Salivary gland ultrastructure of the unfed adult and feeding female of Haemaphysalis (Rhipistoma) leachi (Ixodoidea: Ixodidae)

The paired salivary glands of unfed adult Haemaphysalis (Rhipistoma) leachi contain one type of agranular and three types of granular alveoli connected to a salivary duct system. Type I agranular alveoli consist of one large, central cell surrounded by peripheral cells with numerous basal membrane infoldings indicative of epithelia involved in fluid transport. Glycogen particles, lipid-like droplets, and the parallel pattern of infolded membranes disappeared from the peripheral cells during feeding. Types II, III, and IV granular alveoli contain some agranular interstitial epithelial cells, cap cells, and fundus cells, but are predominantly composed of structurally different granular cell types a, b, c, d, e, and f. Agranular cells develop during the early stages of feeding. Granular a, c, e, and f cells release their granules directly after attachment to the host and possibly are involved in cement secretion required for firm attachment to it. The b cell granules are replaced by b₁ filamentous granules during feeding. Golgi bodies and rough endoplasmic reticulum (RER) participate in the formation of most types of granules. The d cells contain lamella-like structures and condensing vacuoles, probably responsible for lysosome formation. The main salivary duct and all types of alveoli are innervated by neurosecretory axons.     

Fine structure of the corpuscles of stannius in the toadfish.

The micro-anatomy of the corpuscles of Stannius of the toadfish, Opsanus tau, an aglomerular marine teleost, has been studied by light and electron microscopy. The corpuscles are composed of extensively anastomosed cords of epithelial cells which maintain intimate contact with blood capillaries. Most of the epithelial cells contain acidophilic granules which also show a positive reaction with the periodic acid-Schiff technique and aldehyde fuchsin. On the basis of fine structural criteria, three cell types can be recognized. The granular cells contain abundant quantities of granular endoplasmic reticulum, ribosomes, Golgi apparatus with prosecretory granules, coated vesicles, polymorphic mitochondria with lamellar cristae, filaments, microtubules, a cilium, a variety of lysosome-like dense bodies, glycogen particles, lipid droplets, secretory granules and intranuclear lipid-like inclusions. One variety of agranular cell (type I) is characterized by the total absence of secretory granules, but it contains large amounts of granular endoplasmic reticulum and ribosomes, conspicuous profiles of Golgi apparatus, coated vesicles and sometimes an abundance of glycogen. Another variety of agranular cell (type II) has poorly developed cytoplasmic organelles. The perivascular space between the capillary and parenchyma contains connective tissue cells and abundant nerve fibers. The different types of epithelial cells observed in the corpuscles of Stannius of this fish may represent functional stages of the secretory cycle in a single cell type.     

Ultrastructure of salivary glands of Ornithodoros (Ornithodoros) moubata (Ixodoidea: Argasidae)

The paired salivary glands of unfed adult Ornithodoros (Ornithodoros) moubata are composed of type I (agranular) and type II (granular) alveoli. Type I alveoli consis of one large central cell surrounded by peripheral cells having the morphology of fluid-transporting epithelia. Type II alveoli contain granular and agranular cells; the former are comprised of morphologically distinct types of cells (a, b, and c) containing granules of different structures and chemical composition with respect to polysaccharide and protein. The agranular cells are the interstitial and cap cells. Golgi bodies and rough endoplasmic reticulum (RER) are found in all granular cells and apparently are involved in granule formation. No appreciable structural changes were observed in type I alveoli during or after feeding. Type c cell granules are released before granules from types a and b cells and may contain anticoagulant substances that promote the blood flow of the host during the tick feeding. Although the cap cells are not structurally affected by feeding, interstitial cells are developed into transporting epithelia.     

An electron microscope study of the circulating leucocytes of the marine mussel,Mytilus edulis

Circulating leucocytes of the mussel, Mytilus edulis, were studied by electron microscopy. Based on morphological criteria, the leucocytes were classified as agranular and granular leucocytes, dependent upon the presence or absence of specific granules in their cytoplasm. Furthermore, the existing literature is being critically revised, and it is suggested that agranular and granular leucocytes might belong to the same cell line.     

Fine-structural study of leucocytes in the goldfish, Carassius auratus

An electron microscopic study was performed on leucocytes from circulating blood of the goldfish. The leucocytes were divided into eight types: neutrophil, eosinophil, large granular leucocyte (LGL), medium-sized granular leucocyte (MGL), small granular leucocyte (SGL), fine granular leucocyte (FGL), lymphocyte, and monocyte. In this report the thrombocyte was excluded from leucocytes, and LGL, MGL, SGL and FGL were tentatively classified based on the size of intracytoplasmic granules possessed by each cell. The existence of goldfish monocytes was electron microscopically demonstrated for the first time in the present report.     

Microscopical studies on the hemocytes of bivalves and their phagocytic interaction with selected bacteria

Hemocytes represent one of the most important defense mechanisms against foreign material in Mollusca. The morphology, hematological parameters and behaviour of hemolymph cells were studied in the southern quahogMercenaria campechiensis, the eastern oysterCrassostrea virginica, and the blood arkAnadara ovalis challenged with the bacteriaVibrio vulnificus andV. anguillarum. Two general classes of hemocytes (granular and agranular) exist inC. virginica andM. campechiensis. In contrast,A. ovalis possesses 3 general classes (granular, agranular and erythrocytes). Three types of granules were identified by light microscopy. When hemolymph cells were studied by transmission electron microscopy, the cytoplasm of hemolymph cells was noted to contain many organelles, including electron dense granules. Both agranular and granular hemolymph cells were capable of colchicine-sensitive pseudopodial movement and spreading. The results indicate that marine bivalves possess hemolymph blood cells which may play a role in the internal defense paralleling mammalian phagocytes. The morphology of these cells, as determined by light, scanning and transmission electron microscopy, showed some similarity to mammalian-mononuclear phagocytes. The sub-cellular events of molluscan hemocyte phagocytosis ofV. vulnificus andV. anguillarum were studied by both scanning and transmission electron microscopy. The role of these cells and the factors which govern their behavior are of economic and public health importance.     

Structural and functional characterisation of the blood cells of the bivalve mollusc,Scrobicularia plana

Light and electron microscopical studies were carried out in order to characterise the blood cells of the bivalve mollusc, Scrobicularia plana. Three types of haemocytes were recognised: eosinophilic granular haemocytes, basophilic granular haemocytes and basophilic agranular haemocytes. The eosinophilic granulocytes were vesicular and contained large granules whereas the basophilic granulocytes were found to contain small granules and glycogen 'lakes'. The basophilic agranular haemocytes were significantly smaller than the granular haemocytes and had a high nucleus to cytoplasm ratio. Functional characterisation of the blood cells identified activity for the lysosomal enzymes: acid phosphatase, beta-glucuronidase, non-specific esterase and arylsulphatase. There was also a weak staining reaction for phenoloxidase and peroxidase activities. Phagocytosis of Gram-positive bacteria was demonstrated by the haemocytes and antibacterial activity was shown by cell-free haemolymph. Assays to determine release of reactive oxygen species from the haemocytes did not detect any reactive oxygen generation.     

Non-specific cellular responses of rainbow trout to Vibrio anguillarum and its extracellular products (ECPs)

We have studied the early inflammatory response induced by Vibrio anguillarum and by its extracellular products (ECPs) in rainbow trout after intraperitoneal injection. The results showed a very similar inflammatory response which included leucopenia, mainly due to lymphopenia, neutrophilia and an increase in the number of circulating monocytes. Melanomacrophages as well as immature leucocytes were frequently observed circulating in the blood of injected rainbow trout. Monocytes often contain phagocytosed bacteria and other, altered cells including erythrocytes and leucocytes. However, neutrophils only occasionally phagocytosed bacteria. Many circulating leucocytes showed important structural alterations. Neutrophils of trout injected with bacteria and ECPs also showed stronger PAS-staining than those of control trout as well as Döhle bodies and swollen granules. A marked vasodilatation was observed in the kidney and spleen which was coincidental with a mobilization of eosinophilic granular cells and an hypertrophy of sinusoidal endothelial cells showing an increase in the number of cytoplasmic granules. An increase in the number of macrophages and melanomacrophages in the kidney and spleen as well as oedema and leucocyte infiltration in the liver and gills were also noted.     

A Second Granular Cell in the Endocrine Pancreas of the Hagfish Myxine glutinosa?

A light and electron microscopic re-investigation of the pancreatic islet organ of the hagfish, Myxine glutinosa, has confirmed earlier observations that agranular and granular β-cells are the predominant cell types. However, in addition a rare second granular parenchymal cell was observed in which the granules are spherical in shape with a mean diameter of 213 nm, contrasting with the predominantly ellipsoid granules which characterise the β-cell. At present, this allegedly second granular parenchymal cell cannot be unequivocally equated with a named islet cell type and its nature remains somewhat problematic.     

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.     

Acidification of the phagosome in Crassostrea virginica hemocytes following engulfment of zymosan

Phagocytic hemocytes are responsible for engulfing and internally degrading foreign organisms within the hemolymph and tissue of the eastern oyster, Crassostrea virginica. Since rapid acidification of the phagosome lumen is typically essential for activation of hydrolytic and reactive oxygen intermediate (ROI) producing enzymes in vertebrate cells, we measured phagosomal pH in oyster hemocytes by using the emission fluorescence of two fluorescent probes, rhodamine and Oregon Green 488 (OG 488), conjugated to zymosan to determine whether oyster hemocyte phagosomes become acidified after phagocytosis of zymosan. The average pH of 1079 phagosomes within 277 hemocytes 1 h after phagocytosis of zymosan was 3.9 +/- 0.03. Observations of 141 hemocytes with internalized zymosan by light microscopy revealed that, over a 60-min time period, 51% of highly granular hemocytes became partially granular, and 29% became agranular. In addition, 83% of partially granular hemocytes containing zymosan at time = 0 became agranular within 60 min. A comparison revealed that the phagosomes of agranular hemocytes were much more acidic (pH 3.1 +/- 0.02) than those of highly granular hemocytes (4.9 +/- 0.02; P < 0.05). These values are significantly lower than most reported in the literature for blood cells from metazoan organisms.     

Proliferating cells in the rat anterior pituitary during the postnatal period: immunoelectron microscopic observations using monoclonal anti-bromodeoxyuridine antibody

Proliferating cells in the male rat anterior pituitary at 1, 3, 5, and 8 weeks of age were labeled with bromodeoxyuridine (BrdU) and studied by light and electron microscopic immunocytochemistry using anti-BrdU. They decreased in number from 402±31/mm² at 1 week to 50±1.5/mm² at 8 weeks, while their cell area increased by about twofold during this period. They had a slightly higher nucleus/whole cell (N/C) ratio than non-proliferating cells. According to their ultrastructure we classified them into granular and agranular cells. The percentage of granular cells ranged from 73% to 82% of all the proliferating cells during the period studied. They had many granules of various sizes and shapes, and some contained growth hormone and prolactin. Agranular cells, constituting 18–27% of proliferating cells, were small and had a high N/C ratio, indicating their immaturity. Moreover, they showed several features of folliculo-stellate (FS) cells: they showed no secretory granules in the cytoplasm, extended thin cytoplasmic processes, and sometimes they constructed a follicle among them. These results suggest: (1) the majority of proliferating cells were mature cells producing anterior pituitary hormone(s) and (2) most of the agranular proliferating cells maybe FS cells. The possibility of the latter is discussed.     

Fine structure of the Wolffian duct and cytodifferentiation of the epididymis in fetal rats

Summary The fine structure of the Wolffian duct and alterations that occur with the differentiation of the epididymis have been studied in fetal rats ranging in length from 5 to 22 mm (12 to 19 days gestation). Contents of the columnar Wolffian duct cells include basal and perinuclear granular endoplasmic reticulum, sparse apical agranular endoplasmic reticulum, elongate mitochondria, and a small Golgi complex. Large membrane-bounded dense bodies contain cellular organelles and may represent parts of degenerating cells ingested by phagocytosis. During the development of the epididymis from the Wolffian duct in older fetuses, intracytoplasmic confronting cisternae of the granular endoplasmic reticulum become numerous, and the agranular reticulum in the apical part of the cell increases moderately in abundance. Concomitantly, the apical cell surface is modified. Many microvilli are formed, indentations of the plasma membrane appear between the microvilli, and the number of coated vesicles in the apical cytoplasm increases. These changes closely follow the onset of androgen secretion by the fetal testis, and it is suggested that they may occur in response to androgen. The relation of these differentiations to known adult functions of the epididymis is discussed.This study was supported by a research grant from the American Cancer Society (E-500), Program Project HD-02282 of the National Institutes of Health, and Health Sciences Advancement Award FR-02084 from the National Institutes of Health. The author is the recipient of a Research Career Development Award from the National Institute of General Medical Sciences. He wishes to acknowledge the technical assistance of Mrs. Heather Taylor.     

Ribonuclease–gold Labels Chondroitin Sulphate in Guinea Pig Basophil Granules

Basophilic leucocytes are metachromatic granule-containing secretory granulocytes that contain a mixture of granular proteoglycans devoid of heparin. In guinea pigs, isolated basophilic leucocyte granules primarily contain chondroitin sulphate. We have recently demonstrated that an enzyme-affinity– gold technique to image RNA, using the reagent RNase gold, also binds specifically to heparin in human mast cell granules. Such binding is based on the known property of heparin as a competitive inhibitor of RNase. Using similar methods, we show here that RNase–gold binds to the chondroitin sulphate in the secretory granules of guinea pig basophils, thus broadening the applicability of this post-embedding affinity–gold method to studies that require imaging of chondroitin sulphate in routinely prepared electron microscopical samples.     

Ultrastructural changes in the salivary alveoli ofArgas (Persicargas) persicus (Ixodoidea: Argasidae) during and after feeding

Two types of salivary alveoli are present in adultArgas (Persicargas) persicus: agranular type I and granular type II alveoli. Type I alveoli consist of a large central cell surrounded by a constrictor cell and peripheral cells with numerous infoldings of the basal membrane similar to epithelia involved in active transport. The basal infoldings form a previously undescribed successively convoluted membranous pattern which may increase the capability of peripheral cells for active transport. Type II alveoli consist of three granular cells (a, b, c) and two agranular (adlumenal and ablumenal interstitial) cells. Golgi bodies and rough endoplasmic reticulum are probably involved in the granule formation. The granules are discharged within 5–10 min after feeding commences, and presumably contain anticoagulant substances and pharmacologically active agents that promote the blood flow of the host during tick feeding. Although the adlumenal cells are not structurally affected by feeding, ablumenal cells develop into transporting epithelia.     

Structure of hematopoietic nodules in the ridgeback prawn,Sicyonia ingentis: Light and electron microscopic observations

The architecture and fine structure of the epigastric hematopoietic nodules of the ridgeback prawn, Sicyonia ingentis, are described. The nodules consist of a highly branched series of tubules that contain the maturing hemocytes within a connective tissue stroma. Hemocytes can exit the hematopoietic nodules by penetrating through fenestrations in the endothelial cell layer into the central hemal space or by migrating through the outer later of capsular cells and associated collagen fibrils. Four hemocyte categories were observed: agranular, small granule with cytoplasmic deposits, small granule without cytoplasmic deposits, and large granule hemocytes. This classification was based upon the presence, size, and type of cytoplasmic granules and the presence of cytoplasmic deposits. Only agranular cells and small granule hemocytes without cytoplasmic deposits appeared capable of division. Intermediate stages were observed between agranular hemocytes and small granule hemocytes with deposits and between small granule hemocytes without deposits and large granule hemocytes, suggesting existence of two distinct hemocyte lines.     

An ultrastructural study of the submandibular glands of the squirrel monkey, Saimiri sciureus

In squirrel monkey (Saimiri sciureus) the position of submandibular glands in the neck, on either side of the trachea, more closely resembles that of rodents than that of other primates. The glands exhibit seromucous acini and mucous tubules with seromucous demilunes. Electron microscopy shows basal cytoplasmic folds and well-developed intercellular tissue spaces and canaliculi only in relation to seromucous cells. Greatly dilated cisternae of the granular endoplasmic reticulum and prominent Golgi membranes are characteristic of the mucous cells. The secretory granules of seromucous and mucous cells are morphologically distinct and indicate chemically different products for the two cell types. Histochemically, the seromucous cell shows the presence of acid mucosubstance as indicated by the PAS and Alcian blue techniques. Preliminary studies showed no appreciable quantity of amylase in submandibular glands. The intercalated duct cell is juxtaposed with the acinar cell or mucous tubule cell. Short luminal microvilli, prominent Golgi complexes and scant apical granules are notable features of intercalated duct cells. Four cell types compose the striated ducts, viz., granular light cells, agranular dark cells, vesiculated dark cells, and basal cells. Peripheral nerves are found in five different locations: in the connective tissue (interstitial), between adjacent myoepithelial and mucous-secreting cells, in the intercellular space between adjacent secretory cells, and between basal plications of striated ducts and between adjacent myoepithelial and intercalated duct cells.     

Electron microscopy of the skin of the teleost,Hippoglossoides elassodon

Summary The normal skin of the pleuronectid fish, Hippoglossoides elassodon, is described by light and electron microscopy. The epidermis consists of 5 to 9 layers of cells, the majority of which are squamous cells and the minority mucous cells. The squamous cells are characterized by numerous desmosomes and associated cytoplasmic filaments. The mucous cells accumulate mucous droplets in vacuoles of Golgi origin and are observed apparently in the process of releasing their content at the free surface. The dermis consists of alternating lamellae composed of typical collagen fibers. Pigment cells are of three types: melanophores, iridophores (guanophores), and lipophores.This work was supported by Public Health Service Research Grant CA-08158 from the National Cancer Institute.     

Ultrastructural features of the developing hypothalamo-hypophysial axis in the rat

Summary Nerve fibres containing granular vesicles first appear in the median eminence of the rat on the 16th foetal day while secretory granules in the cells of the adenohypophysis are not present till the 17th foetal day. These observations suggest that the differentiation and early activity of pars distalis cells may depend on substances elaborated at nerve terminals in the median eminence. Although the loops of the primary plexus of portal vessels do not develop until the 4th postnatal day, substances released by nerve fibres in the neurohypophysis could reach the pars distalis through vessels already present at the 15th foetal day in the mesenchyme between the diencephalon and the adenohypophysis. This view is supported by the fact that the earliest cells to exhibit ultrastructural evidence of secretory activity are in the rostral pole of the pars distalis, the first region of the gland to become vascularized. The earliest granules to appear in the cells of the pars distalis correspond to those which are considered to contain mucoprotein hormones; somatotrophin type granules were seen only in postnatal tissues.The finding that, in the median eminence, the development of granular vesicles precedes that of agranular vesicles is discussed with reference to the times at which neurosecretory materials and monoamines become detectable in the region.We should like to thank Miss Ann Pearson, Mr. D. Burns, and Mr. J. Nailon for their technical assistance, and Mr. J. Simmons, F.R.P.S., for his help in the preparation of illustrations. This work was supported by grants from the National Health and Medical Research Council of Australia.     

Fine structural study of a possible mechanism of secretion by the interrenal cells of the brown pelican

Summary In the deeper zones of the adrenal gland of the brown pelican, small dense bodies have been observed in the subendothelial space and between adjacent interrenal cells. They appear to be extruded from the interrenal cell by reverse pinocytosis. Intracellularly, similar appearing dense bodies, bounded by a single membrane, are sometimes evident. An interpretation of the foregoing is presented and discussed which suggests that this material may be hormone which is synthesized or organized into droplet form by the agranular endoplasmic reticulum and extruded from the cell either apically or apico-laterally, to be dispersed or rendered soluble in the subendothelial space.Supported in part by the Comly Fund of the Ohio State University, by Grant AM 09658-01 from the National Institute of Arthritis and Metabolic Diseases, National Institutes of Health and Grant DT-8 from the National Institute of Dental Research.Deceased January, 1965.