Survival of human normal thyroid cells after X-ray irradiation

Normal thyroid cells from 25 individuals treated surgically for malignant or benign thyroid tumour were cultured in vitro and radiation induced cytotoxicity was studied. The mean lethal dose (Do), quasi-threshold (Dq), and extrapolation number (n) of survival curves of actively dividing thyroid cells assayed by colony formation were estimated to be 92.9 +/- 2.8 cGy (rad), 58.1 +/- 6.9 cGy and 2.0 +/- 0.1, respectively (average for 25 individuals +/- standard error). These results suggest that proliferating human thyroid cells are more sensitive to X-rays than most other nonhaematologic mammalian cells in similar assays. Cell survival was not significantly affected by sex, age, disease or exposure to atomic bomb radiation of the cell donor. However, the number of samples currently available is too small for definite conclusions in this regard.     

Rice chloroplast RNA polymerase genes: The absence of an intron in rpoC1 and the presence of an extra sequence in rpoC2

Summary The chloroplast genome contains sequences homologous to the Escherichia coli rpoA, rpoB and rpoC genes. The Choroplast rpoC gene is divided into rpoC1 and rpoC2, of which rpoC1 contains an intron. Comparison of the rice rpo genes with those from tobacco, spinach and liverwort revealed unique features of the rice genes; the lack of an intron in rpoC1 and the presence of an extra sequence of 381 by in rpoC2. The intron in rpoC1 is thus optional, and possible intron boundary sites in split rpoC1 genes can be estimated by comparison with rice rpoC1. The extra sequence is located in the middle of rpoC2 and has repeated structures. The amino acid sequence deduced from this sequence is extremely hydrophilic and anionic. The origin and function of this sequence are discussed.     

Treatment of murine SCC VII tumors with localized hyperthermia and temperature-sensitive liposomes containing cisplatin

The release of cisplatin (CDDP) encapsulated in temperature-sensitive unilamellar liposomes to murine SCC VII carcinoma by localized hyperthermia and the effects of the treatment on tumor growth were studied. A transition temperature of the temperature-sensitive liposomes containing cisplatin (LIP-CDDP) was 41 degrees C. Twenty-four hours after injection of LIP-CDDP, the heated tumors (42 degrees C, 60 min) contained 3.3 times more CDDP than the unheated tumors receiving free CDDP. Although the uptake of liposome-associated CDDP by liver was approximately threefold greater at 1.5 h after injection than uptake of free CDDP, it decreased about 50% over a 24-h period. No difference in uptake of the two forms of CDDP by kidney was observed. The combination of LIP-CDDP and localized heating at 42 or 43 degrees C was more effective relative to the amount of CDDP in delaying tumor growth than that of free CDDP and hyperthermia. Treatment with LIP-CDDP plus local heating resulted in a dose-modifying factor of 5.3 when compared with free CDDP and no hyperthermia. The dose-modifying factor was 2.8 when treatment with LIP-CDDP and heat was compared with treatment with free CDDP and heat. Thus CDDP could be released selectively from the temperature-sensitive liposomes by heat and resulted in both a greater uptake of the drug and a delay in tumor growth.     

Efficient introduction of contents of liposomes into cells using HVJ (Sendai virus)

The conditions for efficient introduction of the contents of liposomes into cells were examined using fragment A of diphtheria toxin (DA) as a marker; one molecule of DA can kill a cell when introduced into the cytoplasm. Liposomes containing DA (DA liposomes) were toxic to cells treated with HVJ (Sendai virus) at 4 degrees C just before exposure to DA liposomes at 37 degrees C, but were not toxic to untreated cells. This toxicity was temperature-dependent. DA outside of liposomes was not toxic to HVJ-treated cells. Results also showed that liposomes could fuse with HVJ at 37 degrees but not at 4 degrees C and that liposomes preincubated with HVJ at 37 degrees C could associate with cells. DA liposomes preincubated with HVJ at 37 degrees C were highly toxic to cells. This toxicity was dependent on the duration of preincubation with HVJ and the dose of HVJ. When plasmid DNA coded herpes simplex virus thymidine kinase was trapped in liposomes and fused with Ltk- cells with HVJ, the thymidine kinase activity was expressed in about 10% of the cells. These data show that naked liposomes fuse efficiently with cells with HVJ and that the contents of the liposomes can be introduced into the cytoplasm 100-10 000 times more efficiently by treatment of the cells or liposomes with HVJ.     

Cloning of the Schizosaccharomyces pombe mei3 gene essential for the initiation of meiosis

Summary Cells of the fission yeast Schizosaccharomyces pombe carrying the mei3 mutation are unable to initiate meiosis, being arrested before premeiotic DNA synthesis. A plasmid pDB(mei3)1 containing an 8.6 kilobases (kb) DNA insert which complemented mei3 mutations was isolated from an S. pombe genomic library constructed in the vector pDB248. A HindIII fragment of 2.6 kb subcloned in both orientations into pDB248 complemented the mei3 mutation. The plasmid was designated pDB(mei3)2. The 2.6 kb fragment ligated to the vector YIp32 was integrated into the S. pombe chromosome at the mei3 locus, indicating that the cloned DNA fragment contains the mei3 gene itself. Both pDB(mei3)1 and pDB(mei3)2 allowed partial recovery of meiotic and sporulation ability in mei1 mutants, suggesting a close relationship between the mei1 and mei3 genes. Northern blot analysis with pDB(mei3)2 as the probe indicated that the mei3 mRNA (1.3 kb in length) is more abundant in cells cultured in nitrogen-free sporulation medium than in nitrogen-rich growth medium.     

Metabolism of [14C]GA20 in a Cell-Free System from Developing Seeds of Phaseolus vulgaris L.

The metabolism of [¹⁴C]GA₂₀ during seed maturation of Phaseolusvulgaris was studied using cell-free systems from embryos rangingin age from 10 DAF (day after flowering) to 24 DAF. Enzyme preparationsfrom very immature seeds actively converted GA₂₀ to GA¹, GA₅and GA₆. The ratio of incubation products suggested the biosyntheticpathway of GA₂₀—GA₅—GA₆. Fluctuation in the levelsof endogenous C₁₉-GAs, namely GA₁, GA₄, GA₅, GA₆, GA₈, GA₉ andGA₂₀ was analyzed by GC-SIM using internal standards to compareenzyme activity with the levels of endogenous GAs. AlthoughGA₁, GA₄ and GA₆ showed maximum levels on 20 DAF, enzyme activitydecreased during seed maturation and showed weak activity on20 DAF. ¹Graduate student of the University of Tokyo, Department ofAgricultural Chemistry, Bunkyo-ku, Tokyo 113, Japan. ³Present address: Pesticides Research Laboratory, TakarazukaResearch Center, Sumitomo Chemical Co., Ltd., Takarazuka, Hyogo655, Japan. (Received December 17, 1987; Accepted March 30, 1988)     

Cytotaxonomic study of ferns of Yunnan,southwestern China

A cytotaxonomic study was made of 90 fern species of Yunnan, southwestern China, based on collections from northwestern, central, and southwestern Yunnan and a few Cheng's collections. The results verified most of the formerly reported basic chromosome numbers of Chinese genera, and recorded for the first time the basic numbers ofGymnogrammitis andSorolepidium and Chinese members of several other genera. Cytotaxonomy of some problematical genera was discussed. Biogeographical relationships between Japanese, Chinese, and Himalayan ferns were compared with special reference to local cyto-reproductive variations inConiogramme, Deparia, Onychium, andPteris cretica. The present evidence indicates that most triploid species examined are agamosporous, as general in filicalean ferns, and also suggests the sexual 32-spored sporogenesis inHypodematium crenatum andSorolepidium graciale as in Lindsaeaceae.     

cDNA cloning and sequencing of tobacco chloroplast ribosomal protein L12

Tobacco chloroplast ribosomal protein L12 was isolated as a ssDNA-cellulose-binding protein from a chloroplast soluble protein fraction. Based on the N-terminal amino acid sequence of chloroplast L12, a cDNA clone was isolated and characterized. The precursor protein deduced from the DNA sequence consists of a transit peptide of 53 amino acid residues and a mature L12 protein of 133 amino acid residues. The chloroplast L12 protein was synthesized with a reticulocyte lysate and subjected to nucleic acid-binding assays. L12 synthesized in vitro does not bind to ssDNA, dsDNA nor ribonucleotide homopolymers, but it binds to cellulose matrix.     

Effects of a beta 3-adrenoceptor agonist, BRL 26830A, on insulin and glucagon release in mice.

The beta 3-adrenoceptor agonist, BRL 26830A, which is not inhibited by either beta 1 or beta 2-selective antagonists, has been shown to possess anti-obesity and anti-diabetic actions. However, the effects of this agent on insulin and glucagon release have not yet been substantiated. Therefore, we tested the hypothesis that BRL 26830A promotes insulin and glucagon secretion via beta 3 receptors on pancreatic islet B and A cells. In ICR mice fasted for 48 h, BRL 26830A significantly stimulated insulin secretion from 5 min after administration, markedly decreased blood glucose levels from 30 min after administration, and significantly increased glucagon secretion from 30 min after administration. The administration of a non-selective beta-receptor antagonist, at a dose of 50 mg/kg, 30 min prior to BRL 26830A injection completely abolished the effects induced by BRL 26830A. However, the administration of a beta 1-selective antagonist at doses of 50 or 100 mg/kg did not produce any significant effects. On the action of BRL 26830A, whereas the administration of a beta 2-selective antagonist at 50 mg/kg, a near maximal effective dose, partially abolished the effects of BRL 26830A. BRL 26830A had no effect on insulin, glucagon, or glucose levels in streptozocin (STZ) diabetic mice fasted for 48 h. These results suggest that, in mice, BRL 26830A may promote insulin secretion mainly via beta 3 receptors and partially via beta 2 receptors on pancreatic-islet B cells, and that glucagon may be secreted as the result of hypoglycemia induced by this agent.     

Activity patterns ofChironomus yoshimatsui (Diptera: Chironomidae)

The activity patterns ofChironomus yoshimatsui were investigated experimentally to clarify whether temperature conditions experienced by the larvae and adults had an effect on the timing of adult activities. It was observed that when both larvae and adults were reared at a low temperature of 13°C, the peak of adult evening activities appeared just before simulated nightfall whereas when larvae and/or adults were reared at a high temperature of 23°C, the peak of activities occurred just after simulated night-fall. These results agreed well with field observations of seasonal changes in the timing of evening swarming and mating of this insect. The mechanism of regulating the timing of activities in accordance with temperature conditions is also discussed.