Showing papers by "Colorado State University published in 1988"

A Generalized Model of the Effects of Grazing by Large Herbivores on Grassland Community Structure

Abstract: Current disturbance models do not adequately account for the wide range of responses by grassland plant communities to grazing by large generalist herbivores The evolutionary history of grazing, a

Dynamics of C, N, P and S in grassland soils: a model

Abstract: We have developed a model to simulate the dynamics of C, N, P, and S in cultivated and uncultivated grassland soils. The model uses a monthly time step and can simulate the dynamics of soil organic matter over long time periods (100 to 10,000 years). It was used to simulate the impact of cultivation (100 years) on soil organic matter dynamics, nutrient mineralization, and plant production and to simulate soil formation during a 10,000 year run. The model was validated by comparing the simulated impact of cultivation on soil organic matter C, N, P, and S dynamics with observed data from sites in the northern Great Plains. The model correctly predicted that N and P are the primary limiting nutrients for plant production and simulated the response of the system to inorganic N, P, and S fertilizer. Simulation results indicate that controlling the C:P and C:S ratios of soil organic matter fractions as functions of the labile P and S levels respectively, allows the model to correctly simulate the observed changes in C:P and C:S ratios in the soil and to simulate the impact of varying the labile P and S levels on soil P and S net mineralization rates.

Psychological Testing: Principles and Applications

Abstract: I. INTRODUCTION TO PSYCHOLOGICAL TESTING. 1. Tests and Measurements. 2. Defining and Measuring Psychological Attributes: Ability, Interests, and Personality. 3. Testing and Society. II. PRINCIPLES OF PSYCHOLOGICAL MEASUREMENT. 4. Basic Concepts in Measurement and Statistics. 5. Scales, Transformations, and Norms. 6. Reliability: The Consistency of Test Scores. 7. Using and Interpreting Information about Test Reliability. 8. Validity of Measurement: Content and Construct-Oriented Validation Strategies. 9. Validity for Decisions: Criterion-Related Validity. 10. Item Analysis. III. DEVELOPING MEASURES OF ABILITY, INTERESTS, AND PERSONALITY. 11. The Process of Test Development. 12. Computerized Test Administration and Interpretation. 13. Ability Testing: Individual Tests. 14. Ability Testing: Group Tests. 15. Issues in Ability Testing. 16. Interest Testing. 17. Personality Testing. IV. USING TESTS TO MAKE DECISIONS. 18. Tests and Educational Decisions. 19. Psychological Measurement in Industry. 20. Diagnostic Testing: Clinical Applications. 21. Issues in Multi-Method Assessment. Appendix: Ethical Principles of Psychologists and Code of Conduct. References. Author Index. Subject Index.

Restoration of excitation—contraction coupling and slow calcium current in dysgenic muscle by dihydropyridine receptor complementary DNA

Abstract: Microinjection of an expression plasmid that carries complementary DNA encoding the receptor for dihydropyridine calcium channel blockers of skeletal muscle restores both excitation-contraction coupling and slow calcium current in cultured skeletal muscle cells from mice with muscular dysgenesis. This suggests that the dihydropyridine receptor in the transverse tubule membrane of skeletal muscle functions both as the voltage sensor for excitation-contraction coupling and as the slow calcium channel.

The hyporheic habitat of river ecosystems

Abstract: Contemporary river ecology is based primarily on biogeochemical studies of the river channel and interactions with shoreline vegetation, even though most rivers have extensive floodplain aquifers that are hydraulically connected to the channel. The hyporheic zone, the interstitial habitat penetrated by riverine animals, is characterized as being spatially limited to no more than a few metres, in most cases centimetres, away from the river channel1–9. However, riverine invertebrates were collected in hundreds per sample within a grid of shallow (10 m) wells located on the flood-plain up to 2 km from the channel of the Flathead River, Montana, USA. Preliminary mass transport calculations indicate that nutrients discharged from the hyporheic zone may be crucial to biotic productivity in the river channel. The strength and spatial magnitude of these interactions demonstrate an unexplored dimension in the ecology of gravel-bed rivers.

Outgrowth-regulating actions of glutamate in isolated hippocampal pyramidal neurons

Abstract: The present study examined the effects of glutamate on the outgrowth of dendrites and axons in isolated hippocampal pyramidal-like neurons in cell culture During the first day of culture the survival and outgrowth of these neurons was unaffected by high concentrations (up to 1 nM) of glutamate, quisqualic acid (QA), kainic acid (KA), and N- methyl-D-aspartic acid Beginning on day 2 of culture high levels of glutamate, KA and QA were toxic to the majority of pyramidal neurons, while subtoxic levels of these agents caused a well-defined, dose- dependent, sequence of effects on dendritic outgrowth At increasing concentrations of glutamate, QA, and KA, the following events were observed: (1) dendritic outgrowth rates were reduced, while axonal elongation rates were unaffected; (2) dendritic length was reduced, while axons continued to grow; (3) dendrites regressed dramatically, and axonal outgrowth rate was reduced These dendrite-specific effects of glutamate were apparently mediated at the growth cones since focal application of glutamate to individual dendritic growth cones resulted in suppression of growth cone activity and a regression of the dendrite; axons were unaffected by focal glutamate application Pharmacological tests using glutamate receptor agonists and antagonists demonstrated that receptors of the KA/QA type mediated the glutamate effects on outgrowth and survival The calcium channel blocker Co2+ prevented both glutamate neurotoxicity and glutamate-induced dendritic regression Ionophore A23187 and elevations in extracellular K+ levels each caused a dose-dependent series of outgrowth and survival responses similar to those caused by glutamate Taken together, these results indicate that activation of glutamate receptors leads to the opening of voltage-dependent calcium channels; the resulting increases in calcium influx lead to the observed alterations in dendritic outgrowth and neuronal survival

A General Model for Expansion of Extruded Products

Abstract: The expansions (cross-sectional, longitudinal and volumetric) of corn extrudates made with a single-screw extruder were studied. Longitudinal and Volumetric Expansion Indices were developed to characterize the product's specific length and volume. To explain the results, it was postulated that increased stored energy in the elastic starch melt occurring with higher shear strains favored radial expansion at the expense of longitudinal expansion. An inverse relationship between radial and longitudinal expansions was confirmed. A general expansion model involving dough moisture, melt temperature, and die and screw shear strains described all three expansions and characterized the thermally induced expansions with associated energies of activation.

Chronic neurological sequelae of acute organophosphate pesticide poisoning

Abstract: To evaluate the latent neurological effects of organophosphate pesticide poisoning, this epidemiologic study examined 100 matched-pairs of individuals with previous acute organophosphate pesticide poisoning and nonpoisoned controls No significant difference between poisoned subjects and controls was found on audiometric tests, ophthalmic tests, electroencephalograms, or the clinical serum and blood chemistry evaluations Of the more than 50 scores from the neurological examination, abnormalities were demonstrated among the cases only on measures of memory, abstraction, and mood, and on one test of motor reflexes Differences between the two cohorts were much more apparent in the neuropsychological tests The differences occurred on tests of widely varying abilities including intellectual functioning, academic skills, abstraction and flexibility of thinking, and simple motor skills Twice as many cases as controls (24 vs 12) had Halstead-Reitan Battery summary scores in the range characteristic of individuals with cerebral damage or dysfunction Results from the Minnesota Multiphasic Personality Inventory and the Patient's and Relative's Assessment of Patient Functioning Inventories also revealed greater distress and complaints of disability for the poisoned subjects

Evaluation of vegetation effects on the generation and modification of mesoscale circulations

Abstract: The effects of the presence of vegetation cover on modifying sea breeze and thermally induced upslope flows during daytime were investigated, and the possibility of the generation of mesoscale circulations due to nonuniform vegetation cover was evaluated. Scale analysis and numerical model simulations were used to provide quantitative evaluations of the circulations involved in the two vagetation effects, using several illustrative cases. The cases considered demonstrate that the impact of vegetated surfaces is highly dependent on the environmental conditions as well as vegetation characteristics.

Resource compartmentation and the stability of real ecosystems

Abstract: Gardner and Ashby1 and May2 challenged the tenet that ecological stability increases with species diversity. But May concluded that if species are arranged in 'blocks', stability restrictions are relaxed allowing for greater diversity than in the absence of blocking. Recent investigations suggest that communities may contain tightly coupled subunits whose numbers may increase with diversity3–6. McNaughton7 suggested that species may be arranged in resource compartments and that, within these compartments, species interaction strength would decline as diversity increased. Pimm8 found little evidence of food-web compartmentation within habitats and few examples between habitats but cautioned that binary data sets based on connectedness were not optimal for detecting compartmentation. We provide evidence of resource compartmentation based on structural characteristics of a belowground connectedness web9 and on biomass estimates and nitrogen flux rates from its energy flux-web description. Using other food webs, we demonstrate that the relationship between structure and diversity is similar for different resource compartments, suggesting that these compartments behave as entities.

Transition Metals in the Synthesis and Functionalization of Indoles [New Synthesis Methods (72)]

Abstract: The use of transition-metal complexes as reagents for the synthesis of complex organic compounds has been under development for at least several decades, and many extraordinary organic transformations of profound potential have been realized. However, adoption of this chemistry by the practicing synthetic organic chemist has been inordinately slow, and only now are transition-metal reagents beginning to achieve their rightful place in the arsenal of organic synthesis. Several factors contributed to the initial reluctance of synthetic organic chemists to use organometallic reagents. Lacking education and experience in the ways of elements having d electrons, synthetic chemists viewed organometallic processes as something mysterious and unpredictable, and not to be discussed in polite society. Organometallic chemists did not help matters by advertising their latest advances as useful synthetic methodology, but restricting their studies to very simple organic systems lacking any serious functionality (e.g., the “methyl, ethyl, butyl, futile” syndrome). Happily, things have changed. Organometallic chemists have turned their attention to more complex systems, and more recently trained organic chemists have benefited from exposure to the application of transition metals. This combination has set the stage for major advances in the use of transition metals in the synthesis of complex organic compounds. This review deals with one aspect of this area, the use of transition metals in the synthesis of indoles.

Molecular cloning of a feline leukemia virus that induces fatal immunodeficiency disease in cats.

Abstract: A replication-defective variant of feline leukemia virus was molecularly cloned directly from infected tissue and found to induce a rapid and fatal immunodeficiency syndrome in cats. Studies with cloned viruses also showed that subtle mutational changes would convert a minimally pathogenic virus into one that would induce an acute form of immunodeficiency. The data suggest that acutely pathogenic viruses may be selected against by current methods for isolation of the human and simian immunodeficiency viruses.

Induction of nonspecific acquired resistance and delayed-type hypersensitivity, but not specific acquired resistance in mice inoculated with killed mycobacterial vaccines.

Abstract: A number of nonliving mycobacterial preparations were tested in vivo for their capacity to generate various relevant parameters of cellular immunity. All preparations tested had some detectable activity in raising resistance to challenge with Mycobacterium tuberculosis or with Listeria monocytogenes and in conferring the ability to mount a delayed-type hypersensitivity response to tuberculin. This report presents the first evidence, however, that none of these preparations were able to generate protective T cells capable of adoptive immunization against virulent tuberculosis. These data are discussed in terms of the use of these preparations in generating M. tuberculosis-reactive T-cell lines and the application of these lines in the continuing search for an improved vaccine against tuberculosis.

The Relationship of Surface Pressure Features to the Precipitation and Airflow Structure of an Intense Midlatitude Squall Line

Abstract: Observations from the Oklahoma–Kansas Preliminary Regional Experiment for STORM-Central (OK PRE-STORM) have been used to document the surface pressure features accompanying an intense midlatitude squall line with trailing stratiform precipitation. Three well-known features are observed: a pre-squall mesolow, a squall mesohigh and a wake low. Particular attention is given to the wake low, its life cycle and association with the trailing stratiform portion of the squall line. During the formative stage, the pressure field to the rear of the squall line mesohigh is relatively flat with only weak stratiform precipitation present. As the squall line enters the developing-to-mature stages, a pronounced wake low appears at the back edge of the surface stratiform precipitation area. The squall line at this time is characterized by a strong rear-inflow jet, descending from the upper troposphere, as far as 500 km behind the leading convective line, to the lower troposphere just behind the line. The trailin...

Environmental Influences on Hurricane Intensification

Abstract: Although driven by internal processes, hurricanes are also regulated by conditions in their oceanic and atmospheric surroundings. Sea surface temperature determines an upper bound on the intensity of hurricanes, but most never reach this potential, apparently because of adverse atmospheric conditions. Winds measured by satellite cloud tracking, commercial aircraft, and rawinsondes are composited using a rotated coordinate system designed to preserve the asymmetries in the upper-tropospheric environment. Composites of upper-tropospheric environmental flows for intensifying and nonintensifying hurricanes for a five-year period are compared. Nonintensifying composites indicate stronger mean environmental flow relative to the hurricane motion, unidirectional flow over and near the hurricane center, and slightly weaker radial outflow and/or more pronounced anticyclonic flow surrounding the center in the upper troposphere.

Characteristics and specificity of acquired immunologic memory to Mycobacterium tuberculosis infection.

Abstract: The results herein show that mice infected with Mycobacterium tuberculosis and then exposed to a protracted course of isoniazid chemotherapy possess a heightened state of acquired resistance to subsequent challenge with the homologous organism. Our results provide the first evidence, moreover, that this resistance is mediated by a long-lived, cyclophosphamide- and irradiation-resistant L3T4+ Lyt-2- lymphocyte capable of giving rise to an accelerated re-emergence of resistance in the animal upon rechallenge. Evidence is also provided to show that triggering of this memory-immune T cell population in the re-challenged host was associated with the rapid emergence of non-specific resistance to secondary bacterial infection; however, the accelerated emergence of this population was only observed if the challenge inoculum consisted of the living organism. The relevance of this latter finding to strategies for vaccine development is discussed.

A Generalization of Cohen's Kappa Agreement Measure to Interval Measurement and Multiple Raters

Abstract: Cohen's kappa statistic is frequently used to measure agreement between two observers employing categorical polytomies. In this paper, Cohen's statistic is shown to be inherently multivariate in nature; it is expanded to analyze ordinal and interval data; and it is extended to more than two observers. A nonasymptotic test of significance is provided for the generalized statistic.

Relationships between computerized measurements of motion of frozen-thawed bull spermatozoa and fertility.

Abstract: A computerized system (CellSoft, CRYO Resources, Ltd.) was validated using video tapes of frozen-thawed bull spermatozoa diluted in filtered (0.2 micron) egg yolk-citrate extender (8 X 10(6) spermatozoa/ml) and analyzed at 30 frames/sec for the percentage of motile spermatozoa (greater than or equal to 20 microns/sec) and linear velocity of motile spermatozoa. Virtually all motile spermatozoa were detected and debris rarely were classified as immotile spermatozoa if the extender had been filtered. Variation about the mean for percent motile cells was similar when only 12 rather than 20 or 30 frames/field were analyzed. Use of 20 frames/field was adequate to determine the percentage of motile bull spermatozoa. Five mixtures of live and killed spermatozoa were analyzed (four bulls) to evaluate accuracy. Percent motile spermatozoa was correlated (r = 0.97) with the ratio of live:killed spermatozoa. Mean linear velocity of motile spermatozoa was similar for each mixture (P greater than 0.05). To further evaluate accuracy, percent motile spermatozoa was determined by computer and by "track motility" (20 samples; 0 to 63% motile spermatozoa); values were correlated (r = 0.95). The system was precise (CV of 6% based on triplicate analyses of the same samples) and reasonably accurate for evaluating bull sperm motility if the extender had been filtered and 20 to 25 fields (greater than or equal to 200 spermatozoa) were evaluated. Correlations between measurements of sperm motion and fertility were studied using cryopreserved semen from two fertility trials. For the first, 75-day nonreturn rate data for 20 samples of bull semen (10 bulls) were not significantly correlated with evaluations made by CellSoft. For the second fertility trial, the competitive fertility index (a measure of relative fertility) for nine bulls was correlated (r greater than or equal to 0.68; P less than 0.05) with percent motile spermatozoa, linear velocity and straight-line velocity. Multiple correlations based on six characteristics evaluated by CellSoft, at 0 or 1.5 hours, and the competitive fertility index were greater than or equal to 0.94. Based on the latter data, the system may facilitate prediction of the relative fertility of bull spermatozoa.

Typhoon Structure as Revealed by Aircraft Reconnaissance. Part I: Data Analysis and Climatology

Abstract: This is the first of two papers describing the structure of northwest Pacific tropical cyclones as revealed by U.S. Air Force aircraft reconnaissance. This first paper describes the background philosophy for this research, the types of flight missions flown, data reduction procedures, and the general climatological characteristics of this region's typhoons and tropical storms. Analysis has been performed on 700 mb aircraft data from ova 500 Guam-based, WC-130 aircraft missions into 66 tropical cyclones, two-thirds of which were of typhoon intensity sometime during their life cycle. All flight missions followed similar standardized flight tracks. Data are analyzed for the three seasons of 1980–82. This aircraft dataset is unique in providing wind and pressure-height profile information at radial resolutions of 0.5° (56 km) from a tropical cyclone's center out to 4° radius. This allows a cyclone°s outer-core wind strength to be measured in relation to its inner-core intensity. The varying relations...

An overview of the SR language and implementation

Abstract: SR is a language for programming distributed systems ranging from operating systems to application programs. On the basis of our experience with the initial version, the language has evolved considerably. In this paper we describe the current version of SR and give an overview of its implementation. The main language constructs are still resources and operations. Resources encapsulate processes and variables that they share; operations provide the primary mechanism for process interaction. One way in which SR has changed is that both resources and processes are now created dynamically. Another change is that inheritance is supported. A third change is that the mechanisms for operation invocation—call and send—and operation implementation—proc and in—have been extended and integrated. Consequently, all of local and remote procedure call, rendezvous, dynamic process creation, asynchronous message passing, multicast, and semaphores are supported. We have found this flexibility to be very useful for distributed programming. Moreover, by basing SR on a small number of well-integrated concepts, the language has proved easy to learn and use, and it has a reasonably efficient implementation.

Apical localization of K+ channels in taste cells provides the basis for sour taste transduction.

Abstract: Previous studies have shown that mudpuppy taste receptor cells respond to sour taste stimuli (weak acids) with depolarizing receptor potentials or action potentials that are blocked by the K+ channel blocker tetraethylammonium. Voltage-clamp recordings from isolated taste cells indicated that taste receptor cells exhibit a variety of voltage-dependent conductances and that acids reduce a voltage-dependent K+ current. Since taste stimuli are restricted to the apical surface of the intact tongue, only 1-2% of the taste receptor cell surface is exposed to chemical stimuli. Thus, modification of a K+ conductance would be an effective transduction mechanism in receptor cells only if the majority of K+ channels were located on the apical membrane. We have used a combination of "loose-patch" and whole-cell recording methods to map the distribution of voltage-sensitive K+ and Na+ channels on dissociated Necturus maculosus taste cells. We report here that the K+ conductance is approximately equal to 50-fold greater on apical membrane than on basolateral membrane, whereas the Na+ conductance is distributed evenly. The marked nonuniformity of the voltage-sensitive K+ conductance, together with the block of this conductance by sour stimuli, indicates that K+ current modulation is the mechanism of sour taste transduction.

Canine osteosarcoma. Treatment by amputation versus amputation and adjuvant chemotherapy using doxorubicin and cisplatin.

Abstract: Osteosarcoma was diagnosed in 38 dogs. Thirty-six tumors originated from the appendicular skeleton and two from the axial skeleton. Nineteen of the dogs were treated with amputation alone, and 19 were treated with amputation and adjuvant chemotherapy consisting of doxorubicin and cisplatin. The 36 dogs with appendicular osteosarcoma had complete amputation of the affected limb, whereas the two dogs with osteosarcoma of the axial skeleton had an en bloc resection. The mean survival of the 19 dogs treated with amputation alone was 218 days (median, 175 days). Ten dogs were alive at 6 months and four survived 1 year. None of the dogs survived longer than 16 months. Radiographic lesions consistent with metastatic osteosarcoma were seen after surgery in the nine dogs in which radiographs were taken. The mean survival of the 19 dogs treated with amputation and chemotherapy was 415 days (median, 300 days). Drug toxicity was not observed. Fifteen dogs were alive at 6 months, seven dogs were alive at 1 year, 5 dogs were alive at 2 years, and two dogs were alive at 3 years or longer. One dog is alive and well at 25 months. Radiographic lesions suggestive of metastatic osteosarcoma developed in the other 18 dogs. The 19 dogs treated with amputation and chemotherapy had significantly longer survival times than the dogs treated with amputation alone.