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PubMed1983

Differences in the ultrastructure of the submandibular glands of baboon and Rhesus monkey revealed by the use of different fixatives.

Submandibular glands of adult baboon and Rhesus monkeys were compared after different methods of fixation. In both species, serous acinar cells outnumber mucous acinar cells. In the baboon, serous cells contain secretory granules showing dense cores, moderately dense crescents, and flocculent material. In mucous cells, secretory granules vary in appearance from amorphous to highly ordered depending on fixation. In the Rhesus monkey, serous cells contain the same 3 components of secretory granules as in the baboon. Additionally, a fourth component is represented by a layer of electron-dense material between the crescent and flocculent material. Mucous cells contain electron-dense granules when fixed in Millonig's buffered fixatives, but when Clarke's or Sorensens' buffer is used the granules resemble more typical mucous granules. Duct systems of the two species are similar, but differ mainly in that large foci of glycogen are present in the striated duct cells of the Rhesus monkey.

Animals↗
PubMed1987

Occurrence of gastrin-releasing peptide-like and bombesin-like immunoreactivities in the epidermal sacciform gland cells of the clingfish Lepadogaster candollei.

Gastrin-releasing peptide (GRP)-like and bombesin (BOM)-like immunoreactivities were localized in the exocrine sacciform gland cells and in the surface epidermis of the clingfish Lepadogaster candollei with the use of previously characterized antibodies. The GRP-like and BOM-like peptides show resemblance to those immunohistochemically found in the dermal secretory products of the amphibian skin. The immunoreactive peptides tested in this study are unusual bioactive components of secretory sources of exocrine glands since these peptides were first demonstrated in cells of the neuroendocrine system. The results suggest that such bioactive compounds may exert regulatory activity in the absorptive processes of the skin epithelium and in influencing secretion release from exocrine complexes.

Animals↗
PubMed1999

The heterotrimeric Gi(3) protein acts in slow but not in fast exocytosis of rat melanotrophs.

Besides having a role in signal transduction some trimeric G-proteins may be involved in a late stage of exocytosis. Using immunocytochemistry and confocal microscopy we found that Gi(3)-protein resides mainly in the plasma membrane, whereas Gi(1/2-)protein is preferentially associated with secretory granules. To study the function of trimeric Gi(3)- and Gi(1/2)-proteins, secretory responses in single rat melanotrophs were monitored by patch-clamp membrane capacitance measurements. We report here that mastoparan, an activator of trimeric G-proteins, enhances calcium-induced secretory activity in rat melanotrophs. The introduction of synthetic peptides corresponding to the C-terminal domain of the (&agr;)-subunit of Gi(3)- and Gi(1/2)-proteins indicated that Gi(3 )peptide specifically blocked the mastoparan-stimulated secretory activity, which indicates an involvement of a trimeric Gi(3)-protein in mastoparan-stimulated secretory activity. Flash photolysis of caged Ca(2+)-elicited biphasic capacitance increases consisting of a fast and a slower component. Injection of anti-Gi(3) antibodies selectively inhibited the slow but not the fast component of secretory activity in rat melanotrophs. We propose that the plasma membrane-bound Gi(3)-protein may be involved in regulated secretion by specifically controlling the slower kinetic component of exocytosis.

Animals↗
PubMed2005

Plasma level of endogenous secretory RAGE is associated with components of the metabolic syndrome and atherosclerosis.

OBJECTIVE: Advanced glycation endproducts, AGEs, and its specific receptor, RAGE, are involved in diabetic vascular complications. Endogenous secretory RAGE, esRAGE, has been identified as an alternatively spliced form of RAGE, and shown to act as a decoy receptor for AGE. Here, we measured plasma esRAGE level with a recently developed enzyme-linked immunosorbent assay (ELISA) and examined its association with atherosclerosis in age- and gender-matched 203 type 2 diabetic and 134 nondiabetic subjects. METHODS AND RESULTS: Plasma esRAGE was inversely associated with carotid or femoral atherosclerosis, as quantitatively measured as intimal-medial thickness (IMT) by arterial ultrasound. Stepwise regression analyses revealed that plasma esRAGE was the third strongest and independent factor associated with carotid IMT, following age and systolic blood pressure. Plasma esRAGE was significantly lower in diabetic patients (0.176+/-0.092 ng/mL) than nondiabetic controls (0.253+/-0.111). Of note, in all, diabetic or nondiabetic group, plasma esRAGE was significantly and inversely correlated with components of the metabolic syndrome including body mass index, blood pressure, triglyceride, HbA1c, or an insulin resistance index. Stepwise regression analyses showed that body mass index or insulin resistance index was the major factor determining plasma esRAGE in all, nondiabetic or diabetic population. CONCLUSIONS: esRAGE is a novel and potential protective factor for the metabolic syndrome and atherosclerosis.

Adult↗
PubMed1985

[Immunopathology of the inner ear].

Immunologically mediated tissue lesions or functional disturbances can result from immune responses either to foreign antigens or autoantigenic constituents. Before a disease or a functional disorder can be called an (auto)immune disease, it must be established that immunological processes are involved in its etiology and/or pathogenesis. After reviewing the available data on immunology and on research on immunobiology of the inner ear, as well as clinical observations on disorders of the inner ear of possibly immunological origin, an attempt is made to determine whether (auto)immunopathology can be assumed in some patients with sensineural hearing loss. In patients with disorders presently recognized as autoimmune diseases, no hearing loss has been described so far. However, serum antibodies can be found via the indirect immunofluorescence method in some patients having functional disorders of the inner ear. These serum antibodies interact with normal human inner ear tissue. However, as long as immunopathological mechanisms have not been confirmed, these disorders should merely be called "diseases with autoimmune markers." It has been shown in animal experiments that the production of autoantibodies against inner ear components is associated with morphological and functional changes of the inner ear. The human endolymphatic sac releases secretory IgA into the lumen. Its epithelium contains (intraepithelial) lymphocytes, whereas lymphocytes, plasma cells (IgA, IgG) and macrophages occur in the perisaccular region. In this manner, the inner ear has its own immune system, which can possibly react independently of the systemic immune system.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2001

Intracellular signaling from the endoplasmic reticulum to the nucleus: the unfolded protein response in yeast and mammals.

Cellular survival of endoplasmic reticulum stress requires the unfolded protein response (UPR), a stress response first elucidated genetically in yeast. While we continue to refine our knowledge of the yeast system, especially the breadth and significance of the transcriptional response, conservation of the system's elements has allowed identification of corresponding and additional components of the mammalian UPR. Recent results reveal that the output of the mammalian UPR reaches beyond transcriptional regulation of secretory pathway components to control of general translation, the cell cycle and programmed cell death.

Animals↗
PubMed2002

Sec61beta--a component of the archaeal protein secretory system.

Sec61p/SecYEG complexes mediate protein translocation across membranes and are present in both eukaryotes and bacteria. Whereas homologues of Sec61alpha/SecY and Sec61gamma/SecE exist in archaea, identification of the third component (Sec61beta or SecG) has remained elusive. Using PSI-BLAST, the archaeal counterpart of Sec61beta has been detected. With the identification of the Sec61beta motif, functions for a universal family of archaeal proteins can be predicted and the archaeal translocon system can be definitively detected.

Amino Acid Motifs↗
PubMed1978

Ultrastructure of the harderian gland in male albino rats.

Harderian glands of adult male albino rats were examined by light and transmission electron microscopy. The animals were divided into the following experimental groups: (1) castrated only, (2) castrated with testosterone replacement and (3) sham operated controls. Two types of secretory cells, designated as A and B, comprise the glandular epithelium and are distinguished on the basis of morphologic differences in the following cellular components: cytoplasmic secretory vacuoles, mitochondria and smooth endoplasmic reticulum (SER). Cell type A is more numerous and contains larger secretory vacuoles than cell type B which is characterized by the presence of large numbers of mitochondria and packet-like arrangement of SER profiles. The glandular secretion appears to be elaborated via merocrine mechanisms and consists primarily of lipids and a fibrogranular substance. The latter component may consist of porph,yrin compounds. Nerve endings are found in the connective tissue interstices of the gland. Direct synapses were not observed in association with either gland cells or myoepithelial cells. Castration did not produce significant alterations in the morphology of the glandular epithelium. Results of the investigation suggest that the rat Harderian gland may serve as a useful model for the study of cellular mechanisms involved in the production of human porphyrias.

Animals↗
PubMed1993

Two components in the adrenal nicotinic secretory response revealed by cobalt ramps.

Prolonged stimulation with nicotine (50 microM) enhanced the secretion of catecholamines from perfused cat adrenal glands. The profile of secretion consisted of a quick activation phase to a peak of 7.68 micrograms/min followed by a second inactivation phase which exhibited a t1/2 of 3.75 min. Sustained stimulation with a solution enriched in K+ (59 mM) also evoked a transient secretory response, with a peak release of 8.62 micrograms/2 min and a t1/2 for inactivation of 4.8 min. Co2+ (10 mM) blocked the nicotinic response by 58% and the K(+)-evoked secretory response by over 96%. In the presence of Co2+ (5 mM), continuous perfusion with nicotine produced a transient but large initial secretory response; the gradual decrease of the extracellular Co2+ concentration, [Co2+]0, as a continuous ramp allowed the development of a second component of secretion which inactivated later on. When the glands were continuously stimulated with 59 mM K+ in the presence of Co2+, the first component of secretion was missing; the second component appeared as [Co2+]0 decreases as a ramp. In similar experiments performed in low-Na+ solution (10 mM Na+), only the first secretion component evoked by nicotine was observed. This finding suggests that the second component of secretion depends on Na+ entry through the nicotinic receptor, on the ensuing cell depolarization and on Ca2+ entry through voltage-dependent Ca2+ channels.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Glands↗
PubMed1989

The estrogen-responsive 110K and 74K rat uterine secretory proteins are structurally related to complement component C3.

Estrogens stimulate the synthesis of specific secretory proteins in the rat uterus. Here we show that two of these, polypeptides of relative molecular weight 110,000 (110K) and 74,000 (74K), are structurally related to C3, the third component of complement, a glycoprotein that plays a central role in regulating complement-mediated inflammatory and immune responses. The similarities were based on the observations that (1) NH2-terminal amino acid sequence of the 74K polypeptide showed sequence homology with the beta chain of mouse C3, (2) comparison of the electrophoretic mobilities of the 110K and 74K polypeptides in the presence and absence of reducing agents revealed that they were disulfide-linked subunits of a protein of Mr approximately 180,000, (3) the native protein was immunoreactive with antibodies specific for rat C3, and (4) both polypeptides were immunoprecipitated with antibodies to rat C3.

Amino Acid Sequence↗
PubMed1992

A dihydropyridine-resistant component in the rat adrenal secretory response to splanchnic nerve stimulation.

A study of the effects of dihydropyridine Ca2+ channel modulators on the release of catecholamines from perfused rat adrenal glands, evoked by electrical stimulation of their splanchnic nerves, is presented. Electrically mediated secretory responses were compared to chemically mediated responses (exogenous acetylcholine, nicotine, or high K+). Intensities of stimuli were selected to produce quantitatively similar secretory responses (between 100 and 200 ng per stimulus). The main finding of the study is that responses to transmural stimulation (300 pulses at 1 or 10 Hz) and to acetylcholine were inhibited only partially (about 50%) by isradipine, an L-type Ca2+ channel blocker. In contrast, responses to high K+ (17.5 mM for 2 min) were highly sensitive to isradipine (IC50 = 8.2 nM). Responses to nicotine were also fully inhibited by this drug. Bay K 8644 (an L-type Ca2+ channel activator) potentiated mildly the secretory responses to electrical stimulation at 10 Hz and to acetylcholine, but increased threefold the responses to K+ and nicotine. It is, therefore, likely that responses mediated by high K+ or nicotinic receptors are triggered by external Ca2+ gaining access to the internal secretory machinery through L-type, dihydropyridine-sensitive voltage-dependent Ca2+ channels. However, in addition to nicotinic receptors, the physiological stimulation of adrenal medulla chromaffin cells through splanchnic nerves has other components, i.e., muscarinic receptor stimulation or the release of cotransmitters such as vasoactive intestinal polypeptide. The poorer sensitivity to dihydropyridines of secretory responses triggered by electrical stimulation of splanchnic nerve terminals or exogenous acetylcholine speaks in favor of alternative Ca2+ pathways, probably some dihydropyridine-resistant Ca2+ channels, in modulating the physiological adrenal catecholamine secretory process.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed2006

Inhibition of human immunodeficiency virus type 1 entry by a binding domain of Porphyromonas gingivalis gingipain.

Human immunodeficiency virus (HIV) transmission through saliva is extremely low. Several oral components, including secretory immunoglobulin A and secretory leukocyte protease inhibitor, are known as potential inhibitory agents of HIV oral transmission. Here we examined anti-HIV activity of oral bacterial components. We showed that recombinant protein HGP44 derived from Porphyromonas gingivalis, one of the primary infectious agents of periodontitis, was capable of inhibiting HIV type 1 (HIV-1) replication. HGP44 bound specifically to HIV-1 gp120 and blocked HIV-1 envelope-mediated membrane fusion. These findings suggest that HGP44 of P. gingivalis can inhibit HIV-1 infection by blocking HIV-1 entry.

Adhesins, Bacterial↗
PubMed2006

Evidence for Golgi-independent transport from the early secretory pathway to the plastid in malaria parasites.

The malaria parasite Plasmodium falciparum harbours a relict plastid (termed the apicoplast) that has evolved by secondary endosymbiosis. The apicoplast is surrounded by four membranes, the outermost of which is believed to be part of the endomembrane system. Nuclear-encoded apicoplast proteins have a two-part N-terminal extension that is necessary and sufficient for translocation across these four membranes. The first domain of this N-terminal extension resembles a classical signal peptide and mediates translocation into the secretory pathway, whereas the second domain is homologous to plant chloroplast transit peptides and is required for the remaining steps of apicoplast targeting. We explored the initial, secretory pathway component of this targeting process using green fluorescent reporter protein constructs with modified leaders. We exchanged the apicoplast signal peptide with signal peptides from other secretory proteins and observed correct targeting, demonstrating that apicoplast targeting is initiated at the general secretory pathway of P. falciparum. Furthermore, we demonstrate by immunofluorescent labelling that the apicoplast resides on a small extension of the endoplasmic reticulum (ER) that is separate from the cis-Golgi. To define the position of the apicoplast in the endomembrane pathway in relation to the Golgi we tracked apicoplast protein targeting in the presence of the secretory inhibitor Brefeldin A (BFA), which blocks traffic between the ER and Golgi. We observe apicoplast targeting in the presence of BFA despite clear perturbation of ER to Golgi traffic by the inhibitor, which suggests that the apicoplast resides upstream of the cis-Golgi in the parasite's endomembrane system. The addition of an ER retrieval signal (SDEL) - a sequence recognized by the cis-Golgi protein ERD2 - to the C-terminus of an apicoplast-targeted protein did not markedly affect apicoplast targeting, further demonstrating that the apicoplast is upstream of the Golgi. Apicoplast transit peptides are thus dominant over an ER retention signal. However, when the transit peptide is rendered non-functional (by two point mutations or by complete deletion) SDEL-specific ER retrieval takes over, and the fusion protein is localized to the ER. We speculate either that the apicoplast in P. falciparum resides within the ER directly in the path of the general secretory pathway, or that vesicular trafficking to the apicoplast directly exits the ER.

Amino Acid Sequence↗
PubMed1999

Regulation of the formation and external transport of secretory immunoglobulins.

Secretory IgA (SIgA) is the best defined effector component of the mucosal immune system. Generation of SIgA and secretory IgM (SIgM) in exocrine glands and mucous membranes depends on a fascinating cooperation between local plasma cells that produce polymeric IgA (pIgA, mainly dimers and some larger polymers) and pentameric IgM, and secretory epithelial cells that express the polymeric Ig receptor (pIgR)--also known as transmembrane secretory component. After release from the local plasma cells and diffusion through the stroma, pIgA and pentameric IgM become readily bound to pIgR, and are then actively transported across secretory epithelial cells for extrusion into external secretions after cleavage of pIgR. Much knowledge has recently been obtained at the molecular level about the regulation of pIgR-mediated transport of antibodies. This mechanism is of considerable biological interest because SIgA and SIgM form the first line of specific immunological defense against infectious agents and other harmful substances that may enter the body through the mucosae.

Animals↗
PubMed1997

The unfolded protein response coordinates the production of endoplasmic reticulum protein and endoplasmic reticulum membrane.

The endoplasmic reticulum (ER) is a multifunctional organelle responsible for production of both lumenal and membrane components of secretory pathway compartments. Secretory proteins are folded, processed, and sorted in the ER lumen and lipid synthesis occurs on the ER membrane itself. In the yeast Saccharomyces cerevisiae, synthesis of ER components is highly regulated: the ER-resident proteins by the unfolded protein response and membrane lipid synthesis by the inositol response. We demonstrate that these two responses are intimately linked, forming different branches of the same pathway. Furthermore, we present evidence indicating that this coordinate regulation plays a role in ER biogenesis.

Endoplasmic Reticulum↗
PubMed1995

GH3 cells transfected with gonadotropin-releasing hormone (GnRH) receptor complementary deoxyribonucleic acid release secretogranin-II through a constitutive pathway after GnRH analog-regulated synthesis: evidence that secretory proteins do not contain a sequence that obligates processing through a secretory granule or by regulated secretion.

GGH3 cells (lactotropic GH3 cells transfected with rat GnRH receptor complementary DNA) respond to GnRH agonists with time- and dose-dependent release of secretogranin-II (SII), a molecule believed to be a marker of the regulated pathway of release and a component of secretory granules. Release requires both protein and RNA synthesis and is also stimulated by analogs of the cyclic nucleotides. Release, as such, appears to be determined by the availability of SII, because this process is constitutive once the molecule is synthesized, and intracellular levels are at the same steady state whether the receptor is occupied by an agonist or an antagonist or is unoccupied. This synthetic requirement is consistent with the lag in time from stimulation to release and the inhibitory actions of either cycloheximide or actinomycin-D on secretion as well as the morphologic observation that storage granules (i.e. secretory granules) are absent in these cells. SII, accordingly, can be released constitutively and does not require processing through the so-called regulated secretory pathway. These observations suggest, in addition, that proteins associated with release through regulated pathways do not have "sorting" domains that preclude release via constitutive routes or require processing through secretory granules.

Animals↗
PubMed1984

Morphometric evaluation of lipid droplet associations with secretory vesicles, mitochondria and other components in the lactating cell.

The size, cellular location, and identity of surface-associated components were determined for lipid droplets in lactating cells. Transmission electron-microscopic measurements were made involving 3801 droplets in approximately 211 cells from three rats and 1197 droplets in 66 cells from a mouse. For the purposes of droplet evaluation, cells were divided into seven locations ranging from basal to secreting positions. Droplets were also categorized with respect to contact with other droplets, basolateral plasma membrane, mitochondria, Golgi apparatus, secretory vesicles, and endoplasmic reticulum-cytoplasm (ERC). Data on droplet size showed that droplet growth occurs mainly in the secretory position, confirming previously published findings. Lipid droplets from mouse tissue, although somewhat smaller in size showed similar growth trends to those of the rat. Data on numbers of droplet contacts and percentages of droplet circumferences involved in associations with other cell components showed that the dominant interaction of lipid droplets was with the ERC. However, intimate association of droplets with mitochondria was noted in all cellular locations. In addition, nursed animals exhibited a greater proportion of droplet surface association with secretory vesicles and less in contact with mitochondria in comparison to those not nursed. The significance of these relationships to milk synthesis and secretion is discussed.

Animals↗