[Radiation induced adaptation in peripheral blood reticulocytes of mice]

An in vivo micronucleus assay in mice reticulocytes of peripheral blood for identifying the possibility of induction of adaptive response to various doses of radiation: 2.5 cGy or 5.0 cGy as adapting and 50 cGy or 100 cGy as challenging doses was performed. The most effective inhibition of frequency appearance of micronucleus in RETs of mice (i.e. adaptive response) takes place et the following experimental conditions: 5.0 cGy as adaptive dose and 50 cGy challenging dose. The interval between them were 4 hours. The maximum inhibition of frequency of micronucleus was et 24 h sampling time after exposure of challenging dose. This reduction was statistically significant (p < 0.05; p < 0.01-chi square test).

[Evaluation of individual radiation resistance of rats based on reactions to non-radiation testing]

Presented are the data on radiation sensitivity of various groups of animals preliminary differentiated by their tolerance of acute hypoxia. The processes of blood forming system impairment and reparation are detailed. As was shown, highly resistant to hypoxia rats are distinguished by the best radiation resistance. Survivability of these rats was significantly higher as compared with other groups of animals. Recovery of blood formation by both the red and white chits following exposure to [symbol: see text] of the mean lethal dose proceeded more rapidly in the radiation resistant rats.

Feeding mice palm carotene prevents DNA damage in bone marrow and reduction of peripheral leukocyte counts, and enhances survival following X-ray irradiation

This study examined the effects of palm carotene feeding on DNA damage of bone marrow, recovery of peripheral leukocyte counts, and the survival of mice that received whole-body X-ray irradiation. The palm carotene was composed of alpha- and beta-carotene in a ratio of 1:3. Mice were fed either a basal diet or a carotene diet (50 mg carotene/100 g diet) for 2 weeks, then irradiated. The carotene diet was prepared by the dietary protocol that markedly enhanced the accumulation of carotene in tissues (J. Nutr. 125, 3081, 1995). DNA damage in bone marrow was evaluated by micronucleus assay using peripheral blood. When mice received X-ray (1.5 Gy), marked DNA damage in bone marrow and reduction of peripheral leukocyte count were observed. These changes were significantly attenuated in mice fed the carotene diet. In addition, X-ray (6.5 Gy)-induced survival of mice fed the carotene diet was higher than those fed the basal diet. In mice fed the carotene diet, alpha- and beta-carotene were detected in bone marrow and liver, and concentration of vitamin A in liver was about four times higher compared with that in mice fed the basal diet. These findings suggest that feeding mice palm carotene prevents radiation-induced damages by way of its antioxidant activity and/or vitamin A activity.

Radioprotection of beta-carotene evaluated on mouse somatic and germ cells

In the present paper, the protective effect of beta-carotene was evaluated after whole body exposure of mice to 2 Gy of X-rays. Splenocytes, reticulocytes, bone marrow cells and spermatids were evaluated for the frequency of micronuclei (MN) induced by X-rays. Mice were treated (gavage) with beta-carotene (10, 25 and 50 mg/kg b.w.) for 5 consecutive days and, 4 h after the last treatment, the animals were irradiated. The results obtained showed different frequencies of X-ray-induced-MN between different cell populations analysed and also different response of these cells to the beta-carotene treatment. The radioprotective effect of beta-carotene was observed in splenocytes, reticulocytes, and spermatids but not in bone marrow cells. No dose-response relationship for beta-carotene was detected. The time of sampling, the sensitivity of the cells as well as the antioxidant activity of beta-carotene are discussed as important factors for the radioprotective action of this provitamin.

The micronucleus assay using peripheral blood reticulocytes from X-ray-exposed mice

A new 'fluorescence' variant of the micronucleus assay using supravital staining of peripheral blood reticulocytes with an acridine orange coated slide was recently developed. In this study the application of this method to detect a mutagenic response to low-dose exposure of X-irradiation is reported. The mice were exposed to a single dose of 2.5, 5, 10, 15, 25, and 50 cGy. The induction of micronuclei in peripheral blood reticulocytes was recorded with sampling times of 0, 24, 48, 72, and 96 h after exposure without killing of mice. Dose-dependent effects were observed at sampling times of 24-72 h reaching maximum levels at 48 h after X-ray exposure. A highly significant (p < 0.01) increase of the micronucleated reticulocytes was found for doses of 10, 15, 25, and 50 cGy. Neither the dose of 2.5 nor 5 cGy induced the significant increase in the incidence of micronucleated reticulocytes compared with the respective control group.

Erythropoietin increases hemoglobin during radiation therapy for cervical cancer

PURPOSE

Anemia during radiation therapy independently predicts poor outcome in patients with cervical cancer. Despite a randomized trial demonstrating red cell transfusions improve local control and survival, many patients are not transfused due to toxicity concerns. This study evaluates the efficacy of recombinant human erythropoietin (r-HuEPO) in reversing anemia in patients undergoing radiation therapy.

METHODS AND MATERIALS

Twenty patients with criteria of anemia (Hgb < 12.5 g/dL) and surgically staged cervical cancer FIGO stages IB (n = 7), IIA (n = 1), IIB (n = 9), and IIIB (n = 3), ranging in ages from 23-75 years (median 43), were included in this Phase I/II study. Fifteen were treated with r-HuEPO (200 U/kg/day) and ferrous sulfate 5-10 days prior to initiation of external beam radiation therapy, continuing until Hgb was < or = 14 g/dL or completion of radiation therapy. Five patients were treated with ferrous sulfate alone. An additional 61 historical controls meeting eligibility criteria were analyzed. All received external beam radiation therapy and two intracavitary cesium applications. Cisplatinum chemotherapy (20 mg/m2/week) was given as a radiosensitizer in 14 r-HuEPO patients, 4 concurrent controls, and 17 historical controls.

RESULTS

A marked reticulocytosis was seen in the r-HuEPO group, but not the study controls. In the r-HuEPO group, the mean +/- SD serum Hgb rose + 30% over the course of radiation therapy from a baseline of 10.3 +/- 1.04 g/dL to 13.2 +/- 1.7 g/dL. Average increase in Hgb was 0.5 g/dL per week. Average Hgb during RT was 13.4 g/dL. In study and historical controls, mean initial Hgb levels were 10.7 +/- 1.04 g/dL and 11.1 +/- 1.3g/dL, respectively, remaining unchanged over the course of radiation therapy. Average Hgb levels during radiation therapy were 11.1 g/dL in study controls and 11.4 g/dL in historical controls, significantly lower than r-HuEPO patients (p = 0.0001). Erythropoietin was well tolerated. There were no significant differences in white blood counts (p = 0.6) or platelet counts (p = 0.4) between r-HuEPO patients and both control groups. No patients had blood pressure changes during r-HuEPO therapy. The only possible side effect was deep venous thrombosis, occurring in two patients who were withdrawn from r-HuEPO therapy. Two additional patients developed deep venous thrombosis 9 and 10 days after radiation therapy and r-HuEPO were completed.

CONCLUSION

Erythropoietin appears to be both safe and effective at raising Hgb levels in anemic cervical cancer patients receiving radiation therapy and chemotherapy.

Radioprotective effect of stobadine in the mouse micronucleus test

Induction of micronuclei was studied 40 h post irradiation in peripheral blood reticulocytes of male mice treated or not with stobadine dipalmitate (70.07 mg/kg body weight) at two time intervals (2 h or 1 h) prior to and immediately after 6.5 Gy 60Co exposure. A significant decrease of micronucleated reticulocytes was observed in the group of mice pretreated 2 h (P < 0.05) or 1 h (P < 0.01) before irradiation. 60Co irradiation followed by treatment with stobadine did not lead to the same protective effect in the micronucleus assay. It is therefore assumed that a radical-scavenging mechanism must be involved in radioprotection by stobadine.

[The information value of clinico-hematologic criteria for the early diagnosis of acute radiation sickness in pig-tailed macaques]

Ten pig-tailed monkeys (Macaca nemestrina) were subjected to 60Co radiation at a dose of 6.0-6.5 Gy and a dose rate of 1.2 Gy/min. Acute radiation sickness has developed in the monkeys causing their death on the 16-20 day. In spite of this, the initial reaction was weakly expressed and according to its manifestation it was impossible to evaluate severity and possible outcome of the lesion. At an early stage of the disease (6-24 hours) insufficient was uranin fluorescence in blood plasma, but more informative were the changes in adhesive properties of leukocytes the dynamics of lymphocytes (lymphopenia), reticulocytes (reticulocytopenia) and shifts in reticulograms (increased per cent of juvenile forms).

Establishment of permanent chimerism in a lactate dehydrogenase-deficient mouse mutant with hemolytic anemia

Pluripotent hemopoietic stem cell function was investigated in the homozygous muscle type lactate dehydrogenase (LDH-A) mutant mouse using bone marrow transplantation experiments. Hemopoietic tissues of LDH-A mutants showed a marked decreased in enzyme activity that was associated with severe hemolytic anemia. This condition proved to be transplantable into wild type mice (+/+) through total body irradiation (TBI) at a lethal dose of 8.0 Gy followed by engraftment of mutant bone marrow cells. Since the mutants are extremely radiosensitive (lethal dose50/30 4.4 Gy vs 7.3 Gy in +/+ mice), 8.0-Gy TBI followed by injection of even high numbers of normal bone marrow cells did not prevent death within 5-6 days. After a nonlethal dose of 4.0 Gy and grafting of normal bone marrow cells, a transient chimerism showing peripheral blood characteristics of the wild type was produced that returned to the mutant condition within 12 weeks. The transfusion of wild type red blood cells prior to and following 8.0-Gy TBI and reconstitution with wild type bone marrow cells prevented the early death of the mutants and permanent chimerism was achieved. The chimeras showed all hematological parameters of wild type mice, and radiosensitivity returned to normal. It is concluded that the mutant pluripotent stem cells are functionally comparable to normal stem cells, emphasizing the significance of this mouse model for studies of stem cell regulation.

[Effect of single 60Co whole-body irradiation on the absolute count and degree-of-maturity distribution of reticulocytes in the rat]

Wistar-rats were exposed to a single 60Co-gamma-total body irradiation with 1.5 Gy, 3.0 Gy and 4.5 Gy. The trend of reticulocyte count and the reticulocyte maturation distribution were measured with an automatic analysis system over a period of 30 days. In all animals the reticulocyte count as well as the maturation distribution showed minima at the second and the twelfth day post irradiation. The duration of the minima were dose dependent. The changes of the reticulocyte count and the maturation distribution are equivalent.

Identification of the proteins in direct contact with duck globin mRNA

Proteins in direct contact with translationally active and repressed duck globin mRNA were determined by irradiating blood or lysates with ultraviolet light. Cross-linked proteins from polyribosomes and free mRNP particles were 14C-labeled by reductive methylation and identified on SDS-polyacrylamide gels upon autoradiography. Results indicate that ten cross-linked proteins are common to both polysomal and free mRNP, however, a 44 kDa protein appears to be specific for repressed mRNP particles. Furthermore, the notable lack of cross-linked proteins in the 20-30 kDa range in free mRNP supports the view that the characteristic low molecular mass 'prosomal' proteins, previously found associated with translationally repressed duck globin free mRNP [(1984) EMBO J. 3, 29-34], do not interact directly with the mRNA molecule.

The sensitivity of an actinic reticuloid cell strain to near-ultraviolet radiation and its modification by trolox-C, a vitamin E analogue

Near-UV radiation (365 nm)-induced lethality, as measured by colony-forming ability, showed an actinic reticuloid cell strain to be sensitive relative to normal human fibroblasts, when irradiated at 25 degrees C. This effect was not seen after far-UV (254 nm) irradiation. Trolox-C, a water-soluble analogue of vitamin E, incorporated in the pre-irradiation growth medium or in the post-irradiation plating medium, protected the actinic reticuloid cells to the extent that they were as resistant as normal cells. Plating medium containing Trolox-C did not provide differential protection against inactivation of the two cell strains by wavelengths in the far-UV region. The protection provided by Trolox-C, an analogue of the natural antioxidant vitamin E, suggests some free radical involvement in the aetiology of the disease.

[Experimental study of the antimutagenic properties of 5-methylresorcinol]

A study was made of the effect of 5-methylresorcinol (5-MR) on mutagenic activity of benzo(a)pyrene (BP) and of the action of gamma-radiation in in-vitro and in-vivo systems. The induction of direct gene mutations in Chinese hamster cells V-79 and micronuclei in mouse bone marrow reticulocytes was efficiently suppressed by 5-MR treatment. The antimutagenic activity of 5-MR can be explained by inhibition of free-radical processes.

[Dynamics of changes in the number and proportion of different forms of rat peripheral blood reticulocytes during the initial days after whole body uniform irradiation by 60Co gamma quanta]

In experiments on mongrel albino male rats a study was made of the dynamics of changes in the number of peripheral blood reticulocytes and their count during the first 24 h after total-body uniform exposure to gamma-quanta (60Co, LD100/11, LD45/30, LD12,5/30 and LD0/30). After 12 and 24 h, the number of reticulocytes was shown to be a function of radiation dose. The degree of the reticulocytopenia and a change in the reticulocytograms permitted to estimate the presence of affection as well as its degree and outcome.

Virulent and nonvirulent forms of Plasmodium yoelii are not restricted to growth within a single erythrocyte type

The present studies were designed to investigate whether the erythrocyte preferences displayed by both virulent and nonvirulent forms of Plasmodium yoelii were fastidious growth requirements of these parasites. When inoculated into mice depleted of reticulocytes by lethal irradiation (900 rad), virulent parasites, which have been reported to grow predominantly in mature erythrocytes, gave rise to high parasitemias which were equivalent to those seen in unirradiated, normal mice. In addition, virulent parasites serially passaged in lethally irradiated mice showed properties of enhanced virulence upon inoculation back into normal mice. When inoculated into lethally irradiated mice, nonvirulent P. yoelii, which were reported to preferentially invade reticulocytes, invaded mature erythrocytes, and the infection progressed at a higher level of parasitemia than in unirradiated, normal mice. The inoculation of virulent parasites into mice made reticulocytemic by pretreatment with phenylhydrazine produced infections marked by the invasion of reticulocytes rather than mature erythrocytes, yet these infections remained lethal for the murine host. When nonvirulent parasites were inoculated into reticulocytemic mice, lethal infections resulted in which the parasites predominantly invaded reticulocytes. These results indicate that both the virulent and nonvirulent forms of P. yoelii possess the ability to invade and proliferate within more than one erythrocyte type and that their apparent erythrocyte preferences are not strict growth requirements.

Daily variation in radiosensitivity of circulating blood cells and bone marrow cellularity of mice

Random bred, nocturnal, male Mus musculus (DUB-ICR), on a 12/12 light/dark cycle with lights on at 6 a.m., were exposed to 100 R or 200 R of X-radiation at either noon or midnight to study diurnal radiosensitivity in circulating blood cells and bone marrow cellularity. Hematocrits, reticulocyte and white blood cell counts, daily white blood cell rhythm, and bone marrow cellularity indicate that these mice are more radiosensitive at night. At low doses it is possible that diurnal rhythms in natural, biological radioprotectors such as corticosterone may have more influence on radiation sensitivity than mitotic activity.

Amount of peripheral reticulocytes as biologic dosimetry of ionizing radiation. Experiments in the rabbit

The amount of reticulocytes in peripheral blood generally reflect the bone-marrow status of erythropoiesis and may therefore be useful in evaluating radiation injury. The blood reticulocytes in rabbits exposed to various doses of ionizing radiation were examined using an apparatus capable of microfluorometric quantification of reticulocytes as well as the conventional technique of reticulocyte count. A dose-dependent decrease of reticulocytes was observed. The possibilities of further improvements of the technique using flow cytometry and its application for screening human population are discussed.

Cyclic erythropoiesis in W/Wv mice following a single small dose of 89Sr

Young adult female W/Wv mice were given 0.5 microCi 89Sr/g intravenously, a dose which produces no anemia and only mild transient thrombocytopenia in normal mice. In the W/Wv animals platelet counts fell from 10(6) to 3 x 10(5)/mm3, and hematocrits from 39% to 25% in two weeks. In the following 2 weeks, platelet counts rose to 7 x 10(5), stabilizing at this level. Average hematocrit values were observed to oscillate from a nadir of 26% to a zenith of 42%, with a periodicity of about 16 days. In a repeat experiment we found the average hematocrit fluctuation from 28 to 40%, amplitude of reticulocyte fluctuation 6 to 31%, periodicity of cycle 16 days. Several animals have been observed through as many as six complete cycles. Further study of cyclical erythropoiesis in the W/Wv mouse following hematopoietic injury produced by 89Sr may shed light on the causes of cyclical hematopoiesis observed occasionally in man and other animals.

[Hematologic toxicity of total body irradiation (author's transl)]

Eleven patients with malignant lymphoma were treated with total body irradiation. This therapy was performed during 3 weeks with a midline dose of 70 to 100 rd. Two patients were treated two times after an internal of 3 months. The authors studied the hematologic side effects of this therapy. The irradiation caused a diminution of leucocytes of 73% of the initial value (range 16,7 to 98,4%), the neutrophilic granulocytes were reduced by 60% (24-95%), the thrombocytes were reduced by 57% (12-73%). The lowest values were seen during the fourth and sixth week of observation or one to three weeks after the end of therapy. In patients with hypoplastic anemia the number of reticulocytes was reduced to zero with a further fall of hematocrit and replacement therapy was necessary. The pool of circulating CFUc was reduced to zero in nine of twelve observations up to six weeks after therapy.

[Ultrastructure of the lymph nodes of dogs under prolonged external gamma irradiation]

The purpose of the present investigation was electron microscopy study of lymph nodes of dogs exposed to chronic gamma-irradiation during 6 years (with a total dose of 125 rad/year). The exposure induced changes in the cell composition of the paracortical regions due to a decrease of the count of small lymphocytes and a predominant increase of young blast cells with an altered ultrastructure. Chronic gamma-irradiation led to an increase of the number of plasma cells and emergence of intermediate cell forms due to "plasmatization" of lymphocytes and reticular cells.