Cell cycles in the male accessory glands of mealworm pupae

During the pupal stage of Tenebrio molitor, the accessory reproductive glands of males grow by cell division. Within the secretory epithelium of the bean-shaped accessory glands (BAGs), cell numbers triple. In the tubular accessory glands (TAGs), the increase is 14-fold. There are two mitotic maxima in each gland. The first maximum occurs at 1-2 days while the second is at 4-5 days. The second maximum coincides with the major ecdysteroid peak described by Delbecque et al. [Dev. Biol. 64, 11-30 (1978)]. Nuclei were isolated from TAGs during the pupal mitotic bouts and during mitotic inactivity in the adult. After Feulgen or propidium iodide staining, the DNA content of these nuclear populations was measured by absorption cytophotometry or by fluorescence flow cytometry, respectively. The proportion of cells in each phase of the cycle was calculated using an iterative model. After mitoses have ended in the late pupa, the cells were arrested in G2. [3H]Thymidine was injected into 1- and 4-day pupae to pulse-label cells of the TAGs. After allowing various periods from 4 to 60 hr for cells to progress through G2 to reach mitosis, fractions of labelled mitoses were determined by autoradiography. From the combined cytometric and autoradiographic data, the duration of each phase of the cell cycle was calculated assuming the population was in exponential growth. Cell cycles in 4-day pupal TAGs take 48 hr. G1, S, G2, and, M lasted 13, 14, 17, and 4 hr, respectively.     

Cytodifferentiation in the accessory glands of Tenebrio molitor. X. Ultrastructure of the tubular gland in the male pupa

The tubular accessory gland consists of a simple secretory epithelium surrounded by a muscular coat. Over the pupal instar, the gland increases ten-fold in volume and 15-fold in length. Pupal development is divisible into a phase of mitosis and one of cell growth. During the mitotic phase, cytoplasmic membranes are sparse and nuclei move toward the luminal face of the epithelium to undergo division. In the cell growth phase, the cells become more columnar, a few stacks of rough endoplasmic reticulum are formed, and small dense secretory vesicles appear near the apical surface. The hormonal control of the developmental sequence is discussed.     

Cytodifferentiation in the accessory glands of Tenebrio molitor. XI. Transitional cell types during establishment of pattern

The bean-shaped accessory glands of male Tenebrio consist of a single-layered epithelium which is surrounded by a muscular coat. The epithelial layer, which produces precursors of the wall of the spermatophore, contains eight secretory cell types. Each secretory cell type is in one or more homogenous patches, and discharges granules which form one layer of the eight-layered secretory plug. Maturation begins in cell types 4, 7, and 6 on the last pupal day. A newly identified cell (type 8) in the posterolateral epithelium matures last. Cells of individual types mature in synchrony, and their secretory granules “ripen” in a sequence that is characteristic for each type. As the secretory cells of each patch mature, unusual short-lived cells appear at interfaces between patches. In some cases the secretory granules in these boundary cells have ultrastructural features which are mixtures of the definitive characteristics of granules in adjacent cell types. The transitional cell types disappear at 3–4 days after eclosion. Intermediate cell types are absent in the mature gland and boundaries between the patches are distinct. The transitional cells may form granules of intermediate structural characteristics as a dual response to cellular interaction with adjacent and previously differentiated secretory cells.     

Cytodifferentiation in the accessory glands of Tenebrio molitor I. Ultrastructure of the tubular gland in the post-ecdysial adult male

The tubular accessory reproductive glands of the male mealworm beetle consist of a secretory epithelium surrounded by a thin muscular sheath. Each columnar secretory cell is divisible into three zones: basal which is adjacent to the muscle layer and contains rough endoplasmic reticulum and Golgi, intermediate, which contains endoplasmic reticulum and Golgi zones in the immature gland and is filled with secretory vesicles in the mature gland, and apical. Maturation also involves proliferation and organization of the rough endoplasmic reticulum in the basal and intermediate zone. The process appears to be complete at four days after ecdysis. Parallels with other insect glands and with the mammalian prostate are striking.     

The development of the female accessory gland in the insect Rhodnius prolixus

The specialized cell types and two distinct regions of the adult Rhodnius prolixus cement gland develop from a simple pseudostratified epithelial tube during the 20–22 days of the fifth stadium. Feeding initiates the first phase, proliferation. Cells round up and divide tangentially to the lumen. Following the proliferation phase, differentiative mitoses occur and differentiation, resulting in secretory units (consisting of a ductule, gland cell and cuticular lining), ensues in the distal region. Ductule morphogenesis occurs without pseudocilia, thus differing from other insect glands. The complex changes in cell shape and interaction occur during development of the secretory unit. The secretory cell and end-apparatus develop from a double cell unit at the base of elongating ductules. The inner cell produces a complex end-apparatus of epicuticle that mirrors the microvillar pattern and then it degenerates. The ductules are lined by cuticulin and inner epicuticle while the central gland lumen has a layer of endocuticle as well. The epithelium of the proximal region remains simple producing the thick corrugated cuticle characteristic of the adult secretory duct. The mesodermal covering forms a thick longitudinal striated muscle layer that adheres to the epithelium via desmosomes.     

Cell type-specific gene expression in the Drosophila melanogaster male accessory gland.

The accessory gland of the male Drosophila melanogaster plays a vital role in reproduction. This secretory organ synthesizes products that are transferred to the female and are necessary to elicit the proper physiological and behavioral responses in the female. The accessory gland is composed of two morphologically distinct secretory cell types, the main cells and the secondary cells. Previous studies identified some genes expressed in main cells or in all accessory gland cells. In this paper we use P-element mediated enhancer traps to examine gene expression in the accessory gland. We show that, in addition to genes expressed in main cells only or in all accessory gland secretory cells, there are genes expressed specifically in secondary cells. Each cell type is uniform in the expression of its genes. Our results demonstrate that the two cell types are not only morphologically distinct but also biochemically distinct. We also show that the two cell types differ in their regulation of gene expression in response to mating activity.     

Fine structure of the spermatheca and of the accessory glands in Orchesella villosa (Collembola, Hexapoda)

The spermatheca and the accessory glands of the collembolan Orchesella villosa are described for the first time. Both organs exhibit ultrastructural differences, according to the time of the intermolt in which the specimens were observed. A thick cuticular layer lines the epithelial cells of the accessory glands. In the reproductive phase, they are involved in secretory activity; a moderately dense secretion found in the apical cell region opens into the gland lumen. Cells with an extracellular cistern are intermingled with the secretory cells. These cells could be involved in fluid secretion, with the secretory product opening into the cistern which is filled with an electron-transparent material. After the reproductive phase, the gland lumen becomes filled with a dense secretion. The accessory gland secretion may play a protective role towards the eggs. The spermatheca is located between the accessory glands; its epithelium is lined by a thin cuticle forming spine-like projections into the lumen and consists of cells provided with an extracellular cistern. Secretory cells, similar to those seen in the accessory glands, are missing. Cells with a cistern could be involved in the production of a fluid secretion determining sperm unrolling and sperm motility.     

Trehalase from the bean-shaped accessory glands and the spermatophore of the male mealworm beetle,Tenebrio molitor

Summary InTenebrio molitor, male adults transfer sperm to the female via a spermatophore or sperm sac. The spermatophore is formed from secretions of the bean-shaped accessory glands (BAGs) and the tubular accessory glands (TAGs) of the male beetle. Trehalase is found in the adult BAGs. During the pupal stage, the activity in the BAGs was very low. After adult ecdysis, the total activity increased 100-fold from 0 days to 6 days and reached maximum levels at 9 days. The specific activity increased 20-fold from the time of ecdysis to 6 days thereafter. In the 10 day adult, trehalase levels in testes, seminal vesicles, vas deferens, TAGs, or ejaculatory ducts, were lower by two orders of magnitude than in the BAGs. However, the specific activity in the spermatophore was similar to that in the BAGs. Trehalases in the BAGs and the spermatophores showed very similar properties (soluble, optimum pH of 5.75 andK _m value of 5.4 mM for trehalose). Thus trehalase appears to be secreted from the BAGs and becomes incorporated into the spermatophores.Abbreviations BAG bean-shaped accessory gland - TAG tubular accessory gland     

Little-known accessory glands in female Zygaena moths (Lepidoptera, Zygaenidae)

In the female genital system of Zygaena moths, an additional pair of accessory glands is present besides the Y-shaped sebaceous gland. The term 'Petersen's glands' is proposed for these organs. Anatomy, histology, histochemistry and cytology of Petersen's glands of Zygaena trifolii are described. The sac-like glands, situated in the extreme dorsocaudal part of the abdomen, can be divided into a purely secretory part consisting of acini with large pear-shaped gland cells and a reservoir part with combined secretory and storage function. The secretory cells of the acini are penetrated by long curved ductules or secretory end apparatuses having feltwork consisting of very fine filaments. The cytoplasm is characterized by abundance of smooth tubular endoplasmic reticulum (ATER) and the presence of peroxisomes. This cytoplasmic organization is in accordance with the chemical composition of the sticky secretion, which evidently consists completely of lipids. The ultrastructure of the epithelium lining the reservoir of the glands has both traits of secretory and of transporting epithelia. Besides contributing to the secretion, it may be involved in absorption of residual aqueous phase from the contents of the reservoir.     

Ultrastructure and nature of secretory proteins in the male accessory gland of Drosophila funebris

The ultrastructural differentiation of the secretory cells and the nature of secretory proteins in the male accessory gland of Drosophila funebris have been studied by electron-microscopic and immunological methods. (1) In the pupae at $\text{1}\text{1}\text{2}$ days before eclosion, secretory products can be detected in the lumen, even though most glandular cells are at the initial phase of differentiation. At the time of eclosion both main and secondary cells are fully differentiated, but the whole set of five immunologically active proteins are detectable only on the second to third day of adult life. (2) The secondary cells contain giant protein granules, the so-called filamentous bodies, which become partially fused and the filaments assume a twisted form. Randomly dispersed filaments and closely packed filament bundles are also visible in the gland lumen. Antigenic labelling of ultrathin sections and immunoreplica electrophoresis yielded no evidence for the microtubular nature of these filaments. The secretion stored in the lumen contains in addition a large quantity of flocculent proteins which have their origin in the main cells. (3) During the period of high secretory activity in the 7-day-old male flies no vacuolization and disintegration of either the main or secondary cells have been observed. We conclude that both types of cells have the merocrine secretory mechanism. (4) Ultrastructural alterations in the glandular cells confirmed our previous observation that copulation stimulates RNA and protein synthesis.     

Cellular Differentiation in a Highly Specialized Insect Secretory Organ

The colleterial glands of insects are accessory reproductive structures which produce secretions that are applied to eggs after fertilization and which serve a number of protective functions. The colleterial glands of lepidoptera are of particular interest in the study of the events of cellular differentiation because they undergo rapid development, generally during the pupal adult transformation, and contain highly specialized cells which produce large amounts of a restricted variety of secretory products. The extreme specialization of these organs facilitates parallel studies of differentiation at the biochemical and morphological level. This communication describes the changes in the ultrastructure of cells which will form the protein-secreting segment of the colleterial gland of the moth Actias luna during the period of transition from the undifferentiated state to the acquisition of secretory ability.
An initial stage of general cellular proliferation by mitosis in the presumptive colleterial tissue mass is followed by differentiation of the cells in the absence of further mitosis. Four distinctive cell types are recognized during the phase of differentiation. These types include a chitogenous cell which forms the chitin lining of the main duct, and three cells which cooperate in the formation of a secretory apparatus. Cell A forms two temporary flagella-like structures which assist in the formation of a ductule, which eventually leads from the secretory cell to the main duct. Near the end of the differentiative phase, Cell A degenerates and is phagocitized by Cell B. Cell B becomes the actual secretory element, and acquires cytoplasmic features such as extensive rough endoplasmic reticulum and Golgi apparatus which are associated with synthesis and secretion of protein. The final element, Cell C, remains associated with the ductule which it helps to construct and which traverses its cytoplasm.     

The ultrastructure of the female accessory gland,the cement gland,in the insect Rhodnius prolixus

The cement gland of Rhodnius prolixus is an epidermally derived tubular gland consisting of a distal synthetic region and a proximal muscular duct region. The synthetic region consists of numerous secretory units joined to a central chitinous duct via cuticular ductules. Proteinaceous secretion, synthesized by the goblet-shaped secretory cell, passes through the delicate cuticular lattice of a ductule-end apparatus and out through fine ductules to the central duct. Secretory cells are rich in rough endoplasmic reticulum and mitochondria. Light microscopy, SEM and TEM reveal the delicate lattice-like end apparatus structure, its formation and relationship to the secretory cell. The secretory cell associates via septate junctions with a tubular ductule cell that encloses a cuticle-lined ductule by forming an elaborate septate junction with itself. The ductules are continuous with the cuticle lining of the large central duct that conveys secretion to the proximal area. The proximal muscular duct has a corrugated cuticular lining, a thin epithelium rich in microtubules and thick longitudinal, striated muscles which contract during oviposition, forcing the secretion out. Histochemistry and electrophoresis reveal the secretion as proteinaceous.     

Fine structure of the male accessory glands in Aedes triseriatus

The paired accessory glands of the male mosquito, Aedes triseriatus, consisted of a single layer of columnar epithelial cells enclosed by a richly-nucleated circular muscle layer. Each accessory gland is divided into an anterior gland (AG) with one type of secretory cell, and a posterior gland (PG) with two types. The cells of the AG and those of the anterior region of the PG showed macroapocrine secretion. The mucus secreting cells located at the posterior region of the PG, however, released their contents into the lumen of the gland by rupturing the apical membrane of the cell. The secretion from all cells was in the form of membrane-bound granules which had distinct electron-dense and electron-lucent areas.     

Development of the prepupal Verson's gland of the tobacco hornworm, Manduca sexta, and its hormonal control

The segmentally arranged Verson's glands are epidermal derivatives comprised of three cells: the duct, saccule, and secretory cells. The development of these glands was followed through the 5th instar and larval-pupal transition of Manduca sexta. The glands are relatively small during the feeding stage, begin to grow at wandering, and undergo about a 50-fold increase in size during the prepupal period. The increase in size is due mainly to the hypertrophy of the secretory cell which synthesizes a heterogeneous set of proteinaceous secretory products. Three prominent 11 to 12 kiloDalton (kD) polypeptides are made by the pharate fifth larval gland, whereas the pupal gland produces polypeptides ranging from 14 to 75 kD with a major complex at 30 to 34 kD. The secretory product is poured out onto the surface of the new cuticle at the time of ecdysis and contains all of the major proteins detected in extracts of the whole gland. The accumulation of secretory products by the gland occurs during the prepupal peak of ecdysteroid and is blocked if this rise is prevented by abdominal isolation. Infusion of 30 micrograms 20-hydroxyecdysone (20-HE) into such isolated abdomens caused synthesis of the pupal products. Treatment with the juvenile hormone mimic, methoprene, during the fifth instar showed that the commitment of the glands to produce the pupal proteins is independent of and occurs before the overlying epidermis becomes committed to make pupal cuticle.     

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 tubular accessory gland in Haemaphysalis longicornis (Acari: Ixodidae)

The paired tubular accessory glands in Haemaphysalis longicornis open at the junction of the cervical and the vestibular parts of vagina via short and narrow ducts. The pseudostratified columnar glandular epithelium covered by the muscle layer consists of both secretory and supporting cells. As feeding proceeds, the secretory cells increase in volume. In ovipositing females, well-developed rough endoplasmic reticulum, the Golgi complex, and membranebound granules that are undergoing exocytosis suggest that the secretory cells are involved in protein synthesis. However, in virgin females that fed 10 days, only small dense granules and no secretion activity were observed. The secretions from the tubular accessory gland may be released into the genital tract during the egg passage through the vagina. However, the supporting cells located between the secretory cells become slender during feeding, cohere to each other at the luminal side, and have a very narrow attachment at the basement membrane. Supporting cells probably help maintain secretory cell shape especially during granular discharge into the lumen. © 1994 Wiley-Liss, Inc.     

Fine structure and histochemistry of the spermathecal gland in the mealworm beetle, Tenebrio Molitor

The spermathecal accessory gland of female Tenebrio molitor is examined by histochemicai and electron microscopical techniques. Immediately after ecdysis of the female, neither Golgi regions nor the endoplasmic reticulum of the secretory cells are well developed. In two days' time, the cytoplasm is rich in rough endoplasmic reticulum and the Golgi areas are expanded. Membrane-bound droplets of secretion move from the Golgi zone to a central cavity, formed by the invaginated plasma membrane of this cell. As the secretion accumulates this cavity swells until the fourth day after ecdysis when the females first mate. An efferent cuticular ductule, ensheathed in a ductulecarrying cell, carries the product to the main axial duct of the tubular gland. By histochemical criteria, the product is a glycoprotein.     

Development of the accessory reproductive glands and genital ducts in female Schistocerca gregaria

The accessory reproductive glands of female S. gregaria are tubular extensions of the paired genital ducts, which in the mature female contain large amounts of a proteinaceous secretion used in the formation of the egg pod. In the 4th and 5th-instar female the glands are indistinguishable from the remainder of the mesodermally derived genital ducts. Towards the end of the 5th stadium, however, the accessory gland region only acquires characteristic convolutions which persist throughout the adult stages. At this time the epithelium of the entire ducts becomes reorganized into a unicellular epithelium. Only one cell type occurs throughout the length of the glands, and also in the egg calyces and lateral oviducts. The cells are inactive immediately after final ecdysis and remain in this state until the level of juvenile hormone in the haemolymph rises. The hormone acts directly on the cells triggering a rapid proliferation of organelles associated with protein secretion, and thereby increasing the volume of apical cytoplasm. Microvilli develop at the luminar plasma membrane, while irregular infoldings form at the base of the cells. As the gland matures the major organelle, the rough endoplasmic reticulum, changes from the lamellar to the vesicular form. Secretion is released into the lumen by the ‘microapocrine’ method.     

Developmental Changes in the Bombyxin-and Insulin-like Immunoreactive Neurosecretory System in the Wax Moth, Galleria mellonella

Four medial neurosecretory cells (MNC) and 4 lateral neurosecretory cells (LNC) in each brain hemisphere, and one pair of cells in each thoracic ganglion (TG) of Galleria larva react with antibodies against bombyxin and insulin. Material secreted from the MNC and LNC is released mainly in the corpora allata, and that from the TG through the ventral median nerves. Intrinsic secretory cells of the corpora cardiaca (CC) also contain bombyxin-like, but not insulin-like material. The immunoreactivities all disappear during molts and reappear with resumption of feeding. In the MNC and TG they reappear for less than a day, but in cells of the CC immunoreactivity reappears for the whole feeding period. Before pupation, the LNC become temporarily immunopositive towards the end of feeding period, and the MNC and TG during the wandering period, i.e. at the time of prothoracic gland stimulation. Immunoreactivity disappears during the pupal molt. In pupae it is present in the 4 pairs of MNC and 1–2 pairs of LNC 12–48 hr after ecdysis, and in cells of the CC from 12 hr after ecdysis until the end of the pupal instar. In adult, immunoreactivity is restricted to 2 pairs of the LNC and to CC cells.     

Ecdysteroids accelerate mitoses in accessory glands of beetle pupae

During the 9-day pupal period of Tenebrio molitor (the mealworm beetle), the cells of the male accessory glands undergo divisions for 7 days. There are two maxima in the mitotic activity in the glands in vivo, one at 1 day and the other at 4 days. The latter peak coincides with the large surge of ecdysterone occurring in the pupal stage. By the use of in vitro culture techniques, it has been demonstrated that the first bout of mitosis in both glands proceeds in basal medium, while the second bout of mitosis requires a physiological level of ecdysterone. Ecdysone was less effective than ecdysterone. Sensitivity to ecdysterone did not change significantly between Day 1 and Day 4 of the pupal stage. The results are discussed in relation to the effects of ecdysterone on cell division in mesodermal and ectodermal derivatives.