Global dose distributions of neutrons and gamma-rays on the Moon.

Dose assessment on the lunar surface is important for future long-term crewed activity. In addition to the major radiation of energetic charged particles from galactic cosmic rays (GCRs), neutrons and gamma-rays are generated by nuclear interactions of space radiation with the Moon's surface materials, as well as natural radioactive nuclides. We obtained neutron and gamma-ray ambient dose distributions on the Moon using Geant4 Monte Carlo simulations combined with the Kaguya gamma-ray spectrometer measurement dataset from February 10 to May 28, 2009. The neutron and gamma-ray dose rates varied in the ranges of 58.7-71.5 mSv/year and 3.33-3.76 mSv/year, respectively, depending on the lunar geological features. The lunar neutron dose was high in the basalt-rich mare, where the iron- and titanium-rich regions are present, due to their large average atomic mass. As expected, the lunar gamma-ray dose map was similar to the distribution of natural radioactive elements (238U, 232Th, and 40K), although the GCR-induced secondary gamma-ray dose was significant at ~ 3.4 mSv/year. The lunar secondary dose contribution resulted in an additional dose of 12-15% to the primary GCR particles. Global dose distributions on the lunar surface will help identify better locations for long-term stays and suggest radiation protection strategies for future crewed missions.

Discovery of a Tricyclic ß-Lactam as a Potent Antimicrobial Agent against Carbapenem-Resistant Enterobacterales, Including Strains with Reduced Membrane Permeability and Four-Amino Acid Insertion into Penicillin-Binding Protein 3: Structure-Activity-Relationships and In Vitro and In Vivo Activities.

The current worldwide emergence of carbapenem-resistant enterobacterales (CREs) constitutes an important growing clinical and public health threat. Acquired carbapenemases are the most important determinants of resistance to carbapenems. In the development of the previously reported tricyclic ß-lactam skeleton which exhibits potent antibacterial activities against several problematic ß-lactamase-producing CREs without a ß-lactamase inhibitor, we found that these activities were reduced against clinical isolates with resistance mechanisms other than ß-lactamase production. These mechanisms were the reduction of outer membrane permeability with the production of ß-lactamases and the insertion of four amino acids into penicillin-binding protein 3. Here, we report the discovery of a potent compound that overcomes these resistance mechanisms by the conversion of the alkoxyimino moiety of the aminothiazole side chain in which a hydrophilic functional group is introduced and the carboxylic acid of the alkoxyimino moiety is converted to reduce the negative charge of the whole molecule from 2 to 1. This potent tricyclic ß-lactam is a promising drug candidate for infectious diseases caused by CREs due to its potent therapeutic efficacy in the neutropenic mouse lung infection model and low frequency of producing spontaneously resistant mutants.

Applicability of composite materials for space radiation shielding of spacecraft.

Energetic ion beam experiments with major space radiation elements, 1H, 4He, 16O, 28Si and 56Fe, have been conducted to investigate the radiation shielding properties of composite materials. These materials are expected to be used for parts and fixtures of space vehicles due to both their mechanical strength and their space radiation shielding capabilities. Low Z materials containing hydrogen are effective for shielding protons and heavy ions due to their high stopping power and large fragmentation cross section per unit mass. The stopping power of the composite materials used in this work is intermediate between that of aluminum and polyethylene, which are typical structural and shielding materials used in space. The total charge-changing cross sections per unit mass, σUM, of the composite materials are 1.3-1.8 times larger than that of aluminum. By replacing conventional aluminum used for spacecraft with commercially available composite (carbon fiber / polyether ether ketone), it is expected that the shielding effect is increased by ∼17%. The utilization of composite materials will help mitigate the space radiation hazard on future deep space missions.

A novel tricyclic ß-lactam exhibiting potent antibacterial activities against carbapenem-resistant Enterobacterales: Synthesis and structure-activity-relationships.

A series of tricyclic ß-lactams were synthesized and evaluated for in vitro antibacterial activities against carbapenem-resistant Enterobacterales (CREs). Starting from a reported tricyclic ß-lactam that combined the cephalosporin skeleton having a γ-lactone ring with a carboxylic acid group, which was reported as a unique partial structure of Lactivicin, we identified the compound which shows potent antibacterial activities against all tested CREs by introducing sulfoxide. In addition, the sulfoxide-introduced tricyclic ß-lactam also shows a strong therapeutic efficacy in the neutropenic mouse lung infection model. These results indicate that the tricyclic ß-lactam skeleton will show sufficient therapeutic performance in clinical use and therefore can serve as a scaffold in the search for new antibacterial agents against CREs.

Discovery of 2-Sulfinyl-Diazabicyclooctane Derivatives, Potential Oral ß-Lactamase Inhibitors for Infections Caused by Serine ß-Lactamase-Producing Enterobacterales.

Coadministration of ß-lactam and ß-lactamase inhibitor (BLI) is one of the well-established therapeutic measures for bacterial infections caused by ß-lactam-resistant Gram-negative bacteria, whereas we have only two options for orally active BLI, clavulanic acid and sulbactam. Furthermore, these BLIs are losing their clinical usefulness because of the spread of new ß-lactamases, including extended-spectrum ß-lactamases (ESBLs) belonging to class A ß-lactamases, class C and D ß-lactamases, and carbapenemases, which are hardly or not inhibited by these classical BLIs. From the viewpoints of medical cost and burden of healthcare personnel, oral therapy offers many advantages. In our search for novel diazabicyclooctane (DBO) BLIs possessing a thio-functional group at the C2 position, we discovered a 2-sulfinyl-DBO derivative (2), which restores the antibacterial activities of an orally available third-generation cephalosporin, ceftibuten (CTB), against various serine ß-lactamase-producing strains including carbapenem-resistant Enterobacteriaceae (CRE). It can be orally absorbed via the ester prodrug modification and exhibits in vivo efficacy in a combination with CTB.

Introduction of a Thio Functional Group to Diazabicyclooctane: An Effective Modification to Potentiate the Activity of ß-Lactams against Gram-Negative Bacteria Producing Class A, C, and D Serine ß-Lactamases.

By the emergence and worldwide spread of multi-drug-resistant Gram-negative bacteria, there have been growing demands for efficacious drugs to cure these resistant infections. The key mechanism for resistance to ß-lactam antibiotics is the production of ß-lactamases, which hydrolyze and deactivate ß-lactams. Diazabicyclooctane (DBO) analogs play an important role as one of the new classes of ß-lactamase inhibitors (BLIs), and several compounds such as avibactam (AVI) have been approved by the FDA, along with many derivatives under clinical or preclinical development. Although these compounds have a similar amide substituent at the C2 position, we have recently reported the synthesis of novel DBO analogs which possess a thio functional group. This structural modification enhances the ability to restore the antimicrobial activities of cefixime (CMF) against pathogens producing classes A, C, and D serine ß-lactamases compared with AVI and expands the structural tolerance at the six position. Furthermore, some of these analogs showed intrinsic microbial activities based on multipenicillin binding protein (PBP) inhibition. This is the unique feature which has never been observed in DBOs. One of our DBOs had a pharmacokinetic profile comparable to that of other DBOs. These results indicate that the introduction of a thio functional group into DBO is a novel and effective modification to discover a clinically useful new BLI.

Investigation of shielding material properties for effective space radiation protection.

Geant4 Monte Carlo simulations were carried out to investigate the possible shielding materials of aluminum, polyethylene, hydrides, complex hydrides and composite materials for radiation protection in spacecraft by considering two physical parameters, stopping power and fragmentation cross section. The dose reduction with shielding materials was investigated for Fe ions with energies of 500 MeV/n, 1 GeV/n and 2 GeV/n which are around the peak of the GCR energy spectrum. Fe ions easily stop in materials such as polyethylene and hydrides as opposed to materials such as aluminum and complex hydrides including high Z metals with contain little or no hydrogen. Attenuation of the primary particles in the shielding and fragmentation into more lightly charged and therefore more penetrating secondary particles are competing factors: attenuation acts to reduce the dose behind shielding while fragmentation increases it. Among hydrogenous materials, 6Li10BH4 was one of the more effective shielding materials as a function of mass providing a 20% greater dose reduction compared to polyethylene. Composite materials such as carbon fiber reinforced plastic and SiC composite plastic offer 1.9 times the dose reduction compared to aluminum as well as high mechanical strength. Composite materials have been found to be promising for spacecraft shielding, where both mass and volume are constrained.

Synthesis of 2-Thio-Substituted 1,6-Diazabicyclo[3.2.1]octane Derivatives, Potent ß-Lactamase Inhibitors.

Approval of avibactam by the FDA has led to the recognition of 1,6-diazabicyclo[3.2.1]octane (DBO) derivatives as attractive compounds for ß-lactamase inhibition. We achieved a concise and collective synthesis of 2-thio-substituted DBO derivatives. The synthesis involves diastereoselective photo-induced Barton decarboxylative thiolation, which can be applied to large-scale synthesis. The DBO analogues exhibited strong inhibitory activities against serine ß-lactamases and acceptable solution stabilities for clinical development.

Cefiderocol (S-649266), A new siderophore cephalosporin exhibiting potent activities against Pseudomonas aeruginosa and other gram-negative pathogens including multi-drug resistant bacteria: Structure activity relationship.

The structure-activity relationship (SAR) for a novel series of catechol conjugated siderophore cephalosporins is described with their in vitro activities against multi-drug resistant Gram-negative pathogens including Pseudomonas aeruginosa, Acinetobacter baumannii, Stenotrophomonas maltophilia and Enterobacteriaceae. Cefiderocol (3) was one of the best molecules which displayed well-balanced and potent activities against multi-drug resistant Gram-negative pathogens including carbapenem resistant bacteria among the prepared compounds with the modified C-7 side chain and the modified C-3 side chain. Cefiderocol (3) is a highly promising parenteral cephalosporin for the treatment of multi-drug resistant Gram-negative infection.

Benzyl protection of phenols under neutral conditions: palladium-catalyzed benzylations of phenols.

Benzyl protection of phenols under neutral conditions was achieved by using a Pd(eta3-C3H5)Cp-DPEphos catalyst. The palladium catalyst efficiently converted aryl benzyl carbonates into benzyl-protected phenols through the decarboxylative etherification. Alternatively, the nucleophilic substitution of benzyl methyl carbonates with phenols proceeded in the presence of the catalyst, yielding aryl benzyl ethers.

Catalytic asymmetric hydrogenation of 2,3,5-trisubstituted pyrroles.

Catalytic asymmetric hydrogenation of N-Boc-protected pyrroles proceeded with high enantioselectivity by using a ruthenium catalyst modified with a trans-chelating chiral bisphosphine PhTRAP. The ruthenium catalyst prepared from Ru(eta3-methallyl)2(cod) and (S,S)-(R,R)-PhTRAP in the presence of triethylamine was the most enantioselective for the asymmetric hydrogenation of methyl pyrrole-2-carboxylate, giving the desired (S)-proline derivative with 79% ee in 92% yield. Moreover, 2,3,5-trisubstituted pyrroles bearing a large substituent at the 5-position were hydrogenated with 93-99.7% ee. The asymmetric reduction of 4,5-dimethylpyrrole-2-carboxylate gave only all-cis isomer and created three chiral centers with high degree of stereocontrol in a single process. This is the first highly enantioselective reduction of pyrroles.

Chronic administration of lipopolysaccharide and proteases induces periodontal inflammation and hepatic steatosis in rats.

BACKGROUND: Epidemiologic studies suggest a relationship between periodontitis and liver diseases. A rat periodontitis model was used to investigate whether a causal relationship exists between periodontitis and liver diseases. METHODS: Fourteen male Wistar rats (8 weeks old) were divided into two groups: a periodontitis group in which Escherichia coli lipopolysaccharide (LPS) and Streptomyces griseus proteases were applied into the gingival sulcus for 8 weeks, and a control group using pyrogen-free water instead. After blood samples were collected, periodontal tissues and liver specimens were analyzed. RESULTS: Chronic administration of LPS and proteases to the gingival sulcus induced periodontitis and liver injury, including steatosis with inflammation and sinusoidal fibrosis. Apoptosis, enhanced concentration of 8-hydroxydeoxyguanosine, and activated production of tumor necrosis factor-alpha in liver were observed in the periodontitis group, with increased gingival inflammation, serum LPS, and reactive oxygen species. CONCLUSION: Periodontal inflammation in a rat model induced fatty liver disease through increased serum LPS.

Oxidative damage of periodontal tissue in the rat periodontitis model: effects of a high-cholesterol diet.

Studies suggest an association between consumption of a high-cholesterol diet and periodontitis. We addressed the mechanism by which high dietary cholesterol could be detrimental to periodontal health in a rat model. Feeding a high-cholesterol diet augmented the effects of bacterial pathogens and their products (e.g., lipopolysaccharide and proteases) on production of pro-inflammatory cytokines in fibroblasts. High dietary cholesterol also increased mitochondrial 8-hydroxydeoxyguanosine in the periodontal tissues. These results suggest that excessive tissue oxidative damage induced by high dietary cholesterol could potentiate pro-inflammatory cytokine production by fibroblasts stimulated with bacterial pathogens.

Proliferative response of gingival cells to ultrasonic and/or vibration toothbrushes.

PURPOSE: To evaluate the effects of ultrasonic and/or vibration toothbrushes on cell proliferation and collagen synthesis. METHODS: In eight dogs, teeth and gingivae were stimulated once a day as follows: the first quadrant with an ultrasonic toothbrush (1.6 MHz); the second one with a mechanical vibratory toothbrush (141 Hz); and the third one with a toothbrush generating both the ultrasound and the vibration. The fourth quadrant served as a control. Proliferative activity and collagen synthesis of gingival cells were evaluated by assaying the expression of proliferating cell nuclear antigen (PCNA) and procollagen type I C-peptide (PIP), respectively. RESULTS: After 5 weeks, ultrasonic or vibratory toothbrushes increased the numbers of PCNA-positive fibroblasts and PIP-positive fibroblasts. Toothbrushing with a combination of ultrasound and mechanical vibration increased the numbers of PIP-positive fibroblasts, total fibroblasts and vascular endothelial cells to a greater extent than the one with only ultrasound alone. Vibratory toothbrush, but not the ultrasonic one, induced an increase in collagen density without gingival overgrowth.

Gingival cell proliferation induced by use of a sonic toothbrush with warmed silicone rubber bristles.

BACKGROUND: Toothbrushing promotes gingival cell proliferation, which may occur as the result of the physical stimulation of the gingiva. The present study evaluated the effects of temperature and silicone rubber bristles of a sonic toothbrush on gingival cell proliferation in dogs. METHODS: During the 5-week experimental period, one quadrant in each of eight dogs received a different toothbrushing regimen: a manual toothbrush or a sonic toothbrush with 1) nylon, 2) silicone rubber, or 3) warmed silicone rubber bristles. The proliferative activity of gingival cells was evaluated based on expression of proliferating cell nuclear antigen (PCNA). RESULTS: Use of the sonic toothbrushes produced a higher density of PCNA-positive and total fibroblasts than did use of a manual toothbrush. The warm silicone rubber bristles resulted in a higher density of PCNA-positive fibroblasts compared with the cooler silicone rubber bristle. The number of PCNA-positive basal cells in the junctional epithelium also increased following electric toothbrushing with warmed silicone rubber bristles. CONCLUSIONS: The sonic toothbrush with silicone rubber bristles induced gingival fibroblast proliferation to a greater degree than a manual toothbrush. Warming the silicone rubber bristles increased their stimulatory effects on the proliferative activity of gingival cells.