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1.
The diet of the viperine snake was compared with food availability in the Ebro Delta, a wetland largely occupied by rice fields, in 1990 and 1991. Snake selection of prey type and size was studied seasonally and by snake group: males, females and immature snakes. Overall, feeding activity (percentage of individuals with prey and number of prey per stomach) increased with food availability. Diet analysis showed that viperine snakes mainly foraged on the green frog Rana perezi (adults and tadpoles) and the carp Cyprinus earpio. Conversely, viperine snakes rejected the mosquito fish Gambusia holbroki which is the most abundant species in autumn, when Natrix maura has a low feeding activity. Statistical comparisons between viperine snake diet and prey availability showed that males selected small carp, immature snakes selected tadpoles and, in spring, females selected frogs. The selection of small carp by males may reflect a sexual divergence of trophic niche related to sexual size dimorphism, as females are larger than males. As tadpoles are presumably easier to catch than fish, tadpole selection by immature individuals may reflect variance in capture abilities. In spring, the selection of frogs by females overlapped with vitellogenesis, suggesting that females compensate for the cost of reproduction by selecting green frogs, which have a greater biomass and higher energy content than fish. Carps eaten in spring were smaller than in summer. Moreover, in summer viperine snakes selected smaller carp than the available mean size. This divergent tendency between carp size selection and carp size availability reveals how seasonal diet shifts in prey size selection may be a response to an increase in prey size. 相似文献
2.
3.
Paola A Gilardoni Stefan Schuck Ruth Jüngling Björn Rotter Ian T Baldwin Gustavo Bonaventure 《BMC plant biology》2010,10(1):66
Background
Plants trigger and tailor defense responses after perception of the oral secretions (OS) of attacking specialist lepidopteran larvae. Fatty acid-amino acid conjugates (FACs) in the OS of the Manduca sexta larvae are necessary and sufficient to elicit the herbivory-specific responses in Nicotiana attenuata, an annual wild tobacco species. How FACs are perceived and activate signal transduction mechanisms is unknown. 相似文献4.
Pereyra Paula Evelyn Rubira Hallwass Gustavo Begossi Alpina Giacomin Leandro Lacerda Silvano Renato Azevedo Matias 《Ecosystems》2023,26(5):1095-1107
Ecosystems - Frugivory and seed dispersal by fish is an important mutualistic interaction in complex and species-rich tropical rivers. The local ecological knowledge (LEK) held by fishers can... 相似文献
5.
Molecular characterization of the proteinase-encoding gene, prb1, related to mycoparasitism by Trichoderma harzianum 总被引:11,自引:0,他引:11
Roberto A. Geremia Gustavo H. Goldman Dirk Jacobs W. Ardrtes Silvia B. Vila Marc Van Montagu Alfredo Herrera-Estrella 《Molecular microbiology》1993,8(3):603-613
The soil fungus Trichoderma harzianum is a mycoparasitic fungus known for its use as a biocontrol agent of phytopathogenic fungi. Among other factors, Trichoderma produces a series of antibiotics and fungal cell wall-degrading enzymes. These enzymes are believed to play an important role in mycoparasitism. Among the hydrolytic enzymes, we have identified a basic proteinase (Prb1) which is induced by either autoclaved mycelia, fungal cell wall preparation or chitin; however, the induction does not occur in the presence of glucose. The proteinase was purified and biochemically characterized as a serine proteinase of 31 kDa and pl 9.2. Based on the sequence of three internal peptides, synthetic oligonudeotide probes were designed. These probes allowed subsequent isolation of a cDNA and its corresponding genomic clone. The deduced amino acid sequence indicates that the proteinase is synthesized as a pre-proenzyme and allows its classification as a serine proteinase. Northen analysis shows that the induction of this enzyme is due to an increase in the corresponding mRNA level. 相似文献
6.
Patricia Peres Walter F de Azevedo Júnior Gustavo O Bonilla-Rodriguez 《European journal of biochemistry》2004,271(21):4270-4274
This paper reports the results obtained using the osmotic stress method applied to the purified cathodic and anodic hemoglobins (Hbs) from the catfish Hoplosternum littorale, a species that displays facultative accessorial air oxygenation. We demonstrate that water potential affects the oxygen affinity of H. littorale Hbs in the presence of an inert solute (sucrose). Oxygen affinity increases when water activity increases, indicating that water molecules stabilize the high-affinity state of the Hb. This effect is the same as that observed in tetrameric vertebrate Hbs. We show that both anodic and cathodic Hbs show conformational substrates similar to other vertebrate Hbs. For both Hbs, addition of anionic effectors, especially chloride, strongly increases the number of water molecules bound, although anodic Hb did not exhibit sensitivity to saturating levels of ATP. Accordingly, for both Hbs, we propose that the deoxy conformations coexist in at least two anion-dependent allosteric states, T(o) and T(x), as occurs for human Hb. We found a single phosphate binding site for the cathodic Hb. 相似文献
7.
Gustavo A. Bouchardet da Fonseca Thomas E. Lacher Jr. 《Primates; journal of primatology》1984,25(4):441-449
We report the exudate feeding behavior of two groups of marmosets (Callithrix jacchus penicillata) living permanently in Cerradão, a common woodland formation of Central Brazil. Cerradão is an open canopy formation and marmosets must occasionally descend to the ground in order to move from tree to tree. Even in atypical habitat, exudate eating is the predominant foraging activity. Marmosets are engaged in exudate collection over 70% of the total time spent feeding. They were observed gnawing on seven species of trees, and consumed exudates from four of these species. We compared the degree of utilization of the exudate sources, and examined a number of different characteristics of the exudates. Morphological adaptations that allow for the exploitation of the “exudate-eater niche” may be an important component of the adaptability ofCallithrix marmosets. 相似文献
8.
Randi B. Silver Gustavo Frindt Lawrence G. Palmer 《The Journal of membrane biology》1992,125(1):13-24
Summary Changes in intracellular pH (pH
i
) were measured using the pH indicator, BCECF, in principal cells from split opened cortical collecting tubules (CCTs) derived from rabbits maintained on a normal diet. This monolayer preparation has the advantage of allowing us to visualize the morphological differences in the two major cell types in this nephron segment under transmitted light. The visual identification of the cell types was verified using emission measurements taken from single principal and intercalated cells in the opened tubule which had been exposed to fluorescein isothiocyanate (FITC)-labeled peanut lectin. We confirmed the existence of an amiloride-sensitive Na/H exchange process activated during intracellular acidosis in principal cells. In addition, the exchanger was active under basal conditions and over a wide range of pH
i
. Because the exchanger was active under basal conditions we tested the hypothesis that changes in intracellular Na (Na
i
) would alter pH
i
in a predictable way. Maneuvers designed to alter Na
i
were without significant effects within a 10-min time frame. Specifically, addition of 100 m ouabain to increase Na
i
or exposure of the tubules to 10–5
m amiloride to decrease luminal Na entry and reduce Na
i
did not have an effect on pH
i
. In some experiments we did observe however, after a 30-min exposure to ouabain, a small decrease in pH
i
. These results suggest that Na/H exchange is a major regulator of pH
i
in principal cells. However, regulation of Na transport by changes in pH
i
in principal cells of rabbit CCT via the activity of a Na/H exchanger do not seem to contribute to the feedback control of Na transport.This work was supported by U.S. Public Health Service grants DK27847 to L.G. Palmer and DK11489 to E.E. Windhager. 相似文献
9.
Photo-oxidation of mitotic human chromosomes has been used in conjunction with anti-cytosine and anti-adenosine antibodies to produce R-banding. To elucidate the mechanism of this banding procedure we have examined the effect of photo-oxidation alone on chromosomes and nuclei. With short exposures to light in the presence of dilute methylene blue, C-band areas on chromosomes 1, 9, 16 and the terminal segment of the Y stain poorly. We call this phenomena reverse C-banding. After 18 h of exposure to light the chromosomes are swollen and show very little staining with quinacrine or Giemsa. Quantitative autoradiography shows that their DNA is almost completely extracted. Cytophotometric measurements also confirm that nuclear DNA is progressively extracted according to the length of exposure to light. When chromosomes are exposed to dilute methylene blue alone, without light, G-banded chromosomes result. We suggest the following explanation for these observations. In dilute methylene blue, C-band regions take up the greatest amount of dye and after short periods of photo-oxidation the DNA of these regions is preferentially destroyed resulting in reverse C-banding. Autoradiography in photo-oxidized chromosomes suggested that this preferential destruction of C-segments occurred in our experiments. With more prolonged exposure the DNA of the G-bands regions is preferentially destroyed and staining the remaining DNA with sensitive fluorescent labeled anti-C antibodies results in R-banding. 相似文献
10.
Leonardo Antnio Fernandes Anderson Albino Gomes Beatriz Gomes Guimares Maria de Lourdes Borba Magalhes Partha Ray Gustavo Felippe da Silva 《Protein science : a publication of the Protein Society》2022,31(6)
The binding of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) spike protein to the angiotensin‐converting enzyme 2 (ACE2) receptor expressed on the host cells is a critical initial step for viral infection. This interaction is blocked through competitive inhibition by soluble ACE2 protein. Therefore, developing high‐affinity and cost‐effective ACE2 mimetic ligands that disrupt this protein–protein interaction is a promising strategy for viral diagnostics and therapy. We employed human and plant defensins, a class of small (2–5 kDa) and highly stable proteins containing solvent‐exposed alpha‐helix, conformationally constrained by two disulfide bonds. Therefore, we engineered the amino acid residues on the constrained alpha‐helix of defensins to mimic the critical residues on the ACE2 helix 1 that interact with the SARS‐CoV‐2 spike protein. The engineered proteins (h‐deface2, p‐deface2, and p‐deface2‐MUT) were soluble and purified to homogeneity with a high yield from a bacterial expression system. The proteins demonstrated exceptional thermostability (Tm 70.7°C), high‐affinity binding to the spike protein with apparent K d values of 54.4 ± 11.3, 33.5 ± 8.2, and 14.4 ± 3.5 nM for h‐deface2, p‐deface2, and p‐deface2‐MUT, respectively, and were used in a diagnostic assay that detected SARS‐CoV‐2 neutralizing antibodies. This work addresses the challenge of developing helical ACE2 mimetics by demonstrating that defensins provide promising scaffolds to engineer alpha‐helices in a constrained form for designing of high‐affinity ligands. 相似文献