Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “bivalent”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,045 records · Page 58Linked to original sources
PubMed1996

Recombinant baculovirus influenza A hemagglutinin vaccines are well tolerated and immunogenic in healthy adults.

In a prospective double-blind trial, the reactogenicity and immunogenicity of recombinant baculovirus influenza A vaccines containing purified full-length hemagglutinin (HA) were compared with standard trivalent inactivated vaccine (TIV). The recombinant baculovirus influenza A vaccines (rHA0) were monovalent (containing 45 micrograms of A/Beijing/92[H3] and 15, 45, and 135 micrograms of A/Texas/91[H1]) and bivalent (containing 45 micrograms of both A/Beijing/92 and A/Texas/91). The bivalent rHA0 vaccine produced fewer local side effects than the TIV (50% vs. 88%, P = .003). The hemagglutinin inhibition (HAI) responses (defined as a > or = 4 increase in HAI) to A/Beijing rHA0 in the monovalent A/Beijing/92, the bivalent vaccine, and the TIV were 68%, 76%, and 46%, respectively (P = .086). Increasing doses of A/Texas rHA0 (15 micrograms [60%], 45 micrograms [69%], and 135 micrograms [76%]) and bivalent HA (76%) gave better immunologic responses to H1 than did TIV (31%; P = .003).

Adolescent↗
PubMed1993

Depletion of the helper/inducer (memory) T cell subset using a bispecific antibody-toxin conjugate directed against CD4 and CD29.

We have developed a bispecific antibody that recognizes the CD4 and CD29 antigens simultaneously and that was examined for its ability to target CD4+CD29bright T cells. The premise for using bispecific antibody-toxin conjugates was that monovalent binding to one antigen would not result in internalization while binding through both antigens would predispose toward endocytosis and delivery of the toxin to the cell interior. In this study, we show that the bispecific antibody binds monovalently to CD4 and CD29 and bivalently to both antigens. Both monovalent and bivalent binding rendered the target cells sensitive to complement-mediated lysis, demonstrating that this effector modality cannot take advantage of the dual specificity of the antibody. Bivalent binding, however, allowed modulation of more than 60% of the bound antibody off the surface of CD4+CD29bright cells, which we further exploited to deliver a toxin moiety preferentially to CD4+CD29bright cells. Immunoconjugates incorporating blocked ricin (a ricin holotoxin that has its intrinsic galactose-binding sites blocked by chemically linked affinity ligands) preferentially killed CD4+CD29bright cells in vitro by a factor of 25 in comparison with killing of total CD4+ cells in functional assays. Assays on resting PBL demonstrated a similar specificity of the bispecific immunotoxin for CD4+CD29bright cells with a concomitant relative survival of CD4+CD29dim (CD45RA+). We demonstrated that the potency of the immunotoxin is not only a function of its affinity but also of its propensity to internalize, and that this property is influenced by the degree of bivalent binding. These results open up the possibility of engineering bispecific antibody toxin conjugates for use as therapeutic immunotoxins for selective removal of restricted T cell subsets.

Animals↗
PubMed2005

TP-3 immunotoxins improve antitumor activity in mice with osteosarcoma.

We measured the antitumor activity of two types of TP-3 immunotoxins that target an antigen expressed in tumors associated with osteosarcoma. Development of novel agents for treatment of patients with osteosarcoma is important. We previously described a monovalent-disulfide-stabilized recombinant immunotoxin made from the TP-3 antibody. This agent is called TP-3(dsFv)-PE38 and is cytotoxic to human osteosarcoma cells in vitro. To improve antigen binding, we designed and produced a bivalent immunotoxin, TP-3(dsFv)2-PE38. We evaluated the activity of both molecules in vitro and in vivo using tumor-bearing mice. Compared with the monovalent TP-3 immunotoxin, the bivalent TP-3 immunotoxin showed an approximately sevenfold increase in cytotoxic activity against three osteosarcoma cell lines which react with the TP-3 monoclonal antibody. The apparent affinity of the bivalent TP-3 immunotoxin was 12-fold greater than that of the monovalent TP-3 immunotoxin. The antitumor activities of both TP-3 immunotoxins were measured using severe combined immunodeficient mice bearing osteosarcoma cell line OHS-M1 tumors. The dose at which the bivalent TP-3 immunotoxin produces complete regressions of tumors is (1/2) that of the monovalent TP-3 immunotoxin. Increasing the avidity of TP-3(dsFv)-PE38 significantly improves its cytotoxic activity in vitro and results in a twofold increase in antitumor activity in vivo. Because TP-3-based immunotoxins have good antitumor activity in mice, these molecules merit additional development for possible treatment of osteosarcoma in humans.

Animals↗
PubMed1991

Differentiation between neutrophil-bound antibodies and immune complexes.

It is often unknown whether neutrophil-bound immunoglobulins (NBIg) in patients with chronic diseases consist of bound immune complexes (IC) or of anti-neutrophil antibodies. Until now, the detection of IC in serum by the C1q-binding test has been used to define the nature of NBIg. Here we present studies on methods for characterization of NBIg using a bivalent IC and heat-aggregated IgG as IC models and neutrophil alloantibodies as antibody models. Heat-aggregated IgG was readily detected in the C1q-binding test. However, the bivalent IC, which is capable of binding to both low-affinity Fc receptors (FcRII and FcRIII) on neutrophils was not detected in this test. This was due to failure of the bivalent IC to bind to C1q, as was demonstrated by studies with immobilized C1q. However, the bivalent IC as well as heat-aggregated IgG, when bound to neutrophils from healthy donors, were not or only marginally eluted from the cell surface by lowering the pH, in contrast to a number of different cell-bound antibodies. This led to the observation that eluates, prepared from sensitized cells, showed reactivity with donor neutrophils, whereas eluates, prepared from cells to which immune complexes had bound, did not. Thus, a negative result in the C1q-binding test does not prove that a serum does not contain neutrophil-binding IC, but the reactivity of an eluate can distinguish between anti-neutrophil antibodies and bound IC.

Antigen-Antibody Complex↗
PubMed1994

Relevance of antibody valency in EGF receptor modulation.

Binding characteristics of a monovalent bispecific monoclonal antibody (bsMoAb), which recognizes both epidermal growth factor receptor (EGF-R) and drug doxorubicin (DXR) were compared with those of the parental bivalent MoAb directed against the EGF-R binding site. Scatchard analysis indicated that both MoAbs bound to EGF-R-overexpressing A431 cells with the same affinity. In tracer amounts, both MoAbs also displayed the same capacity to be internalized after binding to the cell surface. However, when the MoAbs were used at saturating concentrations, down-modulation of the receptor was greater with the bivalent MoAb. The bivalent MoAb also inhibited proliferation of A431 cells both in vitro and in vivo whereas the bsMoAb was inhibitory only in vivo. These data suggest that MoAb bivalency is required for EGF-R down-modulation and in vitro cell growth inhibition.

Animals↗
PubMed2006

Unique genomic configuration revealed by microsatellite DNA in polyploid dogroses, Rosa sect. Caninae.

An allopolyploid complex with high genomic integrity has been studied. Dogroses transmit only seven chromosomes (from seven bivalents) through the pollen, whereas 21, 28 or 35 chromosomes (from seven bivalents and 14, 21 or 28 univalents) come from the egg cells. Seedlings derived from two interspecific crosses were analysed with flow cytometry and molecular markers to determine ploidy level, mode of reproduction and genomic constitution. Evidence was obtained for the formation of unreduced male and female gametes, which can take part in fertilization (producing seedlings with higher ploidy than the parental plants) or in apomictic reproduction. Random amplified polymorphic DNA (RAPD) and microsatellite analyses indicated that three seedlings (5%) were derived through apomixis, whereas the other 49 were hybrids. Bivalent formation appears to involve chromosomes that consistently share the same microsatellite alleles. Allele-sharing between the maternally transmitted and highly conserved univalent-forming chromosomes reflected the taxonomic distance between different genotypes. The frequently recombining bivalent-forming chromosomes were taxonomically less informative.

Crosses, Genetic↗
PubMed2006

Ligand valency affects transcytosis, recycling and intracellular trafficking mediated by the neonatal Fc receptor.

The neonatal Fc receptor (FcRn) transports IgG across epithelial cell barriers to provide maternal antibodies to offspring and serves as a protection receptor by rescuing endocytosed IgG and albumin from lysosomal degradation. Here we describe the generation of polarized Madin-Darby canine kidney (MDCK) cells expressing rat FcRn (rFcRn) to investigate the potential requirement for ligand bivalency in FcRn-mediated transport. The rFcRn-MDCK cells bind, internalize and bidirectionally transcytose the bivalent ligands IgG and Fc across polarized cell monolayers. However, they cannot be used to study FcRn-mediated transport of the monovalent ligand albumin, as we observe no specific binding, internalization or transcytosis of rat albumin. To address whether ligand bivalency is required for transport, the ability of rFcRn to transcytose and recycle wild-type Fc homodimers (wtFc; two FcRn-binding sites) and a heterodimeric Fc (hdFc; one FcRn-binding site) was compared. We show that ligand bivalency is not required for transcytosis or recycling, but that wtFc is transported more efficiently than hdFc, particularly at lower concentrations. We also demonstrate that hdFc and wtFc have different intracellular fates, with more hdFc than wtFc being trafficked to lysosomes and degraded, suggesting a role for avidity effects in FcRn-mediated IgG transport.

Animals↗
PubMed1993

Zygotene-pachytene substaging and synaptonemal complex karyotyping of boar spermatocytes.

Synaptonemal complex analysis, by electron microscopy of spread spermatocytes after phosphotungstic acid staining, made possible description of the chromosomal synaptic patterns and the synaptonemal complex karyotype of the pig (Sus scrofa domestica). The autosomal synaptic pattern in conjunction with the sex chromosome morphology and pairing behaviour can serve as a reference for the meiotic cell progression from the zygotene stage to the pachytene. The autosomes started terminal synapsis at early zygotene (Z1) and at mid-zygotene (Z2) some of the small bivalents were completely paired. The extension of pairing between the X and the Y chromosome, and the differentiation of their axes, disclosed seven types of sex bivalent (Types 0-VI). The Type 0 sex bivalent occurred in late zygotene (Z3), at which the X and Y axes began terminal synapsis by their short arms. Each one of the pachytene substages, early, mid-, and late, included two sex bivalent types. By early pachytene (P1-P2) the entire Y chromosome was paired with the X axis. Subsequently, progressive desynapsis and differentiation of the sex chromosome axes defined the mid- (P3-P4) and late pachytene substages (P5-P6). At mid-pachytene, the unpaired XY segments were associated end-to-end and showed differing degrees of complexity (thickening, splitting, despiralization and strandedness). These axial complexities were replaced at late pachytene by fine excrescences along the sex chromosome axes, which still formed a short SC stretch. Additionally, an attempt to construct an SC karyotype for the pig is presented. There was general agreement between the autosomal SC karyotype and the autosomal somatic karyotype when comparisons were made, considering the relative lengths and arm ratios of individual chromosome pairs.

Animals↗
PubMed2000

Chromomeric pattern of maize pachytene chromosomes after trypsin treatment.

The bivalent chromomeres of maize were analyzed by means of enzymatic treatment with trypsin. The aim was to verify if the effect of swelling observed in human meiotic chromosomes also occurs in these bivalents, and if this morphological change allows a greater visual resolution of the chromomeric pattern. Bivalents treated with trypsin showed a structure with sequential and linear distribution of small rings. Comparisons between bivalent morphology, treated and non-treated, indicated a collinearity among the sequences of rings and the chromomeres. The results obtained were considered useful to analyze and to make a chromomere map. This treatment can also provide cytological evidence that may help to understand the pairing process. It was concluded that the ring-shape was caused by trypsin-induced "disjoining" just in the chromomeric but not in the interchromomeric regions.

Chromosomes↗
PubMed2026

Genomic introgressions from wild relatives in the wheat genome alter meiotic dynamics in inter-varietal hybrids.

The use of wild relatives to introduce original diversity in the genome of bread wheat (Triticum aestivum L.) is an interesting approach to face the challenges of sustainable agriculture and the impact of climate change on wheat production. However, the influence of these wild-species introgressions on meiosis in inter-varietal wheat hybrids remains poorly understood. We analyzed the French wheat variety Renan (Re) carrying Aegilops ventricosa (Aev)-derived 2AS/2NS and 7DL/7DvL introgressions, the reference cultivar Chinese Spring (CS), which lacks these introgressions, and their inter-varietal hybrid Chinese Spring × Renan (CSRe). This analysis combined cytogenetic approaches with the assessment of reproductive performance. Furthermore, we generated a cytological atlas of meiosis in wild tetraploid Aev, quantifying bivalent configurations and chiasma frequency. We observed a reduced pollen viability and a slight decrease in floret fertility in the hybrid CSRe. Exploration of the meiotic behavior showed that CSRe exhibited increased numbers of rod bivalents and univalents, leading to a reduced average chiasma number and frequent chromosome bridges and fragmentations, whereas the parental lines maintained stable chromosome pairing. These rearrangements indicate that homologous chromosome pairing and recombination are affected in CSRe. We applied introgression-specific oligo-Fluorescent In Situ Hybridization to localize alien segments in CSRe, providing a novel strategy to investigate the meiotic behavior of introgressed regions. The 2AS/2NS introgressed segments in CSRe were frequently located on rod bivalents or univalents, while 7DL/7DvL segments consistently formed ring bivalents. Our results provide a foundation for guiding alien gene introgression and for understanding the behavior of chromosomes with introgressions in the wheat genome.

Meiosis↗
PubMed1964

GYNOGENESIS IN SALAMANDERS RELATED TO AMBYSTOMA JEFFERSONIANUM.

The oocytes of naturally occurring triploid females of the Ambystoma jeffersonianum complex each contain 84 lampbrush chromosomes. This constitutes hexaploidy (n = 14). The chromosomes are joined into pairs by chiasmata and form 42 bivalents. It is suggested that meiosis in triploid females is preceded by an endomitosis and the resulting sister chromosomes synapse to form pseudo-bivalents. Sperm from diploid males stimulate development of the triploid eggs but do not contribute chromosomes to the triploid nucleus. Bivalents in the oocytes of triploids have twice as many chiasmata as the corresponding bivalents in diploid animals. Such chiasmata cannot result in genetic recombination.

Ambystoma↗
PubMed2001

Low glucosinolate Brassica juncea breeding line revealed to be nullisomic.

The low glucosinolate Brassica juncea breeding line 1058 was derived from a BC1F3 plant of an interspecific cross between high glucosinolate Indian B. juncea (genome AABB, 2n = 36) line 60143 and B. rapa (genome AA, 2n = 20) canola strain CZY. Line 60143 had 2n = 36 chromosomes (18 bivalents at metaphase I) and strain CZY had 2n = 20 chromosomes (10 bivalents). Line 1058 was nullisomic, with 2n - 2 = 34 chromosomes, with 17 bivalents formed at metaphase I and an even chromosomal segregation of 17:17 at anaphase I. In F1 hybrid plants of the cross 1058 x CZY, 98.3% of the pollen mother cells had 10 bivalents and seven univalents. This is evidence that plants of line 1058 are nullisomic, missing one pair of B-genome chromosomes.

Brassica↗
PubMed2005

Codling moth cytogenetics: karyotype, chromosomal location of rDNA, and molecular differentiation of sex chromosomes.

We performed a detailed karyotype analysis in the codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), the key pest of pome fruit in the temperate regions of the world. The codling moth karyotype consisted of 2n = 56 chromosomes of a holokinetic type. The chromosomes were classified into 5 groups according to their sizes: extra large (3 pairs), large (3 pairs), medium (15 pairs), small (5 pairs), and dot-like (2 pairs). In pachytene nuclei of both sexes, a curious NOR (nucleolar organizer region) bivalent was observed. It carried 2 nucleoli, each associated with one end of the bivalent. FISH with an 18S ribosomal DNA probe confirmed the presence of 2 clusters of rRNA genes at the opposite ends of the bivalent. In accordance with this finding, 2 homologous NOR chromosomes were identified in mitotic metaphase, each showing hybridization signals at both ends. In highly polyploid somatic nuclei, females showed a large heterochromatin body, the so-called sex chromatin or W chromatin. The heterochromatin body was absent in male nuclei, indicating a WZ/ZZ (female/male) sex chromosome system. In keeping with the sex chromatin status, pachytene oocytes showed a sex chromosome bivalent (WZ) that was easily discernible by its heterochromatic W thread. To study molecular differentiation of the sex chromosomes, we employed genomic in situ hybridization (GISH) and comparative genomic hybridization (CGH). GISH detected the W chromosome by strong binding of the Cy3-labelled, female-derived DNA probe. With CGH, both the Cy3-labelled female-derived probe and Fluor-X labelled male-derived probe evenly bound to the W chromosome. This suggested that the W chromosome is predominantly composed of repetitive DNA sequences occurring scattered in other chromosomes but accumulated in the W chromosome. The demonstrated ways of W chromosome identification will facilitate the development of genetic sexing strains desirable for pest control using the sterile insect technique.

Animals↗
PubMed1992

Synaptonemal complex analysis of an autosomal trisomy in the horse.

Synaptonemal complex analysis by electron microscopy of a trisomy 28 in a male horse demonstrated a trivalent or a bivalent plus a univalent in primary spermatocytes. Two of the chromosomes making up the trivalent were, most often, completely paired with each other and only partially paired or associated with the third one. Half of the spermatocytes analysed demonstrated heterologous pairing or association between the free axis of the trivalent and the sex bivalent. The pairings remained, to a large extent, into diakinesis-metaphase I. In most pachytene cells one autosomal bivalent showed proximal asynapsis and paired often, heterologously, with the trivalent or the sex bivalent. The horse demonstrated azoospermy, which was due, at least in part, to degeneration at both the spermatocyte and spermatid levels.

Animals↗
PubMed1991

Kinetochore function can be altered by ultraviolet microbeam irradiation without loss of the associated birefringent spindle fibre.

We have irradiated kinetochores of chromosomes in spermatocytes of crane flies (Nephrotoma abbreviata (Loew)) and Nephrotoma suturalis (Loew), while observing the cells using polarization microscopy. Irradiation of a kinetochore of one sex chromosome with 0.106 ergs microns-2, the minimum dose needed to stop movement, had no effect on the birefringence of the irradiated kinetochore's spindle fibre. Irradiation of the kinetochore of an autosomal half-bivalent in anaphase, with the same dose, had no effect on the birefringence of the irradiated kinetochore's spindle fibre, but nonetheless the anaphase movements of all six autosomal half-bivalents were stopped, temporarily, for up to 20 min. Irradiations of the kinetochores of an autosomal half-bivalent with higher doses (0.301 ergs microns-2) caused loss of birefringence of the irradiated kinetochore's spindle fibre, and the movements of all six autosomal half-bivalents were stopped permanently. We argue that the ultraviolet microbeam differentially affects two functions of the kinetochore: (1) a 'signalling' function, and (2) microtubule attachment, with the signalling function being altered at doses lower than that of microtubule attachment.

Animals↗
PubMed1976

Meiotic maturation of mouse oocytes in vitro: inhibition of maturation at specific stages of nuclear progression.

In vitro studies of meiotic maturation of mouse oocytes have been carried out in the presence of several drugs. The individual steps of nuclear progression, including dissolution of the nuclear (germinal vesicle) membrane, condensation of dictyate chromatin into compact bivalents, formation of the first metaphase spindle, and extrusion of the first polar body, are each susceptible to one or more of these drugs. Germinal vesicle breakdown, the initial morphological feature characteristic of meiotic maturation, is inhibited by dibutyryl cyclic AMP. However, even in the presence of dibutyryl cyclic AMP, the nuclear membrane becomes extremely convoluted and condensation of chromatin is initiated but aborts at a stage short of compact bivalents. Germinal vesicle breakdown and chromatin condensation take place in an apparently normal manner in the presence of puromycin, Colcemid, or cytochalasin B. Nuclear progression is blocked at the circular bivalent stage when oocytes are cultured continuously in the presence of puromycin or Colcemid, whereas oocytes cultured in the presence of cytochalasin B proceed to the first meiotic metaphase, form an apparently normal spindle, and arrest. Emission of a polar body is inhibited by all of these drugs. The inhibitory effects of these drugs on meiotic maturation are reversible to varying degrees dependent upon the duration of exposure to the drug and upon the nature of the drug. These studies suggest that dissolution of the mouse oocyte's germinal vesicle and condensation of chromatin are not dependent upon concomitant protein synthesis or upon microtubules. On the other hand, the complete condensation of chromatin into compact bivalents apparently requires breakdown of the germinal vesicle. Failure of homologous chromosomes to separate after normal alignment on the meiotic spindle in the presence of cytochalasin B suggest that microfilaments may be involved in nuclear progression at this stage of maturation. Cytokinesis, in the form of polar body formation, is blocked when any one of the earlier events of maturation fails to take place.

Animals↗
PubMed1981

Autosomal spindle fibres influence subsequent sex-chromosome movement in crane-fly spermatocytes.

In meiosis-I crane-fly spermatocytes 3 autosomal half-bivalents move to each pole in anaphase while the 2 sex-chromosomal univalents remain at the equator. The sex chromosomes move to opposite poles only after the autosomes reach the poles; the sex chromosomes start to move polewards about 25 min after the autosomal half-bivalents have begun to move. We irradiated portions of single autosomal spindle fibres with an ultraviolet microbeam and found that these irradiation altered the subsequent sex-chromosome movements. Two effects were observed. In one, one of the sex chromosomes did not move at all; the sex cin after the autosomal half-bivalents have begun to move. We irradiated portions of single autosomal spindle fibres with an ultraviolet microbeam and found that these irradiation altered the subsequent sex-chromosome movements. Two effects were observed. In one, one of the sex chromosomes did not move at all; the sex cin after the autosomal half-bivalents have begun to move. We irradiated portions of single autosomal spindle fibres with an ultraviolet microbeam and found that these irradiation altered the subsequent sex-chromosome movements. Two effects were observed. In one, one of the sex chromosomes did not move at all; the sex chromosome that remained at the equator would normally have moved to the pole associated with the irradiated autosomal spindle fibre. In the second, both sex chromosomes moved to the same pole, always that of the non-irradiated side. These effects occurred whether or not autosomal anaphase movement was blocked by the irradiation. There was no wavelength dependence for altering sex-chromosome movements. Sex-chromosome movements were altered only when at least one sex-chromosomal spindle fibre was adjacent to the irradiated autosomal spindle fibre; when neither sex chromosome had a spindle fibre adjacent to the irradiated autosomal spindle fibres the chromosomes always moved normally. Irradiation of sex-chromosomal spindle fibres during sex-chromosomal anaphase showed short blockages of movement (usually 5-8 min), and then complete recovery. Direct irradiation of sex-chromosomal spindle fibres (without irradiating autosomal spindle fibres) when the autosomes were in anaphase but the sex chromosomes were in metaphase never caused abnormal sex-chromosome movements. These results eliminate the possibility that when we irradiated autosomal spindle fibres that were adjacent to sex-chromosomal spindle fibres the sex-chromosomal spindle fibres were irradiated inadvertently and were unable to recover from the damage. We suggest that the irradiations of autosomal spindle fibres alter a control system involved in "turning on' sex-chromosomal spindle fibre motors, rather than directly altering the motors. We suggest that interactions between spindle fibres are somehow involved in this control system.

Animals↗
PubMed1983

Prometaphase forces towards opposite spindle poles are not independent: an on/off control system is identified by ultraviolet microbeam irradiations.

Individual spindle fibres in prometaphase spermatocytes of the cricket, Neocurtilla hexadactyla, were irradiated with an ultraviolet microbeam. The stretched heteromorphic bivalent (X2Y) contracted to about 75% of its pre-irradiation length after irradiation of either of its two oppositely directed spindle fibres (i.e., the X2 or Y spindle fibre). The X2Y bivalent also contracted after irradiation of the connection between the kinetochores of the univalent X1 chromosome and the Y chromosome but it did not contract after irradiation of autosomal spindle fibres or of the spindle fibre of the X1 univalent sex chromosome. The spindles sometimes shrank after irradiation, but contraction of the X2Y bivalent was independent of spindle shrinkage. The data strongly suggest that the oppositely directed forces on a bivalent are not independent. One reason is that the X2Y contractions were asymmetrical: during contraction one kinetochore remained fixed in position while the other kinetochore (facing the opposite pole) moved towards the equator. In 75% of the cases the stationary kinetochore was associated with the irradiated spindle fibre. Thus, we suggest that the irradiation of a spindle fibre produces a state analogous to rigor in the irradiated spindle fibre and, because of effects on the control system, produces relaxation of tension in the oppositely directed non-irradiated spindle fibre, so that the kinetochore associated with the non-irradiated spindle fibre moves towards the equator. These experiments have identified a control system that coordinates force production to opposite poles.

Animals↗