Evolutionary regularities of somatic polyploidy expansion in salivary glands of gastropod mollusks. V. Subclasses Opisthobranchia and Pulmonata

Salivary glands of 25 species of euthyneural gastropod mollusks (Opisthobranchia and Pulmonata) have been investigated by means of histochemical methods and DNA cytophotometry in nuclei of cells. The cells of three basic types are distinguished in glandular epithelim: granular cells (with glicoproteid granular inclusions), mucocytes-I (with sulfatic acid mucopolysaccharides) and mucocytes-II (with neutral and acid nonsulfatic polysaccharides and proteins) and so the epithelial ciliated cells and cells of the ducts. It was shown that glandular cells of salivary glands of all discovered mollusks' species are polyploid in different degree. The highest ploidy level estimated by means of DNA content in most of species is 64-128c. The giant polyploidy, attained to 4096c, is discovered in cells of salivary glands of Tritonia diomedea. The functional conditionality connected with features of feeding of different mollusk species and phylogenetic tendencies of expansion of somatic polyploidy in class Gastropoda are discussed. In comparison with allogenic, facultative and small polyploidy manifestation in Prosobranchia the obligatory polyploidization of high degree revealed in cells of salivary glands of Opisthobranchia and Pulmonata is consider to be the original cytological arogenesis. The probable causes of such differences are conneted with euthyneural type of organization of central nervous system and giant polyploidy of neurons in Opisthobranchia and Pulmonata mollusks. The causes, mechanisms and significance of such correlations are unclear for the present.     

Evolutionary regularities of somatic polyploidy in salivary glands of the Gastropod molluscs. II. Subclass Pectinibranchia: order Anisorbranchia

Salivary glands of 5 species of gastropod molluscs of the order Anisobranchia, the most ancient order within the subclass Pectinibranchia, have been investigated by histological and cytochemical methods, including DNA cytophotometry. Glandular cells of the following types were recognized: granular cells (with glycoproteid granular inclusions), mucocytes-I (including sulfatic acid mucopolysaccharides), mucocytes-II (including neutral and acid polysaccharides and proteins), and epithelial ciliated cells. All the described cell types are considered to be independent and their morphofunctional characteristics coincide with those of salivary gland cells of the gastropod molluscs of subclasses Cyclobranchia and Scutibranchia. It has been shown that somatic polyploidy in salivary glands in the Anisobranchia molluscs, likely as in those of other Archaeogastropoda (Cyclobranchia and Scutibranchia), is actually absent.     

The morphofunctional characterization and ploidy levels of the digestive gland cells in prosobranch gastropod mollusks (Prosobranchia: Gastropoda) with special reference to somatic polyploidy

The histological organization and ploidy levels of the digestive gland cells in 34 species of prosobranch gastropod mollusks that belong to the subclasses Patellogastropoda, Vetigastropoda, and Caenogastropoda (orders Littorinimorpha and Neogastropoda) were investigated using histochemical methods and cytophotometry of nuclear DNA. Two general types of differentiated cells, viz., digestive and basophilic (secretory-calcium), were identified in the epithelium of the digestive tubules. In Vetigastropoda and Neogastropoda species, all the cells are mostly diploid. In representatives of Patellogastropoda and Littorinimorpha, the digestive cells are diploid as well, but basophilic cells of many species reach polyploidy levels of 4–8c and in some species, even 4–8–16c. Cases of somatic polyploidy in basophilic cells are considered as adaptive modifications of histogenesis associated with the peculiarities of the environment (intensified metabolism in osmotically tolerant Littorina and Lottia species), the duration of ontogenesis (the short life cycle in Lacunida species), and a specific diet.     

Evolutionary regularities of the somatic polyploidy manifestation in salivary glands of gastropod molluscs. IV. A subclass of Pectinibranchia: Orders Hamiglossa and Toxoglossa (Neogastropoda)

Salivary glands of 12 species of carnivorous gastropod molluscs, making the Neogastropoda group have been investigated by histochemical methods and DNA cytophotometry. We studied the anatomical and histological structure of ordinary (acinous) and accessory (tubular) salivary glands, and of unpaired glands (Leiblen's, "framboisée", and poisonous). Cells of three types were distinguished: granular cells (with glycoproteid granular inclusions), mucocytes-I (with sulfatic acid mucopolysaccharides), and epithelial ciliated cells. In ordinary and accessory glands of the studied Neogastropods, polyploid cells with polyploidy levels from 4c to 16c were revealed together with diploid cells. The functional significance and phylogenetic tendencies of polyploidy manifestation in salivary glands of prosobranch gastropods are discussed.     

Morphofunctional characterization and ploidy levels of cells in the bivalve digestive gland, with special reference to somatic polyploidy

This study investigates the histological organization and ploidy levels of the digestive gland cells in 29 species of marine, brackish water, and freshwater bivalves belonging to 5 subclasses. In all species studied, the digestive gland epithelium consists of two types of differentiated cells: digestive and basophilic. The nuclei of digestive cells contain the diploid quantity of DNA. Basophilic (secretory) cells often remain diploid also; however, in a number of species all or some of the cells showed an increase in the quantity of DNA per nucleus up to 4c. Tetraploidy of basophilic cells in several species of the subclass Anomalodesmata seems to be due to carnivory. In other species, no apparent correlation was found between selective polyploidy of basophilic cells and environmental conditions or biology traits of the bivalves. Additionally, there was no relationship between the occurrence of polyploid cells and the lifespan of the investigated species. In the bivalve mollusks, somatic polyploidy appears to be an adaptation; it is neither a tissue growth strategy nor a component of the cytodifferentiation program.     

Evolutionary regularities of the appearance of polyploidy in salivary glands of gastropod mollusks. III. A subclass of Pectinibranchia: Orders Discopoda, Echinospirida, Aspidophora and Entomostoma (Mesogastropoda)

By means of histological methods and DNA cytophotometry, a study was made of the salivary glands of 16 species of gastropod molluscs belonging to the subclass Pectinibranchia and making a group of Mesogastropoda. Four cell types of salivary glands were distinguished: granular cells (with glycoproteid granular inclusions), mucocytes-I (with sulfatic acid mucopolysaccharides), mucocytes-II (with neutral and acid polysaccharides and proteins), and also the epithelial ciliated cells and mucous duct cells. Data of experiments on starvation and synchronous feeding of molluscs have testified that all described cell types are independent. In some species differentiation on protein and mucous departments within the glandular epithelium was shown. In some marine representatives of the orders Discopoda and Aspidophora polyploid cells with the ploidy levels from 8c to 32c were revealed along with diploid cells. The ecological and phylogenetic regularities of somatic polyploidy manifestation in Mesogastropoda are discussed.     

Evolutionary regularities of somatic polyploidy manifestation in salivary glands of gastropod molluscs. I. Subclasses Cyclobranchia and Scutibranchia

By means of histological and cytochemical methods, including DNA cytophotometry, the salivary glands of 11 species of molluscs of two old gastropod subclasses--Cyclobranchia and Scutibranchia (limpets)--have been investigated. In spite of some anatomical differences, the glandular epithelium of investigated molluscs includes functionally similar cell types: granular cells (with glycoproteid granular inclusions), mucocytes-I (that include sulfatic acid mucopolysaccharides), mucocytes-II (that include neutral and acid polysaccharides and proteins) and also the epithelial ciliated cells. Data of experiments on starvation and synchronous feeding of molluscs testify that all described cell types are independent. According to DNA cytophotometry data, the glandular cell nuclei are diploid in the main; only small part of the nuclei, varying in different species from 0.5 to 5.0%, displayed tetraploid DNA mass. A conclusion is made that in the oldest subclasses of gastropods (Cyclobranchia and Scutibranchia) somatic polyploidy, as a factor of tissue growth in salivary glands, is actually absent.     

A correlated light and electron microscopic study of the structure and secretory activity of the accessory salivary glands of the marine gastropods,Conus flavidus and C. vexillum (neogastropoda,conacea)

The structure and secretory activity of the accessory salivary gland in two species of Conus were examined using routine and histochemical techniques of light, scanning and transmission electron microscopy. The composite layers of the accessory salivary gland of Conus are a luminal epithelium, fibromuscular layer, submuscular layer, and a capsule. In C. flavidus and C. vexillum, the luminal epithelium is formed by epitheliocytes and cytoplasmic processes extending from the secretory cells, whose perikarya form the submuscular layer. The processes carry secretory cell products (chiefly Golgi-derived glycoprotein) across the fibromuscular layer and terminate between epitheliocytes (at the bases of the secretory canaliculi) or beyond the surface of the epithelial cells. Conus vexillum is distinguished from C. flavidus by its high content of lipofuscin. Epitheliocytes are the only microvillated cells in the accessory salivary gland of Conus. In C. flavidus, epitheliocytes extrude secretory granules, various types of cytoplasmic blebs and clear vesicles by apocrine “pinching off”. Clear vesicles are shed from the tips of microvilli. The luminal epithelial cells of C. vexillum similarly egest clear vesicles, but normally undergo additional holocrine secretion to release lipofuscin. The secretions of epitheliocytes appear to be major products of the accessory salivary gland: consideration of secretory activities by both epitheliocytes and secretory cells will therefore be necessary when directly investigating accessory salivary gland function in Conus.     

Ultrastructure of the Juxtaganglionar Organ,a Putative Endocrine Gland Associated with the Cerebral Ganglia of Aplysia juliana

Summary

Electron microscopy was used to examine the morphology of a putative endocrine gland, the juxtaganglionar organ (JO), and its relation to the cerebral ganglia of the hermaphroditic opisthobranch gastropod Aplysia juliana. The JO is a well-vascularized, poorly innervated tissue of glandular cells—rich in mitochondria, lipids, ribosomes, and endoplasmic reticulum, with sparse cilia and membrane-limited secretory granules—within the connective tissue sheath just exterior to the neuronal soma in the dorsal and posterior portions of the cerebral ganglia. The cytology and organization of the JO supports its homology to the dorsal bodies of pulmonate gastropods, which axe endocrine organs known to release one or more female gonadotropic factors.     

B-Chromosomen beiChironomus

In the population “Herrenmühle” ofChironomus plumosus 11% of the individuals contain one supernumerary chromosome. This B-chromosome is present both in germ-line and somatic cells. — InChironomus melanotus 6% of the larvae of the population “Falkau” carry supernumerary chromosomes. These B-chromosomes cannot be found in all nuclei of testis and soma, their number varies between cells within the individual. In both species the B-chromosomes represent centromeric fragments of chromosome IV as can be shown by their structure and pairing behaviour. — The polytene B-chromosome ofCh. plumosus exhibits a banding pattern in the salivary gland nuclei. Furthermore it is able to form an additional nucleolus in the nuclei of the malpighian tubules. InCh. melanotus band structures can be seen only in the B-chromosome of malpighian tubules. The larvae ofCh. melanotus, carrying B-chromosomes, show heterochromatic bodies in the salivary gland nuclei, varying in number and size in the nuclei of the same gland. These bodies are interpreted to be polytenic B-chromosomes divided into subunits.

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Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Immunohistochemical localization of S100A1 and S100A6 in postnatally developing salivary glands of rats

 S100 proteins are calcium-binding proteins of the EF-hand superfamily and are involved in the regulation of a number of cellular processes. The present study deals with the immunohistochemical expression of S100A1 and S100A6 in the rat submandibular and sublingual glands during postnatal development from day 0 to 12 weeks. Expression of S100A1 was particularly concentrated in pillar and transition cells in the granular convoluted tubule (GCT) and in striated duct cells of the submandibular gland age 4 weeks to maturity. None or only weak staining for S100A1 was observed in the duct segment at 0–5 days. On the contrary, immunostaining of S100A6 was present in proacinar cells in undifferentiated submandibular gland at age 3 days to 2 weeks. S100A6 immunoreactivity in rat submandibular gland coexisted with chromogranin reactivity. It is possible that S100A6 regulates secretion of chromogranin in proacinar cells. Secretion of growth factors and biologically active peptides in the GCT are regulated by calcium signals, and S100A1 may be involved in the secretory mechanism of granular cells. S100A1 and S100A6 are potentially of great importance in secretory functions of granular cells and proacinar cells, as well as in rat salivary glands. Accepted: 14 July 1998     

Dextral and sinistral <Emphasis Type="Italic">Amphidromus inversus</Emphasis> (Gastropoda: Pulmonata: Camaenidae) produce dextral sperm

Coiling direction in pulmonate gastropods is determined by a single gene via a maternal effect, which causes cytoskeletal dynamics in the early embryo of dextral gastropods to be the mirror image of the same in sinistral ones. We note that pulmonate gastropod spermatids also go through a helical twisting during their maturation. Moreover, we suspect that the coiling direction of the helical elements of the spermatozoa may affect their behaviour in the female reproductive tract, giving rise to the possibility that sperm chirality plays a role in the maintenance of whole-body chiral dimorphism in the tropical arboreal gastropod Amphidromus inversus (Müller, 1774). For these reasons, we investigated whether there is a relationship between a gastropod’s body chirality and the chirality of the spermatozoa it produces. We found that spermatozoa in A. inversus are always dextrally coiled, regardless of the coiling direction of the animal itself. However, a partial review of the literature on sperm morphology in the Pulmonata revealed that chiral dimorphism does exist in certain species, apparently without any relationship with the coiling direction of the body. Though our study shows that body and sperm chirality follows independent developmental pathways, it gives rise to several questions that may be relevant to the understanding of the chirality of spermatid ultrastructure and spermatozoan motility and sexual selection.     

Serotonergic cerebral cells control activity of cilia in the foregut of the pteropod mollusk <Emphasis Type="Italic">Clione limacina</Emphasis>

Bilaterally symmetrical pair of serotonergic cells, named C1 in Clione, has been described in the cerebral ganglia of all gastropod species. Here we describe a new role of C1 cells in gastropod mollusks: control of activity of ciliated epithelium in the foregut. Detailed morphological investigation of C1 neurons in the pteropod mollusk Clione limacina revealed that these cells among other destinations send their neurites into foregut where they produce intense arborization with large varicosities along the processes. Intracellular stimulation of a single C1 induced pronounced activation (often followed by inhibition) of cilia lining the foregut. This activation was substantially reduced by serotonin antagonist mianserin. Bath application of serotonin also induced transient increase in ciliary transport rate, followed by inhibition of ciliary activity up to its full cessation in some areas of isolated foregut. These data suggest that C1 in Clione may use serotonin to influence cilia in the foregut. Taking into account high homology of serotonergic cerebral cells across studied species we can speculate that these cells may be involved in the neural control of cilia in the foregut in other gastropod mollusks.     

Light and electron microscopy study of the salivary glands of the carnivorous opisthobranch Philinopsis depicta (Mollusca, Gastropoda)

Cephalaspideans are a group of opisthobranch gastropods that comprises carnivorous and herbivorous species, allowing an investigation of the relationship between these diets and the morphofunctional features of the salivary glands. In this study, the salivary glands of the carnivorous cephalaspidean Philinopsis depicta were observed by light and electron microscopy. The secretory epithelium of these ribbon-shaped glands is formed by ciliated cells, granular cells and cells with apical vacuole. In ciliated cells the nucleus and most cytoplasmic organelles are located in the wider apical region and a very thin stalk reaches the base of the epithelium. These cells possess significant amounts of glycogen. Granular cells are packed with electron-dense secretory granules and also contain several cisternae of rough endoplasmic reticulum and Golgi stacks. The other type of secretory cell is mainly characterized by the presence of a large apical vacuole containing secretion. These cells possess high amounts of rough endoplasmic reticulum cisternae and several Golgi stacks. Vesicles with peripheral electron-dense material are also abundant, and seem to fuse to form the apical vacuole. The available data point out to a significant difference between the salivary glands of carnivorous and herbivorous cephalaspidean opisthobranchs, with an intensification of protein secretion in carnivorous species.     

Localization of some enzymes in the main venom glands of viperid snakes

Several secretory and nonsecretory enzymes were localized histochemically in the main venom gland of 13 viperid snakes. All secretory cells show the intracellular oxidative enzymes succinate dehydrogenase and monoamine oxidase. The granular reactions obtained for both enzymes resemble mitochondria in distribution. Distinctive cells with a very high succinate dehydrogenase activity are dispersed among the secretory cells of all species except Atractaspis. Nonspecific acid phosphatase activity is found in the supranuclear region of the secretory cells in species that do not secrete this enzyme and throughout the cytoplasm in snakes that secrete the enzyme. Nonspecific alkaline phosphatase activity occurs in the secretory cells of those snakes whose venom shows this activity. Leucine amino peptidase (aryl amidase) activity is found in the venom and in the secretory cells of all the species. In Vipera palaestinae both the venom and the secretory cells of the main venom gland contain nonspecific esterase, L-amino acid oxidase and phosphodiesterase activities. The localization of phosphodiesterase and L-amino acid oxidase do not show major differences between glands at different intervals from an initial milking. Adenosine-monophosphate phosphatase activity is localized in the supranuclear region of the secretory cells in the glands of Vipera palaestinae and Aspis cerastes. Its activity is found in the venom of Aspis only.     

四川短尾唾液腺的组织学观察

利用生物显微技术观察和研究了四川短尾鼩(Anourosorex squamipes)唾液腺的组织结构。结果表明,腮腺属纯浆液腺,有闰管和分泌管,无颗粒曲管;颌下腺属混合腺,以混合性腺泡为主,有少量浆液性腺泡和黏液性腺泡,有闰管、颗粒曲管和分泌管;舌下腺属纯黏液腺,有闰管和分泌管,无颗粒曲管,但在分泌管上存在有颗粒曲管细胞。     

Development of secretory units of mouse submandibular gland

Summary The fine structure of the secretory units of the mouse submandibular gland was studied according to the developmental sequence. The embryonic submandibular gland consists of terminal tubules and ducts. Myoepithelium is associated only with the terminal tubules, and the cells of the primary intercalated ducts show characteristics of the young striated duct cells. The major changes shortly after birth consist of: 1) opening of the secretory lumina, 2) increasing rough ER and its altered configuration, 3) dilatation of Golgi cisternae and 4) changes in the granular structure. These findings suggest that the salivary secretion first occurs after birth, and acinar differentiation or transformation of the secretory cells of the terminal tubules is induced and profoundly affected by the commencement of the secretory activity. In the intercalated ducts this process is somehow inhibited, and the granular cells found in the adult can be considered as the remnants of the secretory cells of the terminal tubules.     

Morphological changes in the cephalic salivary glands of females and males of <Emphasis Type="Italic">Apis mellifera</Emphasis> and <Emphasis Type="Italic">Scaptotrigona postica</Emphasis> (Hymenoptera,Apidae)

The cephalic salivary glands of some species of bees are exclusive and well developed only in Apinae. These glands were studied with light and scanning electron microscopy in workers, queens and males from the honey bee Apis mellifera, and the stingless bee Scaptotrigona postica in different life phases. The results show that the cephalic salivary glands are present in females of both the species, and in males of S. postica. Nevertheless, they are poorly developed in young males of A. mellifera. In both species, gland growth is progressive from the time of emergence to the oldest age but, in A. mellifera males, the gland degenerates with age. Scanning electron microscopy shows that the secretory units of newly emerged workers are collapsed while in older workers they are turgid. Some pits on the surface of the secretory units correspond to open intercellular spaces. The possible functions of these glands in females and males of both species are discussed.     

Histology and ultrastructure of the salivary glands in Bulla striata (Mollusca, Opisthobranchia)

Abstract. The ribbon‐shaped salivary glands in Bulla striata were studied with light microscopy and transmission electron microscopy (TEM). Secretion is produced in tubules formed by two types of secretory cells, namely granular mucocytes and vacuolated cells, intercalated with ciliated cells. A central longitudinal duct lined by the same cell types collects the secretion and conducts it to the buccal cavity. In granular mucocytes, the nucleus is usually central and the secretory vesicles contain oval‐shaped granular masses attached to the vesicle membrane. Glycogen granules can be very abundant, filling the space around the secretory vesicles. These cells are strongly stained by PAS reaction for polysaccharides. Their secretory vesicles are also stained by Alcian blue, revealing acidic mucopolysaccharides, and the tetrazonium reaction detects proteins in minute spots at the edge of the vesicles, corresponding to the granular masses observed in TEM. Colloidal iron staining for acidic mucopolysaccharides in TEM reveals iron particles in the electron‐lucent region of the vesicles, while the granular masses are free of particles. In vacuolated cells, which are thinner and less abundant than the granular mucocytes, the nucleus is basal and the cytoplasm contains large electron‐lucent vesicles. These vesicles are very weakly colored by light microscopy techniques, but colloidal iron particles could be observed within them. The golf tee‐shaped ciliated cells contain some electron‐dense lysosomes in the apical region. In these cells, the elongated nucleus is subapically located, and bundles of microfibrils are common in the slender cytoplasmic stalk that reaches the basal lamina. The morphological, histochemical, and cytochemical data showed some similarities between salivary glands in B. striata and Aplysia depilans. These similarities could reflect the phylogenetic relationship between cephalaspidean and anaspidean opisthobranchs or result from a convergent adaptation to an identical herbivorous diet.     

Dispersed donor salivary gland cells are widely distributed in the recipient gland when infused up the ductal tree

Abstract

The salivary glands often are severely and permanently damaged by therapeutic irradiation for cancer of the head and neck. The markedly reduced quantity and quality of saliva results in greatly increased susceptibility to dental caries and infection of the oral mucosa and alveolar bone. Recently, subcapsular injection of cultured mouse salivary gland cells has achieved a significant degree of regeneration in a previously irradiated mouse salivary gland; however, the recovery was limited to one lobule. We describe here a method for delivering donor rat salivary gland cells via the main duct that distributes several thousand cells throughout the recipient rat's salivary gland. The donated cells exhibited the cytodifferentiation of the structures in which they lodged, i.e., acini, granular convoluted tubules, and the several types of ducts. This method may facilitate the simultaneous functional recovery of almost all of the lobules of irradiated rat salivary glands.