Anaerobic incorporation of radioactivity from 2,3-14C-succinic acid into citric acid cycle intermediates and related compounds in the sea musselMytilus edulis L

Exposure to air, but not seawater, increases the glutamine content and the glutamine synthetase activity in the marsh clamPolymesoda expansa

Polymesoda expansa spends a considerable portion of its life exposed to air in mangrove swamps where salinity fluctuates greatly. Thus, the aim of this study was to evaluate the effects of aerial exposure (transfer from 10‰ brackish water directly to air) or salinity changes (transfer from 10‰ brackish water directly to 30‰ seawater) on nitrogen metabolism in P. expansa. We concluded that P. expansa is non-ureogenic because carbamoyl phosphate (CPS) III activity was undetectable in the adductor muscle, foot muscle, hepatopancreas and mantle when exposed to brackish water (control), seawater or air for 17 days. It is ammonotelic as it excretes nitrogenous wastes mainly as ammonia in brackish water or seawater. After transfer to seawater for 17 days, the contents of total free amino acids(TFAA) in the adductor muscle, foot muscle, hepatopancreas and mantle increased significantly. This could be related to an increase in protein degradation because exposure to seawater led to a greater rate of ammonia excretion on days 15 and 17, despite unchanged tissue ammonia contents. Alanine was the major free amino acid (FAA) in P. expansa. The contribution of alanine to the TFAA pool in various tissues increased from 43–48% in brackish water to 62–73% in seawater. In contrast, in clams exposed to air for 17 days there were no changes in alanine content in any of the tissues studied. Thus, the functional role of alanine in P. expansa is mainly connected with intracellular osmoregulation. Although 8.5–16.1% of the TFAA pool of P. expansa was attributable to glutamine, the glutamine contents in the adductor muscle, foot muscle,hepatopancreas and mantle were unaffected by 17 days of exposure to seawater. However, after exposure to air for 17 days, there were significant increases in ammonia content in all these tissues in P. expansa, accompanied by significant increases in glutamine content (2.9-, 2.5-, 4.5- and 3.4-fold,respectively). Simultaneously, there were significant increases in glutamine synthetase activities in the adductor muscle (1.56-fold) and hepatopancreas(3.8-fold). This is the first report on the accumulation of glutamine associated with an upregulation of glutamine synthetase in a bivalve species in response to aerial exposure, and these results reveal that the evolution of glutamine synthesis as a means for detoxification of ammonia first occurred among invertebrates.

Carcinogenesis--devolution towards an ancient nucleated pre-eukaryotic level

Because the mitochondria and the cells housing them are obligatory symbionts, the evolutionary history of cells forms the locus minoris resistentiae which is the prerequisite for the carcinogenetic process. During carcinogenesis, the cells devolve towards an ancient anaerobic nucleated pre-eukaryotic level. True carcinogens cause an accumulation of inclusion bodies in the inner, bacterial, mitochondrial membrane. The mitochondrial damage which is detectable only in the early pretumorous stages, results in the respiratory surface with its enzymes being specifically changed, the mitochondrial and nuclear cycles no longer coinciding, the energy generation being forced to reuse the latent, "prehistoric", mode of respiration and the mitochondrial enzyme systems of soil bacterial origin becoming adapted to use other and more versatile metabolic pathways with a wider variety of end-products than classical glycolysis which produces lactate only. Neither external carcinogens nor oncogens are necessary. An increased, prolonged cell replication activity of physiological type is sufficient to initiate and maintain the process in animals with an inherited neoplastic disposition located in the inner mitochondrial membrane. The neoplastic disposition is inherited maternally: in fertilization the ovum does not receive mitochondria from the spermatocyte. The final results are an overall retardation of cell processes and instability in its structural and functional repertoire, the cytoskeleton (differentiation organelle) of the malignant cell manifesting special patterns. The proposed devolutionary mechanism is feasible as DNA packages are physiological components of soil bacterial membrane and can remain dormant (repressed) for years, or for ever, but under suitable conditions can generate seemingly new species, and particularly because enzyme adaptability is the unique privilege of soil bacteria.