[Radiation-induced DNA fragmentation in cells of somatic and generative tissues of Drosophila melanogaster]

The levels of DNA fragmentation (using a neutral version of the "Comet assay" method) in the cells of somatic (brain ganglia) and generative (male gonad) tissues of the inbred individuals of the Drosophila wild-type developing in different conditions of a chronic irradiation were estimated. It was found that the radiobiological effect depends on the genotype and cytotype. Irradiation at low doses (0.42 mGy/h) induces the DNA damage in somatic cells of all the studied lines Drosophila in the same way. With the increase in the intensity of chronic irradiation (3.5mGy/h) a significant level of DNA breaks in neuroblasts was observed only for Harwich and Oregon-R stocks, in the cells of male gonad--for all the studied genotypes.

[Aging rate after continual low dose irradiation of drosophila strains with apoptosis deregulation]

In this article the results of investigations of interrelation between radio-induced apoptosis in larvae nervous system and aging in imago are presented. It was shown that the apoptosis level of larvae nervous ganglion 2.5 folds increased after exposure to ionizing radiation (54 cGy). Irradiation of stocks with higher apoptosis induction sensitivity, bearing mutations of inhibitor apoptosis protein th (allele th1 and th4) and wild type strain Berlin leaded to elevation of activity at all ages and accordingly to decreasing of aging speed. Whereas in stocks with lower apoptosis induction sensitivity (with mutations of genes rpr, grim, hid, dArk and Dcp-1) this effect was not observed. The obtained results suggested that radiation-induced apoptosis could be one of the mechanisms preventing aging.

Irradiation influences the expression of substance P and enkephalin in the rat larynx

The effects of radiotherapy on neuropeptide expression in the rat larynx were studied. Irradiation was given for five days, 6 or 8 Gray daily. Ten days after the end of irradiation, the larynx, the laryngeal nerves and different ganglia related to the larynx were dissected out from irradiated and control animals and processed for neuropeptide immunohistochemistry. There was an increased immunolabelling for two of the neuropeptides tested, substance P and enkephalin, in the innervation of the subglottic glands and in the acetylcholinesterase-positive ganglionic cells of the local ganglia. These cells were interpreted as representing postganglionic parasympathetic ganglionic cells. The changes seen in the subglottic glands were interpreted as most likely being related to the changing pattern of staining seen in the local ganglia. No changes in substance P- and enkephalin expression were observed in other laryngeal structures, the nodose ganglia, superior cervical ganglia or laryngeal nerve paraganglia. Thus, in certain respects neuropeptide expression in the larynx is modulated by radiotherapy. Since neuropeptides have both neurotransmitter and/or neuromodulator effects in airway tissue and since they show effects as growth factors, the occurrence of this plasticity in neuropeptide expression should be taken into consideration in future studies examining the effects of irradiation on normal/diseased airway tissues.

Effects of irradiation on neuropeptide expression in rat salivary gland and spinal cord

It is well-known that a large number of factors can influence the expression of neuropeptides in the nervous system. In the present study, the effects of unilateral and bilateral irradiation to the rat head and neck on the expression of neuropeptides in the innervation of the submandibular gland and in the ganglionic cells of the submandibular ganglion was examined ten days and six months after treatment. Antisera directed against enkephalin and bombesin and immunohistochemical methods were used. The effects of bilateral irradiation on the staining pattern of various neuropeptides in the cervical spinal cord were also studied. In the submandibular gland and in the submandibular ganglionic cells, there was a markedly increased neuropeptide expression ten days after bilateral treatment, as seen after staining with both antisera used, while no changes occurred after unilateral treatment. Six months after treatment, the pattern of neuropeptide expression in the submandibular gland/ganglion corresponded to that seen in controls. Irradiation did not lead to any changes in the staining pattern of neuropeptides in the spinal cord. The observations show that there is a great complexity in the susceptibility of nervous tissues to radiotherapy with respect to influences on the expression of neuropeptides.

Changes in neurons, neuroendocrine cells and nerve fibers in the lamina propria of irradiated bowel

Damage to bowel often complicates radiotherapy for abdominal and pelvic malignancy. The symptoms of chronic irradiation enteropathy, which often include intractable diarrhoea, are generally attributed to vascular injury. We have examined specimens of bowel resected from patients who had been therapeutically irradiated to assess the extent of injury to the enteric nerve plexuses. To facilitate visualisation of nerve fibres and cells of neural or neuroendocrine origin, sections were immunostained with antibodies to neuron-specific enolase or PGP 9.5, widely used markers of nerves and neurons. Electron microscopy was performed in selected cases. In 27 out of 33 specimens the number of nerve fibres in the lamina propria was obviously increased compared to that in control material. Scattered cells with the histological, immunohistochemical and ultrastructural features of ganglion cells were noted within the lamina propria in 23 of the specimens, and in 18 cases so-called neuroendocrine cells, not normally seen in this location, were also present. These radiation-induced changes in the innervation of the bowel may contribute to the symptoms of chronic radiation enteropathy.

An improved technique for hyaluronan histochemistry using microwave irradiation

A hyaluronan binding protein (HABP), extracted from cartilage, was biotin-labelled and used for histochemical localization of hyaluronan (HA) in tissue sections. Various tissues were fixed for a mixture of formaldehyde and glutaraldehyde during microwave irradiation. The microwave oven when set at 700 W and 45 degrees C yielded an intense and specific staining of HA. Under these conditions the relative proportion of the two aldehydes did not influence the staining intensity. Aldehyde fixation during microwave irradiation for HA histochemistry, (1) save time, (2) eliminates the use of cetylpyridinium chloride (CPC), and (3) improves the reproducibility.

The cross-linking reagent dimethyl suberimate modifies the target size of an insect nervous system nicotinic acetylcholine receptor

Radiation inactivation and simple target theory were employed to determine the molecular weight of an insect CNS alpha-bungarotoxin binding component in the presence and absence of a cross-linking reagent, dimethyl suberimate. In the presence of the cross-linker, the number of binding sites decreased, and the apparent molecular weight (236,000) was approximately double the control value (112,000). This, together with sedimentation data, suggests that the lower value represents only a portion of the insect nicotinic receptor molecule. A model is presented to account for the increase in target size and reduction in the number of alpha-[3H]bungarotoxin binding sites in the presence of dimethyl suberimate.

[Effect of ionizing radiation on the functional state of Helix pomatia neurons. Glucose metabolism and ATP levels]

The ATP level in nerve ganglia of Helix pomatia was shown to decrease 15 and 30 min, and 1 and 3 h following irradiation (5.16 C/kg). The decrease was maximum in 60 min. The absorption and utilization of glucose via a pentose-phosphate route and in the Krebs cycle did not substantially change. It is concluded that the energy supply of nerve cells under study is not responsible for the decrease in the ATP level.

[Effect of x-rays on the pacemaker neurons of Helix pomatia]

The effect of superlethal doses of ionizing radiation on exciting and electrical properties of giant neurons of the central nervous system of Helix pomatia has been investigated. At early times following irradiation the excitability does not significantly change whereas the membrane potential, resistance and pump-induced hyperpolarization increase. At later times, a stabilization of these parameters is followed by a diminution of resistance, a decrease of membrane potential and pump-induced hyperpolarization, and even the neuron death.

[Effect of ionizing radiation on the functional state of Helix pomatia neurons. The systems of Na+ and K+ transport]

The influence of ionizing radiation (5.16 C/kg) on passive and active Na+ and K+ transfer within the giant neurons of edible snail (Helix pomatia) has been investigated. It has been shown that ionizing radiation increases passive permeability of membranes, inhibits active ion transport, changes the number and the affinity of functionally active Na+,K+-ATPase molecules. The authors discuss the mechanisms of action of ionizing radiation.

Effect of low power laser irradiation on nociceptive cells in Hirudo medicinalis

The effect of low power Helium-Neon (He-Ne) and Gallium-Arsenide (Ga-As) laser on the nociceptors in Hirudo medicinalis was studied. The results show that low power laser irradiation does not: affect the membrane potential or the excitability of the nociceptive neurons, affect the mechanical pressure required to activate the nociceptors or their action potentials. The results indicate that the analgesic effects reported in humans with "laser-acupuncture" with similar modes of low power laser are likely not explained by effects on nervous tissue.

Inhibition of Ca2+ conductance in identified leech neurons by benzodiazepines

Benzodiazepines (BZs) in micromolar concentrations inhibit Mn2+- and Co2+-sensitive regenerative divalent cation potentials, which are revealed in the presence of tetraethylammonium ion, in leech nociceptive neurons (N cells). This BZ effect is reversible and dose-dependent. The BZs, like Mn2+ and Co2+, inhibit the maximum rate of depolarization (Vmax) and duration of divalent cation potentials at concentrations that do not significantly affect resting membrane potential or Vmax of the Na+-dependent action potential. Ultraviolet-induced BZ binding to micromolar-affinity sites in ganglia and isolated cells irreversibly blocks Ca2+ conductance in neurons without significantly affecting resting membrane potentials. BZ binding studies with leech neuronal membrane show saturable, specific binding in the micromolar concentration range that was similar to BZ binding to synaptosomal membrane fractions. The apparent Kd obtained from the micromolar-affinity BZ binding curve for leech ganglionic membrane preparations agrees well with the apparent Ki estimated from the dose-response curve measuring BZ inhibition of Vmax of the divalent cation potentials. These findings indicate that BZs act like Ca2+-channel antagonists in intact neuronal preparations and are consistent with the hypothesis that BZ binding to micromolar-affinity receptors modulates voltage-gated Ca2+ channels.

Molecular weight estimates of insect cholinergic receptors by radiation inactivation

Molecular weight (MW) estimates for sites to which the radiolabelled cholinergic receptor probes alpha-bungarotoxin and N-methylscopolamine bind in CNS extracts of the cockroach Periplaneta americana have been made by radiation inactivation analysis. The MW of 77,600 determined for [3H]N-methylscopolamine binding sites agrees well with published values for vertebrate muscarinic acetylcholine receptor sites. In contrast, N-[propionyl-3H]propionylated alpha-bungarotoxin binds to a separate membrane component of lower MW (108,000) than previously reported values for vertebrate and insect nicotinic acetylcholine receptors. This appears to represent one or more subunits of the receptor complex, containing the recognition site.

Cell-stage-specific enhancement by caffeine of the frequency of chromatid aberrations induced by X-rays in neural ganglia of Drosophila melanogaster

Caffeine (10(-2) M) induced a high level of chromatid aberrations in neural ganglia of third-instar larvae of Drosophila melanogaster only when it was added to cells in late G2 and mitotic prophase. No aberrations were observed after treatment in late S--middle G2 or C-mitosis. We observed that, in these stages, caffeine strongly increased X-ray-induced damage (500 R). This potentiation was quantitatively similar. But it involved all types of aberration after treatment in C-mitosis, and essentially isochromatid deletions and chromatid exchanges after treatment in S--G2. Some hypotheses are put forth to explain the possible mechanism of action of caffeine in the potentiation of X-ray-induced damage.

[Chromosome aberrations induced by gamma radiation in the somatic cells of a radiosensitive mutant line of Drosophila melanogaster]

Chromosome aberrations induced by gamma-rays in ganglia cells of Drosophila melanogaster larvae have been studied. Two strains of Drosophila were used: radiosensitive mutant rad (2) 201G1 and normal strain. It has been shown that the frequency of cells with chromosome aberrations in radiosensitive larvae is much more than in normal larvae after gamma-irradiation. The ratio of chromosome and chromatid deletions number to the number of exchange type aberrations is the same for both strains. The kinetics of chromosome aberrations induced in rad-larvae is similar to the normal one. The conclusion has been made that the realization of rad (2) 201G1 mutation takes place on the cell level.

DNA repair synthesis in rat retinal ganglion cells treated with chemical carcinogens or ultraviolet light in vitro, with special reference to aging and repair level

A system in which the retinal tissues of noninbred Wistar rats were used in combination with autoradiography was developed for measurement of DNA repair synthesis in ganglion cells of the central nervous system. Retinal tissues in short-term organ culture were treated with various carcinogens plus tritiated thymidine ([methyl-3H]dThd) or were irradiated with UV light and then treated with [methyl-3H]dThd. Preliminary study with retinal tissues from rats at various ages revealed no age-associated changes in the levels of unscheduled DNA synthesis in ganglion cells.

Cytological analysis of X-ray-induced aberrations in spermatocytes I and the somatic ganglia of male Drosophila melanogaster

The correlation between damage induced in somatic cells and that induced in germinal cells of the same genetic pool of individuals is important in establishing the possibility of extrapolation of this damage to the offspring. We have used Drosophila melanogaster to compare cytologically the frequency of aberrations induced in the cells of somatic ganglia and in the spermatocytes I of males irradiated with 625 R X-rays. The spermatocytes were more sensitive than the gangliar cells to radiation: the aberrations induced in the spermatocytes I were three times more frequent than those induced in the ganglia. The distribution of the aberrations was, however, similar. The most important variable element lies in our observing no symmetrical exchanges in the spermatocytes. This result seems to us to be related to the fact that in the males of D. melanogaster there is no crossing-over.