Celiac disease seroprevalence in subjects with dyspeptic symptoms. A study on a Mexican population.

INTRODUCTION AND AIMS: Celiac disease (CD) is an autoimmune enteropathy that develops in genetically susceptible individuals. The typical gastrointestinal manifestation is diarrhea but symptoms of dyspepsia, such as epigastric pain, nausea, or satiety, can sometimes appear. Previous studies have reported that the prevalence of CD in patients with dyspepsia can be as high as 7%. The aim of the present study was to evaluate CD seroprevalence in subjects with dyspeptic symptoms and a control group in a Mexican population. MATERIAL AND METHODS: A case-control study was conducted on blood donors that answered the PAGI-SYM questionnaire for dyspepsia and in whom IgA antibodies to tissue transglutaminase 2 (IgA anti-tTG2) and IgG antibodies to deamidated gliadin peptide (IgG anti-DGP) were determined. CD seroprevalence in subjects with dyspeptic symptoms and in asymptomatic subjects was compared. RESULTS: A total of 427 subjects (76.3% men), with a mean patient age of 34 years (range of 18-65 years) were included. Of those participants, 87 (20.3%) had symptoms of dyspepsia (group A) and 340 (79.6%) were asymptomatic (group B). Antibodies were positive in one (1.15%) of the group A subjects (1/87, 95% CI 0.2-6 %), whereas they were positive in 4 (1.18%) of the group B subjects (4/340, 95% CI 0.4-2.9%, p = 0.59). CONCLUSIONS: CD seroprevalence in the study population with dyspeptic symptoms (1%) was not different from that of the control population. Thus, CD screening in Mexican patients with dyspepsia is not justified.

Frequency of human papillomavirus infection in patients with gastrointestinal cancer. / Frecuencia de infección por virus del papiloma humano en pacientes con cáncer del aparato digestivo.

INTRODUCTION AND AIM: Cancer is the result of the interaction of genetic and environmental factors. It has recently been related to viral infections, one of which is human papillomavirus. The aim of the present study was to describe the frequency of human papillomavirus infection in patients with digestive system cancers. MATERIALS AND METHODS: A prospective, multicenter, observational study was conducted on patients with gastrointestinal cancer at 2public healthcare institutes in Veracruz. Two tumor samples were taken, one for histologic study and the other for DNA determination of human papillomavirus and its genotypes. Anthropometric variables, risk factors, sexual habits, tumor location, and histologic type of the cancer were analyzed. Absolute and relative frequencies were determined using the SPSS version 24.0 program. RESULTS: Fifty-three patients were studied. They had gastrointestinal cancer located in: the colon (62.26%), stomach (18.87%), esophagus (7.55%), rectum (7.55%), and small bowel (3.77%). Human papillomavirus was identified in 11.32% of the patients, 66.7% of which corresponded to squamous cell carcinoma and 33.3% to adenocarcinoma. Only genotype 18 was identified. Mean patient age was 61.8±15.2 years, 56.60% of the patients were men, and 43.40% were women. A total of 15.8% of the patients had a family history of cancer and 31.6% had a personal history of the disease, 38.6% were tobacco smokers, and 61.4% consumed alcohol. Regarding sex, 5.3% of the patients said they were homosexual, 3.5% were bisexual, 29.8% engaged in oral sex, and 24.6% in anal sex. CONCLUSIONS: Our study showed that human papillomavirus infection was a risk factor for the development of gastrointestinal cancer, especially of squamous cell origin.

Improved method for effective rock microporosity estimation using X-ray microtomography.

Petrophysical analysis using X-ray microtomography provides key textural and compositional information, useful to investigate porous media characteristics of hydrocarbon and geothermal reservoirs. Several approaches, used for rock porosity estimation from tomography data, rely mainly on visual or mathematical segmentation algorithms that attempt to obtain thresholding values to segment a phase solved by pixel analysis resolution. Therefore, porosity is evaluated using only pores above pixel resolution (macroporosity), and dismiss pores sized less than the pixel resolution (microporosity) that can be essential to characterize permeability conditions of geothermal reservoirs. Here we propose an improved method to calculate the total effective porosity and simulate the absolute permeability of rock samples. This method combines the analysis of X-ray computed microtomography (µCT) with the interpretation of data using a powerful thresholding method that is based on the greyscale interclass variance. The 3D volume is segmented into three domains: solid, pores above resolution and, an intermediate region where each pore below resolution is linearly combined with solid matrix resulting in a grey scaled pixel equal to this combination. For the intermediate region, the microporosity was calculated employing a Matlab code that provides a new thresholding value containing pores, both above and below resolution (total porosity). Finally, by using this new calculated thresholding value the total effective porosity was obtained and an absolute permeability simulation was implemented only to the connected pores. Our results show that micropores contribute for nearly 50 percent of the total porosity and that microporosity plays a key role in estimating effective porosity, and assessing the geothermal potential of a rock reservoir.

Evaluation of the safety and adjuvant effect of a detoxified listeriolysin O mutant on the humoral response to dengue virus antigens.

Listeriolysin O (LLO) has been proposed as a potential carrier or adjuvant molecule in the vaccination field. However, the cytotoxic and pro-apoptotic effects of LLO are the major limitations for this purpose. Here, we have performed a preclinical safety evaluation and characterized a new potential adjuvant application for a non-cytolytic LLO mutant (dtLLO) to enhance and modulate the immune response against the envelope (E) protein from dengue virus. In addition, we have studied the adjuvant effects of dtLLO on human immune cells and the role of membrane cholesterol for the binding and proinflammatory property of the toxoid. Our in-vivo results in the murine model confirmed that dtLLO is a safer molecule than wild-type LLO (wtLLO), with a significantly increased survival rate for mice challenged with dtLLO compared with mice challenged with wtLLO (P < 0·001). Histopathological analysis showed non-toxic effects in key target organs such as brain, heart, liver, spleen, kidney and lung after challenge with dtLLO. In vitro, dtLLO retained the capacity of binding to plasma membrane cholesterol on the surface of murine and human immune cells. Immunization of 6-8-week-old female BALB/c mice with a combination of dtLLO mixed with E protein elicited a robust specific humoral response with isotype diversification of immunoglobulin (Ig)G antibodies (IgG1 and IgG2a). Finally, we demonstrated that cholesterol and lipid raft integrity are required to induce a proinflammatory response by human cells. Taken together, these findings support a potential use of the dtLLO mutant as a safe and effective adjuvant molecule in vaccination.

Non-Conjugated Chitosan-Based Nanoparticles to Proteic Antigens Elicit Similar Humoral Immune Responses to Those Obtained with Alum.

Biodegradables Chitosan-based Nanoparticles (CS NPs) have been extensively studied as delivery system for therapeutic molecules and as efficient carriers or adjuvants in experimental vaccination. Physicochemical association between CS NPs and antigens is a key step for the biological function as carrier devices. However, for the adjuvant CS NPs property, it is not well known if coupling with vaccine antigens is required or not to potentiate the immune response. To address this issue, in this work, we evaluated the potential adjuvant effect of CS NPs by simply mixing with two different antigens such as Bovine Serum Albumin (BSA) or E protein from Dengue Virus serotype 2 (E protein DENV2). Thus the CS NPs were prepared by ionic gelation with sodium tripolyphosphate, resulting particles among 68 and 188 nm of size. Immunization of 6­8 week old female BALB/c mice, were carried out by intraperitoneal route with a simple combination of CS NPs either with BSA (CS NPs-BSA) at 10 µg or with E protein DENV2 (CS NPs-Protein E) at 5 µg. Combinations with the above antigens with CS NPs elicited robust specific primary and secondary humoral responses comparable to alum, a well-known adjuvant. BSA-specific IgG titers were detectable by day 14 after priming with the CS NPs-BSA formulation, with titers that ranged from 102 to 103 EU ml-. After a second immunization, the anti-BSA titers ranged around 104 EU ml-. In contrast, in the group of mice immunized with the protein alone, BSA-specific serum IgG titers were undetectable at day 14 and 28. For the immunizations with the CS NPs-E protein formulation, we observed also a remarkable specific-antibody production in the primary response, with titers reaching 103 EU ml-. After the booster immunization the anti-E protein DENV2 antibodies titers reached peak values around 104 EU ml-. Interestingly, for both antigens, the combination with CS NPs polarized the immune response to a Th2-like profile, which is characterized mainly by the production of the IgG1 Isotype, confirming that CS NPs can enhance and modulate the humoral immune responses against different antigens independently of physicochemical conjugation. This could represent a simplification in the use of CS NPs as adjuvants in vaccination.

Compromiso nodal y extranodal detectado con PET/CT en linfoma en etapificación / Nodal and extranodal involvement detected by PET/CT in staging lymphoma

Objective: To describe visible nodal and extra-nodal involvement using PET/CT in the different types and subtypes of lymphoma in staging. Patients and method: PET/CT with F18-FDG were reviewed in patients with lymphoma staging, determining frequency and location of nodal and extra-nodal involvement, and intensity of F18-FDG uptake measured by SUVmax. Results: Of the 102 patients with NHL (average SUVmax 13.0 ± 9.7), 86.3% had nodal involvement (51.9% on both sides of the diaphragm, 24.5% only above the diaphragm), and 66.7% extra-nodal compromise (42.6% bone marrow, 22.1% muscle, 16.2% renal). Of the 30 patients with HL (average SUVmax 14.6 ± 6.0), 100% had nodal involvement (63.3% only above the diaphragm, 36.7% above and below the diaphragm), and 30% had extra-nodal involvement (66.7% bone marrow, 22.2% lung). Conclusion: PET/CT is the method of choice in the staging of lymphoma, allowing the detection of nodal and extra-nodal disease in both HL and NHL.

Objetivo: Describir el compromiso nodal y extranodal visible con PET/CT en los distintos tipos y subtipos de linfoma en etapificación. Pacientes y método: Se revisaron los PET/CT con F18-FDG realizados a pacientes con linfoma en etapificación, determinando frecuencia y localización del compromiso nodal y extranodal, e intensidad de captación de F18-FDG medida mediante SUVmax. Resultados: De los 102 pacientes con LNH (SUVmaxpromedio 13,0±9,7), un 86,3% presentó compromiso nodal (51,9% a ambos lados del diafragma, 24,5% sólo sobre el diafragma) y 66,7% compromiso extranodal (42,6% médula ósea, 22,1% muscular, 16,2% renal). De los 30 pacientes con LH (SUVmax promedio 14,6±6,0), el 100% tuvo compromiso nodal (63,3% sólo sobre el diafragma, 36,7% sobre y bajo el diafragma), y 30% compromiso extranodal (66,7% médula ósea, 22,2% pulmón). Conclusión: El PET/CT es el método de elección en la etapificación del linfoma, permitiendo detectar enfermedad nodal y extranodal, tanto en LH como en LNH.

Prevalence of celiac disease and related antibodies in patients diagnosed with irritable bowel syndrome according to the Rome III criteria. A case-control study.

BACKGROUND: The cost-effectiveness for screening for celiac disease (CD) in patients with irritable bowel syndrome (IBS), specifically in the diarrhea (IBS-D) subtype, is beneficial if the prevalence is >1%. However, recent studies have shown controversial results. In this large case-control study, our aim was to determine the prevalence of CD and a panel of related antibodies in patients diagnosed with IBS. MATERIALS AND METHODS: Four hundred IBS patients (Rome III) and 400 asymptomatic healthy controls were prospectively evaluated using antihuman tissue transglutaminase (h-tTG IgA) and deamidated gliadin peptide antibodies (DGP II IgA and DGP II IgG). Duodenal biopsy was performed on the patients that were positive for the h-tTG IgA and/or DGP II IgG antibodies. RESULTS: The mean age of the population was 44.47 ± 18.01 years and 335 (82%) of the subjects were women. Twenty-one patients and six controls had at least one positive test for CD (5.25% VS 1.5%, p = 0.003, OR 3.63 [95% CI 1.4-9.11]). Eighteen patients were positive for h-tTG and/or DGP-II IgG. Histologic confirmation of CD was 2.5% in the IBS patients vs 0.5% in the controls (p = 0.04, OR 5.21). The IBS-D subtype had the highest prevalence for serological positivity (12.7%). CONCLUSIONS: Up to 5.2% of the patients with IBS according to the Rome III criteria were positive for at least one of the CD-related antibodies and 2.5% had biopsy-confirmed CD. Therefore, in our population, screening for CD in subjects with IBS appears to be a reasonable strategy, especially in the IBS-D subgroup.

Biological effects of listeriolysin O: implications for vaccination.

Listeriolysin O (LLO) is a thiol-activated cholesterol-dependent pore-forming toxin and the major virulence factor of Listeria monocytogenes (LM). Extensive research in recent years has revealed that LLO exerts a wide array of biological activities, during the infection by LM or by itself as recombinant antigen. The spectrum of biological activities induced by LLO includes cytotoxicity, apoptosis induction, endoplasmic reticulum stress response, modulation of gene expression, intracellular calcium oscillations, and proinflammatory activity. In addition, LLO is a highly immunogenic toxin and the major target for innate and adaptive immune responses in different animal models and humans. Recently, the crystal structure of LLO has been published in detail. Here, we review the structure-function relationship for this fascinating microbial molecule, highlighting the potential uses of LLO in the fields of biomedicine and biotechnology, particularly in vaccination.

Dynamics of interleukin-21 production during the clinical course of primary and secondary dengue virus infections.

Previous studies have revealed the clinical relevance of pro-inflammatory cytokine production during dengue virus (DENV) infections. In this study, we evaluated the production of interleukin-21 (IL-21), a key soluble mediator mainly produced by CD4+ T cells. The aim of this study was to investigate the role of IL-21 production during the clinical course of primary and secondary DENV infections and the potential association of IL-21 serum levels with the disease pathogenesis. Blood samples from DENV-infected patients were collected on different days after the onset of symptoms. Patients were classified according to their phase of disease (acute vs. convalescent phases), the type of infection (primary vs. secondary), and the clinical severity of their disease (dengue fever (DF) vs. dengue hemorrhagic fever (DHF)). IL-21 levels were measured using a quantitative capture ELISA assay. The levels of IL-21 were significantly elevated in the disease group compared with the control group. IL-21 was detected in primary and secondary DENV infections, with a significantly higher concentration in the convalescent phase of primary infections. IL-21 levels were significantly higher in patients with secondary acute DHF infections when compared with those with secondary acute DF infection. There was a relationship between the elevated serum levels of IL-21 and the production of DENV-specific IgM and IgG antibodies. Taking together, our results show for the first time the involvement of IL-21 during the clinical course of DENV infections. We speculate that IL-21 may play a protective role in the context of the convalescent phase of primary infections and the acute phase of secondary infections.

TREM-1 modulation during early stages of dengue virus infection.

Uncontrolled and intricate production of inflammatory factors is the characteristic feature of dengue infection. The triggering receptor expressed in myeloid cells-1 (TREM-1), expressed on the surface of monocytes and neutrophils, is capable of enhancing and regulating the inflammatory response via the production of different mediators in bacterial and viral infections. Here, both the expression of TREM-1 on human monocytes and neutrophils from peripheral blood of dengue infected individuals, as well as the levels of the soluble form of TREM-1 (sTREM-1) in the sera of these patients were compared against healthy controls. A significant reduction of TREM-1 expression was observed in neutrophils during the first days of infection, followed by a gradual recovery throughout the course of infection. Also, sera from DENV-infected patients exhibited significantly higher sTREM-1 levels than healthy individuals. The difference was more pronounced during the first 5 days after the onset of symptoms. These findings highlight the dynamic process of TREM-1 expression during DENV infection. We hypothesized that increment of free sTREM-1 could be a compensatory mechanism aiming to counteract the inflammatory process elicited during DENV infection.

[General self-efficacy scale validation in Chile]. / Validación de la escala de autoeficacia general en Chile.

BACKGROUND: Self efficacy refers to an individuals belief in his or her capability to produce given achievements and the individuals perception of his or her ability to perform an action. AIM: To evaluate the psychometric properties of the General Self-efficacy Scale in Chilean population. MATERIAL AND METHODS: The study was carried out in 360 subjects, both sexes, 15-65 years of age, from Concepción, Chile, who answered Self-efficacy, Self-esteem and Health Status Perception instruments. Reliability was verified by Cronbachs alpha coefficient and validity by expert re-vision, univariate statistics, correlations among items, item-scale correlations, and correlations with Self-esteem and Perception of Health Status constructs. RESULTS: The structure of the scale is uni-dimensional, homogenous and positively related with the constructs examined. CONCLUSIONS: The General Self-efficacy Scale is a reliable and valid measure of the perception of self-efficacy in the Chilean population.

Validación de la escala de autoeficacia general en Chile / General self-effcacy scale validation in Chile

Background: Self effcacy refers to an individual’s belief in his or her capability to produce given achievements and the individual’s perception of his or her ability to perform an action. Aim: To evaluate the psychometric properties of the General Self-effcacy Scale in Chilean population. Material and Methods: The study was carried out in 360 subjects, both sexes, 15-65 years of age, from Concepción, Chile, who answered Self-efficacy, Self-esteem and Health Status Perception instruments. Reliability was verified by Cronbach’s alpha coefficient and validity by expert re-vision, univariate statistics, correlations among items, item-scale correlations, and correlations with Self-esteem and Perception of Health Status constructs. Results: The structure of the scale is uni-dimensional, homogenous and positively related with the constructs examined. Conclusions: The General Self-efficacy Scale is a reliable and valid measure of the perception of self-efficacy in the Chilean population.

Agresión y violencia en la escuela como factor de riesgo del aprendizaje escolar / Aggression and violence in school as a risk factor of school education

Un problema actual y creciente de salud en la comunidad escolar es la agresión y violencia observada entre los estudiantes, siendo de tal intensidad que ha provocado incidentes negativos en niños y adolescentes, como dificultad en el aprendizaje y abandono escolar, observándose esta problemática transversalmente en diversos contextos culturales y sociales. Esta revisión bibliográfica tiene como objetivo apreciar cómo se da la agresión y violencia entre los escolares, los factores que están involucrados en estos eventos, así como también identificar algunas intervenciones que se han llevado a cabo para prevenir y tratar estas conductas, y los resultados obtenidos. Dentro de los factores que se relacionan con la agresión escolar están los de tipo individual, familiar, escolar y del ambiente. Las intervenciones realizadas han tenido como foco a los padres, profesores y/o alumnos(as), obteniéndose resultados positivos en aquellas con enfoque integral.

A current problem and increasing health in the school community is the observed aggression and violence among students, being of such intensity that has led to adverse incidents in children and adolescents, such a difficulty in learning and school dropout, having this problem across various cultural and social contexts. This bibliographical revisión has the objective to appreciate how the aggression and violence occurs among students,the factors that are involved in these events, as well as to indentify some interventios that have been carried out to prevent and treat these conducís and results. Within the factors that are related with the school aggression are: those of individual type, familiar, school activities and school atmosphere. The interventions made the parents responsibles, teachers and students in general, the results of these objectives has been positive.

Lipopopeptidephosphoglycan from Entamoeba histolytica activates human macrophages and dendritic cells and reaches their late endosomes.

Lipopopeptidephosphoglycan (LPPG) is a complex macromolecule from the surface of Entamoeba histolytica trophozoites. We analysed the interaction between LPPG and human macrophages and dendritic cells (DCs) and found that LPPG is internalized by these cells and activates them. The internalization process involves intracellular traffic from the cell membrane to late endosomes, as shown by co-localization of LPPG with late endosomes marked with FITC-dextran and LAMP-1. LPPG-activated DCs have increased expression of co-stimulatory molecules CD80, CD86 and CD40 and produce pro-inflammatory cytokines TNF-alpha, IL-8 and IL-12. Taken together, these results show that LPPG activates antigen-presenting cells and reaches intracellular compartments that are involved in antigen presentation.

Factores biológicos y psicosociales predictores del estilo de vida promotor de salud / Biological and psychosocial factors that predict health promoting lifestyles

Background: One of the goals of the national health reform is to promote a healthy lifestyle in all the population. The determinants of healthy lifestyles need to be identified to guide people towards this purpose. Aim: To analyze the health promoting lifestyle (HLP) in a community of Concepción and to identify the personal factors that might be predictors of such lifestyle. Material and methods: Pender's health promotion model was used as the conceptual framework for exploring the HLP among 360 persons aged from 15 to 64 years, free from chronic diseases. Data were obtained by a semi structured questionnaire and the following scales were used to measure HLP: perceived health status, perceived self esteem, and perceived self efficacy. Relationships between personal factors and HLP were studied. Data were processed with SAS software and analyzed with descriptive and inferential statistics. Results: Only 52.2 percent of the sample had a healthy lifestyle. The variables sex, age, occupation, access to health care, self esteem, perceived health status and perceived self efficacy had a significant effect on HLP. A regression model showed that self esteem, self efficacy, sex, age, occupation and access to health care explained 30 percent of the variation in health lifestyle. Conclusions: Only half of the studied sample had a healthy lifestyle. The variables obtained with the regression model, should be considered to create effective interventions encouraging persons to integrate healthy behaviors to their life.

[Biological and psychosocial factors that predict health promoting lifestyles]. / Factores biológicos y psicosociales predictores del estilo de vida promotor de salud.

BACKGROUND: One of the goals of the national health reform is to promote a healthy lifestyle in all the population. The determinants of healthy lifestyles need to be identified to guide people towards this purpose. AIM: To analyze the health promoting lifestyle (HLP) in a community of Concepción and to identify the personal factors that might be predictors of such lifestyle. MATERIAL AND METHODS: Pender's health promotion model was used as the conceptual framework for exploring the HLP among 360 persons aged from 15 to 64 years, free from chronic diseases. Data were obtained by a semi structured questionnaire and the following scales were used to measure HLP: perceived health status, perceived self esteem, and perceived self efficacy. Relationships between personal factors and HLP were studied. Data were processed with SAS software and analyzed with descriptive and inferential statistics. RESULTS: Only 52.2% of the sample had a healthy lifestyle. The variables sex, age, occupation, access to health care, self esteem, perceived health status and perceived self efficacy had a significant effect on HLP. A regression model showed that self esteem, self efficacy, sex, age, occupation and access to health care explained 30% of the variation in health lifestyle. CONCLUSIONS: Only half of the studied sample had a healthy lifestyle. The variables obtained with the regression model, should be considered to create effective interventions encouraging persons to integrate healthy behaviors to their life.

Effects of pulp and paper mill effluents on the microplankton and microbial self-purification capabilities of the Biobío River, Chile.

Most studies focus on the ecotoxicity of pulp and paper mill effluents, rather than on how they affect the physicochemical and biological structure and the intrinsic ecological capabilities of the receiving watercourses. We investigated the impact of such effluents on the water quality, microplankton system and microbial self-purification capacity (degradation of polymeric organic compounds via extracellular enzymes) of the Biobío River in Chile. The physicochemical impact on the water quality was indicated by raised conductivity, by the pollution of the water body with nitrate, nitrite and soluble reactive phosphorus, by the appearance of tannin and lignin, and by the steady accumulation of inorganic and organic suspended matter (SPM) along the river. From the biological structure of the microplankton system, very low and declining concentrations of chlorophyll a and heterotrophic flagellate densities were determined. The pulp and paper mill effluents introduced high bacterial abundances and biomass concentrations into the river water. This reflects the effective use made of the abundantly available inorganic and organic nutrients within this industrial and municipal process water by bacteria adapted to these extreme environments, additionally supported by concomitant low grazing pressure derivable from low heterotrophic flagellate abundances. Indeed, in one section of the river affected by a pulp mill, the plant was found to significantly contribute to the self-cleaning capacity of the river. However, this elevated degradation capacity was not enough to compensate for the additionally discharged organic material which, together with the toxic effects of the paper plant effluents, significantly interferes with the ecological status of the Biobío River.

Structure-activity relationships in a series of bisquaternary bisphthalimidine derivatives modulating the muscarinic M(2)-receptor allosterically.

Hexane-bisammonium-type compounds containing lateral phthalimide moieties are well-established ligands of the common allosteric binding site of muscarinic M(2) receptors. Previous structure-activity relationships (SAR) revealed two positively charged centers and two lateral phthalimide moieties in a defined arrangement to be essential of a high allosteric potency. The purpose of this study was to replace one carbonyl group of the phthalimides with hydrogens, hydroxy, alkoxy, phenyl, benzyl, and benzylidene groups in order to check the influence of these substituents on the allosteric activity in antagonist-linked receptors. The analysis of the quantitative SAR indicated that a high allosteric potency is related to a certain amount of rigidity as well as polarizibility and the ability to form hydrophobic interactions.

Ligands for the common allosteric site of acetylcholine M2-receptors: development and application.

Ligands for the allosteric site of acetylcholine M2 receptors are able to retard the dissociation of simultaneously bound ligands for the orthosteric site. This effect promotes receptor occupation by the orthosteric ligand. The allosteric effect opens various therapeutic perspectives, e.g., in organophosphorus poisoning. The aim of our studies was to optimize the affinity of the modulators for the common allosteric binding site of muscarinic M2 receptors, the orthosteric site of which was liganded with the N-methylscolopamine. The phthalimido substituted hexane-bisammonium compound W84 served as a starting point. Previous molecular modelling studies revealed two positive charges and two aromatic imides in a sandwich-like arrangement to be essential for a high allosteric potency. A three-dimensional quantitative structure activity relationship (3D QSAR) analysis predicted compounds with substituents of increasing size on the lateral imide moieties to enhance the affinity for the allosteric binding site. Thus, we synthesized and pharmacologically evaluated compounds bearing "saturated" phthalimide moieties as well as phthalimidines with substituents of systematically increasing size in position 3 or on the aromatic ring at one or both ends of the molecule. Within each series, QSAR could be derived: 1. "Saturation" of the aromatic ring of the phthalimide moiety results in less potent compounds. 2. Increasing the size of the substituents in position 3 of the phthalimide enhances the potency. 3. Putting substituents on the aromatic part of the phthalimide increases the potency more effectively: the introduction of a methyl group in position 5 gave a compound with a potency in the nanomolar concentration range which was subsequently developed as the first radioligand for the allosteric binding site.