Stable programming for map orientation in disarranged embryonic eyes in Xenopus

Development ◽  
1980 ◽  
Vol 55 (1) ◽  
pp. 143-165
Author(s):  
R. M. Gaze ◽  
C. Straznicky
Keyword(s):  
Ionic Strength ◽  
Left Half ◽  
Xenopus Embryos ◽  
Developmental Programme ◽  
The Right ◽  
Low Ionic Strength

In Xenopus embryos of stage 32/33 either the temporal or nasal half of the right eye anlage was replaced by a corresponding left half, giving a right eye in which the grafted half was inverted dorsoventrally. In other embryos either the dorsal or ventral half of the right eye anlage was replaced by a corresponding left half, giving an eye in which the grafted half was reversed nasotemporally. These four types of operation were intended to produce eyes that were disarranged internally but which each had a complete range of positional values. The visuotectal projections from such eyes, recorded later in life, in most cases showed axial reversal of half of the map, reflecting the nature of the operation. The results thus demonstrate that the developmental programme in each of the fused retinal fragments is stable in relation to the eventual orientation of the map from that fragment. Operations to produce eyes with an inverted temporal half, if performed in operating solution of low ionic strength, may result in mirror reduplication and the formation of double nasal maps. It is suggested that this phenomenon may underlie previous reports of reprogramnting of one eye fragment by another.

Stable programming for map orientation in fused eye fragments in Xenopus

Development ◽  
1980 ◽  
Vol 55 (1) ◽  
pp. 123-142
Author(s):  
C. Straznicky ◽  
R. M. Gaze
Keyword(s):  
Compound Eyes ◽  
Xenopus Embryos ◽  
The Face ◽  
Anatomical Arrangement ◽  
Developmental Programme ◽  
The Right

Compound eyes were formed in Xenopus embryos at stages 32/33 by fusion in the right orbit of (1) two right naso-ventral halves, (2) two right ventral halves, (3) two right temporoventral halves, (4) one right and one left naso-ventral half and (5) one right and one left temporo-ventral half. The contralateral visuotectal projections from the operated eyes later showed abnormalities reflecting the anatomical arrangement of the fused fragments. The experiments thus revealed considerable stability of the developmental programme leading to tbe later development of map orientation, in the face of operative disturbance of the types used.

scholarly journals The control by Ca2+ of the polyphosphoinositide phosphodiesterase and the Ca2+-pump ATPase in human erythrocytes

1982 ◽  
Vol 202 (1) ◽  
pp. 53-58 ◽  
Author(s):  
C. Peter Downes ◽  
Robert H. Michell
Keyword(s):  
Ionic Strength ◽  
Erythrocyte Membrane ◽  
Erythrocyte Membranes ◽  
Phosphodiesterase 4 ◽  
Maximal Activation ◽  
Human Erythrocyte Membranes ◽  
The Right ◽  
Phosphatidylinositol 4 ◽  
Low Ionic Strength ◽  
Micromolar Range

1. Both the Ca2+-pump ATPase and the polyphosphoinositide phosphodiesterase of the erythrocyte membrane can, when assayed under appropriate conditions, be activated by Ca2+ in the micromolar range. We have therefore compared the mechanisms and affinities for Ca2+ activation of the two enzymes in human erythrocyte membranes, to see whether the polyphosphoinositide phosphodiesterase would be active in normal healthy erythrocytes. 2. At physiological ionic strength and in the presence of calmodulin, the Ca2+-pump ATPase was activated by Ca2+ in a highly co-operative manner, with half-maximal activation occurring at about 0.3μm-Ca2+. At an optimal Ca2+concentration, calmodulin stimulated the Ca2+-sensitive ATPase activity about 10-fold. 3. Ca2+ activated the polyphosphoinositide phosphodiesterase in a non-co-operative manner. The Ca2+ requirements for breakdown of phosphatidylinositol 4-phosphate and phosphatidylinositol 4,5-bisphosphate were identical, which supports our previous conclusion that Ca2+ activates a single polyphosphoinositide phosphodiesterase that degrades both lipids with equal facility. Added calmodulin did not affect the activity of the polyphosphoinositide phosphodiesterase. 4. At low ionic strength in the absence of Mg2+, half-maximal activation of the phosphodiesterase was at about 3μm-Ca2+. The presence of 1mm-Mg2+ shifted the Ca2+ activation curve to the right, as did elevation of the ionic strength. When the Ca2+-pump ATPase and the polyphosphoinositide phosphodiesterase were assayed in the same incubations and under conditions of intracellular ionic strength and Mg2+concentration, the ATPase was fully activated at 3μm-Ca2+, whereas no polyphosphoinositide phosphodiesterase activity was detected below 100μm-Ca2+. 5. The Ca2+-pump ATPase of the erythrocyte membrane normally maintains the Ca2+ concentration of healthy erythrocytes below approx. 0.1μm. It therefore seems unlikely that the polyphosphoinositide phosphodiesterase of the erythrocyte membrane ever expresses its activity in a healthy erythrocyte.

Conformational Transitions in Escherichia coli Ribosomal RNAs as Visualized by Dedicated STEM

1988 ◽  
Vol 46 ◽  
pp. 176-177
Author(s):  
J.S. Wall ◽  
V. Maridiyan ◽  
S. Tumminia ◽  
J. Hairifeld ◽  
M. Boublik
Keyword(s):  
Ionic Strength ◽  
Three Dimensional ◽  
Conformational Transitions ◽  
Dark Field ◽  
Dimensional Structure ◽  
Ribosomal Rnas ◽  
Field Mode ◽  
Freeze Dried ◽  
High Resolution Images ◽  
Low Ionic Strength

The high contrast in the dark-field mode of dedicated STEM, specimen deposition by the wet film technique and low radiation dose (1 e/Å2) at -160°C make it possible to obtain high resolution images of unstained freeze-dried macromolecules with minimal structural distortion. Since the image intensity is directly related to the local projected mass of the specimen it became feasible to determine the molecular mass and mass distribution within individual macromolecules and from these data to calculate the linear density (M/L) and the radii of gyration.2 This parameter (RQ), reflecting the three-dimensional structure of the macromolecular particles in solution, has been applied to monitor the conformational transitions in E. coli 16S and 23S ribosomal RNAs in solutions of various ionic strength.In spite of the differences in mass (550 kD and 1050 kD, respectively), both 16S and 23S RNA appear equally sensitive to changes in buffer conditions. In deionized water or conditions of extremely low ionic strength both appear as filamentous structures (Fig. la and 2a, respectively) possessing a major backbone with protruding branches which are more frequent and more complex in 23S RNA (Fig. 2a).

An Evaluation of a Plasma Fractionation System

1960 ◽  
Vol 4 (01) ◽  
pp. 031-044
Author(s):  
George Y. Shinowara ◽  
E. Mary Ruth
Keyword(s):  
Biological Activity ◽  
Ionic Strength ◽  
Plasma Proteins ◽  
High Concentration ◽  
Significant Evidence ◽  
Native Proteins ◽  
Mobility Data ◽  
Fractionation Procedure ◽  
The Individual ◽  
Low Ionic Strength

SummaryFour primary fractions comprising at least 97 per cent of the plasma proteins have been critically appraised for evidence of denaturation arising from a low temperature—low ionic strength fractionation system. The results in addition to those referable to the recovery of mass and biological activity include the following: The high solubilities of these fractions at pH 7.3 and low ionic strengths; the compatibility of the electrophoretic and ultracentrifugal data of the individual fractions with those of the original plasma; and the recovery of hemoglobin, not hematin, in fraction III obtained from specimens contaminated with this pigment. However, the most significant evidence for minimum alterations of native proteins was that the S20, w and the electrophoretic mobility data on the physically recombined fractions were identical to those found on whole plasma.The fractionation procedure examined here quantitatively isolates fibrinogen, prothrombin and antithrombin in primary fractions. Results have been obtained demonstrating its significance in other biological systems. These include the following: The finding of 5 S20, w classes in the 4 primary fractions; the occurrence of more than 90 per cent of the plasma gamma globulins in fraction III; the 98 per cent pure albumin in fraction IV; and, finally, the high concentration of beta lipoproteins in fraction II.

scholarly journals A novel procedure for the rapid purification of plastocyanin from pea (Pisum sativum) leaves

1981 ◽  
Vol 193 (1) ◽  
pp. 375-378 ◽  
Author(s):  
A R Ashton ◽  
L E Anderson
Keyword(s):  
Ionic Strength ◽  
Pisum Sativum ◽  
Deae Cellulose ◽  
High Concentrations ◽  
Rapid Purification ◽  
Low Ionic Strength

Plastocyanin is soluble at high concentrations (greater than 3 M) of (NH4)2SO4 but under these conditions will adsorb tightly to unsubstituted Sepharose beads. This observation was utilized to purify plastocyanin from pea (Pisum sativum) in two chromatographic steps. Sepharose-bound plastocyanin was eluted with low-ionic-strength buffer and subsequently purified to homogeneity by DEAE-cellulose chromatography.

scholarly journals Crystallization of tuna ferricytochrome c at low ionic strength.

1990 ◽  
Vol 265 (8) ◽  
pp. 4177-4180
Author(s):  
M H Walter ◽  
E M Westbrook ◽  
S Tykodi ◽  
A M Uhm ◽  
E Margoliash
Keyword(s):  
Ionic Strength ◽  
Ferricytochrome C ◽  
Low Ionic Strength

scholarly journals Reaction of Myosin with 1-Fluoro-2,4-dinitrobenzene at Low Ionic Strength

1969 ◽  
Vol 244 (3) ◽  
pp. 648-657 ◽  
Author(s):  
M Bárány ◽  
G Bailin ◽  
K Bárány
Keyword(s):  
Ionic Strength ◽  
Low Ionic Strength

scholarly journals Measuring pH in low ionic strength glacial meltwaters using ion selective field effect transistor (ISFET) technology

2021 ◽  
Author(s):  
Elizabeth A. Bagshaw ◽  
Jemma L. Wadham ◽  
Martyn Tranter ◽  
Alexander D. Beaton ◽  
Jon R. Hawkings ◽  
...  
Keyword(s):  
Ionic Strength ◽  
Field Effect ◽  
Field Effect Transistor ◽  
Effect Transistor ◽  
Low Ionic Strength ◽  
Measuring Ph
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