urinary loss of water and sodium (CHESTER JONES et al., 1969 b). The urophysis,
when extracted, can thus yield a substance (or more likely substances!) that has
divers effects on teleostean preparations, but it is not known if this reflects a physiological role . Extracts from the urophysis of the mudsucker, Gillichthys mirabilis,
can stimulate an amphibian tissue, the toad urinary bladder (in vitro) and increase
the osmotic transfer of water from its mucosal to serosal side (LACANILAO, 1969).
The exact chemical nature of the substance, or substances, which have these various
actions, is not known. LEDERIS (1969) found that the ability to contract the trout
bladder was not due to histamine, 5-hydroxytryptamine, acetylcholine, bradykinin
or catecholamines in the extract and neither can these materials account for the facilitated osmotic permeability of the toad bladder. GESCHWIND et al. (1968) in a preliminary survey have described the material that acts on the trout bladder as being
polypeptide in its nature, with a molecular weight of about 1000. It is emphasized,
however, that while this material contracts the trout urinary bladder, it is not the
same as that examined by MAETZ et al. (1964). The urophysial extract that elevates
the blood pressure of the eel is also a polypeptide and is inactivated by trypsin but
is unaffected by incubation with thioglycollate (CHAN, CHESTER JONES, and PONNIAH, 1969). The absence of an effect of the latter indicates that disulphide bonds
are not essential for the material's activity, thus distinguishing it from the
neurohypophysial peptides.
(:J) Corpuscles of Stannius. These are islets of tissue present in the caudal regions
of teleostean and holostean fishes (see page 78). RASQUIN (1956) found histological
changes in the appearance of these tissues in the teleost, Astyanax mexicanus, after
it had been transferred to saline solutions. This suggested that they may be involved
in osmoregulatory adjustments. When these tissues are extirpated from the eel there
is a marked decline in plasma sodium concentration of freshwater fish and an elevation of the levels of potassium and calcium (M. FONTAINE, 1964). CHAN et al.
(1967 a) have confirmed these observations. It is also interesting that the blood pressure of freshwater eels drops after removal of the corpuscle of STANNIUS (CHESTER
JONES et al., 1966). It seemed possible that such changes in blood pressure could
influence osmoregulation by altering the GFR. However, BUTLER (1969) was unable to demonstrate any change in the GFR of stanniectomized North American
eels, Anguilla rostrata. The decline in plasma sodium levels can be corrected by injecting the eels with aldosterone, but the calcium and potassium concentration are
unaffected, though corpuscular extracts restore these also (LELOUP-HATEY, 1964;
CHAN et al., 1967a; FONTAINE, 1965).
The search for the chemical identity of the secretion(s) that may be produced
by the corpuscles of STANNIUS has run along a somewhat confusing path. Substances with some properties similar to corticosteroids have been extracted from
corpuscular tissues and may be produced during their in vitro incubation with various steroid substrates. The corticosteroid nature of such substances is in doubt as
these results have not been generally confirmed (see for instance CHESTER JONES
et al., 1965; ARAI, TAJlMA, and T AMAOKI, 1969), though the possibility of species'
differences cannot be ruled out. NANDI (1967) considered the available information
and concluded that 'these data are not inconsistent with the notion that the corpuscles of STANNIUS are steroid storage organs and/or that they actively metabolize
245
when extracted, can thus yield a substance (or more likely substances!) that has
divers effects on teleostean preparations, but it is not known if this reflects a physiological role . Extracts from the urophysis of the mudsucker, Gillichthys mirabilis,
can stimulate an amphibian tissue, the toad urinary bladder (in vitro) and increase
the osmotic transfer of water from its mucosal to serosal side (LACANILAO, 1969).
The exact chemical nature of the substance, or substances, which have these various
actions, is not known. LEDERIS (1969) found that the ability to contract the trout
bladder was not due to histamine, 5-hydroxytryptamine, acetylcholine, bradykinin
or catecholamines in the extract and neither can these materials account for the facilitated osmotic permeability of the toad bladder. GESCHWIND et al. (1968) in a preliminary survey have described the material that acts on the trout bladder as being
polypeptide in its nature, with a molecular weight of about 1000. It is emphasized,
however, that while this material contracts the trout urinary bladder, it is not the
same as that examined by MAETZ et al. (1964). The urophysial extract that elevates
the blood pressure of the eel is also a polypeptide and is inactivated by trypsin but
is unaffected by incubation with thioglycollate (CHAN, CHESTER JONES, and PONNIAH, 1969). The absence of an effect of the latter indicates that disulphide bonds
are not essential for the material's activity, thus distinguishing it from the
neurohypophysial peptides.
(:J) Corpuscles of Stannius. These are islets of tissue present in the caudal regions
of teleostean and holostean fishes (see page 78). RASQUIN (1956) found histological
changes in the appearance of these tissues in the teleost, Astyanax mexicanus, after
it had been transferred to saline solutions. This suggested that they may be involved
in osmoregulatory adjustments. When these tissues are extirpated from the eel there
is a marked decline in plasma sodium concentration of freshwater fish and an elevation of the levels of potassium and calcium (M. FONTAINE, 1964). CHAN et al.
(1967 a) have confirmed these observations. It is also interesting that the blood pressure of freshwater eels drops after removal of the corpuscle of STANNIUS (CHESTER
JONES et al., 1966). It seemed possible that such changes in blood pressure could
influence osmoregulation by altering the GFR. However, BUTLER (1969) was unable to demonstrate any change in the GFR of stanniectomized North American
eels, Anguilla rostrata. The decline in plasma sodium levels can be corrected by injecting the eels with aldosterone, but the calcium and potassium concentration are
unaffected, though corpuscular extracts restore these also (LELOUP-HATEY, 1964;
CHAN et al., 1967a; FONTAINE, 1965).
The search for the chemical identity of the secretion(s) that may be produced
by the corpuscles of STANNIUS has run along a somewhat confusing path. Substances with some properties similar to corticosteroids have been extracted from
corpuscular tissues and may be produced during their in vitro incubation with various steroid substrates. The corticosteroid nature of such substances is in doubt as
these results have not been generally confirmed (see for instance CHESTER JONES
et al., 1965; ARAI, TAJlMA, and T AMAOKI, 1969), though the possibility of species'
differences cannot be ruled out. NANDI (1967) considered the available information
and concluded that 'these data are not inconsistent with the notion that the corpuscles of STANNIUS are steroid storage organs and/or that they actively metabolize
245