bluuebunny/crossref_metadata_2025_split huggingface dataset:
Direct Magnetic Excitation of Cantilevers for Dynamic Force Microscocopy in Liquids
Authors: Lindsay SM 
Published: July 2020

Abstract
The mechanical Q-factor of an AFM cantilever immersed in fluid is reduced to a small value (ca. 3) owing to viscous damping. Thus, a large driving force is needed to excite the cantilever into bending motion in fluid. There are two common methods for exciting cantilevers for dynamic force microscopy in fluids, illustrated in Figure 1. Fig. la illustrates acoustic excitation in which a piezoelectric transducer displaces the base of the cantilever, causing bending motion of the cantilever when the driving frequency is near to a bending resonance of the cantilever. Fig. lb shows magnetic excitation. In magnetic excitation, a magnetic field is used to cause bending of a magnetic cantilever either through magnetostriction or MXB forces.
Acoustic excitation has the highest amplitude at mechanical resonances of the cantilever housing, with the result that the response is dominated by these sharp features,Fig. 2a. In contrast, the response to magnetic excitation is intrinsic to the cantilever, Fig. 2b. Thus, magnetic excitation permits the cantilever to be driven over a wide range of frequencies. This is important for calibration of the amplitude and for experiments involving time and concentration dependence in tip-sample interactions, e.g., anti-body recognition imaging.
Single Protein Mechanics Studied with Afm Techniques
Authors: Carrion-Vazquez M , Oberhauser AF , Fowler SB , Marszalek PE , Clarke J , Fernandez JM 
Published: July 2020

Abstract
The Atomic Force Microscope is a simple instrument capable of imaging single macromolecules with submolecular resolution and measure the forces required to unfold a single protein domain (Fig. 1).
The AFM method of unfolding a tandem modular protein generates a characteristic sawtooth pattern in the force-extension curves (Fig. 2). The measured spaces between the peaks are thought to correspond to the increase in contour length (ΔΔLC) of the protein caused by the unfolding of one of its modules. In order to demonstrate the validity of this model and measure the sensitivity of the AFM we have designed an experiment where we have inserted a cluster of 5 Gly into the loop joining the F and G b-strands of the I27 module of the I band from human cardiac titin. This loop is clearly within the folded structure of the module and hence, if our predictions are correct, unfolding of the I27-5Gly module should reveal an expanded ΔLC. We expect to measure an increase in the contour length increment of ΔΔLC = 5 ✗ 0.38 nm =1.9 nm.
Structural and Organizational Studies of Soluble Tar-Chewchea Complexes by Electron Microscopy and Image Analysis
Authors: Francis Noreen R , Shaikh Tanvir R , Levit Mikhail N , Melanson Linda A , Stock Jeffrey B , DeRosier David J 
Published: July 2020

Abstract
The transmembrane receptor for aspartate, Tar, in Escherichia coliand Salmonellais representative of a large class of receptors that generates chemotaxis responses by regulating the activity of an associated histidine kinase, CheA. Tar is composed of an Nterminal extracellular ligand-binding domain linked through a transmembrane sequence to a C-terminal signaling domain in the cytoplasm. The isolated cytoplasmic domain of Tar fused to a leucine zipper sequence forms soluble ternary complexes with CheA and an adapter protein, CheW. The isolated complex is biochemically active, has a molecular weight of 1,400,000 Daltons, and includes approximately 28 receptor signaling domains for 2 CheA dimers.
Electron microscopy of the complexes indicates well-defined bundles, presumably composed of numerous receptor filaments surrounding a core of CheA dimers and CheW. CheA also interacts with CheY, the response regulator of the bacterial flagellar motor. Immunoelectron microscopy has provided a general picture of the domain organization of the complexes.
2-Photon Excitation Laser Scanning Microscopy for High Resolution Imaging In Scattering Biological Tissues: Applications to Neuroscience
Authors: Svoboda K , Burbach BJ , Lendvai B , Mainen ZF , Maravall M , Nimchinsky E , O’Brien P , Sabatini B , Stern E 
Published: July 2020

Abstract
Optical microscopy has been at the center of biological research, and neuroscience in particular, for a long time. For example, over one hundred years ago advances in microscopical techniques directly led to the discovery that neurons are in fact cells (the so-called ‘neuron doctrine’), and subsequently to the description of the high-resolution structure of the nervous system. More recently, the development of fluorescent indicators of cellular function, including Ca2+, Na+, and pH indicators, has made it possible to image not only the structure of neurons but also aspects of their function. The most important of these has been the measurement of intracellular free calcium concentration, [Ca2+]. Calcium is an important messenger molecule because it couples electrical excitation to biochemical signaling cascades. In addition, in neurons [Ca2+] is also a good indicator of local electrical excitation and thus [Ca2+] imaging allows the measurement of cellular excitability in subcellular compartments that are inaccessible to other methods.
Biological Applications of Chromophores With Large Two-Photon Cross Sections
Authors: Dickinson ME , McCord-Maughon D , Staub K , Levin MD , Parker T , Fraser SE , Marder SR 
Published: July 2020

Abstract
One current limitation of two-photon technology is the lack of optimized fluorochromes for Two-Photon Laser Scanning Microscopy (TPLSM). Recently, Albota et al. (1998) have reported the design and synthesis of a number of bis(styryl)benzene derivatives that have large fluorescence quantum yields and greater two-photon absoption cross sections than any of fluorochromes that are currently used for TPLSM. As a first step in understanding how such molecules could be used in biological experiments, we have tagged a donor-πdonor molecule with biotin. We have successfully used this dye to detect quail nuclei in 2- 4 day old fixed embryos that have been reacted with QCPN, a quail specific monoclonal antibody. We have observed that this molecule gives a very intense signal, among the most intense signals we have been able to measure in our immunoassay. In particular, the brightness was about a factor of four higher than Rhodamine B-labelled streptavidin (containing 3.3 moles of dye per streptavidin tetramer).
Multi-Dimensional Microscopic Analysis of Sea Urchin Development
Authors: Summers R , Martins G , Morrill J 
Published: July 2020

Abstract
Several modalities of microscopic analysis have been employed in the investigation of development in the embryos of the sea urchins Strongylocentrotus purpuratusand Lytechinus variegatus. These include scanning electron microscopy, confocal optical microscopy and multiphoton laser scanning microscopy. These techniques all provide information on embryonic morphogenesis in three-dimensions and may be of use in the analysis of other developing organisms.
Scanning Electron Microscopy. Scanning electron microscopy bridges the gap between light and transmission electron microscopy. Operation in the secondary electron image mode with stereo-pair images combines great depth of field in focus from 10-50,000x with true 3D images of topographical features from whole embryos to macromolecules. The SEM's backscatter electron imaging mode allows one to see and map spatial geographies of colloidal gold labeled probes (e.g. antibodies, lectins) that bind to exposed surfaces of embryos, cells and extracellular matrices.
Contributions of Microscopy to the Diagnosis and Investigation of Aids-Associated Renal Disease
Authors: Howell D N , Szczech L A 
Published: July 2020

Abstract
Microscopy has had a major role in the analysis of renal disorders associated with human immunodeficiency virus (HIV) infection, both as a diagnostic method and as a means of studying pathogenic mechanisms. In the diagnostic realm, microscopic analysis of renal tissue obtained at biopsy and autopsy is a mainstay for the detection of a wide range of glomerular, vascular, and tubulointerstitial diseases. As an investigative tool, microscopy has made an important, albeit somewhat controversial, contribution to our understanding of the pathogenesis of at least one HIV-associated renal lesion.
A variety of ultrastructural alterations have been documented in association with HIV infection. These include tubuloreticular inclusions (most commonly seen in vascular endothelial cells and mononuclear leukocytes)(Fig. la), cylindrical confronting cisternae (typically found in mononuclear leukocytes) (Fig. lb), and nuclear abnormalities such as nuclear bodies and granular change (most often in tubulointerstitial cells) (Fig. lc).
N-Formyl Peptide Receptors Display an Asymmetric Distribution In Migrating Human Neutrophils
Authors: Loitto Vesa-Matti , Rasmusson Birgitta , Magnusson Karl-Eric 
Published: July 2020

Abstract
A debated and yet unanswered question, in regard to polarization and directed movement of phagocytic cells, concerns the distribution of chemoattractant receptors during cell locomotion1. We have therefore studied the instantaneous distribution of N-formyl-peptide receptors on living neutrophils. Using a fluorescent N-formyl-peptide receptor antagonist, tert-butyloxycarbonyl-Phe(D)-Leu-Phe(D)-Leu-Phe-OH (Boc-FLFLF), and a fluorescent receptor agonist, formyl-Nle-Leu-Phe-Nle-Tyr-Lys (fnLLFnLYK), the localization of the chemoattractant receptors could be followed during random migratio2. Neutrophils were adhered to plasma-coated coverslips. A Nomarski differential interference contrast (DIC)- image was taken, and rapidly followed by a fluorescence-image captured with a water-cooled, slow-scan CCD-camera. Then a second DIC-image was directly recorded to reveal the direction of cell movement.
Using fnLLFnLYK we observed that the distribution of N-formyl-peptide receptors was clearly heterogeneous as shown in figure. Fluorescence was concentrated mainly at the rear and front of elongated locomoting cells, leaving the cell body almost non-fluorescent.
Clofoctol-Induced Ultrastructural Changes In Staphylococcus Aureus
Authors: Maleeff Beverly E , Pearson Stewart C , Payne David J , Hart Timothy K 
Published: July 2020

Abstract
Clofoctol [2-(2,4-dichlorobenzyl)-4-(tetramethyl-l,l,3,3-butyl) phenol] is a synthetic antibacterial compound with activity against both Gram-positive1 and Gram-negative2 microorganisms. Although the specific mechanism of Clofoctol action has not been fully elucidated, it is reported to alter the permeability of the cytoplasmic membrane in Bacillus subtilis, and is used clinically to treat upper respiratory tract infections in humans. Staphylococcus aureus is a major human Grampositive pathogen that causes a variety of human diseases ranging from localized skin suppuration and food poisoning to life threatening presentations such as septicemia and endocarditis. Several clinical isolates of S. aureus have recently been identified that are resistant to all currently available antibacterial therapies. Consequently, the identification of new antimicrobial targets in this organism is of paramount importance. The purpose of this study was to investigate the in vitro effects of Clofoctol on S. aureus.
Ultrastructural examination of S. aureus revealed a population of actively dividing cells.
Fatal Encephalitis In Young Children, Taiwan, 1998
Authors: Goldsmith Cynthia S , Shieh Wun-Ju , Pallansch Mark A , Ksiazek Thomas G , Hsueh Chuen , Jung Shih-Ming , Kuo Tseng-Tong , Chen Yi-Ping , Zaki Sherif R 
Published: July 2020

Abstract
During April-July 1998, an increase in fatal cases of neurologic disease in young children occurred in Taiwan, with at least 55 fatalities reported. Concurrently, an outbreak of hand, foot, and mouth disease (HFMD) was also occurring. In fatal cases, the acute illness was characterized by fever, or rash, or mouth ulcers, followed by a rapid cardiopulmonary failure; death frequently occurred within 24 hours of hospitalization. Approximately three-fourths of the fatalities were in children less than 3 years of age. We report here the findings from autopsy specimens from two of the fatal cases of encephalomyelitis.
In Case 1, a 9-year-old female, H&E sections of central neurologic system (CNS) tissue showed perivascular infiltrate, areas of inflammation, necrosis, and neuronal degeneration. Immunohistochemical (IHC) staining was positive when using a monoclonal antibody for enterovirus 71 (EV71), a picornavirus associated with HFMD.
Comparison of the Effect of the Carbamate Herbicides, Barban and Chlorpropham, on Mrc-5 and Hela Cells
Authors: Tate J E , Palisano J R 
Published: July 2020

Abstract
Barban and chlorpropham are common carbamate herbicides that disrupt mitosis by destabilizing plant microtubules. Tubulins, protein subunits of microtubules, in plant and animal cells are highly conserved through evolution. Plant and animal cells have been shown to possess similar microtubule structural proteins, microtubule binding proteins, and organizational proteins. These similarities suggest that herbicides targeting plant microtubules might also affect animal microtubules. Previous tubulin immunofluorescence microscopic studies of HeLa cells, a human cervical cancer cell line, have shown that barban is strongly cytoskeletotoxic and chlorpropham is weakly cytoskeletotoxic. Both barban and chlorpropham have been shown to disrupt mitosis and disorganize spindle apparatus formation in numerous types of mammalian cancer cells.
This investigation was undertaken to examine the effect of barban and chlorpropham on MRC-5 cells, a normal human fibroblast cell line, as well as on HeLa cells. A monoclonal antibody to α-tubulin, a microtubule specific protein, was used to probe the formation of spindle apparatuses in dividing cells.
Morphological Correlates of the Protection Afforded By Varma Mixture In Rat Cornea Exposed to Half Mustard (Cees).
Authors: Petrali JP , Henein M , Ali AH , Devamanoharan PS , Hamilton TA , Varma SD 
Published: July 2020

Abstract
Whole body exposure to the chemical warfare agent, mustard gas, bis-(2-chloroethyl) sulfide, or its laboratory model compound, half mustard, 2-chloroethyl ethyl sulfide (CEES), induces cutaneous, respiratory and ocular impairments. Of these, ocular damage causes the most immediate incapacitation with initial symptoms evident within minutes. This incapacitation is a result of irritation and edema of eyelids, conjunctiva and especially cornea. Development of corneal epithelial lesions and edema leads to deterioration of corneal transmissive and refractive properties with untoward effects on visual acuity. Heretofore, there has been no specific pretreatment, or antidotal therapy for mustard gas-induced ocular impairment. In the present study, we describe morphological correlates of the apparent attenuation of such damage by a mixture compound developed by Varma et al. Varma mixture (VM) consists of compounds known to provide bio-energetic support, prevent oxidative stress, modulate membrane permeability and support tissue metabolism. The mustard agent used in this study was CEES.
Demonstrating Angiogenesis In a Human Testicular Malignant Tumor Using the Scid-Maus Model. Intravital Video Microscopy and Scanning Electron Microscopy of Vascular Corrosion Casts
Authors: Aharinejad S , Schlag M , Abri H , Fink M , Nourani F , Nedwed S , Schlatter P 
Published: July 2020

Abstract
Growth of malignant tumors relies on development of new vessels from the existing vessels, a process called angiogenesis. Little is known about the pattern of chronic vascular growth in the human germ cell testicular cancer. To shed light on this topic, we injected human CRL-2073 testicular cancer cells or saline (sham treated mice) into the testes of SCID-mice and studied the growth of the tumor's vasculature using intravital video microscopy (IVM) on days 7, 14, 21, 28 and 37 after injection. On each day, 4 mice were studied. To better identify microvessels, fluorescein isothiocyanate-dextran (FITC) was injected i.v. prior to IVM. After IVM, one testis was cast with Mercox and studied in a scanning electron microscope (SEM), the other was used for histology. IVM images were transferred to the computer and analyzed using the Lucia morphometry software.
Examination of Large Unilamellar Vesicles (Luvs) Using Cryo-hrsem and Cryo-Stem
Authors: Caran K L , Apkarian R P , Menger F M 
Published: July 2020

Abstract
Vesicles derive their structure from the aqueous environment surrounding and within them. It follows that traditional EM specimen preparation techniques of fixation, dehydration and drying can induce a variety of morphological changes to the membranes. Vitrification of aqueous suspensions of vesicles provides a means for observation of these structures in their fully hydrated unfixed state. Common cryogenic techniques for the visualization of these and other colloidal particles include cryo-TEM of vitrified thin films and freeze-fracture TEM (FF-TEM) of platinum replicas. We report the use of cryo-high resolution SEM (cryo- HRSEM) and cryo-STEM for the study of the morphology of membrane features of synthetic extruded vesicles.
LUVs were prepared by the extrusion method. Dried lipid films of l-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) were hydrated with 0.5 mL of Milli-Q water and stirred for 10 minutes to make suspensions (10 mM in lipids) which were extruded 19 times through a polycarbonate filter with 100 nm pores.
Quantitating Pressure-Induced Optic Nerve Injury In A Rat Model Of Glaucoma.
Authors: Johnson EC , Cepurna WO , Morrison JC 
Published: July 2020

Abstract
Elevated intraocular pressure (IOP) is the most widely recognized risk factor for glaucoma and the target of nearly all current glaucoma therapy. The goal of our laboratory is to understand mechanism by which elevated IOP results in axonal degeneration in the optic nerve.
In order to study the effects of IOP level on the optic nerve, we have developed a number of methods to modulate IOP in the rat. We sclerose the aqueous humor outflow pathways to elevate IOP for a period of weeks to produce focal optic nerve lesions. This method reproduces many of the pathological characteristics of human glaucoma. A modification of this method uses constant light (CL) housing to stabilize the normally wide circadian IOP oscillations, simplifying the correlation of IOP history with lesion size. However, the CL-stabilized IOP in untreated, fellow eyes is above the normal light phase IOP of 20 mm Hg and close to the normal dark, phase value of 30 mm Hg.
Recent Advances In Microscopy Of The Ear
Authors: Trune DR 
Published: July 2020

Abstract
Historically microscopy of the ear has been difficult because it is entirely encased in bone. This not only impeded fixation, embedding, and sectioning of the ear for histology and immunohistochemistry, but also made experimental microscopic observation of the living ear virtually impossible. Numerous recent advancements in microscopy have improved our ability to observe the delicate cellular structures of the ear, as well as utilize high magnification microscopy on living tissue for experimental and physiological studies.
Traditional immunohistochemistry at both the light and electron microscopic levels is now facilitated by better antigen preservation through improvements in decalcification, more permeable plastics, and thousands of commercially produced antibodies. Individual cell surface receptors now can be identified, as well as their upregulation by circulating steroids, drugs, antibodies, and enzymes. Cochlear tissues also can be completely dissociated and the electrophysiology of individual living hair cells recorded with microelectrodes while under microscopic observation.
Surface Morphological Changes Of Hela Cells Exposed To Tamoxifen And Taxol
Authors: Majumdar SK , Valdellon J 
Published: July 2020

Abstract
Tamoxifen and taxol are two promising chemotherapeutic agents currently used in cancer treatment, but each has its own unique mechanism of action. Tamoxifen, known to inhibit the activity of estrogen on malignant mammary gland cells, was recently approved by the FDA for the treatment of breast cancer. Taxol, extracted from the Pacific Yew tree, Taxus brevifolia, is an antimitotic agent that binds specifically to the β-subunit, promoting the assembly and stabilization of tubulin polymers. Studies have shown that tamoxifen and taxol induce cytostatic and cytotoxic effects leading to the death of several cancer cell types in vitro.In this research, the surface ultrastructural effects of both tamoxifen and taxol were investigated in human cervical cancer cells (HeLa).
Exponentially growing cells were treated with 5, 10, 15, and 20 μg/ml of tamoxifen and 1 μg/ml of taxol (LC50) for 24, 48, 72, and 96 hours. For scanning electron microscopy (SEM), the cells were grown on coverslips, fixed in 2% glutaraldehyde followed by 1% osmium tetroxide.
Dynamics Of Mitochondria In ρ° Human Cells Repopulated With Exogenous Mtdna Observed By Transmission Electron Microscopy
Authors: Lu Yun , King Michael P 
Published: July 2020

Abstract
Mitochondrial DNA (mtDNA) mutations have been found associated with several neuromuscular diseases. In order to address further mechanisms of pathogenesis of the specific mtDNA mutations in responsible for these diseases, the ρ° human cell culture system has been established and has been widely used in recent years (4)'(5). This system is based upon the repopulating of human cells, which are completely depleted of mtDNA (termed ρ° cells), with exogenous mitochondria containing the mtDNA of interest. Molecular genetic and biochemical analysis showed that transformants can be obtained with various mitochondrial donors and the respiratory competence can be restored. In this study, the ultrastructural and immunocytochemical variations of mitochondria in human cell lines cultured in this system observed by transmission electron microscopy are reported.
Cell cultures for wild-type 143B, ρ206, and transmitochondrial cell lines have been described previously. Cells were trypsinized and collected from individual culture plates, and then were fixed with 3% paraformaldehyde and 0.04% glutaradehyde in 0.1 M phosphate-buffered saline (PBS) with 4% sucrose (pH 7.6) at RT.
Ultrastructure Of Conidium And Disjunctor Development In The Plant Pathogenic Fungus Monilinia Vaccinii-Corymbosi
Authors: Mims C W , Richardson E A 
Published: July 2020

Abstract
Monilinia vaccinii-corymbosi is the cause of mummy berry disease of commercial blueberries (Vaccinium spp.) grown in the United States and Canada (1). Ovaries of blueberry flowers are infected by the conidia (asexual spores) of this pathogen. However, despite their importance in disease initiation, little is known of the ultrastructural features of these conidia. The only ultrastructural data on these spores has come from the work of Batra (2) who used scanning electron microscopy to describe the morphology of the so-called “disjunctors” which connect adjacent conidia of M. vaccinii-corymbosi. The presence or absence of disjunctors is an important taxonomic character in the genus Monilinia (1) but little is known of their development and exact nature. The objective of this study was, therefore, to elucidate details of conidium and disjunctor development in M. vaccinii-corymbosi.