A Proposal for a Consolidated Structural Model of the CagY Protein of Helicobacter pylori.

CagY is the largest and most complex protein from Helicobacter pylori's (Hp) type IV secretion system (T4SS), playing a critical role in the modulation of gastric inflammation and risk for gastric cancer. CagY spans from the inner to the outer membrane, forming a channel through which Hp molecules are injected into human gastric cells. Yet, a tridimensional structure has been reported for only short segments of the protein. This intricate protein was modeled using different approaches, including homology modeling, ab initio, and deep learning techniques. The challengingly long middle repeat region (MRR) was modeled using deep learning and optimized using equilibrium molecular dynamics. The previously modeled segments were assembled into a 1595 aa chain and a 14-chain CagY multimer structure was assembled by structural alignment. The final structure correlated with published structures and allowed to show how the multimer may form the T4SS channel through which CagA and other molecules are translocated to gastric cells. The model confirmed that MRR, the most polymorphic and complex region of CagY, presents numerous cysteine residues forming disulfide bonds that stabilize the protein and suggest this domain may function as a contractile region playing an essential role in the modulating activity of CagY on tissue inflammation.

Evaluation of the Biological Properties of an Optimized Extract of Polygonum cuspidatum Using Ultrasonic-Assisted Extraction.

Phytochemicals are natural compounds found in plants that have potential health benefits such as antioxidants, anti-inflammatory and anti-cancer properties, and immune reinforcement. Polygonum cuspidatum Sieb. et Zucc. is a source rich in resveratrol, traditionally consumed as an infusion. In this study, P. cuspidatum root extraction conditions were optimized to increase antioxidant capacity (DPPH, ABTS+), extraction yield, resveratrol concentration, and total polyphenolic compounds (TPC) via ultrasonic-assisted extraction using a Box-Behnken design (BBD). The biological activities of the optimized extract and the infusion were compared. The optimized extract was obtained using a solvent/root powder ratio of 4, 60% ethanol concentration, and 60% ultrasonic power. The optimized extract showed higher biological activities than the infusion. The optimized extract contained 16.6 mg mL-1 resveratrol, high antioxidant activities (135.1 µg TE mL-1 for DPPH, and 230.4 µg TE mL-1 for ABTS+), TPC (33.2 mg GAE mL-1), and extraction yield of 12.4%. The EC50 value (effective concentration 50) of the optimized extract was 0.194 µg mL-1, which revealed high cytotoxic activity against the Caco-2 cell line. The optimized extract could be used to develop functional beverages with high antioxidant capacity, antioxidants for edible oils, functional foods, and cosmetics.

Micronutrients of the one-carbon metabolism cycle are altered in mothers and neonates by gestational diabetes and are associated with weight, height and head circumference at birth.

While several studies have previously described the levels of one-carbon metabolism-related micronutrients in women with gestational diabetes mellitus (GDM) and their neonates, the results in these literature reports have been contradictory. We hypothesized that the concentrations of micronutrients involved in the one-carbon cycle are altered in pregnant women and their neonates by GDM, and that these changes could further modify the neonatal anthropometry. Micronutrient levels were measured in 123 pregnant women with normal glucose levels (M-ND) and their neonates (N-ND), as well as in 54 pregnant women with gestational diabetes (M-GDM) and their neonates (M-GDM). Folate and vitamin B12 levels were measured via competitive ELISA, and betaine, choline, and glycine levels were measured via ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS/MS). Vitamin B12 and Glycine were found to be higher in M-GDM compared to M-ND. N-GDM had higher levels of folic acid and vitamin B12 and lower levels of betaine and choline compared to N-ND. In general, neonates presented with high concentrations of micronutrients compared to their mothers, and the fetus/maternal ratio of micronutrients was higher among the N-ND as compared to the N-GDM. Micronutrients were also variably associated with anthropometric measurements. The association of betaine with neonatal anthropometry in N-GDM is highlighted. In summary, our results implicate a potential role of GDM in altering the levels of one-carbon metabolism-related micronutrients among pregnant women and their neonates. Likewise, our results also elucidate a potential association between the concentrations of micronutrients and the weight, height, and head circumference of neonates.

Human papillomavirus genotypes and P16INK4A expression in squamous penile carcinoma in Mexican patients.

BACKGROUND: Approximately 50% of cases of penile carcinoma (PeCa), a rare neoplasm worldwide, are associated with human papillomavirus (HPV). However, the detection of HPV-DNA is not sufficient to consider it the etiological factor in the development of this type of cancer. Currently, the overexpression of P16INK4A is used as a surrogate biomarker of HPV carcinogenesis. Information on PeCa in Mexico is scarce, particularly regarding cases related to HPV and genotype frequency. OBJECTIVE: To evaluate the presence of HPV, its genotypes, and the presence of multiple genotypes, and the expression of P16INK4A, as well as its clinical and histopathological parameters. METHODS: For HPV-DNA detection and P16INK4A expression, we used the INNO-LiPA® test and immunohistochemistry, respectively. RESULTS: Sixty cases of PeCa were evaluated, of which 75% were HPV-non-related histological variants. We found that 58.9% (33/56) of PeCa cases were HPV-DNA positive, while 30.9% of the cases evaluated (17/55) were positive for P16INK4A. HPV16 was the main genotype in 42.9% of the cases, followed by HPV52 in 7.1% and HPV18 in 5.4%. Within the HPV-positive cases, 27.3% had multiple genotypes. All HPV-positive patients under the age of 45 years were positive only for HPV16. CONCLUSIONS: HPV16 was the most commonly detected genotype in PeCa. HPV 31, 35 and 39 were infrequent; however, they were related to a single infection and P16INK4A overexpression; thus, they seem to be relevant in PeCa carcinogenesis. Our results suggest that P16INK4A overexpression could be useful for the classification of HPV-related PeCa. The role of multiple HPV genotypes in the development and prognosis of PeCa is still not completely understood. Thus, it is necessary to define criteria to establish reliable ways to classify HPV-related PeCa that could lead to optimal therapeutic approaches.

La inclusión educativa en la educación a distancia mediante plataformas gestoras / Educational inclusion in distance education through management platforms

La modalidad de educación a distancia por medio de plataformas gestoras, al ser un entorno pedagógico con sus particularidades, requiere de la incorporación de los supuestos teóricos del aprendizaje desarrollador. El objetivo del presente trabajo es analizar la inclusión educativa en el contexto de la educación a distancia, con énfasis en el uso de determinados mediadores como vía pedagógica de solución a esta problemática. Sobre las bases teóricas del aprendizaje desarrollador y las concepciones epistemológicas de los mediadores en el proceso de enseñanza aprendizaje, se desarrollan esquemas sobre la didáctica de los mediadores, elementos fundamentales para garantizar una educación inclusiva en la modalidad de educación a distancia.

The mode of distance education through management platforms, being a pedagogical environment with its particularities, requires the incorporation of the theoretical assumptions of developing learning. The objective of the present work is to analyze educational inclusion in the context of distance education, with emphasis on the use of certain mediators as a pedagogical way of solving this problem. On the theoretical bases of the developing learning and the mediators´ epistemological conceptions in the process of teaching learning, schemes are developed on mediators´ didactics, fundamental elements to guarantee an inclusive education in the modality of distance education.

Synthesis and characterization of a HAp-based biomarker with controlled drug release for breast cancer.

A biocompatible hybrid porous polymer-ceramic material was synthesized to be used as a biomarker in the treatment of breast cancer. This device was equipped with the capacity to release medicaments locally in a controlled manner. The biomaterial was Hydroxyapatite(HAp)-based and had a controlled pore size and pore volume fraction. It was implemented externally using a sharp end and a pair of barbed rings placed opposite each other to prevent relative movement once implanted. The biomarker was impregnated with cis-diamine dichloride platinum (II) [Cl2-Pt-(NH3)2]; the rate of release was obtained using inductively coupled plasma atomic emission spectroscopy (ICP-AES), and release occurred over the course of three months. Different release profiles were obtained as a function of the pore volume fraction. The biomaterial was characterized using scanning electron microscopy (SEM) and Raman spectroscopy.

Transformación a los instrumentos de evaluación a pequeños grupos de estudiantes / Transformation to the evaluation instruments to little groups of students

La evaluación es un componente no personológico dentro de la pedagogía, con múltiples funciones que pueden hacer fluir el aprendizaje o retrasarlo. Esta investigación tiene como finalidad transformar los instrumentos de evaluación del trabajo en grupo en aras de una medida menos subjetiva del propio proceso evaluativo. El trabajo se realiza sobre la base de tres instrumentos de uso común en la evaluación de pequeños grupos de estudiantes. El resultado fundamental es la transformación de los instrumentos de evaluación, tanto a los que se aplican para evaluar al grupo como a los que se aplican para evaluar a los estudiantes de forma independiente. Se concluye que la transformación a los métodos de evaluación a pequeños grupos, puede favorecer la comprensión al realizar la integración entre la evaluación sumativa y la formativa.

The evaluation is a non personological component in pedagogy, with multiple functions that can make flowing learning or to delay it. This investigation has the purpose to turn the instruments of evaluation of group work to achieve a less subjective measure of the evaluative process. This work is performed on the base of three instruments of common use in the evaluation of little group of students. The fundamental result is the transformation of the instruments of evaluation as well as those applied to evaluate the group independently. The transformation to evaluation methods to little groups can favor the understanding to perform the integration between the sumative and the formative evaluation.

Estudio socio-epidemiológico de ancianos accidentados / Social-epidemiological study of elderlies who suffer accident

Introducción: el envejecimiento de los seres humanos es el resultado de la interacción compleja de varios factores: anatómicos, fisiológicos, psicológicos y sociales. Las causas de los accidentes en el adulto mayor son multifactoriales, pudiendo ser intrínsecas o extrínsecas. Existe una alta incidencia de estos en los ancianos. Objetivo: determinar los factores socio-epidemiológico asociados a esta problemática en el municipio de San Juan y Martínez en el año 2013, que permita implementar acciones de salud encaminadas a su prevención y disminución de la alta frecuencia en los ancianos. Material y método: se realizó una investigación retrospectiva, descriptiva y transversal con un universo de 615 pacientes y una muestra de 300 ancianos en el municipio San Juan y Martínez, después de haber sido aprobado su consentimiento informado, con el procedimiento de valor porcentual. Resultados: hubo un predominio del sexo masculino con el 56.0%. Predominó el grupo de edades de 71-80 años, con el 38.7%. La mayoría de estos residía en la zona urbana, con 62.70%, siendo jubilados el 51.1%. Los principales accidentes fueron: caídas con 64.0% y heridas con el 16.3%. Las enfermedades que predominaron fueron: la hipertensión arterial y las del sistema osteomioarticular; se exponen los principales causa intrínsecas y extrínsecas. Conclusiones: las familias moderadamente funcionales fueron las más representativas, donde el anciano recibe el apoyo necesario de las personas a su alrededor. Se diseñó una propuesta educativa que define acciones dirigidas a la prevención de accidentes en los ancianos con el apoyo sus familiares.

Introduction: aging of humans is the result of a complex interaction of anatomical, physiological, psychological and social factors. There are multifactorial causes of accidents in the elderly, could be intrinsic or extrinsic; observing a high incidence of accidents. Objective: to determine socio-epidemiological factors associated with this health problem in San Juan y Martínez municipality during 2013, allowing the implementation of health care actions to prevent and reduce the high frequency of accidents in the elderly. Material and method: a retrospective, descriptive and cross-sectional research which comprised a target group of 615 patients and 300 of them taken as a sample after completing the informed consent. The procedure of percentage value was applied; this study was carried out in San Juan y Martinez municipality. Results: male sex predominated (56.0%). Ages from 71 to 80 prevailed (48.7%). The majority of patients lived in urban zones (62.70%), retired 51.1%. Main accidents were: fall 64.0% and injuries 16.3%. Hypertension and osteomyoarticular diseases were among the most general; intrinsic and extrinsic causes of accidents were described. Conclusions: moderate functional families were the most representative, where the elderly receive the necessary support of those people accompanying them. An educative proposal was designed describing the actions to prevent accidents in the elderly counting on the family support.

In vivo evaluation of implant-host tissue interaction using morphology-controlled hydroxyapatite-based biomaterials.

In medicine, micro-electro-mechanical systems (MEMS) perform several specific functions. The design of bio-packages for MEMS to be implanted into the human body has been an increasing challenge in the last years. Mechanical, chemical and thermal resistance, as well as excellent bonding to silicon surfaces, are needed. Furthermore, ideal bio-packages should minimize post-operative complications and be well accepted by the host. To reach this goal, two different morphology-controlled hydroxyapatite-based porous biomaterials were synthesized, implanted in rats and evaluated mechanically and histologically. The novel biomaterials were prepared at room temperature using synthetic hydroxyapatite micro-particles, silica nanoparticles and water-based resin and compared with a standard hydroxyapatite biomaterial. The morphology (porosity) was controlled to obtain interconnected pores with appropriated pore size and pore volume fraction. All biomaterials were implanted in rats at the dorsal area near the third thoracic vertebra. The rats were killed 2, 7 and 21 days after surgery. Histological analysis revealed that the implants were well accepted by the host and minimal local inflammation was observed. The acute inflammatory response disappeared 21 days after surgery for both novel biomaterials. Additionally, organic matter (collagen) was produced in the interior of the porous biomaterial, indicating that an incipient vascularization process was in progress after 21 days of implantation. Both new biomaterials showed high abrasion resistance, high Young modulus, the appropriate porosity to allow possible vascularization, and good bonding to silicon surfaces.

Geographical variation in human papillomavirus prevalence in Mexican women with normal cytology.

OBJECTIVE: To determine the prevalence of human papillomavirus (HPV) infection and genotype distribution in Mexican women with similar lifestyles from two geographical regions who receive medical care from the Mexican Navy Health System, and to identify the associated sociodemographic and reproductive characteristics. METHODS: Cervical swabs from 671 women, beneficiaries of the Mexican Navy Health System, from two distinct southern coast regions of Mexico, were analyzed. Data were obtained regarding sociodemographic variables and sexual and reproductive history. For HPV detection and typing, PCR with general primers and direct sequencing were performed on extracted DNA. Association with clinical variables was evaluated. RESULTS: Most patients had a normal cytology or low-grade intraepithelial neoplasia. A high prevalence of HPV was found (43.6%), with a significant difference between the two regions studied from the southwest Pacific coast of Mexico (37.6% in Acapulco, Guerrero vs. 49.7% in Lázaro Cárdenas, Michoacán). Some differences were also found associated to HPV type distribution, particularly related to genotypes 18, 58, and 53. Factors influencing these differences could not be identified with the analysis of typical risk factors linked to the acquisition of an HPV infection. CONCLUSIONS: Regional differences in HPV prevalence and distribution show an apparent geographic boundary between the studied populations that deserves further analysis, taking into account other factors such as those related to the sexual partners.

Diseño de microsondas mediante hibridación virtual para el estudio de variantes en los sitios REP-CMT1A / Microarray design using virtual hybridization to study variations in REP-CMT1A sites

Antecedentes: El gen PMP22 se encuentra duplicado en pacientes con Charcot-Marie-Tooth 1A (CMT1A); se ha descrito que el origen de la duplicación es el intercambio desigual de las cromátidas durante la meiosis entre dos regiones de 24 kb denominadas sitios REPCMT1A, encontrándose un REP proximal y un REP distal, los cuales tienen una homología de 98%. Dentro de cada uno de estos sitios existen zonas denominadas puntos calientes de mutación (hot spot), donde se presenta el mayor número de variantes y mutaciones que pudieran dar origen al intercambio desigual. El objetivo de este trabajo fue diseñar un conjunto de microsondas para elaborar un microarreglo con el cual pueda detectarse la presencia de variantes y puntos de mutación en los sitios REP-proximal y REP-distal CMT1A. Material y métodos A partir de las secuencias informadas de los REP distal y proximal, se delimitaron los sitios hot spot dentro de las regiones proximal y distal. Estas secuencias se alinearon, se empalmaron y se detectaron 12 zonas de diferencia secuencial. Resultados y conclusiones. Se diseñaron y analizaron 24 microsondas mediante el programa Genosensor Probe Designer. Las sondas podrán ser sintetizadas y utilizadas en un microarreglo que permita encontrar variaciones, puntos de mutación, y facilitar el diagnóstico de pacientes con CMT1A.

BACKGROUND: Gene PMP22 is duplicated in patients with CMT1A. Duplication is due to an unequal chromatid interchange during meiosis that takes place between two 24 Kb regions named REP-CMT1A proximal and distal sites. Homology is approximately 98%. Within each one of the sites we find zones termed hot spots where a greater number of variants and mutations could give origin to an unequal interchange. The aim of this study was to design a set of probes to create a microarray that could detect the presence of variants and mutation points in distal and proximal REP sites among patients with CMT1A. MATERIAL AND METHODS: With reported sequences of distal and proximal REPs, we determined hot spot sites within proximal and distal regions. These sequences were aligned and matched, hence 12 zones were detected. RESULTS AND CONCLUSIONS: Twenty four probes were designed and analyzed using the Genosensor Probe Designer program. Probes could be synthesized and used in a microarray that is able to find variations and mutation points and facilitates diagnosis of patients with CMT1A.

Estrategias para el diagnóstico clinico y molecular de Charcot-Marie-Tooth 1A: estudio en pacientes mexicanos / Strategies for clinical and molecular diagnosis of Charcot-Marie-Tooth 1A among Mexican patients

Antecedentes: La neuropatía periférica de Charcot-Marie-Tooth (CMT) es la enfermedad hereditaria más común del sistema nervioso periférico humano. El subtipo más frecuente, CMT1A, es asociado a una duplicación de un fragmento de ~1.5 Mb en 17p11.2-p12, que incluye al gen PMP22. Objetivo: Describir diferentes estrategias para el diagnóstico clínico y molecular de CMT1A en pacientes del Instituto Nacional de Rehabilitación. Material y métodos: A 17 pacientes estudiados clínica y electrofisiológicamente que reunieron los criterios para CMT1, se les realizó el estudio molecular mediante electroforesis capilar para detectar la duplicación del gen PMP22. Resultados: Los estudios clínico, bioquímico y electrofisiológico ofrecieron los criterios para establecer el diagnóstico de CMT1. Con la electroforesis capilar se detectó la duplicación del gen PMP22 en siete pacientes que fueron diagnosticados clínica y electrofisiológicamente como CMT1, pudiendo llegar al diagnóstico de CMT1A. Todas las duplicaciones identificadas fueron corroboradas mediante hibridación in situ fluorescente. Conclusión: Los resultados nos permiten asegurar que la electroforesis capilar es un método fácil y confiable para detectar la duplicación del gen PMP22. Además, el aplicar diferentes estrategias tanto clínicas, electrofisiológicas y moleculares en este tipo de pacientes, nos permitieron establecer el diagnóstico correcto y ofrecer asesoramiento genético adecuado.

BACKGROUND: Charcot-Marie-Tooth (CMT) is the most common inherited disorder of the human peripheral nerve. The mos tfrequent subtype, CMT1A, is associated with duplication of approximately 1.5 Mb fragment in 17p11-p12, that includes the PMP22 gene. OBJECTIVE: The aim of this study was to describe different strategies used for clinical and molecular CNT1A diagnoses among patients attending the National Rehabilitation Institute of Mexico (INR). MATERIAL AND METHODS: 17 patients had clinical and electrophysiological features compatible with CMT1. A molecular study using capillary electrophoresis (CE) was performed and a PMP22 gene duplication was detected RESULTS: Clinical, biochemical and electrophysiological studies constituted the inclusion criteria to establish a CMT1 diagnosis. With CE the duplication of the PMP22 gene was observable and we established a possible CMT1A diagnosis in seven patients. All duplications detected by capillary electrophoresis were corroborated using FISH. CONCLUSION: CE is a feasible and reliable method to detect PMP22 gene duplication. Using different clinical, electrophysiological and molecular strategies in this patient population allowed us to establish an accurate diagnosis and offer suitable genetic counseling.

In silico evaluation of a novel DNA chip based fingerprinting technology for viral identification.

The identification of microorganisms by whole genome DNA fingerprinting was tested "in silico". 94 HPV genome sequences were submitted to virtual hybridization analysis on a DNA chip with 342 probes. This Universal Fingerprinting Chip (UFC) constitutes a representative set of probes of all the possible 8-mer sequences having at least two internal and non contiguous sequence differences between all them. A virtual hybridization analysis was performed in order to find the fingerprinting pattern that represents the signals produced for the hybridization of the probes allowing at most a single mismatch. All the fingerprints for each virus were compared against each other in order to obtain all the pairwise distances measures. A match-extension strategy was applied to identify only the shared signals corresponding to the hybridization of the probes with homologous sequences between two HPV genomes. A phylogenetic tree was constructed from the fingerprint distances using the Neighbor-Joining algorithm implemented in the program Phylip 3.61. This tree was compared with that produced from the alignment of whole genome HPV sequences calculated with the program Clustal_X 1.83. The similarities between both trees are suggesting that the UFC-8 is able to discriminate accurately between viral genomes. A fingerprint comparative analysis suggests that the UFC-8 can differentiate between HPV types and sub-types.

Low density DNA microarray for detection of most frequent TP53 missense point mutations.

BACKGROUND: We have developed an oligonucleotide microarray (genosensor) utilizing a double tandem hybridization technique to search for 9 point mutations located in the most frequently altered codons of the TP53 gene. Isolated and multiplexed PCR products, 108 and 92 bp long, from exons 7 and 8, respectively, were obtained from 24 different samples. Single-stranded target DNA was then prepared from isolated or multiplexed PCR products, through cyclic DNA synthesis. Independent ssDNA's were annealed with the corresponding pairs of labeled stacking oligonucleotides to create partially duplex DNA having a 7-nt gap, which contains the sequence that will be interrogated by the capture probes forming double tandem hybridization. In the case of multiplexed ssPCR products, only two stacking oligonucleotides were added per target, therefore the gap for the PCR products having two consecutive codons to be interrogated in exon 7 was 12 nt long, so only single tandem hybridization was produced with these respective probes. RESULTS: 18 codon substitutions were found by DNA sequencing. In 13 of them a perfect correlation with the pattern of hybridization was seen (In 5 no signal was seen with the wt probe while a new signal was seen with the appropriate mutant probe, and in 8 more, as expected, no signal was seen with any probe due to the absence of the corresponding probe in the array). In 3 other cases a mutation was falsely suggested by the combination of the absence of the wild type signal along with a false signal in the other probe. In the other 2 cases the presence of the mutation was not detected due to the production of a false hybridization signal with the wild type probe. In both cases (false mutation or no mutation detected) relatively stable mismatched target/probe duplexes should be formed. These problems could be avoided by the addition of probes to improve the performance of the array. CONCLUSION: Our results demonstrate that a simple TP53 microarray employing short (7-mer) probes, used in combination with single or double tandem hybridization approach and a simple or multiplex target preparation method, can identify common TP53 missense mutations from a variety of DNA sources with good specificity.

New cytotoxic steroids from the Indian Ocean sponge Axinella cf. bidderi.

Four new sterols have been isolated from the marine sponge Axinella cf. bidderi, 17alpha-hydroxy-22,23-epoxy-24-methylcholest-5-en-3beta-ol (1) and 17alpha-hydroxy-22,23-epoxycholest-5-en-3beta-ol (2), together with 3 and 4, which possess respectively the cholestene and the cholestane skeleton with a cyclic enol ether linkage between C-18 and C-22. The structures were elucidated using spectroscopic data. The in vitro activity was evaluated against prostate, ovary, pancreas, colon, and lung cell lines.

Detection of mutations in RET proto-oncogene codon 634 through double tandem hybridization.

We developed a procedure to detect the 7 point mutations at Cys634 of the proto-oncogene RET, which is responsible for medullary thyroid carcinoma (MTC). Genomic DNA was prepared from blood samples obtained from normal and MTC-affected individuals belonging to a family with a history of the disease. The RET genotype for each individual was first established by performing restriction and sequencing analyses. Single-stranded target DNA was prepared by asymmetric polymerase chain reaction (PCR) amplification of a 93-bp fragment containing Cys634. The target was annealed with pairs of prelabeled stacking oligonucleotides designed to create appropriate 7-nucleotide gaps, which served as the sites of subsequent hybridization with glass-immobilized 7-mer probes. The target-stacking oligonucleotide duplexes were hybridized with DNA chips containing a set of eight 7-mer probes designed to detect the wild-type sequence and the seven point mutations described. We tested two sets of immobilized probes containing internal or 5'-terminal codon-634 single-base variations. Both groups of probes were able to discriminatively identify the mutations. The hybridization patterns indicated that the disease in this family was due to the C634Y mutation, in accord with the original sequence analysis. The hybridization-based mutation assignment was additionally supported by determination of the control homozygous and heterozygous hybridization patterns produced with synthetic targets having the normal or codon 634 mutant sequences. The effects of mismatch type and nearest-neighbor sequences on the occurrence of false-positive (mismatched) hybridizations are discussed.

Osteosíntesis en fracturas del fémur en niños / Osteosynthesis of femoral fractures in children

El tratamiento en fracturas de fémur en niños es controversial; históricamente han sido manejadas por métodos conservadores, dando como resultado inmovilizaciones prolongadas y largos periodos de tracción ortopédica, incrementándose el compromiso biomécanico de articulaciones adyacentes. Este estudio se realizó de enero de 1993 a diciembre de 1994 en el Hospital Pediátrico Coyoacán. En pacientes menores de 16 años y de ambos sexos, a los cuales se les practicó osteosíntesis con clavo centromedular tipo Künstcher a foco abierto. Se intervinieron 31 pacientes del sexo masculino y 11 femeninos con una edad promedio de 8 años, 22 pacientes presentaron fractura de fémur derecho y 20 de fémur izquierdo. A todos se les practicó radiometría de miembros pélvicos con una discrepancia de 3 mm en 5 de ellos y sólo 2 presentaron infección de tejidos blandos las cuales remitieron. Mediante la osteosíntesis con clavo centromedular se evita el cabalgamiento, el deslizamiento y la angulación de los cabos fracturarios, disminuyéndose la posibilidad de que se presenten discrepancias en el crecimiento. Como conclusión, no se debe usar el clavo centromedular tipo Künstcher en fracturas diafisarias que afecten el tercio distal o asociadas con un tercer fragmento en las alas de mariposa, porque existe la posibilidad de que dicho fragmento se secuestre

Dolores de crecimiento. Respuesta a los ejercicios de relajación / Growth pain. Response to relaxant exercises

En el periodo de julio de 1990 a julio de 1994 se captaron 77 pacientes cuyo diagnóstico era dolores de crecimiento -definidos de acuerdo al criterio de Naish y Apley-, en la consulta externa del Hospital Infantil de México; se excluyeron a aquellos pacientes con una patología musculoesquelética evidente, o que tuvieran una alteración en sus resultados de laboratorio o de radiología. Fueron 48 hombres y 35 mujeres, la edad osciló entre tres a 19 años. Se estableció un programa de ejercicio de relajación, por medio de estiramiento muscular (técnica de Baxter); obteniéndose una disminución de la frecuencia e intensidad del dolor a partir de algunas semanas de iniciado el tratamiento. Las diferentes teorías que se han propuesto de como los ejercicios mencionados resuelven el problema, nos obliga a pensar en un origen multifactorial del padecimiento

Hemofilia y osteosarcoma. Informe de un caso / hemophilia and osteosarcoma. Case report

La hemofilia es una enfermedad relativamente rara, puede haber pacientes portadores, que si nunca sufren un traumatismo grave pueden no ser descubiertos. Tanto la hemofilia ®A¼ como la ®B¼ o enfermedad de Christmas se heredan de modo recesivo ligado al cromosoma ®X¼, con un incidencia de 10 hemofílicos, por cada 100 varones nacidos. El pseudotumor es un hecho relativamente raro, su incidencia se ha calculado en 1 por ciento al 2 por ciento en hemofílicos graves, en el pseudotumor que se origina a partir de una hemorragia subperióstica puede ocurrir una significativa destrucción ósea, se reporta el caso de un paciente masculino de 17 años de edad con el diagnóstico de hemofilia tipo ®B¼, tratada desde los 6 años, a esta edad presentó un pseudotumor en fémur izquierdo, a la edad de 17 años presenta probable pseudotumora en húmero izquierdo, posterior a la biopsia se reporta sarcoma osteogénico, iniciándose quimioterapia (2 ciclos a base de adriamicina y cisplatino), practicándosele desarticulación de dicho miembro, falleció 8 meses después de la cirugía con metástasis múltiples

El tratmiento del mal luxante del hombro. Estudio comparativo de la técnica García León con la Putti-Platt / Treatment of shoulder dislocation disease. A comparative study of García-León technique with the Putti-Platt procedure

De las luxaciones de la economía corporal, las del hombro ocupan el 50 por ciento y el elevado porcentaje de recurrencias de estas fracturas, hace obligado su tratamiento quirúrgico. El mal luxante del hombro es una patología que se acompaña siempre de la siguiente triada: arrancamiento del borde anterior del labio y cápsula glenoideos, defecto posterolateral de la cabeza del húmero o fractura por compresión, erosión o fractura del labio glenoideo anterior. Aquí, se someten a estudio dos técnicas para el tratamiento de este mal, la de García León cuya base es el principio activo pues maneja las estructuras musculares y tendinosas y la de Putti-Platt basada en las estructuras capsulares y ligamantarias o de principio pasivo. Sabemos que entre más joven es el paciente que presenta por primera vez la lesión, aumantan las posibilidades de padecer el mal luxante y se observó que éste es común durante la segunda o tercera etapa de la vida. La técnica de Putti-Platt, mostró dejar una mayor limitación a la abducción que la de García León. Por lo que se infiere que esta última es una mejor alternativa, aun cuando el cirujano debe manejar todas las técnicas quirúrgicas pues cada una ofrece en su caso diferentes posibilidades