Airway wall dimensions during carbachol-induced bronchoconstriction in rabbits

Sasaki, F., Y. Saitoh, L. Verburgt, and M. Okazawa.Airway wall dimensions during carbachol-inducedbronchoconstriction in rabbits. J. Appl.Physiol. 81(4): 1578-1583, 1996.Airway wall areais an important determinant of airway narrowing. We hypothesized thatin cross-sectioned peripheral airways, the wall area internal to theouter smooth muscle border (inner wall area) would decrease and theairway wall area external to the outer smooth the muscle layer(adventitial area) would increase during bronchoconstriction because ofthe relocation of blood and/or fluid between these compartments. To test this hypothesis, we used anesthetized open-chest rabbits and measured airway wall dimensions and smooth muscle shortening of membranous airways after carbachol-inducedbronchoconstriction using morphometric techniques. Acute (3-min) andsustained (40-min) bronchoconstriction was induced by aerosolnebulization of carbachol and compared with saline treatment. Afterphysiological measurements, the heart base was snared, and the lung andheart were excised en bloc and frozen by using liquid nitrogen while atranspulmonary pressure of 2 cmH₂Owas maintained. The lung was processed for light-microscopicexamination by using a freeze substitution technique. Results show thatadventitial area was significantly decreased aftersustained but not acute bronchoconstriction. The mechanism of thischange, which contradicts our hypothesis, is unclear. However, thedecrease of adventitial area could increase rather than decrease theeffect of lung parenchymal tethering and attenuate airwaynarrowing.

     

Inhibitory effect of oxygen accumulation on the growth of Spirulina platensis

Summary The growth of Spirulina platensis was studied in a light-limited culture under various dissolved oxygen (DO) concentrations. At high DO concentration, e.g. at 1.25 mM DO, the growth rate was decreased up to 36 % compared with that of 0.063 mM DO. The retarded growth rate at high DO concentrations seemed to be coupled with the degeneration of photosynthetic activity in terms of O₂ evolution. Under higher DO concentrations, superoxide dismutase and ascorbate peroxidase activities tended to increase, while the contents of photosynthetic pigment, such phycocyanin, carotenoid and chlorophyll-a decreased distinctly.     

Involvement of plasma membrane potential in the tolerance mechanism of plant roots to aluminium toxicity

H⁺-ATPase activity of a plasma membrane-enriched fraction decreased after the treatment of barley (Hordeum vulgare) seedlings with Al for 5 days. A remarkably high level of Al was found in the membrane fraction of Al-treated roots. A long-term effect of Al was identified as the repression of the H⁺-ATPase of plasma membranes isolated from the roots of barley and wheat (Triticum aestivum) cultivars, Atlas 66 (Al-tolerant) and Scout 66 (Al-sensitive). To monitor short-term effects of Al, the electrical membrane potentials across plasma membranes of both wheat cultivars were compared indirectly by measuring the efflux of K⁺ for 40 min under various conditions. The rate of efflux of K⁺ in Scout was twice that in Atlas at low pH values such as 4.2. Vanadate, an inhibitor of the H⁺-ATPase of the plasma membrane, increased the efflux of K⁺. Al repressed this efflux at low pH, probably through an effect on K⁺ channels, and repression was more pronounced in Scout. Al strongly repressed the efflux of K⁺ irrespective of the presence of vanadate. Ca²⁺ also had a repressive effect on the efflux of K⁺ at low pH. The effect of Ca²⁺, greater in Scout, might be related to the regulation of the net influx of H⁺, since the effect was negated by vanadate. The results suggest that extracellular low pH may cause an increase in the influx of H⁺, which in turn is counteracted by the efflux of K⁺ and H⁺. These results suggest that the ability to maintain the integrity of the plasma membrane and the ability to recover the electrical balance at the plasma membrane through a net influx of H⁺ and the efflux of K⁺ seem to participate in the mechanism of tolerance to Al stress under acidic conditions.     

Possible involvement of ethylene-activated {beta}-cyanoalanine synthase in the regulation of cocklebur seed germination

A possible involvement of ß-cyanoalanine synthase(CAS: EC 4.4.1.9 [EC] ) in germination processes of seeds was demonstratedusing pre-soaked upper seeds of cocklebur (Xanthium pennsylvanicumWallr.). Pretreatment in anoxia not only with KCN but also cysteine,as the substrates for CAS, stimulated the subsequent germinationof cocklebur seeds in air. However, the effect of cysteine wasmanifested even in air when applied together with C₂H₄, andits effect was further enhanced in combination with KCN. Thegermination-stimulating effect of KCN was intensified by C₂H₄only when 0₂ was present. In contrast, serine, another substrateof CAS, was effective in air only when combined with C₂H₄ and/orKCN. The addition of cysteine greatly reduced the cyanogenicglycoside content of seeds, but increased HCN evolution. Onthe other hand, glutathione did not have any effect on cockleburseed germination, HCN evolution or bound cyanogen content, suggestingthat cysteine is not acting as a reducing reagent. It is suggestedthat CAS regulates the process of cocklebur seed germinationby the dual action of enlarging the pool of amino acids andsupplying sulphydryl bases, the latter being more determinatelyimportant. Serine is effective only via the former action, whilecysteine would act via both. Key words: Cyanide, cyanogenic glycoside, ß-cyanoalanine synthase, seed germination, Xanthium pennsylvanicum     

Nanosecond time-resolved infrared spectroscopy distinguishes two K species in the bacteriorhodopsin photocycle.

The photochemical reaction process of bacteriorhodopsin in the nanosecond time range (-120-860 ns) was measured in the 1400-900 cm-1 region with an improved time resolved dispersive-type infrared spectrometer. The system is equipped with a newly developed detection unit whose instrumental response to a 5-ns laser pulse has a full width of the half-maximum of 60 ns. It provides highly accurate data that enabled us to extract a kinetic process one order of magnitude faster than the instrumental response. The spectral changes in the 1400-900 cm-1 region were analyzed by singular value decomposition and resolved into three components. These components were separated by fitting with 10- and 1000-ns exponential functions and a step function, which were convoluted with the instrumental response function. The components with decay time constants of 10 and 1000 ns are named K and KL, respectively, on the basis of previous visible spectroscopy. The spectral shapes of K and KL are distinguishable by their hydrogen-out-of-plane (HOOP) modes, at 958 and 984 cm-1, respectively. The former corresponds to the K intermediate recorded at 77 K and the latter to a K-like photoproduct at 135 K. On the basis of published data, these bands are assigned to the 15-HOOP mode, indicating that the K and KL differ in a twist around the C14-C15 bond.     

In vitro neurotoxicity of amyloid β-peptide cross-linked by transglutaminase

Transglutaminase catalyzes the intermolecular cross-linking of peptides between Gln and Lys residues, forming an -(-glutamyl) lysine bond. Amyloid -peptide, a major constituent of the deposits in Alzheimer disease, contains Lys16, Lys28, and Gln15 which may act as substrates of transglutaminase. Transglutaminase treatment of amyloid -peptide (1–28) and amyloid -peptide (1–40) yielded cross-linked oligomers. Transglutaminase-treated A retarded neurite extension of PC12 cells, and rat cultured neurons of hippocampus and septum, brain areas severely affected by Alzheimer disease, and subsequently caused cell death, whereas the transglutaminase-untreated counterparts did not show harmful effects. The transglutaminase-catalyzed oligomers of amyloid -peptide and their neurotoxicity may be involved in two characteristics in Alzheimer disease, neuronal degeneration and formation of the insoluble deposits.Abbreviations: AD – Alzheimer disease, A – amyloid -peptide, DMEM – Dulbecco's modified Eagle's medium, DMEM/F–12–1:1 mixture of DMEM and Ham's F–12 medium, FCS – fetal calf serum, HS – horse serum, PAGE – polyacrylamide gel electrophoresis, MTT – 3-(4,5-dimethylthiazol–2-yl)–2,5-diphenyltetrazolium bromide, NGF – nerve growth factor, TGase – transglutaminase.     

Detailed Comparative Mapping of Cereal Chromosome Regions Corresponding to the Ph1 Locus in Wheat

Detailed physical mapping of markers from rice chromosome 9, and from syntenous (at the genetic level) regions of other cereal genomes, has resulted in rice yeast artificial chromosome (YAC) contigs spanning parts of rice 9. This physical mapping, together with comparative genetic mapping, has demonstrated that synteny has been largely maintained between the genomes of several cereals at the level of contiged YACs. Markers located in one region of rice chromosome 9 encompassed by the YAC contigs have exhibited restriction fragment length polymorphism (RFLP) using deletion lines for the Ph1 locus. This has allowed demarcation of the region of rice chromosome 9 syntenous with the ph1b and ph1c deletions in wheat chromosome 5B. A group of probes located in wheat homoeologous group 5 and barley chromosome 5H, however, have synteny with rice chromosomes other than 9. This suggests that the usefulness of comparative trait analysis and of the rice genome as a tool to facilitate gene isolation will differ from one region to the next, and implies that the rice genome is more ancestral in structure than those of the Triticeae.