Serial reconstruction of the mitochondrial reticulum in the antarctic flagellate,Pyramimonas gelidicola (Prasinophyceae,Chlorophyta)

Summary A serial reconstruction ofPyramimonas gelidicola McFadden, Moestrup andWetherbee has revealed a large reticulated mitochondrion branching throughout the cell. The possibility of single mitochondria in other members of thePrasinophyceae and the uniformity of the morphology of this organelle within the class is discussed.     

Observations of mitochondria and mitochondrial nuclei by double staining with rhodamine-123 and DAPI in synchronous cultures ofCatharanthus roseus

Mitochondria in cells ofCatharanthus roseus (L.) G. Don in synchronous cell division cultures were observed by double staining using fluorescence microscopy. The cells were stained with 4′-6-diamidino-2-phenylindole (DAPI) first and subsequently stained with rhodamine 123 (r-123). Immediately after staining with r-123, yellowishgreen, elongated and moving mitochondria were observed upon excitation at 485 nm. When the excitation filters were replaced by a UV filter (360 nm), 1 to 7 mitochondrial nucleoids were visible in each mitochondrion in the same field. Changes in the lengths of mitochondria during the cell cycle obtained from the observations under fluorescence microscopy by this staining method suggest the occurrence of multiplication of mitochondria concurrent with the cell cycle ofC. roseus.     

Serial reconstruction and behaviour during cytokinesis of the chondriome ofProrocentrum minimum (Pavillard) Schiller (Pyrrhophyta)

Summary Serial reconstruction of the chondriome of vegetative cells ofProrocentrum minimum (Pavillard) Schiller has revealed a major reticulated mitochondrion and several small satellite mitochondria. During cytokinesis the major portion of the chondriome splits passively with the cell. The significance of this structure and division mechanism is discussed.     

A mitochondrion as the structural basis of the formation of a cell-type-specific organelle inDictyostelium development

Summary The mitochondrion has been mainly given attention as a self-reproductive and respiratory organelle. We report here that the mitochondrion may participate in the formation of a cell-type-specific organelle, coupling with the Golgi complex. During the development ofDictyostelium discoideum, the two types of cells, i.e., the anterior prestalk cells and the posterior prespore cells form a polarized cell mass. Prespore differentiation is characterized by the presence of unique vacuoles named PSVs (prespore-specific vacuoles) in the cytoplasm. Thus the PSV is the most essential organelle to understand the structural basis of cell differention in this organism. In differentiating prespore cells, the mitochondrion exerts a remarkable transformation to form a sort of vacuole (M-vacuole). Using a PSV specific antibody, it was immunocytochemically shown that a PSV antigen (C-10) is localized in the M-vacuole as well as in the lining membrane of PSV. Interestingly, the C-10 antigen was also noticed in the Golgi cisternae that had fused with M-vacuole. Based on these findings, we propose here a promising model which suggests how both mitochondria and Golgi cisternae may be coordinately involved in the PSV formation. This model will provide a new aspect of mitochondrial functions in cell differentiation.     

Zoospore ultrastructure in species ofTrebouxia andPseudotrebouxia (Chlorophyta)

Zoospore ultrastructure (incl. flagellar apparatus) has been investigated in three species ofTrebouxia (T. glomerata, T. erici, T. pyriformis) and one species ofPseudotrebouxia (P. impressa) using an absolute configuration analysis. Zoospores in all taxa studied are nearly identical in ultrastructure and exhibit a very distinctive disposition of cell organelles: cells are naked, biflagellate and considerably flattened along the plane of flagellar beat, the single contractile vacuole is located anteriorly in the ventral region of the cell, the nucleus is anteriorly to centrally located in the dorsal region of the cell. A single dictyosome is located close to the anterior, ventral edge of the nucleus. The chloroplast occupies a posterior position in the cell and usually has an anterior profile in the left region of the cell. There are two branched mitochondria per cell or a single mitochondrial reticulum with profiles anterior to the nucleus (in the dorsal region of the cell), and posterior to the nucleus. In zoospores ofTrebouxia spp. the posterior mitochondrial profile is associated with a microbody, inP. impressa zoospores the anterior mitochondrial profiles are associated with a microbody. The zoospores contain a distinctive system of three ER-cisternae: one system links to both basal bodies and extends to the nucleus, the other two systems subtend the plasmamembrane on the left and right broad cell surfaces and extend to the posterior region of the cell. The flagellar apparatus is structurally identical to that previously described for zoospores ofFriedmannia israelensis and exhibits basal body displacement by one basal body diameter into the 11/5 o'clock direction, a non-striated distal connecting fiber, a cruciate microtubular root system lacking system I fibers and presence of a single system II fiber which connects the basal bodies with the nucleus and runs parallel to one of the ER-strands. The left flagellar roots (X-roots) are subtended by a complex set of amorphous and striated material that connects each left root with both basal bodies.—This study demonstrates the close systematic relationship between the phycobiontsTrebouxia andPseudotrebouxia and the generaFriedmannia, Pleurastrum, andMicrothamnion and supports recent classification schemes which place all these taxa into a single order separate from otherChlorophyta. Dedicated to Prof. DrElisabeth Tschermak-Woess on the occasion of her 70th birthday.     

Stimulation of amino acid transport inSaccharomyces cerevisiae by metabolic inhibitors

Inhibitors of energy metabolism (3-ohlorophenylhydrazonomalononitrile, antimycin A, iodoacetamide, dicyclohexylcarbodiimide) but not of transport (uranyl ions) stimulate at low concentrations the uptake ofl-leucine,l-glutamic acid,l-argimne and, to a lesser degree, of 2-aminoisobutyric acid inSaccharomyces cerevisiae. The effect is apparent only after augmenting the energy reserves of cells by preincubation withd-glueose or, more strikingly, with ethanol. It is absent in a mutant (op₁) lacking the translocation system for ADP-ATP in mitochondria. The presence of two different energy reserves for amino acid transport is indicated (one in energy-poor, the other in energy-rich cells). The stimulating effect appears to be caused by a retarded degradation of the transport proteins as occurs at a lowered level of mitochondria-produced ATP.     

The mitochondrial cycle of Arabidopsis shoot apical meristem and leaf primordium meristematic cells is defined by a perinuclear tentaculate/cage-like mitochondrion

Plant cells exhibit a high rate of mitochondrial DNA (mtDNA) recombination. This implies that before cytokinesis, the different mitochondrial compartments must fuse to allow for mtDNA intermixing. When and how the conditions for mtDNA intermixing are established are largely unknown. We have investigated the cell cycle-dependent changes in mitochondrial architecture in different Arabidopsis (Arabidopsis thaliana) cell types using confocal microscopy, conventional, and three-dimensional electron microscopy techniques. Whereas mitochondria of cells from most plant organs are always small and dispersed, shoot apical and leaf primordial meristematic cells contain small, discrete mitochondria in the cell periphery and one large, mitochondrial mass in the perinuclear region. Serial thin-section reconstructions of high-pressure-frozen shoot apical meristem cells demonstrate that during G1 through S phase, the large, central mitochondrion has a tentaculate morphology and wraps around one nuclear pole. In G2, both types of mitochondria double their volume, and the large mitochondrion extends around the nucleus to establish a second sheet-like domain at the opposite nuclear pole. During mitosis, approximately 60% of the smaller mitochondria fuse with the large mitochondrion, whose volume increases to 80% of the total mitochondrial volume, and reorganizes into a cage-like structure encompassing first the mitotic spindle and then the entire cytokinetic apparatus. During cytokinesis, the cage-like mitochondrion divides into two independent tentacular mitochondria from which new, small mitochondria arise by fission. These cell cycle-dependent changes in mitochondrial architecture explain how these meristematic cells can achieve a high rate of mtDNA recombination and ensure the even partitioning of mitochondria between daughter cells.     

Variety of mitochondrial shapes,sizes, and volumes inChlamydomonas reinhardii

Summary Mitochondria in cells ofChlamydomonas reinhardii, which at an intermediate stage of the vegetative cell cycle have been submitted to gametogenesis under dark and cold conditions, remain more or less unchanged with and without the addition of chloramphenicol. They exist in various number, shapes, and sizes and can be branched or unbranched as well as small or large. Giant mitochondria can be fused to a mitochondrial network, which, in contrast to the previously reported network (Grobe andArnold 1975), lies predominantly in the center of the cell. Mitochondrial volumes were revealed by means of morphometrical analyses from serial sections of four entire cells.     

Morphological changes of giant mitochondria in the unicellular to multicellular phase during parthenogenesis of Ulva partita (Ulvophyceae) revealed by expression of mitochondrial targeting GFP and PEG transformation

A giant mitochondrion that branches and connects as a single mitochondrion in a cell has been observed during specific phases of the cell cycle of unicellular green algae, but has not been observed in multicellular algae. The genus Ulva is a green macroalga in which the haploid and diploid phases are isomorphic and its gametes develop parthenogenetically. The existence or absence of the giant mitochondrion, and its behavior in Ulva partita, were investigated using a parthenogenesis system. To observe the parthenogenesis of gametes and the dynamics of mitochondria by fluorescence microscopy, we developed an experimental system for culturing and observing U. partita on cover slips: gametes were suspended in 6‐well plates filled with artificial seawater, and cover slips were placed on the well bottoms. The gametes settled on the cover slips as spherical cells (1‐cell S phase). These cells grew into larger cells, losing their eyespot (1‐cell L phase), and developed into multicellular thalli. Gene introduction using the polyethylene glycol (PEG) method is available with transformation efficiencies of 9.0–15.1%. Transformation was performed using a plasmid encoding green fluorescent protein (GFP) fused to the mitochondrial targeting sequence, and mitochondria were labeled by GFP fluorescence. This revealed a string‐shaped giant mitochondrion in a cell of the 1‐cell S phase. In the 1‐cell L phase, a reticular mitochondrion was observed. After the initiation of cell division, the reticular mitochondrion was fragmented, and small oval mitochondria were observed in the 5‐cell phase.     

Effects of complete cell recycling on product formation byLactobacillus casei ssp.rhamnosus in continuous cultures

The lactic acid bacteriumLactobacillus casei ssprhamnosus was cultivated in a system with complete cell recycling in order to obtain information on how this cultivation technique affected the microorganisms. Cultivations at two different glucose concentrations (25 g/L and 50 g/L) were performed. Hollow fiber filters were used for separating the cells from the spent broth. The cell recycling was carried out for 128–135 h. Samples were taken three to four times daily for analysis ofd- andl-lactate, glucose concentration, and cell mass. Protein patterns were studied with two-dimensional electrophoresis. A change in the protein pattern was observed. Dry weight of cell mass of 86 g/L was obtained when cultivated on 50 g glucose/L, which was approximately 15 times more than in the batch culture. The percentage ofd-lactate of the total lactate increased with time; when cultivated on 25 g glucose/L, it increased from 3% to 13%. No racemase was detected by the methods used. The data collected from these two recycling experiments show that this is an efficient way to obtain high cell densities, but that the method can affect the product formation pattern of the microorganism.     

Ultrastructure of the plasmodial slime moldPerichaena vermicularis

Summary Mature plasmodia ofPerichaena vermicularis require a light period to induce sporulation. In this paper the ultrastructure and acid phosphatase localization of the mature plasmodium ofPerichaena vermicularis are investigated. Acid phosphatase is localized in vacuoles containing remnants of bacteria and cell organelles. Morphological and histochemical evidence support the interpretation that these vacuoles constitute two types of lysosomes called respectively heterophagic and autophagic vacuoles.Coated vesicles which apparently originate from smooth endoplasmic reticulum are dispersed throughout the plasmodium and frequently associated with lysosomes. Several dumbbellshaped mitochondria are observed in the plasmodium at the onset of fruiting but not during later stages of plasmodiocarp development. Cytoplasmic microtubules are identified inPerichaena vermicularis. Some of these are closely associated with microfilaments.This work was supported by National Science Foundation grants (GB-5884 and GB-8537) to Dr.Ian K.Ross, NSF grant (GB 12371) to Dr.James Cronshaw, and an NSF Traineeship (GZ 445 and 796) to I.Charvat.This constitutes a portion of a thesis presented to the Regents of the University of California by the first author in partial fulfillment of the requirements for the Ph. D. degree.     

Phylogenetic origins of the plant mitochondrion based on a comparative analysis of 5S ribosomal RNA sequences

Summary The complete nucleotide sequences of 5S ribosomal RNAs fromRhodocyclus gelatinosa, Rhodobacter sphaeroides, andPseudomonas cepacia were determined. Comparisons of these 5S RNA sequences show that rather than being phylogenetically related to one another, the two photosynthetic bacterial 5S RNAs share more sequence and signature homology with the RNAs of two nonphotosynthetic strains.Rhodobacter sphaeroides is specifically related toParacoccus denitrificans andRc. gelatinosa is related toPs. cepacia.These results support earlier 16S ribosomal RNA studies and add two important groups to the 5S RNA data base. Unique 5S RNA structural features previously found inP. denitrificans are present also in the 5S RNA ofRb. sphaeroides; these provide the basis for subdivisional signatures. The immediate consequence of our obtaining these new sequences is that we are able to clarify the phylogenetic origins of the plant mitochondrion. In particular, we find a close phylogenetic relationship between the plant mitochondria and members of the alpha subdivision of the purple photosynthetic bacteria, namely,Rb. sphaeroides, P. denitrificans, andRhodospirillum rubrum.     

The ultrastructure of the nauplius eye ofSapphirina (Crustacea: Copepoda)

Summary The ultrastructure of the specialized nauplius eye of three species of the copepod genusSapphirina was investigated. The gross morphology described earlier (Elofsson, 1966a) was confirmed. The ventral cup is covered by a red pigment and the lateral cups by a red and a black pigment. The ultrastructural configuration of the pigment granules was found to differ in the two kinds of pigment cells. The black pigment cell, moreover, contains a large number of transversely banded fibrils and is able to produce reflecting crystals. The pigment granules of the black pigment cell show a variation in electron density. An intimate connexion exists between the black pigment cell and large retinula cells in the lateral cups, indicating an exchange of material. The tapetal cells present in all three cups form crystal platelets contained in two sets of membranes. It is suggested that the ventral cup and part of the lateral cups function as thePecten-eye (Land, 1965). The rhabdomeres of the retinula cells are composed of microvilli measuring 400 Å. The orientation of these seems to exclude polarotactic behaviour. The ventral cup and the four small cells of the lateral cups contain some retinula cells with microvilli arranged parallel to the incoming light. The retinula cells further develop an intricate system of membrane-invaginations penetrating deep into the cell and associated with numerous mitochondria. Retinula cells of the ventral cup and part of the lateral cups contain clear portions filled with granular material only. Retinula and other cells contain attenuated mitochondria with parallel tubuli. The proximal lens in front of each lateral cup consists of one cell. A development from the conjunctival cells is suggested. The results are evaluated in terms of function and evolution.This work has been supported by a grant from the Swedish Natural Science Research Council (2760-2).     

Some observations on the primitive and definitive erythrocytes of the developing chick

Summary The cytological changes in the primitive and definitive erythrocytes of the incubating chick have been followed. Observations have been made on the nucleoli, vital granules, mitochondria,Golgi apparatus, reticulum ofSinigaglia and the reticulation patterns of the basophilic substance. The cells of the primitive and definitive lines are ordinarily readily distinguished from one another. Data are included on the rate of disappearance of the primitive cells from the circulation. They may persist as long as two weeks after hatching. Giant primitive erythrocytes are common during the first week of incubation. The cells have one, two three or four nuclei. The nuclearplasma relationship is maintained somewhere near a constant. These atypical cells are due to aberrations in mitosis. Data on the percentage of mitosis in both types of erythrocytes are also included. The initial activity of the spleen and bone-marrow is reflected in the blood stream. There is a distinct rise in the proportion of young definitive erythrocytes. An attempt is made to correlate the findings ofHall (1934) on the changing affinity of the hemoglobin for oxygen with the changing blood picture. The primitive line does not persist long enough to account for the phenomenon. It is suggested, however, that the hemoglobin of the erythrocytes produced by the yolk sac may differ from that of the cells produced by the spleen and bone-marrow. With Plates I–III.     

Die Mitochondrien vonChlamydomonas reinhardii

Zusammenfassung Dreidimensionale, maßstabgetreue Modelle, die nach elektronenmikroskopischen Bildern von Serienschnitten konstruiert wurden, zeigen, daß in den Zellen vonChlamydomonas reinhardii nur ein geringer Teil der Mitochondrien eine einfache rundliche oder ellipsoidale Form hat. Die meisten Mitochondrien sind langgestreekt und weisen charakteristische Einschnürungen und Verzweigungen auf. Die Einschnürungen sind mitunter so schmal, daß es nicht sicher ist, ob der innere Teil der Mitochondrienhülle noch einen einzigen Innenraum umschließt oder ob das betreffende Mitochondrium 2 getrennte Räume enthält. Durch ihre Verzweigungen können die Mitochondrien Gesamtlängen erreichen, die weit größer sind als die jeweiligen Zelldurchmesser. Die verästelte Form der Mitochondrien kann dazu führen, daß Mitochondrienanschnitte, die in einem Einzelschnitt sogar an entgegengesetzten Zellpolen auftreten, tatsächlich Teile ein- und desselben Mitochondriums sind. Die wirkliche Zahl der Mitochondrien pro Zelle ist infolge dieser besonderen Gestaltung erheblich geringer als man sie aufgrund der Beobachtung von Einzelbildern schätzen würde. Sie betrug in 2 durch Serienschnitte vollständig erfaßten Zellen (+Gameten) 9 bzw. 14 Mitochondrien. Es wird diskutiert, ob bei einer streptomycinbedürftigen Mutante vonChlamydomonas reinhardii die Zuordnung des sd-Gens zum Mitochondrien-Genom in Einklang mit den hier gewonnenen Ergebnissen steht.

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The mitochondria ofChlamydomonas reinhardii

Summary Three-dimensional scale models constructed on the basis of serial section electron microscopy showed that only a little fraction of the mitochondria in the cells ofChlamydomonas reinhardii has a simple spherical or elliptical shape. Most of the mitochondria are elongated, and show characteristical constrictions and branchings. Sometimes the constrictions are so narrow, that it seems not sure whether the inner part of the envelope of a mitochondrion surrounds one single space or whether there are two separate spaces within the mitochondrion concerned. By their branchings the mitochondria can reach overall-lengths much longer than the diameter of the cell. The branched shape of the mitochondria may lead to the result, that profiles of mitochondria occurring in a single section even at opposite poles of the cell are in fact parts of the same mitochondrion. Caused by this exceptional shape, the actual number of mitochondria per cell is considerably smaller than one would estimate from the observation of single electron micrographs. We counted 9 and 14 mitochondria resp. in 2 cells (+ gametes), both completely included in a series of consecutive sections. It is discussed, whether in a streptomycindependent mutant ofChlamydomonas reinhardii the association of the sd-gene with the mitochondrion-genome is in agreement with the results obtained in this study.

     

Cell shape in the algaPediastrum (Hydrodictyaceae; Chlorophyta)

Summary Species ofPediastrum, a genus in which the colonies assemble from aggregating zoospores, differ in the number and form of prongs on peripheral cells and the amount of space between cells of the colony; cell shape appears to be genetically based. Peripheral cells of theP. boryanum colony, for example, have two prongs per cell;P. simplex has one prong per cell. Prong extension is suppressed in the interior cells ofP. boryanum, but prong sites have been reported in scanning electron micrographs of the cell walls. A mutant unicellular strain in which cells of the colony separate after attaining typical form reveals several prong sites (6 or more) in each cell. Multiple suppressed prong sites are evident inP. simplex cells as well. Polyeders, 4- and 5-pronged unicells, occur in the life cycle ofP. simplex. Based on these observations and a recent report byMarchant (1979) of a microtubule organizing center associated with the prongs, it is suggested that several microtubule organizing centers are to be found in zoospores ofPediastrum species and may be related to species differences in cell shape.Research supported in part by Argonne Center for Educational Affairs, U.S. Department of Energy, under contract No. W-31-109-ENG-38.     

Evidence for two compartments of exchangeable calcium in isolated rat liver mitochondria obtained using a45Ca exchange technique in the presence of magnesium,phosphate, and ATP at 37°C

Summary The distribution of calcium between isolated rat liver mitochondria and the extramitochondrial medium at 37°C and in the presence of 2mm inorganic phosphate, 3mm ATP, 0.05 or 1.1mm free magnesium and a calcium buffer, nitrilotriacetic acid, was investigated using a⁴⁵Ca exchange technique. The amounts of⁴⁰Ca in the mitochondria and medium were allowed to reach equilibrium before initiation of the measurement of⁴⁵Ca exchange. At 0.05mm free magnesium and initial extramitochondrial free calcium concentrations of between 0.15 and 0.5 m, the mitochondria accumulated calcium until the extramitochondrial free calcium concentration was reduced to 0.15 m. Control experiments showed that the mitochondria were stable under the incubation conditions employed. The⁴⁵Ca exchange data were found to be consistent with a system in which two compartments of exchangeable calcium are associated with the mitochondria. Changes in the concentration of inorganic phosphate did not significantly affect the⁴⁵Ca exchange curves, whereas an increase in the concentration of free magnesium inhibited exchange. The maximum rate of calcium outflow from the mitochondria was estimated to be 1.7 nmol/min per mg of protein, and the value ofK _0.5 for intramitochondrial exchangeable calcium to be about 1.6 nmol per mg of protein. Ruthenium Red decreased the fractional transfer rate for calcium inflow to the mitochondria while nupercaine affected principally the fractional transfer rates for the transfer of calcium between the two mitochondrial compartments. The use of the incubation conditions and⁴⁵Ca exchange technique described in this report for studies of the effects of agents which may alter mitochondrial calcium uptake or release (e.g., the pre-treatment of cells with hormones) is briefly discussed.     

Biological nitrogen and organic matter removal from tannery wastewater in pilot plant operations in Ethiopia

A whole-cell biotransformation system for the conversion of d-fructose to d-mannitol was developed in Escherichia coli by constructing a recombinant oxidation/reduction cycle. First, the mdh gene, encoding mannitol dehydrogenase of Leuconostoc pseudomesenteroides ATCC 12291 (MDH), was expressed, effecting strong catalytic activity of an NADH-dependent reduction of d-fructose to d-mannitol in cell extracts of the recombinant E. coli strain. By contrast whole cells of the strain were unable to produce d-mannitol from d-fructose. To provide a source of reduction equivalents needed for d-fructose reduction, the fdh gene from Mycobacterium vaccae N10 (FDH), encoding formate dehydrogenase, was functionally co-expressed. FDH generates the NADH used for d-fructose reduction by dehydrogenation of formate to carbon dioxide. These recombinant E. coli cells were able to form d-mannitol from d-fructose in a low but significant quantity (15 mM). The introduction of a further gene, encoding the glucose facilitator protein of Zymomonas mobilis (GLF), allowed the cells to efficiently take up d-fructose, without simultaneous phosphorylation. Resting cells of this E. coli strain (3 g cell dry weight/l) produced 216 mM d-mannitol in 17 h. Due to equimolar formation of sodium hydroxide during NAD⁺-dependent oxidation of sodium formate to carbon dioxide, the pH value of the buffered biotransformation system increased by one pH unit within 2 h. Biotransformations conducted under pH control by formic-acid addition yielded d-mannitol at a concentration of 362 mM within 8 h. The yield Y _{D-mannitol/D-fructose}was 84 mol%. These results show that the recombinant strain of E. coli can be utilized as an efficient biocatalyst for d-mannitol formation.     

The zoospore ofOlpidium brassicae

Summary The ultrastructure of the zoospore ofOlpidium brassicae is described and compared with observations made of other zoospores of the uniflagellatePhycomycetes. The zoospore ofO. brassicae is characterized by an extensive, cone-shaped rhizoplast and a lack of a nuclear cap, as well as a side-body complex or a rumposome. Vacuoles which contain osmiophilic material are termed gamma-like particles. Three-dimensional reconstructions based on serial sectioning were made of the organelles in the region of the nucleus, showing that the zoospore ofO. brassicae contains one or at most two elaborately branched mitochondria. Microbodies have a high degree of interconnection and are in intimate association with the mitochondrion, lipid drops, and the nuclear envelope.     

The fluorophenylalanine sensitive and resistant tobacco cell lines,TX1 and TX 4 1. DNA contents,chromosome numbers,nuclear ultrastructures,and effects of spermidine

Summary The two tobacco cell lines TX 1 (wild type) and TX 4 (Palmer andWidholm 1975), which are respectively sensitive and resistant to pfluorophenylalanine, were studied by light and electron microscopy and scanning cytophotometry. The two cell lines differ in the following respects: TX 1 cells exhibit spherical cells, a chromatin organization like in free-grown plants ofNicotiana tabacum, and mainly diploid and haploid DNA values. TX 4 cells show large elongated (thread-like) cells, a diffuse nuclear ultrastructure, and mainly tetraploid and octoploid DNA values. Chromosome number counts indicate that dividing TX 1 cells own a karyotype close to the diploid one, while dividing TX 4 cells are around the tetraploid state. In addition, the effects of an exogenous polyamine, spermidine, on chromatin organization were investigated. While the wild type cell line, TX1, did not respond to the treatment, the mutant, fluorophenylalanine resistant cell line, TX4, exhibited reduced nuclear size and increased chromatin condensation.