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21.
We present results on cross-mating experiments using Brachionus plicatilis strains collected in three ponds of a coastal marsh (Torreblanca Marsh, Castellón, Spain). These strains were known to differ widely both in morphology and allozyme patterns from a previous study, where they were grouped into three genetically different clonal groups. Although some of the strains co-occurred in the same pond and sexual periods overlapped, no gene flow was found among them. Our first objective was to determine whether behavioral reproductive isolation was responsible for the absence of interbreeding. A second objective was to explore the relationship between sexual isolation and genetic divergence. We performed two experiments. In Experiment 1, we tested five strains from different clonal groups; in Experiment 2, we added a strain from a congeneric species, and strains from different ponds. We recorded male mating behavior in all possible male-female strain pairings. Our data show that males of a strain tend to mate with females of the same strain or genetically similar strains, regardless of the pond they come from. We also found a high positive correlation between isolation distance and genetic distance. These results support the view that mating behavior acts as an important isolating barrier giving cohesion to clonal groups, and structuring populations of this rotifer, and that Brachionus plicatilis is a taxon composed of more than one biological species. 相似文献
22.
M. Pascual J. Balanya A. Latorre L. Serra 《Journal of Zoological Systematics and Evolutionary Research》1997,35(4):159-164
The disribution ranges of Drosophila azteca and D. athabasca overlap in northen California and southern Oregon. Seven populations, four of which are located in this area, were studied. Large random amplified polymorphic DNA (RAPD) variation was found within species; nevertheless, more than half the primers used in the study yielded greater diofference between than within species. A nested analysis of molecular variance (AMOVA) showed that the variance between populations within species was significantly greater than zero for 55% of the oligonucleotides used, which provided evidence for an underlying geographical structure of these populations. Specimens of D. azteca and D. athabasca from Salem (OR), where both species were collected together, presented the highest similarity encountered between species. 相似文献
23.
Speciation in monogonont rotifers 总被引:7,自引:4,他引:3
Monogonont rotifers are cyclical parthenogens livingin limnic habitats with considerable seasonalvariation and often with island-like features. Theoccurrence of bisexual reproduction in these organismsmakes it feasible to define fields for generecombination, i.e. biological species. In thispaper, we analyze the structure of the diversity inmonogonont rotifers using several data sets: taxonomicand intraspecific diversity as reported inidentification keys, morphological variation reportedin ecological studies, and allozyme and matingbehavior patterns. Our analysis suggests that siblingspecies may be frequent in rotifers. Monogonontrotifers seem to meet conditions for an activespeciation, which might be particularly promoted byseasonal specialization and timing of bisexualreproduction. 相似文献
24.
Itziar Alkorta Carlos Garbisu María J. Llama Juan L. Serra 《Biotechnology Techniques》1995,9(2):95-100
Summary The extracellular pectin lyase (PNL, E.C. 4.2.2.10) from Penicillium italicum was utilized in batch and confined in a continuous-flow ultrafiltration membrane reactor. The enzyme catalyzed the decrease in viscosity of pectin solutions at pH 6.0 as well as of different fruit juices at their respective pH. PNL decreased the viscosity of pectin solutions in the membrane (60% after 30 min) more than in the batch (46% after 70 min) reactors, but similar viscosity reduction of fruit juices was achieved in both reactors. The enzyme decreased the viscosity of grape, peach and melon juices to different extents, but failed to do so with apple or pear juices. It can be concluded that the utilization of PNL in a membrane reactor appears of interest for the clarification of fruit juices. 相似文献
25.
M Manca M Bottoni R Eleopra V Tugnoli M C Cristofori G Serra 《Bollettino della Società italiana di biologia sperimentale》1984,60(5):1019-1022
The Authors studied the checkerboard pattern electroretinogram (PERG) behaviour in normal subjects and in patients suffering from traumatic lesion of optic nerve, demyelinating optic neuritis, axonal optic neuritis, retinal vascular disorders and retinitis pigmentosa in order to verify the PERG origin. According to our data the PERG appears to originate from ganglion cells since the signal diminished or disappeared in axonal lesion of optic nerve, as a result of retrograde ganglion cell degeneration. Furthermore, the demyelinating lesions of optic nerve were not able to modify the PERG wave. In patients suffering from retinal receptor disturbances the flash electroretinogram (FERG), which is probably an expression of receptor activity, was greatly impaired, whereas PERGs were either normal or less impaired than FERGs. These data demonstrate the different origin of PERG and FERG. 相似文献
26.
Isolation from neutrophil membranes of a complex containing active NADPH oxidase and cytochrome b-245 总被引:1,自引:0,他引:1
M C Serra P Bellavite A Davoli J V Bannister F Rossi 《Biochimica et biophysica acta》1984,788(1):138-146
The lipid composition and fluidity of basolateral membranes prepared from the mucosa of the proximal, middle and distal thirds of the rat small intestine were determined. Fluidity, as assessed by the fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene and a series of anthroyloxy fatty acid derivatives, is decreased in the distal third as compared to the proximal segments. This pattern is similar to that described previously for microvillus membranes. The decrease in fluidity of the distal as compared to the proximal membranes results from an increase in cholesterol content, cholesterol/phospholipid molar ratio and degree of saturation of the fatty acid residues. In the middle and distal thirds of the gut, the degree of saturation of the fatty acid residues is higher in microvillus as compared to basolateral membranes, accounting in part for the characteristically lower fluidity of the luminal membranes. The specific activity of the basolateral membrane (Na+ + K+)-dependent adenosine triphosphatase is significantly lower in the distal as compared to the proximal and middle thirds of the intestinal mucosa. Studies of the binding of [3H]ouabain indicate that this pattern results from fewer enzyme sites in the distal membranes. 相似文献
27.
A. Barbarino A. Serra E. Menini G. Pizzolato E. Moneta E. Pasargiklian L. de Marinis R. Bova 《Human genetics》1978,42(2):119-127
Summary In two patients with testicular feminization syndrome, one Yq12-positive and the other Yq12-negative, we compared phenotype, gonadal histology and ultrastructure, in vivo steroid response of the testes to the administration of exogenous gonadotropin during adrenal suppression, and of the adrenal gland to ACTH. The assumption that the constitutive Y heterochromatin could function as a regulator of steroid biosynthesis and metabolism, with or without effect at other levels, was not firmly supported by the observations reported here. However, further studies along this line may help elucidate the biologic role of this portion of the Y chromosome in humans. 相似文献
28.
I. Serra M. Alberghina M. Viola A. Mistretta A. M. Giuffrida 《Neurochemical research》1981,6(6):607-618
The effect of CDP-choline on the in vivo incorporation of labeled precursors into DNA, RNA, and proteins in cerebral hemispheres, cerebellum, and brainstem of guinea pigs after hypoxic treatment was studied. The labeling of macromolecules extracted from the various subcellular fractions of these brain regions was also determined. Hypoxic treatment affected macromolecular labeling to a different extent in the three brain regions examined. CDP-choline treatment was not able to reverse the effect of hypoxia on DNA labeling, but it was able to remove the effect of hypoxia on RNA and protein labeling. The action of CDP-choline was particularly evident on the labeling of RNA in nuclei and mitochondria of the cerebellum and on the labeling of proteins in microsomes of the three brain regions examined. 相似文献
29.
Post-translational changes of chromosomal proteins in rat cerebellum during postnatal development 总被引:1,自引:0,他引:1
I. Serra M. Kamiyama G. A. Hashim P. Ragonese B. Lombardo A. M. Giuffrida 《Neurochemical research》1983,8(12):1577-1587
Acetylation, phosphorylation and methylation of nuclear proteins in rat cerebellum at 10 and 30 days of age were investigated in vitro. Isolated nuclei were incubated in the presence of [1-14C]acetyl CoA, S-adenosyl [methyl-3H]methionine and [gamma-32P]ATP and then separated into histones and non histone proteins (NHP), which were further fractionated by polyacrylamide gel electrophoresis. The results obtained indicate that acetylation, phosphorylation and methylation of both basic and acidic proteins decrease from 10 to 30 days of age. Electrophoretic analysis of histones shows that the decrease mainly concerns H1, H3, and H2b fractions. The H3 fraction is always more labeled than the other fractions and shows the major changes during postnatal development. Phosphorylation of H2a and H4 fractions increases from 10 to 30 days of age, whereas acetylation and methylation of these fractions do not show significant changes from 10 to 30 days. The densitometric and radioactive patterns of NHP show considerable changes between 10 and 30 days, especially in the high molecular weight region. The incorporation of 14C-acetyl and 3H-methyl groups and of 32P phosphate appears to be generalized throughout the molecular weight range and decreases from 10 to 30 days of age. The methylation of an as yet unidentified protein with a molecular weight of approximately 110,000 daltons occurred at both ages. 相似文献
30.
J P Deans H M Serra J Shaw Y J Shen R M Torres L M Pilarski 《Journal of immunology (Baltimore, Md. : 1950)》1992,148(6):1898-1905
High molecular mass isoforms of CD45 protein tyrosine phosphatase, predominantly CD45RA, are expressed on naive T cells with increasing density during the first 2 days of cellular activation, and subsequently down-regulated concurrent with increasing expression of the low Mr isoform, CD45RO. We show this to be de novo synthesis of CD45RA dependent upon both RNA and protein synthesis. Using a probe shown to detect mRNA encoding the alternatively spliced abc, ab, bc, and b exon isoforms of CD45, the expression of CD45 was analyzed. Kinetic studies of the transition from high to low Mr CD45 mRNA indicate an immediate decrease in the level of high Mr CD45 mRNA after mitogen stimulation of T cells, quickly followed at 4 h by an increase to above steady state levels. This is consistent with the transitory increase in cell-surface density of CD45RA observed at 1 to 2 days poststimulation. Within 24 h of stimulation the level of high Mr CD45 mRNA declines precipitously such that little or no mRNA encoding any of the alternatively spliced exons is detectable. High levels of CD45 mRNA are detectable at later points but this does not hybridize with the Sfa N1 probe recognizing the abc exons suggesting that only the CD45RO mRNA splicing pattern is operative. We also show that CD45 mRNA have a relatively short t1/2. In mitogen-stimulated cells the t1/2 of high and low m.w. CD45 mRNA was estimated at 2.25 h and 3.5 h, respectively. In unstimulated T cells the t1/2 of high Mr CD45 mRNA was estimated at 2.8 h. CD45 mRNA is super-induced in the presence of the protein synthesis inhibitor, cycloheximide, indicating that the degradation and/or splicing of CD45 mRNA is controlled by a labile pathway, and suggesting that mechanisms may exist in vivo to prolong synthesis of CD45RA. The kinetics of accumulation for high Mr CD45 mRNA are very similar to those of the TCR beta-chain and pp56lck suggesting that these functionally linked signaling molecules are regulated in tandem. This implicates stringent molecular control mechanisms on the production of mRNA encoding either high or low m.w. isoforms, consistent with the fundamental role of CD45 in signal transduction, and the apparent need to selectively and sequentially express functionally distinct external CD45 domains. 相似文献