Analysis of the role of the Spitzenkörper in fungal morphogenesis by computer simulation of apical branching in Aspergillus niger

High-resolution video microscopy, image analysis, and computer simulation were used to study the role of the Spitzenkörper (Spk) in apical branching of ramosa-1, a temperature-sensitive mutant of Aspergillus niger. A shift to the restrictive temperature led to a cytoplasmic contraction that destabilized the Spk, causing its disappearance. After a short transition period, new Spk appeared where the two incipient apical branches emerged. Changes in cell shape, growth rate, and Spk position were recorded and transferred to the fungus simulator program to test the hypothesis that the Spk functions as a vesicle supply center (VSC). The simulation faithfully duplicated the elongation of the main hypha and the two apical branches. Elongating hyphae exhibited the growth pattern described by the hyphoid equation. During the transition phase, when no Spk was visible, the growth pattern was nonhyphoid, with consecutive periods of isometric and asymmetric expansion; the apex became enlarged and blunt before the apical branches emerged. Video microscopy images suggested that the branch Spk were formed anew by gradual condensation of vesicle clouds. Simulation exercises where the VSC was split into two new VSCs failed to produce realistic shapes, thus supporting the notion that the branch Spk did not originate by division of the original Spk. The best computer simulation of apical branching morphogenesis included simulations of the ontogeny of branch Spk via condensation of vesicle clouds. This study supports the hypothesis that the Spk plays a major role in hyphal morphogenesis by operating as a VSC—i.e., by regulating the traffic of wall-building vesicles in the manner predicted by the hyphoid model.

Modeling of Self-similar Traffic

Modeling of self-similar traffic is performed for the queuing system of G/M/1/K type using Weibull distribution. To study the self-similar traffic the simulation model is developed by using SIMULINK software package in MATLAB environment. Approximation of self-similar traffic on the basis of spline functions. Modeling self-similar traffic is carried outfor QS of W/M/1/K type using the Weibull distribution. Initial data are: the value of Hurst parameter H=0,65, the shape parameter of the distribution curve α≈0,7 and distribution parameter β≈0,0099. Considering that the self-similar traffic is characterized by the presence of "splashes" and long-termdependence between the moments of requests arrival in this study under given initial data it is reasonable to use linear interpolation splines.

Analytical pedestrian accident reconstruction using computer simulation. Final report.

Mode of access: Internet.

Further investigation of traffic operations on two-lane, two-way rural highways. Research summary. Final report.

Federal Highway Administration, Washington, D.C.

A computer program (VEHSIM) for vehicle fuel economy and performance simulation (automobiles and light trucks). Volume I: description and analysis. Final report.

National Highway Traffic Safety Administration, Office of Research and Development, Washington, D.C.

A computer program (VEHSIM) for vehicle fuel economy and performance simulation (automobiles and light trucks). Volume II: users guide. Final report.

National Highway Traffic Safety Administration, Office of Research and Development, Washington, D.C.

Development and testing of INTRAS, a microscopic freeway simulation model. Volume 4: program documentation. Final report.

Federal Highway Administration, Office of Research and Development, Washington, D.C.

A computer program (VEHSIM) for vehicle fuel economy and performance simulation (automobiles and light trucks). Volume IV: enhancements. Final report.

National Highway Traffic Safety Administration, Office of Research and Development, Washington D.C.

Research input for computer simulation of automobile collisions. Volume IV: staged collision reconstructions. Final report.

National Highway Traffic Safety Administration, Washington, D.C.

Research input for computer simulation of automobile collisions. Volume III: staged collisions. Tests no. 6 through no. 12. Final report.

National Highway Traffic Safety Administration, Washington, D.C.

A computer program (HEVSIM) for heavy duty vehicle fuel economy and performance simulation. Volume II: users' manual. Final report.

National Highway Traffic Safety Administration, Office of Research and Development, Washington, D.C.

A computer program (HEVSIM) for heavy duty vehicle fuel economy and performance simulation. Volume III: appendices A through F. Final report.

National Highway Traffic Safety Administration, Office of Research and Development, Washington, D.C.

A computer program (HEVSIM) for heavy duty vehicle fuel economy and performance simulation. Volume I: description and analysis. Final report.

National Highway Traffic Safety Administration, Office of Research and Development, Washington, D.C.

Research input for computer simulation of automobile collisions. Interim report.

National Highway Traffic Safety Administration, Washington, D.C.

Research input for computer simulation of automobile collisions. Volume II: staged collisions. Tests no. 1 through no. 5. Final report.

National Highway Traffic Safety Administration, Washington, D.C.