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41.
Plant secondary compounds can prevent feeding by phytophagous insects or, if ingested, can be poisonous to them. Less attention has been paid to the additional effects they have on feeding behavior when they are only weakly deterrent or not deterrent at all. Experiments were carried out on the generalist grass-hopperSchistocerca americana. Individuals were presented either with two cakes of high-quality artificial food with a single deterrent compound added or with two cakes, each with a different added deterrent compound. The deterrents consisted of single plant secondary compounds that were either marginally or strongly deterrent. There were profound differences in feeding behavior between those individuals given identical and those given different cake types, including longer feeding bouts on single cakes when a choice of different cake types was available. The behavioral effects demonstrate that the presence of secondary compounds in one food can influence the patterns of feeding on other available foods and suggest that such chemicals could impact foraging activities in a complex manner. 相似文献
42.
Honorina Martínez-Blanco Angel Reglero Dr. José M. Luengo 《Journal of industrial microbiology & biotechnology》1994,13(3):144-146
Summary The effect of phenylacetic acid (PAA) and several analogs on the activity of isopenicillin N synthase (IPNS) and acyl-CoA: 6-APA acyltransferase (AT) fromPenicillium chrysogenum Wis 54-1255 has been tested. Whereas the substitution on the ring of a hydrogen atom by hydroxy-, methyl- or methoxy- groups did not cause any effect, the presence of halogens (Cl or Br) at positions 3 and/or 4 of PAA strongly inhibited these two enzymes. The replacement of hydrogen atoms by fluorine in certain positions also caused inhibition, but to a lesser extent. 相似文献
43.
Phagocytosis has been used to characterize on a functional basis leukocytes adhered to the aortic endothelium of the rat. After intravenous administration of particles, phagocytosis was observed microscopically in esterase-positive leukocytes adhered to the endothelium in whole mounts of aorta. PolybeadR blue and red, 0.5 and 1 μm particle size, were inadequate because they were insufficiently colored to be identified individually at 400. Fluoresbritetm YG 0.25 and 0.50 μm at doses of 0.2 and 2 ± 0.3 m1/100 g, respectively, produced endothelial lesions. The same occurred with Monastral blue BR (MbB) at 0.3 ml/100 g, red iron at 2 ± 16 mg/100 g and India ink at different concentrations depending on the supplier. At lower particle doses, lesions were not found. Deferoxamine mesylate 1.5 mg/100 g intravenous and allopurinol 5 mg/100 g intraperitoneal administered before the particles diminished the number and intensity of lesions. In none of the cases studied was the percentage of phagocytic cells greater than 50%. Clearance curves of MbB and Fluoresbritetm indicated rapid disappearance of particles from the blood. Results indicate that administration of particulate suspensions is not a good method for characterizing the phagocytic leukocytes adhering to the aortic endothelium because low doses produce rapid clearance of particles, thus impeding sufficient leukocyte loading, and higher doses produce endothelial lesions that often impair reliable counting of the adhering leukocytes. 相似文献
44.
Anne M. Donigan R. Christopher Cavalli Angel A. Pena C. Richard Savage Dianne Robert Soprano Kenneth J. Soprano 《Journal of cellular physiology》1993,155(1):164-170
WI-38 cells, density arrested for short periods of time, can be stimulated to re-enter the cell cycle by epidermal growth factor (EGF) alone. However, cells density arrested for longer periods have a prolonged prereplicative phase when serum stimulated and cannot be stimulated by EGF alone. Radio-ligand binding studies performed on WI-38 cells showed that actively growing cells bind [125I]EGF at relatively low levels that increase to a maximum as the cells become contact inhibited. As the cells enter a state of deeper quiescence, EGF binding falls to one-third to one-fifth the short-term growth arrested levels, remaining constant thereafter. The EGF-receptor complexes internalize more slowly in long-term growth arrested cells, and the rate of ligand association to the receptor is lower than short-term growth arrested cells. The amount of EGF receptor protein in lysates of equal numbers of both short- and long-term quiescent cells remains the same. These results suggest that the failure of long-term growth arrested cells to respond to EGF is not due to dramatic changes in the amount of receptor protein during prolonged quiescence but more likely to an alteration in the ability of these receptors to bind ligand and/or activate the EGF signal transduction pathway. © 1993 Wiley-Liss, Inc. 相似文献
45.
Carme Solà Emili Martínez Lluïsa Camón Angel Pazos† Eduard Rodríguez-Farré 《Journal of neurochemistry》1993,60(5):1821-1834
Abstract: The effect of lindane administration on the specific binding of ligands to different sites on the GABAA receptor-ionophore complex was studied in the rat brain by receptor mapping autoradiography. [3 H]Muscimol (Mus), [3 H]flunitrazepam (Flu), and t -[35 S]butylbicyclophosphorothionate (TBPS) were used as specific ligands of GABA, benzodiazepine, and picrotoxinin binding sites, respectively. Rats received a single oral dose of 30 mg/kg lindane and they were classified into two groups according to the absence or presence of convulsions. Vehicle-treated groups acted as controls. The effect of the xenobiotic on ligand binding was measured in different brain areas and nuclei 12 min or 5 h after its administration. Lindane induced a generalized decrease in [35 S]TBPS binding, which was present shortly after dosing. In addition, [3 H]Flu binding was increased in lindane-treated animals, this modification also appearing shortly after administration but diminishing during the studied time. Finally, lindane induced a decrease in [3 H]Mus binding, which became more evident over time. These modifications were observed both in the presence and in the absence of convulsions. However, an increase in [3 H]-Mus binding was detected shortly after lindane-induced convulsions. The observed decrease in [35 S]TBPS binding is in agreement with the postulated action of lindane at the picrotoxinin binding site of the GABAA receptor chloride channel. The effects observed on the binding of [3 H]Flu and [3 H]Mus may be secondary to the action of lindane as an allosteric antagonist of the GABAA receptor. 相似文献
46.
Angel G. Hernandez Ana Rascon Shirley Kutner Henry Roman Zulaika Campos 《Molecular biology reports》1993,18(3):189-195
A correlation between the ratio of the cell surface protease activity to phosphatase activity and the complexity of the pattern of cell surface exposed polypeptides ofLeishmania promastigotes was demonstrated for various strains grown under similar conditions. The ratio of the cell surface protease activity to acid phosphatase activity was high forL. major andL.b. panamensis and it correlates with the expression of a single polypeptide of 63 KDa on their cell surface. Intermediate and lower ratios of these enzymatic activites relate with more complex radio-iodinated patterns: two main bands inL.b. guyanensis (70 and 58 KDa) andL.b. braziliensis (72 and 60 KDa) and three main bands 65, 50, 27 KDa in allL.m. mexicana strains tested. Evidence is presented that the acid phosphatase located on theL.m. mexicana cell surface is not an artifact due to a secondary absorption of the secreted acid phosphatase from the culture medium. These results confirm theLeishmania antigen cell surface heterogeneity. The implications on the biology ofLeishmania and the clinical manifestation of leishmaniasis are discussed. 相似文献
47.
Miren Atristain Daniel von Schiller Aitor Larrañaga Arturo Elosegi 《Restoration Ecology》2023,31(1):e13779
Aging dams and the rising efforts to restore stream ecosystems are increasing the number of dam decommissioning programs. Although dam decommissioning aims at improving in-stream habitat, biodiversity, and ecosystem functioning in the long term, it might also cause ecological impacts in the short term due to the mobilization of the sediment accumulated in the reservoir. Benthic biofilm in particular can be impaired by episodes of high turbidity and scouring. We conducted a multiple before-after/control-impact experiment to assess the effects of the drawdown of a large dam (42 m tall), a first step to its decommissioning, on biofilm structure (biomass and chlorophyll-a) and functioning (metabolism, nutrient uptake, and organic matter breakdown). Our results show that the reservoir drawdown reduced the autotrophic biofilm biomass (chlorophyll-a) downstream from the dam, which in turn lowered metabolism. However, nitrogen and phosphorus uptake by the biofilm was not affected. Organic matter breakdown was slower below the dam than in nearby undammed reaches before and during drawdown. All drawdown effects quickly disappeared and reaches downstream from the dam approached values found in nearby undammed reaches. Thus, our results indicate that the effects of reservoir drawdown on stream biofilms exist but may be small and disappear rapidly. 相似文献
48.
49.
Edna De la Llata Quiroga Randall Arauz Arturo Tripp Valdez Laura Porras Murillo Manuel Spinola Parallada Ricardo Sánchez-Murillo Elpis J. Chávez 《Journal of fish biology》2023,102(3):669-679
Bull shark (Carcharhinus leucas) is a near-threatened elasmobranch species capable of moving between the fresh and salty waters of tropical and subtropical coastal areas, for which we still lack important ecological information. During their first years of life, bull sharks use estuarine systems as nursery areas, making them highly susceptible to environmental and anthropogenic pressures. We studied the trophic ecology of juveniles found in the Coyote estuary, a potential nursery area in Costa Rica, to understand the potential impact of further bull shark declines and gain knowledge that could aid in their conservation. We analysed the trophic ecology of juvenile bull sharks [81–103 cm total length (TL)] in the Coyote estuary, Costa Rica, using stable isotopes of δ15N and δ13C. Since one problem using this technique in juveniles is the confounding effect of the maternal signature, we sampled different tissues (muscle and plasma), verified the status of the shark's umbilical scar and identified the size at which the isotope signature is a result of the animal's current diet. The isotopic values of the muscle tissue reflected the maternal isotopic signature. In contrast, plasma values reflected the diet of juvenile bull sharks >95 cm TL and with a closed umbilical scar. Juvenile bull sharks fed primarily on teleost fishes of the order Anguilliformes and Siluriformes, and have a high trophic position (≥4.0) in the Coyote estuary. Our findings suggest that this estuary is an important feeding site for juvenile bull sharks of the Pacific of Costa Rica. Thus, the protection of essential habitats such as the Coyote estuary will benefit not only bull shark conservation, but also the conservation of an array of fish species that also use this habitat as a rookery, many of which are of commercial interest. 相似文献
50.