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In an article published in Microscopy and Microanalysis
recently (Jia et al., 2004), it was claimed
that aberration-corrected high resolution transmission electron
microscopy (HRTEM) allows the quantitative measurement of oxygen
concentrations in ceramic materials with atomic resolution. Similar
claims have recently appeared elsewhere, based on images obtained
through aberration correction (Jia et al.,
2003; Jia & Urban, 2004) or very
high voltages (Zhang et al., 2003). Seeing
oxygen columns is a significant achievement of great importance (Spence, 2003) that will doubtlessly allow some
exciting new science; however, other models could provide a better
explanation for some of the experimental data than variations in the
oxygen concentration. Quantification of the oxygen concentrations was
attempted by comparing experimental images with simulations in which
the fractional occupancy in individual oxygen columns was reduced. The
results were interpreted as representing nonstoichiometry within the
bulk and at grain boundaries. This is plausible because previous
studies have shown that grain boundaries can be nonstoichiometric
(Kim et al., 2001), and it is indeed possible
that oxygen vacancies are present at boundaries or in the bulk.
However, is this the only possible interpretation? We show
that for the thicknesses considered a better match to the images is
obtained using a simple model of surface damage in which atoms are
removed from the surface, which would usually be interpreted as surface
damage or local thickness variation (from ion milling, for example).
Advances in Fluorescence, Flow Cytometry and Cytomics
The ecdysial suture is the region of the arthropod exoskeleton that
splits to allow the animal to emerge during ecdysis. We examined the
morphology and composition of the intermolt and premolt suture of the blue
crab using light microscopy and scanning electron microscopy. The suture
could not be identified by routine histological techniques; however 3 of
22 fluorescein isothiocyanate-labeled lectins tested (Lens
culinaris agglutinin, Vicia faba agglutinin, and Pisum
sativum agglutinin) differentiated the suture, binding more intensely
to the suture exocuticle and less intensely to the suture endocuticle.
Back-scattered electron (BSE) and secondary electron observations of
fracture surfaces of intermolt cuticle showed less mineralized regions in
the wedge-shaped suture as did BSE analysis of premolt and intermolt
resin-embedded cuticle. The prism regions of the suture exocuticle were
not calcified. X-ray microanalysis of both the endocuticle and exocuticle
demonstrated that the suture was less calcified than the surrounding
cuticle with significantly lower magnesium and phosphorus concentrations,
potentially making its mineral more soluble. The presence or absence of a
glycoprotein in the organic matrix, the extent and composition of the
mineral deposited, and the thickness of the cuticle all likely contribute
to the suture being removed by molting fluid, thereby ensuring successful
ecdysis.
According to statistics provided by the American Heart Association
for 2002, the latest year available, cardiovascular diseases are the
leading cause of death in both males and females in the United States
with over 434,000 males and 494,000 females dying each year from
cardiovascular-related diseases. This is 36.6% of all deaths in males
and 39.8% in females and represents billions of dollars in health care
costs. Cardiovascular-associated diseases run the gamut from congenital
defects that manifest early in development through diseases such as
stroke and infarcts frequently associated with advanced age.
Investigative techniques to study these diseases are varied and include
a full range of imaging, genomic, and proteomic technologies.
With this issue, Microscopy and Microanalysis begins its
eleventh year of publication. Our journal is getting better
year-by-year. In 2004 this journal published more scientific articles
than in any previous year. The first biological special issue, on
parasites, increased the prominence of the life sciences within these
pages. The growing popularity of the journal is also indicated by
several letters to the editor about matters arising in certain
articles. Such scientific exchanges highlight for our readership the
subtleties of interpretation regarding advances in science,
instrumentation, technique, and theory.
Isolation and culture of thymic epithelial cells (TECs) using
conventional primary tissue culture techniques under conditions employing
supplemented low calcium medium yielded an immortalized cell line derived
from the LDA rat (Lewis [Rt1l] cross DA
[Rt1a]) that could be manipulated in vitro. Thymi
were harvested from 4–5-day-old neonates, enzymically digested using
collagenase (1 mg/ml, 37°C, 1 h) and cultured in low calcium
WAJC404A medium containing cholera toxin (20 ng/ml), dexamethasone (10
nM), epidermal growth factor (10 ng/ml), insulin (10 μg/ml),
transferrin (10 μg/ml), 2% calf serum, 2.5% Dulbecco's
Modified Eagle's Medium (DMEM), and 1% antibiotic/antimycotic.
TECs cultured in low calcium displayed round to spindle-shaped morphology,
distinct intercellular spaces (even at confluence), and dense
reticular-like keratin patterns. In high calcium (0.188 mM), TECs formed
cobblestone-like confluent monolayers that were resistant to
trypsinization (0.05%) and displayed keratin intermediate filaments
concentrated at desmosomal junctions between contiguous cells. Changes in
cultured TEC morphology were quantified by an analysis of
desmosome/membrane relationships in high and low calcium media.
Desmosomes were significantly increased in the high calcium medium. These
studies may have value when considering the growth conditions of cultured
primary cell lines like TECs.
The official journal of Microscopy Society of America, Microbeam
Analysis Society, Microscopical Society of Canada /
Société de, Microscopie du Canada, Mexican Microscopy Society,
Brazilian Society for Microscopy and Microanalysis, Venezuelan Society of
Electron Microscopy, European Microbeam Analysis Society, Australian
Microscopy and Microanalysis Society.
Published in affiliation with Royal Microscopical Society, German
Society for Electron Microscopy, Belgian Society for Microscopy,
Microscopy Society of Southern Africa.
Editor in Chief, Editor, Microanalysis: Charles E. Lyman, Materials
Science and Engineering, Lehigh University, 5 East Packer Avenue,
Bethlehem, Pennsylvania 18015-3195, Phone: (610) 758-4249, Fax: (610)
758-4244, e-mail: charles.lyman@lehigh.edu.
Editor, Biological Applications: Ralph Albrecht, Department of Animal
Sciences, University of Wisconsin-Madison, 1675 Observatory Drive, Madison,
Wisconsin 53706-1581, Phone: (608) 263-3952, Fax: (608) 262-5157, e-mail:
albrecht@ansci.wisc.edu.
Editor, Materials Applications: David J. Smith, Center for Solid State
Science, Arizona State University, Tempe, Arizona 85287-1704, Phone: (480)
965-4540, Fax: (480) 965-9004, e-mail: david.smith@asu.edu.
Editor, Materials Applications: Elizabeth Dickey, Materials Science and
Engineering, Pennsylvania State University, 223 MRL Building, University
Park, PA 16802-7003, Phone: (814) 865-9067, Fax: (814) 863-8561, e-mail:
ecd10@psu.edu.
Editor, Light and Scanning Probe, Microscopies: Brian Herman, Cellular
and Structural Biology, University of Texas at San Antonio, 7703 Floyd Curl
Drive, San Antonio, Texas 78284-7762, Phone: (210) 567-3800, Fax: (210)
567-3803, e-mail: hermanb@uthscsa.edu.
Editor, Biological Applications: Heide Schatten, Veterinary
Pathobiology, University of Missouri-Columbia, 1600 E. Rollins Street,
Columbia, Missouri 65211-5030, Phone: (573) 882-2396, Fax: (573) 884-5414,
e-mail: schattenh@missouri.edu.
Calendar Editor, Book Review Editor: JoAn Hudson, Advanced Materials
Research Labs., Clemson Univ. Research Park, Rm. 105, Anderson, SC 29625,
Phone: (864) 656-7535, Fax: (864) 656-2466, e-mail: joanh@clemson.edu.
Special Section Editor: James N. Turner, Phone: (518) 474-2811, Fax:
(518) 474-8590, e-mail: turner@wadsworth.org.
Expo Editor: William T. Gunning III, Phone: (419) 383-5256,
Fax: (419) 383-3066, e-mail: wgunning@mco.edu.
Quantitative dimensional measurements of micro- and nanometre-sized
structures are urgently required from science and industry. Due to their
very high vertical resolution (down to sub nanometres) and high lateral
resolution (<10 nm) scanning probe microscopes (SPMs) are of great
interest for such metrological applications. Additionally, SPM methods
are able to measure surfaces in a number of modes like contact,
intermittent-contact and non-contact mode. The forces between tip and
sample are low during the measurement and, even in contact mode, reach
only a few nanonewtons. This fact prevents scratching of the measured
surface during the SPM scanning procedure even when very sharp tips are
used.
Special Issue: Frontiers of Electron Microscopy in Materials
Science
The Ninth Frontiers of Electron Microscopy in Materials Science
Conference (FEMMS 2003) was held October 5–10, 2003 at the Claremont
Resort and Spa in Berkeley, CA. Major sponsors for this meeting included
Lawrence Livermore National Laboratory, Argonne National Laboratory,
Lawrence Berkeley National Laboratory, Brookhaven National Laboratory,
Frederick Seitz Materials Research Laboratory, Oak Ridge National
Laboratory, National Science Foundation, and University of California at
Davis. Sponsors also included LEO Electron Microscopy Ltd. (Carl Zeiss
SMT), E. A. Fischione, Inc., Gatan, Inc., Thermo NORAN (Thermo Electron
Corp.), FEI Company, Hitachi-HHTA, JEOL USA, Inc., Seiko Instruments, and
CEOS GmbH.
Atomic Force Microscopy (AFM) has become a ubiquitous tool for
analyzing the topography of a wide variety of materials, especially as
nanoscale features become more significant for both understanding as
well as determining materials properties [1]. Many AFM variations have
also been developed for measuring surface properties beyond
straightforward cartography. In many of these cases, the contrast
mechanisms are often either extremely complex, or not well understood,
even though the principles are simple. For example, Piezo-Force
Microscopy (PFM) is relatively easy to understand and use in a standard
lab for measuring electromechanical properties of materials, but care
must be taken in order to obtain quantitative results as described
below.
To examine new cytochemical aspects of the bacterial adhesion, a
strain 41452/01 of the oral commensal Streptococcus
sanguis and a wild strain of Staphylococcus aureus were
grown with and without sucrose supplementation for 6 days.
Osmiumtetraoxyde (OsO4), uranyl acetate (UA), ruthenium red
(RR), cupromeronic blue (CB) staining with critical electrolytic
concentrations (CECs), and the tannic acid–metal salt technique
(TAMST) were applied for electron microscopy. Cytochemically, only
RR-positive fimbriae in S. sanguis were visualized. By
contrast, some types of fimbriae staining were observed in S.
aureus glycocalyx: RR-positive, OsO4-positive,
tannophilic and CB-positive with ceasing point at 0.3 M
MgCl2. The CB staining with CEC, used for the first time for
visualization of glycoproteins of bacterial glycocalyx, also reveals
intacellular CB-positive substances—probably the monomeric
molecules, that is, subunits forming the fimbriae via extracellular
assembly. Thus, glycosylated components of the biofilm matrix can be
reliably related to single cells. The visualization of intracellular
components by CB with CEC enables clear distinction between S.
aureus and other bacteria, which do not produce CB-positive
substances. The small quantities of tannophilic substances found in
S. aureus makes the use of TAMST for the same purpose
difficult. The present work protocol enables, for the first time, a
partial cytochemical differentiation of the bacterial glycocalyx.
The authors are grateful to the Editor for the opportunity to reply
to the letter by Lupini et al. The authors of the above letter comment
on a set of recent articles in which the novel technique of imaging at
a negative value of the spherical aberration coefficient of the
objective lens in an aberration-corrected transmission electron
microscope (NCSI technique) is methodically described and applied to
the measurement of the occupancy of atomically resolved oxygen columns
in perovskites. In particular, the authors raise doubts about the
possibility of inferring quantitative data from measurements of the
local image intensity at the position of the oxygen atom columns. With
reference to the study by Jia et al. (2003a), the letter authors present an image
simulation on the basis of which it is stated that the observed effect of
a reduced intensity at the oxygen atomic columns should not be interpreted
in terms of reduced oxygen occupancy but can, as the authors claim, be
“better” explained on the basis of the effect of surface
roughness on contrast. In addition, the authors emphasize the work of
Kim et al. (2001) with respect to the
nonstoichiometry of the oxygen occupancy in grain boundaries of
SrTiO3 and criticize our reference to the literature in which
it is reported that oxygen cannot be observed by the scanning transmission
electron microscopy (STEM) technique in Z-contrast. In the following,
we shall demonstrate that in spite of the fact that a nonideal surface
morphology can—as in the application of any (!) electron microscopic
technique whether used in TEM or in STEM—have an effect on local
image intensity, meaningful quantitative measurements of relative
oxygen-atom site occupancies can be carried out employing the NCSI
technique.
From the basic light microscope through high-end imaging systems such
as multiphoton confocal microscopy and electron microscopes, microscopy
has been and will continue to be an essential tool in developing an
understanding of cardiovascular development, function, and disease. In
this review we briefly touch on a number of studies that illustrate the
importance of these forms of microscopy in studying cardiovascular
biology. We also briefly review a number of imaging modalities such as
computed tomography, (CT) Magnetic resonance imaging (MRI), ultrasound,
and positron emission tomography (PET) that, although they do not fall
under the realm of microscopy, are imaging modalities that greatly
complement microscopy. Finally we examine the role of proper imaging
system calibration and the potential importance of calibration in
understanding biological tissues, such as the cardiovascular system,
that continually undergo deformation in response to strain.
Electron tomography is a well-established technique for
three-dimensional structure determination of (almost) amorphous specimens
in life sciences applications. With the recent advances in nanotechnology
and the semiconductor industry, there is also an increasing need for
high-resolution three-dimensional (3D) structural information in physical
sciences. In this article, we evaluate the capabilities and limitations of
transmission electron microscopy (TEM) and high-angle-annular-dark-field
scanning transmission electron microscopy (HAADF-STEM) tomography for the
3D structural characterization of partially crystalline to highly
crystalline materials. Our analysis of catalysts, a hydrogen storage
material, and different semiconductor devices shows that features with a
diameter as small as 1–2 nm can be resolved in three dimensions by
electron tomography. For partially crystalline materials with small single
crystalline domains, bright-field TEM tomography provides reliable 3D
structural information. HAADF-STEM tomography is more versatile and can
also be used for high-resolution 3D imaging of highly crystalline
materials such as semiconductor devices.
This is a report of the adaptation of microwave processing in the
preparation of liver biopsies for transmission electron microscopy (TEM)
to examine ultrastructural damage of mitochondria in the setting of
metabolic stress. Hemorrhagic shock was induced in pigs via 35% total
blood volume bleed and a 90-min period of shock followed by resuscitation.
Hepatic biopsies were collected before shock and after resuscitation.
Following collection, biopsies were processed for TEM by a rapid method
involving microwave irradiation (Giberson,
2001). Samples pre- and postshock of each of two animals were
viewed and scored using the mitochondrial ultrastructure scoring system
(Crouser et al., 2002), a system used to
quantify the severity of ultrastructural damage during shock. Results
showed evidence of increased ultrastructural damage in the postshock
samples, which scored 4.00 and 3.42, versus their preshock controls, which
scored 1.18 and 1.27. The results of this analysis were similar to those
obtained in another model of shock (Crouser et al.,
2002). However, the amount of time used to process the samples was
significantly shortened with methods involving microwave irradiation.
The nucleolus is the main site for synthesis and processing of
ribosomal RNA in eukaryotes. In mammals, plants, and yeast the nucleolus
has been extensively characterized by electron microscopy, but in the
majority of the unicellular eukaryotes no such studies have been
performed. Here we used ultrastructural cytochemical and
immunocytochemical techniques as well as three-dimensional reconstruction
to analyze the nucleolus of Trypanosoma cruzi, which is an early
divergent eukaryote of medical importance. In T. cruzi
epimastigotes the nucleolus is a spherical intranuclear ribonucleoprotein
organelle localized in a relatively central position within the nucleus.
Dense fibrillar and granular components but not fibrillar centers were
observed. In addition, nuclear bodies resembling Cajal bodies were
observed associated to the nucleolus in the surrounding nucleoplasm. Our
results provide additional morphological data to better understand the
synthesis and processing of the ribosomal RNA in kinetoplastids.
Scanning Probe Microscopy (SPM) [1] has been an important tool to
organize matter on the nanometer scale. It has been proved to be a
powerful tool not only for imaging but also for nanofabrication.
SPM-based nanofabrication comprises manipulation of atoms or molecules
and SPM-based nanolithography. SPM-based nanolithography, referred to as
scanning probe lithography (SPL) holds good promise for fabrication of
nanometer-scale patterns as an emerging generic lithography technique
that employs SPM to directly pattern nanometer-scale features under
appropriate conditions. The water meniscus formation between the tip and
the flat substrate, due to the water layer present on any surface of a
material at ambient conditions, has been studied experimentally and
theoretically [2-6] using SPM techniques. The water effect in the
imaging process is well understood [2, 4, 6-8]. Dip pen nanolithogaphy
(DPN) [9] is one example of a technique that uses the water effect to
transfer material from the tip onto sample surface in direct-write
fashion with nanoscopic resolution.
In this article, two simple methods, evaporation-condensation and
catalytic thermal evaporation, were used to investigate the synthesis
of CdS nanostructures for nanoscale optoelectronic applications. To
understand their growth mechanisms, various electron microscopy and
microanalysis techniques were utilized in characterizing their
morphologies, internal structures, growth directions and elemental
compositions. The electron microscopy study reveals that when using the
evaporation-condensation method, branched CdS nanorods and
self-assembled arrays of CdS nanorods were synthesized at 800°C and
1000°C, respectively. Instead of morphological differences, both
types of CdS nanorods grew along the [0001] direction.
However, when using the catalytic thermal evaporation method (Au as the
catalyst), patterned CdS nanowires and nanobelts were formed at the
temperature region of 500–600°C and 600–750°C,
respectively. Their growth direction was along the direction
[1010] instead of [0001].
Based on the microscopy and microanalysis results, we propose some
growth mechanisms in relation to the growth processes of those exotic
CdS nanostructures.