Familial incidence of a toxemia of pregnancy in the guinea pig

Studies of the Mechanism of Action of Urethane in Initiating Pulmonary Adenomas in Mice

“…Some of the nucleic acid derivatives in high doses influence the degree and duration of the anesthetic effect of urethane. Even though it had previously been found that the neoplastic response of individual animals was related to the amount of urethane given rather than the peak concentration or duration of exposure (12) the anesthetic influence of urethane on experimental and control groups was always noted. The dose levels of the derivatives of nucleic acid dealt with herein produced no differences between experimental and control groups in anesthetic effects.…”

“…Both the Swiss and "A" strains have a high incidence of pulmonary adenomas whereas the "C" has a low incidence. References to the specific character of the stocks may be found in a previous report (12). In all experiments the animals tested were matched as to age, weight, sex, and strain.…”

“…This is shown in representative accompanying charts (1 through 8). No test substance was given after injection of the animals with urethane because only the initiatory phase of carcinogenesis was to be studied (24,12,25). The experimental and control animals were similarly maintained after injection to insure that the subsequent growth of the neoplasms would take place under the same conditions.…”

“…Because the general biological importance of nucleic acid to the maintenance of heritable characteristics is generally recognized and, because of the nuclear poisoning effects of urethane (11), much attention has been directed toward the carcinogen's possible influence upon nucleic acid synthesis. Recent experiments have discounted the assumption that urethane has a direct nucleotoxic action in initiating tumors (5,6,12). Evidence perhaps in favor of an influence upon nucleic acids, however, has been reported by Cowen (13).…”

“…Young, rapidly growing mice are much more responsive to standard doses of urethane than are those that are older and more slowly growing (12,15). Since there is a recognized correlation in the rate of synthesis of desoxyribosenucleic acid and the growth rate of the body at a given time (16), it seemed worthwhile to find out to what extent the number of tumors initiated by a single injection of urethane might be influenced by simultaneous exposure of the animals to desoxyribosenucleic acid (DNA), ribosenucleic acid (RNA) their chemical components, precursors, and substances influencing their rate of synthesis.…”