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31.
Effect of lead on the reaction of O-demethylase in p-nitro anisole in the cladoceran Moina macrocopa
L. Martinez-Tabche N. E. Morales M. B. Ramirez C. I. Galar G. H. Cardona 《Journal of Aquatic Ecosystem Stress and Recovery (Formerly Journal of Aquatic Ecosystem Health)》1994,3(4):255-258
The presence of the Mixed-Function Oxydase (MFO) system, in Moina macrocopa was detected through the transformation of p-nitroanisole to para-nitrophenol. The presence of this enzymatic system suggested that this cladoceran participates in the biotransformation of xenobiotics in aquatic ecosystems. This capacity, in conjunction with the aquatic flea's high tolerance to environmental stress, suggested that M. macrocopa could be used in bioremediation efforts to increase ecosystem health. The effects of lead on the MFO system in M. macrocopa, were also studied. Lead acted as an inhibitor of the enzymatic complex. Therefore, induction of MFO-activity as an early warning may not work in waterbodies affected by both inducers of MFO and inhibitors like lead. 相似文献
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J. Fábregas E. D. Morales N. Polanco M. Patiño A. Otero J. F. Tobar 《World journal of microbiology & biotechnology》1996,12(1):47-49
The marine microalga Phaeodactylum tricornutum was cultivated in semi-continuous culture under mixotrophic conditions with the soluble fractions of potato, rye and wheat flours that had been naturally fermented, at 2% or 4% (w/v). The rye flour produced the highest microalgal cellular density of 90×106 cells.ml-1 when supplemented with NaNO3 and NaH2PO4. The autotrophic control only gave 57×106 cells.ml-1. The value of agricultural surpluses, such as rye flour, can therefore be increased by its use in the production of valuable, microalgal biomass which is rich in protein, pigments and fatty acids. 相似文献
35.
Palazon Javier; Bonfill Mercedes; Cusido Rosa M.; Pinol M.T.; Morales Carmen 《Plant & cell physiology》1995,36(2):247-252
Pieces of callus obtained from seedlings of Digitalis purpureawere grown on solid Murashige-Skoog's medium supplemented with1 mg liter1 BA and 0.1 mg liter1 IAA or NAA, withor without phenobarbital (40 mg liter1). The replacementof the natural auxin IAA by the synthetic auxin NAA increasedcallus growth and inhibited organogenesis, whereas the additionof phenobarbital had the opposite effect. Morphometric measurementsrevealed a high ratio of vacuole to cytoplasm (v/v) in calluscells. This ratio was affected by the different treatments inthe same way as the fresh weight. The activity of mitochondrialcytochrome P450scc (the enzyme that provides the precursor,pregnenolone, for the biosynthesis of cardenolide in foxgloveplants) was detected in the relevant fraction of callus grownunder all experimental conditions, and its activity was increasedby the addition of phenobarbital. The different treatments testedincreased the cardenolide content and quantifiable amounts ofdigitoxin were detected in all callus tissues. It is of specialinterest that phenobarbital added to the culture medium increasedthe accumulation of digitoxin. The mechanism affecting the developmentand production of cardenolide in callus tissues of D. purpureaby phenobarbital and the replacement of IAA by NAA is discussed. (Received July 18, 1994; Accepted December 14, 1994) 相似文献
36.
Fa´bregas J. Morales E.D. Lamela T. Cabezas B. Otero A. 《World journal of microbiology & biotechnology》1997,13(3):349-351
The marine microalga Phaeodactylum tricornutum was cultured semi-continuously with the soluble fractions of wheat, rye and boiled potato flours. Fifteen percent of the culture volume was renewed every 3 d. The cell productivities were 0.9×109 cells/l/d, 1.1×109 cells/l/d and 2.6×109 cells/l/d for wheat, rye and potato respectively. The productivity of the autotrophic control was 1.0×109 cell/l/d. When a soluble fraction of raw potato was added, the productivity was enhanced to 4.1×109 cells/l/d, 2.4 times higher than the autotrophic culture. The high productivity of P. tricornutum with the soluble fractions of Solanum tuberosum suggests its usefulness as a source of nutrients for the production of microalgal biomass. 相似文献
37.
A. Falconi M. Borde A. Hernández-Cruz F. R. Morales 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1995,176(5):679-689
Stimulation of the spinal cord of the electric fish Gymnotus carapo, evoked an abrupt increase in the discharge rate of the electric organ. At the maximum of this response, the rate increased an average of 26 ± 11.8%. The duration of the response was 4.9 ± 2.12 s; its latency was 10.4 ± 1.1 ms. Activation of the Mauthner axon played a decisive role in this phenomenon as indicated by the following: (1) recordings from the axon cap of the Mauthner cell demonstrated that the response was evoked if the Mauthner axon was antidromically activated and (2) a response that was similar to that produced by spinal cord stimulation, was elicited by intracellular stimulation of either Mauthner cell. Stimulation of the eighth nerve could also increase the discharge rate of the electric organ. The effect was greater if a Mauthner cell action potential was elicited. The findings described in the present report, indicate the existence of a functional connection between the Mauthner cell and the electromotor system in Gymnotus carapo. This connection may function to enhance the electrolocative sampling of the environment during Mauthner-cell mediated behaviors. This is a novel function for the Mauthner cell.Abbreviations
EHP
extrinsic hyperpolarizing potential
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EOD
electric organ discharge
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M-AIR
Mauthner initiated abrupt increase in rate
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M-cell
Mauthner cell
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M-axon
Mauthner axon
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PM
pacemaker nucleus
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PM-cell
pacemaker cell
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PPn
prepacemaker nucleus
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SPPn
sublemniscal prepacemaker nucleus 相似文献
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39.
C. Larralde J. Morales I. Terrazas T. Govezensky M. C. Romano 《The Journal of steroid biochemistry and molecular biology》1995,52(6):575-580
Female mice are more susceptible to Taenia crassiceps (TC) infection than males. However, after a month parasite load increases massively in both genders reaching thousands of parasites per host. The possibility of hormonal changes in the infected mice was envisaged. Sex hormones levels were assayed after different periods of infection, the parasites present in the peritoneal cavity were collected and gonads, uterus and seminal vesicles were weighed. In male mice, serum estradiol increased to levels 200 times their normal values whilst those of testosterone decreased 90% relative to controls. The weight of seminal vesicles was significantly diminished. Infected female mice also showed a slight increase in estrogen blood levels after 8 weeks of infection and the weight of the uterus was significantly increased relative to controls. Serum estradiol and testosterone were almost undetectable after gonadectomy. Cytokines such as IL-6 are capable of stimulating aromatase activity and we found that splenocytes from infected mice produced amounts of IL-6 higher than control as measured by ELISA. In conclusion T. crassiceps infection triggers a feminization process in the infected hosts. The gonads are required for the parasite to induce higher estrogen synthesis. IL-6 could be involved in the immunoendocrine mechanism used by the parasite to maintain a highly permissive environment for its rapid growth. 相似文献
40.
Summary The production of cellulase byRhizobium species was studied.Rhizobium trifolii cellulase was induced by a variety of polysaccharides, including celluloses and hemicelluloses. Cellobiose and myo-inositol also allowed enzyme expression but mannitol prevented it at concentrations higher than 0.25%. Both soluble and insoluble plant root substances moderately stimulated cellulase production byRhizobium trifolii.Most substances tested did not induce the production of cellulases by the slow-growing, cowpea type rhizobia strain CIAT 79. Effective inducers were carboxymethylcellulose, gluconate and myo-inositol.Cellulase production was very low under all conditions tested. In most cases the enzyme activity was loosely bound to the capsular material. The enzyme in fast-growers is an 1,4--D-glucan-4-glucanohydrolase (endo-glucanase EC 3.2.1.4) with specificity for high molecular weight polysaccharides.There was no correlation between infectiveness ofRhizobium trifolii strains and cellulase production. One strain, which lacks the nodulation plasmid, produced cellulase at the same rate as its parental infective strain. 相似文献