Giant squid

Nerve stimulation results in a net influx of sodium ions, and normal conditions are restored by the outward transport of sodium ions against an electrochemical gradient. While several earlier workers had identified ATPases in the sheath of giant squid axons, it was Skou who first connected the sodium, potassium ATPase [EC 3.6.1.37] with the ion flux of neurons. This discovery culminated... 

Further confirmation of the similarities in biological activities between aphantoxin and PSP was shown by Adelman et al. (1982) (30). They showed that crude preparations of aphantoxins blocked the Na channel of giant squid axon with equal potency as saxitoxin. 

Rajapakse, N., Mendis, E., Byun, H. G., and Kim, S. K. (2005b). Purification and in vitro antioxidative effects of giant squid muscle peptides on free radical-mediated oxidative systems. ]. Nutr. Biochem. 16,562-569. 

The a-dispersion is presently the least clarified. Intracellular structures, such as the tubular apparatus in muscle cells, which connect with the outer cell membranes, could be responsible in all such tissues which contain such cell structures. Relaxation of counterions about the charged cellular surface is another mechanism suggested by us. Last, but not least, relaxational behavior of membranes per se, such as reported recently for the giant squid axon membrane, can account for it (2). The relative contribution of the various mechanisms varies, no doubt, from one case to another and needs further elaboration. 

Animals range in size from no more than a single cell to complex organisms weighing many tons, such as blue whales and giant squid. The majority of all animals inhabit the world s oceans, with fewer in fresh water and even fewer on land. 

The action of "holothurin" on the membrane potential and conductivity of giant squid axon membrane was studied by De Groof Narahashi [85]. The action of holothurin on the outside of the intact axon at a concentration of 2x10 M caused irreversible membrane depolarization, while the membrane potential approached zero. Elimination of Na from outer side of membrane or from both sides led to partial depolarization. A possible mechanism, based on the biomembrane depolarization by glycosides, was proposed to be connected with the increasing membrane permeability for Na ions. 

G6mez-Guillen, S. et al., Effect of heating temperature and sodium chloride concentration on ultrastructure and texture of gels made from giant squid (Dosidicus gigas) with addition of starch, K-carragenan and egg white, Z. Lebens. Unters. Forsch., 202, 221, 1996. 

Zasloff is quick to note that nobody has a clue how a giant squid or an octopus—which have neither antibodies nor white blood cells called lymphocytes—avoids becoming consumed by microbes Over the years, he and his colleagues have uncovered many frog-made peptides that possess potent microbe-killing properties. Such a chemical defense system operates by virtue of the peptides ability to poke holes in the cell membranes that serve to protect bacteria from the outside world. In addition to the peptides, scientists including Zasloff have found hundreds of other types of molecules called alkaloids in amphibian skin. When inside cells, many alkaloids home in on structures called ion channels—tunnel-like assemblies through which important electrolytes pass. These are key cellular fixtures,... 

Simply put, the action potential is caused by a state of disequilibrium between ideal electrical potentials for two ions, sodium and potassium. The equilibrium potentials for Na" " and K can be thought of as the electrical force required to maintain the given ionic gradients across the cell membrane for each ion. For Na" ", the equilibrium potential is approximately 50 mV (with respect to the inside of the membrane) for K +, it is approximately —75 mV. (These values apply to the giant squid axon on which the early investigations on action potentials were conducted. Of course, these values... 

Nerve of giant squid (across cell membrane) 0.070... 

The eyeball of a giant squid, at 18 inches in diameter, is the largest eyeball on the face of the Earth. Newborn babies may cry, but they do not produce any tears until they are one to three months old. Sam Foster sold the first pair of Foster Grant sunglasses at Woolworth s store on the Atlantic City Boardwalk in 1929. 

The spear-type glass microelectrode (Hinke-type) (2) (Figure la) has been used to determine the intracellular pH of the crab muscle fibers (3,4), cytoplasm of the giant squid axon (5), rat sartorius muscle fibers (6), rat atrial muscle fibers (7), vacuole of the algae Nitella flexilis (8), rat kidney tubular fluid (9,10), nerve cells of mollusk ganglia (11), and skeletal muscle fibers of the rat (4,12,13,14). 

Speed of locomotion depends on, in part, the speed at which the nerve signals uavel along axons. To increase this speed, vertebrates have insulated the wires with a metabolicaUy inactive membrane. Invertebrates, by conuast, have increased speed by increasing the diameter of the axons themselves. Both of these advancements reduce resistance to the flow of electrical charge. In the giant squid, Loli fo, this increase in diameter (found within the coaxial cable... 

Humans are animals, and our shared molecular ancestry establishes the basis for the use of animal models in medical research. Depending upon the system being investigated, the animal models may have to be quite similar to humans (an argument for the use of primates in research that focuses on infectious diseases), or they may not have to be similar at all (as is the case when the giant squid, Loli fo, is used to elucidate neural function). The litde lab mouse may indeed lose its position as the default laboratory animal model, but more likely it will just have to make room for other species to share its valued position. After aU, outside appearances can be deceiving, as it is what s inside biochemically that truly counts. 

The giant squid (Architeuthis princes) is well known from its remains found in the stomach of sperm whales, which hunt them at depths of aroimd 1000 m. Paradoxically, the largest invertebrate in the world has not yet been observed by man (estimated up to 25 m, including tentacles). 

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