Since the MCV of rat erythrocytes is smaller than humans


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As demonstrated in (Table 1.)the experimental haematological index of rat is greater than both the standard human male and human female haematological indices, 6.25 x 1012 erythrocytes per litre. The RCC gives the oxygen carrying capacity of the blood. The higher the RCC, is the greater the oxygen carrying capacity of blood. This higher capacity is a requirement for rats as they are highly active organisms, and therefore their cells have a high rate of metabolism. Hence the haematological index of rat needs to be higher than that of humans. Since the MCV of rat erythrocytes is smaller than humans, relatively high number of erythrocytes is required to support the higher haematocrit and haemoglobin content which have ranges almost similar to human ranges.

The experimental rat haematological index is slightly below the standard rat haematological index. The cells need to be distributed homogeneously in the diluted blood solution in order to obtain accurate results.

The erroneous results may be due to insufficient mixing of blood with the preserving fluid before microscopic examination or due to rapid mixing, resulting in rupture of some red blood cells. The value is almost within the range.

There may have been miscount of cells.

As demonstrated in (Table 1.)The experimental haematocrit or the packed cell volume of the rat is within the range of the haematocrit for both standard human male and female haematocrit and the standard rat haematocrit.

The haematocrit is the proportion of blood volume occupied by red blood cells.

The haematocrit depends mainly on the non-cellular component; plasma and the number of erythrocytes in blood. The size of erythrocytes (MCV) also has an effect to a lesser extent. The experimental MCV obtained for the rat are within normal ranges for rat. (as shown on Table 2.) Even though the RCC estimated was slightly below the expected range, the haematocrit falling within the normal range explains that there may have been miscounts during the Neubauer count.

As demonstrated in (Table 1.) The experimental haemoglobin content of rat is slightly above the standard human female haemoglobin content range but within the range of standard human male haemoglobin content.

The haemoglobin content varies mainly depending on the RCC and to some extent the MCH. The standard normal ranges for haemoglobin content varies extensively in healthy organisms, with age, sex ,physiological variations such as pregnancy, ethnic origin and even method used for measuring, including the position of the model organism(that is upright or lying down), when the blood was obtained to be tested. (Ravel,1995). Therefore haemoglobin content of the rat falling slightly off range does not necessarily mean it is ill.

Generally the haemoglobin content ranges of human females is lower than that of human males of the same age. These variation are due to physiological changes in women. . (Ravel,1995; Rushton, et al.,2001). This explains why the higher experimental haemoglobin content of the rat went above the haemoglobin content range of human females.

The higher experimental haemoglobin content of rat 167g/l is within the relatively high standard range of haemoglobin content of human males. This may be due to either a blood disorder of the experimental rat or an adaptation of the rat's blood to survive in enclosed places with low oxygen levels.

Increased haemoglobin content could reflect the rat to have polycythaemia, but not due to an increase in the RCC but decrease in the plasma volume. This is indicated by the haematocrit reading, 50%, suggesting there's relatively high amount of erythrocytes relative to the rest of the blood, even though the value is just within the normal range.

This could be caused due to various reasons including dehydration of rat. Dehydration may be due to chemicals that were used to kill the rat, or due to warming the rat's tail; where blood is usually obtained, thereby increasing blood circulation, easing the extraction of blood from its tail. (Diehl et al.,2001). Dehydration causes the blood to become more concentrated, showing an increase in the haemoglobin content in blood relative to the blood volume.( apparent polycythaemia) (Bain,2004).

There may have been carboxyhaemoglobin in the rat's blood. The presence of carboxyhaemoglobin in blood has an effect on the aberrant haemoglobinometer reading. Carboxyhaemoglobin conversion into azide-methemoglobin is low, resulting in erroneous readings. (Shephard,2000).

The Wintrobe indices, MCV, MCH and MCHC are calculated using the haematocrit, haemoglobin content, and the RCC, which are within normal ranges or very close to the normal ranges. Thus values calculated using them are also within normal ranges..

The white blood cells demonstration shows that the cell sizes and numbers are within normal range without any signs of abnormality in them.

To avoid errors that could occur during microscopic cell counts, modern medicine includes more accurate, automated apparatus' to perform cell counts; which involves the generation of an electrical impulse by each cell passing a sensing zone, and these signals correspond the number of cells. By using these methods the human errors that could occur during microscopic cell counts may be avoided. (Bain,2004).

There are automated apparatus for the measurement of the haematocrit, after the blood sample is centrifuged. (Bain,2004).

The method and area in which blood is obtained, also could be standardised. For instance, rat blood could be drawn from the sublingual vein; with repeated anaesthesia. This way dehydration of the rat is avoided, providing more accurate results. (Diehl et al.,2001).

It is advisable to take into account all the haematological blood tests into (even the ones that are not mentioned) before diagnosis of a disease and to repeat tests in order confirm the accuracy of their results.

Variations of the Wintrobe indices, blood counts, haemoglobin content and/or haematocrit off normal ranges may indicate different blood disorders as types of polycythaemia or anaemia, caused due to varied reasons, as iron deficiency (iron deficiency anaemia), change in shape of erythrocytes (sickle cell anaemia), vitamin deficiencies (pernicious anaemia), anaemia due to haemorrhage (haemorrhage anaemia), due to lysis of erythrocytes as a result of bacterial infections (haemolytic anaemia), and destruction/depression of bone marrow (aplastic anaemia),etc. and thereby aid the diagnosis of diseases which are associated with these blood disorders. (Bain,2004).

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