The precuneus in motor imagery: a magnetoencephalographic study.

Magnetoencephalography was applied to subjects who imagined themselves hurdling in self-centered space. In three of six subjects all 300 trials in the motor imagery condition revealed the precuneus dipole. When we divided the 300 trials into four overlapping blocks (one block = 150 trials), all six subjects showed precuneus activity. The latency of the precuneus dipole was about 220 ms. We suggest that the precuneus activity during motor imagery involves retrieval of spatial information and/or setting up spatial attributes. Only in one subject but twice, the current dipole located in the supplementary motor area was observed 60 ms after activation of the precuneus, which suggests that the signal from the precuneus for motor imagery is transferred to the supplementary motor area.

Simultaneous determination of nicotinic acid and its metabolites in rat urine by micellar electrokinetic chromatography with photodiode array detection.

Nicotinic acid, nicotinamide and their possible metabolites were successfully separated within 17 min by micellar electrokinetic chromatography using 50 mM borate buffer (pH 9.0) containing 150 mM sodium dodecyl sulfate as the running buffer. Calibration curves for all compounds showed good linearity in a range of 5 microg/ml and 250 microg/ml with good correlation. The present method did not require any clean-up procedures and made it possible to determine all metabolites without interference on a photodiode array detector. Urine samples collected from Wistar male rats were analyzed after high-dose oral or intravenous administration of nicotinic acid or nicotinamide. Metabolic pathways of nicotinic acid in male Wistar rats are also discussed.

Lack of chemoprevention effects of the monoterpene d-limonene in a rat multi-organ carcinogenesis model.

Modifying effects of dietary administration of the monoterpene d-limonene were examined using a multi-organ carcinogenesis model. Groups of twenty F344 male rats were treated sequentially with N-diethylnitrosamine (DEN, i.p.), N-methyl-N-nitrosourea (MNU, i.p.), 1,2-dimethylhydrazine (DMH, s.c.), N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN, in drinking water) and dihydroxy-di-N-propylnitrosamine (DHPN, in drinking water) during the first 4 weeks (DMBDD treatment), and then d-limonene was administered in the diet, at the dose of 2.0, 1.0 or 0.5%. The maximal tolerable dose was 2.0% under the present conditions. Further groups were treated with DMBDD or 2.0% d-limonene alone as controls. All surviving animals were killed at week 28, and major organs were examined histopathologically for development of preneoplastic and neoplastic lesions. The incidences and/or multiplicities of renal atypical tubules and adenomas were increased in animals fed 2.0% d-limonene. The immunohistochemical reactivity for alpha2u-globulin in the proximal tubules was greater in rats fed d-limonene than in the carcinogen alone group. No enhancing or inhibitory effect was noted for tumor development in other organs. The present results indicate a lack of any chemopreventive effect of d-limonene in any organ of male rats under the present experimental conditions.

Mechanism for enhancement effect of lipid disperse system on percutaneous absorption.

To clarify the mechanism involved in the enhancement effect of lipid disperse systems (LDS) on percutaneous absorption, the effect of the LDSs of betahistine (BH), prepared using egg phosphatidylcholine (EPC, phase transition temperature, tau m, -15 to -17 degrees C) or hydrogenated soybean phosphatidylcholine (HSPC, tau m, 50 to 60 degrees C), cholesterol, and dicetylphosphate, on the percutaneous absorption of BH, the amount of skin lipids (ceramides, triglycerides, and phospholipids), the fluidity of skin lipids, and the partitioning of LDS-BH into the skin layers were investigated using Wistar and hairless rats. Also examined was whether the LDS penetrated through the stratum corneum (SC) or follicles, using a fluorescent probe (Nile Red). The plasma concentrations of BH were much higher and more sustained after application of a gel formulation containing EPC-LDS and D-limonene (prep. 2) than those after the non-LDS formulation containing D-limonene (prep. 1), whereas the plasma levels after application of a formulation containing HSPC-LDS (prep. 5) were not largely increased compared with those after prep. 1. The content of ceramides (intercellular lipids) and triglycerides (sebaceous gland lipides) in the SC were dramatically decreased by the treatment with prep. 1 and prep. 2, with the more decreased levels of these lipids by the treatment with prep. 2. The phospholipid content of the SC was enhanced by 2-fold following the prep. 2 treatment, indicating the extensive incorporation of LDS lipids into the SC. The histochemical examination of the skin, following application of EPC-LDS with a fluorescent probe, indicated that the LDS lipids penetrated rapidly through the SC and follicles into the viable skins. The fluidity of the SC lipids was dramatically increased following the treatment with the fluid EPC-LDS, whereas the fluidity was significantly decreased by the solid HSPC-LDS. The BH in each skin layer was also significantly increased by the treatment with prep. 2. These results surely demonstrated that the fluid LDS permeated rapidly into the SC and the viable epidermis through the intercellular domains and the follicles in intact vesicles or lipid mixtures, thus ensuring the facilitated transport of LDS-drug through the skin.

Protection by baicalein against ascorbic acid-induced lipid peroxidation of rat liver microsomes.

The effect of baicalein (5,6,7-trihydroxy-2-phenyl-4H-1-benzopyran-4-one), a flavonoid isolated from Scutellaria baicalensis Georgi, on lipid peroxidation in rat liver microsomes was studied. Ascorbic acid-induced lipid peroxidation in microsomes obtained from baicalein-treated rats was inhibited by treatment on different days and at different doses. Iron release induced by ascorbic acid from microsomes of baicalein-treated rats was markedly lower than from microsomes of control rats. However, no statistical differences in total, nonheme and nonprotein-bound (free iron) iron contents could be detected in the two microsomes. The degradation of calf thymus DNA, an indicator of free iron existence, was observed in the reactions of microsomes obtained from control and baicalein-treated rats with ascorbic acid in the presence of bleomycin. These results suggest that baicalein can inhibit lipid peroxidation in microsomes induced by ascorbic acid by forming an inert complex of iron.

Analysis of the potential carcinogenicity of coffee and its related compounds in a medium-term liver bioassay of rats.

The potential carcinogenicity of coffee and related compounds was examined using a medium-term liver bioassay based on the induction of glutathione S-transferase placental form (GST-P)-positive foci in F344 rats. A total of 230 males were initially injected with diethylnitrosamine (200 mg/kg body weight, ip) or saline as controls and 2 wk later were fed on diet or drinking water supplemented as follows for 6 wk: 5% regular instant coffee; 5% decaffeinated instant coffee; freshly brewed coffee, 8 g in 140 ml water; 0.1% caffeine, 0.2% methylglyoxal, 0.2% glyoxal; or 0.3% theophylline in the drinking water (w/v); and 0.4% theobromine in the diet (w/w). All rats were subjected to two-thirds partial hepatectomy at wk 3 and killed at wk 8. The resultant values for GST-P-positive hepatic focus induction were slightly increased with methylglyoxal and decreased with glyoxal and theobromine compared with the corresponding controls. Although the increase in number of foci for methylglyoxal was statistically significant at P < 0.05, the value was within the historical control levels. Regular and decaffeinated instant coffee as well as fresh-brewed coffee, caffeine and theophylline exerted no effects on focus development. Thus, the coffee-related compounds examined demonstrated no obvious enhancing potential, and it is therefore concluded that coffee and its main constituents are not carcinogenic for the rat liver.

Effectiveness of the elcatonin transdermal system for the treatment of osteoporosis and the effect of the combination of elcatonin and active vitamin D3 in rat.

The efficacy of percutaneous elcatonin (EC), a hypocalcemic peptide, in the treatment of experimental osteoporosis in rats was evaluated in vivo. Additionally, the effect of the combined use of EC and active vitamin D3 (1,25(OH)2D3) for the treatment was compared with those of three other groups: 1,25(OH)2D3 alone, estradiol plus 1,25(OH)2D3, and a placebo, and low calcium diet (low Ca). The EC transdermal system and the EC plus 1,25(OH)2D3 system, applied to the rat abdominal skin 6 times for 48 h, significantly increased the ash weight and calcium content of the tibia in the rats, compared with those of placebo group (p < 0.05). The EC systems also slightly lowered the alkaline phosphatase activity in plasma of the morbid rats, without a difference in the plasma calcium content. These EC systems were superior to the 1,25(OH)2D3 system and the estradiol plus 1,25(OH)2D3 system in improving osteoporotic parameters. Thus, the EC systems were concluded to be an efficient drug delivery system for Paget's disease and osteoporosis.

Absence of promotion potential for calcium L-ascorbate, L-ascorbic dipalmitate, L-ascorbic stearate and erythorbic acid on rat urinary bladder carcinogenesis.

The effects of treatment with calcium L-ascorbate, L-ascorbic dipalmitate, L-ascorbic stearate and erythorbic acid on two-stage urinary bladder carcinogenesis in F344 rats after initiation with N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) were examined. Carcinogen was administered at a dose of 0.05% in drinking water for 4 weeks and thereafter the test chemicals were given as a 5% supplement in the diet for the following 32 weeks. No increase in the induction of preneoplastic lesions, papillomas or carcinomas was apparent and it was concluded that none of the test chemicals possess promoting activity for urinary bladder carcinogenesis.

Effect of furosemide on plasma clearance, anticoagulant effect and protein binding of warfarin in rats.

The effect of furosemide on the elimination, anticoagulant effect and the in vitro and in vivo protein bindings of warfarin was examined in rats. The pharmacokinetic parameters of warfarin and prothrombin complex activity (PCA) after a single i.v. coadministration with warfarin (1.2 mg/kg) and furosemide (1.67 mg/kg) were not significantly different as compared with those in the group injected warfarin alone; however when coadministered with 5 mg/kg of furosemide, the elimination rate constant was significantly increased and PCA was markedly enhanced beyond 60 h after administration. The concurrent treatment with warfarin and a higher dose (10 mg/kg) of furosemide caused an increase in the anticoagulant effect of warfarin even at earlier periods after administration. Both the unbound warfarin concentration in serum at 30 min and the amount of warfarin extracted into liver at 2 h after a single i.v. dosing in the coadministered group were significantly increased as compared with those in the group received warfarin alone. Results from in vitro binding studies using bovine serum albumin and rat plasma showed a typical competitive nature of protein binding of warfarin and furosemide at the same binding sites. These results suggest that the interactions, such as the displacement of warfarin binding at albumin binding sites, between warfarin and furosemide are produced, when a high dose of furosemide was coadministered.

Riboflavin photosensitized hemolysis of rat erythrocytes in the presence of serum.

Rat erythrocytes incubated in photoactivated riboflavin system in the presence of serum caused a rapid hemolysis. During the course of illumination, a marked efflux of intracellular K+, increase in osmotic fragility and promotion of lipid peroxidation of the cell occurred prior to hemolysis indicating that riboflavin-induced photohemolysis is colloidosmotic process. In the absence of serum, however, no hemolysis was observed at any time of incubation, suggesting that membrane damages are enhanced by the illumination in the presence of serum. Furthermore, the illumination of cells in the photoactivated riboflavin system in the presence of serum under continued anaerobic conditions did not exhibit any significant hemolysis. These results indicate that the photohemolysis of cells is due to oxidative damages of cell membrane that initiated the hemolysis. Singlet oxygen (1O2) scavengers employed in this study strongly inhibited the photohemolysis, suggesting that cells are damaged oxidatively by 1O2 generated in photoactivated riboflavin system in the presence of serum. Furthermore, triplet quenchers and alpha-tocopherol suppressed this photohemolysis. A reference was made concerning a possible adverse effect of riboflavin on infant erythrocytes in phototherapy.

The effects of various chemicals on the development of hyperplastic liver nodules in hepatectomized rats treated with N-nitrosodiethylamine or N-2-fluorenylacetamide.

The effects of various hepatocarcinogenic, non-hepatocarcinogenic and non-carcinogenic chemicals on the induction of hyperplastic liver nodules by N-nitrosodiethylamine (DEN) or N-2-fluorenylacetamide (2-FAA) as an initiator were studied in male Fischer 344 rats. Rats were injected intraperitoneally with 200 mg of DEN/kg body weight or were fed on basal diet containing 200 ppm of 2-FAA for 2 weeks, and then given various test chemicals starting from week 3. They were also partially hepatectomized in week 3. All animals were killed at the end of week 8 and examined histologically. For quantitative analysis, hyperplastic nodules in the liver were measured with a color video image processor, VIP-21C. The effect of various chemicals in rats treated with DEN or with 2-FAA were compared. The production of hyperplastic liver nodules was greatest in rats treated with strong hepatocarcinogens, and less in rats treated with weak hepatocarcinogens. Very few hyperplastic nodules were produced after treatment with non-hepatocarcinogens or noncarcinogens. Hyperplastic nodules were formed in rats treated with phenobarbital, which is a hepatopromoter. Saccharin, which is a urinary bladder promoter, did not enhance the production of hyperplastic nodules in the liver. These results indicate that many hepatocarcinogens enhance liver carcinogenesis. The classification of chemicals as liver carcinogens is discussed on the basis of the results.