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At least 19 recordsLinked to original sources
PubMed1979

Lithium transport across red cell membrane: a cell membrane abnormality in manic-depressive illness.

In the families of manic-depressive patients, relatives with a history of affective disorders had a significantly higher ratio of mean red cell lithium to plasma lithium in vitro than relatives with no such history. A genetically controlled abnormality in lithium-sodium transport, the mechanism that determines the lithium ratio, may play a role in the etiology of some forms of affective disorders.

Biological Transport↗
PubMed1977

Separation of the Moloney leukemia virus-determined cell surface antigen (MCSA) from known virion proteins associated with the cell membrane.

Cell membranes of Moloney lymphoma cells (YAC, of strain A origin) were solubilized by NP40. The antigenicity of the solubilized protein fraction was assayed by inhibition of the corresponding cytotoxic reaction against YAC target cells. The Moloney leukemia virus (MLV)-determined cell surface antigen (MCSA) was detected with mouse antisera, produced by the repeated inoculation of heavily irradiated YAC cells into syngeneic mice. Virion proteins gp71, p30, p15, p12 and p10 were identified with goat or rabbit antisera against purified Rauscher and Friend leukemia virus proteins. MCSA was found to bind to Con-A--Sepharose and was eluted by mannoside together with H-2A AND GP71. In contrast, p30, p12, p10 and part of p15 and p15(E), were not retained on the column and could be separated from MCSA. Passage of the glycoprotein fraction through Sephadex G-200 led to the separation of MCSA activity from gp71 and H-2A. MCSA eluted between the immunoglobulin (IgG) and the bovine serum albumin (BSA) size markers. MCSA could be also separated from the known viral proteins and from H-2 by velocity centrifugation in sucrose gradients. It sedimented with approximately 6.6 S ahead of gp71 (4.4 S) and H-2 (3.2 S). It is suggested that MCSA may be a glycoprotein with an approximate molecular weight of 110,000 and distinct from the known viral proteins gp71, p30, p15(E), p12, p10 and from H-2.

Animals↗
PubMed1990

Intracellular regulation of ion channels in cell membranes.

Cells communicate with their environment through receptor proteins on the cell membrane. Some ion channels are receptors, whereas others are linked to receptors through guanine nucleotide-binding proteins (G proteins). Ion channels control intracellular concentrations of ions such as calcium, and these concentrations control cell functions such as secretion and cell division. This review summarizes the current state of knowledge about the control of ion channels.

Cell Communication↗
PubMed1976

Cell membrane and cell junctions in differentiation of preimplanted mouse embryos.

Cell membrane and cell junctions in differentiation of preimplanted mouse embryos, (membrana celular y uniones celulares en la diferenciación del embrión de ratón antes de la implantación). Arch. Biol. Med. Exper. 10: 130-134, 1976. The development of cell junctions that seal the peripheral blastomeres could be a decisive step in the differentiation of morulae into blastocysts. The appearance of these junctions is studied by electron microscopy of late morulae and initial blastocysts. Zonulae occludentes as well as impermeability to lanthanum emulsion precedes the appearance of the blastocel and hence might be considered as one of its necessary causes.

Animals↗
PubMed1990

The cell membrane and cell signals: new targets for novel anticancer drugs.

In the concluding Discussion session, emphasis focussed on the potential for interfering selectively with cell membranes and cell signalling in tumour as against normal tissues. There could be no doubt that tremendous advances are being made in our understanding of the molecular changes associated with malignancy and that the information available for the rational design of inhibitors of particular signalling pathways is increasingly sophisticated. There was a consensus that we need more information on the qualitative and quantitative differences in the structure and function of membranes and the signalling machinery in various normal tissues as compared to their cancerous counterparts. Ideally we will develop drug against, for example, specific forms of, let us say, protein kinase C or tyrosine kinase which are found to be predominantly active in neoplastic cells. This may well prove possible, at least in some instances, in which case a safe therapeutic margin will be assured. But differences may in other situations turn out to be in the level of expression rather than purely qualitative in nature, and the scale of the disparate expression may not always be great. Even in such situations, adequate therapeutic selectivity may still be achieved. This may derive from a "damping down" of signalling in the hyperactive tumour. Although there are legitimate concerns regarding the possible toxic effects of administering signal-wrecking molecules in man, we should not be pessimistic as there are clear precedents elsewhere in medicine for drugs acting on membrane signals proving to be safe and effective against expectation informed by hindsight. There may also be concerns about new forms of drug resistance. But this will be so for any new agent or novel target. And with mechanism of action clearly to the fore we should be able to predict resistance pathways in advance and devise appropriate circumvention strategies or targeted second line therapies. There was a palpable buzz at the meeting that this is a valid, different and above all rational approach. Not only that, but the new therapeutic molecules which we discover will themselves prove to be valuable tools with which to probe further into the mechanisms of malignancy and signal transduction. We had expected to see a bewildering amount of new information from the basic sciences of molecularbiology and cell physiology, and we got it. But it was also impressive to witness the number of new compounds coming through which look like real drugs or at least exciting lead compounds. The membrane-active ether lipids are in clinical trial. Bryostatin 1 will shortly join them.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1987

Distinctive populations of basement membrane and cell membrane heparan sulfate proteoglycans are produced by cultured cell lines.

We have investigated the nature and distribution of different populations of heparan sulfate proteoglycans (HSPGs) in several cell lines in culture. Clone 9 hepatocytes and NRK and CHO cells were biosynthetically labeled with 35SO4, and proteoglycans were isolated by DEAE-Sephacel chromatography. Heterogeneous populations of HSPGs and chondroitin/dermatan proteoglycans (CSPGs) were found in the media and cell layer extracts of all cultures. HSPGs were further purified from the media and cell layers and separated from CSPGs by ion exchange chromatography after chondroitinase ABC digestion. In all cell types, HSPGs were found both in the cell layers (20-70% of the total) as well as the medium. When the purified HSPG fractions were further separated by octyl-Sepharose chromatography, very little HSPG in the incubation media bound to the octyl-Sepharose, whereas 40-55% of that in the cell layers bound and could be eluted with 1% Triton X-100. This hydrophobic population most likely consists of membrane-intercalated HSPGs. Basement membrane-type HSPGs were identified by immunoprecipitation as a component (30-80%) of the unbound (nonhydrophobic) HSPG fraction. By immunofluorescence, basement membrane-type HSPGs were distributed in a reticular network in Clone 9 and NRK cell monolayers; by immunoelectron microscopy, these HSPGs were localized to irregular clumps of extracellular matrix located beneath and between cells. The cells did not produce a morphologically recognizable basement membrane layer under these culture conditions. When membrane-associated HSPGs were localized by immunoelectron microscopy, they were found in a continuous layer along the cell membrane of all cell types. The results demonstrate that two antigenically distinct populations of HSPG--an extracellular matrix and a membrane-intercalated population--are found at the surface of several different cultured cells lines; these populations can be distinguished from one another by differences in their distribution in the monolayers by immunocytochemistry and can be separated by hydrophobic chromatography; and basement membrane-type HSPGs are secreted and deposited in the extracellular matrix by cultured cells even though they do not produce a bona fide basement membrane-like layer.

Animals↗
PubMed1992

Effects of inhibitors and ion substitutions on oscillations of cell membrane potential in cells expressing the RAS oncogene.

Previous studies revealed that in NIH fibroblasts expressing the ras oncogene but not in other NIH fibroblasts, bradykinin leads to sustained, calcium dependent oscillations of cell membrane potential by repetitive activation of calcium-sensitive K+ channels. The present study has been performed to test for ion and inhibitor sensitivity of these oscillations. Both, Lys-bradykinin (kallidin) and bradykinin, but not any shorter peptide tested, maintained the oscillations. The oscillations are abolished in the presence of the K+ channel blocker barium (10 mmol/l). The amplitude but not the frequency of the oscillations is dependent on the extracellular potassium concentration. The oscillations are not dependent on the presence of extracellular sodium, bicarbonate or chloride. The oscillations are abolished in the absence of extracellular calcium and their frequency is significantly decreased at reduced extracellular calcium (to 0.2 mmol/l). The oscillations are not inhibited by acute administration of ouabain (0.1 mmol/l), by dimethylamiloride (100 mumol/l), furosemide (1 mmol/l) and hydrochlorothiazide (100 mumol/l), by cobalt (100 mumol/l), zinc (100 mumol/l), gadolinium (100 mumol/l), verapamil (10 mumol/l) and diltiazem (10 mumol/l), but are abolished in the presence of 100 mumol/l lanthanum, 1 mmol/l cadmium, 10 mumol/l nifedipine, 25 mumol/l SK & F 96365 and 200 mumol/l TMB-8. Stimulation of calcium entry by 10 nmol/l ionomycin is frequently followed by oscillations of cell membrane potential even in the absence of bradykinin. In conclusion, in cells expressing the ras oncogene bradykinin leads to sustained activation of calcium channels at the cell membrane, which cause oscillations of the cell membrane potential by triggering intracellular calcium release.

Animals↗
PubMed1991

Bradykinin-induced oscillations of cell membrane potential in cells expressing the Ha-ras oncogene.

Products of ras genes are putative elements of growth factor signal transduction. However, the mechanism of action of these proteins in normal and malignant growth is as yet obscure. To test for functional consequences of ras oncogene expression, electrophysiological experiments were performed on NIH-3T3 fibroblasts transfected with a transforming Ha-ras MMTV-LTR construct expressing the oncogene on treatment with dexamethasone (+ras). Transfected cells in the absence of dexamethasone (-ras) and nontransfected cells in the presence of dexamethasone (oras) served as controls. In -ras and oras, bradykinin induces a single, transient hyperpolarization. In +ras, bradykinin elicits oscillations of cell membrane potential throughout the presence of the hormone by activation of calcium-sensitive K+ channels. The oscillations of cell membrane potential are abolished in the absence of extracellular calcium. As evident from fura 2 fluorescence, bradykinin leads to a transient increase of intracellular calcium both in the presence and absence of extracellular calcium. Oscillations of intracellular calcium could be observed in +ras cells, if bradykinin was applied at reduced extracellular sodium concentration possibly to impair calcium extrusion via the sodium/calcium exchange. Bradykinin induces oscillations of cell membrane potential similarly in -ras cells loaded with GTP[S], a nonhydrolyzable analogue of GTP. Thus, the altered response of ras oncogene expressing cells to bradykinin relates to the GTP binding property of the ras protein. It is concluded that in cells expressing ras oncogene but not in other fibroblasts bradykinin mimicks the effect of growth factors on the cell membrane.

Bradykinin↗
PubMed1990

How to kill cancer cells: membranes and cell signaling as targets in cancer chemotherapy.

Most approaches to cancer chemotherapy have centered around the idea that cytotoxic drugs can be used to eradicate proliferating neoplastic cells. Cytotoxicity is generally thought to evolve from the presence of drug-induced damage to the genetic material, and DNA has served admirably as a primary focus for drug development. Other cellular targets should also be vulnerable, however, and over the past decade the plasma membrane in particular has received considerable attention as a therapeutic locus. In the early stages of this work there were only vague notions as to how membrane disruption could lead to cell death, but recent thinking has coalesced around the idea that cell-surface signal transduction and growth control pathways represent an ideal target for the rational development of new cancer therapies. In this review, we discuss three aspects of signal transduction-phosphoinositide turnover, phosphorylation by protein kinase C, and phosphorylation by protein tyrosine kinases--and summarize the existing evidence that these vital processes can be specifically disrupted, and that such pharmacology offers rich prospects for future therapeutic design.

Humans↗
PubMed1990

Secretory organelle docking at the cell membrane of Paramecium cells: dedocking and synchronized redocking of trichocysts.

We present the first evidence that secretory organelle docking at the cell membrane can be reversed in vivo. In nondischarge (nd) mutants of Paramecium tetraurelia all trichocysts can be detached from the cell surface within 2-3 h by different means, including cytochalasin B (but not D), high cell density, or Ca2+ ionophores. Considering the well-established ultrastructural differences between nd and wild-type (wt) cells, one can conclude that trichocyst docking at the cell periphery involves two docking sites (I, II): Site I ties the organelles to the epiplasm, and site II is the connection to the cell membrane at the fusogenic zone (expressed only in wt cells); both sites are close to the cell surface and only 150 nm apart. When the trigger for detachment of cortically docked trichocysts (high cell density, cytochalasin B) is relieved, trichocysts are synchronously reattached at the cell membrane, within 40-50 min, with a rate of 20-40 organelles/min, which far exceeds spontaneous docking rates. This is therefore also the first report on synchronization of secretory organelle docking. It is shown by radioactive leucine labeling that the same organelles are redocked, because trichocyst biogenesis is minimal under the conditions of de/redocking used. Surprisingly not only redocking but also detachment of trichocysts from the cell surface can be abolished by inhibitors of protein synthesis. Since Ca2+ ionophores mimic the effects of other conditions sufficient to detach trichocysts from the cell surface, we assume that a protein-dependent mechanism sensitive to Ca2+ (or other ions in exchange) may operate in trichocyst detachment. The precise mechanism involved in attachment or detachment of trichocysts remains to be elucidated.

Animals↗
PubMed1989

1-anilino-8-naphthalenesulphonate binding parameters in red cell membranes. Does diabetes mellitus affect cell membrane dynamics?

In this study we report the use of 1-anilino-8-naphthalenesulphonate as a fluorescence probe to investigate the properties of plasma membranes derived from normal and diabetic red blood cells. The binding of 1-anilino-8-naphthalenesulphonate to diabetes-affected erythrocyte membranes, as compared with controls, was measured by means of fluorescence polarization and fluorescence titration techniques. These measurements demonstrated anomalous 1-anilino-8-naphthalenesulphonate binding to pathological red cell membranes. The amount of 1-anilino-8-naphthalenesulphonate bound to diabetic erythrocyte membranes was greater than that of controls. This fluorometric study indicated that the outer monolayer binding of 1-anilino-8-naphthalenesulphonate was markedly augmented in the erythrocyte membranes of diabetic patients. Significant correlations were found between 1-anilino-8-naphthalenesulphonate binding parameters and membrane lipid composition. The correlation between these binding parameters and non-enzymatic protein glycation was poor or moderate. Though the fluorescence intensity and emission maximum were quite similar in both groups investigated, binding studies revealed that there were approximately 1.2 times the number of 1-anilino-8-naphthalenesulphonate binding sites and a 33% increase in the KD value in diabetic membranes, suggesting significant differences in the environment of the 1-anilino-8-naphthalenesulphonate binding sites in these two groups of patients. The results presented in this report indicate that (a) 1-anilino-8-naphthalenesulphonate is a sensitive probe of membrane architecture alterations, and can be used to elucidate the perturbating effects of sterols in membrane systems, and (b) that significant differences in membrane dynamics exist between normal and diabetic red cell membranes.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

The effect of mechanical deformation on the distribution of potassium ions across the cell membrane of sutural cells.

Ionic concentrations of potassium, sodium, and chloride were determined in osteocytes of the rat calvarium. The values were determined by fluorescent microscopy of both intra- and extracellular concentrations. Following the baseline determination, the calvaria were placed in tension by retraction of a microelectrode manipulator, and the fluorescence of the cells were measured again. A statistically significant change in the derived ion distribution was found. Thus, the tensile forces affected the distribution of ions across the cell membranes, increasing intracellular sodium and decreasing intracellular potassium. This would have an effect on the resting cell membrane potential with a change of potential of 8 mV. This has implications in the interpretation of clinical findings.

Animals↗
PubMed1978

F20C, a new fluorescent membrane probe, moves more slowly in malignant and mitogen-transformed cell membranes than in normal cell membranes.

New fluorescent probes of membrane mobility can be introduced into cell membranes at single points with particles of a membrane mobility agent, A2C. The initial entry of fluorescence from the particle into the cell membrane and the subsequent lateral spread of fluorescence have been observed for cells in suspension. A dramatic difference between the behavior of normal lymphocytes and that of mitogen-transformed and mastocytoma cells is found. Both the initial entry and the spreading of fluorescence are much slower in the transformed and tumor cells than in the normal cells at 18 degrees C. Entry and spread of fluorescence in normal cells become slow enough to be observed only at 12 degrees C or below.

Cell Line↗
PubMed1989

Isolation and partial characterization of antigens from basement membranes and streptococcal cell membrane (SCM) employing anti-SCM monoclonal antibody.

Monoclonal antibodies (mAb) against streptococcal cell membrane (SCM) antigen were used to identify specific cross-reactive peptides prepared by trypsin digestion of purified glomerular basement membrane (GBM) and lung basement membrane (LBM). Anti-SCM mAb-coupled HPLC columns were used to affinity isolate soluble LBM, GBM, and SCM antigens which then were sized by HPLC. Alternatively, SCM, GBM, and LBM digests were subjected to an initial separation by HPLC into component polypeptides, followed by affinity purification and ELISA of these fractions using anti-SCM mAb. Comparison of the antigenic reactivities by ELISA of the sized polypeptides on a nanomolar basis permitted the estimation of their individual relative epitope densities. The results for SCM antigens showed increasing epitope density with increasing molecular size, which suggests that intact SCM consists of repeating epitopes. Low mol. wt GBM polypeptides in nanogram amounts inhibited mAb binding to SCM, indicating that these small GBM polypeptides may similarly contain more than a single cross-reactive epitope. The identification of these cross-reactive epitopes in LBM and GBM has important implications for the etiology of post-streptococcal sequelae.

Antibodies, Monoclonal↗