AN EVALUATION OF AN ELECTRONIC INSTRUMENT FOR PASTURE YIELD ESTIMATION

In situations where yield is variable but in which it is not desirable to take too large a cut sample, e.g. on grazed plots, the pasture-yield estimator can be used to improve the accuracy of yield estimation. An outline of the theory and examples of the use of the method are given.     

Global consequences of land use

Land use has generally been considered a local environmental issue, but it is becoming a force of global importance. Worldwide changes to forests, farmlands, waterways, and air are being driven by the need to provide food, fiber, water, and shelter to more than six billion people. Global croplands, pastures, plantations, and urban areas have expanded in recent decades, accompanied by large increases in energy, water, and fertilizer consumption, along with considerable losses of biodiversity. Such changes in land use have enabled humans to appropriate an increasing share of the planet's resources, but they also potentially undermine the capacity of ecosystems to sustain food production, maintain freshwater and forest resources, regulate climate and air quality, and ameliorate infectious diseases. We face the challenge of managing trade-offs between immediate human needs and maintaining the capacity of the biosphere to provide goods and services in the long term.     

Mechanisms of survival of nematode parasites with emphasis on hypobiosis

Mechanisms involved in parasitic nematode survival must be considered with reference to their host and environmental interrelationships since these interrelationhips ultimately influence any parasite adaptations aimed at survival.The most important of the potential environmental constraints are climatic, particularly temperature and humidity, and these can drastically influence larval development and survival.One of the major host factors influencing successful parasite survival is the availability of suitable (susceptible) new hosts to the infective stages of the parasite at the appropriate time for transmission to be achieved. Other host factors that influence parasite survival are those that affect the entrance, establishment and reproduction of the parasite within its new host; mainly problems of acclimatization to a parasitic way of life as well as the countering or adaptation to a variety of host resistance factors, both molecular and cellular, by the parasite.Finally in order for life cycles to be completed, the parasite must evolve means whereby its larval forms can leave the host so that eventual transmission to a new host can be accomplished.In this paper a number of adaptations which enable the parasite to overcome these constraints are discussed. These include such things as larval resistance to environmental effects, the utilization of intermediate hosts or vectors for transmission, seasonally-increased fecundity rates, anti-host immunity stratagems and hypobiosis.This latter phenomenon, hypobiosis or prolonged but temporarily arrested larval development, represents one of the most useful of life cycle adaptations to ensure parasite adaption enables the parasite to synchronize its life cycle to changing environmental or survival and appears to be widespread among parasitic nematodes. Among its benefits, this host conditions. It can thus be of major importance in ensuring survival of the parasite during periods of environmental adversity when conditions for transmission are poor and survival of free-living forms may be minimal. It also enables the parasite to have available large numbers of infective forms at points in the host reproductive cycle which coincide with the production of the susceptible neonates thereby greatly facilitating transmission. Additionally, with certain species of nematodes, occurring as it does at times of the year when the numbers of infective stages may be high while host resources may be limited, oscillations in parasite biomass can be avoided. It thus serves as a highly adaptive mechanism for regulating populations of adult worms, lessening stress on the host and favoring parasite survival as a result.     

Mechanisms of trace metal transport in rivers

Trace metals transported by the Amazon (and Yukon rivers were analytically partitioned among the transport phases: in solutions, ion exchange, organic materials, metallic coatings, and crystalline solids. The distribution for both rivers is similarly proportioned, with copper and chromium transported mainly in the crystalline solids, manganese in coatings, and iron, nickel, and cobalt distributed equally between precipitated metallic coatings and crystalline solids.     

Left ventricular volume determination in the horse by two-dimensional echocardiography: an in vitro study

This study was designed to evaluate the accuracy of two-dimensional echocardiography (2DE) in determining the left ventricular volume (LVV) of the horse in vitro. After examining the shape of the left ventricular silicon rubber casts of four equine hearts, two modified Simpson's rule methods (Model A and Model B) as combinations of conical shapes and one biplane area-length method as a single cone (Model C) were chosen for volume calculations. One long axis and three short axis planes were used for linear and area 2DE measurements, respectively. The ventricular length (L) was calculated from the chordal length (CL) by using a linear regression equation (L = 5.54 + 1.83 CL) obtained by anatomical measurement of these two parameters on 40 normal hearts. The LVV was calculated in 15 formalin-fixed hearts from 2DE measurements with the three geometric models. Left ventricular casts were then made using silicon rubber, and their volumes were determined by water displacement. The calculated volumes were plotted against cast volumes with linear regression analysis. All calculated LVVs correlated well with the cast LVVs (R = 0.921 to 0.957; P less than 0.001). The highest correlation was provided by Model A which best represented the shape of the left ventricle. This model consisted of a truncated cone bordered by the area at the level of the mitral valve and by the area at the level of the chordae tendineae, plus a cone the base of which was the area at the level of the papillary muscles. The results demonstrate the applicability of 2DE for equine LVV determinations in vitro, similar to other species.(ABSTRACT TRUNCATED AT 250 WORDS)     

A lymphomatoid granulomatosis of the lungs in young dogs.

Clinical signs in three young dogs with primary lung neoplasms included cough, weight loss and anorexia. Chest radiographs taken in the terminal stages of the disease showed nodular and diffuse consolidation of the lungs typical of primary neoplasms. Macroscopically the lungs were infiltrated by firm, pale tissue; similar tissue replaced the enlarged bronchial lymph nodes. In two dogs similar deposits were found also in the liver and spleen. The infiltrates were composed of atypical, polymorphous lymphoreticular cells. Invasion of pulmonary blood vessels and of bronchi and bronchioles was striking. The lesions closely resembled those of lymphomatoid granulomatosis, a rare human disease of unknown cause.