Abstract
The purposes of this study were: (1) To ascertain whether intranuclear inclusions, similar to those found in wild rats in England 1 , 2 and China, 3 , 4 occur also in the United States. (2) To discover whether, if present, they are restricted to salivary glands as has been described. 3 (3) To demonstrate whether a virus, responsible for their formation, is transmissible to laboratory rats.
A series of 120 wild rats was collected at 16 different locations in St. Louis. All were trapped or shot on rubbish heaps, except 8 which were captured at a meat packing plant; and all were brown rats (Rattus norvegicus) except 2 which were black (Rattus rattus). Their weights ranged from 45 to 541 gm. with an average of 300.2 gm. There were 50 males and 70 females. The parasites found in 100 members of the series have been described. 5 Tissues were fixed in Zenker's fluid and stained in hematoxylin and eosin. Care was taken to examine all of them with as nearly as possible equal thoroughness.
Nuclear inclusions were found in both the submaxillary glands and kidneys of 24, and in the kidneys alone of 87 of these wild rats. Evidently, therefore, the limitation to the salivary glands reported by Kuttner and Wang 4 for Chinese wild rats did not hold for wild rats in the St. Louis area, but these investigators showed that, when white rats were injected with salivary glands containing inclusions, inclusions were formed in their kidneys. This indicates that a single virus may be responsible in this series for the formation of the nuclear inclusions in both salivary glands and kidneys.
Examination failed to reveal the natural occurrence of nuclear inclusions in the submaxillaries and kidneys of 50 white rats in our colony. An attempt was made to transmit a virus from wild rats to white rats. The kidneys of 2 wild rats, proved to contain typical inclusions, were emulsified in sterile salt solution and passed through a Berkefeld N filter. Four lots, each of 2 rats, were given intraperitoneally 1 cc., subcutaneously 1 cc., intraglandularly (submaxillary) 1 cc., and intracerebrally 0.5 cc., respectively, of the filtrate. They were killed at intervals up to the 20th day but no inclusions could be found in salivary glands, kidneys or nervous system.
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