Many of the diverse functions of cilia depend upon tight control of their length. Steady-state length reflects a balance between rates of ciliary assembly and disassembly, two parameters likely ...controlled by a length sensor of unknown identity or mechanism.
A null mutation in Chlamydomonas CNK2, a member of the evolutionarily conserved family of NIMA-related kinases, reveals feedback regulation of assembly and disassembly rates. cnk2-1 mutant cells have a mild long-flagella (lf) phenotype as a consequence of reduced rates of flagellar disassembly. This is in contrast to the strong lf mutant lf4-7, which exhibits an aberrantly high rate of assembly. Cells carrying both mutations have even longer flagella than lf4-7 single mutants do. In addition to their high rate of assembly, lf4-7 mutants have a CNK2-dependent increase in disassembly rate. Finally, cnk2-1 cells have a decreased rate of turnover of flagellar subunits at the tip of the flagellum, demonstrating that the effects on disassembly are compensated by a reduced rate of assembly.
We propose a model wherein CNK2 and LF4 modulate rates of disassembly and assembly respectively in a feedback loop that is activated when flagella exceed optimal length.
•Chlamydomonas cells null for the CNK2 kinase have a mild long-flagella phenotype•cnk2-1 cells are defective in flagellar disassembly and therefore resorption•The cnk2-1 mutation enhances the long-flagella phenotype of lf4-7 mutants•cnk2-1 cells exhibit a compensatory decrease in incorporation of new tubulin
•The experience of 433 medical physicists during COVID-19 was analysed.•Changes in clinical practice had an impact on treatment planning and quality assurance tasks.•The effects of the changes were ...perceived differently by management vs clinical medical physicists.•There is a clear willingness to learn from this experience.
The COVID-19 pandemic has imposed changes in radiotherapy (RT) departments worldwide. Medical physicists (MPs) are key healthcare professionals in maintaining safe and effective RT. This study reports on MPs experience during the first pandemic peak and explores the consequences on their work.
A 39-question survey on changes in departmental and clinical practice and on the impact for the future was sent to the global MP community. A total of 433 responses were analysed by professional role and by country clustered on the daily infection numbers.
The impact of COVID-19 was bigger in countries with high daily infection rate. The majority of MPs worked in alternation at home/on-site. Among practice changes, implementation and/or increased use of hypofractionation was the most common (47% of the respondents). Sixteen percent of respondents modified patient-specific quality assurance (QA), 21% reduced machine QA, and 25% moved machine QA to weekends/evenings. The perception of trust in leadership and team unity was reversed between management MPs (towards increased trust and unity) and clinical MPs (towards a decrease). Changes such as home-working and increased use of hypofractionation were welcomed. However, some MPs were concerned about pressure to keep negative changes (e.g. weekend work).
COVID-19 affected MPs through changes in practice and QA procedures but also in terms of trust in leadership and team unity. Some changes were welcomed but others caused worries for the future. This report forms the basis, from a medical physics perspective, to evaluate long-lasting changes within a multi-disciplinary setting.
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