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At least 19 recordsLinked to original sources
PubMed1989

Observations of colloidal gold labelled platelet microtubules: high voltage electron microscopy and low voltage-high resolution scanning electron microscopy.

18 nm colloidal gold-antitubulin and 4 nm colloidal gold-antitubulin were used to label microtubules in adherent, fully spread platelets. Both sizes of marker effectively labelled microtubules in the partially extracted platelets. However only the 4 nm gold penetrated the dense microfilament matrix of the inner filamentous zone so that portions of microtubules within this cytoskeletal zone could be tracked. The gold marker could be visualized well with 1 MeV high voltage transmission EM and with 5 kV or greater secondary imaging or 20 kV backscattered imaging of carbon only coated samples. 1 kV secondary imaging permitted high resolution imaging of the surface of tubules and the microfilaments with their respective associated material. Individual gold-antibody complexes were difficult to identify by shape alone due to the tendency of the antibody coats to blend together when in very close approximation and due to the presence of other molecules or molecular aggregates similar in size to the gold-antibody labels. Microtubules were seen to wind in and out of the inner and outer filamentous zones as they encircled the granulomere. Some tubules were seen to "dead end" at the peripheral web. Numerous smaller microtubule loops were present principally in the outer filamentous zone and tubules could be followed as they went from the outer filamentous zone through the inner filamentous zone and into the granulomere.

Blood Platelets↗
PubMed1998

High-voltage high-resolution electron microscopy study of alkaline-earth copper oxides.

Two families of alkaline-earth copper oxides are studied by using high-voltage high-resolution electron microscopy. One is Sr(n-1) Cu(n)O(2n-1) (n = 2, 3), the so-called spin-ladder compounds, and the other is ACuO2 (A = Ca-Sr) crystallizing in the infinite-layer structure, which is a parent structure for all copper oxide superconductors. It is demonstrated in the former compounds that oxygen columns as well as metal columns are directly imaged in a "structure" image. Moreover, twin-related lattice defects, which can be the origin of free Cu2+ spins observed previously in magnetic measurements, have been detected in SrCu2O3. An interesting irradiation effect under a 1,000-kV electron beam has been observed in the infinite-layer compound: An unusual structural phase transformation to a NaCl-type lattice is induced, accompanied by the formation of nm-size twin domains.

Copper↗
PubMedDate not supplied

Distribution and movement of membrane-associated platelet glycoproteins: use of colloidal gold with correlative video-enhanced light microscopy, low-voltage high-resolution scanning electron microscopy, and high-voltage transmission electron microscopy.

Scanning electron microscopy (SEM), especially low-voltage (1 KeV) high-resolution SEM, can be used in conjunction with stereo pair high-voltage (1 MeV) transmission electron microscopy (HVEM) of whole spread cells or thick sections effectively to correlate surface structure with internal structure. Surface features such as microvilli, pits, pseudopodia, ruffles, attached virus, and other surface-related morphologic characteristics can be identified using SEM, while underlying cytoskeletal structure and organelle organization can be viewed by HVEM of the same preparation. However, the need to "prepare" cells for electron microscopy precludes observation in the living state. The use of several types of video-enhanced light microscopy (VLM) permits observation of living cells such that certain surface and internal features can be observed at a relatively high level of resolution or detection. Thus, changes in living cells can be followed, and at appropriate times the cells may be chemically fixed or rapidly frozen and prepared for ultrastructural examination by electron microscopy. We have utilized VLM in conjunction with SEM and HVEM to correlate changes in shape and surface structure with changes in the internal structure of platelets. In addition, we have found it advantageous to use colloidal gold-labeling procedures, because these markers are detectable by all three forms of microscopy. Using this approach we have labeled platelet membrane GPIIb/IIIa, a receptor for RGD-containing adhesive proteins, with gold-fibrinogen or gold-anti-IIb/IIIa. The initial binding and subsequent movement of gold-fibrinogen-IIb/IIIa complexes in living platelets was followed by VLM. The movement of individual labels could be mapped. Subsequent observation by low-voltage (1 KeV) high-resolution SEM and HVEM permits visualization of the same individual receptors tracked by LM. The final position on the membrane or the position-in-transit when fixative was added was determined relative to surface ultrastructure (SEM) and internal, particularly cytoskeletal, ultrastructure (HVEM).

Biological Transport↗
PubMed1995

Analog-digital recording of current and voltage during high voltage DC shocks.

UNLABELLED: Efficient on-line digitization is the prerequisite for computerized analysis of the electrical phenomena occurring during defibrillation. Conventional hardware presently provides only limited time resolution. The performance of various digitization rates for recording of voltage, current, and calculation of derived quantities like impedance, energy, and defibrillator capacitance was investigated. It was assessed both experimentally and by computer simulation of a trapezoidal discharge (of 9 msec duration into a constant resistive load of 50 omega with a defibrillator capacitance of 132 microF). The accuracy achieved with different digitization rates is given. For example, an accuracy of 1% for analog-digital conversion for impedance calculation during this kind of DC shock requires a sampling rate of 8 kHz without, and a rate of 1 kHz with linear interpolation to correct for the hardware dependent error due to sequential sampling. CONCLUSION: Highly efficient analog-digital conversion of delivered voltage and current during DC shocks is available within the limits of conventional inexpensive hardware.

Algorithms↗
PubMed1996

Lambert-Eaton sera reduce low-voltage and high-voltage activated Ca2+ currents in murine dorsal root ganglion neurons.

Voltage-gated Ca2+ channels are categorized as either high-voltage activated (HVA) or low-voltage activated (LVA), and a subtype (or subtypes) of HVA Ca2+ channels link the presynaptic depolarization to rapid neuro-transmitter release. Reductions in transmitter release are characteristic of the autoimmune disorder, Lambert-Eaton syndrome (LES). Because antibodies from LES patients reduce Ca2+ influx in a variety of cell types and disrupt the intramembrane organization of active zones at neuromuscular synapses, specificity of LES antibodies for the Ca2+ channels that control transmitter release has been suggested as the mechanism for disease. We tested sera from four patients with LES. Serum samples from three of the four patients reduced both the maximal LVA and HVA Ca2+ conductances in murine dorsal root ganglion neurons. Thus, even though LES is expressed as a neuromuscular and autonomic disorder, our studies suggest that Ca2+ channels may be broadly affected in LES patients. To account for the specificity of disease expression, we suggest that incapacitation of only a fraction of the Ca2+ channels clustered at active zones would severely depress transmitter release. In particular, if several Ca2+ channels in a cluster are normally required to open simultaneously before transmitter release becomes likely, the loss of a few active zone Ca2+ channels would exponentially reduce the probability of transmitter release. This model may explain why LES is expressed as a neuromuscular disorder and can account for a clinical hallmark of LES, facilitation of neuromuscular transmission produced by vigorous voluntary effort.

Action Potentials↗
PubMed2001

High-voltage electron microscope high-temperature in situ straining experiments to study dislocation dynamics in intermetallics and quasicrystals.

The dynamic behaviour of dislocations in several intermetallic alloys, studied by in situ straining experiments in a high-voltage electron microscope, is compared at room temperature and at high temperatures. In contrast to room temperature, the dislocations move viscously at high temperatures, which is explained by diffusion processes in the dislocation cores. In quasicrystals, the viscous dislocation motion can be interpreted by models on the cluster scale.

Journal Article↗
PubMed1998

[The treatment and rehabilitation of high-voltage electric burns].

High-voltage electric burns is refractory with high rate of amputation (46%) in early stage and unfavorable functional recovery in later stage. Little breakthrough has so far been made in this respect. From Jan. 1985 to Jan. 1996, ninety-six cases with high-voltage burns were treated in our department. Seventy-one cases of various tissue flap grafting were applied to treat early electric burns, among which sixty-four cases were successful. The amputation rate was reduced to 30%. Postoperatively, a long-term rehabilitation training at home was carried out. Most of them achieved a good appearance of the wounded sites and limbs and satisfactory ability to work or self-care. It was suggested that early thorough debridement of necrosis tissue, careful reservation of living tissue, appropriate choice of tissue flap and postoperative rehabilitation training were of great importance to achieve a good prognosis.

Adolescent↗
PubMed1992

Measurement of neuronal surface area using high-voltage electron microscope tomography.

High-voltage electron microscopy (HVEM) and axial tomography were used to reconstruct the three-dimensional structure of dendrites of intracellularly stained neostriatal spiny neurons. Neurons were stained using iontophoretic injection of horseradish peroxidase from an intracellular micropipet. Thick sections were cut on a vibratome, reacted with diaminobenzidine, and embedded in plastic. High-voltage electron microscopy was used to obtain high-resolution images of neuronal processes in 2- to 3-micron plastic sections cut from those blocks. Series of high-voltage electron micrographs were taken at 2 degrees increments of specimen tilt over a range of at least +/- 60 degrees, and three-dimensional reconstructions were generated from the series using an R-weighted backprojection method. An interactive procedure was used to draw the dendritic profiles from slices through the reconstructed volume and to measure volumes and surface areas of the dendrites. Values obtained in this manner matched previous findings using reconstruction from serial thin sections. The HVEM-tomography method offers an alternative to the serial-thin-section method for the quantitative analysis of neuronal shape.

Animals↗
PubMed1994

Understanding the neostriatal microcircuitry: high-voltage electron microscopy.

High voltage electron microscopy (HVEM) and HVEM tomography of selectively stained cell processes in the neostriatum have offered an alternative to serial thin section reconstruction for accurate 3-D visualization and measurement of axons, dendrites, and dendritic spines. Tissue preparation is simple and rapid, allowing examination of large numbers of specimens required for quantitation of neuronal morphology. The resolution of the images exceeds that available from any light microscopic technique and is appropriate for measurement of the finest axons and dendritic spine necks. HVEM tomography allows the direct measurement of dendritic surface area, required for computational modeling of synaptic integration.

Humans↗
PubMed1988

Electrophysiological and ultrastructural studies on reversible neural conduction disturbance after high voltage discharge.

High-voltage condenser discharges exerting a field strength of up to 1000 V/cm (discharge time constant 0.24-8 msec) applied to isolated sciatic frog nerve lead to disturbances of the propagation of action potentials including transient complete block of conduction. Such conduction disturbances are normally reversible within minutes. Inhibition of the activity of the membrane-bound Na+-K+ATPase prevents the recovery from conduction block. Withdrawal of external Ca2+ also prevents recovery, whereas blockade of protein synthesis by cycloheximide has no influence. The velocity of recovery depends on the temperature, with temperature coefficients (Q10) from 1.31 to 1.84 between 2 degrees and 30 degrees C. Transmission electron microscopy of nerves subjected to strong discharges shows alterations of the myelin sheath (splitting and cleft formation) which are, however, not specific for this mechanism of injury. No alterations are seen in the region of the free axoplasmic membrane of the node of Ranvier or in organelles. The results suggest a breakdown of the transmembrane ionic gradient causing the conduction disturbance.

Action Potentials↗
PubMedDate not supplied

In vivo noninvasive evaluation of hairless rat skin after high-voltage pulse exposure.

Short high-voltage pulses have recently been shown to dramatically increase and expedite transdermal drug transport via a mechanism hypothesized to involve electroporation. This study addresses tolerance issues of the method in vivo in hairless rat. Chromametry, transepidermal water loss (TEWL), laser Doppler flowmetry (LDF) and corneometry were jointly used for noninvasive sensing of skin biophysical parameters. Slight increases in skin redness, TEWL and LDF values followed the application of electric pulses. The changes in skin capacitance were nonsignificant. The magnitude of the alterations depended on the electrical features of the pulses. When compared to iontophoresis, high-voltage pulses did not induce stronger alterations of skin functions. This report provides the first in vivo demonstration of the safety of the high-voltage pulses proposed for transdermal delivery.

Animals↗
PubMed1975

Human nervous system tumors. Observations by high voltages electron microscopy.

Thick sections (0.5--2 mu) of biopsies from human nervous system tumors (Schwannoma, ependymoma, medulloblastoma), fixed in aldehydes followed by osmium, and stained with uranyl acetate and lead, have been studied at 2.5 MV, and compared to thin sections of the same material observed by ordinary low voltage electron microscopy. High voltage electron microscopy permits direct observation of cell fine structure in three dimensions, including the spatial relations of organelles. Details of contours of nuclear envelopes, shapes of mitochondria, fine aspects of the structure of cell surfaces and processes, such as the flat sheet-like and irregular cylindrical processes of Schwannoma cells, the small projections and ridges on their surfaces, and microvilli and cilia of ependymoma cells, and other features have been observed. These initial observations demonstrate the applicability of high voltage electron microscopy to further study of neural neoplasms.

Adolescent↗
PubMed1995

Multiple second messenger routes enhance two high-voltage-activated calcium currents in molluscan neuroendocrine cells.

Two types of high-voltage-activated calcium currents were identified in whole-cell voltage-clamp recordings of the neuroendocrine caudodorsal cells, which control egg-laying in the freshwater snail Lymnaea stagnalis. The currents were: (i) a rapidly inactivating high-voltage-activated current, with an activation threshold of -40 mV and maximal amplitude at +10 mV; and (ii) a slowly inactivating high-voltage-activated current, with a threshold of -10 mV and a peak at +30 mV. Both currents were reduced by nifedipine and verapamil, but not by omega-conotoxin GVIA, suggesting that they belong to the L-type family of calcium currents. The voltage-dependence of inactivation of the rapidly inactivating high-voltage-activated current was bell-shaped. Time-constants of inactivation ranged from 10 to 25 ms. Steady-state inactivation was characterized by a potential of half maximal inactivation of -21.7 +/- 3.4 mV and a slope factor of 8.1 +/- 1.7 mV. The voltage-dependence of inactivation of the slowly inactivating high-voltage-activated current was S-shaped. Time-constants of inactivation increased with depolarization up to a maximum of 300 ms. The steady-state inactivation parameters were a potential of half maximal inactivation of +6.8 +/- 2.2 mV and a slope factor of 6.0 +/- 1.1 mV. The membrane-permeable analog of cAMP, 8-chlorophenylthio-cyclic AMP, predominantly increased the slowly inactivating high-voltage-activated current, and shifted its voltage-dependence of activation and inactivation 10 mV to the left. The rapidly inactivating high-voltage-activated current was slightly increased by 8-chlorophenylthio-cyclic AMP. 8-Bromo-cyclic GMP and the phorbol ester, 12-O-tetradecanoyl-13-phorbol acetate, had qualitatively similar effects. Both agents enhanced the rapidly inactivating current and, to a lesser degree, the slowly inactivating current, without affecting their voltage-dependence. The cyclic AMP-dependent protein kinase inhibitor, Walsh inhibitor peptide, antagonized the stimulating effect of 8-chlorophenylthio-cyclic AMP. The broad-spectrum protein kinase inhibitor 1-(5-isoquino-linylsulfonyl)-2-methyl-piperazine (H-7) strongly attenuated the effects of 8-chlorophenylthio-cyclic AMP, 8-bromo-cyclic GMP and 12-O-tetradecanoyl-13-phorbol acetate, suggesting that all treatments increase both types of high-voltage-activated calcium currents through phosphorylation of the channel-complex.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗