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PubMed1995

Bioluminescence in scale-worm photosomes: the photoprotein polynoidin is specific for the detection of superoxide radicals.

Photosomes are the characteristic organelles of the luminous epithelium in the elytral appendages of polynoïd annelids. They are paracrystals of endoplasmic reticulum and emit a flash of bioluminescence in response to stimulation. The series of flashes in response to repetitive stimulation begins with a period of facilitation because the number of reacting photosomes increases in each photogenic cell. Reacting photosomes are coupled to the plasma membrane by dyad junctions which are established under stimulation and dedifferentiate in the resting system. The calcium influx of an action potential propagated through the conducting elytral epithelium triggers the luminous reaction. This reaction is based on a membrane photoprotein, polynoidin, which is specifically triggered by superoxide radicals. These oxy radicals result from the oxydation of riboflavin, which is present in a compartment of the photosomes. Polynoidin proved to be an interesting probe in the detection of superoxide radicals produced by activated white blood cells. Its potential applications are discussed.

Animals↗
PubMed1996

Spermatozoa: models for studying regulatory aspects of energy metabolism.

Spermatozoa are highly specialized cells, and they offer advantages for studying several basic aspects of metabolic control such as the role of adenosine triphosphate-(ATP)-homeostasis for cell function, the mechanisms of fatigue and metabolic depression, the metabolic channelling through the cytoplasm and the organization and regulation of glycolytic enzymes. Spermatozoa of four species with different reproductive modes are introduced and the first results are presented: Spermatozoa of the marine worm Arenicola marina are well adapted to external fertilization in sea water with fluctuating oxygen tension: they are motile for several hours in oxygen-free sea water, even when the ATP level is dramatically reduced. Anaerobic ATP production occurs by alanine, acetate and propionate fermentation probably by the same pathways known from somatic cells of this species. Under aerobic conditions the phosphagen system might function like a shuttle for energy-rich phosphate from mitochondria to the dynein-ATPases. Storage of turkey and carp spermatozoa for several hours without exogenous substrates and oxygen results in the degradation of phosphocreatine and ATP to inorganic phosphate and adenosine monophosphate (AMP), respectively. Despite low energy charges, stored spermatozoa of both species are capable of progressive movements. In carp spermatozoa fatigue of motility is not accompanied by the dramatic acidosis one discusses as an important effect in muscle fatigue. Energy metabolism of boar spermatozoa is typically based on glycolysis consuming extracellular carbohydrates and producing lactate and protons. The sperm seem to tolerate low intracellular pH (< 6.5). The lack of a phosphagen system (no energy shuttle from mitochondria to the distal dynein-ATPases) is probably compensated by a high glycolytic ATP-production in the mitochondria-free piece of the flagellum.

Adenosine Triphosphate↗