DNA breaks and repair in the mouse leukemia L1210 cells exposed to three different types of interstrand DNA cross-linkers

DNA breaks and repair in mouse leukemia L1210 cells treated with 3 different types of cross-linkers, mitomycin C (MMC), 1-(4-amino-2-methyl-5-pyrimidinyl)-methyl-3-(2-chloroethyl)-3-nitroso ure a hydrochloride (ACNU) and SN-07 (a macromolecular antibiotic), were studied. Measured in D37 values, MMC gave the highest number of cross-links per lethal 'hit' directly after the 1-h treatment in the alkaline elution assay, followed by ACNU and SN-07. A good dose-response increase in induced interstrand DNA cross-linking frequency was observed in cells treated with 2.5-10 micrograms/ml MMC and with 10-100 micrograms/ml ACNU for 1 h with and without 24-h post-incubation. After 6-h post-incubation, the highest frequency of cross-linking was observed in cells treated with 2.5 micrograms/ml MMC and 30 micrograms/ml ACNU, while cross-link production continued in the cells treated with SN-07 for 12-h post-incubation. No significant increase in DNA breaks was observed in cells treated with MMC throughout 24-h post-incubation. The highest frequency of single-strand DNA breaks in cells treated with ACNU was observed immediately after the treatment and they disappeared after 6-h post-incubation. After 24-h post-incubation, a marked enhancement of the DNA breaks was observed in cells treated with SN-07 and the cells contained double-strand DNA breaks also. RNA synthesis was not affected in the cells treated with 10 micrograms/ml MMC and slightly inhibited to 70% of control in those treated with 100 micrograms/ml ACNU, while DNA synthesis in both cells was significantly inhibited after 24-h post-incubation. By contrast, both RNA and DNA synthesis were completely inhibited in cells treated with 8.0 micrograms/ml SN-07.     

Identification of a transforming gene of human papillomavirus type 16.

Previously, we observed sequential two-step alteration, growth stimulation, and progression to a more malignant state in NIH 3T3 cells transfected by human papillomavirus type 16 (HPV-16) DNA. In this study, we prepared a cDNA library from RNA extracted from cells transfected with the HPV-16 DNA and isolated cDNA clones which had growth-stimulating activity. Analysis of these cDNA clones indicated that the E7 open reading frame alone is responsible for inducing both steps of this cell transformation.     

Isolation of human retinal genes: recoverin cDNA and gene.

A human retina cDNA library enriched for retina-specific clones was prepared by subtraction with a non-retina population of cDNA in combination with polymerase chain reaction (PCR) amplifications. A highly retina-specific cDNA clone (1190 bp) was obtained through this library encoding a 200 amino acid protein with three calcium binding sites and 87% homology to the bovine photoreceptor protein, recoverin, which has been shown to mediate the recovery of the dark current after photoactivation, and 58% homology to the calcium-binding chick cone protein, visinin. Analysis of the gene indicated a 9-10 kb single-copy gene with at least three exons and two introns. The three exons contained the entire coding sequence, and all of the calcium-binding EF-hand regions were in putative exon 1. The recoverin gene was mapped to human chromosome 17 by hybridization to a panel of human-rodent hybrid DNAs.     

The secondary structure of the colicin E3 immunity protein as studied by 1H-1H and 1H-15N two-dimensional NMR spectroscopy.

By performing 1H-1H and 1H-15N two-dimensional (2D) nuclear magnetic resonance (NMR) experiments, the complete sequence-specific resonance assignment was determined for the colicin E3 immunity protein (84 residues; ImmE3), which binds to colicin E3 and inhibits its RNase activity. First, the fingerprint region of the spectrum was analyzed by homonuclear 1H-1H HOHAHA and NOESY methods. For the identification of overlapping resonances, heteronuclear 1H-15N (HMQC-HOHAHA, HMQC-NOESY) experiments were performed, so that the complete 1H and 15N resonance assignments were provided. Then the secondary structure of ImmE3 was determined by examination of characteristic patterns of sequential backbone proton NOEs in combination with measurement of exchange rates of amide protons and 3JHN alpha coupling constants. From these results, it was concluded that ImmE3 contains a four-stranded antiparallel beta-sheet (residues 2-10, 19-22, 47-49, and 71-79) and a short alpha-helix (residues 31-36).     

Water Soluble Pigments Containing Xylose and Glucose in Gametangia of the Green Alga, Bryopsis maxima

Several water-soluble pigments were purified from gametangiaof Bryopsis maxima by liquid chromatography and characterizedby pyridylamination and high-performance anion-exchange chromatography.The structure of the main red pigment is proposed based on thedata of infrared spectrum, Mass spectrum, ¹H and ¹³C NMR spectraand pyridylamino analysis. As a consequence, this pigment containeda tetrapyrrole with phytol and a sugar chain comprised of xyloseand glucose. The sequence of the sugars in the chain was determinedbased on its Mass spectrum. The pigment was similar to chlorophyll-originpigments observed in other plants. No aldehyde group, however,was present at C5 in the open tetrapyrrole chain. (Received August 3, 1994; Accepted November 10, 1994)     

Correlation of the Period Length of Circadian Rhythms with the Length of Immaturity in Paramecium bursaria

The circadian photoaccumulation rhythm of thirty strains of Paramecium bursaria collected at different places in Japan and China were measured with a microcomputer assisted data collection apparatus. Although most strains showed a period of 23-26 hours in LL, we found two strains of conspicuously different periods; a short period strain (UK1, 21.8 hr) and a long period strain (T316, 28.7 hr). F1 progeny from a cross between the short and the long period strains showed an intermediate period of about 24.7 hours (range 22.5-25.8 hr). The character was not distributed in a Mendelian ratio among the F1 progeny. We isolated a mutant (E2) with short period (21.8 hr) from the stock strain Kz1 by treatment with nitrosoguanidine (MNNG). The progeny of crosses between E2 and UK1, and between E2 and T316 exhibited the short period and the normal period phenotype respectively. Moreover, the progeny from a cross between E2 and a wild type strain (Sj2w) became sexually mature about 25 fissions after conjugation. This length of immaturity is much shorter than that of the progeny from wild type strains (about 50 fissions). This early maturation character was inherited to progeny in a Mendelian ratio. Homozygotes for the early maturation allele (EM2) exhibited mating ability about 15 fissions after conjugation. These data suggest that there is a correlation between the period length of the circadian rhythm and the length of immaturity after conjugation in Paramecium bursaria.     

Morphine-like analgesic actions of enkephalin-like peptides containing the Tyr-Arg unit

The analgesic actions of some synthetically prepared peptides having the Tyr-D-Arg unit at the N terminal portion of met- and leu-enkephalin were measured by the intra-cisternal injection method in mice. Among them, Tyr-D-Arg-Gly-Phe (DR-4) induced the most potent naloxone-reversible analgesia and was also effective by s.c. injection. DR-4 showed the good affinity to mu-receptor, and the resistance to the enzymatic degradation.     

15-Acetoxycostunolide from Magnolia sieboldii

A new germacranolide isolated from M. sieboldii was shown to be 15-acetoxycostunolide by spectroscopic and chemical methods. ¹H NMR spin decoupling and NOE experiments in the presence of a lanthanide shift reagent were used for structure elucidation.     

Effect of organic acid on gastrointertinal motility of rat invitro

The quantity of organic acids ( lactic acid, acetic acid, propionic acid and butyric acid ) in the content of the gastrointestinal tract of germ-free and conventional rats and the $\text{in}$$\text{vitro}$ effects of the organic acid on the motility of the gastrointestinal tract of rats were investigated.Organic acids were detected only in the gastrointestinal contents of conventional rats but not in those of germ-free rats.Lactic acid detected in the stomach of rats stimulated the motility of both small and large bowel while acetic acid, propionic acid and butyric acid found in the cecum stimulated the motility of the large bowel but not of small bowel.     

Formation of biologically active protein from the subunits of islets-activating protein (IAP), a new protein isolated from Bordetella pertussis.

Based on the finding reported in the preceding paper (Kanbayashi, et al.: J. Biochem) that subunits of islets-activating protein (IAP), a new protein purified from the culture media of Bordetella pertussis, were inactive as such, but regained the original biological activities when recombined, the conditions required for recovery of the biological activities were studied. Essentially the same biological activities as the native IAP were recovered when the smallest subunit, F-3, was incubated with one of the other subunits, F-1 and F-2, at a pH of around 7, at temperatures below 30 degrees C and for longer than 12 h. During the incubation, association products were formed which were isolated by gel filtration as homogenous proteins that consisted of two subunits probably in a molar ratio of 1 : 1. The native IAP (consisting of two IAP subunits including F-3) were equipotent in enhancing insulin secretory responses, in inhibiting epinephrine-induced hyperglycemia, in inducing leukocytosis and in increasing histamine sensitivity in experimental animals.