scholarly journals ON THE RECONSTITUTION OF THE CRYSTALLINE COMPONENTS OF THE SEA URCHIN FERTILIZATION MEMBRANE

1970 ◽  
Vol 45 (3) ◽  
pp. 606-614 ◽  
Author(s):  
Joseph Bryan
Keyword(s):  
Ionic Strength ◽  
Sea Urchin ◽  
Divalent Cations ◽  
Reducing Agents ◽  
Alkaline Ph ◽  
Mitotic Apparatus ◽  
Fertilization Membrane ◽  
Crystalline Component ◽  
Tubular Components

The characteristics of the reconstitution of a crystalline component of the sea urchin fertilization membrane are presented. The reassembly of large aggregates of cylindrical or tubular components is effected by the addition of calcium or other divalent cations. The reassembly requires a slightly alkaline pH and is little affected by increasing ionic strength. Reassembly is strongly inhibited by treatment with reducing agents such as dithiothreitol. The role of this protein in the formation of the fertilization membrane and its possible relation to the calcium-insoluble proteins of the mitotic apparatus are discussed.

The role of divalent cations in the activation of the NADP+-specific isocitrate dehydrogenase from Pisum sativum L.

1977 ◽  
Vol 55 (9) ◽  
pp. 928-934 ◽  
Author(s):  
Robert J. Maloney ◽  
David T. Dennis
Keyword(s):  
Ionic Strength ◽  
Stability Constants ◽  
Isocitrate Dehydrogenase ◽  
Divalent Cations ◽  
Free Form ◽  
Saturation Kinetics ◽  
The Difference ◽  
The Stability ◽  
Kinetics Of

A divalent cation electrode was used to measure the stability constants (association constants) for the magnesium and manganese complexes of the substrates for the NADP+-specific isocitrate dehydrogenase (EC 1.1.1.42) from pea stems. At an ionic strength of 26.5 mM and at pH 7.4 the stability constants for the Mg2+–isocitrate and Mg2+–NADP+ complexes were 0.85 ± 0.2 and 0.43 ± 0.04 mM−1 respectively and for the Mn2+–isocitrate and Mn2+–NADP+ complexes they were 1.25 ± 0.07 and 0.75 ± 0.09 mM−1 respectively. At the same ionic strength but at pH 6.0 the Mg2+–NADPH and Mn2+–NADPH complexes had stability constants of 0.95 ± 0.23 and 1.79 ± 0.34 mM−1 respectively. Oxalosuccinate and α-ketoglutarate do not form measureable complexes under these conditions. Saturation kinetics of the enzyme with respect to isocitrate and metal ions are consistent with the metal–isocitrate complex being the substrate for the enzyme. NADP+ binds to the enzyme in the free form. Saturation kinetics of NADPH and Mn2+ indicate that the metal–NADPH complex is the substrate in the reverse reaction. In contrast the pig heart enzyme appears to bind free NADPH and Mn2+. A scheme for the reaction mechanism is presented and the difference between the reversibility of the NAD+ and NADP+ enzyme is discussed in relation to the stability of the NADH and NADPH metal complexes.

scholarly journals SOME STRUCTURAL AND FUNCTIONAL ASPECTS OF THE MITOTIC APPARATUS IN SEA URCHIN EMBRYOS

1962 ◽  
Vol 14 (3) ◽  
pp. 475-487 ◽  
Author(s):  
Patricia Harris
Keyword(s):  
Sea Urchin ◽  
Salt Concentration ◽  
Sea Water ◽  
Divalent Cations ◽  
Cell Stage ◽  
Mitotic Apparatus ◽  
Central Spindle ◽  
Sea Urchin Embryos ◽  
Cilia Formation ◽  
Dividing Cells

The mitotic figures in dividing cells of sea urchin embryos, from first division to the onset of cilia formation, were studied with regard to the filament system and its relation to kinetochores, chromosomes, and poles, as well as to fixation conditions which would best preserve these structures. With regard to fixation, variations in the salt concentration and pH of the fixative indicated that an extraction effect on the chromosomes noted in earlier work was probably due to a combination of neutral pH and salt concentration equivalent to sea water. The presence of the 15 mµ filaments depended on the presence of either of two stabilizing conditions: pH 6.1 or presence of the salts of sea water, presumably the divalent cations of Ca and Mg. Kinetochores and centrioles were unaffected by the fixative variations. The 15 mµ filaments, reported earlier in the central spindle, are also found in great numbers in the asters of early cleavage divisions. However, with successive divisions and reduction in cell size, the aster disappears at about the 32 to 64 cell stage, and the 15 mµ filaments are entirely associated with the central spindle. This disappearance of the aster suggests that it may be, in fact, merely a specialization of large cells for cytokinesis.

scholarly journals Assembly of the sea urchin fertilization membrane: isolation of proteoliaisin, a calcium-dependent ovoperoxidase binding protein.

1985 ◽  
Vol 100 (3) ◽  
pp. 938-946 ◽  
Author(s):  
P J Weidman ◽  
E S Kay ◽  
B M Shapiro
Keyword(s):  
Sea Urchin ◽  
Divalent Cation ◽  
Divalent Cations ◽  
Dependent Manner ◽  
Cortical Granules ◽  
Binding Interaction ◽  
Membrane Assembly ◽  
Calcium Dependent ◽  
Structural Subunit ◽  
Fertilization Membrane

Fertilization of the sea urchin egg is accompanied by the assembly of an extracellular glycoprotein coat, the fertilization membrane. Assembly of the fertilization membrane involves exocytosis of egg cortical granules, divalent cation-mediated association of exudate proteins with the egg glycocalyx (the vitelline layer), and cross-linking of the assembled structure by ovoperoxidase, a fertilization membrane component derived from the cortical granules. We have identified and isolated a new protein, which we call proteoliaisin, that appears to be responsible for inserting ovoperoxidase into the fertilization membrane. Proteoliaisin is a 250,000-Mr protein that binds ovoperoxidase in a Ca2+-dependent manner, with half-maximal binding at 50 microM Ca2+. Other divalent cations are less effective (Ba2+, Mn2+, and Sr2+) or ineffective (Mg2+ and Cd2+) in mediating the binding interaction. Binding is optimal over the physiological pH range of fertilization membrane assembly (pH 5.5-7.5). Both proteoliaisin and ovoperoxidase are found in isolated, uncross-linked fertilization membranes. We have identified several macromolecular aggregates that are released from uncross-linked fertilization membranes after dilution into divalent cation-free buffer. One of these is an ovoperoxidase-proteoliaisin complex that is further disrupted only upon the addition of EGTA. These results suggest that a Ca2+-stabilized complex of ovoperoxidase and proteoliaisin forms one structural subunit of the fertilization membrane.

scholarly journals Role of divalent cations on DNA polymorphism under low ionic strength conditions

1986 ◽  
Vol 14 (12) ◽  
pp. 5099-5109 ◽  
Author(s):  
Sundaram Devarajan ◽  
Richard H. Shafer
Keyword(s):  
Ionic Strength ◽  
Dna Polymorphism ◽  
Divalent Cations ◽  
Low Ionic Strength

scholarly journals Dominating Role of Ionic Strength in the Sedimentation of Nano-TiO2in Aquatic Environments

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Guang’an He ◽  
Rui Chen ◽  
Shushen Lu ◽  
Chengchun Jiang ◽  
Hong Liu ◽  
...  
Keyword(s):  
Ionic Strength ◽  
Natural Organic Matter ◽  
Divalent Cations ◽  
Environmental Water ◽  
Orthogonal Experimental Design ◽  
Aquatic Environments ◽  
Monovalent Cations ◽  
Sedimentation Behavior ◽  
Low Levels

Various factors affect the sedimentation behavior of nanotitanium dioxide (n-TiO2) in water. Accordingly, this study aimed to select the dominating factor. An index of sedimentation efficiency related to n-TiO2concentration was applied to precisely describe the n-TiO2sedimentation behavior. Ionic strength (IS), natural organic matter (NOM) content, and pH were evaluated in sedimentation experiments. An orthogonal experimental design was used to sequence the affecting ability of these factors. Furthermore, simulative sedimentation experiments were performed. The n-TiO2sedimentation behavior was only affected by pH and NOM content at low levels of IS. Moreover, divalent cations can efficiently influence the n-TiO2sedimentation behavior compared with monovalent cations at fixed IS. Seven different environmental water samples were also used to investigate the n-TiO2sedimentation behavior in aquatic environments. Results confirmed that IS, in which divalent cations may play an important role, was the dominating factor influencing the n-TiO2sedimentation behavior in aquatic environments.

scholarly journals Quantitative studies on the polarization optical properties of living cells II. The role of microtubules in birefringence of the spindle of the sea urchin egg.

1981 ◽  
Vol 89 (1) ◽  
pp. 121-130 ◽  
Author(s):  
Y Hiramoto ◽  
Y Hamaguchi ◽  
Y Shóji ◽  
T E Schroeder ◽  
S Shimoda ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Sea Urchin ◽  
Preceding Paper ◽  
Living Cells ◽  
Mitotic Apparatus ◽  
Form Birefringence ◽  
Quantitative Studies ◽  
Sea Urchin Egg ◽  
Interpolar Distance

Birefringence of the mitotic apparatus (MA) and its change during mitosis in sea urchin eggs were quantitatively determined using the birefringence detection apparatus reported in the preceding paper (Hiramoto el al., 1981, J. Cell Biol. 89:115-120). The birefringence and the form of the MA are represented by five parameters: peak retardation (delta p), through retardation (delta t), interpolar distance (D1), the distance (D2) between chromosome groups moving toward poles, and the distance (D3) between two retardation peaks. Distributions of birefringence retardation and the coefficient of birefringence in the spindle were quantitatively determined in MAs isolated during metaphase and anaphase. The distribution of microtubules (MTs) contained in the spindle is attributable to the form birefringence caused by regularly arranged MTs. The distribution coincided fairly well with the distribution of MTs in isolated MAs determined by electron microscopy. Under the same assumption, the distribution of MTS in the spindle in living cells during mitosis was determined. The results show that the distribution of MTs and the total amount of polymerized tubulin (MTs) in the spindle change during mitosis, suggesting the assembly and disassembly of MTs as well as the dislocation of MTs during mitosis.

scholarly journals THE MITOTIC APPARATUS

1965 ◽  
Vol 25 (1) ◽  
pp. 137-144 ◽  
Author(s):  
R. E. Kane
Keyword(s):  
Sea Urchin ◽  
Alkaline Ph ◽  
Experimental Conditions ◽  
Mitotic Apparatus ◽  
Ph Values ◽  
Cent Concentration ◽  
Experimental Approaches ◽  
The Stability ◽  
Related Compounds ◽  
Long Chain

Previous investigations have shown that the mitotic apparatus (MA) can be isolated from dividing sea urchin eggs in water buffered at pH 5.6 and that the addition of 1 M hexanediol to the solution raises the usable pH to 6.4. Long chain glycols appeared to be much more effective than related compounds in increasing the stability of the MA, and the aim of the investigations reported here was to determine the basis of this specificity. These experiments show that this impression of specificity is misleading and that under suitable experimental conditions a variety of compounds can be substituted for the glycols. A number of alcohols will duplicate the action of the glycols in stabilizing the MA at pH 6.4, but they must be used at a similar per cent concentration rather than at a similar molar concentration. Increases in the concentration of alcohol or glycol allow isolation at more alkaline pH values, and a pH-concentration relation for the stability of the MA, covering the range from pH 5.6–8, has been determined. These results indicate that the action of these compounds in stabilizing the mitotic apparatus is non-specific and is similar to their effects on the solubility of proteins. The isolation and stabilization of the mitotic apparatus can thus be viewed as a function of the solubility properties of its constituent proteins, opening a variety of new experimental approaches to this problem.

scholarly journals Calcium-labile mitotic spindles isolated from sea urchin eggs (Lytechinus variegatus).

1980 ◽  
Vol 86 (2) ◽  
pp. 355-365 ◽  
Author(s):  
E D Salmon ◽  
R R Segall
Keyword(s):  
Sea Urchin ◽  
Calcium Ions ◽  
Divalent Cations ◽  
Lytechinus Variegatus ◽  
Mitotic Spindles ◽  
Mitotic Apparatus ◽  
Spindle Microtubules ◽  
Membrane Components ◽  
Low Ionic Strength

We isolated calcium-labile mitotic spindles from eggs of the sea urchin Lytechinus variegatus, using a low ionic strength, EGTA lysis buffer that contined 5.0 mM EGTA, 0.5 mM MgCl2, 10-50 mM PIPES, pH 6.8, with 1% Nonidet P-40 (detergent) and 20-25% glycerol. Isolated spindles were stored in EGTA buffer with 50% glycerol for 5-6 wk without deterioration. The isolated spindles were composed primarily of microtubules with the chromosomes attached. No membranes were seen. Isolated spindles, perfused with EGTA buffer to remove the detergent and glycerol, had essentially the same birefringent retardation (BR) as spindles in vivo at the same mitotic stage. Even in the absence of glycerol and exogenous tubulin, the isolated spindles were relatively stable in the EGTA buffer: BR decayed slowly to about half the initial value within 30-45 min. However, both the rate and extent of BR decay increased with concentrations of Ca2+ above 0.2-0.5 muM as assayed using Ca-EGTA buffers (0.2 mM EGTA, 0.5 mM MgCl2, 50 mM PIPES, pH 6.8, plus various amounts of CaCl2). Microtubules depolymerized almost completely in < 6 min at Ca2+ concentrations of 2 muM and within several seconds at 10 muM Ca2+. Of several divalent cations tested, only Sr2+ caused comparable changes in BR. The absence of membranes in the isolated spindles appeared to be associated with a lack of calcium-sequestering ability. Our results suggest that calcium ions play an important role in the depolymerization of spindle microtubules and that membrane components may function within the mitotic apparatus of living cells to sequester and release calcium ions during mitosis.

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