A back‐of‐the‐envelope risk assessment of star wars

The risks associated with the deployment of a Star Wars system and from a space‐based conflict have been rapidly evaluated on the basis of known facts about SDI‐like programmes. Back‐of‐the‐envelope evaluations indicate that effects of a space‐based conflict might be lethal for life on Earth.     

Chromatin‐ and temperature‐dependent modulation of radiation‐induced double‐strand breaks

Purpose: To investigate the influence of chromatin organization and scavenging capacity in relation to irradiation temperature on the induction of double‐strand breaks (DSB) in structures derived from human diploid fibroblasts.

Materials and methods: Agarose plugs with different chromatin structures (intact cells±wortmannin, permeabilized cells with condensed chromatin, nucleoids and DNA) were prepared and irradiated with X‐rays at 2 or 37°C and lysed using two different lysis protocols (new ice‐cold lysis or standard lysis at 37°C). Induction of DSB was determined by constant‐field gel electrophoresis.

Results: The dose‐modifying factor (DMF_temp) for irradiation at 37 compared with 2°C was 0.92 in intact cells (i.e. more DSB induced at 2°C), but gradually increased to 1.5 in permeabilized cells, 2.2 in nucleoids and 2.6 in naked DNA, suggesting a role of chromatin organization for temperature modulation of DNA damage. In addition, DMF_temp was influenced by the presence of 0.1?M DMSO or 30?mM glutathione, but not by post‐irradiation temperature.

Conclusion: The protective effect of low temperature was correlated to the indirect effects of ionizing radiation and was not dependent on post‐irradiation temperature. Reasons for a dose modifying factor <1 in intact cells are discussed.     

Genetic susceptibility to thymic lymphomas and K‐ras gene mutation in mice after exposure to X‐rays and N‐ethyl‐N‐nitrosourea

Purpose: Ras activation is one of the major mechanisms for the development of murine thymic lymphomas by radiation and chemical carcinogens. To gain insight into the relationship between genetic susceptibility and ras gene mutation, the frequency and spectrum of ras gene mutation was examined in thymic lymphomas from susceptible and resistant mice.

Materials and methods: K‐ and N‐ras mutations in thymic lymphomas that arose in X‐ray‐irradiated and N‐ethyl‐N‐nitrosourea (ENU)‐treated mice of susceptible C57BL/6, rather resistant C3H and their hybrid B6C3F1 were analysed by polymerase chain reaction‐single‐strand conformation polymorphism and subsequent DNA sequencing.

Results: C57BL/6 exhibited a higher incidence of thymic lymphomas after exposure to X‐rays and ENU than C3H, with B6C3F1 being intermediate. K‐ras gene mutations occurred frequently in the pathogenesis of ENU‐induced thymic lymphomas in susceptible C57BL/6 as opposed to resistant C3H. The ras mutations were more frequent in ENU‐induced thymic lymphomas than X‐ray‐induced thymic lymphomas, and with the latter, there was no clear evidence for strain differences, suggesting that the genetic susceptibility to X‐rays was independent of ras activation. The mutations of K‐ras in thymic lymphomas from C57BL/6 were predominantly GGT to GAT in codon 12, whereas this mutation type was never found in those from C3H. No strain difference was observed in the nucleotide sequence or expression levels of O⁶‐alkylguanine alkyltransferase, indicating that this enzyme did not account for the genetic susceptibility to ras activation.

Conclusions: The results indicate that there is a clear strain and carcinogen dependency of K‐ras mutation and that the frequency of ras mutation might determine the genetic susceptibility to ENU‐induced lymphomagenesis, whereas pathways independent of ras activation might determine the susceptibility to X‐ray‐induced lymphomagenesis.     

Decreased c‐Myc expression and its involvement in X‐ray‐induced apoptotic cell death of human T‐cell leukaemia cell line MOLT‐4

Purpose: To investigate the possible involvement of c‐Myc and ceramide‐c‐Jun N‐terminal kinase (JNK) pathway in X‐ray‐induced apoptotic cell death of MOLT‐4 cells.

Materials and methods: The expressions of c‐Myc protein and c‐myc mRNA after X‐irradiation were analysed by Western blotting and RT‐PCR between radiosensitive MOLT‐4 and radioresistant variant Rh‐1a cells with less JNK activation than the parental cells. Apoptotic cell death was determined by a dye exclusion test, the appearance of chromatin condensation and DNA fragmentation. The effect of a JNK activator anisomycin or c‐Myc inhibitor peptides (Int‐H1‐S6A, F8A) on the amount of c‐Myc protein and on the induction of apoptosis was investigated, respectively.

Results: In X‐irradiated MOLT‐4 cells, amounts of both c‐myc mRNA and c‐Myc protein rapidly decreased, which was followed by apoptotic cell death, while little change or limited reduction of c‐Myc protein was observed in X‐irradiated Rh‐1a cells with accompanying higher cell viability. Exposure of MOLT‐4 and Rh‐1a cells to c‐Myc inhibitor peptides similarly induced apoptotic cell death with decreases of c‐Myc protein. Anisomycin rapidly induced JNK activation and a subsequent decrease of c‐Myc protein, causing cell death in MOLT‐4 cells. On the other hand, Rh‐1a cells were more resistant to anisomycin than parental MOLT‐4 cells, showing less JNK activation and a delayed decrease of c‐Myc protein.

Conclusion: A decrease of c‐Myc protein was considered important in X‐ray‐induced apoptotic cell death of MOLT‐4 cells; activation of the JNK pathway caused reduction in the amounts of c‐myc mRNA and c‐Myc protein, and finally induced apoptotic cell death.     

Decomposition of 2‐deoxy‐D‐ribose by irradiation with 0.6 keV electrons and by 0.5 keV ultrasoft X‐rays

Purpose: To compare the molecular decomposition of 2‐deoxy‐D‐ribose induced by 0.6?keV electron irradiation or by 0.5?keV ultrasoft X‐ray irradiation.

Materials and methods: A thin film of 2‐deoxy‐D‐ribose was irradiated by two radiation sources: low‐energy (～0.6?keV) electrons and ultrasoft X‐rays (～0.5?keV). The positive ions that were desorbed from the sample during the irradiation were measured using a quadrupole mass spectrometer. The spectral changes in the X‐ray absorption near edge structure (XANES) were also examined after the irradiation.

Results and discussion: The ions that were desorbed from 2‐deoxy‐D‐ribose due to electron irradiation were mainly H⁺, CH_x⁺, C₂H_x⁺, CO⁺, CH_xO⁺, C₃H_x⁺, C₂H_xO⁺ and C₃H_xO⁺ (x=1, 2, and 3) ions. These ions were the same as those observed in desorption due to ultrasoft X‐ray irradiation. The XANES spectral changes induced by electron irradiation showed C‐O bond cleavage in the molecule and C=O bond formation in the surface residues. These results show that intensive molecular decomposition of the furanose ring structure was induced by both types of irradiation. It is inferred that these irradiation products are primarily produced by secondary electrons (several tens of eV), which are thought to be generated by both types of irradiation when they are applied to the 2‐deoxy‐D‐ribose sample.     

Magnetic field (50 Hz) increases N‐acetyltransferase,hydroxy‐indole‐O‐methyltransferase activity and melatonin release through an indirect pathway

Purpose: To examine whether magnetic fields (MF) affect N‐acetyltransferase (NAT) and hydroxy‐indole‐O‐methyltransferase (HIOMT) activity directly or exert their effect through a cellular pathway that indirectly regulates the activity of these enzymes and melatonin release.

Materials and methods: The pineal glands from Wistar rats were isolated at 10:00?h and exposed to MF (50?Hz, 1?mT) for 4?h in vitro, with or without 1?µM norepinephrine. An additional group of pineals was exposed to MF 30?min before norepinephrine addition. The direct effect of MF on the activity of the enzymes was studied in sonicated glands exposed to MF. NAT activity, HIOMT activity and melatonin release were determined.

Results: In pineal glands isolated in the morning, 4‐h in vitro exposure did not affect the basal release of melatonin from the pineal gland as well as the basal NAT and HIOMT activities. Pineal gland exposure to MF 30?min before norepinephrine addition significantly (p<0.05) increased NAT activity, HIOMT activity and melatonin release (p<0.05). These effects were not observed in pineals co‐treated with MF and norepinephrine or in sonicated glands exposed to MF.

Conclusions: The results suggest that in pineals isolated in the morning, 4‐h MF exposure changes melatonin release by affecting the signal transduction pathway leading from the norepinephrine receptor to NAT and HIOMT and not via a direct effect at the enzyme levels.     

Low‐energy Auger‐ and Photo‐electron Effects on the Degradation of Thymine by Ultrasoft X‐irradiation

Purpose: To investigate quantitatively and qualitatively the production of thymine radicals produced by monochromatic ultrasoft X (USX) ‐ or ⁶⁰Co γ‐rays using electron paramagnetic resonance (EPR) spectroscopy.

Materials and Methods: Thymine was chosen as the DNA component for the irradiation. The EPR experiments of irradiated thymine were performed using an X‐band EPR device installed in a soft X‐ray beamline (BL23SU) in SPring‐8. Sample pellets were irradiated with USX photons in a microwave cavity in a vacuum chamber. EPR measurements of thymine powder pellets irradiated with USX photons at energies of 407 and 538?eV were performed at 77?K or room temperature. For reference, ⁶⁰Co γ‐irradiation to a pellet was also performed at room temperature.

Results: The following three features were found: 1) comparison between the two energies shows that the EPR dose‐response curves are clearly distinguishable from each other: the curve for 407?eV saturated at a lower dose and spin number than that for 538?eV. 2) no evident qualitative difference between the radical species produced at the two energies was observed. 3) the EPR signal of the 538?eV USX‐irradiated sample measured after annealing for 12 days is similar to that obtained with ⁶⁰Co γ‐irradiation.

Conclusions: The difference observed in the EPR dose‐response relationship reflects the difference in the K‐absorption cross‐sections of carbon, nitrogen and oxygen in the thymine molecule which govern the photo‐/Auger electron energy spectrum.     

The scope‐enuwar report

The future role of International Physicians for Prevention of Nuclear War in Europe is examined in the light of the current state of the nuclear arms issue, the continued risk of nuclear proliferation and nuclear terrorism, and the continuation of bitter armed conflict in the former Yugoslavia and elsewhere.     

Inter‐group aggression: The multi‐individual organism and the survival instinct

Inter‐group aggression, carried out at the level of the in‐groups and out‐groups of ethnocentric theory, continued unabated throughout the twentieth century. Its frequency, together with its ferocity, indicates a potent biological cause. We have evolved as social animals, and it is postulated that evolution has proceeded to such an extent that ‘multi‐individual social organisms’, that is, ‘social groups that fight each other are self‐sustaining, self‐replicating wholes containing interdependent parts’. This results from the total integration of individuals into the social structure and culture of the in‐group; individuals are inseparable from their society and evidence for this proposal is given. Cohesion is given through the collective consciousness and collective memory. The analogy is to multicellular organisms that evolved from the association of single cell organisms. All biological organisms are subject to the survival instinct, which is thus the potent biological cause of inter‐group aggression. Groups compete for territory and see other groups as a threat. Prevention of inter‐group aggression should come from the insight that threatening behaviour endangers the integrity of the society of out‐groups, initiating conflict.     

Low‐dose radiotherapy (LD‐RT) and the modulation of iNOS expression in adjuvant‐induced arthritis in rats

Purpose: Low‐dose radiotherapy (LD‐RT) of arthritic joints applied during the peak of the acute inflammatory response improves the clinical and histomorphological development of adjuvant arthritis. The study was undertaken to investigate the cellular composition of the inflammatory infiltrate and the expression of the pro‐inflammatory and anti‐inflammatory enzymes, inducible nitric oxide synthase (iNOS), cyclo‐oxygenase 2 (COX‐2) and haem‐oxygenase 1 (HO‐1), in response to LD‐RT.

Materials and methods: Adjuvant arthritis in female Lewis rats was induced by intradermal injection of heat‐inactivated mycobacterium tuberculosis on day 0. Both arthritic hind paws were sham irradiated (group 1) or X‐irradiated with either 5×1.0?Gy (group 2) or 5×0.5?Gy (group 3) from days 15 to 19 after induction (15 animals/group). On days 21 (n=12 joints/group) and 30 (n=18 joints/group), cryostat sections were analysed histologically and immunohistologically after specific staining for macrophages, iNOS, COX‐2 and HO‐1.

Results: A total of 5×1.0?Gy or 5×0.5?Gy led to a significant reduction of clinical symptoms from days 21 to 29, and a highly significant reduction of cartilage and bone destruction on day 30. Macrophage‐positive areas could be detected continuously throughout the periarticular infiltrate, and were slightly reduced after LD‐RT on days 21 and 30. This reduction was more pronounced after 5×1.0?Gy. Following LD‐RT, the iNOS score was reduced by about 45–50% on days 21 (p<0.05) and 30 (p<0.001). In contrast, the HO‐1 score was increased by about 50% on days 21 (p=0.08) and 30 (p=0.03).

Conclusions: The clinically and histologically observed prevention of the pro‐gression of adjuvant arthritis after LD‐RT given during the peak of the acute inflam‐matory response and the reduction of cartilage and bone destruction in the chronic phase appears to be related to the modulation of iNOS activity by low X‐ray doses.     

Repeated exposure to low‐level extremely low frequency‐modulated microwaves affects baseline and scopolamine‐modified electroencephalograms in freely moving rats

Purpose: To compare in the electroencephalogram of rats the effects of scopolamine (an acetylcholine receptor antagonist) alone and after repeated exposure to low‐level microwaves modulated at extremely low frequency.

Materials and methods: Averaged frequency spectra (0.5–30?Hz) of the electroencephalogram were studied in freely moving rats with carbon electrodes implanted into the somatosensory cortex. The rats were repeatedly (3 days, 30?min?day^?1) exposed to low‐intensity (?0.3?mW?cm^?2) microwaves (915?MHz, 20‐ms pulse duration), amplitude modulated (square‐wave) at extremely low frequency (4?Hz).

Results: The exposure to extremely low frequency microwaves alone significantly enhanced the fast electroencephalographic rhythms (18–30?Hz). This effect was observed neither in subsequent sham‐exposure experiment nor in radiation‐naïve animals. In the microwave‐exposed rats, scopolamine (0.1?mg?kg^?1, subcutaneously) did not cause a slowing in the electroencephalogram that was shown in non‐exposed rats. A similarity between the scopolamine‐induced electroencephalogram effect in the microwave‐exposed rats and that of physostigmine (enhancing the acetylcholine level in the brain) in radiation‐naïve animals was noted. This paradoxical phenomenon stimulates new experimentation for understanding its mechanism(s).

Conclusions: The data obtained provide additional evidence that repeated low‐level exposure to extremely low frequency microwaves can modify an activity of cholinergic system in the brain.     

Androgen and the blocking of radiation‐induced sensitization to Fas‐mediated apoptosis through c‐jun induction in prostate cancer cells

Purpose: To clarify the key mechanism by which androgen makes prostate cancer cells highly resistant to Fas‐mediated apoptosis.

Materials and methods: The role of c‐jun induction by 10?nM dihydrotestosterone (DHT) in 5?Gy radiation‐induced up‐regulation of Fas and sensitization to the apoptosis was studied by using the human prostate cancer cell line LNCaP.

Results: On exposure to 5?Gy radiation, LNCaP cells demonstrated high sensitization to Fas‐mediated apoptosis through increased Fas expression, stabilized p53 expression and binding to p53 response elements within the promoter and first intronic region of the Fas gene. Following treatment with DHT, in vivo binding of p53 to its response elements was strongly inhibited. In addition, DHT significantly up‐regulated c‐jun expression through extracellular stress‐regulated kinase (ERK) activation, and transfection of an antisense oligonucleotide for c‐jun or ERK inhibition by PD98059 cancelled DHT‐mediated suppression of radiation‐induced transactivation of Fas gene and sensitization to Fas‐mediated apoptosis.

Conclusions: Radiation‐induced Fas sensitization in prostate cancer cell was mediated through p53‐dependent transactivation of the Fas gene, which can be blocked by androgen stimulation mainly through induction of c‐jun.     

Therapeutic potential of 5‐[125I]iodo‐2′‐deoxyuridine and methotrexate in the treatment of advanced neoplastic meningitis

Purpose: To assess the therapeutic potential of methotrexate (MTX) and 5‐[¹²⁵I]iodo‐2′‐deoxyuridine (¹²⁵IdUrd) administered sequentially in rats bearing advanced (ten‐day‐old) intrathecal (i.t.) TE671 human rhabdomyosarcoma tumours.

Materials and methods: Nude rats were injected with TE671 cells through an i.t. placed catheter. Ten days later, the animals were injected i.t. over a 12‐day period with (i) saline daily, (ii) MTX every other day, (iii) ¹²⁵IdUrd every other day, or (iv) MTX and ¹²⁵IdUrd on alternating days. Onset of paralysis was determined as a function of time, and the medians for onset (M), percentage of cells killed (% kill), and log cell kill were calculated.

Results: The data show that (i) injection of MTX leads to a moderate delay in the onset of paralysis (M_MTX=29?d versus M_saline=20?d), (ii) administration of ¹²⁵IdUrd is more effective (M_IdUrd=36?d), and (iii) sequential administration of MTX–¹²⁵IdUrd further increases the therapeutic efficacy of ¹²⁵IdUrd (M_MTX–IdUrd=47?d).

Conclusions: Intrathecal injection of MTX–¹²⁵IdUrd is efficacious in the therapy of advanced intrathecal tumours.     

Assessment of DNA damage produced by 125I‐triplex‐forming oligonucleotides in cells

Purpose: Triplex‐forming oligodeoxyribonucleotides (TFOs) bind specifically to their target sequences by forming hydrogen bonds within the major groove of the target duplex. When labeled with Auger‐electron‐emitting radioisotopes, TFOs are able to damage the target gene in a process named antigene radiotherapy. We compared radiotoxicity and the amount of DNA damage produced within cultured cells by two ¹²⁵I‐labeled TFOs, one with a single target in the genome and another with multiple targets.

Materials and methods: Radiotoxicity was measured by clonogenic assay while DNA damage was assessed by the number of histone γ‐H2AX foci formed at the sites of DNA double strand breaks (DSBs).

Results: The TFO with multiple nuclear targets was 1.7 fold more radiotoxic and produced on average 1.9 fold more γ‐H2AX foci per cell than the TFO with a single target.

Conclusion: Since the two methods gave comparable results, measuring the number of γ‐H2AX foci per decay may be a useful procedure for the assessment of cytotoxic effects and the intranuclear localization of radionuclides when they produce DSBs.     

The Biology of non‐violence

This article reviews the examination of aggression in ethology. It concludes that though ethology establishes a biology of aggression, it does not conclude a biological determinism behind human violence. The article begins by examining this miscomprehension. Ethology shows a strong evolutionary tendency for aggression to be non‐violent behaviour. The human, as a higher order social animal, should conform to this. That we do not behave in this way is not a reflection of biology but that of the unique influence of culture on behaviour. Humans tend to non‐violence, biologically; it is culture that alters that tendency. How this is achieved is examined in the latter part of the article. In conclusion, ethologists, from Lorenz onwards, have argued that while aggression is rooted in human biology, violence is not, but has a cultural root. What culture has developed, it can alter, a positive optimistic message from ethology which is too often overlooked.     

IL‐1β, TNFα and IL‐6 induction in the rat brain after partial‐body irradiation: role of vagal afferents

Purpose: To evaluate the central nervous system neuroimmune and inflammatory responses during the prodromal phase of the acute irradiation syndrome in rat brains after partial‐body exposure (head‐protected) and to investigate the potential neural signalling pathways from the irradiated periphery to the non‐irradiated brain.

Material and methods: The study included four groups of rats: one irradiated group and one sham irradiated group, each containing non‐vagotomized and vagotomized rats. In vagotomized rat groups, the subdiaphragmatic vagal section surgery was carried out 45 days before the irradiation exposure. The rats were partial‐body irradiated with the head shielded with ⁶⁰Co γ‐rays to a dose of 15?Gy. They were sacrificed 6?h after the end of exposure. The hypothalamus, hippocampus, thalamus and cortex were then collected, and the concentrations of IL‐1β, TNFα and IL‐6 in each were measured by ELISA assays.

Results: Six hours after irradiation, IL‐1β levels had increased in the hypothalamus, thalamus and hippocampus, and TNFα and IL‐6 levels had increased significantly in the hypothalamus. Vagotomy before irradiation prevented these responses.

Conclusions: It was concluded that the hypothalamus, hippocampus, thalamus and cortex react rapidly to peripheral irradiation by releasing pro‐inflammatory mediators. The results also show that the vagus nerve is one of the major ascending pathways for rapid signalling to the brain with respect to partial body irradiation.     

Antisense radiotherapy: targeting full‐size mdr1 mRNA with 125I‐labelled oligonucleotides

Purpose: Antisense radiotherapy is an approach based on the targeting of mRNA of specific genes by complementary oligonucleotide probes labelled with an Auger‐electron‐emitting radioisotope. Decay of the Auger emitter should specifically destroy the targeted mRNA while producing minimal damage to the rest of mRNA pool and the nuclear DNA. The feasibility of this approach was investigated by using full‐length human multidrug‐resistance gene (mdr1) mRNA as a target.

Materials and methods: Antisense oligonucleotides were labelled with [¹²⁵I] I‐dCTP by primer extension and annealed to target mRNA. Breaks in the target mRNA were analysed by denaturing polyacrylamide gel electriphoresis.

Results: The efficiency of ¹²⁵I‐labelled antisense oligonucleotides in producing RNA strand breaks was tested on short synthetic RNA and DNA targets. The position and specificity of ¹²⁵I‐induced breaks in the full‐length mRNA were then tested and compared with the cleavage of the target by RNase H. The distribution of the breaks in the longer mRNA is different from that in the short RNA targets, most likely due to a complex folding of RNA strands in the full‐length mRNA.

Conclusions: The authors posit that ¹²⁵I‐labelled antisense probes could be useful not only for targeting mRNA, but also as probes for mRNA folding in vivo.     

Molecular Simulation of Ligand‐Binding with DNA: Implications for 125I‐Labeled Pharmaceutical Design

Purpose: By using computer‐assisted molecular modeling software, to assess the effects of structural modification on the interaction of ¹²⁵I‐labeled iodoHoechst ligands and DNA and to design new analogs with specified distances between the Auger‐electron‐emitting ¹²⁵I atom and the DNA central axis.

Materials and methods: The Lamarckian genetic algorithm (AutoDock 3.0) was used to model the interaction between DNA and m‐iodo‐p‐methoxyHoechst (IMH), a ligand whose binding to the minor groove of DNA has been demonstrated (crystal structure) and which is available in the Protein Data Bank. m‐Iodo‐p‐ethoxyHoechst (IEH), a radioligand we had previously synthesized and characterized, was then docked onto DNA, the IEH–DNA complex minimized, and the binding free energy and inhibition constant (K_i) estimated and compared with those for IMH–DNA. Using the protocol, several novel iodoHoechst analogs (IH‐A and IH‐B) were designed. Finally, Insight II was used to measure the distances between the iodine atom (e.g. ¹²⁵I) of these Hoechst analogs and of 5‐iodo‐2′‐deoxyuridine (IdUrd) and the central axis of the targeted DNA, and these values were correlated with the expected/measured DSB yield following ¹²⁵I decay.

Results: The docking of IMH and DNA leads to a ligand–DNA complex approximately 1?Å RMSD (root mean square deviation) from the crystal‐structure position, and the IEH–DNA complex also has a small RMSD (1.27?Å). The distances between the ¹²⁵I atom and the DNA central axis are estimated as 8.61?Å for IMH, 9.20?Å for IEH and 5.7?Å for IdUrd. For the newly designed analogs, the distances from the ¹²⁵I atom to the central DNA axis are 10.92?Å for IH‐A and 16.39?Å for IH‐B.

Conclusion: These software programs can predict the reactivity of newly designed radiolabelled molecules with their targeted DNA molecules by molecular modeling prior to their chemical synthesis.