Dose-response relations for dicentric yields in G0 lymphocytes on man and crab-eating monkey following acute and chronic γ-irradiations

A comparison has been made of dicentric yields in G₀ lymphocytes between man and crab-eating monkey, Macaca fascicularis, after acute and chronic γ-irradiations. With acute irradiation (49.6 rad/min) there was no significant difference between them, but for the chronic irradiation (17.1 rad/h) a significant difference was observed between the species. When the dose-response relations were fitted to the linear-quadratic model (Y = αD + βD²), the species-difference observed for chronic irradiation was almost entirely due to change in the value of β. In addition, after chronic irradiation the β-value for monkey was almost negligible, but that for man was significant. Post-irradiation incubation experiment showed that cells with dicentrics were partly eliminated during the course of chronic irradiation, because there were appreciable reductions of dicentric yields (ca. 25% for both man and monkey at 400 rad) together with mitotic indices (ca. 30% and 60% for man and monkey, respectively, at 400 rad). Accordingly, it would be reasonable to postulate that G₀ repair for dicentrics other than selection mechanism must play a major role in the effects of low dose rate. It can be further suggested that G₀-repair capacity for chromosal damages leading to dicentrics may be different among different primate species.     

Properties of a DNA-dependent ATPase from rat mitochondria.

A DNA-dependent ATPase has been highly purified from rat liver mitochondria and characterized. The enzyme catalyzes the hydrolysis of ATP or dATP in the presence of single-stranded DNA cofactor and a divalent cation. The Km values for ATP and dATP are 0.15 mM and 0.35 mM, respectively. The enzyme activity is highly sensitive to N-ethylmaleimide. The sedimentation coefficient of the enzyme is 8.3 S in a glycerol gradient. From this and data on Sephadex G-200 gel filtration, the molecular weight of the native enzyme was calculated to be about 190,000. All the natural single-stranded DNAs tested were equally effective for the ATPase activity, but synthetic deoxyhomopolymer poly(dC) was found to be more effective than natural single-stranded DNAs. Synthetic and natural RNAs had no effect on the activity.     

Effects of dibromothymoquinone and bathophenanthroline on flash-induced cytochrome f oxidation in spinach chloroplasts

The effects of several electron transport inhibitors on themagnitude and kinetics of cytochrome f oxidation induced byflash illumination were studied in the - and -band regions.On the flash excitation only a fraction of cytochrome f presentin the chloroplasts was oxidized with a half time of 0.1 to0.3 msec and then reduced with a half time of 10 to 25 msec. Dibromothymoquinone (DBMIB) at concentrations which severelysuppressed the reduction of cytochrome f approximately doubledthe magnitude of cytochrome f oxidation caused by a flash, mainlyby inducing an additional slow oxidation of cytochrome f witha half time longer than 1 msec. Enhancement of the cytochromef oxidation was also observed in the presence of bathophenanthroline.Such enhanced oxidation in duced by the two inhibitors was largelydiminished with the addition of reduced 2,6-dichlorophenolindophenolwhich accelerated cytochrome f reduction. In contrast, the inhibitionof cytochrome f reduction by 3-(3,4-dichlorophenyl)-1,1-dimethylurea(DCMU) was not associated with an increase in the magnitudeof cytochrome f oxidation. However, addition of DBMIB to theDCMU-poisoned chloroplasts enhanced cytochrome f oxidation,suggesting that this is related to a block of the electron transportbetween plastoquinone and cytochrome f. The results are explainedby assuming the occurrence of an electron carrier between plastoquinoneand cytochrome f. (Received May 10, 1978; )     

Effect of TNF-alpha on prolactin secretion from rat anterior pituitary and dopamine release from the hypothalamus: comparison with the effect of interleukin-1 beta.

The effects of human recombinant interleukin-1 beta and -6 and tumor necrosis factor-alpha (TNF-alpha) on the releases of PRL and dopamine were examined using monolayer cultures of rat pituitary cells and hypothalamic cells. The release of PRL from rat pituitary cells in 30 min was increased about 2-fold (p less than 0.05) by 10(5) U/l interleukin-1 beta, 10(5) U/l interleukin-6 or 100 micrograms/l TNF-alpha. TNF-alpha at 100 micrograms/l significantly increased PRL release within 5 min incubation and this effect continued throughout the next 30 min of incubation. Incubation for 5 min with TNF-alpha caused dose-dependent stimulation of PRL release. These cytokines did not modulate [3H]-dopamine release from primary cultures of hypothalamic cells. These results suggest that these cytokines stimulate PRL release directly at the pituitary gland, without modifying the release of dopamine from the hypothalamus.     

A second gene for the African green monkey poliovirus receptor that has no putative N-glycosylation site in the functional N-terminal immunoglobulin-like domain.

Using cDNA of the human poliovirus receptor (PVR) as a probe, two types of cDNA clones of the monkey homologs were isolated from a cDNA library prepared from an African green monkey kidney cell line. Either type of cDNA clone rendered mouse L cells permissive for poliovirus infection. Homologies of the amino acid sequences deduced from these cDNA sequences with that of human PVR were 90.2 and 86.4%, respectively. These two monkey PVRs were found to be encoded in two different loci of the genome. Evolutionary analysis suggested that duplication of the PVR gene in the monkey genome had occurred after the species differentiation between humans and monkeys. The NH2-terminal immunoglobulin-like domain, domain 1, of the second monkey PVR, which lacks a putative N-glycosylation site, mediated poliovirus infection. In addition, a human PVR mutant without N-glycosylation sites in domain 1 also promoted viral infection. These results suggest that domain 1 of the monkey receptor also harbors the binding site for poliovirus and that sugar moieties possibly attached to this domain of human PVR are dispensable for the virus-receptor interaction.     

Goblet-like cells in atrophic vaginal smears and their histologic correlation. Possible confusion with endocervical cells.

The occurrence and origin of goblet-like cells seen between clusters of parabasal cells in atrophic vaginal smears were investigated. The goblet-like cells were cytologically identified in the vaginal smears from 23 (19.2%) of 120 patients whose smears showed an atrophic pattern, but without any inflammatory, dysplastic or malignant changes. Histologically, these cells were found in sections from 6 (18.8%) of 32 elderly women with atrophic vaginal epithelium. The goblet-like cells were situated among the squamous cells of the upper layer of the atrophic squamous epithelium from the vagina to the portio. These goblet-like cells in atrophic smears were initially misinterpreted as endocervical cells, which are regarded as a marker of smear adequacy in the cytologic screening for cancer of the uterine cervix. The correct interpretation of these goblet-like cells in smears from postmenopausal and elderly women is thus obviously important in assessing the adequacy of the sample for the detection of abnormal cells.     

Differential effect of UV irradiation on induction of intragenic and intergenic recombination during commitment to meiosis in Saccharomyces cerevisiae

A comparison was made between the induction of intragenic and intergenic recombinations during meiosis in a wild-type diploid of Saccharomyces cerevisiae. Under non-irradiated normal conditions, production of both intragenic and intergenic recombinants greatly increased in the cells with commitment to meiosis. The susceptibility of cells to the induction of both the spontaneous intra- and intergenic recombinations in meiotic cells was similar. However, under condition of UV irradiation, there were striking differences between intra- and intergenic recombinations. Susceptibility to induction of intragenic recombination by UV irradiation was not enhanced at meiosis compared with mitosis, and was not altered through commitment to meiotic processes. In contrast, however, susceptibility to the induction of intergenic recombination by UV irradiation was enhanced markedly during commitment to meiosis compared with mitosis. Genetic analysis suggested that the enhanced susceptibility to recombination during meiosis is specifically concerned with reciprocal-type recombination (crossing-over) but not non-reciprocal-type recombination (gene conversion). Hence it is concluded that the meiotic process appears to be intimately concerned with the mechanism(s) of induction of recombination, especially reciprocal-type recombination.     

Denitrification and Ammonia Formation in Anaerobic Coastal Sediments

Simultaneous determinations of nitrogen gas production, ammonia, and particulate organic nitrogen formation in the coastal sediments of Mangoku-Ura, Simoda Bay, and Tokyo Bay were made by using the ¹⁵N-label tracer method. The rate of nitrogen gas production in the sediment surface layer was about 10⁻² μg atom of N per g per h, irrespective of the location of the sediments examined. [¹⁵N]ammonia and -particulate organic nitrogen accounted for 20 to 70% of the three products, and after several hours of incubation, the major fraction of nondenitrified ¹⁵N in Mangoku-Ura and Simoda Bay sediments was recovered as ammonia. In Tokyo Bay sediments, particulate organic nitrogen was produced at a greater rate than was ammonia. The reduction rate data suggest that the pathway of nitrate reduction to ammonia is important in coastal sediments.     

Neurite formation and membrane changes of mouse neuroblastoma cells induced by valinomycin

A clonal cell line of mouse neuroblastoma cells was found to undergo morphological differentiation in the presence of a K⁺ ionophore, valinomycin, in the assay medium. This effect was blocked by increasing the concentration of KCl of the medium, suggesting that the changes in resting membrane potential and ion fluxes may be involved in the mechanism of the formation of neurites. No enhancement of the neurite formation was observed in salines containing high concentrations of KCl in the absence of valinomycin. Depolarizing agents including veratridine, gramicidin and ouabain did not stimulate the outgrowth of neurites. Neither electrophoretic mobility of the cells nor molecular anisotropy of fluorescence probes in the membranes was modified by the treatment of valinomycin. Instead, it modified the slow binding phase in kinetics of the interaction of 1-anilinonaphthalene-8-sulfonate (ANS) with the cells, which is related to the penetration process of the probe into membranes. Valinomycin also enhanced the fluorescence intensity of ANS by increasing the binding sites in neuroblastoma cells.     

A change in membrane microviscosity of mouse neuroblastoma cells in association with morphological differentiation

Changes in membrane microviscosity as well as in membrane constituents of mouse neuroblastoma clone N-18 were studied in association with neurite formation. The membrane microviscosity studied by fluorescence technique increased with the formation of neurites. The concomitant increase increase in the ratio of cholesterol to phospholipids was also observed.