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M Sabanero

Publications and source records attributed to M Sabanero.

13 recordsLinked to original sources
PubMed1996

Changes of actin cytoskeleton during swelling and regulatory volume decrease in cultured astrocytes.

Swelling of cultured astrocytes exposed to hyposmotic medium modified the organization of the filamentous actin (F-actin) cytoskeleton, making the actin network diffuse in the cell body but concentrated at foci corresponding to the tips of the cell projections retracted by swelling. This change was reversible, and, after 2 h, the actin cytoskeleton tended to recover, and cells regained their flat and stellate shape. Cytochalasins B and D (CB and CD, respectively), which disrupt the actin cytoskeleton, did not affect regulatory volume decrease (RVD) or the swelling-activated efflux of Cl- and inositol, although 10 microM CD increased the basal efflux of taurine. The mercurial p-chloromercuribenzenesulfonate (0.5-1 mM), known to disrupt the membrane cytoskeleton in isosmotic conditions, induced a 46, 50, and 38% release of [3H]taurine, 125I, and [3H]inositol, respectively, causing cell shrinkage and retraction of the cytoskeleton. Coincidently, the swelling-stimulated release of [3H]taurine and 125I was reduced by 60 and 30%, respectively. Results of this study do not exclude the possibility that changes in the actin cytoskeleton elicited by swelling are involved in mechanisms of RVD and only indicate that the disruption caused by cytochalasins is unrelated to that process.

Actins↗
PubMed1995

Encelin: a fungal growth inhibitor.

A known sesquiterpene lactone, encelin, isolated from the Mexican species Montanoa speciosa (Compositae), was assayed for biocidal activity on fungal cells of Mucor rouxii. The results indicate that encelin has a determining action on growth and the morphogenetic process of fungal cells.

4-Butyrolactone↗
PubMed1995

Effects of selected synthetic compounds on growth of Mucor rouxii.

The in vitro activity of four synthetic compounds was tested on fungal cells from Mucor rouxii. The compounds included phenylenediamine, two phenolamines, and quinone. At the concentrations tested (10(-2)-10(-4)M) the compounds exhibited antifungal activity, with the exception of quinone. On the basis of their effects on spore germination, and development of hyphae, phenylenediamine was the more active. The mechanism of action of the compounds is still unknown, but hyphae show morphological alterations and disturb the distribution of calcofluor in the cell wall. This suggests variations in the genesis of the cell wall.

Aniline Compounds↗
PubMed1994

Analysis of Sec 19-1 mutant of Saccharomyces cerevisiae.

Saccharomyces cerevisiae Sec 19-1 cells are secretion mutants defective at 37 degrees C. The cells were analysed in order to ascertain the effect of mutation temperature on cell wall formation. At the restrictive temperature of 37 degrees C, the Sec 19-1 mutants had 37 micrograms/mg N-acetylglucosamine in the wall cells, while the wild type S. cerevisiae showed 84 micrograms/mg hexosamine. The mutants Sec 19-1 showed a maximum activity of chitin synthetase of 0.113 nmoles/min/ml, and the activity increased to 0.33 nmoles/min/ml in the wild type cells. On the other hand, variations of chitin distribution in the wall cells occurred at the restrictive temperature, but changes in actin organization were not evident. The results indicated that the mutation caused variations in the levels of N-acetylglucosamine and chitin synthetase, as well as in cell wall chitin distribution.

Actins↗
PubMed1989

Actin in Mucor rouxii.

Rhodamine-conjugated phalloidin was used to analyze the actin distribution during hyphal formation in Mucor rouxii. The occurrence of actin patches in the cortical region of the cells was seen in the initial stages of growth. A fungal 43 kDa protein was isolated by affinity chromatography on DNase I-sepharose. This peptide was identified on immunoblots when polyclonal antibodies against rabbit muscle actin were used as a probe. These results indicate: (1) that changes in actin localization accompany the hyphal development and (2) the fungal 43 kDa protein shares properties that are common to muscle actin.

Actins↗
PubMed1985

Characterization of a 36,000-dalton protein from the surface of Madin-Darby canine kidney cells involved in cell attachment and spreading.

We have identified and immunochemically characterized a 36,000-dalton membrane glycoprotein from Madin-Darby canine kidney cells. This protein is surface-labeled by lactoperoxidase-mediated iodination and metabolically labeled by [35S]methionine. It binds to Concanavalin A and incorporates 2-D-3H-mannose residues, thus indicating it is a glycoprotein. Rabbit polyclonal antibodies against this protein evenly decorate the external surface of trypsinized, unpolarized cells. The external apical surface of confluent monolayers, grown under culture conditions in which the tight junctions are closed and the cells have acquired polarity, is also evenly stained. The basolateral aspects of the external surface are stained only when the tight junctions are opened by removal of Ca++ or when the antibody has access to the monolayer from the basal side, which indicates an even distribution of this antigen on the surface of polarized cells. The antibody has no inhibitory effect on the opening and resealing of tight junctions in dense cultures, but does inhibit the attachment and spreading of cells on a substrate, which then blocks the establishment of a confluent functional monolayer.

Animals↗
PubMed1983

Isolation and characterization of actin from Entamoeba histolytica.

Actin has been identified and purified partially from trophozoites of Entamoeba histolytica HMI-IMSS by a procedure that minimizes proteolysis. In cellular extracts, Entamoeba actin would copolymerize with muscle actin, but would not bind to DNase I or form microfilaments. Fractionation of the extracts by DEAE-cellulose and Sephadex G-150 chromatography yielded a purified actin that would copolymerize with rabbit skeletal muscle actin or polymerize alone into long filaments at 24 degrees C upon addition of 100 mM KC1 and 2 mM MgCl2. These filaments are not cold-stable and will depolymerize at 4 degrees C in 1 or 2 h. Entamoeba actin filaments bind phallotoxin with the same affinity as muscle actin and decorate with rabbit skeletal muscle heavy meromyosin. Entamoeba actin filaments activate the Mg2+ ATPase of heavy meromyosin to the same Vmax as muscle actin, but the Kapp is 2.8 times higher. Entamoeba actin is a single species with a slightly higher molecular weight than muscle actin (45,000) and a more acidic pI (5.4). The purified actin does not bind to DNase I, produce inhibition of the enzymatic activity, or block the binding of muscle actin. Comparison of the peptides obtained by limit digest with protease V8 from Staphylococcus aureus shows sequences with common mobility between alpha-actin and Entamoeba actin, but additional peptides are present which may account for the different properties of the Entamoeba actin. Finally, in vitro translation of mRNA from trophozoites produces a single polypeptide equivalent to the molecule purified from Entamoeba extracts.

Actins↗
PubMed1983

Trypanosoma cruzi: distribution of fluorescently labeled tubulin and actin in epimastigotes.

Cytoskeletal components were visualized in epimastigote forms of Trypanosoma cruzi by double immunofluorescence microscopy using monospecific antibodies against tubulin and against actin. Intense staining of the flagellum and the edges of the cell body was observed when the cells were stained with anti-tubulin, reflecting the presence of the basal bodies, the flagellar axoneme and the subpellicular microtubules. A less intense staining was seen in the cell body of epimastigotes stained with anti-actin. However, an intense staining was observed with this antibody in the flagellum, in a pattern similar to that observed with anti-tubulin. It is suggested that the paraxial structure, which is formed by a complex array of 6-nm-thick microfilaments is composed, at least in part, of actin.

Actins↗
PubMed1982

Occluding junctions in MDCK cells: modulation of transepithelial permeability by the cytoskeleton.

In MDCK cell monolayers the opening and resealing of occluding junctions can be induced by removal and restoration of calcium to the external medium. The overall changes in permeability of the occluding junctions in the monolayer can be monitored by the drop and recovery of the total transepithelial electrical resistance. We have investigated the effects of cytochalasin B (CB) on this process. When CB is added to sealed monolayers there is a gradual drop in the electrical resistance across the monolayer. This drop is accompanied by a slow disorganization of the microfilament pattern of these cells, including a disturbance of a ring of cortical microfilaments that is normally associated with the junctions. Cells in open monolayers treated with CB will not reseal and have an altered filament distribution. These cells do not have a continuous cortical ring. We have used a voltage scanning technique that uses a microelectrode to measure the resistance at selected points along the junction which surrounds a single cell. In untreated, closed monolayers, the junction is heterogeneous with alternating points of high and low conductance. In closed monolayers treated with CB, although there are low conductance points, we have observed an increased frequency of high conductance points that correlates with the change in the overall conductance. The frequency of high conductance points along the junction and the overall conductance both increase with time of exposure to CB. In an effort to understand the molecular basis for the permeability changes induced by EGTA and CB, we have looked for differences in the protein components of the cell membranes of open, closed, and CB-treated MDCK monolayers. This was done by radioiodinating the surface membrane proteins under control and experimental conditions that bring about permeability changes. No significant differences in the labeled protein patterns were found under these conditions. These results suggest that the permeability changes involve only a structural rearrangement of membrane components. In additions we have observed that about 36% of the surface label remains bound to the insoluble cytoskeletons obtained from cells in control and experimental conditions that alter the permeability of the tight junctions. The iodinated proteins attached to the CS include polypeptides with Mr of greater than or equal to 120K daltons as well as peptides with Mr = 56K, 50K, 36K, and 18K daltons.

Animals↗
PubMed1980

Occluding junctions and cytoskeletal components in a cultured transporting epithelium.

MDCK cells form uninterrupted monolayers and make occluding junctions similar to those of natural epithelia. This aricle explores the relationship between these junctions and the cytoskeleton by combining studies on the distribution of microfilaments and microtubules with the effect of drugs, such as colchicines and cytochalasin B, on the degree of tightness of the occluding junctions. To study the degree of tightness, monolayers were prepared by plating MDCK cells on mylon disks coated with collagen. Disks were mounted as flat sheets between two Lucite chambers, and the sealing capacity of the junctions was evaluated by measuring the electrical resistance across the monolayers. Equivalent monolayers on coverslips were used to study the distribution of microtubules and microfilaments by indirect immunofluorescence staining with antibodies against tubulin and actin. This was done both on complete cells and on cytoskeleton preparations in which the cell membranes had been solubilized before fixation. Staining with antiactin shows a reticular pattern of very fine filaments that spread radially toward the periphery where they form a continuous cortical ring underlying the plasma membrane. Staining with antitubulin depicts fibers that extend radially to form a network that occupies the cytoplasm up to the edges of the cell. Colchicine causes a profound disruption of microtubules but only a 27 percent decrease in the electrical resistance of the resting monolayers. Cytochalasin B, when present for prolonged periods, disrupts the cytoplasmic microfilaments and abolishes the electrical resistance. The cortical ring of filaments remains in place but appears fragmented with time. We find that removal of extracellular Ca(++), which causes the tight junctions to open, also causes the microfilaments and microtubules to retract toward the center of the cells. The process of junction opening and fiber retraction is reversed by the restoration of Ca(++). Colchicine has no effect on either the opening or reversal processes, but cytochalasin B inhibits the resealing of the junctions by disorganizing the filaments in the ring and at the apical border of the cells. These cytochalasin B effects are fully reversible. The correlation among cell shape, cytoskeletal patterns, and electrical resistance in the EGTA-opened and resealed monolayers suggests that microfilaments, through their association with plasma membrane components, play a role in positioning the junctional strands and influence the degree of sealing of the occluding junctions.

Animals↗
PubMedDate not supplied

[Characterization fo mycelial mutants of Mucor rouxii].

The consequences of two different mutations induced with N-methyl-N-nitrosoguanidine (Strain G1) and Trifluoperazine resistance (Strain G5) in Mucor rouxii, were studied. Mutants were stable and exhibited mycelial morphology in aerobiosis. Mutants cells exhibit phenotypic characteristics of slow-growing. The mutants G1 and G5 cultures showed 16.8% and 35.3% of reduction of the growth relative to parental strain. Morphologically mycelia of mutants cell were indistinguishable from wild-type cells, except from reduction in extension and branching of hyphal that has the mutant G5. Calcofluor and FITC-Concanavalin A were used to study the distribution of new cell-wall polymers i.e. Chitin, glucans. The two G1 and G5 strains showed a uniform distribution of fluorescence over the cell surface, indicating that active deposition of new-wall material has occurred. Cellular proteins of mutants and parental strains were labeled with 14C-aminoacid mixture. The proteins pattern revealed that the majority of polypeptides synthesized by parental strain were also synthesized by mutants. It is evident the synthesis preferential of peptides with apparent M(r) > 92K, 60K, 50K, 43K, 38K and 25K. These results indicated that the primary defect of the mutation was not on cellular differentiation. It discuss phenotypic and biochemistry characteristics from mutants.

Drug Resistance, Microbial↗
PubMedDate not supplied

[Inhibition of Mucor rouxii growth by synthetic substances].

Mucor rouxii cells were used to examine the possible antimycotic activities of four substances: phenolamines, phenylendiamine and quinone. These substances are original structures recently synthesized. Assays in plates showed that 10(-2) M of phenolamines and phenylendiamines give rise to halos of growth inhibition. Assays in liquid media using 10(-4) M of substances showed 100% inhibition of spore germination. Specifically, the phenylendiamine showed 49% inhibition on development of mycelium. In these cells the calcofluor distribution changes, suggesting alterations in cell wall. No inhibition of growth was found using the quinone. The activity for substances were evaluated using standard antifungal benomyl. On this basis, the substance phenylendiamine it is an antimycotic active. The mechanism of action is not presently known.

Aniline Compounds↗