358
J . T . D I N G L E A N D M . W E B B
sulphate, but hexosamine, neutral sugars (which may include methyl
pentoses and heptoses (e.g. Schultz-Handt and Eig-Larsen, 1961)
in addition to hexoses such as galactose and mannose) and sialic acid,
occur frequently. The collective term "sialic acid" is used to denote
a family of acylated derivatives of neuraminic acid, different members
of which have been found in mucoproteins from connective tissues
and other sources (e.g. Castellani, Ferri, Bolognani and Graziano,
1960; Barker, Stacey, Tipper and Kirkham, 1959; Gottschalk, 1960).
The isolation, composition and structure of these substances, as well
as analytical methods for their determination have been reviewed in
detail by Gottschalk (1960). The stereo-chemical relationship of jVacetyl neuraminic acid to mannosamine has been established both by
its synthesis (Carroll and Cornforth, 1960), and by its enzymic degradation (Comb and Roseman, 1960). Sialic acid, when this occurs in
mucoproteins, appears to occupy predominantly if not exclusively,
a terminal position, and to be linked glycosidically to another sugar
(Kuhn and Brossmer, 1958; Popenhoe, 1959; Gottschalk, 1960; Spiro,
1962).
In many mucoproteins of this type, the carbohydrate content is
extremely low, and although the constituent sugars may be known
with some degree of certainty, their contents, arrangements and interlinkages within the polysaccharides have not been established.
C. H I S T O L O G I C A L I D E N T I F I C A T I O N
The production of mucins has been described frequently in tissue
and organ culture; the identification of these substances, however,
rests solely on a positive reaction to the periodic acid-Schiff (PAS) or
other histochemical procedures. Although Marshall and Swettenham
(1959) claim to distinguish "muco-" and "glyco-proteins", as well as
the sulphated mucopolysaccharides in tissues by histochemical methods,
these techniques seldom give such unequivocal results. Thus, even in
recent work there is frequent disagreement on the interpretation of
histochemical methods for the demonstration of mucopolysaccharide
and mucoprotein. Velican and Velican (1959), for example, claim
that the metachromatic reaction to toluidine blue of certain mast
cells in sections is abolished by hyaluronidase and is due exclusively
to hyaluronic acid, whereas Schiller and Dorfman (1959), Bloom and
Ringertz (1960) and Parekh and Glick (1962) find heparin to be the
major—if not the exclusive—mucopolysaccharide of peritoneal mast
cells of the rat. According to Hale (1946), hyaluronic acid is not metachromatic. Meyer (1947) also regards hyaluronic acid, isolated preparations of which at concentrations greater than l°/o stain meta-
J . T . D I N G L E A N D M . W E B B
sulphate, but hexosamine, neutral sugars (which may include methyl
pentoses and heptoses (e.g. Schultz-Handt and Eig-Larsen, 1961)
in addition to hexoses such as galactose and mannose) and sialic acid,
occur frequently. The collective term "sialic acid" is used to denote
a family of acylated derivatives of neuraminic acid, different members
of which have been found in mucoproteins from connective tissues
and other sources (e.g. Castellani, Ferri, Bolognani and Graziano,
1960; Barker, Stacey, Tipper and Kirkham, 1959; Gottschalk, 1960).
The isolation, composition and structure of these substances, as well
as analytical methods for their determination have been reviewed in
detail by Gottschalk (1960). The stereo-chemical relationship of jVacetyl neuraminic acid to mannosamine has been established both by
its synthesis (Carroll and Cornforth, 1960), and by its enzymic degradation (Comb and Roseman, 1960). Sialic acid, when this occurs in
mucoproteins, appears to occupy predominantly if not exclusively,
a terminal position, and to be linked glycosidically to another sugar
(Kuhn and Brossmer, 1958; Popenhoe, 1959; Gottschalk, 1960; Spiro,
1962).
In many mucoproteins of this type, the carbohydrate content is
extremely low, and although the constituent sugars may be known
with some degree of certainty, their contents, arrangements and interlinkages within the polysaccharides have not been established.
C. H I S T O L O G I C A L I D E N T I F I C A T I O N
The production of mucins has been described frequently in tissue
and organ culture; the identification of these substances, however,
rests solely on a positive reaction to the periodic acid-Schiff (PAS) or
other histochemical procedures. Although Marshall and Swettenham
(1959) claim to distinguish "muco-" and "glyco-proteins", as well as
the sulphated mucopolysaccharides in tissues by histochemical methods,
these techniques seldom give such unequivocal results. Thus, even in
recent work there is frequent disagreement on the interpretation of
histochemical methods for the demonstration of mucopolysaccharide
and mucoprotein. Velican and Velican (1959), for example, claim
that the metachromatic reaction to toluidine blue of certain mast
cells in sections is abolished by hyaluronidase and is due exclusively
to hyaluronic acid, whereas Schiller and Dorfman (1959), Bloom and
Ringertz (1960) and Parekh and Glick (1962) find heparin to be the
major—if not the exclusive—mucopolysaccharide of peritoneal mast
cells of the rat. According to Hale (1946), hyaluronic acid is not metachromatic. Meyer (1947) also regards hyaluronic acid, isolated preparations of which at concentrations greater than l°/o stain meta-