The RBE for skin tumors and hair follicle damage in the rat following irradiation with alpha particles and electrons

Rat skin was irradiated with cyclotron-accelerated alpha particles with doses ranging from 210 rads to 6850 rads and monoenergetic electrons with doses ranging from 810 rads to 12,300 rads. The beams were modified so that the depth-dose curves were approximately identical with penetrations of about 1.0 mm. Tumors were counted every 4 weeks for 80 weeks, and at death or sacrifice the hair follicle damage was assessed by using "whole mounts" of separated epithelium. The RBE values determined from a comparison of the dose response curves were: acute skin injury, RBE = 3.0+/-1.0; hair follicle survival, RBE = 2.1 +/- 0.7; hair follicle damage, RBE = 2.6 = 0.4; tumor induction, RBE = 2.9+/- 0.5. Within the experimental error, these values were independent of the dose. For both types of radiation, the tumor incidence increased approximately as the square of time and at low doses approximately as the 4th power of dose. The histological characteristics of the tumors and the correlation between the incidence of tumors and damaged hair follicles were independent of the type of radiation. The results were consistent with the hypothesis that structural damage to the hair follicles is a factor in the tumor induction process.     

Changes in the DNA labelling index after beta irradiation of the mouse epidermis

This study looked at the changes in the interfollicular DNA labelling index (LI) with time after strontium-90/yttrium-90 beta irradiation of approximately 100 mm2 of mouse flank skin, after a dose of 100 Gy which produces transitory moist desquamation. Within 24 hr of such a dose the LI of the irradiated area was essentially zero (0.07 +/- 0.03%), whilst those of the side area and of the control area were 15.0 +/- 2.6% and 21.4 +/- 2.7%, respectively. The LI of the side and the control areas then fell within 3-5 days to approximately 4% and approximately 2% respectively, whilst that of the irradiated area rose rapidly to a peak value of 30.2 +/- 1.7% at 10 days post-irradiation. There was a 20% reduction in the diameter of the area with detectable radiation damage within 5 days, and this is primarily due to cell proliferation and migration from the unirradiated margins of the field. In contrast, between days 10 and 20 the major source of repopulation is probably derived from local migration and proliferation of surviving hair follicle basal cells within the irradiated field.     

Skin response to X-irradiation in the guinea-pig.

Skin reaction to X-irradiation has been studied in the albino guinea-pig; early response in limited-field irradiations of the flank is comparable to that commonly seen in rodents, swine and man, and is dose-dependent with a dynamic range from mild erythema to moist desquamation. The peak early skin reaction is seen between 14 and 21 days after irradiation, and declines before 30 days except at the highest doses used. Fractionation of the X-ray dose at 24 hours results in a 'sparing' of about 340 rad. Permanent partial epilation is detectable at doses in excess of 1400 rad, and complete epilation at 1 year occurs in 50 per cent of irradiated fields at 1740 rad. Twenty-four hour two-dose fractionation results in a 'sparing' of about 500 rad for epilation. Palpable dermal 'fibrosis' is detectable at 3 months after irradiation in fields given more than 2070 rad, and at 1 year after irradiation in fields given more than 1800 rad; 50 per cent of fields showed palpable 'fibrosis' at 1 year at 1930 rad. Unlike domestic swine and man, skin fields in the guinea-pig showed no dimensional contraction after X-ray doses which produced gross early skin damage.     

An unexpected effect of hyperthermia on the expression of X-ray damage in mouse skin

The interaction between hyperthermia and X irradiation in the expression of injury to skin was investigated in the tail of adult mice. The X-ray treatments when given alone resulted in skin reactions which ranged in severity from "no observable gross injury" to "moist desquamation over most of the tail," the peak reaction occurring at approximately 20 days. When hyperthermia was given alone, the maximal reaction observed was "foci of moist desquamation, accompanied by severe erythema and edema" which, in contrast to the radiation response, peaked 1 to 2 days after treatment. For the combined treatments, hyperthermia at a temperature between 43.0 and 44.5 degrees C for 30 min was given either 3, 6, 9, or 10 days after X irradiation. When the interval was 3 days, there appeared to be no interaction between the treatments. As the interval was lengthened, so that hyperthermia was given 6 or more days after irradiation, i.e., within 7 days of the time of appearance of gross radiation injury, the severity of the observed skin reaction was greater than the individual responses following either treatment given alone. Using a 9-day interval, it could be seen that both the thermal and radiation reactions were enhanced in a dose-dependent manner. The peak times for each reaction were not significantly altered by the additional treatment. The results are discussed with reference to possible modes of interaction between X irradiation and hyperthermia in an in vivo system.     

Metabolic effects of static magnetic fields on Streptococcus pyogenes

This study aimed to develop a simple experimental system utilising bacterial cells to investigate the dose responses resulting from exposures to static magnetic flux densities ranging from 0.05 to 0.5 T on viability, bacterial metabolism and levels of DNA damage in Streptococcus pyogenes. Exposure of S. pyogenes to a field of 0.3 T at 24 degrees C under anaerobic conditions resulted in a significant (P < 0.05) decrease in growth rate, with an increased mean generation time of 199 +/- 6 min compared to the control cells at 165 +/- 6 min (P < 0.05). Conversely, exposure to magnetic fields of 0.5 T significantly accelerated the growth rate at 24 degrees C compared to control cells, with a decreased mean generation time of 147 +/- 4 min (P < 0.05). The patterns of metabolite release from cells incubated in phosphate buffered saline (PBS) at 24 degrees C and exposed to different magnetic flux densities (0.05-0.5 T) were significantly (P < 0.05) altered, compared to non-exposed controls. Concentrations of metabolites, with the exception of aspartic acid (r = 0.44), were not linearly correlated with magnetic flux density, with all other r < 0.20. Instead, "window" effects were observed, with 0.25-0.3 T eliciting the maximal release of the majority of metabolites, suggesting that magnetic fields of these strengths had significant impacts on metabolic homeostasis in S. pyogenes. The exposure of cells to 0.3 T was also found to significantly reduce the yield of 8-hydroxyguanine in extracted DNA compared to controls, suggesting some possible anti-oxidant protection to S. pyogenes at this field strength.     

Triggering of cryoprotectant synthesis in the woolly bear caterpillar (Pyrrharctia isabella Lepidoptera: Arctiidae)

Isabella tiger moths (Pyrrharctia isabella) overwinter as caterpillars (i.e., woolly bears) that can survive freezing at moderate subzero temperatures. We observed an increase in hemolymph osmolality for field-collected woolly bears during October (325 +/- 47 to 445 +/- 27 mOsmol/liter) and tested the influence of temperature and moisture levels on cryoprotectant production. Laboratory acclimation was done at 5 degrees C in moist conditions and at 25 degrees C acclimation in both dry and moist conditions. Body water contents were diminished by dehydration at 25 degrees C for 4 days (57 +/- 4%). Caterpillars collected in early October did not alter their hemolymph osmolality during cold acclimation, but caterpillars increased by 45% (to 647 +/- 90 mOsmol/liter) after 4 days at 5 degrees C following their collection in late October. Hemolymph composition was markedly changed in caterpillars experiencing dehydration at 25 degrees C (1042 +/- 200 mOsmol/liter; 507 +/- 225 mmol glycerol/liter), whereas caterpillars showed no change in their hemolymph composition when kept moist at 25 degrees C. Our experiments reveal that both dehydration and cold acclimation rapidly induce cryoprotectant synthesis in P. isabella caterpillars. J. Exp. Zool. 286:367-371, 2000.     

Changes of hexose monophosphate pathway and methemoglobin reductase enzyme activity after radiation in guinea pigs

HMP pathway activity changes occurring after exposure to ionizing radiation (LD50 dose) have been investigated. The study was carried out on 18 experimental guinea pigs subjected to 5 successive exposures of 150 rads 3 or 4 days apart. The control animals were sham radiated but were otherwise treated identically as those of the experimental groups. Blood samples were taken by cardiac puncture before radiation and 30 min after each exposure of 150 rads. The red cells were re-suspended in their own plasma and HMP pathway activity was measured in the suspension. The pathway activity showed a consistent but minor reduction in the experimental group, which became statistically significant after the total dose of 750 rads (P less than 0.020). In a separate study the changes induced by ionizing radiation in the erythrocyte enzyme NADH-methemoglobin reductase were measured using the same experimental protocol. The enzyme activity in the red cells of the experimental group varied between 34.90 +/- 2.17 to 161.95 +/- 5.34 I.U./ml erythrocyte pack. Its activity declined toward the initial value after reaching the peak by the 12th day of ionizing radiation with 600 rads (P less than 0.001).     

Red marrow dose measurement in phantom for tele-irradiation of the nasopharynx by cobalt-60 unit

This investigation is to study red marrow dose measurement for the 60Co gamma-ray treatment of nasopharyngeal carcinoma with the aid of Rando phantom. The energy of scattered radiation in space and in tissue was investigated by means of half-value layers with thermoluminescent dosimeters. Other related factors such as field size, SSD, and orientation of primary beams were also investigated. In the non-metastases cases, the red marrow dose is 26 +/- 6 rads which is about 0.40% tumor dose excluding the marrow at the NPC site. For the metastases cases, the red marrow dose is still about 0.40% tumor dose. If the red marrow at the NPC site is included, the red marrow dose is about 14.5% tumor dose for both non-metastases and metastases cases.     

The method for studying of the "magnetic vacuum" effect on color memory in humans

The method for studying the effects of weak magnetic fields and "magnetic vacuum" on the psychophysiological state of a human organism is proposed. This method includes the system of the exposure of a human organism to uniform constant and alternating magnetic fields and the system of computerized psychological tests. The influence of the weakening of constant magnetic field on the psychophysiological state of human organisms was studied. The short-term color memory and reaction rates of 30 subjects have been examined in the local geomagnetic field and in a magnetic field which was reduced in 10 and more times. Statistically significant differences in the color memory test was found in the magnetic field 4 +/- 1 microT in comparison with the results in the geomagnetic field. In the magnetic field 0 +/- 1 microT, slight impairment of color memory was found. Preliminary results in the test of reaction rates showed the tendency to slowing down the reaction rates in the weakened magnetic fields.     

The RBE of 2.2-BeV protons for 30-day lethality in mice

BNL Swiss Albino mice were exposed (five in tandem) in a 2.5-cm I.D. Lucite tube to a parallel beam of 2.2-BeV protons. The LD5o was 1.81+/-0.03 X 10(10) p/cm(2), or 641 rads. The corresponding LD50 for 250-kVp x-rays was 557 rads, yielding an RBE of 0.87. No difference in time pattern of death was observed between the x-irradiated and proton-irradiated animals. It is concluded that, with the exposure geometry used in these experiments, ionization by primary and high-energy secondary protons was the major dose constituent. A comparison is made with other experiments on the lethal effects of protons in which different geometries were employed. There is evidence that, with exposure in material of larger diameter in which there is a larger contribution to dose from lateral scatter, high-LET components of the beam may play a more dominant role. It was also observed in these experiments that the presence of Pseudomonas aeruginosa may result in a lower LD50 and "early death," following either x-irradiation or proton radiation. This may have accounted for some of the "early deaths" following proton irradiation reported earlier.     

The Rejoining Time of Chromatid Breaks Induced by Gamma Radiation in Vicia faba Root Tips at 3 °C

The observation was made previously that the reduction in radiosensitivity in Vicia faba (as measured by postirradiation root growth) by prolonging the exposure time from about 10 minutes to 24 hours is much less marked at 3°C. than at 19°C. If chromosome damage is mainly responsible for the reduced root growth, this observation might be explained by a smaller drop in the "two-hit" aberration component, resulting from an increased time for which breaks are available for rejoining at 3°C. This hypothesis was tested by comparing chromatid aberration frequencies in root meristem cells produced by 105 rads of ⁶⁰Co γ rays, given at dose rates of 19.4 and 0.073 rads per minute. Beans were maintained in aerated water at 2°C. prior to and during irradiation, and at this temperature the rate of development of cells was such that the two different exposure times both occupied a period during which the cell sensitivity was approximately constant. Immediately subsequent to irradiation, the roots were returned to 19°C. and examined cytologically. All chromatid aberrations were less frequent after low dose rate treatment, but only the chromatid interchange reduction was significant. The average time for which breaks are available for reunion, calculated from Lea's G function, was found to be 12 hours (95 per cent C.L. 6 to 24 hours).     

An analysis of the distribution and dose response of chromosome aberrations in human lymphocytes after in vitro exposure to137Cesium gamma radiation

The chromosome aberration yield for human lymphocytes exposed in vitro to various doses of 137Cesium has been studied. Dicentric, total acentric, and excess acentric data were seen to follow a Possion distribution. Calculated total hits demonstrated over-dispersion which could possibly be accounted for by a greater occurrence of single-hit phenomena being repaired than two-hit exchange processes. The resulting distribution generally contained an under-representation of cells with odd numbers of hits and an over-representation of zero- and even-hit classes as compared with Poisson predicted values. The relationship between dicentric yield and dose received in rads was fitted to the linear-quadratic formula Y = alpha D + beta D2 for dicentrics, yielding values of (20.1 +/- 3.8) X 10(-4) (aberrations/cell)/rad and (1.89 +/- 0.75) X 10(-6) (aberrations/cell)/rad2 for alpha and beta respectively. A plot of percent 'normal' cells versus the dose in rads resembled cell survival curves and was fitted to the relation P(D) = 100 e-Y where Y = alpha D + beta D2 with alpha = (23 +/- 11) X 10(-4) rad-1 and beta = (8.3 +/- 2.5) X 10(-6) rad-2. A possible use of scoring 'normal' cells for purposes of biological dosimetry is presented.     

A comparison of the radiation response of the epidermis in two strains of pig

The response of the epidermis was compared in two strains of pig, the English Large White and the G?ttinger Miniature, after irradiation with 90Sr beta rays. The effects of two types of anesthesia were also tested in pigs of each strain, a volatile gas mixture of approximately 70% oxygen, approximately 30% nitrous oxide, and 2% halothane, and an intravenously administered narcotic azaperon/etimodat with the animals breathing air. Strain- and anesthetic-related changes were compared on the basis of dose-effect curves for the incidence of moist desquamation from which ED50 values (+/- SE) were determined, i.e., the dose required to produce this effect in 50% of the fields irradiated. For English Large White pigs anesthetized with the volatile gas mixture, an ED50 of 27.32 +/- 0.52 Gy was obtained for moist desquamation. Irradiation with the azaperon/etomidat anesthesia in this strain of pig produced a significantly higher ED50 of 33.36 +/- 0.76 Gy (P less than 0.001). This appeared to be related to the fact that the animals were breathing air, i.e., a lower oxygen concentration (approximately 21%), at the time of irradiation. For the G?ttinger Miniature pig the ED50 values for moist desquamation were 38.93 +/- 3.12 Gy and 43.36 +/- 1.34 Gy while using the gaseous anesthetic mixture and the azaperon/etomidat anesthesia with the animals breathing air, respectively. These ED50 values are 10-11 Gy higher than those obtained for the English Large White pig under identical conditions of anesthesia, which resulted in a strain difference ratio of approximately 1.35. Radiation under the volatile gas mixture anesthesia resulted in a uniform irradiation response over the skin of the flank in both strains of pig. Radiation under azaperon/etomidat anesthesia resulted in a nonuniform skin response over the flank. The ED50 for moist desquamation was significantly higher in dorsal sites on the flank compared with the ventral area of English Large White pigs; a similar trend was seen in G?ttinger Miniature pigs. This difference in the radiosensitivity over the flank skin while the animals are under azaperon/etomidat anesthesia at the time of irradiation was associated with the animals breathing air and is in agreement with findings published previously for animals under halothane anesthesia and breathing air.     

Effect of ionizing radiation on total protein-bound neutral hexoses in the plasma of mice

Total protein-bound carbohydrates (PBC), as neutral hexoses, were quantified in the plasma of C3H mice as a function of time relative to whole-body exposure to either monoenergetic 14-MeV neutrons or mixed gamma-neutron radiations delivered at a rate of approximately 20 rads/ min. The reported doses, 365 to 530 rads, were those which yielded survivors under the stress of daily bleeding. A striking difference was observed between those radiosensitive animals which died after exposure and the more resistant individuals which, although exposed to identical doses, survived the observation period. In the former population, the PBC concentration rose to high values and remained elevated until the death of the animal. By contrast, the survivors showed little change in PBC, deviating only slightly from their preirradiation base-line values. The mean preirradiation PBC concentration in the mice which survived 30 days, while statistically significant (p < 0.01) only at the lowest reported dose, was consistently lower than that of those which died during the same period. The magnitude of the difference was inversely related to the radiation dose. The refinement of these data to provide an index to radiosensitivity prior to and prognosis after irradiation in otherwise healthy individuals is proposed.     

Botryllus schlosseri (Tunicata) whole colony irradiation: do senescent zooid resorption and immunological resorption involve similar recognition events?

The colonial tunicate Botryllus schlosseri undergoes cyclic blastogenesis where feeding zooids are senescened and resorbed and a new generation of zooids takes over the colony. When non-identical colonies come into direct contact, they either reject each other or fuse. Fusion is usually followed by the resorption of one of the partners in the chimera (immunological resorption). The striking morphological similarities between the two resorption phenomena suggest that both may involve tissue destruction following self-nonself recognition events. Here we attempt to modify these two events by whole colony gamma irradiation assays. Three sets of experiments were performed: 1) different doses of whole colony irradiation for determination of irradiation effects (110 colonies, up to 8,000 rads); 2) pairs of irradiated-nonirradiated isografts of clonal replicates for the potential of reconstruction of the irradiated partners (23 pairs); 3) chimeras of irradiated-nonirradiated partners for analysis of resorption hierarchy. Mortality increased with the irradiation dose. All colonies exposed to more than 5,000 rads died within 19 days, while no colony died below 2,000 rads. The average mortality periods, in days, for doses of 6,000-8,000, 5,000, and 2,500-4,000 rads were 14.4 +/- 3.1 (n = 24), 19.8 +/- 6.0 (n = 15), and 19.6 + 5.1 (n = 22), respectively. Younger colonies (3-6 months old) may survive radiation better than older ones (more than 13 months). Many morphological alterations were recorded in irradiated colonies: ampullar contraction and/or dilation, accumulation of pigment cells within ampullae, abnormal bleeding from blood vessels, sluggish blood circulation, necrotic zones, reduction in bud number, and irregularities in zooid and system structures. With doses of 3,000-4,000 rads and above, irradiation arrested the formation of new buds and interrupted normal takeover, turning the colony into a chaotic bulk of vessels, buds, and zooid segments. Death supervened after a period of up to 1 month of poor condition, which was also characterized by loss of organization in systems. In isografts of irradiated-nonirradiated parts, the normal subclone resorbed all zooids and buds of the irradiated one within less than 1 week, even if it was up to 13 times smaller, without showing any sign of harmful effects. Thus, the irradiated subclone is not reconstituted by sharing blood circulation with a syngeneic part. Under 2,000 rads some of the irradiated zooids within this type of union started to regenerate, and at 1,000 rads no resorption was recorded, even though the number of zooids decreased in the irradiated part.(ABSTRACT TRUNCATED AT 400 WORDS)     

Study of the mechanism of Corynebacterium parvum antitumour activity: Protective effect in mice submitted to sublethal doses of irradiation

Summary The antitumour activity of C. parvum against two different tumours, a lymphosarcoma grafted in XVII mice and a mammary carcinoma grafted in C₃H mice, was a radiosensitive phenomenon. A dose of X-rays as low as 100 rads was sufficient to abrogate the C. parvum-induced protection. The duration of this inhibition increased with augmentation of the X-ray dose. The stimulation of macrophage-phagocytic activity induced by C. parvum was not inhibited by a dose of 500 rads. A chronological parallelism has been demonstrated in the recovery of the C. parvum antitumour effect and the restoration of antibody responsiveness after the suppression of these two activities by 500 rads of X-rays in the case of the C₃H mice grafted with mammary carcinoma cells. No such concomitant recovery has been observed in XVII mice. In these mice, the recovery of C. parvum antitumour activity took place before the restoration of antibody responsiveness.     

Nuclear scintigraphic assessment of radiation-induced intestinal dysfunction

Radiation-induced damage to the intestine can be measured by abnormalities in the absorption of various nutrients. Changes in intestinal absorption occur after irradiation because of loss of the intestinal absorptive surface and a consequent decrease in active transport. In our study, the jejunal absorption of (99m)Tc-pertechnetate, an actively transported gamma-ray emitter, was assessed in C3H/Kam mice given total-body irradiation with doses of 4, 6, 8 and 12.5 Gy and correlated with morphological changes in the intestinal epithelium. The absorption of (99m)Tc-pertechnetate from the intestinal lumen into the circulation was studied with a dynamic gamma-ray-scintigraphy assay combined with a multichannel analyzer to record the radiometry data automatically in a time-dependent regimen. The resulting radioactivity-time curves obtained for irradiated animals were compared to those for control animals. A dose-dependent decrease in absorptive function was observed 3.5 days after irradiation. The mean absorption rate was reduced to 78.8 +/- 9.3% of control levels in response to 4 Gy total-body irradiation (mean +/- SEM tracer absorption lifetime was 237 +/- 23 s compared to 187 +/- 12 s in nonirradiated controls) and to 28.3 +/- 3.7% in response to 12.5 Gy (660 +/- 76 s). The decrease in absorption of (99m)Tc-pertechnetate at 3.5 days after irradiation correlated strongly (P < 0.001) with TBI dose, with the number of cells per villus, and with the percentage of cells in the crypt compartment that were apoptotic or mitotic. A jejunal microcolony assay showed no loss of crypts and hence no measured dose-response effects after 4, 6 or 8 Gy TBI. These results show that dynamic enteroscintigraphy with sodium (99m)Tc-pertechnetate is a sensitive functional assay for rapid evaluation of radiation-induced intestinal damage in the clinically relevant dose range and has a cellular basis.     

Nonstochastic effects of different energy beta emitters on pig skin

Circular areas of pig skin from 1- to 40-mm diameter were irradiated with beta emitters of high, medium, and low energies, 90Sr, 170Tm, and 147Pm, respectively. The study provides information for radiological protection problems of localized skin exposures. During the first 16 weeks after irradiation 90Sr produced a first reaction due to epithelial cell death followed by a second reaction attributable to damage to the dermal blood vessels. 170Tm and 147Pm produced the epithelial reaction only. The epithelial dose response varied as a function of beta energy. The doses required to produce moist desquamation in 50% of 15- to 22.5-mm fields (ED50) were 30-45 Gy from 90Sr, approximately 80 Gy from 170Tm, and approximately 500 Gy from 147Pm. A model involving different methods of epithelial repopulation is proposed to explain this finding. An area effect was observed in the epithelial response to 90Sr irradiation. The ED50 for moist desquamation ranged from approximately 25 Gy for a 40-mm source to approximately 450 Gy for a 1-mm source. The 5-, 9-, and 19-mm 170Tm sources all produced an ED50 of approximately 80 Gy, while the value for the 2-mm source was approximately 250 Gy. It is also suggested that the area effects could be explained by different modes of epithelial repopulation after irradiation. After high energy beta irradiation repopulation would be mainly from the field periphery, while after lower energy irradiation repopulation from hair follicle epithelium would predominate.     

Variations in pO2 and pH response to hyperthermia: dependence on transplant site and duration of treatment.

It has been clearly established that changes in intratumor pO2 and pH occur following hyperthermia, and it has been hypothesized that these changes may, in some way, be related to the ultimate response (i.e., cure) of the lesion. The purpose of this study was twofold: first, to examine the changes in intratumor pH during the course of a hyperthermia treatment at biologically related end point "doses"; second, to examine the response of pO2 after treatment in a different lesion transplant site. During hyperthermia treatment of the tumor transplanted in the leg, intratumor pH was found to drop from a control value of 6.74 +/- 0.17 to 6.47 +/- 0.13 within 15 min following the start of treatment. The values then remained relatively constant throughout the remainder of the treatment (either 1 or 2 h at 43.5 degrees C). Following the subcurative (10% tumor cures at 30 days; 60 min at 43.5 degrees C) treatment the pH began to rise immediately, while after the higher dose (60% tumor cures at 30 days; 120 min at 43.5 degrees C) a slight rise in pH was followed by a continuous drop in pH for up to 4 h, as we have reported previously. Oxygen response in the two transplant sites (leg and flank) was found to be remarkably different even though the tumor cure rate was identical for a given hyperthermia "dose" in terms of time and temperature. In the leg, only very low levels of oxygen can be measured in the tumor 24 h after treatment with either "dose" studied (all measured pO2 values less than or equal to 5 mm Hg). In the flank, the tumor response is dependent on hyperthermia "dose." Only 28% of measured oxygen values are less than or equal to 5 mm Hg 24 h following a subcurative "dose," while 4 h following the higher "dose" there is a nonsignificant trend toward hypoxia (approximately 65% of values less than or equal to 5 mm Hg) with a subsequent shift toward reoxygenation. These latter observations are contrary to results reported previously and tend to contradict some current theories regarding the physiological mechanisms associated with hyperthermia treatment.     

The effects of x-radiation on Taenia pisiformis.

Following the exposure of eggs of T. pisiformis to X-radiation at doses of 10,000, 20,000 and 30,000 rads, hatching and activation in vitro were unaffected. Growth of larvae both in vitro and in vivo was reduced and many irradiated larvae were overcome by the host inflammatory reaction during intra-hepatic development. A negative correlation was established between the log₁₀ number of cysticerci in the abdominal cavities of rabbits 42 days after infection and the radiation dose. Significant abnormalities were induced in the morphology of rostellar hooks of cysticerci following irradiation of eggs although adult cestodes which developed from cysticerci derived from irradiated eggs were normal. Cysticerci exposed to 5000 and 10,000 rads of X-radiation developed to adult worms when fed to dogs but abnormalities were found, principally in the testes, ovaries and vitellaria; segmentation and the genital ducts were affected to a lesser extent.