Norihiro Hashiguchi

Toxicokinetics of intravenous fluoride in rats with renal damage caused by high-dose fluoride exposure

Abstract Fluoride (F) complexes are used in some fields of industry and medicine. F excretion mainly depends on kidney function. Urinary F concentration is measured to monitor the health of workers exposed to F. The toxicokinetics of F were studied by analyzing plasma concentration of F after intravenous injection of 2.86, 5.71 and 8.57 mg/kg into male Wistar rats. A dose–response relationship was recognized between these F doses and renal tissue injury. Blood samples were removed at 0, 10, 20, and 30 min, and after 1, 2, 3, 4, 5, and 6 h after injection. Plasma concentration-vs-time profiles were evaluated by a nonlinear least-squares method for fitting data to polyexponential equations and calculation of relevant pharmacokinetic parameters. Results indicated that a two–compartment model could describe the elimination of F from plasma. The β rate constant, total plasma clearance (Cl) and first-order rate constants (K21, Kel) decreased, and the half-time of the β-phase (t1/2β) was significantly prolonged with increasing dose. The kidney is the main target organ for F toxicity. Acute exposure to high doses of F damages renal tissue and causes renal dysfunction. The Cl of F is mainly dependent on renal F excretion. Since severe kidney damage markedly affected the toxicokinetics of F and decreased its elimination, other nephrotoxic indicators and measurement of plasma F concentration are necessary for monitoring high-dose F exposure.

Hemodialysis effect on serum boron level in the patients with long term hemodialysis

Serum and dialysate boron levels in 17 patients with long term hemodialysis (HD) were determined by inductively coupled plasma emission spectrometry (ICPES). Serum boron level was compared with the value of age matched 467 healthy controls and the relationship between serum and dialysate boron level was analyzed. The results showed that serum boron level was significantly higher at the beginning of HD, and lower at the completion of HD in comparison with controls. Although the dialysate was contaminated with trace boron, HD resulted in an excessive decrease of serum boron, rather than boron exposure from the dialysate. Boron hemodialyzability was almost proportional to the gradient of the boron level at the beginning of HD and it could be controlled by the adjustment of the gradient. In conclusion, the serum boron level was very much disturbed in long term HD patients. If boron excess in serum at the beginning of HD, or deficiency at the completion of HD may contribute to the complications of HD patients, fine adjustment and close surveillance of the gradient should be taken into account.

Analysis of Biological Apatite Orientation in Rat Mandibles

Abstract Recently, significant progress has been made in medical techniques for regenerating bone. However, bone evaluation techniques generally assess bone quantity as opposed to bone quality. The use of c -axis crystallite orientation of biological apatite (BAp) as a bone quality index has recently generated great interest. BAp demonstrates strong crystallographic anisotropy, and preferential alignment of BAp in each bone varies depending on the shape and stress conditions in vivo . In the mandible, complicated bone shape and stress conditions in vivo might be associated with both bone quantity and quality. In this study, we aimed to elucidate changes in the bone microstructure in the mandible using crystallographic orientation of BAp as a bone quality index. Using Crj : CD (SD) IGS female rats, we observed changes in the dentulous mandible during bone growth. Measuring points on the mandible were determined based on its positional relationship with the teeth. For analysis of bone quantity, the area and bone mineral density of cortical bone were evaluated using peripheral quantitative computed tomography (pQCT), while the orientation of the BAp c -axis, as analyzed by a micro-beam X-ray diffraction system, was used to assess bone quality. The results of both bone quantity and quality assessments indicated that changes during bone growth varied depending on the presence of teeth. We concluded that the microstructure (especially the texture) of BAp crystallite changes in correlation with variations in stress distribution in vivo resulting from changes in chewing conditions designed to optimize the dynamic chewing function.

The utility of Gd-DTPA on MRI of head and neck tumors.

頭頸部腫瘍の画像診断において, X線CTと共にMRIは, 必須の検査法となりつつある。特にMRIは軟組織のコントラスト分解能に優れ, 頭蓋底の骨, 含気腔周囲の骨および金属補綴物よりのアーチファクトが少ないことより, 口腔外科領域への応用は非常に有用であると思われる。しかし一方, MRIは疾患特異性は意外に低いとされており, その向上および, 病巣検出能の向上のため著者らは, 頭頸部腫瘍10症例に対してGd-DTPA (gadorinium-diethylenetriamine pentaacetic acid) による造影MRIを施行し, その有用性の検討を行い, 以下の結論を得た。1.扁平上皮癌症例においては, 軽度の造影効果を認め, 造影後, その信号強度は脂肪よりやや低信号強度となった。2.今回の症例においては, 造影前T1強調像, T2強調像にて局在を捉えることができなかった腫瘍は, 造影像にてもその局在を捉えることができなかった。3.上顎洞扁平上皮癌症例において, 造影像にて容易に腫瘍と洞内の粘液貯留との鑑別を行うことができた。4.動きのアーチファクトの影響を受けやすい舌扁平上皮癌症例においてT2強調像同様のコントラスト良好な, かつT1強調像同様の鮮明な画像を得ることができた。5.腺様嚢胞癌再発症例において, 腫瘍は脂肪変性組織により囲まれているため, 造影剤投与によりかえって, 周囲組織とのコントラストは低下した。

A study of the usefulness of MRI in three cases of parotid tumor.

Magnetic Resonance Imaging (以下MRI) はCTに比べ、軟部組織のコントラスト分解能に優れ, 造影剤を使用せず血管構造を把握でき, 3次元方向の任意の断層面での撮像が可能であり, また, CTのごとく頭蓋底の骨や, 含気腔周囲の骨などからアーチファクトがないといわれている。これらのことは耳下腺腫瘍診断には, きわめて有用であると考えられる。今回著者らは3症例の耳下腺腫瘍摘出を経験したので, そのMRI所見にっき検討を加えるとともに, 健側正常耳下腺の観察も併せおこなった。その結果は以下のごとくである。(1) 腫瘍の周囲組織との判別も含め、解剖学的位置関係はそれぞれの像を総合的に, また, 3次元方向よりの所見より, 正確に判断することができた。(2) 下顎後静脈は全例水平断像では判別可能であった。静脈の位置のみより浅葉および深葉にたいする腫瘍の位置を正確に判断できたのは3症例中1症例であった。(3) 良性, 悪性の特徴は腫瘍の形態および内部構造からは判定できなかった。