Publications

Various Mannich bases of chalcones and related compounds displayed significant cytotoxicity toward murine P388 and L1210 leukemia cells as well as a number of human tumor cell lines. The most promising lead molecule was 21 that had the highest activity toward L1210 and human tumor cells. In addition, 21 exerted preferential toxicity to human tumor lines compared to transformed human T-lymphocytes. Other compounds of interest were 38, with a huge differential in cytotoxicity between P388 and L1210 cells, and 42, with a high therapeutic index when cytotoxicity to P388 cells and Molt 4/C8 T-lymphocytes were compared. In general, the Mannich bases were more cytotoxic than the corresponding chalcones toward L1210 but not P388 cells. A ClusCor analysis of the data obtained from the in vitro human tumor screen revealed that the mode of action of certain groups of compounds was similar. For some groups of compounds, cytotoxicity was correlated with the sigma, pi, or molar refractivity constants in the aryl ring attached to the olefinic group. In addition, the IC50 values in all three screens correlated with the redox potentials of a number of Mannich bases. X-ray crystallography and molecular modeling of representative compounds revealed various structural features which were considered to contribute to cytotoxicity. While a representative compound 15 was stable and unreactive toward glutathione (GSH) in buffer, the Mannich bases 15, 18, and 21 reacted with GSH in the presence of the pi isozyme of glutathione S-transferase, suggesting that thiol alkylation may be one mechanism by which cytotoxicity was exerted in vitro. Representative compounds were shown to be nonmutagenic in an intrachromosomal recombination assay in yeast, devoid of antimicrobial properties and possessing anticonvulsant and neurotoxic properties. Thus Mannich bases of chalcones represent a new group of cytotoxic agents of which 21 in particular serves as an useful prototypic molecule.

Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The preparations and antiviral activities of a series (4-17) of potential prodrug forms of the antivirals 2',3'-didehydro-2',3'-dideoxyadenosine (D4A) and 2',3'-didehydro-2',3'-dideoxycytosine (D4C) are reported. The 5'-phenyl- and 5'-methylphosphonates (4, 6, 8, and 10) and their phosphonothionate congeners (5, 7, 9, and 11), with the exception of 10, were inactive in vitro against HIV-1 and HIV-2. However, the 5'-phenyl, 5'-methyl, and 5'-(3'-thymidyl) phosphate diesters (12-17) demonstrated inhibition of the cytopathic effect of HIV-1 and HIV-2 (EC50 approximately 1-60 microM) and cytotoxicities (CC50 approximately 35-200 microM) at concentration levels comparable to those of their parent compounds, D4A and D4C. This strongly suggests that the diesters are hydrolyzed to the nucleosides D4A and D4C and/or their 5'-monophosphates. The facile hydrolysis of 12 and 13 to these products was demonstrated in a medium containing 10% fetal calf serum. The molecules can serve as ready prodrug sources of the free nucleosides and their 5'-monophosphates. Evidently, the phosphonates and phosphonothionates are not similarly cleaved, nor are they phosphorylated to form antivirally active or cytotoxic products. The importance of intracellular formation of these products in the activation of 12-17 is less clear. Potential prodrugs 4-17 are all stable in aqueous solution for hours with the exception of 14. Conjugates 4-17 showed no activity against a series of DNA and RNA viruses.

Owing to the high optical reflectivity of copper, silver, and gold in the infrared region, high laser power is required for laser-based additive manufacturing (L-AM). This increases the risk of damaging the laser optics due to sustained back-reflections and renders L-AM of reflective metals an unsustainable technology. To tackle this issue, a novel, industrially upscalable powder surface modification method is proposed and validated using a CuCr1 alloy. The surface of CuCr1 powder is modified by the outward diffusion of chromium in a nitrogen atmosphere, forming a rim around the powder particles. This doubled the optical absorption of the powder. Consequently, a mere 20% of the laser energy is required to process the surface-modified powder by laser powder bed fusion compared to the virgin CuCr1 powder. The fabricated parts demonstrate a very high thermal conductivity of 370 ± 15 W/(m·K) and tensile strength of 439 ± 19 MPa, after applying a suitable post-heat treatment.

Autoimmune collagen-induced arthritis (CIA) in IFN-gammaR-deficient DBA/1 mice was shown to be reduced in severity by treatment with the bicyclam derivative AMD3100, a specific antagonist of the interaction between the chemokine stromal cell-derived factor-1 (SDF-1) and its receptor CXCR4. The beneficial effect of the CXCR4 antagonist was demonstrable when treatment was initiated between the time of immunization and appearance of the first symptoms. Treatment also reduced the delayed-type hypersensitivity response to the autoantigen, collagen type II. These observations are indicative of an action on a late event in the pathogenesis, such as chemokine-mediated attraction of leukocytes toward joint tissues. The notion of SDF-1 involvement was further supported by the observation that exogenous SDF-1 injected in periarthritic tissue elicited an inflammatory response that could be inhibited by AMD3100. The majority of leukocytes harvested from inflamed joints of mice with CIA were found to be Mac-1(+) and CXCR4(+), and AMD3100 was demonstrated to interfere specifically with chemotaxis and Ca(2+) mobilization induced in vitro by SDF-1 on Mac-1(+)/CXCR4(+) splenocytes. We conclude that SDF-1 plays a central role in the pathogenesis of murine CIA, by attracting Mac-1(+)/CXCR4(+) cells to the inflamed joints.

Additive manufacturing techniques such as laser powder bed fusion (LPBF) enable production of components with highly complex geometries. However, their as-built surface quality and geometrical precision remain insufficient for high-end applications, requiring further post-processing. Unlike horizontal surfaces, inclined up-facing surfaces cannot be improved by in situ remelting, as they remain covered with powder. In this research a dual laser setup replaces the traditional single-laser layout. Surface enhancement is achieved in two steps: a nanosecond pulsed laser is used to remove powder from selected areas via laser-induced shock waves (LISW), so that these surfaces can be remelted with a continuous wave laser. This work presents an investigation of in situ remelting (laser polishing) of inclined surfaces in their as-built orientation, after powder removal by brushing or using LISW. Particular focus is given on the effect of process parameters (laser power, scanning speed, number of scans) on the surface and subsurface quality and dimensional accuracy. As a result, this in situ processing leads to a comparable surface texture on horizontal and inclined surfaces, without introducing any major subsurface defects.

Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.