Ultrastructure of pinealocytes of the cotton rat,Sigmodon hispidus

Summary Fine structural features of pinealocytes of cotton rats (Sigmodon hispidus) were examined. Golgi complexes, mitochondria, endoplasmic reticulum and polysomes are usual organelles seen in the perikaryonal cytoplasm of pinealocytes. Many non-granulated vesicles (40 to 80 nm in diameter) and a few granulated vesicles (about 100 nm in diameter) are associated with the Golgi cisternae. Occasionally, the cisternae contain granular materials. The perikaryonal cytoplasm of pinealocytes is characterized by the presence of inclusion bodies. These bodies are usually round in shape, not bounded by a limiting membrane and composed of fine granular or filamentous materials of high electron-opacity, which are similar in appearance to the substance seen in the nucleolonema. Pinealocyte processes, filled with abundant non-granulated vesicles and some granulated vesicles, are mainly found within the parenchyma and occasionally in perivascular spaces.Supported in part by NSF grant no. PCM 77-05734 and NIH grant no. HD-10202 (Morphology Core)     

Study of streptococcal L forms in the scanning electron microscope. II. Dynamics of the development of structural elements of L colonies at different stages of growth]

The method of scanning electron microscopy showed that the L-colonies of streptococcus were formed by the spherical structures 0.1--1.5 micronm in diameter, elements of polygonal shape (large bodies) 10--30 micronm in size, filamentous structures 01--7 micronm in diameter and structureless matrix. A regular replacement of one form by another was observed in the process of the L-colonies development. Thus, the spherical elements appeared in the lag-phase, and polygonal elements were found mostly at the initial stages of the L-colonies formation; as to the filamentous structures -- they were present at all the developmental stages, but their diameter increased, and their structure and number changed at different growth phases. The spherical elements of the L-colonies formed evenly both on the structureless depth matrix of the colonies, on the filamentous structures in the form of buds on the "large bodies", and the disintegration of the latter. The role of the filamentous structures in the development of the L-colonies is discussed.     

Intranuclear filamentous inclusions in the gastro-entero-pancreatic (GEP) endocrine cells of birds

Summary Intranuclear filamentous inclusions were found in the normal endocrine cells of the avian stomach and pancreas. These inclusions were composed of a bundle of closely packed filaments (6–8 nm in diameter), being ultrastructurally similar to those found in the nucleus of various neurons. Most of them appeared as single rod- or spindle-shaped bodies; aggregations of two or more inclusions were rarely seen within a single nucleus. Cells with an intranuclear inclusion often contained a cytoplasmic fibrillar bundle similar to the intranuclear inclusion.     

Three structures associated with the nucleolus in male rat germinal cells: round body, coiled body, and "nubecula" and general presence of round body at male meiosis.

In addition to chromosomes and nucleoli, three structures, i.e., round body, coiled body, and nubecula, are encountered in the nucleus during the meiotic prophase in male rats. These structures have been examined by electron microscopy in random and serial sections. The round body is a finely fibrillar, proteinaceous structure closely associated with the granular component of a nucleolus in rat spermatocytes and young spermatids. A similar structure has been observed in man, the monkey Macaca mulatta, the gastropod Achatina fulica, and the insect Locusta migratoria. Together with evidence from the literature, these results support the view that the round body is of general occurrence in the male meiocytes of eukaryotes and may, therefore, play a role in meiosis. The coiled body is a group of electron-dense elements called "coils", which average 35 nm in width, except after mid-pachytene when their size almost doubles. The coils are composed of 2-nm-wide filaments and 8 to 10-nm-wide granules, both of which are ribonucleoprotein. The coiled bodies are interpreted to be groups of "spliceosomes", that is, structures containing heterogeneous RNA and small nuclear RNA. A remarkable feature of the coiled body is its temporary disappearance at early pachytene and its reappearance at late pachytene, possibly due to drastic changes in the turnover rate of its component RNAs. The nubecula is a newly identified nuclear inclusion, composed of weakly staining threads loosely organized into a 560 nm-wide spheroid. It has been observed only in early pachytene nuclei.     

Hyphal tip ultrastructure ofAspergillus nidulans andAspergillus giganteus and possible implications of woronin bodies close to the hyphal apex of the latter species

Summary The hyphal tip ultrastructure ofAspergillus nidulans andAspergillus giganteus indicates that their apical organization is very similar to that found in other filamentous fungi. Both species have an area immediately behind the hyphal apex free of all large organelles and containing a high concentration of vesicles. InA. giganteus only one size class of vesicle is clearly evident, with a mean diameter of 72 nm. InA. nidulans two size classes of vesicle were found, with mean diameters of 75 nm and 31 nm. A Spitzenkörper is evident inA. nidulans as an area very close to the tip containing only the smaller vesicles. InA. giganteus one or more apparently mature Woronin bodies were found within the first 1 m of some hyphal apices. The possible significance of their presence is discussed.     

Reovirus core protein mu2 determines the filamentous morphology of viral inclusion bodies by interacting with and stabilizing microtubules

Cells infected with mammalian reoviruses often contain large perinuclear inclusion bodies, or "factories," where viral replication and assembly are thought to occur. Here, we report a viral strain difference in the morphology of these inclusions: filamentous inclusions formed in cells infected with reovirus type 1 Lang (T1L), whereas globular inclusions formed in cells infected with our laboratory's isolate of reovirus type 3 Dearing (T3D). Examination by immunofluorescence microscopy revealed the filamentous inclusions to be colinear with microtubules (MTs). The filamentous distribution was dependent on an intact MT network, as depolymerization of MTs early after infection caused globular inclusions to form. The inclusion phenotypes of T1L x T3D reassortant viruses identified the viral M1 genome segment as the primary genetic determinant of the strain difference in inclusion morphology. Filamentous inclusions were seen with 21 of 22 other reovirus strains, including an isolate of T3D obtained from another laboratory. When the mu2 proteins derived from T1L and the other laboratory's T3D isolate were expressed after transfection of their cloned M1 genes, they associated with filamentous structures that colocalized with MTs, whereas the mu2 protein derived from our laboratory's T3D isolate did not. MTs were stabilized in cells infected with the viruses that induced filamentous inclusions and after transfection with the M1 genes derived from those viruses. Evidence for MT stabilization included bundling and hyperacetylation of alpha-tubulin, changes characteristically seen when MT-associated proteins (MAPs) are overexpressed. Sequencing of the M1 segments from the different T1L and T3D isolates revealed that a single-amino-acid difference at position 208 correlated with the inclusion morphology. Two mutant forms of mu2 with the changes Pro-208 to Ser in a background of T1L mu2 and Ser-208 to Pro in a background of T3D mu2 had MT association phenotypes opposite to those of the respective wild-type proteins. We conclude that the mu2 protein of most reovirus strains is a viral MAP and that it plays a key role in the formation and structural organization of reovirus inclusion bodies.     

Purification and Chemical Composition of Reticulate Bodies of the Meningopneumonitis Organisms

Reticulate bodies of the meningopneumonitis (MP) microorganism were purified from L cells 18 hr after infection by the combination of differential centrifugation in 30% sucrose solution and potassium tartrate density gradient centrifugation. It was ascertained by electron microscopy that purified preparations of reticulate bodies obtained were almost entirely free of host-cell components and of infectious elementary bodies of MP microorganisms. Purified reticulate bodies were easily disrupted by mechanical agitation, and it was observed in shadowed preparation that ribosome-like particles 15 mmu in diameter were scattered from broken reticulate bodies. In shadowed preparations, reticulate bodies were found to range in size from 1.0 to 1.6 mu in diameter, but in cross-section the range was 0.5 to 1.0 mu. In these preparations, the purified reticulate bodies were irregular in shape, round or oval, and were composed of rather homogenous, amorphous, or reticulate material with moderate density. Some particles exhibited a less-dense internal structure, in which a coarse fibrous reticulum was seen. Chemical fractionation of (32)P-labeled purified reticulate bodies showed that they contained three times more ribonucleic acid (RNA) than deoxyribonucleic acid, with the RNA being composed primarily of 21S, 16S, and 4S RNA. No infectivity of purified reticulate bodies could be demonstrated.     

Electron microprobe X-ray analysis of polyphosphate granules in Plesiomonas shigelloides

Electron-dense inclusion bodies were found in most Plesiomonas shigelloides cells, regardless of the incubation time. At the 4-hr incubation period, the size of inclusion bodies was distributed in the range of 50 to 150 nm in diameter, and at the logarithmic phase of growth it increased up to a size visible by light microscope. By an electron microprobe X-ray analysis, phosphorus, potassium, and magnesium were detected in the inclusion bodies which confirms the assumption of Pastian and Bromel (Appl. Environ. Microbiol. 47: 216 (1984] that the inclusion bodies have a very similar elemental composition to the polyphosphate granules of C. diphtheriae.     

Spermatogenesis in animals as revealed by electron microscopy

Summary The early spermatid nuclei of the grasshopper, Acrida lata, have been observed electron microscopically. The irregularly compact chromatin mass appears closely attached to the nuclear envelope. This mass migrates subsequently into a more central portion. It seems to participate in the formation of the nucleolus as a nucleolar organizer. At the time when the chromatin mass and frequently the nucleolus undergo involution, clusters of peculiar granular bodies 130 m in average diameter and 200 A wide filamentous elements among the bodies make their appearance in the nucleoplasm. The particles constituting the granular bodies are composed of DNA, but their matrix consists of RNA. The term microkaryosome is proposed for such granular body, because it is similar in chemical components to karyosome, but the former is smaller in size than the latter. It is suggested that the microkaryosome may be related with the paracrystalline formation of nucleoprotein.     

Electron Microscopy of Measles Virus Replication

Replication of measles virus in HeLa cells was examined by electron microscopy with ultrathin sectioning and phosphotungstic acid negative staining methods. The cytoplasmic inclusion bodies consisted of masses of helical nucleocapsid which was similar in structure to the nucleocapsid found in measles virions. The cytoplasmic helical nucleocapsid appeared to align near the HeLa cell membrane, and the membrane differentiated into the internal membrane of the viral envelope and the outer layer of the short projections. The viral particles were released by a budding process involving incorporation into the viral envelope of membrane which was contiguous to but morphologically altered from the membrane of the HeLa cells. The intranuclear inclusion bodies were composed of tubular structures similar to those found in the cytoplasmic inclusion bodies. These structures aggregated to crystalline arrangement. The relationship between nuclear inclusion body and replication of measles virus was not clear.     

Fine Structure of the Neogregarine Farinocystis tribolii Weiser, 1953. Developmental Stages in Merogony.

SYNOPSIS. The fine structure of schizonts and free merozoites of the neogregarine Farinocystis tribolii Weiser, and their development in the fat body of larval Tribolium castaneum were studied.
The surface of a multinucleate schizont and that of a uninucleate merozoite is covered by a double-layered membrane. Rhoptries and micronemes are present. The cytoplasm is packed with ribosomes and also contains dark bodies. Mitochondria are of the vesicular type. The spherical nucleus of the schizont and merozoite contains a large nucleolus. The anterior end of the merozoite has a typical conoidal complex composed of a conoid and a polar ring with 22 subpellicular mirotubules projecting from it.
New findings are a membranous septum across the body of the merozoite at 2/3 of its length below the nucleus and a highly osmiophilic spiral structure in the perinuclear space close to the Golgi complex. In addition, we found some "developmental stages" of the latter structure.     

THE FINE STRUCTURE OF THE PIGMENT EPITHELIUM IN THE ALBINO RAT

In this report, particular attention is paid to the inclusion bodies found in the apical cytoplasm of the pigment epithelial cell. These bodies are of variable size and form. The smallest (0.4 µ diameter) consist of a granular matrix enclosed by a single membrane, and are similar to the lysosomes of hepatic cells. Larger inclusion bodies contain areas of lamellated material in addition to granular matrix. The largest particles seen (2 µ diameter) are almost entirely lamellar. These different forms seem closely related, for it is possible to find all transitional stages between the smallest and largest particles. The relationship between the lamellar inclusion bodies and the rod outer segments is discussed.     

An Electron Microscope Study of the Rat Ovum

This paper reports on the fine structure of rat oocytes at stages before ovulation, during maturation, fertilization, and early cleavage. The study includes parallel observations on light and electron microscope preparations with attempted correlations. The follicular cells of the ovarian egg are described as sending long processes through the zona pellucida to the egg surface where they mingle with thin projections from the egg itself. No open communication between follicle cell cytoplasm and egg cytoplasm was observed. During maturation and fertilization both types of processes are withdrawn from the zona. The germinal vesicle and later the pronuclei of the fertilized egg are characterized by numerous large nucleoli. These have the form of thick walled vesicles with diameters as great as 8 to 10 µ. The wall is dense in the EM image and appears to consist in part of small granules. The cytoplasm shows several inclusions including mitochondria of usual form and a Golgi component which has the typical fine structure and the distribution described by earlier light studies. Small dense particles, presumably RNP particles, are distributed throughout the cytoplasmic matrix and show no preference for membranes. The endoplasmic reticulum of the oocyte is represented by a scattering only of vesicles, but begins a more extensive and elaborate development with the onset of segmentation. One inclusion of the ooplasm, similar in size to mitochondria, receives special attention. It is a vesicular structure, containing a large number of small vesicles (10 to 50 mµ in diameter) and frequently a central density or nucleoid. They are referred to as multivesicular bodies. Such bodies are found in small number in the ovarian egg, but increase greatly in number during maturation and fertilization. It appears from the micrographs of eggs in these latter stages that these vesicular bodies break down and liberate their content of small vesicles to the surrounding ooplasm. Comments are provided on the apparent significance of the various observations.     

Intranuclear Inclusions in the Ameboid Cells of Protostelium zonatum*

SYNOPSIS. Two morphologically distinct types of intranuclear inclusions are found in ameboid cells of the protostelid mycetozoan Protostelium zonatum. One type of inclusion is a coiled tubular structure which in cross section appears as cisternae and oval to elliptical vesicles 40–60 nm in diameter. These tubular and vesicular structures are formed by a unit membrane that is connected directly with the inner nuclear membrane. The other type of inclusion is a membrane-bound structure that contains amorphous and/or fibrous material. These inclusions usually are present at several locations in a nucleus. No similar structures occur in the cytoplasm.     

Ultrastructure of the thread cells in the slime gland of Japanese hagfishes,Paramyxine atami and Eptatretus burgeri

The thread cells in the slime gland of Japanese hagfishes, Paramyxine atami and Eptatretus burgeri were studied by light and electron microscopy. The mature thread cells are large elements (180 times 80 mu) filled with an intricately coiled thread, approximately 2 mu in diameter. The protein nature of the thread has been confirmed by histochemical examination. In the initial stage of growth, the thread consists of a bundle of distinctly parallel filaments approximately 90-120 A in diameter and a centrally located tubular component approximately 230-260 A in diameter which occurs singly or occasionally as a double and triple structure. The developing thread displays thin filaments, approximately 30-60 A in diameter. The thin filaments are composed of fine fibrous structures, subfilaments, approximately 10-30 A in diameter. On the outer surface of the thread a coating is apparent, giving it a fluffy appearance. Polysomal clusters consisting of five or six ribosomes are predominant. Fine fibrous structures are also found among the threads; they seem to have a spatial relationship with the polysomes and resemble the subfilament constituents of the thin filaments. From these results, it may be suggested that the fine fibrous structures synthesized by polysomes, twist together and coalesce into a thread. The problem of the polysome size and the molecular weight of the fibrous protein synthesized is discussed.     

Annulate lamellae and whorl bodies in the diffuse supraoptic nucleus of the hamster

The ultrastructure of neurons of the diffuse supraoptic nucleus of the hamster has been studied. These neurons show two specializations of the endoplasmic reticulum: annulate lamellae and whorl bodies. From one to three whorl bodies are found in the same neuron. The annulate lamellae and the whorl body cisterns are continuous with the cisterns of the rough endoplasmic reticulum. These neurons present an extraordinarily developed rough endoplasmic reticulum, small mitochondria, neurosecretory vesicles and a Golgi complex filled with electron-dense material. Astrocytic processes of different thickness surround the neurosecretory cells.     

Ultrastructure of freeze-substituted hyphae of the basidiomyceteLaetisaria arvalis

Summary The ultrastructure of freeze-substituted (FS) hyphae ofLaetisaria arvalis is described and compared to that of similar hyphae preserved by conventional chemical fixation (CF). The outline of membrane-bound organelles as well as the plasma membrane was smooth in FS cells. In contrast, hyphae preserved by CF exhibited membrane profiles that were extremely irregular. Centers of presumed Golgi activity were best preserved by FS. Microvesicles, 27–45 nm diameter and hexagonal in transverse section, were observed most readily in FS cells. Filasomes (= microvesicles within a filamentous matrix) were only observed in FS cells. Apical vesicles, 70–120 nm diameter, associated with the centers of Golgi activity and within the Spitzenkörper region exhibited finely granular matrices in FS hyphae, whereas in CF hyphae the contents were coarsely fibrous and less electron-dense. Microvesicles were present at hyphal apices and regions of septa formation. Filasomes were also found at regions of septa formation as well as along lateral hyphal tip cell walls. Microvesicles, but not filasomes, were observed in membrane-bound vesicles (= multivesicular bodies) and in larger vacuoles. Filaments, 5.2–5.4 nm wide, were juxtaposed with centripetally developing septa. Cytoplasmic inclusions, 20–40 m in length, composed of bundles of 6.7–8.0 nm wide filaments were observed in both FS and CF hyphae.     

Ultrastructural analysis of the effects of erythromycin on the morphology and developmental cycle of Chlamydia trachomatis HAR-13

The effect of erythromycin (10 g/ml) on the morphology and developmental cycle of Chlamydia trachomatis HAR-13 was examined by electron microscopy. When the antibiotic was added later than 24 h post infection, the HAR-13 morphology or developmental cycle was not altered. Addition at 18 or 24 h post infection inhibited glycogen production, blocked the transformation of the reticulate body to elementary body, and produced ghost bodies and reticulate bodies twice the diameter of untreated reticulate bodies. When erythromycin was added within 12 h post infection, the conversion of the elementary body to reticulate body was inhibited. Erythromycin (10 g/ml) was bactericidal to strain HAR-13 throughout the developmental cycle.Abbreviations CXM cycloheximide media - IFU inclusion forming units - MEM minimal essential medium     

The fine structure of a microplate-microtubule array,microfilaments and polyhedral body associated microtubules in several species of Anabaena

A microplate-microtubule array was observed in Anabaena sp. (B-378). This structure consists of an arched plate, about 8 nm thick, and various microtubules, 12 nm in diameter and 50 nm long, arranged in rows. The microtubules project at right angles from one side of the plate into the cytoplasm or towards the plasma membrane. Up to twelve microplate-microtubule arrays were observed in a single section of a cell.Microfilaments, about 2.8 nm in diameter and of undetermined length, were observed in four isolates of Anabaena. The microfilaments were always found in bundles, which varied in size, up to 0.63 m across and 0.91 long.Microtubules, 10 nm in diameter and about 150 nm in length, were observed associated with one facet of polyhedral bodies in 8 out of 20 isolates of Anabaena. The microtubules occurred in groups of up to 20 or more, and were always oriented with the long axis parallel to a facet of a polyhedral body. In cross section, the microtubules had an electron transparent lumen 5 nm wide and a wall 2.5 nm thick.These structures are compared to previously deseribed microtubules and microfilaments.     

Rod-shaped tubulated bodies in the endothelia of mesenteric arteries of hypertensive rats.

Weibel-Palade bodies were found in the endothelial cells of the mesenteric arteries of hypertensive rats. They were spherical or rod-shaped and bounded by a single membrane. They measured approximately 0.1 to 0.2 mu in diameter and up to 0.4 mu in length. The majority of them showed microtubular subunits, measuring about 200 A in width. These bodies are thought to originate from Golgi apparatus.