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Summary. A comparative study of the sialic acid content of semen, serum and spermatozoa from several mammalian species was made.The sialic acid content of semen showed a very wide range of concentration in the four species examined, while the sialic acid concentrations in serum were much more uniform. The semen from man and bull contained higher concentrations of sialic acid than the serum of these respective species. The reverse was found in rabbit and dog.Only a small fraction of the total sialic acid in semen was found unbound and spermatozoa were found to contain very little sialic acid.The sialic acid of semen and serum was readily accessible to the action of Receptor Destroying Enzyme (rde) except that of rabbit semen. Using paper chromatography n-acetylneuraminic acid was identified in all the samples. n-Glycolylneuraminic acid was also observed in bovine serum and a trace was found in rabbit serum.

PREVIOUS studies on the localization of fluorene-2,7-di-(sulfonamido-2-naphthalene)-S35 revealed that the presence of a subcutaneously transplanted tumor decreased the uptake of this radioactive compound by the liver and spleen of mice (Argus and Hewson, 1954; Argus, Hewson and Ray, 1956). This phenomenon was demonstrated in both CAF1/Jax mice bearing a squamous cell stomach carcinoma and C3H mice bearing the Barrett mammary adenocarcinoma. Autoradiograms indicated that it is a phagocytic function of the reticuloendothelial system that is impaired (Argus, Hewson and Ray, 1956). Subsequent studies to determine if other stress conditions produce this phenomenon showed that, unlike the presence of a tumor, neither X-irradiation nor cortisone affects the uptake of fluorene-2,7-di-(sulfonamido-2-naphthalene)-S35 by the liver and spleen of mice or rats (Argus, Kane and Ray, 1960;Malejka, Argus and Ray, 1961).In the present studies this localization phenomenon was investigated in hamsters and rats as influenced by the presence of two different types of transplanted tumors (a fibrosarcoma and Walker carcinosarcoma 256). The effect of metastatic tumors existing after surgical removal of the transplanted sarcoma was studied in hamsters, and the effects of liver regeneration (resulting from partial hepatectomy) and of pregnancy were observed in rats. To determine if the phenomenon occurs as a result of the increase in proliferation of liver cells (Laird andBarton, 1959, 1960) caused by the carcinogen, 2-acetylaminofluorene, before the gross appearance of tumors, the uptake of fluorene-2,7-di-(sulfonamido-2-naphthalene)-S35 by the liver and spleen of rats fed the carcinogen, 2-acetylaminofluorene, for varying periods of time was investigated. MATERIALS AND METHODSFluorene-2,7-di-(sulfonamido-2-naphthalene)-S35 having a specific activity of 13,400 disintegrations/sec. /mg. (0-36 /ac/mg.) was prepared as previously reported (Argus and Hewson, 1954). For administration, the radioactive compound was dissolved (9 mg./ml.) in 0 05N NaOH except for a study of two groups of hamsters where the injection medium was dilute sodium bicarbonate and * Present address: