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81.
Gabriela Sánchez-Mejorada Horacio Merchant-Larios Francisco Alonso-deFlorida Luis B. Morales 《Bulletin of mathematical biology》1994,56(1):147-160
Are there enough mast cells in denervated skeletal muscle to account for autopharmacological mediation of the antigen potentials (APs) elicited by microtaps? Through rough qualitative estimations, some authors have suggested a positive answer to this question. However, in view of measurements performed in this investigation of both the density of mast cells and the diffusion coefficient of antigens, the probability of such mediated effects was found to be relatively low:P=0.016 for egg albumin andP=0.004 for ferritin. Therefore, most APs induced by microtaps should be attributed to the direct effect of antigen over the sensitized muscle fibers. Yet, both the density of mast cells found in this work and the known amount of histamine they are capable of releasing when challenged with antigen, support the hypothesis regarding the involvement of these cells when antigen is massively superfused so as to induce Schultz-Dale reactions in muscle strips. Under this circumstance, the direct and mediated mechanisms may coexist. 相似文献
82.
Guerrero Francisco; Blanco Jose M; Rodriguez Valeriano 《Journal of plankton research》1994,16(1):95-103
A comparative analysis was carried out on the several equationsmost commonly used to describe the dependence of the developmentof organisms on temperature. Goodness of fit, number of parameters,ease of fitting data and biological significance were compared. 相似文献
83.
Echevarra Fidel; Bautista Begoa; Guerrero Francisco; Rodrguez Valeriano 《Journal of plankton research》1994,16(10):1441-1447
Very short-term feeding activity of the cladoceran Ceriodaphniasp. was investigated in situ in a eutrophic reservoir in thesouth of Spain, using fluorimetric analysis of the gut pigmentcontent in periods when the water column was relatively mixedor strongly stratified. The results obtained in the mixed watercolumn showed a clear increase in gut pigment content at dawn,a period sampled with high frequency. The accumulation of thecladoceran at the depth of maximum concentration of phytoplankton,and the high gut pigment concentration in cladocerans at thatdepth just after dawn, suggested active feeding of Ceriodaphniaon phytoplankton at that time. During stratification, the abundanceof Ceriodaphnia was higher, but the gut pigment contents werevery low and they did not reflect any clear feeding patterns,with either time or depth. Changes in phytoplankton concentrationand composition between the relatively mixed and the stratifiedwater column suggest a shift in feeding activity from herbivorousto. 相似文献
84.
Raquel Fernández-Durango José A. de Juan Horatio Zimman Francisco J. Moya Mario Garcia de la Coba Arturo Fernández-Cruz 《Journal of neurochemistry》1994,62(4):1482-1488
Abstract: Specific endothelin (ET) binding sites were characterized in membranes prepared from human cerebral cortices using binding assay and cross-linking analysis. The presence of immunoreactive (IR) ET-1 was studied by radioimmunoassay. Saturation binding experiments revealed that the K D and B max for 125 I-ET-1 and 125 l-ET-3 to membranes from gray matter were 25 ± 6 pM and 115 ± 15 fmol/mg of protein and 24 ± 5 p M and 108 ± 13 fmol/mg of protein, respectively. Similar results were obtained for white matter. In the presence of 10 n M sarafotoxin-6c, which is selective for ETB receptors, 125 I-ET-1 and 125 l-ET-3 binding was totally abolished. However, in the presence of 1 μ M BQ123, which is selective for ETA receptors, both bindings were not affected. These results suggest that the human cerebral cortex contains only ETB receptors. Cross-linking of 125 I-ET-1 and 125 l-ET-3 to membranes with disuccinimidyl suberate resulted in the labeling of two bands of 48 and 31 kDa. Concentrations of IR-ET-1 in the gray and white matter were 7.0 ± 3.2 and 2.5 ± 1.7 fmol/g wet weight, respectively. The demonstration of high-affinity ETB receptors and the presence of IRET-1 suggest that the peptide may act as a neurotransmitter or neuromodulator in the human cerebral cortex. 相似文献
85.
Maria Luz Perez José Ramón Valverde Beatriz Batuecas Francisco Amat Roberto Marco Rafael Garesse 《Journal of molecular evolution》1994,38(2):156-168
From the cloned mitochondrial DNAs (mtDNAs) isolated from two bisexual species, one Mediterranean, Artemia salina, and one American, Artemia franciscana, and two parthenogenetic (diploid and tetraploid) strains of Artemia parthenogenetica collected in Spain, physical maps have been constructed and compared. They are extremely different among themselves, much more than the differences between Drosophila melanogaster and D. yakuba and in the same range of different mammalian species such as mouse/rat or man/cow. The nucleotide sequences of two regions of mtDNA encoding parts of the cytochrome c oxidase subunit I (COI) and cytochrome b (Cytb) genes have been determined in the two bisexual species and the two parthenogenetic strains. Comparisons of these sequences have revealed a high degree of divergence at the nucleotide level, averaging more than 15%, in agreement with the differences found in the physical maps. The majority of the nucleotide changes are silent and there is a strong bias toward transitions, with the CT substitutions being highly predominant. The evolutionary distance between the two Artemia parthenogenetica is high and there is no clear relationship with any of the bisexual species, including the one present nowadays in Spain. Using a combination of molecular (mtDNA) and morphological markers it is possible to conclude that all of these Artemia isolates should be actually considered as belonging to different species, even the two Artemia parthenogenetica diploidica and tetraploidica.On sabbatical leave from Departamento de Bioquímica, Facultad de Veterinaria, Universidad Complutense de Madridearly Italian artemiologists to designate the Medi-Beatriz Batuecas died in an accident during the Christmas holy days of 1988 after she had initiated this workCorrespondence to: R. Garesse 相似文献
86.
Victoriano Garre Francisco J. Murillo Santiago Torres-Martínez 《Molecular & general genetics : MGG》1994,244(3):278-286
A 5.6 kb DNA fragment from the fungus Phycomyces blakesleeanus has been cloned and sequenced. The fragment contains a gene that probably codes for the enzyme acetyl-coenzyme A synthetase (facA). The amino acid sequence deduced for the P. blakesleeanns protein is highly homologous to those of acetyl-coA-synthetases from other organisms. When placed under the control of a constitutive promoter from Aspergillus nidulans, the cloned gene complemented a facA mutation of this organism. In P. blakesleeanns, the expression of facA is induced by acetate. 相似文献
87.
Luís C. Duarte Alexandra P. Nobre Francisco M. Gírio M. T. Amaral-Collaço 《Biotechnology Techniques》1994,8(12):859-864
Summary The kinetic parameters of the yeastDebaryomyces hansenii grown in continous cultivation on D-xylose were determined by different methods. While the values obtained for μm by the steady state and the washout methods only gave a 3% difference, the determined Ks values by the steady state and the maximal biomass output methods led a to a 305% difference. The latter method was suggested
to overestimate the Ks value. 相似文献
88.
Zampronio AR Melo MC Silva CA Pelá IR Hopkins SJ Souza GE 《Mediators of inflammation》1994,3(5):365-373
The aim of this study was to investigate the pyrogenic activity of factor(s) released by rat peritoneal macrophages following a brief stimulation with LPS. The effect of this factor on the number of circulating leukocytes and serum Fe, Cu and Zn levels, was also evaluated. The possibility that the content of interleukin (IL)-1beta, IL-6 and tumour necrosis factor (TNF) in the supernatant could explain the observations was investigated. Supernatant produced over a period of 1 h by peritoneal macrophages, following a 30 min incubation with LPS at 37 degrees C, was ultrafiltered through a 10 000 MW cut-off Amicon membrane, sterilized, and concentrated 2.5, 5, 10 and 20 times. The intravenous (i.v.) injection of this supernatant induced a concentration-dependent fever in rats with a maximal response at 2 h. The pyrogenic activity was produced by macrophages elicited with thioglycollate and by resident cells. The supernatants also induced neutrophilia and reduction in Fe and Zn 6 h after the injection. Absence of activity in boiled supernatants, or supernatants from macrophages incubated at 4 degrees C with LPS, indicates that LPS was not responsible for the activity. In vitro treatment with indomethacin (Indo), dexamethasone (Dex), or cycloheximide (Chx) did not modify the release of pyrogenic activity into the supernatant or its effects on the reduction in serum metal levels. Although Chx abolished the production of mediator(s) inducing neutrophilia, and Dex reduced the induction of IL-1beta, TNF and IL-6, injection of the highest concentration of these cytokines detected in the supernatants did not induce fever. In vivo treatment with Dex, but not Indo, abolished the fever induced by the supernatant. These results suggest that macrophages contain pre-formed pyrogenic mediator(s), not related to IL-1beta, IL-6 or TNF, that acts indirectly and independently of prostaglandtn. It also seems likely that the pyrogenic activity is related to the factor responsible for the reduction of serum Fe and Zn levels, but not the neutrophilia. 相似文献
89.
Renu Tuteja Narendra Tuteja Franco Lilliu Bruno Bembi Renzo Galanello Antonio Cao Francisco E. Baralle 《Human genetics》1994,94(3):314-315
We report a novel mutation in exon 9 of the glucocerebrosidase gene of a patient with Gaucher disease and of Sardinian origin. 相似文献
90.
R. Hudson A. I. Melo G. González-Mariscal 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1994,175(5):573-579
It was the purpose of this study to test whether inhibition of estrus in the rabbit by short photoperiod could be simulated by subcutaneous implants of the pineal hormone melatonin. By measuring two non-invasive and readily quantifiable correlates of estrus, emission of the so-called nipple-search pheromone and scent-marking behavior (chinning), it was found that:
- In intact does kept in stimulatory long photoperiod, melatonin suppressed chinning but had no effect on emission of nipple-search pheromone.
- In intact, melatonin-treated does which were returned from inhibitory short day to stimulatory long day, chinning remained suppressed, whereas pheromone emission increased as for the vehicle-treated, control does.
- In ovariectomized does, estradiol administration stimulated both pheromone emission and chinning whereas melatonin failed to suppress these effects.