Genetic action of 131I and 125I on the germ cells of male mice

A study was made of the genetic effects of iodine radioactive isotopes in male germ cells of (CBA X C57Bl)F1 hybrid mice. After a single intraperitoneal administration of Na131I (1.48 to 740 kBq/g) or Na125I (148 to 7400 kBq/g) to males the occurrence of dominant lethal mutations (DLM), reciprocal translocations (RT), and abnormal sperm heads (ASH) was studied. The radioactive iodine isotopes induced DLM at the postmeiotic spermatogenesis stages only. After the effect of the isotopes, the frequency of RT increased insignificantly with dose. The frequency of ASH was only increased with the highest 131I dose. Relative biological effectiveness of 131I and 125I was less than 1 with a reference to the indices under study.     

Genetic effects in mice exposed to the 10-km area around the Chernobyl Atomic Energy Station

Mice (CBAxC57BL) F of both sexes were exposed within the 10 km zone of Chernobyl nuclear power station. Genetic damage of phone chronic effect of increased radiation in exposed adult mice and in the course of embryogenesis was studied. The total absorbed radiation doses in testes varied from 1.85 to 0.42 Gy in embryos and from 3.4 to 2.7 Gy in adult males. Increase of dominant lethal mutations (DLM) and abnormal sperm heads (ASH) was only observed right after the end of exposure of adult males. The yield of reciprocal translocations (RT) in these males was relatively low. Among the males exposed at the stage of early embryogenesis, 4 heterozygotes for RT were revealed. In other males of this group the RT yield was low.     

Genetic effects of radiocarbon in reproductive cells of male mice

The genetic effect of incorporated radiocarbon was studied after single, long-term (33 days) and chronic (6 and 12 months) treatment of male mice (CBA X C57B1) F1 with [14C]glucose. The genetic effect in male germ cells was estimated by 3 tests: DLM frequency in post- and pre-meiotic cells, RT frequency in stem spermatogonia and frequency of abnormal sperm heads. Absorbed doses in the gonads were: 0.22, 0.50 and 1.01 Gy, after a single exposure; 0.74 and 1.47 Gy, after long-term exposures; and 0.006 and 0.031 Gy, after chronic exposure for 6 months; and 0.013 and 0.066 Gy, for 12 months. The results suggest that DLM frequency in post-meiotic cells increased linearly with increasing the dose of 14C single and long-term exposures at a dose of 1.47 Gy only. A chronic treatment with [14C]glucose induced no increase in DLM frequency. RT frequency in stem spermatogonia was statistically significantly higher than the control level after the single and long-term exposure to 14C. A comparison of the results with the results of external single and chronic gamma-irradiation allows the conclusion that the relative genetic efficiency of radiocarbon as compared with that of gamma-rays is about 1.     

Genetic effect of chronic gamma radiation exposure in male mice

The frequency of reciprocal translocations (RT) in mouse spermatogonia induced by gamma-rays at doses of 1.5 to 4.5 Gy and dose rates of 2.7 X 10(-6), 5.8 X 10(-6), 9.4 X 10(-5) and 4.5 Gy/min was studied. A linear increase was observed in the RT frequency with increasing the dose, at all dose rates. At 9.4 X 10(-5) Gy/min the RT frequency was, on average, 10 times lower, as compared to that for a single acute dose rate of 4.5 Gy/min. Further reduction of the dose rate did not result in a decrease of the RT yield, and at the lowest dose rate of 2.7 X 10(-6) Gy/min (the dose being 3.0 Gy) the RT frequency was higher than using the same dose at dose rates of 5.8 X 10(-6) and 9.4 X 10(-5) Gy/min. Possible reasons for an increase in the RT frequency at low dose rates are considered. A study of the frequency of abnormal sperm heads (ASH) has shown that at the dose rate of 9.4 X 10(-5) Gy/min it is independent of an accumulated dose and is equal to the value obtained when exposing to an acute dose of 3.0 Gy. At dose rates of 2.7 X 10(-6) and 5.8 X 10(-6) Gy/min ASH frequencies were only slightly increased at all doses, as compared to the control level.     

Evaluation of the genetic effects of 238Pu incorporated into mice

The genetic effects of 238Pu incorporated into male mice were estimated by several tests. The activity of the administered 238Pu nitrate varied from 7 to 1850 Bq/g of body weight. The average alpha-radiation dose absorbed in the testes ranged from 2 to 96 cGy, with a dose rate of 0.004-1 cGy/day. alpha-Radiation from 238Pu was shown to induce dominant lethal mutations (DLM) and reciprocal translocation (RT), chromosomal fragmentation and formation of abnormal sperm heads (ASH). The effect does not depend on the average alpha-radiation dose absorbed in the testis. The relative genetic efficiency of alpha-radiation, as compared with that of chronic alpha-radiation for the indices under study, was about 10-20.     

β-Amyloid1-42, HIV-1Ba-L (Clade B) Infection and Drugs of Abuse Induced Degeneration in Human Neuronal Cells and Protective Effects of Ashwagandha (Withania somnifera) and Its Constituent Withanolide A

Alzheimer''s disease (AD) is characterized by progressive dysfunction of memory and higher cognitive functions with abnormal accumulation of extracellular amyloid plaques and intracellular neurofibrillary tangles throughout cortical and limbic brain regions. Withania somnifera (WS) also known as ‘ashwagandha’ (ASH) is used widely in Ayurvedic medicine as a nerve tonic and memory enhancer. However, there is paucity of data on potential neuroprotective effects of ASH against β-Amyloid (1–42) (Aβ) induced neuropathogenesis. In the present study, we have tested the neuroprotective effects of Methanol: Chloroform (3:1) extract of ASH and its constituent Withanolide A (WA) against Aβ induced toxicity, HIV-1_Ba-L (clade B) infection and the effects of drugs of abuse using a human neuronal SK-N-MC cell line. Aβ when tested individually, induced cytotoxic effects in SK-N-MC cells as shown by increased trypan blue stained cells. However, when ASH was added to Aβ treated cells the toxic effects were neutralized. This observation was supported by cellular localization of Aβ, MTT formazan exocytosis, and the levels of acetylcholinesterase activity, confirming the chemopreventive or protective effects of ASH against Aβ induced toxicity. Further, the levels of MAP2 were significantly increased in cells infected with HIV-1_Ba-L (clade B) as well as in cells treated with Cocaine (COC) and Methamphetamine (METH) compared with control cells. In ASH treated cells the MAP2 levels were significantly less compared to controls. Similar results were observed in combination experiments. Also, WA, a purified constituent of ASH, showed same pattern using MTT assay as a parameter. These results suggests that neuroprotective properties of ASH observed in the present study may provide some explanation for the ethnopharmacological uses of ASH in traditional medicine for cognitive and other HIV associated neurodegenerative disorders and further ASH could be a potential novel drug to reduce the brain amyloid burden and/or improve the HIV-1 associated neurocognitive impairments     

A pore-forming toxin produced by Aeromonas sobria activates cAMP-dependent Cl- secretory pathways to cause diarrhea

Aeromonas sobria hemolysin (ASH) is one of the major virulence factors produced by A. sobria, a human pathogen that causes diarrhea. We investigated the effects of ASH on Cl(-) transport in human colonic epithelial cells. ASH increased short-circuit currents (Isc) and (125)I efflux from Caco-2 cells, indicating ASH activate Cl(-) secretion. Additions of inhibitors of cyclic AMP dependent Cl(-) channels, glybenclamide and NPPB suppressed the Isc and (125)I efflux increases induced by ASH. And ASH increased the intracellular cyclic AMP concentration. Moreover, ASH stimulated fluid accumulation in the iliac loop test, and glybenclamide and NPPB suppressed this fluid accumulation. Thus, cAMP-dependent Cl(-) secretory pathway could be related with diarrhea induced by A. sobria.     

Frequency of dominant lethal mutations induced by combined exposure to incorporated 137Cs and external gamma-irradiation in mice

The genetic effect of combined exposure to incorporated 137Cs and external gamma-irradiation was studied in germ cells of male mice. The activity of incorporated 137Cs was 3.7 x 10(4) Bq/g. The dose of external gamma-irradiation was 1.5 Gy. In the case of combined exposure, mice were treated with a cesium solution immediately after irradiation. The genetic effect was estimated by the frequency of dominant lethal mutations (DLM) induced at different stages of spermatogenesis. Upon combined exposure to external and internal irradiation, the frequency of DLM in premeiotic cells significantly exceeded the total frequency of DLM induced by separate exposure to external and internal irradiation; i.e., a marked synergistic interaction of external and internal irradiation was observed.     

Chemical protection against genetic effect of radiation in male mice

A study was made of the protective effect of some radioprotective agents against dominant lethal mutations (DLM) in postspermatogonial stages and reciprocal translocations (RT) in spermatogonia induced by gamma-radiation. Among the radioprotective agents used, cystaphos, a combination of cystamine and 5-MOT and a mixture of 6 components proved to be most effective against DLM, and cystaphos, gammaphos and cystamine combined with 5-MOT proved effective against RT. The degree of radioprotective efficacy was relatively low. The efficacy of cystamine in protecting against RT was higher with exposure of gonocytes of 18.5-day embryos than spermatogonia of pubertal animals. The degree of the radioprotective effect varied depending on the stage of spermatogenesis, and, in all cases, it was lower than that observed in studies of protection against lethal effects of ionizing radiation.     

Formation of micronuclei and of clastogenic factor(s) in patients receiving therapeutic doses of iodine-131

The micronucleus (MN) assay in peripheral blood lymphocytes was applied to assess the genotoxic potential of a single dose of iodine-131 (131I) given to six patients for ablation of thyroid remnants after total thyroidectomy. Lymphocytes were taken at various times after 131I therapy (from 2 to 180 days), and evaluated for the presence of MN in the binucleated cells identified after blocking cytokynesis with cytochalasin B. The presence of ultrafiltered, low-molecular weight, clastogenic factor(s) (CFs) in the plasma of 11 patient undergoing 131I therapy was also sequentially assessed.A significantly increased MN frequency was observed in lymphocytes of patients as soon as the first sampling time (2 days after 131I therapy), multifactor analysis of variance (MANOVA): P<0.0001, peaking at day 7 at almost four-fold the spontaneous frequency observed in the pre-therapy samples. MN frequency slowly declined thereafter, reaching the baseline levels at the 180-day time point. When tested against peripheral blood lymphocytes from a healthy donor, the ultrafiltered CFs obtained from 11 patient's plasma induced a significant increase of the MN frequency peaking at day 15. Thereafter, a slow MN frequency decline was observed and the baseline frequency was reached after 180 days. A significant relationship was found between the MN frequency observed in lymphocytes of patients after 131I therapy and the genotoxic CFs activity present in their plasma (P=0.019).These findings suggest that 131I induces a significant increase in the MN frequency of peripheral blood lymphocytes, as well as the formation of transferable CFs which persist for at least 60 days after administration of the radionuclide. The presence of these CFs might be responsible of chromosome aberrations often observed in cultured lymphocytes following X-ray exposure. The possibility of reducing the genotoxic activity of radionuclide therapy by chemoprevention of CFs with antioxidant drugs remains to be explored.     

Changes of the blood lymphocyte subpopulations and their functions following 131I treatment for nodular goitre and 32P treatment for polycythemia vera

The blood lymphocyte population was examined in 34 patients who were treated with 131I for toxic or atoxic nodular goitre. One to three doses of 300-550 MBq of 131I were administered at 1-week intervals. Lymphocyte counts were found to be significantly reduced at both 1 and 6 weeks after treatment. This decrease was accompanied by a changed composition of the lymphocyte subpopulations. The frequency of lymphocytes expressing membrane receptors for C'3 (EAC-rosette forming cells) was significantly reduced at 1 and 6 weeks following 131I administration. At 6 weeks there was a small but statistically significant increase of the frequency of T cells as identified by Leu 1 monoclonal antibodies. This was essentially due to an increased proportion of helper/inducer T cells as identified by Leu 3 monoclonals. 131I treatment also decreased the capacity of lymphocytes to secrete immunoglobulins (Ig) when stimulated with pokeweed mitogen (PWM). The greatest effect was observed for IgM. Secretion of IgG and IgA were less reduced. Mitogenic stimulations of lymphocytes with phytohemagglutinin (PHA) and concanavalin A were not significantly changed. It is concluded that these findings, with the exception of mitogen reactivity, are largely similar to those occurring following external radiation therapy for cancer. It is suggested that blood lymphocytes passing through the continuously irradiated gland are damaged mainly by beta-rays. The effect of 32P treatment on the blood lymphocyte population was examined in 16 patients with polycythemia vera. Before treatment the lymphocyte counts were within the normal range but the expression of certain membrane structures, as identified by monoclonal antibodies against total T cells (Leu 1 and 4), helper/inducer (Leu 3) and suppressor/cytotoxic T cells (Leu 2), were slightly decreased. Moreover, mitogenic responses of the lymphocytes to PHA and PWM-induced Ig secretion were impaired. Following a single oral dose of 32P (150-305 MBq), which normalized the production of erythrocytes and/or platelets, the blood lymphocyte counts were reduced by approximately 40 per cent 12 weeks after treatment. Examination of subsets demonstrated that the proportion of B-cells, as identified by B1 monoclonal antibodies, was decreased by the highest relative extent. On the other hand, lymphocytes expressing the above-mentioned T cell markers were somewhat increased. 32P treatment markedly increased PHA reactivity but it further reduced PWM-induced Ig secretion. The latter observation was in agreement with the finding that serum concentrations of Ig were reduced after treatment.     

Radiation dose rates of differentiated thyroid cancer patients after <Superscript>131</Superscript>I therapy

Postoperative ¹³¹I treatment for differentiated thyroid cancer (DTC) can create a radiation hazard for nearby persons. The present prospective study aimed to investigate radiation dose rates in ¹³¹I-treated DTC patients to provide references for radiation protection. A total of 141 ¹³¹I-treated DTC patients were enrolled, and grouped into a singular treatment (ST) group and a repeated treatment (RT) group. The radiation dose rate of ¹³¹I-treated patients was measured. The rate of achieving discharge compliance and restricted contact time were analyzed based on Chinese regulations. Multivariate logistic regression analysis was used to analyze the independent factors associated with the clearance of radioiodine. The rate of achieving discharge compliance (¹³¹I retention <?400 MBq) was 79.8 and 93.7% at day 2 (D2) for the ST and RT groups, respectively, and reached 100% at D7 and D4, respectively. The restricted contact time with ¹³¹I-treated patients at 0.5 m for medical staff, caregivers, family members, and the general public ranged from 4 to 7 days. Multivariate logistic regression analysis showed that the 24-h iodine uptake rate was the only significant factor associated with radioiodine clearance. For the radiation safety of ¹³¹I-treated DTC patients, the present results can provide radiometric data for radiation protection.     

Evidence for a secretion of thyroxine by isolated hog thyroid cells.

Isolated thyroid cells prepared from hog thyroid glands by tryptic dispersion were incubated with 131I- for 1--6 h. Free [131I]thyroxine was identified in the incubation medium by three chromatographic methods. Neither [131I]iodotyrosines nor [131I]triiodothyronine were detected. The [131I]thyroxine released in the medium by 100 mul of cells (packed cell volume) after a 6-h incubation period amounted to 1.16% (S.E. = +/- 0.39) of the total radioactivity. The medium [131I]thyroxine represented 15--25% of the total [131I]thyroxine synthesized during the 6 h of incubation. Thyrotropin, 1--60 munits/ml, increased the medium [131I]thyroxine content 2-4 fold. Dibutyryl cyclic AMP mimicked the effect of thyrotropin. The amount of medium [131]thyroxine was strictly related to the amount of incubated cells but was independent of the volume of the incubation medium. When prelabeled cells were incubated in the presence of methimazole the increase in medium [131I]thyroxine was quantitatively related to a decrease in the intracellular [131I]thyroxine. Addition of dinitrotyrosine, an inhibitor of the deiodinase activity, induced the release of iodotyrosines in the incubation medium. That the incubation supernatant of isolated thyroid cells did contain free thyroxine but not iodotyrosines suggests that the normal mechanisms of proteolysis of thyroglobulin and deiodination of iodotyrosines inside the cells are preserved. From these data, it was concluded that the thyroxine release by isolated cells represents a real secretion.     

Antagonists of epithelial chloride channels inhibit cAMP synthesis.

In past studies we observed that the chloride channel blocker, diphenylamine-2-carboxylate (DPC) and chemically related drugs (Hoechst compounds 131, 143, 144) inhibited cAMP formation in mouse pituitary tumor cells. The object of this study was to determine whether these drugs inhibited chloride transport in human T-84 colonic carcinoma cells through an effect on cAMP metabolism. Chloride secretion (measured as 125I efflux from isotope-preloaded cells) was stimulated in a concentration-dependent manner by vasoactive intestinal polypeptide (VIP) (EC50 = 1.5 x 10(-10) M) which similarly increased cAMP synthesis (EC50 = 1.6 x 10(-8) M). The cAMP response to VIP was inhibited 17, 52, 55, and 78% maximally by DPC and compounds 144, 143, and 131, respectively. In untreated T-84 cells, 125I secretion fell by 66% after 3 min; VIP (10(-7) M) increased secretion about fivefold over the same period. Both basal and VIP-stimulated 125I secretion were inhibited up to 60% by compound 131. Pretreatment of cells with pertussis toxin did not attenuate the inhibitory effect of channel blockers on either VIP-stimulated cAMP synthesis or 125I secretion. The cationophore, A-23187, which had no effect on cAMP formation, and 8-Br-cAMP both stimulated 125I secretion from T-84 cells. These secretory responses were inhibited by compound 131. The mechanism by which phenylanthranilic acids antagonize cAMP synthesis and its significance is not known; however, the data suggest that this family of drugs may inhibit chloride transport by both cAMP-dependent and independent mechanisms.     

Biological evaluation of ring- and side-chain-substituted m-iodobenzylguanidine analogues

A number of ring- and side-chain-substituted m-iodobenzylguanidine analogues were evaluated for their lipophilicity, in vitro stability, uptake by SK-N-SH human neuroblastoma cells in vitro, and biodistribution in normal mice. As expected, the lipophilicity of m-iodobenzylguanidine increased when a halogen was introduced onto the ring and decreased with the addition of polar hydroxyl, amino, and nitro substitutents. Most of the derivatives showed reasonable stability up to 24 h in PBS at 37 degrees C. While N(1)-hydroxy-N(3)-3-[(131)I]iodobenzylguanidine and 3,4-dihydroxy-5-[(131)I]iodobenzylguanidine generated a more nonpolar product in addition to the free iodide, 3-[(131)I]iodo-4-nitrobenzylguanidine decomposed to a product more polar than the parent compound. The specific uptake of 4-chloro-3-[(131)I]iodobenzylguanidine, 3-[(131)I]iodo-4-nitrobenzylguanidine, and N(1)-hydroxy-N(3)-3-[(131)I]iodobenzylguanidine by SK-N-SH human neuroblastoma cells in vitro, relative to that of m-[(125)I]iodobenzylguanidine, was 117 +/- 10%, 50 +/- 4%, and 12 +/- 2%, respectively. The specific uptake of the known m-iodobenzylguanidine analogues 4-hydroxy-3-[(131)I]iodobenzylguanidine and 4-amino-3-[(131)I]iodobenzylguanidine was 80 +/- 4% and 66 +/- 4%, respectively. None of the other m-iodobenzylguanidine derivatives showed any significant specific uptake by SK-N-SH cells. Heart uptake of 4-chloro-3-[(131)I]iodobenzylguanidine in normal mice was higher than that of m-[(125)I]iodobenzylguanidine at later time points (11 +/- 1% ID/g versus 3 +/- 1% ID/g at 24 h; p < 0.05) while uptake of 3-[(131)I]iodo-4-nitrobenzylguanidine and of N(1)-hydroxy-N(3)-3-[(131)I]iodobenzylguanidine in the heart was lower than that of m-iodobenzylguanidine at all time points. In accordance with the in vitro results, none of the other novel m-iodobenzylguanidine derivatives showed any significant myocardial or adrenal uptake in vivo.     

Uptake of 131I-metaiodobenzylguanidine by 6-23 rat medullary thyroid carcinoma

Uptake of 131iodine-metaiodobenzylguanidine (131I-MIBG) by 6-23 rat medullary thyroid carcinoma (MTC), was studied in vitro and in vivo. In vitro, there was an 8-fold increase in 131I uptake by 6-23 cells when labeled with 131I-MIBG (131I 24 +/- 15 cpm/10(6) cells, 131I-MIBG 196 +/- 9 cpm/10(6) cells). MIBG uptake in vitro was the same at 4 degrees C and 37 degrees C. In contrast, 131I-MIBG uptake by PC-12 rat pheochromocytoma cells were 200 times greater (131I-MIBG 42,412 +/- 6,755 cpm/10(6) cells). 131I-MIBG uptake by rat MTC cells in vitro were of a comparable magnitude to the uptake of 131I-MIBG by rat ileal enterochromaffin cells (RIE-1) and mouse colon cancer cells (MC-26). In vivo, uptake of 131I-MIBG by 6-23 MTC tumor was considerably less than in the normal tissues (muscle, liver, spleen, kidney, adrenal and thyroid). Gamma camera studies of 131I-MIBG uptake by 6-23 MTC tumors growing in Wag-Rij rats were only transiently positive in 1 out of 4 rats studied. We conclude that 131I-MIBG is poorly taken up by rat medullary thyroid carcinoma and is an unpredictable marker for localization of rat MTC.     

Aeromonas sobria hemolysin causes diarrhea by increasing secretion of HCO3-

Aeromonas sobria hemolysin (ASH) is one of the major virulence factors produced by A. sobria, a causative agent of diarrhea in humans. We investigated the effects of ASH on anion transport in human colonic epithelial cells. ASH increased short circuit currents across the intestinal epithelia, which were suppressed by anion channel antagonists, such as carbonic anhydrase inhibitors, and by the removal of external HCO3-. Iliac fluid accumulation was also inhibited by carbonic anhydrase inhibitors. The results suggest that ASH activates HCO3- secretion, whose level correlates with the severity of diarrhea.     

Resveratrol mitigates genotoxicity induced by iodine-131 in primary human lymphocytes

The purpose of this study was to investigate the radioprotective effects of resveratrol as a natural product that protects against genotoxic actions of ¹³¹I in cultured human lymphocytes. Whole-blood samples from human volunteers were treated with resveratrol at doses of 0.5, 1, 5, and 50 μg/mL for 1 h, after which the lymphocytes were incubated with ¹³¹I (100 μCi/1.5 mL) for 2 h. The lymphocyte cultures were then mitogenically stimulated to enable evaluation of the number of micronuclei in cytokinesis-blocked binucleated cells. Incubation of lymphocytes with ¹³¹I induced genotoxicity, which was reflected by an increase in micronuclei frequency. At the doses tested, resveratrol significantly reduced micronuclei frequency. Maximal protective effects occurred at a dose of 1 μg/mL, with total micronuclei values being reduced by 65 % compared to controls. In conclusion, our results indicate protective effects of resveratrol at low doses against genetic damage and adverse effects induced by ¹³¹I administration.