scholarly journals Quiescence Through the Prism of Evolution

2021 ◽  
Vol 9 ◽  
Author(s):  
Bertrand Daignan-Fornier ◽  
Damien Laporte ◽  
Isabelle Sagot
Keyword(s):  
Cell Survival ◽  
Environmental Conditions ◽  
Quiescent Cell ◽  
Unicellular Organisms ◽  
Forms Of Life ◽  
Cell Specialization

Being able to reproduce and survive is fundamental to all forms of life. In primitive unicellular organisms, the emergence of quiescence as a reversible proliferation arrest has most likely improved cell survival under unfavorable environmental conditions. During evolution, with the repeated appearances of multicellularity, several aspects of unicellular quiescence were conserved while new quiescent cell intrinsic abilities arose. We propose that the formation of a microenvironment by neighboring cells has allowed disconnecting quiescence from nutritional cues. In this new context, non-proliferative cells can stay metabolically active, potentially authorizing the emergence of new quiescent cell properties, and thereby favoring cell specialization. Through its co-evolution with cell specialization, quiescence may have been a key motor of the fascinating diversity of multicellular complexity.

A Glossary of the Extant Haptophyta of the World

1995 ◽  
Vol 75 (4) ◽  
pp. 769-814 ◽  
Author(s):  
R.W. Jordan ◽  
A. Kleijne ◽  
B.R. Heimdal ◽  
J.C. Green
Keyword(s):  
Electron Microscope ◽  
Marine Sediments ◽  
Round Table ◽  
Marine Habitats ◽  
The World ◽  
Long Time ◽  
Unicellular Organisms ◽  
Forms Of Life

The Haptophyta comprises a group of microalgae of particular importance in marine habitats, often occurring in ‘bloom’ concentrations, sometimes with devastating effects where the bloom is composed of species toxic to other forms of life. The most familiar species are the coccolithophorids, unicellular organisms encased in calcified scale-like structures, the coccoliths, which are readily preserved in marine sediments and have for a long time been important indicators in micropalaeontological studies. In the middle of this century it was recognized that there was a need to compile and standardize the terminology used in coccolith morphology (Braarud et al., 1955; Halldal & Markali, 1955). This approach was continued by several authors (e.g. Hay et al., 1966; Okada & McIntyre, 1977; Tappan, 1980; Perch-Nielsen, 1985) in published articles, and in the report from a Round Table session at the Rome 1970 Plankton Conference (Farinacci, 1971), which included terms from both fossil and extant taxa. Over the last two decades many new terms have been introduced as observations on coccolith morphology have improved through the use of the electron microscope, and recent glossaries covering various aspects of haptophyte terminology have been published by Heimdal (1993), Kleijne (1993) and Margulis et al. (1993).

scholarly journals Light Harvesting in Fluctuating Environments: Evolution and Function of Antenna Proteins across Photosynthetic Lineage

Plants ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 1184
Author(s):  
Pushan Bag
Keyword(s):  
Environmental Conditions ◽  
Light Harvesting ◽  
Higher Plants ◽  
Point Of View ◽  
Fine Tuning ◽  
Vast Number ◽  
Unicellular Organisms ◽  
And Function ◽  
Pigment Protein Complex ◽  
Antenna Systems

Photosynthesis is the major natural process that can harvest and harness solar energy into chemical energy. Photosynthesis is performed by a vast number of organisms from single cellular bacteria to higher plants and to make the process efficient, all photosynthetic organisms possess a special type of pigment protein complex(es) that is (are) capable of trapping light energy, known as photosynthetic light-harvesting antennae. From an evolutionary point of view, simpler (unicellular) organisms typically have a simple antenna, whereas higher plants possess complex antenna systems. The higher complexity of the antenna systems provides efficient fine tuning of photosynthesis. This relationship between the complexity of the antenna and the increasing complexity of the organism is mainly related to the remarkable acclimation capability of complex organisms under fluctuating environmental conditions. These antenna complexes not only harvest light, but also provide photoprotection under fluctuating light conditions. In this review, the evolution, structure, and function of different antenna complexes, from single cellular organisms to higher plants, are discussed in the context of the ability to acclimate and adapt to cope under fluctuating environmental conditions.

scholarly journals Organellar Evolution: A Path from Benefit to Dependence

2022 ◽  
Vol 10 (1) ◽  
pp. 122
Author(s):  
Miroslav Oborník
Keyword(s):  
Cell Survival ◽  
Metabolic Pathway ◽  
Environmental Conditions ◽  
Metabolic Pathways ◽  
Host Cells ◽  
Anaerobic Conditions ◽  
Mutual Dependence ◽  
Metabolic Functions ◽  
Gradual Shift

Eukaryotic organelles supposedly evolved from their bacterial ancestors because of their benefits to host cells. However, organelles are quite often retained, even when the beneficial metabolic pathway is lost, due to something other than the original beneficial function. The organellar function essential for cell survival is, in the end, the result of organellar evolution, particularly losses of redundant metabolic pathways present in both the host and endosymbiont, followed by a gradual distribution of metabolic functions between the organelle and host. Such biological division of metabolic labor leads to mutual dependence of the endosymbiont and host. Changing environmental conditions, such as the gradual shift of an organism from aerobic to anaerobic conditions or light to dark, can make the original benefit useless. Therefore, it can be challenging to deduce the original beneficial function, if there is any, underlying organellar acquisition. However, it is also possible that the organelle is retained because it simply resists being eliminated or digested untill it becomes indispensable.

The Response of Testes Cells to Low Level, Single dose Helium Particle Irradiation

1982 ◽  
Vol 40 ◽  
pp. 252-253
Author(s):  
D.E. Philpott ◽  
W. Sapp ◽  
C. Williams ◽  
J. Stevenson ◽  
S. Black ◽  
...  
Keyword(s):  
Stem Cell ◽  
Single Dose ◽  
B Cell ◽  
Cell Survival ◽  
Spermatogonial Stem Cell ◽  
Low Doses ◽  
Particle Irradiation ◽  
Stem Cell Survival ◽  
Irradiation Injury ◽  
Radio Sensitivity

Spermatogonial stem-cell survival after irradiation injury has been studied in rodents by histological counts of surviving cells. Many studies, including previous work from our laboratory, show that the spermatogonial population demonstrates a heterogeneous response to irradiation. The spermatogonia increase in radio-sensitivity as differentiation proceeds through the sequence As - Apr - A1 - A2 - A3 - A4 - In - B. The stem (As) cell is the most resistant and the B cell is the most sensitive. The purpose of this work is to investigate the response of spermatogonial cell to low doses (less than 10 0 rads) of helium particle irradiation.

Vibration Isolator System for Electron Microscope

1990 ◽  
Vol 48 (1) ◽  
pp. 182-183
Author(s):  
K. Ohi ◽  
M. Mizuno ◽  
T. Kasai ◽  
Y. Ohkura ◽  
K. Mizuno ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Magnetic Fields ◽  
Environmental Conditions ◽  
Vibration Isolator ◽  
Air Conditioners ◽  
Vibration Isolators ◽  
Large Size ◽  
Electron Microscopes

In recent years, with electron microscopes coming into wider use, their installation environments do not necessarily give their performance full play. Their environmental conditions include air-conditioners, magnetic fields, and vibrations. We report a jointly developed entirely new vibration isolator which is effective against the vibrations transmitted from the floor.Conventionally, large-sized vibration isolators which need the digging of a pit have been used. These vibration isolators, however, are large present problems of installation and maintenance because of their large-size.Thus, we intended to make a vibration isolator which1) eliminates the need for changing the installation room2) eliminates the need of maintenance and3) are compact in size and easily installable.

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