Inhibition of endothelial regeneration by type-beta transforming growth factor from platelets

Damage to the vessel wall is a signal for endothelial migration and replication and for platelet release at the site of injury. Addition of transforming growth factor-beta (TGF-beta) purified from platelets to growing aortic endothelial cells inhibited [3H]thymidine incorporation in a concentration-dependent manner. A transient inhibition of DNA synthesis was also observed in response to wounding; cell migration and replication are inhibited during the first 24 hours after wounding. By 48 hours after wounding both TGF-beta-treated and -untreated cultures showed similar responses. Flow microfluorimetric analysis of cell cycle distribution indicated that after 24 hours of exposure to TGF-beta the cells were blocked from entering S phase, and the fraction of cells in G1 was increased. The inhibition of the initiation of regeneration by TGF-beta could allow time for recruitment of smooth muscle cells into the site of injury by other platelet components.     

Cyclic changes in enzyme activity in synchronized mammalian cell cultures

Activity of the enzymes glucose-6-phosphate dehydrogenase and lactate dehydrogenase increases intermittently in synchronized cultures of Chinese hamster cells. During G(1) phase (3 hours after mitosis), midway through S phase (7 hours after mitosis) and again in late S phase (10 hours after mitosis), rapid increases in activity were observed and correlated with a net increase in cell size and total protein. The evidence suggests that this is a general phenomenon which affects a whole population of proteins and may be the expression of an endogenous cellular rhythm.     

Induction of synaptic potentiation in hippocampus by patterned stimulation involves two events

Electrical stimulation of axons in the hippocampus with short high-frequency bursts that resemble in vivo activity patterns produces stable potentiation of postsynaptic responses when the bursts occur at intervals of 200 milliseconds but not 2 seconds. When a burst was applied to one input and a second burst applied to a different input to the same target neuron 200 milliseconds later, only the synapses activated by the second burst showed stable potentiation. This effect was observed even when the two inputs innervated completely different regions of the postsynaptic cells; but did not occur when the inputs were stimulated simultaneously or when the second burst was delayed by 2 seconds. Intracellular recordings indicated that the first burst extended the decay phase of excitatory postsynaptic potentials evoked 200 milliseconds later. These results suggest that a single burst of axonal stimulation produces a transient, spatially diffuse "priming" effect that prolongs responses to subsequent bursts, and that these altered responses trigger spatially restricted synaptic modifications. The similarity of the temporal parameters of the priming effect and the theta rhythm that dominates the hippocampal electroencephalogram (EEG) during learning episodes suggests that this priming may be involved in behaviorally induced synaptic plasticity.     

First plasma wave observations at uranus

Radio emissions from Uranus were detected by the Voyager 2 plasma wave instrument about 5 days before closest approach at frequencies of 31.1 and 56.2 kilohertz. About 10 hours before closest approach the bow shock was identified by an abrupt broadband burst of electrostatic turbulence at a radial distance of 23.5 Uranus radii. Once Voyager was inside the magnetosphere, strong whistler-mode hiss and chorus emissions were observed at radial distances less than about 8 Uranus radii, in the same region where the energetic particle instruments detected intense fluxes of energetic electrons. Various other plasma waves were also observed in this same region. At the ring plane crossing, the plasma wave instrument detected a large number of impulsive events that are interpreted as impacts of micrometer-sized dust particles on the spacecraft. The maximum impact rate was about 30 to 50 impacts per second, and the north-south thickness of the impact region was about 4000 kilometers.     

Early optical polarization of a gamma-ray burst afterglow

We report the optical polarization of a gamma-ray burst (GRB) afterglow, obtained 203 seconds after the initial burst of gamma-rays from GRB 060418, using a ring polarimeter on the robotic Liverpool Telescope. Our robust (2sigma) upper limit on the percentage of polarization, less than 8%, coincides with the fireball deceleration time at the onset of the afterglow. The combination of the rate of decay of the optical brightness and the low polarization at this critical time constrains standard models of GRB ejecta, ruling out the presence of a large-scale ordered magnetic field in the emitting region.     

中华蟾蜍胚后嗅球神经元自发电活动的发育变化

[目的]探讨中华蟾蜍(Bufo bufo gargarizans)胚后嗅球神经元自发电活的电生理学特性的发育变化。[方法]应用微电极电生理技术,对中华蟾蜍胚后嗅球神经元的自发放电活动进行在体胞外记录。[结果]随着嗅球的发育,其神经元的放电形式逐渐增多,单个放电振幅逐渐增大,且在变态期达最大;连续放电振幅在胚后发育的中期变化不大,但高于发育的早期和成体期;连续簇状放电频率随着发育时期而降低,但在成体期再次升高,而连续单个放电频率只在成体期增大。[结论]随着嗅球的发育,神经元的兴奋性逐步提高,神经元电活动形式逐渐呈现多样化。     

Mapping patterns of c-fos expression in the central nervous system after seizure

A dramatic and specific induction of c-fos was observed in identifiable neuronal populations in vivo after administration of the convulsant Metrazole. This effect was time- and dose-dependent and was abolished by prior treatment with the anticonvulsant drugs diazepam or pentobarbital. About 60 minutes after administration of Metrazole, c-fos messenger RNA reached a maximum and declined to basal levels after 180 minutes. A further decrease below that in normal brain was observed before a return to basal levels after 16 hours. While Metrazole still elicited seizures during this period, reinduction of c-fos was largely refractory. At 90 minutes, c-fos protein was observed in the nuclei of neurons in the dentate gyrus, and in the pyriform and cingulate cortices. Subsequently, c-fos protein appeared throughout the cortex, hippocampus, and limbic system. Thus, seizure activity results in increased c-fos gene expression in particular subsets of neurons.     

Light propagation with phase discontinuities: generalized laws of reflection and refraction

Conventional optical components rely on gradual phase shifts accumulated during light propagation to shape light beams. New degrees of freedom are attained by introducing abrupt phase changes over the scale of the wavelength. A two-dimensional array of optical resonators with spatially varying phase response and subwavelength separation can imprint such phase discontinuities on propagating light as it traverses the interface between two media. Anomalous reflection and refraction phenomena are observed in this regime in optically thin arrays of metallic antennas on silicon with a linear phase variation along the interface, which are in excellent agreement with generalized laws derived from Fermat's principle. Phase discontinuities provide great flexibility in the design of light beams, as illustrated by the generation of optical vortices through use of planar designer metallic interfaces.     

水杨酸对黄瓜植株抗病酶系和白粉病抗性的诱导作用

水杨酸对黄瓜植株抗病酶系和白粉病抗性的诱导作用进行了研究,结果表明,5mmoL/L水杨酸喷雾处理黄瓜幼苗后,植株体内PAL,POD和PPO活性均有所提高。其中PAL,活性升高迅速,在处理后24h即达到最大值;PPO活性在处理后24h开始提高,48h时达到最大值;POD活性在处理后8h即开始升高,48h时达到最大值。并且经水杨酸处理的植株抗病性明显增强,处理后7d对黄瓜白粉病的相对防治效果为51．23％。     

槲皮素对BEL-7402细胞生长抑制作用的研究

[目的]探讨槲皮素对人肝癌细胞株BEL-7402的增殖抑制及凋亡诱导作用。[方法]体外培养BEL-7402细胞,以不同浓度槲皮素处理细胞后,采用酸性磷酸酶（APA）法检测细胞增殖抑制率;光镜观测BEL-7402细胞形态变化;流式细胞仪检测细胞凋亡率。[结果]槲皮素对人肝癌BEL-7402细胞有明显的增殖抑制作用,其72h的IC50为4μg/ml。光学显微镜下可见细胞密度明显降低。经槲皮素作用6、12h后,流式细胞术检测到细胞凋亡率显著增加。[结论]槲皮素对人肝癌细胞的增殖抑制呈浓度相关性,可诱导肝癌细胞凋亡。     

Circadian rhythm in pineal tyrosine hydroxylase

Tyrosine hydroxylase is the rate-limiting enzyme in catecholamine synthesis. The rat pineal gland is richly innervated by sympathetic nerves from the superior cervical ganglia. The activity of tyrosine hydroxylase was measured in rat pineal gland at 4-hour intervals over a daily cycle of 12 hours of light (7 a.m. to 7 p.m.) and 12 hours of darkness. The results indicate a circadian rhythm with the maximum activity, at 11 p.m. to 3 a.m., about triple the low values observed at 3 p.m. The pattern is similar in phase to that previously reported for melatonin and hydroxyindole-O-methyl transferase activity.     

VEGA Balloon Dynamics and Vertical Winds in the Venus Middle Cloud Region

The VEGA balloons provided a long-term record of vertical wind fluctuations in a planetary atmosphere other than Earth's. The vertical winds were calculated from the observed displacement of the balloon relative to its equilibrium float altitude. The winds were intermittent; a large burst lasted several hours, and the peak velocity was 3 meters per second.     

川渝盆地主汛期短时强降水事件日变化特征研究

利用四川盆地和重庆地区1980-2012年主汛期(5-9月)基本站小时降水观测资料,分析了短时强降水事件降水量、频次和强度的日变化特征,研究了短时强降水事件日峰值位相和空间分布特征,事件极值降水日变化和持续时间等分布特征,得出以下主要结论:1)川渝盆地短时强降水事件开始时间的日变化上(01:00-24:00时,北京时间,下同),表现为"V"型结构下典型夜间峰值位相特征;结束时间的日变化上,表现为多个峰值型结构分布.强降水事件持续时间的日变化上,频次和降水量均呈双峰型结构,频次极大峰值出现在3h,而强度上随着持续时间的延长,呈现逐渐增加的趋势;2)短时强降水事件极值开始时间空间分布上,极大频次和极大降水量出现在20:00-01:00时内,主要分布在盆地南部和西部大部分地区;日峰值频次结束时间主要发生在20:00-01:00时和08:00-13:00时两个时段内,主要分布于盆地南部、中部和西部大部分地区;3)短时强降水事件极值降水的日变化上,降水量和频次呈现单峰型结构,白天多为短时间(2~4h)强降水事件出现极值,而傍晚开始至第二天清晨,持续2~10h强降水事件出现极值均有发生;强降水事件极值降水持续时间日变化,1~24h内呈单峰型结构,峰值出现在2h.     

D-对羟基苯海因细菌的发酵工艺优化研究

通过筛菌得到一株野生菌 LLV-6,在诱导剂诱导后利用DL-对羟基苯海因（DL-HPH）为底物经D-海因酶（HYD）和N-氨甲酰-D-氨基酸酰胺水解酶（CAB）两酶水解而获得D-对羟基苯甘氨酸。用LB培养基（含磷酸盐缓冲溶液,pH=7.2）接菌量为0.5%（对数期的菌种）,在37℃、200r、pH7.2条件下培养菌种。在培养12h后加入2%的诱导剂并以500μLDMSO作为促溶剂,33h后收集细胞。通过对细胞酶活力的测定,此时酶活力达到最大值,酶活力为0.57U/L,比优化前提高了2.6倍。     

Microearthquakes at st. Augustine volcano, alaska, triggered by Earth tides

Microearthquake activity at St. Augustine volcano, located at the mouth of Cook Inlet in the Aleutian Islands, has been monitored since August 1970. Both before and after minor eruptive activity on 7 October 1971, numerous shallow-foci microearthquake swarms were recorded. Plots of the hourly frequency of microearthquakes often show a diurnal peaking of activity. A cross correlation of this activity with the calculated magnitudes of tidal acceleration exhibited two prominent phase relationships. The first, and slightly more predominant, phase condition is a phase delay in the microearthquake activity of approximately 1 hour from the time of maximum tidal acceleration. This is thought to be a direct microearthquake-triggering effect caused by tidal stresses. The second is a phase delay in the microearthquake activity of approximately 5 hours, which correlates well with the time of maximum oceanic tidal loading. Correlation of the individual peaks of swarm activity with defined components of the tides suggests that it may be necessary for tidal stressing to have a preferential orientation in order to be an effective trigger of microearthquakes.     

Decay of the GRB 990123 optical afterglow: implications for the fireball model

Broad-band (ultraviolet to near-infrared) observations of the intense gamma ray burst GRB 990123 started approximately 8.5 hours after the event and continued until 18 February 1999. When combined with other data, in particular from the Robotic Telescope and Transient Source Experiment (ROTSE) and the Hubble Space Telescope (HST), evidence emerges for a smoothly declining light curve, suggesting some color dependence that could be related to a cooling break passing the ultraviolet-optical band at about 1 day after the high-energy event. The steeper decline rate seen after 1.5 to 2 days may be evidence for a collimated jet pointing toward the observer.     

Io: an intense brightening near 5 micrometers

Spectrophotometric observations of the jovian satellite Io on 20 and 21 February 1978 (Universal Time) were made from 1.2 to 5.4 micrometers. Io's brightness at 4.7 to 5.4 micrometers was found to be three to five times greater at an orbital phase angle of 68 degrees than at orbital phase angles of 23 degrees (5.5 hours before the brightening) and 240 degrees (20 hours after the brightening). Since the 5-micrometer albedo of Io is near unity under ordinary conditions, the observed transient phenomenon must have been the result of an emission mechanism. Although several such mechanisms were examined, the actual choice is not clear.     

葡聚六糖对烟草悬浮培养细胞活性氧的作用

研究了葡聚六糖对烟草悬浮培养细胞活性氧的作用.结果表明:葡聚六糖可以诱导烟草悬浮细胞活性氧的进发,活性氧进发蜂值出现在30 min,同时活性氧相关酶系活性也升高,超氧化物歧化酶(SOD)活性最高峰在处理后60 min,过氧化物酶(POD)和过氧化氢酶(CAT)变化趋势与活性氧相似.添加不同抑制剂EGTA、新霉素、氯化锂(LiCl)等测定发现,细胞胞内和胞外Ca2+参与调控葡聚六糖诱导的活性氧进发.     

小鼠急性缺氧后淋巴结内肥大细胞的观察

应用组织化学染色法对对照组、缺氧组、牛磺酸预处理缺氧组小鼠淋巴结内肥大细胞的数量、活性、分布范围及组化性质进行研究.结果表明:随着急性缺氧时间的延长,缺氧组和牛磺酸预处理缺氧组小鼠的肥大细胞和脱颗粒数急剧增加,均极显著高于同期对照组(P<0.01),且在急性缺氧5h时肥大细胞出现一个峰值,而在缺氧8h后恢复常压9h再缺氧3h时,肥大细胞脱颗粒数最显著.AB-S染色显示:随着缺氧时间的延长,缺氧组和牛磺酸预处理缺氧组小鼠淋巴结内几乎全部为黏膜肥大细胞(mucosal mast cell MMC).     

烟叶在烘烤过程中氮代谢的研究

研究了烤烟烟叶在烘烤过程中氮代谢规律。结果表明,蛋白质含量随烘烤进程发展逐渐减少,氨基酸含量逐渐增加,且均在变黄中期和定色期有一个快速变化阶段;烤后烟叶中氨基酸和可溶性蛋白含量与鲜叶中可溶性蛋白含量成高度正相关;蛋白酶活性在烘烤开始后24h和60h分别有一个高峰。鲜叶中NO#+-#-3含量与其硝酸还原酶活性显著相关,但不是唯一影响因素;硝酸还原酶活性从烘烤开始就逐渐升高,24h达到最大值,之后迅速失活。NO#+-#-3和NO#+-#-2含量在烘烤初期迅速上升,变黄末达到最大值,在定色阶段快速下降,但烤后含量仍比鲜叶高得多。