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At least 73 records · Page 4Linked to original sources
PubMed1986

Evidence for two cellular sodium compartments in suspensions of smooth muscle cells.

Unidirectional transmembrane fluxes of 24Na were examined in suspensions of enzymatically dispersed toad stomach muscle cells. Compartmental analysis of 24Na influx indicated that 24Na exchange consisted of two kinetically distinguishable components in these cells: a large pool (approximately 45 mmol/l cell H2O) with a rapid rate of exchange [half time (t1/2) approximately 5.8 min] and a smaller pool (approximately 26 mmol/l cell H2O) that exchanged more slowly (t1/2 approximately 69 min). Only the latter appeared ouabain sensitive; thus we postulated that the rate of exchange of this pool might be determined by the inward leak of Na+. Based on this assumption, we derived estimates for Na+ influx rate (0.9 X 10(-12) mol . cm-2 . s-1) and Na+ permeability (0.3 X 10(-8) cm/s), which presumably represent upper limits for these parameters in smooth muscle. The location and significance of the rapidly exchanging pool were not resolved. The exchange of both cellular Na+ pools was increased by the ionophore monensin. Thus we speculated that the rapidly exchanging pool was associated with a small population of permeable (high Na+) smooth muscle cells, while the slowly exchanging pool was associated with smooth muscle cells with normal Na+ permeability (low-Na+ cells).

Animals↗
PubMed1992

Calcium-activated neutral proteinase (calpain) activity in C6 cell line: compartmentation of mu and m calpain.

Calcium-activated neutral proteinase (calpain) activity was determined, including in cytosol and membrane fractions, in rat glioma C6 cell line. The mu and m forms of calpain were separated by DEAE and phenylsepharose column chromatography and with removal of the endogenous inhibitor calpastatin. C6 cells contained more mcalpain than the mu isoform. More than 70% of mcalpain activity was membrane-associated and 20% was cytosolic. Isolated plasma membrane also contained 69% of the mcalpain activity. In contrast, approximately 80% of mucalpain activity was cytosolic and 16% was membranous. Half-maximal activity for mu and mcalpain was obtained at 1 microM and 0.2 mM CaCl2, respectively. Trypsin dissociation of cells reduced activity. Triton X-100 stimulated mcalpain activity of the whole homogenate and the membrane pellet but not of the cytosol. Activity of the myelin marker enzyme adenosine 2'3'-cyclic nucleotide 3'-phosphohydrolase (CNPase), was also found in C6 cells. The identification of calpain and CNPase in C6 cells is in keeping with an interpretation that C6 differentiation resembles, at least in part, that of the myelin-forming oligodendroglial cells.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1990

UM4D4+ (CDw60) T cells are compartmentalized into psoriatic skin and release lymphokines that induce a keratinocyte phenotype expressed in psoriatic lesions.

UM4D4 (CDw60), the surface molecule of a novel antigen-independent T-cell activation pathway, was found to be highly expressed on lesional psoriatic T cells. To examine whether UM4D4 represents a T-cell activation pathway for psoriatic T cells, a T-cell line was initiated from an acute skin lesion and cloned by limiting dilution. Clonality was verified by analysis of T-cell receptor gene rearrangement. All T-cell clones tested, whether CD4+2H4+CD8-, CD4+2H4-CD8-, or CD4-CD8+CD11b-, expressed UM4D4 and were activated by the monoclonal antibody anti-UM4D4. Lesional psoriatic T-cell clones were heterogeneous in the degree of anti-UM4D4-induced proliferation and in their production of IL-2 and gamma-interferon. Lymphokines released by anti-UM4D4 activation were capable of inducing ICAM-1 and HLA-DR expression on cultured normal keratinocytes. Thus, the high expression of UM4D4 on T-cells in psoriatic skin provides an alternative mechanism for T-cell activation that may be operative in the psoriatic lesional milieu. Indeed, activation of lesional T-cells through the UM4D4 molecule resulted in release of lymphokines that directly induced keratinocytes to express a phenotype displayed in psoriatic skin lesions.

Antigens, CD↗
PubMed1987

The in situ kinetics of dopamine beta-hydroxylase in bovine adrenomedullary chromaffin cells. Intravesicular compartmentation reduces apparent affinity for the cofactor ascorbate.

The Km of dopamine beta-hydroxylase for its cofactor, ascorbic acid, was determined in situ in primary cultures of bovine adrenomedullary chromaffin cells and in isolated chromaffin vesicles. A range of intravesicular ascorbate concentrations in chromaffin cell cultures (1.1-31.2 mM) was achieved by varying the number and concentration of ascorbate additions to the culture media. The rate of octopamine synthesis from tyramine displayed a Michaelis-Menten relationship with respect to ascorbate concentration and an apparent Km of dopamine beta-hydroxylase for ascorbate of 15.0 +/- 2.0 mM was determined. In isolated chromaffin vesicles, with an initial intravesicular ascorbate concentration of approximately 10 mM, ascorbate consumption during beta-hydroxylation occurred as a first order process. This indicated that dopamine beta-hydroxylase was not saturated at this initial ascorbate concentration. When isolated chromaffin vesicles were prepared with different intravesicular ascorbate concentrations, the rate of octopamine synthesis displayed a Michaelis-Menten relationship with respect to ascorbate with an apparent Km of 17.0 +/- 5.0 mM. Ascorbate consumption also occurred as a first order process in ascorbate-loaded chromaffin-vesicle ghosts which had initial ascorbate concentrations of approximately 30 mM but which were depleted of other small molecules such as catecholamines. These results indicate that the in situ Km of dopamine beta-hydroxylase for ascorbate (approximately 15 mM) is 25-fold higher than it is for the purified or partially purified enzyme assayed under optimal conditions in vitro (0.6 mM). The factor(s) which decreases the enzyme affinity for ascorbate, relative to in vitro, resides in the chromaffin vesicle interior and is also retained in chromaffin-vesicle ghosts. The mechanism of this effect remains to be determined. The Km value determined in these experiments is close to the estimated intravesicular ascorbate concentration of bovine chromaffin granules in vivo (4), suggesting that the availability of ascorbate could become a factor in regulating the rate of dopamine beta-hydroxylation.

Adrenal Medulla↗
PubMed2004

Discovery of the novel candidate phylum "Poribacteria" in marine sponges.

Marine sponges (Porifera) harbor large amounts of commensal microbial communities within the sponge mesohyl. We employed 16S rRNA gene library construction using specific PCR primers to provide insights into the phylogenetic identity of an abundant sponge-associated bacterium that is morphologically characterized by the presence of a membrane-bound nucleoid. In this study, we report the presence of a previously unrecognized evolutionary lineage branching deeply in the domain Bacteria that is moderately related to the Planctomycetes, Verrucomicrobia, and Chlamydia lines of decent. Because members of this lineage showed <75% 16S rRNA gene sequence similarity to known bacterial phyla, we suggest the status of a new candidate phylum, named "Poribacteria", to acknowledge the affiliation of the new bacterium with sponges. The affiliation of the morphologically conspicuous sponge bacterium with the novel phylogenetic lineage was confirmed by fluorescence in situ hybridization with newly designed probes targeting different sites of the poribacterial 16S rRNA. Consistent with electron microscopic observations of cell compartmentalization, the fluorescence signals appeared in a ring-shaped manner. PCR screening with "Poribacteria"-specific primers gave positive results for several other sponge species, while samples taken from the environment (seawater, sediments, and a filter-feeding tunicate) were PCR negative. In addition to a report for Planctomycetes, this is the second report of cell compartmentalization, a feature that was considered exclusive to the eukaryotic domain, in prokaryotes.

Animals↗
PubMed1995

Electrode configuration and spread of neural excitation: compartmental models of spiral ganglion cells.

A compartmental model of spiral ganglion cells in a potential field was used to predict spike discharges to electrical stimuli. The field was generated by monopolar, bipolar, or quadrupolar point source electrode geometries. The discharges of a population of afferent neurons were modeled to compare the relative spread of excitation. At the same stimulus intensity the spread of excitation was least for the quadrupolar and greatest for the radial bipolar, and this ordering held after equating for maximal spike discharge rates over the three geometries. Excitation spread from quadrupolar stimulation was highly dependent on stimulus intensity.

Electric Stimulation↗
PubMed1995

Localization of protein kinases by anchoring proteins: a theme in signal transduction.

A fundamental question in signal transduction is how stimulation of a specific protein kinase leads to phosphorylation of particular protein substrates throughout the cell. Recent studies indicate that specific anchoring proteins located at various sites in the cell compartmentalize the kinases to their sites of action. Inhibitors of the interactions between kinases and their anchoring proteins inhibit the functions mediated by the kinases. These data indicate that the location of these anchoring proteins provides some of the specificity of the responses mediated by each kinase and suggest that inhibitors of the interaction between the kinases and their anchoring proteins may be useful as therapeutic agents.

Animals↗
PubMed2006

Mosquito midguts and malaria: cell biology, compartmentalization and immunology.

The malaria parasite Plasmodium has an absolute requirement for both a vertebrate and a mosquito host in order to complete its life cycle, and its interactions with the latter provide the focus for this review. The mosquito midgut represents one of the most challenging environments for the survival and development of Plasmodium, and is thus also one of the most attractive sites for novel targeted malaria control strategies. During their attempts to cross the midgut epithelium en route to the salivary glands, motile ookinetes are swiftly detected and labelled by mosquito recognition factors and targeted for destruction by a variety of immune responses that recruit killing factors both from the midgut and from other tissues in the surrounding body cavity. The exact interplay between these factors and the parasite is highly species- and strain-specific, as are the timing and the route of parasite invasion. These features are paramount to determining the success of the infection and the vector competence of the mosquito. Here we discuss recent advances in genomic analyses, coupled with detailed microscopical investigations, which are helping to unravel the identity and roles of the major players of these complex systems.

Animals↗
PubMed1974

Fluxes of a nonelectrolyte and compartmentation in cells of carrot root tissue.

Permeation of thiourea into cells of carrot (Daucus carota L.) storage root discs was found to be governed by its concentration gradient only. The analysis of the course of thiourea efflux from preloaded discs shows two distinct exponential curves, apart from an initial very fast component. Reasons are given for relating the first exponential part of the curve to efflux from the cytoplasm and the second exponential part to efflux from the vacuole.The rate constant for thiourea efflux through the tonoplast is markedly temperature-dependent (activation energy 13.2 kcal mole(-)) and is lowered by 2,4-dinitrophenol and by phenyl mercuric acetate treatments. The rate constant for its efflux through the plasmalemma, on the other hand, has a low activation energy (4.2 kcal mole(-)), which is equal to that of free diffusion of thiourea in aqueous solution, and is not affected by the metabolic inhibitors. Possible reasons for the difference in the properties of the two membranes are discussed.

Journal Article↗
PubMed1991

Compartmentalized mast cell degranulations in the ovarian hilum, fat pad, bursa and blood vessel regions of the cyclic hamster: relationships to ovarian histamine and blood flow.

Ovaries from hamsters on each day of the oestrous cycle at 09.00 h were observed for the number of mast cells, the pattern of mast cell degranulation, histamine concentration and blood flow. On day 4 (pro-oestrus), ovaries were also observed at 9.00, 15.00 and 21.00 h. Mast cell degranulation was evaluated by 3 criteria: (1) no degranulation = less than 5 granules dispersed from the cell; (2) moderate degranulation = 5 or more granules dispersed but less than 15, and (3) extensive degranulation = 15 or more granules released. Blood flow was determined using radio-active microspheres in anaesthetized animals. Mast cells were observed in fat pad (beyond 2 mm of the bursal mesothelium), bursa (within 2 mm of the bursal mesothelium), hilum and near ovarian blood vessels (these 4 regions are collectively called the ovarian complex). The distribution of ovarian mast cells was not uniform. Most mast cells were near ovarian blood vessels (42.2%) and in the fat pad (37.2%). A moderate number of cells were in the bursal wall (20%) and only a few cells were observed in the hilum (0.64%). Mast cell number remained unchanged on days 1-4 of the cycle in each ovarian compartment. However, summation of the number of mast cells in the entire ovarian complex revealed a significant decline in number at 15.00 h on pro-oestrus. Alterations in mast cell degranulation were primarily restricted to 2 periods of the cycle (pro-oestrus and di-oestrus). An increase in moderate but not extensive degranulation was observed in only the fat pad and bursa on day 2 when compared with day 1 values. In most ovarian compartments on pro-oestrus, degranulation was higher than on any other day of the cycle. At 15.00 h on pro-oestrus, extensive degranulation in bursa, fat pad and blood vessel regions (but not hilum) coincided with an increase in ovarian histamine and decline in number of mast cells; ovarian blood flow also increased at the time but remained unchanged the remainder of the cycle.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Glycosyl phosphatidylinositol membrane anchoring of melanotransferrin (p97): apical compartmentalization in intestinal epithelial cells.

Melanotransferrin (p97) is an iron-binding membrane glycoprotein with 40% homology to transferrin and lactoferrin. It was first identified on the basis of its high level of expression in melanoma cells, as compared to normal melanocytes. It is also present in many cultured cell types. In normal tissues, p97 is expressed in fetal intestine, umbilical cord, sweat gland ducts and liver sinusoidal lining cells. Kinetic studies in melanoma cells have suggested that p97 plays a role in iron metabolism. We have examined expression of p97 in cell lines derived from human colorectal carcinomas which express a differentiated phenotype. When polarized, these cells showed a preferred apical distribution of p97, as demonstrated by immunohistochemistry, immune electron microscopy and domain-selective biotinylation. Correspondingly, p97 was only found on the apical brush border of epithelial cells in the fetal intestine. p97 was shown to be anchored to the membrane through a glycosyl phosphatidylinositol moiety by treatment with phophatidylinositol-specific phospholipase C (PI-PLC) and labeling with [14C]ethanolamine. These observations provide a basis for the elucidation of the physiological role of p97 in iron metabolism and its possible role in cell proliferation and malignant cell transformation.

Antigens, Neoplasm↗
PubMed2005

Microanatomy of axon/glial signaling during Wallerian degeneration.

How do myelinated axons signal to the nuclei of cells that enwrap them? The cell bodies of oligodendrocytes and Schwann cells are segregated from axons by multiple layers of bimolecular lipid leaflet and myelin proteins. Conventional signal transduction strategies would seem inadequate to the challenge without special adaptations. Wallerian degeneration provides a model to study axon-to-Schwann cell signaling in the context of nerve injury. We show a hitherto undetected rapid, but transient, activation of the receptor tyrosine kinase erbB2 in myelinating Schwann cells after sciatic nerve axotomy. Deconvolving microscopy using phosphorylation state-specific antibodies shows that erbB2 activation emanates from within the microvilli of Schwann cells, in direct contact with the axons they enwrap. To define the functional role of this transient activation, we used a small molecule antagonist of erbB2 activation (PKI166). The response of myelinating Schwann cells to axotomy is inhibited by PKI166 in vivo. Using neuron/Schwann cell cocultures prepared in compartmentalized cell culture chambers, we show that even transient activation of erbB2 is sufficient to initiate Schwann cell demyelination and that the initiating functions of erbB2 are localized to Schwann cells.

Analysis of Variance↗
PubMed2001

Evidence for a compartmentalized B cell response as characterized by IgG epitope specificity in human ocular toxoplasmosis.

Infectious agents in the eye induce both a local and a systemic humoral immune response. Previously, differences in Ag recognition were observed between systemic and ocular derived IgG of patients with ocular toxoplasmosis. This finding implied a nonrandom distribution of IgG-producing B cells in the inflamed eye. In the present study, we compared the intraocular and systemic B cell responses of patients with ocular toxoplasmosis to a single Toxoplasma gondii Ag. Two series of C-terminally deleted recombinant T. gondii GRA-2 proteins were constructed to delineate IgG B cell epitopes of paired ocular and serum samples. Differences in epitope region recognition between the ocular and systemic compartment were detected in 9 of 13 patients. The difference in distribution of GRA-2 epitopes between paired samples is indicative of a local GRA-2 specific B cell population functionally different from the systemic GRA-2-specific B cell population. Our results suggest a selective activation of a subset of B cells locally in nonlymphoid tissue.

Adolescent↗
PubMed1985

Pityriasis rosea (Gibert): abnormal distribution pattern of antigen presenting cells in situ.

Pityriasis rosea is a skin disease which is obscure in its etiology and pathogenesis. We studied its immunopathology by immunophenotyping the inflammatory cells in situ using monoclonal antibodies that define leukocyte subsets. Findings as to T-cells and their major subsets did not reveal disease-specific data. Monocytes stained only rarely. Neither natural killer cells, B-cells nor plasma cells were ever found. An unexpected finding was the presence within the infiltrates and rarely within the epidermis of cells having the immunophenotype of interdigitating cells (RFD1+). Intense and dendritic staining with anti-T6 and anti-HLA-DR indicated Langerhans cells to be present in the dermal infiltrates, in between these infiltrates in the papillary dermis, and focally within the parakeratotic horny layer. This Langerhans' cell pattern provides evidence for dermal Langerhans cell compartmentalization and transepidermal Langerhans' cell elimination. Such a distribution indicates a change in Langerhans' cell migration processes in pityriasis rosea pathogenesis.

Adult↗
PubMed1993

13C nuclear magnetic resonance studies of malate and citrate synthesis and compartmentation in higher plant cells.

The synthesis of malate and citrate by sycamore cells (Acer pseudoplatanus L.) perfused with KH13CO3 was analyzed using 13C NMR. To perform in vivo experiments, cells were compressed in a 25-mm tube and perfused with an arrangement enabling tight control of the circulating nutrient medium. An original method using paramagnetic Mn2+ that induced a complete loss of the vacuolar malate and citrate signals was developed to discriminate between cytoplasmic and vacuolar pools of malate and citrate. Our results indicated the following. (a) The accumulation of appreciable amounts of malate in sycamore cells required rather high (1 mM) concentrations of bicarbonate at all the pH values tested. (b) Malate was equally labeled at C-1 and C-4, suggesting that malate labeled at C-1 was produced by randomization of C-1 and C-4 by mitochondrial fumarase. Indeed, the separation of the intact organelles from the lysed protoplasts indicated that fumarase activity was essentially limited to the mitochondria. Similarly, citrate was equally enriched at C-1 and C-5 + C-6 carboxyls. (c) Malate appeared first in the cytoplasmic compartment; and when a threshold of cytoplasmic malate concentration was attained, malate molecules were expelled into the vacuole, where they accumulated. On the other hand, citrate accumulated steadily in the vacuole. Pulse-chase experiments demonstrated the central role played by the tonoplast in governing the vacuolar influx of citrate and the permanent exchange of malate between the cytoplasm and the vacuole.

Bicarbonates↗