Biomedical subjects

David Ashford

Publications and source records attributed to David Ashford.

7 recordsLinked to original sources

PubMed2006

Morphologic, immunologic, and molecular methods to detect bacillus anthracis in formalin-fixed tissues.

Due to the importance of Bacillus anthracis as a cause of naturally occurring infection among humans and as an agent of bioterrorism, there is a vital need for rapid and specific assays, including immunohistochemistry (IHC) and polymerase chain reaction (PCR) assays, to detect the bacterium in formalin-fixed tissues. Colorimetric IHC assays were developed using a multistep indirect immunoalkaline phosphatase method with anti-B. anthracis cell wall (EAII-6G6-2-3) and anti-B. anthracis capsule (FDF-1B9) mAbs to detect B. anthracis antigens in formalin-fixed, paraffin-embedded bacterial cultures and tissues. B. anthracis antigens were localized, using both antibodies, in samples from B. anthracis-infected animals and humans. The colorimetric IHC assay with both antibodies was expedient in diagnosing the presence of B. anthracis in formalin-fixed, paraffin-embedded tissue from bioterrorism-associated cases of inhalational and cutaneous anthrax and from a case of naturally occurring cutaneous anthrax. Using the same antibodies, confocal microscopy demonstrated the structure of replicating B. anthracis in tissues. B. anthracis-specific primers were successfully used with PCR to amplify and detect B. anthracis sequences derived from formalin-fixed tissues of anthrax cases. In this study, morphologic, immunologic, and molecular assays were used to study and diagnose 22 veterinary and human anthrax cases.

Animals↗

PubMed2005

An outbreak of leptospirosis, Thailand--the importance of the laboratory.

The reported incidence of leptospirosis increased 30-fold in Thailand between 1995 and 2000. Despite many hypotheses to explain the increase, the true etiology remains unknown. We conducted a review of the national surveillance system for leptospirosis, examining the reporting practices, system attributes, and utilization of laboratory confirmation in two northeastern provinces. Using standard guidelines for evaluation of public health surveillance systems, we assessed the timeliness, completeness, and accuracy of data; the sensitivity and specificity of case ascertainment; and the overall usefulness of the Thai leptospirosis surveillance system. Physicians were interviewed to assess compliance and understanding of the case definition. Capacity for confirmation of leptospirosis by a Thai latex agglutination test was assessed. Completeness for variables critical for linking epidemiologic and laboratory data for leptospirosis was 69%. Twenty-eight percent of 208 provincial surveillance reports were considered timely. Interviewed physicians indicated that the national case definition was difficult to understand and apply, and that laboratory confirmation was infrequently used. Compared to a standardized microscopic agglutination test (MAT) panel, the Thai test was specific, but relatively insensitive. We found that a lack of a standardized case definition for leptospirosis, the infrequent use of confirmatory laboratory testing, and the inability to link clinical, epidemiologic, and laboratory data hindered system utility. This surveillance system for leptospirosis highlights difficulties with surveillance of febrile illnesses in general, and the importance of laboratory confirmation for infections that are difficult to diagnose clinically.

Centers for Disease Control and Prevention, U.S.↗

PubMed2004

A conserved functional role of pectic polymers in stomatal guard cells from a range of plant species.

Guard cell walls combine exceptional strength and flexibility in order to accommodate the turgor pressure-driven changes in size and shape that underlie the opening and closing of stomatal pores. To investigate the molecular basis of these exceptional qualities, we have used a combination of compositional and functional analyses in three different plant species. We show that comparisons of FTIR spectra from stomatal guard cells and those of other epidermal cells indicate a number of clear differences in cell-wall composition. The most obvious characteristics are that stomatal guard cells are enriched in phenolic esters of pectins. This enrichment is apparent in guard cells from Vicia faba (possessing a type I cell wall) and Commelina communis and Zea mays (having a type II wall). We further show that these common defining elements of guard cell walls have conserved functional roles. As previously reported in C. communis, we show that enzymatic modification of the pectin network in guard cell walls in both V. faba and Z. mays has profound effects on stomatal function. In all three species, incubation of epidermal strips with a combination of pectin methyl esterase and endopolygalacturonase (EPG) caused an increase in stomatal aperture on opening. This effect was not seen when strips were incubated with EPG alone indicating that the methyl-esterified fraction of homogalacturonan is key to this effect. In contrast, arabinanase treatment, and incubation with feruloyl esterase both impeded stomatal opening. It therefore appears that pectins and phenolic esters have a conserved functional role in guard cell walls even in grass species with type II walls, which characteristically are composed of low levels of pectins.

Commelina↗

PubMed2003

Cell wall arabinan is essential for guard cell function.

Stomatal guard cells play a key role in the ability of plants to survive on dry land, because their movements regulate the exchange of gases and water vapor between the external environment and the interior of the plant. The walls of these cells are exceptionally strong and must undergo large and reversible deformation during stomatal opening and closing. The molecular basis of the unique strength and flexibility of guard cell walls is unknown. We show that degradation of cell wall arabinan prevents either stomatal opening or closing. This locking of guard cell wall movements can be reversed if homogalacturonan is subsequently removed from the wall. We suggest that arabinans maintain flexibility in the cell wall by preventing homogalacturonan polymers from forming tight associations.

Cell Wall↗

PubMed2003

Leptospirosis in "Eco-Challenge" athletes, Malaysian Borneo, 2000.

Adventure travel is becoming more popular, increasing the likelihood of contact with unusual pathogens. We investigated an outbreak of leptospirosis in "Eco-Challenge" multisport race athletes to determine illness etiology and implement public health measures. Of 304 athletes, we contacted 189 (62%) from the United States and 26 other countries. Eighty (42%) athletes met our case definition. Twenty-nine (36%) case-patients were hospitalized; none died. Logistic regression showed swimming in the Segama River (relative risk [RR]=2.0; 95% confidence interval [CI]=1.3 to 3.1) to be an independent risk factor. Twenty-six (68%) of 38 case-patients tested positive for leptospiral antibodies. Taking doxycycline before or during the race was protective (RR=0.4, 95% CI=0.2 to 1.2) for the 20 athletes who reported using it. Increased adventure travel may lead to more frequent exposure to leptospires, and preexposure chemoprophylaxis for leptospirosis (200 mg oral doxycycline/week) may decrease illness risk. Efforts are needed to inform adventure travel participants of unique infections such as leptospirosis.

Adult↗

PubMed2002

PKC epsilon is associated with myosin IIA and actin in fibroblasts.

Proteins coimmunoprecipitating with protein kinase C (PKC) epsilon in fibroblasts were identified through matrix-assisted laser desorption/ionisation time of flight mass spectrometry (MALDI TOF m/s). This method identified myosin IIA in PKC epsilon immunoprecipitates, as well as known PKC epsilon binding proteins, actin, beta'Cop and cytokeratin. Myosin is not a substrate for PKC epsilon. Immunofluorescence analysis showed that PKC epsilon is colocalised with actin and myosin in actomyosin stress fibers in fibroblasts. Inhibitors of PKC and myosin ATPase activity, as well as microfilament-disrupting drugs, all inhibited spreading of fibroblasts after passage, suggesting a role for a PKC epsilon-actin-myosin complex in cell spreading.

3T3 Cells↗

PubMed2002

Bacillus anthracis aerosolization associated with a contaminated mail sorting machine.

On October 12, 2001, two envelopes containing Bacillus anthracis spores passed through a sorting machine in a postal facility in Washington, D.C. When anthrax infection was identified in postal workers 9 days later, the facility was closed. To determine if exposure to airborne B. anthracis spores continued to occur, we performed air sampling around the contaminated sorter. One CFU of B. anthracis was isolated from 990 L of air sampled before the machine was activated. Six CFUs were isolated during machine activation and processing of clean dummy mail. These data indicate that an employee working near this machine might inhale approximately 30 B. anthracis-containing particles during an 8-h work shift. What risk this may have represented to postal workers is not known, but this estimate is approximately 20-fold less than a previous estimate of sub-5 micro m B. anthracis-containing particles routinely inhaled by asymptomatic, unvaccinated workers in a goat-hair mill.

Aerosols↗