Mimicking Behçet's disease: GM-CSF gain of function mutation in a family suffering from a Behçet's disease-like disorder marked by extreme pathergy.

Behçet's disease (BD) is an inflammatory disease mainly affecting men along the ancient Silk Route. In the present study we describe a Dutch family suffering from BD-like disease with extreme pathergic responses, but without systemic inflammation. Genetic assessment revealed a combination of the human leukocyte antigen (HLA)-B*51 risk-allele together with a rare heterozygous variant in the CSF2 gene (c.130A>C, p.N44H) encoding for granulocyte-macrophage colony-stimulating factor (GM-CSF) found by whole exome sequencing. We utilized an over-expression vector system in a human hepatocyte cell line to produce the aberrant variant of GM-CSF. Biological activity of the protein was measured by signal transducer and activator of transcription 5 (STAT-5) phosphorylation, a downstream molecule of the GM-CSF receptor, in wild-type peripheral mononuclear cells (PBMCs) using flow cytometry. Increased STAT-5 phosphorylation was observed in response to mutated GM-CSF when compared to the wild-type or recombinant protein. CSF2 p.N44H results in disruption of one of the protein's two N-glycosylation sites. Enzymatically deglycosylated wild-type GM-CSF also enhanced STAT-5 phosphorylation. The patient responded well to anti-tumor necrosis factor (TNF)-α treatment, which may be linked to the capacity of TNF-α to induce GM-CSF in phorbol 12-myristate 13-acetate (PMA)-treated PBMCs, while GM-CSF itself only induced dose-dependent interleukin (IL)-1Ra production. The identified CSF2 pathway could provide novel insights into the pathergic response of BD-like disease and offer new opportunities for personalized treatment.

Feasibility and safety of quantitative adenosine stress perfusion cardiac magnetic resonance imaging in pediatric heart transplant patients with and without coronary allograft vasculopathy.

BACKGROUND: Pediatric heart transplant patients require cardiac catheterization to monitor for coronary allograft vasculopathy. Cardiac catheterization has no safe and consistent method for measuring microvascular disease. Stress perfusion cardiac magnetic resonance imaging (MRI) assessing microvascular disease has been performed in adults. OBJECTIVE: To investigate the feasibility and safety of performing cardiac MRI with quantitative adenosine stress perfusion testing in pediatric heart transplant patients with and without coronary allograft vasculopathy. MATERIALS AND METHODS: All pediatric heart transplant patients with coronary vasculopathy at our institution were asked to participate. Age- and gender-matched pediatric heart transplant patients without vasculopathy were recruited for comparison. Patients underwent cardiac MRI with adenosine stress perfusion testing. RESULTS: Sixteen pediatric heart transplant patients, ages 6-22 years, underwent testing. Nine patients had vasculopathy by angiography. No heart block or other complications occurred during the study. The myocardial perfusion reserve for patients with vasculopathy showed no significant difference with comparison patients (median: 1.43 vs. 1.48; P=0.49). Values for both groups were lower than expected values based on previous adult studies. The patients were also analyzed for time after transplant and the number of rejection episodes. Patients within 6 years of transplantation had a nonsignificant trend toward a higher myocardial perfusion reserve (median: 1.57) versus patients with older transplants (median: 1.47; P=0.46). Intra- and interobserver reproducibility were 97% and 92%, respectively. CONCLUSION: Myocardial perfusion reserve is a safe and feasible method for estimating myocardial perfusion in pediatric heart transplant patients. There is no reliable way to monitor microvascular disease in pediatric patients. This method shows potential and deserves investigation in a larger cohort.

Electromyographic adjustments during continuous and intermittent incremental fatiguing cycling.

We studied the sensitivity of electromyographic (EMG) variables to load and muscle fatigue during continuous and intermittent incremental cycling. Fifteen men attended three laboratory sessions. Visit 1: lactate threshold, peak power output, and VO2max . Visits 2 and 3: Continuous (more fatiguing) and intermittent (less fatiguing) incremental cycling protocols [20%, 40%, 60%, 80% and 100% of peak power output (PPO)]. During both protocols, multichannel EMG signals were recorded from vastus lateralis: muscle fiber conduction velocity (MFCV), instantaneous mean frequency (iMNF), and absolute and normalized root mean square (RMS) were analyzed. MFCV differed between protocols (P < 0.001), and only increased consistently with power output during intermittent cycling. RMS parameters were similar between protocols, and increased linearly with power output. However, only normalized RMS was higher during the more fatiguing 100% PPO stage of the continuous protocol [continuous-intermittent mean difference (95% CI): 45.1 (8.5% to 81.7%)]. On the contrary, iMNF was insensitive to load changes and muscle fatigue (P = 0.14). Despite similar power outputs, continuous and intermittent cycling influenced MFCV and normalized RMS differently. Only normalized RMS was sensitive to both increases in power output (in both protocols) and muscle fatigue, and thus is the most suitable EMG parameter to monitor changes in muscle activation during cycling.

Intraoral Radiographic Study of the Pulp Cavity of the Shortfin Mako Shark (Isurus Oxyrinchus).

The shortfin mako shark (Isurus oxyrinchus) is a large pelagic predator that inhabits coastal and ocean waters. It has several teeth arranged in rows that run from the rostral to the lingual face. These teeth are in several stages of maturation, where the teeth closest to the rostral face are more mature and functional and the teeth closest to the lingual face are still in development. The tooth supply of the shark is unlimited throughout its life. The mechanism of tooth replacement follows that, when the front teeth are discarded physiologically, the posterior teeth replace it. This study us used a head and dental arch of I. oxyrinchus. Intraoral radiographs were obtained with the aim to show details of the pulp cavity. The study concluded that the pulp diameter varies according to the stage of dental maturation.

Modulation of mammalian apoptotic pathways by intracellular protozoan parasites.

During intracellular parasitic infections, pathogens and host cells take part in a complex web of events that are crucial for the outcome of the infection. Modulation of host cell apoptosis by pathogens attracted the attention of scientists during the last decade. Apoptosis is an efficient mechanism used by the host to control infection and limit pathogen multiplication and dissemination. In order to ensure completion of their complex life cycles and to guarantee transmission between different hosts, intracellular parasites have developed mechanisms to block apoptosis and sustain the viability of their host cells. Here, we review how some of the most prominent intracellular protozoan parasites modulate the main mammalian apoptotic pathways by emphasizing the advances from the last decade, which have begun to dissect this dynamic and complex interaction.

The Leishmania nicotinamidase is essential for NAD+ production and parasite proliferation.

NAD+ is a central cofactor that plays important roles in cellular metabolism and energy production in all living cells. Genomics-based reconstruction of NAD+ metabolism revealed that Leishmania protozoan parasites are NAD+ auxotrophs. Consequently, these parasites require assimilating NAD+ precursors (nicotinamide, nicotinic acid, nicotinamide riboside) from their host environment to synthesize NAD+ by a salvage pathway. Nicotinamidase is a key enzyme of this salvage pathway that catalyses conversion of nicotinamide (NAm) to nicotinic acid (Na), and that is absent in higher eukaryotes. We present here the biochemical and functional characterizations of the Leishmania infantum nicotinamidase (LiPNC1). Generation of Lipnc1 null mutants leads to a decrease in NAD+ content, associated with a metabolic shutdown-like phenotype with an extensive lag phase of growth. Both phenotypes could be rescued by an add-back construct or by addition of exogenous Na. In addition, Lipnc1 null mutants were unable to establish a sustained infection in a murine experimental model. Altogether, these results illustrate that NAD+ homeostasis is a fundamental component of Leishmania biology and virulence, and that NAm constitutes its main NAD+ source in the mammalian host. The crystal structure of LiPNC1 we solved allows now the design of rational inhibitors against this new promising therapeutic target.

Characterization of Leishmania infantum thiol-dependent reductase 1 and evaluation of its potential to induce immune protection.

The need to develop an effective vaccine against leishmaniasis to prevent the 2 million new cases each year led to the search for antigens able to elicit protection against infection with Leishmania. In this study, we have characterized a parasite-specific protein of Leishmania infantum named thiol-dependent reductase 1 (TDR1). The protein is present in both life cycle stages of L. infantum with a notable higher expression in the amastigote forms, suggesting a role in the interaction between the parasite and the mammalian host. Thiol-dependent reductase 1 is localized in the cytosol, although we were able to detect the protein in the culture medium of both promastigotes and axenic amastigotes, and consequently, TDR1 is considered an excreted/secreted molecule of the parasite. Therefore, we have evaluated the potential of TDR1 recombinant protein to protect against experimental challenge with L. infantum parasites using a murine model. Despite a reduction in spleen parasite load in the chronic phase of disease, TDR1 administration was not effective in the protection of Balb/c mice against visceral leishmaniasis and thus TDR1 do not have a crucial role in the modulation of mammalian host immune response, as observed with its protein counterpart Tc52 of Trypanosoma cruzi.

Exercise and amyotrophic lateral sclerosis.

Amyotrophic Lateral Sclerosis (ALS) is a progressive and fatal neurodegenerative disease in which much burden is geared towards end-of-life care. Particularly in the earlier stages of ALS, many people have found both physiological and psychological boosts from various types of physical exercise for disused muscles. Proper exercise is important for preventing atrophy of muscles from disuse-a key for remaining mobile for as long as possible-and as long as it is possible to exercise comfortably and safely, for preserving cardiovascular fitness. However, the typical neuromuscular patient features a great physical inactivity and disuse weakness, and for that reason many controversial authors have contested exercise in these patients during years, especially in ALS which is rapidly progressive. There is an urgent need for dissecting in detail the real risks or benefits of exercise in controlled clinical trials to demystify this ancient paradigm. Yet, recent research studies document significant benefits in terms of survival and quality of life in ALS, poor cooperation, small sample size, uncontrolled and short-duration trials, remain the main handicaps. Sedentary barriers such as early fatigue and inherent muscle misuse should be overcome, for instance with body-weight supporting systems or non-invasive ventilation, and exercise should be faced as a potential non-monotonous way for contributing to better health-related quality of life.

First Report of Potato yellowing virus (Genus Ilarvirus) in Solanum phureja from Ecuador.

A bacilliform virus, named Potato yellowing virus (PYV), causing chlorosis of leaves was reported in 1992 in potato (Solanum tuberosum) fields in Peru (1) and symptomless wild potatoes (S. fernandezianum) in Chile (4). PYV is reported as an alfamo-like virus (1) (family Bromoviridae) but no sequence information is available for this virus, making its taxonomic position inside the Bromoviridae uncertain (currently this family is organized into five genera: Alfamovirus, Bromovirus, Cucumovirus, Ilarvirus, and Oleavirus). Herein we report the presence of PYV in native potatoes (Solanum phureja) collected from Ecuador where the crop constitutes an important source of income in rural communities. Forty accessions of S. phureja collected in Ecuador in June 1986 and maintained in vitro at the International Potato Center (CIP) germplasm bank were analyzed by double-antibody sandwich (DAS)-ELISA with antiserum raised against a Peruvian isolate of PYV (1). PYV was detected in six accessions (15% of the material) corresponding to cultivars Chaucha Tomate and Chaucha Blanca (from the province of Cañar), Chaucha Negra Ojona and Chaucha Amarilla (Loja Province), and Cuica and Chaucha (Azuay Province). Mechanical inoculation of the indicator plant Physalis floridiana with leaf extracts of these six plants, a PYV isolate from Peru (1) (positive control), and an additional four plants testing negative for PYV (negative controls) induced symptoms of mosaic and leaf deformation only with the six clones from Ecuador and the PYV isolate from Peru. To further confirm the presence of the virus, we used universal PCR primers designed for the Bromoviridae (Ilar1F5: 5'-GCNGGWTGYGGDAARWCNAC-3' and Ilar1R7: 5'-AMDGGWAYYTGYTYNGTRTCACC-3') that target the helicase motif (RNA1) (3). Total RNA was extracted from 200 mg of leaf material (from potato and mechanically inoculated P. floridiana) using Trizol (Invitrogen, Carlsbad, CA) following the manufacturer's instructions and cDNA was synthesized using random hexamer primers. We obtained a reverse transcription-PCR amplified band only from samples that were DAS-ELISA positive to PYV. To identify the virus at the genus level, we cloned the PCR fragments (265 nucleotides) from four of the samples from Ecuador and the Peruvian isolate into plasmid vectors (pGEM-T Easy Vector cloning system; Promega, Madison, WI) for Sanger sequencing (Macrogen, Seoul, Korea). Phylogenetic analysis grouped PYV sequences with those of the genus Ilarvirus. Among the ilarviruses, Fragaria chiloensis latent virus (2) was the closest relative of PYV, with which it shares 77% nucleotide and 85% amino acid sequence identity. PYV isolates from Ecuador split into two different variants (91% identity) that shared 93% nucleotide and 99% amino acid sequence identity with the Peruvian isolate. Collectively, the data suggest that PYV is a distinct ilarvirus and that it is more widely spread among South American potatoes than previously suggested. The GenBank Accession Numbers for the sequences described are: HQ141053 (Loja1), HQ141054 (Azuay), HQ141055 (Cañar), and HQ141056 (Loja2) for the isolates from Ecuador and HQ141057 (PYV-Cañete) for the isolate from Peru. References: (1) S. Fuentes and U. Jayasinghe. Fitopatología 28:22, 1993. (2) I. E. Tzanetakis and R. R. Martin. Virus Res. 112:32, 2005. (3) M. Untiveros et al. J. Virol. Methods 165:97, 2010. (4) J. P. T. Valkonen et al. Potato Res. 35:411, 1992.

Pb-210 in rock and soils of the semi-arid agreste region of Pernambuco, Brazil.

The aim of this research was to determine (210)Pb concentrations in rocks and soils of farms located in the municipalities of Pedra and Venturosa. In these farms, rolled blocks of mafic rock with a high percentage of U(3)O(8) were found. The concentrations of (210)Pb varied from 3.2 to 201 kBq kg(-1) in rock samples and from 195 to 86,400 Bq kg(-1) in soil samples. The high levels of radioactivity found in the samples, indicate the need to conduct more detailed studies to evaluate the risk of radionuclide ingestion due to milk consumption by the population in the state of Pernambuco.

The effect of transport on the physiologic stability of neonates with ductal-dependent single-ventricle lesions.

OBJECTIVE: To compare the status of infants with hypoplastic left heart syndrome (HLHS) or pulmonary atresia-hypoplastic right heart (PA-HRH) before and following transport using the validated Transport Risk Index of Physiologic Stability (TRIPS) score. METHODS: In this retrospective review of infants with HLHS or PA-HRH transported to a Children's Hospital by a pediatric transport team, an increase in TRIPS score (temperature, blood pressure, respiratory status, and response to stimuli) following transport was defined as deterioration. Statistical analyses included t-test (paired and independent), χ2, and McNemar's tests for comparisons between groups with and without deterioration and before and after transport. RESULTS: Our cohort [n = 64; 39 (61%) HLHS and 25 (39%) PA-HRH] was predominantly female (61%), black (56%), and diagnosed antenatally (78%). Median transport time was 20 (10-30) min and age was <12 h in 48 (75%) infants. TRIPS scores worsened after transport in 24 (37.5%) infants, due to temperature (n = 10) or respiratory (n = 7) dysregulation. Infants who deteriorated during transport had HLH more often (83 versus 48%) and lower pH [7.27 (0.12) versus 7.33 (0.07)]. HLH was significantly predictive of deterioration during transport [OR 5.60 (95% C.I. 1.18-26.62)]. CONCLUSIONS: The physiologic deterioration in a third of infants with single ventricle following short transports is intriguing and may have implications on their optimal place of birth.

Serum cystatin C is associated with kidney function but not with cardiovascular risk factors or subclinical atherosclerosis in patients with Systemic Lupus Erythematosus.

Cystatin C (CysC) is a protein considered as an excellent marker of renal function, and it has been suggested as an independent predictor of cardiovascular (CV) risk. We evaluated the association of serum CysC with renal function, CV risk factors, inflammation, and subclinical atherosclerosis in Systemic Lupus Erythematosus (SLE) patients. Sixty-one SLE female patients were selected according to estimated glomerular filtration rate (GFR) > 60 ml/min/1.73m2. Renal function parameters, SLE specific factors, CV risk factors, and inflammatory markers were assessed. Subclinical atherosclerosis was assessed by measuring the carotid-femoral pulse wave velocity (PWV) by Doppler velocimetry. Serum CysC concentration was measured using a particle-enhanced immunonephelometric assay that established 0.59-1.01 mg/l as reference values. Patients with high CysC showed significantly altered creatinine, microalbuminuria, and GFR in addition to a significant higher presence of traditional CV risk factors such as arterial hypertension (p < 0.001), metabolic syndrome (p < 0.001), hypertrigliceridemia (p < 0.001), tobacco habit (p < 0.05), and a strong association with arterial stiffness (p = 0.017). Positive correlation between CysC, homocysteine (r = 0.511; p < 0.001) and fibrinogen levels (r = 0.304; p < 0.02) were also observed. A significantly higher SLICC/ACR score was related to high CysC level (p = 0.011), together with higher endothelin-1 and lower TNF serum concentration (p < 0.005). Considering only patients without any renal impairment (microalbumin/creatinine <30 mg/g), no association between CysC level and CV risk factors, arterial stiffness, or SLE-related factors was found. Serum CysC is a good marker of renal function in SLE patients, but it is not independently associated with cardiovascular risk factor or subclinical atherosclerosis.

NF-κB pathway controls mitochondrial dynamics.

The Optic atrophy 1 protein (OPA1) is a key element in the dynamics and morphology of mitochondria. We demonstrated that the absence of IκB kinase-α, which is a key element of the nonclassical NF-κB pathway, has an impact on the mitochondrial network morphology and OPA1 expression. In contrast, the absence of NF-κB essential modulator (NEMO) or IκB kinase-ß, both of which are essential for the canonical NF-κB pathway, has no impact on mitochondrial dynamics. Whereas Parkin has been reported to positively regulate the expression of OPA1 through NEMO, herein we found that PARK2 overexpression did not modify the expression of OPA1. PARK2 expression reduced the levels of Bax, and it prevented stress-induced cell death only in Bak-deficient mouse embryonic fibroblast cells. Collectively, our results point out a role of the nonclassical NF-κB pathway in the regulation of mitochondrial dynamics and OPA1 expression.

Effect of enterostatin on insulin, glucagon, and somatostatin secretion in the perfused rat pancreas.

Enterostatin is a pentapeptide generated by trypic digestion of procolipase in the small intestine. Both peripheral and central administration of this peptide to rats has been shown to reduce food intake, this reduction being due to specific suppression of fat intake. In perifused pancreatic rat islets, enterostatin has been shown to inhibit the insulin response to a high glucose concentration. In the present study, we have investigated the effect of exogenous enterostatin on insulin, glucagon, and somatostatin secretion by the isolated perfused rat pancreas. Enterostatin, at 100 mmol/l, inhibited the insulin response to 9 mmol/l glucose (by 70%), 0.1 mmol/l tolbutamide (by 40%), and 5 mmol/l arginine (by 70%). Enterostatin had no effect on glucagon and somatostatin release at a maintained glucose level (5.5 mmol/l) or in response to 5 mmol/l arginine. Finally, preinfusion of the rat pancreas with a high enterostatin concentration (500 nmol/l) did not alter the insulin response to glucose, an observation that would rule out a toxic effect of this peptide on the beta-cell. In summary, in the perfused rat pancreas, enterostatin, at putatively physiological concentrations, inhibits insulin secretion without affecting glucagon or somatostatin output, thus pointing to a direct effect of enterostatin on the beta-cell and not through an alpha-cell or delta-cell paracrine effect. Because enterostatin is generated in the small intestine after feeding, it might play a role in the enteroinsular axis as an anti-incretin agent.

Inhibition of insulin and somatostatin secretion and stimulation of glucagon release by homologous galanin in perfused rat pancreas.

Results of studies on the effects of exogenous galanin on islet cell secretion are controversial. Until recently, only pig galanin has been available, and structural dissimilarities among the galanin molecules of different species might have contributed to discrepancies among the study results. Thus, we investigated the influence of synthetic rat galanin (50 nM) on unstimulated insulin, glucagon, and somatostatin release and on the responses of these hormones to arginine (10 mM), glucose (16.6 mM), and vasoactive intestinal polypeptide (VIP; 1 nM) in a homologous animal model, the perfused rat pancreas. In addition, the effect of an equimolar concentration of pig galanin on arginine-induced islet cell secretion was examined. Infusion of rat galanin reduced unstimulated insulin release (approximately 60%, P less than 0.01) and the insulin responses to arginine (approximately 30%, P less than 0.025), glucose (100%, P less than 0.01), and VIP (approximately 80%, P less than 0.025). Galanin also inhibited unstimulated somatostatin secretion (approximately 15%, P less than 0.05) and virtually abolished the somatostatin output evoked by arginine, glucose, and VIP. Conversely, rat galanin increased unstimulated glucagon output (approximately 20%, P less than 0.05), potentiated the glucagon response to arginine (approximately 50%, P less than 0.05) and VIP (approximately 90%, P less than 0.05), and counteracted the suppressor effect of glucose on alpha-cell secretion. Pig galanin inhibited the insulin output elicited by arginine (approximately 45%, P less than 0.05) but did not affect the somatostatin and glucagon responses to the aminogenic stimulus. In conclusion, the opposite effects of galanin on insulin and glucagon secretion favor the concept of galanin as a diabetogenic agent. Galanin also behaves as a potent inhibitor of somatostatin release. Finally, the importance of using homologous galanin to study the biological activity of this peptide must be emphasized.

[Primary meningeal intermediate grade melanocytic neoplasm: case report with radiologic-pathologic correlation]. / Tumeur mélanocytaire méningée primitive de grade intermediaire: confrontation radio-pathologique.

A case of primary meningeal intermediate grade melanocytic neoplasm involving the right C2 nerve root is presented. MRI findings may suggest this rare entity, especially when an extra-axial lesion is located in the posterior fossa or cervical spinal canal and demonstrates shortening of both T1 and T2. Eventually, definitive diagnosis relies on histology which demonstrates spindle-shaped melanocytic cells that are Fontana stained and positive for HMB:45 antigen. Cellularity, pleomorphism, mitotic rate, proliferation index and invasiveness are useful criteria to distinguish among the spectrum of primary melanocytic tumors of the central nervous system ranging from melanocytoma to malignant melanoma.

Effects of galanin on hormone secretion from the in situ perfused rat pancreas and on glucose production in rat hepatocytes in vitro.

UNLABELLED: Galanin is a novel peptide, widely distributed throughout the central and peripheral nervous system, including nerve endings surrounding the pancreatic islets. In dogs, galanin infusion has been reported to induce hyperglycemia along with a reduction of circulating insulin. In this work, we have studied the effect of galanin (a 200 ng bolus followed by constant infusion at a concentration of 16.8 ng/ml for 22-24 min) on insulin, glucagon, and somatostatin secretion in the perfused rat pancreas. In addition, we have investigated the effect of galanin (10 and 100 nM) on glycogenolysis and gluconeogenesis in isolated rat hepatocytes. In the rat pancreas, galanin infusion marked inhibited unstimulated insulin release as well as the insulin responses to glucose (11 mM), tolbutamide (100 mg/liter) and arginine (5 mM). Galanin failed to alter the glucagon and somatostatin responses to glucose, tolbutamide, and arginine. In isolated rat hepatocytes, galanin did not influence glycogenolysis or glucagon phosphorylase a activity. Gluconeogenesis and the hepatocyte concentration of fructose 2,6-bisphosphate were also unaffected by galanin. IN CONCLUSION: in the perfused rat pancreas, galanin inhibited insulin secretion without modifying glucagon and somatostatin output, thus pointing to a direct effect of galanin on the B cell; and in rat hepatocytes, galanin did not affect glycogenolysis or gluconeogenesis; hence, the reported hyperglycemia induced by exogenous galanin does not seem to be accounted for by a direct effect of this peptide on hepatic glucose production.

Stimulatory effect of vasoactive intestinal peptide on glycogenolysis and gluconeogenesis in isolated rat hepatocytes: antagonism by insulin.

We have studied the effect of Vasoactive Intestinal Peptide (VIP) on glycogenolysis and gluconeogenesis (as measured by the conversion of [U-14C]pyruvate into glucose) in hepatocytes isolated from fed rats. The influence of VIP on glycogen phosphorylase alpha and pyruvate kinase activities, as well as on cAMP levels, was also evaluated. In addition, the possible antagonism of insulin on these VIP-mediated effects was investigated. VIP enhanced both glycogenolysis and gluconeogenesis in a dose-dependent manner. At 10(-6) M VIP, both processes were increased 2-fold as compared to the basal values; the calculated half-maximal stimulatory concentrations were 2.5 x 10(-8) M and 4 x 10(-8) M, respectively. VIP also caused a dose-dependent activation of glycogen phosphorylase and inactivation of pyruvate kinase. At 10(-6) M VIP, glycogen phosphorylase a was increased 3-fold and pyruvate kinase activity was reduced by 46%. The addition of 10(-7) M VIP to the incubation medium caused a 2-fold increase of basal cAMP levels. All these VIP-mediated effects were markedly blocked by the presence of 10(-8) M insulin. As compared to glucagon (10(-7) M) the potency of an equimolar concentration of VIP, in terms of stimulation of gluconeogenesis, inactivation of pyruvate kinase, and activation of glycogen phosphorylase ranged from 35-45%. Our results indicate that VIP increases hepatic glucose output through the stimulation of both glycogenolysis and gluconeogenesis. These effects seem to be mediated by a cAMP-dependent mechanism.

Stimulatory effect of exogenous diadenosine tetraphosphate on insulin and glucagon secretion in the perfused rat pancreas.

1. Diadenosine triphosphate (AP3A) and diadenosine tetraphosphate (AP4A) are released by various cells (e.g. platelets and chromaffin cells), and may act as extracellular messengers. In pancreatic B-cells, AP3A and AP4A are inhibitors of the ATP-regulated K+ channels, and glucose increases intracellular levels of both substances. 2. We have studied the effect of exogenous AP3A and AP4A on insulin and glucagon secretion by the perfused rat pancreas. 3. AP3A did not significantly modify insulin or glucagon release, whereas AP4A induced a prompt, short-lived insulin response ( approximately 4 fold higher than basal value; P<0.05) in pancreases perfused at different glucose concentrations (3.2, 5.5 or 9 mM). AP4A-induced insulin release was abolished by somatostatin and by diazoxide. These two substances share the capacity to activate ATP-dependent K+ channels, suggesting that these channels are a potential target for AP4A in the B-cell. 4. AP4A stimulated glucagon release at both 3.2 and 5.5 mM glucose. This effect was abolished by somatostatin. 5. The results suggest that extracellular AP4A may play a physiological role in the control of insulin and glucagon secretion.