Using Molecular Simulation to Explore Unusually Low Moisture Uptake in Amine‐Cured Epoxy Carbon Fiber Reinforced Nanocomposites

Reinforced nanocomposites based on a diamine‐cured diglycidylether of bisphenol A are reported containing a monoamino‐substituted polyhedral oligomeric silsesquioxane (POSS) reagent and polyacrylonitrile fibers. Covalent incorporation of monoamino‐POSS at 2 wt% leads to especially attractive properties, including an increase (20 K) in glass transition temperature (T_g) and thermal stability (increase in char yield of up to 5%). The addition of POSS (2 wt%) in the diglycidylether of bisphenol A (DGEBA) leads to a reduction in moisture uptake of less than 0.30–0.91 wt%, depending on relative humidity (after 6000 h), with little effect on T_g (reduction of 9–11 K compared with 11–22 K in the unmodified DGEBA). Molecular dynamics simulation is used to visualize the cured network structure of these nanocomposites, relating free volume to water uptake. Translation of the properties from neat resin to CFRP is very encouraging with a reduction in the equilibrium moisture absorption of up to 29% in the latter.

     

Optimal Vagus Nerve Stimulation Frequency for Suppression of Spike‐and‐Wave Seizures in Rats

Vagus nerve stimulation (VNS) is used as an adjunctive therapy for drug‐resistant epilepsy and results in a 50% seizure reduction in up to 50% of treated patients. The VNS frequency used in the clinic today is in the range of 10–30 Hz. The evidence for choosing the stimulation frequency is limited, and little knowledge is available on the effect of other VNS frequencies. Deep brain, trigeminal nerve, or spinal cord stimulation studies have suggested the use of stimulation frequencies above 80 Hz for seizure control. Therefore, our objective for the present study was to investigate if VNS using frequencies higher than those currently used in the clinic could be more effective in attenuating seizures. Spike‐and‐wave (SW) discharges were induced in 11 rats, which then were subjected to VNS sessions applied at the frequencies of 10, 30, 80, 130, and 180 Hz combined with control intervals without stimulation. The anticonvulsive effect of VNS was evaluated by comparing the normalized mean power (nMP) and frequency (nMSF) of the SW discharges derived from intracortical recordings collected during the stimulation and control intervals. Compared with the control intervals, all the tested VNS frequencies significantly reduced the nMP (in the range of 9–21%). However, we found that 130 and 180 Hz VNS induced a 50% larger attenuation of seizures than that achieved by 30 Hz VNS. In addition, we found that 80, 130, and 180 Hz VNS induced a significant reduction of the nMSF, that is by 5, 7, and 8%, respectively. These results suggest that a VNS stimulation frequency in the range of 130–180 Hz may be more effective in inhibiting seizures than the 30 Hz VNS applied in the clinic today.     

An intensive surveillance program detected a high incidence of hepatocellular carcinoma among hepatitis B virus carriers with abnormal alpha-fetoprotein levels or abdominal ultrasonography results.

PURPOSE: To study the incidence and treatment outcomes of hepatocellular carcinoma (HCC) detected in an intensive surveillance program (ISP) of hepatitis B virus (HBV) carriers. PATIENTS AND METHODS: We screened 1,018 HBV carriers by serum alpha-fetoprotein (AFP) measurement and abdominal ultrasonography (AUS). Patients with an abnormal AFP level or AUS result were enrolled in an ISP that included Lipiodol computed tomography followed by AFP measurement/AUS every 3 months for 2 years and then every 6 months thereafter. The rest were on routine surveillance for 2 years. RESULTS: A total of 9,849 serum AFP measurements and 3,053 AUSs were performed. After a median follow-up of 4.12 years, we diagnosed 24 HCCs among 78 patients with abnormal screening test results at enrollment (group A); 23 HCCs among 93 patients with only abnormal surveillance test results during follow-up (group B); and nine HCCs among 847 patients with 2 years of normal surveillance (group C). Annual incidence of HCC in the ISP was 760.2 (95% CI, 538.4 to 1,073.7) per 100,000. Mean tumor sizes were 3.02, 2.91, and 4.82 cm in groups A, B, and C, respectively (P = .01). Tumor resection rate of the ISP was 36.2%, although another 29.8% of the patients were eligible for locoregional ablative therapy. CONCLUSION: This study illustrated that a high incidence of relatively small HCCs may be detected by using intensive surveillance of high-risk HBV carriers. However, the surgical resection rate was low, and we were not able to demonstrate clinical benefit with the early detection. Future surveillance studies should consider incorporation of therapy aimed at long-term control of small-sized tumors.     

Role of the intestinal microflora in the formation of DNA and haemoglobin adducts in rats treated with 2-nitrofluorene and 2-aminofluorene by gavage

The role of the intestinal microflora in the metabolic activationof nitroarenes and arylamines was studied in female Wistar ratsthat received a dose of 1 mmol/kg 2-aminofluorene (2-AF) insunflower oil by gavage. Another group received the same doseof 2-nitrofluorene (2-NF). A third group of animals was usedas controls. Germfree (GF) rats, GF rats with a rat microflora(RM) and GF rats with a human microflora (HM) were treated.After treatment with 2-AF significant differences were observedin the formation of haemoglobin (Hb) adducts and DNA adducts.The 2-AF-Hb adduct level (mean ± SD) observed in GF rats(0.57 ± 0.13 µmol/g Hb) was considerably lowerthan that observed in RM rats (5.1 ± 0.6) and in HM rats(6.2 ± 13). DNA adduct levels showed the opposite pattern:levels of adducts co-migrating with deoxyguanosin-8-yl-aminofluorene(dG-C8-AF) in liver tissue were higher in GF rats (4.6 ±1.4 fmol/µg DNA) as compared to RM rats (2.6 ±0.04) or HM rats (2.0 ± 0.7). In lung tissue and whiteblood cells a similar influence of the intestinal microfloraon DNA adduct levels was observed. These results suggest thatthe intestinal microflora cleaves conjugates of 2-AF or N-hydroxy-2-AF,thus facilitating entero-hepatic recirculation of these compoundsand enhancing the formation of reactive intermediates bindingto Hb. The latter is not observed for DNA adduct formation,indicating that most of these adducts have been formed aftera single passage through the liver. After treatment with 2-NF,Hb and DNA adduct levels were much lower. An adduct spot wasobserved that was not presentin rats that received 2-AF. InGF animals only very low levels of DNA adducts co-migratingwith dG-C8-AF or deoxyguanosin-8-yl-acetyl-aminofluorene andno Hb adducts were observed, indicating that the metabolic activityof the microflora is an essential step in both Hb and DNA adductformation.     

A T2* magnetic resonance imaging study of pancreatic iron overload in thalassemia major

We studied the utility of pancreatic magnetic resonance imaging (MRI) in 72 thalassemia major patients (21 diabetic, 51 normoglycemic). Diabetic patients were significantly older (p<0.0001) and had smaller pancreas volume (p<0.0001). The two groups were comparable for ferritin and MRI-T2* heart, liver and pancreas. Pancreatic T2* signals were abnormal in 80% of both groups, and correlated with heart T2*. In normoglycemic patients, cardiac T2* and log-pancreatic T2* values correlated with homeostatic model assessments HOMA-B (beta cell reserve), HOMA-IR (insulin resistance) and fasting insulin/C-peptide levels. This suggested that improved chelation may improve beta cell reserve and prevent pancreatic atrophy.