Visualisation of intra-cardiac structures and radiofrequency lesions using intracardiac echocardiography.

AIMS: Fluoroscopy does not allow identification specific anatomical landmarks during electrophysiological studies. Intra-cardiac echocardiography permits visualization of these structures with excellent accuracy, but the optimal method has not been fully described. The aim of this study was to assess the capability of intra-cardiac echocardiography for the visualization of such structures using two different approaches. We also assessed its capability for the evaluation of radio frequency lesions 20 min after catheter ablation of the cavo-tricuspid isthmus. METHODS: Intra-cardiac echocardiography was performed using a 9 MHz rotating transducer in eight consecutive patients (age range: 37-76 years) after radio frequency ablation of the cavo-tricuspid isthmus. The ultrasound catheter was inserted through the femoral vein into the superior vena cava and was pulled back to the inferior vena cava. The echo catheter was then reinserted through the subclavian vein and advanced into the right ventricular apex and was pulled back from the right ventricular to the superior vena cava. Qualitative evaluation and intra-cardiac measurements were performed off-line. RESULTS: The fossa ovalis, the tricuspid valve, and the terminal crest were visible in all patients regardless of the method of introduction of the echo catheter. Left-sided structures were less accurately seen by intra-cardiac echocardiography. The horizontal diameter of the fossa ovalis was 8.9+/-1.8mm. The cavo-tricuspid isthmus was visible using the femoral approach in three patients. The isthmus could be visualized in all patients, and in three patients together with the ostium of the coronary sinus, using the subclavian approach. radio frequency lesions were not visible 20 min after ablation. Additionally, both the left and right ventricles could be seen using the subclavian approach. CONCLUSIONS: The subclavian approach is feasible, safe and superior to visualize the isthmus. Twenty minutes after radio frequency ablation of the cavo-tricuspid isthmus radio frequency lesions are not visible using intra-cardiac echocardiography.     

Gastro-oesophageal reflux disease: Medical or surgical treatment? Report of an interactive workshop

Gastroesophageal reflux disease (GERD) is the most common disease of the upper gastrointestinal tract. With the introduction of proton pump inhibitors medical treatment of GERD has been significantly improved. However, the development of laparoscopic antireflux surgery resulted in an increasing interest of surgeons in this disease. An interactive meeting was organized in order to develop an agreement between gastoenterologists and surgeons regarding therapeutic decisions and this is the main topic of this paper.     

Sequence comparison of human and yeast telomeres identifies structurally distinct subtelomeric domains

We have sequenced and compared DNA from the ends of three human chromosomes: 4p, 16p and 22q. In all cases the pro-terminal regions are subdivided by degenerate (TTAGGG)n repeats into distal and proximal sub- domains with entirely different patterns of homology to other chromosome ends. The distal regions contain numerous, short (<2 kb) segments of interrupted homology to many other human telomeric regions. The proximal regions show much longer (approximately 10-40 kb) uninterrupted homology to a few chromosome ends. A comparison of all yeast subtelomeric regions indicates that they too are subdivided by degenerate TTAGGG repeats into distal and proximal sub-domains with similarly different patterns of identity to other non-homologous chromosome ends. Sequence comparisons indicate that the distal and proximal sub-domains do not interact with each other and that they interact quite differently with the corresponding regions on other, non- homologous, chromosomes. These findings suggest that the degenerate TTAGGG repeats identify a previously unrecognized, evolutionarily conserved boundary between remarkably different subtelomeric domains.      

Characterization of the pseudorabies virus-specific immunoglobulin M response and evaluation of its diagnostic use in pigs with preexisting immunity to the virus.

Despite preexisting immunity to pseudorabies virus (PRV), pigs may become infected and may or may not show clinical signs of disease. To investigate whether detection of immunoglobulin M (IgM) antibodies to PRV is suitable for diagnosis of recent infection in pigs with (or without) preexisting immunity, the IgM responses of pigs were examined after both experimental and natural infections. Upon inoculation of seronegative pigs with a low dose of a mildly virulent strain of PRV, IgM was first detectable at day 7 postinoculation (p.i.), reached a maximum at day 14 p.i., and became undetectable again at about days 32 to 36 p.i. In inoculated pigs with maternal antibodies against PRV, the IgM response began later and ended sooner, and peak titers were also lower. In immune pigs with maternally derived antibodies, there was apparently no correlation between the virulence of the inoculated strain and the IgM response. The suitability of the IgM enzyme-linked immunosorbent assay (ELISA) for detection of recent infection in the field was compared with that of the virus neutralization (VN) assay and with an ELISA which specifically detects antibodies directed to glycoprotein I (gI) of PRV. Paired sera were obtained from pigs suspected of PRV infection in an area endemic for PRV infection in which vaccination against PRV is often applied. Practically all pigs had antibodies to PRV in the acute phase of the disease. Compared with the VN assay, the specificity of the IgM ELISA was high but its sensitivity was low. However, all three serotests apparently failed to detect some PRV infections. The IgM ELISA appeared to be especially useful as a diagnostic aid for detection of recent infections in pigs with high levels of neutralizing and gI antibodies, probably maternally derived, in the acute phase of the disease. Such pigs may fail to develop a significant rise in VN antibody titer. The IgM ELISA may be the only serotest for monitoring infections in such pigs.     

Stimulation of bone resorption by inflamed nasal mucosa, dermonecrotic toxin-containing conditioned medium from Pasteurella multocida, and purified dermonecrotic toxin from P. multocida.

The effects of inflamed nasal mucosa from pigs with atrophic rhinitis (AR), cell extract from Bordetella bronchiseptica, conditioned medium from Pasteurella multocida, and purified dermonecrotic toxin (DNT) from P. multocida on mouse fetal long bones in organ culture were studied. Inflamed nasal "AR mucosa" stimulated the release of 45Ca from prelabeled cultures, while histologically the formation of calcified matrix was impaired as well. B. bronchiseptica cell extract only transiently increased 45Ca release, but also impaired the formation of matrix. 45Ca release was also stimulated by DNT-containing conditioned medium from P. multocida and by purified DNT. The effect of DNT was biphasic: low doses (1 to 25 ng/ml) slightly stimulated bone resorption, higher doses were inhibitory. The stimulatory action of DNT on 45Ca release was accompanied by an increase in numbers of preosteoclasts and osteoclasts. The significance of these findings for the pathogenesis of AR is discussed.     

Vaccination of pigs against pseudorabies virus with plasmid DNA encoding glycoprotein D

We analysed the ability of a plasmid carrying the gene encoding glycoprotein D (gD) of pseudorabies virus (PRV) to induce humoral and cell-mediated immune responses and assessed the protection provided by PRV-gD DNA vaccination against challenge infection with PRV. Immunization with plasmid PRV-gD induced neutralizing antibodies and lymphocyte proliferative responses both in mice and pigs. Moreover, when challenged with virulent PRV six weeks following the last immunization, PRV-gD DNA vaccinated pigs excreted virus for a significantly shorter period and showed less clinical symptoms than pigs vaccinated with a control plasmid. Thus, in the target animal, DNA vaccination with PRV-gD DNA induces protective immunity against challenge infection.     

Bacterial and mammalian DNA alkyltransferases sensitize Escherichia coli to the lethal and mutagenic effects of dibromoalkanes

Here we confirm and extend our previous studies demonstrating that the mutagenic potency of 1,2-dibromoethane (DBE) and dibromomethane (DBM) is markedly enhanced (not prevented) in bacteria expressing the O6- alkylguanine-DNA alkyltransferase (ATase) encoded by the Escherichia coli ogt gene. We demonstrate that, in close parallel with mutagenesis, the Ogt ATase sensitizes the bacteria to the lethal effects of these carcinogens, suggesting that one or more of the potentially mutagenic lesions induced by DBE and DBM in the presence of Ogt has additional lethal capacity. We further demonstrate that the sensitization to both lethality and mutagenesis by DBE and DBM is a property shared by other DNA alkyltransferases. This objective was accomplished by quantifying the induction of mutations and lethal events in ogt- ada- E. coli expressing an exogenous bacterial or mammalian ATase from a multicopy plasmid. Mammalian recombinant ATases enhanced the lethal and mutagenic actions of DBE and suppressed the lack of sensitivity of the vector- transformed bacteria to DBM. In most cases the order of effectiveness of the ATases ranked: murine > human > Ogt > rat. Further comparisons included the full-length Ada ATase from E. coli and a truncated Ada version (T-ada) that retains the O6-methylguanine binding domain of the protein. The full-length Ada ATase was effective in enhancing the lethality but not the mutagenicity induced by DBE and DBM. The T-ada ATase provided less sensitization than Ada to lethality by DBE, but of the three bacterial ATases T-ada yielded the highest sensitization to mutagenesis by this compound. T-ada and Ada ATases were in general less effective than the mammalian versions, with the exception of the rat recombinant ATase. The effectiveness of the different mammalian and bacterial ATases in promoting the deleterious actions of dibromoalkanes was compared with the effectiveness of these proteins in suppressing the lethal and mutagenic effects induced by N-nitroso-N-methylurea. The ability to sensitize E. coli to the lethal and mutagenic effects of DBE and DBM seems restricted to DNA alkyltransferase, since overexpression of thioredoxin (Trx) or glutaredoxin (Grx1) in ogt- ada- cells showed no effect, in spite of the reported potential of bioactive dihaloethane- derived species to alkylate Trx.