Cytotoxic effect of 1-methyl-4-phenylpyridinium ion on human melanoma cell lines, HMV-II and SK-MEL-44, is dependent on the melanin contents and caused by inhibition of mitochondrial electron transport

MPP+, an oxidative metabolite of a neurotoxin, MPTP, was found to be cytotoxic to human melanoma cell lines, HMV-II and SK-MEL-44. After 3 days of culture in the presence of MPP+, a larger amount of MPP+ was accumulated in HMV-II cells than in SK-MEL-44 cells, which correlated well with the melanin contents; HMV-II cells contain larger amounts of melanin than SK-MEL-44 cells. After 6 days of culture in the presence of MPP+, the cytotoxicity of MPP+ on these cell types was evaluated by counting cell numbers with the dye exclusion test and double-layer soft agar clonogenic assay. It was found that exposure to MPP+ reduced the survival of HMV-II cells more significantly than that of SK-MEL-44 cells. In HMV-II cells, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay was used to elucidate the mechanism of MPP+ lethality. The formazan formation was reduced markedly by the presence of MPP+ at concentrations much lower than those required for cell death. These results suggest that cytotoxicity of MPP+ may be ascribed to its accumulation due to high affinity for melanin, and to inhibition of the enzymes utilizing ubiquinone in the mitochondrial respiratory chain.     

Nutritional characteristics of a neoglycoprotein, casein modified covalently by glucose

Glucose was combined covalently with the epsilon-amino groups of lysyl residues of bovine casein in the presence of sodium cyanoborohydride as a reducing reagent by reductive alkylation, forming stable secondary amine linkages. Solubility characteristics and nutritional values of the neoglycoprotein were examined. The degree of modification (%) of the glucosylated casein was 82.5. Solubility of the modified casein was increased by the attachment of glucose. The modification did not disturb the digestion of casein by pepsin or trypsin. Rat feeding experiments using 10% protein diets demonstrated that the protein efficiency ratio (PER) of the modified casein was 0.35 +/- 0.33 compared with 2.99 +/- 0.29 for the unmodified casein. When the modified casein was supplemented with L-lysine to equal the level of total lysine of unmodified casein, the PER value was increased to 2.21 +/- 0.29. Nitrogen balance experiments showed that the modified casein was digested completely. On the other hand, biological value and net protein utilization of the modified protein were shown to be considerably lower than those of the unmodified casein.     

Induction of mutation in mouse FM3A cells by N4-aminocytidine-mediated replicational errors.

To explore the potential use of a nucleoside analog, N4-aminocytidine, in studies of cellular biology, the mechanism of mutation induced by this compound in mouse FM3A cells in culture was studied. On treatment of cells in suspension with N4-aminocytidine, the mutation to ouabain resistance was induced. The major DNA-replicating enzyme in mammalian cells, DNA polymerase alpha, was used to investigate whether the possible cellular metabolite of N4-aminocytidine, N4-aminodeoxycytidine 5'-triphosphate (dCamTP), can be incorporated into the DNA during replication. Using [3H]dCamTP in an in vitro DNA-synthesizing system, we were able to show that this nucleotide analog can be incorporated into newly formed DNA and that it can serve as a substitute for either dCTP or dTTP. dCamTP in the absence of dCTP maintained the activated calf thymus DNA-directed polymerization of deoxynucleoside triphosphates as efficiently as in its presence. Even in the presence of dCTP, dCamTP was incorporated into the polynucleotide. When dCamTP was used as a single substrate in the poly(dA)-oligo(dT)-directed polymerase reaction, it was incorporated into the polynucleotide fraction. The extent of incorporation was 4% of that of dTTP incorporation when dTTP was used as a single substrate. Even in the presence of dTTP, dCamTP incorporation was observed. A copolymer containing N4-aminocytosine residues was shown to incorporate guanine residues opposite the N4-aminocytosines. However, we were unable to observe adenine incorporation opposite N4-aminocytosine in templates. These cell-free experiments show that an AT-to-GC transition can take place in the presence of dCamTP during DNA synthesis, strongly suggesting that the mutation induced in the FM3A cells by N4-aminocytidine is due to replicational errors.     

Day-night changes in production of carbohydrate and protein by natural phytoplankton population from Lake Biwa, Japan

The ¹³C and gas chromatography-mass spectrometry (¹³C-GC-MS)method was applied to determine the day-night changes in thecomposition of photosynthetic products of the natural phytoplanktonpopulation from Lake Biwa, Japan. Glucose is the most abundantmonosaccharide in acid-hydrolyzable carbohydrate. The contributionof glucose was high in incubatesd samples in daytime and decreasedduring the night. Other monosaccharides (rhamnose, fucose, ribose,arabinose, xylose, mannose and galactose) and amino acids tendedto be produced throughout both day- and night-time. These resultssuggested that the carbon flows from glucose, which might constitutereserve glucan, to other monosaccharides and amino acids duringnight-time. The disproportionate production of glucose (reservedglucan) during daytime was thus partly cancelled out at night.     

Isolation and Characterization of a Photosystem II Core Complex Depleted in the 43 kDa-Chlorophyll-Binding Subunit

The photosystem II core complex purified from digitonin extractsof spinach chloroplasts was resolved into two chlorophyll-proteincomplexes by digitonin polyacrylamide gel electrophoresis aftertreatment with 1 M potassium thiocyanate. One of the chlorophyll-proteincomplexes resolved consisted of 47, 32, 30 and 9 kDa polypeptidesand the other was complementally composed of only the 43 kDapolypeptide. The former complex was highly active in the photoreductionof 2, 6-dichlorophenol indophenol by 1,5-diphenylcarbazide andretained all of the components responsible for the electrontransport from the secondary electron donor (Z) to the primaryelectron acceptor (Q_A). EPR signal II_fast and II_slow were alsopreserved in this complex although their hyperfine structureswere largely modified. The complex was estimated to contain1.8 molecules of plastoquinone A as well as 1.5, 3.7 and 3.9molecules of cytochrome b559, pheophytin and ß-carotene,respectively, per Q_A. These results indicate that potassiumthiocyanate specifically removes the 43 kDa polypeptide fromthe PS II core complex leaving the electron transport systemin an almost intact state. (Received June 17, 1987; Accepted October 23, 1987)     

Salt tolerance of the reed plant Phragmites communis

Reed plants ( Phragmites communis Trinius) were grown at NaCl concentrations up to 500 m M and their growth, mineral contents and leaf blade osmotic potential were determined. Addition of NaCl up to 300 m M did not affect growth significantly. Sucrose, Cl^-and Na⁺ concentrations in the shoots increased with the salinity of the medium and the shoot water content decreased. K⁺ always contributed most to the leaf osmotic potential. Even in the presence of 250 m M NaCl in the rooting medium, the leaf blade contained only 50 mM Na⁺, suggesting that the plants have an efficient mechanism for Na⁺ exclusion. ²²Na⁺ uptake experiments suggested that the retranslo-cation of absorbed Na⁺ from shoots to the rooting medium lowered the uptake of Na⁺.     

Morphology and Hormone Levels of Tobacco and Carrot Tissues Transformed by Agrobacterium tumefaciens I. Auxin and Cytokinin Contents of Cultured Tissues Transformed with Wild-Type and Mutant Ti Plasmids

Carrot and tobacco plants were transformed with Agrobacteriumtumefaciens harboring wild-type, aux^– or cyt^– Tiplasmids. In tobacco, these wild and mutant Ti plasmids inducedthe formation of non-morphogenic galls, galls with shoots, andgalls with roots, respectively. In carrot, however, transformationwith any of these plasmids resulted in only the formation ofamorphous tumors. Determination of IAA and cytokinin contentsshowed that in tobacco, significantly high amounts of cytokininsor IAA are present in the cells transformed with Ti plasmidspossessing cytokinin or IAA biosynthetic genes, respectively.In carrot, cytokinin contents were also high in the cells transformedwith Ti plasmids having cytokinin biosynthetic genes, whereasIAA contents of the cells were similar regardless of the plasmidsused for transformation. These results suggest that the mechanism regulating IAA metabolismmay be different in tobacco and carrot. (Received June 25, 1987; Accepted February 1, 1988)     

Detection of fimbriae and fimbrial antigens on the oral anaerobe Bacteroides gingivalis by negative staining and serological methods

We screened 63 clinical isolates of Bacteroides gingivalis from eight different laboratories for the presence of fimbriae by negative staining and by immunological methods. Techniques used were bacterial agglutination, Ouchterlony immunodiffusion and Western immunoblotting analysis using rabbit anti-fimbriae and anti-fimbrilin sera raised against fimbriae and fimbrilin (a constituent protein of B. gingivalis fimbriae) from B. gingivalis strain 381. In 49 of the 51 strains tested, fimbriae were clearly detected by negative staining, and 30 (60%) of the fimbriate strains were positive in all three of the immunological assays. A total of 37 strains (75%) were positive by immunoblotting analysis, which was the most reliable of the serological methods used in this study. The study shows that the majority of B. gingivalis strains are fimbriate, and that these fimbriae are immunologically related to the fimbriae of B. gingivalis strain 381. Molecular heterogeneity of fimbrilin was discovered by the immunoblotting analysis, when different strains were compared. With most of the strains, including strain 381, the antifimbrilin serum reacted with a protein of apparent molecular mass 43 kDa, but with 15 strains the immuno-reactive protein had an apparent molecular mass of 46 kDa.     

Annual changes in the testicular activity of the river sculpin, Cottus hangiongensis Mori, with emphasis on the occurrence of aberrant spermatids during spermatogenesis

Annual changes in the spermatogenetic activity of the testis were studied histologically in the river sculpin. Coitus hangiongensis , sampled monthly from a river in southern Hokkaido, Japan. A pair of sperm reservoirs, consisting of many anastomosing lacunae, was present along the dorsomedian edge of the paired testes, and functioned also as a sperm-transporting system instead of the typical sperm duct. Spermatogenesis occurred actively in August, yielding an increasing number of mature spermatozoa in October. This process advanced, but slowly during the succeeding winter months, until March. The testis became functionally mature during the spawning period in April and May. In July, small numbers of spermatocytes were found to have appeared already, which indicated a relatively short period of post-spawning testicular regression. In November, germinal cysts containing aberrant binuclear spermatids began to appear within the seminal lobules. The paired nuclei of aberrant spermatids gradually enlarged, and the cells were released into the lumina of the seminal lobules simultaneously with the release of mature spermatozoa from the germinal cysts. During the functional maturity stage, lumina of seminal lobules which had expelled mature spermatozoa to sperm reservoirs became filled with these abnormal bodies. Discussion includes the occurrence of aberrant spermatids which resulted in the formation of 'spermatid masses' as has been described in other cottids.