Biomedical subjects
Publications and source records attributed to J M Rice.
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Poly-d-lysine forms a stochiometric complex with poly(I) . poly(C) which has a higher T(m) (83 C in 0.15 m NaCl) than the uncomplexed double-stranded polyribo-nucleotide (63 C). The complex was superior to poly(I) . poly(C) alone as an interferon inducer in vivo. Significant serum interferon titers were attained in Swiss mice during a 24-hr period after intraperitoneal injection of 10 to 300 mug of poly(I) . poly(C) [1.0 poly-d-lysine] complex, at concentrations of 100 to 1,000 mug/ml. The serum interferon responses (average and maximum titers) of a series of inbred strains of mice to a single intraperitoneal injection of 100 mug of complex decreased in the order: Swiss > DBA/2 > C3H > BALB/c > CF-1 > AKR, C57Bl/6, NZB > SJL > NZW and varied by a factor of approximately 100 from the most to the least responsive.
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Poly-d-lysine of high molecular weight enhances interferon induction in mice by the double-stranded complex of polyinosinic and polycytidylic acids and is superior to diethylaminoethyl-dextran in this respect.
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DNA strand breakage and repair following methyl methanesulfonate (MMS) treatment of primary cell cultures from 14-day fetal Sprague-Dawley rat brain and liver and 12-day fetal C57BL/6 mouse brain and liver, were studied using alkaline sucrose density gradient analysis. Cells were incubated with MMS (7 mM or 14 mM) for 20 min and harvested for alkaline sucrose gradients 40 min or 24 h later. The extent of initial damage in fetal rat and fetal mouse cells was comparable. Fetal mouse brain and liver and rat liver showed nearly complete repair 24 h after treatment. However, fetal rat brain cells showed comparatively little repair after 24 h. The possible significance of a repair deficit in cultured rat fetal brain cells and the striking neurogenic organotropism of transplacentally administered direct-acting alkylating agents in the rat is discussed.
Platinum-DNA adducts in placenta and blood from a woman exposed to 200 mg/m2 of cis-diamminedichloroplatinum(II) (cisplatin) and 300 mg/m2 diamminecyclobutanedicarboxylatoplatinum(II) (carboplatin) for ovarian cancer have been documented by cisplatin-DNA enzyme-linked immunosorbent assay (ELISA) and atomic absorbance spectrometry (AAS). A patas monkey model was used to investigate transplacentally induced cisplatin-DNA damage in fetal tissues. During the last trimester of gestation, 5 patas monkeys were given multiple doses of cisplatin to mimic human ovarian cancer treatment. In spite of careful choice of dose and treatment conditions, cumulative toxicity occurred in monkeys given doses comparable on a mg/m2 basis to those received by the human. A total dose of 12 mg/m2 (0.625 mg/kg body weight), given in the last trimester, supported fetal viability, and multiple tissues, taken by cesarean section, were examined in the fetal monkeys. By cisplatin-DNA ELISA and AAS, maternal tissues from the monkey receiving the highest dose contained approximately twice as much DNA damage as the fetal tissues. A similar relationship was observed when we compared DNA adduct formation in fetal liver and biopsies of liver taken from the monkey dams at cesarean delivery. In all of the monkey pairs studied there were very significant levels of DNA damage in the placenta, and high adduct levels in brains of fetuses that survived treatment. Thus, cisplatin does cross the placenta in the patas monkey. These observations imply that the human fetus, for which the total maternal dose was approximately 5.4 mg platinum drug/kg body weight, may also have sustained some DNA damage.
A previous attempt to model transplacental cisplatin exposure and genotoxicity employed several pregnant Erythrocebus patas monkeys; most of the animals were exposed near the end of gestation and cisplatin-DNA adduct analyses included only genomic DNA. Here, both genomic and mitochondrial DNA adduct formation have been determined in fetuses from two pregnant monkeys exposed at the end of the second trimester of gestation. Multiple fetal tissues were obtained after doses of 0.315 mg cisplatin/kg body weight (5.3 mg/m2 total) on days 101 and 106 of gestation. Cesarean sections were performed 24 h after exposure and 27 d after exposure. Cisplatin genomic (g)-DNA adducts were observed in fetal adrenal, brain, heart, kidney, liver, skin, spleen, and thymus. When placentas from the two animals were divided into four concentric regions at increasing distances from the umbilical cord, and g-DNA was assayed, cisplatin DNA adduct levels were similar in all four regions. Mitochondrial (mt)-DNA adducts were higher than g-DNA adducts in maternal liver and fetal liver, brain and kidney, suggesting that the mitochondria may constitute a particular target for cisplatin genotoxicity. The study demonstrates significant fetal genotoxicity in g-DNA and mt-DNA of patas monkeys exposed to cisplatin in utero, suggesting that similarly exposed human fetuses may also sustain drug-induced DNA damage.
DNA base damage was studied in renal and hepatic chromatin of nickel(II)-injected pregnant female F344/NCr rats and their fetuses under conditions leading to initiation of sodium barbital-promotable renal tumors, but not liver tumors, in the male offspring. Pregnant rats were given a total of 90 or 180 mumol of nickel(II) acetate/kg body wt in a single ip dose on day 17 or in 2 or 4 ip doses between days 12 and 18 of gestation. Control rats received 180 mumol of sodium acetate/kg body wt. The animals were killed 24 or 48 h after the last injection. Chromatin was isolated from livers and kidneys from both adults and fetuses and analyzed by gas chromatography/mass spectrometry with selected ion monitoring. Eleven products derived from the purine and pyrimidine bases in DNA bases were identified and quantified. These were the following: 5-hydroxy-5-methylhydantoin, 5-hydroxyhydantoin, 5-(hydroxymethyl)uracil, cytosine glycol, thymine glycol, 5,6-dihydroxycystosine, 4,6-diamino-5-formamidopyrimidine, 2,6-diamino-4-hydroxy-5-formamidopyrimidine, 8-hydroxyadenine, 2-hydroxyadenine, and 8-hydroxyguanine (8-OH-Gua). Nickel(II) exposure increased the content of these products, especially those derived from purines, in both renal and hepatic chromatin of pregnant rats. The major difference between these two organs was the content of 8-OH-Gua, which increased greatly in the kidney but remained unchanged in the liver.(ABSTRACT TRUNCATED AT 250 WORDS)
As part of an investigation of the structural requirements for the induction, by phenobarbital-type inducers, of a coordinate pleiotropic response consisting of increases in hepatic cytochrome P450 2B (P450 2B) activity, increases in other phase I and II enzyme activities, and liver hypertrophy, we have examined a series of analogues of phenobarbital in which the ethyl/phenyl substitution at the sp3 carbon of the parent molecule was kept constant while the heterocyclic portion of the molecule was modified. The induction of hepatic P450 2B protein and ethoxy-, pentoxy-, and (benzyloxy)resorufin O-dealkylation activities, and epoxide hydration activity and liver/body weight ratio increase were examined in male F344/NCr rats fed the various congeners for 14 days at doses equimolar to 500 ppm phenobarbital. Increases in the measured parameters were maximal in rats fed phenobarbital or 5-ethyl-5-phenylhydantoin. The responses to primidone or 2-ethyl-2-phenylsuccinimide were approximately 65% of maximal, while glutethimide yielded a response approximately 50% of maximal. Induction of this response in rats fed the ring-opened and decarboxylated analogues, (ethylphenylacetyl)urea and 2-ethyl-2-phenylmalonamide, were < 25% of maximal. 5-Ethyl-5-phenyloxazolidinedione caused minimal increases in the measured end points when administered at a dose equimolar to 500 ppm phenobarbital. The profound differences among the congeners in ability to induce P450 2B protein and associated catalytic activities were not due to differences in food consumption by the various groups of rats.(ABSTRACT TRUNCATED AT 250 WORDS)
DNA base damage was studied in renal, hepatic, and pulmonary chromatin of male and female F344/NCr rats that had been given either 50 or 100 mumol of Co(II) acetate/kg body wt in a single ip dose and killed 2 or 10 days later. Control rats received 200 mumol of sodium acetate/kg body wt. Chromatin was isolated from organs and analyzed by gas chromatography/mass spectrometry with selected ion monitoring. The following 11 products derived from purine and pyrimidine bases in DNA were quantified: 5-hydroxy-5-methylhydantoin, 5-hydroxyhydantoin,5-(hydroxymethyl)uracil(5-OHMe-Ura),5- hyd roxycytosine(5-OH- Cyt),thymine glycol, 5,6-dihydroxycytosine,4,6-diamino-5-formamido-pyrimidine (FapyAde),2,6-diamino-4-hydroxy-5-formamidopyrimidine (FapyGua),7,8-dihydro-8-oxoadenine,2-oxoadenine, and 7,8-dihydro-8-oxoguanine. The response was organ-specific. Eight of the DNA base products in renal chromatin of Co(II)-treated rats (mostly 5-OH-Cyt and other pyrimidine products), five in hepatic chromatin (mostly FapyGua and other purine products), and two in pulmonary chromatin (5-OHMe-Ura > FapyAde) were increased by 30% to more than 200% over control levels with increasing Co(II) dose. The renal and hepatic, but not pulmonary, DNA base damage tended to increase with time. No significant differences in response were found between male and female rats. The bases determined were typical products of hydroxyl radical attack on DNA, suggesting a role for this radical in the mechanism(s) of DNA damage caused by Co(II) in vivo. Some of these bases have been shown previously to be promutagenic. The present results imply involvement of oxidative DNA base damage in Co(II)-induced genotoxic and carcinogenic effects.