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At least 775 records · Page 43Linked to original sources
PubMed1983

Role of endoplasmic reticulum in biosynthesis of oat globulin precursors.

Oat (Avena sativa L.) groats were labeled with radioactive leucine and salt-soluble proteins were extracted and analyzed. Polyacrylamide gel electrophoresis followed by fluorography indicated two radioactive polypeptides with molecular weight 58 to 62 kilodaltons which were similar in size to unreduced globulin alpha-beta dimers. The role of endoplasmic reticulum in the synthesis of these globulin polypeptides was investigated by in vivo and in vitro protein synthesis studies. Labeled tissue was fractionated by centrifugation and rough endoplasmic reticulum was isolated. Two polypeptides which had molecular weights of 58 to 62 kilodaltons and were immunoprecipitable with antiglobulin immunoglobulin G were found to be transiently associated with the endoplasmic reticulum. Rough endoplasmic reticulum, as well as membrane-bound polysomes, directed the in vitro synthesis of two polypeptides with molecular weight 58 to 62 kilodaltons corresponding in size to unreduced alpha-beta dimers and could be immunoprecipitated with antiglobulin immunoglobulin G. The translation products of free polysomes did not show this. In pulse-labeling, globulin polypeptides with molecular weight 58 to 62 kilodaltons, as well as the alpha + beta subunits, were labeled in protein bodies.The data suggest that oat globulin polypeptides are synthesized as higher molecular weight precursors on ER-associated polysomes. These precursors are probably transported into protein bodies and cleaved into smaller alpha and beta subunits.

Journal Article↗
PubMed1984

Endoplasmic reticulum as a site of phenylpropanoid and flavonoid metabolism in hippeastrum.

The nature of bound forms of enzymes of phenylpropanoid and flavonoid metabolism have been investigated in Hippeastrum CV Dutch Red Hybrid. Particulate components of petal homogenates were fractionated on sucrose gradients and the EDTA shift method was employed to characterize membranes of the endoplasmic reticulum. In magnesiumcontaining gradients, a portion of phenylalanine ammonia lyase, chalcone synthase, glucosyl transferase, and all of the trans-cinnamate 4-monooxygenase and NADH Cytochrome c reductase (the last an endoplasmic reticulum marker) were associated with membranes equilibrating at 1.18 specific gravity. In gradients lacking magnesium and containing EDTA, the above activities-except chalcone synthase, which was lost-and protein were diminished at 1.18 specific gravity and enhanced at lower densities characteristic of membranes of the smooth endoplasmic reticulum. These results are consistent with the contention that endoplasmic reticulum is a site of phenylpropanoid and flavonoid metabolism in Hippeastrum.

Journal Article↗
PubMed1990

Macrophages and interdigitating reticulum cells in normal human thymus and thymomas: immunoreactivity for interleukin-1 alpha, interleukin-1 beta and tumour necrosis factor alpha.

Pairs of monoclonal/polyclonal antibodies directed against interleukin-1 (IL-1) alpha, IL-1 beta and tumour necrosis factor (TNF) alpha were used for immunocytochemical identification of cytokine-containing cells in cryostat sections of human fetal thymuses and thymomas. In the fetal thymus immunoreactivity for IL-1 alpha was mainly confined to the medulla and was detected in S-100 positive interdigitating reticulum cells. The pattern of immunoreactivity for IL-1 beta was similar to that for IL-1 alpha, but the number of positive cells was much lower. Cells positive for TNF alpha were extremely rare in the fetal thymus. In 11 thymomas macrophages were constantly present and were regularly distributed throughout the tumour, whereas S-100 positive interdigitating reticulum cells were fewer and were characterized by a zonal distribution. Thymoma-associated macrophages were negative for IL-1 beta and were poorly reactive for IL-1 alpha, only a few positive cells being detected in five of the cases. Some macrophages with immunoreactivity for TNF alpha were detected in seven cases; they formed rosettes with surrounding lymphocytes or were located in a perivascular position. A marked immunoreactivity for TNF alpha was constantly detected in mast cell granules, which were observed in nine thymomas but not in fetal thymus. Positive immunoreactivity of interdigitating reticulum cells for IL-1 alpha was confirmed in five reactive lymph nodes and was also observed in Langerhans' cells in dermatopathic lymphadenitis. Our findings suggest that IL-1 alpha is a crucial molecule for interdigitating reticulum cell and Langerhans' cell function.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Expression of ICAM-1, VCAM-1 and ELAM-1 in angiofollicular lymph node hyperplasia (Castleman's disease): evidence for dysplasia of follicular dendritic reticulum cells.

The inducible adhesion molecules mediate important functions in the lymphoid tissues. We have investigated the expression of intercellular adhesion molecule 1 (ICAM-1), endothelial leucocyte adhesion molecule 1 (ELAM-1), vascular cell adhesion molecule 1 (VCAM-1), and platelet endothelial cell adhesion molecule (PECAM/CD31), using immunocytochemistry on cryostat sections of five lymph nodes from patients with Castleman's disease of the hyaline-vascular type. All five cases were characterized by marked hyperplasia of follicular dendritic reticulum cells, which were extensively present even in the mantle zone. Hyperplastic follicular dendritic reticulum cells showed marked expression of VCAM-1, and weak expression of ICAM-1. In two cases, several dysplastic giant cells with aberrant, polyploid nuclei showed aberrant expression of ELAM-1, an endothelium-restricted molecule. Dysplastic giant cells were positive with DRC-1 (an antibody to dendritic reticulum cells), VCAM-1 and occasionally ICAM-1, were negative for the endothelial cell markers factor VIII-related antigen and CD31 and were non-proliferating (Kl-67-). Cells positive for ICAM-1 or VCAM-1 were rare in the interfollicular areas. In all cases vascular hyperplasia was prominent, but endothelial cells were poorly activated in terms of expression of inducible adhesion molecules and of HLA-DR antigens. The possibility that dysplastic follicular dendritic reticulum cells have a pathogenetic role in Castleman's disease is discussed.

Adult↗
PubMed1998

Interdigitating reticulum cell tumor of lymph node: a case report and literature review.

Interdigitating reticulum cell (IRC) tumor is a rare tumor arising from the antigen-presenting cell - interdigitating reticulum cell. A 41-year-old male presented with lumps in the left neck and bone pain. Further investigations revealed multiple left neck and para-aortic lymphadenopathy, and multiple bony lesions. Histological examination of the lymph node showed proliferation of unusual, large, round neoplastic cells mimicking large cell lymphoma. Immunophenotypic and ultrastructural studies confirmed this tumor to be arising from an interdigitating reticulum cell. A review of reported IRC tumors illustrates the variability of this tumor in clinical and pathological features, which differ from other dendritic reticulum cell tumors.

Adult↗
PubMed1987

Intraocular reticulum cell sarcoma: diagnosis by choroidal biopsy.

A patient with uveitis and retinal pigment epithelial detachments underwent an extensive medical examination and pars plana vitrectomy in an attempt to confirm the clinical diagnosis of reticulum cell sarcoma. None of these examinations revealed the presence of malignancy. Transscleral biopsy of subretinal lesions confirmed the histopathological diagnosis of reticulum cell sarcoma. The patient was begun on systemic chemotherapy and external beam radiation to the eye and orbit, with resultant preservation of the eye, vision, and probable extension of life because of early detection of reticulum cell sarcoma by choroidal biopsy. This technique may be advantageous in the diagnosis cases of eyes with clinical evidence of reticulum cell sarcoma, no systemic signs of malignancy, and negative vitreous biopsies.

Aged↗
PubMed1994

Extrafollicular reticulum cells in pathologic lymph nodes.

Extrafollicular reticulum cells in lymph nodes are heterogeneous. They express cytokeratins, desmin, and/or vimentin as their intermediate filament profile. Using those markers, we undertook an immunohistochemical study of human lymph nodes under various pathologic conditions. Samples included 15 simple reactive lymph nodes, 7 follicular hyperplasia, 1 necrotizing lymphadenitis, 4 tuberculous lymphadenitis, 13 malignant lymphoma (9 non-Hodgkin's and 4 Hodgkin's lymphomas), and 11 metastatic adenocarcinoma. In lymph nodes with follicular hyperplasia, cytokeratin and/or desmin expressing reticulum cells displayed a characteristic dendritic meshwork in the subcapsular, perisinusoidal, and paracortical regions. In other forms reactive lymph nodes, they were similarly distributed but were less prominent. By SDS-PAGE and immunoblotting, cytokeratin polypeptides were identified. In necrotizing lymphadenitis, they were increased and the pattern of distribution was disturbed. In tuberculous lymphadenitis, they were also increased and located at nongranulomatous as well as in perigranulomatous areas. In lymphomas the reticular meshwork was entirely obliterated. Cytokeratin or desmin expressing reticulum cells were rarely seen within tumors. The reticular meshwork was also obliterated in metastatic carcinoma. However, the meshwork was maintained in uninvolved areas. In conclusion, extrafollicular reticulum cells displayed characteristic patterns of distribution under various pathologic conditions, and may be implicated in the pathogenesis of those pathologic conditions in human lymph nodes.

Antibodies, Monoclonal↗
PubMed1992

Investigation of usefulness of electroreticulograms obtained from the sheep body surface in estimation of reticulum electrical activity.

The experiments were carried out on 3 sheep with one pair of platinum electrodes chronically implanted in the reticulum wall. The reticulum action potentials were recorded simultaneously from the body surface (using the needle electrodes placed subcutaneously) and from the implanted electrodes using an electroencephalograph Reega XVI Duplex TR. It was found that the two- or three-phase deflections on the electroreticulograms obtained from the body surface were exactly correlated with the series of potential spikes on the records from the implanted electrodes. The number of phases in each deflection was equal to the number of the series of potential spikes during the reticulum excitation. During the reticulum hypotony the decrease in action potentials was observed. That is why we were not able to record the electrical activity from the body surface, while it was still possible to record electroreticulograms from the implanted electrodes.

Action Potentials↗
PubMed1990

Identification of an Mr 70,000 antigen associated with Reed-Sternberg cells and interdigitating reticulum cells.

We obtained a monoclonal antibody that has restricted reactivity with tumor cells [Hodgkin's mononuclear cells and Reed-Sternberg (H-RS) cells] in Hodgkin's disease by immunizing mice with 12-O-tetradecanoyl phorbol-13-acetate-induced H-RS cells. The antibody, anti-IRac, reacted with H-RS cells in 8 of 20 patients who had Hodgkin's disease, as well as with interdigitating reticulum cells in dermatopathic lymph nodes and with cells of three H-RS cell lines, HDLM-1, L428, and KM-H2. The antigen IRac is a protein of molecular weight 70,000 which we found to have the following properties. (a) After 12-O-tetradecanoyl phorbol-13-acetate induction, the expression of IRac was decreased slightly in HDLM and L428 cells but increased in KM-H2. This is in contrast to a rapid decrease in the expression of two other H-RS-cell-associated antigens, CD30 and 2H9, in all 12-O-tetradecanoyl phorbol-13-acetate-treated H-RS cells. Thus, IRac may be associated with H-RS cells at advanced stages of differentiation, and its expression may not be attributable solely to cellular proliferation. (b) IRac was detected rarely in normal or in antigen- or mitogen-activated lymphocytes but was observed frequently in virus-transformed B- or T-lymphocytes. These findings were similar to those with CD30 and 2H9, indicating that the expression of all three of these antigens is probably under a similar regulatory control. (c) IRac was absent from cells in most non-Hodgkin's lymphomas; its expression could not be modulated by treatment of cells with anti-IRac. We conclude that use of IRac could facilitate the diagnosis of Hodgkin's disease and that it may be suitable for immunotherapy or immunoimaging. The expression of IRac in both H-RS cells and interdigitating reticulum cells, along with earlier evidence, indicates that H-RS cells have antigenic and functional similarities to interdigitating reticulum cells or to cells of interdigitating reticulum cell/histiocyte lineage.

Animals↗
PubMed1988

A novel Ca2+ pump expressed in brain, kidney, and stomach is encoded by an alternative transcript of the slow-twitch muscle sarcoplasmic reticulum Ca-ATPase gene. Identification of cDNAs encoding Ca2+ and other cation-transporting ATPases using an oligonucleotide probe derived from the ATP-binding site.

We describe the results of a study designed to identify cDNAs encoding Ca2+-transporting ATPases and other cation-transporting ATPases of the aspartylphosphate class. Rat brain, kidney, and stomach cDNA libraries were screened with an oligonucleotide hybridization probe corresponding to a 23-amino acid sequence from part of the ATP-binding site of the sarcoplasmic reticulum Ca-ATPase. This procedure resulted in the isolation of cDNAs encoding (i) the plasma membrane Ca-ATPase, (ii) an apparent Ca-ATPase that exhibits high amino acid similarity to the sarcoplasmic reticulum Ca2+ pumps, (iii) a transport ATPase of unknown ion specificity and (iv) two Ca-ATPase isoforms encoded by the gene for the slow-twitch muscle sarcoplasmic reticulum Ca-ATPase. Several isoforms of the Na,K-ATPase and gastric H,K-ATPase that had been characterized previously were also identified. The complete nucleotide sequences have been determined for the two classes of cDNA derived from alternatively spliced transcripts of the slow-twitch muscle sarcoplasmic reticulum Ca-ATPase gene. One of these cDNAs, isolated from the stomach library, encodes a Ca-ATPase that is identical to the skeletal muscle enzyme. The second class of cDNA, found in brain, kidney, and stomach libraries, is identical to that of the slow-twitch isoform throughout much of its length but encodes an alternative C terminus and has a different 3'-untranslated sequence. Whereas the muscle isoform consists of 997 amino acids and terminates with the sequence Ala-Ile-Leu-Glu, the second isoform is 1043 amino acids in length due to the replacement of these last 4 amino acids with a 50-amino acid sequence that contains a potential transmembrane domain followed by a consensus sequence for an N-linked glycosylation site.

Adenosine Triphosphatases↗
PubMed1981

Ontogenesis of mitochondrial reticulum in rat diaphragm muscle.

Ontogenesis of mitochrondrial reticulum discovered in rat diaphragm has been studied with an electron microscope by the serial section technique. The amount of mitochondrial material in the diaphragm of rat embryos was found to be small. There are rare inclusions of single mitochondria which form columns paralleling the long axis of muscle fiber. After birth, a progressive increase in the amount of mitochondrial material takes place. This process is accompanied by the appearance of new components inherent in the unitary system of mitochondrial reticulum, namely mitochondrial junctions, as well as branches and tubules of mitochondrial material paralleling Z-discs and localized on the levels of the isotropic regions of sarcomeres. The first mitochondrial junctions were found to appear as early as on the second day, and the mitochondrial branches between the second and the ninth days of postnatal development. For a one-month-old rat, a three-dimensional model of a part of mitochondrial reticulum corresponding to one sarcomere was reconstituted. It revealed columns of mitochondrial material crossing the anisotropic region of sarcomere. Such columns connect two networks of mitochondrial profiles localized on the levels of two isotropic regions of sarcomere. Formation of mitochondrial reticulum is completed within two postnatal months.

Animals↗
PubMed1975

[A case of primary reticulum cell sarcoma of the brain with uveitis (author's transl)].

In 1972, Neault and his co-workers reported seven cases of uveitis associated with intracranial reticulum cell sarcoma. Recently we have experienced a similar case for the first time in Japan. A 32-year-old woman registered on March 10, 1971, complaining of blurred vision in the left eye for about two weeks. By ophthalmic examination, left posterior uveitis was diagnosed but the etiology was unknown. Treatment with corticosteroids was begun, but her left eye continued to fail in spite of the treatment. In August, 1971, she complained of weakness of left arm and leg, and in October, she suffered from severe headache and vomiting. At that time, uveitis appeared in the right eye too. Neurological findings and carotid angiogram indicated a right cerebral lesion. On November 5, 1971, a right frontoparietal craniotomy was performed but no tumor was found. Since then her neurological and eye symptoms had been progressively worse. The patient died on July 12, 1972. Postmortem examination revealed the tumor infiltrating in the bilateral diencephalon, left internal capsule, left lenticular nucleus, left temporal lobe, midbrain, pons, left dentate nucleus, optic chiasma and intracranial portion of the optic nerves. But no tumor was found at any other parts of the body. Histologically the tumor was a reticulum cell sarcoma. The eyeballs were not examined histologically, but the uveitis in this case was thought to be closely related to the intracranial reticulum cell sarcoma. If the uveitis is resistant to the treatment, we must consider a possibility of reticulum cell sarcoma of the brain.

Adult↗
PubMed1990

BiP expression is not increased by the accumulation of PiZ alpha 1-antitrypsin in the endoplasmic reticulum.

PiZ, a mutant human alpha 1-antitrypsin, is associated with liver and pulmonary disease and is characterized by defective secretion and accumulation of the protein in the endoplasmic reticulum. We tested the hypothesis that BiP (a protein that binds newly synthesized protein in the endoplasmic reticulum, prevents secretion of incorrectly folded protein, and solubilizes protein aggregates), could play a part in the retention of PiZ alpha 1-antitrypsin in the endoplasmic reticulum. Subcellular fractions from PiM (normal) and PiZ livers were prepared and analyzed by immunoblotting. No increase of BiP was detected in the PiZ liver. In addition, when total RNA from the same livers were analyzed by slot and Northern blot hybridization, no difference was found in the level of BiP mRNA between PiM and PiZ livers. Similar results were found in clones of CHO and MDCK cells transfected with PiM of PiZ alpha 1-antitrypsin cDNAs. These results indicate that BiP does not play a part in the retention of PiZ alpha 1-antitrypsin and suggest that PiZ protein is not misfolded.

Animals↗
PubMed2005

Disruption of the endoplasmic reticulum by cytotoxins in LLC-PK1 cells.

Prior induction of an endoplasmic reticulum stress response results in protection against reactive cytotoxins in the LLC-PK1 cell line. The purpose of this investigation was to determine therefore if the endoplasmic reticulum was disrupted by iodoacetamide, tert-butylhydroperoxide or sulfamethoxazole hydroxylamine. Toxic concentrations of the three toxins caused a dramatic loss of GRP94 protein within 3-8h of exposure, while induction of GRP78 and calreticulin occurred at 8 and 24h following exposure. There was no evidence of cytosolic elevation of calcium and neither dantrolene nor xestospongin were able to block the cytotoxicity of IDAM and TBHP. Exposure to the toxins led to DNA degradation and cleavage of procaspase-12. There was only evidence of procaspase-3 cleavage after TBHP exposure. These results demonstrate that the ER is disrupted by the reactive cytotoxins examined in LLC-PK1cells and suggest that the cytoprotection against low to moderate concentrations of cytotoxins observed following endoplasmic reticulum stress protein induction is likely due to a mechanism other than maintenance of calcium homeostasis.

Aniline Compounds↗
PubMed2001

Endoplasmic reticulum in the heart, a forgotten organelle?

Our hypothesis is that sarcoplasmic and endoplasmic reticulum Ca2+ stores may be functionally distinct compartments in cardiomyocytes. Sarcoplasmic reticulum Ca2+ store is responsible for control of excitation-contraction coupling whereas endoplasmic reticulum compartment may provide Ca2+ for housekeeping and transcriptional functions.

Animals↗
PubMed2004

Dual sensitivity of sarcoplasmic/endoplasmic Ca2+-ATPase to cytosolic and endoplasmic reticulum Ca2+ as a mechanism of modulating cytosolic Ca2+ oscillations.

The effects of ER (endoplasmic reticulum) Ca2+ on cytosolic Ca2+ oscillations in pancreatic acinar cells were investigated using mathematical models of the Ca2+ oscillations. We first examined the mathematical model of SERCA (sarcoplasmic/endoplasmic reticulum Ca2+-ATPase) to reproduce the highly co-operative inhibitory effect of Ca2+ in the ER lumen on ER Ca2+ uptake in the acinar cells. The model predicts that luminal Ca2+ would most probably inhibit the conversion of the conformation state with luminal Ca2+-binding sites (E2) into the conformation state with cytoplasmic Ca2+-binding sites (E1). The SERCA model derived from this prediction showed dose-response relationships to cytosolic and luminal Ca2+ concentrations that were consistent with the experimental data from the acinar cells. According to a mathematical model of cytosolic Ca2+ oscillations based on the modified SERCA model, a small decrease in the concentration of endoplasmic reticulum Ca2+ (approx. 20% of the total) was sufficient to abolish the oscillations. When a single type of IP3R (IP3 receptor) was included in the model, store depletion decreased the spike frequency. However, the frequency became less sensitive to store depletion when we added another type of IP3R with higher sensitivity to the concentration of free Ca2+ in the cytosol. Bifurcation analysis of the mathematical model showed that the loss of Ca2+ from the ER lumen decreased the sensitivity of cytosolic Ca2+ oscillations to IP3 [Ins(1,4,5)P3]. The addition of a high-affinity IP3R did not alter this property, but significantly decreased the sensitivity of the spike frequency to IP3. Our mathematical model demonstrates how luminal Ca2+, through its effect on Ca2+ uptake, can control cytosolic Ca2+ oscillations.

Binding Sites↗
PubMed1989

AIF4-induced inhibition of the ATPase activity, the Ca2+-transport activity and the phosphoprotein-intermediate formation of plasma-membrane and endo(sarco)plasmic-reticulum Ca2+-transport ATPases in different tissues. Evidence for a tissue-dependent functional difference.

AIF4- inhibits the (Ca2+ + Mg2+)-ATPase activity of the plasma-membrane and the sarcoplasmic-reticulum Ca2+-transport ATPase [Missiaen, Wuytack, De Smedt, Vrolix & Casteels (1988) Biochem. J. 253, 827-833]. The aim of the present work was to investigate this inhibition further. We now report that AIF4- inhibits not only the (Ca2+ + Mg2+)-ATPase activity, but also the ATP-dependent 45Ca2+ transport, and the formation of the phosphoprotein intermediate by these pumps. Mg2+ potentiated the effect of AIF4-, whereas K+ had no such effect. The plasma-membrane Ca2+-transport ATPase from erythrocytes was 20 times less sensitive to inhibition by AIF4- as compared with the Ca2+-transport ATPase from smooth muscle. The endoplasmic-reticulum Ca2+-transport ATPase from smooth muscle was inhibited to a greater extent than the sarcoplasmic-reticulum Ca2+-transport ATPase of slow and fast skeletal muscle.

Adenosine Triphosphatases↗
PubMed1993

Evidence that the putative COOH-terminal signal transamidase involved in glycosylphosphatidylinositol protein synthesis is present in the endoplasmic reticulum.

Nascent proteins destined to be processed to a glycosylphosphatidylinositol (GPI)-anchored membrane form contain NH2-terminal and COOH-terminal signal peptides. The first directs a nascent protein into the endoplasmic reticulum; the second peptide targets the protein to a putative COOH-terminal signal transamidase where cleavage of the peptide and addition of the GPI anchor occur. We recently showed that ATP hydrolysis is required for maturation of GPI proteins at a stage prior to transamidation. Here we show that one of the ATP-requiring proteins involved in processing of GPI-anchored proteins in the endoplasmic reticulum is the immunoglobulin heavy chain binding protein (BiP; GRP 78). This and related findings indicate that GPI transamidase is localized in the endoplasmic reticulum.

Acyltransferases↗