Volume transition effects on the correlations and effective interactions among highly charged microgels.

Recent experimental studies have demonstrated the huge influence that the volume phase transition (VPT) has on the collective structure of highly charged thermo-responsive microgels in aqueous solution with low concentrations of added monovalent salt, thus opening a promising new route for controlling the overall properties of practical colloidal suspensions. We present here an analysis of this structure based on the effective electrostatic potential obtained with the exact methodology of the dressed ion theory (DIT). Starting with a description at the primitive model level, we determine the correlations among the components of our model system (macroions plus monovalent anions and cations) by utilizing the two-density integral equation theory, thus allowing us to consider realistic values for the microgel charges. The resulting microgel structure factors show a good agreement with the reported light scattering measurements, whereas the microscopic pair distributions reveal that in this regime the shrunken states promote an enhanced counterion absorption into the microgels. This packing of counterions inside the microgels induces strongly non-linear correlations among the microions, and in turn provokes a substantial weakening of the microgel-microgel correlations. The ensuing effective interactions are then obtained by contracting the description to the level in which only the macroions are present. We find not only that the magnitude and reach of the corresponding pair potentials are markedly inhibited in the shrunken states, but also that their general form diverges from the conventional screened Coulomb shape. This makes it necessary to rethink the concepts of effective charge and screening length.

The MASTiFF panel-a versatile multiple-allele SNP test for forensics.

Forensic identification tests often need recourse to markers that can successfully type highly degraded DNA, and binary single nucleotide polymorphisms (SNPs) have become the variants of choice for such analyses because of their short amplified fragment lengths. The two main drawbacks of SNPs are their reduced power of discrimination per marker compared with mainstream forensic STRs and an inability to robustly detect mixed DNA-particularly using capillary electrophoresis genotyping systems such as SNaPshot™, where the dye signals are much more imbalanced than those of STR profiles. This study compiled a compact set of multiple-allele SNPs consisting of loci that had three or four nucleotide variants at the same site in order to address the lack of mixture detection capability with binary SNP tests, as well as improving levels of polymorphism per SNP by transitioning to a maximum of six or ten genotypes per locus. We report the development and optimisation of a SNaPshot-based forensic test comprising 27 tri-allelic and 2 tetra-allelic SNPs, which we named MASTiFF: a multiple-allele SNP test for forensics. Assessments of the MASTiFF panel's levels of discrimination power in the five main population groups indicate random match probabilities ranging from 10-15 down to 10-20-improving the levels possible from an equivalent number of binary SNPs. The SNaPshot test was able to detect simple mixtures successfully with more than two alleles observed in 30% of SNPs. From allele frequency data, it is estimated that more than two alleles will be present in at least one MASTiFF SNP in 99.8% of two-person mixtures, making this panel an ideal supplementary test when SNPs are chosen for the analysis of degraded forensic DNA.

Peculiar CADASIL phenotype in monozygotic twins carrying a novel NOTCH3 pathogenetic variant.

BACKGROUND: Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an autosomal dominantly inherited cerebral small vessel disease caused by Neurogenic locus notch homolog protein 3 (NOTCH3) gene mutations. The main clinical features include migraine with aura, recurrent ischemic strokes and dementia. Brain MRI typically shows multiple small lacunar infarcts and severe, diffuse, symmetrical white matter hyperintensities (WMHs), with characteristic involvement of the anterior temporal pole, external capsule, and superior frontal gyrus. Reports of twins with CADASIL are scarce. Herein we describe a pair of monozygotic twins with peculiar CADASIL phenotype, carrying a new NOTCH3 variant. CASE PRESENTATION: Twin A was a 45-year-old male suffering from migraine, obesity, arterial hypertension, and polycythemia (with negative genetic analysis), who complained of a transient, short-lasting (~ 5 minutes) episode of speech difficulties. Brain MRI showed diffuse, symmetrical, confluent periventricular WMHs involving frontal, parietal, and temporal lobes and external capsules, with sparing of anterior temporal poles. Genetic analysis of NOTCH3 gene demonstrated the presence of missense c.3329G>A, p.(Cys1110Tyr) variant, confirming CADASIL diagnosis. Twin B, affected by migraine and polycythemia, as well as his monozygotic twin, presented with a 2-month history of trigeminal neuralgia. Brain MRI demonstrated diffuse WMHs with a pattern of distribution like his twin. Genetic analysis revealed the same NOTCH3 pathogenic variant. CONCLUSIONS: Our monozygotic twins have a strikingly similar neuroimaging picture with sparing of anterior temporal poles. They also have a peculiar phenotype, both presenting polycythemia without genetically confirmed cause. Twin B had trigeminal neuralgia, that is unusual in CADASIL. The possible association of the peculiar findings with the newly reported NOTCH3 variant needs to be confirmed with further observations.

Holoprosencephaly in clomiphene-induced pregnancy: a possible association? A case report and literature review.

Clomiphene is widely used for inducing ovulation. Evidence for congenital abnormalities, in particular central nervous system defects (CNS-D) and in babies born from clomiphene-induced pregnancies is conflicting. The authors report a case of holoprosencephalia (HPE) in a fetus delivered from a mother receiving clomiphene.

The relevance of MRI blood-sensitive sequences in the diagnostic assessment of late-onset epilepsy.

OBJECTIVE: Sporadic cerebral amyloid angiopathy (CAA) is a degenerative brain small vessel disease of ageing resulting from progressive amyloid deposition in small arteries and arterioles of the cortex and leptomeninges. CAA may be diagnosed by the mean of Boston criteria, particularly with the use of the blood-sensitive T2* MRI sequences (GRE and SWI). Epileptic seizures have rarely been reported in CAA. PATIENTS AND METHODS: We describe two patients with late-onset unprovoked seizures due to CAA. A short literature review on this topic is presented. RESULTS: In our two patients with late-onset unprovoked seizures as the first manifestation of CAA, only GRE and SWI sequences lead to a correct diagnosis. In literature, only 15 patients with CAA presenting with seizures have been reported. In these subjects, data on seizures semiology and prognosis are scarce. CONCLUSIONS: Our report highlights the importance to perform blood-sensitive sequences in all subjects with LOE of otherwise unknown etiology, not to miss a diagnosis of CAA.

A self-consistent Ornstein-Zernike jellium for highly charged colloids (microgels) in suspensions with added salt.

This work discusses a jellium scheme, built within the framework of the multicomponent Ornstein-Zernike (OZ) equation, which is capable of describing the collective structure of suspensions of highly charged colloids with added salt, even in the presence of finite-size multivalent microions. This approach uses a suitable approximation to decouple the microion-microion correlations from the macroion-microion profiles, which in combination with the methodology from the dressed ion theory (DIT) gives a full account of the electrostatic effective potential among the colloids. The main advantages of the present contribution reside in its ability to manage the short-range potentials and non-linear correlations among the microions, as well as its realistic characterization of the ionic clouds surrounding each macroion. The structure factors predicted by this jellium scheme are contrasted with previously reported experimental results for microgel suspensions with monovalent salts (2019Phys. Rev. E100032602), thus validating its high accuracy in these situations. The present theoretical analysis is then extended to microgel suspensions with multivalent salts, which reveals the prominent influence of the counterion valence on the makeup of the effective potentials. Although the induced differences may be difficult to identify through the mesoscopic structure, our results suggest that the microgel collapsing transition may be used to enhance these distinct effects, thus giving a feasible experimental probe for these phenomena.

Assessing health effects of environmental contaminants by molecular markers. Studies on methylmercury and polychlorinated biphenyls as examples of translational research in environmental toxicology.

Evaluating the human effects of combinations of neurotoxicants is extremely difficult. Parallel studies correlating exposure parameters and "surrogate" indicators of neural cell function may represent a promising strategy. Molecular markers such as cholinergic muscarinic receptors (MRs) and monoamine oxidase activity (MAO-B) are expressed not only in brain but also in peripheral blood cells. Measurements of MRs and MAO-B in these easily accessible matrices can provide valuable information on early sub-clinical effects of drugs and chemicals in the CNS. In this paper, examples of application of lymphocyte-MRs and platelet-MAO-B as surrogate markers of CNS function in humans are described. They include (i) neuroepidemiological studies examining 7-year-old members of a birth-cohort at the Faroe-Islands prenatally exposed to elevated concentrations of methylmercury (MeHg) and polychlorinated biphenyls; (ii) clinical investigations in a series of unmedicated children with Attention-Deficit/Hyperactivity Disorder (ADHD). The neurochemical markers were examined in association with exposure indicators and neuropsychological tests (Faroe Islands Study) or with specific disease symptoms (ADHD children). Studies of this type have produced valuable information on subclinical responses to low/moderate perinatal exposures to MeHg and/or PCBs, and in addition further supported the applicability of these biomarkers in children with subtle neuropsychiatric disorders. Additional studies investigated the ability of MeHg and/or PCBs to modify the expression of genes codifying for the MR subtypes in rat offspring cerebellum at distinct developmental stages. The results demonstrated persistent gender- and age-related differences in MR density and their associated gene expression pathways. Studies on pathways and metabolic networks involved in developmental toxicity may contribute to elucidate the mode of action of environmental pollutant mixtures and also considerably impact on the risk assessment process.

Macrophyte regional patterns, metrics assessment and ecological integrity of isolated ponds at Austral Patagonia (Argentina).

Anthropogenic and natural changes are threatening pond ecological integrity in Patagonia and tools for bioassessment are required. Macrophytes are good candidates to determine the conservation status of ponds; nevertheless, metric selection procedures should be founded on an adequate knowledge of plant ecological responses. We assessed the main environmental constraints driving variation in macrophyte assemblages, and trophic status at 29 ponds located at the continental and insular Patagonia region. We screened 20 potential macrophyte metrics as indicators of pond condition that included origin (native, endemic, exotic), lifeforms (annual/biannual, perennial), functional groups (submersed, emergent, floating-leaved, landforms), and community attributes. A set of 106 taxa were recorded, and richness per site (10 species) was unexpectedly high for a cold temperate area, reinforcing the value of isolated ponds as habitat for macrophytes in the Patagonian landscape. Natives dominated most assemblages; exotics were present at 24 ponds, contributing with high cover (>45%) at 15% of them. Macrophyte assemblages were driven by natural factors over anthropogenic ones, with temperature, rainfall, pH, conductivity and nutrients explaining most variation in patterns. However, pond eutrophication symptoms (high phosphorous concentration and chlorophyll a) were associated with extensive cattle grazing (manure and trampling) and urbanization (runoff). Generalized linear models captured natural variables (temperature, alkalinity) as most powerful explaining richness measures. Models also indicated that both richness of emergent and endemics were negatively affected by total phosphorous increases. Land cover factors: grasses/herbaceous, mallín and trees (%) in 100 m buffer around ponds appeared as additional ecological drivers of macrophyte patterns, particularly of submersed (>50%) and native richness (36%). Natural and anthropogenic gradients were overlapped, making it difficult to generalize our conclusions. Further studies are needed to test the performance of the macrophyte metrics selected here, which are a vital tool for the conservation of the most austral ponds in South America.

Taurolidine and oxidative stress: a rationale for local treatment of mesothelioma.

Malignant mesothelioma is an asbestos-related, aggressive tumour, resistant to most anticancer therapies. Akt is a key mediator of mesothelioma cell survival and chemoresistance. This study aimed to clarify the mechanism by which taurolidine (TN), a known synthetic compound with antimicrobial and antineoplastic properties, leads to mesothelioma cell death. Apoptosis was studied by annexin V binding, cell cycle analysis, caspase-8 activation, poly(ADP-ribose) polymerase (PARP) cleavage and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labelling (TUNEL). Oxidative stress was measured by nitrite production and DNA oxidative damage. Protein expression and phosphorylation were evaluated by immunoprecipitation and immunoblotting. TN induces cell death of mesothelioma cells, but not of non-neoplastic human mesothelial cells. After TN treatment of mesothelioma cells, Akt but not extracellular signal-regulated kinase (Erk) 1/2 activity is inhibited a in time- and dose-dependent manner. Protein phosphatase (PP)1alpha and PP2A are activated several hours after drug addition. Apoptosis induced by TN is driven by oxidative stress and cell exposure to sulfydryl donors, such as glutathione monoethylester and l-N-acetylcysteine, significantly reduced pro-apoptotic effects and Akt inhibition. Conversely, expression of constitutively activated Akt did not affect cytoxicity elicited by TN, which retained its ability to inhibit the kinase. TN induces mesothelioma cell death via oxidative stress, accompanied by inhibition of Akt signalling. This provides a promising molecular rationale for TN as local treatment of malignant mesothelioma.

Accounting for effective interactions among charged microgels.

We introduce a theoretical approach to describe structural correlations among charged permeable spheres at finite particle concentrations. This theory explicitly accounts for correlations among microions and between microions and macroions and allows for the proposal of an effective interaction among macroions that successfully captures structural correlations observed in poly-N-isopropyl acrylamide microgel systems. In our description the bare charge is fixed and independent of the microgel size, the microgel concentration, and the ionic strength, which contrasts with results obtained using linear response approximations, where the bare charge needs to be adapted to properly account for microgel correlations obtained at different conditions.

Comparative HPLC and ELISA studies for CDT isoform characterization in subjects with alcohol related problems. Prospective application in workplace risk-prevention policy.

Serum carbohydrate-deficient transferrin (CDT) is the most specific marker of chronic alcohol abuse so far. The performance of commercial HPLC over the ELISA method for measurement of CDT was evaluated on a series of 105 serum samples obtained from subjects referred to the Toxicology Laboratory of Salvatore Maugeri Hospital for alcohol-related problems. Compared to ELISA, HPLC analysis was more valuable for determining alcohol-related patterns of CDT isoforms and quantifying serum levels of disialotransferrin that better reflect chronic heavy drinking. Other significant advantages of the HPLC method included reproducible separation and easier detection of glycoform types and genetic transferrin variants that are known to cause falsely high or low results in sera examined by immunoassay. Current scientific evidence indicates that disialotransferrin is the target analyte for CDT determination and HPLC the current CDT analysis reference method. Systematic studies for early assessment of excessive alcohol intake or abuse of alcoholic substances in workers are recommended by the Italian legislation in accordance with the European Alcohol Action Plan (EAAP) launched by the WHO Regional Committee for Europe. These studies are advisable given their potential role in preventing negative effects of alcohol abuse in workplace. A research strategy combining CDT and other laboratory markers with questionnaire and physician interview is recommended for examining subjects with alcohol related problems and the diagnosis of alcoholism. This approach can be applied for alcohol abuse in workplace surveillance.

Chronic Pain Treatment With Cannabidiol in Kidney Transplant Patients in Uruguay.

BACKGROUND: Chronic pain is a major therapeutic problem in kidney transplant patients owing to nephrotoxicity associated with nonsteroidal antiiflammatory drugs. Benefits in chronic pain treatment with cannabidiol (CBD) have been reported. This study assesses the effect, safety, and possible drug interactions in kidney transplant patients treated with CBD for chronic pain. METHODS: We assessed patients who asked to receive CBD for pain treatment. Doses were increased from 50 to 150 mg twice a day for 3 weeks. Creatinine, blood count, liver function, liver enzymes, and drug levels were determined every 48 hours the first week and then once a week thereafter. RESULTS: We assessed 7 patients with a mean age of 64.5 years (range, 58-75 years). CBD initial dose was 100 mg/d, CBD dose reduction to 50 mg/d has been done on day 4 to patient 1 for persistent nausea. Tacrolimus dose reduction in patient 3 was undertaken on days 4, 7, and 21 owing to persisting elevated levels (even before CBD) and itching, and on day 21 in patient 5. Tacrolimus levels decreased in patient 2 but were normal in the control 1 week later. Patients on cyclosporine were stable. Adverse effects were nausea, dry mouth, dizziness, drowsiness, and intermittent episodes of heat. CBD dose decrease was required in 2 patients. Two patients had total pain improvement, 4 had a partial response in the first 15 days, and in 1 there was no change. CONCLUSIONS: During this follow-up, CBD was well-tolerated, and there were no severe adverse effects. Plasma levels of tacrolimus were variable. Therefore, longer follow-up is required.

Assessing individual risk for AMD with genetic counseling, family history, and genetic testing.

PurposeThe goal was to develop a simple model for predicting the individual risk profile for age-related macular degeneration (AMD) on the basis of genetic information, disease family history, and smoking habits.Patients and methodsThe study enrolled 151 AMD patients following specific clinical and environmental inclusion criteria: age >55 years, positive family history for AMD, presence of at least one first-degree relative affected by AMD, and smoking habits. All of the samples were genotyped for rs1061170 (CFH) and rs10490924 (ARMS2) with a TaqMan assay, using a 7500 Fast Real Time PCR device. Statistical analysis was subsequently employed to calculate the real individual risk (OR) based on the genetic data (ORgn), family history (ORf), and smoking habits (ORsm).Results and conclusionThe combination of ORgn, ORf, and ORsm allowed the calculation of the Ort that represented the realistic individual risk for developing AMD. In this report, we present a computational model for the estimation of the individual risk for AMD. Moreover, we show that the average distribution of risk alleles in the general population and the knowledge of parents' genotype can be decisive to assess the real disease risk. In this contest, genetic counseling is crucial to provide the patients with an understanding of their individual risk and the availability for preventive actions.

The Global AIMs Nano set: A 31-plex SNaPshot assay of ancestry-informative SNPs.

A 31-plex SNaPshot assay, named 'Global AIMs Nano', has been developed by reassembling the most differentiated markers of the EUROFORGEN Global AIM-SNP set. The SNPs include three tri-allelic loci and were selected with the goal of maintaining a balanced differentiation of: Africans, Europeans, East Asians, Oceanians and Native Americans. The Global AIMs Nano SNP set provides higher divergence between each of the five continental population groups than previous small-scale AIM sets developed for forensic ancestry analysis with SNaPshot. Both of these characteristics minimise potential bias when estimating co-ancestry proportions in individuals with admixed ancestry; more likely to be observed when using markers disproportionately informative for only certain population group comparisons. The optimised multiplex is designed to be easily implemented using standard capillary electrophoresis regimes and has been used to successfully genotype challenging forensic samples from highly degraded material with low level DNA. The ancestry predictive performance of the Global AIMs Nano set has been evaluated by the analysis of samples previously characterised with larger AIM sets.

First 1500 Kidney Transplants at the Institute of Nephrology and Urology in Uruguay: Analysis of the Results.

BACKGROUND: The Institute of Nephrology and Urology (INU) has performed 75% of kidney transplantations (KT) in Uruguay during its 35 years of activity, with 90.6% from cadaveric donors. We investigated the risk factors (RF) for delayed graft function (DGF) and patient and graft survival (SV). METHODS: We analyzed retrospectively the characteristics and evolution of 1500 KT performed by INU until December 2014. The incidence of DGF and RF for patient and graft SV were analyzed in 4 eras, according to the year that KT was performed. RESULTS: The number of KT per year has progressively increased until reaching 40 KT per million population in 2006, with a decrease of the living donor KT (LDKT) rate. The age of the donors (D) and recipients (R) as well as the time on dialysis (TOD) have progressively increased over the different eras. Five hundred twenty-five R (35%) presented with DGF. The RF for DGF were the age of the R and the D, the TOD, the DDKT, and the warm ischemia time (WIT). In the DDKT group, the cold ischemia time and "died of stroke" were added factors. The death-censored graft SV at 1, 5, 10, and 15 years were 90%, 76%, 62%, and 49%, respectively. They improved as from era I, the patient SV being 92%, 83%, and 75% at 1, 5, and 10 years, in era I; 98%, 93%, and 86% in era II; 98%, 92%, and 83% in era III; and 95% and 90% at 1 and 5 years in era IV (P < .001). The graft SV over the same periods was 76%, 58%, and 40% in era I; 88%, 68%, and 52% in era II; 93%, 81%, and 70% in era III; and 93% and 85% at 1 and 5 years in era IV (P < .0001). The RF for patient SV were diabetes mellitus, era I, lower albuminemia, older age or TOD, and DGF. For kidney SV, the era, the age of the R, TOD, DGF, and D older than 60 years were RF associated with a worse evolution. In DDKT, the RF for the graft SV were the era, younger age of the R, and DGF. The group with the worst graft SV was the one made up of children and adolescents. CONCLUSIONS: Our results relating to patient and graft SV are acceptable and comparable to those mentioned on large records such as the OPNT/SRTR and the Collaborative Transplant Study. This has been the case, even though we have transplanted increasingly aged patients, with increasingly aged donors, or donors with associated pathology. The risk factors that we found both for DGF and SV have also been pointed out by other authors. The validity of some findings has the limitation of being from a retrospective analysis; hence, they should be corroborated by a prospective study.

Inorganic mercury modifies Ca2+ signals, triggers apoptosis and potentiates NMDA toxicity in cerebellar granule neurons.

Hg2+ (0.1 microM-0.5 microM) modified the Ca2+ signals elicited by either KCl or the glutamate-receptor agonist, N-methyl-D-aspartate (NMDA), in cerebellar granule cells (CGCs). Hg2+ enhanced the intracellular Ca2+ transient elicited by high K+ and prevented a complete recovery of the resting intracellular Ca2+ concentration ([Ca2+]i) after either KCl or NMDA stimulation. Higher Hg2+ concentrations (up to 1 microM) increased [Ca2+]i directly. Following the short-term exposure to Hg2+, CGCs underwent apoptosis, which was identified by the cleavage of DNA into large (700-50 kbp) and oligonucleosomal DNA fragments, and by the appearance of typical apoptotic nuclei. Combined treatment with 0.1-0.3 microM Hg2+ and a sublethal NMDA concentration (50 microM) potentiated DNA fragmentation and apoptotic cell death. When the exposure to Hg2+ was carried out in Ca2+-free media or in the presence of Ca2+ channel blockers (L-type or NMDA-R antagonists), the effects on signalling and apoptosis were prevented. Our results suggest that very low Hg2+ concentrations can trigger apoptosis in CGCs by facilitating Ca2+ entry through membrane channels.

Development of the National Kidney Transplantation Program in Uruguay.

The first kidney transplantation (KT) in Uruguay was performed in 1969. We report the rates of KT and survival of patients and grafts up to December 2014. The country has a surface of 176,215 km(2) and a population of 3,286,314 inhabitants (18.6 inhabitants per km(2)). Till December 31, 2014, 1,940 KT have been performed in Uruguay (41.8 pmp that year); 90.4% of them were from cadaveric donors (CD). Median age of recipients (R) was 44 ± 14 years; R older than 55 years increased from 0 to 27% during the period. Our pre-emptive KT program started in 2007. Optimal donors (D) decreased from 65.2% to 35.5%, and D older than 45 years old increased from 9% to 37%. Trauma as cause of death decreased from 49% to 32% and stroke as cause of death increased from 25% to 39%. Patient survival rates at 1, 5, and 8 years were 93%, 87%, and 78%, respectively for KT performed between 1980 and 1989; they were 98%, 93%, and 89%, respectively, for KT performed between 1990 and1999; they were 97%, 91%, and 90%, respectively, for KT performed between 2000 and 2010. In December 2013, there were 1098 patients pmp in renal replacement therapy, 758 pmp in dialysis, and 340 pmp (30.9%) with a functioning graft. Our national KT program is mainly based (90.6%) on cadaveric donation. Epidemiological changes in the characteristics of R and D followed the changes in aging that occurred in the general population and the dialysis population. The survival rates from patients and kidneys are similar to those reported by the European and the American registries.

The influence of neuronal 5-hydroxytryptamine receptor antagonists on non-cholinergic ganglionic transmission in the guinea-pig enteric excitatory reflex.

A partitioned bath made it possible to separate the site of recording of the ascending excitatory reflex of the ileal circular muscle (oral compartment) from the site of reflex induction (caudal compartment), evoked by inflating an intraluminal balloon. In the caudal compartment, blockade of cholinergic ganglionic transmission by hexamethonium (100 microM) and hyoscine (0.3 microM) caused an approximately 65% reduction in the amplitude of reflex contractions, suggesting that the remaining response was mediated by non-cholinergic transmission near the distension site. This non-cholinergic component of ganglionic transmission was insensitive to the action of methiothepin (1 microM), ondansetron (1 microM), tropisetron (1.5 microM), DAU 6285 (1 microM) and renzapride (1 microM), agents that antagonize the action of 5-hydroxytryptamine (5-HT) at neural 5-HT1-like, 5-HT3, 5-HT4 and putative 5-HT1P receptors. These findings suggest that the neural pathways subserving non-cholinergic ganglionic transmission in the ascending excitatory reflex in the guinea-pig ileum do not involve 5-HT as neurotransmitter.

The role of GABAA receptor function in peristaltic activity of the guinea-pig ileum: a comparative study with bicuculline, SR 95531 and picrotoxinin.

1. The peristaltic activity of the guinea-pig ileum was studied in the absence and in the presence of the blockade of GABAA receptors. 2. Bicuculline (1-30 microM), improved at the highest concentrations the efficiency of peristalsis by enhancing the frequency of propulsive contractions and the amount of fluid ejected per unit of time. 3. Neither SR 95531 (0.3-10 microM), a novel GABAA receptor antagonist, which competitively antagonized 3-aminopropane sulphonic acid induced contractions in myenteric plexus-longitudinal muscle preparations (pA2 value: 6.47), nor picrotoxinin (1-30 microM) modified peristaltic parameters or influenced the potentiating effect of bicuculline on peristaltic activity. 4. In myenteric plexus-longitudinal muscle preparations, bicuculline (1-30 microM) enhanced the amplitude of electrically-induced cholinergic contractions without modifying submaximal contractions to applied acetylcholine. SR 95531 and picrotoxinin had no effect on twitch amplitude. In the presence of each of these compounds, bicuculline retained its potentiating effect. 5. The results obtained with SR 95531 and picrotoxinin question the view that GABAA receptors may exert a critical role in intestinal propulsion by modulating the activity of nerve pathways subserving peristalsis. Bicuculline potentiates the peristaltic activity of the ileum probably via a facilitatory effect on enteric cholinergic transmission that is independent of GABAA receptor blockade.

Purine receptors in the guinea-pig internal anal sphincter.

1 In the isolated internal anal sphincter of the guinea-pig, adenosine 5'-triphosphate (ATP) and adenosine induced a concentration-dependent and tetrodotoxin-insensitive relaxation. 2 Pretreatment with theophylline (25-50 microM) had no significant effect on the concentration-response curves obtained with either purine compound. 3 Reactive blue 2 (25-100 microM) shifted the curve to ATP to the right in a dose-dependent fashion leaving that to adenosine unaltered. The antagonism appeared to be non-competitive. 4 Neither reactive blue 2 nor purine receptor occupation by ATP or adenosine altered the electrically-induced non-adrenergic, non-cholinergic inhibitory response. 5 The actions of ATP and adenosine in the guinea-pig internal anal sphincter appear to be mediated by separate receptors. These receptors are not involved in the nerve-mediated relaxation.