Peristomal varices--life threatening or luminal?

Bleeding from the edge of an ileostomy site is a common problem. In those who have undergone a proctocolectomy with ileostomy formation in conjunction with a risk of chronic liver disease (even with normal liver function tests), this may be due to peristomal varices. If this is the case, significant, difficult-to-control and potentially life-threatening bleeding is likely in the future and may require transfusion. Improvements in radiological imaging techniques can give quick, sensitive and specific information to diagnose and guide management in this group. In those patients with major bleeding episodes, an initial conservative management policy should be adopted with the knowledge that, if bleeding persists, propanolol therapy, portosystemic shunt insertion or even liver transplantation may be indicated.

A catalytic loop within Pseudomonas aeruginosa exotoxin A modulates its transferase activity.

Mutagenesis techniques were used to replace two loop regions within the catalytic domain of Pseudomonas aeruginosa exotoxin A (ETA) with functionally silent polyglycine loops. The loop mutant proteins, designated polyglycine Loops N and C, were both less active than the wild-type enzyme. However, the polyglycine Loop C mutant protein, replaced with the Gly(483)-Gly(490) loop, showed a much greater loss of enzymatic activity than the polyglycine Loop N protein. The former mutant enzyme exhibited an 18,000-fold decrease in catalytic turnover number (k(cat)), with only a marginal effect on the K(m) value for NAD(+) and the eukaryotic elongation factor-2 binding constant. Furthermore, alanine-scanning mutagenesis of this active-site loop region revealed the specific pattern of a critical region for enzymatic activity. Binding and kinetic data suggest that this loop modulates the transferase activity between ETA and eukaryotic elongation factor-2 and may be responsible for stabilization of the transition state for the reaction. Sequence alignment and molecular modeling also identified a similar loop within diphtheria toxin, a functionally and structurally related class A-B toxin. Based on these results and the similarities between ETA and diphtheria toxin, we propose that this catalytic subregion represents the first report of a diphthamide-specific ribosyltransferase structural motif. We expect these findings to further the development of pharmaceuticals designed to prevent ETA toxicity by disrupting the stabilization of the transition state during the ADP-ribose transfer event.

Technical report: the Venflon 2 intravenous cannula used for arterial catheterization.

Using conventional guidewire techniques we have found the Venflon 2 (Viggo-Spectramed) to be a safe and effective arteriographic puncture needle. The Venflon 2 offers significant technical advantages and cost savings when compared with traditional needles. Its use and limitations are discussed.

Case report: recurrent liposarcoma of the oesophagus.

A case of recurrent liposarcoma of the oesophagus is presented. The clinical and radiological findings are discussed. Our case displays the characteristic features and behaviour of a common sarcoma arising in a rare site.

Delayed tension pneumothorax complicating staphylococcal pneumonia.

A case is described in which a tension pneumothorax complicated staphylococcal pneumonia 11 months after its onset. The delayed and subacute/chronic nature of the tension pneumothorax is unusual. The case also highlights the difficult differential diagnosis between subpleural lung cysts and encysted pneumothorax.

A study of the effects of glutaraldehyde and formaldehyde on the mechanical behaviour of bovine pericardium.

The inherent variability in the mechanical behavior of bovine pericardium causes difficulties in establishing the effects of treatment procedures used in the manufacture of bioprosthetic cardiac valves. A new experimental technique has been developed in which the specimen acts as its own control, obviating the need to perform large numbers of experiments to obtain statistically significant results. The procedure used is described in detail as is the equipment employed. The technique was used to assess the effect of glutaraldehyde and formaldehyde on the stress/strain response of bovine pericardium. The results show that the fixing process in glutaraldehyde is virtually complete within two hours and causes significant changes in the mechanical behaviour of the tissue. The tissue becomes progressively stiffer as the treatment period is extended, which is especially pronounced at low levels of stress. Formaldehyde storage subsequent to fixing in glutaraldehyde was found to have no effect on the stress/strain response of the bovine pericardium.