Effects of milk powder intervention on bone mineral density and indicators related to bone metabolism in Chinese adolescents.

The study is to determine the effects of milk powder on bone density and metabolism in healthy adolescents. Vitamin D and calcium supplements increased IGF-1 but did not affect bone mineralization or turnover. Higher vitamin D in combination with sufficient calcium supplementation in such populations requires attention. INTRODUCTION: Both calcium and vitamin D play an important role in bone mineralization in adolescents. METHODS: In this one and a half-year randomized controlled trial, 232 participants (aged 12-15 years) were randomly assigned to three intervention groups receiving milk powder fortified with vitamin D 400 IU plus calcium 300, or 600, or 900 mg [Ca3D (n = 54), Ca6D (n = 56), and Ca9D (n = 49)], or one control group maintaining habitual diet [control (n = 73)]. Bone turnover markers, serum intact PTH, 25(OH)D, and IGF-1 levels were measured at baseline and one and a half years, and bone mineral contents and bone areal mineral density were measured by Dual-energy X-ray absorptiometry (DXA) at baseline, one year, and one and a half years. RESULTS: Baseline average serum 25(OH)D level and calcium intake were 29.4 nmol/L and 363.5 mg/day, respectively. There was a significant increase in bone turnover, total body, hip, lumbar spine bone mineral density (BMD), and total body BMC as well as slight fluctuations in 25(OH)D levels over one and a half years without between-group differences. Significantly decreased serum PTH level was only observed in the Ca6D group (31%, p < 0.0001), in which the intervention effect was also significant (p = 0.0029) compared with the control group. IGF-1 levels increased significantly in all intervention groups (18.5 to 22.8%, p < 0.05) but decreased in the control group (16.5%, p < 0.05), and the group by time interaction was also significant (p = 0.0029). CONCLUSIONS: Our study showed that in healthy adolescents with low vitamin D status and calcium intake, mild vitamin D and mild to modest calcium supplements increased IGF-1 but did not affect bone mineralization or turnover. Higher vitamin D in combination with sufficient calcium supplementation in such populations requires attention.

Average spectrum of cochlear activity: a possible synchronized firing, its olivo-cochlear feedback and alterations under anesthesia.

Average spectrum of electrophysiological cochlear activity (ASECA) recorded from the cochlea or the eighth nerve is related to firing of auditory neurons and has been used recently in search of an objective measure of tinnitus both in animal models and in humans. Little is known about neuro-sensory processes underlying the spectral features of ASECA. The present study used awake and/or anesthetized animals and investigated effects of various sounds presented contralaterally and ipsilaterally. Contralateral stimulation with noise bands at frequencies above about 8 kHz and below acoustic interaural cross-talk decreased the amplitude of the 1 kHz peak of ASECA. When presented ipsilaterally noises produced either an increase or a decrease of this spectral peak when the acoustic bandwidth was respectively above or below 1.5 kHz. Pure tones when presented contralaterally had no detectable effect. When presented ipsilaterally pure tones with frequencies higher than about 4 kHz decreased the 1 kHz peak of ASECA. The detailed time course of sound-induced variations of the 1 kHz peak was measured by time averaging. The resulting response patterns resemble PST histograms of the auditory nerve. Sedation and anesthesia deepened the 500 Hz trough of ASECA and shifted it towards 400 Hz. Sedation induced a diminution and anesthesia an almost complete suppression of the decrease of the 1 kHz peak induced by contralateral noise. Overall these data indicate that ASECA would reflect synchronized firings and they provide evidence for an influence of olivo-cochlear feedback sensitive to the state of awakeness.