ROC study and SUV threshold using quantitative multi-modal SPECT for bone imaging.

BACKGROUND: We investigated the clinical performance of a quantitative multi-modal SPECT/CT reconstruction platform for yielding radioactivity concentrations of bone imaging with 99mTc-methylene diphosphonate (MDP) or 99mTc-dicarboxypropane diphosphonate (DPD). The novel reconstruction incorporates CT-derived tissue information while preserving the delineation of tissue boundaries. We assessed image-based reader concordance and confidence, and determined lesion classification and SUV thresholds from ROC analysis. METHODS: Seventy-two cancer patients were scanned at three US and two German clinical sites, each contributing two experienced board-certified nuclear medicine physicians as readers. We compared four variants of the reconstructed data resulting from the Flash3D (F3D) and the xSPECT Bone™ (xB) iterative reconstruction methods and presented images to the readers with and without a fused CT, resulting in four combinations. We used an all-or-none approach for inclusion, compiling results only when a reader completed all reads in a subset. After the final read, we conducted a "surrogate truth" reading, presenting all data to each reader. For any remaining discordant lesions, we conducted a consensus read. We next undertook ROC analysis to determine SUV thresholds for differentiating benign and lesional uptake. RESULTS: On a five-point rating scale of image quality, xB was deemed better by almost two points in resolution and one point better in overall acceptance compared to F3D. The absolute agreement of the rendered decision between the nine readers was significantly higher with CT information either inside the reconstruction (xB, xBCT) or simply through image fusion (F3DCT): 0.70 (xBCT), 0.67 (F3DCT), 0.64 (xB), and 0.46 (F3D). The confidence level to characterize the lesion was significantly higher (3.03x w/o CT, 1.32x w/CT) for xB than for F3D. There was high correlation between xB and F3D scores for lesion detection and classification, but lesion detection confidence was 41% higher w/o CT, and 21% higher w/CT for xB compared to F3D. Without CT, xB had 6.6% higher sensitivity, 7.1% higher specificity, and 6.9% greater AUC compared to F3D, and similarly with CT-fusion. The overall SUV-criterion (SUVc) of xB (12) exceeded that for xSPECT Quant™ (xQ; 9), an approach not using the tissue delineation of xB. SUV critical numbers depended on lesion volume and location. For non-joint lesions > 6 ml, the AUC for xQ and xB was 94%, with SUVc > 9.28 (xQ) or > 9.68 (xB); for non-joint lesions ≤ 6 ml, AUCs were 81% (xQ) and 88% (xB), and SUVc > 8.2 (xQ) or > 9.1 (xB). For joint lesions, the AUC was 80% (xQ) and 83% (xB), with SUVc > 8.61 (xQ) or > 13.4 (xB). CONCLUSION: The incorporation of high-resolution CT-based tissue delineation in SPECT reconstruction (xSPECT Bone) provides better resolution and detects smaller lesions (6 ml), and the CT component facilitates lesion characterization. Our approach increases confidence, concordance, and accuracy for readers with a wide range of experience. The xB method retained high reading accuracy, despite the unfamiliar image presentation, having greatest impact for smaller lesions, and better localization of foci relative to bone anatomy. The quantitative assessment yielded an SUV-threshold for sensitively distinguishing benign and malignant lesions. Ongoing efforts shall establish clinically usable protocols and SUV thresholds for decision-making based on quantitative SPECT.

Police exposure to infectious agents: an audit of protective policies.

BACKGROUND: As first responders, police officers may be exposed to infectious agents such as hepatitis viruses and human immunodeficiency virus. Their risk of infection by these viruses can be reduced with training, monitoring and, with some viruses, vaccination. AIMS: To examine infection prevention policies and practices among police departments and determine provision of vaccination and infection prevention education programmes. METHODS: A questionnaire sent to all police departments in five counties of south-eastern Pennsylvania to capture information about department size, immunization policies and practices, record keeping, infection prevention education and monitoring of exposures. RESULTS: Ninety-six of 168 departments responded (57%). Among these, policies requiring pre-employment physical examinations were almost universal (95%). Vaccination policies were less common with <15% requiring and 50% recommending hepatitis, tetanus or influenza vaccination for officers. Few departments took action to provide (2%) or cover the cost (21%) of vaccination. Fewer than 12% maintained vaccination records. Education about the risk of infectious agents was offered by 60% of the responding departments, but often just once at the start of employment. Fewer than half of the departments had systems to collect exposure information. CONCLUSIONS: Police departments have opportunities to improve policies and practices for infection prevention and control. Accurate documentation of vaccination status is essential to ensure provision of appropriate post-exposure assessment and treatment. Better reporting of exposure will improve understanding of the infection transmission risk, enhancing the ability to offer targeted education and services to officers.

Constitutive protein-DNA interactions on the abscisic acid-responsive element before and after developmental activation of the rab28 gene.

Transcription of the rab28 gene from maize is induced in late embryo development and in response to abscisic acid. We have studied the regulation of the activity of the rab28 promoter in embryos. Two abscisic acid-responsive elements (ABREs) were necessary for expression in embryos of transgenic Arabidopsis and in transient transformation in maize embryos. In vivo footprinting showed that there was protein binding to the ABREs and to other cis elements in the promoter in young embryos before expression of rab28. This shows that the rab28 promoter is in an open chromatin structure before developmental activation. The ABREs are important for the induction and have protein binding in young embryos. Nuclear proteins extracted from embryos before activation of rab28 bound to the ABREs in band shift assays. A complex with different mobility was formed between nuclear proteins and the ABREs after induction of rab28 suggesting a modification of the ABRE-binding factor or an exchange of proteins. The footprints on the ABREs were unaltered by induction with abscisic acid or during developmental activation of rab28. These results indicate that constitutive binding of transcription factor(s) on the ABRE is central in embryonic regulation of the rab28 gene.

Phosphorylation mediates the nuclear targeting of the maize Rab17 protein.

The maize abscisic acid-responsive Rab17 protein localizes to the nucleus and cytoplasm in maize cells. In-frame fusion of Rab17 to the reporter protein beta-glucuronidase (GUS) directed GUS to the nucleus and cytoplasm in transgenic Arabidopsis thaliana and in transiently transformed onion cells. Analysis of chimeric constructs identified one region between amino acid positions 66-96, which was necessary for targeting GUS to the nucleus. This region contains a serine cluster followed by a putative consensus site for protein kinase CK2 phosphorylation, and a stretch of basic amino acids resembling the simian virus 40 large T antigen-type nuclear localization signal (NLS). Mutation of two basic amino acids in the putative NLS had a weak effect on nuclear targeting in the onion cell system and did not modify the percentage of nuclear fusion protein in the Arabidopsis cells. The mutation of three amino acids in the consensus site for CK2 recognition resulted in the absence of in vitro phosphorylated forms of Rab17 and in a strong decrease of GUS enzymatic activity in isolated nuclei of transgenic Arabidopsis. These results suggest that phosphorylation of Rab17 by protein kinase CK2 is the relevant step for its nuclear location, either by facilitating binding to specific proteins or as a direct part of the nuclear targeting apparatus.

Risk factors associated with the acquisition of amikacin-resistant gram-negative bacilli in central New Jersey hospitals.

A case-control study was performed in central New Jersey hospitals to evaluate the potential patient factors associated with the acquisition of amikacin-resistant gram-negative bacilli (ARGNB). Univariate analysis revealed an association between numerous patient factors, and multivariate analysis revealed four factors to be associated independently with ARGNB: the number of hospital admissions during the prior year, previous aminoglycoside exposure, intubation, and intensive-care-unit admission.

Ac/Ds transposon mutagenesis in Arabidopsis thaliana: mutant spectrum and frequency of Ds insertion mutants.

Using a two-component Ac/Ds system consisting of a stabilized Ac element (Acc1) and a non-autonomous element (DsA), 650 families of plants carrying independent germinal DsA excisions/transpositions were isolated. Progenies of 559 of these Acc1/DsA families, together with 43 families of plants selected for excision/transposition of wild-type (wt) Ac, were subjected to a broad screening program for mutants exhibiting visible alterations. This resulted in the identification of 48 mutants showing a wide variety of mutant phenotypes, including embryo lethality (24 mutants), chlorophyll defects (5 mutants), defective seedlings (2 mutants), reduced fertility (5 mutants), reduced size (3 mutants), altered leaf morphology (2 mutants), dark green, unexpanded rosette leaves (3 mutants), and aberrant flower or shoot morphology (4 mutants). To whether these mutants were due to transposon insertions, a series of Southern blot experiments was performed on 28 families, comparing in each case several mutant plants with others showing the wild-type phenotype. A preliminary analysis revealed in 4 of the 28 families analyzed a common, novel DsA fragment in all mutant plants, which was present only in heterozygous plants with wt phenotype, as expected for DsA insertion mutations. These four mutants included two showing embryo lethality, one with dark green, unexpanded rosette leaves and stunted inflorescences, and one with curly growth of stems, leaves and siliques. Further evidence for DsA insertion mutations was obtained for one embryo lethal mutant and for the stunted mutant, while in case of the second embryo lethal mutant, the DsA insertion could be separated from the mutant locus by genetic recombination.

Selection for enhanced germinal excision of Ac in transgenic Arabidopsis thaliana.

Gene tagging in Arabidopsis thaliana using the autonomous Ac (Activator) transposable element has so far been hampered by low frequencies of germinal transposition events. Here we describe a procedure by which the frequency of independent germinal reinsertions has been much improved by a process of long-term selection on kanamycin for the continued growth of tissues in which somatic excisions have occurred. Growth on artificial media increased the somatic excision frequency, and the long-term selection procedure channelled somatic transposition events into the germline. This resulted in an overall germinal excision frequency in the progeny of longterm selected plants of 15%, as confirmed by Southern blotting, with 63% of the plants bearing excision events having detectable reinsertions of the Ac element. This compares with a germinal excision frequency of approximately 1% when no long-term selection is employed. However, offspring from individual plants tended to have identical germinal Ac reinsertion patterns, thus the critical parameter for evaluating the system for tagging purposes is the frequency of individual plants yielding offspring with reinsertions, which was 64%. This high frequency, when coupled to the enhanced germinal transposition rate overall, easily allows the generation of a large population of plants with independent reinsertions.

A bacterial position effect: when the F factor in E. coli K12 is integrated in cis to a chromosomal gene that is flanked by IS1 repeats the elements are activated so that amplification and other regulatory changes that affect the gene can occur.

In Escherichia coli K12 the argF gene is located within Tn2901, a genomic unit of approx. 12 kb that is flanked by IS1 elements in direct repeat. When strains in which the F factor is integrated in cis to Tn2901 are subjected to the appropriate selection, regulatory changes that result in over-production of the argF-encoded ornithine transcarbamylase occur at relatively high frequencies. When amplification occurs, the F factor is required only for the initial exchange between the IS1 elements, homologous recombination between tandem repeats of Tn2901 being independent of the F status of the cell. While amplification of Tn2901 is frequent in some Hfr strains, in others regulatory changes that do not involve amplification are predominant. The transfer region of the F factor does not contribute to the position effect.

Amplification of the ArgF region in strain HfrP4X of E. coli K-12.

In E. coli K-12 the argF gene is flanked by ISI sequences in direct repeat. Mutants that overproduce the argF-coded enzyme ornithine transcarbamylase can be selected; we have shown that in one class of these mutants there is an approximately forty five-fold amplification of the region bounded by the ISI repeats. This class of mutants has been detected only in strains in which the F-factor is integrated in cis to the region.

Genetic factors affecting recovery of nonpoint mutations in the region of a gene coding for ornithine transcarbamylase: involvement of both the F factor in its chromosomal state and the recA gene.

Mutants of E. coli K12 that overproduce ornithine transcarbamylase can be identified in Car- strains because they permit utilization of citrulline as a carbamyl phosphate source, due to reversal of the normal OTCase reaction; they are called Cut mutants (citrulline utilizers). Hfr strains that carry the F factor adjacent to argF (one of two duplicate genes that code for ornithine transcarbamylase in E. coli K12) yield more Cut mutants than do F+ or F- strains, or Hfr strains in which the F factor is not adjacent to argF. When Hfr strains in which the F factor is integrated adjacent to argF are made recA, they yield few Cut mutants. Many of the Cut mutants recovered from one of the Hfr strains used in the investigation (Hfr P4X) are unstable; the properties of these unstable mutations suggest that they carry aberrations in the region of the argF gene. Thus, the increased yields of Cut mutants probably result from aberrations that occur when the F factor is integrated adjacent to argF. The nature of these aberrations is not yet known. The unstable Cut mutants are to a large extent stabilized by recA; such stabilization is one of the properties of duplications. Other data indicate that the aberrations may be more complex than simple gene duplications; in particular properties of segregants and some recombinants derived from unstable Cut mutants are most easily interpreted by assuming that segregation from, and possibly formation of, the unstable mutants occurs in several stages.

Clinical findings, early endoscopy, and multivariate analysis in patients bleeding from the upper gastrointestinal tract.

A simple system has been developed to identify patients with upper gastrointestinal tract haemorrhage who run a high risk of continued bleeding or rebleeding. The system is based on six items of patient data available at or soon after arrival in hospital. It was evaluated in a prospective study of 66 patients with upper gastrointestinal tract haemorrhage. Over half of the patients classified by the system into a high-risk category either continued bleeding or rebled after apparent cessation (as against one out of 33 patients in the low-risk category). The high-rish group also had a higher mortality (21%) than those in the low-risk group (nil). The addition or subtraction of early endoscopic findings made little difference to the accuracy of prognosis.

Specialized transducing phages derived from phage P22 that carry the pro AB region of the host, Salmonella typhimurium: genetic evidence for their structure and mode of transduction.

Two independently isolated specialized transducing phages, P22pro-1 and P22pro-3, have been studied. Lysates of P22pro-1 contain a majority of transducing phages which can go through the lytic cycle only in mixed infection; these defective phages transduce by lysogenization in mixed infection and by substitution in single infection. A few of the transducing phages in P22pro-1 lysates appear to be non-defective, being able to form plaques and to transduce by lysogenization in single infection. Transduction by P22pro-3 lysates is effected by non-defective transducing phages, which transduce by lysogenization; these lysates also contain a majority of defective phages which do not co-operate in mixed infection. The P22pro-1 genome is thought to contain an insertion of bacterial DNA longer than the terminal repetition present in P22 wild type, so that at maturation a population of differently defective phages is produced. The exact structure of the P22pro-3 genome is open to conjecture, but it seems clear that the insertion of bacterial DNA is smaller than that in P22pro-1. Both P22pro-1 and P22pro-3 are defective in integration at ataA under non-selective conditions, although both integrate on medium that lacks proline.