A growth factor-induced, spatially organizing cytoskeletal module enables rapid and persistent fibroblast migration

Directional migration requires robust front/back polarity. We find that fibroblasts treated with platelet-derived growth factor (PDGF) and prepolarized by plating on a fibronectin line substrate exhibit persistent migration for hours. This does not occur in the absence of PDGF or on uniformly coated fibronectin substrates. Persistent migration arises from establishment of two functional modules at cell front and back. At the front, formation of a zone containing podosome-like structures (PLS) dynamically correlates with low RhoA and myosin activity and absence of a contractile lamella. At the back, myosin contractility specifically controls tail retraction with minimal crosstalk to the front module. The PLS zone is maintained in a dynamic steady state that preserves size and position relative to the cell front, allowing for long-term coordination of front and back modules. We propose that front/back uncoupling achieved by the PLS zone is crucial for persistent migration in the absence of directional cues.

Behavioral Implications of Knockout for the Dyslexia-Risk Gene Dcdc2 in Mice

Several genetic linkage and epidemiological studies have provided strong evidence that DCDC2 is a candidate gene for developmental dyslexia, a disorder that impairs a person’s reading ability despite adequate intelligence, education, and socio-economic status. Studies investigating embryonic intra-ventricular RNA interference (RNAi) of Dcdc2, a rat homolog of the DCDC2 gene in humans, indicate disruptions in neuronal migration in the rat cortex during development. Interestingly, these anatomical anomalies are consistent with post mortem histological analysis of human dyslexic patients. Other rodent models of cortical developmental disruption have shown impairment in rapid auditory processing and learning maze tasks in affected subjects. The current study investigates the rapid auditory processing abilities of mice heterozygous for Dcdc2 (one functioning Dcdc2 allele) and mice with a homozygous knockout of Dcdc2 (no functioning Dcdc2 allele). It is important to note that this genetic model for behavioral assessment is still in the pilot stage. However, preliminary results suggest that mice with a genetic mutation of Dcdc2 have impaired rapid auditory processing, as well as non-spatial maze learning and memory ability, as compared to wildtypes. By genetically knocking out Dcdc2 in mice, behavioral features associated with Dcdc2 can be characterized, along with other neurological abnormalities that may arise due to the loss of the functioning gene.

The biologic and signaling effects of Tiam1 overexpression in colorectal carcinoma

Cellular migration is essential to many normal cellular processes. In tumor cells, aberrant activation of the normal pathways regulating migration is one of the critical steps in the development of metastasis. Previously, I demonstrated for the first time that overexpression of Tiam1, a guanine nucleotide exchange factor (GNEF) for small G proteins in the Rho family, could alter migration in colorectal tumor cells. ^ This dissertation focuses on the roles of Tiam1 in promoting cell migration, survival, and metastasis of colorectal carcinoma cells, utilizing the model system I developed. To determine the in vivo phenotype of the migratory cell lines, athymic nude mice were injected with cells into the orthotopic site. Several of the mice injected with cells of increased migratory potential had metastases. Thus, the in vitro selection for increased migration resulted in increased metastatic potential in vivo, and therefore, the Tiam1-overexpressing cells provide a model to examine signal transduction pathways important to this process. ^ To examine effects of Tiam1 signaling on small G proteins critical to cellular functions associated with migration, I examined the activation status of the small G proteins Rac, Rho, and Cdc42. The cells of increased migratory potential have increased GTP-bound Rac and Rho, compared to control SW480 cells. Cells that overexpress Tiam1 are more migratory and are resistant to detachment-induced death, or anoikis. To determine which effects and phenotypes were Tiam1-specific, we utilized siRNA to downregulate Tiam1 expression. These results demonstrate that Tiam1 is sufficient but not required for the migration of colorectal carcinoma cells in our model system, and that the biologically selected cells have additional changes that promote migration besides the increase in Tiam1. I also show that Tiam1 protects colorectal carcinoma cells from detachment-induced death, but is not required for anoikis resistance in the biologically selected migratory cells. ^ In summary, my studies demonstrate a heretofore-unknown regulator of phenotypes critical to the development of colorectal carcinoma metastases, overexpression of Tiam1. Understanding the mechanism by which Tiam1 contributes to cellular migration and metastasis is crucial to developing desperately needed new therapies for colorectal carcinoma. ^

INFANT MORTALITY IN THE MEXICAN AMERICAN COMMUNITY: AN ANALYSIS OF DIFFERENTIALS IN INFANT, NEONATAL, AND POSTNEONATAL MORTALITY BY ETHNICITY AND PARENTAL NATIVITY, 1974-75 SINGLE LIVE BIRTH COHORT, HARRIS COUNTY, TEXAS

The paradoxically low infant mortality rates for Mexican Americans in Texas have been attributed to inaccuracies in vital registration and idiosyncracies in Mexican migration in rural areas along the U.S.-Mexico border. This study examined infant (IMR), neonatal (NMR), and postneonatal (PNMR) mortality rates of Mexican Americans in an urban, non-border setting, using linked birth and death records of the 1974-75 single live birth cohort (N = 68,584) in Harris County, Texas, which includes the city of Houston and is reported to have nearly complete birth and death registration. The use of parental nativity with the traditional Spanish surname criterion made it possible to distinguish infants of Mexican-born immigrants from those of Blacks, Anglos, other Hispanics, and later-generation, more Anglicized Mexican Americans. Mortality rates were analyzed by ethnicity, parental nativity, and cause of death, with respect to birth weight, birth order, maternal age, legitimacy status, and time of first prenatal care.^ While overall IMRs showed Spanish surname rates slightly higher than Anglo rates, infants of Mexican-born immigrants had much lower NMRs than did Anglos, even for moderately low birth weight infants. However, among infants under 1500 grams, presumably unable to be discharged home in the neonatal period, Mexican Americans had the highest NMR. The inconsistency suggested unreported deaths for Mexican American low birth weight infants after hospital discharge. The PNMR of infants of Mexican immigrants was also lower than for Anglos, and the usual mortality differentials were reversed: high-risk categories of high birth order, high maternal age, and late/no prenatal care had the lowest PNMRs. Since these groups' characteristics are congruent with those of low-income migrants, the data suggested the possibility of migration losses. Cause of death analysis suggested that prematurity and birth injuries are greater problems than heretofore recognized among Mexican Americans, and that home births and "shoebox burials" may be unrecorded even in an urban setting.^ Caution is advised in the interpretation of infant mortality rates for a Spanish surname population of Mexican origin, even in an urban, non-border area with reportedly excellent birth and death registration. ^

Joseph Blanco White, traductor de Shakespeare en el contexto de la emancipación hispanoamericana

Joseph Blanco White fue uno de los primeros en traducir a Shakespeare al castellano y fue el primero en defender el valor de traducirlo. En España, la obra de Shakespeare era juzgada defectuosa por no cumplir con los requisitos neoclásicos de unidad y decoro; era vista, además, como emblema del poderío británico. Blanco White, por el contrario, defiende a Shakespeare como poeta-genio universal. Propone que todas sus obras, incluidas las dramáticas, deben ser traducidas y leídas como poesía lírica, lo cual para él implica que, a diferencia de una representación teatral, éstas poseen un alto grado de abstracción que las libera de toda atadura contextual. El presente artículo analiza estas ideas a la luz de las ataduras biográficas y culturales, no de Shakespeare, sino del mismo Blanco White. Su partida a Inglaterra en 1810 y el contexto multilingüe en el que trabajó lo han situado en los márgenes de la historia literaria española. Sin embargo, este artículo propone rescatar, desde un punto de vista comparatista, sus traducciones y algunos de sus aportes críticos, entre ellos, su visión de Shakespeare más allá de las rivalidades entre España e Inglaterra y su incorporación de un público hispanoamericano como interlocutor.

Inmigración y trabajo irregular en la agricultura: trabajadores tamaulipecos en Estados Unidos y jornaleros magrebíes en Andalucía

Tanto en Estados Unidos como en España, la escasez de mano de obra local dispuesta a aceptar las condiciones sociolaborales imperantes en la agricultura, unida a la dificultad de inspeccionar y regular un sector donde la movilidad de trabajadores es constante, ha conducido a que la agricultura sea la actividad donde encuentran empleo más fácilmente los trabajadores migrantes indocumentados. En Estados Unidos la demanda de empleo en la agricultura ha venido siendo cubierta principalmente por trabajadores mexicanos; mientras, en España, los jornaleros procedentes de Marruecos constituyen el colectivo de inmigrantes con mayor presencia en el sector agrario. Este artículo, fundamentado en una metodología cualitativa, analiza, por una parte, la situación socio-laboral de los inmigrantes procedentes de Marruecos en la agricultura de Andalucía, región situada en el sur de España. Por otra parte, examina la situación de los jornaleros de Tamaulipas, región situada en el noreste de México, empleados de forma estacional en el sector agrario estadounidense

Inmigración y trabajo irregular en la agricultura: trabajadores tamaulipecos en Estados Unidos y jornaleros magrebíes en Andalucía

Tanto en Estados Unidos como en España, la escasez de mano de obra local dispuesta a aceptar las condiciones sociolaborales imperantes en la agricultura, unida a la dificultad de inspeccionar y regular un sector donde la movilidad de trabajadores es constante, ha conducido a que la agricultura sea la actividad donde encuentran empleo más fácilmente los trabajadores migrantes indocumentados. En Estados Unidos la demanda de empleo en la agricultura ha venido siendo cubierta principalmente por trabajadores mexicanos; mientras, en España, los jornaleros procedentes de Marruecos constituyen el colectivo de inmigrantes con mayor presencia en el sector agrario. Este artículo, fundamentado en una metodología cualitativa, analiza, por una parte, la situación socio-laboral de los inmigrantes procedentes de Marruecos en la agricultura de Andalucía, región situada en el sur de España. Por otra parte, examina la situación de los jornaleros de Tamaulipas, región situada en el noreste de México, empleados de forma estacional en el sector agrario estadounidense

Inmigración y trabajo irregular en la agricultura: trabajadores tamaulipecos en Estados Unidos y jornaleros magrebíes en Andalucía

Tanto en Estados Unidos como en España, la escasez de mano de obra local dispuesta a aceptar las condiciones sociolaborales imperantes en la agricultura, unida a la dificultad de inspeccionar y regular un sector donde la movilidad de trabajadores es constante, ha conducido a que la agricultura sea la actividad donde encuentran empleo más fácilmente los trabajadores migrantes indocumentados. En Estados Unidos la demanda de empleo en la agricultura ha venido siendo cubierta principalmente por trabajadores mexicanos; mientras, en España, los jornaleros procedentes de Marruecos constituyen el colectivo de inmigrantes con mayor presencia en el sector agrario. Este artículo, fundamentado en una metodología cualitativa, analiza, por una parte, la situación socio-laboral de los inmigrantes procedentes de Marruecos en la agricultura de Andalucía, región situada en el sur de España. Por otra parte, examina la situación de los jornaleros de Tamaulipas, región situada en el noreste de México, empleados de forma estacional en el sector agrario estadounidense

(Table 1) Geochemical and geothermometry data from fibrous calcite vein fills in the Dabashan Fold Belt, China

Fibrous calcite veins with organic inclusions have been widely considered as indicators of oil and gas generation and migration under overpressure. Abundant fibrous calcite veins containing organic-bearing inclusions occur in faulted Lower Paleozoic through Triassic hydrocarbon source rocks in the Dabashan Foreland Belt (DBF). d13CPDB and d18OPDB values of the fibrous calcite range from - 4.8 to -1.9 to per mil and - 12.8 to - 8.4 per mil respectively, which is lighter than that of associated carbonate host rocks ranging from - 1.7 to + 3.1 per mil and - 8.7 to - 4.5 per mil. A linear relationship between d13CPDB and d18OPDB indicates that the calcite veins were precipitated from a mixture of basinal and surface fluids. The fibrous calcite contains a variety of inclusions, such as solid bitumen, methane bearing all-liquid inclusions, and vapor-liquid aqueous inclusions. Homogenization temperatures of aqueous inclusions range from 140 to 196° with an average of 179°. Salinities of aqueous inclusions average 9.7 wt% NaCl. Independent temperatures from bitumen reflectance and inclusion phase relationships of aqueous and methane inclusions were used to determine fluid pressures. Results indicate high pressures, elevated above typical lithostatic confining pressure, from 150 to 200 MPa. The elevated salinity and high temperature and pressure conditions of the fibrous calcite veins argue against an origin solely from burial overpressure resulting from clay transformation and dehydration reactions. Instead fluid inclusion P-T data and geochemistry results and regional geology indicate abnormally high pressures during fluid migration. These findings indicate that tectonic stress generated fracture and fault fluid pathways and caused migration of organic bearing fluids from the DBF during the Yanshan orogeny.

Ion concentrations and extracelluar pH of Calanus glacialis in Billefjorden, Svalbard

Arctic shelf zooplankton communities are dominated by the copepod Calanus glacialis. This species feeds in surface waters during spring and summer and accumulates large amounts of lipids. Autumn and winter are spent in dormancy in deeper waters. Lipids are believed to play a major role in regulating buoyancy, however, they cannot explain fine-tuning of the depth distribution. To investigate whether ion exchange processes and acid-base regulation support ontogenetic migration as suggested for Antarctic copepods, we sampled C. glacialis in monthly intervals for 1 yr in a high-Arctic fjord and determined cation concentrations and the extracellular pH (pHe) in its hemolymph. During the winter/spring transition, prior to the upward migration of the copepods, Li+ ions were exchanged with cations (Na+, Mg2+, and Ca2+) leading to Li+ concentrations of 197 mmol/L. This likely decreased the density and promoted upward migration in C. glacialis. Our data thus suggest that Li+ has a biological function in this species. Ion and pHe regulation in the hemolymph were not directly correlated, but the pHe revealed a seasonal pattern and was low (5.5) in winter and high (7.9) in summer. Low pHe during overwintering might be related to metabolic depression and thus, support diapause.