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C Arregui

Publications and source records attributed to C Arregui.

5 recordsLinked to original sources
PubMed1992

Peanut agglutinin binding glycoproteins in the chick retina: their presence in Müller glia cells.

The histological and cellular distribution and some biochemical characteristics of components that bind peanut agglutinin (PNA), a lectin that recognizes preferentially terminal galactose-beta (1-3) N-acetyl galactosamine disaccharide residues of glycoconjugates, were studied in chick retinal tissue and in dissociated retinal cells after their differentiation in culture. In sections of retinal tissue from animals 7 days after hatching (Rp7), in addition to the inner and outer segments of the photoreceptor layer, the plexiform and optic fiber layers were stained with rhodamine-labeled PNA, indicating that, besides photoreceptor cells, other cellular types contribute to the PNA staining. We present evidence indicating that at least part of this staining is provided by Müller glia cells. In cultures of dissociated cells from retinas at embryonic day 7 (R7), photoreceptor-like cells and flat Müller glia-derived cells but not neurons were stained with rhodamine-labeled PNA. Furthermore, Müller glia cells isolated from Rp7 were also brightly stained with PNA. Western blot assays of extracts from R7 showed the presence of PNA binding glycoproteins of 31-33 kDa and a component that migrates at the dye front. In addition to the components detected in R7, extracts from R14 and Rp7 showed the presence of a major PNA binding glycoprotein of 175 kDa and a minor glycoprotein of 220 kDa. Extracts from the photoreceptor layer contain the 175 and 220 kDa glycoproteins, indicating their association with photoreceptor cells. The 31-33 kDa components were detected in extracts from the remnant inner retina, suggesting their association with the Müller glia cells. Supporting this view, these components and not those of 175 and 220 kDa were detected in cell cultures enriched in flat Müller glia-derived cells. Only the 31-33 kDa components and the component that migrates at the dye front were detected in extracts from cell cultures enriched in photoreceptor-like cells, suggesting the need of some environmental element for the expression of the 175 and 220 kDa components in the differentiated photoreceptor cells.

Animals↗
PubMed1991

Tyrosinated and detyrosinated microtubules in axonal processes of cerebellar macroneurons grown in culture.

We have used the monoclonal antibody YL 1/2 (Tyr) specific for tyrosinated tubulin, and a polyclonal antibody (Glu) specific for detyrosinated tubulin to visualize the distribution of microtubules and microtubule assembly sites during axonal outgrowth. Cerebellar macroneurons growing in culture initially extend several short and thin neurites which have the potential to differentiate either as axons or dendrites (Ferreira and Caceres: Developmental Brain Research 49:205-213, 1989). At the onset of axonal outgrowth the Tyr antibody labels the minor neurites, the axon, and its growth cone, while the Glu antibody only shows immunoreactivity in the axonal shaft. After nocodazole treatment, the Tyr staining disappears, whereas that produced by the Glu antibody remains practically unchanged. When nocodazole was removed, tyrosinated microtubules reappeared first at the tip of the axon, in a more distal region than that occupied by detyrosinated microtubules; another focal site of tyrosinated tubulin incorporation was detected in the cell body. Incorporation of tyrosinated tubulin into growing axons was also studied after taxol treatment. After long incubation periods in the presence of taxol, the Tyr staining disappeared from the axon but remained in the cell body; however, immunoreactivity in this site was negative when the cells were preincubated in the presence of protein synthesis inhibitors. Release from taxol results in the reappearance of Tyr immunoreactivity at the distal end of the axon. Taken collectively, the present results indicate 1) that in cerebellar macroneurons axonal differentiation is accompanied by a temporal and spatial differentiation of microtubules and 2) that there is an active site of tyrosinated tubulin assembly at the tip of axonal processes, and they suggest that the highly tyrosinated domain in this region is a consequence of rapid microtubule turnover and tubulin tyrosine ligase activity.

Alkaloids↗
PubMed1990

Specific antibodies for tyrosinated and detyrosinated tubulin recognize retina tubulin subpopulations that do not participate in the posttranslational tyrosination/detyrosination cycle.

We have used the monoclonal YL 1/2 (Tyr antibody) and polyclonal (Glu antibody) antibodies, specific for tyrosinated and detyrosinated tubulin, respectively, to determine the levels and cellular distribution of these tubulin species in chick retina during development. At embryonic day 4, detyrosinated tubulin was restricted to the ganglion cells of the fundic region. As development progresses, immunofluorescence also appears, first, in the outermost zone of the retina and then in the plexiform layers. The Tyr antibody staining was found in the different layers and it was fairly homogeneous in distribution. Analysis by dot immunobinding showed that the ratios of tyrosinated to detyrosinated tubulin obtained at different ages do not agree with those obtained previously by an enzymatic method based on the incorporation of [14C]tyrosine. We found that the lack of coincidence is due to the fact that a fraction of the tubulin species determined by the Tyr and Glu antibodies does not participate in the posttranslational tyrosination/detyrosination cycle. This is a novel concept that should be considered in the interpretations of immunofluorescence studies concerning the cellular distribution of tyrosinated and detyrosinated tubulin.

Animals↗
PubMed1989

Tyrosination state of tubulin and the activity of tubulin:tyrosine ligase and tubulin carboxypeptidase in the developing retina of the chick.

The tyrosination state of tubulin and the enzymes involved in the tubulin tyrosination/detyrosination cycle--tubulin:tyrosine ligase and tubulin carboxypeptidase--were determined in chick retina during development. The amount of tyrosinable (tyrosinated plus detyrosinated) tubulin increased approximately 110% from embryonic day 7 to 14. Then it decreased, and by day 19 it was similar to the value on day 7. This result did not change after hatching, at least up to day 20. The proportion of tyrosinated and detyrosinated tubulin significantly changed with the development of the animal. At embryonic day 7, these tubulin species were at a proportion of 70 and 30%, respectively, and after hatching, the values inverted, to 30 and 70%, respectively. This change did not correlate with the activity of the ligase relative to that of the carboxypeptidase, as measured in vitro. This observation suggested that a change in the turnover rate of microtubules, in the proportion of assembled and nonassembled tubulin pools, or in both had occurred. Coincident with the last possibility, the proportion of assembled tubulin was found to increase during the development of the animal. This finding suggests that the tyrosination state of tubulin may be determined, at least in part, by the assembly state.

Animals↗