大鼠心脏血压超负荷诱导左心室HSP70基因表达

本工作应用热休克蛋白７０（ＨＳＰ７０）核酸分子杂交方法,测定了大鼠腹主动脉缩窄后左心室ＨＳＰ７０ｍＲＮＡ的水平。结果表明：大鼠腹主动脉缩窄后４ｈ,动脉血压已明显升高,并持续在高水平上;大鼠左心室重／体重比在第三天开始增加,然后持续升高,第４周时比对照组增加５９％;左心室ＨＳＰ７０ｍＲＮＡ在腹主动脉缩窄后４ｈ已明显升高,１ｄ,２ｄ,１ｗ均维持在高水平,１ｗ后逐渐消失。实验结果提示：大鼠心肌负荷增加早期,左心室ＨＳＰ７０ｍＲＮＡ表达明显增加。     

Volatile anesthetics inhibit NMDA-stimulated45Ca uptake by rat brain microvesicles

We have previously shown that volatile anesthetics inhibit glutamate-stimulated [³H]MK-801 binding to the ionophore of NMDA receptor complexes in rat brain. In the present study, we examined the influence of enflurane and halothane on NMDA-stimulated⁴⁵Ca uptake by a microvesicle fraction isolated from rat brain. NMDA stimulated⁴⁵Ca uptake (30 sec) by rat brain microvesicles by up to 70% with an EC₅₀ of 1.4±0.5 M. The NMDA-stimulated⁴⁵Ca uptake was inhibited by MK-801 and D-AP-5 with IC₅₀'s of 10 M. Enflurane and halothane inhibited⁴⁵Ca uptake stimulated by 100 M NMDA by as much as 60–80% with IC₅₀'s of 0.2–0.3 mM, concentrations achieved during routine clinical use. Basal⁴⁵Ca uptake measured in the absence of agonist was not affected by the anesthetics. Glycine did not affect the level of NMDA-stimulated⁴⁵Ca uptake, but markedly reduced the inhibition of uptake caused by enflurane and halothane. Preincubation of microvesicles with NMDA resulted in a desensitization of NMDA-stimulated⁴⁵Ca uptake, with a t_1/2 of 20 sec. Enflurane and halothane diminished both the extent and rate of development of this desensitization, as did glycine. These findings support the idea that volatile anesthetic interference with neurotransmission at NMDA receptor complexes contributes to the development of the anesthetic state.     

Interactions between size and temperature influence fecundity and longevity of a tortricid moth,Zeiraphera canadensis

Females of Zeiraphera canadensis Mut. & Free., the spruce bud moth, were reared in the laboratory at constant and alternating temperatures, and in an outdoor insectary, to (1) determine the effects of temperature, age and size on several reproductive parameters and, (2) to test the hypothesis that body size-temperature interactions influence longevity and realized fecundity. Egg maturation was linearly related to age and large moths developed eggs at a higher rate than small ones. Mcan lifetime oviposition rate reached a maximum and remained stable at temperatures 20° C while the mean lifetime rate of egg maturation increased linearly with temperature, indicating that higher temperatures adversely affect oviposition. The production of nonviable eggs increased with age but also with temperature, suggesting high temperature (25° C) reduces egg quality and/or hinders fertilization. The realized fecundity and longevity of females reared under an alternating temperature regime (mean 20° C) was significantly less than that of females reared at constant 20° C. Similar realized fecundity, longevity and mean lifetime oviposition rates for females reared at temperatures alternating between 10 and 25° C (mean 20° C) and those at constant 25° C reflected the inability of females to recover from elevated diurnal temperatures. Longevity was positively related to female body size at constant 15 and 20° C but the relationships were negative for moths exposed to diurnal temperatures equal to or exceeding 25° C. Due to the reduced longevity of large moths at high temperatures, linear regressions between size and realized fecundity were only significant at constant temperatures 20° C. At higher temperatures, the size-fecundity relationship became curvilinear as a result of the diminished reproductive output of large individuals. Reduced fecundity and longevity of large females at high temperatures may have been due to elevated internal temperatures of large-bodied moths. Large females in a controlled-environment chamber maintained at 25° C developed an internal temperature excess (i.e. temperature above ambient) of nearly 2° C while small-bodied females exceeded ambient by only 0.3° C. However, when held at 20° C, the temperature excess of large-bodied moths was much less than 1° C and small-bodied females did not differ from ambient. Such interactions between temperature and body size suggest that there should be stabilizing selection toward moderate-sized individuals and may explain the absence of size-related effects on fecundity and longevity previously reported for several other lepidopterans.     

南极长城站微生物区系调查

1992～1993年的夏季,对南极中国长城站的陆地进行了微生物区系的现场调查。先后采集各种类型上样多个。其中对有生态意义的25个样进行了不同类型微生物的分离和计数;中温培养下每克湿土壤菌量为10²～10⁶,用马丁培养基对真菌进行分离培养和计数,每克湿土含菌量为10²～10⁴;0℃下分离计数,发现低温下微生物的数量较中温的多,每克湿土壤含菌为10³～10⁶。对该地区烃氧化菌进行了特别调查,以长城站为中心东西宽0．4Km,南北长1Km的范围内烃氧化菌发育最为活跃,但距长城站距离越远,烃氧化菌数量越少。     

Topography of short portal vessels in the rat pituitary gland: a scanning electron-microscopic and morphometric study of corrosion cast replicas

We applied scanning electron microscopy combined with imaging and morphometric techniques to analyze the dorsal topography and morphology of short portal vessels linking the capillary beds of the pituitary neural and anterior lobes in adult male albino rats. The pituitary microvasculature was replicated by intracarotid injection of Batson's No. 17 compound producing plastic casts that were advantageous for comprehensive morphometric analyses using an imaging device. The analysis revealed the existence of two types of portal vessels having quantitatively different morphological properties. The bilateral venular plexus of 3–4 vessels located at the base of the infundibular stalk (each venule measuring 300 m in length and 32 m in diameter) appears to be the major part of the short portal system in the dorsum of the rat pituitary gland. Narrower capillary-like shunt vessels (6.8 m in diameter), of about the same length as the venules, were situated throughout other subregions of the intermediate lobe cleft. The short portal vessels of both types made direct anastomoses with the capillary networks in the neural and anterior lobes. The neural lobe capillaries were twice as numerous (1324 per mm²), and only half as wide (6.2 m), as the sinusoidal capillaries in the anterior lobe (density of 637 per mm²; diameter of 13.7 m). The topographical position of the portal venular system suggests that the caudolateral subregions of the pituitary neural and anterior lobes have a functional relationship dependent on rapid interlobe transfer of neurohumoral factors such as hormones via the portal blood. This process appears to be supplemented throughout the rest of the cleft between the two lobes by a small number of capillary shunts that supply the epithelial cell lobules of the intermediate lobe in situ. The findings collectively indicate that this portal system provides a constant stream of neurohumoral information that is shared moment-by-moment between the pituitary neural and anterior lobes.     

Nitrogen addition promotes terrestrial plants to allocate more biomass to aboveground organs: A global meta-analysis

A significant increase in reactive nitrogen (N) added to terrestrial ecosystems through agricultural fertilization or atmospheric deposition is considered to be one of the most widespread drivers of global change. Modifying biomass allocation is one primary strategy for maximizing plant growth rate, survival, and adaptability to various biotic and abiotic stresses. However, there is much uncertainty as to whether and how plant biomass allocation strategies change in response to increased N inputs in terrestrial ecosystems. Here, we synthesized 3516 paired observations of plant biomass and their components related to N additions across terrestrial ecosystems worldwide. Our meta-analysis reveals that N addition (ranging from 1.08 to 113.81 g m⁻² year⁻¹) increased terrestrial plant biomass by 55.6% on average. N addition has increased plant stem mass fraction, shoot mass fraction, and leaf mass fraction by 13.8%, 12.9%, and 13.4%, respectively, but with an associated decrease in plant reproductive mass (including flower and fruit biomass) fraction by 3.4%. We further documented a reduction in plant root-shoot ratio and root mass fraction by 27% (21.8%–32.1%) and 14.7% (11.6%–17.8%), respectively, in response to N addition. Meta-regression results showed that N addition effects on plant biomass were positively correlated with mean annual temperature, soil available phosphorus, soil total potassium, specific leaf area, and leaf area per plant. Nevertheless, they were negatively correlated with soil total N, leaf carbon/N ratio, leaf carbon and N content per leaf area, as well as the amount and duration of N addition. In summary, our meta-analysis suggests that N addition may alter terrestrial plant biomass allocation strategies, leading to more biomass being allocated to aboveground organs than belowground organs and growth versus reproductive trade-offs. At the global scale, leaf functional traits may dictate how plant species change their biomass allocation pattern in response to N addition.     

Microbial nitrogen and phosphorus co-limitation across permafrost region

The status of plant and microbial nutrient limitation have profound impacts on ecosystem carbon cycle in permafrost areas, which store large amounts of carbon and experience pronounced climatic warming. Despite the long-term standing paradigm assumes that cold ecosystems primarily have nitrogen deficiency, large-scale empirical tests of microbial nutrient limitation are lacking. Here we assessed the potential microbial nutrient limitation across the Tibetan alpine permafrost region, using the combination of enzymatic and elemental stoichiometry, genes abundance and fertilization method. In contrast with the traditional view, the four independent approaches congruently detected widespread microbial nitrogen and phosphorus co-limitation in both the surface soil and deep permafrost deposits, with stronger limitation in the topsoil. Further analysis revealed that soil resources stoichiometry and microbial community composition were the two best predictors of the magnitude of microbial nutrient limitation. High ratio of available soil carbon to nutrient and low fungal/bacterial ratio corresponded to strong microbial nutrient limitation. These findings suggest that warming-induced enhancement in soil nutrient availability could stimulate microbial activity, and probably amplify soil carbon losses from permafrost areas.     

大鼠脑突触质膜糖皮质激素受体样抗原的免疫电镜研究

本文利用ABC金标记法(受体-抗受体中的单克隆抗体-生物素化马抗鼠IgG-金标链霉亲和素),首次在电镜下观察到大鼠脑突触质膜的外表面存在有糖皮质激素受体样抗原,为神经细胞膜上可能存在有糖皮质激素受体提供了形态学依据。     

OxyR介导的细菌氧化胁迫应答调控机制研究进展

OxyR属于LysR型转录因子家族的氧化胁迫调控蛋白,是细菌抵抗氧化胁迫压力的重要调控因子。OxyR能够通过调控过氧化氢酶和过氧化物酶等抗氧化基因的表达清除H₂O₂、参与铁代谢控制胞内过氧化物的产生以及修复生物大分子氧化损伤,从而抵抗氧化胁迫。OxyR的基因表达调控功能依赖于其还原态和氧化态之间的转变,改变调控蛋白对下游基因调控区的亲和能力。氧化态OxyR识别启动子区的结合序列,激活或抑制过氧化氢酶等基因的表达。还原态和氧化态的转换依赖于在氧化状态下分子间二硫键的形成。本文综述了近年来细菌OxyR调控基因表达的最新研究进展,有助于深入理解OxyR在细菌抵抗氧化胁迫的作用方式,为相关致病菌的防治奠定分子基础。     

Genomic insights into selection for heterozygous alleles and woody traits in Populus tomentosa

Heterozygous alleles are widespread in outcrossing and clonally propagated woody plants. The variation in heterozygosity that underlies population adaptive evolution and phenotypic variation, however, remains largely unknown. Here, we describe a de novo chromosome-level genome assembly of Populus tomentosa, an economic and ecologically important native tree in northern China. By resequencing 302 natural accessions, we determined that the South subpopulation (Pop_S) encompasses the ancestral strains of P. tomentosa, while the Northwest subpopulation (Pop_NW) and Northeast subpopulation (Pop_NE) experienced different selection pressures during population evolution, resulting in significant population differentiation and a decrease in the extent of heterozygosity. Analysis of heterozygous selective sweep regions (HSSR) suggested that selection for lower heterozygosity contributed to the local adaptation of P. tomentosa by dwindling gene expression and genetic load in the Pop_NW and Pop_NE subpopulations. Genome-wide association studies (GWAS) revealed that 88 single nucleotide polymorphisms (SNPs) within 63 genes are associated with nine wood composition traits. Among them, the selection for the homozygous AA allele in PtoARF8 is associated with reductions in cellulose and hemicellulose contents by attenuating PtoARF8 expression, and the increase in lignin content is attributable to the selection for decreases in exon heterozygosity in PtoLOX3 during adaptive evolution of natural populations. This study provides novel insights into allelic variations in heterozygosity associated with adaptive evolution of P. tomentosa in response to the local environment and identifies a series of key genes for wood component traits, thereby facilitating genomic-based breeding of important traits in perennial woody plants.