Crop production in the USA is frequently limited by a lack of pollinators.

Most of the world's crops depend on pollinators, so declines in both managed and wild bees raise concerns about food security. However, the degree to which insect pollination is actually limiting current crop production is poorly understood, as is the role of wild species (as opposed to managed honeybees) in pollinating crops, particularly in intensive production areas. We established a nationwide study to assess the extent of pollinator limitation in seven crops at 131 locations situated across major crop-producing areas of the USA. We found that five out of seven crops showed evidence of pollinator limitation. Wild bees and honeybees provided comparable amounts of pollination for most crops, even in agriculturally intensive regions. We estimated the nationwide annual production value of wild pollinators to the seven crops we studied at over $1.5 billion; the value of wild bee pollination of all pollinator-dependent crops would be much greater. Our findings show that pollinator declines could translate directly into decreased yields or production for most of the crops studied, and that wild species contribute substantially to pollination of most study crops in major crop-producing regions.

Limited phenological and dietary overlap between bee communities in spring flowering crops and herbaceous enhancements.

Wild bee populations have undergone declines in recent years across much of the Western world, and these declines have the potential to limit yield in pollination-dependent crops. Highbush blueberry, Vaccinium corymbosum, and tart cherry, Prunus cerasus, are spring-blooming crops that rely on the movement of pollen by bees and other insects for pollination. Wild bee populations can be increased on farmland by providing floral resources, but whether the addition of these plants translates into increased pollinator density on crop flowers has not been documented in most cropping systems. To determine the importance of providing additional floral resources for wild bee pollinator communities, we selected blueberry fields and tart cherry orchards with and without herbaceous floral enhancements in western Michigan, USA. The bee communities visiting crop flowers, enhancements and control grassy field margins were sampled over a 5-yr period. In addition, the pollen diets of the most abundant wild bee crop pollinators were quantified across Michigan to better understand their foraging niches and to identify potentially important alternative host plants. The presence of floral enhancements did not increase the abundance of wild bees on either blueberry or cherry flowers during bloom. The bee community visiting blueberry was evenly composed of short-season bees that fly only during the spring and long-season bees that fly in both spring and summer. In contrast, the bee community visiting cherry was dominated by short-season spring bees. The majority of pollen collected by the wild bee communities visiting blueberry and cherry was from spring-flowering woody plants, with limited use of the herbaceous enhancements. Enhancements attracted greater abundance and species richness of bees compared to control areas, including twice as many floral specialists. Conserving summer-flying, grassland-associated bees is an appropriate goal for pollinator conservation programs. However, herbaceous enhancements may not provide adequate resources for the wild bees that pollinate spring-flowering crops. This study demonstrates that an examination of the pollen collected by wild bees across their flight periods can identify plant species to help them persist in intensively managed landscapes.

Genetic engineering strategies to prevent the effects of antibody and complement on xenogeneic chondrocytes.

Advances in animal transgenesis may allow using xenogeneic chondrocytes in tissue-engineering applications for clinical cartilage repair. Porcine cartilage is rejected by humoral and cellular mechanisms that could be overcome by identifying key molecules triggering rejection and developing effective genetic-engineering strategies. Accordingly, high expression of α1,2-fucosyltransferase (HT) in xenogeneic cartilage protects from galactose α1,3-galactose (Gal)-mediated antibody responses. Now, we studied whether expression of a complement inhibitor provides further protection. First, porcine articular chondrocytes (PAC) were isolated from non-transgenic, single and double transgenic pigs expressing HT and moderate levels of human CD59 (hCD59) and their response to human serum was assessed. High recombinant expression of human complement regulatory molecules hCD59 and hDAF was also attained by retroviral transduction of PAC for further analyses. Complement activation on PAC after exposure to 20 % human serum for 24 hours mainly triggered the release of pro-inflammatory cytokines IL-6 and IL-8. Transgenic expression of HT and hCD59 did not suffice to fully counteract this effect. Nevertheless, the combination of blocking anti-Gal antibodies (or C5a) and high hCD59 levels conferred very high protection. On the contrary, high hDAF expression attained the most dramatic reduction in IL-6/IL-8 secretion by a single strategy, but the additional inhibition of anti-Gal antibodies or C5a did not provide further improvement. Notably, we demonstrate that both hCD59 and hDAF inhibit anaphylatoxin release in this setting. In conclusion, our study identifies genetic-engineering approaches to prevent humoral rejection of xenogeneic chondrocytes for use in cartilage repair.

In Contrast to Anti-C5 Therapy, Cobra Venom Factor Does Not Prevent Rejection of Xenogeneic Cartilage in Mice.

BACKGROUND: The use of xenogeneic chondrocytes may benefit the development of clinical tissue-engineering applications for cartilage repair. However, cartilage xenografts are slowly rejected by humoral and cellular mechanisms to which galactose α1,3-galactose (Gal) antigen and complement contribute. Accordingly, transgenic expression of human α1,2-fucosyltransferase (HT) in porcine cartilage helps to protect from the Gal-mediated immune response. Here, we aimed to assess the effect of the broadly used complement inhibitor cobra venom factor (CVF) in comparison with anti-C5 therapy in α1,3-galactosyltransferase knockout (Gal KO) mice transplanted with porcine cartilage. METHODS: Gal KO mice grafted with control or HT-transgenic cartilage were left untreated or treated systemically with either anti-C5 antibody or CVF for 5 weeks. The degree of rejection was evaluated by use of histopathological analysis, and serum anti-Gal antibodies were measured in all cohorts. RESULTS: The rejection process of control cartilage was well advanced by 5 weeks after transplantation in untreated Gal KO mice, whereas enhanced graft survival characterized by reduced cellular immune infiltrate was found in mice grafted with HT cartilage and/or treated with anti-C5. In contrast, CVF administration led to inconsistent results, with some grafts showing no improvement or even increased amounts of granulocytes. Regarding antibody titers, the anti-Gal immunoglobulin (Ig)M increased in the control transplant cohort and remained unchanged in the HT-graft recipients at 5 weeks after transplantation. Notably, a strong anti-Gal IgM response was readily detected in CVF-treated mice of both transplanted cohorts. CONCLUSIONS: CVF does not present advantages over anti-C5 therapy for preventing rejection of xenogeneic porcine cartilage.

Inhibition of complement component C5 protects porcine chondrocytes from xenogeneic rejection.

OBJECTIVE: Tissue-based xenografts such as cartilage are rejected within weeks by humoral and cellular mechanisms that preclude its clinical application in regenerative medicine. The problem could be overcome by identifying key molecules triggering rejection and the development of genetic-engineering strategies to counteract them. Accordingly, high expression of α1,2-fucosyltransferase (HT) in xenogeneic cartilage reduces the galactose α1,3-galactose (Gal) antigen and delays rejection. Yet, the role of complement activation in this setting is unknown. DESIGN: To determine its contribution, we assessed the effect of inhibiting C5 complement component in α1,3-galactosyltransferase-knockout (Gal KO) mice transplanted with porcine cartilage and studied the effect of human complement on porcine articular chondrocytes (PAC). RESULTS: Treatment with an anti-mouse C5 blocking antibody for 5 weeks enhanced graft survival by reducing cellular rejection. Moreover, PAC were highly resistant to complement-mediated lysis and primarily responded to human complement by releasing IL-6 and IL-8. This occurred even in the absence of anti-Gal antibody and was mediated by both C5a and C5b-9. Indeed, C5a directly triggered IL-6 and IL-8 secretion and up-regulated expression of swine leukocyte antigen I (SLA-I) and adhesion molecules on chondrocytes, all processes that enhance cellular rejection. Finally, the use of anti-human C5/C5a antibodies and/or recombinant expression of human complement regulatory molecule CD59 (hCD59) conferred protection in correspondence with their specific functions. CONCLUSIONS: Our study demonstrates that complement activation contributes to rejection of xenogeneic cartilage and provides valuable information for selecting approaches for complement inhibition.

Radial nerve innervation of the first dorsal interosseous muscle: A functional study.

A recent cadaver study described that 25% of the superficial radial nerves (SRN) investigated sent a contributing nerve branch into the first dorsal interosseous (1DI) muscle. This high degree of anatomical variation was unexpected, as the 1DI muscle is typically viewed as receiving its innervation from the ulnar nerve. The purpose of this study was to explore this possible SRN innervation of the 1DI muscle using electrophysiological tests on living subjects. Fourteen subjects participated and procedures were completed on their upper extremities bilaterally. Subjects were positioned supine and testing for the presence of a compound motor action potential (CMAP) was completed to determine if the 1DI muscle could be stimulated with activation of the ulnar nerve and the SRN. In all the 28 extremities examined, ulnar nerve stimulation resulted in clear elicitation of a CMAP in the 1DI muscle but stimulation of the SRN did not. The obtained findings do not support an atypical voluntary motor innervation of the 1DI muscle by the SRN with an incidence approaching the 25% reported previously.

Characterization of cartilage from H-transferase transgenic pigs.

Cartilage engineering is the object of intense research as a result of major medical needs and therapeutic prospects. Porcine xenogeneic cells/tissues may help in the development of clinical applications such as articular cartilage repair. However, unmodified porcine cartilage is rejected in primates by humoral and cellular mechanisms. We previously showed that porcine articular chondrocytes (PAC) isolated from H-transferase (HT) transgenic pigs show markedly reduced expression of the Galalpha1,3Gal antigen (alphaGal) and prolonged survival when transplanted into alpha1,3galactosyltransferase-deficient mice. In this work, we further studied the protective mechanisms of HT transgenic expression in cartilage, particularly its effects on monocyte adhesion. To this end, PAC isolated from control and HT transgenic pigs were assayed for human complement deposition and adhesion to the human monoblastic cell line U937. Consistent with a reduction in complement activation by the classical pathway, the HT transgenic PAC showed a 2-fold reduction in the deposition of complement components C4 and C3 relative to controls. Adhesion of U937 cells to HT PAC was also diminished under various conditions. This reduction was more dramatic at high effector:target ratios and especially observed when combined with anti-alphaGal antibodies (5-fold difference). Nevertheless, this effect was also observed in the absence of anti-alphaGal. antibodies and after tumor necrosis factor treatment. These results suggest that HT expression on porcine chondrocytes protects them from both humoral and cellular rejection.

Investigation of a cluster of Legionella pneumophila infections among staff at a federal research facility.

An epidemiologic investigation was conducted in response to a case of Legionella pneumonia in a scientist working at a federal research facility. A survey of 80 individuals working at the facility revealed that 13 (16%) had sustained prior infections with Legionella pneumophila serogroup 1 (Lps1) as measured by anti-Lps1 antibodies. Antibody-positive individuals' offices clustered around an air cooling tower and a heating, ventilation, and air conditioner unit (odds ratio = 5). On multivariate logistic regression analysis, individuals of non-white race (adjusted odds ratio = 8) and smokers (adjusted odds ratio = 36) were also found to be at higher risk of past infection. Marked Legionella growth was noted in the cooling tower's water reservoir and potable hot water system, where suboptimal operating temperatures were noted. Subsequent increase in the hot water temperatures as well as a complete renovation of the affected building's air handling and potable water systems led to a reduction in Legionella species colonization.

Asthma in Missouri: recent trends and sociodemographic risk factors.

This study describes recent trends in asthma morbidity and mortality rates across Missouri, and identifies several population-based risk factors that account for the geographic variation in asthma hospitalizations and emergency room visits among counties. The percentage of African-American residents was the best predictor of high asthma treatment rates, explaining 77% of the variation in hospitalizations and 57% of the variation in ER visits. All other sociodemographic predictors combined explained less than 10% of the statewide variation in rates.

Apoptosis in regenerating and denervated, nonregenerating urodele forelimbs.

Denervated limbs of larval salamanders fail to regenerate if amputated and, unlike adult limbs, undergo regression. The cellular basis of the tissue loss is poorly understood. We used TUNEL staining of larval axolotl limbs fixed and sectioned at intervals after bilateral amputation and unilateral denervation to investigate the role of apoptosis during normal limb regeneration and denervated limb regression. In the first week after amputation a small percentage of apoptotic cells was found in both innervated and denervated limbs. During the second week the apoptotic index remained low in the mitotically active mesenchymal cells of the regenerating limbs, but increased twofold in the nondividing, dedifferentiated cells of the regressing limbs. TUNEL-positive cells resembling apoptotic bodies were restricted primarily to the dedifferentiated area beneath the wound epithelium, but were also present within the wound epithelium itself. Macrophages were identified immunohistochemically and were also found in increased numbers in distal areas of the denervated regressing limbs. The results suggest a role for apoptosis in the early phase of normal regeneration and indicate that denervated limb regression involves an increased rate of apoptosis and removal of apoptotic bodies by macrophages and the wound epithelium.

Pharmacological and immunohistochemical characterization of calmodulin-stimulated (Ca(2+)+Mg(2+))-ATPase in cultured porcine aortic endothelial cells.

Plasma membrane (Ca(2+)+Mg(2+))-ATPase and Ca(2+) transport activities, best characterized in human erythrocytes, are stimulated by calmodulin and thought to play a crucial role in the termination of cellular Ca(2+) signaling in all cells. In plasma membranes isolated from cultured porcine aortic endothelial cells, the (Ca(2+)+Mg(2+))-ATPase was not readily measured. This is in part because of an overabundance of nonspecific Ca(2+)- and/or Mg(2+)-activated ecto-5'-nucleotide phosphohydrolases. Moreover, addition of exogenous calmodulin (10(-9) to 10(-6) mol/L) produced no measurable stimulation of ATPase activities, suggesting a permanently activated state or, alternatively, a complete lack thereof. To establish and verify the presence of a calmodulin-regulated (Ca(2+)+Mg(2+))-ATPase activity in these endothelial cells, immunohistochemical localization using a monoclonal mouse anti-(Ca(2+)+Mg(2+))-ATPase antibody (clone 5F10) was applied to intact pig aorta endothelium, cultured endothelial monolayers, and isolated endothelial plasma membrane fractions. This approach clearly demonstrated Ca(2+) pump immunoreactivity in each of these preparations. To confirm functional calmodulin stimulation of the (Ca(2+)+Mg(2+))-ATPase, 10(-5) mol/L calmidazolium (R24571) was added to the isolated plasma membrane preparation, which lowered the (Ca(2+)+Mg(2+))-ATPase activity from 143.0 to 78.15 nmol P(i)/mg protein x min(-1). This calmidazolium-reduced activity could then be stimulated 113.1+/-0.8% in a concentration-dependent manner by the addition of exogenous calmodulin (10(-7) to 2 x 10(-6) mol/L) with an EC(50) of 3.45+/-0.04 x 10(-7) mol/L (n=4). This represents a competitive lowering of the apparent calmodulin affinity by approximately 100 compared with other unopposed calmodulin-stimulated processes. Together, these findings support evidence for the presence of a calmodulin-stimulated plasma membrane (Ca(2+)+Mg(2+))-ATPase activity in cultured porcine aortic endothelial cells.

Tissue macrophages associated with angiogenesis in chronic airway inflammation in rats.

Angiogenesis is a feature of chronic inflammation produced by Mycoplasma pulmonis infection of the respiratory tract. The mechanism of this angiogenesis is unknown, but cellular growth factors and matrix remodeling proteases produced by inflammatory cells are likely to be involved. The goal of this study was to determine the relationship between changes in the number, shape, and distribution of ED2-immunoreactive macrophages and the development of angiogenesis in the tracheal mucosa of Wistar rats after M. pulmonis infection. In pathogen-free rats, ED2-positive cells were scattered in the airway mucosa (261 +/- 42 cells/mm2 of surface, mean +/- SE). Most cells were irregularly shaped and had moderate ED2 immunoreactivity. No lymphoid tissue was present. The number of ED2-positive cells increased rapidly after infection, was 120% above baseline at 1 wk, and remained significantly increased throughout the 4-wk study (P < 0.05). Angiogenesis was first detected at 2 wk, and at 3 wk the vessel length density was nearly 8-fold the pathogen-free value. At 3 and 4 wk, focal sites of angiogenesis coincided with discrete clusters of round, strongly immunoreactive ED2-positive cells (1,340 +/- 124 cells/mm2) in polyp-like collections of mucosal lymphoid tissue. The close association of distinctive ED2-positive cells with angiogenic blood vessels suggests a relationship between a subset of tissue macrophages and the angiogenesis associated with M. pulmonis infection. The time course of the changes indicates that the initial influx of ED2-positive macrophages precedes the angiogenesis, and the rounding of the cells parallels the growth of new vessels.

Glucocorticoid-induced apoptosis of dendritic cells in the rat tracheal mucosa.

Dendritic cells are antigen-presenting cells that constitutively express high levels of major histocompatibility complex class II (Ia) antigen on their plasma membrane. Previous studies have shown that the number of dendritic cells in the rat airway mucosa decreases rapidly after glucocorticoid treatment. We sought to determine whether apoptosis contributes to this steroid-induced cell decrease. Dendritic cells in tracheal whole mounts were revealed by immunoperoxidase staining using the OX-6 (anti-Ia) monoclonal antibody. In untreated rats, a dense network of Ia-immunoreactive (Ia+) cells with highly branched cytoplasmic processes was observed just beneath the tracheal epithelium (1,405 +/- 140 cells/mm2 mucosa; mean +/- SEM, n = 6). In rats treated with dexamethasone (10 mg/kg, intraperitoneally), four distinct changes in dendritic cell morphology were evident 4 to 8 h after injection: (1) appearance of large Ia+ granules in cytoplasmic processes, (2) narrowing of cytoplasmic processes, (3) loss of Ia immunoreactivity from the cell surface, and (4) fragmentation of cells into small Ia+ bodies. These changes accompanied a 56% decrease in the number of Ia+ cells over 8 h. The contribution of apoptosis to this decrease in Ia+ cells was determined by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) of nucleosomal DNA fragments in histologic sections. The number of TUNEL+ bodies increased from a control value of 174 +/- 47 bodies/mm2 mucosa to 2,108 +/- 294 bodies/mm2 mucosa at 4 h and 936 +/- 343 bodies/ mm2 mucosa at 8 h (n = 4 rats per time point). The location of TUNEL+ bodies closely corresponded to that of Ia+ cells stained in adjacent histologic sections. We conclude that apoptosis contributes to the rapid decrease in airway dendritic cells after glucocorticoid treatment.

Repeated ambulance use by patients with acute alcohol intoxication, seizure disorder, and respiratory illness.

Three chronic conditions were examined--acute alcohol intoxication, seizure disorder, and respiratory illness--to quantify the extent of repetitive emergency medical services (EMS) use in a defined population. Urban EMS system ambulance data from 1992 to 1994 were analyzed for the three designated conditions with respect to transports by condition and individual patient. Analysis by chi2 was used for comparing proportions. Analysis of variance after square root transformation was used to evaluate differences among means. The total number of transports analyzed was 15,541: 7,488 for acute alcohol intoxication, 4,670 for respiratory illness, and 3,383 for seizure disorder. These transports involved 8,692 patients who were transported at least once for one of the three designated conditions. The mean number of transports for alcohol was 1.96 (95% confidence intervals [CI]: 1.92, 2.01), seizure 1.32 (95% CI: 1.27, 1.36), and respiratory 1.18 (95% CI: 1.15, 1.21). Of 369 patients transported five or more times during the study period, 260 (70.5%) were for alcohol, 56 (15.2%) for seizure, and 53 (14.4%) for respiratory complaints. This group comprised only 4.3% of patients, but 28.4% of all transports. Acute alcohol intoxication resulted in more repetitive ambulance transports than either seizure disorder or respiratory illness. A small number of patients were responsible for a large number of transports. Focused intervention for patients with high ambulance transport deserves further study.

Amino acids critical for the functions of the bovine papillomavirus type 1 E2 transactivator.

The N-terminal domain of the bovine papillomavirus type 1 E2 protein is important for viral DNA replication, for transcriptional transactivation, and for interaction with the E1 protein. To determine which residues of this 200-amino-acid domain are important for these activities, single conservative amino acid substitutions have been generated in 17 residues that are invariant among all papillomavirus E2 proteins. The resulting mutated E2 proteins were tested for the ability to support viral DNA replication, activate transcription, and cooperatively bind to the origin of replication with the E1 protein. We identified five mutated proteins that were completely defective for transcriptional activation and either were defective or could support viral DNA replication at only low levels. However, several of these proteins could still interact efficiently with the E1 protein. In addition, we identified several mutated proteins that were unable to efficiently cooperatively bind to the origin with the E1 protein. Although a number of the mutated proteins demonstrated wild-type activity in all of the functions tested, only 3 out of 17 mutated viral genomes were able to induce foci in a C127 focus formation assay when the mutations were generated in the background of the entire bovine papillomavirus type 1 genome. This finding suggests that the E2 protein may have additional activities that are important for the viral life cycle.

Effect of dexamethasone treatment on the regional distribution of neutral endopeptidase activity in the rat trachea.

Treating rats with the glucocorticoid dexamethasone has been shown to reduce the amount of plasma extravasation produced in the trachea by tachykinins released from sensory nerves. We sought to determine whether dexamethasone works by increasing the activity of neutral endopeptidase (NEP), the principal enzyme thought to be responsible for degrading tachykinins in the airways. Rats were treated for 2 days with either saline or 4 mg/kg/day of dexamethasone, a dose we found to be maximally effective in reducing tachykinin-induced plasma extravasation. The tracheas were then removed and processed to reveal NEP-specific histofluorescence. Tissue sections were photographed through a fluorescence microscope, and the relative intensity of fluorescent staining was quantified in five regions of the tracheal wall using computerized image analysis. In the saline-treated rats, the rank order of fluorescent staining was perichondrium > chondrocytes = submucosal >> epithelium > lamina propria. Neither the amount nor distribution of NEP fluorescence was altered in the dexamethasone-treated rats. Biochemical measurements of NEP activity in tracheal homogenates (nmol product/h/mg protein) likewise revealed no significant difference between the two groups (34.1 +/- 3.5 vs 29.0 +/- 3.2; mean +/- SEM, n = 8). These findings suggest that dexamethasone may be working through a mechanism unrelated to NEP activation.

Characterization of ruthenium red as an inhibitor of neurogenic inflammation in the rat trachea.

1. We investigated the ability of ruthenium red, an inorganic dye with capsaicin antagonist properties, to inhibit capsaicin-induced plasma extravasation in the rat trachea. 2. The amount of plasma extravasation produced by intravenous capsaicin was reduced dose-dependently by i.v. ruthenium red. Complete inhibition was achieved with a dose of 5 mumol/kg. 3. The inhibitory effect of ruthenium red persisted for at least 16 hr after its administration, but was not present 24 hr later. 4. Ruthenium red did not reduce the amount of plasma extravasation produced by electrical stimulation of the vagus nerve, nor the amount produced by intravenous substance P or platelet-activating factor. 5. Prior exposure to a high dose of capsaicin reduced the amount of plasma extravasation produced by a second capsaicin exposure 48 hr later. However, giving ruthenium red 30 min before the initial capsaicin exposure largely prevented this loss of sensory nerve function. 6. We conclude that systemic administration of ruthenium red produces long-lasting, selective, and reversible inhibition of capsaicin-induced plasma extravasation in the rat trachea. Moreover, ruthenium red attenuates the long-term, desensitizing effect of capsaicin on sensory nerves.

A mutational analysis of the amino terminal domain of the human papillomavirus type 16 E7 oncoprotein.

The human papillomavirus type 16 (HPV-16) E7 oncoprotein shares structural and functional similarity with the adenovirus (Ad) E1A protein and the SV40 large tumor antigen (TAg). Like these other DNA tumor virus oncoproteins, HPV-16 E7 interacts with the "pocket proteins," a family of host cellular proteins that include the retinoblastoma tumor suppressor protein and can cooperate with the ras oncogene to transform primary rodent cells. Mutational analyses have indicated that amino acid sequences outside of the pRB binding region are also important for the cellular transformation property of HPV-16 E7. These sequences include an amino terminal domain of the E7 protein that is similar to a portion of conserved region 1 of Ad E1A. In this study it is shown that the homologous amino acid sequences in Ad E1A and SV40 TAg are functionally interchangeable with the amino terminal HPV-16 E7 domain in transformation assays. Deletion analysis across the amino terminus of HPV-16 E7 indicated that the overall integrity of the entire CR1 homology domain is important for the biological activity of the HPV E7 oncoprotein.

Differential effects of phosphoramidon and captopril on NK1 receptor-mediated plasma extravasation in the rat trachea.

We sought to confirm the identity of the tachykinin receptor subtype that mediates plasma extravasation in the rat trachea, and assess the respective contributions of neutral endopeptidase (NEP) and angiotensin-converting enzyme (ACE) in regulating this tachykinin-induced response. To achieve these aims, we determined the relative potencies of several natural tachykinins and receptor-selective synthetic agonists, both before and after inhibiting NEP with phosphoramidon and ACE with captopril. We also determined the effects of these peptidase inhibitors, and the NK-1 receptor antagonist L-703,606, on the plasma extravasation produced by capsaicin, which releases tachykinins endogenously from sensory nerve endings. We found that the rank order of potency for producing plasma extravasation in the rat trachea was NK-1 receptor agonist ([Sar9, Met(O2)11] SP) > substance P > neurokinin A > neurokinin B. The NK-2 ([Nle10]NKA (4-10)) and NK-3 ([MePhe7]NKB) receptor agonists were without effect. We observed no change in the relative potencies of these peptides after giving rats phosphoramidon or captopril, which suggests that the different peptide potencies are not simply the consequence of different rates of enzymatic degradation. Nevertheless, the responses to substance P and neurokinin A were clearly potentiated in rats given phosphoramidon, indicating that NEP effectively degrades tachykinins in vivo. No significant potentiation was evident for any peptide in rats given captopril. Similarly, the plasma extravasation produced by capsaicin was potentiated in rats given phosphoramidon, but not in those given captopril. Pretreating rats with L-703,606 abolished the response to capsaicin.(ABSTRACT TRUNCATED AT 250 WORDS)