Paracrystalline Arrays in the Mitochondria of the Peritrichous Ciliate Carchesium polypinum1,2

SYNOPSIS Intramitochondrial inclusions of a paracrystalline nature were observed in the peritrichous ciliate Carchesium polypinum This ciliate was found growing in the effluent of a sewage treatment plant. When paracrystalline inclusions were present, there was one per mitochondrion. A variety of profiles was encountered, all presumably of the same structure. Cross-sections revealed packed, spherical masses of 100-150 A diameter with dense walls 30-40 A thick and a variety of core densities. In more longitudinal sections the paracrystalline array appeared as long. electron-dense, finely filamentous elements oriented in parallel arrays and regularly spaced with a diameter of 60-100 A. Mitochondria tended to cluster, and between closely apposed mitochondria a dense, amorphous material was present. Numerous bud-like processes projected from mitochondria. Structural evidence, particularly the arrangement and core densities of these arrays, suggests a filamentous type of viral infection.     

Electronmicroscopical observations on yolk and yolk formation in Ophryotrocha labronica LaGreca and Bacci

Summary In Ophryotrocha labronica LaGreca & Bacci mature yolk granules are found only in the ovocyte. Other typical yolk elements are lipid droplets, small vesicular bodies, multivesicular bodies and dense bodies. The two last-mentioned also appear in the accompanying nurse cell and from there obviously pass over unchanged into the ovocyte through a specific intercellular bridge, the fusome.The mature yolk granules are considered as aggregates of mitochondrial, endoplasmic and Golgi material, to which also is added pinocytotically incorporated external material. Mitochondria apparently play a fundamental role in the process, as the multivesicular bodies, most likely the direct precursors to the yolk granules, in all probability represent transformed mitochondria.Labelling with ³H-thymidine during vitellogenesis reveals presence of DNA in the yolk granules. From the labelling pattern, which shows DNA-synthesis both in the ovocyte and the nurse cell nucleus, it is concluded that the labelled material present in the cytoplasm of both cells — most of it in yolk granules and dense bodies — is of nuclear origin. The possible mitochondrial nature of yolk granule DNA is discussed.The author is indebted to Dr. Bertil Åkesson, Zoological Institute, Lund, for kindly supplying the initital material for the Ophryotrocha cultures. The excellent technical assistance of Mrs. Mariann Carleson is gratefully acknowledged. My thanks are also due to Mrs. Siv Nilsson for skilful assistance with the photography. This work has been supported by the Swedish Natural Science Research Council and Kungliga Fysiografiska Sällskapet, Lund.     

Cytochemical and fine structural analysis of oogenesis in the gastropod, Ilyanassa obsoleta

An analysis of differentiating oocytes of the gastropod, Ilyanassa obsoleta, has been made by techniques of light and electron microscopy. Early previtellogenic oocytes are limited by a smooth surfaced oolemma and are associated with each other by maculae adhaerentes. Previtellogenic oocytes are also distinguished by a large nucleus containing randomly dispersed aggregates of chromatin. Within the ooplasm are Golgi complexes, mitochondria and a few cisternae of the rough endoplasmic reticulum. When vitellogenesis begins, the oolemma becomes morphologically specialized by the formation of microvilli. One also notices an increase in the number of organelles and inclusions such as lipid droplets. During vitellogenesis there is a dilation of the saccules of the Golgi complexes and cisternae of the endoplasmic reticulum. Associated with the Golgi complexes are small protein-carbohydrate yolk precursors encompassed by a membrane. These increase in size by fusing with each other. The “mature” yolk body is a membrane-bounded structure with a central striated core and a granular periphery. At maturity a major portion of the ooplasmic constituents such as as mitochondria and lipid droplets occupy the animal region while the bulk of the population of yolk bodies are situated in the vegetal hemisphere. The follicle cells incompletely encompass the developing oocyte. In addition to the regularly occurring organelles, follicle cells are characterized by the presence of large quantities of rough endoplasmic reticulum and Golgi complexes whose saccules are filled with a dense substance. Associated with the Golgi saccules are secretory droplets of varied size. Amongst the differentiating oocytes and follicle cells are Leydig cells. These cells are characterized by a large vacuole containing glycogen. A possible function for the follicle and Leydig cells is discussed.     

Histochemical studies on the yolk-nucleus in fish oogenesis

Summary A histochemical study of the oogenesis of two species of fresh water fishes, Channa maruleus and Heteropneustes fossilis, was undertaken to reveal the origin, structure, histochemical nature, and function of the so-called yolk-nucleus. The basophilic substance of the yolk-nucleus, which is situated in the juxta-nuclear cytoplasm, gradually accumulates adjacent to the nuclear membrane. It is a homogeneous, spherical mass. In Channa, some basophilic, dense bodies develop in the yolk-nucleus. Histochemical tests show that the yolk-nucleus and dense bodies are rich in RNA and proteins. Mitochondria of lipoprotein composition and lipid inclusions, composed of unsaturated phospholipids, appear in association with the yolk-nucleus. Throughout previtellogenesis, the yolk-nucleus continues to proliferate its basophilic, RNA-containing substance and other inclusions. Finally it disintegrates while lying in the peripheral cytoplasm of the larger oocytes which show the synthesis of yolk bodies. During yolk formation, lipid inclusions and mitochondria start disappearing from view but the RNA-containing substance, originated from the yolk-nucleus of previtellogenesis, continues to persist among the growing yolk bodies. The latter arise de novo from the ground cytoplasm, under the influence of the RNA-containing substance, mitochondria and lipid inclusions of previtellogenesis.This work was carried out in the Department of Zoology, University of Gorakhpur, Gorakhpur, India.Population Council Post-Doctoral Fellow.     

ANNOUNCEMENTS

Summary

The oogenesis of the calcareoous sponge Sycon ciliatum has been studied by electron microscopy. In this species, oogonia probably derive from choanocytes through loss of collar and flagellum and formation of phagosome-like inclusions. Oogonia can be occasionally found within flagellated chambers and show a prominent rough endoplasmic reticulum, several mitochondria and polygonal dense granules. The latter are also visible in choanocytes. Oocytes lie in the mesohyl beneath the choanoderm. They contain a nucleolated nucleus, vesiculated granules and phagosome-like inclusions involved in the formation of fibrillar yolk material. Mature eggs are large, irregularly shaped, and filled with fibrillar yolk inclusions. A second ultrastructural confirmation of the carrier-cell mediated fertilization of calcareous sponges is also given.     

Ultrastructural studies on the formation of yolk granules in the statoblast of a fresh-water bryozoan,Pectinatella gelatinosa

The formation of protein-carbohydrate yolk in the statoblast of a fresh-water bryozoan, Pectinatella gelatinosa, was studied by electron microscopy. Two types (I and II) of yolk cells were distinguished. The type I yolk cells are mononucleate and comprise a large majority of the yolk cells. The type II yolk cells are small in number; they become multinucleate by fusion of cells at an early stage of vitellogenesis. In both types of yolk cells, electron-dense granules (dense bodies) are formed in Golgi or condensing vacuoles, which are then called yolk granules. For the formation of yolk granules, the following processes are considered: 1. Yolk protein is synthesized in the rough-surfaced endoplasmic reticulum (RER) of the yolk cells. 2. The synthesized protein condenses in the cisternal space of the RER and is packaged into small oval swellings, which are then released from the RER as small vesicles (Golgi vesicles, 300-600 A in diameter). 3. The small vesicles fuse with one another to form condensing vacuoles, or with pre-existing growing yolk granules. 4. In the matrix of the condensing vacuoles or growing yolk granules, electron-dense fibers are fabricated and then arranged in a paracrystalline pattern to form the dense body. 5. After the dense body reaches its full size, excess membrane is removed and eventually the yolk granules come to mature. Toward the end of vitellogenesis of the yolk cells, the cytoplasmic organelles are ingested by autophagosomes derived from multivesicular bodies and disappear.     

Development of woronin bodies from microbodies inFusarium oxysporum f. sp.lycopersici

Summary Woronin bodies are cytoplasmic organelles which commonly lie near the septa in ascomycetous fungi. Although these organelles were observed nearly 100 years ago, little is known about their origin and development. The present ultrastructural investigation describes the ontogeny of Woronin bodies inFusarium oxysporum f. sp.lycopersici [Sacc.] Snyd. and Hans. In this fungus, Woronin bodies are produced by microbodies. Development of the Woronin body begins with the appearance of electron dense material within the microbody. This material aggregates adjacent to the membrane of the microbody and condenses into a single paracrystalline inclusion. Following its formation, the inclusion is gradually extruded and is eventually separated from the parent organelle by an exocytotic mechanism. After the separation, the paracrystalline inclusion is found at the septal pore. Although many recent electron microscopic studies have used various terms to designate these membrane bound organelles, inFusarium these inclusions are believed to correspond to the Woronin bodies initially described by light microscopists.     

不同发育时期哲罗鱼卵黄的超微结构

应用透射电镜观察了不同发育时期哲罗鱼(Hucho taimen)卵黄的超微结构.根据哲罗鱼卵黄物质在卵母细胞中的加工合成、积累以及卵母细胞中参与卵黄颗粒形成的细胞器的变化,可将该鱼卵黄发生分为4个特征时期,即卵黄发生前期、卵黄泡期、卵黄积累期和卵黄积累完成期.卵黄发生前期是指卵母细胞发育过程中的卵黄物质开始积累前的时期,此时期核仁不断分裂,出现线粒体云和早期的滤泡细胞层、基层和鞘细胞层;卵黄泡期特点主要是细胞器不断变化产生卵黄泡和皮层泡;卵黄积累期的滤泡膜由内向外依次为放射带、颗粒细胞层、基层和鞘细胞层,此时外源性卵黄前体物质不断经过血液汇集于鞘细胞层,后经微胞饮作用穿过胶原纤维组成的基层,经过多泡体作用转运至颗粒细胞内,在细胞内经过加工和修饰形成小的卵黄蛋白颗粒,卵黄蛋白颗粒经微胞饮穿过放射带进入卵母细胞边缘形成的空泡中,不断积累形成卵黄球;进入卵黄积累完成期,卵黄球体积变大,向细胞中心聚集,填满大部分卵母细胞,卵黄积累完毕.     

Fine structure of the developing oocytes in adultArgas (Persicargas) arboreus (Ixodoidea: Argasidae)

The structure of the developing oocytes in the ovary of unfed and fed femaleArgas (Persicargas) arboreus is described as seen by scanning (SEM) and transmission (TEM) electron microscopy. The unfed female ovary contains small oocytes protruding onto the surface and its epithelium consists of interstitial cells, oogonia and young oocytes. Feeding initiates oocyte growth through the previtellogenic and vitellogenic phases of development. These phases can be observed by SEM in the same ovary.The surface of isolated, growing oocytes is covered by microvilli which closely contact the basal lamina investing the ovarian epithelium and contains a shallow, circular area with cytoplasmic projections and a deep pit, or micropyle, at the epithelium side. In more advanced oocytes the shell is deposited between microvilli and later completely covers the surface.Transmission EM of growing oocytes in the previtellogenic phase reveals nuclear and nucleolar activity in the emission of dense granules passing into the cytoplasm and the formation of surface microvilli. The cell cytoplasm is rich in free ribosomes and polysomes and contains several dictyosomes associated with dense vesicles and mitochondria which undergo morphogenic changes as growth proceeds. Membrane-limited multivesiculate bodies, probably originating from modified mitochondria, dictyosomes and ribosomal aggregates, are also observed. Rough endoplasmic reticulum is in the form of annulate lamellae. During vitellogenesis, proteinaceous yolk bodies are formed by both endogenous and exogenous sources. The former is involved in the formation of multivesicular bodies which become primary yolk bodies, whereas the latter process involves internalization from the haemolymph through micropinocytosis in pits, vesicles and reservoirs. These fuse with the primary yolk bodies forming large yolk spheres. Glycogen and lipid inclusions are found in the cytoplasm between the yolk spheres.     

Subcellular organization of the yolk syncytial-endoderm complex in the preimplantation yolk sac of the shark,Rhizoprionodon terraenovae

Summary The structure of the yolk syncytial-endoderm complex of the preimplantation yolk sac of the shark is examined by light- and transmission electron microscopy. The yolk syncytium is bounded by a membrane that is anchored to the plasmalemma of adjacent endoderm cells by desmosomes. Enlarged nuclei, rough endoplasmic reticulum, Golgi complexes, mitochondria, and other cellular organelles populate the syncytium. Microtubules and filamentous elements are also observed free in the syncytium. Yolk is present as pleomorphic droplets, the profiles of which are generally spherical but may be vesicular, especially at the periphery of large yolk droplets. Occasionally, large yolk droplets have a paracrystalline configuration. Small yolk droplets are modulated through the Golgi complex of the yolk syncytium, and it is suggested that acid hydrolases are added there. Small yolk droplets released from the maturing face of the Golgi complex are sequestered in membrane-limited packets. The membrane of the packets fuses with the membrane enveloping the yolk syncytium and the yolk droplets are released into the yolk syncytialendoderm interspace. Subsequently, the yolk droplets are endocytosed by the endoderm. Yolk droplets disperse and fuse to form the large irregular yolk inclusions of the endoderm. Yolk metabolites are transported out of the endoderm through the yolk sac endothelium. The yolk sac endoderm thus mediates the transfer of metabolites from the yolk mass to the extraembryonic circulation.     

Regional differences in the pattern of vitellogenesis in the painted frog Discoglossus pictus

During oocyte growth in the frog Discoglossus pictus two patterns of vitellogenesis are described. The first one consists of the transformation of multivesicular bodies into yolk platelets; the second is the result of a typical endocytotic process, as described in other species. The peculiarity in Discoglossus vitellogenesis consists of a regional difference of these features of vitellogenesis in vitellogenic oocytes: the multivesicular bodies transforming into yolk platelets are found only in the germinative area—the central portion of the animal half—whereas deep crypts with numerous endocytotic pits are found only in the vegetal half. The probable meaning of this regional difference in vitellogenic oocytes is discussed.     

A comparative histochemical study of fish (Channa maruleus) and amphibian (Bufo stomaticus) oogenesis

Summary Comparative histochemical studies on the fish (Channa maruleus) and amphibian (Bufo stomaticus) oogenesis demonstrate a great similarity in the growth and differentiation of their egg follicle. The ooplasm, germinal vesicle and egg-membranes show distinct morphological and cytochemical changes during previtellogenesis and vitellogenesis.During previtellogenesis the various components of the follicle are engaged in the synthesis of protoplasm as shown by the proliferation of yolk nucleus substance, mitochondria and some lipid bodies in the ooplasm and of nucleoli in the germinal vesicle. The substance of the yolk nucleus consisting of proteins, lipoproteins and RNA first appears adjacent to the nuclear membrane. Numerous mitochondria of lipoprotein composition, and some lipid bodies consisting of unsaturated phospholipids lie in association with the yolk nucleus which forms substratum for the former. The lipid bodies, present inside the germinal vesicle, follicular epithelium, and adjacent to the plasma membrane in association with some pinocytotic vacuoles, have been considered to play a significant role in the active transport of some substances from the environment into the ooplasm and from the latter into the germinal vesicle. The follicular epithelium itself is very poorly developed, negating its appreciable role in the contribution of specific substances into the oocyte, which seem to be contributed by the germinal vesicle showing a considerable development of nuclear sap, basophilic granules and nucleoli consisting of RNA and proteins; many large nucleoli bodily pass into the cytoplasm during the previtellogenesis of Channa, where their substance is gradually dissolved. The intense, diffuse, basophilic substance of the cytoplasm is believed due to free ribosomes described in many previous ultrastructural studies.During vitellogenesis, the various deutoplasmic inclusions, namely carbohydrate yolk, proteid yolk and fatty yolk, are deposited in the ooplasm. The carbohydrate yolk bodies rich in carbohydrates originate in association with the plasma membrane and correspond to vesicles and cortical granules of previous studies. The proteid yolk consisting of proteins and some lipoproteins, and fatty yolk containing first phospholipids and some triglycerides and then triglycerides only are deposited under the influence of yolk nucleus substance, mitochondria and cytoplasm. The mitochondria and yolk nucleus substance foreshadow in some way the pattern of these two deutoplasmic inclusions and persist at the animal pole of mature egg while the other inclusions of previtellogenesis disappear from view. The pigment granules, which also show a gradient from the animal to vegetal pole in Bufo, are also formed in association with yolk nucleus substance and mitochondria. Some glycogen also appears in both the species. The nuclear membrane becomes irregular due to the formation of lobes. The lipid bodies of the germinal vesicle come to lie outside the nuclear membrane, suggesting active transport of some substances into the ooplasm; many nucleoli bodily pass into the ooplasm of Bufo, where they are gradually absorbed. The amount of basophilic granules is considerably increased in the germinal vesicle during vitellogenesis. Various egg-membranes such as outer epithelium, thin theca, single-layered follicular epithelium, zona pellucida or vitelline membrane surround the vitellogenic oocytes. The zona pellucida formed between the oocyte and follicle cells consists of a carbohydrate-protein complex. The follicle cells show lipid droplets, mitochondria and basophilic substance in their cytoplasm. The various changes that occur in the components of the follicle during vitellogenesis seem to be initiated by gonadrotrophins formed under the influence of specific environmental conditions.The author wishes to express sincere appreciation and gratitude to Dr. Gilbert S. Greenwald, who has made the completion of this investigation possible.Ph. D. Population Council Post-doctoral Fellow.     

The cytoplasmic organization of hyphal tip cells in the fungusAllomyces macrogynus

Summary Light and transmission electron microscopy were used to examine hyphal tip cells of the fungusAllomyces macrogynus (Chytridiomycetes). A well defined apical body, i.e., Spitzenkörper, was observed at the extreme apex of hyphal cells. This distinctive, spherical cytoplasmic region consisted of a granular matrix devoid of ribosomes and most organelles. To our knowledge this is the first report describing such a structure in hyphae of an aseptate fungus. Vesicles (45–65 nm diameter) were concentrated in the peripheral cytoplasm of the apex, while relatively few were observed within the Spitzenkörper. Filasomes, spherical patches of dense fibrillar material containing a microvesicle core, were abundant in the apical regions near the plasma membrane. Microtubules traversed the Spitzenkörper at various angles and were in close association with the plasma membrane. Microfilaments were observed as individual elements in the cytoplasm or were organized into bundles. Individual microfilaments were frequently in close association with the plasma membrane, vesicles and microtubules. In the immediate subapical region mitochondria, multivesicular bodies, microbodies, Golgi equivalents and nuclei were abundant.Abbreviations CW cell wall - F filasome - M mitochondria - N nucleus - PM plasma membrane - TEM transmission electron microscopy     

Ultrastructural studies of differentiation in the oocyte of the polyclad turbellarian,Prostheceraeus floridanus

Oocyte differentiation in the polyclad turbellarian Prostheceraeus floridanus has been examined to determine the nature of oogenesis in a primitive spiralian. The process has been divided into five stages. (1) The early oocyte: This stage is characterized by a large germinal vesicle surrounded by dense granular material associated with the nuclear pores and with mitochondria. (2) The vesicle stage: The endoplasmic reticulum is organized into sheets which often contain dense particles. Vesicles are found in clusters in the cytoplasm, some of which are revealed to be lysosomes by treatment with the Gomori acid phosphatase medium. (3) Cortical granule formation: Cortical granules are formed by the fusion of filled Golgi vasuoles which have been released from the Golgi saccules. The association between the endoplasmic reticulum and Golgi suggests that protein is synthesized in the ER and transferred to the Golgi where polysaccharides are added to form nascent cortical granules. (4) Yolk synthesis: After a large number of cortical granules are synthesized, yolk bodies appear. They originate as small membrane-bound vesicles containing flocculent material which subsequently increase in size and become more compact. Connections between the forming yolk bodies and the endoplasmic reticulum indicate that yolk synthesis occurs in the ER. (5) Mature egg: In the final stage, the cortical granules move to the periphery and yolk platelets and glycogen fill the egg. At no time is there any evidence of uptake of macromolecules at the oocyte surface. Except for occasional desmosomes between early oocytes, no membrane specialization or cell associations are seen throughout oogenesis. Each oocyte develops as an independent entity, a conclusion supported by the lack of an organized ovary.     

Sperm tail differentiation in the nudibranch mollusc Hypselodoris tricolor (gastropoda,opisthobranchia)

The sperm axoneme of Hypselodoris tricolor forms from a single centriole that is located initially beneath the plasma membrane and then migrates to the nuclear surface. A conspicuous centriolar adjunct-like formation is present in the neck of midspermatids, but it becomes very reduced at the end of spermiogenesis. In spermatocyte and spermatid mitochondria, intracristal bodies originate from the accumulation of a dense material in some cristae. From our observations and foregoing reports, it may be concluded that the process of sperm tail differentiation in opisthobranchs resembles that in pulmonates, whereas it differs in many respects from that occurring in prosobranchs. The appearance of intracristal bodies in modified mitochondria seems to be a special feature of spermatogenesis in the opisthobranchs that does not occur in the two other groups of gastropod molluscs.     

Further morphological and histochemical studies on the yolk nucleus and associated cell components in the developing oocyte of the Indian wall lizard

In March through April when the oocyte growth in the ovaries of the wall lizard (Hemidactylus) is very rapid, the yolk nucleus continues to persist through various stages of previtellogenesis. This persisting yolk nucleus and associated cell components have been studied with histochemical techniques. The spherical and dense yolk nucleus stains for protein, lipoprotein and RNA. It does not form any close morphological association with the other cell components such as the mitochondria, lipid bodies (L₂), spaces or canals, diffuse sudanophilic substance and dense bodies, which are arranged into three zones round the yolk nucleus proper. The mitochondria stain for lipoprotein; the L₂ bodies consist of phospholipid; the spaces do not contain any material demonstrable with histochemical techniques; and the ooplasm containing the diffuse sudanophilic substance and dense bodies shows lipoprotein, protein and RNA. Eventually, the yolk nucleus disintegrates, and its substance as well as the other cell components are distributed in the cortical ooplasm of oocytes which are ready to form the yolk bodies. Concepts of the origin, morphology, cytochemistry and function of the yolk nucleus in the oocytes of invertebrates and vertebrates, which have come about recently through the application of cytochemical and submicroscopical techniques, are discussed.     

Core formation and the acquisition of fusion competence are linked during secretory granule maturation in Tetrahymena

The formation of dense core secretory granules is a multistage process beginning in the trans Golgi network and continuing during a period of granule maturation. Direct interactions between proteins in the membrane and those in the forming dense core may be important for sorting during this process, as well as for organizing membrane proteins in mature granules. We have isolated two mutants in dense core granule formation in the ciliate Tetrahymena thermophila, an organism in which this pathway is genetically accessible. The mutants lie in two distinct genes but have similar phenotypes, marked by accumulation of a set of granule cargo markers in intracellular vesicles resembling immature secretory granules. Sorting to these vesicles appears specific, since they do not contain detectable levels of an extraneous secretory marker. The mutants were initially identified on the basis of aberrant proprotein processing, but also showed defects in the docking of the immature granules. These defects, in core assembly and docking, were similarly conditional with respect to growth conditions, and therefore are likely to be tightly linked. In starved cells, the processing defect was less severe, and the immature granules could dock but still did not undergo stimulated exocytosis. We identified a lumenal protein that localizes to the docking-competent end of wildtype granules, but which is delocalized in the mutants. Our results suggest that dense cores have functionally distinct domains that may be important for organizing membrane proteins involved in docking and fusion.     

Solitary bodies (S-bodies) in the parasitic red algaHarveyella mirabilis (Choreocolaceae,Cryptonemiales)

Summary Unusual spherical cytoplasmic inclusions identical to S-bodies described previously in three angiosperms were found in all cells of the parasitic red algaHarveyella mirabilis collected from several locations in the northeast Pacific. The inclusions are ca. 60–80 nm and consist of an outer double membrane bounding a granular mantle and a DNase sensitive central core. S-bodies are dispersed throughout the cytoplasm and are associated occasionally with nuclei, plastids, mitochondria, ER, and vacuoles. They have not been observed in any other alga except in host algal cells, connected to parasite cells by cellular pit connections. The possible function of these inclusions is considered with respect to the parasitic nature ofHarveyella mirabilis.     

Overproduction of Campylobacter Ferritin in Escherichia coli and Induction of Paracrystalline Inclusion by Ferrous Compound

The ferritin gene (cft) of Campylobacter jejuni was overexpressed in cells of Escherichia coli using a T7 RNA polymerase expression system. Many round particles which were the same size as the ferritin particles purified from C. jejuni were observed in the lysate of the cft-overexpressed E. coli cells. Since most of them were devoid of a central electron dense core consisting of ferric irons, the Campylobacter ferritins overproduced in E. coli seemed to be apoferritin. When large amounts of ferrous iron (supplied as FeSO₄) were added to culture medium, the cft-overexpressed cells formed large inclusion bodies of paracrystalline arrays comprised of ferritin particles with central electron dense cores. The addition of ferric irons did not produce paracrystalline inclusion.