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ALAIN THIÉRY NICOLAS RABET GABRIEL NÈVE 《Biological journal of the Linnean Society. Linnean Society of London》2007,90(1):55-60
The shape of the resting eggs of a large branchiopod crustacean, the Anostraca Tanymastix stagnalis , is represented very accurately by analytical expressions. The occurrence of atypical shape of some T. stagnalis eggs may be viewed as a simple change of the analytical expression describing the usual egg shape. Their unusual shape may be explained by a higher embryo volume within an envelope of a given size. Biological implications are briefly discussed and hypothesized in an evolutionary point of view. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 90 , 55–60. 相似文献
4.
P. Usobiaga J. J. Calvete J. L. Saíz M. T. Eirín J. González-Rodríguez 《European biophysics journal : EBJ》1987,14(4):211-218
Sedimentation equilibrium and low-angle laser-light scattering were used to determine the molar mass of the glycoprotein moieties in the complexes of sodium dodecyl sulphate with the human platelet membrane glycoproteins IIb (GPIIb), IIIa (GPIIIa), and the (GPIIb) and (GPIIb) subunits of GPIIb. The values obtained by both procedures, except those for GPIIb, agree within experimental error with those calculated from their chemical composition: GPIIb (114,000 g mol-1), GPIIb (22,200 g mol-1), and GPIIIa (91,500 g mol-1). The molar mass of GPIIb determined by light scattering (142,000 g mol-1) and sedimentation equilibrium at different solvent densities (134,000 g mol-1) also agree, within experimental error, with the values calculated either from its chemical composition (136,500 g mol-1) or from the sum of the molar masses of its subunits. However the molar mass determined by sedimentation equilibrium at constant solvent density, is consistently underestimated (116,000 g mol-1).High-performance size-exclusion chromatography in sodium dodecyl sulphate solutions overestimates the molar mass of these glycoproteins and their Stokes radii, and therefore the maximal frictional ratios derived from them.Abbreviations GPIIb
glycoprotein IIb
- GPIIIa
glycoprotein IIIa
- GPIIb and GPIIb
and subunits of GPIIb, respectively
- CM-GPIIb
CM-GPIIb, and CM-GPIIIa, totally reduced and carboxymethylated forms of GPIIb, GPIIb, and GPIIIa, respectively
- SDS
sodium dodecyl sulphate
- eosin-ITC
eosin-5-isothiocyanate 相似文献
5.
Hildemar Scholz 《Plant Systematics and Evolution》1987,155(1-4):277-282
The syntypes ofBromus madritensis var.delilei
Boiss. comprise two different elements: specimens ofB. haussknechtii
Boiss. and ofB. fasciculatus
C. Presl s.l. By its lectotypification and on the basis of new morphological characters, the validation ofB. fasciculatus subsp.delilei (Boiss.)H. Scholz 1971 was substantiated. This subspecies represents the eastern marginal segregate of the south-Mediterranean species.B. fasciculatus var.alexandrinus
Thell. is a minor variant of the typical subspecies.Dedicated to Prof.K. H. Rechinger on the occasion of his 80th birthday. 相似文献
6.
Role of cell-cycle in regulating neuroepithelial cell shape during bending of the chick neural plate
Summary Neuroepithelial cells transform from spindle-shaped to wedge-shaped within the median and paired dorsolateral hinge points of the bending neural plate, but the mechanisms underlying these localized changes are unclear. This study was designed to evaluate further the hypothesis that localized wedging of neuroepithelial cells during bending involves basal cellular expansion resulting from alteration of the cell-cycle. Neurulating chick embryos were treated with tritiated thymidine, and transverse sections through the midbrain were examined autoradiographically. Parameters of the cell-cycle as well as nuclear position and size were assessed in the median hinge point, which contains predominantly wedge-shaped cells, and in adjacent lateral areas of the neural plate, which contain predominantly spindle-shaped cells. Both the DNA-synthetic phase and non-DNA synthetic portion of the cell-cycle were significantly longer in the median hinge point than in lateral neuroepithelial areas, some nuclei in both regions were located basally during these phases, and virtually all basal nuclei in the median hinge point were large. Additionally, the mitotic phase was significantly shorter in the median hinge point than in lateral areas. We present a model to explain how alteration of the cell-cycle in the median hinge point could generate wedging of cells in this region. 相似文献
7.
阔叶树的叶形曲线方程:—适于叶面积计算的数学模型 总被引:3,自引:0,他引:3
树木的叶形可以看作一个平面几何图形。这种几何图形可用解析方程给予表达,我们把这种解析方程称为叶形曲线方程。由于叶形是一个左右对称,而上下不对称的图形,也就是说叶的最宽处绝大多数不在叶的中部,少数在 相似文献
8.
The cytoplasmic resistivities and membrane breakdown potentials of normal (AA), sickle-cell-trait (AS), and sickle (SS) red
blood cells have been measured by the biophysical methodology of resistive pulse spectroscopy over a range of osmolalities.
At isotonicity, the average membrane breakdown potentials are virtually identical for the three types of cells occurring at
about 1150 V/cm. Average isotonic cytoplasmic resistivities are somewhat higher for the SS cells (166.7±7.49 ohm-cm) compared
to the AA (147.6±1.98 ohm-cm) or AS cells (148.7±1.79 ohm-cm). As medium osmolality is varied, the differences in resistive
properties become enlarged, especially at very low and very high osmolalities. At high osmolalities, both types of sickle
cells show a large increase in internal resistivity compared to the normals; at low osmolality, the SS samples exhibit a distinctly
different membrane breakdown characteristic, decreasing in this parameter, whereas the other two groups increase.
Of the 15 SS samples tested, three displayed much higher cytoplasmic resistivities at isotonicity: 218.2±5.25 ohm-cm, compared
to an average of 153.5±3.46 ohm-cm for the other 12. The relationship between these high resistivities and the subfraction
of irreversibly sickled cells in the sample is discussed. 相似文献
9.
L. W. D. van Raamsdonk 《Plant Systematics and Evolution》1985,149(3-4):287-297
The pollen fertility and seed formation of six species of theOrnithogalum umbellatum/angustifolium complex and of seven related species were studied. Four types of pollen grains could be recognized. The pollen fertility varied greatly in this complex and is not related to the ploidy level. The seed formation ofO. umbellatum showed an adaptation to a subcontinental-Mediterranean climate, that ofO. angustifolium to an Atlantic climate. In both cases raindrops seem to be important for pollination, in view of the absence of insect pollinators. After open pollination 113 seedlings were obtained in four species. Their chromosome numbers were determined. Nearly all the cultivated seedlings were aneuploid, which points to a positive selection of euploids in nature, because aneuploid individuals are rare in the wild.Biosystematic Studies on theOrnithogalum umbellatum/angustifolium Complex III.—Previous parts of this series are Part I: Taxonomy. Proceeding Kon. Ned. Acad. Wet. series C,85 (4), 563–574 (1982) andvan Raamsdonk (1984). 相似文献
10.
Human erythrocytes were incubated in isotonic solutions of different monovalent cations. The apparent size of the red cells
measured on scanning electron microscopic pictures decreases in the order Li+>Na+=K+>Rb+. These differences in size are abolished after pretreatment with trypsin, which removes a large part of the charges associated
with membrane glycoproteins. Shape alterations are also observed. Normal biconcave shapes are visible after Na+ or K+ incubation, whereas Li+ leads to flabby, flattened cells with a certain tendency to crenation, and Rb+ causes more pronounced biconcavity with a certain tendency to cupping. The overall effects of pretreatment with trypsin are
similar to those of Li+. Our results provide evidence that the electrostatic repulsion of glycoproteins and other charged membrane components may
play an essential role in maintaining red cell shape. 相似文献