Effects of mixed neutron-gamma total-body irradiation on physical activity performance of rhesus monkeys

Behavioral incapacitation for a physical activity task and its relationship to emesis and survival time following exposure to ionizing radiation were evaluated in 39 male rhesus monkeys (Macaca mulatta). Subjects were trained to perform a shock avoidance activity task for 6 hr on a 10-min work/5-min rest schedule in a nonmotorized physical activity wheel. Following stabilization of performance, each subject received a single, pulsed dose of mixed neutron-gamma, whole-body radiation (n/gamma = 3.0) ranging between 1274 and 4862 rad. Performance testing was started 45 sec after exposure. A dose-response function for early transient incapacitation (ETI) during the first 2 hr after irradiation was fitted, and the median effective dose (ED50) was calculated to be 1982 rad. More subjects experienced both incapacitation and emesis in this study than has been reported for other behavioral tasks in similar radiation fields. Analysis done on the relationship of dose to ETI, emesis, and survival time found (a) a significant relationship between the radiation dose and the number and duration of ETIs; (b) no correlation between emesis and dose, survival time, or ETI; (c) no relation between survival time and ETI at any dose; and (d) no significant difference in survival time for dose groups between 1766 +/- 9 (SEM) and 2308 +/- 23 rad.     

The electrical activity of the monkey brain in the period of early transient incapacity during gamma-irradiation at high dose rates

Changes in the electroencephalogram (EEG) of Macaca fascicularis during early transient incapacitation (ETI) were shown to correlate with the dynamics of clinical manifestations of the damage. Irradiation caused desynchronization of EEG followed by a generalized retardation of its fluctuations reaching the maximum at the height of ETI. EEG disturbances in animals during the comatose phase of ETI indicated a severe inhibition of the brain cortex functional activity.     

Induction of Hsp70 by desiccation, ionising radiation and heat-shock in the eutardigrade Richtersius coronifer

The physiology and biochemistry behind the extreme tolerance to desiccation shown by the so-called anhydrobiotic animals represents an exciting challenge to biology. The current knowledge suggests that both carbohydrates and proteins are often involved in protecting the dry cell from damage, or in the repair of induced damage. Tardigrades belong to the most desiccation-tolerant multicellular organisms, but very little research has been reported on the biochemistry behind desiccation tolerance in this group. We quantified the induction of the heat-shock protein Hsp70, a very wide-spread stress protein, in response to desiccation, ionising radiation, and heating, in the anhydrobiotic tardigrade Richtersius coronifer using an immuno-westernblot method. Elevated levels of Hsp70 were recorded after treatment of both heat and ionising radiation, and also in rehydrated tardigrades after a period of desiccation. In contrast, tardigrades in the desiccated (dry) state had reduced Hsp70 levels compared to the non-treated control group. Our results suggest that Hsp70 may be involved in the physiological and biochemical system underlying desiccation (and radiation) tolerance in tardigrades, and that its role may be connected to repair processes after desiccation rather than to biochemical stabilization in the dry state.     

The effect of ionizing radiation at superhigh doses on the processes of dopamine release and reuptake by nerve endings in different sections of the brain]

Rats exposed to fast 24 MeV electrons (100 Gy) at the state of early transient incapacity (ETI) exhibited active release and reuptake of dopamine in nerve terminals of the striatum. No changes in the indices under study were found in rats exposed to 25 Gy radiation that did not cause the ETI development. The in vitro irradiation of the isolated synaptosomes (100 Gy) inhibited dopamine reuptake and increased the number of sites of 3H-spiperone binding to D2-receptors in a membrane fraction isolated from the striatum.     

Radiobiological considerations of re-irradiation tolerance of the spinal cord

Re-irradiation tolerance of the spinal cord depends upon the volume of the spinal cord irradiated, the total dose, the dose per fractional, the elapsed time between the treatments and the region of the spinal cord involved. Clinical data on the retreatment tolerance of the spinal cord are sparse and inconclusive. Radiobiological laboratory evidence has indicated the presence of long term recovery of the spinal cord damage. Fractionation sensitivity during reirradiation is comparable with the first session of radiation treatment. After an initial dose of 45 Gy, 50% recovery has been reported by Schultheiss and Stephens for an elapsed period of two years for re-irradiation considerations.     

Effect of cycloheximide on skin and renal radiation tolerance in the rat

The effect of cycloheximide (CHM) on skin and renal radiation tolerance in the rat has been studied. When administered 24 hr prior to a range of single radiation doses to the hind limbs, the drug protected against skin damage. When administered at intervals of 45 min to 100 hr prior to single-dose irradiation of the kidneys, no protection against renal injury, as manifested by blood pressure, urine creatinine level, and lethality, was observed. CHM-induced alteration in the cell cycle may confer radioprotection to a rapidly proliferating cell renewal system such as the skin and exert no radioprotective action in slowly proliferative tissue such as kidney.     

Crystal structure of a Kunitz-type trypsin inhibitor from Erythrina caffra seeds

The trypsin inhibitor DE-3 from Erythrina caffra (ETI) belongs to the Kunitz-type soybean trypsin inhibitor (STI) family and consists of 172 amino acid residues with two disulphide bridges. The amino acid sequence of ETI shows high homology to other trypsin inhibitors from the same family but ETI has the unique ability to bind and inhibit tissue plasminogen activator. The crystal structure of ETI has been determined using the method of isomorphous replacement and refined using a combination of simulated annealing and conventional restrained least-squares crystallographic refinement. The refined model includes 60 water molecules and 166 amino acid residues, with a root-mean-square deviation in bond lengths from ideal values of 0.016 A. The crystallographic R-factor is 20.8% for 7770 independent reflections between 10.0 and 2.5 A. The three-dimensional structure of ETI consists of 12 antiparallel beta-strands joined by long loops. Six of the strands form a short antiparallel beta-barrel that is closed at one end by a "lid" consisting of the other six strands coupled in pairs. The molecule shows approximate 3-fold symmetry about the axis of the barrel, with the repeating unit consisting of four sequential beta-strands and the connecting loops. Although there is no sequence homology, this same fold is present in the structure of interleukin-1 alpha and interleukin-1 beta. When the structure of ETI and interleukin-1 beta are superposed, the close agreement between the alpha-carbon positions for the beta-strands is striking. The scissile bond (Arg63-Ser64) is located on an external loop that protrudes from the surface of the molecule and whose architecture is not constrained by secondary structure elements, disulphide bridges or strong electrostatic interactions. The hydrogen bonds made by the side-chain amide group of Asn12 play a key role in maintaining the three-dimensional structure of the loop. This residue is in a position corresponding to that of a conserved asparagine in the Kazal inhibitor family. Although the overall structure of ETI is similar to the partial structure of STI, the scissile bond loop is displaced by about 4 A. This displacement probably arises from the fact that the structure of STI has been determined in a complex with trypsin but could possibly be a consequence of the close molecular contact between Arg63 and an adjacent molecule in the crystal lattice.     

Amphibian defenses against ultraviolet-B radiation

As part of an overall decline in biodiversity, amphibian populations throughout the world are disappearing. There are a number of potential causes for these declines, including those related to environmental changes such as increasing ultraviolet-B (UV-B) radiation due to stratospheric ozone depletion. UV-B radiation can kill amphibian embryos or can cause sublethal effects that can harm amphibians in later life stages. However, amphibians have defenses against UV-B damage that can limit damage or repair it after exposure to UV-B radiation. These include behavioral, physiological, and molecular defenses. These defenses differ interspecifically, with some species more able to cope with exposure to UV-B than others. Unfortunately, the defense mechanisms of many species may not be effective against increasing persistent levels of UV-B radiation that have only been present for the past several decades due to human-induced environmental damage. Moreover, we predict that persistent UV-B-induced mortality and sublethal damage in species without adequate defenses could lead to changes in community structure. In this article we review the effects of UV-B radiation on amphibians and the defenses they use to avoid solar radiation and make some predictions regarding community structure in light of interspecific differences in UV-B tolerance.     

An Arabidopsis Mutant Tolerant to Lethal Ultraviolet-B Levels Shows Constitutively Elevated Accumulation of Flavonoids and Other Phenolics

The isolation and characterization of mutants hypersensitive to ultraviolet (UV) radiation has been a powerful tool to learn about the mechanisms that protect plants against UV-induced damage. To increase our understanding of the various mechanisms of defense against UVB radiation, we searched for mutations that would increase the level of tolerance of Arabidopsis plants to UV radiation. We describe a single gene dominant mutation (uvt1) that leads to a remarkable tolerance to UVB radiation conditions that would kill wild-type plants. Pigment analyses show a constitutive increase in accumulation of UV-absorbing compounds in uvt1 that increases the capacity of the leaves to block UVB radiation and therefore is likely to be responsible for the elevated resistance of this mutant to UVB radiation. These increases in absorption in the UV region are due, at least in part, to increases in flavonoid and sinapate accumulation. Expression of chalcone synthase (CHS) mRNA was shown to be constitutively elevated in uvt1 plants, suggesting that the increases in absorption may be a consequence of changes in gene expression. Expression of CHS in uvt1 was shown to be still inducible by UV, indicating that the uvt1 lesion may not affect the UV-mediated regulation of CHS gene expression. Our data support an important role for UV screens in the overall protection of plants to UVB radiation. The uvt1 mutant could prove to be an important tool to elucidate further the exact role of UV-absorbing pigments in UV protection as well as the relative contribution of other mechanisms to the overall tolerance of plants to UV radiation.     

Physiological changes leading to anhydrobiosis improve radiation tolerance in Polypedilum vanderplanki larvae

High tolerance against various extreme environments exhibited by some anhydrobionts might be due to being almost completely desiccated, a state where little or no chemical reactions occur. We have shown that anhydrobiotic larvae of Polypedilum vanderplanki have higher tolerance against both high- and low-linear energy transfer (LET) radiation than hydrated larvae. It is of great interest to know how the desiccating larvae gain radiation tolerance. We therefore examined effects of high-LET radiation on four kinds of larvae: (1) normal hydrated (intact) larva, (2) intermediates between the anhydrobiotic and normal hydrated state, (3) almost completely dehydrated (anhydrobiotic) larvae, and (4) immediately rehydrated larvae that are assumed to have a similar molecular profile to anhydrobiotic larvae. The intermediates and immediately rehydrated larvae survived longer after high-LET radiation than intact larvae, indicating that radiation tolerance could be enhanced even in hydrated larvae. Physiological changes toward anhydrobiosis, e.g. accumulation of protectants or increasing damage repair capacity, correlate with improved radiation tolerance in hydrated larvae. In addition, almost complete desiccation further enhanced radiation tolerance, possibly in a different way from the hydrated larvae.     

Binding of the Kunitz-type trypsin inhibitor DE-3 from Erythrina caffra seeds to serine proteinases: a comparative study.

The effect of pH and temperature on kinetic and thermodynamic parameters (i.e., k(on),k(off),Ka,delta G0, delta H0 and delta S0 values) for the binding of the Kunitz-type trypsin inhibitor DE-3 from Erythrina caffra seeds (ETI) to bovine beta-trypsin, bovine alpha-chymotrypsin, the human tissue plasminogen activator, human alpha-, beta- and gamma-thrombin, as well as the M(r) 33,000 and M(r) 54,000 species of the human urinary plasminogen activator (also named urokinase) has been investigated. At pH 8.0 and 21.0 degrees C: (i) values of the second-order rate constant (K(on)) for the proteinase:ETI complex formation vary between 8.7 x 10(5) and 1.4 x 10(7)/M/s; (ii) values of the dissociation rate constant (k(off)) for the proteinase: ETI complex destabilization range from 3.7 x 10(-5) to 1.4 x 10(-1)/s; and (iii) values of the association equilibrium constant (Ka) for the proteinase:ETI complexation change from < 1.0 x 10(4) to 3.8 x 10(11)/M. Thus, differences in k(off) values account mostly for the large changes in Ka values for ETI binding. The affinity of ETI for the serine proteinases considered can be arranged as follows: bovine beta-trypsin > human tissue plasminogen activator > bovine alpha-chymotrypsin > human alpha-, beta- and gamma-thrombin approximately M(r) 33,000 and M(r) 54,000 species of the human urinary plasminogen activator. Moreover, the serine proteinase:ETI complex formation is an endothermic, entropy-driven, process.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hyperthermia in a differentiating murine erythroleukemia cell line: cell killing by heat and radiation

The survival response of Friend erythroleukemia cells (a differentiating cell system) to heat and radiation has been examined. The Friend erythroleukemia cells (FELC) were more heat and radiation sensitive than V79 cells, and the heat and radiation survival curves possessed shoulders, showing the ability of the cells to accumulate sublethal damage. Thermal tolerance was expressed after prolonged heating at 41.0-42.0 degrees C. Thermal radiosensitization by heating at 42.0 or 45.0 degrees C was greatest for simultaneous heat and radiation treatments, and recovery occurred when the cells were incubated at 37 degrees C between the heat and radiation or radiation and heat treatments. Arrhenius analysis of the FELC heat survival data showed that the curve for thermal inactivation possessed a break at about 43.0 degrees C and that the thermal inactivation energies above and below the break point were comparable to those for V79 cells and other cell lines reported in the literature.     

Acute post-irradiation canine intestinal blood flow

Radiation-induced early transient incapacitation (ETI) is accompanied by severe systemic hypotension, during which arterial blood pressure often decreases to less than 50 per cent of normal. One haemodynamic compensatory mechanism is increased peripheral resistance due to vasoconstriction. This vasoconstriction in the small intestine of dogs is disproportionately increased during haemorrhagic or endotoxic shock, and intestinal ischaemia is frequent. In an attempt to elucidate mechanisms underlying radiation-induced ETI and the gastrointestinal radiation syndrome, canine intestinal submucosal blood flow was measured by the hydrogen polarographic technique, both before and after exposure to gamma radiation. Systemic blood pressures, blood gases and haematocrits were determined simultaneously. Data obtained from 12 sham-irradiated dogs and 12 irradiated dogs indicated that 90 Gy, whole-body, gamma radiation produced a 31 per cent decrease in systemic mean blood pressure beginning within 20 min post-irradiation and lasting for at least 90 min. However, the intestinal submucosal blood flow did not decrease as anticipated, but it exhibited an actual post-irradiation increase. This increase in post-irradiation intestinal submucosal blood flow began within 5 min after irradiation and lasted for at least 90 min. Post-irradiation haematocrits were 10.5 per cent higher than those obtained before irradiation and those obtained from sham-irradiated subjects. Histopathological examination of ileal mucosa revealed significant pathologic lesions in some irradiated animals within two hours after exposure.     

Effector-triggered immunity mediated by the Pto kinase

Pto was the first disease-resistance gene cloned from a plant that confers recognition of a specific pathogen. The intracellular protein kinase that it encodes activates an immune response in tomato (Solanum lycopersicum) to bacterial speck disease by interacting with either the AvrPto or AvrPtoB type III effector proteins that are delivered into the plant cell by Pseudomonas syringae pathovar tomato. This recognition event triggers signaling pathways leading to effector-triggered immunity (ETI), which inhibits pathogen growth. During the past 15 years, ~25 genes have been identified by loss-of-function studies to have a role in Pto-mediated ETI. Here, we review the experimental approaches that have been used in these studies, discuss the proteins that have been identified and characterized, and present a current model of Pto-mediated ETI.     

Effects of UV-B radiation on photosynthesis and growth of terrestrial plants

The photosynthetic apparatus of some plant species appears to be well-protected from direct damage from UV-B radiation. Leaf optical properties of these species apparently minimizes exposure of sensitive targets to UV-B radiation. However, damage by UV-B radiation to Photosystem II and Rubisco has also been reported. Secondary effects of this damage may include reductions in photosynthetic capacity, RuBP regeneration and quantum yield. Furthermore, UV-B radiation may decrease the penetration of PAR, reduce photosynthetic and accessory pigments, impair stomatal function and alter canopy morphology, and thus indirectly retard photosynthetic carbon assimilation. Subsequently, UV-B radiation may limit productivity in many plant species. In addition to variability in sensitivity to UV-B radiation, the effects of UV-B radiation are further confounded by other environmental factors such as CO₂, temperature, light and water or nutrient availability. Therefore, we need a better understanding of the mechanisms of tolerance to UV-B radiation and of the interaction between UV-B and other environmental factors in order to adequately assess the probable consequences of a change in solar radiation.Abbreviations A_max light and CO₂ saturated rate of oxygen evolution - Ci internal CO₂ concentration - F_v/F_m ratio of variable to total fluorescence yield - PAR photosynthetically active radiation (400–700 nm) - PS II Photosystem II - _app apparent quantum yield of photosynthesis - SLW specific leaf weight - UV-B ultraviolet-B radiation between 290–320 nm     

刺桐属胰蛋白酶抑制剂的结构与生物活性关系

刺桐胰蛋白酶抑制剂（ETI）属于丝氨酸蛋白酶抑制剂,它能和胰蛋白酶及瑞替普酶（r-PA）等精氨酸特征性的丝氨酸蛋白酶发生了可逆亲合作用,根据此特性可将ETI作为固定配基制备成亲合填料,用于大规模高效分离r-PA,满足临床对溶栓制剂r-PA的大量需求,本对刺桐属胰蛋白酶抑制剂的结构与抑制活性关系进行综述。     

Phosphorylation of human INO80 is involved in DNA damage tolerance

Double strand breaks (DSBs) are the most serious type of DNA damage. DSBs can be generated directly by exposure to ionizing radiation or indirectly by replication fork collapse. The DNA damage tolerance pathway, which is conserved from bacteria to humans, prevents this collapse by overcoming replication blockages. The INO80 chromatin remodeling complex plays an important role in the DNA damage response. The yeast INO80 complex participates in the DNA damage tolerance pathway. The mechanisms regulating yINO80 complex are not fully understood, but yeast INO80 complex are necessary for efficient proliferating cell nuclear antigen (PCNA) ubiquitination and for recruitment of Rad18 to replication forks. In contrast, the function of the mammalian INO80 complex in DNA damage tolerance is less clear. Here, we show that human INO80 was necessary for PCNA ubiquitination and recruitment of Rad18 to DNA damage sites. Moreover, the C-terminal region of human INO80 was phosphorylated, and overexpression of a phosphorylation-deficient mutant of human INO80 resulted in decreased ubiquitination of PCNA during DNA replication. These results suggest that the human INO80 complex, like the yeast complex, was involved in the DNA damage tolerance pathway and that phosphorylation of human INO80 was involved in the DNA damage tolerance pathway. These findings provide new insights into the DNA damage tolerance pathway in mammalian cells.     

Analysis of DNA Repair and Protection in the Tardigrade Ramazzottius varieornatus and Hypsibius dujardini after Exposure to UVC Radiation

Tardigrades inhabiting terrestrial environments exhibit extraordinary resistance to ionizing radiation and UV radiation although little is known about the mechanisms underlying the resistance. We found that the terrestrial tardigrade Ramazzottius varieornatus is able to tolerate massive doses of UVC irradiation by both being protected from forming UVC-induced thymine dimers in DNA in a desiccated, anhydrobiotic state as well as repairing the dimers that do form in the hydrated animals. In R. varieornatus accumulation of thymine dimers in DNA induced by irradiation with 2.5 kJ/m² of UVC radiation disappeared 18 h after the exposure when the animals were exposed to fluorescent light but not in the dark. Much higher UV radiation tolerance was observed in desiccated anhydrobiotic R. varieornatus compared to hydrated specimens of this species. On the other hand, the freshwater tardigrade species Hypsibius dujardini that was used as control, showed much weaker tolerance to UVC radiation than R. varieornatus, and it did not contain a putative phrA gene sequence. The anhydrobiotes of R. varieornatus accumulated much less UVC-induced thymine dimers in DNA than hydrated one. It suggests that anhydrobiosis efficiently avoids DNA damage accumulation in R. varieornatus and confers better UV radiation tolerance on this species. Thus we propose that UV radiation tolerance in tardigrades is due to the both high capacities of DNA damage repair and DNA protection, a two-pronged survival strategy.     

Radiation induced oxidative stress: II Studies in liver as a distant organ of tumor bearing mice

Since the radiation dose tolerance of normal tissues/organs away from the site of tumor influences the success of radiation therapy of cancer, and antioxidant status is likely to be one of the factors to determine the tolerance; the radioresponse of antioxidant enzymes has been examined in the liver as a representative distant organ in the tumorbearing mice.Swiss albino male mice (7–8 weeks old) with Ehrlich solid tumor in the thigh pad were irradiated with different doses of radiation (0–9 Gy) at a dose rate of 0.0153 Gy/s and the specific activities of enzymes involved in the free radical metabolism were determined in the liver. Except GST, the activities of SOD, DTD and Gly I as well as the GSH content were found to be higher in the liver of tumorbearing mice compared to the nontumor bearing mice. The catalase activity progressively decreased with dose in both the groups of mice. However, the activity was relatively higher in the liver of tumor bearing mice than the control. Thus, the radioresponse of antioxidant enzymes seemed to be significantly different in the liver of tumorburdened mice compared to controls. The enhanced activities might be due to relatively more damage caused by radiation. The higher levels of NO· and peroxidative damage in the liver of tumorbearing mice probably suggest this possibility. These findings of the present work might have some serious implications as the increased radiationdamage of the distant normal organs (due to tumor burden) is likely to adversely affect the therapeutic gain.