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Search Results: 1 - 10 of 1813 matches for " Horacio Merchant-Larios "
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Selective and constructive mechanisms contribute to neural circuit formation in the barrel cortex of the developing rat  [PDF]
Eileen Uribe-Querol, Eduardo Martínez-Martínez, Luis Rodrigo Hernández, Patricia Padilla Cortés, Horacio Merchant-Larios, Gabriel Gutiérrez-Ospinac
Advances in Bioscience and Biotechnology (ABB) , 2013, DOI: 10.4236/abb.2013.47103
Abstract: The cellular strategy leading to formation of neuronal circuits in the rodent barrel cortex is still a matter of controversy. Both selective and constructive mechanisms have been proposed. The selective mechanism involves an overproduction of neuronal processes and synapses followed by activity dependent pruning. Conversely, a constructive mechanism would increase the number of axons, dendrites, and synapses during development to match functionality. In order to discern the contributions of these two mechanisms in establishing a neuronal circuit in the somatosensory cortex, morphometric analysis of dendritic and axonal arbor growth was performed. Also, the number of synapses was followed by electron microscopy during the first month of life. We observed that axonal and dendritic arbors retracted distal branches, and elongated proximal branches, resulting in increased arbor complexity. This neuronal remodeling was accompanied by the steady increase in the number of synapses within barrel hollows. Similarly, the content of molecular markers for dendrites, axons and synapses also increased during this period. Finally, cytochrome oxidase activity rose with age in barrels indicating that the arbors became more complex while synapse density and metabolic demands increased. Our results support the simultaneous use of both selective and constructive mechanisms in establishing the barrel cortex circuitry.

In vitro secretion and activity profiles of matrix metalloproteinases, MMP-9 and MMP-2, in human term extra-placental membranes after exposure to Escherichia coli
Veronica Zaga-Clavellina, Guadalupe Garcia-Lopez, Arturo Flores-Pliego, Horacio Merchant-Larios, Felipe Vadillo-Ortega
Reproductive Biology and Endocrinology , 2011, DOI: 10.1186/1477-7827-9-13
Abstract: Full-thickness membranes were mounted on a Transwell device, constituting two independent chambers, Escherichia coli (1×10 (6) CFU/mL) were added to either the amniotic or the choriodecidual face or to both. Secretion profiles of MMP-2, MMP-9, TIMP-1, TIMP-2, and TIMP-4 were quantified by ELISA and gelatinolytic activity by zymography. Immunoreactivity for MMP-2 and MMP-9 was revealed by immunohistochemistry and the collagen content was assessed by the hydroxyproline assay.Levels of MMP-9 in CHD and AMN increased 4- and 8-fold, respectively, after simultaneous infection. MMP-2 secreted to the medium by CHD increased a mean of 3 times after direct stimulation. Secretion profiles of TIMP-1, TIMP-2, and TIMP-4 remained without significant changes. Collagen content was significantly decreased (4-fold) in infected membranes, and was associated with loss of structural continuity and co-localization with immunoreactive forms of MMP-2 and MMP-9.Infection of chorioamniotic membranes with E. coli induces an increase in the secretion of inactive forms and an association to ECM of active forms of MMP-2 and MMP-9 without changes in TIMP-1, -2, and -4. These changes could explain the significant decrease of collagen content and loss of structural continuity.During human pregnancy, multiple strategies are displayed to keep the fetus in an immunologically privileged environment in the amniotic cavity delimited and surrounded by the extra-placental membranes [1,2]. This tissue is highly organized as a bi-laminated complex formed from fetal-derived amnion (AMN) and chorion, which, interdigitate with the maternal decidua and constitute the choriodecidua (CHD) layer. The integrity of all these cell types, in close association with their extracellular matrix (ECM), preserves the membrane's structure and tensile strength to warrant its role as a selective barrier between the fetal and maternal compartments [3].The chorioamniotic ECM is composed of several different types of collagen arra
RNAi-Mediated Gene Silencing in a Gonad Organ Culture to Study Sex Determination Mechanisms in Sea Turtle
Itzel Sifuentes-Romero,Horacio Merchant-Larios,Sarah L. Milton,Norma Moreno-Mendoza,Verónica Díaz-Hernández,Alejandra García-Gasca
Genes , 2013, DOI: 10.3390/genes4020293
Abstract: The autosomal Sry-related gene, Sox9, encodes a transcription factor, which performs an important role in testis differentiation in mammals. In several reptiles, Sox9 is differentially expressed in gonads, showing a significant upregulation during the thermo-sensitive period (TSP) at the male-promoting temperature, consistent with the idea that SOX9 plays a central role in the male pathway. However, in spite of numerous studies, it remains unclear how SOX9 functions during this event. In the present work, we developed an RNAi-based method for silencing Sox9 in an in vitro gonad culture system for the sea turtle, Lepidochelys olivacea. Gonads were dissected as soon as the embryos entered the TSP and were maintained in organ culture. Transfection of siRNA resulted in the decrease of both Sox9 mRNA and protein. Furthermore, we found coordinated expression patterns for Sox9 and the anti-Müllerian hormone gene, Amh, suggesting that SOX9 could directly or indirectly regulate Amh expression, as it occurs in mammals. These results demonstrate an in vitro method to knockdown endogenous genes in gonads from a sea turtle, which represents a novel approach to investigate the roles of important genes involved in sex determination or differentiation pathways in species with temperature-dependent sex determination.
In vitro secretion profiles of interleukin (IL)-1beta, IL-6, IL-8, IL-10, and TNF alpha after selective infection with Escherichia coli in human fetal membranes
Veronica Zaga-Clavellina, Guadalupe Garcia-Lopez, Hector Flores-Herrera, Aurora Espejel-Nu?ez, Arturo Flores-Pliego, Diana Soriano-Becerril, Rolando Maida-Claros, Horacio Merchant-Larios, Felipe Vadillo-Ortega
Reproductive Biology and Endocrinology , 2007, DOI: 10.1186/1477-7827-5-46
Abstract: Explants of chorioamniotic membranes from 10 women (37–40 weeks of gestation) were mounted and cultured in a Transwell system, which allowed us to test the amnion and choriodecidua compartments independently. Escherichia coli (1 × 10 6 CFU/mL) was added to either the amniotic or the choriodecidual regions or both; after a 24-h incubation, the secretion of IL-1beta, IL-6, TNFalpha, IL-8, and IL-10 in both compartments was measured using a specific ELISA. Data were analyzed by Kruskal-Wallis one-way analysis of variance.After stimulation with Escherichia coli, the choriodecidua compartment showed an increase in the secretion of IL-1beta (21-fold), IL-6 (2-fold), IL-8 (6-fold), and IL-10 (37-fold), regardless of which side of the membrane was stimulated; TNFalpha secretion augmented (22-fold) also but only when the stimulus was applied simultaneously to both sides. When the amnion was stimulated directly, the level of IL-1beta (13-fold) rose significantly; however, the increase in IL-8 secretion was larger (20-fold), regardless of the primary site of infection. TNFalpha secretion in the amnion compartment rose markedly only when Escherichia coli was simultaneously applied to both sides.Selective stimulation of fetal membranes with Escherichia coli results in a differential production of IL-1beta, IL-6, TNFalpha, IL-8, and IL-10. These tissues were less responsive when the amnion side was stimulated. This is in agreement with the hypothesis that the choriodecidua may play a primary role during an ascending intrauterine infection, being the main barrier to progression of the infection into the amniotic cavity. Therefore, the tissue-specific capacities for the secretion of these immune modulators could be a determining factor for the degree of severity of the inflammation process in fetal membranes.Pregnancy is the result of a fine immunological privilege that allows the fetus to co-habit the maternal uterus, preventing rejection of the fetal allograft [1]. There are epid
Aspectos moleculares de la determinación del sexo en tortugas
Leda Carolina Torres Maldonado,Horacio Merchant Larios
Ciencia Ergo Sum , 2006,
Abstract: La determinación del sexo en vertebrados puede estar controlada por factores genéticos o por factores ambientales. Hasta el momento los mecanismos moleculares relacionados con la determinación sexual por temperatura (DST) no se conocen con exactitud. En los diferentes grupos de vertebrados se han estudiado algunos genes que participan en la cascada de la determinación del sexo, los cuales se encuentran conservados tanto en estructura como en función, como ejemplo tenemos a los genes Sox9, Dax1 y Dmrt1. La tortuga marina Lepidochelys olivacea presenta DST; en esta especie se ha estudiado la expresión de los genes Sox9, Dax1 y Dmrt1 en tejido gonadal en distintas etapas del desarrollo embrionario, se observa que la temperatura tiene efecto sobre su expresión. Se sugiere que éstos podrían formar parte de la cascada de genes que regulan la diferenciación gonadal en L. olivacea.
Bases moleculares de la determinación sexual en mamíferos
Verónica Díaz Hernández,Horacio Merchant Larios
Ciencia Ergo Sum , 2008,
Abstract: Se correlacionan conceptos clásicos de la diferenciación sexual con mecanismos moleculares de la determinación sexual en mamíferos. El paradigma de Jost estableció que la diferenciación sexual fetal depende de la actividad endócrina de los testículos. En la gónada embrionaria indiferenciada se establecen redes moleculares a partir de vías alternativas de expresión que determinan la formación de ovarios o testículos. Tomando al ratón como modelo, describimos el hallazgo de varios genes que se activan o reprimen a partir de la expresión del Sry en los machos y las vías alternas encontradas en las hembras. Concluimos que todavía queda por conocerse el alcance que tienen los datos del ratón como modelo para extrapolarse a otros mamíferos incluido el humano.
Silencing of hpv16 e6 and e7 oncogenic activities by small interference rna induces autophagy and apoptosis in human cervical cancer cells
Jonathan Salazar-León,Fabiola Reyes-Román,Angélica Meneses-Acosta,Horacio Merchant
Journal of Nucleic Acids Investigation , 2011, DOI: 10.4081/jnai.2011.e10
Abstract: Cervical cancer is the second most common form of death by cancer in women worldwide and has special attention for the development of new treatment strategies. Human Papilloma Virus (HPV) persistent infection is the main etiological agent of this neoplasia, and the main cellular transformation mechanism is by disruption of p53 and pRb function by interaction with HPV E6 and E7 oncoproteins. This generates alterations in cellular differentiation and cellular death inhibition. Thus, HPV E6 and E7 oncogenes represent suitable targets for the development of gene therapy strategies against cervical cancer. An attractive technology platform is developing for post-transcriptional selective silencing of gene expression, using small interference RNA. Therefore, in the present study, we used SiHa cells (HPV16+) transiently transfected with specific siRNA expression plasmids for HPV16 E6 and E7 oncogenes. In this model we detected repression of E6 and E7 oncogene and oncoprotein expression, an increase in p53 and hypophosphorylated pRb isoform protein expression, and autophagy and apoptosis morphology features. These findings suggest that selective silencing of HPV16 E6 and E7 oncogenes by siRNAs, has significant biological effects on the survival of human cancer cells and is a potential gene therapy strategy against cervical cancer.
Intravenous lignocaine in tinnitus.
Merchant S,Merchant N
Journal of Postgraduate Medicine , 1985,
Demographic review, clinical and histological presentation of patients with primary thyroid carcinoma presenting at tertiary care hospital
Merchant D
theHealth , 2012,
Abstract: Background: Thyroid disorders are commonly seen in clinical practice. This study was conducted to describe demographic features, clinical presentation and histological pattern and its association with gender and ethnic region in patients with primary thyroid carcinoma presenting in Aga Khan University Hospital (AKUH), Karachi, Pakistan.Methods: In a cross-sectional design, study was conducted in the outpatient and inpatient medical units of AKUH from December 2009 till September 2010. Patients (n=55) of primary thyroid carcinoma of age ≥14 years were included in the study. Patients were evaluated by history, clinical examination, biochemical, histological and radiological investigations. Data was recorded on specified proforma after written informed consent.Results: Out of 55 cases 44 (80%) papillary, 6 (11%) follicular, 2(3.6%) medullary, 1 (1.8%) anaplastic and 2 (3.6%) had Hurthle cell carcinoma. Thyroid carcinoma was prevalent among females 38 (69%) as compared to males 17 (31%). The mean age (SD) was 41.8 (15.5) years. Most of them were Urdu speaking 19 (34.5%) followed by Sindhi 10 (18.2%), 2 (3.6%) had family history of thyroid carcinoma and other endocrine disorder. Various clinical presentations included neck swelling/mass in 54 (98%), weight loss in 34 (62%), cervical lymphadenopathy in 28 (51%), Dyspnea in 12 (22%), Dysphagia in 9 (16.4%), recent change of voice in 11 (20%), superior vena caval syndrome and stridor each in 2 (3.6%) of the patients.Conclusion: Thyroid carcinoma was common in females and prevalent in 3rd and 4th decades of life. Papillary carcinoma was the commonest among histological types, prevalent in Urdu speaking population with mass in the anterior neck and weight loss were common presenting features.
Top-Down Spatial Categorization Signal from Prefrontal to Posterior Parietal Cortex in the Primate
Hugo Merchant
Frontiers in Systems Neuroscience , 2011, DOI: 10.3389/fnsys.2011.00069
Abstract: In the present study we characterized the strength and time course of category-selective responses in prefrontal cortex and area 7a of the posterior parietal cortex during a match-to-sample spatial categorization task. A monkey was trained to categorize whether the height of a horizontal sample bar, presented in rectangular frame at one of three vertical locations, was “high” or “low,” depending on whether its position was above or below the frame’s midline. After the display of this sample bar, and after a delay, choice bars were sequentially flashed in two locations: at the top and at the bottom of the frame (“choice” epoch). If the monkey timed its response to the display of the choice bar that matched the sample bar, he was rewarded. We found that cells in prefrontal cortex discriminated category early after the initial sample bar was shown, and continued to differentiate “up” from “down” trials throughout the delay and choice periods. In contrast, parietal cells did not differentiate category until the choice period. Therefore, our results support the notion of a top-down categorical signal that originates in prefrontal cortex and that is only represented in parietal cortex when it is necessary to express the categorical decision through a movement.
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