A SMALL PARTICULATE COMPONENT OF THE CYTOPLASM

A particulate component of small dimensions (100 to 150 A) and high density is described in the ground substance of the cytoplasm of mammalian and avian cells. In many cell types that seem to have in common a high degree of differentiation, the new component is preferentially associated with the membrane of the endoplasmic reticulum; whereas in other cell types, characterized by rapid proliferation, it occurs more or less freely distributed in the ground substance of the cytoplasm. In the Discussion an attempt is made to integrate the observations presented in this paper with the already available cytological, histochemical, and cytochemical information.     

The cytochemical demonstration of glycoproteins and glycolipids in Sarcocystis muris sarcocysts]

An electron cytochemical study of glycoproteins and glycolipids was made for the mature sarcocysts of Sarcocystis muris. Glycoprotein structures as branched fibrilles were seen on the surface of the sarcocyst wall. The fibrillar and granular glycoprotein structures were found in the ground substance of sarcocysts near the cyst wall and in the septae. In the plasmalemma of two types of cyst stages (merozoites and intermediate cells), glycoprotein fibrillar structures were revealed connecting these two cell types with each other. The third type cyst stages, i.e. the metrocytes, are situated separately without any fibrillar connections between them and other cyst stages being observed. This question is discussed in terms of the problem of cytodifferentiation. The fibrillar and granular glycoprotein material is scattered over the cytoplasm of the cyst stages, being especially concentrated in micronemes, rhoptries and around amylopectin granules. The control ultrathin sections were treated with saliva or pronase for the aims of protein identification in the material under study. In addition to glycoprotein, some glycolipids material was detected in the sarcocysts in the form of drops surrounded with thin glycoproteinaceous layers. Glycolipids were found in the ground substance of sarcocysts near the cyst stages and in the parasite cell cytoplasm around the micronemes and rhoptries. The data obtained are discussed in connection with the functional role glycoproteins and glycolipids play in S. muris.     

The Fine Structure of Blastema Cells and Differentiating Cartilage Cells in Regenerating Limbs of Amblystoma Larvae

Regenerating forelimbs of larval salamanders, Amblystoma punctatum, were fixed in OsO₄ at various intervals after amputation and were sectioned for study with the electron microscope. The dedifferentiated cells comprising the early blastema were found to have a fine structure similar to that of other undifferentiated cells and to have lost all of the identifying morphological features of their tissues of origin. The cytoplasm of such cells is characterized by numerous free ribonucleoprotein granules and a discontinuous vesicular endoplasmic reticulum. The cells have more abundant cytoplasm and are in closer contact with each other than was previously realized. The layer of condensed ground substance investing most differentiated cell types is lacking. After a period of rapid cell division, the morphology of the blastema cell changes. Cytoplasm is now sparse and contains a high concentration of free ribonucleoprotein granules, but little endoplasmic reticulum. The differentiating cartilage cell, however, develops an extensive, highly organized endoplasmic reticulum and the Golgi apparatus also appears to become more highly differentiated and more extensive at this time. Small vesicles appear throughout the cytoplasm at the time the new cisternae originate and may contribute to their formation. These and other changes in the cytoplasmic organelles are discussed.     

Shedding of peripheral cytoplasm - a mechanism of liver cell atrophy in human amyloidosis.

A liver biopsy specimen from a case of primary amyloidosis was investigated by electron microscopy. The cytoplasmic periphery of the hepatocytes showed degenerativechanges which are interpreted as indicating shedding of peripheral parts of the cytoplasm. Two main variants of this process could be discerned: 1) Protrusion and sequestration of hernia-like blebs of cytoplasm, and 2) shedding of vesicles derived from degenerated endoplasmic reticulum. In the latter case transient defects of the plasma membrane seem to be relevance. Endoplasmic reticulum and cytoplasmic ground substance appeared to be shed preferentially, whereas mitochondria are retained within the cell. As a consequence the fractional volume of the mitochondria in the cytoplasm of atrophic cells is markedly increased. Shedding of peripheral cytoplasm, therefore, seems to be an effective mechanism enabeling the cell to adapt the mass and the composition of its cytoplasm to an unfavourable environment.     

STRUCTURE AND FUNCTION OF THE ALGAL PYRENOID. I. ULTRASTRUCTURE AND CYTOCHEMISTRY DURING ZOOSPOROGENESIS OF TETRACYSTIS EXCENTRICA1

The fine structure of the pyrenoid in the mature vegetative cell of Tetracystis excentrica Brown and Bold is described. During zoosporogenesis, the pyrenoid undergoes regression, and the ultrastructure of this process is described in detail. The ground substance undergoes dissolution, and reticulate fibrillar structures appear as well as intruding chloroplast thylakoids. Pyrenoid-associated starch plates diminish, and quantities of starch not associated with the pyrenoid are produced. New pyrenoids appear late in the division cycle after all other major organelles associated with the motile cell have been formed. Zoospore pyrenoids develop in thylakoid-free spaces of the chloroplast which are similar to the DNA-containing regions. The new pyrenoid ground substance, which is loosely fibrillar, arises in close proximity to starch grains which may be formed in the stroma. Then the zoospore pyrenoid produces 2 hemispherical starch plates identical to those in the mature vegetative cell. Zoospore pyrenoids lack the 2 convoluted thylakoids between the starch plates and the ground substance characteristic of those in the mature vegetative cell. Instead, the thylakoids are identical to those of the chloroplast at first, and then develop into a convoluted state in the vegetative cell. Cytochemical tests for DNA, RNA, and protein were made for the cytoplasm, nucleus, nucleolus, and pyrenoid. Conclusive evidence is presented for the presence of RNA in the cytoplasm and nucleolus, DNA in the nucleus, and protein in the pyrenoid. The tests did not conclusively demonstrate the presence or absence of DNA and RNA in the pyrenoid; however, they suggested that small amounts of both DNA and RNA may be present.     

Cytology of a chromophobe pituitary adenoma. A case report

A pituitary tumor with suprasellar and extrasellar extension was investigated by means of the squash-smear cytologic technique. The dominant cell type was large, round to oval cells, with pale-staining, finely granular cytoplasm. The nuclei of these cells often contained single or multiple inclusions of uncertain nature. There also were cells with eosinophilic cytoplasm, usually collected in small nests. Hyperchromatic "naked" nuclei, in various shapes, were immersed in a homogeneous, faintly staining ground substance. Mitotic figures were detected easily. Cytology of these combined cell types allowed the intraoperative diagnosis of a rather pleomorphic pituitary adenoma.     

The structure of the surface apparatus in sarcocysts of Sarcosporidia in the persistence process

The structure of the sarcocyst surface apparatus (SSA) was investigated for two sarcosporidian species: Sarcocystis muris (non-pathogenic) and S. fusiformis (pathogenic). The surface membrane, being the main SSA subsystem, makes numerous vesicle-like protrusions with different ultrastructural patterns. This made it possible to distinguish between four and three types of these protrusions in S. fusiformis and S. muris, respectively. Vesicles of similar structure, pinched off from the fully formed protrusions, were classified, correspondingly, in the same four and three different types. A presumable functional role of both protrusions and membrane-coated vesicles in pathogenicity of different sarcosporidian species is proposed. The vesicles pinched off from corresponding protrusions may be involved in transporting certain substance complexes from the sarcocyst to the harbouring host cell. In addition, another way of substance transporting was observed, when the cystic substances, not surrounded with any membrane coating, are thrown from open protrusions directly into the immediate cytoplasm of the host cell.     

Microanatomy and ultrastructure of the foot of the infaunal bivalve Tegillarca granosa (Bivalvia: Arcidae)

In this study, the morphology and ultrastructure of the foot of Tegillarca granosa was compared with the bivalves from different habitats. The sediment of habitat of T. granosa is mostly a mixture of sand (68.93%) and mud (24.12%). The foot is wedge-shaped with multiple projections on the surface and covered with ciliary tufts. The epithelial layer is simple and composed of ciliated columnar epithelia and mucous cells. Although the mucous cells are distributed mostly in the epithelial layer, they are developed even in the connective tissues and muscle layers, and the mucous cells mostly contain acidic carboxylated mucosubstances. From the TEM observation, secretory cells are classified into three types. Type A secretory cell has a goblet form and is most widely distributed among the three types. Type B secretory cell has an oval form and the secretory granule has fibrous substance. Type C secretory cell has an elongated elliptic form and membrane-bounded secretory granules. The muscle fiber bundles are composed mainly of smooth muscle fibers. The smooth muscle fibers can be divided into two types. Type A muscle fibers have evenly distributed thick microfilaments between the thin microfilaments of cytoplasm. Type B muscle fiber has cluster of condensed microfilaments in the medulla cytoplasm while the cortical cytoplasm has loose distribution of thin microfilaments.     

Localization of glycoconjugates in the tissue structures of man and animals

By means of concanavalin A (Con A) labelled with fluorescein isotiocyonate in cryostate sections of some human and animal organs (skin, heart, thymus) localization of clycoconjugates containing hexoses and reacting with this lectin has been studied. Glycoconjugates are revealed along the periphery of all cellular elements, in Z-lines and in intercalated disks of the myocardial muscle fibers, in the connective tissue ground substance and also in that of the basal membranes of epithelium, endothelium, muscle fibers (sarcolemma), in cytoplasm of epithelioreticulocytes of the thymus. In fibroblasts of the L-cells culture, glycoconjugates are also localized in cytoplasm. When N-acetylglucosamin is added to the labelled Con A solution, the ability of lectin to react with tissue components is inhibited.     

CHONDROGENESIS, STUDIED WITH THE ELECTRON MICROSCOPE

The role of the cells in the fabrication of a connective tissue matrix, and the structural modifications which accompany cytodifferentiation have been investigated in developing epiphyseal cartilage of fetal rat by means of electron microscopy. Differentiation of the prechondral mesenchymal cells to chondroblasts is marked by the acquisition of an extensive endoplasmic reticulum, enlargement and concentration of the Golgi apparatus, the appearance of membrane-bounded cytoplasmic inclusions, and the formation of specialized foci of increased density in the cell cortex. These modifications are related to the secretion of the cartilage matrix. The matrix of young hyaline cartilage consists of groups of relatively short, straight, banded collagen fibrils of 10 to 20 mµ and a dense granular component embedded in an amorphous ground substance of moderate electron density. It is postulated that the first phase of fibrillogenesis takes place at the cell cortex in dense bands or striae within the ectoplasm subjacent to the cell membrane. These can be resolved into sheaves of "primary" fibrils of about 7 to 10 mµ. They are supposedly shed (by excortication) into the matrix space between the separating chondroblasts, where they may serve as "cores" of the definitive matrix fibrils. The diameter of the fibrils may subsequently increase up to threefold, presumably by incorporation of "soluble" or tropocollagen units from the ground substance. The chondroblast also discharges into the matrix the electrondense amorphous or granular contents of vesicles derived from the Golgi apparatus, and the mixed contents of large vacuoles or blebs bounded by distinctive double membranes. Small vesicles with amorphous homogeneous contents of moderate density are expelled in toto from the chondroblasts. In their subsequent evolution to chondrocytes, both nucleus and cytoplasm of the chondroblasts undergo striking condensation. Those moving toward the osteogenic plate accumulate increasingly large stores of glycogen. In the chondrocyte, the enlarged fused Golgi vesicles with dense contents, massed in the juxtanuclear zone, are the most prominent feature of the cytoplasm. Many of these make their way to the surface to discharge their contents. The hypertrophied chondrocytes of the epiphyseal plate ultimately yield up their entire contents to the matrix.     

Age-related quantitative changes in the organelles of rat neocerebellar Purkinje cells.

A quantitative study regarding the age-related changes occurring in the somatic organelles of the neocerebellar Purkinje cell is carried out, using female rats aged 2 to 24 months. Standard manual morphometric techniques are used to calculate the following parameters: somatic volume, volumetric fractions and absolute volumes of the intracellular structures as well as the membrane profile concentration, the membrane surface concentration and the mean surface of the rough endoplasmic reticulum cisternae per cell (RER-S). From a statistical point of view, all the cell components significantly modify their volumetric fractions (except the multivesicular bodies and nucleolus; the latter in relation to the nucleus) and their absolute volumes (except the mitochondria and the multivesicular bodies); the parameters regarding the reticulum are also modified during ageing. There is a linear trend between the age and either the somatic volume of the RER-S or the absolute volumes of the following structures: mitochondria, dense bodies, ground substance and total cytoplasm. A linear correlation is also observed between the cell volume and either the RER-S or the absolute volume of intracellular structures (the Golgi apparatus, the multivesicular bodies and nucleolus being excluded). Anatomophysiological considerations about the findings are discussed. The role of the ground substance as the major modulator of the volumetric plasticity of the Purkinje cell during ageing, is emphasized as a conclusion.     

Identification of genes associated with tumor development in CaSki cells in the cosmic space

It is important to understand the mechanisms of tumor development for curing cervical cancer. However, the molecular basis determining the different characteristics of tumor remains unclear. Space environment as a special study model can expand the study field of tumor development. To approach this, after human cervical carcinoma CaSki cells were flown on “Shen Zhou IV” space shuttle mission, the cell morphology and proliferation was investigated after flying to ground. We found that the growth of 48A9 CaSki cell (flight group) became slow compared with ground groups. Observation of cells by light microscopy revealed differences in cell morphology between ground controls and flight groups, and the flight group exhibited morphologic differences, characterized by rounder, smoother, decreased, smaller and low-adhension cells. Transmission electron microscope images showed the structure of the ultrastructural characteristics of 48A9 CaSki cells were clearly distinct from those of the ground CaSki cells in aspects of mitochondrion, cytoplasm, nucleus and ribosomes. MTT and soft agar assay showed that 48A9 CaSki cells grew slowly compared to ground control. Furthermore, suppression subtractive hybridization combining with reverse Northern blot was used to identify differently expression genes between flight and ground groups. These differentially expressed genes included cytoskeleton, cell differentiation, cell apoptosis, signal transduction, DNA repair, protein synthesis, substance metabolism, and antigen presentation. The identification of differently expressed genes which is likely to increase our understanding of the molecular processes underlying tumor development will provide new insight into tumor development mechanisms, and may facilitate the development of new anticancer strategies.     

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.     

Micromechanical modeling of the epimysium of the skeletal muscles

A micromechanical model has been developed to investigate the mechanical properties of the epimysium. In the present model, the collagen fibers in the epimysium are embedded randomly in the ground substance. Two parallel wavy collagen fibers and the surrounding ground substance are used as the repeat unit (unit cell), and the epimysium is considered as an aggregate of unit cells. Each unit cell is distributed in the epimysium with some different angle to the muscle fiber direction. The model allows the progressive straightening of the collagen fiber as well as the effects of fiber reorientation. The predictions of the model compare favorably against experiment. The effects of the collagen fiber volume fraction, collagen fiber waviness at the rest length and the mechanical properties of the collagen fibers and the ground substance are analyzed. This model allows the analysis of mechanical behavior of most soft tissues if appropriate experimental data are available.     

油樟油细胞和粘液细胞的发育解剖学研究

利用薄切片法对油樟茎叶油细胞和粘液细胞发育的研究结果表明,油细胞最早发生于第二叶原基以及茎端皮层和髓的基本分生组织中。未出现油细胞以前,在上述器官的基本分生组织和原分生组织中,难以区分油细胞的原始细胞与周围细胞,当油细胞原始细胞呈现出体积较大,液泡化程度较低,细胞核大而明显的特征才明显可辨,以后经过液泡融合,油细胞成熟和油细胞的细胞质解体阶段而成为一贮油的囊,而且油囊连接在杯形构造上,粘液细胞的早期发育过程与油细胞的相同,而在细胞液泡化的后期,靠近大液泡的细胞质中产生粘液物质。并扩散到大液泡中,粘液物质不断产生,变浓,占据整个细胞腔,细胞质解体后而成为完全成熟的粘液细胞,因此可见,油细胞和粘液细胞是同源的,也可能粘液细胞是由油细胞转化而来的。     

Some new findings about Hofbauer cells in the chorionic villi of the human placenta

The cytological structure of the Hofbauer cells was investigated in human placentas of the first and second trimesters of gestation. These cells are found in the stromal channel system of the chorionic villi core. Their walls, which are supported by collagen fiber bundles, are produced by reticulum cells and fibroblasts. The cytoplasmic processes of the Hofbauer cells are in contact with the walls of the channels without being associated with them by desmosomal complexes. Some of these cells have features in common with macrophages, such as cytoplasmic processes, larger vacuoles, many pinocytotic vesicles and intracytoplasmic granules. This system of vacuoles and vesicles enables micropinocytotic activity and phagocytosis. This type of Hofbauer cell resembles the typical macrophages. These cells may play a role in the regulation of stromal water content, transportation of ions and the flow of interstitial fluid. The most original finding of this study are long tubes observed in some Hofbauer cells and extending between the nucleus and the extracellular ground substance through the cytoplasm. One of these tubular formations resembles a cilium in structure with three limiting membranes and is filled with a slightly electron-dense substance. This type of Hofbauer cell may transport information between the nucleus and the extracellular ground substance by means of these tubular structures.     

The chicken trigeminal ganglion. I. An anatomical analysis of the neuron types in the adult

An anatomical analysis of the chicken trigeminal ganglion was made using light microscopy on specimens prepared by usual chemical fixation or freeze-drying methods and by electron microscopy. Two types of neurons were consistently seen, dark and light cells. Dark cells contained a dense cytoplasm with Nissl substance distributed evenly throughout, whereas light cells had a less dense cytoplasm containing clumps of Nissl substance. The Nissl bodies in light cells contained only a few small cisternae of granular endoplasmic reticulum as compared with many stacked cisternae in Nissl bodies of dark cells. The ratio of dark to light cells was approximately 62:38 in all regions of the ganglion. Dark cells were consistently smaller than light cells. In the seven-day old chick, the mean diameters of the dark and light neurons were 21.4 μ and 29.5 μ respectively; in the adult the values were 29.9 μ and 39.7 μ respectively. It is concluded that the dark and light cells belong to two distinct neuronal cell populations.     

The structure of cytoplasm in directly frozen cultured cells. I. Filamentous meshworks and the cytoplasmic ground substance

Cultured fibroblasts or epithelial cells derived from Xenopus laevis embryos were directly frozen, freeze-substituted by an improved method, and then either critical-point-dried and viewed as whole mounts, or embedded and thin sectioned. In thin regions of these cells, where ice crystal artifacts are absent, the cytoplasm consisted of a dense, highly interconnected meshwork of filaments, embedded in a finely granular ground substance. The meshwork in directly frozen, intact cells was compared with that in cells that were lysed (physically, with detergents, or with filipin), or fixed with glutaraldehyde before freezing. Although filaments tended to be less numerous in lysed cells, their overall organization was the same as that in intact cells. However, fixation with glutaraldehyde before freezing distorted the meshwork to variable degrees depending on the osmolarity of the fixation buffer, and also obscured the granular ground substance which is obvious in directly frozen cells. With optimal preparative methods, the cytoplasm of these directly frozen cells is shown to consist of a cytoskeleton composed of discrete interwoven filaments interconnected by numerous finer filaments and a readily extractable granular matrix which presumably represents aggregations of cytoplasmic proteins.     

山羊草属不同细胞质对小麦籽粒蛋白含量及组分的影响研究

以山羊草属（Aegilops)6种不同异源细咆质的异质小麦品系Chris为材料,与生产上广泛种植的9个常规小麦品种正反杂交,系统地研究了供试6种蚌源细胞质对其F1籽粒蛋白含量的影响,同时对单芒山草(Ae．uniaristata)、二角山羊草(Ae.bicorins)细胞质对籽粒蛋门组分含量的影响亦进行了研究。结果表明：(1)在以6种异源细胞质材料为母本的杂交组合中,78%的组合其蛋白含量高于反交对照。尤以单芒、二角山羊草细胞质的正效应最为显著,平均提高2个以上百分点,最高达3．7个百分点。(2)供试单芒、二角异源细胞质对籽粒清蛋白和球蛋白的含量影响最大,对醇溶蛋白和谷蛋白含量的影响相对较小,其效应值大小因特定组合而异。(3)供试异源细胞质对籽粒蛋白质含量和组成的影响均存在显著的核质互作效应。通过异源细胞质的途径来改良小麦籽粒的蛋白含量和组分是一条有效可行的方法,只要选择合适的核质组合即可达到改良目的。