Biomedical subjects

B B Czaban

Publications and source records attributed to B B Czaban.

5 recordsLinked to original sources

PubMed1993

Ultraviolet microbeam irradiation of chromosomal spindle fibres in Haemanthus katherinae endosperm. I. Behaviour of the irradiated region.

We used an ultraviolet microbeam to irradiate chromosomal spindle fibres in metaphase Haemanthus endosperm cells. An area of reduced birefringence (ARB) was formed at the position of the focussed ultraviolet light with all wavelengths we used (260, 270, 280, and 290 nm). The chromosomal spindle fibre regions (kinetochore microtubules) poleward from the ARBs were unstable: they shortened (from the ARB to the pole) either too fast for us to measure or at rates of about 40 microns per minute. The chromosomal spindle fibre regions (kinetochore microtubules) kinetochore-ward from the ARBs were stable: they did not change length for about 80 seconds, and then they increased in length at rates of about 0.7 microns per minute. The lengthening chromosomal spindle fibres sometimes grew in a direction different from that of the original chromosomal spindle fibre. The chromosome associated with the irradiated spindle fibre sometimes moved off the equator a few micrometers, towards the non-irradiated half-spindle. We discuss our results in relation to other results in the literature and conclude that kinetochores and poles influence the behaviour of kinetochore microtubules.

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PubMed1992

Rhodamine-labelled phalloidin stains components in the chromosomal spindle fibres of crane-fly spermatocytes and Haemanthus endosperm cells.

In crane-fly spermatocytes and Haemanthus endosperm, all metaphase and anaphase chromosomal spindle fibres were stained with rhodamine-labelled phalloidin. In crane-fly spermatocytes, each kinetochore was stained with rhodamine-labelled phalloidin at diakinesis of prophase and after colcemid caused metaphase spindles to depolymerize. Since phalloidin stains actin filaments, the distributions of rhodamine-labelled phalloidin-stained material in crane-fly spermatocytes and Haemanthus endosperm suggest that actin filaments might interact with microtubules to produce forces that move chromosomes during cell division, either directly or via an intermediate motor molecule.

Animals↗

PubMed1985

The kinetic polarities of spindle microtubules in vivo, in crane-fly spermatocytes. I. Kinetochore microtubules that re-form after treatment with colcemid.

In newly formed chromosomal spindle fibres we determined the kinetic polarities of the microtubules, that is, the ends to which tubulin monomers add. Spindles disappeared after cells were continuously immersed in colcemid; then portions of the cells were continuously irradiated with a microbeam of near-ultraviolet light to reverse locally the effect of the colcemid. From the following lines of evidence we conclude: that microtubules are organized by the chromosomes; and that tubulin monomers add to the chromosomal spindle fibres at the kinetochore. When chromosomes were irradiated chromosomal spindle fibres grew in different directions, not necessarily focussed to a common pole; this would not occur if the chromosomal spindle fibres were organized by poles. Chromosomal spindle fibres were sometimes associated with only some of the chromosomes; this would not occur if the fibres were organized by the poles. Thus, chromosomal spindle fibres are organized solely by chromosomes; these spindle fibres are functional since the associated chromosomes moved in anaphase. When chromosomes were irradiated the re-formed spindle fibres grew up to 10 microns past the edges of the irradiating spot. Experimentally, free tubulin did not diffuse more than 4-5 microns from the irradiated spot. Thus we conclude that the tubulin monomers add at the kinetochores and not at the distal ends of the fibres.

Animals↗

PubMed1985

The kinetic polarities of spindle microtubules in vivo, in crane-fly spermatocytes. II. Kinetochore microtubules in non-treated spindles.

We determined the kinetic polarities of chromosomal spindle fibre microtubules in vivo: either the kinetochore or pole ends of chromosomal spindle fibres were irradiated with near-ultraviolet light to prevent depolymerization by colcemid. Irradiations began either just before or just after colcemid addition; cells were continually irradiated and continuously immersed in colcemid. Irradiations of kinetochore ends of chromosomal spindle fibres prevented depolymerization; irradiations of pole ends did not. Therefore, since colcemid acts by binding to the 'on' (assembly) ends of microtubules, the on ends of chromosomal spindle fibre microtubules are at the kinetochores. That is, in untreated chromosomal spindle fibres in vivo tubulin monomers add to kinetochore microtubules at the kinetochore ends. Tubulin diffused from the irradiation sites: irradiations of the cytoplasm sometimes prevented depolymerization of chromosomal spindle fibres. Prevention of chromosomal spindle fibre depolymerization was dependent on the distance of the irradiated region from the nearest chromosome; the longer the distance the less likely was it that the irradiation prevented depolymerization. On the other hand, prevention of chromosomal spindle fibre depolymerization was not dependent on the distance from the irradiated spot to the nearer pole. This analysis, too, we argue, strongly suggests that the kinetochore ends of the chromosomal spindle fibres are the on ends.

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PubMedDate not supplied

Microinjection into crane-fly spermatocytes.

We were successful in microinjecting fluorescently labelled material into crane-fly spermatocytes. In our experiments, we obtained four results. (i) In most attempts, the membrane stretched around the micropipette and prevented entry of fluorescent material, even when the micropipette appeared to be pushed completely through the cell. This confirms suppositions from earlier micromanipulation experiments that the elastic membrane prevents the micropipette needle from entering the cell. (ii) In some attempts, cells lysed upon contact with the micropipette. (iii) In other attempts, we successfully injected fluorescent material into cells. (iv) Fluorescent material left the cells after injection, often passing into adjacent cells. Although our success rate is low, microinjection into crane-fly spermatocytes is indeed possible.

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