Reciprocity to Increase Participation of Compatible Living Donor and Recipient Pairs in Kidney Paired Donation.

Inclusion of compatible living donor and recipient pairs (CPs) in kidney paired donation (KPD) programs could increase living donor transplantation. We introduce the concept of a reciprocity-based strategy in which the recipient of a CP who participates in KPD receives priority for a repeat deceased donor transplant in the event their primary living donor KPD transplant fails, and then we review the practical and ethical considerations of this strategy. The strategy limits prioritization to CPs already committed to living donation, minimizing the risk of unduly influencing donor behavior. The provision of a tangible benefit independent of the CP's actual KPD match avoids many of the practical and ethical challenges with strategies that rely on finding the CP recipient a better-matched kidney that might provide the CP recipient a future benefit to increase KPD participation. Specifically, the strategy avoids the potential to misrepresent the degree of future benefit of a better-matched kidney to the CP recipient and minimizes delays in transplantation related to finding a better-matched kidney. Preliminary estimates suggest the strategy has significant potential to increase the number of living donor transplants. Further evaluation of the acceptance of this strategy by CPs and by waitlisted patients is warranted.

Evaluation of Alternatives to Carbamate and Organophosphate Insecticides Against Thrips and Tomato Spotted Wilt Virus in Peanut Production.

Thrips are important pests of peanut. They cause severe feeding injuries on peanut foliage in the early season. They also transmit Tomato spotted wilt virus (TSWV), which causes spotted wilt disease. At-plant insecticides and cultivars that exhibit field resistance to TSWV are often used to manage thrips and spotted wilt disease. Historically, peanut growers used the broad-spectrum insecticides aldicarb (IRAC class 1A; Temik) and phorate (IRAC class 1B; Thimet) for managing thrips and thereby reducing TSWV transmission. Aldicarb has not been produced since 2011 and its usage in peanut will be legally phased out in 2018; therefore, identification of alternative chemistries is critical for thrips and spotted wilt management. Here, eight alternative insecticides, with known thrips activity, were evaluated in field trials conducted from 2011 through 2013. In addition, different application methods of alternatives were also evaluated. Imidacloprid (Admire Pro), thiamethoxam (Actara), spinetoram (Radiant), and cyantraniliprole (Exirel) were as effective as aldicarb and phorate in suppressing thrips, but none of the insecticides significantly suppressed spotted wilt incidence. Nevertheless, greenhouse assays demonstrated that the same alternative insecticides were effective in suppressing thrips feeding and reducing TSWV transmission. Spotted wilt incidence in the greenhouse was more severe (∼80%) than in the field (5­25%). In general, field resistance to TSWV in cultivars only marginally influenced spotted wilt incidence. Results suggest that effective management of thrips using alternative insecticides and subsequent feeding reduction could improve yields under low to moderate virus pressure.

Feeding preference and movement of Nezara viridula and Euschistus serous (Hemiptera: Pentatomidae) on individual cotton plants.

Experiments were conducted in an environmental growth chamber to determine the movement and feeding preferences of Nezara viridula (L.) and Euschistus serous (Say) on individual cotton plants. Fifth instars were caged by species on a single cotton plant (FM 9063 B2F) containing four discrete boll sizes ranging from 1.1 to 3.0 cm in diameter over a period of 5 d per replication. Two digital video cameras were simultaneously focused on each of the four bolls per plant to visually confirm stink bug resting and movement. During the study, a total of 4,080 h of video footage was recorded and analyzed. Results showed that N. viridula and E. serous did not prefer the exact same boll sizes. In a trial with eight stink bugs per plant, N. viridula spent more time on the three larger boll classes, 1.6-2.0, 2.1-2.5, and 2.6-3.0 cm. In a separate trial with one stink bug per plant, N. viridula spent more time on the larger boll classes while E. serous exhibited the strongest preference for 1.1-1.5 and 2.1-2.5 cm bolls. N. viridula moved more often than E. serous and both species moved more often during photophase compared with scotophase. Regardless of species or number of bugs released, bolls in the smallest boll size class fell off the plant about 3 d after the bugs were released. These results confirm that scouts who are estimating stink bug damage should select bolls in the 2.1-2.5 cm diameter boll size class.

Development of sampling plans for cotton bolls injured by stink bugs (Hemiptera: Pentatomidae).

Cotton, Gossypium hirsutum L., bolls were sampled in commercial fields for stink bug (Hemiptera: Pentatomidae) injury during 2007 and 2008 in South Carolina and Georgia. Across both years of this study, boll-injury percentages averaged 14.8 +/- 0.3 (SEM). At average boll injury treatment levels of 10, 20, 30, and 50%, the percentage of samples with at least one injured boll was 82, 97, 100, and 100%, respectively. Percentage of field-sampling date combinations with average injury < 10, 20, 30, and 50% was 35, 80, 95, and 99%, respectively. At the average of 14.8% boll injury or 2.9 injured bolls per 20-boll sample, 112 samples at Dx = 0.1 (within 10% of the mean) were required for population estimation, compared with only 15 samples at Dx = 0.3. Using a sample size of 20 bolls, our study indicated that, at the 10% threshold and alpha = beta = 0.2 (with 80% confidence), control was not needed when <1.03 bolls were injured. The sampling plan required continued sampling for a range of 1.03-3.8 injured bolls per 20-boll sample. Only when injury was > 3.8 injured bolls per 20-boll sample was a control measure needed. Sequential sampling plans were also determined for thresholds of 20, 30, and 50% injured bolls. Sample sizes for sequential sampling plans were significantly reduced when compared with a fixed sampling plan (n=10) for all thresholds and error rates.

Monitoring Tribolium castaneum (Herbst) in pilot-scale warehouses treated with beta-cyfluthrin: are residual insecticides and trapping compatible?

Integrated pest management strategies for cereal processing facilities often include both pheromone-baited pitfall traps and crack and crevice applications of a residual insecticide such as the pyrethroid cyfluthrin. In replicated pilot-scale warehouses, a 15-week-long experiment was conducted comparing population trends suggested by insect captures in pheromone-baited traps to direct estimates obtained by sampling the food patches in untreated and cyfluthrin-treated warehouses. Warehouses were treated, provisioned with food patches and then infested with all life stages of Tribolium castaneum (Herbst). Food patches, both those initially infested and additional uninfested, were surrounded by cyfluthrin bands to evaluate if insects would cross the bands. Results show that insect captures correlated with population trends determined by direct product samples in the untreated warehouses, but not the cyfluthrin-treated warehouses. However, dead insects recovered from the floor correlated with the insect densities observed with direct samples in the cyfluthrin-treated warehouses. Initially, uninfested food patches were exploited immediately and after six weeks harbored similar infestation densities to the initially infested food patches. These data show that pest management professionals relying on insect captures in pheromone-baited traps in cyfluthrin-treated structures could be deceived into believing that a residual insecticide application was suppressing population growth, when the population was actually increasing at the same rate as an untreated population.

Sampling stink bugs (Hemiptera: Pentatomidae) for population estimation and pest management in southeastern cotton production.

Stink bugs (Hemiptera: Pentatomidae) were sampled in commercial cotton, Gossypium hirsutum L., fields in 2007 and 2008 in South Carolina and Georgia. The main species collected with the beat cloth and sweep net methods were green stink bug, Acrosternum hilare (Say) (63 and 57%, respectively); brown stink bug, Euschistus servus (Say) (23 and 18%, respectively); and southern green stink bug, Nezara viridula (L.) (14 and 22%, respectively). Average stink bug densities were 0.145 +/- 0.010 (mean +/- SEM) for adults and 0.250 +/- 0.027 for nymphs per 3.7 m of row by using the beat cloth method. Average stink bug densities were 0.291 +/- 0.016 for all adults and 0.137 +/- 0.018 for all nymphs per 50 sweeps. A density of two southern green stink bugs per 3.7 m of row by using the beat cloth method required 43 samples (reliability or precision, Dx = 0.3) for population estimation, whereas 88 samples were necessary for a density of two southern green stink bugs per 50 sweeps. At low densities, the sweep net was a more cost-reliable sampling method for all species and life stages. For adult stink bugs, the beat cloth method became more reliable at densities of 1.0, 3.2, and 5.8 stink bugs per 3.7 m of cotton row for southern green stink bug, brown stink bug, and green stink bug, respectively. Sequential sampling consistently reduced sample size for all insects compared with a fixed sampling plan.

Preliminary Results Comparing Thin Plate Splines with Finite Element Methods for Modeling Brain Deformation during Neurosurgery using Intraoperative Ultrasound.

Brain shift compensation attempts to model the deformation of the brain which occurs during the surgical removal of brain tumors to enable mapping of presurgical image data into patient coordinates during surgery and thus improve the accuracy and utility of neuro-navigation. We present preliminary results from clinical tumor resections that compare two methods for modeling brain deformation, a simple thin plate spline method that interpolates displacements and a more complex finite element method (FEM) that models physical and geometric constraints of the brain and its material properties. Both methods are driven by the same set of displacements at locations surrounding the tumor. These displacements were derived from sets of corresponding matched features that were automatically detected using the SIFT-Rank algorithm. The deformation accuracy was tested using a set of manually identified landmarks. The FEM method requires significantly more preprocessing than the spline method but both methods can be used to model deformations in the operating room in reasonable time frames. Our preliminary results indicate that the FEM deformation model significantly out-performs the spline-based approach for predicting the deformation of manual landmarks. While both methods compensate for brain shift, this work suggests that models that incorporate biophysics and geometric constraints may be more accurate.

Evaluation of Alternatives to an Organophosphate Insecticide with Selected Cultural Practices: Effects on Thrips, Frankliniella fusca, and Incidence of Spotted Wilt in Peanut Farmscapes.

Peanut growers use a combination of tactics to manage spotted wilt disease caused by thrips-transmitted Tomato spotted wilt virus (TSWV). They include planting TSWV-resistant cultivars, application of insecticides, and various cultural practices. Two commonly used insecticides against thrips are aldicarb and phorate. Both insecticides exhibit broad-spectrum toxicity. Recent research has led to the identification of potential alternatives to aldicarb and phorate. In this study, along with reduced-risk, alternative insecticides, we evaluated the effect of conventional versus strip tillage; single versus twin row seeding pattern; and 13 seed/m versus 20 seed/m on thips density, feeding injury, and spotted wilt incidence. Three field trials were conducted in Georgia in 2012 and 2013. Thrips counts, thrips feeding injuriy, and incidence of spotted wilt were less under strip tillage than under conventional tillage. Reduced feeding injury from thrips was observed on twin-row plots compared with single-row plots. Thrips counts, thrips feeding injury, and incidence of spotted wilt did not vary by seeding rate. Yield from twin-row plots was greater than yield from single-row plots only in 2012. Yield was not affected by other cultural practices. Alternative insecticides, including imidacloprid and spinetoram, were as effective as phorate in suppressing thrips and reducing incidence of spotted wilt in conjunction with cultural practices. Results suggest that cultural practices and reduced-risk insecticides (alternatives to aldicarb and phorate) can effectively suppress thrips and incidence of spotted wilt in peanut.

Economic Injury Level of the Neotropical Brown Stink Bug Euschistus heros (F.) on Cotton Plants.

In Brazil, the Neotropical brown stink bug, Euschistus heros (F.) (Hemiptera: Pentatomidae), commonly disperses from soybeans to cotton fields. The establishment of an economic treatment threshold for this pest on cotton crops is required. Infestation levels of adults of E. heros were evaluated on cotton plants at preflowering, early flowering, boll filling, and full maturity by assessing external and internal symptoms of injury on bolls, seed cotton/lint production, and fiber quality parameters. A completely randomized experiment was designed to infest cotton plants in a greenhouse with 0, 2, 4, 6, and 8 bugs/plant, except at the full-maturity stage in which only infestation with 8 bugs/plant and uninfested plants were evaluated. Results indicated that the preflowering, early-flowering, and full-maturity stages were not affected by E. heros. A linear regression model showed a significant increase in the number of internal punctures and warts in the boll-filling stage as the population of bugs increased. The average number of loci with mottled immature fibers was significantly higher at 4, 6, and 8 bugs compared with uninfested plants with data following a quadratic regression model. The seed and lint cotton was reduced by 18 and 25% at the maximum level of infestation (ca. 8 bugs/plant) in the boll-filling stage. The micronaire and yellowing indexes were, respectively, reduced and increased with the increase of the infestation levels. The economic injury level of E. heros on cotton plants at the boll-filling stage was determined as 0.5 adult/plant. Based on that, a treatment threshold of 0.1 adult/plant can be recommended to avoid economic losses.

Seasonal Population Dynamics of Megacopta cribraria (Hemiptera: Plataspidae) in Kudzu and Soybean, and Implication for Insecticidal Management in Soybean.

Megacopta cribraria (F.), an invasive species introduced from Asia in 2009, is now prolific in the southeastern United States. Megacopta cribraria develops primarily on kudzu and soybean completing two generations. It is not well understood how this economic pest is affected by changes in geographic distribution in the United States or how population levels have changed since its establishment. The effect of insecticide application timing on field populations of M. cribraria is not well documented. These studies seek to understand how population dynamics of M. cribraria vary with geographic regions in Georgia. Effect of application timing on populations throughout the growing season was also examined. Weekly from 2012 to 2013, all life stages were enumerated from kudzu and soybean environments at several locations throughout Georgia from sweeps samples and flight intercept captures. Coordinates were recorded for locations, and classified as belonging to the Piedmont or Coastal Plain region of the state. Single spray trials were conducted from 2011-2014, and applications were made to soybean at intervals throughout the season. From 2012 to 2015, two kudzu patches near Griffin, GA, were monitored to detect population changes. Differences in population dynamics from locations around the state were found, but no clear effect of latitude, longitude, or region was observed. Insecticide applications applied in July suppressed nymph populations significantly better than treatments made earlier or later. Megacopta cribraria populations declined in 2014 and 2015 compared with 2012 and 2013. These studies provide the critical information for M. cribraria management in soybean in the southeastern United States.

Investigation of ground level and remote-sensed data for habitat classification and prediction of survival of Ixodes scapularis in habitats of southeastern Canada.

In southeastern Canada, most populations of Ixodes scapularis Say, the Lyme disease vector, occur in Carolinian forests. Climate change projections suggest a northward range expansion of I. scapularis this century, but it is unclear whether more northerly habitats are suitable for I. scapularis survival. In this study, we assessed the suitability of woodlands of the Lower Great Lakes/St. Lawrence Plain region for I. scapularis by comparing tick egg survival in four different woodlands. Woodlands where I. scapularis are established, and sand dune where I. scapularis do not survive, served as positive and negative control sites, respectively. At two woodland sites, egg survival was the same as at the positive control site, but at two of the sites survival was significantly less than either the positive control site, or one of the other test sites. Egg survival in all woodland sites was significantly higher than in the sand dune site. Ground level habitat classification discriminated among woodlands in which tick survival differed. The likelihood that I. scapularis populations could persist in the different habitats, as deduced using a population model of I. scapularis, was significantly associated with variations in Landsat 7 ETM+ data (normalized difference vegetation index [NDVI] and Tasselled Cap indices). The NDVI index predicted habitat suitability at Long Point, Ontario, with high sensitivity but moderate specificity. Our study suggests that I. scapularis populations could establish in more northerly woodland types than those in which they currently exist. Suitable habitats may be detected by ground-level habitat classification, and remote-sensed data may assist this process.

Dual effects of lysophosphatidic acid on human airway smooth muscle cell proliferation and survival.

Lysophosphatidic acid (LPA) is a phospholipid growth mediator found in serum at 2-20 microM. In many cell types, including human airway smooth muscle (HASM) cells, LPA-induced proliferation occurs at 10-100 microM LPA. At these concentrations LPA forms Ca2+ precipitates. The potential involvement of Ca2+ and Ca2+ LPA precipitates in LPA-induced HASM cell mitogenesis was investigated. In the absence of extracellular Ca2+, 10 and 30 microM LPA stimulated HASM cell mitogenesis. However, with 100 microM LPA in the absence of extracellular Ca2+, HASM cells exhibited a profound shape change and loss of viability, determined to be apoptosis by both DNA staining and assessment of cytosolic nucleosomal reactivity. A bioassay based on the adenosine 3':5'-cyclic monophosphate response of C62B rat glioma cells was used to measure the bioactivity of LPA solutions prepared in Ca2+ free and Ca2+ containing medium. After 24 h, a 100 microM LPA solution in Ca2+ free medium contained markedly greater bioactivity than a 100 microM LPA solution made in Ca2+ containing medium. In summary, formation of Ca2+ LPA precipitates decreases the amount of biologically active LPA in solution, and high concentrations of bioactive LPA achieved in Ca2+ free but not in Ca2+ containing medium induce apoptosis of HASM cells.

Keypoint Transfer Segmentation.

We present an image segmentation method that transfers label maps of entire organs from the training images to the novel image to be segmented. The transfer is based on sparse correspondences between keypoints that represent automatically identified distinctive image locations. Our segmentation algorithm consists of three steps: (i) keypoint matching, (ii) voting-based keypoint labeling, and (iii) keypoint-based probabilistic transfer of organ label maps. We introduce generative models for the inference of keypoint labels and for image segmentation, where keypoint matches are treated as a latent random variable and are marginalized out as part of the algorithm. We report segmentation results for abdominal organs in whole-body CT and in contrast-enhanced CT images. The accuracy of our method compares favorably to common multi-atlas segmentation while offering a speed-up of about three orders of magnitude. Furthermore, keypoint transfer requires no training phase or registration to an atlas. The algorithm's robustness enables the segmentation of scans with highly variable field-of-view.

Inhibition of invasion of murine mammary carcinoma cells by the tyrosine kinase inhibitor genistein.

Tyrosine kinases are ubiquitous enzymes that have been shown to be involved in many cellular functions, including growth and differentiation. Recent studies have shown that they are also involved in integrin signal transduction pathways. Since integrins are known to be involved in cellular adhesion and thus in invasion and metastasis, the possible involvement of tyrosine kinases in invasion was tested. Tumor cell invasion was measured using filter inserts coated with Matrigel, a substance that closely resembles the natural basement membrane. A highly metastatic subline of BALB/c mammary carcinoma (410.4) cells was shown to invade nearly three times as much as a low metastatic subline (168.1). Genistein, an inhibitor of tyrosine kinases, was found to inhibit invasion of 410.4 cells with an EC50 of approximately 1 microM. At a concentration of 37 microM, there was almost complete inhibition of invasion by genistein, whereas the structural analog, daidzein, which does not inhibit tyrosine kinases, had only a small effect. At higher concentrations (370 microM), daidzein also caused marked inhibition. Genistein was able to inhibit invasion at concentrations having little effect on cell growth. However, for daidzein, most of the effect on invasion was apparently due to its effect on growth inhibition. The relatively specific effect of genistein to inhibit tumor invasion suggests a role for tyrosine phosphorylation in this process. Genistein or other tyrosine kinase inhibitors may be effective inhibitors of tumor invasion and metastasis.

Lysophosphatidic acid enhances contractility of isolated airway smooth muscle.

The effects of the simple phospholipid mediator lysophosphatidic acid (LPA) on the contractile responsiveness of isolated tracheal rings from rabbits and cats were assessed. In both species, LPA increased the contractile response to the muscarinic agonist methacholine, but LPA did not induce contraction on its own. Conversely, LPA decreased the relaxation response to the beta-adrenergic-agonist isoproterenol in both species. Concentrations of LPA as low as 10(-8) M were effective, and the effects of LPA were rapidly reversed on washing. Phosphatidic acid was much less effective, requiring higher concentrations and producing only a minimal effect. Contractions induced by serotonin and by substance P also were enhanced by LPA, but KCl-induced contractions were unaffected. LPA inhibited the isoproterenol-induced relaxation of KCl-precontracted rings, similar to its effects on methacholine-precontracted rings, and relaxation induced by the direct adenylyl cyclase activator forskolin was inhibited in a manner similar to that induced by isoproterenol. Epithelium removal did not alter the contraction-enhancing effect of LPA. The ability of LPA to both enhance contraction and inhibit relaxation of airway smooth muscle suggests that LPA could contribute to airway hypercontractility in asthma, airway inflammation, or other types of lung injury.

Regulation of histamine H1 receptor-mediated phosphoinositide hydrolysis by histamine and phorbol esters in DDT1 MF-2 cells.

The regulation of histamine-stimulated phosphoinositide turnover by histamine and phorbol esters was examined in intact DDT1 MF-2 cells grown in suspension culture. Histamine increased the incorporation of 32P into phosphatidylinositol (PI) in these cells, and this stimulation was inhibited by the H1 antagonist diphenhydramine but not by the H2 antagonist cimetidine. Pretreatment of cells with histamine or with phorbol 12-myristate 13-acetate (PMA) or other activators of protein kinase C induced a marked decrease in the subsequent stimulation by histamine. PMA, but not histamine, also decreased the ability of epinephrine to stimulate PI labelling through alpha 1-adrenoceptors. Thus, histamine appears to induce homologous desensitization of histamine H1 receptor-mediated PI turnover, whereas direct activation of protein kinase C in the absence of receptor occupancy by agonist induces nonspecific heterologous desensitization of both histamine H1- and alpha 1-adrenoceptor-mediated responses.

Neuropeptide Y promotes GTP photo-incorporation into a 55 kDa protein.

Incubation of bovine hippocampal membranes with [alpha-32P]GTP and exposure to ultraviolet light resulted in the labelling of seven species with apparent molecular masses of 200, 74, 55, 53, 50, 43 and 40 kDa. Labelling of the 55 kDa species was greatly enhanced in the presence of carboxyl terminal fragments [neuropeptide Y-(18-36)] of neuropeptide Y. Labelling occurred with [alpha-32P]GTP but not [alpha-32P]ATP. A group of putative direct G protein activating peptides including mastoparan, melittin, substance P and adrenocorticotropic hormone (ACTH)-(1-24), were also able to stimulate the labelling of this protein. Labelling of the 55 kDa protein could be demonstrated in bovine brain but not peripheral tissues. Western blot analysis using an antibody against the common alpha subunit of G proteins recognized a protein co-migrating with the 55 kDa GTP-binding protein. These findings demonstrate the existence of a previously uncharacterized neuronal protein, with an apparent molecular mass of 55 kDa, that binds GTP in response to neuropeptide Y and other peptides.

Modulation of alpha1B-adrenoceptor expression by agonist and protein kinase inhibitors.

The agonist-induced up-regulation of alpha1B-adrenoceptors in clone H99 of transfected Chinese hamster ovary cells that we reported previously (Zhu et al., 1996) was further investigated. Studies with a larger number of clones revealed that the up-regulation observed in H99 cells is atypical and that most other clones exhibit down-regulation under the same conditions. The role of protein kinases in the up-regulation of alpha1B-adrenoceptors in clone H99 was further investigated. Surprisingly, the protein kinase inhibitor staurosporine induced a similar up-regulation. Neither the selective protein kinase C inhibitor GF109203X nor the activator phorbol 12-myristate, 13-acetate altered receptor expression. The tyrosine kinase inhibitors genistein and its weaker analog daidzein did not induce up-regulation but blocked the up-regulation induced by epinephrine and by staurosporine. Up-regulation was blocked by the protein synthesis inhibitor cycloheximide. These studies suggest multiple mechanisms by which different protein kinases can modulate the expression of transfected alpha1B-adrenoceptors.

Down-regulation of alpha 2-adrenoceptor subtypes.

To characterize further the alpha 2-adrenoceptor subtypes in terms of their regulation, monolayers of cells expressing either the alpha 2A (CHO-A2AR cells) or alpha 2C (OK cells) subtype were preincubated with norepinephrine for various times and the extent of receptor down-regulation was assessed. Exposure to 30 microM norepinephrine caused a similar time course and extent of down-regulation (approximately 50%) in both cells lines. The extent of down-regulation caused by 0.3 microM norepinephrine in OK cells was similar to that with 30 microM norepinephrine in CHO-A2AR cells, although the time course was somewhat slower. Reversal of the down-regulation of the alpha 2-adrenoceptor caused by 30 microM norepinephrine was more rapid in the CHO-A2AR than in the OK cell. With 0.3 microM norepinephrine, reversal of down-regulation of the alpha 2-adrenoceptor in the OK cell was slightly faster than that of the CHO-A2AR cell with 30 microM norepinephrine. These data indicate that although norepinephrine is more potent in causing down-regulation of the alpha 2C (OK cells) as compared to the alpha 2A subtype (CHO-A2AR cells), the time courses for down-regulation and its reversal are similar for the two subtypes.

Regulation of hamster alpha 1B-adrenoceptors expressed in Chinese hamster ovary cells.

Chinese hamster ovary (CHO) cells were stably transfected to express the hamster alpha 1B-adrenoeceptor, and the function and agonist-induced regulation of the binding properties of these receptors were characterized. The cells expressed approximately 230,000 receptors per cell, with a KD for [3H]prazosin of 140 pM. In assays of competition by epinephrine for [3H]prazosin binding to receptors on intact cells, 88% of the receptors were in a low affinity form. The protein kinase C activator phorbol 12-myristate, 13-acetate (PMA) did not further increase the fraction in the low affinity form, but the protein kinase C inhibitor staurosporine reduced the low affinity fraction to 51%. In sucrose density gradient centrifugation assays of receptor internalization, the percentage of receptors in the light vesicle fraction was 25% for control cells, 53% for epinephrine-pretreated cells, 44% for PMA-pretreated cells, and 53% for cells pretreated with epinephrine plus PMA. Staurosporine completely blocked PMA-induced internalization, but only partially inhibited epinephrine-induced internalization. These results suggest a relationship between low affinity binding and internalization for alpha 1B-adrenoceptors and the involvement of protein kinase C in both processes. Longer-term (24 h) exposure of cells to epinephrine induced an unexpected up-regulation of receptor density of approximately 2-fold that was accompanied by an increase in maximal agonist-stimulated phosphoinositide turnover. These studies document several regulatory differences between alpha 1B-adrenoceptors expressed in transfected CHO cells and those natively expressed in DDT1 MF-2 hamster smooth muscle cells, and they provide additional information on the molecular mechanisms involved in agonist-induced regulation of alpha 1B-adrenoceptors.