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In MRI examination, RF heating of implants will affect the safety of implant wearers. The conductivity of various tissues in the human body is significantly different, and the medium conductivity will affect the distribution of the RF electric field. Therefore, it is necessary to study the RF heating of different medium conductivity. Based on the analysis of the principle of MRI RF heating, this study build the model of the bird cage coil, ASTM standard phantom and lead, and the conductivity of several typical human tissues is selected as the conductivity in the experiment. Then calculate the power deposition of the lead at 64 MHz. The results show that the medium conductivity has no effect on the distribution of electric field and power deposition, and the hot spot distribution remains unchanged under different conductivity; The smaller the conductivity is, the larger the power deposition of the lead is, and the greater the temperature rise of the lead caused by RF heating is; The change of conductivity and power deposition is approximately linear. At the limit of 2 W/kg whole body specific absorption rate(SAR), the conductivity decreases, and the wire power deposition increases sharply.
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ObjectiveTo investigate the intestinal absorption characteristics of multi-index components in Danggui Buxuetang with drug absorption simulating system （DASS） established by everted intestinal sac model. MethodThe intestinal absorption solution at different time points after administration of Danggui Buxuetang was collected and detected by high performance liquid chromatography （HPLC）， acetonitrile （A）-0.2% glacial acetic acid solution （B） was used as the mobile phase for gradient elution （0-16 min， 15%-23%A； 16-20 min， 23%-28%A； 20-25 min， 28%-30%A； 25-30 min， 30%A； 30-35 min， 30%-65%A； 35-45 min， 65%-95%A）， the detection wavelength was 302 nm. HPLC fingerprint of intestinal absorption solution was established and the common peak was calibrated， and the relative cumulative absorption rate of each index component was calculated. The relative cumulative absorption curves of components were fitted with various mathematical models by DDSolver 1.0 to explore the absorption law of different components. ResultThe absorption process of C2 （calycosin-7-glucoside） and C6 in Danggui Buxuetang was in line with zero-order equation， C9 was best fitted by Weibull equation， and the remaining 7 components were in line with Makoid-Banakar equation. C1 with C2， C3， C5， C7 and C10， C2 with C5 and C7， C3 with C4， C5， C7 and C10， C4 with C6 and C10， C5 with C7， C6 with C10， C7 with C10， C8 with C9 were absorbed simultaneously during the absorption process. With the prolongation of time， the overall cumulative absorption rate of Danggui Buxuetang increased. At 120 min， the overall cumulative absorption rate of Danggui Buxuetang exceeded 38%， and reached 49.14% at 180 min. ConclusionTen ingredients in Danggui Buxuetang are absorbed in the jejunum， but absorption law of various components is different， which shows that the intestinal absorption of compound preparations of traditional Chinese medicine （TCM） has multiple characteristics. Intestinal absorption study of TCM compound preparations with chemical composition as the index can reveal some of its absorption law， but it is not complete.
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Objective: To prepare glycyrrhizic acid (GL)-Pluronic F127 (F127)/polyethylene glycol 1000 vitamin E succinate (TPGS) mixed nanomicelles (MMs) and improve oral absorption of GL. Methods: GL-F127/TPGS-MMs was prepared by thin film dispersion method. The encapsulation efficiency and drug loading of MMs were used as evaluation indexes. The formulation and process, including the ratio of F127 to TPGS, the concentration of polymer and GL, hydration temperature and time, were optimized by the single factor experiment. The morphology of MMs was investigated by transmission electron microscopy. The single-pass perfusion model was established in rats to investigate the intestinal absorption characteristics of GL-F127/TPGS-MMs with absorption rate constant (Ka) and apparent absorption coefficient (Papp) as evaluation indexes. Results: The optimal formulation and process of GL-F127/TPGS-MMs were as follows: TPGS 180 mg, F127 270 mg, GL 70 mg, hydration temperature 50 ℃ and hydration time 3 h. The prepared GL-F127/TPGS-MMs had good clarity and the particle size, polydispersity index, and Zeta potential were (28.20 ± 5.63) nm, 0.20 ± 0.06, and (-5.24 ± 1.55) mV, respectively. The encapsulation efficiency and drug loading were (97.57 ± 5.29) % and (13.13 ± 0.71) %, respectively. The MMs were spherical with distinct vesicle structure. The absorption of GL in the jejunum segment was significantly higher than that in the ileum segment (P < 0.05). Compared with raw GL, GL-F127/TPGS-MMs had a statistically significant higher absorption rate in the intestinal segment (P < 0.05). Conclusion: The prepared GL-F127/TPGS-MMs could significantly improve the absorption of GL in vivo.
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OBJECTIVE@#To investigate the effects of millimeter wave (MMW) exposure on apoptosis of human melanoma A375 cells and explore the mechanisms.@*METHODS@#Through electromagnetic field calculation we simulated MMW exposure in cells and calculated the specific absorption rate (SAR). The optimal irradiation parameters were determined according to the uniformity and intensity of the SAR. A375 cells were then exposed to MMV for 15, 30, 60, or 90 min, with or without pretreatment with the caspase-3 inhibitor AC-DEVD-fmk (10 μmol/L) for 1 h at 90 min before the exposure. CCK-8 assay was used to assess the changes in the viability and Annexin-V/ PI staining was used to detect the apoptosis of the cells following the exposures; Western blotting was used to detect the expression of caspase-3 in the cells.@*RESULTS@#The results of electromagnetic field calculation showed that for optimal MMV exposure, the incident field needed to be perpendicular to the bottom of the plastic Petri dish with the antenna placed below the dish. CCk-8 assay showed that MMW exposure significantly inhibited the cell viability in a time-dependent manner ( < 0.05); exposures for 15, 30, 60, and 90 min all resulted in significantly increased apoptosis of the cells ( < 0.05). The cells with MMW exposure showed significantly increased expression of caspase-3. The inhibitory effect of MMW on the cell viability was antagonized significantly by pretreatment of the cells with AC-DEVD-fmk ( < 0.05), which increased the cell viability rate from (36.7±0.09)% to (59.8±0.06)% ( < 0.05).@*CONCLUSIONS@#35.2 GHz millimeter wave irradiation induces apoptosis in A375 cells by activating the caspase-3 protein.
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Humans , Apoptosis , Caspase 3 , Metabolism , Caspase Inhibitors , Pharmacology , Cell Line, Tumor , Cell Survival , Electromagnetic Fields , Enzyme Activation , Magnetic Field Therapy , Melanoma , Pathology , Therapeutics , Time FactorsABSTRACT
Aim To prepare evodiamine butyryl deriva-tive (EBD) and evodiamine butyryl derivative-loaded solid lipid nanoparticles (EBDLN), and study its re-lease in vitro,and to investigate its in situ gastrointesti-nal absorption. Methods EBD was prepared by a one-step synthetized method, and then EBDLN was prepared by a film dispersion method. Dynamic dialy-sis was used to evaluate drug release in vitro,and sin-gle-pass gastrointestinal perfusion was employed to study the gastrointestinal absorption of EDM,EBD and EBDLN. Results In identical release media, there were identical drug release tendencies of EBD and EB-DLN, but the release rate of EBDLN was faster than EBD. Compared with EDM and EBD, the Kavalues and Pappvalues of EBDLN in every perfusion segment increased significantly. The Kaof EBDLN in stomach, duodenum, jejunum, ileum and colon was 110.14-fold,56.70-fold,51.23-fold,45.70-fold and 127.23-fold of free EDM respectively. The Pappvalue of EB-DLN was 9.74-fold, 4.48-fold, 3.82-fold and 11.3-fold of that of free EDM. Conclusion EBDLN has sustained effect and can enhance the gastrointestinal absorption of EDM and EBD.
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Objective To preliminarily explore the application of terahertz spectroscopy in the early detection of lung cancer by comparing the differences among lung cancer tissues,paracancerous tissues,and normal lung tissues with terahertz spectroscopy and screen the suitable terahertz frequency for specific diagnosis of lung cancer.Methods Thirty groups of lung tissue samples from non-small cell lung cancer patients at stage of Ⅰ to Ⅲ A were collected,and each group contained lung cancer tissue,paracancerous tissues,and normal lung tissue from the same patient.These lung cancer specimens included 17 cases of adenocarcinoma,10 cases of squamous cell carcinoma,2 cases of large cell lung cancer,and 1 case of sarcomatoid carcinoma.Terahertz spectroscopy from 0.2 THz to 2.0 THz was used to detect these tissue samples,and the absorption coefficient was compared.Results ① The absorption coefficient was significantly higher in the lung cancer tissues than the normal lung tissues.② Terahertz spectroscopy at a frequency of 0.8 to 1.4 THz may have the specific diagnostic value of lung cancer.Conclusion Since the absorption rate is higher in the lung cancer than the normal lung tissue,which is suggested that terahertz spectroscopy may be regarded as a novel non-invasive diagnostic approach for lung cancer.The specific diagnostic value of the terahertz frequency may be 1.4-2.0 THz for lung cancer.
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Objective To investigate the effects of moisture-proof materials and contents on hygroscopicity of Yixinshu Capsules; To improve moisture-proof function of Yixinshu Capsules. Methods The hygroscopicity performance of Yixinshu Capsules was analyzed with the indexes of moisture absorption rate and critical relative humidity (CRH), and effects of soluble starch, maize starch, dextrin, lactose, mannitol, calcium hydrogen phosphate, ethylcellulose, microcrystalline cellulose, hypromellose and low-substituted hydroxypropyl cellulose on hygroscopicity of Yixinshu Capsules were compared. The effects of optimized excipients and capsule contents after granulation on hygroscopicity of Yixinshu Capsules were tested. Results Lactose, microcrystalline cellulose and mannitol were the most appropriate moisture-proof excipients for Yixinshu Capsules with balanced moisture absorption rate of 18.04%, for which the best proportion of Yixinshu Capsules to excipients was 1 to 0.1 (wt%). The balanced moisture absorption rate of the powders were 14.87%, 14.39%, and 15.38%, respectively, whereas the granules were 10.75%, 10.29%, and 11.13%, respectively. Conclusion The selected excipients can effectively reduce the hygroscopic rate of the Yixinshu Capsules, and its granules can promote the moisture resistance of Yixinshu Capsules.
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Objective To investigate the specific absorption rate (SAR)in 3.0T MR brain examination.Methods All 280 patients underwent 3 .0 MR brain examination.And the patients were divided into three groups:a group of 0-3 years old without hands intersection, inluding 40 cases through conventional MRI examination,40 cases through MRA,as well as 40 cases through DWI;a group of more than 20 years old without hands intersection,including 40 cases through conventional MRI examination,40 cases through MRA,as well as 40 cases through DWI;a group of more than 20 years old with hands intersection,consisting of 40 cases through MRA.The SAR values of each group were recorded,respectively.And the independent samples t test was used to compare statistical difference of different SAR values between groups.Results Compared the group of 0-3 years old without hands intersection and the group of more than 20 years old without hands intersection,the SAR values of all six sequences in front group were significantly higher than that those in latter one,but not exceed the safety standard of 3 w/kg in the United States FDA.There was no significant statistical differences in the SAR values of two groups which more than 20 years old with hands intersection or not (P>0.05).Conclusion The SAR values of each sequence in the group of 0-3 years old without hands intersection were significantly higher than those in the group of more than 20 years old without hands intersection,but in a safe and reasonable range.The brain scanning with two hands intersect of 20 years old and above,and there was no significant increase on the SAR values in the brain examination of the group of more than 20 years old with hands intersection.So it is of great significance to guide the daily work,settle doubts and improve success rates of the MR examination.
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Objective To investigate the specific absorption rate (SAR)in 3.0T MR brain examination.Methods All 280 patients underwent 3 .0 MR brain examination.And the patients were divided into three groups:a group of 0-3 years old without hands intersection, inluding 40 cases through conventional MRI examination,40 cases through MRA,as well as 40 cases through DWI;a group of more than 20 years old without hands intersection,including 40 cases through conventional MRI examination,40 cases through MRA,as well as 40 cases through DWI;a group of more than 20 years old with hands intersection,consisting of 40 cases through MRA.The SAR values of each group were recorded,respectively.And the independent samples t test was used to compare statistical difference of different SAR values between groups.Results Compared the group of 0-3 years old without hands intersection and the group of more than 20 years old without hands intersection,the SAR values of all six sequences in front group were significantly higher than that those in latter one,but not exceed the safety standard of 3 w/kg in the United States FDA.There was no significant statistical differences in the SAR values of two groups which more than 20 years old with hands intersection or not (P>0.05).Conclusion The SAR values of each sequence in the group of 0-3 years old without hands intersection were significantly higher than those in the group of more than 20 years old without hands intersection,but in a safe and reasonable range.The brain scanning with two hands intersect of 20 years old and above,and there was no significant increase on the SAR values in the brain examination of the group of more than 20 years old with hands intersection.So it is of great significance to guide the daily work,settle doubts and improve success rates of the MR examination.
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Objective: To compare intestinal absorption features of berberine hydrochloride phospholipid solid dispersions (BBH-PSD) by rat single-pass perfusion model, and to explore the mechanism of berberine bioavailability increasing mechanism by phospholipid solid dispersion technology. Methods: The single-pass perfusion model was established in rats, the concentration of berberine in intestinal perfusion was determined by HPLC, and phospholipid solid dispersion technology promoting intestinal absorption of berberine was investigated. Results: Compared with berberine, BBH-PSD could promote much more absorption of berberine in various intestinal segments, especially in jejunum, and the mechanism was related to improving permeability and strengthen simple diffusion of berberine. The Ka and Papp values of BBH and BBH-PSD in jejunum were obviously higher than BBH (P < 0.05); When the volumetic flow rate of BBH-PSD was 0.2, 0.4, and 0.8 mL/min, Ka and Papp were both higher than BBH (P < 0.05); The increasing mass concentration was not obvious to intestinal absorption of BBH, while the increasing mass concentration of BBH-PSD obviously increased the intestinal absorption of BBH (P < 0.05). Conclusion: Intestinal absorption characteristics of berberine phospholipid solid dispersion is beneficial to improve berberine oral bioavailability, and it can provide a scientific basis for the development of new dosage forms of berberine hydrochloride.
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OBJECTIVE:To establish mathematical model of liquid volume added of TCM medicinal broth decoction machine to accurately calculate liquid volume added in the process of medicinal herb decocting,so as to guarantee the quality of medicinal herb decocting. METHODS:The water absorption rate of representative TCM decoction piece with high use frequency were deter-mined,and cluster analysis of water absorption rate of TCM decoction piece was conducted according to closely related index as density,size,shape,moisture. TCM decoction piece with similar water absorption rate were bracketed together,so that of single ingredient TCM decoction piece can be estimated by water absorption of representative TCM decoction piece;the quantity of water evaporation and liquid extrusion were determined among different types of decoction machine (powered by electric and gas);ac-cording to the above parameters,mathematical model of liquid volume of TCM medicinal broth prepared by different types of de-coction machine had been established,and validated with TCM formula. RESULTS:Factors that affected the liquid volume added included the water absorption of each ingredient,the quantity of water evaporation and extrusion function. The mathematical model was liquid volume added=water absorption of each ingredient × quality of decoction piece+the quantity of water evaporation+re-quired amount of liquid-parameters of extrusion function×total weight of decoction piece;in validation test,the percentage of the practical amount of liquid to required amount was within ±5%. CONCLUSIONS:Established model can promote the accuracy li-quid volume added and guarantee the quality of TCM decoction when using TCM decoction machine.
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Objective: To study the rat intestinal absorption characteristic of puerarin loaded O-carboxymethyl chitosan (CMCS) microspheres in situ. Methods: Single-pass intestinal perfusion (SPIP) model was used for rat in situ and HPLC to determine the concentration of puerarin. The effects of different perfusion rate, drug concentration, and intestinal segments on intestinal absorption were investigated, and the absorption characteristics of the puerarin and puerarin loaded O-CMCS microspheres were compared. Results: Perfusion rate had significant effect on the absorption rate constants (Ka) and the apparent absorption coefficient (Papp) (P 0.05); Ka and Papp of drug loaded microspheres in jejunum and ileum showed no significant difference, but they were significantly higher than that in duodenum (P < 0.05); The drug loaded microspheres and puerarin had the significant difference in Ka and Papp in jejunum (P < 0.05). Conclusion: The absorption mechanism of puerarin in the microspheres is passive diffusion, puerarin is absorbed well in jejunum and ileum, and puerarin loaded O-CMCS microspheres can significantly improve the absorption of puerarin.
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Objective To investigate the safety and effectiveness of high intensity focused ultrasound (HIFU ) in the treat‐ment of uterine fibroid (<4 cm) .Methods Retrospectively studied 79 single fibroid (<4 cm) patients that treated with HIFU in our hospital from January 2011 to February 2013 .Evaluated the improvement of post‐treatment ,shrinkage of fibroid volume and HIFU‐related adverse reaction .Results All the 79 patients were successfully cured by HIFU treatment .The shrinkage rate of fi‐broid was 79 .0% (four point spacing 57 .9% ,92 .1% ) after 2‐year treatment ;Symptom severity score (SSS) and uterine fibroid symptom and quality of life score (UFS‐QOL) were significantly improved ;and there was no adverse reaction .Conclusion HIFU can be safely used in the treatment of small uterine fibroids (diameter<4 cm ) .
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Objective: To optimize the purification technology for flavone from Alpiniae Oxyphyllae Fructus (FAOF) with macroporous resins. Methods: Static and dynamic adsorption-desorption were used to select the best one from 15 different type macroporous resins; With the content of flavone as index, the purification technology parameters of flavone were optimized. Results: HP20 type resin showed the best purifying profile, its optimum technology conditions were as follows: sample injection concentration was 1.518 mg/mL, sample flow rate was 1.0 mL/min, quantity of adsorption was 50 mL, desorption rate was 1.0 mL/min, eluted by 6 BV 30% ethanol. Conclusion :The flavone could be isolated from Alpiniae Oxyphyllae Fructus by HP20 macroporous resins.
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Objective: Meglucumin cocrystal (MGC) is a new cocrystal compound which consists of curcumin with meglumine by hydrogen bond. The intestinal absorption parameter changes of MGC would be observed and be compared with curcumin. Methods: The intestine in rats was cannulated for in situ perfusion to study the absorption mechanism of MGC; UV was used to determine the concentration of MGC, to calculate the order of the absorption rate constants (Ka), and apparent permeability coefficients (Papp). Results: The Ka and Papp of MGC in the duodenum has significantly increased compared with the colon (P0.05) in other isolated regions of the intestine. The order was: duodenum>jejunum>ileum>colon; And that of Papp was: duodenum>jejunum>colon>ileum. The Ka and Papp in the whole intestine were (9.966±0.030)×10-3 min-1and (6.871±0.013)×10-3 cm/min respectively for the MGC which were 1.53 times and 2.21 times higher than these of curcumin. Conclusion: MGC is a better intestinal absorption characteristic than these of curcumin, suggesting that the bioavailability of MGC may be increased.
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A specific absorption rate (SAR) measurements system has been developed for compliance testing of personal mobile phone in a brain phantom material contained in a Perspex box. The volume of the box has been chosen corresponding to the volume of a small rat and illuminated by a 3G mobile phone frequency (1718.5 MHz), and the emitted radiation directed toward brain phantom .The induced fields in the phantom material are measured. Set up to lift the plane carrying the mobile phone is run by a pulley whose motion is controlled by a stepper motor. The platform is made to move at a pre-determined rate of 2o per min limited up to 20o. The measured data for induced fields in various locations are used to compute corresponding SAR values and inter comparison obtained. These data are also compared with those when the mobile phone is placed horizontally with respect to the position of the animal. The SAR data is also experimentally obtained by measuring a rise in temperature due to this mobile exposures and data compared with those obtained in the previous set. To seek a comparison with the safety criteria same set of measurements are performed in 10 g phantom material contained in a cubical box. These results are higher than those obtained with the knowledge of induced field measurements. It is concluded that SAR values are sensitive to the angular position of the moving platform and are well below the safety criteria prescribed for human exposure. The data are suggestive of having a fresh look to understand the mode of electromagnetic field -bio interaction.
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Absorption , Animals , Brain/radiation effects , Cell Phone , Electromagnetic Fields , Humans , Phantoms, Imaging , Radiometry , RatsABSTRACT
Objective To determine the power-time-ablation scope correlogram of a water-cooled single needle electrode radiofrequency (RF) ablation system and to establish a theoretical basis for its practical application.Methods RF ablations were performed using a water-cooled single needle electrode radiofrequency ablation system developed by the authors using fresh ox liver as well as liver and muscles of healthy adult New Zealand white rabbits.The temperature of the ablation area was monitored using a multichannel thermometric system.The maximum ablation scope was determined by detecting the rim at which the temperature was no less than 50 °C.The specific absorption rate (SAR) of the isolated liver tissue was calculated.Results In the treatment voltage range of 100-130V,the process was smooth and steady.No impedance variation was obvious.The maximum diameter of a single ablation was 51 cm.With the treatment voltage at 140-170 V,a larger ablation area could be reached in less time,but eventually the impedance began to increase while the ablation area was no longer expanded.When the treatment voltage reached the range of 180-200 V the impedance almost always increased rapidly out of limits,and the treatment system stopped automatically.The measured SAR value was consistent with the theoretical value.Pathology confirmed that both liver tissue and muscle tissue manifested typical coagulative necrosis.Conclusions The power amplifier,cooling,thermometric and control sections of the RF ablation system worked stably,and the practical ablation effect met the design and clinical treatment requirements.
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OBJECTIVE: To investigate the mechanism of in situ intestinal absorption of mangiferin in rats.METHODS: The in situ intestinal perfusion model was employed.HPLC/UV was developed to determine the concentration of mangiferin in intestinal circulated fluid.The effects of mangiferin concentration,bile and absorption site on the absorption parameters were studied.RESULTS:The mangiferin at a concentration from 5.0 to 25.0 ?g?mL-1 had no influence on the intestinal absorption kinetics(Ka) but it did at a concentration below 12.5 ?g?mL-1 in biliary duct-ligated rats.The absorption rate constants(Ka) in descending order were 0.164 h-1(ileum),0.132 h-1(jejunum),0.125 h-1(colon) and 0.107 h-1(duodenum),respectively.CONCLUSION: The absorption of mangiferin is in line with first-order kinetics with passive diffusion absorption mechanism.Mangiferin is well absorbed at all segments of intestine in rats,and bile is conducive to the increase of the permeability coefficient of Mangiferin in intestine.
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This study was performed to determine the effect of three different concentrations of soy-isoflavones on calcium and phosphorus balance in either sham-operated or ovariectomized female rats. Seventy-two 16-week old Sprague-Dawley rats underwent sham operation or bilateral ovariectomy. They were provided diets containing different levels of soy isoflavones for 6 weeks: 50 ppm (low isoflavone intake; LI), 250 ppm (medium isoflavone intake; MI) and 500 ppm (high isoflavone intake; HI). The subsequent fecal and urinary excretions of calcium and phosphorus were then measured. In the sham-operated rats, body weight gains and food efficiency ratio of the MI and HI groups were significantly lower than the control group while food intake was not different. However, there was no significant difference in the ovariectomized rats. The fecal excretion of calcium was significantly lower in the LI, MI and HI groups than the control group in sham operated rats, and significantly lower in the HI group than the control group in ovariectomized rats. Also, apparent absorption rate of calcium and phosphorus did not show any significant difference among groups. Urinary excretion of calcium and phosphorus was significantly lower in the HI group than the LI group in the sham-operated rats. Urinary excretion of calcium was significantly higher in the control ovariectomized rats than in the control sham-operated rats. Retention of calcium and phosphorus did not show any significant difference in both groups. From the above result, we see that isoflavone intake increases calcium retention through an increase in calcium absorption and also suppresses the increase of calcium excretion in urine in ovariectomy. Therefore, it is suggested that isoflavone intake is recommended for menopausal women who experience sharp bone loss due to the decrease in estrogen hormone.
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Animals , Female , Humans , Rats , Absorption , Body Weight , Calcium , Diet , Eating , Estrogens , Isoflavones , Ovariectomy , Phosphorus , Rats, Sprague-DawleyABSTRACT
Objective:To investigate the characteristics of calcium metabolism and identify the calcium intake that produces plateau retention in premenarche Chinese girls. Method:Forty-nine healthy premenarche Chinese girls (9-11.5 y) were recruited, and divided into four groups respectively receiving one of four different doses of calcium intakes for 6 d, 600 mg (usual diet),900 mg (containing 250 ml milk),1 200 mg (containing 250 ml milk and 750 mg CaCO3) and 1 500 mg calcium (250 ml milk and 1500 mg CaCO3) per day. Calium in 3-day urine and stool,and 3-d duplicated food samples were collected to assess the calcium equilibrium during the treatment period. Results: There were no significant differences in apparent calcium absorption among the four groups (55%, 53%, 52% and 52%). The relationship between calcium intake and calcium retention was fitted into a non-liner regression model which showed that the calcium retention was approaching the plateau when calcium intake reached 1100mg/d. Conclusion: The apparent calcium absorption was 53%?0.12% in Chinese premenarche girls with dietary calcium intakes ranged between 600 to 1500 mg/d. Calcium retention approached its plateau when calcium intake reached 1 100 mg/d in Chinese premenarche girls.