Showing papers by "University of Saskatchewan published in 1992"

Assessing Avian Diets Using Stable Isotopes I: Turnover of 13C in Tissues

Abstract: Studies of birds that use stable isotopes as dietary tracers require estimates of how quickly stable isotopes in tissues are replaced by isotopes derived from the diet. However, isotopic turnover rates in animals in general, and birds in particular, are poorly understood. We established the turnover rates of '3C in tissues of grown Japanese Quail (Coturnixjaponica) by switching the diet of an experimental group from a wheat-based (C3) diet to a corn-based (C4) diet and sampled tissues periodically for 212 days. An exponential model described patterns of isotopic turnover in all tissues. Turnover rates for quail tissues were ranked liver > blood > muscle > bone collagen with the half life of carbon ranging from 2.6 days in liver to 173.3 days in bone collagen. A similar diet-switch experiment was conducted on captive American Crows (Corvus brachyrhynchos) and feather samples were assayed isotopically. Stable isotope values of crow feathers reflected diet during periods of growth. We suggest that stable isotope analysis could be used to determine relative contributions of endogenous and exogenous nutrient sources for feather growth and egg production in captive and wild birds.

The Use of β-Agonists and the Risk of Death and near Death from Asthma

Abstract: Background. Morbidity and mortality from asthma appear to be increasing, and it has been suggested that medications used to treat asthma are contributing to this trend. We investigated a possible association between death or near death from asthma and the regular use of β2-agonist bronchodilators. Methods. Using linked health insurance data bases from Saskatchewan, Canada, we conducted a matched case–control study of subjects drawn from a cohort of 12,301 patients for whom asthma medications had been prescribed between 1978 and 1987. We matched 129 case patients who had fatal or near-fatal asthma with 655 controls (who had received medications for asthma but had not had fatal or near-fatal events) with respect to region of residence, age, receipt of social assistance, and previous hospitalization for asthma. Results. The use of β-agonists administered by a metered-dose inhaler was associated with an increased risk of death from asthma (odds ratio, 2.6 per canister per month; 95 percent confidence...

Assessing Avian Diets Using Stable Isotopes II: Factors Influencing Diet-Tissue Fractionation

Abstract: Studies using stable-isotope analysis to infer diet require a knowledge of how stable-isotope ratios in consumer tissues are related to dietary values. We determined 61'3C and 6'5N diet-tissue fractionation factors for blood, liver, muscle, bone collagen and feathers of domestic chickens (Gallus gallus), Japanese Quail (Coturnix japonica) and Ring-billed Gulls (Larus delawarensis) and for blood and feather samples of adult Peregrine Falcons (Falco peregrinus) raised on known isotopic diets. In most cases tissues were enriched in 613C and 615N compared to diet. However, fractionation values differed among species, diets, and tissue types and this variation must be considered in isotope dietary studies. We found little evidence that isotopic fractionation factors are influenced by age in adult birds and provide fractionation factors appropriate for granivores feeding in a C-3 biome and for higher trophic-level piscivores and carnivores. American Crows (Corvus brachyrhynchos) raised on a perch diet grew faster and showed lower nitrogen diet-tissue fractionation values than crows raised on a plant-based diet. We suggest that nutritional stress caused substantial increases in diet-tissue fractionation values due either to: (1) mobilization and redeposition of proteins elsewhere in the body; or (2) amino acid composition changes in tissues.

Systematic study of insulator-metal transitions in perovskites RNiO3 (R=Pr,Nd,Sm,Eu) due to closing of charge-transfer gap.

Abstract: The detailed behavior of the phase transitions was mapped out for the series R${\mathrm{NiO}}_{3}$ as a function of the rare earth (R). A sharp insulator-metal transition is observed, which depends strongly on R.Forsmall$R it occurs at a higher temperature than the antiferromagnetic ordering (measured by muon-spin relaxation). By increasing either the temperature or the size of R, an insulator-metal transition is observed, most probably caused by the closing of the charge-transfer gap, induced by increase in the electronic bandwidth.

Analytical Methods Validation: Bioavailability, Bioequivalence, and Pharmacokinetic Studies

Abstract: 0 This is a summary report of the conference on "Analytical Methods Validation: Bioavailability, Bioequivalence and Pharmacokinetic Studies." The conference was held from December 3 to 5,1990, in the Washington, D.C., area and was sponsored by the American Association of Pharmaceutical Scientists, the US. Food and Drug Administration, Federation International Pharmaceutique, Health Protection Branch (Canada), and the Association of Official Analytical Chemists. The report presents our assessment of the major agreements and issues discussed at the conference. The report is also intended to provide guiding principles for validation of analytical methods used in bioavailability, bioequivalence, and pharmacokinetics studies in humans and animals. The objectives of the conference were as follows: (1) to reach a consensus on what should be required in analytical methods validation and the procedures to establish validation; (2) to determine processes of application of the validation procedures in bioavailability, bioequivalence, and pharmacokinetics studies; and (3) to develop a report on analytical methods validation that may be referred to in developing future formal guidelines. Acceptable standards for documenting and validating analytical methods with regard to processes, parameters, or data treatments are discussed because of their importance in assessing pharmacokinetic, bioavailability, and bioequivalence studies. Other topics that were considered essential in the conduct of pharmacokinetic studies or in establishing bioequivalency criteria, including measurement of drug metabolites and stereoselective determinations, are also discussed. ___ -. ~. ~ _ _ Analytical methods that are used for the quantitative determination of drugs and their metabolites in biological samples play a significant role in evaluation and interpretation of bioavailability, bioequivalence, and pharmacokinetic data. It is essential to use well-characterized and fully validated analytical methods to yield reliable results that can be satisfactorily interpreted. Analytical methods and techniques are constantly being changed and improved; in many instances, these methods are at the cutting edge of the technology. It is also important to emphasize that each analytical technique has its own characteristics, which will vary from drug to drug. Moreover, the appropriateness of the technique may be influenced by the ultimate objective of the study. Specific validation criteria are needed for methods intended for analysis of each analyte (drug and/or metabolite). Although validation of each method will be independent of those of other methods, there may be situations in which comparison of the methods will be necessary (e.g., when more than one method has been used in a long-term study). When sample analysis is conducted at more than one site, it is necessary to validate the analytical methodb) at each site and provide appropriate validation information for different sites to establish interlaboratory reliability. Unless a method is used on a regular basis, providing confidence in its continued validity, it is essential to document that the method is still valid before analysis of samples in the study. Adequate validation for methods not used on a regular basis often consists of running a standard curve with new quality-control samples to show that the responses, relationship, and general characteristics of the method are similar to previous valida-

Alarm signals in fishes

Abstract: the evolutionary questions surrounding alarm signalling remain unresolved, but we should now have a better understanding of the elements that must be considered in the balance sheet. The amplification that may occur in alarm signalling may be a key to understanding its evolution. The benefit to receivers will often go far beyond the response of a few nearby schoolmates over a few minutes, the response that has traditionally been measured. Distant fish may receive the signal by secondary transmission, and individuals that are not even present at the time may learn about predator stimuli through cultural transmission. These effects, such as learned response to predator odour or avoidance of an area, may persist for days or much longer, and work on invertebrates implies that there may be the potential for changes in morphology and life history. Thus one signal, such as release of alarm pheromone, could alter predation risk for many individuals over long periods of time. Anything that increases the total benefit to receivers will affect the evolutionary balance sheet. Increase in number of benefits and beneficiaries of a signal will increase the likelihood that the sender will receive adequate kin-selection benefits to drive the evolution of alarm displays. Likewise, to have many individuals avoiding predation would increase the post-signal benefits, such as reduced predation in the region (Trivers, 1971), to senders that survived. Similarly, anything that decreases the cost or increases the direct benefit to the sender will favour alarm signalling. Alarm signals that do double duty as predator deterrents, or aposematic displays, and distress signals that call in mobbers or secondary predators will have lower net cost than signals that only exist to warn others. It may be common for the sender's display to evolve primarily in response to direct benefits to the sender while the reaction of conspecific receivers is selected by their survival. Selection on receivers that reduces their response threshold will make signalling cheaper for the sender. The variety of life histories and biological adaptations in the fishes, combined with the potential of several different, independently evolved alarm signals should provide many avenues of approach and potential research subjects for examining the evolution of these systems. There have been many interesting effects reported in other groups of animals that may occur in fishes and which would extend both the biological interest of these systems and their generality. I have mentioned the morphological and life cycle responses found in invertebrates. Birds show deceitful alarm signalling (Munn, 1986; Moller, 1988), in which senders give false alarm calls to distract receivers from food or other resources. Audience effects occur in domestic chickens (Marler, 1986); they are more likely to give an alarm call if with a companion than when alone. Vervet monkeys assess the reliability of individual signallers and tend to ignore signals from untrustworthy individuals (Cheney and Seyfarth, 1988). Birds can acquire and transmit the identity of individual predators that prey on their species, in contrast to other individuals of the same predatory species that do not (Conover, 1987). The many effects of alarm signalling that have been documented or proposed in fishes or other organisms indicate that this phenomenon must be taken into account in any examination of foraging tactics or predator-prey interaction or any of the several areas of decision making that could be influenced by information on predation risk. Alarm signalling is probably much more widespread than was previously thought. Alarm pheromones are not just an obscure feature of the ostariophysans, although that group alone includes over 6000 species, but also occur in various forms in darters (150 species), gobies (2000 species), sculpins (300 species) and perhaps others. Distress sounds occur in over 24 families (Myrberg, 1981). Alarm calls occur in at least some holocentrids (60 species) and possibly in cods (only 55 species, but some economic value). Visual alarm signals have been reported in gobies (2000 species) and bioluminescent displays in a batrachoidid (65 species). Yet only a small fraction of fishes have been carefully examined for alarm or distress signalling. If we multiply the range of effects by the number of potential species involved, we have a subject area of some general importance in understanding the interactions between prey and predators. The prime requirement in this field, as in so many others, is for carefully designed studies, particularly in the wild, that take account of the whole suite of possible effects that may occur in alarm signalling. These studies should try to include all the participants in the system, including the predator(s), the signaller, and the various classes of receivers. They should also consider both the ultimate and proximate factors at work in each system. Very often proximate mechanisms can tell us important things about the ultimate factors that may be possible.

Brain cytochrome oxidase in Alzheimer's disease.

Abstract: A recent demonstration of markedly reduced (-50%) activity of cytochrome oxidase (CO; complex 4), the terminal enzyme of the mitochondrial enzyme transport chain, in platelets of patients with Alzheimer's disease (AD) suggested the possibility of a systemic and etiologically fundamental CO defect in AD To determine whether a CO deficiency occurs in AD brain, we measured the activity of CO in homogenates of autopsied brain regions of 19 patients with AD and 30 controls matched with respect to age, postmortem time, sex, and, as indices of agonal status, brain pH and lactic acid concentration Mean CO activity in AD brain was reduced in frontal (-26%: p less than 001), temporal (-17%; p less than 005), and parietal (-16%; not significant, p = 0055) cortices In occipital cortex and putamen, mean CO levels were normal, whereas in hippocampus, CO activity, on average, was nonsignificantly elevated (20%) The reduction of CO activity, which is tightly coupled to neuronal metabolic activity, could be explained by hypofunction of neurons, neuronal or mitochondrial loss, or possibly by a more primary, but region-specific, defect in the enzyme itself The absence of a CO activity reduction in all of the examined brain areas does not support the notion of a generalized brain CO abnormality Although the functional significance of a 16-26% cerebral cortical CO deficit in human brain is not known, a deficiency of this key energy-metabolizing enzyme could reduce energy stores and thereby contribute to the brain dysfunction and neurodegenerative processes in AD

Establishment of stable, cell-mediated immunity that makes "susceptible" mice resistant to Leishmania major.

Abstract: Cell-mediated, but not antibody-mediated, immune responses protect humans against certain pathogens that produce chronic diseases such as leishmaniasis. Effective vaccination against such pathogens must therefore produce an immunological "imprint" so that stable, cell-mediated immunity is induced in all individuals after natural infection. BALB/c mice "innately susceptible" to Leishmania major produce antibodies after substantial infection. In the present study, "susceptible" mice injected with a small number of parasites mounted a cell-mediated response and acquired resistance to a larger, normally pathogenic, challenge. This vaccination strategy may be applicable in diseases in which protection is dependent on cell-mediated immunity.

MELAS: Clinical features, biochemistry, and molecular genetics

Abstract: We studied 23 patients with clinically defined mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS), 25 oligosymptomatic or asymptomatic maternal relatives, and 50 mitochondrial disease control subjects for the presence of a previously reported heteroplasmic point mutation at nt 3,243 in the transfer RNA(Leu(UUR)) gene of mitochondrial DNA. We found a high concordance between clinical diagnosis of MELAS and transfer RNA(Leu(UUR)) mutation, which was present in 21 of the 23 patients with MELAS, all 11 oligosymptomatic and 12 of 14 asymptomatic relatives, but in only five of 50 patients without MELAS. The proportion of mutant genomes in muscle ranged from 56 to 95% and was significantly higher in the patients with MELAS than in their oligosymptomatic or asymptomatic relatives. In subjects in whom both muscle and blood were studied, the percentage of mutations was significantly lower in blood and was not detected in three of 12 asymptomatic relatives. The activities of complexes I + III, II + III, and IV were decreased in muscle biopsies harboring the mutation, but there was no clear correlation between percentage of mutant mitochondrial DNAs and severity of the biochemical defect.

The Development of a New Instrument: "Views on Science- Technology-Society" (VOSTS)

Abstract: Educators who plan science lessons, who develop science curricula, or who evaluate learning, often wonder about students' preconceptions of the material to be taught. Until now, attention has mainly focused on traditional science content (Driver, 1988; West and Pines, 1985). However, content related to the nature of science (for example, science's epistemology and its social context) is receiving increased attention because of interest in teaching science through a science-tech-nology-society (STS) approach or teaching science in concert with the history and philosophy of science (Bybee, 1987; Hodson, 1988; Posner and Strike, 1989; Gruen-der and Tobin, 1991); What are high school students' preconceptions concerning the epistemology and sociology of science? This question is addressed in two related articles that stem from the same research study. This first article describes the development of a new research instrument that monitors students' views on a broad range of STS topics,

Reduction of intestinal viscosity through manipulation of dietary rye and pentosanase concentration is effected through changes in the carbohydrate composition of the intestinal aqueous phase and results in improved growth rate and food conversion efficiency of broiler chicks.

Abstract: The effect of dietary rye (0, 200, 400 and 600 g/kg substituting for wheat) and pentosanase concentration (0, 1, 2, 4, 8, 16 g/kg) on weight gain, molecular weight distribution of soluble carbohydrates in the intestinal lumen and lumenal viscosity in broiler chicks was investigated. A 4 x 6 factorial design was used with four replicates per treatment and six birds per replicate pen. Diets were fed from 1 to 19 d of age, at which time body weight, food intake and intestinal viscosity and molecular weight distribution of carbohydrate complexes in proximal and distal gut sections were determined. Weight gain and food conversion efficiency (FCE) improved with increasing pentosanase and decreasing rye concentration. Intestinal viscosity, which rose as digesta passed from the proximal to distal small intestine, fell with pentosanase addition and decreasing rye concentration. Intestinal viscosity, which correlated positively with reduced weight gain and FCE, was in turn correlated with the lumenal concentration of soluble high-molecular-weight carbohydrates (HMC, greater than 500 kDa), which constituted less than 15% of the total lumenal carbohydrate concentration. The arabinose and xylose content of the HMC increased with increasing rye concentration, suggesting that HMC composition in addition to concentration may determine intestinal viscosity. The results indicate that pentosanase isolated from rye by extraction methods may not be representative of those released by digestion.

Students' Preconceptions about the Epistemology of Science

Abstract: The North American confusion of science with technology can cloud epistemic views. This should be kept in mind as one reads the following analysis of students' views on the epistemology of science. Chances are great that when students talk about science, they are probably talking about technology, specifically medical and environmental technological investigations.

Classes of graphs which approximate the complete Euclidean graph

Abstract: LetS be a set ofN points in the Euclidean plane, and letd(p, q) be the Euclidean distance between pointsp andq inS. LetG(S) be a Euclidean graph based onS and letG(p, q) be the length of the shortest path inG(S) betweenp andq. We say a Euclidean graphG(S)t-approximates the complete Euclidean graph if, for everyp, q ?S, G(p, q)/d(p, q) ≤t. In this paper we present two classes of graphs which closely approximate the complete Euclidean graph. We first consider the graph of the Delaunay triangulation ofS, DT(S). We show that DT(S) (2?/(3 cos(?/6)) ? 2.42)-approximates the complete Euclidean graph. Secondly, we define?(S), the fixed-angle?-graph (a type of geometric neighbor graph) and show that?(S) ((1/cos?)(1/(1?tan?)))-approximates the complete Euclidean graph.

Risk of Fatal and Near-Fatal Asthma in Relation to Inhaled Corticosteroid Use

Abstract: Objective. —To examine the relationship between patterns of use of inhaled beclomethasone dipropionate and the risk of fatal and near-fatal asthma. Design. —Nested case-control analysis of a historical cohort; a further analysis. Setting. —The 12 301 residents of Saskatchewan aged 5 to 54 years who were dispensed 10 or more asthma drugs from 1978 to 1987. Patients. —The 129 persons who experienced asthma death (n=44) and near-death (n=85) and their 655 controls matched as to age and date of entry into the cohort, with the additional matching criteria of at least one hospitalization for asthma in the prior 2 years, region of residence, and having received social assistance. Main Outcome. —Life-threatening attacks of asthma defined as death due to asthma or the occurrence of hypercarbia, intubation, and mechanical ventilation during an acute attack of asthma. Results. —After accounting for the risk associated with use of other medications and adjustment for markers of risk of adverse events related to asthma, subjects who had been dispensed, on average, one or more metered-dose inhalers of beclomethasone per month over a 1-year period had a significantly lower risk of fatal and near-fatal asthma (odds ratio, 0.1; 95% confidence interval, 0.02 to 0.6). Conclusion.—These data support recent guidelines from several countries that recommend the use of inhaled corticosteroids in moderate and severe asthma. ( JAMA . 1992;268:3462-3464)

Aging produces a specific pattern of striatal dopamine loss: implications for the etiology of idiopathic Parkinson's disease.

Abstract: To examine the possible causal contribution of normal or accelerated aging to the neurodegenerative process of Parkinson's disease, we measured the influence of aging on subregional striatal dopamine and homovanillic acid levels in postmortem brain of 23 neurologically and psychiatrically normal human subjects 14-92 years old. We observed a significant decline in striatal dopamine levels and increase in the homovanillic acid/dopamine molar ratios with increasing age. The dopamine loss, on average, was of the same magnitude in the caudate nucleus and the putamen (-60% in the 84-year-old group as compared with the 22-year-old group), with the caudal component of both nuclei being more affected than the rostral subdivisions. The level of subregional dopamine metabolism, as measured by the homovanillic acid/dopamine ratio, in our young individuals (mean age, 22 years) was found to be inversely correlated to the degree of subregional dopamine loss suffered by the individuals in the older age groups. We conclude the following: (a) Striatal subdivisions with physiologically higher dopamine metabolism are not at a greater risk of suffering dopamine neuronal damage with advancing age, as would seem to be implied by the oxidative stress hypothesis; thus, formation of dopamine-derived oxy radicals in the human striatum appears unlikely to be a primary factor responsible for the age-related striatal dopamine loss. (b) The regional and subregional pattern of striatal dopamine loss in normal aging differs substantially from the pattern typically observed in idiopathic Parkinson's disease; therefore, the cause of idiopathic Parkinson's disease cannot be primarily an age-dependent neurodegenerative process.

A new tropomyosin essential for cytokinesis in the fission yeast S. pombe.

Abstract: MUTATIONS in the Schizosaccharotnyces pombe cdc8 gene impair cytokinesis1. Here we clone cdc8+ and find that it encodes a novel tropomyosin. Gene disruption results in lethal arrest of the cell cycle, but spore germination, cell growth, DNA replication and mitosis are all unaffected. Haploid cdc8 gene disruptants are rescued by expression of a fibroblast tropomyosin complementary DNA. Immunofluorescence microscopy of wild type and cdc8 gene distruptants indicates that cdc8 tropomyosin is present in two distinct cellular distributions: in dispersed patches, and during cytokinesis as a transient medial band. Collectively these results indicate that cdc8 tropomyosin has a specialized role which, we suggest, is to form part of the F-actin contractile ring at cytokinesis. These results establish the basis for further genetic studies of cytokinesis and of contractile protein function in S. pombe.

Atmospheric pressure and gravity

Abstract: SUMMARY Gravity Green's functions for a column load of a model atmosphere on a spherical, elastic Earth are presented and they are used to evaluate the contribution of global atmospheric pressure variations to local gravity. The Green's functions are found to be relatively insensitive to the details of the model atmosphere, but they are dependent on the temperature at the base of the column, and on the relative height difference between the base of the column and the gravity station. The total signal that global pressure systems contribute to gravity is about 30 μgal, of which about 90 per cent is produced by the atmosphere within 50 km of the gravity station. A zone between 50 and 1000km from the gravity station contributes a couple of μgal, as does the remainder of the globe. This pattern, the coherence scale of pressure fluctuations, the time and spatial scales appropriate to the hydrostatic approximation, and the distance of the gravity station from the oceans, suggest a division of the globe into local, regional, and global zones. Data requirements, processing details, and the reliability of the computed signal are different in each zone. The local zone is within about 50 km of the gravity station. Within this zone pressure changes rapidly in time, but is spatially coherent, so that hourly observations of pressure and temperature at the gravity site alone are sufficient to compute an accurate correction, except when a front is passing through. The regional zone extends from the edge of the local zone to between several hundred and a thousand kilometres. The signal from this zone is small and is only weakly coherent with the signal from the central zone, so that a rather sparse array of hourly samples of pressure and temperature are required. The gravity signal from the global zone can reach about a μgal. It varies on a time-scale of days, and is influenced by the response of the oceans to pressure variations. Previously reported observations that the admittance between local pressure and gravity residuals depends on epoch, frequency, or site, are most probably due to incorrect modelling. A proper local, regional, temperature, and global correction can adequately account for the gravity signal from the atmosphere to within a few tens of ngal in the diurnal band, and about 100 ngal in the days to seasonal band, except during extreme weather conditions. The application of the local correction lowers the power spectral density of the gravity residuals in every band from seasonal to hourly. The regional, global, and temperature corrections lower the residual noise in the seasonal and synoptic bands, but are not consistently effective at periods less than about half a day.

Confocal Laser Microscopy and Digital Image Analysis in Microbial Ecology

Abstract: Microbial ecologists have extensively explored the potential applications of light microscopy for more than five decades (Henrici and Johnson, 1935; Perfil’ev and Gabe, 1969; Casida, 1969, 1972, 1975, 1976; Staley, 1971; Caldwell and Hirsch, 1973; Caldwell et al., 1973, 1975; Caldwell and Tiedje, 1975a,b; Labeda et al., 1976; Hirsch, 1977, 1980; Geesey et al., 1978; Marshall, 1986). Now traditional microscopy has given way to “microvisualization” (Friedhoff, 1991) greatly accelerating research. Microorganisms are no longer merely photographed; instead, they are digitally “imaged” using fluorescent molecular probes, confocal laser microscopy, and computer image analysis. The chemical and biological relationships between a microorganism and its microenvironment are seen directly, nondestructively, in situ, and in “real time” (Lawrence and Caldwell, 1990). Consequently, it is no longer necessary to disrupt microbial communities when studying the molecular or behavioral aspects of their ecology.

Facultative sex ratio manipulation in American kestrels

Abstract: For animals that are sexually dimorphic in size, the larger sex is expected to be more costly to raise to independence. Manipulating offspring sex ratios may thus be one means by which parents can fine-tune their reproductive effort to resource availability. Parents in poor physical condition or during poor food years should produce more of the cheaper (smaller) sex. We examined the sex ratios of 259 broods of American kestrels (Falco sparverius) between 1988 and 1990 in relation to food abundance (small mammals) and various attributes to the parents. The proportion of males at hatching increased as the food supply declined, and both male and female parents in poor physical condition were more likely to have male-biased broods than those in good condition. The mortality of eggs and young did not appear to be responsible for the biased sex ratios. The sex ratio was independent of the laying date; however, it was correlated with female body size. Small females produced more sons, perhaps because small size is more detrimental for females than males.

The incidence and prognosis of central nervous system disease in systemic lupus erythematosus.

Abstract: In a review of our experience with systemic lupus erythematosus (SLE) since 1975, we found 48 of 266 patients with major central nervous system (CNS) manifestations for which a non-SLE explanation could not be identified. Eleven patients developed more than one type of CNS event. The commonest symptom was seizure (18 patients), followed by brainstem dysfunction (12 patients), psychosis (11 patients), organic brain syndrome (11 patients) and stroke (7 patients). In 19% of cases, CNS manifestations were accompanied by a flare of multisystem SLE disease activity. Anticonvulsants were able to be discontinued safely in the majority of patients with seizures. Most CNS events were self-limited, reversible and not associated with poor outcome unless accompanied by multisystem disease activity. Therapy with corticosteroids did not appear to offer substantial benefit.

Improvements in immunostaining samples embedded in methacrylate: localization of microtubules and other antigens throughout developing organs in plants of diverse taxa.

Abstract: Microtubules are important in plant growth and development. Localizing microtubules in sectioned material is advantageous because it allows any tissue of interest to be studied and it permits the positional relations of the cells within the organ to be known. We describe here a method that uses semi-thin (0.5-2 μm) sections of material embedded in butyl-methylmethacrylate, to which 10 mM dithiothreitol was added. After removing the embedding material and using indirect immunofluorescence staining, we obtain clear images of microtubules, actin microfilaments, callose and pulse-fed bromodeoxyuridine. This method works on the root tissues of Arabidopsis thaliana(L.) Heynh, Pinus radiataD. Don, Zamia furfuraceaAit., Azolla pinnataR. Br. and on sporophytic tissues of Funaria hygrometricaHedw. In general, most of the cells in the organs studied are successfully stained. Using this method, we find that interphase meristematic cells in all of these species have microtubules not only in the usual cortical array but also throughout their cytoplasm. The presence of the calcium chelator ethylene glycol-bis(β-aminoethyl ether)N,N,N',N'-tetraacetic acid EGTA in fixation buffers led to some tissue damage, and did not enhance the preservation of microtubules. The common assumption that EGTA-containing buffers stabilize plant microtubules during fixation appears unwarranted.

Behavioral defenses against avian brood parasitism in sympatric and allopatric host populations

Abstract: The brown-headed cowbird (Molothrus ater) is a widespread, obligate brood parasite of North American passerine birds. In southern Manitoba, where hosts are sympatric with cowbirds, American robins (Turdus migratorius) ejected parasitic eggs from all experimentally parasitized clutches (N = 25) and no eggs were accepted for more than four days. In contrast, robins in northern Manitoba, an area where cowbirds do not breed, accepted parasitic eggs in 33% of nests (N = 18) for at least five days. Acceptance of experimental cowbird eggs by a second host, the yellow warbler (Dendroica petechia), was similar in allopatric (100% of 20 nests) and sympatric (88.6% of 35 nests) populations, but models of a female cowbird elicited greater nest defense by warblers in the area of sympatry. Neither host rejected eggs of conspecifics, thus, rejection of cowbird eggs was not an epiphenomenon of conspecific brood parasitism. These results support the hypothesis that recognition of cowbirds and their eggs evolved as adaptations to counter cowbird parasitism and not some other selection pressure. The expression of anti-parasite defenses by some individuals within allopatric populations further suggests these traits may be controlled genetically but persist in such areas either through the continued introgression of rejecter genes from sympatric populations or because of the low cost of rejection behavior when parasitism is absent or rare.

Heavy metal and metallothionein concentrations in Atlantic Canadian seabirds.

Abstract: Seabird tissues, collected during the 1988 breeding season from colonies on the Atlantic coast of Canada, were analyzed for toxic metals—Cd, Hg and Pb—and 18 other trace elements. Metallothionein (MT) was measured in kidney, and kidneys and livers underwent histopathological examination. Levels of most essential trace elements appear to be closely regulated in seabird tissues; values were in good agreement with those previously reported in the published literature. Liver-Se concentrations in Leach's storm-petrels (Oceanodroma leucorhoa) (77.6+7.49 μg/g dry weight) were much higher than values normally reported for freeliving birds and mammals. Cd levels varied greatly among individuals, but were always higher in kidney than in liver. Highest mean Cd concentrations (183+65 μg/g dry weight) were in kidneys of the planktivorous Leach's storm-petrels from the Gulf of St. Lawrence. A few individuals of this species had values >300 μg/g dry weight. Cd and metallothionein (MT) concentrations were positively correlated in kidneys of Leach's storm-petrels (r=0.692), Atlantic puffin (Fratercula arctica) (r=0.845) and herring gull (Larus argentatus) (r=0.866). Concentrations of total Hg varied greatly among species and individuals, but were consistently higher in liver than in kidney. Highest mean levels (21+28 μg/g) were in livers of the piscivorous double-crested cormorant (Phalacrocorax auritus) from Saint John Harbour in the Bay of Fundy. Concentrations of Hg and Se were positively correlated (r=0.736) in livers of Leach's storm-petrel, but not in other species. Pb concentrations were consistently greatest in bone, with mean levels being highest in herring gulls from a colony in the Bay of Fundy (63+36 μg/g). Histological examination of liver and kidney failed to reveal indications of tissue damage associated with elevated levels of heavy metals.