Video digitizer analysis of birefringence along the lengths of single chromosomal spindle fibres. I. Description of the system and general results

1984 ◽  
Vol 65 (1) ◽  
pp. 21-40
Author(s):  
C.J. Schaap ◽  
A. Forer
Keyword(s):  
Published Data ◽  
Spindle Fibre ◽  
Single Spot ◽  
Definition Of ◽  
Oriented Material ◽  
Spindle Fibres ◽  
Operator Definition ◽  
New System ◽  
As If ◽  
In Cells

A new system, based on a video digitizer interfaced to a microcomputer, has been developed to quantify birefringence of individual chromosomal spindle fibres from videotaped images of spindles. (The system also can be used for any other purpose that requires the analysis of video intensities.) Retardations along the lengths of single chromosomal spindle fibres have been studied throughout metaphase and anaphase in cells kept at constant temperatures. The instrumental readings are accurate to within less than 0.06 nm retardation, but operationally the retardation values along a single chromosomal spindle fibre can vary by up to 0.15 nm, primarily because of variation in operator definition of the spindle fibre. Retardations vary with position along the fibre. During anaphase the retardations along a given chromosomal spindle fibre do not move poleward, but rather change as if the oriented material is disorganized at the kinetochore. The retardation at the kinetochore of a chromosomal spindle fibre does not change during anaphase, except for nonpredictable jumps of 20–30% that sometimes occur. Thus there is no ‘decay of birefringence’ during anaphase, such as has been described in other species. In this regard our data, that pertain only to single chromosomal spindle fibres, differ from those previously published; we argue that this is because the published data deal with mixtures of chromosomal and continuous spindle fibres, and because changes in birefringence can appear to occur, artefactually, when measurements of birefringence are made at a single spot in a spindle.

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.

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.

International Telecommunication Union

1957 ◽  
Vol 11 (3) ◽  
pp. 538-538
Keyword(s):  
Experimental Data ◽  
Technical Assistance ◽  
Study Groups ◽  
Great Difficulty ◽  
Consultative Committee ◽  
Sufficient Time ◽  
International Telecommunication Union ◽  
International Telecommunication ◽  
Definition Of ◽  
New System

The eighth plenary assembly of the International Radio Consultative Committee (CCIR) was held in Warsaw from August 9 to September 13, 1956, under the chairmanship of Professor Pawel Szulkin (Poland). The assembly elected with an absolute majority Dr. E. Metzler (Switzerland) as Director. The assembly considered a report which dealt with the activities of the fourteen established study groups as well as proposals to reorganize the study groups. The Warsaw decisions modifying procedures experimentally for the future were the outcome of proposals by the Organization and Finance Committees, the CCIR Secretariat and of discussions of the problem in the plenary assembly. The study groups were to remain the same in number and the allocation of work was in general the same, though it was felt desirable to give a more precise definition of their terms of reference. Among the resolutions adopted by the assembly, a number dealt with the length, content and quantity of documents submitted to the chairmen of the study groups, emphasizing that these should be as short as possible, as few as possible and that they should contain only the minimum indispensable mathematical formulae or numerical and experimental data. The new system was also expected to improve the position of distant countries which had so far experienced great difficulty in receiving preliminary documentation in sufficient time before plenary assemblies. The Technical Assistance Committee recommended the creation of a joint CCIR-International Telegraph and Telephone Consultative Committee (CCITT) committee to consider the ways and means whereby technical assistance was at present granted and to make suggestions for improvements, as far as telecommunication was concerned, to the ITU Administrative Council.

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.

Does actin produce the force that moves a chromosome to the pole during anaphase?

1985 ◽  
Vol 63 (6) ◽  
pp. 585-598 ◽  
Author(s):  
Arthur Forer
Keyword(s):  
Spindle Fibre ◽  
Apparent Contradiction ◽  
Spindle Poles ◽  
Ultraviolet Microbeam ◽  
The Face ◽  
Spindle Fibres ◽  
Rule Out ◽  
Do So

Chromosomes move towards spindle poles because of force produced by chromosomal spindle fibres. I argue that actin is involved in producing this force. Actin is present in chromosomal spindle fibres, with consistent polarity. Physiological experiments using ultraviolet microbeam irradiations suggest that the force is due to an actin and myosin (or myosin-equivalent) system. Other physiological experiments (using inhibitors in "leaky" cells or antibodies injected into cells) that on the face of it would seem to rule out actin and myosin on closer scrutiny do not really do so at all. I argue that in vivo the "on" ends of chromosomal spindle fibre microtubules are at the kinetochores; I discuss the apparent contradiction between this conclusion and those from experiments on microtubules in vitro. From what we know of treadmilling in microtubules in vitro, the poleward movements of irradiation-induced areas of reduced birefringence (arb) can not be explained as treadmilling of microtubules: additional assumptions need to be made for arb movements toward the pole to be due to treadmilling. If arb movement does indeed represent treadmilling along chromosomal spindle fibre microtubules, treadmilling continues throughout anaphase. Thus I suggest that chromosomal spindle fibres shorten in anaphase not because polymerization is stopped at the kinetochore (the on end), as previously assumed, but rather because there is increased depolymerization at the pole (the "off" end).

scholarly journals An expanded view of the eukaryotic cytoskeleton

2013 ◽  
Vol 24 (11) ◽  
pp. 1615-1618 ◽  
Author(s):  
James B. Moseley
Keyword(s):  
Complex System ◽  
Cell Biology ◽  
Linear Polymers ◽  
Polymer Systems ◽  
History Of ◽  
Definition Of ◽  
Future Work ◽  
Biology Research ◽  
In Cells

A rich and ongoing history of cell biology research has defined the major polymer systems of the eukaryotic cytoskeleton. Recent studies have identified additional proteins that form filamentous structures in cells and can self-assemble into linear polymers when purified. This suggests that the eukaryotic cytoskeleton is an even more complex system than previously considered. In this essay, I examine the case for an expanded definition of the eukaryotic cytoskeleton and present a series of challenges for future work in this area.

scholarly journals Electroporation can cause artefacts due to solubilization of cations from the electrode plates. Aluminum ions enhance conversion of inositol 1,3,4,5-tetrakisphosphate into inositol 1,4,5-trisphosphate in electroporated L1210 cells

1991 ◽  
Vol 277 (3) ◽  
pp. 883-885 ◽  
Author(s):  
J W Loomis-Husselbee ◽  
P J Cullen ◽  
R F Irvine ◽  
A P Dawson
Keyword(s):  
Experimental System ◽  
Experimental Medium ◽  
Assay Medium ◽  
L1210 Cells ◽  
Aluminum Ions ◽  
Inositol 1,4,5 Trisphosphate ◽  
The Difference ◽  
High Concentrations ◽  
As If ◽  
In Cells

1. In electroporated L1210 cells, Ins(1,3,4,5)P4 causes Ca2+ release, owing to its conversion into Ins(1,4,5)P3, but this does not happen in cells permeabilized by digitonin treatment [Cullen, Irvine, Drøbak & Dawson (1989) Biochem. J. 259, 931-933]. 2. If the assay medium is subjected to electroporation by using a commercially available electroporation apparatus and then the cells are added and permeabilized with digitonin, the cells behave as if they had been electroporated. 3. Electroporation causes the release of high concentrations of Al3+ into the experimental medium, and addition of these concentrations of Al3+ into the experimental medium mimics the effect of electroporation on the conversion of Ins(1,3,4,5)P4 into Ins(1,4,5)P3. 4. It is concluded that the difference between electroporated and digitonin-permeabilized L1210 cells in this experimental system can be attributed to dissolution of Al3+ from the electroporation cuvette. Al3+ contamination may thus be a serious problem when using this apparatus.

Ciceronian and Heraclean Professiones

1918 ◽  
Vol 12 (1) ◽  
pp. 38-45 ◽  
Author(s):  
Jefferson Elmore
Keyword(s):  
Subject Matter ◽  
Good Case ◽  
Interesting Article ◽  
The Subject ◽  
Puzzling Problem ◽  
Difficult Part ◽  
New System ◽  
Opening Section ◽  
As If

Perhaps the most difficult part of the famous inscription from Heraclea (around which so many controversies have raged) is the opening section of the extant text, where from a given form of procedure it is required to determine the subject matter. A solution of this puzzling problem, which I proposed some months ago, has recently been made the subject of an interesting article in this journal by Dr. E. G. Hardy. Mr. Hardy has long been engaged in this field, and has rendered much useful service. In this article, however, he seems to be interested in my views chiefly in their relation to his own theory. This is apparent in his agreements with me. For example, one aim of my study was to identify the professiones of Cicero's letters ad Att. xiii. 33, 1, and ad Fam. xvi. 23, 1, with those provided for in the first section of the inscription. It appeared that the returns mentioned by Cicero were registrations of property, that they were to be made yearly, and that they had their prototype in the annual property census of Egypt. It also seemed clear that Caesar's recensus populi of 46 was modelled on the Egyptian kατ' oίkíαm άπoγραφήiKíαν. With these preliminary conclusions (by no means unimportant in themselves) Mr. Hardy is not unwilling to agree. He even goes so far as to say that I have made a good case for ‘a new system of professiones somehow relating to property and introduced in 46.’ He thinks too that the settlement of the frumentations as a part of a more comprehensive legislative scheme (as my view implies) would be most appropriate. So far so good, but when it comes to the vital point of admitting a connection between these matters and vv. 1–19 of the Tablet he draws back as if from some fatal step.

scholarly journals Next-to-leading-order QCD corrections to heavy quark fragmentation into $${}^1S^{(1,8)}_0$$ quarkonia

2021 ◽  
Vol 81 (7) ◽  
Author(s):  
Feng Feng ◽  
Yu Jia ◽  
Wen-Long Sang
Keyword(s):  
Heavy Quark ◽  
Fragmentation Function ◽  
Short Distance ◽  
Decomposition Method ◽  
Heavy Quarkonium ◽  
Leading Order ◽  
Quark Fragmentation ◽  
Definition Of ◽  
Perturbative Corrections ◽  
Operator Definition

AbstractWithin NRQCD factorization framework, in this work we compute, at the lowest order in velocity expansion, the next-to-leading-order (NLO) perturbative corrections to the short-distance coefficients associated with heavy quark fragmentation into the $${}^1S_0^{(1,8)}$$ 1 S 0 ( 1 , 8 ) components of a heavy quarkonium. Starting from the Collins and Soper’s operator definition of the quark fragmentation function, we apply the sector decomposition method to facilitate the numerical manipulation. It is found that the NLO QCD corrections have a significant impact.

scholarly journals КОНЦЕПЦІЯ РЕАЛІЗАЦІЇ ДЕРЖАВНОЇ МИТНОЇ СПРАВИ В КОНЦЕПТУАЛЬНИХ ДОКУМЕНТАХ

2019 ◽  
Vol 14 ◽  
pp. 323-331
Author(s):  
О. П. Федотов
Keyword(s):  
The State ◽  
Significant Part ◽  
Definition Of ◽  
New System

Статтю присвячено дослідженню теоретичних засад концепції реалізації державної мит­ної справи в концептуальних документах. Надано авторське визначення поняття «концеп­ція реалізації державної митної справи». Доведено, що поняття «концепція» практично пов'язане з концептуальністю державної митно" справи. Встановлено, що вагомою складо­вою концепції с процес виконання її пріоритетної мети. Акцентовано увагу на тому факті, що власна концепція реалізації державної митної справи, яка буде розроблятися та впро­ваджуватися в діяльність новітньою Державною фіскальною службою України, не повинна прийматися спонтанно задля уникнення ризиків, що стане запорукою належної реалізації державної митної справи.   The Article researches theoretical bases of a conception of implementing the state customs in conceptual documents. There is represented the author's definition of the concept of implementing the state customs affair. It is proved that the concept is practically connected with conceptual novation of state customs affair associated with customs. It was found that a significant part of the concept is the process of implementation of its priority goal. Attention is focused on the fact that the proper implementation of the concept of state customs affairs, which will be developed and implemented by new system of State Customs Service of Ukraine it should not be spontaneously taken to avoid risks will ensure proper implementation of the state customs affairs.

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