Guenter Albrecht-Buehler

The phagokinetic tracks of 3T3 cells

This paper describes a technique of visualizing tracks of cultured cells moving on a glass substrate covered with gold particles. It leads to the following observations: -If the tracks of many cells are examined, cell line characteristic track patterns become apparent. -In several cases, second or third generation descendents of 3T3 cells were observed to repeat track patterns of their ancestor cell. -If a 3T3 cell collides with another 3T3 cell or a nonmigrating BSC-1 cell, it forms an outgoing track from the impact area as if the cell was elastically reflected at the target.

Phagokinetic tracks of 3T3 cells: Parallels between the orientation of track segments and of cellular structures which contain actin or tubulin

Phagokinetic tracks were used to determine the current direction of migration in 3T3 cells. Comparing this direction with the orientation of actin or tubulin-containing cellular structures by indirect immunofluorescence, the following results were obtained. First, the main actin-containing bundles were located at the bottom and tail end of 3T3 cells and ran parallel to the current or preceding direction of migration. Second, the 3 micrometer long rod-like structure (primary cilium), which contains tubulin and which has been observed by other investigators in transmission electron microscopy (Barnes, 1961; Sorokin, 1962; Wheatley, 1969) and in indirect immunofluorescence (Osborn and Weber, 1976), was oriented predominantly parallel to the substrate and to the current movement direction. It seems possible that the primary cilium has a role in the directional control of a migrating 3T3 cell, and that the main actin containing bundles act as substrate-attached rails along which the nucleus and bulk cytoplasm slide during displacement of the cells.

The orientation of centrioles in migrating 3T3 cells.

Abstract Based on electron microscopic examination of 20 migrating 3T3 cells, the paper suggests that one centriole of a pair is preferentially oriented perpendicular, the other parallel to the substrate. The finding is interpreted as further support for the possibility that centrioles are involved in the control of migration in 3T3 cells.

In Defense of “Nonmolecular” Cell Biology

Publisher Summary This chapter describes the detailed molecular interactions and discusses in more general terms the question of how applicable molecular explanations are to whole-cell functions. It discusses two examples from the field of cell motility, the explanation which does not depend significantly on molecular knowledge. One example derives the fundamental aspects of the mechanical designs of cells showing amoeboid movement, such as 3T3 mouse fibroblasts. The other example describes the emergence of structure and possibly rudimentary intelligence among the colonies of the flagellated algal cells Chlamydomonas . As the cellular functions are derived from large numbers of molecular details, many small errors are accumulated to render meaningless the resulting explanation. The new and sufficient concepts of cell biology must be developed in ways that recognize explicitly the place of cells within the hierarchy of organization of biology that ranges from ecologies to macromolecules.

The ultrastructure of primary cilia in quiescent 3T3 cells

Abstract Electron microscopy was used to investigate primary cilia in quiescent 3T3 cells. As in the case of primary cilia of other cell types, their basal centriole was found to be a focal point of numerous cytoplasmic microtubules which terminate at the basal feet. There are also intermediate filaments which appear to converge at the basal centriole. Cross-striated fibers of microtubular diameter, reminiscent of striated rootlets of ordinary cilia, appear associated with the proximal end of the basal centriole. Usually less than nine cross-banded basal feet surround the basal centriole in a well-defined plane perpendicular to the centriolar axis. The ciliary shaft was found to be entirely enclosed in the cytoplasm of fully flattened cells. In rounded cells, it could be found extending to the outside of the cell. Periodic striations along the entire shaft were observed after preparing the cells in a special way. The tip of the shaft showed an electron-dense specialization. Several unusual forms of primary cilia were observed which were reminiscent of olfactory flagella or retinal rods. Using tubulin antibody for indirect immunofluorescence, a fluorescent rod is visible in the cells [18] which we demonstrate is identical with the primary cilium.

Asymptotically increasing compliance of genomes with Chargaff's second parity rules through inversions and inverted transpositions.

Chargaffs second parity rules for mononucleotides and oligonucleotides (CIImono and CIIoligo rules) state that a sufficiently long (>100 kb) strand of genomic DNA that contains N copies of a mono- or oligonucleotide, also contains N copies of its reverse complementary mono- or oligonucleotide on the same strand. There is very strong support in the literature for the validity of the rules in coding and noncoding regions, especially for the CIImono rule. Because the experimental support for the CIIoligo rule is much less complete, the present article, focusing on the special case of trinucleotides (triplets), examined several gigabases of genome sequences from a wide range of species and kingdoms including organelles such as mitochondria and chloroplasts. I found that all genomes, with the only exception of certain mitochondria, complied with the CIItriplet rule at a very high level of accuracy in coding and noncoding regions alike. Based on the growing evidence that genomes may contain up to millions of copies of interspersed repetitive elements, I propose in this article a quantitative formulation of the hypothesis that inversions and inverted transposition could be a major contributing if not dominant factor in the almost universal validity of the rules.

Microspike-mediated particle transport towards the cell body during early spreading of 3T3 cells☆

Abstract Freshly trypsinized 3T3 cells send out microspikes of 0.2 μm diameter and up to 10 μm length within 20 min after attachment to a glass substratum. The microspikes move actively and eventually attach to the substratum. Subsequently, lamellae flow out between lines of attached microspikes. If, however, colloidal gold particles of 0.2–0.4 μm diameter and clusters of gold particles up to 4 μm in diameter are placed on the substratum and a microspike attaches to them, we observed two reactions of the microspikes to this contact. They either retract upon contact, transporting the attached particles to the cell surface at a speed of 0.2 μm/sec, or the particles flow toward the cell body while the microspike stays in place. This action results in the clearing of a circular area around each spreading cell before lamellae flow out. “Clearing” proceeds at serum concentrations between 1 and 20% and in concentrations of colchicine up to 20 μm/ml. In concentrations of cytochalasin B higher than 5 μg/ml, however, particle removal is completely inhibited, although the microspikes are still produced by the cell. Transmission electron microscopy shows that the microspikes contain mostly longitudinally oriented microfilaments and only a few microtubules, if any.

Is Cytoplasm Intelligent Too

Ever since modern computers arrived on the scene, the concept of “intelligence” has been greatly demystified and replaced by “data processing capacity.” Even the last bastions of mystical meaning in the word “intelligence,” namely the aspects of “creativity” and “awareness,” are being secularized. Computerists are exploring whether the use of look-up tables, tree searches, and pseudo-random number generators can replace the old-fashioned, mystical terms.

Reversible compression of cytoplasm

Abstract Incubation for 3 min in 1 M sorbitol causes animal cells to lose 50–75% of their water content. Upon return to normal medium, the ultrastructure and morphology of the cells return to normal within 3 min. Mitoses continue normally; migration patterns and growth curves also return to normal. An intriguing aspect of irreversibility was observed when blebbing microplasts switched to ruffling. They would have continued to bleb without the prior episode of dehydration in sorbitol. During incubation with 1 M sorbitol the shrunken cells appear to store excess surface area in numerous, rapidly forming microvilli. The cytoplasm is also altered. Bundles of individual microfilaments and intermediate filaments condense into homogeneous streaks of materials which retain their birefringence. In contrast, microtubules display a clearly visible exclusion zone around each individual tubule. Sharply outlined patches of tiny granules appear in electron micrographs. The results are discussed with respect to the morphological compartmentalization and the viscoelasticity of the cytoplasm.

Local inhibition of centripetal particle transport where LETS protein patterns appear on 3T3 cells.

WE try here to establish a link between a motility phenomenon in animal cells and the presence of the so-called ‘large external transformation-sensitive (LETS)’ protein on the surface of the cells. Through studies of this protein a new and still puzzling aspect of animal cell surfaces became apparent. Originally discovered as a major surface glycoprotein of molecular weight 220,000–250,000 which disappeared on cell transformation (for review, see ref. 1), it has since become quite likely that various differently named surface glycoproteins—galactoprotein a (ref. 2), fibroblast surface antigen3, Zeta protein4, ‘cell-surface protein’ (CSP)5, and ‘cold-insoluble globulin’ (CIG)6–8—which were studied independently by different investigators, are identical to or at least very closely related to LETS protein.