PARABIOSIS IN STRAINS OF CARIES-SUSCEPTIBLE AND CARIES-RESISTANT RATS

¹ Harvard School of Dental Medicine, Boston, Mass.

1. The mortality rate of littermate and non-littermate pairs was 37 per cent and 62 per cent, respectively. An additional 3 per cent of the littermate pairs and 33 per cent of the non-littermate pairs were lost due to separation. The non-littermate pairs healed less satisfactorily and looked less healthy. The percentage of useful pairs obtained was 60 per cent for littermates and 5 per cent for non-littermates.

2. The rate of blood interchange among the non-littermate pairs varied considerably. Vascular channels did not develop across the muscle fusion in at least 1 pair of non-littermate rats.

3. After injection of trypan blue into 1 parabiont, the gross color changes in the uninjected parabiont during the following several hours appeared to be reliable criteria for estimation of the effectiveness of circulatory exchange. This technic was simple to execute, easy to read, and did not noticeably affect the health or future usefulness of the animals.

4. Parabiosis, per se, did not alter caries activity among caries-susceptible and caries-resistant rats. The failure of a caries-resistant parabiont to cause any modification in the caries initiation and progression of his caries-susceptible parabiont, and vice versa, does not mean that these negative results conclusively eliminate the possibility of a blood-borne determinant of the degree of proneness to caries.