An ultrastructural study of the mature spermatozoid of Equisetum

1977 ◽  
Vol 277 (953) ◽  
pp. 131-158 ◽  
Keyword(s):  
Nuclear Envelope ◽  
Smooth Endoplasmic Reticulum ◽  
Posterior Part ◽  
Male Gamete ◽  
Multilayered Structure ◽  
Wall Material ◽  
Basal Bodies ◽  
Posterior Half ◽  
Structural Differentiation ◽  
Membrane Bound

The male gamete of Equisetum is the largest and structurally most complex of those so far known in living pteridophytes. The ultrastructure of the mature gametes, is described with particular reference to the influence of the multilayered structure (MLS) on its form. In Equisetum this organelle comprises a band of over 300 microtubules, underlain along its anterior edge by a lamellar strip, 15-20 µm in length, and forming a sinistral spiral of 2 1/2 gyres. The tubules extend from the strip, at an angle of about 40°, to form a broad sheath around the twisted pyriform nucleus located in the posterior half of the cell. From the anterior tip of the lamellar strip to the posterior end of the nucleus the gamete completes a helix of 3 1/2 gyres, traversed throughout by the microtubular band. As a result of growth of this band during spermatid metamorphosis, and the 40° angle between the elates of the lamellar strip and the microtubules, the strip is displaced anteriorly and laterally relative to the nucleus. In the mature gamete, although the strip and the nucleus remain interconnected by the microtubular band, only the posterior half of the strip lies directly above the anterior third of the nucleus. The precise interrelationship between nucleus and MLS is illustrated by reconstructions which display the spermatozoids as they would appear if uncoiled. The 80-120 flagella are inserted outside that part of the micro tubular band lying anterior to the nucleus. Their basal bodies retain the proximal cartwheel and stellate transition regions found already in spermatids, but in the mature gametes they are invested with collars of osmiophilic material. The axonemes depart at 10° tangentially from the helix and extend backwards parallel with the tubules of the microtubular band. In consequence of the overlapping gyres of the helix the flagella lie in a spiral groove, similar to that found in cycad spermatozoids. From this groove the plasma membrane closely follows the external surface of the microtubular band. Contrasting with other archegoniates, maximal structural differentiation of the MLS is found in the mature spermatozoid. Flat-bottomed keels are present on the microtubules overlying the lamellar strip in which three distinct strata can be recognized. The two outer, consisting of alternating plates of electron-opaque and electron- transparent material, are separated by a continuous electron-opaque sheet. The innermost stratum comprises a continuous layer of finely granular material. Overlying the external anterior rim of the microtubular band is an osmiophilic crest. This retains the regularly banded substructure found in spermatids, but in mature spermatozoids is far more prominent than at any other time during spermatogenesis. It contains an electron-transparent lumen and is continuous with both the anterior ends of the microtubules and the anteriormost lamellar plates. Between the inner gyres of the MLS the crest is confluent with extensive sheets of smooth endoplasmic reticulum. Underlying the lamellar strip is a spiral mitochondrion with prominent dilated cristae. The central cytoplasm contains at least 100 pleomorphic mitochondria, together with from 15 to 25 amyloplasts and a few microbodies. In the nucleus, in addition to condensed chromatin, are several spherical electron-opaque bodies and aggregations of membrane-bound vesicles. Structures identical in appearance with the former also occur in the cytoplasm, and it is suggested that they may be nuclear in origin, as are similar bodies in animal spermatogenesis. The vesicles may represent portions of redundant nuclear envelope whose extrusion into the cytoplasm was prevented by the ensheathing microtubular band. Pores are still present in the nuclear envelope, where this is not invested by the band. The mature spermatozoids are liberated from antheridia within mucilaginous sacs bounded by fibrillar cell wall material, thought to contain lipid droplets promoting their dispersal when in contact with water. On escaping from the sacs the spermatozoids elongate slightly, and profiles of disrupted flagella are frequently encountered. Occasionally the microtubular band ensheathing the posterior part of the nucleus also becomes disorganized. There is no evidence of the utilization of amyloplast starch as an energy source during motility, and, in contrast to ferns and bryophytes, there is no sequestration of the central cytoplasm by the swimming spermatozoids.

scholarly journals Properties of membrane-bound bilirubin UDP-glucuronyltransferase in rough and smooth endoplasmic reticulum and in the nuclear envelope from rat liver

1989 ◽  
Vol 259 (3) ◽  
pp. 659-663 ◽  
Author(s):  
F Vanstapel ◽  
L Hammaker ◽  
K Pua ◽  
N Blanckaert
Keyword(s):  
Endoplasmic Reticulum ◽  
Nuclear Envelope ◽  
Rat Liver ◽  
Smooth Endoplasmic Reticulum ◽  
Membrane System ◽  
Permeability Barrier ◽  
Membrane Bound ◽  
Marker Studies ◽  
High Degree ◽  
Regulatory Properties

We examined regulatory properties of bilirubin UDP-glucuronyltransferase in sealed RER (rough endoplasmic reticulum)- and SER (smooth endoplasmic reticulum)-enriched microsomes (microsomal fractions), as well as in nuclear envelope from rat liver. Purity of membrane fractions was verified by electron microscopy and marker studies. Intactness of RER and SER vesicles was ascertained by a high degree of latency of the lumenal marker mannose-6-phosphatase. No major differences in the stimulation of UDP-glucuronyltransferase by detergent or by the presumed physiological activator, UDPGlcNAc, were observed between total microsomes and RER- or SER-enriched microsomes. Isolated nuclear envelopes were present as a partially disrupted membrane system, with approx. 50% loss of mannose-6-phosphatase latency. The nuclear transferase had lost its latency to a similar extent, and the enzyme failed to respond to UDPGlcNAc. Our results underscore the necessity to include data on the integrity of the membrane permeability barrier when reporting regulatory properties of UDP-glucuronyltransferase in different membrane preparations.

Ultrastructural aspects of conidiogenesis in the entomogenous hyphomycete Nomuraea rileyi

1982 ◽  
Vol 60 (1) ◽  
pp. 26-33 ◽  
Author(s):  
J. C. Pendland ◽  
D. G. Boucias
Keyword(s):  
Endoplasmic Reticulum ◽  
Nuclear Envelope ◽  
Smooth Endoplasmic Reticulum ◽  
Wall Layer ◽  
The Other ◽  
Wall Material ◽  
Nomuraea Rileyi ◽  
Conidium Formation ◽  
Woronin Body

Conidia in Nomuraea rileyi are produced basipetally from a phialide apex. Production of primary and all successive conidia appears to be enteroblastic, and only the inner, newly formed wall layer of the phialide surrounds developing conidia. Conidium formation ceases as layers of inner wall material accumulate at the phialide apex. In some cases, a pluglike structure resembling a Woronin body may cause cessation of conidiogenesis. Conidia are delimited by formation of a double septum. Since one half of the septum forms the base of the "older" conidium and the other half forms the apex of the next conidium, separation of successive conidia is schizolytic. Plasmalemmasomes, lomasomes, and smooth endoplasmic reticulum are often seen in association with septa and walls of conidiogenous cells. Transverse fibrils may be observed in some walls. Extensive vacuolization is common in older cells. Glycogen is present in conidiogenous cells and in conidia, which become very electron dense as they mature. An extranuclear plaque, an ascomycetous characteristic, may be observed on the nuclear envelope.

An Ultrastructural Study of the Differentiation of the Spermatozoid of Equisetum

1973 ◽  
Vol 12 (1) ◽  
pp. 95-129
Author(s):  
J. G. DUCKETT
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Wall ◽  
Nuclear Envelope ◽  
Outer Surface ◽  
Single Layer ◽  
Multilayered Structure ◽  
The Other ◽  
Basal Bodies ◽  
Parallel Plates ◽  
Anterior Edge

The ultrastructure of spermatogenesis in Equisetum is described with particular reference to the origin and development of the multilayered structure (MLS) and nuclear metamorphosis. Simultaneously with the formation of centrioles, by the fragmentation of the blepharoplast, in young spermatids, the MLS appears in their vicinity. This comprises 4 layers recalling the Vierergruppe of bryophyte spermatids. The outer layer, or microtubular band, consists of juxtaposed microtubules. The three inner lamellar strata, which lie along the anterior edge of the microtubular band, are composed of parallel plates oriented at 35-45° to the axes of the microtubules. Keels are present on the microtubules where these overlie the lamellar layers. A mitochondrion lies subjacent to the lamellar layers and on the outer surface of the anterior edge of the microtubular band is a crest of osmiophilic material. The position of the osmiophilic crest suggests that it may have a role in microtubule synthesis. However, its persistence in the mature gametes after microtubular elongation has ceased, and its banded substructure, reminiscent of flagellar roots, perhaps indicate that its function is mainly mechanical in holding the microtubular band together. Approximately oval in shape and overlain by less than 50 short microtubules initially, the lamellar strata and subjacent mitochondrion rapidly increase in length. Eventually they form a strip 15-20 µm in length overlain by over 300 microtubules. This extensive microtubular band in Equisetum is more likely related to the final shape of the nucleus in the mature gamete than to the presence of numerous flagella. The entire MLS now becomes associated with the nucleus. The microtubular band is closely adpressed to the nuclear envelope and acts as a cytoskeletal framework along which the nucleus undergoes elongation and coiling. Initially the lamellar strip and mitochondrion run along the nuclear envelope with one of their edges touching it and the other projecting into the cytoplasm. However, continuous elongation of the microtubules throughout nuclear metamorphosis results in the gradual separation of the strip and mitochondrion beyond the anterior tip of the nucleus. Simultaneously, the posterior parts of the nucleus become ensheathed by rearward extension of the microtubular band. The centrioles arrange themselves in a single layer on the outer surface of the microtubular band and during the early stages of nuclear metamorphosis give rise to flagella from their distal ends, concomitantly undergoing differentiation into basal bodies. Intense Golgi activity during early and mid-spermatid stages is thought to be related to the accumulation of mucopolysaccharides between the cell wall and cell membrane. In the mid-spermatids rough endoplasmic reticulum is closely associated with the plastids which later accumulate starch, a characteristic feature of spermatogenesis in archegoniate plants.

scholarly journals The centrin-based cytoskeleton of Chlamydomonas reinhardtii: distribution in interphase and mitotic cells.

1988 ◽  
Vol 107 (2) ◽  
pp. 635-641 ◽  
Author(s):  
J L Salisbury ◽  
A T Baron ◽  
M A Sanders
Keyword(s):  
Nuclear Envelope ◽  
Polyclonal Antibodies ◽  
Flagellar Apparatus ◽  
Immunogold Labeling ◽  
Basal Bodies ◽  
Flagellar Roots ◽  
Cell Biol ◽  
Immunofluorescence Studies ◽  
Descending Fibers

Monoclonal and polyclonal antibodies raised against algal centrin, a protein of algal striated flagellar roots, were used to characterize the occurrence and distribution of this protein in interphase and mitotic Chlamydomonas cells. Chlamydomonas centrin, as identified by Western immunoblot procedures, is a low molecular (20,000-Mr) acidic protein. Immunofluorescence and immunogold labeling demonstrates that centrin is a component of the distal fiber. In addition, centrin-based flagellar roots link the flagellar apparatus to the nucleus. Two major descending fibers extend from the basal bodies toward the nucleus; each descending fiber branches several times giving rise to 8-16 fimbria which surround and embrace the nucleus. Immunogold labeling indicates that these fimbria are juxtaposed to the outer nuclear envelope. Earlier studies have demonstrated that the centrin-based linkage between the flagellar apparatus and the nucleus is contractile, both in vitro and in living Chlamydomonas cells (Wright, R. L., J. Salisbury, and J. Jarvik. 1985. J. Cell Biol. 101:1903-1912; Salisbury, J. L., M. A. Sanders, and L. Harpst. 1987. J. Cell Biol. 105:1799-1805). Immunofluorescence studies show dramatic changes in distribution of the centrin-based system during mitosis that include a transient contraction at preprophase; division, separation, and re-extension during prophase; and a second transient contraction at the metaphase/anaphase boundary. These observations suggest a fundamental role for centrin in motile events during mitosis.

The growth of the pollen tube wall in Oenothera organensis

1975 ◽  
Vol 18 (3) ◽  
pp. 519-532
Author(s):  
H.G. Dickinson ◽  
J. Lawson
Keyword(s):  
Pollen Tube ◽  
Tube Wall ◽  
Wall Material ◽  
Fibrillar Material ◽  
Stage Of Development ◽  
Large Numbers ◽  
Membrane Bound ◽  
Pollen Tube Wall ◽  
Different Sources ◽  
Dictyosome Vesicles

The growth of the pollen tube wall of Oenothera is effected by the expulsion of fibrillar material from the cytoplasm into the developing wall. This material may also be seen in the cytoplasm, contained in membrane-bound vesicles. It is not clear how the content of the vesicles is discharged, but it appears not to involve the participation of microtubules. The source of the cytoplasmic fibrillar bodies depends upon the stage of development of the pollen tube. The earilest growth is derived from the inclusion into the wall of vesicles containing pre-formed materials present in the grain on pollination. During the next stage of growth the wall is derived from the content of double-membraned inclusions also present in the pollen. The content of the former vesicles is not so similar to the wall as the latter, but intermediates between the 2 types of vesicle may be seen in the cytoplasm, indicating that the former are formed from the latter. Most of the tube wall is derived from the products of dictyosomes in the pollen grain or tube. These dicytosomes are few in number and they must be exceedingly active. This, and the observation that dictyosome vesicles are frequently associated with banked complexes of mitochondria, indicates that some steps in the metabolism of the vesicular content, perhaps phosphorylation, take place distant from the dicytosomes. These different sources of fibrillar material presumably permit the rapid starting of tube growth, without any attendant metabolism. However, it would be impossible to include enough pre-formed wall material in the grain to enable the full growth of the tube, so once started, it seems that the tube then relies on the elaboration of simple reserves for the contruction of its wall. These reserves are likely to be held in the pollen, and may be the large numbers of starch grains characteristic of the pollen cytoplasm.

scholarly journals The ultrastructure of cell division in Euglena gracilis

1978 ◽  
Vol 31 (1) ◽  
pp. 25-35
Author(s):  
M.A. Gillott ◽  
R.E. Triemer
Keyword(s):  
Cell Division ◽  
Nuclear Envelope ◽  
Basal Body ◽  
Euglena Gracilis ◽  
Equatorial Region ◽  
Basal Bodies ◽  
Cleavage Furrow ◽  
Free Zone ◽  
Prophase Nucleus

The ultrastructure of mitosis in Euglena gracilis was investigated. At preprophase the nucleus migrates anteriorly and associates with the basal bodies. Flagella and basal bodies replicate at preprophase. Cells retain motility throughout division. The reservoir and the prophase nucleus elongate perpendicular to the incipient cleavage furrow. One basal body pair surrounded by a ribosome-free zone is found at each of the nuclear poles. The spindle forms within the intact nuclear envelope- Polar fenestrae are absent. At metaphase, the endosome is elongated from pole to pole, and chromosomes are loosely arranged in the equatorial region. Distinct, trilayered kinetochores are present. Spindle elongates as chromosomes migrate to the poles forming a dumb-bell shaped nucleus by telophase. Daughter nuclei are formed by constriction of the nuclear envelope. Cytokinesis is accomplished by furrowing. Cell division in Euglena is compared with that of certain other algae.

An ultrastructural study of the spermatozoid of the fern, Marsilea vestita

1975 ◽  
Vol 17 (3) ◽  
pp. 633-645
Author(s):  
D.G. Myles
Keyword(s):  
Nuclear Envelope ◽  
Ultrastructural Study ◽  
Spiral Structure ◽  
Multilayered Structure ◽  
Condensed Chromatin ◽  
Posterior Region ◽  
Cytoplasmic Vesicle ◽  
Marsilea Vestita ◽  
Shaped Cell ◽  
Dense Band

The ultrastructure of the mature spermatozoid of Marsilea vestita was studied after its release from the microspore and prior to its penetration of the egg. The psermatozoid is a pear-shaped cell with a complex spiral structure coiled around the edge in the narrow anterior end. This coil is composed of a large mitochondrion, elongated nucleus with highly condensed chromatin, a ribbon of microtubules, and a dense band of material (flagellated band) into which the flagella are inserted. There are over a hundred flagella protruding from each spermatozoid along the length of the coil. At the anterior tip of the coil is a short multilayered structure. It is not known what maintains the helical shape of the coil. The microtubular ribbon could be involved, but it is also possible that either the flagellated band, the condensed chromatin, or both, are sufficiently rigid to retain their shpaes unaided. When the spermatozoid is first released from the microspore it includes a cytoplasmic vesicle in the posterior region containing plastids, mitochondria, and other organelles. This vesicle is shed, taking the nuclear envelope with it, before the spermatozoid reaches the egg.

Studies on the site of addition of sialic acid and glucosamine to rat α1-acid glycoprotein

1977 ◽  
Vol 55 (4) ◽  
pp. 408-414 ◽  
Author(s):  
J. C. Jamieson
Keyword(s):  
Endoplasmic Reticulum ◽  
Sialic Acid ◽  
Rat Liver ◽  
Golgi Complex ◽  
Smooth Endoplasmic Reticulum ◽  
Main Site ◽  
Acid Glycoprotein ◽  
Membrane Bound ◽  
Polypeptide Chains

Ultrasonic extracts of rough and smooth endoplasmic reticulum fractions and Golgi fractions from rat liver were examined by immunoelectrophoresis using antiserum to α1-acid glycoprotein. Rough endoplasmic reticulum fractions contained only sialic acid free α1-acid glycoprotein, whereas smooth endoplasmic reticulum and Golgi fractions also contained sialic acid containing α1-acid glycoprotein. Determination of the sialic acid contents of immune precipitates isolated from the extracts suggested that the Golgi complex was the main site of addition of sialic acid to α1-acid glycoprotein. Immunological studies on puromycin extracts of polyribosomes showed that polypeptide chains of α1-acid glycoprotein and albumin were assembled mainly on membrane-bound polyribosomes. Evidence is presented from incorporation studies with labelled leucine and glucosamine that initial glycosylation of α1-acid glycoprotein occurs mainly or entirely after release of nascent polypeptide from the ribosomal site.

Comparison of the repair of permanent tympanic membrane perforations by hydrocolloidal dressing and paper patch

1995 ◽  
Vol 109 (11) ◽  
pp. 1041-1047 ◽  
Author(s):  
Odd Spandow ◽  
Sten Hellström ◽  
Michael Dahiström ◽  
Lennart Bohlin
Keyword(s):  
Simple Technique ◽  
Posterior Part ◽  
Alternative Methods ◽  
Posterior Half ◽  
Occlusive Dressing ◽  
Tympanic Membrane Perforations ◽  
Significant Difference ◽  
One Year ◽  
A Prospective Study ◽  
Inferior Quadrant

AbstractThirty consecutive patients with permanent perforations of their tympanic membranes (TM) present from 2.5 to 50 years (mean 18.7 years) were admitted to a prospective study using two alternative methods of dressings for closure of the perforations. An adhesive-coated hydrocolloid material was compared with a conventional dressing of vaseline impregnated rice paper patch after de-epithelialization of the perforation border. Nine of the permanent TM perforations (30 per cent), five with the hydrocolloidal dressing and four with the rice paper patch had healed when followed-up after one year. The size of eight of the central perforations that had healed was equal to or less than 25 per cent of the TM. Also one perforation with a size of 65 per cent had healed. Seven perforations were located in the posterior part of the TM:Jour in the posterior-superior quadrant, one in the inferior quadrant, one had engulfed the posterior half of the TM and one included the anterior-inferior quadrant. Only two perforations out of 14, with a size of 25 per cent or less, located in the anterior-inferior quadrant, healed. No significant difference was demonstrated between the two types of dressings. Both groups noted an immediate improvement in hearing of 10.8 and 9.3 dB, respectively, after application of the dressing.The study demonstrates that application of an occlusive dressing or paper patch in 30 per cent of patients can promote the healing of long-standing perforations. The chances for healing are better if the perforation is located in the posterior part of the TM. This simple technique immediately improved hearing and should be tried before a patient is referred for myringoplasty surgery.

scholarly journals Proteolytic activation and solubilization of endoplasmic-reticulum cyclic AMP phosphodiesterase activity

1983 ◽  
Vol 213 (1) ◽  
pp. 99-105 ◽  
Author(s):  
S R Wilson ◽  
M D Houslay
Keyword(s):  
Endoplasmic Reticulum ◽  
Proteinase Inhibitors ◽  
Smooth Endoplasmic Reticulum ◽  
Limited Proteolysis ◽  
Proteolytic Activation ◽  
Freeze Thaw ◽  
Membrane Bound ◽  
Time Courses ◽  
Triton X ◽  
Thiol Proteinase

Dithiothreitol led to the activation and solubilization of the cyclic nucleotide phosphodiesterase activities associated with the smooth and various rough subfractions of rat liver endoplasmic reticulum. The activity in each of the subfractions exhibited somewhat different time courses, and sensitivities to dithiothreitol concentration, in respect of their solubilization and activation. Both activation and solubilization by dithiothreitol could be blocked by either thiol proteinase inhibitors or excess bovine serum albumin. Freeze-thaw solubilization was not blocked by the thiol proteinase inhibitor antipain and did not lead to the activation of the enzyme. After dithiothreitol-induced solubilization, all of the enzymes exhibited non-linear Lineweaver-Burk plots indicative of apparent negative co-operativity. In contrast, after freeze-thaw solubilization the enzyme in the smooth-endoplasmic-reticulum-plus-Golgi fraction still obeys Michaelis kinetics, as does the membrane-bound enzyme. It is possible to mimic the action of dithiothreitol in solubilizing and activating the enzyme by limited proteolysis with trypsin. Triton X-100 is highly efficient at solubilizing these enzymes, yet has little effect on their activities. Charged detergents exhibit highly selective effects on the enzymes as regards their solubilization and activity expressed.

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