The photolytic release of copper from the copper penicillamine complex [Cu(II)6Cu(I)8(D-penicillamine)12Cl]5−

The light sensitivity of CuPen ([Cu(II)₆Cu(I)₈(D-penicillamine)₁₂Cl]⁵⁻ was examined. The wavelength range of the photolytic activity was determined in the visible and near-ultraviolet region of the electromagnetic spectrum. No photolytic activity was observed above 450 nm. The quantum yield of copper release was measured between 450 nm and 250 nm and was found to increase from 0 to 0.1. A shoulder around 400 nm corresponding to electronic absorption and CD features was observed in the photo-action spectrum. Inhibition of formazan formation from nitroblue tetrazolium mediated by xanthine oxidase-generated superoxide was used to quantify the copper release as a result of the photolytic decomposition of CuPen. The influence of oxygen on the photolytic reaction was investigated by EPR and electronic absorption spectroscopy. In the absence of oxygen, visible light induces almost total bleaching. However, EPR reveals only slight changes in the spin concentration. Upon introduction of aerobic EDTA all of the copper is immediately oxidised to Cu(II).     

Affinities of muscarinic drugs for [3H]N-methylscopolamine (NMS) and [3H]oxotremorine (OXO) binding to a mixture of M1−M4 muscarinic receptors: Use of NMS/OXO-M ratios to group compounds into potential agonist,partial agonist,and antagonist classes

The relative affinities of various muscarinic drugs in the antagonist ([³H]N-methyl scopolamine ([³H]NMS)) and agonist ([³H]Oxotremorine-m ([³H]OXO-M)) binding assays using a mixture of tissues containing M₁–M₄ receptor subtypes have been determined. [³H]NMS bound with high affinity (K_d=25±5.9 pM; n=3) and to a high density (B_max=11.8±0.025 nmol/g wet weight) of muscarinic receptors. [³H]OXO-M appeared to bind to two binding sites with differing affinities (K_d1=2.5±0.1 nM; K_d2=9.0±4.9 M; n=4) and to a different population of binding sites (B_max1=5.0±0.26 nmol/g wet weight; B_max2=130±60 nmol/g wet weight). Well known antagonists exhibited high affinity for [³H]NMS binding but a lower affinity for [³H]OXO-M binding. The opposite was true for acetylcholine and other known agonists. However, pilocarpine and McN-A-343 had similar affinities for sites labeled by both radioligands. Using the ratios of antagonist-to-agonist binding affinities, it was possible to group compounds into apparently distinct full agonist (ratios of 180–665; e.g. carbachol, muscarine, OXO-M, OXO-S and arecoline), partial agonist (ratios of 14–132; e.g. McN-A-343, pilocarpine, aceclidine, bethanechol, OXA-22 and acetylcholine) and antagonist (ratios of 0.22–1.9; e.g. atropine, NMS, pirenzepine, methoctramine, 4-DAMP and p-fluorohexahydrosialo-difenidol) classes. These data suggest that the NMS/OXO-M affinity ratios using a mixture of M₁–M₄ muscarinic receptors may be a useful way to screen and group a large number of compounds into apparent agonist, partial agonist, and antagonist classes of cholinergic agents.     

The effectiveness of the high-LET radiations from the boron neutron capture [<Superscript>10</Superscript>B(n,α)<Superscript>7</Superscript>Li] reaction determined for induction of chromosome aberrations and apoptosis in lymphocytes of human blood samples

Provided that a selective accumulation of ¹⁰B-containing compounds is introduced in tumor cells, following irradiation by thermal neutrons produces high-LET alpha-particles (⁴He) and recoiling lithium-7 (⁷Li) nuclei emitted during the capture of thermalized neutrons (0.025 eV) from ¹⁰B. To estimate the biological effectiveness of this boron neutron capture [¹⁰B(n,α)⁷Li] reaction, the chromosome aberration assay and the flow cytometry apoptosis assay were applied. At the presence of the clinically used compounds BSH (sodium borocaptate) and BPA (p-boronophenylalanine), human lymphocytes were irradiated by sub-thermal neutrons. For analyzing chromosome aberrations, human lymphocytes were exposed to thermally equivalent neutron fluences of 1.82 × 10¹¹ cm^?2 or 7.30 × 10¹¹ cm^?2 (corresponding to thermal neutron doses of 0.062 and 0.248 Gy, respectively) in the presence of 0, 10, 20, and 30 ppm of BSH or BPA. Since the kerma coefficient of blood increased by 0.864 × 10^?12 Gy cm² per 10 ppm of ¹⁰B, the kerma coefficients in blood increase from 0.34 × 10^?12 cm² (blood without BSH or BPA) up to 2.93 × 10^?12 Gy cm² in the presence of 30 ppm of ¹⁰B. For the ¹⁰B(n, α)⁷Li reaction, linear dose–response relations for dicentrics with coefficients α = 0.0546 ± 0.0081 Gy^?1 for BSH and α = 0.0654 ± 0.0075 Gy^?1 for BPA were obtained at 0.062 Gy as well as α = 0.0985 ± 0.0284 Gy^?1 for BSH and α = 0.1293 ± 0.0419 Gy^?1 for BPA at 0.248 Gy. At both doses, the corresponding ¹⁰B(n, α)⁷Li reactions from BSH and BPA are not significantly different. A linear dose–response relation for dicentrics also was obtained for the induction of apoptosis by the ¹⁰B(n, α)⁷Li reaction at 0.248 Gy. The linear coefficients α = 0.0249 ± 0.0119 Gy^?1 for BSH and α = 0.0334 ± 0.0064 Gy^?1 for BPA are not significantly different. Independently of the applied thermal neutron doses of 0.062 Gy or 0.248 Gy, the ¹⁰B(n, α)⁷Li reaction from 30 ppm BSH or BPA induced an apparent RBE of about 2.2 for the production of dicentrics as compared to exposure to thermal neutrons alone. Since the apparent RBE value is defined as the product of the RBE of a thermal neutron dose alone times a boron localization factor which depends on the concentration of a ¹⁰B-containing compound, this localization factor determines the biological effectiveness of the ¹⁰B(n, α)⁷Li reaction.