Molecular recognition of redox-switchable bis-crown moieties assembled on a dicobalt complex.

A new dinuclear complex of cobalt(III) having double bis-crown moieties (1) was synthesized in a one-pot multistep reaction between the dinucleating ligand (H(2)L(1)), Co(OAc)(2) x 4 H(2)O, and 4'-aminomethylbenzo-15-crown 5-ether under aerobic conditions. The complex was characterized by UV-vis, IR, NMR, and CSI-mass spectroscopies, and the axial coordination of the 4'-aminomethylbenzo-15-crown 5-ether on both cobalt centers was confirmed. The bis-crown moieties of 1 acted as a potassium ion binding site with a large association constant (K) of 1.97 x 10(5) M(-1) (1:1) caused by the preorganized bis-crown structure. Solvent extraction of K(+) (potassium picrate) with 1 was investigated by UV-vis and NMR, and the extracted K(+) was quantified by an atomic absorption/flame emission spectrophotometer. The cyclic voltammogram of 1 showed irreversible redox waves at -0.57 V and +0.16 V versus Ag/AgCl in DMF, which are ascribed to the Co(III) and Co(II) redox couple. The large peak separation (Delta0.73 V) of this redox couple indicates the association and dissociation of the axial amine on the cobalt centers. The irreversible reduction peak of 1 at -0.57 V was shifted in the positive direction by 80 mV in the presence of the potassium ion, showing the complexation of 1 with the potassium ion. The reversible formation and decomposition of the double bis-crown moieties in 1 caused by the electrical stimulus were also investigated by thin-layer UV-vis spectroelectrochemistry. The switching of the double bis-crown structure of 1 was established over four trials with response to electrical energy.

Magnetometric evaluation of the effects of man-made mineral fibers on the function of macrophages using the macrophage cell line RAW 264.7.

The toxic effects of man-made mineral fibers (MMMFs) have been evaluated by cell magnetometry using alveolar macrophages (AMs). Recently, on the other hand, the murine macrophage cell line, RAW 264.7, became available and has been used as an in vitro model of AMs. The objective of this study was to determine whether or not cell magnetometry using RAW 264.7 cells can be used to evaluate the toxic effects of MMMFs. RAW 264.7 cells were exposed to one of the MMMFs, potassium octatitanate (PT) or silicon carbide whisker (SiC) at 0, 20, 40 and 60 microg/ml, or chrysotile as a positive control at 0, 15, 20 and 25 microg/ml. The toxic effects of fibers were evaluated by cell magnetometry and LDH assay. For this comparison, AMs were also exposed to chrysotile fibers (CF). In the RAW 264.7 cells exposed to PT 20, 40, 60 or SiC 20, 40, 60, CF 15, 20 and 25 microg/ml, significant delayed relaxation were observed compared with the respective control. In the LDH assay, significant increases in LDH in the supernatant of the cells exposed to PT 20, 40, 60, SiC 20, 40, 60 and CF 15, 20, 25 microg/ml were observed. In AMs exposed to CF 20, 25 microg/ml significant delayed relaxation and significant increases in LDH compared with the control were observed. The levels of MMMFs that induced significant differences were similar for cell magnetometry and LDH. The levels of CF that induced significant differences in cell magnetometry and LDH were identical for RAW 264.7 cells and AMs. Our results suggest that cell magnetometry using RAW 264.7 cells is adequate to evaluate the cytotoxicity of exposure to MMMFs.

Behavior of new type of rock wool (HT wool) in lungs after exposure by nasal inhalation in rats.

OBJECTIVES: Previous types of rock wool has been recently replaced with high-temperature wool (HT wool). HT wool is characterized by a chemical composition with a higher concentration of Al(2)O(3) and a lower concentration of SiO(2), lower biopersistence, and a higher melting point than previous types of rock wool. To evaluate the safety of HT wool, an asbestos substitute, we examined the biopersistence of HT wool in the lungs, based on changes in fiber count according to the length and fiber size (length and width), by performing a nose-only inhalation exposure study in rats. METHODS: Male Fischer 344 rats were exposed to fibers at the target exposure concentration of 30 mg/m(3) continuously for 3 hours daily for 5 consecutive days. Rats were sacrificed shortly after exposure, and 1, 2, and 4 weeks after exposure, and their lung tissues were incinerated at a low temperature. Then, fiber counts and sizes in the lungs were analyzed using a phase contrast microscope. RESULTS: The fiber count in the lungs 4 weeks after exposure significantly decreased from the baseline value (shortly after exposure). The half-life of fibers calculated from the approximation curve was 34 days for all fibers and 11 days for fibers longer than 20 µm. CONCLUSIONS: Both the length and width significantly decreased 4 weeks after exposure, probably because fibers were ingested by alveolar macrophages, discharged to outside of the body by mucociliary movement, or lysed by body fluid. In future studies, it is necessary to examine the long-term persistence of fibers in the lungs.

A pancreatic abscess 7 years after a pancreatojejunostomy for calcifying chronic pancreatitis.

We present herein a case of a 75-year-old Japanese man who had developed a pancreatic abscess 7 years after a longitudinal pancreatojejunostomy for chronic pancreatitis. The patient, a heavy drinker of alcohol, underwent surgical decompression of a ductal obstruction to relieve persistent abdominal pain due to severely calcifying chronic pancreatitis. After the surgery, he stopped drinking alcohol and was treated with insulin to control secondary diabetes mellitus. Thereafter, his symptoms disappeared. Seven years after the surgery, however, he was hospitalized due to obstructive jaundice, high-grade fever, and right hypochondria pain. Ultrasound and computed tomographic scans of the abdomen both disclosed a cystic mass, approximately 6 cm in size, in the pancreatic head. Magnetic resonance imaging strongly suggested a pancreatic abscess with necrotic fluid and debris. First, percutaneous transhepatic cholangiodrainage (PTCD) was done to treat the progressively obstructive jaundice. Subsequently, fine-needle aspiration of the pancreatic abscess was performed under ultrasound guidance. Enterococcus avium and Klebsiella oxytoca were revealed by culture of abscess aspirates. He was successfully cured by treatment with both appropriate antibiotic and continuous PTCD for the obstructive jaundice.