Biochemistry of the cell cycle

Lloyd, David

doi:10.1042/bj2420313

Cited by 21 publications

(4 citation statements)

References 135 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Thus, a cell will attain maximum volume just prior to division and the average cell volume will be smallest in newly divided cells. This method of cell cycle analysis is entirely nonperturbing and circumvents many problems associated with the production of synchronous cultures for such studies, e.g., perturbation of metabolism during synchrony induction (35). Thus, the technique is unique in allowing differential cell cycle analysis in large numbers of cells from cultures displaying cell cycle heterogeneity.…”

Section: Discussionmentioning

confidence: 99%

Quantification and Characterization of Phagocytosis in the Soil Amoeba Acanthamoeba castellanii by Flow Cytometry

Avery¹,

Harwood²,

Lloyd³

1995

Appl Environ Microbiol

Self Cite

View full text Add to dashboard Cite

Phagocytosis in the common grazing soil amoeba Acanthamoeba castellanii was characterized by flow cytometry. Uptake of fluorescently labelled latex microbeads by cells was quantified by appropriate setting of thresholds on light scatter channels and, subsequently, on fluorescence histograms. Confocal laser scanning microscopy was used to verify the effectiveness of sodium azide as a control for distinguishing between cell surface binding and internalization of beads. It was found that binding of beads at the cell surface was complete within 5 min and 80% of cells had beads associated with them after 10 min. However, the total number of phagocytosed beads continued to rise up to 2 h. The prolonged increase in numbers of beads phagocytosed was due to cell populations containing increasing numbers of beads peaking at increasing time intervals from the onset of phagocytosis. Fine adjustment of thresholds on light scatter channels was used to fractionate cells according to cell volume (cell cycle stage). Phagocytotic activity was approximately threefold higher in the largest (oldest) than in the smallest (newly divided) cells of A. castellanii and showed some evidence of periodicity. At no stage in the cell cycle did phagocytosis cease. Binding and phagocytosis of beads were also markedly influenced by culture age and rate of rotary agitation of cell suspensions. Saturation of phagocytosis (per cell) at increasing bead or decreasing cell concentrations occurred at bead/cell ratios exceeding 10:1. This was probably a result of a limitation of the vacuolar uptake system of A. castellanii, as no saturation of bead binding was evident. The advantages of flow cytometry for characterization of phagocytosis at the single-cell level in heterogeneous protozoal populations and the significance of the present results are discussed.

show abstract

Section: Discussionmentioning

confidence: 99%

Quantification and Characterization of Phagocytosis in the Soil Amoeba Acanthamoeba castellanii by Flow Cytometry

Avery¹,

Harwood²,

Lloyd³

1995

Appl Environ Microbiol

Self Cite

View full text Add to dashboard Cite

show abstract

“…Biosynthesis of the nucleic acids, proteins, complex lipids and polysaccharides, and assembly of membranes and subcellular structures all occur with a slower dynamic (the epigenetic time domain). Cell division (Lloyd, 1987) takes at least 10 min (for the bacterium Vibrio natriegens), 90 min (for the yeast, Saccharomyces cerevisiae), 24 h (for human liver cells during organ regeneration after damage), or 5 d (for the bioluminescent marine dinoflagellate Piromonas). The duration of the cell cycle domain is genetically and environmentally controlled.…”

Section: T H E Molecular-genetic-cellular Levelmentioning

confidence: 99%

Biological Rhythms as Organization and Information

Lloyd

Rossi²

1993

Biological Reviews

View full text Add to dashboard Cite

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.

show abstract

“…The second messenger cyclic adenosine monophosphate (CAMP) is a phylogenetically old growth regulator that is important in the proliferative adaptation of yeast to the level of nutrients in the environment, as evidenced by a number of cell-cycle mutants with altered cAMP levels or altered CAMP-kinase (reviewed by Lloyd, 1987). In mammalian cells, cAMP has been linked both to stimulation and to inhibition of proliferation (Whitfield et al, 1987;Olashaw and Pledger, 1988, for recent reviews).…”

mentioning

confidence: 99%

Cyclic adenosine monophosphate acts synergistically with dexamethasone to inhibit the entrance of cultured adult rat hepatocytes into S‐phase: With a note on the use of nucleolar and extranucleolar [³H]‐thymidine labelling patterns to determine rapid changes in the rate of onset of DNA replication

Vintermyr

Mellgren

Bøe

et al. 1989

Journal Cellular Physiology

View full text Add to dashboard Cite

Analogs of cyclic adenosine monophosphate (cAMP) (N6benzoyl cAMP and N6monobutyryl cAMP) as well as agents that increased the intracellular level of cAMP (glucagon and isobutylmethylxanthine) inhibited the EGF-stimulated DNA replication of adult rat hepatocytes in primary culture independently of cell density. This inhibition was strongly potentiated by the glucocorticoid dexamethasone. The effect of cAMP (and dexamethasone) was not due to toxicity, because the inhibition was reversible and the cell ultrastructure preserved. cAMP acted by decreasing the rate of transition from G1- to S-phase, the duration of G2- and S-phase of the hepatocyte cell cycle being unaffected. DNA replication started in the extranucleolar compartment of the nucleus and ended in the nucleolar compartment as described earlier for cells grown in the absence of cAMP (O.K. Vintermyr and S.O. Døskeland, J. Cell. Physiol., 1987, 132:12-21). The action of cAMP was very rapid: significant inhibition of the transition was noted 2 hr after the addition of glucagon/IBMX and half-maximal inhibition after 4 hours. The determination of extranucleolarly labelled nuclei in cells pulse-labelled with [3H]thymidine allowed precise analysis of rapid changes in the probability of transition from G1- to S-phase. The extranucleolar labelling index could also be determined in cells continuously exposed to [3H]thymidine.

show abstract

Biochemistry of the cell cycle

Cited by 21 publications

References 135 publications

Quantification and Characterization of Phagocytosis in the Soil Amoeba Acanthamoeba castellanii by Flow Cytometry

Quantification and Characterization of Phagocytosis in the Soil Amoeba Acanthamoeba castellanii by Flow Cytometry

Biological Rhythms as Organization and Information

Contact Info

Product

Resources

About