Localization of the functional sites on the alpha chain of acetylcholine receptor

A comprehensive synthetic approach, previously developed in this laboratory, has been applied to systematically screen the entire extracellular part (residues 1-210) of the alpha chain of the Torpedo californica acetylcholine receptor (AChR) for the profiles of the continuous regions that are recognized by antibodies against free, or membrane-sequestered, AChR; the regions recognized by AChR-primed T cells; the regions that bind alpha-bungarotoxin and cobratoxin; and an acetylcholine-binding region. Eight continuous antigenic sites were localized in this part of the alpha chain by all of the antisera tested. The sites were independent of the host species from which the antisera were obtained and were also similar to antisera against the isolated pentameric AChR or against the membrane-sequestered AChR. Six regions were found to stimulate AChR-primed T cells (T sites). Three of the T sites coincided with regions recognized by antibodies. At least two T sites had no detectable antibody responses directed to them. Five toxin-binding regions were localized, and may constitute distinct sites or, alternatively, different faces in one (or more) sites. Some of these regions coincided with regions recognized by anti-AChR antibodies. One of the toxin-binding regions bound acetylcholine, and immunization with this peptide induced experimental autoimmune myasthenia gravis.     

Quantitative relationships between growth and respiration

Red bean seedlings were grown from germination in the dark under three constant temperature coinditions (20, 25 and 30 C). Measurements of biomass and respiratory activities of their axes and cotyledons were made at one or two-day intervals. Two components of the axis respiration (constructive and maintenance respiration) were assumed, and they were evaluated separately. The constructive respiration coefficient was little affected by temperature, and was about 0.10 in every temperature treatment. The maintenance coefficient was on the other hand great affected by temperature, and the values were 0.036, 0.048 and 0.074 (mg C·mg C^?1·day^?1) in 20 C, 25 C and 30 C, respectively. The cumulative respiratory loss of carbon from the cotyledon during the experimental period was least in 20 C from among the three temperature conditions, and it was 40% of the total respiratory loss from the whole seedling. In 25 C and 30 C the losses were 47 and 46%, respectively. On the basis of these data concerning the respiratory losses and biomass changes, the carbon balance during the experimental period was examined, and some concepts of growth efficiencies were discussed.     

An analysis of age-and size-dependent flowering: A critical-production model

Three critical phenomena of flowering can be recognized in nature: critical age, critical initial size and critical switchover size. In order to understand the ecological significance of these flowering phenomena from the viewpoint of matter production, a simple model of flowering phenomean (critical-production model) was studied, assuming that plant flowering is controlled by the productive capacity of the plant (critical-production model, under the condition that plants forecast environmental conditions affecting matter production. Thus, we concluded that all three critical phenomena are various manifestation of the same critical-production principle. Then, using the model simulation, the reliability of each critical phenomenon for securing a given critical production was investigated in relation to the photosynthetic productivity of the habitat. The main predictions obtained from the simulation were as follows: 1) Only annual and biennial plants will show critical age phenomena, and most biennials will be facultative. 2) Among perennials, the critical initial size phenomenon will appear in low productive habitats, whereas in high productive habitats the critical switchover size phenomenon will be observed.     

Puccinia carici-adenocauli, a new rust fungus onCarex, and its anamorph,Aecidium adenocauli

Field observations and inoculation experiments showed thatAecidium adenocauli onAdenocaulon himalaicum was an anamorph of aPuccinia onCarex hakonensis andC. uda. From comparative morphology with caricicolous puccinias, the rust on theseCarex species was considered as a new species and was named asPuccinia carici-adenocauli. Contribution No. 142, Laboratory of Plant Pathology and Mycology, Institute of Agriculture and Forestry, University of Tsukuba     

Monoamine metabolites,iron induced seizures,and the anticonvulsant effect of tannins

Intracortical injections of iron ions have been shown to induce recurrent seizures and epileptic discharges in the EEG. (–)-Epigallocatechin (EGC) and (–)-epigallocatecatechin-3-O-gallate (EGCG), isolated from green tea leaves, have been reported to prevent or diminish the occurrence of epileptic discharges induced by iron ions, and to inhibit catechol-O-methyltransferase. Iron ions significantly increased DOPAC and HVA levels in the intrastriatal perfusate 140 and 180 minutes, respectively, after injection. EGC and EGCG inhibited the increases induced by iron ions. Furthermore, EGCG decreased the HVA level in the perfusate 200 minutes after injection whether or not iron ions were injected. Iron ions had no effect on the 5-HIAA level, and EGC and EGCG raised it. These results suggest that formation of an epileptic focus induced by iron ions might be accompanied by activation of dopaminergic neurons, and that EGC and EGCG inhibit that hyperactivity.     

H2 production from starch by a mixed culture of Clostridium butyricum and Rhodobacter sp. M[h]19

A photosynthetic bacterium having ability to produce H2 from acetic, butyric and lactic acids, Rhodobacter sp. M-19 was isolated. H2 was produced from starch in a batch culture by Clostridium butyricum and in a two-step batch culture by C. butyricum and Rhodobacter sp. M-19 in yields of 1.9 and 3.6 mol H2/mol glucose, respectively. A mixed culture of C. butyricum and Rhodobacter sp. M-19 produced H2 from starch with a yield of 6.6 mol H2/mol glucose in a fed-batch culture. © Rapid Science Ltd. 1998     

H2 production from starch by a mixed culture of Clostridium butyricum and Enterobacter aerogenes

A mixed continuous culture of Clostridium butyricum and Enterobacter aerogenes removed O2 in a reactor and produced H2 from starch with yield of more than 2 mol H2/mol glucose without any reducing agents in the medium. Co-immobilized cells of the bacteria on porous glass beads evolved H2 from starch at 1.3 l/l.h, with H2 yield of 2.6 mol H2/ mol glucose at dilution rate of 1.0 h–1 in a continuous culture.