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首页> 外文期刊>Journal of Theoretical Biology >Simulation of Density Gradients of Astral Microtubules at Cell Surface in Cytokinesis of Sea Urchin Eggs
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Simulation of Density Gradients of Astral Microtubules at Cell Surface in Cytokinesis of Sea Urchin Eggs

机译：海胆卵细胞胞质分裂中细胞表面星形微管密度梯度的模拟

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Astral microtubules extend close to the cell surface just before cytokinesis in sea urchins eggs. At this time, a small region with a constant area is considered around a point on the egg surface. To calculate the number of microtubules that reach the surface region, i.e. the microtubule density at the point, a simple mathematical model was set up. The density was estimated at many surface points in multipolar and distorted eggs by using the model. A contour map was drawn to investigate the density gradients. The gradient patterns were compared with the distributions of contractile-ring microfilaments. The simulated cases were: (1) an unusual distribution of contractile-ring microfilaments in an egg that had polyasters and was compressed by a coverslip; (2) formation of contractile-ring microfilaments at the equatorial region in compressed eggs with a centrally-located mitotic apparatus; (3) normal furrowing in the plane of the spindle midpoint in eggs inserted into a glass loop or confined in a capillary; (4) failure of furrow formation in spherical eggs treated with ethyl urethane and revival of furrowing by pushing the equatorial surface closer to the spindle. These simulations proposed the hypothesis that contractile-ring microfilaments form at the surface regions where the microtubule has a local minimum, not a local maximum. In addition, it was suggested that the probability of the formation of contractile-ring microfilaments is dependent on how abruptly the density gradient changes at the local-minimum point. These results support the idea that the gradient pattern of the microtubule density determines whether and where contractile-ring microfilaments appear.
机译：在海胆卵细胞胞质分裂之前，星状微管延伸至细胞表面附近。这时，在蛋表面上的一点周围考虑一个面积恒定的小区域。为了计算到达表面区域的微管的数量，即该点的微管密度，建立了简单的数学模型。使用该模型可以估算多极蛋和扭曲蛋中许多表面点的密度。绘制等高线图以研究密度梯度。将梯度图案与收缩环微丝的分布进行比较。模拟的情况是：（1）收缩环微丝在鸡蛋中不寻常地分布，该鸡蛋具有多头并被盖玻片压缩; （2）利用位于中央的有丝分裂装置在压缩卵中的赤道区域形成收缩环微丝; （3）将卵插入到玻璃环中或限制在毛细管中，在主轴中点的平面内正常犁沟; （4）用乙基氨基甲酸酯处理的球形蛋中的犁沟形成失败，并且通过将赤道表面推向主轴附近，犁沟得以恢复。这些模拟提出了这样的假设，即在微管具有局部最小值而不是局部最大值的表面区域形成收缩环微丝。另外，有人提出，形成收缩环微丝的可能性取决于密度梯度在局部最小点上突变的程度。这些结果支持这样的想法，即微管密度的梯度模式决定了收缩环微丝是否出现以及出现在何处。

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