The effect of pollen source on seed traits and dispersability in the heterocarpic annual Crepis sancta

不同花粉来源对一年生植物种子性状和扩散能力的影响 与扩散有关的性状进化和表达与其他生活史功能交织在一起，并在各种生理约束条件下表现出 来。这种关系可以在近交水平和扩散性之间得到预测，而且在解剖学和个体发育上联系在一起，从而使 某个选择压力可能影响另外的一个。虽然近交对生殖成功和扩散策略的影响都引起了广泛关注，但只有 少数研究同时考虑了这两者。此外，此类研究通常依赖于繁殖和扩散的表示：使用自交与异源杂交表示繁殖水平，使用扩散比表示扩散策略。本研究利用菊科Crepis sancta的授粉实验，以两种不同的方式扩展 繁殖和扩散的二分表示法。首先，我们使用授粉处理来表示一种统一连续体，即从亲缘授粉的自交到距离较远的邻居授粉。其次，我们不仅测量了繁殖成功率和扩散比，还测量了一整套连续的与形态和扩散相关的性状。研究结果显示，头状花序的比例，以及扩散的和非扩散的瘦果在自花传粉处理中都显著低于异源杂交处理。尽管自花授粉的植物很少产生不扩散的种子，但花粉来源对扩散比的影响统计上不显著。瘦果的生物量随亲本植物之间的距离增加而增加，但冠毛宽度没有增加，从而导致授粉对下落速度的影响不显着。总之，花粉来源主要影响与生殖产量有关的性状，但对主要与扩散有关的性状没有显著影响。繁殖和扩散性状对花粉来源变化响应的这种差异表明，与扩散有关的选择可能很弱和/或被其他因素所掩盖。     

Preparation of multivesicular liposomes

A novel type of liposome, named here multivesicular liposomes, was prepared by evaporation of organic solvents from chloroform-ether spherules suspended in water. Within each spherule were numerous water droplets that contained solutes to be trapped in liposomes upon solvent evaporation. Liposome preparations of different average diameters were made, varying from $\text{29 ± 10 μ}\text{m}$ to $\text{5.6 ± 1.7 μ}\text{m}$. The liposomes were morphologically characterized by light microscopy and transmission electron microscopy. Materials successfully trapped within the liposomes ranged in molecular size from glucose to nucleic acids. Extremely high percentages of encapsulation (up to 89%) were achieved.     

Adenosine deaminase and immunodeficiency: An in vitro model

We have examined the effect of adenosine and EHNA, a competitive inhibitor of adenosine deaminase (ADA), upon the ability of human peripheral blood lymphocytes to respond to mitogen. Addition of adenosine at concentrations greater than 10 μm (10^?5m) resulted in inhibition of lymphocyte proliferation at 48 hr of culture, provided that the culture medium was relatively free of ADA activity. The actual concentrations of adenosine remaining in inhibited cultures at the time of harvest were considerably lower than those added initially. EHNA alone also inhibited PHA response (and to a lesser extent PWM and Con A responses), but only at high concentrations. Noninhibitory concentrations of EHNA and adenosine together acted synergistically to produce profound inhibition of lymphocyte proliferation. This may provide an in vitro model to explore further the mechanism of the immunodeficiency associated with deficiency of ADA. Adenosine deaminase activity in stimulated cultures did not differ significantly from that found in unstimulated cultures, and the activity per protein or per DNA actually decreased in stimulated versus unstimulated cultures.     

Binding of ATP and messenger RNA by the beta-subunit of eukaryotic initiation factor 2.

In addition to forming a ternary complex with Met-tRNA(f) and GTP, eukaryotic initiation factor 2 (eIF-2) recognizes a specific site in mRNA molecules. Both binding activities are regulated by ATP, which itself binds tightly and specifically to eIF-2. Denaturation of eIF-2 with urea leads to complete loss of Met-tRNA(f) binding activity, while mRNA binding activity is stable. Hence, distinct conformational features in eIF-2 are required for ternary complex formation and for binding of mRNA. Chromatography of eIF-2 over ATP-agarose, in denaturing conditions that induce polypeptide subunit dissociation, results in selective retention of the beta-subunit of eIF-2. Isolated beta-subunit is capable of binding mRNA as well as ATP. Cibacron blue 3G-A binds tightly to eIF-2 and inhibits the binding of mRNA. This inhibition is relieved upon addition of ATP, showing that Cibacron blue 3G-A competes with ATP for eIF-2. eIF-2 beta subunit, active in binding of mRNA, is recovered upon chromatography of eIF-2 in denaturing conditions over matrix-bound Cibacron blue 3G-A. These results show that the ability of eIF-2 to bind mRNA and its ability to bind ATP are both lodged within remarkably stable domains of its beta-subunit. During initiation of protein synthesis, the eIF-2 beta subunit may thus interact with three ligands important for translational control: Met-tRNA(f), mRNA and ATP.