Various types of the pituitary folliculo-stellate cells involving the Siperstein's corticotroph in the normal rats

The differentiation of the folliculo-stellate (F-S) cells was electronmicroscopically investigated in the normal male adult rats from the Wistar, Wistar-Imamichi, Holzmann, Spraque-Dowley and Donryu strains. The F-S cells may be divided into the five types according to the granulation. Each type is, however, provided with the common characteristic features, i.e., the stellate shape due to projecting the cytoplasmic processes and a tendency to embrace an acidophil. The first type is an agranular independent or anastomosing immature cell. It is different in shape and arrangement from the follicular cell, but similar in agranularity and immaturity to it. The second is a slightly differentiated cell, in which scanty small secretory granules 50--100 nm in diameter begin to appear near the plasma membrane. The third is a moderately differentiated cell providing the regularly row arrangement of secretory granules 100--200 nm in diameter along the plasma membrane, corresponding, in fine structure, with a corticotroph. The fourth is a fully differentiated cell with heavy granulation, whose secretory granules 150--250 nm in diameter are accumulated in the whole cytoplasm, suggesting the storing type. It is difficult to determine whether the fourth type coincides with a hypergranulated corticotroph or a stellate thyrotroph. The fifth is a kind of fully differenetiated cell which may refer to the releasing phase of the fourth type, being characterized by the dispersion or loss of minute secretory granules of low density as large as 50 nm in diameter, associated with the cored vesicles. The population densith of the above five types increased in the sequence, 5th leads to 4th leads to 1st leads to 3rd type in the gland. Namely, the 3rd (corticotroph) type and 1st (agranular) type are predominantly distributed, and the 5th (releasing) type and 4th (hypergranulated) type are rarely.     

A fourth type of neuroglial cell in the adult central nervous system

Labeling central nervous tissue from mature animals with antibodies to NG2 chondroitin sulfate proteoglycan reveals the existence of large numbers of NG2 positive cells, at least some of which are oligodendroglial progenitors. It is generally agreed that these cells differ from the classically defined neuroglia, since they are antigenetically different from astrocytes, oligodendrocytes, or microglial cells. Although the NG2 positive cells have been well characterized in light microscopic preparations, examination of the labeled cells by electron microscopy have not led to general agreement about their morphological features. The basic reason for this is that it is difficult to obtain good preservation of the fine structure of NG2 labeled neurons. Since these NG2 positive cells are abundant in the central nervous system, it was decided to examine routinely prepared tissue from the brains of mature monkeys and rats by electron microscopy to determine if there is a neuroglial cell type whose presence has been overlooked. It soon became evident that there is a fourth type of neuroglial cell. These cells have pale, irregular shaped nuclei with a thin rim of heterochromatin beneath the nuclear envelope, and they have pale cytoplasm. Superficially they resemble astrocytes, which is the probable reason why the presence of this fourth type of neuroglial cell has been largely overlooked. However, the fourth type of neuroglial cell, here referred to as a ß neuroglial cell, has no intermediate filaments in its cytoplasm, the mitochondria are thinner than those of astrocytes, centrioles are frequently encountered in their cytoplasm, and when they are adjacent to capillaries they are always separated from the basal membrane by an astrocytic processes.     

Developmental patterns of the hermaphroditic gonad in dicyemid mesozoans (Phylum Dicyemida)

Abstract. The development of the hermaphroditic gonad, the infusorigen, was studied in fixed specimens of 16 species belonging to four genera ( Conocyema, Dicyema, Dicyemennea , and Pseudicyema ) of dicyemid mesozoans. In addition, the literature on the cell lineages of infusorigens of eight other species was reviewed. After an agamete (axoblast) undergoes an unequal first division, excluding a small cell (the paranucleus), the resulting large cell divides to form the infusorigen. Five infursorigen cell lineage patterns can be identified: type I, both the first oogonium and the first spermatogonium are produced at the third division; type II, the first spermatogonium is produced at the second division and the first oogonium is produced at the third division; type III, the first spermatogonium is produced at the second division and the first oogonium is produced at the fourth division; type IV, the first oogonium is produced at the second division and the first spermatogonium is produced at the third division; and type V, the first oogonium is produced at the second division and the first spermatogonium is produced at the fourth division. Later development is similar in members of all genera. Mature infusorigens are similarly organized in all species examined. Sizes of agametes and infusorigen axial cells, the number of infusorigens, and the type of reproductive strategy were not correlated with infusorigen developmental patterns or cell lineage patterns.     

Ultrastructural study of the endocrine cells of the abomasum mucosa in pre-ruminant calves

During a systematic ultrastructural study on the endocrine/paracrine cells of the gastro-intestinal tract of ruminants, the aim of present work is to describe these cells in the abomasum of suckling calf. Taking into account all the cytological details, and especially the morphological appearance and the cytochemical reactivity of secretory granules, several endocrine cell types can be distinguished. Some of them (EC, D, D1) are common to all three of the glandular regions, whereas others are typical of cardiac and proper gastric glands: they are ECL, X, A-like and a fourth type, whose classification is uncertain. The last type (G cells) is detectable in pyloric glands only. The cardiac and proper gastric glands of the suckling calf abomasum contain two additional cell types, not present in bulls, A-like cells and the fourth type, and contain D1 cells which form a heterogeneous family. These data show a morphofunctional similarity between the abomasum of the suckling calf and the stomach of non-ruminant mammals.     

Affiliation of large numbers of fibroblasts with larval muscle fibers

Muscle fibers from fourth and fifth instar caterpillars were examined with scanning and thin section electron microscopy. Scanning micrographs showed that early fifth instar specimens had a population of cells lying beneath the basal lamina over the surface of the muscle fiber and in conjunction with tracheoles and nerves. At least two cell types were present. One type could be categorized as tracheoblasts of their close association with the tracheoles and the presence of taenidia within the tracheoblast cytoplasm in sectioned material. A second cell type, characterized by long filamentous processes, contained extensive rough endoplasmic reticulum and cisternae swollen with an electron-dense substance similar in appearance to the basal lamina. This ultrastructural appearance is characteristic of vertebrate fibroblasts and certain types of insect hemocytes. Early and late fourth instar specimens had few cells on their muscle fiber surfaces. Measurements of the basal lamina thickness were taken from thin sections of nondigested muscle fibers of early fourth, late fourth, and early fifth instar animals. The results showed that the basal lamina underwent a large increase in thickness between the fourth and fifth instars. The proliferation of cells which appeared to be in an actively synthesizing state paralleled the increase in basal lamina thickness. This suggests the hypothesis that these cells are active in connective tissue formation, and contribute to the formation of the basal lamina that lies over both them and the muscle fiber.     

Ependyma and supraependymal structures in some areas of the fourth ventricle in the rat

The ependyma was investigated in five areas of the rat ventricle system by means of both light and electron microscopy. The columnar, cuboidal and flattened types of the ependymal cells were mainly seen. All of them were seen in the fourth ventricle, while in the aqueductus cerebri and in the central canal the flattened type of the cell was lacking. An unusual variation as to the form of the ependymal cells was found on the roof of the fourth ventricle. Three groups of intraventricular structures were found in all investigated parts of the ventricle system: supraependymal globular structures containing irregularly arranged cristae, supraependymal protrusions appearing as homogeneous contents, and nerve profiles including nerve endings and nerve axons. The morphological characteristics of the ependyma and intraventricular profiles in the fourth ventricle allow to suppose a certain role of these structures in the exchange of various materials between the CSF, ependyma and neuropile.     

The fine structure of developing type 'B' dermal glands in Rhodnius prolixus

The fine structure of the developing type 'B' dermal gland, the more common type in fifth instar larvae of Rhodnius, is described. Each gland consists of three cells responsible for secretion of the duct, saccule and secretion product or precursors, and a fourth capsule cell. The cuticular linings of the duct and saccule are secreted and shed synchronously with the cuticle of the body surface. Mechanisms of secretion and discharge are suggested.     

Inner cell allocation in the mouse morula: the role of oriented division during fourth cleavage

Two populations of blastomeres become positionally distinct during fourth cleavage in the mouse embryo; the inner cells become enclosed within the embryo and the outer cells form the enclosing layer. The segregation of these two cell populations is important for later development, because it represents the initial step in the divergence of placental and fetal lineages. The mechanism by which the inner cells become allocated has been thought to involve the oriented division of polarized 8-cell blastomeres, but this has never been examined in the intact embryo. By using the technique of time-lapse cinemicrography, we have been able for the first time to directly examine the division planes of 8-cell blastomeres during fourth cleavage, and find that there are three, rather than two, major division plane orientations; anticlinal (perpendicular to the outer surface of the blastomere), periclinal (parallel to the outer surface of the blastomere), and oblique (at an angle between the other two). The observed frequencies of each type of division plane orientation provide evidence that the inner cells of the morula must derive from oriented division of 8-cell blastomeres, in accordance with the polarization hypothesis. Analysis of fourth cleavage division plane orientation with respect to either lineage or division order reveals that it is not associated with lineage from either the 2- or the 4-cell stage, but has a slight statistical association with fourth cleavage division order. The lack of association between division plane orientation and lineage supports the prediction that packing patterns and intercellular interactions within the 8-cell embryo during compaction play a role in determining fourth cleavage division plane orientation and thus, the positional fate of the daughter 16-cell blastomeres.     

Histology of digestion in nymphs of Rhipicephalus appendiculatus fed on rabbits and cattle naive and resistant to the ticks

Nymphs feeding on ears of four rabbits and four calves (Bos taurus) were examined during first and third or fourth infestations and also during the moulting period. The gut caecae were removed and examined by histochemistry and light and electron microscopy. Attachment sites of the nymphs were biopsied from all hosts and cell counts made by light microscopy. Resistance was expressed by reduction in numbers of ticks completing engorgement and reduced engorgement weights. The gut was comprised of a proliferative stem cell; a digestive cell that differentiated into a sessile type ingesting by pinocytosis and a motile type ingesting by phagocytosis; and a cell secreting a glycoprotein with acid phosphatase activity into the lumen. The gut grew during the early stages of feeding to accommodate the expansion during engorgement. On rabbits and cattle resistant to ticks the stem cells were damaged, with moribund nuclei and poorly differentiated cytoplasm. Thus there were fewer digestive and secretory cells and the gut did not expand to accommodate a full blood meal. The attachment sites were dominated by mononuclear cells and neutrophils in both host species at the first infestations but at the third or fourth infestations there was a considerable increase in proportions of eosinophils and basophils. Host granulocytes were traced to the lumen of the tick gut and to motile digestive cells which destroyed them by phagocytosis.     

Effect of antigenic stimulation on acid deoxyribonuclease activity in lymphocytes: I. Antibody-induced response

The effect of antigen-induced stimulation on acid deoxyribonuclease (DNase) activity in BALB/c mouse lymphoid cells was determined. Increase in acid DNase activity was found in intact spleen cell populations of mice from the second or fourth day after immunization with pneumococcal polysaccharide type III and from the fourth day after immunization with SRBC. DNase determinations performed with spleen cell fractions prepared from SRBC-immunized mice, showed that the rise in the enzyme activity was confined to the fraction containing the antibody-forming cells. The DNase activity was also increased in spleen cell cultures, stimulated with SRBC in vitro. Rise in the activity of this enzyme was also observed in peritoneal cell populations taken from SRBC-immunized mice. This change was maximal on the second day after immunization, when no appreciable increase in DNase activity of spleen cells was yet detected. The results obtained suggest, that acid DNase is an enzyme involved in the proliferative/maturation response to antigenic stimulation. It is a consequence of antigenic stimulation rather than being involved in the process of afferent stimulation.     

The 'Inka cell' and its associated cells: ultrastructure of the epitracheal glands in the gypsy moth,Lymantria dispar

The epitracheal glands in pharate and young pupae of Lymantria dispar are located at the base of ventrolateral tracheal trunks in the prothoracic and first through eighth abdominal segments. Each gland is composed of four cells the ultrastructure of which is described in this paper. One large cell and one smaller cell have an endocrine function, while a third cell is exocrine. A fourth cell forms a canal running from the exocrine cell into the trachea. The large endocrine cell, but not the smaller endocrine cell has released its secretions in freshly moulted pupae. The exocrine cell is assumed to be involved in the pupal moult events as well. The physiological role of the different cell types is discussed: The large endocrine cell (type I endocrine cell) is supposedly homologous with the 'Inka cell', which produces ecdysis triggering hormone (ETH) and was previously described in Manduca sexta; the functions of the smaller endocrine cell (type II endocrine cell) and the exocrine cell remain unknown.     

A, B, D cells and a fourth cell type in long-term cultures of fetal rat pancreas.

Whole pancreases from fetal rats of 13 days and 18 days gestation were explanted onto rayon grids and grown in organ culture. Cultures were fixed in Bouin's fluid, sectioned and stained with the fluorescent antibody techniques for glucagon and insulin, aldehyde fuchsin for B cells, pseudoisocyanin for D cells and a silver technique for the fourth cell type. The 13-day explants were fixed after 10 days in culture. A, B and D and the fourth cell type were seen, indicating that precursors of all four endocrine cell types must be present in the fetal pancreas shortly after the formation of the pancreatic bud (11 days). Further, the presence of these four cell types in the walls of tubules in these cultures indicates the tubules as the site of origin of all the endocrine tissue. The 18-day explants were collected every other day of culture from 2 to 30 days in a long-term experiment. A number of large islets with well granulated B cells was still present after 30 days of culture. The relative abundance of cell types at different stages was estimated as follows: 18-day fetal controls, A greater than B=4 greater than D; after 2 to 10 days in culture, B greater than A greater than or equal to D; after 18 to 30 days in culture, B greater than D greater than A greater than 4.     

New cell types of the pancreatic islets in the crucian carp,Carassius carassius

Summary The pancreatic islets ofCarassius carassius have been studied by electron microscopy. 1. Besides A-, B- and D-cells, two new cell types, the fourth and the fifth, have been identified. The fourth cell type is numerous; it occurs interposed among the other types of islet cells or in small clusters. The secretory granules (90–280 mg in diameter) are round or oval and usually with much lower electron density than α- and δ-granules. The secretory granules of the fifth type of cell (approximately 140–240 mμ in diameter) contain finely granular material and an electron dense core that is round or often tetra- or hexagonal. 2. The islet cells with clear cytoplasmic matrix generally contain large numbers of fine, agranular and cored vesicles 400–680 ? in diameter. They appear, in bead-like chains, or randomly scattered throughout the cytoplasm, or often clustered in aggregates close to the secretory granules and show evidence of incorporation into the secretory granules. The two types of vesicles may be formed by constriction or pinching-off of the tubular smooth endoplasmic reticulum.     

Fourth ventricular floor in human embryos: scanning electron microscopic observations

The ultrastructural surface features of the normal fourth ventricular floor of seven human embryos ranging from Carnegie stage 14 to stage 19 (crown-rump length: 7.6-16.2 mm) were examined by using scanning electron microscopy (SEM). Low-power SEM views showed the median sulcus, sulcus limitans, and neuromeres, transient structures characteristic of the earlier embryonic period. High-power SEM observation revealed supraependymal cells (SE cells) and supraependymal fibers (SE fibers) which exhibited a characteristic localization, as well as generalized surface-membrane modifications such as microvilli and cilia. SE cells could be classified into two major groups. The type 1 SE cells seem to possess neuronal functions, as deduced from morphological similarities to their counterparts in adults and the specialized distribution closely related to neuromeres. The type 2 SE cell morphologically resembled the phagocytic SE cell described in related literature. SE fibers ran a course either rostrocaudally in the median sulcus or mediolaterally on the neuromeres, most frequently near the interneuromeric cleft; they made contact with type 1 SE cells and ependymal surface modifications and then penetrated the ependymal layer.     

The ganglion cell layer of the retina of the rat: a Golgi study.

In whole-mounts of Golgi stained rat retinae four cell types are described in the ganglion cell layer. Three of these cell types are considered to be analogous to the alpha, delta and gamma cells described in the cat retina by Boycott & W?ssle (1974). The fourth cell type is thoughtt to be a displaced amacrine cell. All the cell types described are present in all parts of the retina. There is no evidence for an increase in dendritic field size with increasing distance from the optic disk.     

A,B, D cells and A fourth cell type in longterm cultures of fetal rat pancreas

Summary Whole pancreases from fetal rats of 13 days and 18 days gestation were explanted onto rayon grids and grown in organ culture. Cultures were fixed in Bouin’s fluid, sectioned and stained with the fluorescent antibody techniques for glucagon and insulin, aldehyde fuchsin for B cells, pseudoisocyanin for D cells and a silver technique for the fourth cell type. The 13-day explants were fixed after 10 days in culture. A, B and D and the fourth cell type were seen, indicating that precursors of all four endocrine cell types must be present in the fetal pancreas shortly after the formation of the pancreatic bud (11 days). Further, the presence of these four cell types in the walls of tubules in these cultures indicates the tubules as the site of origin of all the endocrine tissue. The 18-day explants were collected every other day of culture from 2 to 30 days in a long-term experiment. A number of large islets with well granulated B cells was still present after 30 days of culture. The relative abundance of cell types at different stages was estimated as follows: 18-day fetal controls, A>B=4>D; after 2 to 10 days in culture, B>A⩾4>D; after 18 to 30 days in culture, B>D>A>4.     

Stains for A, B, and D cells in fetal rat islets.

Ten techniques often used for identification of A, B, and D cells in adult islets of Langerhans were applied to fetal rat pancreas. Modifications were tried with many of these techniques. Two indole methods (xanthydrol and postocoupled benxylidene reactions) and a cryostat technique using o-phthaladehyde failed to stain fetal islets. Phosphotungstic acid hematoxylin and lead hematoxylin lightly stained fetal A cell granules in Helly's fixed tissue. The Grimelius silver nitrate technique stains adult rat A cells but failed to stain fetal cells. A modification of this technique stained fetal A cells and a possible 4th cell type. The specificity of this method was confirmed by restaining stained cells with a fluorescent antibody technique and with pseudoisocyanin. B cells, as previously reported, were readily stained by the aldehyde fuchsin technique. Fetal D cells were not stained by the Hellerstrom-Hellman alcoholic silver nitrate method, nor did they display pseudoisocyanin metachromasia after acid hydrolysis; they did fluoresce brightly with this technique when viewed with UV light. It was thus possible to distinguish the three usual cell types, plus a possible fourth type, in the fetal rat pancreas.     

Qualitative modeling of mechanoelectrical feedback in a ventricular cell

Mechanical changes in the heart muscle can influence its electrical properties through a process called mechanoelectrical feedback (MEF). This feedback can operate via changes in calcium dynamics during the cross-bridge cycle or via mechanosensitive (stretch-activated) channels. We present a four-variable ordinary differential equation (ODE) system that caricatures the electrical and mechanical activity of a ventricular cell and their mutual interactions. A three-variable excitable system with restitution properties of the FitzHugh-Nagumo type is coupled to a fourth equation which describes changes in cell length during a lightly loaded contraction. The resulting four-variable system models MEF in a cell and can be incorporated into spatially distributed models for mechanoelectric behavior during wave propagation in the cardiac tissue.     

Pyruvate kinase isozymic shifts of differentiating chick myogenic cells in vivo and in culture.

Developing chick skeletal muscle undergoes an isozymic shift from type K pyruvate kinase to type M during development. A major increase in pyruvate kinase activity follows the isozymic shift, resulting in at least 40-fold higher specific activities by adulthood. Similar isozymic changes occur in primary cultures of myogenic cells from 12-day-old chick embryos. Cultures initially contain only type K pyruvate kinase. Type M appears by the fourth day of culture and accounts for 80–90% of the activity by the eleventh day. Type M did not accumulate when cell fusion was prevented by removing Ca²⁺ from the growth medium or when protein synthesis was inhibited by cycloheximide.     

Degenerative changes and carotenoid uptake in the silk gland of the silkworm Bombyx mori

In the middle silk gland of the silkworm Bombyx mori, especially in the middle region, structural changes were studied in relation to absorbing activity, using a transplantation method. The physiologically active gland, which was prepared by the decapitation at the feeding stage of the fourth larval instar, maintained a normal structure when placed in the larval body cavity during the middle stage of the fourth instar or during the early stage of the fifth (last) larval instar. But, if the gland was placed there during the fourth larval-larval pharate stage, histolytic changes, e.g. invagination of tunica propria, its separation from the cell and contraction of the cell, took place in the tissue. These results suggest that, once activated, cells in the middle region of the middle silk gland undergo degenerative changes even in the presence of the corpus allatum hormone during the larval-larval pharate period.