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991.
Spinalona anophtalma n. gen. n. sp. is describedon parthenogenetic and ephippial females andmales from material collected in a temporary lagoonlocated in the Neovolcanic Province from Mexico at analtitude of 2507 m above sea level. It ischaracterized by a strong armature of the antenna,postabdomen and postabdominal claw, no compound eyeor ocellus, the exopod of thoracic limb IIIwith only four setae and that of P5 with only three setae.This new taxon has no relationwith blind Alona from hypogean habitats. 相似文献
992.
The hydrological structure of the French coastal part of the eastern English Channel is strongly linked with tidal regimes and riverine input. Two distinct water masses are separated by a frontal area and drift along the coast in SW–NE direction. These two water masses are well-mixed during the entire year. We studied the seasonal dynamic of nitrogenous nutrients, chlorophyll a and organic particulate carbon and nitrogen at two stations, characteristic of these water masses, during the year 1994. Results show (i) a winter stock of nitrate and ammonium, (ii) a pre-bloom period corresponding to the use of ammonium, (iii) a high bloom period of short duration using nitrate, (iv) a post-bloom period with little phytoplanktonic activity probably limited by nutrients other than nitrogen and (v) an autumnal period of reconstitution of stock. The essential difference between the two stations is the importance of winter stock of nutrients and of bloom chlorophyll a concentration, with the coastal station richer than the offshore one. An assumption about the nitrogen available for new production in this area gives a value of 57% of the winter stock of inorganic nitrogen. 相似文献
993.
J.-P. Bénitah J.R. Balser E. Marban G.F. Tomaselli 《The Journal of membrane biology》1997,155(2):121-131
Extracellular acidosis affects both permeation and gating of the expressed rat skeletal muscle Na+ channel (μ1). Reduction of the extracellular pH produced a progressive decrease in the maximal whole-cell conductance and
a depolarizing shift in the whole-cell current-voltage relationship. A smaller depolarizing shift in the steady-state inactivation
curve was observed. The pK of the reduction of maximal conductance was 6.1 over the pH range studied. An upper limit estimate
of the pK of the shift of the half-activation voltage was 6.1. The relative reduction in the maximal whole-cell conductance
did not change with higher [Na+]
o
. The conductance of single fenvalerate-modified Na+ channels was reduced by extracellular protons. Although the single-channel conductance increased with higher [Na+]
o
, the maximal conductances at pH 7.6, 7.0 and 6.0 did not converge at [Na+]
o
up to 280 mm, inconsistent with a simple electrostatic effect. A model incorporating both Na+ and H+ binding in the pore and cation binding to a Gouy-Chapman surface charge provided a robust fit to the single-channel conductance
data with an estimated surface charge density of 1e−/439?2. Neither surface charge nor proton block alone suffices to explain the effects of extracellular acidosis on Na+ channel permeation; both effects play major roles in mediating the response to extracellular pH.
Received: 14 May 1996/Revised: 19 September 1996 相似文献
994.
Maria Manuela M. Caniça Chang Y. Lu Rajagopal Krishnamoorthy Gérard C. Paul 《Journal of molecular evolution》1997,44(1):57-65
The molecular diversity of inhibitor-resistant TEM (IRT) enzymes was explored using a strategy which involved DNA amplification
by polymerase chain reaction (PCR), analysis of restriction fragment length polymorphism (RFLP), and direct nucleotide sequencing.
The study of plasmid-borne genes from 27 strains, resistant to amoxicillin and β-lactamase-inhibitor combinations, identified
mutations resulting in amino acid change at positions 69, 244, 275, and 276 known to be associated with the IRT phenotype
and a mutation at nucleotide position 162 in the promoter region. These mutations were found to lie on two different gene
sequences, described here as ``TEM-1B like' and ``TEM-2 like' restriction linkage groups. Further analysis, of nucleotide
sequences of promoter and coding regions of the β-lactamases, confirmed that a given mutation causing IRT phenotype could
be associated with two different gene sequence frameworks and two different causal mutations could lie on identical gene sequence
framework. These data argue in favor of convergent phenotypic evolution of IRT enzymes under the selective pressure imposed
by the intensive clinical use of β-lactam–β-lactamase inhibitor combinations.
Received: 18 March 1996 / Accepted: 15 July 1996 相似文献
995.
Bertrand Dommée Andrée Biascamano Nicole Denelle Jean-Louis Bompar John D. Thompson 《American journal of botany》1995,82(6):734-740
Natural populations of Thymelaea hirsuta have previously been shown to comprise four distinct sexual morphs: males, females, protogynous individuals, i.e., first female then male, and protandrous individuals, i.e., first male then female. The objective of the present study has been to confirm the genetic basis of this sexual tetramorphism by quantifying morph ratios in the open-pollinated progeny of the four sexual phenotypes growing in a natural population. All four phenotypes were recovered in the progeny of each morph. All observed plants displayed a single sexual phenotype, thus confirming the genetic basis of the tetramorphism. The progeny sex ratios indicate that the genetic determination of sex in this species may be influenced by cytoplasmic factors, while the observed levels of functional female fertility suggest a near-dioecious system. The evolutionary significance of this tetramorphism as a transitional stage in the evolution of dioecy is discussed. 相似文献
996.
The effect of phosphinothricin concentration on embryo production from an embryogenic callus of Chancellor (Vitis L. complex interspecific hybrid) was tested. Embryogenic callus was cultured on medium supplemented with nine phosphinothricin concentrations (0, 0.1, 0.5, 1, 1.5, 2, 3, 5, and 10 mg/l). The highest number of embryos per plate was observed at 0.5 mg/l phosphinothricin. The use of phosphinothricin to stimulate embryo production did not affect embryo germination and plantlet formation. Three germination techniques were compared. Embryo dehydration or growth on Transfergelsolidified medium gave higher germination rates than chilling treatments. Most germinated somatic embryos produced secondary embryos from the hypocotyl after a few weeks of culture. Regardless of the germination technique, the plantlet conversion rate was very low.Abbreviations AC
activated charcoal
- 2,4-D
2,4-dichlorophenoxyacetic acid
- BA
6-benzylaminopurine
- MS
Murashige and Skoog (1962) basal medium
- NN
Nitsch and Nitsch (1969) medium
- PPT
phosphinothricin 相似文献
997.
Esterase zymograms were obtained following polyacrylamide slab gel electrophoresis of protein extractsFusarium sambucinum and related species originating from different geographic locations and different matrices. The sites of esterase activity were recorded, and the Rfs were calculated. The data were used for the construction of phenograms by cluster analysis and nonlinear mapping by computerized classification techniques. The fifteen isolates ofF. sambucinum, the eight isolates ofF. torulosum and the six isolates ofF. spec. nov. each had identical profiles, and are therefore electrophoretically distinct species. The isolates ofF. sarcochroum, one ofF. sambucinum sensu lato (BBA 64280) and fifteen isolates ofF. sambucinum were electrophoretically indistinguishable from each other. We assume they are synonymous. The isolate ofF. bactridioides, one ofF. sambucinum sensu lato (BBA 64993) and eight isolates ofF. torulosum had uniform EST patterns, therefore the two species are electrophoretically identical. We assume they are also synonymous. The remaining three isolates ofF. sambucinum sensu lato are somewhat closely related toF. sambucinum isolates on the basis of our investigations. 相似文献
998.
Emmanuel Martin Valère Cacheux Hélène Cavé Jean Michel Lapierre Denis Le Paslier Bernard Grandchamp 《Human genetics》1995,96(6):668-670
CDKN4/p27Kip1 is a cyclin-dependent kinase (Cdk) inhibitor implicated in G1 phase arrest, which negatively regulates G1 phase progression in response to TGF, and might represent a tumor suppressor gene. We report here the chromosomal assignment of the human CDKN4 gene to chromosome 12p12.3 in close proximity to highly polymorphic microsatellite markers. 相似文献
999.
Réjean Plamondon 《Biological cybernetics》1995,72(4):295-307
This paper proposes a kinematic theory that can be used to study and analyze rapid human movements. It describes a synergy
in terms of the agonist and antagonist neuromuscular systems involved in the production of these movements. It is shown that
these systems have a log-normal impulse response that results from the limiting behavior of a large number of interdependent
neuromuscular networks, as predicted by the central limit theorem. The delta log-normal law that follows from this model is
very general and can reproduce almost perfectly the complete velocity patterns of an end-effector. The theory accounts for
the invariance and rescalability of these patterns, as well as for the various observations that have been reported concerning
the change in maximum and mean velocities, time to maximum velocity, etc., under different experimental conditions. Movement
time, load effects, and control strategies are discussed in a companion paper.
Received: 15 February 1993/Accepted in revised form: 15 September 1994 相似文献
1000.
Cecilia Ballaré Marcela Barrio Paula Portela Jose Mordoh 《Cancer immunology, immunotherapy : CII》1995,41(1):15-22
FC-2.15 is a murine IgM monoclonal antibody (mAb) that recognizes a cell-surface antigen (Ag2.15) expressed in most tumor-proliferating cells of human breast carcinomas and other neoplasias. In this study the cytotoxic ability of mAb FC-2.15, its cell-surface binding properties and endocytosis in Ag2.15-expressing (Ag2.15+) cells were investigated. A51Cr-release assay was used to test the FC-2.15-mediated cytotoxicity. When human serum was used as source of complement, FC-2.15 exerted a strong cytotoxic effect against human Ag2.15+ cells such as MCF-7 (breast cancer cell line), primary breast carcinoma cells, polymorphonuclear leukocytes and chronic myeloid leukemia cells. The mAb concentration range was 1–50 g/ml. Cytotoxicity was completely abolished when complement was inactivated. Only 3.8±2.9% of MCF-7 cells survived the treatment with FC-2.15 in the presence of human serum. A flow-cytometry assay was performed to study the Ag2.15 expression of the surviving cells and they were found to be Ag2.15–. FC-2.15 did not mediate antibody-dependent cell cytotoxicity when different effector cells were used. Scatchard analysis with125I-FC-2.15 on MCF-7 cells demonstrated an affinity constant of 6.9×107 M–1 and 2.8×106 antigenic sites/cell.125I-FC-2.15 was internalized to cytoplasmic vesicles reaching a maximum of 27% after 6 h incubation, followed by the release of labeled degradation products to the supernatant. FC-2.15 appears to exert its cytotoxic effect mainly in the presence of human complement, it reacts with intermediate affinity with a high-density surface antigen, and it is slowly internalized by Ag2.15+ cells. 相似文献