STUDIES IN THE BLOOD CYTOLOGY OF THE RABBIT : I. BLOOD COUNTS IN NORMAL RABBITS

THE HEMOCYTOLOGICAL CONSTITUTION OF ADULT MALE RABBITS FROM FIFTEEN STANDARD BREEDS

A study of the red blood cells, hemoglobin, blood platelets, and the total and individual white blood cells was made on 180 male rabbits of known age and representing fifteen standard breeds. An attempt was made to eliminate or bold constant such variables as age, sex, season, time of examination, technical errors, food, housing, and disease. The mean, variance of the mean, and standard deviation were calculated for each breed sample and for the group as a whole. An analysis of the variance showed that the variation between the breed samples was significantly greater than the variation within the breed samples for the red blood cells, hemoglobin, blood platelets, total white blood cells, basophiles, eosinophiles, and lymphocytes per cubic millimeter and in per cent and the neutrophiles in per cent. No significant variations were detected in the monocytes except when the breeds were divided into heavy and light breeds. No variation in the neutrophiles per cubic millimeter was detected; a large number of the breeds had exactly the same mean neutrophile level. Characteristic blood formulae were found for the various breed samples having an adequate numerical representation. It was concluded that the varying blood formulae could not be explained on any other, except an hereditary (genetic) basis.

CHANGES IN THE BONE MARROW AND BLOOD CELLS OF DEVELOPING RABBITS

1. The full number of erythroid cells in the blood stream of the rabbit is reached by the 3rd week of life. 2. During this period, there is a predominance of erythrogenesis in the bone marrow. 3. During the 2nd week of life the bone marrow is in a state of hyperplasia owing to the needs of the body for blood and the small space available for the marrow. 4. This hyperplasia is reduced as the growth of the bone permits the marrow to spread. The control of the growth of the bones has an important bearing on hematopoiesis. 5. During the first 3 weeks of life, the chemical factors for the multiplication of red cells as well as for the elaboration of hemoglobin become available. 6. The amount of hemoglobin does not increase as rapidly as the number of cells, so that the macrocytic anemia of the fetus becomes reduced. The proportion of hemoglobin per red cell characteristic of the adult rabbit is reached by the 3rd month. 7. Further evidence on the intravascular origin of red blood cells is given. 8. The development of all of the white blood cells, with the exception of the monocyte, goes on at a slower rate than that of the red cells. 9. The monocytes reach their full number in the blood stream in the 1st week of life; granulocytes and lymphocytes by the 5th and 6th months. 10. Each of the three strains of white cells has a different rate of development. 11. The question as to whether the stem cell or primitive cell is identical with the lymphocyte is discussed.

Identification of rabbit eosinophils and heterophils in cutaneous healing wounds

The study of wound healing has traditionally used the rabbit as an experimental model. We have recently localized the production of the multifunctional cytokine, TGF-alpha, to eosinophils in rabbit skin wounds. It was evident that during the process of TGF-alpha localization, the distinction between the two granulocytic cell types, eosinophils and heterophils, was impossible by conventional histochemical techniques. This paper describes a rapid method to distinguish these two granulocytes by virtue of their endogenous peroxidases and differential resistance to blockade by inhibitors. In sections that have been blocked by hydrogen peroxide, the peroxidase substrate 3,3'-diaminobenzidine, together with nickel chloride (DAB-Ni), preferentially stained the cytoplasm of rabbit eosinophils while sparing those of heterophils. This selective DAB staining of rabbit eosinophil peroxidase in H2O2-blocked rabbit wounds was verified at the ultrastructural level by electron microscopy. We applied this technique to quantify eosinophil and heterophil infiltration into the 21-day rabbit cutaneous healing wound model. Heterophils were found infiltrated into all three layers of the wound (clot > granulation > base), but eventually all disappeared by day 21. As with the heterophils, eosinophils which had infiltrated into the clot and base of the wound had disappeared by day 21. Unlike the heterophils, eosinophils in the granulation layer of the wound continued to increase up to day 21. The continually increased and sustained presence of the eosinophils together with their demonstrated production of TGF-alpha, in the granulation layer of the healing would suggests that these cells play an important role in the organizational aspects of healing wounds.

CONCERNING THE RELATIVE RESPONSE TO BLOOD GAINS AND BLOOD LOSSES; AND HABITUATION TO AN EXCESS OF BLOOD PIGMENT

The effects of very gradually increasing or diminishing the amount of circulating hemoglobin have been studied in rabbits. Contrary to expectation it was found that when the pigment was increased by the injection of a small quantity of compatible blood every day during some weeks the erythropoietic tissue did not lessen its activities. The hemoglobin percentage mounted gradually yet considerably when even as little as 1/100 of the amount of blood initially possessed by the animal was injected each day; and the figure it finally attained must in some instances at least have been expressive of a superabundance. To this superabundance the animal itself evidently contributed through its persisting erythropoietic activity. The results were very different when rabbits were bled daily to the same small amount that was injected into their fellows. The marrow became abnormally active, and this activity continued undiminished throughout the long period of the bleedings. The organism is evidently far more susceptible to blood losses than to blood gains, a fact which is scarcely surprising when one considers that throughout its differentiation as a going concern it has had to cope with exigencies of the first sort only. Rabbits in which the hemoglobin is very gradually increased by the injection of strange blood become so accustomed to the abundance of pigment that even a slight falling off causes the erythropoietic tissue to become abnormally active to maintain the new status quo. Good reasons exist for referring the habituation thus manifested to readjustments in the functioning of the physiological mechanisms which mediate between oxygen demand and erythropoietic response. Too little recognition has been given to the rôle of these mechanisms in such relation. No evidence was obtained of any effective readjustment to protect the erythropoietic tissue from the stimulus of daily small blood losses.

An enquiry into the Relative Toxicity of Benzene and Toluene

In our investigation of our subject we have perused the literature, analysed the data of other workers, conducted a number of animal experiments, considered the bearings clinical and pathological of a case of presumed toluene poisoning, and conducted an investigation into the blood state and symptoms of co-workers with this case and yet are unable to give a categorical answer to the question. What are the relative toxicities of toluene and benzene? We would almost feel inclined to echo the words of another worker in the experimental field with regard to benzene, Neumann (1915), who concludes: “The fact that my results so often do not correspond either with one another or with those of Selling, so often indeed do not correspond to expectation, justifies the conclusion that, although benzene is to be regarded as a powerful leucotoxin, it manifests great individual differences in its mode of action and it is very difficult to lay down exactly what action is to be expected.”

We should be inclined to put the case somewhat differently however and put forward the following view as our tentative finding.

The actions of benzene and toluene are very similar. That of benzene is the more powerful because it is a more volatile substance and can therefore reach higher concentration than toluene. This greater volatility at the same time is a reason why it is eliminated more quickly and its effects are less lasting than those produced by toluene. The action of both these substances is on young body cells, probably whatever they are and wherever they may be found, but is most easily discoverable because of its action on the young bone marrow cell and the consequent effect on the cells of the peripheral blood. It is not a specific action but operates, according to circumstances, on the stem cells of the myeloid leucocyte or the erythrocyte. This does not mean that the substances have little or no effect on the lymphocyte, for the lymphoid tissue in the body is so very abundant that it would only be in extreme cases that the effect on that cell would be manifest peripherally. Like many poisons, indeed like many of the drugs which are used in Medicine, the first effects of these substances are stimulating. Leucocytosis, erythrocytosis and possibly thrombocytosis are early manifestations or the manifestation of slighter action, with histological evidence of hyperplasia. This is succeeded by the truly toxic or destructive action and the production of leucopenia, anaemia, thrombopenia and the effects due to action on other organs. The ultimate result in clinical terms is an agranulocytic anaemia accompanied by purpura haemorrhagica and, as the pathological manifestation an aplastic bone marrow. The fatal termination is commonly an infection to which there is no resistance possible in an individual deprived of defence cells and possibly also of defensive substances in the body fluids. Powerful solvents of fat as both these chemical substances are, they produce an action through this means also, on nerve cells, capillary endothelium and parenchyma of organs with consequences represented in nervous symptoms and in haemorrhages. This then is our reading of the results of our investigation and explanation of the variability which may be found, a variability which is regarded mainly as one of phase, although we do not exclude idiosyncrasy altogether as explanation.

STUDIES ON THE BLOOD CYTOLOGY OF THE RABBIT : IX. BLOOD PLATELET COUNTS ON HEALTHY MALE RABBITS

1. Repeated platelet counts, 991 in number, were made on 148 adult male rabbits of various breeds and types which were specifically selected on the basis of physical fitness and continued freedom from disease. The observations extended over a 2½ year period (1929–32). 2. A unimodal, peaked, moderately asymmetrical distribution curve was obtained and an analysis of the results gave the following values: the mean, 532,645 platelets per c.mm.; the median, 520,604 per c.mm.; the mode, 503,962 platelets per c.mm. respectively. 3. The extent of the variation among the counts is shown by the standard deviation of 124,960. High platelet counts were found to occur more frequently than low counts, a result that is reflected in a significant skew to the right in the frequency curve. 4. It was calculated that in healthy male rabbits a platelet count of less than 220,000 or more than 845,000 per c.mm. should be considered abnormal.

STUDIES IN THE BLOOD CYTOLOGY OF THE RABBIT : VII. OBSERVATIONS ON RABBITS INOCULATED WITH A TRANSPLANTABLE MALIGNANT NEOPLASM

Successive blood counts at weekly intervals were made on rabbits inoculated with a transplantable malignant neoplasm of epithelial origin. There were 78 animals distributed in 9 groups; the period of observation after inoculation was 2 months. The results have been considered with respect to the character of the tumor process as determined by postmortem examination, the animals being classified as deaths, probable deaths, probable recoveries, and recoveries. The blood findings have been analyzed on the basis of the values derived from normal rabbits. A comparison has also been made with the results of preinoculation counts. In rabbits in which the tumor process was of pronounced or well marked severity, the numbers of monocytes became greatly increased; the neutrophiles and the total white blood cells were also increased; the eosinophiles, and to a less extent, the basophiles and lymphocytes were decreased; the red cell count was decreased and the hemoglobin content was lowered. In rabbits which recovered from the tumor inoculation, there were no outstanding changes in the blood picture when the findings for the entire observation period were considered. In the group of probable recoveries, the results were variable; there was, however, a definite although moderate increase of monocytes, and in general, the findings reflected the mildness of the disease when compared with those of the fatal cases and the group of probable deaths.

STUDIES IN THE BLOOD CYTOLOGY OF THE RABBIT : VI. BLOOD CELL RELATIONSHIPS IN GROUPS OF NORMAL RABBITS WITH RESPECT TO TIME

1. Statistical analyses have been made of the weekly variations in the blood counts of groups of normal rabbits to find whether there exists any relationship between the numerical changes occurring in the various cell types. Consecutive blood counts and differential white cell determinations on five groups of normal male rabbits comprising 45 animals in all were made at weekly intervals from October, 1927, to June, 1929, the number of observations on each group varying from eight to thirty-five. 2. The following relationships between the varying group means were found to be consistent and significant:—The number of the red blood cells varied with the amount of hemoglobin per cubic millimeter and with the number of lymphocytes. There was an inverse relationship between the amount of hemoglobin and the number of monocytes. The neutrophiles varied in number with the monocytes; the basophiles with the eosinophiles; and the eosinophiles with the monocytes. Other associations not always similar but of high significance as far as the combined values were concerned, were the relations of the red blood cells with the basophiles and the monocytes. The relations of the neutrophiles with the red blood cells and the hemoglobin were very irregular. 3. Significant association of the white blood cells with variations in the red blood cells and the hemoglobin content were observed. The numerical variations in the group means of the total white cells were associated with similar variations in the group means of the neutrophiles, the lymphocytes, the monocytes, the basophiles, and the eosinophiles almost to the degree of their numerical occurrence in the peripheral blood. 4. With the exception of the total white cells, approximately only half the variations in the group levels of the various cells and of the hemoglobin content can be accounted for on the basis of simultaneous associations with each other. 5. The red blood cells, the lymphocytes, and the basophiles as one group, the eosinophiles and the monocytes as another group, and the hemoglobin content and the neutrophiles as a third group, described a definite shift from a high to a low numerical value during the 2 year observation period. From the standpoint of the magnitude of the shift, the basophiles, the eosinophiles, the monocytes, the lymphocytes, and the red blood cells participated in the order mentioned. The neutrophiles were only slightly affected and the hemoglobin content relatively not at all. 6. No significant relationship was ever found, even in the component groups, between the weekly mean values of the following: the hemoglobin with the basophiles, the eosinophiles, or the lymphocytes; the neutrophiles with the basophiles or the eosinophiles; and the lymphocytes with the eosinophiles or the monocytes.

STUDIES IN THE BLOOD CYTOLOGY OF THE RABBIT : V. CONSECUTIVE LYMPHOCYTE AND MONOCYTE OBSERVATIONS ON GROUPS OF NORMAL RABBITS

Consecutive weekly observations on the lymphocyte and monocyte counts of the peripheral blood were made on 5 groups of normal rabbits, a total of 45 animals, during a period of 20 months from October, 1927 to July, 1929. Individual groups were examined 8 to 35 weeks. The results are analyzed on the basis of the mean group values of each week. In the case of the 4 groups followed 13 to 35 weeks, there was a general tendency for the lymphocyte mean values to become increased; with the group observed 8 weeks, the level of mean values showed little change. The general trend of the monocyte mean values was also in the direction of higher levels but it was less pronounced than that of the lymphocytes. The period of greatest irregularity in the mean values of the lymphocytes was in the late winter and spring months of both years. With the monocytes, periods of fluctuating values occurred in the fall of 1927, the spring and early summer of 1928, and in the late winter, spring, and early summer of 1929. There was a certain degree of parallelism in the case of two groups examined during the same months with respect to the direction and time of occurrence of a change in the level of lymphocyte and monocyte mean values. The general levels of lymphocyte and monocyte mean values in the groups examined during 1927–28 were higher than in the groups of 1928–29. The results based upon the trends of mean group values obtained from consecutive weekly observations showed no evidence of a consistent numerical relationship between lymphocytes and monocytes.

STUDIES IN THE BLOOD CYTOLOGY OF THE RABBIT : II. CONSECUTIVE ERYTHROCYTE AND HEMOGLOBIN OBSERVATIONS ON GROUPS OF NORMAL RABBITS

Observations are reported on the consecutive weekly erythrocyte counts and the hemoglobin contents of the peripheral blood in 5 groups of normal rabbits, comprising 45 animals, during a period of 20 months from October, 1927 to July, 1929. The duration of individual group examinations varied from 8 to 35 weeks. The results are analyzed on the basis of the weekly mean values of each group. On the whole, the erythrocyte values were quite uniform within a narrow range of variation, while the hemoglobin content was comparatively irregular within a wider range of variation. The major changes in the levels of mean values of both the red cells and the hemoglobin, however, were found to be statistically significant. The directions or trends in the levels of the erythrocyte and hemoglobin mean values did not necessarily move in opposite directions. The general levels of the erythrocyte and hemoglobin mean values were not identical for two consecutive years, those of 1927-28 being higher than those of 1928-29. The fluctuations of both red cell and hemoglobin mean values observed in one group of animals were also usually observed in another group examined during the same months.