Search

• A method to quantify atomic resolution first moment STEM images was developed. • The images are modelled as a superposition of derivatives of 2D Lorentzian peaks. • The unknown parameters are estimated using the least squares estimator. • The estimated parameters allow determination of atom counts in each atomic column. • First moment STEM imaging shows promise compared to HAADF STEM for atom counting. Through a simulation-based study we develop a statistical model-based quantification method for atomic resolution first moment scanning transmission electron microscopy (STEM) images. This method uses the uniformly weighted least squares estimator to determine the unknown structure parameters of the images and to isolate contributions from individual atomic columns. In this way, a quantification of the projected potential per atomic column is achieved. Since the integrated projected potential of an atomic column scales linearly with the number of atoms it contains, it can serve as a basis for atom counting. The performance of atom counting from first moment STEM imaging is compared to that from traditional HAADF STEM in the presence of noise. Through this comparison, we demonstrate the advantage of first moment STEM images to attain more precise atom counts. Finally, we compare the integrated potential extracted from first-moment images of a wedge-shaped sample to those values from the bulk crystal. The excellent agreement found between these values proves the robustness of using bulk crystal simulations as a reference library. This enables atom counting for samples with different shapes by comparison with these library values. [ABSTRACT FROM AUTHOR]

A new methodology is presented to count the number of atoms in multimetallic nanocrystals by combining energy dispersive X‐ray spectroscopy (EDX) and high angle annular dark field scanning transmission electron microscopy (HAADF STEM). For this purpose, the existence of a linear relationship between the incoherent HAADF STEM and EDX images is exploited. Next to the number of atoms for each element in the atomic columns, the method also allows quantification of the error in the obtained number of atoms, which is of importance given the noisy nature of the acquired EDX signals. Using experimental images of an Au@Ag core–shell nanorod, it is demonstrated that 3D structural information can be extracted at the atomic scale. Furthermore, simulated data of an Au@Pt core–shell nanorod show the prospect to characterize heterogeneous nanostructures with adjacent atomic numbers. [ABSTRACT FROM AUTHOR]

The Bayesian genetic algorithm (BGA) is a powerful tool to reconstruct the 3D structure of mono-atomic single-crystalline metallic nanoparticles imaged using annular dark field scanning transmission electron microscopy. The number of atoms in a projected atomic column in the image is used as input to obtain an accurate and atomically precise reconstruction of the nanoparticle, taking prior knowledge and the finite precision of atom counting into account. However, as the number of parameters required to describe a nanoparticle with atomic detail rises quickly with the size of the studied particle, the computational costs of the BGA rise to prohibitively expensive levels. In this study, we investigate these computational costs and propose methods and control parameters for efficient application of the algorithm to nanoparticles of at least up to 10 nm in size., Competing Interests: Conflict of Interest. No competing interest is declared., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Microscopy Society of America. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

The search for alternatives that minimize the generation of tailings and enable their reuse, leads to characterization studies with the objective of a better understanding of the physical, chemical and mineralogical properties of iron ore tailings. The increase in demand for high-quality ore overlapping ore extraction with increasingly lower iron concentration levels, is part of the challenge of mineral exploitation. In view of the aforementioned needs, a more detailed characterization of the tailings contributes to the improvement of the mineral processing stage and the reuse of the generated tailings. To this end, an analysis of the characteristics of the tailings was carried out through physical, chemical and mineralogical characterization, with emphasis on quantitative electron microscopy - QEM. The tests revealed that the predominant phases are hematite and quartz and, to a lesser extent, goethite, gibbsite and kaolinite. As for the degree of release, hematite/magnetite has 88.13% of its particles totally free, 0.53% associated with quartz and 6.77% associated with goethite. The chemical composition is 32.29% Fe, 47.92% SiO2, 2.76% Al2O3, and 2.14% PPI. In this scenario, mineralogical characterization, as a main component of geometallurgy, makes it possible to propose alternatives that improve the ore beneficiation process and the reuse of tailings.

Nowadays, aberration corrected transmission electron microscopy (TEM) is a popular method to characterise nanomaterials at the atomic scale. Here, atomically resolved images of nanomaterials are acquired, where the contrast depends on the illumination, imaging and detector conditions of the microscope. Visualization of light elements is possible when using low angle annular dark field (LAADF) STEM, annular bright field (ABF) STEM, integrated differential phase contrast (iDPC) STEM, negative spherical aberration imaging (NCSI) and imaging STEM (ISTEM). In this work, images of a NdGaO 3 -La 0.67 Sr 0.33 MnO 3 (NGO-LSMO) interface are quantitatively evaluated by using statistical parameter estimation theory. For imaging light elements, all techniques are providing reliable results, while the techniques based on interference contrast, NCSI and ISTEM, are less robust in terms of accuracy for extracting heavy column locations. In term of precision, sample drift and scan distortions mainly limits the STEM based techniques as compared to NCSI. Post processing techniques can, however, partially compensate for this. In order to provide an outlook to the future, simulated images of NGO, in which the unavoidable presence of Poisson noise is taken into account, are used to determine the ultimate precision. In this future counting noise limited scenario, NCSI and ISTEM imaging will provide more precise values as compared to the other techniques, which can be related to the mechanisms behind the image recording. [ABSTRACT FROM AUTHOR]

Aberration correction in scanning transmission electron microscopy (STEM) has greatly improved the lateral and depth resolution. When using depth sectioning, a technique during which a series of images is recorded at different defocus values, single impurity atoms can be visualised in three dimensions. In this paper, we investigate new possibilities emerging when combining depth sectioning and precise atom-counting in order to reconstruct nanosized particles in three dimensions. Although the depth resolution does not allow one to precisely locate each atom within an atomic column, it will be shown that the depth location of an atomic column as a whole can be measured precisely. In this manner, the morphology of a nanoparticle can be reconstructed in three dimensions. This will be demonstrated using simulations and experimental data of a gold nanorod. [ABSTRACT FROM AUTHOR]

The cell entry mechanism of Autographa californica multiple nucleopolyhedrovirus (AcMNPV) is not fully understood. Previous studies showed that AcMNPV entered host cells primarily through clathrin-mediated endocytosis, and could efficiently infect cells via fusion with the plasma membrane after a low-pH trigger. However, whether AcMNPV enters cells via these two pathways simultaneously, and the exact manner in which AcMNPV particles are internalized into cells remains unclear. In this study, using single-virus tracking, we observed that AcMNPV particles were first captured by pre-existing clathrin-coated pits (CCP), and were then delivered to early endosomes. Population-based analysis of single-virus tracking and quantitative electron microscopy demonstrated that the majority of particles were captured by CCPs and internalized via invagination. In contrast, a minority of virus particles were not delivered to CCPs, and were internalized through direct fusion with the plasma membrane without invagination. Quantitative electron microscopy also showed that, while inhibition of CCP assembly significantly impaired viral internalization, inhibition of endosomal acidification blocked virus particles out of vesicles. Collectively, these findings demonstrated that approximately 90% of AcMNPV particles entered cells through clathrin-mediated endocytosis and 10% entered via direct fusion with the plasma membrane. This study will lead toward a better understanding of AcMNPV infection.

In this paper, we propose an algorithm to obtain a three-dimensional reconstruction of a single nanoparticle based on the method of atom counting. The location of atoms in three dimensions has been successfully performed using simulations of high-angle-annular-dark-field images from only three zone-axis projections, [110], [310] and [211], for a face-centred cubic particle. These three orientations are typically accessible by low-tilt holders often used in high-performance scanning transmission electron microscopes. [ABSTRACT FROM AUTHOR]

Recently, imaging scanning transmission electron microscopy (ISTEM) has been proposed as a promising new technique combining the advantages of conventional TEM (CTEM) and STEM (Rosenauer et al., 2014 [1] ). The ability to visualize light and heavy elements together makes it a particularly interesting new, spatially incoherent imaging mode. Here, we evaluate this technique in term of precision with which atomic column locations can be measured. By using statistical parameter estimation theory, we will show that these locations can be accurately measured with a precision in the picometer range. Furthermore, a quantitative comparison is made with HAADF STEM imaging to investigate the advantages of ISTEM. [ABSTRACT FROM AUTHOR]

An efficient model-based estimation algorithm is introduced to quantify the atomic column positions and intensities from atomic resolution (scanning) transmission electron microscopy ((S)TEM) images. This algorithm uses the least squares estimator on image segments containing individual columns fully accounting for overlap between neighbouring columns, enabling the analysis of a large field of view. For this algorithm, the accuracy and precision with which measurements for the atomic column positions and scattering cross-sections from annular dark field (ADF) STEM images can be estimated, has been investigated. The highest attainable precision is reached even for low dose images. Furthermore, the advantages of the model-based approach taking into account overlap between neighbouring columns are highlighted. This is done for the estimation of the distance between two neighbouring columns as a function of their distance and for the estimation of the scattering cross-section which is compared to the integrated intensity from a Voronoi cell. To provide end-users this well-established quantification method, a user friendly program, StatSTEM, is developed which is freely available under a GNU public license. [ABSTRACT FROM AUTHOR]

Precipitates and their associated strain fields significantly influence mechanical properties and, consequently, the industrial performance of aluminum alloys. In this work, we present a direct measurement of strains induced by η′ and η precipitates in an Al-Zn-Mg-Cu alloy using aberration-corrected high-resolution transmission electron microscopy and quantitative strain analysis. The results demonstrate that the strain induced by precipitates in the Al-Zn-Mg-Cu alloy shows significant tensile strains perpendicular to the longitudinal direction of the precipitate discs on the side of the discs and along the longitudinal direction at both ends of the η′ and η precipitates. This strain field can be described by an equivalent dislocation model, in which the lattice mismatch between the precipitate and the matrix is equivalent to a series of dislocation pairs along the precipitate/matrix interfaces. [ABSTRACT FROM AUTHOR]

AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) and NMDA (N-methyl-d-aspartate) glutamate receptors are driving forces for synaptic transmission and plasticity at neocortical synapses. However, their distribution pattern in the adult rat neocortex is largely unknown and was quantified using freeze fracture replication combined with postimmunogold-labeling. Both receptors were co-localized at layer (L)4 and L5 postsynaptic densities (PSDs). At L4 dendritic shaft and spine PSDs, the number of gold grains detecting AMPA was similar, whereas at L5 shaft PSDs AMPA-receptors outnumbered those on spine PSDs. Their number was significantly higher at L5 vs. L4 PSDs. At L4 and L5 dendritic shaft PSDs, the number of gold grains detecting GluN1 was ~2-fold higher than at spine PSDs. The number of gold grains detecting the GluN1-subunit was higher for both shaft and spine PSDs in L5 vs. L4. Both receptors showed a large variability in L4 and L5. A high correlation between the number of gold grains and PSD size for both receptors and targets was observed. Both receptors were distributed over the entire PSD but showed a layer- and target-specific distribution pattern. The layer- and target-specific distribution of AMPA and GluN1 glutamate receptors partially contribute to the observed functional differences in synaptic transmission and plasticity in the neocortex., (© The Author(s) 2022. Published by Oxford University Press.)

Abstract: Off-axis electron holography is a method for the transmission electron microscope (TEM) that measures the electric and magnetic properties of a specimen. The electrostatic and magnetic potentials modulate the electron wavefront phase. The error in measurement of the phase therefore determines the smallest observable changes in electric and magnetic properties. Here we explore the summation of a hologram series to reduce the phase error and thereby improve the sensitivity of electron holography. Summation of hologram series requires independent registration and correction of image drift and phase wavefront drift, the consequences of which are discussed. Optimization of the electro-optical configuration of the TEM for the double biprism configuration is examined. An analytical model of image and phase drift, composed of a combination of linear drift and Brownian random-walk, is derived and experimentally verified. The accuracy of image registration via cross-correlation and phase registration is characterized by simulated hologram series. The model of series summation errors allows the optimization of phase error as a function of exposure time and fringe carrier frequency for a target spatial resolution. An experimental example of hologram series summation is provided on WS2 fullerenes. A metric is provided to measure the object phase error from experimental results and compared to analytical predictions. The ultimate experimental object root-mean-square phase error is 0.006rad (2π/1050) at a spatial resolution less than 0.615nm and a total exposure time of 900s. The ultimate phase error in vacuum adjacent to the specimen is 0.0037rad (2π/1700). The analytical prediction of phase error differs with the experimental metrics by +7% inside the object and −5% in the vacuum, indicating that the model can provide reliable quantitative predictions. [Copyright &y& Elsevier]

Abstract: A new graphical software (STEM_CELL) for analysis of HRTEM and STEM-HAADF images is here introduced in detail. The advantage of the software, beyond its graphic interface, is to put together different analysis algorithms and simulation (described in an associated article) to produce novel analysis methodologies. Different implementations and improvements to state of the art approach are reported in the image analysis, filtering, normalization, background subtraction. In particular two important methodological results are here highlighted: (i) the definition of a procedure for atomic scale quantitative analysis of HAADF images, (ii) the extension of geometric phase analysis to large regions up to potentially 1μm through the use of under sampled images with aliasing effects. [Copyright &y& Elsevier]

A decade ago, a statistics-based method was introduced to count the number of atoms from annular dark-field scanning transmission electron microscopy (ADF STEM) images. In the past years, this method was successfully applied to nanocrystals of arbitrary shape, size, and composition (and its high accuracy and precision has been demonstrated). However, the counting results obtained from this statistical framework are so far presented without a visualization of the actual uncertainty about this estimate. In this paper, we present three approaches that can be used to represent counting results together with their statistical error, and discuss which approach is most suited for further use based on simulations and an experimental ADF STEM image.

Siphonous plants represent an alternate scheme to the way most macroscopic plants are constructed. They are single, often large (1–2 m), sometimes morphologically complex, multinucleate (coenocytic) cells where the whole of the cytoplasm is a continuum. Caulerpa mexicana Sond. ex Kütz. is a siphonous tropical marine green alga characterized by four morphologically distinct regions and, as with other members of the genus, by the presence of a dense network of anastomosing cylindrical cell wall in growths called trabeculae. Based on the results of this study, we propose several roles for trabeculae: (i) They are structural components, which likely add some small amount of support in compression but add considerable strength in tension. (ii) As extensions of the cell wall and plasma membrane, they act as diffusion channels from the cell exterior to the interior cytoplasm. It is possible that trabeculae also play a role in determining cell shape through developmental positioning and placement patterns, thus facilitating the diverse shapes found in the morphologically distinct regions of Caulerpa sp. [ABSTRACT FROM AUTHOR]

Abstract: The accuracy of maximum entropy reconstruction of Z-contrast STEM images has been evaluated with the effects of experimental variables and noise taken into account by the means of image simulation. As the specimen contains atom species of greatly different atomic numbers, special attention is given to the reliability of the position and composition of lighter atoms that are determined from Z-contrast images in the presence of heavier atoms. When the noise is moderate (SNR >2.5), the position of atom columns can be measured within an accuracy of 0.03nm. With a higher signal-to-noise ratio (SNR >5) the composition of lighter atoms can be resolved reliably from the Z-contrast images. However, when image noise increases, the relative intensity of lighter atoms may deviate from the actual value in the specimen object function. [Copyright &y& Elsevier]

Abstract: Electron microscopy has been used to measure the mass of biological nanoparticles since the early 60s, and is the only way to obtain the mass of large structures or parameters such as the mass-per-length of filaments. The ability of this method to sort heterogeneous samples both in terms of mass and shape promises to make it a key tool for proteomics down to the single cell level. A new multiplatform software package, MASDET, that can be run under MATLAB or as a standalone program is described. Based on a user-friendly graphical interface MASDET streamlines mass evaluation and greatly increases the speed of required optimisation procedures. Importantly, the immediate application of Monte-Carlo simulations to describe multiple scattering is possible, allowing the mass analysis of thicker samples and the generation of mass thickness maps. [Copyright &y& Elsevier]

The effects of imaging parameters have been studied on their roles of the severe mismatches between experimental and simulated high-resolution transmission electron micrographs of sapphire along the direction. Image simulation and convergent-beam electron diffraction techniques have been performed on misalignments of the electron beam and the crystal specimen. Based on this study, we have introduced an approach to achieve reliable simulation for experimental images of sapphire on the projection by the use of iterative digital image matching. [ABSTRACT FROM AUTHOR]

Synopsis Current evidence of the effect of hormone replacement therapy (HRT) on skin lipids, of postmenopausal women is scanty and indirect. Here, we report the ultrastructural differences in epidermal lipids between postmenopausal subjects who were and were not on HRT and a comparison is made with younger subjects. Biopsies were obtained from arms and legs, in a blinded, no-treatment, study conducted on postmenopausal subjects who were and were not on HRT and younger subjects. The ultrastructure of skin lipids and the lipid coverage of underlying corneocytes were compared for biopsies obtained from different subjects. Qualitative assessment as well as quantitative estimation of lipid-covered regions of corneocytes shows that skin lipids do not cover corneocytes effectively in postmenopausal women who are not on HRT. However, women who are on HRT show significantly improved lipid coverage of corneocytes, which is comparable with the younger subjects. This implies that HRT should improve the lipid coverage and skin condition of postmenopausal women. [ABSTRACT FROM AUTHOR]

Lattice-distortion analysis from high-resolution transmission electron micrographs offers a convenient and fast tool for direct measurement of strains in materials over a large area. In the present work, we have evaluated the accuracy of the strain measurement when the effects of the realistic experimental variables are explicitly taken into account by the use of image simulation techniques. These variables are focal setting and variation, local thickness and orientation of the sample, as well as misalignments of the sample and the incident beam. The evaluation reveals that consistency of image features and contrast within the micrographs is desired for the analysis to eliminate effects of the variations of local focus value and specimen thickness. After proper orientation of a crystalline specimen, the misorientation of the object will not notably influence the strain measurement even though a local bending may exist within the sample. However, the incident beam of the microscope needs to be aligned carefully as the beam misalignment may introduce a notable artefact around the interface region. [ABSTRACT FROM AUTHOR]

Abstract: Precise knowledge of crystal thickness and orientation is critical for reliable interpretation of high-resolution transmission electron micrographs. In this paper, we propose a criterion of S 2 (T, u, v), which measures the crystal thickness by intensity matching of the selected-area Fourier transform of experimental holograms with the calculated electron diffraction pattern at a series of trial thicknesses (T) and crystal tilts (u, v). This criterion has been demonstrated successfully for local thickness determination from a simulated high-resolution image of a wedge-shaped YBa2Cu3O7−δ and from an experimental hologram of a Si crystal. [Copyright &y& Elsevier]

A small sample tilt away from a main zone axis orientation results in an elongation of the atomic columns in ADF STEM images. An often posed research question is therefore whether the ADF STEM image intensities of tilted nanomaterials should be quantified using a parametric imaging model consisting of elliptical rather than the currently used symmetrical peaks. To this purpose, simulated ADF STEM images corresponding to different amounts of sample tilt are studied using a parametric imaging model that consists of superimposed 2D elliptical Gaussian peaks on the one hand and symmetrical Gaussian peaks on the other hand. We investigate the quantification of structural parameters such as atomic column positions and scattering cross sections using both parametric imaging models. In this manner, we quantitatively study what can be gained from this elliptical model for quantitative ADF STEM, despite the increased parameter space and computational effort. Although a qualitative improvement can be achieved, no significant quantitative improvement in the estimated structure parameters is achieved by the elliptical model as compared to the symmetrical model. The decrease in scattering cross sections with increasing sample tilt is even identical for both types of parametric imaging models. This impedes direct comparison with zone axis image simulations. Nonetheless, we demonstrate how reliable atom-counting can still be achieved in the presence of small sample tilt. • Elliptical Gaussian peaks are introduced to quantify ADF STEM image intensities. • Their performance is compared quantitatively to symmetrical Gaussian peaks. • There is a qualitative improvement in the presence of sample tilt. • Quantitatively, the performance is the same for symmetrical and elliptical peaks. • Reliable atom-counting remains possible in the presence of sample tilt. [ABSTRACT FROM AUTHOR]

In the freshwater snail Biomphalaria glabrata the formation and composition of yolk granules and the role of the follicle cells were studied by histochemical and electron microscopical techniques. The rough endoplasmic reticulum and the Golgi apparatus appeared to be involved in yolk formation, which is a continuous process throughout oogenesis. From the very beginning of yolk formation two main types of yolk granules were distinguished morphologically. However, with histochemical and enzyme cytochemical methods no differences were observed between these types. The granules acquire lysosomal enzymes after oviposition, indicating that their main function is probably digestion of perivitelline fluid, which contains nutrients for the developing embryo. Yolk formation and the activity of the follicle cells were studied in successive stages of oogenesis by quantitative electron microscopy. The data strongly suggest that the follicle cells are involved in the formation of the follicular cavity and hence in the ovulation process. [ABSTRACT FROM AUTHOR]

The cerebral ganglia of the freshwater snail Lymnaea stagnalis contain two clusters of neurosecretory Caudo-Dorsal Cells (CDC). These cells produce a neurohormone which stimulates ovulation. Ganglion transplantation and quantitative electron microscopy show that neuronal isolation of the cerebral ganglia complex (CCC) results in an activation of the CDC. It was, therefore, concluded that the CDC are controlled by an inhibitory neuronal input originating outside the cerebral ganglia. Ultrastructural studies on synaptic degeneration in the CCC suggest that this input reaches the CDC via a special type of synapse-like structure, the type C-SLS. Furthermore, transplantation of CCC into acceptor snails leads to a reduced release and an increased intracellular breakdown of neurohormone in the CDC of the nervous system of the acceptors. It is supposed that these phenomena are caused by the release of an (unknown) factor from the transplanted CCC. Special attention was given to the formation and degradation of a peculiar type of neurohormone granule, the large electron dense granule. The physiological significance of the neuronal and non-neuronal control mechanisms which regulate CDC activity is discussed. [ABSTRACT FROM AUTHOR]

The process of neurosecretion in the Caudo-Dorsal Cells (CDC) of the freshwater snail Lymnaea stagnalis, which produce an ovulation hormone, shows a diurnal rhythmicity. Synthesis, transport and release of the neurosecretory material (NSM) is high during the evening and the early night and low during the rest of the day, while storage of NSM mainly occurs during the daytime. In the present study the role of the eyes in the regulation of the CDC-rhythm was investigated. During a 24-hr period, at time intervals of 6 hrs, cerebral ganglia, which contain CDC, of blinded and control snails (5 per group) were fixed and the CDC were studied with quantitative electron microscopical methods. The CDC of the controls showed a distinct diurnal rhythmicity. Blinding, on the other hand, clearly affected this rhythmicity. The results indicate that after blinding the circadian CDC-rhythms of individual snails are no longer synchronous with each other ('interanimal desynchronization'). It is suggested that the rhythm of CDC neurosecretory activity is synchronized by the natural light/dark cycle via the eyes. The information from the eyes probably reaches the CDC via a nervous pathway. True synapses and three types of synapse-like structures were found on the CDC. Their role in the regulation of CDC-activity is discussed. The effect of blinding is specific for the CDC; blinding does not influence the diurnal rhythmicity of another type of cerebral neurosecretory cells, the Light Green Cells (LGC). The CDC within a cluster act synchronously. This synchrony does not depend upon the presence of the eyes. Some structures which may be involved in establishing this synchrony, such as subsurface cisterns, desmosome-like structures and 'specific release sites', are described. [ABSTRACT FROM AUTHOR]

Granule exocytosis was quantitatively investigated in the perinatal rat anterior pituitary at the electron microscopic level. Both the number of cells in the process of exocytosis and the number of extruded granules per cell profile found in a standardized area of section were counted. The first distinct figure of exocytosis was detected in the anterior pituitary of fetal rats on day 18.5 of gestation, although occasional cells on day 17.5 had structures resembling granule extrusion. The frequency of cells showing granule discharge was very low on day 18.5 of gestation, but it sharply increased on day 19.5; a similar level was maintained up to day 21.5 of gestation. While the number of exocytosed granules per cell profile was almost unchanged during the fetal and neonatal period up to day 3 after birth. The frequency of cells undergoing exocytosis decreased near the time of birth, after which it transiently increased and dropped again to a minimum at 12 h after delivery. During days 1 to 3 of postnatal life, cells in the process of exocytosis were less frequent compared to fetuses between day 19.5 and 21.5. Both the number of cells undergoing exocytosis and the number of discharged granules per cell profile first exceeded the fetal values on the 6th postnatal day and were remarkably augmented between days 9-20 of the neonatal period. These data are discussed in relation to the hormone secreting activity of the anterior pituitary gland of perinatal rats. [ABSTRACT FROM AUTHOR]

Quantitative differences in cellular association of adrenomedullary chromaffin cells with other types of cells, mainly supporting cells, were studied. Adrenaline (A) and noradrenaline (NA) cells were compared. Electron micrographs (12000 x) of profiles of A and NA cells, bordering against other types of cells, were used for quantitative evaluation. Supporting cells constituted the majority of the non-chromaffin cell types. Occurrence frequencies of chromaffin cells contiguous with other types of cells were: (1) higher for A cells (68.9%, 199/289) than for NA cells (11.0%, 34/309) in case of small contact regions (χ-test: P<0.001) and (2) higher for NA cells (68.3%, 211/309) than for A cells (9.7%, 28/289) in case of extended contact regions ( P<0.001). In conclusion, the extent of cellular association with supporting cells was remarkably lower in A cells than in NA cells. Such an arrangement is likely to be appropriate for the extensive, homogeneous control and amplified response characteristic of A cells, and for the close range, complex control and more diverse responses characteristic of NA cells. [ABSTRACT FROM AUTHOR]

Immunocytochemical staining demonstrates striking differences in staining intensity among individual crustacean hyperglycemic hormone (CHH)-producing cells in the eyestalk of the crayfish Astacus leptodactylus. Based on these differences we arbitrarily subdivided the CHH-cells into three categories representing increasing immunoreactivity respectively: + cells, + + cells, and + + + cells. Electron microscopic investigations reveal that these differences in immunostaining are correlated with differences in the numerical density of the neurosecretory granules in the cytoplasm and that these may reflect differences in activity among the CHH-cells. Morphometric analyses at the light- and electron-microscopic levels indicate that the three distinguished categories of immunopositive cells represent different stages in the CHH-synthesizing process of the cells. The results of the present study demonstrate the application of the PAP-technique at the light-microscopic level as a method to obtain information pertaining to the dynamics of secretory activity of the CHH-cells. [ABSTRACT FROM AUTHOR]

In the lateral lobes of the cerebral ganglia of the pulmonate freshwater snail Lymnaea stagnalis (L.) one large neurosecretory canopy cell (CC) and two droplet cells (DC) are present. With the gangliontransplantation technique and with quantitative electron microscopy it is shown that photoperiodic stimuli control the neurosecretory activity of the CC via a stimulatory extrinsic neural pathway. The eyes do not play an important role in this regulatory process. The neurosecretory activity of the DC is not affected by differences in photoperiod. The significance of the photoperiodic control of CC activity is discussed in relation to the pathway for the endocrine control of reproduction which is known to be photoperiod-dependent. [ABSTRACT FROM AUTHOR]

Mineralized pieces of tendons from the tibio-tarsus of turkeys were (i) shock-frozen, freeze-dried, embedded and cut without staining, or (ii) fixed, embedded and stained after sectioning. Micrographs were taken with an electron microscope on longitudinally cut sections. The center-to-center distances of neighboring apatitic needles within collagen fibrils were measured. For shock-frozen and freeze-dried specimens, the average of these distances is 4.7 nm and the most frequent value 4.2 nm; for fixed and stained specimens, 3.8 nm and 3.6 nm, respectively. Laser diffraction of the electron micrographs showed a dumbbell-like intensity pattern (two diffuse maxima of intensity on the equator, one on each side of the central spot), giving an average distance of about 6 nm. This value represents the upper range of the direct measurements. The measurements demonstrate that the arrangement of the collagen microfibrils is mainly preserved during mineralization. However, using laser diffraction, distances of 9-11 nm were also observed. Such large distances can also be demonstrated by X-ray diffraction on collagen fibrils stained under special conditions. This may indicate that special conditions of apatitic mineralization or staining may alter the arrangement of the microfibrils. [ABSTRACT FROM AUTHOR]

The collembolan Orchesella cincta possesses a well-developed coelomoduct kidney. The presence of podocytes in the wall of the sacculus and the fact that the epithelium of the nephridial tubule has the ultrastructural characteristics of resorbing cells, indicate that this is an 'ultrafiltration-reabsorption' kidney. Apparently also the rectum is lined by a reabsorptive epithelium; the cells possess an extensive system of apical and basal infoldings. This view is sustained by the fact that the stereology of the apical channel system varies in animals kept under different moisture conditions. During the intermoult period, both organs are subject to strong morphological changes, which are obviously related to the feeding rhythm. [ABSTRACT FROM AUTHOR]

The glandular lobe of the corpus cardiacum (CC) of Locusta migratoria contains secretory cells and axon terminals. It is generally accepted that the glandular cells produce an adipokinetic hormone which stimulates the release of diglycerides from the fat body. The axon terminals are supposed to be involved in the regulation of the secretory activity of these cells. CC were transplanted into locust hosts. The secretory activity of the glandular cells and axons was studied in the transplants as well as the intact host CC. Quantitative electron microscopical examination of the glandular cells of the CC in animals both at rest and after flight shows that only in the host CC the secretory activity of the glandular cells is stimulated by flight, as indicated by an increase in the activity of the Golgi zones and in the number of exocytotic pits. In the axon terminals release of secretory products, indicated by synaptic vesicles and membrane indentations, is reduced as a result of the transplantation. It is concluded that the glandular cells need excitatory input from outside the CC for stimulation of their secretory activity. Furthermore, it is proposed that the transplanted glandular cells decrease the level of activity of the intact host cells by way of a negative feedback mechanism. [ABSTRACT FROM AUTHOR]

The glandular lobe of the corpus cardiacum of Locusta migratoria is characterized by the presence of one type of secretory cells containing secretory granules with a diameter of 2000-3000 Å, and of axons with small granules (diameter 950 Å). The axons form synaptic contacts with the cells. The secretory products of the glandular cells are released by exocytosis in the gland proper. In the axon terminals, release is indicated by the presence of synaptic vesicles and omega-shaped indentations. In order to study possible changes in the secretory activity of the gland during flight, three groups of locusts were studied with quantitative electron microscopical methods, i.e., resting insects, insects having flown for 5 min (short flight, SF), and insects after prolonged flight (PF, 60 min). After flight, greater secretory activity of the glandular cells is indicated by a marked increase in the number of exocytotic pits in SF and PF insects, by an enlarged nuclear volume as well as an increased amount of secretory products in the Golgi cisterns of PF animals. Flight also causes greater release activity in the axon terminals. From these results it is concluded that an intrinsic hormone, apparently the adipokinetic hormone, is released from the glandular lobe and regulates the substrate supply from the fat body during flight. It is suggested that the secretory activity of the glandular cells is controlled by the axon terminals on these cells. [ABSTRACT FROM AUTHOR]

The neurosecretory Caudo-Dorsal Cells (CDC) in the cerebral ganglia of the freshwater pulmonate snail Lymnaea stagnalis produce an ovulation stimulating hormone. Previously it has been shown that neuronal and non-neuronal inputs are involved in the regulation of their activity. The degree of autonomy of these cells has been investigated by studying with morphometric methods the ultrastructure of CDC maintained in vitro. CDC of isolated cerebral ganglia which were cultured for 7 days show a considerable rate of synthesis, transport and release of neurohormone. Apparently these processes can proceed in the absence of neuronal and hormonal inputs from outside the cerebral ganglia. Completely isolated CDC, however, do not show neurosecretory activity in vitro; active Golgi zones, indicating the formation of neurosecretory elementary granules, are absent from such cells. Isolation does not seem to affect general cell functions such as protein synthesis and respiration. It is suggested that a neuronal input, originating within the cerebral ganglia, is necessary for the stimulation of CDC neurosecretory activity. Techniques are described for the isolation and culture of neurosecretory cells of L. stagnalis. [ABSTRACT FROM AUTHOR]

The neurosecretory Dark Green Cells (DGC) in the pleural and parietal ganglia of the freshwater snail Lymnaea stagnalis seem to be involved in osmoregulation. Previous experiments have indicated that changes of the osmolality of the environment induce activity changes of the DGC. Furthermore, it was shown that information on environmental osmolality reaches the DGC via the blood. In the present study right pleural and parietal ganglion complexes were cultured for 3 days in vitro under different osmotic conditions. Quantitative electron microscopy revealed that, compared with the control osmolality (130 mOsm/kg HO), osmolalities of 160 and 190 mOsm/kg HO caused a reduced synthesis and an increased storage of neurohormone in the DGC. Apparently, the activity of the DGC depended on the osmotic pressure of the medium. It is proposed that in vivo the osmotic pressure of the blood (which is related to the osmolality of the environment) regulates DGC activity. [ABSTRACT FROM AUTHOR]

The corona radiata containing all geniculo-cortical and cortico-geniculate fibers was transected in adult cats. One year after the operation synaptic architecture of laminae A and A of the decorticated LGN was investigated utilizing electron-microscopy and Golgi-EM. It was found that synaptic glomeruli became embedded in heavily gliotic neuropile, which contained the dendrites of surviving relay cells in addition to retinal axons and interneuronal processes. In contrast to the intact LGN, where the relay cell dendrites are exclusively postsynaptic, many morphologically identified relay neuronal dendrites of the decorticated LGN also contained large, round synaptic vesicles associated with distinct presynaptic sites. In 60% of all glomeruli, the large presynaptic dendrites of relay neurons occupied a central position and were postsynaptic to retinal axons and interneuronal dendrites/axons, but were presynaptic to other relay dendrites or interneuronal dendritic profiles. Occasional dendro-dendritic synapses between relay cell processes could be observed in the extraglomerular neuropile. Relay cell presynaptic dendrites formed unequivocal Gray I-type synapses, in accordance with the supposed excitatory character of relay cell output. Since sprouting of extrinsic or intrinsic axons could not be observed after decortication, it is proposed that the partial synaptic reorganization of the LGN was primarily due to the compensatory 'axonization' of relay cell dendrites. It is further suggested that the electrophysiologically demonstrated expansion of retinal receptive fields in the chronically decorticated LGN was accomplished by the formation of dendro-dendritic synapses between relay cells and interneurons. [ABSTRACT FROM AUTHOR]

Acute retrograde ultrastructural changes resulting from complete removal of areas 17, 18 and 19 were used to develop criteria for identification of principal or projective neurons (P-cells) and local interneurons (I-cells) in the dorsal lateral geniculate nucleus (LGNd) of monkeys. Four and six days after axotomy, marked chromatolytic alterations and diminution of rough endoplasmic reticulum were noted in 89 examined neurons of medium or large size, with rich cytoplasmic matrix, large mitochondria, and exhibiting only postsynaptic sites on the perikarya and dendrites. Seventeen other neurons showing no signs of degeneration had a pale matrix, small dense mitochondria and both postsynaptic and presynaptic sites on their perikarya and dendrites. It was concluded that the former group represented P-cells and the latter was characteristic of I-cells. The morphologic criteria derived from this study were applied to the quantitative analysis of neuronal populations in separate magnocellular and parvocellular laminae. The findings indicate that the latter contain 4.4% of I-cells whereas the former have 15.6% of this neuronal category. The dissimilarity suggests the more preeminent role of I-cells in the magnocellular laminae where they could maintain the transient responses of Y-cells which are known to be the predominant population among the P-cells of these laminae. [ABSTRACT FROM AUTHOR]

Four types of synapses: axo-axonic, axo-dendritic, axon-spine, and axo-somatic were distinguished in the supraoptic nucleus in the rat. The density of synaptic terminals (boutons) in this nucleus is 35.17·10/mm hence there are over 5 million boutons on each side, and on the average 596 per neuron. Only about one third of the axon terminals in this nucleus originate outside the nucleus and its immediate neighbourhood. Two thirds appear to be of intranuclear or otherwise of local origin. This could be explained by assuming either numerous intranuclear axon collaterals or interneurons having richly arborizing axons, or possibly both. [ABSTRACT FROM AUTHOR]

A quantitative electron microscopic study of synaptic terminal degeneration was performed in the supraoptic nucleus (NSO) after a variety of major transections or ablations, destroying or interrupting in different combinations the afferent pathways known from earlier and own light microscopic degeneration studies. Solutions of a set of equations, expressing the percentage degenerations in synaptic profiles after different combinations in which the several pathways are interrupted by the various interferences, enabled the authors to give the following percentage numbers for afferent synapses from different sources. 32.7% of supraoptic afferents originate from the brain stem probably representing the monoaminergic innervation of this nucleus. The medial basal hypothalamus (21.0%), amygdala (13.5%), septum (13.5%), hippocampus (8.5%) and olfactory tubercle and further rostral cortical region (17.0%) are the other main sites of origin of supraoptic nucleus afferents. There are no supraoptic afferents from the optic nerve, superior cervical ganglion or fimbria hippocampi. [ABSTRACT FROM AUTHOR]

Copyright of Diabetologia is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Quantitative electron microscopic studies have been carried out on the human thymus. According to the equation L=(2 n)/ F (Hennig, 1963) we have calculated that there is less than 0.204 mm nerve per 1 mm thymus tissue inside the blood-thymus-barrier (level of significance of 0.95). This result is compared to the degree of innervation in brown adipose tissue, which contains more than 160 mm nerve per 1 mm tissue. The biological significance of the paucity of neuronal elements in the thymus is undetermined. [ABSTRACT FROM AUTHOR]

Copyright of Zeitschrift Für Die Gesamte Experimentelle Medizin Einschließlich Experimentelle Chirurgie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The neurosecretory Dark Green Cells (DGC) in the pleural and parietal ganglia of the freshwater pulmonate Lymnaea stagnalis are involved in osmoregulation, producing a diuretic hormone. The secretory activity of these cells is dependent on the osmolarity of the environment. In order to investigate whether the regulation of this activity is under nervous control, two experiments were carried out in which the right pleural and parietal ganglion complex (PPC) was transplanted into acceptor snails. The light and electron microscopic observations in the first experiment-transplantation of the PPC into control snails, kept under normal conditions-indicate that degeneration in transplants occurs only during the first week of transplantation and is mainly restricted to neuronal processes of non-neurosecretory cells (non-NSC) of which the cell bodies are located outside the PPC. Degenerated nervous elements are eliminated by phagocytozing amoebocytes and glial cells. Degeneration of neurosecretory elements was only very seldom observed. Like most non-NSC, the DGC and the three other neurosecretory cell (NSC) types in the right parietal ganglion show a normal morphology. Moreover, up to at least 6 weeks after transplantation the NSC remain capable of synthesizing, transporting and releasing their neurosecretory material (NSM). Apparently these processes can proceed in the absence of nervous input from outside the PPC. After 3 and 6 weeks of transplantation outgrowth was noted of both non-NSC and NSC axons. In the second experiment groups of acceptor snails were exposed during one week to different environmental osmolarities. Thereafter the NSC activities of the transplanted DGC and of the DGC in the acceptor's own nervous system were determined by quantitative light and electron microscopy. The following observations apply to both transplanted and acceptor DGC. Compared with the control condition (tap water) exposure of snails to demineralized water leads to a significant increase in nuclear and cytoplasmic volumes and in the extent of the granular endoplasmic reticulum (GER) and the Golgi apparatus. Moreover, the activity of the Golgi apparatus is strongly enhanced. In the DGC axon endings located in the pleuroparietal connective the release of NSM is raised markedly above control level. Conversely, exposure to a 0.08 M NaCl solution (hypertonic to the blood) reduces the secretory activity of the DGC, as is obvious from the decrease of nuclear and cytoplasmic volumes, the smaller extent of the GER and of the Golgi apparatus and the lower Golgi activity. The number of cytosomes is increased dramatically, which accounts for the breakdown of elementary granules and of other cytoplasmic constituents. The NSM of the DGC is partly broken down in the axon endings by lysosomal action. Its release takes place at a low rate. Since these changes in neurosecretory activity occur in a similar fashion in transplanted and in acceptor DGC it is concluded that the response of the DGC to environmental osmolarity is not regulated via nervous pathways to the PPC. The only significant difference between transplanted and acceptor DGC concerns the higher number of clear vesicles in the DGC axon endings of transplants. Some explanations for this phenomenon are discussed. Possible mechanisms of regulation of DGC neurosecretory activity are considered. [ABSTRACT FROM AUTHOR]

Copyright of Zeitschrift Für Zellforschung und Mikroskopische Anatomie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Electron microscopic studies have been carried out on the innervation of the mammalian anterior pituitary and parathyroids. The total area of grid squares (2.25·10mm) examined was 2000 per gland and species. In the pituitary pars distalis and in the parenchyma of the parathyroid gland we did not observe a single axon profile. According to the equation $$L_V = \frac{{2n}}{F}$$ proposed by Hennig (1963) we have calculated that there might be-if any-0.133 mm of nerves per 1 mm tissue in those two endocrine glands (level of significance 0.95). Comparing these results to the degree of innervation in brown adipose tissue containing more than 160 mm nerve per 1 mm tissue we can not imagine that such a small degree of innervation is of any biological importance. In the pituitary pars tuberalis two types of axon terminals have been found both inside and outside the basement membrane surrounding the epithelial complexes. One type contains 'synaptic' and two populations of smaller dense-cored vesicles, the other one contains a population of larger granules which have some properties of the classical elementary granules. Further investigations have to clarify the functional significance of those nerve endings. [ABSTRACT FROM AUTHOR]