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991.
Four human colon adenocarcinoma cell line variants with different metastatic potential were used to examine whether a correlation exists between actin level, state of actin polymerization and invasiveness of tumour cells. Monomeric (G), total (T) and filamentous (F) actin were determined in the cytosolic fraction of these cells. A statistically significant decrease in G actin level and increase in the state of actin polymerization (measured by F:G actin ratio) were found in the cytosol of three cell variants with higher metastatic potential and invasiveness (EB3, 3LNLN, 5W) compared with the parental cell line (LS180). Our experimental data lead to the conclusion that there is a correlation between the metastatic capacity of human colon adenocarcinoma cells and the state of actin polymerization. 相似文献
992.
Little research has been done on egg diapause and the embryonic development of water mites. The aim of this study was to check the impact of temperature and periods of light on hatching of larvae of Eylais extendens. Three batches of eggs which were spawned on 30 July were placed at one of three temperatures (4, 10 and 20 °C) and two periods of light (7 and 14 h per day). Egg hatching (both, percentage of hatched larvae and rate of hatching) was found to differ between 4 versus 10 °C and between 4 versus 20 °C, but not between 10 versus 20 °C. The periods of light had no influence on hatching. This synchronization of hatching, enabling the eggs to emerge from diapause in the spring, could be considered an evolutionary adaptation aimed at postponing hatching of late-spawned eggs until a time allowing for completion of the full development cycle, including the parasitic larval stage. 相似文献
993.
Changes in Brain Energy Metabolism and Protein Synthesis Following Transient Bilateral Ischemia in the Gerbil 总被引:17,自引:13,他引:4
Thaddeus S. Nowak Jr. Richard L. Fried W. David Lust Janet V. Passonneau 《Journal of neurochemistry》1985,44(2):487-494
The time course of the reduction in brain protein synthesis following transient bilateral ischemia in the gerbil was characterized and compared with changes in a number of metabolites related to brain energy metabolism. The recovery of brain protein synthesis was similar following ischemic periods of 5, 10, or 20 min; in vitro incorporation activity of brain supernatants was reduced to approximately 10% of control at 10 or 30 min recirculation, showed slight recovery at 60 min, and returned to 60% of control activity by 4 h. Protein synthesis activity was indistinguishable from control at 24 h. One minute of ischemia produced no detectable effect on protein synthesis measured after 30 min reperfusion; longer periods of ischemia resulted in progressive inhibition, with 5 min producing the maximal effect. Pentobarbital (50 mg/kg) increased by 1-2 min the threshold ischemic duration required to produce a given effect. Whereas most metabolites recovered quickly following 5 min ischemia, glycogen showed a delayed recovery comparable to that seen for protein synthesis. These results are discussed in relation to possible mechanisms for the coordinate regulation of brain energy metabolism and protein synthesis. An improved method for the fluorimetric measurement of guanine nucleotides is described. 相似文献
994.
Cross-hybridizing snake satellite, Drosophila, and mouse DNA sequences may have arisen independently 总被引:2,自引:0,他引:2
Previous reports have interpreted hybridization between snake satellite DNA
and DNA clones from a variety of distant taxonomic groups as evidence for
evolutionary conservation, which implies common ancestry (homology) and/or
convergence (analogy) to produce the cross- hybridizing sequences. We have
isolated 11 clones from a genomic library of Drosophila melanogaster, using
a cloned 2.5-kb snake satellite probe of known nucleotide sequence. We have
also analysed published sequence data from snakes, mice, and Drosophila.
These data show that (1) all of the cross-hybridization between the snake,
fly, and mouse clones can be accounted for by the presence of either of two
tandem repeats, [GATA]n and [GACA]n and (2) these tandem repeats are
organized differently among the different species. We find no evidence that
these sequences are homologous apart from the existence of the simple
repeat itself, although their divergence from a common ancestral sequence
cannot be ruled out. The sequences contain a variety of homogeneous
clusters of tandem repeats of CATA, GA, TA, and CA, as well as GATA and
GACA. We suggest that these motifs may have arisen by a self-accelerating
process involving slipped-strand mispairing of DNA. Homogeneity of the
clusters might simply be the result of a rate of accumulation of tandem
repeats that exceeds that of other mutations.
相似文献
995.
Eugeniusz Nowak und Peter Berthold 《Journal of Ornithology》1987,128(4):405-422
Zusammenfassung Unsere Kenntnis der saisonalen Wanderungen von Lebewesen ist nicht ausreichend. Dies wird vor allem bei Schutzmaßnahmen regelmäßig deutlich; die bisher angewandten Methoden der Markierung sind nicht optimal und kaum zu verbessern. Insbesondere für den Schutz wandernder Tiere besteht ein verstärkter Bedarf an qualitativ und quantitativ neuwertigen Informationen über den Zugablauf, die rasch zur Verfügung stehen sollten.In letzter Zeit wurde eine Reihe verschiedener neuer Methoden zur Erforschung von Tierwanderungen erprobt, wobei die Satelliten-Telemetrie (ST) am aussichtsreichsten erscheint. Wir geben eine Literaturübersicht über die bisherigen Untersuchungen mit ST, machen einen Forschungsvorschlag im Auftrag des Naturschutz-Ressorts der Bundesregierung und diskutieren die ST im Hinblick auf Schutzvorhaben. Aus jüngster Zeit liegen erste publizierte Berichte über satellitentelemetrische Untersuchungen der Wanderungen des Karibus, des Eisbären, Schwarzbären, des Kamels, von einigen Walarten, der Kegelrobbe, der Westindischen Rundschwanzsirene, des Dugongs, der unechten Karett- und der Lederschildkröte, des Riesenhais sowie von vier grßen Vogelarten vor; einige weitere Experimente sind im Gange. Pionieruntersuchungen der Wanderungen des Weißkopfseeadlers, von Schwänen und des Riesensturmvogels in Amerika haben die Möglichkeit der Anwendung der ST im Bereich des Vogelzuges belegt; Untersuchungen der vollständigen Jahres-Wanderstrecken von Vogelarten fehlen aber noch gänzlich. Satelliten-Telemetrie ist insbesondere in der Lage, den Verlauf von Wanderungen nahezu lückenlos zu beschreiben, so daß sich zusammen mit Zusatzinformationen räumlich-zeitliche Ökodiagramme von wandernden Individuen aufstellen lassen. Neben der Wanderroute lassen sich Rastplätze, Biotopwahl, Verweildauer, Zugstrategien u. a. m. genau ermitteln. Derartig genaue Zuganalysen sind für internationale Schutzmaßnahmen wie z. B. die Bonner Konvention von grundlegender Bedeutung.Es wird ein Plan vorgestellt, von der Bundesrepublik Deutschland aus mittels eines Experimentalsatelliten (u. U. TUB SAT 1 der Technischen Universität Berlin) eine Satelliten-Telemetrie-Untersuchung am Weißstorch durchzuführen, und zwar an mit Sendern ausgerüsteten Vögeln sowohl auf der Westroute über Spanien als auch auf der Ostroute über den östlichen Mittelmeerraum. Das Projekt wird im einzelnen beschrieben. Das wichtigste zu erwartende Ergebnis ist ein Ökodiagramm des Storchenzuges von Europa bis Südafrika und zurück, aus dem u. a. konkrete Schutzmaßnahmen abgeleitet werden könnten. Daneben sind neue Erkenntnisse im Bereich der Grundlagenforschung, z. B. über die Orientierung, über Methoden der Öffentlichkeitsarbeit u. a. zu erwarten. Das Storchvorhaben würde zum ersten Mal die gesamte Jahres-Wanderstrecke einer ziehenden Vogelart erfassen.
Satellite telemetry in the study of animal migration: a review
Summary Our knowledge of annual migration in animals is insufficient, and the hitherto applied methods of individual marking are neither optimal nor can they essentially be improved. This problem becomes especially clear when dealing with conservation projects. With regard to the conservation of migrating animals, there is a great need for more qualitative and quantitative information about their migration systems, and this information should soon be available. In the last decades, a number of new methods for the investigation of animal migration have been tested. Among these, satellite radio tracking (SRT) appears to be most promising. Here we present a literature review of that new method, a research proposal by order of the nature conservancy department of the Government of the Federal Republic of Germany (FRG), and a discussion on the relevance of satelite radio tracking to conservation projects.Recently, reports of investigations using SRT have been published forRangifer terandus, Ursus maritimus, Ursus americanus, Camelus dromedarius, Physeter catodon and related species,Halichoerus gryphus, Trichechus manatus, Dugong dugon, Caretta caretta, Dermochelys coriacea, Cetorrhinus maximus as well as for four large bird species (see 5). Pioneer studies withHaliaeetus leucocephalus, Cygnus buccinator, C. columbianus andMacronectes giganteus have shown that SRT is feasible for the study of bird migration. Coverage of the overall migratory movements of a migratory species within a year, however, has, to date, not been obtained.SRT makes it possible to describe migratory routes almost completely, and so, in combination with additional information, spatial-temporal eco-diagrams of migrating individuals can be obtained. In addition to the migratory routes, resting places, habitat preferences, duration of stop-over periods, migration strategies, etc., can be established. All these data are of basic importance for the realization of conservation projects such as the Bonn Convention.The following research proposal is presented in some detail: White Storks from the FRG, equipped with transmitters, should be tracked with SRT along the western route via Spain as well as along the eastern route via the eastern Mediterranean; this should be done using an experimental satellite (possibly TUB SAT 1 of the Technical University of Berlin). The most important result would be to obtain an eco-diagram of Stork migration from Europe to South Africa and back; this would be helpful in the organization of stork protection measures. In addition, results concerning the mechanisms of orientation, methods of public relations, etc. are to be expected. In this White Stork project, the entire annual migration of a bird species could be fully understood for the first time.相似文献
996.
Stereochemistry of phosphoenolpyruvate carboxylation catalyzed by phosphoenolpyruvate carboxykinase 总被引:1,自引:0,他引:1
The stereochemistry of the carboxylation of phosphoenolpyruvate to yield oxalacetate, catalyzed by chicken liver phosphoenolpyruvate carboxykinase and by Ascaris muscle phosphoenolpyruvate carboxykinase, was determined. The substrate (Z)-3-fluorophosphoenolpyruvate was used for the stereochemical analysis. The carboxylation reaction was coupled to malate dehydrogenase to yield 3-fluoromalate, and the stereochemistry of the products was identified by 19F NMR. In separate experiments, the enantiomeric tautomers of 3-fluorooxalacetate were shown to be utilized by malate dehydrogenase to yield (2R,3R)- and (2R,3S)-3-fluoromalate in nearly identical amounts. The products were identified by 19F NMR. When (Z)-3-fluorophosphoenolpyruvate was used as a substrate for phosphoenolpyruvate carboxykinase from avian liver and from Ascaris, and malate dehydrogenase was used to trap the product, only a single diastereomer was observed. This product was shown to be (2R,3R)-3-fluoromalate in each case. The assignments were based on coupling constants taken from Keck et al. [Keck, R., Hess, H., & Rétey, J. (1980) FEBS Lett. 114, 287]. These results indicate that the stereochemistry of carboxylation, catalyzed by chicken phosphoenolpyruvate carboxykinase and by Ascaris phosphoenolpyruvate carboxykinase, is identical and takes place from the si side of the enzyme-bound phosphoenolpyruvate. The carboxylation reaction was run both in H2O and in D2O. No deuterium incorporation into fluoromalate was shown to occur. The product 3-fluorooxalacetate is thus released from phosphoenolpyruvate carboxykinase as the keto form and is reduced more rapidly by reduced nicotinamide adenine dinucleotide with malate dehydrogenase than by the occurrence of tautomerization. 相似文献
997.
Magdalena Nowak Piera Rebuffat Giuseppina Mazzocchi Gastone G. Nussdorfer Ludwik K. Malendowicz 《Cell and tissue research》1989,256(2):241-246
Summary In the hamster, the weight of the adrenal glands increases during the course of gestation, with the highest value at day 5. In comparison to non-pregnant control animals, there were no changes in the volume of the zona glomerulosa (ZG) and zona fasciculata (ZF), while the volume of the zona reticularis (ZR) increased notably. The average volume of ZG-cells rose at day 5 of pregnancy and thereafter gradually decreased to that of control hamsters. A marked drop in the volume of ZF-cells was seen at days 5 and 10 of pregnancy, whereas at day 15 the cells were larger than in controls. At day 5 of pregnancy, a conspicuous increase in the cell volume was found in ZR, followed by lower values at day 10 and again higher than in control hamsters at day 15. The total number of parenchymal cells in hamster adrenal cortex increased at day 10 of gestation, then underwent a marked decrease, reaching the control value at the final day of pregnancy; this drop was mainly due to a reduction in the number of ZF-cells. The changes in the cell volume were paralleled by rather proportional changes in the volume of the mitochondrial compartment and in the quantity of smooth endoplasmic reticulum. The volume of the lipid-droplet compartment significantly rose in the course of gestation in both ZF- and ZR-cells. The cortisol output by adrenal homogenates gradually decreased during pregnancy.Study performed in partial fulfillment of the Ph.D. Thesis of Magdalena Nowak 相似文献
998.
effective pharmacological procedures are described which markedly increase activity of serotonin N-acetyltransferase (NAT), the key regulatory enzyme in melatonin biosynthesis, during the daytime (in light) and counteract suppressive effects of light on NAI activity at night in the hen retina and pineal gland. Of the tested compounds, and their combinations, the most effective were: “aminophylline + spiroperidol + alpha-methyl-p-tyrosine” for the retina, and “aminophylline + yohimbine (+ alpha-methyl-p-tyrosine)” for the pineal gland. The results give strong support to the concept that the dopaminergic (C2-receptor) and noradrenergic (alpha2-adrenergic receptor) mechanisms control NAT activity, and melatonin synthesis, in the hen retina and pineal gland, respectively. 相似文献
999.
T Torlińska L K Malendowicz J Paluszak J Ko?lik M Nowak K W Nowak J Godlewski 《Acta physiologica Polonica》1989,40(5-6):530-534
The study was designed to evaluate some parameters of carbohydrate metabolism in the rat as influenced by 4-APP, an adenine analogue. Adult female rats were injected with 1 mg 4-APP/100 g body weight/day for 3 days. 4-APP evoked a marked enlargement of the liver with lipid droplets accumulation in hepatocytes. This was accompanied by a marked lowering of the liver glycogen content. Within 3 days 4-APP did not change serum glucose, insulin and free fatty acid concentration. Serum glycogenolytic activity studied in an in vitro system showed 7 times as high glucose releasing ability in 4-APP treated rats as that of the serum of control animals. 4-APP resulted also in a marked enlargement of the adrenal medulla and lowered adrenaline and noradrenaline concentrations in the gland. The possibility of an activation of glycogenolysis in the liver of 4-APP treated rats has been discussed. 相似文献
1000.
The modification of avian phosphoenolpyruvate carboxykinase by a variety of sulfhydryl reagents leads to inhibition. The inhibition is related to the loss of 1 highly reactive cysteine residue of the 13 cysteines present in the enzyme. Inhibition by reagents which yield a mixed disulfide was rapidly reversed by thiols. Reagents specific for vicinal sulfhydryl configurations were not potent inhibitors. The cysteine-modified enzyme continues to bind Mn2+ with the same stoichiometry and dissociation constant as the native enzyme. All of the substrates also bind to thiol-modified inactive enzyme. The modification of the reactive cysteine with the spin-labeled iodoacetate derivative leads to inactive enzyme with spin label stoichiometrically incorporated. The EPR spectrum showed an immobilized spin label on the enzyme. EPR studies of the perturbation of the phosphoenolpyruvate carboxykinase-bound spin label by bound Mn2+ showed a dipolar interaction between the two spins, estimated to be 10 A apart. The perturbation of the 1/T1 and 1/T2 values of the 31P resonances of ITP by spin-labeled enzyme indicates that this portion of the nucleotide binds 8-10 A from the spin label. These results indicate that the reactive cysteine is close to but not at the active site of the enzyme. The thiol group must be free and in its reduced form for the enzyme to be active. Perhaps modification of this group prevents conformational change(s) upon ligand binding necessary for the catalytic process. 相似文献