Measurements Of Cell Dimensions Research Articles

High-accuracy measurement of cell dimensions of niobium α-phase in niobium–oxygen system

High-accuracy measurement of cell dimensions of niobium α-phase in niobium–oxygen system

High-accuracy measurement of cell dimensions of the vanadium α- and β-phases in V–O system

High-accuracy measurement of cell dimensions of the vanadium α- and β-phases in V–O system

MRI based non-invasive detection of cardiomyocyte hypertrophy and cell-volume changes

Summary A new approach has been developed to detect myocardial cell-hypertrophy, by measuring the intra-cellular lifetime of water in a mouse model of hypertensive heart disease, and validating the MRI marker against measurements of cell dimensions on stained heart slices. Background Cardiomyocyte hypertrophy occurs in cardiomyopathies and in response to pressure overload. However, only endomyocardial biopsies allow detection, with the inherent risks of invasive catheter-based procedures. Noninvasive detection of cardiomyocyte hypertrophy using imaging may detect disease at a subclinical stage and potentially guide therapy. To-date, no imaging-technique has been validated to detect hypertrophic response at the cellular level. We developed a novel measure of cell size based on the MRI determination of the intra-cellular lifetime (τic) of water, using pre/post-contrast T1 measurements and a 2-site H-exchange model (2SXmodel). We hypothesized that τic correlates positively with the histological measure of cardiomyocyte volume (Vic) in a rodent model of hypertensive heart disease. Methods L-NAME (3mg/ml) or placebo were administered respectively to 17 (bw=37.2±2.3g) and 13 (bw=37.5 ±2.5g) male-wild-type mice. Mice were imaged at baseline and 7-weeks after treatment on a 4.7T-small-animal MRI-system. T1 (>5T1 measurement/mouse) was quantified with a modified Look-Locker gradient-echo-cine technique, before and after fractionated GadoliniumDPTA administration. Minor (Dmin) and major (Dmaj) cell-diameters were measured by FITC-labeled wheat germ-agglutinin staining of cell membranes. Morphometric analysis was performed with a computer-based system. Vic was calculated from Dmin and Dmaj celldiameters using a cylindrical cell-shape approximation. Results L-NAME-treated-mice developed hypertrophy (weightindexed LVMass 4.1±0.4 for L-NAME vs. 2.2±0.3μg/g for placebo, p<0.001). Vic (from histology) was substantially higher in L-NAME-treated-animals (19.4*10 3 ,I QR 917.1*10 3 μmm 3 vs. 10.7*10 3 , IQR 9.3*10 3 μmm 3 ; p<0.0001), while Dmaj/Dmin was smaller (3.4 vs. 4.2, p<1e-7), compared to controls. τic was significantly higher in L-NAME-treated animals (0.453±0.10 vs. 0.234 ±0.06, p<0.0001). τic increased significantly from baseline to 7-weeks in animals treated with L-NAME (p<0.0001) (Figure 1). τic strongly correlated with the minor cell diameter (r=0756, P<0.001), Vic (r=0.875, r<0.001) (Figure 1), and more weakly with the major cell-diameter (r=0.478, p=0.02). τic also correlated with weight-indexed LVMass (r=0.71, p<0.001). τic demonstrated an increase from baseline to 7-week (0.177 ±0.15), which follows the increase of LVmass (39.43 ±36.6μg/g) in the same interval (r=0.69, p<0.001).

How Does Stall Force Affect Contractions of a Biological Spring, Vorticella convallaria?

The stalk of Vorticella convallaria, a sessile peritrich, is considered as a model biological spring for bio-inspired actuators because of its remarkable speed and force. When stimulated, the stalk of Vorticella contracts over a few hundreds micrometers in a few milliseconds, and its energy source is not ATP but Ca2+. Because major components of the spasmoneme, the contractile organelle inside the stalk, are EF-hand Ca2+-binding proteins including spasmin and centrin, the spasmonemal contraction is thought to be related to other centrin-based motility mechanisms. This study describes how stall force affects contractions of live Vorticella. To impede contractions, we applied hydrodynamic drag force to Vorticella in a microfluidic channel with Poiseuille flow of viscous PVP solution. This method enables controlling the stall force by changing flow rate and the viscosity of the solution. Cell dimension measurements show that the zooid is elongated by the flow in relaxed and contracted states keeping roughly constant volume. As the stall force increases, the end-to-end length of the contracted stalk increases while that of the relaxed stalk is almost constant, and maximum contraction speed decreases while contractions take longer time. Furthermore, the time lag in contraction commencement between the zooid and the stalk also increases. We measured time differences in movement start among polystyrene beads attached to the stalk, and they increase with increasing stall force. These increasing time lags imply that the stalk cannot contract until it develops force great enough to overcome the stall force. The stall force affects the relaxation of Vorticella because relaxations take longer time as the stall force increase and the extending stalk resumes its contraction after the stall force is removed. It seems that although the spasmoneme retains contractile force, the stall force extends the stalk.

Effects of Heart Disease on Cardiac Ion Current Density Versus Current Amplitude

See related article, pages 1406–1415 It is well established that heart disease can profoundly change cardiac action potentials.1 Action potential abnormalities are caused by derangements in cardiac ion channel expression and function, often called “ion channel remodeling,” that can cause serious, sometimes lethal, arrhythmias.2 The literature regarding arrhythmogenic ion channel remodeling is vast and complicated.2 A PubMed search with the single key word phrase “cardiac channel remodeling” returned 50 publications in 2007 alone, indicating a high level of research activity. A variety of cardiac disease processes, including myocardial infarction, valvular heart disease, various cardiomyopathies, arrhythmias, and hypertensive heart disease, can cause ion channel remodeling.2,3 Many of these cause cardiac hypertrophy, defined as an increase in myocardial cell mass. Because cardiomyocyte number is relatively fixed in adult life, hypertrophy is typified by an increase in cardiomyocyte size, allowing for increased heart mass with the same number of cells. Cell dimension measurements are the most direct means to characterize cardiomyocyte hypertrophy. In electrophysiological studies, cellular hypertrophy is often assessed by determining cell capacitance. The lipid bilayer (electrically resistive) cell membrane acts as a capacitor separating the electrically conducting intracellular solution from the conductive extracellular solution. Electric current passes across cardiac cell membranes to charge their capacitance, even when no current traverses ion channels. Capacitance is a function of intrinsic capacitive properties (indicated by the “dielectric constant”), the capacitive (in this case, cell membrane) surface area, and the thickness of the capacitor. The thickness and intrinsic capacitive properties of cell membranes are fairly constant, so the dominant factor determining cell capacitance is the total membrane surface area. Cell size increases with cardiac hypertrophy. Augmented cell size is accompanied by increased cell surface area, therefore inevitably increasing cell capacitance. Because hypertrophy increases cell size, increased whole-cell current amplitude is …

Diagenesis and low-temperature metamorphism of Mt. Medvednica, Croatia: Mineral assemblages and phyllosilicate characteristics

New mineral paragenetic, illite Kübler index, chlorite “crystallinity”, apparent crystallite thickness, lattice strain, and K-white mica geobarometric data proved that the Eoalpine (Paleozoic-Mesozoic) metamorphic complex was affected by medium-pressure, high-temperature anchizonal regional metamorphism, whereas the Jurassic ophiolitic mélange and the Late Cretaceous-Paleocene sedimentary sequence of Mt. Medvednica were diagenetically altered. Mineral chemical investigations carried out on phyllosilicate flakes found in various microstructural positions revealed complete mineral chemical homogenization of chlorite and K-white mica of selected slate samples from the Eoalpine (Paleozoic-Mesozoic) metamorphic complex. One possible explanation of this feature is an Alpine (Cretaceous) regional metamorphic event with polyphase deformational history. Variscan low-temperature metamorphism overprinted by an Alpine (Cretaceous) event, with temperatures at least as high as those of the Variscan one, may be an alternative, although more complicated explanation. However, no isotope geochronological evidence supports this assumption. At present only one metamorphic event can be detected. Its physical conditions were ca. 350-400 °C on the basis of illite Kübler index and chlorite Al(IV) empirical thermometers and 3-4 kbar using K-white mica b cell dimension measurements.

How precise are measurements of unit-cell dimensions from single crystals?

The results of single-site and many-site measurements of cell dimensions from single crystals are compared for Bond and four-circle diffractometers using samples of corundum (essentially pure rhombohedral alpha-Al2O3, aluminum oxide) of high diffraction quality, where the effects of small changes in temperature and composition (Cr2O3, chromium oxide, in solid solution) can be taken into account. Similar comparisons are made for four-circle diffractometer measurements on ruby (alpha-Al2O3, with 0.46 wt % Cr in solid solution). The precisions are some parts in 10(5). There is partial support for the Taylor-Kennard [Acta Cryst. (1986), B42, 112-120] dictum that standard uncertainties (s.u.s) of cell parameters from routine four-circle diffractometer measurements are less than those for many-site measurements by factors of 5 for cell lengths and 2.5 for cell angles. For organic crystals, independent repetitions of adequate quality for comparison and analysis of routine four-circle diffractometer measurements are available only for alpha-oxalic acid dihydrate and anthracene. The experimental standard uncertainties given for these two crystals agree reasonably well with the sample s.u.s at room temperature, but appreciably less well at approximately 100 K, again giving partial support to the Taylor-Kennard dictum. The relation between specimen characteristics and attainable precision is emphasized; the precisions for routine measurements on good quality organic crystals are some parts in 10(4). Area-detector measurements of cell dimensions have also been appraised; currently published s.u.s from such measurements appear to be highly unreliable, and this is supported by a recent analysis of the operation of such diffractometers [Paciorek et al. (1999). Acta Cryst. A55, 543-557]. Formulation of a standard protocol for such measurements is badly needed. The dangers inherent in high degrees of replication are illustrated by recounting Kapteyn's Parable of the Chinese Emperor. Attention is drawn to the fact that there has been little improvement in claimed precisions over the past 40-60 years.

Estimating phytoplankton carbon from microscopic counts: an application for riverine systems

Algal biomass, in addition to cell numbers, is a measure of the successful conversion of inorganic to organic carbon. Consequently, carbon is the main currency used in aquatic models and in flux and budget studies. On the other hand, microscopic observation and counts remain the only means for determining species composition and biomass, which is relevant to many aspects of aquatic ecology. In this study, we focus on the way to convert biovolume to carbon biomass for algal assemblages of two rivers, using a computerized system that records dimensions of phytoplankton (Gosselain & Hamilton, 2000). We first compare different equations found in the literature for converting algal cell volume to cellular carbon content. We then evaluate the accuracy of a biomass estimate based on less time-consuming measurements, using pre-determined biovolume values instead of measuring cells in all samples. Biovolume/carbon equations are evaluated using total phytoplankton carbon biomass determined from measured chlorophyll a. Equations established for freshwater taxa seem to provide better estimates of algal biomass in the two case studies presented here, the Rideau and Meuse rivers (Canada and Belgium, respectively) than do more numerous equations defined for marine taxa. Furthermore, equations that make a distinction between diatoms and other algae appear more appropriate than those considering all algal groups as a whole. Finally, mean values of algal biovolumes, determined using sufficient measurements of cell dimensions from representative sampling series, may prove sufficient for carbon estimates of taxa in relatively homogenous size ranges. The careful choice of appropriate volumetric shapes and taxa categories remains of prime importance to get precise results.

Comparison of Conventional Transmitted Light and Confocal Microscopy for Measuring Wood Cell Dimensions by Image Analysis

A comparison was made between conventional transmitted light microscopy and confocallaser scanning microscopy (CLSM) as the source of digital images for the measurement of wood cell dimensions by image analysis. When compared with confocal microscopy, transmitted light microscopy using 20 μm thick, safranin stained sections overestimated wall thickness by up to 50% and underestimated lumen area by up to 4% due to the effects of out-of-focus haze. Confocal microscopy using 20 μm thick, safranin stained sections, was found to produce more accurate images of the wood cells compared to transmitted light microscopy using thick sections. Images obtained by optical sectioning were comparable to the quality that might be obtained by thin sectioning of resin embedded wood. For example bordered pit chambers were easily resolved in single optical sections but were not resolved in transmitted light images. Confocal microscopy can be performed on sections as thick as 120 μm and by acquiring optical sections more than 5 μm below the surface of the section distortion of cells caused by sectioning can be avoided. Image quality declined with depth leading to substantial changes in cell dimensions at depths beyond 10-20 μm and significant errors in cell dimensions beyond 80 μm depth. Image brightness was also found to decline with depth, more rapidly in water than in immersion oil. A comparison of measurements of cell dimensions in water and in immersion oil indicated that wall thickness changes significantly during drying but that other dimensions remain almost the same in dry compared to wet seetions.

Morphology Favors an Endothelial Cell Pathway for Longitudinal Conduction within Arterioles

We examined the morphological parameters of arteriolar endothelial and smooth muscle cell dimensions and gap junctional surface areas to obtain an indication of the coupling capacity of each cell type. Silver nitrate staining was utilized to define cell borders of endothelial and smooth muscle cells in arterioles of several vascular beds from two species. From video images of silver-stained arterioles, the mean endothelial cell length of hamster cheek pouch arterioles (diameter 20 to 110 μm) was found to be 141 ± 2 μm. Mean endothelial cell width was 7 ± 0.2 μm in the same arterioles. Mean smooth muscle cell length in hamster cheek pouch arterioles of diameter 80 to 150 μm was 66 ± 3 μm, with an average cell width of 8 ± 0.2 μm. Dimensions of both endothelial and smooth muscle cells varied moderately with arteriole size and tissue type, but no general trends were seen. Based on the measured dimensions and the specific orientation of cell types within the arteriole, it was calculated that in hamster cheek pouch arterioles (60 μm diameter), 6 or 7 endothelial cell lengths would constitute a 1-mm segment of vessel, whereas approximately 140 smooth muscle cell widths would be required to span the same length. Estimates of connexin43 gap junctional plaque surface areas in each cell type suggest that endothelial cell junctional surface area is approximately eight times that of smooth muscle cells. Thus, combined measurement of cell dimensions and orientation with estimates of junctional plaque density leads to the conclusion that the endothelial cell layer forms a more permissive pathway for longitudinal conduction of signals through the blood vessel.

Very low- and low-grade metamorphism in the Trinity Peninsula Group (Permo-Triassic) of northern Graham Land, Antarctic Peninsula

AbstractThe Permo-Triassic Trinity Peninsula Group is a widespread, regionally metamorphosed metasedimentary sequence in northern Graham Land, Antarctica, which forms the local ‘basement’ to the mainly Jurassic–Cretaceous Antarctic Peninsula magmatic arc. The metamorphic grade, thermal evolution and pressure series of this major tectono-stratigraphical unit are largely unknown. Determining the nature of the metamorphism has relied hitherto on conventional optical identifications of the major phases, mainly in rare volcanic beds. However, diagnostic mineral parageneses are generally absent and the precise metamorphic grade is unknown or has to be inferred over large areas. Using white mica (illite) crystallinity of interbedded mudrocks, the Trinity Peninsula Group is now shown to have been pervasively altered mainly at anchizonal and epizonal grades. Conditions ranged from upper anchizonal in the northeast to thoroughly epizonal in the southwest. Outwith thermal aureoles near plutonic intrusions, the alteration temperatures ranged mainly from 250 to 325 °C, exceeding 300 °C in the highest-grade (epizone/greenschist facies) parts of the sequence. The facies series, K-white mica b cell dimension measurements and mineral phases present are characteristic of an intermediate pressure series altered under moderate geothermal gradients (&lt;35 °C/km), corresponding to burial depths of c. 7–10 km. Unroofing and substantial erosion of the Trinity Peninsula Group took place during polyphasal vertical tectonic movements linked to the development of the magmatic arc in northern Graham Land. The geological setting of the Trinity Peninsula Group is ambiguous and could have been a foreland (or back-arc) basin or the mid- to upper levels of an accretionary prism.

Growth and division of Escherichia coli under microgravity conditions

The growth rate in glucose minimal medium and time of entry into the stationary phase in pepton cultures were determined during the STS 42 mission of the space shuttle Discovery. Cells were cultured in plastic bags and growth was stopped at six different time points by lowering the temperature to 5°C, and at a single time point, by formaldehyde fixation. Based on cell number determination, the doubling time calculated for the flight samples of glucose cells was shorter (46 min) than for the ground samples (59 min). However, a larger cell size expected for more rapidly growing cells was not observed by volume measurements with the electronic particle counter, nor by electron microscopic measurement of cell dimensions. Only for cells fixed in flight was a larger cell length and percentage of constricted cells found. An optical density increase in the peptone cultures showed an earlier entry into the stationary phase in flight samples, but this could not be confirmed by viability counts. The single sample with cells fixed in flight showed properties indicative of growth stimulation. However, taking all observations together, we conclude that microgravity has no effect on the growth rate of exponentially growing Escherichia coli cells.

Microzooplankton and tintinnid species-specific assemblage structures: patterns of distribution and year-to-year variations in the Weddell Sea (Antarctica)

Silicoflagellates, large heterotrophic dinoflagellates, radiolarians, tintinnids and micro- crustaceans were counted in 72 screened (15 urn) samples retrieved at 0-150 m from the Weddell Sea in January 1989. Tintinnid species were identified and biomass estimates were carried out for all groups on the basis of measurements of cell dimensions. Dinoflagellates dominated the micro- heterotrophic community at all stations and depths (65% of overall microzooplanktonic carbon in the 0-150 m interval), followed by the tintinnids (18%), microcrustaceans (16%) and radiolarians (1%). All groups, with the exception of silicoflagell ates, peaked noticeably in the vicinity of the southern end of the transect (76-77°S). Relationships between concentrations of chlorophyll a and microzooplanktonic biomass were present, yet not altogether consistent, but both phyto- and microzooplankton seemed to generally respond to regional enhancements associated with the ice edge. Comparison with similar Weddell and Weddell-Scotia data retrieved in February-March 1987 and November 1988-December 1989, respectively, are highly coherent in terms of microplankton ic abundances, their geographic and vertical distribution patterns, and the specific make-up and distribution of tintinnid assemblages. Analyses of the oral diameters of tintinnid morphotypes suggest that the latitudinal and vertical distribution of their five dominant taxa (which account for >90% of all individuals) is structured so as to maximize resource partitioning.

Conformation of the oleate chains in crystals of cholesteryl oleate at 123 K.

At 123 K, crystals of cholesteryl cis-9-octadecenoate (cholesteryl oleate, C45H78O2) are monoclinic, space group P2(1) with unit cell dimensions a = 12.356(2), b = 8.980(3), c = 18.382(2) A, beta = 85.49(2) degrees, and have two molecules in the unit cell. The crystal structure including all H atoms has been determined from 3812 independent X-ray reflections with sin theta/lambda less than 0.61 A-1 and refined to give Rw = 0.08. At 123 K, the crystal structure consists of an antiparallel efficient packing of cholesteryl ring systems to form layers that are very similar to those observed in the room temperature structure. The oleate chains that protrude from these layers have a somewhat different packing arrangement from the room temperature structure because they have undergone a conformational change. At 123 K, the oleate chains are well ordered and are almost fully extended except for a kink at the cis double bond. The oleate chains at 123 K are 1.7 A longer than at 295 K due in part to an uncoiling whereby their helical character is lost. On cooling, there is a substantial change in the unit cell beta-angle from obtuse (93.3 degrees) to acute (85.5 degrees) which involves a shearing motion of 2.5 A between adjacent molecular layers. Cell dimension measurements at 10 temperatures in the range 295 K to 123 K show that much of the change occurs in two narrow ranges centered at 262 K and 215 K.

Influence of framework aluminum gradients on the catalytic activity of Y zeolites: Cracking of gas-oil on Y zeolites dealuminated by different procedures

The catalytic cracking of gas-oil has been studied in a series of REHY and HY zeolite catalysts dealuminated by “deep bed” calcination, steaming, and SiCl 4 treatment. The samples have been characterized by X-ray diffraction, pyridine adsorption, and X-ray photoelectron spectroscopy (XPS). It has been found that the framework Si Al ratio determined by XPS (surface Si Al and that determined from unit cell dimension measurements (bulk Si Al ) differ, indicating a gradient in the concentration of the framework aluminum normal to the surface of the zeolite crystallites. When the gas-oil cracking activity is plotted versus unit cell dimension, three different volcano curves are obtained, with activity maxima located at about 24.59, 24.35, and 24.33 Å for deep bed, steamed, and SiCl 4-treated zeolites, respectively. These results, together with the behavior of the selectivity curves to gasoline, light cycle oil (LCO), gases, coke, and butene butane ratio, are discussed on the basis of Si Al gradients. Comparison of the cracking behavior of a short molecule such as n-heptane with that of gas-oil, in relation to the acidity of the samples measured by pyridine adsorption, supports the idea that gas-oil does not penetrate the zeolite deeply and, therefore, that the activity of the catalyst is controlled by the framework Si Al ratio close to the external surface, instead of the bulk Si Al ratio of the zeolite crystallites.

Leaf development in the anisophyllous shoots of Pellionia daveauana (Urticaceae)

The dorsiventral shoot system of Pellionia daveauana (Godefr.) N.E. Br. is characterized by opposite pairs of dimorphic leaves. The small dorsal leaves differ from the large ventral leaves by having a reduced leaf blade, fewer tissue layers in the epidermis and mesophyll, a reduced vascular system and significantly smaller cell size in all tissue layers. The observations reported here document the developmental basis of these morphological and histological differences. Although both dorsal and ventral leaves appear to be initiated simultaneously, the volume of the ventral leaf primordium is greater than that of the dorsal leaf primordium and growth in length occurs over a longer time period. Early plate meristem activity results in the elaboration of the ventral leaf blade, while plate meristem activity is lacking in dorsal leaves. During ventral leaf expansion periclinal divisions in adaxial and abaxial protoderm and ground meristem give rise to multiple epidermis and new mesophyll layers, respectively. Similar periclinal divisions in dorsal leaves occur at an earlier developmental stage and are restricted in extent. Measurements of cell dimensions show that cell enlargement also ceases at an early developmental stage in dorsal leaves. Development of the ventral leaf is characterized by a relatively long period of cell division and enlargement. In contrast, early cessation of cell division and precocious cell maturation result in the distinctive structural features of the dorsal leaf blade.

Ethylene-Induced Growth of Petals and Styles in the Immature Carnation Inflorescence

SummaryFlowering stems of glasshouse carnations, cv White Sim, were cut when the corolla protuded about 5.0 mm above the calyx and were treated with c. 10 vpm ethylene for 24 h in closed chambers or a free-flow system. Petals elongated and the inflorescence (plus stem) gained fresh weight; the styles also elongated, increased their fresh weight but became visibly thinner than the untreated controls. Measurement of cell dimensions indicated that part of the growth was due to increased cell elongation in the basal part of the petal. These observations are discussed in relation to the very different response of the mature flower to ethylene.

Accurate determination of cell dimensions of the triclinic crystal para nitro-phenoxy acetic acid

The possible ways of eliminating the factors which affect the measurement of cell dimensions in the case of single crystals in general are illustrated by actual application to the triclinic crystal para nitro-phenoxy acetic acid.

Solute distributions at non-planar, solid-liquid growth fronts: IV. Ripening of cells and dendrites behind the growth front

Simple cells, broken cells and dendrites are distinguished and the conditions under which they occur are described for aluminium base alloys with copper 0.2 to 10 wt% Cu. The ripening of simple cells behind the growth front is described with particular reference to (a) mechanisms of ripening, (b) changes in scale of solute distribution and (c) the effects of orientation. It is concluded that previous measurements of cell dimensions on sections or from decanted interfaces, relate not to the actual growth front but to a post solidification re-arrangement. Changes in secondary arm spacings were followed for broken cellular and dendritic morphologies. It was observed that while broken cells coarsened by a ripening mechanism similar to that for simple cells, dendrites coarsen in an essentially different pattern with only small changes in secondary arm spacings.

Precision measurements of cell dimensions of certain cobalt-doped nickel ferrites

Careful experimental techniques combined with suitable mathematical corrections of the experimental data have yielded accurate values of the cell dimensions of ferrites of composition Ni 1− x Co x Fe 2 O 4. The implications of the changing cell dimensions are discussed in terms of the valuance of cobalt.