Activation of the Ha-, Ki-, and N-ras genes in chemically induced liver tumors from CD-1 mice.

We compared the profile of ras gene mutations in spontaneous CD-1 mouse liver tumors with that found in liver tumors that were induced by a single i.p. injection of either 7,12-dimethylbenz(a)anthracene (DMBA), 4-aminoazobenzene, N-hydroxy-2-acetylaminofluorene, or N-nitrosodiethylamine. By direct sequencing of polymerase chain reaction-amplified tumor DNA, the carcinogen-induced tumors were found to have much higher frequencies of ras gene activation than spontaneous tumors. Furthermore, each carcinogen caused specific types of ras mutations not detected in spontaneous tumors, including several novel mutations not previously associated with either the carcinogen or mouse hepatocarcinogenesis. For example, the model compound DMBA is known to cause predominantly A to T transversions in Ha-ras codon 61 in mouse skin and mammary tumors, consistent with the ability of DMBA to form bulky adducts with adenosine. Our results demonstrate that the predominant mutation caused by DMBA in mouse liver tumors is a G to C transversion in Ki-ras codon 13 (DMBA is also known to form guanosine adducts), illustrating the influence of both chemical- and tissue-specific factors in determining the type of ras gene mutations in a tumor. 4-Aminoazobenzene and N-hydroxy-2-acetylaminofluorene also caused the Ki-ras codon 13 mutation. In addition, we found that N-nitrosodiethylamine, 4-aminoazobenzene, and N-hydroxy-2-acetylaminofluorene all caused G to T transversions in the N-ras gene (codons 12 or 13). This is the first demonstration of N-ras mutations in mouse liver tumors, establishing a role for the N-ras gene in mouse liver carcinogenesis. Finally, comparison of the ras mutations detected in the direct tumor analysis with those detected after NIH3T3 cell transfection indicates that spontaneous ras mutations (in Ha-ras codon 61) are often present in only a small fraction of the tumor cells, raising the possibility that they may sometimes occur as a late event in CD-1 mouse hepatocarcinogenesis.     

Genotoxicity of naturally occurring indole compounds: correlation between covalent DNA binding and other genotoxicity tests

3-Methylindole (3MI), melatonin (Mel), serotonin (Ser), and tryptamine (Tryp) were evaluated in vitro for their potential to induce DNA adducts, DNA strand breaks, chromosomal aberrations (Abs), inhibition of DNA synthesis, and mutations. All compounds produced DNA adducts in calf thymus DNA in the presence of rat liver S9. In cultured rat hepatocytes, all produced DNA adducts but none induced DNA strand breaks. In Chinese hamster ovary cells, 3MI and Mel produced DNA adducts, Abs, and inhibition of DNA synthesis with and without S9, except that Mel without S9 did not form adducts. Ser formed DNA adducts, was an equivocal Abs inducer, and suppressed DNA synthesis. Tryp induced neither adducts nor Abs, but did suppress DNA synthesis with S9. Ser and Tryp were less cytotoxic than 3MI and Mel. Mel, Ser, and Tryp failed to induce mutations in Salmonella and E. coli strains with or without S9. 3MI and Mel produced DNA adducts but not mutations in Salmonella TA100 with S9. 3MI and its metabolite indole 3-carbinol also did not induce mutations in a shuttle vector system in human cells. The lack of correlation between DNA adducts and other genotoxicity endpoints for these indole compounds may be due to the higher sensitivity of the (32)P-postlabeling adduct assay or it may indicate that the indole-DNA adducts per se are not mutagenic and are not able to induce strand breaks or alkali-labile lesions. The indole-induced Abs may result from cytotoxicity and suppression of DNA synthesis with minimal if any contribution from DNA adducts.     

Cysteine protease isoforms from Trypanosoma cruzi, cruzipain 2 and cruzain, present different substrate preference and susceptibility to inhibitors

Cysteine-proteinases from parasitic protozoa have been recently characterized as factors of virulence and pathogenicity in several human and veterinary diseases. In Chagas' disease, the chronic infection caused by Trypanosoma cruzi, structure-functional studies on cysteine proteases were thus far limited to the parasite's major isoform, a cathepsin L-like lysosomal protease designated as cruzipain, cruzain or GP57/51. Encoded by a large gene family, cruzipain is efficiently targeted by synthetic inhibitors, which prevent parasite intracellular growth and differentiation. We have previously demonstrated that the multicopy cruzipain gene family includes polymorphic sequences, which could encode functionally different isoforms. We report here a comparative kinetic study between cruzain, the archetype of the cruzipain family, and an isoform, termed cruzipain 2, which is expressed preferentially by the mammalian stages of T. cruzi. Heterologous expression of the catalytic domain of cruzipain 2 in Saccharomyces cerevisae yielded an enzyme that differs markedly from cruzain with respect to pH stability, substrate specificity and sensitivity to inhibition by natural and synthetic inhibitors of cysteine proteases. We suggest that the structural-functional diversification imparted by genetic polymorphism of cruzipain genes may have contributed to T. cruzi adaptation to vertebrate hosts.     

Use of transgenic animals for carcinogenicity testing: considerations and implications for risk assessment

Advances in genetic engineering have created opportunities for improved understanding of the molecular basis of carcinogenesis. Through selective introduction, activation, and inactivation of specific genes, investigators can produce mice of unique genotypes and phenotypes that afford insights into the events and mechanisms responsible for tumor formation. It has been suggested that such animals might be used for routine testing of chemicals to determine their carcinogenic potential because the animals may be mechanistically relevant for understanding and predicting the human response to exposure to the chemical being tested. Before transgenic and knockout mice can be used as an adjunct or alternative to the conventional 2-year rodent bioassay, information related to the animal line to be used, study design, and data analysis and interpretation must be carefully considered. Here, we identify and review such information relative to Tg.AC and rasH2 transgenic mice and p53+/- and XPA-/- knockout mice, all of which have been proposed for use in chemical carcinogenicity testing. In addition, the implications of findings of tumors in transgenic and knockout animals when exposed to chemicals is discussed in the context of human health risk assessment.     

Pulse oximetry during helicopter transport

The study objective was to determine if pulse oximetry readings obtained during helicopter transport were indicative of subsequent arterial blood-gas measured saturations. A prospective study design was chosen. Data were gathered on a convenience sample of patients 18 years and older not under cardiopulmonary resuscitation; 101 patients were used for the study. Pulse oximeter readings of oxygen saturation and heart rate were recorded along with simultaneous vital signs. Arterial saturation in blood gases drawn in the emergency department were added to the patient record. Improper functioning of the pulse oximeter was recorded on 10 (9.9%) of the patients. No correlation was found between the probe type and the documented problems (PHI = 0.009). The pulse oximeter saturation readings were not significantly different from arterial saturation in blood gases when compared by paired samples t-test (t = 0.880, p = 0.383). There was also no significant difference between the patient's heart rate sensed by the pulse oximeter and the simultaneous palpated pulse rate. Percent saturation readings by repeated measures were statistically different (p < 0.05) showing a minimal improvement in saturation over time. Based on this study's findings, the authors feel the pulse oximeter can be a valuable adjunct to patient care during helicopter transport.     

A phase I study of 5-fluorouracil, leucovorin and levamisole

 Purpose: The activity of 5-fluorouracil (5-FU) against colon cancer is enhanced by leucovorin and the combination of 5-FU and levamisole has activity in the adjuvant treatment of colonic malignancies. The combination of 5-FU with both leucovorin and levamisole may provide additional benefit in the treatment of colon cancer. Methods: A phase I study to assess qualitative and quantitative toxicities of this three-drug combination and to determine a dose for further phase II testing was undertaken. The role of levamisole as an immunomodulator was also assessed. Results: A group of 38 patients with incurable etastatic malignancies received 119 cycles of treatment at eight dose levels. 5-FU (375 mg/m² per day) and leucovorin (200 mg/m² per day) were administered intravenously (days 1–5). Levamisole was administered orally (days 1–3 and 15–17) at doses from 30 to 470 mg/m² per day. Patients received both 5FU/leucovorin and 5-FU/leucovorin/levamisole in random order for their initial two cycles. All subsequent treatments were with the three-drug combination. Toxicities included nausea, vomiting, stomatitis, thrombocytopenia and granulocytopenia. Diarrhea was the dose-limiting toxicity at 470 mg/m² per day levamisole. The addition of levamisole resulted in more toxicity than 5-FU and leucovorin alone. No clinical responses were seen with this regimen. The addition of levamisole resulted in more immunomodulation than 5-FU and leucovorin alone as evidenced by release of neopterin from monocytes. Conclusion: With this schedule and dose of 5-FU and leucovorin, the maximum tolerated dose of levamisole was 354 mg/m². However, given the lack of response and the absence of dose-dependent immunomodulation, this may not be the appropriate dose for further phase 11 studies. Received: 20 October 1995 / Accepted: 16 June 1996     

Late effects of hematopoietic cell transplantation among 10-year adult survivors compared with case-matched controls.

PURPOSE: To determine late effects of hematopoietic cell transplantation (HCT) on health problems and health-related quality of life for 10-year survivors. PATIENTS AND METHODS: Four hundred five adults consented to the study before HCT. Medical records and standardized self-report measures were maintained prospectively. After 10 years, 137 survivors and nontransplant controls, case-matched on age, sex, and race, completed self-report of medical problems, symptoms, and health-related quality of life. RESULTS: Survivors and controls had similar rates of hospitalization and most diseases, but survivors reported an average of 3.5 medical problems versus 1.7 for controls (P < .001). Survivors reported more musculoskeletal stiffness, cramps, weakness and joint swelling (P < .001), cataract surgery (P < .001), hepatitis C (P = .004), sexual problems for men (P = .01) and women (P < .001), restrictions in social function (P = .002), memory and attention concerns (P = .003), urinary frequency or leaking (P = .006), use of psychotropic medication (P = .009), and denial of life and health insurance (P < .001). Survivors and controls did not differ in self-reported rates of osteoporosis, hypothyroidism, employment, marital satisfaction, divorce, or psychological health. CONCLUSION: Although indistinguishable in many respects, survivors had more medical needs than controls. Health problems were not focused on specific diseases or limited to survivors with readily identifiable risk factors. Musculoskeletal problems require both screening and research into etiologies and effective treatments. Osteoporosis and hypothyroidism may be underdiagnosed. Survivors require screening for sexual problems, urinary frequency, mood and need for antidepressants or benzodiazepines.