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.

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.     

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.     

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.     

Thyroid responses to altered photoperiod in the soft-shelled turtle Lissemys punctata punctata bonnoterre

The aim of the current investigation was to investigate the effect of photoperiod on thyroid activity in soft-shelled turtles (Lissemys punctata punctata). Thirty days exposure of short photoperiod with 2L:22D increased relative weight, follicular epithelial height and peroxidase activity of the thyroid gland; whereas exposure of long photoperiod with 22L:2D for 30 days showed reversed changes to those of the short photoperiod in adult female turtles. These findings indicate that short photoperiod stimulates thyroid activity and long photoperiod inhibits its activity in soft-shelled turtles. It is suggested that photoperiod exerts its action on thyroid activity presumably via gonads and/or pineal-gonadal axis in turtles.     

适度放牧增加内蒙古典型草原甲烷氧化菌丰度和甲烷吸收

微生物氧化是大气甲烷唯一的生物汇.认识草原甲烷(CH₄)通量对不同利用方式的响应是制定低碳高效草原管理体系的基础.本研究通过测定内蒙古中部典型草原在放牧、割草和围封管理下生态系统的CH₄通量和土壤甲烷氧化菌丰度,旨在确定不同利用方式对内蒙古典型草原生态系统CH₄吸收的影响,验证甲烷氧化菌功能基因(pmoA)丰度调控CH₄通量.测定草原是连续5年实施4种不同利用处理的试验草原,4个处理为全植物生长季(5—9月)放牧(T₁)、春夏5月和7月放牧(T₂)、秋季割草(T₃)和围封禁牧(T₀).在测定植物生物量和土壤理化特征的基础上,采用静态箱置法测定草原植物生长季CH₄通量,采用分子技术测定草原表层土壤甲烷氧化菌pmoA功能基因的丰度.结果表明: 放牧显著促进CH₄吸收,增加甲烷氧化菌丰度(即每克干土pmoA功能基因拷贝数),其在生长季的变化范围是6.9×10⁴~3.9×10⁵.T₁处理下植物生长季的CH₄平均吸收量为(68.21±3.01) μg·m^-2·h^-1,显著高于T₂、T₃和T₀处理22.1%、37.5%和30.9%.草原CH₄吸收与甲烷氧化菌丰度呈极显著正相关,与土壤砂粒占比呈显著正相关,而与土壤粉粒占比、土壤水分含量、土壤铵态氮和硝态氮含量,以及植物地上生物量呈显著负相关.表明不同利用方式下内蒙古典型草原都是CH₄的汇,而适度放牧可增加草原土壤砂粒占比,降低土壤无机氮含量和植被生物量,提高土壤甲烷氧化菌丰度和CH₄吸收.本结果对制定低排放草原管理体系具有重要意义.     

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.     

Dynamic characteristics of metal element content and return of Casuarina equisetifolia litter at different distances to the coastline

精确估算生态系统内部环境梯度引起的养分循环差异, 对评估其生态功能十分重要。为探讨不同距海生境对木麻黄(Casuarina equisetifolia)凋落叶金属元素含量及养分归还动态的影响, 以福建省惠安赤湖国有防护林场木麻黄凋落叶为研究对象, 按照离海由近及远的顺序设置5个距离(T₁到T₅), 收集凋落叶测定金属元素含量。结果表明: 1)海岸梯度环境对木麻黄凋落叶各元素含量及归还量具有显著影响, 由基干林带向林内元素含量、归还量呈线性规律, 总体上近海高于远海, 按照离海由近及远元素含量逐渐降低, 铁(Fe)、铜(Cu)、锌(Zn)和锰(Mn)在T₄后上升, 归还量变化趋势与含量相似。2)凋落叶元素含量在不同月份存在显著差异, Na、Fe、Cu、Zn具有相似性, 6月、11月存在明显低谷; Mn在2至4月下降后波动上升。归还量总体表现为钠(Na)、Cu相似, 5、8、次年1月出现峰值;Mn、Fe、Zn相似, 5、8、11、次年1月出现峰值。3)土壤Na含量按照离海由近及远逐渐降低, 其他元素波动变化, 各距离之间差异不明显。4)凋落叶Na-Fe含量存在显著正相关关系, Na-Zn、Fe-Cu、Fe-Zn含量存在极显著正相关关系; 土壤与凋落叶相同元素含量间存在正相关关系, Na和Cu达到显著水平。究其原因, 叶片元素含量差异受叶凋落时间差异造成的重吸收差异影响大; 月间差异因植物生命活动对元素需求量存在差异; 归还量差异与凋落叶量及元素含量有关。     

不同海岸距离上木麻黄凋落叶金属元素含量及归还量动态特征

精确估算生态系统内部环境梯度引起的养分循环差异, 对评估其生态功能十分重要。为探讨不同距海生境对木麻黄(Casuarina equisetifolia)凋落叶金属元素含量及养分归还动态的影响, 以福建省惠安赤湖国有防护林场木麻黄凋落叶为研究对象, 按照离海由近及远的顺序设置5个距离(T₁到T₅), 收集凋落叶测定金属元素含量。结果表明: 1)海岸梯度环境对木麻黄凋落叶各元素含量及归还量具有显著影响, 由基干林带向林内元素含量、归还量呈线性规律, 总体上近海高于远海, 按照离海由近及远元素含量逐渐降低, 铁(Fe)、铜(Cu)、锌(Zn)和锰(Mn)在T₄后上升, 归还量变化趋势与含量相似。2)凋落叶元素含量在不同月份存在显著差异, Na、Fe、Cu、Zn具有相似性, 6月、11月存在明显低谷; Mn在2至4月下降后波动上升。归还量总体表现为钠(Na)、Cu相似, 5、8、次年1月出现峰值;Mn、Fe、Zn相似, 5、8、11、次年1月出现峰值。3)土壤Na含量按照离海由近及远逐渐降低, 其他元素波动变化, 各距离之间差异不明显。4)凋落叶Na-Fe含量存在显著正相关关系, Na-Zn、Fe-Cu、Fe-Zn含量存在极显著正相关关系; 土壤与凋落叶相同元素含量间存在正相关关系, Na和Cu达到显著水平。究其原因, 叶片元素含量差异受叶凋落时间差异造成的重吸收差异影响大; 月间差异因植物生命活动对元素需求量存在差异; 归还量差异与凋落叶量及元素含量有关。     

Thyroidal modulation following hypo- and hyper-thermia in the soft-shelled turtle Lissemys punctata punctata Bonnoterre

The aim of the current study was to investigate the effects of ambient temperature on thyroid activity of the soft-shelled turtle (Lissemys punctata pucntata). Turtles exposed to low ambient temperature (10 degrees C for 15 days) showed a significant decrease in relative thyroid weight, follicular cell size (cell became squamous from cuboidal type) and epithelial height in both the peripheral and central follicles of the gland, with the appearance of homogeneous colloid materials in the follicular lumen. Thyroid peroxidase activity declined significantly. In contrast, high ambient temperatures (32/34 degrees C for 15 days) caused reverse changes to those observed after exposure with low ambient temperature. No significant difference was marked in thyroid activity between 32 and 34 degrees C temperature treatments. The findings provide evidence that low ambient temperature inhibits thyroid activity and high ambient temperature stimulates the gland activity in soft-shelled turtles. Ambient temperature acts presumably via the hypothalamo-hypophysial (TRF-TSH) axis which in turn alters thyroid function in turtles.     

外源瘦素注射对昆明和大理地区大绒鼠适应性产热的影响

小型哺乳动物通过产热能力的调整来应对环境的胁迫。为探究外源瘦素对不同地区大绒鼠(Eothenomys miletus)适应性产热的影响,选取云南昆明和大理地区捕获的大绒鼠各14只,置于25℃±1℃,光周期为12L∶12D的环境中,每日腹腔注射瘦素,持续28 d。以LT502电子天平每两天测定大绒鼠的体重,采用食物平衡法每两天测定大绒鼠摄食量,以便携式呼吸代谢测量系统每7天测定静止代谢率(RMR)、非颤抖性产热(NST)。第28天处死动物后,采用酶联免疫吸附法测定线粒体蛋白含量、线粒体细胞色素c氧化酶(COX)活性、解偶联蛋白1(UCP1)含量、血清三碘甲状腺原氨酸(T3)、甲状腺素(T4)、瘦素水平以及促甲状腺激素释放激素(TRH)和促肾上腺皮质激素释放激素(CRH)水平。结果表明,注射瘦素后昆明和大理地区大绒鼠的体重和摄食量显著降低,RMR和NST增强,肝脏中线粒体蛋白含量和COX活性,褐色脂肪组织(BAT)中COX活性和UCP1含量,及血清T3、T4、T3/T4比值、TRH和CRH浓度均增加。瘦素水平与体重、摄食量呈负相关,血清T3水平与NST和UCP1含量呈正相关。此外,注射前昆...     

Effects on temperature on spontaneous and thyroxine-stimulated locomotor activity of Atlantic cod

Spontaneous locomotor activity of cod Gadus morhua maintained at 6° C tripled from February to May. In contrast, locomotor activity of cod held at 2° C was significantly lower than at 6° C (between 25 and 65% lower) and the seasonal increase was smaller. Plasma levels of both thyroxine (T₄) and triiodothyronine (T₃) did not differ between 2 and 6° C. T₄ injection increased locomotor activity by 10% for both temperature regimes. These data indicate that low water temperature reduces locomotor activity associated with migration in cod and that thyroid hormones are not involved in this decrease. This study provides a possible mechanism through which cold waters may affects migration and distribution of cod via its Effects on locomotor activity and swimming speed.     

残次苹果发酵产物对连作土壤环境及‘平邑甜茶’幼苗生长的影响

在盆栽条件下,研究残次苹果发酵产物对连作土壤环境及平邑甜茶幼苗生长的影响,为减轻苹果连作障碍提供理论依据。试验以连作土壤为对照(CK),设置溴甲烷灭菌连作土壤(T₁)、连作土壤施加苹果发酵产物(T₂)、连作土壤施加灭菌苹果发酵产物(T₃)处理,测定了土壤和平邑甜茶幼苗的相关指标。结果表明: T₁、T₂、T₃能显著促进平邑甜茶幼苗的生长,其中以T₁和T₂的效果较好,其根系呼吸速率、株高、地径、鲜质量、干质量分别比CK提高了107.3%、50.6%、42.4%、171.7%、225.3%和104.4%、50.6%、42.3%、171.8%、225.5%。T₂和T₃提高了连作土壤中养分转化相关酶的活性,过氧化氢酶、脲酶、中性磷酸酶和蔗糖酶活性分别比CK提高了44.5%、169.5%、23.4%、169.3%和23.7%、72.6%、1.5%、121.5%;T₁处理的过氧化氢酶和蔗糖酶活性与CK无显著差异,脲酶和中性磷酸酶活性分别降低了40.8%和41.6%。T₂土壤铵态氮、硝态氮、速效磷和速效钾含量分别较CK提高了18.6%、50.6%、14.0%和36.7%;T₃只提高了速效氮的含量,铵态氮和硝态氮含量分别提高了7.0%和23.6%;T₁与CK相比速效养分含量有所降低。T₁和T₂显著降低了土壤放线菌和真菌数量,增加了细菌数量;T₃处理的细菌、放线菌和真菌数量均较CK显著降低。实时荧光定量PCR分析发现,T₁、T₂和T₃处理的层出镰孢菌、串珠镰孢菌、腐皮镰孢菌和尖孢镰孢菌基因拷贝数均较CK有不同程度的降低。表明苹果发酵产物处理能抑制连作土壤病原菌,改善土壤环境,促进平邑甜茶幼苗生长,可作为一种减轻苹果连作障碍的方法。     

Spectroscopic study and G-quadruplex DNA binding affinity of two bioactive papaverine-derived ligands

The interactions of G-quadruplex DNA with two oxidation products of papaverine, 6a,12a-diazadibenzo-[a,g]fluorenylium derivative (1) and 2,3,9,10-tetramethoxy-12-oxo-12H-indolo[2,1-a]isoquinolinium cation (2) were investigated. Their activity against telomerase was assessed using the conventional telomeric repeat amplification protocol (TRAP) assay. Effect of TRAP buffer and oligonucleotide length on the DNA-binding affinity of 1 and 2 were also studied. Three quadruplex-forming oligonucleotides with human telomeric sequence: dG₃(T₂AG₃)₃ (htel21), dAG₃(T₂AG₃)₃ (htel22), and d(T₂AG₃)₄ (htel24) were used in these investigations. Both ligands were capable of interacting with G4 DNA with binding stoichiometry indicating that two ligand molecules bind to G-quadruplex, which agrees with the binding model of end-stacking on terminal G-tetrads. Circular dichroism spectra revealed that preferences of quadruplex-forming oligonucleotide to adopt a particular topological structure may be also affected by the external ligand that binds to quadruplex. Telomerase activity was suppressed at very low ligand 1 and ligand 2 concentrations with an appreciable selectivity comparing with inhibition of Taq polymerase.     

施用污泥等废料对稀土矿废弃地土壤中麻疯树生长和元素吸收的影响

城市污泥等废料可以用于调理稀土矿废弃地土壤,而能源植物麻疯树有望成为稀土矿废弃地的先锋植物。本研究通过向稀土矿废弃地土壤中添加污泥(T₁)、污泥+蔗渣(T₂)、污泥+蔗渣+钝化剂(T₃),并以矿区土壤为对照(CK),研究盆栽条件下各处理对麻疯树生长和元素吸收的影响。结果表明: 与CK相比,T₁仅显著提高麻疯树株高,T₂、T₃显著提高麻疯树株高、地径和生物量,其中总生物量提高184.7%以上;3个处理均显著促进麻疯树对N、P、K、Cu的吸收;T₁、T₂显著提高基质中可交换态Zn、Cd、Ni比例,T₃则相反,并显著降低Zn、Cd、Ni在基质中的迁移系数和活性系数,抑制麻疯树对Zn、Pb、Cd、Ni的吸收,抑制率达36.1%以上。隶属函数综合评价结果表明,各处理对麻疯树生长的促进顺序为T₂>T₃>T₁>CK,对麻疯树吸收Cu、Zn、Pb、Cd、Ni的抑制顺序为T₃>CK>T₂>T₁。混施污泥和蔗渣显著促进麻疯树生长和元素吸收,进一步加入钝化剂则显著抑制麻疯树对重金属的吸收,但不影响麻疯树生长。     

温度驯化对布氏田鼠肝脏温敏瞬时受体电位通道蛋白表达的影响

肝脏是哺乳动物基础代谢产热的关键器官。温敏瞬时受体电位通道蛋白(Thermosensitive transient receptor potential channels,Thermo-TRPs)参与了调控肝细胞的生理功能。为了解Thermo-TRPs是否参与肝脏的代谢产热,以成年布氏田鼠(Lasiopodomys brandtii)为研究对象,测定了不同驯化温度下6种Thermo-TRPs在肝脏中的表达,分析其与肝脏产热相关蛋白和信号通路蛋白的关系。结果显示：(1)与高温组相比,低温增加了肝脏解偶联蛋白1(uncoupling protein 1,UCP1)的表达;而与常温组相比,低温降低了肝脏解偶联蛋白3 (uncoupling protein 3,UCP3)的表达;(2) 6种Thermo-TRPs均在肝脏中表达,与高温组相比,低温显著降低了TRP vanilloid 4 (TRPV4)的表达,同时显著增加了腺苷酸活化蛋白激酶(AMP-activated protein kinase,AMPK)的表达;(3)低温显著增加了布氏田鼠血清三碘甲状腺原氨酸(T₃)...     

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.     

Antogonistic effects of retinoic acid and triiodothyronine in the expression of corticoid-binding globulin (CBG) by cultured fetal hepatocytes

Cultures of rat fetal hepatocytes were used to investigate the effects and interplay of triiodothyronine (T₃) and retinoic acid (RA) in the regulation of gene expression of CBG, compared to that of -fetoprotein (AFP). The cultured cells showed cytological features typical to hepatocytes and actually synthesized CBG and AFP, as evidenced from in situ hybridization with specific radioactive and cell mRNA levels disappeared with a half-life of about 2 days, thereby reflecting the decrease previously seen in hepatic CBG mRNA contents during embryonic life. The K_d values for CBG binding were unchanged under these conditions. Culturing of hepatocytes in the presence of T₃ resulted in dose-dependent stimulations of both medium CBG and cell mRNA levels, with an EC₅₀ concentration of about 10⁻⁹ M. In sharp contrast, RA caused a reduction in CBG biosynthesis (IC₅₀ = 1.7 × 10⁻⁷ M) and, in addition, antagonized the stimulatory influence of T₃. Under the same experimental conditions, AFP synthesis failed to be affected in a similar fashion. We conclude that thyroid hormones and RA directly act on hepatocytes to specifically regulate the expression of CBG in an antagonistic way.     

Seasonal Patterns of Adrenomedullary Hormones and Glycemia in the Soft-Shelled Turtle Lissemys punctata punctata

The aim of the present study was to acertain the seasonal pattern of adrenomedullary hormones and of glycemia in Lissemys turtles. Both the norepinephrine and epinephrine concentrations as well as blood glucose levels varied seasonally which began to rise from February, became maximum during April–May (early summer), declined during June–September (late summer) and were extremely low subsequently (October–January). The seasonal adrenomedullary hormonal and glycemic cycles however do not coincide with the annual ovarian cycle, thereby indicating that the adrenomedullary and glycemic cycles are out of phase with the ovarian cycle in turtles. The possible mechanisms of seasonality of the adrenal medulla and glycemia are discussed.     

模拟增雨对巴里坤湖干涸湖底沉积物CO2通量的影响

明确湖泊沉积物碳过程对气候变化的响应,是全面了解湖泊生态系统碳收支的重要环节.为探究未来降雨增加对沉积物碳通量的影响,本研究以新疆哈密巴里坤盐湖干涸湖底原状沉积物为对象,基于1960年以来新疆哈密地区降雨量增加速率(4mm.10a-1)以及植物生长季多年降雨量分布特征,以2016年生长季(5-10月)降雨量(86 mm...