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Cytochromes P450 are expressed in proliferating cells in Barrett's metaplasia.

The expression of cytochromes P450 (CYP) in Barrett's esophagus and esophageal squamous mucosa was investigated. Esophagectomy specimens from 23 patients were examined for CYP expression of CYP1A2, CYP3A4, CYP2C9/10, and CYP2E1 by immunohistochemical analysis, and the expression of CYP1A1, CYP3A4, CYP1B1, CYP2E1, and CYP2C9/10 in these tissues was further confirmed by reverse transcription polymerase chain reaction. Immunohistochemical analysis of esophageal squamous mucosa (n = 12) showed expression of CYP1A2, CYP3A4, CYP2E1, and CYP2C9/10 proteins, but it was noted that cells within the basal proliferative zone did not express CYPs. Immunohistochemical analysis of Barrett's esophagus (n = 13) showed expression of CYP1A2, CYP3A4, CYP2E1, and CYP2C9/10 that was prominent in the basal glandular regions, which are areas containing a high percentage of actively proliferating cells. Immunohistochemical staining for both proliferating cell nuclear antigen and the CYPs further supported the colocalization of CYP expression to areas of active cell proliferation in Barrett's esophagus, whereas in the esophageal squamous epithelium, CYP expression is limited to cells that are not proliferating. RT-PCR with amplification product sequence analysis confirmed CYP1A1, CYP3A4, CYP1B1, CYP2E1, and CYP2C9/10 mRNA expression in Barrett's esophagus. These data suggest that the potential ability of cells in Barrett's esophagus to both activate carcinogens and proliferate may be important risk factors affecting carcinogenesis in this metaplastic tissue.

Barrett Esophagus↗

Dystrophin localization and gene expression in the developing nervous system of the chick.

The presence and distribution of dystrophin was studied in selected areas of the chick embryo nervous system and in primary cultures. Dystrophin was examined at the protein level by immunocytochemistry and at the transcriptional level by a semiquantitative reverse transcriptase-polymerase chain reaction analysis. Immunofluorescence staining shows that dystrophin is present early during embryogenesis in dorsal root ganglia, spinal cord, and ciliary ganglia and colocalizes with neurofilament subunits. Cultured dorsal root ganglion, spinal cord, and ciliary ganglion neurons show immunoreactivity for dystrophin, both in cell bodies and along fibers. Dystrophin mRNA level in ciliary and dorsal root ganglia is higher than in spinal cord throughout development and shows a tissue-specific pattern of expression. In primary cultures of dorsal root ganglia and ciliary ganglia, dystrophin mRNA level increases with time in vitro. However, in spinal cord cultures, dystrophin mRNA drastically decreases with time in vitro, but it is significantly increased when embryonic muscle extract is added to the cultures. Our results show that dystrophin is present in neurons from different areas of embryonic chick nervous system and that its mRNA level is developmentally regulated both in vivo and in vitro.

Animals↗

VGluT2 immunochemistry identifies thalamocortical terminals in layer 4 of adult and developing visual cortex.

A vesicular glutamate transporter, VGluT2, has been suggested to be the transporter utilized in the thalamocortical pathway. We examined the reliability of this marker in identifying and discriminating thalamic terminals in adult and developing ferret visual cortex. We studied brain sections stained for the transporter protein and/or anterogradely filled thalamocortical or intracortical axons, by using light, confocal, and electron microscopy. Under light microscopy, VGluT2 immunoreactivity (ir) in adult animals [past postnatal day (P)90] and in neonatal animals as early as P27 formed a dense band in layer 4 and appeared as scattered puncta in layers 6 and 1. Confocal dual-labeling analyses of P46 and adult striate cortices indicated that VGluT2 was present in thalamocortical axons, suggesting that thalamic projections utilize this transporter during postnatal development as well as adulthood. In contrast, extracellularly filled intracortical axons failed to colocalize with VGluT2-ir, suggesting that no significant terminal population originating in cortex contained VGluT2 in layer 4. Electron microscopic analysis revealed that, in adult layer 4, VGluT2-ir was present in large terminals, forming asymmetric synapses. Similar to anterogradely labeled thalamocortical terminals, VGluT2-ir synaptic terminals were different from their unlabeled counterparts in terms of terminal area (0.6 vs. 0.3 microm), synaptic length (486 vs. 353 nm), and preference for synapsing on spines (77% vs. 59%). Moreover, no significant differences were found between VGluT2-ir and anterogradely labeled thalamocortical terminals. Comparable similarities were also demonstrated at P46. These results indicate that thalamocortical terminals in layer 4 of visual cortex utilize VGluT2 and suggest that this marker can be used to identify thalamic axons specifically in adult and developing animals.

Animals↗

CTGF/Hcs24, hypertrophic chondrocyte-specific gene product, interacts with perlecan in regulating the proliferation and differentiation of chondrocytes.

Connective tissue growth factor/hypertrophic chondrocyte-specific gene product 24 (CTGF/Hcs24) plays important roles in the control of the proliferation and differentiation of chondrocytes in vitro. To clarify the mechanisms of regulation by CTGF/Hcs24 with respect to cartilage metabolism, we investigated the interaction between CTGF/Hcs24 and heparan sulfate proteoglycan perlecan. An immunofluorescence study showed that CTGF/Hcs24 was colocalized with heparan sulfate and perlecan in human chondrosarcoma-derived chondrocytic cell line HCS-2/8 in vitro. Northern blot analysis showed that perlecan, syndecan-1, -2, and -4 transcripts were detected in HCS-2/8 cells. Particularly, expression of the perlecan gene increased markedly in HCS-2/8 cells by recombinant CTGF/Hcs24 (rCTGF/Hcs24) treatment. We also found that CTGF/Hcs24 interacted with perlecan from HCS-2/8 cells in vitro. Furthermore, CTGF/Hcs24-stimulated gene expression of the aggrecan gene, as well as DNA/proteoglycan synthesis, was diminished when HCS-2/8 cells were pretreated with heparinase, indicating that the effects of CTGF/Hcs24 on chondrocytes occurred through the interaction between CTGF/Hcs24 and heparan sulfate on the cells. An in vivo study using mouse growth plate revealed that CTGF/Hcs24 produced by hypertrophic chondrocytes was localized from the proliferative to the hypertrophic zone, whereas perlecan was predominantly localized in the prehyphertrophic zone. Consistent with such findings in vivo, the binding of (125)I-rCTGF/Hcs24 to maturing chondrocytes was at higher levels than that to chondrocytes in hypertrophic stages. These findings suggest that CTGF/Hcs24 produced in the hypertrophic region may act on chondrocytes in the proliferative and maturative zone via some heparan sulfate proteoglycan, such as perlecan.

Aged↗

Detection and characterization of protein aggregates by fluorescence microscopy.

Aggregation may compromise the stability as well as the biological activity of protein drugs. Detection of protein aggregates is needed in the process of protein characterization and during optimization of pharmaceutical formulations. This paper describes a technique, which consists of analysing protein aggregates by fluorescence microscopy after staining with the hydrophobic probe Nile Red. Dilution, filtration or other modifications of the sample are not needed. Assessment of aggregation was possible in highly concentrated protein samples (193 mg/ml). Fluorescence microscopy observations allowed the detection and characterization of protein aggregates not easily detected by spectroscopic techniques. Nile Red was shown to be very sensitive for the detection and analysis of immunoglobulin aggregates. Nile Red, Congo red and Thioflavine T stainings were compared. Nile Red and Thioflavine T fluorescence were colocalized. The diameter of immunoglobulin aggregates was determined, and the number of aggregates was correlated with 90 degrees light scattering measurements. Studies of human calcitonin aggregates brought to light new aspects of the human calcitonin aggregation mechanisms. Thus, Nile Red staining not only allows detection of very low levels of protein aggregates, but also contributes to a better understanding of the complex mechanisms governing protein aggregation.

Antibodies↗

Chelation of synaptic zinc induces overexcitation in the hilar mossy cells of the rat hippocampus.

Complete removal of synaptic zinc by the chelator dietyldithiocarbamate (DEDTC; 500 mg/kg i.p.) in rat was followed by convulsive behaviour including wet dog shakes alternating immobility. Histological analysis 1 day after DEDTC administration detected expression of heat shock protein in the hippocampus restricted to hilar cells. These cells colocalize the marker for neurons and the glutamate receptor GluR2/3 showing that they are excitatory neurons. Additionally, they projected to the contralateral dentate gyrus. Therefore, they correspond to hilar mossy cells. These data show that the synaptic zinc has a role in normal hippocampus avoiding overexcitation, that would impair functionality even in absence of pathological or exoexcitotoxic phenomena.

Action Potentials↗

Evidence for the involvement of T cell costimulation through the B-7/CD28 pathway in atherosclerotic plaques from apolipoprotein E knockout mice.

Antigen-specific T cell activation is thought to influence the initiation and progression of the atherosclerotic plaque. For the T cell activation program to be functional, it is essential not only to facilitate T cell receptor engagement by antigen-presenting cells (APC), but also to deliver requisite costimulatory signals. The most widely comprehended costimulatory pathway involves the ligation of CD28 expressed on T cells by CD80 and CD86 upregulated on APCs. We hypothesized that signals of costimulation should be localized to plaque areas that correspond to the presence of the provoking autoantigen. Atherosclerotic plaques from apoE knockout (KO) mice at different stages of maturation were studied immunohistochemically by monoclonal antibodies to respective markers of primary and secondary lymphocyte activation. Subsequently, flow cytometry studies were conducted in spleen cells from C57BL/6 and apoE KO mice aiming to determine whether the presence of plaques is associated with increased expression of costimulatory signals. We found that regardless of the maturation stage, CD80 and CD86 were evident within the plaques, and colocalized with the presence of markers of dendritic cells and with expression of the extensively investigated autoantigen-oxidized LDL. FACS analysis studies showed that splenocytes from aged atherosclerotic apoE KO mice exhibited increased expression on B cells (which represent APCs) of CD80 and CD86 as compared to their young apoE or naïve C57BL/6 litters that have no plaques. These results suggest that primary T cell activation may assume a functional proinflammatory program within the plaque by involvement of CD28/B7 costimulatory pathway.

Animals↗

cis-clerodane diterpene lactones from Amphiachyris dracunculoides.

Four cis-ent-neoclerodane lactones, amphiacrolide A [2], amphiacrolide B [3], amphiacrolide C [4] and amphiacrolide D [5] were isolated from the aerial parts of Amphiachyris dracunculoides, and their structures established by physical and chemical methods. High field 1H- and 13C-nmr assignments were made for each compound and some of their derivatives by using one- and two-dimensional nmr techniques including nOe difference, COSY, and CH-correlation of one-bond and multiple bond (COLOC) relationships. A chemical correlation of the amphiacrolides to gutierolide [1], a compound with absolute stereochemistry determined by X-ray analysis, established the stereochemistry for the group. Consequently, a compound having reported properties identical with amphiacrolide D [5] must have its structure revised to contain the beta-faced epoxide. Amphiacrolide A [2] had not been reported previously.

Diterpenes↗

Measurement accuracy in confocal microscopy.

Confocal laser scanning microscopy provides optical serial sections through thick biological samples, making it possible to perform both three-dimensional visualization and three-dimensional quantitative analysis. On human lymphocytes, we measured geometrical features, cell contents in DNA and in cyclin A and CDK1 proteins, localization and colocalization of these two proteins. Cells were acquired at a vertical sampling step of 0.5 micron, which gives sufficient information about cell labelling. For the purpose of obtaining fast and reliable data at a reduced time cost, we examined various possibilities to simplify acquisition. For example, it might be possible to increase the vertical sampling step to 2.0 microns while preserving an acceptable accuracy of measurements. Further limiting the acquisition to the central sections appeared to give only rough estimations about the whole cells. Finally, we compared confocal microscopy to conventional two-dimensional epifluorescence microscopy. Confocal microscopy appeared slightly less accurate as regards content estimation, but was an invaluable tool when investigating three-dimensional structures and, more especially, localization of proteins.

Cells, Cultured↗

Characterization of ABCB9, an ATP binding cassette protein associated with lysosomes.

We have cloned full-length human and mouse cDNAs of ABCB9, which encodes a predicted multiple-spanning transmembrane domain and a nucleotide-binding domain with Walker motifs. It is therefore designated as a "half" ATP binding cassette (ABC) transporter. Northern analysis shows that the ABCB9 mRNA is expressed at a high level in testes and moderate levels in brain and spinal cord. A splice variant mRNA deleted in the last pair of predicted transmembrane segments was shown to be expressed in human tissues. Phylogenetic analysis indicates that ABCB9 is closely related to TAP1 and TAP2, two "half" ABC proteins found in endoplasmic reticulum. ABCB9 protein colocalized with the lysosomal markers, LAMP1 and LAMP2, in transfected cells. ABCB9 protein appears to be most highly expressed in the Sertoli cells of the seminiferous tubules in mouse and rat testes. These cells have high levels of phagocytosis and secretory activities. These findings pave the way for further investigation into the potential novel function of ABCB9 in lysosomes.

ATP-Binding Cassette Transporters↗

Maturation and endosomal targeting of beta-site amyloid precursor protein-cleaving enzyme. The Alzheimer's disease beta-secretase.

The amyloidogenic Abeta peptide is liberated from the amyloid precursor protein (APP) by two proteolytic activities, beta-secretase and gamma-secretase. Recently, a type I membrane protein termed BACE (beta-site APP cleaving enzyme) with characteristics of an aspartyl protease has been identified as the beta-secretase. We undertook a series of biochemical and morphological investigations designed to characterize the basic properties of this protein. Initial studies indicated that BACE undergoes N-linked glycosylation at three of four potential sites. Metabolic pulse-chase experiments revealed that after core glycosylation, BACE is rapidly and efficiently transported to the Golgi apparatus and distal secretory pathway. BACE was also found to be quite stable, being turned over with a t(12) of approximately 16 h. Retention of BACE in the endoplasmic reticulum by introduction of a C-terminal dilysine motif prevented complex carbohydrate processing and demonstrated that propeptide cleavage occurs after exit from this organelle. BACE exhibited intramolecular disulfide bonding but did not form oligomeric structures by standard SDS-polyacrylamide gel electrophoresis analysis and sedimented as a monomer in sucrose velocity gradients. Immunofluorescence studies showed a largely vesicular staining pattern for BACE that colocalized well with endosomal, but not lysosomal, markers. Measurable levels of BACE were also detected on the plasma membrane by both immunostaining and cell surface biotinylation, and cycling of the protein between the cell membrane and the endosomes was documented. A cytoplasmic dileucine motif was found to be necessary for normal targeting of BACE to the endosomal system and accumulation of the protein in this intracellular site.

Amino Acid Motifs↗

Medullary epithelial cells of the human thymus express a highly diverse selection of tissue-specific genes colocalized in chromosomal clusters.

Promiscuous expression of tissue-specific self-antigens in the thymus imposes T cell tolerance and protects from autoimmune diseases, as shown in animal studies. Analysis of promiscuous gene expression in purified stromal cells of the human thymus at the single and global gene level documents the species conservation of this phenomenon. Medullary thymic epithelial cells overexpress a highly diverse set of genes (>400) including many tissue-specific antigens, disease-associated autoantigens, and cancer-germline genes. Although there are no apparent structural or functional commonalities among these genes and their products, they cluster along chromosomes. These findings have implications for human autoimmune diseases, immuno-therapy of tumors, and the understanding of the nature of this unorthodox regulation of gene expression.

Animals↗

EHD proteins associate with syndapin I and II and such interactions play a crucial role in endosomal recycling.

EHD proteins were shown to function in the exit of receptors and other membrane proteins from the endosomal recycling compartment. Here, we identify syndapins, accessory proteins in vesicle formation at the plasma membrane, as differential binding partners for EHD proteins. These complexes are formed by direct eps15-homology (EH) domain/asparagine proline phenylalanine (NPF) motif interactions. Heterologous and endogenous coimmunoprecipitations as well as reconstitutions of syndapin/EHD protein complexes at intracellular membranes of living cells demonstrate the in vivo relevance of the interaction. The combination of mutational analysis and coimmunoprecipitations performed under different nucleotide conditions strongly suggest that nucleotide binding by EHD proteins modulates the association with syndapins. Colocalization studies and subcellular fractionation experiments support a role for syndapin/EHD protein complexes in membrane trafficking. Specific interferences with syndapin-EHD protein interactions by either overexpression of the isolated EHD-binding interface of syndapin II or of the EHD1 EH domain inhibited the recycling of transferrin to the plasma membrane, suggesting that EH domain/NPF interactions are critical for EHD protein function in recycling. Consistently, both inhibitions were rescued by co-overexpression of the attacked protein component. Our data thus reveal that, in addition to a crucial role in endocytic internalization, syndapin protein complexes play an important role in endocytic receptor recycling.

Amino Acid Sequence↗

Differential expression of estrogen receptors alpha and beta in the reproductive tracts of adult male dogs and cats.

Expression of estrogen receptors (ERs) in the reproductive tracts of adult male dogs and cats has not been reported. In the present study, ERalpha and ERbeta were localized by immunohistochemistry using ER-specific antibodies. ERalpha was found in interstitial cells and peritubular myoid cells in the dog testis, but only in interstitial cells of the cat. In rete testis of the dog, epithelial cells were positive for ERalpha staining, but in the cat, rete testis epithelium was only weakly positive. In efferent ductules of the dog, both ciliated and nonciliated cells stained intensely positive. In the cat, ciliated epithelial cells were less stained than nonciliated epithelial cells. Epithelial cells in dog epididymis and vas deferens were negative for ERalpha. In the cat, except for the initial region of caput epididymis, ERalpha staining was positive in the epithelial cells of epididymis and vas deferens. Multiple cell types of dog and cat testes stained positive for ERbeta. In rete testis and efferent ductules, epithelial cells were weakly positive for ERbeta. Most epithelial cells of the epididymis and vas deferens exhibited a strong positive staining in both species. In addition, double staining was used to demonstrate colocalization of both ERalpha and ERbeta in efferent ductules of both species. The specificity of antibodies was demonstrated by Western blot analysis. This study reveals a differential localization of ERalpha and ERbeta in male dog and cat reproductive tracts, demonstrating more intensive expression of ERbeta than ERalpha. However, as in other species, the efferent ductules remained the region of highest concentration of ERalpha.

Animals↗

The second-largest subunit of the mouse DNA polymerase alpha-primase complex facilitates both production and nuclear translocation of the catalytic subunit of DNA polymerase alpha.

DNA polymerase alpha-primase is a replication enzyme necessary for DNA replication in all eukaryotes examined so far. Mouse DNA polymerase alpha is made up of four subunits, the largest of which is the catalytic subunit with a molecular mass of 180 kDa (p180). This subunit exists as a tight complex with the second-largest subunit (p68), whose physiological role has remained unclear up until now. We set out to characterize these subunits individually or in combination by using a cDNA expression system in cultured mammalian cells. Coexpression of p68 markedly increased the protein level of p180, with the result that ectopically generated DNA polymerase activity was dramatically increased. Immunofluorescence analysis showed that while either singly expressed p180 or p68 was localized in the cytoplasm, cotransfection of both subunits resulted in colocalization in the nucleus. We identified a putative nuclear localization signal for p180 (residues 1419 to 1437) and found that interaction with p68 is essential for p180 to translocate into the nucleus. These results indicate that association of p180 with p68 is important for both protein synthesis of p180 and translocation into the nucleus, implying that p68 plays a pivotal role in the newly synthesized DNA polymerase alpha complex.

3T3 Cells↗

Expression of p67 (Munc-18), Cdk5, P-NFH and syntaxin during development of the rat cerebellum.

Cyclin-dependent kinases (cdks), which regulate the cell division cycle, have also been found in postmitotic neurons. Cdk5, isolated from neural tissue, has been shown to phosphorylate neurofilaments (NFs). Instead of cyclins, however, other neuron-specific activators of cdk5 have been identified including a 67-kD protein (p67) which is identical to a syntaxin-binding protein (n-sec-1, Munc 18) that is thought to play a role in synaptic vesicle trafficking and transmitter release. These functions for p67 are not mutually exclusive since regulation of edk5 phosphorylation of cytoskeletal proteins may modulate axonal dynamics during growth, synaptogenesis and vesicle transport. To gain further insight into the role of p67 in neural tissue, we carried out a Western blot and immunohistochemical analysis of the developing rat cerebellum using antibodies to cdk5, p67, syntaxin and phosphorylated and nonphosphorylated neurofilaments. We assumed that spatiotemporal colocalizations of antigens might correlate with proposed functions for p67. The immunoblots showed that all antigens were developmentally regulated, and increased in expression from PN2 to the adult, with p67 and cdk5 showing a close temporal correlation. Immunohistochemically, p67 colocalized with cdk5 and P-NFH in selected fiber tracts, particularly those in the deep cerebellum. For the most part, p67 also showed strong colocalization patterns with syntaxin in regions of synaptogenesis throughout development such as the molecular layer and glomeruli of the inner nuclear layer. Finally, certain fiber tracts, the afferent fibers, climbing and mossy fibers and particularly the basket cell fibers that envelop and innervate Purkinje cell somata and dendrites, displayed colocalization of cdk5 and P-NFH without expressing any p67. Given the limitations of colocalization data in defining functional relationships, the results are consistent with the hypothesis that p67 is a multifunctional protein, its activity during cerebellum development dependent upon the neuronal phenotype, its location and its state of developmental maturation.

Animals↗

Does platelet-derived growth factor-A chain stimulate proliferation of arterial mesenchymal cells in human atherosclerotic plaques?

Previous studies have indicated the focal presence of growth factors and focal low levels of cell proliferation in human atherosclerotic plaques. Using human carotid plaques and an antibody to platelet-derived growth factor (PDGF)-A chain, we have begun to assess growth factor significance by spatially correlating growth factor gene expression with actual cell proliferation. Since PDGF is a mitogen for smooth muscle and related cells and since inflammatory cells (eg, macrophages) can also proliferate in these lesions, it was important to exclude inflammatory cell proliferation from this consideration. Therefore, we have used a triple immunolabeling approach, combining the above anti-PDGF-A chain antibody with an inflammatory cell cocktail (CD68+CD45 for monocyte/macrophages and lymphocytes) and adding an anti-proliferating cell nuclear antigen (PCNA) antibody to mark proliferating cells. In the carotid atherosclerotic plaques, PDGF immunostaining was distributed focally, preferentially in the fibrous cap and vascularized regions, and was present in two distinct patterns: cytoplasmic and diffuse extracellular staining. When we considered colocalization within the same cells, cytoplasmic PDGF-A staining did not appear to colocalize with inflammatory markers. PCNA nuclear staining combined with PDGF cytoplasmic staining of the same cell was detected extremely rarely. Considering colocalization within the same microscopic fields, PDGF-A staining was detected more frequently than noninflammatory PCNA positivity. Quantitative logistic regression analysis demonstrated that localization in vascularized regions and (independently) the presence of PDGF-A are good predictors of noninflammatory cell proliferation, within the same microscopic fields. Therefore, PDGF-A and other factors especially associated with vascularized regions may be involved in the regulation of mesenchymal cell proliferation in human atherosclerotic plaques.

Antibodies↗

Epstein-Barr virus infection of renal proximal tubule cells: possible role in chronic interstitial nephritis.

Chronic interstitial nephritis frequently accompanies renal diseases of different etiologies. Far less common is the entity of primary interstitial nephritis wherein the glomerular and vascular structures of the kidney are not the primary focus of the disease process. Using in situ hybridization and the polymerase chain reaction, we detected DNA from the Epstein-Barr Virus (EBV) exclusively in renal tissue of patients with the idiopathic variety of chronic interstitial nephritis. The EBV genome, but not that of cytomegalovirus or adenovirus, was detected primarily in renal proximal tubule cells. Furthermore, the CD21 antigen, which serves as the receptor for EBV in B lymphocytes, was detected by immunocytochemistry primarily on proximal tubule cells and was markedly upregulated in the EBV-infected tissue. Western blot analysis of primary cultures of normal proximal tubule cells identified a 140-kDa protein, confirming the expression of the CD21 antigen. Colocalization experiments using proximal and distal tubule markers confirmed that EBV DNA and the CD21 antigen are found primarily in proximal tubule cells. EBV infection of renal proximal tubular cells may participate in evoking a cellular immune response that results in a damaged renal interstitium.

Adult↗