238
J. A. ALLEN AND M. R. OARRElT
protein did not alter with adaptation suggesting that the latter hypothesis is unlikely. Schoffeniels (1964) also rejects this possibility and
claims that any total number of moles of amino acids in a cell depends
on a balance between synthesis and breakdown of these substances in
the cell. He postulates that the rate of amino acid production, as well as
the rates of transamination and dehydrogenation are directly dependent
on the ionic composition of the cell.
The sea urchin Strongylocentrotus droebmhiensis (Mueller) exhibits
isosmotic intracellular regulation (Lange, 1964) but it is less efficient
than euryhaline invertebrates. The increased length of time needed t o
adapt to new salinity conditions allowed Lange (1964) to study the
stages of isosmotic intracellular regulation. He found that this is in
response to increased cellular volume. Thus when an animal is placed in
dilute sea water the cells take up water by osmosis. The animal
remains swollen for a week and on the eighth day it returns t o its normal
size. The cause may be a change in permeability of the cell membrane
to amino acids and taurine which allows these substances to be excreted
together with inorganic ions and water or, there may be a change in
the equilibrium between amino acids and, for example, protein which
has the effect of removing some of the osmotically active substances
thus causing the osmotic excretion of water. Lange (1964) does not
consider this latter explanation likely because taurine, which he regards
as an excretory product, would not go into a combination in the cell.
The change is probably a transitory process, since sea urchins living in
dilute sea water still contain high concentrations of intracellular amino
acids. The original properties of the cell membranes must be restored
once the cell volume is regulated. Lange (1964) regards the correlation
between salinity and the concentration of intracellular amino acids
which " enables the animal to keep their intracellular salinity on a level
compatable with life " as being an expression of one of the processes
which makes the regulation of cell volume possible. But, the presence
of large quantities of taurine in stenohaline species might suggest that
it is present as a matter of course, and is simply utilized by some animals
as a regulatory substance.
Although never suggested for marine invertebrates, the considerable
quantities of taurine present in muscle may play a part in energy release
(Bascheri and Fromageot, 1962). Taurine appears to have a facilitating
effect on the action of insulin on extracellular glucose in mammals
(Macallum and Sivertz, 1942 ; Donadio and Fromageot, 1964).
The function of isethionic acid in ion balance of nerve cells has
already been mentioned (p. 230). Taurine itself also appears t o play a
part in nerve function. It is a structural analogue of y-aminobutyric
J. A. ALLEN AND M. R. OARRElT
protein did not alter with adaptation suggesting that the latter hypothesis is unlikely. Schoffeniels (1964) also rejects this possibility and
claims that any total number of moles of amino acids in a cell depends
on a balance between synthesis and breakdown of these substances in
the cell. He postulates that the rate of amino acid production, as well as
the rates of transamination and dehydrogenation are directly dependent
on the ionic composition of the cell.
The sea urchin Strongylocentrotus droebmhiensis (Mueller) exhibits
isosmotic intracellular regulation (Lange, 1964) but it is less efficient
than euryhaline invertebrates. The increased length of time needed t o
adapt to new salinity conditions allowed Lange (1964) to study the
stages of isosmotic intracellular regulation. He found that this is in
response to increased cellular volume. Thus when an animal is placed in
dilute sea water the cells take up water by osmosis. The animal
remains swollen for a week and on the eighth day it returns t o its normal
size. The cause may be a change in permeability of the cell membrane
to amino acids and taurine which allows these substances to be excreted
together with inorganic ions and water or, there may be a change in
the equilibrium between amino acids and, for example, protein which
has the effect of removing some of the osmotically active substances
thus causing the osmotic excretion of water. Lange (1964) does not
consider this latter explanation likely because taurine, which he regards
as an excretory product, would not go into a combination in the cell.
The change is probably a transitory process, since sea urchins living in
dilute sea water still contain high concentrations of intracellular amino
acids. The original properties of the cell membranes must be restored
once the cell volume is regulated. Lange (1964) regards the correlation
between salinity and the concentration of intracellular amino acids
which " enables the animal to keep their intracellular salinity on a level
compatable with life " as being an expression of one of the processes
which makes the regulation of cell volume possible. But, the presence
of large quantities of taurine in stenohaline species might suggest that
it is present as a matter of course, and is simply utilized by some animals
as a regulatory substance.
Although never suggested for marine invertebrates, the considerable
quantities of taurine present in muscle may play a part in energy release
(Bascheri and Fromageot, 1962). Taurine appears to have a facilitating
effect on the action of insulin on extracellular glucose in mammals
(Macallum and Sivertz, 1942 ; Donadio and Fromageot, 1964).
The function of isethionic acid in ion balance of nerve cells has
already been mentioned (p. 230). Taurine itself also appears t o play a
part in nerve function. It is a structural analogue of y-aminobutyric