Different mechanisms for Arabidopsis thaliana hybrid necrosis cases inferred from temperature responses.

Temperature is a major determinant of plant growth, development and success. Understanding how plants respond to temperature is particularly relevant in a warming climate. Plant immune responses are often suppressed above species-specific critical temperatures. This is also true for intraspecific hybrids of Arabidopsis thaliana that express hybrid necrosis due to inappropriate activation of the immune system caused by epistatic interactions between alleles from different genomes. The relationship between temperature and defence is unclear, largely due to a lack of studies that assess immune activation over a wide range of temperatures. To test whether the temperature-based suppression of ectopic immune activation in hybrids exhibits a linear or non-linear relationship, we characterised the molecular and morphological phenotypes of two different necrotic A. thaliana hybrids over a range of ecologically relevant temperatures. We found both linear and non-linear responses for expression of immunity markers and for morphological defects depending on the underlying genetic cause. This suggests that the influence of temperature on the trade-off between immunity and growth depends on the specific defence components involved.

Multiple-locus variable-number tandem-repeat analysis of meticillin-resistant Staphylococcus aureus discriminates within USA pulsed-field gel electrophoresis types.

Many isolates of meticillin-resistant Staphylococcus aureus (MRSA) are indistinguishable when compared using the standard pulsed-field gel electrophoresis (PFGE) typing method. This may present a problem when investigating local outbreaks of MRSA transmission in a healthcare setting. It also impedes investigation of the widely disseminated community-acquired MRSA (USA 300-0114) in the inpatient setting, which is displacing other traditional hospital-acquired PFGE types. Combination of methods, including multiple-locus sequence typing (MLST), spa typing and staphylococcal cassette chromosome mec (SCCmec) typing, have been used with, or in place of, PFGE to characterise MRSA for epidemiological purposes. These methods are technically challenging, time-consuming and expensive and are rarely feasible except in large laboratories in tertiary care medical centres. Another method, which is simpler and with faster turnaround time, is multiple-locus variable-number tandem-repeat analysis (MLVA). We investigated the utility of MLVA to distinguish common PFGE types. The results suggest that MLVA can be used to identify unrelated strains with identical PFGE patterns or confirm close genetic composition of linked isolates. MLVA could potentially be used in conjunction with PFGE to validate relationships, but further prospective evaluation of these relationships will be required in order to define the proper role, if any, for use of this method in hospital epidemiology.

Shock outcome prediction before and after CPR: a comparative study of manual and automated active compression-decompression CPR.

We report on a study designed to compare the relative efficacy of manual CPR (M-CPR) and automated mechanical CPR (ACD-CPR) provided by an active compression-decompression (ACD) device. The ECG signals of out-of-hospital cardiac arrest patients of cardiac aetiology were analysed just prior to, and immediately after, cardiopulmonary resuscitation (CPR) to assess the likelihood of successful defibrillation at these time points. The cardioversion outcome prediction (COP) measure previously developed by our group was used to quantify the probability of return of spontaneous circulation (ROSC) after counter-shock and was used as a measure of the efficacy of CPR. An initial validation study using COP to predict shock outcome from the patient data set resulted in a performance of 60% specificity achieved at 100% sensitivity on a blind test of the data. This is comparable with previous studies and provided confidence in the robustness of the technique across hardware platforms. Significantly, the COP marker also displayed an ability to stratify according to outcomes: asystole, ventricular fibrillation (VF), pulseless electrical activity (PEA), normal sinus rhythm (NSR). We then used the validated COP marker to analyse the ECG data record just prior to and immediately after the chest compression segments. This was initially performed for 87 CPR segments where VF was both the pre- and post-CPR waveform. An increase in the mean COP values was found for both CPR types. A signed rank sum test found the increase due to manual CPR not to be significant (p>0.05) whereas the automated CPR was found to be significant (p<0.05). This increase was larger for the automated CPR (1.26, p=0.024) than for the manual CPR (0.99, p=0.124). These results indicate that the application of CPR does indeed provide beneficial preparation of the heart prior to defibrillation therapy whether manual or automated CPR is applied. The COP marker shows promise as a definitive, quantitative determinant of the immediate positive effect of both types of CPR regardless of the details of use. In work of a more exploratory nature we then used the validated COP marker to analyse the ECG pre- and post-CPR for all rhythm types (212 traces). We show a significant increase in the COP measure (p<0.001 in both cases) as indicated by a shift in the median COP marker distribution values. This increase was more pronounced for automated ACD-CPR than for manual CPR. However, a detailed statistical analysis carried out between the groups adjusted for pre-CPR value showed no significant difference between the two methods of CPR (p=0.20). Similarly, adjusting for length of CPR showed no significant difference between the groups. Secondary, subgroup analysis of the ECG according to the length of time for which CPR was performed showed that both types of CPR led to an increase in the likelihood of successful defibrillation after increasing durations of CPR, however results were less reliable after longer periods of continuous CPR.

A cost-effective weighing chamber for particulate matter filters.

Particulate matter (PM) is a ubiquitous air pollutant that has been receiving increasing attention in recent years due in part to the association between PM and a number of adverse health outcomes, including mortality and increases in emergency room visits and respiratory symptoms, as well as exacerbation of asthma and decrements in lung function. As a result, the ability to accurately sample ambient PM has become important, both to researchers and to regulatory agencies. The federal reference method for the determination of fine PM as PM2.5 in the atmosphere recommends that particle-sampling filters be conditioned and weighed in an environment with constant temperature and relative humidity (RH). It is also recommended that vibration, electrostatic charges, and contamination of the filters from laboratory air be minimized to reduce variability in filter weight measurements. These controls have typically been maintained in small, environmentally controlled "cleanrooms." As an alternative to constructing an elaborate cleanroom, we have designed, and presented in this paper, an inexpensive weighing chamber to maintain the necessary level of humidity control.

Analysis of mutants of tetanus toxin Hc fragment: ganglioside binding, cell binding and retrograde axonal transport properties.

Tetanus toxin binds neuronal tissue prior to internalization and trafficking to the central nervous system. Binding of the carboxy-terminal 50 kDa HC fragment of tetanus toxin to polysialogangliosides is important for this initial cell binding step. Using the three-dimensional structure of HC, mutants were designed to investigate the role of individual residues in ganglioside binding. Mutant proteins were tested for binding to GT1b gangliosides, to primary motoneurons and for their ability to undergo retrograde transport in mice. Two classes of mutant were obtained: (i) those containing deletions in loop regions within the C-terminal beta-trefoil domain which showed greatly reduced ganglioside and cell binding and did not undergo retrograde transport and (ii) those that showed reduced ganglioside binding, but retained primary neuronal cell binding and retrograde transport. The second class included point mutants of Histidine-1293, previously implicated in GT1b binding. Our deletion analysis is entirely consistent with recent structural studies which have identified sugar-binding sites in the immediate vicinity of the residues identified by mutagenesis. These results demonstrate that ganglioside binding can be severely impaired without abolishing cell binding and intracellular trafficking of tetanus toxin.

Retrieval of the albedo and phase function from exiting radiances with radiative perturbation theory.

We use radiative perturbation theory to develop a retrieval technique for determining the radiative properties of a scattering medium, such as the Earth's atmosphere, based on measurements of the radiation emerging at either the top or bottom of the medium. In a previous paper [J. Quant. Spectrosc. Radiat. Transfer 54, 695 (1995)] we have shown the capacity of radiative perturbation theory to describe variations in exiting intensity as a linear combination of the parameters that characterize the scattering medium. Here we show that it is possible to set up a matrix relation such that the matrix inversion solves the inverse scattering problem. Using simulated data, we observe that the quality of the solution can be controlled by studying the singular values associated with the kernel matrix, obtaining in this way a stable solution, even in the presence of noise.

Information content of the kernel matrix for the phase function retrieval problem.

We investigate the information content of the radiation measurements to be used in the retrieval of the scattering properties of the atmosphere with the perturbation technique that we previously introduced. Applying this technique to different sets of data, we obtained solutions with varying accuracy. An analysis of these solutions shows that selecting linearly independent data in directions corresponding to small values of the scattering angle increases the number of pieces of information. (This result is in accord with conclusions reached by other researchers, based on a variety of criteria.) This information content should be largely independent of the method or methods employed to perform the inversion procedure.

Investigating biological response in the UVB as a function of ozone variation using perturbation theory.

In order to determine a biological response to ultraviolet radiation, calculations of biologically weighted dose rates are required, which in turn involve the integral over wavelength of an action spectrum multiplied by appropriate surface flux data. To determine a biologically weighted dose rate accurately, a reasonable wavelength resolution is required, involving a full radiative transfer solution to be performed for each wavelength in order to obtain the surface flux information. If biologically weighted dose rates are needed as a function of ozone variation, then the number of radiative transfer solutions quickly makes a large number of ozone variations cumbersome. This paper shows that the perturbation theory developed for atmospheric radiative transfer by Box and co-workers can predict surface fluxes and hence biologically weighted dose rates for a large range of ozone variations very efficiently. The method is then extended to calculate radiation amplification factors. Results for biologically weighted dose rates are presented for a large range of solar zenith angles and ozone loadings using perturbation theory and a full radiative transfer code and show that the perturbation predictions never deviate very far from the radiative transfer solutions.

Telomerase activity in the differential diagnosis of papillary carcinoma of the thyroid.

BACKGROUND: Although fine-needle aspiration (FNA) is 90% sensitive in the detection of papillary carcinoma (PC) of the thyroid, its specificity has been reported as low as 52%. Consequently, patients who have an FNA suspicious for PC may undergo operation for a benign process. The ribonucleoprotein telomerase has been noted to be activated in a wide variety of carcinomas. We examined 30 PCs for telomerase activity to determine whether this would be a useful adjunct to FNA in the diagnosis of lesions suspicious for PC. METHODS: Standard telomere repeat amplification protocol assays were performed on fresh frozen tissue samples from 30 PCs, 3 benign nodules, and 10 normal thyroids. RESULTS: Telomerase activity was documented in 20 of 30 (67%) of the PCs, 0 of 3 benign nodules, and 0 of 10 normal thyroids. In all, 11 of the 20 PCs had FNA cytology that was nondiagnostic of PC, and 2 of the benign nodules had FNA that was suspicious for PC. CONCLUSIONS: The telomerase assay appears useful in the distinction of benign from malignant thyroid lesions that have FNA suspicious for but not diagnostic of PC. On the basis of these findings, a prospective trial examining telomerase activity in FNAs suspicious for thyroid cancer has been initiated.

An evaluation of two methods for increasing self-initiated verbalizations in autistic children.

Three children with autism and mental retardation were treated for deficits in self-initiated speech. A novel treatment package employing visual cue fading was compared with a graduated time-delay procedure previously shown to be effective for increasing self-initiated language. Both treatments included training multiple self-initiated verbalizations using multiple therapists and settings. Both treatments were effective, with no differences in measures of acquisition of target phrases, maintenance of behavioral gains, acquisition with additional therapists and settings, and social validity.

Treatment of elective mute behavior in two developmentally delayed children using modeling and contingency management.

Most classification schemes differentiate elective mutism from language problems seen in the developmentally delayed population. Two preschool developmentally delayed children were treated for speech reluctance using modeling and contingency management. Employing a multiple baseline across therapists, it was found that these treatment components were effective in increasing frequency of labeling behavior in both children. Results were maintained at follow-up. Generalization to new words and to spontaneous speech were also noted, and suggest that characteristics of elective mutism in this population may be similar to what is found in the general population.

Investigation of protein structure by means of 19F-NMR. A study of hen egg-white lysozyme.

A 19F-labeled derivative of hen egg-white lysozyme, in which the six epsilon-amino groups are trifluoroacetylated (LF6), was prepared by reaction of lysozyme with S-ethyltrifluorothioacetate. The reaction mixture was fractionated by cation-exchange chromatography at pH 7.3. A comparison of the circular dichroic spectra and the activity towards Micrococcus lysodeikticus of both LF6 and native lysozyme reveals that the labeling causes no major conformational changes of the polypeptide backbone. Assignment of the six resonances present in the 19F-NMR spectrum of LF6 was accomplished by using a variety of techniques: specific chemical modifications, the effect of the inhibitor (GlcNAc)3, 19F-shift/pH information and relaxation parameters.

Information content analysis of aerosol remote-sensing experiments using singular function theory. 2: Scattering measurements.

We employ the singular function theory, which is the natural framework within which to discuss the analysis of first kind Fredholm integral equations, to analyze fully the information available from an aerosol aureole scattering experiment. This information is, of course, of two kinds: first, the number of pieces of information available for a given experimental error level and, second, the type (or location) of this information. To appreciate fully the latter, we apply this theory to the inversion of eleven synthetic data sets. These inversions are compared with those obtained previously from an extinction experiment.

Information content analysis of aerosol remote-sensing experiments using singular function theory. 1: Extinction measurements.

An important early step in any planned remote-sensing experiment is an analysis of the information content of the equations which will ultimately be inverted. In this paper, we employ the singular function theory, which is the natural framework within which to discuss the analysis of first kind Fredholm integral equations. Using this theory, we are able to fully analyze the information available from an aerosol extinction experiment. It is important to appreciate that this information is actually of two forms: first, the number of pieces of information available for a given experimental error level, and second, the type (or location) of this information. To fully appreciate the latter, we apply this theory to the inversion of eleven synthetic data sets, including three multimodal model size distributions.

Experimental validation of the solar aureole technique for determining aerosol size distributions.

This paper describes the inversion procedures by including multiple scattering contributions to almucantar radiance in the solar aureole region and discusses the retrieved size distribution results by comparing them with ground truth measurements. The agreement between the two sets of results is good and provides yet another experimental validation to show that the solar aureole technique is a simple, practical, and accurate method for obtaining the columnar size distribution of atmospheric aerosols. Comparisons between the results obtained by the two approximations--single and multiple scattering--show that the size distribution retrievals obtained by the latter are more accurate than those obtained by the former. Retrieved estimates of surface albedo show that even though surface albedo cannot be accurately determined from solar aureole measurements, these measurements can provide reasonable estimates. A recommendation is made for the use of solar aureole measurements from satellites to retrieve the size distribution and concentration of stratospheric and upper tropospheric aerosols.

Alternate approach to the analysis of solar photometer data.

The standard technique of analyzing solar photometer data to determine atmospheric optical depth and the spectral solar constant is shown to inadvertently weight the data unequally. A new approach is proposed which equally weights all the data. Assuming that the deviations of the data points result from real random variations of optical depth during the period of the measurements, this latter approach is shown to yield more reliable results.

Finite bandwidth and scattered light effects on the radiometric determination of atmospheric turbidity and the solar constant.

Multispectral solar radiometric measurements are routinely performed at a large number of sites, using equipment of varying degrees of sophistication. From the standard Langley plot technique, one may extract the total optical thickness of the atmosphere (and hence the aerosol component) plus the extraterrestrial solar flux. With increasing concern about possible climatic effects of increased turbidity, or changes in the solar constant, it is becoming more important to know the expected accuracy of these results. In this paper, we analytically examine the effects of finite filter bandwidth (in the absence of spectral lines) and find them to be less than one part in a thousand. This is compared with our earlier results on the effects of scattered light, which turns out to be typically an order of magnitude larger.