Efficacy of Contrast-enhanced Computed Tomography for the Treatment Strategy of Colonic Diverticular Bleeding.

OBJECTIVE: Diverticular bleeding is the most common cause of acute lower gastrointestinal bleeding, and its incidence has recently increased. However, the treatment strategy of diverticular bleeding has not yet been established. The aim of the study was to investigate the efficacy of contrast-enhanced computed tomography (CECT) to determine the indication for urgent colonoscopy to achieve hemostasis. METHODS: A total of 124 patients diagnosed with diverticular bleeding between 2012 and 2013 in our hospital were analyzed. The clinical behavior, factors related to detecting bleeding diverticula, and risk factors for early rebleeding of diverticular bleeding were evaluated. RESULTS: Clinical behavior: Bleeding diverticula were identified in 23 of 124 (19%) patients and most of them (16/23; 70%) were located in the ascending colon. Hemostasis was achieved in all 23 cases, however, six (26%) developed early rebleeding. Factors for detecting bleeding diverticula: In patients in whom extravasation was detected using CECT, the endoscopic detection rate of bleeding diverticula was 60% (12/20), while bleeding diverticula were detected in only 31% (11/35) of patients in whom extravasation was not detected using CECT (p<0.05). The interval between the first hematochezia and colonoscopy in which the bleeding point was detected by colonoscopy (median 23.5 hours) was shorter than that in which bleeding diverticula were not detected (median 43.6 hours) (p<0.01). Risk factors for short term rebleeding: Using a univariate analysis, atherosclerotic comorbidity, anti-inflammatory drugs including low-dose aspirin, antithrombotic agents, vital signs on admission, hemoglobin level on hospitalization, and extravasation on CECT were not found to be significant risk factors. CONCLUSION: The finding of extravasation on CECT is the most important factor for identifying and treating bleeding diverticula by colonoscopy. In such cases, urgent colonoscopy is recommended.

New index for the stability of a type I collagen affected by hydrophobic environment.

Effects of hydrophobic environment adjusted by various alcohols on the structural stability of calfskin collagen (CSC) were studied to elucidate the nature of collagen-monomer interaction in adhesion. The stability of CSC in aqueous alcohol solutions was represented by its denaturation temperature, Td, measured by DSC. The hydrophobicity of the alcohol solutions was quantified with their specific dielectric constants, epsilon(r), calculated from their concentrations. The effect of each alcohol to stabilize or destabilize CSC was evaluated by the initial slope of each Td vs. epsilon(r) plot, denoted as -(dTd/d epsilon(r))ini and termed as stabilization power. Results showed that a hydrophobic environment with a smaller epsilon(r) lowered the stabilization power. Stabilization power ranged from -3 (strong destabilization) for phenol (epsilon(r) =12) to +0.3 (weak stabilization) for glycerol (epsilon(r)=47). In view of the encouraging results obtained in this study, the new index was therefore helpful in predicting the effects of new dental materials of known epsilon(r) values on the stability of dentinal collagen.

Effect of HEMA adsorption on the stability of native and denatured type I tendon collagen.

Adsorption behavior and stabilization/destabilization effects of 2-hydroxyethyl methacrylate (HEMA) on a bovine tendon collagen (BTC) (type I), either native (N) or thermally denatured (D), were studied by IR spectroscopy and differential scanning calorimetry (DSC). The amount of HEMA adsorbed was larger on BTC(D) than on BTC(N), because BTC(D) had a larger specific surface area (SSA) as revealed from SSA measurement. Denaturation temperature (Td) of BTC(N), measured by DSC in aqueous HEMA solution, decreased from 63 degrees C to 40 degrees C with increasing HEMA concentration (CHEMA) up to 20 wt%. This destabilization might be caused by the loss of hydrophobic stabilization of the helix structure as CHEMA was increased. At CHEMA > 20 wt%, the structure of collagen was restabilized presumably due to the dehydration effect conferred by HEMA at higher concentration. BTC(D) with little helix content, however, showed only a weak endothermic peak in the DSC measurement and the Td at 40 degrees C was independent of CHEMA.

Dual role of vitamin C in an oxygen-sensitive system: discrepancy between DNA damage and cell death.

Although vitamin C is considered to act both as pro-oxidant and antioxidant, the mechanisms underlying these actions are still unclear. Using the oxygen-sensitive system of a strict anaerobe, Prevotella melaninogenica, we investigated both the pro-oxidant and antioxidant mechanisms of vitamin C. In the presence of vitamin C, the 8-hydroxydeoxyguanosine (8OHdG) formation induced by oxygen exposure was enhanced, probably due to the action of vitamin C on hydrogen peroxide generated during oxygen exposure: while catalase almost completely suppressed the enhancing effect of vitamin C, 8OHdG formation induced by hydrogen peroxide was enhanced by vitamin C. By contrast, the presence of vitamin C inhibited bacterial cell death, membrane damage, and lipid peroxidation induced by oxygen exposure. Sodium azide showed similar effects to vitamin C, thus the antioxidant action of vitamin C may be due to its quenching of the singlet oxygen generated in this system. Both the pro-oxidant and antioxidant effects of vitamin C were observed only in acidic conditions.