Strategies for error reduction in high-magnification stereoscopic measurements based on error equation calculations

1983 ◽  
Vol 41 ◽  
pp. 704-705
Author(s):  
George C. Ruben ◽  
Kenneth A. Marx
Keyword(s):  
In Vitro Model ◽  
Freeze Fracture ◽  
Calf Thymus Dna ◽  
High Magnification ◽  
Double Stranded Dna ◽  
Error Magnitude ◽  
Calf Thymus ◽  
Dna Organization ◽  
Vitro Model

We have used freeze-fracture TEM to visualize toroidal shaped spermidine Calf Thymus DNA complexes. DNA collapsed into these complexes represents an in vitro model system for the packaging of double stranded DNA in bacteriophage and virus heads. Both freeze fracture TEM and biochemical data support a circumferential DNA winding model for DNA organization in the hydrated torus. To better understand this microscopic DNA organization we made stereoscopic measurements of surface DNA topology in high-resolution eucentric tilt views of freeze-etch, single direction shadowed, low Pt-C metal (9Å) replicas. Here we calculate and discuss the error magnitude associated with these modern high-magnification stereoscopic measurements. Freeze fracture TEM was performed on spermidine-condensed Calf Thymus DNA samples as previously described. Micrographs (105 x with a JEM 100 CX) were printed at 2.5 x 105 for measurement with a floating-mark stereometer (SB 190 Mirror Stereoscope, Cartographic Eng. Ltd.). Figure 1 shows the DNA torus we made measurements on.

Torus Circumference and Thickness Parameters From a Linear DNA Size Series Suggest How Toruses Self-Assemble

1985 ◽  
Vol 43 ◽  
pp. 522-523
Author(s):  
George C. Ruben ◽  
Kenneth A. Marx
Keyword(s):  
Tertiary Structure ◽  
Dna Complexes ◽  
Tertiary Structures ◽  
Self Assembling ◽  
Double Stranded Dna ◽  
Calf Thymus ◽  
Dna Organization ◽  
Condensed Dna ◽  
Dna Size

Certain double stranded DNA bacteriophage and viruses are thought to have their DNA organized into large torus shaped structures. Morphologically, these poorly understood biological DNA tertiary structures resemble spermidine-condensed DNA complexes formed in vitro in the total absence of other macromolecules normally synthesized by the pathogens for the purpose of their own DNA packaging. Therefore, we have studied the tertiary structure of these self-assembling torus shaped spermidine- DNA complexes in a series of reports. Using freeze-etch, low Pt-C metal (10-15Å) replicas, we have visualized the microscopic DNA organization of both calf Thymus( CT) and linear 0X-174 RFII DNA toruses. In these structures DNA is circumferentially wound, continuously, around the torus into a semi-crystalline, hexagonal packed array of parallel DNA helix sections.

Deep-etched, replicated DNA toruses held on edge in ice demonstrate a complex 3-D substructure by extensive tilting along shadowing direction

1983 ◽  
Vol 41 ◽  
pp. 714-715
Author(s):  
George C. Ruben ◽  
Kenneth A. Marx
Keyword(s):  
Companion Paper ◽  
Dna Topology ◽  
Biochemical Data ◽  
Dna Structures ◽  
Double Stranded Dna ◽  
Yield Information ◽  
Calf Thymus ◽  
Dna Organization ◽  
Condensed Dna

Torus shaped spermidine-DNA structures formed in vitro are thought to have a DNA organization similar to certain double stranded DNA bacteriophage and viruses. For this reason we have used freeze-etch low Pt-C metal replica TEM to visualize toruses formed from a variety of condensed DNAs. Both Calf Thymus DNA and circular and linear ϕX-174 RFII DNA freeze-etch TEM and biochemical data support a circumferential DNA winding model for hydrated spermidine-condensed DNA toruses. Heretofore, we utilized stereoscopic measurements from tilt views of thin replicas (60-90 Å) of toruses to yield information about the DNA topology and thickness of these objects. In a companion paper in these proceedings we examine the precision of such stereoscopic measurements on tilt micrographs of a torus. In our attempts to visualize DNA toruses we have noted that deep-etched toruses are generally suspended above the surface by virtue of a residual attachment to the ice.

Discrimination of monomer from multimer DNA disk-shaped toruses by freezeetch TEM

1984 ◽  
Vol 42 ◽  
pp. 210-211
Author(s):  
George C. Ruben ◽  
Kenneth A. Marx
Keyword(s):  
Biochemical Data ◽  
Dna Structures ◽  
Ice Surface ◽  
Double Stranded Dna ◽  
Data Support ◽  
Dna Organization ◽  
Trivalent Cations

In vitro collapse of DNA by trivalent cations like spermidine produces torus (donut) shaped DNA structures thought to have a DNA organization similar to certain double stranded DNA bacteriophage and viruses. This has prompted our studies of these structures using freeze-etch low Pt-C metal (9Å) replica TEM. With a variety of DNAs the TEM and biochemical data support a circumferential DNA winding model for hydrated DNA torus organization. Since toruses are almost invariably oriented nearly horizontal to the ice surface one of the most accessible parameters of a torus population is annulus (ring) thickness. We have tabulated this parameter for populations of both nicked, circular (Fig. 1: n=63) and linear (n=40: data not shown) ϕX-174 DNA toruses. In both cases, as can be noted in Fig. 1, there appears to be a compact grouping of toruses possessing smaller dimensions separated from a dispersed population possessing considerably larger dimensions.

An in vitro model for investigation of vitamin A effects on wound healing

2021 ◽  
pp. 1-6
Author(s):  
Hoda Keshmiri Neghab ◽  
Mohammad Hasan Soheilifar ◽  
Gholamreza Esmaeeli Djavid
Keyword(s):  
Wound Healing ◽  
Endothelial Cell ◽  
Vitamin A ◽  
In Vitro Model ◽  
Cellular Proliferation ◽  
Endothelial Cell Migration ◽  
Normal Fibroblast ◽  
Anti Inflammatory ◽  
Vitro Model

Abstract. Wound healing consists of a series of highly orderly overlapping processes characterized by hemostasis, inflammation, proliferation, and remodeling. Prolongation or interruption in each phase can lead to delayed wound healing or a non-healing chronic wound. Vitamin A is a crucial nutrient that is most beneficial for the health of the skin. The present study was undertaken to determine the effect of vitamin A on regeneration, angiogenesis, and inflammation characteristics in an in vitro model system during wound healing. For this purpose, mouse skin normal fibroblast (L929), human umbilical vein endothelial cell (HUVEC), and monocyte/macrophage-like cell line (RAW 264.7) were considered to evaluate proliferation, angiogenesis, and anti-inflammatory responses, respectively. Vitamin A (0.1–5 μM) increased cellular proliferation of L929 and HUVEC (p < 0.05). Similarly, it stimulated angiogenesis by promoting endothelial cell migration up to approximately 4 fold and interestingly tube formation up to 8.5 fold (p < 0.01). Furthermore, vitamin A treatment was shown to decrease the level of nitric oxide production in a dose-dependent effect (p < 0.05), exhibiting the anti-inflammatory property of vitamin A in accelerating wound healing. These results may reveal the therapeutic potential of vitamin A in diabetic wound healing by stimulating regeneration, angiogenesis, and anti-inflammation responses.

A new in vitro model for pre-transplantation diagnosis of frozen/thawed human ovarian tissue

2011 ◽  
Vol 71 (05) ◽  
Author(s):  
M Salama ◽  
K Winkler ◽  
KF Murach ◽  
S Hofer ◽  
L Wildt ◽  
...  
Keyword(s):  
In Vitro Model ◽  
Ovarian Tissue ◽  
Human Ovarian Tissue ◽  
Vitro Model
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