Energy required to pinch a DNA plectoneme

DNA supercoiling plays an important role from a biological point of view. One of its consequences at the supramolecular level is the formation of DNA superhelices named plectonemes. Normally separated by a distance on the order of 10 nm, the two opposite double strands of a DNA plectoneme must be brought closer if a protein or protein complex implicated in genetic regulation is to be bound simultaneously to both strands, as if the plectoneme was locally pinched. We propose an analytic calculation of the energetic barrier, of elastic nature, required to bring closer the two loci situated on the opposed double strands. We examine how this energy barrier scales with the DNA supercoiling. For physically relevant values of elastic parameters and of supercoiling density, we show that the energy barrier is in the k_{B}T range under physiological conditions, thus demonstrating that the limiting step to loci encounter is more likely the preceding plectoneme slithering bringing the two loci side by side.

Intralesional infliximab in noninfectious cutaneous granulomas: three cases of necrobiosis lipoidica

BACKGROUND

Necrobiosis lipoidica is a rare granulomatous noninfectious skin disease. Treatment of this chronic debilitating disease is of importance because ulceration of the plaques may induce important psychological and physical morbidity.

OBJECTIVE

Infliximab, an anti-TNF-α chimeric monoclonal antibody used intravenously and intralesionally for other extradermatological granulomatous diseases including Crohn's disease and sarcoidosis, was administered by intradermal injection in necrobiosis lipoidica. The aim of this study was to evaluate the efficacy and safety profile of a locally delivered drug compared to its systemic use.

PATIENTS AND METHODS

Weekly injections of intralesional infliximab for 3 weeks were followed by a 1-week treatment interruption. This treatment schedule was repeated thrice.

RESULTS

Two patients who benefitted from complete treatment experienced almost complete remission for up to 18 months. The third patient, who had treatment interruptions, showed partial improvement. No serious side effects were noticed, although the injections caused pain.

CONCLUSIONS

This is the first report about the efficacy and safety of a therapy consisting of intralesional injections of infliximab for a granulomatous skin disease. Although this approach was clearly effective for necrobiosis lipoidica, the disease recurred several months after treatment interruption, raising the question of the need for maintenance therapy. Further controlled long-term trials are thus necessary.

Long-term control with etanercept (Enbrel) of a severe acrodermatitis continua of Hallopeau refractory to infliximab (Remicade)

Hallopeau's acrodermatitis is characterized by the presence of aseptic pustules on an inflammatory basis of the periungual or subungual region. The cyclic recurrences induce important physical and psychological morbidity. By analogy to the efficacy of TNF-alpha antagonists in the treatment of generalized pustular psoriasis, our patient illustrates the long-term efficacy and safety of etanercept (Enbrel) in the treatment of Hallopeau's acrodermatitis refractory to infliximab (Remicade). This treatment alternative should in consequence be considered in patients with a recalcitrant form of a potentially debilitating disease.

Endoscopy water source: tap or sterile water?

The purpose of this study was to determine whether the endoscopic water source holds potential for transmission of pathogens. Phase I of the study used tap water and clean water bottles; Phase II used sterile water and steam-sterilized water bottles. In both phases, a control bottle filled with water from the appropriate source was set up. Cultures were taken from both the controls and endoscopy water sources before the day's procedures were started and at the end of the day. Each phase contained 100 to 106 sets of samples. Many of the tap water samples were positive for normal flora found in city water sources. No clinically significant complications were identified during either phase of the study. The use of tap water and clean water bottles was found to carry no greater risk than using sterile water and sterile bottles. The practice of using tap water will result in significant cost savings. Further study will be needed to look at the integrity of the endoscope and water bottle design in preventing transmission of pathogens.