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PubMedDate not supplied

Localization of nitric oxide synthase in the tree shrew retina.

Nitric oxide (NO) is a novel neuronal messenger that likely influences retinal function by activating retinal guanylyl cyclase to increase levels of cGMP. In the present study, the localization of neuronal nitric oxide synthase (nNOS, Type I NOS) in the cone-dominant tree shrew retina was studied using NADPH-d histochemistry and nNOS immunocytochemistry. Both NADPH-d and nNOS-immunoreactivity (IR) labeled the inner segments of rods and the myoids of a regular subpopulation of cones, with their corresponding nuclei outlined. The labeled cone myoids were co-localized with a marker for short-wave-sensitive (SWS) cones (S-antigen) and also displayed the regular triangular packing and density (7%) characteristic of SWS cones in tree shrew and other mammalian retinas. These measures confirmed the identity of the labeled cones as SWS cones. Photoreceptor ellipsoids of all cones were strongly labeled by NADPH-d reactivity, but lacked nNOS-IR. Another novel finding in tree shrew retina was that both NADPH-d and nNOS-IR labeled Muller cells, which have not been labeled by nNOS-IR in other mammalian retinas. Consistent with findings in rod-dominant retinas, two types of amacrine cells at the vitreal edge of the inner nuclear layer and a subpopulation of displaced amacrine cells at the scleral edge of the ganglion cell layer were labeled by both NADPH-d and nNOS-IR. Processes of these labeled cells were seen to extend into the inner plexiform layer, where dense punctate label was seen, especially in the central sublamina. These results show that localization of NOS in the cone-dominant tree shrew retina shares some common properties with rod-dominant mammalian retinas, but also shows some species-specific characteristics. The new finding of nNOS localization in tree shrew SWS cones and rods, but not in other cones, raises interesting questions about the roles of NO in the earliest level of visual processing.

Animals↗
PubMed1981

Reactions of nitric oxide with tree and fungal laccase.

The reactions of nitric oxide (NO) with the oxidized and reduced forms of fungal and tree laccase, as well as with tree laccase depleted in type 2 copper, are reported. The products of the reactions were determined by NMR and mass spectroscopy, whereas the oxidation states of the enzymes were monitored by EPR and optical spectroscopy. All three copper sites in fungal laccase are reduced by NO. In addition, NO forms a specific complex with the reduced type 2 copper. NO similarly reduces all of the copper sites in tree laccase, but it also oxidizes the reduced sites produced by ascorbate or NO reduction. A catalytic cycle is set up in which N2O, NO2-, and various forms of the enzyme are produced. On freezing of fully reduced tree laccase in the presence of NO, the type 1 copper becomes reoxidized. This reaction does not occur with the enzyme depleted in type 2 copper, suggesting that it involves intramolecular electron transfer from the type 1 copper to NO bound to the type 2 copper. When the half-oxidized tree laccase is formed in the presence of NO, a population of molecules exists which exhibits a type 3 EPR signal. A triplet EPR signal is also seen in the same preparation and is attributed to a population of the enzyme molecules in which NO is bound to the reduced copper of a half-oxidized type 3 copper site.

Basidiomycota↗
PubMedDate not supplied

Molecular Property eXplorer: a novel approach to visualizing SAR using tree-maps and heatmaps.

The tremendous increase in chemical structure and biological activity data brought about through combinatorial chemistry and high-throughput screening technologies has created the need for sophisticated graphical tools for visualizing and exploring structure-activity data. Visualization plays an important role in exploring and understanding relationships within such multidimensional data sets. Many chemoinformatics software applications apply standard clustering techniques to organize structure-activity data, but they differ significantly in their approaches to visualizing clustered data. Molecular Property eXplorer (MPX) is unique in its presentation of clustered data in the form of heatmaps and tree-maps. MPX employs agglomerative hierarchical clustering to organize data on the basis of the similarity between 2D chemical structures or similarity across a predefined profile of biological assay values. Visualization of hierarchical clusters as tree-maps and heatmaps provides simultaneous representation of cluster members along with their associated assay values. Tree-maps convey both the spatial relationship among cluster members and the value of a single property (activity) associated with each member. Heatmaps provide visualization of the cluster members across an activity profile. Unlike a tree-map, however, a heatmap does not convey the spatial relationship between cluster members. MPX seamlessly integrates tree-maps and heatmaps to represent multidimensional structure-activity data in a visually intuitive manner. In addition, MPX provides tools for clustering data on the basis of chemical structure or activity profile, displaying 2D chemical structures, and querying the data based over a specified activity range, or set of chemical structure criteria (e.g., Tanimoto similarity, substructure match, and "R-group" analysis).

Cluster Analysis↗
PubMed2005

Climate dependency of tree growth suppressed by acid deposition effects on soils in northwest Russia.

Increased tree growth in temperate and boreal forests has been proposed as a direct consequence of a warming climate. Acid deposition effects on nutrient availability may influence the climate dependency of tree growth, however. This study presents an analysis of archived soil samples that has enabled changes in soil chemistry to be tracked with patterns of tree growth through the 20th century. Soil samples collected in 1926, 1964, and 2001, near St. Petersburg, Russia, showed that acid deposition was likely to have decreased root-available concentrations of Ca (an essential element) and increased root-available concentrations of Al (an inhibitor of Ca uptake). These soil changes coincided with decreased diameter growth and a suppression of climate-tree growth relationships in Norway spruce. Expected increases in tree growth from climate warming may be limited by decreased soil fertility in regions of northern and eastern Europe, and eastern North America, where Ca availability has been reduced by acidic deposition.

Acid Rain↗
PubMed2006

Uptake of iron cyanide complexes into willow trees.

The uptake of iron cyanide into willows was studied. Trees were grown in solutions with Prussian blue, ferricyanide, or ferrocyanide. Iron cyanide speciation in solution was determined by HPLC during the experiment. Total cyanide and total iron in solution and trees were measured at the end of the experiments. Ferrocyanide wasthe dominating species in most solutions at the end. Ferricyanide was preferably taken up from solutions. Between 20 and 83% of the cyanide was lost from the solutions, and up to 28% could be recovered from the plants, mainly from roots. Cyanide could also be detected in stems and leaves of most exposed trees. Uptake was increased when no other nitrogen source but cyanide was present in solutions. Iron contents in exposed trees, compared to controls, increased significantly. The ratio of iron to cyanide remained rather stable in solution, but changed to higher values inside the plants. This indicates that iron and cyanide were taken up together as a complex, which was dissolved inside plants, and then cyanide was metabolized. No toxic effects could be seen. The study shows that trees can take up and metabolize iron cyanide complexes, making phytoremediation of iron cyanide waste a feasible option.

Chromatography, High Pressure Liquid↗
PubMed2004

Phytoseiid mites on unsprayed apple trees in Oregon, and other western states (USA): distributions, life-style types and relevance to commercial orchards.

In unsprayed apple trees in eastern Oregon, Galendromus flumenis (Chant), Galendromus occidentalis (Nesbitt), Typhlodromus caudiglans Schuster and Metaseiulus citri (Garman and McGregor) were common phytoseiid mites; common plant-feeding mites were the eriophyid, Aculus schlechtendali Nalepa, the brown mite, Bryobia rubrioculus (Scheuten) and Eotetranychus spp.; apple rust mites seemed to be the primary prey for phytoseiids; the spider mites, Tetranychus urticae Koch and Panonychus ulmi (Koch) were scarce except for a few local outbreaks; the stigmaeid Zetzellia mali (Ewing) was at 10% of sites and its densities were inversely related to phytoseiid densities; phytoseiids were absent at some sites, particularly at high elevations where winters are severe. In seven Oregon ecoregions, G. flumenis was often at lower elevations in valleys with moderate winters; T. caudiglans was often at higher elevations; G. occidentalis was often at intermediate elevations, in young trees, and near where pesticides were used; it dominated in unsprayed trees only in almost treeless, sage-covered areas; M. citri was usually in older apple trees near agriculture. In mixed phytoseiid populations, M. citri, a generalist, and G. occidentalis, a specialist, occurred more often than expected; G. occidentalis was mostly found with T. caudiglans, a generalist; G. flumenis, a generalist, occurred less with others, possibly because it competes with both specialists and generalists. Analyses of species' distributions with multiple regression and genetic models gave explanatory r2s of 0.019-0.318. Of 29 variables, altitude of site, intensity of agricultural management, tree age, plant types, and Z. mali levels helped explain phytoseiid species presence. In the western USA, G. flumenis dominated in middle-southern latitudes; T. caudiglans dominated in the north near the Canadian border; G. occidentalis dominated in middle latitudes in parts of Washington, Idaho, Montana, and Wyoming; M. citri was at a few sites in these four states. Distributional and independent variable data were used to predict species presence at sites in Oregon with a 70% success rate. We discuss phytoseiid life-style types, community dynamics, presence in organic/conventional orchards, and trends as more selective IPM methods are used in apple orchards.

Animals↗
PubMed2002

Field and pulping performances of transgenic trees with altered lignification.

The agronomic and pulping performance of transgenic trees with altered lignin has been evaluated in duplicated, long-term field trials. Poplars expressing cinnamyl alcohol dehydrogenase (CAD) or caffeate/5-hydroxy-ferulate O-methyltransferase (COMT) antisense transgenes were grown for four years at two sites, in France and England. The trees remained healthy throughout the trial. Growth indicators and interactions with insects were normal. No changes in soil microbial communities were detected beneath the transgenic trees. The expected modifications to lignin were maintained in the transgenics over four years, at both sites. Kraft pulping of tree trunks showed that the reduced-CAD lines had improved characteristics, allowing easier delignification, using smaller amounts of chemicals, while yielding more high-quality pulp. This work highlights the potential of engineering wood quality for more environmentally benign papermaking without interfering with tree growth or fitness.

Alcohol Oxidoreductases↗
PubMed2004

Genetic markers applied in regression tree prediction models.

Classification and regression tree (CART) modelling was used to determine infectious hypodermal and haematopoietic necrosis virus (IHHNV) resistance and susceptibility in Penaeus stylirostris. In a previous study, eight random amplified polymorphic DNA (RAPD) markers and viral load values using real-time quantitative PCR were obtained and used as the training data set in order to create numerous regression tree models. Specifically, the genetic markers were used as categorical predictor variables and viral load values as the dependent response variable. To determine which model has the highest predictive accuracy for future samples, RAPD fingerprint data was generated from new Penaues stylirostris IHHNV resistant and susceptible individuals and used to test the regression models. The best performing tree was a four terminal node tree with three genetic markers as significant variables. Marker-assisted breeding practices may benefit from the creation of regression tree models that apply genetic markers as predictive factors. To our knowledge this is the first study to use RAPD markers as predictors within a CART prediction model to determine viral susceptibility.

Animals↗
PubMed2003

Pollen dispersal of tropical trees (Dinizia excelsa: Fabaceae) by native insects and African honeybees in pristine and fragmented Amazonian rainforest.

Tropical rainforest trees typically occur in low population densities and rely on animals for cross-pollination. It is of conservation interest therefore to understand how rainforest fragmentation may alter the pollination and breeding structure of remnant trees. Previous studies of the Amazonian tree Dinizia excelsa (Fabaceae) found African honeybees (Apis mellifera scutellata) as the predominant pollinators of trees in highly disturbed habitats, transporting pollen up to 3.2 km between pasture trees. Here, using microsatellite genotypes of seed arrays, we compare outcrossing rates and pollen dispersal distances of (i) remnant D. excelsa in three large ranches, and (ii) a population in undisturbed forest in which African honeybees were absent. Self-fertilization was more frequent in the disturbed habitats (14%, n = 277 seeds from 12 mothers) than in undisturbed forest (10%, n = 295 seeds from 13 mothers). Pollen dispersal was extensive in all three ranches compared to undisturbed forest, however. Using a twogener analysis, we estimated a mean pollen dispersal distance of 1509 m in Colosso ranch, assuming an exponential dispersal function, and 212 m in undisturbed forest. The low effective density of D. excelsa in undisturbed forest (approximately 0.1 trees/ha) indicates that large areas of rainforest must be preserved to maintain minimum viable populations. Our results also suggest, however, that in highly disturbed habitats Apis mellifera may expand genetic neighbourhood areas, thereby linking fragmented and continuous forest populations.

Alleles↗
PubMed2005

Autocrine/paracrine regulation of the growth of the biliary tree by the neuroendocrine hormone serotonin.

BACKGROUND & AIMS: The biliary tree is the target of cholangiopathies that are chronic cholestatic liver diseases characterized by loss of proliferative response and enhanced apoptosis of cholangiocytes, the epithelial cells lining the biliary tree. The endogenous factors that regulate cholangiocyte proliferation are poorly understood. Therefore, we studied the role of the neuroendocrine hormone serotonin as a modulator of cholangiocyte proliferation. METHODS: The presence of the serotonin 1A and 1B receptors on cholangiocytes was evaluated. We then tested whether the activation of such receptors by the administration of the selective agonists modifies cholangiocyte proliferation and functional activity both in vivo and in vitro. In addition, the intracellular signal mediating the serotonin receptor action in cholangiocytes was characterized. We studied the expression and secretion of serotonin by cholangiocytes and the effects of the neutralization of the secreted hormone on the growth of the biliary tree. RESULTS: Cholangiocytes express the serotonin 1A and 1B receptors. Their activation markedly inhibits the growth and choleretic activity of the biliary tree in the bile duct-ligated rat, a model of chronic cholestasis. Such changes are mediated by enhanced d -myo-inositol 1,4,5-triphosphate/Ca 2+ /protein kinase C signaling and the consequent inhibition of the adenosine 3',5'-cyclic monophosphate/protein kinase A/Src/extracellular signal-regulated kinase 1/2 cascade. Cholangiocytes secrete serotonin, the blockage of which enhances cholangiocyte proliferation in the course of cholestasis. CONCLUSIONS: We observed the existence of an autocrine loop based on serotonin that limits the growth of the biliary tree in the course of chronic cholestasis. Our novel findings might open new approaches for the management of cholangiopathies.

Animals↗
PubMed2001

A voluntary registry for peanut and tree nut allergy: characteristics of the first 5149 registrants.

BACKGROUND: A voluntary registry of individuals with peanut and/or tree nut allergy was established in 1997 to learn more about these food allergies. OBJECTIVE: The purpose of this study was to elucidate a variety of features of peanut and tree nut allergy among the first 5149 registry participants. METHODS: The registry was established through use of a structured questionnaire distributed to all members of the Food Allergy and Anaphylaxis Network and to patients by allergists. Parental surrogates completed the forms for children under the age of 18 years. RESULTS: Registrants were primarily children (89% of registrants were younger than 18 years of age; the median age was 5 years), reflecting the membership of the Network. Isolated peanut allergy was reported by 3482 registrants (68%), isolated tree nut allergy by 464 (9%), and allergy to both foods by 1203 (23%). Registrants were more likely to have been born in October, November, or December (odds ratio, 1.2; 95% CI, 1.18-1.23; P <.0001). The median age of reaction to peanut was 14 months, and the median age of reaction to tree nuts was 36 months; these represented the first known exposure for 74% and 68% of registrants, respectively. One half of the reactions involved more than 1 organ system, and more than 75% required treatment, frequently from medical personnel. Registrants with asthma were more likely than those without asthma to have severe reactions (33% vs 21%; P <.0001). In comparison with initial reactions, subsequent reactions due to accidental ingestion were more severe, more common outside the home, and more likely to be treated with epinephrine. CONCLUSIONS: Allergic reactions to peanut and tree nut are frequently severe, often occur on the first known exposure, and can become more severe over time.

Adolescent↗
PubMed2001

Peanut and tree nut allergic reactions in restaurants and other food establishments.

BACKGROUND: The clinical features of food-allergic reactions in restaurants and other food establishments have not been studied. Of the registrants in the United States Peanut and Tree Nut Allergy Registry (PAR), 13.7% have reported reactions associated with such establishments. OBJECTIVE: The purpose of this study was to determine the features of allergic reactions to peanut and tree nut in restaurant foods and foods purchased at other private establishments (eg, ice cream shops and bakeries). METHODS: Telephone interviews were conducted through use of a structured questionnaire. Subjects/parental surrogates were randomly selected from among the 706 PAR registrants who reported a reaction in a restaurant or other food establishment. RESULTS: Details were obtained for 156 episodes (29 first-time reactions) from 129 subjects/parental surrogates. Most reactions were caused by peanut (67%) or tree nut (24%); for some reactions (9%), the cause was a combination of peanut and another nut or was unknown. Symptoms began at a median of 5 minutes after exposure and were severe in 27% of reactions. Overall, 86% of reactions were treated (antihistamines, 86%; epinephrine, 40%). Establishments commonly cited were Asian food restaurants (19%), ice cream shops (14%), and bakeries/doughnut shops (13%). Among meal courses, desserts were a common cause (43%). Of 106 registrants with previously diagnosed allergy who ordered food specifically for ingestion by the allergic individual, only 45% gave prior notification about the allergy to the establishment. For 83 (78%) of these 106 reactions, someone in the establishment knew that the food contained peanut or tree nut as an ingredient; in 50% of these incidents, the food item was "hidden" (in sauces, dressings, egg rolls, etc), visual identification being prevented. In 23 (22%) of the 106 cases, exposures were reported from contamination caused primarily by shared cooking/serving supplies. In the remaining 21 subjects with previously diagnosed allergy, reactions resulted from ingestion of food not intended for them, ingestion of food selected from buffet/food bars, or skin contact/inhalation (residual food on tables, 2; peanut shells covering floors, 2; being within 2 feet of the cooking of the food, 1). CONCLUSIONS: Restaurants and other food establishments pose a number of dangers for peanut- and tree nut-allergic individuals, particularly with respect to cross-contamination and unexpected ingredients in desserts and Asian food. Failure to establish a clear line of communication between patron and establishment is a frequent cause of errors.

Humans↗
PubMed1989

Evolutionary relationship of archaebacteria, eubacteria, and eukaryotes inferred from phylogenetic trees of duplicated genes.

All extant organisms are though to be classified into three primary kingdoms, eubacteria, eukaryotes, and archaebacteria. The molecular evolutionary studies on the origin and evolution of archaebacteria to date have been carried out by inferring a molecular phylogenetic tree of the primary kingdoms based on comparison of a single molecule from a variety of extant species. From such comparison, it was not possible to derive the exact evolutionary relationship among the primary kingdoms, because the root of the tree could not be determined uniquely. To overcome this difficulty, we compared a pair of duplicated genes, elongation factors Tu and G, and the alpha and beta subunits of ATPase, which are thought to have diverged by gene duplication before divergence of the primary kingdoms. Using each protein pair, we inferred a composite phylogenetic tree with two clusters corresponding to different proteins, from which the evolutionary relationship of the primary kingdoms is determined uniquely. The inferred composite trees reveal that archaebacteria are more closely related to eukaryotes than to eubacteria for all the cases. By bootstrap resamplings, this relationship is reproduced with probabilities of 0.96, 0.79, 1.0, and 1.0 for elongation factors Tu and G and for ATPase subunits alpha and beta, respectively. There are also several lines of evidence for the close sequence similarity between archaebacteria and eukaryotes. Thus we propose that this tree topology represents the general evolutionary relationship among the three primary kingdoms.

Adenosine Triphosphatases↗
PubMed1997

Tree rings, carbon dioxide, and climatic change.

Tree rings have been used in various applications to reconstruct past climates as well as to assess the effects of recent climatic and environmental change on tree growth. In this paper we briefly review two ways that tree rings provide information about climate change and CO2: (i) in determining whether recent warming during the period of instrumental observations is unusual relative to prior centuries to millennia, and thus might be related to increasing greenhouse gases; and (ii) in evaluating whether enhanced radial growth has taken place in recent decades that appears to be unexplained by climate and might instead be due to increasing atmospheric CO2 or other nutrient fertilization. It is found that a number of tree-ring studies from temperature-sensitive settings indicate unusual recent warming, although there are also exceptions at certain sites. The present tree-ring evidence for a possible CO2 fertilization effect under natural environmental conditions appears to be very limited.

Journal Article↗
PubMed2003

Effects of 15N application frequency on nitrogen uptake efficiency in citrus trees.

Two irrigation systems were used to compare nitrogen uptake efficiency in citrus trees and to evaluate the NO3- runoff in "Navelina" orange trees [Citrus sinensis (L.) Osbeck] on Carrizo citrange rootstock (Citrus sinensis x Poncirus trifoliata Raf.). These were fertilized with 125 g N as labelled K15NO3 and grown outdoors in containers filled with a sand-loamy soil. Two groups of 3 trees received this N dose either in five equally split applications by a flooding irrigation system or in 66 applications by drip. Trees were harvested at the end of the vegetative cycle (December) and the isotopic ratios of 15N/14N were measured in the soil-plant system. The N uptake efficiency of the whole tree was higher with drip irrigation (75%) than with flooding system (64%). In the 0-90 cm soil profile, the N immobilized in the organic fraction was similar for both irrigation methods (around 13 %), whereas the N retained as NO3- was 1% of the N applied under drip and 10% under flooding. In the last case, most of NO3- remained under root system and it could be lost to leaching either by heavy rainfalls or excessive water applications. These results showed that a drip irrigation system was more efficient for improving water use and N uptake from fertilizer, in addition to potentially reduced leaching losses.

Citrus↗
PubMed1993

Physiological effects of work stress and pesticide exposure in tree planting by British Columbia silviculture workers.

Tree planters in British Columbia have reported symptoms that are congruent with musculoskeletal stress and organophosphate or carbamate pesticide intoxication. The purpose of this research was to determine the existence of any physiological or biochemical correlate supporting the existence of these potential hazards in tree planting. Worker's health complaints were assessed from regularly distributed questionnaires. Blood samples were obtained from 14 male and three female Canadian subjects before and after tree planting work on 10 occasions throughout a tree planting season. The strenuous physical challenge of tree planting was confirmed by a significant elevation of serum enzyme activity (ESEA) at the beginning of the season, which did not return to a normal level during the remainder of the season. Significant (p < or = 0.05) inhibition of erythrocyte acetylcholinesterase activity (AChE) postwork was observed in 15.9% of individuals, and a significant group mean prework-postwork difference of AChE or plasma pseudocholinesterase (PChE) was observed on two days of testing, indicating a potential toxicological hazard from pesticide absorption. No correlation was found between the degree of ESEA or cholinesterase inhibition and the number of health complaints.

Acetylcholinesterase↗
PubMed1993

Ergonomics aspects of tree-planting using 'multipot' technology.

The highlights of a descriptive study on the ergonomics and occupational health and safety aspects of tree-planting in Québec are presented. The study was planned to consider the most representative geographical sites, planting technologies, and planting organizations. Semi-directed interviews were made with a mixed group of 48 male and female tree-planters and physiological measurements were made on four male planters. Tools and other equipment were also examined. An analysis of the work identified the main elements of the planting cycle, and the high cardiac rate in the working planters was related more to his manual transportation of seedlings and travel on rough paths than to planting per se. A tree-planter will typically travel 2.4 km carrying 16.8 kg of material and equipment in order to plant an average of 1245 seedlings daily. One out of two interviewed planters reported having a work-related accident or incident during his or her lifetime planting career. The body parts reported most frequently injured were the lower extremities (knee, foot, ankle), the skin, the eyes, and the wrist. Recommendations on the development of appropriate tools and footwear for tree-planters and for further research on repetitive strain injury induced by tree-planting have been made.

Accidents, Occupational↗
PubMed1998

Health of tree swallows (Tachycineta bicolor) nesting in pesticide-sprayed apple orchards in Ontario, Canada. I. Immunological parameters.

The degree of pesticide exposure and its effects on the immune system and its development were determined in 16-d-old tree swallow (Tachycineta bicolor) chicks from 4 sprayed apple orchards and three nonsprayed sites in southern Ontario, Canada, during 1994-1995. Persistent contaminant residues were measured in tree swallow eggs and in each chick hepatic ethoxyresorufin O-deethylase (EROD) activity; body, immune organ, and liver masses; lymphocyte blastogenesis response; respiratory burst and phagocytic responses; hemarological evaluation; and histological development of thymus, bursa of fabricius, and spleen were determined. Chemicals sprayed on apple orchards were mainly ethylene bisdithiocarbamate and myclobutanil fungicides and organophosphorus, carbamate, and synthetic pyrethroid insecticides. During the period between oviposition of the first egg in each nest to d 16 after hatching, individual nests in orchards were exposed to between 4 and 11 individual chemical applications and up to 3 mixtures of pesticide sprays. Concentrations of pesticides, polychlorinated biphenyls (PCBs), and lead and arsenic residues in tree swallow eggs and liver were low and not variable among sites except p,p'-DDE, which was as high as 2.29 microg/g wet weight in eggs. EROD activity was not different among sites. Organochlorine and trace metal residues and EROD activity were not correlated with any immune parameter. In sprayed birds, we found a significantly increased blastogenic response to pokeweed mitogen (12.5 microg/ml). However, nests were initiated over a period of several weeks and we also found changes in other tree swallow immune parameters that were related to the date of chick collection. Hematological parameters, bursal and thymic masses, phagocytic response, and thymic development were all correlated with the day the chicks were 16 d of age. After accounting for the collection date of birds from each nest, we found cell proliferation in the cortex and delayed thymic involution correlated positively with increasing spray exposure. We also found that birds in sprayed orchards were slightly anemic compared to birds from nonsprayed sites, and there were smaller bursal masses and an increase in relative heterophil concentrations in the sprayed orchard birds. The local inflammation may have been caused by trematode parasite infections, although pesticide exposure also correlated positively with these parameters. This is the first study of the immunology and effects of current pesticide exposures in wild passerines; therefore it is difficult to predict the long-term consequences of the apparent stimulated immune systems in sprayed birds. However, some environmental contaminants that overtly stimulate the immune system in mammals have induced hypersensitivity and/or autoimmunity. Therefore we speculate that these effects are possible in tree swallows.

Animals↗