Bacteriological aspects of penicillin therapy

The Effect on the Rous No. 1 Fowl Sarcoma Virus of Berkefeld Filtration with and without Previous Repeated Freezing and Thawing

“…The results of the concluding experiment-s of the present work (Table III) Table III demonstrate this clearly; they are at variance with those reported by Selbie and McIntosh (1939 Secondly, the method of extracting the Rous virus employed by Selbie and McIntosh (1939) consisted of coarse mincing of the tumour material followed by grinding with sand. Repeated freezing and thawing was then applied to the resulting preparation, and may well have contributed to the achieving of complete disintegration of the tumour and the maximum extraction of virus from it.…”

“…I fowl sarcoma (Epstein, 1951) it was found th.-.t when Rous tumour material was repeatedly frozen and thawed and then extracted, no such greater liberation of virus took place than where no treatment was applied. Virus suspensions made from the treated material had less tumourproducing activity than those made from similar untreated samples; thus the suggestion made by Selbie and McIntosh (1939) was not confirmed.…”

“…However, although no increased liberation of virus from Rous material subjected to repeated freezing and thawing could be demonstrated to account for the increased tumour-producing activity of Berkefeld filtrates made from such material reported by Selbie and McIntosh (1939), there remained another possible explanation of their finding. The increaged tumour-producing activity of Berkefeld filtrates prepared from Rous tumour subjected to repeated applications of cold might have been due to some action ofthe cold on the virus whereby its physical state was altered in such a way as to aRow it to pass the filter with greater facility than where no treatment was applied.…”

“…I fowl sarcoma material which had been subjected to repeated applications of cold possessed a greater tumour-producing activity than those prepared from similar material which had not been subjected to this'treatment (Selbie and McIntosh, 1939). In explanation of this finding Selbie and McIntosh (1939) suggested that the freezing broke up the tissue fragments,'and thus allowed a greater liberation of virus than would otherwise have been possible.…”

“…In the present work, however, disintegration of the tumour material was brought about mechanicall before the cold was applied, and would seem to have been so complete that the repeated freezing and thawing could not have any further effect. This is considered to be the most likely explanation of the contradiction between the findings reported by Selbie and McIntosh (1939) A titration method has been employed in which preparations whose tumourproducing activities were to be compared have been diluted in serial tenfold steps with saline and inoculations made with each dilution.…”