Osmotic and motional properties of intracellular water as influenced by osmotic swelling and shrinkage of <i>Xenopus</i> Oocytes

Cameron, Ivan L.; Merta, Phillip; Fullerton, Gary D.

doi:10.1002/jcp.1041420320

Cited by 17 publications

(10 citation statements)

References 23 publications

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“…Alternatively, the swelling of the egg in liquid water is related to the gel-like properties of the capsule. Cameron and colleagues (Cameron et al, 1990) showed that about 80% of a frog egg's water is osmotically inactive, and further suggested that this water is bound to cell proteins; an idea that supports the notion of the cytoplasm being a gel. The swelling of gels does not simply depend on the difference in ionic concentration between the gel and the medium in which they are placed but on the elasticity of the polymer matrix, with the swollen gel exerting lower restraining forces on the diffusing water molecules (Yasuda et al, 1971;Gunt et al, 2007).…”

Section: Incubation In Aqueous Versus Vapour Phasesmentioning

confidence: 92%

Phenotypic differences in terrestrial frog embryos: effect of water potential and phase

Andrewartha

Mitchell

Frappell

2008

Journal of Experimental Biology

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SUMMARYThe terrestrial embryos of many amphibians obtain water in two ways; in a liquid phase from the substrate on which eggs are deposited, and in a vapour phase from the surrounding atmosphere. We tested whether the mode of water flux (liquid or vapour) affected the morphology and metabolic traits of the terrestrial Victorian smooth froglet (Geocrinia victoriana) embryos by incubating eggs both with a liquid water source and at a range of vapour water potentials. We found that embryos incubated with a liquid water source (ψ π =0 kPa) were better hydrated than embryos incubated with a vapour water source (ψ v =0 kPa), and grew to a larger size. Eggs incubated in atmospheres with lower ψ v values showed significant declines in mass and in the thickness of the jelly capsule, while embryos primarily showed reductions in dry mass, total length, tail length and fin height. The most significant deviations from control (ψ v =0 kPa) values were observed when the ψ v of the incubation media was less than the osmotic water potential (ψ π ) of the embryonic interstitial fluid (approximately -425 kPa). Despite the caveat that a ψ v of 0 kPa is probably difficult to achieve under our experimental conditions, the findings indicate the importance for eggs under natural conditions of contacting liquid water in the nesting substrate to allow swelling of the capsule.

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Section: Incubation In Aqueous Versus Vapour Phasesmentioning

confidence: 92%

Phenotypic differences in terrestrial frog embryos: effect of water potential and phase

Andrewartha

Mitchell

Frappell

2008

Journal of Experimental Biology

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“…The reports of Cameron et al (1988b, 1997), Fullerton et al (2006b) and Fullerton and Cameron (2007) indicated that the OUW fraction can range from 1.6 to 1.7 g/g in a mammalian erythrocyte (Cameron et al, 1988a), 1.8–2.2 g/g in mammalian lens cells (Cameron et al, 1988a, 1988b), 1.3 g/g in sea urchin eggs (Merta et al, 1983), 1.2–1.7 g/g in the toad oocyte (Cameron et al, 1990) and 2.8 g/g in frog‐skeletal muscle as calculated from data of Overton (1902, cited in Ling 2006). These values and the measured total non‐bulk water fraction in rabbit skeletal muscle 2.39–3.75 g/g (Cameron et al, 2008; see Table 6) all indicate that more than half of all of cell water has non‐bulk physical properties.…”

Section: Application Of the Shm To Cellsmentioning

confidence: 99%

“…The data in Table 7 give the size of water‐of‐hydration fractions in g of water/g of DM, less extracted lipids, in the toad oocyte (Cameron et al, 1990). The extent of water in each of the hydration fractions was measured by the proton NMR titration method.…”

Section: Application Of the Shm To Cellsmentioning

confidence: 99%

“…The measured extent of this bound water fraction on proteins ranges from 0.2 to 0.4 g of water/g of DM. Evidence for a similar ‘bound water’ fraction in cells stems from reports on four cell systems in which it has been measured: frog skeletal muscle (Ling and Negendank, 1970), human erythrocyte (Cameron et al, 1988a), toad oocyte (Cameron et al, 1990) and rabbit skeletal muscle (Cameron et al, 2008). Again it is commonly held or tacitly assumed by protein chemists and cell biologists that all water above the bound water fraction of 0.2–0.4 g/g of DM is free or bulk‐like in its physical properties.…”

Section: Introductionmentioning

confidence: 98%

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The molecular stoichiometric hydration model (SHM) as applied to tendon/collagen, globular proteins and cells

2011

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This report describes and documents the presence of multiple water-of-hydration fractions on proteins and in cells. Initial studies of hydration fractions in g of water/g of DM (dry mass) for tendon/collagen led to the development of the molecular SHM (stoichiometric hydration model) and the development of methods for calculating the size of hydration fractions on a number of different proteins of known amino acid composition. The water fractions have differences in molecular motion and other physical properties due to electrostatic interactions of polar water molecules with electric fields generated by covalently bound pairs of opposite partial charge on the protein backbone. The methods allow calculation of the size of four hydration fractions: single water bridges, double water bridges, dielectric water clusters over polar-hydrophilic surfaces and water clusters over hydrophobic surfaces. These four fractions provide monolayer water coverage. The predicted SHM hydration fractions match closely measured hydration fraction values for collagen and for globular proteins. This report also presents water sorption findings that support the SHM. The SHM is applicable for cell systems where it has been studied. In seven cell systems studied, more than half of all of the cell water had properties unlike those of bulk water. The SHM predicts and explains the commonly cited and measured bound water fraction of 0.2-0.4 g of water/g of DM on proteins. The commonly accepted concept that water beyond this bound water fraction can be considered bulk-like water in its physical properties is unwarranted.

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“…For the single lipid resonance, they calculated a T 1 of 459 ± 32 ms and a T 2 of 24.44 ± 4.10 ms. In a different study, Cameron et al (14) calculated T 1 relaxation rate constants for resonance bands of defined chemical shift ranges in packed oocytes from unsuppressed spectra. A 1.8 ppm range containing the largest lipid peak gave a T 1 of 443 ± 9 ms (mean ± SEM).…”

Section: Discussionmentioning

confidence: 99%

Water and lipid MRI of the Xenopus oocyte

Sehy¹,

Ackerman

2001

Magnetic Resonance in Med

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Oocytes of Xenopus laevis are large, single cells that provide a promising model system for the exploration of the MR biophysics fundamental to more complex living systems. Previous studies have generally employed 2D spin-echo sequences with an image slice thickness greater than the thickness of the cellular volumes of interest. Also, the large cytoplasmic lipid signal has typically been ignored. This study describes separate, highresolution 3D measurements of the water and lipid spin densities, T 1 and T 2 relaxation time constants, and the water apparent diffusion rate constant (ADC) in the Xenopus oocyte without significant partial volume artifacts. The lipid spin-density and values for water MR properties varied monotonically from the vegetal to animal poles, indicating that the border between the poles is not sharply demarcated. The Xenopus laevis oocyte is a well-established cell model used in many branches of modern experimental biology. This versatile cell provides a promising model platform upon which to explore fundamental aspects of the MR biophysics underlying more complex living systems. In particular, the ability to spatially resolve the intracellular compartment allows the direct testing of hypotheses regarding various MR properties of the cytoplasm and nucleus. Recent efforts to integrate confocal microscopy and MR imaging will likely augment the capability of such experiments (1).Aguayo et al. (2) reported the first MR images of the Xenopus oocyte in 1986. Along with intriguing contrast between intracellular regions, the authors described a strong chemical shift artifact from cytoplasmic lipid. Posse and Aue (3) further characterized this lipid signal using a 4D spectroscopic imaging technique. Both studies localized the lipid signal to the cytoplasm, with little or no lipid signal arising from the nucleus. Since these initial studies, several investigators have calculated spin densities and T 2 and/or T 1 relaxation time constants for the oocyte nucleus, animal pole, and vegetal pole in control or altered cells (4 -6). The effect of the unknown, spatially varying lipid spin-density on these calculations, if any, has been largely ignored. Further, these studies have routinely employed 2D spin-echo sequences with slice profiles thicker than the cellular volumes of interest (VOIs), raising concerns regarding partial volume effects. This shortcoming is especially detrimental to studies of the nucleus, which has a diameter of only 300 m.Herein we present separate, high-resolution 3D measurements of the water and lipid spin densities, T 1 and T 2 relaxation time constants, and the water apparent diffusion coefficient (ADC) in the Xenopus oocyte without significant partial volume artifacts. We challenge the conventional binary segmentation of the oocyte cytoplasm into vegetal and animal poles and recognize cylindrical symmetry about the vegetal-animal (V-A) axis. Lipid-specific imaging is demonstrated for which water suppression is achieved via high diffusion weighting in the imaging sequence. We corr...

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Osmotic and motional properties of intracellular water as influenced by osmotic swelling and shrinkage of Xenopus Oocytes

Cited by 17 publications

References 23 publications

Phenotypic differences in terrestrial frog embryos: effect of water potential and phase

Phenotypic differences in terrestrial frog embryos: effect of water potential and phase

The molecular stoichiometric hydration model (SHM) as applied to tendon/collagen, globular proteins and cells

Water and lipid MRI of the Xenopus oocyte

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