Sorting and directed transport of membrane proteins during development of hippocampal neurons in culture

Hippocampal neurons in culture develop morphological polarity in a sequential pattern; axons form before dendrites. Molecular differences, particularly those of membrane proteins, underlie the functional polarity of these domains, yet little is known about the temporal relationship between membrane protein polarization and morphological polarization. We took advantage of viral expression systems to determine when during development the polarization of membrane proteins arises. All markers were unpolarized in neurons before axonogenesis. In neurons with a morphologically distinguishable axon, even on the first day in culture, both axonal and dendritic proteins were polarized. The degree of polarization at these early stages was somewhat less than in mature cells and varied from cell to cell. The cellular mechanism responsible for the polarization of the dendritic marker protein transferrin receptor (TfR) in mature cells centers on directed transport to the dendritic domain. To examine the relationship between cell surface polarization and transport, we assessed the selectivity of transport by live cell imaging. TfR-green fluorescent protein-containing vesicles were already preferentially transported into dendrites at 2 days, the earliest time point we could measure. The selectivity of transport also varied somewhat among cells, and the amount of TfR-green fluorescent protein fluorescence on intracellular structures within the axon correlated with the amount of cell surface expression. This observation implies that selective microtubule-based transport is the primary mechanism that underlies the polarization of TfR on the cell surface. By 5 days in culture, the extent of polarization on the cell surface and the selectivity of transport reached mature levels.

Directional Guidance of Nicotiana alata Pollen Tubes in Vitro and on the Stigma1

Pollen tubes navigate the route from stigma to ovule with great accuracy, but the cues that guide them along this route are not known. We reproduced the environment on the stigma of Nicotiana alata by immersing pollen in stigma exudate or oil close to an interface with an aqueous medium. The growth of pollen in this culture system mimicked growth on stigmas: pollen grains hydrated and germinated, and pollen tubes grew toward the aqueous medium. The rate-limiting step in pollen germination was the movement of water through the surrounding exudate or oil. By elimination of other potential guidance cues, we conclude that the directional supply of water probably determined the axis of polarity of pollen tubes and resulted in growth toward the interface. We propose that a gradient of water in exudate is a guidance cue for pollen tubes on the stigma and that the composition of the exudate must be such that it is permeable enough for pollen hydration to occur but not so permeable that the supply of water becomes nondirectional. Pollen tube penetration of the stigma may be the most frequently occurring hydrotropic response of higher plants.

Endothelin 3 promotes neural crest cell proliferation and mediates a vast increase in melanocyte number in culture.

Mutations in the endothelin 3 (EDN3) gene severely affect the development of neural crest-derived melanocytes. In this paper, we report the action of EDN3 on neural crest cells in vitro. The presence of EDN3 leads to a large increase in the number of cells, the majority of which eventually differentiate into melanocytes that aggregate to form a reproducible pigmentation pattern. Quantitative analysis of the effect of different culture conditions revealed that EDN3 initially promotes neural crest cell proliferation. This phase of expansion, which can be prolonged for a few weeks if the cells are replaced regularly, is followed by both a decrease in cell proliferation and the onset of melanocytic differentiation. Therefore, EDN3 is a potent mitogen for early neural crest cell precursors that can give rise to melanocytes.

Self-renewal of primitive human hematopoietic cells (long-term-culture-initiating cells) in vitro and their expansion in defined medium.

A major goal of experimental and clinical hematology is the identification of mechanisms and conditions that support the expansion of transplantable hematopoietic stem cells. In normal marrow, such cells appear to be identical to (or represent a subset of) a population referred to as long-term-culture-initiating cells (LTC-ICs) so-named because of their ability to produce colony-forming cell (CFC) progeny for > or = 5 weeks when cocultured with stromal fibroblasts. Some expansion of LTC-ICs in vitro has recently been described, but identification of the factors required and whether LTC-IC self-renewal divisions are involved have remained unresolved issues. To address these issues, we examined the maintenance and/or generation of LTC-ICs from single CD34+ CD38- cells cultured for variable periods under different culture conditions. Analysis of the progeny obtained from cultures containing a feeder layer of murine fibroblasts engineered to produce steel factor, interleukin (IL)-3, and granulocyte colony-stimulating factor showed that approximately 20% of the input LTC-ICs (representing approximately 2% of the original CD34+ CD38- cells) executed self-renewal divisions within a 6-week period. Incubation of the same CD34+ CD38- starting populations as single cells in a defined (serum free) liquid medium supplemented with Flt-3 ligand, steel factor, IL-3, IL-6, granulocyte colony-stimulating factor, and nerve growth factor resulted in the proliferation of initial cells to produce clones of from 4 to 1000 cells within 10 days, approximately 40% of which included > or = 1 LTC-IC. In contrast, in similar cultures containing methylcellulose, input LTC-ICs appeared to persist but not divide. Overall the LTC-IC expansion in the liquid cultures was 30-fold in the first 10 days and 50-fold by the end of another 1-3 weeks. Documentation of human LTC-IC self-renewal in vitro and identification of defined conditions that permit their extensive and rapid amplification should facilitate analysis of the molecular mechanisms underlying these processes and their exploitation for a variety of therapeutic applications.

Myelin-associated neurite growth-inhibitory proteins and suppression of regeneration of immature mammalian spinal cord in culture.

Neurite outgrowth across spinal cord lesions in vitro is rapid in preparations isolated from the neonatal opossum Monodelphis domestica up to the age of 12 days. At this age oligodendrocytes, myelin, and astrocytes develop and regeneration ceases to occur. The role of myelin-associated neurite growth-inhibitory proteins, which increase in concentration at 10-13 days, was investigated in culture by applying the antibody IN-1, which blocks their effects. In the presence of IN-1, 22 out of 39 preparations from animals aged 13-17 days showed clear outgrowth of processes into crushes. When 34 preparations from 13-day-old animals were crushed and cultured without antibody, no axons grew into the lesion. The success rate with IN-1 was comparable to that seen in younger animals but the outgrowth was less profuse. IN-1 was shown by immunocytochemistry to penetrate the spinal cord. Other antibodies which penetrated the 13-day cord failed to promote fiber outgrowth. To distinguish between regeneration by cut neurites and outgrowth by developing uncut neurites, fibers in the ventral fasciculus were prelabeled with carbocyanine dyes and subsequently injured. The presence of labeled fibers in the lesion indicated that IN-1 promoted regeneration. These results show that the development of myelin-associated growth-inhibitory proteins contributes to the loss of regeneration as the mammalian central nervous system matures. The definition of a critical period for regeneration, coupled with the ability to apply trophic as well as inhibitory molecules to the culture, can permit quantitative assessment of molecular interactions that promote spinal cord regeneration.

Anna Popovitch,In the Shadow of Althusser: Culture and Politics in Late Twentieth-Century Argentina, Ann Arbor, umi Dissertation Publishing, 2011, 238 páginas

Fil: Starcenbaum, Marcelo. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación. Instituto de Investigaciones en Humanidades y Ciencias Sociales (UNLP-CONICET); Argentina.

False anglicisms in the Spanish language of fashion and beauty

Many works have already dealt with anglicisms in Spanish, especially in science and information technologies. However, despite the high and growing number of English terms incorporated daily by the language of fashion, it has received comparative less attention in lexicographic and terminological studies than that of other areas, such as science or business. For several reasons, which include prestige or peer pressure, Spanish has not only adopted English words with new meanings and usage, but also contains other forms based on English patterns which users seem to consider more accurate or expressive. This paper concentrates on false anglicisms as indicators of some of the special relationships and influences between languages arising from the pervasive presence of English. We shall look at the Spanish language of fashion, which, in addition to genuine anglicisms, has for some time been using English words with different meanings, or even created items of its own (or imported them from other languages) with the appearance of English words. These false anglicisms, which have proven extremely popular in receiving languages (not only in Spanish) have frequently been disseminated by youth magazines and the new digital media, both in general spheres and in fashion-specific contexts.

Evaluation of the Implementation of CLIL (Content and Language Integrated Learning) Methodology in the Didactics of the English Language in Preschool Education Course Taught in the Preschool Education Teacher Undergraduate Program at the University of Alicante

Although it is known that the Spanish current Educative System promotes using the Communicate Approach to teach foreign languages in schools, other recently designed approaches are also used to help students improve their skills when communicating in a foreign language. One of these approaches is Content and Language Integrated Learning, also known as CLIL, which is used to teach content courses using the English language as the language of instruction. This approach improves the students’ skills in English as the same time as they learn content from other areas. The goal of this thesis is to present a research project carried out at the University of Alicante during the academic year 2011-2012. With this research we obtained results that provide quantitative and qualitative data which explains how the use of the CLIL methodology affects the English level of students in the “Didactics of the English Language in Preschool Education” course in Preschool Education Teacher Undergraduate Program as students acquire the contents of the course.