The molecular basis for the absence of N-glycolylneuraminic acid in humans

N-Glycolylneuraminic acid (NeuGc) is abundantly expressed in most mammals, but it is not detectable in humans. The expression of NeuGc is controlled by cytidine monophospho-N-acetylneuraminic acid (CMP-NeuAc) hydroxylase activity. We previously cloned a cDNA for mouse CMP-NeuAc hydroxylase and found that the human genome contains a homologue. We report here the molecular basis for the absence of NeuGc in humans. We cloned a cDNA for human CMP-NeuAc hydroxylase from a HeLa cell cDNA library. The cDNA encodes a 486-amino acid protein, and its deduced amino acid sequence lacks a domain corresponding to the N-terminal 104 amino acids of the mouse CMP-NeuAc hydroxylase protein, although the human protein is highly identical (93%) to the rest of the mouse hydroxylase protein. The N-terminal truncation of the human hydroxylase is caused by deletion of a 92-base pair-long exon in human genomic DNA. The human hydroxylase expressed in COS-7 cells exhibited no enzymatic activity, and a mouse hydroxylase mutant, which lacks the N-terminal domain, was also inactive. A chimera composed of the human hydroxylase and the N-terminal domain of the mouse hydroxylase displayed the enzyme activity. These results indicate that the human homologue of CMP-NeuAc hydroxylase is inactive because it lacks an N-terminal domain that is essential for enzyme activity. The absence of NeuGc in human glycoconjugates is due to a partial deletion in the gene that encodes CMP-NeuAc hydroxylase.     

Synaptic physiology and ultrastructure in comatose mutants define an in vivo role for NSF in neurotransmitter release

N-Ethylmaleimide-sensitive fusion protein (NSF) is a cytosolic protein thought to play a key role in vesicular transport in all eukaryotic cells. Although NSF was proposed to function in the trafficking of synaptic vesicles responsible for neurotransmitter release, only recently have in vivo experiments begun to reveal a specific function for NSF in this process. Our previous work showed that mutations in a Drosophila NSF gene, dNSF1, are responsible for the temperature-sensitive paralytic phenotype in comatose (comt) mutants. In this study, we perform electrophysiological and ultrastructural analyses in three different comt alleles to investigate the function of dNSF1 at native synapses in vivo. Electrophysiological analysis of postsynaptic potentials and currents at adult neuromuscular synapses revealed that in the absence of repetitive stimulation, comt synapses exhibit wild-type neurotransmitter release at restrictive (paralytic) temperatures. In contrast, repetitive stimulation at restrictive temperatures revealed a progressive, activity-dependent reduction in neurotransmitter release in comt but not in wild type. These results indicate that dNSF1 does not participate directly in the fusion of vesicles with the target membrane but rather functions in maintaining the pool of readily releasable vesicles competent for fast calcium-triggered fusion. To define dNSF1 function further, we used transmission electron microscopy to examine the distribution of vesicles within synaptic terminals, and observed a marked accumulation of docked vesicles at restrictive temperatures in comt. Together, the results reported here define a role for dNSF1 in the priming of docked synaptic vesicles for calcium-triggered fusion.     

Aquacultural approaches to recycling of dissolved nutrients in secondarily treated domestic wastewaters—I Nutrient uptake and release by artificial food chains

Wastewater based artificial food chains composed of sequential monocultures of a suspended unicellular green alga, of an herbivorous cladoceran crustacean, and of an herbivorous or a carnivorous teleost fish and of filamentous green algae were studied in an effort to find efficient, potentially economically viable mechanisms for the biological capture (tertiary treatment) of nutrients (especially nitrate and phosphate) in wastewaters processed by small to medium size two-stage treatment plants that primarily handle domestic and agricultural wastes.All experiments were carried out on laboratory scale systems with a low technology approach to keep apparatus and procedures as simple and reliable as possible.Among all organisms tested as components of the artificial food chains only the unicellular green alga Scenedesmus, the filamentous green algae Cladophora and Ulothrix, the cladoceran crustaceans Daphnia magna and Daphnia pulex, and the teleost fishes Notemigonus crysoleucas, Pimephales promelas and Notropis lutrensis were found to be suitable.Unmodified secondarily treated domestic effluents were both iron deficient and lacking in buffering capacity necessary for optimal algal growth. Additions of both ferrous iron (1 ppm) and carbon dioxide (5%) were required to achieve good quality cultures suitable for feeding cladocerans. Most removal of nutrients occurred in the first algal stage of the food chain. Nitrate removal averaged 78%, phosphate removal 55% in buffered algal cultures. In unbuffered cultures nitrate removal was 30%, phosphate removal 98%. The near complete removal of phosphate in unbuffered algal cultures was probably due to physico-chemical precipitation of phosphate complexes formed as a result of high pH levels (pH > 10) reached within 24 h of culture initiation. Cladoceran and fish stages added nutrients (mostly ammonia and phosphate) back into the effluent. A final stage of Ulothrix and Cladophora algae removed nutrients regenerated by cladocerans and fishes. A 12 h light–12 h dark cycle statistically significantly reduced levels of nutrient removal by both unbuffered and buffered algal cultures below removal rates measured in algae cultured in continuous light. Daily harvesting rates of 25–75% of culture volumes had no significant effect upon removals of nitrate by buffered algal cultures; phosphate removals were inversely proportional to harvesting rates in these cultures.Important theoretical and technical points are discussed.     

Superconducting properties of the composite-processed Nb3Sn superconductor with the Cu-Sn-Zn matrix

Effects of the Zn addition to the Cu-Sn matrix of the Nb₃Sn composite tape have been investigated by measuring the matrix work-hardening behaviour, the rate of Nb₃Sn layer formation and the pertinent superconducting properties. The Zn addition drastically enhances the diffusion rate of Nb₃Sn formation at each Sn level in the matrix examined, leading to sufficient superconducting properties even at a low Sn level of 3.5 at. %; a sample containing 3.5 at. % Sn and 15 at. % Zn in the matrix exhibits a critical temperature and critical current density comparable with those of samples at a Sn level of 7 at. %. The upper critical field obtained for a sample with the 6 at. % Cu-6 at. % Sn-4 at. % Zn matrix beyond 200 kOe. The work-hardening of the composite matrix is found to be essentially a function of Sn level, and insensitive to the Zn addition.     

Effect of short‐term anaerobic conditions on the production of volatiles,activity of alcohol acetyltransferase and other quality traits of ripened bananas. Sumithra K Wendakoon. Yoshinori Ueda. Yoshihiro Imahori. Megumi Ishimaru. Journal of the Science of Food and Agriculture, 2006; 86: 1475–1480

The original article to which this Erratum refers was published in Journal of the Science of Food and Agriculture, 2006; 86: 1475–1480.     

The effect of intraperitoneal and intra-aortic chemotherapy for unresectable gastric cancer

Regional chemotherapy was given 16 unresectable gastric cancer patients. Two types of the chemotherapy, intraperitoneal (IP) and intraaortic (IA) administration, were carried out. The control group was comprised of 17 patients. The response of the chemotherapy for primary tumor was 36.4% in the IP group and 20% in the IA one. Among these patients, 2 of 11 in IP and 1 of 5 in IA were able to resect the primary tumor. The 50% survival time of IP, IA and control was 347, 227 and 78 days, respectively. One-year survival rates of IP, IA and control were 68%, 29% and 0%, respectively. IP showed a significantly longer survival rate than controls (p < 0.001). All but one patient was able to stay at home. Intraperitoneal chemotherapy showed both local and systemic effects in unresectable gastric cancer.     

Evaluation of the genotoxicity of stevioside and steviol using six in vitro and one in vivo mutagenicity assays

Stevioside, a constituent of Stevia rebaudiana, is commonly used as a non-caloric sugar substitute in Japan. The genetic toxicities of stevioside and its aglycone, steviol, were examined with seven mutagenicity tests using bacteria (reverse mutation assay, forward mutation assay, umu test and rec assay), cultured mammalian cells (chromosomal aberration test and gene mutation assay) and mice (micronucleus test). Stevioside was not mutagenic in any of the assays examined. The aglycone, steviol, however, produced dose-related positive responses in some mutagenicity tests, i.e. the forward mutation assay using Salmonella typhimurium TM677, the chromosomal aberration test using Chinese hamster lung fibroblast cell line (CHL) and the gene mutation assay using CHL. Metabolic activation systems containing 9000 g supernatant fraction (S9) of liver homogenates prepared from polychlorinated biphenyl or phenobarbital plus 5,6-benzoflavone-pretreated rats were required for mutagenesis and clastogenesis. Steviol was weakly positive in the umu test using S.typhimurium TA1535/pSK1002 either with or without the metabolic activation system. Steviol, even in the presence of the S9 activation system, was negative in other assays, i.e. the reverse mutation assays using S.typhimurium TA97, TA98, TA100, TA102, TA104, TA1535, TA1537 and Escherichia coli WP2 uvrA/pKM101 and the rec-assay using Bacillus subtilis. Steviol was negative in the mouse micronucleus test. The genotoxic risk of steviol to humans is discussed.