Freeze-Etching Simplified

1968 ◽  
Vol 26 ◽  
pp. 102-103
Author(s):  
Russell L. Steere
Keyword(s):  
Electron Microscopy ◽  
Special Equipment ◽  
Specimen Tube ◽  
Freeze Etching ◽  
The Cost

Freeze-etching, as a tool in the preparation of biological specimens for electron microscopy, has seen relatively little use since it was introduced in 1957. The involved procedure, originally described, and, until recently, the cost of special equipment, must certainly have played a part in the failure of freeze-etching to become a commonly used technique. Efforts to solve some of the problems have resulted in the development of a modified freeze-etching module that can fit on nearly any vacuum evaporator and will permit the production of good specimens by an unskilled technician in less than one-half hour.The freeze-etching module (Fig. 1) consists of a collar (A) with two opposing hollow tubes supported by small collars so that the specimen end of the specimen tube (D) can rotate within the rotatable cold shroud (F).

Freeze-Fracture Replication of Frozen Outer Segments of Rat Retinal Rods

1969 ◽  
Vol 27 ◽  
pp. 392-393
Author(s):  
Thomas S. Leeson ◽  
C. Roland Leeson
Keyword(s):  
Electron Microscopy ◽  
Cross Section ◽  
Outer Segment ◽  
Freeze Fracture ◽  
X Ray Diffraction ◽  
X Ray ◽  
Outer Segments ◽  
Retinal Rods ◽  
Temperature Electron ◽  
Freeze Etching

Numerous previous studies of outer segments of retinal receptors have demonstrated a complex internal structure of a series of transversely orientated membranous lamellae, discs, or saccules. In cones, these lamellae probably are invaginations of the covering plasma membrane. In rods, however, they appear to be isolated and separate discs although some authors report interconnections and some continuities with the surface near the base of the outer segment, i.e. toward the inner segment. In some species, variations have been reported, such as longitudinally orientated lamellae and lamellar whorls. In cross section, the discs or saccules show one or more incisures. The saccules probably contain photolabile pigment, with resulting potentials after dipole formation during bleaching of pigment. Continuity between the lamina of rod saccules and extracellular space may be necessary for the detection of dipoles, although such continuity usually is not found by electron microscopy. Particles on the membranes have been found by low angle X-ray diffraction, by low temperature electron microscopy and by freeze-etching techniques.

scholarly journals Fracture faces of frozen membranes: 50th anniversary

2016 ◽  
Vol 27 (3) ◽  
pp. 421-423
Author(s):  
Daniel Branton
Keyword(s):  
Electron Microscopy ◽  
Lipid Bilayers ◽  
Fracture Process ◽  
Relative Proportion ◽  
50Th Anniversary ◽  
Biological Membranes ◽  
Bilayer Membrane ◽  
Biological Cells ◽  
Membrane Surfaces ◽  
Freeze Etching

In 1961, the development of an improved freeze-etching (FE) procedure to prepare rapidly frozen biological cells or tissues for electron microscopy raised two important questions. How does a frozen cell membrane fracture? What do the extensive face views of the cell’s membranes exposed by the fracture process of FE tell us about the overall structure of biological membranes? I discovered that all frozen membranes tend to split along weakly bonded lipid bilayers. Consequently, the fracture process exposes internal membrane faces rather than either of the membrane’s two external surfaces. During etching, when ice is allowed to sublime after fracturing, limited regions of the actual membrane surfaces are revealed. Examination of the fractured faces and etched surfaces provided strong evidence that biological membranes are organized as lipid bilayers with some proteins on the surface and other proteins extending through the bilayer. Membrane splitting made it possible for electron microscopy to show the relative proportion of a membrane’s area that exists in either of these two organizational modes.

scholarly journals Visual multiple cross displacement amplification for the rapid identification of S. agalactiae immediately from vaginal and rectal swabs

AMB Express ◽  
2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Xueqin Cheng ◽  
Zhiqian Dou ◽  
Jing Yang ◽  
Dexi Liu ◽  
Yulong Gu ◽  
...  
Keyword(s):  
Pathogen Detection ◽  
Clinical Specimen ◽  
Rapid Identification ◽  
Sample Collection ◽  
Special Equipment ◽  
Multiple Cross ◽  
Rectal Swabs ◽  
Cost Efficient ◽  
The Cost ◽  
Positive Results

AbstractStreptococcus agalactiae (S. agalactiae) is an important pathogen that can lead to neonatus and mother infection. The current existing techniques for the identification of S. agalactiae are limited by accuracy, speed and high-cost. Therefore, a new multiple cross displacement amplification (MCDA) assay was developed for test of the target pathogen immediately from vaginal and rectal swabs. MCDA primers screening were conducted targeting S. agalactiae pcsB gene, and one set of MCDA primers with better rapidity and efficiency was selected for establishing the S. agalactiae-MCDA assay. As a result, the MCDA method could be completed at a constant temperature of 61 °C, without the requirement of special equipment. The detection limit is 250 fg (31.5 copies) per reaction, all S. agalactiae strains displayed positive results, but not for non-S. agalactiae strains. The visual MCDA assay detected 16 positive samples from 200 clinical specimen, which were also detected positive by enrichment/qPCR. While the CHROMagar culture detected 6 positive samples. Thus, the MCDA assay is prefer to enrichment/qPCR and culture for detecting S. agalactiae from clinical specimen. Particularly, the whole test of MCDA takes about 63.1 min, including sample collection (3 min), DNA preparation (15 min), MCDA reaction (45 min) and result reporting (6 s). In addition, the cost was very economic, with only US$ 4.9. These results indicated that our S. agalaciae-MCDA assay is a rapid, sensitive and cost-efficient technique for target pathogen detection, and is more suitable than conventional assays for an urgent detection, especially for 'on-site' laboratories and resource-constrained settings.

DURATION OF ACARICIDAL ACTION OF THE DRUG «KENEM» AND ECONOMIC JUSTIFICATION FOR THE PROTECTION OF CATTLE FROM IXODIC MITES

Habarshy ◽  
2021 ◽  
pp. 50-60
Author(s):  
A.B. Myrzhiyeva ◽  
M.Zh Suleimenov ◽  
Uslu Ugur ◽  
A.S. Ibazhanova ◽  
L.O Zhanteliyeva L.O
Keyword(s):  
Economic Feasibility ◽  
Point Of View ◽  
Scientific Article ◽  
Special Equipment ◽  
Practical Point ◽  
Acaricidal Efficacy ◽  
Economic Justification ◽  
Long Duration ◽  
Similar Drug ◽  
The Cost

The scientific article presents the duration of acaricidal effect of «Kenem» drug, and its economic feasibility for protecting cattle against ixodic ticks. As a result of the study, the acaricidal efficacy and the duration of the residual acaricidal effect of drugs are important components in the planning of anti-tick measures. From a practical point of view, the economic feasibility of treating cattle against ixodic ticks in the presented conditions of acaricides in the southern regions is considered important. Despite the fact that the cost of the drug per 100 head exceeds the cost of a similar drug by 1 788.15 tenge, the frequency of its use is less, and additional installations are not required. This is due to the long duration of residual acaricidal effect of Kenem, which is 30 days, which allows to reduce the number of therapeutic measures.When calculating the economic feasibility for the use of acaricides to protect cattle against ixodic ticks, the most convenient way to prevent the sucking of ixodic ticks to animals is the local application of Kenem, which does not require special equipment and special skills of technical staff. Drug duration is 30 days, therefore the cost of its use for the entire season of active ticks per 1 animal is 44% cheaper, compared to veteran, i.e. 1,421.4 tenge.

CURRENT RATIONALE ISSUES LABOR COSTS IN THE COST OF MILITARY PRODUCTS AT DIFFERENT STAGES OF THE LIFE CYCLE

2021 ◽  
Vol 3 (5) ◽  
pp. 52-61
Author(s):  
D. V. ZVEREV ◽  
◽  
I. I. SAVELEV ◽  
Keyword(s):  
Life Cycle ◽  
The State ◽  
Regulatory Framework ◽  
Labor Intensity ◽  
Labor Costs ◽  
Special Equipment ◽  
Frame Work ◽  
The Cost

Based on the experience of checking the validity of prices for military products supplied within the frame-work of the state defence order, problematic issues of rationing of labor costs have been identified. The im-perfection of the current regulatory framework in the field of substantiating the labor intensity of work is shown. Proposals for the standardization of labor at various stages of the life cycle of weapons, military and special equipment are reasoned.

Chloroplast division in spinach leaves examined by scanning electron microscopy and freeze-etching

1980 ◽  
Vol 46 (1) ◽  
pp. 87-96
Author(s):  
N. Chaly ◽  
J.V. Possingham ◽  
W.W. Thomson
Keyword(s):  
Electron Microscopy ◽  
Green Light ◽  
Cell Area ◽  
Low Intensity ◽  
Spinach Leaf ◽  
Freeze Etching ◽  
Leaf Disks ◽  
Scanning Electron ◽  
Spinach Leaves

Spinach leaf disks were cultured for 5 days in low-intensity green light and then were transferred to high-intensity white light. Harvests over the next 16 h established that cell area increased by about 80% and chloroplast number per cell increased by about 65%, while the percentage of dumbbell-shaped chloroplasts per cell decreased by 65%. Freeze-etch replicas of fixed and unfixed leaf disks, as well as scanning electron-microscope preparations of fixed material, contained dumbbell-shaped chloroplasts constricted to various degrees. Freeze-etch replicas of unfixed cells from young leaf bases, in which the number of chloroplasts per cell is known to be rapidly increasing, also contained many constricted chloroplasts. It is concluded that dumbbell-shaped chloroplasts occur in vivo and represent a stage in the division of chloroplasts.

Time to hemostasis: a comparison of manual versus mechanical compression of the femoral artery

1995 ◽  
Vol 4 (2) ◽  
pp. 149-156 ◽  
Author(s):  
MA Bogart
Keyword(s):  
Femoral Artery ◽  
Demographic Data ◽  
Mechanical Compression ◽  
Manual Compression ◽  
Special Equipment ◽  
Group 2 ◽  
A Prospective Study ◽  
The Cost ◽  
Mean Time ◽  
Pressure Dressing

BACKGROUND: Compression of the femoral artery to achieve hemostasis is necessary following angiographic and interventional cardiovascular procedures. OBJECTIVES: To evaluate length of time to hemostasis with manual versus mechanical compression of the femoral artery. METHODS: In a prospective study of 503 patients randomized into one of three groups, manual compression with a pressure dressing or vascular stasis button was used on groups 1 and 3, respectively. Mechanical compression with a pressure dressing was used on group 2. The length of time to hemostasis was measured in minutes. Demographic data, current medications, risk factors, laboratory values, and procedural data were analyzed. RESULTS: Mean time to hemostasis was 22 minutes with manual compression and 31 minutes with mechanical compression. Crossover from mechanical to manual compression to achieve hemostasis occurred in 21 of 168 patients (13%). CONCLUSIONS: Results of this study show that advantages of manual compression include shorter time to hemostasis, no requirement for special equipment, and the ability to remove arterial and venous sheaths simultaneously. Disadvantages include upper extremity fatigue and human resource considerations. If the operator is a nurse, the cost of compression increases and the ability to meet patient needs may be restricted. Although mechanical compression is a "hands free" approach, arterial hemostasis is prolonged, special equipment is required, and the total cost per procedure is higher.

Components and mechanism of action of ATP-driven proton pomps

1979 ◽  
Vol 57 (12) ◽  
pp. 1351-1358 ◽  
Author(s):  
Marcelo Alfonzo ◽  
Efraim Racker
Keyword(s):  
Electron Microscopy ◽  
Electron Micrographs ◽  
Proton Pump ◽  
Mechanism Of Action ◽  
Proton Channel ◽  
Proton Pumps ◽  
Positive Staining ◽  
Freeze Etching ◽  
Opening And Closing ◽  
Exchange Activity

We have studied the composition of ATP-driven proton pumps from bovine heart mitochondria and have reconstituted the oligomycin-sensitive ATPase complex from its individual components. The complex contains 9 to 10 subunits of which 5 are assembled in the soluble F1 protein, 2 are required for the attachment of F1 to the membrane and 2 form the proton channel within the membrane. With the help of information obtained from studies of the chloroplast and the bacterial proton pumps, we can tentatively assign a function to each of the subunits of the pump. The position of F1 outside of the membrane seen in electron micrographs of negatively stained preparations, does not appear to be an artifact. Evidence from immunological studies, chemical derivatizations as well as further electron microscopy (positive staining and freeze–etching), support this statement. We describe in this paper a 28 000-dalton polypeptide which has been isolated from the mitochondria membrane and is required for the reconstitution of oligomycin-sensitive ATPase and 32Pi–ATP exchange activity. We propose a mechanism of action of the proton pump in which the key energy-yielding reaction is the binding of Mg2+ to the protein. The function of the proton gradient is to displace Mg2+ from this site to permit cyclic repetition of the binding process. Essential for this scheme is the cyclic opening and closing of the proton channel. We have outlined our present approaches to test this hypothesis.

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