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Align-ju STUDENT
Erythrocyte inclusions
These , as the name suggests , are found inside the erythrocytes and must be identified , especially if infectious organisms are suspected .
Howell – Jolly bodies are small , dark purple and circular and are often located eccentrically ( Figure 5 ). They are the remains of a red blood cell ' s nucleus . These are often seen during regeneration , but if regeneration is not present they can be associated with splenic or bone marrow disease . Occasionally they can be seen in healthy animals .
Mycoplasma bacteria ( Mycoplasma haemofelis , a common cause of feline infectious anaemia ( FIA ) in cats ) appear as small , regular purple dots , often as a small chain inside or attached to the erythrocyte ( Figure 7 ). This must not be confused with stain precipitate . If a mycoplasma infection is suspected , a polymerase chain reaction ( PCR ) test should be carried out .
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Figure 7 . Mycoplasma Haemofelis .
Leucocytes
Figure 5 . Howell – Jolly body .
Heinz bodies are small circular blebs that protrude from the cell and have a clear white crescent on one side , next to the cell ' s surface ( Figure 6 ). In cats , they are associated with oxidative toxin damage to the erythrocyte surface .
Leucocytes derive from two cells of origin : lymphoid and myeloid ( Table 1 , p . 48 ). The myeloid stem cells also generate erythrocytes .
Mammals have a significant pool of neutrophils in the bone marrow , whereas other leucocytes are produced on demand . Most leucocytes exist in the blood for only a few hours and are destined either for tissue pools ( in the case of eosinophils and monocytes ) or for mucosal loss ( in the case of neutrophils ). Lymphocytes , however , are essentially recycled / recirculated . Neutrophils , especially in cats , have a marginating pool where they adhere to and roll along the blood vessel wall . It is this pool that accounts for the marked physiological increases and decreases seen with blood pressure changes .
Thrombocytes
Figure 6 . Heinz body .
Thrombocytes or platelets are small anucleate cells , which are responsible for aiding clotting . These are normally small , round to oval , with pink / purplestaining cytoplasm . They are often miscounted on automated analysis , due to the variation in their size and shape . Platelets can also clump ( Figure 8 , p . 48 ) following venepuncture , which will also lead to miscounting . Thrombocytopenia is rare in cats and any low platelet count should always be followed up by blood film analysis . If macroplatelets ( giant platelets ; Figure 9 , p . 48 ) are present , then a manual count can be performed to assess a minimal platelet count .
Volume 38 ( 6 ) • December 2023
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