Search PubMed⌕ Search

Biomedical subjects

R Fragoso

Publications and source records attributed to R Fragoso.

At least 19 recordsLinked to original sources
PubMed2002

Analysis of the formed track in solid state materials using atomic force microscopy.

The track formation in solid state materials, from the theoretical point of view, is still under study. One way to understand the track formation mechanisms and radiation damage of the charged particles in some materials such as polymers, glasses and minerals, is to analyse the surface topography effects. In this work, the track formation analysis in polycarbonate material is presented using an atomic force microscope (AFM) to characterise the evolution of the track on the material surface and beyond a thin layer of the surface material. The AFM is very useful to obtain valuable information at the level of the atomic structure of the materials and of the nuclear tracks, due to its high resolution and very easy operation involving also a simple sample preparation. The results show the development of the formed track by means of induced surface effects after being exposed to ionising radiation and chemical etching.

Microscopy, Atomic Force↗
PubMed1996

Intrathymic signals in thymocytes are mediated by p38 mitogen-activated protein kinase.

Thymocytes develop into mature functional T cells in the inductive environment of the thymus where thymocyte-stromal cell interactions and cytokines provide survival and differentiation signals as cues for thymocyte maturation. Disruption of the thymic microenvironment results in attenuation of T cell maturation, suggesting that intrathymic signals are essential for differentiation and repertoire selection. We have previously shown that several inducible nuclear factors such as AP-1, NF-AT, and NF-kappaB are activated in response to intrathymic signals. Here we demonstrate that in thymocytes p38 mitogen-activated protein (MAP) kinase, a member of the MAP kinase family of proteins that include the extracellular-signal regulated kinases and Jun aminoterminal kinases, is highly activated in response to intrathymic signals in vivo. These studies suggest a role for p38 MAP kinase in T cell survival and differentiation.

Animals↗
PubMed1996

Autosomal dominant congenital epiphyseal dysplasia limited to the femoral heads.

A father and son with unusual congenital skeletal symptoms, mainly characterized by short stature and epiphyseal dysplasia limited to the femoral heads are described. The comparative analysis with other spondyloepiphyseal dysplasias supports the notion that the syndrome reported here is a distinct autosomal dominant connective tissue disorder.

Adult↗
PubMed1995

Molecular characterization of the fragile-X syndrome in the Mexican population.

The fragile X (fra-X) syndrome is the most frequent form of inherited mental retardation. Facial dysmorphism, macroorchidism and a folate-sensitive fragile site on Xq27.3 are commonly associated features. The gene causing this disorder, designated as FMR1, is X-linked and shows an unusual inheritance mode. A multistep amplification of the CGG repeats at the 5' end of the FMR1 gene has been recently identified as the cause of the fra-X syndrome. Different numbers of repeats define three gene forms (normal, premutated and mutated), whose ranges show little variation in the populations studied so far. We analyzed 18 Mexican individuals with the fra-X syndrome, 40 of their relatives (first and second degree), and 76 healthy individuals without antecedents of mental retardation. Southern blot and PCR permitted the assessment of the number of CGG repeats and the methylation state of the FMR1 gene for the normal, premutated, and mutated alleles. The results showed no statistical differences when compared with those from other populations. No cytogenetic expression of the Xq27.3 fragile site in 50% of the affected males and in all the affected and carrier females was observed. This finding emphasizes the necessity of a molecular analysis in fra-X cases and their relatives in order to provide a more adequate genetic counseling.

Base Sequence↗
PubMed1994

Identification of upstream signals regulating interleukin-6 gene expression during in vitro treatment of human B cells with pokeweed mitogen.

The present studies have characterized the regulation of interleukin-6 (IL-6) gene expression during pokeweed mitogen (PWM)-driven human B-cell differentiation. PWM induced an early and transient increase in the expression of immediate-early response genes of the jun/fos leucine zipper family (c-jun, jun B, c-fos, and fos-B). The induction of c-jun mRNA by PWM was concentration dependent. Nuclear run-on assays showed that PWM treatment is associated with an increased rate of c-jun gene transcription. The induction of c-jun mRNA precedes the induction of IL-6 gene expression and IL-6 secretion by the B cells. c-Jun antisense, but not sense, oligodeoxynucleotide (ODN) significantly decreases PWM-related B-cell (1) proliferation; (2) IL-6 mRNA induction; (3) IL-6 secretion; and (4) nuclear extract binding to AP-1 in electrophoretic mobility shift assay. In contrast, c-Fos anti-sense ODN did not effect either IL-6 mRNA induction or IL-6 secretion triggered in B cells by PWM. The results further show activation of c-Raf-1 kinase in PWM-treated B cells. Raf-1 acts upstream to mitogen-activated protein (MAP) kinase; therefore, studies were performed to assay for MAP kinase activation in these cells. The results show an increase in phosphorylation of myelin basic protein (MBP) and c-Jun "Y" peptide in PWM-treated B cells. Taken together, these findings suggest that PWM is able to initiate an intracytoplasmic signaling cascade in normal human splenic B cells, which, at least in part, involves serine/threonine protein kinases. These results show transient induction of immediate-early response genes in B cells and support a potential role for the c-jun gene product in regulation of IL-6 transcription and secretion.

B-Lymphocytes↗
PubMed1993

Centromeric association of a microchromosome in a Turner syndrome patient with a pseudodicentric Y.

A 12-year-old patient with Turner syndrome was found to have a complex mosaicism for a microchromosome (MC) and a psu dic(Y)(q11). The MC was smaller than Yp, appeared pale in G, C and late replicating bands, had a pair of small centromeric dots, was associated with other chromosomes in most metaphases, and was rather stable both in size and during mitosis. The psu dic(Y) was Cd-positive only at the active centromere, had two pericentromeric heterochromatic regions, and lacked the Yq12 band. No cells with both abnormal chromosomes were found. To evaluate the association of the MC with all ordinary chromosomes, 857 G-banded cells with the marker were screened. The MC was considered as "associated" whenever the distance between it and other chromosome(s) was equal to, or smaller than, 18p. Out of 848 associations registered, 489 (57.7%) were centromeric, 202 (23.8%) telomeric, and 157 (18.5%) interstitial; i.e., centromeric associations were overrepresented (P < 0.001) and showed a random distribution, except for an excessive involvement of chromosome 8. This association pattern, also exhibited by two similar MCs in human beings, the minute Y of a marsupial and certain B chromosomes in plants, probably reflects the Rabl orientation of chromosomes in interphase.

Centromere↗
PubMed1989

Achalasia microcephaly syndrome in a patient with consanguineous parents: support for a.m. being a distinct autosomal recessive condition.

A 4 9/12-year-old boy with achalasia microcephaly syndrome (AMS), born to a consanguineous couple, is reported. Comparative analysis of this case and the patients previously described in a Mexican family supports the notion that the syndrome is a distinct autosomal recessive condition. It is interesting that the area of origin and ethnicity of both the present and the previously reported cases is northwest Mexico.

Abnormalities, Multiple↗
PubMed1986

Ehlers-Danlos features with progeroid facies and mild mental retardation. Further delineation of the syndrome.

A syndrome characterized by progeroid facies, multiple nevi, mild mental retardation, skin hyperextensibility, bruisability, moderate skin fragility, joint hypermobility principally in digits, is described in two unrelated patients. Electron microscopy of the skin showed some fragmentation of the elastic fibers' portion and moderate electrodensity in the amorphous portion. Since a practically identical constellation of clinical features was previously reported in three patients, the individualization of a distinct connective tissue disorder, probably autosomal dominant, with variable expressivity is concluded.

Adolescent↗
PubMed1985

Cortical blindness, growth and psychomotor retardation and postaxial polydactyly: a probably distinct autosomal recessive syndrome.

A 14-month-old female infant with a syndrome mainly consisting of cortical blindness, psychomotor retardation and postaxial polydactyly (type B in hands and type A in feet) was studied. Two deceased sibs were similarly affected. Differential diagnosis and the review of medical literature permit the individualization of a distinct syndrome with a probable autosomal recessive pattern of inheritance.

Blindness↗
PubMed1984

A new psychomotor retardation syndrome with peculiar facies and marfanoid habitus.

We studied four sibs, two males and two females, who presented psychomotor retardation, typical flat facies and some features of the Marfan phenotype such as tall stature, long and slim limbs, arm span larger than height, "arachnodactyloid" hands and feet, little subcutaneous fat and muscle hypotonia. It is concluded that the aggregate of morphoneurological anomalies constitute a new syndrome probably inherited in an autosomal recessive fashion.

Adolescent↗
PubMed1982

49,XXXXX syndrome.

A 3-year-old 49,XXXXX girl, the seventeenth case in medical literature, is described. A typical characteristic of the syndrome is the round face with epicanthal folds, hypertelorism, broad flat nasal bridge, upward slant of the palpebral fissures, enlarged round mandible and pointed chin, somewhat resembling trisomy 21. The apparent stronger selection against 49,XXXXX aneuploidy versus the 49,XXXXY suggested by the much higher frequency of the latter is probably due to the more severe congenital cardiopathy which may be related to the number of inactivated X chromosomes.

Abnormalities, Multiple↗