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D Grahn

Publications and source records attributed to D Grahn.

At least 19 recordsLinked to original sources
PubMed1992

The comparative tumorigenic effects of fission neutrons and cobalt-60 gamma rays in the B6CF1 mouse.

In the period from 1971 to 1986, both sexes of the B6CF1 (C57BL/6 x BALB/c) mouse were exposed at 110 +/- 7 days of age to single, 24 once-weekly or 60 once-weekly doses of fission neutrons or 60Co gamma rays. A small group of males was also exposed to gamma rays for 22 h/day, 5 days/week, for either 23 or 59 weeks, the elapsed times for the 24 and 60 once-weekly series. All mice were followed for their natural lifetimes. A gross pathology report is available on 32,000 animals, and a histopathology record is available on about 19,000. About 85% died with or from one or more neoplastic diseases. The principal tumors observed at death were of lymphoreticular (45-60%), vascular (20%), or pulmonary (35-50%) origin. From 4 to 10% died with fibrosarcomas, hepatocellular tumors, ovarian tumors, and tumors of the Harderian, adrenal, and pituitary glands. Dose-response equations (linear and linear-quadratic) were fitted to the data for deaths from and occurrences of eight different individual or groups of tumors. Equations were constrained through the control intercepts and fitted separately for the two sexes, the two radiation qualities, and all exposure patterns for the two intervals of 600-799 days and 800-999 days from first exposure. RBE values were derived from the ratios of linear coefficients of dose-response curves. RBE values increased as dose was protracted, largely due to the reduced effectiveness of protracted gamma irradiation; however, about 28% of the increase can be attributed to the increase in neutron-induced injury caused by dose protraction. Highest RBE values were seen for tumors of epithelial tissue origin and the lowest for tumors of connective tissue origin. The range for significant values was from about 2 to over 50. Nonneoplastic diseases accounted for about 5% of all deaths, and 10% were classified as from unknown causes. Neither category responded to differences in radiation quality or exposure patterns.

Age Factors↗
PubMed1991

Protection against late effects of radiation by S-2-(3-aminopropylamino)-ethylphosphorothioic acid.

We have demonstrated that S-2-(3-aminopropylamino)ethylphosphorothioic acid (WR2721) administered to mice 30 min prior to a relatively low dose of ionizing radiation is effective in protecting against radiation-induced carcinogenesis and subsequent life shortening. Female C57BL/6JANL x BALB/cJANL F1 mice, 200 per group, were exposed to gamma radiation at a dose of 206 cGy. Additional groups of 200 animals were sham treated, given injections of 400 mg/kg of WR2721, or administered WR2721 and the irradiated with 60Co photons at doses of 206 cGy or 417 cGy. Mice were treated at 110 days of age. They were housed five to a cage and were checked daily throughout life. All deceased animals were necropsied, and tissues were removed and fixed for histopathological analysis. Over 90% of the animal deaths were due to tumor involvement. WR2721 afforded significant protection (P = 0.0016) against radiation-induced malignancies (i.e., a total of 164 tumor codes were used) following a dose of 206 cGy. Protection against lymphoreticular tumors in particular was significant (P = 0.0165). Subsequent survival time in WR2721-protected animals (compared with matched irradiated controls) was extended by 65 days. Mice irradiated with 417 cGy following administration of WR2721 exhibited a response similar to those irradiated without the protector at a dose of 206 cGy (P = 0.26). Cumulative survival curves for unirradiated mice were unaffected by a single dose of WR2721. These data indicate a potential novel benefit for radioprotectors in cancer therapy. WR2721 and similar aminothiols may be effective adjuvants for reducing the risk of therapy-induced secondary cancers in patients who have an excellent prognosis for cure and long-term survival.

Amifostine↗
PubMed1991

Issues about neutron effects: the JANUS program.

The impact of the biological end point selected as a synoptic measurement of mortality for the detection of protraction effects and the estimation of RBE values was investigated. Life shortening was chosen as an end point because it summarizes, in a single index, the cumulative effect of all injuries experienced by an organism. Cumulative mortality at a single time point and the hazard function (age-specific failure rate) were chosen to incorporate progressively more information, respectively, about the distribution of mortality through time. Data for both sexes of the B6CF1 mouse exposed to fission neutrons from the JANUS biomedical research reactor and 60Co gamma rays were analyzed. Three basic patterns of exposure were compared: single exposures, 24 equal once-weekly exposures, and 60 equal once-weekly exposures. The interpretation of results was influenced by the biological end point used as the synoptic measurement. An augmented response with protraction of the neutron exposure depended on the accumulated dose using the life-shortening response while this effect was nonexistent when cumulative mortality or the hazard function was used. A reduced effectiveness of protracted gamma-ray exposures was apparent for all end points. The hazard function analyses suggest that the time domain must be considered in the detection of protraction effects for either radiation quality and the subsequent estimation of RBE values.

Animals↗
PubMed1989

Life shortening in mice exposed to fission neutrons and gamma rays. VIII. Exposures to continuous gamma radiation.

Data are presented on the mean aftersurvival of male B6CF1 mice exposed for 22 h per day, 5 days per week, to 60Co gamma radiation at dose rates of 1.36 to 12.64 x 10(-3) cGy/min for 23 weeks or 1.36 to 6.32 x 10(-3) cGy/min for 59 weeks. For deaths from all causes, linear dose-response curves were obtained with slopes (days of life lost/cGy) of 0.158 +/- 0.016 and 0.077 +/- 0.002 for 23- and 59-week exposures, respectively. These values were not significantly altered when the analysis was restricted to those mice dying with tumors (92% of the total) or to those presumably dying from tumors (82% of the total). Analysis of mortality rates showed that about 90% of the radiation-specific excess mortality was tumor related. The 59-week exposure series induced only a small increase in the number of days of life lost/cGy/weekly fraction over that induced by 23 weeks of irradiation, 4.53 +/- 0.15 compared to 3.64 +/- 0.36 days lost/cGy/weekly fraction. This lower than expected value for 59 weeks of exposure may signal the approach to the final linear, additive, injury term postulated from earlier studies at this laboratory with low-dose-rate, daily, duration-of-life 60Co gamma irradiation.

Animals↗
PubMed1989

Dose-response modeling of life shortening in a retrospective analysis of the combined data from the JANUS program at Argonne National Laboratory.

Life shortening was investigated in both sexes of the B6CF1 (C57BL/6 x BALB/c) mouse exposed to fission neutrons and 60Co gamma rays. Three basic exposure patterns for both neutrons and gamma rays were compared: single exposures, 24 equal once-weekly exposures, and 60 equal once-weekly exposures. Ten different dose-response models were fitted to the data for animals exposed to neutrons. The response variable used for all dose-response modeling was mean after-survival. A simple linear model adequately described the response to neutrons for females and males at doses less than or equal to 80 cGy. At higher neutron dose levels a linear-quadratic equation was required to describe the life-shortening response. An effect of exposure pattern was observed prior to the detection of curvature in the dose response for neutrons and emerged as a potentially significant factor at neutron doses in the range of 40-60 cGy. Augmentation of neutron injury with dose protraction was observed in both sexes and began at doses as low as 60 cGy. The life-shortening response for all animals exposed to gamma rays (22-1918 cGy) was linear and inversely dependent upon the protraction period (1 day, 24 weeks, 60 weeks). Depending on the exposure pattern used for the gamma-ray baseline, relative biological effectiveness (RBE) values ranged from 6 to 43. Augmentation, because it occurred only at higher levels of neutron exposure, had no influence on the estimation of RBEm.

Animals↗
PubMed1988

Genetic injury in hybrid male mice exposed to low doses of 60Co gamma-rays or fission neutrons. III. Frequencies of abnormal sperm and reciprocal translocations measured during and following long-term weekly exposures.

Male B6CF1 mice were exposed to either fission neutrons or 60Co gamma-rays at once-weekly doses approaching occupational levels for periods up to 60 weeks. Both during and after the irradiation sequence, the mice were screened to determine the incidence of abnormal epididymal sperm and of reciprocal chromosome translocations in metaphase spermatocytes. Abnormal sperm frequencies equilibrated with dose/week by 10 weeks and also showed an additive nonlinear seasonal increment. The relative biological effectiveness (RBE) for these damages is 12 +/- 1. After exposures ended, sperm frequencies in gamma-irradiated mice quickly returned to near-normal levels. Neutron-irradiated males showed a significantly elevated level of abnormalities for approximately 30 weeks--a paradoxical finding--as no clear evidence of cumulative injury was seen during exposure. When assayed at 10 and 25 weeks of exposure but not later, translocation frequencies demonstrated an increment, significant in the neutron series, attributed to irradiated spermatocytes. Dose-response analysis with cumulative dose up to the 60-week maximum gave an RBE of 45 +/- 10. Post exposure, the incidence of translocations subsided slightly, but the RBE remained above 30.

Animals↗
PubMed1988

Heritable protein variants induced by exposure to ethylnitrosourea: heritability, subcellular location, and tissue distribution.

The heritability, subcellular location, and tissue distribution of liver protein alterations found in the two-dimensional electrophoresis patterns of 4 offspring from male mice treated with N-ethyl-N-nitrosourea (ENU) were studied. Mice homozygous for each of the 4 ENU-induced protein variants were found to be viable and fertile, although the number of homozygous offspring from crosses between heterozygous carriers of one variant (ENU 2) was less than that expected for a nondetrimental trait. Two of the proteins altered by ENU-induced mutations were associated with the crude mitochondrial fraction, another was found predominantly in the microsomal fraction, and the fourth was associated with the mitochondrial, microsomal, and cytosol fractions. All of the ENU-induced mutations affected proteins that were not liver-specific; i.e., the proteins were found in other tissues in addition to the liver.

Animals↗
PubMed1988

Implications of new technologies and shifting priorities on the understanding of genetic injury.

Some areas of radiation genetics still contain gaps of knowledge, as these studies lost priority when the emphasis in experimental mutagenesis shifted toward the effect of chemical mutagens. This shifted emphasis, however, was accompanied by the development of a better understanding of genetic injury at the molecular level. At the opposite end of the spectrum, more attention was paid to estimates of the direct health costs of the genetic burden in humans and the capacity to make prenatal diagnoses, and to consider reasonable clinical and biochemical intervention. Although, as yet, there are no completely reliable direct methods to estimate the radiation-induced mutation rate in humans, we have come to rely upon data from experimental animals to predict event frequency and extrapolate from these data to predict human health consequences. What will the future offer? Certainly, we should develop a better understanding of molecular genetic damage and, possibly, a better extrapolation model for predicting mutation rate, but many aspects of expected health consequences may remain elusive. We still may have to rely upon (1) an inadequate human population genetic baseline, (2) sometimes arguable perceptions of man-mouse extrapolation models, (3) changing perceptions of gene-environment interactions, and (4) changing levels of short-term selection pressure against detrimental mutations.

Chromosomes↗
PubMed1988

Life shortening in mice exposed to fission neutrons and gamma rays. VII. Effects of 60 once-weekly exposures.

A total of 6316 B6CF1 mice were exposed to 60 equal once-weekly doses of 0.85-MeV fission neutrons (0.033 to 0.67 cGy per weekly fraction) or 60Co gamma rays (1.67 to 10 cGy per weekly fraction) and were observed until they died. The mean aftersurvival times showed that the dose-response curves for both neutron and gamma-ray exposures were indistinguishable from linear over all doses except the highest neutron dose. The relative biological effectiveness (RBE) for neutrons, calculated as the ratio of the initial slopes of the dose-response curves, was about 20 for both males and females. Essentially the same value was obtained by a number of other analyses of the data. Virtually all of the radiation-specific excess mortality could be attributed to tumors; after decrementation of the population for nontumor deaths, the value of the RBE was not significantly changed.

Animals↗
PubMed1987

Fever and aging: central nervous system prostaglandin E2 in response to endotoxin.

The pathophysiology of the blunted febrile response often seen in elderly individuals with infection is not well understood. In this study, we attempted to determine the impact of aging on prostaglandin E2 release from the brain in response to endotoxin (LPS) stimulation. Eight young (4-6 month) and eight old (24-28 month) BALB/c mice were studied. Right and left half brains from old and young mice were either stimulated with LPS or control solution. Each mouse provided a stimulated and a control value. Results were reported for each mouse as the difference (stimulated minus control) in picograms of PGE2 released per milligram tissue and as the percent of baseline (control). Significant stimulation was demonstrated in the young mice, mean difference being +3.7 pg/mg, SD = 2.2 (Student's paired t, p less than 0.01) or +44% of control. In the old mice the mean difference was +2.9 pg/ml, SD = 6.7, or +22%, which was not statistically significant. Moreover, in three of eight old mice, there was a lack of PGE2 stimulation. The authors conclude that in a select group of old mice ("nonresponders"), the failure to mount a febrile response to an infection may be related to diminished release of PGE2 from the brain.

Aging↗
PubMed1986

Genetic injury in hybrid male mice exposed to low doses of 60Co gamma-rays or fission neutrons. II. Dominant lethal mutation response to long-term weekly exposures.

Male B6CF1 mice were exposed to once-weekly doses of either fission neutrons or 60Co gamma-rays for periods up to one year and mated periodically to screen for the induction of dominant lethal mutations. Two independent experiments were performed, each involving a control and three dose levels of both neutrons and gamma-rays. Neutron doses were between 0.125 and 2.67 rad/week and gamma-ray levels were between 5 and 32 rad/week. Data on both pre- and post-implantation fetal deaths were obtained. Analyses that were intended to identify the potential contribution from age- or time-dependent factors, which could include changes in radiosensitivity and in spontaneous rates plus any cumulative damage to the stem cell population did not reveal a consistent significant contribution to the mutation rate/rad/week. Direct comparisons of these data with data from males exposed to single doses confirm that weekly neutron irradiation is significantly more effective than single doses for the induction of postimplant fetal losses, whereas single doses of gamma-rays are more effective than the same dose divided into weekly fractions. Neutron-induced augmentation appears limited in these data to lethal mutations induced in meiotic and postmeiotic cell stages. The relative biological effectiveness (RBE) of neutrons rises from 5 +/- 1 to 12 +/- 1 for single vs. weekly doses. Rates of preimplant loss, although significant, are not a sensitive measure of genetic injury at the low doses used here. They are extremely sensitive to litter size and best estimated in litters of seven or more implants along with appropriate statistical control of concurrent variation in the number of corpora lutea.

Animals↗
PubMed1986

Life shortening in mice exposed to fission neutrons and gamma rays. VI. Studies with the white-footed mouse, Peromyscus leucopus.

Some of the studies on late effects of neutron and gamma radiation previously carried out with the C57BL6 X BALB/c F1 hybrids of Mus musculus have been repeated with the white-footed mouse, Peromyscus leucopus, a cricetid rodent of a different subfamily, with differing physiological characteristics and a different spectrum of pathologies. Among the more important findings were the following: For both species, the life shortening per rad at low doses of either radiation was the same percentage of the life span. The limiting values of the relative biological effectiveness for life shortening from all causes of death were about the same for the two species, ranging from 8 to 16, depending on the method of calculation. Fractionated neutron exposures failed to produce significant life shortening in Peromyscus over that observed at single doses. Tumor-related deaths accounted for at least 70 to 75% of the radiation-specific excess mortality in Peromyscus.

Animals↗
PubMed1985

Central nervous regulation of body temperature in vertebrates: comparative aspects.

Thermal fluctuations affect, and are responded to by, nearly all forms of life. The basic vertebrate template has guided and shaped the ways that animals in this subphylum cope with thermal challenges. This has led to a situation where there are major similarities in the neuronal mechanisms which sense temperature and control the responses to temperature change in all vertebrates, from fish to mammals. The PO/AH is the most important single integration site for temperature regulation and (except for birds) is also important in the sensing of core temperature. Other portions of the brainstem as well as the spinal cord are also involved in thermal control and can sense, integrate, and produce appropriate efferent signals to varying degrees. Peripheral thermal input to the hypothalamic areas is via the brainstem reticular areas. A number of studies has related the thermal response characteristics of CNS single neurons to the thermoregulatory output of intact animals. These studies have been performed on neurons in whole animal, brain slice, and tissue culture preparation. These neurophysiological studies of central neurons are informative, but are sometimes difficult to interpret because of the chronic lack of definite criteria to differentiate generalized thermal sensitivity from thermal sensitivity utilized for regulating body temperature. Recent neuroanatomical work has illustrated that many areas previously implicated in the thermoregulatory network (such as the septum, various hypothalamic nuclei, the midbrain reticular formation, and the midbrain raphé nuclei) receive direct projections from PO/AH neurons. When compared, the neurophysiological and neuroanatomical characteristics of the preoptic nucleus and anterior hypothalamic area are similar, but not identical. The broad differences in the responses that vertebrates utilize to deal with thermal change is largely determined by the respiratory medium (water or air) and whether metabolic energy (endothermy) or ambient temperature (ectothermy) is of primary importance in the determination of internal temperature. A number of physiological systems are perturbed in water breathing ectotherms when the ambient temperature is altered. In these vertebrates long-term acclimation is very important and has a major effect on temperature selection. Air breathing ectotherms are less adversely affected by temperature change; long-term thermal acclimation is less important and has little effect upon temperature selection; large thermal changes are often initiated by these animals. Endotherms rely on insulation and a high, variable metabolic rate to maintain a constant internal temperature.(ABSTRACT TRUNCATED AT 400 WORDS)

Amphibians↗
PubMed1985

Fever and aging.

The pathogenesis and clinical relevance of fever is reviewed. The interrelationship between fever and other biologic responses to infection is summarized. A blunted or absent fever response to infections observed in some elderly patients may be due to defects in thermoregulation. These abnormalities in thermoregulation may include impairment of both behavioral and physiologic responses.

Aged↗
PubMed1985

Life shortening in mice exposed to fission neutrons and gamma rays. IV. Further studies with fractionated neutron exposures.

When mice were exposed to a total dose of 240 rad of fission neutrons divided into two, four, or six fractions given at 1-week intervals, more life shortening was observed than was seen after a single exposure. Maximum life shortening was observed with four fractions, although the value for six fractions was not significantly lower. Much of the augmentation effect was attributable to an increase in early deaths during the first 200-300 days after exposure, although differences persisted throughout the lifetime of the animals. The changes in life shortening were associated with changes in the distribution of causes of death; however, decrementation of the populations for any given specific cause of death failed to eliminate completely the differences in mean aftersurvival time.

Animals↗
PubMed1985

Validity of urinary catheter specimen for diagnosis of urinary tract infection in the elderly.

Twenty elderly nursing home patients with long-term indwelling bladder catheters were studied to evaluate the validity of the microbiology of urine samples obtained from catheters that had not been changed for at least 30 days. Paired urine samples from "old" catheters and newly inserted catheters were compared for quantitative and qualitative microbiology. Urine microbiology for old catheters was highly sensitive but had poor specificity.

Aged↗
PubMed1985

Life shortening in mice exposed to fission neutrons and gamma rays. V. Further studies with single low doses.

Data are presented on the mean after survival of female B6CF1 mice exposed to single doses of neutrons (1 to 40 rad) or gamma rays (22.5, 45, and 90 rad). For gamma-ray exposures and for neutron exposures up to 10 rad, the dose-response curves are indistinguishable from linear; higher neutron doses produce significant departures and linearity. Consequently, in these data, an upper limit of the relative biological effectiveness (RBE) exists for life shortening from all causes of death after single neutron exposures; this value is 15.0 +/- 5.1. The RBE depends on the cause of death, ranging from 2 to 5 for lymphoreticular tumors to 23-24 for lung tumors.

Animals↗