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1.
The avian embryo exchanges the oxygen and carbon dioxide withthe ambient air by diffusion. The respiratory organ is the chorioallantois,endowed with a rich circulation. Between ambient air and chorioallantoiccapillary blood are interposed the porous shell fibrous shellmembranes, and the chorioendothelium which compose the diffusionbarrier. The air cell is formed between the two shell membranesin the blunt end of the egg. The diffusion barrier is dividedinto an outer barrier (shell plus outer membrane) and an innerbarrier (inner membrane plus chorioendothelium and capillaryblood). The resistance to gas diffusion (the reciprocal of thediffusive conductance) in the outer barrier is almost fixedthroughout incubation while that in the inner barrier decreasesas the embryo develops. Because of the fixed outer barrier conductance,the embryo is obliged to take up oxygen under hypoxic conditionsagainst increasing metabolism with development and encountersa relative respiratory acidosis. In connection with the diffusivehypoventilation caused by the fixed outer barrier conductancethe respiratory factors of the allantoic circulation changeprogressively with development to moderate the restraint ofgas exchange through the shell. Blood oxygen capacity and hemoglobinincrease with development in association with an increase inerythrocyte count and hematocrit value. In addition, a progressiveleftward shift of the oxygen dissociation curve occurs. Theincreases in the allantoic blood flow and chorioallantoic capillaryvolume contribute to the increasing conductance of the innerbarrier. Furthermore regulation of acid base balance is inferredin the developing embryo. 相似文献
2.
KOUCHI HIROSHI; NAKAJI KIYOKAZU; YONEYAMA TADAKATSU; ISHIZUKA JUNJI 《Annals of botany》1985,56(3):333-346
Well-nodulated soya bean (Glycine max L.) plants were allowedto assimilate 13CO2 for 10 h in the light, under steady-stateconditions in which CO2 concentration and 13C abundance wereboth strictly controlled at constant levels. The respiratoryevolution of 13CO2 from roots and nodules and 13C incorporationinto various metabolic fractions were measured during the 13CO2feeding and subsequent 48 h chase period. CO2 respired from nodules was much more rapidly labelled with13C than that from roots. The level of labelling (percentageof carbon currently assimilated during the 13COM2 feeding period)of CO2 respired from nodules reached a maximum of about 87 percent after 4 h of steady-state l3CO2 assimilation and thereafterremained fairly constant. The absolute amount of labelled carbonevolved by the respiration of the nodules during the 10 h 13CO2feeding period was 1·5-fold that of root respiration.These results demonstrated that the currently assimilated (labelled)carbon was preferentially used to support nodule respiration,while root respiration relied considerably on earlier (non-labelled)carbon reserved in the roots. Sucrose pools were mostly composed of currently assimilatedcarbon in all tissues of the plants, since the levels of labellingaccounted for 8691 per cent at the end of the 13CO2 feeding.In the nodules, the kinetics and levels of sucrose labellingwere in fairly good agreement with those of respired CO2, whilein the roots, the level of labelling of respired CO2 was significantlylower than that of sucrose. Succinate and malate were highly labelled in both roots andnodules but they were labelled much more slowly than sucroseand respired CO2. The kinetics and levels of labelling of theseKrebs cycle intermediates resembled those of major amino acidswhich are derived directly from Krebs cycle intermediates. Itis suggested that large fractions of organic acids in noduleswere physically separate from the respiration site. Glycine max L., Soya bean, 13CO2 assimilation, respiratory evolution of 13CO2, carbon metabolism in root nodules 相似文献
3.
MUNENORI NOGUCHI HIROSHI INOUE TOSHIHIRO ATAGO SHOGO NAKAMURA 《The Journal of eukaryotic microbiology》1997,44(2):127-133
ABSTRACT. The effects of organic solvents on the ATPase activity and the sliding disintegration of axonemes from Chlamydomonas were investigated. The axonemal ATPase was markedly activated by methanol accompanying with marked inhibition of the sliding disintegration of axonemes. On the contrary, glycerol inhibited the ATPase activity without serious inhibition of the sliding disintegration. As far as the axonemes are not irreversibly denatured by extremely high concentration of solvents, the effects of solvents both on the ATPase and the ability of sliding are reversible. Therefore, the inhibition of sliding accompanied by the activation of ATPase is probably due to an inability to couple the hydrolysis of ATP to sliding between dynein and microtubule in the presence of methanol. The axonemal ATPase was less sensitive to vanadate inhibition after exposure to methanol. This indicates that methanol makes the dyneinADP.Pi complex unstable and increases product release. On the other hand, glycerol and ethylene glycol seem to stabilize the force generation responsible for the sliding through stabilizing the dynein.ADP.Pi complex. 相似文献
4.
Effect of Inorganic Phosphate on the Biosynthesis of Purine and Pyrimidine Nucleotides in Suspension-Cultured Cells of Catharanthus roseus 总被引:1,自引:0,他引:1
The levels of purine and pyrimidine nucleotides in suspensioncultures of Catharanthus roseus were determined 24 h after stationary-phasecells were transferred to fresh complete (+Pi)or phosphate-deficient (Pi) Murashige-Skoogmedium. The levels of ATP, GTP, UTP and CTP were from approx.3 to 5-fold greater in the cells grown in +Pimedium than in the cells grown in Pi medium.The levels of almost all other nucleotides were slightly higherin the cells in +Pi medium. The rates of de novoand salvage biosynthesis of purine and pyrimidine nucleotideswere estimated from the rates of incorporation of radioactivityfrom [14C]formate, [214C]glycine, NaH14CO3, [614C]orotate,[814C]adenine, [814C]adenosine, [214C]uraciland [214C]uridine. The results indicated that the activityof both the de novo and the salvage pathway was higher in thecells in +Pi medium than in the cells in Pimedium. The rate of degradation estimated from the rate of releaseof 14CO2 from labelled purines and pyrimidines indicated thatdegradation of uridine was significantly reduced in the cellsin +Pi medium, but no significant difference wasfound in the degradation of adenine, adenosine and uracil. Thepossible role of Pi in the control of the biosynthesis of nucleotidesand in the degradation of uridine is discussed. Catharanthus roseus, Madagascar periwinkle, suspension culture, inorganic phosphate, nucleotides, purines, pyrimidines, biosynthesis, degradation 相似文献
5.
Growth, respiratory activities and electrophoretic characteristicsof phosphatase and catalase in three strains of Ceratocystisfimbriata (sweet potato strain, coffee strain and prune strain)differing in pathogenicity on sweet potato roots were investigated.There were no significant differences in either growth kineticsor respiratory activity among the strains. Potassium cyanideand antimycin A inhibited oxygen uptake in sweet potato andprune strains. The oxygen uptake of endoconidia of coffee strainwas stimulated by these inhibitors. Mitochondria were preparedfrom endoconidia and mycelia of each strain, and enzyme activitiesof the electron transport system were measured. NADH2: cytochromec oxidoreductase activity of coffee strain was higher than thatof the other strains. The electrophoretic phosphatase patternof coffee strain was identical with that of sweet potato strain,but differed from that of prune strain. On the other hand, thecatalase zymogram from prune strain was closely related to thatof sweet potato strain, but not to that of coffee strain.
1This paper constitutes part 79 of the phytopathological chemistryof sweet potato with black rot and injury. (Received May 22, 1969; ) 相似文献
6.
Abstract Phenotypic variability of Cardamine flexuosa (Cruciferae) was examined in response to different lengths of exposure to low temperature (5°C) at the juvenile stage, and to two photoperiod regimes (8 and 16 hrs day-lengths) in the subsequent growth period. The results indicated that this species had a facultative chilling or long-day requirement for flowering. The long-day and chilling treatments both caused an earlier onset of stem internode elongation. Longer chilling treatments reduced the number of nodes and increased internode length under both long and short photoperiod regimes. Prolonged chilling treatments followed by long-day photoperiod remarkably induced more numerous basal branches and inflorescences, as a result producing more siliques. Remarkable rosette leaves Were formed at the base of the main stem when partial chilling and the short-day treatment suppressed stem internode elongation. The responses to chilling and long-day treatment closely resembled the synchronized flowering of this species in spring in the field. Delayed flowering under the short-day treatment resembled size- or age-dependent flowering in late summer to autumn in the field populations. 相似文献
7.
KOUKI ONO MASAHIRO OKIHASHI HIROSHI INUI KAZUTAKA MIYATAKE SHOZABURO KITAOKA YOSHIHISA NAKANO 《The Journal of eukaryotic microbiology》1994,41(6):536-539
Isocitrate lyase was purified to homogeneity from ethanol-grown Euglena gracilis. The specific activity was 0.26 μmol/min/mg protein. The molecular mass of the enzyme was calculated to be 380 kDa by gel filtration on a Superose 6 column. The subunit molecular mass of the enzyme was 116 kDa as determined by SDS-polyacrylamide gel electrophoresis. These results showed that the native form of this enzyme was a trimer composed of three identical subunits. The pH optimum for cleavage and condensation reactions was 6.5 and 7.0, respectively. The Km values for isocitrate, glyoxylate and succinate were 3.8, 1.3 and 7.7 mM, respectively. Isocitrate lyase absolutely required Mg for enzymatic activity. This is the first report of the purification of isocitrate lyase to homogeneity from Euglena gracilis. 相似文献
8.
HANSEN ALEXANDER P.; YONEYAMA TADAKATSU; KOUCHI HIROSHI 《Journal of experimental botany》1992,43(1):9-14
Fully symbiotic or nitrate treated (3 d, 4·0 mol m3)soybean (Glycine max [L.] Merr.) cv. Bragg and a nitrate tolerantsupernodulating soybean mutant nts 1007 were exposed to 13Cenriched CO2 for a period of 10 h. During this period and forthe subsequent 24 h, continuous measurements of 13CO2 and 12CO2evolution of their root systems were undertaken. Three harvestsduring the experiment allowed determinations of the distributionof recently fixed carbon in different plant organs. These measurementsindicated higher dependence of N2 fixation in nts 1007 on recentlyfixed carbon (RFC) by showing elevated RFC concentrations innodules as well as their augmented respiration. Root respirationof both genotypes was generally more reliant on stored carbon. Nitrate induced in all measured parameters a clear responsein the mutant analogous to the wild type, but quantitative differencesremained throughout. Nodule respiratory activity, the relativespecific activity (RSA), and the utilization of RFC were substantiallyreduced, but remained higher in nts 1007 than in Bragg, whilethe demand of roots for RFC increased in Bragg more than inthe supernodulator. The elevated carbon requirement of the nodulecomplement of the mutant and a high dependence on recently fixedcarbon could be attributed to higher nodule growth and maintenancecosts of the supernodulating genotype and were not associatedwith augmented nitrogen fixation activity. This less efficientutilization of carbon and the associated almost parasitic characterof the nodule complement of nts 1007 is considered to be thecause of reduced growth of the mutant. No evidence was foundfor a physiologically based nitrate tolerance in terms of nitrogenfixation. Key words: Glycine max, nitrate, N2fixation, respiration, carbon partitioning, steady-state labelling 相似文献
9.
10.
HISASHI OKAMOTO AKIKO MIZUNO KIYOSHI KATOU YOSHINA ONO YASUKO MATSUMURA HIROSHI KOJIMA 《Plant, cell & environment》1984,7(2):139-147
Abstract A new experimental system was devised for the simultaneous measurement of elongation rate and the activity of the spatially separate electrogenic ion pumps of a hypocotyl segment excised from a seedling of Vigna unguiculata L. Walp. under enforced intra-organ perfusion by artificial solutions. The pathway of the perfusion medium was apoplastic space, including xylem vessels as main routes. The elongation rate of the segment was highly dependent on the perfusion pressure applied. It was possible to increase the growth rate under pressurized perfusion by 10-30 times as much as that without perfusion. Elongation rate was also dependent on respiration under perfusion, being retarded reversibly by anoxia a few minutes after the activities of the electrogenic ion pumps were stopped. Perfusion pressure had a little influence on the membrane potential (Vpx) below a breakdown level (c. 130 kPa). Perfusion of mannitol or sorbitol solution of appropriate concentration reduced the elongation rate reversibly. 相似文献