Electron micrographs of microtubules

Fig. 78a-c. Electron micrographs of microtubules of graphite carbon. Parallel dark lines correspond to the (002) lattice images of graphite. A cross-section of each tubule is illustrated a tube consisting of five graphitic sheets, diameter 6.7 nm b two-sheet tube, diameter 5.5 nm c seven-sheet tube, diameter 6.5 nm, which has the smallest hollow diameter (2.2 nm) [477]... 

Fig. 12. Dependence of oscillation on the balance between stabilizers and destabilizers. The ratio of destabilizer to stabilizer is plotted along the x-axis, the magnitude of oscillations on the y-axis. On the right side of the diagram assembly leads to oligomers (excess of destabilizer), on the left side to microtubules (excess of stabilizer), in both cases without oscillations. Oscillations can be generated at intermediate ratios. Electron micrographs of microtubules and oligomers are shown as insets. From [16]...

Fig. 2.25. Electron micrographs of microtubules. (A) In longitudinal section, from a meristematic cell of a root tip of Jumperm. (B) As seen in transverse section, from a cell of the nectary of Euphorbia. Each microtubule is made up of a number of more or less spherical sub-imits which can be clearly seen. By courtesy of Myron C. Ledbetter, Brookhaven National Laboratory, and Blackwell Scientific Publications.

Figure 2. Electron micrograph of cross section of flagellum of mouse sperm, taken near the tip. The axoneme contains nine outer pairs of doublet microtubules and two central singlet microtubules. Several dynein arms and the fibrous sheath of the sperm are also shown.

Figure 3. Electron micrographs of myelinated axons of Xenopus laevis. Upper figure Cross section of axon showing microtubules in groups in association with membrane-bound organelles. Lower figure Longitudinal section of axon showing neurofilaments and microtubules in close proximity to membrane-bound organelles. (Courtesy of Dr. R. Smith.)...

Figure 5.2 Micrographs of metal-coated lipid tubules. Top panel shows scanning electron micrograph of copper-plated microtubules (bar = 2.0 (Jim), while bottom panel shows optical micrograph of iron-coated microtubules embedded in acrylic-urethane clear coating (bar = 25 p,m). Reprinted from Ref. 135 with permission of Wiley-VCH.

Figure 19-23 (A) Diagram of a cross-sectional view of the outer portion of a lamellibranch gill cilium. This has the 9+2 axoneme structure as shown in Fig. 1-8 and in (B). The viewing direction is from base to tip. From M. A. Sleigh.329 (B, C) Thin-section electron micrographs of transverse (B) and longitudinal (C) sections of wild-type Chlamydomonas axonemes. In transverse section labels A and B mark A and B subtubules of microtubule doublets oa, ia, outer and inner dynein arms, respectively sp, spokes cpp, central pair projections bk, beaks. From Smith and Sale.329a...

Figure 4. Electron micrograph of longitudinal sections of Chlamydomonas reinhardtii Dang. A. Control cell B. Cell treated 1 h with 1.0-1.5 g/ml nonylphenol C. Chloroplast d. dichtyosome f. flagella m. mitochondrion mi. microtubules n. nucleus p. pyrenoid pi. plasmalemma.

Fig. 1 Electron micrograph of a negatively stained microtubule assembled from purified tubulin and docetaxel. The left side shows the lateral projection of the protofilaments forming a microtubule cylinder 24nm in diameter which has opened into a sheet on the right side. There are also tubulin oligomers in the image...

Electron microscopy (EM) has played a central role in many aspects of research on microtubules and their main protein component, tubulin. MTs were first identified in electron micrographs of plant material [1], Characteristics of the basic structural aspects of MTs were also determined by EM, revealing that MTs are hollow tubes composed of protofilaments (pf). There are most often 13 pfs, but this number can vary at least from 9 to 16. Subsequent work showed that the pfs are composed of aP-tubulin dimers arranged head-to-tail. 

Figure 34.22. Microtubule Arrangement. Electron micrograph of a cross section of a flagellar axoneme shows nine microtubule doublets surrounding two singlets. [Courtesy of Dr. Joel Rosenbaum.]...

In recent years the biological importance of the cytoskeletal structures—microtubules, intermediate filaments, and microfilaments (actin)—has attracted the attention of many cell biologists. In striated muscle, myosin and actin filaments together with Z lines are the main cytoskeletal structures to form sarcomeres of the myofibril. However, myosin and actin are contractile proteins, and some of the proteins constituting the Z line are classified as actin-associated proteins. Therefore, cell membrane attachment proteins, intermediate filaments, and some other structural proteins are described in this section. There has not been any report on muscle microtubules, although their presence is shown in some electron micrographs of sectioned samples. 

Figure 2. Electron micrographs of in vitro polymerized microtubules from R (A) and S (B) biotypes of Eleusine in the presence of 10 M oryzalin. Although good microtubules are formed in the extracts of the resistant biotype, only fragments or structures that represent limited polymers of tubulin were found in the S. Inset shows a higher magnification of an individual microtubule (polymerized without oryzalin) revealing the beaded" structure typical of microtubules. Bar = 0.5 pm...

Figure 4. Electron micrograph of the effects of taxol on the R biotype of Eleusine. The walls in this figure have extensive groups of microtubules (arrows) along the wavy wall (w). Bar = 0.5 pm.

Figure 2. Hyperamplification of the centrosome in PARP-1 -/- mouse embryonic fibroblasts, a-d) normal mouse embryo fibroblast (MEF). e,0 PARP-1 -/- MEF. a) Electron micrograph of the centrosome, consisting of a pair of centrioles situated perpendicular to each other, b-f) The centrosomes were stained in red, the microtubules in green and DNA in blue. b,c) One or two centrosomes were found in the interphase, d) In mitosis the centrosomes translocate to each pole and become the spindle poles, e) Abnormal numbers of the centrosomes were found in PARP-1 -/- MEF. 0 Abnormal spindles were found in mitoses of PARP-1 -/- MEF.

Fig. 6 Dark-field electron micrographs of freeze-dried specimens, (A) Yeast nuclear pore complexes full-scale is 1.024 /urn (in collaboration with Qing Yang and Christopher Akey. Boston University). (B). Yeast spindle pole bodies with microtubules attached full-scale is 2,048 /xm (in collaboration with Esther Bullitt, Boston University).

Fig. 2. Electron micrograph of a rat kidney tubule cell in metaphase. The two kinetochores ( ki", "k2 ) of one chromosome are shown, as are chronriosomal microtubules C ch") and one pole ("p ), marked by a pair of centrioles. Approximately X40,000. ( From Jokelainen. 1967. J. Ultrastruct. Res., 19 19 4.)...

Fig. 3. Electron micrograph of metaphase in the micronucieus of the ciliate Blepharisma sp. showing both chromosomal microtubules (e.g., arrows at left) and interpolar microtubules (e.g., arrow at right). Note the fine fibrous material around the microtubules. X50,000. (From Jenkins. 1967. J. CeU. Biol., 34 463-481.)...

Fig. 16. Electron micrograph of a blood lily Haemanthus katherinae) chromosome in early mitotic prometaphase. Unipolar malorientation to a pole toward the left is suggested by the chromosomal microtubule arrangement at the two sister kinetochores ("ki/ The overall spindle axis is indicated by the arrow at the lower left side. The circle is a stain mark. XI 2,000. (From Bajer and Mole -Bajer. 1969. Chromosoma, 27 448-484.)...

Fig. 20. Electron micrograph of a late division stage in the dinoflagellate Gyrodinium cohnii showing a portion of the nucleus with one channel lined by the nuclear envelope and filled with microtubules. Two chromosomes are labeled chm/ and the association of a third chromosome and the channel membrane is indicated by an arrow. X47,500. (From Kubai and Ris. 1969. /. Ce//5/o/., 40 508-528.)...

Fig. 2.2(b) Transmission electron micrographs of Bombyx mori sensilla trichodea (above, x 20 000 and 40 000) and s. basiconica (below, x 20 000). Fixation by freeze substitution results in almost round cross-sectional profiles of the dendrites, containing a regular array of microtubules. Pore tubules are well fixed in the outer parts of the hair (courtesy of Steinbrecht, 1980). 

Fig. 16.2 (A) Transmission electron micrograph of three polypyrrole nanotubules. (B) Scanning electron micrograph of an array of capped polypyrrole microtubules.

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