The ultrastructure of Ulothrix mucosa. I. Mitosis and cytokinesis

1986 ◽  
Vol 64 (1) ◽  
pp. 156-165 ◽  
Author(s):  
G. M. Lokhorst
Keyword(s):  
Fine Structure ◽  
Cleavage Plane ◽  
Spindle Pole ◽  
Wall Material ◽  
Cleavage Furrow ◽  
Cell Wall Material ◽  
Generic Level ◽  
Green Algal ◽  
Microtubular System ◽  
Frequent Presence

For the most part, the fine structure of the cytokinetic apparatus of Ulothrix mucosa Thuret has been found to possess distinctive ulvophycean features including initiation of the cleavage furrow when the nucleus is still in interphase, replication of the lateral centrioles at prophase and their changed position near the polar fenestrae of the broad metaphase spindle pole, the semiclosed condition of the nuclear envelope throughout most mitotic stages, and the rapid completion of the cleavage furrow following restoration of the interphase condition in daughter nuclei. However, outstanding characteristics reminiscent of the typical chlorophycean pattern are also found, including the frequent presence of a microtubular system, which appears to be most distinct in the final developmental stage of the cleavage furrow, and the quick descent of the sets of centrioles along the telophase nuclei until they are close to the cleavage plane opposite each other, which is particularly reminiscent of a chlorococcalean behaviour. Comparison of the fine structure of the cytokinetic apparatuses within Ulothrix reveals variation in the pattern of deposition of cell wall material onto the intervening new septum, and in the biogenesis of the ingrowing plasmalemma. It is stated that comparative cytological analyses which show cell variability at the generic level (as in Ulothrix) continue to be useful and are needed before recommendations may be made as to the validity of the modern green algal classifications in use today.

scholarly journals FINE STRUCTURE OF CELL DIVISION IN CHLAMYDOMONAS REINHARDI

1968 ◽  
Vol 38 (2) ◽  
pp. 403-425 ◽  
Author(s):  
Ursula G. Johnson ◽  
Keith R. Porter
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Cell Division ◽  
Cleavage Plane ◽  
Basal Bodies ◽  
Cleavage Furrow ◽  
Body Formation ◽  
Division Spindle ◽  
Spindle Microtubules ◽  
Mitotic Nucleus

Cell division in log-phase cultures of the unicellular, biflagellate alga, Chlamydomonas reinhardi, has been studied with the electron microscope. The two basal bodies of the cell replicate prior to cytokinesis; stages in basal body formation are presented. At the time of cell division, the original basal bodies detach from the flagella, and the four basal bodies appear to be involved in the orientation of the plane of the cleavage furrow. Four sets of microtubules participate in cell division. Spindle microtubules are involved in a mitosis that is marked by the presence of an intact nuclear envelope. A band of microtubules arcs over the mitotic nucleus, indicating the future cleavage plane. A third set of microtubules appears between the daughter nuclei at telophase, and microtubules comprising the "cleavage apparatus" radiate from the basal bodies and extend along both sides of the cleavage furrow during cytokinesis. Features of cell division in C. reinhardi are discussed and related to cell division in other organisms. It is proposed that microtubules participate in the formation of the cleavage furrow in C. reinhardi.

Synchrotron infrared microspectroscopy reveals the response of Sphagnum cell wall material to its aqueous chemical environment

2018 ◽  
Vol 15 (8) ◽  
pp. 513
Author(s):  
Ewen Silvester ◽  
Annaleise R. Klein ◽  
Kerry L. Whitworth ◽  
Ljiljana Puskar ◽  
Mark J. Tobin
Keyword(s):  
Cell Wall ◽  
Cell Walls ◽  
Chemical Environment ◽  
Wall Material ◽  
Organic Soils ◽  
Cell Wall Material ◽  
Acid Base ◽  
Widespread Species ◽  
Flowing Liquid ◽  
Infrared Microspectroscopy

Environmental contextSphagnum moss is a widespread species in peatlands globally and responsible for a large fraction of carbon storage in these systems. We used synchrotron infrared microspectroscopy to characterise the acid-base properties of Sphagnum moss and the conditions under which calcium uptake can occur (essential for plant tissue integrity). The work allows a chemical model for Sphagnum distribution in the landscape to be proposed. AbstractSphagnum is one the major moss types responsible for the deposition of organic soils in peatland systems. The cell walls of this moss have a high proportion of carboxylated polysaccharides (polygalacturonic acids), which act as ion exchangers and are likely to be important for the structural integrity of the cell walls. We used synchrotron light source infrared microspectroscopy to characterise the acid-base and calcium complexation properties of the cell walls of Sphagnum cristatum stems, using freshly sectioned tissue confined in a flowing liquid cell with both normal water and D2O media. The Fourier transform infrared spectra of acid and base forms are consistent with those expected for protonated and deprotonated aliphatic carboxylic acids (such as uronic acids). Spectral deconvolution shows that the dominant aliphatic carboxylic groups in this material behave as a monoprotic acid (pKa=4.97–6.04). The cell wall material shows a high affinity for calcium, with a binding constant (K) in the range 103.9–104.7 (1:1 complex). The chemical complexation model developed here allows for the prediction of the chemical environment (e.g. pH, ionic content) under which Ca2+ uptake can occur, and provides an improved understanding for the observed distribution of Sphagnum in the landscape.

Fine structure of the haplosporidan Kernstab, a persistent, intranuclear mitotic apparatus

1975 ◽  
Vol 18 (2) ◽  
pp. 327-346
Author(s):  
F.O. Perkins
Keyword(s):  
Fine Structure ◽  
Nuclear Envelope ◽  
Light Microscope ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Interphase Nuclei ◽  
Mitotic Apparatus ◽  
Pole Body

The fine structure of the haplosporidan mitotic apparatus is described from observations of plasmodial nuclei of Minchinia nelsoni, M. costalis, Minchinia sp., and Urosporidium crescens. The apparatus, which is the Kernstab of light-microscope studies, consists of a bundle of microtubules terminating in a spindle pole body (SPB) at each end of the bundle. A few microtubules extend from SPB to SPB, but most either extend from an SPB and terminate in the nucleoplasm or lie in the nucleoplasm, free of either SPB. The bundle lengthens during mitosis, increasing the SPB-to-SPB distance by a factor of 2 to 3 as compared to interphase nuclei. SPBs are not in contact with the nuclear envelope, being found always in the nucleoplasm which is delimited by the nuclear envelope throughout mitosis. The mitotic apparatus is persistent through interphase, at least in a form which is not significantly different from that found in mitotic nuclei.

scholarly journals Influence of Lignin on Digestibility of Forage Cell Wall Material

1986 ◽  
Vol 62 (6) ◽  
pp. 1703-1712 ◽  
Author(s):  
H. G. Jung ◽  
K. P. Vogel
Keyword(s):  
Cell Wall ◽  
Wall Material ◽  
Cell Wall Material

Observations on the Fine Structure of the Eyespot and Associated Organelles in the Dinoflagellate Glenodinium Foliaceum

1969 ◽  
Vol 5 (2) ◽  
pp. 479-493 ◽  
Author(s):  
J. D. DODGE ◽  
R. M. CRAWFORD
Keyword(s):  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Lamellar Body ◽  
Ventral Side ◽  
Close Packing ◽  
Hexagonal Close Packing ◽  
Osmiophilic Granules ◽  
Algal Groups ◽  
Posterior Direction ◽  
Microtubular System

The eyespot of the marine dinoflagellate Glenodinium foliaceum is a flattened orange structure, more or less trapezoid in shape with an anterior hook-like projection. It is situated on the ventral side of the organism in the vicinity of the flagellar bases at the anterior end of the sulcus. In the electron microscope the eyespot is seen to contain two layers of osmiophilic granules 80-200 nm in diameter which usually show hexagonal close-packing. The eyespot is surrounded by a triple-membraned envelope and is not connected to any other organelle. Adjacent to the eyespot is a distinctive organelle termed the ‘lamellar body’. This consists of a stack of up to 50 flattened vesicles or disks, each 16 nm thick and about 750 nm wide, the whole being orientated in an antero-posterior direction. The lamellae are continuous, at the ends of the stack, with rough endoplasmic reticulum and are joined together by occasional bridges at their edges. The bases of the two flagella lie just ventral to the lamellar body and from them roots arise which pass by the eyespot and join the subthecal microtubular system. The eyespot of Glenodinium is unique both in structure and the presence of the associated lamellar body. It differs from eyespots which have been described from other algal groups and also from the more complex ocellus found in certain dinoflagellates belonging to the order Warnowiaceae. The method by which the eyespot functions is discussed and it is suggested that unidirectional stimuli could be perceived by shading of the lamellar body.

Cytoplasmic microtubular system implicated in de novo formation of a Rabl-like orientation of chromosomes in fission yeast

2001 ◽  
Vol 114 (13) ◽  
pp. 2427-2435 ◽  
Author(s):  
Bunshiro Goto ◽  
Koei Okazaki ◽  
Osami Niwa
Keyword(s):  
Fission Yeast ◽  
De Novo ◽  
Nuclear Periphery ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Limited Area ◽  
Cytoplasmic Microtubule ◽  
Random Arrangement ◽  
Triplex Structure ◽  
Microtubular System

Chromosomes are not packed randomly in the nucleus. The Rabl orientation is an example of the non-random arrangement of chromosomes, centromeres are grouped in a limited area near the nuclear periphery and telomeres are located apart from centromeres. This orientation is established during mitosis and maintained through subsequent interphase in a range of species. We report that a Rabl-like configuration can be formed de novo without a preceding mitosis during the transition from the sexual phase to the vegetative phase of the life cycle in fission yeast. In this process, each of the dispersed centromeres is often associated with a novel Sad1-containing body that is contacting a cytoplasmic microtubule laterally (Sad1 is a component of the spindle pole body (SPB)). The Sad1-containing body was colocalized with other known SPB components, Kms1 and Spo15 but not with Cut12, indicating that it represents a novel SPB-related complex. The existence of the triplex structure (centromere-microtubule-Sad1 body) suggests that the clustering of centromeres is controlled by a cytoplasmic microtubular system. Accordingly, when microtubules are destabilized, clustering is markedly reduced.

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