Masahisa Saito

Assessment of the best gait parameter in relation to bone status in community-dwelling young–old and old–old women in Japan

Even if physical exercise contributes to bone health of the elderly, intense activities have the potential to worsen the risk of osteoporosis. This fact and the inevitable decrease of mobility with age increase the likelihood that the mobility parameter that best benefits bone health differs with age. The aim of this study was to objectively assess the gait parameter that most strongly influences bone health of young-old and old-old women. Subjects comprised 200 community-dwelling elderly women (132 young-old, 68 old-old) registered at welfare centers for the aged. Bone status was examined in the right heel by quantitative ultrasound (QUS) and indicated as stiffness index (SI). Gait parameters including usual and maximum walking speed (UWS and MWS, respectively), daily walking steps (DWS), obstacle-negotiating gait, and stair-climbing were examined objectively. Other bone-related physical factors (body components, handgrip strength, and masticatory function) were measured and adjusted while performing assessment. After adjustment for covariates, multiple linear regression analysis showed that MWS had the strongest association with SI in young-old women and DWS had the strongest association with SI in old-old women. To prevent osteoporosis, brisk walking exercise and engaging in movement in everyday life, respectively, should be advocated for young-old women and old-old women in Japan.

Zebrafish mutants of the neuromuscular junction: swimming in the gene pool

This review provides an overview of zebrafish mutants with dysfunctional acetylcholine receptors or related proteins at the neuromuscular junction (NMJ). The NMJ, which has served as the classical model of the chemical synapse, uses acetylcholine as the neurotransmitter, and mutations of proteins involved in the signaling cascade lead to a variety of behavioral phenotypes. Mutants isolated after random chemical mutagenesis screening are summarized, and advances in the field resulting from these mutants are discussed.

Ultrasound parameters of bone health and related physical measurement indicators for the community‐dwelling elderly in Japan

Deteriorated bone strength, which approaches osteoporosis, increases the likelihood that an elderly person will not able to live independently. However, few data are available pertaining to bone health and various physical objective indicators. The aim of the present study was to objectively assess bone health by quantitative ultrasound (QUS) and identify related physical measurement indicators among the elderly to aid the health promotion strategies in Japan. A cross‐sectional study was performed at five welfare centers for the aged in the suburban area of Takatsuki city, Japan. Subjects comprised community‐dwelling persons (134 men, 240 women) aged ≥60 years and registered at welfare centers. QUS of the right‐heel was conducted and recorded as stiffness index (SI). Physical factors including body components (fat and muscle mass), handgrip strength, daily physical activity, daily walking steps, maximum and usual walking speed and maximum bite force were examined objectively during the period May–June 2005. SI in women was lower than that in men (P < 0.01) and decreased significantly with age (P < 0.01). The SI correlated with six physical items in men and with all items in women. Multiple linear regression analysis showed that muscle mass, usual walking speed and maximum bite force were the strongest physical indicators of male SI; and muscle mass, maximum walking speed and maximum bite force were the strongest indicators of female SI. Muscle training, daily walking exercise and oral health care should be included in health promotion programs for the bone health of elderly women and men in Japan.

Pharmacokinetics and effects after intravenous administration of high-dose boron to rat

Abstract Boron (B) compounds have been widely used in the chemical industry, agriculture, and environmental science. The kinetics and toxicity of B were studied by analyzing several serum and urine parameters after a single intravenous injection of sodium tetraborate solution (B: 85.7 mg/kg) in Wistar male rats. Blood samples were removed at 0, 1, 2, 4, and 6 h after injection. The serum parameters studied included: B, Na, Ca, K, P, Mg, γ-GTP, AST, ALT, BUN, Cr, CK, LDH and ALD. Plasma concentration-time profiles of B were evaluated by a nonlinear least-squares method for fitting data to polyexponential equations and calculation of relevant pharmacokinetic parameters. Urine samples were collected from the bladder following infusion. The urinary parameters that were studied included urine volume and excretion of B, Cr and NAG. Results indicated that a two-compartment model could describe the elimination of B from plasma after intravenous administration. Urine volume significantly increased. A diuretic effect of B was noted.

Measurements of ionic concentrations along with endocochlear potential in wild-type and claudin 14 knockout mice

OBJECTIVE To examine whether the changes in endolymphatic ion concentrations were involved in hair cells degeneration in claudin-14 knockout (KO) mice (Cldn14-/-), we measured the endocochlear potential (EP) along with concentrations of K+, Na+, H+, or Ca2+ ([K]e, [Na]e, pHe, [Ca]e) in Cldn14-/-, in which hair cells were selectively damaged, and compared with measurements in wild type mice (Wt). METHODS We used the Cldn14-/- from 3 weeks of age, in which the auditory brain responses (ABR) was severely diminished. Using double-barreled ion-selective microelectrodes, we measured [K]e, [Na]e, pHe, and [Ca]e in both Wt and Cldn14-/- at 8-10 weeks of age. RESULTS (1) In Wt, the EP was +92mV. [K]e, [Na]e, pHe, and [Ca]e were 169mM, ∼1.0mM, 7.50, and 395nM, respectively. In the Cldn14-/-, the EP was +96mV. [K]e, [Na]e, pHe, and [Ca]e were 167mM, ∼1.0mM, 7.73, and 179nM, respectively. No significant differences in the above values were observed between Wt and Cldn14-/-. (2) A significant linear correlation between EP and [Ca]e (R=0.93) was observed for both Wt and Cldn14-/-, but no correlation was observed between EP and K+, Na+, or H+. CONCLUSION These findings suggest that (1) the changes in endolymphatic ion concentrations might not be involved in hair cells degeneration in Cldn14-/-, (2) [Ca]e might be regulated by EP in both Wt and Cldn14-/-.