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El objetivo fue identificar la influencia existente entre las experiencias didácticas a través de las canciones de YouTube y las mejoras en las competencias básicas del idioma inglés en los universitarios, el cual reveló una correlación positiva media (rs=0.664) entre las experiencias didácticas usando canciones de YouTube y el mejoramiento de las competencias en inglés. Un 60.4% de los estudiantes universitarios prefieren aprender inglés presencialmente, mientras que el 47.3% beneficia de la integración de TICs y fomenta la participación en clase. Con una significancia bilateral (P < 0.05), se confirma la importancia de la planificación didáctica (rs=0.498), toma de decisiones (rs=0.582) e innovación (rs=0.636) en el desarrollo de habilidades comunicacionales en inglés.

En el contexto actual de pandemia el modelo de Gobierno Digital ha sido impulsado por diferentes Estados como una estrategia para incrementar la eficacia y eficiencia, facilitar ciertas operaciones, elevar la transparencia, economizar tiempo e inversión en función del Gobierno a los múltiples usuarios. A partir de la importancia que el Gobierno Digital tiene para muchos países, incluido Perú, es establecer qué aspectos son tomados, para la modernización de las instituciones públicas, para su análisis y reflexión. En función a esto, el objetivo de este artículo es analizar las variables e indicadores asumidos en la literatura científica en el periodo de 2018 a 2022 para medir el Gobierno Electrónico y la modernización en las instituciones públicas. Los resultados indican que existe relación entre el Gobierno Digital, Entidades Públicas y Modernización. Se evidencia que en la sociedad existe consenso, al concebir que las tecnologías de información y comunicación estén relacionadas de manera directa con el Gobierno Digital y Modernización de las Entidades Públicas. Se debe reforzar la preparación del empleado y del ciudadano para que puedan apropiarse del conocimiento necesario para darle un uso apropiado de las bondades que le ofrece el Gobierno Digital en las entidades públicas.

El agente causal de la hidatidosis en nuestro país es el Echinococcus granulosus. Este parásito toma como hospedadores definitivos a los cánidos y como intermediarios a los rumiantes, porcinos, especies selváticas y al hombre. En las plantas faenadoras durante la inspección de los órganos se decomisan y eliminan todos aquellos con lesiones sospechosas de hidatidosis. Esto aporta importantes datos para conocer la enfermedad, su distribución, evaluar los planes de control y erradicación yvalorar nuevas técnicas de diagnóstico y tratamiento. Existen dos puntos críticos en los que el referido diagnóstico macroscópico casi invariablemente falla aquellos órganos en los cuales los metacestodes están presentes, pero no visibles macroscópicamente y los que son decomisados por presentar lesiones similares a hidatidosis pero de etiología diferente. Este último aspecto es el que se estudió considerando como hipótesis la falta de relación entre los diagnósticos macroscópico y microscópico. Los órganos con lesiones macroscópicas fueron remitidos al laboratorio, se seleccionaron las muestras, se caracterizaron morfológicamente, topográficamente y se procesaron mediante las técnicas de rutina de inclusión en parafina y coloración con hematoxilina y eosina. El diagnóstico histopatológico positivo se basó en la observación de la morfología de los quistes. Sobre un total de 105 muestras diagnosticadas como hidatidosis, 15 resultaron negativas al diagnóstico histopatológico DOI:http://dx.doi.org/10.19137/cienvet2013-1513

Abstract: The role of CD4+ T-cells in immunity against tuberculosis has been extensively studied. However, the function of CD8+ T-cells in co-infections of HIV-1 and M. tuberculosis (VIH/Mtb) is not well understood. To evaluate the functionality of CD8+ T-cells from HIV+ patients having active TB, several immunological parameters were assayed. Results indicate that both HIV+ groups (with and without active TB), having the same viral load and peripheral blood CD4+ T and amount of lymphocytes in the blood, displayed different alterations in the ex vivo frequency for CD95 and CD127 markers in CD8+ T-cells, naive and memory positive cells, while for the HLA-DR marker, differences were observed in the total cell population. Moreover, CD8+ T- cells from TB-active patients, cultured for 72 h in the presence of PPD, showed a low proliferation rate and a high frequency of induced apoptosis as well as lower production of IFN-y IL-10 and TNF-a cytokines compared to healthy control cells. These results support the hypothesis that CD8+ T-cells lose their functionality against Mtb during an HIV-1 infection, which could be responsible for the activation of TB in VIH/Mtb co-infected patients. Resumen: El papel de las células TCD4+ en la inmunidad contra la tuberculosis ha sido ampliamente estudiado. Sin embargo, la función de las células TCD8+ en la co-infección VIH-1 y M. tuberculosis (VIH/Mtb) no está bien comprendida. Para determinar la funcionalidad de estas células TCD8+ de pacientes VIH+ con TB (tuberculosis) pulmonar activa se usaron diferentes parámetros inmunológicos. Los resultados indican que ambos grupos de pacientes VIH+ (con o sin TB activa) con la misma carga viral y cantidad de linfocitos TCD4+ en sangre, presentaron diferentes alteraciones en la frecuencia ex vivo para las moléculas CD95 y CD127 en células TCD8+ totales, vírgenes y memoria positivas, mientras que para la molécula HLA-DR, las diferencias fueron observadas en la población celular total. Además, las células TCD8+ de los pacientes con TB activa cultivadas por 72 h en presencia de PPD, presentaron baja proliferación y alta frecuencia de apoptosis inducida, así como baja producción de IFN-y IL-10 y TNF-a en comparación a los Controles sanos. Estos datos sustentan la hipótesis que las células T CD8+ pierden su funcionalidad contra el Mtb durante la infección con VIH-1, lo cual puede ser responsable de la activación de la TB en los pacientes co-infectados.

The health implications of urban development, particularly in rapidly changing, low-income urban neighborhoods, are poorly understood. We describe the Healthy Neighborhoods Study (HNS), a Participatory Action Research study examining the relationship between neighborhood change and population health in nine Massachusetts neighborhoods. Baseline data from the HNS survey show that social factors, specifically income insecurity, food insecurity, social support, experiencing discrimination, expecting to move, connectedness to the neighborhood, and local housing construction that participants believed would improve their lives, identified by a network of 45 Resident Researchers exhibited robust associations with self-rated and mental health. Resident-derived insights into relationships between neighborhoods and health may provide a powerful mechanism for residents to drive change in their communities., (Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Pediatric emergency medicine physicians may be able to use point-of-care ultrasound (POCUS) as a tool to evaluate abdominal wall masses. We present a case of a 2-month-old infant with a lower abdominal mass identified as a hernia sac by POCUS. It was initially thought to represent a Spigelian-type abdominal wall hernia but subsequently determined to be an unusual presentation of an inguinal hernia with testicular entrapment. We review each of these diagnoses in addition to relevant POCUS findings.

Migraines are common, incapacitating, and often stress inducing for pediatric patients and parents alike. According to the Agency for Healthcare Research and Quality, more than 1 million Americans seek emergency care every year due to migraines, with increasing frequency among adolescents. The disease can vary in severity and character, often mimicking life-threatening conditions, requiring prompt nuanced recognition by emergency personnel and implementation of an effective treatment strategy. Development of emergency department guidelines for the management of pediatric migraines should be based on up-to-date evidence supporting safe, appropriate therapies for children.

Objective: We examined the connections (1) between the design of the built environment and walking, (2) between the design of the built environment and obesity, and (3) between walking and obesity and income in urban settings in China., Methods: Six neighborhoods with different built environment characteristics, located in the Chinese cities of Shanghai and Hangzhou, were studied. Data on walking and other physical activity and obesity levels from 1070 residents were collected through a street intercept survey conducted in 2013. Built environment features of 527 street segments were documented using the Irvine-Minnesota Inventory-China (IMI-C) environmental audit. Data were analyzed using the State of Place™ Index., Results: Walking rates, household income and Body Mass Index (BMI) were related; neighborhoods with a higher State of Place™ Index were associated with higher rates of walking., Conclusion: This study began to establish an evidence base for the association of built environment features with walking in the context of Chinese urban design. Findings confirmed that the associations between "walkable" built environment features and walking established in existing research in other countries, also held true in the case of Chinese neighborhoods., (Copyright © 2014 Elsevier Inc. All rights reserved.)

China faces rising rates of overweight, obesity, and physical inactivity among its citizens. Risk is highest in China's rapidly growing cities and urban populations. Current urban development practices and policies in China heighten this risk. These include policies that support decentralization in land use planning; practices of neighborhood gating; and policies and practices tied to motor vehicle travel, transit planning, and bicycle and pedestrian infrastructure. In this paper, we review cultural, political, and economic issues that influence overweight, obesity, and inactivity in China. We examine key urban planning features and policies that shape urban environments that may compromise physical activity as part of everyday life, including walking and bicycling. We review the empirical research to identify planning and design strategies that support physical activity in other high-density cities in developing and developed countries. Finally, we identify successful strategies to increase physical activity in another growing, high-density city - New York City - to suggest strategies that may have relevance for rapidly urbanizing Chinese cities., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Enhanced cortical cholinergic signaling associated with nicotinic acetylcholine receptor (nAChR) stimulation has been linked with pro-cognitive actions in a variety of performance domains, including attentional tasks. Improvements in stimulus selection with the nAChR agonist nicotine have been reported but its effects on visual spatial selective attention are unclear. Employing a double-blind, placebo-controlled design, this study examined the acute actions of nicotine (6 mg) in 24 non-smokers performing a visual search task of spatial attention that was probed with behavioral performance measures and the N2pc component of the event-related potentials (ERPs), which served as a neural index of spatial attentional selection. Nicotine did not affect behavioral performance indices. In high symptomatic subjects (as indexed by greater increases in heart rate post-administration), nicotine was associated with an N2pc amplitude enhancement while in low symptomatic individuals it was associated with an N2pc difference amplitude decrease. Nicotine modulation of the ERP marker of spatial attentional selection corroborates in general the attentional effects of nAChR agonists and extends these properties to include altered selective mechanisms during visual spatial processing., (Copyright © 2011 Elsevier Inc. All rights reserved.)

We studied the ex vivo and in vitro expression of CD95/Fas and CD127 receptors in total, naive and memory CD8+ T cells from HIV infected patients with different blood counts of CD4+ T cells. In addition, spontaneous and induced apoptosis were determined in vitro using a viral antigen (Env), along with an evaluation of their specific proliferative capacity. The obtained results demonstrated that patients with low counts of CD4+ T cells (CD4 < 250/microL), showed ex vivo, a high expression of CD95/Fas and a low expression of CD127 in all CD8+ T cell subgroups, as compared with patients with bigger counts of CD4+ T cells in blood (CD4> 250/microL). In vitro analyses using Env antigen showed that CD8+ T cells displayed a similar expression of both receptors, with a higher incidence of spontaneous and induced apoptosis and a diminished proliferative capacity as compared with controls. Results indicate how the progression of VIH infection in non-treated patients is related to a decrease of CD8+ T cells in blood, characterized by failures in their proliferative capacity and apoptosis frequency, which is demonstrated by the altered expression of CD127 and CD95/Fas expression.

Background: Inter-rater reliability is an important element of environmental audit tools. This paper presents results of reliability tests of the Irvine-Minnesota Inventory, an extensive audit tool aimed at measuring a broad range of built environment features that may be linked to active living., Methods: Inter-rater reliability was measured by percentage agreement between observers. Reliability was tested on a broad range of sites in both California and Minnesota., Results: For the variables that remained in the inventory, in tests conducted at the University of California-Irvine, 76.8% of the variables had >80% agreement among the three raters. In tests conducted at the University of Minnesota, 99.2% of the variables had >80% agreement among the two raters., Conclusions: Reliability was high for most items. The inventory was modified to eliminate items with low reliability. Differences in the use of the inventory and the goals of the research led to generally higher reliability in Minnesota. Those differences, limitations, and directions for future research are discussed.

Background: Researchers and policymakers increasingly identify active living-including walking and bicycling for travel and recreation-as a potential strategy to increase rates of physical activity in the United States. Understanding the impact of the built environment on physical activity levels requires reliable methods to measure potentially relevant built environment features. This paper presents an audit tool-the Irvine Minnesota Inventory-that was designed to measure a wide range of built environment features that are potentially linked to active living, especially walking., Methods: The inventory was created through a literature review, focus group interviews, a panel of experts, and field testing in 27 settings. The inventory was developed in 2003-2004., Results: The Irvine Minnesota Inventory includes 162 items, organized into four domains: accessibility (62 items), pleasurability (56 items), perceived safety from traffic (31 items), and perceived safety from crime (15 items). (Some items are in multiple domains.) The inventory includes both a paper version and a version in Microsoft Access, to allow data to be input directly into the computer., Conclusions: Limitations of methods used to develop the inventory are discussed. Strategies are offered for using the Irvine Minnesota Inventory to systematically and reliably measure characteristics of the built environment that are potentially linked to active living.

Background: Walking or bicycling to school could contribute to children's daily physical activity, but physical environment changes are often needed to improve the safety and convenience of walking and cycling routes. The California Safe Routes to School (SR2S) legislation provided competitive funds for construction projects such as sidewalks, traffic lights, pedestrian crossing improvements, and bicycle paths., Methods: A cross-sectional evaluation examined the relationship between urban form changes and walking and bicycle travel to school. Surveys were distributed to parents of third- through fifth-grade children at ten schools that had a completed SR2S project nearby. Two groups were created based on whether parents stated that their children would pass the SR2S project on the way to school or not., Results: Children who passed completed SR2S projects were more likely to show increases in walking or bicycle travel than were children who would not pass by projects (15% vs 4%), based on parents' responses., Conclusions: Results support the effectiveness of SR2S construction projects in increasing walking or bicycling to school for children who would pass these projects on their way to school.

Muscarinic activation of bovine tracheal smooth muscle (BTSM) is involved in cyclic guanosine monophosphate (cGMP) production mediated through soluble (sGC) and membrane-bound (mGC) guanylyl cyclases. A muscarinic- and NaCl-sensitive mGC exists in BTSM regulated by muscarinic receptors coupled to G proteins. To identify the mGCs expressed in BTSM, reverse transcriptase/polymerase chain reaction (RT-PCR) from total RNA was performed using degenerate oligonucleotides for amplification of a region conserved among GC catalytic domains. Cloning of amplification products revealed that 76% of all BTSM GC transcripts corresponded to the sGC beta1 subunit and 24% to the B-type (C-type NP 1-22 [CNP]-sensitive) GC receptor. cGMP production by BTSM membrane and soluble fractions confirmed that sGC activity is 3-fold with respect to mGC activity. RT-PCR using specific oligonucleotides revealed that A (atrial NP-sensitive) and C (guanylin-sensitive) mGC subtypes are also expressed in BTSM. Stimulation of basal plasma membrane GC activity by CNP was higher than that by ANP, whereas guanylin showed no effect, indicating that CNP-sensitive guanylyl cyclase (GC-B) is the predominant functional BTSM mGC subtype. Strong adenosine triphosphate inhibition of CNP-stimulated mGC activity supports the finding that the tracheal mGC isoform belongs to the natriuretic peptide-sensitive mGCs. Additionally, CNP was able to reverse the chloride inhibition of BTSM mGC activity, suggesting that this is a novel G protein-coupled GC-B receptor.

The effects of carbachol on the cyclic GMP (cGMP) content of bovine tracheal smooth muscle in the absence of phosphodiesterase inhibitors were evaluated. Carbachol (1 x 10(-5) M) induced two cGMP peaks, at 20 and 60 sec. Both cGMP signals were carbachol concentration-dependent (1 x 10(-11) to 1 x 10(-5) M), the first being higher than the second. The cGMP signal induction was studied using an inhibitor of the soluble guanylyl cyclase (GC), 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), and a nitric oxide (NO) synthase inhibitor, Nomega(6)-nitro-L-arginine methyl ester (NAME). ODQ (1 x 10(-7) M) did not affect the second cGMP peak but abolished the first peak, suggesting that a soluble GC may be involved. NAME (1 x 10(-4) M) did not affect the cGMP signals, but changed their 2:1 ratio and also induced a time-shift of the first peak to 10 sec and the second to 50 sec. These results indicate that the NO-soluble GC cascade is not responsible for these muscarinic effects on cGMP levels.

Membrane-bound guanylyl cyclase (GC) is regulated by muscarinic receptors (mAChRs). Carbamylcholine (CC) induces a "dual" biological response on GC activity. Thus, an activation is observed at 0.1 nM and a maximal response at 1 nM CC. However, at higher agonist concentration (> 100 nM), there is an agonist-dependent inhibition of GC. This CC dual response is affected by 4-DAMP and HDD (M3 antagonists), which produce a right-shift of the CC curve; the maximal CC dose response with 4-DAMP is more potent than that with HDD. Moreover, AFDX-DS (an M2 antagonist) increases basal activity and decreases the agonist-dependent inhibition. Neither the CC response nor the CC maximal dose responses are affected by pirenzepine (PZ, M1 antagonist). The agonist-dependent stimulation of GC activity is inhibited by 4-DAMP showing a -log IC50 = 8.4 +/- 0.4, while AFDX116 DS poorly inhibits such activity with a -log IC50 = 5.0 +/- 0.2. The agonist-independent (basal) GC activity also was inhibited by 4-DAMP, in a dose-dependent manner, with an IC50 = 8.5 +/- 0.2. Nonetheless, other muscarinic antagonists (PZ and HDD) were not able to inhibit this basal GC. Pertussis toxin treatment produces a complete blockade of the agonist-dependent inhibition of GC with a full expression of the agonist-dependent activation of membrane-bound GC. These results indicate that membrane-bound GC is regulated by muscarinic agents through two opposite signaling pathways; one involves the activation of GC via an M3 mAchR coupled to a PTX-insensitive G protein, while the GC inhibition is mediated through a PTX-sensitive Gi/o protein possibly coupled to an M2 mAChR.

A biochemical characterization of a Mg(2+)-ATPase activity associated with a plasma membrane fraction isolated from airway (tracheal) smooth muscle was performed. This enzyme is an integral part of the membrane remaining tightly bound after 0.6 M KCl extraction. This enzyme activity showed a cold inactivation in the presence of ATP and Mg2+. Also, this Mg(2+)-ATPase was stimulated by monovalent anions being Cl-, the best anion for such stimulation, even though Br- and I- were good substitutes and F- was ineffective. This Cl--stimulated activity showed a powerful nucleosidetriphosphatase activity having the following divalent cation specificity: Mg2+ > Mn2+ > Ca2+, where Zn2+ and Fe2+ were ineffective. This ATPase activity was not inhibited by ouabain oligomycin C and vanadate indicating that neither P- or F-ATPases were associated with this enzyme activity. However, the existence of a V-ATPase was shown by the significant inhibition causes by bafilomycin A1. Additionally, this V-ATPase seems to be coupled to Cl- conductor because duramycin inhibited this ATPase activity. The presence of a H+ pump associated to this V-ATPase was shown indirectly, through the stimulatory effect produced by uncouplers such as FCCP and 1799, which were able to produce significant stimulation of this V-ATPase indicating the existence of a H(+)-ATPase. Finally, the immunodetection of a 72 kDa polypeptide using a specific antibody against the A subunit (72 kDa) of V-ATPase from chromaffin granule demonstrated the presence of a V-ATPase in this plasma membrane fraction.

In this work, we show evidence to support the existence of a Ca2+ calmodulin (CAM) dependent protein kinase and a substrate, a 17 kilodaltons (KDA) polypeptide being both associated to sarco(endo)plasmic reticulum vesicles from tracheal smooth muscle. Anti-CAM drugs such as compound 48/80 inhibited this protein kinase activity and this inhibition was reversed in the presence of Ca2+CAM. Moreover, as a result of this phosphorylation, there is a significant increase in the ATP dependent Ca2+ transport in these sarco(endo)plasmic vesicles.

A mammalian plasma-membrane-bound guanylyl cyclase is inhibited by NaCl and this inhibition is dependent on GTP concentrations and independent of the chloride salt type. This chloride inhibition is reversed by GTP analogs such as GTP gamma S, suggesting the involvement of G proteins. When the ability of bacterial toxins to affect this chloride-sensitive guanylyl cyclase was examined, pertussis toxin decreased the basal activity and the chloride sensitivity was greatly reduced. Cholera toxin induced a slight activation of the basal activity, without significant changes in the NaCl inhibition. These data indicate that G proteins regulate the chloride sensitivity of this guanylyl cyclase activity. Another property described here is the ability of ATP and analogs to inhibit the basal activity. However, these nucleotides did not modify the chloride sensitivity of the membrane-bound guanylyl cyclase activity.

Subcellular fractions isolated from tracheal smooth muscle have been identified using biochemical markers and measuring the [3H]QNB muscarinic receptor binding activity in these fractions. This muscarinic receptor (mAchR) activity was slightly enriched 1.6 times in the crude mitochondrial fraction (M), 2.6 times in the crude microsomal fraction (P), and greatly enriched in the highly purified plasma membranes fractions, being 5.3 times in a heavy plasma membrane fraction designed as P2 and 9.1 times in a light plasma membrane fraction named P1 fraction. The muscarinic receptor subtypes present in the subcellular fractions were identified using competition experiments. The binding of five selective antagonists, pirenzepine, AF-DX 116, hexahydrodifenidol, methoctramine and 4-DAMP were examined. In this sense, the M1 antagonist pirenzepine showed pKi's values between 6.44-7.45 and the M2 antagonist AF-DX 116 showed pKi's values ranging from 6.75 to 7.45 being the lowest pKi's values here described. The antagonist hexahydrodifenidol showed higher affinities than pirenzepine-derivated compounds with pKi's values from 7.25 to 7.65. The antagonist 4-DAMP exhibited pKi's values from 8.18-8.41. Finally, methoctramine showed similar affinities as 4-DAMP, with pKi's ranging from 8.09 to 8.22 suggesting the existence of M2 receptors in these fractions. These data suggest that M2 mAchR are present in all particulate fractions here studied. It is important to emphasize that the M2 muscarinic receptor presents in the light plasma membrane fraction (P1) shows poor selectivity towards the muscarinic antagonists being different from the M2 mAchRs associated with other subcellular fractions isolated from bovine tracheal smooth muscle.

Protons generated inside the cells during metabolic activity have to be extruded through active mechanisms from the intracellular to the extracellular space. One of the systems involved in proton transport across membranes are the V-ATPases, which are oligomeric complexes that have been found in several subcellular organelles energizing such organelle through a proton gradient and a membrane potential. In this paper, a V-ATPase activity has been described at the plasma membranes fractions isolated from airway smooth muscle. This activity was measured as a Cl- stimulated Mg2+ ATPase. This Cl- activating effect was also shared by others halogens as I- and Br- but not F-. This Cl- stimulated ATPase is a nucleotide triphosphatase being unable to hydrolyze mono and dinucleotides. The divalent cations showed the following sequence of activation (Mg2+ > Mn2+ > Ca2+) of the Cl- activated Mg2+ ATPase. This Cl- stimulated Mg2+ ATPase was insensitive to ouabain, vanadate, sodium azide and rutamicina. NEM (N-ethylmaleimide) partially inhibited this activity but a complete inhibition was observed with p-CMB (p-chloromercurbenzoate ). Several specific proton transport inhibitors were employed to show the presence of a H+ pump activity. Thus, the strong inhibition induced by DCCD suggest the existence of hydrophobic subunits related to a proton channel. In addition, protonophores as 1799 and FCCP stimulated the Cl- stimulated ATPase indicating the presence of a H+ pump in these plasma membranes vesicles. The chloride requirement could be explained by the existence of a chloride conductor coupled to the proton pump (H+ ATPase-type V) due to the inhibitory effect of duramycin.(ABSTRACT TRUNCATED AT 250 WORDS)

We have studied the composition of ATP-driven proton pumps from bovine heart mitochondria and have reconstituted the oligomycin-sensitive ATPase complex from its individual components. The complex contains 9 to 10 subunits of which 5 are assembled in the soluble F1 protein, 2 are required for the attachment of F1 to the membrane and 2 form the proton channel within the membrane. With the help of information obtained from studies of the chloroplast and the bacterial proton pumps, we can tentatively assign a function to each of the subunits of the pump. The position of F1 outside of the membrane seen in electron micrographs of negatively stained preparations, does not appear to be an artifact. Evidence from immunological studies, chemical derivatizations as well as further electron microscopy (positive staining and freeze-etching), support this statement. We describe in this paper a 28 000-dalton polypeptide which has been isolated from the mitochondria membrane and is required for the reconstitution of oligomycin-sensitive ATPase and 32Pi-ATP exchange activity. We propose a mechanism of action of the proton pump in which the key energy-yielding reaction is the binding of Mg2+ to the protein. The function of the proton gradient is to displace Mg2+ from this site to permit cyclic repetition of the binding process. Essential for this scheme is the cyclic opening and closing of the proton channel. We have outlined our present approaches to test this hypothesis.

Vasoactive intestinal peptide (VIP) has been shown to be steroidogenic in monolayer cultures of a murine adrenal tumor but must be present at concentrations about 100-fold greater than ACTH to elicit the same degree of stimulation. Both peptides enhanced cAMP synthesis, although there was again a difference of 2 orders of magnitude in the dose-response curves. In contrast, VIP stimulated adenyl cyclase activity of tumor membranes in the same concentration range as ACTH. Maximum activity with VIP was less than that with ACTH in the absence or presence of a saturating amount of guanylyl imido-diphosphate. Saturating amounts of both peptides stimulated activity to levels greater than that with either ACTH or VIP alone, but the activity was not fully additive. An o-nitrophenyl sulfenyl derivative of ACTH inhibited ACTH-stimulated adenyl cyclase activity but not VIP-stimulated activity. Low concentrations of calcium potentiated the ability of submaximal doses of ACTH to stimulate adenyl cyclase but had no effect on the response to VIP. Concentrations of secretin or glucagon comparable to that of VIP did not stimulate steroidogenesis in intact cells. These data suggest that VIP may bind to a unique receptor which may be distinct from that of ACTH.