Modification of expression of the malignant phenotype in radiation-initiated cells

Carcinogenesis is a multistage process consisting minimally of initiation and promotion/progression stages. Radiation and many environmental xenobiotics are potent initiating agents. We have shown that initiation of carcinogenesis in vivo by these agents is a common cellular event. In the irradiated thyroid (5 Gy) at least one in 20 cells is initiated. Initiation by both radiation and chemicals has also been shown to be a common cellular event in the mammary gland. Initiation therefore is most likely not the sole rate-limiting event in the carcinogenic process. The propensity of the initiated cell to express the malignant phenotype is modulated by many factors, including environmental chemicals and physiological and genetic factors. Scopal and abscopal physiological factors can either enhance or suppress the progression of initiated cells to a frank tumour. For example, prolactin enhances the rate of progression of radiation and chemically initiated mammary tumours while glucocorticoids suppress this progression. TSH enhances the progression of radiation-initiated thyroid tumours while a scopal factor associated with unirradiated thyroid cells suppresses progression of this tumour type.     

Immunocytochemical localization of lactoferrin in human neutrophils

Summary The subcellular localization of lactoferrin in human neutrophils was studied by an electron-microscopic immunoperoxidase method. This molecule was detected in small granules of blood polymorphonuclear leukocytes. A morphometrical analysis showed that there was no significant difference in the mean size between lactoferrin-positive and myeloperoxidase-negative granules. In contrast, the mean size of myeloperoxidase-positive granules was significantly larger than that of lactoferrin-positive granules. This indicates that lactoferrin is contained in the myeloperoxidase-negative, secondary, granules of human neutrophils. In immature bone marrow mononuclear neutrophils, lactoferrin was present in cytoplasmic granules of somewhat larger size than lactoferrin-positive granules of polymorphonuclear leucocytes. A morphometrical study showed that the mean size of lactoferrin-positive granules was significantly greater in immature bone marrow cells than in polymorphonuclear leucocytes. This indicates that lactoferrin-positive granules decrease in size as the cells mature. Besides cytoplasmic granules, lactoferrin was demonstrated in the Golgi complex and a part of the rough endoplasmic reticulum of immature bone marrow neutrophils, probably myelocytes and early metamyelocytes. These results show that lactoferrin is synthesized and packed into secondary granules in immature bone marrow neutrophils and therefore that the secondary granules are a type of secretory granule.     

Cell cycle specificity of tumor necrosis factor and its receptor

Phase specificity in the TNF cytotoxic effect and the number of TNF binding receptors was investigated using L-M cells incubated synchronously from the S phase. TNF cytotoxicity was observed to occur at various levels during the cell cycle, with peak effect in the G2-M phase. Analysis with 125I-labeled TNF to determine the number of receptors binding TNF in the various cell phases shewed a phase specificity with the maximum number occurring in the G2-M phase, similar to the peak in cytotoxicity. The results suggest the existence of a cell cycle specificity in the cytotoxicity of TNF which is apparently related to changes in the number of receptors capable of binding TNF.     

Mutagenicity of nitro- and amino-substituted phenazines in Salmonella typhimurium

The nitro- and amino-substituted phenazines were synthesized and assayed for their mutagenicity in Salmonella typhimurium strains TA98 and TA98NR. Of 7 tested nitrophenazines, 4 were mutagenic in the absence of a microsomal metabolic activation system (S9 mix) and were more mutagenic in TA98 than in TA98NR. The order of mutagenicity of nitrophenazines in TA98 is 1.7- less than 2- less than 2.8- less than 2.7-substituted phenazine. Of 7 tested amino derivatives, 4 exhibited mutagenic activity with S9 mix in TA98. 1-Nitro-, 1-amino, 1.6-dinitro-, 1.9-dinitro-, 1.6-diamino- and 1.9-diamino-phenazine were not mutagenic. As regards the relationship between mutagenic potency and chemical structure of the phenazines, the results suggested that structural requirements favoring mutagenic activity were the presence of substituents at the 2 and/or 7 position. Furthermore, 2.7-disubstituted phenazines were extremely mutagenic, 2.7-dinitrophenazine and 2.7-diaminophenazine induced 36,450 and 12,110 rev./nmole, respectively. In the preliminary study, 2.7-diaminophenazine was identified by gas chromatography/mass spectrometry from the reaction mixture of m-phenylenediamine and hydrogen peroxide.     

The complete sequence of the rice (Oryza sativa) chloroplast genome: intermolecular recombination between distinct tRNA genes accounts for a major plastid DNA inversion during the evolution of the cereals

Summary The entire chloroplast genome of the monocot rice (Oryza sativa) has been sequenced and comprises 134525 bp. Predicted genes have been identified along with open reading frames (ORFs) conserved between rice and the previously sequenced chloroplast genomes, a dicot, tobacco (Nicotiana tabacum), and a liverwort (Marchantia polymorpha). The same complement of 30 tRNA and 4 rRNA genes has been conserved between rice and tobacco. Most ORFs extensively conserved betweenN. tabacum andM. polymorpha are also conserved intact in rice. However, several such ORFs are entirely absent in rice, or present only in severely truncated form. Structural changes are also apparent in the genome relative to tobacco. The inverted repeats, characteristic of chloroplast genome structure, have expanded outward to include several genes present only once per genome in tobacco and liverwort and the large single copy region has undergone a series of inversions which predate the divergence of the cereals. A chimeric tRNA pseudogene overlaps an apparent endpoint of the largest inversion, and a model invoking illegitimate recombination between tRNA genes is proposed which accounts simultaneously for the origin of this pseudogene, the large inversion and the creation of repeated sequences near the inversion endpoints.     

A sensitive method for the detection of mutagenic nitroarenes: construction of nitroreductase-overproducing derivatives of Salmonella typhimurium strains TA98 and TA100

'Classical nitroreductase' is an enzyme involved in the intracellular metabolic activation of mutagenic nitroarenes. The nitroreductase gene of Salmonella typhimurium TA1538 was cloned into pBR322 and the plasmids harboring the gene were introduced into TA98 and TA100. The resulting strains (YG1021 and YG1026) had more than 50 times higher nitrofurazone-reductase activity than TA1538 containing pBR322, and were extremely sensitive to the mutagenic action of 2-nitrofluorene, 1-nitropyrene and 2-nitronaphthalene. These results indicate that the new strains permit the efficient detection of mutagenic nitroarenes.     

Suppression of Inhibitory Effects of Copper on Enzymatic Activities by Copper-Binding Substances from Athyrium yokoscense Assayed in vitro

A metal-tolerant fern, Athyrium yokoscense, is capable of growingin highly copper-contaminated soil, but cupric chloride inhibitedthe activities of some enzymes extracted from the fern. Thefunction in the detoxification of copper of two copper-bindingsubstances was investigated by examination of their effectson various enzymes assayed in vitro, i.e. acid phosphatase (orthophosphoric-monoesterphosphohydrolase [acid optimum], EC 3.1.3.2 [EC] ), glucose-6-phosphatedehydrogenase (D-glucose-6-phosphate: NADP⁺ 1-oxidoreductase,EC 1.1.1.49 [EC] ) and isocitrate dehydrogenase (threo-Ds-isocitrate:NADP⁺ oxidoreductase [decarboxylating], EC 1.1.1.42 [EC] ). The twocopper-binding substances, whose apparent molecular weightsare 9.5 kDa and 2 kDa, were previously obtained from the solublecytoplasmic fraction of the fern root. The 9.5-kDa substance,which is a cysteine-rich peptide induced as a result of exposureof the fern to copper, was found to suppress almost entirelythe inhibitory effects of the metal on the enzymes. The suppressoractivity of the peptide was nearly as effective as that of ethylenediaminetetraaceticacid. The 2-kDa substance, which is also found in fern thathas not been exposed to copper, had a more modest suppressoractivity. These results indicate that the 9.5-kDa substancemay contribute to the copper-tolerance of the fern growing incopper-contaminated soil. (Received August 26, 1988; Accepted March 17, 1989)     

Longitudinal changes of dominance rank among the females of the Koshima group of Japanese monkeys

The changes of dominance rank among female Japanese monkeys of the Koshima group over a period of 29 years from 1957 were studied. The dominance rank order was relatively stable in the early population growing phase, while large scale-changes of dominance rank order occurred successively in the phase of population decrease brought about by the severe control of artificial feeding after 1972. Nevertheless, the rank order of several females of the highest status was stable. Furthermore, the reproductive success of these highest status females was high (Mori, 1979a;Watanabe et al., in prep.). Divergence of the dominance rank order fromKawamura's rules (Kawamura, 1958) was observed in the following respects: (1) Some females significantly elevated their rank depending on the leader males. (2) If mothers died when their daughters were still juveniles or nulliparous, the dominance rank of some of these offspring females was significantly lower than the mother's one. However 55% of daughters which lost their mothers at a young age inherited the mother's rank. (3) Dominance among sisters whose mother had died when at least one of the daughters was under 6 years old followed the rule of youngest ascendancy in 60% (Kawamura, 1958), and in 80% when both of the daughters were nulliparous at the mother's death. The mean rate of aggressive interactions for each female with subordinates to her was calculated by dividing the total aggressive interactions between the female in question and her subordinates by the number of subordinate females to the female in question. A female which showed a high rate of aggressive interactions with her subordinates was categorized as an “Attacker”, and a female showing a lower rate was categorized as a “Non-attacker”. Similarly, categories of “Attacked”, and “Non-attacked” were distinguished by using the rate of aggressive interactions with dominant females. Several females which were once categorized in one category in a year were repeatedly categorized in the same category over different years. The “Attacked” tended to be females of higher rank, and “Non-attackers” tended to be females of lower rank. “The second-higher-status females”, were “Attacked”, and their rank was unstable. In particular, females of lower rank within the lineage of the highest rank suffered this kind of severe status. Most of the daughters of these females showed a sharp drop of rank, and died when they were still at a young age, i.e. “the second-higher-status females” displayed low fitness. “Non-attackers” were significantly “Non-attacked”; i.e. they were females which showed a non-social attitude. Females which underwent a drop of rank tended to be “Non-attackers”. The most important factor which determined the females' rank was the memory of their dominance relations under the influence of their mother [dependent rank (Kawai, 1958)] in their early life during development. This finding corresponds well with the results in baboons obtained byWalter (1980); the target females of aggressive interactions by adolescent females were determined by the rank of the mothers when these adolescent females were born.