Influence of Hyperthyroidism on Superoxide Radical and Hydrogen Peroxide Production by Rat Liver Submitochondrial Particles

Administration of daily doses of 0.1 mg of 3, 5, 3'-triiodothyronine (T₃)/kg body weight for 3 consecutive days to fed rats elicited a calorigenic response in the animals, in concomitance with a 36% increase in the rate of O₂ consumption by the liver. In these conditions, liver submitochondrial particles (SMP) from T₃-treated rats exhibited marked increases in the rate of superoxide radical generation, both in the presence of NADH (142%) or succinate (152%). Furthermore, liver SMP from hyperthyroid animals released hydrogen peroxide at higher rates than those of euthyroid rats, either under basal conditions or in the succinate-supported process, both in the absence and presence of antimycin-A. It is concluded that the hyperthyroid state in the rat leads to a drastic enhancement in the capacity of liver mitochondria to produce active oxygen species, which correlates with the elevated respiratory rate observed in the intact organ.     

Kupffer Cell Function in Thyroid Hormone-Induced Liver Oxidative Stress in the Rat

The influence of thyroid hormone (L-3, 3', 5-triiodothyronine, T₃) on Kupffer cell function was studied in the isolated perfused rat liver by colloidal carbon infusion. Rates of carbon uptake were determined from the influent minus effluent concentration difference and the flow rate, and the respective carbon-induced respiratory activity was calculated by integration of the area under the O₂ curves during carbon infusion. In the concentration range of 0.2 to 2.0 mg of carbon/ml, livers from euthyroid rats exhibited a sigmoidal-type kinetics of carbon uptake, with a Vmax of 4.8 mg/g liver/min and a concentration of 0.82 mg/ml for half-maximal rate; carbon-induced O₂ uptake presented a hyperbolic-type kinetics, with a Vmax of 4.57 μmol of O₂/g liver and a Km of 0.74 mg of carbon/ml, which significantly correlates with the carbon uptake rates. Light-microscopy showed that carbon was taken up exclusively by non-parenchymal cells, predominantly by Kupffer cells. Thyroid calorigenesis was found in parallel with increased rates of hepatic O₂ consumption and thiobarbituric acid reactive substances (TBARS) formation, glutathione (GSH) depletion, and higher sinusoidal lactate dehydrogenase (LDH) efflux compared to control values. In the concentration range of 0.25 to 0.75 mg/ml, carbon infusion did not modify liver LDH efflux in control rats, while it was significantly enhanced in T₃-treated animals. In this latter group, higher carbon concentrations (1 and 1.3 mg/ml) led to loss of viability of the liver. At 0.25 to 0.75 mg of carbon/ml, both the rates of carbon uptake and the associated carbon-induced respiratory activities were significantly increased by T₃ treatment, effects that were abolished by pretreatment of the rats with gadolinium chloride (GdCl₃). In addition, GdCl₃ decreased by 50% the changes induced by T₃ in hepatic GSH content and TBARS formation. It is concluded that hyperthyroidism enhances Kupffer cell function, correlated with the increased number of liver macrophages observed histologically, which may represent an alternate source of reactive O₂ species to that induced in parenchymal cells, thus contributing to the enhanced oxidative stress status developed.     

Induction of NADP-dependent malic dehydrogenase activity in brain of singi fish, heteropneustes fossilis (bloch), by 3,5,3′-triiodothyronine

For elucidation of thyroid hormone-induced responsiveness of fish brain, various doses (0.012, 0.025, 0.05, 0.1, 0.25, 0.5, 1, 2 and 4 μg/g) of triiodothyronine (T₃) were injected in Singi fish, Heteropneustes fossilis (Bloch), for 3 consecutive days and the changes in cytosolic NADP-dependent malic enzyme (ME, EC 1.1.1.40) activity in whole brain tissue were determined. Compared to the control, the ME activity increased with lower doses (0.012, 0.025 and 0.05 μg/g) and decreased with higher doses (1, 2 and 4 μg/g) of T₃, showing a biphasic nature of thyroid hormone action. The enzyme activity remained unaltered with 0.1, 0.25 and 0.5 μg of T₃/g in comparison to the control. Immersion of the fishes in cycloheximide-containing medium (0.5 mg/l) inhibited the T₃ (0.025 μg/g)-induced rise in ME activity. On the other hand, the NAD-dependent cytosolic malate dehydrogenase (EC 1.1.1.37) activity and the total protein content of brain cytosol remained unaltered with all doses of T₃ used. The thyroid hormone specificity of cytosolic NADP-dependent malic enzyme in fish brain is thus documented.     

Interaction of thyroid hormone and steroidogenic acute regulatory (StAR) protein in the regulation of murine Leydig cell steroidogenesis

The steroidogenic acute regulatory (StAR) protein, a novel phosphoprotein, is a crucial factor involved in intramitochondrial cholesterol transportation, the rate-limiting step in steroidogenesis. The present investigations were undertaken to elucidate involvement of thyroid hormone and StAR protein in the regulation of steroidogenesis in mouse Leydig cells. Treatment of cells with triiodothyronine (T₃) coordinately augmented the levels of StAR protein, StAR mRNA, and steroid production, and these responses were progressively dependent on expression of steroidogenic factor 1 (SF-1). With regard to steroidogenesis and StAR expression, the T₃ response requires both on-going mRNA and protein synthesis. In addition, the effects of T₃ were acutely modulated at the steroidogenic machinery and luteinizing hormone receptor (LHR) function, while these levels were suppressed following longer periods of exposure to T₃. Furthermore, the inhibition of SF-1 expression by DAX-1 markedly abolished T₃-mediated StAR expression in a time frame, which was consistent with decreased steroid biosynthesis. Specific involvement of SF-1 was further confirmed by assessing the 5′-flanking region of the mouse StAR gene, which identified a region between −254 and −110 bp that was essential for T₃ function. Importantly, it was found that the SF-1 binding site at position −135 bp of the 5′-flanking region was greatly involved in T₃-mediated reporter activity. Electrophoretic mobility shift assays (EMSA) also demonstrated involvement of SF-1 in T₃ function. The relevance of T₃-mediated LHR function was investigated in mice rendered hypo-and hyperthyroid, which accounted for up-regulation in the former and down-regulation in the latter group, respectively. These findings demonstrate a key role of thyroid hormone in maintaining mouse Leydig cell function, where thyroid hormone and StAR protein coordinately regulate steroid hormone biosynthesis.     

Studies on the protective role of vitamin C and E against polychlorinated biphenyl (Aroclor 1254)--induced oxidative damage in Leydig cells

Free radical production and lipid peroxidation are potentially important mediators in testicular physiology and toxicology. Polychlorinated biphenyls (PCBs) are global environmental contaminants that cause disruption of the endocrine system in human and animals. The present study was conducted to elucidate the protective role of vitamin C and E against Aroclor 1254-induced changes in Leydig cell steroidogenesis and antioxidant system. Adult male rats were dosed for 30 days with daily intraperitoneal (ip) injection of 2 mg/kg Aroclor or vehicle (corn oil). One group of rats was treated with vitamin C (100 mg/kg bw/day) while the other group was treated with vitamin E (50 mg/kg bw/day) orally, simultaneously with Aroclor 1254 for 30 days. One day after the last treatment, animals were euthanized and blood was collected for the assay of serum hormones such as luteinizing hormone (LH), thyroid stimulating hormone (TSH), prolactin (PRL), triiodothyronine (T₃), thyroxine (T₄), testosterone and estradiol. Testes were quickly removed and Leydig cells were isolated in aseptic condition. Purity of Leydig cells was determined by 3β-hydroxysteroid dehydrogenase (3β-HSD) staining method. Purified Leydig cells were used for quantification of cell surface LH receptors and steroidogenic enzymes such as cytochrome P₄₅₀ side chain cleavage enzyme (P₄₅₀scc), 3β-hydroxysteroid dehydrogenase (3β-HSD) and 17β-hydroxysteroid dehydrogenase (17β- HSD). Leydig cellular enzymatic antioxidants superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), γ-glutamyl transpeptidase (γ-GT), glutathione-S-transferase (GST) and non-enzymatic antioxidants such as vitamin C and E were assayed. Lipid peroxidation (LPO) and reactive oxygen species (ROS) were also estimated in Leydig cells. Aroclor 1254 treatment significantly reduced the serum LH, TSH, PRL, T₃, T₄, testosterone and estradiol. In addition to this, Leydig cell surface LH receptors, activities of the steroidogenic enzymes such as cytochrome P₄₅₀scc, 3β-HSD, 17β-HSD, antioxidant enzymes SOD, CAT, GPX, GR, γ-GT, GST and non-enzymatic antioxidants such as vitamin C and E were significantly diminished whereas, LPO and ROS were markedly elevated. However, the simultaneous administration of vitamin C and E in Aroclor 1254 exposed rats resulted a significant restoration of all the above-mentioned parameters to the control level. These observations suggest that vitamin C and E have ameliorative role against adverse effects of PCB on Leydig cell steroidogenesis.     

Metabolic effects of thyroid hormones at a low temperature in the snake

1. 1.|The metabolic role of the thyroid gland was studied in intact snakes, Naja naja and Ptyas korros treated with tri-iodo-thyronine (T₃) and thyroxine (T₄) and in thyroidectomized (Tx) N. naja kept at 21°C by analyzing tissue composition and glycogen phosphorylase a activity.

2. 2.|Liver weight was unaffected by thyroid hormone injection in both species but decreases in liver glycogen followed T₃ or T₄ injection, and there was an increase in liver glycogen in N. naja. These changes in liver glycogen were accompanied by a decrease in glycogen phosphorylase a activity with T₃ injection. T₃ decreased muscle glycogen in Ptyas and Tx increased it in N. naja.

3. 3.|T₃ increased % liver lipid in Ptyas but not in Naja.

4. 4.|Between species, there were differences in liver weight, blood glucose level, cholesterol level and % muscle lipid.

5. 5.|The results showed that thyroid hormones affected carbohydrate and lipid metabolism at a low temperature of 21°C, although the significance is not known.

Estrogen antagonism on T3 and growth hormone control of the liver microsomal low-affinity glucocorticoid binding site (LAGS)

Male rat liver microsomes contain a low-affinity glucocorticoid binding site (LAGS) capable of binding all natural glucocorticoids and progesterone with a K_d from 20 to 100 nM. The LAGS level is under endocrine control by T₃, glucocorticoids and GH. These hormones act synergistically at physiological concentrations to increase the LAGS level. Since female rats show a LAGS level that is much lower than the males (0.15 vs 23 pmol/mg protein, respectively), here we investigated whether estradiol could decrease the LAGS in the male rat. Orchiectomized (OX) male rats showed a higher LAGS level than intact rats. This effect was reversed by implanting a Sylastic capsule containing testosterone. When the OX rats were implanted for 20 days with estrogen capsules that provided an estradiol level in serum of 40 pg/ml, their LAGS level decreased from 23 to 0.2 pmol/mg protein. This effect was not observed in intact male rats and can be partially reversed by testosterone implants into OX rats. Both hypophysectomized male rats and hypothyroid-orchiectomized male rats showed very low levels of LAGS. Administration of physiological doses of GH and/or T₃ to these rats greatly increased their LAGS level (from 0.3 to 15 and 16 pmol/mg protein, respectively). Implantation of estrogen capsules to these rats two weeks prior to starting treatment completely inhibited the increase in the LAGS level in response to T₃, and significantly decreased the response to hGH, and to a combination of hGH and T₃. These results suggest that physiological estradiol levels can antagonize the LAGS induction by T₃ and hGH in the male rat, and could be responsible for the low level of LAGS in the female rat. Moreover, estrogen capsules also inhibited the increase in the body and hepatic weights observed after hGH treatment, which suggests a powerful inhibitory effect of low estradiol levels on the male rat liver functions under regulation by T₃ and/or GH.     

Measurement of whole blood phagocyte chemiluminescence in the Wistar rat

The factors influencing the rat whole blood chemiluminescence (CL): concentrations of blood, luminol, zymosan or opsonized zymosan, volume of the reaction mixture, storage time of blood samples and the presence of anticoagulants were evaluated. The CL micromethod described provides a fast and sensitive tool for the determination of metabolic activity of phagocytes in the microlitre range of rat whole blood. © 1997 John Wiley & Sons, Ltd.     

Nyctohemeral Rhythms of Gonadal, Thyroid and Pineal Function in the Hyperprolactinemic Male Rat

In young adult male rats bearing a donor anterior pituitary gland grafted for 3 weeks under a kidney capsule, serum prolactin (PRL) concentrations were elevated and exhibited a rhythm with the highest values in the light phase. Serum PRL in control animals did not exhibit a significant rhythm. Eutopic pituitary PRL content, manifesting a biphasic (12-hr) rhythm with crests during the day and night in controls, exhibited a similar pattern in grafted rats though an overall reduction in pituitary PRL content was seen in the grafted animals. Neither the normal biphasic serum testosterone rhythm nor the normal 24-hr rhythm (nocturnal surge) of pineal N-acetyltransferase activity and melatonin content were altered in the hyperprolactinemic rats. Serum thyroxine (T₄) and triiodothyronine (T₃) and their free indices (FT₄ I, FT₃ I) and serum thyrotropin (TSH) were highest during the day in controls and grafted rats and a 12-hr rhythmic component was detected in data for these variables. In the grafted animals, the 12-hr component was reflected in an additional peak at night detectable by testing of means. The overall serum T₄ FT₄ I, and TSH levels were lower in grafted rats though overall T₃ and FT₃I levels did not differ between grafted and controls. T₃ uptake (T₃ U) values were similar between controls and grafted rats, in both cases exhibiting a fall during the night. Changes in serum thyronines could not be explained by changes in serum binding as assessed by the T₃U₃ and thus may represent changes in thyroidal secretion of T₄. The rhythm in serum PRL of grafted rats suggests the presence of rhythmic circulating factor(s) capable of influencing ectopic lactotrophs. The reduced eutopic pituitary PRL content suggests a role for PRL in influencing eutopic lactotrophs in the pituitary-grafted hyperprolactinemic male rat model. Though circulating testosterone and pineal melatonin synthesis were not altered in this model, thyroid function appeared to be so.     

Annona squamosa seed extract in the regulation of hyperthyroidism and lipid-peroxidation in mice: Possible involvement of quercetin

Annona squamosa (Custard apple) seeds are generally thrown away as waste materials. The extract of these seeds was evaluated for its possible ameliorative effect in the regulation of hyperthyroidism in mouse model. Serum triiodothyronine (T₃), thyroxine (T₄) concentrations, hepatic glucose-6-phospatase (G-6-Pase) and 5′-mono-deiodinase (5′DI) activity were considered as the end parameters of thyroid function. Simultaneously hepatic lipid peroxidation (LPO), superoxide dismutase (SOD) and catalase (CAT) activities were investigated to observe its hepatotoxic effect, if any.

L-T₄ administration (0.5 mg/kg/d for 12 days, i.p.) increased the levels of serum T₃ and T₄, activity of hepatic G-6-Pase, 5′DI and LPO with a parallel decrease in SOD and CAT activities. However, simultaneous administration of the Annona seed extract (200 mg/kg) or quercetin (10 mg/kg) to T₄-induced hyperthyroid animals for 10 days, reversed all these effects indicating their potential in the regulation of hyperthyroidism. Further, the seed extract did not increase, but decreased the hepatic LPO suggesting its safe and antiperoxidative nature. Quercetin also decreased hepatic LPO. When relative efficacy was compared with that of propyl thiouracil (PTU), a standard antithyroidic drug, experimental seed extract appeared to be more effective. Phytochemical analyses including HPLC revealed the presence of quercetin in the seed extract and the results on the effects of quercetin suggested the involvement of this phytochemical in the mediation of antithyroidal activity of Annona squamosa seed extract.     

不同带长微喷带灌溉对麦田土壤水分分布和干物质积累及籽粒产量的影响

为了研究麦田用微喷带灌溉的适宜带长,2015—2016和2016—2017两年度以‘济麦22’为材料,设置了带宽80 mm微喷带下带长为60 m (T₁)、80 m (T₂)和100 m (T₃) 3个处理的试验,试验小区长度等于带长,试验小区内沿灌溉方向每20 m为一个取样区段,依次命名为A、B、C、D、E,分析不同带长微喷带灌溉对麦田土壤水分和干物质积累的影响.结果表明:1)两年度不同处理A区段拔节期、开花期灌水后0~40 cm土层土壤相对含水量为T₁23,B区段为T₁、T₂3,C区段为T₁>T₂、T₃,D区段为T₂>T₃;各处理区段间土壤相对含水量的变异系数为T₁23.2)不同处理A、B区段小麦开花后20、30 d的叶面积指数和冠层光截获率、开花后干物质积累量、成熟期干物质积累量均无显著差异,C区段上述指标为T₁>T₂、T₃,D区段为T₂>T₃;不同处理开花后20、30 d叶面积指数、冠层光截获率及开花后干物质积累量为T₁>T₂>T₃,成熟期干物质积累量为T₁、T₂>T₃.3)不同处理A、B区段籽粒产量均无显著差异,C区段为T₁>T₂、T₃,D区段为T₂>T₃,整畦籽粒产量为T₁、T₂>T₃.4)两年度不同处理籽粒产量、水分利用效率为T₁、T₂>T₃,灌溉水利用效率为T₁>T₂>T₃.综合考虑籽粒产量和水分利用效率,本试验条件下带宽80 mm、带长60 m的处理(T₁)是节水高产的最优处理,带长为80 m的处理(T₂)是较优处理.研究结果可为山东省小麦利用微喷带进行节水高产灌溉提供理论依据.     

不同水肥一体化方式对苹果氮素吸收利用特性及产量和品质的影响

以‘嘎啦/八棱海棠’为试材,借助¹⁵N同位素示踪技术,研究了撒施(T₁)、滴灌施氮(T₂)和渗灌施氮(T₃)对嘎啦苹果氮素吸收利用、分配特性和产量品质的影响,以期进一步完善苹果园水肥一体化技术,挖掘提高氮素利用率的途径。结果表明: T₃处理苹果叶片的叶面积、叶绿素和氮含量显著高于T₁和T₂处理。各时期土壤矿化氮(N_min)含量在20~40 cm土层表现为T₃＞T₂＞T₁处理,在0~20 cm土层表现为T₂＞T₃＞T₁处理。同一器官的Ndff值(树体各器官从肥料中吸收到的¹⁵N占该器官全氮量的比例)在各时期均以T₃处理最高,T₂其次,T₁处理最低。果实成熟期的树体¹⁵N利用率表现为T₃＞T₂＞T₁处理,其中T₃处理的树体¹⁵N利用率为24.2%,分别是T₂和T₁处理的1.19和1.65倍。果实成熟期T₁处理的¹⁵N分配率在营养器官最高,T₂处理在贮藏器官最高,T₃处理在生殖器官最高。各处理的单果重、产量、可溶性固形物、硬度、可溶性糖及糖酸比均以T₃处理最高,T₂其次,T₁处理最低。渗灌施氮处理显著促进了嘎啦苹果树体叶片生长和氮素利用,并提高了果实产量和品质。     

有机肥对设施番茄周年栽培土壤环境和产量的影响

日光温室早春茬-秋冬茬连作栽培番茄是我国北方设施蔬菜周年栽培的主要种植模式之一。以该种植模式下农户习惯施肥量为对照(CK,100%化肥),设15%(T₁)、30%(T₂)、45%(T₃)、60%(T₄)、75%(T₅)、100%有机肥替代化肥(T₆)处理,探讨有机肥替代部分化肥对土壤环境和番茄产量的影响。结果表明: 土壤细菌数量随有机肥用量的增加总体呈现上升趋势;放线菌数量以T₁处理最多,为12.12×10⁶ cfu·g^-1。有机肥替代部分化肥可提高土壤脲酶活性,降低过氧化氢酶活性,提高土壤有机质、速效磷和速效钾含量,说明有机肥对改善设施土壤理化性质、促进养分积累具有显著效果。其中,T₁处理蔗糖酶活性和速效磷含量最高,分别为1.36 mg·^-1、305.4 mg·kg^-1,T₂处理的速效钾含量最高,为582.6 mg·kg^-1。T₂处理>0.25 mm水稳性团聚体含量最大,为94.2%。各有机肥处理可改善番茄果实品质,提高产量,其中,T₁处理番茄红素含量最高,达5.69,糖酸比以T₁和T₂处理最好,分别为8.19、8.70;产量以T₁处理最高,T₂处理次之,较CK分别增产16.6%、5.8%。综上,农户习惯施肥量中15%~30%的化肥用有机肥替代为该种植模式下较佳的施肥措施。     

微喷带长宽对不同区段麦田水分和小麦旗叶叶绿素荧光特性的影响

2014—2015和2015—2016年小麦生长季,设置微喷带长宽组合处理:带宽65 mm下设置带长60 m (T₁)、80 m (T₂)和100 m (T₃)处理,带宽80 mm下设置带长60 m (T₄)、80 m (T₅)和100 m (T₆)处理,研究不同组合对麦畦各区段(沿微喷带铺设方向分为D₁至D₆)水分和旗叶叶绿素荧光特性的影响.结果表明: 拔节期灌溉,带宽65 mm下喷洒均匀系数为T₁>T₂、T₃,带宽80 mm下为T₄、T₅>T₆;开花期灌溉,带宽65 mm下为T₁>T₂>T₃,带宽80 mm下为T₄>T₅>T₆.65 mm带宽下,T₁开花期灌溉后各区段0～40 cm土层平均土壤相对含水量,以及花后20和30 d旗叶实际光化学效率(Φ_PSII)、非光化学猝灭系数(NPQ)、电子传递效率(ETR)和籽粒产量均无显著差异;T₂为D₁、D₂>D₃>D₄>D₅;T₃为D₁、D₂>D₃>D₄>D₅、D₆.各区段花后20和30 d旗叶Φ_PSII、NPQ、ETR以及成熟期各区段干物质积累量为T₁>T₂、T₃.80 mm带宽下,T₄开花期灌溉后各区段0～40 cm土层平均土壤相对含水量,以及花后20和30 d旗叶Φ_PSII、NPQ、ETR和籽粒产量无显著差异,T₅为D₁、D₂、D₃>D₄、D₅;T₆为D₁、D₂、D₃>D₄>D₅>D₆.各区段花后20和30 d旗叶Φ_PSII、NPQ、ETR以及成熟期各区段干物质积累量为T₄、T₅>T₆.籽粒产量和水分利用效率为T₁、T₄、T₅>T₂、T₃、T₆,灌溉效益T₁、T₄优于T₅处理.本试验条件下,带宽65 mm下T₁和带宽80 mm下T₄为节水高产的最优处理,T₅为较优处理.     

不同冬季覆盖作物对稻田甲烷和氧化亚氮排放的影响

采用静态箱-气相色谱法对不同冬季覆盖作物处理［免耕直播黑麦草-双季稻(T₁)、免耕直播紫云英 双季稻(T₂)、翻耕移栽油菜-双季稻(T₃)、免耕直播油菜-双季稻(T₄)和冬闲-双季稻(CK)］下稻田甲烷（CH₄）和氧化亚氮（N₂O）排放进行观测,分析了不同冬季覆盖作物对稻田CH₄和N₂O排放的影响.结果表明：在冬季作物生长期,不同冬季覆盖作物稻田CH₄和N₂O总排放量与对照（CK）的差异均达到极显著水平（P<0.01）;T₃和T₁处理的稻田CH₄和N₂O排放量最高,其CH₄排放量分别为0.88 和0.60g·m^-2,N₂O排放量分别为0.23 和0.20 g·m^-2;冬季作物还田后,各处理早、晚稻田CH4排放量均明显高于对照.早稻田CH₄排放量最高的为T₁和T₂处理,分别达21.70和20.75 g·m^-2;晚稻田CH₄排放量最高的为T₃和T₄处理,分别为58.90和54.51 g·m^-2.各处理早、晚稻田N₂O总排放量均显著高于对照,T₁、T₂、T₃和T₄处理的早稻田N₂O总排放量分别比对照增加53.7%、12.2%、46.3%和29.3%,晚稻田分别比对照增加28.6%、3.8%、34.3%和27.6%.     

钨酸钠对苹果幼苗15N吸收利用、13C积累及果实品质的影响

分别以1年生苹果砧木M9T337幼苗和5年生烟富3/SH6/平邑甜茶为试材,开展盆栽和田间试验,并结合¹⁵N、¹³C同位素示踪技术,研究不同浓度(0、0.5、1、1.5 mmol·L^-1,分别用CK、T₁、T₂和T₃表示)硝酸还原酶(NR)抑制剂钨酸钠对苹果幼苗¹⁵N吸收利用、¹³C积累和成熟期果实品质的影响。结果表明: 盆栽试验中,喷施0.5~1.0 mmol·L^-1钨酸钠可显著抑制幼苗地上部生长,但对根系生长影响不显著;当钨酸钠浓度达到1.5 mmol·L^-1时可显著抑制根系生长。同一时期各处理叶片NR活性与钨酸钠浓度呈负相关,均表现为CK>T₁>T₂>T₃。随处理时间的延长,叶片硝态氮含量总体表现为先升高后降低的趋势,同一时期各处理硝态氮含量与钨酸钠浓度呈正相关,均表现为T₃>T₂>T₁>CK。喷施钨酸钠可不同程度地降低幼苗各器官¹⁵N吸收量和¹⁵N利用率,且钨酸钠浓度越高,抑制幼苗氮素吸收和利用的效果越显著。随钨酸钠浓度的提高,地上部¹³C积累量呈先升高后降低的趋势,在T₂处理时达到最高;幼苗整株¹³C积累量呈相似的规律。田间试验结果表明,喷施钨酸钠可降低成熟期叶片和果实的氮含量,果皮花青苷含量、果实可溶性固形物、可溶性糖含量和糖酸比均不同程度提高,其中T₂处理的效果最好。综上,T₂处理(1.0 mmol·L^-1钨酸钠)可有效抑制幼苗地上部生长,降低¹⁵N吸收利用,提高¹³C积累,有利于果实品质的提高。     

Seasonal Thyroid Cycle of the Soft-shelled Turtle, Lissemys p. punctata (Bonnoterre)

The current study was undertaken to ascertain the seasonal influence of thyroid activity in female soft-shelled turtles, Lissemys p. punctata. Thyroid gland was studied month-wise throughout the year from relative gland weight, histology, epithelial height, glandular peroxidase activity, and RIA of T₃ and T₄ levels from blood serum and the thyroid gland. The values of all the parameters, except those of T₃ and T₄, were higher during March through May, decreased from June through August and began to rise thereafter (September through February). Whereas T₃ and T₄ levels were highest in May, lower during June to November and began to rise thereafter. The difference in the peaks between T₃ and T₄ levels and other parameters have been explained. The findings suggest that thyroid activity of Lissemys turtles varies seasonally and that seasonal factors like temperature play an important role in influencing thyroid activity in soft-shelled turtles.     

有机氮替代无机氮对旱作全膜双垄沟播玉米产量和水氮利用效率的影响

为了促进黄土高原西部半干旱区水氮高效利用和农业的可持续性生产,探索适宜的有机氮替代无机氮水平,于2016—2018年在甘肃农业大学旱作农业综合实验站进行了3年的大田试验,设置了6个处理:单施化学氮肥不施有机肥(T₁)、有机肥50%替代化学氮肥(T₂)、有机肥37.5%替代化学氮肥(T₃)、有机肥25%替代化学氮肥(T₄)、有机肥12.5%替代化学氮肥(T₅)和不施氮肥对照(CK),研究了有机氮替代无机氮对全膜双垄沟播玉米种植系统产量、经济效益、水氮利用效率的影响.结果表明: 氮肥施用显著增加了玉米产量和水氮利用效率.在200 kg·hm^-2施氮水平下,有机肥氮替代处理在干旱年份表现出明显的增产增效作用;而在丰水年,有机氮替代无机氮处理籽粒产量、水氮利用效率与对照无显著差异.总体来说,与单施化肥相比,50%和37.5%替代处理籽粒产量分别增加15.6%和18.2%,收获指数分别增加35.1%和27.0%;水分利用效率、降水利用效率、氮肥农学利用效率和偏生产力分别增加17.4%、15.7%、15.6%、155.2%和22.3%、17.7%、18.0%、179.3%.表明在相等的总氮量投入下,50%和37.5%是该地区全膜双垄沟播玉米有机氮替代无机氮的适宜水平,建议在生产中推广应用.     

不同水肥耦合下双季稻氮磷吸收、利用与流失差异

为优化双季稻水肥管理措施,在福建省东部双季稻区设置田间径流小区试验,研究了T₀(对照,未施肥+常规灌溉)、T₁[习惯施肥(273 kg N·hm^-2, 59 kg P·hm^-2, 112 kg K·hm^-2)+常规灌溉]、T₂[优化施肥(240 kg N·hm^-2, 52 kg P·hm^-2, 198 kg K·hm^-2)+常规灌溉]和T₃(优化施肥+节水灌溉)4种水肥耦合处理下双季稻产量、养分吸收利用及田面水氮、磷流失变化。结果表明: 与T₀相比,T₁、T₂和T₃处理早稻稻谷产量显著提高了0.7、1.0和1.1倍,晚稻稻谷产量显著提高了0.9、1.1和1.0倍;T₁、T₂和T₃处理早、晚稻植株地上部分,尤其稻谷氮、磷吸收量增加显著,早稻稻谷氮吸收量分别增加1.1、1.2和1.2倍,磷吸收量增加0.9、1.4和1.6倍,晚稻稻谷氮吸收量增加0.8、1.0和1.0倍,磷吸收量增加0.7、0.9和0.9倍。T₃比T₁处理早稻氮、磷肥农学利用率分别显著增加71.1%和69.2%,晚稻分别显著增加26.4%和25.0%,但田面水可溶性总氮流失量减少了16.0%,并以硝态氮流失为主;T₂与T₃处理早晚稻氮、磷肥农学利用率差异均不显著。本试验中的优化水肥管理措施(T₃)既能促进水稻氮、磷吸收利用,提高双季稻产量,又能降低早稻田面水氮素尤其是硝态氮的流失。本研究可为福建省东部双季稻区水肥利用管理和氮、磷面源污染防治提供理论支持。     

污泥堆肥对黄梁木幼苗生长和元素吸收的影响

污泥含有丰富的有机质和植物所需的营养元素,将污泥堆肥后用作苗木栽培基质逐渐成为新型的污泥生态化处置途径.通过7个月的盆栽试验,研究污泥堆肥不同添加量,即0%(CK)、25%(T₁)、50%(T₂)、75%(T₃)、100%(T₄)对黄粱木幼苗生长及营养元素和重金属吸收的影响,以及栽培后基质中元素变化特征.结果表明: 污泥堆肥添加量对黄梁木生长有显著影响,纯污泥(T₄)中黄梁木苗木不能正常生长,移栽两周后植株全部死亡,而T₁、T₂和T₃处理则显著增加了黄梁木株高、地径和总生物量,其中,T₂处理效果最佳,3个生长指标均显著高于其他处理;T₂、T₃处理显著促进黄梁木对N、P、K以及重金属(Cu、 Zn、Pb、Cd)的吸收,而T₁处理仅对N和Pb吸收有显著促进作用;同一处理条件下,黄梁木对污泥堆肥重金属吸收能力表现为Zn>Cu>Pb>Cd.盆栽试验结束时,污泥混合基质中有机质,以及N、P、K含量较高,但仍残留一定量重金属,不过均低于农用污泥污染物控制标准,具有再次利用的价值.