Observations on the relationship between “chloride-type” and “pseudobranch-type” cells in the gills of a fish,Oligocottus maculosus

Summary Chloride cells in gill epithelium of Oligocottus maintained in sea water have a much branched system of agranular cytoplasmic tubules, numerous mitochondria, and a prominent apical crypt. The mitochondria are randomly dispersed and do not show preferential orientation with respect to the tubules.After brief exposure of fish to sea water diluted 1/100 with glass distilled water, the mitochondria and tubules become rearranged into parallel arrays and the apical crypts disappear. The appearance of these cells is similar to that of pseudobranch cells in Fundulus heteroclitus (Copeland and Dalton, 1959).These data suggest that chloride cells and pseudobranch cells represent different adaptive forms of a single cell type and that transformation from the chloride cell configuration to that of pseudobranch cells can be induced by osmotic stress.This work was performed in 1963 when the author was enrolled in the Fine Structure Training program of the Department of Biological Structure, University of Washington. Financial aid was provided by the United States Public Health Service (Grant No. 5T1 GM-136).     

斑衣蜡蝉雌性生殖系统超微结构

【目的】明确斑衣蜡蝉Lycorma delicatula雌成虫生殖系统整体形态及超微结构特征,为蜡蝉总科昆虫分类及系统发育探讨提供更多形态学证据。【方法】采用光学显微镜与透射电子显微镜,观察斑衣蜡蝉雌成虫生殖系统整体形态和各主要器官的超微结构。【结果】斑衣蜡蝉雌成虫生殖系统主要包括1对卵巢、1个中输卵管、1个交配囊、1个交配囊管、1个前阴道、1个后阴道、1个受精囊、1个受精管和2根受精囊附腺。卵巢为端滋式,由14根卵巢小管组成,卵室由固有膜、滤泡细胞和卵细胞组成,卵巢小管中的滋养细胞清晰可见;中输卵管位于前阴道基部,由中输卵管腔、上皮细胞、肌肉鞘和基膜组成;交配囊膨大呈圆球状,囊壁由上皮细胞、肌肉层和基膜组成;交配囊管呈圆柱状,连接交配囊和后阴道,由肌肉鞘、上皮细胞层和管腔组成;前、后阴道超微结构相似,主要由肌肉鞘、基膜、上皮细胞和管腔组成,但后阴道上皮细胞细胞核周围存在分泌颗粒,且管腔内有大量微绒毛,而前阴道壁内包含有大量囊泡结构;受精管从中输卵管末端延伸至受精囊,由基膜、厚层肌肉鞘和管腔组成;受精囊为受精管近末端略膨大的囊状结构,由肌肉鞘、基膜、上皮细胞和囊腔构成;雌性受精囊附腺着生于受精囊末端,为均匀的螺旋管状,主要由肌肉层、上皮细胞层和附腺中心管腔组成。【结论】斑衣蜡蝉雌性生殖系统与已报道的蜡蝉总科其他类群的雌性生殖系统结构相似,但卵巢小管数目有差异;蝉亚目中不同总科雌成虫雌性附腺与受精囊附腺的形态特征存在明显区别;斑衣蜡蝉雌性生殖系统超微结构与叶蝉总科和沫蝉总科昆虫也存在部分差异。这些差异是否可以作为头喙亚目高级阶元的划分依据仍有待于进一步研究。     

Ultrastructure of the basiepithelial nerve plexus of the sea urchin,Centrostephanus longispinus

Summary In submandibular glands of rabbits both adrenergic and cholinergic axons are intimately associated with parenchymal cells of the intercalary ducts and the granular tubules, lying beneath the basement membrane and often in the space between the parenchymal cell and an associated myoepithelial cell. The submandibular acini receive a less intimate and less plentiful innervation by adrenergic and cholinergic axons which remain outside the basement membrane and are still associated with Schwann cells. Occasional axons of both adrenergic and cholinergic type occur beneath the basement membrane of submandibular striated ducts in intimate association with basal parts of the cells.In the parotid glands numerous adrenergic and cholinergic axons are found beneath the basement membrane of acini and intercalary ducts in intimate association with the cells.This work has been helped by the technical assistance of Mr. P.S.A. Rowley     

Ultrastructure of the coxal gland of the horseshoe crab Limulus polyphemus: Evidence for ultrafiltration and osmoregulation

Electron microscopic examination of the paired coxal glands of the horseshoe crab Limulus polyphemus, focusing on urinary and vascular channels, shows six morphologically distinct regions. Each of four nephridial lobes consists of two cortical layers surrounding a medulla. The outer and inner cortexes contain blood vessels separated by a basement membrane from the urinary space lined by podocytes. Podocyte foot processes are applied to the basement membrane, interdigitate with those from other podocytes, and have a filtration slit diaphragm between them. Cortical morphology demonstrates ultrafiltration of blood, a previously undescribed function of the gland, as well as possible endocytic reabsorption of materials by the podocytes. The medulla drains into the stolon connecting the four lobes. These two areas have urinary tubules of cuboidal epithelium featuring microvillous-like apical projections, cytoplasmic vesicles and vacuoles, elaborate lateral interdigitations with septate junctions, and basal invaginations containing numerous mitochondria. These tubules are closely surrounded by blood channels, lined by a basement membrane containing embedded support cells. The medulla and stolon morphology are suggestive of both ion transport and water movement, in keeping with the gland's role in osmoregulation. The stolon empties into the end sac in the base of the most posterior lobe. It is lined by tall epithelium exhibiting apical overlap, blunt projections into the lumen, apparent endocytic vesicles, and basal plasma membrane infoldings with mitochondria. The end sac drains into the conducting nephric duct, the proximal end of which is lined by a cuticle. J. Morphol. 234:233–252, 1997. © 1997 Wiley-Liss, Inc.     

Comparison of the ability of basement membranes produced by corneal endothelial and mouse-derived Endodermal PF-HR-9 cells to support the proliferation and differentiation of bovine kidney tubule epithelial cells in vitro

The proliferation and morphological differentiation of bovine kidney collecting-tubule epithelial cells has been examined as a function of substrata and plasma factors. Collecting kidney tubule explant maintained in vitro gave rise to two distinct cell populations; one was composed mostly of fibroblastic cells whereas the other was epithelioid (EP cells). The proliferation of fibroblastic cells when exposed to serum-supplemented medium was best expressed when cells were maintained on a basement membrane produced by bovine corneal endothelial cells. This basement membrane has a composition, which in previous studies has been shown to favor the proliferation of mesenchymal cells. In contrast, the proliferation of EP cells was best expressed when cells were maintained on a basement membrane produced by the mouse-derived endodermal cell line PF-HR-9 (HR-9-BM). This basement membrane has a biochemical composition very similar to the basement membrane underlying the kidney tubules. Although the fibroblast confluent monolayer maintained on bovine corneal endothelial cell extracellular matrix did not undergo morphogenesis, the confluent monolayer of EP cells maintained on HR-9-BM shows hemicyst formation, suggesting that they were capable of vectorial fluid transport. They also built a complex three-dimensional kidney tubulelike network. Some tubules became grossly visible and floated into the tissue culture medium, remaining tethered to the cell monolayer at either end of the tubule. On an ultrastructural level, the tubules consisted of cells held together with junctional complexes arranged so as to form a lumen. The smallest lumen were bordered by 2-3 cells, and the largest ones by 8-15 cells. The lumens of the larger tubules did contain granular fibrillar and amorphous debris. Low-density EP cell cultures maintained on HR-9-BM could be induced to proliferate at a rate approaching that of cultures exposed to serum when they were exposed to medium supplemented with high-density lipoprotein (HDL, 750 micrograms protein/ml) and transferrin (50 micrograms/ml). When exposed to HDL concentrations equal or lower than 250 micrograms protein/ml, low-density cultures proliferated at a slow rate and readily formed tubulelike structures. This observation indicates that EP cells do not need to reach confluence to undergo morphogenesis, and that HDL, which in the presence of transferrin supports the cell proliferation, can favor their differentiation into tubulelike structures once its concentration becomes limiting for mitogenesis.     

The Harderian gland of the Cheesman's gerbil (Gerbillus cheesmani ) of the Kuwaiti desert

The Harderian gland is a large orbital structure. Several functions have been ascribed to the gland such as lubrication of the eye, a source of pheromones, thermoregulartory lipids and photoprotective secretions and a part of the retinal-pineal axis. In the present study, the Harderian gland of the Cheesman's gerbil, Gerbillus cheesmani, is described for the first time. The gland is located around the posterior portion of the eyeball. The gland is compound tubular, surrounded by a thin connective tissue capsule. Only one secretory epithelial cell type was recognized, characterized by the presence of lipid vacuoles and cytoplasmic slashes in high numbers; the former being more concentrated towards the apical part while the latter being more concentrated towards the central and basal parts. Some of the cytoplasmic slashes contained electron dense filamentous structures. Similar structures were observed in the lipid vacuoles. Thus, a functional relationship between the cytoplasmic slashes and the lipid vacuoles is suggested. A unique structure was observed, termed dome-like cells, located between the epithelial cells and the basement membrane. These cells were characterized by the extensive presence of pleomorphic mitochondria and compact lamellae of granular endoplasmic reticulum (GER) in the form of finger prints. The gland was found to be actively secreting porphyrins as well as lipids. Cellular debris was also seen in the tubular lumina. Myoepithelial cells with their spindle shape and elongated nuclei were evident between the basement membrane and the secretory epithelium. Sparse interstitial tissue was observed in-between the gland tubules of both male and female gerbils. Macrophages, dendritic melanocytes and lymphocytes are the most represented cellular components of the interstitium. Further studies are required to investigate the function of the dome-like cells as well as the role of lymphocytes in the rodents Harderian gland.     

Cytological differentiation in the uropygial gland.

Ultrastructural changes were studied in the cells undergoing secretory differentiation in zone I of the tubules of the uropygial gland of White Plymouth Rock chickens. A layer of basal cells and four secretory stages are recognized as the cells migrate from the periphery to the lumen of tubules and progressively elaborate a secretion product. Basal cells, containing rough endoplasmic reticulum and free ribosomes, rest on the basement membrane and are the source from which secretory cells arise. Dilated perinuclear cisternae and the proliferation of smooth endoplasmic reticulum in the form of vesicles, invaginated sacs and cusp-shaped cisternae indicate the onset of lipgenesis in stage I cells. The perinuclear cisternae are more dilated and the endoplasmic reticulum is composed on saccules and cisternae in stage II cells. Stage III cells are characterized by concentric lamellae of endoplasmic reticulum surrounding secretory droplets. Dilated cisternae of endoplasmic reticulum and secretory droplets both contain a reticular substance. The perinuclear cisternae of stage III cells have returned to normal dimensions. Large mature lucent secretory droplets, lined with electron-dense material, fill the cytoplasm ostage IV cells which degenerate and release their secretory product into the tubule lumen. Spherical membrane-bound compartments containing a mottled substance of moderate electron density occur in basal cells and all subsequent secretory stages. These mottled bodies are surrounded by saccules of endoplasmic reticulum in stage II cells and are intimately associated with secretory droplets in stage III cells, but there is no evidence that they give rise to secretory droplets and their role in secretory differentiation is unknown.     

An unusual type of secretory cell in the ventral pedal gland of the gastropod mollusc Buccinum undatum L.

The ventral pedal gland in the foot of the mature female whelk Buccinum undatum L. consists of a shallow pouch containing a layer of elongated cells which partially penetrate a basement membrane overlying layers of smooth muscle. This glandular epithelium contains acid mucopolysaccharide cells, ciliated and interstitial cells as well as the upper parts of a new type of subepidermal gland cell. These gland cells consist of an elongated extracellular tubular duct formed by an invagination of the cell membrane and lined by numerous microvilli. Into this duct are discharged packets of a densely staining secretion. The secretion packets are produced in Golgi regions around the nuclei of the cells and are passed up through the cell to the base of the duct through or along an extensive assemblage of microtubules. The secretion packets show organized internal structure and may contain aromatic aldehydes and protein associated with the sclerotization of the egg capsules, which pass through the gland after leaving the genital tract.     

Passive immunization with anti-laminin immunoglobulin G modifies the integrity of the seminiferous epithelium and induces arrest of spermatogenesis in the guinea pig

In the testis, the base of the Sertoli cells is in contact with the basement membrane matrix, in which the laminins constitute the major noncollagenous components. We have previously demonstrated that antibodies against a preparation enriched in basement membranes of seminiferous tubules (STBM) or a noncollagenous fraction of STBM passively transferred induced modifications to the basement membranes and focal sloughing of the seminiferous epithelium in the rat. In the present report, we tested the effect of passive immunization with anti-laminin IgG on the limiting membrane of the seminiferous tubules, spermatogenesis, and maintenance of the blood-testis barrier in the adult guinea pig. Rabbit antibodies to laminin 1 (IgG fraction) were injected in adult male guinea pigs (GP). Nonimmunized GP and GP immunized with normal rabbit serum IgG were used as controls. Measurements of variations in the diameter and lumen of the tubules and in the size of individual components of the tubular limiting membrane showed that the highest percentage of tubules with reduced lumen occurred 30 days after passive immunization with anti-laminin, when the limiting membrane was thickest and lesions to the seminiferous epithelium were most severe. The lesions included thickening of the limiting membrane, infolding in the basal lamina, deposits of immune complexes coincident with sloughing of pachytene spermatocytes and spermatids, and vacuolization of the Sertoli cells. Mononuclear cell infiltration of the tubules was rare. Permeability tracer studies revealed that Sertoli cell tight junctions remained impermeable. Fifty and 80 days after treatment, the basement membrane of the tubules and the progression of the spermatogenesis were normal. Passive immunization with anti-laminin IgG provided a valuable experimental model for the in vivo study of the influence of the basement membrane on the issue of spermatogenesis and the integrity of the seminiferous epithelium.     

Excurrent duct system of the male turtle Chrysemys picta

The epididymis and efferent duct system of the turtle Chrysemys picta were examined. Seminiferous tubules are drained by a series of ducts that form a rete exterior to the tunica albuginea. The rete is located lateral to the testis and consists of anastamosing tubules of varying diameters, lined by a simple epithelium consisting of squamous to cuboidal cells. The rete is highly vascularized. A series of tubules (efferent ductules) connect the rete to the epididymis proper. The efferent ductules are highly convoluted, running between the epididymal tubules and are of varying diameters. The simple columnar epithelium lining these tubules possesses tight junctions, with every third or fourth cell possessing long cilia that protrude into the lumen. The cytoplasm of these epithelial cells contains abundant mitochondria. In the central portion of the efferent ductule, epithelial cells possess granules that appear to be secreted into the lumen by an apocrine process. The epididymis proper is a single, long, highly convoluted tubule that receives efferent ductules along its entire length. It is lined by a pseudostratified epithelium containing several cell types. The most abundant cell (vesicular cell) lacks cilia, but has a darkly staining apical border due to numerous small vesicles immediately beneath the luminal membrane. The small vesicles appear to fuse with each other basally to form larger vesicles. These cells appear to have an absorptive function, and occasionally sperm are embedded in their cytoplasm. The second-most abundant cell is a basal cell found along the basement membrane. The number of these cells fluctuates throughout the year, being most abundant in late summer and early fall. A small narrow cell with an oval nucleus and darkly staining cytoplasm, extending from the basement membrane to the apical surface, is present in small numbers, particularly in the caudal regions of the epididymis. This cell is frequently found in association with another narrow cell having a rounded nucleus and abundant mitochondria in its cytoplasm.     

Ultrastructure of the tubular nephron of the lizard Podarcis (= Lacerta) Taurica

The proximal, intermediate, and distal convoluted tubules of the neprhon of Podarcis (= Lacerta) taurica were examined by electron microscopy. Proximal tubule cells have large, apical cytoplasmic protrusions and microvilli interpreted to function in urate secretion. Adjacent cells are bound apically by tight junctions and desmosomes but interdigitate in their basal region. This situation is repeated in the other tubules with significant differences in intercellular space width. The basal surfaces bear numerous cytoplasmic processes. The intermediate tubule has proximal and distal segments each with dark, ciliated, and light cells, the cuboidal dark cells with dense cytoplasm constituting the main bulk of the wall. As the cells of the proximal and distal segments resemble those of the proximal and distal convoluted tubules, respectively, the intermediate tubule is considered as a transition region. The ciliated cell body has two broad processes extending from the lumen, one to the basement membrane and one to a foot process of a light cell. The light cell is surrounded by dark and ciliated cells. It does not reach the lumen, but contacts the basement membrane through a process running below a ciliated cell to form a mushroom-shaped structure in tubule cross-section, the light cell process forming the stalk and a ciliated cell the cap. The cilia probably propel the glomerular filtrate towards the distal convoluted tubule. This latter tubule has initial, middle, and terminal zones, all nonciliated but with different lumen widths and cell shapes.     

The Fine Structure of the Epithelial Cells of the Mouse Prostate : II. Ventral Lobe Epithelium

The fine structure of the epithelial cells of one component of the prostatic complex of the mouse—the ventral lobe—has been investigated by electron microscopy. This organ is composed of small tubules, lined by tall simple cuboidal epithelium, surrounded by smooth muscle and connective tissue. Electron micrographs of the epithelial cells of the ventral lobe show these to be limited by a cell membrane, which appears as a continuous dense line. The nucleus occupies the basal portion of the cell and the nuclear envelope consists of two membranes. The cytoplasmic matrix is of moderately low density. The endoplasmic reticulum consists of elongated, circular, and oval profiles representing the cavities of this system bounded by rough surfaced membranes. The Golgi apparatus appears localized in a region between the apical border and the nucleus, and is composed of the usual elements found in secretory cells (3, 9). At the base of the cells, a basement membrane is visible in close contact with the outer aspect of the cell membrane. A space of varying width, which seems to be occupied by connective tissue, separates the epithelial cells from the surrounding smooth muscle fibers and the blood vessels. Bodies with the appearance of portions of the cytoplasm, mitochondria, or profiles of the endoplasmic reticulum can be seen in the lumina of the acini and on the bases of these pictures and others of the apical region the mechanism of secretion by these cells is discussed. The fine structural organization of these cells is compared with that of another component of the mouse prostate—the coagulating gland.     

Gross and fine structure of the pseudo branch of the climbing perch, Anabas testudineus (Bloch)

The structure of the glandular pseudobranch of the air-breathing fish Anabas testudineus is described on the basis of light and electron microscopy. It is shown that the pseudobranch has the same basic structure as a typical gill, although in this case it is not freely exposed to the water.
Individual secondary lamellae can be recognized in which well-defined, but narrow, blood channels are present between typical pillar cells. The epithelial layer is mainly represented by enlarged mitochondria-rich cells which constitute a large proportion of the whole organ. Mitochondria-rich cells contain an abundant endoplasmic reticulum which is in close contact with the mitochondria and becomes concentrated near the vascular borders of the cell and opens directly into the basement lamina.
The presence of numerous pinocytotic vesicles in the enlarged pillar cell flanges may transfer material to the blood channels. The precise nature and role of any materials released in this way remains to be investigated.     

Cellular and subcellular localization of paralemmin-1, a protein involved in cell shape control,in the rat brain,adrenal gland and kidney

Paralemmin-1 is a phosphoprotein, lipid-anchored to the cytoplasmic face of membranes and implicated in plasma membrane dynamics and cell process formation. We report an immunoperoxidase histochemical analysis of the cellular and subcellular localization of paralemmin-1 in the rat tissues where its expression is highest: the brain, the adrenal gland and the kidney. Paralemmin-1 is detected throughout the brain, in neuronal perikarya, axons and dendrites including dendritic spines and also in glial processes. In the adrenal gland, paralemmin-1 is highly expressed in the medulla. The kidney displays a pattern of differential paralemmin-1 expression in various structures and cell types, with high concentrations in cells of the parietal epithelium of Bowman’s capsule, intermediate tubules, distal tubules and principal cells of outer medullary collecting ducts. Mosaics of paralemmin-positive and paralemmin-negative cells are observed in proximal tubules, the parietal epithelium of Bowman’s capsule and the endothelium of many blood vessels. Plasma membrane association in epithelia is often polarized: paralemmin-1 concentrates at the apical membranes of adrenal chromaffin cells, but at the basolateral plasma membranes of proximal and distal tubule cells in the kidney. Paralemmin-1 immunoreactivity exhibits a spotted pattern and can be seen both at plasma membranes and within the cytoplasm, where it is often associated with endomembranes. This discontinuous distribution and the detergent extraction properties of paralemmin-1 suggest an association with lipid microdomains. The findings are consistent with a role for paralemmin-1 in the formation and stabilization of plasma membrane elaborations, in neurons as well as in other cell types.     

The fine structure of the colleterial glands of Hyalophora cecropia (Lepidoptera)

The structure of cells in the colleterial glands of the Cecropia silkmoth was examined. Morphologically and functionally the gland is divided into two regions, a tubular one in which columnar protein-synthesizing cells are located, and an expanded region in which flattened cells with very different structure are most prominent. The fine structure of the latter cells which are presumed to secrete a phenolic glucoside, closely resembles that of cells described in the colleterial glands of orthopterans. The protein-secreting cells have many features normally associated with pancreatic acinar, and other cells of similar function. Among these are extensive rough endoplasmic reticulum, an elaborate Golgi complex, and a modest number of mitochondria. Other features which are less usual in cells of this type are an elaborate secretory apparatus consisting of a cuticular tubule inserted into a microvilli-lined cavity at the apical end of the cell, and large numbers of cytolysomes, myelin figures, and lipid droplets. A chitogenous cell with a very distinct and specific type of ultrastructure is found associated with the secretory cell. This cell type is attached to the cuticular elements of the gland, and the main features of its cytoplasm are extensive bundles of microtubules which presumably serve as supportive elements for the secretory cells.     

Ultrastructure of the radula protractor of Busycon canaliculatum

Summary The distribution of the sarcoplasmic reticulum and sarcolemmic tubules in the radula protractor muscle of the whelk, Busycon canaliculatum, has been investigated. The sarcoplasmic reticulum consists of an interconnected system of cisternae and tubular channels. The cisternae are closely associated with the sarcolemma. The tubular channels project from the cisternae into the interior of the cell and run parallel to the long axis of the myofilaments. Parallel tubular channels are interconnected with one another by short branches. This finding of an elaborate sarcoplasmic reticulum supports previous physiological work on this smooth muscle which indicated the presence of an intracellular compartmentalization of calcium ions. There is also an extensive system of tubular invaginations of the sarcolemma which we have termed sarcolemmic tubules. These tubules are 600 Å in diameter and about 0.5 microns in length. There is a substructure associated with the leaflet of the tubular membrane bordering the extracellular space. The sarcolemmic tubules penetrate only half a micron from the surface of the cell and interdigitate with the sarcoplasmic reticulum associated with the sarcolemma. Calculations have shown that the surface area of this smooth muscle cell is more than doubled by the presence of sarcolemmic tubules.     

The ultrastructural characterization of mitochondria‐rich cells as a response to variations in salinity in two types of teleostean pseudobranch: milkfish (Chanos chanos) and Mozambique tilapia (Oreochromis mossambicus)

The pseudobranchs of two euryhaline teleost species, the milkfish (Chanos chanos ) and the Mozambique tilapia (Oreochromis mossambicus ), were studied after acclimization to different salinities using optical and electron microscopy. The milkfish pseudobranch was the lamellae‐free type, with separate lamellae along the filaments containing two groups of mitochondria (Mt)‐rich cells: chloride cells (CCs) and pseudobranch type cells (PSCs). Conversely, the tilapia pseudobranch was the embedded type, covered with connective tissues and with only one group of Mt‐rich PSCs. Chloride cells were identified according to the apical openings and branched tubular networks around randomly distributed and diversely shaped Mt. Pseudobranchs type cells, however, were characterized according to the orderly arrangement of parallel tubules around closely packed Mt; both the tubules and the Mt were distributed in the vascular side of the cell, but were absent from the apical region. Compared with those of seawater (SW)‐acclimated milkfish, the pseudobranchial lamellae of freshwater (FW) specimens were longer on average, and the Mt of the CCs had fewer cristae, were less electron‐dense, and were often vacuolated. The Mt in the PSCs of FW‐acclimated milkfish and tilapia were larger and more electron‐dense than those of their SW‐acclimated counterparts; in addition, more tubules were found to aggregately surround the Mt and basolateral membranes in the PSCs of fish from the hypo‐osmotic environment. Conversely, the PSCs of tilapia were periodic acid‐Schiff (PAS)‐positive, and Mt in PSCs were concentrated with more parallel arrays of the tubule system than those of milkfish. Therefore, salinity‐dependent changes in the ultrastructures of PSCs suggest their potential role in energy metabolism of both lamellae‐free and embedded pseudobranchs, whereas the PAS‐positive staining characteristics suggest a role in releasing or storaging polysaccharides in the embedded pseudobranch. J. Morphol. 278:390–402, 2017. © 2017 Wiley Periodicals, Inc.     

Fine structure of the posterior salivary gland ofEledone cirrosa andOctopus vulgaris

Summary The posterior salivary gland of Octopods comprises a parenchyma of branching tubules in a connective tissue stroma. The tubules are lined by either of two distinct epithelia.Type A is composed predominantly of columnar cells containing large granules whose contents vary in appearance from cell to cell.Type B consists of three cell types: A circumferential layer of processes ofstriated cells containing radially orientated infoldings of the cellular membrane, between which are packed numerous mitochondria;cistern cells which contain an invaginated system of membrane loops, the interior of which is in communication with the lumen; andlumen lining cells. All these cells send processes to the basement membrane of the tubule, so that both epithelia are pseudostratified. The functional significance of this cytological specialisation is discussed.Thanks are due to Prof. J. Z. Young F. R. S. and Prof. E. G. Gray for helpful discussion and use of facilities during the course of this study, and to Prof. Young for the loan of the Cajal preparations. I also wish to thank Miss E. Franke for excellent technical assistance.     

Development of mouse mammary gland: identification of stages in differentiation of luminal and myoepithelial cells using monoclonal antibodies and polyvalent antiserum against keratin

The development of the mouse mammary gland was studied immunohistochemically using monoclonal antibodies against cell surface and basement membrane proteins and a polyclonal antibody against keratin. We have identified three basic cell types: basal, myoepithelial, and epithelial cells. The epithelial cells can be subdivided into three immunologically related cell types: luminal type I, luminal type II, and alveolar cells. These five cell types appear at different stages of mammary gland development and have either acquired or lost one of the antibody-defined antigens. The cytoplasmic distribution of several of these antigens varied according to the location of the cells within the mammary gland. Epithelial cells which did not line the lumen expressed antigens throughout the cytoplasm. These antigens were demonstrated on the apical site in situations where the cells lined the lumen. One antigen became increasingly basolateral as the cells became attached to the basement membrane. The basal cells synthesize laminin and deposit it at the cell base. They are present in endbuds and ducts and are probably the stem cells of the mammary gland. Transitional forms have been demonstrated which developmentally link these cells with both myoepithelial and (luminal) epithelial cells.