[Research advances in the calculating method of nitrogen use efficiency (NUE) in cultivated lands].

Nitrogen use efficiency (NUE) has received worldwide concern in the sphere of agronomic science and environmental science, and it is fundamentally important for evaluating N utilization status and optimizing N fertilization management in cultivated lands. In recent years, in consideration of low values and great variations of NUE in China' s cultivated lands, some scholars have discussed on the traditional concept and calculating method of NUE, and also have proposed some substituted NUE calculating methods. In this paper, we summarized some disadvantages of both conventional concept and calculating method of NUE, i.e. the subtraction method and the 15N labeling method. Furthermore, we particularly introduced several substituted NUE calculation methods and discussed research directions in the future. In summary, we strongly suggested the establishment of a comprehensive evaluation index system of N utilization in good accordance with the current agricultural production status in China, based on a correct understanding of the dialectical relationships among N application rate, crop yield, N utilization and N loss.

[Effects of different potassium fertilizer application periods on the yield and quality of Fuji apple].

In order to ascertain the effects of potassium fertilizer application periods on apple production, we conducted a field experiment and analyzed the differences in apple yield, fruit quality, potassium fertilizer use efficiency, and nutrient concentrations in leaves and fruits among treatments with differences in timing of potassium application. The results indicated that, compared with no potassium-applied treatment (CK), all potassium fertilizer application treatments significantly increased the apple yield by 4.3%-33.2%, meanwhile, it also obviously improved the fruit quality. In comparison with the application of 100% potassium fertilizer as a base, the application of 50% or 100% of potassium fertilizer at the fruit enlargement stage (the remaining 50% applied as a base or after flowering) significantly increased the apple yield by 20.5% - 27.7% and improved the fruit quality. Compared with the application 100% potassium fertilizer at the stage of fruit enlargement, the evenly split application as base flowering stage and at the fruit enlargement: stage not only contributed to a higher yield, better quality and higher potassium use efficiency, but also maintained a relatively stable potassium concentration level in leaves. However, the split potassium fertilizer application at the flowering and fruit enlargement stages resulted in the significant decrease in concentration of calcium in fruit, which would be negative to fruit quality. In conclusion, our research suggested that evenly split application of potassium fertilizer as a base and at the fruit enlargement stage was the suitable period for apple production in Fuji apple orchards in this region.

[Discussion on the calculation method of nitrogen use efficiency (NIUE) in long-term field experiments under wheat and maize rotation systems].

In recent years, some scholars from China have deeply discussed about the concept, connotation and calculating method of nitrogen use efficiency (NUE), and have raised questions and also put forward some improved methods for NUE calculation in cultivated lands. In this paper, we compared advantages and disadvantages of these improved NUE calculation methods by using the data from a 5-year positioning field experiment under a wheat-maize rotation system. The results indicated that it made mistakes when the traditional subtraction method was used to calculate NUE for wheat season and maize season separately, since the soil fertility level of experimental plots had differed significantly from each other after several seasons or years of different fertilization managements. Additionally, the calculated NUE increased markedly with the cropping season going, thus making it difficult to mirror the actual situation of N utilization in cultivated lands. For the wheat-maize rotation system, the cumulative NUE calculation method considered wheat season and maize season as a whole part, and skillfully avoided mistakes which could be caused by inhomogeneity of soil fertility levels between experimental plots. Moreover, the calculated NUE were comparably smaller, with smaller coefficient variations (CVs), in contrast with the traditional subtraction method. The NUE calculated by using the ratio method were bigger, with the smallest CVs, than that computed by using the cumulative calculation method. The soil N balance method took a thoughtful consideration about the budgets and losses of soil nutrients before and after crop growth, but obtained the largest values of NUE and CVs within these methods.

Involvement of GSK3 and PP2A in ginsenoside Rb1's attenuation of aluminum-induced tau hyperphosphorylation.

Environmental agent aluminum, a well-known neurotoxin, has been proposed to play a role in the development of Alzheimer's disease (AD), and produced clinical and pathological features which were strikingly similar to those seen in AD brain, such as neurofibrillary tangles. Ginsenoside Rb1, highly abundant active component of ginseng, has been demonstrated to be neuroprotective against various neurotoxins. In this study we investigated the effect of Rb1 on aluminum-induced tau hyperphosphorylation in ICR mice. Mice were exposed to aluminum chloride (200 mg/kg/day) for 6 months followed by a post treatment of Rb1 (20 mg/kg/day) for another 4 months. Aluminum exposure induced the cognitive ability by Morris water maze, and upregulated the tau phosphorylation level at Ser396 accompanied by increasing p-GSK and decreasing PP2A level in motor, sensory cortex and hippocampal formation. Post treatment of Rb1 significantly improved the learning and memory and reduced the tau phosphorylation by reversing the p-GSK3 and PP2A level. Our results indicate that ginsenoside Rb1 protected mice against Al-induced toxicity. The possible mechanism may be its role in preventing tau hyperphosphorylation by regulating p-GSK3 and PP2A level, which implicate Rb1 as the potential preventive drug candidate for AD and other tau pathology-related neuronal degenerative diseases.

Ginsenoside Rb1 protects PC12 cells against ß-amyloid-induced cell injury.

Excessive accumulation of ß-amyloid (Aß) has been proposed as a pivotal event in the pathogenesis of Alzheimer's disease. Possible mechanisms underlying Aß-induced neuronal cytotoxicity include oxidative stress and apoptosis. Reactive oxygen species (ROS) have been proposed to be involved in the apoptotic mechanism of Aß-induced cytotoxicity. Ginsenoside Rb1 (GRb1), which is among the key compounds of ginsenoside, found in ginseng, may be a potent scavenger of ROS. To examine the potential protective effect of GRb1 in Aß25-35-induced cytotoxicity, cells were pre-treated with GRb1 for 24 h, and then Aß25-35 was added to the medium for an additional 24 h. Exposure to Aß led to the accumulation of ROS and lipid peroxidation, eventually causing a decrease in the Bcl-2/Bax ratio, caspase-3 activation, cell apoptosis and cell death. Pre-treatment with GRb1 not only inhibited Aß-induced ROS overproduction and lipid peroxidation, but also increased the Bcl-2/Bax ratio and attenuated caspase-3 activation, thereby improving cell survival. GRb1 may therefore act as a ROS scavenger, and such antioxidant properties may play a protective role against Aß-induced cell injury. Further exploration of GRb1 antioxidant properties may provide novel therapeutic strategies for the treatment of Alzheimer's disease.

Effects of ATP sensitive potassium channel opener on the mRNA and protein expressions of caspase-12 after cerebral ischemia-reperfusion in rats.

OBJECTIVE: To investigate effects of K(ATP) opener on the expressions of caspase-12 mRNA and protein, and to explore the role of endoplasmic reticulum (ER) stress pathway in the mechanism of K(ATP) opener protecting against neuronal apoptosis after cerebral ischemia-reperfusion. METHODS: Two hundred rats were randomly divided into four groups: sham operation group, ischemia-reperfusion group, K(ATP) opener group, and K(ATP) blocker group. The middle cerebral artery occlusion (MCAO) model was established by intraluminal suture occlusion method; neuronal apoptosis was detected by TUNEL staining. The mRNA and protein expressions of caspase-12 were detected by semi-quantitative RT-PCR and immunohistochemical staining, respectively. RESULTS: In ischemia-reperfusion group, K(ATP) opener group and K(ATP) blocker group, the number of apoptotic cells and the mRNA and protein expressions of caspase-12 gradually increased following cerebral reperfusion, and reached the peak at 24 h. In K(ATP) opener group, the number of apoptotic cells was significantly less than that in ischemia-reperfusion group and K(ATP) blocker group at 12 h, 24 h, 48 h and 72 h (P< 0.05 or P< 0.01); while the mRNA and protein levels of caspase-12 were significantly less than those in ischemia-reperfusion group and K(ATP) blocker group at all times (P< 0.05 or P< 0.01). There were no differences between the ischemia-reperfusion group and K(ATP) blocker group at each time (P> 0.05). CONCLUSION: K(ATP) opener may protect neurons from apoptosis following the cerebral ischemia-reperfusion by inhibiting ER stress pathway.

Cannabinoids inhibit ATP-activated currents in rat trigeminal ganglionic neurons.

The present study aimed to investigate whether cannabinoids could modulate the response mediated by ATP receptor (P2X purinoceptor). Whole-cell patch-clamp recording was performed on cultured rat trigeminal ganglionic (TG) neurons. The majority of TG neurons were sensitive to ATP (67/75, 89.33%). Extracellular pretreatment with WIN55212-2, a cannabinoid receptor 1 (CB1 receptor) agonist, reduced ATP-activated current (I(ATP)) significantly. This inhibitory effect was concentration-dependent and was blocked by AM281, a specific CB1 receptor antagonist. Pretreatment with WIN55212-2 at 1×10(-13), 1×10(-12), 1×10(-11), 1×10(-10), 1×10(-9) and 1×10(-8) mol/L reduced I(ATP) (induced by 1×10(-4) mol/L ATP) by (8.14±3.14)%, (20.11±2.72)%, (46.62±3.51)%, (72.16±5.64)%, (80.21±2.80)% and (80.59±3.55)%, respectively. The concentration-response curves for I(ATP) pretreated with and without WIN55212-2 showed that WIN55212-2 shifted the curve downward, and decreased the maximal amplitude of I(ATP) by (58.02±4.21)%. But the threshold value and EC(50) (1.15×10(-4) mol/L vs 1.27×10(-4) mol/L) remained unchanged. The inhibition of I(ATP) by WIN55212-2 was reversed by AM281, suggesting that the inhibition was mediated via the CB1 receptor. Pretreatment with forskolin [an agonist of adenylyl cyclase (AC)] or 8-Br-cAMP reversed the inhibition of I(ATP) by WIN55212-2. These results suggest that the inhibitory effect of cannabinoids on I(ATP) is mediated via the CB1 receptors, that lead to inhibition of the AC-cAMP-PKA signaling pathway.

Pinacidil reduces neuronal apoptosis following cerebral ischemia-reperfusion in rats through both mitochondrial and death-receptor signal pathways.

OBJECTIVE: To investigate effect of pinacidil, an ATP sensitive potassium channel (K(ATP)) opener, on the neuronal apoptosis and its signaling transduction mechanism following focal cerebral ischemia-reperfusion in rats. METHODS: One hundred male Wistar rats were randomly divided into four groups: A, sham-operated group; B, ischemia-reperfusion group; C, K(ATP) opener treatment group; and D, K(ATP) opener and blocker treatment group. The middle cerebral artery occlusion (MCAO) model was established by using the intraluminal suture occlusion method, neuronal apoptosis was determined by TUNEL staining, and expressions of caspase-8, caspase-9 and caspase-3 mRNA were detected by in situ hybridization. RESULTS: (1) The numbers of apoptotic neurons at 12 h, 24 h, 48 h, and 72 h were significantly less in group C than in groups B and D (P< 0.01 or P< 0.05); and there was no difference between groups B and D at all time points (P> 0.05). (2) The expressions of caspase-3 mRNA and caspase-8 mRNA at all times and the expressions of caspase-9 mRNA at 12 h, 24 h, 48 h, 72 h were significantly lower in group C than in groups B and D (P< 0.01 or P< 0.05); and there were no differences between groups B and D at all time points (P> 0.05). CONCLUSIONS: K(ATP) opener can significantly decrease the neuronal apoptosis and the expressions of caspase-3, caspase-8 and caspase-9 mRNAs following cerebral ischemia-reperfusion. The neuronal apoptosis may be decreased by the inhibition of both mitochondrial and death-receptor signal pathways.

[Protective effect of ATP sensitive potassium channel opener on cerebral ischemia/reperfusion injury and its signal transduction mechanism].

OBJECTIVE: To study the protective effect of ATP sensitive potassium channel(K( ATP))opener against neuronal apoptosis following focal cerebral ischemia/reperfusion (I/R) and its signal transduction mechanism. METHODS: Two hundred male Wistar rats were randomly divided into four groups: sham operation group (A group), I/R group (B group), K( ATP) opener treatment group (C group) and K( ATP) opener and blocker treatment group (D group). The middle cerebral artery occlusion (MCAO) by intraluminal suture method was used to reproduce cerebral ischemia, and perfusion was restored 2 hours after MCAO. Five rats in each group were used. Brain sections were made 6, 12, 24, 48 and 72 hours after I/R injury, and neuronal apoptosis was detected by terminal deoxynucleotidyl transferase-mediated deoxyuridine 5 triphosphate nick end labeling (TUNEL). The expressions of caspase-3 and caspase-9 proteins were detected by immunohistochemical method. Another five rats in each group were used for assessing the expressions of caspase-3 mRNA and caspase-9 mRNA by reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: The number of apoptotic neurons, the expression of caspase-3 and caspase-9 mRNA and protein in B, C and D groups were significantly higher than A group at all time points (P<0.05 or P<0.01). The number of apoptotic neurons, the expressions of caspase-3 and caspase-9 mRNA and protein in C group were significantly lower than B and D groups at all time points (P<0.05 or P<0.01). There were no differences between B and D groups at all time points (all P>0.05). CONCLUSION: K( ATP) opener can significantly mitigate neuronal apoptosis and inhibit the expressions of caspase-3 and caspase-9 mRNA and protein after cerebral I/R injury. This result indicates that K( ATP) opener can decrease neuronal apoptosis by inhibiting mitochondria signaling pathway.

Action of aluminum on high voltage-dependent calcium current and its modulation by ginkgolide B.

AIM: To investigate the effect of aluminum (Al) on high voltage-dependent calcium current (I(HVA)) and its modulation by ginkgolide B (Gin B). METHODS: The whole-cell, patch-clamp technique was used to record IHVA from acutely isolated hippocampal CA1 pyramydal neurons in rats. RESULTS: Al 0.1 mmol/L (low concentration) reduced I(HVA); Al 0.75 and 1.0 mmol/L (high concentrations) increased I(HVA), and Al decreased and increased I(HVA) at intermediate concentrations of 0.25 and 0.5 mmol/L. The increase of I(HVA) by Al 1.0 mmol/L was enhanced by the adenylyl cyclase (AC) agonist forskolin and was partly abolished by the cyclic adenosine monophosphate (cAMP)-dependent protein kinase A (PKA) antagonist H-89, whereas the decrease observed with Al 0.1 mmol/L was neither reversed by forskolin nor affected by H-89. Gin B had no effect on I(HVA) in normal neurons, but canceled the increase in I(HVA) by 1.0 mmol/L Al. CONCLUSION: The results indicate that the mechanism of Al affecting I(HVA) differs at different concentrations, and this may be attributed to its complex actions. Gin B could prevent neurons from injury by inhibiting calcium influx.