Cross-sectional Particle Research Articles

A phenotypic study of intraflagellar transport and FLA10 in the lf4 mutant of Chlamydomonas reinhardtii

Flagellar length is a controlled mechanism in the biflagellate alga Chlamydomonas reinhardtii. Several long flagellar mutants have been isolated and used to demonstrate that this is a dynamic process. We characterized the morphology of the lf4 mutant using immunofluorescence (IMF) and scanning and transmission electron microscopy (TEM). Using IMF, the FLA10p and LF4p localized to flagella in a punctate pattern, likely indicating intraflagellar transport (IFT) particles. No bulbous tips were observed in lf4, unlike the lf2 and lf3 mutants as reported by Tam and coworkers (2003, 2007). Multiple IFT particles were observed in cross‐sectional and longitudinal flagellar ultrastructure of lf4 using TEM. Plus, an as yet unidentified electron‐dense structure in an lf4 cross‐section was observed to connect the outer doublet microtubules to the cell membrane. Quantification of IFT particles per length, area and volume of flagella revealed that there were twice as many IFT particles in cross sections of lf4 vs. wild‐type cells. The regulation of flagellar length appears to involve not only regulation of flagellar assembly and disassembly by IFTs but also other signal pathways operating in flagellar assembly and disassembly.

Quantitative studies of oncornaviruses in thin sections.

SUMMARY A thin sectioning procedure was used to detect and enumerate oncornavirus particles in tumour-cell culture fluids, tumour homogenates, mouse blood plasma, mouse and human milk specimens, and density gradient fractions of these specimens. Oncornaviruses studied included mouse mammary tumour, murine sarcoma, ESP-1, and RD-114 viruses. In this procedure particles were sedimented on to small membrane filter discs in the ultracentrifuge using inexpensive commercially available adapters and tubes. Particles in cross sections of the disc were counted and their total number determined by relating the effective surface area of a field to the surface area of the entire membrane disc. Particles may be reliably identified and counted in preparations containing predominately cellular debris. Linear dose response plots were obtained in serial dilution experiments utilising vaccinia virus, adenovirus type 2, and murine sarcoma virus, demonstrating the reliability of the procedure and its wide applicability. The counts obtained for adenovirus and vaccinia virus preparations were comparable to counts obtained for the same preparations in other laboratories by established methods. Statistically reliable counts have been obtained using sample vol. of 0.01 ml or less.