Interactions entre mitochondries et chloroplastes dans la cellule. III. Evolution des échanges gazeux des spores de Funaria hygrometrica au cours d'un séjour à l'obscurité

1980 ◽  
Vol 58 (8) ◽  
pp. 841-846
Author(s):  
D. Chevallier ◽  
F. Nurit ◽  
R. Douce
Keyword(s):  
Liquid Medium ◽  
Mitochondrial Respiration ◽  
Rapid Decrease ◽  
Quiescent State ◽  
Funaria Hygrometrica ◽  
General Metabolism ◽  
Short Period ◽  
Échanges Gazeux

In darkness, in an inorganic liquid medium the spores of Funaria hygrometrica demonstrate a rapid increase from low to high metabolism activity with mitochondrial respiration functioning at its maximal value. The spore respiration is high during a short period of time corresponding to the transformation of the proplastids into chloroplasts. Then, the spore respiration slows down progressively. This diminution is due to a rapid decrease of the general metabolism. Under these conditions, the germination cannot take place and the spores appear to return to a quiescent state.

Effects of cyromazine on the mechanical properties of the larval integument of Lucilia cuprina (Diptera: Calliphoridae)

1993 ◽  
Vol 83 (3) ◽  
pp. 389-393 ◽  
Author(s):  
A. C. Kotze ◽  
S. E. Reynolds
Keyword(s):  
Mechanical Properties ◽  
Manduca Sexta ◽  
Normal Diet ◽  
Rapid Decrease ◽  
Lucilia Cuprina ◽  
Larval Cuticle ◽  
Short Period ◽  
Third Instar Larvae

AbstractThe effect of cyromazine on the mechanical properties of the larval integument of Lucilia cuprina (Wiedemann) was measured using third instar larvae 2–3 h after moulting placed on liver containing 1 ppm cyromazine. Cuticle stiffness (Δ force (N)/δ strain) was approximately 20–30% higher in treated larvae (relative to controls) after 6–10 h treatment, after which time stiffness decreased to levels well below controls. Larvae placed on 1 ppm cyromazine early in the second instar also showed a short period of slightly elevated cuticle stiffness (relative to controls) after 3–5 h treatment. Third instar larvae placed on cyromazine-treated diet for 8 h then transferred to normal diet showed the same short period of elevated stiffness (at 6–10 h) followed by rapid decrease in stiffness to levels well below controls and greatly reduced growth as larvae fed cyromazine continually. A slight increase in cuticle stiffness appears to be only an early and temporary effect of cyromazine poisoning in L. cuprina. These results are discussed in relation to the previously documented effects of cyromazine on the mechanical properties of the larval cuticle of Manduca sexta (Linnaeus).

scholarly journals Intermittent swimming in live sea urchin sperm.

1980 ◽  
Vol 84 (1) ◽  
pp. 1-12 ◽  
Author(s):  
B H Gibbons
Keyword(s):  
Sea Urchin ◽  
Divalent Cations ◽  
Dark Field ◽  
Proximal Region ◽  
Ionophore A23187 ◽  
Quiescent State ◽  
Sodium Barbital ◽  
Dark Field Microscopy ◽  
Short Period ◽  
Live Sperm

Sperm of the sea urchin Tripneustes gratilla repeatedly start and stop swimming when suspended in seawater and observed by dark-field microscopy. While in the quiescent state, which usually lasts about a second, the sperm assume s shape resembling a cane, with a sharp bend of approximately 3.4 rad in the proximal region of the flagellum and very little curvature in the rest of the flagellum except for a slight curve near the tip. The occurrence of quiescence requires the presence of at least 2 mM Ca2+ in the seawater, and the percentage of sperm quiescent at any one time increases substantially when the sperm are illuminated with blue light. With intense illumination, close to 100% of the sperm become quiescent, and this percentage decreases gradually to approximately 0.3% over a 10(4)-fold decrease in light intensity. An increased concentration of K+ in the seawater also increases the percentage of quiescence, with a majority of the sperm being quiescent in seawater containing 80 mM KCl. The induction of quiescence by light or by increased KCl is completely inhibited by 10 micrometers chlorpromazine, and approximately 90% inhibited by 1 mM procaine or sodium barbital. Sperm treated with the divalent-cation ionophore A23187 swim quite normally, although for a relatively short period, in artificial seawater lacking divalent cations, but are abruptly arrested upon addition of 0.04--0.2 mM free Ca2%. The flagellar waveform of these arrested sperm is almost identical to that of light-induced quiescence in the live sperm. The results support the hypothesis that quiescence is induced by a rise in intracellular Ca2%, perhaps as a consequence of a membrane depolarization, and that it is similar to the arrest response in cilia.

scholarly journals Chromosome behaviour in the male ferret and mole during anoestrus

1936 ◽  
Vol 121 (822) ◽  
pp. 192-206 ◽  
Keyword(s):  
Seasonal Variation ◽  
Breeding Season ◽  
Reproductive Organs ◽  
Quiescent State ◽  
Chromosome Behaviour ◽  
Histological Changes ◽  
Short Period ◽  
Cytological Changes

The breeding season of many Mammals is restricted to a relatively short period of the year. In such species usually both sexes exhibit a more or less well-defined seasonal variation in their reproductive organs. Several investigators have found that these variations in the male consist chiefly of alteration in the size of the testes and epididymis, accompanied by marked histological and cytological changes leading to a complete absence of sperms during the quiescent or anoestrous period. The cyclic histological changes in the testes and in the accessory organs have been described in detail in the ferret ( Putorius furo, L .) by Allanson (1932), and in the mole ( Talpa europea, L .) by Tandler and Grosz (1912) and Allanson ( unpublished ). It was found in both genera that during the breeding season spermatogenesis is complete and very active in the rapidly growing testis, but after that period the reproductive organs return to a quiescent state and sperms are entirely absent.

scholarly journals Bioenergetic Pathways in the Sperm of an Under-Ice Spawning Fish, Burbot (Lota lota): The Role of Mitochondrial Respiration in a Varying Thermal Environment

Biology ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 739
Author(s):  
Deepali Rahi ◽  
Borys Dzyuba ◽  
Tomas Policar ◽  
Oleksandr Malinovskyi ◽  
Marek Rodina ◽  
...  
Keyword(s):  
Mitochondrial Respiration ◽  
Energy Production ◽  
Cold Water ◽  
Thermal Environment ◽  
Acid Oxidation ◽  
Quiescent State ◽  
Lota Lota ◽  
Time Points ◽  
Inhibitor Treatment

Regarding the sperm of cold-water fish, the contributions of different bioenergetic pathways, including mitochondrial respiration, to energy production at the spawning temperature and its adaptation at the maximum critical temperature (CTmax) are unclear. The roles of glycolysis, fatty acid oxidation, oxidative phosphorylation (OXPHOS) at 4 °C, and OXPHOS at 15 °C for energy production in burbot (Lota lota) spermatozoa were studied by motility and the oxygen consumption rate (OCR) (with and without pathway inhibitors and the OXPHOS uncoupler). At both temperatures, the effects of the inhibitors and the uncoupler on the motility duration, curvilinear velocity, and track linearity were insignificant; in addition, the OCRs in activation and non-activation media differed insignificantly and were not enhanced after uncoupler treatment. After inhibitor treatment in both media, OXPHOS was insignificantly different at the 2, 30, and 60 s time points at 4 °C but was reduced significantly at the 30 and 60 s time points after treatment with sodium azide at 15 °C. In conclusion, for burbot sperm at both the spawning temperature and the CTmax, the energy synthesized via OXPHOS during motility was insufficient. Therefore, the majority of the energy required to sustain motility was derived from pre-accumulated energy produced and stored during the quiescent state of the spermatozoa.

scholarly journals Warburg Effect, Glutamine, Succinate, Alanine, When Oxygen Matters

Biology ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 1000
Author(s):  
Frédéric Bouillaud ◽  
Noureddine Hammad ◽  
Laurent Schwartz
Keyword(s):  
Mitochondrial Respiration ◽  
Warburg Effect ◽  
Aerobic Glycolysis ◽  
Glucose Consumption ◽  
Glycolytic Flux ◽  
Atp Production ◽  
Lactate Release ◽  
General Metabolism ◽  
Cellular Bioenergetics ◽  
The Warburg Effect

Cellular bioenergetics requires an intense ATP turnover that is increased further by hypermetabolic states caused by cancer growth or inflammation. Both are associated with metabolic alterations and, notably, enhancement of the Warburg effect (also known as aerobic glycolysis) of poor efficiency with regard to glucose consumption when compared to mitochondrial respiration. Therefore, beside this efficiency issue, other properties of these two pathways should be considered to explain this paradox: (1) biosynthesis, for this only indirect effect should be considered, since lactate release competes with biosynthetic pathways in the use of glucose; (2) ATP production, although inefficient, glycolysis shows other advantages when compared to mitochondrial respiration and lactate release may therefore reflect that the glycolytic flux is higher than required to feed mitochondria with pyruvate and glycolytic NADH; (3) Oxygen supply becomes critical under hypermetabolic conditions, and the ATP/O2 ratio quantifies the efficiency of oxygen use to regenerate ATP, although aerobic metabolism remains intense the participation of anaerobic metabolisms (lactic fermentation or succinate generation) could greatly increase ATP/O2 ratio; (4) time and space constraints would explain that anaerobic metabolism is required while the general metabolism appears oxidative; and (5) active repression of respiration by glycolytic intermediates, which could ensure optimization of glucose and oxygen use.

Changes in tissue pH after circulatory arrest

1961 ◽  
Vol 200 (4) ◽  
pp. 743-745 ◽  
Author(s):  
Jack W. Crowell ◽  
Berwind N. Kaufmann
Keyword(s):  
Cerebral Cortex ◽  
Sodium Bicarbonate ◽  
Circulatory Arrest ◽  
Rapid Decrease ◽  
Metabolic Inhibitors ◽  
Tissue Ph ◽  
Short Period ◽  
Initial Ph ◽  
Ph Electrodes ◽  
Made In

The circulation of dogs was stopped by fibrillation of the heart, and needle pH electrodes were placed in various tissues of dogs. The pH electrodes were connected to a continuous recording pH meter and the pH of the tissues was measured for a period of 1 hour following circulatory arrest. A few incidental studies on metabolic inhibitors, hypothermia and alkalinizing agents were made in addition to studies on the normal animals. It was found that the initial pH in the normal animals was 7.2–7.3, but within a short period of time decreased to values lethal to an animal with a normal circulation. The cerebral cortex showed the most rapid decrease in pH following circulatory arrest. The injection of sodium bicarbonate before circulatory arrest was of little value in preventing the development of acidity. Oxythiamine was effective in preventing the development of severe acidity but appears of little practical use. Hypothermia to 25°C proved effective in retarding the development of severe acidity in the two animals studied.

The Origin of the Moon and its Relationship to the Origin of the Solar System

1962 ◽  
Vol 14 ◽  
pp. 133-148 ◽  
Author(s):  
Harold C. Urey
Keyword(s):  
Solar System ◽  
The Moon ◽  
The Past ◽  
The Earth ◽  
Short Period ◽  
Origin Of The Moon

During the last 10 years, the writer has presented evidence indicating that the Moon was captured by the Earth and that the large collisions with its surface occurred within a surprisingly short period of time. These observations have been a continuous preoccupation during the past years and some explanation that seemed physically possible and reasonably probable has been sought.

the effects of resonance with Jupiter in the system of short-period comets

1974 ◽  
Vol 22 ◽  
pp. 193-203
Author(s):  
L̆ubor Kresák
Keyword(s):  
Structural Effects ◽  
Order Resonance ◽  
Mean Motion ◽  
Short Period ◽  
The Mean ◽  
Compound Effect ◽  
Low Order

AbstractStructural effects of the resonance with the mean motion of Jupiter on the system of short-period comets are discussed. The distribution of mean motions, determined from sets of consecutive perihelion passages of all known periodic comets, reveals a number of gaps associated with low-order resonance; most pronounced are those corresponding to the simplest commensurabilities of 5/2, 2/1, 5/3, 3/2, 1/1 and 1/2. The formation of the gaps is explained by a compound effect of five possible types of behaviour of the comets set into an approximate resonance, ranging from quick passages through the gap to temporary librations avoiding closer approaches to Jupiter. In addition to the comets of almost asteroidal appearance, librating with small amplitudes around the lower resonance ratios (Marsden, 1970b), there is an interesting group of faint diffuse comets librating in characteristic periods of about 200 years, with large amplitudes of about±8% in μ and almost±180° in σ, around the 2/1 resonance gap. This transient type of motion appears to be nearly as frequent as a circulating motion with period of revolution of less than one half that of Jupiter. The temporary members of this group are characteristic not only by their appearance but also by rather peculiar discovery conditions.

Models of comets with strongly variable nongravitational effects

1999 ◽  
Vol 173 ◽  
pp. 381-387
Author(s):  
M. Królikowska ◽  
G. Sitarski ◽  
S. Szutowicz
Keyword(s):  
Cometary Nucleus ◽  
Spin Axis ◽  
Reactive Force ◽  
Orbital Elements ◽  
Cometary Nuclei ◽  
Short Period ◽  
Basic Parameters ◽  
Polar Radius ◽  
Cometary Activity ◽  
Nongravitational Effects

AbstractThe nongravitational motion of five “erratic” short-period comets is studied on the basis of published astrometric observations. We present the precession models which successfully link all the observed apparitions of the comets: 21P/Giacobini-Zinner, 31P/Schwassmann-Wachmann 2, 32P/Comas Solá, 37P/Forbes, and 43P/Wolf-Harrington. We used the Sekanina's forced precession model of the rotating cometary nucleus to include the nongravitational terms into equations of the comet's motion. Values of six basic parameters (four connected with the rotating comet nucleus and two describing the precession of spin-axis of the nucleus) have been determined along the orbital elements from positional observations of the comets. The solutions were derived with additional assumptions which introduce instantaneous changes of modulus of reactive force,Aand of maximum of cometary activity with respect to perihelion time. The present precession models impose some contraints on sizes and rotational periods of cometary nuclei. According to our solutions the nucleus of 21P/Giacobini-Zinner with oblateness along the spin-axis of about 0.32 (equatorial to polar radius of 1.46) is the most oblate among five investigated comets.

Covering of cometary nucleus by refractory crust and its evolution into asteroid-like body

1999 ◽  
Vol 173 ◽  
pp. 365-370
Author(s):  
Kh.I. Ibadinov
Keyword(s):  
Laboratory Experiments ◽  
Cometary Nucleus ◽  
Sublimation Rate ◽  
Cometary Nuclei ◽  
Short Period Comet ◽  
Short Period ◽  
Brightness Decrease ◽  
Crust Thickness ◽  
Ice Sublimation ◽  
Period Comet

AbstractFrom the established dependence of the brightness decrease of a short-period comet dependence on the perihelion distance of its orbit it follows that part of the surface of these cometary nuclei gradually covers by a refractory crust. The results of cometary nucleus simulation show that at constant insolation energy the crust thickness is proportional to the square root of the insolation time and the ice sublimation rate is inversely proportional to the crust thickness. From laboratory experiments resulted the thermal regime, the gas productivity of the nucleus, covering of the nucleus by the crust, and the tempo of evolution of a short-period comet into the asteroid-like body studied.

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