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Liu X, Oh S, Peshkin L, Kirschner MW. Computationally enhanced quantitative phase microscopy reveals autonomous oscillations in mammalian cell growth. Proc Natl Acad Sci U S A 2020; 117:27388-27399. [PMID: 33087574 PMCID: PMC7959529 DOI: 10.1073/pnas.2002152117] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The fine balance of growth and division is a fundamental property of the physiology of cells, and one of the least understood. Its study has been thwarted by difficulties in the accurate measurement of cell size and the even greater challenges of measuring growth of a single cell over time. We address these limitations by demonstrating a computationally enhanced methodology for quantitative phase microscopy for adherent cells, using improved image processing algorithms and automated cell-tracking software. Accuracy has been improved more than twofold and this improvement is sufficient to establish the dynamics of cell growth and adherence to simple growth laws. It is also sufficient to reveal unknown features of cell growth, previously unmeasurable. With these methodological and analytical improvements, in several cell lines we document a remarkable oscillation in growth rate, occurring throughout the cell cycle, coupled to cell division or birth yet independent of cell cycle progression. We expect that further exploration with this advanced tool will provide a better understanding of growth rate regulation in mammalian cells.
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Affiliation(s)
- Xili Liu
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115
| | - Seungeun Oh
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115
| | - Leonid Peshkin
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115
| | - Marc W Kirschner
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115
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Gilbert K, Hammond KD, Brodsky VY, Lloyd D. An appreciation of the prescience of Don Gilbert (1930-2011): master of the theory and experimental unravelling of biochemical and cellular oscillatory dynamics. Cell Biol Int 2020; 44:1283-1298. [PMID: 32162760 DOI: 10.1002/cbin.11341] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Accepted: 03/08/2020] [Indexed: 11/08/2022]
Abstract
We review Don Gilbert's pioneering seminal contributions that both detailed the mathematical principles and the experimental demonstration of several of the key dynamic characteristics of life. Long before it became evident to the wider biochemical community, Gilbert proposed that cellular growth and replication necessitate autodynamic occurrence of cycles of oscillations that initiate, coordinate and terminate the processes of growth, during which all components are duplicated and become spatially re-organised in the progeny. Initiation and suppression of replication exhibit switch-like characteristics, that is, bifurcations in the values of parameters that separate static and autodynamic behaviour. His limit cycle solutions present models developed in a series of papers reported between 1974 and 1984, and these showed that most or even all of the major facets of the cell division cycle could be accommodated. That the cell division cycle may be timed by a multiple of shorter period (ultradian) rhythms, gave further credence to the central importance of oscillatory phenomena and homeodynamics as evident on multiple time scales (seconds to hours). Further application of the concepts inherent in limit cycle operation as hypothesised by Gilbert more than 50 years ago are now validated as being applicable to oscillatory transcript, metabolite and enzyme levels, cellular differentiation, senescence, cancerous states and cell death. Now, we reiterate especially for students and young colleagues, that these early achievements were even more exceptional, as his own lifetime's work on modelling was continued with experimental work in parallel with his predictions of the major current enterprises of biological research.
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Affiliation(s)
- Kay Gilbert
- School of Biosciences, Cardiff University, Sir Martin Evans Building, Park Place, Cardiff, CF10 3AT, Wales, UK
| | | | - Vsevolod Y Brodsky
- Koltsov Institute of Developmental Biology, Russian Academy of Sciences, Moscow, 117808, Russia
| | - David Lloyd
- School of Biosciences, Cardiff University, Sir Martin Evans Building, Park Place, Cardiff, CF10 3AT, Wales, UK
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Lloyd D, Murray DB, Aon MA, Cortassa S, Roussel MR, Beckmann M, Poole RK. Temporal metabolic partitioning of the yeast and protist cellular networks: the cell is a global scale-invariant (fractal or self-similar) multioscillator. JOURNAL OF BIOMEDICAL OPTICS 2018; 24:1-17. [PMID: 30516036 PMCID: PMC6992908 DOI: 10.1117/1.jbo.24.5.051404] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 11/01/2018] [Indexed: 06/09/2023]
Abstract
Britton Chance, electronics expert when a teenager, became an enthusiastic student of biological oscillations, passing on this enthusiasm to many students and colleagues, including one of us (DL). This historical essay traces BC's influence through the accumulated work of DL to DL's many collaborators. The overall temporal organization of mass-energy, information, and signaling networks in yeast in self-synchronized continuous cultures represents, until now, the most characterized example of in vivo elucidation of time structure. Continuous online monitoring of dissolved gases by direct measurement (membrane-inlet mass spectrometry, together with NAD(P)H and flavin fluorescence) gives strain-specific dynamic information from timescales of minutes to hours as does two-photon imaging. The predominantly oscillatory behavior of network components becomes evident, with spontaneously synchronized cellular respiration cycles between discrete periods of increased oxygen consumption (oxidative phase) and decreased oxygen consumption (reductive phase). This temperature-compensated ultradian clock provides coordination, linking temporally partitioned functions by direct feedback loops between the energetic and redox state of the cell and its growing ultrastructure. Multioscillatory outputs in dissolved gases with 13 h, 40 min, and 4 min periods gave statistical self-similarity in power spectral and relative dispersional analyses: i.e., complex nonlinear (chaotic) behavior and a functional scale-free (fractal) network operating simultaneously over several timescales.
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Affiliation(s)
- David Lloyd
- Cardiff University, School of Biosciences, Cardiff, Wales, United Kingdom
| | - Douglas B. Murray
- Keio University, Institute for Advanced Biosciences, Tsuruoka, Japan
| | - Miguel A. Aon
- National Institutes of Health, National Institute on Aging, Laboratory of Cardiovascular Science, Baltimore, Maryland, United States
| | - Sonia Cortassa
- National Institutes of Health, National Institute on Aging, Laboratory of Cardiovascular Science, Baltimore, Maryland, United States
| | - Marc R. Roussel
- University of Lethbridge, Alberta RNA Research and Training Institute and Department of Chemistry and Biochemistry, Alberta, Canada
| | - Manfred Beckmann
- Institute of Biological, Environmental and Rural, Sciences, Aberystwyth, Wales, United Kingdom
| | - Robert K. Poole
- University of Sheffield, Department of Molecular Biology and Biotechnology, Firth Court, Western Bank, Sheffield, United Kingdom
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Papagiannakis A, Niebel B, Wit EC, Heinemann M. Autonomous Metabolic Oscillations Robustly Gate the Early and Late Cell Cycle. Mol Cell 2016; 65:285-295. [PMID: 27989441 DOI: 10.1016/j.molcel.2016.11.018] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Revised: 09/26/2016] [Accepted: 11/09/2016] [Indexed: 10/20/2022]
Abstract
Eukaryotic cell division is known to be controlled by the cyclin/cyclin dependent kinase (CDK) machinery. However, eukaryotes have evolved prior to CDKs, and cells can divide in the absence of major cyclin/CDK components. We hypothesized that an autonomous metabolic oscillator provides dynamic triggers for cell-cycle initiation and progression. Using microfluidics, cell-cycle reporters, and single-cell metabolite measurements, we found that metabolism of budding yeast is a CDK-independent oscillator that oscillates across different growth conditions, both in synchrony with and also in the absence of the cell cycle. Using environmental perturbations and dynamic single-protein depletion experiments, we found that the metabolic oscillator and the cell cycle form a system of coupled oscillators, with the metabolic oscillator separately gating and maintaining synchrony with the early and late cell cycle. Establishing metabolism as a dynamic component within the cell-cycle network opens new avenues for cell-cycle research and therapeutic interventions for proliferative disorders.
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Affiliation(s)
- Alexandros Papagiannakis
- Molecular Systems Biology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, the Netherlands
| | - Bastian Niebel
- Molecular Systems Biology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, the Netherlands
| | - Ernst C Wit
- Probability and Statistics, Johann Bernoulli Institute of Mathematics and Computer Science, University of Groningen, Nijenborgh 9, 9747 AG Groningen, the Netherlands
| | - Matthias Heinemann
- Molecular Systems Biology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, the Netherlands.
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Hararuk O, Smith MJ, Luo Y. Microbial models with data-driven parameters predict stronger soil carbon responses to climate change. GLOBAL CHANGE BIOLOGY 2015; 21:2439-2453. [PMID: 25504863 DOI: 10.1111/gcb.12827] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Accepted: 10/18/2014] [Indexed: 06/04/2023]
Abstract
Long-term carbon (C) cycle feedbacks to climate depend on the future dynamics of soil organic carbon (SOC). Current models show low predictive accuracy at simulating contemporary SOC pools, which can be improved through parameter estimation. However, major uncertainty remains in global soil responses to climate change, particularly uncertainty in how the activity of soil microbial communities will respond. To date, the role of microbes in SOC dynamics has been implicitly described by decay rate constants in most conventional global carbon cycle models. Explicitly including microbial biomass dynamics into C cycle model formulations has shown potential to improve model predictive performance when assessed against global SOC databases. This study aimed to data-constrained parameters of two soil microbial models, evaluate the improvements in performance of those calibrated models in predicting contemporary carbon stocks, and compare the SOC responses to climate change and their uncertainties between microbial and conventional models. Microbial models with calibrated parameters explained 51% of variability in the observed total SOC, whereas a calibrated conventional model explained 41%. The microbial models, when forced with climate and soil carbon input predictions from the 5th Coupled Model Intercomparison Project (CMIP5), produced stronger soil C responses to 95 years of climate change than any of the 11 CMIP5 models. The calibrated microbial models predicted between 8% (2-pool model) and 11% (4-pool model) soil C losses compared with CMIP5 model projections which ranged from a 7% loss to a 22.6% gain. Lastly, we observed unrealistic oscillatory SOC dynamics in the 2-pool microbial model. The 4-pool model also produced oscillations, but they were less prominent and could be avoided, depending on the parameter values.
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Affiliation(s)
- Oleksandra Hararuk
- Department of Microbiology and Plant Biology, University of Oklahoma, Norman, OK, USA; Computational Science Laboratory, Microsoft Research, Cambridge, UK
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Lloyd D. Encystment in Acanthamoeba castellanii: a review. Exp Parasitol 2014; 145 Suppl:S20-7. [PMID: 24726698 DOI: 10.1016/j.exppara.2014.03.026] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Revised: 03/02/2014] [Accepted: 03/04/2014] [Indexed: 10/25/2022]
Abstract
Differentiation of Acanthamoeba castellanii trophozoites involves massive turnover of cellular components and remodelling of organelle structure and function so as to produce a cryptobiotic cell, resistant to desiccation, heat, freezing, and chemical treatments. This review presents a summary of a decade of research on the most studied aspects of the biochemistry of this process, with emphasis on problems of biocide and drug resistances, putative new targets, molecular and cell biology of the process of encystment, and the characteristics of the encysted state. As well as the intrinsic pathogenicity of the organism towards the cornea, and the ability of related species to invade the human brain, its propensity for harbouring and transmitting pathogenic bacteria and viruses is considerable and leads to increasing concerns. The long-term survival and resistance of cysts to drugs and biocides adds another layer of complexity to the problem of their elimination.
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Affiliation(s)
- David Lloyd
- School of Biosciences, Cardiff University, Cardiff, Wales CF10 3AT, UK.
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Lloyd D, Cortassa S, O'Rourke B, Aon MA. What yeast and cardiomyocytes share: ultradian oscillatory redox mechanisms of cellular coherence and survival. Integr Biol (Camb) 2012; 4:65-74. [PMID: 22143867 PMCID: PMC3348865 DOI: 10.1039/c1ib00124h] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The coherent and robust, yet sensitively adaptable, nature of organisms is an astonishing phenomenon that involves massive parallel processing and concerted network performance at the molecular level. Unravelling the dynamic complexities of the living state underlines the essential operation of ultradian oscillations, rhythms and clocks for the establishment and maintenance of functional order simultaneously on fast and slower timescales. Non-invasive monitoring of respiration, mitochondrial inner membrane potentials, and redox states (especially those of NAD(P)H, flavin, and the monochlorobimane complex of glutathione), even after more than 50 years research, continue to provide both new insights and biomedical applications. Experiments with yeast and in cardiac cells reveal astonishing parallels and similarities in their dynamic biochemical organization.
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Affiliation(s)
- David Lloyd
- School of Biosciences, Cardiff University, Museum Avenue, Cardiff CF10 3AT Wales, UK.
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Hinrichsen RD. The frequency of the behavioral response inParamecium tetraureliadisplays an ultradian rhythm: a regulatory role for the inositol signaling pathway. BIOL RHYTHM RES 2010. [DOI: 10.1080/09291010903411500] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Michel U, Hardeland R. On the chronobiology ofTetrahymena. III. Temperature compensation and temperature dependence in the ultradian oscillation of tyrosine aminotransferase∗∗. ACTA ACUST UNITED AC 2008. [DOI: 10.1080/09291018509359867] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Affiliation(s)
- David Lloyd
- Microbiology, BIOSI 1, Main Building, Cardiff University, PO Box 915, Cardiff CF10 3TL Wales, UK.
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Nagao R, Epstein IR, Gonzalez ER, Varela H. Temperature (Over)Compensation in an Oscillatory Surface Reaction. J Phys Chem A 2008; 112:4617-24. [PMID: 18433166 DOI: 10.1021/jp801361j] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Raphael Nagao
- Instituto de Química de São Carlos, Universidade de São Paulo, C.P. 780, CEP 13560-970, São Carlos - SP, Brasil, and Department of Chemistry and Volen Center for Complex Systems, MS 015, Brandeis University, Waltham, Massachusetts 02454-9110
| | - Irving R. Epstein
- Instituto de Química de São Carlos, Universidade de São Paulo, C.P. 780, CEP 13560-970, São Carlos - SP, Brasil, and Department of Chemistry and Volen Center for Complex Systems, MS 015, Brandeis University, Waltham, Massachusetts 02454-9110
| | - Ernesto R. Gonzalez
- Instituto de Química de São Carlos, Universidade de São Paulo, C.P. 780, CEP 13560-970, São Carlos - SP, Brasil, and Department of Chemistry and Volen Center for Complex Systems, MS 015, Brandeis University, Waltham, Massachusetts 02454-9110
| | - Hamilton Varela
- Instituto de Química de São Carlos, Universidade de São Paulo, C.P. 780, CEP 13560-970, São Carlos - SP, Brasil, and Department of Chemistry and Volen Center for Complex Systems, MS 015, Brandeis University, Waltham, Massachusetts 02454-9110
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Abstract
Ultradian rhythms are those that cycle many times in a day and are therefore measured in hours, minutes, seconds or even fractions of a second. In yeasts and protists, a temperature-compensated clock with a period of about an hour (30-90 minutes) provides the time base upon which all central processes are synchronized. A 40-minute clock in yeast times metabolic, respiratory and transcriptional processes, and controls cell division cycle progression. This system has at its core a redox cycle involving NAD(P)H and dithiol-disulfide interconversions. It provides an archetype for biological time keeping on longer time scales (e.g. the daily cycles driven by circadian clocks) and underpins these rhythms, which cannot be understood in isolation. Ultradian rhythms are the foundation upon which the coherent functioning of the organism depends.
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Affiliation(s)
- David Lloyd
- Microbiology, School of Biosciences, Cardiff University, Wales, UK.
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Murray DB, Lloyd D. A tuneable attractor underlies yeast respiratory dynamics. Biosystems 2006; 90:287-94. [PMID: 17074432 DOI: 10.1016/j.biosystems.2006.09.032] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2006] [Revised: 09/12/2006] [Accepted: 09/13/2006] [Indexed: 11/25/2022]
Abstract
Our understanding of the molecular structure and function in the budding yeast, Saccharomyces cerevisiae, surpasses that of all other eukaryotic cells. However, the fundamental properties of the complex processes and their control systems have been difficult to reconstruct from detailed dissection of their molecular components. Spontaneous oscillatory dynamics observed in self-synchronized continuous cultures is pervasive, involves much of the cellular network, and provides unique insights into integrative cell physiology. Here, in non-invasive experiments in vivo, we exploit these oscillatory dynamics to analyse the global timing of the cellular network to show the presence of a low-order chaotic component. Although robust to a wide range of environmental perturbations, the system responds and reacts to the imposition of harsh environmental conditions, in this case low pH, by dynamic re-organization of respiration, and this feeds upwards to affect cell division. These complex dynamics can be represented by a tuneable attractor that orchestrates cellular complexity and coherence to the environment.
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Affiliation(s)
- Douglas B Murray
- The Systems Biology Institute, 953 Shinanomachi Research Park, Keio University School of Medicine, 35 Shinanomachi, Shimjuku-ku, Tokyo 160-852, Japan.
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Lloyd D, Murray DB. The temporal architecture of eukaryotic growth. FEBS Lett 2006; 580:2830-5. [PMID: 16545376 DOI: 10.1016/j.febslet.2006.02.066] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2006] [Accepted: 02/25/2006] [Indexed: 11/19/2022]
Abstract
Coherence of the time structure of growing organisms depends on a metronome-like orchestration. In a continuously perfused culture of Saccharomyces cerevisiae the redox state of the cell shows a temperature-compensated oscillation manifest in respiratory cycles, which are measured by continuous and non-invasive electrodes of probes such as dissolved oxygen and probes such as fluorometric NAD(P)H. Although the entire transcriptome exhibits low-amplitude oscillatory behaviour, transcripts involved in the vast majority of metabolism, stress response, cellular structure, protein turnover, mRNA turnover, and DNA synthesis are amongst the top oscillators and their orchestration occurs by an intricate network of transcriptional regulators. Therefore cellular auto-dynamism is a function of a large ensemble of excitable intracellular components of that self-organized temporally and spatially that encompasses mitochondrial, nuclear, transcriptional and metabolic dynamics, coupled by cellular redox state.
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Affiliation(s)
- David Lloyd
- Microbiology, Cardiff School of Biosciences, (BIOSI 1, Main Building), Cardiff University, P.O. Box 915, Cardiff CF10 3TL, Wales, UK.
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Lloyd D. Effects of uncoupling of mitochondrial energy conservation on the ultradian clock-driven oscillations in Saccharomyces cerevisiae continuous culture. Mitochondrion 2005; 3:139-46. [PMID: 16120353 DOI: 10.1016/j.mito.2003.08.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2003] [Revised: 08/26/2003] [Accepted: 08/27/2003] [Indexed: 10/27/2022]
Abstract
Protonophores have several different perturbative effects on dissolved O2 concentrations in continuous cultures of Saccharomyces cerevisiae. As well as uncoupling energy conservation from mitochondrial electron transport in vivo, they reset ultradian clock-driven respiratory oscillations and produce cell cycle effects. Thus, additions at low concentration (1.25 microM) of either m-chlorocarbonyl-cyanide phenylhydrazone (CCCP) or 5-chloro-3-t-butyl-2-chloro-4(1)-nitrosalicylanilide (S13) led to phase resetting of the 48 min ultradian clock-driven respiratory oscillations. At 2.5 microM CCCP or 4 microM S13, transient inhibition of oscillatory respiration (for 5 h) preceded synchronisation of the cell division cycle seen as a slow (9 h period) wave that enveloped the 48 min oscillation. At still higher concentrations of CCCP (5 microM), the cell division cycle was prolonged by about 7 h, and during this phase, the respiratory oscillation became undetectable. The significance of these observations with respect to the time-keeping functions of the ultradian clock is discussed.
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Affiliation(s)
- David Lloyd
- Microbiology (BIOSI 1), Cardiff University, P.O. Box 915, Cardiff, Wales CF10 3TL, UK.
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Lloyd D, Salgado LEJ, Turner MP, Suller MTE, Murray D. Cycles of mitochondrial energization driven by the ultradian clock in a continuous culture of Saccharomyces cerevisiae. MICROBIOLOGY (READING, ENGLAND) 2002; 148:3715-3724. [PMID: 12427961 DOI: 10.1099/00221287-148-11-3715] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
A continuous culture of Saccharomyces cerevisiae IFO 0233, growing with glucose as the major carbon and energy source, shows oscillations of respiration with a period of 48 min. Samples taken at maxima and minima indicate that (i) periodic changes do not occur as a result of carbon depletion, (ii) intrinsic differences in respiratory activity occur in washed organisms and (iii) a respiratory inhibitor accumulates during respiratory oscillations. Plasma membrane and inner mitochondrial membranes generate transmembrane electrochemical potentials; changes in these can be respectively assessed using anionic or cationic fluorophores. Thus flow cytometric analyses indicated that an oxonol dye [DiBAC(4)(3); bis(1,3-dibutylbarbituric acid)trimethine oxonol] was excluded from yeasts to a similar extent (in >98% of the population) at all stages, showing that the plasma membrane potential was maintained at a steady value. However, uptake of Rhodamine 123 was greatest at that phase characterized by a low respiratory rate. Addition of uncouplers of energy conservation [CCCP (m-chlorocarbonylcyanide phenylhydrazone) or S-13(5-chloro-3-t-butyl-2-chloro-4(1)-nitrosalicylanilide)] to the continuous cultures increased the respiration, but had only a transient effect on the period of the oscillation. Electron microscopy showed changes in mitochondrial ultrastructure during the respiratory oscillation. At low respiration the cristae were more clearly defined due to swelling of the matrix; this corresponds to the 'orthodox' conformation. When respiration was high the mitochondrial configuration was 'condensed'. It has been shown previously that a temperature-compensated ultradian clock operates in S. cerevisiae. It is proposed that mitochondria undergo cycles of energization in response to energetic demands driven by this ultradian clock output.
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Affiliation(s)
- David Lloyd
- Microbiology (BIOSI 1, Main Building), Cardiff University, PO Box 915, Cardiff CF10 3TL, Wales, UK1
| | - L Eshantha J Salgado
- Microbiology (BIOSI 1, Main Building), Cardiff University, PO Box 915, Cardiff CF10 3TL, Wales, UK1
| | - Michael P Turner
- Microbiology (BIOSI 1, Main Building), Cardiff University, PO Box 915, Cardiff CF10 3TL, Wales, UK1
| | - Marc T E Suller
- Microbiology (BIOSI 1, Main Building), Cardiff University, PO Box 915, Cardiff CF10 3TL, Wales, UK1
| | - Douglas Murray
- School of Applied Science, University of the South Bank, 103 Borough Road, London SET 0AA, UK2
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Lloyd D, Eshantha L, Salgado J, Turner MP, Murray DB. Respiratory oscillations in yeast: clock-driven mitochondrial cycles of energization. FEBS Lett 2002; 519:41-4. [PMID: 12023015 DOI: 10.1016/s0014-5793(02)02704-7] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Respiratory oscillations in continuous yeast cultures can be accounted for by cyclic energization of mitochondria, dictated by the demands of a temperature-compensated ultradian clock with a period of 50 min. Inner mitochondrial membranes show both ultrastructural modifications and electrochemical potential changes. Electron transport components (NADH and cytochromes c and c oxidase) show redox state changes as the organisms cycle between their energized and de-energized phases. These regular cycles are transiently perturbed by uncouplers of energy conservation, with amplitudes more affected than period; that the characteristic period is restored after only one prolonged cycle, indicates that mitochondrial energy generation is not part of the clock mechanism itself, but is responding to energetic requirement.
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Affiliation(s)
- David Lloyd
- Microbiology (BIOSI 1, Main Building), Cardiff University, P.O. Box 915, Cardiff, UK.
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Murray DB, Roller S, Kuriyama H, Lloyd D. Clock control of ultradian respiratory oscillation found during yeast continuous culture. J Bacteriol 2001; 183:7253-9. [PMID: 11717285 PMCID: PMC95575 DOI: 10.1128/jb.183.24.7253-7259.2001] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A short-period autonomous respiratory ultradian oscillation (period approximately 40 min) occurs during aerobic Saccharomyces cerevisiae continuous culture and is most conveniently studied by monitoring dissolved O(2) concentrations. The resulting data are high quality and reveal fundamental information regarding cellular dynamics. The phase diagram and discrete fast Fourier transformation of the dissolved O(2) values revealed a square waveform with at least eight harmonic peaks. Stepwise changes in temperature revealed that the oscillation was temperature compensated at temperatures ranging from 27 to 34 degrees C when either glucose (temperature quotient [Q(10)] = 1.02) or ethanol (Q(10) = 0.82) was used as a carbon source. After alteration of the temperature beyond the temperature compensation region, phase coherence events for individual cells were quickly lost. As the cell doubling rate decreased from 15.5 to 9.2 h (a factor of 1.68), the periodicity decreased by a factor of 1.26. This indicated that there was a degree of nutrient compensation. Outside the range of dilution rates at which stable oscillation occurred, the mode of oscillation changed. The oscillation in respiratory output is therefore under clock control.
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Affiliation(s)
- D B Murray
- School of Applied Science, South Bank University, London SE1 0AA, United Kingdom.
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Wang S, Pogue R, Morré DM, Morré DJ. NADH oxidase activity (NOX) and enlargement of HeLa cells oscillate with two different temperature-compensated period lengths of 22 and 24 minutes corresponding to different NOX forms. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1539:192-204. [PMID: 11420117 DOI: 10.1016/s0167-4889(01)00107-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
NOX proteins are cell surface-associated and growth-related hydroquinone (NADH) oxidases with protein disulfide-thiol interchange activity. A defining characteristic of NOX proteins is that the two enzymatic activities alternate to generate a regular period length of about 24 min. HeLa cells exhibit at least two forms of NOX. One is tumor-associated (tNOX) and is inhibited by putative quinone site inhibitors (e.g., capsaicin or the antitumor sulfonylurea, LY181984). Another is constitutive (CNOX) and refractory to inhibition. The periodic alternation of activities and drug sensitivity of the NADH oxidase activity observed with intact HeLa cells was retained in isolated plasma membranes and with the solubilized and partially purified enzyme. At least two activities were present. One had a period length of 24 min and the other had a period length of 22 min. The lengths of both the 22 and the 24 min periods were temperature compensated (approximately the same when measured at 17, 27 or 37 degrees C) whereas the rate of NADH oxidation approximately doubled with each 10 degrees C rise in temperature. The rate of increase in cell area of HeLa cells when measured by video-enhanced light microscopy also exhibited a complex period of oscillations reflective of both 22 and 24 min period lengths. The findings demonstrate the presence of a novel oscillating NOX activity at the surface of cancer cells with a period length of 22 min in addition to the constitutive NOX of non-cancer cells and tissues with a period length of 24 min.
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Affiliation(s)
- S Wang
- Department of Foods and Nutrition, Purdue University, West Lafayette, IN, USA
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21
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Abstract
Period homeostasis is the defining characteristic of a biological clock. Strict period homeostasis is found for the ultradian clocks of eukaryotic microbes. In addition to being temperature-compensated, the period of these rhythms is unaffected by differences in nutrient composition or changes in other environmental variables. The best-studied examples of ultradian clocks are those of the ciliates Paramecium tetraurelia and Tetrahymena sp. and of the fission yeast, Schizosaccharomyces pombe. In these single cell eukaryotes, up to seven different parameters display ultradian rhythmicity with the same, species- and strain-specific period. In fission yeast, the molecular genetic analysis of ultradian clock mechanisms has begun with the systematic analysis of mutants in identified candidate genes. More than 40 "clock mutants" have already been identified, most of them affected in components of major regulatory and signalling pathways. These results indicate a high degree of complexity for a eukaryotic clock mechanism. BioEssays 22:16-22, 2000.
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Affiliation(s)
- F Kippert
- Biological Timing Lab, Institute of Cell, Animal and Population Biology, University of Edinburgh, Edinburgh, Scotland, United Kingdom.
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22
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Abstract
The time structure of a biological system is at least as intricate as its spatial structure. Whereas we have detailed information about the latter, our understanding of the former is still rudimentary. As techniques for monitoring intracellular processes continuously in single cells become more refined, it becomes increasingly evident that periodic behaviour abounds in all time domains. Circadian timekeeping dominates in natural environments. Here the free-running period is about 24 h. Circadian rhythms in eukaryotes and prokaryotes allow predictive matching of intracellular states with environmental changes during the daily cycles. Unicellular organisms provide excellent systems for the study of these phenomena, which pervade all higher life forms. Intracellular timekeeping is essential. The presence of a temperature-compensated oscillator provides such a timer. The coupled outputs (epigenetic oscillations) of this ultradian clock constitute a special class of ultradian rhythm. These are undamped and endogenously driven by a device which shows biochemical properties characteristic of transcriptional and translational elements. Energy-yielding processes, protein turnover, motility and the timing of the cell-division cycle processes are all controlled by the ultradian clock. Different periods characterize different species, and this indicates a genetic determinant. Periods range from 30 min to 4 h. Mechanisms of clock control are being elucidated; it is becoming evident that many different control circuits can provide these functions.
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Affiliation(s)
- D Lloyd
- Microbiology Group (PABIO), University of Wales Cardiff, UK
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23
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Ruoff P, Rensing L, Kommedal R, Mohsenzadeh S. Modeling temperature compensation in chemical and biological oscillators. Chronobiol Int 1997; 14:499-510. [PMID: 9298285 DOI: 10.3109/07420529709001471] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
All physicochemical and biological oscillators maintain a balance between destabilizing reactions (as, for example, intrinsic autocatalytic or amplifying reactions) and stabilizing processes. These two groups of processes tend to influence the period in opposite directions and may lead to temperature compensation whenever their overall influence balances. This principle of "antagonistic balance" has been tested for several chemical and biological oscillators. The Goodwin negative feedback oscillator appears of particular interest for modeling the circadian clocks in Neurospora and Drosophila and their temperature compensation. Remarkably, the Goodwin oscillator not only gives qualitative, correct phase response curves for temperature steps and temperature pulses, but also simulates the temperature behavior of Neurospora frq and Drosophila per mutants almost quantitatively. The Goodwin oscillator predicts that circadian periods are strongly dependent on the turnover of the clock mRNA or clock protein. A more rapid turnover of clock mRNA or clock protein results, in short, a slower turnover in longer period lengths.
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Affiliation(s)
- P Ruoff
- School of Technology and Science, Stavanger College, Norway.
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24
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Kippert F. The ultradian clocks of eukaryotic microbes: timekeeping devices displaying a homeostasis of the period. Chronobiol Int 1997; 14:469-79. [PMID: 9298283 DOI: 10.3109/07420529709001469] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Temperature compensation of their period is one of the canonical characteristics of circadian rhythms, yet it is not restricted to circadian rhythms. This short review summarizes the evidence for ultradian rhythms, with periods from 1 minute to several hours, that likewise display a strict temperature compensation. They have been observed mostly in unicellular organisms in which their constancy of period at different temperatures, as well as under different growth conditions (e.g., medium type, carbon source), indicates a general homeostasis of the period. Up to eight different parameters, including cell division, cell motility, and energy metabolism, were observed to oscillate with the same periodicity and therefore appear to be under the control of the same central pacemaker. This suggests that these ultradian clocks should be considered as cellular timekeeping devices that in fast-growing cells take over temporal control of cellular functions controlled by the circadian clock in slow-growing or nongrowing cells. Being potential relatives of circadian clocks, these ultradian rhythms may serve as model systems in chronobiological research. Indeed, mutations have been found that affect both circadian and ultradian periods, indicating that the respective oscillators share some mechanistic features. In the haploid yeast Schizosaccharomyces pombe, a number of genes have been identified where mutation, deletion, or overexpression affect the ultradian clock. Since most of these genes play roles in cellular metabolism and signaling, and mutations have pleiotropic effects, it has to be assumed that the clock is deeply embedded in cellular physiology. It is therefore suggested that mechanisms ensuring temperature compensation and general homeostasis of period are to be sought in a wider context.
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Affiliation(s)
- F Kippert
- Institute of Cell, Animal and Population Biology, University of Edinburgh, Scotland, UK.
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25
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Kippert F. A temperature-compensated ultradian clock of Tetrahymena: oscillations in respiratory activity and cell division. Chronobiol Int 1996; 13:1-13. [PMID: 8761932 DOI: 10.3109/07420529609040837] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Both a circadian clock and an ultradian clock (period 4-5 h) have previously been described for the ciliated protozoon Tetrahymena. The present communication demonstrates the existence of yet another cellular clock: an ultradian rhythm with a period of about 30 min. The period was found to be well temperature-compensated over the range studied, i.e., between 19 degrees C and 33 degrees C. Ultradian rhythmicity was initiated by dilution of stationary-phase cultures, which were kept previously in a light-dark cycle, into fresh medium. LD treatment during stationary phase was an absolute requirement, since cultures kept in either LL or DD did not produce the ultradian rhythmicity after refeeding. The clock exerts control over respiration; the observed oscillation in oxygen uptake is just a hand of the clock: after a limitation of oxygen supply had ended, the rhythm resumed with the same phase and period as that in control cultures. The clock exerts temporal control also over cell division; in the refed culture cell division resumed with an oscillation in the number of dividing organisms. The period of this oscillation corresponded to that of the rhythm in respiratory activity, indicating that the same ultradian clock may exert control over different cellular functions. Analysis of a second Tetrahymena strain indicates that period length of the ultradian clock is a strain-specific characteristic.
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Affiliation(s)
- F Kippert
- Institute of Physiological Chemistry, University of Tübingen
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26
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Kippert F. An ultradian clock controls locomotor behaviour and cell division in isolated cells of Paramecium tetraurelia. J Cell Sci 1996; 109 ( Pt 4):867-73. [PMID: 8718678 DOI: 10.1242/jcs.109.4.867] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
An ultradian clock operates in fast growing cells of the large ciliate, Paramecium tetraurelia. The period of around 70 minutes is well temperature-compensated over the temperature range tested, i.e. between 18 degrees C and 33 degrees C. The Q10 between 18 degrees C and 27 degrees C is 1.08; above 27 degrees C there is a slight overcompensation. The investigation of individual cells has revealed that two different cellular functions are under temporal control by this ultradian clock. First, locomotor behaviour, which is an alternation between a phase of fast swimming with only infrequent turning, and a phase of slow swimming with frequent spontaneous changes of direction. In addition, the ultradian clock is involved in the timing of cell division. Generation times are not randomly distributed, but occur in well separated clusters. At all of the six temperatures tested, the clusters are separated by around 70 minutes which corresponds well to the period of the locomotor behaviour rhythm at the respective temperatures. Whereas the interdivision times were gradually lengthened both above and below the optimum growth temperature, the underlying periodicity remained unaffected. Also cells of different clonal age had identical periods, suggesting that neither the differences in DNA content, not other changes associated with ageing in Paramecium have an effect on the clock. A constant phase relationship was observed between the rhythm in locomotor behaviour and the time window for cell division; this strongly suggests that the same ultradian clock exerts temporal control over both processes.
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Affiliation(s)
- F Kippert
- Institute of Physiological Chemistry, University of Tübingen, Germany
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27
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Power JM, Ringo JM, Dowse HB. The effects of period mutations and light on the activity rhythms of Drosophila melanogaster. J Biol Rhythms 1995; 10:267-80. [PMID: 7488764 DOI: 10.1177/074873049501000309] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Strains of Drosophila melanogaster homozygous for alleles of the period gene (perO, perL, perS, and per+) were reared for multiple generations either in light:dark cycles (LD), continuous illumination (LL), or chronic darkness (DD). The locomotor activity of adult flies from these cultures was monitored in either LL or DD. Flies that were reared and tested in DD had a lower proportion of individuals with normal circadian rhythms than flies reared in LD or LL and tested in DD. The activity rhythms of DD-reared DD-tested animals, when present, showed phase coherence within two out of seven populations, while 8 out of 10 LL-reared DD-tested showed phase coherence. Flies tested in LL were largely devoid of circadian rhythms regardless of their rearing environment. Ultradian rhythms were more evident under conditions disruptive to circadian rhythmicity, but were observed in the presence and absence of circadian rhythms. The periods of the ultradian rhythms of LL-reared DD-tested and LD-reared DD-tested flies varied significantly among genotypes, while in other rearing and testing regimes, no relationship was found.
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Affiliation(s)
- J M Power
- Department of Zoology, University of Maine, Crono 04469, USA
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28
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Abstract
While it is generally acknowledged that modern science began with the quantification of time in the measurement of linear physical processes in space by Galileo and Newton, the biological sciences have only recently developed appropriate experimental and mathematical methods for the description of living systems in terms of processes of non-linear, recursive dynamics. We now recognize that living organisms have patterns of exquisitely timed processes that are as intricate as their spatial structure and organization. Self-similarities of life processes in time and space have evolved to generate an ensemble of oscillators within which analogous functions may be discerned on many different time scales. The increasing complexity of periodic relationships on and between the many levels of biological organization are uncovered by current research. Recent efforts to reformulate the foundation of physics from the quantum to the cosmological level by using the concept of information as the common denominator integrating time, structure and energy remind us of an apparently analogous suggestion in the chronobiological literature which also describes the periodic dynamics of living systems as information processing. In this paper we review the periodic processes of living systems on all levels from the molecular, genetic and cellular to the neuroendocrinological, behavioural and social domains. Biological rhythms may be conceptualized as the evolution of ever more complex dynamics of information transduction that optimize the temporal integrity, development, and survival of the organism.
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Affiliation(s)
- D Lloyd
- Microbiology Group (PABIO), University of Wales College of Cardiff, Wales, UK
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29
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30
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31
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Abstract
Ultradian oscillations with periods between 5 min and 4 h have been described in cell-free extracts, single-celled eukaryotes, cultured cells and embryos. Whereas some of these potentially oscillatory systems (e.g. glycolysis) may only exhibit this type of behaviour rarely if at all in vivo, other ultradian oscillators in lower eukaryotes are rhythms and probably have timekeeping functions. Rhythms with ultradian periods of 10 min to 20 h in oxygen consumption and carbon dioxide production have also been studied in endotherm animals: these rhythms may be modified by variations of environmental parameters and by circadian and infradian synchronizers. Interspecies and interstrain differences strongly suggest that these rhythms are endogenous and have a genetic origin. We suggest that the temporal organization of biochemical and physiological processes facilitates optimization of thermodynamic maintenance of the organism within the random fluctuations of its physicochemical environment and contributes to genetic selection.
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Affiliation(s)
- D Lloyd
- Microbiology Group, School of Pure and Applied Biology, University of Wales College of Cardiff, U.K
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32
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33
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Rensing L, Hardeland R. The cellular mechanism of circadian rhythms--a view on evidence, hypotheses and problems. Chronobiol Int 1990; 7:353-70. [PMID: 2097068 DOI: 10.3109/07420529009059146] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
A stable period length is a characteristic property of circadian oscillations. The question about whether higher frequency oscillators (0.5-8 hr) contribute to or establish the stable circadian periodicity cannot be answered at present. A sequential coupling of quantal subcycles appears possible on the basis of known "ultradian" oscillations. There is, however, no supporting evidence for such a concept. Phase response curves of the circadian clock derived from various perturbing pulses allow qualitative conclusions concerning the perturbed clock process. Deductions from computer simulations also allow conclusions about the phase of this oscillatory process. The distinction between processes (a) essential to the clock mechanism, (b) maintaining and controlling the clock (inputs) and (c) depending on the clock (outputs) on the basis of "oscillatory" and "change of psi or tau after perturbation" seems to be useful but not stringent. Protein synthesis may be an essential or input process. Oscillatory changes of this process may be due to periodic translational control or RNA-supply. Circadian changes in protein concentration and/or activity may depend on periodic synthesis, proteolysis, covalent modifications or aggregations. Specific essential proteins have not been identified conclusively. The large overlap between the group of agents and treatments that phase shift the clock and the group that induces stress proteins suggest that the latter may play a role in the controlling (input) or essential domain. The role of membranes in the clock mechanism is not clear: concepts assuming an essential function are based on circumstantial evidence. The membrane potential as well as Ca2+ may be involved in either input or essential function. Ca(2+)-calmodulin may also be important as concluded from inhibitor experiments. It is tempting to assume that a calmodulin-dependent kinase is part of a periodic protein phosphorylation process, yet it is not clear whether the periodic protein phosphorylation that has been observed is essential or is just another output process.
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Affiliation(s)
- L Rensing
- Biology Department, University of Bremen, Germany
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34
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Jenkins H, Griffiths A, Lloyd D. Simultaneous operation of ultradian and circadian rhythms inChlamydomonas reinhardii. ACTA ACUST UNITED AC 1989. [DOI: 10.1080/09291018909360013] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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35
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Balzer I, Neuhaus-Steinmetz U, Hardeland R. Temperature compensation in an ultradian rhythm of tyrosine aminotransferase activity in Euglena gracilis Klebs. EXPERIENTIA 1989; 45:476-7. [PMID: 2566511 DOI: 10.1007/bf01952036] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Tyrosine aminotransferase activity of Euglena oscillates with an ultradian period of approximately 4-5 h. The oscillation frequency in the time series was determined by cosine fitting. Experiments which were performed between 16 and 31.5 degrees C revealed temperature compensation.
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Affiliation(s)
- I Balzer
- I. Zoologisches Institut, Universität Göttingen, Federal Republic of Germany
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36
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Balzer I, Neuhaus‐Steinmetz U, Quentin E, van Wüllen M, Hardeland R. Concomitance of circadian and circa‐4‐hour ultradian rhythms inEuglena gracilis. ACTA ACUST UNITED AC 1989. [DOI: 10.1080/09291018909359994] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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37
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Millet B, Botton AM, Hayoum C, Koukkari WL. An experimental analysis and comparison of three rhythms of movements in bean (Phaseolus vulgaris L.). Chronobiol Int 1988; 5:187-93. [PMID: 3219754 DOI: 10.3109/07420528809079560] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Three types of rhythmic movements of Phaseolus vulgaris L. (pole beans) were examined collectively and their characteristics compared. Although the ultradian rhythms of shoot circumnutation and leaf movement, as well as the circadian rhythm of leaf movement, occurred simultaneously, each rhythm could be expressed independently of the other two. Shoot circumnutation and ultradian leaf movements displayed the same period (80 min at 25 degrees C and Q10 congruent to 2), while the period of the circadian leaf movements was not temperature dependent (Q10 congruent to 1). Interaction into the plant between two ultradian rhythms (shoot circumnutation and ultradian leaf movement) with the same period and coexistence in the pulvinus of an ultradian with a circadian rhythm are discussed.
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Affiliation(s)
- B Millet
- Laboratoire de Botanique, Faculté des Sciences, Besançon, France
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38
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Kippert F. Endocytobiotic coordination, intracellular calcium signaling, and the origin of endogenous rhythms. Ann N Y Acad Sci 1987; 503:476-95. [PMID: 3304083 DOI: 10.1111/j.1749-6632.1987.tb40631.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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39
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40
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41
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Dowse HB, Ringo JM. Further evidence that the circadian clock in Drosophila is a population of coupled ultradian oscillators. J Biol Rhythms 1987; 2:65-76. [PMID: 2979652 DOI: 10.1177/074873048700200106] [Citation(s) in RCA: 83] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
We hypothesize that ultradian oscillators are coupled to yield a composite circadian clock in Drosophila. In such a system, period would be a function of the tightness of coupling of these oscillators, increasing as coupling loosens. Ultradian oscillations would become apparent under weak coupling or in the absence of coupling. A new technique for calculating signal-to-noise ratio (SNR) for biological rhythms to characterize their precision has yielded support for this hypothesis. SNR of rhythms of the allelic series of mutations at the period (per) locus of Drosophila melanogaster were compared. Per(o) was the noisiest, grading through perL, per+, and pers, the least noisy. SNR decreases significantly with increasing period in pers, per+, and perL; per(o) typically has multiple ultradian oscillations and the lowest SNR. At least 70% of perL individuals also exhibit ultradian periodicities.
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Affiliation(s)
- H B Dowse
- Department of Zoology, University of Maine, Orono 04469
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42
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Lloyd D, Edwards SW. Temperature‐compensated ultradian rhythms in lower eukaryotes: Periodic turnover coupled to a timer for cell division. ACTA ACUST UNITED AC 1986. [DOI: 10.1080/09291018609359923] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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43
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Silyn‐Roberts H, Engelmann W, Grell KG. Thalassomyxa australisrhythmicity I. temperature dependence. ACTA ACUST UNITED AC 1986. [DOI: 10.1080/09291018609359909] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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44
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Hardeland R, Harnau G, Rüsenberg M, Balzer I. Multiplicity or uniformity of cellular temperature compensation mechanisms? ACTA ACUST UNITED AC 1986. [DOI: 10.1080/09291018609359904] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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45
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Thompson WD, Evans AT, Campbell R. The control of fibrogenesis: stimulation and suppression of collagen synthesis in the chick chorioallantoic membrane with fibrin degradation products, wound extracts and proteases. J Pathol 1986; 148:207-15. [PMID: 3009765 DOI: 10.1002/path.1711480304] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The chick chorioallantoic membrane model (CAM) has previously been used to demonstrate cell proliferation, characteristic of both angiogenesis and fibrogenesis, after exposure to fibrin degradation products. This model has now been adapted for quantitative in vivo assay of collagen polypeptide synthesis and prolyl hydroxylase activity. The CAM exhibits oscillations in the level of labelled collagen, a pattern attributable to rapid intracellular degradation and proline recycling following a brief labelling period. Both collagen synthesis and prolyl hydroxylase activity are stimulated by fibrin degradation products (less than 50 000 MW). Such stimulation occurs by 3 h and precedes the rise in general protein synthesis. Extracts of healing mouse skin wounds, rich in proteases, inhibited collagen synthesis, as did pure plasmin. Conversely, stimulation was achieved when proteolytic activity was neutralized by soybean trypsin inhibitor. These findings help to explain the observation that fibroblasts and endothelial cells proliferate and migrate centrally in an inflammatory lesion without depositing collagen, whilst in a milieu of high proteolytic activity. More peripherally, where proteases are inactivated by antiproteases in inflammatory exudate, such cell movement ceases and collagen deposition is observed.
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