The effects of environmental low-dose irradiation on tolerance to chemotherapeutic agents

The nuclear disaster at Chernobyl, Ukraine, in April of 1986 continues to impact the environment on many different levels. Studies of epidemiological, environmental, and genetic impacts have been prolific since the accident, revealing interesting results concerning the effects of radiation. The long-tailed field mouse, Apodemus flavicollis, was collected from distinct localities near the Chernobyl site and evaluated based on in vivo responses to the current clinically employed chemotherapeutic agents bleomycin (BLM) and vinblastine (VBL), as well as the immune modulator lipopolysaccharide (LPS). Maximum tolerable doses of three different cancer drugs were administered to the rodents from three different lifestyles: native mice living and reproducing in a radioactive environment, native mice living and reproducing in an uncontaminated region, and laboratory-reared mice (Mus musculus BALB/c) with a known sensitivity to the chemical agents tested. The endpoints employed include micronucleus formation, immune cell induction, differential gene expression, and chemotherapeutic side effects such as lethargy and weight loss. In accordance with the well-studied phenomenon termed radio-adaptation, we observed varied tolerance to chemotherapeutic treatment dependent on history of ionizing radiation exposure. The results of the present study demonstrate a differential response to chemotherapeutic treatment with respect to previous levels of radiation exposure, suggesting a potential benefit associated with low-dose radiation exposure. Data reported herein could have a profound impact on the development of novel cancer treatments involving low-dose ionizing radiation.

Effect of millimeter waves on natural killer cell activation

Millimeter wave therapy (MMWT) is being widely used for the treatment of many diseases in Russia and other East European countries. MMWT has been reported to reduce the toxic effects of chemotherapy on the immune system. The present study was undertaken to investigate whether millimeter waves (MMWs) can modulate the effect of cyclophosphamide (CPA), an anticancer drug, on natural killer (NK) cell activity. NK cells play an important role in the antitumor response. MMWs were produced with a Russian-made YAV-1 generator. The device produced modulated 42.2 +/- 0.2 GHz radiation through a 10 x 20 mm rectangular output horn. Mice, restrained in plastic tubes, were irradiated on the nasal area. Peak SAR at the skin surface and peak incident power density were measured as 622 +/- 100 W/kg and 31 +/- 5 mW/cm2, respectively. The maximum temperature elevation, measured at the end of 30 min, was 1 degrees C. The animals, restrained in plastic tubes, were irradiated on the nasal area. CPA injection (100 mg/kg) was given intraperitoneally on the second day of 3-days exposure to MMWs. All the irradiation procedures were performed in a blinded manner. NK cell activation and cytotoxicity were measured after 2, 5, and 7 days following CPA injection. Flow cytometry of NK cells showed that CPA treatment caused a marked enhancement in NK cell activation. The level of CD69 expression, which represents a functional triggering molecule on activated NK cells, was increased in the CPA group at all the time points tested as compared to untreated mice. However, the most enhancement in CD69 expression was observed on day 7. A significant increase in TNF-alpha level was also observed on day 7 following CPA administration. On the other hand, CPA caused a suppression of the cytolytic activity of NK cells. MMW irradiation of the CPA treated groups resulted in further enhancement of CD69 expression on NK cells, as well as in production of TNF-alpha. Furthermore, MMW irradiation restored CPA induced suppression of the cytolytic activity of NK cells. Our results show that MMW irradiation at 42.2 GHz can up-regulate NK cell functions.

Children undergoing repeated exposures for radiation therapy do not develop tolerance to propofol: clinical and bispectral index data

BACKGROUND

The purpose of this study was to apply clinical criteria and Bispectral Index monitor data for evaluating the development of tolerance to propofol in children undergoing repeated drug exposure.

METHODS

Children undergoing multiple sessions of radiation therapy during anesthesia for various malignancies were given a predetermined dose of propofol at each session. Heart rate, blood pressure, oxygen saturation, respiratory rate, requirement of additional propofol, and time to emergence and discharge were recorded. The Bispectral Index was monitored continuously, and parameters were extracted and averaged for each week of therapy.

RESULTS

Fifteen children (aged 2.5-10 yr) were treated for an average of 5 weeks (24 +/- 6 sessions). There were no significant differences in physiologic parameters or requirements of additional propofol between the weeks of treatment. Bispectral Index data analysis showed that although a nonlinear change with time for each parameter could not be rejected, the differences between the first and last intervals were nonsignificant.

CONCLUSIONS

Overall changes with time resulted from random fluctuations without a consistent trend. Combined with clinical data, Bispectral Index parameters showed that tolerance to propofol does not develop in children undergoing repeated exposures to the drug during radiation therapy.

Neuronal outgrowth of PC-12 cells after combined treatment with nerve growth factor and a magnetic field: Influence of the induced electric field strength

In view of possible therapeutic applications of magnetic fields, the effect of an enhancement of neuronal outgrowth at higher figures of flux density and induced field strength was investigated. On the average sinusoidal magnetic field treatment at 100 microTrms/50 Hz did not change nerve growth factor (NGF) induced neurite outgrowth to a statistically significant extent. These results suggest that further increasing the induced field strength by using either higher flux densities and/or more sophisticated wave forms might be necessary to cause the neuronal response of PC-12 cells, as seen in other experiments.

Behavioral and cognitive effects of microwave exposure

This paper presents an overview of the recent behavioral literature concerning microwave exposure and discusses behavioral effects that have supported past exposure standards. Other effects, which are based on lower levels of exposure, are discussed as well, relative to setting exposure standards. The paper begins with a brief discussion of the ways in which behavioral end points are investigated in the laboratory, together with some of the methodological considerations pertinent to such studies when radio frequency (RF) exposure is involved. It has been pointed out by several sources that exposure to RF radiation can lead to changes in the behavior of humans and laboratory animals that can range from the perceptions of warmth and sound to lethal body temperatures. Behavior of laboratory animals can be perturbed and, under certain other conditions, animals will escape and subsequently avoid RF fields; but they will also work to obtain a burst of RF energy when they are cold. Reports of change of cognitive function (memory and learning) in humans and laboratory animals are in the scientific literature. Mostly, these are thermally mediated effects, but other low level effects are not so easily explained by thermal mechanisms. The phenomenon of behavioral disruption by microwave exposure, an operationally defined rate decrease (or rate increase), has served as the basis for human exposure guidelines since the early 1980s and still appears to be a very sensitive RF bioeffect. Nearly all evidence relates this phenomenon to the generation of heat in the tissues and reinforces the conclusion that behavioral changes observed in RF exposed animals are thermally mediated. Such behavioral alteration has been demonstrated in a variety of animal species and under several different conditions of RF exposure. Thermally based effects can clearly be hazardous to the organism and continue to be the best predictor of hazard for homosapiens. Nevertheless, similar research with man has not been conducted. Although some studies on human perception of RF exist, these should be expanded to include a variety of RF parameters.

Effects of 50 Hz electromagnetic field exposure on apoptosis and differentiation in a neuroblastoma cell line

Experiments were carried out to assess whether a magnetic field of 50 Hz and 1 mT can influence apoptosis and proliferation in the human neuroblastoma cell line LAN-5. TUNEL assays and poly-ADP ribose polymerase (PARP) expression analysis were performed to test apoptosis induction, and the WST-1 assay was used to calculate the proliferation index in a long term exposure. No alterations were found in cellular ability to undergo programmed cell death, but a small increase in the proliferation index was evidenced after 7 days of continuous exposure. Also, a slight and transient increase of B-myb oncogene expression was detected after 5 days of exposure. Combined exposures of cells to EMF and to chemical agents which interfere with proliferation, such as the differentiative agent retinoic acid and the apoptotic inducer camptothecin, showed an antagonistic effect of magnetic fields against the differentiation of the LAN-5 cells and a protective effect towards apoptosis.

Effects of 50 Hz magnetic fields on fMLP-induced shape changes in invertebrate immunocytes: The role of calcium ion channels

Plasma membrane Ca(2+) channels in immunocytes from the mussel Mytilus galloprovincialis exposed to 50 Hz sine wave magnetic fields (MFs) of various strengths were studied. At levels of 300 microT and above, MFs reduce shape changes in immunocytes induced by the chemotactic substance N-formyl-Meth-Leu-Phe, and this effect involves L-type Ca(2+) channels. Upon the addition of the Ca(2+) blocker verapamil to molluscan immunocytes exposed to MFs results in a synergistic cytotoxic action, while in the presence of the Ca(2+) opener SDZ-202, 791, a reactivation of the cells is observed. This suggests that, as previously reported for potassium channels, the damage to Ca(2+) channels induced by short exposure to MF at appropriate intensities is not permanent.

Effect of coexposure to 50 Hz magnetic fields and an aneugen on human lymphocytes, determined by the cytokinesis block micronucleus assay

Interference of 50 Hz extremely low frequency magnetic fields (ELF-MF) with the known aneugen vinblastine (VBL) on micronucleus formation was tested with the in vitro cytokinesis block micronucleus assay in human lymphocyte cultures. Isolated lymphocyte cultures were prepared from 18 individuals. Three groups of quadruplicate cultures from six unrelated individuals were exposed to 50 Hz ELF-MF of background (bkg), 80 and 800 microT, respectively, during the complete incubation period (72 h). Twenty-four hours after culture initiation, one replicate culture from each individual within each ELF-MF group was exposed to 0, 5, 10, or 15 ng/ml VBL. The isolated lymphocyte cultures were scored for the presence of micronuclei, the nuclear division index (NDI), and apoptosis. As expected, increased VBL concentration resulted in an increased micronucleus and apoptosis frequency and in a decreased NDI. In the presence of VBL, there was a systematic tendency for increased micronucleus and apoptosis frequency in the ELF-MF exposed groups compared to the bkg group. In the absence of VBL, we observed no statistically significant effect of ELF-MF on micronucleus induction or apoptosis frequency, but the NDI was significantly higher in the 800 microT group compared to the other groups, suggesting an effect of ELF-MF on cell proliferation. An interaction between ELF-MF and VBL on NDI was observed. This interaction reflected the drastic decrease in NDI due to coexposure to VBL.

A 60 Hz magnetic field does not affect the incidence of squamous cell carcinomas in SENCAR mice

Two groups of SENCAR mice were treated with a single dose of carcinogen and then, for 23 weeks, with a chemical tumor promoter to induce skin tumors. During this period, one group was coexposed to a 2 mT power frequency (60 Hz) magnetic field, while the other was exposed to sham conditions. Application of the tumor promoter ceased after 23 weeks, but the exposure to sham conditions or magnetic fields continued for an additional 29 weeks. No difference was found between the two groups of mice in terms of the incidence of total tumors (P =.297) or squamous cell carcinomas (SSC) (P =.501). In summary, there was no evidence to support the hypotheses that 60 Hz magnetic fields (MF) can influence the development of either papillomas or SSC under our defined experimental conditions. The overall results add to previous animal studies that find no association between exposure to 60 Hz MF and the incidence of benign or malignant tumors.

Susceptibility to effects of UVB radiation on induction of contact hypersensitivity as a risk factor for skin cancer in humans

Normal, healthy human volunteers and patients with proved history of non-melanoma skin cancer have been tested for their capacity to develop contact hypersensitivity to dinitrochlorobenzene (DNCB) following exposure of buttock skin to acute, low-dose ultraviolet B (UVB) radiation. Using a radiation protocol that achieves virtually complete depletion of normal-appearing Langerhans cells from irradiated skin, it was learned that approximately 60% of healthy volunteers developed vigorous contact hypersensitivity (CH) when 2000 micrograms DNCB was painted on the irradiated site. These individuals were designated UVB-resistant, and were distinguished from other individuals, designated UVB-susceptible, who failed to develop contact hypersensitivity following an identical treatment protocol. It was then discovered that virtually all (92%) skin cancer patients exposed to UVB and DNCB failed to develop CH, i.e., were UVB-susceptible. In subsequent experiments, epicutaneous application of 2000 micrograms DNCB to unirradiated skin of UVB-susceptible individuals revealed a further distinction between normal persons and skin cancer patients. Approximately 45% of the latter (and none of the former) remained unresponsive (failed to develop contact hypersensitivity following this second attempt at sensitization), implying that they had been rendered immunologically tolerant. These tolerant individuals responded normally to the unrelated hapten, diphencyprone. We conclude that human beings resemble inbred strains of laboratory mice in that some individuals are UVB-susceptible, whereas others are UVB-resistant. Because the incidence of UVB-susceptibility was significantly higher in skin cancer patients, and as specific unresponsiveness could be demonstrated only in these patients, we propose that UVB-susceptibility, as we define it in this hapten system, may be a risk factor for the development of skin cancer.

Tolerance of previously irradiated mouse kidneys to cis-diamminedichloroplatinum(II)

In this study the tolerance of previously irradiated kidneys to retreatment with chemotherapy was assessed. cis-Diamminedichloroplatinum(II) (c-DDP) was given to groups of mice at 1, 3, or 6 months after bilateral renal irradiation with single doses of 8-14 Gy. Renal function was measured monthly (by clearance of 51Cr ethylenediaminetetraacetic acid) from 4-35 weeks after c-DDP injection and results were compared with function after X-rays alone or drug alone. At early testing times (during the first 11 weeks after c-DDP injection) the renal function of mice given drug at 1 or 3 months after irradiation was very similar to that seen after drug alone. c-DDP given at 6 months caused slightly more damage than either drug or X-rays alone, but these results could be explained in terms of additive toxicities. At later testing times (11-35 weeks after c-DDP injection), renal function was much worse in all animals which had received previous irradiation, with the greatest damage when c-DDP was given 6 months after X-rays. This may be partly due to additional cell killing by the drug causing the expression of subclinical radiation injury. It is also possible that c-DDP pharmacokinetics was altered in animals with previously irradiated kidneys, leading to higher drug exposures in these mice.

The effect of alpha-interferon, cyclosporine A, and radiation-induced immune suppression on morphine-induced hypothermia and tolerance

An interconnection between the immune and the central nervous systems has been suggested by investigators studying the actions of several types of immune modifying agents and procedures upon opiate related phenomena. These studies have included the effects of altering immune system function by administration of either alpha-interferon, cyclosporine or radiation exposure upon naloxone-precipitated opiate withdrawal and upon opioid antinociceptive effects. The present study extends these earlier investigations by examining the effect of immune modulation upon opiate induced hypothermia. The results demonstrate that interferon and cyclosporine have no effects on baseline temperature or morphine induced hypothermia, while irradiation exposure elicits hyperthermia without affecting morphine-induced hypothermia. Finally, neither cyclosporine nor irradiation affect the development of tolerance to morphine induced hypothermia, while a single injection of the immune system modifier interferon was able to prevent the development of such tolerance. These observations suggest that yet another opiate-related phenomenon may be regulated at least in part by the immune system. These results together with our previous findings are further evidence of a link between the immune system and the CNS mediated through the opioid system. In addition, these studies further support our earlier hypothesis that "Interferon" is one of the endogenous substances which serves to prevent the development of tolerance and dependence to endogenous opioids.

An appraisal of the role of radiation therapy in the management of nonseminomatous germ-cell tumors of the testis in the era of effective chemotherapy

Patients with nonseminomatous germ-cell tumors of the testis can be divided into two broad groups. The first includes patients with negative lymphograms or small-volume metastases confined to the abdominal nodes. The overall cure rate with orchiectomy and nodal irradiation is 80%. A policy of early detection of relapse and treatment with chemotherapy is advocated. Adopting this approach, no deaths have occurred in this group of patients treated in 1976 and 1977, and only one (associated with acute myeloblastic leukemia) occurred in 1975. The second group consists of patients with other stage categories who receive chemotherapy as initial treatment, followed in stage II and II and selected stage IV patients by radiation therapy to sites of initial involvement and surgery. Preliminary experience has shown this to be a practicable and promising approach. The prognosis for stage IV patients depends upon metastatic site and volume; in those patients with limited lung disease 80% are surviving disease-free.

Preventive central nervous system irradiation in children with acute nonlymphocytic leukemia

In this study of children with acute nonlymphocytic leukemia an attempt was made to prevent central nervous system relapse and to determine whether this therapy, coupled with multiagent chemotherapy, would be successful in prolonging durations of complete remission. Central nervous system relapses were prevented by irradiation, although patients who received this therapy did no better than those who did not receive irradiation. A small group of patients received irradiation to the liver and spleen, but this modality also failed to improve the duration of remission. Control of extramedullary leukemia, in this study, failed to improve remission duration because bone marrow relapse was not prevented or delayed. It is unlikely that focal therapy will have a significant impact in acute nonlymphocytic leukemia until longer marrow remissions are achieved.