Changes in the self ultraviolet fluorescence of HeLa cells undergoing ionizing irradiation

A study was made of the influence of irradiation on the ultra-violet fluorescence respond of the resting HeLa cells being in the stationary growth phase. No change in the cell ultra-violet fluorescence (UVF) intensity was seen immediately after irradiation (1.5 hours). The time dynamics observation of fluorescence intensity changes after irradiation demonstrated the highest values of UVF on the 3rd day--at the start proliferating point. At doses of 10 and 500 rad the action of irradiation on HeLa cells has an opposite UVF respond, compared with the control. The effect of the 500 rad dose irradiation increases the cell UVF intensity on the 3rd recultivating day, but the 10 rad dose irradiation makes it lower compared to the control level. Radiometric analysis makes it clear that HeLa cell UVF changes are not related to the change of protein synthesis with the precursors of 3H-tryptophan.     

Developmental-stage-dependent radiosensitivity of neural cells in the ventricular zone of telencephalon in mouse and rat fetuses

Pregnant ICR mice were treated with single whole-body X-radiation at a dose of 0.24 Gy on day 10, 13, or 15 of gestation. Fetuses were obtained from mothers during 1 and 24 hours after irradiation. Pyknotic cells in the ventricular zone of telencephalon were counted in serial histological sections. Incidence of pyknotic cells peaked during 6 and 9 hours after irradiation in each gestation day group. Then, dose-response curves were obtained 6 hours after 0-0.48 Gy of irradiation. All three dose-response curves showed clear linearity in the dose range lower than 0.24 Gy. Ratios of radiosensitivity estimated from the slopes of dose-response curves in day 10, 13, and 15 groups were 1, 1.4, and 0.4, respectively. These demonstrated that ventricular cells in the day 13 fetal telencephalon were the most radiosensitive among the three different age groups. In order to confirm the presence of the highly radiosensitive stage common to mammalian cerebral cortical histogenesis, pregnant F344 rats were treated with single whole-body gamma-irradiation at a dose of 0.48 Gy on day 13, 14, 15, 17, or 19 of gestation. The incidence of pyknotic cells in the ventricular zone of telencephalon was examined microscopically during 1 and 24 hours after irradiation. The peak incidence was shown 6 hours after irradiation in all the treated groups, and the highest peak incidence was shown in day-15-treated group. The developmental stage of telencephalon of day 15 rat fetuses was comparable to that of day 13 mouse fetuses. Thus, the highest radiosensitivity in terms of acute cell death was shown in the same developmental stage of brain development, i.e., the beginning phase of cerebral cortical histogenesis, in both mice and rats.     

Preserving effects of melatonin on the levels of glutathione and malondialdehyde in rats exposed to irradiation

In this study we investigated whether pretreatment with melatonin was protective against the injury of the central nervous system (CNS) in rats receiving LD(50) whole body irradiation. The wistar rats were randomized into four groups: i) the control group (CG), ii) melatonin-administered group (MG; 1 mg/kg body weight), iii) irradiated group (RG; 6.75 Gy, one dose), and iv) melatonin-administered and irradiated group (MRG). Blood samples were drawn from the rats 24 h after the treatment and plasma glutathione levels were assayed. Plasma glutathione level was significantly higher in RG than CG. The melatonin pretreatment prevented GSH increase induced by irradiation. Lipid peroxidation and glutathione levels of rat cerebral cortex were determined in all groups after 24 h. Cortical malondialdehyde (MDA) was significantly higher in the RG. The melatonin pretreatment prevented cortical MDA increase induced by irradiation. Cortical GSH was significantly lower in RG than the CG. The melatonin pretreatment prevented cortical GSH decrease induced by irradiation. Tissue samples were obtained from cerebral cortex and hypothalamus which also were affected by ionizing irradiation in the CNS and were evaluated with electron microscopy. Histopathological findings showed that LD(50) whole body irradiation resulted in damage of the neuronal cells of CNS. The results obtained from this study demonstrated that pretreatment with melatonin prevented the damage that develops in CNS following irradiation. The beneficial effect of melatonin can be related to protection of the CNS from oxidative injury and preventing the decrease in the level of cortical glutathione.     

Regulation of lipid oxidation and structural state of the nuclear membrane after the irradiation of tumor-bearing animals

Changes of antioxidative activity (AOA), lipid composition and microviscosity of different membrane regions in tumor cell nuclei and in the liver of tumor-host with Ehrlich ascite carcinoma (EAC) after irradiation were studied. On the basis of the obtained data the analysis of the control system of lipid oxidation in the membrane was carried out. This control system involves a relationship between AOA changes, lipid composition, their oxidative ability and the nuclear membrane structure. It was shown that after irradiation the control system in the nuclei of tumor cells had the same state as before irradiation and was different from the normal one. The control system in the nuclei of tumor-host liver after irradiation starts to work in a regime which is characteristic of irradiated cells. It was shown that the principle difference in the control system functioning in tumor and tumor-host nuclei disappeared after irradiation.     

A role for the angiotensin IV/AT4 system in mediating natriuresis in the rat

Angiotensin II (AngII) or Angiotensin IV (AngIV) was infused into the renal artery of anesthetized rats while renal cortical blood flow was measured via laser Doppler flowmetry. The infusion of AngII produced a significant elevation in mean arterial pressure (MAP) with an accompanying decrease in cortical blood flow, glomerular filtration rate (GFR), urine volume, and urine sodium excretion. The infusion of AngIV induced significant increases in renal cortical blood flow and urine sodium excretion, without altering MAP, GFR, and urine volume. Pretreatment infusion with a specific AT1 receptor antagonist, DuP 753, blocked or attenuated the subsequent AngII effects, while pretreatment infusion with the specific AT4 receptor antagonist, Divalinal-AngIV, blocked the AngIV effects. These results support distinct and opposite roles for AngII and AngIV, i.e. AngII acts as an anti-natriuretic agent, while AngIV acts as a natriuretic agent.     

Effects of single gamma-irradiation on the activity of ornithine decarboxylase in the thymus and pulmonary tissue]

In studying the dose (0.1-6 Gy) and time (2 h to 180 days) dependence of ornithine decarboxylase activity, it was found that deviations from the control were more pronounced in the thymus than in the pulmonary tissue. The radiation effect was a function of dose and time after irradiation. A nonmonotonous type of the dose-response curve was observed 7 days after irradiation: the radiation effect with a low dose (0.1 Gy) was opposite to that with sublethal doses (1-6 Gy).     

Two UV-sensitive targets in dorsoanterior specification of frog embryos

Previous work has shown that ultraviolet (UV) irradiation of fertilized frog eggs yields embryos that lack dorsal and anterior structures. The eggs fail to undergo the cortical/cytoplasmic rotation that specifies dorsoventral polarity, and they lack an array of parallel microtubules associated with the rotation. These eggs can be rescued by tilting with respect to gravity, and normal dorsoanterior development occurs. We find here that UV irradiation of Xenopus prophase I oocytes or Rana metaphase I oocytes also causes the dorsoanterior deficient syndrome, but the UV target is different from that in fertilized eggs. Tilting eggs, irradiated as oocytes, with respect to gravity, does not rescue dorsoanterior development, although lithium treatment does. The UV dose required to produce dorsoanterior deficiency for Rana metaphase I oocytes is much less than that for fertilized eggs, and the oocytes can form the array of parallel microtubules and undergo the cortical/cytoplasmic rotation after fertilization. Despite these features of normal development, no dorsoanterior structures form. While the UV target in fertilized eggs is thought to be the parallel microtubules (Elinson & Rowning, 1988; Devl Biol. 128, 185-197), the UV target in the oocytes may be a dorsal determinant.     

Radiation changes in the lipid levels in liver and thymus chromatin of gamma-irradiated rats

A study was made of the lipid content of liver and thymus chromatin of intact and gamma-irradiated (10 Gy) rats 10 and 40 min after irradiation. The composition of the chromatin-bound phospholipids was shown to differ from that of phospholipids of intact nuclei and a nuclear membrane by a much larger content of cardiolipin and sphingomyelin. A decrease in the lipid phosphorus level, increase in the amount of total cholesterol, and a 1.7-fold increase in the cholesterol/phospholipids ratio were observed after irradiation: 40 min after exposure these indices were normalized. The opposite changes were noted in the lipid content of the thymus chromatin: 10 min after irradiation no changes were detected while after 40 min more than a 1.5-fold increase in the cholesterol amount and the cholesterol/phospholipids ratio was registered. The content of cardiolipin was reliably decreased in the chromatin of both organs throughout the entire period of observation.     

Role of the motor area of the cortex in the performance of the postural escape reaction

It has been shown on three dogs that unilateral ablation of the cortical motor area temporally disturbs previously acquired and opposite to the innate postural escape reaction to electric stimulation of the contralateral forepaw by increasing its pressure on the support. After 3-4 months of repeated training, compensation is possible. Bilateral ablation of the motor cortex elicits stable and unreversible disturbance of the acquired reaction. In reorganization of postural coordinations, motor cortex functions are connected with the inhibition of innate coordinations preventing performance of the reaction.     

Plant smells---important determinants in the behavior and rate of development of ixodid disease vectors]

Experiments with nymphs of Ixodes persulcatus and Dermacentor marginatus have shown that the rate and degree of engorgement, dropping off from the mouse, metamorphosis longevity and weight of emerging imagoes change under plant odour influence. The influence of acetone extract vapours of pepper, poplar buds, linden and aspen was tested. Under the influence of the vapour, acting as an attractant for the adults, engorgement weight of their nymphs and the weight of imagoes emerging from them increased; attractants change the nymph-imago metamorphosis duration as well. Repellent acting odours, as a rule, produce an opposite reaction. The phenomenon of the inversion of the infected D. marginatus reaction to the odour is proved in nymphs. Attractant for naive adult ticks (poplar buds) increased the time of feeding and weight of nymphs in comparison with the control. Just the opposite: nymphs infected with tick-borne encephalitis (TBE) virus produce an opposite reaction--weight decrease under influence of poplar buds as the repellent. Importance of the above phenomena for the ticks distribution and TBE epizootiology is discussed.     

Different teratogenic efficacy to mouse fetal CNS of 5-azacytidine in combination with X-irradiation depends on the sequence of successive application.

The single treatment of pregnant mice on day 12 post conception with 5-azacytidine (AzaCr), followed by a single irradiation dose of 200 rad two hours later, is exclusively neurotoxic to the fetus, as shown by a severe hypoplasia of the parieto-occipital regions of the telencephalon. This effect is explicable by the specific function of the mitotic cell population for the integrity of the cortex wall. Combining these two hazards in the reverse manner, i.e., irradiation followed by AzaCr, resulted in no general hypoplastic effect in the forebrain and only caused a depletion of cells in the marginal cortex. This indicates a significantly diminished AzaCr sensitivity of fetal cortical cells subsequent to X-irradiation. In addition, rosette-like cell clustering in the cortex of all X-irradiated animals occurs to a similar degree, irrespective of any additional AzaCr-treatment. The only conformity between these different schedules is that a great portion of the surviving cells is most likely in the DNA synthesizing phase at the time of irradiation. It is therefore concluded that rosette formation starts perferentially from cells injured during the S-phase.     

Hemodynamic component in cerebral compensatory processes following unilateral exclusion of the somatosensory cortex]

In experiments on anesthetised and awake cats the dynamics of the cerebral blood flow was studied by the thermoelectric method in one hemisphere in experimental lesion of the somatosensory zone of the opposite one. Temporary exclusion of the cortical area by cold produced evident hemodynamic changes, i. e. a two-phase vasoreaction and an initial blood flow decrease followed by a prolonged increase of blood supply, in the other hemisphere. Analogous vasoreactions were seen on unilateral extirpation of the cortical layer of the somatosensory zone, as well. Such vasoreactions indicate enhanced activity of the cortical structures in the intact hemisphere and may be considered as a compensatory reaction to the local lesion of certain cortical areas.     

Regulation of Histamine Release and Synthesis in the Brain by Muscarinic Receptors

The cholinergic modulation of histamine release and synthesis was studied in rat brain slices or synaptosomes labeled with L-[3H]histidine. Carbachol in increasing concentrations progressively reduced the K+-induced [3H]histamine release from cortical slices. Pirenzepine, a preferential M1-receptor antagonist, reversed the carbachol effect in an apparently competitive manner and with Ki values of 1-6 X 10(-8) M. 11-[(2-[(Diethylamino)methyl]-1-piperidinyl)acetyl]-5,11-dihydro-6H- pyrido[2,3-b][1,4]benzodiazepine-6-one (AF-DX 116), considered a preferential M2-receptor antagonist, reversed the carbachol effect with a mean Ki of approximately 2 X 10(-7) M. Oxotremorine behaved as a partial agonist in the modulation of histamine release. Neostigmine, an acetylcholinesterase inhibitor, inhibited the K+-induced release of [3H]histamine from cortical slices, and the effect was largely reversed by pirenzepine, an observation suggesting a modulation by endogenous acetylcholine. The effects of carbachol and pirenzepine were observed with slices of other brain regions known to contain histaminergic nerve terminals or perikarya, as well as with cortical synaptosomes. The two drugs also modified, in opposite directions, [3H]histamine formation in depolarized cortical slices. In vivo oxotremorine inhibited [3H]histamine formation in cerebral cortex, and this effect was reversed by scopolamine. When administered alone, scopolamine failed to enhance significantly the 3H- labeled amine formation, a finding suggesting that muscarinic receptors are not activated by endogenous acetylcholine released under basal conditions. It is concluded that muscarinic heteroreceptors, directly located on histaminergic nerve terminals, control release and synthesis of histamine in the brain. These receptors apparently belong to the broad M1-receptor category and may correspond to a receptor subclass displaying a rather high affinity for AF-DX 116.     

Analysis of interhemispheric asymmetries in the space-time organization of human cortical potentials

The study of spatial organization of human cortical potentials with multichannel recording (48 leads) has shown, that different functional conditions of brain (quiet alertness, excitation after caffeine administration, intellectual strain, negative emotional shifts, inhibition after administration of neuroleptics) are accompanied by synchronization changes in the left and right hemispheres specific of each brain condition. Similar shifts may be recorded both in states similar by their phenomenological characteristics (after administration of caffeine and during intellectual strain) and during the opposite levels of alertness (emotional strain and administration of neuroleptics).     

Effect of gamma irradiation on mechanical properties of human cortical bone: influence of different processing methods

The secondary sterilisation by irradiation reduces the risk of infectious disease transmission with tissue allografts. Achieving sterility of bone tissue grafts compromises its biomechanical properties. There are several factors, including dose and temperature of irradiation, as well as processing conditions, that may influence mechanical properties of a bone graft. The purpose of this study was to evaluate the effect of gamma irradiation with doses of 25 or 35?kGy, performed on dry ice or at ambient temperature, on mechanical properties of non-defatted or defatted compact bone grafts. Left and right femurs from six male cadaveric donors aged from 46 to 54?years, were transversely cut into slices of 10?mm height, parallel to the longitudinal axis of the bone. Compact bone rings were assigned to the eight experimental groups according to the different processing method (defatted or non-defatted), as well as gamma irradiation dose (25 or 35?kGy) and temperature conditions of irradiation (ambient temperature or dry ice). Axial compression testing was performed with a material testing machine. Results obtained for elastic and plastic regions of stress-strain curves examined by univariate analysis are described. Based on multivariate analysis it was found that defatting of bone rings had no significant effect on any mechanical parameter studied, whereas irradiation with both doses decreased significantly the ultimate strain and its derivative toughness. The elastic limit and resilience were significantly increased by irradiation with the dose 25?kGy, but not 35?kGy, when the time of irradiation was longer. Additionally, irradiation at ambient temperature decreased maximum load, elastic limit, resilience, and ultimate stress. As strain in the elastic region was not affected, decreased elastic limit resulted in lower resilience. The opposite phenomenon was observed in the plastic region, where in spite of the lower ultimate stress, the toughness was increased due to the increase in the ultimate strain. The results of our study suggest that there may be an association between mechanical properties of bone tissue grafts and the damage process of collagen structure during gamma irradiation. This collagen damage in cortical bone allografts containing water does not depends on the temperature of irradiation or defatting during processing if dose of gamma irradiation does not exceed 35?kGy.     

Effects of gamma-irradiation on the gonadal cells of Drosophila melanogaster under varying conditions of hybrid dysgenesis

Comparative analysis was carried out with respect to the results of combined effects of gamma-irradiation and transposition of mobile elements in Drosophila, depending on the succession of their application. As turned out, introduction of the P and hobo elements into the M' line, prior to irradiation, resulted in decreased number of unfertilized eggs and reduced the proportion of flies killed at the larval and pupal stages. However, opposite effects were shown, when the P element was introduced following irradiation: the number of unfertilized eggs and that of the flies killed at the larval and pupal stages has significantly increased, as compared to the control. Interaction between the processes induced at the level of DNA repair both by gamma-irradiation and the P' elements' transposition is suggested.     

Unveiling the effects of the secretome of mesenchymal progenitors from the umbilical cord in different neuronal cell populations

It has been previously shown that the secretome of Human Umbilical Cord Perivascular Cells (HUCPVCs), known for their mesenchymal like stem cell character, is able to increase the metabolic viability and hippocampal neuronal cell densities. However, due to the different micro-environments of the distinct brain regions it is important to study if neurons isolated from different areas have similar, or opposite, reactions when in the presence of HUCPVCs secretome (in the form of conditioned media-CM). In this work we: 1) studied how cortical and cerebellar neuronal primary cultures behaved when incubated with HUCPVCs CM and 2) characterized the differences between CM collected at two different conditioning time points. Primary cultures of cerebellar and cortical neurons were incubated with HUCPVCs CM (obtained 24 and 96 h after three days of culturing). HUCPVCs CM had a higher impact on the metabolic viability and proliferation of cortical cultures, than the cerebellar ones. Regarding neuronal cell densities it was observed that with 24 h CM condition there were higher number MAP-2 positive cells, a marker for fully differentiated neurons; this was, once again, more evident in cortical cultures. In an attempt to characterize the differences between the two conditioning time points a proteomics approach was followed, based on 2D Gel analysis followed by the identification of selected spots by tandem mass spectrometry. Results revealed important differences in proteins that have been previously related with phenomena such as neurl cell viability, proliferation and differentiation, namely 14-3-3, UCHL1, hsp70 and peroxiredoxin-6. In summary, we demonstrated differences on how neurons isolated from different brain regions react to HUCPVCs secretome and we have identified different proteins (14-3-3 and hsp70) in HUCPVCs CM that may explain the above-referred results.     

Interhemispheric connections in the visual cortex of cats reared with bilateral strabismus

We have determined the spatial distribution of retrograde labelled callosal cells after microiontophoretic horseradish peroxidase injections into the single cortical columns of area 17, 18 in cats reared with bilateral convergent strabismus. The obtained strabismus angle was in the range 10-35 degrees. The zone of labelled cells was located asymmetrically in respect to location of injected column in opposite hemisphere. Some cells were revealed in the transition zone 17/18 and their retinotopic coordinates corresponded to the injected column, as was shown in intact cats. Other labelled cells were located in areas 17, 18, in clusters approximately in 1000 mkm from marginal clusters of transition zone. Analysis of labeling in lateral geniculate nucleus has shown that most of the injected columns were driven by ipsilateral eye. The data obtained may be interpreted as evidence of eye-specificity of monosynaptic callosal connections. The functional role in such connections changes in cats with bilateral strabismus is discussed.     

Memory Consolidation in the Cerebellar Cortex

Several forms of learning, including classical conditioning of the eyeblink, depend upon the cerebellum. In examining mechanisms of eyeblink conditioning in rabbits, reversible inactivations of the control circuitry have begun to dissociate aspects of cerebellar cortical and nuclear function in memory consolidation. It was previously shown that post-training cerebellar cortical, but not nuclear, inactivations with the GABA_A agonist muscimol prevented consolidation but these findings left open the question as to how final memory storage was partitioned across cortical and nuclear levels. Memory consolidation might be essentially cortical and directly disturbed by actions of the muscimol, or it might be nuclear, and sensitive to the raised excitability of the nuclear neurons following the loss of cortical inhibition. To resolve this question, we simultaneously inactivated cerebellar cortical lobule HVI and the anterior interpositus nucleus of rabbits during the post-training period, so protecting the nuclei from disinhibitory effects of cortical inactivation. Consolidation was impaired by these simultaneous inactivations. Because direct application of muscimol to the nuclei alone has no impact upon consolidation, we can conclude that post-training, consolidation processes and memory storage for eyeblink conditioning have critical cerebellar cortical components. The findings are consistent with a recent model that suggests the distribution of learning-related plasticity across cortical and nuclear levels is task-dependent. There can be transfer to nuclear or brainstem levels for control of high-frequency responses but learning with lower frequency response components, such as in eyeblink conditioning, remains mainly dependent upon cortical memory storage.