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Biomedical subjects

Y Ikarashi

Publications and source records attributed to Y Ikarashi.

142 records · Page 8Linked to original sources
PubMed1990

Correlations among chemical constituents, cytotoxicities and tissue responses: in the case of natural rubber latex materials.

Natural rubber latex films obtained from 40 different brands of rubber gloves were tested by quantitative chemical analyses, two cytotoxicity tests (agar-diffusion assay using L929 cells and colony assay using V79 cells) and 7-day implantation test in the rabbit muscle. Multiple regression analysis of these data showed that dithiocarbamate accelerators caused the toxicities whereas antioxidants did not. Thickness of inflammatory layer was the most useful parameter to evaluate tissue response among 13 histological parameters investigated. There were good correlations between the cytotoxicity indices and the thickness of inflammatory layer.

Animals↗
PubMed1989

Morphological changes and neural cell adhesion molecule expression in mouse cerebrum primary cultures following long-term exposure to phorbol ester.

The effect of phorbol 12-myristate 13-acetate (PMA) on development of brain cells in culture was investigated. Chronic treatment of brain cells from fetal ICR mouse with PMA resulted in a time-dependent loss of specific [3H]phorbol 12,13-dibutyrate binding, generally called 'down-regulation'. In contrast to control culture, neurons cultured in PMA (162 nM)-containing medium exhibited aggregation and neurite fasciculation, and then the neural cell adhesion molecule (N-CAM) was expressed selectively on neurons. Also, the number of astrocytes, which were positively stained with anti-glial fibrillary acidic protein antibody, decreased by treatment with PMA. These results suggest that the normal development of cultured brain cells is interrupted by PMA treatment, which may involve protein kinase C (PKC) in the differentiation of neural cells and cell-cell (neuron-neuron, neuron-astrocyte etc.) interaction as PKC is believed to be a receptor for PMA and is down-regulated by chronic treatment with PMA.

Animals↗
PubMed1989

[The process of developing and improving the analytical method of benzene in organic solvents for household use: interlaboratory collaborative study].

A method for the determination of benzene in spot remover using gas chromatography (GC) and high-performance liquid chromatography (HPLC) was developed. The method was evaluated by collaborative study. There are various types of household products containing organic solvents. The collaborative study clarified that a clean-up procedure is necessary for the analysis of products other than spot remover. Thus, our improved method adopted the head space method in GC and microdiffusion method in HPLC as the clean-up procedure.

Benzene↗
PubMed1989

[Alpha-bromocinnamaldehyde, its mutagenicity and contents in commercial products].

The amount of alpha-bromocinnamaldehyde (BCA), an anti-mildew agent, in some commercial products, was examined by high performance liquid chromatography (HPLC) using the following conditions: column, Nucleosil 50-5 (Nagel, 250 mm x 4.6 mm i.d.); mobile phase, hexane-chloroform (12:5); flow rate, 1.0 ml/min; detector, ultraviolet detector; detection wavelength, 290 nm. Large amounts of BCA were detected in anti-mildew mat (10,700-43,500 micrograms/g), anti-mildew cloth (1,100 micrograms/g) and BCA gel (10,050 micrograms/g). BCA was also tested for mutagenicity against Salmonella typhimurium TA100, TA98 and TA2637, with and without metabolic activation (S9 mix). The result showed that BCA was a very potent mutagen and induced 1.0 x 10(6) of revertants per mg against TA100 without S9 mix. The mutagenicity decreased to 1.3 x 10(4) revertants per mg in the presence of S9 mix.

Aldehydes↗
PubMed1988

Immediate and long-term effects of radiation on the immune system of specific-pathogen-free mice.

Studies on the immediate and long-term effects of radiation on the immune system of specific-pathogen-free mice are summarized in this paper. There was a striking difference in the radiation response of lymphocyte subsets; B cells consist of a fairly radiosensitive homogeneous population, whereas T cells consist of a large percentage (greater than 90 per cent) of radiosensitive and a small percentage (less than 10 per cent) of extremely radioresistant subpopulations. Ly 1+ and Ly 2+ lymphocytes appear equally radiosensitive, although the percentage of radioresistant cells was slightly larger for the former (approximately 5.5 per cent) than the latter (approximately 2.5 per cent). There was a significant strain difference in the radiosensitivity of immune-response potential in mice; immunocompetent cells of C3H mice were more radioresistant than those of BALB/c, C57BL/6, and B10.BR mice. Studies on the long-term effect of radiation on immune system in mice indicated no evidence for accelerated ageing of the immunologic functions when radiation exposure was given to young adults. Preliminary results on the enhancing effect of low dose radiation on cytotoxic T cell response in vitro are also discussed.

Animals↗
PubMed1986

Tissue structure of rat brain after microwave irradiation using maximum magnetic field component.

A novel microwave instrument has recently been designed by New Japan Radio Co. Ltd., to provide more homogeneous distribution of the rapidly deposited heat in the rodent brain. Being the first commercial unit which concentrates the maximum magnetic field component of irradiation, rather than the usual electric field, it provides complete enzymatic inactivation in a typical rat brain when a power of 9 kW (90% of maximum) is applied for 0.80 s at the standard operating frequency of 2450 MHz. Tissue structural integrity was investigated in animals sacrificed by this approach or by the usual decapitation to see if any tissue disruption or pressure-induced spreading, a major problem with other microwave devices, might also be of concern for this new unit. Histological examination of tissue samples employed both light and electron microscopy. Using Luxol Fast Blue in the light microscopy, the microwave irradiated tissues exhibited a decreased affinity for the staining agent, an appearance of slight vacuoles, and the disappearance of fine fibrils in the parenchyma. However, the interfacial areas between distinct brain regions remained well preserved. Electron microscopic observation indicated that microwave irradiated tissue caused protein denaturation accompanied by the aggregation of nuclear chromatin, the disappearance of Nissl bodies, ribosomes and neurofilaments, and noticeably irregular myelin sheaths. However, the essential structure of nerve cell membranes and synaptic membranes were maintained, and synaptic vesicles were clearly defined. These results indicated that the rapid heating of brain tissue with maximal magnetic field concentration of the irradiation does not result in significant tissue disruption, pressure-induced spreading or cell breakdown.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Determination of choline and acetylcholine levels in rat brain regions by liquid chromatography with electrochemical detection.

Regional choline (Ch) and acetylcholine (ACh) in rat brain were clearly determined by high-performance liquid chromatography with electrochemical detection. The method is based on that of Potter et al.: the hydrogen peroxide that is enzymatically produced from both compounds is measured and a successful improvement of the method, particularly for purification, is described. Recoveries were 96.1 +/- 1.4% for Ch and 95.6 +/- 2.2% for ACh and amounts as low as 10 pmol could be determined. Prior to measuring the compounds, a newly developed magnetic field microwave instrument (10 kW) was utilized for the rapid inactivation of brain enzymes. The levels of Ch and ACh in brain regions were compared with those reported elsewhere.

Acetylcholine↗
PubMed1985

Postmortem changes in catecholamines, indoleamines, and their metabolites in rat brain regions: prevention with 10-kW microwave irradiation.

Postmortem changes in catecholamines, indoleamines, and their metabolites in rat brain regions following decapitation were determined by LCEC. In the three regions studied neurotransmitter levels declined after decapitation, whereas the metabolite levels increased. Microwave irradiation at 10 kW rapidly inactivated brain enzymes and thus prevented the postmortem changes.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1984

[A simple method for determination of choline (Ch) and acetylcholine (ACh) in rat brain regions using high-performance liquid chromatography with electrochemical detection (HPLC-ED)].

A simple method for the determination of choline (Ch) and acetylcholine (ACh) in rat brain regions by application of high performance liquid chromatography with electrochemical detection (HPLC-ED) is described. Separation of endogenous Ch, ACh, and ethylhomocholine (EHC) as internal standard on a chemcosorb 3C-18 column is followed by electrochemical detection of hydrogen peroxide (H2O2) derived from the compounds. H2O2 was enzymatically produced in the reaction coil (10 m). The assay limit for quantitation was 10--30 pmole for both compounds. The brain tissue was homogenized with 15%-1N formic acid in acetone and centrifuged. The supernatant was washed with either once and then blown off using N2 gas before an aqueous solution was immediately applied for analysis. Recovery rates were 96.1 +/- 1.4% for Ch and 95.6 +/- 2.2% for ACh. The levels of Ch and ACh in rat brain regions after sacrifice either by decapitation or microwave irradiation (10 kW, 2450 MHz, Magnetic-field type) were compared with those previously reported.

Acetylcholine↗
PubMed1984

Study of the use of the microwave magnetic field for the rapid inactivation of brain enzymes.

A new model of a microwave device was developed with a power of 10 kW at 2450 MHz. In order to accomplish even distribution of heating with minimum trauma and with a maximum certainty about enzyme inactivation, a modified magnetic field distribution was utilized rather than the conventional electric field. An integrated tuning system was used to increase efficiency and distribution of microwave energy absorption. This increased the ability of the instrument to properly inactivate the enzymes in the brain of both mice and large rats. In general, the time of irradiation for the rat was 600 to 900 msec and for the mice, 100 to 330 msec. The animal chambers used were designed so as not to impair breathing or too severely restrict movement. The effects of these improvements on microwave irradiation were confirmed by 1) observation of brain appearance, 2) effects on succinic dehydrogenase and cholinesterase activity, 3) measurement of regional temperatures in the animal's brain, 4) thermograms of the brain, 5) electron microscopic examination of brain tissue and 6) measurement of endogenous acetylcholine and catecholamines.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1984

The relationship between serum hormone levels and reproductive ability in aging male rats.

The relation between fertility and hormonal levels was studied in aging male rats. Reproductive ability was inspected at 30, 31, 59, 60, 93 and 94 weeks of age, and the serum hormone levels were determined by the radioimmunoassay. Reproductive ability decreased with aging (mating rates: 15/20, 11/20, 3/20 and 6/20 at 30, 31, 59 and 60 weeks, respectively) and no male mated at 93 and 94 weeks. Serum testosterone levels in males without reproductive activity were significantly lower than those in males with reproductive activity. LH and FSH showed the lowest level in 95 weeks. The highest value of LH was found at 60 weeks in males without reproductive activity having low testosterone levels. The highest value of prolactin appeared in 95 weeks which was three times higher than those in the other groups. The results suggest that the loss in the reproductive activity in aging rats starts with a decrease in libido, which is followed by a high gonadotropin and low testosterone condition, and accomplished under a low gonadotropin and high prolactin circumstance.

Aging↗
PubMed1984

[Thermographic analysis of the brain temperature in rats following microwave irradiation].

A thermoviewer, a new model of JTG-500 (JEOL, Japan) was utilized for finding the effect of microwave heat energy absorption and its conductivity in the brains of rats and mice following microwave irradiation (MWR). The frozen head was cut in either the sagittal, frontal or horizontal plane. After the frozen brain returned to room temperature (27-28 degrees C), the parts were put together with scotch tape and place in the exposure chamber. The rat's brain was irradiated at 6 kW for 0.6 sec and the mouse's brain was irradiated at 6 kW for 0.12 sec. Within 2 min. after irradiation, one side of each head was removed from the body and set in front of the camera unit. Each frame of a thermal image with its temperature information was stored in a data memory and the image of the brain surface was displayed at a flickerfree TV rate under the most optimum display condition. The temperature resolution of the device was 0.05 degrees C. In the individual rat planes, the highest energy was efficiently centralized in the middle of each individual plane and was distributed to the periphery showing phased decreases in temperature. The temperature differences recorded in the rat's sagittal, frontal and horizontal sections were; 4.6 degrees C, 5.0 degrees C and 3.4 degrees C, respectively. Temperature differences in rat brains irradiated by MWR were known to be below 5.0 degrees C under these experimental conditions. In the mouse planes, the highest level of microwave energy was also centralized in the middle of each individual section.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1979

Haemolysis of various mammalian erythrocytes in sodium chloride, glucose and phosphate-buffer solutions.

Mouse, rat, rabbit, hamster, cow, pig, sheep, guinea-pig, dog and human erythrocytes were studied. A 0.9% or stronger solution of sodium chloride completely prevented haemolysis; sheep and pig erythrocytes appeared the more fragile, while human and dog erythrocytes were not haemolized in concentrations of 0.4% or more. Haemolysis of human, rabbit, cow, hamster, guineapig, pig and sheep erythrocytes was not observed in solutions of 0.4% or more of glucose. Except for sheep, human and dog erythrocytes, haemolysis was depressed in rate but not completely prevented by phosphate-buffer solution of pH 7.0.

Adult↗
PubMedDate not supplied

Application of sensitive mouse lymph node assay for detection of contact sensitization capacity of dyes.

A sensitive mouse lymph node assay (SLNA) is a test method for the detection of contact allergens. The sensitization potential of test chemicals is determined by assessing total lymph node activation response induced by application of the chemical. In this study, we examined whether the SLNA would have a sufficient competence for determination of sensitization capacity of coloured chemicals routinely. Prior to this study, we investigated application of an Alamar Blue dye (non-radioisotope reagent) as an alternative to [3H]thymidine for measurement of cell proliferation. However, the Alamar Blue assay is useful for determining cell number but is not applicable to detect lymph node cell proliferation activity for 24-h culture in the SLNA. The SLNA was applied to evaluate the sensitization capacity of 20 dyes. Most of the sensitizing dyes were correctly determined as a sensitizer. Some chemicals that were known as strong sensitizers showed strong lymph node responses. Comparing the results of the SLNA with data from guinea-pig tests, the same predictions of sensitization capacity were made in nine out of ten cases. The SLNA also detected 13 of the 17 chemicals that were identified to be contact allergens by the human patch test. These data showed that the evaluation of the SLNA was not influenced by the colour property of the test chemicals and that the SLNA was a sufficiently sensitive robust screen test for the identification of contact allergens.

Allergens↗
PubMedDate not supplied

Effects of subacutely administered saiboku-to, an oriental herbal medicine, on pharmacodynamics and pharmacokinetics of diazepam in rodents.

Subacute treatment with saiboku-to (2000 mg/kg, p.o., once a day) for 7 days induced an anxiolytic-like effect in rats. It did not, however, produce any other effects, such as sedative and hypnotic effects, anticonvulsive and muscle relaxant effects except for anxiolytic effect observed in diazepam-injected rats or mice. Diazepam (1.0 mg/kg, s.c.) induced anxiolytic-like effect was enhanced in saiboku-to treated rats as an additional effect of that induced by saiboku-to. To elucidate whether the enhancement of the anxiolytic-like effect following combined administration of diazepam and saiboku-to is due to the inhibition of hepatic drug-metabolizing enzymes, the pharmacokinetics of diazepam were further investigated in saiboku-to treated rats. The pharmacokinetic studies clearly demonstrated that subacute treatment with saiboku-to did not affect plasma concentration and protein binding rate of diazepam, and the activities of hepatic drug-metabolizing enzymes related to diazepam metabolism. These results, taken together, suggest that the enhancement of diazepam-induced anxiolytic-like effect observed in saiboku-to-treated rats is not due to an inhibition of diazepam metabolism.

Animals↗