Oestrogen and progesterone receptors in mammary tumours of male SHN mice grafted with pituitaries in comparison with females.

Mammary tumour induced by pituitary grafting in SHN male mice is promising as an animal model for male breast cancer. In this study, these mice (group MC) were found to differ little from the intact female SHN (group FC) in cytosolic oestrogen receptor (OR) level in either normal or neoplastic mammary glands. On the other hand, Progesterone receptor (PR) level in normal glands tended to be lower in group MC than in group FC, which was recovered by chronic treatment with oestradiol benzoate (group OB). Little difference in PR level in mammary tumours was seen between groups MC and FC. Mammary tumorigenesis was significantly inhibited by chronic treatment with dihydrotestosterone to male mice with pituitary grafts (group DHT). This is associated with the significant decline in PR level in normal mammary glands, while not in mammary tumours. There were no significant correlations between OR and PR levels in normal or neoplastic mammary glands, or between normal and neoplastic mammary glands in OR or PR in all groups except group MC, in which the correlation between OR and PR in mammary tumour was significant. All findings indicate that OR and PR states in mammary tumours of male mice induced by pituitary grafting are essentially similar to the spontaneous mammary tumours of females as postulated in the human.

Microleakage through dentin after crown cementation.

This study investigated the relationship between type of luting cement for artificial crowns and microleakage through dentinal tubules. Standardized preparations were made on intact human premolars, and crowns were made in a base metal alloy using conventional techniques. The castings were randomly assigned to the following luting agent groups: zinc phosphate (ZP), polycarboxylate (PC), glass ionomer (GI), phosphate ester composite resin (GMA/PE), and a composite resin with a NPG-GMA dentin bonding agent (GMA/NPG). Then they were cemented in a standardized manner. The specimens were artificially aged, stained, sectioned, and microleakage occurred through dentinal tubules toward the pulp measured. The rank in order from least to most (best to worst) leakage was GMA/NPG, GI, GMA/PE, PC, and ZP. Material GMA/NPG recorded significantly less leakage than all other materials. Therefore, the results of this study suggest that material GMA/NPG may reduce pulpal sensitivity and pathosis.

Mammary tumour induction by pituitary grafting in male mice: an animal model for male breast cancer.

Isologous anterior pituitary grafting, 4 each, to 3-4-month-old SHN and SLN male mice resulted in an appearance of mammary tumours from 8 months of age and the incidence at 12 months reached 53.8% in each strain. All tumours were diagnosed as type B adenocarcinomas. In association with the results, normal mammary gland growth and mouse mammary tumour virus (MMTV)-gp52 antigen levels in the submaxillary glands were stimulated by the treatment in these strains. The effect of pituitary grafting was much less in GR/A male mice in which no mammary tumours appeared.

Effects of Chinese herbal medicines on DNA-synthesizing enzyme activities in mammary tumors of mice.

Sho-saiko-to (SST) and Juzen-taiho-to (JTT), Japanese modified Chinese herbal prescriptions, suppressed the activities of thymidylate synthetase and thymidine kinase involved in de novo and salvage pathways for pyrimidine nucleotide synthesis, respectively, in mammary tumors of SHN mice with the reduction of serum prolactin level. These results indicate that SST and JTT may have the antitumor effects on mammary tumors.

The similar mammary tumour potentials in virgins and breeders of SHN mice.

Spontaneous mammary tumour potential was compared between virgins and breeders of a high mammary tumour strain of SHN mice. Virgins were essentially similar to breeders in both the cumulative and the monthly incidences of mammary tumours. DNA synthesizing enzyme activities and the number and the weight of mammary tumours also differed little between groups. While the number of preneoplastic mammary hyperplastic alveolar nodules (HAN) was significantly higher in breeders than in virgins, little difference was observed between groups in the end-bud formation and the duct growth of normal glands and the growth of HAN. These results indicate that in SHN mice virgins have similar mammary tumour potential to breeders, which is much advantageous for practical use of this strain as an animal model for human breast and other types of cancers.

Adsorption Affinity of Divalent Heavy Metal Ions for Metal Oxides Evaluated by Modeling with the Frumkin Isotherm

Adsorption of divalent heavy metal ions, M(II), on metal oxides is important to determine the behavior of ions in waters and soils. The amount of adsorbed Pb(II), Cu(II), Zn(II), Co(II), Ni(II), and Mn(II) ions on the two oxides MnO2 and Fe2O3 was measured as a function of the pH and concentration of the ions under the conditions where no mono- and polynuclear hydroxo complexes play a role in the adsorption. The adsorption affinity of these ions for the oxides was evaluated with a model that considers simultaneous (1:1) and (1:2) exchange reactions between M2+ aqua ions and surface hydroxyl protons (surface complexation) obeying the Frumkin isotherm. From the model parameters, it was found that the affinity order for (1:1) complex formation is Cu2+ > Mn2+ > Zn2+ > Co2+ > Ni2+ for MnO2 and Pb2+ > Cu2+ > Zn2+ > Co2+ for Fe2O3. A large affinity of Mn2+ for MnO2 was ascribed to the oxidation of this ion by MnO2. A good correlation between the stability constants of (1:1) surface complexes and those of (1:1) hydroxo complexes in solution was obtained. The adsorption affinities of ions here are the affinities for deprotonated hydroxyl sites with negative charge, since for all the ions the oxides are common and the deprotonation properties of hydroxyl sites are the same. The good correlation suggests that the two reactions are similar: From electrostatic theory including crystal field corrections, the both reactions could be regarded as due to ionic bond formation between the positive charge of metal ions and the negative charge of deprotonated sites on oxides or hydroxide ions in solution, as we have suggested previously. Copyright 1997 Academic Press. Copyright 1997Academic Press

The Co2+ Adsorption Properties of Al2O3, Fe2O3, Fe3O4, TiO2, and MnO2 Evaluated by Modeling with the Frumkin Isotherm

Adsorption of Co(II) ions on metal oxides is related to radioactive 60Co(II) (de)contamination of nuclear power plants, Co(II) ion retention in soils as a plant nutrient, concentration of Co(II) in deep-sea manganese nodules, and other applications. Here, the amount of adsorbed Co(II) on metal oxides was measured as a function of the pH and concentration of Co(II) ions, and the adsorption properties of metal oxides were evaluated with a model that considers simultaneous (1:1) and (1:2) exchange reactions between Co2+ aqua ions and surface hydroxyl protons obeying the Frumkin isotherm. The possibility of participation of mono- and polynuclear Co(II) hydroxo complexes in the adsorption was examined, and it was suggested that these species play no role under the conditions here. From the model parameters, it was found that the Co2+ adsorption ability of metal oxides increases in the order Al2O3 < Fe2O3 < TiO2 < Fe3O4 < MnO2, showing a good correlation to the electronegativity Xi of the lattice metal ions of the oxides. The Co2+ adsorption was divided into two processes: (1) deprotonation of surface hydroxyl sites and (2) bonding of Co2+ to the deprotonated sites with a negative charge. With increasing Xi, process 1 increases possibly due to the decrease in the donor electron density responsible for covalent bonds with protons, while process 2 changes only slightly. It was suggested that process 2 is due to ionic bond formation ("electrostatic contact adsorption"), which is independent of the donor electron density, and the correlation of the overall process to Xi found here was ascribed to process 1 above. Copyright 1997 Academic Press. Copyright 1997Academic Press

Surface Hydroxyl Site Densities on Metal Oxides as a Measure for the Ion-Exchange Capacity.

Hydroxyl groups on metal oxide in water are the sites for ion exchange, and the surface hydroxyl site density on oxides is a measure of the ion-exchange capacity. Here, the Grignard reagent method was applied to determine the surface hydroxyl site density of oxide samples. The results were similar to those reported for different oxides with other methods (dehydration by heating, tritium exchange, crystallographic calculations, etc.), and they are comparable with those calculated from the closest packing of hydroxide ions. A mechanism of hydroxylation is proposed: lattice oxide ions (extremely strong bases) are exposed to aqueous solutions and are neutralized by water to become hydroxide ions. Also, the saturated deprotonation method was applied to hematite, and it was found that all the acid hydroxyl groups on hematite were deprotonated in very high concentrations of alkali solutions ( approximately 5 mol dm-3 NaOH), and from the saturated amount of OH- consumed by deprotonation, the same result as that by the Grignard method was obtained. It is shown that all hydroxyl groups take part in ion exchange and that the unusually small values reported elsewhere with the saturated (de)protonation method may contain errors. Hetero- or homogeneity of hydroxyl groups in contact with water as ion-exchange sites is also discussed. It is suggested that intensely hydrated layers at the oxide/water interface may result in homogeneous discrete sites. The development of microstructures in the oxides was suggested from the measured values of specific surface areas, and the effect of the microstructure environments on the reactivity of internal surface hydroxyl sites is discussed. Copyright 1999 Academic Press.