Olav Behnke

An Actin-Like Component in Sperm Tails of A Crane Fly (Nephrotoma Suturalis Loew)

Decorated actin-like filaments were seen in spindles after crane fly spermatocytes were glycerinated and then treated with rabbit skeletal muscle heavy meromyosin (HMM). Both ATP and pyrophosphate inhibited the HMM reaction. In prometaphase, metaphase, and mid-anaphase cells, actin-like filaments were seen near regions where chromosomal spindle fibres are seen in living cells, and were oriented in the pole-to-pole direction. In the interzone of anaphase cells, actin-like filaments were not oriented in a preferential direction when they were not associated with the microtubules attached to the sex chromosomes. No filaments were seen in glycerinated spindles not treated with HMM. We discuss reasons why filaments might not be seen without prior HMM treatment, and we discuss the possible role of the actin-like filaments in the spindles. — Spindle microtubules often were not seen in cells treated with HMM. This depended on the stage of division: in prometaphase no microtubules were seen; in metaphase microtubules were seen, in apparently normal numbers; in mid-anaphase, microtubules between the autosomes and the poles were seen in reduced numbers, those associated with the equatorial sex-chromosomes were seen in apparently normal numbers, while those between the separating autosomal half-bivalents were not seen. Microtubules were not seen in glycerinated spindles not treated with HMM, suggesting that HMM in some way affects microtubule stability. The question of microtubule stability is briefly discussed.

Cytochalasin B: Does It Affect Actin-Like Filaments?

An in vitro system was used to test the purported action of cytochalasin B. At concentrations 100 times those used for experiments in vivo, cytochalasin B did not cause the breakdown of F-actin, did not inhibit the transformation of G-actin to F-actin, did not inhibit the binding of heavy meromyosin to F-actin, and did not inhibit the adenosine triphosphate-induced release of heavy meromyosin from F-actin.

From megakaryocytes to platelets: platelet morphogenesis takes place in the bloodstream

Abstract: We studied megakaryocyte processes formed in rat bone marrow and spleen, using both the transmission and scanning electron microscopes. Some processes were bulky, others slender and beaded. The bulky megakaryocyte processes developed a specialized arrangement of organelles at the site at which they entered the lumen: filaments present around the outside of the process seemed to support a central cylinder in which organelles flowed along microtubules.

Intratumoral phenotypic diversity of cloned human lung tumor cell lines and consequences for analyses with monoclonal antibodies

Cloned cell lines and a number of subclones from these lines were established in vitro from biopsies of small cell lung carcinomas and squamous cell lung carcinomas. The cloned cultures, including the cloned subclones, were analyzed in respect to morphology, karyotype, growth rates, clonogenicity in semisolid agar medium, and tumorigenicity in nude mice. A remarkable biologic diversity was found in respect to most of these biologic features. In addition, four murine monoclonal antibodies with high specificity for lung tumor cells were generated. Their reactivity pattern to clonogenic cells was for some clones different as compared to the nonclonogenic cells. Subclones of tumor cells not binding the antibody were identified for each monoclonal antibody. It is concluded that intratumoral phenotypic diversity may have a severe negative impact on the use of monoclonal antibodies in cancer diagnosis/therapy. The work also indicates that a mixture of antibodies may be more useful in tumor diagnosis than individual antibodies and perhaps even therapy, particularly if they bind to the clonogenic part of a cell population.