Ca-sensitive Na transport in sheep omasum.
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Na transport across a preparation of sheep omasum was studied. All tissues exhibited a serosa-positive short-circuit current (Isc), with a range of 1-4 microeq. h-1. cm-2. A Michaelis-Menten-type kinetic was found between the Na concentration and the Isc (Michaelis-Menten constant for transport of Na = 6.7 mM; maximal transport capacity of Na = 4.16 microeq. h-1. cm-2). Mucosal amiloride (1 mM), phenamil (1 or 10 microM), or serosal aldosterone (1 microM for 6 h) did not change Isc. Removal of divalent cations (Ca and Mg) enhanced Isc considerably from 2.61 +/- 0.24 to a peak value of 11.18 +/- 1.1 microeq. h-1. cm-2. The peak Isc (overshoot) immediately declined to a plateau Isc of approximately 6-7 microeq. h-1. cm-2. Na flux measurements showed a close correlation between changes in Isc and Na transport. Transepithelial studies demonstrated that K, Cs, Rb, and Li are transported, indicating putative nonselective cation channels, which are inhibited by divalent cations (including Ca, Mg, Sr, Ba) and by (trivalent) La. Intracellular microelectrode recordings from the luminal side clearly showed changes of voltage divider ratio when mucosal divalent cations were removed. The obtained data support the assumption of a distinct electrogenic Na transport mechanism in sheep omasum. (+info)
Borrmann's type IV gastric cancer: clinicopathologic analysis.
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OBJECTIVE: To determine whether there is a specific pattern of clinicopathological features that could distinguish Borrmann's type IV gastric cancer from other types of gastric cancer. DESIGN: A retrospective study of patients with advanced gastric cancer treated between 1985 and 1995. SETTING: The Department of Surgery, Sendai National Hospital, a 716-bed teaching hospital. PATIENTS: The clinicopathologic features of 88 patients with Borrmann's type IV carcinoma of the stomach were reviewed from the database of gastric cancer. The results were compared with those of 309 patients with other types of gastric carcinoma. MAIN OUTCOME MEASURES: Gender, age, tumour size, depth of invasion, histologic type, cancer-stromal relationship, histologic growth pattern, nodal involvement, lymphatic and vascular invasion, type of operation, cause of death and 5-year survival. RESULTS: Women were afflicted as commonly as men in the Borrmann's type IV group. These patients tended to be younger and to have larger tumours involving the entire stomach than patients with other types of cancer. Histologic type was commonly diffuse and scirrhous, and serosal invasion was prominent with infiltrative growth. Nodal involvement and lymphatic invasion were more common in patients with Borrmann's type IV than in those with other types of gastric cancer. The disease was advanced in most instances and a total gastrectomy was performed in 55% of the patients. The survival rate of patients with Borrmann's type IV tumour was lower than for patients with other types of gastric cancer (p < 0.005, log-rank test). CONCLUSIONS: In Borrmann's type IV gastric cancer, early detection and curative resection are crucial to extend the patient's survival. Aggressive postoperative chemotherapy is recommended when a noncurative resection is performed. (+info)
The serous demilune of rat sublingual gland is an artificial structure produced by conventional fixation.
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The ultrastructure of the secretory end-piece of the rat sublingual gland was examined in samples prepared by rapid freezing and freeze-substitution method, and results were analyzed in combination with 3-D images reconstructed by computer graphics from light micrographs of serial sections. Fixation by rapid freezing followed by freeze-substitution preserved cellular ultrastructures, especially the membrane structure, in perfect condition, and demonstrated the terminal portion of the sublingual gland to be a compound branched tubulo-alveolar gland with serous cells distributed throughout the end-pieces. All the serous cells aligned with mucous cells to surround a common lumen, leaving no demilune structure. In contrast, samples fixed by the conventional immersion method showed distended mucous cells displacing the serous cells toward the basal portion of the acinus to form the demilune structure. The luminal space was also compressed and appeared disconnected from the serous cells. From these observations, the serous demilune that for more than 130 years has been believed to be an actual histological entity was proved to be an artificial structure produced through compression by the hydrated and expanded mucous cells during immersion fixation. (+info)
Inducible expression of the gp49B inhibitory receptor on NK cells.
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Murine NK cells express inhibitory receptors belonging to the C-type lectin-like (Ly-49, CD94/NKG2) and Ig superfamily-related (gp49) receptors. The murine gp49B receptor displays structural homology with human killer inhibitory receptors, and was previously identified to be a receptor on mast cells and activated NK cells. The gp49B receptor is highly related to gp49A, a receptor with unknown function. In this study, using a novel mAb produced against soluble gp49B molecules that cross-reacts with gp49A, we examined the cellular distribution and function of these receptors. gp49 is constitutively expressed on cells of the myeloid lineage throughout development, as well as on mature cells. Importantly, gp49 is not expressed on spleen- and liver-derived lymphocytes, including NK cells, but its expression is induced in vitro on NK cells following IL-2 stimulation, or in vivo by infection with murine CMV. Molecular studies revealed that both the immunoreceptor tyrosine-based inhibitory motif-containing gp49B as well as immunoreceptor tyrosine-based inhibitory motif-less gp49A receptors are up-regulated on NK cells following murine CMV infection. When co-cross-linked with NK1.1, gp49B can inhibit NK1.1-mediated cytokine release by NK cells. Taken together, these studies demonstrate that the expression of gp49B on NK cells is regulated, providing the first example of an in vivo activation-induced NK cell inhibitory receptor, in contrast to the constitutively expressed Ly49 family. (+info)
Mist1 expression is a common link among serous exocrine cells exhibiting regulated exocytosis.
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Mist1 is a basic helix-loop-helix transcription factor that represses E-box-mediated transcription. Previous studies have suggested that the Mist1 gene is expressed in a wide range of tissues, although a complete characterization of Mist1 protein accumulation in the adult organism has not been described. In an effort to identify specific cell types that contain the Mist1 protein, antibodies specific for Mist1 were generated and used in Western blot and immunohistochemical assays. Our studies show that the Mist1 protein is present in many different tissues but that it is restricted to cell types that are exclusively secretory in nature. Pancreatic acinar cells, serous or seromucous cells of the salivary glands, chief cells of the stomach, and secretory cells of the prostate and seminal vesicle show high levels of Mist1 protein, whereas nonserous exocrine cells, including the mucus-producing cells of the salivary glands, remain Mist1 negative. These results identify Mist1 as the first transcription factor that exhibits this unique serous-specific expression pattern and suggest that Mist1 may have a key role in establishing and maintaining a pathway responsible for the exocytosis of serous secretions. (+info)
Comparative morphology and histochemistry of glands associated with the vomeronasal organ in humans, mouse lemurs, and voles.
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The vomeronasal organ (VNO) is a chemosensory structure of the vertebrate nasal septum that has been recently shown to exist in nearly all adult humans. Although its link to reproductive behaviors has been shown in some primates, its functionality in humans is still debated. Some authors have suggested that the human VNO has the capacity to detect pheromones, while others described it as little more than a glandular pit. However, no studies have utilized histochemical techniques that would reveal whether the human VNO functions as a generalized gland duct or a specialized chemosensory organ. Nasal septal tissue from 13 humans (2-86 years old) were compared to that of two adult lemurs (Microcebus murinus) and eight adult voles (four Microtus pennsylvanicus and four Microtus ochrogaster). Sections at selected intervals of the VNO were stained with periodic acid-Schiff (PAS), alcian blue (AB), AB-PAS, and PAS-hematoxylin procedures. Results revealed typical well-developed VNOs with tubuloacinar glands in Microtus and Microcebus. VNO glands were AB-negative and PAS-positive in voles and mouse lemurs. Homo differed from Microtus and Microcebus in having more branched, AB and PAS-positive glands that emptied into the VNO lumen. Furthermore, the human VNO epithelium had unicellular mucous glands (AB and PAS-positive) and cilia, similar to respiratory epithelia. These results demonstrate unique characteristics of the human VNO which at once differs from glandular ducts (e.g., cilia) and also from the VNOs of mammals possessing demonstrably functional VNO. (+info)
Functional and molecular characterization of an anion exchanger in airway serous epithelial cells.
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Serous cells secrete Cl(-) and HCO(3)(-) and play an important role in airway function. Recent studies suggest that a Cl(-)/HCO(3)(-) anion exchanger (AE) may contribute to Cl(-) secretion by airway epithelial cells. However, the molecular identity, the cellular location, and the contribution of AEs to Cl(-) secretion in serous epithelial cells in tracheal submucosal glands are unknown. The goal of the present study was to determine the molecular identity, the cellular location, and the role of AEs in the function of serous epithelial cells. To this end, Calu-3 cells, a human airway cell line with a serous-cell phenotype, were studied by RT-PCR, immunoblot, and electrophysiological analysis to examine the role of AEs in Cl(-) secretion. In addition, the subcellular location of AE proteins was examined by immunofluorescence microscopy. Calu-3 cells expressed mRNA and protein for AE2 as determined by RT-PCR and Western blot analysis, respectively. Immunofluorescence microscopy identified AE2 in the basolateral membrane of Calu-3 cells in culture and rat tracheal serous cells in situ. In Cl(-)/HCO(3)(-)/Na(+)-containing media, the 8-(4-chlorophenylthio)adenosine 3',5'-cyclic monophosphate (CPT-cAMP)-stimulated short-circuit anion current (I(sc)) was reduced by basolateral but not by apical application of 4, 4'-diisothiocyanostilbene-2,2'-disulfonic acid (50 microM) and 4, 4'-dinitrostilbene-2,2'-disulfonic acid [DNDS (500 microM)], inhibitors of AEs. In the absence of Na(+) in the bath solutions, to eliminate the contributions of the Na(+)/HCO(3)(-) and Na(+)/K(+)/2Cl(-) cotransporters to I(sc), CPT-cAMP stimulated a small DNDS-sensitive I(sc). Taken together with previous studies, these observations suggest that a small component of cAMP-stimulated I(sc) across serous cells may be referable to Cl(-) secretion and that uptake of Cl(-) across the basolateral membrane may be mediated by AE2. (+info)
Rapid activation of basolateral potassium transport in human colon by oestradiol.
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1. We investigated the effect of oestradiol on basolateral potassium channels in human colonic epithelium. 2. Ion transport was quantified using short circuit current (I:(sc)) measurements of samples mounted in Ussing chambers. Serosal K transport was studied using nystatin permeabilization of the apical membrane. Intracellular pH changes were quantified using spectroflouresence techniques. 3. Experiments were performed with either 10 nM or 1 microM Ca(2+) in the apical bathing solution. With 10 nM Ca(2+) in the apical bathing solution addition of oestradiol (1 nM) to the basolateral bath produced a rapid increase in current (delta I(K)=11.2+/-1.2 microA.cm(-2), n=6). This response was prevented by treatment of the serosal membrane with tolbutamide (1 microM). With 1 microM Ca(2+) in the apical bathing solution addition of oestradiol produced a rapid fall in current (delta I(K)=-12.8+/-1.4 microA.cm(-2)), this response was prevented by treatment of the basolateral membrane with tetra-pentyl-ammonium (TPeA). These responses were rapid and occurred independently of protein synthesis. 4. Inhibition of basolateral Na(+)/H(+) exchange with either amiloride or a low sodium bathing solution prevented this response. These responses were prevented by inhibition of protein kinase C (PKC) with bis-indolyl-maleimide. 5. Oestradiol (1 nM) produced a rapid intracellular alkanization (mean increase=0.11 pH units; n=6; P<0.01). 6. These results suggest that oestradiol rapidly modulates serosal K transport in human colon. These effects depend upon intact Na(+)/H(+) exchange and protein kinase C. We propose a non-classical, possibly membrane linked, mechanism for oestradiol action in human colonic epithelium. (+info)