Showing papers by "University of Nevada, Reno published in 1989"

Shared values: impact on staff nurse job satisfaction and perceived productivity.

Abstract: A nationwide study on the impact of shared values on staff nurse job satisfaction and perceived productivity was done in 24 hospitals under different auspices, some of which were also Magnet Hospitals. Data were obtained from a 25% random sample of the staff nurse population (N = 2,336), 58% of the head nurse group, 65% of the clinical experts, and 66% of the top management. Staff nurses and clinical experts had more value congruence than did staff nurses and head nurses. A significant inverse correlation was found between value congruence and nurse job satisfaction and quality care. Explanations of the finding center on recent role changes for both staff nurses and head nurses, power differential, and evolving clarity of the staff nurse role. A serendipitious finding was that staff nurses reported fewer factors as important to their job satisfaction and perceived environment conducive to quality patient care than did other members of the nursing department. However, factors important to staff nurses were very important.

The verbal action of the listener as a basis for rule-governance.

Abstract: In the traditional behavior-analytic account, most psychologically significant behavior (i.e., that of whole organisms in and with a context) is thought ultimately to be contingency shaped. An important subset of this behavior is rule-governed (Skinner, 1966, 1969, Chapter 6). Skinner (1969, p. 146) provides a worthwhile example. An outfielder moves to catch a ball. Following its trajectory, he moves under it and grasps it with his glove. Skinner views this event as contingency shaped. The outfielder is simply responding, as he has done hundreds of times before, based on the effects his behavior has on moving toward the ball. Skinner contrasts this with the ship captain moving to “catch” a descending satellite. The trajectory of the satellite is analyzed in detail. Mathematical models are consulted that take into account a host of factors such as wind speed and drag coefficients. Its place of impact is predicted and approached. This behavior is not controlled directly by the past consequences of the captain trying to catch satellites. The behavior has not had an opportunity to be shaped by such consequences—it is controlled by rules.

Autonomic regulation of a chloride current in heart

Abstract: In isolated heart cells, beta-adrenergic receptor stimulation induced a background current that was suppressed by simultaneous muscarinic receptor stimulation. Direct activation of adenylate cyclase with forskolin also elicited this current, suggesting regulation by adenosine 3',5'-monophosphate (cAMP). This current could be recorded when sodium, calcium, and potassium currents were eliminated by channel antagonists or by ion substitution. Alteration of the chloride equilibrium potential produced changes in the reversal potential expected for a chloride current. Activation of this chloride current modulated action potential duration and altered the resting membrane potential in a chloride gradient-dependent manner.

Spontaneous electrical activity of interstitial cells of Cajal isolated from canine proximal colon

Abstract: Interstitial cells of Cajal (ICC) have been suggested as pacemaker cells in the gastrointestinal tract. A method was developed to isolate ICC from the slow-wave pacemaker region of the canine proximal colon. These cells were identified under phase-contrast microscopy, and their identity was verified by comparing their ultrastructure with the morphology of ICC in situ. Patch-clamp experiments demonstrated that these cells are excitable; voltage-dependent inward and outward currents were elicited by depolarization. Inward current transients were identified as calcium currents. A portion of the outward current appears to be due to Ca2+-activated K channels commonly expressed in these cells. ICC were also spontaneously active, generating electrical depolarizations similar in waveform to slow-wave events of intact colonic muscles. These findings are consistent with the hypothesis that ICC initiate rhythmicity in the colon.

What best predicts computer proficiency

Abstract: Identifying variables that predict computer aptitude can help educators and employers target potential students and employees. The authors examine a number of possible explanatory variables including demographic profiles, high school achievements, prior computer training and experience, cognitive styles, and problem-solving abilities.

Nonhumans have not yet shown stimulus equivalence.

Abstract: Recently, two published articles have reported finding stimulus equivalence in nonhumans. One suggested that equivalence was due to the mediation of names. The procedure used trained all components of all tested relations. Because nothing was derived, the defining characteristics of equivalence were not achieved. In the second study a definition of equivalence was proposed that fails to distinguish functional stimulus classes from equivalence classes. The resulting data are not clearly relevant to stimulus equivalence in Sidman's sense of the term. Stimulus equivalence has not yet been shown in nonhumans.

Ca2+-activated K channels of canine colonic myocytes

Abstract: K channels in enzymatically dispersed circular smooth muscle cells from the canine proximal colon were studied with the patch-clamp technique. The most prominent channel in cell-attached and excised, inside-out patches was a K channel, which had slope conductances of approximately 100 pS at a holding potential of 0 mV in a physiological K+ gradient and approximately 200 pS in symmetrical 140 mM K+ solutions. The relative permeabilities of the channel for monovalent cations were 1.0 K+:0.5 Rb+: less than 0.07 Li+:less than 0.07 Na+. The channels were activated by potential and intracellular Ca2+. At Ca2+ concentrations less than 10(-7) M, channel openings were rare except at very positive potentials. At Ca2+ concentrations between 10(-7) and 10(-6) M the probability of channel opening increased steeply, and the voltage for channel activation shifted to a negative potential range, which cells experience during electrical slow wave events in situ. The effect of Ca2+ on the open-state probability of single channels was mainly due to a decrease in mean close time. Channels were blocked by 1 mM tetraethylammonium applied to the outside of the patch but up to 10 mM tetraethylammonium applied to the inside of the patch, and 4-aminopyridine applied to either side did not block the channel. The data suggest that this channel mediates a current important in the termination of electrical slow waves, which are the primary excitable event in colonic circular muscles.

Liberty, Manners, and Politeness in Early Eighteenth-Century England

Abstract: In the early eighteenth century, the language of politeness became a major fixture of English discourse. Centring on the term ‘politeness’ and consisting of a vocabulary of key words (such as ‘refinement’, ‘manners’, ‘character’, ‘breeding’, and ‘civility’) and a range of qualifying attributes (‘free’, ‘easy’, ‘natural’, ‘graceful’, and many others), the language was used to make a wide range of objects intelligible. Though the word ‘polite’ had been in the English language from at least the fifteenth century, denoting the state of being polished or neat in quite literal and concrete ways, the term entered on its significant career only in the mid-seventeenth century, when it began to convey the meanings of studied social behaviour of the sort inspired by and associated with princely courts. However, in the late seventeenth and early eighteenth century, ‘politeness’ grew to cover a range of meanings, considerably freed from the initial association with courts. Several broad categories of usage of the term ‘polite’ are indicative: as a behavioural and moral standard for members of an elite (e.g. ‘polite gentlemen’, ‘polite ladies’, ‘polite society’, ‘polite conversation’); as an aesthetic standard for many kinds of human artifacts and products (e.g. ‘polite arts’, ‘polite towns’, ‘polite learning’, ‘polite buildings’); and as a way of generalizing about and characterizing society and culture (‘polite age’, ‘polite nation’, ‘polite people’). In the latter usage, ‘politeness’ was frequently deployed retrospectively as an attribute of classical civilizations. ‘Politeness’ helped recast the renaissance model of history, in which modernity was separated from its true ancestor, the ancient world, by the vast dark gulf of the middle ages: the ‘politest’ nations were ancient Greece and ancient Rome; the ‘politest’ ages, the spells of Hellenic and Roman creativity.

Participation of Ca currents in colonic electrical activity.

Abstract: Canine colonic myocytes were studied with the whole cell patch-clamp technique. In 1.8 mM Ca2+, inward currents were evoked by depolarization. Currents activated positive to -50 mV, peaked at approximately 0 mV, and reversed at approximately +50 mV. Inward current was potentiated by high external Ca2+ concentration and BAY K8644 and was decreased by low external Ca2+, nifedipine, and Mn2+, indicating that the current was carried by Ca2+. Overlap of the activation-inactivation properties indicated a "window current" range (-40 to -20 mV) in which inward current might be sustained for long durations at potentials achieved during electrical slow waves. Voltage-clamp protocols simulating physiological depolarizations elicited sustained inward currents. Maximum changes in intracellular Ca2+ resulting from sustained inward currents were calculated, which suggested that depolarizations at the level of slow waves may increase cell Ca2+ sufficiently to cause contraction. The data suggest that electrical slow waves in colonic myocytes are due in part to inward Ca current. This current appears to be sufficient to explain the relationship between slow waves and contractions and provides an explanation for the mechanical threshold in colonic muscles.

On the significance of C3—C4 intermediate photosynthesis to the evolution of C4 photosynthesis

Abstract: Evidence is drawn from previous studies to argue that C3—C4 intermediate plants are evolutionary intermediates, evolving from fully-expressed C3 plants towards fully-expressed C4 plants. On the basis of this conclusion, C3—C4 intermediates are examined to elucidate possible patterns that have been followed during the evolution of C4 photosynthesis. An hypothesis is proposed that the initial step in C4-evolution was the development of bundle-sheath metabolism that reduced apparent photorespiration by an efficient recycling of CO2 using RuBP carboxylase. The CO2-recycling mechanism appears to involve the differential compartmentation of glycine decarboxylase between mesophyll and bundle-sheath cells, such that most of the activity is in the bundlesheath cells. Subsequently, elevated phosphoenolpyruvate (PEP) carboxylase activities are proposed to have evolved as a means of enhancing the recycling of photorespired CO2. As the activity of PEP carboxylase increased to higher values, other enzymes in the C4-pathway are proposed to have increased in activity to facilitate the processing of the products of C4-assimilation and provide PEP substrate to PEP carboxylase with greater efficiency. Initially, such a ‘C4-cycle’ would not have been differentially compartmentalized between mesophyll and bundlesheath cells as is typical of fully-expressed C4 plants. Such metabolism would have limited benefit in terms of concentrating CO2 at RuBP carboxylase and, therefore, also be of little benefit for improving water- and nitrogen-use efficiencies. However, the development of such a limited C4-cycle would have represented a preadaptation capable of evolving into the leaf biochemistry typical of fully-expressed C4 plants. Thus, during the initial stages of C4-evolution it is proposed that improvements in photorespiratory CO2-loss and their influence on increasing the rate of net CO2 assimilation per unit leaf area represented the evolutionary ‘driving-force’. Improved resourceuse efficiency resulting from an efficient CO2-concentrating mechanism is proposed as the driving force during the later stages.

Activation of C3 and binding to Aspergillus fumigatus conidia and hyphae.

Abstract: Complement activation by Aspergillus fumigatus may play a crucial role in stimulating binding and killing of this organism by phagocytes. We examined the amount and type of C3 deposited on resting conidia, swollen conidia, and hyphae of A. fumigatus after incubation in pooled human serum. All three life forms of A. fumigatus were potent activators of the complement cascade, with deposition on the organisms of similar amounts of C3 per unit of surface area. The rate of deposition was slowest for resting conidia, although maximal deposition was still achieved within 40 min. The roles of the alternative and classical pathways were assessed by use of serum chelated with magnesium EGTA [magnesium ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid] and with an alternative pathway reconstituted from the six purified alternative-pathway proteins. Complement activation by resting conidia was mediated by the alternative pathway. In contrast, there was a progressive dependence on the classical pathway as the fungal particles matured into swollen conidia and then hyphae. Treatment with hydroxylamine, which disrupts ester linkages, removed 89 to 95% of the C3 bound to all three forms of A. fumigatus. This released C3 contained a mixture of C3b and iC3b, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography. These data demonstrate that although all three forms of A. fumigatus are potent activators of the complement system, the transition from resting conidia to swollen conidia to hyphae results in progressive changes in the manner in which the fungal particles interact with the complement system. The lack of participation of the classical pathway in complement activation by resting conidia may have important implications regarding their ability to effectively stimulate phagocytes.

Effects of dietary fish oil on human mammary carcinoma and on lipid-metabolizing enzymes.

Abstract: The growth rate of a human mammary carcinoma, MX-1, was significantly reduced in athymic “nude” mice fed fish oil. Tumors from the fish oil-fed animals also showed a greater sensitivity to two anti-neoplastic agents, mitomycin C and doxorubicin. Mitochondria were isolated from control livers, host livers and tumors from fish oil-and corn oil-fed animals, and increased levels of 20∶5n−3 and 22∶6n−3 were found in mitochondrial lipids in all three tissues from the fish oil-fed animals. To investigate the effect of dietary n−3 fatty acids on lipid metabolism, the activity of the acyl-CoA:carnitine acyltransferase and three acyl-CoA desaturases were measured. Carnitine acyltransferase activity toward all four acyl-CoA substrates tested was markedly increased in mitochondria from liver by feeding fish oil. In mitochondria from tumors, feeding fish oil resulted in an increased activity toward only 18∶3n−3. These data suggest that fish oil may induce an increase in the oxidation of fatty acids. The Δ9-desaturase activity was decreased in microsomes from liver and tumor from fish oil-fed animals. However, both the Δ6 and Δ5 desaturases were increased in tumor and in control liver as a result of feeding fish oil. The Δ5 desaturase was not altered in microsomes from the host animals. The effect of fish oil on the Δ5 and Δ6 desaturases may involve alterations to metabolism of specific polyunsaturated fatty acids especially in the tumor tissue.

Water use efficiency and carbon isotope composition of plants in a cold desert environment

Abstract: The effects of the availabilities of water and nitrogen on water use efficiency (WUE) of plants were investigated in a sagebrush steppe. The four species studied wereArtemisia tridentata (shrub),Ceratoides lanata (suffrutescent shrub),Elymus lanceolatus (rhizomatous grass), andElymus elymoides (tussock grass). Water and nitrogen levels were manipulated in a two-by-two factorial design resulting in four treatments: control (no additions), added water, added nitrogen, and added water and nitrogen. One instantaneous and two long-term indicators of WUE were used to testa priori predictions of the ranking of WUE among treatments. The short-term indicator was the instantaneous ratio of assimilation to transpiration (A/E). The long-term measures were 1) the slope of the relationship between conductance to water vapor and maximum assimilation and 2) the carbon isotope composition (δ13C) of plant material. Additional water decreased WUE, whereas additional nitrogen increased WUE. For both A/E and δ13C, the mean for added nitrogen alone was significantly greater than the mean for added water alone, and means for the control and added water and nitrogen fell in between. This ranking of WUE supported the hypothesis that both water and nitrogen limit plant gas exchange in this semiarid environment. The short- and long-term indicators were in agreement, providing evidence in support of theoretical models concerning the water cost of carbon assimilation.

Macroscopic K+ currents in single smooth muscle cells of the rabbit portal vein.

Abstract: 1. Single smooth muscle cells isolated from rabbit portal vein were voltage clamped at room temperature using the whole-cell configuration of the patch-clamp technique. These cells exhibited a mean resting potential of -47.9 mV and a mean input resistance of 376 M omega. 2. Using small tip diameter micropipettes (to avoid dialysis of the cells), depolarizing voltage-clamp pulses from a holding potential of -50 mV elicited two distinct outward currents: a quasi-instantaneous background current and a time-dependent current that did not appear to inactivate (delayed rectifier). Upon return to the holding potential, an outward tail current decaying back to the holding current was observed. 3. The time course of development of the tail current as estimated from envelopes of tail current protocols followed the kinetics of activation of the delayed rectifier elicited during the preceding test pulse. The tail current reversed close to the equilibrium potential for K+ ions indicating that it is mainly carried by potassium ions. 4. Using large tip diameter micropipettes to internally dialyse the cells (EGTA = 0.1 mM; ATP = 5 mM), two additional outward currents having transient kinetics were revealed: a smooth transient outward current (Ito) and spontaneous transient outward currents (STOCs). Ito was found to be mainly selective for K+ ions and exhibited voltage-dependent inactivation with half-maximal availability near -40 mV. 5. Removal of calcium from the bathing solution significantly reduced the background current and abolished both Ito and STOCs. The delayed rectifier current appeared to be insensitive to this procedure. The two types of transient outward currents were never recorded when EGTA was elevated to 5 mM inside the micropipette whereas the background and delayed rectifier currents were not affected. These results suggested that Ito and the spontaneous transient outward currents are activated by internal calcium. 6. External application of TEA (0.5-20 mM) blocked all four outward currents. Calcium replacement by barium significantly reduced the background current and Ito, and had small effects on the delayed rectifier current. When potassium was replaced with caesium (130 mM) and TEA (20 mM) inside the pipette, none of the outward currents described was ever observed. In about 60% of the cells dialysed with this solution a small inward Ca2+ current was revealed. 7. External application of caffeine (5 mM) abolished STOCs in cells in which this activity was present under control conditions. In cells lacking this type of activity under control conditions caffeine induced and later abolished this type of current.(ABSTRACT TRUNCATED AT 400 WORDS)

CAMEL ratings and the CD market

Abstract: This article investigates the relationship between CD rates as a measure of bank risk and the confidential CAMEL scores assigned to a bank as a result of an onsite examination. CAMEL ratings determine whether a bank is placed on the “problem list” and expresses the examiner's belief that the bank should be subjected to enhanced surveillance. In the view of regulators, CAMEL ratings are based on inside information and hence should be confidential. The empirical results in this article suggest that CAMEL ratings are primarily proxies for available market information about the quality of a bank.

Paradigm Conflict, Types of Conversion, and Conversion Theories

Abstract: The present paper identifies two predominant perspectives of researchers investigating new religious conversion: Agency Assigned to the Convert (active versus passive) and Level of Analysis (intraindividual versus interindividual). A typology of both types and theories of religious conversion is proffered. The Agency perspective is paradigmatic and dichotomizes conversion research. The level of analysis perspective is subparadigmatic and differentiates types and theories of conversion within each of the two larger paradigmatic perspectives. It is argued that the present typology facilitates: 1) an appreciation of the underlying metatheoretical assumptions and conceptual priorities of contemporary conversion researchers, 2) an integrated social psychological understanding of diverse conversion experiences, and 3) an appreciation of how the tension and conflict between the two paradigmatic perspectives tends to reflect and reproduce the larger tension and conflict between "status quo" and "new society" groups in contemporary American society. Richardson (1985a) has argued that a new paradigm has emerged in contemporary studies of religious conversion and is most apparent in conversion studies with either a social psychological or sociological emphasis. The basis for this argument can be seen in the way that conversion is conceptualized. In the old paradigm, conversion is generally viewed in passivist and deterministic terms, whereas in the new paradigm conversion is generally explained from the standpoint of active agency (i.e., self-directed behavior), personal choice, meaning, and negotiation. In a very real sense, the "old" and "new" paradigms provide diametrically opposed ways of conceptualizing the same phenomena.

Molecular basis for defective secretion of the Z variant of human alpha-1-proteinase inhibitor: secretion of variants having altered potential for salt bridge formation between amino acids 290 and 342.

Abstract: Human alpha-1-proteinase inhibitor (A1PI) deficiency, associated with the Z-variant A1PI (A1PI/Z) gene, results from defective secretion of the inhibitor from the liver. The A1PI/Z gene exhibits two point mutations which specify amino acid substitutions, Val-213 to Ala and Glu-342 to Lys. The functional importance of these substitutions in A1PI deficiency was investigated by studying the secretion of A1PI synthesized in COS cells transfected with A1PI genes altered by site-directed mutagenesis. This model system correctly duplicates the secretion defect seen in individuals homozygous for the A1PI/Z allele and shows that the substitution of Lys for Glu-342 alone causes defective secretion of A1PI. The substitution of Lys for Glu-342 eliminates the possibility for a salt bridge between residues 342 and 290, which may decrease the conformational stability of the molecule and thus account for the secretion defect. However, when we removed the potential to form a salt bridge from the wild-type inhibitor by changing Lys-290 to Glu (A1PI/SB-290Glu), secretion was not reduced to the 19% of normal level seen for A1PI/Z-342Lys; in fact, 75% of normal secretion was observed. When the potential for salt bridge formation was returned to A1PI/Z-342Lys by changing Lys-290 to Glu, only 46% of normal secretion was seen. These data indicate that the amino acid substitution at position 342, rather than the potential to form the 290-342 salt bridge, is the critical alteration leading to the defect in A1PI secretion.

Stimulus equivalence and rule following

Abstract: The present study examined the occurrence of a novel behavior pattern with respect to a novel configuration of stimuli enabled by the participation of those stimuli in equivalence classes. In Experiment 1, functional substitutabilities were established via equivalence between two independent sets of musical stimuli. Aspects of stimuli from the two sets were then compounded to produce novel stimulus configurations. Behavioral components enabled by each separate class combined to produce novel musical performances and accurate descriptions of them. In Experiment 2, the impact of experimenter-provided names for equivalence classes on the musical performances was investigated in naive subjects by establishing similar classes without experimenter-provided names. The results indicated few differences in the playing performances under these conditions. These experiments demonstrated a possible method for the analysis of rule following.

Light adaptation/acclimation of photosynthesis and the regulation of ribulose-1,5-bisphosphate carboxylase activity in sun and shade plants.

Abstract: The consequences of light adaptation and acclimation of photosynthesis on photosynthetic nitrogen use efficiency (NUE), particularly as it relates to the efficiency of ribulose-1,5-bisphosphate carboxylase (Rubisco) use in photosynthetic CO2 assimilation, was studied in the sun species Glycine max and the shade species Alocasia macrorrhiza. Both G. max and A. macrorrhiza were found to possess the capacity for light acclimation of CO2 assimilation, but over distinctly different ranges of photon flux density (PFD). For each species, light acclimation of photosynthesis had little effect on the rate of photosynthesis per unit Rubisco protein or the light response of Rubisco carbamylation and CA 1P metabolism. In contrast, photosynthesis per unit Rubisco protein was significantly higher in G. max than in A. macrorrhiza, due in part to a lower total (fully carbamylated) molar activity (activity per unit enzyme) of A. macrorrhiza Rubisco than that of G. max. Comparison of the light response of Rubisco regulatory mechanisms between G. max and A. macrorrhiza indicated some degree of adaptation, such that carbamylation was higher and CA 1P levels lower at lower PFDs in the shade species than the sun species. However, this adjustment was not sufficient for Rubisco in low light grown A. macrorrhiza to be fully active at the growth PFD. Photosynthesis in A. macrorrhiza appeared to become RuBP regeneration-limited at lower PFDs than G. max, and this was probably the determinant of the light saturated rate of photosynthesis in the shade species. The low efficiency of Rubisco use in A. macrorrhiza was a major contributing factor to its five- to sixfold lower photosynthetic NUE than G. max. Shade species such as A. macrorrhiza appear to make far from maximal use of Rubisco protein N.

Knowledge-Based Systems for Management Decisions

Abstract: Knowledge-based systems for management decisions , Knowledge-based systems for management decisions , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Glutathione peroxidase activity in insects: A reassessment

Abstract: In vertebrate species, cytotoxic H2O2 and other lipid or organic hydroperoxides (ROOH) formed in aerobic metabolism are removed by a selenoprotein, glutathione peroxidase (GPOX). The GPOX activity in most rat tissues ranges from 100 to 1,000 units (1 unit = 1 nmol NADPH oxidized·mg protein−1·min−1), except for muscles (20–30 units). In contrast, GPOX activities of two strains of the housefly (Musca domestica), cabbage looper (Trichoplusia ni), southern armyworm (Spodoptera eridania), and black swallowtail butterfly (Papilio polyxenes), were found to be in the range 2–12 units. Trivial GPOX activity was detected in the confused flour beetle (Tribolium confusum). In the earthworm (Lumbricus terrestris), banana slug (Ariolimax columbianus), and market squid (Loligo opalescens), the GPOX activity ranged from 1 to 5 units. Tissue selenium concentrations were about 500–1,000 ppb for adult M. domestica, 600 ppb in T. confusum, 32 ppb in T. ni, 17 ppb in S. eridania, and 31 ppb in P. polyxenes larvae. The form of selenium incorporated at such high levels in tissues of invertebrates such as M. domestica remains an unresolved issue. Peroxidase activity of non-selenium glutathione-S-transferase (GT) against ROOH may compensate for the low GPOX activity. Catalase (CAT) has high activity and wide subcellular distribution in insects. This may be an evolutionary adaptation to GT's inability to catalyze the reduction of H2O2. The GT's peroxidase and CAT activities were not assessed for other invertebrate species, and warrants an investigation due to their reported low GPOX levels.

Activation and binding of opsonic fragments of C3 on encapsulated Cryptococcus neoformans by using an alternative complement pathway reconstituted from six isolated proteins.

Abstract: Encapsulated Cryptococcus neoformans yeast cells are potent activators of the complement system. We examined the interaction of the yeast cells with an alternative complement pathway reconstituted from isolated factor D, factor B, factor H, factor I, C3, and properdin. Incubation of encapsulated cryptococci with the reconstituted pathway led to activation and binding of C3 fragments to the yeast cells that was quantitatively and qualitatively identical to that observed with normal human serum. Incubation with either normal serum or a mixture of isolated proteins led to binding of 4 x 10(7) to 5 x 10(7) C3 molecules to the yeast cells. The kinetics for activation and binding of C3 were identical, with maximum binding observed after a 20-min incubation. Immunoglobulin G was not needed for optimal activation kinetics. C3 fragments eluted from the yeast cells by treatment with hydroxylamine and subsequent analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis demonstrated the presence primarily of iC3b on yeast cells incubated with either normal serum or the reconstituted pathway. Ultrastructural examination of the opsonized yeast cells showed that the cryptococcal capsule was the site for binding of C3 activated from normal serum or the reconstituted pathway, with a dense accumulation of C3 at the periphery of the capsule. Thus, incubation of encapsulated cryptococci in the reconstituted pathway led to deposition of opsonic complement fragments at a site that was appropriate for interaction with phagocyte receptors. Cryptococci opsonized with the reconstituted pathway showed a markedly enhanced interaction with cultured human monocytes compared with unopsonized yeast cells, indicating that the alternative pathway alone is opsonic for yeast cells. However, the results indicate that additional serum factors are needed for optimal opsonization of yeast cells because a 35% reduction in the number of cryptococci bound to macrophages was observed with cryptococci opsonized with the reconstituted pathway compared with that observed when yeast cells were opsonized with normal serum.

Robust Control of Robotic Manipulators

Abstract: This paper introduces a new control system design methodology that allows the use of linearly controlled manipulators in fast, more complex maneuvers. This is made possible by guaranteeing a prescribed degree of relative stability while constraining the system state variables and inputs. The closed-loop linear system is also assigned desirable eigenvectors. The robustness of the system is evaluated using a new measure of robustness. The design methodology is applied to a 2-D.O.F. robotic manipulator. Simulation results demonstrate that the final design must be a compromise between robustness, relative stability, and other considerations.

Comparative aspects of propionate metabolism.

Abstract: 1. 1. The catabolism of propionate has been studied extensively in vertebrates and the major pathway has been shown to be its derivatization to propionyl-CoA, carboxylation to d -methylmalonyl-CoA, isomerization to L -methylmalonyl-CoA and then conversion to succinyl-CoA via a vitamin B12 dependent methylmalonyl-CoA mutase. 2. 2. By contrast, in all insect species studied to date, many of which do not contain detectable levels of vitamin B12, the major metabolic pathway of propionate is its conversion to 3-hydroxypropionate and then to acetate. Carbon-3 of propionate becomes the carboxyl carbon of acetate and carbon-2 of propionate becomes the methyl carbon of acetate. 3. 3. A number of species of non-insect arthropods and other invertebrates contain relatively high levels of vitamin B12 and catabolize propionate by the same pathway as that of vertebrates. Under anoxic conditions, some invertebrates, including bivalves, convert succinate to propionate. 4. 4. In plants, evidence has been presented for the metabolism of propionate to both acetate and succinate. Micro-organisms posses a myriad of pathways by which they produce and catabolize propionate.

Perennially ice-covered Lake Hoare, Antarctica: physical environment, biology and sedimentation

Abstract: Lake Hoare (77 degrees 38' S, 162 degrees 53' E) is a perennially ice-covered lake at the eastern end of Taylor Valley in southern Victoria Land, Antarctica. The environment of this lake is controlled by the relatively thick ice cover (3-5 m) which eliminates wind generated currents, restricts gas exchange and sediment deposition, and reduces light penetration. The ice cover is in turn largely controlled by the extreme seasonality of Antarctica and local climate. Lake Hoare and other dry valley lakes may be sensitive indicators of short term (< 100 yr) climatic and/or anthropogenic changes in the dry valleys since the onset of intensive exploration over 30 years ago. The time constants for turnover of the water column and lake ice are 50 and 10 years, respectively. The turnover time for atmospheric gases in the lake is 30-60 years. Therefore, the lake environment responds to changes on a 10-100 year timescale. Because the ice cover has a controlling influence on the lake (e.g. light penetration, gas content of water, and sediment deposition), it is probable that small changes in ice ablation, sediment loading on the ice cover, or glacial meltwater (or groundwater) inflow will affect ice cover dynamics and will have a major impact on the lake environment and biota.