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91.
Antonio Bode Benita Casas Emilio Fernández Emilio Marañón Pablo Serret Manuel Varela 《Hydrobiologia》1996,341(3):225-234
Summary Chlorophyll-a and primary production on the euphotic zone of the N-NW Spanish shelf were studied at 125 stations between 1984 and 1992. Three geographic areas (Cantabrian Sea, Rías Altas and Was Baixas), three bathymetric ranges (20 to 60 m, 60 to 150 m and stations deeper than 200 m), and four oceanographic stages (spring and autumn blooms, summer upwelling, summer stratification and winter mixing) were considered. One of the major sources of variability of chlorophyll and production data was season. Bloom and summer upwelling stages have equivalent mean and maximum values. Average chlorophyll-a concentrations approximately doubled in every step of the increasing productivity sequence: winter mixing — summer stratification — high productivity (upwelling and bloom) stages. Average primary production rates increased only 60% in the described sequence. Mean (± sd) values of chlorophyll-a and primary production rates during the high productivity stages were 59.7 ± 39.5 mg Chl-a m–2 and 86.9 ± 44.0 mg C m–2 h–1, respectively. Significant differences in both chlorophyll and primary production resulted between geographic areas in most stages. Only 27 stations showed the effects of the summer upwelling that affected coastal areas in the Cantabrian Sea and Rías Baixas shelf, but also shelf-break stations in the Rías Altas area. The Rías Baixas area had lower chlorophyll than both the Rías Altas and the Cantabrian Sea areas during spring and autumn blooms, but higher during summer upwelling events. On the contrary, primary production rates were higher in the Rías Baixas area during blooms in spring and autumn. Mid-shelf areas showed the highest chlorophyll concentrations during high productivity stages, probably due to the existence of frontal zones in all geographic areas considered. The estimated phytoplankton growth rates were comparable to those of other coastal upwelling systems, with average values lower than the maximum potential growth rates. Doubling rates for upwelling and stratification stages in the northern and Rías Altas shelf areas were equivalent, despite larger biomass accumulations during upwelling events. Low turnover rates of the existing biomass in the Rías Baixas shelf in upwelling stages suggests that the accumulation of phytoplankton was due mainly to the export from the highly productive rías, while the contribution of in situ production to these accumulations was relatively lower. 相似文献
92.
Xp-duplications with and without sex reversal 总被引:5,自引:0,他引:5
Annette Baumstark Gotthold Barbi Mahmoud Djalali Claudia Geerkens Beate Mitulla Torsten Mattfeldt José Carlos Cabral de Almeida Fernando Regla Vargas Juan Clinton Llerena Jr Walther Vogel Walter Just 《Human genetics》1996,97(1):79-86
Duplications in Xp including the DSS (dosage sensitive sex reversal) region cause male to female sex reversal. We investigated two patients from families with Xp duplications. The first case was one of two sisters with karyotype 46,XY, der(22), t(X;22)(p11.3;p11)mat and unambiguous female genitalia. The living sister was developmentally retarded, and showed multiple dysmorphic features and an acrocallosal syndrome. The second case was a boy with a maternally inherited direct duplication of Xp21.3-pter with the breakpoint close to the DSS locus. He had multiple abnormalities and micropenis, but otherwise unambiguous male genitalia. We performed quantitative Southern blot analysis with probes from Xp22.13 to p21.2 to define the duplicated region. Clinical, cytogenetic, and molecular data from both patients were compared with those of previously reported related cases. A comparison of the extragenital symptoms revealed no differences between patients with or without sex reversal. In both cases, the symptoms were non-specific. Among 22 patients with a duplication in Xp, nine had unambiguous female genitalia and a well-documented duplication of the DSS region. Two patients with duplication of DSS showed ambiguous external genitalia. From these data, we conclude that induction of testicular tissue may start in these patients, but that the type of genitalia depends on the degree of subsequent degeneration by a gene in DSS. 相似文献
93.
Saxifraga pentadactylis subsp. almanzorii , an endemic to the subalpine nucleus of Sierra de Gredos (central Spain), differs from its closest relative, subsp. willkommiana , by its less showy petals. An artificial crossing program was carried out in order to assess the degree of reproductive isolation between the subspecies. To facilitate interpretation of the results, the program was extended to 10 other interspecific hybrid combinations within sect. Saxifraga . All the data gathered are congruent with the occurrence of two evolutionary scenarios. Interspecific crossings, rendering moderate to high seed-set (in obtaining the F1 ), and vigorous but relatively sterile F1 offspring, reveal reproductive barriers at the level of the F1 fertility, probably originated as a byproduct of divergent evolution. In contrast, intraspecific crossings within S. pentadactylis resulted in seed-set values lower than expected (in obtaining the F1 ), in a majority of weak non-viable F1 offspring but also in a few fertile F1 hybrid specimens which were able to originate F2 offspring. This second pattern reveals reproductive barriers at the level of the F1 vitality, probably arisen in a quite abrupt fashion. The lower P/O for subsp. almanzorii as compared to subsp. willkommiana , together with the rest of the evidence suggest that the reproductive barriers between them might be the product of active selection against hybridization achieved by incrementing the levels of autogamy in the former. 相似文献
94.
Joaquin Royo Isabel Diaz Pablo Rodriquez-Palenzuela Pilar Carbonero 《Plant molecular biology》1996,31(5):1051-1059
The geneItr1, encoding trypsin inhibitor BTI-CMe, has been obtained from a genomic library ofHordeum vulgare L. The gene has no introns and presents in its 5-upstream region 605 bp that are homologous to the long terminal repeats (LTR) of the copia-like retro-transposon Bare-1. Functional analysis of theItr1 promoter by transient expression in protoplasts derived from different barley tissues, has shown that in this system theItr1 promoter retains its endosperm specifity and thetrans-regulation mediated by theLys3a gene. The proximal promoter extending 343 bp upstream of the translation initiation ATG codon is sufficient to confer fullGUS expression and for endosperm specifity. In protoplasts derived from thelys3a mutant, Risø 1508,GUS activity was less than 5% of that obtained with the same constructs in the protoplasts of wild-type Bomi from which it derives. Gel retardation experiments, after incubation with proteins obtained from both types of endosperm nuclei, also show differential patterns. Possible reasons for these differences are discussed.Equal authours 相似文献
95.
Relationship between the levels of wheat-rye metaphase I chromosomal pairing and recombination revealed by GISH 总被引:3,自引:0,他引:3
The metaphase I and anaphase I stages of meiosis of wheat×rye hybrids carrying the ph1b mutation were analyzed by genomic in situ hybridization. This technique allows distinction between three different types of
wheat-rye associations in metaphase I configurations as well as detection of wheat-rye recombinant chromosomes in anaphase
I cells. The frequency of associations between wheat and rye chromosomes greatly exceeded the level of wheat-rye recombination
found in the three hybrids examined. Extremely distal associations, which account for about 50% of the total wheat-rye metaphase
I chromosomal pairing, can explain such a discrepancy between metaphase I and anaphase I data. It is further discussed whether
these associations reflect very distally located chiasmata or nonchiasmatic pairing. The sizes of the segments exchanged in
wheat-rye recombinant chromosomes provide cytological evidence that wheat-rye recombination is restricted to the distal chromosomal
regions.
Received: 24 August 1995; in revised form: 27 February 1996 / Accepted: 28 March 1996 相似文献
96.
Akihiro Ohira Eugene de Juan Jr Yasuo Tano Charles A. Wilson 《The Histochemical journal》1996,28(9):607-611
Summary It has been proposed that basic fibroblast growth factor (basic FGF) mediates the neovascular response in a variety of conditions,
including diabetic retinopathy and branch retinal vein occlusion. To test the hypothesis that basic FGF was released from
retinal stores as a result of retinal ischaemia, transient retinal ischaemia was induced, followed by 48 h of reperfusion,
in the rat by combined central retinal vasculature and optic nerve ligation. The immunolocalization of basic FGF was studied
in the retina. We found that basic FGF in the normal retina is present around the deeper retinal vessels and in the neuronal
tissue of the outer plexiform layer. In the eyes that had ischaemia followed by reperfusion, there was moderate cellular oedema
with retinal swelling, and mitoses in the inner nuclear and plexiform layers. There were no changes evident at the immunohistochemical
level either in the intensity or distribution of stores of basic FGF. We conclude from these data that stores of basic FGF
are not altered dramatically under the conditions of transient experimental ischaemia and reperfusion in the rat, despite
the presence of cellular proliferation. 相似文献
97.
Thehigh growth(hg) locus in mice produces a 30–50% increase in weight gain of homozygous individuals. Here we report that the microsatellite markerD10Mit69is deleted in high growth mice. The deletion ofD10Mit69was uncovered in a screen of the high growth mouse and its progenitor strains for available markers in thehgregion. We demonstrate thathgandD10Mit69cosegregate in a cross of congenic strains C57BL/6J-hghg× C57BL/6J. These results suggest that deletion of a region aroundD10Mit69is responsible for the high growth effect. MarkerD10Mit69will be utilized as an entry point to physical cloning of thehg-containing segment. A dense map of markers aroundhgconstructed here should allow identification of markers in homologous regions in domestic animals and humans, which may be utilized to assess the role of thehglocus in these other species. 相似文献
98.
Silica biomorphs are inorganic self-organized precipitates resulting from a crystal aggregation process controlled by a metal silicate membrane. They display morphological and symmetric properties of living organisms and form under physico-chemical conditions similar to some geochemical conditions suggested for the chemical precipitation of Precambrian chert precursors. In consequence, these inorganic precipitates are proposed as an alternative interpretation to be considered when trying to decipher the biogenicity of putative Precambrian microbiotas. 相似文献
99.
100.
Juan Núez-Farfn Rodolfo Dirzo 《Evolution; international journal of organic evolution》1994,48(2):423-436
It has been assumed that herbivores constitute a selective agent for the evolution of plant resistance. However, few studies have tested this hypothesis. In this study, we look at the annual weed Datura stramonium for evidence of current natural selection for resistance to herbivorous insects. Paternal half-sib families obtained through controlled crosses were exposed to herbivores under natural conditions. The plants were damaged by two folivorous insects: the tobacco flea beetle Epitrix parvula and the grasshopper Sphenarium purpurascens. Selection was estimated using a multiple-regression analysis of plant size and of damage by the two herbivores on plant fitness measured as fruit production for both individual phenotypes and family breeding values (genetic analysis). Directional phenotypic selection was detected for both larger plant size and lower resistance to the flea beetles, whereas stabilizing phenotypic selection was revealed for resistance to S. purpurascens. However, performing the same analyses on the breeding values of the characters revealed directional and stabilizing selection only for plant size. Thus, no agreement existed between the results of the two types of analyses, nor was there any detectable potential for genetic change in the studied population because of selection on herbivore resistance. The narrow-sense heritability of every trait studied was small (all <0.1) and not different from zero. The potential for evolutionary response to natural selection for higher resistance to herbivores in the studied population of D. stramonium is probably limited by lack of genetic variation. Natural selection acts on phenotypes, and the detection of phenotypic selection on resistance to herbivores confirms their ecological importance in determining plant fitness. However, evolutionary inferences based solely on phenotypic selection analyses must be interpreted with caution. 相似文献