BICARBONATE STIMULATION OF CALCIFICATION AND PHOTOSYNTHESIS IN TWO HERMATYPIC CORALS1

A wide range of bicarbonate concentrations was used to monitor the kinetics of bicarbonate (HCO₃^?) use in both photosynthesis and calcification in two reef‐building corals, Porites porites and Acropora sp. Experiments carried out close to the P. porites collection site in Barbados showed that additions of NaHCO₃ to synthetic seawater proportionally increased the calcification rate of this coral until the concentration exceeded three times that of seawater (6 mM). Photosynthetic rates were also stimulated by HCO₃^? addition, but these became saturated at a lower concentration (4 mM). Similar experiments on aquarium‐acclimated colonies of Indo‐Pacific Acropora sp. showed that calcification and photosynthesis in this coral were enhanced to an even greater extent than P. porites, with calcification continuing to increase above 8 mM HCO₃^?, and photosynthesis saturating at 6 mM. Calcification rates of Acropora sp. were also monitored in the dark, and, although these were lower than in the light for a given HCO₃^? concentration, they still increased dramatically with HCO₃^? addition, showing that calcification in this coral is light stimulated but not light dependent.     

刺激兔延髓孤束核等区域对皮层诱发性下颌运动的抑制作用

本实验使用连续单相方波脉冲(波宽:0.6ms,频率:80-150Hz,电压:1-7V)刺激麻醉兔延髓孤束核、最后区、网状结构内2/3区域的背侧部以及三叉脊束核等区域,观察对皮层诱发性下颌运动的影响。刺激孤束核、最后区以及网状结构,抑制皮层诱发性下颌运动。刺激三叉脊束核常使皮层诱发性下颌运动增强。     

刺激家兔中脑导水管周围灰质抑制束旁核伤害性放电的脊髓上机制

本工作比较了家兔脊髓背侧1/2进行横切前后刺激中脑中央灰质对束旁核伤害性放电的抑制率的改变。实验表明中央灰质既可通过公认的脊髓下行纤维抑制脊髓水平的痛传递,减弱束旁核单位的痛敏放电,也可通过某种脊髓上机制实现对束旁核的抑制。我们对这两种机制的相对重要性作了分析。用直11个束旁核痛敏单位所作的计算表明,在脊髓切割前,刺激中央灰质可使束旁核痛敏放电抑制67.5%,脊髓背侧1/2横切后,同样的中脑刺激只能使痛敏放电抑制42.9%。如以切割前的抑制率作为直100%,则切割可使抑制减弱36.5%,这一部分抑制应当是由被切断的脊髓下行纤维实现的,其余63.5%则可能主要通过脊髓上机制来实现。考虑到脊髓背半部横切不可能全部切断下行纤维,故实际上脊髓上机制的重要性不会有上述数值表示的那么大。     

EXTRACELLULAR STIMULATION OF EPIDERMAL DNA SYNTHESIS

The removal of the topmost cell layers of the epidermal stratum corneum by stripping initiates a series of biochemical events which alters the normal homeostatic control of and results in the acceleration of the cell cycle in basal cells which are ten to twenty cell layers removed from the site of stripping. One measure of accelerated events is a stimulation of thymidine incorporation into epidermal DNA at time intervals following stripping. Two peaks of maximal stimulation occur between 12 and 24 hr and 48 and 54 hr after stripping. Stimulation of thymidine incorporation into epidermal DNA by limited stripping is a useful technique for studying the stripping-initiated signal at the stratum corneum and its subsequent translation at the proliferative cell receptor site.     

甲醇对蚕豆气孔开启的影响

在一定的深度范围内,甲醇能促进蚕豆气孔的开启,最适浓度为１．５％,与６－苄基腺嘌呤（６－ＢＡ）有协同增效作用,对脱落酸（ＡＢＡ）有拮抗作用。     

MRI中电磁场对神经及心脏刺激的研究进展

电磁场对人体产生的生物效应近年来引起人们的极大关注。文章先简单介绍了电磁场生物效应的早期研究,然后着重介绍现代磁共振医学成像应用中时变电磁场对神经和心脏刺激的潜在危险,并对该领域的研究方法和研究进展做出综述和展望。     

血小板生成刺激因子对巨核血小板系统体外生成的影响

本 文应用血小板生成液体培养体系及纯化的血小板生成刺激因子(TSF)研究了 TSF对巨核细胞成熟及血小板生成的作用。TSF 在0.5—2U/ml 浓度范围内能够刺激巨核细胞DNA 合成,胞浆成熟,胞体直径增加以及血小板直径增加,但对巨核细胞与血小板计数没有影响。实验表明 TSF 作为一种血小板生成素,通过促进巨核细胞分化成熟,以增加血小板体积的方式,促进血板小生成。