Chromosome aberrations in workers of nuclear-power plants

The frequencies of chromosome aberrations in 135 workers from nuclear-power plants were compared with those in 135 age-matched controls. A total of 135,000 cells was scored. The frequencies of dicentric chromosome were 1.67 × 10⁻³ in the exposed group and 0.49 × 10⁻³ in the control group and those of chromosome-type deletion were 3.33 × 10⁻³ and 1.10 × 10⁻³, respectively. The frequencies of all types of chromosome aberrations in the exposed subjects were higher than those in the control group, but no significant trend of dose-dependent increase was observed when only the exposed group were considered. Poisson regression analysis, with both exposed and control included, showed that there was a significant association of chromosome aberration with radiation dose and the duration of work, but not with age, smoking habit and alcohol intake. It was also found that recent exposure to radiation, within the last 5 years, had contributed more to the observed chromosome aberration than earlier exposure.     

NMDA Receptor antagonists prevent acute ammonia toxicity in mice

We proposed that acute ammonia toxicity is mediated by activation of NMDA receptors. To confirm this hypothesis we have tested whether different NMDA receptor antagonists, acting on different sites of NMDA receptors, prevent death of mice induced by injection of 14 mmol/Kg of ammonium acetate, a dose that induces death of 95% of mice. MK-801, phencyclidine and ketamine, which block the ion channel of NMDA receptors, prevent death of at least 75% of mice. CPP, AP-5, CGS 19755, and CGP 40116, competitive antagonists acting on the binding site for NMDA, also prevent death of at least 75% of mice. Butanol, ethanol and methanol which block NMDA receptors, also prevent death of mice. There is an excellent correlation between the EC₅₀ for preventing ammonia-induced death and the IC₅₀ for inhibiting NMDA-induced currents. Acute ammonia toxicity is not prevented by antagonists of kainate/AMPA receptors, of muscarinic or nicotinic acetylcholine receptors or of GABA receptors. Inhibitors of nitric oxide synthase afford partial protection against ammonia toxicity while inhibitors of calcineurin, of glutamine synthetase or antioxidants did not prevent ammonia-induced death of mice. These results strongly support the idea that acute ammonia toxicity is mediated by activation of NMDA receptors.     

Rapid screening of an SH2-containing gene using PCR amplification method

Summary To isolate a novel gene that contains an SH2 domain, we devised a rapid and nonradioactive cDNA library screening method using polymerase chain reaction (PCR). For PCR amplification, we designed degenerate oligonucleotide primers from the multialigned DNA sequences of SH2 domains. This method offers an inexpensive and efficient approach for the isolation of clones of interest from cDNA libraries.     

Production of high fructo-oligosaccharide syrup with two enzyme system of fructosyltransferase and glucose oxidase

Summary A novel two enzyme system of fructosyltransferase and glucose oxidase to enhance the content of the net fructo—oligosaccharide (FOS) fractions in the industrial production of FOS syrup from sucrose was devised. The net FOS content in the commercial FOS syrup has been limited only to 55–60 % due to the accumulation of glucose which acts as a feedback inhibitor of the fructosyltransferase. By supplementing glucose oxidase to the conventional FOS reaction system, we could convert the glucose to gluconic acid readily separable from neutral sugars by simple ion exchange operation in the next step. The simultaneous removal of glucose was proved effective in proceeding the reaction by fructosyltransferase further by relieving the product inhibition caused by glucose. By this way, we could raise the net FOS content as high as 90 %.     

Cultivation of mammalian cells as aggregates in bioreactors: effect of calcium concentration of spatial distribution of viability

Recombinant human kidney epithelial 293 cells were cultivated as aggregates in suspension. The concentration calcium ion, in the range of 100 muM to 1mM, affected the rate of aggregate formation. During the course of cultivation the size distribution of aggregates shifted and the fraction of larger aggregates increased. This effect was more profound in cultures with a high calcium concentration. Scanning and transmission microscopic examination of the aggregates revealed that cell packing was greater in the high calcium cultures and that ultrastructural integrity was retained in aggregates from both low and high calcium cultures. Confocal microscopy was applied to examine the viability of cells in the interior of the aggregates. High viability was observed in the aggregates obtained from exponentially growing cultures. Aggregates from the high calcium culture in the stationary phase exhibited lower viability in the interior. With its ease of retention in a perfusion bioreactor, aggregate cultures offer an alternative choice for large-scale operation. (c) 1993 John Wiley & Sons, Inc.     

REGENERATION AND SEXUAL DIFFERENTIATION OF GRIFFITHSIA JAPONICA (CERAMIACEAE,RHODOPHYTA) THROUGH SOMATIC CELL FUSION1

Hybrid cells were obtained from somatic cell fusion among male, female, and tetrasporangial plants in Griffithsia japonica Okamura by a wound-healing process. Isolated fusion cells regenerated new mature plants with mixed reproductive structures. The plants regenerated from hybrid cells between male and female plants developed into 1) spermatangiate, 2) carpogonial, 3) bisexual with spermatangia and carpogonial branches, 4) mixed-phase with spermatangia and tetrasporangia, or 5) bisexual/mixed-phase plants with spermatangia, carpogonial branches, and tetrasporangia. About 70% of the plants regenerated from hybrid cells between male and female plants produced tetrasporangia that were always formed with spermatangia on a single cell. Some of those tetrasporangia released tetraspores, six of which gave rise to mature plants. The plants regenerated from hybrid cells between male and tetrasporangial plants developed into spermatangiate, tetrasporangiate, or mixed-phase plants with spermatangia and tetrasporangia. The plants regenerated from hybrid cells between female and tetrasporangial plants developed into carpogonial, tetrasporangiate, or mixed-phase plants with carpogonial branches and tetrasporangia. All types of reproductive structures we re functional.     

Cell separation from high cell density broths of Alcaligenes eutrophus by using a coagulant

Summary Alcaligenes eutrophus was successfully recovered from high cell density broths by pre-treatment with polyaluminium hydroxide chloride silicate as a coagulant at 36–90 mg Al/l. The optimum pH range for cell coagulation was 10–12. Subsequent centrifugation (45×g) and filtration (pore size 0.5 mm) gave a cell recovery of higher than 90%. The energy demand for cell recovery with the coagulant was only 3–11% of that without it.     

瑞氏七鳃鳗乳酸脱氢酶（LDH）同工酶凝胶电泳分析

本文用聚丙烯酰胺凝胶电泳方法,对瑞氏七鳃鳗五种不同组织（骨骼肌、心、肾、肠、鳃）中ＬＤＨ同工酶进行了分析研究,结果表明,ＬＤＨ同工酶具有组织特异性,其中骨骼肌中含有五种ＬＤＨ同。酶,即ＬＤＨ１、ＬＤＨ２、ＬＤＨ３、ＬＤＨ４、ＬＤＨ５,鳃含有ＬＤＨ１和ＬＤＨ４而肾和心只含有ＬＤＨ１,肠只含有ＬＤＨ４。