The Experts below are selected from a list of 9054 Experts worldwide ranked by ideXlab platform
Akos Sveiczer - One of the best experts on this subject based on the ideXlab platform.
-
cell length growth patterns in fission yeast reveal a novel size control mechanism operating in late g2 phase
Biology of the Cell, 2016Co-Authors: Anna Horvath, Anna Raczmonus, Peter Buchwald, Akos SveiczerAbstract:Background information Because cylindrically shaped fission yeast cells grow exclusively at their tips, cell volume is proportional to length and can be easily monitored by time-lapse microscopy. Here, we analysed the growth pattern of individual cells from several fission yeast strains to determine the growth Function that describes them most adequately and to perform size control studies. Results The growth pattern of most cells during their growth period is best described by a Bilinear Function (i.e., two linear segments of different growth rates separated by a rate-change point). Linear growth patterns were also observed in several cases, but exponential ones only rarely. Since the Bilinear patterns are separated into two segments by a breakpoint, we examined the existence of size control by regression analyses of the appropriate growth parameters in both segments. This confirmed the existence of known size controls in late G1, mid-G2 and late G2 during the fission yeast cycle. The present analyses also revealed that, contrary to the commonly accepted current view, late G2 size control is a general characteristic third event in the cycle. The level of the critical late G2 size that needs to be reached in an individual fission yeast cell is influenced by the growth rate of the cell in a manner similar to budding yeast, suggesting an evolutionary conserved mechanism. Conclusions The present study of individual cell growth patterns in wild-type and several cell cycle mutant fission yeast strains confirmed that, for most cells, growth is best described by a Bilinear Function. Three different size control mechanisms were found to operate in the different strains, and, as a novel observation, cell size was always found to be monitored before mitotic onset, irrespective of the existence of any earlier size checkpoints. Significance Studying the pattern of growth and the mechanism of size control helps to clarify the connections between cell growth and division, since their coordination must work properly to maintain size homeostasis. In this study, we argue that most individual fission yeast cells grow following a Bilinear pattern, and we confirm the existence of three different size control mechanisms.
-
cell length growth in fission yeast an analysis of its Bilinear character and the nature of its rate change transition
Fems Yeast Research, 2013Co-Authors: Anna Horvath, Anna Raczmonus, Peter Buchwald, Akos SveiczerAbstract:During their mitotic cycle, cylindrical fission yeast cells grow exclusively at their tips. Length growth starts at birth and halts at mitotic onset when the cells begin to prepare for division. While the growth pattern was initially considered to be exponential, during the last three decades an increasing amount of evidence indicated that it is rather a Bilinear Function [two linear segments separated by a rate change point (RCP)]. The main focus of this work was to clarify this and to elucidate the further question of whether the rate change occurs abruptly at the RCP or more smoothly during a transition period around it. We have analyzed the individual growth patterns obtained by time-lapse microscopy of 60 wild-type cells separately as well as that of the ‘average’ cell generated from their superposition. Linear, exponential, and Bilinear Functions were fitted to the data, and their suitability was compared using objective model selection criteria. This analysis found the overwhelming majority of the cells (70%) to have a Bilinear growth pattern with close to half of them showing a smooth and not an abrupt transition. The growth pattern of the average cell was also found to be Bilinear with a smooth transition.
Anna Horvath - One of the best experts on this subject based on the ideXlab platform.
-
cell length growth patterns in fission yeast reveal a novel size control mechanism operating in late g2 phase
Biology of the Cell, 2016Co-Authors: Anna Horvath, Anna Raczmonus, Peter Buchwald, Akos SveiczerAbstract:Background information Because cylindrically shaped fission yeast cells grow exclusively at their tips, cell volume is proportional to length and can be easily monitored by time-lapse microscopy. Here, we analysed the growth pattern of individual cells from several fission yeast strains to determine the growth Function that describes them most adequately and to perform size control studies. Results The growth pattern of most cells during their growth period is best described by a Bilinear Function (i.e., two linear segments of different growth rates separated by a rate-change point). Linear growth patterns were also observed in several cases, but exponential ones only rarely. Since the Bilinear patterns are separated into two segments by a breakpoint, we examined the existence of size control by regression analyses of the appropriate growth parameters in both segments. This confirmed the existence of known size controls in late G1, mid-G2 and late G2 during the fission yeast cycle. The present analyses also revealed that, contrary to the commonly accepted current view, late G2 size control is a general characteristic third event in the cycle. The level of the critical late G2 size that needs to be reached in an individual fission yeast cell is influenced by the growth rate of the cell in a manner similar to budding yeast, suggesting an evolutionary conserved mechanism. Conclusions The present study of individual cell growth patterns in wild-type and several cell cycle mutant fission yeast strains confirmed that, for most cells, growth is best described by a Bilinear Function. Three different size control mechanisms were found to operate in the different strains, and, as a novel observation, cell size was always found to be monitored before mitotic onset, irrespective of the existence of any earlier size checkpoints. Significance Studying the pattern of growth and the mechanism of size control helps to clarify the connections between cell growth and division, since their coordination must work properly to maintain size homeostasis. In this study, we argue that most individual fission yeast cells grow following a Bilinear pattern, and we confirm the existence of three different size control mechanisms.
-
cell length growth in fission yeast an analysis of its Bilinear character and the nature of its rate change transition
Fems Yeast Research, 2013Co-Authors: Anna Horvath, Anna Raczmonus, Peter Buchwald, Akos SveiczerAbstract:During their mitotic cycle, cylindrical fission yeast cells grow exclusively at their tips. Length growth starts at birth and halts at mitotic onset when the cells begin to prepare for division. While the growth pattern was initially considered to be exponential, during the last three decades an increasing amount of evidence indicated that it is rather a Bilinear Function [two linear segments separated by a rate change point (RCP)]. The main focus of this work was to clarify this and to elucidate the further question of whether the rate change occurs abruptly at the RCP or more smoothly during a transition period around it. We have analyzed the individual growth patterns obtained by time-lapse microscopy of 60 wild-type cells separately as well as that of the ‘average’ cell generated from their superposition. Linear, exponential, and Bilinear Functions were fitted to the data, and their suitability was compared using objective model selection criteria. This analysis found the overwhelming majority of the cells (70%) to have a Bilinear growth pattern with close to half of them showing a smooth and not an abrupt transition. The growth pattern of the average cell was also found to be Bilinear with a smooth transition.
Peter Buchwald - One of the best experts on this subject based on the ideXlab platform.
-
cell length growth patterns in fission yeast reveal a novel size control mechanism operating in late g2 phase
Biology of the Cell, 2016Co-Authors: Anna Horvath, Anna Raczmonus, Peter Buchwald, Akos SveiczerAbstract:Background information Because cylindrically shaped fission yeast cells grow exclusively at their tips, cell volume is proportional to length and can be easily monitored by time-lapse microscopy. Here, we analysed the growth pattern of individual cells from several fission yeast strains to determine the growth Function that describes them most adequately and to perform size control studies. Results The growth pattern of most cells during their growth period is best described by a Bilinear Function (i.e., two linear segments of different growth rates separated by a rate-change point). Linear growth patterns were also observed in several cases, but exponential ones only rarely. Since the Bilinear patterns are separated into two segments by a breakpoint, we examined the existence of size control by regression analyses of the appropriate growth parameters in both segments. This confirmed the existence of known size controls in late G1, mid-G2 and late G2 during the fission yeast cycle. The present analyses also revealed that, contrary to the commonly accepted current view, late G2 size control is a general characteristic third event in the cycle. The level of the critical late G2 size that needs to be reached in an individual fission yeast cell is influenced by the growth rate of the cell in a manner similar to budding yeast, suggesting an evolutionary conserved mechanism. Conclusions The present study of individual cell growth patterns in wild-type and several cell cycle mutant fission yeast strains confirmed that, for most cells, growth is best described by a Bilinear Function. Three different size control mechanisms were found to operate in the different strains, and, as a novel observation, cell size was always found to be monitored before mitotic onset, irrespective of the existence of any earlier size checkpoints. Significance Studying the pattern of growth and the mechanism of size control helps to clarify the connections between cell growth and division, since their coordination must work properly to maintain size homeostasis. In this study, we argue that most individual fission yeast cells grow following a Bilinear pattern, and we confirm the existence of three different size control mechanisms.
-
cell length growth in fission yeast an analysis of its Bilinear character and the nature of its rate change transition
Fems Yeast Research, 2013Co-Authors: Anna Horvath, Anna Raczmonus, Peter Buchwald, Akos SveiczerAbstract:During their mitotic cycle, cylindrical fission yeast cells grow exclusively at their tips. Length growth starts at birth and halts at mitotic onset when the cells begin to prepare for division. While the growth pattern was initially considered to be exponential, during the last three decades an increasing amount of evidence indicated that it is rather a Bilinear Function [two linear segments separated by a rate change point (RCP)]. The main focus of this work was to clarify this and to elucidate the further question of whether the rate change occurs abruptly at the RCP or more smoothly during a transition period around it. We have analyzed the individual growth patterns obtained by time-lapse microscopy of 60 wild-type cells separately as well as that of the ‘average’ cell generated from their superposition. Linear, exponential, and Bilinear Functions were fitted to the data, and their suitability was compared using objective model selection criteria. This analysis found the overwhelming majority of the cells (70%) to have a Bilinear growth pattern with close to half of them showing a smooth and not an abrupt transition. The growth pattern of the average cell was also found to be Bilinear with a smooth transition.
Anna Raczmonus - One of the best experts on this subject based on the ideXlab platform.
-
cell length growth patterns in fission yeast reveal a novel size control mechanism operating in late g2 phase
Biology of the Cell, 2016Co-Authors: Anna Horvath, Anna Raczmonus, Peter Buchwald, Akos SveiczerAbstract:Background information Because cylindrically shaped fission yeast cells grow exclusively at their tips, cell volume is proportional to length and can be easily monitored by time-lapse microscopy. Here, we analysed the growth pattern of individual cells from several fission yeast strains to determine the growth Function that describes them most adequately and to perform size control studies. Results The growth pattern of most cells during their growth period is best described by a Bilinear Function (i.e., two linear segments of different growth rates separated by a rate-change point). Linear growth patterns were also observed in several cases, but exponential ones only rarely. Since the Bilinear patterns are separated into two segments by a breakpoint, we examined the existence of size control by regression analyses of the appropriate growth parameters in both segments. This confirmed the existence of known size controls in late G1, mid-G2 and late G2 during the fission yeast cycle. The present analyses also revealed that, contrary to the commonly accepted current view, late G2 size control is a general characteristic third event in the cycle. The level of the critical late G2 size that needs to be reached in an individual fission yeast cell is influenced by the growth rate of the cell in a manner similar to budding yeast, suggesting an evolutionary conserved mechanism. Conclusions The present study of individual cell growth patterns in wild-type and several cell cycle mutant fission yeast strains confirmed that, for most cells, growth is best described by a Bilinear Function. Three different size control mechanisms were found to operate in the different strains, and, as a novel observation, cell size was always found to be monitored before mitotic onset, irrespective of the existence of any earlier size checkpoints. Significance Studying the pattern of growth and the mechanism of size control helps to clarify the connections between cell growth and division, since their coordination must work properly to maintain size homeostasis. In this study, we argue that most individual fission yeast cells grow following a Bilinear pattern, and we confirm the existence of three different size control mechanisms.
-
cell length growth in fission yeast an analysis of its Bilinear character and the nature of its rate change transition
Fems Yeast Research, 2013Co-Authors: Anna Horvath, Anna Raczmonus, Peter Buchwald, Akos SveiczerAbstract:During their mitotic cycle, cylindrical fission yeast cells grow exclusively at their tips. Length growth starts at birth and halts at mitotic onset when the cells begin to prepare for division. While the growth pattern was initially considered to be exponential, during the last three decades an increasing amount of evidence indicated that it is rather a Bilinear Function [two linear segments separated by a rate change point (RCP)]. The main focus of this work was to clarify this and to elucidate the further question of whether the rate change occurs abruptly at the RCP or more smoothly during a transition period around it. We have analyzed the individual growth patterns obtained by time-lapse microscopy of 60 wild-type cells separately as well as that of the ‘average’ cell generated from their superposition. Linear, exponential, and Bilinear Functions were fitted to the data, and their suitability was compared using objective model selection criteria. This analysis found the overwhelming majority of the cells (70%) to have a Bilinear growth pattern with close to half of them showing a smooth and not an abrupt transition. The growth pattern of the average cell was also found to be Bilinear with a smooth transition.
G K Von Schulthess - One of the best experts on this subject based on the ideXlab platform.
-
pet attenuation coefficients from ct images experimental evaluation of the transformation of ct into pet 511 kev attenuation coefficients
European Journal of Nuclear Medicine and Molecular Imaging, 2002Co-Authors: Cyrill Burger, Gerhard W Goerres, S Schoenes, Alfred Buck, Albert Lonn, G K Von SchulthessAbstract:The CT data acquired in combined PET/CT studies provide a fast and essentially noiseless source for the correction of photon attenuation in PET emission data. To this end, the CT values relating to attenuation of photons in the range of 40–140 keV must be transformed into linear attenuation coefficients at the PET energy of 511 keV. As attenuation depends on photon energy and the absorbing material, an accurate theoretical relation cannot be devised. The transformation implemented in the Discovery LS PET/CT scanner (GE Medical Systems, Milwaukee, Wis.) uses a Bilinear Function based on the attenuation of water and cortical bone at the CT and PET energies. The purpose of this study was to compare this transformation with experimental CT values and corresponding PET attenuation coefficients. In 14 patients, quantitative PET attenuation maps were calculated from germanium-68 transmission scans, and resolution-matched CT images were generated. A total of 114 volumes of interest were defined and the average PET attenuation coefficients and CT values measured. From the CT values the predicted PET attenuation coefficients were calculated using the Bilinear transformation. When the transformation was based on the narrow-beam attenuation coefficient of water at 511 keV (0.096 cm–1), the predicted attenuation coefficients were higher in soft tissue than the measured values. This bias was reduced by replacing 0.096 cm–1 in the transformation by the linear attenuation coefficient of 0.093 cm–1 obtained from germanium-68 transmission scans. An analysis of the corrected emission activities shows that the resulting transformation is essentially equivalent to the transmission-based attenuation correction for human tissue. For non-human material, however, it may assign inaccurate attenuation coefficients which will also affect the correction in neighbouring tissue.