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排序方式: 共有472条查询结果,搜索用时 15 毫秒
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3.
Stimulation of T lymphocyte proliferation by monoclonal antibodies against GD3 ganglioside 总被引:3,自引:0,他引:3
K Welte G Miller P B Chapman H Yuasa E Natoli J E Kunicka C Cordon-Cardo C Buhrer L J Old A N Houghton 《Journal of immunology (Baltimore, Md. : 1950)》1987,139(6):1763-1771
Cell-surface gangliosides are presumed to play a role in cell growth and differentiation. With the use of monoclonal antibodies directed against GD3, a disialoganglioside expressed predominantly by cells of neuroectodermal origin, we have found that GD3 is expressed by a subpopulation of cells of the immune system including: 1) fetal thymocytes in subcortical regions and near vessels, 2) lymph node lymphocytes in interfollicular areas and near vessels, and 3) a small subset of T cells in the peripheral blood. Mouse monoclonal antibodies (two IgGs, one IgM, and F(ab')2 fragments) reacting with GD3 were found to stimulate proliferation of T cells derived from peripheral blood. Proliferation of T cells was observed even in cultures depleted of macrophages, suggesting that activation by anti-GD3 was not dependent on the presence of accessory cells. T cell proliferation was maximum between days 5 and 7 of stimulation and was preceded by expression of interleukin 2 receptors. No stimulation was observed with control antibodies of the identical isotype or with monoclonal antibodies recognizing the gangliosides GD2 or GM2. During stimulation by anti-GD3 monoclonal antibodies, there was an expansion of the GD3+ pool of T cells, but depletion of GD3+ T cells prior to stimulation abrogated the response. Proliferation induced by binding to GD3 could be augmented by exogenous interleukin 2 and phytohemagglutinin. Anti-CD3 (T3) monoclonal antibodies had little or no effect. These results demonstrate that binding to GD3 on the surface of T cells can elicit signals for T cell proliferation. 相似文献
4.
5.
A method for analysis of back shape in scoliosis 总被引:2,自引:0,他引:2
The shape of the back is an important factor in the clinical assessment of various spinal disorders, in particular scoliosis. A method of analysis of back surface shape is described which was designed to present most of the numerical parameters needed to assess the progress of the disease as it affects body shape. Measurements of back surface shape and manually marked anatomical landmarks were taken from a television/computer surface measurement system in which a plane of light was scanned over the back and from moiré topographs. The anatomical landmarks were used to define reference planes from which successive analyses were matched. Asymmetry in the transverse plane was illustrated by horizontal cross-sections and skin surface angles. The lateral deformity was shown by an estimate of the line of the vertebral bodies beneath the skin, derived by adding an extra lateral displacement to the palpated positions of the spinous processes, proportional to the rotation of the skin in the transverse plane. This model was used to estimate vertebral end-plate angles and Cobb angles. Lateral sections showed kyphosis and lordosis. Correlations of Lateral Asymmetry from the surface shape analysis with Cobb angle from X-ray measurements in three groups of patients (totalling 119 subjects) were in the range r = 0.77 to r = 0.94, p less than 0.0001. The analysis has reduced follow-up X-ray examinations at the Nuffield Orthopaedic Centre because it indicates quantitatively and with complete safety both lateral asymmetry and deformity in the transverse plane. 相似文献
6.
Steroidal saponins from the rhizomes of Polygonatum orientale. 总被引:6,自引:0,他引:6
7.
Gerald Houghton 《Bulletin of mathematical biology》1966,28(4):487-500
A two-dimensional nonlinear integro-differential equation with time-varying coefficients describing the behavior of the fluttering
wing-body systems typical of natural flight mechanisms has been deduced from the Navier-Stokes equation which generalizes
local pressure and velocity distributions in the externally oscillating air field. The resulting equation for the wing forces
is combined with an analogous expression for the forces of gravitation and acceleration associated with the body. The air
acceleration force, not previously considered in bio-physical models of insect and bird flight, is shown to arise from a formal
analysis of unsteady or time-varying contributions to the velocity field, while the square form of the conventional steady
state aerodynamic forces is derived from the intertial terms in the Navier-Stokes equation with the aid of the approximations
of Newtonian impact theory. Previous calculations (Houghton, 1964) have indicated that the contribution to gravitational stability
of air acceleration and aerodynamic life are roughly in the ratio of 3:1. 相似文献
8.
Joseph G. Major Jr. Melinda E. Wales John E. Houghton Julie A. Maley Jeffrey N. Davidson James R. Wild 《Journal of molecular evolution》1989,28(5):442-450
Summary Aspartate transcarbamoylase (ATCase, EC 2.1.3.2) is the first unique enzyme common to de novo pyrimidine biosynthesis and
is involved in a variety of structural patterns in different organisms. InEscherichia coli, ATCase is a functionally independent, oligomeric enzyme; in hamster, it is part of a trifunctional protein complex, designated
CAD, that includes the preceding and subsequent enzymes of the biosynthetic pathway (carbamoyl phosphate synthetase and dihydroorotase).
The complete complementary DNA (cDNA) nucleotide sequence of the ATCase-encoding portion of the hamster CAD gene is reported
here. A comparison of the deduced amino acid sequences of the hamster andE. coli catalytic peptides revealed an overall 44% amino acid similarity, substantial conservation of predicted secondary structure,
and complete conservation of all the amino acids implicated in the active site of theE. coli enzyme. These observations led to the construction of a functional hybrid ATCase formed by intragenic fusion based on the
known tertiary structure of the bacterial enzyme. In this fusion, the amino terminal half (the “polar domain”) of the fusion
protein was provided by a hamster ATCase cDNA subclone, and the carboxyl terminal portion (the “equatorial domain”) was derived
from a clonedpyrBI operon ofE. coli K-12. The recombinant plasmid bearing the hybrid ATCase was shown to satisfy growth requirements of transformedE. coli pyrB
− cells. The functionality of thisE. coli-hamster hybrid enzyme confirms conservation of essential structure-function relationships between evolutionarily distant
and structurally divergent ATCases. 相似文献
9.
The phylogeny of Greya Busck (Lepidoptera: Prodoxidae) was inferred from
nucleotide sequence variation across a 765-bp region in the cytochrome
oxidase I and II genes of the mitochondrial genome. Most parsimonious
relationships of 25 haplotypes from 16 Greya species and two outgroup
genera (Tetragma and Prodoxus) showed substantial congruence with the
species relationships indicated by morphological variation. Differences
between mitochondrial and morphological trees were found primarily in the
positions of two species, G. variabilis and G. pectinifera, and in the
branching order of the three major species groups in the genus. Conflicts
between the data sets were examined by comparing levels of homoplasy in
characters supporting alternative hypotheses. The phylogeny of Greya
species suggests that host-plant association at the family level and larval
feeding mode are conservative characters. Transition/transversion ratios
estimated by reconstruction of nucleotide substitutions on the phylogeny
had a range of 2.0-9.3, when different subsets of the phylogeny were used.
The decline of this ratio with the increase in maximum sequence divergence
among taxa indicates that transitions are masked by transversions along
deeper internodes or long branches of the phylogeny. Among transitions,
substitutions of A-->G and T-->C outnumbered their reciprocal
substitutions by 2-6 times, presumably because of the approximately 4:1
(77%) A+T-bias in nucleotide base composition. Of all transversions,
73%-80% were A<-->T substitutions, 85% of which occurred at third
positions of codons; these estimates did not decrease with an increase in
maximum sequence divergence of taxa included in the analysis. The high
frequency of A<-->T substitutions is either a reflection or an
explanation of the 92% A+T bias at third codon positions.
相似文献
10.
Methanolic extracts of seven herbs (Acorus calamus, Acorus gramineus, Bupleurm facaltum, Dioscorea batatas, Epimedium koreanum, Poria cocos and Zizyphi jujuba) used in traditional Korean medicine for improvement of memory and cognition in old age were tested for cholinesterase inhibitory properties using the Ellman colorimetric method. Significant inhibition of the enzyme at 200 microg/ml was observed for extracts from A. calamus and E. koreanum. The possible bases for the reputation of these and the other herbs tested are discussed in the light of previous investigations into their chemistry and biological activity. 相似文献