scholarly journals SUBMICROSCOPIC ORGANIZATION OF THE POSTSYNAPTIC MEMBRANE IN THE MYONEURAL JUNCTION

1963 ◽  
Vol 17 (3) ◽  
pp. 571-586 ◽  
Author(s):  
Bertalan Csillik
Keyword(s):  
Nitrate Solution ◽  
Lead Nitrate ◽  
Postsynaptic Membrane ◽  
Molecular Organization ◽  
Polarization Microscopy ◽  
Striated Muscles ◽  
Electron Microscopic ◽  
Supramaximal Stimulation ◽  
Subneural Apparatus ◽  
Good Agreement

Cross-striated muscles of frogs and rats were fixed in 3.3 per cent lead nitrate solution. Frozen sections 30 micra thick were mounted in different media and observed by polarization microscopy. The subneural apparatus of myoneural junctions exhibits a strong birefringence in these sections. Birefringence is exerted by a highly organized lipoprotein framework (postsynaptic material) which builds up the "organites" (junctional folds) of the postsynaptic membrane. Synaptic cholinesterase is closely associated with this material. Freezing and/or formalin fixation results in a destruction of the molecular organization of the postsynaptic material, but does not influence the synaptic enzyme activity. It is hypothesized from this study that the junctional folds (postsynaptic "organites") consist of regularly arranged, sheet-like lamellar micellae in the frog and of less regular, mainly radially arranged submicroscopic units in the rat. The micellar organization as revealed by polarization analysis is in good agreement with the electron microscopic findings reported in the literature. Intramicellar protein molecules of the resting postsynaptic membrane are arranged longitudinally, lipids transversely. Supramaximal stimulation or treatment with acetylcholine + eserine results in a disorganization of proteins and a rearrangement of lipids. Denervation results in a rearrangement of lipids without any significant alterations of proteins. All these functional stresses influence only the molecular and not the micellar structure of the membrane. The function of the organized lipoprotein framework as an acetylcholine receptor is suggested.

THE MOLECULAR ORGANIZATION OF HUMAN ALPHA 2-MACROGLOBULIN. AN IMMUNO ELECTRON MICROSCOPIC STUDY WITH MONOCLONAL ANTIBODIES

1987 ◽  
Author(s):  
E Delain ◽  
M Barrav ◽  
J Tapon-Bretaudière ◽  
F Pochon ◽  
F Van Leuven
Keyword(s):  
Monoclonal Antibodies ◽  
Binding Sites ◽  
Divalent Cations ◽  
The Other ◽  
Molecular Organization ◽  
Cellular Receptor ◽  
Electron Microscopic ◽  
Microscopic Method ◽  
Bait Region ◽  
Electron Microscopic Method

Electron microscopy is a very convenient method to localize the epitopes of monoclonal antibodies (mAbs) at the surface of macromolecules for studying their tree-dimensional organization.We applied this immuno-electron microscopic method to human ct2-macroglobulin (ct2M). 29 anti-α2M mAbs have been tested with the four different forms of a2M : native and chymotrypsin-transformed tetramers, and the corresponding dimers, obtained by dissociation with divalent cations. These mAbs can be classified in three types : those which are specific for 1) the H-like transformed molecules, 2) the native molecules, and 3) those which can react with both forms of α2M.1) Among the H-like α2M specific mAbs, several react with the 20 kD-domain which is recognized by the cellular receptor of transformed a2M. This domain is located at the carboxyterminal end of each monomer. One IgG binds to the end of two adjacent tips of the H-like form.The other mAbs of this type bind to the α2M tips at non-terminal positions. Intermolecular connections built polymers of alternating α2M and IgG molecules.2) Among the native a2M-specific mAbs some are able to inhibit the protease-induced transformation of the native α2M. The binding sites of these mAbs are demonstrated on the native half-molecules. One of these mAbs was also able to react with transformed dimers, in a region corresponding very likely to an inaccessible epitope in the tetrameric transformed α2M molecule.3) Among the mAbs of this type, only two were able to inhibit the protease-induced transformation of α2M. Obviously, their epitopes should be close to the bait region of α2M. The other mAbs reacting with both α2M forms did not inhibit the α2M transformation.All these mAbs can be distinguished by the structure of the immune complexes formed with all forms of α2M. The epitopes are more easily located on the dimers and on the H-like transformed α2M than on the native molecules.From these observations, we propose a new model of the tree-dimensional organization of the human α2M in its native and transformed configurations, and of its protease-induced transformation.

An Electron Microscopic Study of the Muscle-fibres of the Diaphragm

1951 ◽  
Vol s3-92 (19) ◽  
pp. 323-332
Author(s):  
M. M. BLUHM ◽  
C. SITARAMAYYA
Keyword(s):  
Sarcomere Length ◽  
Muscle Fibres ◽  
Striated Muscles ◽  
Rat Diaphragm ◽  
Electron Microscopic ◽  
Adult Type ◽  
Isotonic Contraction ◽  
Acetyl Choline ◽  
Adult Rat ◽  
Passive Stretching

Myofibrils of rat diaphragm of various ages, in different states of activity, after denervation, and after acetyl choline contracture, were studied by electron microscopy. A comparative study of other rodent diaphragms and of human diaphragm was also made. Myofibrils from diaphragm are similar to those of other striated muscles. The differentiation into A and I bands is due to differences in the substance present round the actomyosin filaments in those regions. The Z disk is extra-sarcomere; it-appears even before any differentiation of the fibril into A and I bands is recognizable. At the age of about 42 days, the myofibrils in rat diaphragm are completely differentiated and conform tothe adult type. The sarcomere length in adult rat diaphragm is between 2 and 3 µ. The adult rat diaphragm contains two types of fibrils which differ, though not sharply, in their extensibility and thickness. The A and I bands react differently to a variety of stimuli. Thus, passive stretching affects the I band almost exclusively, while contraction affects both bands; here, again, the effect depends on the type of contraction; isotonic contraction shortens both A and I, whereas isometric contraction shortens A and lengthens I. In the denervated muscle the A band is shortened. On thewhole, the A band seems to play the major role in contraction. The H disk is intra-sarcomere and appears during contraction, especially when the muscle is stimulated in the stretched state. The M and N lines also are intra-sarcomere. Evidence regarding their nature and appearance is discussed.

Influence of Manganese Ions on the Electrodeposition Process of Lead Dioxide in Lead Nitrate Solution

2019 ◽  
Vol 55 (5) ◽  
pp. 364-369
Author(s):  
Yingwu Yao ◽  
Chunjiao Huang ◽  
Haishu Dong ◽  
Feng Wei ◽  
Xin Chen
Keyword(s):  
Lead Dioxide ◽  
Nitrate Solution ◽  
Lead Nitrate ◽  
Manganese Ions ◽  
Electrodeposition Process

Detection of endogenous magnetic nanoparticles with a tunnelling magneto resistance sensor

2010 ◽  
Vol 368 (1927) ◽  
pp. 4371-4387 ◽  
Author(s):  
A. Ionescu ◽  
N. J. Darton ◽  
K. Vyas ◽  
J. Llandro
Keyword(s):  
Magnetic Nanoparticles ◽  
Magnetite Nanoparticles ◽  
Quantum Interference ◽  
Blocking Temperature ◽  
Superconducting Quantum Interference Device ◽  
Electron Microscopic ◽  
Freeze Dried ◽  
Shell Forming ◽  
Magneto Resistance ◽  
Good Agreement

The magnetotactic bacterium Magnetospirillum sp. has been cultured and the properties of its endogenous magnetic nanoparticles characterized. Electron-microscopic analyses indicate that the endogenous magnetite nanoparticles in Magnetospirillum sp. are coated with a 3–4 nm thick transparent shell, forming a magnetosome. These magnetite nanoparticles had diameters of 50.9±13.3 nm, in good agreement with the diameter of 40.6±1.2 nm extracted from magnetometry. Each Magnetospirillum sp. bacterium contained chains of 5–25 magnetosomes. Superconducting quantum interference device magnetometry results indicate that the extrinsic superparamagnetic response of the bacterial solution at room temperature can be attributed to the reversal of the magnetization by physical rotation of the nanoparticles. The intrinsic blocking temperature of a sample of freeze-dried bacteria was estimated to be 282±13 K. A tunnelling magneto resistance sensor was used to detect the stray fields of endogenous magnetic nanoparticles in static and quasi-dynamic modes. Based on the tunnelling magneto resistance sensor results, the magnetic moment per bacterium was estimated to be approximately 2.6×10 −13  emu. The feasibility of this detection method either as a mass-coverage device or as part of an integrated microfluidic circuit for detection and sorting of magnetosome-containing cells was demonstrated.

scholarly journals Structure of C protein purified from cardiac muscle.

1985 ◽  
Vol 100 (1) ◽  
pp. 208-215 ◽  
Author(s):  
H C Hartzell ◽  
W S Sale
Keyword(s):  
Cardiac Muscle ◽  
Gel Filtration ◽  
Thick Filament ◽  
Protein Molecule ◽  
Striated Muscles ◽  
Electron Microscopic ◽  
C Protein ◽  
Chicken Heart ◽  
Structural Support ◽  
Electron Microscopic Data

C protein is a component of the thick filament of striated muscles. Although the function of C protein remains unknown, a variety of evidence suggests that C protein may regulate actin-myosin interaction or be involved in structural support or elasticity of the sarcomere. We have previously proposed (Hartzell, H. C., 1984, J. Gen. Physiol., 83:563-588) that C protein is involved in regulating twitch relaxation in cardiac muscle. To gain further insight into the function of C protein, we have studied the structure of C protein purified from chicken heart. C protein was purified from extracts of detergent-washed myofibrils by sequential hydroxylapatite and DEAE-Sephacel chromatography. C protein was judged greater than 95% pure by SDS PAGE. The polypeptide subunit had a molecular weight of 155,000 and the native molecule sedimented on linear sucrose or glycerol gradients at 4-5S. For electron microscopy, purified C protein was dialyzed and diluted into a volatile buffer in 50% glycerol, aspirated onto mica, dried under vacuum, and rotary platinum-shadowed. Replicas revealed particles of relatively homogeneous overall dimensions. Over half of the particles were V-shaped. The "arm" lengths of the V-shaped particles were 22 +/- 4.5 nm (SD). Gel filtration on Sephacryl S-300 demonstrated that purified C protein had a Stokes' radius of 5.07 nm. Measurements of viscosity gave an intrinsic viscosity of 16.5 cm3/g. These data are consistent with the electron microscopic data and suggest that C protein in heart muscle is asymmetric. The C protein molecule is large enough to extend from the surface of a thick filament to adjacent thin or thick filaments.

scholarly journals ADSORTION ISOTHERM OF LEAD ON CALCIUM CARBONATE

2019 ◽  
Vol 50 (Special) ◽  
Author(s):  
Al-Hassoon & et al.
Keyword(s):  
Calcium Carbonate ◽  
Adsorption Capacity ◽  
Mathematical Description ◽  
Nitrate Solution ◽  
Lead Nitrate ◽  
High Capacity ◽  
Langmuir Equation ◽  
Bonding Energy ◽  
Lead Adsorption ◽  
Single Batch

This study investigate the effect of concentration of lead ions (Pb2+) at 0,1, 2, 3, 4, 5, 10,20,30, 40,50 and 100 mg L-1, concentrations of the quantity of the adsorbed Pb on surface of calcium carbonate at a temperature of 298° Kelvin with all other variables remained constant, was carried out and this experiment was conducted in a single batch and using lead nitrate solution . The results showed that quantity of the adsorbed lead increased from 2.6 to 1924 mg kg-1 Calcium carbonate, and when single and two surface  Langmuir, Freundlich, Temkin, Dubinin and Polani equations were applied, they were able to describe lead adsorption on the surface of calcium carbonate at the used concentrations. The two surface Langmuir equation was  most efficient in used mathematical description of  lead adsorption, and the bonding energy (K) with the first and second surfaces were  4.02 and 1613.42 L mg-1 respectively. The adsorption capacity (Xm) values with the first and second surfaces were 0.25 and 0.89 mg    kg -1 respectively , and this clearly indicated to high capacity of the second surface (carbonate surface) to adsorb lead.

scholarly journals Differences in structure and distribution of the molecular forms of acetylcholinesterase.

1989 ◽  
Vol 108 (6) ◽  
pp. 2301-2311 ◽  
Author(s):  
S N Abramson ◽  
M H Ellisman ◽  
T J Deerinck ◽  
Y Maulet ◽  
M K Gentry ◽  
...  
Keyword(s):  
Electric Organ ◽  
Synaptic Cleft ◽  
Postsynaptic Membrane ◽  
Molecular Forms ◽  
Local Concentration ◽  
Differential Distribution ◽  
Electron Microscopic ◽  
Catalytic Subunits ◽  
Electric Organs ◽  
Asymmetric Form

Two structurally distinct molecular forms of acetylcholinesterase are found in the electric organs of Torpedo californica. One form is dimensionally asymmetric and composed of heterologous subunits. The other form is hydrophobic and composed of homologous subunits. Sequence-specific antibodies were raised against a synthetic peptide corresponding to the COOH-terminal region (Lys560-Leu575) of the catalytic subunits of the asymmetric form of acetylcholinesterase. These antibodies reacted with the asymmetric form of acetylcholinesterase, but not with the hydrophobic form. These results confirm recent studies suggesting that the COOH-terminal domain of the asymmetric form differs from that of the hydrophobic form, and represent the first demonstration of antibodies selective for the catalytic subunits of the asymmetric form. In addition, the reactive epitope of a monoclonal antibody (4E7), previously shown to be selective for the hydrophobic form of acetylcholinesterase, has been identified as an N-linked complex carbohydrate, thus defining posttranslational differences between the two forms. These two form-selective antibodies, as well as panselective polyclonal and monoclonal antibodies, were used in light and electron microscopic immunolocalization studies to investigate the distribution of the two forms of acetylcholinesterase in the electric organ of Torpedo. Both forms were localized almost exclusively to the innervated surface of the electrocytes. However, they were differentially distributed along the innervated surface. Specific asymmetric-form immunoreactivity was restricted to areas of synaptic apposition and to the invaginations of the postsynaptic membrane that form the synaptic gutters. In contrast, immunoreactivity attributable to the hydrophobic form was selectively found along the non-synaptic surface of the nerve terminals and was not observed in the synaptic cleft or in the invaginations of the postsynaptic membrane. This differential distribution suggests that the two forms of acetylcholinesterase may play different roles in regulating the local concentration of acetylcholine in the synapse.

Volume and osmotic properties of human neutrophils

Blood ◽  
1993 ◽  
Vol 81 (10) ◽  
pp. 2774-2780 ◽  
Author(s):  
HP Ting-Beall ◽  
D Needham ◽  
RM Hochmuth
Keyword(s):  
Network Formation ◽  
Membrane Surface ◽  
Surface Membrane ◽  
Human Neutrophils ◽  
Electron Microscopic ◽  
Membrane Area ◽  
Membrane Surface Area ◽  
Transmission Electron ◽  
Spherical Cells ◽  
Good Agreement

Quantitative models describing the dynamics of human neutrophils in the microcirculation require accurate morphometric parameters such as volume and surface membrane area. Using both a micropipette technique and video light microscopy (LM) to measure the diameters of the spherical cells, we have accurately determined the volume of the human neutrophil. Our value, 299 +/- 32 microns 3, is in good agreement with our earlier results, but 55% larger than that reported by Schmid- Schonbein et al (Blood 56:866, 1980). However, the measurements of Schmid-Schonbein et al were based on the actual mass of the cells derived from transmission electron microscopic (TEM) images. The membrane surface area, at lysis, was calculated to be 2.6 times its initial projected area. After lysis, the cells do not reduce their size, indicative of the possibility of a F-actin network formation that would stiffen the structure. Further, we show that neutrophils behave as ideal osmometers when exposed to anisotonic solutions at 21 degrees C, as predicted by the Boyle-Van't Hoff relationship. The calculated Ponder's value, R, is 0.77, which corresponds to 77% of the cell volume being osmotically active under isotonic conditions. However, at 37 degrees C, the cells are able to regulate their volumes toward the original volumes after an osmotic stress.

Lead Hydroxide Nanowires Obtained from Lead Nitrate Solution by Adding Chloride Ions

2010 ◽  
Vol 123-125 ◽  
pp. 719-722 ◽  
Author(s):  
Jin Cheng ◽  
Xiao Ping Zou ◽  
Xiang Min Meng ◽  
Gang Qiang Yang ◽  
Xue Ming Lü ◽  
...  
Keyword(s):  
Sodium Chloride ◽  
Nitrate Solution ◽  
Lead Nitrate ◽  
Chloride Ions ◽  
Solution Phase ◽  
Controlled Experiments ◽  
Selected Area Electron Diffraction ◽  
Nitrate Precursor ◽  
Lead Hydroxide ◽  
Phase Chemical

The synthesis of lead hydroxide nanowires by solution-phase chemical reactions of lead nitrate with alkali by adding sodium chloride was reported. The obtained lead hydroxide nanowires have a length of a few micrometers and a diameter of about several tens of nanometers. The selected-area electron diffraction reveals that these lead hydroxide nanowires are single crystalline. Controlled experiments indicate that lead hydroxide nanowires prefer to form at higher concentration of chloride ions in lead nitrate precursor solutions, such as Cl- : Pb2+ = 5:1 and 6:1.

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