Strictures of the sigmoid colon: barium enema evaluation

PURPOSE

To assess the accuracy of radiologic interpretation, in the absence of clinical information, in the differentiation of benign and malignant sigmoid strictures at barium enema examination.

MATERIALS AND METHODS

On two occasions, four independent observers retrospectively assessed examination findings in 78 patients with documented sigmoid strictures (43 benign, 35 malignant). Each stricture was graded by using a five-point scale (definitely malignant to definitely benign).

RESULTS

No significant difference existed between the areas under the receiver operating characteristic curves for the two assessments with any observer. Consensus findings indicated agreement among at least three of the four observers in 68 (87%) and 66 (85%) cases at the first and second assessments, respectively. One benign stricture was called malignant at both assessments. When consensus existed, the positive predictive value for malignant strictures was 96% at both assessments (sensitivity, 63% and 66%). Nine malignant strictures were called benign, three at both assessments. When consensus existed, the positive predictive value for benign strictures was 84% and 88% at the first and second assessments, respectively (sensitivity, 88% and 86%, respectively).

CONCLUSION

The differentiation between a benign and a malignant sigmoid stricture can be made in most cases at barium enema examination. When a stricture appears malignant, the diagnosis is usually correct, but caution is advised when a stricture appears benign.

Quorum sensing as an integral component of gene regulatory networks in Gram-negative bacteria

Bacterial cell-to-cell communication (quorum sensing) relies upon the interaction of a small diffusible signal molecule with a sensor or transcriptional activator to couple gene expression with cell population density. In Gram-negative bacteria, it is now clear that N-acylhomoserine lactones bind directly to LuxR homologues and can be synthesized via one of three unrelated bacterial protein families and by transgenic plants. New chemical classes of signal molecules have been identified, some of which exhibit crosstalk with N-acylhomoserine-lactone-mediated quorum sensing. As the determinant of cell population density, quorum sensing is emerging as an integral component of bacterial global gene regulatory networks responsible for facilitating bacterial adaptation to environmental stress. N-acylhomoserine lactones are produced during experimental animal and human infections, and a function beyond quorum sensing has been suggested by their intrinsic immunomodulatory and pharmacological activities.

The role of RsmA in the regulation of swarming motility in Serratia marcescens

Swarming motility is a multicellular phenomenon comprising population migration across surfaces by specially differentiated cells. In Serratia marcescens, a network exists in which the flhDC flagellar regulatory master operon, temperature, nutrient status, and quorum sensing all contribute to the regulation of swarming motility. In this study, the rsmA (repressor of secondary metabolites) gene (hereafter rsmA(Sm)) was cloned from S. marcescens. The presence of multicopy, plasmid-encoded rsmA(Sm) expressed from its native promoter in S. marcescens inhibits swarming. Synthesis of N-acylhomoserine lactones, presumably by the product of smaI (a luxI homolog isolated from S. marcescens), was also inhibited. Knockout of rsmA(Sm) on the S. marcescens chromosome shortens the time before swarming motility begins after inoculation to an agar surface. A single copy of the chromosomal PrsmA(Sm)::luxAB reporter of rsmA(Sm) transcription was constructed. Using this reporter, the roles of the flhDC flagellar regulatory master operon, temperature and autoregulation in the control of rsmA(Sm) expression were determined. Our findings indicate that RsmA(Sm) is a component of the complex regulatory network that controls swarming.

Supplementation of islet culture medium with insulin may have a beneficial effect on islet secretory function

Recent reports suggest that apoptosis resulting from the disruption of the normal cell-matrix relationship (anoikis) during islet isolation could lead to a loss of islet tissue in culture. Insulin is known to have a role in cell growth and survival, and this study was undertaken to assess any beneficial effect on islets by supplementing the islet culture medium with insulin. Human and porcine islets were cultured in medium supplemented with 0, 10, 100, and 1,000 ng x mL(-1) insulin. Secretory function was assessed by perifusion at days 1 and 8. The results demonstrated a significant variation in stimulation index between isolations for human islets, but there was no effect relating to the concentration of insulin in the medium or time in culture. For porcine islets, there was a significant (p < 0.001) improvement in secretory function for islets cultured in 10 and 100 ng x mL(-1) insulin, relative to 0 and 1,000 ng x mL(-1) insulin. There was no interisolation variation or effect of time in culture. In conclusion, the secretory function of porcine islets benefited from the addition of 10 to 100 ng x mL(-1) insulin to the culture medium, but interisolation variation in human islet secretory function did not allow any specific effect of the insulin to be determined.

Role of flhDC in the expression of the nuclease gene nucA, cell division and flagellar synthesis in Serratia marcescens

We investigated in Serratia marcescens the functions of the flhDC operon, which controls motility and cell division in enteric bacteria. Included in our evaluations were investigation of cell division, flagellar synthesis and regulation of the expression of nuclease (encoded by the nucA(Sm) gene, one of the virulence factors). Interruption of the chromosomal flhDC operon in S. marcescens CH-1 resulted in aberrant cell division and loss of nuclease and flagella. Expression of nucA(Sm) and other mutated phenotypes was restored in the flhDC mutant by the induction of overexpression of flhDC in a multicopy plasmid. Multicopied flhDC also induced the formation of differentiated cells (polyploid aseptate cells with oversynthesis of peritrichous flagella) in broth culture using minimal growth medium. Expression of the flhDC operon showed positive autoregulation, and was growth phase dependent (upregulated in early log phase). In addition, flhDC expression was inhibited when the temperature increased from 30 to 37 degrees C, and when osmolarity was increased, but was not influenced by glucose catabolite repression. These results show that FlhD/FlhC is a multifunctional transcriptional activator involved in the process of cell differentiation, swarming and virulence factor expression.

Quorum sensing and the population-dependent control of virulence

One crucial feature of almost all bacterial infections is the need for the invading pathogen to reach a critical cell population density sufficient to overcome host defences and establish the infection. Controlling the expression of virulence determinants in concert with cell population density may therefore confer a significant survival advantage on the pathogen such that the host is overwhelmed before a defence response can be fully initiated. Many different bacterial pathogens are now known to regulate diverse physiological processes including virulence in a cell-density-dependent manner through cell-cell communication. This phenomenon, which relies on the interaction of a diffusible signal molecule (e.g. an N-acylhomoserine lactone) with a sensor or transcriptional activator to couple gene expression with cell population density, has become known as 'quorum sensing'. Although the size of the 'quorum' is likely to be highly variable and influenced by the diffusibility of the signal molecule within infected tissues, nevertheless quorum-sensing signal molecules can be detected in vivo in both experimental animal model and human infections. Furthermore, certain quorum-sensing molecules have been shown to possess pharmacological and immunomodulatory activity such that they may function as virulence determinants per se. As a consequence, quorum sensing constitutes a novel therapeutic target for the design of small molecular antagonists capable of attenuating virulence through the blockade of bacterial cell-cell communication.

PAR1 thrombin receptor-G protein interactions. Separation of binding and coupling determinants in the galpha subunit

Signal transfer between the protease-activated PAR1 thrombin receptor and membrane-associated heterotrimeric G proteins is mediated by protein-protein interactions. We constructed a yeast signaling system that resolves domain-specific functions of binding from coupling in the Galpha subunit. The endogenous yeast Galpha subunit, Gpa1, does not bind to PAR1 and served as a null structural template. N- and C-terminal portions of mammalian G(i2) and G(16) were substituted back into the Gpa1 template and gain-of-function assessed. The C-terminal third of G(16), but not of G(i2), provides sufficient interactions for coupling to occur with PAR1. The N-terminal two-thirds of G(i2) also contains sufficient determinants to bind and couple to PAR1 and overcome the otherwise negative or missing interactions supplied by the C-terminal third of Gpa1. Replacement of the N-terminal alpha-helix of G(i2), residues 1-34, with those of Gpa1 abolishes coupling but not binding to PAR1 or to betagamma subunits. These data support a model that the N-terminal alphaN helix of the Galpha subunit is physically interposed between PAR1 and the Gbeta subunit and directly assists in transferring the signal between agonist-activated receptor and G protein.

FXY2/MID2, a gene related to the X-linked Opitz syndrome gene FXY/MID1, maps to Xq22 and encodes a FNIII domain-containing protein that associates with microtubules

Opitz G/BBB syndrome (OS) is a genetically heterogeneous disorder with an X-linked locus and an autosomal locus linked to 22q11.2. OS affects multiple organ systems with often variable severity even between siblings. The clinical features, which include hypertelorism, cleft lip and palate, defects of cardiac septation, hypospadias, and anorectal anomalies, indicate an underlying disturbance of the developing ventral midline of the embryo. The gene responsible for X-linked OS, FXY/MID1, is located on the short arm of the human X chromosome within Xp22.3 and encodes a protein with both an RBCC (RING finger, B-box, coiled coil) and a B30.2 domain. The Fxy gene in mice is also located on the X chromosome but spans the pseudoautosomal boundary in this species. Here we describe a gene closely related to FXY/MID1, called FXY2, which also maps to the X chromosome within Xq22. The mouse Fxy2 gene is located on the distal part of the mouse X chromosome within a region syntenic to Xq22. Analysis of genes flanking both FXY/MID1 and FXY2 (as well as their counterparts in mouse) suggests that these regions may have arisen as a result of an intrachromosomal duplication on an ancestral X chromosome. We have also identified in both FXY2 and FXY/MID1 proteins a conserved fibronectin type III domain located between the RBCC and B30.2 domains that has implications for understanding protein function. The FXY/MID1 protein has previously been shown to colocalize with microtubules, and here we show that the FXY2 protein similarly associates with microtubules in a manner that is dependent on the carboxy-terminal B30.2 domain.

Quorum sensing-dependent regulation and blockade of exoprotease production in Aeromonas hydrophila

In Aeromonas hydrophila, the ahyI gene encodes a protein responsible for the synthesis of the quorum sensing signal N-butanoyl-L-homoserine lactone (C4-HSL). Inactivation of the ahyI gene on the A. hydrophila chromosome abolishes C4-HSL production. The exoprotease activity of A. hydrophila consists of both serine protease and metalloprotease activities; in the ahyI-negative strain, both are substantially reduced but can be restored by the addition of exogenous C4-HSL. In contrast, mutation of the LuxR homolog AhyR results in the loss of both exoprotease activities, which cannot be restored by exogenous C4-HSL. Furthermore, a substantial reduction in the production of exoprotease by the ahyI+ parent strain is obtained by the addition of N-acylhomoserine lactone analogs that have acyl side chains of 10, 12, or 14 carbons. The inclusion of N-(3-oxododecanoyl)-L-homoserine lactone or N-(3-oxotetradecanoyl)-L-homoserine lactone at 10 microM in overnight cultures of A. hydrophila abolishes exoprotease production in azocasein assays and reduces the activity of all the exoprotease species seen in zymograms.

The spectrum of prevention: developing a comprehensive approach to injury prevention

OBJECTIVE

The purpose of this paper is to describe the "spectrum of prevention", a framework for developing multifaceted approaches to injury prevention. The value of the tool is that it can help practitioners develop and structure comprehensive initiatives.

METHODS

The spectrum is comprised of six inter-related action levels: (1) strengthening individual knowledge and skills, (2) promoting community education, (3) educating providers, (4) fostering coalitions and networks, (5) changing organizational practices, and (6) influencing policy and legislation. Activities at each of these levels have the potential to support each other and promote overall community health and safety.

CONCLUSIONS

The spectrum of prevention is a tool which can help practitioners and policy leaders move beyond a primarily educational approach to achieve broad community goals through injury prevention strategies that include policy development. This framework has been endorsed and applied in a variety of disciplines, however it has not been formally evaluated, a process that could clarify the scope of its effectiveness.

Continuous infusion cyclosporine and nifedipine to day +100 with short methotrexate and steroids as GVHD prophylaxis in unrelated donor transplants

Unrelated donor marrow transplantation is associated with an increased incidence of graft-versus-host disease (GVHD) compared with sibling donor transplants. Forty-one patients undergoing unrelated donor transplants were treated with a GVHD prophylaxis regimen that consisted of continuous infusion cyclosporine from day -1 to 100 days post transplant along with nifedipine, glucocorticoids and short-course methotrexate. The regimen was well-tolerated in this cohort with mostly high risk disease. Fifty-one percent of patients developed acute GVHD, which was grade III-IV in 22% of patients. Six of 22 patients at risk for chronic GVHD developed extensive chronic GVHD, five of whom were adults. In patients <18 years of age, there was a >40% chance of 2 year disease-free survival. Use of continuous infusion cyclosporine with nifedipine as an immunosuppressant and protectant against cyclosporine-induced toxicities in unrelated donor transplants is well-tolerated, and results in acute GVHD incidence favorable to that reported with bolus cyclosporine.

The mouse Peutz-Jeghers syndrome gene Lkb1 encodes a nuclear protein kinase

The protein kinase gene LKB1 has recently been identified as the gene mutated in the Peutz-Jeghers cancer predisposition syndrome. This condition is characterized by inherited susceptibility to a range of cancers but in particular those of the gastrointestinal tract. Here we have characterized the mouse Lkb1 gene. The mouse Lkb1 gene consists of 10 exons covering approximately 15 kb in length, maps to mouse chromosome 10 and encodes a protein showing strong sequence similarity to human LKB1. The 3" end of Lkb1 in the mouse is in very close proximity to the 3" end of an apparently unrelated gene R29144/1 and it seems probable that overlapping transcripts of the two genes are produced. Using transfection of Lkb1 cDNAs we have shown that Lkb1 is most likely a nuclear protein and have defined a nuclear localization signal within the protein sequence. Thus the defect in Peutz-Jeghers syndrome may directly result in changes in gene expression in the nucleus of target cells.

Cloning, sequencing, and role in virulence of two phospholipases (A1 and C) from mesophilic Aeromonas sp. serogroup O:34

Two different representative recombinant clones encoding Aeromonas hydrophila lipases were found upon screening on tributyrin (phospholipase A1) and egg yolk agar (lecithinase-phospholipase C) plates of a cosmid-based genomic library of Aeromonas hydrophila AH-3 (serogroup O34) introduced into Escherichia coli DH5alpha. Subcloning, nucleotide sequencing, and in vitro-coupled transcription-translation experiments showed that the phospholipase A1 (pla) and C (plc) genes code for an 83-kDa putative lipoprotein and a 65-kDa protein, respectively. Defined insertion mutants of A. hydrophila AH-3 defective in either pla or plc genes were defective in phospholipase A1 and C activities, respectively. Lecithinase (phospholipase C) was shown to be cytotoxic but nonhemolytic or poorly hemolytic. A. hydrophila AH-3 plc mutants showed a more than 10-fold increase in their 50% lethal dose on fish and mice, and complementation of the plc single gene on these mutants abolished this effect, suggesting that Plc protein is a virulence factor in the mesophilic Aeromonas sp. serogroup O:34 infection process.

Structure and chromosomal mapping of the TNF-alpha inducible endothelial protein 1 (Edp1) gene in the mouse

EDP1 was identified as a human gene activated transcriptionally by tumour necrosis factor alpha in endothelial cells. Here we have characterised the mouse Edp1 gene. We show that the gene encodes a highly conserved protein and describe its intron/exon structure. The presence of related genes in the sequence databases suggests that Edp1 is part of a gene family. Fine mapping of the gene in the mouse genome indicates that, as expected from its location on human chromosome 17, the mouse Edp1 gene maps to mouse chromosome 11. However, surprisingly, the gene does not map to the expected region of mouse chromosome 11 suggesting that a change in the order of genes has occurred within a conserved linkage group.

A comparison of maximum cystometric bladder capacity with maximum environmental voided volumes

The aim of the study was, to determine whether maximum cystometric capacity accurately reflects the maximum functional bladder volume in women with urinary incontinence. We performed a retrospective chart review involving 85 women between the ages of 22 and 89 with primary complaints of urinary incontinence. The maximum cystometric capacity as determined by cystometry was compared with the maximum environmental voided volumes as recorded in a 24-hour voiding diary, using Pearson's correlation coefficients and paired t-tests. Patients diagnosed as having a small bladder capacity (< 300 ml maximum volume) based on cystometry were also examined with contingency table analysis to determine whether the bladder volumes in the voiding diaries supported the diagnosis of a small bladder. In 85 subjects the average maximum cystometric capacity was 14.7% less than the maximum volume recorded in the voiding diary. The correlation between the maximum cystometric capacity and maximum functional bladder volume was r = 0.473 (P < 0.001). However, there was a statistically significant difference between the two volumes by paired t-test analysis (P = 0.006). Using cystometry to diagnose small bladder capacity showed a sensitivity of 62.9% and a specificity of 71.2% when using voiding diary volumes as the criterion standard. The positive predictive value was 51.4% and the negative predictive value was 84.0%. These results suggest that whereas the maximum bladder capacity measured by cystometry correlates with maximum environmental bladder capacity as determined by 24-hour voiding diaries, there is a statistically significant difference. The diagnosis of a small bladder should not be based on office cystometry alone.

Construction and analysis of luxCDABE-based plasmid sensors for investigating N-acyl homoserine lactone-mediated quorum sensing

Plasmid reporter vectors have been constructed which respond to activation of LuxR and its homologues LasR and RhlR (VsmR) by N-acyl homoserine lactones (AHLs). The expression of luxCDABE from transcriptional fusions to PluxI, PlasI and PrhlI respectively, occurs in the presence of activating AHLs. A profile of structure/activity relationships is seen where the natural ligand is most potent. The characterisation of individual LuxR homologue/AHL combinations allows a comprehensive evaluation of quorum sensing signals from a test organism.

Engineering the luxCDABE genes from Photorhabdus luminescens to provide a bioluminescent reporter for constitutive and promoter probe plasmids and mini-Tn5 constructs

The luxCDABE operon of Photorhabdus luminescens has been cloned and engineered as an easily mobilisable cassette flanked by sites for commonly used restriction enzymes. Constitutive and promoter probe plasmids utilising the P. luminescens luxCDABE have been constructed using a number of compatible replicons and antibiotic markers. Complementary to these plasmids, a range of promoterless and constitutive luxCDABE mini-Tn5 derivatives has been constructed. The potential of coupling mini-Tn5 luxCDABE promoter probe transposons with automated luminometry and photometry to screen for mutants that exhibit growth phase variation in gene expression is demonstrated.