Variation Of Cell Volume Research Articles

Phase coexistence in PZT solid solutions at MPB

Abstract In Pb(ZrxTi1−x)O3 solid solutions corresponding to the morphotropic phase boundary. the molar volume fraction xVCR+ (1-x)VCT and porosity per volume unit P exhibits a similar variation trend on sintering temperature, reaching simultaneously a minimum for 1140°C. This specific behaviour is explained by a simple mechanism of pore closure induced by thermal lattice expansion. evaluated on the basis of FT and FR unit cell volume variation. previously measured by X-ray diffraction.

Experimental results on cell volume, growth rate, and macronuclear DNA variation in a ciliated protozoan

AbstractSome species of ciliated protozoans vary their body volume when fed on preys of different sizes. This peculiarity has offered us the opportunity to examine the relationship between changes in cell volume, amount of macronuclear DNA (maDNA), and cell division rates in subclones derived from a single clone of the ciliate Blepharisma japonicum (Order Heterotrichida). Our results demonstrate that food‐induced size changes in this single‐celled organism are accompanied by substantial changes in maDNA content and in reproduction (cell division) rate. We find a strong, direct linear correlation between cell volume and maDNA quantity, and an inverse linear correlation between cell volume and reproduction rate. No correlation between cell reproduction rate and maDNA amount was found. We conclude that food‐induced coordinate change in cell volume, maDNA content, and cell division rate in this organism may be an effective mechanism for rapid phenotypic change in response to variable environmental conditions.

Effect of Escherichia coli heat-stable enterotoxin on cell volume and intracellular inorganic ions of rat intestinal cells

1.--Electron micrographs of rat jejunum mucosa incubated for 1 h in the presence of Escheria coli heat-stable enterotoxin (STa) in the lumen shows alterations of villous cells as well as of crypt cells. The brush border of mature enterocytes is partially desintegrated and covered with a thick mucus. Crypts are occupied on half of their height by cells very similar to Paneth cells, loaded with numerous large dark inclusions. 2.--Cell volume and intracellular inorganic ion concentrations have been estimated in mucosal scrapings of jejunum sacs, incubated in vitro for 1 or 3 h. The quick action (1 h of incubation) of STa is a swelling of the intestinal calls accompanied by an increase in Na+, Cl- and Ca2+ intracellular concentrations and a decrease in the K+ and Mg2+ ones. The delayed action (3 h of incubation) is an increase of extracellular space and a decrease in cell volume; and at the same time the intracellular concentration of Na+, Cl-, K+, Ca2+ and Mg2+ is augmented. 3.--After 3 h of incubation intestinal cells from the other levels of intestine (duodenum, ileum and colon) show the same variations in cell volume and intracellular inorganic ion concentrations under the influence of STa, as those recorded in the jejunum. 4.--The present work favours the hypothesis that all intestinal cells, villous or cryptic, are involved in the alteration of fluid ion transport ending in diarrhea.

Anomalous Ferromagnetism in the Dense Kondo System Ce(Rh1-xCox)3B2

Information on the nature of the anomalous ferromagnetic state and paramagnetic Kondo state of CeRh3B2 is gained by studying the evolution of the crystallographic, magnetic, and transport properties across the pseudoternary compounds Ce(Rh1-xCox)3B2. Unit cell volume variation with Co concentration parameter x indicates that the valence of Ce is increasing from a nearly trivalent value in the Rh-rich region to a high value for x > 0.3 and saturates around x ≈ 0.5. The destruction of ferromagnetism for x > 0.5 thus goes hand in hand with the delocalization of the Ce magnet moment.

Etude des transitions de phase du sulfate dibasique de plomb PbSO4, 2PbO: Influence de la vitesse de montee en temperature et de L'histoire thermique

Basic lead sulfate, PbSO4·2PbO, was studied by means of DTA, X-ray diffraction and scanning electron microscopy. DTA runs at different heating rates showed that two kinds of thermal evolution are possible for PbSO4·2PbO. IfT<40 deg h−1, we have the “normal” process according to the following transitions: IfT>40 deg h−1 theΒ-PbSO4·2PbO phase appears at 440 ‡C, but is unstable and breaks down into monobasic and tetrabasic lead sulfates. Reaction enthalpies were evaluated and correlated with the cell volume variations determined by X-ray diffraction. An interpretation of the existence of two types of process is proposed.

Effect of alloying on the Nd&amp;lt;inf&amp;gt;2&amp;lt;/inf&amp;gt;Fe&amp;lt;inf&amp;gt;14&amp;lt;/inf&amp;gt;B-type tetragonal structure in the pseudoternary systems Er&amp;lt;inf&amp;gt;2&amp;lt;/inf&amp;gt;(Fe,TM)&amp;lt;inf&amp;gt;14&amp;lt;/inf&amp;gt;B for TM = Mn and Co

The pseudoternary systems Er 2 (Fe,Mn) 14 B and Er 2 (Fe,Co) 14 B have been studied and we report an unusual variation of the unit cell volume with composition across the limited range of formation of the tetragonal Nd 2 Fe 14 B-type phase. Compositions outside of this range are multiphase consisting of known intermetallic compounds.

Algal populations and characteristics of oxygen exchange of effluent samples from a facultative oxidation pond

Abstract Algal populations in a facultative oxidation pond were monitored over a 12 month period. The relationships between cell counts of individual species and characteristics of oxygen exchange, determined from changes in dissolved oxygen concentration in response to varying light flux density, were investigated by correlation analysis. These measurements were made in the laboratory at a constant temperature (15°C). Microalgae (Chlorella spp.) usually made up at least 80% of the total cell numbers, whereas Euglena acus, E. gracilis, and Ankistrodesmus falcatus var. acicularis separately made up less than 10% of the total counts. However, when cell volumes were considered, E. acus usually made the greatest contribution, and this species accounted for 86% (=r2) of the variation in total cell volume. The detectable pigment concentration in the water was closely related to the numbers of E. acus present (r=0.81, P <0.001) but not to the numbers of microalgae (r=0.00). Cell counts of E. acus were highly correlated with the light saturated rate of net oxygen production (Pn max) and to the rate under limiting light supply (6) because of the high detectable pigment contribution from this species. It was calculated that E. acus contributed, on average, about 44% of the total rate of net oxygen production, whereas the proportion attributed to the microalgae was 8%.

A model of the heterogeneity of red cell hemoglobin concentration

A model of red cell hemoglobin concentration has been developed and computer simulations performed to investigate quantitatively the relationship among the intraindividual heterogeneities of cell hemoglobin content, volume, and hemoglobin concentration. In the model, the cell volume and hemoglobin content frequency distributions and their joint distributions are described by Gaussian probability distributions. The frequency distributions of cell hemoglobin concentration are determined from the joint probability distributions by summing the joint probabilities of the variate pairs the ratios of which equal the specified concentration. For the parameter values considered, the mean cell hemoglobin concentration closely approximates the average (i.e., statistical mean) concentration. The heterogeneity of cell hemoglobin concentration increases with increasing coefficients of variation of cell hemoglobin content and cell volume and with decreasing correlation coefficients. When the correlation coefficient is greater than 0.7, cell hemoglobin concentration shows less relative dispersion that the component indices.

Diffuse phase transitions in Pb(Zr, Ti)O3solid solutions with up to 3 % Ti content

Abstract Using X-rays the volume content of neighbouring phases and the temperature variation of unit cell volume have been investigated in the vicinity of phase transitions between the para-, ferro-and antiferroelectric states for Pb(Zr, Ti)O3 ceramic with Ti content up to 3%. The diffuse nature of the phase transitions has been confirmed in the solid solutions.

Composition dependence of lattice parameters in ANb 1− xV xO 4 systems where A = Ce, Nd

The room-temperature lattice parameters of a series of CeNb 1− x V x O 4 and NdNb 1− x V x O 4 compounds (0 ≤ x ≤ 1) have been measured. Substitution of vanadium for niobium in both CeNbO 4 and NdNbO 4 drives the structure from monoclinic (fergusonite type) to tetragonal (scheelite type) at x = 0.296 and 0.346, respectively. In both systems, there is an expansion of the long-axis dimension of the fergusonite structure as x increases, despite the fact that vanadium is a smaller ion than niobium. This leads to an anomalous variation of the unit cell volume with concentration. The composition dependence of the strain parameters, which are a measure of the relative distortion of the monoclinic lattice, is found to fit a Landau mean-field model, thus demonstrating a thermodynamic correspondence between composition and temperature.

An Examination of Cell Volume in Dominant Phytoplankton Species of the Central and Southern Adriatic Sea

AbstractThe phytoplankton biomass expressed as total cell volume is often of doubtful value due to cell size and volume variations in the organisms present. Cell volume calculations for 95 phytoplankton species and volume‐frequency diagrams for 25 dominant species were analyzed for the Adriatic Sea. Recommendations for more precise work dealing with phytoplankton cell volume and biomass are given. Temporal variations in the average microplankton cell volume are presented and discussed.

Sodium and potassium transport in trout (Salmo gairdneri) erythrocytes.

The principal pathways of Na+ and K+ transport in trout erythrocytes have been characterized. Approximately 50% of K+ influx in steady-state erythrocytes was inhibited by ouabain (1 mM) and 46% by furosemide (1 mM). Furosemide-sensitive K+ influx was a saturable function of external K+ concentration with a Km of 25 mM. This flux component was also inhibited by SITS (4-acetamido-4'-isothiocyanatostilbene-2'2-disulphonate) (concentration required for 50% inhibition, I50 = 7.6 X 10(-6)M) and by the removal of external Cl-. An increase in cell volume stimulated furosemide-sensitive K+ influx and cell shrinkage inhibited this flux. K+ efflux was mainly furosemide-sensitive (64% of total). This pathway was unaffected by variations in extracellular K+ concentration and is therefore not exchange diffusion. However, it was affected by variations in cell volume in a similar way to the furosemide-sensitive K+ influx. Na+ influx was only slightly sensitive to furosemide (13% of total) but this component was very sensitive to changes in cell volume; decreased cell volume increased Na+ influx whilst increased cell volume inhibited Na+ influx. Furosemide-sensitive K+ influx was unaffected by variations in external Na+ concentration. Similarly, furosemide-sensitive Na+ influx was unaffected by variations in external K+ concentration. This indicates that the passive influxes of Na+ and K+ were not coupled, in contrast to the situation in avian erythrocytes. The opposite effects of cell volume upon passive Na+ and K+ fluxes are in good agreement with the net movements of these cations during volume regulation in erythrocytes of the flounder (Cala, 1977) and the toadfish (Lauf, 1982).

A new spin label method for the measurement of erythrocyte internal microviscosity

A new spin-label method for the measurement of the internal microviscosity of erythrocyte is presented. The spin label used is 2,2′,5,5′-tetramethyl-3-maleimidopyrrolidinyl- N-oxyl (MAL-5) which penetrates inside the red blood cell and binds covalently on cytoplasmic glutathione. After washing off the external label, 98% of the electron paramagnetic signal is due to the labelled glutathione. This signal allows one to measure the rotational correlation time of the label. A calibration curve established with spin-labelled glutathione in sucrose solutions of increasing viscosity is used to convert the measured rotation times into viscosity units. This method avoids the use of unphysiological salts like potassium ferricyanide, and permits the study of red blood cells in various suspension media. In normal human subjects, the mean value of microviscosity is 4.45 ± 0.16 mPa·s at 20°C in isotonic saline (25 subjects) and 6 ± 0.25 mPa·s in plasma. The variations of microviscosity as a function of the osmolarity of the medium are explained according to a theoretical model taking into account the variations of the red blood cell volume and the viscometric properties of haemoglobin.

Isovolumetric sphering of erythrocytes for more accurate and precise cell volume measurement by flow cytometry.

AbstractTypical mammalian erythrocytes are biconcave disks. Flow cytometric light‐scattering measurements of red cell volume show large, orientation‐dependent variations in signal size. To eliminate errors caused by shape factors, we sphere erythrocytes isovolumetrically on an Auto‐Analyzer manifold (Technicon Instruments Corp., Tarrytown, N. Y.) using a carefully controlled ratio of concentrations of a salt of long chain sulfated fatty alcohol (e.g.), sodium dodecyl sulfate (SDS) to albumin in neutrally buffered isotonic saline, producing a suspension with at least 2 1/2 hours of stability with respect to cell volume, cell count and retention of hemoglobin. A two‐step manifold modification of this procedure is preferred. It uses the endogeneous serum protein and a first SDS‐saline reagent without added albumin at a low dilution, and further dilution with a second SDS‐saline containing a very low concentration of glutaraldehyde. This bypasses a serious shelf life problem with the albumin‐SDS reagent.Microhematocrit and Coulter electronic impedance measurements were correlated with light‐scattering measurements on our own flow cytometer system of unsphered, sphered, and sphered and fixed samples. These reveal marked superiority over unsphered samples (e.g., reduced coefficients of variation of cell volume and improved correlation with microhematocrit) of the sphered and of the sphered and lightly fixed cells. The resulting tighter unimodal cell volume distributions also provide the following advantages: (1) The separation of signals of large platelets from that of the smallest red cells is substantially increased permitting better resolution of microcytic red cells in some abnormal bloods, and (2) bimodality of red cell volume distribution in abnormal bloods is more easily resolved.

GROWTH RESPONSES OF THE DIATOM, CYCLOTELLA CRYPTICA (BACILLARIOPHYCEAE), TO GIBBERELLIC ACID1

ABSTRACTThe plant hormone, gibberellic acid (GA), stimulated growth of a marine diatom, Cyclotella cryptica Reimann, Lewin and Guillard. Four concentrations of GA (5 × 20 × 25 × and 35 × 10−6 g/mL) were added to axenic cultures of C. cryptica. Changes in cell densities, measured by cell counts and turbidimetric readings, confirmed that GA at 20 × 10−6 g/mL produced maximum stimulation. There was an increase in the total number of cells produced and a shorter lag phase of growth at this concentration. Coulter counter measurements of cell size, as well as ocular micrometer measurements, indicated there was no significant variation in cell volumes of GA grown cells over that of the controls.

Relations among variations in human red cell volume, density, membrane area, hemoglobin content and cation content

It is shown how variations in different properties of red cells can be inter-related provided relations exist among these properties at the single cell level. On the basis of the cell density dependence on cell volume and hemoglobin content, and the assumed volume dependence on red cell cation and hemoglobin content, nine relations among the variations in red cell volume, density, membrane area, hemoglobin content and cation content, and their correlations are derived. Values of seven correlation coefficients are theoretically predicted and are shown to be consistent with the experiments performed by density fractionated red blood cells. The cell volume dependence on cation and hemoglobin content obtained from relations among variations is compared with the predictions obtained by the existing model about the osmotic behavior of the red blood cell. Furthermore, it is shown that data on the variations of the red cell properties indicate the existence of the relation among cation content, hemoglobin content, and membrane area at the level of a single cell.

Hydrogen absorption in beryllium substituted Mg 2Ni

The alloys Mg 2Ni 1– x Be x ( x = 0.15 and 0.25) retain the Mg 2Ni structure showing a lattice dilation proportional to the beryllium content. The pressure-composition isotherms are reported for the dissociation of hydrided samples. The results suggest that there are two type of interstices able to absorb up to 4 H atoms per formula unit. The heats of formation obtained from the van't Hoff relationship show an increased stability for the hydrides of the beryllium substituted alloys compared to the pure Mg 2Ni. The results suggest that the electronic factors are more important for hydride stability than variations in the unit cell volume.

Passive potassium transport in low potassium sheep red cells: dependence upon cell volume and chloride.

The major pathway of passive K influx (ouabain-insensitive) was characterized in low-K type (LK) red cells of sheep. 1. Passive K transport in these cells was highly sensitive to variations in cell volume; it increased threefold or more in cells swollen osmotically by 10%, and decreased up to twofold in cells shrunken 5-10%. Active K influx was insensitive to changes in cell volume. Three different methods for varying cell volume osmotically all gave similar results. 2. The volume-sensitive pathway was specific for K in that Na influx did not vary with changes in cell volume. 3. The volume-sensitive K influx was a saturable function of external K concentration. It was slightly inhibited by Na, whereas K influx in shrunken cells was unaffected by Na. 4. Passive K influx was dependent on the major anion in the medium in that replacement of Cl with any of six other anions resulted in a reduction of K influx by 50-80% (replacement of Cl by Br caused an increase in K influx). The activation of K influx by Cl followed sigmoid kinetics. 5. Passive K influx is inhibited by anti-L antibody. The antibody affected only that portion of influx which was Cl-dependent and volume-sensitve. Of the subfractions of the antibody, it is anti-L1 which inhibits passive K transport. 6. Pretreatment of cells with iodoacetamide reduced the sensitivity of K influx to cell volume in that the influx was reduced in swollen IAA-treated cells and increased in shrunken IAA-cells. 7. Intracellular Ca has no role in altering passive K transport in LK sheep cells. Therefore, the major pathway of passive K transport in LK sheep red cells is sensitive to changes in cell volume, specific for K, dependent on Cl, and inhibited by anti-L1 antibody, The minor pathway, observed in shrunken cells, has none of these properties.

Quaternary adamantine selenides and tellurides of the form I III IV VI 4

The preparation of a range of polycrystalline Selenides and Tellurides of the form I III IV VI 4 was undertaken. Twelve Selenides with quaternary composition were prepared but the eight Tellurides attempted did not grow as quaternaries. Single crystal samples of CuGaSnSe 4 were grown by vapour transport. X-Ray powder photography confirmed that the quaternary Selenides have tetragonal Chalcopyrite structure with a c/a ratio of approximately 2. A systematic variation of unit cell volume and of c/a was found over the entire range of compounds grown.

Analysis of individual cell volume variation during freezing

Analysis of individual cell volume variation during freezing