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排序方式: 共有252条查询结果,搜索用时 15 毫秒
1.
2.
M. Pilar López M. Jose Gómez-Lechón Jose V. Castell 《In vitro cellular & developmental biology. Plant》1988,24(6):511-517
Summary This study examines the factors involved in the rapid glycolysis and glycogenolysis that occur during the first stages of
hepatocyte culture: a) Shortly after seeding glycolysis, estimated as lactate released to culture medium, increased 10 times
in comparison to that reported in vivo. By 8 to 9 h of culture, hepatocytes were nearly glycogen-depleted even in the presence
of insulin. b) 6-Phosphofructo-2-kinase remained 100% active during this period. The proportion of the initial active phosphorylase
(87%) decreased to 57% by 7 h of culture. c) Fructose 2,6-bisphosphate content was initially similar to that found in liver
of fed animals, decreased after seeding and increased thereafter up to four times the initial concentration. In spite of changes
in the concentration of this activator, the glycolytic rate remained high and constant. d) ADP and AMP increased sharply after
cell plating, reaching values 1.7 and 3.5 times higher. The rise in AMP levels may be involved in the activation of glycolysis
and glycogenolysis, because this metabolite is known to act as an allosteric activator of phosphofrucktokinase and glycogen
phosphorylase. This metabolic situation resembles that of cells under hypoxia.
Part of this work was presented at the 38th Annual Meeting of the Tissue Culture Association, Washington, DC, May 1987. 相似文献
3.
D J Harvey J F Godber M P Timmerman L M Castell C C Ashley 《Biochemical and biophysical research communications》1985,128(3):1180-1189
The fluorescent Ca2+ indicator, quin 2, has been used in isolated striated muscle fibres. There is a distinct quin 2 fluorescence peak at lambda 500 nm upon excitation at lambda 339 nm after axial injection of the potassium salt of quin 2, pH 7.1. Single voltage-clamp or current clamp electrical stimulation resulted in a distinct transient change in the fluorescence at lambda 500 nm which was not observed at lambda 400 nm, the peak of the fibre autofluorescence. Ca2+ buffering is marked at high quin 2 concentrations (greater than or equal to 400 microM) producing a slow decay of force and fluorescence. At lower concentrations (8-30 microM) of quin, the decay of force is within the range observed in non-injected control fibres. A Kd of 457 nM at 5 mM free Mg2+ suggests an upper resting free Ca2+ concentration of 310 nM at 12 degrees C. 相似文献
4.
Site-specific recombination and topoisomerization by Tn21 resolvase: role of metal ions. 总被引:6,自引:3,他引:3
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The resolvase from the transposon Tn21 catalyses site-specific recombination between the two res sites on its DNA substrate both in the absence and presence of Mg2+ ions. This contrasts with reports on the resolvase from gamma-delta (Tn1000) and on other recombinational proteins that are homologous to Tn21 resolvase but which need Mg2+ for their activity. Magnesium ions could enhance the activity of Tn21 resolvase, as did a number of other cations but some metal ions such as Ni2+ inhibit recombination. The metal ions are not directly involved in the catalytic process but probably affect recombination by altering the conformation of the DNA. Tn21 resolvase relaxes its DNA substrate in the presence and in the absence of Mg2+, and also in ionic conditions that inhibit recombination. Hence, the topoisomerization reflects an activity of resolvase that is distinct from recombination. However, the two activities are functions of the same DNA-protein complex. The complex contains about 6 molecules of the resolvase dimer per molecule of DNA. 相似文献
5.
During a one year period, 944 dogs from the Municipal kennel of Barcelona were examined to detect animals with suspected dermatophytosis. Only a few animals (1.8%) presented skin lesions but none of them had dermatophytosis. A representative number of dogs without visible skin lesions (n=172), selected at random, were used to carry out a seasonal study of the mycobiota of their fur. Fifteen isolates belonging to the genera Microsporum and Trichophyton were isolated from 14 of the 172 (8.1%) dogs without lesions. The identity of these fungi was Microsporum gypseum (6/15), Trichophyton terrestre (4/15), M. canis (2/15), M. cookei (2/15) and Trichophyton ajelloi (1/15) (one strain each of M. gypseum and T. ajelloi were isolated from one dog). Species of Penicillium (% prevalence=89.5%), Alternaria (86.6%), Cladosporium (84.9%), Aspergillus (77.3%), Scopulariopsis (65.7%) and Chrysosporium (64.5%) were the most prevalent. No significant differences in the fungal biota were observed with respect to age, gender, hair length or between mixed and pure breed dogs. A large number of isolates, including species belonging to the genera Beauveria, Chrysosporium, Malbranchea and Scopulariopsis, that macroscopically and/or microscopically resemble dermatophytes and may be mistaken for them, produced a red color change in Dermatophyte Test Medium. No significant seasonal difference was detected among the isolates belonging to the the most frequently encountered genera, with the exception of Scopulariopsis (higher in summer and autumn) and Chrysosporium (higher in summer). Species from other genera, with lower occurrence also presented significant differences in their seasonal distribution. Arthrinium, Aureobasidium, Chaetomium and Phoma spp. presented maximum prevalence peaks in spring, Fusarium, Paecilomyces, Phoma and Rhizopus spp. in summer and Geotrichum and Mucor spp. in autumn. The Microsporum and Trichophyton species were more frequently isolated in summer. 相似文献
6.
Resprout and mature plant shoot growth, leaf water status and gas exchange behavior, tissue nutrient content, flowering, and production were studied for co-occurring shallow-rooted (Arbutus unedo L.) and deeprooted (Quercus ilex L.) Mediterranean tree species at the Collserola Natural Park in Northeast Spain Resprouts showed higher growth rates than mature plant shoots. During fall, no differences in eco-physiological performance of leaves were found, but mobilization of carbohydrates from burls strongly stimulated growth of fall resprouts compared to spring resprouts, despite low exposed leaf area of the fall shoots. During summer drought, resprouts exhibited improved water status and carbon fixation compared to mature plant shoots. Shoot growth of Q. ilex was apparently extended due to deep rooting so that initial slower growth during spring and early summer as compared to A. unedo was compensated. Tissue nutrient contents varied only slightly and are postulated to be of minor importance in controlling rate of shoot growth, perhaps due to the relatively fertile soil of the site. Fall flowering appeared to inhibit fall shoot growth in A. unedo, but did not occur in Q. ilex. The results demonstrate that comparative examinations utilizing vegetation elements with differing morphological and physiological adaptations can be used to analyze relatively complex phenomena related to resprouting behavior. The studies provide an important multi-dimensional background framework for further studies of resprouting in the European Mediterranean region. 相似文献
7.
This study describes the development of a simple, rapid and reproducible microassay for determining the intracellular LDH activity of rat hepatocytes present in a co-culture system with other cells. The procedure involves treatment of cellular homogenates with an anti-LDH antiserum that specifically inhibits the LDH activity of rat hepatocytes. The assay is performed in 96-well plates and LDH activity can be measured directly in the same wells using a colorimetric method. The difference in LDH activity values measured before and after antiserum incubation reflects the LDH content of the hepatocytes in the sample. The advantages of this method are the small number of cells required, a reduction in sample handling and the possibility of differentiating LDH activity in hepatic and non-hepatic cells. The possible applications of this technique as a parameter for biochemical data and as a test for cytotoxicity studies in co-cultures are also discussed. 相似文献
8.
9.
Dennis R. Sinar John R. Fletcher Donald O. Castell 《Prostaglandins & other lipid mediators》1981,21(4):581-590
Intraluminal esophageal manometry with a sleeve catheter was used to compare the magnitude of decrease in lower esophageal spincter (LES) pressure produced by an arterial or venous infusion of prostaglandin E1 in cats. Arterial PGE1 produced significantly lower LES pressures than venous PGE1 (p < 0.05). Maximal decrease of 75% in basal LES pressure occurred with an associated 15% decrease in systolic blood pressure. The site of action of PGE1 in producing LES hypotension was studied by injection of either edrophonium, or bethanechol during the maximal PGE1 effects. Bethanechol, which acts directly on sphincteric smooth muscle, produced an increase in LES pressure during both saline and PGE1 infusion, while the increases in LES pressure seen with edrophonium during saline infusion were blocked during the PGE1 infusion. From these studies, we conclude that PGE1 produces LES hypotension in the cat by an inhibitory effect on the cholinergic pathway responsible for maintaining LES tone. These studies pharmacologically reproduce the LES pressure abnormality previously reported in the cat during acid-induced esophagitis and support the hypothesis that PGE1 may be involved in the pathogenesis of acute acid-induced lower esophageal sphincter abnormalities. 相似文献
10.
Summary Using data from three fires in northeastern Spain, we tested a condition necessary to support the idea that fire has been
a factor in the evolution of the resprouting habit: populations of all resprouting species within a community should show
high levels of genet survival after fires and show a low coefficient of variation. Species with high mean survival values
were:Quercus ilex L.,Phillyrea latifolia L., andViburnum tinus L., with 88, 86 and 83% survival respectively; these groups had resprouts emerging from rootcrowns. Then followedArbutus unedo L. (75%),Pistacia lentiscus L. (73%),Erica arborea L. (77%),Erica multiflora L. (57%) andJuniperus oxycedrus L. (55%). This last group had resprouts from lignotubers or burls. These two groups also differed in the variability around
the mean: the first showed a lower coefficient of variation, 6–12, and the second ranged from 19 to 26. Slope exposure had
no significant influence on the process of resprouting, but soil depth did, with precipitation as a covariate. In the shallow
soil category, the difference in genet survival between southern and northern exposures was 14% (71% vs. 57%); while the difference
in the deep soil category was low, 5% (87% vs. 82%). There was no significant interaction. The component of variance for soils
was larger than that for species-specific effects; substantial overlap of the within-species variance indicated that species
responded as if they were a single hypothetical population, in which most of the variation in chances of survival was due
to the soil conditions. The possession of the resprouting habit did not ensure a high performance. Hence, we find weak support
for fire as a factor in the evolution of the resprouting habit. 相似文献