Bioinformatic identification of Single Nucleotide Polymorphisms (SNPs) in keratin-associated protein genes in alpacas (Vicugna pacos) / Identificación bioinformática de Polimorfismos de Nucleótido Simple (PNSs) en genes de proteínas asociadas a queratinas en alpacas (Vicugna pacos)

Abstract This study aims to identify single nucleotide polymorphisms (SNPs) within KRTAP genes in alpacas (Vicugna pacos), which play a fundamental role in defining their physico-mechanical properties and potentially the quality of alpaca fiber, the primary product of their breeding. Thirty-four KRTAP genes, as annotated in the reference genome VicPac3.1, were investigated. Utilizing the reference genome, along with nine additional genomes and reads from 300 reduced representation DNA libraries of alpacas, SNPs were identified. Minor allele frequency (MAF) and genotyping rates were computed using PLINK software, while Illumina Scores were determined for each SNP using Illumina Design Studio software. Markers meeting the criteria of MAF ≥ 0.05, genotyping rate > 45%, and Illumina Score ≥ 0.6 per SNP were selected. A total of 67 SNPs were identified within intronic, exonic, and untranslated regions of KRTAP genes. Among these, 35 SNPs were incorporated into the 76K Alpaca SNP microarray, with 32 SNPs subsequently validated in a population of 936 alpacas. In conclusion, our findings delineate SNPs within KRTAPs that hold potential utility in genome-wide association studies, thereby facilitating the integration of modern breeding technologies into alpaca breeding programs.

Resumen Este estudio tiene como objetivo identificar polimorfismos de nucleótido simple (PNSs) dentro de los genes KRTAP en alpacas (Vicugna pacos), que juegan un papel fundamental en la definición de sus propiedades físico-mecánicas y la calidad de la fibra de alpaca, producto principal de su crianza. Se investigaron treinta y cuatro genes KRTAP, tal como están anotados en el genoma de referencia VicPac3.1. Utilizando el genoma de referencia, junto con nueve genomas adicionales y lecturas de 300 bibliotecas de representación reducida de ADN de alpacas, se identificaron los PNSs. La frecuencia de los alelos menores (MAF) y las tasas de genotipificación se calcularon utilizando el software PLINK, mientras que los Illumina Score se determinaron para cada PNS utilizando el software Illumina Design Studio. Se seleccionaron marcadores que cumplían con los criterios de MAF ≥ 0.05, tasa de genotipado > 45% e Illumina Score ≥ 0.6 por PNS. Se identificaron un total de 67 PNSs dentro de regiones intrónicas, exónicas y/o no traducidas de genes KRTAP. Entre estos, se incorporaron 35 PNSs al microarray 76K Alpaca SNP, y posteriormente se validaron 32 PNSs en una población de 936 alpacas. En conclusión, nuestros hallazgos identificaron los PNSs dentro de los KRTAP que tienen una utilidad potencial en estudios de asociación de todo el genoma, facilitando así la integración de tecnologías de reproducción modernas en los programas de reproducción de alpacas.

Genome-Wide Association Study of Fiber Diameter in Alpacas.

The aim of this study was the identification of candidate genomic regions associated with fiber diameter in alpacas. DNA samples were collected from 1011 female Huacaya alpacas from two geographical Andean regions in Peru (Pasco and Puno), and three alpaca farms within each region. The samples were genotyped using an Affymetrix Custom Alpaca genotyping array containing 76,508 SNPs. After the quality controls, 960 samples and 51,742 SNPs were retained. Three association study methodologies were performed. The GWAS based on a linear model allowed us to identify 11 and 35 SNPs (-log10(p-values) > 4) using information on all alpacas and alpacas with extreme values of fiber diameter, respectively. The haplotype and marker analysis method allowed us to identify nine haplotypes with standardized haplotype heritability higher than six standard deviations. The selection signatures based on cross-population extended haplotype homozygosity (XP-EHH) allowed us to identify 180 SNPs with XP-EHH values greater than |3|. Four candidate regions with adjacent SNPs identified via two association methods of analysis are located on VPA6, VPA9, VPA29 and one chromosomally unassigned scaffold. This study represents the first analysis of alpaca whole genome association with fiber diameter, using a recently assembled alpaca SNP microarray.

Reliability and validity in Mexico of the Spanish version of the Children's Fear Survey Schedule - Dental Subsca.

AIM: Low attendance and abandonment of dental treatment caused by dental fear varies from 6% to 20%. Various specific scales have been used to evaluate and measure dental fear, like Children´s Fear Survey Schedule - Dental Subscale, which is considered the "gold standard", due to its efficacy and validity. However, not all the studies that have been conducted have performed the Exploratory Factorial and Confirmation Analysis to infer the validity of the scale's content, which is why this study has as its main objective to analyse the confidentiality and validation of this scale. MATERIALS AND METHODS: In a sample of 163 school age children, from 6 to 12 years old, of both genders, from a public school, a Children's Fear Survey Schedule - Dental Subscale was applied to measure dental fear. The internal consistency of the scale was estimated with the Cronbach's alpha, we also performed the Exploratory Factorial Analysis with the method of the main component with Varimax rotation and the Confirmatory Factorial Analysis to confirm the structure of the factors. RESULTS: The Cronbach's alpha was obtained with a .837 (p?.05). The adequate coefficients were determined with the Kaiser-Meyer-Olkin (KMO = .843) and the Bartlett's test of specificity (?2 = 565,325, p= .000), in which there was a good adequate data, expressing an appropriate and intercorrelation between items or strongly related. The factorial structure showed four factors extracted, 4 factors explain the 53.57% of the accumulated variation; 14 items were above the .40. The statistics of the second and third model obtained adequate values in the statistics of goodness of fit index. CONCLUSION: The Mexican version of the CFSS-DS in the present study gives us data about the adaptation and validation of the dental fear scale of CFSSS-DS by the Exploratory Factorial Analysis through a model of structural equations. This means that this instrument is a trusting and valid tool to measure dental fear in the children's population of Mexico.

Cytogenetic Mapping of 35 New Markers in the Alpaca (Vicugna pacos).

Alpaca is a camelid species of broad economic, biological and biomedical interest, and an essential part of the cultural and historical heritage of Peru. Recently, efforts have been made to improve knowledge of the alpaca genome, and its genetics and cytogenetics, to develop molecular tools for selection and breeding. Here, we report cytogenetic mapping of 35 new markers to 19 alpaca autosomes and the X chromosome. Twenty-eight markers represent alpaca SNPs, of which 17 are located inside or near protein-coding genes, two are in ncRNA genes and nine are intergenic. The remaining seven markers correspond to candidate genes for fiber characteristics (BMP4, COL1A2, GLI1, SFRP4), coat color (TYR) and development (CHD7, PAX7). The results take the tally of cytogenetically mapped markers in alpaca to 281, covering all 36 autosomes and the sex chromosomes. The new map assignments overall agree with human-camelid conserved synteny data, except for mapping BMP4 to VPA3, suggesting a hitherto unknown homology with HSA14. The findings validate, refine and correct the current alpaca assembly VicPac3.1 by anchoring unassigned sequence scaffolds, and ordering and orienting assigned scaffolds. The study contributes to the improvement in the alpaca reference genome and advances camelid molecular cytogenetics.

Genomics and animal production / Genómica y producción animal

Abstract Developing countries have the challenge of achieving food security in a world context that is affected by climate change and global population growth. Molecular Genetics and genomics are proposed as technologies that will help to achieve sustainable food security. Technologies that have been developed in the last decade such as the development of genetic markers, genetic maps, genomic selection, next-generation sequencing, and DNA editing systems are discussed. Examples of some discoveries and achievements are provided.

Resumen Los países en vías de desarrollo tienen el reto de alcanzar seguridad alimentaria en un contexto mundial afectado por el cambio climático y crecimiento poblacional global. La genética molecular y la genómica son propuestas como tecnologías que ayudarán a alzanzar una seguridad alimentaria sostenible. Tecnologías que han sido desarrolladas en la última década como el desarrollo de marcadores moleculares, mapeo genético, selección genómica, secuenciamiento de próxima generación y sistemas de edición de ADN son discutidos. Se proveen ejemplos de algunos descubrimientos y logros.

Single molecule sequencing of nucleic acids in real time (SMRT) to characterize transcriptomes and mRNA isoforms / Secuenciación de moléculas individuales de ácidos nucleicos en tiempo real (SMRT) para caracterizar transcriptomas e isoformas de ARNm

Abstract Our efforts are oriented to assess bovine Y-chromosome gene expression patterns. One set of genes that are of interest are the so-called X-degenerate Y-chromosome genes that are located in the male-specific region of the Y-chromosome (MSY). This region contains 95% of the DNA of the Y chromosome. These genes are single copy and have an X-chromosome homolog. Both, the Y-encoded and X-encoded homologs have ubiquitous expression profiles. However, some genes, like SRY that regulates male sex determination, have functions that are more specific. Identifying DNA sequence differences between these homologs will allow evaluation of their spatial and temporal expression patterns. Identification of the Y-encoded mRNAs and their isoforms will allow our understanding of tissue specific expression of isoforms in male tissues. The latter will facilitate our evaluation of gene function in male sex differentiation and fertility. Hence, we hypothesized that each of these X-degenerate gene homologs generate isoforms and that differential expression patterns exist between sexes and across tissues. To investigate the latter we used a new generation sequencing (NGS) technology that generates long sequencing reads with a range between 1000 to 10,000 base pairs in length. Single molecule real time (SMRT) isoform sequencing (IsoSeq) of several tissues (liver, lung, adipose, muscle, hypothalamus and testis) was carried out. Transcript sequences were used for bioinformatics analysis and isoform characterization. Given the focus of this manuscript the SMRT technology we are only presenting results obtained with the analysis of the bUTY and bUTX genes.

Resumen Nuestros esfuerzos están orientados a evaluar patrones de expresión génica del cromosoma Y bovino. Los genes de interés son los denominados genes X-degenerados que se encuentran en la región específica masculina del cromosoma Y (MSY). Esta región contiene el 95% del ADN del cromosoma Y. Estos genes son de copia única y tienen un homólogo en el cromosoma X. Ambos homólogos tienen perfiles amplios de expresión. Sin embargo, algunos genes, como el SRY que regula la determinación del sexo masculino, tienen funciones más específicas. La identificación de las diferencias de secuencia de ADN entre estos homólogos permitirá evaluar sus patrones de expresión espacial y temporal. La identificación de los ARNm codificados en el cromosoma Y y de sus isoformas permitirán analizar la expresión específica de sus isoformas en tejidos masculinos. Esto último facilitará nuestra evaluación de función génica en la diferenciación sexual masculina y la fertilidad. Por lo tanto, planteamos la hipótesis de que cada uno de estos genes homólogos degenerados del X genera isoformas y que existen patrones de expresión diferencial entre sexos y tejidos. Para investigar esto último, utilizamos una tecnología de secuenciación de nueva generación (NGS) que genera lecturas de secuenciación largas con un rango de longitud de 1000 a 10,000 pares de bases. Se secuenciaron los transcriptomas en varios tejidos (hígado, pulmón, adiposo, muscular, hipotálamo y testículo). Se utilizaron las secuencias generadas para el análisis bioinformático y la caracterización de isoformas. Siendo el foco de este manuscrito la tecnología SMRT, solo presentamos los resultados obtenidos con el análisis de los genes bUTY y bUTX.

Chromosomal Localization of Candidate Genes for Fiber Growth and Color in Alpaca (Vicugna pacos).

The alpaca (Vicugna pacos) is an economically important and cultural signature species in Peru. Thus, molecular genomic information about the genes underlying the traits of interest, such as fiber properties and color, is critical for improved breeding and management schemes. Current knowledge about the alpaca genome, particularly the chromosomal location of such genes of interest is limited and lags far behind other livestock species. The main objective of this work was to localize alpaca candidate genes for fiber growth and color using fluorescence in situ hybridization (FISH). We report the mapping of candidate genes for fiber growth COL1A1, CTNNB1, DAB2IP, KRT15, KRTAP13-1, and TNFSF12 to chromosomes 16, 17, 4, 16, 1, and 16, respectively. Likewise, we report the mapping of candidate genes for fiber color ALX3, NCOA6, SOX9, ZIC1, and ZIC5 to chromosomes 9, 19, 16, 1, and 14, respectively. In addition, since KRT15 clusters with five other keratin genes (KRT31, KRT13, KRT9, KRT14, and KRT16) in scaffold 450 (Vic.Pac 2.0.2), the entire gene cluster was assigned to chromosome 16. Similarly, mapping NCOA6 to chromosome 19, anchored scaffold 34 with 8 genes, viz., RALY, EIF2S2, XPOTP1, ASIP, AHCY, ITCH, PIGU, and GGT7 to chromosome 19. These results are concordant with known conserved synteny blocks between camelids and humans, cattle and pigs.

Evaluation of SNP Genotyping in Alpacas Using the Bovine HD Genotyping Beadchip.

Alpacas are one of four South American Camelid species living in the highlands of the Andes. Production of alpaca fiber contributes to the economy of the region and the livelihood of many rural families. Fiber quantity and quality are important and in need of a modern breeding program based on genomic selection to accelerate genetic gain. To achieve this is necessary to discover enough molecular markers, single nucleotide polymorphisms (SNPs) in particular, to provide genome coverage and facilitate genome wide association studies to fiber production characteristics. The aim of this study was to discover alpaca SNPs by genotyping forty alpaca DNA samples using the BovineHD Genotyping Beadchip. Data analysis was performed with GenomeStudio (Illumina) software. Because different filters and thresholds are reported in the literature we investigated the effects of no-call threshold (≥0.05, ≥0.15, and ≥0.25) and call frequency (≥0.9 and =1.0) in identifying positive SNPs. Average GC Scores, calculated as the average of the 10% and 50% GenCall scores for each SNP (≥0.70) and the GenTrain score ≥ 0.25 parameters were applied to all comparisons. SNPs with minor allele frequency (MAF) ≥ 0.05 or ≥ 0.01 were retained. Since detection of SNPs is based on the stable binding of oligonucleotide probes to the target DNA immediately adjacent to the variant nucleotide, all positive SNP flanking sequences showing perfect alignments between the bovine and alpaca genomes for the first 21 or 26 nucleotides flanking the variant nucleotide at either side were selected. Only SNPs localized in one scaffold were assumed unique. Unique SNPs identified in both reference genomes were kept and mapped on the Vicugna_pacos 2.0.2 genome. The effects of the no-call threshold ≥ 0.25, call frequency = 1 and average GC ≥ 0.7 were meaningful and identified 6756 SNPs of which 400 were unique and polymorphic (MAF ≥ 0.01). Assignment to alpaca chromosomes was possible for 292 SNPs. Likewise, 209 SNPs were localized in 202 alpaca gene loci and 29 of these share the same loci with the dromedary. Interestingly, 69 of 400 alpaca SNPs have 100% similarity with dromedary.

Machine learning meets genome assembly.

MOTIVATION: With the recent advances in DNA sequencing technologies, the study of the genetic composition of living organisms has become more accessible for researchers. Several advances have been achieved because of it, especially in the health sciences. However, many challenges which emerge from the complexity of sequencing projects remain unsolved. Among them is the task of assembling DNA fragments from previously unsequenced organisms, which is classified as an NP-hard (nondeterministic polynomial time hard) problem, for which no efficient computational solution with reasonable execution time exists. However, several tools that produce approximate solutions have been used with results that have facilitated scientific discoveries, although there is ample room for improvement. As with other NP-hard problems, machine learning algorithms have been one of the approaches used in recent years in an attempt to find better solutions to the DNA fragment assembly problem, although still at a low scale. RESULTS: This paper presents a broad review of pioneering literature comprising artificial intelligence-based DNA assemblers-particularly the ones that use machine learning-to provide an overview of state-of-the-art approaches and to serve as a starting point for further study in this field.

Fate of atrazine in a soil under different agronomic management practices.

Agricultural management affects the movement of atrazine in soil and leaching to groundwater. The objective of this study was to determine atrazine adsorption in a soil after 20 years of atrazine application under agronomic management practices differing in tillage practice (conventional and zero tillage), residue management (with and without residue retention) and crop rotation (wheat-maize rotation and maize monoculture). Atrazine sorption was determined using batch and column experiments. In the batch experiment, the highest distribution coefficient Kd (1.1 L kg(-1)) at 0-10 cm soil depth was observed under zero tillage, crop rotation and residue retention (conservation agriculture). The key factor in adsorption was soil organic matter content and type. This was confirmed in the column experiment, in which the highest Kd values were observed in treatments with residue retention, under either zero or conventional tillage (0.81 and 0.68 L kg(-1), respectively). Under zero tillage, the fact that there was no soil movement helped to increase the Kd. The increased soil organic matter content with conservation agriculture may be more important than preferential flow due to higher pore connectivity in the same system. The soil's capacity to adsorb 2-hydroxyatrazine (HA), an important atrazine metabolite, was more important than its capacity to adsorb atrazine, and was similar under all four management practices (Kd ranged from 30 to 40 L kg(-1)). The HA adsorption was attributed to the type and amount of clay in the soil, which is unaffected by agronomic management. Soils under conservation agriculture had higher atrazine retention potential than soils under conventional tillage, the system that predominates in the study area.

Global phylogeography of the dolphinfish (Coryphaena hippurus): the influence of large effective population size and recent dispersal on the divergence of a marine pelagic cosmopolitan species.

Pelagic fish that are distributed circumtropically are characterised by a low population structure level as a result of a high capacity for dispersion and large population sizes. Nevertheless, historical and contemporary processes, including past demographic and/or range expansions, secondary contact, dispersal, gene flow, and the achievement of large effective population sizes, may play a part in the detection of divergence signals, especially in the case of tropical pelagic species, whose distribution range depends strongly on the sea surface temperature. The connectivity and historical demography of Atlantic, Indian, Pacific and Mediterranean populations of dolphinfish (Coryphaena hippurus) was studied using partial sequences of the mitochondrial DNA NADH dehydrogenase subunit 1 (ND1). AMOVA analyses revealed significant inter-oceanic divergence with three phylogroups located in the Indo-Pacific, Eastern Atlantic, and Mediterranean Sea, the last one being the most divergent. However, it was not possible to clearly observe any genetic differentiation between the Indo-Pacific and Atlantic populations, as has been reported for most tropical pelagic species of tuna and billfishes. This supports the assumption of recent dispersal among basins facilitated by the actual continuous distribution of dolphinfish populations. Moreover, the lack of a divergence signal for populations separated by the Panamanian Isthmus reveals that genetic drift does not exert a strong influence on tropical pelagic species with large effective population sizes.

Comparative RH maps of the river buffalo and bovine Y chromosomes.

Radiation hybrid maps were constructed for river buffalo and cattle Y chromosomes. A total of 41 cattle-derived Y-chromosome molecular markers were selected and tested with 2 previously described 5,000-rad whole-genome radiation hybrid (RH) panels (river buffalo - BBURH(5000) and cattle - BTARH(5000)) for generation of maps. Among the initial 41 selected markers, a subset of 26 markers generated PCR products suitable for scoring with the BBURH(5000) panel. Of these, 19 markers (73%) were distributed in 1 linkage group spanning 341.3 cR. Retention frequencies (RF) for individual markers ranged from 17.8% for SMCY to 56.7% for BTY1, with an average RF of 37.6%. From the selected markers, 37 generated reliable scores using the BTARH(5000) panel. The newly constructed BTAY RH map contains 28 markers distributed within 1 linkage group. Twenty-four of these markers had been previously mapped on BTAY using a 7,000-rad cattle-hamster WG-RH panel and 4 markers were mapped for the first time (ZFY, SeqRep, RepSeqS4 and BTY1). The length of the BTAY RH map was estimated to be 602.4 cR. Retention frequencies for individual mapped markers ranged from 10% (INRA126) to 63.3% (SeqRep), with an average RF of 35.3%. RH marker positions along the Y chromosome were compared between BBUY and BTAY, which revealed differences in the order of some of the markers. The BBUY pseudoautosomal region (PAR) is delineated by 3 BTAY PAR markers (MAF45, TGLA325 and UMN2008). These markers are telomeric in both species but are not found in the same order. Here we have demonstrated the effective use of bovine Y chromosome markers for the development of the first BBUY RH map. Likewise, these set of markers can be used for comparative assessment of Y chromosomes in other members of the Bovidae family.

[History of cranial surgery, cerebral tumor surgery and epilepsy surgery in Mexico]. / Historia de la cirugía de cráneo, de los tumores cerebrales y de la epilepsia en México.

The first report of intra-cerebral tumor surgery was provided by Bennett & Goodle, in London, 1884. Worldwide this kind of surgery was performed in France by Chipault, in Italy by Durante, in the United States by Keen and in Deutchland by Krause & Oppenheim. Lavista in Mexico City operated on intra-cerebral tumor in 1891, and the report was printed in 1892. In the same publication, Lavista exhibited the first cases of epilepsy surgery. Since now, it is the first report of this kind of surgery in the Spanish-speaking world.

Local adaptation and pronounced genetic differentiation in an extremophile fish, Poecilia mexicana, inhabiting a Mexican cave with toxic hydrogen sulphide.

We investigated genetic differentiation and migration patterns in a small livebearing fish, Poecilia mexicana, inhabiting a sulfidic Mexican limestone cave (Cueva del Azufre). We examined fish from three different cave chambers, the sulfidic surface creek draining the cave (El Azufre) and a nearby surface creek without the toxic hydrogen sulphide (Arroyo Cristal). Using microsatellite analysis of 10 unlinked loci, we found pronounced genetic differentiation among the three major habitats: Arroyo Cristal, El Azufre and the cave. Genetic differentiation was also found within the cave between different pools. An estimation of first-generation migrants suggests that (i) migration is unidirectional, out of the cave, and (ii) migration among different cave chambers occurs to some extent. We investigated if the pattern of genetic differentiation is also reflected in a morphological trait, eye size. Relatively large eyes were found in surface habitats, small eyes in the anterior cave chambers, and the smallest eyes were detected in the innermost cave chamber (XIII). This pattern shows some congruence with a previously proposed morphocline in eye size. However, our data do not support the proposed mechanism for this morphocline, namely that it would be maintained by migration from both directions into the middle cave chambers. This would have led to an increased variance in eye size in the middle cave chambers, which we did not find. Restricted gene flow between the cave and the surface can be explained by local adaptations to extreme environmental conditions, namely H2S and absence of light. Within the cave system, habitat properties are patchy, and genetic differentiation between cave chambers despite migration could indicate local adaptation at an even smaller scale.

Gene selection based on multi-class support vector machines and genetic algorithms.

Microarrays are a new technology that allows biologists to better understand the interactions between diverse pathologic state at the gene level. However, the amount of data generated by these tools becomes problematic, even though data are supposed to be automatically analyzed (e.g., for diagnostic purposes). The issue becomes more complex when the expression data involve multiple states. We present a novel approach to the gene selection problem in multi-class gene expression-based cancer classification, which combines support vector machines and genetic algorithms. This new method is able to select small subsets and still improve the classification accuracy.

Stereotactically-guided biopsies of brainstem tumors.

INTRODUCTION: More than 10 years ago, the goal of our work had been to obtain a tissue sample of infiltrating lesions of the brainstem that had been diagnosed using computerized axial tomography (CAT). At that time, biopsies were believed to be indispensable when starting treatment of tumors. With time our objectives changed. Biopsies remained necessary, since until 1 year before the writing of this article we had not had the benefits of magnetic resonance imaging (MRI) at our Hospital. We also decided that carrying out sound statistics, confirmed by biopsies, was in itself a good procedure, especially in a country in which, to date, no serial studies of brainstem tumors had been undertaken. METHODS: We analyzed all of the patients diagnosed with posterior fossa tumors between March 1989 and March 2002 at the Hospital Infantil de México Federico Gómez (HIM). A preoperative TAC of the cranium was performed on every patient. Stereotactically-guided biopsies during tomography allowed precise control of penetration. Material obtained was sent to the Department of Pathology for analysis. RESULTS: Fifty patients were diagnosed with infiltrating tumors of the brainstem: 30 cases of low-grade astrocytomas, 13 cases of high-grade astrocytomas, 2 cases of primitive neuroectodermic tumors, 2 cases of rhabdoid tumors, 1 case of ependymoma, and 2 patients had non-specified tumors. The most frequent symptoms and signs were ataxia and disturbances of the cranial nerves. There was no mortality caused by penetration, and follow-up studies of more than 5 years were carried out. DISCUSSION: The results from our series were similar to those in the literature. In our case, follow-up studies were undertaken for longer periods. In the first section of our work, we suggest the need for stereotactic biopsies in order to arrive at a precise diagnosis in environments in which MRI may be unavailable. CONCLUSION: At present, presumptive diagnosis of infiltrating brainstem lesions may be adequately undertaken with imaging methods, such as MRI. However, we believe that a stereotactically-guided biopsy provides an accurate method for diagnosing lesions of the brainstem. In our case, this procedure has been carried out entirely in the tomography room, without any complications of disease or mortality.

First published record of a neurosurgical procedure on the North American continent, Mexico City, by Pedro Arias de Benavides, 1561: Secretos de Chirurgia, Valladolid, Spain, 1567.

The first published account of a neurosurgical intervention performed on the North American continent is described. The operation took place in Mexico City in 1561. The neurosurgical intervention was performed by a Spanish surgeon, Pedro Arias de Benavides, on a 13-year-old boy who had sustained head trauma that caused an open depressed cranial fracture and exposed the cerebrum. A description of this case was first published in Valladolid, Spain, 6 years after the event, in a book entitled Secretos de Chirurgia ("Secrets of Surgery").

[Pierre Ochart, third printer in Mexico City and editor of the first medical book in America, Opera medicinalia, by Dr. Francisco Bravo, 1570]. / Pierre Ochart, troisième imprimeur à Mexico et editeur du premier livre de médecine d'Amérique, Opera medicinalia, du docteur Francisco Bravo, 1570.

The first medical book edited in the American Continent was printed by Pierre Ochart in Mexico City (1570). He was born in Normandy in the City of Rouen, France, and learned the profession of printer in Mexico City. We have done an examination of the book written by Francisco Bravo, a Spanish doctor in medicine who practiced in Mexico City since the XVIth century second half.