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Biomedical subjects

R Herrera

Publications and source records attributed to R Herrera.

At least 37 records · Page 2Linked to original sources
PubMed1998

A role for the MEK/MAPK pathway in PMA-induced cell cycle arrest: modulation of megakaryocytic differentiation of K562 cells.

In vitro megakaryocytic differentiation of the pluripotent K562 human leukemia cell line is induced by PMA. Treatment of K562 cells with PMA results in growth arrest, polyploidy, morphological changes, and increased cell-cell and cell-substrate adhesion. These PMA-induced changes in K562 cells are preceded by a rapid rise in the activity of MEK (MAP kinase/extracellular regulated kinases) that leads to a sustained activation of ERK2 (extracellular regulated kinase; MAPK). Blockade of MEK1 activation by PD098059, a recently described specific MEK inhibitor [D. T. Dudley et al. (1995). Proc. Natl. Acad. Sci. USA 92, 7686-7689], reverses both the growth arrest and the morphological changes of K562 cells induced by PMA treatment. These changes are not associated with a disruption of PMA-induced down-regulation of BCR-ABL kinase or early integrin signaling events but are associated with a block of the cell-surface expression of the gpIIb/IIIa (CD41) integrin, a cell marker of megakaryocytic differentiation. These results demonstrate that the PMA-induced signaling cascade initiated by protein kinase C activation requires the activity of the MEK/ERK signaling complex to regulate cell cycle arrest, thus regulating the program that leads to the cell-surface expression of markers associated with megakaryocytic differentiation.

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMed1998

PMA-induced phenotypic changes in K562 cells: MAPK-dependent and -independent events.

Erythroid and megakaryocyte lineages are closely linked and may share a common bipotent progenitor. However, the mechanisms associated with cell lineage commitment are not fully understood. The K562 erythroleukemia cell line serves as a model to study the biochemical changes associated with erythroid and megakaryocyte (E/M) differentiation. We have previously established that PMA-induced megakaryocyte differentiation of K562 cells requires the activity of the MEK/MAPK pathway (Herrera et al Exp Cell Res 1998; 238: 407-414). Here, we show that the PMA-induced phenotypic changes of K562 cells such as polylobulation of the nucleus and Pyk2 expression are independent of MAPK activation. In addition, we also demonstrate that inhibition of the basal activity of the extracellular regulated kinase (ERK/MAPK) pathway enhances the erythroid phenotype of these cells. These results suggest that the MAPK pathway regulates the E/M lineage commitment of K562 cells.

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMed1998

Topical paromomycin/methylbenzethonium chloride plus parenteral meglumine antimonate as treatment for American cutaneous leishmaniasis: controlled study.

We determined the efficacy of the combination of the topical formulation 15% paromomycin sulfate/12% methylbenzethonium chloride (MBCL) and a short course (7 days) of parenteral meglumine antimonate (pentavalent antimony [Sb]) as treatment of American cutaneous leishmaniasis in Colombian patients. Patients were randomly assigned in unequal allocation (2:1:1:1) to group 1 (topical paromomycin/MBCL plus injectable Sb for 7 days), group 2 (topical placebo plus injectable Sb for 7 days), group 3 (topical paromomycin/MBCL plus injectable Sb for 3 days), and group 4 (injectable Sb for 20 days). Cure was defined as complete reepithelialization of all lesions without relapse. Cure rates among groups were as follows: 58% (34 of 59), group 1; 53% (16 of 30), group 2; 20% (6 of 30), group 3; and 84% (26 of 31), group 4. Seventy-one percent of the organisms identified to the species level were Leishmania braziliensis panamensis. We conclude that 10 days of therapy with paromomycin/MBCL does not augment the response of cutaneous leishmaniasis (predominately due to L. braziliensis panamensis) to a short course of treatment with meglumine antimonate.

Antiprotozoal Agents↗
PubMed1998

Fever after craniofacial surgery in the infant under 24 months of age.

A retrospective review was undertaken of 126 consecutive craniofacial procedures involving a transcranial component, performed at the Children's Medical Center at Dallas, between 1990 and 1994. Standard postoperative axillary temperature measurements were recorded until discharge. Age at surgery of less than 24 months correlated very strongly with a postoperative temperature of greater than 38 degrees C (r = -0.92). The incidence of postoperative fever was high in all age groups, yet there was still a significant difference between the group younger than 2 years and the group in which surgery was performed after the age of 2 years across all postoperative temperature ranges, from >38 degrees C to >39.5 degrees C (p < 0.001, chi-square test). The white blood cell count was elevated above the age-related normal in 67 percent of febrile patients. There was no correlation between type or duration of surgical procedure, length of intensive care or hospital stay, or the need for blood transfusion and the development of a significant postoperative fever. There were minor infectious complications in four patients (3 percent), only one of which was a wound problem related to the surgery. All infectious complications were easily identifiable clinically. There was no mortality or serious infections. The development of postoperative fever, and an elevated white blood cell count, is to be expected in pediatric patients undergoing craniofacial procedures. The routine laboratory investigation of postoperative fever in pediatric craniofacial patients under 2 years of age without procedures involving transgression of the paranasal sinuses is not warranted unless there are associated clinical indicators.

Age Factors↗
PubMed1998

Modulation of hepatocyte growth factor-induced scattering of HT29 colon carcinoma cells. Involvement of the MAPK pathway.

Hepatocyte growth factor (HGF)/scatter factor modulates the motility of HT29 colon carcinoma cells in vitro by inducing morphological changes that depend on the type of extra-cellular matrix (ECM) ligand; HGF-induced scattering of HT29 cells is observed if cells are grown on plastic coated with serum proteins but not laminin. The absence of scattering correlates with a lack of cell spreading on laminin and it is not due to impaired HGF induced tyrosine phosphorylation of the E-cadherin/desmosome component, (gamma)-catenin, or lack of activation of mitogen activated protein kinase (MAPK). Treatment of HT29 cells with phorbol 12-myristate, 13-acetate (PMA), but not arachidonic acid, restored the ability of the cells to spread on laminin in an integrin-dependent manner. Moreover, the addition of both PMA and HGF restored the ability of these cells to scatter on laminin in a synergistic manner. This event correlated with increased tyrosine phosphorylation of paxillin and activation of MAPK. Moreover, when the MEK (MAPK kinase)/MAPK pathway was blocked by the MEK inhibitor PD098059, HGF-induced scattering of HT29 cells was blocked. Thus, HGF modulation of HT29 cell motility is regulated by both integrin and growth factor-dependent signaling and implicates MAPK in the modulation of intercellular adhesion and epithelial cell motility.

Actins↗
PubMed1998

Three-dimensional evaluation of lumbar orthosis effects on spinal behavior.

The effects of the lumbosacral Lumbostab orthosis on intervertebral mobility, spinal geometry, and the geometrical deformations of discs have been investigated with a three-dimensional (3-D) reconstruction technique of the lumbar spine. Positions studied are neutral standing, maximal flexion, extension, left lateral bending, and left axial rotation. Results from this preliminary study indicate that the orthosis has a tendency to reduce vertebral mobility and discal deformations mainly at the upper segments (L1-L3), while it seems to increase vertebral displacements and discal deformations at the lower levels.

Adult↗
PubMed1997

Interleukin-3-induced phosphorylation of BAD through the protein kinase Akt.

BAD is a distant member of the Bcl-2 family that promotes cell death. Phosphorylation of BAD prevents this. BAD phosphorylation induced by interleukin-3 (IL-3) was inhibited by specific inhibitors of phosphoinositide 3-kinase (PI 3-kinase). Akt, a survival-promoting serine-threonine protein kinase, was activated by IL-3 in a PI 3-kinase-dependent manner. Active, but not inactive, forms of Akt were found to phosphorylate BAD in vivo and in vitro at the same residues that are phosphorylated in response to IL-3. Thus, the proapoptotic function of BAD is regulated by the PI 3-kinase-Akt pathway.

Androstadienes↗
PubMed1996

Adhesion through the interaction of lymphocyte function-associated antigen-1 with intracellular adhesion molecule-1 induces tyrosine phosphorylation of p130cas and its association with c-CrkII.

The B-lymphoblastoid cell line JY undergoes homotypic aggregation in a lymphocyte function-associated antigen-1 (LFA-1)-mediated, intracellular adhesion molecule-1 (ICAM-1)-dependent manner when stimulated with phorbol 12-myristate 13-acetate or anti-LFA-1 antibodies. Under conditions that lead to cell aggregation, we observed rapid tyrosine phosphorylation of p130cas, a protein previously identified to be phosphorylated on tyrosine in both v-src- and v-crk-transformed cells. Phosphorylation of p130cas was dependent on binding of LFA-1 to its ligand, ICAM-1, as demonstrated by the use of anti-ICAM-1 antibodies. Several observations suggest that this event may be an important step in the signaling pathway initiated by LFA-1. p130cas phosphorylation was rapidly reversible upon disengagement of the LFA-1-ICAM-1 complex and required cell adhesion since binding of phorbol 12-myristate 13-acetate-stimulated JY cells to purified ICAM-1 or cross-linking of either LFA-1 or ICAM-1 was not sufficient to induce phosphorylation of p130cas. The integrin-stimulated phosphorylation of p130cas created binding sites that were recognized in vitro by the SH2 domain of c-CrkII, a key adaptor protein involved in cell differentiation and transformation. Moreover, we also showed that the LFA-1-stimulated tyrosine phosphorylation of p130cas induces the formation of a p130cas.CrkII and p130cas.CrkL complex in intact cells. This observation suggests that adhesion mediated by the interaction of LFA-1 and ICAM-1 initiates a signaling cascade that involves the activation of protein tyrosine kinases and leads to the regulation of protein-protein interaction via SH2 domains, a key process shared with growth factor signaling pathways.

Antibodies↗
PubMed1996

The product of the cbl oncogene forms stable complexes in vivo with endogenous Crk in a tyrosine phosphorylation-dependent manner.

The cellular homologs of the v-Crk oncogene product are composed exclusively of Src homology region 2 (SH2) and SH3 domains. v-Crk overexpression in fibroblasts causes cell transformation and elevated tyrosine phosphorylation of specific cellular proteins. Among these proteins is a 130-kDa protein, identified as p130cas, that forms a stable complex in vivo with v-Crk. We have explored the role of endogenous Crk proteins in Bcr-Abl-transformed cells. In the K562 human chronic myelogenous leukemia cell line, p130cas is not tyrosine phosphorylated or bound to Crk. Instead, Crk proteins predominantly associate with the tyrosine-phosphorylated proto-oncogene product of Cbl. In vitro analysis showed that this interaction is mediated by the SH2 domain of Crk and can be inhibited with a phosphopeptide containing the Crk-SH2 binding motif. In NIH 3T3 cells transformed by Bcr-Abl, c-Cbl becomes strongly tyrosine phosphorylated and associates with c-Crk. The complex between c-Crk and c-Cbl is also seen upon T-cell receptor cross-linking or with the transforming, tyrosine-phosphorylated c-Cbl. These results indicate that Crk binds to c-Cbl in a tyrosine phosphorylation-dependent manner, suggesting a physiological role for the Crk-c-Cbl complex in Bcr-Abl tyrosine phosphorylation-mediated transformation.

3T3 Cells↗
PubMed1995

The effects of high altitude on hypothalamic-pituitary secretory dynamics in men.

OBJECTIVE: Individuals adapted to high altitude (HA) have abnormalities in endocrine function and specifically in the pituitary-thyroid axis and aldosterone regulation. In this study we assessed hypothalamic-pituitary function in men adapted to high altitude living using exogenous administration of synthetic hypothalamic hormones. DESIGN: Growth hormone releasing hormone (Geref 1-29) 1 microgram/kg, TRH 500 micrograms, GHRH 100 micrograms and ovine corticotrophin releasing hormone (oCRH) 1 microgram/kg were simultaneously administered intravenously to two groups of men: 12 born and raised in the city of Pasto, Colombia, South America, located at an altitude of 2600 m in the southern Colombian Andes (HA group) and 10 men living at sea level (SL) in Tampa, Florida. MEASUREMENTS: The following hormones were measured: GH, IGF-I, TSH, T4, free T4, free T3, PRL, ACTH, beta-endorphin and cortisol. IGF binding protein-3 (IGFBP-3) and cortisol binding globulin (CBG) were also measured. RESULTS: GH response to GHRH in HA men was exaggerated compared to SL men, and IGF-I concentration was also significantly increased in the presence of normal levels of IGFBP-3. No differences in TSH or PRL responses were found following TRH. HA men had lower basal total T4 levels, but higher free T4 and free T3 concentrations. The basal ACTH concentrations in the HA men were significantly lower than SL, although the response to oCRH was still present. beta-Endorphin basal levels were similar at HA and SL but the response to oCRH at HA was blunted. At HA, basal cortisol levels as well as CBG were elevated compared to SL and, in contrast to SL, did not increase significantly after endogenous ACTH secretion. CONCLUSIONS: This study is the first description of exaggerated GH response to the administration of GHRH in HA men and also of a significant increase in IGF-I concentration in the same subjects in the presence of normal levels of IGFBP-3. An altered hypothalamic-pituitary response was found in HA men after administration of oCRH characterized by a significantly lower basal ACTH concentration at HA, although the response to oCRH was present but the beta-endorphin response to oCRH was blunted. At HA, basal cortisol levels, as well as CBG, were elevated and the cortisol levels did not significantly increase after endogenous ACTH secretion. We have characterized the differences in hypothalamic-pituitary dynamics after the administration of TRH, GnRH and oCRH in HA men comparing their response to age/sex matched SL men.

Adaptation, Physiological↗
PubMed1995

Glycosylation sites encoded by exon 2 of the human insulin receptor gene are not required for the oligomerization, ligand binding, or kinase activity of the insulin receptor.

Asparagine-linked glycosylation of the insulin receptor is required for complete biosynthesis and acquisition of function. However, the relative role of each individual glycosylation site has not been elucidated. Previously, it has been shown that removal, by site-directed mutagenesis, of the four amino terminal glycosylation sites (N16,N25,N78, and N111) results in a mutant insulin receptor that remained in the endoplasmic reticulum as an unprocessed proreceptor (Collier E., Carpentier J.-L., Beitz L., Caro L. H. P., Taylor S. I., and Gorden P. [1993] Biochemistry 32, 7818-7823). In the present study, the contribution of these independent glycosylation sites to dimerization and insulin binding has been evaluated. Chinese hamster ovary cells were transfected with the wild-type human insulin receptor cDNA, or cDNA that had Q substituted for N at one, two, or all four of these glycosylation sites. Electrophoretic characterization of the proteins immunoprecipitated from 35S-labeled cells showed that both the wild-type and the quadruple mutant receptor had similar profiles, indicating that the mutant receptor is capable of undergoing dimerization. Analysis of the biochemical properties of this mutant showed that this receptor binds insulin, but ligand binding does not result in kinase stimulation. We demonstrated that the absence of kinase activation is not a property of the mutated receptor since the wild-type proreceptor behaves in a similar manner. Only partial glycosylation in this region of the receptor is required for its targeting to the cell membrane since single and double glycosylation mutants were found processed to their alpha and beta subunits on the cell surface.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Activators of protein kinase C stimulate association of Shc and the PEST tyrosine phosphatase.

Using the yeast two-hybrid system, complementary DNA clones were isolated from a HeLa cell library encoding proteins that interacted with p52shc. One of these clones encoded the non-catalytic, COOH-terminal half of the cytosolic protein tyrosine phosphatase PTP-PEST. Expression of truncated forms of p52shc in the two-hybrid system revealed that the amino-terminal half of p52shc was sufficient for interaction with PTP-PEST. The p52 and p66 forms of Shc, but not the p46 form, bound to a glutathione S-transferase fusion protein containing the region of PTP-PEST isolated from the two-hybrid screen. Similarly, when HeLa cell lysates were immunoprecipitated with PTP-PEST antiserum, p52shc and p66shc proteins, but not p46shc, co-precipitated. Shc-PTP-PEST complex formation was stimulated 6-8-fold by the protein kinase C activator phorbol 12-myristate 13-acetate, while epidermal growth factor and serum had no effect. Phorbol 12-myristate 13-acetate also stimulated phosphorylation of p52shc and p66shc. The muscarinic agonist carbachol (also an activator of protein kinase C) stimulated complex formation 3-5-fold in SH-SY5Y neuroblastoma cells. These results suggest a role for PTP-PEST in G protein receptor signaling and in cross-talk between G protein receptor and tyrosine kinase receptor pathways.

Adaptor Proteins, Signal Transducing↗
PubMed1994

Expression of alpha 1-chimaerin (rac-1 GAP) alters the cytoskeletal and adhesive properties of fibroblasts.

The small GTP-binding protein rac-1, a member of the ras gene superfamily of GTPases, is thought to be a key component of a signal transduction pathway that mediates cell membrane ruffling and actin stress fiber formation induced by growth factors. rac-1 protein is regulated by the interplay of several activities: proteins that enhance GDP dissociation (GDP Dissociation Stimulator, GDS), inhibit nucleotide exchange (GDP Dissociation Inhibitor, GDI), or accelerate GTP hydrolysis (GTPase Activating Protein, GAP). We have assessed the relative contribution of the rac-1/GAP interactions to the overall activity of rac-1 by expressing alpha 1-chimaerin, a rac-1-specific GAP, in fibroblasts. NIH 3T3 cells were transfected with alpha 1-chimaerin cDNA-containing expression vector and stable clones were established. Extracts prepared from alpha 1-chimaerin-expressing cells showed rac-1 GAP activity that was regulated by phosphatidylserine and phorbol ester. The cells expressing alpha 1-chimaerin showed a distinct phenotype. They had altered adhesive properties as measured by their ability to bind to a fibronectin-coated glass surface, suggesting that the expression of a rac-1 GAP alters the assembly of integrin receptors, actin and cytoskeletal proteins such as vinculin and talin. Direct demonstration of this phenomenon was achieved by studying the organization of actin stress fiber and formation of focal adhesions in the alpha 1-chimaerin expressing cells following stimulation by growth factors. Mock transfected cells, upon serum or lysophosphatidic acid stimulation, organize actin as a dense array of parallel fibers running the length of the cell. This process did not take place in the cells expressing rac-1 GAP. Similarly, the formation of focal adhesions as measured by the appearance of vinculin clusters was impaired in the alpha 1-chimaerin expressing cells. These results demonstrate that expression of a GAP for rac-1 in fibroblasts produces profound changes in the cytoskeletal organization and suggest that GAP activity negatively regulates rac-1 function.

3T3 Cells↗
PubMed1994

Surgical intervention for the complications of meningococcal-induced purpura fulminans.

Purpura fulminans is an infrequent but sometimes catastrophic illness that usually complicates a viral, rickettsial or bacterial infection. This communication presents a retrospective review of 152 patients with meningococcemia hospitalized at Children's Medical Center of Dallas from January, 1983, through December, 1993. Eighteen (11.9%) of the 152 patients developed purpura fulminans. Thirteen (72%) of the 18 patients with purpura fulminans needed one or more surgeries including skin grafts, local debridement, microvascular flaps or amputations. Five patients (28%) died.

Amputation, Surgical↗