PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Cell membrane”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4Linked to original sources
PubMed2007

Densin is a novel cell membrane protein of Sertoli cells in the testis.

Cell-cell interactions between Sertoli cells and germ cells are crucial for the maturation of germ cells in spermatogenesis but the structural and functional aspects of the interactions remain to be fully elucidated. Densin is a junction protein suggested to play a role in establishment of specific cell-cell contacts in the post-synaptic densities of the brain and the slit diaphragm of the kidney podocyte. In the present study, densin was discovered to be expressed in the testis of the man and the mouse. Expression of densin at the gene and the protein level was studied by using RT-PCR and Western blotting analyses, and the localization of densin was explored with immunofluorescence staining. RT-PCR and Western blotting analyses showed that densin is expressed at the gene and the protein levels. Immunofluorescence staining localized the expression of densin to the cell membranes of Sertoli cells suggesting that densin may be an adherens junction protein between Sertoli cells and developing germ cells. Densin is a novel testicular protein expressed in the cell membranes of Sertoli cells. Its functional role remains to be assessed.

Adult↗
PubMed1989

Sequestrocytes: a manifestation of transcellular cross-bonding of the red cell membrane in sickle cell anemia.

An unusual form of red cells (called sequestrocytes) that circulate in the peripheral blood of patients with sickle cell anemia has been identified. In wetmount light microscopy preparations, sequestrocytes appear as massively vacuolated erythrocytes. We have shown by transmission electron microscopy and scanning electron microscopy that the morphology of sequestrocytes can be accounted for on the basis of transcellular cross-bonding of the cell membrane. Initially, endocytotic vesicles span the cytoplasmic space, forming putative cytoskeletal fusion zones. Points of fusion of the membrane skeleton bridging the cytoplasmic compartment expand laterally to form linear fusion zones that entrap lakes of hemoglobin within pseudovacuoles. Sequestrocytes can be isolated in the densest layer (1.159 g ml-1 or greater) of an arabinogalactan density gradient. These cells can be generated in increased numbers in sickle cell blood by incubating samples in 1.5 mM-acetylphenylhydrazine (APH) solution for two hours at 37 degrees C. Their formation is partially blocked by incubation with the reducing agent, dithiothreitol (DTT). Our results suggest that these cells represent an expression of oxidative membrane injury in sickle cell anemia.

Adult↗
PubMed1997

In K562 and HL60 cells membrane ageing during cell growth is associated with changes in cholesterol concentration.

In a cell culture model of aging we have previously shown that there is an age-related decrease in the lipid dynamics of the proerythropoetic K562 cell membranes, as determined by the generalized polarization (GP) of the phase-sensitive lipid probe 2-dimethylamino-6-lauroylnaphthalene (Laurdan) (T. Parasassi, M. Di Stefano, G. Ravagnan, O. Sapora and E. Gratton. Exp. Cell Res., 202 (1992) 432-439). In the present study we also extended our observations to the lymphoblastoid HL60 cell line. In both K562 and HL60 cells during the four days after the last cell culture medium renewal the GP Laurdan value increased in a linear fashion indicating a time-dependent decrease in lipid dynamics. The initial membrane physical properties were almost completely restored upon renewal of the cell culture medium. We measured lipid composition, including individual and total phospholipids, free and esterified cholesterol at the first ('young') and at the fourth ('aged') day after culture medium renewal. We found that the decreased membrane lipid 'fluidity' at the fourth day of cell growth was associated with a 40% increase in cholesterol concentration in both cell lines. This increase in cholesterol concentration was reversible 24 h following the culture medium change. We conclude that in K562 and HL60 cells the 'age-related' decrease in membrane lipid dynamics is mediated by an 'age-related' increase in cell cholesterol content.

2-Naphthylamine↗
PubMed1973

Cell membranes.

Explore the source record for details and available documents.

Cell Division↗
PubMedDate not supplied

Membrane cell markers in human leukemias and lymphomas.

The availability of B- and T-cell membrane markers has provided new approaches and concepts in the study of lymphoproliferative diseases; The present status of knowledge in monoclonal B-cell proliferations, T-cell proliferations such as the Sézary syndrome and chronic lymphocytic leukemia of T-cell origin, acute lymphoblastic leukemias and non-Hodgkin lymphomas is briefly reviewed.

Antibody Formation↗
PubMed1999

A proteolytic pathway that controls the cholesterol content of membranes, cells, and blood.

The integrity of cell membranes is maintained by a balance between the amount of cholesterol and the amounts of unsaturated and saturated fatty acids in phospholipids. This balance is maintained by membrane-bound transcription factors called sterol regulatory element-binding proteins (SREBPs) that activate genes encoding enzymes of cholesterol and fatty acid biosynthesis. To enhance transcription, the active NH(2)-terminal domains of SREBPs are released from endoplasmic reticulum membranes by two sequential cleavages. The first is catalyzed by Site-1 protease (S1P), a membrane-bound subtilisin-related serine protease that cleaves the hydrophilic loop of SREBP that projects into the endoplasmic reticulum lumen. The second cleavage, at Site-2, requires the action of S2P, a hydrophobic protein that appears to be a zinc metalloprotease. This cleavage is unusual because it occurs within a membrane-spanning domain of SREBP. Sterols block SREBP processing by inhibiting S1P. This response is mediated by SREBP cleavage-activating protein (SCAP), a regulatory protein that activates S1P and also serves as a sterol sensor, losing its activity when sterols overaccumulate in cells. These regulated proteolytic cleavage reactions are ultimately responsible for controlling the level of cholesterol in membranes, cells, and blood.

Animals↗
PubMed2004

Chrysotile fibers penetrate Escherichia coli cell membrane and cause cell bursting by sliding friction force on agar plates.

A mixture (50 microl) consisting of Escherichia coli cells, chrysotile fibers, and 200 mM NaCl was added to 2% agar plates and spread with a plastic stir stick. An apparatus was developed to generate a sliding friction force on the surface of the plate by applying a fixed vertical reaction force to the stir stick while turning the plate. This operation was defined as chrysotile-exposure. The number of living cells, expressed as colony forming units, was reduced in proportion to the duration of chrysotile-exposure. The decrease in the number of living cells was greater following 120 s of chrysotile-exposure than crocidolite- or amosite-exposure. There was no decrease in the number of living cells exposed to chrysotile on 0.5% agar even after 120 s. The number of living cells after chrysotile-exposure decreased with increasing chrysotile concentration. Leakage of beta-galactosidase from cells increased with increasing duration of chrysotile-exposure. Transmission and scanning electron microscopy observation of E. coli revealed chrysotile penetration of the cell membrane. These results show that chrysotile fibers destroy cells by penetration. The driving force for the chrysotile penetration was the sliding friction force, as the number of living cells following chrysotile-exposure decreased with increasing exposure times, but did not decrease following chrysotile-exposure on a low concentration of agar, which provided cells with low sliding friction force.

Journal Article↗
PubMed1991

Membrane cell permeabilization with saponin and multiparametric analysis by flow cytometry.

Saponin, a detergent like molecule, can permeabilize cell membranes without destroying them, and thus can be used for the detection of intracellular antigens on intact cells with a flow cytometer. First experiments were reported that demonstrated the detection of intracytoplasmic antigens such as intermediate filaments and CD3 in T acute lymphoblastic leukemia (ALL). Further experiments were also performed to prove that intranuclear structures were equally accessible: dyes such as propidium iodide (PI) and monoclonal antibodies (mAb) such as Ki67 could penetrate the nucleus and lead to the analysis of DNA content and to the discrimination between the different cell cycle phases (G0, G1, S, G2-M). This rapid and sensitive method retained sufficient integrity of cells being treated to enable differentiation of cell types on the basis of morphology. Furthermore, it did not alter membrane expression of most antigens. Therefore, it was of particular interest for multiparametric analysis, especially for simultaneous study of membrane and intracellular structures.

Aneuploidy↗
PubMed2000

Purification and characterization of a 200 kDa fructosyllysine-specific binding protein from cell membranes of U937 cells.

Amadori-modified proteins are bound by macrophages and monocytes via fructosyllysine-specific receptors. Detergent extracts from U937 cell membranes were used to purify the binding proteins by affinity purification on glycated polylysine coated magnetic beads followed by SDS-PAGE. Two proteins of 200 and 100kDa were isolated. MS-analysis of the 200 kDa protein showed high homologies with cellular myosin heavy chain, type A. Both fructosyllysine specific binding proteins, cellular myosin heavy chain and nucleolin, are glycosylated.

Amino Acid Sequence↗
PubMed1998

Noise-induced transient microlesions in the cell membranes of auditory hair cells.

Several types of nonauditory cells recover from transitory mechanically induced microlesions in their cell membranes. We report evidence that hair cells in the auditory papilla of the alligator lizard suffered similar membrane wounding when exposed to noise loud enough to induce a temporary threshold shift. Lucifer yellow, a molecular marker that does not normally penetrate through the cell membrane into the cytoplasm, was introduced into the extracellular fluid bathing the basolateral membrane of the hair cells. We assessed the effect of loud noise on the function of the ear by measuring compound action potentials of the auditory nerve before exposure to the noise, immediately after cessation of the noise, and after recovering overnight. Hair cells that were exposed to the noise took up much more Lucifer yellow than hair cells that were not exposed. We propose that the Lucifer yellow entered the hair cells via noise-induced lesions in their cell membranes, and that the cells were able to survive and recover functionally.

Action Potentials↗
PubMed1992

Exercise-induced cholesterol depletion and Na+,K(+)-ATPase activities in human red cell membrane.

Red cell membranes were isolated from blood samples obtained from athletes during exhaustive exercise on a bicycle ergometer and during the subsequent recovery period of 60 min. Plasma lactate levels were also determined. During exercise, cell membranes were progressively depleted of cholesterol and, at exhaustion, membrane cholesterol was less than 80% of the initial level. A parallel decline in Na+,K(+)-ATPase was also noted, while phospholipid reduction was around 5%. During recovery, the erythrocyte membrane cholesterol and Na+,K(+)-ATPase increased, but at a slow rate and were inversely proportional to plasma lactate content.

Adult↗
PubMed1975

Analysis of soluble melanoma cell membrane antigens in metastatic cells of various organs and further studies of antigens present in primary melanoma.

In malignant melanoma, using Sephadex G-200 chromatography and polyacrylamide gel electrophoresis (PAGE), it has been possible to separate two types of skin reactive antigens. The first, found in Sephadex fraction II and PAGE region a appears specific for melanoma. Allogeneic extracts have produced positive reactions in many patients with skin or ocular melanoma, and have given negative reactions in patients with other types of cancer or in patients with ocular lesions simulating melanoma. The second group of antigens, in Sephadex fraction III and PAGE region b were less specific. These antigens produced positive skin reactions in some patients with breast cancer, as well as in patients with melanoma. Reactivity to PAGE region a appeared to be confined to one protein band, but three different bands in region b gave positive reactions. A study was made of the presence or absence of similar antigens in metastatic deposits of malignant melanoma. Metastatic lesions in the following tissues were analyzed: liver, lung, adrenal, skin, and colon. These were compared with pooled primary skin melanomas by skin testing in the same patients. The tumor-associated melanoma antigen, found in Sephadex fraction II and PAGE region a appeared to be strongest in adrenal, lung, and liver metastases. It was found that the protein yield in this region was not indicative of the strength of the antigen. Therefore, a careful, detailed analysis of the protein bands present in PAGE regions a and b from primary skin melanoma was conducted. Only one band in PAGE region a was found to be responsible for positive skin reactivity. This band was found to be a glycolipoprotein. Further studies were also conducted in order to determine whether or not some of the antigens present might be fetal antigens. Some of the protein bands present in Sephadex fraction III and PAGE region b of melanoma appeared to be similar to some of the PAGE region b proteins present in fetal skin cells. Two bands from fetal skin also had the same location on PAGE as two bands from ductal breast cancer, although the relationship to melanoma region b antigens was not exact. These fetal proteins, which seemed to be present both in ductal breast cancer cell membranes and in melanoma cell membranes, might account for the positive skin reactivity seen in this region, and also for the cross reactivity of skin tests with this antigen.

Adrenal Gland Neoplasms↗
PubMed1999

Protein kinase A anchoring proteins are required for vasopressin-mediated translocation of aquaporin-2 into cell membranes of renal principal cells.

The antidiuretic hormone arginine-vasopressin (AVP) regulates water reabsorption in renal collecting duct principal cells by inducing a cAMP-dependent translocation of water channels (aquaporin-2, AQP-2) from intracellular vesicles into the apical cell membranes. In subcellular fractions from primary cultured rat inner medullary collecting duct (IMCD) cells, enriched for intracellular AQP-2-bearing vesicles, catalytic protein kinase A (PKA) subunits and several protein kinase A anchoring proteins (AKAPs) were detected. In nonstimulated IMCD cells the majority of AQP-2 staining was detected intracellularly but became mainly localized within the cell membrane after stimulation with AVP or forskolin. Quantitative analysis revealed that preincubation of the cells with the synthetic peptide S-Ht31, which prevents the binding between AKAPs and regulatory subunits of PKA, strongly inhibited AQP-2 translocation in response to forskolin. Preincubation of the cells with the PKA inhibitor H89 prior to forskolin stimulation abolished AQP-2 translocation. In contrast to H89, S-Ht31 did not affect the catalytic activity of PKA. These data demonstrate that not only the activity of PKA, but also its tethering to subcellular compartments, are prerequisites for cAMP-dependent AQP-2 translocation.

Animals↗
PubMedDate not supplied

[Isolation and characteristics of vaccinia virus proteins associated with cell membranes of infected cells].

The proteins of vaccinia virus associated with plasma membrane infected cells BHK-21, p60, p45, p42, p40,p35,p34,p28,p23 were isolated from plasma membranes using affinity chromatography, gel-electrophoresis and passive elution. An immunochemical characterization was carried out using specific antiserum to these proteins. Investigation of temporal regulation of proteins synthesis in infected cells showed that proteins p60, p45, p42, p40, p28 were late, and p35, p34, p23--early-late proteins. Immunochemical analysis of vaccinia virus mRNA cell-free translational products was carried out using specific antiserum. The polypeptide-precursors of viral proteins were identified.

Animals↗