Biomedical subjects

A Cuadrado

Publications and source records attributed to A Cuadrado.

At least 55 records · Page 3Linked to original sources

PubMed1993

Acylphosphatase synergizes with progesterone during maturation of Xenopus laevis oocytes.

Xenopus laevis oocytes are physiologically arrested in the G2/M phase border of the first meiotic division. A number of different stimuli can trigger off the re-entry into the cell cycle as a consequence of activation of either membrane-dependent or -independent intracellular signals. This system has been widely used to study signal transduction mechanisms induced by hormones. Among those more intensively researched, special attention has been devoted to elucidate the mechanism of activation induced by progesterone. However, despite intense efforts to understand the intracellular signalling mechanism of progesterone, a clear notion of the most relevant events involved in this process has not yet been elucidated. We provide evidence that acylphosphatase, an enzyme responsible for the regulation of membrane pumps in eukaryotic cells, synergizes with progesterone for induction of oocyte maturation. We deduced that this synergism may be related to the regulation of intracellular Ca2+ levels for several reasons: (1) maturation of oocytes by extracellular Ca2+ is blocked by acylphosphatase; (2) both progesterone and acylphosphatase drastically reduced Ca2+ uptake; (3) progesterone-induced maturation does not depend on a rise in intracellular Ca2+, since microinjection of EGTA, a calcium chelator, does not affect maturation induced by progesterone.

Acid Anhydride Hydrolases↗

PubMed1993

[Aneurysm of the atrial septum associated with interatrial communication: a study of 12 cases by 2-dimensional color echocardiography].

Between 1983-1991 we have studied 5,221 two-dimensional echocardiography in patients suffering cardiopathies. Twelve (0.22%) had an aneurysm of the atrial septum associated with atrial septal defect. Eight patients had other cardiac anomalies. The criteria used to diagnosis the aneurysm were: 1) The atrial septum central part protrudes in the atrium. 2) 6 mm aneurysm base. 3) Minimum distance from the base to the protrusion top 6 mm. The aneurysm was located in the oval fossa in 6 patients (50%) and in the other 6 patients the aneurysm was situated in the ostium secundum. The aneurysm base measured 7.79 +/- 1 mm and the left or right septum displacement was of 7.37 +/- 1.82 mm. The left displacement was observed in 10 patients (83.3%) and the right in 2 patients (16.6%). The spontaneous closure of atrial septal defect by the aneurysm was showed in 2 (16.6%) patients and in one (8%) was necessary the surgical closure. The other 9 patients: five rested along the follow-up without any change and other 4 patients died because of cardiac malformation. To conclude the atrial septal aneurysm associated with atrial septal defect in an unusual cardiopathy. Two dimensional echocardiography and Doppler color was diagnostic in all infants.

Echocardiography↗

PubMed1993

H-ras and raf-1 cooperate in transformation of NIH3T3 fibroblasts.

We examined the effect of overexpression of growth factor-regulated second messenger enzymes, alone and in combination, on transformation of NIH3T3 cells. Signal transducers included phospholipase C-gamma (PLC-gamma), protein kinase C-gamma (PKC-gamma), and two proto-oncogenes, c-H-ras and c-raf-1. Three of these proteins, PLC-gamma, PKC-gamma and Raf-1, did not transform NIH3T3 cells alone or in combination. c-H-ras, which under its own promoter control has low transforming activity, also did not cooperate with PLC-gamma or PKC-gamma. In contrast, the combination of normal or oncogenic p21 H-Ras with the Raf-1 kinase dramatically increased transformation efficiency. The level of Ras protein required for transformation was reduced in Raf-1 co-transfectants, implying that, at low levels of p21 Ras, p74 Raf-1 is rate limiting. As transformation by Ras depends on jun-mediated transcriptional events, we also examined H-ras and c-raf-1 cooperation in transcriptional transactivation of TPA-responsive element (TRE)-dependent reporters. Like the H-ras/c-raf-1 cooperation in transformation, we observed this synergistic stimulation of TRE-dependent transcription. This pathway for transformation and transcriptional activation by increased levels of normal Ras and Raf may be important in tumors that show overexpression but lack mutationally activated forms of these two proto-oncogenes.

3T3 Cells↗

PubMed1993

Phosphorylcholine: a novel second messenger essential for mitogenic activity of growth factors.

Growth factor stimulation of quiescent cells induces a series of intracellular early and late events that ultimately lead to DNA synthesis and cell division. We describe here that production of phosphorylcholine is an essential component of the late events involved in the induction of DNA synthesis by platelet-derived growth factor (PDGF-BB), a prototype mitogen for fibroblasts. Moreover, phosphorylcholine itself is mitogenic when added exogenously to NIH3T3 cells, further indicating its role as a crucial intracellular messenger for DNA synthesis. Choline kinase, the first step in the route of phosphatidylcholine synthesis appears to be the critical regulatory enzyme in phosphorylcholine production, indicating that regulation of choline kinase represents a key step during mitogenic stimulation. We also describe that several growth factors (PDGF-AA, basic FGF, EGF and phorbol esters) rely on their ability to generate phosphorylcholine for their proliferating activity. In contrast, DNA synthesis induced by serum did not require phosphorylcholine. Moreover, the requirement for phosphorylcholine production in PDGF-stimulated cells can be over-ruled by addition of insulin. Thus, cell proliferation in NIH3T3 cells can be triggered off by alternative pathways and one of them involves generation of phosphorylcholine.

3T3 Cells↗

PubMed1992

Platelet-derived growth factor stimulation of GTPase-activating protein tyrosine phosphorylation in control and c-H-ras-expressing NIH 3T3 cells correlates with p21ras activation.

Platelet-derived growth factor (PDGF) stimulation of NIH 3T3 cells leads to the rapid tyrosine phosphorylation of the GTPase-activating protein (GAP) and an associated 64- to 62-kDa tyrosine-phosphorylated protein (p64/62). To assess the functions of these proteins, we evaluated their phosphorylation state in normal NIH 3T3 cells as well as in cells transformed by oncogenically activated v-H-ras or overexpression of c-H-ras genes. No significant GAP tyrosine phosphorylation was observed in unstimulated cultures, while PDGF-BB induced rapid tyrosine phosphorylation of GAP in all cell lines analyzed. In NIH 3T3 cells, we found that PDGF stimulation led to the recovery of between 37 and 52% of GAP molecules by immunoprecipitation with monoclonal antiphosphotyrosine antibodies. Furthermore, PDGF exposure led to a rapid and sustained increase in the levels of p21ras bound to GTP, with kinetics similar to those observed for GAP tyrosine phosphorylation. The PDGF-induced increases in GTP-bound p21ras in NIH 3T3 cells were comparable to the steady-state level observed in serum-starved c-H-ras-overexpressing transformants, conditions in which these cells maintained high rates of DNA synthesis. These results imply that the level of p21ras activation following PDGF stimulation of NIH 3T3 cells is sufficient to support mitogenic stimulation. Addition of PDGF to c-H-ras-overexpressing cells also resulted in a rapid and sustained increase in GTP-bound p21ras. In these cells GAP, but not p64/62, showed increased tyrosine phosphorylation, with kinetics similar to those observed for increased GTP-bound p21ras. All of these findings support a role for GAP tyrosine phosphorylation in p21ras activation and mitogenic signaling.

3T3 Cells↗

PubMed1992

[Application of bidimensional echocardiography in the diagnosis of ventricular septal defect].

Between 1985-1990 we studied by means of two-dimensional echocardiography 286 patients with isolated ventricular septal defect (VSD). A hundred and sixty three being male and 123 female, as a mean age of 5 +/- 3 months. Sixty two cases (22.3%) reveales associated anomalies and in other 63 (22.4%) there was in the evolution an aneurysm of the septum membranous. The projections used were apical 4-chamber, with or without aortic root; parasternal long-short axis of great arterias or at ventricular level; subcostal 4-chamber; right oblique outlet right outflow tract and left oblique outlet left and right outflow tracts. Patients with VSD smaller than 3 mm were excluded. Perimembranous defects, 189 cases (66%), were more frequent than muscular, 91 31.8%), and subarterial defects, 6 (2.1%). Only 19 (9 apical muscular, 6 perimembranous outlet and 4 perimembranous trabecular) were initially misclassified. The diameter of the VSD was large in subarterial (0.85 +/- 0.1 cm) and perimembranous outlet VSD (0.75 +/- 0.5 cm) compared with the rest. Each group of defects was more easily shown by one particular projection except trabecular muscular defect. In conclusion, we are able to state that two-dimensional echocardiography enables us to discover the size and situation of isolated ventricular defects.

Child↗

PubMed1992

[Aortic atresia with situs inversus].

We report a case of mitro-aortic atresia with situs inversus. The patient was studied with two-dimensional echocardiography and the diagnosis was confirmed in the necropsy. Our newborn infant is the second case reported with this abnormality and the first in our country.

Abnormalities, Multiple↗

PubMed1992

[Angioplasty of a stenosed Blalock-Taussig shunt. Its long-term assessment].

A Blalock-Taussig shunt was performed in a child of 14 months diagnosed with tetralogy of Fallot associated with a complete atrioventricular defect. Seven months later, a balloon dilatation was performed because the shunt was stenosed in the site of the distal anastomosis. Repeat angiography we proved the patency of the shunt without restenosis 4 year later.

Anastomosis, Surgical↗

PubMed1990

Increased tyrosine phosphorylation in ras transformed fibroblasts occurs prior to manifestation of the transformed phenotype.

Murine fibroblasts transformed by ras oncogenes exhibited an increased amount of tyrosine phosphorylated proteins compared to normal cells. The pattern of phosphorylation was similar to that observed in cells chronically stimulated with EGF or PDGF, and is probably due to autocrine stimulation of receptor tyrosine kinases. NIH 3T3 cells transfected with H-ras under the control of a glucocorticoid inducible promoter were used to determine the temporal relationship among expression of p21H-ras oncoprotein, increase in tyrosine phosphorylation and appearance of the transformed morphology. Enhanced tyrosine phosphorylation was observed more than 24 hours before evidence of morphological changes. These results suggest that full transformation by ras oncogenes requires cooperation with tyrosine protein kinases.

Actins↗

PubMed1990

Expression of protein kinase CI in NIH 3T3 cells increases its growth response to specific activators.

In order to investigate the effects of protein kinase C (PKC) expression on cellular growth and morphology, we established mouse fibroblast cell populations which expressed the rat pkc-gamma gene under the control of a retroviral promoter. NIH 3T3 stable transfectants displayed a three-fold increase in total PKC levels. These cells appeared morphologically unaltered but exhibited a stronger mitogenic response to 12-O-tetradecanoylphorbol-13-acetate (TPA) and cardiolipin (CL) as well as enhanced growth in semisolid medium in the presence of TPA. Thus, at these enzyme levels, PKC conferred growth advantages to NIH 3T3 cells only in response to specific activators.

Animals↗

PubMed1990

The probability of G1 cells to enter into S increases with their size while S length decreases with cell enlargement in Allium cepa.

The distribution of cell surface area projection (cell size) has been measured at birth and at initiation of DNA synthesis in steady-state populations of Allium cepa root meristems. The conditional probability, P(I/G1), that initiation occurs given that the event of being in G1 also occurs has been estimated from these data. P(I/G1) was found to increase when cells became larger. The distribution of G1 duration has been constructed from indicated cell size distributions. The absolute frequencies of G1 times showed a maximum in the zone of cells with short G1 periods; about 14% of cells appear to enter into S with G1 congruent to 1 h. These results suggest that the increase of P(I/G1) was due to cell enlargement and not to cell aging. By comparing the cell size distribution at initiation of S and at the end of this period, a drastic reduction of cell size variability during DNA replication was observed and both curves were seen as rather similar in shape although they obviously had different modal points. These observations support that there is a negative correlation between the initiation size and the duration of genome duplication, and that cells which initiate DNA synthesis with the same size have a similar replication time. From this hypothesis, a plot of S duration versus cell size at initiation of this period was constructed by comparing the distributions of cell size at start and end of replication; this plot was also consistent with the existence of a negative correlation between cell initiation size and S length.

Allium↗

PubMed1990

Overexpression of phospholipase C-gamma in NIH 3T3 fibroblasts results in increased phosphatidylinositol hydrolysis in response to platelet-derived growth factor and basic fibroblast growth factor.

Overexpression of phospholipase C-gamma in fibroblasts led to increased tyrosine phosphorylation of this enzyme in response to platelet-derived growth factor and basic fibroblast growth factor. This correlated with increased phosphoinositide release but not with enhanced mitogenicity. Thus, phospholipase C-gamma-mediated phosphoinositide metabolism may not be limiting in the signaling pathways initiated by these growth factors.

Animals↗

PubMed1990

Regulation of protein kinase C activity in neuronal differentiation induced by the N-ras oncogene in PC-12 cells.

Expression of the N-ras oncogene under the control of the glucocorticoid-responsive promoter in the pheochromocytoma cell line UR61, a subline of PC-12 cells, has been used to investigate the differentiation process to neuronal cells triggered by ras oncogenes (I. Guerrero, A. Pellicer, and D. E. Burstein, Biochem. Biophys. Res. Commun. 150:1185-1192, 1988). Using ras-inducible cell lines, we observed that expression of the oncogenic N-ras p21 protein interferes with the ability of phorbol esters to induce downregulation of protein kinase C. This effect was associated with the appearance of immunologically detectable protein kinase C as well as the activity of the enzyme as analyzed either by binding of [3H]phorbol-12,13-dibutyrate in intact cells or by in vitro kinase activity. These results indicate a relationship between ras p21 and protein kinase C in neuronal differentiation in this model system. Comparison to the murine fibroblast system suggests that this relationship may be functional.

Adrenal Gland Neoplasms↗

PubMed1990

C127 cells resistant to transformation by tyrosine protein kinase oncogenes.

C127 is a nontumorigenic mouse cell line widely used in in vitro transformation assays due to its normal morphological appearance and its very low levels of spontaneous transformation. We now report that C127 cells are resistant to transformation by tyrosine protein kinase oncogenes derived from growth factor receptors such as the retroviral v-fms and the human trk transforming genes. In contrast, these cells could be efficiently transformed by members of the ras oncogene family and by serine/threonine kinase oncogenes such as v-mos and v-raf. C127 cells were also found to be resistant to transformation by v-src, the prototype of a large family of tyrosine protein kinase oncogenes whose products are associated with the inner side of the plasma membrane. However, morphologically normal C127 cells expressing pp60v-src acquired a transformed phenotype upon continuous passage in vitro. Somatic cell hybrids (neoR, hygroR) obtained by fusion of G418-resistant C127 cells expressing p70trk (neoR) and hygromycin-resistant NIH3T3 cells (hygroR) exhibited transformed properties as determined by their ability to grow in semisolid agar. In contrast, no such growth was observed when these neoR p70trk-containing C127 cells were fused to control hygroR C127 cells. These results indicate that C127 cells may either lack or express insufficient levels of certain critical substrate(s) necessary for the onset of transformation by tyrosine protein kinase oncogenes.

Animals↗

PubMed1989

Cell size of proliferating plant cells increases with temperature: implications in the control of cell division.

As chemical reactions related to the regulation of cell proliferation are governed by availability, amount, and concentration of relevant molecules, it has been suggested that cell size is an important factor in the control of cell cycle. We have measured the size of proliferating cells of Allium cepa roots in which growth rate was modified by changes in growth temperature. Two independent cell size parameters have been measured by cytophotometry: cell surface area projection and cell protein content. Average cell sizes of both the proliferating cell population and the subpopulation at the end of mitosis show that cell size increases with growth rate. Calculation of cell size at initiation of DNA replication clearly indicates that average cell size at this point is not growth invariant but positively correlated with growth rate.

Allium↗

PubMed1989

Exponential pattern of cell age distribution in dividing cells of plant meristems.

In order to determine the pattern of cell age distribution in proliferating cells of Allium cepa roots we have measured by cytophotometry two cell size parameters, protein content and surface area projection, in cells that correspond to the entire proliferating population or only to the ana-telophase subpopulation. The size values of ana-telophase cells have been employed to construct theoretical size distributions for the entire proliferating cell population of the root meristem by assuming either a uniform or an exponential cell age distribution. Statistical comparison of theoretical distributions with the experimental one rules out a uniform cell age distribution and strongly favours an exponential age distribution similar to that found in bacteria.

Cell Division↗

PubMed1987

Regulation of G2 by cell size contributes to maintaining cell size variability within certain limits in higher plants.

The variability of (1) surface area projection (size) at which cells terminate DNA replication, (2) the area at which they initiate mitosis, (3) the area at which they divide, (4) the duration of G2, and (5) the duration of G2 plus mitosis (in fact, prophase + metaphase + anaphase) has been estimated in steady-state cell populations of Allium cepa root meristems. The coefficient of variation of cell area at termination of DNA synthesis was found to be 14% while the coefficient of variation of cell area at mitosis initiation was 13%. As there is also a substantial variability of G2 (the coefficient of variation was estimated to be 38%), the combination of these data indicates that cell size regulation of G2 contributes to maintaining cell size variability (and therefore DNA concentration) within certain limits. Mitosis also varies but less than G2 (the coefficient of variation of G2 + mitosis was found to be 31%). As the coefficient of variation of cell area at division (14%) is hardly larger than the coefficient of variation of cell area at initiation of mitosis, it can be suggested that coordination between cell size and mitosis duration helps to avoid a significant increase in the variability of cell size at the end of the division cycle.

Allium↗

PubMed1985

The effect of partial protein synthesis inhibition on cell proliferation in higher plants.

Meristematic cells from Allium cepa L. roots can attain a steady state of growth in the presence of anisomycin at concentrations that effectively reduce the rate of protein synthesis. Under these conditions the lengths of cell cycle periods increase but not in the same proportion as the generation time (t). Mitosis is hardly affected and S period is slightly lengthened. G2 increases less in proportion to t, while G1 is extended much higher in proportion to t. Natural synchronous populations have been used to study cell cycle parameters during transition from the physiological steady state to the new one created by the presence of the drug. G2 was the same during transition as during steady-state growth. G1 was much shorter during transition. Average cell mass at division was reduced, and a negative correlation was observed between the length of G2 and the size of the cell at termination of DNA synthesis. We propose that in higher plants, G2 length is regulated by cell mass at completion of DNA synthesis (G2 being shorter in big cells than in small cells), though there is no cell size requirement for mitosis.

Allium↗