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PubMed2001

Antigenotoxic properties of selenium: studies in the wing spot test in Drosophila.

The genotoxic activity of three selenium compounds (sodium selenite, sodium selenate, and selenious acid) and the antigenotoxic effects of sodium selenite in combination with the chromium compound potassium dichromate were studied using the wing spot test of Drosophila melanogaster. This assay is based on the principle that the loss of heterozygosity of suitable recessive markers, multiple wing hairs (mwh) and flare-3 (flr[3]), can lead to the formation of mutant clones of larval cells, which are then expressed as spots on the wings of the adult flies. Pretreatment and chronic cotreatment was comparatively used for the antigenotoxicity study. From the results obtained, it was evident that all selenium compounds are unable to increase the frequency of any of the three categories of spots recorded (small, large, and twin spots). Nevertheless, the antigenotoxic effects of sodium selenite were clearly demonstrated, in both cotreatment and pretreatment, by a complete suppression of those clones induced by potassium dichromate. Therefore, the D. melanogaster wing spot test was revealed to be a good assay, not only for evaluating genotoxic activity but also for detecting antigenotoxic effects in vivo.

Animals↗
PubMed1998

Sensitive enzymatic assay for erythrocyte creatine with production of methylene blue.

We developed a new, highly sensitive enzymatic method for quantifying creatine in erythrocytes, which comprises creatine amidinohydrolase, sarcosine oxidase, and peroxidase. In the present method, an N-methylcarbamoyl derivative of methylene blue, 10-N-methylcarbamoyl-3,7-bis(dimethylamino)phenothiazine (MCDP), was used as a sensitive chromogenic compound. Potassium ferrocyanide was used to prevent nonspecific oxidation of MCDP. The enzymatic method exhibited good analytical performance: precision, within-run CVs <1.0% and between-day CVs <2.0%; average analytical recovery, 99.3% +/- 1.8%; detection limit, 1.0 micromol/L in hemolysate; and linearity, at least up to 500 micromol/L as creatine concentration in hemolysate. Excellent agreement was observed between the present method (y) and HPLC (x), y = 1.029x - 0.002 micromol/g hemoglobin, r = 0.9998, S(y/x) = 0.053 micromol/g hemoglobin (n = 110). No significant interference was produced by various compounds, including guanidino compounds, amino acids, and reducing materials. The reference intervals (mean +/- 2 SD) for erythrocyte creatine obtained from 60 males and 60 females were (in micromol/g hemoglobin) 1.18 +/- 0.52 (0.66-1.70) for males and 1.35 +/- 0.49 (0.86-1.84) for females. Using this method, we documented changes in erythrocyte creatine in patients with various hemolytic conditions, including hemolytic anemia, liver cirrhosis, renal insufficiency, and chronic renal failure treated with hemodialysis with or without the administration of erythropoietin. We conclude that the use of MCDP allows sensitive measurement of erythrocyte creatine and that MCDP with potassium ferrocyanide can improve the sensitivity of assays that use peroxidase for detection of H2O2.

Adult↗
PubMed1951

Experiments on the role of potassium in the blocking of neuromuscular transmission by curare and other drugs.

1. Experiments with perfused frog muscles and with isolated frog muscles immersed in Ringer's solution have failed to show any effect of curare in liberating potassium from muscle tissue. This makes it difficult to suppose that the paralytic effect of curare can be attributed to cation exchange between curare and K whereby a labile potassium compound needed for stimulation is removed from the neuromuscular junction. 2. Similar negative results were obtained with dihydro-beta-erythroidine and myanesin. 3. A small liberation of K from perfused muscle does result from treatment with acetylcholine. This is probably due to the contracture of the muscle since the effect is largely eliminated by previous treatment of the muscle with curare. The amount of potassium lost in this way from perfused muscles is too small to detect when muscles are analyzed after immersion in Ringer's solution with and without acetylcholine. It is concluded that there is no significant cation exchange between acetylcholine and K in muscle, but only a small loss of K due to the contracture produced by the acetylcholine.

Acetylcholine↗
PubMed2003

Crystal structure and spectroscopic characterization of K8(VO)2O(SO4)6.

Red and yellow dichroistic crystals of a vanadium(V) compound, potassium (mu-oxo, di-mu-sulfato)bis(oxodisulfatovanadate), K(8)(VO)(2)O(SO(4))(6), have been obtained from the ternary catalytic model melt system K(2)S(2)O(7)[bond]K(2)SO(4)[bond]V(2)O(5). By slow cooling of the melt from 420 to 355 degrees C, crystal growth occurred, using solid V(2)O(5) crystals present in the melt as nucleation promoter. The compound crystallizes in the monoclinic space group P2(l) with a = 13.60(9) A, b = 13.93(9) A, c = 14.05(9) A, beta = 90.286(10) degrees, and Z = 2. It contains two VO(6) octahedra linked together by a mu-oxo and two mu-sulfato bridges. Furthermore, each octahedron has two monodentate sulfate ligands, making the dimeric entity coordinatively saturated. IR spectroscopy shows bands arising from V[bond]O[bond]V and V[double bond]O stretches as well as splitting of sulfate bands due to the different degrees of freedom present for different conformations of sulfate ligands. The coordination of vanadium in K(8)(VO)(2)O(SO(4))(6) is discussed in relation to the reaction mechanism of SO(2) oxidation catalysis.

Journal Article↗
PubMed2003

Synthesis and structural analysis of the polymetallated alkali calixarenes [M4(p-tert-butylcalix[4]arene-4H)(thf)x]2.n THF (M=Li, K; n=6 or 1; x=4 or 5) and [Li2(p-tert-butylcalix[4]arene-2H)(H2O)(mu-H2O)(thf)].3 THF.

To study the structures and reactivities of alkali metallated intermediates of calix[4]arenes, three compounds were isolated: [Li(4)(p-tert-butylcalix[4]arene-4H)(thf)(4)](2).6 THF (1), [Li(2)(p-tert-butylcalix[4]arene-2H)(H(2)O)(mu-H(2)O)(thf)].3 THF (2), and [K(4)(p-tert-butylcalix[4]arene-4H)(thf)(5)](2).THF (3). The structure of 1 is shown to be dependent on the coordinating solvent. Partial hydrolysis of 1 leads to the formation of 2. The potassium compound 3 features a different structure to that of 1, due to a higher coordination number as well as stronger cation-pi-bonding interactions.

Journal Article↗
PubMed2006

Interleukin-1beta expression in murine J774A.1 macrophages exposed to platinum compounds: the role of p38 and ERK 1/2 mitogen-activated protein kinases.

Although skin and respiratory sensitizing properties of platinum compounds have been proved in humans and mice, little is known about signal transduction pathways leading to cytokine production in the induction phase. It is generally assumed that induction of skin sensitization, but not skin irritation, is associated with a rapid increase in the IL-1beta mRNA expression. In this study, IL-1beta expression and a role of mitogen-activated protein kinases (MAPKs) in this process were investigated in murine macrophages J774A.1 exposed to four platinum compounds. Potassium tetrachloroplatinate (K(2)PtCl(4); TCPP), ammonium tetrachloroplatinate ((NH(4))(2)PtCl(4); TCPA), ammonium hexachloroplatinate ((NH(4))(2)PtCl(6); HCPA) showed a very similar range of cytotoxic concentrations (IC(50) values: 238 microM+/-30; 269 microM+/-39 and 245 microM+/-31, respectively) as assessed in the 24-h MTT reduction test. Cytotoxicity of cis-diammineplatinum dichloride (cisplatin) was considerably higher (IC(50) of 23 microM+/-4). While increased expression of IL-1beta mRNA was observed in the macrophages exposed to each test compound, IL-1beta protein production was detected in cell lysates after treatment with TCPP, TCPA and HCPA for 24h (concentration range of 150-350 microM) as well as for 2h (450-650 microM). The treatment with each compound resulted in the phosphorylation of both p38 MAPK and ERK 1/2 (p44/42). Blocking the activation of p38 MAPK as well as ERK 1/2 with specific inhibitors (SB203580 and U0126, respectively) down-regulated the IL-1beta expression. Interestingly, the skin irritant sodium dodecyl sulfate did not trigger phosphorylation of these kinases, nor induced IL-1beta production. These data suggest that p38 MAPK and ERK 1/2 play an important role in induction of IL-1beta expression in J774A.1 macrophages exposed to test platinum compounds.

Animals↗
PubMed2006

Centrosymmetric aliovalent KTP isomorphs KM(III)0.5Nb0.5OPO4 (M = Cr and Fe).

Aliovalent KTP isomorphic compounds potassium chromium niobium oxide phosphate, KCr0.5Nb0.5OPO4, and potassium iron niobium oxide phosphate, KFe0.5Nb0.5OPO4, exhibit structures that differ from that of the non-centrosymmetric KTiOPO4. There are two crystallographically independent octahedral sites, M1 and M2, statistically occupied by Nb and Cr (or Fe) atoms. The M1O6 and M2O6 octahedra are connected alternately to form a chain with a cis-trans arrangement. The Nb atoms prefer the M2 sites arranged in a cis-like configuration. Each PO4 tetrahedon has the P atom on a twofold axis. Site-splitting at the K-atom position is observed in both compounds. In the isomorphous structures, one Nb atom lies on an inversion centre and the other on a twofold axis. Similarly with the pairs of Fe/Cr sites, one is on an inversion centre and the other on a twofold axis.

Journal Article↗
PubMed2000

Nitric oxide induces the synthesis of vascular endothelial growth factor by rat vascular smooth muscle cells.

Vascular endothelial growth factor (VEGF) is known to induce the release of nitric oxide (NO) from endothelial cells. However, the effect of NO on VEGF synthesis is not clear. Accordingly, the effect of endogenous and exogenous NO on VEGF synthesis by rat vascular smooth muscle cells (VSMCs) was investigated. Two in vitro models were used: (1) VSMCs stimulated to produce NO by treatment with interleukin (IL)-1beta (10 ng/mL) and (2) VSMCs lipotransfected with pKecNOS plasmid, containing the endothelial constitutive NO synthase (ecNOS) cDNA. The synthesis of NO was inhibited by N(omega)-nitro-L-arginine methyl ester (L-NAME, 2 to 5 mmol/L) or diaminohydroxypyrimidine (DAHP, 2.5 to 5 mmol/L), inhibitors of NOS and GTP cyclohydrolase I, respectively. Some cells treated with L-NAME or DAHP were supplemented with L-arginine (10 mmol/L) or tetrahydrobiopterin (BH(4); 100 micromol/L), respectively. In addition, we studied the effect of sodium nitroprusside (SNP; 10 and 100 micromol/L) and chemically related compounds, potassium ferrocyanide and ferricyanide, on VEGF generation. IL-1beta induced iNOS expression and NO generation and significantly upregulated VEGF mRNA expression and protein synthesis. L-NAME and DAHP totally inhibited NO generation and decreased the IL-1beta-upregulated VEGF synthesis by 30% to 40%. Supplementation with L-arginine or BH(4) increased NO generation by L-NAME- or DAHP-treated cells, and VEGF synthesis was augmented by addition of BH(4). The cells generating NO after pKecNOS transfection released significantly higher amounts of VEGF than cells transfected with control plasmids. Inhibition of NO generation by L-NAME decreased VEGF synthesis. In contrast to the effect of endogenous NO, we observed the inhibition of VEGF synthesis in the presence of high (10 or 100 micromol/L) concentrations of SNP. This effect was mimicked by chemically related ferricyanide and ferrocyanide compounds, suggesting that the inhibitory effect of sodium nitroprusside may be mediated by an NO-independent mechanism. The results indicate that endogenous NO enhances VEGF synthesis. The positive interaction between endogenous NO and VEGF may have implications for endothelial regeneration after balloon angioplasty and for angiogenesis.

Animals↗