The role of CT and staging laparoscopy in the staging of gastric cancer.

AIM: To assess the relative roles of computed tomography (CT) and diagnostic laparoscopy in the staging process of patients with potentially curable gastric cancer. MATERIALS AND METHODS: Fifty-two patients underwent laparoscopy and CT as part of staging; 36 patients underwent surgery without laparoscopy. Pathological findings at laparoscopy or surgery were compared with initial CT reports, and analysis of the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) was performed. RESULTS: Of the patients who underwent laparoscopy and CT, six were staged as positive for peritoneal disease (PD), of which five (83%) were positive for PD at laparoscopy. Forty-six patients were reported at CT as negative for PD, of which 40 (87%) were negative at laparoscopy. Of 36 patients with no advanced disease at CT, who had surgery without diagnostic laparoscopy, nine (25%) were positive at surgery for PD. The overall sensitivity of CT for PD was therefore 25%, the specificity was 99%, the PPV was 86%, and the NPV was 83%. CONCLUSION: CT is not sufficiently sensitive to detect or exclude PD in patients with gastric cancer, although is highly specific. Staging laparoscopy is an essential adjunct to imaging in all patients being considered for curative surgery for gastric cancer.

Abeta deposition and related pathology in an APP x PS1 transgenic mouse model of Alzheimer's disease.

A transgenic mouse bearing mutant transgenes linked to familial forms of Alzheimer's disease (AD) for the amyloid precursor protein and presenilin-1 (TASTPM) showed Abeta plaque deposition and age-related histological changes in associated brain pathology. The Abeta present was of multiple forms, including species with a C-terminus at position 40 or 42, as well as an N-terminus at position 1 or truncated in a pyro-3-glutamate form. Endogenous rodent Abeta was also present in the deposits. Laser capture microdissection extracts showed that multimeric forms of Abeta were present in both plaque and tissue surrounding plaques. Associated with the Abeta deposits was evidence of an inflammatory response characterised by the presence of astrocytes. Also present in close association with the deposits was phosphorylated tau and cathepsin D immunolabelling. The incidence of astrocytes and of phosphorylated tau and cathepsin D load showed that both of these potential disease markers increased in parallel to the age of the mice and with Abeta deposition. Immunohistochemical labelling of neurons in the cortex and hippocampus of TASTPM mice suggested that the areas of Abeta deposition were associated with the loss of neurons. TASTPM mice, therefore, exhibit a number of the pathological characteristics of disease progression in AD and may provide a means for assessment of novel therapeutic agents directed towards modifying or halting disease progression.

Modulation of KCNQ2/3 potassium channels by the novel anticonvulsant retigabine.

Retigabine is a novel anticonvulsant with an unknown mechanism of action. It has recently been reported that retigabine modulates a potassium channel current in nerve growth factor-differentiated PC12 cells (), however, to date the molecular correlate of this current has not been identified. In the present study we have examined the effects of retigabine on recombinant human KCNQ2 and KCNQ3 potassium channels, expressed either alone or in combination in Xenopus oocytes. Application of 10 microM retigabine to oocytes expressing the KCNQ2/3 heteromeric channel shifted both the activation threshold and voltage for half-activation by approximately 20 mV in the hyperpolarizing direction, leading to an increase in current amplitude at test potentials between -80 mV and +20 mV. Retigabine also had a marked effect on KCNQ current kinetics, increasing the rate of channel activation but slowing deactivation at a given test potential. Similar effects of retigabine were observed in oocytes expressing KCNQ2 alone, suggesting that KCNQ2 may be the molecular target of retigabine. Membrane potential recordings in oocytes expressing the KCNQ2/3 heteromeric channel showed that application of retigabine leads to a concentration-dependent hyperpolarization of the oocyte, from a resting potential of -63 mV under control conditions to -85 mV in the presence of 100 microM retigabine (IC(50) = 5.2 microM). In control experiments retigabine had no effect on either resting membrane potential or endogenous oocyte membrane currents. In conclusion, we have shown that retigabine acts as a KCNQ potassium channel opener. Because the heteromeric KCNQ2/3 channel has recently been reported to underlie the M-current, it is likely that M-current modulation can explain the anticonvulsant actions of retigabine in animal models of epilepsy.

Localization of the type VI voltage-gated sodium channel protein in human CNS.

The cellular distribution of the type VI human voltage-gated sodium channel (Type VI) was examined in selected human brain regions. Antibodies designed to be specific to rat and human Type VI were raised against a synthetic peptide from the predicted NH2-terminal of the protein, and used for an immunohistochemical investigation. Immunoblot experiments showed that purified antibodies specifically detected the presence of Type VI in transfected cells and human brain membrane preparations. Immunohistochemistry on perfusion fixed human tissue revealed a predominantly somato-dendritic distribution of Type VI in major output neurons of the cerebellum, cerebral cortex and hippocampus. The observed localisation of this channel may reflect an important role in the integration of synaptic input in the human CNS.

Modulation of E2F activity via signaling through surface IgM and CD40 receptors in WEHI-231 B lymphoma cells.

Stimulation of the phenotypically immature B cell lymphoma WEHI-231 with anti-IgM induces G1 arrest followed by apoptotic cell death, which can be reversed by stimulation via the CD40 receptor. Here, we show that cells expressing bcl-xL (WEHI-bcl-xL) arrest at G0/G1 following culture with anti-IgM but do not undergo apoptosis. These arrested cells can be induced to reenter the cell cycle by ligation of CD40. We have therefore used these cells as a model to study the regulation of the transcription factor E2F, which is critically involved in transit through the cell cycle. We found that anti-IgM treatment induces the appearance of an inhibitory DNA binding complex containing the pRB-related pocket protein p130 together with E2F and a concomitant decrease in "free" E2F, consisting of E2F1 and its partner DP1; these effects were reversed following stimulation via CD40. These changes in free E2F levels were regulated by changes in E2F1 gene transcription, which is at least partly a result of control of E2F1 promoter activity through its E2F binding sites. Transient transfection experiments showed that either E2F1 or the viral oncoprotein E1A, which sequesters pocket proteins, including p130, overcame anti-IgM-induced cell cycle arrest in WEHI-bcl-xL. Taken together, these results indicate that in WEHI-231 sIgM ligation induces the accumulation of hypophosphorylated p130 with consequent inhibition of E2F1 gene transcription and cell cycle arrest. Conversely, ligation of CD40 causes hyperphosphorylation of p130, thereby releasing the repression of E2F1 and other E2F-regulated genes, enabling the cells to reenter the cycle. These results, therefore, provide novel insights into the mechanisms whereby antigen receptors on immature B cells deliver inhibitory signals (leading to negative selection of self-reactive B cells) and how these signals can be modulated by positive signals generated via CD40.

Isolation of a Xenopus laevis genomic clone representing a novel N-cadherin related gene.

We have isolated a Xenopus laevis genomic sequence distinct from, but sharing high sequence similarity with N-cadherin. We present evidence that the gene represented by this sequence, named XNcad3, resides at a separate locus to the two previously isolated N-cadherin clones from this species. Extensive analysis could detect no expression of XNcad3 in embryonic or adult tissues. It seems likely that XNcad3 represents a non-expressed pseudogene, or perhaps a novel cadherin with a restricted expression pattern.

Discordance between accumulated p53 protein level and its transcriptional activity in response to u.v. radiation.

In response to DNA damage, the transcriptional activity of p53 rises. This has been thought to be due to an increase in the level of p53 protein. By comparing the p53 protein level and its ability to transactivate target genes Waf1/Cip1 and mdm2 in both T22 and NIH3T3 cells irradiated with u.v., a discordance between the p53 protein level and its transcriptional activity was observed. When the cells were irradiated with 10 J/m2 of u.v., there was a substantial increase in expression of Waf1/ Cip1 and mdm2. However, little increase in Waf1/Cip1 and mdm2 expression was observed in T22 and NIH3T3 cells 8 or 9 h after exposure to 50 J/m2 of u.v., although the p53 protein level accumulated to its highest level under these conditions. Interestingly, a significant increase in Waf1/Cip1 expression was seen 24 h after irradiation in NIH3T3 cells, indicating that the inhibition of p53 transcriptional activity is reversible. Discordance between the transcriptional activity of p53 and its protein level was further studied using a cell line expressing the p53 reporter plasmid RGC delta fosLacZ. Using double immunofluorescence staining, the coexpression of p53 and beta-galactosidase from the reporter plasmid in the same cells was investigated. The observed lack of correlation between the elevated p53 and beta-galactosidase and expression in u.v. irradiated cells strongly indicates that the ability of p53 to transactivate its target genes is not simply correlated to its protein level. The results indicate that the transcriptional activity of p53 may be negatively regulated.

Physical and functional interactions between p53 and cell cycle co-operating transcription factors, E2F1 and DP1.

One way in which wild-type p53 is able to regulate cell cycle progression is thought to be via the induction of its downstream target gene Waf1/CIP1, thus indirectly regulating the transcriptional activity of E2F. The E2F transcription factors are known to be key effectors of the cell cycle. We report here that there is a physical and functional interaction between p53 and two of the components of the E2F transcription factors, E2F1 and DP1. The expression of wild-type p53 can inhibit the transcriptional activity of E2F, and the expression of both E2F1 and DP1 can also downregulate p53-dependent transcription. The transcriptional activity of p53 is known to be inhibited by the direct binding of mdm2, but we demonstrate here that both E2F1 and DP1 can inhibit p53 transcriptional activity independently of mdm2. Detailed studies of protein-protein interactions have provided evidence that E2F1 and its co-operating factor DP1 can complex with p53 both in vitro and in vivo.

Effects of central venous catheter placement on upper extremity duplex US findings.

PURPOSE: The upper extremity veins of 17 patients who underwent operative central venous catheter placement were studied prospectively with color duplex sonography to determine which duplex changes, if any, could be due to the presence of the catheter alone and to determine if these waveform changes could mimic the dampened waveform seen peripheral to central nonvisualized or nonocclusive thrombosis or proximal stenosis. PATIENTS AND METHODS: The subclavian, internal jugular, and brachiocephalic veins were examined with color duplex sonography immediately before and after catheter placement. Images obtained before and after catheterization were reviewed by two radiologists for (a) spectral broadening in both the vein of insertion and the brachiocephalic vein, (b) transmission of atrial pulsations, and (c) respiratory phasicity. RESULTS: In all cases, atrial pulsatility and respiratory phasicity were present before and after catheter placement. There was no statistically significant change in the amount of spectral broadening after catheter placement. A mild increase in the peak blood flow velocity of 7 cm/sec (P = .04) in the ipsilateral brachiocephalic vein was demonstrated; however, no significant increase in velocity could be shown in the vein of insertion. CONCLUSION: In this clinical setting, the hemodynamic changes within the vein from the catheter placement are minimal. Any damping of the venous waveform seen with sonography performed to rule out upper extremity deep venous thrombosis secondary to indwelling catheter--for example, loss of atrial pulsatility or respiratory phasicity--is presumably due to the presence of venous thrombosis or stenosis.

Comparison of the biodistribution of manganese-54 DTPA and gadolinium-153 DTPA in dogs.

The biodistribution of [54Mn]DTPA and [153Gd]DTPA dimeglumine were investigated and compared following i.v. administration to fasting anesthetized dogs. Unlike most previously reported metal ion-DTPA complexes, [54Mn]DTPA showed high uptakes in several organs including the liver, bile, pancreas, bowel, and kidney. This uptake was independent of the pH of the injected solution. Accumulation in these organs suggests a potential role for [Mn]DTPA as a paramagnetic contrast agent for NMR imaging. With the exception of the kidneys, [153Gd]DTPA showed no evidence of tissue specific uptake over the course of 4 hr, consistent with it being an extracellular ion that is cleared by glomerular filtration.