Septate junctions between digestive vacuoles in human malacoplakia

Typical septate junctions between digestive vacuoles in phagocytic cells of human malacoplakia are described in this paper. Evidence for a honeycomb pattern of hexagonal subunits is presented for their cleft material. Junctions were not observed between other organelles or in cells other than phagocytes. It is assumed that the septate junctions described here may reflect a pathological change in the organization of the membrane components of digestive organelles.     

Localisation of oxytocin, vasopressin and parts of precursors in the human neonatal adrenal

Being a possible alternative source for the production of vasopressin (AVP) and oxytocin (OXT), a study was undertaken of the fetal adrenal. The concentrations of these peptides within the fetal adrenal turned out to be low, viz., approx. 1 pg/mg in the rat and within the pg/g range in the human. Immunocytochemistry was performed either on conventional autopsy material kept till 12 years in paraffin blocks, or on more recently obtained formalin or glutaraldehyde-paraformaldehyde fixed material. In both types of material staining was good. In order to localize AVP cells, anti-AVP, an antibody against its associated neurophysin (anti-NSN) or an antibody raised against the c-terminal glycopeptide part of the AVP precursor (anti-GP) was used. OXT cells were localized by means of anti-OXT or an auto-antibody of a multiple sclerosis patient (auto-MS) probably recognizing OXT-neurophysin. The antibodies were characterized on human and rat brain material. In the external zone of the definitive cortex, apart from parenchyma cells, anti-AVP, anti-NSN and anti-GP stained fibre-like structures running in the connective tissue septa and around parenchyma cells and the cytoplasma of these cells. Anti-OXT and auto-MS stained droplets in the cytoplasm of the fetal zone cells. Similar distinct staining patterns for AVP and OXT cells were obtained in human anencephalics. These observations show that the peptides are not derived from the fetal brain, but are rather produced in the fetal adrenal cortex.(ABSTRACT TRUNCATED AT 250 WORDS)     

Junctional structures in digestive epithelia of a cephalopod

Intercellular junctions have been studied in the epithelia of digestive organs of Sepia officinalis (digestive gland, digestive duct appendages and caecum) by conventional staining, lanthanum tracer and freeze-fracturing techniques. In the three organs studied the same junctional complex occurs, consisting of a belt desmosome, a septate junction and gap junctions. The septate junction is of pleated-sheet type and the gap junction has its particles on the P face of the fracture. Circular structures have been found in the digestive gland septate junctions. Neither continuous nor tight junctions have been found. These results show that Cephalopods have junctional structures very close to those of other Molluscs and of Annelids. Some small differences between the septate junctions of the three organs could be related to their different physiology.     

Localisation of oxytocin,vasopressin and parts of precursors in the human neonatal adrenal

Summary Being a possible alternative source for the production of vasopressin (AVP) and oxytocin (OXT), a study was undertaken of the fetal adrenal. The concentrations of these peptides within the fetal adrenal turned out to be low, viz., approx. 1 pg/mg in the rat and within the pg/g range in the human. Immunocytochemistry was performed either on conventional autopsy material kept till 12 years in paraffin blocks, or on more recently obtained formalin or glutaraldehyde-paraformaldehyde fixed material. In both types of material staining was good. In order to localize AVP cells, anti-AVP, an antibody against its associated neurophysin (anti-NSN) or an antibody raised against the c-terminal glycopeptide part of the AVP precursor (anti-GP) was used. OXT cells were localized by means of anti-OXT or an auto-antibody of a multiple sclerosis patient (auto-MS) probably recognizing OXT-neurophysin. The antibodies were characterized on human and rat brain material. In the external zone of the definitive cortex, apart from parenchyma cells, anti-AVP, anti-NSN and anti-GP stained fibre-like structures running in the connective tissue septa and around parenchyma cells and the cytoplasma of these cells. Anti-OXT and auto-MS stained droplets in the cytoplasm of the fetal zone cells. Similar distinct staining patterns for AVP and OXT cells were obtained in human anencephalics. These observations show that the peptides are not derived from the fetal brain, but are rather produced in the fetal adrenal cortex. Future research will have to determine the physiological meaning of the presence of these peptides in the fetal adrenal, e.g., in their contribution to amniotic fluid peptides, their possible role in fetal stress, steroidogenesis etc. The presence of an alternative source of these peptides in the fetus makes it necessary, further-more, to reconsider their possible functions in the process of labour.In honour of Prof. P. van Duijn     

COEXISTENCE OF GAP AND SEPTATE JUNCTIONS IN AN INVERTEBRATE EPITHELIUM

The intercellular junctions of the epithelium lining the hepatic caecum of Daphnia were examined. Electron microscope investigations involved both conventionally fixed material and tissue exposed to a lanthanum tracer of the extracellular space. Both septate junctions and gap junctions occur between the cells studied. The septate junctions lie apically and resemble those commonly discerned between cells of other invertebrates. They are atypical in that the high electron opacity of the extracellular space obscures septa in routine preparations. The gap junctions are characterized by a uniform 30 A space between apposed cell membranes. Lanthanum treatment of gap junctions reveals an array of particles of 95 A diameter and 120 A separation lying in the plane of the junction. As this pattern closely resembles that described previously in vertebrates, it appears that the gap junction is phylogenetically widespread. In view of evidence that the gap junction mediates intercellular electrotonic coupling, the assignment of a coupling role to other junctions, notably the septate junction, must be questioned wherever these junctions coexist.     

Intercellular junctions in the hepatopancreas of the lobster Nephrops norvegicus

The hepatopancreas of the lobster has recently been found to be a rich source of material from which to isolate arthopod gap junctions biochemically (Finbow et al., 1983a; 1984). It has therefore been studied here to assess the features of these intercellular junctions and any others that may be present, in vivo. The tissue consists of columnar epithelial cells which possess apical microvilli and basal infoldings. In thin sections the lateral borders of these cells are characterized by desmosomes and smooth septate junctions as well as by gap junctions. The desmosomes exhibit no apparent freeze fracture profile but the septate junctions display parallel rows of ridges or aligned intramembranous particles (IMPs) with complementary grooves on the other membrane half; these IMPs shift in their preferential fracturing plane depending on whether the tissue has first been fixed, always remaining on the EF if unfixed. The IMPs or connexons, of which the gap junctions are composed, fracture onto the E face, leaving complementary pits on the P face, regardless of whether the tissue is fixed or not. At the base of the pancreatic cells, the lateral borders are thrown into interdigitating folds which display endocytotic profiles and possible internalization of junction-bearing membranes. This phenomenon, which is readily visualized both after tracer incubation and in replicas, may represent junctional degradation relating to membrane turnover.     

A freeze fracture and thin section study of intestinal cell membranes and intercellular junctions of a nematode, Ascaris

The microvillar and lumenal plasma membrane P-face of Ascaris intestinal cells is shown to be covered by relatively large (13 nm) particles at a fairly high density (1000/μm²), while the E-face has virtually none. The P-face of the lateral cell membranes, those separating the cells, have fewer and smaller (8 nm) particles. The intestinal cells are also shown to be connected by an apical complex of smooth septate and tricellular junctions similar to those found between some insect midgut cells. A periodic layer of tannic acid staining material is found on the cytoplasmic sides of the smooth septate junction, and when the intercellular space is filled with lanthanum, smoothly curved, 10 nm wide septal walls can be seen. Below the belt of septate junctions are a large number of gap junctions. These have closely packed arrays of particles on the P-face with some particle aggregates adhering to the closely packed pit arrays on the E-face.     

Junctional types in the tissues of an onychophoran: the apparent lack of gap and tight junctions in Peripatus

The Onychophora are a rare group of primitive invertebrates, relatively little investigated. Tissues from a range of their digestive, secretory and excretory organs have been examined to establish the features of their intercellular junctions. Glutaraldehyde-fixed cells from the midgut and rectum, as well as the renal organ, mucous gland, salivary gland, epidermis, CNS and testis from specimens of Peripatus acacioi, have been studied by thin section and freeze-fracture electron microscopy. Adjacent cells in the epithelia of all these tissues are joined by apical zonulae adhaerentes, associated with a thick band of cytoskeletal fibrils. These are followed by regular intercellular junctional clefts, which, in thin sections, have the dense, relatively unstriated, appearance of smooth septate junctions (SSJ). However, freeze-fracture reveals that only the midgut has what appear to be characteristic SSJs with parallel alignments of closely-packed rows of intramembranous particles (IMPs); these IMPs are much lower in profile than is common in such junctions elsewhere. The mucous gland, testis, rectal and renal tissues exhibit, after freeze-fracture, the characteristic features of pleated septate junctions (PSJ) with undulating rows of aligned but separated junctional particles. Suggestions of tricellular septate junctions are found in replicas at the interfaces between 3 cells. In addition, renal tissues exhibit scalariform junctions in the basal regions of their cells. Between these basal scalariform and apical septate junctions, other junctions with reduced intercellular clefts are observed in these renal tissues as well as the rectum, but these appear not to be gap junctions. Such have not been unequivocally observed in any of the tissues studied from this primitive organism; the same is true of tight junctions.     

Isolation and characterization of autophagic vacuoles from rat kidney cortex

The number of autophagic vacuoles in the proximal tubule cells of the rat kidney increased considerably after 3 h of vinblastine treatment. This increase was paralleled by stimulated proteolysis in an homogenate prepared from the cortex. We have taken advantage of this expansion in autophagic vacuoles in an effort to isolate these organelles from rat kidney cortex on a discontinuous Metrizamide gradient. Autophagic vacuoles have recently been purified from liver but not from other tissues. The purity of the isolated fraction was 95% of which 55% consisted of typical intact autophagic vacuoles containing sequestered organelles and 45% of other types of secondary lysosome. On plane section many of these displayed one or several intramatrical vesicles or flap like processes forming apparent vesicles at the pole of the organelles, which occasionally contained pinocytosed membranous material. These lysosomes were designated microautophagic vacuoles. It is suggested that the microautophagic vacuoles could be the morphological expression of uptake into lysosomes of small portions of cytosol. The isolated autophagic vacuole fraction was enriched in lysosomal enzymes (acid phosphatase and cathepsin D activities) and displayed high proteolytic rates, especially at acid pH.     

Degenerative regression of the digestive tract in the colonial ascidian Botryllus schlossen (Pallas)

Summary Degenerative changes in the digestive tract of zooids of Botryllus schlosseri were studied by light and electron microscopy. Three main processes occurred in the tissues: contraction, involution and phagocytosis. The contraction of epidermis and peribranchial epithelium in which cytoplasmic microfilaments probably participate, seemed to have a special role in compressing the underlying organs. During contraction most of the body cavities collapsed, the branchial walls disintegrated and the fragments were rapidly taken up by large phagocytes. The gut epithelium retained its apparent continuity longer, though isolated phagocytes infiltrated it to eliminate single cells. Cell degeneration came about chiefly either through swelling and lysis of cells or through loss of water and condensation of cytoplasm and nucleus.The fate of all regressed tissues was to be engulfed and digested by wandering phagocytes. However, it was also observed that numerous cells of different epithelia could act as fixed phagocytes by engulfing cell debris and entire cells into heterophagic vacuoles.     

THE INTRACELLULAR DISTRIBUTION OF FERRITIN FOLLOWING MICROINJECTION

Ferritin solutions were microinjected into the ground cytoplasm of intact amebae. At several time-intervals after injection the cells were fixed and the distribution of the protein in various organelles was studied with the aid of the electron microscope. Individual molecules of ferritin were found randomly dispersed throughout the ground cytoplasm and the ground nucleoplasm. Within the mitochondria, the ferritin was localized between the outer and inner membranes. Aggregates of ferritin were found in vacuoles, some of which could be identified as food vacuoles. The findings, which provide evidence for a rapid penetration of large molecules into the nucleus, the outer compartment of the mitochondria, and the digestive vacuoles, are discussed in relation to other reports on intracellular permeability.     

Effects of tropic hormones on ultrastructure and synthesis of androgens in adrenals of male pseudohermaphrodite rats

Summary Ultrastructural and biochemical study of the adrenals in the pseudohermaphrodite (tfm) rat reveals hypertrophic adrenocortical cells. The cytoplasm of the cells in the zonae fasciculata and reticularis contains an exceptionally well developed smooth endoplasmic reticulum closely applied to mitochondria and lipid droplets. Mitochondria are more numerous than in normals and have especially abundant tubular cristae. More lipid droplets (appearing as empty vacuoles) are surrounded by pleomorphic mitochondria.The incubation study indicates that the capacity of rat adrenal cortex of producing androgens is greater in tfm than in normal animals. Hypophysectomy and castration result in a significant decrease in androgen biosynthesis by tfm rat adrenals and cause a reduced concentration of plasma testosterone. Administration of tropic hormones to hypophysectomizedcastrated rats appears to stimulate their adrenal androgenesis. It is suggested that in tfm rats the higher than normal luteinizing hormone (LH) together with adrenocorticotropic hormone (ACTH) stimulates the hypertrophy of cellular organelles in the adrenal cortex and causes an accompanying increase in androgenic steroids which may be responsible, at least in part, for the increased level of plasma androgens.     

A DISTINCTIVE CELL CONTACT IN THE RAT ADRENAL CORTEX

Extensive cell contacts which resemble septate junctions occur between cells in the three major zones of the rat adrenal cortex. Characteristically, they extend between small intercellular canaliculi and the periendothelial space, frequently interrupted by gap junctions and rarely by desmosomes. Zonulae occludentes have not been identified in the adrenal cortex. Along this distinctive cell contact, the cell membranes of apposing cells are separated by 210–300 a bisected by irregularly spaced 100–150-A extracellular particles which are often circular in profile. In lanthanum preparations, these particles appear to form a continuous chain throughout the intercellular space and are visualized as an alveolate structure in sections parallel to the plane of the cell membrane. The cell membrane in the area of septate-like contact does not differ from nonjunctional areas of the cell membrane in freeze-fracture replicas. The cell contact retains its integrity after cell dispersion and after the separation of cell membranes from disrupted cells. The intercellular particles also persist after brief extraction in lipid solvents. Besides adherence, possible functions of this adrenal contact include maintenance of the width of the extracellular space, the provision of channels between intercellular canaliculi and the bloodstream, and utilization as cation depots. Similar structures are also present between adrenal cortical cells of several other species and between interstitial cells of the testis. This type of cell contact may, in fact, be a typical feature of steroid-hormone-secreting tissues in vertebrates.     

Change of form of septate and gap junctions during development of the insect midgut

In insects, smooth septate junctions join cells derived from the embryonic midgut, and pleated septate junctions are found in all other tissues. Relatively little is known about either type of septate junction or the relationship between them, but they have been treated as two different junctions in the literature. The gap junctions which are associated with these septate junctions also differ. Crystalline gap junctions are found in the midgut, associated with smooth septate junctions, and irregular gap junctions are found in tissues where pleated septate junctions are located. We have examined the development of smooth septate junctions and crystalline gap junctions and the relationship between them, by studying the embryogenesis of the midgut in Manduca sexta (tobacco hornworm). At 56 hr of development (hatching is at 104 hr) pleated septate junctions and irregular gap junctions joined the midgut epithelial cells. At 65 hr, the septate junctions had disappeared, but gap junctions persisted. At 70 hr, smooth septate junctions had replaced the earlier pleated septate junctions and gap junctions associated with these smooth septate junctions were often of the crystalline form. In later embryos, the smooth septate junctions matured and enlarged, while all gap junctions became crystalline in form.     

Internal defenses of the snail Biomphalaria glabrata.

We describe three distinct types of cells among Biomphalaria glabrata hemocytes: large cells with a tubulo-vesicular compartment, a component of the endocytic system, and with numerous mitochondria and large aggregates of glycogen particles; medium-size cells poor in organelles and glycogen; and small cells with organelles and few secretory granules. Other small hemocytes can be interpreted as juvenile cells. B. glabrata hemocytes contain few enzymes and do not show specific secretory granules, except for a subpopulation of large cells richer in acid phosphatase vesicles. Hemocytes have different aspects corresponding to different physiological states and their transitions: in quiescent hemocytes, the cell cortex is narrow and organelles are scattered in the cytoplasm, both in circulating cells characterized by thin-folded filopods and large macropinocytic vacuoles and in sedentary cells in which extended filopods connect to the extracellular matrix. In stress-activated hemocytes, the cortical region is thickened by polymerization of actin, and organelles are gathered around the nucleus. Fixed phagocytes are components of the connective tissue; the presence of numerous lysosomes and residual bodies and of acid phosphatase and peroxidase activities suggests a high phagocytic activity.     

The digestive cells of the hepatopancreas in Aplysia depilans (Mollusca, Opisthobranchia): ultrastructural and cytochemical study

Digestive cells are the most abundant cell type in the digestive diverticula of Aplysia depilans. These are tall columnar or club shaped cells, covered with microvilli on their apical surface. A large number of endocytic vesicles containing electron-dense substances can be found in the apical zone, but the presence of many heterolysosomes of large diameter is the main feature of these cells. Glycogen particles and some lipid droplets were also observed. Peroxisomes with a circular or oval profile were common, but crystalline nucleoids were not detected in them, although a dense spot in the matrix was observed in a few cases. These organelles were strongly stained after cytochemical detection of catalase activity. The Golgi stacks are formed by 4 or 5 cisternae, with dilated zones containing electron dense material. Arylsulphatase activity was detected in the Golgi stacks and also in lysosomes. Cells almost entirely occupied by a very large vacuole containing a residual dense mass seem to be digestive cells in advanced stages of maturation. The observation of semithin and ultrathin sections indicates that these very large vacuoles are the result of a fusion among the smaller lysosomes. Some images suggest that the content of these large vacuoles is extruded into the lumen of the digestive diverticula.     

日本沼虾生精细胞与支持细胞之间的连接关系

用透射电镜技术研究了日本沼虾精子发生过程中不同细胞之间的连接关系。结果表明,从精原细胞期到次级精母细胞期,在生精细胞之间存在间隙连接与分隔连接与分隔连接,并且两种连接相互邻接,桥粒仅在精原细胞之间发现;从精原细胞期到精细胞期,在生精细胞与支持细胞之间也存在相互邻接的间隙连接与分隔连接,两类细胞之间有大量桥粒,形成血淋巴－精巢屏障,这种屏障可保持生精细管内环境的稳定性;精子发生的不同时期,支持细胞之     

Septate junctions in the gastrodermal epithelium of Phialidium: A fine structural study utilizing ruthenium red

The septate junctions of the gastrodermis of the hydromedusa, Phialidium gregarium, are composed of septa (80 A thick) which bridge the gap (130 A) between the outer leaflets of the plasma membranes of adjacent cells. The septa are parallel walls, presumably continuous around the cells, and en face show a periodicity of 110 A. Examination of material fixed in a ruthenium red-containing mixture shows that this dye penetrates the interseptal compartments and illucidates the finer structure of the septa. A model of an interpretation of the three-dimensional structure of the junction is presented and relevance of the results to current theories of cell communication is discussed.     

Structure of the subgenual organ in the green lacewing, Chrysoperla carnea

REM and TEM studies of the subgenual organ in Chrysoperla carnea (Neuroptera: Chrysopidae) show that it is composed of three scolopidia, each with one sensory, one scolopale and one cap cell. The distal part of the dendrite shows a cilium with a '9 + 0' structure. The cross-handing pattern of the ciliary root has a periodicity of bands of about 61 nm. The scolopale material in a certain part of the scolopale cell is organized into five rods. The cell bodies of all three cap cells form a lens-like structure. the velum, which is fixed to the leg wall and the trachea with an extracellular material. The importance of the velum is discussed. Four types of intercellular junction are found; spot desmosomes. belt desmosomes, septate junctions and gap junctions.     

Studies on Stenostomum grande Child, 1902 (Platyhelminthes,Catenulida): fine structure of the digestive tract and the endocytotic activity of the gastrodermis

Abstract The digestive tract and its endocytotic activity in the catenulid Stenostomum grande were studied by electron microscopy. The pharynx was typical of the simplex type. At the mouth, between the integumental epithelium and the pharyngeal epithelium proper, was a transition zone. Among the epithelial cells of this transition were monociliated sensory cells and the necks of bucco-pharyngeal secretory cells of two types. The pharyngeal epithelium proper was densely ciliated, with long ciliary rootlets and mitochondria. It was surrounded by two layers of muscles. The gastrodermis consisted of phagocytes and typical secretory Minotian cells. It was underlain by a delicate basal lamina and muscle fibers. Distinctive of the phagocytes was the presence of differentiated cilia, cup-shaped mitochondria, and vacuoles with dense inclusions. Morphological differences between pharyngeal and gastrodermal cilia suggest functional differences. Experiments using latex beads as tracers and the identification of acid phosphatase in cytoplasmic vacuoles pointed to a high level of endocytotic and digestive activity in the phagocytes. Our data demonstrate that the basic structure of the digestive tract in S. grande conforms well to that of other free-living platyhelminths, but it does have ultrastructural peculiarities.