Dietary mannitol increased the absorption of calcium and magnesium in rats

The effect of mannitol on bone‐related mineral absorption and retention and the mechanism was investigated in this study. Fourteen 8‐week‐old male Wistar rats in experiment 1 and same number and age cecectomized Wistar male rats in experiment 2 were divided into two subgroups of seven animals, respectively, fed diets containing 0 or 4% mannitol for 28 days. Mineral balance tests were determined twice during days 8–12 and days 22–26, and the rats were slaughtered on day 28 both in experiment 1 and experiment 2. The whole caecum and colon were collected with the content to analyse tissue weight, content weight, content's pH and moisture, organic acids' concentration and mineral levels. In experiment 1, Ca absorption and retention and Mg absorption were significantly increased by mannitol feeding during days 8–12. Caecal total weight, tissue weight and content weight were increased, the pH of caecum and colon was reduced, and the concentrations of caecal short‐chain fatty acids (SCFAs) were modified by mannitol feeding. In experiment 2, during days 8–12 and days 22–26, Ca absorption and retention were significantly lowered by mannitol feeding in cecectomized rats; however, mannitol feeding decreased Mg absorption during days 8–12, but did not impact Mg retention. Colonic total weight, tissue weight and content weight were significantly increased, and colonic pH was reduced by mannitol feeding. In conclusion, dietary mannitol increased the absorption of Ca and Mg and the caecum markedly contributed to this promoting effect of mannitol.     

Binding Sites for Ca2+-Channel Effectors and Ryanodine in Periplaneta americana—Possible Targets for New Insecticides

The calcium channel and the ‘calcium release channel’ of muscle membrane of the cockroach Periplaneta americana have been characterized. Biological assays with calcium channel blockers and ryanodine on different insects and acari revealed pronounced insecticidal effects with ryanodine, but not with calcium channel blockers, at concentrations between 0·1 and 300 μg ml⁻¹. Skeletal muscle membranes derived either from the tubular network or from the sarcoplasmatic reticulum of P. americana were characterized with respect to the binding of the dihydropyridine (DHP) [³H]isradipine (PN 200-110), the phenyl-alkylamine [³H]verapamil and the alkaloid [³H]ryanodine. Preliminary binding studies with the benzothiazepine [³H]diltiazem suggest a low-affinity binding site with a IC₅₀ value of 3·3 μM . All binding sites tested were sensitive to treatment with proteinase K. Optimal conditions for binding of the radioligand ryanodine revealed the highest specific binding at pH 8 and at calcium chloride concentrations between 100 and 500 μM . EGTA at 10 μM abolished 95% of the ryanodine binding. Binding studies with calcium channel binding sites revealed a pronounced effect of low Ca²⁺ concentrations on specific isradipine binding, whereas verapamil and diltiazem binding were only reduced by the presence of 200 μM EGTA. With respect to high Ca²⁺ concentrations, specific binding of diltiazem, isradipine and verapamil was reduced by 73, 40 and 20%, respectively, at 5 mM Ca²⁺. Radioligand binding experiments showed high-affinity binding sites for ryanodine and isradipine. K_D values of 0·95 nM (B_max=550 fmol mg⁻¹ protein) and 0·75 nM (B_max=213 fmol mg⁻¹ protein) were determined respectively. A lower-affinity binding site was identified in binding studies with verapamil (K_D=7·4 nM and B_max=27 fmol mg⁻¹ protein). [³H]isradipine displacement studies with several dihydropyridines revealed the following ranking of affinity: nitrendipine>isradipine>Bay K8664≪nicardipine. Displacement of [³H]verapamil binding by effectors of the phenylalkylamine binding site showed that bepridil and S(-)verapamil had the highest affinities of the compounds tested followed by (±)verapamil, nor-methylverapamil and R(+)verapamil.     

果实袋对黄冠梨果皮Ca含量和花斑病发生的影响

黄冠梨果实套袋后果皮Ca素积累明显降低,不同的果实袋会影响到黄冠梨花斑病的发生,花斑病发病率与果皮Ca素营养水平呈显著负相关关系.     

Occurrence of prophage and historical perspectives associated with the dissemination of huanglongbing in mainland China

Huanglongbing (HLB), associated with a non-culturable bacterium ‘Candidatus Liberibacter asiaticus’ (CLas), is a highly destructive citrus disease with a long but poorly documented history in China. No effective treatment for HLB is available. The identification of new prophages in abundant CLas genomic sequence data provides new insights into both the diversity of CLas strains and HLB management. In this study, CLas populations from nine provinces were surveyed for the presence of prophage. Two major prophage typing groups (PTGs) were discovered to be associated with two different altitude regions: strains of CLas in PTG1 from high altitude regions (HAR) mainly contained prophage Type 1 only or Types 1 and 3, whereas strains of CLas in PTG2 from low altitude regions (LAR) mainly contained prophage Type 2. The discovery of these CLas population patterns provides evidence for independent origins of HLB in HAR and LAR. Guangdong province is the generally recognized domestic region of origin for HLB and is primarily responsible for the dissemination of HLB in LAR through transport of seedlings. Both Yunnan and Sichuan provinces are the probable regions of origin for HLB in HAR. PTG2 was further divided into two subgroups: PTG2-1, found in Guangdong, Fujian and Guangxi and PTG2-2, found in Jiangxi, Zhejiang and Hunan. These regions and prophage types are correlated with early and late introductions of HLB in LAR. These molecular analyses were supported by studying the history of the dissemination of HLB in historical documents.     

Characterization of Ca-ATPase activity in gill microsomes of freshwater mussel, Lamellidens marginalis (Lamarck) and heavy metal modulations

Freshwater mussel Lamellidens marginalis showed a Ca²⁺-stimulated ATPase activity in the microsomal fraction of gill. Mg²⁺ was also found to be an activating cation for this ATPase enzyme. Ca²⁺ ATPase showed maximal activity at 40 °C and between pH 7.5–8.0. Substrate specificity of Ca²⁺ ATPase was highest with ATP, followed by GTP and other trinucleotides such as UTP, CTP and ADP also showed some amount of hydrolysis. Ca²⁺ ATPase showed slight inhibition with ruthenium red and sodium vanadate and is insensitive to sodium azide, ouabain, oligomycin B and phenylalanine. Heavy metals like Hg²⁺, Cu²⁺ and Zn²⁺ showed 50% inhibition of Ca²⁺ ATPase activity at concentrations of 0.25 mM, 0.5 mM and 1 mM, respectively whereas Cd²⁺ and Ni²⁺ showed 39% and 28% inhibition of enzyme activity at 1 mM concentrations.     

Mn~(2+)对四尾栅藻生长及Ca~(2+)、Mg~(2+)吸收的影响

通过实验室模拟培养的方法,采用6个不同Mn2+浓度(0、10、100、1000、10000、30000nmol/L)的培养处理,对四尾栅藻(Scenedesmus quadricauda)的生物量、叶绿素a含量、培养基中Ca2+、Mg2+离子的含量分别进行了测定。结果表明,不同Mn2+浓度对各指标均有显著影响,其中对叶绿素a含量的影响达极显著(P<0.01);低Mn2+浓度(0~1000nmol/L)促进四尾栅藻细胞生长和叶绿素a的合成,而高浓度Mn2+(30000nmol/L以上)抑制四尾栅藻细胞生长,导致生物量下降;叶绿素a含量显著降低(P<0.05);四尾栅藻细胞吸收的Ca2+、Mg2+与其生物量成正比。在所设置的浓度范围内,Mn2+并未表现出与Ca2+、Mg2+之间明显的拮抗作用。     

渗透胁迫下玉米幼叶细胞Ca2+分布及超微结构变化

采用改进的焦锑酸钙沉淀细胞化学方法,探讨了渗透胁迫条件下玉米幼叶胞内Ca2+的分布及细胞超微结构的变化,旨在进一步探讨Ca2+与渗透胁迫诱导胞内信息转导过程的关系。结果表明:干旱胁迫初期,胞质Ca2+浓度升高,液泡失水,叶绿体、细胞核Ca2+浓度升高,起到了调节胞内Ca2+浓度的作用;随着胁迫时间的延长,细胞超微结构遭到破坏,同时,叶绿体及细胞核中Ca2+浓度呈继续上升趋势,二者超微结构受到破坏的程度愈发严重,直至解体。说明:Ca2+介导了渗透胁迫诱导的细胞生理过程,Ca2+对细胞核骨架的可塑性发挥着重要作用。     

苏尼特羊营养补偿初期钙、磷、氮代谢研究

将45只处于妊娠后期(90～150 d)的苏尼特母羊随机分成4组,以不同的营养水平(ME:0.20、0.33、0.44、0.86MJ·kg-1·W-0.75·d-1)分组饲养,分娩后进行补偿生长试验,研究妊娠后期不同营养限制程度的母羊在补偿初期(分娩后0～6周)对饲料中钙、磷以及氮的代谢规律.结果表明,受限制各组母羊在补偿初期,随着受限程度的降低,钙、磷平衡(g·d-1)值呈升高的趋势,氮平衡(g·d-1)值呈下降的趋势.     

外源NO对Ca(NO3)2胁迫下黄瓜幼苗生长和抗氧化系统的影响

本研究以黄瓜为试材,采用营养液水培,研究了外源NO对Ca(NO3)2胁迫下黄瓜幼苗生长和抗氧化酶系的影响.结果显示,在70mmol·L-1的Ca(NO3)2胁迫下,植株生长受到抑制,干重和叶绿素含量显著下降,叶片和根系抗氧化酶SOD、POD、CAT和APX活性均升高,膜脂过氧化产物MDA及可溶性 蛋白含量增加.而叶面喷施NO供体SNP显著缓解了Ca(NO3)2胁迫对黄瓜幼苗生长的抑制,植株干重显著增加.同时,抗氧化酶活性、可溶性蛋白和叶绿素含量也有不同程度的上升,MDA含量显著下降.以上表明,NO能够增强黄瓜幼苗对Ca(NO3)2胁迫的耐性.喷施SNP对正常营养液培养的黄瓜幼苗无显著影响.     

钙对赭曲霉毒素A(OTA)诱导拟南芥毒性的抑制作用

为丰富赭曲霉毒素A (ochratoxinA,OTA)的植物毒性及其作用机理,探究钙在OTA诱导的植物毒性调控作用机理,本研究采用添加外源Ca2+,钙离子螯合剂乙二醇双(2-氨基乙基醚)四乙酸(ethylenebis(oxyethylenenitrilo) tetraacetic acid,EGTA)及OTA等处理离体拟南芥(Arabidopsis thaliana)叶片,通过形态学观察,叶片相对电导率、活性氧含量(reactive oxygen species,ROS)和丙二醛(malondialdehyde,MDA)含量的测定等研究钙对OTA诱导的拟南芥毒性的影响,结果表明,在一定浓度范围内(0～50 mmol/L),外源Ca2+单独处理,拟南芥叶片形态学无明显变化,EGTA与OTA分别处理均会引起拟南芥叶片失绿、坏死病斑的形成,而Ca2+与OTA共同处理,能显著抑制OTA诱导的拟南芥叶片失绿、坏死病斑的形成,EGTA加剧OTA的毒性作用;OTA处理使拟南芥叶片相对电导率升高,细胞膜通透性增大,外源钙能显著抑制OTA引起的拟南芥叶片相对电导率升高(P＜0.05),20 mmol/L Ca2+的抑制作用最强,抑制率为61.32％.此外,OTA处理使拟南芥叶片细胞ROS的爆发及MDA的积累,对拟南芥造成氧化损伤,钙能显著抑制OTA诱导的拟南芥ROS爆发(P＜0.05),减少MDA的生成,抑制率分别为29.7％和71.4％.研究结果说明OTA能诱导拟南芥的植物毒性,钙能显著抑制OTA诱导的拟南芥植物毒性,钙在拟南芥受外界胁迫中起重要作用.