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41.
J. G. Howieson 《Plant and Soil》1985,88(3):367-376
Summary Nine media used to grow rhizobia were examined for their ability to maintain a stable low pH during the growth ofR. meliloti Large fluctuations in the pH of all media were recorded within 72 h, indicating their unsuitability for use in the selection of acid tolerant rhizobia. Morpholino-ethanesulphonic acid (MES) was assessed for its ability to buffer the pH of the media whilst still permitting rapid growth ofR. meliloti, R. trifolii, andBr. lupini. With 30.7 mM MES, the pH of a defined medium containing galactose, arabinose, and glutamate did not change from the initial value of 5.5 even though rhizobial numbers increased from 104 to 109 cells.ml–1. Even at a buffer concentration of 15.3 mM, pH only increased from 5.5 to 5.6. There was no effect of the buffer on rhizobial growth. 相似文献
42.
Magnus Appelberg 《Hydrobiologia》1985,121(1):19-25
During exposure to soft water, acidified to pH 4.0, the haemolymph concentrations of Na+, K+, and Cl– decreased whereas the Ca2+ concentration fluctuated in Astacus astacus. The haemocyte content of K+ decreased from 9% to 2% of the total haemolymph K+ content after exposure to pH 3.7 for 3 days. Within 14 days, 250 µg Al3+ l–1, as Al2(SO4)3 at pH 5.0, reduced the haemolymph Na+ content in Astacus astacus and Pacifastacus leniusculus, however, the effects were less pronounced than earlier reported for fish. Disturbed ion regulation, mainly depending on low pH, is thought to contribute to the absence of these species in acid waters. 相似文献
43.
甘薯(Ipomoea batatas)叶光合作用“午睡”现象初探 总被引:1,自引:0,他引:1
在探讨叶片光合产物水平与光合机构运转关系时,我们曾观测到田间甘薯叶片干重增长速率日变化进程中有明显的中午降低即“午睡”现象(图1)。为了揭示这一现象的形成机理,在人工气候室作了以下一些研究。 相似文献
44.
Meiofauna of a sewage-polluted sandy beach, where sand alone constituted > 90%, was surveyed. Nematodes dominated the fauna
numerically at all stations, followed by harpacticoid copepods. Most of the animals were confined to the top 5 cm of the sediment.
A seasonal pattern was observed in the distribution of the fauna. There were significant spatial and temporal variations in
mean meiofauna density, attributed to organic discharge via sewage and prevailing environmental conditions in the study area. 相似文献
45.
Agglutinating activity of gliadin-derived peptides from bread wheat: implications for coeliac disease pathogenesis 总被引:1,自引:0,他引:1
S Auricchio G De Ritis M De Vincenzi E Mancini M Minetti O Sapora V Silano 《Biochemical and biophysical research communications》1984,121(2):428-433
The PT-digest of bread wheat gliadin was very active in agglutinating undifferentiated human K562(S) cells. This activity was quantitatively, but not qualitatively, similar to that of Con A or WGA. Moreover, Con A-induced cell agglutination was inhibited by mannan and mannose, WGA-induced agglutination by NAG only, and cell agglutination induced by bread wheat gliadin peptides was inhibited by each of these three saccharides. Not only was mannan the most active saccharide in preventing cell agglutination induced by bread wheat gliadin peptides, but it was also able to dissociate agglutinated cells. As compared to the PT- digest of whole bread wheat gliadin, the digest obtained from purified A-gliadin was tenfold more active. The PT-digest of durum wheat gliadin did not show any agglutinating activity. 相似文献
46.
Evidence for the Neurotrophic Regulation of Collagen-Tailed Acetylcholinesterase in Immature Skeletal Muscle by β-Endorphin 总被引:1,自引:1,他引:0
Laurence W. Haynes Margaret E. Smith Derek G. Smyth† 《Journal of neurochemistry》1984,42(6):1542-1551
Abstract: Acetylcholinesterase (AChE) was extracted in a high-saline medium from gastrocnemius muscles of rat embryos and young rats aged 14 days'gestation to 40 days post partum. The molecular forms of the enzyme were separated by low-salt precipitation, followed by velocity sedimentation. During gestation, all molecular forms increased in activity, particularly the 16 S (A12 ) form. During the first 2 weeks of life, there was a large increase in the activity of soluble AChE (G forms), whilst the activity of insoluble AChE (A forms) was reduced. Denervation of the muscle reversed the change in the relative proportions of the molecular forms. The embryonic pattern of activities of AChE forms persisted in cultures of myotubes obtained at 20 days'gestation and maintained in the absence of spinal cord. When myotubes were maintained in medium previously conditioned by developing spinal cord explants, 16 S AChE declined while the soluble (4 and 6 S) forms increased in activity in a manner resembling that seen in early postnatal muscles in vivo . β-Endorphin (β-EP) immunoreactivity was detected in the spinal cord-conditioned medium and was identified by HPLC and ion-exchange chromatography as β-EP-(l–31) plus its shortened and N -acetylated forms. Cultivation of myotubes in the presence of synthetic camel β-EP resulted in a reversible change in the pattern of AChE forms which was similar to that seen with spinal cord-conditioned medium. These studies provide evidence for the neuroregulation of AChE A and G forms in immature skeletal muscle. A major candidate for this role is β-EP, produced and released by developing spinal cord. 相似文献
47.
Edith Doucet Jacques Bourbon Michel Rieutort Lea Marin Claude Tordet 《In vitro cellular & developmental biology. Plant》1987,23(3):189-198
Summary Lung organ culture has been a widely used system for studying differentiation and maturation of alveolar epithelium through
various culture conditions. The purpose of this work was to carefully characterize in vitro lung biochemical diffeentiation
through isolation of surfactant fraction from tissue and to search for optimal culture conditions. Fetal rat lung was explanted
on the 18th gestational day for studying glycogen storage, and on the 20th gestational day for studying surfactant accretion,
and cultivated for 48 h. Morphologic differentiation was studies byelectron microscopy tissue explanted on the 17th or 18th
gestational days and cultivated for various times. Glycogen storage was greater on fluid medium, although less than occurring
in vivo. Cellular integrity and surfactant accumulation were maximal on a semisolid medium containing 0.5% agar. Use of O2-CO2 instead of air-CO2 for gassing the explants slighlty decreased phospholipid accumulation. Among media used in previous lung culture studies,
Waymouth MB 752/1 was the only one to allow net glycogen accumulation in vitro. The most favorable media for surfactant phospholipid
accretion were Waymouth MB 752/1, Eagle’s minimum essential and its Dulbeccco’s modification, CMRL 1066, and NCTC 109. They
allowed a 12- to 14-fold increase of surfactant fraction phospholipids in vitro, which is similar to the increase occurring
in vivo during the same peiod. Ham’s F10 and F12 media allowed a six fold increase. RPMI 1640 and medium 199 (M199) allowed
only a three fold increase. Phospholipid concentration in nonsurfactant fraction only doubled during culture, and differences
between various media were much less marked. DNA concentration changed little during culture. Morphologic differentiation
of epithelial cells was advanced as compared with in vivo timing in a medium allowing maximal surfactant accretion (Waymouth
MB 752/1) but not in a medium allowing low surfactant increase (RPMI 1640). The possible role of compositional differences
between media is discussed. 相似文献
48.
A conventional balance study with 48 male weanling rats was conducted to determine true absorption and endogenous fecal excretion
of manganese (Mn) in relation to dietary Mn supply, following the procedures of a previously adapted isotope dilution technique.
After 10 d on a diet with 1.5 ppm Mn, eight animals each were assigned to diets containing 1.5, 4.5, 11.2, 35, 65, or 100
ppm Mn on a dry-matter basis. Three days later, each rat was given an intramuscular54Mn injection and kept on treatment for a balance period of 16 d.
Apparent Mn absorption assessed for the final 8 d, averaged 8.6 μg/d without significant treatment effects, although Mn intake
ranged from 18.6 to 1200 μg/d, in direct relation to dietary Mn concentrations. Mean fecal excretion of endogenous Mn for
the six treatments was 0.9, 2.7, 7.4, 11.0, 16.3, and 17.7 μg/d, respectively. These values delineate the rates to which true
absorption exceeded apparent rates. True absorption, as percent of Mn intake, averaged 28.7, 15.9, 11.7, 6.1, 3.4, and 2.0,
respectively, as compared with mean values of 23.9, 10.9, 6.2, 3.4, 1.2, and 0.5 for percent apparent absorption. It was concluded
that both true absorption and endogenous fecal excretion markedly responded to Mn nutrition and that the reduction in the
efficiency of true absorption was quantitatively the most significant homeostatic response for maintaining stable Mn concentrations
in body tissues. 相似文献
49.
Single-channel conductance fluctuations are analysed for gramicidin A incorporated into binary-mixed black lipid membranes of charged phosphatidic acid and neutral lecithin in different molar ratios. At very low Ca++ concentrations in the electrolyte (i.e. in the presence of EDTA) homogeneous lipid mixtures are identified through their conductance and life time probability distributions for integral gramicidin pores. As for the pure lipid components, the conductance histograms each show a single maximum with regular width and for all channels a single mean lifetime is found.For Ca++-levels (10-6–10-5
M) that are close to the critical demixing concentration (10-4
M) unusually broad conductance distributions and reduced lifetimes are found provided the PC content, x, of the membrane is close to the critical mixture (x
crit0.5). We interpret this as a first example of the coupling of a membrane function (the transport of ions) to a lipid matrix with locally fluctuating composition close to a critical demixing point.For
the conductance histogram of gramicidin A in an equimolar mixture of PA and PC shows two well-separated maxima. A correlation analysis between conductance and lifetime of the single pores shows that the two channel populations also differ significantly in their mean channel lifetime, *. This finding is interpreted as being direct evidence for Ca++-induced lateral phase separation in black lipid membranes, as has been postulated recently.Abbreviations used HEPES
N-2-hydroxyethyl-piperazine-N-2-ethane-sulfonic acid
- EDTA
ethylenediaminetetraacetic acid 相似文献
50.
The observations that liveMycobacterium leprae after entry into cultured peritoneal macrophages from mice, reduced the EA rosetting macrophages, have been exploited to
determine the minimum inhibitory concentration of diamino diphenyl sulphone and rifampicin. Diamino diphenyl sulphone showed
a minimum inhibitory concentration of 0.028 μg/ml and rifampicin 0.11μg/ml when given externally. However, there was accumulation of diamino diphenyl sulphone inside the macrophages. At an external
concentration of 0.028 μg/ml the concentration inside the macrophage was 0.5μg/ml. The minimum inhibitory concentration for diamino diphenyl sulphone in this assay system is higher by several folds and
that for rifampicin is slightly lower, than what is reported earlier with mice foot pad experiments. The minimum inhibitory
concentration reported in this assay system is quite close to what is observed forin vitro inhibition ofMycobacterium lufu with both the drugs 相似文献