2. Introduction
Carbohydrates- ( hydrated carbon)
are important organic compounds
that include sugars, starch, cellulose
and polymers that are mostly linked
to proteins.
3. The he role of carbohydrates in
cellular metabolism has been known
for many years, carbohydrates have
been more recently implicated in a
wide range of cellular functions
including:
7. Glycogen and Mucin are the two
main entities to be considered in
tissue carbohydrate demonstration
8. Polysaccharides
A polysaccharide is a large
macromolecule composed of
multiple monosaccharides joined by
covalent bonds referred to as
glycosidic linkages.
9. Glycogen
Glycogen is the only polysaccharide
found in animals that frequently is
evaluated by histochemical
techniques.
10. Simple polysaccharide with consists
of branched or straight chains D-
glucose units found intra cytoplasmic
serves as a major form of stored
energy reserves in humans.
11. In EM the glycogen occur in the
following forms;
Alpha: found as rosettes forms or
clusters of beta particles measured
60-250 nm in diameter.
12. Beta: occur as free particles or as a
part of a rosettes formation 20-40nm
Gamma: non-particulate found
between beta particles in the alpha
rosettes.
13. Normally glycogen found in:
Greatest amount in: liver, cardiac and
skeletal muscles.
Significant amount in: hair follicle,
endometrial gland
15. Fixation and Section Preparation
Fixative containing alcohol or picric
acid are favorable for glycogen
demonstration eg; bouins and
Rossman solution, 80% alcohol .
16. Aqueous fixative eg; formalin give
adequate fixation.
Suza-zenker are contraindicated.
At EM: potassium permanganate and
glutraldehyde
17. Streaming artifacts (Polarization)
One of the difficulties associated
with the fixation of glycogen.
Definition: the tendency of glycogen
to stream through the cell with the
fixative toward one pole when it
fixed at RT.
20. H&E:
cells containing abundant glycogen
will stain deeply compared with those
containing little(weak red).
21. Periodic Acid-Schiff Reaction
(PAS)
The PAS technique is without
question the most versatile and
widely used technique for the
demonstration of carbohydrates or
glycoconjugates.
22. The PAS technique may aid in the
differential diagnosis of tumors
through the detection of mucins or
glycogen.
23. Mechanism of the PAS
technique
The PAS stain is a histochemical
reaction in that the periodic acid
oxidizes the carbon to carbon bond
forming aldehydes which react to
the fuchsin-sulfurous acid which
form the magenta color.
27. Mechanism of Bests carmine
Hydrogen bonding formation
between OHˉ groups on the glycogen
and H atom of the carminic acid
28.
29. Hexamine sliver technique
Give similar result to PAS reaction.
Principle:
Following chromic acid oxidation, aldehydes
are formed from glycogen, these will reduce a
hexamine silver nitrate to black compounds.
30. Enzyme control
Use to specified the techniques applied in
glycogen demonstration:
Alpha amylase: extracted from hog
pancreas and Bacillus subtilis and
Aspergillus oryzea.both branched or
straight chain glycogen are digested, these
releases glucose and maltose.
31. Beta amylase: obtained from sweet
potato digest straight chain and release
maltose alone.
Diastase: commonly used as it is; easy,
stable, cheep, extracted from malt and
contain both alpha and beta amylase
34. Medical importance
Some glycogen storage diseases :
A-von Gierke disease (deficiency of
Glucose-6-phosphatase)
B-Pompe disease(deficiency of Acid
maltase)
35. Also demonstration of glycogen can
help in diagnosis of carcinomas of
Bladder,Kidney,Liver,ovary and
adenocarcinoma of
Pancrease,Lung,Seminoma
Mesothelioma
36. Mucin
High molecular weight glycolized
protein secreted by specialized
epithelial cells and connective tissue
cells
38. In contrast to the
glycosaminoglycan's, which are
strongly acidic polyanions, the
polysaccharide chains of the mucins
vary from neutral or weakly acidic to
strongly acidic.
39. mucoid carbohydrates can be
divided into three main types:
1.Mucopolysaccharides
2.Mucoprotein
3.Mucolipids
41. when the polysaccharides less than 4%
we called glycoprotein and classified
with mucoprotein and can not be
distinguished from them . PAS---positive
42. Glycolipids
Made up of fatty acids combined
with carbohydrates , usually
galactose the cerebrosides are the
most important glycolipids PAS---
positive
43. Functions of mucins
1.Lubricator function
2.Environment for ionic and molecular
diffusion
3.Cell to cell adhesion with specific cell
surface
44. Protective role (innate immunity) from
microbes and chemical and mechanical
agents throughout GIT, Respiratory
tract ,reproductive system .
50. 2. Complex acid mucopolysaccharides:
In addition to glucuronic acid –sulfated
glucosamine units are includes e g chondroitin
which occur in cartilages and connective tissues
also heparin and heparan are others examples
51. Acid mucin : divided into sulfated
and carboxylated mucin
Sulfated mucin: divided into
strongly and weakly
52. Strongly sulfated mucin: divide into
strongly sulfated epithelial and strongly
sulfated connective tissue mucin
(proteoglycan )
53. Strongly sulfated CT mucin
Strongly sulfated CT mucin:
Highly sulfated substances produced by
fibroblast ,endothelial, osteocytes ,
chondrocytes ,mast cells , react at low PH
with cationic dyes and PAS negative.
54. The following types
1. Chondroitin sulfate A : found in
cartilage
2. C,S,B: found in aorta , heart valves ,
dermis of skin.
55. 3. C,S,C : in cartilage ,umbilical cord ,
dermis of skin.
4- Heparin/heparan sulfate: heparan found
in aorta , cardiac CT, and heparin in mast
cells.
69. Demonstration of mucins
Aqueous fixatives (formalin) are
satisfactory.
Muco polysaccharide are better
preserved in alcoholic fixatives
70. Hyaluronic acid when occur free is better
fixed in 10% formal-alcohol or 10 %
formal sublimate.
Other fixatives 2% calcium acetate in
10%formalin
71. Mucin staining
1/ H&E:
Mucin take up the eosin ,unless
Ehrlich Hematoxylin is used where
acid mucin stains blue.
72. 2/ PAS: Mucin containing a reactive
hexose component will be PAS
positive, these include:
1. Neutral mucin
2. N acetyl sialomucin
81. Alcian blue involving critical
electrolyte concentration(CEC)
CEC is point at which the amount of
electrolyte ,such as magnesium
chloride, in alcian blue solution is
sufficient to prevent staining.
84. 0,5-0.6 M ---only strongly sulfated
stain blue
0.7-0.8 M ---heparin/heparan stain
blue
85. 4/ Dialyzed iron –prussian blue
tech.
This is another popular technique for
demonstration acid mucins.
At low PH colloidal iron will be
adsorbed onto tissue polyanions (
sulphate , carboxylate group)
86. and subsequently ,visualized by
conversion to ferric ferrocyanide
using (Perl's tech)
It is more sensitive ,but complex
87. 5/ Southgate mucicarmine tech-
The rationale : not fully understood
,the aluminum/carmine compound
appear to be positively charged and
combined with negatively charged
acid mucosubstances.
90. Sulfated and carboxylated mucins
are metachromatic while neutral
mucin is orthochromatic.
Sulfated mucin at PH3 and
carboxylated at PH5
91. Combined alcian blue PAS methods
Acid mucins and neutral mucins are
separated , also useful to demonstrate
any mucins . First all acid mucin
stained with alcian blue leaving only
neutral mucin to be demonstrated by
PAS reaction.
92. Alcian blue-Alcian yellow
Used to distinguished b/w sulphate and
carboxylate, involving initial staining
with low Ph. alcian blue, followed high
Ph. alcian yellow
Result :
sulphate mucin- blue
carboxylate mucin -yellow
93. Aldehyde fuchsin –Alcian blue
technique
Separate sulphate from carboxylate.
The rationale:
Depends on the greater affinity of
aldehyde fuchsin for sulphate mucin .
94. so that by first staining with this
solution sulphate stained purple
,rendering carboxylated mucin to be
stain by alcian blue (counterstaining
95. Blocking tech and Enzyme
controls
Improved specificity, by enzyme
action or by blocking staining
(chemical action )
96. Blocking
Methylation:
using hydrochloric acid in methyl alcohol for
blocking the staining reaction of carboxylated
mucin by esterification of carboxyl group and
sulphate group by desulphation.
97. Methylation and Saponification:
After Methylation ,saponification with
potassium hydroxide in ethyl alcohol ,
will restore the staining of carboxyl
groups but sulphate groups still blocked.
99. Other types of carbohydrates
Chitin:
This is hyaline substance wide
distributed in non human tissue for
example exoskeleton of insects.
100. In human only seen lining the wall of
hydatid cyst of lung or liver due to
infestation of larvae of dog tapeworm
Echinococcus granulosus.
PAS positive Diastase resistance
101. Starch
Can be found in tissue as
contaminant from surgical gloves
powder.
PAS positive with iodine pale blue-
Diastase labile