Directional growth is a function of polarized cells such as neurites, pollen tubes, and fungal hyphae. Correct orientation of the extending cell tip depends on signaling pathways and effectors that mediate asymmetric responses to specific environmental cues. In the hyphal form of the eukaryotic fungal pathogen Candida albicans, these responses include thigmotropism and galvanotropism (hyphal turning in response to changes in substrate topography and imposed electrical fields, respectively) and penetration into semisolid substrates. During vegetative growth in C. albicans, as in the model yeast Saccharomyces cerevisiae, the Ras-like GTPase Rsr1 mediates internal cellular cues to position new buds in a prespecified pattern on the mother cell cortex. Here, we demonstrate that Rsr1 is also important for hyphal tip orientation in response to the external environmental cues that induce thigmotropic and galvanotropic growth. In addition, Rsr1 is involved in hyphal interactions with epithelial cells in vitro and its deletion diminishes the hyphal invasion of kidney tissue during systemic infection. Thus, Rsr1, an internal polarity landmark in yeast, is also involved in polarized growth responses to asymmetric environmental signals, a paradigm that is different from that described for the homologous protein in S. cerevisiae. Rsr1 may thereby contribute to the pathogenesis of C. albicans infections by influencing hyphal tip responses triggered by interaction with host tissues.The growth and behavior of living cells is achieved by a process of vectorial metabolism in which growth is directed or restricted to specific cellular locations under the influence of endogenous and exogenous signals and stimuli. For example, in the model yeast Saccharomyces cerevisiae, budding yeast cell growth involves polarization in a direction that is prescribed by proteins that provide internal cues. These proteins include cortically localized bud-site selection proteins that recruit and activate the major polarity establishment Rho GTPase Cdc42 either adjacent to or directly opposite the site of emergence by the previous daughter cell (12, 13). In contrast to the case for budding cells in S. cerevisiae, where positional landmarks are internal, pheromones provide mating yeast cells with extracellular signals that override the internal cues so that the growth of the mating projection (shmoo) is oriented in the direction of the putative mating partner (13).During yeast cell growth in Candida albicans, an opportunistic fungal pathogen of humans, the direction of polarity establishment is controlled, as it is in S. cerevisiae, by internal cues at the mother cell cortex (23,30,57,64). C. albicans also grows in a filamentous hyphal morphology that is not exhibited by S. cerevisiae. Understanding how hyphal morphogenesis occurs and is regulated has generated a great deal of interest because the hyphal form of C. albicans has been associated with the invasion of host tissues and mortality (54,65).The hyphae of C. albicans and other human and plant fun...

Daily weather data commonly used in simulation models of agricultural or ecological systems are sometimes incomplete, frequently contain errors, and are often in an inconvenient format. The WeatherMan is a user‐oriented software package designed to assist in preparing daily weather data for use with simulation models. The software can import or export daily weather files with any column format (including the Decision Support System for Agrotechnology Transfer ver. 2.1 and ver. 3.0 files) and convert the data to desirable units. Data are checked and flagged for possible errors on import. Several techniques are available for filling in missing values and erroneous data on export. WeatherMan also contains two methods (WGEN and SIMMETEO) for stochastically generating sequences of daily weather data. Both methods can be parameterized from the daily data and the second method uses monthly means from any secondary data source. Summary statistics of raw and generated data can be graphed or presented in tables.

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In the northern sector of Roman Carthage, east of the cardo maximus (the main N-saxis of the city), the defensive wall of ca. 425 A.C. (the so-called Theodosian Wall) has been shown to lie along thefoot of the winding escarpment known as the Teurf el-Sour. This escarpment was wholly or largely created by urban buildup of the Roman period, and its line is determined by that of the Wall, not vice versa. What earlier excavators took to be an earth rampart of the A rab period proves to be a roadway running along behind the Wall.The street grid of the A ugustan colony extends into this sector, though with significant irregularities. The built-up area extends north of decumanus VI, although this was theoretically the limit of the city. It is not yet possible to date the first occupation of the area, but it was flourishing by the late 4th century. The 6th century was a period of decline, with some at least of the buildings abandoned, but the area was redeveloped in the 7th century, though with a much lower standard of living.