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1.
Selective inhibition of growth by pentitols was observed when Klebsiella aerogenes M-7 which could not utilize pentitols was grown on pentoses. D-Arabitol inhibited the growth on D-arabinose as a sole carbon source, but had no effect on the growth on L-arabinose, D-xylose, and D-ribose. Similarly, L-arabitol inhibited the growth on D-arabinose and L-arabinose, ribitol inhibited the growth on D-arabinose and L-arabinose, and xylitol inhibited the growth on D-xylose. From the following reasons, we postulated that the selective growth inhibition by pentitols was due to the competitive inhibition of pentose isomerase reaction by the cell by pentitols. (i) D-Arabinose transport activity was not inhibited by pentitols. (ii) Induction of D-arabinose and L-arabinose isomerases was not inhibited by D- and L-arabitol, respectively. (iii) The specificity of growth inhibition by pentitols was the same as that of competitive inhibition of pentose isomerases by pentitols. 相似文献
2.
From the end of August to early May on average 506400 goose days were spent on the farmland of Filsø, 92% by pink-footed geese, 7% by greylag geese and 1% by bean geese. 36% of the goose days were spent on stubbles (autumn), 38% on stubbles with undersown seed grass (autumn-spring), and 21% on new-sown barley fields (spring).
Geese feeding on spring barley consume kernels left on the surface or in the upper surface layers. In 1982 and 1983 trials were set up to quantify the effect of grazing. The effect on yield and plant structure was measured by comparing ungrazed (exclosures) and grazed plots. Grazing by geese significantly reduced the grain yield (7-20%), but the reduction was not proportional to goose usage. The maximum reduction in sprout density was observed in 1982 in an area with heavy goose usage; sprout density was reduced by 72%, but the subsequent yield in the same area was only reduced by 8%. Plants on grazed plots compensated for the reduced sprout density by having more tillers with ears and grains of higher weight. The effect of grazing on stubble, seed grass, and winter cereals on Filsø is discussed. 相似文献
Geese feeding on spring barley consume kernels left on the surface or in the upper surface layers. In 1982 and 1983 trials were set up to quantify the effect of grazing. The effect on yield and plant structure was measured by comparing ungrazed (exclosures) and grazed plots. Grazing by geese significantly reduced the grain yield (7-20%), but the reduction was not proportional to goose usage. The maximum reduction in sprout density was observed in 1982 in an area with heavy goose usage; sprout density was reduced by 72%, but the subsequent yield in the same area was only reduced by 8%. Plants on grazed plots compensated for the reduced sprout density by having more tillers with ears and grains of higher weight. The effect of grazing on stubble, seed grass, and winter cereals on Filsø is discussed. 相似文献
3.
Studies on cell adhesion and recognition. I. Extent and specificity of cell adhesion triggered by carbohydrate-reactive proteins (glycosidases and lectins) and by fibronectin 总被引:19,自引:12,他引:7
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《The Journal of cell biology》1981,88(1):127-137
The extent and the specificity of the initial cell attachment induced by various proteins coated on plastic surfaces have been studied with the following results: (a) Cell adhesion on the surfaces coated with sialidase and beta-galactosidase was as strong as on concanavalin A and limulus lectin-coated surfaces and the reactions were strongly inhibited by glycosidase inhibitors or by competitive substrates. The adhesion on sialidase was inhibited by 2-deoxy-2,3-dehydro-N- acetylneuraminic acid and by polysialoganglioside (GT1b) at low concentration (0.05-0.1 mM). The cell adhesion on beta-galactosidase coat was inhibited by 1,4-D-galactonolactone and beta-methylgalactoside but not by alpha-methylgalactoside. Thus, the initiation of cell adhesion on glycosidase surfaces could be mediated through the interactions of the specific binding sites of the enzyme surface with the cell surface substrates under physiological conditions. (b) Cell adhesion on various lectins could be blocked by various competing monosaccharides at the concentrations similar to the inhibitory concentrations for binding of lectins from solution to the cells. (c) Cell adhesion on fibronectin surfaces as well as on gelatin-coated surfaces was equally inhibited by GT1b at relatively high concentrations (0.25-0.5 mM). Lower concentrations of GT1b (0.05-0.1 mM) inhibited the cell adhesion on surfaces of Limulus lectin and sialidase. It is suggested that the cell adhesion mediated by fibronectin is based on yet unknown interactions in contrast to a specific cell adhesion through glycosidases and lectins. 相似文献
4.
The α-amylase of the beetle Callosobruchus chinensis. Purification and action pattern 总被引:2,自引:2,他引:0
Callosobruchus chinensis larval amylase was isolated and purified in five steps, which included co-precipitation with glycogen and column chromatography on ECTEOLA-cellulose. The enzyme was homogeneous by disc gel electrophoresis on polyacrylamide. The alpha-amylase nature was evidenced by the action on amylopectin beta-amylase limit-dextrin, by the effect on the substrate-iodine complex and by the action pattern on several polysaccharide substrates. These action patterns are compared with those of other alpha-amylases. 相似文献
5.
Growth and differentiation of opossum kidney cells on microscopically transparent microporous membranes 总被引:2,自引:0,他引:2
The growth and differentiation of opossum kidney cells on the recently-developed microscopically transparent microporous membrane are described. Confluent monolayers grown on membranes had twice the cell density of monolayers grown on plastic. Electron microscopy revealed junctional complexes in membrane-grown cells as well as in those cells grown on plastic. Cells grown on membranes, however, displayed more numerous and longer microvilli in addition to demonstrating a greater growth activity. There was an approximate two-fold increase in sodium-dependent phosphate transport per unit area by cells grown on membranes compared to the transport by cells grown on plastic. Phosphate transport by monolayers grown on both membranes and plastic was inhibited by parathyroid hormone (PTH). 相似文献
6.
The strength of the long-range electrostatic repulsion forces on HeLa cells is measured by agglutinative titration using low molecular weight polylysine (M.W. 11,000). Repulsion forces, found to be present on the smaller HeLa cells from density-inhibited suspension cultures, are weakened by incubation of the cells in hypotonic NaCl solutions. Repulsion forces, found to be absent on the larger cells from fast growing cultures, can be induced on these cells by incubation in hypertonic NaCl solutions. Both effects of anisotonicity are reversible, and disappear on restoration of the medium to normal tonicity. Induction of repulsion forces on fast growing cells is prevented by previous treatment of the cells with neuraminidase. Neuraminidase also abolishes repulsion on density-inhibited cells. It is proposed that alterations of the cell size, produced by anisotonicity or occurring during growth in isotonic suspension medium, affect mutual cell adhesiveness by modifying the strength of the repulsion forces generated by cell surface sialic acids. 相似文献
7.
T C Welbourne P Phenix C Thornley-Brown C J Welbourne 《Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine (New York, N.Y.)》1976,153(3):539-542
The effects of scillaren and dinitrophenol on bilirubin excretion by the perfused rat liver were studied. Both compounds inhibited bile flow, scillaren by 20 to 40%, and dinitrophenol by 60 to 80%. Bilirubin excretion was also impaired. However, the effect of scillaren on bilirubin excretion was less than that on bile flow, as indicated by an increase in the bile bilirubin concentration, whereas dinitrophenol had a greater effect on bilirubin excretion than on bile flow. Dinitrophenol also inhibited the hepatic removal of unconjugated bilirubin from the perfusate, probably because it impaired the initial uptake and/or storage of unconjugated bilirubin by the perfused liver. 相似文献
8.
Growth of larvae of Acheta domesticus to the adult stage on an artificial diet was improved significantly by the addition of 0.1% rutin to the diet. Fecundity was also increased. These results cannot be explained by a stimulation of feeding by rutin. They appear to be due to an effect on the utilization of the food, brought about possibly by an action on gut movement, on gut transport or on the microbiol flora. 相似文献
9.
N. Sharon 《Biology of the cell / under the auspices of the European Cell Biology Organization》1984,51(2):239-245
Carbohydrate-lectin interactions serve as the basis of recognition by phagocytic cells of particles and of various target cells. Such interactions occur in the following systems: between sugars on the surface of the phagocytic cells and lectins on the surface of other cells—the best studied example is the binding of mannose-specific Escherichia coli and related organisms via their surface lectins to oligo-mannose residues on macrophages; between lectins on the surface of phagocytic cells and sugars on particles or other cells—phagocytosis of zymosan and of sialidase-treated erythrocytes, mediated respectively by mannose-specific and galactose-specific lectins on macrophages, belongs to this category; by extracellular lectins that form bridges between sugars on both types of cell—as shown by enhancement of phagocytosis of staphylococci by wheat germ agglutinin, and by lectin-dependent killing of target cells by macrophages. These interactions may play an important role in the activities of phagocytic cells in vivo. They may provide an initial host defense mechanism immediately after microbial infection, operate in tissues where phagocytic activity is poor, and participate in tumor rejection. 相似文献
10.
Nasledov GA Katina IE Kobzeva MA 《Rossi?skii fiziologicheski? zhurnal imeni I.M. Sechenova / Rossi?skaia akademiia nauk》2004,90(3):327-338
The effects of calcium release blocker dantrolene was tested on electrically evoked twitches and on contractures induced by potassium depolarization, by acetylcholine or caffeine. It was shown that the first: developmental, stage of potassium or acetylcholine contracture is inhibited by dantrolene and is not influenced by calcium free medium, therefore we may interpret it as based on a "voltage-dependent Ca release" (VDCR) mechanism of activation, whereas depolarization directly opens the rhyanodin receptor calcium channels. On the contrary, the next stage: the long-lasting plateau of contracture, is directly dependent on external Ca2+ and inhibited by dantrolene, and therefore can be described as "calcium induced Ca-release" (CICR) activation mechanism. In this case stored calcium is also released by rhyanodine receptors, although by means of entering the extracellular Ca2+. Finally, the last stage of low amplitude is not influenced by dantrolene nor by calcium-free medium. Therefore the activation of contraction on this stage is not based on the Ca2+ release through the rhyanodin receptor calcium channels. 相似文献
11.
Regulation of fructosyltransferase activity by carbohydrates, in solution and immobilized on hydroxyapatite surfaces 总被引:2,自引:0,他引:2
Steinberg D Rozen R Bromshteym M Zaks B Gedalia I Bachrach G 《Carbohydrate research》2002,337(8):701-710
We tested the effect of several carbohydrates on the activity of cell-free fructosyltransferases (FTF) in solution and immobilized onto hydroxyapatite (HA) and found an inhibitory dose-dependent effect of glucose on FTF activity, both on the surface and in solution. Glucose at 160 mM inhibits FTF activity by 75% both on HA and in solution. Fructose at 160 mM inhibited FTF activity by 25% in solution and by 15% on HA. Levan inhibited FTF activity by 30% in solution, while dextrans and inulin had a limited effect on FTF activity. Circular dichroism and infrared analysis demonstrated no major changes in the chemical structure of fructans synthesized by cell-free FTF on HA and in solution, in the presence or absence of glucose. However, as verified by size-exclusion chromatography, glucose inhibited the synthesis of high molecular-weight fructans. The results indicate that glucose, a byproduct of the FTF enzymatic reaction, is the main carbohydrate affecting FTF activity. Selective inhibition of high molecular-weight fructan production by glucose, may indicate that two mechanisms are involved in the synthesis of fructans, both in solution and on the surface. 相似文献
12.
Concentrations of ATP and ADP and their dynamics during cultivation (2, 5, 9 and 13 days) of a highly productive strains of P. nigricans on a mineral medium in the presence of various carbon sources, such as glucose, succinate or acetate were studied. It was shown that the levels of ATP and ADP in the mycelium depended on the carbon source: the maximum and minimum ATP concentrations were found on the glucose and acetate media respectively, the maximum and minimum ADP concentrations showed inverse dependence. The concentrations of both adenylates on the same carbon source depended on the strain. The dynamics of the adenylates levels during cultivation showed an analogous dependence on the carbon source and the strain. Thus, the highly productive strain was characterized by a constant ATP level on glucose and succinate and variation on acetate, while the ADP level was characterized by a decrease by the 9th day of cultivation on any of the carbon sources. The low productive strain was characterized by variations in the level of ATP in any media used, stability of the ADP level by the 2nd--9th day of cultivation on the glucose medium and by the 2nd--5th day of cultivation on the succinate medium and a decrease by the 9th day of cultivation on the acetate and succinate media. The ratio of ATP/ADP at the phase of griseofulvin biosynthesis (9 days) markedly increased in both the strains when cultivated on the media with any of the carbon sources. 相似文献
13.
Weems YS Kim L Humphreys V Tsuda V Weems CW 《Prostaglandins & other lipid mediators》2003,71(1-2):55-73
The objective of this experiment was to determine the effect of AA, LH, or PSPB on secretion of PGE2, PGF2alpha, or progesterone by ovine caruncular endometrium of the estrous cycle or placental tissue of pregnancy in vitro. Ovine caruncular endometrium of the estrous cycle (days 8, 11, 13, and 15) or caruncular/placental tissue on days 8, 11, 13, 15, 20, 30, 40, 50, 60, and 90 postbreeding were incubated in vitro with vehicle, AA, LH, or PSPB in M-199 for 4 and 8 h. Secretion of PGF2alpha by caruncular endometrium of non-bred ewes on days 13 and 15 and by caruncular/placental tissue of bred ewes on days 13, 15, 20, 30, and 40 was increased (P < or = 0.05) when incubated with vehicle and declined (P < or = 0.05) after day-40 in bred ewes. Secretion of PGF2alpha by day-15 caruncular endometrium of non-bred ewes and bred ewes was increased (P < or = 0.05) by AA on days 13 and 15 and by LH on day-15. Secretion of PGF2alpha by caruncular/placental tissue from bred ewes was (P < or = 0.05) by AA on days 13, 15, 20, 30, and 40 and by LH on days 15, 20, 30, and 40, after which the response decreased (P < or = 0.05). Secretion of PGF2alpha by caruncular endometrium of non-bred ewes during the estrous cycle or by caruncular/placental tissue of bred ewes during the first trimester was not affected by PSPB (P > or = 0.05). Secretion of PGE2 by caruncular endometrium of non-bred ewes did not change (P > or = 0.05) and was increased (P < or = 0.05) by caruncular/placental tissue on days 13-90 from bred ewes when incubated with vehicle. Secretion of PGE2 by endometrium from non-bred ewes was not affected (P > or = 0.05) by AA, LH, or PSPB, but was increased (P < or = 0.05) by AA or LH on days 13-50 and by PSPB on days 60 and 90 when incubated with caruncular/placental tissue from bred ewes. Secretion of progesterone by placental tissue of bred ewes increased (P < or = 0.05) on day-50 and continued to increase through day-90. In summary, uterine/placental tissue secretion of PGF2alpha is not reduced until the end of the first trimester of pregnancy in ewes. In addition, LH appears to play a role in luteolysis of non-bred ewes by stimulating caruncular endometrial secretion of PGF2alpha and on day-5 postbreeding to prevent luteolysis during early pregnancy by stimulating caruncular/placental secretion of PGE2 throughout the first trimester of pregnancy in sheep. Secretion of PGE2 by caruncular/placental tissue after day-50 of pregnancy appears to be regulated by PSPB, not LH. 相似文献
14.
Foraging by wildlife on anthropogenic foods can have negative impacts on both humans and wildlife. Addressing this issue requires reliable data on the patterns of anthropogenic foraging by wild animals, but while direct observation by researchers can be highly accurate, this method is also costly and labor‐intensive, making it impractical in the long‐term or over large spatial areas. Camera traps and observations by guards employed to deter animals from fields could be efficient alternative methods of data collection for understanding patterns of foraging by wildlife in crop fields. Here, we investigated how data on crop‐foraging by chacma baboons and vervet monkeys collected by camera traps and crop guards predicted data collected by researchers, on a commercial farm in South Africa. We found that data from camera traps and field guard observations predicted crop loss and the frequency of crop‐foraging events from researcher observations for crop‐foraging by baboons and to a lesser extent for vervets. The effectiveness of cameras at capturing crop‐foraging events was dependent on their position on the field edge. We believe that these alternatives to direct observation by researchers represent an efficient and low‐cost method for long‐term and large‐scale monitoring of foraging by wildlife on crops. 相似文献
15.
Data on dietary preferences, filter-feeding mechanisms and ingestion rates of algae by tilapias are outlined and discussed. Quantitative data on algal ingestion by filter-feeding are incorporated into a bioenergetic model, demonstrating that under most conditions tilapias are unable to fulfil basic maintenance requirements and hence lose weight. It is concluded that the apparently high volumes of algae ingested by tilapias must be achieved by other means, by particulate feeding on aggregations of algae in the water column or flocculent surface scums of cyanobacteria or by grazing on periphytic mats. 相似文献
16.
Activated eosinophils upregulate the metastasis suppressor molecule E-cadherin on prostate tumor cells. 总被引:3,自引:0,他引:3
P M Furbert-Harris D Parish-Gause K A Hunter T R Vaughn C Howland J Okomo-Awich K Forrest I Laniyan A Abdelnaby O A Oredipe 《Cellular and molecular biology, including cyto-enzymology》2003,49(7):1009-1016
Cell adhesion molecules (CAMs) play an important role in cancer metastasis by facilitating attachment to vascular endothelia, invasion and spread into secondary tissue sites. We have shown that activated eosinophils (EosA) inhibited the growth of prostate cancer (Pca) cells in vitro. In the present study, we examined the ability of EosA 24 hr conditioned supernatants (EosAcs) to modulate the expression of ICAM-1, VCAM-1, ELAM-1, E-cadherin and N-cadherin expression on human Pca cell lines, Du-145 and PC-3 by flow cytometry. TNF-alpha, IL-10 and IL-12 were also evaluated. ICAM-1, expressed on PC-3 and DU 145 cells, was enhanced by TNF-alpha and IL-10. ELAM-1 was present on DU 145 cells but absent on PC-3. TNF-alpha and IL-10 enhanced ELAM-1 on DU 145, but EosA 24 hr supematants failed to do so. All three cytokines, namely IL-10, IL-12 and TNF-alpha-induced ELAM-1 on PC-3 tumor cells. Although VCAM-1 was absent on DU 145 and PC-3 cells, it was expressed on DU-145 cells after exposure to EosA: tumor cell co-cultures, and was expressed on PC-3 following exposure to IL-10 and IL-12. N-cadherin and E-cadherin were both expressed on DU-145. While N-cadherin was expressed on PC-3 cells, E-cadherin was not. N-cadherin was enhanced on DU-145 and PC-3 cells following exposure to EosA co-culture and upregulated on PC-3 by IL-10 and EosA 24 hr supernatants, but decreased by IL-12. E-cadherin was up-regulated on DU 145 cells following co-culture with EosA and was induced on PC-3 by IL-10 and IL-12, but not by EosA co-culture and 24 hr supematants. In conclusion, inflammatory and non-inflammatory cytokines modulate CAM expression on Pca cells; EosA and EosA 24 hr supernatants also exerted modulatory activity of CAM expression. Most significantly, the metastasis suppressor molecule, E-cadherin was enhanced on DU 145 cells by EosA and induced on PC-3 by IL-10 and IL-12 both of which are produced by EosA. This suggests potential use of these cytokines in immunotherapeutic strategies for prostate cancer and its metastasis. 相似文献
17.
Predominant role of hydrocarbon solubilization in the microbial uptake of hydrocarbons 总被引:4,自引:0,他引:4
Using EDTA and proteolytic enzymes to suppress hydrocarbon solubilization, direct evidence is presented in support of the mechanism of liquid hydrocarbon uptake by microbial cells predominantly from the solubilized or accommodated substrate. EDTA (2-5mM) strongly inhibited growth of three yeast species and one bacterial species on n-hexadecane and the inhibition was removed by surfactant-emulsified and surfactant-solubilized alkane and also by excess addition of Ca(2+). EDTA had no inhibitory effect on the growth of the organisms on soluble substrates such as sodium acetate and nutrient broth or on n-pentane, a volatile alkane which was primarily transported by diffusion from gas phase. EDTA was shown to have no significant effect on the adsorption of cells on alkane drops. EDTA inhibition of growth was considered to be due to suppression of alkane solubilization, brought about by the solubilizing factor(s) produced by cells. It was shown that this chelating agent did not inhibit the growth of yeast on solubilized alkane but strongly inhibited its growth on alkane drops. It was demonstrated that adherent capacity of microbial cell to oil phase was closely related to the state of hydrocarbon emulsification and had no relationship to the ability of organisms to grow on hydrocarbon. Certain proteolytic enzymes inhibited the growth of yeast on alkane, presumably by digesting the alkane solubilizing protein, but not on glucose, and the inhibition was removed by a supply of surfactant-emulsified and surfactant-solubilized alkane. Specific solubilization of various hydrocarbon types during growth of the prokaryotic bacterial strain was demonstrated. The specific solubilization of hydrocarbon was strongly inhibited strain was demonstrated. The specific solubilization of hydrocarbon was strongly inhibited by EDTA, and the inhibition was removed by excess Ca(2+). It was concluded that specific solubilization of hydrocarbons is an important mechanism in the microbial uptake of hydrocarbons. 相似文献
18.
In conclusion, an estimate of the intracranial volumetric effects produced in anesthetized dogs by histamine, acetylcholine and CO2 shows that, on a basis of equiactivity on CBF, the effects of histamine on the intracranial content are twice greater than those produced by acetylcholine and CO2. This difference may be explained by a greater activity of histamine on the intracranial capacitance vessels and/or by an increase in the fluid escape from blood to the brain produced by histamine. Data obtained after the production of an acute, cold induced brain lesion support the second possibility. 相似文献
19.
The effects of predation by carabid and staphylinid beetles and birds (blue- and great-tits) on mature larvae of the codling moth Cydia pomonella were investigated in a field experiment. The number of predatory beetles on the ground beneath eight of 16 apple trees was reduced by an insecticide spray, and tits were excluded from the trunks and lower branches of eight trees by means of Terylene netting. Beetles had no significant effect on survival of larvae on trees, but only 8% of larvae survived to adulthood on trees exposed to blue- and great-tits, whereas on trees protected from them 48% survived. Larvae were taken rapidly by the tits from the time larvae first built cocoons in summer and, by the time the majority of larvae had emerged from apples in late summer or autumn, tits had removed most from cocoons beneath flakes of bark glued to trees. Thus tits fed on larvae mainly in summer and autumn. On trees protected from tits, 8% of mature larvae were killed by fungi, of which Verticillium lecanii was most important. It was calculated that, of the larvae maturing in apples, 44% failed to build cocoons on the trees, 47% were taken by tits, then 1% were killed by fungi. Larvae failing to build cocoons on trees may build them on the ground. Of larvae in cocoons planted on or in the ground in 1975, only one (0.3%) persisted through the winter; 98.6% disappeared, and 1.1% were found dead, covered by fungi; in 1976, all larvae disappeared by December. Larvae disappeared even in the absence of predators, and are thought to have moved in response to damp ground conditions. 相似文献