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Biomedical subjects

B M Ryan

Publications and source records attributed to B M Ryan.

26 records · Page 2Linked to original sources
PubMed1998

Exposure to 60 Hz magnetic fields and risk of lymphoma in PIM transgenic and TSG-p53 (p53 knockout) mice.

The results of a number of epidemiology studies suggest that exposure to power frequency (50 and 60 Hz) magnetic fields may be a risk factor for hematopoietic neoplasia. To generate experimental data to test this hypothesis, the influence of magnetic field exposure on lymphoma induction was determined in two strains of mice that are genetically predisposed to the disease. PIM mice, which carry the pim-1 oncogene, are highly sensitive to lymphoma induction by N-ethyl-N-nitrosourea (ENU); ENU-treated PIM mice were studied as a 'high incidence' lymphoma model. TSG-p53 (p53 knockout) mice, in which the p53 tumor suppressor gene has been deleted from the germ line, develop lymphoma as an age-related change; hemizygous TSG-p53 mice were studied as a 'low incidence' lymphoma model. Beginning 1 day after a single i.p. injection of 25 mg ENU/kg body wt, groups of 30 PIM mice/sex were exposed for 18.5 h/day to pure, linearly polarized, transient-free 60 Hz magnetic fields at field strengths of 0 (sham control), 0.02, 2.0 or 10.0 Gauss (G). An additional group of 30 PIM mice/sex was exposed intermittently (1 h on, 1 h off) to 10.0 G fields. Groups of 30 TSG-p53 mice/sex were exposed continuously to magnetic field strengths of 0 (sham control) or 10.0 G; TSG-p53 mice received no ENU. Studies were terminated after 23 weeks of magnetic field exposure. Lymphoma incidence in male PIM mice exposed continuously to 10.0 G magnetic fields was significantly reduced from that seen in sex-matched sham controls; survival, lymphoma incidence and lymphoma latency in other groups of PIM mice did not differ from sham controls. Survival and lymphoma incidence in all groups of TSG-p53 mice was 7% or less, regardless of magnetic field exposure regimen. These data do not support the hypothesis that exposure to magnetic fields is a significant risk factor for lymphoid neoplasia in mice with a genetic predisposition to the disease.

Animals↗
PubMed1998

The development of hepatic granulomas following interferon-alpha2b therapy for chronic hepatitis C infection.

Hepatic granulomas have been detected in cases of chronic hepatitis C virus (CHCV) infection. Here we report upon three selected cases of CHCV infection who were treated with IFN alpha, in whom hepatic granulomas were absent on initial liver biopsies, but in whom granulomas developed following IFN alpha therapy. In one case, complete regression of these granulomas was noted 17 months following discontinuation of treatment, more strongly implicating IFN alpha in the aetiopathogenesis of such granulomas in this case. These findings suggest that IFN alpha may have a biological role in the pathogenesis of granulomatous liver disease in these patients. All three cases were poor/non-responders to IFN alpha, suggesting that the development of hepatic granulomas during IFN alpha therapy may be associated with a poor response to treatment.

Adult↗
PubMed1998

Alendronate-induced esophagitis: case report of a recently recognized form of severe esophagitis with esophageal stricture--radiographic features.

Alendronate sodium, an aminobiphosphonate used primarily to treat osteoporosis in postmenopausal women, is known to cause esophagitis. A 71-year-old woman experienced severe, acute esophagitis and severe stricture of the esophagus due to oral alendronate therapy. Unlike in previous cases, she had taken alendronate for 10 months before the onset of complications and the stricture proved resistant to dilation.

Administration, Oral↗
PubMed1996

Developmental toxicity study of 60 Hz (power frequency) magnetic fields in rats.

Considerable public concern has developed regarding possible adverse reproductive outcomes resulting from exposure to power frequency magnetic fields (MF). To identify possible effects of MF exposure on fetal development, timed-pregnant female Sprague-Dawley rats (55/ group) received continuous exposure to linearly polarized, transient-free 60 Hz MF at field strengths of 0 Gauss (G; sham control), 0.02 G, 2 G, or 10 G, or intermittent (1 hr on/1 hr off) exposure to 10 G fields. Dams received MF or sham exposures for 18.5 hr/day on gestation days 6 through 19. A positive control group of 15 dams received daily oral doses of 85 mg ethylenethiourea (ETU)/kg body weight on gestation days 11, 12, and 13; positive control dams received no MF exposure. Ambient and experimentally generated MF were monitored continuously throughout the study. Experimentally generated MF were within 2% of the target field strengths at all times, and ambient MF to which sham controls were exposed did not exceed 0.7 mG at any point in the study. No evidence of maternal toxicity was identified in any MF-exposed dam; mean maternal body weight and organ weights in groups exposed to MF did not differ from those in sham controls. Comparisons of fetal viability and body weight demonstrated no biologically significant differences between MF-exposed groups and sham controls. Similarly, a battery of gross external, visceral, skeletal, and cephalic examinations demonstrated no significant differences in the incidence of fetal malformations or anomalies in MF-exposed groups vs. sham controls. By contrast, 100% of the fetuses in the positive control group treated with ETU demonstrated malformations and reduced body weight. Exposure of pregnant Sprague-Dawley rats to 60 Hz at field strengths up to 10 G during gestation days 6-19 did not produce biologically significant effects in either dams or fetuses. These results do not support the hypothesis that exposure to pure, linearly polarized 60 Hz MF is a significant risk factor for the developing fetus.

Abnormalities, Drug-Induced↗
PubMedDate not supplied

Two-generation reproduction study and immunotoxicity screen in rats dosed with phenol via the drinking water.

This study evaluated the potential reproductive toxicity of phenol in a rat two-generation reproduction study, which included additional study endpoints, such as sperm count and motility, developmental landmarks, histological evaluation of suspect target organs (liver, kidneys, spleen, and thymus), weanling reproductive organ weights, and an immunotoxicity screening plaque assay. Phenol was administered to 30 Sprague-Dawley rats/sex/group in the drinking water at concentrations of 0, 200, 1000, or 5000 ppm. Parental (P1) animals were treated for 10 weeks prior to mating, during mating, gestation, lactation, and until sacrifice. The F1 generation (P1 offspring) was treated using a similar regimen, while the F2 generation was not treated. After mating, 10 P1 males/group were evaluated using standard clinical pathology parameters and an immunotoxicity screening plaque assay. Significant reductions in water and food consumption were observed in the 5000-ppm group in both generations; corollary reductions in body weight/body weight gain were also observed. Mating performance and fertility in both generations were similar to controls, and no adverse effects on vaginal cytology or male reproductive function were observed. Vaginal opening and preputial separation were delayed in the 5000-ppm group, and were considered to be secondary to the reduction in F1 body weight. Litter survival of both generations was reduced in the 5000-ppm group. Absolute uterus and prostate weights were decreased in the F1 generation at all dose levels; however, no underlying pathology was observed and there was no functional deficit in reproductive performance. Therefore, these findings were not considered to be adverse. No evidence of immunotoxicity was noted in the 5000-ppm group. The effects noted at the high concentration were presumed to be associated with flavor aversion to phenol in the drinking water. Based on a comprehensive examination of all parameters, the no-observable-adverse-effect level (NOAEL) for reproductive toxicity of phenol administered in drinking water to rats is 1000 ppm. The corresponding daily intake of phenol for an adult rat at the NOAEL of 1000 ppm is equivalent to about 70 mg/kg/day for males and 93 mg/kg/day for females.

Administration, Oral↗