ELECTRON MICROSCOPE STUDY OF A DIPLOGRAPTUS SPECIES

Specimens of Diplograptus sp. from the late Middle Ordovician Lebanon Limestone in central Tennessee have been isolated from the matrix and examined with transmission electron microscopes at 60 and 650 kv. The fine structure of the fusellar layer in the metasicula and in the thecae is a mesh formed from fibers. The cortical layer has two sublayers, one of which is a mesh that is closely similar to the mesh of the fusellar layer and the other is formed from two sets of long fibers that are oriented at moderate to high angles to each other. The prosicula outer wall is a loosely-woven, open mesh formed of fibers that are 0.080–0.165 microns in diameter. The spiral thread appears to be a band that is also formed of interwoven fibers. The longitudinal rod is a bundle of long fibers. Prosicula microstructures of this Diplograptus are significantly different from those in an Orthograptus of the O. quadrimucronatus (Hall) group.     

Fine Structure of Zygotes and Oocysts of Eimeria nieschulzi*

SYNOPSIS. Mature macrogamonts were present in the small intestine of rats 5.5 to 7.5 days postinoculation with Eimeria nieschulzi oocysts; oocysts were present at 6 to 7.5 days. Types I and II wall-forming bodies in macrogamonts began to undergo ultrastructural changes within zygotes to form the outer and inner layers of the oocyst wall. Before and during oocyst wall formation a total of 5 membranes (M1–5) were formed at or near the surface of the zygote. The outer and inner oocyst wall layers formed between M2 and M3, and M4 and M5, respectively. The mature oocyst was loosely surrounded by M1 and M2, had an electron-dense outer layer, 100–275 nm thick, and an electron-lucent inner layer, 160–180 nm thick. It also contained an electron-lucent line consisting of M3 and M4 interposed between the outer and inner layers of the oocyst wall. The micropyle, measuring 935 × 47 nm, was located in the outer layer of the oocyst wall and consisted of 10–14 alternating layers of electron-dense and lucent material. The sporont of mature oocysts was covered by M5, immediately beneath which were M6 and M7. The sporont contained a nucleus and nucleolus, lipid and amylopectin bodies, mitochondria, ribosomes, as well as smooth and rough endoplasmic reticulum. Canaliculi, Golgi complexes, and types I and II wall-forming bodies were absent.     

Teratocarcinoma differentiation: plasminogen activator activity associated with embryoid body formation.

Changes in plasminogen activator activity have been examined as a clonal line of mouse embryonal carcinoma cells aggregate and differentiate to form cystic embryoid bodies in vitro. Within the first 10 days of study, the pluripotent embryonal carcinoma cells aggregate; a layer of endodermal cells appears on the outside of the aggregate forming an embryoid body; a basement membrane forms between the outer layer of endodermal cells and the internal cells; a cyst forms within the embryoid body; and the internal cells assume a columnar appearance along the inner portion of the basement membrane. After the formation of the endodermal layer, there is a rise in intracellular plasminogen activator activity. This rise continues for up to 25 days in culture, providing that the three-dimensional integrity of the embryoid bodies is maintained by culturing them on bacterial petri dishes. Selective removal of the outer endodermal layer of cells reduces the plasminogen activatory activity of the resulting embryoid body cores. Intracellular and secreted plasminogen activator activity of simple embryoid bodies composed of only two cell types can be increased by culturing the embryoid bodies in dbcAMP, theophylline, or cholera toxin. These results suggest that the embryoid body endodermal cells are the source of a cAMP-inducible plasminogen activator activity.     

Ultrastructure and composition of the conidial wall of Cladosporium cladosporioides

Transmission electron microscopy revealed that the conidial wall of Cladosporium cladosporioides was constituted of an electron-lucent inner layer and an electron-dense outer layer. The conidial surface is covered by rodlet fascicles which can be removed by ultrasonication. Ultrastructurally, the 100,000 X g ultracentrifugation pellet of the ultrasonicated extract containing the rodlet layer appeared as an amorphous structure containing probably internal wall material anchoring the rodlet fascicles on the wall. The total conidial wall was essentially composed of beta(1----3)glucans and melanin. Lipid, salt, and galactan represented the main components of the 100,000 X g ultracentrifugation pellet of the ultrasonicated extract. Cladosporium cladosporioides produced melanin via the pentaketide pathway. Tricyclazole inhibited melanin synthesis but did not interfere with allergen production. This suggests that the wall components associated with melanin are not allergenic factors.     

Localization of the cellulase activity of Bacteroides cellulosolvens

The major portion of cellulase activity of Bacteroides cellulosolvens was cell-associated. Cells grown on cellulose had a distinctive morphology, characterized by an amorphous outer cell wall layer with irregular, 'fluffy' projections. These cells had greater cell-associated cellulase activity than the cellobiose grown cells which exhibited a smooth, distinct outer layer. It is suggested that the outer layer characteristic of cellulose grown cells is the location of cellulase activity and the site for close cellulose-cell contact.     

The use of radioautography for investigating wall secretion in plant cells

Summary The paper summarises results of simple radioautographic experiments using tritiated glucoses to investigate wall secretion in plant cells. In outer root cap cells, labelled material was first concentrated in the Golgi bodies; it later appeared in vesicles, and was incorporated into the wall immediately under the plasmalemma. It finally collected mainly in the slime layer surrounding the root tip. Biochemical analyses have indicated that this material was pectic in nature. In inner root cap and epidermal cells, labelled material incorporated into the walls and also the cell plates of dividing cells was also apparently mainly derived from Golgi bodies. In meristematic (less differentiated) cells, however, the endoplasmic reticulum was more frequently labelled than the Golgi bodies near walls that had incorporated derivatives of labelled glucose. Considerable incorporation of labelled derivatives into the wall thickenings in coleoptile xylem cells was often detected; nearby elements of the endoplasmic reticulum were again frequently labelled in these cells and less often, Golgi bodies and the cytoplasm in the region occupied by microtubules contained radioactivity. Labelling of starch grains in the plastids was generally observed, but not in cells secreting large amounts of wall materials (outer root cap and older xylem cells); however, addition of larger amounts of exogenous glucose to outer root cap cells, following their incubation in tritiated glucose, promoted such incorporation. The paper finally sets forth some considerations on experimental techniques for radioautography that might be of more general application.     

Budding in the Dimorphic Fungus Phialophora dermatitidis

Ultrastructural comparisons of yeast and hyphal bud formation in Phialophora dermatitidis reveal that bud initiation is characterized by a blastic rupture of the outer portion of the yeast or hyphal wall and the emergence of a bud protuberance through the resulting opening. The wall of the emerging bud is continuous, with only an inner wall layer of the parental yeast or hypha. The outer, ruptured portion of the parental wall typically forms a collar around the constricted emergence region of the developing bud. The cytoplasm within the very young emerging bud invariably contains a small number of membrane-bound vesicles. The septum formed between the daughter bud and the parental yeast or hypha is a complete septum devoid of a septal pore, septal pore plug, or any associated Woronin bodies characteristic of simple septa of the moniliform or true hyphae. These observations suggest that yeast bud formation and lateral hyphal bud formation in the dimorphic fungus P. dermatitidis involve a growth process which occurs identically in both the yeast and mold phase of this human pathogenic organism.     

Electron Microscopic Observations on the Structure of the Envelopes of Mature Elementary Bodies and Developmental Reticulate Forms of Chlamydia psittaci

Purified suspensions of Chlamydia psittaci were prepared from L cells. Thin sections of intact elementary bodies and intact developmental reticulate bodies and of their purified envelopes were observed by electron microscopy. In both intact organisms and partially purified envelopes, two membranous structures, each appearing in electron micrographs as two darkly stained layers, were observed. In the elementary body sections, the outer membrane was round, apparently rigid, and was not soluble in 0.5% sodium dodecyl sulfate. The inner layer was irregular in shape and was completely removed by detergent treatment. We interpret these results to indicate that the outer rigid layer of the envelope is the cell wall and the inner layer is the cytoplasmic membrane. When the fragile reticulate body envelopes were similarly studied, the outer cell wall was clearly visible, and some evidence of an inner membrane was seen. After treatment with nucleases and detergent, all evidence of inner or cytoplasmic membrane was removed, but the outer cell wall remained. Thus, it appears that the cell wall of this organism is continuous throughout the growth cycle and that the fragility and lack of rigidity of the reticulate body cell is due to changes in chemical composition or structure of the cell wall.     

Electron microscope studies on Leucothrix mucor

Summary Electron microscopic studies of thin sections of filaments, knots, resettes, gonidia, and gonidial-forming filaments of Leucothrix mucor were carried out. The cell wall is typical of gram-negative bacteria, with a double outer layer of variable thickness, a single thin middle layer which is probably peptidoglycan, and a double inner layer which is the cell membrane. The transverse septa of these filaments show two peptidoglycan layers, and no clearly demarked outer layer. During gonidial formation, there is a gradual rounding up of the cells, and the transverse septa become part of the gonidial wall. The cell membrane contains many invaginations, both along the outer wall and along the transverse septa. Thin sections through rosettes show the holdfast as material which is a heavily-staining amorphous material peripheral to the outer wall layer. Sections through knots show highly contorted cell walls, closely appressed. Fibrillar nuclear material, ribosomes, and storage granules can be seen within the cytoplasmic matrix.     

The fine structure of the virgular apparatus in Cystograptus vesiculosus

Fragments of a virgular apparatus (nematularium), assigned to Cystograptus vesiculosus (Nicholson 1868), etched out of calcareous intercalations of early Llandoverian age from the South Urals, were investigated with the TEM and the light microscope. The extrarhabdosomal portion of the nematularium is a three-vaned, single-walled structure, built exclusively of fusellar tissue without any cortical covering. Its surface is free of cortical bandages. No traces of an extension of the nema (virgula) proper were found at the junction of all three vanes. The membranous portion of each vane is made of narrow, densely packed strips set at 6–12^o to its thickened rim. These microfusellus-like units show highly characteristic undulations of their outer pellicle, providing an additional reinforcement of the structure. Thickened rims are made by the merging of numerous microfuselli which, in their outer part, have a pellicle with a thick outer lamella. A reconstruction of the fine structure of the nematularium is suggested and possible explanations of its morphogenesis and function are discussed. Graptoloidea, nematularium, nema, virgula, ultrastructure, morphogenesis, function, early Llandoverian, southern Urals.     

The microneme protein MIC4, or an MIC4-like protein, is expressed within the macrogamete and associated with oocyst wall formation in Toxoplasma gondii

The expression and localisation of MIC4, or an immuno-cross reacting MIC4-like protein, was examined in the enteric forms of Toxoplasma gondii using immunocytochemistry. In addition to being located within the micronemes of the merozoites, MIC4 or the MIC4-like protein was present within the macrogamete and was associated with the developing oocyst wall. The macrogamete is characterised by two types of structurally distinct wall forming bodies (WFB1 and 2). However, by immuno-electron microscopy, it was possible to identify two populations of dense granules (WFB1) which appear to form sequentially during macrogamete development. The first granules to form (WFB1a) stained positively with anti-MIC4 and were followed by MIC4 negative granules (WFB1b). During oocyst wall formation, the WFB1a and b sequentially released their contents onto the surface with WFB1a material forming an anti-MIC4 positive outer veil, while the WFB1b forms the electron dense outer layer of the oocyst wall. The inner layer was formed by WFB2. Thus, for the first time, it was possible to identify two populations of dense granules (WFB1a and b) involved in the formation of different parts of the oocyst wall. It was not possible to analyse the contents of macrogametes by western blot to unequivocally identify the antigen recognised by the polyclonal antisera as MIC4.     

Fine Structure of the Oocyst Wall of Eimeria nieschulzi

SYNOPSIS. Oocysts of Eimeria nieschulzi from the laboratory rat, Rattus, norvegicus , were studied by scanning and transmission electron microscopy. Oocysts had a rough outer wall with apparent random depressions. The oocyst wall is composed of 2 layers: an osmiophilic outer layer consisting of a rough external and smooth internal surface, and a relatively thick, electron-lucent inner layer. The outer layer is composed of a dense, coarsely granular matrix. The inner layer consists of homogeneous fine granular material interspersed with coarse osmiophilic granules and contains one closely applied membrane on the outermost surface. Several raised lenticular areas are seen on the coarse outer surface of the inner layer. These layers are 102 (75–128) and 176 (135–204) nm thick, respectively.
The sporocyst wall is thin, consisting of 3 to 4 unit membranes, and measures 27 (18–34) nm thick.     

Fine Structure of Established Callus Cultures of Taraxacum officinale Weber

The nodular, brown callus cultures of Taraxacum officinale growslowly on a modified White's medium. A section of nodule revealsa meristematic layer bounded both internally and externallyby parenchymatous tissue. No other types of tissue occur withinthe callus. The cells of the inner parenchyma are often compressedand senescing, whereas in the outer tissue localized de-differentiationapparently contributes to the development of new nodules duringcallus growth. Fine-structural observations of both meristematic and parenchymatoustissues show the normal complement of higher plant cell organellesexcept for the apparent absence of cytoplasmic microtubules.The rough endoplasmic reticulum cisternae are often alignedparallel to the cell wall or in whorls and may show pores, thusresembling annulate lamellae. Numerous lipid bodies, up to 7µm wide, occur and these are sometimes invested by arraysof apparently membranous material. The mitochondria are frequentlyhighly branched and often show a scalariform arrangement ofcristae. The plastids show few internal membranes despite cultureof the callus under continuous illumination. Lomasomes are very common in all cells and in the parenchymatissue membranous wall bodies also occur. The latter bodiesare much larger than lomasomes and consist of wall overgrowthsin which vesicular, myelin-like or isolated membranous elementsare enmeshed in fibrillar material. It is suggested that membranouswall bodies may originate from the amalgamation and subsequentproliferation of several adjacent lomasomes. Taraxacum officinale Weber, dandelion callus cultures, fine structure     

Ultrastructural Changes During Encystment of Schizopyrenus russelli*

Ultrastructural changes associated with the encystment of Schizopyrenus russelli have been studied by electron microscopy. Before encystment small “black bodies” appear in the cytoplasm and later migrate toward the periphery. The outer cyst wall is secreted at this stage as a thin discontinuous layer which thickens and subsequently becomes continuous. Concomitant with this, the endoplasmic reticulum surrounds the mitochondria. The inner cyst wall later appears as a multilayered structure which presumably is cast off from the plasma membrane. Between the inner and outer layers of the cyst wall, there is a middle, less electron-dense layer wherein extruded cytoplasmic material is found embedded at certain places.     

A Histochemical Study of Cytoplasmic Changes During Wall Layer Formation in the Oospore of Albugo candida

The young multinucleate oogonium in Albugo is double-walled with an outer layer exhibiting a negative staining reaction for insoluble polysaccharides and an inner layer which is strongly PAS-positive. The oogonial nuclei exhibit an unusual staining behaviour with aniline blue showing an outer dark blue sheath of proteins surrounding a central hyaline nuclear core. Various histochemical localizations were performed for tracing the chronological sequence of development of the wall layers of the oospore. The first wall of the fertilized oospore was laid at the interphase of the periplasm and the ooplasm. Subsequent wall layers were formed both on the inner and outer side of the first oosporic wall. The second oosporic wall was formed just internal to the first one and exhibited faint PAS positivity. The third wall of the oospore was formed external to the first one and the PAS-negative material for this was apparently contributed by the periplasm. This wall layer at later stages acquired a ridged appearance and these ridges in a mature oospore appear as distinct “pegs”. The last wall to be formed is the innermost one and it completely surrounds the central ooplasm. This wall layer is callosic in nature.     

The development of the macrogamete and oocyst wall in Eimeria maxima: immuno-light and electron microscopy

We have identified, and followed the development of three macrogamete organelles involved in the formation of the oocyst wall of Eimeria maxima. The first were small lucent vacuoles that cross-reacted with antibodies to the apple domains of the Toxoplasma gondii microneme protein 4. They appeared early in development and were secreted during macrogamete maturation to form an outer veil and were termed veil forming bodies. The second were the wall forming bodies type 1, large, electron dense vacuoles that stained positively only with antibodies raised to an enriched preparation of the native forms of 56 (gam56), 82 (gam82) and 230 kDa (gam230) gametocyte antigens (termed anti-APGA). The third were the wall forming bodies type 2, which appeared before the wall forming bodies type 1 but remain enclosed within the rough endoplasmic reticulum and stained positively with antibodies raised to recombinant versions of gam56 (anti-gam56), gam82 (anti-gam82) and gam230 (anti-gam230) plus anti-APGA. At the initiation of oocyst wall formation, the anti-T. gondii microneme protein 4 positive outer veil detached from the surface. The outer layer of the oocyst wall was formed by the release of the contents of wall forming bodies type 1 at the surface to form an electron dense, anti-APGA positive layer. The wall forming bodies type 2 appeared, subsequently, to give rise to the electron lucent inner layer. Thus, oocyst wall formation in E. maxima represents a sequential release of the contents of the veil forming bodies, wall forming bodies types 1 and 2 and this may be controlled at the level of the rough endoplasmic reticulum/Golgi body.     

Fine structure of the oocyst walls of Isospora serini and Isospora canaria and excystation of Isospora serini from the canary, Serinus canarius L.

Oocysts of Isospora serini and Isospora canaria, from the canary Serinus canarius, were broken, added to a cell suspension, fixed in Karnovsky's fluid, and studied in the electron microscope. The oocyst wall of each species had an electron-lucent inner layer, a more osmiophilic middle layer and an outer layer of electron-lucent (I. serini) or electron-dense material interspersed with some electron-lucent material (I. canaria). A few, relatively large lipid-like bodies were present in the outer or middle layer of the oocyst wall of I. canaria. As many as 9 membranes were present in the oocyst wall of I. canaria and 3 in that of I. serini. When exposed to a trypsin-sodium taurocholate fluid, sporozoites of I. serini excysted from 5-month-old sporocysts in vitro, but not from sporocysts stored for more than 6 months. No excystation occurred in 15-month-old I. canaria sporocysts. Similarities and differences in excystation between I. serini and other Isospora, Eimeria, and Sarcocystis species are discussed.     

Ricerche Sull'ultrastruttura della Parete Cellulare

Abstract

A study about the cell wall of AVENA coleoptile epidermis cells. — A new type of lamellae structures embedded in the outer periclinal wall of oat coleoptile epidermis cells has been observed. These structures are present more frequently in the inner non-cutinized portion of the cell wall; their orientation, most often parallel to the cell surface, follows a regular pattern. They are formed by alternate layers of electrontransparent and electron-dense bands. The thickness of these lamellar bodies is about 200–300 Å; their length is rather difficult to determinate. They are bounded by a 30–40 Å thick membrane; the inner compartment is formed by a central highly manganophilic zone 50–70 Å thick where several thin lamellae can be seen and by two lateral zones about 40–50 Å in thickness.

Embedded in the cutinized portion of the wall some elliptical bodies have also been observed, surroundedd by a single membrane, 20 Å in thickness. The interior of these bodies shows thin lamellae enclosed in an electron-transparent stroma.

In experimental conditions unfavourable to growth, the frequency of these structures falls greatly. When the cell distension comes to end, their aspect undergoes deep changes. It is proposed in this paper that these new structures are involved in cell wall growth and development.     

Characteristics of the cytodifferentiation of omega-particle symbiotic bacteria from the micronucleus of Paramecium caudata clone M1-48]

The structure of the omega-particle-bacteria, growing in the micronucleus of Paramecium caudatum (Ciliata, Protozoa), was studied by electrom microscopy in the course of their life cycle. The cytoplasm of the spindle-shaped vegetative cells contains a large number of dense particles and transparent regions comprising the fibrillar material. Such cells, via several intermediate stages, are transformed into elongated twisted cells that are regarded as spores. The spore consists of two parts: homogeneous, and that containing the membrane system and rounded light bodies. The membranes are often double and connected with the fibrils. The cell wall is constructed, during all stages, of the outer membrane layer and the inner electron-dense layer.     

ELECTRON MICROSCOPY OF PHIALIDES AND CONIDIOGENESIS IN TRICHODERMA SATURNISPORUM

Each phialide had a thick-walled neck region located immediately below a light microscopically inconspicuous collarette. The thickened wall of the phialide neck was multilaminate, with layers of different electron transmission properties. A developmental stage in the formation of the first conidial initial was observed. Conidial initials blew out through the thickened neck region, increased in size, and were eventually delimited by centripetally developing septa. Mature, winged conidia had an electron-opaque outer wall layer and an electron-transparent inner wall layer. The wing was formed by separation of these outer and inner wall layers and buckling or wrinkling of the outer layer. As early as they could be discerned, conidial initials had developed the electron-opaque wall layer which characterized mature conidia. Each conidium-delimiting septum became bilayered; the upper layer formed part of the conidial base, and the lower layer became a portion of the wall of the next conidial initial. Phialides lacked an electron-opaque wall layer, and they possessed areas of abundant rough endoplasmic reticulum, as well as free ribosomes. Lipid globules were also abundant, especially in conidia. The distinction between phialides and annellides was questioned.