Turner C M, Aslam N, Dye C
Parasitology Laboratory, I.B.L.S., University of Glasgow.
Parasitology. 1995 Sep;111 ( Pt 3):289-300. doi: 10.1017/s0031182000081841.
This study had 2 objectives: first, to investigate how the processes of slender form replication, of differentiation from dividing slender to non-dividing stumpy forms, and of stumpy mortality, combine to determine the initial (acute-phase) growth rate of Trypanosoma brucei populations; second, to determine how acute-phase growth rates influence parasite densities during the subsequent, chronic phase of infection. During the acute phase, slender and stumpy populations both grew approximately exponentially, the latter more slowly than the former. Mathematical models showed how this difference in slender and stumpy growth rates can be explained in terms of heterogeneous replication and differentiation rates. Stumpy life-expectancy was determined for one stock and found to be age-dependent with a half-life of 48-72 h, much larger than observed population doubling times of 5-10 h. A comparison of cloned stocks showed that the highest parasite densities during the chronic phase were associated with the highest acute-phase growth rates of both the whole parasite population and of the subpopulation of slender forms. By contrast, high chronic-phase parasitaemias artificially produced following rapid syringe passage were associated with low acute-phase growth rates of slender forms. Syringe-passaging is a laboratory procedure which selects for virulent parasites, but these parasites behave differently from naturally virulent stocks.
其一，研究细长形态复制、从分裂的细长形态向不分裂的粗短形态分化以及粗短形态死亡的过程如何共同决定布氏锥虫群体的初始（急性期）生长速率；其二，确定急性期生长速率如何影响后续感染慢性期的寄生虫密度。在急性期，细长形态群体和粗短形态群体均近似呈指数增长，后者比前者增长得慢。数学模型表明，细长形态和粗短形态生长速率的这种差异可根据异质复制和分化速率来解释。测定了一个虫株的粗短形态预期寿命，发现其与年龄有关，半衰期为48 - 72小时，远大于观察到的5 - 10小时的群体倍增时间。对克隆虫株的比较表明，慢性期最高的寄生虫密度与整个寄生虫群体以及细长形态亚群体的最高急性期生长速率相关。相比之下，快速注射器传代后人工产生的高慢性期虫血症与细长形态的低急性期生长速率相关。注射器传代是一种选择毒性寄生虫的实验室操作，但这些寄生虫的行为与天然毒性虫株不同。
