Using 3D animations to teach intracellular signal transduction mechanisms: taking the arrows out of cells

Traditional methods of teaching intracellular biological processes and pathways use figures or flowcharts with the names of molecules linked with arrows. Many veterinary students, presented with such material, simply memorize the names or chemical structures of the molecules and are then likely to forget the material once the examination is completed. To address this problem, the authors designed, created, and field-tested new teaching media that incorporate realistic three-dimensional (3D) animations depicting the dynamic changes that occur in intracellular molecules during cellular activation. Testing found that veterinary students taught using traditional teaching media (e.g., lectures, handouts, textbooks) are proficient in memorizing the names and order of intracellular molecules but unable to appreciate the interactions between these elements or their spatial relationships within cells. In contrast, more than 90% of veterinary students taught using 3D animations not only recall the facts about the intracellular elements but also develop accurate mental images of the interactions among these molecules and their spatial relationships. These findings strongly suggest that the comprehension of complex biological processes by veterinary students can be enhanced by the use of dynamic 3D depictions of these processes in the classroom.     

Prediction of irrigation return flows through a hierarchical modeling approach

The quantity of water available for irrigation is getting scarce in many countries and it assumes great importance for assured crop production, especially in view of the erratic behavior of the monsoon. Thus, there is a pressing need to improve the water efficiency of irrigation systems. One-way of improving the efficiency of the irrigation system is reusing the return flow from the irrigation system. This task requires quantification of return flow, which still remains as a grey area in irrigation water management. The estimation of return flow from the irrigation system is usually obtained using thumb rules depending upon the site-specific conditions like command area conditions and soil properties. In this paper, a hierarchical modeling technique, namely, regression tree is developed for return flow estimation. Regression tree is built through binary recursive partitioning. The effective rainfall, inflow, consumptive water demand, and percolation loss are taken as predictor variables and return flow is treated as the target variable. The applicability of the hierarchical model is demonstrated through a case study of Periyar-Vaigai Irrigation System in Tamil Nadu, India. The model performance shows a good match between the simulated and the field measured return flow values. Results of statistical analysis indicated that the correlation coefficients are high for both single as well as double crop seasons.     

Inheritance of leaf angle in Triticum aestivum L.

Summary A 6×6 diallel was prepared to study the inheritance of leaf angle in T. aestivum L. Genetic analysis in terms of diallel cross parameters and graphic analysis indicated the control of additive gene effects in the expression of this character. The results of F₁ analysis were supported by the analysis of F₂ data.     

Hybrid grass-clump dwarfness in wheat: Physiology and genetics

Summary The growth of all grass-clump dwarfs is sensitive to temperature with low temperature giving rise to the grass-clump phenotype and high temperature producing normal phenotype. A continuous temperature of 26°C is required for normal growth of Type 1 dwarfs, a continuous temperature of 21°C is required for normal growth of Ty[e 2 dwarfs and a continuous temperature of 16°C is required for normal growth of Type 3 dwarfs.Genetic studies show that the inheritance of the grass-clump characteristic is due to three complementary dominant genes.The grass-clump growth habit is produced as a result of the temperature sensitivity of the apical meristem. In grass-clump plants low temperature treatment results in the cessation of cell division, DNA synthesis and phospholipid synthesis in the apical meristem. The primary temperature lesion has not been identified. Prolonged low temperature treatment of grass-clump plants results in extensive cell necrosis in a region just below the apical meristem; this cell death results in the permanent inactivation of the apical meristem.Supported in part by the National Research Council of Canada.     

Decreased osmotic fragility of red blood cells of Eimeria adenoeides-infected turkeys

The osmotic fragility of red blood cells (RBC) from Eimeria adenoeides-infected turkey poults was compared with that of RBC from control and water-deprived poults. At different hypotonic NaCl concentrations, lysis of RBC from infected poults was 10 to 35% less on day 4 postinoculation (PI) and 50 to 65% less on day 7 PI than that of controls. Red blood cells of poults deprived of water for 3 days were also resistant to lysis; the percent lysis was roughly the same as that of RBC from infected poults at day 7 PI. Incubating control RBC in plasma from infected poults, in extracts of infected ceca, or at different pH levels did not increase their resistance to lysis, suggesting that neither a stabilizing factor in the plasma that had rapid effect on the RBC nor a transient shift in blood pH was involved. Mean RBC size differed little among infected, water-deprived, and control poults (14.0-14.2 X 8.0-8.1 X 3.8 microns). However, although 3.5% of RBC population of control and water-deprived poults were immature (mid to late polychromatic erythrocytes), only 0.4% of the RBC of infected poults were immature. The data suggest that reduced water intake as well as other factors may be involved in the decreased osmotic fragility of RBC from poults infected with E. adenoeides.     

Breeding for Highly Fertile Isolates of Nectria haematococca MPVI that are Highly Virulent on Pea and In Planta Selection for Virulent Recombinants

ABSTRACT The heterothallic ascomycete Nectria haematococca mating population VI (anamorph Fusarium solani) is a broad host range pathogen. Field isolates of this fungus that are pathogenic on pea tend to be female sterile, of low fertility, and the same mating type (MAT-1), whereas female fertile isolates of either mating type that are highly fertile tend to be nonpathogenic on this plant. To facilitate genetic analysis of traits that may be important in the ability of N. haematococca to parasitize peas, a breeding project was undertaken to produce hermaphroditic isolates of each mating type that are highly fertile and highly virulent on peas. Although the association of high virulence on peas with female sterility and the MAT-1 mating type was not completely broken, isolates with high fertility and high virulence on peas were bred within two generations. Highly virulent progeny were also isolated by an alternative method in which pea plants were inoculated with a mixture of ascospores from a cross between two moderately virulent parents. Whereas all ascospores isolated without selection in planta had lower virulence than the parents, many isolates recovered from diseased tissue were more virulent than the parental isolates. Some of the recovered isolates were shown by restriction fragment length polymorphism analysis to be genetic recombinants of the parents, demonstrating that the pea tissue selected virulent recombinants. All highly virulent isolates tested had the ability to detoxify the pea phytoalexin pisatin, again showing a link between this trait and pathogenicity on the pea.     

Presettlement and modern disturbance regimes in coast redwood forests: Implications for the conservation of old-growth stands

Coast redwood (Sequoia sempervirens), a western North American conifer of ancient lineage, has a paradoxical combination of late-successional characteristics and strong adaptations to disturbance. Despite its shade tolerance and heavy dominance of the canopy on many sites, redwood saplings are uncommon in upland old-growth stands. Information needed to ensure the conservation of old-growth redwood forests has been limited. In this review paper, we integrate evidence on redwood biology with data on the historic and modern disturbance regimes to help clarify the degree to which key attributes of redwood forests may have been dependent upon periodic disturbance. Available evidence suggests that episodes of fire, flooding, and slope failure prior to European settlement were frequent but predominantly of low to moderate severity and extent, resulting in broadly uneven-aged forests. The majority of fires prior to European settlement were apparently of human origin. Frequency and severity of the major disturbance agents have been radically changed in modern times. Fires have been largely excluded, and flooding has been altered in ways that have often been detrimental to old-growth redwoods on alluvial terraces. However, because of the apparent anthropogenic origin of most presettlement fires, the long-term evolutionary role of fire for coast redwood is ecologically ambiguous. With fire exclusion, redwood possibly could be displaced to some extent on upland sites by increasing abundance of fire-sensitive competitors. Alternatively, redwood may be able to maintain dominance by vegetative sprouting and new seedling establishment on root-wad mounds, fallen logs, and on soil exposed by slope failure. Future research priorities are suggested that will help resolve some of the current ambiguities.     

Current and historical inputs of mercury to high-latitude lakes in Canada and to Hudson Bay

Sediment cores collected from several lakes in northern Canada have been analyzed for mercury and several other chemical contaminants. Sites ranged from the Experimental Lakes Area of northwestern Ontario, north to Cornwallis Island, and west to the southern Yukon. Cores were sliced at sites of collection and individual slices were freeze dried and analyzed for Pb-210 and Cs-137 to estimate average time intervals of deposition. The earliest date estimated by Pb-210 was about 1850, and mercury concentrations in some lakes were clearly increasing before then, assuming no vertical movements of mercury within the sediments. Extrapolation of dates downward to deeper slices, assuming a constant sedimentation rate, indicated that in some lakes mercury inputs increased slowly even in the 1500's, more rapidly after 1750, and more rapidly yet over the current century. These increases are interpreted as increased fluxes of mercury to the lakes as a result of long-range transport of atmospheric mercury, since there are no local industrial sources of mercury. Slices taken near the bottom of a core are taken to estimate the geological component while elevations in excess of that in surface slices are taken to represent contamination from fallout. This partitioning suggests that sediments in the eastern Northwest Territories are dominated by pollution, while those from the western Northwest Territories are influenced more by their geological settings. Two cores from Hudson Bay suggest that mercury is increasing there too, but has not yet exceeded geological sources. Mercury shows little or no tendency to decline in the most recent slices; indicating that inputs of mercury remain at or near their historical maxima. Given relatively high and continuing inputs of mercury to northern lakes it seems likely that some portion of that mercury may find its way into the food chain, hence the long-term prospect is for increasing levels of mercury in northern fish.