Tumor cells secrete a vascular permeability factor that promotes accumulation of ascites fluid

Tumor ascites fluids from guinea pigs, hamsters, and mice contain activity that rapidly increases microvascular permeability. Similar activity is also secreted by these tumor cells and a variety of other tumor cell lines in vitro. The permeability-increasing activity purified from either the culture medium or ascites fluid of one tumor, the guinea pig line 10 hepatocarcinoma, is a 34,000- to 42,000-dalton protein distinct from other known permeability factors.     

Performance of three infiltration models under surge irrigation

Three models were developed to predict infiltration under a surge-flow irrigation regime. One model (2P) utilized the Kostiakov-Lewis infiltration equation. The other two models (2PF and 3P) utilized the modified Kostiakov-Lewis infiltration equation. All three models combined continuous-flow furrow irrigation volume-balance hydraulic models presented by Reddell and Latortue (1986, 1988) with a numerical variation of the Cycle Ratio-Time Model (CRTM) for surge irrigation presented by Blair and Smerdon (1987). The volume–balance component of the models estimated the soil's continuous-flow furrow irrigation infiltration function using first surge-cycle advance data. The numerical CRTM component used the estimated infiltration function in conjunction with the surge-flow irrigation infiltration opportunity-time to predict infiltration. An assessment of overall model accuracy was based upon an infiltrated volume root mean square error (RMSE) statistic. Overall, the 2PF model returned the lowest RMSE values and the 3P model was the next most accurate. The 2P model was the least accurate. While the 2PF model was the most accurate, this model has limited applicability since it requires inflow and outflow measurements throughout an irrigation event to evaluate the soil's basic infiltration constant. Despite its good overall performance, anomalous results from the 3P model suggest that further testing is needed. Although the 2P model was the least accurate of the three models evaluated here, and although it consistently underpredicted infiltration, it appears to be the most stable and effective of the three models evaluated. Received: 22 May 2000     

Differential responses of Central American and Mexican pine species and Pinus radiata to infection by the pitch canker fungus

Seedlings from a wide array of 23 species, varieties,and geographic races were screened for resistance topitch canker using artificial inoculation in agreenhouse. Seed to represent these taxa weregenerally collected in natural stands. In addition,seedlings from 79 families of P. radiata fromcommercial populations from Chile and New Zealand werescreened in a separate experiment. There was littlevariation in resistance among the commercial P.radiata families, with over 98% mortality. Similarresults were obtained with native P. radiatapopulations. All close relatives of P. radiata(sub-section Patula) were very susceptible. However,a number of closed-cone pine species (specifically,from sub-section Oocarpa) were generally veryresistant, with survival approaching 100%. Inaddition, in P. oocarpa, P. jaliscana, and P. tecunumanii from low elevation provenances anextremely high frequency of trees suffered no apparentdamage from the pathogen (92%, 85% and 80%,respectively).     

Looking backward to move forward: early detection of neurodegenerative disorders

Early detection of neurodegenerative disorders would provide clues to the underlying pathobiology of these diseases and would enable more effective diagnosis and treatment of patients. Recent advances in molecular neuroscience have begun to provide the tools to detect diseases like Alzheimer's disease, Parkinson's disease, and others early in their course and potentially even before the development of clinical manifestations of disease. These genetic, imaging, clinical, and biochemical tools are being validated in a number of studies. Early detection of these slowly progressive diseases offers the promise of presymptomatic diagnosis and, ultimately, of disease-modifying medications for use early in disease and during the presymptomatic period.     

Regulation of extravascular coagulation by microvascular permeability

Extravascular coagulation is a prominent feature of such important pathological processes as cellular immunity and neoplasia and has been thought to result from procoagulants associated with the inflammatory or tumor cells peculiar to these entities. It was found that increased microvascular permeability alone is sufficient to induce equivalent extravascular coagulation in several normal tissues. The results indicate that saturating levels of procoagulant are present even in normal tissues and that microvascular permeability is a rate-limiting step in extravascular coagulation.     

Barley yield response to irrigation and potential profits in the Texas High Plains

Summary Irrigated winter barley (Hordeum vulgare L.) can be a profitable alternative to some low profit major crops in the Texas High Plains. A six-year evaluation of yield response related to total spring irrigation water, applied by surface methods (furrow), and seasonal precipitation resulted in a multivariate function explaining 74% of the yield variation. Predicted yields varied from a low of 3.69 Mg ha^–1 to a maximum 6.18 Mg ha^–1 with 0 and 389 mm, respectively, based on average monthly precipitation quantities. Precipitation is skewed to less than average in th semi-arid Texas High Plains. Using modal precipitation amounts of 40% of average precipitation, yield estimates were reduced to 2.29 Mg ha^–1 with zero spring irrigation and to 5.63 Mg ha^–1 at the peak with 450 mm. A second multivariate yield response function related to alternative timings of single and multiple spring irrigations explained 76% of the variation in yields. Among all combinations of 1, 2, 3, and 4 spring irrigations, irrigation water-use efficiency was estimated to be highest with one application at the boot stage of development. All other single and combinations of multiple irrigations resulted in lower water-use efficiencies. A comparison of enterprise budgets of four irrigation timing alternatives and levels of application indicated highest profit over variable costs, $ 287 ha^–1, was attained by applying a total of 307 mm in three spring applications at the boot, head, and milk stages. A lower level of 217 mm applied at boot and milk stages was $ 12 ha^–1 less profitable and a higher level of 425 mm was $ 24 ha^–1 less profitable. When fixed costs of irrigation facilities, land, and machinery were considered, returns to management and risk were highest, $ 101 ha^–1, with 217 mm. Using 40% of average precipitation, profits were reduced $ 65 ha^–1 with 217 mm and $ 69 ha^–1 with 307 mm spring irrigation levels.Respectively, agricultural economist, research scientist, and research associate, Texas Agr. Exp. Station, Amarillo, Texas; Emeritus Extension agronomist, Texas Agr. Ext. Service, Amarillo, Texas; agricultural engineer, Texas Agr. Exp. Station, Amarillo, Texas     

Trace Metal Fluxes in a Sphagnum Peatland – Humic Lake System as a Consequence of Drainage

The study was conducted in a small (7.4 ha) peatland system with a humic lake concentrically surrounded by Sphagnum mat (Caricetum limosae) and Sphagnum bog (Ledo-Sphagnetum) in the Mazurian Lakeland in North-Eastern Poland. The peatland was situated in a forested catchment with a total area of 16.25 ha, and was influenced by surface drainage, artificially designed for forestry purposes. The content of zinc (Zn), cadmium (Cd), lead (Pb), copper (Cu) and hydrogen (H) ions was analysed in waters from precipitation, humic lake, mat, bog and surface outflow. The yearly budget of these ions, expressed as difference between atmospheric inflow and surface outflow, for the whole catchment was presented. The drainage of the peatland system over three years was accompanied by an increase in pH of lake, mat and bog waters. The whole catchment retention of H⁺ and trace metals studied decreased yearly in absolute values under these conditions. The peatland system began to leach Pb into surface waters and lost its ability to intercept Cd. These effects could be caused by intensity of outflow of water and sulphates and lowering of water storage. However, the potential to retain Zn and Cu ions was preserved.