Taxol Induces Microtubule-Rough Endoplasmic Reticulum Complexes and Microtubule-Bundles in Cultured Chondroblasts

Abstract. Taxol induces a vast increase in the number of microtubules (MTs) in functional chondroblasts. The drug also induces a marked change in MT distribution. In control cultures, anti-tubulin stains long, fine, sinuous filaments radiating from a perinuclear center. In taxol-treated cells, anti-tubulin stains stubby, straight, chevron-like structures that assume a striking antipodal distribution. Such MT-bundles are relatively stable: they persist for over 48 h after removal of taxol, and even for 16–24 h in Colcemid. Many of these supernumerary MTs bind to, and align on, the cytoplasmic face of the rough endoplasmic reticulum (RER). In binding, the MTs displace the numerous ribosomes that normally stud the surface of the cisternae of the RER. The bound MTs form a remarkably uniform layer with center-to-center spacings of 40 nm. The attached parallel arrays of MTs achieve lengths of over 10 μm. These bound MTs not only dislodge ribosomes from the RER surface, but they also zip together adjacent ER complexes, forming tiers of two to eight cisternae. Numerous cytoplasmic bundles of hexagonally-ordered MTs are also induced. When closely aligned, the MTs assume a crystalline configuration with a six-fold symmetry, a central MT being surrounded by six equidistant MTs. A single cell can have over 100 MT-bundles and the number of MTs per bundles varies from 2–30. The forces aggregating cytoplasmic MT-bundles probably differ from those that bind MTs to the RER. Taxol also fragments the prominent Golgi complex that characterizes actively secreting chondroblasts. No obvious morphologic relationship has yet been detected between these induced MTs and other organelles such as intermediate-sized filaments, microfilaments, mitochondria, Golgi cisternae, or secretory vesicles.     

Cytogenetic and biochemical investigations on fibroblast cultures and clones with one and two active X chromosomes of a 69,XXY triploidy

Bromodeoxyuridine replication patterns showed that fibroblasts from a 69,XXY triploidy carried either one or two early replicating X chromosomes. The activity of alpha-galactosidase A measured in single cells fell into two classes with a ratio of 1:2. Dilute plating produced clones of both types with the activity of alpha-galactosidase A corresponding to the number of active X chromosomes. To our knowledge, this is the first report on clones of a triploidy with different numbers of active X chromosomes, and on a gene-dosage effect of an X-linked gene using triploid cells with one active X as control.     

Degradation ofn-alkane-1-sulfonates byPseudomonas

We have isolated two strains ofPseudomonas, AJ 1 and AJ 2, growing on the C₄–C₇ and the C₈–C₁₂ n-alkane-1-sulfonates, respectively, as the only source of their carbon and energy. The alkane sulfonates are dissimilated by these strains, ultimately to yield carbon dioxide, water and sulfate. In the primary oxidation reaction(s) the corresponding fatty acid and sulfate are formed. The fatty acid is subsequently degraded by Β-oxidation. For strain AJ 1, growing on the lower alkane sulfonates, we could exclude various pathways of degradation which might have been present in addition to the one mentioned above.