Addendum: Analysis of chromosome movement in crane fly spermatocytes by ultraviolet microbeam irradiation of individual chromosomal spindle fibres. II. Action spectra for stopping chromosome movement and for blocking ciliary beating and myofibril contractions

1981 ◽  
Vol 59 (10) ◽  
pp. 867-867
Author(s):  
Peggy J. Sillers ◽  
Arthur Forer
Keyword(s):  
Chromosome Movement ◽  
Ciliary Beating ◽  
Microbeam Irradiation ◽  
Action Spectra ◽  
Ultraviolet Microbeam ◽  
Spindle Fibres

Analysis of chromosome movement in crane fly spermatocytes by ultraviolet microbeam irradiation of individual chromosomal spindle fibres. II. Action spectra for stopping chromosome movement and for blocking ciliary beating and myofibril contractions

1981 ◽  
Vol 59 (9) ◽  
pp. 777-792 ◽  
Author(s):  
Peggy J. Sillers ◽  
Arthur Forer
Keyword(s):  
Absorption Spectra ◽  
Ultraviolet Light ◽  
Action Spectrum ◽  
Chromosome Movement ◽  
Ciliary Beating ◽  
Action Spectra ◽  
Light Passing ◽  
Block Movement ◽  
Two Peaks ◽  
Spindle Fibres

Chromosome-to-pole movement in crane fly spermatocytes was temporarily blocked by ultraviolet light focussed to a 4-μm-diameter spot on single chromosomal spindle fibres. Since similar irradiation of the interzonal region did not alter chromosome-to-pole movement, this effect was specific to spindle fibres. The action spectrum for blocking chromosome movement in this specific way had two peaks, one at 270 nm and one at 290 nm. To block movement, irradiations with 280-nm-wavelength light required two to four times more energy than irradiations with 270- or 290-nm-wavelength light.Action spectra were obtained for blocking ciliary beating and for blocking myofibril contraction. The action spectrum for blocking ciliary beating had a broad peak, between 260 nm and 280 nm, whilst that for blocking myofibril contraction had two peaks, at 270 and 290 nm, just like that for blocking chromosome movement. We discuss the similarities and differences in the various action spectra, and we compare the action spectra to absorption spectra of spindle components and to other action spectra (e.g., that for depolymerizing actin-containing filaments).Absorption spectra were obtained for ultraviolet light passing through spindle fibres as well as for ultraviolet light passing through the interzone.

Analysis of chromosome movement in crane fly spermatocytes by ultraviolet microbeam irradiation of individual chromosomal spindle fibres. I. General results

1981 ◽  
Vol 59 (9) ◽  
pp. 770-776 ◽  
Author(s):  
Peggy J. Sillers ◽  
Arthur Forer
Keyword(s):  
Ultraviolet Light ◽  
Monochromatic Light ◽  
The Other ◽  
Spindle Fibre ◽  
Chromosome Movement ◽  
Opposite Pole ◽  
Other Hand ◽  
Ultraviolet Microbeam ◽  
The Difference ◽  
Spindle Fibres

Single chromosomal spindle fibres in anaphase Nephrotoma ferruginea (crane fly) spermatocytes were irradiated with monochromatic ultraviolet light focussed to a 4-μm spot by means of an ultraviolet microbeam apparatus. The movement of the half-bivalent associated with the irradiated spindle fibre was either unaffected or the half-bivalent stopped moving; i.e., the effect was all-or-none. When the half-bivalent associated with the irradiated spindle fibre did stop moving, the partner half-bivalent moving towards the opposite pole (i.e., the half-bivalent with which the first half-bivalent was previously paired) also stopped moving: all other half-bivalents moved normally. In over 90% of the 69 cases the movements of the two half-bivalents were only temporarily blocked; when movement resumed both half-bivalents resumed movement at the same time, after stoppage times ranging from 2 min to more than 15 min. In a few cases the half-bivalents never resumed poleward motion.When half-bivalents that had stopped movement finally resumed movement they often did not reach the poles; i.e., they "lagged" and remained separate from the other chromosomes. This result occurred only in spermatocytes of N. ferruginea. In spermatocytes of N. suturalis or N. abbreviata, on the other hand, the stopped half-bivalents did not lag but always reached the poles.Half-bivalent pairs that stopped moving in N. ferruginea spermatocytes did so for shorter times than did those previously reported (after irradiation of chromosomal spindle fibres) in N. suturalis spermatocytes. We suggest that the difference is due to our use of monochromatic ultraviolet light as opposed to the previous use of heterochromatic ultraviolet light. We assume that different wavelengths of monochromatic light produce different effects, that any given monochromatic irradiation produces only one effect (albeit different effects at different wavelengths), but that heterochromatic irradiations can produce multiple effects.Irradiation of the interzone (between separating half-bivalents) had no effect on the chromosome-to-pole movements of the half-bivalents. Therefore the stoppage of movement of half-bivalent pairs is specific for irradiation of chromosomal spindle fibres. On the other hand, irradiation of the interzone often blocked pole-to-pole elongation.

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

1993 ◽  
Vol 105 (2) ◽  
pp. 571-578 ◽  
Author(s):  
B.B. Czaban ◽  
A. Forer ◽  
A.S. Bajer
Keyword(s):  
Ultraviolet Light ◽  
Spindle Fibre ◽  
Microbeam Irradiation ◽  
Ultraviolet Microbeam ◽  
Spindle Fibres

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.

Action spectrum for changes in spindle fibre birefringence after ultraviolet microbeam irradiations of single chromosomal spindle fibres in crane-fly spermatocytes

1983 ◽  
Vol 62 (1) ◽  
pp. 1-25
Author(s):  
P.J. Sillers ◽  
A. Forer
Keyword(s):  
Ultraviolet Light ◽  
Action Spectrum ◽  
The Other ◽  
Spindle Fibre ◽  
Chromosome Movement ◽  
Ultraviolet Microbeam ◽  
Two Peaks ◽  
Wavelength Light ◽  
Spindle Fibres ◽  
In Cells

Single chromosomal spindle fibres in Nephrotoma suturalis (crane-fly) spermatocytes in metaphase and anaphase were irradiated with monochromatic ultraviolet light focussed to a 2 micrometer spot. In cells in both metaphase and anaphase either the birefringence of the irradiated spindle fibre was altered in the irradiated region, or there was no change, depending on the dose and wavelength of ultraviolet light used for the irradiation. When there was an area of reduced birefringence (ARB), it moved poleward regardless of whether the associated chromosome moved poleward. When cells were irradiated in early metaphase they remained in metaphase until the ARB reached the pole. In some cells irradiated in late metaphase the chromosomes began anaphase before the ARB reached the pole; in many such cells anaphase was abnormal in that all six half-bivalents separated at the start of anaphase but none moved polewards. In all cases the ARB moved poleward at the same speed as subsequent chromosome movement; that is, at about 0.8 micrometer/min. In cells irradiated in anaphase, spindle fibre birefringence was reduced independently of blockage of chromosome movement. Because birefringence and movement were altered independently there were four classes of results: (1) in some cases there was no effect on the movement of the chromosome associated with the irradiated spindle fibre and no effect on the birefringence of the irradiated spindle fibre. (2)In some cases, primarily with 260 nm wavelength light, there was no effect on the movement of the chromosome associated with the irradiated spindle fibre and there was an effect on the birefringence of the irradiated spindle fibre. (3) In some cases, primarily with 290 nm wavelength light, there was an effect on the movement of the chromosome associated with the irradiated spindle fibre and no effect on the birefringence of the irradiated spindle fibre. (4) In some cases, primarily with 270 nm and 280 nm wavelength light, there was an effect on the movement of the chromosomes associated with the irradiated spindle fibre and there was an effect on the birefringence of the irradiated spindle fibre. The action spectrum for reducing spindle fibre birefringence in crane-fly spermatocytes had two peaks, one at 260 nm and the other, less sensitive, at 280 nm. For irradiations at 270 nm, 280 nm and 290 nm, five to fifty times more energy was needed to reduce spindle fibre birefringence than to stop chromosome movement, but for irradiations at 260 nm five times less energy was needed to reduce spindle fibre birefringence than to stop chromosome movement. The action spectrum for reducing spindle fibre birefringence is quite different from that for stopping chromosome movement.

The behaviour of microtubules in chromosomal spindle fibres irradiated singly or doubly with ultraviolet light

1989 ◽  
Vol 94 (4) ◽  
pp. 625-634
Author(s):  
P. Wilson ◽  
A. Forer
Keyword(s):  
Ultraviolet Light ◽  
Single Fibre ◽  
The Other ◽  
Microbeam Irradiation ◽  
Other Hand ◽  
Ultraviolet Microbeam ◽  
Spindle Fibres

Areas of reduced birefringence (ARBs) produced by ultraviolet microbeam irradiation are areas of depolymerized microtubules. ARBs probably move poleward either by microtubule subunit addition at the kinetochore and loss at the pole, or by microtubule subunit addition at one edge of the ARB and loss from the other edge. In this paper we have used two approaches to try to distinguish between these two models. First, we determined whether the edges of the ARB move at the same rate; if ARB motion is due solely to addition at the kinetochore and loss at the pole, with the ARB edges unable to exchange subunits, then the two edges of each ARB should move at the same rate. On the other hand, if the exchange is at the ARB edges, then, from data from microtubules in vitro, the poleward edge should move much faster than the kinetochoreward edge. We found that the two edges of the ARB move at the same rate about half the time, but half the time they do not. Second, we studied the behaviour of two ARBs on a single fibre. If ARB motion is due solely to subunit addition at the kinetochore and loss at the pole, then the two ARBs must move poleward together. We found that after two ARBs are formed on a single fibre the region between the ARBs is unstable and rapidly depolymerizes. These results do not fit either model and suggest that influences of kinetochores and poles or other factors need to be considered that are not duplicated in experiments on microtubules in vitro.

Sex-chromosome anaphase movements in crane-fly spermatocytes are coordinated: ultraviolet microbeam irradiation of one kinetochore of one sex chromosome blocks the movements of both sex chromosomes

1987 ◽  
Vol 88 (4) ◽  
pp. 441-452
Author(s):  
JULIA A. M. SWEDAK ◽  
ARTHUR FORER
Keyword(s):  
Sex Chromosomes ◽  
Sex Chromosome ◽  
The Other ◽  
Signal System ◽  
Spindle Fibre ◽  
Spindle Axis ◽  
Ultraviolet Microbeam ◽  
Block Motion ◽  
Block Movement ◽  
Spindle Fibres

Sex chromosomes in crane-fly spermatocytes move polewards at anaphase after the autosomes have reached the poles. In Nephrotoma abbreviate the sex chromosomes are 8 μm long by 3.5 μm wide and have two orientations when they move: the long axis of the sex chromosome is either perpendicular or parallel to the spindle axis. We assume (1) that when a sex chromosome is perpendicular to the spindle axis it has a chromosomal spindle fibre to each pole, one from each kinetochore, as in other species; and (2) that when a sex chromosome is parallel to the spindle axis each kinetochore has spindle fibres to both poles, i.e. that the latter sex chromosomes are maloriented. We irradiated one kinetochore of one sex chromosome using an ultraviolet microbeam. When both sex chromosomes were normally oriented, irradiation of a single kinetochore permanently blocked movement of both sex chromosomes. Irradiation of non-kinetochore chromosomal regions or of spindle fibres did not block movement, or blocked movement only temporarily. We argue that ultraviolet irradiation of one kinetochore blocks movement of both sex chromosomes because of effects on a ‘signal’ system. The results were different when one sex chromosome was maloriented. Irradiation of one kinetochore of a maloriented sex chromosome did not block motion of either sex chromosome. On the other hand, irradiation of one kinetochore of a normally oriented sex chromosome permanently blocked motion of both that sex chromosome and the maloriented sex chromosome. We argue that for the signal system to allow the sex chromosomes to move to the pole each sex chromosome must have one spindle fibre to each pole.

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