The role of Dufour's gland secretions in bees

ABSTRACT. Dufour's gland of bees is often hypertrophied and an extremely rich source of diverse natural products. In the ground-dwelling bees the secretion is mostly used for lining the brood cell with a hydrophobic lining. Whereas in several species the secretion is smeared on the cell walls without any modification, in others the hydrophobic lining is formed only after a chemical transformation of the secretion. The diversity of the chemical means by which hydrophobicity of the brood cells is achieved suggests that it has evolved repeatedly in the bees. In addition to lining their brood cells, several species use Dufour's gland secretion to mark their nest entrance. Analyses of single glands from various species reveal that each bee possesses its own individual composition, expressed in specific relative amounts of each component. Interestingly in the social halictid Evylaeus malachurum , nestmates (considered as sisters) are more similar to each other than non-related bees. The possible functional evolution of the glandular exudate from structural functions to communication and its implications for our understanding of eusociality in bees, is discussed.     

The chemical chaperone sodium 4-phenylbutyrate improves the secretion of the protein C<Subscript>A267T</Subscript> mutant in CHO-K1 cells trough the GRASP55 pathway

Some inherited coagulation factor deficiencies are caused by intracellular retention or degradation of misfolded proteins, and chemical chaperones have been shown to reverse protein misfolding. The purpose of the present study was to investigate whether chemical chaperones may improve secretion of the protein C_A267T (PC_A267T) mutant in a cellular model. Using stably transfected Chinese hamster ovary cells (CHO-K1) expressing PC_A267T we demonstrate that sodium 4-phenylbutyrate (PBA) increased the secretion of PC_A267T by approximately 4-fold in comparison with untreated cells, and that this secretion seemed to follow an unconventional pathway via the Golgi reassembly stacking protein (GRASP55).     

The nonclassic secretion of thioredoxin is not sensitive to redox state

Thioredoxin (Trx) is a cytosolic, redox-active protein that is secreted from many cells and has several extracellular functions. In activated lymphocytes, the pathway of secretion does not involve the Golgi apparatus. Levels of extracellular Trx are decreased by the antioxidant N-acetylcysteine. Hence, the secretion of Trx could be altered by the redox status of the cell or the protein. To study Trx mutants, we characterized the secretion of human Trx from Chinese hamster ovary cells. Secretion of human Trx is unaffected by brefeldin A, slow but efficient, and sensitive to low temperature and factors in serum. We demonstrate that N-acetylcysteine reduces the cellular level of Trx but not the proportion secreted; thus this chemical does not block the nonclassic pathway for Trx secretion. Furthermore, we find that mutations in either the active site or the dimerization site of Trx do not alter its secretion. Thus the nonclassic secretion of Trx is not dependent on the redox status of either the cell or the protein.     

The epidermis of Timarete filigera (Polychaeta, Cirratulidae): histochemical and ultrastructural analysis of the gland cells

The aim of this study was to verify whether different living conditions of Polychaeta are correlated with morphological and functional differences in the organization of the integument. For this purpose, we decided to study the epidermis of Timarete filigera, a non-tubicolous polychaete. With this objective in mind, we have identified the various cellular types responsible for mucous secretion in the epidermis of this species and defined the histochemical composition of the mucus produced by different types of gland cells. Three types of gland cells have been identified by histochemical and ultrastructural studies in the epidermis of this polychaete. The histochemistry was carried out using standard techniques and peroxidase-labelled lectins. In type 1 cells, the secretory granules contain neutral glycoproteins with glucosidic residues of GalNAc, Galbeta 1,3 GalNAc, glucosidic and/or mannosidic residues. In type 2 cells, the secretory granules contain acid glycoproteins mainly sulphated with glucosidic residues of GalNAc, Galbeta 1,3 GalNAc, glucosidic and/or mannosidic residues, and some terminal sialic acid. In type 3 cells, the residual granules have the same chemical composition as that of granules present in type 2 cells. The secretion of these glandular mucous cells consists of mainly sulphated acidic glycoproteins and GAG resistant to testis jaluronidase. In these cells, the residual granules have the same chemical composition as that of their secretion. The heterogeneity of mucus composition may be correlated with its different functions.     

Chemical Chaperones Curcumin and 4-Phenylbutyric Acid Improve Secretion of Mutant Factor H R127H by Fibroblasts from a Factor H-Deficient Patient

Factor H (FH) is one of the most important regulatory proteins of the alternative pathway of the complement system. Patients with FH deficiency have a higher risk for development of infections and kidney diseases because of the uncontrolled activation and subsequent depletion of the central regulatory component C3 of the complement system. In this study, we investigated the consequences of the Arg(127)His mutation in FH (FH(R127H)) previously described in an FH-deficient patient, on the secretion of this protein by skin fibroblasts in vitro. We observed that, although the patient cells stimulated with IFN-γ were able to synthesize FH(R127H), the mutant protein was largely retained within the endoplasmic reticulum (ER), whereas normal human fibroblasts stimulated with IFN-γ secrete FH without retention in the ER. Moreover, the retention of FH(R127H) provoked enlargement of ER cisterns after treatment with IFN-γ. A similar ER retention was observed in Cos-7 cells expressing the mutant FH(R127H) protein. Despite this deficiency in secretion, we show that the FH(R127H) mutant is capable of functioning as a cofactor in the Factor I-mediated cleavage of C3. We then evaluated whether a treatment could increase the secretion of FH, and observed that the patient's fibroblasts treated with the chemical chaperones 4-phenylbutiric acid or curcumin increased the secretion rate of FH. We propose that these chemical chaperones could be used as alternative therapeutic agents to increase FH plasma levels in FH-deficient patients caused by secretion delay of this regulatory protein.     

Membrane Potential and Catecholamine Secretion by Bovine Adrenal Chromaffin Cells: Use of Tetraphenylphosphonium Distribution and Carbocyanine Dye Fluorescence

Changes in plasma membrane potential of isolated bovine adrenal chromaffin cells were measured independently by two chemical probe methods and related to corresponding effects on catecholamine secretion. The lipophilic cation tetraphenylphosphonium (TPP+) and the carbocyanine dye 3,3'-dipropylthiadicarbocyanine [DiS-C3-(5)] were used. The necessity of evaluating the subcellular distribution of TPP+ among cytoplasmic, mitochondrial, secretory granule, and bound compartments was demonstrated and the resting plasma membrane potential determined to be -55 mV. The relationship between membrane potential and catecholamine secretion was determined in response to variations in extracellular K+ and to the presence of several secretagogues including cholinergic receptor ligands, veratridine, and ionophores for Na+ and K+. The dependence of potential on K+ concentration fit the Goldman constant field equation with a Na/K permeability ratio of 0.1. The dependence of both K+- and veratridine-evoked catecholamine secretion on membrane potential exhibited a potential threshold of about -40 mV before a significant rise in secretion occurred. This is likely related to the threshold for opening of voltage-sensitive Ca2+ channels. Acetylcholine and nicotine evoked a large secretory response without a sufficiently sustained depolarization to be detectable by the relatively slow potential sensitive chemical probes. Decamethonium induced a detectable depolarization of the chromaffin cells. Veratridine and gramicidin evoked both membrane depolarization and catecholamine release. By contrast the K ionophore valinomycin evoked significant levels of secretion without any depolarization. This is consistent with its utilization of an intracellular source of Ca2+ and the independence of its measured secretory response on extracellular Ca2+.     

Secretory cells in Piper umbellatum (Piperaceae) leaves: A new example for the development of idioblasts

This work aims to investigate the origins and development of secretory cells in Piper umbellatum (L.) Miq. (Piperaceae) leaves as well as the course and the nature of their secretion. The results were compared with studies in oil-secreting cells of several species. Fully expanded fresh leaves were sectioned and subjected to different histochemical tests. Leaves in different developmental stages were fixed and processed for study under light and scanning and transmission electron microscopy techniques. The secretory cells show mixed secretion made up of hydrophobic (oleoresin) and hydrophilic (phenolic compounds and alkaloids) compounds. Secretory cells originate either from the protodermis or the ground meristem. The growth of these cells occurs primarily by increasing the volume of the central vacuole, which corresponds to an extraplasmatic space connected to a protuberance of the wall. Electron-opaque compounds are observed initially in leucoplasts, while electron-dense compounds occur in small vesicles in the cytoplasm. Both are accumulated in the central vacuole which is already developed. Besides the mixed chemical nature of the secretion identified in secretory cells of P. umbellatum leaves, these secretory cells differ from those that have already been described mainly because of the development of the central vacuole prior to the accumulation of the secretion.     

Glycoconjugate histochemistry and nNOS immunolocalization in the mantle and foot epithelia of Tapes philippinarum (bivalve mollusc)

Glycosaminoglycans and NO synthase probably regulate mucous cell secretion in the skin of Tapes philippinarum. We have demonstrated the presence of "protein" cells, "glycogen" cells, "phenol" cells and five types of mucous cells, with different chemical composition of the mucus in the mantle epithelium of T. philippinarum. The foot epithelium contained "protein" cells and two types of mucous cells. Using biotinylated lectins, in the mantle and foot epithelia we have shown specific sites for the following oligosaccharides: alpha-D-glucose, alpha-D-mannose, alpha-L-fucose, alpha-D-1,3-N-acetyl-galactosamine and alpha-N-acetyl-glucosamine. nNOS immunoreactivity in the intraepithelial and intradermal cells and in the mucocytes suggested a regulatory role of NO in mucus secretion, as demonstrated also in other invertebrates.     

Chemical and electric transmission in the carotid body chemoreceptor complex

Carotid body chemoreceptors are complex secondary receptors. There are chemical and electric connections between glomus cells (GC/GC) and between glomus cells and carotid nerve endings (GC/NE). Chemical secretion of glomus cells is accompanied by GC/GC uncoupling. Chemical GC/NE transmission is facilitated by concomitant electric coupling. Chronic hypoxia reduces GC/GC coupling but increases G/NE coupling. Therefore, carotid body chemoreceptors use chemical and electric transmission mechanisms to trigger and change the sensory discharge in the carotid nerve.     

THE RATE OF GROWTH OF THE DAIRY COW : III. THE RELATION BETWEEN GROWTH IN WEIGHT AND INCREASE OF MILK SECRETION WITH AGE.

It is shown that from 2 years, the age when milk secretion usually begins, to 9 years, the age of maximum body weight, the increase of milk secretion with age follows the course of growth in body weight— both can be accurately represented by the equation of a monomolecular chemical reaction having a velocity constant of approximately the same numerical value. While increase in milk secretion and increase in body weight with age follow the same course, it is shown that increasing body weight contributes only about 20 per cent to increasing milk secretion with age. The fact that milk secretion and body weight follow the same course, even though they are largely independent of each other indicates that increase in body weight is a good measure of growth of the dairy cow; this fact also shows that the increase of milk secretion with age may be used as a measure of growth. The fact that milk secretion, like body weight, follows the course of a chemical reaction, adds further support to the theory that growth is limited by a chemical reaction.     

Temporally resolved, independent stages of individual exocytotic secretion events.

The stages of the complex events involved in exocytotic secretion after vesicle-cell membrane fusion have been examined at the level of individual vesicles. Catecholamine flux from single bovine adrenal medullary cells was measured with carbon-fiber microelectrodes firmly touching the cell surface. The data reveal that secretion during exocytotic events has three distinct stages: a small increase in catecholamine flux, a rapid, but not instantaneous, rise to a maximum, followed by an exponential decrease in the flux. These stages are interpreted in the following ways. The initial stage corresponds to catecholamine secretion through a fusion pore. The rate of pore expansion appears to control the rise time of the flux to its maximum value. The final exponential stage is consistent with chemical dissociation of the intravesicular matrix or gel.     

Cellular interaction between mouse pancreatic alpha-cell and beta-cell lines: possible contact-dependent inhibition of insulin secretion

The endocrine cells in the pancreatic islet have cellular communication between the heterotypic cells as well as the homotypic cells. The present study was conducted to elucidate the cellular interaction between pancreatic alpha cells and beta cells utilizing differentiated mouse cell lines (i.e., alphaTC clone 6 and betaTC cells). Co-culture of these two cell lines on a gyratory shaker generated numerous cellular aggregates of homogenous size within 48 h. Immunohistochemical staining for insulin and glucagon demonstrated that betaTC cells were located in the central core of each aggregate, while alphaTC cells formed a mantle layer surrounding the betaTC cells. This segregation was observed regardless of the ratios of the two cell types employed. Although glucagon at concentrations of 10(-8) M or higher stimulated insulin secretion from betaTC cells in both monolayer and aggregates, an increase in the ratio of alphaTC/betaTC cells in aggregate cultures was accompanied by a decrease in secreted insulin and a rise in intracellular insulin content of the betaTC component. The inhibitory effect of alphaTC cells on betaTC insulin secretion was not limited to aggregate culture, since insulin secretion from betaTC cells was also suppressed, and intracellular insulin content increased, by co-culture of alphaTC with betaTC cells in monolayer. On the other hand, the secreted and intracellular insulin of betaTC cells was not affected by alphaTC cells in a Transwell co-culture system in which direct cell-to-cell contacts were prevented by a semipermeable membrane that permitted chemical communication via medium metabolites. These data suggest that the insulin secretion from betaTC cells may be inhibited possibly as a result of the contact with alphaTC cells.     

Recent advances in the pharmacologic regulation of fertility in men.

An updated review of research into contraceptives for men is presented. New concepts of the pharmacologic effects of chemical agents on germinal stem cells and spermatogenic arrest, and the effect of new compounds that act at the post-testicular level but do not affect androgen production are discussed. The latest results of studies on steroidal compounds that inhibit pituitary secretion of gonadotropin and hence result in suppression of spermatogenesis and testosterone secretion are presented. The newer contraceptive pills for men are also evaluated. The major drawback to the development of chemical contraceptives for men is the fear of genetic damage and impotence. New and continued research into this type of contraception is urgently needed.     

IGF-1 induced vascular endothelial growth factor secretion in head and neck squamous cell carcinoma

Elevated vascular endothelial growth factor (VEGF) levels correlate with increased progression and poor prognosis of head and neck squamous cell carcinomas (HNSCC). VEGF expression is regulated by hypoxia and cytokines, including insulin-like growth factor-1 (IGF-1). In this report, we examined IGF-1 signaling and VEGF expression in SCC-9 cells. IGF-1 and the chemical hypoxia agent, cobalt chloride, each stimulated VEGF secretion and VEGF promoter activation. Cobalt chloride increased Hif-1alpha protein levels and HIF-1 dependent activation of the enolase promoter. IGF-1 increased these parameters only in the presence of cobalt chloride. IGF-1 stimulated PI-3K/Akt and Erk/MAPK pathways in SCC-9 cells, each contributing to Hif-1alpha expression and VEGF secretion. SCC-9 cells express the VEGF receptors Flk-1 and neuropilin-1, with VEGF treatment increasing VEGF promoter activity and VEGF secretion that was attenuated by the Flk-1 tyrosine kinase inhibitor, ZM 323881. These results demonstrate the presence of an IGF-1 regulated VEGF autocrine loop in HNSCC.     

The antenna cleaner gland in Messor rufitarsis (hymenoptera, formicidae)

TEM and SEM analysis of the tibio-tarsal antennal cleaner in Messor rufitarsis reveals a pore region on the surface of the basitarsus. These pores are originating from a cluster of highly prismatic epidermal cells that fill the anterior hemolymph space of the leg almost completely. Within the cytoplasma of the cells, basal labyrinth, nucleus/rough endoplasmic reticulum, 'secondary lysosomes', a lot of smooth endoplasmic reticulum and distal microvilli regions can be distinguished indicating that the cells are 'class I' gland cells. Their secretion appears to be transported to the antennal cleaner apparatus via a subcuticular space and pores. It is suggested that the secretion might be used for cleaning of the antenna and/or chemical communication. SEM examination of six additional species indicates that an antennal cleaner gland might be present throughout the ants.     

THE RATE OF DECLINE OF MILK SECRETION WITH THE ADVANCE OF THE PERIOD OF LACTATION

It is shown that the course of decline of milk secretion with the advance of the period of lactation may be expressed by the equation of a monomolecular chemical reaction; that is, the percentage decline of milk secretion with the advance of the stage of lactation is constant. This substantiates the idea that milk secretion is limited by a chemical reaction, and, in general, brings lactation into the class of processes the speed of which is determined by the concentration of a limiting substance.     

Apolipoprotein[a] secretion from hepatoma cells is regulated in a size-dependent manner by alterations in disulfide bond formation

Apolipoprotein[a] (apo[a]) is a large disulfide linked glycoprotein synthesized by hepatocytes. We have examined the role of disulfide bond formation in the processing of apo[a] using human and rat hepatoma cells expressing apo[a] isoforms containing varying numbers of kringle 4 (K4) domains, following treatment with DTT. Hepatoma cells expressing 6- or 9-K4 isoforms revealed approximately 90% inhibition of apo[a] secretion following DTT treatment, although larger isoforms containing 13- or 17-K4 domains demonstrated continued secretion (up to 30% of control values), suggesting that a fraction of the larger isoforms is at least partially DTT resistant. Wash-out experiments demonstrated that these effects were completely reversible for all isoforms studied, with no enhanced degradation associated with prolonged intracellular retention. DTT treatment was associated with enhanced binding of apo[a] with the endoplasmic reticulum-associated chaperone proteins calnexin, calreticulin, and BiP, which was reversible upon DTT removal. The chemical chaperone 6-aminohexanoic acid, previously demonstrated by others to rescue defective apo[a] secretion associated with alterations in glycosylation, failed to alter the secretion of apo[a] following DTT treatment. The demonstration that DTT modulates apo[a] secretion in a manner influenced by both the type and number of K4 repeats extends understanding of the mechanisms that regulate its exit from the endoplasmic reticulum.     

Production cell analysis and compound-based boosting of small extracellular vesicle secretion using a generic and scalable production platform

Extracellular vesicles (EVs) are a novel format of advanced therapeutical medicinal products (ATMPs). They can act regenerative or immune-modulatory as cell therapy substitutes or as a platform for designer exosomes. The biotechnological production of therapeutic EVs is still very much uncharted territory so standardized host cells, production setups, and isolation methods are not yet implemented. In this work, we present a tangential flow filtration (TFF) and fast-performance liquid chromatography (FPLC)-based size exclusion chromatography (SEC) purification setup that is compatible for industry applications. Moreover, we evaluated a series of potential host cell lines regarding their EV productivity, characteristics, and biological functionality. It was found that telomerase-immortalized Wharton's jelly mesenchymal stromal cells (WJ-MSC/TERT273) secrete high amounts of EVs per cell with regenerative capabilities. On the other hand, Cevec's amniocyte producer cells® (CAP®) and human embryonic kidney (HEK293) suspension cells are suitable platforms for designer EVs with high yields. Finally, we aimed to boost the EV secretion of HEK293 cells via chemical adjuvants and verified four compounds that heighten cellular EV secretion in a presumably cAMP-dependent manner. A combination of fenoterol, iodoacetamide, and dinitrophenol increased the EV yield in HEK293 cells threefold and cellular secretion rate fivefold.     

Effect of 4-hydroxynonenal,a lipid peroxidation product,on exocytosis in HL-60 cells

Our work analysed the effect of 4-hydroxynonenal (HNE), a chemotactic aldehydic end-product of lipid peroxidation, on exocytosis in HL-60 cells. We measured the release of beta-glucuronidase, an enzyme of azurophil granules, from the cells incubated at 37 degrees C for 10 min in the presence of HNE concentrations ranging between 10(-8) and 10(-5) M. The release of lactate dehydrogenase was assayed to test cell viability. HNE (1 microM) was able to induce a significant and strong stimulation of beta-glucuronidase secretion without leading to cytotoxic effects. The finding that HNE could increase the exocytotic secretion from HL-60 cells together with its known chemotactic property supports the hypothesis that this lipid peroxidation product may play an important role as a chemical mediator of inflammation; moreover it is noteworthy that micromolar concentrations of HNE have actually been found in exudates from acute and chronic inflammations.     

Study on pathway and characteristics of ion secretion of salt glands of Limonium bicolor

Recretohalophytes with specialized salt-secreting structures, including salt glands and salt bladders, can secrete excess salts from plant tissues and enhance salinity tolerance of plants. However, the pathway and property of salt secretion by the salt gland has not been elucidated. In the article, Limonium bicolor Kuntze was used to investigate the pathway and characteristics of salt secretion of salt gland. Scanning electron microscope micrographs showed that each of the secretory cells had a pore in the center of the cuticle, and the rice grain-like secretions were observed above the pore. The chemical composition of secretions from secretory pores was mainly NaCl using environmental scanning electron microscope technique. Non-invasive micro-test technology was used to directly measure ion secretion rate of salt gland, and secretion rates of Na⁺ and Cl^? were greatly enhanced by a 200-mmol/L NaCl treatment. However, epidermal cells and stoma showed little secretion of ions. In conclusion, our results provide evidence that the salt glands of L. bicolor have four secretory pores and that NaCl is secreted through these pores of salt gland.