Scintillation and autoradiographic studies on 63 nickel uptake in Pseudomonas tabaci

1984 ◽  
Vol 69 (1) ◽  
pp. 87-105
Author(s):  
R.H. Al-Rabaee ◽  
D.C. Sigee
Keyword(s):  
Acetic Acid ◽  
Electron Microscope ◽  
Physical Development ◽  
Bacterial Cells ◽  
Electron Microscope Autoradiography ◽  
Resolution Electron ◽  
Nickel Uptake ◽  
Microscope Autoradiography ◽  
High Resolution Electron Microscope ◽  
Silver Grains

Scintillation studies on the uptake of 63Ni2+ by Pseudomonas tabaci demonstrate an incorporation of approximately 2.5 nmol per 10(10) bacterial cells, in medium containing 12 nmol (8.3 microCi) per ml. Over 80% of the incorporated Ni2+ is lost from the cells during washing, fixation and dehydration with ethanol. The remaining insoluble (bound) 63Ni2+ has the highest level in cells fixed in acetic acid/ethanol (0.4 nmol/10(10) cells), with smarter amounts in paraformaldehyde- and glutaraldehyde-fixed cells. The radioactive level in aldehyde-fixed cells represents a total Ni2+ uptake of about 10(−18) g or 10(4) atoms per cell. Light- and electron-microscope autoradiography corroborated the scintillation studies in demonstrating a higher retention of label by cells fixed in acetic acid/ethanol, possibly reflecting a higher retention of medium Mr proteins with this type of fixation. High-resolution electron-microscope autoradiography involving gold latensification with physical development demonstrated a clear localization of silver grains to the central nucleoid region (seen most clearly over the discrete nucleoid of aldehyde-fixed cells) and within this to the chromatin (seen most clearly over the condensed chromatin of acetic acid/ethanol-fixed cells). It is suggested that the incorporated 63Ni2+ labels mainly central, genetically inactive DNA, while peripheral, actively transcribing DNA has little associated radioactivity. The pattern of cation association seen in this bacterium shows a number of close similarities to the situation seen in dinoflagellate cells.

Electron microscope autoradiography of isolated molecules

1978 ◽  
Vol 36 (2) ◽  
pp. 192-193
Author(s):  
M. Bouteille ◽  
E. Delain ◽  
N. Angelier
Keyword(s):  
Electron Microscope ◽  
High Efficiency ◽  
Specific Activity ◽  
Molecular Complexes ◽  
Electron Microscope Autoradiography ◽  
Microscope Autoradiography ◽  
Loop Technique ◽  
Silver Grains ◽  
Isolated Molecules

The LIGOP method of electron microscope autoradiography which consists in a combination of coating Ilford emulsion with the loop technique and developing with gold latensification and phenidon has proved to provide small, compact developed silver grains with high efficiency.This has made it possible to use this technique with very small materials such as isolated molecules of molecular complexes.The method was assayed first with 3H-Thymidine labelled T7 phages DNA molecule with 630,000 cpm/μg specific activity (fig. 1). The molecules were spread using the adsorption technique constrasted by rotatory shadowing with platinum and then subjected to autoradiography. The Labelling was sufficient to obtain quantitative data in which the spread molecules were considered as a material comparable to a “hot line”. The efficiency (45%) and the HD value (1600 Å) were calculated.The method was also applied to transcription units of pleurodeles oocytes nucleoli (fig. 2) labelled in vitro with 3H-Uridine.

The Cytoplasmic Incorporation of Tritiated Thymidine During Oogenesis in Pteridium Aquilinum

1971 ◽  
Vol 8 (2) ◽  
pp. 467-487
Author(s):  
D. C. SIGEE ◽  
P. R. BELL
Keyword(s):  
Electron Microscope ◽  
Tritiated Thymidine ◽  
Pteridium Aquilinum ◽  
Egg Cell ◽  
Cell Periphery ◽  
Short Term ◽  
Electron Microscope Autoradiography ◽  
Microscope Autoradiography ◽  
Silver Grains ◽  
Stable Molecule

The short-term incorporation of tritiated thymidine into the cytoplasm of cells undergoing oogenesis was investigated in Pteridium aquilinum using electron-microscope autoradiography. There was substantial uptake into the central cell and egg cell during the 6-h labelling period. The quantity and distribution of the label incorporated into the cytoplasm were closely similar in cells fixed immediately after the labelling period and in those immersed for a further 18 h in unlabelled thymidine. This suggested that incorporation was into a stable molecule, with little nucleoside turnover and no subsequent migration within the cytoplasm. Enzyme studies indicated that the tritiated thymidine was incorporated almost entirely into DNA, most probably the DNA undergoing replication. Within the cytoplasm the label was markedly and consistently concentrated in plastids and mitochondria. This localization was not, however, complete and 5-40% was attributable to sites in the ground cytoplasm. A gradient of incorporated label was demonstrated within the cytoplasm in both central cells and egg cells. Concentration was high adjacent to the nucleus and low at the cell periphery. This gradient could be satisfactorily explained by the distribution of the plastids and mitochondria within the cytoplasm, the labelling of the organelles being irrespective of their position. The results of statistical examination of the frequencies of the silver grains associated with the mitochondria and plastids were considered to indicate general uptake of label directly into the DNA of these organelles without nuclear participation.

Quantitation of Fluorophosphate - Reactive Esterase Sites in Rat Liver Using Electron Microscope Autoradiography

1975 ◽  
Vol 33 ◽  
pp. 466-467
Author(s):  
G. C. Budd
Keyword(s):  
Electron Microscope ◽  
Rat Liver ◽  
Smooth Endoplasmic Reticulum ◽  
Average Concentration ◽  
Electron Microscope Autoradiography ◽  
Cytoplasmic Granules ◽  
Diisopropyl Fluorophosphate ◽  
Microscope Autoradiography ◽  
Cytoplasmic Structures ◽  
Silver Grains

Following the application of 10-4 molar tritium labeled diisopropyl fluorophosphate (3H-DFP) to fresh or glutaraldehyde fixed rat liver, fluorophosphate-reactive (FPR) sites within the hepatocytes were measured using quantitative electron microscope autoradiography (EMARG). Based on the distribution of autoradiographic silver grains, most of the FPR sites were concentrated in the rough and smooth endoplasmic reticulum and associated ground cytoplasm. Cytoplasmic granules, comprising autophagic and residual granules also contained FPR sites. The average concentration of sites within each of these cytoplasmic structures was obtained from combined morphometric and grain density analyses of the EMARGs and light microscope sections of the same epoxy embedded liver specimens.

The secretion of the eggshell of Schistocerca gregaria, analysis of the kinetics of secretion in vitro by light and electron microscope autoradiography

1981 ◽  
Vol 50 (1) ◽  
pp. 225-243
Author(s):  
S.J. Kimber
Keyword(s):  
Electron Microscope ◽  
Schistocerca Gregaria ◽  
Similar Rate ◽  
Follicle Cells ◽  
Electron Microscope Autoradiography ◽  
Golgi Bodies ◽  
Microscope Autoradiography ◽  
Grain Distribution ◽  
Silver Grains

The secretion of the 2 main layers (endochorion and exochorion) of the eggshell of the desert locust Schistocerca gregaria was investigated using light and electron microscope autoradiography. Follicles undergoing endochorion secretion were labelled using a 3 min ‘pulse’ of [3H]leucine in vitro followed by a 0-115 min non-radioactive ‘chase’. Immediately after the pulse the silver grains were distributed over the cytoplasm and organelles including rough endoplasmic reticulum, while by 2 and 5 min Golgi bodies contained radioactivity. By 12 min from the beginning of the chase the cell apex containing small secretory vesicles was labelled. By 20 min most of the silver grains were over the endochorion. The half-transport time (t50) was 14–15 min (from mid pulse), the lag time was 9–10 min and the percentage transport rate was 14–15% per min. When a 3 min pulse of [3H]galactose was used to label exochorion precursors, the shorter t50 (11 min) and the clumped grain distribution in light microscope autoradiographs after 0-min chase suggested that galactose was incorporated in Golgi bodies. The secretion of exochorion precursors appears to occur at a similar rate to that of endochorion precursors (approximately 15% per min). The results indicate that the follicle cells are among the fastest secreting cells.

Electron microscopy and diffraction studies of polyimides

1983 ◽  
Vol 41 ◽  
pp. 28-29
Author(s):  
O.C. de Hodgins ◽  
K. R. Lawless ◽  
R. Anderson
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Structural Features ◽  
Inert Atmosphere ◽  
Polyimide Films ◽  
Resolution Electron ◽  
The Matrix ◽  
High Resolution Electron Microscope ◽  
Diffraction Patterns ◽  
Polymeric Samples

Commercial polyimide films have shown to be homogeneous on a scale of 5 to 200 nm. The observation of Skybond (SKB) 705 and PI5878 was carried out by using a Philips 400, 120 KeV STEM. The objective was to elucidate the structural features of the polymeric samples. The specimens were spun and cured at stepped temperatures in an inert atmosphere and cooled slowly for eight hours. TEM micrographs showed heterogeneities (or nodular structures) generally on a scale of 100 nm for PI5878 and approximately 40 nm for SKB 705, present in large volume fractions of both specimens. See Figures 1 and 2. It is possible that the nodulus observed may be associated with surface effects and the structure of the polymers be regarded as random amorphous arrays. Diffraction patterns of the matrix and the nodular areas showed different amorphous ring patterns in both materials. The specimens were viewed in both bright and dark fields using a high resolution electron microscope which provided magnifications of 100,000X or more on the photographic plates if desired.

An Analysis of Dissociation of Molecules in a High Resolution Electron Microscope

1973 ◽  
Vol 31 ◽  
pp. 486-487
Author(s):  
Mihir Parikh
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Cross Sections ◽  
Resolving Power ◽  
Peak Intensity ◽  
Molecular Film ◽  
Resolution Electron ◽  
Dissociation Cross Section ◽  
High Resolution Electron Microscope ◽  
The Stability

It is well known that the resolution of bio-molecules in a high resolution electron microscope depends not just on the physical resolving power of the instrument, but also on the stability of these molecules under the electron beam. Experimentally, the damage to the bio-molecules is commo ly monitored by the decrease in the intensity of the diffraction pattern, or more quantitatively by the decrease in the peaks of an energy loss spectrum. In the latter case the exposure, EC, to decrease the peak intensity from IO to I’O can be related to the molecular dissociation cross-section, σD, by EC = ℓn(IO /I’O) /ℓD. Qu ntitative data on damage cross-sections are just being reported, However, the microscopist needs to know the explicit dependence of damage on: (1) the molecular properties, (2) the density and characteristics of the molecular film and that of the support film, if any, (3) the temperature of the molecular film and (4) certain characteristics of the electron microscope used

Incorporation of Cholesterol into Peripheral Nerve Myelin

1972 ◽  
Vol 30 ◽  
pp. 334-335
Author(s):  
Frank A. Rawlins
Keyword(s):  
Electron Microscope ◽  
Sciatic Nerve ◽  
Electron Microscope Autoradiography ◽  
Myelin Sheaths ◽  
Microscope Autoradiography ◽  
Grain Distribution ◽  
Sciatic Nerves ◽  
Autoradiographic Analysis ◽  
Old Mice ◽  
Short Times

Several speculations exist as to the site of incorporation of preformed molecules into myelin. The possibility that an autoradiographic analysis of cholesterol-1,2-H3 incorporation at very short times after injection might shed some light in the solution of that problem led to the present experiment.Cholesterol-1,2-H3 was injected intraperitoneally into 24 tenday old mice. The animals were then sacrificed at 10,20,30,40,60,90,120 and 180 min after the injection and the sciatic nerves were processed for electron microscope autoradiography. To analyze the grain distribution in the autoradiograms of cross and longitudinal sections from each sciatic nerve myelin sheaths were subdivided into three compartments named: outer 1/3, middle 1/3 and inner 1/3 compartments.It was found that twenty min. after the injection of cholesterol -1.2-H3 (Figs. 1 and 2), 55% of the total number of grains (t.n.g) found in myelin were within the outer 1/3 compartment, 9% were within the middle 1/3 and 36% within the inner 1/3 compartment

Feasibility of Molecular Structure Determination With a High Resolution Electron Microscope

1968 ◽  
Vol 26 ◽  
pp. 338-339
Author(s):  
T. A. Welton
Keyword(s):  
Electron Microscope ◽  
Substrate Surface ◽  
Helical Axis ◽  
Base Plane ◽  
Resolution Electron ◽  
High Resolution Electron Microscope ◽  
High Degree ◽  
Degree Of Order ◽  
Purine Pyrimidine

An ultimate design goal for an improved electron microscope, aimed at biological applications, is the determination of the structure of complex bio-molecules. As a prototype of this class of problems, we propose to examine the possibility of reading DNA sequence by an imaginable instrument design. This problem ideally combines absolute importance and relative simplicity, in as much as the problem of enzyme structure seems to be a much more difficult one.The proposed technique involves the deposition on a thin graphite lamina of intact double helical DNA rods. If the structure can be maintained under vacuum conditions, we can then make use of the high degree of order to greatly reduce the work involved in discriminating between the four possible purine-pyrimidine arrangements in each base plane. The phosphorus atoms of the back bone form in projection (the helical axis being necessarily parallel to the substrate surface) two intertwined sinusoids. If these phosphorus atoms have been located up to a certain point on the molecule, we have available excellent information on the orientation of the base plane at that point, and can then locate in projection the key atoms for discrimination of the four alternatives.

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