Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Spindle Apparatus”

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 145 records · Page 8Linked to original sources
PubMed1999

The clinical associations of mitotic spindle autoantibodies in a South Australian cohort.

BACKGROUND: The mitotic spindle apparatus (MSA) is a unique structure of microtubules and associated proteins involved in the segregation and reorganisation of chromosomes during cell division. Autoantibodies to the MSA (anti-MSA) are reported to occur rarely, but are easily identified during the immunofluorescent detection of anti-nuclear antibodies (ANA), and are generally reported as part of that investigation. AIMS: As the clinical significance of these antibodies is unknown, our aim was to identify the clinical features of subjects identified with anti-MSA, and in a subset investigate the co-association with organ specific anti-thyroid antibodies. METHODS: All ANA results from the three major immunology laboratories serving South Australia between January 1993 and June 1998 were retrospectively reviewed to identify anti-MSA subjects. Clinical details were extracted from hospital or general practice records using a standard proforma. Thyroid autoantibodies were measured using standard technique. A control group of consecutive ANA positive, anti-MSA negative individuals had anti-thyroid antibodies measured. Statistical comparison used chi2 test. RESULTS: Fifty-five subjects (43F) were identified with mean age 59.8 (range 17-91); 39 had specific diagnoses, with 16 identified as part of non-specific investigations. 'Arthritis' broadly accounted for the largest group, transient inflammatory arthritis n=7, degenerative joint disease n=6, rheumatoid arthritis n=5. Adenocarcinoma and mesothelioma accounted for one case each. Thirty-two subjects had anti-thyroid antibodies tested, with ten of 21 and two of 11 positive among the groups with anti-MSA titre >1:80 and <1:40 respectively, chi2=2.7, p=0.1. Anti-thyroid antibodies were detected more frequently among the high titre anti-MSA group (ten of 21) compared with high titre positive ANA, negative anti-MSA group (two of 11), RRisk 4.4, chi2=5.34, p=0.02. CONCLUSION: This study confirmed the relative rarity of anti-MSA and that its association is primarily with rheumatic diseases. The coincidence of mesothelioma is novel with only two previous reports of malignancy and anti-MSA. The co-association of high titre anti-MSA and thyroid autoantibodies suggest that the latter should be a follow up investigation if the former is identified as part of an investigative screen.

Adolescent↗
PubMed2003

Cytokinesis: relative alignment of the cell division apparatus and the mitotic spindle.

The cell division apparatus is assembled at different stages of the cell cycle in different eukaryotic organisms. Mechanisms exist in all organisms, however, to ensure that the cell division apparatus and the mitotic spindle are aligned perpendicular to each other. Such an alignment ensures that each daughter cell receives a nucleus and that the cell division apparatus does not cleave and destroy the genetic material. The interaction(s) of astral microtubules with the cell cortex appears to play an important role in establishing perpendicularity between chromosome segregation and cell division machinery.

Animals↗
PubMed1981

A differential staining technique for simultaneous visualization of mitotic spindle and chromosomes in mammalian cells.

A new technique has been devised for staining the mitotic spindle in mammalian cells while preserving spindle structure and chromosome number. The cells are trypsinized and fixed with a 3:1 methanol:acetic acid solution containing 4 mM MgCl2 and 1.5 mM CaCl2 at room temperature. The cells are then placed on slides and treated with 5% perchloric acid before staining with a 10% acetic acid solution containing safranin O and brilliant blue R. The preserved spindles appear dark blue against a light cytoplasmic background with chromosomes stained bright red. Individual chromosomes and chromatids are clearly visible. Positioning of the chromosomes relative to the spindle apparatus is readily ascertained allowing easy study of mitotic spindle and chromosome behavior.

Animals↗
PubMed1984

Studies of a microtubule-associated protein using a monoclonal antibody elicited against mammalian mitotic spindles.

We have devised a procedure for the identification of individual molecules which are associated with the mitotic spindle apparatus and cytoskeleton in mammalian cells. We prepared monoclonal antibody-producing hybridomas by immunizing mice with mitotic spindles isolated from cultured HeLa cells. Among several antibody-producing clones obtained, one hybridoma (22MA2) produced an antibody that recognizes a putative microtubule-associated protein which exhibits unusual distribution characteristics in cultured cells. Immunofluorescence studies showed that during mitosis the 22MA2 antigen is distributed in parallel with the spindle fibers of the mitotic apparatus, and that during interphase the antigen is always associated to a limited extent with cytoplasmic microtubules. Also, the co-distribution of the antigen with microtubules was found to be Colcemid sensitive. However, the 22MA2 antibody immunofluorescently stained the nuclei of cells in the exponential growth phase, but did not stain the nuclei of cells that had grown to confluence. This nuclear fluorescence appears to be directly related to cell density rather than nutritional (serum) factors in the growth medium. The results suggest that the antigen undergoes some change in structure or distribution in response to changes in the proliferative capacity of the cell. Biochemical analyses of cytoplasmic, nuclear, and mitotic spindle subcellular fractions show that the antigen exhibits a polypeptide molecular weight of 240,000 is found in various mammalian cells ranging from marsupial to human, and is particularly susceptible to proteolysis.

Animals↗
PubMed1984

Influence of ethanol on chromosome segregation during the first and second meiotic divisions in the mouse egg.

This study was carried out to investigate the influence of ethanol on chromosome segregation during the first and second meiotic divisions. Female mice were given a single intragastric injection of a dilute solution of ethanol either just before or at various times after the HCG injection for inducing superovulation. The mice were mated, and the chromosome constitution of fertilized eggs was determined at the first cleavage mitosis. The technique employed allowed the male- and female-derived pronuclear sets to remain as two discrete groups. Exposure from 1.5 h before to 17 h after the HCG injection induced a high incidence of aneuploidy (15-25%) involving in over 90% of cases only one chromosome, so that either 19 or 21 instead of the normal complement of 20 chromosomes were present in one of the two sets (a previous study using a "marker" chromosome has demonstrated that the nondisjunction induced here invariably involves the female set). We suggest these findings draw attention to the susceptibility of chromosome segregation in female germ cells to interference by ethanol and that the mode of action is likely to be via interference with the normal functioning of the spindle apparatus. It is possible that interference with meiotic chromosome segregation by spindle-acting agents such as ethanol might account for a proportion of human spontaneous abortions with similar chromosomal defects where no other obvious cause is apparent.

Aneuploidy↗
PubMed2002

Meiotic prophase abnormalities and metaphase cell death in MLH1-deficient mouse spermatocytes: insights into regulation of spermatogenic progress.

The MLH1 protein is required for normal meiosis in mice and its absence leads to failure in maintenance of pairing between bivalent chromosomes, abnormal meiotic division, and ensuing sterility in both sexes. In this study, we investigated whether failure to develop foci of MLH1 protein on chromosomes in prophase would lead to elimination of prophase spermatocytes, and, if not, whether univalent chromosomes could align normally on the meiotic spindle and whether metaphase spermatocytes would be delayed and/or eliminated. In spite of the absence of MLH1 foci, no apoptosis of spermatocytes in prophase was detected. In fact, chromosomes of pachytene spermatocytes from Mlh1(-/-) mice were competent to condense metaphase chromosomes, both in vivo and in vitro. Most condensed chromosomes were univalents with spatially distinct FISH signals. Typical metaphase events, such as synaptonemal complex breakdown and the phosphorylation of Ser10 on histone H3, occurred in Mlh1(-/-) spermatocytes, suggesting that there is no inhibition of onset of meiotic metaphase in the face of massive chromosomal abnormalities. However, the condensed univalent chromosomes did not align correctly onto the spindle apparatus in the majority of Mlh1(-/-) spermatocytes. Most meiotic metaphase spermatocytes were characterized with bipolar spindles, but chromosomes radiated away from the microtubule-organizing centers in a prometaphase-like pattern rather than achieving a bipolar orientation. Apoptosis was not observed until after the onset of meiotic metaphase. Thus, spermatocytes are not eliminated in direct response to the initial meiotic defect, but are eliminated later. Taken together, these observations suggest that a spindle assembly checkpoint, rather than a recombination or chiasmata checkpoint, may be activated in response to meiotic errors, thereby ensuring elimination of chromosomally abnormal gamete precursors.

Adaptor Proteins, Signal Transducing↗
PubMed1997

The serine/threonine phosphatase PP5 interacts with CDC16 and CDC27, two tetratricopeptide repeat-containing subunits of the anaphase-promoting complex.

The evolutionarily conserved multisubunit complex known as the cyclosome or anaphase-promoting complex is involved in catalyzing the ubiquitination of diverse substrates in M phase, allowing their destruction by the 26 S proteasome and the completion of mitosis. Three of the eight subunits of the anaphase-promoting complex (CDC16, CDC23, and CDC27) have been shown to be phosphorylated in M phase, and their phosphorylation is required for the anaphase-promoting complex to be active as a ubiquitin ligase. Several subunits of the anaphase-promoting complex contain tetratricopeptide repeats, a protein motif involved in protein/protein interactions. PP5 is a serine/threonine phosphatase that also contains four copies of the tetratricopeptide repeats motif. Here we show by a combination of two-hybrid analysis and in vitro binding that PP5 interacts with CDC16 and CDC27, two subunits of the anaphase-promoting complex. Only the NH2-terminal domain of PP5, containing all four tetratricopeptide repeats, is required for this physical interaction. Deletion analysis suggests that the site of binding to PP5 is localized to the COOH-terminal block of tetratricopeptide repeats in CDC16 and CDC27. In addition, indirect immunofluorescence showed that PP5 localizes to the mitotic spindle apparatus. The direct interaction of PP5 with CDC16 and CDC27, as well as its overlapping spindle localization in mitosis, suggests that PP5 may be involved in the regulation of the activity of the anaphase-promoting complex.

Amino Acid Sequence↗
PubMed1992

Combined antimicrotubule activity of estramustine and taxol in human prostatic carcinoma cell lines.

Estramustine (EM) and taxol, two antimicrotubule agents with distinct and apparently opposing mechanisms of action, were found to be effective in combination in the preclinical treatment of EM-resistant and sensitive, wild-type human prostatic carcinoma cell lines. Estramustine combined with 1 nM taxol (concentration 100-fold less than that measured in plasma of patients treated with taxol) produced greater than additive effects on the inhibition of cell survival of both wild-type and EM-resistant cells. When taxol was used with another microtubule-destabilizing drug, vinblastine, no significantly increased cytotoxicity was observed. Other effects on wild-type and EM-resistant cells produced by the combination of EM and taxol included (a) an increased proportion of the cells in the S phase of the cell cycle; (b) no mitotic block; and (c) an increase in the percentage of micronucleated cells from a control value of less than 1% to greater than 20% after drug treatment. Immunofluorescent microscopic analysis of the effect of this drug combination on the mitotic spindle apparatus revealed specific examples of aberrant mitotic figures, including multiple asters, cells with two distinct spindles, and tripolar spindles able to traverse mitosis and complete cytokinesis. These data provide supportive preclinical evidence for the potential development of an EM/taxol combination clinical regimen either for prostate or other cancers.

Alkaloids↗
PubMed1983

Taxol-requiring mutant of Chinese hamster ovary cells with impaired mitotic spindle assembly.

In the accompanying paper (Cabral, F., 1982, J. Cell. Biol., 97:22-29) we described the isolation and properties of taxol-requiring mutants of Chinese hamster ovary cells. We now show that at least one of these mutants, Tax-18, has an impaired ability to form a spindle apparatus. Immunofluorescence studies using antibodies to tubulin demonstrate that, when incubated in the absence of taxol, Tax-18 forms only a rudimentary spindle with few and shortened microtubules associated with the spindle poles. Furthermore, midbodies were not observed, consistent with an absence of cytokinesis. Essentially normal spindles and midbodies are seen in the presence of taxol. Electron microscopic examination indicates that centrioles and kinetochores are morphologically normal in the mutant strain. Pole-to-kinetochore microtubules were seen but interpolar microtubules were not. Taxol-deprived mutant cells stained with anti-centrosome serum show an elevated centriole content, indicating that the defect in Tax-18 does not affect centriole replication or prevent progression through the cell cycle. Although Tax-18 cells do not form a complete spindle in the absence of taxol, cytoplasmic microtubule assembly occurs in association with microtubule-organizing centers, and microtubules with apparently normal morphology exist throughout the cytoplasm. Observation of chromosome movement indicates that the defect in these cells occurs after prometaphase. These studies demonstrate that the formation of spindle microtubules requires cellular conditions that are different from those required for cytoplasmic microtubule formation. They further show that a normal spindle may be necessary for cytokinesis but not for progress of the cells through the cell cycle.

Alkaloids↗
PubMed1997

Glutathione oxidation is associated with altered microtubule function and disrupted fertilization in mature hamster oocytes.

We hypothesized that depletion of glutathione (GSH) with diamide, a relatively specific GSH oxidant, may alter the meiotic spindle apparatus in mature hamster oocytes. Immunofluorescent analysis of oocytes exposed to diamide for 1.5 or 3 h revealed time- and concentration-dependent disruption of spindle morphology accompanied by chromosome clumping. In oocytes first cultured in diamide for 1.5 h and then in diamide-free medium for 1.5 or 3 h, microtubules appeared to repolymerize, but normal spindle structure was not regained. HPLC confirmed that diamide oxidized oocyte GSH under conditions identical to those associated with spindle-related abnormalities. Exposure of oocytes to 25 or 50 microM diamide before in vitro fertilization did not affect their ability to undergo fertilization. A significant proportion of the fertilized oocytes that had been exposed to 50 microM diamide before insemination exhibited abnormal multiple female pronuclei with an apparently normal male pronucleus. These observations indicate that mature hamster oocytes are susceptible to oxidative stress during the critical period that precedes fertilization and provide further evidence that GSH plays important roles in oocyte spindle function and pronucleus development.

Animals↗
PubMed1978

Cytological characteristics and classification of spindle inhibitors according to their effects on segmentation mitoses.

The effects of spindle inhibitors and of protein synthesis inhibitors on segmentation mitoses allow us to classify them into six groups : 1. Colchicine type : destruction of the whole achromatic apparatus and centrospheres without storing of dense bodies; 2. Quinoline type : same effect on the achromatic apparatus, but blocked centrospheres with accumulation of dense bodies; 3. Chloralhydrate type : Incomplete destruction of achromatic apparatus, spindle residue which maintains the chromosomes in a star shape, inactive centrospheres sequestered by the reticulum, but without accumulation of dense bodies; 4. Phenylurethane type : Incomplete and reversible action, which leads to easy production of pluripolar mitoses; 5. Carboxylic acid type : dissociation of the spindle, sometimes with blocking of the centrosphere, together with profound chromosome changes without primitive breaks; the intensity and quality of their action is related to the number of carbon atoms in the acid considered; 6. Protein synthesis inhibitor type : (cycloheximide, pederin) characterized by a stop of the nuclear cycle at telo-prophase when the action is sufficient, chromosome abnormalities, sometimes, reduced to strings of beads, and freeing of asters; at weaker concentrations mitosis is possible, but the congression of chromosomes at the equator is abnormal because of functional disturbance of the kinetochores. The nature and grading of these effects, their association (or non - association) to chromosome damage, the soundness of the spindle when only the chromosomes are affected (nitrogen mustard) make this one of the tests which gives the most specific data about the action of antimitotic substances.

Amides↗
PubMed1975

What moves chromosomes, microtubules or microfilaments?

An investigation of the spindle apparatus of crane-fly (Nephrotoma suturalis) spermatocytes has been undertaken using methods that permit combined light and electron microscopy of selected cells. At the ultrastructural level, spindles contain microtubules in a granular matrix. Microtubules have been classified as kinetochore microtubules (which connect to kinetochores of chromosomes) and non-kinetochore microtubules (not attached to kinetochores). Kinetochore microtubules are distributed in densely packed bundles, which are the birefringent chromosomal fibers seen in living cells. Actin filaments were not observed in spindles of unglycerinated cells or in cells fixed in glutaraldehyde containing tannic acid, which negatively stains F-actin in situ and thus can be used to aid the localization of actin filaments in non-muscle cells. The absence of actin filaments in the spindle coupled with their presence in the "contractile ring" of spermatocytes fixed during cytokinesis is evidence against the hypothesis that chromosome movements are microfilament-based. The results are compatible with the hypothesis that microtubules are involved in the mechanism of chromosome transport. The details of that mechanism remain to be clarified.

Actins↗
PubMed1976

The blepharoplast of Marsilea: its de novo formation and spindle association.

Blepharoplast formation and function has been investigated by light and electron microscopy in developing microspores of the water fern Marsilea vestita. When single-celled microspores are hydrated they undergo a series of 9 cell divisions producing 7 sterile cells plus 32 spermatids. The blepharoplast, a densely staining, spherical inclusion (0-5-1-0 mum in diameter) interpenetrated by numerous lightly stained channels, is a precursor organelle for the production of the 100-150 basal bodies of the motile sperm. During development it arises twice in the dividing spermatogenous cells; first in telophase of the second to last or 7th division, and again in telophase of the next to last or 8th division. The blepharoplast first forms on the distal side of the nucleus during telophase of the 7th division but soon degenerates as the cell enters prophase and metaphase of the 8th division. The blepharoplast first forms on the distal side of the nucleus during telophase of the 7th division but soon degenerates as the cell enters prophase and metaphase of the 8th division. During telophase of the 8th division the blepharoplast again arises in the cytoplasm near a small indentation of the nuclear envelope. The forming blepharoplast consists of a sphere of lightly stained flocculent material within which 2 plaques separated by 40-50 nm arise. Each plaque possesses 2 dense layers (20 nm) separated by a light layer (10 nm). During subsequent development the distal layer of each plaque becomes progressively more densely stained. Light-staining channels appear within the accumulating dense material a-d 2 hemispherical blepharoplasts emerge. The blepharoplasts become spherical through continued growth and finally separate from each other as they move to the spindle poles during prophase of the last or 9th division. The blepharoplast appears to act as a microtubule organizing centre during formation of the spindle apparatus in prophase of the 9th division. While it remains at the pole throughout mitosis it does not continue to serve as the focal point for the spindle tubules. During metaphase-anaphase of the 9th division the blepharoplast swells, and the channels at its surface begin transforming into procentrioles and finally basal bodies. The results support the contention that basal bodies in Marsilea arise de novo, since no preexisting template such as a centriolar pinwheel is observed and sine the intermediates which initially occur are structurally dissimilar from a procentriole.

Microtubules↗
PubMed1986

Taxol-dependent mutants of Chinese hamster ovary cells with alterations in alpha- and beta-tubulin.

Chinese hamster ovary cell mutants resistant to the microtubule stabilizing drug taxol were isolated in a single step. Of these 139 drug-resistant mutants, 59 exhibit an absolute requirement for taxol for normal growth and division, 13 have a partial requirement, and 69 grow normally without the drug. Two-dimensional gel analysis of whole cell proteins reveal "extra" spots representing altered tubulins in 13 of the mutants. Six of these have an altered alpha-tubulin and seven have an altered beta-tubulin. Cells with an absolute dependence on taxol become large and multinucleated when deprived of the drug. In contrast, partially dependent cells exhibit some multinucleation, but most cells appear normal. In one mutant that has an absolute dependence on taxol, the cells appear to die more quickly and their nuclei do not increase in size or number. As previously found for another taxol-dependent mutant (Cabral, F., 1983, J. Cell. Biol., 97:22-29), the taxol dependence of the mutants described in this paper behaves recessively in somatic cell hybrids, and the cells are more susceptible to being killed by colcemid than are the wild-type parental cells. When compared with wild-type cells, taxol-dependent mutants have normal arrays of cytoplasmic microtubules but form much smaller mitotic spindles in the presence of taxol. When deprived of the drug, however, these mutants cannot complete assembly of the mitotic spindle apparatus, as judged by tubulin immunofluorescence. Thus, the defects leading to taxol dependence in these mutants with defined alterations in alpha- and beta-tubulin appear to result from the cell's inability to form a functional mitotic spindle. Reversion analysis indicates that the properties of at least one alpha-tubulin mutant are conferred by the altered tubulin seen on two-dimensional gels.

Alkaloids↗
PubMed1993

Assignment of the nuclear mitotic apparatus protein NuMA gene to human chromosome 11q13.

A monoclonal antibody that was specific for a nuclear matrix protein was obtained and used to screen a human lambda gt11 expression library. Several partial cDNA clones were isolated and sequenced. The sequence for this protein was shown to be identical to that of NuMA, a 236-kDa nuclear mitotic spindle apparatus protein. NuMA has been recently characterized by two independent studies, and is thought to be part of a family of proteins that is required for the completion of mitosis. In this report, the chromosomal localization and copy number of the NuMA gene are analyzed using cDNA clones. High-resolution in situ hybridization reveals a single pair of signals on sister chromatids of human chromosome 11 at band q13. Stringent Southern analysis of human genomic DNA resulted in simple restriction patterns. These results together indicate that the NuMA gene is present as a single copy on human chromosome 11q13.

Antibodies, Monoclonal↗
PubMed1996

Distribution of gamma-tubulin differs in primary and secondary oocytes of Ephestia kuehniella (Pyralidae, Lepidoptera).

In a previous study, barrel-shaped spindles were found in metaphase I oocytes of Ephestia kuehniella (Pyralidae, Lepidoptera). Aster microtubules (MTs) were missing (Wolf, 1993: Cell Motil Cytoskeleton 24:200-204). This points to an acentriolar organization of the spindle apparatus. The present study was aimed at the question of whether gamma-tubulin, a newly detected member of the tubulin superfamily that has often been identified in microtubule-organizing centers, plays a role in the nucleation of MTs in meiotic spindles of the moth. To this end, the distribution of gamma-tubulin was examined in oocytes of E. kuehniella using an antibody against gamma-tubulin in combination with indirect immunofluorescence. The antibody evenly decorated spindle MTs in metaphase I oocytes of the moth. Enhanced staining of the spindle poles was not detectable. In subsequent stages of meiosis, gamma-tubulin was gradually lost from spindle MTs and was then found at the surface of the so-called elimination chromatin. Female meiosis in Lepidoptera is achiasmatic. The elimination chromatin, i.e., modified and persisting synaptonemal complexes, is believed to keep homologous chromosomes linked until the onset of anaphase I. In meiosis I of female Lepidoptera, the elimination chromatin persists at the spindle equator between the segregating chromatin masses. It is plausible to assume that gamma-tubulin is involved in spindle organization in the absence of canonical centrosomes. In MTs of metaphase II spindles of E. kuehniella, gamma-tubulin was no longer detectable with our immunological approach. This points to a far-reaching change in spindle organization during transition from meiosis I to meiosis II.

Animals↗
PubMed1985

An hypothesis regarding the origin of aneuploidy in man: indirect evidence from an experimental model.

Recent studies have clearly demonstrated that aneuploidy may be induced in about 10 to 20% of oocytes and recently ovulated eggs when female mice are given an intragastric injection of a dilute solution of ethanol. Similar rates of aneuploidy have also been observed when recently ovulated eggs are briefly exposed in vitro to a dilute solution of ethanol in tissue culture medium. These findings are briefly reviewed, and observations made on the possible underlying mechanism of induction of chromosome malsegregation in the ethanol exposed groups. Attention is drawn to evidence from a wide range of studies on the effect of ethanol, acetaldehyde (its primary metabolite), and anaesthetics on cell division and chromosome segregation in an attempt to substantiate an hypothesis regarding the mode of action of these agents. In the light of this information, it is hypothesised that exposure to ethanol probably interferes with the normal functioning of the cytoskeletal elements of the spindle apparatus, or its precursor elements, during the first or second meiotic divisions. An attempt is also made to account for the very high incidence of aneuploid conceptuses in man, a high proportion of which are spontaneously aborted. It is hypothesised that exposure to ethanol and other spindle active agents during appropriate stages of oogenesis (in particular during the first meiotic division), and possibly also during spermatogenesis, may be important aetiological factors in a proportion of those cases of spontaneous abortion with a numerical chromosome anomaly for which no other obvious cause is recognised. If it is valid to extrapolate from these experimental findings to the clinical situation in man, it is suggested that attention should also be drawn to the potentially greater hazard to the conceptus which could result from maternal alcohol consumption at and shortly before conception.

Acetaldehyde↗
PubMed1991

Formation of the tetraploid intermediate is associated with the development of cells with more than four centrioles in the elastase-simian virus 40 tumor antigen transgenic mouse model of pancreatic cancer.

The development of pancreatic cancer in transgenic mice expressing the simian virus 40 tumor antigen placed under controlling regions of the elastase I gene is characterized by the sequential appearance of tetraploid and then multiple aneuploid cell populations. Pancreatic tissues from such transgenic mice were studied between 8 and 32 days of age. Virtually 100% of acinar cell nuclei had immunohistochemically detectable tumor antigen by 18 days. Tetraploid cells were demonstrated by DNA content flow cytometry by 20 days and were associated with the appearance of interphase cells that had 5-11 centrioles per cell in single thin sections of pancreatic tissue examined by electron microscopy. Mitotic cells also were observed that had 5 or more centrioles per cell that were incorporated into the poles of bipolar or at least tripolar spindle apparatuses. These observations indicate that formation of the tetraploid intermediate in the diploid----tetraploid----aneuploid sequence of pancreatic tumor formation in elastase-simian virus 40 tumor antigen transgenic mice is accompanied by the development of cells with 5 or more centrioles that can be incorporated into the poles of abnormal mitotic spindles. We speculate that cells with more than 4 centrioles are predisposed to the formation of multipolar mitoses that may yield daughter cells with chromosomal gains and losses, resulting in the subsequent development of aneuploid tumors.

Animals↗