigation, the source leaves of the water-stressed plants recovered to prestress values within 4 d. Well-watered cotton overexpressing heat shock protein 101 had identical rates of fluorescence yield decline as nontransgenic cotton. These results suggest that the delayed decline in fluorescence yield of water-stressed tissue exposed to prolonged elevated respiratory demand can be used as a sensitive indicator of water-deficit stress responses.
Data are reported from drug diversion cases involving health care workers who were investigated by the Cincinnati Police Division Pharmaceutical Diversion Squad over an 11-year period. This type of information is rarely available because few U.S. police jurisdictions dedicate resources to prescription drug diversion surveillance. Data from 1992 through 2002 show that opioids were the drugs most commonly diverted by health care workers, followed by benzodiazepines. Nurses, nursing assistants, and medical assistants were involved in almost three quarters of all cases. Hospitals were the most common sources of complaint to police, followed by pharmacies. Health care professional associations are advised to promote greater awareness of drug misuse and dependence concerns among their memberships, and health care facilities that stock pharmaceuticals liable for misuse and diversion are advised to increase the security of their supplies.
Plants are constantly challenged with various abiotic stresses in their natural environment. Elevated temperatures have a detrimental impact on overall plant growth and productivity. Many plants increase their tolerance to high temperatures through an adaptation response known as acquired thermotolerance. To identify the various mechanisms that plants have evolved to cope with high temperature stress, we have isolated a series of Arabidopsis mutants that are defective in the acquisition of thermotolerance after an exposure to 38 degrees C, a treatment that induces acquired thermotolerance in wild-type plants. One of these mutants, atts02, was not only defective in acquiring thermotolerance after the treatment, but also displayed a reduced level of basal thermotolerance in a 30 degrees C growth assay. The affected gene in atts02 was identified by positional cloning and encodes digalactosyldiacylglycerol synthase 1 (DGD1) (the atts02 mutant was, at that point, renamed dgd1-2). An additional dgd1 allele, dgd1-3, was identified in two other mutant lines displaying altered acquired thermotolerance, atts100 and atts104. Expression patterns of several heat shock proteins (HSPs) in heat-treated dgd1-2 homozygous plants were similar to those from identically treated wild-type plants, suggesting that the thermosensitivity in the dgd1-2 mutant was not caused by a defect in HSP induction. Lipid analysis of wild-type and mutant plants indicated a close correlation between the ability to acquire thermotolerance and the increases in digalactosyldiacylglycerol (DGDG) level and in the ratio of DGDG to monogalactosyldiacylglycerol (MGDG). Thermosensitivity in dgd1-2 and dgd1-3 was associated with (1) a decreased DGDG level and (2) an inability to increase the ratio of DGDG to MGDG upon exposure to a 38 degrees C sublethal temperature treatment. Our results suggest that the DGDG level and/or the ratio of DGDG to MGDG may play an important role in basal as well as acquired thermotolerance in Arabidopsis.
Plants, as sessile organisms, employ multiple mechanisms to adapt to the seasonal and daily temperature fluctuations associated with their habitats. Here, we provide genetic and physiological evidence that the FtsH11 protease of Arabidopsis contributes to the overall tolerance of the plant to elevated temperatures. To identify the various mechanisms of thermotolerance in plants, we isolated a series of Arabidopsis thaliana thermo-sensitive mutants (atts) that fail to acquire thermotolerance after pre-conditioning at 38 degrees C. Two allelic mutants, atts244 and atts405, were found to be both highly susceptible to moderately elevated temperatures and defective in acquired thermotolerance. The growth and development of the mutant plants at all stages examined were arrested after exposure to temperatures above 30 degrees C, which are permissive conditions for wild-type plants. The affected gene in atts244 was identified through map-based cloning and encodes a chloroplast targeted FtsH protease, FtsH11. The Arabidopsis genome contains 12 predicted FtsH protease genes, with all previously characterized FtsH genes playing roles in the alleviation of light stress through the degradation of unassembled thylakoid membrane proteins and photodamaged photosystem II D1 protein. Photosynthetic capability, as measured by chlorophyll content (chl a/b ratios) and PSII quantum yield, is greatly reduced in the leaves of FtsH11 mutants when exposed to the moderately high temperature of 30 degrees C. Under high light conditions, however, FtsH11 mutants and wild-type plants showed no significant difference in photosynthesis capacity. Our results support a direct role for the A. thaliana FtsH11-encoded protease in thermotolerance, a function previously reported for bacterial and yeast FtsH proteases but not for those from plants.
PCR has become one of the most popular techniques in functional genomics. Projects in both forward and reverse genetics routinely require PCR amplification of thousands of samples. Processing samples to extract DNA of sufficient purity for PCR is often a limiting step. We have developed a simple 96-well plate-based high-throughput DNA extraction method that is applicable to many plant species. The method involves a simple incubation of plant tissue samples in a DNA extraction buffer followed by a neutralization step. With the addition of a modified PCR buffer, the extracted DNA enabled the robust amplification of genomic fragments from samples of Arabidopsis, tobacco, sorghum, cotton, moss, and even pine needles. Several thousand DNA samples can be economically processed in a single day by one person without the use of robotics. This procedure will facilitate many technologies including high-throughput genotyping, map-based cloning, and identification of T-DNA or transposon-tagged mutants for known gene sequences.