Investigation of the air kerma response of spherical ionization chambers for unfolded pulse height distributions of (60)Co and (137)Cs using the EGS4 Monte Carlo code

Data required for the determination of the absolute air kerma rate for (60)Co and (137)Cs gamma-rays using spherical cavity chambers were calculated using the EGS4 Monte Carlo system. Mass energy-absorption coefficient ratio and the stopping power ratio were calculated for a 10 cm(3) primary standard graphite-walled ionization chamber from the unfolded energy pulse height distributions of (60)Co and (137)Cs sources. Wall correction factors and non-uniformity correction factors for two graphite and one air equivalent plastic walled ionization chambers were also calculated with EGS4 code. The wall correction factors were compared with those determined by an experimental extrapolation method. To check the accuracy of the calculations the results were compared with those obtained from other primary standard laboratories such as NIST and NRCC. For a 10 cm(3) graphite ionization chamber, the mass energy-absorption coefficient ratios were 0.99917 for (60)Co and 1.0004 for (137)Cs. The values differed by 0.02-0.05 % for (60)Co and 0.11 % for (137)Cs from those of two laboratories. The stopping power ratios were 0.99984 for (60)Co and 1.0087 for (137)Cs. Comparison with NIST values showed differences of 0.06 % for (60)Co and 0.04 % for (137)Cs. The wall correction factors were obtained and they were different by 0.6-1.1 % for (60)Co and (137)Cs compared to the experimental linear extrapolation method. These values were compared with Monte Carlo derived values from other laboratories. The non-uniformity correction factors were also calculated and they differed from unity, the traditional value used in most standard national metrology laboratories.     

Scoring system for risk stratification of viral reactivation during prophylactic antiviral treatment in Korean patients with hepatitis B undergoing anticancer chemotherapy: A multicenter study

Prophylactic antiviral therapy is recommended for hepatitis B virus (HBV)‐infected patients with malignancies who are undergoing systemic chemotherapy. In the current study, we aimed to develop a risk scoring system to guide the selection of prophylactic antiviral agents. In this retrospective analysis, we included consecutive chronic hepatitis B patients who received antiviral prophylaxis for chemotherapy of solid or hematologic malignancies at three large‐volume hospitals in Korea. The primary endpoint was HBV reactivation. The inverse probability treatment weighting method was used to minimize selection bias in terms of antiviral assignments. A total of 419 patients were enrolled: 129 patients received lamivudine (LAM), 216 received telbivudine (LdT), and 74 received entecavir (ETV), respectively. Of these, 36 patients developed on‐treatment HBV reactivation (LAM, 17; LdT, 18; ETV, 1). Multivariate analysis identified three independent predictors for reactivation: hepatitis B e‐antigen positivity, HBV DNA level, and type of malignancy. Accordingly, a risk scoring system was developed wherein one point was assigned for each of the risk factors. HBV reactivation occurred more frequently in the high‐risk group (score ≥ 2) than in the low‐risk group (hazards ratio, 14.17; P < 0.001). ETV exhibited superior prophylactic efficacy over LdT or LAM in the high‐risk group, whereas no significant difference was noted in the low‐risk group. The prognostic scoring system was useful for risk stratification of chemotherapy‐related HBV reactivation. High genetic barrier agents appear to be vital for high‐risk patients, whereas cost‐effectiveness may be more relevant for low‐risk patients.     

Venom allergen-like protein 28 in Clonorchis sinensis: four epitopes on its surface and the potential role of Cys124 for its conformational stability

Parasitology Research - Venom allergen-like (VAL) proteins are important to host-parasite interactions. We previously demonstrated that a Clonorchis sinensis VAL (CsVAL) protein-derived synthetic...     

Inhibition of Mycoplasma pneumoniae by Actinomycin D

Growth of Mycoplasma pneumoniae was completely prevented by 0.06 mug of actinomycin D/ml, and 0.00375 mug/ml caused 90% inhibition. It thus appears that M. pneumoniae is more susceptible to actinomycin D than previously reported. Low concentrations (0.019 mug/ml) of the antibiotic primarily inhibited ribonucleic acid synthesis and high concentrations (20 mug/ml) inhibited both ribonucleic and deoxyribonucleic acid synthesis.     

Peroral immunization with Helicobacter pylori adhesin protein genetically linked to cholera toxin A2B subunits

Helicobacter pylori is a major cause of gastric-associated diseases. To evaluate the efficacy of a possible vaccine antigen against H. pylori infection, the chimaeric construct adhesin--CTXA2B, derived from H. pylori adhesin genetically coupled to cholera toxin (CTX) subunits A2 and B (CTXA2B), was expressed in Escherichia coli as an insoluble recombinant chimaeric protein. The protein was then purified by denaturation, renaturation and size-exclusion chromatography. The composition of purified adhesin--CTXA2B was verified by SDS/PAGE and Western blotting with antibodies to antigenic components of adhesin and CTXB, and confirmed as a chimaeric protein with G(M1)-ganglioside binding activity and adhesin epitopes by a G(M1)-ELISA developed using antibodies to adhesin. Oral immunization of mice with adhesin--CTXA2B induced higher levels of mucosal IgA and serum IgG antibodies to H. pylori adhesin and to CTXB than in mice immunized with adhesin or CTXA2B alone. Adhesin--CTXA2B was also demonstrated to be a potential protective antigen in a mouse model of H. pylori infection. The immunization of mice with adhesin--CTXA2B protected 62.5% of mice infected with H. pylori SS1 strain, whereas adhesin immunization was not able to confer protection to mice. This protection may be correlated with high levels of mucosal IgA and serum IgG antibodies against H. pylori adhesin. Taken together, the results indicate that the genetically linked CTXA2B acts as a useful mucosal adjuvant, and that the adhesin-CTXA2B chimaeric protein could be a potential component in future H. pylori vaccine development.     

Simultaneous sterno-thoracic cardiopulmonary resuscitation improves short-term survival rate in canine cardiac arrests

We have reported previously that simultaneous sterno-thoracic cardiopulmonary resuscitation (SST-CPR) using a device that compresses the sternum and constricts the thorax circumferentially during a compression systole that can be achieved using standard cardiopulmonary resuscitation (STD-CPR). This study was designed to assess whether SST-CPR improves the survival rate of dogs with cardiac arrest compared with STD-CPR. Twenty-nine mongrel dogs (19-31 kg) were enrolled in this study. After 4 min of ventricular fibrillation induced by an AC current, animals were randomized to be resuscitated by either STD-CPR (n=15) or SST-CPR (n=14). Defibrillation was attempted 10 min after the induction of cardiac arrest. Standard advanced cardiac life support was started if defibrillation was unsuccessful. Aortic blood pressure, coronary perfusion pressure, and end tidal CO(2) tension were measured during CPR and the post-resuscitation period. Survival was determined 12 h after the induction of cardiac arrest. SST-CPR resulted in a significantly (P<0.001) higher systolic arterial pressure (91+/-47 vs 47+/-24 mmHg), diastolic pressure (43+/-24 vs 17+/-10 mmHg), coronary perfusion pressure (35+/-25 vs 13+/-9 mmHg), and end tidal CO(2) tension (9+/-4 vs 3+/-2 mmHg). Two of 15 animals (13%) resuscitated by STD-CPR and seven of 14 animals (50%) resuscitated by SST-CPR survived for 12 h after cardiac arrest (P<0.05). In conclusion, SST-CPR improves the short-term survival rate in canine cardiac arrest compared with STD-CPR.     

Cationic lipid emulsions containing heavy oils for the transfection of adherent cells.

A new cationic emulsion system with high density was prepared increasing in vitro transfection efficiencies of adherent cells. Lipiodol with a density of 1.3 (g/ml) was selected to increase the density of the DNA/emulsion complex. Cationic lipid emulsions were formulated with mixtures of lipiodol and squalene as the oil phase and 1,2-dioleoyl-sn-glycero-3-trimethylammonium-propane (DOTAP) as a cationic lipid. These emulsions were used to find the correlation between the density and the in vitro transfection efficiency. The physical characteristics of the new emulsion formulations were also determined. Heavier DNA/cationic lipid emulsion complex showed higher in vitro transfection efficiency on adherent cell lines in the presence of 10% serum compared to lighter ones. The cationic lipid emulsion formulated with lipiodol and DOTAP was more stable and showed better in vitro transfection efficiency than other carriers without lipiodol. Due to the high density of the carrier, the DNA/carrier complex sank to the bottom of the wells, thereby increasing the contact between the complex and adherent cells. The new lipiodol emulsion with high density showed superior transfection activities on adherent cells in the presence of serum.     

Diffusion-weighted MRI of intracerebral hemorrhage clinically undifferentiated from ischemic stroke

This report describes diffusion-weighted MRI findings of some intracerebral hemorrhages clinically undifferentiated from ischemic stroke. We treated patients with characteristic features of intracerebral hemorrhages that could distinguish themselves from ischemic lesion on diffusion-weighted imaging. Therefore, we think diffusion-weighted imaging could be an emergency screening tool for ischemic stroke as an alternative to computed tomography, and the EP should be familiar with the diffusion-weighted imaging findings of intracerebral hemorrhage as well as cerebral infarction.     

A Sos proteomimetic as a pan-Ras inhibitor

Aberrant Ras signaling is linked to a wide spectrum of hyperproliferative diseases, and components of the signaling pathway, including Ras, have been the subject of intense and ongoing drug discovery efforts. The cellular activity of Ras is modulated by its association with the guanine nucleotide exchange factor Son of sevenless (Sos), and the high-resolution crystal structure of the Ras–Sos complex provides a basis for the rational design of orthosteric Ras ligands. We constructed a synthetic Sos protein mimic that engages the wild-type and oncogenic forms of nucleotide-bound Ras and modulates downstream kinase signaling. The Sos mimic was designed to capture the conformation of the Sos helix–loop–helix motif that makes critical contacts with Ras in its switch region. Chemoproteomic studies illustrate that the proteomimetic engages Ras and other cellular GTPases. The synthetic proteomimetic resists proteolytic degradation and enters cells through macropinocytosis. As such, it is selectively toxic to cancer cells with up-regulated macropinocytosis, including those that feature oncogenic Ras mutations.

The Ras-specific guanine nucleotide exchange factor Son of sevenless (Sos) mediates the conversion of Ras from its inactive GDP-bound form to the active GTP-bound state (1). Sos catalyzes nucleotide exchange via insertion of a critical helical segment (αH) between the conformationally dynamic Switch I and II regions that flank the Ras nucleotide binding pocket leading to disruption of water-mediated and direct interactions between the protein and the cofactor (Fig. 1A) (2). Given the biomedical importance of the conformationally dynamic Sos-binding interface of Ras, several rational design and screening strategies have been attempted to develop ligands for this interface (3, 4). Recent efforts to engage the Ras G12C (5, 6) and the G12D isoforms (7, 8) suggest that targeted screens may afford small molecules and peptide macrocycles as potential leads. The structure of the Ras–Sos complex provides a basis for the rational design of Sos helix mimics that engage the Ras switch regions. Our group has previously developed a conformationally stabilized α-helix mimic to target the Ras–Sos protein–protein interaction (PPI) (9, 10). The stabilized α-helix was shown to bind Ras at the orthosteric binding site and inhibit Sos-mediated nucleotide exchange, Ras activation, and phosphorylation of the downstream effector protein ERK (11), a well-characterized kinase implicated in cell proliferation and differentiation. However, this compound preferred to bind Ras in its nucleotide-free form, suggesting that a single Sos helix is likely insufficient to properly engage the dynamic Ras interface in its nucleotide-bound form. While wild-type Ras toggles between its two nucleotide-bound forms (Fig. 1A), the oncogenic forms of Ras remain activated in their GTP-bound states (3). Therefore, a compound that preferentially engages the nucleotide-free form of Ras may have limited biological utility.Open in a separate windowFig. 1.Overview of the Ras activation cycle and design of a Sos-based proteomimetic. (A) The cellular activity of Ras is tightly controlled as part of a balanced feedback loop. Oncogenic mutations shift this balance and increase the cellular concentration of Ras-GTP leading to aberrant downstream signaling. The molecular model shows the complex between Ras (gray ribbon) and its guanine exchange factor Sos (green). Sos inserts a helical hairpin (pink and blue helices) into the nucleotide binding pocket of Ras to mediate nucleotide exchange. The Ras nucleotide binding pocket is highlighted in yellow. Segments of Sos are not shown to highlight interactions of the helical hairpin with Ras (PDB code: 1NVW). (B) The molecular models depict critical Sos helices and the design of a constrained Sos proteomimetic as a Ras inhibitor. GDP, guanosine 5′-diphosphate; GTP, guanosine 5′-triphosphate; GAP, GTPase activating protein; GEF, guanine nucleotide exchange factor.Our prior results with the Sos helix mimic encapsulate a critical challenge in developing minimal protein secondary-structure mimics. Although mimics of protein secondary structures have proven to be a potent class of PPI inhibitors (12–15), many protein interfaces feature binding epitope complexity beyond what can be captured by reproduction of minimal elements of protein structure (16–19). We hypothesized that the introduction of additional contact residues from Sos may allow engagement of nucleotide-bound Ras (Fig. 1B). Sos inserts αH into the switch region of Ras, but analysis of the complex shows that several other residues from Sos also interact with Ras (SI Appendix, Fig. S1). The conformation of the αH helix, itself, is controlled by the αI domain as part of a hairpin helix organization. The αI helix makes important electrostatic contacts with the Ras effector loop in the Switch I region.We sought to develop a tertiary-structure mimic of Sos that encompasses critical binding residues from the helix–loop–helix motif to determine if the additional contacts allow engagement of nucleotide-bound Ras (Fig. 1B). We utilized a recently described synthetic approach from our group to capture the conformation of the Sos αH and αI helices. In prior efforts, we learned that helix dimers may be stabilized by judicious substitution of a surface salt bridge with a covalent bond and appropriate sculpting of the dimeric interface to coerce knob-into-hole helix packing (20, 21). These stabilized proteomimetics are termed crosslinked helix dimers or CHDs. Here, we show that Sos CHDs are proteolytically stable, selectively cell permeable, and engage the Sos-binding surface of nucleotide-bound Ras with high specificity in biochemical and cellular contexts. We utilized a combination of rational design principles and computational modeling to exploit previously unexplored and underutilized pockets at the target interface (22, 23). The optimized proteomimetic binds wild-type and mutant Ras forms with nanomolar to low micromolar affinities, modulates nucleotide exchange, engages Ras and other Ras subfamily GTPases as demonstrated by chemoproteomic assays, inhibits downstream activation of the Ras-mediated signaling cascade, and is selectively toxic to cancer cells with oncogenic Ras mutations.