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Biomedical subjects

N Kanematsu

Publications and source records attributed to N Kanematsu.

At least 19 recordsLinked to original sources
PubMed2006

Scatter factors in proton therapy with a broad beam.

In the absence of a predictor of beam output in proton therapy using a broad beam, the beam output is obtained for individual treatments by calibrating the beam monitors. The calibration is carried out under conditions similar to the treatment conditions but with a phantom instead of the patient. However, the dose in the phantom a priori differs from that in the patient. In order to deliver the accurate dose, a correction factor has been introduced to correct the difference. This correction factor is referred to as a scatter factor in an analogy with photon therapy, and is defined as the ratio of the dose at the prescription point in the patient to the dose at the calibration point in the phantom. Under the calibration conditions at Hyogo Ion Beam Medical Center (HIBMC), the range compensator and the collimator, which are usually required in proton therapy with a broad beam, are not used. Therefore the scatter factor includes the effects of the devices as well as the difference between the dose in the patient and that in the phantom. We have developed an estimator using a dose calculation based on the pencil beam algorithm and implemented it in a treatment planning system (TPS) for clinical use. This estimator estimates the scatter factor by calculating the ratio of the doses under the same conditions in the TPS. In order to evaluate the performance of the estimator, demonstrations were carried out for cases with measurable outcomes using a gantry nozzle at HIBMC. We observed 2-3% differences between the measurements and the estimations. These differences were considered to result from the limitations of the dose calculation algorithm in modelling the beam and the patient.

Humans↗
PubMed2001

Vesicular prurigo pigmentosa cured by minocycline.

We present a case of prurigo pigmentosa associated with vesicles that we call 'vesicular prurigo pigmentosa'. The subject was treated using minocycline with good results and no recurrence of the lesions over a 2-year period.

Adult↗
PubMed2000

Improved branching ratio measurement for the decay K(0)(L) --> &mgr;(+)&mgr;(-)

We report results from Experiment 871, performed at the BNL AGS, of a measurement of the branching ratio K(0)(L)-->&mgr;(+)&mgr;(-) with respect to the CP-violating mode K(0)(L)-->pi(+)pi(-). This experiment detected over 6200 candidate &mgr;(+)&mgr;(-) events, a factor of 6 more than that seen in all previous measurements combined. The resulting branching ratio gamma(K(0)(L)-->&mgr;(+)&mgr;(-))/gamma(K(0)(L)-->pi(+)pi(-)) = (3. 474+/-0.057)x10(-6) leads to a branching fraction B(K(0)(L)-->&mgr;(+)&mgr;(-)) = (7.18+/-0.17)x10(-9), which is consistent with the current world average, and reduces the uncertainty in this decay mode by a factor of 3.

Journal Article↗
PubMed2000

Dentinogenic ghost cell tumor: histologic aspects, immunohistochemistry, lectin binding profiles, and biophysical studies.

Dentinogenic ghost cell tumor accompanied with calcifying odontogenic cyst (COC) was described in terms of its clinical, histological, immunohistochemical, lectin binding and biophysical properties. The case was a 38-year-old Japanese female, in whom the tumor had arisen in the right mandibular premolar and molar region. Material obtained by partial mandibulectomy was used. Decalcified paraffin sections were used to detect keratins, involucrin, and lectin binding; and non-decalcified thin sections were used for biophysical analysis. The lesion comprising dentinogenic ghost cell tumor and COC contained odontogenic epithelium with ghost cells, eosinophilic amorphous materials and osteodentin. Some of the eosinophilic material had undergone transformation into osteodentin. Keratins in odontogenic epithelia showed positive PKK1 staining in peripheral tumor cells, and stainings with KL1 and involucrin were positive in centrally located cells. Lectin binding in the amorphous materials was comparatively strong for PNA, and SBA, moderate for WGA, RCA-1, and UEA-1, and slight for DBA and ConA. Lectin binding affinities were higher in the amorphous materials than in the osteodentin. Elemental analysis with an electron probe X-ray microanalysis of the amorphous materials and osteodentin showed a pattern similar to that found in the normal dentin. The biologic properties of the eosinophilic amorphous materials suggested the material to be poorly calcified osteodentin, which gradually transformed into the well-calcified type.

Adult↗
PubMed1996

Persistence of circadian oscillation while locomotor activity and plasma melatonin levels became aperiodic under prolonged continuous light in the rat.

In order to examine the mechanism for a loss of circadian rhythms in several functions under prolonged continuous light (LL), rats were blinded following LL over 5 months, and the mode of reappearance of circadian rhythms were analyzed in locomotor activity and plasma melatonin levels. Locomotor activity and plasma melatonin levels in individual rats became aperiodic after the exposure to LL. On the day of blinding, plasma melatonin levels showed circadian rhythms having a peak coincided with the activity time of locomotor rhythm which was restored after blinding. The time of melatonin peak was not related to the time of blinding (onset of darkness) nor to the initial time of blood sampling. Circadian rhythm in plasma melatonin levels reappeared faster than those in locomotor activity. The findings suggest that aperiodism developed in these functions under prolonged LL is not due to disruption of the circadian oscillation but to uncoupling of overt functions from the circadian pacemaker.

Animals↗
PubMed1994

Immediate response to light of rat pineal melatonin rhythm: analysis by in vivo microdialysis.

Melatonin in the extracellular space of the pineal gland was measured continuously for 4 consecutive days from single, freely moving rats by means of in vivo microdialysis. A robust circadian rhythm was observed in the pineal extracellular melatonin under both light-dark (LD) and continuous dark (DD) conditions, the patterns of which were almost identical for 4 days within individuals but varied substantially among individuals. The offset phase of melatonin rhythm was more stable than the onset phase. Light-induced phase shift of melatonin rhythm was measured in individual rats, which had been entrained to LD and subsequently released into DD. On the 1st day in DD, a 3-min light pulse of 200 lx was applied either at circadian time (CT) of 17 or 22 h (5 and 10 h after the dark onset, respectively). The light pulse rapidly suppressed the nocturnal melatonin level. The rate as well as the level of melatonin suppression was significantly greater by the pulse at CT22 than at CT17. A phase shift of the melatonin rhythm was calculated on the 2nd and 3rd days in DD. Significant phase delay shift was observed after the pulse at CT17 and advance shift after the pulse at CT22 of approximately 1 h in either case. Because the amount of phase shift was not different between the 2nd and 3rd days in DD, the phase shift of pineal melatonin rhythm by single light pulse seems to be completed immediately.

Animals↗
PubMed1994

Bone formation under the influence of bone morphogenetic protein/self-setting apatite cement composite as a delivery system.

Self-setting apatite cement (apatite cement) with a phase of hydroxyapatite (HAP) was employed as a delivery system for bone morphogenetic protein (BMP). A composite of BMP and apatite cement (BMP/HAP composite) was implanted both in thigh muscle and surgically created defect of a critical size of 5 mm, which is a size that does not heal spontaneously in the femur of mice, to evaluate its osteogenetic potential as an augmentation and reconstructive material for clinical usage. The histological and immunohistochemical assessment of proteoglycans reiterated osteogenesis in the muscle tissue. On day 14 postimplantation of BMP/HAP composite, chondroid tissue was formed in the muscle, and HAP particles were seen in newly formed chondroid tissue. On the 21st day, endo-chondral ossification had occurred, however, small HAP particles remained in the newly formed bone, i.e., HAP particles and newly formed osseous tissues coexisted in a central area. BMP/HAP composite was incorporated by newly formed osseous tissue in the experimented animals. HAP particle found in BMP/HAP composite implanted into the bone defect was resorbed and replaced by osseous tissue. The apatite cement was proved to have advantages for its shaping as well as collapsing properties, and thus, apatite cement containing BMP is suggested as a favorable augmentation material in clinical usage for delivery system of BMP.

Animals↗
PubMed1994

[Regulation mechanism of melatonin rhythm in the pineal gland by light: experimental studies by in vivo microdialysis].

Light has dual effects on the pineal melatonin; one is the entrainment of the circadian rhythm and the other is suppression of the melatonin synthesis. It is not known whether the entraining and suppressing effects of light are mediated by the same pathway or not. To elucidate the mechanism of the dual effects of light, (1) the sensitivity of the retina, (2) effects of acetylcholine agonist and, (3) the arrhythmicity induced by longterm continuous light, were studied by measuring melatonin continuously from a single rat by means of in vivo microdialysis. Pineal melatonin was suppressed by light more strongly at the late dark phase than at midnight, and by green light (520nm) than by red light (660nm). Pineal melatonin measured by microdialysis was decreased rapidly by a short light exposure and the melatonin rhythm was shifted on the following days. Microinjection of cholinergic agonist, carbachol, into the suprachiasmatic nucleus neither suppressed nor entrained the pineal melatonin rhythm. Immediately after the blinding, rats showed the circadian rhythm in pineal melatonin which had been abolished under long-term continuous light. While, it took several days for the locomotor rhythm to reappear. It is concluded that, (1) suppression of the pineal melatonin by light depends on the circadian phase and on the wavelength of light, (2) the threshold for light suppression is lower than that for phase-shift, (3) the melatonin rhythm starts to phase-shift on the following day of light pulse. (4) Acetylcholine is unlikely to be involved in the photic transmission both to the circadian clock and to the pineal, (5) arrhythmicity induced by long-term continuous light seems to be due to masking for the melatonin rhythm, and to uncoupling from the clock for the locomotor rhythm.

Animals↗
PubMed1992

Light suppression of nocturnal pineal and plasma melatonin in rats depends on wavelength and time of day.

Effects of light on the pineal and plasma melatonin were examined in Wistar and Long-Evans rats at two different times in the dark phase (light off from 18.00 h to 06.00 h) using lights of two different monochromatic wavelengths but with the same irradiance. The green light pulse (520 nm) given at 24.00 h suppressed the pineal and plasma melatonin to the day-time level for at least 2 h, while the red light (660 nm) pulse given at the same time of the day suppressed pineal melatonin only transiently and did not suppress the plasma melatonin at all. Both green and red lights given at 4.00 h suppressed the pineal and plasma melatonin to a similar extent. The results demonstrated that the suppression of melatonin by light depends on the wavelength of light and the circadian phase.

Animals↗
PubMed1992

Entrainment of methamphetamine-induced locomotor activity rhythm to feeding cycles in SCN-lesioned rats.

Suprachiasmatic nuclei (SCN)-lesioned rats, showing a locomotor activity rhythm with a circadian period by chronic methamphetamine treatment, were subjected to the periodic food restriction (RF) of 4 h per every 27 h and 24 h. All rats were phase set by the feeding schedule of both 24-h and 27-h periods. Phase angle differences between the activity onset and food presentation were more positive under the RF with a period of 27 h than that of 24 h. Methamphetamine-induced locomotor rhythm showed a stable entrainment to RF of the 27-h period in all rats. Under the RF of the 24-h period, on the other hand, some rats showed circabidian rhythms, i.e., an activity band appeared at every second food presentation. After the termination of feeding schedule, the locomotor rhythm started to free-run from the phase set by the previous feeding schedule in all rats examined. Methamphetamine-induced locomotor rhythm was shown to be entrained by the RF with a predictable manner of an oscillation theory.

Animals↗
PubMed1991

Incorporation of fatty acids by Streptococcus mutans.

In a series of investigations into the cariogenicity of Streptococcus mutans, we studied the incorporation of exogenous fatty acids with reference to glucosyltransferase secretion and membrane fatty acid changes. When cells were grown with different fatty acids, both saturated and unsaturated fatty acids were readily incorporated into the membrane lipids and were biotransformed and elongated preferentially to the longer 16- and 18-carbon-chain fatty acids. This incorporation and chain-elongation led to significant changes in fatty acids composition. By adding fatty acids to the medium, it was possible to appropriately modify the degree of unsaturation and the relative ratio between specific fatty acids in the membrane lipids of S. mutans.

Fatty Acids↗
PubMed1990

Mutagenicity of cadmium, platinum and rhodium compounds in cultured mammalian cells.

The induction of mutation by cadmium chloride (CdCl2), platinum tetrachloride (PtCl4), and rhodium trichloride (RhCl3.3H2O) was measured utilizing the hypoxanthine-guanine phosphoribosyl transferase (HGPRT) locus in V-79 cells. Cadmium chloride at a concentration of 0.05 microM induced ford mutation in V-79 cells 4 times that of their control mutation frequency. Platinum tetrachloride at a concentration of 15 microM and 300 microM rhodium trichloride also induced ford mutation in V-79 cells at rates of around 7 and 4 times control rates, respectively. Platinum is often, and rhodium sometimes added to dental metallic alloys to improve their metallurgic characteristics and cadmium has been mingled in such alloys as well. Moreover, metallic dental drugs such as K2PtCl4 are used a dentine desensitizers. Thus, the genetic hazards of metal ions including cadmium, platinum, and rhodium that dissolve from dental materials and drugs must be investigated and caution exercised for their safe use in dental clinics.

Animals↗
PubMed1990

Investigation of DNA reactivity of endodontic agents by rec-assay.

Eight endodontic agents were tested for their reactivity with DNA by the rec-assay system. Employing 2 strains of Bacillus subtilis with different recombination capacities, the assay suggested that DNA damage is produced by agents for root canal cleaning containing sodium hypochloride. Other endodontic drugs, including disinfectants for caries cavities, sedatives for pulp, root canal disinfectants, and pulp devitalizing agents containing phenol, camphor, tricresol, formalin, and paraformaldehyde were also positive by rec-assay and would seem to potentially of damage cellular DNA in Bacillus subtilis. Though no clear evidence exists that drugs showing positive results by rec-assay induce malignant tumors in the oral region, these agents should be used carefully since they would seem to possibly cause genetic toxicity in mammalian cells.

Camphor↗