On the dynamics of the adenylate energy system: homeorhesis vs homeostasis.

Biochemical energy is the fundamental element that maintains both the adequate turnover of the biomolecular structures and the functional metabolic viability of unicellular organisms. The levels of ATP, ADP and AMP reflect roughly the energetic status of the cell, and a precise ratio relating them was proposed by Atkinson as the adenylate energy charge (AEC). Under growth-phase conditions, cells maintain the AEC within narrow physiological values, despite extremely large fluctuations in the adenine nucleotides concentration. Intensive experimental studies have shown that these AEC values are preserved in a wide variety of organisms, both eukaryotes and prokaryotes. Here, to understand some of the functional elements involved in the cellular energy status, we present a computational model conformed by some key essential parts of the adenylate energy system. Specifically, we have considered (I) the main synthesis process of ATP from ADP, (II) the main catalyzed phosphotransfer reaction for interconversion of ATP, ADP and AMP, (III) the enzymatic hydrolysis of ATP yielding ADP, and (IV) the enzymatic hydrolysis of ATP providing AMP. This leads to a dynamic metabolic model (with the form of a delayed differential system) in which the enzymatic rate equations and all the physiological kinetic parameters have been explicitly considered and experimentally tested in vitro. Our central hypothesis is that cells are characterized by changing energy dynamics (homeorhesis). The results show that the AEC presents stable transitions between steady states and periodic oscillations and, in agreement with experimental data these oscillations range within the narrow AEC window. Furthermore, the model shows sustained oscillations in the Gibbs free energy and in the total nucleotide pool. The present study provides a step forward towards the understanding of the fundamental principles and quantitative laws governing the adenylate energy system, which is a fundamental element for unveiling the dynamics of cellular life

Tissue specificity of the mitochondrial forms of malic enzyme in herring tissues

1. 1. The activity of malic enzyme per wet weight or per milligram of mitochondrial protein in herring tissues showed significant tissue specificity. 2. 2. The specific activity of herring malic enzyme per mg of mitochondria from testes was 30 times greater than that of malic enzyme found in mitochondria of ovaries. 3. 3. The NAD(P)-dependent mitochondrial malic enzyme was present in all tissues tested and testis mitochondria contained the highest activity of this molecular form. 4. 4. Herring skeletal muscle mitochondria contained nearly identical activities of both molecular forms, the NADP- and NAD(P)-dependent malic enzyme, respectively. 5. 5. The results extend and support the proposal that mitochondria of some fish may contain two molecular forms of malic enzyme and have a unique intramitochondrial pahtway for malate metabolism

Body Morphometry and Development of the Digestive System of Grey Partridge (Perdix Perdix) Depending on Age and Gender

ABSTRACT The experiment used 100 grey partridges (Perdix perdix L.), which were reared first in confinement and later in aviaries. Partridges were lighter and had greater body dimensions at 36 weeks compared to 12 weeks except for trunk length. Older birds showed greater values (p>0.05) of compactness and lower values of massiveness and long-leggedness. Significant differences were found for keel length in females. At 36 weeks, male and female partridges had significantly greater total intestinal length, males had significantly longer small intestine and rectum, and females were characterized by significantly longer caeca and greater (p<0.05) intestine to body length ratio. Older birds had significantly greater gizzard weight and percentage and heart percentage (males and females), as well as significantly lower liver weight (males) and spleen weight and percentage. The present study provided information on the growth and development of farmed grey partridges before release into the natural environment

Body Morphometry and Development of the Digestive System of Grey Partridge (Perdix Perdix) Depending on Age and Gender

<div><p>ABSTRACT The experiment used 100 grey partridges (Perdix perdix L.), which were reared first in confinement and later in aviaries. Partridges were lighter and had greater body dimensions at 36 weeks compared to 12 weeks except for trunk length. Older birds showed greater values (p>0.05) of compactness and lower values of massiveness and long-leggedness. Significant differences were found for keel length in females. At 36 weeks, male and female partridges had significantly greater total intestinal length, males had significantly longer small intestine and rectum, and females were characterized by significantly longer caeca and greater (p<0.05) intestine to body length ratio. Older birds had significantly greater gizzard weight and percentage and heart percentage (males and females), as well as significantly lower liver weight (males) and spleen weight and percentage. The present study provided information on the growth and development of farmed grey partridges before release into the natural environment.</p></div