Solution Radioactivated by Hadron Radiation Can Increase Sister Chromatid Exchanges

When energetic particles irradiate matter, it becomes activated by nuclear reactions. Radioactivation induced cellular effects are not clearly understood, but it could be a part of bystander effects. This investigation is aimed at understanding the biological effects from radioactivation in solution induced by hadron radiation. Water or phosphate buffered saline was activated by being exposed to hadron radiation including protons, carbon- and iron-ions. 1 mL of radioactivated solution was transferred to flasks with Chinese hamster ovary (CHO) cells cultured in 5 mL of complete media. The induction of sister chromatid exchanges (SCE) was used to observe any increase in DNA damage responses. The energy spectrum and the half-lives of the radioactivation were analyzed by NaI scintillation detector in order to identify generated radionuclides. In the radioactivated solution, 511 keV gamma-rays were observed, and their half-lives were approximately 2 min, 10 min, and 20 min. They respectively correspond to the beta+ decay of ¹⁵O, ¹³N, and ¹¹C. The SCE frequencies in CHO cells increased depending on the amount of radioactivation in the solution. These were suppressed with a 2-hour delayed solution transfer or pretreatment with dimethyl sulfoxide (DMSO). Our results suggest that the SCE induction by radioactivated solution was mediated by free radicals produced by the annihilated gamma-rays. Since the SCE induction and DMSO modulation are also reported in radiation-induced bystander effects, our results imply that radioactivation of the solution may have some contribution to the bystander effects from hadron radiation. Further investigations are required to assess if radioactivation effects would attribute an additional level of cancer risk of the hadron radiation therapy itself.     

Unique distributions of natriuretic hormones in dog brain

We examined the regional distributions of atrial natriuretic polypeptide (ANP) and digoxin-like immunoreactivity (DLI) in dog brain, using specific radioimmunoassay. The molecular form of the dog brain ANP was similar to that of alpha-hANP, in gel filtration and reversed-phase HPLC. Distribution of ANP in dog brain differed from rat brain. A significant amount of ANP-like immunoreactivity (ANPLI) was observed in the periaqueductal grey, ventral thalamus and spinal cord, however, only a trace amount was seen in the hypothalamus. The DLI was widely distributed in the dog brain, especially with over 2 ng/g wet wt. of the immunoreactivity content in mammillary body, septum, striatal body, hypothalamus and periaqueductal grey. Different from the localizations of natriuretic hormones in rat brain, the periaqueductal grey matter in dog brain may be an important source of both natriuretic hormones.     

Modulation of brain progestin and glucocorticoid receptors by unsaturated fatty acid and phospholipid

In an attempt to learn how nonsteroidal factors modulate brain progestin and glucocorticoid receptors, the effects of saturated and unsaturated fatty acids, and phosphatidylinositol on the binding of [3H]R5020 or [3H]dexamethasone, determined by sucrose density gradient and gel filtration on LH20, were examined in the cerebral cortical cytosol from 10-day-old female rats which contain a considerable amount of progestin and glucocorticoid receptors. Unsaturated fatty acids such as oleic (C18:1), arachidonic (C20:4) and docosahexaenoic acid (C22:4) depressed the [3H]R5020 or [3H]dexamethasone binding in increasing order, but saturated fatty acids had no effect. Arachidonic and docosahexaenoic acids, which were strong inhibitors, lowered the binding dose dependently. The fatty acid inhibition on brain progestin and glucocorticoid receptors was thus a function of acid dose and degree of acid unsaturation. Interestingly, prostaglandin D2 did not show any effect. Among phospholipids tested the inhibitory effect of phosphatidylinositol on the [3H]R5020 binding was evident, but no significant effect was found with phosphatidylethanolamine, phosphatidylcholine, phosphatidylserine or sphingomyelin. The phosphatidylinositol inhibition was dose dependent. Analysis on kinetics and Scatchard plot have revealed the noncompetitive type of inhibition by arachidonic acid and phosphatidylinositol. From these results it is suggested that the unsaturated nonestrified fatty acid, arachidonic acid, and phosphoinositides modulate the brain progestin and, possibly, glucocorticoid receptors through their binding at sites different from steroid binding sites on the respective receptor molecules.     

A homologous radioimmunoassay for guinea pig corticosteroid-binding globulin

A rapid, specific, and sensitive (requiring only 20 fmole of antigen equivalent to 0.007 microliter of serum) radioimmunoassay (RIA) was developed for the measurement of guinea pig corticosteroid-binding globulin (CBG). CBG was purified to homogeneity from guinea pig serum by affinity chromatography and used for immunization, as the standard and as the radiolabeled trace in the RIA. The antiserum to CBG was raised in rabbits. It was judged specific by immunoelectrophoresis and by comparison of RIA values with steroid-binding assay profiles obtained on serum separated on the basis of size and ion-exchange properties. The results of the radioimmunoassays agree with those of a steroid-binding assay run on identical samples. The sensitivity of the assay allows detection of CBG in serial serum samples, other biologic fluids such as milk, and cell culture supernatants.     

Formation of Hydrogen Peroxide by NAD(P)H Oxidation with Isolated Cell Wall-Associated Peroxidase from Cultured Liverwort Cells, Marchantia polymorpha L.

Hydrogen peroxide was formed in isolated cell walls from Marchantiapolymorpha L. in the presence of MnCl₂ by either NADH or NADPHoxidation. This reaction was stimulated by phenols such as 2,4-dichlorophenolor p-coumarate, suggesting a reaction similar to that proposedfor the last step of lignification in higher plant cells, althoughbryophytes have been reported to be devoid of lignin. (Received June 16, 1987; Accepted March 3, 1987)     

Polyamine oxidase from water hyacinth: purification and properties

Polyamine oxidase was purified to homogeneity from leaves of water hyacinth by the criterion of sodium dodecyl sulfate gel electrophoresis (SDS disc PAGE). The enzyme showed a high specificity for spermidine and spermine (K_m values 28 micromolar and 20 micromolar, respectively). The optimal pH of the enzyme for both spermidine and spermine was 6.5. The molecular weight of the enzyme estimated by Sephadex G-200 gel filtration was 87,000, while SDS disc PAGE gave a single band at the molecular weight of 60,000. Octamethylenediamine and quinacrine were strong inhibitors of the enzyme, but p-chloromercuribenzoate was without effect. A prosthetic group in the enzyme was identified as flavin adenine dinucleotide.     

Chromatic Regulation of Photosystem Composition in the Cyanobacterial Photosynthetic System: Kinetic Relationship between Change of Photosystem Composition and Cell Proliferation

Kinetics of the change of photosystem (PS) composition in cyanobacteriainduced by chromatic light were studied in relation to cellproliferation. The study was made for two unicellular strains,Synechococcus NIBB 1059 and Synechocystis (Aphanocapsa) PCC6714. We found that (1) the change to a higher or lower PS I/IIratio was due to acceleration or suppression of apparent PSI formation, and (2) it progressed on a similar time scale tothat of the cell proliferation. The apparent rate constant ofthe change in the PS I/II ratio was proportional to that ofcell proliferation, µ, when this was low, but at highvalues of µ the increase in the rate constant of the changein the PS I/II ratio became smaller, causing a deviation fromthe linear relationship. Results indicate that under autotrophicconditions, the photoregulated composition change occurs asa result of thylakoid development, which accompanies cell proliferation. (Received June 23, 1986; Accepted December 5, 1986)     

Studies of the mortality of A-bomb survivors. 8. Cancer mortality, 1950-1982

This study extends an earlier one by 4 years (1979-1982) and includes mortality data on 11,393 additional Nagasaki survivors. Significant dose responses are observed for leukemia, multiple myeloma, and cancers of the lung, female breast, stomach, colon, esophagus, and urinary tract. Due to diagnostic difficulties, results for liver and ovarian cancers, while suggestive of significant dose responses, do not provide convincing evidence for radiogenic effects. No significant dose responses are seen for cancers of the gallbladder, prostate, rectum, pancreas, or uterus, or for lymphoma. For solid tumors, largely due to sex-specific differences in the background rates, the relative risk of radiation-induced mortality is greater for women than for men. For nonleukemic cancers the relative risk seen in those who were young when exposed has decreased with time, while the smaller risks for those who were older at exposure have tended to increase. While the absolute excess risks of radiation-induced mortality due to nonleukemic cancer have increased with time for all age-at-exposure groups, both excess and relative risks of leukemia have generally decreased with time. For leukemia, the rate of decrease in risk and the initial level of risk are inversely related to age at exposure.     

Cell lineage analysis of the primitive and visceral endoderm of mouse embryos cultured in vitro

Cell lineages of the primitive endoderm and the visceral endoderm of mouse embryos were examined by culturing whole embryos in vitro. The primitive endoderm and visceral endoderm cells could be labelled by incubation of embryos in a medium containing horse radish peroxidase (HRP). HRP localization was chased throughout the culture period. The results show that the visceral endoderm derives from the primitive endoderm, and the visceral endoderm forms only the extra-embryonic endoderm (yolk sac endoderm) of the conceptus. The definitive endoderm which is probably derived from the head process, newly appears on the ventral surface of the embryo.