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81.
Aonio Bernao Isabel Meseguer María Victorina Aguilar María Carmen Martínez Para María José González Mu?oz 《Journal of trace elements in medicine and biology》2004,18(1):33-39
This 12-day study was conducted to evaluate the effects of three different levels of dietary chromium (100, 200, and 500 microg/day) in the form of chromium picolinate (CrPic) on growth and protein use in weaned rats. No significant effect of CrPic on body weight gain, food intake, or food conversion rate was observed. Elevated doses of CrPic seemed to increase muscle mass, either by stimulating protein anabolism by activation of insulin by chromium or by lowering protein degradation. However, these effects had no repercussions on overall growth, suggesting that any anabolic effect of chromium due to the action of insulin was probably marginal. 相似文献
82.
Michel Tibayrenc Francisco J. Ayala 《Evolution; international journal of organic evolution》1988,42(2):277-292
A genetic interpretation of the zymograms of 524 Trypanosoma cruzi stocks from various hosts and representing a broad geographical range (United States to Southern Brazil) reveals high genetic variability (only one monomorphic locus out of 15) and suggests that this parasite has a diploid structure. The data do not give any indication of Mendelian sexuality, although many opportunities are present for genetic exchange between extremely different genotypes. The population structure of T. cruzi appears to be multiclonal and complex. The natural clones evidenced by isozyme analysis are numerous (43 different ones are recorded among 121 stocks assayed at 15 gene loci) and exhibit a large range of genotypes, in a nonhierarchical structure; it is not possible to cluster them into a few strictly delimited groups which could represent natural taxa. The available data suggest that the genetic variability of T. cruzi reflects the long separate evolution of multiple clones. It is suggested that long clonal evolution may explain the present biological and medical variability of the causative agent of Chagas' disease. 相似文献
83.
A. Torres-Barragán E. Zavaleta-Mejía Carmen González-Chávez Ronald Ferrera-Cerrato 《Mycorrhiza》1996,6(4):253-257
A field experiment was carried out to determine the effects of the inoculation of onion (Allium cepa L.) with Glomus sp. Zac-19 on the development of onion white rot (Sclerotium cepivorum Berk.) and on onion production. Mycorrhization delayed onion white rot epidemics by 2 weeks and provided a significant protection
against the disease for 11 weeks after onion transplanting, as compared with nonmycorrhizal controls. Mycorrhizal plants showed
an increase of 22% in yield, regardless of the presence of the white rot pathogen.
Accepted: 8 January 1996 相似文献
84.
Leirla Salazar Hafida Fsihi Edda de Rossi Giovanna Riccardi Carmen Rios Stewart T. Cole Howard E. Takiff 《Molecular microbiology》1996,20(2):283-293
The genus Mycobacterium is composed of species with widely differing growth rates ranging from approximately three hours in Mycobacterium smegmatis to two weeks in Mycobacterium leprae. As DNA replication is coupled to cell duplication, it may be regulated by common mechanisms. The chromosomal regions surrounding the origins of DNA replication from M. smegmatis, M. tuberculosis, and M. leprae have been sequenced, and show very few differences. The gene order, rnpA-rpmH-dnaA-dnaN-recF-orf-gyrB-gyrA, is the same as in other Gram-positive organisms. Although the general organization in M. smegmatis is very similar to that of Streptomyces spp., a closely related genus, M. tuberculosis and M. leprae differ as they lack an open reading frame, between dnaN and recF, which is similar to the gnd gene of Escherichia coli. Within the three mycobacterial species, there is extensive sequence conservation in the intergenic regions flanking dnaA, but more variation from the consensus DnaA box sequence was seen than in other bacteria. By means of subcloning experiments, the putative chromosomal origin of replication of M. smegmatis, containing the dnaA-dnaN region, was shown to promote autonomous replication in M. smegmatis, unlike the corresponding regions from M. tuberculosis or M. leprae. 相似文献
85.
Acyl Group Migrations in 2-Monoolein 总被引:6,自引:0,他引:6
Anna Millqvist Fureby Carmen Virto Patrick Adlercreutz Bo Mattiasson 《Biocatalysis and Biotransformation》1996,14(2):89-111
Acyl migration in 2-monoolein dissolved in solvents under conditions common in lipid modification reactions has been studied. The effects on acyl migration of solvent, incubation temperature, water activity, polar additives and solid additives have been investigated. Extensive acyl migration occured in aliphatic hydrocarbons and water-miscible alcohols under dry conditions. The acyl migration rate could be decreased in several nonpolar solvents by adding a small amount of water or an alcohol. Increasing water activity had no effect in isooctane, but decreased the acyl migration rate dramatically in methyl tert-butyl ether and methyl isobutyl ketone. Several commonly used enzyme supports catalysed acyl migration, showing that supports with surface charges could catalyse acyl migration. 相似文献
86.
A New Pressure Probe Method to Determine the Average Volumetric Elastic Modulus of Cells in Plant Tissue 总被引:1,自引:0,他引:1
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A new in vivo method was used to determine an average volumetric elastic modulus ([epsilon]ave) for nongrowing cells in plant tissue. This method requires that both the relative transpiration rate, T, of the tissue and the average turgor pressure decay rate, (dP/dt)ave, of the cells are measured after the water source is removed from the plant tissue. Then [epsilon]ave is calculated from the equation [epsilon]ave = (-dP/dt)ave/T. This method was used to determine [epsilon]ave for cortical cells in stems of pea seedlings (Pisum sativum L.). The results demonstrate that [epsilon]ave increases from virtually zero at low P (approximately 0.01MPa) to approximately 10 MPa at high P (approximately 0.5 MPa). Analyses of the results indicate that the relationship between [epsilon]ave and P can be approximated by a linear function and more accurately approximated by a saturating exponential function: [epsilon]ave = [epsilon][infinity symbol][1 - exp {-k(P - Po)}], where Po is a plateau pressure (approximately 0.01 MPa), k is a rate constant (approximately 7 per MPa), and [epsilon][infinity symbol] (approximately 10 MPa) is the hypothetical maximum value of [epsilon]ave as P -> [infinity symbol]. Solutions for the turgor pressure decay (due to transpiration) as functions of time and symplasmic water mass (after the water source is removed) are derived. 相似文献
87.
Summary Contents of arginine, ornithine, urea and ammonia in wine were monitored during aging process by two flor veil-forming yeast strains. The patterns of yeast growth were different for the two strains studied. Urea excretion and uptake were dependent on yeast strain, so that finished wines showed different concentrations of urea. The effect of limited aeration was also investigated for Saccharomyces cerevisiae var. capensis. The results indicated that aeration promoted yeast growth in veil, thus reducing urea concentration until its exhaustion in wine. 相似文献
88.
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
89.
The short term effect of NO3 − (12 mM) on nitrate reductase (NR. EC 1.6.6.1) activity has been studied in the roots, nodules and leaves of different genotypes of Vicia faba L. at the end of vegetative growth. Root and leaf NR activity responded positively to NO3 − while nodule activity, where detected, proved to he strongly inhibited. The withdraw of this NO3 − from the solution consistently reduced activity in the roots and leaves but surprising, promoted a significant increase in nodule activity, which matched or surpassed that of control plants On the other hand, nodules developed in the presence of 8 mM NO3 − expressed an on average 141% higher level of NR activity than did controls. This effect was observed even in nodules with negligible control activity. In any case, a naturally occurring mutant (VF17) lacking root and nodule NR activity is described. The results indicate that in V. faba. the effects of NO3 − and plant genotype on NR activity depended on plant organ and time of NO3 − application, hut the distribution of NO3 − reduction through the plain was mainly dependent on plant genotype, and to a lesser extent on NO: supply and plant age. 相似文献
90.
James R. Bunzow Ge Zhang Claudia Bouvier Carmen Saez Oline K. Ronnekleiv Martin J. Kelly David K. Grandy 《Journal of neurochemistry》1995,64(1):14-24
Abstract: We have cloned and expressed a rat brain cDNA, TS11, that encodes a μ-opioid receptor based on pharmacological, physiological, and anatomical criteria. Membranes were prepared from COS-7 cells transiently expressing TS11 bound [3H]diprenorphine with high affinity (KD = 0.23 ± 0.04 nM). The rank order potency of drugs competing with [3H]diprenorphine was as follows: levorphanol (Ki = 0.6 ± 0.2 nM) ≈β-endorphin (Ki = 0.7 ± 0.5 nM) ≈ morphine (Ki = 0.8 ± 0.5 nM) ≈ [d -Ala2, N-Me-Phe4,Gly-ol5]-enkephalin (DAMGO; Ki = 1.6 ± 0.5 nM) ? U50,488 (Ki = 910 ± 0.78 nM) > [d -Pen2,5]-enkephalin (Ki = 3,170 ± 98 nM) > dextrorphan (Ki = 4,100 ± 68 nM). The rank order potencies of these ligands, the stereospecificity of levorphanol, and morphine's subnanomolar Ki are consistent with a μ-opioid binding site. Two additional experiments provided evidence that this opioid-binding site is functionally coupled to G proteins: (a) In COS-7 cells 50 µM 5′-guanylylimidodiphosphate shifted a fraction of receptors with high affinity for DAMGO (IC50 = 3.4 ± 0.5 nM) to a lower-affinity state (IC50 = 89.0 ± 19.0 nM), and (b) exposure of Chinese hamster ovary cells stably expressing the cloned μ-opioid receptor to DAMGO resulted in a dose-dependent, naloxone-sensitive inhibition of forskolin-stimulated cyclic AMP production. The distribution of mRNA corresponding to the μ-opioid receptor encoded by TS11 was determined by in situ hybridization to brain sections prepared from adult female rats. The highest levels of μ-receptor mRNA were detected in the thalamus, medial habenula, and the caudate putamen; however, significant hybridization was also observed in many other brain regions, including the hypothalamus. 相似文献