Jianbao Zhang

Evaluation to the antioxidant activity of total flavonoids extract from persimmon (Diospyros kaki L.) leaves

Persimmon leaves are commonly consumed as beverages, but are also used as a popular folk medicine in China. The purpose of this work is to assess the antioxidant activity of an extract of total flavonoids from persimmon leaves (TFPL). The effect of TFPL on total antioxidant activity, reducing power, 1,1-diphenyl-2-picrylhydrazyl (DPPH()) radical scavenging, superoxide anion (()O(2)(-)) radical scavenging, hydroxyl (OH()) radical scavenging and metal chelating activities was examined. We found that TFPL possesses considerable amounts of flavonoids (192μg catechin equivalent/g of extract). The effect of this extract in total antioxidant activity, scavenging activity of superoxide anion and hydroxyl radical, reducing power and iron chelating activity was significantly better than that of rutin. However, the effect of TFPL in free radical scavenging of DPPH() was significantly not as good as than rutin. In addition, TFPL significantly decreased the level of reactive oxygen species (ROS) and malondialdehyde (MDA), while increasing the activity of catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in MC3T3-E1 cells in a dose-dependent manner. In conclusion, TFPL possess potent antioxidant and free radical scavenging activities. These antioxidant activities could contribute, at least in part, to the traditionally claimed therapeutic benefits of persimmon leaves.

Effects of Different Extremely Low-Frequency Electromagnetic Fields on Osteoblasts

It is well known that the extremely low-frequency electromagnetic field (EMF) can promote the healing of bone fractures, but its mechanism remains poorly understood. The purpose of this study was to examine the response of neonatal rat calvarial bone cells to the rectangular electromagnetic field (REMF), triangular electromagnetic field (TEMF), sinusoidal electromagnetic field (SEMF), and pulsed electromagnetic field (PEMF). The stimulatory effects of EMF were evaluated by the proliferation (methyltetrazolium colorimetric assay), differentiation (alkaline phosphatase (ALP) activity), and mineralization (area of mineralized nodules of the cells). REMF treatment of osteoblasts increased cellular proliferation and decreased ALP activity (p < 0.05). TEMF had an accelerative effect on the cellular mineralized nodules (p < 0.05). SEMF treatment of osteoblasts decreased the cellular proliferation, increased ALP activity, and suppressed mineralized nodules formation (p < 0.05). PEMF promoted the proliferation of osteoblasts, inhibited their differentiation, and increased the mineralized nodules formation (p < 0.05). Moreover, the effects of PEMF on osteoblasts were concerned with the extracellular calcium, P2 receptor on the membrane, and PLC pathway, but the response of osteoblasts on SEMF was only related to PLC pathway. The results suggested that the waveforms of EMF were the crucial parameters to induce the response of osteoblasts.

Relationship between scalp potential and autonomic nervous activity during a mental arithmetic task

The cerebral cortex had massive bidirectional connections to autonomic nervous system and mental performance can induce change of autonomic activity, but which regions are related to autonomic function is not clear. The study was to analyze the scalp positions which may affect cardiac autonomic nervous activity during a mental arithmetic (MA) task. Forty-three healthy male subjects were voluntarily participated in the study. Sympathetic and parasympathetic activities were estimated with heart rate variability. Scalp potential was determined by the wavelet packet parameters and approximate entropy (ApEn) of Electroencephalogram (EEG). The results showed that heart rate and the normalized low frequency power component were significantly increased (p<0.01) and the high frequency power component was decreased (p<0.01). Meanwhile relative wavelet packet energy in alpha band of EEG at P3, P4, Pz, O1, O2 and Oz electrodes were decreased and the beta band of EEG at the same electrodes were increased significantly (p<0.01). ApEn was significantly increased in MA (p<0.01). Moreover, changes of brain activity were earlier than the changes of autonomic activity and significantly correlations existed between heart rate variability and wavelet packet energy (p<0.05). In addition, a significant positive correlation between HR change and the laterality ratio score of alpha band in P3 v P4 (p<0.05) were observed. It is noted that cerebral conscious activity enhanced with the decrease of parasympathetic activity and increase of sympathetic activity, and the right post-central areas dominated sympathetic activity during stress-inducing mental tasks.

Effects of mental tasks on the cardiorespiratory synchronization.

The cardiovascular and respiratory systems are functionally related to each other, but it is unclear if the cerebral cortex can affect their interaction. The effect of a mental task on the synchronization between cardiovascular and respiratory systems was investigated in the article. Electroencephalogram (EEG), electrocardiogram (ECG) and respiratory signal (RES) were collected from 29 healthy male subjects during the mental arithmetic (MA) task and the synchrogram was used to estimate the strength of cardiorespiratory synchronization. Our results showed that MA task significantly increased the breath rate, the heart rate and the EEG power spectral energy in theta band at FC3, FC4 and C4 electrodes (p<0.01), decreased the duration of cardiorespiratory synchronization epochs (p<0.05). Moreover the duration of cardiorespiratory synchronization epochs during MA task was negatively correlated with the EEG power spectral energy in theta band at FC3, FC4 and C4 electrodes and the sympathetic activity (p<0.05). The results demonstrated that ANS and cerebral cortex are implicated in the changes of cardiorespiratory synchronization during MA task.

Effects of PEMF and glucocorticoids on proliferation and differentiation of osteoblasts

Pulsed electromagnetic fields (PEMF) can promote bone healing, while use of dexamethasone induces bone loss and osteoporosis. There is no report available on the combined effects of PEMF and dexamethasone on the activity of osteoblasts. Here, we investigated the effects of PEMF and dexamethasone on the proliferation and differentiation of MC3T3-E1 osteoblasts. Our results showed that PEMF and dexamethasone respectively increased and decreased the proliferation of MC3T3-E1 osteoblasts, meanwhile PEMF eliminated the effect of dexamethasone on MC3T3-E1 osteoblasts. Moreover, we also found that dexamethasone combined with PEMF upregulated the mRNA expression of IGF-1 at the early stage after the stimulation of PEMF and improved the decrease of COX-2 mRNA expression induced by dexamethasone at the late stage after the stimulation of PEMF. PEMF may be beneficial to improve dexamethasone-induced bone loss and osteoporosis.

Effects of extremely low frequency electromagnetic fields on intracellular calcium transients in cardiomyocytes

Abstract Calcium transients play an essential role in cardiomyocytes and electromagnetic fields (EMF) and affect intracellular calcium levels in many types of cells. Effects of EMF on intracellular calcium transients in cardiomyocytes are not well studied. The aim of this study was to assess whether extremely low frequency electromagnetic fields (ELF-EMF) could affect intracellular calcium transients in cardiomyocytes. Cardiomyocytes isolated from neonatal Sprague-Dawley rats were exposed to rectangular-wave pulsed ELF-EMF at four different frequencies (15 Hz, 50 Hz, 75 Hz and 100 Hz) and at a flux density of 2 mT. Intracellular calcium concentration ([Ca2+]i) was measured using Fura-2/AM and spectrofluorometry. Perfusion of cardiomyocytes with a high concentration of caffeine (10 mM) was carried out to verify the function of the cardiac Na+/Ca2+ exchanger (NCX) and the activity of sarco(endo)-plasmic reticulum Ca2+-ATPase (SERCA2a). The results showed that ELF-EMF enhanced the activities of NCX and SERCA2a, increased [Ca2+]i baseline level and frequency of calcium transients in cardiomyocytes and decreased the amplitude of calcium transients and calcium level in sarcoplasmic reticulum. These results indicated that ELF-EMF can regulate calcium-associated activities in cardiomyocytes.

Flavonoids from persimmon (Diospyros kaki) leaves (FPL) attenuate H2O2-induced apoptosis in MC3T3-E1 cells via the NF-κB pathway

The leaves of persimmon (Diospyros kaki L.) have long been used in Chinese medicine for the treatment of paralysis, frostbite, burns, and to stop bleeding. Flavonoids of persimmon leaves (FPL) are known for their antioxidant activity in murine osteoblast MC3T3-E1 cells, but their mechanisms in osteoblast cells injured by oxidative stress are unknown. In this study, the effects of FPL on oxidative damage were investigated by addressing their potential therapeutic or toxic effects on H2O2-stimulated MC3T3-E1 cells. MC3T3-E1 cells were pretreated with FPL (1.25, 2.5 and 5 μg mL(-1)) for 24 h and were then exposed to 250 μM H2O2 for an additional 6 h. FPL pre-incubated with MC3T3-E1 cells did not present any cytotoxicity, instead they increased cell viability and ΔΨm in a dose-dependent manner when challenged with H2O2. Treatment with this pro-incubated FPL also significantly suppressed the production of MDA and NO and the activity of iNOS. The mRNA expression of iNOS, COX-2, Bax, Bcl-2, and caspase-3 and the protein expression of NF-κB/p65 showed that FPL significantly inhibited apoptosis in H2O2-stimulated MC3T3-E1 cells. These results suggest that the molecular mechanism of FPL in anti-apoptosis was associated with the suppression of the translocation of NF-κB/p65 into the nucleus. The protective effect of FPL could provide a promising approach for the treatment of osteoporosis.

Effect of distinct sources of Ca2+ on cardiac hypertrophy in cardiomyocytes

It is believed that intracellular calcium (Ca2+) overload can cause the cardiac hypertrophy, but it is possible that the Ca2+ entering the cytoplasm through distinct pathways will induce various effects on cardiomyocytes. The aim of the present study is to explore the effect of different sources of Ca2+ on cardiomyocyte hypertrophy. The cardiomyocytes isolated from neonatal Sprague–Dawley rats were treated with three agents (ionomycin, caffeine and angiotensin II [Ang II]) that increased the intracellular Ca2+ concentration via different pathways. Treatments with ionomycin, caffeine and Ang II for 24 h caused a significant increase in resting [Ca2+]i by 108.0 ± 7.8%, 102.0 ± 6.9% and 59.8 ± 3.3%, respectively. Caffeine and Ang II increased the cell surface area of cardiomyocytes and the mRNA level of atrial natriuretic peptide, brain natriuretic peptide and β-myosin heavy chain, but ionomycin did not. Moreover, sarcoplasmic reticulum Ca2+-ATPase (SERCA2a) activity and the amplitudes of the twitch [Ca2+]i transients were reduced in the caffeine-treated group and Ang II-treated group. Furthermore, cardiomyocyte hypertrophy induced by caffeine was inhibited by cyclosporin A (CsA) and KN93, whereas cardiomyocyte hypertrophy induced by Ang II was inhibited by KN93, but not CsA. Our results show that cardiomyocyte hypertrophy is associated with SERCA2a activity, contractile performance and signaling pathways of CaMKII and/or calcineurin, whereas the Ca2+ overload is not sufficient to cause the cardiomyocyte hypertrophy.

Fluid shear stress induces calcium transients in osteoblasts through depolarization of osteoblastic membrane

Intracellular calcium transient ([Ca(2+)]i transient) induced by fluid shear stress (FSS) plays an important role in osteoblastic mechanotransduction. Changes of membrane potential usually affect [Ca(2+)]i level. Here, we sought to determine whether there was a relationship between membrane potential and FSS-induced [Ca(2+)]i transient in osteoblasts. Fluorescent dyes DiBAC4(3) and fura-2AM were respectively used to detect membrane potential and [Ca(2+)]i. Our results showed that FSS firstly induced depolarization of membrane potential and then a transient rising of [Ca(2+)]i in osteoblasts. There was a same threshold for FSS to induce depolarization of membrane potential and [Ca(2+)]i transients. Replacing extracellular Na(+) with tetraethylammonium or blocking stretch-activated channels (SACs) with gadolinium both effectively inhibited FSS-induced membrane depolarization and [Ca(2+)]i transients. However, voltage-activated K(+) channel inhibitor, 4-Aminopyridine, did not affect these responses. Removing extracellular Ca(2+) or blocking of L-type voltage-sensitive Ca(2+) channels (L-VSCCs) with nifedipine inhibited FSS-induced [Ca(2+)]i transients in osteoblasts too. Quantifying membrane potential with patch clamp showed that the resting potential of osteoblasts was -43.3mV and the depolarization induced by FSS was about 44mV. Voltage clamp indicated that this depolarization was enough to activated L-VSCCs in osteoblasts. These results suggested a time line of Ca(2+) mobilization wherein FSS activated SACs to promote Na(+) entry to depolarize membrane that, in turn, activated L-VSCCs and Ca(2+) influx though L-VSCCs switched on [Ca(2+)]i response in osteoblasts.

The role of oxygen-increased respirator in humans ascending to high altitude

BackgroundAcute mountain sickness (AMS) is common for people who live in low altitude areas ascending to the high altitude. Many instruments have been developed to treat mild cases of AMS. However, long-lasting and portable anti-hypoxia equipment for individual is not yet available.MethodsOxygen-increased respirator (OIR) has been designed to reduce the risk of acute mountain sickness in acute exposure to low air pressure. It can increase the density of oxygen by increasing total atmospheric pressure in a mask. Male subjects were screened, and eighty-eight were qualified to perform the experiments. The subjects were divided into 5 groups and were involved in some of the tests at 4 different altitudes (Group 1, 2: 3700 m; Group 3,4,5: 4000 m, 4700 m, 5380 m) with and without OIR. These tests include heart rate, saturation of peripheral oxygen (SpO2), malondialdehyde (MDA), superoxide dismutase (SOD), blood lactate (BLA) and PWC (physical work capacity) -170.ResultsThe results showed that higher SpO2, lower heart rate (except during exercise) and better recovery of heart rate were observed from all the subjects ’with OIR’ compared with ’without OIR’ (P<0.05). Moreover, compared with ’without OIR’, subjects ’with OIR’ in Group 1 had lower concentrations of MDA and BLA, and a higher concentration of SOD (P<0.05), while subjects ’with OIR’ in Group 2 showed better physical capacity (measured by the PWC-170) (P<0.05). The additional experiment conducted in a hypobaric chamber (simulating 4,000 m) showed that the partial pressure of oxygen in blood and arterial oxygen saturation were higher ’with OIR’ than ’without OIR’ (P<0.05).ConclusionsWe suggested that OIR may play a useful role in protecting people ascending to high altitude before acclimatization.