Role of vesicular nucleotide transporter VNUT (SLC17A9) in release of ATP from AR42J cells and mouse pancreatic acinar cells.

ATP is released from cells in response to various stimuli. Our previous studies on pancreas indicated that pancreatic acini could be major stores of secreted ATP. In the present study, our aim was to establish the role of the vesicular nucleotide transporter (VNUT), SLC17A9, in storage and release of ATP. Freshly prepared acini from mice and AR42J rat acinar cells were used in this study. We illustrate that in AR42J cells, quinacrine (an ATP store marker) and Bodipy ATP (a fluorescent ATP analog) co-localized with VNUT-mCherry to vesicles/granules. Furthermore, in acini and AR42J cells, a marker of the zymogen granule membranes, Rab3D, and VNUT co-localized. Dexamethasone treatment of AR42J cells promoted formation of acinar structures, paralleled by increased amylase and VNUT expression, and increased ATP release in response to cholinergic stimulation. Mechanical stimulus (pressure) and cell swelling also induced ATP release, but this was not influenced by dexamethasone, most likely indicating different non-zymogen-related release mechanism. In conclusion, we propose that VNUT-dependent ATP release pathway is associated with agonist-induced secretion process and downstream purinergic signalling in pancreatic ducts.

Crystal structure of imidazole glycerol phosphate synthase: a tunnel through a (beta/alpha)8 barrel joins two active sites.

BACKGROUND: Imidazole glycerol phosphate synthase catalyzes a two-step reaction of histidine biosynthesis at the bifurcation point with the purine de novo pathway. The enzyme is a new example of intermediate channeling by glutamine amidotransferases in which ammonia generated by hydrolysis of glutamine is channeled to a second active site where it acts as a nucleophile. In this case, ammonia reacts in a cyclase domain to produce imidazole glycerol phosphate and an intermediate of purine biosynthesis. The enzyme is also a potential target for drug and herbicide development since the histidine pathway does not occur in mammals. RESULTS: The 2.1 A crystal structure of imidazole glycerol phosphate synthase from yeast reveals extensive interaction of the glutaminase and cyclase catalytic domains. At the domain interface, the glutaminase active site points into the bottom of the (beta/alpha)(8) barrel of the cyclase domain. An ammonia tunnel through the (beta/alpha)(8) barrel connects the glutaminase docking site at the bottom to the cyclase active site at the top. A conserved "gate" of four charged residues controls access to the tunnel. CONCLUSIONS: This is the first structure in which all the components of the ubiquitous (beta/alpha)(8) barrel fold, top, bottom, and interior, take part in enzymatic function. Intimate contacts between the barrel domain and the glutaminase active site appear to be poised for crosstalk between catalytic centers in response to substrate binding at the cyclase active site. The structure provides a number of potential sites for inhibitor development in the active sites and in a conserved interdomain cavity.

Crystal structure of Bacillus subtilis YabJ, a purine regulatory protein and member of the highly conserved YjgF family.

The yabJ gene in Bacillus subtilis is required for adenine-mediated repression of purine biosynthetic genes in vivo and codes for an acid-soluble, 14-kDa protein. The molecular mechanism of YabJ is unknown. YabJ is a member of a large, widely distributed family of proteins of unknown biochemical function. The 1.7-A crystal structure of YabJ reveals a trimeric organization with extensive buried hydrophobic surface and an internal water-filled cavity. The most important finding in the structure is a deep, narrow cleft between subunits lined with nine side chains that are invariant among the 25 most similar homologs. This conserved site is proposed to be a binding or catalytic site for a ligand or substrate that is common to YabJ and other members of the YER057c/YjgF/UK114 family of proteins.

Factors predicting the use of multiple psychotropic medications.

BACKGROUND: Recent studies have questioned the appropriateness of some types of psychotropic medication prescribing, especially by general practitioners. The purpose of this study is to investigate factors that predict prescribing of multiple psychotropic medications, a class that may represent more complicated cases. METHOD: This study analyzed data from the 1989 National Ambulatory Medical Care Survey (NAMCS). Multiple logistic regression methods were used to determine variables that predicted the provision or ordering of multiple psychotropic medications during a single office visit. RESULTS: Patients who visited psychiatrists were six times more likely to receive psychotropics in combination than patients visiting general practitioners. Patients diagnosed as manic were four times more likely to receive multiple psychotropics, and those diagnosed as schizophrenic were three times more likely Patients visiting physicians in the Northeast and South were significantly less likely to receive psychotropics in combination than patients in the Midwest. CONCLUSION: Although general practice physicians contribute to the use of multiple psychotropic medications, patients visiting psychiatric specialists are much more likely to be provided combination therapy.

Applications of lipid-coated microbubble ultrasonic contrast to tumor therapy.

Lipid-coated microbubbles (LCM) make an excellent diagnostic ultrasonic contrast agent in experimental tumor systems. LCM have been shown to aggregate in brain tumors and subcutaneous tumors after intravenous administration, and to provide persistent image enhancement for many minutes. In this work, experimental subcutaneous Walker Carcinosarcoma is insonated after the bubbles are given intravenously. Selective necrosis, lymphocyte proliferation and hemorrhage within the tumor can be demonstrated. Preliminary data are given to demonstrate this phenomenon. The mechanism of the effect is discussed in the context of both heating and cavitation.

Intraoperative neurosonography: application and technique.

Intraoperative neurosonography was performed in 44 patients with contact transdural or transgyral scanning technique. Localization of intracranial pathology included primary brain tumors (24), metastatic tumors (11), aneurysms (two), abscesses (two), arteriovenous malformation (one), thrombosed arteriovenous malformations (two), and plasmacytoma (one). Sonographic guidance was used in transdural decompression of three cystic lesions, therapeutic and diagnostic aspiration of two abscesses, and biopsy of three solid lesions. The expertise of the physician-sonographer with sonographic equipment facilitates accurate and expedient intraoperative neurosurgical localization of pathology.

Intraoperative ultrasound detection of metastatic tumors in the central cortex.

Real-time sector ultrasonography precisely located metastatic tumors of the central motor cortex during craniotomy in two patients. In these two cases, the only surface abnormality was swelling of several overlying gyri. Intraoperative ultrasonography precisely located the 1.5- and 2.5-cm-diameter tumors to a position below a specific gyrus, enabling the surgeon to excise the tumors through small, accurately placed cortical windows. The precise location minimized exploratory probing and the size of the cortical incision required to identify and remove the tumors. This technique will have general application in similar situations when the cortical surface gives no indication of underlying tumor location. By charting the best trajectory for the surgical approach, this technique may replace a variety of stereotactic and computed tomography-guided techniques for biopsy of deep brain tumors.

Operant control of precentral neurons: bilateral single unit conditioning.

Two Macaca mulatta monkeys were reinforced to operantly control a precentral neuron's firing pattern while a contralateral unit was monitored simultaneously. The results from 38 complete experiments indicate the following: (a) upon altering to the operant task, both the contingent and the non-contingent neurons changed firing patterns from preconditioning levels. However, as the monkey brought the contingent unit under operant control, there were no significant changes in the firing pattern of the non-contingent neuron; (b) when the contingencies were reversed so that the monkeys were reinforced to control the originally non-contingent neuron, the firing pattern off the originally contingent neuron returned to near baseline levels. These data indicate that although many precentral units may change firing patterns when the monkey attends to the operant task, the reinforced changes in firing pattern are not the result of a generalized phenomenon at the spinal level.

Neuronal activity in chronic ferric chloride epileptic foci in cats and monkey.

The firing patterns of neurons surrounding sites of ferric chloride (FeCl3) injection were studied in 6 cats and 1 Macaca mulatta monkey. Although a few neurons fired in poorly structured bursts similar to what has been described for some neurons in alumina foci in monkeys, no well-formed bursts were recorded. In addition, EEG spikes were not recorded chronically in two cats, nor were EEG spikes recorded during corticography. We could not confirm the reliability of this preparation in cats as a model of chronic epilepsy.

Operant control of precentral neurons: control of modal interspike intervals.

The objects of these experiments were: (a) to determine modal interspike intervals (ISIs) of precentral cells involved in repetitious, gross motor movements; (b) to compare those modal ISIs to the modal ISIs of similar neurons under operant control; and (c) to determine if monkeys could change the modal ISIs of operantly controlled precentral neurons. Data were obtained from 4 monkeys conditioned to produce tonic firing of precentral neurons and one monkey trained to produce repetitious movements of the neck and contralateral limbs. Results are: (a) the modal ISIs from operantly controlled precentral units do not differ significantly from precentral neurons involved in repetitive gross motor movements; and (b) while under operant control, the monkeys cannot modify significantly the modal ISI of the majority of precentral neurons.

Biphasic effects of imipramine in experimental models of epilepsy.

In a variety of laboratory models of experimental epilepsy, imipramine exerts a biphasic action on the CNS as manifested by antiepileptic properties at low doses and convulsant effects at higher doses. In mice, imipramine (17.5-25 mg/kg, i.p.) blocks maximal electroshock seizures while exerting little or no effect on pentylenetetrazol-induced seizures. In cats, imipramine (2.5-15 mg/kg, i.v.) reduces penicillin and estrogen-induced epileptiform discharge, shortens afterdischarge duration and elevates afterdischarge threshold. Higher doses in mice induce neurotoxicity, including clonic seizures. In cats, doses above 20 mg/kg intensify chemically and electrically induced seizures and induce spontaneous epileptiform episodes. Such a biphasic action of imipramine may limit the drug's clinical utility as an antiepileptic agent and may provide an interesting tool for studies of catecholamines and brain excitability.