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Biomedical subjects

F Montoya

Publications and source records attributed to F Montoya.

At least 19 recordsLinked to original sources
PubMed2006

[Modelling of the geometry of the external auditory canal by the finite elements method].

The aim of this work is to design a computerized 3-D model of the human external ear, based on the finite elements method. The method consists to splitting a specific special area in a simple element net connected between themselves by nodes. The elements are associated to equations that define their physical characteristics. We realize a coupling with the middle ear model to know the behaviour of both systems with an acoustic excitation without the use of real measures or biological models. The model simulates the acoustic and biomechanic characteristics of the human external auditory canal. The development of a computerized model allows a better knowledge of the external ear mechanic-acoustic behaviour, this makes easier understand the physiology of the human external ear.

Acoustic Impedance Tests↗
PubMed2004

Intrapartum fetal pulse oximetry and fetal heart rate decelerations.

OBJECTIVES: To determine the behavior of fetal oxygenation (FSpO(2)) in different patterns of fetal heart rate decelerations (FHR). METHODS: A total of 787 decelerations were studied. RESULTS: FSpO(2) decreased significantly during decelerations, especially when the alteration was prolonged. CONCLUSIONS: Modifications in FHR occur simultaneously with alterations in FSpO(2), although the latter do not persist in time. Different degrees of FSpO(2) seen prior to deceleration are an expression of fetal respiratory status.

Adolescent↗
PubMed2002

[Computerized 3-D model to study biomechanics of the middle ear using the finite element method].

Based on known data about the behavior of the sound transmission mechanism, we generate a model that reproduces the real mechanics of the middle ear by the finite elements method in the most exact manner possible. We designed a computerized model to simulate the biomechanic behavior of the ear drum/ossicular chain. The investigation focused on a possible clinical application, given that the variables necessary for simulation of several conditions can be introduced in our model: tympanic perforation, fixation of the ossicular chain, chain interruption, etc. Introducing the characteristics of the lesion virtually in a simulator program market is possible to reach conclusions about the conductive hypoacusis created and about therapeutic possibilities. The 3-D modelling of the tympanic membrane, malleus, incus and stapes is presented, considering form, weight, density, Young's module (N/m2) and Poisson coefficient for the different parts of each ossicle. The modeling of the union of the different tympanic-ossicular elements, including muscles and ligaments, is also shown.

Biomechanical Phenomena↗
PubMed2001

Prevalence of HFE mutations in people from North Africa living in southern France.

The two main mutations of the HFE (haemochromatosis) gene, C282Y and H63D, were found previously to be rare or absent among Africans. Dried blood samples of 1276 newborns from southern France were analysed for both HFE mutations, and the origins of the four grandparents of each newborn were recorded. The allele frequency of C282Y and H63D was 3.0% +/- 0.7% and 16.9% +/- 1.5% respectively. In a subgroup of 171 newborns with four North African ancestries (mainly from Morocco and Algeria) the allele frequency was 0.9%+2.5%-0.2% for the C282Y and 13.2% +/- 3.6% for H63D. HFE mutations are not absent in individuals with North African origins living in southern Europe. This finding has implications for the diagnosis and screening of hereditary haemochromatosis in these populations.

Africa, Northern↗
PubMed1999

[Mycoplasma pneumoniae meningoencephalitis].

BACKGROUND: Severe central nervous system diseases, such as encephalitis, have been reported in association with Mycoplasma pneumoniae infections. CASE REPORT: After an ENT infection, a 9-year-old boy with Down's syndrome developed encephalitis revealed by an acute alteration in consciousness. Head computed tomography showed, after 2 weeks, an infiltration in the basal ganglia region. The diagnosis of Mycoplasma pneumoniae encephalitis was made; recovery was complete in a few weeks. CONCLUSION: Mycoplasma pneumoniae infection should be considered in all cases of acute encephalopathy; yet the pathogenesis of the disorder is unknown and the treatment uncertain.

Acute Disease↗
PubMed1999

Increase in granulocyte-macrophage-colony-stimulating factor secretion and the respiratory burst with decreased L-selectin expression in hyper-IgE syndrome patients.

BACKGROUND: The hyper-IgE syndrome is a primary immunodeficiency characterized by severe recurrent abscesses, pneumonia with pneumatocele formation, and elevated serum IgE. Eosinophilia, neutrophil chemotactic defects, and marked tissue damage are frequently present in this syndrome. OBJECTIVE: To study whether functional changes in cytokines, adhesion molecules, and neutrophils might help explain these clinical observations. METHODS: The following functions were analyzed in patients with the hyper-IgE syndrome and in controls: (1) production of granulocyte-macrophage-colony-stimulating factor by peripheral blood mononuclear cells by ELISA; (2) respiratory burst and reactive oxygen intermediates production by peripheral neutrophils using the luminol-enhanced chemiluminescense technique; and (3) expression of L-selectin on granulocytes and lymphocytes by flow cytometry. RESULTS: Patients with hyper-IgE syndrome had significantly increased production of granulocyte-macrophage-colony-stimulating factor by resting or stimulated mononuclear cells, increased generation of reactive oxygen intermediates by neutrophils treated with opsonized zymosan, and reduced L-selectin expression on quiescent and activated granulocytes and lymphocytes. CONCLUSIONS: Our results suggest that an important feature of the hyper-IgE syndrome is the increased production of granulocyte-macrophage-colony-stimulating factor, which may explain the reduced L-selectin expression, decreased chemotaxis, and increased oxygen radical production and tissue damage in this disease.

Adolescent↗
PubMed1998

Interleukin 4 and interferon-gamma secretion by antigen and mitogen-stimulated mononuclear cells in the hyper-IgE syndrome: no TH-2 cytokine pattern.

BACKGROUND: Enhanced production of TH-2 cytokines plays a key role in increased IgE production in allergic diseases. Reports about the cytokine profile secreted by peripheral blood mononuclear cells of patients with hyper-IgE syndrome, however, are controversial, suggesting alternative causes for increased IgE production in this syndrome. OBJECTIVE: We wished to determine whether mononuclear cells from patients with hyper-IgE syndrome have a pattern of interleukin-4 (IL-4) and interferon-gamma (IFN-gamma) production characteristic of a predominance of TH-2 cells and whether the cytokine production pattern is constant over time. METHODS: IL-4 and IFN-gamma secretion by peripheral blood mononuclear cells stimulated with phytohemagglutinin and D. pteronyssinus was measured by ELISA in culture supernatants. Patients with the hyper-IgE syndrome were evaluated 3 times at 4-week intervals and compared with asthmatic patients and normal subjects. RESULTS: In PHA-stimulated cultures, patients with hyper-IgE syndrome had an IL-4 and IFN-gamma secretion similar to that of controls, while asthmatic patients had increased IL-4 and decreased IFN-gamma production. Cultures stimulated with D. pteronyssinus showed a variable pattern of secretion for both cytokines. CONCLUSIONS: In allergic diseases, increased serum IgE level is the result of a TH-2 pattern of cytokine production, with high IL-4 and decreased IFN-gamma protein secretion. The increased serum IgE concentration typical of the hyper-IgE syndrome is likely the result of a different immunoregulatory process.

Adolescent↗
PubMed1998

A study of granulocyte respiratory burst in patients with allergic bronchial asthma.

The respiratory burst of phagocytes plays an important role in the tissue damage that accompanies the inflammatory response. One of these conditions is allergic bronchial asthma, therefore, to evaluate the activation state of peripheral granulocytes the generation of reactive oxygen metabolites was evaluated using Luminol-enhanced chemiluminescence (LCL) and reduction of cytochrome C by superoxide. The resting granulocytes of the asthmatic patients under crisis showed a higher LCL compared to the noncrisis patients and control subjects. The granulocytes stimulated with PMA presented a significant increase in the respiratory burst in both groups of asthmatics. The granulocytes of noncrisis asthmatics challenged with Ops-Zym and with fMLP + Ops-Zym showed a higher metabolic activity, whereas the asthmatics under crisis presented no difference between reactive oxygen generation and that of the control group. The quantitative analysis of superoxide generation by granulocytes of the same patients did not show differences among the groups. Our findings suggest that the granulocytes of crisis and noncrisis asthmatics seem to be in a hyperreactive state and with a higher metabolic response when compared to the control group. However, the patients present a different behavior depending on stimulus used to activate cells. This could indicate that in peripheral blood exist different granulocyte populations depending on the inflammatory response taking place in the respiratory tract.

Adult↗
PubMed1997

Generation of the HLA-B35, -B5, -B16, and B15 groups of alleles studied by intron 1 and 2 sequence analysis.

HLA-B is the most polymorphic of the major histocompatibility complex classical class I loci. This polymorphism is mainly in exons 2 and 3, which code for the molecule's alpha 1 and alpha 2 domains and include the antigenic peptide binding site. Recent studies have indicated that not only exons but also the intron 2 region may be involved in the generation of certain HLA-B alleles such as B*3906 and B*1522. To study the degree of intron 2 participation and the mechanisms that generate polymorphism at the HLA-B locus, intron 1 and 2 sequences from the HLA-B35, -B5, -B16 and -B15 groups of alleles were obtained. A group-specific intronic polymorphism was found: namely, B*5301 shows intron 1 and 2 sequences identical to those found in all B35 alleles studied. On the other hand, B*5101 and B*52012 show the same intron 1 and 2 sequences and their intron 1 is the same as that found in the B35 group. This suggests that B5 and B35 groups of alleles may have arisen from a common ancestor. All known B16 alleles show the same introns 1 and 2, with the exception of B*39061 and B*39062, and all B15 alleles also bear the same introns 1 and 2, with the exception of B*1522. Variability at intron 1 is more restricted than at intron 2, and the use of intron 1 for HLA-B allele phylogenetic analysis is better for grouping alleles of a postulated common origin. In conclusion, there is a remarkable conservation of intronic sequences within related HLA-B alleles, which probably reflects a common origin and perhaps a selective force avoiding DNA changes. Intronic sequences are also potentially useful to design DNA typing strategies.

Alleles↗
PubMed1997

Distribution of capsular types and antimicrobial susceptibility of invasive isolates of Streptococcus pneumoniae in Colombian children. Pneumococcal Study Group in Colombia.

Streptococcus pneumoniae is the leading bacterial cause of childhood pneumonia in the developing world. This study describes the type distribution and antimicrobial susceptibility of invasive pneumococcal isolates from Colombian children and is part of the Sistema Regional de Vacunas (SIREVA), a PAHO regional initiative designed to determine the ideal serotype composition of a protein polysaccharide pneumococcal conjugate vaccine for use in children less than 5 years old in Latin America. In Colombia, during the study period, centres in Bogota, Medellin, and Cali collected 324 S. pneumoniae isolates from invasive diseases, 238 (73.5%) from children under the age of 2. Pneumonia was the clinical diagnosis in 41.3% cases, meningitis in 41%, and sepsis in 11.2%. The seven most frequent types included 14(21.9%), 5(10.5%), 23F(9.6%), 1(9%), 6B(9%), 19F(7.1%), and 6A(6.2%). The frequency of diminished susceptibility to penicillin (DSP) was 12%, with 8.9% of isolates showing intermediate level resistance and 3.1% showing high level resistance. Among DSP isolates, 23% were also resistant to cefotaxime, 33.3% to erythromycin, 48.7% to chloramphenicol, and 74.3% to trimethoprim/sulfamethoxazole. Multiple resistance was detected in 59% of the isolates that have DSP. Penicillin resistance was associated with types 23F (53.8%) and 14 (25.6%). These data provides information on capsular types prevalent in Colombia that will not only allow the formulation of an ideal vaccine for the region but also reinforce the need for ongoing regional surveillance.

Anti-Bacterial Agents↗
PubMed1997

[High- and low-risk molecular sequences in autoimmune diseases. An analysis of type I diabetes in Latin America].

Type I diabetes is an autoimmune and a polygenic disease, in which MHC-class II genes contribute to 48% of the disease. The aim of the present study, is to provide a guideline to understanding the molecular association of these genes, through the immunogenetic analysis of 3 Latin american mestizo populations. We included 606 individuals, 349 patients with DMDI and 257 healthy controls coming from 3 geographical areas: Mexico City, Mexico; Caracas, Venezuela and Medellin, Colombia. The results clearly indicate that in mestizo groups, the diabetogenic haplotypes are from mediterranean ancestry, while protection is due to Amerindian genes. It was demonstrated that the relevant sequences for IDDM expression are located to DRB1 and DQB1 loci with a minimal contribution of DQA1 residues. The sequences determining peptide recognition and the induction of TH1 cells mediating the cellular autoimmune response are in positions DRB1-57 and 74 (an aspartic acid and a glutamic acid respectively, confer protection), modulated by D-57 in the DQ, 8 chain. These data show that DRB1-DQB1 haplotypes are central for IDDM expression and open new pathways for the disease management.

Adolescent↗
PubMed1996

Prenatal aspects of giant fetal cranial haemangio-endothelioma.

A case of a large vascular lesion of the skull is reported. The lesion was discovered at 22 weeks' gestation and it rapidly increased in size, reaching 8 cm a month later. Tumor echogenicity was the same as that for soft tissues and colour Doppler examination revealed intense vascularization. Cordocentesis showed features of the Kasabach-Merritt syndrome and very high plasma levels of alpha-fetoprotein. A Caesarean section was performed to avoid dystocia and led to the birth of a baby with cardiac failure in the immediate neonatal period. Biopsies of the mass led to the diagnosis of a non-malignant haemangio-endothelioma. The mass was removed and plastic surgery performed. The baby is alive and well 9 months after the operation.

Adult↗
PubMed1994

Factors that influence the outcome of the intrauterine insemination with husband's sperm.

A retrospective analysis was undertaken in 160 intrauterine insemination with husband's sperm (IUIH) cycles, performed in 45 couples. The male factor represented the main indication (80%). Women who conceived had a lower duration of infertility (4.4 years +/- 3.0 vs 7.7 +/- 2.98). A significantly and pardoxically lower motility (3+ and 2+) was observed in raw specimens within conceptional cycles. However in prepared specimens in conceptional cycles the percentage of motility 3+ and 2+ was significantly increased (80.6% +/- 8.1 versus 70.7% +/- 20.2). The most significant difference was found in regard to a better response to preparation among conceptional cycles, expressed as the percentual increase in motility 3+ and 2+ (55.6% +/- 3.9 vs 41.3% +/- 19.4).

Adult↗